HK1152959B - Aqueous coating composition comprising polyurethanes and vinyl polymers - Google Patents

Description

Aqueous coating composition containing polyurethane and vinyl polymer

The present invention relates to an aqueous coating composition comprising at least two different polymers having certain film-forming properties, a process for making such a composition and a coating obtained therefrom.

It is known in the art to use aqueous polymer dispersions of vinyl polymers or polyurethanes as binders for aqueous compositions for making coatings, wherein the vinyl polymers or polyurethanes provide the coating with a binder material.

It is also known to use vinyl polymers and polyurethanes in combination in aqueous polymer dispersions to further improve the properties of the resulting coatings, whereby the presence of each type of polymer (vinyl polymer or polyurethane) will improve certain properties of the coating compared to the use of the other type of polymer alone.

US 5817735 describes a primer composition comprising a polyurethane and a polyacrylate, wherein the polyurethane component has a glass transition temperature (Tg) in the range of 20 to 50 ℃ and the acrylate component has a Tg in the range of 10 to 90 ℃. US 6384131 discloses a composition comprising a polyurethane dispersion and a water dilutable resin (such as a polyacrylate) for use in low VOC basecoat/clearcoat coatings with the aim of achieving low VOC levels.

US 6437036 and US 6342558 describe a thermosetting water-borne primer comprising a polyurethane polymer, an acrylic polymer and a crosslinking component. The Tg of the polyurethane should be less than 0 ℃ and the Tg of the polyacrylate should be at least 20 ℃ higher than the Tg of the polyurethane. The aim is to obtain formulations which are resistant to grinding wheel abrasion (stone chipping) and have a very low VOC.

GB 2362387 discloses a mixture of a multiphase acrylate consisting of acrylates with a Tg > 20 ℃ and acrylates with a Tg < 20 ℃ and polyurethanes to achieve good hardness properties.

WO 05/23947 discloses an aqueous composition comprising a polyurethane and a polymer dispersion having a minimum film forming temperature above ambient temperature.

US 5547710 discloses a polyurethane and a polymerization product having a Tg of 25 to 100 ℃ and having epoxy groups and epoxy-reactive groups.

US 6566438 describes a polyurethane/polymer hybrid having a high film hardness.

US 5137961 describes surfactant-free aqueous polymer dispersions comprising an anionic water-dispersible polyurethane and a vinyl polymer, wherein: the weight ratio of polyurethane to vinyl polymer is from 80: 20 to 30: 70.

US 6787596 discloses a solvent-free hybrid dispersion of a polyurethane polymer having a high solids content of the polymer, obtainable by multistage preparation of a polyurethane-based dispersion followed by preparation of the hybrid dispersion.

EP 0666275 discloses a process for preparing polyurethane/acrylic polymer dispersions for film laminate adhesives, preferably, which are prepared in the absence of organic solvents.

WO 99/16805 describes an aqueous polymer dispersion comprising a water-dispersible polyurethane and a vinyl (preferably acrylic) polymer in a weight ratio in the range 30/70 to 5/95.

A problem with existing compositions is that they do not enable the resulting coating to have both toughness and flexibility, as it is expected that these two properties generally work against each other.

Typically, the film gains stiffness at the expense of reducing the elastic properties of the film. Surprisingly, we have now found that a specific combination of polyurethane and vinyl polymer in an aqueous composition can lead to unexpectedly good properties, such as a very advantageous balance of: 1) toughness (such as impact resistance); 2) flexibility (such as fracture growth rate and elasticity); and 3) obtaining a coating that is not tacky, this balance being maintained in particular in the case of compositions that are coloured. Designing such coatings is a difficult task because the three properties are expected to work against each other, e.g. tough coatings usually have very low elasticity.

Special problems arise when pigments are added to clear coating compositions. In this case, the hardness of the coating generally increases, but the elasticity of the coating will generally decrease, which makes the coating unsuitable for flexible substrates.

The properties of the coatings obtained from the compositions of the present invention depend on the choice of the particular type of polyurethane having a lower isocyanate (NCO)/isocyanate-reactive group (e.g., OH) ratio and the amount of that polyurethane in the overall aqueous composition, in combination with a soft (low Tg) vinyl polymer, wherein the ratio of polyurethane to vinyl polymer is such that the amount of polyurethane is in excess relative to the amount of vinyl polymer. The coating composition designed using the above specific parameters has excellent elongation at break (whether it is used as a pigmented coating or just as a transparent pigment-free coating), very good hardness and impact resistance, and results in a film with greatly reduced tackiness, preferably one that is not tacky.

According to the present invention, there is provided an aqueous coating composition comprising:

(i) from 50 to 95 weight percent of a polyurethane obtained by the reaction of (a) an isocyanate-terminated prepolymer and (b) an active hydrogen chain extending compound, the isocyanate-terminated prepolymer being obtained from the reaction of components comprising:

(1)10 to 40 weight percent of at least one polyisocyanate, at least 50 weight percent of which is at least one aliphatic polyisocyanate;

(2)0 to 10 wt% of at least one isocyanate reactive compound having a weight average molecular weight in the range of 50 to 500g/mol comprising ionic or potentially ionic water dispersing groups;

(3)50 to 89 wt% of at least one isocyanate reactive compound having a weight average molecular weight in the range of 501 to 5000 g/mol;

(4)0 to 10 wt% of at least one isocyanate reactive compound not included in (2) having a weight average molecular weight in the range of 50 to 500 g/mol;

wherein the NCO/OH ratio is in the range of 1.75 to 1.05 and (1), (2), (3) and (4) add up to 100%;

(ii)5 to 50 weight percent of a vinyl polymer having a Tg below ambient temperature;

wherein (i) and (ii) total 100%; and

(iii) a liquid medium comprising ≤ 10 wt% of an organic solvent.

For the purposes of the present invention, an "aqueous dispersion" of a polymer or an "aqueous composition" comprising a polymer refers to a dispersion or composition of the polymer in a liquid medium in which water is the main component or as the sole component. Such dispersions typically comprise colloidally dispersed polymer particles, i.e. they are typically in the form of an aqueous polymer latex.

For the purposes of the present invention, ambient temperature is defined as 25+/-3 ℃, more preferably 25 ℃.

As is apparent from the above, the term "polyurethane" used in the present specification may refer to one or more polyurethanes, which are applicable not only to a polymer (or prepolymer) having only a urethane bond formed from an isocyanate group and a hydroxyl group, but also to a polymer, prepolymer, or polymer segment having a bond formed from an isocyanate group and a group such as a primary or secondary amine (urea bond) or thiol in addition to a urethane bond. The carbamate group is defined as-O-C (═ O) -NH-, and the urea group is defined as-HN-C (═ O) -NH-. The term NCO/OH as used herein is the reaction of an isocyanate group (-NCO) with an isocyanate-reactive group (such as-OH, -NH)₂The ratio of-NH-, -SH-).

The ratio of urethane/urea groups (i.e.urethane/urea) in the polyurethane is preferably >1, more preferably > 1.3, even more preferably > 1.75, most preferably > 2. Having a urethane/urea ratio >1 is advantageous because it helps to obtain the desired properties for coatings having the composition of the present invention.

Preferably, the polyurethane has a weight average molecular weight of at least 50,000g/mol as measured by Gel Permeation Chromatography (GPC) using THF (tetrahydrofuran) or HFIP (hexafluoroisopropanol) as the solvent (depending on which solvent is the better solvent for the particular polyurethane) and polystyrene as a standard.

Preferably, the weight average particle diameter (Dw) (i.e. the particle size, since the particles are substantially spherical) of the polyurethane is less than 200nm, more preferably in the range of 20 to 150nm, most preferably 30 to 100 nm.

The isocyanate-terminated prepolymer preferably comprises 15 to 35 wt% of at least one polyisocyanate (a) (1). The polyisocyanate (a) (1) used to prepare the isocyanate-terminated prepolymer comprises at least 70 wt%, more preferably at least 90 wt%, most preferably at least 95 wt%, especially 100 wt% of an aliphatic (which term includes cycloaliphatic) polyisocyanate, preferably a diisocyanate. The term "aliphatic polyisocyanate" (for the sake of clarity) refers to compounds in which all isocyanate groups are directly bonded to aliphatic or cycloaliphatic groups, whether or not aromatic groups are also present. The term "aromatic polyisocyanate" (for clarity) refers to a compound in which all isocyanate groups are directly bonded to aromatic groups, whether or not aliphatic groups are also present.

Examples of suitable aliphatic polyisocyanates include ethylene diisocyanate, 1, 6-hexamethylene diisocyanate, isophorone diisocyanate, cyclohexane-1, 4-diisocyanate, 4' -dicyclohexylmethane diisocyanate, cyclopentylene diisocyanate, p-tetramethylxylene diisocyanate (p-TMXDI) and its meta isomer (m-TMXDI), hydrogenated 2, 4-toluene diisocyanate, hydrogenated 2, 6-toluene diisocyanate, and 1-isocyanato-1-methyl-3 (4) -isocyanatomethyl-cyclohexane (IMCI). The aliphatic polyisocyanates improve hydrolytic stability, resistance to UV degradation and do not yellow.

Preferred aliphatic polyisocyanates are selected from the group consisting of isophorone diisocyanate, 4' -dicyclohexylmethane diisocyanate, 1, 6-hexamethylene diisocyanate, and mixtures thereof.

Mixtures of polyisocyanates can be used, as can polyisocyanates modified by the introduction of urethane, allophanate, urea, biuret, carbodiimide, uretonimine or isocyanurate residues.

Examples of suitable aromatic polyisocyanates include, but are not limited to, p-xylylene diisocyanate, 1, 4-phenylene diisocyanate, 2, 4-toluene diisocyanate, 2, 6-toluene diisocyanate, 4 '-methylene bis (phenyl isocyanate), polymethylene polyphenyl polyisocyanates, 2, 4' -methylene bis (phenyl isocyanate), and 1, 5-naphthylene diisocyanate. Aromatic isocyanates (if used) include 2, 4 '-methylenebis (phenyl isocyanate) and 4, 4' -methylenebis (phenyl isocyanate). Aromatic polyisocyanates tend to provide chemical resistance and toughness, but may yellow when exposed to UV light.

It will be understood that the isocyanate-reactive compounds (a) (2) to (a) (4) include polyols and isocyanate-reactive compounds other than polyols (e.g. diamines, thiols or aminoalcohols); however, the isocyanate-reactive compound preferably consists entirely or essentially of the polyol reactant.

The polyurethane preferably has internal water-dispersible groups built into its structure (preferably on the lateral and/or terminal positions) during its synthesis, such that such groups preferably render the polyurethane self-water-dispersible. The internal water-dispersing groups described above may form part of the isocyanate-reactive components (a) (2), (a) (3) and/or the polyisocyanates (a) (1) and/or, less preferably, they may form part of the active hydrogen chain extending compounds (b).

The isocyanate-terminated prepolymer is preferably obtained from 1 to 10% by weight, more preferably 3 to 8% of the isocyanate-reactive compound (a) (2).

Thus, while the polyurethane is substantially dispersible in water, either simply by using an external surfactant (if the polyurethane has no internal dispersing groups) or by high shear mixing, thereby forming a stable dispersion in water, the polyurethane has more preferred dispersibility if internal dispersing groups are present and, optionally or if desired, combined with an external surfactant. The internal water-dispersing groups described above are more typically chain-pendant groups, which may be ionic (preferably anionic) or non-ionic, or a combination of ionic and non-ionic.

Anionic water-dispersing groups include, for example, -SO₃ ^-、-OSO₃ ^-、-PO₃ ^-In particular the carboxylate group-CO₂ ^-。

Any potentially anionic water-dispersing groups present in the prepolymer may be converted to anionic salt groups by: the acid groups are neutralized before, after, or simultaneously with the formation of the aqueous dispersion of the prepolymer. In case acid groups are additionally present in the final polyurethane or are only present in the final polyurethane by incorporation of acid groups additionally or only during the chain extension step, the conversion of the above groups into anionic salt groups may be achieved by: these acid groups are neutralized during or after the formation of the final polyurethane dispersion.

Most preferably, the dispersing group is incorporated into the prepolymer (and/or less preferably, as part of the chain extender component) by using a non-ionized carboxylic acid group which is then neutralized to a carboxylic acid ionic group using a reagent such as: tertiary amines, examples of which include Triethylamine (TEA), triethanolamine, dimethylaminoethyl methacrylate, dialkylalkanolamines (such as dimethylethanolamine, dimethylisopropanolamine DMIPA, and the like), N-methylmorpholine, N-ethylmorpholine, N-ethylpiperidine, N-methylpiperidine, dimethylbenzylamine, dimethylcyclohexylamine; an alkali metal hydroxide (such as K hydroxide, Na hydroxide or Li hydroxide) or a quaternary ammonium hydroxide. Ammonia itself may also be used. Combinations of the above agents may be used, and the above combinations may be used simultaneously or in different steps with different agents. An example is to add TEA to the prepolymer and use DMIPA in the aqueous phase. Examples of reactants for achieving the above combination include diols and triols having a carboxyl group, particularly dihydroxyalkanoic acids. The most preferred polyol having carboxyl groups is 2, 2-dimethylolpropionic acid (DMPA). Another preferred example is 2, 2-dimethylol n-butyric acid (DMBA). Mixtures of DMPA and DMBA may also be used.

The isocyanate-terminated prepolymer is preferably obtained from 55 to 80% by weight of the isocyanate-reactive compound (a) (3).

The isocyanate-terminated compound (a) (3) is preferably a polymeric diol, but may include a polyol having a functionality of 2 or more. The polymeric polyol preferably has a weight average molecular weight (hereinafter referred to as Mw) in the range of 501 to 4000g/mol, more preferably in the range of 700 to 3000 g/mol. Such polyols may in principle be selected from any of the various chemical classes of polyols that have been used or suggested for use in polyurethane synthesis. Specifically, the polyol may be a polyester polyol, a polyesteramide polyol, a polyether polyol, a polythioether polyol, a polycarbonate polyol, a polyacetal polyol, a polyvinyl polyol, and/or a polysiloxane polyol. More preferably, the polyol is selected from polyester polyols, polycarbonate polyols, polyether polyols and/or polysiloxane polyols, and particularly preferably, the polyol is selected from polyether polyols and/or polyester polyols.

Polyester polyols that may be used include hydroxyl terminated reaction products of polyols. It is also possible to use polyesters obtained by polymerizing lactones or lactones into which carboxyl groups have been incorporated. Polyesteramides may be obtained by including aminoalcohols such as ethanolamine in polyesterification mixtures.

Polyether polyols which may be used include the products obtained by: polymerizing the cyclic oxide; or one or more such oxides may be added to the polyfunctional initiator. Particularly useful polyether polyols include polyoxypropylene diols and triols, poly (oxyethylene-oxypropylene) diols and triols, and polytetramethylene ether glycols.

The isocyanate-reactive compound (a) (3) may also contain nonionic water-dispersing groups. The nonionic water-dispersing groups are usually polyoxyalkylene side groups, in particular Polyoxyethylene (PEO) groups. Such a group can be obtained, for example, by: the diol having PEO side chains is used as a reactant in the formation of the prepolymer and/or (less preferably) as part of the chain extender component.

If desired, the PEO chains may contain other alkylene oxide units in addition to ethylene oxide units. Thus, PEO chains can be used in which up to 60% of the alkylene oxide units are propylene oxide units, the remainder being ethylene oxide units.

The isocyanate-terminated prepolymer is preferably derived from 1 to 10 wt%, more preferably 2 to 7 wt% of the isocyanate-reactive compound (a) (4).

The isocyanate-reactive compounds (a) (4) are preferably diols. The diol preferably has an Mw in the range from 50 to 450g/mol, more preferably in the range from 70 to 200 g/mol.

Examples of the compound (a) (4) include ethylene glycol, neopentyl glycol, 1-propanol, butanediol, 1, 4-cyclohexyldimethanol, 1, 4-bishydroxymethylcyclohexane, 1, 3-bis (4-hydroxycyclohexyl) propane, perhydrogenated bisphenol A and the like.

The isocyanate reactive compounds (a) (3) and (a) (4) may also include one or more organic monoalcohols.

The active hydrogen-containing chain extending compound that can react with the prepolymer component is preferably an amino-alcohol, an aliphatic, cycloaliphatic, aromatic, araliphatic or heterocyclic primary diamine or primary polyamine (i.e., having 3 or more amine groups), an aliphatic, cycloaliphatic, aromatic, araliphatic or heterocyclic secondary diamine or secondary polyamine (i.e., having 3 or more amine groups), hydrazine or substituted hydrazine, or polyhydrazine (preferably dihydrazine).

Chain extenders that are miscible with water are preferred. Water itself can be used as an indirect chain extender because it slowly converts some of the terminal isocyanate groups in the prepolymer to amino groups (via labile carbamate groups) and the modified prepolymer molecules then undergo chain extension. If the above-mentioned active hydrogen chain extender (which is also referred to as a direct chain extender compound) is used, it will provide the predominant chain extension reaction.

Examples of the above-mentioned direct chain extender usable herein include ethylenediamine, diethylenetriamine, triethylenetetramine, propylenediamine, butylenediamine, hexamethylenediamine, cyclohexanediamine, piperazine, 2-methylpiperazine, phenylenediamine, tolylenediamine, xylylenediamine, tris (2-aminoethyl) amine, 3-dinitrobenzidine, 4' -diaminodiphenylmethane, methanediamine, m-xylylenediamine, isophoronediamine, and an adduct of diethylenetriamine and an acrylic ester or a hydrolysate thereof. The following compounds may also be used: for example hydrazine (e.g. in the form of its monohydrate), azines (such as acetone azine), substituted hydrazines (such as dimethylhydrazine, 1, 6-hexamethylene-bis-hydrazine, carbodihydrazide), dihydrazides of dicarboxylic acids and sulphonic acids (such as dihydrazide of adipic acid, oxalic acid dihydrazide, isophthalic acid dihydrazide), hydrazides prepared by reacting lactones and hydrazine (gamma-hydroxybutyrylhydrazine), bis-semi-carbodihydrazide and bis-hydrazinodicarbonate of diols. Other suitable classes of chain extending compounds are the so-called "Jeffamine" compounds (available from Huntsman) with a functionality of 2 or 3. These are diamines or triamines based on propylene oxide (PPO) or ethylene oxide (PEO), such as "Jeffamine" T403 and "Jeffamine" D-400.

Preferably, the active hydrogen chain extender compound is or includes hydrazine (typically in the form of its monohydrate) or a diamine or triamine (typically a diamine) having a molecular weight of less than 300 g/mol.

When the chain extender is a direct compound (other than water), such as a polyamine, diamine or hydrazine, for example, the chain extender may be added to the aqueous dispersion of the prepolymer, for example, using in-line mixing; or it may, for example, be present in an aqueous medium in which the prepolymer has been dispersed; or it may for example simply be added to the water together with the prepolymer.

The total amount of chain extender compounds (isocyanate-reactive groups) used other than water is preferably such that the ratio of active hydrogens in the chain extender to isocyanate (NCO) groups in the prepolymer is preferably in the range of 0.4 to 2.0, more preferably in the range of 0.6 to 1. Of course, if only water is used as indirect chain extender, this ratio does not apply, since the water which acts as indirect chain extender and dispersion medium is present in an excess relative to the total amount of residual NCO groups.

The isocyanate-terminated prepolymer may be prepared in a conventional manner by: a stoichiometric excess of polyisocyanate is reacted with the isocyanate-reactive compound (and any other reactants) under substantially anhydrous conditions at a temperature of from about 30 ℃ to about 130 ℃ until the reaction between the isocyanate groups and the isocyanate-reactive groups, which are typically all hydroxyl groups, is substantially complete. During the preparation of the isocyanate-terminated prepolymer, the reactants are preferably used in a ratio corresponding to a ratio of isocyanate groups to isocyanate-reactive groups (preferably all hydroxyl groups) (NCO/OH) of about 1.7 to 1.1, more preferably 1.6 to 1.1, most preferably 1.5 to 1.3.

This preferred ratio contributes to the balanced properties of the coatings obtained from the compositions of the present invention.

If desired, a catalyst such as dibutyltin dilaurate or stannous octoate may be used to assist in prepolymer formation, but optionally no catalyst is used during prepolymer formation.

Diluents such as organic solvents or reactive components may optionally be added before, during or after prepolymer formation to control viscosity, with the proviso that: such addition does not impair the obtainment of a final dispersion free of solvent (and therefore such solvent needs to be removed as much as possible subsequently). Suitable organic solvents that may be used include acetone, methyl ethyl ketone, dimethylformamide, diglyme, N-methylpyrrolidone, N-ethylpyrrolidone, ethyl acetate, the diacetate of ethylene glycol and propylene glycol, the alkyl ether of the monoacetate of ethylene glycol and propylene glycol, toluene, xylene, sterically hindered alcohols such as t-butanol and diacetone alcohol. Preferred solvents are water-miscible solvents such as N-methylpyrrolidone, dialkyl ethers of acetone and glycol acetate, or mixtures of N-methylpyrrolidone and methyl ethyl ketone.

Preferably, the aqueous coating composition comprises ≥ 55 wt.% and more preferably ≥ 60 wt.% of the polyurethane (i) obtained by reaction of components (a) and (b). Preferably, the aqueous coating composition comprises 90% by weight or less, more preferably 85% by weight or less of polyurethane (i) obtained by reaction of components (a) and (b).

Preferably, the aqueous coating composition comprises ≥ 10 wt.%, more preferably ≥ 15 wt.%, of the vinyl polymer (ii) having a Tg below ambient temperature. Preferably, the aqueous coating composition comprises 50 wt.% or less, more preferably 40 wt.% or less, even more preferably 40 wt.% or less＜30 wt% of a vinyl polymer (ii) having a Tg lower than ambient temperature.

In the case where the vinyl polymer is formed in situ with the polyurethane, the solvent used in the prepolymer (if having appropriate solvent characteristics) may be or may comprise (e.g. optionally in combination with an organic solvent of the type described above) a monomer or mixture of monomers which are subsequently polymerised to form the vinyl polymer. Preferably, the vinyl polymer is formed in situ.

The polyurethanes are preferably prepared in the form of aqueous dispersions by: dispersing the isocyanate-terminated polyurethane prepolymer (optionally held in an organic solvent medium which may comprise or consist of monomers of a vinyl polymer, also known as a reactive diluent) in an aqueous medium, preferably taking advantage of the self-dispersible nature of the prepolymer resulting from the internal dispersing groups in the isocyanate-terminated prepolymer, but optionally additionally using a free surfactant if desired; the prepolymer is then chain extended with the active hydrogen compound in the aqueous phase, either as it is present in the aqueous phase during dispersion or added subsequently (i.e., in this embodiment chain extension may occur during and/or after the dispersion into water).

In an alternative embodiment, the prepolymer of the polyurethane may be dispersed in an aqueous medium in which the preformed vinyl polymer is already present, and then chain extended as described above. In an alternative embodiment, known as mass dispersion, the prepolymer may be dispersed in an aqueous medium in which the monomer component of the vinyl polymer has been dispersed, and then chain extended as described above. The monomer component of the vinyl polymer is then polymerized as described below.

The prepolymer may be dispersed in water using techniques well known in the art. Preferably, the prepolymer is added to water while stirring, or alternatively, water may be stirred into the components of the prepolymer.

Chain extension may be carried out at elevated temperature, reduced temperature or at ambient temperature. Conventional temperatures are from about 5 ℃ to 90 ℃, more preferably from 10 ℃ to 60 ℃.

It is well known that the glass transition temperature (Tg) of a polymer is the temperature at which the polymer transitions from a glassy, brittle state to a plastic, rubbery state. The glass transition temperature of the polymers in the examples was calculated by the Fox equation. Thus, the Tg (kelvin) of a copolymer with "n" copolymerized comonomers is according to the equation "1/Tg ═ W₁/Tg₁+W₂/Tg₂+…………W_n/Tg_n", by the weight fraction W of each comonomer species and the Tg value (kelvin) of the homopolymer obtained from the various comonomers. The calculated Tg (kelvin) can be easily converted to ℃.

In a preferred embodiment, the vinyl polymer has a Tg of 20 ℃ or less, more preferably 15 ℃ or less, most preferably 10 ℃ or less, especially 5 ℃ or less.

In another aspect of the invention, the vinyl polymer is a heterophasic polymer, meaning that: the vinyl polymer comprises at least one soft phase (Tg < 25 ℃, more preferably ≦ 20 ℃) and a hard phase (Tg ≧ 25); or vinyl polymers, are prepared by a technique known as energy feeding (described in us patent 3804881), resulting in a gradient particle morphology, provided that: the total Tg of the vinyl polymer (based on the comonomers in all phases) calculated according to the Fox equation is below ambient temperature.

The vinyl polymer may also be an oligomer-supported polymer, which means that a vinyl oligomer having a low weight average molecular weight Mw (typically 5000 to 50000 daltons) is first prepared as a stabilizer for the second phase, and then, in this second phase, the vinyl polymer is prepared in the presence of the vinyl oligomer and the polyurethane. In this case the polymer is a vinyl polymer, which should preferably have a Tg below ambient temperature, the Tg of the oligomer can vary, but it is preferred that the total Tg of the oligomer and the polymer is below ambient temperature.

Preferably, the vinyl polymer has a weight average molecular weight (Mw) of at least 200000g/mol, more preferably 250,000g/mol or more, most preferably 500,000g/mol or more.

The particle size of the vinyl polymer is preferably between 20 and 800nm, more preferably between 25 and 600nm, most preferably between 30 and 400 nm.

As used herein, vinyl polymer refers to a homopolymer or copolymer obtained by addition polymerization (using a free radical initiated process, typically in an aqueous medium), preferably by aqueous emulsion polymerization, of a monomer composition comprising one or more monomers of the formula CH₂＝CR¹R²Monomer (I) wherein R¹And R²Each independently selected from the group consisting of H, optionally substituted alkyl having 1 to 20 carbon atoms (more preferably 1 to 8 carbon atoms), optionally substituted alkyl having 5 to 20Cycloalkyl of carbon atoms, optionally substituted acyl and others. The above ethylenically unsaturated monomers are referred to herein as vinyl monomers. Examples of such monomers include 1, 3-butadiene, isoprene, styrene, alpha-methylstyrene, divinylbenzene, acrylonitrile, methacrylonitrile, vinyl halides (such as vinyl chloride), vinyl esters (such as vinyl acetate, vinyl propionate, vinyl laurate), vinyl esters of branched alkane carboxylic acids (e.g. VeoVa)^TM9 and VeoVa^TMVeoVa is a trademark of Shell), heterocyclic vinyl compounds, alkyl esters of monoethylenically unsaturated dicarboxylic acids, such as di-n-butyl maleate and di-n-butyl fumarate, and ethylenically unsaturated mono-or dicarboxylic acids, such as acrylic acid, methacrylic acid, 2-carboxyethyl acrylate, fumaric acid, maleic acid and itaconic acid, and optionally substituted alkyl esters thereof having from 1 to 20 carbon atoms.

In a preferred embodiment of the present invention, the vinyl polymer comprises an acrylic polymer. In this context, acrylic polymer refers to a homopolymer or copolymer obtained by addition polymerization of a monomer composition comprising at least 40% by weight of one or more monomers of formula CH₂＝CR³-COOR⁴Monomer (II) wherein R³Is H or methyl, R⁴Is H, an optionally substituted alkyl group having 1 to 20 carbon atoms (more preferably 1 to 8 carbon atoms) or a cycloalkyl group having 5 to 20 carbon atoms. Such monomers are referred to herein as acrylic monomers. More preferably, the monomer composition comprises at least 50 wt% of acrylic monomer, in particular at least 60 wt% of acrylic monomer. Examples of such acrylic monomers include methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, isopropyl (meth) acrylate, n-propyl (meth) acrylate, and hydroxyalkyl (meth) acrylates such as hydroxyethyl (meth) acrylate and 2-hydroxypropyl (meth) acrylate. Preferred acrylic monomers include methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, and 2-ethylhexyl (meth) acrylate.

Where the vinyl polymer comprises an acrylic polymer, the monomer composition used to form the acrylic polymer may be vinyl, in addition to the acrylic monomer defined above and copolymerized with the acrylic monomer described above.

Preferably, the vinyl polymer comprises 8 wt.% or less, more preferably 5 wt.% or less, most preferably 2 wt.% or less, particularly 0.5 wt.% or less, most particularly 0 wt.% of monomers containing ionic or potentially ionic water-dispersing groups. This provides additional colloidal stability.

The vinyl polymer may generally advantageously comprise comonomers to provide an adhesion function and/or a crosslinking function to the resulting polymer coating. Examples of such comonomers, some of which have been mentioned above, include acrylic and methacrylic monomers having at least one free carbonyl, carboxyl, hydroxyl, epoxy, acetoacetoxy or amino group, such as acrylic and methacrylic acid (and their amides, hydroxyalkyl and aminoalkyl esters), glycidyl acrylate, glycidyl methacrylate, diacetone acrylamide, acetoacetoxyethyl methacrylate, t-butylaminoethyl methacrylate and dimethylaminoethyl methacrylate; other adhesion promoting monomers include heterocyclic vinyl compounds such as vinyl pyrrolidone, vinyl imidazole, phenoxyethyl (meth) acrylate, and tetrahydrofurfuryl (meth) acrylate and cyclic ureido compounds. The vinyl polymer may also contain monomers that will crosslink (or "pre-crosslink") in situ in the polymer, i.e., crosslink while the polymer is being formed (rather than crosslink after coating formation as with the crosslinking monomers mentioned above); examples of such monomers include allyl methacrylate, tetraethylene glycol methacrylate and divinylbenzene.

The above monomers (described in the preceding paragraph) are generally used in amounts of 0.05 to 15 wt.%, more usually 0.5 to 10 wt.% or 1 to 6 wt.%, relative to the total weight of monomers used in the polymerization.

As noted above, in an alternative embodiment of the invention, the amino functionality may be incorporated into the heterophasic polymer by: polymers containing monomeric units of an ethylenically unsaturated acid (such as acrylic acid or methacrylic acid) are prepared, and then at least a portion of the carboxylic acid groups are converted to amino groups (as part of the amino ester groups) by an imidization reaction using an alkylenimine (such as ethylenimine or propyleneimine).

The vinyl polymer, if preformed, preferably has a solids content of between 20 and 70 wt%, more preferably between 30 and 60 wt%, most preferably between 35 and 55 wt%.

As noted above, the polyurethane and vinyl polymer may be combined in a blend, for example, after the polyurethane is prepared, the preformed vinyl polymer is post-added. Alternatively, the vinyl polymer may be prepared in the presence of a polyurethane (prepared in situ). If the vinyl polymer is prepared in its presence during and/or after the formation of the polyurethane, the resulting combination is referred to as a hybrid. The use of heterocycles allows further tailoring of the properties of the coatings obtained from the compositions of the invention.

The vinyl polymer, if formed in situ, is made by an aqueous free radical polymerization process, and the polymerization may be carried out simultaneously with, or after, the chain extension step of the polyurethane, or partially simultaneously with and partially after the chain extension step.

All of the monomers to be polymerized in the hybrid may be present at the beginning of the polymerization, or in case all or part of the monomers to be polymerized are introduced after the aqueous prepolymer dispersion is formed, some or all of these monomers may be added to the reaction medium during the polymerization process (added in one or more stages or added continuously). Alternatively, some or all of the monomers may be converted to polymers and present in the aqueous phase before the urethane prepolymer is dispersed in the aqueous phase.

When preparing the hybrid, the monomers used to prepare the in situ prepared polymer may be introduced at any suitable stage in the process. For example, when an aqueous dispersion of a urethane prepolymer is formed in a polyurethane-forming process, all of the monomers of the vinyl polymer may be added to the prepolymer before the prepolymer is dispersed in water; or all of the monomers may be added after dispersion (or already added to the water before the prepolymer is dispersed in the water); or a part of the monomers is added to the prepolymer before the above-mentioned dispersion, and the rest is added after the above-mentioned dispersion. In the case where all or a portion of the monomers are added to the prepolymer before the prepolymer is dispersed in water, the monomers may be added to the prepolymer after the prepolymer is formed or before it is formed, or some of the monomers may be added after the prepolymer is formed and some of the monomers may be added before the prepolymer is formed. In the case where any monomer is added prior to prepolymer formation, the monomer may (as described above) provide at least part of the solvent system for the reaction used to form the prepolymer (if the prepolymer has the appropriate solvent characteristics). Specific examples of such processes are described in detail in patents US 5137961 and US 4664430.

Polymerizing a monomer composition to form a vinyl polymer typically requires the use of a free radical generating initiator to initiate polymerization. Suitable free radical generating initiators include inorganic peroxides such as K, Na persulphate or ammonium, hydrogen peroxide or percarbonate; organic peroxides such as acyl peroxides (including, for example, benzoyl peroxide), alkyl hydroperoxides (such as t-butyl hydroperoxide (tBHPO) and cumene hydroperoxide); dialkyl peroxides such as di-tert-butyl peroxide; peroxy esters such as t-butyl perbenzoate and the like; mixtures may also be used. The peroxy compounds are in some cases advantageously used in combination with suitable reducing agents, such as sodium or potassium pyrosulfate or sodium or potassium bisulfite and erythorbic acid (redox systems). Azo compounds, such as azoisobutyronitrile, may also be used. EDTA (EDTA is ethylenediaminetetraacetic acid) may also be usefully employed as part of the redox initiator system. In particular, an initiator system is used which partitions between the aqueous and organic phases, for example a combination of tert-butyl hydroperoxide, erythorbic acid and fe. The amount of initiator or initiator system used is conventional, for example in the range from 0.05 to 6% by weight, based on the total amount of monomers used.

The molecular weight of the vinyl polymer may be controlled by catalyzing chain transfer agents, such as mercaptans, e.g., n-dodecyl mercaptan, n-octyl mercaptan, t-dodecyl mercaptan, mercaptoethanol, isooctyl thioglycolate, C, or by using chain transfer agents, such as₂-C₈Mercaptocarboxylic acids and esters thereof (e.g., 3-mercaptopropionic acid and 2-mercaptopropionic acid); halogenated hydrocarbons are, for example, carbon tetrabromide and trichlorobromomethane. In Catalytic Chain Transfer Polymerization (CCTP), free radical polymerization is carried out using catalytic amounts of selected transition metal complexes, specifically selected cobalt chelates, which act as catalytic chain transfer agents.

Combinations of conventional chain transfer agents and catalytic chain transfer agents may also be used.

Aqueous polymerization of preformed vinyl polymers generally requires the presence of stabilizing and/or dispersing materials such as the oligomers described in WO95/29963 for the preparation of oligomer-supported polymers, in the preparation of aqueous latexes of vinyl polymers it is necessary to use conventional emulsifiers such as anionic and/or nonionic emulsifiers such as Na salts of dialkyl sulfosuccinates, sulfated oils, alkylsulfonic acids, Na salts of alkyl esters of sulfuric acid, Na, K and NH₄Salts (such as sodium lauryl sulfate), C_22-24Fatty alcohols, ethoxylated fatty acids and/or fatty amines, and Na, K and NH of fatty acids₄Salts, such as sodium stearate and sodium oleate are generally used in amounts of 0.1 to 5% by weight, based on the weight of the total vinyl monomers used. However, when an in situ process is used to form the vinyl polymer, the polyurethane polymer containing internal dispersing groups generally does not require the use of a separately added conventional emulsifier, since the polyurethane itself acts as an effective dispersant for the polymerization, but conventional emulsifiers can still be used if desired。

In an embodiment of the present invention, there is provided a process for preparing an aqueous coating composition as described herein, the process comprising the steps of:

(I) (i) reacting components (a) (1) to (a) (4) together to form an isocyanate-terminated prepolymer;

(ii) dispersing the isocyanate-terminated prepolymer in water;

(iii) chain extending the isocyanate-terminated prepolymer by reaction with an active hydrogen chain extending compound to form polyurethane; and is

(II) blending at least a preformed vinyl polymer having a Tg below ambient temperature.

In a further embodiment of the present invention, there is provided a process for preparing an aqueous coating composition as described herein, the process comprising the steps of:

(I) (i) reacting components (a) (1) to (a) (4) together to form an isocyanate-terminated prepolymer;

(ii) dispersing the isocyanate-terminated prepolymer in water;

(iii) chain extending the isocyanate-terminated prepolymer by reaction with an active hydrogen chain extending compound to form polyurethane; and is

(II) mixing the monomers and then reacting under conditions sufficient to effect emulsion polymerization to form a vinyl polymer having a Tg below ambient temperature.

In both of the above process embodiments, one of ordinary skill in the art will appreciate that: preferred sequences in step (I) are (I), (ii), then (iii); however, step (II) may also be carried out in step (I) after step (I) has been carried out, i.e. the monomers of step (II) may be added to the isocyanate-terminated prepolymer before carrying out step (II) or (iii).

Any or all of the above-described processes for preparing polyurethane and/or vinyl polymers may be carried out by techniques involving in-line mixing (described in Research Disclosure (2002), 457 (may), page 772-774) or by the batch dispersion techniques described above.

In the composition of the present invention, it is preferred that: the weight average particle diameter (Dw) (i.e., particle size, since the particles are substantially spherical) of any polyurethane vinyl polymer hybrid particle is in the range of 20 to 400nm, more preferably in the range of 30 to 150 nm. (it should be understood that Dw also applies to, for example, bimodal or multimodal particle size distributions and to the average of unimodal distributions). Smaller particle sizes may result in more transparent coatings, which is preferred.

There is further provided according to the present invention an aqueous coating composition which is substantially free of solvent. By "substantially solvent-free coating composition" is meant that the liquid medium of the composition comprises less than 5% by weight of organic solvent, more preferably less than 2% by weight of organic solvent, and most preferably no organic solvent at all. It is to be understood that no solvent at all means that no solvent is added, e.g. some small amount of solvent in the composition is a result of the addition of additives etc. (in this specification, organic plasticizers are also included within the term "solvent", such organic plasticizers (e.g., coalescing solvents) are also used in the art to lower the minimum film-forming temperature, but strictly speaking they are not solvents). In a particularly preferred embodiment of the invention, the compositions described herein are all solvent-free and thus plasticizer-free. Preferably, the polyurethane and vinyl polymers are prepared using a solventless process.

Preferably, the composition of the invention comprises a thermoplastic polyurethane and/or a vinyl polymer, but no thermosetting polymer, since the thermosetting polymer itself has a lower elongation at break. Preferably, the polyurethane and vinyl polymer are thermoplastic polymers.

The solids content of the aqueous composition of the invention is generally in the range of about 20-65 wt.%, more usually in the range of 30 to 55 wt.%, relative to the total weight. If desired, the solids content can be adjusted by adding water or removing water, for example by distillation or ultrafiltration.

In a further embodiment, there is provided an uncolored coating composition as described herein which when coated into a film results in a non-tacky film having an elongation at break of no less than 300%, more preferably no less than 390%. Preferably, the elongation at break is 800% or less, more preferably 600% or less.

The compositions of the present invention may be used, for example, to provide, if suitably formulated, films, including polishes, varnishes, lacquers or coatings, and the like. The compositions of the present invention may also be used to provide inks or adhesives. Optional additional additives or components (to form the composition) include, but are not limited to, defoamers, rheology control agents, thickeners, dispersion stabilizers (typically surfactants), wetting agents, fillers, extenders, fungicides, bactericides, antifreeze agents, crosslinking agents, coalescing agents, waxes, and pigments.

Preferably, the composition of the invention (if a crosslinkable composition) is crosslinkable at ambient temperature or below ambient temperature.

In one embodiment, there is provided a composition as described herein, further comprising up to 10 wt% of a crosslinking agent based on total polymer weight (polyurethane and vinyl polymer). The cross-linking agent is preferably selected from, but not limited to, the group comprising the following types: urea-formaldehyde, melamine-formaldehyde, carbodiimides, aziridines, isocyanates, epoxies, silanes, and/or mixtures thereof. Preferably, crosslinking occurs at or near ambient temperature and does not require excessive application of heat, such as baking. In another embodiment, the polyurethane is autoxidisable with unsaturated fatty acids incorporated into the polymer.

In a particularly preferred embodiment, the compositions described herein further comprise a pigment and/or a chain extender. Pigments that can be used in the present invention include, for example, titanium dioxide, iron oxide, chromium-based compounds, and metal phthalocyanine compounds. To achieve properties such as color, opacity and hiding power, pigments are finely divided inorganic or organic powders (usually having a particle size in the range of 0.1 to 10 μm, obtained by, for example, milling or grinding). They are usually incorporated into the coating compositions in the form of a dry powder or as a homogeneous dispersion of the pigments in a suitable carrier medium. Titanium dioxide (white pigment) is the most preferred pigment herein. Extenders that can be used include calcium carbonate and ceramic clays.

There is further provided a composition having a Pigment Volume Concentration (PVC) in the range of 10 to 70%, preferably in the range of 10 to 50%, more preferably in the range of 15 to 40% as described herein, wherein PVC is defined as follows:

wherein "binder" refers to the solid polymer in the composition of the first embodiment of the present invention.

In a further embodiment of the invention there is provided a pigmented composition as described herein having a pigment volume concentration PVC of 20 +/-2% which when applied to form a film results in a non-tacky film having an impact resistance of at least 35N, preferably at least 40N, when measured as described hereinafter.

In a further embodiment, there is provided a pigmented composition as described herein having a pigment volume concentration PVC of 20 +/-2% which, when applied to form a film, results in a tack-free film having an elongation at break of greater than or equal to 300%. Preferably, the elongation at break is 600% or less, more preferably 500% or less, most preferably 480% or less.

When pigments are added to the clear (unpigmented) coating compositions of the present invention, a decrease in elongation at break is generally observed, which can be defined in a quantitative manner as the ratio of (elongation of the unpigmented coating minus the elongation of the pigmented coating) to the elongation of the clear coating.

In a preferred embodiment, there is provided a pigmented composition as described herein having a pigment volume concentration PVC of 20 +/-2% which when applied to form a film results in a non-tacky film having an elongation at break which is reduced by less than 30%, more preferably by less than 25%, most preferably by less than 20% compared to an equivalent unpigmented film.

In another embodiment of the present invention, there is provided a composition having a pigment volume concentration PVC of 20 +/-2%, which composition when coated as a pigmented film resultsA non-tacky film having a hardness in the range of 15 to 35 seconds, an elongation at break > 300% and an impact resistance of at least 30N. Preferably, the composition has a reduction in elongation at break of less than 30% when compared to an equivalent unpigmented film.

The composition of the present invention may be combined with one or more additional binders. The combination may be prepared by blending or by in situ. The combination by blending can be achieved by simple mixing with stirring, or can be achieved by mixing the components together by an in-line mixing process.

These additional binders may have a monomodal or bimodal particle size distribution, which may be single phase, multiphase, seed polymer or oligomer supported polymers, or may be made by an energy addition process. These additional binders may be self-crosslinking or may be pre-crosslinked.

These additional binders may be vinyl polymers, alkyd polymers, polyesters, epoxy polymers, fluoropolymers, or other polyurethanes and/or hybrids of any of the above polymers, such as polyurethane/acrylics and urea alkyds. Preferably, any additional binder is a vinyl polymer.

The amount of the composition of the present invention of the pre-additional binder combination is determined by the desired balance of properties. Higher amounts of the composition of the invention (e.g. 20% w/w) will result in higher impact resistance, higher toughness and a higher level of elongation at break than lower amounts (e.g. 5% w/w).

In a particular embodiment, there is provided a pigmented composition according to the invention (alone or in combination with other binders) having a pigment volume concentration PVC of 20 +/-2%, which composition when coated into a film gives a non-tacky film having an impact resistance of at least 30N, which has a reduction in elongation at break of less than 30% when compared to an equivalent non-pigmented film.

In a further specific embodiment, a pigmented composition according to the invention is provided (alone or in combination with other binders) with a pigment volume concentration PVC of 20 +/-2%, which composition when applied as a film results inA non-tacky film having a hardness in the range of 15 to 35 seconds.

In another embodiment, a pigmented composition according to the invention is provided (alone or in combination with other binders) with a pigment volume concentration PVC of 20 +/-2%, which composition when applied as a film resultsA non-tacky film having a hardness in the range of 15 to 35 seconds and an impact resistance of at least 30N, which has a reduction in elongation at break of less than 30% when compared to an equivalent uncolored film.

In another embodiment, there is provided an aqueous coating composition comprising:

(i) from 50 to 95 weight percent of a polyurethane obtained by the reaction of (a) an isocyanate-terminated prepolymer and (b) an active hydrogen chain extending compound, the isocyanate-terminated prepolymer being obtained from the reaction of components comprising:

(1)10 to 40 weight percent of at least one polyisocyanate, at least 50 weight percent of which is at least one aliphatic polyisocyanate;

(2)0 to 10 wt% of at least one isocyanate reactive compound having a weight average molecular weight in the range of 50 to 500g/mol comprising ionic or potentially ionic water dispersing groups;

(3)50 to 89 wt% of at least one isocyanate reactive compound having a weight average molecular weight in the range of 501 to 5000 g/mol;

(4)0 to 10 wt% of at least one isocyanate reactive compound not included in (2) having a weight average molecular weight in the range of 50 to 500 g/mol;

wherein the NCO/OH ratio is in the range of 1.75 to 1.05;

a carbamate/urea ratio > 1; and is

(1) The sum of (2), (3) and (4) is 100%;

(ii)5 to 50 wt% of a vinyl polymer having a Tg below ambient temperature, a weight average molecular weight of at least 200000g/mol and comprising ≤ 8 wt% of monomers containing ionic or potentially ionic groups;

wherein (i) and (ii) total 100%; and

(iii) a liquid medium comprising ≤ 10 wt% of an organic solvent;

the composition further comprises a pigment, wherein the pigment volume concentration is in the range of 10 to 70%, and

the aqueous coating composition is obtained when having a pigment volume concentration PVC of 20 +/-2% and is coated to form a filmA non-tacky film having a hardness in the range of 15 to 35 seconds, an impact resistance of at least 30N, and a fracture generation rate of not less than 300%.

The invention further provides a method of coating a substrate surface with an aqueous composition as defined above. The coated composition may be allowed to dry naturally at ambient temperature, or the drying process may be facilitated by heating. Preferably, the substrate comprises an architectural surface. Preferably, the surface is porous, more preferably the surface is a wood surface. In particular, the compositions of the present invention are suitable for providing a protective coating base for wood substrates (e.g., wood flooring, window frames), plastic articles, metals, and paper.

The invention further provides a coating obtainable from the above composition.

The invention further provides a substrate having a coating as obtained above.

Also provided is a film obtained from the above composition.

The invention will now be further illustrated by the following examples, to which, however, the invention is in no way limited. All parts, percentages and ratios are by weight unless otherwise indicated.

The materials used

DMPA ═ dimethylolpropionic acid

Priplast 3192 ═ polyester polyol based on dimer fatty acid, from Uniquema, with Mw of 2000 and OH number of 56

MMA ═ methyl methacrylate

BA ═ n-butyl methacrylate

IPDI ═ isophorone diisocyanate (aliphatic)

Ionol CP ═ butylated hydroxytoluene

TEA ═ triethylamine

BDG ═ butyl diglycol (coalescent)

Dehydran 1293 ═ siloxane-based antifoam from Cognis

Borchigel L75 ═ associative thickeners available from Borchers

3-aminopropanol in the form of an AMP-90 ═ 90% solution

Surfynol 104E ═ wetting agent available from Air Products

NeoCryl BT-24 ═ vinyl Polymer dispersions from DSM Neoresins BV

Tioxide Kronos 2190 ═ white pigment from Kronos

NPG ═ neopentyl glycol

Note that: MMA: BA in the range of 0: 100 to 100: 0 was used to prepare the following vinyl polymers.

Example 1(E1) preparation of polyurethane vinyl hybrid (80/20)

At 2000cm equipped with a thermometer and overhead stirrer³The flask was charged with DMPA (44.0g), Priplast 3192(623.1g), MMA (73.8g), BA (146.2g), IPDI (212.9g) and Ionol CP (0.33 g). The NCO/OH ratio was 1.50.

The mixture was heated to 50 ℃ and tin octoate (0.16g) was then added. The reaction was allowed to exotherm to 90 ℃. After the exotherm was complete, the reaction was held at 90 ℃ for 1 hour and another portion of tin octoate (0.16g) was added. Thereafter, the reaction temperature was maintained at 90 ℃ for an additional 1.5 hours.

The NCO content of the isocyanate-terminated prepolymer was 2.32% (theoretical 2.44%). After cooling the prepolymer to 75 ℃, TEA (29.9g) was added.

The dispersion of the isocyanate-terminated prepolymer was prepared by the following steps: 950.1g of TEA-neutralized, isocyanate-terminated prepolymer was added to 1615g of deionized water over 1 hour. During the dispersion, the temperature of the isocyanate terminated prepolymer was maintained at 70 ℃ and the temperature of the dispersion was controlled at 25 ℃. When the addition of the prepolymer was complete, a 15.2% hydrazine solution (45.4g) was added along with water (15.0g) to achieve chain extension (0.85 based on residual NCO content SA). SA herein has the meaning of stoichiometric equivalent.

After 15 minutes of completion of the chain extension, a 10% aqueous tBHPO solution (9.26g) was added together with a 1% aqueous FeEDTA solution (0.92 g). Free radical polymerization was carried out by adding 2.5% aqueous solution of erythorbic acid (22.2g) (pH adjusted to 8) to prepare a polyurethane vinyl hybrid dispersion.

The batch was filtered through a filter fabric to remove any coagulum formed during the reaction. The resulting aqueous binder dispersion had a solids content of 35%. The total polyurethane/vinyl polymer ratio of example 1 was 80/20 wt%, the vinyl polymer having a calculated Tg of-10 ℃.

Example 2(E2) -preparation of polyurethane vinyl hybrid

Example E2 was prepared as above example E1, except that the vinyl polymer was made to have a calculated Tg of-30 ℃ according to the Fox equation by varying the weight fraction of comonomer.

Example 3(E3) -preparation of polyurethane vinyl hybrid

Example E3 was prepared as above example E1, except that the vinyl polymer was made to have a calculated Tg of-50 ℃ according to the Fox equation by varying the weight fraction of comonomer.

Comparative example 1(CE1) -preparation of polyurethane vinyl hybrid

Example CE1 was prepared as above in example E1, except that the vinyl polymer was made to have a calculated Tg of 105 ℃ according to the Fox equation by varying the weight fraction of comonomer.

Comparative example 2(CE2) -preparation of a polyurethane vinyl hybrid (NCO `)OH ratio > 1.75)

At 2000cm equipped with a thermometer and a cantilever stirrer³The flask was charged with DMPA (44.0g), Priplast 3192(565.0g), MMA (220.0g), IPDI (271.0g) and Ionol CP (0.33 g). The NCO/OH ratio was 2.0.

The mixture was heated to 50 ℃ and tin octoate (0.16g) was then added. The reaction was allowed to exotherm to 90 ℃. After the exotherm was complete, the reaction was held at 90 ℃ for 1 hour and another portion of tin octoate (0.16g) was added. Thereafter, the reaction temperature was maintained at 90 ℃ for an additional 1.5 hours.

The NCO content of the isocyanate-terminated prepolymer was 4.38% (theoretical 4.66%). After cooling the prepolymer to 75 ℃, TEA (29.9g) was added.

The dispersion of the isocyanate-terminated prepolymer was prepared by the following steps: 950.1g of TEA-neutralized, isocyanate-terminated prepolymer was added to 1615g of deionized water over 1 hour. During the dispersion, the temperature of the isocyanate terminated prepolymer was maintained at 70 ℃ and the temperature of the dispersion was controlled at 25 ℃. When the addition of the prepolymer was complete, a 15.2% hydrazine solution (86.3g) was added along with water (15.0g) to achieve chain extension (0.85 based on residual NCO content SA).

After 15 minutes of completion of the chain extension, a 10% aqueous tBHPO solution (9.26g) was added together with a 1% aqueous FeEDTA solution (0.92 g). The radical polymerization was carried out by adding 2.5% aqueous solution of erythorbic acid (22.2g) (pH adjusted to 8) to prepare a polyurethane vinyl hybrid dispersion.

The batch was filtered through a filter fabric to remove any coagulum formed during the reaction. The resulting aqueous binder dispersion had a solids content of 35%.

The total polyurethane/vinyl polymer ratio in CE2 was 80/20 wt%, with the vinyl polymer having a calculated Tg of 105 ℃.

Comparative example 3(CE3) -preparation of polyurethane vinyl hybrid

Comparative example CE3 was prepared as comparative example CE2 above, except that the vinyl polymer had a calculated Tg of-50 ℃.

COMPARATIVE EXAMPLE 4(CE4) preparation of polyurethane vinyl hybrid (20/80)

At 1000cm equipped with a thermometer and overhead stirrer³The flask was charged with DMPA (20.0g), Priplast 3192(283.2g), MMA (33.5g), BA (66.5g), IPDI (96.8g) and Ionol CP (0.15 g). The NCO/OH ratio was 1.50.

The mixture was heated to 50 ℃ and tin octoate (0.08g) was then added. The reaction was allowed to exotherm to 90 ℃. After the exotherm was complete, the reaction was held at 90 ℃ for 1 hour and another portion of tin octoate (0.08g) was added. Thereafter, the reaction temperature was maintained at 90 ℃ for an additional 1.5 hours.

The NCO content of the isocyanate-terminated prepolymer was 2.23% (theoretical 2.44%). After cooling the prepolymer to 75 ℃, TEA (13.6g) was added.

The dispersion of the isocyanate-terminated prepolymer was prepared by the following steps: 246.5g of TEA-neutralized, isocyanate-terminated prepolymer was added to 1636.2g of deionized water over a period of 1 hour. During the dispersion, the temperature of the isocyanate terminated prepolymer was maintained at 70 ℃ and the temperature of the dispersion was controlled at 25 ℃. When the addition of the prepolymer was complete, a 15.2% hydrazine solution (11.4g) was added along with water (15.0g) to achieve chain extension (0.85 based on residual NCO content SA). SA herein has the meaning of stoichiometric equivalent.

After 15 minutes of completion of the chain extension, additional vinyl monomer was added to the reactor. The monomer phases were MMA (112.7g) and BA (223.3g), the monomer phases were swollen for 30 minutes and then a 10% aqueous tBHPO solution (38.4g) was added together with a 1% aqueous FeEDTA solution (3.8 g). The radical polymerization was carried out by adding 2.5% aqueous solution of erythorbic acid (46.1g) (pH adjusted to 8) to prepare a polyurethane vinyl hybrid dispersion. After the addition of isoascorbic acid was completed for 15 minutes, the batch was cooled to room temperature. The monomer was added to the reactor a second time at room temperature. The monomer phase was MMA (128.8g) and BA (255.2g), and the monomer phase was swollen for 30 minutes. The radical polymerization was carried out by adding 2.5% aqueous solution of erythorbic acid (46.1g) (pH adjusted to 8) to prepare a polyurethane vinyl hybrid dispersion.

The batch was filtered through a filter fabric to remove any coagulum formed during the reaction. The resulting aqueous binder dispersion had a solids content of 35%.

The total polyurethane/vinyl polymer ratio in CE4 was 20/80 wt% and the vinyl polymer had a calculated Tg of-10 ℃.

Transparent formulations

To 100 grams of the aqueous adhesive dispersion prepared in the above example were added, while stirring, butyl diglycol (BDG, 2.5g) and Dehydran 1293(1.0 g). The viscosity of the formulation was adjusted to be in the range of 500 to 2000mpa.s with 50 wt% Borchigel L75.

Colored formulations

The pigment paste was prepared by: water (16.9g), AMP-90(0.6g), Dehydran 1293(1.4g), Surfynol 104E (1.4g), NeoCryl BT-24(8.9g) and Tioxide Kronos 2190(70.8g) were mixed under high shear.

To 88 parts of the clear formulation prepared above, 30 parts of pigment paste were added, resulting in a pigment volume concentration PVC of about 20%.

Testing for tack

A 120 μm wet film of clear formulation or pigmented formulation was cast onto a glass plate and left to dry at ambient temperature for 4 hours. Then, a piece of cotton wool (about 1 cm) was laid³0.1g) was placed on the dried film and a 1kg weight was placed on top of the batt for 10 seconds. If the piece of batting can be removed from the substrate by hand on the filmA film is considered to be non-tacky if it leaves no lint or mark on it. The results are shown in Table 1.

Measurement ofHardness of

As used hereinHardness is a standard measure of hardness, which determines how the viscoelastic properties of a film formed from a composition slow down the rocking motion that deforms the surface of the film, and utilizes Erichsen according to DIN53157^TMHardness meter measurement, in which a thin film is cast on a glass plate at room temperature with a wet film thickness of 80 μm, and then left to stand for 30 minutes. The film was then transferred to an oven at 60 ℃ and allowed to stand for 16 hours. The results are expressed asAnd second. The results are listed in table 1 below.

Determination of elongation at Break

A 400 μm wet film of clear formulation or pigmented formulation was cast onto a glass plate containing release paper. The film was dried at ambient conditions for 4 hours and then aged at 50 ℃ for 16 hours. Then, the film was removed from the glass plate. At least 5 dumbbell-shaped specimens were cut from the free film using a DIN52-910-53 cutter. The thickness of these films was measured. Using Instron^TM5565 the stress-strain test is carried out at a draw-speed (draw-bench speed) of 100 mm/min. The results are listed in table 2 below.

Impact resistance on wood

A 250 μm wet film of the pigmented formulation was coated on knife wood and dried at ambient conditions for 4 hours and then aged at 50 ℃ for 16 hours. The test panels were then calibrated at 22 ℃ and 50% relative humidity for 6 hours. Then, impact tests were carried out in accordance with DIN 51155 (at room temperature of 20+/-3 ℃). Impact resistance may be used to indicate, for example, to what extent hailstone resistance is. The results are listed in table 2 below.

TABLE 1

TABLE 2

a) The U/Ua ratio being the ratio of carbamate/urea

b) PU/V is the ratio of polyurethane/vinyl polymer, in% by weight

Comparative example CE1 has a high Tg vinyl polymer (ii), which results in a pigmented coating with lower impact resistance.

Comparative example CE2 has an NCO/OH ratio > 1.75 and a vinyl polymer with the same (high) Tg as CE1, which results in a pigmented coating with lower impact resistance and both an unpigmented coating and a pigmented coating with lower elongation values.

Comparative example CE3 had an NCO/OH ratio > 1.75, which resulted in a pigmented coating with lower impact resistance.

Comparative example CE4 had an inverted polyurethane/vinyl polymer ratio of 20/80 (in wt.%), indicating that a large amount of soft vinyl polymer gave a coating that was tacky and had lower impact resistance.

Claims (18)

1. An aqueous coating composition comprising:

(i) from 50 to 95 weight percent of a polyurethane obtained by the reaction of (a) an isocyanate-terminated prepolymer and (b) an active hydrogen chain extending compound, the isocyanate-terminated prepolymer being obtained from the reaction of components comprising:

(1)10 to 40 weight percent of at least one polyisocyanate, at least 50 weight percent of which is at least one aliphatic polyisocyanate;

(2)0 to 10 wt% of at least one isocyanate reactive compound having a weight average molecular weight in the range of 50 to 500g/mol containing ionic or potentially ionic water dispersing groups;

(3)50 to 89 wt% of at least one isocyanate reactive compound having a weight average molecular weight in the range of 501 to 5000 g/mol;

(4)0 to 10 wt% of at least one isocyanate-reactive compound not included in (2) having a weight average molecular weight in the range of 50 to 500g/mol,

wherein the NCO/OH ratio is in the range of 1.75 to 1.05, and

(1) the sum of (2), (3) and (4) is 100%;

(ii)5 to 50 wt% of a vinyl polymer having a Tg below ambient temperature, defined as 25+/-3 ℃, wherein the vinyl polymer has a weight average molecular weight of at least 200000g/mol

Wherein (i) and (ii) total 100%; and

(iii) a liquid medium comprising ≤ 10 wt% of an organic solvent.

2. The composition of claim 1, wherein the vinyl polymer comprises 8 wt.% or less of monomers containing ionic or potentially ionic water-dispersing groups.

3. The composition of any one of the preceding claims 1 or 2, further comprising a pigment, wherein the pigment volume concentration PVC is in the range of 10 to 70%, wherein the pigment volume concentration PVC is defined as follows:

wherein binder refers to the solid polymer in the composition.

4. A composition according to any of the preceding claims 1-2 having a pigment volume concentration PVC of 20 +/-2%, which composition when coated as a film gives a non-tacky film having an impact resistance of at least 30N, wherein the pigment volume concentration PVC is defined as follows:

wherein binder refers to the solid polymer in the composition.

5. The composition according to any one of the preceding claims 1-2, which when coated as a film gives a tack-free film with an elongation at break of ≥ 300%.

6. Composition according to any one of the preceding claims 1-2, which, when coated as a pigmented film with a pigment volume concentration PVC of 20 +/-2% >, resultsA non-tacky film having a hardness in the range of 15 to 35 seconds, wherein the pigment volume concentration PVC is defined as follows:

wherein binder refers to the solid polymer in the composition.

7. The composition of any of the preceding claims 1-2, wherein the aliphatic isocyanate is selected from the group consisting of isophorone diisocyanate, 4' -dicyclohexylmethane diisocyanate, 1, 6-hexamethylene diisocyanate, and mixtures thereof.

8. A composition as claimed in any one of the preceding claims 1-2, wherein the weight of the active hydrogen chain extender is such that the ratio of active hydrogen in the chain extender to isocyanate groups in the prepolymer is in the range of from 0.4 to 2.0.

9. The composition of any of the preceding claims 1-2, wherein the polyurethane has urethane and urea linkages and the polyurethane and vinyl polymer are present as part of a hybrid.

10. Composition according to any one of the preceding claims 1-2, wherein the carbamate/urea ratio is > 1.

11. The composition of any of the preceding claims 1-2, which is substantially free of solvent.

12. The composition of any of the preceding claims 1-2 having a pigment volume concentration of 20 +/-2%, which when coated into a film results in a non-tacky film having a reduction in elongation at break of less than 30% compared to an equivalent non-pigmented film, wherein the pigment volume concentration PVC is defined as follows:

wherein binder refers to the solid polymer in the composition.

13. A composition according to any one of the preceding claims 1-2, which when coated as a pigmented film having a pigment volume concentration PVC of 20 +/-2%Hardness of 15 to 35 secondsA non-tacky film in the range of having an elongation at break of not less than 300% and an impact resistance of at least 30N, wherein the pigment volume concentration PVC is defined as follows:

wherein binder refers to the solid polymer in the composition.

14. The composition of claim 13, having a reduction in elongation at break of less than 30% when compared to an equivalent unpigmented film.

15. A coating obtained from the composition of any one of claims 1 to 14.

16. A method of coating a surface of a substrate with a composition according to any one of claims 1 to 14, the method comprising the steps of: applying the composition to the surface; the composition is then dried.

17. The method of claim 16, wherein the substrate is selected from the group consisting of wood, plastic, metal, and paper.

18. A film obtained from the composition of any one of claims 1 to 14.