EP0964751B1 - Process for producing scratch resistant coatings and its use, in particular for producing multilayered coats of enamel - Google Patents

Abstract

The present invention relates to a process for producing scratch-resistant coatings which comprises applying a coating composition which in the cured state has a storage modulus E' in the rubber-elastic range of at least 107.6 Pa and a loss factor tan delta at 20° C. of not more than 0.10, the storage modulus E'0 and the loss factor having been measured by dynamic mechanical thermoanalysis on homogeneous free films having a film thickness of 40±10 mum. The present invention additionally relates to the use of the process for producing multicoat finishes and also to coating compositions suitable for this process.

Description

The present invention relates to a method for producing scratch-resistant coatings, especially scratch-resistant Coating systems.

The present invention also relates to methods suitable for this method Coating agents.

In recent years, the development has become more acid and etch resistant Clearcoats for automotive OEM painting have made great strides. In newer ones There is now increasing demand from the automotive industry for scratch-resistant materials Clear varnishes, which in the other properties at the same time the previous property level maintained.

Currently, there is one for the quantitative assessment of scratch resistance Coating various test methods, such as testing using the BASF brush test, using the AMTEC wash brush system or Various test methods from automobile manufacturers, among others However, the disadvantage is that the individual test results cannot be correlated in every case, i.e. that the Test results for one and the same coating depending on the test method selected can be very different and passing a scratch resistance test u.U. no conclusions about the behavior in another scratch test allowed.

There is therefore a desire for a method for the quantitative assessment of the Scratch resistance, which is reliable with the help of only one examination of the sample Statements about the scratch resistance of the coating are possible. In particular, the result of this investigation should provide reliable conclusions on the scratch resistance of the coating in the various above Allow scratch resistance tests.

In the literature there are already some studies on the physical Processes in the creation of scratches and correlations derived from them between the scratch resistance and other physical parameters of the Coating described. A current overview of various literature Scratch-resistant coatings can be found, for example, in J.L. Courter, 23rd Annual International Waterborne, High-Solids and Powder Coatings Symposium, New Orleas 1996.

In addition, for example, in the article by S. Sano et al., "Relationship Between Viscoelastic Property and Scratch Resistance of Top-Coat Clear Film", Toso Kagaku 1994, 29 (12), pages 475-480, the scratch resistance of various, thermal curing melamine / acrylate or isocyanate / acrylate systems with the aid of a wash brush test and the scratch resistance found is related to the viscoelastic properties of the coating.

The authors conclude from the test results described there that Coatings show good scratch resistance if either so-called "inter-crosslinking molecular weight" is less than 500 or if the Glass transition temperature is 15 ° C or lower. In the case of clear lacquer films in Automotive sector, however, it is necessary to achieve sufficient Hardness of the coatings the glass transition temperature above 15 ° C. Improving the scratch resistance by increasing the number of In practice, networking points often lead to diverse problems such as for example, insufficient storage stability and often only incomplete Reaction from all networking sites.

Also in the article by M. Rösler, E. Klinke and G. Kunz in Farbe + Lack, Heft 10, 1994, pages 837 - 843, the scratch resistance of different coatings examined using various test methods. It was found that hard paints with the same load a higher damage and thus less Show scratch resistance than soft paints.

Furthermore, the conference report by B.V. Gregorovich and P.J. Mc Gonical, Proceedings of the Advanced Coatings Technology Conference, Illinois, USA, November 3-5, 1992, pages 121-125, found that by the Increasing the plastic character (toughness) of coatings Scratch resistance due to the improved plastic flow (healing of the Scratches) is improved, but increasing the plastic character Limits are set by the other properties of the coating.

Furthermore, from P. Betz and A. Bartelt, Progress in Organic Coatings, 22 (1993), Pages 27 - 37, various methods for determining the scratch resistance of Known coatings. This article also points out that the scratch resistance of coatings other than that Glass transition temperature, for example, due to the homogeneity of the Network is influenced.

This article suggests the scratch resistance of the clear coat by incorporating siloxane macromonomers because these siloxane macromonomers lead to an increased homogeneity of the clear lacquer surface and above 60 ° C for an improved plastic flow to lead.

Finally, for example from Loren W. Hill, Journal of Coatings Technology, Vol. 64, No. 808, May 1992, pages 29 to 41, the relationship between Storage module and networking density known. Notes or information on how Scratch-resistant coatings can be obtained, however, are included in this article not included.

Furthermore, EP-A-540 884 describes a method for producing Multicoat paint systems in particular in the automotive sector Use of free-radically and / or cationically polymerizable, silicone-containing Clear varnishes known, in which the application of the clear varnish under lighting with light of a wavelength of over 550 nm or in the absence of light takes place and then the clearcoat layer using high-energy Radiation is hardened. The surfaces obtained in this way should have a good visual appearance Behavior and have good scratch resistance. Details of the Amount of scratch resistance and information on how the scratch resistance was determined, however, are not included in EP-A-540 884.

Finally, EP-A-568 967 also describes a process for the preparation of Multicoat paint systems in particular in the automotive sector Use of radiation-curable clearcoats known. According to EP-A-568 In 967, however, it is essential to the invention that in order to achieve Clear lacquer layers with a high optical quality are initially a thermal curing clearcoat and then a radiation-curable clearcoat is applied.

The present invention is therefore based on the object of a method for To provide manufacture of scratch-resistant coatings. there should the coating agents used in this process be a have good storage stability (at least 8 weeks when stored at 50 ° C) and lead to coatings which at the same time lead to a high scratch resistance Chemical resistance, good moisture resistance and good polishability. These coating agents should also be used as a clear coat and / or top coat for the production of a multi-layer coating, especially in the motor vehicle sector, be suitable. Furthermore, the cured coating compositions should be one good weather resistance, good acid / base resistance and good Resistance to bird droppings, etc., a high gloss and a good Appearance.

In addition, the objective assessment of the scratch resistance of the hardened Coating based on the test method selected physical parameters. This procedure should Determination of the physical parameters can be used practically and with Adequate accuracy is as adequate as possible for the visual assessment Enable characterization of scratch resistance.

This object is surprisingly achieved by a method for producing scratch-resistant coatings, which is characterized in that a coating agent is used which, after curing, has a storage module E 'in the rubber-elastic range of at least 10 ^7.6 Pa and a loss factor tan δ at 20 ° C. of at most 0.10, the storage module E 'and the loss factor tan δ having been measured using dynamic mechanical thermal analysis on homogeneous free films with a layer thickness of 40 ± 10 μm.

The present application also relates to the use of the Process for producing a multi-layer coating and for this process suitable coating agents.

It is surprising and was not predictable that only by measuring the Viscoelastic properties using dynamic mechanical thermal analysis (hereinafter also called DMTA for short) on free films universal, representative selection criterion for the provision of Coating agents that lead to scratch-resistant coatings are available stands. The results of the DMTA measurements are the results of different test methods of scratch resistance correlated, so that only Using the results of the DMTA measurements, statements about the results in other scratch resistance tests, e.g. the BASF brush test or the AMTEC test or various test methods of the automobile manufacturer possible are.

It is also surprising that varnishes that only have one at the test temperature medium or even a small plastic part, but a very high one Have memory module in the rubber-elastic area, nevertheless coatings with a high scratch resistance. It is particularly advantageous that these coating compositions of the invention lead to coatings that at the same time as the high scratch resistance, good polishability, good Moisture resistance, good weather resistance, good chemicals as well Acid / base resistance and high gloss. Furthermore, the invention Coating agent with a good storage stability of 8 weeks Storage at 50 ° C.

In the following, the methods used in the method according to the invention are first described Production of scratch-resistant coatings explained in more detail.

It is essential to the invention that the coating agent is selected such that the cured coating agent in the rubber-elastic region has a storage modulus E 'of at least 10 ^7.6 Pa, preferably of at least 10 ^8.0 Pa, particularly preferably of at least 10 ^8.3 Pa, and has a loss factor at 20 ° C of a maximum of 0.10, preferably of a maximum of 0.06, the memory module E 'and the loss factor tan δ using dynamic mechanical thermal analysis on homogeneous free films with a layer thickness of 40 ± 10 µm have been measured. The loss factor tan δ is defined as the quotient of the loss module E "and the memory module E '.

Dynamic mechanical thermal analysis is a well known Measuring method for determining the viscoelastic properties of Coatings and described for example in Murayama, T., Dynamic Mechanical Analysis of Polymeric Material, Esevier, New York, 1978 and Loren W. Hill, Journal of Coatings Technology, Vol. 64, No. 808, May 1992, pages 31 to 33rd

The measurements can be carried out, for example, using the MK II, MK devices III or MK IV from Rheometrics Scientific.

The memory module E 'and the loss factor tanδ are free on homogeneous Films measured. The free films are produced in a known manner by that the coating agent is applied and cured on substrates on which the coating agent is not liable. Examples are suitable substrates Glass, Teflon and especially called polypropylene. Polypropylene has the Advantage of good availability and is therefore usually considered Carrier material used.

The layer thickness of the free films used for the measurement is generally 40 ± 10 µm.

The special selection of the coating agent based on the value of the memory module in the rubber-elastic range and the loss factor at 20 ° C the cured Coating agent enables the provision of Coating agents with the desired property profile of a good one Scratch resistance with good polishability, chemicals and Moisture resistance as well as weather resistance, because both parameters by simple DMTA measurements can be determined. Furthermore, the resulting Coatings have a high gloss and an acid and base resistance that is comparable to the corresponding values of conventional, thermal hardened paints.

It is surprising that varnishes that only have one at the test temperature medium or even a small plastic part, but a high to have a very high memory module in the rubber-elastic range, Coatings with a high scratch resistance result.

The scratch resistance of the cured coatings is preferred Help of the in Fig. 2 on page 28 of the article by P. Betz and A. Bartelt, Progress in Organic Coatings, 22 (1993), pages 27-37, described BASF brush tests, which, however, with regard to the weight used (2000 g instead of that there 280 g) was modified, assessed as follows.

In this process, the paint surface is covered with a sieve fabric a mass is damaged. The screen mesh and the lacquer surface are thoroughly wetted with a detergent solution. The test board is by means of a motor drive in lifting movements under the screen fabric pushed back.

To manufacture the test panels, an ETL with a layer thickness of 18 - 22 µm, then a filler with a layer thickness of 35 - 40 µm, then a black basecoat with a layer thickness of 20 - 25 µm and finally that applied coating agent to be tested with a layer thickness of 40 - 45 µm and hardened in each case. The boards are at least 2 after application of the paints Stored for weeks at room temperature before the test is carried out.

The test specimen is made of nylon mesh (No. 11, 31 µm mesh size, Tg 50 ° C) covered eraser (4.5 x 2.0 cm, wide side perpendicular to the direction of scratching). The coating weight is 2000 g.

Before each test, the screen mesh is renewed, the direction of rotation is Fabric stitches parallel to the direction of scratching. With a pipette, approx. 1 ml of one freshly stirred 0.25% Persil solution applied in front of the eraser. The number of revolutions of the motor is set so that 80 in a time of 80 s Double strokes can be carried out. After the exam, the remaining one Washing liquid rinsed with cold tap water and the test board with Blown compressed air dry. The gloss is measured according to DIN 67530 before and after damage (measuring direction perpendicular to the scratch direction).

The coating compositions of the invention have a clear improved scratch resistance in the BASF brush test. This preferably indicates Coating agents according to the invention in the cured state Scratch resistance that the delta gloss value after the BASF brush test of cured coating agent applied over a basecoat maximum 8, is preferably at most 4 and particularly preferably 0.

The acid / base resistance is checked using the so-called BART test ( B ASF A CID R ESISTANCE T EST):
The above-described steel sheets coated with ETL, filler, basecoat and topcoat are exposed to further temperature loads on a gradient oven (30 min 40 ° C, 50 ° C, 60 ° C and 70 ° C). Before this, the test substances (sulfuric acid 1%, 10%, 36%; sulfurous acid 6%; hydrochloric acid 10%; sodium hydroxide solution 5%) are applied in a defined manner using a pipette. Following exposure to the substances, they are removed under running water and the damage is assessed visually after 24 hours on a predefined scale: grading Appearance 0 no defect 1 slight marking 2 Marking / matting / no softening 3 Marking / dulling / color change / softening 4 Cracks / beginning of etching through 5 Clear varnish removed Coating agents with the corresponding viscoelastic properties mentioned above are preferably curable coating agents by means of UV or electron radiation, in particular by means of UV radiation. In addition, coating compositions based on Ormocer are also suitable, for example.

These radiation-curable coating compositions usually contain at least one, preferably several radiation-curable binders, in particular based on ethylenic unsaturated prepolymer and / or ethylenically unsaturated oligomer, possibly one or more reactive diluents, possibly one or more Photoinitiators and, if applicable, customary auxiliaries and additives,

Radiation-curable coating compositions are preferably used, the Viscosity at 23 ° C less than 100 s flow time in a DIN 4 cup, especially preferably less than 80 s run-out time in the DIN 4 cup.

The binders used in these radiation-curable coating compositions are, for example, (meth) acrylic-functional (meth) acrylic copolymers, polyether acrylates, polyester acrylates, unsaturated polyesters, epoxy acrylates, urethane acrylates, amino acrylates, melamine acrylates, silicone acrylates and the corresponding methacrylates. It is preferred to use binders which are free from aromatic structural units. The use of epoxy acrylates leads to hard, scratch-resistant coatings, but they generally show weather resistance in need of improvement. Urethane (meth) acrylates and / or polyester (meth) acrylates are therefore preferably used, particularly preferably aliphatic urethane acrylates.
Aqueous dispersions of the radiation-curable binders mentioned are also suitable as binders in the coating compositions according to the invention.
In addition, essentially silicone-free, particularly preferably silicone-free binders are preferably used, since the resulting coating compositions have an improved overcoatability compared to silicone-containing coating compositions.

The polymers or oligomers used as binders usually have a number average molecular weight from 500 to 50,000, preferably from 1,000 to 5,000.

Polymers are preferred in the coating compositions according to the invention and / or oligomers used, at least 2, especially per molecule preferably have 3 to 6 double bonds. Preferably, the ones used Binder also has a double bond equivalent weight of 400 to 2,000, particularly preferably from 500 to 900. The binders also prove 23 ° C preferably has a viscosity of 250 to 11,000 mPa.s.

Polyester (meth) acrylates are known in principle to the person skilled in the art. you are through different methods can be produced. For example, acrylic acid and / or Methacrylic acid used directly as an acid component in the construction of the polyester become. There is also the possibility of hydroxyalkyl esters Use (meth) acrylic acid as alcohol component directly in the construction of the polyester. However, the polyester (meth) acrylates are preferred by acrylating Polyesters made. For example, those containing hydroxyl groups can initially Polyesters are built up, which are then reacted with acrylic or methacrylic acid become. It is also possible first to build up polyesters containing carboxyl groups be then with a hydroxyalkyl ester of acrylic or methacrylic acid be implemented. Unreacted (meth) acrylic acid can be washed out, Distill or preferably by reacting with an equivalent amount of one Mono- or diepoxide compound using suitable catalysts, such as e.g. Triphenylphosphine, are removed from the reaction mixture. In terms of further details on the production of the polyester acrylates are in particular the DE-OS 33 16 593 and DE-OS 38 36 370 and also to EP-A-54 105, the DE-AS 20 03 579 and EP-B-2866 referenced.

Polyether (meth) acrylates are also known in principle to the person skilled in the art. they are can be produced by various methods. For example, those containing hydroxyl groups Polyether esterified with acrylic acid and / or methacrylic acid be, by reacting di- and / or polyhydric alcohols with various amounts of ethylene oxide and / or propylene oxide according to well known Methods (see e.g. Houben-Weyl, Volume XIV, 2, Macromolecular Substances II, (1963)) can be obtained. Polymerization products of tetrahydrofuran can also be used or butylene oxide.

Flexibilization of the polyether (meth) acrylates and the polyester (meth) acrylates is possible, for example, that corresponding OH-functional Prepolymers or oligomers (polyether or polyester base) with longer-chain, aliphatic dicarboxylic acids, especially aliphatic Dicarboxylic acids with at least 6 carbon atoms, such as adipic acid, Sebacic acid, dodecanedioic acid and / or dimer fatty acids. This The flexibility reaction can take place before or after the addition of acrylic or Methacrylic acid can be carried out on the oligomers or prepolymers.

Furthermore, epoxy (meth) acrylates are also well known to and need for the skilled worker therefore not to be explained in more detail. They are usually made by by adding acrylic acid to epoxy resins, for example to epoxy resins based on bisphenol A or other commercially available epoxy resins.

Flexibility of the epoxy (meth) acrylates is analogous, for example possible that corresponding epoxy-functional prepolymers or oligomers with longer-chain, aliphatic dicarboxylic acids, especially aliphatic Dicarboxylic acids with at least 6 carbon atoms, such as adipic acid, Sebacic acid, dodecanedioic acid and / or dimer fatty acids are implemented. This The flexibility reaction can take place before or after the addition of acrylic or Methacrylic acid can be carried out on the oligomers or prepolymers.

Urethane (meth) acrylates are also well known to those skilled in the art and require therefore not to be explained in more detail. They can be obtained through Implementation of a di- or polyisocyanate with a chain extender from the group of the diols / polyols and / or diamines / polyamines and / or Dithiols / polythiols and / or alkanolamines and subsequent implementation of the remaining free isocyanate groups with at least one Hydroxyalkyl (meth) acrylate or hydroxyalkyl esters of other ethylenic unsaturated carboxylic acids.

1.) das Äquivalentverhältnis der NCO-Gruppen zu den reaktiven Gruppen des Kettenverlängerungsmittels (Hydroxyl-, Amino- bzw. Mercaptylgruppen) zwischen 3 : 1 und 1 : 2, bevorzugt bei 2 : 1, liegt und

2.) die OH-Gruppen der Hydroxialkylester der ethylenisch ungesättigten Carbonsäuren in stöchiometrischer Menge in bezug auf die noch freien Isocyanatgruppen des Präpolymeren aus Isocyanat und Kettenverlängerungsmittel vorliegen.

The amounts of chain extender, di- or polyisocyanate and hydroxyalkyl ester are preferably chosen so that

1.) the equivalent ratio of the NCO groups to the reactive groups of the chain extender (hydroxyl, amino or mercaptyl groups) is between 3: 1 and 1: 2, preferably 2: 1, and

2.) the OH groups of the hydroxyalkyl esters of the ethylenically unsaturated carboxylic acids are present in a stoichiometric amount in relation to the free isocyanate groups of the prepolymer from isocyanate and chain extender.

It is also possible to manufacture the polyurethane acrylates by first a Part of the isocyanate groups of a di- or polyisocyanate with at least one Hydroxyalkyl ester is implemented and the remaining isocyanate groups then reacted with a chain extender. Also in In this case, the amounts of chain extender, isocyanate and Hydroxyalkyl esters are chosen so that the equivalent ratio of the NCO groups the reactive groups of the chain extender between 3: 1 and 1: 2, is preferably 2: 1 and the equivalent ratio of the remaining NCO groups to the OH groups of the hydroxyalkyl ester is 1: 1. Of course all intermediate forms of these two processes are also possible. For example some of the isocyanate groups of a diisocyanate can first be mixed with a diol implemented, then another part of the isocyanate groups with the hydroxyalkyl ester and subsequent to it the rest Isocyanate groups are reacted with a diamine.

These various manufacturing processes for polyurethane acrylates are known (cf. e.g. EP-A-204 161) and therefore do not require a more detailed description.

The urethane (meth) acrylates can be made more flexible, for example, by that corresponding isocyanate-functional prepolymers or oligomers with longer-chain, aliphatic diols and / or diamines, especially aliphatic Diols and / or diamines with at least 6 carbon atoms are implemented. This The flexibility reaction can take place before or after the addition of acrylic or Methacrylic acid can be carried out on the oligomers or prepolymers.

Urethanacrylat Crodamer UVU 300 der Firma Croda Resins Ltd., Kent, GB; aliphatisches Urethantriacrylat Genomer 4302 der Firma Rahn Chemie, CH; aliphatisches Urethandiacrylat Ebecryl 284 der Firma UCB, Drogenbos, Belgien; aliphatisches Urethantriacrylat Ebecryl 294 der Firma UCB, Drogenbos, Belgien; aliphatisches Urethantriacrylat Roskydal LS 2989 der Firma Bayer AG, Deutschland aliphatisches Urethandiacrylat V94-504 der Firma Bayer AG, Deutschland aliphatisches hexafunktionelles Urethanacrylat Viaktin VTE 6160 der Firma Vianova, Österreich aliphatisches Urethandiacrylat Laromer 8861 der Firma BASF AG sowie davon abgewandelte Versuchsprodukte

The following commercially available products may also be mentioned as examples of suitable binders:

Crodamer UVU 300 urethane acrylate from Croda Resins Ltd., Kent, GB; aliphatic urethane triacrylate genomer 4302 from Rahn Chemie, CH; aliphatic urethane diacrylate Ebecryl 284 from UCB, Arzneimittelbos, Belgium; aliphatic urethane triacrylate Ebecryl 294 from UCB, Drugsbos, Belgium; aliphatic urethane triacrylate Roskydal LS 2989 from Bayer AG, Germany aliphatic urethane diacrylate V94-504 from Bayer AG, Germany aliphatic hexafunctional urethane acrylate Viaktin VTE 6160 from Vianova, Austria aliphatic urethane diacrylate Laromer 8861 from BASFspr

The binder is preferably used in the coating compositions according to the invention in an amount of 5 to 90% by weight, particularly preferably 20 to 70% by weight, each based on the total weight of the coating agent in the case of Clear lacquers or the weight of the coating agent without pigments and Fillers used in the case of pigmented systems.

The coating compositions according to the invention can optionally also have one or more Contain reactive thinners. The reactive diluents can be ethylenic be unsaturated compounds. The reactive diluents can be mono-, di- or be polyunsaturated. They usually serve to influence the viscosity and the paint properties, such as the crosslink density.

The reactive diluent (s) are used in the inventive Coating agents preferably in an amount of 0 to 70 wt .-%, particularly preferably from 15 to 65% by weight, in each case based on the total weight of the coating composition in the case of clear coats or on the weight of the Coating agent without pigments and fillers in the case of pigmented systems, used.

Examples of reactive diluents are (meth) acrylic acid and its esters, Maleic acid and its esters or half esters, vinyl acetate, vinyl ether, Vinyl ureas and the like used. Examples include alkylene glycol di (meth) acrylate, Polyethylene glycol di (meth) acrylate, 1,3-butanediol di (meth) acrylate, Vinyl (meth) acrylate, allyl (meth) acrylate, glycerol tri (meth) acrylate, Trimethylolpropane tri (meth) acrylate, trimethylolpropane di (meth) acrylate, styrene, Vinyl toluene, divinylbenzene, pentaerythritol tri (meth) acrylate, Pentaerythritol tetra (meth) acrylate, dipropylene glycol di (meth) acrylate, hexanediol di (meth) acrylate, Ethoxyethoxyethyl acrylate, N-vinylpyrrolidone, phenoxyethyl acrylate, Dimethylaminoethyl acrylate, hydroxyethyl (meth) acrylate, butoxyethyl acrylate, Isobornyl (meth) acrylate, dimethylacrylamide and dicyclopentyl acrylate, which in the EP-A-250 631 described long-chain linear diacrylates with a Molecular weight from 400 to 4000, preferably from 600 to 2500. For example the two acrylate groups can be separated by a polyoxibutylene structure. 1,12-Dodecyl diacrylate and the reaction product of can also be used 2 moles of acrylic acid with one mole of a dimer fatty alcohol, which is generally 36 C atoms. Mixtures of the monomers mentioned are also suitable.

Mono- and / or diacrylates, such as e.g. Isobornyl acrylate, hexanediol diacrylate, tripropylene glycol diacrylate, Laromer® 8887 from BASF AG and Actilane® 423 from Akcros Chemicals Ltd., GB, used. Isobornyl acrylate, hexanediol diacrylate and Tripropylene glycol diacrylate used.

The coating compositions according to the invention optionally contain, preferably in Proportions of 0 to 10 wt .-%, preferably in UV-cured Preparations 2 to 6 wt .-%, based on the weight of the coating agent without pigments and fillers, usual, in radiation-curable coating agents Photoinitiators used, for example benzophenones, benzoins or Benzoin ether, preferably benzophenone in UV preparations. It can too for example those commercially available under the names Irgacure® 184, Irgacure® 1800 and Irgacure® 500 from Ciba Geigy, Grenocure® MBF from Rahn and Products available from Lucirin® TPO from BASF AG are used.

The coating compositions of the invention may also contain usual auxiliaries and / or additives, for example light stabilizers (e.g. HALS compounds, benzotriazoles, oxalanilide, etc.), slip additives, Polymerization inhibitors, matting agents, defoamers, leveling agents and film-forming aids, e.g. Cellulose derivatives, or others, in top coats additives usually used. These usual tools and / or additives are usually used in an amount of up to 15% by weight, preferably 2 to 9 % By weight, based on the weight of the coating composition without pigments and without fillers.

The coating compositions according to the invention come in particular as clear lacquers used, so that they usually no or only transparent fillers and does not contain opaque pigments. But it is also the use of pigmented coating agents possible. In this case, the Coating agent 2 to 40 wt .-%, based on the total weight of the Coating agent, one or more pigments. Furthermore, the Coating agent in this case still 1 to 20 wt .-%, based on the Total weight of the coating agent, one or more fillers included.

The coating compositions of the invention can on glass and various metal substrates, such as Aluminum, steel, various Iron alloys, etc., are applied. They are preferred as clear or Topcoat in the field of automotive painting (automobile series and Automotive refinishing) used. Of course they can Coating agent in addition to application on a wide variety of metals also on other substrates, such as wood, paper, plastics, mineral substrates or similar be applied. They are also in the area the coating of packaging containers and in the area of the coating of films for the furniture industry and the like used.

For the production of coatings on metal substrates, the Coating agents according to the invention preferably on primed or with a Base coat coated metal sheets or metal strips applied. As Primers can use the primers commonly used become. Both conventional and aqueous basecoats come as basecoats for use. Furthermore, it is also possible to use the inventive To apply coating agents to metal substrates, initially with a Electrocoating and then with a functional layer and wet-in-wet were coated with a basecoat. With the procedures mentioned it is however, generally required that the basecoat and the filler or Functional layer before application of the coating agent according to the invention be branded.

(1) ein pigmentierter Basislack auf die Substratoberfläche angebracht wird,

(2) die Basislackschicht getrocknet oder vernetzt wird,

(3) auf der so erhaltenen Basislackschicht ein transparenter Decklack aufgebracht wird und anschließend

(4) die Decklackschicht gehärtet wird,

dadurch gekennzeichnet, daß als Decklack ein erfindungsgemäßes Beschichtungsmittel eingesetzt wird.The present invention therefore also relates to a process for the production of multi-layer coatings, in which

(1) a pigmented basecoat is applied to the substrate surface,

(2) the basecoat film is dried or crosslinked,

(3) a transparent topcoat is applied to the basecoat layer thus obtained and then

(4) the top coat layer is hardened,

characterized in that a coating agent according to the invention is used as the topcoat.

The coating compositions of the invention are particularly suitable as Topcoat for producing a multi-layer coating in the field of automotive series and / or automotive refinishing of automobile bodies and their parts as well as truck bodies etc.

The coating films are cured by means of radiation, preferably by means of UV radiation. The facilities and conditions for these hardening methods are known from the literature (see e.g. R. Holmes, U.V. and E.B. Curing Formulations for Printing Inks, Coatings and Paints, SITA Technology, Academic Press, London, United Kindom 1984) and need no further description.

The invention is explained in more detail below on the basis of exemplary embodiments explained. All parts mean parts by weight, unless expressly something other is indicated.

Examples 1 to 4

The coating compositions 1 to 4 are prepared from the components listed in Table 1 with vigorous stirring using a dissolver or a stirrer. A free film applied over polypropylene with a layer thickness of 40 ± 10 μm was produced from each of these clearcoats 1 to 4 and examined by means of DMTA. The film is cured with 2 Hg UV lamps. The irradiated dose is approximately 1800 mJ / cm ² . The viscoelastic parameters of the homogeneous, hardened free films were determined by means of DMTA measurements. The storage module E 'determined in this way in the rubber-elastic range and the loss factor tan δ at 20 ° C. are each given in Table 2.

Furthermore, the scratch resistance of the cured coating of these coating compositions of Examples 1 to 4 was determined using the BASF brush test by measuring the drop in gloss. For this purpose, the respective coating agent was burned onto a metal sheet, which had previously been baked with a commercially available electrocoating from BASF Lacke + Farben AG, Münster (layer thickness 18-22 µm), with the commercially available filler Ecoprime 130 from BASF Lacke + Farben AG, Münster (30 min 130 ° C; dry film thickness 35 - 40 µm) and with a commercially available aqueous basecoat from BASF Lacke + Farben AG, Münster (baked 30 min 130 ° C; dry film thickness 20 - 25 µm), with a dry film thickness of 40 - 45 µm applied and hardened by means of UV radiation (radiated energy 1800 mJ / cm ² ).

The BASF brush test was used to evaluate this overall structure Scratch resistance determined. The results are also shown in Table 2. Table 2 also shows the polishability, the acid / base resistance, the Storage stability and the ability to be painted over with itself.

Comparative Example 1 1. Production of an acrylic resin

In a laboratory reactor with a usable volume of 41 equipped with a Stirrer, two dropping funnels for the monomer mixture resp. Initiator solution Nitrogen inlet tube, thermometer and reflux condenser are 758 g one Aromatic hydrocarbon fraction with a boiling range of 158 ° C - Weighed in 172 ° C. The solvent is heated to 140 ° C. After reaching of 140 ° C, a monomer mixture of 1108 g of ethyl hexyl acrylate, 55 g Styrene, 404 g of 4-hydroxibutyl acrylate and 16 g of acrylic acid within 4 hours, and an initiator solution of 63 g of t-butyl perethylhexanoate in 95 g of the described aromatic solvent evenly within 4.5 hours dosed the reactor. With the dosage of the monomer mixture and the Initiator solution is started at the same time. After completing the The reaction mixture is metered into the initiator at 140 ° C. for a further two hours held and then cooled. The resulting polymer solution has one Solids content of 62% (determined in a forced air oven at 130 ° C. for 1 h), a Acid number of 9 and a viscosity of 21 dPas (measured on a 60% Dissolving the polymer solution in the aromatic solvent described below Use an ICI-plate-cone viscometer at 23 ° C).

2. Preparation of a blocked isocyanate 1

In the apparatus described above, equipped with one dosing vessel and one Reflux coolers are 504.0 g of a commercially available isocyanurate trimer Hexamethylene diisocyanate and 257.2 g of the aromatic described above Weighed out solvent. The solution is heated to 50 ° C. Then the Dosing vessel a mixture of 348.0 g of diethyl malonate, 104.0 g of ethyl acetoacetate and 2.5 g of a 50% solution of sodium p-dodecylphenolate in xylene metered into the solution over a period of 2 hours so that the Temperature does not exceed 70 ° C. It is then slowly heated to 90 ° C and kept this temperature for 6 hours. Then another 2.5 g of sodium pdodecylphenolate solution added and it is kept at 90 ° C until the Content of NCO groups in the reaction mixture has reached 0.48%. Then be 35.1 g of n-butanol were added. The solution obtained has a non-volatile content of 59.6% (measured in a convection oven for 60 minutes at 130 ° C) and a viscosity of 590 mPaùs, measured in an ICI plate cone viscometer at 23 ° C.

3. Preparation of a blocked isocyanate 2

The blocked isocyanate 2 is prepared analogously to the preparation of the blocked isocyanates 1 with the only difference that instead of 504.0 g of the hexamethylene diisocyanate trimere now 666.1 g of a commercially available Isocyanurate trimers of isophorone diisocyanate are used.

4. Production of a transparent topcoat

38,5 Teile Acrylatharz

28,6 Teile Setamine US-138, handelsübliches Melaminharz

3,6 Teile Isocyanat 1

4,0 Teile Isocyanat 2

9,8 Teile Xylol

1,7 Teile UV-Absorber auf Basis Benztriazol

1,5 Teile eines handelsüblichen Lichtschutzmittels auf Basis eines sterisch gehinderten Amins

5,3 Teile Xylol

5,0 Teile Butanol

2,0 Teile Verlaufsmittel (5-%ige Lösung eines mit Polyether substituierten Polydimethylsiloxans in Xylol)

The transparent topcoat is produced by weighing acrylate resin, isocyanate 1, isocyanate 2 and aminoplast resin in the order given below and mixing well by stirring with a laboratory turbine stirrer, then adding the first amount of xylene and also stirring well. The UV absorber and the radical scavenger are premixed separately with (the second amount) xylene until they are completely dissolved and then added to the first part of the formulation and likewise stirred well. Then n-butanol and the leveling agent are added and mixed in well. The paint obtained is optionally adjusted for application with xylene to a viscosity of 23 seconds, measured in a DIN-4 cup at 20 ° C.

38.5 parts of acrylic resin

28.6 parts of Setamine US-138, commercially available melamine resin

3.6 parts of isocyanate 1

4.0 parts of isocyanate 2

9.8 parts xylene

1.7 parts of UV absorber based on benzotriazole

1.5 parts of a commercially available light stabilizer based on a sterically hindered amine

5.3 parts of xylene

5.0 parts butanol

2.0 parts leveling agent (5% solution of a polyether-substituted polydimethylsiloxane in xylene)

Analogously to Example 1, this coating agent V1 became a homogeneous one free film applied over polypropylene with a layer thickness of 40 ± 10 µm manufactured and examined by means of DMTA (curing conditions 20 min / 140 ° C).

The values of the memory module E 'thus determined in the rubber-elastic range and the loss factor tan δ at 20 ° C are shown in Table 2.

Table 2 also shows the storage stability of the coating material and the results of testing the cured coating for Polishability, moisture resistance, acid / base resistance and paintability specified.

Furthermore, the scratch resistance of the coating agent V1 cured coating analogous to Example 1 using the BASF brush test determined by measuring the drop in gloss. For this purpose, the coating agent V1 to that described in Example 1, with an electrocoat, filler and metal sheet provided with a basecoat with a dry film layer thickness of 40 - 45 µm applied and thermally hardened together with the basecoat (20 min 140 ° C). The BASF brush test was then used to determine this overall structure Scratch resistance determined. The ΔGlanz values determined are also in Table 2 shown.

Comparative Example 2

Analogously to Example 1 of EP-A-540 884, a coating agent V2 is produced from the following components with intensive stirring using a dissolver or a stirrer: 44.5 parts Novacure 3200 (aliphatic epoxy acrylate from Interorgana) 32.2 parts Ebecryl 264 (aliphatic urethane acrylate from UCB) 3.0 parts Irgacure 184 (photoinitiator from CIBA GEIGY) 10.0 parts Dirpopylenglykoldiacrylat 10.0 parts trimethylolpropane 0.3 parts Ebecryl 350 (silicone acrylate from UCB)

Analogously to Example 1, this coating agent V2 was used to produce a free film applied over polypropylene with a layer thickness of 40 ± 10 μm, hardened by means of UV radiation (radiated energy 1800 mJ / cm ² ) and examined by means of DMTA. The values of the memory module E 'determined in this way in the rubber-elastic range and of the loss factor tan δ at 20 ° C. are shown in Table 2.

In Table 2 is also the result of testing the cured Coating specified with regard to paintability.

Furthermore, the scratch resistance of the cured coating of this coating agent V2 was determined analogously to Example 1 using the BASF brush test by measuring the drop in gloss. For this purpose, the coating agent V2 was applied to the metal sheet described in Example 1, provided with an electrocoat, filler and basecoat, with a dry film thickness of 40-45 μm and cured by means of UV radiation (radiated energy 1800 mJ / cm ² ). The scratch resistance of this overall structure was then determined using the BASF brush test. The determined Δ gloss values are also shown in Table 2.

Comparative Example 3 1. Production of an acrylic resin

In a laboratory reactor with a useful volume of 4l equipped with a Stirrer, two dropping funnels for the monomer mixture resp. Initiator solution Nitrogen inlet tube, thermometer and reflux condenser are 879 g Aromatic hydrocarbon fraction with a boiling range of 158 ° C - Weighed in 172 ° C. The solvent is heated to 140 ° C. After reaching of 140 ° C an initiator mixture 1 from 87 g of the above aromatic solvent mixture and 87 g t-butyl peroctoate within 4.75 Hours evenly metered into the reactor. 15 minutes after the start of the addition the initiator mixture is a monomer mixture of 819 g butyl methacrylate, 145 g of methyl methacrylate and 484 g of hydroxypropyl methacrylate within 4 Hours dosed. After the end of the initiator metering, the reaction mixture kept at 140 ° C for two more hours and then cooled. The resulting polymer solution has a solids content of 60% (determined in a convection oven for 1 h at 130 ° C) and an OH number of 130 (based on Solid content).

2. Preparation of an isocyanate

23 g of a commercially available 90% isocyanurate trimer of Hexamethylene diisocyanate and 64 g of a commercially available 70% Isocyanurate trimers of isophorone diisocyanate are mixed with 6.5 g of butyl acetate and 6.5 g of the aromatic solvent mixture described above mixed well.

3. Production of a transparent top coat

78,0 Teile Acrylatharz

35,0 Teile Isocyanat

8,0 Teile Butylglykolacetat

5,5 Teile Butylacetat

1,5 Teile UV-Absorber auf Basis Benztriazol

1,0 Teile eines handelsüblichen Lichtschutzmittels auf Basis eines sterisch gehinderten Amins

3,0 Teile Xylol

3,0 Teile Verlaufsmittel (5-%ige Lösung eines mit Polyether substituierten Polydimethylsiloxans in Xylol)

The transparent topcoat is produced by weighing the acrylic resin and mixing it well by stirring with a laboratory turbine stirrer, then adding the solvents other than xylene and the leveling agent and also stirring them in well. The UV absorber and the radical scavenger are premixed separately with xylene until they are completely dissolved and then added to the first part of the formulation and also stirred well. The isocyanate is added shortly before application. The paint obtained is optionally adjusted for application with xylene to a viscosity of 23 seconds, measured in a DIN-4 cup at 20 ° C.

78.0 parts of acrylic resin

35.0 parts isocyanate

8.0 parts of butyl glycol acetate

5.5 parts of butyl acetate

1.5 parts of UV absorber based on benzotriazole

1.0 part of a commercially available light stabilizer based on a sterically hindered amine

3.0 parts xylene

3.0 parts leveling agent (5% solution of a polyether-substituted polydimethylsiloxane in xylene)

Analogously to Example 1, this coating agent V3 was a free, over Polypropylene applied film with a layer thickness of 40 ± 10 microns and examined using DMTA (curing conditions 20 min / 140 ° C).

The values of the memory module E 'thus determined in the rubber-elastic range and the loss factor tan δ at 20 ° C are shown in Table 2.

Table 2 also shows the storage stability of coating material V3 and the results of the test of the cured coating with regard to the Polishability, moisture resistance and chemical resistance specified.

Furthermore, the scratch resistance of the coating agent V3 cured coating analogous to Example 1 using the BASF brush test determined by measuring the drop in gloss. For this purpose the coating agent V3 to that described in Example 1, with an electrocoat, filler and metal sheet provided with a basecoat with a dry film layer thickness of 40 - 45 µm applied and thermally hardened together with the basecoat (20 min 140 ° C). The BASF brush test was then used to determine this overall structure Scratch resistance determined. The ΔGlanz values determined are also in Table 2 shown.

Summary of test results:

The high scratch resistance of the conventional, optimized for scratch resistance Clear varnish (comparative example 1) is obtained with an early increase in the tan δ value reached. However, this has other disadvantages, e.g. a lesser Storage stability, poor polishability and poor chemical resistance, connected.

The coating agent of comparative example V2 is characterized by a high tan δ at 20 ° C and good scratch resistance, but at the same time poor paintability.

The very scratch-sensitive two-component clearcoat (comparative example 3), the but is also characterized by good acid resistance in contrast, a late increase in the tan δ value and a low value of the Storage module E 'in the rubber-elastic area.

In comparison to the conventional clearcoat of comparative example 1 optimized for scratch resistance, the coating composition according to the invention is distinguished by a higher storage modulus E 'in the rubber-elastic range of at least 10 ^7.6 Pa and a later increase in the loss factor tan δ and a correspondingly low tan δ value at 20 ° C. off. This makes it possible to provide a coating agent that leads to coatings with excellent scratch resistance (e.g. little or no scratching in the BASF brush test, Δ gloss less than or equal to 8, improved scratch resistance in the AMTEC brush test) with good polishability and good resistance to chemicals and moisture , In addition, the coating compositions of the invention are distinguished by an improved storage stability compared to the conventional clearcoat of comparative example 1 which has been optimized for scratch resistance. Composition of the coating compositions of Examples 1 to 4 example 1 2 3 4 Viaktin 76.0 - - - Larom 8777 - 41.6 - - Larom.PO84F - 10.0 - - EBEC. 5129 - 10.0 - - urethane - - - 76.0 V94 / 504-2 - - 50.0 - HDDA 20.0 31.9 45.0 20.0 Anyway Scroll. 184 4.0 - - 4.0 Anyway Scroll. 500 - 4.0 - - Gen.MBF - - 4.0 - Add. - 2.0 - - Byk 333 - 0.5 - - Byk 306 - - 1.0 - total 100.0 100.0 100.0 100.0

Claims (16)

1. A coating composition which in the cured state has a storage modulus E' in the rubber-elastic range of at least 10^7,6 Pa and a loss factor tanδ at 20°C of not more than 0.10, the storage modulus E' and the loss factor having been measured by dynamic mechanical thermoanalysis on free films having a film thickness of 40 ± 10 µm.
2. A coating composition as claimed in claim 1 wherein the coating composition in the cured state has a storage modulus E' in the rubber-elastic range of at least 10^8.0 Pa, preferably of at least 10^8.3 Pa, and/or a loss factor tanδ at 20°C of not more than 0.06.
3. A coating composition as claimed in claim 1 or 2 wherein the coating composition in the cured state has a scratch resistance such that the delta gloss value following the BASF brush test of the cured coating composition applied over a basecoat is not more than 8, preferably not more than 4 and, with particular preference, is 0.
4. A coating composition as claimed in any of claims 1 to 3 wherein the coating composition is curable by means of UV radiation or electron beams.
5. A coating composition as claimed in claim 4 wherein the coating composition has a viscosity at 23°C of less than 100 s, preferably less than 80 s, efflux time in the DIN 4 cup.
6. A coating composition as claimed in claim 4 or 5 wherein the coating composition comprises one or more polyester (meth)acrylates and/or polyurethane (meth)acrylates as binders and/or wherein the binder employed is substantially silicone-free.
7. A coating composition as claimed in any of claims 4 to 6 which comprises one or more mono- and/or diacrylates as reactive diluents.
8. A process for producing scratch-resistant coatings, which comprises employing a coating composition which after curing has a storage modulus E' in the rubber-elastic range of at least 10^7.6 Pa and a loss factor tans at 20°C of not more than 0.10, the storage modulus E' and the loss factor having been measured by dynamic mechanical thermoanalysis on free films having a film thickness of 40 ± 10 µm.
9. A process as claimed in claim 8, wherein the coating composition in the cured state has a storage modulus E' in the rubber-elastic range of at least 10^8.0 Pa, preferably of at least 10^8.3 Pa, and/or a loss factor tanδ at 20°C of not more than 0.06.
10. A process as claimed in claim 8 or 9, wherein the coating composition in the cured state has a scratch resistance such that the delta gloss value following the BASF brush test of the cured coating composition applied over a basecoat is not more than 8, preferably not more than 4 and, with particular preference, is 0.
11. A process as claimed in any of claims 8 to 10, wherein the coating composition is curable by means of UV radiation or electron beams.
12. A process as claimed in claim 11, wherein the coating composition has a viscosity at 23°C of less than 100 s, preferably less than 80 s, efflux time in the DIN 4 cup.
13. A process as claimed in claim 11 or 12, wherein the coating composition comprises one or more polyester (meth)acrylates and/or polyurethane (meth)acrylates as binders and/or wherein the binder employed is substantially silicone-free.
14. A process as claimed in any of claims 11 to 13, which comprises one or more mono- and/or diacrylates as reactive diluents.
15. A process for producing multicoat finishes, in which

    (1) a pigmented basecoat is applied to the substrate surface,

    (2) the basecoat film is dried or crosslinked,

    (3) a transparent topcoat is applied atop the resultant basecoat film, and then

    (4) the topcoat film is cured,

    which comprises using a coating composition as claimed in any of claims 1 to 7 as the topcoat.
16. A process as claimed in claim 15, which is used to produce multicoat finishes in the automotive sector.