GB2186281A

GB2186281A - Reactive paints

Info

Publication number: GB2186281A
Application number: GB08630804A
Authority: GB
Inventors: Horst Dalibor
Original assignee: SYNTHOPOL CHEMIE DR KOCH
Current assignee: SYNTHOPOL CHEMIE DR KOCH
Priority date: 1985-12-23
Filing date: 1986-12-23
Publication date: 1987-08-12
Also published as: JPS62230864A; DE3545948C1; DE3545948C2; GB2186281B; GB8630804D0; JP2536855B2

Abstract

Reactive paints suitable for the preparation of coatings, primers, primer surfacers and spray surfacers, comprises:- (A and A') Binder components, having hydroxyl groups, (B) Polyisocyanates as curing agents, (C) Inert organic solvents, (D) Other conventional paint additives wherein the components A & A' (calculated as solid resins) comprise the following:- A. 10.00-90.00% by weight of copolymers based on (a) 70.00-21.00% by weight of styrene and/or vinyltoluene, (b) 2.00-0% by weight of acrylic, methacrylic and/or itaconic acid, (c) 10.00-39.00% by weight of one or more hydroxyalkyl esters of acrylic acid and/or methacrylic acid, having 2 to 8 carbon atoms in the alkyl radical, (d) 0-20.00% by weight of one or more alkyl esters of methacrylic acid, having 1 to 8 carbon atoms in the alkyl radical, and (e) 0-38.00% by weight of butyl acrylate and/or 2-ethylhexyl acrylate, the components (a), (b), (c) (d) and (e) being selected to be present in such quantities that these add up to 100% by weight and the copolymers having a hydroxyl group content of 1-5% by weight, and A'. 90.00-10.00% by weight of epoxide resins, the components A and A' being selected to be present in such quantities that these add up to 100% by weight. %

Description

SPECIFICATION Reactive paints for the preparation of coatings, primers, primer surfacers and spray surfacers, and process for the preparation of coatings The invention relates to reactive paints for the preparation of coatings, primers, primer surfaces and spray surfacers and to a process for the preparation of such coatings.

It is the object of the invention to make available such reactive paints of the above type which should have the following properties and thus give surprising effects which are advantageous in several directions.

1. The coating agents are distinguished by outstanding adhesion in the form of primers to steel, aluminum and zinc, and also have improved adhesion to the top coat which is to be applied.

2. The coating agents of the above-mentioned type are primer surfacers and spray surfacers of high surfacing power, which can be free of chromates and which, after application, show quick drying and sandability.

3. The coating agents of the above-mentioned type give, after application, an anti-corrosive priming which has good anti-corrosive properties and in which the adhesion to the metallic substrate is not impaired by the action of water.

4. The coating agents of the above-mentioned type give dry coatings after a relatively short time.

5. The coating agents applied in the form of primers should, after a drying period of 25 minutes at 25"C, reach a dry rating of 3 at a dry layer thickness of about 50 m.

6. The coating agents applied in the form of primers should, after a drying period of 5 days at 25"C and a subsequent salt-spray test according to ASTM 117-64 after exposure for 240 hours, show no blistering or subcoat rusting. Even when the primer is exposed mechanically by means of a knife, no blisters or subcoat rusting should be visible.

7. In the case of the coating agents applied in the form of primers, there should be no blistering in the damp heat test according to DIN 50,017 under constant conditions of 40"C and 100% relative humidity on steel, aluminum and zinc sheets after a test period of 25 days (600 hours exposure).

8. In combination with polyisocyanates, the binder mixture should give air-drying primer surfacers which are intended to replace the conventional primer in automobile finishing and, after subsequent drying, the application of the conventional paint surfacer. This means that the novel primer surfacer prepared with the binder according to the invention is applied in one spray run to the metal surface and allows the previous two-run application of primer, (drying) and paint surfacer to be eliminated.

9. A further advantage is that the same polyisocyanate can be used for the primer surfacer and the two-component reactive paint applied subsequently and based on acrylic resin/polyisocyanate, whereby outstanding adhesion and corrosion resistance are achieved.

10. The primer surfacer according to item 8 is sandable after just 30 minutes.

11. The binder mixture in combination with polyisocyanates, as a high-film surfacer with film thicknesses of up to 200 ,lem, should be dry in 30 minutes at 60"C, so that a more rapid operational sequence in paint shops is obtained.

12. The binder mixture should be storage-stable in spite of the presence of carboxyl groups in the copolymer resin and epoxide groups in the epoxide resin. This means that only a negligible rise in viscosity takes place on storage of the binder mixture.

As is known, reactive automobile finishing and refinishing paints based on acrylic resins and polyisocyanates, such as are described, for example, in German Patent Specifications 2,858,096, 2,858,097 and 2,858,105, have very advantageous properties with respect to good gloss retention, to the resistances to premium gasoline and cleansers and to the surface hardness of the top coat system.

However, the primers which in automobile refinishing are applied to the sheet steel substrate still require improvement. The existing primers are based on quick-drying polyesters, but the coatings thus produced have unsatisfactory corrosiori properties. Moreover, the adhesion between the polyester primers and the reactive paint coatings requires improvement.

The component A, which is present as a copolymer, is produced in a manner known per se by polymerization in the presence of polymerization initiators (individually or as a mixture) of the vinyl compounds in organic inert solvents.

In a preferred embodiment for preparing the co-polymers, inert organic solvents having a boiling range from about 120 to about 18000 are heated to the boil under an inert blanketing gas and are copolymerized, with gradual addition of the monomer mixture of the vinyl compounds, in the course of 2 to 8 hours, preferably 4 to 6 hours, in the presence of at least one polymerization initiator, preferably two polymerization initiators, water of reaction being removed continuously from the boiling reaction batch by azeotropic distillation with return of the water free distillate. After the end of the addition of the vinyl monomers, the polymerization is continued until the latter are in the coplymerized state, which requires about 2 to about 8 hours, preferably 3.5 to 5 hours.

In a special embodiment as claimed in claim 1, the copolymers present have been obtained by combined polymerization of a) 50.9% by weight of styrene, b) 17.4% by weight of methyl methacrylate, c) 1.8% by weight of acrylic acid d) 14.8% by weight of hydroxyethyl acrylate and e) 15.0% by weight of 2-ethylhexyl acrylate.

In another preferred embodiment as claimed in claim 1, the copolymers present have been obtained by combined polymerization of a) 24.9% by weight of styrene, c) 1.1% by weight of acrylic acid, d) 30.5% by weight of hydroxyethyl methacrylate and e) 43.8% by weight of butyl acrylate.

Examples of polymerization initiators which can be used, individually or as a mixture, are: diacyl peroxides, ketone peroxides, alkyl hydroperoxides, alkyl peresters, for example benzoyl peroxide, hydroxyheptyl peroxide, 1-hydroxycyclohexyl peroxide, t-butyl perbenzoate, tert.-butyl peroxyoctoate, di-tert.-butyl peroxide and all peroxides, the half lives of which are within a temperature range from 50 to 150"C.

Preferred embodiments include the following peroxide combinations: dibenzoyl peroxide/cumene hydroperoxide, dibenzoyl/di-tert.-butyl peroxides, tert.-butyl peroctoate/cumene hydroperoxide, tert.-butyl peroctoate/di-tert.-butyl peroxide, tert.-butyl perbenzoate/cumene hydroperoxide and tert.-butyl perbenzoate/di-tert.-butyl peroxide.

The monomers d are alkyl esters of methacrylic acid, having 1 to 8 carbon atoms in the alkyl radical, for example methyl, ethyl, propyl, isopropyl, n-butyl, isobutyl, sec.-butyl, tert.-butyl, amyl, hexyl, heptyl and octyl methacrylates.

The monomers c are hydroxyalkyl esters of acrylic acid and/or methacrylic acid, having 2 to 8 carbon atoms in the alkyl radical, for example 2-hydroxyethyl, 2-hydroxypropyl, butanediol mono hydroxybutyl, hydroxyamyl, hydroxyhexyl, hydroxyheptyl and hydroxyoctyl acrylates and/or methacrylates.

The monomers e are, for example, n-butyl, isobutyl, sec.-butyl, tert.-butyl and/or 2-ethylhexyl acrylates.

The epoxide resins used can in principle be the epoxide resins known to those skilled in the art. Epoxide resins based on bisphenol A, such as

in which n has a value from zero to ten, or bisphenol F and epichlorohydrin are particularly preferred. Further examples of epoxide resins are epoxy novolak resins of the diglycidyl ethers of hydrogenated bisphenol A or cycloaliphatic polyepoxide compounds, such as are described, for example, in H. Jahn "Epoxidharze [Epoxide resins]", VEB Deutscher Verlag fur Grundtoffindustrie Leipzig, 1969, or in H. Batzer and F. Lohse in "Ullmanns Enzyklopadie der technischen Chemie [Ullmann's Encyclopedia of Industrial Chemistry]'', volume 10, pages 563 et seq., 4th edition, Verlag Chemie, Weinheim 1975.

Preferably, the epoxide resins used as the component A' are based on reaction products of epichlorohydrin with bisphenol A, with epoxide equivalents of about 400 to about 1,000, the most preferred range being between about 500 and about 600.

The binder mixture is prepared by mixing solutions of components A and solutions of component A' in inert organic solvents, if necessary with heating to 80 to 150"C.

Additions of low-viscosity epoxide resins can also be advantageous in the preparation of the binder mixture. The diglycidyl ethers of aliphatic diols, for example of 1,4-butanediol, 1,6hexanediol or neopentyl glycol, are particularly suitable for this purpose.

Since reactions of component A with component A' on mixing are possible, especially when hot, it can be advantageous to add effective quantities of a catalyst, which accelerates the modifying reaction, to the mixture of the epoxide resin and the copolymer containing carboxyl groups. Particularly preferred catalysts are alkali metal compounds, such as sodium, lithiu potassium, rubidium and cesium compounds-individually or as a mixture-for example t a carbonates, bicarbonates, formates and hydroxides, quaternary ammonium or phosphonium com pounds such as, for example, tetramethyiammonium chloride or iodide, benzyltrimethylammonium chloride and tetrabutylphosphonium chloride or acetate.

In general, it is sufficient to add from about 0.005% by weight to about 0.5% by weight of the abovementioned modifying catalysts, the % by weight relating to the weight of the copolymer present and the epoxide compound(s). All those modifying catalysts of the abovementioned type can be used which go into solution at least during the addition and/or while holding at the modifying temperature, but the modifying catalysts should be free of constituents which can have an adverse effect in the further processing and curing.

Polyisocyanates are used for curing the binder mixture. Examples of these are: 3,5,5-trimethyl 1-isocyanato-3-isocyanatomethylcyclohexane, di-(2-isocyanatoethyl) bicyclo[2,2,1]hept-5-ene-2,3- dicarboxylate, 2,4-toluylene diisocyanate, 2,6-toluylene diisocyanate, 4,4'-diphenylmethane diisocyanate, dianisidine diisocyanate, toluidine diisocyanate, hexamethylene diisocyanate, dicyclohexyl-4,4'-methane diisocyanate, cyclohexane 1,4-diisocyanate, 1 ,5-naphthylene diisocyanate, 4,4'-diisocyanatodiphenyl ether, 2,4,6-toluene triisocyanate, triphenylmethane 4,4'-4"-triisocyanate, ethylene diisocyanate, propylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, 1,3-dimethylbenzene diisocyanate, 1 ,4-dimethylcyclohexane diisocyanate, 1-methylcyclohexane 2,4-diisocyanate, 4,4'-methylene-bis-(cyclohexyl diisocyanate), phenylene diisocyanate, naphthylene diisocyanate, 3-isocyanatomethyl-3,5,5-trimethylcyclohexyl isocyanate, lysine diisocyanate, triphenylmethane triisocyanate, trimethylbenzene 2,4,6-triisocyanate, 1-methylbenzene 2,4, 6-triisocyanate and diphenyl 2,4,4'-triisocyanate; diisocyanates or triisocyanates prepared by reacting a polyisocyanate with a low-molecular diol or triol (for example ethylene glycol, propylene glycol, 1,3-butylene glycol, neopentyl glycol, 2,2,4-trimethyl-1 ,3-pentanediol, hexanediol, trimethylolpropane or trimethylolethane); and cyanurates which are obtained by reacting the said diisocyanates with cyclization.

Particularly valuable polyisocyanates are triisocyanates which contain biuret groups and which are obtained by reacting 3 moles of diisocyanate and one mole of water, for example the biuret from hexamethylene diisocyanate or 4,4'-methylene-bis-(cyclohexyl isocyanate) or 3-isocyanato methyl-3,5.5-trimethylcyclohexyl isocyanate. Polyisocyanates obtained by heterocyclic cyclization from 3 moles of diisocyanates, for example hexamethylene diisocyanate, are also suitable.

In place of the polyisocyanates, it is also possible to use polyisocyanate-donor compounds, and also reaction products, containing isocyanate groups, of polyhydric alcohols, for example ethylene glycol, propylene glycol, hexanediol, trimethylolpropane or trimethylolethane, with polyisocynates, for example the reaction product of 1 mole of trimethylolpropane with 3 moles of toluylene diisocyanate, and also trimerized or polymerized isocyanates such as are described, say, in German Patent Specification 951,168.

If desired, the curing of the binder mixture with the polyisocyanates as curing agents can be accelerated by the addition of curing catalysts. Suitable curing catalysts for this purpose are stannous acylates or stannous alkoxides, which may be substituted by hydroxyl, halogen, keto or other groups and which do not adversely affect the curing reaction. Amongst the stannous acylates which can be used as a curing catalyst component, the divalent tin salts of mono- and di-carboxylic acids having 1 to 54 carbon atoms are mentioned; these carboxylic acids can be saturated acids such as acetic acid, 2-ethylhexanoic acid or ethylphthalic acid, and can be unsaturated, such as oleic acid, linoleic acid, oleostearic acid, ricinoleic acid and the like.For clarification, stannous acetate, stannous propionate, stannous oxalate, stannous butyrate, stannous tartrate, stannous valerate, stannous octanoate, stannous stearate, stannous oleate, dibutyltin dilaurate and the like may be mentioned as suitable stannous acylates. Amongst the stannous alkoxides which can be used as curing catalysts, the divalent tin salts of saturated or unsaturated, straight-chain or branched alcohols having 1 to 18 carbon atoms should be mentioned.

Examples of stannous alkoxides suitable for this purpose are stannous methoxide, stannous isopropoxide, stannous butoxide, stannous t-butoxide, stannous 2-ethylhexoxide, stannous tridecanoxide, stannous heptadecanoxide, stannous phenoxide and o-, m- and p-stannous cresoxides and the like.

The coating agents, which contain the binder mixture of components A, A' and, if appropriate, A" and the polyisocyanates as curing agents, are prepared by thorough mixing of the various required components in the necessary quantities and used in accordance with the rules known for formulations containing reactive components.

The total quantity of isocyanate groups in the coating agents must be sufficient for the isocyanate groups to be able to react with the reactive hydrogen atoms which are present at the start of curing or are formed in the course of the curing reaction.

0.5 to 1. 10 equivalents, preferably 0.8 to 1.05 equivalents, of isocyanate are used per reactive hydrogen atom.

The concentration of stannous salt in the coating agent can be between 0.1 and 10% by weight, preferably 0.5 to 2% by weight, relative to the weight of the binder mixture and the polyisocyanates.

In the preparation of the copolymers A, inert organic solvents, individually or as a mixture, are used which allow adjustment to the desired boiling range from about 120 to 180"C and are suitable for holding the copolymer A in solution and also, during the preparation of the binder mixture by addition of the epoxide compounds as the component A', for giving solutions which are free of turbidity. Examples of these are aromatic solvents and esters having boiling points from 120 to about 1800C.

In the preparation of the reactive paint coating agents by mixing the binder mixture with polyisocyanates and the conventional constituents, such as are usual for the preparation of primers, primer surfacers and spray surfacers, inert organic solvents are additionally used, which are likewise conventional in the paint industry and the boiling points of which can be substantially lower, in order to achieve rapid drying by evaporation of the solvents in the curing reactive paint coating agent.

The conventional constituents for the preparation of primers, primer surfacers and spray surfacers also include nitrocellulose solutions in inert organic solvents, which are usual in the paint industry.

Preparation of copolymer 1 940 g of an aromatic solvent mixture having boiling points of 140-160"C (ShellsolS A) are heated with 450 g of ethylglycol acetate to 160"C in a reaction vessel which is fitted with a stirrer, thermometer, reflux condenser with water separator and inert gas inlet. A mixture con sisting of: 610 9 of methyl methacrylate, 997 g of hydroxyethyl methacrylate, 990 g of styrene, 43 g of acrylic acid, 674 g of n-butyl acrylate, 70 g of di-tert.-butyl peroxide and 70 g of dibenzoyl peroxide, 75% dispersed or dissolved in water, is added evenly over 7 hours.While the monomer mixture is running in, the distillation temperature falls to 150"C. The polymerization is then continued for a further 5 hours, and a solids content of 70% by weight in the solvent mixture is obtained. For measuring the viscosity, the copolymer solution is diluted to 60% by weight with a commercially available aromatic solvent Shellsolssm A (described in the company brochure Shellsole A from Esso AG) and ethylglycol acetate in a volume ratio of 2:1. The viscosity is 1500-1800 cP at 20"C. The acid number of the copolymer as a solid resin has a value of 11-13 and the hydroxyl number of the solid resin is 120.

Reference Example 1: Preparation of binder mixture 1 2500 g of copolymer 1 are held at 90"C for 1-2 hours with 2320 g of an epoxide resin based on a reaction product of epichlorohydrin and bisphenol A, which has an epoxide equivalent of 450-530 and is dissolved to 70% in xylene. The following characteristic data are obtained for the solution of the binder mixture: 72% by weight of solids, acid number of the solid binder mixture resin 7, hydroxyl number of the solid binder mixture resin 200-230. The viscosity of binder mixture 1 is 13,000-15,000 cP at 20"C.

Reference Example 2: Preparation of binder mixture 2 1750 g of copolymer 1, dissolved to 72% by weight in Shellsolo A and ethylglycol acetate in a volume ratio of 2:1, 750 g ethylglycol acetate, 140 g of xylene, 230 g of 98/100% butyl acetate, 100 g of calcium naphthenate (4% by weight calcium content), 100 g of silicone oil solution L 050, dissolved to 1% in xylene, and 480 g of epoxide resin based on epichlorohydrin and bisphenol A, dissolved to 33% in ethylglycol acetate/xylene in a volume ratio of 2:1 and having an epoxide equivalent of 2,400-4,000, relative to 100% epoxide resin, are mixed.

Application Example 1: a. Preparation of a master paint 750 g of talc, 940 g of titanium dioxide A HR (anatase), 2170 g of aluminum silicate ASP 400, 940 g of zinc phosphate, 140 g of yellow iron oxide and 280 g of zinc oxide were added to the solution of binder mixture 2, obtained above in reference example 2, in a dissolver. This material to be ground is then put into a bead mill until a grain fineness of less than 25 item has been reached. Then, 480 g of Bentone paste (contains 10% by weight of Bentone 34 and 4% by weight of Bykumen 40% as a wetting agent) and 750 g of nitrocellulose solution, 20% by weight in butyl acetate, from E 400 nitrocellulose cotton, are added in a mixer.

b. Preparation of the curing agent solution 3650 g of triisocyanate, which has been prepared from 3 moles of hexamethylene diisocyanate and one mole of water and has an NCO content of 21% by weight, relative to the 100% curing agent, are dissolved in 1,800 g of xylene, 2,600 g of ethylglycol acetate and 1,950 g of butyl acetate.

c. Preparation of the reactive coating agent mixture 4 parts by volume of the master paint according to section a are mixed with 1 part by volume of curing agent solution and adjusted with a solvent mixture, consisting of 2,800 g of xylene, 4,000 g of ethylglycol acetate and 3,200 g of butyl acetate, to a spraying viscosity of 20 to 25 seconds, measured at 20"C in a DIN cup with a 4 mm flow orifice.

d. Processing of the reactive coating agent mixture The reactive coating agent mixture obtained is filled into a spraying apparatus. In two to three spray passes, dry film thicknesses of 50 ,um are obtained as primer on pickled sheet steel. The drying time is about 2 hours at 23"C. Forced drying at 60-80"C within 20 or 15 minutes respectively is possible. The coating obtained is also sandable-if necessary-after the drying times. This primer can be overpainted with alkyd resin topcoats or with two-component topcoats based on polymers, containing hydroxyl groups, and polyisocyanates, in particular aliphatic polyisocyanates.Commercially available topcoats from the automobile refinishing sector, for example acrylic 2-component topcoats according to German Patent Specification 2,851,613, Example 2, and German Patent Specification 2,851,614, Example 2, can be used.

After storing for 7 days at room temperature, the sheets coated with the abovementioned primer are subjected to the following tests: 1. Salt spray mist test according to DIN 50,021 (480 hours test), 2. Exposure in the damp heat test according to DIN 50,017 for 240 hours (c on the surface and in a cut; d on the surface and in a cut).

The evaluation was then carried out by the following criteria: a. Degree of blistering according to DIN 53,209 on the surface and in a cut.

b. Adhesion according to DIN 53,151 on the surface and in the cut.

Re 1. Assessment after the 480 hours salt spray test: a. mO/gO on the surface; m3/g5 in the cut, b. GtO on the surface; 3 mm disbonding in the cut.

Re 2. Assessment after the 240 hours damp heat test: c. mO/gOl on the surface and mO/gO in the cut, d. Gt1 on the surface; 3 mm disbonding in the cut.

Comparable commercially available, good two-component primer surfacers showed poorer adhesion or none at all in the salt spray test and also increased blistering. The differences manifested themselves to an even greater extent in the damp heat test. All the products were chromate-free materials, like the product according to the invention.

Preparation of copolymer 7 450 g of butyl acetate and 4,1 70 g of xylene are filled into a reaction flask fitted with stirrer, thermometer, reflux condenser with water separator and inert gas inlet, and heated up to reflux at about 133-137"C.

In the course of 4 hours, a solution consisting of 2,400 g of styrene, 87 g of acrylic acid, 710 g of hydroxyethyl acrylate, 835 g of methyl methacrylate, 720 g of 2-ethylhexyl acrylate and 70 g of di-tert.-butyl peroxide.

is allowed to run uniformly into the boiling solvent mixture.

After the end of the addition, the mixture is kept under reflux for a further 4 hours by heating, in order to complete the polymerization.

The solids content of this copolymer solution is 51% by weight. The copolymer has an acid number of 13-15 and a hydroxyl number of 80-85. The viscosity of the copolymer solution is 250-280 seconds, measured at 20"C in a DIN cup with 4 mm flow orifice.

Reference Example 3: Preparation of binder mixture 3 350 9 of a commercially available epoxide resin based on epichlorohydrin and bisphenol A, designated EpikoteS 1001 (described in the Shell AG company brochure Epikotes 1001) are added to 2,100 g of the copolymer solution 7 obtained above, and 450 9 of xylene, 350 g of butyl acetate and 200 9 of methylglycol acetate are then added and the mixture is stirred until a homogeneous solution is obtained.

Application Example 2 a. Preparation of a master paint for an automobile refinishing surfacer The binder mixture 3 obtained in Reference Example 3 is mixed in the conventional manner with 1,000 g of titanium dioxide RN 59, 2,300 g of ASP 600, 150 9 of yellow iron oxide, 1,000 g of zinc phosphate ZP 10, 800 g of talc AT extra, 300 g of zinc oxide NT, 100 9 of Bentone 38 paste, 10% by weight in 86% by weight of xylene and 4% by weight of Bykumen (wetting agent), 100 g of silicone oil LO 50, 1% in xylene, and 800 9 of nitrocellulose cotton E 400, 20% in butyl acetate, and homogenized.

b. Curing agent solution The curing agent solution used is a commercially available polyisocyanate designed Desmoduro N (described in the Bayer AG company brochure Desmodurs N as a reaction product of 3 moles of hexamethylene diisocyanate and one mole of water).

c. Preparation of the reactive coating agent mixture (automobile refinishing surfacer) 420 9 of Desmodur N (75 /0 by weight of polyisocyanate and 25% by weight of solvent) are mixed with the master paint obtained above according to a.

A solvent mixture of 2,500 g of ethylglycol acetate, 2,000 g of Shellsolo A, 4,000 g of xylene and 1,500 g of butyl acetate is used.for adjusting the spraying viscosity.

d. Processing of the reactive coating agent mixture (automobile refinishing surfacer) The procedure followed is as stated in Application Example 1, section d. Testing of the applied automobile refinishing surfacer coat gave properties comparable to those indicated at the end of Application Example 1.

A further preferred embodiment as claimed in claim 1 contains copolymers which have been obtained by combined polymerization of a) 48.0052.00% by weight of styrene, c) 31.00-34.00% by weight of hydroxyethyl methacrylate and e) 14.00-21.00% by weight of butyl acrylate.

The most preferred embodiment from this group of preferred copolymers is illustrated by the preparation of the following copolymer 8.

Preparation of copolymer 8 1,200 g of aromatic solvent mixture having a boiling point of 162-177"C are heated to about 165-173"C at rising reflux temperature in a reaction flask fitted with stirrer, thermometer, reflux condenser with water separator and inert gas inlet.

In the course of 7 hours, a solution consisting of 1,200 9 of styrene, 672 9 of n-butyl acrylate, 1,328 g of hydroxyethyl methacrylate, 90 g of dibenzoyl peroxide 75% (dispersed in water) and 90 9 of di-tert.-butyl peroxide is allowed to run uniformly into the boiling solvent mixture. After the end of the addition, reflux is maintained by heating for a further 4 hours, in order to complete the polymerization. 600 g of butyl acetate were then added and the mixture was thoroughly stirred.

The solids content of this copolymer solution is 70% by weight. The copolymer has an acid number of 4-5 and a hydroxyl number of about 140. The viscosity of the copolymer solution is 18,000 cP, measured at 250C in a DIN cup with a 4 mm flow orifice.

As indicated in Table Vl for copolymers 2, 3, 4, 5, 6 and 7, this copolymer 8 can be processed together with epoxide resins as a binder mixture to give a master paint as a primer surfacer. The coatings prepared with this copolymer meet the object of the invention, mentioned at the outset.

Table V Viscosity rise after the preparation of binder mixture 1 according to Example 1 as a function of time at 50"C in the absence of catalysts (viscosity measurement at 20"C).

Days Viscosity cP 1 13,960 3 15^240 10 15,240 20 14,600 The above viscosity measurements show very clearly that only a slight rise in viscosity has take place after 20 days on storage at 50"C. This means that, in spite of the presence of carboxyl groups in the copolymer resin and epoxide groups in the epoxide resin, the binder mixture is storage-stable when stored at outdoor temperatures and that only a negligible rise in viscosity takes place.

Preparation of copolymers 2 to 6 The copolymers 2 to 6 are preparated in the same way as described above for the preparation of copolymer 1. The numerical data given in Table 1 which follows relate to percent by weight.

As distinct from the solvent mixture used in the preparation of copolymer 1, the preparation of copolymers 2 to 6 is carried out in accordance with the data in Table II.

Table I

Monomers Copolymer 2 Copolymer 3 Copolymer 4 Copolymer 5 Copolymer 6 Styrene 68.3 48.7 48 58.2 30 Hydroxyethyl methacrylate 30.4 30 30.2 30 30 Acrylic acid 1.3 1.3 1.3 1.3 1.3 Methyl methacrylate 20 18.4 n-butyl acrylate 20.5 10.5 20.3 Solids content in % by weight 70 70.2 70.3 71.1 70 Viscosity of the 60% by weight solution in SolvessoR 100/ButoxylR at 20 C 3,240 cP 3,290 cP 1,240 cP 2,280 cP 1,430 cP Table II

Copolymer running-in Solvent mixture Final polymer- Reflux tem- Polymerization No. time of the in weight ratio ization timeP perature initiators in monomer % by weight 2 7 Shellsol+ A: 3 160 C DTBT+: 2.1 DBP++: 2.1 Butoxyl++= 2:1 3 7 " 3 160 C DTBP: 2.1 DBP: 2.1 4 7 " 3 160 C DTBP: 2.1 DBP: 2.1 5 7 " 3 160 C DTBP: 2.1 DBP: 2.1 6 7 " 5 155/153 C DTBP: 2.1 DBP: 2.1 + DTBP = di-tert.-butyl peroxide ++ DBP = dibenzoyl peroxide moistened with 25% by weight of water +++ relative to the weight of the monomers employed + in hours ++ ButoxylR consists of 3-methoxy-n-butyl acetate + ShellsolR A aromatic solvent mixture having boiling points of 140-160 C Procedure in Reference Examples 4 to 8 In Reference Examples 4 to 8, the procedure according to the process data in Example 1 is followed.

Different experimental data are indicated in Table III which follows. The percentage data relate to the solids content in % by weight of the copolymer employed and to the solids content in % by weight of the epoxide resin. The acid numbers and hydroxyl numbers relate to the solids content of the binder mixtures.

Table III Preparation of binder mixtures 4 to 8

Example 4 Example 5 Example 6 Example 7 Example 8 Copolymer in No. 2 No. 3 No. 4 No. 5 No. 6 % by weight 50 50 50 50 50 Epoxide resin in % by weight 50 50 50 50 50 solids content in % by weight 71 71 71.6 72.8 70 Viscosity at 20 C 26,400 cP 27,500 cP 16,600 cP 13,600 cP Hydroxyl number 230 230 230 230 142 Acid number 7 7 8 6 12 Table IV Viscosity rise after preparation of the binder mixture in the absence and presence of a catalyst (binder mixture 1 according to Reference Example 1) Temperature 25 C

24 hours 48 hours 72 hours without catalyst 14,400 cP 14,560 cP 14,560 cP 0.5% by weight of potassium hydroxide 14,400 cP 14,880 cP 15,760 cP 0.5% by weight of tetramethyl- 14,400 cP 14,880 cP 15,200 cP ammonium chloride 0.5% by weight of tetrabutyl- 14,400 cP 14,880 cP 15,200 cP phosphonium bromide Temperature 80 C

15 minutes 30 minutes 45 minutes 60 minutes without catalyst 14,400 cP 14,560 cP 14.720 cP 14.880 cP 0.5% by weight of potassium hydroxide 14,880 cP 15,200 cP 15,680 cP 16,000 cP 0.5% by weight of tetramethyl- 14,560 cP 14,880 cP 15,360 cP 15,680 cP ammonium chloride 0.5% by weight of tetrabutyl- 14,560 cP 15,040 cP 15,520 cP 15,760 cP phosphonium bromide Temperature 100 C

15 minutes 30 minutes 45 minutes 60 minutes without catalyst 14,880 cP 14,880 cP 15,520 cP 15,680 cP 0.5% by weight of potassium hydroxide 15,200 cP 15,680 cP 16,000 cP 16,560 cP 0.5% by weight of tetramethyl- 14,880 cP 15,200 cP 15,680 cP 16,000 cP ammonium chloride 0.5% by weight of tetrabutyl- 14,800 cP 15,200 cP 15,840 cP 16,160 cP phosphonium bromide The above investigations show that the binder mixture is fairly storage-stable in the absence or in the presence of catalysts, even at elevated temperatures.This means that only a negligible rise in viscosity takes place in conventional storage of the binder mixture at external temperatures Table VI Preparation of a master paint as a primer surfacer

Appl.Ex.+ 3 Appl.Ex. 4 Appl.Ex. 5 Appl.Ex. 6 Appl.Ex. 7 Appl.Ex. 8 Acrylic resin Cop.++3: 18.5 Cop. 2: 18.5 Cop.4: 18.5 Cop. 6: 18.5 Cop.2: 18.5 Titanium dioxide A 59 10.0 10.0 10.0 10.0 10.0 10.0 (anatae) Aluminium silicate ASP 600 19.0 19.0 19.0 19.0 23.0 23.0 Yellow iron oxide 1.5 1.5 1.5 1.5 1.5 1.5 Zinc phosphate 10.0 10.0 10.0 10.0 ZP 10 10.0 10.0 Talc AT extra 8.0 8.0 8.0 8.0 8.0 8.0 Zinc oxide S-NT 3.0 3.0 3.0 3.0 3.0 3.0 Methylglycol Ethylglycol acetate 8.0 8.0 8.0 acetate 8.0 7.0 7.0 Butyl acetate 5.0 5.0 5.0 5.0 3.5 3.5 Sil. LD50/1% x 1.0 1.0 1.0 1.0 1.0 1.0 Xylene 3.5 3.5 3.5 3.5 4.5 4.5 DBTL Butyl acetate 4.5 4.5 4.5 4.5 1.0 1.0 1% x Bentone 38 + Bykumen 8.0 8.0 8.0 8.0 1.0 1.0 Nitrocellulose E 400, 20% by weight dissolved in 8.0 8.0 butyl acetate EpikoteR 1001 as solids in % 25.0 25.0 15.0 15.0 50.0 50.0 Solids content of the 70.7 71.4 69.7 70.0 72.0-73.0 71.3 binder mixture Viscosity cP 30,700 40,000 12,000 13,600 13,000-15,000 26,400 Acid number 10 10 12 12 6 - 8 7.1 Hydroxyl number 175 173 142 142 210 - 230 230.0 + Application example ++ Copolymer

Claims

1. A reactive paint for the preparation of coatings, primers, primer surfacers and spray surfacers prepared by mixing: (A, A', if appropriate A") compounds, carrying hydroxyl groups, as binder components, (B) polyisocyanates as curing agents, (C) insert organic solvents and, if appropriate, (D) further additives conventional in reactive paints, which comprises, as the components (A and A'), calculated as solid resins, A.

10.00-90.00% by weight of copolymers based on a) 70.0021.00% by weight of styrene and/or vinyltoluene, b) 2.000% by weight of acrylic, methacrylic and/or itaconic acid, c) 10.00-39.00% by weight of one or more hydroxyalkyl esters of acrylic acid and/or methacrylic acid, having 2 to 8 carbon atoms in the alkyl radical, d) 0-20.00% by weight of one or more alkyl esters of methacrylic acid, having 1 to 8 carbon atoms in the alkyl radical, and e) 0-38.00% by weight of butyl acrylate and/or 2-ethylhexyl acrylate, the components a), b), c), d) and e) being selected to be present in such quantities that these add up to 100% by weight and the copolymers having a hydroxyl group content of 1-5% by weight, and A'.

90.00-10.00% by weight of epoxide resins, the components A and A' being selected to be present in such quantities that these add up to 100% by weight.

2. A reactive paint as claimed in claim 1, wherein component A represents copolymers based on: a) 51.00-30.00% by weight of styrene and/or vinyltoluene, b) 1.00-2.00% by weight of acrylic, methacrylic and/or itaconic acid, c) 14.00-39.00% by weight of one or more hydroxyalkyl esters of acrylic acid and/or methacrylic acid, having 2 to 8 carbon atoms in the alkyl radical, d) 10.00-20.00% by weight of one or more alkyl esters of methacrylic acid, having 1 to 8 carbon atoms in the alkyl radical, and e) 13.00-20.00% by weight of butyl acrylate and/or 2-ethylhexyl acrylate, the components a), b), c), d) and e) being selected to be present in such quantities that these add up to 100% by weight.

3. A reactive paint as claimed in claim 1, wherein component A represents copolymers based on a) 49.00-51.00% by weight of styrene and/or vinyltoluene, b) 2.00-1.00% by weight of acrylic, methacrylic and/or itaconic acid, c) 16.00-14.00% by weight of one or more hydroxyalkyl esters of acrylic acid and/or methacrylic acid, having 2 to 8 carbon atoms in the alkyl radical, d) 18.00-16.00% by weight of one or more alkyl esters of methacrylic acid, having 1 to 8 carbon atoms in the alkyl radical, and e) 18.00-15.00% by weight of butyl acrylate and/or 2-ethylhexyi acrylate, the components a), b), c), d) and e) being selected to be present in such quantities that these add up to 100% by weight.

4. A reactive paint as claimed in claim 1, wherein component A represents copolymers based on a) 29.00-31.00% by weight of styrene and/or vinyltoluene, b) 1.00-2.00% by weight of acrylic, methacrylic and/or itaconic acid, c) 32.00-14.00% by weight of one or more hydroxyalkyl esters of acrylic acid and/or methacrylic acid, having 2 to 8 carbon atoms in the alkyl radical, d) 20.00-18.00% by weight of one or more alkyl esters of methacrylic acid, having 1 to 6 carbon atoms in the alkyl radical, and e) 21.00-18.00% by weight of butyl acrylate and/or 2-ethylhexyl acrylate, the components a), b), c), d), and e) being selected to be present in such quantities that these add up to 100% by weight.

5. A reactive paint as claimed in claim 1, wherein component A represents copolymers based on: a) 50.00-61.00% by weight of styrene and/or vinyltoluene, b) 1.00-2.00% by weight of acrylic, methacrylic and/or itaconic acid, c) 39.00-14.00% by weight of one or more hydroxyalkyl esters of acrylic acid and/or methacrylic acid, having 2 to 8 carbon atoms in the alkyl radical, and (e) 24.00-9.00% by weight of butyl acrylate and/or 2-ethylhexyl acrylate, the components a), b), c), and e) being selected to be present in such quantities that these add up to 100% by weight.

6. A reactive paint as claimed in claim 1, wherein component A represents copolymers based on a) 48.00-52.00% by weight of styrene, c) 31.00-34.00% by weight of hydroxyethyl methacrylate and e) 14.00-21.00% by weight of butyl acrylate, the components a), c) and e) being selected to be present in such quantities that these add up to 100% by weight.

7. A reactive paint as claimed in any of claims 1 to 6, wherein up to 10% by weight of nitrocellulose conventional in the paints industry is additionally used as a further component A".

8. A process for the preparation of coatings, primers, primer surfacers and spray surfacers by applying a paint based on compounds carrying hydroxyl groups, polyisocyanates, solvents and, if appropriate, conventional additives to a substrate and curing at room temperature or an elevated temperature of up to 80"C, which comprises using a paint as claimed in any of claims 1 to 7.