CN119816568A - Water-based coating material containing cellulose nanofibers - Google Patents

Abstract

The present invention relates to an aqueous coating material comprising one or more polymer binders; one or more types of cellulose nanofibers; and one or more non-polymeric polycarboxylic acids and/or salts thereof; and optionally one or more pigments. The present invention further relates to a wet-on-wet method for producing a multi-layer coating system and a multi-layer coating system obtainable according to the method. The present invention further relates to the use of an uncolored aqueous coating material for producing a colored aqueous coating material; and the use of at least one type of cellulose nanofibers and one or more non-polymeric polycarboxylic acids and/or salts thereof in an aqueous coating material comprising a polymer binder and a pigment in the production of a multi-layer coating system.

Description

Aqueous coating material containing cellulose nanofibers

The present invention relates to an aqueous coating material comprising a polymeric binder, further comprising one or more types of cellulose nanofibers and one or more non-polymeric polycarboxylic acids and/or salts thereof. The invention further relates to a method for producing a multilayer coating on a substrate, wherein an aqueous coating composition is used as a pigmented base coat material, preferably in an automotive coating. The invention further relates to the multilayer coating system thus obtained, and furthermore, to the use of cellulose nanofibers and non-polymeric polycarboxylic acids in aqueous coating materials containing polymeric binders and pigments, and to the use of the coating materials as primer materials in the production of multilayer coating systems.

Background

Particularly in automotive finishes (finishing), but also in other fields where good decorative effects are desired and at the same time effective protection against corrosion of the coating, it is known practice to provide the substrate with a plurality of coatings disposed one on top of the other.

The multi-coat paint system is preferably applied by the so-called "wet-on-wet" method, meaning that the pigmented basecoat material is applied first and, after a short flash time, is applied again with the clearcoat material without a baking step. Subsequently, the undercoat layer and the clear coat layer are baked together. The wet-on-wet method is of particular interest in the application of automotive color and/or metallic effect paints.

Economic and environmental reasons have led to the development of multi-coating systems using aqueous basecoat materials. The coating materials used to produce these basecoats must be able to be processed by the reasonable "wet-on-wet" processes customary today, i.e., after a very short initial drying period, without a baking step, they must be able to be recoated with a transparent topcoat without exhibiting defects in their visual appearance.

Furthermore, the coating material must also exhibit sufficient stability upon storage. A conventional test is to store the material at 40 ℃ and then determine any viscosity change after storage. In particular, basecoat materials containing colored pigments and/or effect pigments (such as metallic effect pigments) should be storage stable, otherwise sedimentation of the pigment particles will occur as a result.

In the case of metallic effect paints used in the "wet-on-wet" process, there are additional problems that must be addressed. The metallic effect is critically dependent on the dispersion of the metallic pigment particles in the coating material, the size and shape of the metallic pigment particles, the rheological properties of the coating material, the application of the coating material, and the orientation of the metallic pigment particles in the coating. The metallic effect basecoat materials which can be processed by the "wet-on-wet" method must therefore provide a coating in which the metallic pigments are present in an advantageous spatial orientation after application and in which the orientation is so rapidly fixed that they are no longer negatively affected during further finishing operations.

A suitable parameter for characterizing the metallic effect primer is light reflection, in particular the change in direction of the light reflection, which is typically expressed in terms of flop index. The metallic effect basecoat exhibiting a low flop index appears to be uniform when viewed from several angles and curves. In order to achieve a low flop index, the metallic effect pigments must exhibit random orientation within the basecoat.

However, metallic effect basecoats featuring high flop indexes are still becoming increasingly popular. Such coatings exhibit different appearances when viewed from different angles and curved surfaces. In order to achieve a high flop index, the metallic effect pigments within the basecoat must exhibit an orientation that is substantially parallel to the underlying substrate.

One way to achieve a high flop index is to manually apply a composition containing a metallic effect pigment having a low non-volatile fraction. However, manual application limits the use of such compositions in vehicle production and OEM vehicle finishing.

Also known from the prior art is the practice of increasing flop index by adding polyamide waxes having different acid numbers. For example, EP 0877063 A2, WO 2009/100938 A1, EP 2457961 A1 and EP 3183303 A1 describe aqueous coating materials comprising polyamides having an acid number of 30mg KOH/g polyamide or <10mg KOH/g polyamide. However, the use of polyamides and other water insoluble components in aqueous coating materials may result in incompatibility between these compounds and the water soluble components of the composition. This results in particular in the pelletization of the processing by the "wet-on-wet" method and/or the pelletization of the incorporation of polyamides into the coating material, and/or the insufficient storage stability of such coating materials (delamination (demixing) or phase separation), in particular at relatively high temperatures (such as, for example, temperatures of about 40 ℃). In addition, polyamides may result in poor leveling and/or poor appearance.

EP 1153989 A1 discloses aqueous coating materials comprising polyamides having an acid number of >30mg KOH/g polyamide and, as further rheology auxiliaries, metal silicates composed of very small, usually nanoscale, particles. However, the disadvantage of the presence of such metal silicates in aqueous coating materials, especially in combination with polyamides having an acid number of >30mg KOH/g polyamide, may generally be the occurrence of pinholes and/or lumps in the case of processing by means of the "wet-on-wet" method. Furthermore, the use of metal silicates is undesirable because of their high surface area, they interact strongly with other formulation components (especially dispersing additives and/or binders having groups with pigment affinities). Minimizing these interactions requires high levels of dilution. However, this dilution can particularly adversely affect the shear stability and recycle line stability of the coating material.

Another method of producing a rheology-stable coating material is disclosed, for example, in US10,898,923B2, which describes the use of cellulose nanofibers in an aqueous effect pigment formulation. However, these formulations are limited to a maximum solids content of 10% by weight, based on the total weight of the coating material.

It is an object of the present invention to provide an aqueous coating material allowing a solids content of more than 10% by weight based on the total weight of the coating material. Even without the use of rheology control agents from the group consisting of polyamides and metal silicates, the aqueous coating materials should have excellent storage stability and viscosity stability. In particular, the aqueous coating materials provided by the present invention should be readily supplemented with similar colored pigments and/or effect pigments to form colored aqueous coating materials having storage stability and viscosity stability.

Furthermore, such coating materials should provide good optical and color properties as well as good leveling properties for the multilayer coating, and in the case of coating materials containing metallic effect pigments, improved flop, especially if used as a pigmented basecoat material in a multilayer coating system. Preferably, the aqueous coating material of the present invention is easy to apply in a so-called wet-on-wet coating process and is suitable for use in automotive coatings.

Disclosure of Invention

These objects are achieved by providing an aqueous coating material comprising

A) One or more polymeric binders

B) One or more types of cellulose nanofibers, and

C) One or more non-polymeric polycarboxylic acids and/or salts thereof, and

D) Optionally one or more pigments.

The above-mentioned aqueous coating material is hereinafter also referred to as "the aqueous coating material of the present invention" or "the aqueous coating material according to the present invention".

A further subject of the invention is a process for producing a multi-layer paint system on a substrate, comprising the steps of:

(1) Producing a cured first coating on the substrate, optionally by applying a coating material to the substrate and subsequently curing the composition;

(2) Creating one or more basecoats on the coating obtained in step (1) by applying one or more of the same or different waterborne basecoat materials;

(3) Producing one or more clearcoats on one or more top-most basecoats by applying a clearcoat material, and

(4) Co-curing the one or more basecoat layers and the one or more clearcoat layers;

Wherein the method comprises the steps of

At least one of the basecoat materials is an aqueous coating material according to the present invention.

The above-described process for producing a multicoat paint system on a substrate is also referred to hereinafter as the "process according to the invention" or the "process according to the invention".

The invention further provides a multilayer coating system obtainable by the method of the invention.

A further subject matter of the invention is the use of the uncoloured aqueous coating material according to the invention as a universal aqueous coating composition for the production of coloured aqueous coating materials according to the invention.

Yet another subject of the present invention is the use of at least one type of cellulose nanofibres as used in the aqueous coating material of the present invention together with one or more non-polymeric polycarboxylic acids and/or salts thereof as used in the aqueous coating material of the present invention in an aqueous coating material comprising one or more polymeric binders as in the aqueous coating material of the present invention and one or more pigments as defined above and below in the production of a multilayer coating system.

A further subject matter of the invention is the use of the pigmented aqueous coating material according to the invention as a base coat material, preferably in automotive coatings.

Detailed Description

Water-based paint material

The term "coating material" refers to a product in the form of a liquid, paste or powder that, when applied to a substrate, forms a film having protective, decorative and/or other specific properties (DIN ISO 4618:2006). The expression "aqueous coating material" is known to the skilled person. It basically refers to liquid coating materials whose volatile content is not solely based on organic solvents.

In fact, any such coating material based on organic solvents contains only organic solvents and does not contain water for dissolving and/or dispersing the components, or is a coating material to which water is not explicitly added during its production, whereas water enters the composition only in the form of contaminants, atmospheric moisture and/or solvents of any particular additives employed. Such compositions will be referred to as solvent-based or "organic solvent-based" in comparison to aqueous coating materials.

In the context of the present invention, "aqueous" should preferably be understood to mean that the coating material comprises a water fraction of at least 20wt. -%, preferably at least 25wt. -%, very preferably at least 50wt. -%, in each case based on the total amount of solvents (i.e. water and organic solvents) present. The water fraction is in turn preferably 60 to 100wt. -%, more particularly 65 to 90wt. -%, very preferably 70 to 80-wt. -%, in each case based on the total amount of solvent present.

The coating material of the present invention has a relatively high solids content. It is therefore preferred that the composition has a solids content of 10wt. -% or 11wt. -% to 65wt. -%, preferably 15wt. -% to 50wt. -%, more particularly 20wt. -% to 45wt. -%, based in each case on the total weight of the coating material and measured according to DIN EN ISO 3251 (month 6 2008) as detailed in the examples section of the present specification. In view of the high solids content, the coating material of the invention has good environmental properties without any adverse effect on its storage stability.

The coating material of the invention preferably has a pH in the range of 4 to 10, more preferably in the range of 5 to 10, even more preferably in the range of 7 to 10, more particularly in the range of 7 to 9, measured in each case at 23 ℃.

Preferably, the aqueous coating material of the present invention is pigmented and thus comprises one or more pigments selected from the group consisting of colored pigments and effect pigments.

More preferably, the aqueous coating material of the present invention is a pigmented base coat material, particularly preferably for automotive coatings.

Polymer adhesive

The term "binder" in the sense of the present invention and in accordance with DIN EN ISO 4618 (German version, date: 3. 2007) preferably refers to those non-volatile parts of the composition of the invention responsible for forming films, except for any pigments and fillers, and more particularly to the polymeric resins responsible for forming films. The non-volatile portion may be determined by the methods described in the examples section.

Thus, curing of a coating is understood to mean the conversion of such a layer into a ready-to-use (service-ready) state, in other words into a state in which a substrate finished with the coating in question can be transported, stored and used in its intended manner. The cured coating is then in particular no longer soft or tacky, but is adjusted to a solid coating which no longer exhibits any substantial change in its properties (such as hardness or adhesion to a substrate) even if further exposed to curing conditions as described below Wen Shao.

As is known, the coating materials can in principle be cured physically and/or chemically, depending on the components present, in particular the polymeric binders and crosslinking agents, which also belong to the binders.

In the case of chemical curing, thermochemical curing and photochemical-chemical curing are considered. For example, where the coating material is thermochemically curable, it may be self-crosslinking and/or externally crosslinking. In the context of the present invention, an indication that the coating material is self-crosslinking and/or externally crosslinking means that the coating material comprises a polymer as binder and optionally a crosslinking agent as binder, which are capable of crosslinking in response to each other. The main mechanism and also the binder that can be used and the crosslinking agent (i.e., film-forming component) as the binder will be described later.

In the context of the present invention, the term "physically curable" or the term "physical curing" means the formation of a cured coating by the loss of solvent from a polymer solution or polymer dispersion, wherein the curing is achieved in particular by inter-ring formation of polymer chains. These types of coating materials are typically formulated as one-component coating materials.

In the context of the present invention, "thermochemically curable" or the term "thermochemically cured" means the crosslinking of a coating (formation of a cured coating) initiated by a chemical reaction of reactive functional groups, wherein the energy activation of the chemical reaction may be performed by thermal energy. Different functional groups complementary to each other may here react with each other (complementary functional groups), and/or the formation of the cured coating is based on the reaction of self-reactive groups (in other words functional groups that react with each other with their own kind of groups). Examples of suitable complementary reactive functions and self-reactive functions are known, for example, from german patent application DE 199 30 6615 a1, page 7, line 28 to page 9, line 24.

In thermochemically curable one-component systems, the components used for crosslinking (such as, for example, an organic polymer as binder and a crosslinking agent as binder) coexist with each other, in other words, in one component. The requirement for this is that the components to be crosslinked react effectively with one another, i.e. enter into the curing reaction, only at relatively high temperatures, for example typically above 100 ℃. As an exemplary combination, mention may be made of hydroxy-functional polyesters and/or polyurethanes with melamine resins and/or blocked polyisocyanates as crosslinkers.

In thermochemically curable two-component systems, the components to be crosslinked (such as, for example, an organic polymer as binder and a crosslinking agent) are present as at least two components separately from one another, which are not combined until shortly before application. This form is selected when the components for crosslinking undergo an effective reaction with each other even at ambient temperatures such as 20 ℃ or slightly elevated temperatures, e.g., 40 ℃ to 90 ℃. As an exemplary combination, mention may be made of hydroxy-functional polyesters and/or polyurethanes and/or poly (meth) acrylates with free polyisocyanates as crosslinkers.

In the context of the present invention, "actinically-chemically cured", or the term "actinically-chemically cured", refers to the fact that it is also curable by the application of actinic radiation, which is electromagnetic radiation such as Near Infrared (NIR) and UV radiation, more particularly UV radiation, and also particulate radiation such as electron beams. Curing by UV radiation is usually initiated by free radical or cationic photoinitiators. Typical actinically curable functional groups are carbon-carbon double bonds, in which case free radical photoinitiators are usually employed. Thus, the actinic curing is likewise based on chemical crosslinking.

Of course, in curing of coating materials that are identified as being chemically curable, there will always be physical curing, in other words, inter-ring formation of polymer chains. Physical curing may even be dominant. However, as long as it includes at least a portion of the chemically curable film-forming component, this type of coating material is identified as being chemically curable.

In the case of a purely physically cured coating material, the curing is preferably carried out between 15 ℃ and 90 ℃ over a period of 2 to 48 hours. In this case, the curing differs from the flashing and/or intermediate drying, in the appropriate case only in the duration of the coating conditioning. In addition, it is not advisable to distinguish between flash evaporation and intermediate drying. For example, for a coating produced by applying a physically curable coating material, it will be possible to first undergo flash evaporation or intermediate drying at 15 ℃ to 35 ℃ for a duration of, for example, 0.5 to 30 minutes, and then undergo curing at 50 ℃ for a duration of 5 hours.

In principle, and in the context of the present invention, the curing of the thermochemically curable one-component system may preferably be carried out at a temperature of from 100 ℃ to 250 ℃, preferably from 100 ℃ to 180 ℃, for a duration of from 5 to 60 minutes, preferably from 10 to 45 minutes, as these conditions are generally necessary for a chemical crosslinking reaction to convert the coating into a cured coating. It is thus the case that the flash-off and/or intermediate drying stage carried out before curing takes place at a lower temperature and/or in a shorter time. In this case, for example, the flash evaporation may be performed at 15 to 35 ℃ for a duration of, for example, 0.5 to 30 minutes, and/or the intermediate drying may be performed at a temperature of, for example, 40 to 90 ℃ for a duration of, for example, 1 to 60 minutes.

In principle, and in the context of the present invention, the curing of the thermochemically curable two-component system is carried out at a temperature of 15 ℃ to 90 ℃ (e.g. in particular 40 ℃ to 90 ℃) for a duration of 5 to 80 minutes, preferably 10 to 50 minutes. It is thus the case that the flash-off and/or intermediate drying stage carried out before curing takes place at a lower temperature and/or in a shorter time. In this case, it is no longer advisable to distinguish, for example, between the concepts of flash evaporation and intermediate drying. The flash or intermediate drying stage prior to curing may be carried out, for example, at 15 ℃ to 35 ℃ for a duration of, for example, 0.5 to 30 minutes, but at least at a lower temperature and/or for a shorter time than the subsequent curing.

Of course, this does not exclude that the thermochemically curable two-component system cures at a higher temperature. For example, in the wet-on-wet coating method of the present invention as described later more precisely, the undercoat layer or two or more undercoat layers are cured together with the transparent coating layer. For example, when both thermochemically curable one-component and two-component systems (e.g., one-component primer materials and two-component clearcoat materials) are present within the layer, co-curing is, of course, guided by the curing conditions necessary for the one-component system.

All temperatures stated in the context of the present invention should be understood as the temperature of the chamber in which the coated substrate is located. Thus, this does not mean that the substrate itself is required to have the temperature in question.

Since the aqueous coating materials of the present invention may use different curing mechanisms, the one or more polymeric binders PB as used in the coating materials of the present invention may differ in their composition.

Thus, the one or more polymeric binders PD of the present invention may be selected from the group consisting of physically dry polymeric binders, thermo-chemically curable binders and/or radiation curable binders.

In particular, the one or more polymeric binders PB are preferably nonionic and/or anionically stabilized polymeric binders. However, anionically stabilized polymeric binders are more preferred as the one or more polymeric binders PB used in the aqueous coating materials of the invention.

Nonionic stable polymeric binders

Nonionic stabilization of polymeric binders in aqueous coating compositions is typically accomplished by incorporating water-soluble nonionic moieties in the polymeric binder. Such moieties are preferably selected from the group comprising or consisting of poly (oxyalkylene) moieties, polylactone moieties such as polybutylactone moieties, polyalcohol moieties such as polyvinyl alcohol moieties and also polyvinylpyrrolidone moieties, more particularly poly (oxyethylene) moieties and/or poly (oxypropylene) moieties.

Anionically stabilized polymeric binders

Anionic stabilization of polymeric binders in aqueous coating compositions is typically achieved by introducing anionic groups into the polymeric binder. Such anionic groups are preferably introduced in the form of acidic groups, such as carboxylic acid groups, and the acidic groups are then at least partially neutralized.

In the aqueous coating materials of the present invention, anionically stabilized polymeric binders are preferred over nonionic stabilized polymeric binders because their use in combination with cellulose nanofibers and a non-polymeric polycarboxylic acid results in a multilayer coating having even better color matching and flop characteristics.

It is particularly preferred to use an anionically stabilized polymeric binder which has a certain electrophoretic mobility at a pH of 8.0. The electrophoretic mobility may be determined here as described in the examples section. Thus, in a preferred embodiment of the present invention, the at least one anionically stabilized polymer binder has an electrophoretic mobility of-2.5 to-15 (μm/s)/(V/cm), preferably-2.5 to-10 (μm/s)/(V/cm), more preferably-4 to-8 (μm/s)/(V/cm), more particularly-5 to-8 (μm/s)/(V/cm), at a pH of 8.0.

Furthermore, it is advantageous if the anionically stabilized polymer binder is present in the aqueous coating composition according to the invention in a defined total amount. Thus, in a preferred embodiment of the present invention, the at least one anionically stabilized polymer binder is present in a total amount of 20 to 80wt. -%, preferably 30 to 70wt. -%, more particularly 40 to 70wt. -%, in each case based on the total solids content of the coating composition. If more than one anionically stabilized polymer binder is used, the above ranges of amounts are based on the total amount of anionically stabilized polymer binder in the composition. The use of at least one anionically stabilized polymeric binder in combination with one or more cellulose nanofibers and one or more non-polymeric polycarboxylic acids in the above-described amounts results in particularly good flop index and also good optical and color characteristics in the pigmented aqueous base coating without adversely affecting the storage stability of the compositions of the invention. Furthermore, the use of the above-described amounts of anionically stabilized polymeric binders results in effective fixation of the orientation of the effect particles in the effectively pigmented aqueous basecoat formed from the effect pigment-containing aqueous coating composition of the present invention during flash evaporation, and thus subsequent application of additional coating compositions has no adverse effect on the orientation of the effect particles and thus on the flop index.

Polyurethane-polyurea-particles (PPP)

In the context of the present invention, it has proven advantageous for the anionically stabilized polymer binder to comprise anionically stabilized polyurethane-polyurea particles (PPP) dispersed in water.

Thus, the anionically stabilized polymer binder preferably comprises anionically stabilized polyurethane-polyurea particles (PPP) which are dispersed in water and have an average particle size of preferably 40 to 2000nm and a gel fraction of at least 50%, the anionically stabilized polyurethane-polyurea particles (PPP) comprising in each case in reactive form:

(Z.1.1) at least one isocyanate group-containing polyurethane prepolymer which contains groups as anionic groups and/or which can be converted into anionic groups, and

(Z.1.2.) at least one polyamine containing two primary amino groups and one or two secondary amino groups.

Anionically stabilized polyurethane-polyurea particles (PPP) are dispersed in water or are present in the form of aqueous dispersions. The fraction of water in the dispersion is preferably 45 to 75wt. -%, preferably 50 to 70wt. -%, more preferably 55 to 65wt. -%, in each case based on the total amount of the dispersion. It is preferred that the dispersion to some extent consists of at least 90wt. -%, preferably at least 92.5wt. -%, very preferably at least 95wt. -% and more preferably at least 97.5wt. -% polyurethane-polyurea particles (PPP) and water (the relevant value is obtained by summing the amount of particles (i.e. the amount of polymer determined via the solid content) and the amount of water).

Anionically stabilized polyurethane-polyurea particles (PPP) are polymer particles based on polyurethane-polyureas. The anionically stabilized polyurethane-polyurea particles (PPP) preferably have a gel fraction of at least 50% (for the measurement method, see the examples section) and preferably have an average particle size (AVERAGE PARTICLE size) (also referred to as average particle size (MEAN PARTICLE size)) of 40 to 2000 nanometers (nm) (for the measurement method, see the examples section). Thus, polyurethane-polyurea particles (PPP) constitute a microgel. The reason is that, in one aspect, the polymer particles are in the form of relatively small particles or microparticles, and that, in another aspect, they are at least partially intramolecular crosslinked. The latter means that the polymer structure present in the particles is equivalent to a typical macroscopic network with a three-dimensional network structure. However, macroscopically, microgels of this kind still contain discrete polymer particles.

Since microgels represent structures intermediate between branched and macroscopically crosslinked systems, they combine the features of macromolecules with network structure and insoluble macroscopic networks which are soluble in suitable organic solvents, and thus the fraction of crosslinked polymer can only be determined, for example, after separation of the solid polymer, removal of water and any organic solvents and subsequent extraction. The phenomenon utilized here is such that microgel particles, which are thus initially soluble in a suitable organic solvent, retain their internal network structure after separation and behave like macroscopic networks in solids. Crosslinking can be verified via experimentally available gel fractions. Finally, the gel fraction is the fraction of polymer in the microgel that cannot be dispersed in a solvent as isolated solid molecules. It is necessary here to rule out further increases in gel fraction caused by the crosslinking reaction after isolation of the polymer solids. The insoluble fraction in turn corresponds to the fraction of polymer present in the form of intramolecular cross-linked particles or particle fractions.

The polyurethane-polyurea particles (PPP) preferably have a gel fraction of 50%, preferably at least 60%, more preferably at least 70%, more particularly at least 80%. Thus, the gel fraction may be up to 100% or close to 100%, such as, for example, 99% or 98%. In this case, the entire, or almost the entire, polyurethane-polyurea polymer is then in the form of crosslinked particles.

The polyurethane-polyurea particles (PPP) have an average particle size of 40 to 2000nm, preferably 40 to 1500nm, more preferably 100 to 1000nm, still more preferably 110 to 500nm, more particularly 120 to 300 nm. Particularly preferred ranges are from 130 to 250nm.

The polyurethane-polyurea particles (PPP) comprise in each case in reactive form:

(Z.1.1) at least one polyurethane prepolymer which contains isocyanate groups and contains groups which are anionic groups and/or which can be converted into anionic groups, and also

(Z.1.2) at least one polyamine containing two primary amino groups and one or two secondary amino groups.

The expression "polyurethane-polyurea particles (PPP) here comprise in each case a polyurethane prepolymer (Z.1.1) and a polyamine (Z.1.2) in reactive form" means that the aforementioned NCO-containing polyurethane prepolymer (Z.1.1) and also the polyamine (Z.1.2) are used in the preparation of the polyurethane-polyurea particles (PPP) and these two components react with one another to form urea compounds.

The polyurethane-polyurea particles (PPP) are preferably composed of these two components (z.1.1) and (z.1.2), meaning that they are prepared from these two components. Polyurethane-polyurea particles (PPP) dispersed in water can be obtained, for example, by a specific three-stage process.

In the first step (I) of the process, the composition (Z) is prepared.

Composition (Z) comprises at least one, preferably exactly one specific intermediate (Z.L) containing isocyanate groups and blocked primary amino groups. The preparation of the intermediate (Z.1) comprises reacting at least one polyurethane prepolymer (Z.1.1) containing isocyanate groups and groups which are anionic groups and/or which can be converted into anionic groups with at least one compound (Z.1.2) which is derived from a polyamine (Z.1.2) and contains at least two blocked primary amino groups and at least one free secondary amino group.

For the purposes of the present invention, component (z.1.1) is referred to as prepolymer for ease of understanding.

The prepolymer (z.1.1) contains groups which are anionic groups and/or which can be converted into anionic groups (i.e. groups which can be converted into anionic groups by using known and also neutralizing agents, such as bases, specified later on). As the skilled person knows, these groups are, for example, carboxylic acid groups, sulfonic acid groups and/or phosphonic acid groups, more particularly carboxylic acid groups (functional groups which can be converted into anionic groups by means of neutralizing agents), and also anionic groups derived from the above-mentioned functional groups, such as more particularly carboxylate, sulfonate and/or phosphonate groups, preferably carboxylate groups. It is known to introduce such groups to increase dispersibility in water. Depending on the selected conditions, the groups may be present in one form (e.g., carboxylic acid) or another (carboxylate), either proportionately or almost entirely, for example, by using a neutralizing agent described later herein.

For introducing the groups, during the preparation of the prepolymer (z.1.1), starting compounds may be used which, in addition to the groups (preferably hydroxyl groups) used for the reaction in the preparation of the urethane bonds, further contain the abovementioned groups, for example carboxylic acid groups. In this way, the groups in question are introduced into the prepolymer.

The corresponding compounds envisaged for the introduction of the preferred carboxylic acid groups include-as long as they contain carboxyl groups-polyether polyols and/or polyester polyols. However, preference is given to using low molecular weight compounds which in any case have at least one carboxylic acid group and at least one functional group which is reactive toward isocyanate groups, preferably hydroxyl groups. The expression "low molecular weight compound" in the context of the present invention means that the compound in question has a molecular weight of less than 300 g/mol. A range from 100 to 200g/mol is preferred. Examples of compounds preferred in this sense are, for example, monocarboxylic acids containing two hydroxyl groups, such as dihydroxypropionic acid, dihydroxysuccinic acid and dihydroxybenzoic acid. More particularly, they are α, α -dimethylol alkanoic acids such as 2, 2-dimethylol acetic acid, 2-dimethylol propionic acid, 2-dimethylol butyric acid and 2, 2-dimethylol valeric acid, especially 2, 2-dimethylol propionic acid.

Thus, the prepolymer (Z.1.1) preferably contains carboxylic acid groups. They preferably have an acid number of from 10 to 30mg KOH/g, more particularly from 15 to 23mg KOH/g, based on the solids content (for the measurement methods, see the examples section).

The prepolymer (Z.1.1) is preferably prepared by reaction of a diisocyanate with a polyol. Examples of suitable polyols are saturated or ethylenically unsaturated polyester polyols and/or polyether polyols, as described for example in WO 2018/01311 A1 and WO 2016/091546 A1. Preferably the polyol used to prepare prepolymer (Z.1.1) is a polyester diol prepared using dimer fatty acid. Especially preferred are polyester diols prepared using dicarboxylic acids, wherein at least 50wt. -%, preferably 55wt. -% to 75wt. -% of the dicarboxylic acids used are dimer fatty acids.

Dimer fatty acids are oligomers in the form of unsaturated monomeric fatty acids. Fatty acids are saturated or unsaturated, in particular unbranched monocarboxylic acids having 8 to 64 carbon atoms.

In addition, for the preparation of the polymers (Z.1.1), polyamines, such as diamines and/or amino alcohols, can also be used. Examples of diamines include hydrazine, alkyl diamines or cycloalkyl diamines such as propylene diamine and 1-amino-3-aminomethyl-3, 5-trimethylcyclohexane, and examples of amino alcohols include ethanolamine or diethanolamine.

For polyisocyanates suitable for the preparation of polyurethane prepolymers containing isocyanate groups (Z.1.1), reference is made to the published specifications WO 2018/01311 A1 and WO 2016/091546 A1. Aliphatic diisocyanates such as hexamethylene diisocyanate, isophorone diisocyanate (IPDI), dicyclohexylmethane 4,4' -diisocyanate, 2, 4-or 2, 6-diisocyanato-1-methylcyclohexane and/or m-tetramethylene xylene diisocyanate (m-TMXDI) are preferably used.

The number average molecular weight of the prepolymer can vary widely and is in the range from 2000 to 20 g/mol, preferably from 3500 to 6000g/mol, for example (for measurement methods, see the examples section).

Prepolymer (Z.1.1) contains isocyanate groups. It preferably has an isocyanate content of 0.5 to 6.0wt. -%, preferably 1.0 to 5.0wt. -%, particularly preferably 1.5 to 4.0wt. -%, based on the solids content (for the measurement method, see the examples section).

The hydroxyl number of the prepolymer is preferably less than 15mg KOH/g, more particularly less than 10mg KOH/g, still more preferably less than 5mg KOH/g, based on the solids content (for the measurement method, see the examples section).

The prepolymer (Z.1.1) can be prepared as described in WO 2018/01311 A1 and WO 2016/091546 A1.

As already indicated above, the groups which are present in the prepolymer (z.1.1) and which can be converted into anionic groups can also be present proportionally as anionic groups, for example, by using neutralizing agents. In this way, the water dispersibility of the prepolymer (z.1.1) and thus also of the intermediate (Z.1) can be adjusted. Neutralizing agents contemplated include, in particular, known basic neutralizing agents such as, for example, alkali and alkaline earth metal carbonates, bicarbonates or hydroxides, such as, for example, liOH, naOH, KOH or Ca (OH) ₂. Also suitable for neutralization and preferably used in the context of the present invention are organic nitrogen-containing bases such as amines, like ammonia, trimethylamine, triethylamine, tributylamine, dimethylaniline, triphenylamine, dimethylethanolamine, methyldiethanolamine or triethanolamine, and also mixtures thereof.

If it is desired that the neutralizing groups-in particular carboxylic acid groups-which can be converted to anionic groups, the neutralizing agent can be added, for example, in such an amount that 35% to 65% of the groups are neutralized (degree of neutralization). Preferably from 40% to 60% (for calculation methods, see examples section).

The compound (z.1.2 a) comprises two blocked primary amino groups and one or two free secondary amino groups.

Blocked amino groups as known are those in which a hydrogen group inherently present on the nitrogen in the free amino group has been substituted by a reversible reaction with a blocking agent. In view of the end-capping, the amino group cannot react via a condensation or addition reaction like the free amino group and is therefore non-reactive in this respect and thus differs from the free amino group. The primary amino groups of the compounds (Z.1.2 a) can be blocked with blocking agents known per se, such as, for example, with ketones and/or aldehydes. In the case of such capping, ketimines and/or aldimines are produced and water is released. Groups of this kind can be unblocked by the addition of water.

If an amino group is not designated as either blocked or free, then the free amino group is mentioned.

Preferred blocking agents for blocking the primary amino groups of the compounds (Z.1.2 a) are ketones. Particularly preferred among these ketones are those as an organic solvent (Z.2) as described later. The reason is that the solvent (Z.2) must in any case be present in the composition (Z) to be prepared in stage (I) of the process. Thus, by using a ketone (Z.2) for capping, the corresponding preferred production process for capping an amine can be employed without having to isolate the potentially undesirable capping agent in a costly and inconvenient manner. Instead, a solution of the blocked amine can be used directly to prepare intermediate (Z.1). Preferred end-capping agents are acetone, methyl ethyl ketone, methyl isobutyl ketone, diisopropyl ketone, cyclopentanone or cyclohexanone, with particular preference being given to the ketones (Z.2) methyl ethyl ketone and methyl isobutyl ketone.

Preferred end-capping with ketones and/or aldehydes, in particular ketones, and the associated preparation of ketimines and/or aldimines, have the advantage that, in addition, primary amino groups are optionally end-capped. The secondary amino groups present are obviously not blocked and therefore remain free. Thus, by means of the preferred capping reactions described for the corresponding polyamines (Z.1.2) containing free secondary and primary amino groups, compounds (Z.1.2 a) containing one or two free secondary amino groups in addition to the two capped primary amino groups can be readily prepared.

The compound (z.1.2 a) preferably has two blocked primary amino groups and one or two free secondary amino groups, and has only blocked primary amino groups and only free secondary amino groups as secondary amino groups.

The compound (z.1.2 a) preferably has a total of three or four amino groups selected from the group of blocked primary amino groups and free secondary amino groups.

Particularly preferred compounds (Z.1.2 a) are those which consist of two blocked primary amino groups, one or two free secondary amino groups and also aliphatic saturated hydrocarbon groups.

Similar preferred embodiments are valid for polyamines (z.1.2) which contain free primary amino groups instead of blocked primary amino groups. Examples of preferred polyamines (Z.1.2) of the compounds (Z.1.2 a) which can also be prepared by capping primary amino groups are diethylenetriamine, 3- (2-aminoethyl) aminopropylamine, dipropylenetriamine, and also N1- (2- (4- (2-aminoethyl) piperazin-1-yl) ethyl) -ethane-1, 2-diamine (one secondary amino group, two primary amino groups to be capped) and triethylenetetramine, and also N, N' -bis (3-aminopropyl) ethylenediamine (two secondary amino groups, two primary amino groups to be capped).

If a certain amount of polyamine is blocked, the blocking may result in, for example, a fraction of 95mol% or more of primary amino groups being blocked (the fraction may be determined by IR spectroscopy; see the examples section). For example, in the case of a polyamine in the unblocked state having two free primary amino groups, and then in the case of an amount of primary amino groups of the amine being blocked, in the context of the present invention, it is said that if more than 95 mole% of the fraction of primary amino groups present in the amount employed are blocked, the amine has two blocked primary amino groups.

The preparation of intermediate (Z.1) involves reacting prepolymer (z.1.1) with compound (z.1.2 a) by addition reaction of isocyanate groups from (z.1.1) with free secondary amino groups from (z.1.2 a). This reaction, which is known per se, then leads to the attachment of the compound (z.1.2 a) to the prepolymer (z.1.1) to form urea linkages, ultimately yielding intermediate (Z.1).

Intermediate (Z.1) may be prepared as described in WO 2018/01311 A1 and WO 2016/091546 A1.

The fraction of intermediate (Z.1) is from 15 to 65wt. -%, preferably from 25 to 60wt. -%, more preferably from 30 to 55wt. -%, especially preferably from 35 to 52.5wt. -% and in a very specific embodiment from 40 to 50wt. -%, in each case based on the total amount of composition (Z).

The composition (Z) further comprises at least one specific organic solvent (Z.2). At a temperature of 20 ℃, the solvent (Z.2) has a solubility in water of at most 38wt. -% (for the measurement method, see examples section). The solubility in water at a temperature of 20 ℃ is preferably less than 30wt. -%. The preferred range is from 1 to 30wt. -%. Thus, the solvent (Z.2) has a fairly moderate solubility in water, and more particularly is not fully miscible with water, or has an infinite solubility in water.

Examples of solvents (Z.2) are methyl ethyl ketone, methyl isobutyl ketone, diisobutyl ketone, diethyl ether, butyl ether, dipropylene glycol dimethyl ether, ethylene glycol diethyl ether, toluene, methyl acetate, ethyl acetate, butyl acetate, propylene carbonate, cyclohexanone, or mixtures of these solvents. Preferred is methyl ethyl ketone, which has a solubility of 24wt. -% in water at 20 ℃. Therefore, no solvent (Z.2) is a solvent such as acetone, N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, tetrahydrofuran, dioxane, N-formyl morpholine, dimethylformamide or dimethyl sulfoxide.

The effect of selecting a specific solvent (Z.2) having only limited water solubility is in particular that when the composition (Z) is dispersed in an aqueous phase, which occurs in step (II) of the process, it is not possible to directly form a homogeneous solution, whereas the crosslinking reaction (addition reaction of free primary amino groups and isocyanate groups to form urea bonds) occurring in step (II) proceeds in a limited volume, thus enabling the formation of microparticles as defined above.

The fraction of the at least one organic solvent (Z.2) is from 35 to 85wt. -%, preferably from 40 to 75wt. -%, more preferably from 45 to 70wt. -%, especially preferably from 47.5 to 65wt. -% and in a very specific embodiment from 50 to 60wt. -%, in each case based on the total amount of the composition (Z).

In the present invention, it has emerged that, for the result of the combination of the choice of intermediate (Z.1) and of the specific solvent (Z.2) in composition (Z) as specified above, a polyurethane-polyurea dispersion comprising polyurethane-polyurea particles (PPP) having the desired particle size and gel fraction can be provided according to steps (II) and (III) described below.

The components (Z.1) and (Z.2) described preferably together represent at least 90wt. -% of the composition (Z). The two components preferably constitute at least 95wt. -%, more particularly at least 97.5wt. -% of the composition (Z). Very particularly preferably, the composition (Z) consists of these two components. In this context, it can be noted that in the case of using neutralizing agents as described above, these neutralizing agents are contained in the intermediate when the amount of intermediate (Z.1) is calculated. Thus, the solids content of composition (Z) preferably corresponds to the fraction of intermediate (Z.1) in composition (Z). Thus, the composition (Z) preferably has a solids content of 15 to 65wt. -%, preferably 25 to 60wt. -%, more preferably 30 to 55wt. -%, especially preferably 35 to 52.5wt. -% and in a very specific embodiment from 40 to 50wt. -%.

Thus, particularly preferred compositions (Z) comprise in total at least 90wt. -% of components (Z.1) and (Z.2) and comprise only organic solvents apart from intermediate (Z.1).

In step (II) of the process described herein, composition (Z) is then dispersed in water, which reaction is an addition reaction, accompanied by deblocking of the blocked primary amino groups of intermediate (Z.1) and reaction of the resulting free primary amino groups with the isocyanate groups of intermediate (Z.1) and also with the deblocked intermediate produced from intermediate (Z.1).

Step (II) of the process of the present invention may be carried out as described in WO 2018/01311 A1 and WO 2016/091546 A1.

The fraction of polyurethane-polyurea particles (PPP) in the dispersion is preferably 25 to 55wt. -%, preferably 30 to 50wt. -%, more preferably 35 to 45wt. -%, in each case based on the total amount of the dispersion (similar to that determined via the solids content determination as described above for intermediate (Z.1)).

The polyurethane-polyurea particles (PPP) preferably have an acid number of from 10 to 35mg KOH/g, more particularly from 15 to 23mg KOH/g (for the measurement methods, see the examples section). Furthermore, the polyurethane-polyurea particles have very little or no hydroxyl groups. Thus, the OH number of the particles is less than 15mg KOH/g, more particularly less than 10mg KOH/g, more preferably less than 5mg KOH/g (for measurement methods, see examples section).

The anionically stabilized polyurethane-polyurea particles (PPP) dispersed in water preferably have an electrophoretic mobility of-6 to-8 (μm/s)/(V/cm) at a pH of 8.0.

Furthermore, the coating composition may comprise anionically stabilized polyurethane-polyurea particles (PPP) in a total amount of 10 to 50wt. -%, preferably 20 to 45wt. -%, more particularly 23 to 40wt. -%, in each case based on the total solids content of the coating composition. The use of anionically stabilized polyurethane-polyurea particles (PPP) in combination with at least one non-polymeric polycarboxylic acid in the total amounts described above results in a high flop index. Furthermore, the use of this binder leads to an effective fixation of the effect particles EP oriented during flashing of the coating composition according to the invention and thus does not negatively affect the high flop index even when applying a layer of a further coating composition.

Other anionically stabilized polymers (asP)

According to the invention, it may be advantageous to use an anionically stabilized polymer (asP) as anionically stabilized polymer binder in addition to or instead of the anionically stabilized polyurethane-polyurea particles (PPP) described above.

Particularly preferably, the composition of the invention comprises at least two anionic stable polymeric binders which are different from each other, wherein the first anionic stable polymeric binder is the above-mentioned anionic stable polyurethane-polyurea particles (PPP) and the second anionic stable polymeric binder is the below-described anionic stable polymer (asP).

In the context of the present invention, it has therefore proved to be advantageous if the at least one anionically stabilized polymer binder is an anionically stabilized seed-core-shell polymer (asP) dispersed in water. Thus, it is particularly preferred according to the invention that the preparation of the anionically stabilized polymer (asP) comprises a continuous free radical emulsion polymerization of three mixtures (A), (B) and (C) of ethylenically unsaturated monomers, if the at least one anionically stabilized polymer binder comprises at least one anionically stabilized polymer (asP) which is dispersed in water and has an average particle size of from 100 to 500nm, where

O mixture (a) comprises at least 50wt. -% of a vinylaromatic monomer and the polymer prepared from mixture (a) has a glass transition temperature of from 10 to 65 ℃,

O mixture (B) comprises at least one polyunsaturated monomer and the polymers prepared from mixture (B) have a glass transition temperature of from-35 ℃ to 15 ℃, and

O mixture (C) comprises at least one anionic monomer and the polymer prepared from mixture (C) has a glass transition temperature of from-50 ℃ to 15 ℃,

And wherein

I. the mixture (A) is first polymerized,

Then polymerizing the mixture (B) in the presence of the polymer prepared according to i, and

Thereafter polymerizing the mixture (C) in the presence of the polymer prepared according to ii.

The glass transition temperature is determined as detailed in the examples section.

An anionically stabilized polymer (asP) is dispersed in water. Thus, the anionically stabilized polymer (asP) is in the form of an aqueous dispersion. In this context, the expression "dispersed in water or aqueous dispersion" is known to the skilled person. It is meant primarily a system whose dispersion medium contains not only or predominantly organic solvents (also referred to as solvents) but also a significant fraction of water. The aqueous dispersion preferably comprises a water fraction of 55 to 75wt. -%, particularly preferably 60 to 70wt. -%, in each case based on the total weight of the dispersion.

Preferably, exactly one of the above polymers (asP) is dispersed in water. The preparation of anionically stabilized polymers (asP) involves the continuous free radical emulsion polymerization of three mixtures (A), (B) and (C) of ethylenically unsaturated monomers using water-soluble initiators, as described, for example, in WO 2017/088988 A1.

The separate polymerization stages in the preparation of the anionically stabilized polymers (asP) may be carried out, for example, in so-called "starved feed" polymerization (also referred to as "starved feed (STARVE FEED)" or "starved feed (STARVE FED)" polymerization). Starved feed polymerization in the sense of the present invention is emulsion polymerization in which the amount of free ethylenically unsaturated monomer in the reaction solution (also referred to as reaction mixture) is minimized over the entire reaction time. This means that the ethylenically unsaturated monomers are metered in such a way that the fraction of free monomers in the reaction solution does not exceed 6.0wt. -%, preferably 5.0wt. -%, more preferably 4.0wt. -%, particularly advantageously 3.5wt. -%, based in each case on the total amount of monomers used in the respective polymerization stage, over the entire reaction time.

The concentration of the monomers in the reaction solution may here be determined by gas chromatography, for example as described in publication WO 2017/088988 A1. The fraction of free monomer can be controlled by the initiator amount, initiator addition rate, interaction of the monomer addition rates, and by the choice of monomer. Not only does the metering slow down, but also increases the initial amount, and also prematurely begins to add initiator, helps to maintain the free monomer concentration below the above-noted limit.

For the purposes of the present invention, it is preferred to carry out polymerization stages ii.and iii.under starved feed conditions. This has the advantage that the formation of new particle nuclei in both polymerization stages is effectively minimized. Conversely, particles (and thus also referred to below as seeds) present after stage i. can be further grown in stage ii. by polymerization of the monomer mixture B (and thus also referred to below as nuclei). It is also possible that the particles present after stage ii. (also referred to below as seed and core containing polymer) are further grown in stage iii. by polymerization of monomer mixture C (hence also referred to below as shell), ultimately producing a polymer containing seed, core and shell containing particles. Stage i. of course, can also be carried out under starved feed conditions.

The mixtures (A), (B) and (C) are mixtures of ethylenically unsaturated monomers, and the mixtures (A), (B) and (C) are different from one another. Thus, they each contain different monomers and/or different proportions of at least one defined monomer. The fractions of the monomer mixture are preferably matched to one another as follows. The fraction of mixture (a) is from 0.1 to 10wt. -%, the fraction of mixture (B) is from 60 to 80wt. -% and the fraction of mixture (C) is from 10 to 30wt. -%, in each case based on the sum of the individual amounts of mixtures (a), (B) and (C).

Mixture (a) comprises at least 50wt. -%, in particular at least 55wt. -% of vinylaromatic compounds. One such preferred monomer is styrene. The mixture (A) is free of monomers having functional groups containing heteroatoms, other than vinylaromatic compounds. It is particularly preferred that the monomer mixture (A) comprises at least one monounsaturated ester of (meth) acrylic acid having an alkyl group and at least one monoethylenically unsaturated monomer containing a vinyl group, wherein the groups arranged on the vinyl group are aromatic or mixed saturated aliphatic-aromatic groups, in which case the aliphatic portion of the group is an alkyl group.

The monomers present in the mixture (a) are selected such that the polymers prepared therefrom have a glass transition temperature of from 10 ℃ to 65 ℃, preferably from 30 ℃ to 50 ℃. For a usable estimate of the glass transition temperature expected in the measurement, the Fox equation (Fox equation) known to the skilled person may be used.

The polymer prepared by emulsion polymerization of the monomer mixture (a) in stage i. Preferably has a particle size of 20 to 125nm (for particle size measurements, see examples section).

The mixture (B) comprises at least one polyethylenically unsaturated monomer, preferably at least one dienically unsaturated monomer, in particular exclusively dienically unsaturated monomers. One such preferred monomer is 1, 6-hexanediol diacrylate. Preferably, the monomer mixture (B) likewise contains no monomers having heteroatom-containing functional groups. It is particularly preferred that the monomer mixture (B) comprises, in addition to at least one polyethylenically unsaturated monomer, at least the following further monomers. First, at least one monounsaturated ester of (meth) acrylic acid having an alkyl group, and next to that at least one monoethylenically unsaturated monomer containing a vinyl group, wherein the groups arranged on the vinyl group are aromatic or mixed saturated aliphatic-aromatic groups, in which case the aliphatic portion of the group is an alkyl group.

The fraction of polyunsaturated monomers is preferably from 0.05mol% to 3mol%, based on the total molar amount of monomers in the monomer mixture (B).

The monomer mixtures (A) and (B) are preferably free of hydroxy-functional monomers and free of acid-functional monomers. Thus, the monomer mixtures (a) and (B) contain 0wt. -% of hydroxy-functional monomers and acid-functional monomers, based on the sum of the individual amounts of the mixtures (a), (B) and (C).

The monomers present in the mixture (B) are selected such that the polymers prepared therefrom have a glass transition temperature of from-35℃to 15℃and preferably from-25℃to +7℃.

The polymer obtained after stage ii. Preferably has a particle size of 80 to 280nm, preferably 120 to 250 nm.

The monomers present in the mixture (C) are selected such that the polymers prepared therefrom have a glass transition temperature of from-50℃to 15℃and preferably from-20℃to +12℃.

The ethylenically unsaturated monomers of the mixture (C) are preferably selected such that the resulting polymer comprising seed, core and shell has an acid number of from 10 to 25. Thus, the mixture (C) preferably comprises at least one alpha, beta-unsaturated carboxylic acid, in particular (meth) acrylic acid.

It is further preferred to select the ethylenically unsaturated monomers of mixture (C) such that the resulting polymer comprising seed, core and shell has an OH number of 0 to 30, preferably 10 to 25. All of the above acid numbers and OH numbers are calculated based on the monomer mixture used as a whole.

Particularly preferably, the monomer mixture (C) comprises at least one alpha, beta-unsaturated carboxylic acid, at least one monounsaturated ester of (meth) acrylic acid having an alkyl group substituted by a hydroxyl group, and at least one monounsaturated ester of (meth) acrylic acid having an alkyl group.

It is particularly preferred that neither the monomer mixture (A) nor the monomer mixture (B) or (C) comprise polyurethane polymers having at least one polymerizable double bond.

After its preparation, the anionically stabilized polymer (asP) has an average particle size of from 100 to 500nm, preferably from 125 to 400nm, very preferably from 130 to 300nm, and also has a glass transition temperature T _g of from-20 ℃ to-5 ℃.

The aqueous dispersion of the anionically stabilized polymer (asP) preferably has a pH of 5.0 to 9.0, more preferably 7.0 to 8.5, very preferably 7.5 to 8.5.

For example, the pH may be kept constant during the preparation by using a base as further identified below, or alternatively may be deliberately set after the preparation of the anionically stabilized polymer (asP). The described stages i.to iii. Are preferably carried out without addition of acids or bases known for setting the pH and the pH is set only after the preparation of the polymer by addition of organic nitrogen-containing bases, sodium hydrogencarbonate, borates and also mixtures of the abovementioned substances.

The solids content of the aqueous dispersion of the anionically stabilized polymer (asP) is preferably from 15% to 40% and more preferably from 20% to 30%.

The anionically stabilized polymers (asP) used in particular in the context of the present invention are preparable by reacting:

50 to 85wt. -% of a mixture (A) of vinylaromatic monomers and 15 to 50wt. -% of monounsaturated esters of (meth) acrylic acid having alkyl groups,

O 1 to 4wt. -% of a polyethylenically unsaturated monomer, 60 to 80wt. -% of a mixture (B) of a monounsaturated ester of (meth) acrylic acid having an alkyl group and 16 to 39wt. -% of a vinyl aromatic monomer, and

O 8 to 15wt. -% of an alpha-beta unsaturated carboxylic acid, 10 to 20wt. -% of a mixture (C) of a monounsaturated ester of (meth) acrylic acid having an alkyl group substituted by a hydroxyl group and 65 to 82wt. -% of a monounsaturated ester of (meth) acrylic acid having an alkyl group,

Wherein the method comprises the steps of

I. the mixture (A) is first polymerized,

Then polymerizing the mixture (B) in the presence of the polymer prepared according to i, and

Thereafter polymerizing the mixture (C) in the presence of the polymer prepared according to ii.

The numbers above (in wt. -%) are in each case based on the total weight of the mixture (a) or (B) or (C), respectively.

An anionically stabilized polymer (asP) dispersed in water, in other words an aqueous dispersion of the polymer (asP), advantageously has a defined electrophoretic mobility. Thus, it is preferred according to the invention that the anionically stabilized polymer (asP) dispersed in water has an electrophoretic mobility of-2.5 to-4 (μm/s)/(V/cm) at a pH of 8.0.

Furthermore, the coating composition may comprise the anionically stabilized polymer (asP) in a total amount of 1 to 30wt. -%, preferably 5 to 20wt. -%, more particularly 5 to 10wt. -%, in each case based on the total solids content of the coating composition. The use of anionically stabilized polymers (asP) in the total amounts described above in combination with at least one non-polymeric polycarboxylic acid results in a high flop index. Furthermore, the use of binders leads to an effective fixation of the effect particles EP oriented during the flashing of the coating composition according to the invention, so that even when a layer of a further coating composition is applied, a high flop index is not adversely affected.

As an anionically stabilized polymer binder, the coating composition of the invention may comprise at least one of the above anionically stabilized polymers (asP) or the above anionically stabilized polyurethane-polyurea particles (PPP). Preferably, the coating composition comprises at least one of the above described anionically stabilized polymers (asP) as an anionically stabilized polymer binder and also the above described anionically stabilized polyurethane-polyurea particles (PPP). It is particularly preferred that these polymers are present in the composition in a certain weight ratio. Thus, it is advantageous according to the invention if the aqueous coating composition has a weight ratio of anionically stabilized polymer (asP) to anionically stabilized polyurethane-polyurea particles (PPP) of from 1:10 to 1:1, more particularly from 1:6 to 1:4.

Additional polymeric binders

In addition to the at least one anionically stabilized polymeric binder, the coating composition of the present invention may comprise at least one additional binder, more particularly at least one polymer selected from the group consisting of polyurethanes, polyesters, polyacrylates and/or copolymers of said polymers, more particularly polyesters and/or polyurethane polyacrylates.

The additional binder is different from the anionically stabilized polymer binders (PPP) and (asP). Preferred polyesters are described, for example, in DE 4009858 A1, column 6, line 53 to column 7, line 61 and column 10, line 24 to column 13, line 3, and in WO 2014/033135 A1, page 28, lines 13 to 33. The polymers described as binders are preferably hydroxy-functional and particularly preferably have an OH number in the range from 20 to 200mg KOH/g, more preferably from 50 to 150mg KOH/g. More preferably at least two mutually different hydroxy-functional polyesters are used as further binders.

The total amount of all polymer binders is preferably from 9 to 60wt. -%, more preferably from 20 to 50wt. -% and most preferably from 30 to 45wt. -%, based on the total weight of the aqueous coating material of the present invention.

Cellulose nanofibers

In the literature, the term "cellulose nanofibers" may also be referred to as "cellulose nanofibrils", "fibrillated cellulose" or "nanocellulose crystals", all of which are in the form of fibers. The term "cellulose nanofibers" is a generic term that encompasses natural as well as functionalized cellulose nanofibers, such as carboxylated or vulcanized or otherwise modified and/or surface functionalized cellulose nanofibers. However, the backbone carrying such groups is always cellulose.

Of course, cellulose derivatives that are not fibrous in shape do not fall under the term "cellulose nanofibers". In particular, hydroxyalkyl cellulose, for example dissolved in an aqueous medium, is not covered under the term "cellulose nanofiber" as used herein. Since these water-compatible cellulose types are completely dissolved in water, they do exhibit different (molecular) dimensions and thus do show completely different rheological behaviour, suitable for wallpaper pastes and the like (A.Goldschmidt, H.J.Streitberger, BASF Handbook on Basics of Coatings Technology [ Basf paint technical foundation handbook ],2003, wenson company (Vincent z Network), pages 47-49).

The cellulose nanofibers preferably have a number average fiber diameter in the range of preferably 2 to 800nm, more preferably 2 to 500nm, even more preferably 2 to 250nm and most preferably 2 to 150 nm.

The cellulose nanofibers preferably have a number average fiber length in the range of preferably 0.04 to 20 μm, more preferably 0.04 to 15 μm, even more preferably 0.04 to 10 μm.

The aspect ratio determined by dividing the number average fiber length by the number average fiber diameter is preferably in the range of preferably 20 to 10000, more preferably 20 to 5000, and even more preferably 20 to 1000.

Numerical averages of fiber length, diameter, and aspect ratio of cellulose nanofibers are determined as specified in the experimental section of the present invention.

The cellulose nanofibers for use may be those obtained by defibrating a cellulose material and stabilizing it in water. As used herein, cellulosic material refers to cellulosic primary material in various forms. Specific examples include pulp (e.g., grass-derived pulp such as wood pulp, jute, abaca, and kenaf), natural cellulose such as cellulose produced by microorganisms, regenerated cellulose obtained by dissolving cellulose in a cuprammonium solution, a solvent for morpholine derivatives, or the like and subjecting the dissolved cellulose to spinning, and fine cellulose obtained by subjecting a cellulose material to mechanical treatment such as hydrolysis, alkaline hydrolysis, enzymatic decomposition, jet treatment, vibration ball milling, or the like to depolymerize the cellulose.

The method for defibrating the cellulose material is not particularly limited as long as the cellulose material remains in a fibrous form. Examples of the method include mechanical defibration treatment using a homogenizer, a grinder, or the like, chemical treatment using an oxidation catalyst, or the like, and biological treatment using a microorganism, or the like.

For cellulose nanofibers, anionically modified cellulose nanofibers can be and are preferably used. Examples of anionically modified cellulose nanofibers include carboxylated cellulose nanofibers, carboxymethylated cellulose nanofibers, sulfated cellulose nanofibers, and the like. Anionically modified cellulose nanofibers can be obtained, for example, by introducing functional groups such as carboxyl groups and carboxymethyl groups into a cellulose material by known methods, washing the resulting modified cellulose to produce a dispersion of modified cellulose, and defibrating the dispersion. Carboxylated cellulose is also known as "oxidized cellulose".

For example, oxidized cellulose is obtained by oxidizing a cellulose material in water using an oxidizing agent in the presence of a compound selected from the group consisting of N-oxy compounds, bromides, iodides, and mixtures thereof.

The amount of the N-oxy compound is not particularly limited as long as the amount is a catalytic amount that can disintegrate cellulose into nanofibers.

The amount of bromide or iodide may be appropriately selected within a range that promotes the oxidation reaction.

As the oxidizing agent, a known oxidizing agent can be used. Examples include halogens, hypohalous acids, halous acids, perhalous acids, salts thereof, halogen oxides, peroxides, and the like. It is preferable to set the conditions such that the amount of carboxyl groups in the oxidized cellulose is 0.2mmol/g or more by mass based on the solid content of the oxidized cellulose. For example, the amount of carboxyl groups can be adjusted by adjusting the oxidation reaction time, adjusting the oxidation reaction temperature, adjusting the pH in the oxidation reaction, and adjusting the amount of N-oxyl compounds, bromides, iodides, oxidizing agents, and the like.

Carboxymethylated cellulose can be obtained by mixing a cellulose material and a solvent, mercerizing using 0.5 to 20 times moles of an alkali metal hydroxide per glucose residue of the cellulose material as a mercerizing agent at a reaction temperature of 0 to 70 ℃ for a reaction time of about 15 minutes to 8 hours, and then adding thereto 0.05 to 10.0 times moles of a carboxymethylating agent per glucose residue, followed by a reaction at a reaction temperature of 30 to 90 ℃ for a reaction time of about 30 minutes to 10 hours.

The degree of carboxymethyl substitution per glucose unit in the modified cellulose obtained by introducing carboxymethyl groups into the cellulose material is preferably 0.02 to 0.50.

The thus obtained anionically modified cellulose may be dispersed in an aqueous solvent to form a dispersion, and then defibrated with a pulverizer. The defibration method is not particularly limited. In performing mechanical defibration, the pulverizer for use may be any one of a high-speed shearing pulverizer, a collision machine pulverizer, a bead mill pulverizer, a high-speed rotary pulverizer, a colloid mill pulverizer, a high-pressure pulverizer, a roller mill pulverizer, and an ultrasonic pulverizer. These pulverizers may be used in combination of two or more.

In addition, cellulose obtained by neutralizing the above oxidized cellulose with an alkaline neutralizing agent can also be suitably used as a cellulose-based rheology control agent. Neutralization using such neutralizing agents improves the water-resistant adhesion of rheology control agents, including cellulose nanofibers. The neutralizing agent for oxidized cellulose used in this specification is a neutralizing agent of an organic base larger than an inorganic metal salt group such as sodium hydroxide. Preferred examples of the neutralizing agent include organic bases such as quaternary ammonium salts and amines (primary, secondary and tertiary amines). Preferred quaternary ammonium salts are quaternary ammonium bases. Examples of amines include alkyl amines and alcohol amines. Examples of alkylamines include N-butylamine, N-octylamine, dibutylamine, triethylamine, and the like. Examples of the alcohol amine include N-butylethanolamine, N-methylethanolamine, 2-amino-2-methyl-1-propanol, dimethylethanolamine, dibutylethanolamine, methyldiethanolamine, and the like.

The content of the neutralizing agent is not particularly limited as long as a part or all of the oxidized cellulose can be neutralized. However, the content of the neutralizing agent is preferably 0.2 to 1.0 equivalent in terms of neutralizing equivalent based on the acid groups contained.

The content of cellulose nanofibers is preferably in the range of 0.05 to 1.5wt. -%, more preferably 0.06 to 1.0wt. -%, and most preferably 0.07 to 0.7wt. -%, based on the total weight of the aqueous coating material of the present invention.

Examples of commercial products of cellulose nanofibers include Rheocrysta (registered trademark, manufactured by first industry pharmaceutical co. (Dai-Ichi Kogyo Seiyaku co., ltd.)), cebina Fine (length 0.5 to 10 μm, diameter 15 to 100 nm), celluforce NCV100 (length 44 to 108nm, diameter 2.3 to 4.5 nm).

Non-polymeric polycarboxylic acids

The aqueous coating material of the present invention contains at least one non-polymeric polycarboxylic acid or salt thereof, preferably at least one monomeric polycarboxylic acid or salt thereof, even more preferably at least one monomeric dicarboxylic acid or salt thereof.

According to the present invention, the term "polycarboxylic acid" refers to an aliphatic or aromatic carboxylic acid having at least two carboxylic acid groups per molecule, such as 2 to 4, more preferably 2 or 3 and most preferably 2 carboxylic acid groups. These carboxylic acid groups may be converted, in whole or in part, to anionic groups by neutralizing agents.

The at least one non-polymeric polycarboxylic acid preferably has a melting point of 80 ℃ to 165 ℃, more preferably 85 ℃ to 150 ℃, preferably 90 ℃ to 140 ℃, more particularly 95 ℃ to 120 ℃.

The at least one non-polymeric polycarboxylic acid is most preferably a dicarboxylic acid. Dicarboxylic acids according to the invention are compounds having exactly two carboxylic acid groups per molecule.

In this context, it is particularly preferred that the dicarboxylic acids have the general formula (I)

M^+-OOC-R¹-COO^-M⁺(I)

Wherein the method comprises the steps of

Two M ⁺ are each independently of the other a monovalent cation, preferably selected from the group consisting of H ⁺, an alkali metal cation such as Na ⁺、K⁺, an ammonium ion NH ₄ ⁺ and a cation of the formula N (R ²)₄ ⁺, wherein the residues R ² are each independently of the other H, an alkyl residue and a hydroxyalkyl residue, the alkyl residue preferably comprising 1 to 6, more preferably 1 to 4, even more preferably 1 to 3 and most preferably 1 or 2, in particular 1 carbon atom, and the hydroxyalkyl residue preferably comprising 2 to 6, more preferably 2 to 4, even more preferably 2 to 3 and most preferably 2 carbon atoms, and

R ¹ is absent (i.e., M ^+-OOC-COO^-M⁺) or is a divalent residue of a saturated or unsaturated, aliphatic or aromatic, straight chain, branched or cyclic hydrocarbon, the residue R ¹ preferably contains from 1 to 72, preferably from 2 to 40, more preferably from 3 to 30, even more preferably from 3 to 18, more particularly 4 to 9, such as 4, 5, 6, 7 or 8 carbon atoms.

Where R ¹ contains more than 20, or even more than 30 carbon atoms, the residue R ¹ is preferably a residue of a dimer fatty acid, dimers and trimers not being considered polymers herein. Such groups optionally and preferably comprise one or more carbon-carbon double bonds and/or cyclic, in particular alicyclic, hydrocarbon groups.

Preferred monovalent cations M ⁺ are, for example, cations of the formula (CH ₃)₂ (alkyl-OH) NH ⁺, such as protonated dimethylethanolamine.

The use of the abovementioned dicarboxylic acids, in particular azelaic acid, in combination with other mandatory ingredients, and in the case of effect pigments contained in aqueous coating materials, is particularly advantageous for obtaining high flop indexes without causing a reduction in the storage stability of the aqueous coating material parts or adversely affecting the optical and tinting properties of the coatings produced from these compositions.

Polycarboxylic acids as used according to the invention are commercially available, for example, from Merck company (Merck).

The at least one non-polymeric polycarboxylic acid is preferably used in a specific total amount. It is therefore particularly preferred according to the invention that the aqueous coating material comprises at least one non-polymeric polycarboxylic acid, more particularly a dicarboxylic acid of formula (I), in a total amount of 0.05 to 5wt. -%, preferably 0.10 to 4wt. -%, more preferably 0.20 to 3wt. -%, more particularly 0.25 to 1wt. -%, in each case based on the total weight of the coating material.

Pigment

Preferably, the aqueous coating material of the present invention further comprises one or more pigments selected from the group consisting of colored pigments and effect pigments.

Colored pigments

Colored pigments are known to the person skilled in the art and are described, for example, in Rompp-Lexikon Lacke and Druckfarben, georg THIEME VERLAG, stuttgart, new York, 1998, pages 176 and 451. The terms "color pigment" and "color pigment" are interchangeable.

Suitable colored pigments may be inorganic or organic pigments and are preferably selected from the group consisting of (i) white pigments such as titanium dioxide, zinc white, zinc sulfide or lithopone, (ii) black pigments such as carbon black, iron manganese black or spinel black, (iii) colored pigments such as ultramarine green, ultramarine blue, manganese blue, ultramarine violet, manganese violet, iron oxide red, molybdenum red, ultramarine red, iron oxide brown, mixed brown, spinel phases and corundum phases, iron oxide yellow, bismuth vanadate, (iv) organic pigments such as monoazo pigments, bisazo pigments, anthraquinone pigments, benzimidazole pigments, quinacridone pigments, quinophthalone pigments, diketopyrrolopyrrole pigments, dioxazine pigments, indanthrone pigments, isoindoline pigments, azomethine pigments, thioindigo pigments, metal complex pigments, pyrenone pigments, perylene pigments, phthalocyanine pigments, aniline black, and (v) mixtures thereof.

The one or more colored pigments are preferably used in a specific total amount. Thus, in a preferred embodiment of the first subject matter of the present invention, the aqueous coating composition preferably comprises the colored pigment CP in a total amount of 1wt.% to 40wt.%, preferably 2wt.% to 35wt.%, more preferably 5wt.% to 30wt.%, in each case based on the total weight of the coating composition.

Effect pigments EP

The one or more effect pigments EP are preferably selected from the group consisting of lamellar aluminium pigments, aluminium pigments in the form of "cornflakes" and/or "silver elements", aluminium pigments coated with organic pigments (for example under the trade name "Friend"Commercially available from Toyo aluminum products Co., ltd (Toyal)), glass sheets (e.g., under the trade name") "Commercially available from Eckart"), interference layer coated glass flakes, gold bronze, oxidized bronze, iron oxide-aluminum pigments, pearlescent pigments, metal oxide-mica pigments, layered graphite, flake iron oxide, multilayer effect pigments composed of PVD films, and mixtures thereof, more particularly layered aluminum pigments.

In this context, it has proved to be particularly advantageous if passivated lamellar aluminum pigments are used. Thus, the aqueous coating material portion of the present invention can be ensured to have high storage stability. Thus, the layered aluminium pigment is preferably treated with a passivating agent selected from the group consisting of silanes, organic polymers, chromium compounds, phosphoric acid derivatives, molybdenum derivatives and mixtures thereof, in particular chromium compounds. Derivatives in this context are compounds in which an H atom or functional group has been replaced by another atom or another atom group, and/or in which one or more atoms/atom groups have been removed.

Furthermore, in this context, it has proved to be advantageous if the layered aluminum pigments have a defined platelet thickness and average particle size. The layered aluminium pigments preferably have a platelet thickness of 200 to 500nm and an average particle size D ₅₀ of 10 to 25 μm, more particularly 10 to 20 μm (for the measurement method, see the examples section).

The effect pigment or pigments are preferably used in a specific total amount. Preferably, the aqueous coating material comprises at least one effect pigment EP, more particularly a layered aluminium pigment, in a total amount of 1 to 20wt. -%, preferably 2 to 15wt. -%, more preferably 2.5 to 10wt. -%, more particularly 3 to 7wt. -%, in each case based on the total weight of the coating material. The use of effect pigments, in particular the above-mentioned layered aluminium pigments, in combination with at least one polymeric binder, preferably at least one anionically stabilized polymeric binder and also at least one non-polymeric polycarboxylic acid and at least one cellulosic nanofibrous material in the total amounts mentioned results in particularly high flop indices, but is not detrimental to the other optical and colouring properties of the coating.

Packing material

The aqueous coating material of the present invention preferably contains one or more fillers. The distinction between fillers and pigments in the present invention is not critical. To distinguish between the two, it is typically referenced to the refractive index. If the refractive index is ≡ 1.7, the substance is considered to be a pigment, and if the refractive index is <1.7, the substance is considered to be a filler. The filler is preferably selected from the group consisting of carbonates, silicates such as talc, silica such as precipitated or fumed silica and sulfates such as barium sulfate.

Additional components

In addition to the mandatory polymeric binder PB, cellulose nanofibers CF and non-polymeric polycarboxylic acids described above, the aqueous coating material of the present invention may contain one or more further components such as neutralizing agents, thickeners, crosslinking agents and solvents, but also other additives such as leveling agents, dispersants, wetting agents, defoamers or catalysts.

Neutralizing agent

The neutralizing agent is preferably selected from the group of inorganic bases, primary amines, secondary amines, tertiary amines and mixtures thereof, in particular dimethylethanolamine. Neutralizing agents, in particular dimethylethanolamine, are particularly preferred for neutralizing at least one non-polymeric polycarboxylic acid. In this way, the solubility of the non-polymeric polycarboxylic acid in the aqueous coating material can be increased.

In this context, it is preferred that the at least one neutralizing agent, in particular dimethylethanolamine, is present in a total amount of 0.25 to 5wt. -%, preferably 0.3 to 4wt. -%, more preferably 0.5 to 3wt. -%, more particularly 1 to 3wt. -%, in each case based on the total weight of the coating material. The use of neutralizing agents, in particular dimethylethanolamine, in combination with at least one solvent L within the above-mentioned amounts ensures a sufficient dissolution of the non-polymeric polycarboxylic acid and thus a homogeneous incorporation of the coating material according to the invention and also a high storage stability.

Thickening agent

The thickener is preferably selected from the group consisting of phyllosilicates, (meth) acrylic acid- (meth) acrylate copolymers, hydrophobically modified ethoxylated polyurethanes, hydrophobically modified polyethers, non-fibrous hydroxyalkyl celluloses, polyamides and mixtures thereof, in particular (meth) acrylic acid- (meth) acrylate copolymers and/or hydrophobically modified ethoxylated polyurethanes. The (meth) acrylic acid- (meth) acrylate copolymer is obtainable by the reaction of (meth) acrylic acid with (meth) acrylate. Depending on the length of the carbon chain in the (meth) acrylate, these copolymers have an associative thickening effect (ASE or HASE thickener). Copolymers containing only C ₁-C₄ alkyl (meth) acrylates do not have an associative thickening effect (ASE thickener). In contrast, copolymers containing (meth) acrylates having chain lengths of more than four carbon atoms have an associative thickening effect (HASE thickener). Hydrophobically modified ethoxylated polyurethanes are obtainable by reaction of diisocyanates with polyethers and subsequent reaction of the prepolymers with hydrophobic alcohols. Such polyurethanes are also known as HEUR thickeners. It is particularly preferred to use a combination of a non-associative thickening (meth) acrylic acid- (meth) acrylate copolymer and a hydrophobically modified ethoxylated polyurethane.

It is preferred in this context that the at least one thickener, more particularly the (meth) acrylic- (meth) acrylate copolymer and/or the hydrophobically modified ethoxylated polyurethane is present in a total amount of 0.015 to 3wt. -%, preferably 0.03 to 2wt. -%, more preferably 0.04 to 1wt. -%, more particularly 0.05 to 0.7wt. -%, in each case based on the total weight of the coating material.

According to a particularly preferred embodiment of the invention, the aqueous coating material does not comprise phyllosilicates and/or polyamides, more particularly does not comprise phyllosilicates and does not comprise polyamides. This means that the phyllosilicate and/or the polyamide, more particularly the phyllosilicate and the polyamide, are present in a total amount of 0wt. -%, based on the total weight of the coating material. Surprisingly, the use of non-polymeric polycarboxylic acids without the additional use of polyamides and/or phyllosilicates leads to flop indexes comparable to those used with polyamides and/or phyllosilicates. However, when at least one non-polymeric polycarboxylic acid is used, there is no undesired separation phenomenon and no reduced shear stability.

Crosslinking agent

In the case where the mandatory polymeric binder is a thermochemically curable binder, a crosslinking agent is typically present. The crosslinking agent is preferably selected from the group consisting of melamine-formaldehyde resins, polyisocyanates, blocked polyisocyanates, polycarbodiimides and mixtures thereof, in particular melamine-formaldehyde resins.

In this context, it is preferred that the at least one crosslinker, in particular the melamine-formaldehyde resin, is present in a total amount of 1 to 10wt. -%, preferably 2 to 6wt. -%, more preferably 3 to 5wt. -%, more particularly 4 to 6wt. -%, in each case based on the total weight of the coating material. The above total amounts ensure adequate crosslinking of the aqueous coating material.

Organic solvents

As an additional component of the aqueous coating material of the present invention, one or more organic solvents may be included in the coating material. In addition to mandatory water, such solvents may be particularly useful for dissolving one or more non-polymeric polycarboxylic acids and thus allowing for uniform incorporation of these.

The organic solvent is preferably selected from the group consisting of alkoxy-C ₂-C₁₀ alcohols, ketones, esters, amides, methylals, butyrals, 1, 3-dioxolanes, glycerol formal and mixtures thereof, in particular 1-methoxy-2-propanol.

The combined amount of water and one or more organic solvents is preferably in the range of 0.3 to 30wt. -%, preferably 1.5 to 30wt. -%, more preferably 3 to 18wt. -%, more particularly 6 to 18wt. -%, in each case based on the total weight of the coating material. The use of the above amounts of at least one organic solvent and/or water may increase the solubility of the at least one non-polymeric polycarboxylic acid in the aqueous coating material.

Method for producing a multi-layer paint system

The present invention also provides a method for producing a multi-layer paint system on a substrate, the method comprising the steps of:

(1) Producing a cured first coating on the substrate, optionally by applying a coating material to the substrate and subsequently curing the composition;

(2) Creating one or more basecoats on the coating obtained in step (1) by applying one or more of the same or different waterborne basecoat materials;

(3) Producing one or more clearcoats on one or more top-most basecoats by applying a clearcoat material, and

(4) Co-curing the one or more basecoat layers and the one or more clearcoat layers;

Wherein the method comprises the steps of

At least one of the basecoat materials is a pigmented aqueous coating material according to the invention.

In the method of the present invention, a multi-coat paint system is built on a substrate.

According to the invention, the substrate is preferably selected from the group consisting of metal substrates, plastics, glass and ceramics, more particularly from the group consisting of metal substrates.

Contemplated metal substrates include substantially substrates comprising or consisting of, for example, iron, aluminum, copper, zinc, magnesium, and alloys thereof, as well as steels in any of a very broad variety of forms and compositions. Preferred substrates are steel substrates, especially typical steel substrates as used in the automotive industry. Prior to step (1) of the method of the invention, the metal substrate may be pretreated in a conventional manner-i.e. for example, cleaned and/or provided with a known conversion coating.

Suitable plastic substrates are in principle substrates which comprise or consist of polar plastics such as polycarbonates, polyamides, polystyrenes, styrene copolymers, polyesters, polyphenylene oxides and blends of these plastics, (ii) reactive plastics such as PUR-RIM, SMC, BMC and also (iii) polyolefin substrates of the polyethylene and polypropylene type having a high rubber content such as PP-EPDM and also surface-activated polyolefin substrates. The plastic may also be fiber reinforced, more particularly using carbon fibers and/or metal fibers. The plastic substrate may also be pretreated, more particularly by cleaning, before step (1) of the method of the invention, in order to improve the adhesion of the first coating.

In addition, as the base material, those containing both metal and plastic portions can also be used. For example, this type of substrate is a vehicle body containing plastic parts.

Step (1)

In step (1) of the method of the invention, a cured first coating layer may be produced on the substrate by applying a coating material to the substrate (S) and optionally subsequently curing.

The coating material of step (1) may be an electrocoat coating material and may also be a primer coating material. However, the primer coating material according to the invention is not the primer coating applied in step (2) of the method of the invention.

The process of the invention is preferably carried out with a metal substrate. Thus, the first coating is preferably a cured electrocoat. Thus, in a preferred embodiment of the method of the present invention, the coating material is an electrocoat coating material applied to the substrate by electrodeposition coating. For example, suitable electrocoat coating materials and also their curing are described in WO 2017/088988 A1.

Step (2)

In step (2) of the process of the present invention, one primer layer is produced (alternative 1), or two or more directly continuous primer layers are produced (alternative 2).

These layers are produced by directly applying an aqueous primer material to the substrate (S) or directly to the cured coating obtained in step (1) or by directly and continuously applying two or more primer materials to the substrate or to the cured coating obtained in step (1).

Thus, after having been produced, the primer layer according to alternative 1 of step (2) is arranged directly on the substrate or directly on the cured coating obtained in step (1).

The direct continuous application of two or more primer materials to the cured coating obtained in step (1) (alternative 2) is understood as follows:

The application of the first basecoat material produces a first basecoat layer directly on the cured first coating layer of step (1). The at least one further primer layer is then produced directly on the first primer layer. Where two or more additional primer layers are produced, they are produced directly in succession. For example, it is possible to produce exactly one further base coat, in which case in the finally produced multicoat paint system the base coat is arranged directly underneath the first or only clear coat. If two or more basecoats are applied, it may be preferred that the first basecoat produced directly on the substrate or directly on the cured first coating is based on a color-ready basecoat material. The second layer and the optional third layer are based on the same color-and/or effect-imparting primer material or on a first color-and/or effect-imparting primer material and on a second, different color-and/or effect-imparting primer material.

The primer materials may be the same or different. Two or more primer layers may also be produced from the same primer layer material, as well as one or more additional primer layers from one or more other primer layer materials. However, at least one of the waterborne basecoat materials used in step (2) comprises the pigmented waterborne coating material of the present invention.

Alternative 1 to step (2) of the method according to the invention, preferred embodiments in the context of the invention encompass the production of a primer layer.

The primer layer is not cured separately, but is cured with the clear coat material. In particular, the coating material as used in step (2) of the method of the invention does not cure alone as the coating material referred to as the surface coating agent (surfacer) in the context of the standard method. Thus, in step (2), the primer layer is preferably not exposed to temperatures above 100 ℃ for a period of more than 1 minute, and particularly preferably not exposed to temperatures above 100 ℃ at all.

The primer layer material is applied such that after curing in step (4), the primer layer and the individual primer layer each have a layer thickness of, for example, 5 to 50 micrometers, preferably 6 to 40 micrometers, particularly preferably 7 to 35 micrometers. In a first alternative of step (2), it is preferred to produce the primer layer with a relatively high layer thickness of 15 to 50 micrometers, preferably 20 to 45 micrometers. In the second alternative of step (2), the individual primer layers tend to have a comparatively lower layer thickness, if only one primer layer is produced, the entire system still has a layer thickness lying within this order of magnitude. For example, in the case of two primer layers, the first primer layer preferably has a layer thickness of 5 to 35 microns, more particularly 10 to 30 microns, the second primer layer preferably has a layer thickness of 5 to 35 microns, more particularly 10 to 30 microns, and the overall layer thickness preferably does not exceed 50 microns.

Step (3)

In step (3) of the method of the present invention, the clear coat is produced directly on one of the basecoats or on the topmost basecoat. The production is accomplished by applying a clear coat material accordingly. Suitable transparent coating materials are described, for example, in WO 2006042585A1, WO 20090778182 A1 or else WO 20080774490 A1.

After application, the clearcoat material or corresponding clearcoat is preferably flashed and/or intermediate dried at 15 ℃ to 35 ℃ for a time of 0.5 to 30 minutes.

The clearcoat material is applied in such a way that the layer thickness of the clearcoat after curing in step (4) is, for example, from 15 to 80 micrometers, preferably from 20 to 65 micrometers, particularly preferably from 25 to 60 micrometers.

Step (4)

In step (4) of the method of the present invention, there is co-curing of the primer layer and the clearcoat layer or multiple primer layers and clearcoats.

The co-curing is preferably carried out at a temperature of 100 ℃ to 250 ℃, preferably 100 ℃ to 180 ℃, for a duration of 5 to 60 minutes, preferably 10 to 45 minutes.

The method of the present invention allows for the production of a multi-coat paint system on a substrate without the need for a separate curing step.

With respect to further preferred embodiments of the method of the invention, especially with respect to the primer materials used therein and the composition of these primer materials, the statements made regarding the coating materials of the invention are valid mutatis mutandis.

Multi-coat paint system

After the end of step (4) of the process of the invention, the result is a multi-coat paint system of the invention.

It is particularly preferred that the surface of the multi-coat paint system has a flop index of from 8 to 30, preferably from 10 to 30, more particularly from 12.5 to 30. Although preferably no polyamide and/or layered metallosilicate is present, this high flop index is achieved by using the pigmented aqueous coating material according to the invention. In this context, the flop index achieved with the composition according to the invention is comparable to the flop index of a composition which does comprise polyamide and/or phyllosilicate.

With respect to further preferred embodiments of the multi-coat paint system of the present invention, comments made regarding the coating composition of the present invention and also the method of the present invention are valid mutatis mutandis.

Use of the invention

A further subject matter of the invention is the use of the uncoloured aqueous coating material according to the invention as a universal aqueous coating composition for the production of coloured aqueous coating materials according to the invention.

Yet another subject of the present invention is the use of at least one type of cellulose nanofibres as defined above together with one or more non-polymeric polycarboxylic acids and/or salts thereof as defined above in an aqueous coating material comprising one or more polymeric binders as defined above and one or more pigments as defined above, in the production of a multilayer coating system.

A further subject matter of the invention is the use of the pigmented aqueous coating material according to the invention as a base coat material.

The above-described uses are particularly useful for improving flop index and color matching as compared to multilayer coating systems comprising a pigmented waterborne basecoat that does not comprise polyamide and/or layered metallosilicate.

Subsequent color matching eliminates the need to dispose of the aqueous coating composition directly after production or because of storage, out of specification and thus must be disposed of. This results in improved environmental balance and efficiency in the production of basecoat layers and also in the production of paint systems using these coating compositions.

With respect to further preferred embodiments of the use of the present invention, comments made regarding the coating material of the present invention, the method of the present invention and the multi-coat paint system of the present invention are valid mutatis mutandis.

Experimental part/example part

Description of the method

Solids content (solid, non-volatile fraction)

The non-volatile fraction was determined according to DIN EN ISO 3251 (date: month 6 of 2008). It involves weighing 1g of the sample into an aluminium pan that has been previously dried, drying it in a drying oven at 125 ℃ for 60 minutes, allowing it to cool in a dryer, and then re-weighing. The residue corresponds to the non-volatile fraction relative to the total amount of sample used. The volume of the non-volatile fraction can optionally be determined according to DIN 53219 (date: 8 in 2009), if necessary.

Glass transition temperature T _g

For the purposes of the present invention, the glass transition temperature T _g is determined experimentally on the basis of DIN 51005 "Thermal Analysis (TA) -the term" and DIN 53765 "thermal analysis Dynamic Scanning Calorimetry (DSC)". This involved weighing 15mg of sample into a sample boat and introducing it into a DSC instrument. After cooling to the starting temperature, the 1 st and 2 nd measurement runs were carried out with a 50ml/min inert gas sweep (N ₂) at a heating rate of 10K/min, with cooling again to the starting temperature between the measurement runs. The measurement is typically performed in a temperature range from about 50 ℃ below the expected glass transition temperature to about 50 ℃ above the glass transition temperature. For the purposes of the present invention, the glass transition temperature is the temperature at which half the change in specific heat capacity (0.5. DELTA.c _p) is achieved in the 2 nd measurement run, according to DIN 53765, part 8.1. The temperature is determined from a DSC diagram (graph of heat flow versus temperature). Which is the temperature at the intersection of the centerline between the extrapolated baselines and the measured curve before and after the glass transition.

Particle size

The average particle size of the spherical polymer particles was determined by dynamic light scattering (photon correlation spectroscopy (PCS)) according to DIN ISO 13321 (date: 10. 2004). Here, the average particle size means the measured average particle size (Z-average value). Measurements were performed using Malvern Nano S90 (from Markov instruments (Malvern Instruments)) at 25.+ -. 1 ℃. The instrument covers the size range from 3 to 3000nm and is equipped with a 4mW He-Ne laser at 633 nm. The respective samples were diluted with particle-free deionized water as a dispersion medium and then measured in a 1ml polystyrene cell with a suitable scattering intensity. Evaluation was performed using a digital correlator with the aid of Zetasizer analysis software version 7.11 (from malvern instruments). The measurement was performed five times and the measurement was repeated on a second freshly prepared sample. For an aqueous dispersion of an anionically stabilized polymer (asP), the average particle size refers to the arithmetic numerical average of the measured average particle sizes (Z-average; numerical average). For an aqueous dispersion of anionically stabilized polyurethane-polyurea particles (PPP), the average particle size refers to the arithmetic mean of the average particle size (volume average). The standard deviation determined 5 times here is +.4%.

For cellulose nanofibers, the numerical average fiber diameter, length, and thus aspect ratio calculated, were obtained from Atomic Force Microscope (AFM) measurements. Representative samples of CNF were imaged. In the resulting image, the diameter and fiber length of at least 100 fibers were determined. The aspect ratio is derived from the ratio of these values.

Determination of acid value

The acid number was determined according to DIN EN ISO 2114 (date: 6. 2002) using "method A". The acid number corresponds to the mass (in mg) of potassium hydroxide required to neutralize 1g of the sample under the conditions specified in DIN EN ISO 2114. The acid numbers reported here correspond to the total acid numbers indicated in the DIN standard and are based on the solids content.

Determination of OH number

The OH number was determined in accordance with DIN 53240-2 (date: month 11 of 2007). In this process, the OH groups are reacted by acetylation with an excess of acetic anhydride. Excess acetic anhydride is then cleaved by the addition of water to form acetic acid, and the entire acetic acid is back-titrated with ethanolic KOH. The OH number indicates the amount of KOH (in mg) (on a solids basis) that is equal to the amount of acetic acid bound in the acetylation of 1g of the sample.

Determination of number average molecular weight and weight average molecular weight

The number average molecular weight (Ms) was determined by Gel Permeation Chromatography (GPC) in accordance with DIN 55672-1 (date: 8 th month of 2007). Furthermore, the method can be used to determine the weight average molecular weight (Mw) and also the polydispersity d (the ratio of the weight average molecular weight (M _w) to the number average molecular weight (M _n)) in addition to the number average molecular weight. Tetrahydrofuran was used as eluent. This determination was made against polystyrene standards. The column material consisted of styrene-divinylbenzene copolymer.

Determination of the gel fraction of polyurethane-polyurea particles (PPP)

In the context of the present invention, the gel fraction of polyurethane-polyurea particles (PPP) is determined gravimetrically. Here, first, the polymer present was separated from a sample of the aqueous dispersion (initial mass 1.0 g) by freeze-drying. After determining the curing temperature-when the temperature is further reduced, the resistance of the sample does not show a further change above this temperature-the completely frozen sample undergoes its main body, typically in the drying vacuum pressure range between 5 mbar and 0.05 mbar, at a drying temperature 10 ℃ below the curing temperature. By gradually increasing the temperature of the heated surface below the polymer to 25 ℃, a rapid freeze-drying of the polymer is achieved, after a drying time of typically 12 hours, the amount of polymer separated (solid fraction, determined via freeze-drying) is constant and no longer undergoes any change even upon prolonged freeze-drying. Subsequent drying at a temperature of 30 ℃ of the surface under the polymer reduces the ambient pressure to a maximum (typically between 0.05 and 0.03 mbar) to achieve optimal drying of the polymer.

The isolated polymer was then sintered in a forced air oven at 130 ℃ for 1 minute and thereafter extracted in excess tetrahydrofuran at 25 ℃ for 24 hours (tetrahydrofuran to solid fraction ratio = 300:1). The insoluble portion (gel portion) of the isolated polymer was then separated on a suitable frit, dried in a forced air oven at 50 ℃ for 4 hours, and then re-weighed.

It was further determined that at a sintering temperature of 130 ℃ the gel fraction of the particles was found to be independent of the sintering time, varying over a sintering time between one and twenty minutes. Thus, the crosslinking reaction after separation of the polymer solids can be excluded from further increasing the gel fraction.

The gel fraction determined in this way according to the invention is also referred to as gel fraction (freeze-drying).

In parallel, the gel fraction, also referred to below as gel fraction (130 ℃) was determined gravimetrically by separating the polymer sample from the aqueous dispersion (initial mass 1.0 g) at 130 ℃ for 60 minutes (solids content). The mass of the polymer was determined, after which the polymer was extracted in an excess of tetrahydrofuran at 25 ℃ for 24 hours in a procedure similar to that described above, the insoluble fraction (gel fraction) was separated off and dried and weighed.

Solubility in water

The solubility of the organic solvent in water at 20 ℃ was determined as follows. The organic solvent in question and water are combined and mixed in a suitable glass vessel, and the mixture is subsequently equilibrated. The amounts of water and solvent are here chosen such that the equilibrium results in two phases which are separated from one another. After equilibration, a sample of the aqueous phase (i.e., the phase containing more water than the organic solvent) was collected using a syringe, and the sample was diluted with tetrahydrofuran at a ratio of 1/10 and subjected to gas chromatography to determine the fraction of solvent (see section 8. Solvent content for conditions).

If no two phases are formed, the solvent is miscible with water in any weight ratio, regardless of the amounts of water and solvent. Thus, the infinitely water-soluble solvent (e.g., acetone) is at least not solvent (Z.2).

Determination of surface charge by means of electrophoresis

The surface charge was determined by measurement with a Zetasizer Nano from Malvern (Malvern) at a pH range of 3 to 10. Measurement was started at the pH of the sample after dilution. The pH is adjusted using HCl and/or NaOH. Samples were measured in 10mmol/1 KCl.

Isocyanate content

The isocyanate content, hereinafter also referred to as NCO content, is determined by potentiometric back titration of the excess amine with 0.1N hydrochloric acid by adding a 2% N, N-dibutylamine solution in excess xylene to a homogeneous solution of the sample in acetone/N-ethylpyrrolidone (1:1vol%) based on DIN EN ISO 3251, DIN EN ISO 1 1909 and DIN EN ISO 14896. The NCO content of the polymer can be calculated back on the basis of the solids content via the fraction of polymer in solution (solids content).

Neutralization degree

The degree of neutralization x of the component is calculated from the amount of species of carboxylic acid groups present in the component (determined via the acid number) and the amount of species of neutralizing agent used.

Equivalent mass of amine

The amine equivalent mass (solution) was used to determine the amine content of the solution and was determined as follows. The sample under investigation was dissolved in glacial acetic acid at room temperature and titrated for 0.1N perchloric acid in glacial acetic acid in the presence of crystal violet. The amine equivalent mass (solution) is obtained from the initial mass of the sample and from the consumption of perchloric acid, the mass of the solution of basic amine required to neutralize one mole of perchloric acid.

Degree of capping of primary amino groups

The degree of capping of the primary amino groups was determined by means of IR spectroscopy using a Nexus FT-IR spectrometer (from Nicolet) with the aid of an IR cell (d=25 mm, kbr window) at an absorption maximum of 3310cm ^-1, based on the concentration series of the amine used and standardized to the absorption maximum at 1166cm ^-1 (internal standard) at 25 ℃.

Determination of dry film thickness (dry layer thickness)

Method 12A according to DIN EN ISO 2808 (date: 5 th 2007) using a composition from ElektroPhysikThe 3100-4100 instrument determines film thickness.

Determination of flop index

To determine the brightness or flop index, a correspondingly coated substrate (e.g., the multi-coat system in part 5 of the working example below) was subjected to measurement using a spectrophotometer (e.g., an X-Rite MA60b+ba multi-angle spectrophotometer). The surface is irradiated with a light source. Spectral detection is performed in the visible range at various angles. In view of the normalized spectral values and also the reflection spectrum of the light source used, spectral measurements obtained in this way can be used to calculate color values in the CIEL color space, where L represents the luminance, a represents the red-green value, and b represents the yellow-blue value.

The method is described, for example, in ASTM E2194-12, especially for paints in which the pigments comprise at least one effect pigment. The derived value, which is commonly used to quantify the so-called metallic effect, is the so-called flop index, which describes the relationship between brightness and viewing angle. From the luminance values determined for viewing angles of 15 °, 45 ° and 110 °, the flop index (FI _xRite) can be calculated according to the following formula

Where L represents the luminance values measured at the respective measurement angles (15 °, 45 °, and 110 °).

Storage stability measurement

To determine storage stability, the coating material was adjusted to a pH of 8.0 using deionized water and dimethylethanolamine and to a spray viscosity of 100±5mpa x at a shear load of 1000s ^-1, as measured using a rotary viscometer (Rheolab QC instrument with C-LTD80/QC adjustment system, from An Dongpa company (Anton Paar)) at 23 ℃. Further measurements of viscosity were made after 4 weeks of storage at 23 ℃ and after 4 weeks of storage at 40 ℃. A coating material is considered to be storage stable if the viscosity change after storage is small compared to the viscosity of freshly prepared coating material.

Working examples

The following examples of the invention and comparative examples are illustrative of the invention and should not be construed as imposing any limitation.

Regarding the indicated formulation components and their amounts, the following factors should be considered. When referring to a commercial product or a preparation scheme as described elsewhere, that reference (independently of the primary name chosen for the component in question) is just the commercial product or just the product prepared with the scheme in question.

Thus, in the case of a formulation component having the main name "melamine-formaldehyde resin" and in the case of a commercial product indicated for that component, the melamine-formaldehyde resin is used in the form of exactly that commercial product. Thus, if it is to be concluded that the amount of active substance (melamine-formaldehyde resin) is to be taken into account any further components present in the commercial product, such as solvents.

Thus, if a preparation scheme for the formulation components is mentioned, and if such a preparation yields, for example, a polymer dispersion having defined non-volatile portions, the dispersion is used exactly. The primary factor is not the principal name that has been selected, the term "polymer dispersion" or simply the active substance, such as "polymer", "polyester", or "polyurethane modified polyacrylate". This must be taken into account if conclusions are to be drawn regarding the amount of active substance (polymer).

1. Production of polymer binder PM

1.1 Anionically stabilized Polymer Dispersion D1

Anionically stabilized polymers (asP) dispersed in water were prepared according to preparation example "BM2" on pages 63 to 66 of WO 2017/088988 A1. At a pH of 8, dispersion D1 had an electrophoretic mobility of-2.7 (μm/s)/(V/cm).

1.2 Anionically stabilized polyurethane-polyurea particle (PPP) dispersions D2

Anionically stabilized polyurethane-polyurea particles (PPP) dispersed in water were prepared according to preparation example "PD1" on pages 75 and 76 of WO 2018/01311 A1. At a pH of 8, dispersion D2 had an electrophoretic mobility of-6.7 (μm/s)/(V/cm).

1.3 Dispersion D3 of anionically stabilized polyurethane particles

Anionically stabilized polyurethane particles dispersed in water were prepared according to preparation example H in DE19914055 A1. At a pH of 8, dispersion D3 had an electrophoretic mobility of-3 (μm/s)/(V/cm).

1.4 Dispersion D4

Anionically stabilized polyurethane-modified polyacrylates in water were prepared according to the preparation examples found in DE 4437535A 1, page 7, line 55 to page 8, line 23.

At a pH of 8, dispersion D4 had an electrophoretic mobility of-4.2 (μm/s)/(V/cm).

Preparation of CNF solution

A cellulose nanofiber solution (CNF solution) was prepared from dried Celluforce NCV-100 by stepwise addition of solid CNF to deionized water while vigorously stirring. After the desired amount of 3wt. -% CNF in water is reached, stirring is continued until a clear solution is formed.

3. Preparation of filler paste and coloring paste

3.1 Preparation of barium sulfate paste F1

The barium sulfate paste F1 was prepared from 54.00 parts by weight of barium sulfate (Blanc fix Micro, available from Sasa Ha Liben chemical company (Sachtleben Chemie)), 0.3 parts by weight of defoamer (Agitan 282, available from Ming Ling chemical company (Mu nzing Chemie)), 4.6 parts by weight of 2-butoxyethanol, 5.7 parts by weight of deionized water, 3 parts by weight of polyester (prepared according to example D of DE A4009858, column 16, lines 37-59) and 32.4 parts by weight of polyurethane by means of professional grinding and subsequent homogenization.

3.2 Preparation of Talc paste F2

Talc paste F2 was prepared from 28 parts by weight of talc (Micro Talc IT Extra, available from Mongolian minerals Co., ltd.) (Mondo Minerals)), 0.4 parts by weight of an antifoaming agent (Agitan 282, available from Ming Linne chemical Co., ltd.), 1.4 parts by weight184 (Available from BYK Chemie, wessel)), 0.6 parts by weight of the acrylate thickener Rheovis AS130 (available from Basf SE), 1 part by weight of 2-butoxyethanol, 3 parts by weight of Pluriol P900 (available from Basf SE), 18.4 parts by weight of deionized water, 47 parts by weight of the acrylate polymer (adhesive dispersion A from application WO 91/15528A 1) and 0.2 parts by weight of an aqueous dimethylethanolamine solution (10 wt. -% in water) were prepared by professional grinding and subsequent homogenization.

3.3 Preparation of white paste colorant paste 1

The white paste was prepared by a milling process from 50 parts by weight Titan Rutil 2310 (from Kang Nuosi global company (KRONOS WORLDWIDE), rutile form, produced using the chlorine method), 6 parts by weight of polyester prepared in DE 40 09 858 A1 (example D, column 16, lines 37-59), 24.7 parts by weight of the binder dispersion prepared in EP 022 8003B2 (page 8, lines 6-18), 10.5 parts by weight of deionized water, 4 parts by weight of 2,4,7, 9-tetramethyl-5-decynediol (52% in BG; from Basv), 4.1 parts by weight of butanediol, 0.4 parts by weight of 10% dimethylethanolamine in water and 0.3 parts by weight of Acrysol RM-8 (from Dow chemical company (The Dow Chemical Company)).

3.4 Preparation of black paste colorant paste 2

Black paste A black paste was prepared from 57 parts by weight of a polyurethane dispersion prepared according to WO 92/15405, page 13, line 13 to page 15, line 13, 10 parts by weight of carbon black (from Kabot Co., ltd. (Cabot Corporation)1400 Carbon black), 5 parts by weight of a polyester prepared according to DE 40 09 858 A1, example D, column 16, lines 37-59, 6.5 parts by weight of a 10% strength aqueous dimethylethanolamine solution, 3 parts by weight of a commercial polyetherP900, available from basf), 7 parts by weight of butyl diglycol and 11 parts by weight of deionized water.

3.5 Preparation of pale yellow paste colorant paste 3

The pale yellow paste was prepared with 49 parts by weight of polyurethane dispersion prepared according to binder dispersion A of WO 92/15405, 8.0 parts by weight of Disperbyk 184 commercially available from Pick chemical company, 37 parts by weight of Bayferrox 3910 commercially available from Lanxess (Lanxess) and 6 parts by weight of completely desalted water.

3.6 Preparation of blue paste colorant paste 4

The red paste was prepared with 52.04 parts by weight of polyurethane dispersion prepared according to adhesive dispersion A of WO 92/15405, 4.0 parts by weight of Disperbyk 184 commercially available from Pick chemical company, 0.3 parts by weight of defoamer Agitan 282 commercially available from Ming Ling chemical company, 33.03 parts by weight of Heucodur Blue 550 commercially available from Kaubach GmbH, germany, 5.6 parts by weight of completely desalted water, 3 parts by weight of propylene glycol ether and 3 parts by weight of polyether commercially available from Basv companyP900 and 2 parts by weight of 10wt.% of an acrylic acid based thickener Rheovis AS130 (basf) in demineralised water.

4. Production of aqueous coating materials

Amounts in parts by weight and amounts in percentages are in each case weight percentages unless otherwise indicated.

4.1 Production of waterborne base coat materials BL1 to BL4

To produce the hybrid varnishes ML, melamine slurry and aluminum pigment slurry, the respective components in the following table were homogenized at room temperature. The polycarboxylic acid formulation is produced by homogenizing a non-polymeric polycarboxylic acid in solvent L and adding a neutralizing agent at room temperature. The polyamide wax dispersion is produced by homogenizing the polyamide at room temperature in a corresponding amount of deionized water with stirring.

The waterborne basecoat material was produced as follows:

(a) The mixed varnish ML was homogenized with melamine slurry at room temperature,

(B) The ingredients listed under the item "basecoat component" in the table are homogenized successively in the order described therein with the mixture obtained according to (a),

(C) Homogeneously incorporating an aluminum pigment paste into the mixture obtained according to (b) at room temperature with stirring,

(D) The ingredients listed under the item "additive component" in the table are successively homogeneously incorporated into the mixture obtained according to (c) in the order described therein, and

(E) The polycarboxylic acid preparation, if present, is homogeneously incorporated into the mixture obtained according to (d).

The composition was then adjusted to a pH of 7.8 to 8.2 using deionized water and dimethylethanolamine and to a spray viscosity of 100±5mpa x at a shear load of 1000s ^-1, as measured at 23 ℃ using a rotational viscometer (Rheolab QC instrument with C-LTD80/QC regulatory system, from An Dongpa company (Anton Paar)) with a viscosity not yet below the above values.

TABLE 1

* Comparative example ¹ in butanediol 52wt. -% (Basf company)

² Anionically stabilized polymer binders (aqueous dispersions of anionically stabilized polymers asP)

³ Melamine-formaldehyde resin

⁴ According to page 28, ll.13-33, example BE1, of WO2014/033135

⁵ Anionically stabilized polymer binders (aqueous dispersions of anionically stabilized polyurethane-polyurea particles PPP)

⁶ Basiff Co Ltd

⁷ Basiff Co Ltd

⁸ Alu-Stapa Hydromic 2156 (65 wt. -% pigment, commercially available from Altana-Eckart)

⁹ Alu-Stapa Hydromic 2192 (65 wt. -% pigment, commercially available from Altana-Eckart)

¹⁰ According to DE-A-4009858, column 16, ll.37-59, example D

¹¹ Commercially available from King Industries, inc

¹² Commercially available from winning corporation (Evonik)

¹³ Commercially available from Pick chemical Co., ltd

¹⁴ Dicarboxylic acids of the formula (I), wherein R ¹＝(CH₂)₄

¹⁵ Diethanolamine (DEA)

¹⁶ Cellulose Nanofiber (CNF) -solution (3% in water) (fiber trade name: celluforce NCV-100)

4.2 Production of waterborne base coat materials BL5 to BL10

The waterborne base coat material bl5×to bl1=produced as described in section 4.1. However, the components used are those from the following table (the superscript numbers have the same definition as in the table in section 4.1).

TABLE 2

5. Production of multi-coat paint systems

5.1 Multi-coat paint System Using BL1, BL2, BL3 and BL4

With standard cathodic electrocoating materials (from BASF Coatings)500 Gray), the steel plate was coated with a standard commercial surface coating agent (UniBlock FC737555, available from basf coatings company (BASF Coatings GmbH)) in two spray passes (pass) using an ESTA Bell (ECO Bell 1 from ABB), and after a flash time of 10 minutes at 23 ℃, the thus coated plate was subsequently cured at 150 ℃ for 20 minutes, the resulting dry layer thickness was about 35 μm.

The corresponding waterborne basecoat material was then applied in two spray passes (pass) using ESTA Bell (ECO Bell 6-F), flashing for 45 seconds between each spray pass. The plates were then flashed at 23 ℃ for 10 minutes and subsequently dried at 80 ℃ for 10 minutes. The resulting total dry layer thickness of the corresponding coating material was about 14 μm.

After the basecoat material was dried, a commercial clearcoat material (DuraGloss FF700025, available from basf coatings company) was applied using Bell (Eco Bell 1), which was subsequently cured at 150 ℃ for 20 minutes after a flash time of 10 minutes at 23 ℃, the resulting dry layer thickness was about 40 μm. Method 12A according to DIN EN ISO 2808 (date: 5 th 2007) using a method from Ilifex statin Kluyveromyces Limited (ElektroPhysik)The 3100-4100 instrument determines layer thickness.

5.2 Multi-coat paint System Using BL5 or BL6 as the 1 st primer material, BL7, BL9 and BL10 as the 2 nd primer material

Using a coating material (from basf coating company) coated with a standard cathodic electrocoat material800 Grain).

The first primer material was applied using ESTA bell (EcoBell 3). The plate was then flashed at 23 ℃ for 4 minutes. The resulting total layer thickness of the corresponding coating material was about 12 μm.

Thereafter, a second primer layer was first applied using the same ESTA bell type (EcoBell 3), resulting in a layer thickness of about 10 μm. Subsequently, a layer of about 4 μm of the second primer layer was applied using a pneumatic application with AGMD Devilbiss bell. After flashing at 23 ℃ for 4min, the film was dried at 80 ℃ for 10min.

After the basecoat material was dried, a commercial clearcoat material (ProGloss FF990365, available from basf coatings company) was applied using Bell (Eco Bell 2), which was subsequently cured at 140 ℃ for 20 minutes after a flash time of 5 minutes at 23 ℃, the resulting dry layer thickness was about 42 μm.

6. Results

6.1 Storage stability

The base coat materials BL2 (pH 8; total solids: 30 wt.%; CNF solids: 0.5 wt.%), BL3 (pH 8; total solids: 31 wt.%; CNF solids: 0.3 wt.%), and BL4 (pH 8; total solids: 30 wt.%; CNF solids: 0.16 wt.%) of the present invention were subjected to the above-described storage stability test, the results of which are shown in Table 3 below.

TABLE 3 Table 3

On the one hand, the viscosity stability by employing CNF is much higher compared to the lower solid concentration of CNF (comparison BL4 versus BL3 versus BL 2) and on the other hand, in particular compared to comparison example BL 1. However, the comparison BL1 shows a viscosity increase of 239% after 4 weeks of storage at 40℃and BL2 shows only a slight change of 16%, wherein a measurement error of 10% has to be taken into account.

The stability of the inventive pigment containing base coat material BL7 (pH: 8; total solids: 21.2 wt.%; CNF solids: 0.0 wt.%; polycarboxylic acid solids: 0.0 wt.%), the comparative effect pigment containing base coat material BL8 (pH: 7.9; total solids: 20.9 wt.%; CNF solids: 0.5 wt.%; polycarboxylic acid solids: 0.0 wt.%), the comparative effect pigment containing base coat material BL9 (pH: 7.8; total solids: 19.8 wt.%; CNF solids: 0.0 wt.%; polycarboxylic acid solids: 0.1 wt.%), and the base coat material BL10 (pH: 8; total solids: 19.4 wt.%; CNF solids: 0.5 wt.%; polycarboxylic acid solids: 0.1 wt.%) were subjected to the storage stability test is shown in the following table 4.

TABLE 4 Table 4

The viscosity reduction of the CNF-based basecoat after 4 weeks at 40 ℃ is lower compared to BL9 and BL 10. The viscosity reduction was 22% while the viscosity reduction of a comparable CNF-free system based on LRD was 39%. This means that the stored product has better stability against sagging.

6.2 Flop index

Comparative basecoat BL1 (pH: 8; total solids: 30wt. -%; CNF solids: 0.0wt. -%; polycarboxylic acid solids: 0.3wt. -%) and inventive basecoat material BL2 (pH: 8; total solids: 30wt. -%; CNF solids: 0.5wt. -%; polycarboxylic acid solids: 0.3wt. -%), BL3 (pH: 8; total solids: 31wt. -%; CNF solids: 0.3wt. -%; polycarboxylic acid solids: 0.3wt. -%) and BL4 (pH: 8; total solids: 30wt. -%; CNF solids: 0.16wt. -%; polycarboxylic acid solids: 0.3wt. -%) were used in the production of the multicoat system as described in section 5 above. The results are shown in table 5 below.

TABLE 5

The above base coat materials BL2, BL3 and BL4 are used in the same multilayer coating system and differ in that they contain different amounts of cellulose nanofiber solids, i.e. 0.5wt. -%, 0.3wt. -% and 0.16wt. -%, all based on the total weight of the respective base coat materials. Table 5 clearly shows that the solids content of the cellulose nanofibers has only a small effect on the flop index. Even using higher amounts in BL2 does not negatively affect the flop index, if any, but conversely, the flop index is even higher than BL3 and BL 4. Furthermore, in all three inventive examples, the flop index was increased compared to comparative example BL1 using layered metallosilicate.

The multi-coat system as shown in table 6 below comprises two base coats and is prepared as detailed in section 5.2 above. The first basecoat material was comparative basecoat material BL5 (pH: 8.6; total solids: 34wt. -%; CNF solids: 0.0wt. -%; polycarboxylic acid solids: 0.0wt. -%) -for examples C1 and C2-or inventive basecoat material BL6 (pH: 8.4; total solids: 34wt. -%; CNF solids: 0.3wt. -%; polycarboxylic acid solids: 0.1wt. -%) -for examples I1 and I2.

A second primer layer is wet-on-wet applied over the top or first primer layer.

The second basecoat was prepared from comparative effect pigments containing basecoat material BL7 (pH: 8.0; total solids: 21.2 wt.%; CNF solids: 0.0 wt.%; polycarboxylic acid solids: 0.0 wt.%; comparative effect pigments containing basecoat material BL8 (pH: 7.9; total solids: 20.9 wt.%; CNF solids: 0.5 wt.%; polycarboxylic acid solids: 0.0 wt.%; or containing basecoat material BL10 (pH: 8.0; total solids: 19.4 wt.%; CNF solids: 0.5 wt.%; polycarboxylic acid solids: 0.1 wt.%; effect pigment of the invention for example I2). The results are shown in table 6 below.

TABLE 6

* Coatings not according to the invention

^a Layered metal silicate

^b Cellulose nanofibers

In all of examples C1, C2, I1 and I2 above, only the second basecoat contained metallic effect pigment, while the first basecoat contained only colored pigment, but no metallic effect pigment (see table 2).

In comparative example C1, layered Metallosilicate (LMS) was used as rheology control agent for both layers, and no non-polymeric polycarboxylic acid was contained in either of the two primer layers. The flop index is the lowest flop index (14.0) compared to the other examples. In comparative example C2, the same first primer layer as comparative example C1 was used, followed by a second primer layer containing cellulose nanofibers instead of layered metal silicate, but no non-polymeric polycarboxylic acid was also present. The flop index was slightly increased (14.6).

Example I1 of the present invention shows that the use of the basecoat of the present invention formed from basecoat material BL6 has and unexpectedly tends to increase the flop of the combined duplex basecoat structure, and that the metallic effect pigment-containing layer does not contain a non-polymeric polycarboxylic acid. The flop index was 15.5. The best results are provided in example I2 of the present invention, namely that the two base coats (the coloured layer and the metallic effect coloured layer) contain cellulose nanofibres and non-polymeric polycarboxylic acid, thus providing a flop index of 16.7.

Claims (17)

1. An aqueous coating material comprising

A) One or more polymeric binders;

b) One or more types of cellulose nanofibers, and

C) One or more non-polymeric polycarboxylic acids and/or salts thereof.

2. The aqueous coating material of claim 1, further comprising

D) One or more pigments selected from the group consisting of colored pigments and effect pigments.

3. The aqueous coating material according to claim 1 or 2, wherein,

One of the one or more polymeric binders includes one or more anionically stabilized polymeric binders.

4. A water-borne coating material according to any one or more of claims 1 to 3, wherein the one or more types of cellulose nanofibers are selected from the group consisting of anionically modified cellulose nanofibers.

5. An aqueous coating material according to any one or more of claims 1 to 3, wherein the anionically modified cellulose nanofibers comprise sulfate groups.

6. The aqueous coating material according to any one of claims 1 to 5, wherein the one or more types of cellulose nanofibers have a diameter in the range of from 2 to 500nm and a length in the range of from 0.04 to 20 μιη.

7. The aqueous coating material according to any one or more of claims 1 to 6, the one or more non-polymeric polycarboxylic acids and/or salts thereof having the following general formula (I)

M^+-OOC-R¹-COO^-M⁺(I)

Wherein the method comprises the steps of

Two M ⁺ are, independently of one another, monovalent cations, and

R ¹ is absent or is a divalent residue of a saturated or unsaturated, aliphatic or aromatic, straight chain, branched or cyclic hydrocarbon.

8. The aqueous coating material of claim 7, wherein,

The monovalent cation is selected from the group consisting of H ⁺, alkali metal cations, NH ₄ ⁺ and cations of the formula N (R ²)₄ ⁺), wherein the residues R ² are independently of one another H, alkyl residues and hydroxyalkyl residues, and

R ¹ is absent or contains from 1 to 72 carbon atoms.

9. The aqueous coating material according to any one or more of claims 2 to 8, wherein the one or more colored pigments are selected from the group consisting of:

(i) White pigments such as titanium dioxide, zinc white, zinc sulfide or lithopone;

(ii) Black pigments such as carbon black, iron-manganese black, or spinel black;

(iii) Color pigments such as ultramarine green, ultramarine blue, manganese blue, ultramarine violet, manganese violet, iron oxide red, molybdenum red, ultramarine red, iron oxide brown, mixed brown, spinel phases and corundum phases, iron oxide yellow, bismuth vanadate;

(iv) Organic pigments such as monoazo pigments, disazo pigments, anthraquinone pigments, benzimidazole pigments, quinacridone pigments, quinophthalone pigments, diketopyrrolopyrrole pigments, dioxazine pigments, indanthrone pigments, isoindoline pigments, isoindolinone pigments, azomethine pigments, thioindigo pigments, metal complex pigments, pyrenone pigments, perylene pigments, phthalocyanine pigments, nigrosine pigments, and

(V) Mixtures thereof, and/or

The one or more effect pigments are selected from the group consisting of:

(vi) Layered aluminium pigments, aluminium pigments in the form of "cornflakes" and/or "silver elements", aluminium pigment (vii) glass flakes coated with organic pigments, glass flakes coated with interference layers,

(Viii) Gold bronze and oxidized bronze, and the metal bronze,

(Ix) Iron oxide-aluminum pigments, pearlescent pigments, metal oxide-mica pigments, lamellar graphite, platelet-shaped iron oxides, multilayer effect pigments composed of PVD films and mixtures thereof.

10. The aqueous coating material according to any one or more of claim 1 to 9, comprising, based on the total weight of the aqueous coating material,

9 To 60wt. -% of the one or more polymeric binders;

0.05 to 1.5wt. -% of the one or more types of cellulose nanofibers, and

0.05 To 5wt. -% of the one or more non-polymeric polycarboxylic acids and/or salts thereof.

11. The aqueous coating material of claim 910, further comprising 1 to 40wt. -% of the one or more colored pigments, and/or based on the total weight of the aqueous coating material

1 To 20wt. -% of the one or more effect pigments.

12. The aqueous coating composition according to any one or more of claims 1 to 11, having a solids content ranging from 10wt. -% to 65wt. -%.

13. A method for producing a multi-coat paint system on a substrate, the method comprising the steps of:

(1) Producing a cured first coating on the substrate, optionally by applying a coating material to the substrate and subsequently curing the composition;

(2) Creating one or more basecoats on the coating obtained in step (1) by applying one or more of the same or different waterborne basecoat materials;

(3) Producing one or more clearcoats on one or more top-most basecoats by applying a clearcoat material, and

(4) Co-curing the one or more basecoat layers and the one or more clearcoat layers;

Wherein the method comprises the steps of

At least one of the basecoat materials is an aqueous coating material according to any one or more of claims 2 to 12.

14. A multilayer coating system obtainable by the method according to claim 13.

15. Use of the aqueous coating material according to claim 1 as a universal aqueous coating composition for producing the coloured aqueous coating material according to claims 2 to 12.

16. Use of at least one type of cellulose nanofibers as defined in claims 1 to 12 together with one or more non-polymeric polycarboxylic acids and/or salts thereof as defined in claims 1 to 12 in an aqueous coating material comprising one or more polymeric binders as defined in claims 1 to 12 and one or more pigments as defined in claims 2 to 12, for the production of a multilayer coating system.

17. Use of a pigmented aqueous coating material according to any one or more of claims 2 to 12 as a base coat material.