JP2006117797A - Water-based primer composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a water-based primer composition capable of being used as a one-package type which can give a coating film excellent in water resistance, polishability, and adhesion to a substrate. <P>SOLUTION: The water-based primer composition comprises (A) an emulsion-polymerized polymer comprising (a) styrene, (b) an acid group-containing polymerizable unsaturated monomer, (c) a hydroxy group-containing polymerizable unsaturated monomer, and (d) other polymerizable unsaturated monomers as comonomers, wherein the amount of styrene used is 30 wt.% or higher based on the entire monomer, (B) a water-based urethane resin, (C) an acrylic resin comprising (e) a bridged alicyclic hydrocarbon group-containing polymerizable unsaturated monomer, (b) an acid group-containing polymerizable unsaturated monomer, (c) a hydroxy group-containing polymerizable unsaturated monomer, and (f) other polymerizable unsaturated monomers as comonomers, and (D) a pigment, wherein the pigment (D) is present in an amount of 100 to 350 pts.wt. per 100 pts.wt. total resin solids content in the composition, and the pigment (D) comprises an extender in an amount of 50 to 200 pts.wt. per 100 pts.wt. total resin solids content in the composition. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a water-based undercoating composition that can form a coating film excellent in water resistance and abrasiveness and is useful as a primer or primer surfacer in the field of automobile repair coating.

  Conventionally, as an undercoat paint composition such as primer or primer surfacer in the field of automotive repair paint, organic solvent-type acrylic lacquer paint or two-component urethane from the viewpoint of quick drying, adhesion, water resistance, polishing workability, etc. Paint was used. However, in recent years, from the viewpoint of environmental protection, in the automobile repair coating industry, conversion from organic solvent-based paints to water-based paints has been promoted, and various water-based undercoat paints have been proposed. For example, in Patent Document 1, the present applicant has proposed an aqueous one-component undercoat composition containing a specific amount of pigment using an acrylic copolymer emulsion having a specific amount of styrene as a copolymer component as a film-forming component. According to such a composition, it is possible to form a coating film excellent in water resistance and polishing properties while being water-based and one-pack type, but there are cases where the adhesion of the coating film to the coated surface after submersion is insufficient. It was. Patent Document 2 proposes an aqueous two-component undercoat coating composition containing an emulsion polymer having a specific styrene copolymerization component and a water-dispersible polyisocyanate as a film-forming component and a specific amount of pigment. Such a composition can form an undercoat film that is excellent in water resistance, solvent resistance, abrasiveness, and finish after top coating, but since it is a two-component type, it must be weighed and mixed during use. There was a problem of having to.

Japanese Patent Laid-Open No. 2001-131460 Japanese Patent Laid-Open No. 2001-262053

  An object of the present invention is to provide an aqueous undercoating composition that can be used as a one-pack type that is excellent in water resistance and polishing properties, and also has excellent adhesion to a coated surface.

As a result of intensive studies to solve the above problems, the present inventors have found that the present invention is based on an aqueous undercoating composition comprising a specific amount of a specific emulsion polymer, a water-based urethane resin, a specific acrylic resin, and a specific composition pigment. Reached. That is, the present invention
1. (A) (a) styrene, (b) an acid group-containing polymerizable unsaturated monomer, (c) a hydroxyl group-containing polymerizable unsaturated monomer, and (d) other polymerizable unsaturated monomers as copolymerization components, and styrene The amount of (a) used is 30% by weight or more based on the weight of all monomers, an emulsion polymer,
(B) an aqueous urethane resin,
(C) (e) Bridged alicyclic hydrocarbon group-containing polymerizable unsaturated monomer, (b) Acid group-containing polymerizable unsaturated monomer, (c) Hydroxyl group-containing polymerizable unsaturated monomer, and (f) Other polymerizations A coating composition mainly comprising an acrylic resin having a weight average molecular weight in the range of 5,000 to 100,000 and a (D) pigment having a polymerizable unsaturated monomer as a copolymerization component,
The pigment (D) is contained in an amount of 100 to 350 parts by weight with respect to 100 parts by weight of the total resin solids in the composition, and the extender pigment in the pigment (D) is 50 to 100 parts by weight with respect to 100 parts by weight of the total resin solids. An aqueous undercoating composition comprising 200 parts by weight.
2. The emulsion polymer (A) is (a) 30-80% by weight of styrene, (b) 1-10% by weight of an acid group-containing polymerizable unsaturated monomer, and (c) 5-30% by weight of a hydroxyl group-containing polymerizable unsaturated monomer. And (d) in a copolymer aqueous dispersion obtained by emulsion polymerization of a monomer mixture (I) comprising 5 to 64% by weight of other polymerizable unsaturated monomers, (a) 20 to 70% by weight of styrene, ( b) a monomer comprising 1 to 10% by weight of an acid group-containing polymerizable unsaturated monomer, (c) a hydroxyl group-containing polymerizable unsaturated monomer of 5 to 50% by weight, and (d) another polymerizable unsaturated monomer of 5 to 74% by weight. 2. The aqueous undercoat paint composition according to 1, which is obtained by adding the mixture (II) and emulsion polymerization;
3. The blending ratio of the emulsion polymer (A), the aqueous urethane resin (B) and the acrylic resin (C) is based on the total solid weight of the emulsion polymer (A), the aqueous urethane resin (B) and the acrylic resin (C). Item 1 or 2, wherein the emulsion polymer (A) is 10 to 80% by weight, the aqueous urethane resin (B) is 10 to 80% by weight, and the acrylic resin (C) is 10 to 80% by weight. Water-based undercoat paint composition according to item,
4). 4. The aqueous undercoat coating composition according to any one of items 1 to 3, further comprising a silane coupling agent (E),
5. 5. A coating method comprising applying the aqueous undercoat paint composition according to any one of items 1 to 4 to a surface to be coated,
6). After applying the water-based undercoat paint composition according to any one of items 1 to 4 on the surface to be coated, a base coat paint is applied onto the coated surface, and a top clear paint is applied onto the base paint film. How to paint,
About.

  According to the aqueous undercoating composition of the present invention, it can be used as a one-pack type, and can form an undercoating film excellent in water resistance, solvent resistance, adhesion to the coated surface or top coating film. it can. In addition, since the undercoat coating film has a specific pigment concentration, it has excellent base concealing properties, good polishing properties, less surface irregularities, and after the top coat is applied on the coating film. There is an effect that it is possible to form a multilayer coating film having an excellent appearance without adversely affecting the color tone.

Emulsion polymer (A)
In the present invention, the emulsion polymer (A) is used for improving the water resistance and abrasiveness of the coating film formed from the aqueous undercoat coating composition of the present invention, and contains styrene (a) and an acid group. It contains a polymerizable unsaturated monomer (b), a hydroxyl group-containing polymerizable unsaturated monomer (c) and other polymerizable unsaturated monomers (d) as copolymerization components, and the amount of styrene used is based on the weight of all monomers. 30% by weight or more.

  In addition, the emulsion polymer (A) is used for the purpose of suppressing the solvent resistance of the coating film formed from the aqueous undercoat coating composition of the present invention, and curbing of the coating film when it is overcoated on the coating film. The weight average molecular weight is preferably 50,000 or more, preferably 100,000 or more, and more preferably 100,000 to 500,000.

  In this specification, the weight average molecular weight is a value obtained by converting a weight average molecular weight measured by gel permeation chromatography (“HLC8120GPC” manufactured by Tosoh Corporation) based on the weight average molecular weight of polystyrene. Columns are “TSKgel G-4000H × L”, “TSKgel G-3000H × L”, “TSKgel G-2500H × L”, “TSKgel G-2000H × L” (both manufactured by Tosoh Corporation, trade names) ), Mobile phase: tetrahydrofuran, measurement temperature: 40 ° C., flow rate: 1 cc / min, detector: RI.

  The emulsion polymer (A) is obtained by dispersing a copolymer having monomers (a), (b), (c) and (d) as copolymerization components in water, and the average of the copolymer dispersed particles. The particle diameter can be in the range of 100 to 500 nm, preferably 100 to 300 nm.

  In this specification, an average particle diameter shall be measured with the particle size distribution analyzer "Nanomizer N-4" (a brand name, the Coulter company make).

  In the present invention, the amount of styrene (a) used is 30% by weight or more in all monomers, and if it is less than 30% by weight, the abrasiveness and water resistance of the coating film formed from the aqueous undercoat coating composition are insufficient. This is not preferable.

  The acid group-containing polymerizable unsaturated monomer (b) is used for improving the stability of the dispersed particles of the emulsion polymer (A). For example, acrylic acid, methacrylic acid, crotonic acid, maleic acid, Carboxyl group-containing polymerizable unsaturated monomers such as itaconic acid and β-carboxyethyl acrylate; 2-acrylamido-2-methylpropane sulfonic acid, allyl sulfonic acid, styrene sulfonic acid sodium salt, sulfoethyl methacrylate, and Examples thereof include polymerizable unsaturated monomers having a sulfonic acid group such as sodium salt and ammonium salt; and phosphoric acid group-containing polymerizable unsaturated monomers such as “Light Ester PM” (manufactured by Light Ester Co.). Or it can use in combination of 2 or more types. Of these, (meth) acrylic acid is preferred.

  The hydroxyl group-containing polymerizable unsaturated monomer (c) is used to improve the stability of the dispersed particles of the emulsion polymer (A), and when a curing agent is used in the composition and / or top coating composition of the present invention. In, for example, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, hydroxybutyl (meth) C2-C8 hydroxyalkyl (meth) acrylate such as acrylate; N-methylolacrylamide; allyl alcohol; ε-caprolactone-modified acrylic monomer of C2-C8 hydroxyalkyl (meth) acrylate; diethylene glycol (meth) Acrylate, triethylene glycol ( Poly) alkylene glycol (meth) acrylate such as acrylate), polyethylene glycol (meth) acrylate, dipropylene glycol (meth) acrylate, tripropylene glycol (meth) acrylate, polypropylene glycol (meth) acrylate and polyethylene polypropylene glycol (meth) acrylate These can be used, and these can be used alone or in combination of two or more.

  The other polymerizable unsaturated monomer (d) is a monomer copolymerizable with the monomers (a), (b) and (c), and includes methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl ( (Meth) acrylate, isopropyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, n-hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, n-octyl (meth) acrylate, decyl ( Linear or branched alkyl (meth) acrylates such as meth) acrylate, stearyl (meth) acrylate, “isostearyl acrylate” (manufactured by Osaka Organic Chemical Co., Ltd.), lauryl (meth) acrylate; cyclohexyl (meth) acrylate, t -Cycloal such as butylcyclohexyl (meth) acrylate (Meth) acrylate; methoxydiethylene glycol (meth) acrylate, methoxytriethylene glycol (meth) acrylate, methoxypolyethylene glycol (meth) acrylate, methoxydipropylene glycol (meth) acrylate, methoxytripropylene glycol (meth) acrylate, mexypolypropylene Glycol (meth) acrylate, ethoxydiethylene glycol (meth) acrylate, ethoxytriethylene glycol (meth) acrylate, ethoxypolyethylene glycol (meth) acrylate, ethoxydipropylene glycol (meth) acrylate, ethoxytripropylene glycol (meth) acrylate, ethoxy polypropylene Glycol (meth) acrylate, propoxydie Lenglycol (meth) acrylate, propoxytriethylene glycol (meth) acrylate, propoxypolyalkylene glycol (meth) acrylate, propoxydipropylene glycol (meth) acrylate, propoxytripropylene glycol (meth) acrylate, propoxypolypropylene glycol (meth) acrylate Alkoxypolyalkylene (meth) acrylates such as; alkoxyalkyl (meth) acrylates such as methoxyethylene glycol (meth) acrylate and ethoxyethylene glycol (meth) acrylate; dimethylaminoethyl (meth) acrylate, N-butoxymethylacrylamide, N, Nitrogen-containing compounds such as N-dimethylacrylamide; epoxy groups such as glycidyl (meth) acrylate Organic (meth) acrylate; vinyl acetate, vinyl propionate, α-methylstyrene, vinyl toluene, acrylonitrile, methacrylonitrile, butadiene, isoprene and other vinyl monomers, allyl (meth) acrylate, ethylene glycol di (meth) acrylate, 1 , 6-hexanediol di (meth) acrylate, 1,1,1-trishydroxymethylethanedi (meth) acrylate, triallyl isocyanurate, polyvinyl compounds such as divinylbenzene, and the like. More than one species can be used.

  The copolymerization of the monomer (a), monomer (b), monomer (c) and monomer (d) is produced by emulsion polymerization of these monomer mixtures in the presence of water and an emulsifier using a polymerization initiator. can do.

  As the emulsifier, an anionic emulsifier and a nonionic emulsifier are suitable. Examples of the anionic emulsifier include sodium salts and ammonium salts such as alkylsulfonic acid, alkylbenzenesulfonic acid, and alkylphosphoric acid. Nonionic emulsifiers include, for example, polyoxyethylene oleyl ether, polyoxyethylene stearyl ether, polyoxyethylene lauryl ether, polyoxyethylene tridecyl ether, polyoxyethylene phenyl ether, polyoxyethylene nonylphenyl ether, polyoxyethylene octyl Phenyl ether, polyoxyethylene monolaurate, polyoxyethylene monostearate, polyoxyethylene monooleate, sorbitan monolaurate, sorbitan monos Areto, sorbitan monostearate, sorbitan trioleate, polyoxyethylene sorbitan monolaurate, and the like.

  Also, a polyoxyalkylene group-containing anionic emulsifier having an anionic group and a polyoxyalkylene group such as a polyoxyethylene group or a polyoxypropylene group in one molecule, or the anionic group and polymerizable unsaturated in one molecule Reactive anionic emulsifiers having groups may be used.

  The emulsifier can be used in the range of 0.1 to 15% by weight, preferably 0.5 to 12% by weight, based on the total weight of monomers used in the production of the emulsion polymer (A).

  Examples of the polymerization initiator include a water-soluble polymerization initiator and an oil-soluble polymerization initiator. Examples of the water-soluble polymerization initiator include cumene hydroperoxide, tert-butyl peroxide, and tert-butyl peroxylaurate. Organic peroxides such as tert-butylperoxyisopropyl carbonate, tert-butylperoxyacetate, diisopropylbenzene hydroperoxide; azobis (2-methylpropiononitrile), azobis (2-methylbutyronitrile), 4, 4 '-Azobis (4-cyanobutanoic acid), dimethylazobis (2-methylpropionate), azobis [2-methyl-N- (2-hydroxyethyl) -propionamide], azobis {2-methyl-N- [ 2- (1-hydroxybutyl)]-propion Azo compounds; such as potassium persulfate, ammonium persulfate, persulfates such as sodium persulfate, etc., and oil-soluble polymerization initiators include benzoyl peroxide, octanoyl peroxide, lauroyl peroxide, stearoyl Organic peroxides such as peroxides; azo compounds such as azobisisobutyronitrile and azobis (2,4-dimethylvaleronitrile). These can be used alone or in combination of two or more. In the present invention, it is preferable to use a water-soluble polymerization initiator among the polymerizable initiators. The amount of the polymerization initiator used is generally in the range of 0.1 to 5% by weight, particularly 0.2 to 3% by weight, based on the total weight of the monomers used for the production of the emulsion polymer (A). The inside is preferable.

In the present invention, the emulsion polymer (A) is prepared from the monomers (a) and (b), which are copolymerization components, from the viewpoint of the abrasiveness and film-forming property of the coating film formed from the resulting aqueous undercoat coating composition. ), (C) and (d) are desirably selected so that the glass transition temperature is in the range of 20 to 70 ° C, preferably 30 to 60 ° C. In this specification, the glass transition temperature (absolute temperature) is a value calculated from the following equation.
1 / Tg = W1 / T1 + W2 / T2 + ... Wn / Tn
W1, W2 ... Wn in the formula is weight% of each monomer (= (blending amount of each monomer / total weight of monomer) × 100), and T1, T2 ... Tn are homopolymers of each monomer. Glass transition temperature (absolute temperature). In addition, the glass transition temperature of the homopolymer of each monomer is a value according to Polymer Hand Book 4th Edition, and the glass transition temperature of the monomer not described in the literature is such that the homopolymer has a weight average molecular weight of about 50,000. And the value obtained by measuring the glass transition temperature by differential scanning thermal analysis is used.

  In the present invention, it is preferable that the emulsion polymer (A) has a core-shell structure from the viewpoint of the film-forming property of the aqueous undercoat coating composition. As the emulsion polymer (A), styrene (a) 30 to 80% by weight, acid group-containing polymerizable unsaturated monomer (b) 1 to 10% by weight, hydroxyl group-containing polymerizable unsaturated monomer (c) 5 to 30% by weight, and other polymerizable unsaturated monomer (d) 5 to 5% In a copolymer dispersion obtained by emulsion polymerization of a monomer mixture (I) comprising 64% by weight, styrene (a) 20 to 70% by weight, acid group-containing polymerizable unsaturated monomer (b) 1 to 10% by weight %, A monomer mixture (II) consisting of 5 to 50% by weight of a hydroxyl group-containing polymerizable unsaturated monomer (c), and 5 to 74% by weight of other polymerizable unsaturated monomer (d), and then emulsion polymerization. It is desirable that

  In the present invention, the total amount of styrene (a) used in the emulsion polymer having the core-shell structure is 30% by weight or more based on the weight of all monomers used in the production of the emulsion polymer.

  The weight ratio of the monomer mixture (I) that can be a core component and the monomer mixture (II) that can be a shell component is the monomer ratio with respect to 100 parts by weight of the monomer mixture (I) from the viewpoint of the balance between film forming property and water resistance. It is appropriate that the mixture (II) is 25 to 400 parts by weight, preferably 45 to 230 parts by weight.

  In the emulsion polymer having the core-shell structure, the other in the monomer mixture (I) is used for the purpose of improving physical properties such as solvent resistance and water resistance of the coating film formed from the aqueous undercoat coating composition of the present invention. The polymerizable unsaturated monomer (d) of the poly vinyl compound is not more than 10% by weight, particularly in the range of 0.1 to 8% by weight, based on the weight of the monomer used in the production of the emulsion polymer (A). It is desirable to contain within.

  In the emulsion polymer having the core-shell structure, the emulsion polymerization of the monomer mixture (I) and the monomer mixture (II) is carried out using the polymerization initiator in the presence of water and the emulsifier by a conventionally known method. It can be carried out.

Water-based urethane resin (B)
In this invention, water-based urethane resin (B) is mix | blended in order to improve the water resistance of the coating film formed from the water-based undercoat coating composition of this invention, and adhesiveness with a base material, and is well-known conventionally Can be used without limitation. As the aqueous urethane resin (B), a urethane prepolymer obtained by reacting polyisocyanate, polyol and hydroxy acid is usually dispersed in water in the presence of a chain extender and / or an emulsifier as necessary. Can be mentioned.

  Examples of polyisocyanates include aliphatic diisocyanate compounds such as hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, dimer acid diisocyanate, and lysine diisocyanate; burette-type adducts and isocyanurate ring adducts of these diisocyanate compounds; isophorone diisocyanate, 4, 4 '-Methylenebis (cyclohexyl isocyanate), methylcyclohexane-2,4- (or-2,6-) diisocyanate, 1,3- (or 1,4-) di (isocyanatomethyl) cyclohexane, 1,4-cyclohexane diisocyanate Alicyclic diisocyanate compounds such as 1,3-cyclopentane diisocyanate and 1,2-cyclohexane diisocyanate; Turret type adduct, isocyanurate ring adduct; xylylene diisocyanate, metaxylylene diisocyanate, tetramethyl xylylene diisocyanate, tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate, 1,5-naphthalene diisocyanate, 1,4-naphthalene diisocyanate 4,4'-toluidine diisocyanate, 4,4'-diphenyl ether isocyanate, (m- or p-) phenylene diisocyanate, 4,4'-biphenylene diisocyanate, 3,3'-dimethyl-4,4'-biphenylene diisocyanate, Aromatic diisocyanate compounds such as bis (4-isocyanatophenyl) sulfone and isopropylidenebis (4-phenylisocyanate); these diisocyanates -Burelet type adduct, isocyanurate ring adduct; triphenylmethane-4,4 ', 4 "-triisocyanate, 1,3,5-triisocyanatobenzene, 2,4,6-tri Polyisocyanate compounds having three or more isocyanate groups in one molecule such as isocyanatotoluene and 4,4'-dimethyldiphenylmethane-2,2 ', 5,5'-tetraisocyanate; burettes of these polyisocyanate compounds Type adducts, isocyanurate cycloadducts; ethylene glycol, propylene glycol, 1,4-butylene glycol, dimethylolpropionic acid, polyalkylene glycol, trimethylolpropane, hexanetriol and other isocyanate groups in excess of hydroxyl groups At a ratio of polyiso Urethane adduct obtained by reacting a Aneto compound; these urethane adducts of views - let type adducts can include an isocyanurate ring adducts.

  Examples of the polyol include those having a weight average molecular weight in the range of 200 to 10,000, such as polyethylene glycol, polypropylene glycol, polyethylene-propylene (block or random) glycol, polytetramethylene ether glycol, polyhexamethylene ether. Polyether polyols such as glycol and polyoctamethylene ether glycol; dicarboxylic acids (adipic acid, succinic acid, sebacic acid, glutaric acid, maleic acid, fumaric acid, phthalic acid, etc.) and glycols (ethylene glycol, propylene glycol, 1, 4 Polybutane obtained by condensation polymerization with butanediol, 1,6-hexanediol, 3-methyl-1,5-pentanediol, neopentyl glycol, bishydroxymethylcyclohexane, etc. Polyester polyols such as polyethylene adipate, polybutylene adipate, polyhexamethylene adipate, polyneopentyl adipate, poly-3-methylpentyl adipate, polyethylene / butylene adipate, polyneopentyl / hexyl adipate; polycaprolactone polyol, poly-3 -Methyl valerolactone polyol; polycarbonate polyol; ethylene glycol, diethylene glycol, triethylene glycol, 1,2-propylene glycol, 1,4-butanediol, tetramethylene glycol, hexamethylene glycol, decamethylene glycol, octanediol, tricyclode Candimethylol, hydrogenated bisphenol A, cyclohexanedimethanol, 1,6 hexanediol Low molecular weight glycols; and the like, may be used alone or in combination.

  Examples of the hydroxy acid include dimethylolacetic acid, dimethylolpropionic acid, and dimethylolbutyric acid.

  In the production of the urethane prepolymer, it is desirable that the mixing ratio of the above components is such that the equivalent ratio of isocyanate group / hydroxyl group is in the range of 1.1 to 1.9. The prepolymer synthesis reaction can be carried out based on a conventionally known method.

  The aqueous urethane resin (B) can be neutralized with a neutralizing agent. The neutralizing agent is not particularly limited as long as it can neutralize the carboxyl group. For example, sodium hydroxide, potassium hydroxide, trimethylamine, dimethylaminoethanol, 2-methyl-2-amino-1-propanol , Triethylamine, ammonia and the like. The neutralizing agent is preferably used in a proportion of usually 0.5 to 2.0 equivalents, preferably 0.7 to 1.3 equivalents, relative to 1 equivalent of the carboxyl group.

  In the present invention, as the water-based urethane resin (B), the glass transition temperature of the formed coating film is −60 ° C. to 20 ° C. from the viewpoint of water resistance and abrasiveness of the coating film formed from the aqueous undercoat coating composition of the present invention. It is desirable that the temperature be in the range of -50 ° C, preferably -50 ° C to 0 ° C. The glass transition temperature of the coating film formed from the aqueous urethane resin (B) is a value measured at a heating rate of 10 ° C./min by scanning thermal analysis.

Acrylic resin (C)
In this invention, acrylic resin (C) is mix | blended in order to improve the film forming property of the water-based undercoat coating composition of this invention, and the adhesiveness with respect to a base material, and a bridged alicyclic hydrocarbon group containing A weight comprising a polymerizable unsaturated monomer (e), an acid group-containing polymerizable unsaturated monomer (b), a hydroxyl group-containing polymerizable unsaturated monomer (c), and another polymerizable unsaturated monomer (f) as a copolymerization component A resin having an average molecular weight of 5,000 or more and 100,000, preferably 10,000 to 60,000.

  Examples of the bridged alicyclic hydrocarbon group-containing polymerizable unsaturated monomer (e) include isobornyl (meth) acrylate, tricyclodecanyl (meth) acrylate, adamantyl (meth) acrylate, and particularly isobornyl (meth). Acrylate is preferred. The water resistance of the formed coating film can be improved by copolymerization of the monomer.

In the present invention, from the viewpoint of storage stability of the water-based undercoating composition and water resistance of the coating film formed from the water-based undercoating composition, the proportion of each monomer that forms the acrylic resin (C) is acrylic resin ( Based on the total monomers used in the production of C),
The bridged alicyclic hydrocarbon group-containing polymerizable unsaturated monomer (e) is 10 to 60% by weight, preferably 20 to 50% by weight,
The acid group-containing polymerizable unsaturated monomer (b) is 1 to 20% by weight, preferably 2 to 5% by weight,
The hydroxyl group-containing polymerizable unsaturated monomer (c) is desirably contained in an amount of 1 to 20% by weight, preferably 3 to 15% by weight.

  Other polymerizable unsaturated monomers (f) include methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, n-butyl (meth) acrylate, Isobutyl (meth) acrylate, n-hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, n-octyl (meth) acrylate, decyl (meth) acrylate, stearyl (meth) acrylate, “isostearyl acrylate” (Osaka Organic) Chemicals), linear or branched alkyl (meth) acrylates such as lauryl (meth) acrylate; cycloalkyl (meth) acrylates such as cyclohexyl (meth) acrylate and t-butylcyclohexyl (meth) acrylate; methoxydiethylene glycol (Meth) acrylate, methoxytriethylene glycol (meth) acrylate, methoxypolyethylene glycol (meth) acrylate, methoxydipropylene glycol (meth) acrylate, methoxytripropylene glycol (meth) acrylate, mexypolypropylene glycol (meth) acrylate, ethoxydiethylene glycol ( (Meth) acrylate, ethoxytriethylene glycol (meth) acrylate, ethoxypolyethylene glycol (meth) acrylate, ethoxydipropylene glycol (meth) acrylate, ethoxytripropylene glycol (meth) acrylate, ethoxypolypropylene glycol (meth) acrylate, propoxydiethylene glycol ( (Meth) acrylate, propoxytrie Alkoxypolyalkylene (meth) acrylates such as lenglycol (meth) acrylate, propoxypolyalkylene glycol (meth) acrylate, propoxydipropylene glycol (meth) acrylate, propoxytripropylene glycol (meth) acrylate, and propoxypolypropylene glycol (meth) acrylate ; Alkoxyalkyl (meth) acrylates such as methoxyethylene glycol (meth) acrylate and ethoxyethylene glycol (meth) acrylate; nitrogen-containing compounds such as dimethylaminoethyl (meth) acrylate, N-butoxymethylacrylamide and N, N-dimethylacrylamide Epoxy group-containing (meth) acrylates such as glycidyl (meth) acrylate; vinyl acetate, vinyl propionate , Styrene, alpha-methyl styrene, vinyl toluene, acrylonitrile, methacrylonitrile, butadiene, vinyl monomers such as isoprene, and the like. These may be used singly or two or more kinds.

  The acrylic resin (C) is a resin that can also be used as a dispersant for the pigment (D) described later in some cases, and the storage stability of the aqueous undercoat coating composition and the acrylic resin (C) as a pigment dispersant. From the viewpoint of pigment dispersibility when used, it is desirable that the other polymerizable unsaturated monomer (f) contains an alkoxy polyalkylene (meth) acrylate as a part of the component.

In the alkoxy polyalkylene (meth) acrylate, the repeating unit of the oxyalkylene group is preferably in the range of 2 to 100.
When the alkoxypolyalkylene (meth) acrylate is used, the amount used is 1 to 40% by weight, preferably 3 to 40% by weight based on the total weight of the monomers used for the production of the acrylic resin (C). A range of 20% by weight is preferred.

  The acrylic resin (C) can be produced by a known method. For example, radical polymerization of azobisisobutyronitrile, azobisdimethylvaleronitrile, azobismethylbutyronitrile, benzoyl peroxide, ammonium persulfate, etc. It can manufacture by superposing | polymerizing in an organic solvent using a catalyst. Moreover, it is desirable to neutralize the acid group of the acrylic copolymer obtained here with a neutralizing agent.

  Examples of the neutralizing agent include amine compounds such as ammonia, ethylamine, diethylamine, triethylamine, propylamine, dipropylamine, monoethanolamine, diethanolamine, butylamine, ethylenediamine, methylethanolamine, dimethylethanolamine, and dimethylpropanolamine. In particular, dimethylethanolamine is preferred.

  The acrylic resin (C) has a weight average molecular weight in the range of 5,000 to 100,000, preferably in the range of 10,000 to 60,000. When the weight average molecular weight is less than 5,000, the water resistance and water adhesion of the coating film may be lowered. On the other hand, when it exceeds 100,000, the appearance of the coating film tends to be lowered, which is not preferable.

  In this invention, as a compounding quantity of the said emulsion polymer (A), water-based urethane resin (B), and acrylic resin (C), emulsion polymer (A), water-based urethane resin (B), and acrylic resin (C) The emulsion polymer (A) is 10 to 80% by weight, preferably 20 to 60% by weight, and the aqueous urethane resin (B) is 10 to 80% by weight, preferably 20 to 60% by weight, based on the total solid weight. And the acrylic resin (C) is within the range of 10 to 80% by weight, preferably 20 to 60% by weight.

  When the amount of the emulsion polymer (A) is less than 10% by weight, the water resistance of the formed coating film may be insufficient, and when it exceeds 80% by weight, the formed coating film becomes hard and the coated surface or the top coating film. Adhesiveness to may be insufficient. If the water-based urethane resin (B) is less than 10% by weight, the adhesion to the coated surface or the top coat film may be insufficient, and if it exceeds 80% by weight, the film formed from the composition of the present invention. When polishing, it may be difficult to polish. If the acrylic resin (C) is less than 10% by weight, the formed coating film becomes hard and the adhesion to the coated surface or the top coating film may be insufficient. If it exceeds 80% by weight, the water resistance of the formed coating film May be insufficient.

Pigment (D)
In the present invention, the pigment (D) is blended in order to improve the base concealing property and the polishing property, for example, a colored pigment such as titanium white, carbon black, or bengara; a metallic pigment such as fine aluminum powder; Conventional pigments such as extender pigments such as clay, talc, mica, barita and silica; antirust pigments such as phosphate pigments such as aluminum tripolyphosphate, aluminum phosphomolybdate and zinc phosphate may be used in combination. it can. The pigment (D) is desirably mixed and dispersed in the acrylic resin (C).

  In the present invention, the pigment (D) is blended in an amount of 100 to 350 parts by weight, preferably 120 to 250 parts by weight, based on 100 parts by weight of the resin solid content contained in the composition of the present invention. When the blending amount is less than 100 parts by weight, the abrasiveness is inferior. On the other hand, when it exceeds 350 parts by weight, the film-forming property becomes insufficient, and the appearance of the coating film when it is overcoated on the coating film by the aqueous undercoat coating composition of the present invention. And the coating performance such as water resistance deteriorates, which is not preferable. The extender pigment is blended in an amount of 50 to 200 parts by weight, preferably 70 to 160 parts by weight, based on 100 parts by weight of the total resin solid content in the composition. If the amount is less than 50 parts by weight, the abrasiveness is inferior, and if it exceeds 200 parts by weight, the water resistance and adhesion are deteriorated, which is not preferable.

  The aqueous undercoat coating composition of the present invention can also contain a rust preventive pigment from the viewpoint of the corrosion resistance and adhesion of the formed coating film. When blending the anticorrosive pigment, the blending amount is generally 10 parts by weight or less, preferably 1 to 6 parts by weight, based on 100 parts by weight of the total resin solid content in the composition. Can do.

Further, in the present invention, the composition of the pigment can be appropriately adjusted according to the type of the base material and the top coat film, but it has a good base concealing property on the surface to be coated without adversely affecting the finish after the top coat. In order to obtain the lightness (L ^* value) based on the L * a * b * color system defined in JIS Z 8729 of the coating film formed from the aqueous undercoat coating composition of the present invention, It is desirable to set it as 55-80.

Here, the L ^* value means the brightness of the coating film. For example, the L ^* value 100 means pure white, and the L ^* value 0 means pure black. In this specification, L ^* is a value measured using a colorimeter (trade name, “Color Computer SM-7”, manufactured by Suga Test Instruments Co., Ltd.).

Silane coupling agent (E)
In the aqueous undercoat coating composition of the present invention, a silane coupling agent can be contained in order to improve the adhesion of the formed coating film to the coated surface. Examples of the silane coupling agent include N-phenyl-γ-aminopropyltrimethoxysilane, N-β (aminoethyl) γ-aminopropylmethyldimethoxysilane, N-β (aminoethyl) γ-aminopropyltrimethoxysilane, Amino-based silane coupling agents such as N-β (aminoethyl) γ-aminopropyldimethoxyethoxysilane, γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane; γ-glycidoxypropyltrimethoxysilane, γ -Epoxy silane coupling agents such as glycidoxypropylmethyldimethoxysilane; Mercapto silane coupling agents such as 3-mercaptopropyltrimethoxysilane; Imidazole silane coupling agents such as trialkoxysilylimidazolesilane You can. These may be used alone or in combination of two or more. When the silane coupling agent is blended, the blending amount is 15% by weight or less based on the total resin solid content of the composition from the viewpoint of adhesion to the coated surface and the storage stability of the composition of the present invention. The preferred range is 1 to 10% by weight, more preferably 3 to 10% by weight.

  Further, in the present invention, a hydrophilic organic solvent is used for the purpose of improving the solubility or dispersibility of the acrylic resin (C) in water and improving the film forming property and finishing property of the aqueous undercoat coating composition of the present invention. 1 to 200% by weight, preferably 5 to 100% by weight, based on the total resin solids in the composition. Such a hydrophilic organic solvent may be blended at any stage, and may be blended as an organic solvent used as a reaction solvent in the synthesis stage of the acrylic resin (C).

  Examples of the hydrophilic organic solvent include alcohol solvents such as methanol, ethanol, isopropanol, n-butanol and isobutanol; ether solvents such as dioxane and tetrahydrofuran; ethylene glycol monomethyl ether, ethylene glycol monoethyl ether and ethylene glycol mono n-propyl ether, ethylene glycol monoisopropyl ether, ethylene glycol mono n-butyl ether, ethylene glycol monoisobutyl ether, ethylene glycol mono tert-butyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol mono n-propyl ether, diethylene glycol monoisopropyl Ether, diethylene glycol Ethylene glycol ether solvents such as n-butyl ether, diethylene glycol monoisobutyl ether, diethylene glycol mono tert-butyl ether; propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol mono n-propyl ether, propylene glycol monoisopropyl ether, dipropylene glycol Propylene glycol ether solvents such as monomethyl ether, dipropylene glycol monoethyl ether, dipropylene glycol mono n-propyl ether, dipropylene glycol monoisopropyl ether; esters such as ethyl acetate, butyl acetate, isobutyl acetate and 3-methoxybutyl acetate System solvents, and these may be used alone or in combination. It can be used.

  If necessary, the composition of the present invention may further contain additives such as organic solvents other than the hydrophilic organic solvent, dispersants, antifoaming agents, leveling agents, thickeners, preservatives, rust inhibitors, and the like. be able to. In addition, the aqueous undercoat composition of the present invention can be used for coating as a one-pack type, and since it has a functional group such as a hydroxyl group in the composition, it is an isocyanate compound or a block polyisocyanate compound. Moreover, it is also possible to mix | blend suitably the hardening | curing agent which can react with hydroxyl groups, such as a melamine resin, and it can also be made into 2 liquid type as needed.

Coating The method of the present invention is a coating method characterized by coating the surface to be coated with the aqueous undercoating composition obtained as described above.

  The coated surface to which the composition of the present invention is applied is not particularly limited, and examples thereof include a substrate such as metal or plastic; a coated surface formed by providing a coating film on the substrate, and the like. Especially, it is suitable for the repair painting surface of an automobile body. When performing repair coating, the damaged part is first polished, putty-filled if necessary, and then the composition of the present invention is applied by a conventionally known method such as spray coating so that the dry film thickness becomes 10 to 100 μm. be able to.

  The method of the present invention is a coating method in which the aqueous undercoat paint composition is applied on the surface to be coated, then the base coat paint is applied on the applied surface, and the top clear paint is applied on the base coating film. .

  In the method of the present invention, it is generally desirable that the surface of the undercoat before applying the base coat paint is appropriately polished with water-resistant abrasive paper or the like.

  As the base coat paint and the top clear paint, conventionally known curable and lacquer types can be used without limitation. For example, an acrylic resin or a fluororesin containing a crosslinkable functional group such as a hydroxyl group is used as a main ingredient, and block polyisocyanate, A curable paint containing isocyanate or melamine resin as a curing agent, a lacquer paint mainly composed of cellulose acetate butyrate-modified acrylic resin, and the like can be suitably used.

  These base coat paints and clear paints can contain paint additives such as pigments, fiber derivatives, additive resins, UV absorbers, light stabilizers, surface conditioners, and curing catalysts as necessary. .

  Of these, when a coating containing a polyisocyanate curing agent is used as the top clear coating, the polyisocyanate curing agent partially penetrates into the base coat coating from the top clear coating. In this case, it can react with the hydroxyl group, and the curing agent component can be used in the water-based paint or the amount can be reduced, and the adhesion between the base coat film and the top clear film can be improved. .

  Next, an Example is given and this invention is demonstrated more concretely.

Production of emulsion polymer Production Example 1
A 2-liter glass reaction vessel equipped with a stirrer, thermometer, and cooling tube was charged with 300 parts of deionized water and 1 part of sodium dodecylbenzenesulfonate, and the air inside was replaced with nitrogen. The temperature was raised to 82 ° C. to dissolve. In a separate container, 320 parts of deionized water, 20 parts of sodium dodecylbenzenesulfonate, and 1 part of ammonium persulfate are added and stirred well. 280 parts of styrene, 20 parts of n-butyl acrylate, 40 parts of 2-hydroxyethyl methacrylate A monomer mixture consisting of 15 parts of acrylic acid, 20 parts of acrylic acid and 40 parts of 1.6-hexanediol diacrylate was added and stirred to make an emulsion, and the emulsion was continuously dropped into the previous reaction vessel over 2 hours. After completion of the dropwise addition, the mixture was aged at the same temperature for 30 minutes, and 160 parts of deionized water, 20 parts of sodium dodecylbenzenesulfonate and 1 part of ammonium persulfate were added and stirred well in a separate container, and then 200 parts of styrene and n-butyl acrylate. An emulsion prepared by adding and stirring a monomer mixture comprising 60 parts, 120 parts of 2-hydroxyethyl methacrylate and 20 parts of acrylic acid was continuously added dropwise to the glass reaction vessel over 2 hours. After completion of the dropping, the mixture was aged at the same temperature for 2 hours and then cooled to 40 ° C. to obtain an emulsion polymer (A-1) having an average particle diameter of 150 nm and a solid content of 50%. The emulsion polymer (A-1) had a glass transition temperature of 58 ° C. and a weight average molecular weight of 300,000.

Production Example 2
In Production Example 1, an emulsion polymer (A-2) was obtained in the same manner as in Production Example 1 except that the monomer composition was as shown in Table 1.

Production of urethane resin emulsion Production Example 3
115.5 parts of polybutylene adipate having a number average molecular weight of 2000, 115.5 parts of polycaprolactone diol having a number average molecular weight of 2000, 23.2 parts of dimethylolpropionic acid, 6.5 parts of 1,4-butanediol and 120. One part was charged in a polymerization vessel and reacted for 7 hours at 85 ° C. in a nitrogen stream with stirring to obtain a prepolymer having an NCO content of 4.0%. Next, the prepolymer was cooled to 50 ° C., and 165 parts of acetone was added and dissolved uniformly. Then, 15.7 parts of triethylamine was added with stirring, and 600 parts of deionized water was added while maintaining the temperature at 50 ° C. or lower. After maintaining the aqueous dispersion at 50 ° C. for 2 hours to complete the water extension reaction, acetone is distilled off at 70 ° C. or lower under reduced pressure, and the pH is adjusted to 8.0 with triethylamine and deionized water to obtain a solid content. A 35% urethane resin emulsion (B-1) was obtained. The glass transition temperature of the coating film of the urethane resin emulsion (B-1) was −40 ° C.

Production of acrylic resin Production Example 4
500 parts of ethylene glycol monobutyl ether was added to the reaction vessel, and the temperature was raised to 115 ° C. under a nitrogen stream. After reaching 115 ° C., 200 parts of methyl methacrylate, 200 parts of n-butyl acrylate, 300 parts of isobornyl acrylate, 110 parts of styrene, 50 parts of hydroxyethyl acrylate, 40 parts of acrylic acid, “NF biisomer S20W” (Note 1) A mixture of 100 parts and 10 parts of azobisisobutyronitrile was added over 3 hours and aged for 2 hours. After completion of the reaction, the reaction mixture was neutralized with diethylmethanolamine in an equivalent amount, and further 250 parts of propylene glycol monopropyl ether was added to obtain an acrylic resin solution (C-1) having a weight average molecular weight of 45,000 and a solid content of 50%.
(Note 1) “NF biisomer S20W”: trade name, manufactured by Daiichi Kogyo Seiyaku Co., Ltd., methoxypolyethylene glycol monomethacrylate (molecular end is methoxy group, and contains 45-mer of C ₂ H ₄ O group in the molecule) Methacrylate)
Preparation of pigment dispersion paste Production Example 5
170 parts of deionized water, 40 parts of “JR806” (trade name, manufactured by Teika, titanium white), 1 part of “MA-7” (trade name, manufactured by Mitsubishi Chemical Corporation, carbon black), “light calcium carbonate” ( Trade name, Takehara Chemical Industry Co., Ltd., calcium carbonate) 80 parts, “MICRO ACE S-3” (trade name, manufactured by Nippon Talc Co., Ltd.), 75 parts, “K-WHITE 140W” (trade name, manufactured by Teika Corporation, 5 parts of rust preventive pigment) and 60 parts of acrylic resin solution (C-1) were added, and the mixture was stirred and mixed with a disper for 15 minutes, and further dispersed with a sand mill for 30 minutes to obtain a pigment dispersion paste (D-1).

Production Example 6
In the above production example 5, instead of 60 parts of the acrylic resin solution (C-1), “BYK181” (trade name, manufactured by Big Chemie, polyfunctional polymer alkanol ammonium salt-based dispersant, active ingredient 65%, Arihashi Alicyclic A pigment-dispersed paste (D-2) was obtained in the same manner as in Production Example 5 except that 46 parts of the formula polymerizable unsaturated monomer copolymerization was not used.

Preparation of primer surfacer compositions Examples 1-5 and Comparative Examples 1-6
In the composition shown in Table 2 below, each emulsion polymer and urethane resin emulsion (B-1) and ethylene glycol monobutyl ether were stirred for 30 minutes, and then each pigment dispersion paste obtained in Production Example 5 or 6 was added. The stirring was continued for another hour. In this, an antifoamer and a silane coupling agent were added in the composition shown in Table 2, and after adjusting with triethylamine so that the coating pH was 8.0, stirring was further continued for 1 hour, and each primer surfacer was adjusted. Created. Further, L ^* values of coating films formed from the respective primer surfacers were measured according to the method described in the specification, and are also shown in Table 2.

(Note 2) Silane coupling agent: “KBM-403” (trade name, manufactured by Shin-Etsu Chemical Co., Ltd., 3-glycidoxypropyltrimethoxysilane)
(Note 3) Antifoaming agent: “BYK024” (trade name, manufactured by Big Chemie)
A performance test 300 × 100 × 0.8 mm galvanized plate was polished with # 240 paper and degreased to obtain a coated plate. The primer surfacer compositions of Examples and Comparative Examples were spray-coated on the degreased surface so as to have a dry film thickness of 60 to 70 μm, dried at 60 ° C. for 30 minutes, and then water-polished with # 400 paper. Furthermore, “PG2K metallic base No. 123” (manufactured by Kansai Paint Co., Ltd., hydroxyl group-containing acrylic resin-containing base coat paint) is spray-coated to a dry film thickness of 15 μm, left to stand for 10 minutes, and then forced to dry at 60 ° C. for 10 minutes. And then spray-painting the clear paint in which “PG2K clear M” (trade name, manufactured by Kansai Paint Co., Ltd., hydroxyl group-containing acrylic resin paint) is mixed with a polyisocyanate curing agent immediately before use so that the dry film thickness is 50 μm. Each test coated plate was obtained by forced drying at 60 ° C. for 20 minutes. Each obtained test coating board was used for the following performance test. The results are also shown in Table 2.
(* 1) Abrasiveness: Evaluated by the presence or absence of clogging of paper when water-polished with # 400 paper after coating each primer surfacer composition. (○: Good without clogging, △: Some clogging, ×: Clogging)
(* 2) Water-resistant adhesion: After each test coating plate was dipped in 20 ° C. water for 7 days and taken out, the coating film was cross-cut so as to reach the substrate, and an adhesive tape was applied to the coating surface to strongly peel off. The subsequent coating surface was evaluated. (◎: No peeling, ○: Border missing, △: Partial peeling, x: Full peeling)
(* 3) Water resistance: Each test coating plate was immersed in a constant temperature water bath at 40 ° C. for 10 days and then taken out, and the state of the coating film after standing for 1 hour was visually evaluated. (○: No abnormality, △: Glossy, ×: Glossy, blistering)

Claims (6)

(A) (a) styrene, (b) an acid group-containing polymerizable unsaturated monomer, (c) a hydroxyl group-containing polymerizable unsaturated monomer, and (d) other polymerizable unsaturated monomers as copolymerization components, and styrene The amount of (a) used is 30% by weight or more based on the weight of all monomers, an emulsion polymer,
(B) an aqueous urethane resin,
(C) (e) Bridged alicyclic hydrocarbon group-containing polymerizable unsaturated monomer, (b) Acid group-containing polymerizable unsaturated monomer, (c) Hydroxyl group-containing polymerizable unsaturated monomer, and (f) Other polymerizations A coating composition mainly comprising an acrylic resin having a weight average molecular weight in the range of 5,000 to 100,000 and a (D) pigment having a polymerizable unsaturated monomer as a copolymerization component,
The pigment (D) is contained in an amount of 100 to 350 parts by weight with respect to 100 parts by weight of the total resin solids in the composition, and the extender pigment in the pigment (D) is 50 to 100 parts by weight with respect to 100 parts by weight of the total resin solids. An aqueous undercoating composition comprising 200 parts by weight. The emulsion polymer (A) is (a) 30-80% by weight of styrene, (b) 1-10% by weight of an acid group-containing polymerizable unsaturated monomer, and (c) 5-30% by weight of a hydroxyl group-containing polymerizable unsaturated monomer. And (d) in a copolymer aqueous dispersion obtained by emulsion polymerization of a monomer mixture (I) comprising 5 to 64% by weight of other polymerizable unsaturated monomers, (a) 20 to 70% by weight of styrene, ( b) a monomer comprising 1 to 10% by weight of an acid group-containing polymerizable unsaturated monomer, (c) a hydroxyl group-containing polymerizable unsaturated monomer of 5 to 50% by weight, and (d) another polymerizable unsaturated monomer of 5 to 74% by weight. The aqueous undercoat paint composition according to claim 1, which is obtained by emulsion polymerization by adding the mixture (II). The blending ratio of the emulsion polymer (A), the aqueous urethane resin (B) and the acrylic resin (C) is based on the total solid weight of the emulsion polymer (A), the aqueous urethane resin (B) and the acrylic resin (C). The emulsion polymer (A) is 10 to 80% by weight, the aqueous urethane resin (B) is 10 to 80% by weight, and the acrylic resin (C) is 10 to 80% by weight. 2. The aqueous undercoat paint composition according to 2. The aqueous undercoat paint composition according to any one of claims 1 to 3, further comprising a silane coupling agent (E). A coating method comprising coating the surface to be coated with the water-based undercoating composition according to any one of claims 1 to 4. After applying the water-based undercoat paint composition according to any one of claims 1 to 4 to a surface to be coated, a base coat paint is applied to the coated surface, and a top clear paint is applied to the base paint film. How to paint.