JPH04337376A - Method for forming coating film - Google Patents

Abstract

PURPOSE:To form a coating film having excellent finishing appearance, recoatability, etc., by successively forming a specific colored base coat and a specified clear top coat on a substrate by a two coat one bake method. CONSTITUTION:A substrate is coated with (A) a colored base coating composition containing (i) a hydroxyl group-containing vinylic resin, (ii) an amino resin, (iii) a polyorganosiloxane having on the average two or more of silanol groups and/or alkoxysilane groups in one molecule and having a number-average mol.wt. of >=1000, (iv) metal flake powder and/or mica powder, and (v) an organic solvent as essential components, and subsequently with (B) a clear top coating composition containing (vi) a resin having silanol groups and/or hydrolyzable groups directly bonded to silicon atoms, hydroxyl groups and epoxy groups, and (vii) an organic solvent as essential components to form a coating film having an improved appearance.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a new method for forming a coating film, and more particularly, to a method for forming a coating film that has an excellent finished appearance.

0002

BACKGROUND OF THE INVENTION Conventionally, there has been a demand for improvements in finished appearance, coating performance, etc. in top coats, particularly top coats for automobile exterior panels. In addition, there is a strong demand for the development of low-temperature curing coatings for the purpose of reducing energy costs and for the purpose of making it possible to apply the same paint to the exterior of automobiles where steel plate base materials and plastic base materials are integrated. There is.

[0003] The currently mainstream paints for automobiles are thermosetting acrylic resin/melamine resin systems, thermosetting polyester resin/melamine resin systems, etc.
These paints are close to the limit in terms of high level smoothness, and
There is also room for improvement in the performance of various coating films. Further, there is a problem that the low temperature curing property is not sufficient. Furthermore, there are still problems such as peeling of the paint film and environmental pollution due to condensates (such as formalin) generated during baking.

The present applicant proposed a coating composition for automobiles in Japanese Patent Laid-Open No. 2-160879 as a coating material with excellent low-temperature curability. The paint is a silicone paint composition made by blending a metal chelate compound into a copolymer containing a polysiloxane macromonomer containing a silanol group and/or an alkoxysilane group and a vinyl monomer containing an oxirane group as monomer components. , this is a metallic base coat (paint containing aluminum flake pigment)
/Apply to both clear top coats, 2 coats/1 coat
Paints finished using the baking method have the disadvantage that the metallic base coat is affected by the clear top coat and the orientation of the aluminum flake pigment changes, making it impossible to obtain a paint film with an aluminum luster (sparkling, white). In addition, when a thermosetting acrylic resin/melamine resin based metallic base coat is used, the clear top coat begins to harden before the metallic base coat begins to harden, resulting in wrinkles, wrinkles, etc. on the paint film. It has the disadvantage of causing defects.

[0005] Furthermore, when a defect occurs in the finish coating, the same type of metallic base coat and clear top coat are usually recoated to repair the defective part.
Those using the above-mentioned silicone-based coating compositions also had the problem that adhesion between the coating films (top clear coat and metallic base coat to be recoated) was insufficient.

[0006]

[Means for Solving the Problem] As a result of extensive research in order to eliminate the above-mentioned drawbacks, the present inventors have found that by forming a clear top coat on a specific colored base coat, the finish quality, recoatability, etc. The present inventors have discovered that it is possible to provide a coating film with excellent properties, and have completed the present invention.

That is, the present invention provides a top coating method in which a colored base coat and a clear top coat are sequentially formed on a material and finished using a two-coat, one-bake method, in which the coating composition for forming the colored base coat includes: (1) a hydroxyl group-containing vinyl resin; (2) Amino resin (3) Polyorganosiloxane with a number average molecular weight of 1000 or more and having an average of two or more silanol groups and/or alkoxysilane groups in one molecule (4) Metal flake powder and/or mica powder and (5)
) A coating composition for forming a clear top coat using a coating composition containing an organic solvent as an essential component, (1) a resin having a silanol group and/or a hydrolyzable group directly bonded to a silicon atom; ) A coating film forming method characterized by using a coating composition containing an organic solvent as an essential component.

Next, the method of the present invention will be specifically explained.

Colored base coat The colored base coat is made of (1) hydroxyl group-containing vinyl resin (
2) Amino resin (3) Polyorganosiloxane with a number average molecular weight of 1000 or more and having an average of two or more silanol groups and/or alkoxysilane groups in one molecule (hereinafter sometimes simply abbreviated as "polyorganosiloxane") (4
) Metal flake powder and/or mica powder (hereinafter sometimes simply referred to as "metal flakes") (5) Formed from a base coat coating composition containing an organic solvent as an essential component.

The hydroxyl group-containing vinyl resin has a hydroxyl group in its molecule and preferably has a hydroxyl value of about 20 to 200, preferably about 50 to 150. When the hydroxyl value is less than 20, the curing speed of the base coat film becomes slower than the curing speed of the top coat film, and the top coat film cures before the base coat film hardens, resulting in wrinkles etc. on the cured top coat film. It is undesirable because it causes defects and the finished appearance of the coating film is deteriorated, and the coating film performance (water resistance, impact resistance, etc.) deteriorates due to insufficient curing. On the other hand, if the hydroxyl value is greater than about 200, a large amount of unreacted hydroxyl groups will remain in the coating film, resulting in a decrease in coating film performance (water resistance, weather resistance, etc.), which is not preferable.

[0011] The hydroxyl group-containing vinyl resin may contain a carboxyl group in its molecule. In particular, carboxyl groups have the effect of increasing the reaction rate between hydroxyl groups and amino groups, between hydroxyl groups and silanol groups and/or alkoxysilane groups, and between silanol groups and/or alkoxysilane groups and improving the finish of the coating film. The carboxyl group has a resin acid value of about 0 to 50, preferably about 5 to 20.

The hydroxyl group-containing vinyl resin is a (co)polymer obtained by radical polymerization of the hydroxyl group-containing polymerizable unsaturated monomer (a) and, if necessary, other polymerizable unsaturated monomers (b). Combination can be used.

Examples of the hydroxyl group-containing polymerizable unsaturated monomer (a) include (a-1) to (a-5).

(a-1) Hydroxy alkyl vinyl ether: hydroxybutyl vinyl ether, etc. (a-2
) allyl alcohol and methallyl alcohol, (a-3
)(meth)acrylic acid hydroxyalkyl ester:
Hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, hydroxybutyl (meth)acrylate, etc. (a-4) (Poly)alkylene glycol monoacrylate: ethylene glycol monoacrylate, polyethylene glycol monoacrylate, etc., (a-5 ) (a-1) to (a-4) and lactones (e.g., ε-caprolactone, γ-valerolactone), etc.;

In addition, other polymerizable unsaturated monomers (b)
For example, methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate,
C1-24 alkyl or cycloalkyl esters of (meth)acrylic acid such as hexyl (meth)acrylate, octyl (meth)acrylate, lauryl (meth)acrylate, cyclohexyl (meth)acrylate, etc.: (meth)acrylic acid; crotonic acid, itaconic acid,
Carboxy group-containing compounds such as (anhydrous) maleic acid, fumaric acid, 2-carboxyethyl (meth)acrylate, etc.: Vinyl aromatic compounds such as styrene vinyl toluene, etc.: perfluorobutylethyl (meth)acrylate, perfluoroiso Perfluoroalkyl (meth)acrylates and (meth)acrylonitrile such as nonylethyl (meth)acrylate, perfluorooctylethyl (meth)acrylate, olefins,
Examples include fluoroolefins, vinyl esters, cyclohexyl or alkyl vinyl ethers, and aryl ethers.

The hydroxyl group-containing vinyl resin can be produced by a conventionally known method, for example, by adding a mixture of the above monomer (a) and, if necessary, other monomers (b) to a substantially inert organic solvent. In the presence of a radical polymerization initiator, about 80 to 22
This can be carried out by continuing the reaction at 0°C for about 4 to 18 hours.

Examples of organic solvents include aromatic hydrocarbons such as xylene and toluene; esters such as ethyl acetate, propyl acetate, and butyl acetate; ketones such as acetone and methyl ethyl ketone; ethylene glycol, cellosolve, butyl cellosolve, and cellosolve acetate. Examples include ether systems such as. These organic solvents can be used alone or in combination of two or more.

Further, usable radical polymerization initiators include, for example, 2,2-azoisobutyronitrile, 2,
Examples include azo initiators such as 2'-azobis(2,4-dimethylvaleronitrile); peroxide initiators such as benzoyl peroxide, lauryl peroxide, and tert-butyl peroctoate.

The molecular weight of the hydroxyl group-containing vinyl resin may be in the range of about 2,000 to 80,000, preferably about 4,000 to 20,000 in terms of number average molecular weight. When the molecular weight is less than about 2,000, the melt viscosity of the base coat decreases too much during baking and the orientation of the metal flakes changes, making it difficult to obtain a coating with a metallic feel.On the other hand, when the molecular weight exceeds about 80,000, the coating workability decreases. This is not preferable because it reduces the

Amino resins are used as crosslinking agents, and include methylolated amino resins obtained by reacting amino components such as melamine, urea, benzoguanamine, acetoguanamine, steroguanamine, spiroguanamine, and dicyandiamide with aldehydes. . Examples of aldehydes include formaldehyde, paraformaldehyde, acetaldehyde, and benzaldehyde. Furthermore, etherification of this methylolated amino resin with a suitable alcohol can also be used. Examples of alcohols used for etherification include methyl alcohol,
Examples include ethyl alcohol, n-propyl alcohol, i-propyl alcohol, n-butyl alcohol, i-butyl alcohol, 2-ethylbutanol, and 2-ethylhexanol. As the amino resin, melamine with a high degree of etherification, that is, melamine with an average of 3 or more methyl ethers per triazine nucleus, or melamine resin in which a part of the methoxy group is replaced with an alcohol having 2 or more carbon atoms is used. can. Among them, low molecular weight melamine having an average degree of condensation of about 2 or less and a mononuclear proportion of about 50% by weight or more is preferable from the viewpoint of high solidity. Preferably, a curing catalyst is added.

[0021] Polyorganosiloxane is used as a crosslinking agent for hydroxyl group-containing vinyl resins together with the amino resin, and also as a self-crosslinking resin, and has an average of 2 or more per molecule, preferably 2 to 2 polyorganosiloxanes. Contains 10 silanol groups and/or alkoxysilane groups and has a number average molecular weight of 1000 or more, preferably 1000 to 5000
0 polyorganosiloxane. This polyorganosiloxane preferably has a ladder structure part,
For example, it can be obtained by hydrolyzing and condensing a silane compound containing a trifunctional silane represented by the following general formula (I) as an essential component.

RX Si(OR')4-X...(I)
(In the formula, R and R' may be the same or different,
It represents a hydrocarbon group having 1 to 13 carbon atoms, and x represents 1. ) Examples of the above R and R' include a methyl group, an ethyl group, a propyl group, a butyl group, a phenyl group, and the like.

The above-mentioned silane compound to be hydrolyzed and condensed may be only the trifunctional silane of formula (I), but if necessary, in addition to the trifunctional silane, It may contain a difunctional or monofunctional silane having a value of 2 or 3, in which (I)
It is preferable that the silane of the formula is contained in an amount of 30% by weight or more, more preferably 80% by weight or more.

Representative examples of the silane of formula (I) include methyltrimethoxysilane, methyltriethoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane, isobutyltrimethoxysilane, isobutyltriethoxysilane, and ethyltrimethoxysilane. can be mentioned. Examples of difunctional or monofunctional silanes that may be used in combination with the silane of formula (I) include dimethyldimethoxysilane, diphenyldimethoxysilane, diphenyldiethoxysilane, diisobutyldimethoxysilane, diisobutyldipropoxysilane, and trimethylmethoxysilane. can be mentioned.

The hydrolytic condensation of the silane compound is carried out by mixing the silane compound with a water-soluble solvent (for example, an alcohol solvent, a cellosolve solvent, etc.) as necessary, and adding a mineral acid such as hydrochloric acid, sulfuric acid, or phosphoric acid, or formic acid. , in the presence of an organic acid such as acetic acid and water, preferably at a pH of 6 or below, at 20°C.
This is carried out by allowing the hydrolysis and condensation reactions to proceed while stirring at about 100° C. for about 30 minutes to 20 hours.

The molecular weight of the polyorganosiloxane can be adjusted as appropriate by adjusting the amount of water used, the type and amount of catalyst, reaction temperature, reaction time, etc.

[0027] In the polyorganosiloxane resin, the number of silanol groups and/or alkoxysilane groups is 1.
If the average number is less than 2 in a molecule, the curing speed of the base coat film will be slower than the curing speed of the top coat film, and the top coat film will begin to harden before the base coat film is cured, resulting in a hardened top coat film. It has the disadvantage that it causes defects such as sagging and deteriorates the finished appearance of the coating film.

Furthermore, when the number average molecular weight of the polyorganosiloxane resin is less than 1000, there is a drawback that the melt viscosity of the base coat decreases during baking, the orientation of the metal flakes changes, and a coating film with a metallic feel cannot be obtained.

The metal flakes give a metallic feel to the coating film, and examples of the metal flakes include aluminum flakes, nickel flakes, copper flakes,
Examples include brass flakes and chrome flakes, and examples of mica powder include pearl mica and colored pearl mica.

Examples of organic solvents include aromatic hydrocarbons such as xylene and toluene; esters such as ethyl acetate, propyl acetate, and butyl acetate; ketones such as acetone and methyl ethyl ketone; ethylene glycol, cellosolve, butyl cellosolve, and cellosolve acetate. Examples include ether systems such as. These organic solvents can be used alone or in combination of two or more. Further, from the viewpoint of finishability, those having a boiling point of about 150° C. or lower are preferable, but are not limited thereto.

In the base coat coating composition, the blending ratio of the hydroxyl group-containing resin, amino resin, and polyorganosiloxane as a binder is based on 100 parts by weight of the total amount of the three components (resin solid content), 5 parts by weight of the hydroxyl group-containing resin, ~
90 parts by weight, preferably 30-60 parts by weight, 5-50 parts by weight of amino resin, preferably 10-40 parts by weight, 1-40 parts by weight of polyorganosiloxane, preferably 5-30 parts by weight.
Parts by weight, more preferably 5 to 20 parts by weight.

If the amount of the hydroxyl group-containing resin is less than 5 parts by weight, the adhesion to the substrate will decrease, while if it exceeds 90 parts by weight, the finished appearance of the coating film and the coating performance (water resistance, processability, etc.) will deteriorate. decreases. If the blending ratio of the amino resin is less than 5 parts by weight, the crosslinking density of the hydroxyl group-containing resin will be low, resulting in poor water resistance and
Impact resistance is significantly impaired, and if more than 50 parts by weight is added, problems such as decreased mechanical properties and adhesion to the substrate will occur. Furthermore, if the blending ratio of organopolysiloxane is less than 1 part by weight, the effect of accelerating the curing speed of the base coat film is small and the finished appearance of the paint film cannot be improved. Sexuality decreases.

In addition to the above-mentioned components, the base coat coating composition may optionally contain organic pigments, inorganic pigments, pigment dispersants, polymer particles, ultraviolet absorbers, coating surface conditioners, curing catalysts, and cellulose acetate. (and derivatives thereof),
It may also contain other paint additives.

[0034] Pigments that may be contained in the paint include:
For example, organic pigments (e.g., quinacridone-based pigments such as quinacridone red, azo-based pigments such as pigment red, phthalocyanine-based materials such as phthalocyanine blue, phthalocyanine green, etc.), inorganic pigments (e.g., titanium oxide, barium sulfate,
(calcium carbonate, baryta, clay, silica, etc.), carbon pigments (carbon black), etc.

Clear Top Coat The clear top coat has silanol groups and/or hydrolyzable groups directly bonded to silicon atoms (hereinafter referred to as "
abbreviated as "hydrolyzable silyl group". ) having a resin (hereinafter referred to as
Abbreviated as "base resin for top coat." ) and an organic solvent as essential components.

The hydrolyzable group possessed by the base resin for top coat is a residue that can be hydrolyzed in the presence of water to produce a silanol group, such as a C1-5 alkoxy group; a phenoxy group, a tolyloxy group, Aryloxy groups such as paramethoxyphenoxy, paranitrophenoxy, benzyloxy; acyloxy groups such as acetoxy, propionyloxy, butanoyloxy, benzoyloxy, phenylacetoxy, formyloxy, and N(R1 )2, -ON(R1)2, -
ON=C(R1)2, -NR2COR1 (wherein, each R1 is the same or different and represents a C1-8 alkyl group, aryl group, or aralkyl group, and R2
represents H and a C1-8 alkyl group. ), etc.

The base resin for the top coat has a silanol group and/or a hydrolyzable silyl group in the molecule, and preferably has excellent curability and coating performance (acid resistance, scratch resistance, weather resistance, etc.). It is a resin that has at least one silanol group and/or hydrolyzable silyl group in one molecule because it can form a coating film. Types of the resin include, for example, vinyl polymers, polyester resins, and polyethers. Examples include polyester resins.The molecular weight of these resins is about 5,000 to 100 in the case of vinyl polymers.
,000, preferably in the range of about 6,000 to 20,000, and in the case of polyester and polyether polyesters, about 1,000 to 30,000, preferably about 2
It is desirable to have a number average molecular weight in the range of ,000 to 10,000.

In the base resin for the top coat used in the present invention, it is preferable to use a vinyl polymer that exhibits excellent weather resistance, acid resistance, and scratch resistance among the above-mentioned resins. The vinyl polymer will be described below.

The vinyl polymer is a vinyl monomer (c) obtained by radical polymerization of vinyl monomers (c) having silanol groups and/or hydrolyzable groups.
), copolymers of vinyl monomers (c) and (d) obtained by radical polymerization reaction of vinyl monomers (c) and other vinyl monomers (d), pre-copolymers of vinyl monomers (c) and (d), First, a vinyl polymer having a functional group is produced, and then a group that reacts complementary to the functional group of the polymer and a silanol and/or hydrolyzable silyl group (the group reacts complementary to [For example, a copolymer of glycidyl (meth)acrylate and other vinyl monomer (d) with γ-amino Vinyl monomers (d) other than those made by reacting propyltrimethoxysilane or (meth)acrylic acid with the acid monomer component that is the (meth)acrylic acid.
A product prepared by reacting a copolymer with γ-glycidoxypropyltrimethoxysilane, etc.) can be used.

Examples of the vinyl monomer (c) include γ-(meth)acryloxyethyltrimethoxysilane,
γ-(meth)acryloxypropyltrimethoxysilane, γ-(meth)acryloxypropyltriethoxysilane, γ-(meth)acryloxypropyltripropoxysilane, γ-(meth)acryloxypropylmethyldimethoxysilane, γ- (meth)acryloxypropylmethyldiethoxysilane, γ-(meth)acryloxypropylmethyldipropoxysilane, γ-(meth)acryloxybutylphenyldimethoxysilane, γ-(meth)acryloxybutylphenyldiethoxysilane, γ -(meth)acryloxybutylphenyldipropoxysilane, γ
-(meth)acryloxypropyldimethylmethoxysilane, γ-(meth)acryloxypropyldimethylethoxysilane, γ-(meth)acryloxypropylphenylmethylmethoxysilane, γ-(meth)acryloxypropylphenylmethylethoxysilane, γ - acrylic silane compounds such as (meth)acryloxypropyltriacetoxysilane, vinyl silane compounds such as vinyltrimethoxysilane, vinyltriethoxysilane, etc.;
Allylsilane compounds such as allyltriethoxy, 2
Examples include styrylsilane compounds such as -styrylethyltrimethoxysilane. In addition, these monomers and, for example, silane compounds (such as trimethoxysilane,
It also includes those having a radically polymerizable unsaturated group, a cyclosane bond, and a silanol and/or hydrolyzable silyl group in the molecule obtained by reacting with triethoxysilane, etc.).

Other vinyl monomers (d) include, for example, methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, propyl acrylate, propyl methacrylate, butyl acrylate, butyl methacrylate, Esters of acrylic acid or methacrylic acid and monohydric alcohols having 1 to 22 carbon atoms, such as 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, lauryl acrylate, lauryl methacrylate, stearyl acrylate, stearyl methacrylate; 2-hydroxyethyl, 2-hydroxyethyl methacrylate, hydroxypropyl (meth)acrylate, butanediol monoacrylate, "Plaxel FM-1"
”, “Plaxel FM-2”, “Plaxel FM-3”
, "Plaxel FA-1", "Plaxel FA-2",
"Plaxel FA-3" (both manufactured by Daicel Chemical Co., Ltd.)
Manufacturer, trade name, caprolactone-modified (meth)acrylic acid 2
hydroxyl group-containing vinyl monomers such as acrylic acid, methacrylic acid, (anhydrous) maleic acid; acrylamide, methacrylamide, N-methylolacrylamide,
Amide vinyl monomers such as N-methylol methacrylamide; dimethylaminoethyl methacrylate, 2-diethylamine ethyl methacrylate, methacrylic acid te
Amino vinyl monomers such as rt-butylaminoethyl; aromatic vinyl monomers such as styrene and vinyltoluene; (meth)acrylonitrile monomers such as acrylonitrile and methacrylonitrile, perfluorobutylethyl (meth)acrylate, perfluoroisononylethyl (meth)acrylate, perfluoroalkyl vinyl monomers such as perfluorooctylethyl (meth)acrylate, and fluoroolefins such as chlorotrifluoroethylene; cyclohexyl or alkyl vinyl ethers; aryl ethers; vinyl esters; olefins: etc. Examples include compounds having one polymerizable unsaturated bond in one molecule.

The base resin for top coat used in the present invention may also be one in which at least one group selected from hydroxyl group, carboxyl group, amino (amide) group, etc. is introduced. The use of resins into which these groups have been introduced has the advantage of improved curability and improved coating film performance such as acid resistance, scratch resistance, and weather resistance. As a method for introducing these groups into a resin, for example, in the production of a vinyl polymer, a hydroxyl group-containing vinyl monomer, a carboxyl group-containing vinyl monomer, and an amino (or amide) type vinyl monomer are used as the other vinyl monomer (d) component. It can be introduced by using vinyl monomers. When using these monomer components, each monomer component accounts for about 5 to 50% by weight, preferably about 10 to 4% by weight, based on the vinyl polymer.
It is used in a range of 0% by weight.

Examples of organic solvents include hydrocarbon solvents such as heptane, toluene, xylene, octane, and mineral spirits; esters such as ethyl acetate, n-butyl acetate, isobutyl acetate, methyl cellosolve acetate, and butyl carbitol acetate; solvents, ketone solvents such as methyl ethyl ketone, methyl isobutyl ketone, diisobutyl ketone, ethanol, isopropanol,
Alcohol solvents such as n-butanol, sec-butanol, and isobutanol, and ether solvents such as n-butyl ether, dioxane, ethylene glycol monomethyl ether, and ethylene glycol monoethyl ether can be used.

The clear coating composition used in the clear top coat of the present invention can be obtained by dissolving or dispersing the base resin for the top coat in an organic solvent. Moreover, this product can be used as a non-aqueous dispersion type coating composition using it as a dispersion stabilizer.

[0045] In addition to the base resin and organic solvent described above, curing catalysts for silanol groups and/or hydrolyzable silyl groups, stabilizers, etc. may be added to the clear coating composition as required.

Examples of the curing catalyst include p-toluenesulfonic acid, dodecylbenzenesulfonic acid, trichloroacetic acid, phosphoric acid, mono-n-propyl phosphoric acid, monoisopropyl phosphoric acid, mono-n-butyl phosphoric acid, monoisobutyl phosphoric acid, mono- Monoalkyl phosphoric acid such as -tert-butyl phosphoric acid, monooctyl phosphoric acid, monodecyl phosphoric acid, di-n-propyl phosphoric acid, diisopropyl phosphoric acid, di-n-butyl phosphoric acid, diisobutyl phosphoric acid, di-tert-butyl phosphoric acid, dioctyl phosphoric acid, didecyl phosphoric acid dialkyl phosphoric acid, β-hydroxyethyl (meth)acrylate phosphate ester, mono-
n-propyl phosphite, monoisopropyl phosphite, mono-
n-butyl phosphorous acid, monoisobutyl phosphorous acid, mono-te
Monoalkyl phosphorous acids such as rt-butyl phosphorous acid, monooctyl phosphorous acid, monodecyl phosphorous acid, di-n-propyl phosphorous acid, diisopropyl phosphorous acid, di-n-butyl phosphorous acid, diisobutyl phosphorous acid, di-tert-butyl Acidic compounds such as dialkyl phosphorous acids such as phosphorous acid, dioctyl phosphorous acid, and didecyl phosphorous acid; tetraisopropyl titanate, tetrabutyl titanate, tin octylate, dibutyltin diacetate, dibutyltin dioctoate, dibutyltin dilaurate, dibutyltin dimaleate, etc. Tin-containing compounds; Basic compounds such as butylamine, tert-butylamine, dibutylamine, hexylamine, ethylenediamine, triethylamine, isophoronediamine, imidazole, lithium hydroxide, sodium hydroxide, potassium hydroxide, and sodium methylate can be mentioned. , at least one of these is used.

These curing catalysts are usually blended in an amount of about 0.05 to 20 parts by weight, preferably about 0.1 to 10 parts by weight, based on 100 parts by weight of the base resin for the top coat.

Further, the stabilizer improves the storage stability of the paint, and includes, for example, C1-10 monohydric alkyl alcohol such as methyl alcohol, ethyl alcohol, propyl alcohol, butyl alcohol, trimethyl orthoformate, orthoformate, etc. Hydrolyzable esters such as triethyl acid and tripropyl orthoformate are included.

Furthermore, the clear coating composition may contain a hydrolyzable resin containing a hydroxyl group and/or a carboxyl group (for example, polyester polyol, polyether polyol, acrylic polyol, acrylic polycarboxylic acid, acrylic polyol polycarboxylic acid, etc.), if necessary. Silyl group-containing compounds (e.g., tetramethoxysilane, methyltrimethoxysilane, dimethyldimethoxysilane, phenyltrimethoxysilane, ethyltriethoxysilane, etc.), ultraviolet absorbers, antioxidants, light stabilizers, and other additives for various paints, etc. can be blended.

[0050] In the method of the present invention, for example, a chemical conversion treated steel plate is coated with an electrodeposition paint, and an intermediate coat (sometimes omitted) is applied.
The paint film is coated with a primer suitable for various plastic materials, the paint film is coated with an intermediate paint (sometimes omitted), and then a colored base paint composition is applied, and then a top clear paint composition is applied. This can be done by painting things. The above electrodeposition paint and intermediate coating paint usually have a coating content of 140 to 190, although it varies depending on the type of paint.
Bake for 30-90 minutes at ℃. Application of the pigmented base and top clear coating compositions can be carried out using conventional coating methods, such as electrostatic or non-electrostatic coating machines. Further, the thickness of the colored base coat is preferably about 10 to 50 μm (after curing). After applying the paint, it is left at room temperature for several minutes, or it is force-dried at about 50 to 80°C for several minutes, and then a clear paint composition is applied. The thickness of the clear coating is 20~
100 μm (after curing) is preferred. Next, the object to be coated is
It can be cured by heating at about 20 to 180°C for about 30 to 90 minutes.

[0051]

[Operation and Effects of the Invention] In the method of the present invention, the paint for the colored base coat finished by the two-coat one-bake method contains a polyorganosiloxane having two or more silanol groups and/or alkoxysilane groups in one molecule as a binder component. When heated, reactions between silanol groups (or silanol groups produced by hydrolysis of alkoxysilane groups) and reactions between silanol groups and hydroxyl groups in the hydroxyl group-containing resin occur rapidly at relatively low temperatures. Since this reaction occurs faster than the curing reaction of the clear coat paint, the viscosity of the base coat paint increases faster than that of the clear coat paint at the early stage of baking. It is considered that for this reason, a base coating film was formed that could withstand the shrinkage force of the coating film due to the volume change caused by the curing of the clear coat paint and the volatilization of the solvent, and the finished appearance of the coating film was improved. Furthermore, when the colored base coat paint was applied to a cured clear top coat film and recoated, an improvement in the adhesion between both coats was observed.

[0052]

[Examples] The present invention will be explained in more detail with reference to Examples below.

[0053] Hereinafter, "parts" and "%" mean "parts by weight" and "% by weight," respectively.

Production Example 1 In an organic solvent of 85 parts of xylene and 15 parts of n-butanol, 30 parts of styrene, 40 parts of n-butyl methacrylate,
10 parts of 2-ethylhexyl acrylate, 18 parts of 2-hydroxyethyl acrylate, and 2 parts of acrylic acid were reacted to obtain a number average molecular weight of 6,600 and a resin solid content of 5.
A hydroxyl group-containing acrylic resin solution (I-1) with a Gardner foam viscosity of 0% and a Gardner foam viscosity of J was obtained.

Production Example 2 In an organic solvent of 85 parts of xylene and 15 parts of n-butanol, 30 parts of styrene, 30 parts of n-butyl methacrylate,
By reacting monomers of 15 parts of 2-ethylhexyl acrylate and 25 parts of 2-hydroxyethyl acrylate,
A hydroxyl group-containing acrylic resin solution (I-2) having a number average molecular weight of 5000, a resin solid content of 50%, and a Gardner foam viscosity of B was obtained.

Production Example 3 Phenyltrimethoxysilane 198 parts Deionized water
54 parts 98% sulfuric acid
Mix 0.002 parts and heat at 60℃ for 5 minutes.
After reacting for a period of time, methanol was removed under reduced pressure, and xylene was added to obtain a polyorganosiloxane liquid (Ro-1) having a solid content of 50% and a Gardner viscosity of AB. The obtained polyorganosiloxane had a number average molecular weight of about 5,000 and had an average of 6 silanol groups per molecule.

Production Example 4 Methyltrimethoxysilane 136
Diphenyldimethoxysilane 182
partially deionized water
90 parts 60% phosphoric acid
Mix 1 part, 6
After reacting at 0°C for 10 hours, methanol was removed under reduced pressure, and butyl acetate was added to obtain a polyorganosiloxane liquid (Ro-2) with a solid content of 50% and a Gardner viscosity of D. The obtained polyorganosiloxane has a number average molecular weight of about 150.
00, and had an average of 10 silanol groups per molecule.

Paint composition for colored base coat Paint I-1 112 parts of the resin solution (I-1) obtained in Production Example 1 (56 parts in solid content), 40 parts of Yuban 20SE (Note 1) (24 parts in solid content) ), resin solution obtained in Production Example 3 (Ro-1) 40
(solid content: 20 parts), 20 parts of aluminum paste, and 1 part of Raybow #3 (Note 2) was stirred, then Swasol 1000 (Note 3) was added to reduce the paint viscosity for 15 seconds (Ford Cup #4/20). The temperature was adjusted to ℃ (hereinafter, the same meaning is indicated) and used for the test.

(Note 1) Yuban 20SE: manufactured by Mitsui Toatsu Chemical Co., Ltd., butyl etherified melamine resin solution with a solid content of approximately 60%, trade name.

(Note 2) Raybow #3: Silicone surface conditioner liquid made by Raybow Chemical Co., Ltd. with an active ingredient of approximately 1%.
Product name.

(Note 3) Swazol 1000: Cosmo Oil Co., Ltd., petroleum-based aromatic solvent, trade name.

Paint I-2 Paint I-1 was manufactured using the same formulation as Paint I-1 except that resin solution (A-2) was used instead of resin solution (A-1). -2 was obtained.

Paint I-3 Paint I-1 was manufactured using the same formulation as Paint I-1 except that the resin solution (Ro-2) was used instead of the resin solution (Ro-1). I got -3.

Coating I-4 Coating I-1 was manufactured using the same formulation as Coating I-1 except that the resin solution (Ro-1) was not used.
I got 4.

Production Example 5 Styrene
100 parts n-butyl acrylate
450 parts 2-ethylhexyl methacrylate
200 parts methyl methacrylate
150 parts γ-methacryloxypropyltrimethoxysilane 100 parts Azobisisobutyronitrile
A mixture of 20 parts of 11
The mixture was added dropwise at 0° C. over 3 hours and aged at the same temperature for 2 hours. The number average molecular weight of the obtained transparent polymer by GPC was 20,000.

Production Example 6 Styrene
100 parts n-butyl acrylate
450 parts 2-ethylhexyl methacrylate
200 parts 2-hydroxyethyl methacrylate
150 parts γ-methacryloxypropyltrimethoxysilane 100 parts Azobisisobutyronitrile
A mixture of 20 parts of 11
The mixture was added dropwise at 0° C. over 3 hours and aged at the same temperature for 2 hours. The number average molecular weight of the obtained transparent polymer by GPC was 20,000.

Production Example 7 Methyl methacrylate
150 parts n-butyl methacrylate
500 parts 1,4-butanediol monoacrylate
200 parts γ-methacryloxypropyltrimethoxysilane 150 parts Azobisisobutyronitrile
500 parts of xylene, 5 parts of n-butanol
The mixture was added dropwise to 00 parts of a mixed solvent at 120° C. over 3 hours, and then further aged at the same temperature for 2 hours. The number average molecular weight of the obtained transparent polymer was determined by GPC to be 18,000.

Coating compositions for clear top coat Coating compositions (II-1 to 7) Blend in the proportions (solid content) shown in Table 1, diluted with Swasol 1000 to a solid content of 50%, and then and diluted with Swasol 1000 to a paint viscosity of 22 seconds.

[0069]

[Table 1]

In Table 1, the types of catalysts *1 to *3 are as follows.

*1: Dibutyltin dilaurate *2: Dioctyl phosphate *3: Dioctyl phosphate/laurylamine = 1/
0.3 (weight ratio) Preparation of coated plate A dull steel plate (chemically treated) was coated with epoxy resin-based cationic electrodeposition paint (25 μm), heated and cured at 170°C for 30 minutes, and then applied as an intermediate coat with Lugabake AM (trade name). (manufactured by Kansai Paint Co., Ltd., polyester resin/melamine resin automotive paint) was applied so that the dry film thickness was 30 μm, and baked at 140° C. for 30 minutes. Next, the coated surface was sanded with #400 sandpaper, drained and dried, and the coated surface was wiped with petroleum benzene to prepare the material.

[0072] After applying the colored base coat paint by air spray painting, the clear top coat paint was applied immediately after leaving it for 3 minutes. The film thickness is 15% each in dry film thickness.
~20 μm and 35 to 45 μm. Then 10 at room temperature
Leave to stand for 30 minutes at 140°C (however, for recoatability, bake the first time at 160°C for 30 minutes, and bake the second time at 120°C.
℃ for 30 minutes). The coating performance and appearance are shown in Table 2.

[0073]

[Table 2]

Test method (*1) Appearance: The coating film was examined for wrinkles and wrinkles. ◎ No abnormality, ○ Slightly observed, × Many observed.

(*2) Image clarity: Image clarity measuring instrument (IMAG)
E GLARITY METER, manufactured by Suga Test Instruments Co., Ltd.). The numbers in the table are ICM values from 0 to 100.
%, the larger the value, the better the image clarity (image clarity), and the ICM value of 80 or more indicates extremely excellent image clarity.

(*3) Metallic feel: The sparkle and whiteness of the metal when viewed from the front was visually evaluated. ◎Shiny and white, △No sparkle and less white.
×There is no glitter and no whiteness at all.

(*4) Water resistance: After a sample coated plate was immersed in 40°C warm water for 240 hours, the state of blistering on the coated surface was visually evaluated. ◎ No abnormality, △ Slightly observed, × Significantly observed.

(*5) Recoatability: The same base paint and clear paint as in Examples and Comparative Examples were coated on the surface of the coating film, and a coating film was obtained by baking at 120° C. for 30 minutes. Crosscuts are made in the resulting coating film using a utility knife, and cellophane tape is applied to the coating surface, which is then rapidly peeled off to determine the adhesion between the first and second coatings (clear coating/base coating). was evaluated. ◎ No peeling observed at all, △ Slight peeling observed, × Significant peeling observed.

Claims (1)

[Claims] Claim 1: In a top coating method in which a colored base coat and a clear top coat are sequentially formed on a material and finished using a two-coat, one-bake method, the coating composition for forming the colored base coat comprises: (1) a hydroxyl group-containing vinyl resin (2) Amino resin (3) Polyorganosiloxane with a number average molecular weight of 1000 or more and having an average of two or more silanol groups and/or alkoxysilane groups in one molecule (4) Metal flake powder and/or mica powder and (5
) A coating composition for forming a clear top coat using a coating composition containing an organic solvent as an essential component, (1) a resin having a silanol group and/or a hydrolyzable group directly bonded to a silicon atom; ) A coating film forming method characterized by using a coating composition containing an organic solvent as an essential component.