JP5217161B2 - Baking paint composition and paint finishing method - Google Patents

Description

  The present invention relates to a new and useful baked paint composition, and more particularly to a baked paint composition suitable as a top coat used for laminated paint finishing and a paint finish method using the baked paint composition.

  More specifically, regarding a baking coating composition comprising a vinyl copolymer having a primary hydroxyl group and a phosphoric acid group and a curing agent containing a functional group that reacts with a hydroxyl group as essential components, rather than a conventional baking coating, In particular, the present invention relates to a highly practical baking coating composition having excellent surface hardness and solvent resistance, and a coating finishing method using the baking coating composition.

  Mainly in the field of paint such as IT home appliances such as personal computers and mobile phones, and metal paints for automobile parts, etc., there is a demand for a top coating film with high surface hardness, excellent durability, and good finished appearance. ing.

  Usually, an acrylic resin / melamine resin-based baking paint is used for a clear coating of a metal coating such as a magnesium alloy used for a material of an IT device or the like. It is required to have excellent wear resistance, solvent resistance, gloss and the like.

  As a conventional hydroxyl group-containing acrylic resin / melamine resin-based baking paint, for example, as an acrylic resin, a specific hydrophilic group-containing polymerizable unsaturated monomer (a), a hydroxyl group-containing polymerizable unsaturated monomer (b), a phosphate group A coating composition using a resin [A] having a hydroxyl value of 30 to 200 mg KOH / g, which is obtained by copolymerizing a monomer mixture comprising the polymerizable unsaturated monomer (c) and other polymerizable unsaturated monomer (d) (for example, In addition, it is described that it is possible to form a coating film that is excellent in coating film performance and in finished appearance, but is used for clear coating of metal coating such as magnesium alloy. For coatings, surface hardness, abrasion resistance, and solvent resistance are not sufficient.

JP 2001-279164 A

  Therefore, the object of the present invention is to provide a baked paint composition having a good appearance and excellent surface hardness, abrasion resistance, and solvent resistance, and a paint finishing method using the baked paint composition. It is in.

The present inventors, as a result of intensive studies in an attempt to solve the above problems, a primary hydroxyl group and a glass transition temperature (Tg) 8 5 ~1 0 0 specific vinyl copolymer ℃ having phosphoric acid group (A) and , A baked coating composition containing a melamine resin (B) , wherein a solid content weight ratio (A / B) of the vinyl copolymer (A) and the melamine resin (B) is 90/10 to 50 / The baking coating composition characterized by being in the range of 50 has a good coating film appearance, excellent surface hardness, abrasion resistance, and solvent resistance, and the baking coating composition is laminated. The present invention has been completed by finding out that it is suitable as a clear coat paint for forming a coating film.

That is, the present invention is baked paint primary hydroxyl group and a glass transition temperature having a phosphoric acid group (Tg) 8 5 ~1 0 0 specific vinyl copolymer ℃ and (A), containing the melamine resin (B) It is a composition, Comprising: Solid content weight ratio (A / B) of the said vinyl copolymer (A) and the said melamine resin (B) is a range used as 90 / 10-50 / 50, It is characterized by the above-mentioned. A baked paint composition is provided.

Furthermore, the present invention provides a paint finishing method, wherein after forming a base coat on a substrate, a top coat made of the baking coating composition according to claim 1 or 2 is formed on the base coat. Is to provide.

  The top coating composition of the present invention has a good coating film appearance and can form a coating film having excellent surface hardness, abrasion resistance, and solvent resistance. It is particularly suitable as a coating material.

The vinyl copolymer (A ) used in the present invention has a primary hydroxyl group and a phosphate group, and
A vinyl copolymer having a glass transition temperature (Tg) of 8 5 ~1 0 0 ℃, 1 primary hydroxyl group-containing vinyl monomer and phosphoric acid group-containing vinyl monomer with styrene and methyl methacrylate and / or It contains tertiary butyl methacrylate and other vinyl monomers, and the content of the phosphoric acid group-containing vinyl monomer is 0.1 to 2% by weight, and styrene and methyl methacrylate and / or A vinyl copolymer having a hydroxyl value of 20 to 200 mg KOH / g based on a primary hydroxyl group obtained by copolymerizing a vinyl monomer mixture having a content of butyl methacrylate of 50 to 90% by weight ; surface hardness, abrasion resistance, it is possible to form a coating film excellent as solvent resistance.

  As a method for preparing the vinyl copolymer (A), for example, a vinyl resin containing a primary hydroxyl group-containing vinyl monomer, a phosphate group-containing vinyl monomer, and other vinyl monomers. Examples thereof include a method of copolymerizing a monomer mixture in the presence of a radical initiator, a method of reacting a primary hydroxyl group-containing vinyl copolymer with phosphoric acid to form a phosphate ester, and the like. The former method of copolymerizing the mixture in the presence of a radical initiator is simple and preferred.

  Examples of the primary hydroxyl group-containing vinyl monomer include hydroxyalkyl (meth) acrylates such as 2-hydroxyethyl (meth) acrylate and 4-hydroxybutyl (meth) acrylate; 2-hydroxyethyl vinyl ether, 4- Hydroxyl-containing vinyl ethers such as hydroxybutyl vinyl ether; Hydroxyl-containing allyl ethers such as 2-hydroxyethyl allyl ether; Polyoxyalkylenes obtained from polyether polyols such as polyethylene glycol and unsaturated carboxylic acids such as (meth) acrylic acid Glycol monoesters;

“Placcel FA-1” (a monomer obtained by adding 1 mol of ε-caprolactone to 1 mol of 2-hydroxyethyl acrylate, manufactured by Daicel Chemical Industries, Ltd.), “Placcel FM-1”, “Placcel FM-3” , “Placcel FM-5” (a monomer obtained by adding 1 mol, 3 mol, and 5 mol of ε-caprolactone to 1 mol of 2-hydroxyethyl methacrylate, manufactured by Daicel Chemical Industries, Ltd.), “TONE M -100 "(a monomer obtained by adding 2 mol of ε-caprolactone to 1 mol of 2-hydroxyethyl acrylate, manufactured by Union Carbide, USA).

  In addition, to these primary hydroxyl group-containing vinyl monomers, 2-hydroxypropyl (meth) acrylate, 3-hydroxybutyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, 3-chloro-2-hydroxypropyl ( Secondary hydroxyalkyl (meth) acrylates such as meth) acrylate; adducts of epoxy group-containing unsaturated monomers such as glycidyl (meth) acrylate and acids such as acetic acid; unsaturated such as (meth) acrylic acid Hydroxyl groups other than primary hydroxyl groups such as adducts of various monoepoxy compounds other than epoxides of α-olefins such as carboxylic acids and “Cardura E” (phenylglycidyl ether manufactured by Shell of the Netherlands) It is possible to use vinyl-containing monomers in combination, but hydroxyl-containing vinyl-based monomers The vinyl monomer containing a hydroxyl group other than the primary hydroxyl group is preferably 50 mol% or less, more preferably 10 mol% or less, based on 100 mol% of the total amount of monomers.

  Next, the phosphoric acid group-containing vinyl monomer may be one in which a part of the phosphoric acid group is esterified, for example, acid phosphoxyethyl methacrylate, 3-chloro-2-acid phosphoxypropyl methacrylate, Examples include acid phosphooxypolyoxyethylene glycol monomethacrylate, methacryloyloxyethyl acid phosphate monoethanolamine half salt, and the like.

Further, as the other vinyl monomers, for example, methylcarbamoyl luer acrylate, ethyl (meth) acrylate, n- propyl (meth) acrylate, iso- propyl (meth) acrylate, n- butyl (meth) acrylate, isobutyl Alkyl esters of alkyl alcohols having 1 to 22 carbon atoms such as (meth) acrylate, 2-ethylhexyl (meth) acrylate, lauryl (meth) acrylate and (meth) acrylic acid; benzyl (meth) acrylate, phenethyl (meta ) Aralkyl (meth) acrylates such as acrylate; Cycloalkyl (meth) acrylates such as cyclohexyl (meth) acrylate and isobornyl (meth) acrylate; Methoxyethyl (meth) acrylate, Methoxybutyl (meth) acrylate Alkoxyalkyl (meth) acrylates;

Unsaturated carboxylic acids such as (meth) acrylic acid, 2-carboxyethyl (meth) acrylate, crotonic acid, itaconic acid, maleic acid, fumaric acid; monomethyl itaconate, mono-n-butyl itaconate, monomethyl maleate, maleate Monoesters of unsaturated dicarboxylic acids such as mono-n-butyl acid, monomethyl fumarate, mono-n-butyl fumarate (half-esters); monovinyl esters of saturated dicarboxylic acids such as monovinyl adipate and monovinyl succinate Unsaturated polycarboxylic acid anhydrides such as maleic anhydride and itaconic anhydride; Unsaturated monocarboxylic acid anhydrides such as acrylic anhydride and methacrylic anhydride; Unsaturated carboxylic acids such as acrylic acid and methacrylic acid Acid anhydrides and mixed acid anhydrides of acetic acid, propionic acid, benzoic acid and other saturated carboxylic acids Vinyl monomers having a carboxylic anhydride group such as: trimethylsilyl (meth) acrylate, dimethyl-t-butylsilyl (meth) acrylate, 1-ethoxyethyl (meth) acrylate, 2- (meth) acryloyloxytetrahydrofuran, etc. Vinyl monomers containing blocked carboxyl groups of

Diesters of unsaturated dicarboxylic acids such as maleic acid, fumaric acid, itaconic acid, and monohydric alcohols; vinyl acetate, vinyl propionate, vinyl pivalate, vinyl versatate, vinyl benzoate, "Beova" (Netherlands) Carboxylic acid vinyl esters such as vinyl esters manufactured by Kiel Ciel; alkyl esters of various crotonic acids such as methyl crotonic acid and ethyl crotonic acid; cyano group-containing vinyl such as (meth) acrylonitrile and crotononitrile Monomers: 2-dimethylaminoethyl (meth) acrylate, N- [2- (meth) acryloyloxy] ethylmorpholine, vinylpyridine, N-vinylcarbazole, N- (2-dimethylamino) ethyl (meth) Acrylamide, N- (2-diethylamino) ethyl (meth) acrylic Amino group-containing vinyl monomers such as amide, N- (2-dimethylamino) ethylcrotonic acid amide, N- (2-diethylamino) ethylcrotonic acid amide, 2-dimethylaminoethyl vinyl ether, 2-diethylaminoethyl vinyl ether ;

Epoxy group-containing vinyl monomers such as glycidyl (meth) acrylate, methyl glycidyl (meth) acrylate, 3,4-epoxycyclohexylmethyl (meth) acrylate, vinylcyclohexene oxide, glycidyl vinyl ether, methyl glycidyl vinyl ether, and allyl glycidyl ether 5-membered cyclic carbonate-containing vinyl-based monomer such as 2,3-carbonate propyl (meth) acrylate, 2-methyl-2,3-carbonate propyl (meth) acrylate, 3,4-carbonate butyl (meth) acrylate 5- [N- (meth) acryloylcarbamoyloxymethyl] -5-ethyl-1,3-dioxan-2-one, 5- [N- {2- (meth) acryloyloxy} ethylcarbamoyloxymethyl] -5 6-membered ring cyclocarbonate group-containing vinyl monomers such as ethyl-1,3-dioxan-2-one;

Carbamate group-containing vinyl monomers such as methyl N- (meth) acryloylcarbamate and ethyl N- [2- (meth) acryloyloxy] ethylcarbamate; “Biscoat 8F, 8FM, 3F or 3FM” [Osaka Fluorine-containing (meth) acrylic monomer produced by Organic Chemical Co., Ltd.], purple cyclohexyl (meth) acrylate, di-perfluorocyclohexyl fumarate, N-iso-propyl perfluorooctanesulfonamidoethyl (meth) acrylate, etc. (Per) fluoroalkyl group-containing vinyl monomers; fluoroolefins such as vinyl fluoride, vinylidene fluoride, tetrafluoroethylene, chlorotrifluoroethylene, hexafluoropropylene; chlorination of vinyl chloride, vinylidene chloride, etc. Olefin; ethylene , Propylene, isobutylene, 1-butene, 1-hexene and other α-olefins; styrene, α-methylstyrene, p-tert-butylstyrene, o-methylstyrene, p-methylstyrene, etc. Body;

Sulfonamide group-containing vinyl monomers such as p-styrenesulfonamide and N-methyl-p-styrenesulfonamide; sulfones such as styrenesulfonic acid, vinylsulfonic acid and 2-acrylamido-2-methyl-propanesulfonic acid Acid group-containing vinyl monomers or their organic amine salts; vinyltrimethoxysilane, allyltrimethoxysilane, trimethoxysilylethyl vinyl ether, 3- (meth) acryloyloxypropyltrimethoxysilane, 3- (meth) acryloyloxy Hydrolyzed silyl group-containing vinyl monomers such as propyltriethoxysilane, 3- (meth) acryloyloxypropylmethyldimethoxysilane, 3- (meth) acryloyloxypropylmethyldichlorosilane;

Alkyl vinyl ethers such as ethyl vinyl ether, n-butyl vinyl ether, isobutyl vinyl ether and n-hexyl vinyl ether; cycloalkyl vinyl ethers such as cyclopentyl vinyl ether, cyclohexyl vinyl ether and methylcyclohexyl vinyl ether; carbonyl group-containing vinyl-based units such as acrolein and methyl vinyl ketone Polymers-containing vinyl monomers such as “Blenmer PME” (manufactured by NOF Corporation); methacrylic acid methoxy-methoxycarbonyl-methyl ester, acrylic acid acetylamino-methoxycarbonyl-methyl ester, etc. Is mentioned.

Using these various vinyl monomers having a glass transition temperature (Tg) 8 5 ~1 0 0 ℃ vinyl copolymer To synthesize (A) include styrene, such as methyl methacrylate, tertiary butyl methacrylate It is effective to contain a vinyl monomer having a glass transition temperature of more than 100 ° C. as the other vinyl monomer. Among them, a copolymer having good compatibility with an amino resin and high surface hardness is effective. In order to obtain a polymer, the total content of styrene and methyl methacrylate and / or tertiary butyl methacrylate is based on the total amount of the vinyl monomer mixture used for the synthesis of the vinyl copolymer (A). it is important that 50 to 90% by weight, it is favorable preferable 70 to 90 wt%. At this time, with respect to the total amount of the vinyl monomer mixture, with the content of styrene is 2-40% by weight, it is preferable that the content of methyl methacrylate and / or tertiary chromatography butyl methacrylate is 10 to 90 wt%, Among them in the content of styrene is 5 to 20 wt%, and more preferably the content of methyl methacrylate and / or tertiary chromatography butyl methacrylate is 50 to 80 wt%.

  In order to prepare the vinyl copolymer (A) using various vinyl monomers as listed above, a solution polymerization method, a non-aqueous dispersion polymerization method, a photopolymerization method, a bulk polymerization method, etc. Various polymerization methods such as can be applied. Among these, the solution polymerization method in which a polymerization initiator or a molecular weight modifier is used in the presence of organic solvents is the simplest, and the obtained vinyl copolymer (A) solution is Since the polymer can be mixed with the amino resin (B) in the form of a solution without separation, the composition for baking coating of the present invention is preferable.

  Examples of the polymerization initiator include 2,2′-azobis (isobutyronitrile), 2,2′-azobis (2,4-dimethylvaleronitrile), 2,2′-azobis (2-methylbutyronitrile). Azo compounds such as nitrile); tert-butylperoxypivalate, tert-butylperoxybenzoate, tert-butylperoxy-2-ethylhexanoate, benzoyl peroxide, lauroyl peroxide, acetyl peroxide, di- Examples thereof include peroxides such as tert-butyl peroxide, dicumyl peroxide, tert-butyl hydroperoxide, cumene hydroperoxide, methyl ethyl ketone peroxide, and diisopropyl peroxycarbonate.

  Moreover, as an organic solvent used when applying the solution polymerization method, any of various organic solvents can be used, and they may be used alone or in combination of two or more. Of course.

  Examples of the organic solvent include a mixture of various hydrocarbons such as white spirit and mineral spirit; aliphatic or alicyclic such as hexane, heptane, octane, cyclohexane, cyclopentane, and cyclooctane. Hydrocarbons: aromatic hydrocarbons such as toluene, xylene, ethylbenzene, “HAWS” (high aromatic hydrocarbon mixed solvent manufactured by Shell of the Netherlands), etc .; ethyl acetate, butyl acetate, amyl acetate , Esters such as ethylene glycol monomethyl ether acetate, ethylene glycol monoethyl ether acetate, ethylene glycol monobutyl ether acetate; methanol, ethanol, n-propanol, i-propanol, n-butanol, sec-butanol, tert- Alcohols such as butanol, n-amyl alcohol, i-amyl alcohol, tert-amyl alcohol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether; acetone, methyl ethyl ketone, methyl isobutyl ketone, methyl amyl ketone, cyclohexanone Ketones such as;

Ethers such as dimethoxyethane, tetrahydrofuran, dioxane, diisopropyl ether, di-n-butyl ether; chlorinated hydrocarbons such as chloroform, methylene chloride, carbon tetrachloride, trichloroethane, tetrachloroethane; N-methylpyrrolidone, dimethylformamide, Examples thereof include dimethylacetamide and ethylene carbonate.

  The vinyl copolymer (A) thus obtained preferably has a weight average molecular weight in the range of 500 to 30,000, among which the coating film appearance, surface hardness, abrasion resistance and solvent resistance are preferred. Since a more excellent coating film can be formed, the range of 3,000 to 15,000 is particularly preferable.

The hydroxyl value of the vinyl copolymer (A), the surface hardness, wear resistance, because it can form a solvent resistant Yu is the coating film, the hydroxyl value based on the primary hydroxyl group is 20 to 200 mg KOH / g Der Ri, it is good Masui is 50~150mgKOH / g.

  The glass transition temperature (Tg) of the vinyl copolymer in the present invention is a value calculated by the following well-known Fox equation. The glass transition temperature (Tg) of the homopolymer used for the calculation is shown below. For those not described in the glass transition temperature (Tg) of the homopolymer, values generally described in the literature can be used. The glass transition temperature (Tg) of the homopolymer can also be determined by a differential scanning calorimetry method or a dynamic viscoelasticity measurement method.

[Fox's formula]
1 / Tg = Σ (Wn / Tgn)
Tg: Glass transition temperature of polymer (absolute temperature)
Wn: weight fraction of monomer n Tgn: glass transition temperature (absolute temperature) of homopolymer of monomer n

[Tg of homopolymer]
Styrene (St) homopolymer: 100 ° C.
Homopolymer of methyl methacrylate (MMA): 105 ° C
Methacrylic acid (MAA) homopolymer: 130 ° C.
Homopolymer of 2-hydroxyethyl methacrylate (2HEMA): 55 ° C
Homopolymer of 4-hydroxybutyl acrylate (4HBA): -80 ° C
Homopolymer of lauryl methacrylate (LMA): -65 ° C
Homopolymer of stearyl acrylate (STA): 30 ° C
n-butyl methacrylate (nBMA) homopolymer: 20 ° C.
Tertiary butyl methacrylate (tBMA) homopolymer: 107 ° C
Homopolymer of n-butyl acrylate (nBA): -54 ° C
Homopolymer of acid phosphoxyethyl methacrylate: 50 ° C
Homopolymer of dimethylaminoethyl methacrylate (DM): 18 ° C

Examples of the melamine resin used as the curing agent (B), for example, a melamine emissions, formalin, acetaldehyde, condensates obtained by reacting an aldehyde compound such as glyoxal; or these condensates, alcohols, In particular, compounds obtained by partial or complete etherification with a lower alcohol having 1 to 4 carbon atoms may be mentioned.

  The baking coating composition of the present invention includes, for example, the vinyl copolymer (A) or an organic solvent solution thereof, an amino resin (B), and if necessary, a vinyl copolymer (A) and an amino resin (B ) Is accelerated by mixing a curing catalyst, an organic solvent for dilution, various additives, and the like.

Examples of the vinyl copolymer (A) and solid weight ratio of melamine resin (B) (A / B) , surface hardness, abrasion resistance, because it can form a solvent resistant Yu is the coating film, 90 / 10-50 / 50 and Ri range der made, it is favorable preferable is a range among them the 85 / 15-60 / 40.

  As the curing catalyst, an acidic catalyst such as a strong acid catalyst or a weak acid catalyst is used. Examples of the strongly acidic catalyst include inorganic acids such as hydrochloric acid, nitric acid and sulfuric acid, organic acids such as sulfonic acid, and esters thereof, ammonium salts, onium salts and the like. Salt, benzoic acid, trichloroacetic acid and the like are preferable.

  As the sulfonic acid, for example, aromatic sulfonic acids such as dodecylbenzenesulfonic acid, naphthalene disulfonic acid and p-toluenesulfonic acid, aliphatic sulfonic acids such as methanesulfonic acid and ethanesulfonic acid, salts or esters thereof are preferable.

  As the weakly acidic catalyst, for example, phosphoric acids, phosphoric acid monoesters, phosphoric acids such as phosphites, or esters thereof are preferable.

  Examples of phosphoric acids and esters thereof include phosphoric acid, pyrophosphoric acid, monooctyl phosphate, monopropyl phosphate, monolauryl phosphate, dioctyl phosphate, dipropyl phosphate, dilauryl phosphate, mono (2- (meth) acryloyloxyethyl) acid phosphate, and the like. Is mentioned.

  As the addition amount of the curing catalyst, the content in the top coating composition of the present invention is usually in the range of 0 to 10% by weight, particularly in the range of 0.01 to 5% by weight. It is preferable.

  Examples of the organic solvent for dilution include “Solvesso 100” and “Solvesso 150” (all manufactured by Exxon), aromatic hydrocarbons such as toluene and xylene; aliphatic hydrocarbons such as hexane and cyclohexane; ethanol , Butanol, isobutanol and other alcohols; various organic solvents such as ethyl acetate, n-butyl acetate, amyl acetate, cellosolve acetate, and other organic solvents are appropriately selected in consideration of solubility and boiling point can do.

  Various additives such as a leveling agent, a rheology control agent, an ultraviolet absorber, and a light stabilizer can be added to the top coating composition according to the present invention as necessary. In addition, various compounds such as compounds containing two or more epoxy groups in one molecule, polyisocyanate compounds, silane coupling agents such as epoxy silane and amino silane, hydrolyzable silyl group-containing compounds such as methyl silicate and ethyl silicate It is possible to use a curing system in combination as long as the performance is not deteriorated.

  As a paint finishing method using the baked paint composition of the present invention, a base coat is formed on a substrate, and then a top coat made of the baked paint composition of the present invention is formed on the base coat. For example, after diluting the base coat paint to the desired viscosity with various thinners, paint it on the substrate with an air spray gun, electrostatic paint gun, minibell paint gun, etc. at a film thickness of about 10-30 μm. Then, after baking at a predetermined temperature for a predetermined time, or after a flash time of 2 to 5 minutes at room temperature, a clear coating composition comprising the baking coating composition of the present invention is obtained as desired. After diluting to a viscosity, it is applied to a film thickness of about 20-50 μm, then set for 5-10 minutes, then 20 minutes in an electric oven, gas oven, etc. For example, a coating method that performs baking for about an hour.

  In the system using a thinner with a low volatilization rate as represented by the aqueous base coat paint as the base coat paint, it can be forcedly dried (preheated) at a predetermined temperature during the flash time. .

  Further, as a paint finishing method of the present invention, for example, an over top when a coating film is formed by a 3-coat 2-bake method in which an over-top clear is applied after the 2-coat 1-bake method is applied. -The method of using the baking coating composition of the present invention as a clear can also be mentioned, and a three-coat one-bake method in which three layers of intermediate coating, base, and clear are coated with wet-on-wet and then baked at a predetermined temperature. The method of using the baking coating composition of the present invention as a clear when forming a coating film can also be mentioned.

  The base coat paint that can be used in the paint finishing method using the baked paint composition of the present invention is not particularly limited, but is preferably a composition of a hydroxyl group-containing acrylic resin and a melamine resin, a hydroxyl group-containing alkyd system. Composition of resin and melamine resin, Composition of hydroxyl group-containing polyester resin and melamine resin; Composition of hydroxyl group-containing resins and block isocyanate; Composition of carboxyl group-containing resin and epoxy group-containing resin; Hydrolyzed silyl group-containing resin And those in which at least one of organic pigments, inorganic pigments and metal pigments is blended with those in a combination of two or more of these.

  As the base coat paint, in addition to the conventional organic solvent solution type, a solution type high solid type, non-aqueous dispersion type resin type, and aqueous base coat can be used for the purpose of reducing the discharge amount of the organic solvent. The use of an aqueous base coat is the most effective for reducing the amount.

  The aqueous base coat resin used at this time is not limited to these illustrative examples, and any form of base coat paint using a water-soluble or water-dispersible resin may be used. Can be used in the present invention.

  As the water-soluble or water-dispersible resin, various water-soluble resins or water-dispersed resins can be used. For example, an acid group such as a carboxyl group or a sulfonic acid group contained in the resin A water-soluble or water-dispersible polyester resin, water-soluble or water-dispersible vinyl resin, water-soluble or water-dispersible polyurethane resin, water-soluble or water-dispersible polyester polyurethane resin obtained by neutralization with a base or an inorganic base; A water-soluble or water-dispersible vinyl resin obtained by neutralizing a basic group such as an amino group contained in the resin with an organic acid or an inorganic acid;

Anionic surfactants, cationic surfactants, amphoteric surfactants or nonionic surfactants are used as emulsifiers, and vinyl monomers are potassium persulfate, ammonium persulfate, hydrogen peroxide, cumene hydro An emulsion obtained by emulsion polymerization in the presence of a radical initiator such as peroxide;

In the emulsion polymerization, emulsification is carried out using a specific vinyl monomer having a surfactant site in itself as a part of the vinyl monomer without using a surfactant. Soap-free emulsion obtained by polymerization:

Various surfactants as described above are added to a polyester resin, a vinyl resin, an epoxy resin, a polyurethane resin, and a polyester polyurethane resin obtained by performing a polymerization reaction in an organic solvent, and the solvent is changed from an organic solvent to water. A water-dispersible polyester resin, a water-dispersible vinyl resin, a water-dispersible epoxy resin, a water-dispersible polyurethane resin or a water-dispersible polyester polyurethane obtained by an emulsification method (post-emulsification) that causes phase inversion and dispersion in water. resin;

In the post-emulsification method as described above, an anionic site, a cationic site or a nonionic site is previously formed on the side chain or terminal of the polyester resin, vinyl resin, epoxy resin, polyurethane resin or polyester polyurethane resin. After adding self-emulsifying properties by introducing a surface active site such as when each resin is synthesized or by introducing it after the synthesis, only post-emulsification is performed without adding various emulsifiers. Water dispersible polyester resin, water dispersible vinyl resin, water dispersible epoxy resin, water dispersible polyurethane resin or water dispersible polyester polyurethane resin respectively obtained by

In order to enhance the dispersion stability of each water-dispersible resin obtained by the above-described post-emulsification method, each emulsifier is added to each resin and then obtained by post-emulsification. Water-dispersible polyester resins, water-dispersible vinyl resins, water-dispersible epoxy resins, water-dispersible polyurethane resins or water-dispersible polyester polyurethane resins;

A water-dispersible vinyl resin in a form obtained by transferring a non-water-dispersible vinyl resin obtained in an aliphatic hydrocarbon to an aqueous medium by means such as neutralization; Water-dispersible vinyl resin in a form obtained by dispersing and polymerizing vinyl monomers in the presence of a polymer for use;

Obtained by reacting a resin having an addition-reactive functional group as disclosed in JP-A-6-212049 with a resin having another functional group capable of reacting with this addition-reactive functional group Water-dispersibility in the form obtained by polymerizing hydrophobic vinyl monomers in the presence of a water-dispersible resin obtained by phase-inversion emulsification of an acid group-containing graft resin in the form Resin etc. are mentioned.

  Furthermore, both the water-dispersible resin and the emulsion in the form of so-called crosslinked particles in which the dispersoid of the water-dispersible resin described above is crosslinked can be used in carrying out the coating finishing method of the present invention. However, it goes without saying that these resins may be used in combination of two or more.

  Among these, particularly preferable forms include emulsion resins, internally cross-linked emulsion resins, water-dispersible polyurethane resins, water-dispersible polyester polyurethane resins and the like because of the simplicity of the preparation method.

  The base coat paint that can be used in the paint finishing method of the present invention can be used as it is as a lacquer type, or as a curable type by adding a crosslinking agent or a curing catalyst having reactivity with the functional groups of each resin, Any shape can be used.

  For example, when each resin as described above has a hydroxyl group, it is desirable to use an amino resin or a polyisocyanate containing blocked isocyanate as the crosslinking agent. When each resin has an epoxy group, the crosslinking agent is used. As the crosslinking agent, it is desirable to use a polyepoxy compound or an epoxy group-containing resin as the crosslinking agent when each resin has a carboxyl group.

  Among them, as the aqueous base coat paint, a combination of a water-soluble resin having a hydroxyl group or a water-dispersible resin and an amino resin is preferable. Examples of typical amino resins in this case include Cymel 301, Cymel 303, Cymel 325, Cymel 327 [all manufactured by Mitsui Chemicals, Inc.], Nicalak MW-3, Nicalak MX43 [all manufactured by Sanwa Chemical Co., Ltd.], Uban 120 [manufactured by Mitsui Chemicals, Inc.], Watersol S- 695 [manufactured by Dainippon Ink & Chemicals, Inc.], BEETLE BE3020, BEETLE BE3021, BEETLE BE3751 [all manufactured by BIP Limited, UK] and the like.

  Furthermore, the above-mentioned paint for base coat containing a water-soluble or water-dispersible resin can be added with cross-linked resin fine particles or rheology control agent capable of imparting pseudo plasticity for the purpose of improving the appearance of paint finish.

  As these rheology control agents, inorganic or organic agents can be used. Typical examples include water-soluble cellulose ether, hydroxyethyl cellulose, methyl cellulose, carboxyl cellulose, polyvinyl alcohol, vinyl pyrrolidone ( (Co) polymer, (meth) acrylic acid (co) polymer, (meth) acrylamide (co) polymer, styrene-maleic anhydride copolymer, ethylene-maleic anhydride copolymer, and the like.

  The base coat paint that can be used in the paint finishing method of the present invention contains various metallic powders or various organic or inorganic color pigments as pigments, such as aluminum powder, copper powder, mica powder, titanium dioxide. Iron oxide, calcium carbonate, carbon black, phthalocyanine blue, toluidine red, perylene, quinacridone, benzidine yellow and the like.

  Furthermore, the above-mentioned paint for base coat includes various organic solvents for adjusting the coating viscosity, or additives and organic solvents for ensuring long-term storage stability as a paint, Various additives such as a preparation agent, a leveling agent, an ultraviolet absorber, an antioxidant, an antifoaming agent, and a plasticizer can also be blended.

  Various coating methods such as air spray coating, electrostatic spray coating, rotary atomizing electrostatic coating, etc. are employed as the coating method for both the base coat paint and the top clear paint. be able to.

  The baking coating composition and coating finishing method of the present invention thus obtained are mainly applied to iron products, stainless steel, magnesium alloys, aluminum, brass, polystyrene, polyethylene, polypropylene, acrylic resins, polycarbonate resins, ABS resins and the like. can do.

  As described above, the baking coating composition and the coating finishing method of the present invention can provide a coating film having excellent surface hardness, abrasion resistance, and solvent resistance. It is preferable for materials or automobile parts, and particularly suitable for metal members such as magnesium alloys and aluminum.

  Next, the present invention will be described more specifically with reference to reference examples, examples and comparative examples. In the following, all parts and percentages are by weight unless otherwise specified.

Reference Example 1 [Preparation of Vinyl Copolymer (A)]
550 parts of xylene and 300 parts of n-butanol were added to a reaction vessel equipped with a stirrer, a thermometer, a cooler, and a nitrogen introduction tube, and the temperature was raised to 115 ° C. and maintained at this temperature. Next, 128 parts of styrene, 726 parts of methyl methacrylate, 130 parts of 2-hydroxyethyl methacrylate, 10 parts of methacrylic acid, 6 parts of acid phosphooxyethyl methacrylate, 25 parts of tert-butylperoxy-2-ethylhexanate, -3 parts of tert-butyl peroxide and 150 parts of xylene were added dropwise over 4 hours.

  The reaction was continued for 5 hours after completion of the dropwise addition to obtain a vinyl copolymer (A-1) solution having a nonvolatile content of 50%. The obtained vinyl copolymer (A-1) was a vinyl copolymer having a primary hydroxyl group and a phosphate group having a weight average molecular weight of 12,000 and a glass transition temperature (Tg) of 97 ° C. It was. In addition, the hydroxyl value based on the primary hydroxyl group of a vinyl-type copolymer (A-1) was 56 mgKOH / g.

Reference example 2 (same as above)
A vinyl copolymer having a non-volatile content of 50% was obtained in the same manner as in Reference Example 1 except that the addition amount of methacrylic acid was changed from 10 parts to 6 parts and the addition amount of acid phosphooxyethyl methacrylate was changed from 6 parts to 10 parts. A solution of A-2) was obtained. The obtained vinyl copolymer (A-2) was a vinyl copolymer having a primary hydroxyl group and a phosphate group having a weight average molecular weight of 12,000 and a glass transition temperature (Tg) of 97 ° C. It was. The hydroxyl value based on the primary hydroxyl group of the vinyl copolymer (A-2) was 56 mgKOH / g.

Reference example 3 (same as above)
To the same reaction vessel as in Reference Example 1, 550 parts of xylene and 300 parts of n-butanol were added, and the temperature was raised to 115 ° C. and kept at this temperature. Next, 100 parts of styrene, 700 parts of t-butyl methacrylate, 24 parts of butyl acrylate, 160 parts of 2-hydroxyethyl methacrylate, 10 parts of methacrylic acid, 6 parts of acid phosphoxyethyl methacrylate, tert-butyl peroxy-2- 25 parts of ethyl hexanate, 3 parts of di-tert-butyl peroxide and 150 parts of xylene were added dropwise over 4 hours.

  The reaction was continued for 5 hours after completion of the dropwise addition to obtain a solution of a vinyl copolymer (A-3) having a nonvolatile content of 50%. The obtained vinyl copolymer (A-3) was a vinyl copolymer having a primary hydroxyl group and a phosphate group having a weight average molecular weight of 12,000 and a glass transition temperature (Tg) of 90 ° C. It was. The hydroxyl value based on the primary hydroxyl group of the vinyl copolymer (A-3) was 69 mgKOH / g.

Reference example 4 (same as above)
To the same reaction vessel as in Reference Example 1, 550 parts of xylene and 300 parts of n-butanol were added, and the temperature was raised to 115 ° C. and kept at this temperature. Next, 100 parts of styrene, 680 parts of methyl methacrylate, 44 parts of lauryl methacrylate, 160 parts of 2-hydroxyethyl methacrylate, 10 parts of methacrylic acid, 6 parts of acid phosphoxyethyl methacrylate, tert-butylperoxy-2-ethylhexa 25 parts of nate, 3 parts of di-tert-butyl peroxide and 150 parts of xylene were added dropwise over 4 hours.

  The reaction was continued for 5 hours after completion of the dropwise addition to obtain a vinyl copolymer (A-4) solution having a nonvolatile content of 50%. The obtained vinyl copolymer (A-4) was a vinyl copolymer having a primary hydroxyl group and a phosphate group having a weight average molecular weight of 13,000 and a glass transition temperature (Tg) of 83 ° C. It was. The hydroxyl value based on the primary hydroxyl group of the vinyl copolymer (A-4) was 69 mgKOH / g.

Reference example 5 (same as above)
To the same reaction vessel as in Reference Example 1, 550 parts of xylene and 300 parts of n-butanol were added, and the temperature was raised to 115 ° C. and kept at this temperature. Next, 830 parts of methyl methacrylate, 160 parts of 2-hydroxyethyl methacrylate, 10 parts of methacrylic acid, 25 parts of tert-butylperoxy-2-ethylhexanate, 3 parts of di-tert-butyl peroxide and 150 parts of xylene Was added dropwise over 4 hours.

  The reaction was continued for 5 hours after completion of the dropwise addition to obtain a solution of a vinyl copolymer (a-1) having a nonvolatile content of 50%. The obtained vinyl copolymer (a-1) was a vinyl copolymer having a primary hydroxyl group having a weight average molecular weight of 12,000 and a glass transition temperature (Tg) of 95 ° C. The hydroxyl value based on the primary hydroxyl group of the vinyl copolymer (a-1) was 69 mgKOH / g.

Reference Example 6 (same as above)
To the same reaction vessel as in Reference Example 1, 550 parts of xylene and 300 parts of n-butanol were added, and the temperature was raised to 115 ° C. and kept at this temperature. Next, 100 parts of styrene, 700 parts of t-butyl methacrylate, 30 parts of butyl acrylate, 160 parts of 2-hydroxyethyl methacrylate, 10 parts of methacrylic acid, 25 parts of tert-butyl peroxy-2-ethyl hexanate, di- 3 parts of tert-butyl peroxide and 150 parts of xylene were added dropwise over 4 hours.

  The reaction was continued for 5 hours after the completion of the dropwise addition to obtain a solution of a vinyl copolymer (a-2) having a nonvolatile content of 50%. The obtained vinyl copolymer (a-2) was a vinyl copolymer having a primary hydroxyl group having a weight average molecular weight of 13,000 and a glass transition temperature (Tg) of 89 ° C. The hydroxyl value based on the primary hydroxyl group of the vinyl copolymer (a-2) was 69 mgKOH / g.

Reference example 7 (same as above)
To the same reaction vessel as in Reference Example 1, 550 parts of xylene and 300 parts of n-butanol were added, and the temperature was raised to 115 ° C. and kept at this temperature. Next, 741 parts of methyl methacrylate, 83 parts of lauryl methacrylate, 160 parts of 2-hydroxyethyl methacrylate, 10 parts of methacrylic acid, 6 parts of acid phosphoxyethyl methacrylate, 25 parts of tert-butylperoxy-2-ethylhexanate, 3 parts of di-tert-butyl peroxide and 150 parts of xylene were added dropwise over 4 hours.

  The reaction was continued for 5 hours after completion of the dropwise addition to obtain a solution of a vinyl copolymer (a-3) having a nonvolatile content of 50%. The obtained vinyl copolymer (a-3) was a vinyl copolymer having a primary hydroxyl group and a phosphate group having a weight average molecular weight of 13,000 and a glass transition temperature (Tg) of 73 ° C. It was. The hydroxyl value based on the primary hydroxyl group of the vinyl copolymer (a-3) was 69 mgKOH / g.

Reference Example 8 (same as above)
In a reaction vessel similar to that of Reference Example 1, 600 parts of Swazol 1000 (aromatic solvent manufactured by Cosmo Oil Co., Ltd.) and 200 parts of n-butanol were added, and the temperature was raised to 115 ° C. and kept at this temperature. Next, 435 parts of methyl methacrylate, 100 parts of n-butyl methacrylate, 180 parts of stearyl acrylate (long chain branched alkyl acrylate manufactured by Osaka Organic Chemical Industry Co., Ltd.), 200 parts of 4-hydroxybutyl acrylate, 30 parts of dimethylaminoethyl methacrylate Part, 5 parts of acid phosphoxyethyl methacrylate and 50 parts of 2,2′-azobisisobutyronitrile were added dropwise over 3 hours.

  After the completion of the dropwise addition, the reaction was continued for 30 minutes, and then 5 parts of 2,2'-azobisisobutyronitrile and 100 parts of Swazol 1000 were added dropwise over 1 hour, and stirring was continued for 1 hour at 115 ° C. A solution of vinyl copolymer (a-4) having a content of 50.1% was obtained. The obtained vinyl copolymer (a-4) was a vinyl copolymer having a primary hydroxyl group and a phosphate group having a weight average molecular weight of 13,000 and a glass transition temperature (Tg) of 20 ° C. It was. The hydroxyl value based on the primary hydroxyl group of the vinyl copolymer (a-4) was 82 mgKOH / g.

Reference Example 9 (Preparation of emulsion for aqueous base coat paint)
After adding 117 parts of ion-exchanged water to a flask equipped with a thermometer, reflux condenser, stirrer, nitrogen inlet tube and dropping funnel, ammonium salt of sulfate of 5 parts of ion-exchanged water and 5 mol of nonylphenol ethylene oxide adduct A mixture of 0.11 part and 0.11 part of methyl methacrylate was added and the temperature was raised to 80 ° C. At the same temperature, 20 parts of ion-exchanged water, 0.4 parts of ammonium salt of sulfate of ethylene oxide 5-mole adduct of nonylphenol, 41 parts of methyl methacrylate, 11 parts of styrene, 42 parts of butyl acrylate, 3 parts of methyl methacrylate and allyl methacrylate Firstly, 6 parts of 120.4 parts of 3 parts of mixture (I) were added and stirred for 15 minutes, then a mixture of 0.075 parts of ammonium persulfate and 2.5 parts of ion-exchanged water was added at the same temperature. And then a mixture of the remaining 114.4 parts of the mixture (I) with 5 parts of hydroxypropyl methacrylate and a mixture of 0.25 parts of ammonium persulfate and 10 parts of ion-exchanged water. Were simultaneously added dropwise at the same temperature over 4 hours. Furthermore, it hold | maintains at the same temperature for 1 hour, and it abbreviates as an emulsion (Em-1) with a non volatile matter of 40%.

Reference Example 10 (Preparation of paint for organic solvent base coat)
After blending each component with the blending composition shown in Table 1 below, Ford Cup No. The viscosity according to 4 was adjusted to 13 seconds to obtain an organic solvent base coat paint (base 1).

Footnotes in Table 1 “A-322”: Acrylic resin (solution type) manufactured by Dainippon Ink & Chemicals, Inc.
"Acridic A-322", 50% non-volatile content
"L-117-60": n-Butylated melamine resin manufactured by Dainippon Ink & Chemicals, Inc.
"Super Becamine L-117-60", non-volatile content 60%
・ "7160N": Aluminum paste manufactured by Toyo Aluminum Industry Co., Ltd.
“Alpaste 7160N”, 65% non-volatile content

Reference Example 11 (Preparation of aqueous base coat paint)
Each component was blended with the blending composition shown in Table 2 to obtain an aqueous base coat paint (Base 2).

Footnotes in Table 2, “S-695”: Water-soluble melamine resin manufactured by Dainippon Ink & Chemicals, Inc.
"Watersol S-695", 65% non-volatile content
"WXM-760b": water-based aluminum paste manufactured by Toyo Aluminum Industry Co., Ltd.
"Alpaste WXM-760b", 58% non-volatile content
・ "TT-935": thickener manufactured by Rohm & Haas Japan
"Primal TT-935", non-volatile content 30%

Examples 1 to 4, Reference Example 12 and Comparative Examples 1 to 4
Each component is blended with the blending composition shown in Tables 3 to 4 to obtain a baking coating composition, and then the viscosity is 30 seconds (Ford) with a mixed solvent of xylene / diethylene glycol butyl ether = 90/10 (weight ratio). Cup # 4/20 ° C.), the clear coat paint (clear 1 to 3 ) used in the present invention, the reference clear coat paint (clear 4), and the comparative clear coat paint (clear 5 to 7) . Got.

Next, in Examples 1 to 3, Reference Example 12 and Comparative Examples 1 to 3, electrodeposited intermediate coated water polishing board (made by Nippon Route Service Co., Ltd.) The base coat paint (Base 1) obtained in Reference Example 7 was applied on the coated plate) by air spray so that the dry coating film became 20 μm, set for 3 minutes, and then the clear coating was applied thereon. The coating materials for coating (clears 1 to 7) were each applied so that the dry coating film had a thickness of 35 μm, allowed to stand at room temperature for 10 minutes, and then cured for 20 minutes in an electric hot air dryer at 140 ° C. atmosphere.

Further, in Example 4 and Comparative Example 4, on the electrodeposition intermediate coating water polishing board (coated board obtained by water polishing a coated steel sheet coated with polyester / melamine paint) manufactured by Nippon Route Service Co., Ltd. In addition, the base coat paint (base 2) obtained in Reference Example 8 was applied by air spray so that the dry coating film became 20 μm, set for 3 minutes, and then forcedly dried at 80 ° C. for 10 minutes. After cooling to room temperature, the clear coat paint (Clear 3) obtained in Example 3 and the clear coat paint (Clear 5) obtained in Comparative Example 1 were further dried so that the dry coating film became 35 μm. After coating and leaving at room temperature for 10 minutes, it was cured for 20 minutes in an electric hot air dryer at 140 ° C. atmosphere.

The coating on the resultant coated plate, along with measuring the 20 ° gloss and pencil hardness degree, was xylene rubbing test and aluminum orientation test. The results are collectively shown in Tables 5-6. The xylene rubbing test and the aluminum orientation test were evaluated as follows.

-Xylene rubbing test: The state of the coating film after being rubbed back and forth on the coating film 10 times with a felt soaked in xylene was visually judged according to the following evaluation criteria.
Evaluation criteria ○: No change.
Δ: Some change.
X: There is a change.

Aluminum orientation test: The presence or absence of unevenness in the metallic color of the coating film was visually evaluated according to the following criteria.
Evaluation criteria ○: No return unevenness.
Δ: Slight return unevenness.
X: There is glossiness.

Claims (3)

The glass transition temperature having a primary hydroxyl group and phosphoric acid group (Tg) 8 5 ~1 0 0 ℃ vinyl copolymer of (A), a baking coating composition containing a melamine resin (B),
The vinyl copolymer (A) comprises a primary hydroxyl group-containing vinyl monomer, a phosphate group-containing vinyl monomer, styrene, methyl methacrylate and / or tertiary butyl methacrylate, and other vinyl monomers. The content of the phosphate group-containing vinyl monomer is 0.1 to 2% by weight, and the content of styrene and methyl methacrylate and / or tertiary butyl methacrylate is 50 to 90% by weight. A vinyl copolymer having a hydroxyl value of 20 to 200 mgKOH / g based on a primary hydroxyl group obtained by copolymerizing a certain vinyl monomer mixture,
A baking coating composition, wherein the solid content weight ratio (A / B) of the vinyl copolymer (A) and the melamine resin (B) is in a range of 90/10 to 50/50 . The content of styrene with respect to the vinyl monomer mixture is 2 to 40% by weight, and the content of methyl methacrylate and / or tertiary butyl methacrylate with respect to the vinyl monomer mixture is 10 to 90% by weight. The baking coating composition according to claim 1 . 3. A paint finishing method comprising: forming a base coat on a substrate, and then forming a top coat comprising the baking coating composition according to claim 1 or 2 on the base coat.