JPH0699651B2 - Paint finish method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention relates to a coating finishing method, and more particularly to a so-called 2-coat 1-baking method.

[Problems to be Solved by Conventional Techniques and Inventions] In recent years, in automotive topcoating, a so-called 1 coat 1 is used in which a thermosetting paint containing a metallic powder and / or a coloring pigment is applied and then baked and cured as it is. Instead of baking finish, a thermosetting paint (base coat) mixed with metallic powder and / or coloring pigment is applied, and then a thermosetting clear paint (top coat) colored so that it is uncolored or does not impair transparency. There is an increasing number of so-called 2-coat 1-bake coating finishing methods in which a base coat and a top coat are baked at the same time. Such a two-coat one-bake coating finish has an excellent finished appearance, and the conventional one-coat one-bake metallic coating has a drawback that the coating film is easily attacked by an acid, but it is improved. In solid color coating, there is an advantage that a coating film having excellent weather resistance can be obtained by finishing the coating with 2 coats and 1 bake. However, the conventional 2-coat 1-bake method generally applies amino alkyd resin paint, thermosetting acrylic resin paint, etc. as the base coat paint, and leaves it for 2 to 5 minutes to evaporate a certain amount of solvent and then immediately apply the same top The coating material for coating is applied, and then it is baked and hardened for 20 to 30 minutes in an atmosphere of a hot air drying oven temperature of 140 to 150 ° C. Here, sources of hot air include heavy oil, propane gas, butane gas,
City gas or electric power is generally used, but since it is heated and hardened in a hot air drying furnace or an electric heating furnace, it has a drawback that it causes an increase in energy cost due to fuel and electric power consumed as a heat source.

On the other hand, in the automobile industry, plasticization of outer panels and parts is rapidly progressing. If the material is steel plate,
As the paint resin system used, so-called baked one-pack type paints such as the above-mentioned aminoalkyd resin paints and thermosetting acrylic paints are usually adopted. However, when the material is made into plastic, the heat resistant temperature of the material is low in some cases, and it is not appropriate to use a normal baking one-pack type paint for plastic.

Therefore, as a low temperature curing type coating, a combination of a polyol type resin and an isocyanate prepolymer, an aminoplast type using a curing catalyst, a combination of an acrylic resin having a tertiary amino group as a functional group and a polyfunctional epoxy resin, or the like is considered or considered. Partly adopted. However, polyol type resin-
Both the isocyanate prepolymer system and the tertiary amino group-epoxy resin curing system are two-pack type and have a major drawback in workability such as pot life as compared with the one-pack type. Although the low temperature curing type aminoplast system is a one-pack type, it has a drawback that storage stability is poor because a large amount of curing catalyst is used. Separately, if an isocyanate prepolymer obtained by blocking an isocyanate prepolymer with an appropriate blocking agent is used, a one-pack type polyol type resin-isocyanate prepolymer curing system is obtained, but at present, the dissociation temperature of the blocking agent is high and the low temperature curing type resin system is used. It is hard to say. As mentioned above, in the industrial world, from the viewpoint of coating workability, various physical properties, and weather resistance, and from the viewpoint of material conversion and energy saving, there is a demand for the rapid development of a one-component curable resin paint that is excellent in storage stability. It is the actual situation.

[Means for Solving Problems] The inventors of the present invention have earnestly studied in order to obtain a curable resin coating composition for two-coat / one-bake coating finish in accordance with the above-mentioned requirements, and as a result, as a resin for a base coating composition, polymerization was performed. Using a resin composition containing a vinyl polymer having a polymerizable unsaturated group and an oligomer having a polymerizable unsaturated group as a main component, on the other hand, as a resin for a top coat coating, at least a polymerizable unsaturated group in one molecule The present invention has been completed by finding that such a requirement can be surprisingly improved by using a resin composition containing a vinyl-based polymer composed of a vinyl-based monomer having one or more siloxy groups as a main component. Came to let.

That is, the present invention applies a coating material (base coat) containing a curable resin as a main component, in which a metallic powder and / or a coloring pigment is mixed, and then, a clear coating material containing a curable resin as a main component is applied to the coated surface. In the coating finishing method of coating (topcoat) and then curing, the vinyl-based polymer having a polymerizable unsaturated bond, each having a number average molecular weight of 1,500 to 50,000, as an essential component of the base coat coating composition. 20-80% by weight of (A)
And 20 to 80% by weight of an oligomer (B) having a polymerizable unsaturated bond, which is an esterified product of a polyhydric alcohol and (meth) acrylic acid and has a number average molecular weight of 200 to 1,000, and a polymerization medium (C). Of 0.01 to 10% by weight, and, on the other hand, as an essential component of the top coat coating composition, each in a molecule, a polymerizable unsaturated bond and at least one A vinyl-based polymer (D) obtained by polymerizing a vinyl-based monomer having a siloxy group together with a vinyl-based monomer other than the vinyl-based monomer capable of copolymerization in the presence of a radical generator. A polyisocyanate compound (E) having reactivity with a hydroxyl group produced from the polymer (D), and a siloxy group dissociation promoting catalyst (F), an OH group produced from the polymer (D), and As the equivalent ratio of NCO groups in the compound (E) (OH group / NCO group) is 1 / 0.5 to 1/3, and,
Forming a composite cured coating film by using the resin composition for coating material containing 0.001 to 10% by weight of the dissociation promoting catalyst (F) based on the polymer (D).
The present invention aims to provide a new and useful coating finishing method.

That is, according to the present invention, after the coating composition [I] for the specific base coat is applied, and then the coating composition [II] for the specific top coat is repeatedly applied, the above-mentioned coating composition [I] When coating [I], oxygen in the air is shut off, and by the action of the polymerization catalyst or the polymerization initiator (C),
The polymerizable unsaturated bond (hereinafter, also referred to as a polymerizable unsaturated group) in the vinyl polymer (A) and the polymerizable unsaturated group in the vinyl oligomer (B) react to form a coating film. On the other hand, at the time of coating the above-mentioned coating composition [II],
Mainly, the hydroxyl group in the vinyl polymer (D) and the siloxy group in the polymer (D) are supplied by being converted into a hydroxyl group and a silanol group by the action of water in the air. It is intended to provide a novel coating finishing method in which both of these other hydroxyl groups and the polyisocyanate group in the polyisocyanate compound (E) react to form a strong coating film. It is a thing.

The vinyl polymer (A) having a polymerizable unsaturated group, which is one component of the composition used in the method of the present invention, has a number average molecular weight of 1500.
-60,000, preferably 2000-30000. Molecular weight 1500
If it is less than 60%, it is difficult to obtain a coating film having sufficient processability, and if it exceeds 60,000, the coating workability is deteriorated, which is not preferable. The polymerizable unsaturated group in the vinyl polymer (A) is a functional group which undergoes a copolymerization reaction with the polymerizable unsaturated group of the vinyl oligomer (B), and the content thereof is 1000 g of the vinyl polymer (A).
It is usually 0.1 to 5, preferably 0.2 to 3.

There are various methods for obtaining this vinyl polymer (A), but the most preferable method is to use a skeleton polymer having at least one functional group such as a hydroxyl group, a carboxyl group, an acid anhydride group, and an epoxy group. In this method, the functional group is reacted with a polymerizable monomer having a mutually reactive functional group. Specific examples thereof include a method of reacting a polymerizable polybasic acid (anhydride) with an epoxy group-containing skeleton polymer, a method of reacting a hydroxyl group-containing skeleton polymer with a polymerizable polybasic acid anhydride, and a carboxyl group (acid anhydride). Group) containing skeleton polymer with polyvalent aquatic group containing polymerizable monomer or epoxy group containing polymerizable monomer, hydroxyl group and carboxyl group (acid anhydride) containing skeleton polymer with isocyanate group containing polymerizable monomer There are ways.

Examples of the (polyvalent) hydroxyl group-containing polymerizable monomer used by the above method include β-hydroxyethyl (meth) acrylate, β-hydroxypropyl (meth) acrylate,
There are trimethylolpropane mono (meth) acrylate, glycerin mono (meth) acrylate, etc., and examples of polymerizable monobasic acids include (meth) acrylic acid, itaconic acid monomethyl ester, etc. ), Only the representative ones are exemplified (anhydrous).
Maleic acid, fumaric acid, (anhydrous) itaconic acid, etc.,
Examples of the epoxy group-containing polymerizable monomer include glycidyl (meth) acrylate and (meth) allyl glycidyl ether, and examples of the isocyanate group-containing polymerizable monomer include β-hydroxyethyl (meth) acrylate / toluene diisocyanate adduct. , (Meth) allyl alcohol / hexamethylene diisocyanate adduct and the like. Examples of the polymerizable monomer that forms a skeleton polymer in combination with the functional group-containing polymerizable monomer described above include methyl (meth) acrylate, ethyl (meth) acrylate, (meth)
Propyl acrylate, diethyl itaconate, styrene,
There is α-methylstyrene and the like.

The above-mentioned method for producing the vinyl polymer (A) and the skeleton polymer having each functional group can be obtained by a known and conventional method in the presence of a known and commonly used radical generator.

The other component, the vinyl-based oligomer (B), has a polymerizable unsaturated group and has a number average molecular weight of 200 to 1,000. When the molecular weight is less than 200, it is evaporated and scattered at the time of bake hardening, and when it exceeds 1,000, the fluidity of the composition is inferior and curing does not proceed sufficiently and the coating film tends to be inferior in chemical resistance, which is not preferable. The polymerizable unsaturated group content is preferably in the range of 2 to 5 per molecule.

There are various such oligomers, the most preferred of which are glycerin, trimethylolpropane, pentaerythritol, pentanediol, 2,2-
Dimethyl-3-hydroxypropyl-2,2-dimethyl-
An esterification product of 1 mol of a polyhydric alcohol such as 3-hydroxypropionate and 2 mol or more of (meth) acrylic acid; β-hydroxypropyl (meth) acrylate,
It is an esterification product of a hydroxyl group-containing polymerizable monomer such as β-hydroxybutyl (meth) acrylate and (meth) acrylic acid.

In addition, 1 mol of a polyvalent carboxylic acid (anhydride) such as (anhydrous) maleic acid, (anhydrous) itaconic acid, (anhydrous) phthalic acid, (anhydrous) trimellitic acid, and 2 mol or more of a hydroxyl group-containing polymerizable monomer Esterified product; Reaction product of hydroxyl group-containing polymerizable monomer, polyvalent carboxylic acid (anhydride) and epoxy group-containing polymerizable monomer such as glycidyl (meth) acrylate, (meth) acrylic glycidyl ether; polyvalent carboxylic acid (anhydride) 1) Ester of 1 mol and 2 mol or more of epoxy group-containing polymerizable monomer; reaction product of polyhydric alcohol, polyvalent carboxylic acid (anhydride) and epoxy group-containing polymerizable monomer; Besides, polymerizable monomers containing active hydrogen such as itaconic acid, N-methylol (meth) acrylamide, crotonic acid, etc. and toluene diisocyanate. Sulfonates, hexamethylene diisocyanate, reaction products of such polyisocyanates, such as polyhydric alcohol adducts of these isocyanates; esterified products of a carboxyl group-containing polymerizable monomer and the epoxy resin can also be used as an oligomer.

Next, the polymerization initiator (C) means the vinyl-based polymer (A) listed above.
It accelerates the copolymerization reaction between the polymerizable unsaturated group in the vinyl-based oligomer (B) and the polymerizable unsaturated group in the vinyl-based oligomer (B), and an ordinary radical initiator can be used. Representative examples of the radical initiator include acyl peroxide, ketone peroxide, hydroperoxide, etc., such as benzoyl peroxide and its nuclear-substituted derivatives, lauroyl peroxide, methyl ethyl ketone peroxide, cyclohexane peroxide, cumene hydroperoxide, etc. Examples thereof include peroxides and azo compounds such as azobisisobutyronitrile.

And the blending amount is 0.01 to 10% by weight, and preferably 0.
1-5% by weight is suitable. If the amount is less than 0.01% by weight, the curability is poor and sufficient coating performance cannot be obtained. On the contrary, if the amount is more than 10% by weight, the stability of the coating becomes a problem.

When the obtained composition is used as a base coat paint, an inorganic or organic color pigment, a dye, and a METAC powder may be added to the composition to prepare the paint by a conventional coating method.

Here, as the coloring pigment, for example, titanium white, red iron oxide,
Inorganic compounds such as oxide yellow, organic compounds such as toluidine red, phthalocyanine blue, and benzidine yellow.Metallic powders include aluminum powder, copper powder, mica powder, titanium oxide-coated mica powder, MIO (mica-like oxidation). Iron etc. can be used.

Next, the above-mentioned composition for top coating composition [II] to be overcoated on the above-mentioned base coating composition, that is, the top coating composition, contains the vinyl polymer (D), respectively. A resin composition comprising a component, a polyisocyanate compound (E) component, and a dissociation accelerating catalyst (F) component is used. The vinyl polymer (D) is, for example, each in one molecule. , A vinyl-based monomer having a polymerizable unsaturated bond and at least one siloxy group together, and, if necessary, a vinyl-based monomer capable of copolymerization other than the vinyl-based monomer Is intended to be obtained by polymerizing in the presence of a radical generator, in which case, for example, a vinyl monomer having a polymerizable unsaturated group / siloxy group as described above And 100% by weight, it is appropriate to use Te than in a ratio such that from 99 to 0% by weight of the monomer copolymerizable with Naru other vinyl monomers.

The coating resin composition for a top coat [II] is prepared by reacting the siloxy group in the vinyl monomer having both a polymerizable unsaturated group and a siloxy group with water in the air to form a vinyl polymer (D). A resin composition which becomes a process for forming a hydroxyl group and reacts with the hydroxyl group in the polyisocyanate compound (E) having reactivity with the hydroxyl group to form a strong coating film. The topcoat paint using the resin composition can be a highly practical one-pack paint having excellent storage stability or storage stability.

As described above, the polymerizable unsaturated group / siloxy group-containing vinyl monomer for preparing the vinyl polymer (D) used in the top coat coating composition is as described above.
It refers to a compound in the form of a combination of a polymerizable unsaturated group and a siloxy group bonded to a carbon atom, represented by the following formula, in one molecule.

These vinyl monomers are, for example, trialkylchlorosilane or triphenylchlorosilane in the presence of a hydrochloric acid scavenger such as triethylamine or pyridine,
A compound obtained by reacting triallylchlorosilane, dialkylchlorosilane, dialkyldichlorosilane, dialkylhydrosilane, etc. with a hydroxyl group-containing vinyl-based monomer (a) as described below is designated, and representative of them Trimethylsiloxyethyl (meth) acrylate, trimethylsiloxypropyl (meth) acrylate, trimethylsiloxybutyl (meth) acrylate, triethylsiloxyethyl (meth) acrylate,
Examples thereof include tributylsiloxypropyl (meth) acrylate and triphenylsiloxyalkyl (meth) acrylate. These can be used alone or as a mixture of two or more kinds.

Moreover, as the hydroxyl group-containing vinyl-based monomer (a), β-hydroxyethyl (meth) acrylate, β-
Hydroxypropyl (meth) acrylate or β-
Typical examples are hydroxyalkyl (meth) acrylates such as hydroxybutyl (meth) acrylate, N-methylolated (meth) acrylamide and the like. And the amount of these vinyl monomers used is 1-10
0% by weight is good, and preferably 5 to 90% by weight. If it is less than 1% by weight, the effect of the monomer cannot be expected.

Typical other vinyl-based monomers copolymerizable with the vinyl-based monomer having a polymerizable unsaturated group / siloxy group are alkyl (meth) acrylates having 1 to 22 carbon atoms, styrene, vinyltoluene, t -Butyl styrene, α-methyl styrene, glycidyl (meth) acrylate, 2-ethoxyethyl (meth) acrylate,
(Meth) acrylonitrile, cyclohexyl (meth) acrylate, diesters of maleic acid or fumaric acid with C _{1 to} C ₁₈ monohydric alcohols, N, N dialkylaminoalkyl (meth) acrylates, or phosphate group-containing (meth ) Acrylates, fluorine-containing vinyl monomers such as vinyl acetate, hexafluoropropylene, and tetrafluoroethylene.

In order to obtain the vinyl polymer (D) constituting the composition of the present invention, a known conventional method using the above-mentioned monomers, for example, a solution polymerization method using a radical generator is used. You can

The vinyl polymer (D) thus obtained preferably has a number average molecular weight (n) of 500 to 50,000.

When n of the vinyl-based polymer (D) is less than 500, the physical properties of the coating film cannot be sufficient, and the trialkyl of the vinyl-based polymer (D) is attempted to exhibit the physical properties of the coating film. If the hydroxyl value generated after the siloxy groups and the like are liberated (hereinafter referred to as "OH value"), it is not preferable because the coating becomes brittle, and conversely, when it exceeds 50,000, It is not preferable because defects are likely to appear in the appearance, the gloss, the feeling of flesh and the workability of painting.

Next, typical examples of polyisocyanates which are other components constituting the composition of the present invention include aromatic diisocyanates such as tolylene diisocyanate, diphenylmethane diisocyanate or xylylene diisocyanate; tetramethylene diisocyanate, hexamethylene diisocyanate or trimethyl. Aliphatic diisocyanates such as hexane diisocyanate; isophorone diisocyanate, methylcyclohexane-2,4- (or 2,6-) diisocyanate, 4,4'-methylenebis (cyclohexylisocyanate) or 1,3-di (isocyanatomethyl) -cyclohexane Alicyclic diisocyanates such as these, and each of these diisocyanates, ethylene glycol, propylene glycol, neopentyl glycol Is a polyhydric alcohol such as trimethylol propane; a polyester resin having a functional group capable of reacting with an isocyanate group and having an extremely low molecular weight (including oil-modified type); Or a polymer of the above-mentioned diisocyanates (including an oligomer). Among these, a polyisocyanate prepolymer composed of an aliphatic diisocyanate is preferable from the viewpoint of weather resistance. And, as a compounding ratio of these polyisocyanates and the vinyl polymer (D), OH groups / NCO groups produced are 1 /
The range of 0.5 to 1/3 (equivalent ratio) is preferable from the viewpoint of coating film performance.

The composition of the present invention, when exposed to the atmosphere, is hydrolyzed by a reaction with moisture in the air to generate a hydroxyl group capable of reacting with a curing agent. In order to accelerate this hydrolysis, it is necessary to use a specific catalyst, that is, the dissociation promoting catalyst (F). Specific examples of such catalysts include, but are not limited to, phosphoric acid, phosphoric acid ester, phosphorous acid ester, p-toluenesulfonic acid and amines thereof, benzoic acid, trichloroacetic acid, trifluoroacetic acid, naphthalenedisulphonic acid. And acidic catalysts such as amine salts thereof, ethylenediamine, N-β-aminoethyl-γ-aminopropyltrimethoxysilane, butylamine, dibutylamine, t-butylamine, hexylamine, triethylamine, and other amines, potassium hydroxide, and hydroxide. lithium,
Alkali catalysts such as sodium hydroxide, alkyl titanium hydrochloride, octylate, dibutyltin dilaurate, and metal salts of carboxylic acids such as lead octylate, sulfide type such as monobutyltin sulfide, dioctyltin sulfide, dioctyltin mercapite, mercaptide type Compounds that generate fluorine ions such as organic tin compounds, tetraethylammonium fluoride and cesium fluoride are effective.
The addition amount of these curing catalysts is 0.001 to 10% by weight, preferably 0.005 to 8% by weight, based on the vinyl polymer (D).

Further, since the composition of the present invention does not generate a hydroxyl group capable of reacting with the curing agent unless it is exposed to the atmosphere, the composition of the present invention is a one-pack type composition having good stability. However, in order to ensure long-term storage stability, it is only necessary to capture a small amount of water that enters for some reason.
That is, long-term stability is ensured by adding a water-binding agent having reactivity with water. Further, this water binder may be used by mixing it in the initial stage when the vinyl polymer (D) is produced. Examples of the water-binding agent having reactivity with water include trialkyl orthoformates such as trimethyl orthoformate, triethyl orthoformate and tributyl orthoformate; trialkyl orthoacetate such as trimethyl orthoacetate, triethyl orthoacetate and tributyl orthoacetate. Trialkyl orthoborates such as tributyl orthoborate and triethyl orthoborate; Tetra (substituted) such as tetramethyl silicate, tetraethyl silicate, tetrabutyl silicate, tetra (2-methoxyethyl) silicate or tetra (2-chloroethyl) silicate Alkyl silicates alone; Tetraphenyl silicates, tetrabenzyl silicates, and similar substances of the above tetra (substituted) alkyl silicates (hereinafter abbreviated as "same effect simple substance"); Dimer of silicate, trimers, tetramers, hexamers, "Ethyl Silicate 40" (Colcoat (stock) product,
Mixtures of tetramers of tetraethyl silicate, pentamers, hexamers, etc.), such as each of the above-mentioned tetra (substituted) alkyl silicates alone, hydrolyzable ester compounds such as condensates of the same effect simple substance of the silicates, phenyl isocyanate, p There are compounds having an isocyanate group such as -chlorophenyl isocyanate, benzenesulfonyl isocyanate, p-toluenesulfonyl isocyanate, and isocyanate ethyl methacrylate (NCO group-containing monomer manufactured by Dow Chemical Co.).

The amount used is 0.1 to 3 with respect to the vinyl polymer (D).
0% by weight, preferably 0.5 to 20% by weight is good.

Since the obtained composition is used as a top coat paint, it can be used as it is as a clear paint, but if necessary, a coloring pigment or dye can be appropriately added to the extent that the transparency is not impaired. The prepared base coat paint and top coat paint may be mixed with various conventional additives such as a leveling agent, an ultraviolet absorber and a pigment dispersant, if necessary.

The base coat paint thus blended is applied as the first layer to reach a semi-dry or dry state, then the second layer is coated with the top coat composition and heated at room temperature or low temperature to generate radicals and the top coat composition. The polymerization reaction of the polymerizable unsaturated group contained in the base coat paint, which has been air-shielded by repeated coating, proceeds to cause curing. on the other hand,
In topcoat paints, the siloxy groups contained form hydroxyl groups due to the water content in the air, and the reaction with polyisocyanates that are reactive with these hydroxyl groups promotes curing, resulting in a composite with excellent flatness and smoothness. A cured coating film is formed.

For the coating of base coat paints and top coat paints using the composition of the present invention, air spray coating, electrostatic spray coating, etc. are suitable for sufficiently exerting a cosmetic effect. (Dry film thickness is the same below) 5 to 50 μm, preferably 10 to 20 μm, and the thickness of the top coat paint is 10 to 100 μm.
m, preferably 10-60 μm.

The drying conditions for the wet coating of the base coat paint and the coating interval between the base coat and the top coat are about 20 ° C. for 1 to 45 minutes, preferably 2 to 20 minutes, and when the base coat coating is forcibly dried, it is 60. All you need to do is warm it with warm air at ~ 80 ° C for 0.5-5 minutes. That is, the top coat is applied after the coating film of the base coat has reached a touch-dry or semi-cured dry state under the above drying conditions. It is preferable to dry the topcoat by hot air at 60 to 100 ° C for about 30 to 60 minutes from the viewpoint of curability and productivity, but depending on the type and properties of the basecoat paint and topcoat paint. It does not matter if the drying and curing conditions are changed appropriately.

As described above, by performing the two-coat one-bake coating method using the composition of the present invention, gloss can be obtained by drying at room temperature or low temperature which is lower than the heat resistant temperature of ordinary plastic materials.
This composition can form a composite coating film with excellent feeling of flesh and coating performance, and provides a coating finish comparable to that of conventional thermosetting acrylic resin paints and aminoalkyd resin paints. The coating system using the product is extremely effective in saving heat source and improving the coating workability by the metal / plastic integral coating method. Furthermore, the composition of the present invention is a one-pack type and excellent in storage stability. It greatly contributes to the improvement of sex.

[Examples] Next, the present invention will be specifically described with reference to Production Examples, Examples, and Comparative Examples. In the following, all parts are by weight unless otherwise specified.

Production Example 1 [Preparation Example of Vinyl Polymer (A)] 890 parts of xylene was charged into a four-necked flask equipped with a stirrer, an inert gas inlet, a thermometer and a condenser, and 120 ° C.
And then 5 parts of azobisisobutyronitrile (AIBN) and tert-butyl peroxyoctoate (TBPO). Ten
The mixture of 4 parts was added dropwise over 4 hours, and the mixture was kept at the same temperature for 20 hours. Then, 3 parts of 2-methylbenzimidazole, 3 parts of hydroquinone and 111 parts of glycidyl methacrylate were added, and the mixture was heated to 120 ° C for 6 hours. When heated, non-volatile content 52.1%, viscosity (Gardner viscosity, 25 ° C or below) I-
A resin solution having J, a number average molecular weight of 10,000 and an acid value of 2.4 was obtained. Hereinafter, this vinyl polymer solution is abbreviated as (I-1).

Production Example 2 [Same as above] 270 parts of methyl methacrylate, 210 of ethyl acrylate
Part, β-hydroxyethyl methacrylate 130 parts, n
10 parts of dodecyl mercaptan, 15 parts of azobisisobutyronitrile, 5 parts of benzoyl peroxide and 2000 parts of ethyl acetate were heated to 80 ° C. for 15 hours. Then ethyl acetate
After distilling off 1700 parts, 49.5 parts of maleic anhydride was added, and the mixture was heated at 80 ° C for 1 hour to have a nonvolatile content of 69.2% and a viscosity of Y-
A resin solution having Z, a number average molecular weight of 4000 and an acid value of 42.5 was obtained. Hereinafter, this vinyl-based polymer is abbreviated as (I-2).

Production Example 3 [Preparation Example of Vinyl Polymer (D)] Toluene (500 parts) and isobutyl acetate (50 parts) were charged in a four-necked flask equipped with a stirrer, an inert gas inlet, a thermometer and a condenser, and 110 ° C. Then, a monomer mixture consisting of 260 parts of trimethylsiloxyethyl methacrylate, 390 parts of n-butyl methacrylate, 150 parts of n-butyl acrylate and 200 parts of styrene, 50 parts of azobisisobutyronitrile and 450 parts of isobutyl acetate were added. The mixture consisting of 6 drops was added over 6 hours, and the mixture was kept at the same temperature for 10 hours to give a nonvolatile content of 50.9% and a viscosity (Gardner viscosity, 25 ° C).
The same applies hereinafter) C-D, a resin solution having a number average molecular weight of 10,000 and an OH number of 36 was obtained. Hereinafter, the vinyl polymer solution (I
-3) is abbreviated.

Production Example 4 [Same as above] 400 parts of triphenylsiloxyethyl methacrylate,
A resin was obtained in the same manner as in Production Example 3 except that 320 parts of n-butyl methacrylate, 120 parts of n-butyl acrylate, and 160 parts of styrene were used instead.

A resin having a nonvolatile content of 50.2%, a viscosity DE, a number average molecular weight of 11,000 and an OH number of 36 was obtained. Hereinafter, this vinyl polymer solution is abbreviated as (I-4).

Production Example 5 [Preparation Example of Comparative Vinyl Polymer] 170 parts of β-hydroxyethyl methacrylate, 200 parts of styrene, 477 parts of n-butyl methacrylate, 150 parts of n-butyl acrylate, 3 parts of methacrylate were replaced. A resin was obtained in the same manner as in Production Example 3 except that it was used.
A resin solution having a nonvolatile content of 50.3%, a viscosity KL, a number average molecular weight of 14,000 and an OH number of 36 was obtained. Hereinafter, this vinyl polymer is abbreviated as (I-5).

Production Example 6 [Same as above] 500 parts of toluene and 50 parts of isobutyl acetate were placed in a four-necked flask equipped with a stirrer, an inert gas inlet, a thermometer and a condenser, and kept at 105 ° C, and then β-hydroxy. From a monomer mixture consisting of 130 parts of ethyl methacrylate, 407 parts of methyl methacrylate, 360 parts of ethyl acrylate, 100 parts of n-butyl acrylate and 3 parts of methacrylic acid, and 7 parts of azobisisobutyronitrile and 393 parts of isobutyl acetate. The resulting mixture was added dropwise over 4 hours, and the mixture was kept at the same temperature for 10 hours to give a nonvolatile content of 50.6%,
A resin solution having a viscosity W, a number average molecular weight of 15,000 and an OH number of 28 was obtained. Hereinafter, the obtained vinyl-based polymer solution (I-
It is abbreviated as 6).

The vinyl-based polymer solutions obtained in each of the above production examples were evaluated according to the conventional coating method in accordance with the formulations shown in Tables 1 and 2 in order to evaluate the physical properties of the coating film by the 2-coat 1-bake coating method. A coating material was separately obtained, and then coating and curing was carried out by the following coating method, and physical properties tests were conducted on each item as shown in the same table. The results are summarized in the same table.

Coating method: A surface-treated steel sheet coated with an epoxy ester resin-based electrodeposition primer was used to form a coating film for the intermediate coat surfacer, and each base coat paint adjusted to a viscosity of 10 to 20 seconds (Ford cup # 4/20 ° C) was applied on it. Coating was performed using an air spray gun so that the dry film thickness was 15 to 20 μm. This is left at room temperature for 5 minutes, and then each topcoat paint whose viscosity is adjusted to 20-40 seconds (Ford cup # 4/20 ℃) is applied by an air spray gun to a dry film thickness of 30-40 μm. After stacking for 10 minutes, the polyisocyanate prepolymer curing system was 60 ° C for 30 minutes, and the aminoplast curing system was 100
The product was baked and dried at ℃ for 20 minutes.

The coating film physical property test was performed after baking and drying, after leaving it at room temperature for 3 days.

Judgment criteria ◎… Very good ×… No [Effects of the Invention] As described above, the composition used in the method of the present invention is excellent in coating workability and low-temperature curability as compared with conventional aminoalkyd resin paints and thermosetting acrylic resin paints, and is a one-part composition. It is a 2-coat 1-bake paint that has excellent storage stability as a mold,
The resulting coating film has coating properties of extremely high practicality.

Claims (1)

[Claims] 1. A coating material (base coat) containing a metallic powder and / or a coloring pigment and containing a curable resin as a main component is applied, and then a clear coating containing a curable resin as a main component (on the coated surface). In the coating finishing method of applying a top coat) and then curing, a vinyl polymer having a polymerizable unsaturated bond, each having a number average molecular weight of 1,500 to 50,000, as an essential component of the above base coat coating material ( 20 to 80% by weight of A) and 20 to 80% by weight of an oligomer (B) having a polymerizable unsaturated bond, which is an esterified product of a polyhydric alcohol and (meth) acrylic acid and has a number average molecular weight of 200 to 1,000. % Of the polymerization medium (C)
Using a resin composition for coating containing 0.01 to 10 wt%,
On the other hand, as an essential component of the coating material for the top coat, each in one molecule, respectively, with a polymerizable unsaturated bond,
A vinyl polymer obtained by polymerizing a vinyl monomer having a vinyl monomer having at least one siloxy group and a copolymerizable vinyl monomer other than the vinyl monomer in the presence of a radical generator ( D)
A polyisocyanate compound (E) having reactivity with a hydroxyl group produced from the polymer (D) and a siloxy group dissociation promoting catalyst (F) produced from the polymer (D).
The equivalent ratio of the OH group and the NCO group in the compound (E) (OH group /
NCO group) is 1 / 0.5 to 1/3, and the dissociation promoting catalyst (F) is 0.001 based on the polymer (D).
A coating finishing method, characterized in that a composite cured coating film is formed by using a resin composition for coating contained in an amount of -10% by weight.