CN113597454B

CN113597454B - Resin composition for aqueous coating material and coating film

Info

Publication number: CN113597454B
Application number: CN202080022181.1A
Authority: CN
Inventors: 大桥祐纪; 加贺悠太; 荒木阳介
Original assignee: Harima Chemical Inc
Current assignee: Harima Chemical Inc
Priority date: 2019-03-19
Filing date: 2020-03-18
Publication date: 2023-07-25
Anticipated expiration: 2040-03-18
Also published as: JPWO2020189714A1; MY196253A; SG11202109832PA; AU2020240710A1; JP7341222B2; CN113597454A; WO2020189714A1

Abstract

The present invention provides a resin composition for water paint capable of producing water paint, which can form a coating film with excellent initial gloss, initial water resistance and gloss retention. The resin composition for aqueous coating materials of the present invention contains a copolymer comprising a styrene monomer unit, an acrylic monomer unit and an unsaturated fatty acid salt unit and having a glass transition temperature of-4 to 40 ℃, and can produce an aqueous coating material capable of forming a coating film having excellent initial gloss, initial water resistance and gloss retention.

Description

Resin composition for aqueous coating material and coating film

Technical Field

The present invention relates to a resin composition for water-based paint and a coating film.

Background

Conventionally, solvent-based paint has been widely used for coating the surface of a building material such as an exterior packaging material for building construction. As the solvent-based resin used for the solvent-based paint, a styrene- (meth) acrylate copolymer having styrene and (meth) acrylate as main monomer units is generally used from the viewpoint of excellent initial gloss and initial water resistance.

On the other hand, in recent years, in the field of paints, in order to improve the burden on the use environment and the global environment caused by volatile organic compounds, the transfer from solvent-based paints containing organic solvents to aqueous paints containing aqueous solvents is rapidly proceeding. With the shift to aqueous paint, development of resins for aqueous paint has progressed, but the resins for aqueous paint have problems of insufficient initial gloss and insufficient initial water resistance compared with solvent resins such as styrene- (meth) acrylate copolymer.

Accordingly, patent document 1 discloses a resin composition for paint containing a resin emulsion obtained by emulsion-polymerizing a monomer component, wherein a plurality of emulsifiers are used in the emulsion-polymerizing of the monomer component.

Prior art literature

Patent literature

Patent document 1: japanese patent application laid-open No. 2017-125219

Disclosure of Invention

The invention aims to solve the technical problems

However, the coating film of the aqueous coating material produced using the resin composition for coating material still has a problem of insufficient initial gloss.

Further, there is a problem that the gloss of a coating film of an aqueous coating material prepared using the resin composition for coating material is lowered with time (initial water resistance is insufficient) due to adhesion of water or the like.

The invention provides a resin composition for an aqueous coating material, which can be used for preparing an aqueous coating material capable of forming a coating film with excellent initial gloss and initial water resistance.

Technical means for solving the technical problems

The resin composition for water-based paint of the present invention comprises: a copolymer comprising a styrene monomer unit, an acrylic monomer unit and an unsaturated fatty acid salt unit, and having a glass transition temperature of-4 to 40 ℃.

The coating film of the present invention is a cured product of a coating layer formed by applying the resin composition for an aqueous coating material to an object to be coated.

ADVANTAGEOUS EFFECTS OF INVENTION

The resin composition for water-based paint of the present invention can produce a water-based paint capable of forming a coating film having excellent initial gloss and initial water resistance.

Detailed description of the invention

The resin composition for aqueous coating comprises: a copolymer comprising styrenic monomer, acrylic monomer units, and unsaturated fatty acid salt units.

The styrene monomer constituting the copolymer is not particularly limited, and examples thereof include: styrene, α -methylstyrene, p-methylstyrene, t-butylstyrene, chlorostyrene, vinyltoluene, etc., are preferable from the viewpoint of initial gloss of a coating film formed from the resin composition for an aqueous coating material. The styrene monomer may be used alone or in combination of two or more.

The styrene monomer may have a functional group such as an alkyl group such as a methyl group or a tert-butyl group, a nitro group, a nitrile group, an alkoxy group, an acyl group, a sulfone group, a hydroxyl group, or a halogen atom on the benzene ring.

The content of the styrene monomer unit in the copolymer is preferably 5% by mass or more, more preferably 10% by mass or more, still more preferably 15% by mass or more, still more preferably 20% by mass or more, and particularly preferably 25% by mass or more, from the viewpoint of initial gloss of a coating film formed from the resin composition for an aqueous coating material. The content of the styrene monomer unit in the copolymer is preferably 50 mass% or less, more preferably 45 mass% or less, still more preferably 40 mass% or less, and particularly preferably 35 mass% or less, from the viewpoint of weather resistance of a coating film formed from the resin composition for an aqueous coating material.

The acrylic monomer constituting the copolymer is not particularly limited, and examples thereof include: alkyl (meth) acrylates such as methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, t-butyl (meth) acrylate, sec-butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, n-octyl (meth) acrylate, tridecyl (meth) acrylate, n-lauryl (meth) acrylate, dodecyl (meth) acrylate, stearyl (meth) acrylate, and the like; alicyclic (meth) acrylates such as cyclohexyl (meth) acrylate, isobornyl (meth) acrylate, dicyclopentenyl (meth) acrylate, dicyclopentenyloxyethyl (meth) acrylate, dicyclopentanyl (meth) acrylate, adamantyl (meth) acrylate, nitrogen-containing (meth) acrylic monomers such as (meth) acrylonitrile, (meth) acrylamide, diacetone (meth) acrylamide, acrylic acid, methacrylic acid, itaconic acid, crotonic acid, oleic acid, fumaric acid, citraconic acid, (anhydrous) maleic acid, and (anhydrous) citraconic acid.

The acrylic monomer is preferably an alkyl (meth) acrylate or (meth) acrylic acid, more preferably an alkyl (meth) acrylate or methacrylic acid, and particularly preferably an alkyl acrylate or an alkyl methacrylate or methacrylic acid. The acrylic monomer may be used alone or in combination of two or more. (meth) acrylate means acrylate or methacrylate. (meth) acrylic refers to acrylic or methacrylic.

The content of the acrylic monomer unit in the copolymer is preferably 30 mass% or more, more preferably 40 mass% or more, still more preferably 50 mass% or more, and particularly preferably 55 mass% or more, from the viewpoint of weather resistance of a coating film formed from the resin composition for an aqueous coating material. The content of the acrylic monomer unit in the copolymer is preferably 80% by mass or less, more preferably 75% by mass or less, and particularly preferably 70% by mass or less, from the viewpoint of initial gloss of a coating film formed from the resin composition for an aqueous coating material.

The number of carbon atoms in the alkyl group of the alkyl (meth) acrylate is preferably 1 or more, more preferably 2 or more, and particularly preferably 3 or more, from the viewpoint of initial gloss of a coating film formed from the resin composition for an aqueous coating material. The number of carbon atoms of the alkyl group of the alkyl (meth) acrylate is preferably 15 or less, more preferably 12 or less, and particularly preferably 10 or less from the viewpoint of the drying property of the aqueous coating material formed from the resin composition for an aqueous coating material.

The alkyl (meth) acrylate preferably contains methyl (meth) acrylate, isobutyl (meth) acrylate, 2-ethylhexyl (meth) acrylate and n-butyl (meth) acrylate, more preferably contains methyl methacrylate, isobutyl methacrylate, 2-ethylhexyl acrylate and n-butyl acrylate.

The content of the alkyl (meth) acrylate unit in the copolymer is preferably 30% by mass or more, more preferably 40% by mass or more, still more preferably 50% by mass or more, and particularly preferably 55% by mass or more, from the viewpoint of weather resistance of a coating film formed from the resin composition for an aqueous coating material. The content of the alkyl (meth) acrylate unit in the copolymer is preferably 80% by mass or less, more preferably 75% by mass or less, and particularly preferably 70% by mass or less, from the viewpoint of initial gloss of a coating film formed from the resin composition for an aqueous coating material.

The content of the (meth) acrylic acid unit in the copolymer is preferably 0.01 mass% or more, more preferably 0.05 mass% or more, and particularly preferably 0.1 mass% or more from the viewpoint of stability of emulsion particles in the aqueous coating material. The content of the (meth) acrylic acid unit in the copolymer is preferably 4% by mass or less, more preferably 3% by mass or less, still more preferably 2% by mass or less, and particularly preferably 1% by mass or less, from the viewpoint of initial water resistance of a coating film formed from the resin composition for an aqueous coating material.

The content of the methacrylic acid unit in the copolymer is preferably 0.01 mass% or more, more preferably 0.05 mass% or more, and particularly preferably 0.1 mass% or more, from the viewpoint of stability of emulsion particles in the aqueous coating material. The content of the methacrylic acid unit in the copolymer is preferably 4% by mass or less, more preferably 3% by mass or less, still more preferably 2% by mass or less, and particularly preferably 1% by mass or less, from the viewpoint of initial water resistance of a coating film formed from the resin composition for an aqueous coating material.

The unsaturated fatty acid salts constituting the copolymer are reactive emulsifiers. The reactive emulsifier has an emulsifying effect. The unsaturated fatty acid salt is a salt of monocarboxylic acid represented by RCOOH, and the substituent represented by R contains at least one unsaturated bond. In the case of unsaturated fatty acid salts, they are incorporated into the polymeric chains of the copolymer by free radical polymerization at the unsaturated bond. The unsaturated fatty acid salts may be used alone or in combination of two or more.

Since the copolymer contains unsaturated fatty acid salt units, the copolymer has a hydrophobic portion and a hydrophilic portion. The copolymer can be dispersed in an aqueous medium by adopting a micelle structure in which a hydrophobic portion is located on the inner side and a hydrophilic portion is located on the outer side, and can constitute an aqueous coating material. The aqueous medium is not particularly limited, and examples thereof include: water, alcohol solvents (e.g., methanol, ethanol, propanol, isopropanol, butanol, etc.), glycol ether solvents (e.g., ethylene glycol monoethyl ether, propylene glycol monomethyl ether, diethylene glycol butyl ether, etc.), etc., preferably water.

Unsaturated fatty acid salts contain an unsaturated bond in the substituent R. The substituent R takes a structure bent at an unsaturated bond portion. The substituent R is bent to change the hydrophobic portion of the copolymer into a state where it is suitably contained in the micelle while being bent, thereby improving the dispersibility of the copolymer in an aqueous medium.

The unsaturated bond in the substituent R is not particularly limited, but is preferably an ethylenically unsaturated bond such as an ethylenically unsaturated double bond (carbon-carbon double bond) and an ethylenically unsaturated triple bond (carbon-carbon triple bond), and more preferably an ethylenically unsaturated double bond. The ethylenically unsaturated double bond has a cis double bond and a trans double bond, and is preferably a cis double bond because the hydrophobic moiety in the copolymer can be contained in the micelle properly while being entrapped therein.

The number of unsaturated bonds in the substituent R is preferably 1 to 6, more preferably 1 to 5, particularly preferably 1 to 4. When the number of carbon atoms of the substituent R is 11 or more, it is preferable that the number of carbon atoms is counted from the carbon at the end of the substituent R (the end of the longest chain in the substituent R), and an unsaturated bond is formed between the 3 rd and subsequent carbons, more preferably from the carbon at the end of the substituent R, and an unsaturated bond is formed between the 5 th and subsequent carbons, particularly preferably from the carbon at the end of the substituent R, and an unsaturated bond is formed between the 6 th and subsequent carbons.

The number of carbon atoms of the unsaturated fatty acid salt (the number of all carbon atoms of the unsaturated fatty acid salt) is preferably 4 or more, more preferably 12 or more, and particularly preferably 16 or more from the viewpoint of stability of emulsion particles in the aqueous coating material. The number of carbon atoms of the unsaturated fatty acid salt (the number of all carbon atoms of the unsaturated fatty acid salt) is preferably 30 or less, more preferably 28 or less, particularly preferably 26 or less, from the viewpoint of water solubility of the unsaturated fatty acid salt.

The unsaturated fatty acid (IUPAC name) as a raw material of the unsaturated fatty acid salt is not particularly limited, and examples thereof include: butenoic acid (C4), pentenoic acid (C5), hexenoic acid (C6), heptenoic acid (C7), octenoic acid (C8), nonenoic acid (C9), decenoic acid (C10), undecenoic acid (C11), dodecenoic acid (C12), tridecenoic acid (C13), tetradecenoic acid (C14), pentadecenoic acid (C15), hexadecenoic acid (C16), heptadecenoic acid (C17), octadecenoic acid (C18), nonadecenoic acid (C19), eicosenoic acid (C20), heneicosenoic acid (C21), docosenoic acid (C22), tricosenoic acid (C23), tetracosenoic acid (C24), pentacosenoic acid (C25), hexacosenoic acid (C26), heptacosenoic acid (C27), octacosenoic acid (C28), nonacosenoic acid (C29), triacontenoic acid (C30), and the like, preferably containing octadecenoic acid. In addition, the number of carbon atoms included in the unsaturated fatty acid is the whole number in brackets.

Specific examples (conventional names) of unsaturated fatty acids as raw materials of unsaturated fatty acid salts include, for example: myristoleic acid (C14, 1, B5), palmitoleic acid (C16, 1, B7), linoleic acid (C18, 4, B3, 6, 9, 12), iso-oleic acid (C18, 1, B7), oleic acid (C18, 1, B9), elaidic acid (C18, 1, B9), linoleic acid (C18, 2, B6, 9), alpha-linolenic acid (C18, 3, B3, 6, 9), gamma-linolenic acid (C18, 3, B6, 9, 12), cod liver oleic acid (C20, 1, B11), arachic acid (C20, 1, b11), eicosadienoic acid (C20, 2, B6, 9), arachidonic acid (C20, 3, B6, 9, 12), eicosapentaenoic acid (C20, 5, B3, 6, 9, 12, 15), erucic acid (C22, 1, B9), docosahexaenoic acid (C22, 6, B3, 6, 9, 12, 15, 18), nervonic acid (C24, 1, B9), and the like, preferably contain palmitoleic acid, oleic acid, and linoleic acid, more preferably contain oleic acid and linoleic acid, and particularly preferably contain oleic acid. Note that the symbols in brackets represent in order: the total number of carbon atoms, the number of ethylenically unsaturated double bonds, and the position of the ethylenically unsaturated double bonds. Bn, m, & p represents an ethylenically unsaturated double bond between the carbon and carbon of the nth and (n+1) th, mth and (m+1) th, and p and (p+1) th, counted from the end of the substituent R.

The unsaturated fatty acid salts may be used alone, as described above, two or more kinds may be used in combination, or salts of animal and vegetable oil fatty acids containing a plurality of unsaturated fatty acids may be used.

Examples of the fatty acid salts of animal and vegetable oils include: soybean oil fatty acid salt, cottonseed oil fatty acid salt, tall oil fatty acid salt (salt of a mixture of palmitic acid, stearic acid, oleic acid and linoleic acid), corn oil fatty acid salt, rice bran oil fatty acid salt, safflower oil fatty acid salt, sunflower oil fatty acid salt, linseed oil fatty acid salt, fish oil fatty acid salt, dehydrated castor oil fatty acid salt, palm oil fatty acid salt, tallow fatty acid salt, rapeseed oil fatty acid salt, olive oil fatty acid salt and the like, preferably tall oil fatty acid salt.

The unsaturated fatty acid salt may also be a derivative thereof. The derivative of the unsaturated fatty acid salt is not particularly limited, and examples thereof include: polymeric fatty acid salts, salts of unsaturated carboxylic acid adducts, salts of epoxidized unsaturated fatty acids, salts of hydroxylated unsaturated fatty acids, salts of epoxidized and hydroxylated unsaturated fatty acids, salts of sulphonylated unsaturated fatty acids, and the like, are preferred polymeric fatty acid salts, more preferred dimeric and trimeric acid salts, and particularly preferred dimeric acid salts. The derivative of the unsaturated fatty acid salt needs to have an unsaturated bond in the molecule.

The polymerized fatty acid salt is a salt of a compound obtained by polymerizing an unsaturated fatty acid salt in the presence of a catalyst such as clay, for example: dimer acid salts (salts of dimers of unsaturated fatty acids), trimer acids (salts of trimers of unsaturated fatty acids), and tetramer acids (salts of tetramers of unsaturated fatty acids), and the like, preferably dimer acid salts, trimer acid salts, preferably including dimer acid salts and trimer acid salts. The polymerized fatty acid salt may be used alone or in combination of two or more.

The polymerized fatty acid salt may be partially hydrogenated but needs to leave unsaturated bonds.

Examples of the salt of the unsaturated carboxylic acid adduct include a salt of a compound obtained by an addition reaction of an α, β -unsaturated carboxylic acid with an unsaturated bond of the unsaturated fatty acid. Specifically, for example, there may be mentioned: salts of an adduct of maleic acid or an anhydride thereof with an unsaturated fatty acid, salts of an acrylic acid adduct with an unsaturated fatty acid, and the like. The salt of the unsaturated carboxylic acid adduct needs to leave an unsaturated bond.

The salt of the epoxidized unsaturated fatty acid is, for example, a salt of a compound obtained by epoxidizing an unsaturated bond of an unsaturated fatty acid with peracetic acid, hydrogen peroxide or the like. The salt of the hydroxylated unsaturated fatty acid is a salt obtained by hydrolyzing a salt of an epoxidized unsaturated fatty acid to introduce 2 hydroxyl groups. The salt of the sulfonized unsaturated fatty acid is a salt of a compound obtained by performing a sulfonization reaction of an unsaturated bond of the unsaturated fatty acid with sulfuric acid or the like. Salts of epoxidized unsaturated fatty acids, salts of hydroxylated unsaturated fatty acids, and salts of sulphonylated unsaturated fatty acids need to leave unsaturated bonds.

The content of the unsaturated fatty acid salt unit in the copolymer is preferably 0.5 mass% or more, more preferably 0.7 mass% or more, and particularly preferably 1.0 mass% or more from the viewpoint of stability of emulsion particles in the aqueous coating material. The content of the unsaturated fatty acid salt unit in the copolymer is preferably 5.0 mass% or less, more preferably 4.5 mass% or less, from the viewpoint of initial water resistance of a coating film formed from the resin composition for an aqueous coating material.

The content of the dimer acid salt in the polymerized fatty acid salt is preferably 5% by mass or more, more preferably 15% by mass or more, more preferably 40% by mass or more, more preferably 60% by mass or more, more preferably 70% by mass or more, and particularly preferably 80% by mass or more, from the viewpoint of initial water resistance of a coating film formed from the resin composition for an aqueous coating material.

The content of the dimer acid salt in the polymerized fatty acid salt is preferably 99 mass% or less, more preferably 97 mass% or less, still more preferably 95 mass% or less, and particularly preferably 87 mass% or less, from the viewpoint of initial gloss of a coating film formed from the resin composition for an aqueous coating material.

The content of the trimer acid salt in the polymerized fatty acid salt is preferably 1% by mass or more, more preferably 3% by mass or more, more preferably 5% by mass or more, more preferably 7% by mass or more, more preferably 10% by mass or more, and particularly preferably 13% by mass or more, from the viewpoint of initial water resistance of a coating film formed from the resin composition for an aqueous coating material.

The content of the trimer acid salt in the polymerized fatty acid salt is preferably 95% by mass or less, more preferably 85% by mass or less, still more preferably 40% by mass or less, still more preferably 30% by mass or less, and particularly preferably 20% by mass or less, from the viewpoint of the initial gloss of a coating film formed from the resin composition for an aqueous coating material.

The unsaturated fatty acid salt preferably contains a monomeric unsaturated fatty acid salt (monomeric acid salt), a dimeric acid salt, and a trimeric acid salt. The monomeric unsaturated fatty acid salt (monomeric acid salt) refers to an unsaturated fatty acid salt that does not polymerize.

When the unsaturated fatty acid salt contains the monomeric acid salt, the dimeric acid salt and the trimeric acid salt, the content of the monomeric acid salt in the unsaturated fatty acid salt is preferably 0.5 mass% or more, more preferably 1 mass% or more, still more preferably 2 mass% or more, and particularly preferably 3 mass% or more, from the viewpoint of the initial gloss of a coating film formed from the aqueous coating resin composition. The content of the monomeric acid salt in the unsaturated fatty acid salt is preferably 10 mass% or less, more preferably 8 mass% or less, still more preferably 6 mass% or less, and particularly preferably 5 mass% or less, from the viewpoint of initial water resistance of a coating film formed from the resin composition for an aqueous coating material.

When the unsaturated fatty acid salt contains a monomeric acid salt, a dimeric acid salt and a trimeric acid salt, the content of the dimeric acid salt in the unsaturated fatty acid salt is preferably 10% by mass or more, more preferably 20% by mass or more, still more preferably 50% by mass or more, and particularly preferably 70% by mass or more, from the viewpoint of the initial water resistance of a coating film formed from the aqueous coating resin composition. The content of the dimer acid salt in the unsaturated fatty acid salt is preferably 95% by mass or less, more preferably 90% by mass or less, and particularly preferably 85% by mass or less, from the viewpoint of initial gloss of a coating film formed from the resin composition for an aqueous coating material.

When the unsaturated fatty acid salt contains a monomeric acid salt, a dimeric acid salt and a trimeric acid salt, the content of the trimeric acid salt in the unsaturated fatty acid salt is preferably 0.5% by mass or more, more preferably 1% by mass or more, still more preferably 10% by mass or more, and particularly preferably 70% by mass or more, from the viewpoint of the initial water resistance of a coating film formed from the aqueous coating resin composition. The content of the trimer acid salt in the unsaturated fatty acid salt is preferably 90 mass% or less, more preferably 85 mass% or less, and particularly preferably 80 mass% or less, from the viewpoint of initial gloss of a coating film formed from the resin composition for an aqueous coating material.

The copolymer may contain a reactive emulsifier other than the unsaturated fatty acid salt as a monomer unit. Reactive emulsifiers other than unsaturated fatty acid salts have emulsifying action. Reactive emulsifiers other than unsaturated fatty acid salts have at least 1 unsaturated bond in the molecule and are incorporated into the copolymer by radical polymerization at the unsaturated bond.

The unsaturated bond is not particularly limited, but is preferably an ethylenically unsaturated bond such as an ethylenically unsaturated double bond (carbon-carbon double bond, c=c) or an ethylenically unsaturated triple bond (carbon-carbon triple bond), and more preferably an ethylenically unsaturated double bond. There may be a plurality of unsaturated bonds in the molecule.

The ethylenically unsaturated double bond is, for example, an unsaturated bond contained in a functional group such as an alkenyl group, a (meth) allyloxyalkyl group, or a (meth) acryloyl group. The term (meth) allyl refers to an allyl group or a methallyl group. (meth) acryl means acryl or methacryl.

Examples of the alkenyl group include: vinyl, (meth) allyl, 1-propenyl, 2-methyl-1-propenyl, isopropenyl, and the like.

The reactive emulsifier other than the unsaturated fatty acid salt is not particularly limited, and examples thereof include: a sulfate salt of a polyoxyalkylene phenyl ether having at least 1 functional group containing an ethylenically unsaturated double bond in a molecule, a sulfate salt of a polyoxyethylene alkyl ether having at least 1 functional group containing an ethylenically unsaturated double bond in a molecule (ester sodium salt, ester ammonium salt, etc.), a sulfate salt of a polyoxyethylene alkylphenyl ether having at least 1 functional group containing an ethylenically unsaturated double bond in a molecule (ester sodium salt, ester ammonium salt, etc.), a sulfate salt of a polyoxyalkylene alkyl ether having at least 1 functional group containing an ethylenically unsaturated double bond in a molecule (ester sodium salt, ester ammonium salt, etc.), a sulfate salt of a polyoxyalkylene alkylphenyl ether having at least 1 functional group containing an ethylenically unsaturated double bond in a molecule (ester sodium salt, ester ammonium salt, etc.), a acid phosphate dispersant having at least 1 functional group containing an ethylenically unsaturated double bond in a molecule (meth) and the like. The reactive emulsifier other than the unsaturated fatty acid salt may be used alone or two or more of them may be used in combination.

Reactive emulsifiers other than unsaturated fatty acid salts preferably have ethylenically unsaturated double bonds near the molecular terminals. The term "near the molecular end" refers to a carbon-carbon bond portion formed by the terminal carbon and the 2 nd and 3 rd carbons from the terminal carbon (1 st) in a molecular chain formed by bonding carbon atoms. Reactive emulsifiers other than unsaturated fatty acid salts preferably have an ethylenically unsaturated double bond between the terminal carbon (carbon 1) and the carbon bonded to the terminal carbon (carbon 2). Reactive emulsifiers other than unsaturated fatty acid salts preferably have an ethylenically unsaturated double bond between carbon 2 and carbon 3, counting from the terminal carbon.

The reactive emulsifier other than the unsaturated fatty acid salt is preferably a sulfate salt of a polyoxyalkylene phenyl ether having at least 1 functional group containing an ethylenically unsaturated double bond in the molecule, more preferably a sulfate ammonium salt of a polyoxyalkylene phenyl ether having at least 1 functional group containing an ethylenically unsaturated double bond in the molecule, still more preferably a sulfate ammonium salt of a polyoxyethylene phenyl ether having at least 1 functional group containing an ethylenically unsaturated double bond in the molecule.

The sulfate salt of a polyoxyalkylene phenyl ether having at least 1 functional group containing an ethylenically unsaturated double bond in the molecule is preferably an ammonium polyoxyethylene styrenated propenylphenyl ether sulfate salt, a sodium polyoxyethylene styrenated propenylphenyl ether sulfate salt, an ammonium polyoxyethylene propenylphenyl ether sulfate salt, a sodium polyoxyethylene propenylphenyl ether sulfate salt, more preferably an ammonium polyoxyethylene styrenated propenylphenyl ether sulfate salt and a sodium polyoxyethylene styrenated propenylphenyl ether sulfate salt.

Examples of the reactive emulsifier other than the unsaturated fatty acid salt include: anhydride-modified rosin glycidyl acrylate (JP-A-4-256429), a dispersant described in JP-A-63-23725, a dispersant described in JP-A-63-240931, a dispersant described in JP-A-62-104802, and the like.

The reactive emulsifier can be obtained as a commercially available product. Examples of such commercial products include: KAYAMER PM-1 (manufactured by Nippon chemical Co., ltd.), KAYAMER PM-2 (manufactured by Nippon chemical Co., ltd.), KAYA MER PM-21 (manufactured by Nippon chemical Co., ltd.), SE-10N (manufactured by Asahi chemical Co., ltd.), NE-10 (manufactured by Asahi chemical Co., ltd.), NE-20 (manufactured by Asahi chemical Co., ltd.), NE-30 (manufactured by Asahi chemical Co., ltd.), NEW FRONTIER A229E (manufactured by first industrial Co., ltd.), NEW FRONTIER N-117E (manufactured by first industrial Co., ltd.), NEW FRONT IER N250Z (manufactured by first industrial Co., ltd.), akuaron RN-20 (manufactured by first industrial Co., ltd.), akuaron RN-2025 (manufactured by first industrial Co., ltd.), akuaron BC-1025 (manufactured by first industrial Co., ltd.), akuaron AR-1025 (manufactured by first industrial Co., ltd.), akuaron HS-10 (manufactured by first industrial Co., ltd.), akuron KH-1025 (manufactured by first industrial Co., ltd.), akuaron KH-5 (manufactured by first industrial Co., ltd.), elsho-5 (manufactured by first industrial Co., ltd.), akuwana Tsuk-180, etc., ladie (manufactured by Ladie Kapro). The reactive emulsifier is preferably akuaron AR-1025 (manufactured by first industry pharmaceutical).

The content of the monomer unit derived from the reactive emulsifier other than the unsaturated fatty acid salt in the emulsifier component of the copolymer is preferably 0 to 70% by mass, more preferably 0 to 50% by mass, and particularly preferably 0 to 30% by mass, from the viewpoint of improving the initial water resistance of the coating film formed from the aqueous coating resin composition. "0% by mass" means that the copolymer does not contain a monomer unit derived from a reactive emulsifier other than an unsaturated fatty acid salt.

When the copolymer contains, as monomer units, a reactive emulsifier containing an unsaturated fatty acid salt and a compound other than the unsaturated fatty acid salt, the content of all monomer units derived from the reactive emulsifier in the copolymer is preferably 0.5 mass% or more from the viewpoint of stability of emulsion particles in the aqueous coating material. When the copolymer contains, as monomer units, a reactive emulsifier containing an unsaturated fatty acid salt and a compound other than the unsaturated fatty acid salt, the copolymer is preferably 4% by mass or less, more preferably 2% by mass or less, and still more preferably 1% by mass or less, from the viewpoint of initial water resistance of a coating film formed from the aqueous coating resin composition.

When the copolymer contains, as a monomer unit, a reactive emulsifier containing an unsaturated fatty acid salt and a compound other than the unsaturated fatty acid salt, the ratio of the total amount of the compound other than the unsaturated fatty acid salt to the total amount of the unsaturated fatty acid salt (total amount of the compound other than the unsaturated fatty acid salt/unsaturated fatty acid salt) in the reactive emulsifier is preferably 0.2 or more. In the reactive emulsifier, the ratio of the total amount of the compounds other than the unsaturated fatty acid salts to the total amount of the unsaturated fatty acid salts (total amount of the compounds other than the unsaturated fatty acid salts/unsaturated fatty acid salts) is preferably 3 or less, more preferably 2 or less, still more preferably 1.5 or less, and still more preferably 0.5 or less. The ratio of the total amount of the compounds other than the unsaturated fatty acid salt to the total amount of the unsaturated fatty acid salt is preferably 0.2 or more, since the stability of emulsion particles in the aqueous coating material is improved. When the ratio of the total amount of the compounds other than the unsaturated fatty acid salt to the total amount of the unsaturated fatty acid salt is 3 or less, the initial gloss and the initial water resistance of a coating film formed from the resin composition for an aqueous coating material are improved, and therefore, it is preferable.

The copolymer may contain fatty acid modified monomer units. The fatty acid-modified monomer is a compound obtained by reacting a drying oil fatty acid and/or a semi-drying oil fatty acid with an epoxy group-containing polymerizable unsaturated monomer by a known method. It is to be noted that unsaturated fatty acids (unpolymerized unsaturated fatty acids) may be used instead of or in combination with the drying oil fatty acids and/or the semi-drying oil fatty acids. The unsaturated fatty acid may be used alone or in combination of two or more.

The content of the fatty acid-modified monomer unit in the copolymer is preferably 1% by mass or more, more preferably 2% by mass or more, and particularly preferably 3% by mass or more, from the viewpoint of improving the initial water resistance of a coating film formed from the resin composition for an aqueous coating material. The content of the fatty acid-modified monomer unit in the copolymer is preferably 10 mass% or less, more preferably 8 mass% or less, and particularly preferably 6 mass% or less, from the viewpoint of stability of emulsion particles in the aqueous coating material.

The drying oil fatty acid and the semi-drying oil fatty acid are fatty acids having an oxidatively curable polymerizable unsaturated group. Examples of the drying oil fatty acid and the semi-drying oil fatty acid include: fish oil fatty acid, dehydrated castor oil fatty acid, safflower oil fatty acid, linseed oil fatty acid, soybean oil fatty acid, sesame oil fatty acid, poppy oil fatty acid, perilla oil fatty acid, sesame oil fatty acid, grape seed oil fatty acid, corn oil fatty acid, tall oil fatty acid, sunflower oil fatty acid, cottonseed oil fatty acid, walnut oil fatty acid, rubber seed oil fatty acid, and the like, preferably tall oil fatty acid.

The drying oil fatty acid and/or semi-drying oil fatty acid may be, for example, non-drying oil fatty acids such as coconut oil fatty acid, hydrogenated coconut oil fatty acid, palm oil fatty acid, etc., as required; caproic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, and the like.

Examples of the polymerizable unsaturated monomer containing an epoxy group include: glycidyl (meth) acrylate, β -methyl glycidyl (meth) acrylate, 3, 4-epoxycyclohexylmethyl (meth) acrylate, 3, 4-epoxycyclohexylpropyl (meth) acrylate, allyl glycidyl ether, and the like, preferably glycidyl (meth) acrylate, more preferably glycidyl methacrylate.

The salt of the unsaturated fatty acid salt is not particularly limited, and examples thereof include: alkali metal salts of sodium, potassium, lithium, etc.; alkaline earth metal salts such as calcium and barium; alkanolamines such as monoethanolamine, diethanolamine and triethanolamine, and organic amine salts such as triethylamine; ammonium salts and the like are preferably alkali metal salts and alkaline earth metal salts, more preferably alkali metal salts, still more preferably sodium salts and potassium salts, and particularly preferably potassium salts.

The glass transition temperature Tg of the copolymer constituting the resin composition for aqueous coating is preferably-4 ℃ or higher, more preferably 1 ℃ or higher, and particularly preferably 6 ℃ or higher, from the viewpoint of improving the initial water resistance and gloss retention of a coating film formed from the resin composition for aqueous coating. The glass transition temperature Tg of the copolymer constituting the resin composition for aqueous coating is preferably 40 ℃ or less, more preferably 35 ℃ or less, more preferably 25 ℃ or less, more preferably 23 ℃ or less, and particularly preferably 19 ℃ or less, from the viewpoint of improving the initial gloss of a coating film formed from the resin composition for aqueous coating.

The glass transition temperature (Tg) of the copolymer was measured by a Differential Scanning Calorimeter (DSC) apparatus according to JIS K7121-1987.

The method for producing the copolymer constituting the resin composition for aqueous coating is not particularly limited, and examples thereof include: (1) A method for producing a copolymer by emulsion-polymerizing a monomer composition containing a styrene monomer, an acrylic monomer, and an unsaturated fatty acid salt as a reactive emulsifier in an aqueous medium in the presence of a widely used radical polymerization initiator; (2) A method for producing a copolymer by radical polymerization of a monomer composition containing a styrene monomer, an acrylic monomer and an unsaturated fatty acid salt in an organic solvent (for example, xylene, toluene, methyl isobutyl ketone, etc.) in the presence of a widely used radical polymerization initiator, is preferable from the viewpoint of the amount of the remaining solvent. When the copolymer is produced by the production method of (2), the copolymer thus obtained may be separated, and if necessary, the separated copolymer may be dispersed in an aqueous medium using a dispersing machine having a high energy shearing ability. Examples of the radical polymerization initiator include azo compounds, peroxide compounds, sulfide compounds, sulfoxide compounds, and diazo compounds.

The resin composition for an aqueous coating material may be dispersed in an aqueous medium to produce an aqueous coating material. The content of the copolymer (content of solid content) constituting the resin composition for an aqueous coating material in the aqueous coating material is preferably 10 to 90% by mass, more preferably 15 to 80% by mass, and particularly preferably 20 to 60% by mass.

In addition, the copolymer constituting the resin composition for an aqueous coating material can form an aqueous coating material which is well dispersed in an aqueous medium and is slightly homogeneous because the copolymer contains an unsaturated fatty acid salt as a reactive emulsifier as a monomer unit. Further, when the resin composition for an aqueous coating material is dispersed in an aqueous medium, an emulsifier may not be used, or the amount of the emulsifier used may be suppressed.

The aqueous coating material may contain, for example, a non-reactive emulsifier, a pigment, a film-forming auxiliary agent, an antifoaming agent, a thickener, a preservative, a mold inhibitor, a pH adjuster, a metal drier, and other widely used additives, as required.

Examples of the non-reactive emulsifier include anionic emulsifiers, cationic emulsifiers, nonionic emulsifiers, and the like, and anionic emulsifiers are preferable. The non-reactive emulsifier may be used alone or in combination of two or more.

Examples of the anionic emulsifier include: sodium lauryl sulfate, ammonium lauryl sulfate, sodium dodecylbenzenesulfonate, sodium polyoxyethylene alkyl ether sulfate, sodium polyoxyethylene alkylphenyl ether sulfate, ammonium polyoxyethylene alkylphenyl ether sulfate, sodium polyoxyethylene alkylsulfonyl succinate, polyoxyalkylene polycyclic phenyl ether sulfate salts (e.g., sodium polyoxyethylene polycyclic phenyl ether sulfate, ammonium polyoxyethylene polycyclic phenyl ether sulfate, sodium polyoxypropylene polycyclic phenyl ether sulfate, ammonium polyoxypropylene polycyclic phenyl ether sulfate, etc.), and the like. The anionic emulsifier is preferably a polyoxyalkylene polycyclic phenyl ether sulfate, preferably a polyoxyethylene polycyclic phenyl ether sulfate, more preferably an ammonium polyoxyethylene polycyclic phenyl ether sulfate.

Examples of the cationic emulsifier include: alkyl trimethyl ammonium chloride, and the like.

Examples of the nonionic emulsifier include: polyoxyethylene alkyl ether, polyoxyethylene alkyl phenyl ether, polyoxyethylene fatty acid ester, polyoxyethylene polyoxypropylene block polymer, and the like. They may be used singly or in combination of 2 or more.

The content of the non-reactive emulsifier in the aqueous coating material is preferably 0 to 5 parts by mass, more preferably 0 to 3 parts by mass, and still more preferably 0 to 2 parts by mass, relative to 100 parts by mass of the copolymer. "0 parts by mass" means that the water-based paint does not contain a non-reactive emulsifier.

The surface of an object to be coated (for example, a building material such as an exterior packaging material used for building construction) is coated with the aqueous coating material obtained, and the aqueous coating material may be applied to the surface of the object to be coated to form a coating layer, and the aqueous medium in the coating layer is evaporated and removed to be cured to form a coating film, and the surface of the object to be coated is coated with the coating film.

Here, as described above, the copolymer constituting the resin composition for an aqueous coating material contains an unsaturated fatty acid salt unit as a reactive emulsifier as a monomer unit in a molecule. The unsaturated fatty acid salt is bonded to the copolymer by copolymerization because it has an unsaturated bond in the molecule, and further, because it has an aliphatic group, elution of a coating film component can be prevented even when a coating film formed from the resin composition for an aqueous coating material is exposed to water. Therefore, in a coating film formed of the aqueous coating material, unsaturated fatty acid salt units constituting the copolymer do not flow out from the surface of the coating film without being released from the copolymer.

Further, when the aqueous coating composition is dispersed in an aqueous medium to prepare an aqueous coating, it is possible to dispense with the use of an emulsifier or reduce the amount of the emulsifier used, as described above.

Therefore, the amount of free emulsifier in the coating film formed from the aqueous coating material is extremely small, and voids caused by the outflow of the emulsifier formed on the surface of the coating film are reduced or suppressed in the middle of the formation of the coating film or in a state of being exposed to water after the formation of the coating film.

Therefore, penetration of moisture into the interior of the coating film through voids on the surface of the coating film is reduced or suppressed, and the coating film has excellent initial water resistance. Further, the unsaturated fatty acid salt unit in the copolymer can improve leveling property at the time of forming a coating film, and the initial gloss of the coating film is also excellent.

Examples

[ Synthesis of fatty acid-modified monomer ]

The following compounds were supplied to a reaction vessel, and reacted at 160℃while stirring in the reaction vessel, to effect an addition reaction of tall oil fatty acid and glycidyl methacrylate for about 90 minutes, to obtain a fatty acid-modified monomer. After the completion of the reaction, 0.08 parts by mass of hydroquinone was supplied into the reaction vessel. The tall oil fatty acid contained 2 mass% of palmitic acid and 2 mass% of stearic acid as saturated fatty acids, and 46 mass% of oleic acid and 41 mass% of linoleic acid as unsaturated fatty acids. The addition reaction of the epoxy group of glycidyl methacrylate and the carboxyl group of tall oil fatty acid was monitored by measuring the amount of the remaining acid component.

Tall oil fatty acid: 260.00 parts by mass

Glycidyl methacrylate: 136.00 parts by mass

4-methoxyphenol (p-hydroxynisol): 0.70 part by mass

Tetrabutylphosphonium bromide: 0.40 part by mass

Triphenylphosphine: 0.40 part by mass

[ emulsifier ]

(Synthesis of unsaturated fatty acid salt 1)

Distilled water 344.92 parts by mass and a 48% by mass aqueous potassium hydroxide solution 44.73 parts by mass were supplied into the reaction vessel, and the mixture was kept at 95℃for about 1 hour while stirring. Next, 110.35 parts by mass of an unsaturated fatty acid shown below was supplied into the reaction vessel, and the reaction was carried out while stirring at 95 ℃ for 3 hours, whereby a potassium salt (reactive emulsifier) of an unsaturated fatty acid having a solid content concentration of 25% by mass was obtained. In table 1, the potassium salts of the obtained unsaturated fatty acids are represented by adding "K salts" to the end of the trade name of the reactive emulsifier as a raw material. Hereinafter, the "potassium salt" is denoted as "K salt".

Unsaturated fatty acid 1: trade name "Haridimer 200 (DA-200)" manufactured by Harima chemical Co., ltd "

Unsaturated fatty acid 2: trade name "Tsunodyme 395" manufactured by Soy food industry Co., ltd "

Unsaturated fatty acid 3: trade name "Tsunodyme 228" manufactured by Confucius of Constipation food industry "

(Synthesis of unsaturated fatty acid salt 2)

The unsaturated fatty acid in tall oil fatty acid and maleic anhydride are subjected to an addition reaction to obtain an adduct. The adduct was prepared as a potassium salt by the method of synthesis 1 of an unsaturated fatty acid salt, to give a potassium salt of an unsaturated fatty acid (BK-73B K salt, potassium salt of oleic acid) having a solid content concentration of 25% by mass (reactive emulsifier).

Tall oil fatty acid contains 2 mass% of palmitic acid and 2 mass% of stearic acid as saturated fatty acids, and oleic acid 46 mass% and 41 mass% of linoleic acid as unsaturated fatty acids.

(Synthesis of unsaturated fatty acid salt 3)

A reaction product obtained by reacting an unsaturated fatty acid (trade name "Haridimer 200 (DA-200)", manufactured by Harima chemical Co., ltd.) with N, N-dimethylaminoethanol was prepared as a potassium salt according to the method of synthesis 1 of an unsaturated fatty acid salt, to obtain a potassium salt (DA-200 Mabs salt) of an unsaturated fatty acid having a solid content concentration of 25% by mass (reactive emulsifier).

(Synthesis of unsaturated fatty acid salt 4)

Distilled water 471.91 parts by mass and a 48% by mass aqueous potassium hydroxide solution 47.38 parts by mass were supplied into the reaction vessel, and the mixture was kept at 95℃for about 1 hour while stirring. Next, 110.08 parts by mass of tall oil fatty acid (trade name "Hartall FA-1" manufactured by Harima chemical industry Co., ltd.) was supplied into the reaction vessel, and the reaction was carried out while stirring at 95 ℃ for 3 hours, whereby a potassium salt (FA-1K salt) of tall oil fatty acid having a solid content concentration of 19.4 mass% was obtained (reactive emulsifier). The potassium salt of tall oil fatty acid comprises the potassium salt of oleic acid and the potassium salt of linoleic acid.

(Synthesis of saturated fatty acid salt 1)

Distilled water 676.89 parts by mass and a 48% by mass aqueous potassium hydroxide solution 46.83 parts by mass were supplied into the reaction vessel, and the mixture was kept at 95℃for about 1 hour while stirring. Next, 109.67 parts by mass of stearic acid as a saturated fatty acid was supplied into the reaction vessel, and the reaction was carried out while stirring at 95 ℃ for 3 hours, whereby a potassium salt of stearic acid (K stearate salt) having a solid content concentration of 15 mass% (non-reactive emulsifier) was obtained.

(other emulsifiers)

First Industrial pharmaceutical Co., ltd. Trade name "Akuaron AR-1025" (reactive emulsifier, ammonium salt of polyoxyethylene styrenated propenyl phenyl ether sulfate)

Polyoxyethylene polycyclic phenyl ether sulfate

Japanese emulsifier Co Ltd. Trade name "Newcol 707-SF" (non-reactive emulsifier)

f-O-(CH ₂ CH ₂ O)n-SO ₃ X

f: polycyclic phenyl group, X: na or NH ₄

First Industrial pharmaceutical Co., ltd. Trade name "Hitenol LA-12" (non-reactive emulsifier)

Ammonium Polyoxyethylene lauryl Ether sulfate

The contents and iodine values (solids) of the potassium salts of monomeric acids (potassium salts of monomeric acids K), potassium salts of dimeric acids (potassium salts of dimeric acids K) and potassium salts of trimeric acids (potassium salts of trimeric acids K) are shown in Table 1.

[ monomer composition ]

Monomer compositions 1 to 16 containing styrene, methyl methacrylate, isobutyl methacrylate, 2-ethylhexyl acrylate, n-butyl acrylate, cyclohexyl methacrylate, fatty acid-modified monomers, diacetone acrylamide and methacrylic acid in the specified amounts shown in Table 2 were prepared.

Examples 1 to 25 and comparative examples 1 to 7

(production of resin composition for Water-based paint)

Emulsifiers having the compositions (mass%) shown in tables 3 to 5 were prepared. Half of the amount of the emulsifier and 91.5 parts by mass of distilled water were supplied to the reaction vessel in the specified amounts shown in tables 3 to 5. The inside of the reaction vessel was stirred while nitrogen was supplied thereto to replace nitrogen, and water containing an emulsifier in the reaction vessel was heated to 90 ℃ and then maintained.

Next, to a mixture of 100 parts by mass of the monomer compositions shown in tables 3 to 5 and the remaining half of the emulsifier, 55.2 parts by mass of distilled water and 0.74 parts by mass of ammonium persulfate were added, and the mixture was stirred at a high speed by using a high-speed dispersing machine, whereby the mixture was emulsified to prepare a monomer emulsion.

It took 3 hours to drop the monomer emulsion into the reaction vessel. The reaction solution in the reaction vessel was kept at 90℃for 2 hours to carry out radical polymerization, thereby synthesizing a copolymer. After that, the reaction solution in the reaction vessel was cooled to 40 ℃ or lower, and then the reaction solution was adjusted to pH9 with 28 mass% aqueous ammonia, whereby a resin composition for an aqueous coating material having a solid content (copolymer) concentration of 40 mass% was obtained.

The content (mass%) and the supply amount (parts by mass) of the emulsifier shown in tables 3 to 5 represent the amount of the solid component.

(production of Water-based paint)

A paint raw material liquid was prepared by uniformly mixing 8.55 parts by mass of water, 17.09 parts by mass of pigment (titanium oxide), 0.70 parts by mass of pigment dispersant (trade name "DISPRBYK-190" manufactured by BYK Chemie Co., ltd.) and 0.09 parts by mass of Defoamer (trade name "SN Defosamer 777" manufactured by San Nopco Co.).

The aqueous paint was prepared by mixing 26.43 parts by mass of the paint raw material liquid, 1.81 parts by mass of an emulsifier (trade name "Newcol 707-SF" manufactured by japan emulsifier corporation), 27.00 parts by mass (solid content) of a resin composition for aqueous paint, 40.50 parts by mass of water, 2.20 parts by mass of a film forming aid (diethylene glycol butyl ether), 0.10 parts by mass of an antifoaming agent (trade name "SN Defoamer 777" manufactured by San Nopco corporation), 0.40 parts by mass of a thickener (trade name "Primal RM-12W" manufactured by Dow Chemical japan corporation), 1.46 parts by mass of a metal drier (trade name "DIC 3111TL" manufactured by DIC corporation), and 0.10 parts by mass of an auxiliary agent (adipic dihydrazide) uniformly. The amount of the resin composition for water-based paint is a solid content.

The following points were used as evaluation criteria for initial gloss and initial water resistance of the obtained aqueous coating materials, and the results of measurement of gloss retention are shown in tables 3 to 5. The aqueous paint of comparative example 4 was not evaluated due to gelation.

(initial gloss)

The aqueous paint was applied to a stainless steel plate (150 mm in the longitudinal direction, 70mm in the transverse direction, 0.8mm in the thickness) using a film applicator (trade name "AP100" manufactured by Taiyou machine company) (manufactured by Taiyou machine company) to form a coating layer.

The coating layer on the stainless steel plate was dried in a room at 23 ℃ and a relative humidity of 50% for 16 hours, and the water contained in the coating layer was evaporated and removed to form a coating film. The 20 ° specular reflectance (20 ° G) of the obtained coating film was measured, and the measured value was converted into specular gloss according to JIS Z8741. The obtained specular gloss was used as "initial specular gloss", and "this was used as a reference for evaluation of initial gloss".

(initial Water resistance)

The initial specular gloss of the coating film was measured by forming the coating film at the same point as the initial gloss.

A polyvinyl chloride pipe having an inner diameter of 43mm was prepared, and silicone grease was applied to the entire surface of the end face of the first opening in the pipe. So that the pipeline is tightly attached to the coating film. The treatment was performed so that the coated surface of the silicone grease of the pipe was entirely in close contact with the coating film.

After 15g of distilled water was supplied into the tube, the second opening in the tube was blocked with a synthetic resin film, and the test piece was produced so that the distilled water in the tube was not evaporated. The test body was kept standing in a room having a relative humidity of 50% at 23℃for 24 hours.

Then, after distilled water in the pipe was removed, the pipe was taken out from the coating film, and after the water on the coating film was sufficiently wiped off, the pipe was left to stand in a room at 23℃and a relative humidity of 50% for 1 hour.

The specular gloss of the coating film after the water resistance test (specular gloss after the water resistance test) was measured in the same manner as the initial specular gloss. The gloss retention was calculated based on the following formula. The higher the gloss retention means the better the initial water resistance.

Gloss retention (%) =100×specular gloss after water resistance test/initial specular gloss

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Industrial applicability

The aqueous coating material comprising the aqueous coating material resin composition of the present invention can be used to form a coating film having excellent initial gloss and initial water resistance on the surface of an object to be coated such as a building material, and can coat the surface of the object to be coated.

(cross-reference to related applications)

The present application claims priority based on japanese patent application No. 2019-51959, filed on 3 months 19, the disclosure of which is incorporated herein by reference in its entirety.

Claims

1. A resin composition for water-based paint, which comprises:

comprises 5 to 50 mass% of a styrene monomer unit, 30 to 80 mass% of an acrylic monomer unit, and 0.5 to 5.0 mass% of an unsaturated fatty acid salt unit, and has a glass transition temperature of-4 to 40 ℃.

2. The resin composition for aqueous coating material according to claim 1, wherein,

the unsaturated fatty acid salt contains polymerized fatty acid salt and/or oleic acid salt.

3. The resin composition for aqueous coating material according to claim 2, wherein,

the polymeric fatty acid salt contains a dimer acid salt.

4. The resin composition for aqueous coating material according to any one of claim 1 to 3, wherein,

the unsaturated fatty acid salt contains potassium salt.

5. The resin composition for aqueous coating material according to any one of claim 1 to 3, wherein,

the copolymer is an emulsion polymer of a monomer composition comprising a styrenic monomer, an acrylic monomer, and an unsaturated fatty acid salt as a reactive emulsifier.

6. The resin composition for aqueous coating material according to claim 5, wherein,

the monomer composition is an emulsion polymer comprising a styrene monomer, an acrylic monomer, and a monomer composition containing an unsaturated fatty acid salt and a reactive emulsifier for a compound other than the unsaturated fatty acid salt.

7. A coating film which is a cured product of a coating layer formed by applying the resin composition for an aqueous coating material according to any one of claims 1 to 6 to an object to be coated.