DE4143664B4 - Prodn. of multilayer film on lacquer - by forming non-hardened film on substrate, coating with aq. lacquer, and hardening - Google Patents

Abstract

Mfr. of a multilayer film (I) on a lacquer is carried out by: (i) formation of a non-hardened film on a substrate with a cationically separable lacquer; (ii) coating with an aq. lacquer of the non-hardened film from an electrically sepd. film in a wet-on-wet system of paint application; (iii) hardening of both films by heat, in which the electrically sepd. film now in wt. 10 pref. 7 wt% or less after curing by heat, and the aq. lacquer consists of (a) a polyester resin opt. modified with urethane and having an acid number within 10-100 and a hydroxyl number within 20-300 and (b) a water-soluble or dispersable amino resin. Also claimed is the coated prod.. Pref. the cationically electrically sepd. lacquer is; (A) a resin with (pref. prim) hydroxy gps. and cationic gps. and has a hydroxy equivalent with 20-5000 pref. 200-1000 and an amino number of 3-200 (KOH mg/g solid); (B) an epoxy resin with at least 2 functional epoxy gps. which have on ave. one epoxy gp. per mole bonded directly onto an alicyclic ring and/or a bridged alicyclic ring; and (c) or contains a blocked polyisocyanate cpd. as the main component.

Description

The The invention relates to a method for forming a multi-layered Films of paints or paints according to a so-called Two-coating one-baking process on a substrate containing the The following steps comprise: forming an uncured film from a cationic electrically depositable paint on the substrate, thereafter Coating the unhardened Films with an aqueous Paint in a wet-on-wet process and then cure below Heating of both films.

In In the past, it has been common practice, a cationic one Electrodepositable paint by electrodeposition and hardening to use under heating for coating and then one Paint for an intermediate coating or a paint for a cover slip Apply and then warm to harden.

by virtue of a reduction in the number of stages in the application of the Paints, economic exploitation of resources and prevention of pollution there is a need for development a method for producing a film of paints according to one Two-coating one-baking process, one with a cationic one Electrodepositable coating coated surface in addition to an aqueous paint for one intermediate coating or a top coat is coated without the previously coated surface is cured with electrodepositable paint under heating, and in which both Films of paint are cured simultaneously while heating. However, no such method has yet been practically used.

If for example, after coating with a paint of the organic solvent type a coated surface from a non-hardened, cationic electrical or Electrodepleted (the expressions electrically or electro-deposited are used synonymously) paint is heated, so that both Cured films of paint can be the unhardened coated swells or corrodes surface from the cationically electrodeposited paint through the organic solvent, contained in the paint of the organic solvent type is what causes that in the coated surface after hardening under heating impressions and protrusions, Wrinkles or shrinkage occur.

If alternatively an aqueous paint, the main one made of a polyester resin and a fully etherified melamine resin exists, instead of the previously mentioned Paint of the organic solvent type used will, the bugs, such as impressions and protrusions, wrinkles occur or shrinking, almost not on, but there is the difficulty that the Basic substances or substances of low molecular weight, when heating of the uncured cationically electrodeposited film evaporate in large quantities migrate into the top applied film and the curing reaction prevent with the result that the upper film not sufficiently hardened becomes. Furthermore, there is also the disadvantage that the film from aqueous paint even no sufficient smoothness or expressiveness of the image gloss.

Out JP 52-065534 A is already a method for coating a Substrate known by a two-coat-one-baking process. In this method, an electroconductive metal substrate is used a cationic electrodeposition coating as an undercoating, with a coating coating coated.

Of the present invention is based on the object, the above-mentioned disadvantages in the manufacture of a multi-layered film of paints by deposition of a cationically electrodepositable paint and an aqueous paint to prevent a two-coat-one-baking process.

• (i) für den kationisch elektrisch abzuscheidenden Film ein Anstrichstoff verwendet wird, der (A) ein Harz mit Hydroxylgruppen und kationischen Gruppen und (D) eine blockierte Polyisocyanatverbindung umfasst, und mit dem nach dem Härten unter Erhitzen ein Film erzeugt wird, der gegenüber dem ungehärteten Film eine Filmgewichtsverringerung von 10 Gew.-% oder weniger aufweist und wobei
• (ii) für den wässrigen Anstrichstoff ein Lack verwendet wird, der hauptsächlich a) ein Polyesterharz oder ein mit einem Urethan modifiziertes Polyesterharz mit einer Säurezahl innerhalb des Bereiches von 10 bis 100 und einer Hydroxylzahl innerhalb des Bereichs von 20 bis 300 und b) ein wasserlösliches oder -dispergierbares Aminoharz und c) ein Alkyl-verethertes Benzoin enthält.

The above object is achieved, according to the invention, by a method for producing a multilayer film on a substrate, characterized in that the following steps are carried out: forming an uncured film of a cationically electrodepositable paint on the substrate, then coating the uncured film with an aqueous paint in a wet-on-wet process and then curing and heating both films, wherein

• (I) for the cationically electrically deposited film, a paint is used, which (A) comprises a resin having hydroxyl groups and cationic groups and (D) a blocked polyisocyanate compound, and with which after curing with heating a film is produced, which is opposite uncured film has a film weight reduction of 10 wt .-% or less, and wherein
• (ii) using, for the aqueous paint, a paint comprising mainly a) a polyester resin or a urethane-modified polyester resin having an acid number within the range of 10 to 100 and a hydroxyl number within the range of 20 to 300 and b) a water-soluble one or -dispersible amino resin and c) an alkyl-etherified benzoin.

There the inventive method a process for producing a multi-layered film of paints, based on the so-called two-coating-one-baking process, is where an aqueous paint on a film of unhardened A film of a cationically electrodepositable paint according to a so-called wet-on-wet process is applied and then both films of paint hardened at the same time is, is the cure level under heating, which otherwise after the application of the electrodepositable Coating, but required before applying the aqueous paint is no longer necessary. This is not just to that effect Advantage that the Reduced manufacturing cost of the multilayer paint film can be but also to the effect that the inventive method safe and hygienic is because it does not require organic Solvent too use; so there is no pollution and resources can be saved.

Of the according to the inventive method formed multilayer film of paints has smoothness, gloss and a pronounced Image gloss, film adhesion, resistance across from Moisture, anti-chipping properties and hardenability, Properties that are better than those of the movies after the before mentioned known methods are obtained. Continue to enter the technical Effects on effects that no Bagging (or no impressions), Wrinkles, shrinkage or depression and protrusions formed become.

The inventive method will be closer in the following he purifies.

cationic electrically depositable paint

Of the cationically electrodepositable paint or paint (these expressions are used synonymously) used in the present invention is one that gives a film of paint, with a film weight reduction after curing with heating of 10 Wt% or less. When a cationically electrodepositable A paint which undergoes film weight reduction after curing Heating over 10% by weight, when used, generally deteriorates the smoothness and accuracy of image gloss of a film of an aqueous paint, the on the film of cationically electrically depositable paint is applied.

berechnet.The "film weight reduction" (X), due to the curing under heating, of the cationically electrodepositable paint is a value obtained by performing the cationic electrodeposition on a substrate under ordinary conditions in an electrodeposition bath, pulling the substrate out of the bath , washes the coated surface of the substrate, heats the substrate at 105 ° C for 3 hours to substantially remove all moisture in the substrate, measures the weight (Y) of the film of paint, heats the film of paint at 170 ° C for 20 minutes for three-dimensionally crosslinking the paint film, measuring the weight (Z) of the film of paint, and from the measured values Y and Z according to the following equation:

calculated.

The cationically electrodepositable paint used in the method of the present invention is not particularly limited as long as it has a film weight reduction after curing with heating of 10 wt% or less, preferably 7 wt% or less, more at least 5% by weight or less, and (A) a resin having hydroxyl groups and cationic groups, and (D) a blocked polyisocyanate compound.

One electrically deposited film of paint, with this cationically electrodepositable paint is formed, is cured at a temperature below about 250 ° C. Especially when connections, which metals, such as lead, zirconium, cobalt, aluminum, manganese, Contain copper, zinc, iron, chromium and nickel, alone or in Mixture be admixed as a catalyst, the film of electrically deposited Paint under heating at a temperature as low as from about 70 to 160 ° C hardened become.

Accordingly The cationically electrodepositable paint has different excellent benefits, like that at low temperature of not more than 160 ° C in the absence of a tin catalyst hardened can be. Furthermore contains it is not a masked isocyanate compound or a derivative thereof, and This will be the aforementioned avoided various disadvantages in its use. He is volumetric shrinkage due to thermal decomposition, free and shows a good adhesion. It is free of aromatic urethane bonds or aromatic Urea bonds, and thereby its weather resistance not deteriorated. He has excellent corrosion resistance, curability and bath stability.

• (i) Ein Reaktionsprodukt, das durch Umsetzung eines Polyepoxyharzes mit einem Kationisierungsmittel gebildet wird;
• (ii) ein Polykondensationsprodukt aus einer Polycarbonsäure und einem Polyamin (vgl. US-Patentschrift 2 450 940 A), protoniert mit einer Säure;
• (iii) ein Polyadditionsprodukt aus einem Polyisocyanat und einem Polyol und einem Mono- oder Polyamin, protoniert mit einer Säure;
• (iv) ein Copolymeres aus einem Acryl- oder Vinyl-Monomeren, welches eine Hydroxylgruppe enthält, und eines, welches eine Aminogruppe enthält, protoniert mit einer Säure (vgl. japanische Patentveröffentlichungen Nrn. 12395/1970 und 12396/1970);
• (v) ein Addukt aus einem Polycarbonsäure-Harz und einem Alkylenimin, protoniert mit einer Säure (vgl. US-Patentschrift 3 403 088); etc.

The resin (A) containing hydroxyl groups and cationic groups and used in the cationically electrodepositable paint (hereinafter referred to as "base resin (A)") is a resin containing hydroxyl groups and contains a sufficient number cationic groups to form a stable aqueous dispersion. As the base resin (A), for example, the following can be mentioned:

• (i) a reaction product formed by reacting a polyepoxy resin with a cationizing agent;
• (ii) a polycondensation product of a polycarboxylic acid and a polyamine (see US Patent 2,450,940 A) protonated with an acid;
• (iii) a polyaddition product of a polyisocyanate and a polyol and a mono- or polyamine protonated with an acid;
• (iv) a copolymer of an acrylic or vinyl monomer containing a hydroxyl group and one containing an amino group protonated with an acid (see Japanese Patent Publication Nos. 12395/1970 and 12396/1970);
• (v) an adduct of a polycarboxylic acid resin and an alkyleneimine protonated with an acid (see U.S. Patent 3,403,088); Etc.

As the specific examples of these cationic resins and the methods for their preparation, for example, in Japanese Patent Publication Nos. 12395/1970 and 12396/1970 and the GB 1 327 071 A as well as the US 2 450 940 A . 3 403 088 A and 3 963 663 A will be described, a detailed description of the specific examples of these cationic resins and the process for their preparation is replaced by the specification of these references in the present application.

When Base resin (A) is particularly preferred in the present invention a reaction product obtained by reacting a polyepoxide compound with excellent anti-corrosion property is obtained and obtained from a polyphenol compound and epichlorohydrin with a Cationizer. This compound is derived from the group (i) covered above.

in einem Molekül und mit einem zahlendurchschnittlichen Molekulargewicht im Bereich von im allgemeinen mindestens 200, bevorzugt 400 bis 4000, mehr bevorzugt 800 bis 2000, geeignet. Als solche Polyepoxidverbindung kann man die, die per se bekannt sind, verwenden, beispielsweise den Polyglycidylether einer Polyphenolverbindung, welche durch Umsetzung einer Polyphenolverbindung mit Epichlorhydrin in Anwesenheit eines Alkalis erhalten wird.The said polyepoxide compound is a compound having at least 2 epoxy groups

in a molecule and having a number average molecular weight ranging generally from at least 200, preferably from 400 to 4000, more preferably from 800 to 2000. As such a polyepoxide compound, those known per se may be used, for example, the polyglycidyl ether of a polyphenol compound obtained by reacting a polyphenol compound with epichlorohydrin in the presence of an alkali.

As a polyphenol compound which can be used in the above reaction, there may be mentioned, for example, bis (4-hydroxyphenyl) -2,2-propane, 4,4'-dihydroxybenzophenone, bis (4-hydroxyphenyl) -1,1- ethane, bis (4-hydroxyphenyl) -1,1-isobutane, bis (4-hydroxy-tert-butyl-phenyl) -2,2-propane, bis (2-hy droxynaphthyl) methane, 1,5-dihydroxynaphthalene, bis (2,4-dihydroxyphenyl) methane, tetra (4-hydroxyphenyl) -1,1,2,2-ethane, 4,4'-dihydroxydiphenyl ether, 4, 4'-Dihydroxydiphenylsulfone, phenol novolak and cresol novolak.

dargestellt wird.Among the aforementioned polyepoxide compounds particularly preferred for the preparation of the base resin (A), the polyglycidyl ether is a polyphenol compound having a number average molecular weight of at least about 380, more preferably 800 to 2000, and an epoxy equivalent of 190 to 2,000, preferably 400 to 1000, in particular one represented by the following formula:

is pictured.

The Polyepoxide compound may be partially mixed with a polyol, polyether polyol, Polyester polyol, polyamidoamine, a polycarboxylic acid and polyisocyanate reacted and, furthermore, it can be combined with ε-caprolactone or a Acrylic monomers may be graft polymerized.

on the other hand can as cationizing agent for the introduction a cationic group in the polyepoxide compound are called: an aliphatic, alicyclic or aromatic-aliphatic primary or secondary Amin, a tertiary Amine salt, a secondary Sulfide salt and a tertiary one Phosphine salt. These react with the epoxy group to form a cationic group. It is still possible to use the cationic group by implementing a tertiary Aminomonoisocyanats, which consists of a tertiary amino alcohol and a Diisocyanate has been obtained with a hydroxyl group of the epoxy resin introduce.

• (1) Primäre Amine, wie Methylamin, Ethylamin, n- oder Isopropylamin, Monoethanolamin und n- oder Isopropanolamin;
• (2) sekundäre Amine, wie Diethylamin, Diethanolamin, Di-n- oder Isopropanolamin, N-Methylethanolamin und N-Ethylethanolamin; und
• (3) Polyamine, wie Ethylendiamin, Diethylentriamin, Hydroxyethylaminoethylamin, Ethylaminoethylamin, Methylami nopropylamin, Dimethylaminoethylamin und Dimethylaminopropylamin.

As examples of the amine compound in the cationizing agent, there may be mentioned, for example, the following amines:

• (1) primary amines such as methylamine, ethylamine, n- or isopropylamine, monoethanolamine and n- or isopropanolamine;
• (2) secondary amines such as diethylamine, diethanolamine, di-n- or isopropanolamine, N-methylethanolamine and N-ethylethanolamine; and
• (3) polyamines such as ethylenediamine, diethylenetriamine, hydroxyethylaminoethylamine, ethylaminoethylamine, methylaminopropylamine, dimethylaminoethylamine and dimethylaminopropylamine.

From These amines are preferably alkanolamines having hydroxyl groups. Also may be a primary amino group the polyamine with ketone in advance for masking or blocking (this expressions are used synonymously) of the group, and then For example, the active hydrogen can be reacted with an epoxy group.

Except the Amine compounds can a basic compound such as ammonia, hydroxylamine, hydrazine, Hydroxyethylhydrazine and an N-hydroxyethyl imidazoline compound to similar ones Be used way. Basic groups using this Compounds can be formed can with an acid, especially preferably with a water-soluble organic carboxylic acid, such as Formic acid, acetic acid, glycolic acid and Lactic acid, be protonated to form cationic groups.

In addition, tertiary amines, such as triethylamine, triethanolamine, N, N-dimethylethanolamine, N-methyldiethanolamine, N, N-diethyl and N-ethyldiethanolamine, may be used in advance an acid be protonated, and they can then with an epoxy group to form quaternary salts be implemented.

Next the salts of tertiary Amines can Salts of sulfides such as diethyl sulfide, diphenyl sulfide, tetramethylene sulfide or thiodiethanol and boric acid, carbonic acid or an organic monocarboxylic acid, reacted with an epoxy group to form tertiary sulfonium salts become.

In addition, salts can of phosphines, such as triethylphosphine, phenyldimethylphosphine, diphenylmethylphosphine or triphenyl phosphine, and such acids as mentioned above, reacted with an epoxy group to form quaternary phosphonium salts become.

When Hydroxyl groups of the base resin (A) can be mentioned, for example: primary Hydroxyl groups of alkanolamines such as said cationizing agent, of ring opened Caprolactone and general polyols; and secondary hydroxyl groups of epoxy resin. Of these, primary hydroxyl groups are alkanolamines prefers.

When such alkanolamines are those associated with the cationizing agent listed as examples were preferred.

Of the Content of hydroxyl groups in the base resin (A) is preferably so to calculate that he as hydroxyl group equivalent in the range of 20 to 5000, in particular 100 to 1000, lies. Especially is the primary hydroxyl group preferably in the range of 200 to 1000. The content of cationic Groups are preferably in excess of the lower one Limit required to stably disperse the base resin (A), and generally it is preferably in the range of 3 to 200, in particular from 10 to 80, calculated as amine number KOH mg / g of Solids. However, if the cationic group content is below 3, it is possible to use it after an aqueous dispersion using a surfactant Was prepared by means of. In this case, however, it is preferable adjust the cationic group so that the pH of the aqueous dispersed Mass generally in the range of 4 to 9, more preferably of 6 to 7, lies.

The Base resin (A) contains Hydroxyl groups and canonical groups and is usually of free epoxy groups.

to Preparation of the cationically electrodepositable paint For example, the base resin (A) can be stably dispersed in water become. As required, the resulting aqueous dispersion a color pigment, such as carbon black or carbon black, titanium white, lead white, lead oxide and red iron oxide, an extender pigment, such as clay and talc, an anti-corrosion pigment, such as strontium chromate, lead chromate, basic lead chromate, red Lead, lead silicate, basic lead silicate, lead phosphate, basic Lead phosphate, lead polyphosphate, lead silicochromate, chrome yellow, Lead cyanamide, calcium plumbate, lead suboxide, lead sulfate and basic Lead sulfate, may be added, or other additives may be added become. As other additives, for example, a small Amount of a dispersant or a nonionic surfactant By means such as a means of blistering or peeling of the coated surface prevents and a cure activator mentioned become.

In order to in particular the electrically deposited paint at low Temperature of not more than 160 ° C sufficiently hardenable is, it is effective, one kind or at least two kinds of metal compounds as a catalyst selected from a lead compound, a zirconium compound, a cobalt compound, an aluminum compound, a manganese compound, a copper compound, a zinc compound, an iron compound, a chromium compound and a nickel compound.

specific Examples of these metal compounds include chelated compounds, such as zirconium acetylacetonate, cobalt acetylacetonate, aluminum acetylacetonate and manganese acetylacetonate; the reaction product of chelation from compounds with β-hydroxyamino structures with lead (II) oxide; and carboxylates such as lead 2-ethylhexanoate, lead cantanoate, naphthhex-lead, Lead octanoate, lead benzoate, lead acetate, lead lactate, lead formate, Lead gypsum and zirconium octanoate.

The mentioned metal compounds in an amount, calculated as metal content, by weight the total solids content, of base resin (A) and the polyisocyanate compound (D) of generally not more than 10% by weight, preferably not more than 5% by weight.

One cationically electrodepositable paint containing (A) a resin with hydroxyl groups and cationic groups and (D) a blocked one Containing polyisocyanate compound as main components.

When Resin (A) can the same resins as the base resin (A) are used, as is above for the electrodepositable paint (i) has been described.

on the other hand For example, the blocked polyisocyanate compound (D) can be added by addition reaction a polyisocyanate compound having a substantially stoichiometric Amount of an isocyanate blocking agent can be prepared, and it is as a hardener for the Formation of a crosslinked paint film mainly by Urethanization reaction with the base resin (A) as mentioned above.

The Polyisocyanate compounds include aromatic, aliphatic and alicyclic polyisocyanate compounds containing at least 2, normally and preferably 2 to 3, isocyanate groups (NCO) contained in one molecule. Examples of these are polyisocyanate compounds, such as tolylene diisocyanate, Xylylene diisocyanate, phenylene diisocyanate, bis (isocyanatomethyl) cyclohexane, Tetramethylene diisocyanate, hexamethylene diisocyanate, methylene diisocyanate and isophorone diisocyanate; and prepolymers with terminal Isocyanate obtained by reacting an excess amount of the polyisocyanate compound with a low molecular weight compound, the active ones Contains hydrogen, such as ethylene glycol, propylene glycol, trimethylolpropane, hexanetriol or castor oil, to be obtained.

Under these polyisocyanate compounds are isophorone diisocyanate, xylylene diisocyanate and similar compounds prefers.

on the other hand becomes the isocyanate blocking agent with one or more isocyanate groups react in the polyisocyanate by addition reaction and block the isocyanate group or groups. It is important, that the blocked polyisocyanate compound formed as a result of the addition reaction Room temperature is stable and when heated to a temperature above its Dissociation temperature releases a blocking agent and a or re-forms a plurality of free isocyanate groups.

Especially must the used cationically in the present invention coatable paint a film weight reduction, conditional by hardening under heating, of 10% by weight or less. It is preferable a blocking agent with a relatively low molecular weight of 130 or less to use. Specific examples thereof include phenol-type blocking agents such as phenol, cresol, xylenol, chlorophenol and ethylphenol; Lactam-type blocking agents such as ε-caprolactam, δ-valerolactam, γ-butyrolactam and β-propiolactam; Blocking agents of the active methylene type, such as ethylacetoacetate and acetylacetone; Blocking agents of the alcohol type, such as methanol, Ethanol, propanol, butanol, amyl alcohol, ethylene glycol monomethyl ether, Ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, Propylene glycol monomethyl ether, benzyl alcohol, methyl glycolate, butyl glycolate, Diacetone alcohol, methyl lactate and ethyl lactate; blocking agents of the oxime type, such as formamidoxime, acetaldoxime, acetoxime, methyl ethyl ketoxime, Diacetylmonoxime and cyclohexanoxime; Blocking agents of the mercaptan type, such as butylmercaptan, hexylmercaptan, t-butylmercaptan, thiophenol, Methylthiophenol and ethylthiophenol; Blocking agents of the amide type, such as acetamide and benzamide; Blocking agents of the imide type, such as Succinimide and maleimide; Blocking agents of the amine type, such as xylidine, Aniline, butylamine and dibutylamine; Blocking agents of the imidazole type, such as imidazole and 2-ethylimidazole; Blocking agents of the imine type, such as ethyleneimine and propyleneimine; and similar. Among these are because of their good balance between the stability of the paint and the hardenability of the paint film particularly preferably the blocking agents of the oxime type, for example methylethylethoxime.

When blocked polyisocyanate compounds, which are particularly suitable can be can for example mentioned are: with methyl ethyl ketoxime double blocked isophorone diisocyanate and with methyl ethyl ketoxime doubly blocked xylylene diisocyanate.

The Amount of the blocked polyisocyanate compound (D) used is, is not critical and may be appropriate to appropriate quietly the type of base resin (A) used, and within the Range of the minimum amount sufficient, the resulting Thermosetting film of paint, up to the maximum Amount that the bath stability not deteriorated, selected In general, however, it is preferably in such a range that the weight ratio of the Content of solids in blocked polyisocyanate compound (D) to the base resin (A) 0.05 to 1.5, especially 0.1 to 0.7, more preferably 0.2 to 0.5.

The base resin (A) and the above-described blocked polyisocyanate compound (D) can be converted into a cationically electrodepositable paint in the same manner as described in (i) above by mixing them, the mixture is stably dispersed in water, optionally Dis persion is kneaded with the same type and amount of dye pigment, anti-corrosion pigment or similar additives and / or metal catalysts.

The Thickness of a film of paint, by electrodeposition of the thus prepared cathodically electrodepositable paint is obtained on a suitable substrate is not strictly limited. however is a thickness ranging from 3 to 300 μm, based on the cured film of paint, is appropriate, and the film of paint can by heating at a temperature of, for example, 70 to 250 ° C, preferred 120 to 160 ° C, hardened become.

The method for producing the electrodeposited paint film on the substrate using the above-mentioned cathodic electrodepositable paint is not particularly limited but ordinary conditions for the cathodic electrodeposition may be used. For example, as mentioned above, the base resin (A) and the blocked polyisocyanate compound (D) are dispersed in water, the resulting aqueous dispersion is mixed as needed with pigments, a curing catalyst and other additives, the mixture is at a solids concentration of the bath within the range of 5 to 40% by weight, preferably 10 to 25% by weight, and the pH of the bath is adjusted within a range of 5 to 8, preferably 5.5 to 7. Thereafter, using this electrodeposition bath, electrodeposition is carried out under the following conditions with, for example, a carbon plate (5 cm × 15 cm × 1 cm) used as the anode and, for example, a zinc-phosphated steel (5 cm × 15 cm × 0.7 mm) used as the cathode. bath temperature: 20 to 35 ° C, preferably 25 to 30 ° C. DC current density: 0.005 to 2 A / cm ² , preferably 0.01 to 1 A / cm ² Tension: 10 to 500 V, preferably 100 to 300 V. Energy supply time: 0.5 to 5 minutes, preferably 2 to 3 minutes.

To the method according to the invention becomes the coated substrate after the cationic electrodeposition withdrawn from the electrodeposition bath, washed with water, and then the drops of water are deposited on the electrode Film surface, more preferably all the moisture that is in the electrodeposited Film is present, by drying with hot air or similar Way away. Subsequently becomes an aqueous paint or a paint applied to the film in a wet-on-wet manner, and the both films are simultaneously cured with heating.

Aqueous paint

• (a) ein Polyesterharz oder ein mit einem Urethan modifiziertes Polyesterharz mit einer Säurezahl innerhalb des Bereiches von 10 bis 100 und eine Hydroxylzahl innerhalb des Bereiches von 20 bis 300 und
• (b) ein wasserlösliches oder -dispergierbares Aminoharz und
• (c) ein Alkyl-verethertes Benzoin.

The aqueous paint used in the process according to the invention contains mainly:

• (a) a polyester resin or a urethane-modified polyester resin having an acid value within the range of 10 to 100 and a hydroxyl value within the range of 20 to 300 and
• (b) a water-soluble or -dispersible amino resin and
• (c) an alkyletherified benzoin.

in the The following is the aqueous paint described more concretely.

(a) polyester resin

The polyester resin (a) may be a polyester resin of the conventional type prepared by condensation reaction of an alcohol component with an acid component and containing an acid group and a hydroxyl group. Specific examples thereof include oil-free polyester resins obtained by condensing an alcohol component selected from polyhydric alcohols such as ethylene glycol, diethylene glycol, propylene glycol, butanediol, pentanediol, 2,2-dimethylpropanediol, glycerin, trimethylolpropane and pentaerythritol; monohydric alcohols or monoepoxy compounds having a glycidyl group in the molecule (for example, "Cadura E", trademark for a product of Shell Co.) optionally together with the aforementioned polyhydric alcohol and an acidic component selected from polybasic acids such as phthalic anhydride, isophthalic acid, tetrahydrophthalic anhydride , Hexahydrophthalic anhydride, maleic anhydride, succinic anhydride, adipic acid, sebacic acid, trimellitic anhydride and pyromellitic anhydride, and optionally monobasic acids used, such as benzoic acid and t-butylbenzoic acid; and oil-modified polyester resins obtained by reacting three components, ie, the aforementioned alcohol and acid components, and an oil component selected from castor oil, dehydrated castor oil, tung oil, safflower oil, soybean oil, linseed oil, tall oil, coconut oil and the like, and fatty acid mixtures containing at least one of their fatty acids can be obtained. In addition, polyester resins obtained by grafting an acrylic resin or vinyl resin on the aforementioned polyester resins.

The Use of urethanized polyester resins or urethane polyester resins as the polyester resin (a) gives an aqueous paint which further improved storage stability, Anti-effervescent properties or anti-blistering properties, Accuracy of image shine, smoothness and anti-chipping properties has. It is therefore preferred to use aqueous paints containing urethane-modified polyester resins.

such Urethane-modified polyester resins can be obtained by reacting the above mentioned Polyester resin with an acid group and the hydroxyl group, preferably the oil-free, from those previously mentioned Alcohol and acid components were obtained with a polyisocyanate compound, preferably one Diisocyanate compound with an excess of hydroxyl groups, to be obtained. As the polyisocyanate compound which is used for the modification of the polyester can be mentioned, for example aromatic diisocyanate compounds such as tolylene diisocyanate and 4,4'-diphenylmethane diisocyanate; aromatic-aliphatic Polyisocyanate compounds, such as xylylene diisocyanate and m- or p-tetramethylxylylene diisocyanate; aliphatic or alicyclic polyisocyanates, such as hexamethylene diisocyanate and isophorone diisocyanate, and their biurea compounds (biuretized Compounds) and their isocyanurates, trimethylhexamethylene diisocyanate, hydrogenated xylene diisocyanate and hydrogenated 4,4'-diphenylmethane diisocyanate. Under these are tolylene diisocyanate, xylylene diisocyanate and isophorone diisocyanate in terms of increase the storage stability the aqueous paints prepared therefrom prefers.

Although the amount of polyisocyanate compound used, within a big one Range, depending on the type of polyester resin to be modified and the grade its modification, it can be varied, it is in general Cheap, the polyisocyanate compound is within a range of 1 to 40 wt .-%, preferably 4 to 30 wt .-%, more preferably 4 to 20 Wt .-%, based on the weight of the polyester to use.

It is important that the Polyester resin (a) used in the aqueous paint of the present invention becomes, an acid number within the range of 10 to 100, preferably 10 to 80, and more preferably 10 to 60, and a hydroxyl number within the range from 20 to 300, preferably 30 to 200, and more preferably 30 to 160, owns. If the acid number of the polyester resin used is less than 10 difficult to disperse the polyester resin in aqueous media. On the other hand, if the acid number 100 exceeds, does this to that the formed film of paint reduced resistances opposite water and chemicals shows. When the hydroxyl value of the polyester resin smaller than 20, the formed film has insufficient curability whereas if she goes over 300, the formed film has a reduced resistance to water and chemicals.

The Polyester resin (a) has a weight-average molecular weight within the range of generally 1000 to 20,000 and preferred 3000 to 15,000.

The Polyester resin (a) having the aforementioned properties, may be in water by neutralization of at least 20%, preferably at least 40% of the acid groups present with a basic substance solved or dispersed. As a basic substance used in neutralization can be used for example mentioned ammonia, methylamine, ethylamine, dimethylamine, diethylamine, trimethylamine, Triethylamine, dimethylethanolamine, diethanolamine, triethanolamine and similar. Among these are mono-, di- or Trialkanolamines, such as diethanolamine, dimethylethanolamine and triethanolamine, prefers.

(b) Amino resin:

The Amino resin (b), which serves as a crosslinking agent for the crosslinking of the above mentioned Polyester resin component in aqueous paints may be, for example: di-, tri-, tetra-, penta- and Hexamethylolmelamines and their alkyl (preferably methyl) etherified Links; and urea-formaldehyde condensates; Urea-melamine-copolycondensation.

The amino resin (b) is preferably hydrophilic to the extent that it is water-soluble or can be stably dispersed in water without undergoing phase separation or sedimentation. Particularly preferred are melamine derivatives such as di-, tri-, tetra-, penta- and hexamethylolmelamines and their alkyl (be preferably methyl) etherified compounds.

• (i) Die Verwendung der vollständig veretherten Verbindung der methylolierten Melamine bewirkt eine Erhöhung in der Beständigkeit gegenüber der Blasenbildung, aber die Vernetzungs-Reaktionstemperatur ist so hoch und die Vernetzungsreaktion verläuft ungenügend, so daß, um den Anstrichstoff-Film bei einer Temperatur in der Größenordnung von 140 bis 150°C härten zu können, ein Säurekatalysator verwendet werden muß
• (ii) Mit Melaminen, die Methylolgruppen (-CH₂OH) und Ethergruppen (-CH₂OR) zusammen enthalten, ist die Anfangs-Härtungsgeschwindigkeit des Films aus Anstrichstoff hoch, und daher muß kein saurer Katalysator verwendet werden, während die Härtung auf der Oberfläche des Films aus Anstrichstoff beginnt, bevor das Wasser und die Lösungsmittel ausreichend aus dem aufgetragenen Anstrichstoff-Film verdampfen, wodurch eine Blasenbildung auftreten würde.
• (iii) Melamine, die Iminogruppen (> NH) und Alkylethergruppen (-CH₂OR) gemeinsam enthalten, vernetzen mit dem Polyesterharz bei 140 bis 150°C in Abwesenheit eines Säurekatalysators. Die Vernetzungsreaktion verläuft in relativ langsamer Geschwindigkeit, und die Selbsthärtung verläuft nicht so schnell wie bei den Methylolgruppen. Daher beginnt die Vernetzungsreaktion nicht, bevor die organischen Lösungsmittel, Wasser und ähnliche verdampft sind, und der Anstrichstoff-Film schmilzt und fließt, wodurch ein An strichstoff-Film mit ausgezeichneter Glätte und guter Härtbarkeit, ohne daß Blasenbildung stattfindet, gebildet wird.

The relationship between the aforementioned preferred melamine derivatives and the performance of the paint film formed with aqueous paints containing melamine derivatives will be described below.

• (i) The use of the fully etherified compound of the methylolated melamines causes an increase in blistering resistance, but the crosslinking reaction temperature is so high and the crosslinking reaction is insufficient, so that the paint film is at a temperature of the order of magnitude to cure from 140 to 150 ° C, an acid catalyst must be used
• (ii) With melamines containing methylol groups (-CH ₂ OH) and ether groups (-CH ₂ OR) together, the initial curing rate of the paint film is high, and therefore, no acid catalyst must be used while curing on the film Surface of the film of paint begins before the water and solvents evaporate sufficiently from the applied paint film causing blistering.
• (iii) melamines containing imino groups (> NH) and alkyl ether groups (-CH ₂ OR) co-crosslink with the polyester resin at 140 to 150 ° C in the absence of an acid catalyst. The crosslinking reaction proceeds at a relatively slow rate and self-curing is not as fast as with the methylol groups. Therefore, the crosslinking reaction does not start before the organic solvents, water and the like are vaporized, and the paint film melts and flows, thereby forming a primer film excellent in smoothness and good curability without occurrence of blistering.

Therefore are water-soluble or dispersible amino resins containing one or more imino groups contain, for example, melamine resins containing imino groups, as the amino resin contained in the aqueous paint is used, particularly well suited.

(c) Alkyletherified benzoin:

Of the aqueous paint, used in the invention will, contains an alkyletherified benzoin (c) in addition to the aforementioned two Main components, i. the polyester resin (a) and the amino resin (b), blending the alkyletherified benzoin is preferred since the occurrence of blistering or sagging of the aqueous paint It can be considerably reduced and the smoothness, accuracy of the image gloss and other properties of the resulting aqueous paint can be improved.

The Alkyletherified benzoin (c) is an alkyl (preferably with 1 to 4 carbon atoms) etherified derivative of benzoin. specific Examples thereof include benzoin methyl ether, benzoin ethyl ether, Benzoin n-propyl ether, benzoin isopropyl ether, benzoin n-butyl ether, Benzoin isobutyl ether and the like Links. You can used alone or in two or more in the mixture. Under these are particularly preferably benzoin ethyl ether and benzoin methyl ether.

The Procedure for the addition of the alkyletherified benzoin to the aqueous paint is not particularly limited and it can be added by various methods, for example (1) according to a Method in which the alkyletherified benzoin is added when the pigment is dispersed, (2) according to a method wherein the etherified benzoin to the aqueous solution of Polyester (a) is added at room temperature or at elevated temperature and stirring or (3) the alkyletherified benzoin may be added when the polyester resin (a) is produced. any one this method does not improve the blistering adversely affected and generally a suitable method is selected, wherein the pigment content in the paint and the melting point of the paint alkyl-etherified benzoin used. Among the previously mentioned Method, the method (2) is preferred.

The Alkyl-etherified benzoin prevents the appearance of bubbles (popping) of the aqueous paint and is effective to control the film thickness at which blistering occurs to improve.

The aqueous paint used in the process of the present invention can be prepared by dissolving or dispersing the aforementioned polyester resin (a), amino resin (b) and alkyl etherified benzoin (c) in an aqueous medium. The mixing ratios of the respective components are not critical and can be varied widely, depending on the physical properties the film of paint required for the aqueous paint formed. In general, the polyester resin (a) is in an amount in the range of 50 to 90% by weight, preferably 55 to 85% by weight, and more preferably 60 to 80% by weight, based on the total weight of polyester resin (a ) and the amino resin (b). The amino resin (b) is in an amount in the range of 50 to 10% by weight, preferably 45 to 15% by weight, and more preferably 40 to 20% by weight, based on the total weight of the polyester resin (a) and of the amino resin (b).

The Alkyl etherified benzoin (c) is present in an amount of 0.1 to 10% by weight, preferably 0.5 to 5 wt .-%, and more preferably 1 to 3 wt .-%, based on the total weight of the polyester resin (a) and the amino resin (b), included.

The aqueous paints, that in the inventive method can be further used various modifiers and Auxiliaries, such as agents that prevent sagging, or agents, prevent them from running down (these terms are used synonymously), a defoamer, a leveling agent, a boiling retardant, a cure activator (acid catalyst) and the like included as needed. It is also possible to use organic solvents, which are freely miscible with water, such as alcohols, ether-alcohol mixtures, Esters, ketones, in quantities not above 20% by weight and preferably not more than 15 Wt .-%, based on the content of solid resin (weight), to mix.

to Improvement of the film thickness, the retention property of the paint film, the coating processability and the physical properties of the paint film may be inorganic Pigments, such as titanium oxide, barium sulfate, calcium carbonate and clay, and mixtures of such inorganic pigments with various ones Pigments for the coloring in amounts within the range of usually 1 to 200 parts by weight and especially 70 to 120 parts by weight per 100 parts by weight of total resin solids be mixed.

Of the as prepared above aqueous paint is with Water adjusted so that he to Coating has a suitable viscosity, and then according to a Coating process for Himself, such as by means of a spray coating process or an electrostatic Coating process, on the uncured film from the cationic electrodepositable paint, as described above was formed after a wet-on-wet process applied. The thickness of the applied film can be generally in the range of 30 to 50 μm in the flat part, based on the cured film thickness.

Of the multi-layered film of paint, a film of the cationic electrodepositable paint and a film of the aqueous paint comprises and so formed, is then heated to the two films simultaneously to harden. The heating temperature, the for the hardener of the two composite films is not critical, and they can depend on be varied by the types of composite films. A suitable heating temperature is in the range of usually 70 to 250 ° C and preferably 120 to 160 ° C.

at In the present invention, the film is made of paint the aqueous paint also as a cover paint film, and thus the process of the invention for the Two-coat finish can be used by coating both of the cationically electrodepositable paint and of the aqueous paint he follows. Most preferably, the aqueous paint is used as an interlayer paint used to apply a topcoat on top of (finishing with solid dye or metal finishing).

The The present invention is further illustrated by the examples. All parts and percentages in the following examples are expressed by weight.

I. Preparation Examples

I-1. Production of the base resin (A)

(1) Base Resin (A-1)

A bisphenol A type epoxy resin having an epoxy equivalent of 950 (trademark "Epicoat 1004 ", a product of Shell Chemicals Co., Ltd.) (1900 parts) is dissolved in 993 parts of butyl cellosolve To the resulting solution is added 210 parts of diethanolamine dropwise at a temperature of 80 to 100 ° C, and then the resulting mixture kept at 100 ° C for 2 hours to obtain a base resin (A-1) having a resin solid content of 68%, a primary hydroxyl equivalent of 528 and an amine value of 53.

(2) base resin (A-2)

To 39 parts of monoethanolamine, which is kept at 60 ° C in a reactor 100 parts of N, N-dimethylaminopropylacrylamide are added dropwise given, the mixture is at 60 ° C. while Implemented for 5 hours, wherein a monoethanolamine adduct of N, N-dimethylaminopropylacrylamide is obtained.

Separated is a reactor with 950 parts of bisphenol A diglycidyl ether with an epoxy equivalent of 190, 340 parts of propylene glycol diglycidyl ether with one epoxy equivalent of 340, 456 parts of bisphenol A and 21 parts of diethanolamine, and the content gets to 120 ° C heated and reacted until the epoxy value is 1.02 mmol / g. Then The reaction product with 479 parts of ethylene glycol monobutyl ether diluted cooled, and while the reaction system at 100 ° C 158 parts of diethanolamine and 43 parts of monoethanolamine adduct of the N, N-dimethylaminopropylacrylamide added, and the resulting Mixture is put over until the viscosity stops rising, with a base resin (A-2) having a resin solid content of 80%, a primary hydroxyl group of 518 and an amine number of 54.

(3) base resin (A-3)

One Reactor is charged with 950 parts of bisphenol A digylcidyl ether with a epoxy equivalent of 190, 330 parts epoxy resin XB-4122 (trademark for one product from Ciba Geigy Ltd.) with an epoxy equivalent of 330, 456 parts Bisphenol A and 21 parts of diethanolamine. The content becomes to 120 ° C heated and reacted until the epoxy value is 1.02 mmol / g. Then is the reaction product with 489 parts of ethylene glycol monobutyl ether diluted cooled, and subsequently the reaction system is at 90 ° C held. 126 parts diethanolamine, 53.5 parts monoethanolamine adduct of N, N-dimethylaminopropylacrylamide and 18.5 parts of N-methylaminoethanol are added and the resulting mixture is reacted until the viscosity does not increase, the base resin (A-3) having a resin solid content of 80%, a primary hydroxyl group equivalent of 592 and an amine number of 55 is obtained.

I-2. Production of a pigment paste

Pigment paste (P-1)

One Base resin (12.5 parts) is mixed with 4.4 parts of 10% formic acid, then 15 parts of deionized water are added with stirring. To the resulting mixture are further 10 parts titanium white, 10 parts Clay, 1 part carbon and 2 parts basic lead silicate added. The resulting mixture is dispersed in a ball mill for 24 hours. Then 11 parts of deionized water are added, with a Paste (P-1) having a solids content of 50% is obtained.

I-third Production of the cationic Electrodepositable paint (K-2)

(1) base resin (a-4) (1) Bisphenol type epoxy resin ("Araldite # 6071", trademark, manufactured by Ciba Geigy Ltd.) 930 parts (2) Bisphenol type epoxy resin ("Araldite GY2600", trademark, manufactured by Ciba Geigy Ltd.) 380 parts (3) Polycaprolactone diol ("Praxel # 205" trademark, manufactured by Daicel Chemical Industries, Ltd.) 550 parts (4) dimethylbenzylamine acetate 2.6 parts (5) p-nonylphenol 79 parts (6) Methyl isobutyl ketone-ketiminated monoethanolamine 71 parts (7) diethanolamine 105 parts (8) butyl cellosolve 180 parts (9) Cellosolve 525 parts

The The above components (1) to (6) are mixed at 150 ° C for 2 Hours implemented. Thereafter, the components (7) to (9) with the reaction mixture, and the resulting mixture is at 80 to 90 ° C while Implemented 3 hours, wherein a base resin with a solids content of 75% (a-4) is obtained.

(2) pigment paste

A pigment paste with a solids content of 50% is prepared, which consists of: quaternized base resin with a set solids ratio of 60% (a-4) 5.73 parts titanium white 14.5 parts carbon 0.54 parts Extender pigment (clay) 7.0 parts lead silicate 2.3 parts dibutyltin 2.0 parts deionized water 27.49 parts consists.

(3) production of a cationically electrodepositable paint (K-2)

Two Types of aqueous emulsions, each having a solids content of 32% are used of the aforementioned Base resin produced. The composition and the admixed amounts are listed in the following table.

Then 318.75 parts of the aqueous emulsion with 59.56 parts of the aforementioned Pigment paste and 280.59 parts of deionized water to make a cationically electrodepositable bath having a solids content mixed by 20%.

I-4. Producing a aqueous paint:

(1) Polyester resin

(1-1) Polyester Resin (a-1):

One Polyester resin obtained by reacting a mixture of 19.6 parts Ethylene glycol, 18.5 parts trimethylolpropane and 46.7 parts phthalic anhydride at 160 to 230 ° C while 7 hours was obtained, with 15.7 parts of tolylene diisocyanate at 120 ° C implemented. Subsequently were 5.2 parts of trimellitic anhydride was added, and the mixture was reacted at 180 ° C for 1 hour, wherein a urethane-modified polyester resin (a-2) having a weight average Molecular weight of 6000, an acid number of 40 and a hydroxyl number obtained from 112.

(1-2) Polyester resin (a-2):

One Polyester resin obtained by reacting 19.3 parts of ethylene glycol, 18.2 parts of trimethylolpropane and 46.2 parts of phthalic anhydride at 160 to 230 ° C while 7 hours, was with 16.8 parts of xylylene diisocyanate at 120 ° C implemented. Then, 5.1 parts of trimellitic anhydride was added, and the mixture was at 180 ° C while Implemented 1 hour, wherein a urethane-modified polyester resin (a-2) having a weight-average molecular weight of 6200, an acid number of 40 and a hydroxyl number of 110 was obtained.

(1-3) Polyester Resin (a-3):

One Polyester resin obtained by reacting a mixture of 27.7 Divide ethylene glycol, 10.3 parts glycerol and 50.0 parts phthalic anhydride at 160 to 230 ° C while 7 hours, was reacted with 9.7 parts of tolylene diisocyanate at 120 ° C. Subsequently were 8.3 parts of phthalic anhydride added and the mixture was reacted at 160 ° C for 3 hours, wherein a urethane-modified polyester resin (a-3) having a weight average Molecular weight of 4500, an acid number of 50 and a hydroxyl number of 200 was obtained.

(2) Preparation of a aqueous paint:

The previously mentioned Polyester resin and other components were as shown in Table 1 mixed mixing amounts and dispersed, wherein aqueous paints (S-1) to (S-5) were obtained.

• (1*) Name der Komponente (a): a-1 bis a-3 sind die, die in (1) von Herstellungsbeispiel I-4 erhalten wurden.
• (2*) Name der Komponente (b): (b-1): "Cymel 703" (Iminogruppen enthaltendes Melaminharz, hergestellt von Mitsui Cyanamide Co., Ltd.)
• (3*) Name der Komponente (c): (c-1): Benzoinethylether
• (4*) Organisches Lösungsmittel: Diethylenglykol-monoethylether

In Table 1, the respective blending amounts of the components (a) to (c) are based on solid contents, and the paint for an intermediate coat of the known organic solvent type used in B-5 is "Amilac Sealer" (trade name for one Polyester resin type, manufactured by Kansai Paint Co., Ltd.).

• (1 *) Name of Component (a): a-1 to a-3 are those obtained in (1) of Preparation Example I-4.
• (2 *) Name of component (b): (b-1): "Cymel 703" (imino group-containing melamine resin, manufactured by Mitsui Cyanamide Co., Ltd.)
• (3 *) Name of Component (c): (c-1): Benzoin ethyl ether
• (4 *) Organic solvent: diethylene glycol monoethyl ether

The respective blending amounts of components (a), (b) and (c) to 100 parts by weight total solids content in the components (a), (b) and (c).

When Pigment are 80 parts titanium white, 20 parts barium sulfate and 0.3 part of carbon per 100 parts by weight of the total solids content the components (a) and (b) used.

These pigments are introduced into the reactor along with a portion of component (a) and deionized Water was added and dispersed using glass beads as a dispersion medium in 1 hour so that the particle size of the particles measured by a grindometer was about 5 μm or less.

II. Examples

In the respective baths of cationically electrodepositable paint with controlled Temperature at 30 ° C were steel plates treated with zinc phosphate, immersed, and then at 200 to 300 V for 3 minutes, an electrodeposition carried out. The electrocoated panels were pulled out of the baths, washed with water and at 100 ° C while 10 minutes hydroextraction-dried. It became one of the aqueous paints (S-1) to (S-5) on the uncured, electric deposited surface according to one Wet-on-wet process spray-coated and at room temperature during Let stand for 5 minutes, and then was heated to the two To harden films of paints.

The Coating levels and the results of the experiments regarding The properties of the formed films of paint are in Table 2 listed.

In Table 2:
(Note 1) The cationically electrodepositable paint (K-3) was prepared in the same manner as the cationic electrodepositable paint (K-2-1) except that methyl ethyl ketoxime (blocking agent) of the dimerized isophorone diisocyanate in the aforementioned cationic electrodepositable paint Coating (K-2-1) was replaced by diphenylmethane diisocyanate diblocked with 2-ethylhexylglycol.
(Note 2) Drying of the cationically electrodeposited paint film at 100 ° C for 10 minutes after washing with water caused the removal of almost all the moisture by evaporation while no crosslinking reaction (hardening) occurred. Heating at 160 ° C for 30 minutes (baking) caused cure by cross-linking.
(Note 3) "Amilac Black" used as a topcoat paint is a trade mark for a thermosetting melamine / polyester paint of an organic solvent type, manufactured by Kansai Paint Co., Ltd.
(Note 4) Procedures for performing the tests on the properties
Of the following points, items (3) to (5) were carried out with coated plates coated with the cationically electrodepositable paint and aqueous paint and cured as described above. Items (6) to (9) were carried out with coated plates coated with Amilac Black on its cured aqueous paint-coated surface after firing at 140 ° C for 30 minutes.

(1) weight reduction by heating

A copper plate having a weight Where was subjected to cationic electrodeposition at 30 ° C at 200 to 300 V for 3 minutes in an electrodeposition bath, pulled out of the bath and washed with water. After removing all or almost all of the moisture in the resultant paint film by heating at 105 ° C for 3 hours, the weight (Y) of the paint film was determined, and then the paint film became 170 ° C for 20 minutes heated to harden it three-dimensionally. Subsequently, the weight (Z) of the film of paint was measured. These measured values were entered into the following formula, and the weight reduction (X) of the film of paint was calculated:

(2) Limit on the film thickness for the Sag or run down

10 × 45 cm steel plates, each of which was treated with zinc phosphate and a series of holes with a diameter of 10 mm, along the longer side of it at distances were formed by 4 cm, were subjected to a cationic electrodeposition subjected (thickness: 20 microns as a hardened deposition film) and dried by hydroextraction. From immediately after coating with an aqueous paint until settling and baking, the plates were held vertically, So that the Holes horizontally were arranged. The boundary film thickness (unit: μm) for the run was reported as maximum film thickness defined, with no dropout in the perimeter the holes was observed under these conditions.

(3) smoothness

The smoothness the coated surfaces of the plates containing the aqueous paints were visually observed. Samples that do not shrink, no pinholes (small holes) show, neither orange peel nor have depression, were with O rated. The ones where a low occurrence of these errors was observed, were rated Δ, and the, at which is a big one Number of such errors was rated X.

(4) hardness of the film of paint

The Hardness of coated surfaces of the plates covered with the aqueous paint were coated in a room with constant temperature using a TUKON microhardness tester made by American Chain & Cable Company, determined. Larger values show higher Hardness.

(5) hardenability

The gloss reduction of the aqueous paint film surface was visually observed after rubbed with mullet impregnated with xylene 10 times. The hardenability was rated with three ratings rated:
O: normal, Δ: gloss reduction occurs.

(6) Anti-chipping properties

The experiments were carried out using a Stein-Jettest device (JA-400 type, manufactured by Suga Shikenki Co., Ltd.). The coated test panels were mounted vertically in a sample holder in the tester, and 50g of crushed quality 7 bricks were flung against the surface at an air pressure of 4kg / cm ^{2 as} determined by a pneumometer equipped with the tester that the crushed stones bounced vertically against the test plate. The degree of feathering or chipping due to the collision of the stones has been rated with 5 ratings ranging from good (0) to poor (X).

(7) Adhesion

The adhesion was cut through the crosscut cellophane tape peel test (1 x 1 mm, 100 pieces), where the character "O" means no peeling.

(8) Moisture resistance

In a blister box or blister box, which at a temperature of 50 ° C and at maintained at a relative humidity of 98 to 100% RH, the samples were stored for 5 days. They were then taken out and then examine if a source occurs. The character "O" indicates that no swelling occurs, and the character "Δ" indicates that a source occurs.

Claims (22)

A method of producing a multilayer film on a substrate, characterized by performing the steps of: forming an uncured film of a cationically electrodepositable paint on the substrate, then coating the uncured film with an aqueous paint in a wet-on-wet manner And then curing under heating of both films, wherein (i) the cationically electrodeposited film is used a paint comprising (A) a resin having hydroxyl groups and cationic groups and (D) a blocked polyisocyanate compound, and U.S. 4,134,741 said film is formed under heating to have a film weight reduction of 10% by weight or less from the uncured film; and wherein (ii) the aqueous paint is used with a paint mainly comprising a) a polyester resin or a urethane modified polyester resin having an acid number within the range of 10 to 100 and a hydroxyl value within the range of 20 to 300, and b) a water-soluble or dispersible amino resin and c) an alkyl-etherified benzoin. Method according to claim 1, characterized in that that for the cationic electrically deposited film a paint is used with the after hardening under heating, a film is produced which is opposite to the uncured film has a film weight reduction of 7% by weight or less. Method according to claim 1, characterized in that that this Resin (A) primary Contains hydroxyl groups and cationic groups. Method according to claim 1, characterized in that that this Resin (A) is the reaction product obtained by reacting a polyepoxide compound, obtained from a polyphenol compound and epichlorohydrin, with a cationizing agent has been obtained. Method according to claim 4, characterized in that that the Polyepoxide compound, a polyglycidyl ether of a polyphenol compound is with a number average molecular weight of 800 to 2000 and one epoxy equivalent from 190 to 2000. Process according to Claim 1, characterized in that the resin (A) contains a hydroxyl equivalent internally half of the range from 20 to 5000 owns. Method according to claim 3, characterized that this Resin (A) a primary hydroxyl in the range of 200 to 1000 possesses. Method according to claim 1, characterized in that that this Resin (A) has an amine number in the range of 3 to 200, calculated as KOH (mg / g solids). Method according to claim 1, characterized in that that the blocked polyisocyanate compound (D) a polyisocyanate compound is that selected from the group is composed of isophorone diisocyanate and xylylene diisocyanate, wherein the polyisocyanate compound with a blocking agent with a molecular weight of 130 or less is blocked. Method according to claim 9, characterized in that that this Blocking agent is an oxime-type blocking agent. Method according to claim 1, characterized in that that the blocked polyisocyanate compound (D) is selected from the group which from methyl ethyl ketoxime-blocked isophorone diisocyanate and methyl ethyl ketoxime-diblockiertem Xylylene diisocyanate exists. Method according to claim 1, characterized in that that this weight ratio the solids content of the blocked polyisocyanate compound (D) to the resin (A) is within the range of 0.05 to 1.5. Method according to claim 1, characterized in that that the cationically electrodepositable paint continues to be at least a metal compound selected from the group consisting of a lead compound, a zirconium compound, a cobalt compound, an aluminum compound, a manganese compound, a copper compound, a zinc compound, an iron compound, a chromium compound and a nickel compound, and that they are in such amount is present that the Metal content, based on the total weight of the resin (A) and the Polyisocyanate compound (D), not more than 10 wt .-% is. Method according to claim 1, characterized in that that this Polyester resin (a) in the aqueous paint is a urethane-modified polyester resin. Method according to claim 14, characterized in that that this Urethane-modified polyester resin is obtained from a polyester resin and a polyisocyanate compound selected from the group of tolylene diisocyanate, Xylylene diisocyanate and isophorone diisocyanate. Method according to claim 1, characterized in that that this Polyester resin (a) a weight average molecular weight within the range of 1000 to 20,000. Method according to claim 1, characterized in that that this Polyester resin (a) is a polyester resin obtained by neutralization of at least 20% of the acid groups present with a basic one Substance in a water-soluble or -dispersible state is. Method according to claim 1, characterized in that that this Amino resin (b) in the aqueous resin Melamine resin is. Method according to claim 1, characterized in that that this Amino resin (b) a water-soluble or dispersible amino resin having an imino group. Method according to claim 1, characterized in that that the aqueous paint 50 to 90% by weight of the polyester resin and 50 to 10% by weight of the amino resin, based on the total weight of polyester resin (a) and amino resin (b) contains. Method according to claim 1, characterized in that that the aqueous paint 0.1 to 10 wt .-% of the alkyl-etherified benzoin, based on the Total weight of polyester resin (a) and amino resin (b) contains. Method according to claim 1, characterized in that that the hardening under heating at a temperature of 70 to 250 ° C is performed.