FR2511617A1 - Wet on wet coating of metals, esp. steel - by applying aq. blocked isocyanate compsn., followed by applying epoxy compsn. and opt. third coating and hardening - Google Patents

Abstract

A substrate is coated by applying a compsn.

Description

 The present invention relates to an article having a multilayer coating and a method for producing such an article. More particularly, the invention relates to a process for the preparation of an article carrying a multilayer coating in which the coatings are applied by a wet / wet technique, followed by curing of the one-step multilayer coating.

It is possible to protect metal surfaces and give them an aesthetic appearance by applying on these surfaces / up to eight layers of paint. In the automotive industry, it is customary to apply three or more layers. These layers are as follows:
(1) a primer or basecoat for providing protection against corrosion;
(2) an intermediate layer for providing a good surface polish and thickness for gravel impact resistance; and
(3) a topcoat giving an aesthetic appearance.

 If desired, the topcoat may itself comprise two layers, namely a colored base topcoat and a clear topcoat.

 Normally, the primer is water-based and electroplated to a thickness of about 15 to 20 microns. The intermediate layer may be either organic solvent based or aqueous based and is typically applied to the spray-cured primer coating to a thickness of about 30 to 40 microns. The topcoat may be either organic solvent based or aqueous based and is typically spray applied to a thickness of about 35 to 40 microns on the intermediate layer.

A disadvantage of the coating system just described is that the application of each layer requires a separate curing step.
This process, in addition to requiring a lot of time, requires considerable energy consumption.

 The present invention is an improvement to the coating technique described above. More specifically, the invention allows the application of the base layer and the intermediate layer on the substrate by a wet / wet technique in which a hardening step is used to harden both the base and the middle layer. The method according to the invention not only provides good corrosion protection and good appearance, but it can also provide the finished product with improved qualities, such as improved resistance to batt, solvents and grading. backwash, comparatively / similar scrapings applied in separate steps with separate curing cycles (dry / dry technique).

 In accordance with the present invention, a method of coating a substrate is provided. This method comprises applying to a substrate at least two coating compositions, at least one thereof containing blocked isocyanate functionality, and at least one of them containing 1,2-epoxy functionality. Coating compositions containing blocked isocyanate functionality and 1,2-epoxy functionality are sequentially applied to the substrate without the need to harden the initially applied coating. In addition, the coating compositions are in a substantially continuous superposition relationship with each other so as to form a multilayer coating. The coated substrate is heated to a temperature sufficient to cure the multilayer coating.

According to a specific embodiment of the invention, the coated substrate is prepared by:
(A) applying to the substrate a first coating composition containing blocked isocyanate functionality to form a first coating thereon;
(B) applying to the first coating, prior to curing, a second coating composition containing 1,2-epoxy functionality to form a multilayer coating;
(C) sufficient heating of the coated substrate to form the multilayer coating.

 The invention also provides coated articles or articles produced by the aforesaid process.

Surprisingly, it has been found that when
the multilayer coating is heated to a temperature sufficient to unblock the isocyanate groups, for example between 150 and 2000 C, there appears to be some interaction between the resulting coatings in a cured product.

This is a surprising phenomenon, since the reaction between isocyanates and 1,2-epoxy groups does not occur at such low temperatures. Although we do not wish to be bound by any theory, it is believed that it is possible that the blocked isocyanate groups react, under the curing conditions employed, at least in part with moisture to form amines, for example toluene diisocyanate can form toluene diamine which is highly reactive with the 1,2 epoxy functionality under the curing conditions employed.

 Japanese Patent Application 26657/72 discloses a method for coating a substrate comprising the anionic electrodeposition application of a resin containing amine or ammonia neutralized carboxylic acid groups. A second polyisocyanate-containing organic solvent-soluble coating composition is then applied to the first coating by a wet / wet technique and the two coatings are fired together in one step.

 Japanese patent application 26656/72 is similar to Japanese application 26657/72 mentioned above, except that the second coating is based on a polyepoxide. it is stated in these documents that the curing mechanism involves the crosslinking of the isocyanate or polyepoxide in the second layer with the carboxylic acid groups in the first layer.

 None of these two documents mention the use of two coatings, one of which would use a blocked isocyanate functionality while the other would contain a 1,2-epoxy functionality, as it is the case according to the present invention.

In US Patent 4,175,018 to Gacesa,
a method for coating an article such as a continuous web / flat sheet is described. This method involves placing the metal sheet in an aqueous electrodeposition bath containing both the water-soluble resins and water-insoluble emulsified resins. The metal sheet is electrodeposited and then applied to the layer thus deposited, a topcoat, without having first baked the electrodeposited layer. The metal carrying the two layers is then transferred to a cooking station where both layers are fired simultaneously. This patent describes a wide variety of coating compositions that can be used for electrodeposition coating. It refers to cationic electrodeposition compositions, such as those described in US Pat. No. 3,984,299 which describes compositions comprising acid-solubilized polyepoxydeamine adducts in combination with fully blocked isocyanate cyanates. However, it is not part of this document that it is particularly desirable to choose a primer composition containing blocked isocyanate groups. When coating compositions described herein contain blocked isocyanates, they are among many other primer coating compositions that do not contain blocked isocyanates.

 US Pat. No. 4,175,018 also discloses that it is possible for the topcoat to be one of those commonly used, for example acrylic substances, polyesters, alkyds, epoxies and fluoropolymers. The fact that epoxy-type topcoats are listed among many others does not teach the choice of epoxy compositions and use them in combination with a primer containing blocked isocyanates. Moreover, although this document refers to compositions In the state of the art, epoxy type finishes are understood to mean coating compositions which are derived from resins containing 1,2-epoxy groups, for example, epoxy esters and epoxides. ethers in which the epoxy functionality is consumed by reaction with acids and alcohols and may not even contain 1,2 epoxy functionality.

 In U.S. Patent 4,208,262 to Kubo et al., There is disclosed a method for coating an article, wherein the article is electroplated in a bath containing a water-dilutable cationic resin and a powdery resin. . The coated article is then subjected, without curing the first layer, to additional electro-deposition in a bath containing an ionic resin (without the powdery resin). Then, the coated article is fired for crosslinking and curing between layers.

 The cationic resin of the first layer may be an adduct of a primary or secondary amine with an epoxy resin which is neutralized with an acid. The epoxy resin may be partially esterified or etherified, or may be an adduct with an isocyanate.

 The powdered resin can be chosen from a very large number of substances known in the powder coatings technology and preference is given to epoxy resins. Curing agents may be added to the epoxy resin, including amines, amides, anhydrides, various isocyanates, isocyanurates, urea, melamine resin, amidine, imide and the like, the preference being for blocked isocyanate.

 The second coating may be anionic or cationic, with preference being given to the cationic coating.

Examples of anionic coating compositions include those based on the following resins: maleinized oil resins, polybutadiene resin, epoxy ester resin, acrylic resin, phenolic resin, and mixtures of these resins. With regard to the cationic coating compositions, epoxy resins, epoxy-urethane resins, acrylic resins, polyamide resins or mixtures of these resins may be used.

 Although it is possible to find among the many resins described in US Pat. No. 4,208,262 a primary layer containing a blocked isocyanate and a secondary coating which may contain an epoxy resin, this patent did not contain any teaching that it would have failed to select these products. No relation between the isocyanates blocked in the first layer and the 1,2-epoxy functionality in the second layer is described in order to obtain a cured product.

 According to a preferred embodiment of the present invention, the blocked isocyanate-containing coating composition is a primary composition which is applied to a substrate, the coating composition containing the 1,2-group functionality. epoxy is an intermediate layer which is applied to the primary layer containing the blocked isocyanate before curing.

 The primary coating composition may be based on an organic solvent or preferably on an aqueous basis. Examples of suitable coating compositions for primary coatings which contain blocked isocyanate curing agents are described in US Pat. Nos. 3,799,854, 4,031,050, 3,922,253, 4,009,133, 4,038,232, 4,101,486 and US Pat. , 3,935,087 and 3,883,383.

 A preferred primer composition is a water-based system comprising an acid solubilized polyepoxide-amine adduct in combination with a blocked isocyanate curing agent.

 Polyepoxides are polymers having a 1,2-epoxy equivalence of greater than 1 and preferably of about 2 or more. Preferred polyepoxides are those which are bifunctional with respect to the epoxy.

 Specific preferred polyepoxides are polyglycidyl ethers of cyclic polyols, and more particularly polyglycidyl ethers of polyphenols such as bisphenol A. Examples of polyphenols other than bisphenol A are 1,1-bis (4-hydroxyphenyl) ethane. and 2-methyl-1,1-bis- (4-hydroxyphenyl) propane.

 In addition to the polyphenols, other cyclic solvents can be used for the preparation of the polydehyde glycidyl ether derivatives / cyclic polyol. Examples of other cyclic polyols are alicyclic polyols, in particular cycloaliphatic polyols, such as, for example, 1,2-cyclohexanediol, 1,3-bis (hydroxymethyl) cyclohexane and hydrogenated bisphenol A.

 Cyclic alkylation adducts such as oxide / ethylene or propylene adducts, alicyclic polyols and polyphenols mentioned above can also be used as the cyclic polyol component.

 Examples of other polyepoxides are polyglycidyl ethers of polyfunctional alcohols, such as ethylene glycol and propylene glycol.

 Polyglyoid esters of polycarboxylic acids which are produced by reacting epichlorohydrin or a similar epoxy compound with an aliphatic or aromatic polycarboxylic acid can also be used. Examples of polycarboxylic acids are dicarboxylic acids, such as adipic acid and dimerized linoic acid.

 It is also possible to use epoxy group-containing acrylic polymers, such as those prepared by reacting glycidyl methacrylate with other copolymerizable vinyl monomers. The polymers can be prepared by solution polymerization techniques in the presence of the free radical catalyst as described in U.S. Patent 3,988,281.

Poiyepoxides such as the preferred polyglycidyl ethers of cyclic polyols may also be subjected to reaction for chain lengthening and increasing molecular weight. For example, they can be reacted with active hydrogen-containing substances which react with the epoxy groups; these substances may be those containing primary hydroxy groups. Examples of chain extending substances are polymeric polyols such as polyester polyols, and especially polylactone polyols. Chain lengthening of epoxy-containing polymeric substances with polymeric polyols is described in US Pat. No. 4,148,772 to
Marchetti, Zwack and Jerabek, which was assigned to the present plaintiff.

 The organic amine which reacts with the polyepoxide may be ammonia, or a primary, secondary or tertiary amine, or mixtures thereof. For the introduction of cationic salt groups into the epoxy-amine adduct, the polyepoxide-amine adduct is at least partially neutralized to form amine salts in the case of ammonia, primary amines and secondary amines, and quarternary ammonium salts in the case of tertiary amine.

 The preferred amines are monoamines. Polyamines such as ethylene diamine and piperazine may be used, but they are not preferred because they are multifunctional in the amine position / function and have a greater tendency than monoamines to form a gel. from the reaction mixture.

 Secondary and tertiary amines are preferred over primary amines because the primary amines are bifunctional and have a greater tendency to transform the reaction mixture into a gel.

 Examples of suitable monoamines are the mixed mono, diakyl and trialkyl amines and alkyl-aryl amines, as well as the corresponding substituted amines in which the substituents do not adversely affect the polyepoxide zamine reaction. Specific examples of such amines are ethylamine and diethylamine.

Examples of substituted amines are hydroxy-containing amines such as alkanolamines, dialkanolamines, alkyl alkanolamines and aryl alkanolamines containing from 2 to 18 carbon atoms in the alkanol, alkyl and aryl chains. Specific examples include ethanolamine, N-methylethanoamine, diethanolamine and N phenylethanolamine.

Mixtures of the various amines mentioned above can be used. The reaction of the amines with the polyepoxide takes place when the amine is mixed with the poly
The reaction can be carried out without solvent or, if desired, in the presence of a suitable organic solvent. The reaction may be exothermic and it may be desirable to cool. However, it can be used to accelerate the reaction heating at a moderate temperature, that is to say in the range of 50 to 1500C.

 The reaction product of the amine with the polyepoxide reaches its cationic character by at least partial neutralization, for example by treatment with an acid, to form secondary or tertiary amine salts. Examples of such acids include organic and inorganic acids such as formic acid, acetic acid, lactic acid and phosphoric acid.

The degree to which the neutralization takes place depends on the particular product used. It is only necessary to use enough neutralizing agent to solubilize or disperse the product in water. In practice, the amount of neutralizing agent used should be sufficient to provide at least 30% of the total theoretical neutralization.

 In addition to the amines described above, a fraction of the amine which is reacted with the polyepoxide may be a ketimine or a polyamine, as described in US Pat. No. 4,104,147 (more particularly in the passage of that patent from column 6, line 23, to column 7, line 23). The ketimine groups break down when the polyepoxy amine adduct is dispersed in water, and give free primary amine groups which can be reactive with a curing agent, as described in more detail below.

In general, most cationic polymers
Usable for the purpose of the invention have average molecular weights (calculated values) in the range of 500 to 5000, and preferably 1000 to 3000 and contain from about 0.1 to 3.0, and preferably from about 0.3 to 1.0 milliequivalents of cationic nitrogen per gram of resin solids. Naturally, those skilled in the art must use their knowledge to achieve a judicious combination of molecular weight and cationic group content to arrive at a satisfactory polymer.

 In the preparation of the blocked organic polyisocyanate, any suitable organic polyisocyanate may be used. Representative examples are aliphatic compounds such as trimethylene and tetramethylene diisocyanates; cycloalkylene compounds such as 1,4cyclohexane diisocyanate; aromatic compounds such as p-phenylene diisocyanate; aliphatic-aromatic compounds such as 4,4'-diphenylene methane diisocyanate, 2,4- or 2,6-tolylene diisocyanates or mixtures thereof.

Higher polyisocyanates, such as, for example, triisocyanates, and especially triphenylmethane-4,4 ', 4 "-triisocyanate, may be used.

 As the blocking agent, according to the present invention, any suitable aliphatic, cycloaliphatic or alkylaromatic monoalcohol type compound and any phenolic compound, for example lower aliphatic alcohols containing from 1 to 4 carbon atoms, especially ethanol, may be used as blocking agent. and n-butyl alcohol; cycloaliphatic alcohols such as cyclohexanol; alkyl aromatic alcohols such as phenylcarbinol and methylphenylcarbinol; phenol compounds such as phenol itself, substituted phenols in which the substituents should not adversely affect the coating operations, such as, for example, cresol and nitrophenol. If desired, small amounts of monoalcohols having even higher molecular weight, which are relatively nonvolatile as plasticizers in coatings made according to the present invention.

 Other blocking agents include oximes such as methyl ethyl ketoxime and cyclohexanone oximes as well as lactams such as epsilon-caproactam. It is particularly desirable to use oximes and lactams because the polyisocyanates blocked with these agents will deblock and react at relatively low temperatures.

 The polyisocyanate curing agent can be used in two ways, which are similar.

The polyisocyanate can be completely blocked, i.e. no free isocyanate groups remain, and then added to the acid-solubilized polyepoxydeamine adduct to form a two-component system. Alternatively, the polyisocyanate may be partially blocked, for example, it is a semi-blocked diisocyanate, so that there are still remaining reactive isocyanate groups. The partially blocked isocyanate can then be reacted with the polyepoxide via active hydrogen functionalities, for example hydroxyl, present in the polyepoxide under conditions which do not release the isocyanate.This reaction has the effect of completely blocking the isocyanate thereby making it an integral part of the polymer molecule and constituting a one-component system. Systems with two comnosaffsJ er; Preferred are / are described in U.S. Patent 4,031,050. The one-component systems are described in U.S.

No. 3,922,253. Normally, the blocked isocyanate-containing composition contains at least 2. and preferably 2 to 10, and more preferably 2.5 to 7,% blocked isocyanate functionality based on the weight of isocyanate.

 The resinous products according to the invention are usually prepared so that all the epoxy functionality is consumed. However, when dispersed in water, any epoxy functionality that may still exist, is eventually hydrolysed.

 Aqueous dispersions of the above resinous products are particularly suitable for electroplating, but can also be applied by conventional coating techniques.

 The term "dispersion", as used herein, refers to an aqueous two-phase translucent or opaque resinous system in which the resin is the dispersed phase while the water constitutes the phase. - - - - - - continues. The average diameter / particles of the resinous phase is generally less than 10 and preferably less than 5 micrometers. The particles may be spherical or elongated or invisible under a microscope. By the term "dispersion" is meant also homogeneous aqueous solutions which appear optically transparent.

 The concentration of the resinous products in the aqueous medium is dependent on the process parameters and is generally not critical, but usually the bulk of the aqueous dispersion is water. The aqueous dispersion may for example contain from about 2 to 75% by weight of resin solids.

 In addition to water, the aqueous medium may contain a coalescing solvent. The fact of using coalescing solvents makes it possible to obtain, in certain cases, the appearance of the film deposited. These solvents include hydrocarbons, alcohols, esters, ethers and ketones. Preferred coalescing solvents include monoalcohols, glycols and polyols, as well as ketones and ether alcohols. Among the particular coalescing solvents, mention may be made of isopropanol, butanol, isophorone, 4-methoxy-methylpentanone-2, ethylene and propylene glycols, ethylene glycol, monobutyl and monohexyl ethers of ethylene glycol. and 2-ethylhexanol.The amount of coalescing solvent is not particularly critical and is generally between about 0.1 and 40% by weight, preferably between about 0.5 and 5% by weight, based on the weight total of the aqueous medium.

 In most cases, the dispersion, if desired, includes a pigment composition and various additives such as surfactants or wetting agents. The pigment compositions can be of any conventional type, including, for example, iron oxides, lead oxides, strontium chromate, carbon black, coal dust, titanium dioxide, talc , barium sulphate, as well as colored pigments such as cadmium yellow, cadmium red, chrome yellow or others. The pigment content of the dispersion is usually expressed as a pigment / resin ratio. In the practice of the present invention, pigment / resin ratios of about 0.05 to 0.5: 1 are usually used. The other additives just mentioned are present in the present invention. the dispersion at a rate of about 0.01 to 3% by weight relative to the total weight of the solids of the resin.

 In the electrodeposition process using the aqueous dispersion described above, the aqueous dispersion is placed in contact with a conductive anode of electricity and a cathode which is also electrically conductive, the surface to be coated being the cathode. While this is in contact with the aqueous dispersion, an adherent film of the coating composition is deposited on the cathode when a voltage is applied between the electrodes.

 The conditions under which electrodeposition is carried out are, in general, similar to those used in the electroplating of other types of coatings. The applied voltage can vary widely and can be, for example, as low as 1 volt or as high as several thousand volts, but in practice it is between about 50 and 500 volts. The current density is usually between 1.0 amperes and 15 amperes for about 0.09 m 2 and tends to decrease during electroplating, indicating the formation of a self-insulating film.

 It is desirable to electrodeposit these coatings from a dispersion having a pH of from about 3 to about 9.

 Although the application of the coating composition containing isocyanate groups blocked on a substrate has been described more specifically with reference to electrodeposition of aqueous-based cationic coating compositions, it is clear that the invention is equally applicable to aqueous-based anionic coating compositions, which can also be applied by electrodeposition, as well as non-ionic aqueous coating compositions and organic solvent-based coating compositions, which can be applied by non-electrophoretic.

 In addition to electroplating, it is possible to use to apply the coating composition to the substrate to any conventional coating method such as dip coating, spraying, scrubbing or rolling. Typically, the primer coating has a thickness of about 5 to 30 and preferably 10 to 20 microns.

 The primary layer can be used on many substrates. For applications in the automotive field, steel is the usual substrate and may be made of untreated steel or pretreated steel, such as steel which has been treated with iron phosphate or with zinc phosphate, in a pre-treatment known to those skilled in the art. In addition to steel, other metals can naturally be used, such as aluminum, copper, magnesium and alloys of these metals.

Other substrates may be used, provided that they are not subject to adverse effects from the components of the coating composition or firing operations, and may be evoked for example from glass, ceramics, wood and wood. plastics. Examples of plastics include elastomeric plastics, such as high density polyurethane foam, which is used for making many elastomeric parts of automobiles.

 After the primary layer containing blocked isocyanate groups has been applied to the substrate, the intermediate layer, which contains a resin containing 1,2-epoxy groups, is applied to the primer layer without first hardening the primer layer. By the term "intermediate layer" (English "saler") is meant coating compositions which contain or contain only relatively few pigments; by this is also meant compositions containing high pigment loads and which, when applied to primary layers, are termed surfacing agents of the primary layer.

 The resinous binder present in the intermediate layer must be at least partly a resin containing 1,2-epoxy groups. If the epoxy resin is the only resinous binder, it must be a resin containing 1,2-epoxy film-forming groups. Alternatively, if the epoxy resin is used in combination with another resinous ingredient, the combination should form a film-forming resinous binder. Examples of such resinous ingredients are drying oils, alkyd resins, saturated polyester resins, polyurethane resins such as poly (ester-urethane) resins and acrylic resins.

 Examples of suitable epoxy resins are those mentioned above, relating to the preparation of primer compositions, with polyglycidyl ethers of cyclic polyols being preferred. The molecular weight of the polyepoxides is preferably at least about 350, and more preferably at least 800, so that optimum grit and solvent resistance can develop. The most advantageous molecular weight is between 800 and 30,000. The lower molecular weights, where possible, are calculated values, while the higher molecular weights, which can not be calculated, are values based on gel permeation chromatography using a standard of polystyrene and are an indication of weight average molecular weight. As the polyepoxide, it contains a 1,2-epoxy functionality greater than T, preferably at least 1.4, and more preferably at least 2.

 Drying oils are esters of fatty acids obtainable from a natural source or which can be prepared by reaction of a fatty acid with a polyol. The drying oils all contain at least one fraction of polyunsaturated fatty acids. Drying oils are oils which have an iodine number of about 85 to 185, as determined by US ASTM D-1467 and therefore include so-called semi-sictives oils.

 Examples of suitable natural drying oils are flaxseed oil, soybean oil, safflower oil, perilla oil, tung oil, oiticica oil, poppy, sunflower oil, tall oil t-oil, nut oil, castor oil, dehydrated castor oil, herring oil, menhaden oil, sardine oil and others.

 Examples of drying oils obtained by reacting fatty acids with polyols are fatty acid products, such as oleic, linoleic and linolenic acids with various polyols such as 1,4-butanediol, glycerol, trimethylolpropane, pentaerythritol and sorbitol.

 Drying oils may be modified with other acids, including saturated, unsaturated or aromatic acids, such as adipic acid, maleic acid and phthalic acid. The acid-modified oils are made by transesterification of the ester, for example by forming a diou monoglyceride by alcoholysis followed by esterification with a modifying acid.

 An alkyd resin is a product obtained by reacting a mixture of a di and / or a triacid and a fatty acid with a polyol. Typical polyacids include phthalic acid, maleic anhydride and trimellitic anhydride. Typical fatty acids include linoleic or linolenic acids or drying oils such as the drying oils mentioned above. In practice, the polyols are in particular ethylene glycol, glycerol, trimethylolpropane, pentaerythritol and sorbitol.

 The saturated polyester resins are formed from saturated or aromatic polycarboxylic acids and polyols. Typical saturated aliphatic polycarboxylic acids are those containing from about 2 to about 1 carbon atoms, such as, for example, succinic acid, azelaic acid and adipic acid. Examples of aromatic polycarboxylic acids are phthalic acid and trimellitic acid. Many polyols can be reacted with the above acids to form the desired saturated polyesters. The most useful are diols such as ethylene glycol, 1,4-butanediol, neopentyl glycol, sorbitol, pentaerythritol and trimethylolpropane.

The acrylic polymer which is used for the practice of the present invention is prepared by free-radical initiated polymerization of a mixture of copolymerizable acrylic monomers by solution polymerization techniques.
The acrylic monomer mixture can be chosen from a very wide variety of polymerizable acrylic monomers. Examples include vinyl-type aromatic monomers, such as styrene and vinyl toluene; alkyl esters of acrylic and methacrylic acid containing from about 1 to 20 carbon atoms in the alkyl group, such as, for example, methyl methacrylate, 2-ethylhexyl acrylate and butyl methacrylate; acrylic monomers containing active hydrogens, in particular hydroxyl groups, for example hydroxyalkyl acrylates, or hydroxyalkyl methacrylates, and in particular hydroxyethyl acrylate, hydroxyethyl methacrylate and hydroxypropyl acrylate; and an alpha, beta-ethylenically unsaturated carboxylic acid, such as, for example, acrylic acid or methacrylic acid.

 As indicated above, the interlayer composition preferably comprises a mixture of an epoxy resin with one or more of the resins selected from those just mentioned. Preferably, the epoxy resin comprises from about 40 to 100% by weight of the resinous binder and the other resin is from about 0 to 60% by weight. The percentages vary depending on the identities of the epoxy resin and the other resinous binder, as well as the thickness and properties desired to be imparted to the coating. The following exemplary embodiments indicate typical interlayer compositions.

 The interlayer compositions may be aqueous-based or solvent-based, with the solvent-based compositions being preferred. In order to produce water-based compositions, the intermediate layer compositions are usually provided with ionized groups or with groups which can easily be converted into ionized groups, for example an acrylic resin or an alkyd resin is prepared with carboxylic acid groups. unreacted which can be neutralized with a base such as an amine, and the resulting product is dispersed in an aqueous medium. For solvent-based compositions, the resins are dissolved in suitable solvents. According to the resinous binders used, the solvents which may be employed may be aliphatic, cycloaliphatic or aromatic hydrocarbons, esters, ethers, ketones and the like. alcohols, such as those conventionally used in coating compositions.

Examples of such compounds include toluene, xylene, butyl acetate, 2-butoxyethyl acetate, 2-ethoxyethanol, 2-butoxyethanoyl, acetone, methyl isobutyl ketone, and butyl alcohol. . In general, the resin solids of the interlayer composition are at least 40% by weight.

 The interlayer compositions may also contain pigments and adjuvant substances which are well known to those skilled in the art. Examples of pigments are those mentioned above with respect to the formulation of the primer compositions. Usually, the pigmentation of the intermediate layer is up to a concentration of about 30% by volume of pigment.

 Examples of builder substances include, but are not limited to, thickeners, defoamers, adhesion additives, coalescing acids, and the like. The amount of adjuvant substances to be used in the interlayer composition generally does not exceed about 2% by weight based on the total weight of this intermediate layer.

 In addition to the optional ingredients listed above, a curing agent such as amine or amide-aldehyde condensate may be added to the formulation if desired. However, since the application of the interlayer to the primer layer by the wet / wet technique according to the invention provides an excellent cured product after heating, without a curing agent, it is not necessary at all to include a curing agent in the interlayer compositions.

 For the application of the interlayer composition on the primary layer by the wet / wet technique according to the invention, the primary layer is applied as described above and then, before curing the primary layer, the intermediate layer is applied. Preferably, the primer is air-dried or heated to a high temperature for a short period of time, sufficient to dry the primary coating, but insufficient to cure the product. In the drying step, care must be taken not to de-ionize the isocyanates, otherwise the hardening of the primary layer and insufficient development of physical properties that the present invention achieves. The drying temperature is mainly determined by the nature of the isocyanate used, its blocking agent and the presence of catalyst. As is well known to those skilled in the art, these factors determine at what temperature the isocyanate will unblock.

The following exemplary embodiments indicate drying schedules that can be used with coating compositions containing particular blocked isocyanate groups. In practice, drying programs of 1300 can be used for 10 minutes or less.

 In the present context, where it is stated that the coating compositions are applied sequentially without first drying the initially applied coating, the following is meant: in the initially applied coating, there are sufficient groups functional groups, for example blocked isocyanate groups, present for subsequent hardening with the sequentially applied coating. "Curing" is understood to mean that the composite coating or film develops better physical properties as the curing process evolves. Examples of better physical properties are solvent resistance, hardness and chip resistance.

 Typically, the intermediate layer is spray-applied to the primer composition, although it may be applied by any other conventional coating technique, such as brushing, rolling, spreading and the like. However, the spray is preferred which provides the coating system with the best appearance. Typically, the intermediate layer has a thickness of about 20 to 50, and preferably about 25 to 45 microns.

 Once the intermediate layer has been applied, the coating system is generally cured by heating at an elevated temperature for a time sufficient to result in a solvent resistant coating. The curing time and temperature depend on the identity of the blocked isocyanate which acts as a curing agent and the presence of catalysts in the primer composition. In practice, the curing can be carried out at a temperature of about 150 to 4000 ° C for about 15 to 45 minutes.

 For automotive coatings, a topcoat is usually applied to the intermediate layer. The topcoats are well known to those skilled in the art and may be either aqueous-based or organic-based. Furthermore, the topcoat may be thermoplastic or thermosetting. The topcoat may be a system comprising a pigmented or colored basecoat and, thereon, an unpigmented or transparent lacquer.

 Examples of suitable topcoat compositions are those compositions which are based on acrylic polymers, drying oils, alkyd resins, saturated polyester resins, resins, epoxy and epoxy resins, and polyurethane resins. as mixtures of these resins. Examples of such polymers have been described above.

 Usually, the topcoats are pigmented to impart color to the finished article. Examples of pigments are in particular those described above, as well as metallic pigments, such as aluminum, copper and bronze. Normally, the ratio of pigment to binder is between about 0.1 and 1.5: 1.

 The topcoat composition may be aqueous-based or solvent-based, with the solvent-based composition being preferred. Examples of suitable solvents and diluents are those mentioned above.

 The topcoat compositions can be applied to the interlayer either by brushing, spraying, dipping, pouring or any other technique known in the art. However, the spray technique is preferred.

 Normally, the topcoat is cured in the temperature range of from 820C to 204C and preferably from about 1070C to 1380C for about 10 to 40 minutes.

 The topcoat composition may be applied to the intermediate layer after it has been fully cured or, alternatively, the intermediate layer may be only, for example, air-dried or flash drying, for about 30 seconds to 10 minutes, at a temperature below 1300C, and the topcoat is applied to the interlayer and it is the entire system which is then cured at higher temperatures which are indicated more above. Usually, the topcoat has a thickness of about 20 to 50, and preferably 25 to 45 microns.

 The topcoat composition may be a single layer, as generally described, or alternatively a system having a colored basecoat covered by a transparent topcoat. Examples of such systems are described in U.S. Patent 3,639,147.

 In general, the topcoat compositions described in general terms above may be used for making the colored basecoat.

The transparent upper layer can be made with resins such as those described in general terms above, but without pigments. In systems thus comprising a colored basecoat and a transparent topcoat, the colored basecoat is usually applied to the interlayer by a wet / wet technique or is applied to a pre-cured interlayer. The colored basecoat is then subjected to cure temperatures as described above in general terms. Alternatively, the transparent top layer can be applied to the colored basecoat by a wet / wet technique and it is the overall coating system which is then cured at elevated temperature.

 Although the present invention has been described more particularly with reference to a combination of a base layer and an intermediate layer, the reactive coating system may be made by any other combination, such as an interlayer combination and topcoat. For example, an intermediate layer composition containing a blocked isocyanate group can be applied to a previously hardened primer layer, and then, on the intermediate layer, applying the topcoat composition containing a 1,2-epoxy resin, by a technique wet / wet.

 The present invention can also be implemented in the context of the coating compositions for coating with a colored base coat and a transparent top layer. For example, it may be the colored basecoat that contains blocked isocyanate groups, while the transparent topcoat contains a 1,2-epoxy resin and is applied to the basecoat by a wet / wet technique.

 it is also possible not to use the intermediate layers indicated above and to apply the topcoat by the wet / wet technique directly on the primary layer. For example, a topcoat composition containing 1,2 epoxy resins can be wet / wet applied to a primary layer containing NCO groups and the entire system is cured in one step. In a system comprising a colored basecoat and a lacquer layer, a 1,2-epoxy resin containing the basecoat, wet / wet, can be applied to a primary layer containing NCO groups and harden the surface. resulting multilayer coating. A transparent topcoat can then be applied to the cured basecoat and the top transparent layer cured in a separate step.

 Although the invention has been described more specifically with reference to the coating of automobiles, it is quite clear that it applies to all coatings of all types of industries, such as the industry of (in general and even any type of industry without any exclusivity.

The invention is further illustrated by the following examples, which do not limit it in any way. In these examples, as well as throughout the foregoing description, parts and percentages are parts and percentages by weight unless otherwise indicated.
EXAMPLES
PRIMARY LAYERS
Example A
Example A relates to a cationic electrodepositable primer composition based on an acid-solubilized polyepoxide-anion adduct having a fully blocked organic polyisocyanate curing agent as described in US Pat.
No. 4,031,050. The composition contains about 3.70% by weight of latent NCO functionality.

Example B
Example B relates to a cationic electrodepositable primer composition similar to that of Example A above containing only 2.48% by weight of latent NCO functionality.

Example C
Example C consists of a cationic electrodepositable primer composition in which the resinous binder is to be considered as prepared as described in general terms in FR-OS 2 752 255. The product contains about 5% by weight. weight of latent NCO functionality and is available near the Company.
Vianova Kunstharz, under the trade name RESYDROL
SVK.

Example D
Example D consists of an anionic electrodepositable primer composition, wherein the resin binder is a bisphenol polyglycidyl ether (epoxy equivalent weight of about 875-1000) added to a tall oil fatty acid, which was neutralized with dimethylethanolamine.

Example E
Example E represents a solvent-based primer composition comprising 50 parts by weight of a styrene-allyl alcohol copolymer having a hydroxyl number of 0.45 equivalents of OH per 100 grams of copolymer, commercially available where it is delivered by the company Monsanto Company under the name RJ 101, 50 parts by weight of toluene diisocyanate completely blocked with 2-ethylhexanol, and 80 parts by weight of xylene, as well as a small amount of tin catalyst .

Example F
Example F consists of a cationic electrodeposition primer composition based on an acid solubilized polyhepoxide-amine adduct and a polyester as curing agent, prepared as described in general terms in US Pat. Example V of European Patent Application 012463. The polyester crosslinking agent is an adduct of trimellitic anhydride and Versatic acid glycidyl ester (CARDURA E).

INTERMEDIATE LAYERS
Example G
Example G consists of an intermediate layer composition based on a mixture of an alkyd resin based on castor oil and an epoxy resin. The weight ratio of the alkyd resin to the epoxy resin was 40/60 based on the resin solids. The intermediate layer is pigmented with TiO2, barium sulfate and mica. The castor oil alkyd resin had an iodine number of 30 and a hydroxyl number of 90 (measured on a solution of 80% resin in 2-ethoxyethyl acetate). The epoxy resin is a polyglycidyl ether having a bispnenol A having an epoxy weight / equivalent of about 485 (EPON 1001).

 The interlayer composition had a solids content of 60%, a pigment to binder ratio of 1 and a Ford cup viscometer viscosity of 30 seconds, measured with a No. 4 Ford cup at 200 C.

Example H
Example H represents an interlayer composition similar to that of Example G but having a solids content of 58, a pigment / binder ratio of 0.9 and a weight ratio of alkyd to epoxy. 40/60.

Example I
Example I represents an intermediate layer composition based on a blend of 40% by weight castor oil alkyd resin, 15% by weight soybean based alkyd resin, 20% by weight weight of an aminoplast resin and 25% by weight of an epoxy resin; the percentages by weight relate to. total weight of the resinous components. The interlayer composition is pigmented with titanium dioxide, barium sulfate and mica.

 The castor oil alkyd resin has an iodine number of 35 and a hydroxyl number of 105 (measured on an 80% resin solution). The soy oil based alkyd resin has an iodine number of 30 and a hydroxyl number of 70 (measured on an 80% resin solution). The aminoplast was a condensation product of butylated ureaformaldehyde. The epoxy resin was a polyphenyl bisphenol A ether polyether having an epoxy equivalent weight of about 500.

 The interlayer composition had a solids content of 72%, a pigment / binder ratio of 1.06 and an 80 second Ford cup viscosity of 80 seconds measured at 200 ° C.

Example J
Example J relates to an intermediate layer composition based on a mixture of 32% by weight of castor oil based alkyd resin according to the example
I, 9.5% by weight of soybean based alkyd resin according to Example I, 9.5% by weight of a polyether, 4.5% by weight of a blocked isocyanate, 25, 5% by weight of an aminoplast resin, 14% by weight of a polyglycidyl ether of bisphenol A having an epoxy equivalent of about 500 and 5% of a bisphenol A polyglycidyl ether having an epoxy equivalent of about 185. The polyether was a poly (oxytetramethylene) glycol having a molecular weight of 1000. The blocked isocyanate was an aliphatic polyisocyanate (average NCO functionality of 3), commercially available from Bayer Aktiengesellschaft under the trade name DESMODUR N. , completely blocked with methyl ethyl ketoxime. The aminoplast was a mixed mecanurea-formaldehyde condensation product.

 The interlayer composition had a solids content of 60%, was pigmented as shown in Example I, had a pigment / binder ratio of 0.83 and Ford n 4 cup viscosity of 50 seconds.

Example K
Example K relates to an anti-grit coating composition based on a blend of 52.7 wt.% Urethanized polyester, 10.8 wt.% Polyether of Example J, 19 wt. Example I and 17.5% by weight of a melamine-for-aldehyde condensation product. The coating composition was pigmented with titanium dioxide, barium sulfate, kaolin and talc. The urethanized polyester had a hydroxyl number of 15 (measured on a 55% resin solution) *
The coating composition had a solids content of 54%, and a pigment / binder ratio of 1.11.

Example L
Example L consists of an anti-scouring coating composition based on a mixture of 57% by weight of a urethanized polyester, according to Example K, 6% by weight of a polyether according to the example I, 19% by weight of a bisphenol A polyglycidyl ether having an epoxy equivalent of about 185, and 18% by weight of a methylated melamine-formaldehyde condensation product. The coating composition was pigmented as shown in Example K.

 The coating composition had a solids content of 60% and a pigment / binder ratio of 1.08, as well as Ford NO 4 cup viscosity of 60 seconds at 200C.

Example M
Example M consists of an interlayer composition based on a mixture of an alkyd resin, an epoxy resin and an aminoplast. The interlayer composition was pigmented with titanium dioxide and barium sulfate. The interlayer composition had a solids content of 60%, a pigment / binder ratio of 0.9 and Ford nO 4 cup viscosity of 90 seconds.

Example N
Example N represents a 40% by weight solution in 2-butoxyethanol of EPON 1001 (epoxy equivalent weight of about 485).

Example O
Example O consists of a 50% by weight solution in 2-butoxyethanol of a styrene allyl alcohol copolymer having a hydroxyl number of 0.45 equivalence of OH per 100 grams of copolymer put on the market by Monsanto Company under the trade name RJ-101.

Example P
Example P is a 40% by weight solution in 2-butoxyethanol of an epoxy resin defunctionalized with ammonia (bisphenol polyglycidyl ether)
A) which had an epoxy equivalent of 2372 before reaction with ammonia.

Example Q
Example Q is a 50 wt.% Solution in 2-butoxyethanol of EPON 1001 (epoxy equivalent of 485).

Example R
Example R is an interlayer composition which was prepared by kneading together 200 parts by weight (150 parts by weight solids) of EPON 1001 (epoxy equivalent weight of 485), 100 parts of butyl and 50 parts of ASP 170 clay. The mixture was diluted to 10% solids with butyl acetate.

Example S
Example S is an intermediate layer composition obtained by defunctionalization of 50 parts by weight of EPON 1001 (weight of epoxy equivalent /% O) with 9.4 parts of phenol. The product of the defunctionalized reaction was diluted with 26 parts by weight. parts of butyl acetate and then combined with 19.8 parts by weight of ASP 170 clay.

Example T
Example T is an interlayer composition in which the resinous binder was prepared by solution polymerization of 40% butyl acrylate, 15% styrene, 15% methyl methacrylate, 15% hydroxypropyl methacrylate, and 15% glycidyl methacrylate; the percentages by weight are based on the total weight of the monomers. The monomers were polymerized in a 1/11/18 mixture of water, 2-phenoxyethanol and 2,2,4-trimethylpentane-1,3-diol monoisobutyrate, constituting the solvent, in the presence of an initiator consisting of with 2-t-butylazo-2-cyanobutane. The reaction product contained 75% polymer solids. The reaction product (52 parts by weight) was mixed with 26 parts by weight of butyl acetate and 13 parts by weight of ASP 1708 clay.
FINISHING LAYERS
Example U
Example U is a white, non-aqueous coating composition made of acrylic polymer with an aminoplast as a curing agent. The coating composition had a solids content of 66%, a pigment / binder ratio of 1 and Ford nO 4 cup viscosity of about 40 seconds.

Example V
Example V is a base coat system co (lorea and layer / varnish, in which the colored base coat contains an aluminum pigment plus colored pigments in a resinous binder comprising a polyester resin and a Aminoplast resin: The base coat had a solids content of 37% and a pigment / binder ratio of about 0.15.

The varnish layer is a 40% resin solids solution of an acrylic resin and an aminoplast as a curing agent.

Example I
The present example aims to compare three coating systems with respect to their hardness and solvent resistance. One of the coating systems employed a primer composition containing blocked isocyanoyate groups and an interlayer composition applied to the primer layer by a wet / wet technique, with the curing of the one-step multilayer coating. The second coating system was similar to the first, but the intermediate layer was applied to the primer by a dry / dry technique, i.e., the primer was first cured prior to application of the intermediate layer and this intermediate layer were cured in a second step. The third coating was simply constituted by the intermediate layer directly applied to the substrate and cured without first applying a primer. The substrate was a pretreated steel plate, subjected to ferrous phosphatation
The results of the tests are summarized in the Table below:
Table I

<tb><SEP> \ <SEP><SEP> Systsme <SEP><SEP><SEP> Layer <SEP><SEP> Layer
<tb><SEP> \ <SEP> Layer <SEP> Layer <SEP> inter <SEP> The example <SEP> A (4) <SEP> of <SEP> places. <SEP> A ()
<tb><SEP> mediated <SEP> of <SEP> cooked <SEP> during <SEP> 19 <SEP> min. <SEP> dried <SEP> during
<tb><SEP> \ <SEP> ltex. <SEP> G <SEP> (3) <SEP> to <SEP> 200OC + <SEP> Layer <SEP> In <SEP> 5 <SEP> Min. <SEP> to <SEP> 130 Cf
<tb> Vessel <SEP> \ <SEP> Intermediate <SEP> of <SEP> Layer <SEP> Intended
<tb><SEP> l1exe the <SEP> G (3) <SEP> diary <SEP> of
<tb><SEP> Pex. <SEP> G (3)
<Tb>
Hardness Persoz (1) in seconds 290 290 310
Solvent resistance (2) 10 seconds 30 seconds 5 minutes
(1) Persoz hardness determined according to the AFNOR standard
NT 30-016; the higher the value, the greater is
hardness.

(2) Solvent resistance was determined by placing a
drop of solvent on the cured coating and measuring
the time it took for the coating to soften
smooth. The solvent consisted of the following mixture:
Constituent Percentage by weight
Acetone 46
2-hydroxyethyl acetate 34
Toluene 12
Xylene 8
(3) The intermediate layer was applied by spraying
and cured for 19 minutes at 2000C; Thickness 35
micrometers.

(4) Primary applied cationic electrodeposition layer
on the substrate from an electroplating bath
at 20% solids at 280 volts for two minutes,
bath temperature of 25 C, coating thickness 15-18 mi
cromètres.

Example II
In this example, six different coating systems are compared with respect to their chip resistance. Two of the coating systems included the application of an intermediate layer containing epoxy resin groups on a primary layer containing wet / wet / blocked isocyanate groups. Four coating systems included the application of an intermediate layer containing epoxy resin groups to a cured isocyanate group-containing primer layer, i.e. dry / dry. In two of the coating systems, an anti-grit layer was used between the primer and the interlayer. The results of the tests are shown in Table II below:
Table II
Method
Application Dry / Dry Wet / Mbuillé
Primary layer Ex. A (1) Ex. A (1) Ex. A (1) Ex. A (1) Ex. A (2) Ex. A (2)
Anti coating
chipping No No No 'Ex. K (3) No Ex. L (3)
Inter layer
medial Ex. M (4) Ex. I (4) Ex. J (4) Ex. 1 (4) Ex. H (4) Ex. I (4)
Layer Resistance to gravelling (7)
finish
Ex. U (5) poor average good average good good
7 5 3 6 1 4
Ex.V (6) average average good good good average
7 6 3 4 1 5 (1) Electrodeposition primer applied to a
steel substrate pretreated by phosphating
from an electroplating bath at 20% solids,
under 280 volts for 120 seconds, temperature of
bath 250C. Coating cured for 30 minutes at 1800C;
thickness 15 micrometers.

(2) As the note (1), but coating dried for 5 minutes
at 1300C.

(3) Spray-applied anti-gravilant coating
under a thickness of 15-20 micrometers; inter layer
mediator applied by wet / wet spraying
on the anti-grit layer.

(4) Intermediate layer applied by spraying, hard
for 22 minutes at 1700 C; 35 micrometer thickness
very.

(5) Spray applied, hardened topcoat
for 25 minutes at 1400C; thickness of the layer
35 micrometers.

(6) Colored base coat applied by spraying,
thickness of the layer 12 micrometers. Layer of varnish
applied by wet / wet spraying, on the
basecoat, cured for 25 minutes at 1400 C;
thickness of this layer 35 micrometers.

(7) The grading resistance according to
the Renate 1081 method, according to which
drops 1 kg of bolts from a height of 5 meters
on a coated sheet placed at an angle of 450. The
numerical values presented in Table II, cor
correspond to the percentage of peeling of the coating,
from the substrate. For example, the number 1 indicates
about 10% of chipping had occurred, while
the number 7 indicates that the flaking was approximately
70%. The lower the value, the less there is
coating from the substrate and better
is the resistance to gravel. The indication of
"good", "average" and "bad" in Table II
corresponds to a visual subjective evaluation based on
on a microscope examination of the diameter, the depth
and the geometry of the individual impacts.

Example III
In this example, four different coating systems are compared in terms of hardness and solvent resistance. The first system was an anionic electrodeposition primer composition without blocked isocyanate groups and an intermediate layer composition containing an epoxy resin applied to the primer layer by a dry / dry technique. The second coating system is similar to the first, except that the intermediate layer is applied to the primer layer by a wet / wet technique.

The third coating system is similar to the first, but the primer is applied by cationic electrodeposition and contains blocked isocyanate groups. The fourth coating system is similar to the third, but the intermediate layer is applied to the primer layer by impregnated / wet technique. The results of the tests are summarized in Table III below:

<tb><SEP> Table <SEP> III
<tb> Coating- <SEP> thode, <SEP> Sec / sec <SEP> Wet /
<tb><SEP> ment <SEP> dappl1i.ocan <SEP> Ilica- <SEP> Wet / <SEP> Dry / dry <SEP> hearing
<tb><SEP> wet
<tb> Primary <SEP> Layer <SEP> Ex. <SEP> D (1) <SEP> Ex. <SEP> D (2) <SEP> Ex. <SEP> A (3) <SEP> Ex-. <SEP> A (4)
<tb> Layer <SEP> intermediate <SEP> (5) <SEP> Ex. <SEP> H <SEP> Ex. <SEP> H <SEP> Ex. <SEP> H <SEP> - <SEP> Ex. <SEP> H
<Tb>
Trial
Persoz hardness in dry. 220 198 280 306
Resistance to the glenoid (6) 2 minutes 1.5 minutes 76 minutes 76 minutes
Resistance to solvents (see Ex.I) 10 seconds 8 seconds 20 seconds 1 minute
40 second (1) Primary applied anionic electrodeposition layer
on a steel substrate pre-treated by phosphating
iron, from an electroplating bath at 12%
solid, at 280 volts for 120 seconds, temperature
bath temperature 270C. Coating cured for 30 minutes
at 1800 C, thickness 25 micrometers.

(2) Same as (1), but coating dried for 5 minutes
at 1300C.

(3) Primary applied cationic electrodeposition layer
on a steel substrate pre-treated with iron phosphating
from an electroplating bath with 12% solids,
under 280 volts, for 120 seconds, temperature of
bath 270 C. Coating cured for 30 minutes at 1800C,
thickness 15 micrometers.

(4) Same as (3) but coating dried for 5 minutes
at 1300C.

(5) Intermediate layer applied by spraying, hard
for 20 minutes at 1800 C, layer thickness
35 micrometers.

(6) Solvent resistance was determined by placing
a drop of xylene on the hardened coating and in me
the time it took for the coating to become
softens.

Example IV
This example relates to the determination of the influence of the final cure temperature on the hardness and solvent resistance of coatings applied by a wet / wet technique, according to the present invention. For comparison purposes, an intermediate layer applied to a primer was also evaluated by a dry / dry technique and an intermediate layer applied directly to a substrate, without the prior application of a primer layer. The results are summarized in Table IV below: Table IV

<tb><SEP> 44 <SEP> Dry <SEP> Zou <SEP> Mouiflel <SEP> Wet / <SEP> Wet /
<tb><SEP> ~, <SEP> ex <SEP> N <SEP> U) <SEP> wet <SEP> wet
<tb><SEP> ment
<tb><SEP> Primary <SEP> Layer <SEP> No <SEP> Ex. <SEP> A (1) <SEP> Ex. <SEP> A (2) <SEP> Ex. <SEP> A (2) ) <SEP>'Ex.<SEP> A <2)
<tb><SEP> XX <SEP> Intermediate <SEP> (3) <SEP> Ex. <SEP> H <SEP> Ex. <SEP> H <SEP> Ex. <SEP> H <SEP> Ex <SEP > H <SEP> Ex. <SEP> H
<tb><SEP>]<SEP> of <SEP> 19 <SEP> min. <SEP> X <SEP> min. <SEP> t <SEP> min. <SEP> X <SEP> min. <SEP> O <SEP> min.
<Tb>

<SEP> Test <SEP> hardening <SEP> to <SEP> to <SEP> to <SEP> to <SEP> to
<tb><SEP> of <SEP> the <SEP> X <SEP> X <SEP> l, ed <SEP>
<tb><SEP> D <SEP> X <SEP> X <SEP> aE <SEP> O
<tb><SEP> V) <SEP>. <SEP> X <SEP> a3 <SEP> tM
<tb><SEP> 3 <SEP> 1 <SEP> R <SEP> i <SEP> 8iD
<tb><SEP> i1 <SEP> w <SEP> BbU5
<tb><SEP> A = <SEP> gUh <SEP> /
<tb> gst <SEP> {8 <SEP> /
<tb> Hardness Persoz in seconds 290 290 310 306 undetected
Resistance to solvents (see Ex. I) 10 sec. 30 sec. 5 min. 1 min. 8 sec.

40 sec.

(1) Electrodeposition primer applied to an iron phosphated pre-treated steel substrate from a 20% solids plating bath at 280 volts for 120 seconds, bath temperature 25 C. Cured coating for 19 minutes at 200 C; thickness 15 micrometers.

(2) As note (1), but coating dries for 5 minutes at 130 C.

(3) Intermediate layer applied by spraying, thickness 35 micrometers.

Example V
This example relates to the determination of the influence of the amount of blocked isocyanate groups on the solvent resistance of the cured coating applied by a wet / wet technique according to the present invention.

The results of the tests are summarized in Table V below:
Table V

<tb> Coating
<tb> Primary <SEP> Layer <SEP> (1) <SEP> Ex. <SEP> A <SEP> Ex. <SEP> B <SEP> Ex. <SEP> A <SEP> Ex. <SEP> B
<tb> Layer <SEP> Intermediate <SEP> (2) <SEP> Ex. <SEP> H <SEP> Ex. <SEP> H <SEP> Ex. <SEP> N <SEP> Ex. <SEP> N
<tb><<SEP>%<SEP> of <SEP> groups
<tb> Resistance <SEP> 00 <SEP> latent <SEP> 3.70 <SEP> 2.48 <SEP> 3.70 <SEP> 2.48
<tb> to <SEP> solvents
<tb> (eg <SEP> I) <SEP> 5 <SEP> min. <SEP> 3 <SEP> min. <SEP> 1 <SEP> min. <SEP> 25 <SEP> sec.
<Tb>

<SEP> 30 <SEP> sec. <SEP> 45 <SEP> sec. <SEP> 15 <SEP> sec.
<Tb>

(1) Primary applied cationic electrodeposition layer
on a steel substrate pre-treated with iron phosphating
from an electroplating bath at 20% solids
under 280 volts for 120 seconds, bath temperature
250 C. Coating cured for 5 minutes at 1300C, thick
15 micrometers.

(2) Intermediate layer applied by spraying, hard
cie for 19 minutes at 2000 C, thickness 35 micrometers.

Example VI
In this example, two different primary layers containing blocked isocyanate groups, applied with intermediate layers by a wet / wet technique, are compared. The results of the tests are summarized in Table VI below:
Table VI

<tb> Coating
<tb> Layer <SEP> primary <SEP> Ex. <SEP> A (1) <SEP> Ex. <SEP> C (2)
<tb> Layer <SEP> Intermediate <SEP> (3) <SEP> Ex. <SEP> H <SEP> Ex. <SEP> H
<tb><SEP>%<SEP> of <SEP> groups <SEP> NCO <SEP> 5
<tb><SEP> 3.70 <SEP> 5
<tb><SEP> Test
<Tb>
Xylene resistance 6 min. 4 min.

Solvent resistance 1 min. 45 sec.

 (see Ex. I) 30 sec.

(1) cationic electrodeposition primer app
on a phospha pre-treated steel substrate
iron temperature from a 20% electrodeposition bath
in solids, at 280 volts for -120 seconds, tempe
250 C bath temperature. The coating was dried during
3 minutes at 1200C, thickness 15 micrometers.

(2) cationic cationic electrodeposition primary layer
on a phospha pre-treated steel substrate
iron temperature from a 20% electrodeposition bath
in solids, under 280 volts for 120 seconds, tempe
bath 250C. The coating, was dried during
3 minutes at 1200C, thickness 15 micrometers.

(3) Intermediate layer applied by spraying, hardened
for 17 minutes at 2000C, 35 micrometers thick.

(4) Solvent resistance was determined by scraping
and
firstly the coated plates / then having them
a drop of solvent and measuring the duration for that
the coating softens.

Example VII
This example relates to a comparison of the xylene resistances of intermediate layers containing epoxy resin groups of various molecular weights.

The intermediate layers are applied to a primer containing isocyanate groups blocked by a wet / wet technique according to the present invention.

The results are summarized in Table VII below:

<tb><SEP> Table <SEP> VII
<tb> Reveal <SEP> Method
<tb><SEP> S
<tb><SEP>XD>
<tb><SEP> CV
<tb><SEP> 1 <SEP> 8
<tb><SEP> P <SEP> (D
<tb><SEP> B
<tb><SEP> id <SEP> 3
<tb><SEP> co <SEP> tn
<tb><SEP> Xo <SEP> \
<tb><SEP> BW
<tb><SEP> H- <SEP> H
<tb><SEP> this <SEP> this
<tb><SEP> oO <SEP> 8
<tb><SEP> \ <SEP> cr
<tb><SEP> 3 <SEP>: 3 <SEP> p)
<tb><SEP> tH, <SEP> c
<tb><SEP>><SEP> H
<tb><SEP> to <SEP>
<tb><SEP> O <SEP> O
<tb><SEP> F8
<tb><SEP> H <SEP> H
<tb><SEP> D} <SEP> cn
<tb><SEP> 00
<tb><SEP> BW
<tb><SEP> S <SEP> H
<tb><SEP> lo <SEP> o
<tb> Primary layer Ex. A (1) Ex. A (2) Ex. A (1) Ex. A (2) Ex. A (1) Ex. A (2) Ex. A (1) Ex. A (2) Ex. A (1) Ex. A (2)
Molecular weight of the epoxy resin (3) in the intermediate layer 530 (4) 530 (4) 377 (5) 377 (5) 1000 (6) 1000 (6) 4500 (7) 4500 (7) 1250 (8) 1250 (8)
Resistance to xylene 30 sec. 1 min. 30 sec. 10 sec. > 6 min. 1 min. > 6 min. > 6 min. > 6 min. 2 min.

50 sec. 10 sec.

(1) Cationic electrodeposition primer applied to a phosphatized pretreated steel substrate from a 20% solids plating bath at 280 volts for 120 seconds, bath temperature 25 C. The coating was dried for 5 minutes at 130 ° C., 15 meters thick.

(2) As the note (1), but the coating was duroi for 30 minutes at 180 C.

(3) All epoxy resins are polyglycidyl ethers of bisphenol A dissolved in a mixture of organic solvents (25 parts of SOLVESSO 100, 2-butoxyethanol and 2-ethoxyethyl acetate) at Ford n 4 cup viscosity of 25 to 30 seconds and applied to form a film or film of 35 microns.

(4) Available commercially under the name EPIKOTE 834.

(5) Available commercially as EPIKOTE 828.

(6) Available commercially as EPIKOTE 1001.

(7) Available commercially as EPIKOTE 1007.

(8) Available commercially under the name ARALDITE 7072.

Example VIII
In this example, various intermediate layers having different functional groups are compared.

The intermediate layers are applied to primary layers containing isocyanate groups blocked by the wet / wet technique. One of the intermediate layers contained only hydroxyl groups derived from a styrene-allyl alcohol polymer. A second intermediate layer contained only primary amine groups, derived from an epoxy resin defunctionalized with ammonia. The third intermediate layer contained only epoxy groups derived from a polyglycidyl ether of bisphenol A. The results of the tests are summarized in Table VIII below: TABLE VIII

<tb><SEP> m
<tb><SEP> Q
<tb><SEP> 8
<tb><SEP> S
<tb><SEP> 9
<tb><SEP> rt
<tb><SEP> lE
<tb><SEP> Aw
<tb><SEP> wo
<tb><SEP> y
<tb> w <SEP>
<tb> oK
<tb> 3 <SEP> o
<tb> D
<tb> U1 <SEP>
<tb> Fh <SEP>
<tb> 3
<tb> o
<tb> n <SEP> (D
<tb> w <SEP> 5
<tb> gold
<tb> B <SEP> o
<tb> kn <SEP> N
<tb> 3 <SEP> o
<tb> Y- <SEP> n
<tb> p
<tb><SEP> o
<tb> N
<tb> D
<tb> wO <SEP> o3
<tb><SEP> o
<tb> 3 <SEP> .n
<tb> 3
<tb> U1 <SEP> i
<tb> a <SEP> o
<tb> Hn
<tb> 3
<tb><SEP> o
<tb><SEP> ts
<tb> Primary layer (2) Ex. A Ex. A Ex. A Ex. A Ex. A Ex. A Ex. A Ex. A Ex. A
Intermediate layer (3) Ex. 0 Ex. 0 Ex. 0 Ex. P Ex. P Ex.P Ex. Q Ex.Q Ex.Q
Resistance to acetone (4) 6 6 6 13 10 10 100 100 100 (1) Temperature and duration of curing or drying of the primer.

(2) Cationic electrodeposition primer applied to a zinc phosphated pretreated steel substrate from an electroless plating bath at 20% solids at 200 volts, for 3 minutes, bath temperature 26 C, coating thickness 15 micrometers.

(3) Intermediate layer applied by run-off to the primer and cured at 177 ° C. for 30 minutes, thickness 37.5 microns.

(4) Number of double rubs / under the normal pressure of the hand, with a cloth saturated with acetone required to soften the coating.

Example IX
This example relates to the comparison of various primary layers with and without blocked isocyanate functionality and intermediate layers with and without epoxy functionality. One of the primary layers containing blocked isocyanate functionality was sprayed onto a substrate, a second primary layer also containing a blocked isocyanate functionality was deposited by cationic electrodeposition on the substrate and the third primary layer, without blocked isocyanate functionality, was applied to the substrate by cationic electrodeposition. Three intermediate layer compositions were used. An intermediate layer contained an epoxy functionality derived from a polyglycidyl ether and bisphenol A and had an epoxy equivalent weight of about 475. The second interlayer had a phenol-functionalized epoxy resin and the third intermediate layer was a polymer. acrylic prepared with glycidyl methacrylate. The results of the tests are summarized in Table IX below.

<SEP> Table <SEP> IX
<tb> Coating <SEP> and <SEP> Application <SEP> Drying <SEP> to <SEP> Air <SEP> 1210C <SEP> 1820C
<tb><SEP> thickness <SEP> 5 <SEP> minutes <SEP> 20 <SEP> o <SEP> X
<tb><SEP> Fa <SEP> prima <SEP> ire <SEP> H <SEP> (10.16 <SEP> pn) <SEP> Ex. <SEP> u <SEP> Ex. <SEP> P <SEP> Ex. <SEP> b <SEP> Ex. <SEP> s <SEP> Ex. <SEP> o <SEP> Ex. <SEP> 8 <SEP> | <SEP> w <SEP> Ex. <SEP> E
<tb> t <SEP> intermediate <SEP> (2)
<tb><SEP>!<SEP> Nr <SEP>><SEP> N <SEP> FX <SEP> to <SEP> a <SEP> /
<tb><SEP> W <SEP> O <SEP> O <SEP> S <SEP> Ex. <SEP> R <SEP> Ex. <SEP> S <SEP> Ex. <SEP> o <SEP> Ex <SEP> R <SEP> - <SE> O <SEP> N <SEP> X <SEP> P <SEP> 4 <SEP> y <SEP> /
<tb> Resistance <SEP> to <SEP> Acetone <SEP>> 100 <SEP>! <SEP>> 100 <SEP>> 100 <SEP> oR, <SEP> 65 <SEP><10<SEP><10<SEP><10
<tb> $ .y <SEP> primary <SEP> (17.78 <SEP> ym) <SEP> X <SEP> w <SEP> ss <SEP><<SEP> 8 <SEP> 5 <SEP> ~
<tb> 8 <SEP> intermediate <SEP> (2)
<tb><SEP>Do;<SEP>n;<SEP> Ex. <SEP> R <SEP> Ex. <SEP> S <SEP> Ex. <SEP> T (4) <SEP> Ex. <SEP> R <SEP> Ex. <SEP> S <SEP > Ex. <SEP> T <SEP> Ex. <SEP> R <SEP> Ex. <SEP> S <SEP> Ex. <SEP> T
<tb><SEP> V <SEP><D
<tb> I <SEP> primary <SEP> H
<tb><SEP> n <SEP> Ex. <SEP> F <SEP> Ex. <SEP> F <SEP> Ex. <SEP> F <SEP> Ex. <SEP> F <SEP> Ex. <SEP > F <SEP> Ex. <SEP> F <SEP> Ex. <SEP> F <SEP> Ex. <SEP> F <SEP> Ex.F
<tb><SEP> Layer <SEP> = d <SEP> 0 <SEP> 8 <SEP> = d <SEP> rrJ <SEP> O <SEP>&num;<SEP> xW <SEP> x
<tb><SEP><SEP>> in) <SEP> Ex. <SEP> R <SEP> Ex. <SEP> 5 (7) <SEP> Ex. <SEP> T <SEP> Ex. <SEP> R <SEP> Ex. <SEP> 5 (8) <SEP> Ex.T <SEP> Ex. <SEP> R <SEP> Ex. <SEP> S (9) <SEP> Ex. <SEP> T
<tb><SEP> v
<tb> Resistance <SEP> to <SEP> acetone <SEP>> 100 (5) <SEP><10<SEP><10<SEP>> 100 <SEP><10<SEP> 10-15 <SEP ><10<SEP><10<SEP><10
<tb><SEP> Rm <SEP> m <SEP> m <SEP>"<SEP> X <SEP> vX <SEP> XnXX <SEP> $ '
<tb><SEP> X <sep> ox <SEP> r \ <SEP> x <SEP> 8
<tb> -, <SEP> primary <SEP> X, <SEP> rn <SEP> P <SEP> i3 <SEP> vi <SEP> o <SEP> vi <SEP> m <SEP> (3)
<tb><SEP> Ln
<tb>(15,24-17,78; zn) <SEP> Ex. <SEP> A <SEP> Ex. <SEP> A <SEP> Ex. <SEP> A <SEP> Ex. <SEP> A <SEP> Ex. <SEP> A <SEP> Ex. <SEP> A <SEP> Ex. <SEP> A <SEP> Ex. <SEP> A <SEP> Ex. <SEP> A
<tb><SEP> AX <SEP> wF <SEP> m <SEP> aX <SEP> M <SEP> vX <SEP> x <SEP> vx <SEP> Xw <SEP> p3 <SEP> d
<tb> O <SEP> Ex. <SEP> R <SEP> Ex. <SEP> s <SEP> Ex. <SEP> T <SEP> Ex. <SEP> m <SEP> Ex. <SEP> e <SEP> m <SEP> 8 <SEP> d <SEP> m <SEP> r <SEP>>
<tb><SEP> I
<tb><SEP> t <SEP> ico
<tb><SEP> IP,
<tb> t <SEP> Intermediate <SEP> W <SEP> Ex. <SEP> R <SEP> Ex. <SEP> S <SEP> Ex. <SEP> T <SEP> Ex. <SEP> R <SEP > Ex. <SEP> V <SEP> Ex. <SEP> T <SEP> Ex. <SEP> R <SEP> Ex. <SEP> S <SEP> Ex. <SEP> T
<tb> Acetone Resistance <SEP><10<SEP><10<SEP><10<SEP> X <SEP> X <SEP> VX <SEP> X <SEP> X
<tb><SEP><SEP>><SEP> 8 <SEP>><SEP>:><SEP> 8 <SEP> 0 <SEP><SEP><SEP> 8 <SEP>><SEP> w
<tb><SEP> h <SEP> x <SEP> u <SEP> x <SEP> x <SEP> A <SEP> xW. <SEP> x <SEP> O <SEP> x <SEP> m <SEP > x <SEP> x <SEP> U <SEP> O
<tb><SEP> O <SEP>&verbar;<SEP> Q <SEP> it <SEP> ç <SEP> n
<tb><SEP><SEP><SEP><SEP> D <SEP> O <SEP> tn <SEP> d
<tb><SEP> U1 <SEP> Co <SEP>! <SEP> (D
<tb><SEP> w <SEP> e3 <SEP> w <SEP> m <SEP> M <SEP> v <SEP> U
<tb><SEP> A <SEP> x <SEP> x <SEP> x <SEP> x <SEP> x <SEP> x <SEP> x <SEP> x <SEP> x
<tb><SEP> 0s <SEP> O <SEP> O <SEP> cn <SEP>
<tb><SEP> O <SEP> O <SEP> I <SEP> e <SEP> O <SEP> U1
<tb><SEP> / s <SEP> x <SEP> 8 / <SEP> x <SEP> x <SEP> x <SEP> x <SEP> ~ <SEP> / \ <SEP> xW <SEP> x <SEP> A <SEP> x <SEP> x
<tb><SEP> gO <SEP> cD
<tb><SEP> H- <SEP> O
<tb><SEP> A <SEP> xw <SEP> xm <SEP> xW <SEP> xw <SEP> Xw <SEP> A <SEP> x <SEP> xw <SEP> A <SEP> x <SEP> xW <SEP> g
<tb><SEP> O <SEP> O <SEP> O <SEP> O <SEP> L0
<tb><SEP> I <SEP>><SEP> o <SEP> m <SEP> w <SEP> ca <SEP> W
<tb><SEP> O <SEP> s
<tb><SEP> W <SEP> W <SEP> W <SEP>, v <SEP> W <SEP> M <SEP>, \ <SEP> W <SEP> tXI
<tb><SEP> N <SEP> W <SEP> and <SEP> X <SEP> A <SEP> X <SEP> X <SEP> X <SEP> X <SEP> X <SEP> X
<tb><SEP> X <SEP> X <SEP>
<tb><SEP><SEP> D <SEP><SEP> F3 <SEP> n3 <SEP> 0 <SEP> F3 <SEP> D3 <SEP> 0 <SEP> F3 <SEP> W
<tb><SEP> 6 <SEP> 0 <SEP> F3
<Tb>

(1) Sprayed on pre-steel plate
treated by zinc phosphating.

(2) All intermediate layers were applied by
spray and cured at 1820C for 30 minutes.

(3) Applied by cationic electrodeposition on a subs
Pretreated by zinc phosphating under 2Q0 volts
for 3 minutes, bath temperature 260C.

(4) Thickness of 35.56 μm.

(5) Unexpected degree of hardening, thought to be due to
a "hitting" of the intermediate layer on the layer
primary and its mixture with it.

(6) Intermediate layer applied by direct spray
on a phospha pre-treated steel substrate
zinc.

(7) Thickness of 38.10 pm.

(8) Thickness of 31.75 ym.

(9) Thickness of 22.86 μm.

(10) Thickness 49.53 μm.

(11) Thickness of 24.13 m.

Claims (27)

 Process for coating a substrate, characterized in that it comprises:  (A) the substrate application of at least two coating compositions, at least one of which contains blocked polyisocyanate functionality and at least one of which contains a 1,2-epoxy functionality, said coating compositions being applied sequentially to the substrate, without first drying the initially applied layer and being superimposed substantially continuously on one another, so as to form a multilayer coating;  (B) heating the coated substrate to a temperature sufficient to cure the multilayer coating.  2. Process for coating a substrate, characterized in that it comprises:  (A) applying to a substrate a first coating composition containing blocked isocyanate functionality to form a first coating on said substrate,  (B) applying to said first coating, prior to curing, a second coating composition containing a 1,2-epoxy functionality to form a multilayer coating,  (C) heating the coated substrate to a temperature sufficient to cure the multilayer coating.  3. Method according to claim 1, characterized in that the substrate is metal.  4. Method according to claim 2, characterized in that the substrate is metal.  5. Method according to one of claims 3 or 4, characterized in that the metal is steel.  6. Method according to claim 2, characterized in that the first coating composition is a water-based composition.  7. Process according to claim 6, characterized in that the first coating composition contains cationic salt groups.  The method of claim 7, characterized in that the first coating composition is an acid-solubilized polyepoxide-amine adduct.  9. Method according to one of claims 1 or 2, characterized in that the blocked isocyanate is derived from an aromatic polyisocyanate.  10. Process according to claim 9, characterized in that the aromatic polyisocyanate is the tolylene diisocyanate.  11. Method according to one of claims 1 or 2, characterized in that the blocking agent is an alcohol containing from 2 to 10 carbon atoms.  12. Process according to claim 11, characterized in that the alcohol is selected from 1-ethylhexano and 2-butoxyethanol.  13. Method according to one of claims 1 or 2, characterized in that the isocyanate is present in the film-forming composition in the form of a completely blocked organic polyisocyanate.  14. Method according to one of claims 1 or 2, characterized in that implements 2 to 10% of isocyanate functionality based on the weight of the resin solids of the coating composition.  15. The method of claim 1, characterized in that the coating composition containing a 1,2-epoxy functionality contains a polyepoxide.  16. The method of claim 2, characterized in that the coating composition containing a 1,2-epoxy functionality contains a polyepoxide.  17. Method according to one of claims 15 or 16, characterized in that the polyepoxide has a molecular weight of at least about 800.  18. Method according to one of claims 15 or 16, characterized in that the polyepoxide is a polyglycidyl ether of a cyclic polyol.  19. Method according to one of claims 1 or 2, characterized in that the coating composition containing a 1,2-epoxy functionality comprises a mixture of a polyepoxide and a polymer selected from alkyd resins, saturated polyesters and acrylic polymers.  20. The method of claim 2, characterized in that the second coating composition is based on organic solvents.  21. The method of claim 2, characterized in that the first coating composition is applied by electrodeposition.  22. The method of claim 21, characterized in that the electrodeposition is a cationic electrodeposition.  23. The method of claim 2, characterized in that the second coating composition is applied by spraying.  24. Method according to one of claims 1 or 2, characterized in that it comprises a drying step between the applications of the coatings.  25. The method of claim 1, characterized in that it comprises the step of applying a coating composition after (B) and curing this coating composition.  26. The method of claim 2, characterized in that it comprises the step of applying a third coating composition after (B), said third coating composition containing heat reactive curing groups.  27. The coated article, characterized in that it is prepared by the process according to any one of claims 1 to 4, 6 to 8, 10, 12, 15, 16, 20 to 23, 25 and 26.