|||||||||||| US005194334A United States Patent (19) 11 Patent Number: 5,194,334 Uerdingen et al. (45) Date of Patent: Mar. 16, 1993

(54) PROCESS FOR THE PRODUCTION OF 52 U.S.C...... 428/416; 156/196; SHEET METAL/ DUROPLAST COMPOSTE 156/245; 156/315; 264/135; 525/31 ELEMENTS (56) References Cited 75) Inventors: Walter Uerdingen, Leverkusen; Bert U.S. PATENT DOCUMENTS Brassat, Krefeld; Karl-Ludwig Noble, 2,384,269 9/1945 Bake...... 56/315 Cologne; Bernhard Hess, Moers; 3,508,951 4/1970 Shimp et al...... 525/31 Heino Miller, Leverkusen; Heinz 3,551,517 12/1970 Dowbenko et al. ... 428/416 Eichner, Moenchen-Gladbach, all of 3,844,030 i0/1974 Wilkinson ...... 264/135 Fed. Rep. of Germany 4,673,706 6/1987 Atkins ...... 525/31 73) Assignee: DSM. N.V., Heerlen FOREIGN PATENT DOCUMENTS 0182642 10/1986 European Pat. Off. . 21 Appl. No.: 603,264 55-117653 9/1980 Japan ...... 428/416 Primary Examiner-John J. Gallagher (22) Filed: Oct. 25, 1990 Attorney, Agent, or Firm-Connolly & Hutz Related U.S. Application Data (57) ABSTRACT 63) Continuation of Ser. No. 208,675, Jun. 20, 1988, aban The use of molding compositions based on unsaturated doned. resins containing specific reactive groups and of sheet metals with a specially selected coating results (30) Foreign Application Priority Data in sheet metal/duroplast composite elements having Jul. 2, 1987 (DE) Fed. Rep. of Germany ...... 3721849 excellent adhesion. 51) int. Cl...... B32B 15/08; C09J 5/04 12 Claims, No Drawings 5,194,334 1. 2 cured without shrinking so that they are free from inter PROCESS FOR THE PRODUCTION OF SHEET naq stresses, sink marks and wavyness after cooling. Accordingly, the use of molding compositions of this METAL/DUROPLAST COMPOSITEELEMENTS type guarantees the composite elements a particularly This application is continuation of application Ser. 5 good appearance (EP-A 119 131). No. 07/208,675, filed Jun. 20, 1988, now abandoned. Practical tests have now shown that molding compo This invention relates to a process for the production sitions based on unsaturated polyester resins of standard of composite elements of corrosion-proofed sheet metal composition adhere inadequately to untreated or con and molding compositions based on unsaturated polyes ventionally pretreated metal sheets after hardening. It ter resins characterized by excellent adhesion, to com 10 does not matter whether the metal sheets are of iron or posite elements produced by this process and to their aluminium or by which of the standard methods, for use in the construction of motor vehicles, particularly as example zinc phosphating or zinc chromating, they body parts. have been pretreated. The same applies even when the Sheet metal/ composite elements combine the metal sheet is coated with a lacquer of standard compo advantages of both their constituent materials. The 15 sition applied by coil coating as protection against cor sheetmetal surface is smooth, hard, resistant to deforma rosion. tion, free from sink marks and wavyness and can be Accordingly, it has not hitherto been possible, for the painted without difficulty. Its electrical conductivity is purpose of establishing a sufficiently strong bond be desirable in many cases. Advantages of the plastic in tween plastic and sheet metal, to manage without mea clude inter alia low weight, resistance to corrosion, 20 sures of the type described above, such as for example vibration and noise damping capacity, heat insulation the provision of undercuts or the separate application of capacity and simple and inexpensive molding, even of a primer to the sheet metal. The need for additional complicated shapes. measures such as these also represents a significant tech Accordingly, sheet metal/plastic composite elements nical disadvantage because the provision of undercuts are suitable for numerous applications, for example for 25 the production of furniture parts and appliance hous limits the structural possibilities available and necessi ings, but especially for use as the outer skin of motor tates additional effort both at the design stage and at the vehicles, cf. FR-P 1567 839, DE-OS 23 15 161. processing stage. The separate application of a primer In the manufacture of such elements, the sheet metal involves an additional step; resulting tacky surfaces can component and the plastic.-component may be made 30 complicate handling of the sheet metal. separately and then bonded to one another. However, Accordingly, the object of the present invention is to the separate forming and handling of the sheet metal provide composite elements of sheet metal and molding component and the plastic component and their subse compositions based on unsaturated polyester resins, quent bonding involve several operations which it is characterized by good adhesion and also a process for desirable to reduce in number for reasons of economy. 35 their production which are not attended by any of the Possibilities in this direction are described in FR-P 1296 disadvantages of the prior art. 103 and 2479 123. In this case, the plastic is directly It has surprisingly been found that this object can be extruded or molded onto the sheet metal, a firm bond achieved by the use of certain molding compositions being established either by mechanical anchorage (coat and by the use of sheet metals having a specially ing of the sheet metal edges, undercuts) or by primers adapted coating. applied beforehand to the sheet metal. Further rationali Accordingly, the present invention relates to a pro zation can be obtained by deep drawing the sheet metal cess for the production of sheet metal/duroplast com and applying the plastic in one and the same mold posite elements of corrosion-proofed sheet metal and a (EP-A 170 819). molding composition based on unsaturated polyester The most suitable for the production of com 45 resin, the molding composition being applied to the posite elements of the type in question are plastics of sheet metal after forming thereof by compression mold which the coefficient of thermal expansion differs very ing and hardening at elevated temperature in one and little from that of the sheet metal used in the tempera the same operation (i.e. without either a special interme ture range through which the elements pass during their diate surface treatment or the application of an adhesive production and in their subsequent use. Steel and alu 50 after forming of the sheet metal), characterized in that 1. minium sheet have linear expansion coefficients of ap the unsaturated polyester resin on which the molding proximately 11 and approximately 24x 10-6K-1. Non composition is based contains polyepoxides in a quan reinforced plastics have values of from about 60 to tity corresponding to 5 to 200, preferably 15 to 110 and 120x10K, depending on their structure. Their use more preferably to 35 to 90 mmol epoxide groups per in the production of composite elements of the type in 100 g of organic binder of the molding composition question gives rise to a number of disadvantages, includ and/or reaction thereof with ag-ethylenically unsatu ing above all deflection in the event of changes in tem rated monoproducts or dicarboxylic acids copolymeriz perature ("bimetal effect”) and the gradual loss of adhe able under the curing conditions, the mono- and dicar sion under thermal shock conditions. boxylic acids having molecular weights below 800, Both can render the parts useless. preferably below 500 and more preferably below 300, By contrast, duroplastic parts produced by hardening and 2. the metal sheet is corrosion-proofed by stove from highly filled, reinforced molding compositions lacquering and, on that side to which the polyester resin based on unsaturated polyester resins have coefficients molding composition is applied, is coated with a primer of linear thermal expansion of approximately 10 to which contains 25X106 K. Accordingly, they can be expected to 65 a) polyepoxides in a quantity corresponding to 5 to show more favorable behavior. In addition, unsaturated 2,00, preferably 10 to 120 and more preferably 10 to 80 polyester resins can be modified by addition of so-called mval of epoxide groups per 100 g of the organic binder low-profile additives in such a way that they can be of this primer and/or 5,194,334 3 4. b) reaction products of the polyepoxides a) with ag Ethylene glycol, propane-1,2-diol, diethylene glycol, ethylenically unsaturated mono- or dicarboxylic acids dipropylene glycol and neopentyl glycol are particu copolymerizable under the curing conditions, the larly suitable. mono- or dicarboxylic acids having molecular weights The acid values of the A may be between below 800, preferably below 500 and more preferably 0 and 100 and preferably between 0 and 50, their OH 300, and/or values may their molecular weights determined as num c) 2.5 to 50, preferably 5 to 40 and more preferably 5 ber averages Mn may be between about 500 and 5,000 to 30% by weight, based on the organic binder of this and preferably between about 1,000 and 3,000 (as mea primer, of unsaturated polyester containing 0.1 to 0.6 sured by vapor pressure osmometry in dioxane and and preferably 0.2 to 0.4 equivalent copolymerizable 10 acetone; in the event of differing values, the lower value is regarded as the correct value). ethylenic double bonds per 100 gunsaturated polyester Suitable B copolymerizable with the poly c), esters A are unsaturated compounds preferably bearing The present invention also relates to the composite a-substituted vinyl groups or 3-substituted allyl groups, elements produced by this process and to their use in the 15 of the type commonly encountered in polyester tech manufacture of motor vehicles. nology, more especially unsubstituted styrene itself, but The molding composition also for example nucleus-chlorinated, -alkylated and Unsaturated polyester resins are mixtures of af3 -alkenylated styrenes, the alkyl or alkenyl groups con ethylenically unsaturated polyesters and monomers taining from 1 to 4 carbon atoms, such as for example copolymerizable therewith which generally contain vinyl toluene, divinyl benzene, a-methyl styrene, tert A. 30 to 80% by weight of unsaturated polyester and butyl styrenes, chlorostyrenes, allyl vinyl benzene; 8.70 to 20% by weight of copolymerizable . vinyl esters of C2-C6 carboxylic acids, preferably vinyl In the context of the invention, ag-ethylenically acetate, vinyl pyridine, vinyl naphthalene, vinyl cyclo unsaturated polyesters A are the usual polycondensates hexane; acrylic acid and methacrylic acid and esters of at least one ag-ethylenically unsaturated dicarbox 25 thereof with saturated or unsaturated C1-C4 alcohols, ylic acid generally containing 4 to 6 carbon atoms or such as methyl, ethyl, butyl, vinyl, allyl, methallyl and ester-forming derivatives thereof, optionally in admix vinyl (meth)acrylates, also amides and nitriles of acrylic ture with up to 200 mol-%, based on the unsaturated and methacrylic acid; maleic acid, citraconic acid, mes dicarboxylic acid component, of one or more C4-C20 aconic acid and fumaric acid and semiesters and diesters dicarboxylic acids which do not contain any radically 30 thereof containing 1 to 4 carbon atoms in the alcohol polymerizable double bonds (or ester-forming deriva component, (optionally substituted) semiamides and tives thereof),with at least one polyhydroxyl com diamides thereof, also cyclic derivatives of maleic and pound, more especially a dihydroxyl compound, con citraconic acid, such as maleic anhydride, and cyclic taining 2 to 30 and preferably 2 to 8 carbon atoms, i.e. imides, such as N-methyl, N-phenyl and N-cyclohexyl polyesters of the type described in J. Björksten et al. 35 maleic imides; allyl compounds, such as allyl benzene, "Polyesters and their Applications”, Reinhold Publish and allyl esters, such as allyl acetate, diallyl , ing Corp., N.Y., 1956. diallyl isophthalate, diallyl fumarate, diallyl carbonate, Examples of preferred unsaturated dicarboxylic acids triallyl phosphate, triallyl cyanurate. Styrene and nu or their derivatives are maleic acid or maleic anhydride cleus substitution products of styrene are particularly and fumaric acid. However, mesaconic acid, citraconic preferred. acid, itaconic acid or chloronaleic acid for example In addition to unsaturated polyester resin, the mold may also be used. ing compositions may of course also contain low-profile Dicarboxylic acids which do not contain any radi additives of the type described, for example, in DE-PSS cally polymerizable double bonds may comprise ali 1241983, 1694 657 and 1953 062. Preferred low-profile 45 additives are, for example, polymers of acrylates and phatic, saturated C4-C10 dicarboxylic acids, cycloali methacrylates, such as polymethyl methacrylate and phatic and aromatic C8-C10 dicarboxylic acids. Pre polyethyl acrylate, homo- and copolymers of vinyl ferred dicarboxylic acids which do not contain any compounds, such as and polyvinyl acetate, radically polymerizable double bonds are phthalic acid, cellulose esters, such as cellulose acetate propionate and isophthalic acid, terephthalic acid, hexaand tetrahy SO butyrate, the molecular weights being between 10,000 drophthalic acid, endomethylene tetrahydrophthalic and 10,000,000. Substances of relatively low molecular acid, succinic acid, glutaric acid, adipic acid, sebacic weight, which are liquid to resin-like at room tempera acid, hexachloroendomethylene tetrahydrophthalic ture and, accordingly, are not "thermoplasts' in the acid, tetrachlorophthalic acid, hexachloro- and tetra accepted sense, but have the character of , bromophthalic acid. Preferred polyesters contain ma 55 have also been recommended as low-profile additives leic acid residues of which up to 20 mol-% may be (AT-PS 220369), including for example dibutyl phthal replaced by phthalic acid or isophthalic acid residues. ate and . Combinations of both Ester-forming derivatives are understood to include groups of compounds have also been described as ad esters (particularly those with low-boiling monohydric vantageous (DE-OS 3426425). alcohols, such as methyl or ethyl alcohol), acid anhy Low-profile additives are generally used in quantities drides and acid halides. of from 5 to 25% by weight and preferably in quantities Preferred dihydric alcohols are ethylene glycol, pro of from 8 to 20% by weight, based on the sum of unsatu pane-1,2-diol and propane-1,3-diol, diethylene glycol, rated polyester resin and low-profile additive. dipropylene glycol, butane-1,3-diol, butane-1,4-diol, In addition to unsaturated polyester resin, the mold neopentyl glycol, 2-ethylpropane-1,3-diol, hexane-1,6- 65 ing compositions may contain up to 400% by weight diol, cycloaliphatic diols, such as perhydrobisphenol A, and preferably from 30 to 200% by weight, based on the bisalkoxylated bisphenols, such as for example bisethox sum of unsaturated polyester resin and low-profile addi ylated . tive, of reinforcing material. Suitable reinforcing mate 5,194,334 5 6 rials are, in particular, fibrous materials including, for in the case of mixtures of compounds of different molec example, inorganic fibers, such as metal, asbestos, car ular weight). bon and glass fibers, also organic fibers, such as cotton, Preferred polyepoxides include polyepoxide com , polyester and polyacrylonitrile fibers. Glass pounds, preferably polyglycidyl ethers, based on poly fibers, carbon fibers and aramide fibers are preferred. hydric phenols, for example of pyrocatechol, resorci In addition to unsaturated polyester resin, the mold nol, hydroquinone, of 4,4'-dihydroxydiphenyl methane, ing compositions may contain up to 300% by weight of 4,4'-dihydroxy-3,3'-dimethyl diphenyl methane, of and preferably from 30 to 150% by weight, based on the 4,4'-dihydroxydiphenyl dimethyl methane (bisphenol sum of unsaturated polyester resin and low-profile addi A), of 4,4'-dihydroxydiphenyl methyl methane, of 4,4'- tive, of (non-reinforcing) fillers, such as for example O dihydroxydiphenyl cyclohexane, of 4,4'-dihydroxy-3,3'- chalk, talcum, quartz and shale powder, kaolin, calcite, dimethyl diphenyl propane, of 4,4'-dihydroxydiphenyl, dolomite, mica, heavy spar, kieselguhr, alumina, alu of 4,4'-dihydroxydiphenyl sulfone, of tris-(4-hydroxy minium oxide hydrate, glass beads or coal dust phenyl)-methane, of the chlorination and bromination To protect the unsaturated polyester resin against products of the diphenols mentioned above, particu 15 larly of bisphenol A; of novolaks (i.e. reaction products premature polymerization, the molding compositions of monohydric or polyhydric phenols with aldehydes, may contain polymerization inhibitors in concentrations particularly formaldehyde, in the presence of acidic of 0.001 to 1% by weight and preferably in concentra catalysts), of diphenols obtained by esterification of 2 tions of from 0.01 to 0.5% by weight, based on unsatu mol of the sodium salt of an aromatic hydroxycarboxy rated polyester resin A --B. Preferred polymerization 20 lic acid with 1 mol of a dihalogen alkane or dihalogen inhibitors are, for example, monohydric and polyhydric dialkyl ether (cf. GB-P 1,017,612), of polyphenols ob phenols, such as hydroquinone, toluhydroquinone, 4 tained by condensation of phenols and long-chain halo tert-butyl pyrocatechol, 2,6-di-tert-butyl-p-cresol, gen paraffins containing at least two halogen atoms (cf. naphthohydroquinone, also quinones, such as p-ben GB-P 1,024,288). zoquinone, chloranil, naphthoquinone, as well as 25 Other suitable polyepoxides are glycidyl esters of amines, preferably secondary aryl amines and deriva polybasic aromatic, aliphatic and cycloaliphatic carbox tives thereof, copper salts of organic acids, addition ylic acids which do not contain any double bonds co compounds of copper(I) halides with phosphites. These polymerizable under the curing conditions, for example and other preferred inhibitors are described in Houben phthalic acid diglycidyl ester, adipic acid diglycidyl Weyl, "Methoden der Organischen Chemie', 4th Edi 30 ester, hexahydrophthalic acid diglycidyl ester, and tion, Vol. XIV/1, pp. 433-453, Georg Thieme Verlag, glycidyl esters of reaction products of 1 mol of an aro Stuttgart, 1961. matic or cycloaliphatic dicarboxylic acid anhydride and The molding compositions generally contain 0.1 to mol of a diol or 1/n mol of a polyol containing in 3% by weight and preferably 0.5 to 2% by weight, hydroxyl groups per molecule. based on the sum of unsaturated polyester resin and 35 Glycidyl ethers of polyhydric alcohols, for example low-profile additive, of radical formers capable of initi of 1,4-butanediol, glycerol, trimethylolpropane, penta ating the copolymerization of unsaturated polyester A erythritol, and of glycols may also be and monomer B as polymerization initiators. Preferred used. Compounds containing glycidyl groups attached examples of such radical formers are peroxides, particu to heteroatoms, such as N,N'-diglycidyloxamide or larly diacyl peroxides, such as dibenzoyl peroxide and bis-glycidyl mercaptomethyl benzene, are also suitable di-p-chlorobenzoyl peroxide; peroxy esters, such as as are glycidyl compounds derived from hydantoins tert-butyl peroxybenzoate, tert-butyl peroctoate, dicy and isocyanuric acid. clohexyl peroxydicarbonate; alkyl peroxides, such as Finally, epoxidation products of polyunsaturated bis-(tert-butyl peroxy)-butane, dicumyl peroxide, tert compounds are mentioned, including for example epox butyl cumyl peroxide; hydroperoxides, such as cumene 45 idation products of vegetable oils and their conversion hydroperoxide, tert-butyl hydroperoxide, cyclohexa products, of diolefins and polyolefins, such as butadi none hydroperoxide, methyl ethyl ketone hydroperox ene, vinyl cyclohexene, 1,5,9-cyclododecatriene, and of ide; perketals; ketone peroxides, such as acetyl acetone polymers and copolymers still containing epoxidizable peroxide. double bonds, for example based on polybutadiene, Other preferred polymerization initiators are perox polyisoprene, butadiene/styrene copolymers. Polymers ide-free compounds which form radicals with cleavage of unsaturated monoepoxides, for example of meth of a C-C-bond, for example benzpinacol silyl ether (de acrylic acid glycidyl ester or allyl glycidyl ether, are scribed inter alia in Kunststoffe 68 (1978), no. 9, pp also mentioned. 553-555). Preferred polyepoxides are bisphenol-A-diglycidyl Other standard additives for the molding composi 55 ether and reaction products of bisphenol-A-diglycidyl tions are, for example, pigments, dyes, thickeners, lubri ether with bisphenol A in such a ratio that the reaction cants and release agents, such as zinc stearate, flame product contains on average more than one 1,2-epoxide proofing agents, UV absorbers and stabilizers against group per molecule. thermal degradation. Preferred mono- and di-carboxylic acids containing According to the invention, the molding composi 60 copolymerizable double bonds, of which the reaction tions contain polyepoxides or reaction products thereof products with the polyepoxides may be used in the same with unsaturated mono- or dicarboxylic acids. Polye way as the polyepoxides themselves, are preferably poxides in the context of the invention include aliphatic, C3-C5 mono- and C4-C6 dicarboxylic acids, such as for cycloaliphatic, aromatic and heterocyclic compounds example acrylic acid, methacrylic acid, crotonic acid, which contain on average more than 1 1,2-epoxide 65 vinyl acetic acid, tiglic acid, maleic acid, fumaric acid, group and preferably more than 1.5 1,2-epoxide groups citraconic acid, mesaconic acid, itaconic acid and aco per molecule. Preferred polyepoxides have molecular nitic acid. Acrylic, methacrylic, maleic and fumaric weights below 2,000 (determined as a number average acid are preferred. In reaction products of polyepoxides 5,194,334 7 8 with dicarboxylic acids, the ratio of epoxide to carboxyl products of the type defined in (1), pages 174 et seq. and groups in the polyepoxides and dicarboxylic acids is 0.4 in (2), page 637; and suitable acrylate resins are prefera to 0.6 and preferably about 1:2. bly products of the type described in (1), pages 229 et To prepare the molding compositions, the liquid and seq and in (2), pages 613 et seq. soluble components are preferably first mixed using Particular preference is attributed to dissolvers, stirrers or the like. Compounding with fillers lacquers as so-called "one-pot systems' with binders of and reinforcing materials to form prepregs (SMC) or I) polyisocyanates containing on average at least 1.8 dough-like molding compositions (BMC) has been re and preferably at least 2 blocked isocyanate groups per peatedly described, for example in Kunststoff-Hand molecule and buch, Vol. VIII "Polyester", Edited by R. Vieweg and 10 II) polymers containing H atoms capable of reacting L. Goerden, Carl-Hanser-Verlag, Munchen 1973, pages with isocyanate groups. 483 et seq. and 491 et seq. The molding compositions Starting materials for the preparation of component I are normally stored until the necessary viscosity is 3: reached and are then applied to the metal sheet with (i) organic polyisocyanates, preferably diisocyanates forming and curing preferably in heated presses or in 15 corresponding to the following formula jection molding machines. The coated metal sheet 2 Q(NCO)2 The protection of the metal sheets against corrosion in which Q is an aliphatic hydrocarbon radical contain consists of a stoving lacquer which, for economic rea ing 4 to 12 carbon atoms, a cycloaliphatic hydrocarbon sons, is preferably applied by coil coating. However, 20 radical containing 6 to 15 carbon atoms, an aromatic the coating facing the molding composition to be ap hydrocarbon radical containing 6 to 15 carbon atoms or plied may also combine the properties of corrosion an araliphatic hydrocarbon radical containing 7 to 15 prevention and priming in a single layer. In this case, carbon atoms. the coatings on both sides of the metal sheet are virtu Examples of preferred diisocyanates such as these are ally identical, differing from one another solely in the 25 tetramethylene diisocyanate, hexamethylene diisocya fact that the coating facing the molding composition to nate, dodecamethylene diisocyanate, 1,4- be applied additionally contains components a, b and/or diisocyanatocyclohexane, 3-isocyanatomethyl-3,5,5- cas defined herein. trimethyl cyclohexyl isocyanate ("isophorone diisocya However, a process in which the primer coating is nate'), 4,4'-diisocyanatodicyclohexyl methane, 4,4'- applied to the already corrosion-proofed metal sheet is 30 diisocyanatodicyclohexyl-2,2-propane, 1,4- preferred. In this case, the coating facing the molding diisocyanatobenzene, 2,4- and 2,6-diisocyanatotoluene composition to be applied consists of at least 2 layers. A or mixtures of these isomers, 4,4'- or 2,4'- two-layer coating which consists of the corrosion-inhib diisocyanatodiphenyl methane, 4,4'-diisocyanatodiphe iting stoving lacquer as the first layer and of the primer nyl-2,2-propane, p-xylylene diisocyanate and a,a,a",a'- coating as the second layer is particularly preferred. 35 tetramethyl-m- or -p-xylylene diisocyanate and mix Except for the presence of component a, b, or c, the tures containing these compounds. stoving lacquer layer and the priming layer may contain It is of course also possible to use the polyisocyanates the same components. However, as shown in the Exam of relatively high functionality known perse in polyure ples, the stoving lacquer and the priming layer may thane chemistry or even modified polyisocyanates differ in their other components as well. For a particu known per se, for example polyisocyanates containing larly preferred coating, it has proved considerable ad carbodiimide groups allophanate groups, isocyanurate vantage to select the coating materials for the two suc groups, urethane groups and/or biuret groups. Exam cessive layers in such a way that they are virtually ples of higher polyisocyanates such as these are tris-(6- identical and differ solely in the fact that the second isocyanatohexyl)-biuret, optionally in admixture with layer additionally contains components a, b and/or c as 45 its higher homologs, tris-(6-isocyanatohexyl)-isocyanu defined herein. rate, optionally in admixture with its higher homologs, Since both coating compositions are virtually identi as obtained by trimerization of hexamethylene diisocya cal, the coating containing the primer may also be ap nate, for example in accordance with DE-OS 2839 133, plied in the same way, i.e. preferably by stoving by the and other known isocyanurate polyisocyanates obtain coil-coating process. 50 able by trimerization of aliphatic and/or aromatic diiso Suitable binders for the stoving lacquer and the cyanates, such as for example "isophorone diisocya primer layer are those based on alkyd resins, oil-free nate', diisocyantotoluene or hexamethylene diisocya polyesters, epoxy resins, acrylate resins and preferably nate. Other suitable polyisocyanates are the urethane on polyurethane resins. As is normally the case for polyisocyanates known perse which may be obtained, stoving lacquer binders, two-component resins are used, 55 for example, by reaction of excess quantities of 2,4- i.e. mixtures of uncrosslinked reactive resins and cross diisocyanatotoluene or of "isophorone diisocyanate' linking agents which are capable of reacting with the with simple polyhydric alcohols having molecular reactive groups of the uncrosslinked resins to form a weights of 62 to 300, more especially with trimethylol polymeric network. propane, and subsequent removal of the unreacted di The alkyd resins suitable as stoving lacquer binders isocyanate excess by distillation. are preferably products of the type described in (1) H. Where monofunctional polyisocyanates are used, the Wagner, H. F. Sarx, Lackkunstharze, Carl Hanser Ver quantity in which they are used should preferably be lag. Minchen 1971, pages 86 et seq. and in (2) Ullmanns gauged in such a way that the functionality of the result Encyclopädie der technischen Chemie, 4th Edition, ing blocked polyurethane prepolymers does not fall Vol. 15, Verlag Chemie, Weinheim 1978, pages 616 et 65 below the minimum functionality indicated below. seq.; suitable oil-free polyesters are preferably products (ii) Polyether and/or polyester polyols of the type of the type defined in (1), pages 86 et seq and in (2), known per se in polyurethane chemistry, preferably pages 625 et seq; suitable epoxy resins are preferably polyether and polyester diols having molecular weights 5,194,334 10 of 300 to 2,000. The polyethers containing hydroxyl monoethyl ether and diethylene glycol monomethyl groups which may be used are obtained, for example, by ether, phenols, such as phenol, cresol and xylenol, and polyaddition of cyclic ethers, such as preferably propy heterocyclic compounds, such as triazoles, imidazo lene oxide or even butylene oxide, tetrahydrofuran, lines, imidazoles and tetrahydropyridines. styrene oxide and/or epichlorohydrin, on their own, for 5 The blocking agents may be used either individually example in the presence of boron trifluoride, or by addi or in admixture. Preferred blocking agents are c tion of these compounds, optionally in admixture or caprolactam, butanone oxime and malonic acid diethyl successively, with starter components containing reac ester. tive hydrogen atoms, such as alcohols and amines, for The polyurethane prepolymers (component I) suit example water, ethylene glycol, 1,3- or 1,2-propylene 10 able as polyisocyanate I may be prepared by conven glycol, bisphenol A or aniline. tional state-of-the-art methods, for example by reaction The polyesters containing hydroxyl groups which of polyisocyanates (i) with polyols of relatively high may be used are, for example, reaction products of molecular weight (ii) and polyols of low molecular preferably polyhydric, more preferably dihydric and, weight (iii), the molar ratio of the isocyanate groups in optionally, also trihydric alcohols with preferably poly- 15 the polyisocyanate (i) to the hydroxyl groups in the basic, more preferably dibasic carboxylic acids. Instead polyols (ii) and (iii) being from 1.5 to 3.0. To block the of the free carboxylic acids, it is also possible to use the isocyanate groups, the resulting polyurethane prepoly corresponding carboxylic acid anhydrides or corre mers containing free isocyanate groups are then revers sponding carboxylic acid esters of lower alcohols for ibly blocked with suitable monofunctional compounds preparing the polyesters. 20 (iv). The synthesis of polyurethane prepolymers (I) is The alcohols used in the synthesis of the polyesters described, for example, in DE-PS 1644 813. are, for example, ethylene glycol, 1,2- and 1,3-propy Component I comprises both reaction products of the lene glycol, butane-1,4-diol, hexane-1,6-diol, neopentyl polyisocyanates (I) and blocking agents (iv) and glycol, octane-1,8-diol, 2-ethylhexane-1,3-diol, 1,4-bish blocked polyisocyanate prepolymers based on the ydroxymethyl cyclohexane, diethylene glycol, dipro- 25 above-mentioned compound (i) and (ii) and/or (iii). pylene glycol, trimethylolpropane, glycerol and penta The polymers containing isocyanate-reactive H erythritol. atoms (component II) are polyester or polyether poly Carboxylic acids which may be used in the synthesis ols, polyhydric low molecular weight alcohols, poly of the polyesters are, for example, adipic acid, succinic amines, polyepoxypolyols, polyhydroxyacrylates or acid, suberic acid, azelaic acid, sebacic acid, phthalic 30 mixtures of these products. acid, isophthalic acid, terephthalic acid, tetrahydroph The polyester polyols and polyether polyols are com thalic acid, hexahydrophthalic acid, maleic acid, fu pounds known perse in polyurethane chemistry having maric acid, saturated and unsaturated fatty acids, such molecular weights of 300 to 10,000 and preferably 300 as for example stearic acid, oleic acid, ricinoleic acid, to 5,000. They are preferably formed from the above linoleic acid, ricinene acid, linolenic acid, eleostearic 35 described synthesis components (ii) of the polyurethane acid and fatty acid mixtures obtained from natural oils, prepolymers(I). The low moleciilar weight alcohols are such as for example linseed oil, soybean oil, ground nut polyalcohols of known type containing at least 2 hy oil, safflower oil, castor oil or wood oil. droxy groups per molecule and having molecular (iii) optionally low molecular weight polyols having weights of 62 to 300. molecular weights of 62 to 300. Examples of polyols 40 Suitable polyamines are preferably difunctional or such as these suitable for use in accordance with the polyfunctional, aliphatic or cycloaliphatic amines, such invention are ethanediol, propane-1,2- and -1,3-diol, as 1,2-diaminoethane, tetramethylenediamine, hexa butane-1,4- and -1,3-diol, pentanediols, hexanediols, methylenediamine, dodecamethylenediamine, 1,4- octanediols, such as for example 2-ethyl hexane-1,3- diaminocyclohexane, 1,4-bis-aminomethyl cyclohex diol, trimethylolpropane, glycerol and pentaerythritol. 45 ane, "isophorone' diamine,4,4'-diaminodicyclohexyl Representatives of the above-mentioned polyisocya methane, 2,2-bis-(4-aminocyclohexyl)propane or m- or nate and hydroxyl compounds suitable for use in the p-xylylenediamine. 4,4'-Diamino-3,3'-di-methyl dicy production of the binders according to the invention are clohexyl methane is particularly preferred. described, for example, in high polymers, Vol. XVI, Components (I) and (II) are preferably used in such "Polyurethane Chemistry and Technology', edited by 50 quantities that the molar ratio of blocked isocyanate Saunders-Frisch, Interscience Publishers, N.Y., Lon groups to hydroxyl and/or amino groups is 0.5 to 2 and don, Vol. I, 1962, pages 32 to 42 and pages 44 to 54 and preferably 0.8 to 1.5. Vol. II, 1964, pages 5-6 and 198-199 and in Kunststoff Polyepoxides a) or reaction products thereofb) with Handbuch, Vol. VII, edited by Viewegchtlen, Carl af3-ethylenically unsaturated mono- and dicarboxylic Hanser Verlag, MUnchen, 1966, for example on pages 55 acids are understood to be compounds of the type de 54-71. scribed in the foregoing as constituents of the moulding (iv) Isocyanate-monofunctional compounds which compositions. Of these compounds, polyglycidyl ethers are suitable for reversibly blocking isocyanate groups, based on bisphenol A and addition products thereof of the type described for example in Z. W. Wicks, with acrylic, methacrylic acid, maleic an fumaric acid Progress in Organic Coatings 9, 3-28 (1981). Examples 60 are preferred. of blocking agents such as these suitable for the prepara According to the invention, polyepoxides known as tion of component (I) of the polyurethane lacquers are crosslinkers from lacquer chemistry, such as for exam lactams, such as caprolactam for example, oximes, such ple triglycidyl isocyanurate or triglycidylurazole, may as acetone oxime, methyl ethyl ketone oxime and cyclo also be used in accordance with the invention. hexanone oxime, C-H-acid compounds, such as malonic 65 In the context of definition c), unsaturated polyesters acid esters, acetoacetic acid esters and acetyl acetone, c) are understood to be compounds of the type de alcohols, such as the simple monoalcohols containing 1 scribed in the foregoing as component A of the molding to 4 carbon atoms, 2-ethylhexanol, ethylene glycol compositions. These unsaturated polyesters c) are pref 5,194,334 11 12 erably used in styrene-free form. Polyesters c) of maleic and chromated aluminium sheets are particularly pre anhydride, phthalic anhydride and propylene glycol are ferred. preferred. The stoving lacquers corresponding to the above Alternatively, esterification products of ag-ethyleni description are preferably applied to the metal sheet by cally unsaturated monocarboxylic acids (preferably 5 coil coating and, depending on their chemical composi containing 3 to 6 carbon atoms) with polyhydroxyl tion, are stoved at metal temperatures of from 100° C. to compounds containing at least 2 hydroxyl groups (and 280 C. and preferably in the range from 140° C. to 260 preferably 2 to 24 carbon atoms) may also be used as C. unsaturated polyesters c). It is immaterial whether the After coating, the metal sheets are formed by stan molecule is actually built up by the esterification of an 10 dard methods, preferably by deep drawing. However, unsaturated acid with a polyol or otherwise. Suitable the process according to the invention may also be af3-unsaturated monocarboxylic acids are, for example, applied to metal sheets formed by other methods, for acrylic acid, methacrylic acid, crotonic acid, tiglic acid example by rolling. and substitution products thereof. Acrylic and meth The molding composition is applied in heated molds acrylic acid are preferred. Examples of polyols are 15 of the type typically used in the processing of unsatu aliphatic and cycloaliphatic diols, such as (optionally rated polyester resins, preferably in steel molds, by branched) a,c)-dihydroxyalkanes, polyhydroxyalkanes, or by injection molding at ten perhydrogenated products of polyhydric phenols, such peratures in the range from 60° C. to 200 C., preferably as perhydrobisphenol A; polyalkylene glycols, such as at temperatures in the range from 80 C. to 180° C. and (optionally branched) polyethylene and polypropylene more preferably at temperatures in the range from 120 glycols; addition products of alkylene oxides, prefera C. to 17O C. bly ethylene or propylene oxide, with polyhydric aro matic or saturated aliphatic carboxylic acids, such as EXAMPLES isophthalic acid, trimellitic acid or adipicacid, or with In the following Examples, percentages are percent polyhydric phenols, such as bisphenol A. Examples of 25 ages by weight and parts are parts by weight, unless polyesters falling within this group, of which the mole otherwise stated. cule is built up purely formally by esterification of an The prepregs (SMC) and dough-like molding compo af3-ethylenically unsaturated monocarboxylic acid sitions (BMC) were prepared in the usual way (as de with a diol, are the addition products of polyisocyanates scribed, for example, in Kunststoff-Handbuch Vol. and mono(meth)acrylic acid esters of glycols, for exam 30 VIII, "Polyester", edited by R. Vieweg and L. Go ple the addition product of 2,4-tolylene diisocyanate erden, Carl Hanser Verlag, MUnchen, 1973, pages 482 and hydroxypropyl methacrylate. et seq. and 491 et seq.). Preferred representatives of the group of alternative The polyester resin molding composition was applied polyesters c) have molecular weights of from about 250 in a 200 ton press using a 200x300mm panel mold. 0.3 to about 2,000. The acrylates and methacrylates of the 35 mm thick sheet metal strips 3 cm wide and approx. 19 ethoxylation and propoxylation products of bisphenol cm long were placed in the mold heated to 150 c. and A are particularly preferred. the necessary quantity of molding composition intro Metal sheets suitable for use in accordance with the duced, followed by compression molding for 90 sec invention also include those which consist of two or onds to form a 2 mm thick plate. more layers of different metals of the type mentioned The adhesion between the metal and the plastic was above (same or different thickness). Examples are gal determined either by the roller peel test according to vanized steel sheets, bimetallic or sandwich sheets. DIN 53289 or subjectively. In the latter case, the sheet Sheets provided with inorganic coatings may also be metal strip was loosened at one corner with a knife and used. peeled off with pliers. Evaluation was based on a scale 45 of 1 to 5 in which The unsaturated polyesters c) may be dissolved in 1 = very strong adhesion; the sheet torn off is at least typical lacquer solvents, such as butyl acetate or gaso 50% covered by adhering hardened molding com line. In addition, the lacquers may contain typical addi position; 5=no adhesion. tives, such as fillers, pigments and auxiliaries. Polyester resin molding compositions Production of the sheet metal/duroplast composite 50 elements Prepregs were made in the usual way (see for exam The composite elements according to the invention ple Kunststoff-Handbuch, Vol. VIII "Polyester', ed are produced by ited by R. Vieweg and L. Goerden, Carl Hanser Ver l. coating the metal with at least one lacquer coating lag, MUnchen 1973, pages 482 et seq. and 491 et seq.) having the composition defined above, 55 from the formulations shown in the Table (quantities in 2. forming the coated metal sheet, parts by weight). They had a glass fiber content of 25% 3. applying the molding composition to the formed (staple length 26/26/52 mm). The prepregs were ma sheet in a heated mold or injection mold. tured by storage at 23 C. and, once moldable, were It is possible to use 0.02 to 2.0 mm, preferably 0.1 to compression-molded in the manner described above, 1 mm and more preferably 0.1 to 0.5 mm thick metal four pretreated metal strips being placed in the mold sheets. Sheets of aluminium or steel are preferred, al (nold temperature 150° C). To evaluate adhesion, eight though it is also possible in accordance with the inven strips were peeled off by hand. The roller peel test tion to use sheets of noble metals, alloys or other cold according to DIN 53289 was optionally carried out on formable metals. another eight strips to determine peel strength. The metal sheets are normally pretreated by conven 65 tional methods, for example by passivation, chromating, SMC 1 SMC2 SMC3 zinc phosphating or by the application of wash primers UPresins (see below) 56.0 39.2 39.2 in thin layers. Phosphated and passivated steel sheets LP additive (see below) 24.0 24.0 24.0 5,194,334 13 14 -continued as Diacrylate, in the form of a 75% solution in butyl acetate. SMC 1 SMC2 SMC3 Component 6 (example of component a)) Diacrylate (see below) - 6.8 - Commercial epoxy resin as described above as start Bisepoxide (see below) - 16,8 5 Polyvinyl acetate solution 0.0 10.0 10.0 ing product for "diacrylate" ((R) Lekutherm X 20, a (see below) product of Bayer AG), in the form of a 75% solution in Styrene 0.0 10.0 10.0 butyl acetate. Wetting agent 2.7 2.7 2.7 Hydroxyl-containing polyester I Tert-butyl perbenzoate 1.4 .4 .4 Polyfunctional hydroxyl-containing polyester based p-Benzoquinone (10% in styrene) 0.6 0.6 0.6 10 Cobalt naphthenate solution (1% Co) .0 1.0 1.0 on phthalic anhydride, maleic anhydride, adipic acid, Zinc stearate 5.0 5.0 5.0 trimethylolpropane and propane-1,2-diol having an Chalk 175 175 175 average molecular weight Mn of 960 and an OH value MgO paste (35% paste in carrier 2.9 2.9 2.9 of 165. resin) Hydroxyl-containing polyester-polyether mixture II 15 Mixture of a bisphenol-A-started propylene oxide polyether having a functionality of 2 and an OH value DEFINITIONS USED IN THE TABILES: of 200 and a polyester based on adipic acid, isophthalic UP resin = a 65% solution in styrene of an unsatu acid, hexanediol and trimethylolpropane, OH value 400, rated polyester based on maleic anhydride/1,2-propy in the form of a 70% f solution in ethyl glycol aceta lene glycol. The acid value of the 100% polyester was 20 te/xylene (1:1). 20 and the viscosity of the styrene solution 1,600 mPa.- sec at 20 C. LP additive=a 70% solution in styrene of a saturated Primer Cornpositions polyester based on adipic acid/ethylene glycol/1,2-pro Comparison pylene glycol in a molar ratio of 1:0.6:0.4. The acid 25 P1 P2 P3 P4 P4 P6 Polyester/polyether 24.7 24.7 24.7 24.7 24,7 24. value of the 100% polyester was 11 and the viscosity of mixture II the styrene solution 1,400 mPa.sec at 20° C.; Component 2 33.0 33.0 33.0 33.0 33.0 33.0 Diacrylate=an 80% styrene solution of the reaction Component 4 11.5 5.8 - - m product of 2 mol methacrylic acid and 1 mol of a com Component 3 O- 7.7 15.3 - - -- 30 Component 5 O --- 15.3 - - mercial epoxy resin based on bisphenol A having an Component 6 ------15.3 m epoxide equivalent according to DIN 16945 of 185 to Wetting agent 0.2 0.2 0.2 0.2 0.2 0.2 200 ((R) Lekutherm X 20, a product of Bayer AG); Silica gel 0.6 0.6 0.6 0.6 0.6 0.6 Bisepoxide=an 80% solution in styrene of the com Titanium dioxide 7.3 7.3 7.3 7.3 7.3 7.3 Magnetite 0.4 0.4 0.4 0,4 0.4 0.4 mercial epoxy resin mentioned above; Carbon black 0, 0. 0.1 0.1 0. 0. Polyvinyl acetate solution = a 40% solution in styrene 35 Ethyl glycol acetate 4.0 4.0 4.0 4.0 4.0 4.0 of polyvinyl acetate having an acid value of 3 and a Butyl acetate 0.7 0.7 0.7 0.7 0.7 0.7 viscosity of 5,000 mPa.sec at 23 C. Xylene 4.5 2.5 0.7 0.7 0.7 0.7 The following materials are used in the stoving lac quers and primer compositions shown in the Example. The resins, pigments and additives (quantities in parts Component 1 by weight) were made into a paste in the usual way. The e-caprolactam-blocked NCO prepolymer based on lacquers were adjusted by dilution with solvent (solvent 2,4- toluylene diisocyanate, a propane-1,2-diol-started naphtha 200) to a viscosity corresponding to a flow out propylene oxide polyether having a functionality of 2, an average molecular weight M of 1,000 and an OH time of 100 seconds (DIN 53211, DIN-4-cup). value of 112, trimethylolpropane and diethylene glycol, 45 in the form of a 65% solution in ethylene glycol aceta Stoving Laquers - te/xylene (1:1 parts by weight). The content of masked SLI SL2 SL3 NCO groups was 4.6%. Component 1 33.5 34.4 31.9 Component 2 OH-containing polyester I 12.0 12. 1.4 50 4,4'-diamino-3,3'-dimethyl dicyclohexyl - 4.8 e-caprolactam-blocked NCO prepolymer based On methane 2,4-toluylene dilisocyanate, trimethylolpropane, butane Wetting agent, 10% in solvent aphtha 100 up - 13 1,3-diol, a bisphenol A-started propylene oxide poly Bentonite, 10% in solvent naphtha 100/ 3.4 3.S 3.2 ether having a functionality of 2 and an OH value of Antiterra U (85:5) Zinc chronate 15.2 5.6 200, a polyester based on adipic acid and diethylene Microtalcun 13. - 12.9 glycol having a functionality of 2 and an OH value of 55 Blanc Fixe Micro 12. re 42, in the form of a 70% solution in ethylene glycol Blanc Fixe F -- 4.5 acetate/xylene (1:1 parts by weight). The content of Iron oxide black - 3.2 Titanium dioxide 13.5 3.5 a masked NCO groups was 16%. Carbon black 1.7 - O Component 3 (example of component c) Polyester-based foam inhibitor 2.2 0.4 Unsaturated polyester based on maleic anhydride, 60 Solvent naphtha 200 15, 18.2 VD phthalic acid and propylene glycol having an acid value Dilution with SN 200 to application 70 100 70 of 12, in the form of a 75% solution in butyl acetate. viscosity (DIN-4-cup) sec sec SCC Component 4 (example of component b)) Layer thickness in pum (dry film) approx. 20 5 10 Dimethacrylate of ethoxylated bisphenol A contain ing 3.8 mval/g ethylenically unsaturated groups. 65 Metal sheets Component 5 (example of component b)) All the tests described here were carried out with 0.3 Diacrylate based on bisphenol A, identical with the mm thick metal sheets. The following types were used: styrenefree component of the product described above S1: untreated and degreased steel 5,194,334 15 16 S2 : galvanized steel S3 : zinc-phosphated steel Pretreated Adhesion Peel strength S4 : passivated steel Test no. metal (hand test) (N/mm2) S5 : galvanized, passivated steel 22 (Comp.) A. 5 nm.(1) All: chromated aluminium and 5 23 (Comp.) B 4. n.g.() A12: untreated aluminium. 24 O 2 I.g. Production of the lacquered metal sheets 25 E 2-3 0.58 26 F 2-3 1.03 The anti-corrosion stoving lacquer was applied to the 27 G -2 O.99 variously pretreated metal sheets, aired for 10 minutes 28 (Comp.) H 4 0.24 and then stoved (peak metal temperature 241 C.). The 10 29 I 1 1.29 primer composition was then applied and stoved after 30 K 1.65 airing for 10 minutes (peak metal temperature 241 C.). 31 N 2-3 0.60 The composition of the coil coating lacquer layers is (see note shown in the following Table. (under Examples 10-21

Composition of the laquer coatings A B C D E F G H K L M N O Metal sheet S1 S2 S3 S4 S4 AL S1 S5 S5 S5 S5 S5 AL AL2 Stoving Lacquer - SL3 SL2 SL2 SL2 SL2 SL3 SL2 SL2 SL2 SL2 SL2 SL2 SL Layer thickness (um) - 10 5 5 5 5 5 5 s 5 5 5 5 5 Primer Composition - - Pl P2 P3 P3 Pl P6 P5 P4 P3 P2 P5 P2 Layer thickness (Lm) - - 20 20 20 20 20 20 20 20 20 20 20 20 Stoving Lacquer, back - - SLl SL1 SLl SLl SLI SLl SLl SLI SLl SLl SLl Layer thickness (um) - - 20 20 20 20 20 20 20 20 20 20 -

Measurements on coated metal sheets: s MCC moldinding compositionsiti were applied as de What is claimed is: fscribed above to the prepared sheet metal strips. The 1. A process for the production of sheet metal/duro ollowing Examples show the results of the adhesion 30 plast composites comprising corrosion-proofedw sheet tests. metal and a molding composition applied to the sheet EXAMPLE 1 to 9 (Comparison Examples) metal after forming thereof by compression molding and curing at elevated temperature is a single operation SMC was used for coating. wherein 35 said molding composition comprises an unsaturated Test no. Pretreated metal Adhesion (hand test) polyester resin and: i) polyepoxides in a quantity 1 A 5 corresponding to 5-200 mmol epoxide groups per 2 B 5 100 g organic binder of the molding composition; 3 C 5 ii) reaction products of said polyepoxides with 4. E 4-5 5 G 5 40 alpha, beta-ethylenically unsaturated mono- or 6 F 4-5 dicarboxylic acids copolymerizable under the cur 7 H 5 ing conditions, the mono- or dicarboxylic acids 8 I 4. having molecule weights below 800; or iii) mix 9 O 5 tures of polyepoxides and said production products 45 and said metal sheet is pre-treated with a stoving lacquer EXAMPLES 10 to 21 based on a binder component composed of alkyl SMC 2 was used for coating. resins, oil-free polyesters, epoxy resins, acrylate resins, or polyurethane resins and the stoving lac 50 quer is further coated on the side to which the Pretreated Adhesion Peel strength polyester resin molding composition is applied Test no. metal (hand test) (N/mm) with a primer composition based on a binder com 10 (Comp.) A 5 nm.() 11 D 2 ng.(2) ponent composed of alkyl resins, oil-free polyes 12 E 2-3 ng. ters, epoxy resins, acrylate resins, or polyurethane 13 F 2-3 0.51 55 resins and additionally containing at least one of 14 G 2 1.20 the following: 15 (Comp.) H 4-5 .. a) polyepoxides in a quantity of 5-200 mval epox 6 I 57 7 K 1-2 1.29 ide groups per 100 g organic binder of said 8 L 2-3 0.58 primer composition and/or 19 M 2 1.3. 60 b) reaction products of the polyepoxides a) with 20 N 2 0.84 alpha, beta-ethylenically unsaturated mono- or 21 (Comp.) O 5 nm.() dicarboxylic acids copolymerizable under hard n.m. not measurable (metal strip becomes detached when lifted off the coating at a corner). ening conditions, the Inono- or dicarboxylic ng.(2) not measured. acids having molecular weights below 800, and 65 /or c) 2.5-50% by weight, based on the organic binder EXAMPLES 22 to 3 of said primer composition of unsaturated poly SMC 3 was used for coating. ester containing 0.1-0.6 equivalents of copoly 5,194,334 17 18 merizable ethylenic double bonds per 100 g of tion corresponds to a quantity of 10 to 80 mval epoxide unsaturated polyester c), or mixtures a), b) and c) groups per 100 g of said primer composition. wherein the binder components of the stoving lac 6. A process as claimed in claim 1, characterized in quer and the primer composition are selected such that the primer composition contains component c) and that the binder component of the stoving lacquer component c) is present in a quantity of 5 to 40% by differs from the binder component of the primer weight. composition and wherein the stoving lacquer does 7. A process as claimed in claim 6, characterized in not contain a), b) or c). that component c) is present in a quantity of 5 to 30% 2. A process as claimed in claim 1, characterized in by weight. that the quantity of polyepoxide for the unsaturated O polyester resin of said molding composition corre 8. A process as claimed in claim 1, characterized in sponds to a quantity of 15 to 110 mmol epoxide groups that the primer composition contains component c) and per 100 g organic binder of said molding composition. component c) contains 0.2 to 0.4 equivalents of copoly 3. A process as claimed in claim 1, characterized in merizable ethylenic double bonds per 100 g of compo that the quantity of polyepoxide for the unsaturated 15 nent c). polyester resin of said molding composition corre 9. Composite elements produced by the process sponds to a quantity of 35 to 90 mmol epoxide groups claimed in claim 1. per 100 g organic binder of said molding composition. 10. A motor vehicle comprising the composite ele 4. A process as claimed in claim 1, characterized in ment of claim 9. that the primer composition contains component a) and 20 11. A process according to claim 1, wherein the sto the quantity of polyepoxide in the primer composition ving lacquer is stored before application of the primer corresponds to a quantity of 10 to 120 mval epoxide composition. groups per 100 g of organic binder of said primer com 12. A process according to claim 11, wherein the position. primer composition is stored before application of the 5. A process as claimed in claim 4, characterized in 25 molding composition. that the quantity of polyepoxide in said primer composi k k k k sk

30

35

45

50

55

65 UNITED STATES PATENT ANDTRADEMARK OFFICE CERTIFICATE OF CORRECTION PATENT NO. : 5,194,334 DATED : March 16, 1993 INVENTOR(S) : Uerdingen, et al. It is certified that error appears in the above-indentified patent and that said Letters Patent is hereby Corrected as shown below: At Col. 16, line 33 "is" should read: --in--. At Col. 16, lines 45 and 53, the word "alkyl it should read: --alkyd--. At Col. 18, lines 21 and 24, the word "stored it should read: -stoved--.

Signed and Sealed this Twenty-sixth Day of July, 1994 Attest: (a (eam

BRUCELEHMAN Attesting Officer Commissioner of Patents and Trademarks