JP2012021106A - Aqueous 2-pack type clear coating composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an aqueous 2-pack type clear coating composition having a good polishing operability even under the condition of forced drying, and suitable for forming a clear coated film excellent in finished appearance after the polishing.SOLUTION: In this aqueous 2-pack type clear coating composition containing (I) acrylic resin emulsion obtained by dispersing an acrylic resin obtained by polymerizing a polymerizable unsaturated monomer component in the presence of an organic solvent by separating the monomer as multiple stages, with water, and (II) a polyisocyanate curing agent, the polymerizable unsaturated monomer component (A) contains an epoxy group-containing monomer, a methacrylate having a 3-4C alkyl group and a monomer containing a hydroxy group, and the polymerizable unsaturated monomer component (B) contains a carboxylic group-containing monomer and a hydroxy group-containing monomer, the content of the methacrylate having the 3-4C alkyl group is in the range of 20 to 65 mass%, and the content of the polymerizable unsaturated monomer having a methacryloyl group is in the range of 30 to 90 mass% based on the whole amount of polymerizable unsaturated monomers.

Description

  The present invention relates to an aqueous two-part clear coating composition.

  In recent years, environmental pollution and effects on the human body have been taken into account, and the number of cases in which water-based paints are used instead of solvent-based paints has increased considerably.

  For example, the outer plate portion of an automobile body is generally coated with a multilayer coating film composed of an undercoating film, an intermediate coating film, a top coating film, and a clear coating film for the purpose of providing corrosion protection and aesthetics. Among these coating films, the base coating composition, the intermediate coating composition, and the top coating composition that form the base coating film, the intermediate coating film, and the top coating film are being made water-based. With regard to the clear coating composition, it is difficult to achieve the same performance and finished appearance as the solvent-based clear coating composition, and the development thereof is required.

  For example, the present applicant has proposed an aqueous clear coating composition containing a hydroxyl group- and acid group-containing particulate resin aqueous dispersion and a crosslinking agent in Patent Document 1 and exhibiting a specific viscosity.

  Patent Document 2 discloses an acrylic polyol aqueous dispersion obtained by water-dispersing a specific acrylic polyol obtained by polymerization including solution polymerization for producing a core and solution polymerization for producing a shell, and sulfonic acid. An aqueous two-component curable composition containing a curing agent containing a polyisocyanate having a group is disclosed.

  According to the water-based clear coating composition described in these patent documents, it is possible to form a clear coating film having excellent smoothness and gloss and having no appearance of coating surface abnormalities such as wax, The clear coating film is obtained by high-temperature baking of so-called two-coat one-bake, which is an advantageous condition in terms of finish and physical properties of the coating film.

  By the way, also in the field of automobile repair coating, water-based paints are required from the viewpoint of improving the environment at repair sites.

  Because automobile bodies are equipped with parts that are sensitive to high temperatures such as gasoline tanks, electrical equipment, and computers, repair coatings cannot be baked at high temperatures when repairing automobile bodies and are forced under relatively mild conditions. It is common to perform drying.

  Also, at the repair site, the top coat clear coating is completely removed to match the finished appearance so that the repair coating is indistinguishable from the unrepaired part, and to remove dust and dirt adhering to the repair coating. Polishing with a compound or the like is usually performed before drying.

  In this way, the water-based clear paint composition used for automobile repair coating has a finish similar to that of the solvent-based clear paint composition under forced drying conditions that do not affect parts in the automobile body. In addition, the coating film is required to have excellent polishing workability.

  However, as described above, it is difficult to design a heat-curable water-based clear coating composition that has excellent coating film properties and excellent finished appearance, as described above, and the coating composition described in Patent Documents 1 and 2 above. However, although it is effective with respect to abnormal coating surfaces of clear coatings such as armpits, sacks, etc., there is still room for improvement with respect to the polishing workability of the clear coating film dried under milder conditions and the finish after polishing.

WO2007 / 013684 pamphlet JP 2009-212244 A

  An object of the present invention is to provide an aqueous two-component clear coating composition suitable for forming a clear coating film having good polishing workability even under forced drying conditions and having an excellent finished appearance after polishing.

As a result of intensive studies on the above-mentioned problems, the present inventors have obtained by polymerizing a polymerizable unsaturated monomer (A) having a specific composition and a polymerizable unsaturated monomer (B) having a specific composition in multiple stages. The present inventors have found that an acrylic resin emulsion obtained by dispersing an acrylic resin in water and a composition containing polyisocyanate can form a clear coating film excellent in polishing workability and finishability, and have reached the present invention.
That is, the present invention
1. An aqueous two-component clear coating composition comprising an acrylic resin emulsion (I) and a polyisocyanate curing agent (II), wherein the acrylic resin emulsion (I) has different compositions in the presence of an organic solvent. An acrylic resin obtained by polymerizing an unsaturated monomer component in multiple stages is obtained by water dispersion, and the polymerizable unsaturated monomer component (A) used in at least one stage of polymerization is ,
Epoxy group-containing polymerizable unsaturated monomer (a1),
Methacrylate (a2) having an alkyl group having 3 to 4 carbon atoms,
The polymerizable unsaturated monomer component (B), which contains the hydroxyl group-containing polymerizable unsaturated monomer (a3) and the other polymerizable unsaturated monomer (a4) and is used in at least one other stage polymerization,
Carboxyl group-containing polymerizable unsaturated monomer (b1),
Comprising a hydroxyl group-containing polymerizable unsaturated monomer (b2) and another polymerizable unsaturated monomer (b3),
In the total polymerizable unsaturated monomer used for the production of the acrylic resin emulsion (I), the content of the methacrylate having an alkyl group having 3 to 4 carbon atoms is in the range of 20 to 65% by mass, and the methacryloyl group An aqueous two-component clear coating composition characterized in that the content of the polymerizable unsaturated monomer having a water content is in the range of 30 to 90% by mass;
2. The aqueous two-component clear coating according to 1, wherein the methacrylate (a2) having an alkyl group having 3 to 4 carbon atoms in the polymerizable unsaturated monomer component (A) contains n-butyl methacrylate and i-butyl methacrylate. Composition,
3. The other polymerizable unsaturated monomer (a4), which is a copolymerization component of the polymerizable unsaturated monomer component (A), includes a polymerizable unsaturated monomer having an isobornyl group as a part of the component. The aqueous two-component clear coating composition according to claim,
4). The other polymerizable unsaturated monomer (b3) contained in the polymerizable unsaturated monomer component (B) includes a methacrylate having an alkyl group having 3 to 4 carbon atoms as a part of the component. The aqueous two-component clear coating composition according to any one of the above,
5. Any one of Items 1 to 4, wherein the amount of the carboxyl group contained in the polymerizable unsaturated monomer component (B) with respect to 1 mol of the epoxy group contained in the polymerizable unsaturated monomer component (A) is in the range of 3 to 30 mol. Or an aqueous two-component clear coating composition according to claim 1,
6). 6. The aqueous two-component clear coating composition according to any one of items 1 to 5, wherein the weight average molecular weight of the acrylic resin before water dispersion is in the range of 5,000 to 100,000.
7). The acrylic resin emulsion (I) is a core-shell type acrylic resin emulsion having a copolymer of a polymerizable unsaturated monomer component (A) as a core and a copolymer of a polymerizable unsaturated monomer component (B) as a shell 1 Item 7. The aqueous two-component clear coating composition according to any one of Items 6 to 6,
8). 8. The hydroxyl value per solid content of the acrylic resin emulsion (I) is 70 to 170 mg KOH / g, and the acid value per solid content is within the range of 5 to 50 mg KOH / g. Aqueous two-component clear coating composition,
About.

  According to the aqueous two-component clear coating composition of the present invention, since the storage stability of the acrylic resin emulsion is very good, the composition of a plurality of polymerizable unsaturated monomer components used in the production of the acrylic resin emulsion is reduced. It has the advantage that it can be designed widely. By combining the emulsion with polyisocyanate, a clear coating film excellent in polishing workability and finish after polishing can be formed even under forced drying conditions.

  The aqueous two-component clear coating composition of the present invention is a composition comprising an acrylic resin emulsion (I) and a polyisocyanate curing agent (II).

Acrylic resin emulsion (I);
The acrylic resin emulsion (I) in the present invention is an emulsion obtained by dispersing in water an acrylic resin obtained by polymerizing polymerizable unsaturated monomer components having different compositions in multiple stages in the presence of an organic solvent. is there.

As the polymerizable unsaturated monomer component (A) in at least one stage for producing the acrylic resin, an epoxy group-containing polymerizable unsaturated monomer (a1),
Methacrylate (a2) having an alkyl group having 3 to 4 carbon atoms,
It contains a hydroxyl group-containing polymerizable unsaturated monomer (a3) and other polymerizable unsaturated monomers (a4).

  In the present invention, the epoxy group-containing polymerizable unsaturated monomer (a1) is reacted with a carboxyl group contained in the polymerizable unsaturated monomer component (B) described later, and a copolymer of the polymerizable unsaturated monomer component (A) A monomer used for grafting a copolymer of the polymerizable unsaturated monomer component (B) to further improve the water dispersion stability of the acrylic resin emulsion (I), such as glycidyl (meth) acrylate, β -Methyl glycidyl (meth) acrylate, 3,4-epoxycyclohexylmethyl (meth) acrylate, 3,4-epoxycyclohexylethyl (meth) acrylate, 3,4-epoxycyclohexylpropyl (meth) acrylate, allyl glycidyl ether, etc. These can be used alone or in combination of two or more It can be used.

  Examples of the methacrylate (a2) having an alkyl group having 3 to 4 carbon atoms include n-propyl methacrylate, i-propyl methacrylate, n-butyl methacrylate, i-butyl methacrylate, tert-butyl methacrylate, and the like. Can be used alone or in combination of two or more.

  In the present invention, it is suitable that the monomer (a2) contains n-butyl methacrylate and i-butyl methacrylate, and the proportion of i-butyl methacrylate used is 80 to 100 parts by mass of n-butyl methacrylate. It is suitable from the point of the abrasiveness of a clear coating film that it is adjusted in the range of 800 mass parts, especially 200-500 mass parts.

  The hydroxyl group-containing polymerizable polymerizable unsaturated monomer (a3) is used for introducing a hydroxyl group for reacting with the polyisocyanate curing agent (II) described later into the acrylic resin emulsion (I), and for the acrylic resin emulsion (I). Monomers copolymerized to contribute to water dispersibility, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) Monoesterified product of (meth) acrylic acid such as acrylate and dihydric alcohol having 2 to 8 carbon atoms; ε-caprolactone modification of monoesterified product of (meth) acrylic acid and dihydric alcohol having 2 to 8 carbon atoms Body; allyl alcohol, etc., which can be used alone or in combination of two or more. Can be used.

  The other polymerizable unsaturated monomer (a4) is a polymerizable unsaturated monomer other than the monomer (a1), monomer (a2) and monomer (a3), such as methyl (meth) acrylate, ethyl (meth). (Meth) acrylates having an alkyl group having 1 to 2 carbon atoms such as acrylate; n-propyl acrylate, i-propyl acrylate, n-butyl acrylate, i-butyl acrylate, tert-butyl acrylate, etc. Acrylate having 4 alkyl groups; n-hexyl (meth) acrylate, n-octyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, nonyl (meth) acrylate, tridecyl (meth) acrylate, lauryl (meth) acrylate, Stearyl (meth) acrelan , “Isostearyl acrylate” (trade name, manufactured by Osaka Organic Chemical Co., Ltd.), cyclohexyl (meth) acrylate, methylcyclohexyl (meth) acrylate, t-butylcyclohexyl (meth) acrylate, cyclododecyl (meth) acrylate, tricyclodecanyl Alkyl or cycloalkyl (meth) acrylate having 6 or more carbon atoms such as (meth) acrylate; polymerizable unsaturated monomer having isobornyl group such as isobornyl (meth) acrylate; polymerization having adamantyl group such as adamantyl (meth) acrylate Polymerizable unsaturated monomers having a tricyclodecenyl group such as tricyclodecenyl (meth) acrylate; aromatic rings such as benzyl (meth) acrylate, styrene, α-methylstyrene, vinyltoluene Polymerizable unsaturated monomer: vinyltrimethoxysilane, vinylmethyldimethoxysilane, vinyltriethoxysilane, vinylmethyldiethoxysilane, vinyltris (2-methoxyethoxy) silane, vinyltriisopropoxysilane, γ- (meth) acryloyloxy Propyltrimethoxysilane, γ- (meth) acryloyloxypropylmethyldimethoxysilane, γ- (meth) acryloyloxypropyltriethoxysilane, γ- (meth) acryloyloxypropylmethyldiethoxysilane, γ- (meth) acryloyloxypropyl Addition of tri-n-propoxysilane, γ- (meth) acryloyloxypropyltriisopropoxysilane, vinyltriacetoxysilane, β- (meth) acryloyloxyethyltrimethoxysilane, etc. Polymerizable unsaturated monomer having a decomposable silyl group; perfluoroalkyl (meth) acrylate such as perfluorobutylethyl (meth) acrylate and perfluorooctylethyl (meth) acrylate; polymerization having a fluorinated alkyl group such as fluoroolefin Unsaturated monomers; vinyl compounds such as N-vinylpyrrolidone, ethylene, butadiene, chloroprene, vinyl propionate, vinyl acetate; 2-acryloyloxyethyl acid phosphate, 2-methacryloyloxyethyl acid phosphate, 2-acryloyloxypropyl acid phosphate Phosphoric acid group-containing polymerizable unsaturated monomers such as 2-methacryloyloxypropyl acid phosphate; (meth) acrylic acid, maleic acid, crotonic acid, β-carboxyethyl Carboxyl group-containing polymerizable unsaturated monomers such as acrylate; (meth) acrylonitrile, (meth) acrylamide, methylenebis (meth) acrylamide, ethylenebis (meth) acrylamide, 2- (methacryloyloxy) ethyltrimethylammonium chloride, glycidyl (meth) Nitrogen-containing polymerizable unsaturated monomers such as adducts of acrylate and amines; at least two polymerizable unsaturated groups such as allyl (meth) acrylate and 1,6-hexanediol di (meth) acrylate in one molecule Polymerizable unsaturated monomer having: 2-acrylamido-2-methylpropanesulfonic acid, 2-sulfoethyl (meth) acrylate, allylsulfonic acid, 4-styrenesulfonic acid, etc .; sulfones such as sodium salt and ammonium salt of these sulfonic acids Polymerizable unsaturated monomers having a group; polymerizable unsaturated monomers having an acid anhydride group such as maleic anhydride, itaconic anhydride, citraconic anhydride, etc., may be used alone or in combination of two or more. be able to.

  In the present invention, the other polymerizable unsaturated monomer (a4) preferably contains a polymerizable unsaturated monomer having an isobornyl group as a part of the component from the viewpoint of the abrasiveness of the clear coating film.

  Examples of the isobornyl group-containing polymerizable unsaturated monomer include isobornyl (meth) acrylate, and can be used alone or in combination.

  When the isobornyl group-containing polymerizable unsaturated monomer is used, the amount used is 25 to 75% by mass, preferably 40 to 65% by mass, in the other polymerizable unsaturated monomer (a4). It is desirable from the viewpoint of the abrasiveness of the clear coating film.

  The acrylic resin for producing the acrylic resin emulsion (I) in the present invention comprises the polymerizable unsaturated monomer component (B) as a copolymer component in addition to the polymerizable unsaturated monomer component (A).

Such polymerizable unsaturated monomer component (B) is:
Carboxyl group-containing polymerizable unsaturated monomer (b1),
It comprises a hydroxyl group-containing polymerizable unsaturated monomer (b2) and other polymerizable unsaturated monomers (b3).

  As the carboxyl group-containing polymerizable unsaturated monomer (b1), an aqueous dispersion group is introduced into the acrylic resin emulsion (I) and reacted with an epoxy group contained in the copolymer of the polymerizable unsaturated monomer component (A). It is also a monomer used to introduce a functional group to be used, and specifically includes (meth) acrylic acid, maleic acid, crotonic acid, β-carboxyethyl acrylate, etc., and these may be used alone or in combination of two or more. Can be used.

  The hydroxyl group-containing polymerizable unsaturated monomer (b2) is the same as the compounds listed in the hydroxyl group-containing polymerizable unsaturated monomer (a3) and can be used alone or in combination of two or more thereof. .

  The other polymerizable unsaturated monomer (b3) is a polymerizable unsaturated monomer other than the monomer (b1) and the monomer (b2), and examples thereof include methyl (meth) acrylate, ethyl (meth) acrylate, and n-propyl. (Meth) acrylate, i-propyl (meth) acrylate, n-butyl (meth) acrylate, i-butyl (meth) acrylate, tert-butyl (meth) acrylate, n-hexyl (meth) acrylate, n-octyl (meta ) Acrylate, 2-ethylhexyl (meth) acrylate, nonyl (meth) acrylate, tridecyl (meth) acrylate, lauryl (meth) acrylate, stearyl (meth) acrylate, “isostearyl acrylate” (trade name, manufactured by Osaka Organic Chemical Co., Ltd.) , Cyclohexyl (meth) Alkyl or cycloalkyl (meth) acrylate such as acrylate, methylcyclohexyl (meth) acrylate, t-butylcyclohexyl (meth) acrylate, cyclododecyl (meth) acrylate, tricyclodecanyl (meth) acrylate; isobornyl (meth) acrylate, etc. Polymerizable unsaturated monomer having an isobornyl group; Polymerizable unsaturated monomer having an adamantyl group such as adamantyl (meth) acrylate; Polymerizable unsaturated monomer having a tricyclodecenyl group such as tricyclodecenyl (meth) acrylate Saturated monomer; aromatic ring-containing polymerizable unsaturated monomer such as benzyl (meth) acrylate, styrene, α-methylstyrene, vinyltoluene, etc .; 2-acryloyloxyethyl acid phosphate, 2-methacryloyloxye Phosphoric acid group-containing polymerizable unsaturated monomers such as tilacic acid phosphate, 2-acryloyloxypropyl acid phosphate, 2-methacryloyloxypropyl acid phosphate; 2-acrylamido-2-methylpropanesulfonic acid, 2-sulfoethyl (meth) acrylate, Allyl sulfonic acid, 4-styrene sulfonic acid, etc .; polymerizable unsaturated monomers having sulfonic acid groups such as sodium salt and ammonium salt of these sulfonic acids; acid anhydride groups such as maleic anhydride, itaconic anhydride, citraconic anhydride, etc. Polymerizable unsaturated monomers having vinyl; etc .; vinyltrimethoxysilane, vinylmethyldimethoxysilane, vinyltriethoxysilane, vinylmethyldiethoxysilane, vinyltris (2-methoxyethoxy) silane, vinyltriisopropoxy Silane, γ- (meth) acryloyloxypropyltrimethoxysilane, γ- (meth) acryloyloxypropylmethyldimethoxysilane, γ- (meth) acryloyloxypropyltriethoxysilane, γ- (meth) acryloyloxypropylmethyldiethoxysilane , Γ- (meth) acryloyloxypropyltri-n-propoxysilane, γ- (meth) acryloyloxypropyltriisopropoxysilane, vinyltriacetoxysilane, β- (meth) acryloyloxyethyltrimethoxysilane, etc. Polymerizable unsaturated monomer having a silyl group; perfluoroalkyl (meth) acrylate such as perfluorobutylethyl (meth) acrylate and perfluorooctylethyl (meth) acrylate; fluoroolefin, etc. Polymerizable unsaturated monomers having a fluorinated alkyl group; vinyl compounds such as N-vinylpyrrolidone, ethylene, butadiene, chloroprene, vinyl propionate, vinyl acetate; (meth) acrylonitrile, (meth) acrylamide, methylenebis (meth) acrylamide , Nitrogen-containing polymerizable unsaturated monomers such as ethylenebis (meth) acrylamide, 2- (methacryloyloxy) ethyltrimethylammonium chloride, adducts of glycidyl (meth) acrylate and amines; allyl (meth) acrylate, 1,6 -Polymerizable unsaturated monomer etc. which have at least 2 polymerizable unsaturated groups in 1 molecule, such as hexanediol di (meth) acrylate, etc. are mentioned, These can be used individually or in combination of 2 or more types.

  In addition, the other polymerizable unsaturated monomer (b3) contains a methacrylate having a C3-4 alkyl group as a part of the component from the viewpoint of finish after the clear coating film is polished. Is suitable.

  The methacrylate having an alkyl group having 3 to 4 carbon atoms can be appropriately selected from the compounds listed in the description of the monomer (a2) and used in other polymerizable unsaturated monomers (b3). The content of is preferably 10% by mass or more, preferably 60% by mass or more, more preferably 80% by mass or more, and the total amount of the monomer (b3) has a C 3-4 alkyl group. It may be.

  In this invention, content of the methacrylate which has a C3-C4 alkyl group is 20-65 mass% in the all polymerizable unsaturated monomer used for manufacture of acrylic resin emulsion (I), Preferably it is 40. The content of the polymerizable unsaturated monomer having a methacryloyl group is in the range of ˜60 mass%, and is preferably in the range of 30˜90 mass%, preferably 50˜80 mass%.

  When the content of the methacrylate having an alkyl group having 3 to 4 carbon atoms is less than 20% by mass, the finish and polishing workability of the coating film formed from the clear coating composition of the present invention are insufficient, while 65% by mass. If it exceeds 50%, the finish after polishing is insufficient, which is not preferable.

  In the present specification, the polymerizable unsaturated monomer having a methacryloyl group is a compound having a methacryloyl group in the molecule, for example, methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, i-propyl methacrylate, n-butyl. Methacrylate, i-butyl methacrylate, tert-butyl methacrylate, n-hexyl methacrylate, n-octyl methacrylate, 2-ethylhexyl methacrylate, nonyl methacrylate, tridecyl methacrylate, lauryl methacrylate, isostearyl methacrylate, cyclohexyl methacrylate, methylcyclohexyl methacrylate, t- Butylcyclohexyl methacrylate, cyclododecyl methacrylate, tricyclodecanyl methacrylate Alkyl or cycloalkyl methacrylates such as methacrylates; methacrylates having isobornyl groups such as isobornyl methacrylate; methacrylates having adamantyl groups such as adamantyl methacrylate; methacrylates having cyclodecenyl groups such as tricyclodecenyl methacrylate; methacrylic acid; benzyl Methacrylate; γ-methacryloyloxypropyltrimethoxysilane, γ-methacryloyloxypropylmethyldimethoxysilane, γ-methacryloyloxypropyltriethoxysilane, γ-methacryloyloxypropylmethyldiethoxysilane, γ-methacryloyloxypropyltri-n-propoxy Silane, γ-methacryloyloxypropyltriisopropoxysilane, β-methacryloyloxyethyltri Methacrylates having alkoxysilyl groups such as methoxysilane; Perfluoroalkyl methacrylates such as perfluorobutylethyl methacrylate and perfluorooctylethyl methacrylate; Phosphorus groups such as 2-methacryloyloxyethyl acid phosphate and 2-methacryloyloxypropyl acid phosphate Methacrylate; monoesterified product of methacrylic acid such as 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, 3-hydroxypropyl methacrylate, 4-hydroxybutyl methacrylate, etc. and dihydric alcohol having 2 to 8 carbon atoms; methacrylic acid and carbon Ε-caprolactone modified product of monoesterified product with dihydric alcohol of 2 to 8; methacrylic acid; methacrylonitrile, methacryl Mido, methylenebismethacrylamide, ethylenebismethacrylamide, 2- (methacryloyloxy) ethyltrimethylammonium chloride, adducts of glycidyl methacrylate and amines; polymerization properties such as allyl methacrylate and 1,6-hexanediol dimethacrylate Methacrylate having at least two unsaturated groups in one molecule; glycidyl methacrylate, β-methylglycidyl methacrylate, 3,4-epoxycyclohexylmethyl methacrylate, 3,4-epoxycyclohexylethyl methacrylate, 3,4-epoxycyclohexylpropyl methacrylate, etc. And epoxy group-containing methacrylate of 2-sulfoethyl methacrylate and its sodium salt and ammonium salt.

  If the content of the polymerizable unsaturated monomer having a methacryloyl group in the total polymerizable unsaturated monomer used in the production of the acrylic resin emulsion (I) is outside this range, the polishing property of the formed clear coating film is not good. It is not preferable because it is sufficient.

In the acrylic resin emulsion (I), the proportion of the monomers (a1) to (a4) in the polymerizable unsaturated monomer component (A) can be adjusted as appropriate as long as it is within the scope of the present invention.
The monomer (a1) is 0.1 to 40% by mass, preferably 0.5 to 25% by mass,
The monomer (a2) is 35 to 74.9% by mass, preferably 40 to 64.5% by mass,
The monomer (a3) is 15 to 54.9% by mass, preferably 20 to 44.5% by mass,
The monomer (a4) is 10 to 49.9% by mass, preferably 15 to 39.5% by mass,
Can be within the range of

Moreover, the use ratio of these monomers (b1) to (b3) in the polymerizable unsaturated monomer component (B) can be appropriately adjusted as long as it is within the scope of the present invention.
Monomer (b1) is 5 to 60% by mass, preferably 10 to 50% by mass,
The monomer (b2) is 20 to 75% by mass, preferably 25 to 65% by mass,
The monomer (b3) is 20 to 75% by mass, preferably 25 to 65% by mass,
Can be in the range of

  Further, in these polymerizable unsaturated monomer components (A) and (B), the carboxyl group contained in the polymerizable unsaturated monomer component (B) with respect to 1 mol of the epoxy group contained in the polymerizable unsaturated monomer component (A). From the viewpoint of the storage stability of the acrylic resin emulsion (I), the finish of the clear coating film, and the polishing properties, the amount is adjusted to be in the range of 3 to 30 mol, particularly 6 to 20 mol. Is suitable.

  The polymerizable unsaturated monomer components (A) and (B) are used in a mass ratio of monomer component (A) / monomer component (B) of 60/40 to 95/5, particularly 70/30 to 90/10. It is suitable from the point of the water dispersion stability of acrylic resin emulsion (I) and the finishing property of a clear coating film to exist in the range.

  In the present invention, the polymerization of the polymerizable unsaturated monomer components (A) and (B) is not particularly limited. For example, the polymerizable unsaturated monomer component (A) is heated in the presence of an organic solvent. ) Is dropped to polymerize, and the polymerizable unsaturated monomer component (B) is dropped and polymerized in the copolymer solution of the polymerizable unsaturated monomer component (A) to obtain an acrylic resin emulsion (I ) Is desirable because it tends to have excellent water dispersibility and storage stability.

  Moreover, you may add suitably the polymerization by polymerizable unsaturated monomer components other than the said polymerizable unsaturated monomer component (A) and (B) as needed.

  The reaction temperature for polymerizing the monomers (A) and (B) is usually in the range of about 60 to about 200 ° C., preferably about 70 to about 160 ° C., and the reaction time is usually about 10 hours or less, preferably about 0.5 to about 6 hours.

  In said reaction, it is preferable to add a polymerization initiator suitably. Examples of such polymerization initiators include benzoyl peroxide, octanoyl peroxide, lauroyl peroxide, stearoyl peroxide, cumene hydroperoxide, tert-butyl peroxide, di-tert-amyl peroxide, and t-butyl. Organic peroxides such as peroxy-2-ethylhexanoate, tert-butyl peroxylaurate, tert-butyl peroxyisopropyl carbonate, tert-butyl peroxyacetate, diisopropylbenzene hydroperoxide; azobisisobutyro Nitrile, azobis (2,4-dimethylvaleronitrile), azobis (2-methylpropiononitrile), azobis (2-methylbutyronitrile), 4,4′-azobis (4-cyanobuta Acid), dimethylazobis (2-methylpropionate), azobis [2-methyl-N- (2-hydroxyethyl) -propionamide], azobis {2-methyl-N- [2- (1-hydroxy Butyl)]-propionamide}; persulfates such as potassium persulfate, ammonium persulfate, sodium persulfate, and the like.

  These polymerization catalysts may be used alone or in combination of two or more. Moreover, there is no problem even if the kind and amount of the polymerization initiator are different during the polymerization of the polymerizable unsaturated monomer component (A) and the polymerizable unsaturated monomer component (B).

  The blending amount of the polymerization initiator is 0.01 to 20 parts by weight, particularly 0.1 to 15 parts by weight, more particularly 0.3 to 10 parts by weight based on 100 parts by weight of the polymerizable unsaturated monomer used at that stage. The range of parts by mass is preferable from the viewpoint of water dispersion stability of the resulting acrylic resin emulsion (I).

  The polymerization is usually carried out in the presence of an organic solvent. The selection of the organic solvent can be appropriately performed in consideration of the polymerization temperature, ease of handling during emulsion production, and long-term storage stability of the resulting aqueous dispersion.

  An organic solvent can also be added when the acrylic resin is dispersed in water.

  As the organic solvent, alcohol solvents, cellosolve solvents, carbitol solvents and the like are preferable. Specifically, for example, alcohol solvents such as n-butanol; ethylene glycol monobutyl ether, ethylene glycol monoisopropyl ether, ethylene glycol monomethyl ether, propylene glycol monomethyl ether, propylene glycol monopropyl ether, propylene glycol mono n-butyl ether, Examples thereof include cellosolve solvents such as dipropylene glycol monomethyl ether and dipropylene glycol mono n-butyl ether; carbitol solvents such as diethylene glycol monobutyl ether and diethylene glycol monoethyl ether.

  Further, as the organic solvent, an inert organic solvent that is not mixed with water other than the above can also be used as long as it does not hinder the water dispersion stability of the acrylic resin emulsion (I). Examples thereof include aromatic hydrocarbon solvents such as toluene and xylene, ester solvents such as ethyl acetate and butyl acetate, and ketone solvents such as methyl ethyl ketone and cyclohexanone.

  The acrylic resin obtained as described above has a weight average molecular weight within the range of 5,000 to 100,000, particularly 10,000 to 50,000, more particularly 10,000 to 30,000. It is suitable from the viewpoints of the water dispersion stability of the resin emulsion (I), the finish of the clear coating film, smoothness, abrasiveness, and the like.

  In this specification, the weight average molecular weight of the acrylic resin is “HLC-8120GPC” (trade name, manufactured by Tosoh Corporation) as a gel permeation chromatograph, and “TSKgel G4000HXL” is used as a column. A total of four “TSKgel G3000HXL” and one “TSKgel G2000HXL” (trade name, all manufactured by Tosoh Corporation) were used, a differential refractometer was used as a detector, a mobile phase; tetrahydrofuran, Measurement can be performed under the conditions of measurement temperature: 40 ° C., flow rate: 1 mL / min.

  In the present invention, the acrylic resin emulsion (I) can be obtained by dispersing the acrylic resin in water.

  As a method of water dispersion, a part or all of anionic groups such as carboxyl groups contained in the acrylic resin are neutralized with a basic compound and dispersed in water, or an aqueous medium containing a basic compound It is also possible to add and disperse the acrylic resin therein.

  Examples of the basic compounds for neutralization include ammonia, diethylamine, ethylethanolamine, diethanolamine, triethanolamine, monoethanolamine, monopropanolamine, isopropanolamine, ethylaminoethylamine, hydroxyethylamine, triethylamine, tributylamine, Examples thereof include organic amines such as dimethylethanolamine and diethylenetriamine; alkali metal hydroxides such as caustic soda and caustic potash; 0.1 to 1.5 equivalents, preferably 0.5 to the carboxyl group in the acrylic resin. It is appropriate to use ˜1.2 equivalents.

  The acrylic resin emulsion (I) obtained as described above is a core-shell type acrylic emulsion having a copolymer of a polymerizable unsaturated monomer component (A) as a core and a polymerizable unsaturated monomer component (B) as a shell. The average particle diameter can be within a range of 0.05 to 1.0 μm, preferably 0.08 to 0.8 μm.

  In this specification, the average particle size is diluted with a submicron particle analyzer N4 (trade name, manufactured by Beckman Coulter, Inc., particle size distribution measuring device) to a concentration suitable for measurement with deionized water, The value measured at room temperature (about 20 ° C.).

  The hydroxyl value per solid content of the acrylic resin emulsion (I) is in the range of 70 to 170 mgKOH / g, particularly 100 to 120 mgKOH / g, and the acid value per solid content is 5 to 50 mgKOH / g, 20 to 35 mgKOH / g. g, more particularly in the range of 20 to 30 mg KOH / g, is suitable from the viewpoint of the finish of the clear coating film to be formed, the polishability, the finish after the polishing operation, and the like.

  The coating form of the aqueous two-component clear coating composition of the present invention is a two-component composition in which the main component containing the acrylic resin emulsion (I) and the polyisocyanate curing agent (II) described below are mixed immediately before use. it can.

  The ratio of the acrylic resin emulsion (I) resin solid content in the total resin solid content contained in the main agent may be 60% by mass or more, particularly 80% by mass or more.

  In addition to the acrylic resin emulsion (I), the main agent is required to include a modifying resin, an antifoaming agent, a thickening agent, an ultraviolet absorber, a light stabilizer, a surface conditioner, an organic solvent, and the like as necessary. It can mix | blend according to the objective.

Polyisocyanate curing agent (II);
As the polyisocyanate curing agent (II) to be combined with the acrylic resin emulsion (I) in the present invention, those conventionally known in the field of water-based paints can be used without limitation. For example, polyisocyanate is self-emulsified in water. And those obtained by forcibly dispersing them with a stirrer and the like, and those obtained by modifying polyisocyanate with an anionic or nonionic compound.

  Examples of the polyisocyanate include aliphatic diisocyanates such as hexamethylene diisocyanate and trimethylhexamethylene diisocyanate; cyclic aliphatic diisocyanates such as hydrogenated xylylene diisocyanate and isophorone diisocyanate; tolylene diisocyanate and 4,4′-diphenylmethane diisocyanate. Aromatic diisocyanates; triphenylmethane-4,4 ′, 4 ″ -triisocyanate, 1,3,5-triisocyanatobenzene, 2,4,6-triisocyanatotoluene, 4,4′-dimethyldiphenylmethane Organic polyisocyanate itself, such as a polyisocyanate compound having three or more isocyanate groups, such as -2,2 ', 5,5'-tetraisocyanate, or each of these organic compounds Polyisocyanate with a polyhydric alcohol, an adduct of low molecular weight polyester resin or water, etc., or cyclic polymer of the organic polyisocyanate comrades described above, even and an isocyanate-biuret, or the like.

Aqueous two-component clear coating composition The aqueous two-component clear coating composition of the present invention described above is prepared by mixing the main component containing the acrylic resin emulsion (I) and a curing agent immediately before use and diluting as necessary. can do.

  The paint can be applied to the surface of various base materials. Examples of the base material include metals such as iron and aluminum; inorganic base materials such as slate plates and PC plates; organic base materials such as plastics; Etc. These coated surfaces may be coated with a water-based or solvent-type paint.

  Examples of the coating method of the aqueous two-component coating composition of the present invention include air spray coating, airless spray coating, electrostatic coating, brush coating, roller coating, lysing gun, universal gun, dipping, roll coater, curtain flow coater, Examples thereof include a roller curtain coater and a die coater. The roller curtain coater and the die coater can be selected as appropriate according to the use of the base material and the like, and may be applied a plurality of times.

  As a dry film thickness, it is 1-500 micrometers, for example, Preferably it can be in the range of 10-100 micrometers.

  The paint of the present invention can form a clear coating film excellent in finish and polish even under forced drying conditions, but the drying method of the formed coating film is not particularly limited and is baked or dried at room temperature. Needless to say, drying may be performed.

  Here, baking drying, forced drying, and room temperature drying are not strictly distinguished, but for example, drying atmosphere temperature is 100 to 200 ° C., particularly 120 to 180 ° C., baking drying is 40 ° C. or more and less than 100 ° C. In particular, the condition of 50 ° C. to 90 ° C. can be forced drying, and the condition of less than 50 ° C., particularly 40 ° C. or less can be room temperature drying.

  Moreover, when using this coating material for repair coatings, such as a motor vehicle, the repair clear film formed may be grind | polished as needed after repair coating. As a polishing method, after the repair clear coating film is water-polished using water-resistant abrasive paper, the polishing surface can be polished sequentially with a compound for rough polishing and a compound for final polishing, thereby improving gloss. Thus, it is possible to obtain a repair clear coating film in which the difference in appearance from the unrepaired portion is not noticeable.

Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to only these examples. In the following examples, “part” and “%” mean “part by mass” and “% by mass”, respectively.
≪Manufacture of acrylic polyol aqueous dispersion≫
Production Example 1
50 parts of propylene glycol monopropyl ether was put into a glass four-necked flask equipped with a thermometer, a stirrer, a reflux condenser, and a nitrogen inlet, and the temperature was raised to 120 ° C. under a nitrogen stream while stirring. When the temperature reached 120 ° C., the following mixed solution 1 was added dropwise over 4 hours, and after completion of the addition, the temperature was maintained at 120 ° C. for 1 hour.
≪Mixed solution 1≫
5 parts of styrene,
13 parts of n-butyl methacrylate,
i-butyl methacrylate 31.5 parts,
2-ethylhexyl acrylate 5 parts,
10 parts of isobornyl acrylate,
20 parts of 2-hydroxyethyl methacrylate,
0.5 part of glycidyl methacrylate,
1.5 parts of t-butylperoxy-2-ethylhexanoate.
Subsequently, while the temperature of 120 ° C. was maintained, the following mixed solution 2 was added dropwise to the flask over 1 hour, and after completion of the addition, the mixture was maintained at 120 ° C. for 1.5 hours to obtain an acrylic polyol solution.
≪Mixed solution 2≫
6 parts i-butyl methacrylate,
6 parts 2-hydroxyethyl methacrylate,
3 parts acrylic acid,
0.3 parts of t-butylperoxy-2-ethylhexanoate.
The resin solid content of the obtained acrylic polyol solution was 77.5%, and the weight average molecular weight was 15000. Subsequently, propylene glycol monopropyl ether was distilled off from the obtained acrylic polyol solution under reduced pressure until the solid content became 85%. This was cooled to 95 ° C., 2.41 parts of dimethylethanolamine was added, and the mixture was stirred for 30 minutes. Further, deionized water was added dropwise over 2 hours with stirring so that the resin solid content was 45%, and the acid value per resin solid content was 21.4 mgKOH / g, and the hydroxyl value per resin solid content was 112 mgKOH / g. Acrylic polyol aqueous dispersion No1 having an average particle size of 0.12 μm was obtained.

Production Examples 2 to 14 and Production Examples 16 to 17
An acrylic polyol aqueous dispersion was obtained in the same manner as in Production Example 1 except that the contents and blending amounts in Production Example 1 were as shown in Table 1 below.

Production Example 15 of Acrylic Polyol Water Dispersion Obtained by One-Step Polymerization 15
50 parts of propylene glycol monopropyl ether was put into a glass four-necked flask equipped with a thermometer, a stirrer, a reflux condenser, and a nitrogen inlet, and the temperature was raised to 120 ° C. under a nitrogen stream while stirring. When the temperature reached 120 ° C., the following mixed solution was added dropwise over 4 hours, and after completion of the addition, the temperature was maintained at 120 ° C. for 1 hour.
≪Mixed solution≫
5 parts of styrene,
13 parts of n-butyl methacrylate,
37.5 parts of i-butyl methacrylate,
5.5 parts of 2-ethylhexyl acrylate,
10 parts of isobornyl acrylate,
26.0 parts 2-hydroxyethyl methacrylate,
3 parts acrylic acid,
1.8 parts of t-butylperoxy-2-ethylhexanoate,
Subsequently, a solution prepared by dissolving 0.5 part of t-butylperoxy-2-ethylhexanoate in 5 parts of propylene glycol monopropyl ether was dropped over 1 hour while maintaining the temperature of 120 ° C. Further, after completion of dropping, the mixture was kept at 120 ° C. for 1.5 hours to obtain an acrylic polyol solution. The obtained acrylic polyol had a resin solid content of 74.3 mass% and a weight average molecular weight of 20000.

  Subsequently, propylene glycol monopropyl ether was distilled off from the obtained acrylic polyol solution under reduced pressure until the solid content became 85%. This was cooled to 95 ° C., 2.41 parts of dimethylethanolamine was added, and the mixture was stirred for 30 minutes. Furthermore, 100 parts of deionized water was added dropwise over 2 hours with stirring to adjust the resin solid content to 45%, but it was extremely high viscosity and difficult to handle. When deionized water was further added, the resin solid content was 20%, the viscosity became 2000 cps, and it became possible to handle it as an aqueous dispersion.

(*) Storage stability test About each acrylic polyol aqueous dispersion obtained by the said manufacture example, the storage stability test was done according to the following test method.
Storage stability: 800 g of each aqueous dispersion was put in a glass bottle having a capacity of about 1 L, and stored in a constant temperature room at 40 ° C. for 120 days. Then, it returned to room temperature, the state in a container was observed visually, and the following reference | standard evaluated. The results are shown in Table 1.
A: No sedimentation or viscosity change is observed.
○: Sediment generation and viscosity change are slightly observed, but return to the original state by stirring.
Δ: Sediment generation or viscosity change is observed,
X: Significant generation of sediment and / or significant viscosity change is observed.

≪Manufacture of aqueous clear paint composition≫
Example 1
In the container, the acrylic polyol aqueous dispersion No. 1 obtained in Production Example 1 was used. 1 715 parts (solid content 322 parts), Bihijoule VPLS-2319 (trade name, manufactured by Sumika Bayer Urethane Co., Ltd., hexamethylene diisocyanate nonionic modified polyisocyanate compound, NCO content 18%) 225 parts, The mixture was stirred and mixed while adding deionized water to 35% to obtain an aqueous clear coating composition.

Examples 2 to 14 and Comparative Examples 1 to 3
In Example 1 above, an aqueous clear coating composition was obtained in the same manner as Example 1 except that the formulation was as shown in Table 2 below. In addition, emulsion No. having a solid content of 20%. For No. 15, no deionized water was added.

≪Preparation and evaluation of test plate≫
(* 1) Finishing property Each aqueous clear coating composition obtained above was spray-coated on a polypropylene plate so that the dry film thickness was 50 μm. Next, it was dried at 80 ° C. for 30 minutes using an electric hot air drier, and allowed to stand for 1 day to prepare a test coated plate. Then, the surface state was visually observed and evaluated according to the following criteria.
A: Level with very good smoothness,
○: Smooth and good level,
Δ: Slightly at least one of swell, gloss, and chili skin is seen, a slightly problematic level,
X: At least one of swell, gloss, and chili skin is remarkably problematic.
(* 2) “Letan WB Eco Base 411 Special Black” (trade name, water-based paint for repairing automobiles manufactured by Kansai Paint Co., Ltd.) is spray-coated on the abrasive electrodeposition plate to a dry film thickness of 15 μm, and obtained above. Each aqueous clear coating composition thus obtained was spray-coated at 20 ° C. so that the dry film thickness was 50 μm. Thereafter, the test plate was kept horizontally for 20 minutes, then dried at 80 ° C. for 30 minutes using an electric hot air dryer, and cooled to room temperature to prepare a test plate. Each test plate was water-polished using # 2000 water-resistant abrasive paper, and then polished for 60 seconds using a coarse polishing compound on a rough polishing buff, and the degree of removal of paper scratches by the water-resistant abrasive paper was visually evaluated. Further, the finishing buff was polished for 60 seconds using the finishing compound, the buffing scratches were removed, and the finished gloss was visually determined.
(2-1) How to remove paper scratches ◎: No vapor scratches,
○: There are almost no vapor scratches.
Δ: Some paper scratches remain
X: Vapor scratches remain remarkably.
(2-2) Finished gloss ◎: Gloss is very good.
○: Good gloss,
Δ: Gloss slightly decreased,
X: Gloss is greatly reduced.

Claims (8)

An aqueous two-component clear coating composition comprising an acrylic resin emulsion (I) and a polyisocyanate curing agent (II), wherein the acrylic resin emulsion (I) has different compositions in the presence of an organic solvent. An acrylic resin obtained by polymerizing an unsaturated monomer component in multiple stages is obtained by water dispersion, and the polymerizable unsaturated monomer component (A) used in at least one stage of polymerization is ,
Epoxy group-containing polymerizable unsaturated monomer (a1),
Methacrylate (a2) having an alkyl group having 3 to 4 carbon atoms,
The polymerizable unsaturated monomer component (B), which contains the hydroxyl group-containing polymerizable unsaturated monomer (a3) and the other polymerizable unsaturated monomer (a4) and is used in at least one other stage polymerization,
Carboxyl group-containing polymerizable unsaturated monomer (b1),
Comprising a hydroxyl group-containing polymerizable unsaturated monomer (b2) and another polymerizable unsaturated monomer (b3),
In the total polymerizable unsaturated monomer used for the production of the acrylic resin emulsion (I), the content of the methacrylate having an alkyl group having 3 to 4 carbon atoms is in the range of 20 to 65% by mass, and the methacryloyl group A water-based two-component clear coating composition characterized in that the content of the polymerizable unsaturated monomer having a water content is in the range of 30 to 90 mass%. The aqueous two-component clear according to claim 1, wherein the methacrylate (a2) having an alkyl group having 3 to 4 carbon atoms in the polymerizable unsaturated monomer component (A) contains n-butyl methacrylate and i-butyl methacrylate. Paint composition. The other polymerizable unsaturated monomer (a4) which is a copolymerization component of the polymerizable unsaturated monomer component (A) contains a polymerizable unsaturated monomer having an isobornyl group as a part of the component. The aqueous two-component clear coating composition as described. The other polymerizable unsaturated monomer (b3) contained in the polymerizable unsaturated monomer component (B) comprises a methacrylate having an alkyl group having 3 to 4 carbon atoms as a part of the component. The aqueous two-component clear coating composition according to any one of the above. The amount of the carboxyl group contained in the polymerizable unsaturated monomer component (B) with respect to 1 mol of the epoxy group contained in the polymerizable unsaturated monomer component (A) is in the range of 3 to 30 mol. 2. An aqueous two-component clear coating composition according to item 1. The aqueous two-component clear coating composition according to any one of claims 1 to 5, wherein the weight average molecular weight of the acrylic resin before water dispersion is in the range of 5,000 to 100,000. The acrylic resin emulsion (I) is a core-shell type acrylic emulsion having a copolymer of a polymerizable unsaturated monomer component (A) as a core and a copolymer of a polymerizable unsaturated monomer component (B) as a shell. The aqueous two-component clear coating composition according to any one of 1 to 6. The hydroxyl value per solid content of the acrylic resin emulsion (I) is in the range of 70 to 170 mgKOH / g, and the acid value per solid content is in the range of 5 to 50 mgKOH / g. An aqueous two-component clear coating composition.