JPH1147686A - Formation of double-layered film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To impart an excellent rubbed fault property, waterproof adhesiveness and cold-hot cycle characteristic by forming a continuous powder coating film by drying preliminarly a thermosetting powder coating material and applying onto a matter to be coated, applying a water-dilutive coating material thereto and baking and curing powder coating film and the water-dilutive coating material. SOLUTION: At the time of coating an automobile, the coated film 4 of the thermosetting powder coating material obtained by adding a pigment, a surface regulating agent, etc., to a thermosetting resin and a curing agent is formed on a base material 1 on which a base coat 2 and an intercoat 3 are applied at first in order. The powder coating material is incorporated with a powder solid color coating material and a powder clear coating material and applied by an electrostatic spray coating, etc., and subjected to a predrying with a heating means such as oven to form the continuous powder coating film 4. Then the coating film 5 of the water-dilutive coating material is formed on the powder coating film 4, and the water-dilutive coating material is prepared by incorporating a water-based resin obtained from an acrylic resin, polyester resin, alkyd resin, etc. A double-layered film 10 is formed lastly by taking and curing each coating film 4 and 5.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coating for automobiles, which uses a low-pollution and resource-saving powder coating and a water-based diluting coating and has excellent coating performance, water adhesion resistance and thermal cycle characteristics. Providing a membrane.

[0002]

2. Description of the Related Art In the coating of automobiles, conventionally, a color base paint is applied as a top coat on an undercoated and intermediate coated plate for imparting corrosion resistance and weather resistance, and then this coating film is applied. A two-coat, one-bake coating method (hereinafter referred to as a 2C1B coating method) in which a clear coating is applied by wet-on-wet without curing, and finally, the color base coating and the clear coating obtained by the above coating are cured together. Call). Most of the paints used in this coating method are usually solvent-based paints, that is, solvent-diluted paints, because of their availability.

In recent years, from the viewpoint of environmental protection and the like, the development of a low-pollution and resource-saving paint has been proposed. In view of such a situation, conversion from the solvent-based paint to a water-based paint or a powder paint has been attempted. It is very preferable to use an aqueous paint having a low volatile substance content (that is, a water-dilutable paint) or a powder paint that is easily recovered. In the 2C1B coating method, for example, an aqueous paint is used as the color base paint, or It is conceivable to use a powder coating as the clear coating.

[0004] Examples of the application of the water-based color base paint include JP-A-58-168664 and JP-A-1-287183. Japanese Patent Laid-Open No. 5
Japanese Patent Application Laid-Open No. 8-168664 discloses a color base paint using an aqueous polyurethane dispersant.
No. 83 discloses an aqueous color base paint containing an acrylic emulsion, a urethane emulsion and a crosslinking agent, respectively.

However, any of the color base paints described in the above publications has a problem in the orientation of the pigment contained in the coating film, and causes problems such as irregularities due to the pigment on the surface of the formed coating film. May occur.

[0006] Japanese Patent Application Laid-Open No. 6-233965 discloses a method of applying a powder clear after coating a color base paint.
A coating method for C1B is disclosed. Such a powder coating has the easiness of handling and storage stability of being solid at room temperature, but has a high viscosity when melted by heating, so that it is difficult to apply and it is difficult to obtain a smooth and high-appearing coating film. In the powder coating, special processing such as controlling the particle size distribution of the powder coating is required in order to improve the above-mentioned properties of the coating, so that the number of manufacturing steps naturally increases.

Therefore, as described above, when a powder clear coating film is formed on a color base coating film, traces of particles remain on the outermost surface of the powder coating film after curing even if the particle size distribution of the powder coating material is reduced. Since it remains, irregularities occur on the surface. When light shines on a coating film having an uneven surface, diffuse reflection may occur. Diffuse reflection is not preferred in the field of automotive coatings, since the hue and hue of the final coating can be changed by the viewing angle.

[0008] As another problem, paints for automobiles may be damaged by a cleaning brush during automatic car washing in a car washer. In order to improve the abrasion resistance, it has been proposed to increase the crosslink density at the time of curing of the topcoat paint including the base paint and the clear paint as a countermeasure. Since the elongation is low (that is, the coating film is brittle), the water adhesion resistance is not improved, and it is not possible to cope with tension shrinkage such as a thermal cycle.

[0009]

SUMMARY OF THE INVENTION It is an object of the present invention to overcome the above disadvantages and to provide a low-pollution and resource-saving coating system to provide a high appearance and excellent abrasion resistance, water resistance and thermal cycling characteristics. The purpose is to provide a coating method to be applied.

[0010]

SUMMARY OF THE INVENTION The present invention provides
(I) pre-drying and applying the thermosetting powder coating;
(Ii) making the powder coating a continuous film; (iii) applying a water-dilutable coating on the powder coating; and (iv) baking and curing the powder coating and the water-diluting coating. And a method for forming a multilayer film.

In the present invention, the water-dilutable coating material contains at least one hydroxyl group-containing resin selected from the group consisting of an acrylic resin, a urethane resin, an epoxy resin and a polyester resin. .

In the present invention, "preliminary drying" means heating and drying at 80 to 120 ° C. for 5 to 15 minutes until a continuous film is formed. The coating after predrying is substantially uncured.

[0013]

EFFECT OF THE INVENTION A low-pollution and resource-saving paint system can be used, and high appearance, resistance to water adhesion and thermal cycle characteristics, and high abrasion resistance to a brush for washing in a car washing machine can be imparted. Further, since the water-based coating is provided on the powder coating, the unevenness of the powder coating can be flattened.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in more detail. The base material suitable for the present invention is a metal coated object suitable for a car body such as an automobile (including motorcycles and buses), for example, iron, steel, aluminum, tin, zinc, etc.
And alloys containing these metals, and plated or vapor-deposited products of these metals. The base material used is usually a degreased state or a base material which has been previously subjected to a chemical conversion treatment with a phosphate or a chromate.

[0015] The base material is usually coated with an undercoat,
A suitable intermediate coating is applied to provide weather resistance and flatness. The undercoat is preferably a cationic electrodeposition coating from the viewpoint of corrosion resistance. In addition, the intermediate coating can be performed using a weather-resistant dark gray, gray or white-based conventional intermediate coating.

If desired, a blackout coating for sash may be performed after the above-mentioned undercoating and intermediate coating.

In the method of the present invention, first, a thermosetting powder coating is applied to a substrate on which the above-mentioned undercoating and intermediate coating have been applied in order (step (i)).

The above-mentioned thermosetting powder coating material contains, for example, a thermosetting resin and a curing agent as coating film forming components as main components, and further comprises a pigment, a surface conditioner, and other additives. Powder coatings containing these components include powder solid color coatings and powder clear coatings.

As the thermosetting resin suitable for the powder coating used in the present invention, a thermosetting resin which is solid at room temperature is preferable. For example, acrylic resin, polyester resin (including alkyd resin), epoxy resin And the like. One or more thermosetting resins are preferably selected depending on the use of the coating film to be formed. For example,
Acrylic resin when it is necessary to form a coating film with good weather resistance, polyester resin when it is necessary to form a coating film with excellent coating properties such as impact resistance, or excellent corrosion resistance When it is necessary to obtain a coated film, an epoxy resin is suitable.

The powder coating may optionally contain a mixture of two or more of the above thermosetting resins.

Typical examples of acrylic resin include acrylic acid, methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, ter acrylate
Examples thereof include those obtained by polymerizing acrylic monomers such as t-butyl, glycidyl acrylate, glycidyl methacrylate, and 2-methylglycidyl methacrylate by an ordinary method, and also include copolymers of these with styrene.

Typical examples of the polyester resin include:
Polyhydric alcohols such as ethylene glycol, propanediol, pentanediol, hexanediol, neopentyl glycol, trimethylolpropane, pentaerythritol, and terephthalic acid, isophthalic acid, phthalic acid, succinic acid, glutaric acid, adipic acid, sebacic acid,
Examples thereof include those obtained by reacting a carboxylic acid such as β-oxypropionic acid by a conventional method, and alkyd resins.

A typical example of the epoxy resin is a compound having two or more oxiranes in a molecule, for example, a glycidyl ether resin represented by a condensation reaction product of bisphenol A and epichlorohydrin, An alicyclic epoxy resin, a flocculent aliphatic epoxy resin, a novolak type epoxy resin and the like can be mentioned.

The glass transition temperature (T
g) is preferably 25 to 80 ° C. Tg is 2
When the temperature is lower than 5 ° C., the resin particles are fused to the pulverizer due to heat generated during the pulverization, so that the production is difficult. When the Tg exceeds 80 ° C., it is difficult to obtain surface smoothness in the formed coating film. Are not preferred.

In the powder coating, the thermosetting resin is:
A resin containing both an epoxy group-containing acrylic resin and a polycarboxylic acid is preferred.

The epoxy group-containing acrylic resin includes an epoxy group-containing monomer such as glycidyl acrylate or glycidyl methacrylate in an amount of 35 to 65% by weight and another ethylenically unsaturated monomer which does not react with the epoxy group in an amount of 65 to 35% by weight. And obtained by copolymerizing
A resin having a glass transition temperature of 25 to 80 ° C is exemplified. On the other hand, examples of the polycarboxylic acid include fatty acids, alicyclic and aromatic dicarboxylic acids, and other polycarboxylic acids. For example, decanedicarboxylic acid is preferable.
The epoxy resin / carboxyl group equivalent ratio of these resins and polycarboxylic acids is determined from the viewpoint of curability and coating film hardness.
The range of 10/6 to 10/10 is preferred.

The thermosetting resin is prepared by mixing the epoxy group-containing monomer and the polyvalent carboxylic acid in the above-mentioned ratio and, if desired, adding a coating surface adjusting agent and an anti-repellent agent.
It can be produced by a powder production step known in the art, which comprises kneading, cooling, pulverizing, classification and the like. If the amount of the epoxy group-containing monomer is less than 35% by weight, the degree of freedom in resin design is reduced, which is not practical. If it exceeds 65% by weight, the curability is reduced.

The curing agent suitable for the powder coating used in the present invention can be appropriately selected depending on the type of the functional group of the thermosetting resin. Examples thereof include aliphatic polycarboxylic acids such as blocked isocyanate and sebacic acid, and amino acids. Examples include blast resin, aliphatic acid anhydride, triglycidyl isocyanate, amine-based curing agent, dicyandiamide, phenol resin, epoxy resin, alkylmethylmelamine resin, and benzoguanamine resin.

In the combination of the thermosetting resin and the curing agent, for example, the mixing ratio of the acrylic resin or the polyester resin and the melamine resin is 9: 1 to 5:
5, preferably 8: 2 to 6: 4. If the ratio is more than the above, the strength of the coating film is insufficient, and if the ratio is less than the above, cracks occur in the coating film. Alternatively, the mixing ratio of the thermosetting resin containing a hydroxyl group to the polyisocyanate compound is 0.3: 1 by weight.
~ 1.5: 1 is preferred. If the amount is more than the above, the water resistance decreases, and if the amount is less than the above, poor curing results, which is not preferable.

Pigments suitable for such powder coatings include, for example, titanium dioxide, carbon black, phthalocyanine blue, phthalocyanine green, carbazole violet, anthrapyridine, azo orange, yellow,
Colored pigments such as flavanthrone yellow, isoindoline yellow, azo yellow, indathrone blue, dibromanzathrone red, perylene red, azo red, anthraquinone red, quinacridone red, and violet; barita powder, precipitated barium sulfate, barium carbonate ,
Gypsum, clay, silica, white carbon, diatomaceous earth, talc, magnesium carbonate, extender pigments such as alumina white, gloss white, and satin white, and bright pigments such as aluminum flake and mica powder. The above pigments can be used alone or in combination of two or more.

The powder coating may contain the pigment in an amount of usually 1 to 70% by weight based on the solid content of the resin in the coating (ie, the total amount of the thermosetting resin and the curing agent). .

The additives that can be included in the powder coating include:
Curing catalyst such as dodecylbenzene sulfonic acid, surface conditioner such as silicone or acrylic oligomer (typically, dimethyl silicone, methyl silicone, etc.), antioxidant plasticizer such as benzophenone, ultraviolet absorber, benzoin, anti-sagging Agents, thickeners and the like.

The above additives may be contained in an amount of 0.1 to 5% by weight based on the solid content of the powder coating.

The powder coating may be a conventional powder clear coating.

In the step (i) of the method of the present invention, when a powder clear coating is used, in order to facilitate the volatilization of the volatile matter at the time of forming the coating and to make the coating higher in appearance,
The average particle size is preferably 15 μm or less, and the standard deviation of the particle size distribution is preferably 20 μm or less. Furthermore, in order to effectively prevent blocking of the powder clear coating itself during storage, the average particle size is 0.001 to 10 μm, the glass transition temperature is 50 to 150 ° C., and the dissolution parameter (SP) value is 9
It is preferable to use one in which the resin fine particles of Nos. 1 to 15 are present on at least the surface of the powder particles.

In order to adhere the fine resin particles to the surface of the powder coating particles prepared by the above procedure, fine silica particles may be further added as an external additive. Examples of such silica fine particles include a surface conditioner such as silicone or an acrylic oligomer (typically, dimethyl silicone, methyl silicone, or the like).

The coating film formed from the powder clear paint is
It may be colorless and transparent or colored and transparent. In the case of a colored powder clear paint, the above-mentioned pigment may be contained, for example, in an amount of 1 to 70% by weight based on the resin solid content (that is, the total amount of the base resin and the curing agent) in the paint.

The method for preparing the powder coating is a technique known in the art. It is, for example, after the raw material preparation step, pre-mixed, melt-kneaded, cooled, crushed,
Classifying and filling for adjusting the particle size distribution.

The powder coating produced by the above process is preferably pulverized and classified to an average particle size of 5 to 40 μm.

The above-mentioned powder coatings including the powder solid color coating and the powder clear coating are applied by electrostatic coating, particularly preferably by electrostatic spray coating (for example, corona charging method or tribocharging method), Then, using a conventional heating means such as an oven, at 80 to 120 ° C. for 5 to 15 minutes.
A continuous powder coating is formed by pre-drying for minutes. In forming such a continuous coating film, in order to obtain a desired hue and color depth, the above-mentioned coating and preliminary drying steps are usually repeated in order.

In step (iii) of the method of the present invention, step (i)
A water-dilutable paint is applied on the powder coating formed in i).

The aqueous resin contained in the water-dilutable paint is basically an aqueous solution of an acrylic resin, a polyester resin, an alkyd resin, a urethane resin and a polyamide resin.

Examples of the acrylic resin include acrylic acid, methacrylic acid, and one of derivatives of acrylic acid or methacrylic acid.
Known ones obtained by polymerizing seeds or two or more kinds can be used. Derivatives of acrylic acid or methacrylic acid include 2-hydroxyethyl acrylate,
Hydroxypropyl acrylate, 2-hydroxyethyl methacrylate, hydroxypropyl methacrylate, hydroxybutyl acrylate, hydroxyl-containing derivatives such as hydroxybutyl methacrylate, dimethylaminoethyl acrylate, nitrogen-containing alkyl acrylate or methacrylate such as dimethylaminoethyl methacrylate, acrylic acid amide, Polymerizable amides such as methacrylamide, N-methylolacrylamide,
Examples include polymerizable nitriles such as acrylonitrile and methacrylonitrile, and polymerizable nitriles such as methacrylonitrile, and alkyl acrylates or alkyl methacrylates such as methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, n-butyl acrylate, and 2-ethylhexyl acrylate. it can.

Such acrylic resins include carboxyl group monomers such as crotonic acid, itaconic acid, maleic acid, and fumaric acid, allyl alcohol, methallyl alcohol, Plaxel FM-1 and FM-2 (all of which are available from Daicel Chemical Industries, Ltd.). Hydroxyl group-containing monomers such as industrial products), polymerizable aromatic compounds such as styrene, α-methylstyrene, vinyltoluene and t-butylstyrene, vinyl compounds such as ethylene and vinyl propionate, and dienes such as butadiene and isoprene. One or more compounds may be copolymerized.

As the urethane resin, a known resin obtained by a polycondensation reaction between a diisocyanate compound and a diol compound can be used.

As the diisocyanate compound, 1,2-
Ethylene diisocyanate, 1,4-tetramethylene diisocyanate, 1,6-hesamethylene diisocyanate,
2,2,2,4-trimethyl-1,6-hexamethylene diisocyanate, 2,4,4-trimethyl-1,6-hexamethylene diisocyanate, 1,12-dodecane diisocyanate, ω, ω'-diisocyanatodiisocyanate Propyl ether, cyclobutane-1,3-diisocyanate, cyclohexane-
1,3-diisocyanate, cyclohexane-1,4-diisocyanate, 2,2-diisocyanato-1-methylcyclohexane, 2,6-diisocyanato-1-methylcyclohexane, 3-isocyanatomethyl-3,5,5-trimethylcyclohexyl Isocyanate (isophorone diisocyanate), 2,5-bis-8- (isocyanatomethyl) -8-methyl-1,4-methano-decahydronaphthalene, 3,5-bis (isocyanatomethyl) -8-methyl-1 1,4-methano-decahydronaphthalene, 1,5-bis (isocyanatomethyl)
-4,7-methano-hexahydroindane, 2,5-bis (isocyanatomethyl) -4,7-methano-hexahydroindane, 1,6-bis (isocyanatomethyl) -4,7-methano-
Hexahydroindane, 2,6-bis (isocyanatomethyl) -4,7-methano-hexahydroindane, 1,5-bis (isocyanato) -4,7-methano-hexahydroindane, 2,5-bis ( Isocyanato) -4,7-methano-hexahydroindane, 1,6-bis (isocyanato) -4,7-
Methano-hexahydroindane, 2,6-bis (isocyanato) -4,7-methano-hexahydroindane, dicyclohexyl-2,4'-diisocyanate, dicyclohexyl
-4,4'-diisocyanate, 2,4-hexahydrotoluylene diisocyanate, 2,6-hexahydrotoluylene diisocyanate, perhydro-2,4'-diphenylmethane diisocyanate, perhydro-4,4'-diphenylmethane diisocyanate, ω, ω'-Diisocyanato-1,4-
Diethylbenzene, 1,3-phenylene diisocyanate, 1,4-phenylene diisocyanate, 4,4′-diisocyanatodiphenyl, 4,4′-diisocyanato-3,3 ′
-Dichlorodiphenyl, 4,4'-diisocyanato-3,3'-
Dimethyldiphenyl, 4,4'-diisocyanato-3,3'-
Diphenyl-diphenyl, 2,4'-diisocyanato-3,
3'-diphenylmethane, 4,4'-diisocyanatodiphenylmethane, naphthalene-1,5-diisocyanate, toluylene diisocyanate, 2,4-toluylene diisocyanate, 2,6-toluylene diisocyanate, m-xylylene-diisocyanate, diphenylmethane -2,4 '
Aliphatic, cycloaliphatic, araliphatic and aromatic diisocyanates such as -diisocyanate, diphenylmethane-4,4'-diisocyanate.

On the other hand, examples of the diol compound include aliphatic diols such as neopentyl glycol and hexanediol, dihydric alcohols including 1,2-alkylene oxide, ethylene oxide, propylene oxide, and the like, 1,4-cyclohexanediol, Alicyclic diols such as 4'-dihydroxycyclohexyl-2,2-propane, aromatic dihydric alcohols such as bis (ethoxylated) bisphenol A, bis (propoxylated) bisphenol A, polyethylene oxide diol, polyethylene oxide Polyether diols such as propylene oxide diol, polypropylene oxide diol, and polytetraethylene oxide diol; polyester diols comprising the above-mentioned various diol compounds and polycarboxylic acids or anhydrides; Diols having an acid group such as diols, polycaprolactone diols, and dimethylolpropionic acid are exemplified. Two or more of these diols may be used in combination, but it is preferable to use a diol having an acid group as an essential component from the necessity of making the urethane resin aqueous.

As the polyester resin, a known resin obtained by a polycondensation reaction between polybasic acid and polyhydric alcohol can be used. Examples of the polybasic acid include linear dibasic acids such as oxalic acid, succinic acid, succinic anhydride, adipic acid, azelaic acid, and sebacic acid, phthalic acid, phthalic anhydride, isophthalic acid, terephthalic acid, and tetrahydroanhydride. Aromatic fatty acids such as phthalic acid, hexahydrophthalic acid, hexahydrophthalic anhydride, tetrabromophthalic anhydride, trimellitic acid, trimellitic anhydride, pyromellitic acid, and pyromellitic anhydride, maleic acid, maleic anhydride, fumaric acid And unsaturated dibasic acids such as itaconic acid. These polybasic acids may be used in combination of two or more. Examples of the polyhydric alcohol include glycols such as ethylene glycol, propylene glycol, 1,3-butylene diol, 1,6-hexanediol, diethylene glycol, neopentyl glycol, and triethylene glycol, hydrogenated bisphenol A, bisphenol dihydroxypropyl Ether, glycerin, triethylolethane, trimethylolpropane, pentaerythritol and the like can be used. These polyhydric alcohols may be used in combination of two or more.

As the above-mentioned polybasic acid and polyhydric alcohol, other than those exemplified above, other materials usable as ordinary polyester resin raw materials can be used. Further, for the purpose of adjusting the amount, a monobasic acid or a monohydric alcohol can be used according to a conventional method.

The above-mentioned polyester resin is prepared by using linseed oil, drill oil, euca deer oil, castor oil, coconut oil, hydrogenated coconut oil,
Alkyd resins which have been esterified with known drying oils such as Cardura E (manufactured by Shell Chemical Co., Ltd.), rice sugar fatty acids, tall oil fatty acids, soybean oil, octylic acid and the like, and fatty acids can also be used. A rosin-modified or phenol-modified polyester resin may be used.

The polycarboxylic acids and anhydrides constituting the polyester diols included in the above examples include:
For example, maleic acid, fumaric acid, mesaconic acid, dithraconic acid, itaconic acid, glutaric acid, adipic acid, isophthalic acid, terephthalic acid and the like can be mentioned. As the polycarboxylic acid, a dicarboxylic acid is preferred.

As the polyamide resin, a known resin obtained by a polycondensation reaction between a diamine and a polybasic acid or an amino acid can be used.

As the diamine, ethylenediamine, tetramethylenediamine, hexamethylenediamine, piperazine, 4,4′-diaminodiphenylether, 1,4-diamine
Diaminocyclohexane, 1,12-diaminododecane,
1,7-diaminoheptane, 1,8-diaminonaphthalene and the like.

The polybasic acids include oxalic acid, succinic acid,
Linear dibasic acids such as succinic anhydride, adipic acid, azelaic acid, sebacic acid, phthalic acid, phthalic anhydride, isophthalic acid, terephthalic acid, tetrahydrophthalic anhydride, hexahydrophthalic acid, hexahydrophthalic anhydride, tetrabromo Aromatic acids such as phthalic anhydride, trimellitic acid, trimellitic anhydride, pyromellitic acid, and pyromellitic anhydride, maleic acid, maleic anhydride, fumaric acid,
And unsaturated acids such as itaconic acid.

The amino acids include alanine, histidine, serine, alphinin, aspartic acid, glutamic acid, phenylalanine and the like.

The above polybasic acids and amino acids may be used in combination of two or more.

The water-dilutable paint contains an aqueous resin, an amino resin, a non-yellowing polyfunctional blocked isocyanate compound and the like. The aqueous resin preferably contains a polysiloxy group in order to improve the water resistance of the coating film. As a method for introducing a polysiloxy group into the above various resins,
(1) A method of simultaneously copolymerizing a polysiloxane macromer during the synthesis of the resin, and (2) a method of modifying the resin with polysiloxane.

In the application of the method (1), as a polysiloxane macromer that can be used when copolymerizing an acrylic resin, trimethylsilyl-terminated polymethylsilylpropyl methacrylate can be used. Polysiloxane macromer that can be used when copolymerizing a polyester resin, for example, as a polybasic acid component,
As a polysiloxy group-containing dibasic acid such as dimethylpolysiloxane both terminal dicarboxylic acid, a polyhydric alcohol component,
Polysiloxy group-containing diols such as dimethylpolysiloxane at both ends are exemplified. In the case of copolymerizing a urethane resin, a polysiloxane macromer that can be used is a diamine component, for example, a polysiloxy group-containing diamine such as dimethylpolysiloxydiamine or diphenylpolysiloxydiamine, and a polybasic acid component is a polyester resin. And the above-mentioned polysiloxy group-containing dibasic acids.

In the application of the above method (2), the modification with the polysiloxane is performed by adding a polysiloxane having a functional group such as an acid group, a hydroxyl group, a silanol group, an alkoxysilyl group, an epoxy group, an amino group to the various resins. And heating.

The water-based resin contained in the water-dilutable paint used in the present invention includes the above-mentioned acrylic resin, polyester resin,
An alkyd resin, a urethane resin, a polyamide resin, or the like is made aqueous by a conventional method (that is, an acid group such as a carboxyl group of each resin is neutralized with a basic substance and made aqueous). Examples of the basic substance include monomethylamine, dimethylamine, trimethylamine, monoethylamine, triethylamine, monoisopropylamine, diisopropylamine, diethylenetriamine, triethylenetetramine, monoethanolamine, diethanolamine, triethanolamine, monoisopropanolamine, and diethanolamine. Isopropanolamine, diethylethanolamine, morpholine, methylmorpholine, piperazine, ammonia, sodium hydroxide, potassium hydroxide, lithium hydroxide and the like.

As the aqueous resin which is the main component in the water-dilutable paint of the present invention, at least one selected from the group consisting of the above-mentioned aqueous acrylic resin, urethane resin, epoxy resin and polyester resin is used.

The amino resin contained in the water-dilutable paint used in the present invention acts as a cross-linking agent for the aqueous resin, and includes, for example, an alkyl etherified melamine resin (eg, a methylated melamine resin, n- Butoxy group such as butylated melamine resin and isobutylated melamine resin, methoxy group, ethoxy group, n-butoxy group, t-butoxy group, etc.).

The non-yellowing polyfunctional blocked isocyanate compound contained in the water-dilutable paint used in the present invention has the same effect as the above-mentioned amino resin, and together with the amino resin, the acid resistance of the coating film is improved. Is to improve. Examples of such non-yellowing polyfunctional blocked isocyanate compounds include, for example, those obtained by partially or completely blocking aliphatic polyfunctional isocyanates and alicyclic polyfunctional isocyanates with a blocking agent so as to be easily thermally dissociated. 4'-Diphenylmethane diisocyanate (MDI) Blocked similarly to 4,4'-methylenebis (cyclohexylisocyanate) (hydrogenated MDI) or blocked isocyanate monomer so that it can be thermally dissociated with other monomers. Examples include polymerized polyfunctional blocked isocyanates, with isophorone diisocyanate blocked with methyl ethyl ketone oxime being most preferred.

In the water-dilutable paint used in the present invention,
The mixing ratio (weight ratio) of the aqueous resin to the total amount of the amino resin as the crosslinking agent and the non-yellowing polyfunctional blocked isocyanate compound is 30:70 to 90:10, preferably 50:50 to 80:20. It is. When the amount of the aqueous resin is less than 30% by weight or the amount of the crosslinking agent exceeds 70% by weight, the acid resistance of the coating film is reduced when the amino resin in the crosslinking agent is large, and when the non-yellowing polyfunctional blocked isocyanate compound is large, the coating film is not cured. The strength may be insufficient. On the other hand, when the amount of the aqueous resin exceeds 90% by weight or the amount of the crosslinking agent is less than 10% by weight, poor curing of the aqueous resin occurs, and the water resistance of the coating film decreases.

Further, in the water-dilutable paint, the mixing ratio (weight ratio) of the amino resin as a crosslinking agent and the non-yellowing polyfunctional blocked isocyanate compound is 50:50 to 90:
10, preferably 70:30 to 90:10. When the content of the amino resin is less than 50% by weight, poor curing of the resin occurs to reduce the water resistance of the coating film.
If it exceeds, the acid resistance of the coating film is reduced.

The water-dilutable paint used in the present invention may contain, in addition to the above-mentioned film-forming components, additives known in the art, for example, a curing catalyst such as dodecylbenzenesulfonic acid, a silicone or acrylic oligomer. And the like (typically dimethyl silicone, methyl silicone, etc.), antioxidants such as benzophenone, plasticizers, ultraviolet absorbers, viscosity control agents, defoamers, thickeners and the like.

In the water-dilutable paint, the above additives may be contained in an amount of 0.01 to 5% by weight based on the solid content of the resin in the paint.

In the method of the present invention, the coating film formed by applying the water-dilutable coating material may be colorless and transparent (that is, a clear coating film) or colored (for example, a solid color coating film). You may. When the coating film is colored, a pigment and / or a dye exhibiting a desired color is added to the above-mentioned paint component. Any of such pigments and / or dyes known in the art can be used. When the water-dilutable coating film is a colored coating film, the same pigment as described for the powder coating is applied to the resin solid content in the coating by 1%.
May be included in amounts of up to 70% by weight.

The water-dilutable coating material is diluted with water to a suitable coating viscosity (15 to 90 seconds / 20 ° C./Ford cup # 4) at the time of use.

In step (iii) of the method of the present invention, the above water-dilutable paint may be applied and then pre-dried at 60 to 100 ° C. for 5 to 15 minutes. The heating conditions may vary depending on the water-dilutable paint used.

In step (iv) of the method of the present invention, the powder coating and the water-dilutable coating are subjected to bake hardening. The baking hardening of the coating film is carried out at a temperature of 100 to 200 ° C. by a usual method.
By heating for 10 to 60 minutes. The curing conditions may vary depending on the type of paint used.

[0072]

The present invention will be described below with reference to examples.
The present invention is not limited to the following examples. In the following Preparation Examples and Examples, parts,% and ratios are all
Unless indicated otherwise, parts by weight,% by weight and weight ratio are indicated. Preparation of base resin for paint (i) Preparation of base resin for thermosetting powder clear paint 63 parts by weight of xylene was placed in a 2 L kolben and heated at 130 ° C.
The temperature rose. There, glycidyl methacrylate 55 parts by weight, styrene 25 parts by weight, methyl methacrylate 20
A mixture of 8 parts by weight of t-butylperoxy-2-ethylhexanoate was added dropwise over 3 hours while blowing nitrogen. 30 minutes after the completion of the dropping, t-butylperoxy-2
0.5 parts by weight of -ethylhexanoate was added dropwise over 30 minutes. After aging for 1 hour, the solvent was removed to obtain a solid resin. The solvent removal conditions were as follows: 5 mmHg, 1
It was kept at 30 ° C. for 1 hour. The glass transition temperature of the base resin thus obtained was 50 ° C., and the number average molecular weight was 2500.

(Ii) Production of Non-Cross-Linked Resin Fine Particles In a reaction vessel equipped with a stirrer, a cooler, and a temperature controller, 380 parts by weight of deionized water, a nonionic surfactant MON2
2 parts by weight (manufactured by Sanyo Chemical Co., Ltd.) were charged and dissolved while maintaining the stirring temperature at 80 ° C., and a solution prepared by dissolving 1 part by weight of ammonium persulfate in 10 parts by weight of ionic water as a polymerization initiator was added. Next, a mixed solution comprising 61 parts by weight of methyl methacrylate, 36 parts by weight of styrene, and 3 parts by weight of n-butyl methacrylate was continuously stirred for 60 minutes. Thus, an emulsion having a nonvolatile content of 20% and a particle size of 0.03 to 0.05 μm was obtained. The emulsion was spray-dried to obtain non-crosslinked resin fine particles having a melting parameter of 10, a glass transition temperature of 110 ° C, and an average particle size of 0.03 to 0.05 µm.

(Iii) Production of Acrylic Hydroxy Group-Containing Resin 36 parts by weight of diethylene glycol monobutyl ether and 114 parts by weight of methoxypropanol were charged into a reaction vessel equipped with a stirrer, a temperature controller and a cooling tube, and heated to 11
It was set to 0 ° C. 27 parts by weight of methacrylic acid, styrene 3
A monomer solution consisting of 5 parts by weight, 63 parts by weight of methyl methacrylate, 58 parts by weight of 2-hydroxyethyl methacrylate, 117 parts by weight of n-butyl acrylate, and 9 parts by weight of t-butyl peroxy-2-ethylhexanoate was charged into a reaction vessel. The solution was added dropwise over 3 hours, and the reaction was continued for 2 hours. Thereafter, 28 parts by weight of dimethylethanolamine and 522 parts by weight of deionized water were added to obtain an acrylic hydroxyl group-containing resin. The resulting hydroxyl-containing resin has an acid value of 5
7, the nonvolatile content was 30%, and the number average molecular weight was 8,000.

(Iv) Production of Polysiloxy Group-Containing Acrylic Hydroxyl-Containing Resin 36 parts by weight of diethylene glycol monobutyl ether and 114 parts by weight of methoxypropanol were charged into a reaction vessel equipped with a stirrer, a temperature controller, and a cooling pipe, and heated. 11
It was set to 0 ° C. 27 parts by weight of methacrylic acid, styrene 3
5 parts by weight, methyl methacrylate 63 parts by weight, 2-hydroxyethyl methacrylate 58 parts by weight, n-butyl acrylate 117 parts by weight, FM-0711 (manufactured by Chisso, polydimethylsiloxy methacrylate, molecular weight 1000) 30
A monomer solution consisting of 9 parts by weight of t-butylperoxy-2-ethylhexanoate was added dropwise to the reaction vessel over 3 hours, and the reaction was continued for 2 hours. afterwards,
28 parts by weight of dimethylethanolamine are added to deionized water 52
2 parts by weight were added to obtain a polysiloxy group-containing acrylic hydroxyl group-containing resin. The resulting hydroxyl-containing resin has an acid value of 5
7, the nonvolatile content was 30%, and the number average molecular weight was 8,800.

Next, the following coating composition was prepared using the produced base resin. (A) Preparation of thermosetting powder clear coating composition (I) 70 parts by weight of base resin obtained from (i), 1,10-
Decanedicarboxylic acid (DDA) 23.4 parts by weight, benzoin 1.0 part by weight, polysiloxane surface conditioner YF-391
After mixing 0.3 parts by weight of 9 (manufactured by Toshiba Silicone), the mixture was melted and kneaded in a buscon kneader (manufactured by Buss), pulverized and classified (150 mesh) to obtain a thermosetting powder clear coating composition (I). Obtained. In this powder coating composition, the COOH / epoxy functional group ratio was 0.75, and the average particle size of the resin in the coating was 25 μm. The particle size was measured using Microtrack MK-2 (manufactured by Nikkiso Co., Ltd.).

(B) Thermosetting Powder Clear Coating Composition
Preparation of (II) In the same manner as in Example 1, a powder coating having an average particle size of 9 μm was produced by jet pulverization. Next, this powder coating 10
2 parts by weight of the non-crosslinked resin fine particles obtained in Production Example 6 were added to 0 parts by weight. By dry-mixing with a Henschel mixer, a thermosetting powder clear coating composition (II) having the non-crosslinked resin fine particles adhered to the powder coating particle surfaces was obtained. In this powder clear coating composition, the COOH / epoxy functional group ratio was 0.75.

(C) Thermosetting Powder Solid Color Paint Composition
Preparation of (III) 70 parts by weight of the base resin obtained from the above (i), 1,10-
Decanedicarboxylic acid (DDA) 23.4 parts by weight, benzoin 1.0 parts by weight, polysiloxane surface conditioner YF-3919
(Manufactured by Toshiba Silicone) 0.3 parts by weight, titanium dioxide 40
After mixing the parts by weight, the mixture was melt-kneaded in a buscon kneader (manufactured by Buss), pulverized and classified (150 mesh) to obtain a thermosetting powder solid coating composition. In this powder coating composition, the COOH / epoxy functional group ratio was 0.75, and the average particle size of the coating was 25μ. The particle size was measured using Microtrack MK-2 (manufactured by Nikkiso Co., Ltd.).

(D) Water-dilutable clear coating composition (1)
333 parts by weight of the acrylic hydroxyl group-containing resin prepared above, 20 parts by weight of Cymel 303 (manufactured by Mitsui Cytec, acrylated melamine resin), 35 parts by weight of a methylethylketoxime-blocked isophorone diisocyanate compound, 0.1 part by weight of dibutyltin dilaurate And 0.2 parts by weight of p-toluenesulfonic acid were mixed to prepare a water-dilutable clear coating composition (1). The obtained clear coating composition (1) was used with Ford cup # 4 before use.
Dilute with deionized water at 0 ° C. for 30 seconds.

(E) Water-dilutable clear coating composition (2)
Preparation of Polyacryloxy Group-Containing Acrylic Hydroxyl-Containing Resin 333 Instead of the Acrylic Hydroxyl-Containing Resin
Except for using parts by weight, in the same manner as in the above (d),
A water-dilutable clear coating composition (2) was prepared. The resulting clear coating composition (2) was diluted with deionized water using a Ford cup # 4 at 20 ° C. for 30 seconds before use.

(F) Water-dilutable clear coating composition (3)
Preparation of Polysiloxy Group-Containing Acrylic Hydroxyl-Containing Resin 67
Parts by weight, 212 parts by weight of Neoretz XR-9603 (manufactured by ICI, urethane emulsion, nonvolatile content 33%), Cymel 3
03 (Mitsui Cytec, acrylated melamine resin) 1
0 parts by weight and 0.2 parts by weight of p-toluenesulfonic acid were mixed to prepare a water-dilutable clear coating composition (3). The obtained clear coating composition (3) was diluted with deionized water using a Ford cup # 4 at 20 ° C. for 30 seconds before use.

(G) Water-dilutable solid color paint composition
Preparation of (4) 335 parts by weight of acrylic hydroxyl group-containing resin, 100 parts by weight of CR-97 (titanium pigment manufactured by Ishihara Sangyo Co., Ltd.), 67 deionized water
Glass beads were added to a titanium pigment dispersion liquid consisting of parts by weight, and dispersed by an SG mill for 30 minutes to remove the glass beads to obtain a titanium pigment paste. Titanium pigment paste 2
50 parts by weight, 10 parts by weight of a polysiloxy group-containing acrylic hydroxyl group-containing resin, 10 parts by weight of Cymel 303, 15 parts by weight of a methyl ethyl ketone oxime-blocked isophorone diisocyanate compound, 0.1 part of dibutyltin dilaurate.
05 parts by weight of p-toluenesulfonic acid and 0.1 parts by weight of p-toluenesulfonic acid.
It was prepared in the same manner as described above.

Example 1 Hereinafter, a method for forming a multilayer film according to the present invention will be described with reference to FIG. 0.8 mm thick, 1
0 cm x 50 cm dull steel plate 1 and cationic electrodeposition paint 2
("Power Top U-50" manufactured by Nippon Paint Co., Ltd.) is electrodeposited so as to have a dry film thickness of about 25 μm.
Bake for a minute. Next, on the obtained electrodeposition coating film 2, an intermediate coating material 3 (“Olga P-2” manufactured by Nippon Paint Co., Ltd.)
Is spray-coated so as to have a dry film thickness of about 40 μm,
Bake at 140 ° C. for 30 minutes.

The thermosetting powder clear coating composition (I) 4 prepared in the above (a) was applied on the base material formed as described above so that the dry film thickness became 20 μm. Thereafter, the film was dried at 110 ° C. for 5 minutes to form a continuous film. Next, the water-diluted clear coating composition (1) 5 prepared in (d) above is applied on the powder clear coating film so as to have a dry film thickness of 25 μm, and baked at 140 ° C. for 30 minutes to form a multilayer. The film 10 was obtained.

Example 2 Example 1 was repeated except that the water-dilutable clear coating composition (1) applied to the second layer was replaced with the water-dilutable clear coating composition (2) prepared in (e). Similarly, a multilayer film was obtained.

Example 3 Example 1 was repeated except that the water-dilutable clear coating composition (1) applied to the second layer was replaced with the water-diluted clear coating composition (3) prepared in (f). Similarly, a multilayer film was obtained.

Example 4 A water-diluted solid color paint composition (4) prepared from (g) of the water-diluteable clear paint composition (1) to be coated on the second layer
A multilayer film was obtained in the same manner as in Example 1 except that the above procedure was replaced.

Examples 5 to 7 The same procedures as in Example 1 were carried out except that the thermosetting powder clear coating composition (I) applied to the first layer was replaced with the thermosetting powder clear coating composition (II). In the same way as 1-3,
A multilayer film was obtained.

Examples 8 to 10 The same procedures as in Examples 8 to 10 were carried out except that the thermosetting powder clear coating composition (I) applied to the first layer was replaced with a thermosetting powder clear coating composition (III). A multilayer film was obtained in the same manner as in Examples 1 to 3.

Comparative Example In Example 1, the thermosetting powder clear coating composition (I) prepared in (a) was applied to a dry film thickness of 20 μm and baked at 140 ° C. for 30 minutes. Thus, a single-layer film of a thermosetting powder clear paint was obtained.

Evaluation Method The coating film performance of the multilayer film or the single-layer film produced in Examples 1 to 10 and Comparative Example was evaluated by the following method. (1) Acid Resistance Test Six drops of 1N sulfuric acid were dropped on the surfaces of the coating films prepared in Examples 1 to 10 and Comparative Example, and left for 24 hours.
The change of the coating film surface after 24 hours was visually evaluated according to the following evaluation criteria. The results are summarized in Table 1. Evaluation criteria: No abnormalities: ○ There is whitening or gloss blur: △ There is blistering or cracking: ×

(2) Appearance evaluation (gloss measurement) The surfaces of the coating films prepared in Examples 1 to 10 and Comparative Example were measured for gloss at 60 ° using a gloss meter manufactured by Suga Test Instruments. The results are summarized in Table 1.

(3) Water Resistance Test The substrates having the coating films produced in Examples 1 to 10 and Comparative Example were immersed in warm water at 40 ° C. and left for 10 days. Thereafter, changes in the coating film surface were visually evaluated according to the following evaluation criteria. The results are summarized in Table 1. Evaluation criteria: No abnormalities: ○ Blisters and cracks: ×

[0094]

[Table 1]

In Table 1 above, the abbreviations for the types of paints used are as follows. (I): Thermosetting powder clear coating composition (I) (II): Thermosetting powder clear coating composition (II) (III): Thermosetting powder solid color coating composition (III) ( 1): Water-dilutable clear coating composition (1) (2): Water-dilutable clear coating composition (2) (3): Water-dilutable clear coating composition (3) (4): Water-diluted solid color Paint composition (4)

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view of a multilayer film manufactured by a multilayer film forming method of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Dull steel plate, 2 ... Cathodic electrodeposition coating, 3 ... Intermediate coating, 4 ... Thermosetting powder clear coating (I) coating, 5 ...
Coating film of water-dilutable clear coating composition (1), 10 ... multilayer film.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI B32B 27/30 B32B 27/30 A 27/36 27/36 27/38 27/38 27/40 27/40

Claims (5)

[Claims] 1. An object to be coated is coated with (i) a thermosetting powder coating, (ii) a preliminary drying of the powder coating to form a continuous film, and (iii) a powder coating. A method of forming a multilayer film, comprising applying a water-dilutable coating material thereon, and (iv) baking and curing the powder coating film and the water-dilutable coating film. 2. The method according to claim 1, wherein the substrate is a substrate on which an undercoat and an intermediate coat are sequentially formed. 3. The pre-drying condition is 80 to 120 ° C. and 5 times.
2. The method of claim 1, wherein the time is between about 15 minutes. 4. The water-dilutable paint mainly comprises at least one hydroxyl-containing resin selected from the group consisting of aqueous acrylic resin, urethane resin, epoxy resin and polyester resin. Item 7. The method according to Item 1. 5. An article having a multilayer film formed by the method according to claim 1.