JP6925724B2 - Multi-layer coating film forming method - Google Patents

Description

The present invention relates to a method for forming a multi-layer coating film having excellent adhesion to a substrate, water resistance and cold heat load resistance.

Conventionally, for the purpose of imparting excellent appearance, performance, etc. on a base material, a coating composition is applied onto the base material, and the formed wet coating film is cured to form a coating film. It has been. The coating film is generally required to have high adhesion to the base material, and more recently, it is also required to have high cold and heat load resistance.

In Patent Document 1, a coating agent containing a specific polyester resin, an epoxy resin and an organic solvent and having a content ratio of the polyester resin and the epoxy resin within a specific range adheres to a base material or a metal vapor deposition layer. It is described that a coating film having high properties and having sufficient resistance even when subjected to cold shock treatment or hot water treatment can be formed. However, even with the coating agent, there is a problem that the adhesion to the substrate, the water resistance, and the cold heat load resistance may be insufficient, especially when the coating film to be formed is relatively thick.

Japanese Unexamined Patent Publication No. 2013-189507

The present invention has been made in consideration of the above circumstances, and an object of the present invention is to provide a method for forming a multi-layer coating film having excellent adhesion to a base material, water resistance and cold heat load resistance.

According to one aspect of the invention
Item 1. On the substrate
Step (1): A step of applying a primer composition (A) containing a polymer-type silane coupling agent to form a primer layer.
Step (2): A step of coating the undercoat coating composition (B) on the substrate on which the primer layer is formed in the step (1) to form an undercoat coating film.
Step (3): The topcoat coating composition (C) containing the hydroxyl group-containing acrylic resin (c1) and the polyisocyanate compound (c2) is coated on the base material on which the undercoat coating film is formed in the step (2). A method for forming a multi-layer coating film, which includes a step of forming a top coat coating film.
Item 2. On the substrate
Step (1): A step of applying a primer composition (A) containing a polymer-type silane coupling agent to form a primer layer.
Step (2): The topcoat coating composition (C) containing the hydroxyl group-containing acrylic resin (c1) and the polyisocyanate compound (c2) is coated on the substrate on which the primer layer is formed in the step (1). A method for forming a multi-layer coating including a step of forming a topcoat coating,
Is provided.

The method for forming a multi-layer coating film of the present invention can achieve the effect of being able to form a multi-layer coating film having excellent adhesion to a substrate, water resistance, and cold heat load resistance.

Hereinafter, the method for forming a multi-layer coating film of the present invention will be described in more detail.

One aspect of the multi-layer coating film forming method of the present invention is
On the substrate
Step (1): A step of applying a primer composition (A) containing a polymer-type silane coupling agent to form a primer layer.
Step (2): A step of coating the undercoat coating composition (B) on the substrate on which the primer layer is formed in the step (1) to form an undercoat coating film.
Step (3): The topcoat coating composition (C) containing the hydroxyl group-containing acrylic resin (c1) and the polyisocyanate compound (c2) is coated on the base material on which the undercoat coating film is formed in the step (2). To form a topcoat coating,
It is characterized by including.

The material of the substrate multilayer coating film forming method is applied in the substrate present invention is not particularly limited, inorganic materials, organic materials, or may be any of a hybrid material of organic and inorganic.

Examples of the inorganic material include metal materials such as iron, aluminum, brass, copper, tin, stainless steel, zinc-plated steel, and zinc alloy (Zn-Al, Zn-Ni, Zn-Fe, etc.) plated steel; glass; Examples include cement; steel; polysiloxane, and the like.

The organic material is a material containing an organic resin, and examples of the organic resin include acrylic resins such as polymethylmethacrylate, polyethylene terephthalate, polyethylene naphthalate, poly-1,4-cyclohexanedimethylene terephthalate, and polyethylene-1. Polyester resins such as 2-diphenoxyetane-4, 4'-dicarboxylate, polybutylene terephthalate, and epoxy resins represented by commercial products such as Epicoat (trade name: Yuka Shell Epoxy Co., Ltd.). Polycarbonate resin, polyimide resin, novolak resin, phenol resin, acrylonitrile-butadiene-styrene (ABS) resin, vinylidene chloride resin, polyurethane resin, cellulose ester (eg, triacetyl cellulose, diacetyl cellulose, propionyl cellulose, butyryl cellulose, acetyl propionyl) Cellulose, nitrocellulose), polyamide, polystyrene (eg, syndiotactic polystyrene), polyolefin (eg, polypropylene, polyethylene, polymethylpentene), polysulfone, polyethersulfone, polyarylate, polyetherimide, polyetherketone, etc. Be done.

Further, the organic material may contain pigments and / or fibers as a part of its components.

Examples of the pigment include calcium carbonate, silica, barium sulfate, barium carbonate, talc, clay, kaolin, aluminum hydroxide, magnesium oxide, aluminum oxide and the like.

Further, examples of the fiber include glass fiber, aramid fiber, carbon fiber, cellulose fiber and the like.

Therefore, various fiber reinforced plastic materials (Fiber Reinforced Plastics: hereinafter referred to as FRP material or simply FRP) are included in the above organic materials.

Primer composition (A)
The primer composition (A) is a composition containing a polymer-type silane coupling agent.

The polymer-type silane coupling agent is an organosilicon compound having an organic chain as a main chain and having an alkoxysilyl group and two or more reactive functional groups other than the alkoxysilyl group. Here, the "polymer" of the present invention refers to a molecule formed by polymerizing two or more kinds of constituent units.

Examples of the reactive functional group include at least one of an epoxy group, a mercapto group and an isocyanate group.

The polymer-type silane coupling agent is a polymer containing a plurality of structural units (I) having an alkoxysilyl group and a plurality of structural units (II) having a reactive functional group other than the alkoxysilyl group, preferably 5 or more each. Is preferable.

The structural unit (I) is preferably represented by the following general formula (i).
General formula (i)

In the general formula (i), R ¹ represents a hydrogen atom or a methyl group, and R ² and R ³ each independently represent an alkyl group having 1 to 4, preferably 1 to 3, and more preferably 1 to 2. , L represents an alkylene group having 1 to 6 carbon atoms or an arylene group having 6 to 10 carbon atoms, and n represents an integer of 0 to 2. L is preferably an alkylene group having 1 to 6 carbon atoms.

The structural unit (II) is preferably represented by the following general formula (ii).
General formula (ii)

In the general formula (i), R ⁴ represents a hydrogen atom or a methyl group, and M represents an alkylene group having 1 to 6 carbon atoms or an arylene group having 6 to 10 carbon atoms. N is a reactive functional group, specifically an amino group, an epoxy group, a mercapto group, an isocyanate group, a (meth) acryloyl group, a vinyl group, an allyl group, an oxetane group, a hydroxyl group, an aziridine group, an oxazoline group and a carbonyl group. , Hydrazide group, imino group, aldehyde group, acid anhydride group, aziridine group, ureido group, sulfide group. M is preferably an alkylene group having 1 to 6 carbon atoms. N is preferably an epoxy group, a mercapto group and an isocyanate group, and more preferably an epoxy group and a mercapto group.

In the polymer-type silane coupling agent, it is preferable that the total of the structural unit (I) and the structural unit (II) accounts for 60 mol% or more, preferably 80 mol% or more in the entire polymer.

The polymer-type silane coupling agent preferably has a functional group equivalent of 100 to 400 g / mol, preferably 200 to 400 g / mol, and more preferably 250 to 400 g / mol.

Polymeric silane coupling agent has a viscosity 500~6000mm ² / s, preferably 800~4000mm ² / s, more preferably is suitably a 1000~4000mm ² / s.

In the polymer type silane coupling agent, the number of reactive functional groups other than the alkoxysilyl group is preferably 2 to 10, preferably 2 to 5, and more preferably 2 to 3 with respect to the alkoxysilyl group. ..

Commercially available polymer-type silane coupling agents include; X-12-981S and X-12-984S as N having an epoxy group; and X-12 as N having a mercapto group. -1154, X-12-1156; N is an isocyanate group includes X-12-1159L; N is a (meth) acryloyl group, X-12-1048 Examples of those in which N is an amino group include X-12-972F. Both of these are manufactured by Shin-Etsu Silicone.

The primer composition (A) can further contain a substrate resin and a cross-linking agent, if necessary, but the effects of the present invention can be exhibited even if these are not substantially contained.

Examples of the substrate resin include acrylic resin, polyester resin, alkyd resin, and urethane resin.

Examples of the cross-linking agent include melamine resin, urea resin, polyisocyanate compound, and blocked polyisocyanate compound.

The primer composition (A) can further contain a pigment, if necessary, and further appropriately contains various additives such as a thickener, a plasticizer, a filler, a sagging agent, and a pigment dispersant. Can be done.

The primer composition (A) containing the polymer-type silane coupling agent used in the present invention is diluted with an organic solvent so that the active ingredient is in the range of 1 to 40% by weight, preferably 2 to 20% by weight. It is preferably used as an organic solvent solution. In the present specification, the active ingredient means a residue obtained by removing a diluent such as water or an organic solvent from a sample.

As the organic solvent, a solvent that does not substantially react with the silane coupling agent can be used. Specifically, for example, an aromatic hydrocarbon-based organic solvent, an aliphatic hydrocarbon-based organic solvent, and the like. Ketone-based organic solvents, ester-based organic solvents, and alcohol-based organic solvents can be used.

Examples of the aromatic hydrocarbon-based organic solvent include toluene, xylene and the like, and these can be used alone or in combination of two or more.

Examples of the aliphatic hydrocarbon-based organic solvent include n-butane, n-hexane, n-heptane, n-pentane, n-octane, n-nonane, n-decane, n-undecane, n-dodecane, and n-tridecane. Linear alkanes such as n-tetradecane, n-pentadecane, n-hexadecan, n-heptadecane; 2-methylbutane, 2,2-dimethylpropane, 2-methylpentane, 3-methylpentane, 2,2-dimethylbutane, 2,3-dimethylbutane, 2-methylhexane, 3-methylhexane, 2,3-dimethylpentane, 2,4-dimethylpentane, 2,2,3-trimethylpentane, 2,2,4-trimethylpentane, 3 , 4-Diethylhexane, 2,6-dimethyloctane, 3,3-dimethyloctane, 3,5-dimethyloctane, 4,4-dimethyloctane, 3-ethyl-3-methylheptane, 2-methylnonane, 3-methylnonan , 4-Methylnonane, 5-Methylnonane, 2-Methylundecane, 3-Methylundecane, 2,2,4,6,6-pentamethylheptane and other branched alkanes; cyclopentane, t-decalin, cyclohexane, methylcyclohexane, Ethylcyclohexane, 1,2-dimethylcyclohexane, 1,3-dimethylcyclohexane, 1,4-dimethylcyclohexane, propylcyclohexane, isopropylcyclohexane, 1,2-methylethylcyclohexane, 1,3-methylethylcyclohexane, 1,4- Examples thereof include cycloalkanes such as methylethylcyclohexane, 1,2,3-trimethylcyclohexane, 1,2,4-trimethylcyclohexane and 1,3,5-trimethylcyclohexane, which are used alone or in combination of two or more. can do. Among them, the aliphatic hydrocarbon-based organic solvent is preferably linear or branched.

Examples of the ketone-based organic solvent include acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, ethyl isoamyl ketone, diisobutyl ketone, methylhexyl ketone, and isophorone, which can be used alone or in combination of two or more. can.

Examples of the ester-based organic solvent include ethyl acetate, butyl acetate, isobutyl acetate, diethylhexyl acetate, cyclohexyl acetate, 3-methoxybutyl acetate, propylene glycol monomethyl ether acetate, dipropylene glycol monomethyl ether acetate, ethylene glycol monoethyl ether acetate, and diethylene glycol. Examples thereof include monoethyl ether acetate, which can be used alone or in combination of two or more. Among them, the ester-based organic solvent is preferably linear or branched. Further, the ester-based organic solvent preferably has 4 to 8 carbon atoms.

Examples of the alcohol-based organic solvent include isopropanol, n-butyl alcohol, 2-hydroxy-4-methylpentane, 2-ethylhexyl alcohol, cyclohexanol, ethylene glycol, diethylene glycol, 1,3-butylene glycol, and ethylene glycol monoethyl ether. , Ethylene glycol monobutyl ether, diethylene glycol monomethyl ether and the like, and these can be used alone or in combination of two or more. Among them, the alcohol-based organic solvent is preferably linear or branched. Further, the alcohol-based organic solvent preferably has 1 to 8 carbon atoms.
The above organic solvent can be used alone or in combination of two or more.

As a coating method of the primer composition (A), a conventionally known coating method can be used. The primer composition (A) is a commonly used coating machine such as an air spray, an airless spray, an electrostatic air spray, a flow coater, a rotary atomizing coating machine, a coating machine in a dipping format, or a brush, a roller, and a wiping. It can be applied using a cloth or the like.

The dry film thickness of the primer layer obtained by applying the primer composition (A) on the substrate is 1 μm or less, preferably 0.01, from the viewpoint of adhesion to the substrate, water resistance, and cold heat load resistance. It is preferably ~ 1 μm, more preferably 0.1 to 0.7 μm. When the dry film thickness of the primer coating film is less than 1 μm, it is preferably applied using a brush, and when it is 1 μm or more, it is preferably applied using a rotary atomization coating machine.

The film thickness of the primer layer can be adjusted by adjusting the coating amount. The coating amount is usually, 0.05 to 20 g / ^{m 2} in terms of active ingredient, preferably in the range of 0.1 to 10 g / ^{m 2.} Cause partial amount applied is not applied to the substrate becomes less than 0.05 g / m ^2, poor adhesion and film properties of the base material and the coating film, On the other hand, if the coating amount exceeds 20 g / m ^2, It is not preferable because the performance of the coating film is deteriorated, and the appearance and adhesion of the coating film are deteriorated due to the difference in the curing speed between the surface and the inside of the coating film.

Further, the primer layer can be cured at room temperature or by heating. Specifically, for example, it may be maintained at a room temperature of 20 ° C. for about 10 to 30 minutes, and when heating, for example, at a temperature of 40 to 80 ° C., preferably 40 to 60 ° C. 1 It is preferable to heat for ~ 30 minutes, preferably 10 to 20 minutes.
Undercoat paint composition (B)
As the undercoat coating composition (B), conventionally known ones can be used without limitation, but from the viewpoint of adhesion, water resistance and cold heat load resistance, it is preferable to contain a hydroxyl group-containing acrylic resin (b1).

The hydroxyl group-containing acrylic resin (b1) can be obtained from, for example, a method known per se from a hydroxyl group-containing polymerizable unsaturated monomer and another polymerizable unsaturated monomer copolymerizable with the hydroxyl group-containing polymerizable unsaturated monomer, for example, organic. It can be produced by copolymerizing by a method such as a solution polymerization method in a solvent or an emulsion polymerization method in water.

The hydroxyl group-containing polymerizable unsaturated monomer is a compound having one or more hydroxyl groups and one or more polymerizable unsaturated bonds in one molecule. Examples of the hydroxyl group-containing polymerizable unsaturated monomer include a monoesterified product of (meth) acrylic acid and a divalent alcohol having 2 to 8 carbon atoms, for example, 2-hydroxyethyl (meth) acrylate and 2-hydroxypropyl (meth). Acrylate, 3-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, etc .; ε-caprolactone modified product of a monoesterified product of the (meth) acrylic acid and a divalent alcohol having 2 to 8 carbon atoms; N. -Hydroxymethyl (meth) acrylamide; allyl alcohol, (meth) acrylate having a polyoxyethylene chain having a hydroxyl group at the molecular end, and the like can be mentioned. These can be used alone or in combination of two or more.

The blending ratio of the hydroxyl group-containing polymerizable unsaturated monomer is 5 to 40% by mass, particularly preferably 10 to 40% by mass, and more preferably 10 to 30% by mass with respect to the total amount of the monomer components. ..

The hydroxyl group-containing acrylic resin (b1) preferably contains an alicyclic hydrocarbon group-containing polymerizable unsaturated monomer as another polymerizable unsaturated monomer copolymerizable with the hydroxyl group-containing polymerizable unsaturated monomer.

The coating obtained because the hydroxyl group-containing acrylic resin (b1) contains an alicyclic hydrocarbon group-containing polymerizable unsaturated monomer as a copolymerization component, so that the glass transition temperature rises and the polarity decreases. It improves the water resistance of the film.

Representative examples of the alicyclic hydrocarbon group include a cyclohexyl group, a cyclooctyl group, a cyclododecyl group, an isobornyl group, an adamantyl group, a tricyclodecanyl group and the like.

Specific examples of the alicyclic hydrocarbon group-containing polymerizable unsaturated monomer include cyclohexyl (meth) acrylate, methylcyclohexylmethyl (meth) acrylate (eg, 4-methylcyclohexylmethyl (meth) acrylate), and ethylcyclohexylmethyl. (Meta) acrylate (eg 4-ethylcyclohexylmethyl (meth) acrylate), methoxycyclohexylmethyl (meth) acrylate (eg 4-methoxycyclohexylmethyl (meth) acrylate), tert-butylcyclohexyl (meth) acrylate, cyclooctyl Cycloalkyl (meth) acrylates such as (meth) acrylate and cyclododecyl (meth) acrylate; isobornyl (meth) acrylate, tricyclodecanyl (meth) acrylate, adamantyl (meth) acrylate, 3,5-dimethyladamantyl (meth) Examples thereof include acrylate and 3-tetracyclododecyl (meth) acrylate, and preferred examples thereof include cyclohexyl (meth) acrylate and isobornyl (meth) acrylate.

The blending ratio of the alicyclic hydrocarbon group-containing polymerizable unsaturated monomer is preferably in the range of 20 to 40% by mass, preferably 25 to 35% by mass, based on the total amount of the monomer components.

The other polymerizable unsaturated monomer copolymerizable with the hydroxyl group-containing polymerizable unsaturated monomer is one in one molecule other than the above-mentioned hydroxyl group-containing polymerizable unsaturated monomer and the alicyclic hydrocarbon group-containing polymerizable unsaturated monomer. It is a compound having an unsaturated bond of, and specific examples thereof are listed below (1) to (7).

(1) Acid group-containing polymerizable unsaturated monomer: A compound having one or more acid groups and one unsaturated bond in one molecule, for example, (meth) acrylic acid, crotonic acid, itaconic acid, malein. Carboxyl group-containing polymerizable unsaturated monomers such as acids and maleic anhydride; sulfonic acid group-containing polymerizable unsaturated monomers such as vinyl sulfonic acid and sulfoethyl (meth) acrylate; 2- (meth) acryloyloxyethyl acid phosphate, Acidic phosphate ester-based polymerizable unsaturated monomers such as 2- (meth) acryloyloxypropyl acid phosphate, 2- (meth) acryloyloxy-3-chloropropyl acid phosphate, 2-methacryloyloxyethylphenyl phosphate, etc. be able to. These can be used alone or in combination of two or more.

(2) Monoesteride of acrylic acid or methacrylic acid and a monovalent alcohol having 1 to 20 carbon atoms: for example, methyl (meth) acrylate, ethyl (meth) crylate, propyl (meth) acrylate, n-butyl (meth). Acrylate, Isobutyl (meth) acrylate, tert-butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, isooctyl (meth) acrylate, isomyristyl (meth) acrylate, isostearyl acrylate (manufactured by Osaka Organic Chemical Industry Co., Ltd., trade name) ), Lauryl (meth) acrylate, tridecyl (meth) acrylate, stearyl (meth) acrylate, tetrahydrofurfuryl (meth) acrylate, etc.

(3) Aromatic polymerizable unsaturated monomer: For example, styrene, α-methylstyrene, vinyltoluene and the like.

When the aromatic polymerizable unsaturated monomer is used as a constituent component, the blending ratio thereof is preferably in the range of 3 to 50% by mass, particularly 5 to 40% by mass, based on the total amount of the monomer components.

(4) Glycidyl group-containing polymerizable unsaturated monomer: A compound having one glycidyl group and one unsaturated bond in one molecule, specifically, glycidyl acrylate, glycidyl methacrylate and the like.

(5) Nitrogen-containing polymerizable unsaturated monomer: For example, acrylamide, methacrylamide, dimethylacrylamide, N, N-dimethylpropylacrylamide, N-butoxymethylacrylamide, N-methylolacrylamide, N-methylolmethacrylamide, diacetoneacrylamide, N, N-dimethylaminoethyl (meth) acrylate, vinylpyridine, vinylimidazole, etc.

(6) Other vinyl compounds: For example, vinyl acetate, vinyl propionate, vinyl chloride, Beova 9 which is a vinyl ester of versatic acid, Beova 10 (Japan epoxy resin) and the like.

(7) Unsaturated bond-containing nitrile compound: For example, acrylonitrile, methacrylonitrile and the like.

As these other polymerizable unsaturated monomers, one kind or two or more kinds can be used.

In the present specification, "(meth) acrylate" means acrylate or methacrylate, and "(meth) acrylic acid" means acrylic acid or methacrylic acid. Further, "(meth) acryloyl" means acryloyl or methacryloyl, and "(meth) acrylamide" means acrylamide or methacrylamide.

The hydroxyl group-containing acrylic resin (b1) has a glass transition temperature (Tg) of 20 to 100 ° C., particularly 50, from the viewpoint of adhesion and cold heat load resistance of the coating film obtained by coating the undercoat coating composition (B). It is preferably in the range of ~ 100 ° C.

In the present specification, the glass transition temperature Tg of the hydroxyl group-containing acrylic resin is a value calculated by the following formula.
1 / Tg (K) = W1 / T1 + W2 / T2 + ... Wn / Tn
Tg (° C.) = Tg (K) -273
In the formula, W1, W2, ... Wn is the mass fraction of each monomer, and T1, T2 ... Tn is the glass transition temperature Tg (K) of the homopolymer of each monomer.
The glass transition temperature of the homopolymer of each monomer is determined by POLYMER HANDBOOK Fourth Edition, J. Mol. Brandrup, E.I. h. Immunogut, E.I. A. The glass transition temperature of a monomer, which is a value according to Grulke (1999) and is not described in the document, is obtained by synthesizing a homopolymer of the monomer so that the weight average molecular weight is about 50,000, and the glass transition thereof. Use the value when the temperature is measured by differential scanning calorimetry.

The hydroxyl group-containing acrylic resin (b1) has a weight average molecular weight in the range of 5,000 to 100,000, particularly 5,000 to 50,000, from the viewpoint of adhesion, water resistance, and cold heat load resistance. preferable.

Further, in the present specification, the weight average molecular weight and the number average molecular weight are the retention times (retention capacity) measured using a gel permeation chromatograph (GPC), and the retention time (retention capacity) of standard polystyrene having a known molecular weight measured under the same conditions. It is a value obtained by converting the molecular weight of polystyrene by (retention capacity). The columns are "TSKgel G-4000H x L", "TSKgel G-3000H x L", "TSKgel G-2500H x L", "TSKgel G-2000H x L" (all manufactured by Tosoh Corporation, trade name). The mobile phase was: tetrahydrofuran, the measurement temperature was 40 ° C., the flow velocity was 1 ml / min, and the detector was RI.

Determining the composition of the polymerizable unsaturated monomer so that the solubility parameter (SP value) of the hydroxyl group-containing acrylic resin (b1) is within the range of 8.7 to 9.2 is the undercoat coating composition (B). ) Is preferable from the viewpoint of adhesion and cold heat load resistance of the coating film obtained by coating the coating material, and a more preferable SP value range is in the range of 8.8 to 9.1.

The solubility parameter (Solubility Parameter, "SP value" is an abbreviation) represents a measure of the intermolecular interaction of liquid molecules. The SP value of the homopolymer of the polymerizable monomer is determined by J.I. Paint Technology, vol. 42,176 (1970). The SP value of the copolymer polymer of the polymerizable monomer mixture can be calculated and obtained by the following formula.
SP value = SP1 x fw1 + SP2 x fw2 + ......... + SPn x fwn
In the above formula, SP1, SP2, ..... SPn represent the SP value of the homopolymer of each polymerizable monomer, and fw1, fw2, ..... fwn are mass fractions of each polymerizable unsaturated monomer with respect to the total amount of monomers. Represents.

In the undercoat coating composition (B) according to the present invention, the content of the hydroxyl group-containing acrylic resin (b1) is the total solid content of the undercoat coating composition (B) from the viewpoint of adhesion, cold heat load resistance, and the like. As a reference, it is preferably in the range of 15 to 90% by mass, preferably 20 to 85% by mass, and more preferably 25 to 80% by mass.

As used herein, the term "solid content" means a non-volatile component such as a resin, a curing agent, or a pigment contained in the composition, which remains after being dried at 110 ° C. for 1 hour. Therefore, for example, for the total solid content of the undercoat coating composition (B), the undercoat coating composition (B) is weighed in a heat-resistant container such as an aluminum foil cup, and the undercoat coating composition (B) is placed on the bottom surface of the container. After spreading, it is dried at 110 ° C. for 1 hour, the mass of the components in the undercoat coating composition (B) remaining after drying is weighed, and the undercoat coating composition before drying is weighed. It can be calculated by obtaining the ratio of the mass of the component remaining after drying to the total mass of (B).

The undercoat coating composition (B) can contain a hydroxyl group-containing polyester resin (b2).

The hydroxyl group-containing polyester resin (b2) can be generally obtained by subjecting a polyhydric alcohol and a polybasic acid to an esterification reaction with an excess of hydroxyl groups by a method known per se. A polyhydric alcohol is a compound having two or more hydroxyl groups in one molecule, and a polybasic acid is a compound having two or more carboxyl groups in one molecule.

Examples of the polyhydric alcohol include ethylene glycol, propylene glycol, diethylene glycol, trimethylene glycol, tetraethylene glycol, triethylene glycol, dipropylene glycol, 1,4-butanediol, 1,3-butanediol, and 2,3-. Butanediol, 1,2-butanediol, 3-methyl-1,2-butanediol, 1,2-pentanediol, 1,5-pentanediol, 1,4-pentanediol, 2,4-pentanediol, 2 , 3-Dimethyltrymethylene Glycol, Tetramethylene Glycol, 3-Methyl-4,3-Pentanediol, 3-Methyl-4,5-Pentanediol, 2,2,4-trimethyl-1,3-Pentanediol, 1 , 6-Hexanediol, 1,5-hexanediol, 1,4-hexanediol, 2,5-hexanediol, neopentyl glycol, hydroxypivalate neopentyl glycol ester and other divalent alcohols; these divalent Polylactone diols obtained by adding lactones such as ε-caprolactone to alcohol; ester diols such as bis (hydroxyethyl) terephthalate; alkylene oxide adducts of bisphenol A, polyether diols such as polyethylene glycol, polypropylene glycol and polybutylene glycol Classes: α-olefin epoxides such as propylene oxide and butylene oxide, monoepoxy compounds such as Cardura E10 [Glysyl ester of synthetic highly branched saturated fatty acids, trade name, manufactured by Shell Chemical Co., Ltd .]; glycerin, trimethylolpropane, trimethylolethane, etc. Trivalent or higher alcohols such as diglycerin, triglycerin, 1,2,6-hexanetriol, pentaerythritol, dipentaerythritol, sorbitol, mannit; these trivalent or higher alcohols are supplemented with lactones such as ε-caprolactone. Addition of polylactone polyols; 1,4-cyclohexanedimethanol, tricyclodecanedimethanol, hydrogenated bisphenol A, hydrogenated bisphenol F, hydrogenated bisphenol A, hydrogenated bisphenol F, and other alicyclic polyvalent alcohols; Tris (Hydroxyalkyl) isocyanurate, ε-caprolactone modified form of the tris (hydroxyalkyl) isocyanurate, tris (hydroxyethyl) isocyanurate, and other rings having a nurate structure. State polyol compound; and the like.

The polybasic acid is, for example, an aromatic polybasic acid such as terephthalic acid, isophthalic acid, phthalic acid, naphthalenedicarboxylic acid, 4,4'-biphenyldicarboxylic acid, diphenylmethane-4,4'-dicarboxylic acid and its anhydride; Alicyclic dicarboxylic acids such as hexahydroisophthalic acid, hexahydroterephthalic acid, hexahydrophthalic acid, tetrahydrophthalic acid and their anhydrides; adipic acid, sebacic acid, suberic acid, succinic acid, glutaric acid, maleic acid, chloromaleine. Alipid polybasic acids such as acids, fumaric acids, dodecanedic acids, pimelic acids, azelaic acids, itaconic acids, citraconic acids and dimer acids and their anhydrides; lower alkyl esters such as methyl esters and ethyl esters of these dicarboxylic acids. Examples thereof include trivalent or higher valent polybasic acids such as trimellitic acid, trimellitic anhydride, pyromellitic acid, pyrometic anhydride, trimesic acid, methylcyclohexcentricarboxylic acid, tetrachlorohexene polybasic acid and its anhydride.

The introduction of hydroxyl groups can be carried out, for example, by using a polyhydric alcohol having three or more hydroxyl groups in one molecule in combination.

Further, at the time of the reaction between the polybasic acid and the polyhydric alcohol, a monobasic acid, an oil component (including this fatty acid) and the like may be used if necessary. Examples of monobasic acid include benzoic acid and t-butyl benzoic acid, and examples of oil components include castor oil, dehydrated castor oil, safflower oil, soybean oil, linseed oil, tall oil, palm oil and the like. Examples thereof include these fatty acids, and these can be used alone or in combination of two or more. Further, the polyester resin may be modified with an epoxy compound such as butyl glycidyl ether, alkylphenyl glycidyl ether, neodecanoic acid glycidyl ester, if necessary.

The hydroxyl group-containing polyester resin (b2) preferably has a hydroxyl group value of 50 to 200 mgKOH / g from the viewpoints of scratch resistance, hardness, appearance, adhesiveness, resistance to a composition containing an ultraviolet absorber, etc. of the obtained coating film. Is 50 to 150 mgKOH / g and has a number average molecular weight of 2,000 to 20,000, preferably 2,000 to 15,000.

In the undercoat coating composition (B), the content of the hydroxyl group-containing polyester resin (b2) is 15 based on the total solid content of the undercoat coating composition (B) from the viewpoint of adhesion, cold heat load resistance, and the like. It is preferably in the range of ~ 90% by mass, preferably 20 to 85% by mass, and more preferably 25 to 80% by mass.

Further, the undercoat coating composition (B) preferably further contains a polyisocyanate compound (b3) from the viewpoint of adhesion, cold heat load resistance, and the like.

The polyisocyanate compound (b3) is a compound having at least two isocyanate groups in one molecule, and is, for example, an aliphatic polyisocyanate, an alicyclic polyisocyanate, an aromatic aliphatic polyisocyanate, an aromatic polyisocyanate, or the like. Examples thereof include derivatives of polyisocyanates.

Examples of the aliphatic polyisocyanate include trimethylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, pentamethylene diisocyanate, 1,2-propylene diisocyanate, 1,2-butylene diisocyanate, 2,3-butylene diisocyanate, and 1,3. An aliphatic diisocyanate such as −butylene diisocyanate, 2,4,4- or 2,2,4-trimethylhexamethylene diisocyanate, diisocyanate dimerate, methyl 2,6-diisocyanatohexanate (common name: lysine diisocyanate); 2 , 6-Diisocyanatohexanoic acid 2-isocyanatoethyl, 1,6-diisocyanato-3-isocyanatomethylhexane, 1,4,8-triisocyanatooctane, 1,6,11-triisocyanatoundecane, 1, , 8-Diisocyanato-4-isocyanatomethyloctane, 1,3,6-triisocyanatohexane, 2,5,7-trimethyl-1,8-diisocyanato-5-isocyanatomethyloctane and other aliphatic triisocyanates, etc. Can be mentioned.

Examples of the alicyclic polyisocyanate include 1,3-cyclopentenediisocyanate, 1,4-cyclohexanediisocyanate, 1,3-cyclohexanediisocyanate, and 3-isocyanatomethyl-3,5,5-trimethylcyclohexylisocyanate (common name). : Isophorone diisocyanate), 4-methyl-1,3-cyclohexylene diisocyanate (common name: hydrogenated TDI), 2-methyl-1,3-cyclohexylene diisocyanate, 1,3- or 1,4-bis (isocyanato) Alicyclic diisocyanates such as methyl) cyclohexane (common name: hydrogenated xylylene diisocyanate) or a mixture thereof, methylenebis (4,1-cyclohexanediyl) diisocyanate (common name: hydrogenated MDI), norbornan diisocyanate; 1,3,5 -Triisocyanatocyclohexane, 1,3,5-trimethylisocyanatocyclohexane, 2- (3-isocyanatopropyl) -2,5-di (isocyanatomethyl) -bicyclo (2,2,1) heptane, 2- (3-Isocyanatopropyl) -2,6-di (isocyanatomethyl) -bicyclo (2,2,1) heptane, 3- (3-isocyanatopropyl) -2,5-di (isocyanatomethyl)- Bicyclo (2,2,1) heptane, 5- (2-isocyanatoethyl) -2-isocyanatomethyl-3- (3-isocyanatopropyl) -bicyclo (2,2,1) heptane, 6- (2) -Isocyanatoethyl) -2-isocyanatomethyl-3- (3-isocyanatopropyl) -bicyclo (2,2,1) heptane, 5- (2-isocyanatoethyl) -2-isocyanatomethyl-2- (3-Isocyanatopropyl) -bicyclo (2,2,1) -heptane, 6- (2-isocyanatoethyl) -2-isocyanatomethyl-2- (3-isocyanatopropyl) -bicyclo (2,2) , 1) Alicyclic triisocyanates such as heptane can be mentioned.

Examples of the aromatic aliphatic polyisocyanate include methylenebis (4,1-phenylene) diisocyanate (common name: MDI), 1,3- or 1,4-xylylene diisocyanate or a mixture thereof, ω, ω'-diisocyanato-. Arophilic aliphatic diisocyanates such as 1,4-diethylbenzene, 1,3- or 1,4-bis (1-isocyanato-1-methylethyl) benzene (common name: tetramethylxylylene diisocyanate) or a mixture thereof; 1,3 , 5-Triisosocyanatomethylbenzene and other aromatic aliphatic triisocyanates and the like can be mentioned.

Examples of the aromatic polyisocyanate include m-phenylene diisocyanate, p-phenylenedi isocyanate, 4,4'-diphenyldiisocyanate, 1,5-naphthalenediisocyanate, and 2,4-tolylene diisocyanate (common name: 2,4-tolylene diisocyanate). TDI) or 2,6-tolylene diisocyanate (common name: 2,6-TDI) or a mixture thereof, aromatic diisocyanates such as 4,4'-toluene diisocyanate and 4,4'-diphenyl ether diisocyanate; triphenylmethane-4 , 4', 4''-triisocyanate, 1,3,5-triisocyanatobenzene, 2,4,6-triisocyanatotoluene and other aromatic triisocyanates; 4,4'-diphenylmethane-2,2' , 5, 5'-Tetraisocyanate and other aromatic tetraisocyanates and the like.

Examples of the polyisocyanate derivative include the above-mentioned polyisocyanate dimer, trimmer, biuret, allophanate, uretdione, uretoimine, isocyanurate, oxadiazine trione, and polymethylene polyphenyl polyisocyanate (Crude MDI, Polymeric MDI). , Crude TDI and the like.

As the polyisocyanate compound (b3), the above-mentioned aliphatic diisocyanate, alicyclic diisocyanate and derivatives thereof can be preferably used from the viewpoint of adhesion to a base material, cold heat load resistance and the like.

Further, as the polyisocyanate compound (b3), a prepolymer obtained by reacting the polyisocyanate and its derivative with a compound capable of reacting with the polyisocyanate under the condition of excess isocyanate group may be used. Examples of the compound capable of reacting with the polyisocyanate include compounds having an active hydrogen group such as a hydroxyl group and an amino group. Specific examples thereof include polyhydric alcohols, low molecular weight polyester resins, amines and water. Can be used.

The polyisocyanate compound (b3) is a copolymer of an isocyanate group-containing polymerizable unsaturated monomer, or a polymerizable non-polymerizable monomer other than the isocyanate group-containing polymerizable unsaturated monomer and the isocyanate group-containing polymerizable unsaturated monomer. A copolymer with a saturated monomer may be used.

Further, the polyisocyanate compound (b3) may be a polyisocyanate compound in which the isocyanate group is blocked with a blocking agent, that is, a so-called blocked polyisocyanate compound.

Examples of the blocking agent include phenol-based agents such as phenol, cresol, xylenol, nitrophenol, ethylphenol, hydroxydiphenyl, butylphenol, isopropylphenol, nonylphenol, octylphenol, and methyl hydroxybenzoate; Oximes such as γ-butyrolactam and β-propiolactam; aliphatic alcohols such as methanol, ethanol, propyl alcohol, butyl alcohol, amyl alcohol and lauryl alcohol; ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol mono Ether systems such as butyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, propylene glycol monomethyl ether, and methoxymethanol; benzyl alcohol, glycolic acid, methyl glycolate, ethyl glycolate, butyl glycolate, lactic acid, methyl lactate, ethyl lactate, lactic acid. Alcohols such as butyl, methylolurea, methylolmelamine, diacetone alcohol, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate; formamide oxime, acetamide oxime, acetoxime, methyl ethyl ketooxime, diacetyl monooxime, benzophenone oxime, cyclohexane oxime, etc. Oxime-based; active methylene-based such as dimethyl malonate, diethyl malonate, ethyl acetoacetate, methyl acetoacetate, acetylacetone; butyl mercaptan, t-butyl mercaptan, hexyl mercaptan, t-dodecyl mercaptan, 2-mercaptobenzothiazole, thio Mercaptans such as phenol, methylthiophenol, ethylthiophenol; acidamides such as acetoanilide, acetoaniside, acetotolide, acrylamide, methacrylicamide, acetateamide, stearate amide, benzamide; succinide imide, phthalateimide, maleateimide, etc. Imid-based; diphenylamine, phenylnaphthylamine, xylidine, N-phenylxylidine, carbazole, aniline, naphthylamine, butylamine, dibutylamine, butylphenylamine and other amine-based; imidazole, 2-ethylimidazole and other imidazole-based; urea, thiourea , Ethyleneurea, ethylenethiourea, diphenylurine Urea type such as element; Carbamic acid ester type such as N-phenylcarbamic acid phenyl; Imine type such as ethyleneimine and propyleneimine; Sulfite type such as sodium bisulfite and potassium bisulfite; Azol type compound and the like can be mentioned. .. Examples of the azole compound include pyrazole, 3,5-dimethylpyrazole, 3-methylpyrazole, 4-benzyl-3,5-dimethylpyrazole, 4-nitro-3,5-dimethylpyrazole, 4-bromo-3, Pyrazole or pyrazole derivatives such as 5-dimethylpyrazole, 3-methyl-5-phenylpyrazole; imidazole or imidazole derivatives such as imidazole, benzimidazole, 2-methylimidazole, 2-ethylimidazole, 2-phenylimidazole; 2-methylimidazoline , 2-Pyrazole imidazoline and other imidazoline derivatives and the like.

Among them, preferred blocking agents include oxime-based blocking agents, active methylene-based blocking agents, pyrazoles or pyrazole derivatives.

When blocking (reacting the blocking agent), a solvent can be added as needed. The solvent used for the blocking reaction may be one that is not reactive with the isocyanate group. For example, acetone, ketones such as methyl ethyl ketone, esters such as ethyl acetate, and N-methyl-2-pyrrolidone (NMP). Such solvents can be mentioned.

The polyisocyanate compound (b3) can be used alone or in combination of two or more.

When the undercoat coating composition (B) contains the above-mentioned polyisocyanate compound (b3), the blending ratio thereof is the amount of isocyanate groups (block) of the polyisocyanate compound (b3) from the viewpoint of adhesion, cold heat load resistance and the like. The equivalent ratio (NCO / OH) of the hydroxyl group-containing acrylic resin (b1) and the total hydroxyl group amount of the hydroxyl group-containing polyester resin (b2) is usually 0.5 to 2.0, particularly 0. It is preferable to use the ratio within the range of 6 to 1.5.

Further, since the polyisocyanate compound (b3) can react with a hydroxyl group at a relatively low temperature to form a crosslinked coating film, it is particularly preferably used when the base material is a material that is easily thermally deformed such as an organic material. be able to.

When the undercoat coating composition (B) contains the polyisocyanate compound (b3), the undercoat coating composition (B) can contain a urethanization reaction catalyst.

Specific examples of the urethanization reaction catalyst include tin octylate, dibutyltin diacetate, dibutyltin di (2-ethylhexanoate), dibutyltin dilaurate, dioctyltin diacetate, and dioctyltindi (2). -Ethylhexanoate), dibutyltin oxide, dibutyltin sulfite, dioctyltin oxide, dibutyltin fatty acid salt, lead 2-ethylhexanoate, zinc octylate, zinc naphthenate, fatty acid zincs, bismuth octanate, 2- Organic metal compounds such as bismuth ethylhexanoate, bismuth oleate, bismuth neodecanoate, bismuth versaticate, bismuth naphthenate, cobalt naphthenate, calcium octylate, copper naphthenate, tetra (2-ethylhexyl) titanate; tertiary amine Etc., and these can be used individually or in combination of two or more.

When the above urethanization reaction catalyst is used, the amount of catalyst is 0.0001 to 0.5% by mass, particularly 0.0005 to 0.1, based on the total solid content of the undercoat coating composition (B). It is preferably in the range of mass%.

When the undercoat coating composition (B) contains the above-mentioned urethanization reaction catalyst, the undercoat coating composition (B) has acetic acid, propionic acid, butyric acid, isopentanoic acid, and hexanoic acid from the viewpoints of storage stability, curability, and the like. , 2-Ethylbutyric acid, naphthenic acid, octylic acid, nonanoic acid, decanoic acid, 2-ethylhexanoic acid, isooctanoic acid, isononanoic acid, lauric acid, palmitic acid, stearic acid, oleic acid, linoleic acid, neodecanoic acid, versatic acid , Organic acids such as isobutyric anhydride, itaconic anhydride, acetic acid anhydride, citraconic anhydride, propionic anhydride, maleic anhydride, butyric anhydride, citric anhydride, trimellitic anhydride, pyromellitic anhydride, phthalic anhydride; hydrochloric acid, Inorganic acids such as phosphoric acid; metal coordinating compounds such as acetylacetone and imidazole compounds may be contained.

The undercoat coating composition (B) includes resins other than (b1) and (b2), solvents, pigments, cross-linking agents other than (b3), catalysts, and ultraviolet absorbers, as long as the effects of the present invention are not impaired. , Light stabilizers, antioxidants, surface conditioners, defoamers, emulsifiers, surfactants, antifouling agents, wetting agents, thickeners, dyes, gloss adjusters, etc. Additives and the like can be appropriately contained.

The undercoat coating composition (B) may be in the form of a melt, a solution, a suspension, or an emulsion, but the hydroxyl group-containing acrylic resin (b1) and / or the hydroxyl group-containing polyester resin (b2) in the solvent. It is preferable that the solution is in the form of a solution in which is dissolved, from the viewpoint of productivity and workability. In this case, the undercoat coating composition (B) contains a hydroxyl group-containing acrylic resin (b1) and / or a hydroxyl group-containing polyester resin (b2) and a solvent.

Examples of the solvent include ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone and cyclohexanone, cellosolves such as methyl cellosolve, ethyl cellosolve and butyl cellosolve, esters such as ethyl acetate and butyl acetate, and aromatic hydrocarbons such as toluene and xylene. , Alcohols such as methanol, ethanol, propanol and butanol, tetrahydrofuran, dimethylformamide, petroleum hydrocarbons and the like.

Examples of the pigment include bright pigments, coloring pigments, extender pigments and the like. The pigment can be used alone or in combination of two or more.

Examples of the brilliant pigment include aluminum (including vapor-deposited aluminum), copper, zinc, brass, nickel, glass flakes, aluminum oxide, mica, titanium oxide and / or iron oxide-coated aluminum oxide, titanium oxide and the like. / Or an iron oxide-coated mica or the like.

Examples of the coloring pigment include titanium oxide, zinc oxide, carbon black, molybdenum red, Prussian blue, cobalt blue, azo pigment, phthalocyanine pigment, quinacridone pigment, isoindolin pigment, slene pigment, and perylene. Examples thereof include based pigments, dioxazine based pigments, and diketopyrrolopyrrole based pigments.

Examples of the extender pigment include clay, kaolin, barium sulfate, barium carbonate, calcium carbonate, talc, silica, alumina white and the like.

When the undercoat coating composition (B) contains the above pigment, the content of the pigment is 1 to 70% by mass, preferably 5 to 60% by mass, based on the total solid content of the undercoat coating composition (B). %, More preferably in the range of 15 to 50% by mass.

In the method for forming a multi-layer coating film of the present invention, the undercoat coating composition (B) is coated on the primer layer to form an undercoat coating film.

The coating method of the undercoat coating composition (B) is not particularly limited, and examples thereof include air spray coating, airless spray coating, rotary atomization coating, curtain coat coating, and the like. Can be formed. Of these, methods such as air spray coating and rotary atomization coating are preferable. When painting, electrostatic electricity may be applied if necessary.

The undercoat coating film can be made into a cured coating film by heating or leaving at room temperature. The heating can be performed by a known heating means. Specifically, for example, it can be performed by hot air heating, infrared heating, high frequency heating, or the like.

In the present invention, the cured coating film is a cured and dried state defined in JIS K 5600-1-1, that is, the center of the coated surface is strongly sandwiched between the thumb and the index finger, and the coated surface is dented by fingerprints. The coating film is in a state where it does not adhere, the movement of the coating film is not felt, and the center of the coated surface is rapidly and repeatedly rubbed with the fingertip to leave no scratches on the coated surface. On the other hand, the uncured coating film is a state in which the coating film has not reached the cured and dried state, and also includes a touch-dried state and a semi-cured and dried state defined in JIS K 5600-1-1.

When the undercoat coating film (B) is applied to form an undercoat coating film and then the undercoat coating film is heat-cured, the heating temperature is determined from the viewpoints of productivity, workability, thermal stability of the base material, and the like. Therefore, it is preferably in the range of 40 to 150 ° C., preferably 50 to 140 ° C., and more preferably 70 to 130 ° C. The heating time is preferably in the range of 15 minutes to 24 hours, preferably 30 to 120 minutes.

The coating film thickness of the undercoat coating film is preferably in the range of 5 to 70 μm, preferably 10 to 60 μm, and more preferably 15 to 50 μm as the cured film thickness.

Topcoat paint composition (C)
The topcoat coating composition (C) contains a hydroxyl group-containing acrylic resin (c1) and a polyisocyanate compound (c2).

The hydroxyl group-containing acrylic resin (c1) is an acrylic resin having one or more hydroxyl groups in one molecule. Among them, the glass transition temperature (Tg) of the hydroxyl group-containing acrylic resin (c1) is −20 ° C. to 50 ° C., preferably −15, from the viewpoint of obtaining a multi-layer coating film having excellent adhesion, water resistance and cold heat load resistance. It is preferably an acrylic resin having a temperature of about 50 ° C., more preferably −10 to 40 ° C.

The hydroxyl group-containing acrylic resin (c1) can be obtained from, for example, a method known per se, for example, a hydroxyl group-containing polymerizable unsaturated monomer and another polymerizable unsaturated monomer copolymerizable with the hydroxyl group-containing polymerizable unsaturated monomer. It can be produced by copolymerizing by a method such as a solution polymerization method in an organic solvent or an emulsion polymerization method in water.

As the hydroxyl group-containing polymerizable unsaturated monomer, the hydroxyl group-containing polymerizable unsaturated monomer described in the explanation column of the hydroxyl group-containing acrylic resin (b1) can be used.

Further, as another polymerizable unsaturated monomer copolymerizable with the hydroxyl group-containing polymerizable unsaturated monomer, the alicyclic hydrocarbon group-containing polymerizable unsaturated monomer described in the explanation column of the hydroxyl group-containing acrylic resin (b1) is described. As specific examples of the monomer and other polymerizable unsaturated monomer copolymerizable with the hydroxyl group-containing polymerizable unsaturated monomer, the polymerizable unsaturated monomer listed in (1) to (7) can be used.

The glass transition temperature (Tg) of the hydroxyl group-containing acrylic resin (c1) is adjusted, for example, by adjusting the type and compounding ratio of the polymerizable unsaturated monomer used in the synthesis of the hydroxyl group-containing acrylic resin (c1). can do.

The polyisocyanate compound (c2) is a compound having at least two isocyanate groups in one molecule. Further, the polyisocyanate compound (c2) may be a polyisocyanate compound in which an isocyanate group is blocked with a blocking agent, that is, a so-called blocked polyisocyanate compound.

As the polyisocyanate compound (c2), the polyisocyanate compound described in the explanation column of the polyisocyanate compound (b3) can be used.

As the polyisocyanate compound (c2), aliphatic diisocyanates, alicyclic diisocyanates and derivatives thereof can be preferably used from the viewpoints of adhesion, cold heat load resistance and the like.

In the topcoat coating composition (C), the blending ratio of the hydroxyl group-containing acrylic resin (c1) and the polyisocyanate compound (c2) is the same as that of the polyisocyanate compound (c2) from the viewpoint of adhesion, cold heat load resistance, and the like. The equivalent ratio (NCO / OH) of the isocyanate group (including the blocked isocyanate group) to the hydroxyl group of the hydroxyl group-containing acrylic resin (c1) is usually 0.5 to 2.0, particularly 0.6 to 1.5. It is preferable to use it at a ratio within the range.

The topcoat coating composition (C) includes a resin other than (c1), a catalyst, a solvent, a pigment, a cross-linking agent other than the polyisocyanate compound (c2), and an ultraviolet absorber, as long as the effects of the present invention are not impaired. Other commonly used in the field of coating such as light stabilizers, antioxidants, surface conditioners, defoamers, emulsifiers, surfactants, antifouling agents, wetting agents, thickeners, dyes, gloss adjusters, etc. Additive components and the like can be appropriately contained.

As the catalyst, for example, the urethanization catalyst described in the explanation column of the undercoat coating composition (B) can be used.

The topcoat coating composition (C) may be in the form of a melt, a solution, a suspension, or an emulsion, but the hydroxyl group-containing acrylic resin (c1) and the polyisocyanate compound (c2) are dissolved in the solvent. The solution form is preferable from the viewpoint of productivity and workability. In this case, the topcoat coating composition (C) contains a hydroxyl group-containing acrylic resin (c1), a polyisocyanate compound (c2), and a solvent.

Examples of the solvent include ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone and cyclohexanone, cellosolves such as methyl cellosolve, ethyl cellosolve and butyl cellosolve, esters such as ethyl acetate and butyl acetate, and aromatic hydrocarbons such as toluene and xylene. , Alcohols such as methanol, ethanol, propanol and butanol, tetrahydrofuran, dimethylformamide, petroleum hydrocarbons and the like.

As the pigment, for example, the pigment described in the explanation column of the undercoat coating composition (B) can be used.

In the method for forming a multi-layer coating film of the present invention, the topcoat coating composition (C) is coated on the undercoat coating film or the intermediate coating film described later to form a topcoat coating film. The top coating film or the intermediate coating film may be an uncured coating film or a cured coating film.

The coating method of the topcoat coating composition (C) is not particularly limited, and examples thereof include air spray coating, airless spray coating, rotary atomization coating, curtain coat coating, and the like. Can be formed. Of these, methods such as air spray coating and rotary atomization coating are preferable. When painting, electrostatic electricity may be applied if necessary.

The coating film thickness of the topcoat coating film is preferably in the range of 5 to 70 μm, preferably 10 to 60 μm, and more preferably 15 to 50 μm as the cured film thickness.

The topcoat coating film can be made into a cured coating film by heating or allowing it to stand at room temperature. Above all, from the viewpoint of production efficiency and the like, it is preferable to obtain a cured coating film by heating. The heating can be performed by a known heating means. Specifically, for example, it can be performed by hot air heating, infrared heating, high frequency heating, or the like.

When the topcoat coating film (C) is applied to form a topcoat coating film and then the topcoat coating film is heat-cured, the heating temperature is determined from the viewpoints of productivity, workability, thermal stability of the base material, and the like. Therefore, it is preferably in the range of 40 to 150 ° C., preferably 50 to 140 ° C., and more preferably 70 to 130 ° C. The heating time is preferably in the range of 15 minutes to 24 hours, preferably 30 to 120 minutes.

Further, in the method for forming a multi-layer coating film of the present invention, the undercoat coating film may be cured before the coating of the topcoat coating composition (C), and the undercoat coating film may be cured in an uncured state. The topcoat coating composition (C) may be applied to form a topcoat coating film, and then the undercoat coating film and the topcoat coating film may be cured at the same time. Above all, it is preferable to use the latter method from the viewpoint of energy saving and the like.

Further, in the method for forming a multi-layer coating film of the present invention, an intermediate coating film different from these coating films may be formed between the undercoat coating film and the topcoat coating film. Further, the intermediate coating film may be a single layer or two or more layers.

When forming the intermediate coating film, each of the undercoat coating film, the intermediate coating film, and the topcoat coating film may be cured or may be cured at the same time. Above all, from the viewpoint of energy saving and the like, it is preferable to cure the undercoat coating film, the intermediate coating film and the topcoat coating film at the same time.

The intermediate coating film can be formed by coating the intermediate coating composition.

As the intermediate coating composition, a known coating composition can be used. Specifically, for example, a coating composition containing a substrate resin having a crosslinkable functional group and a crosslinking agent can be used. Above all, from the viewpoint of cold heat load resistance and the like, it is preferable to use a coating composition containing a hydroxyl group-containing acrylic resin and a polyisocyanate compound.

In addition, the intermediate coating composition includes catalysts, solvents, pigments, ultraviolet absorbers, light stabilizers, antioxidants, surface conditioners, antifoaming agents, emulsifiers, surfactants, antifouling agents, wetting agents, and thickeners. Other additive components usually used in the field of coating such as thickeners, dyes and gloss adjusters can be appropriately contained.

When the undercoat coating film, the intermediate coating film formed as required, and the topcoat coating film are simultaneously heat-cured, the heating temperature is determined from the viewpoints of productivity, workability, thermal stability of the base material, and the like. It is preferably in the range of 40 to 150 ° C., preferably 50 to 140 ° C., and more preferably 70 to 130 ° C. The heating time is preferably in the range of 15 minutes to 24 hours, preferably 30 to 120 minutes.

Another aspect of the method for forming a multi-layer coating film of the present invention is
On the substrate
Step (1): A step of forming a primer layer using the composition (A) containing a polymer-type silane coupling agent.
Step (2): The topcoat coating composition (C) containing the hydroxyl group-containing acrylic resin (c1) and the polyisocyanate compound (c2) is coated on the substrate on which the primer layer is formed in the step (1). It is characterized by including a step of forming a topcoat coating film.

The base material, primer composition (A) and topcoat coating composition (C) in another aspect of the multi-layer coating film forming method of the present invention are described in one aspect of the multi-layer coating film forming method of the present invention. The same as can be used.

In another aspect of the method for forming a multi-layer coating film of the present invention, the topcoat coating composition (C) is coated on the primer layer to form a topcoat coating film. The primer layer may be an uncured coating film or a cured coating film.

Further, in another aspect of the method for forming a multi-layer coating film of the present invention, an intermediate coating film different from these coating films and the above-mentioned undercoat coating film is formed between the primer layer and the topcoat coating film. You may. The intermediate coating film is the intermediate coating film described in one aspect of the method for forming a multi-layer coating film of the present invention. The intermediate coating film may be a single layer or two or more layers.

When forming the intermediate coating film, each of the intermediate coating film and the top coating film may be cured or may be cured at the same time. Above all, from the viewpoint of energy saving and the like, it is preferable to cure the intermediate coating film and the top coating film at the same time.

The intermediate coating film can be formed by coating the intermediate coating composition described in one aspect of the method for forming a multi-layer coating film of the present invention.

The coating method of the primer composition (A), the intermediate coating composition and the top coating composition (C) used as needed is the method described in one aspect of the multi-layer coating film forming method of the present invention. Can be adopted.

Hereinafter, the present invention will be described in more detail with reference to Production Examples, Examples and Comparative Examples. However, the present invention is not limited thereto. In each example, "parts" and "%" are based on mass unless otherwise specified. The film thickness of the coating film is based on the cured coating film.

Production of Primer Composition (A) Production Example 1
"X-12-981S" (trade name, polyfunctional silane coupling agent having an epoxy group and an ethoxysilyl group, number of functional groups (relative to alkoxysilyl group): 3, viscosity: 1000 mm ² / s, functional group equivalent : 290 g / mol, manufactured by Shin-Etsu Silicone Co., Ltd.) was diluted with butyl acetate so that its active ingredient was 10%, and stirred to obtain a primer composition (A-1).

Manufacturing example 2
"X-12-984S" (trade name, polyfunctional silane coupling agent having an epoxy group and an ethoxysilyl group, number of functional groups (relative to alkoxysilyl group): 3, viscosity: 2000 mm ² / s, functional group equivalent : 270 g / mol, manufactured by Shin-Etsu Silicone Co., Ltd.) was diluted with butyl acetate so that its active ingredient was 10%, and stirred to obtain a primer composition (A-2).

Manufacturing example 3
"X-12-1154" (trade name, polyfunctional silane coupling agent having a mercapto group and a methoxysilyl group, number of functional groups (relative to alkoxysilyl group): 3, viscosity: 1500 mm ² / s, functional group equivalent : 240 g / mol, manufactured by Shin-Etsu Silicone Co., Ltd.) was diluted with butyl acetate so that its active ingredient was 10%, and stirred to obtain a primer composition (A-3).

Manufacturing example 4
"X-12-1156" (trade name, polyfunctional silane coupling agent having a mercapto group and a methoxysilyl group, number of functional groups (relative to alkoxysilyl group): 5, viscosity: 5000 mm ² / s, functional group equivalent : 210 g / mol, manufactured by Shin-Etsu Silicone Co., Ltd.) was diluted with butyl acetate so that its active ingredient was 10%, and stirred to obtain a primer composition (A-4).

Production example 5
"X-12-1159L" (trade name, polyfunctional silane coupling agent having isocyanate group and methoxysilyl group, number of functional groups (relative to alkoxysilyl group): 2, viscosity: 4000 mm ² / s, functional group equivalent : 360 g / mol, manufactured by Shin-Etsu Silicone Co., Ltd.) was diluted with butyl acetate so that its active ingredient was 10%, and stirred to obtain a primer composition (A-5).

Production example 6
"KBM403" (trade name, 3-glycidoxypropyltrimethoxysilane, monofunctional silane coupling agent having an epoxy group and a methoxysilyl group, manufactured by Shin-Etsu Silicone Co., Ltd.) so that its active ingredient is 10%. Diluted with butyl acetate and stirred to obtain a primer composition (A-6).

Production example 7
"KBM803" (trade name, 3-mercaptopropyltrimethoxysilane, a monofunctional silane coupling agent having a mercapto group and a methoxysilyl group, manufactured by Shin-Etsu Silicone Co., Ltd.) is butyl acetate so that its active ingredient is 10%. The primer composition (A-7) was obtained by diluting and stirring with.

Production Example 8
"KBM9007" (trade name, 3-isocyanatepropyltriethoxysilane, a monofunctional silane coupling agent having an isocyanate group and an ethoxysilyl group, manufactured by Shin-Etsu Silicone Co., Ltd.) is butyl acetate so that its active ingredient is 10%. The primer composition (A-8) was obtained by diluting and stirring with.

Production Example 9 of Production of Hydroxy Group-Containing Acrylic Resin (b1)
45 parts of butyl acetate was placed in a reaction vessel equipped with a thermometer, a thermostat, a stirrer, a reflux condenser, a nitrogen introduction tube and a dropping device, and the mixture was stirred at 115 ° C. while blowing nitrogen gas into the reaction vessel. A monomer mixture consisting of 30 parts of methacrylate, 30 parts of isobornyl acrylate, 5 parts of styrene, 35 parts of 2-ethylhexyl acrylate and 4 parts of 2,2'-azobisisobutyronitrile was added dropwise at a uniform rate over 4 hours. Further, it was aged at the same temperature for 1 hour. After that, a mixture of 15 parts of butyl acetate and 1.0 part of 2,2'-azobisisobutyronitrile was added dropwise to the reaction vessel over 3 hours, and after completion of the addition, the mixture was aged for 1 hour and then diluted with butyl acetate. , A hydroxyl group-containing acrylic resin (b1-1) solution having a solid content of 50% was obtained. The obtained hydroxyl group-containing acrylic resin (b1-1) has a glass transition temperature (Tg) of 16.5 ° C., a solubility parameter (SP value) of 8.64, a hydroxyl value of 129.3 mgKOH / g, and a weight average molecular weight. It was 15,000.

Production Examples 10 to 14
In Production Example 9, hydroxyl group-containing acrylic resin (b1-2) to (b1-6) solutions having a solid content of 50% were obtained in the same manner as in Production Example 9, except that the monomer compounding composition was as shown in Table 1. rice field. Table 1 also shows the glass transition temperature (Tg), solubility parameter (SP value), hydroxyl value, and weight average molecular weight of each hydroxyl group-containing acrylic resin.

Production Example 15 of Production of Hydroxyl-Containing Polyester Resin (b2)
66 parts (0.43 mol) of hexahydrophthalic anhydride, 71 parts (0.43 mol) of isophthalic acid, 47 parts of neopentyl glycol (47 parts) in a reaction vessel equipped with a stirrer, a thermometer, a rectification tower and a water separator. 0.45 mol), 68 parts (0.5 mol) of trimethylol propane were charged, heated to 200 to 220 ° C., and reacted until the acid value became 1 or less. Next, the mixture was cooled to 160 ° C., 28 parts (0.18 mol) of hexahydrophthalic anhydride was added, and the reaction was continued as it was, and the reaction was terminated when the acid value reached 40. After cooling to 80 ° C., cyclohexanone was added to obtain a polyester resin (b2-1) solution having a solid content of 50%. The obtained resin (b2-1) had a number average molecular weight of 2600 and a hydroxyl value of 110 mgKOH / g.

Production example 16
66 parts (0.43 mol) of hexahydrophthalic anhydride, 71 parts (0.43 mol) of isophthalic acid, 47 parts of neopentyl glycol (47 parts) in a reaction vessel equipped with a stirrer, a thermometer, a rectification tower and a water separator. 0.45 mol), 68 parts (0.5 mol) of trimethylol propane were charged, heated to 200 to 220 ° C., and reacted until the acid value became 1 or less. Next, the mixture was cooled to 160 ° C., 46 parts (0.3 mol) of hexahydrophthalic anhydride was added, and the reaction was continued as it was, and the reaction was terminated when the acid value reached 65. After cooling to 80 ° C., cyclohexanone was added to obtain a polyester resin (b2-2) solution having a solid content of 50%. The obtained resin (b2-2) had a number average molecular weight of 2700 and a hydroxyl value of 77 mgKOH / g.

Production Example 17 of Production of Undercoat Paint Composition (B)
138 parts (69 parts solid content) and 80 parts of "CR-95" (trade name, manufactured by Ishihara Sangyo Co., Ltd., titanium oxide pigment, solid content 100%) of a hydroxyl group-containing acrylic resin (b1-1) solution in a wide-mouthed glass bottle. The glass beads were added and sealed, and the mixture was dispersed in a paint shaker for 30 minutes, and then the glass beads were removed to obtain a pigment-dispersed paste. Next, 218 parts (solid content 149 parts) of the obtained pigment dispersion paste, "Sumijour N-3300" (trade name, manufactured by Sumika Bayer Urethane Co., Ltd., isocyanurate ring adduct of hexamethylene diisocyanate, solid content content 100). %) 31 parts, dibutyltin diacetate 0.04 parts and "Disparon LF-1985-50" (trade name, manufactured by Kusumoto Kasei Co., Ltd., surface conditioner, solid content content 50%) 0.1 parts (solid content 0) (0.05 parts) was mixed uniformly, and further diluted and stirred with butyl acetate so that the solid content became 30% to obtain an undercoat coating composition (B-1).

Production Examples 18 to 25
Undercoat coating compositions (B-2) to (B-9) having a solid content of 30% were obtained in the same manner as in Production Example 17, except that the compounding composition was as shown in Table 2 in Production Example 17. The compounding composition shown in Table 2 depends on the solid content mass of each component.

Production Example 26 of Production of Hydroxy Group-Containing Acrylic Resin (c1)
45 parts of butyl acetate was placed in a reaction vessel equipped with a thermometer, a thermostat, a stirrer, a reflux condenser, a nitrogen introduction tube and a dropping device, and the mixture was stirred at 115 ° C. while blowing nitrogen gas, and 2-hydroxyethyl was added therein. A monomer mixture consisting of 25 parts of acrylate, 28 parts of styrene, 47 parts of n-butyl acrylate and 4 parts of 2,2'-azobisisobutyronitrile was added dropwise at a uniform rate over 4 hours, and further aged at the same temperature for 1 hour. bottom. After that, a mixture of 15 parts of butyl acetate and 1.0 part of 2,2'-azobisisobutyronitrile was added dropwise to the reaction vessel over 3 hours, and after completion of the addition, the mixture was aged for 1 hour and then diluted with butyl acetate. , A hydroxyl group-containing acrylic resin (c1-1) solution having a solid content of 50% was obtained. The obtained hydroxyl group-containing acrylic resin (c1-1) had a glass transition temperature (Tg) of −14 ° C., a hydroxyl value of 121 mgKOH / g, and a weight average molecular weight of 15,000.

Production Examples 27 and 28
In Production Example 26, a hydroxyl group-containing acrylic resin (c1-2) and (c1-3) solutions having a solid content of 50% were obtained in the same manner as in Production Example 26 except that the monomer compounding composition was as shown in Table 3. rice field. Table 3 also shows the glass transition temperature, hydroxyl value, and weight average molecular weight of each hydroxyl group-containing acrylic resin.

Production Example 29 of Production of Topcoat Coating Composition (C)
140 parts (solid content 70 parts) of hydroxyl group-containing acrylic resin (c1-1) solution, "Sumijour N-3300" (trade name, manufactured by Sumika Bayer Urethane Co., Ltd., isocyanurate ring adduct of hexamethylene diisocyanate, solid content contained Rate 100%) 30.4 parts, dibutyltin diacetate 0.02 parts and "Disparon LF-1985-50" (trade name, manufactured by Kusumoto Kasei Co., Ltd., surface conditioner, solid content content 50%) 0.1 parts (0.05 parts of solid content) was uniformly mixed, and further diluted and stirred with butyl acetate so that the solid content became 30% to obtain a topcoat coating composition (C-1).

Production Examples 30, 31
In Production Example 29, topcoat coating compositions (C-2) and (C-3) having a solid content of 30% were obtained in the same manner as in Production Example 29, except that the compounding composition was as shown in Table 4. The compounding composition shown in Table 4 depends on the solid content mass of each component.

Preparation of test plate (base material)
Base material (a): The surface of a glass plate having a size of 100 mm × 150 mm × 3.0 mm was degreased with isopropyl alcohol to obtain a base material (a).

Base material (b): Polycarbonate (PC) plate The surface of a 100 mm × 150 mm × 3.0 mm polycarbonate (PC) plate was degreased with isopropyl alcohol to obtain a base material (b).

Base material (c): Fiber reinforced plastic (FRP) plate The surface of a fiber reinforced plastic (FRP) plate having a size of 100 mm × 150 mm × 3.0 mm was degreased with isopropyl alcohol to obtain a base material (c).

Base material (d): The surface of an acrylonitrile-butadiene-styrene (ABS) plate 100 mm × 150 mm × 3.0 mm acrylonitrile-butadiene-styrene (ABS) plate was degreased with isopropyl alcohol to obtain a base material (d).

Base material (e): Glass fiber reinforced polypropylene (GFPP) plate The surface of a glass fiber reinforced polypropylene (GFPP) plate having a size of 100 mm × 150 mm × 3.0 mm was degreased with isopropyl alcohol to obtain a base material (e).

Example 1
The primer composition (A-1) was applied onto the substrate (a) using a brush so that the film thickness was 0.5 μm, and the primer layer was formed by setting at room temperature for 10 minutes. Next, the undercoat coating composition (B-3) was coated with an air spray so that the cured film thickness was 30 μm, and the setting was performed at room temperature for 10 minutes to form an uncured undercoat coating film. Next, the topcoat coating composition (C-2) was applied onto the uncured undercoat coating film using an air spray so that the cured film thickness was 35 μm, and the setting was performed at room temperature for 10 minutes. An uncured topcoat was formed. Then, the uncured undercoat film and the uncured topcoat film were heated at 90 ° C. for 1 hour to be cured to obtain a test plate.

Examples 2 to 24, Comparative Examples 1 to 8
Each of the base material, the primer composition (A), the undercoat coating composition (B), the topcoat coating composition (C), and the film thickness are the same as in Example 1 except that they are as shown in Table 5. A test plate was obtained.

Evaluation test Each of the obtained test plates was evaluated by the following test method. The evaluation results are shown in Table 5.
(Test method)
<Water resistance (adhesion with base material)>
Each test plate was immersed in warm water at 40 ° C. for 10 or 30 days. Next, on the coated surface of each test plate, 100 2 mm × 2 mm goban stitches were made according to JIS K 5600-5-6 (1990), an adhesive tape was attached to the surface, and then the surface was rapidly peeled off. The residual state of the Goban-grain coating film was examined, and the water resistance of each test plate was evaluated from the viewpoint of adhesion to the substrate according to the following criteria.

⊚: Remaining number / total number = 100 / 100, no edge chipping ○: Remaining number / total number = 100 / 100, with edge chipping Δ: Remaining number / total number = 99 to 90 / 100 pieces ×: remaining number / total number = 89 pieces or less / 100 pieces.

<Water resistance (appearance)>
The water resistance of each test plate after being immersed in warm water at 40 ° C. for 10 days or 30 days was evaluated from the viewpoint of appearance according to the following criteria.

⊚: No change in appearance with respect to the coating film before the test ○: Slight gloss, blistering or discoloration is observed with respect to the coating film before the test, but there is no problem when it is made into a product. Level Δ: Slight gloss, cracks, blister or discoloration is observed with respect to the coating film before the test, and the product is inferior. Or discoloration is seen.

<Cold and heat load resistance (appearance)>
For each test plate, a cold heat cycle test of 500 cycles was carried out with "-30 ° C for 3 hours → cooling 3 hours → 70 ° C 90% RH 3 hours → cooling 3 hours" as one cycle, and the appearance was determined according to the following evaluation criteria. The cold and heat load resistance was evaluated from the above points.

⊚: No change in appearance with respect to the coating film before the test ○: Slight gloss, blistering or discoloration is observed with respect to the coating film before the test, but there is a problem when it is made into a product. No level Δ: Slight gloss, cracks, blister or discoloration was observed with respect to the coating film before the test, and the product was inferior. Blisters or discoloration are seen.

Claims (4)

On the substrate
Step (1): A step of applying a primer composition (A) containing a polymer-type silane coupling agent which is an organic solvent solution having an active ingredient in the range of 1 to 40% by weight to form a primer layer.
Step (2): A step of coating the undercoat coating composition (B) on the substrate on which the primer layer is formed in the step (1) to form an undercoat coating film.
Step (3): The topcoat coating composition (C) containing the hydroxyl group-containing acrylic resin (c1) and the polyisocyanate compound (c2) is coated on the base material on which the undercoat coating film is formed in the step (2). A method for forming a multi-layer coating film, which comprises a step of forming a top coat coating film. On the substrate
Step (1): A step of applying a primer composition (A) containing a polymer-type silane coupling agent which is an organic solvent solution having an active ingredient in the range of 1 to 40% by weight to form a primer layer.
Step (2): The topcoat coating composition (C) containing the hydroxyl group-containing acrylic resin (c1) and the polyisocyanate compound (c2) is coated on the substrate on which the primer layer is formed in the step (1). A method for forming a multi-layer coating film, which comprises a step of forming a top coat coating film. The method for forming a multilayer coating film according to claim 1 or 2, wherein the polymer-type silane coupling agent contains at least one selected from an epoxy group, a mercapto group, and an isocyanate group and an alkoxysilyl group. The method for forming a multi-layer coating film according to claims 1 to 3, wherein the thickness of the primer layer is 1 μm or less.