Coating composition for leather

Abstract

To provide a coating composition for leather, capable of forming a coating film on a leather surface, which suppresses adhesion of stains and allows adhered stains to be easily removed.SOLUTION: A coating composition for leather contains a particle including a first polymer having a repeating unit derived from an unsaturated carboxylic ester and a liquid medium.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a coating composition for leather.

Background Art

[0002] Leathers such as natural leather and synthetic leather are widely used, for example, in automobile interiors, furniture such as sofas, and clothing such as coats. It is known that it is difficult to remove stains when stains such as so-called denim stains and ballpoint pen stains adhere to the surface of leather.

[0003] Therefore, by applying a coating to the surface of leather, it has been practiced to easily remove the above-mentioned stains (Japanese Patent Application Laid-Open No. 2007-191820).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] The present invention has been made based on the above circumstances, and an object thereof is to provide a coating composition for leather that can form a coating film on the surface of leather that can suppress the adhesion of stains and easily remove the adhered stains.

Means for Solving the Problems

[0006] The invention made to solve the above problems is a coating composition for leather containing particles including a first polymer having a repeating unit derived from an unsaturated carboxylic acid ester and a liquid medium.

Effects of the Invention

[0007] According to the coating composition for synthetic leather of the present invention, a coating film that can suppress the adhesion of dirt (hereinafter, also referred to as "excellent in stain resistance") and can easily remove the adhered dirt (hereinafter, also referred to as "excellent in dirt removability") can be formed on the surface of leather.

Mode for Carrying Out the Invention

[0008] Hereinafter, the coating composition for leather of the present invention will be described in detail.

[0009] The coating composition for leather (hereinafter, also simply referred to as "coating composition") contains particles (hereinafter, also referred to as "[A] particles") having a repeating unit derived from an unsaturated carboxylic acid ester and a liquid medium (hereinafter, also referred to as "[B] liquid medium"). The coating composition preferably contains polyvinyl alcohol (hereinafter, also referred to as "[C] PVA"). Further, the coating composition may contain a crosslinking agent (hereinafter, also referred to as "[D] crosslinking agent") as a suitable component. Further, the coating composition may contain other components (hereinafter, also referred to as "other components") other than [A] particles, [B] liquid medium, [C] PVA, and [D] crosslinking agent within a range that does not impair the effects of the present invention.

[0010] Since the coating film formed by the coating composition can form a dense film by emulsion fusion, the adhesion of dirt can be suppressed. Further, since the film formed by the coating composition exhibits hydrophilicity as a coating film, the adhered dirt can be easily removed.

[0011] Furthermore, the coating film formed by the coating composition has reduced gloss. Since low gloss is also required for the coating of synthetic leather, according to the coating composition, a low gloss coating film that meets this requirement can be formed. Generally, a matting agent is blended in the coating of leather to exhibit low gloss, but the addition of the matting agent tends to reduce the stain resistance. According to the coating composition, since the matting agent can be not blended or the blending amount of the matting agent can be reduced, both stain resistance and low gloss can be achieved.

[0012] The coating composition is used to coat the surface of leather to form a coating film. The coating method for leather is not particularly limited, and examples include known coating methods using a bar coater or the like. As the upper limit of the film thickness of the coating film formed on the surface of leather, for example, a dry film thickness of 100 μm is preferable, and 80 μm is more preferable. As the lower limit of the above film thickness, a dry film thickness of 1 μm is preferable, and 2 μm is more preferable.

[0013] The leather is not particularly limited and may be natural leather or synthetic leather. In this specification, "synthetic leather" means leather other than natural leather. The material of the synthetic leather is not particularly limited, and examples include polyurethane and polyvinyl chloride. In addition, examples of the synthetic leather include synthetic leather used for automobile interiors, furniture such as sofas, and clothing such as coats.

[0014] Hereinafter, each component contained in the coating composition will be described.

[0015] <[A] particles> [A] particles contain a first polymer (hereinafter, also referred to as "polymer (Pa)") having a repeating unit derived from an unsaturated carboxylic acid ester. [A] particles are usually latex-like particles dispersed in a [B] liquid medium using the [B] liquid medium as a dispersion medium.

[0016] [A] particles may contain a second polymer having a repeating unit derived from a fluorine-containing ethylene monomer (hereinafter, also referred to as "polymer (Pb)"). [A] particles may contain other polymers other than polymer (Pa) and polymer (Pb), but preferably do not contain other polymers. [A] particles may contain components other than polymers.

[0017] The coating composition can contain one or more [A] particles.

[0018] [Polymer (Pa)] Polymer (Pa) has a repeating unit derived from an unsaturated carboxylic acid ester (hereinafter, also referred to as "repeating unit (Ia)"). Polymer (Pa) may have other repeating units other than repeating unit (Ia). [A] particles can contain one or more polymers (Pa).

[0019] (Repeating unit (Ia)) Repeating unit (Ia) is a repeating unit derived from an unsaturated carboxylic acid ester. Polymer (Pa) can have one or more repeating units (Ia).

[0020] As the unsaturated carboxylic acid, an ethylenically unsaturated carboxylic acid is preferable, and examples thereof include mono- or dicarboxylic acids such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, fumaric acid, and itaconic acid. Among these, acrylic acid or methacrylic acid is preferable.

[0021] Examples of the unsaturated carboxylic acid ester include alkyl esters of unsaturated carboxylic acids, hydroxyalkyl esters of unsaturated carboxylic acids, alkylene glycol esters of unsaturated carboxylic acids, amino group-containing esters of unsaturated carboxylic acids, polymerizable group-containing alkoxysilanes, and the like. In the present specification, "alkyl ester" means an ester containing a linear, branched, or cyclic alkyl group.

[0022] Examples of the alkyl esters of unsaturated carboxylic acids include alkyl esters of (meth)acrylic acid such as methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, lauryl (meth)acrylate, cyclohexyl (meth)acrylate, and allyl (meth)acrylate. In the present specification, "(meth)acrylic acid" includes both "acrylic acid" and "methacrylic acid".

[0023] Examples of the hydroxyalkyl esters of unsaturated carboxylic acids include hydroxyalkyl esters of (meth)acrylic acid such as 2-hydroxyethyl (meth)acrylate and 3-hydroxypropyl (meth)acrylate.

[0024] Examples of the alkylene glycol esters of unsaturated carboxylic acids include polyalkylene glycol esters of (meth)acrylic acid such as polyethylene glycol (meth)acrylate, and alkylene glycol di(meth)acrylates such as ethylene glycol di(meth)acrylate.

[0025] Examples of the amino group-containing esters of unsaturated carboxylic acids include amino group-containing esters of (meth)acrylic acid such as 1,2,2,6,6-pentamethyl-4-piperidyl (meth)acrylate and dimethylaminoethyl (meth)acrylate.

[0026] Examples of the polymerizable group-containing alkoxysilanes include compounds represented by the following formula (b). R 3 n Si(OR 4 ) 4-n ·····(b)

[0027] In the above formula (b), R 3 is a monovalent organic group having 1 to 8 carbon atoms. However, at least one of R 3 has a polymerizable group. R 4 is a monovalent organic group having 1 to 8 carbon atoms. n is an integer of 0 to 3. R3 When there are a plurality of them, the plurality of Rs 3 are the same or different. R 4 When there are a plurality of them, the plurality of Rs 4 are the same or different.

[0028] The compound represented by the above formula (b) forms a repeating unit represented by the following formula (c) in the polymer (Pa). R 5 m SiO (4-m) / 2 ·····(c)

[0029] In the above formula (c), R 5 is a monovalent organic group having 1 to 8 carbon atoms. However, at least one of R 5 is a group derived from a group having a polymerizable group. m is a number from 0 to 3. When there are a plurality of Rs 5 the plurality of Rs 5 are the same or different.

[0030] In the above formulas (b) and (c), R 3 and R 5 Examples of the polymerizable group in include vinyl group, 1-propenyl group, (meth)acryloyl group, etc. Among these, (meth)acryloyl group is preferred. Examples of the monovalent organic group having a polymerizable group represented by R 3 include γ-(meth)acryloyloxypropyl group, etc. As the monovalent organic group of R 3 and R 5 an alkyl group having 1 to 8 carbon atoms is preferred, and a methyl group and an ethyl group are more preferred. R 4Examples of the monovalent organic group represented by include alkyl groups having 1 to 8 carbon atoms, aryl groups, acyl groups, etc. Examples of the alkyl group include methyl group, ethyl group, n-propyl group, i-propyl group, n-butyl group, sec-butyl group, t-butyl group, n-pentyl group, etc. Examples of the aryl group include phenyl group, methylphenyl group, ethylphenyl group, chlorophenyl group, bromophenyl group, fluorophenyl group, etc. As the acyl group, an acyl group having 1 to 6 carbon atoms is preferable, and examples thereof include acetyl group, propionyl group, butyryl group, valeryl group, caproyl group, etc.

[0031] As the lower limit of the content ratio of the repeating unit (Ia) in the polymer (Pa), 30% by mass is preferable and 60% by mass is more preferable with respect to all the repeating units constituting the polymer (Pa). As the upper limit of the above content ratio, 98% by mass is preferable and 95% by mass is more preferable.

[0032] (Other repeating units) Examples of the other repeating units include repeating units derived from monomers described in International Publication No. 2014 / 112252, etc. Specifically, unsaturated carboxylic acids, carbonyl group-containing compounds, alkoxysilanes, α,β-unsaturated nitriles, conjugated dienes, aromatic vinyl compounds, vinyl ethers, allyl ethers, etc. are included. The polymer (Pa) can have one or more other repeating units.

[0033] Examples of the unsaturated carboxylic acid include those similar to those exemplified as the unsaturated carboxylic acid in the above repeating unit (Ia).

[0034] Examples of the carbonyl group-containing compounds include (meth)acrylamide, N,N-dimethyl(meth)acrylamide, N,N-diethyl(meth)acrylamide, N-isopropyl(meth)acrylamide, diacetone(meth)acrylamide, N,N-dimethylaminopropyl(meth)acrylamide, N-hydroxyethyl(meth)acrylamide, acryloylmorpholine, acrolein, etc.

[0035] Examples of the alkoxysilane include methyltriethoxysilane and the like.

[0036] Examples of the α,β-unsaturated nitrile include acrylonitrile, methacrylonitrile, α-chloroacrylonitrile, α-ethylacrylonitrile, vinylidene cyanide, and the like.

[0037] Examples of the conjugated diene include 1,3-butadiene, 2-methyl-1,3-butadiene, 2,3-dimethyl-1,3-butadiene, 2-chloro-1,3-butadiene, and the like.

[0038] Examples of the aromatic vinyl compound include styrene, α-methylstyrene, p-methylstyrene, vinyltoluene, chlorostyrene, divinylbenzene, p-hydroxystyrene, sodium styrene-4-sulfonate, and the like.

[0039] Examples of the vinyl ether include ethyl vinyl ether, propyl vinyl ether, butyl vinyl ether, cyclohexyl vinyl ether, 2-hydroxyethyl vinyl ether, 3-hydroxypropyl vinyl ether, 4-hydroxybutyl vinyl ether, 2-aminoethyl vinyl ether, and the like.

[0040] Examples of the allyl ether include methyl allyl ether, ethyl allyl ether, propyl allyl ether, butyl allyl ether, hydroxyethyl allyl ether, hydroxypropyl allyl ether, hydroxybutyl allyl ether, allyl glycidyl ether, ethylene glycol monoallyl ether, propylene glycol monoallyl ether, and the like.

[0041] When the polymer (Pa) has other repeating units, the lower limit of the content ratio of the other repeating units in the polymer (Pa) is preferably 0.1% by mass, more preferably 1% by mass, based on all the repeating units constituting the polymer (Pa). The upper limit of the above content ratio is preferably 30% by mass, more preferably 15% by mass.

[0042] [Polymer (Pb)] The polymer (Pb) has a repeating unit derived from a fluorine-containing ethylenic monomer (hereinafter also referred to as "repeating unit (IIb)"). The polymer (Pb) may have other repeating units other than the repeating unit (IIb). When the [A] particles contain the polymer (Pb), the [A] particles can contain one or more kinds of the polymer (Pb). By further containing the polymer (Pb) in the [A] particles, the stain resistance and stain removability can be further improved.

[0043] (Repeating unit (IIb)) The repeating unit (IIb) is a repeating unit derived from a fluorine-containing ethylenic monomer. The polymer (Pb) can have one or more kinds of the repeating unit (IIb).

[0044] A fluorine-containing ethylene monomer is a compound having an ethylenic carbon-carbon double bond and a fluorine atom. Examples of the fluorine-containing ethylene monomer include olefin fluorides, chlorofluoroolefins, (meth)acrylates having a fluorine atom, perfluoroalkyl vinyl ethers, and the like. Examples of the olefin fluoride include vinylidene fluoride, ethylene tetrafluoride, propylene hexafluoride, and the like. Examples of the chlorofluoroolefin include ethylene trichlorofluoride, and the like. Examples of the (meth)acrylate having a fluorine atom include a compound represented by the following formula (a), 3-[4〔1-trifluoromethyl-2,2-bis〔bis(trifluoromethyl)fluoromethyl〕ethynyloxy〕benzoyloxy]-2-hydroxypropyl (meth)acrylate, and the like. Examples of the perfluoroalkyl vinyl ether include trifluoromethyl trifluorovinyl ether, heptafluoropropyl trifluorovinyl ether, and the like.

[0045]

Chemical formula

[0046] In the above formula (a), R 1 is a hydrogen atom or a methyl group. R 2 is a monovalent fluorinated hydrocarbon group having 1 to 18 carbon atoms.

[0047] Examples of R 2 in the formula (a) include a fluoroalkyl group having 1 to 12 carbon atoms, a fluoroaryl group having 6 to 16 carbon atoms, a fluoroaralkyl group having 7 to 18 carbon atoms, and the like. Among these, a fluoroalkyl group having 1 to 12 carbon atoms is preferred. R 2Preferable specific examples thereof include a 2,2,2-trifluoroethyl group, a 2,2,3,3,3-pentafluoropropyl group, a 1,1,1,3,3,3-hexafluoropropan-2-yl group, a β-(perfluorooctyl)ethyl group, a 2,2,3,3-tetrafluoropropyl group, a 2,2,3,4,4,4-hexafluorobutyl group, a 1H,1H,5H-octafluoropentyl group, a 1H,1H,9H-hexadecafluoro-1-nonyl group, a 1H,1H,11H-icosadecafluoroundecyl group, and a perfluorooctyl group.

[0048] Among these, as the fluorine-containing ethylenic monomer, an olefin fluoride is preferable, vinylidene fluoride, tetrafluoroethylene, or hexafluoropropylene is more preferable, vinylidene fluoride or hexafluoropropylene is even more preferable, and vinylidene fluoride is particularly preferable. When using these compounds as the fluorine-containing ethylenic monomer, the stability of the system is further improved during emulsion polymerization, and [A] particles can be formed more effectively.

[0049] As the lower limit of the content ratio of the repeating unit (IIb) in the polymer (Pb), 70% by mass is preferable, and 80% by mass is more preferable with respect to all the repeating units constituting the polymer (Pb). As the upper limit of the above content ratio, 100% by mass is preferable, and 90% by mass is more preferable.

[0050] (Repeating units derived from other monomers) As the other monomers, monomers described in International Publication No. 2014 / 112252 and the like can be used. For example, unsaturated carboxylic acids, α,β-unsaturated nitriles, carbonyl group-containing compounds, conjugated dienes, aromatic vinyl compounds, vinyl ethers, allyl ethers, polymerizable group-containing alkoxysilanes, unsaturated carboxylic acid esters, and the like can be mentioned. The polymer (Pb) can have one or more other repeating units.

[0051] Examples of the unsaturated carboxylic acid include those similar to those exemplified as the unsaturated carboxylic acid in the repeating unit (Ia) of the above polymer (Pa).

[0052] Examples of the α,β-unsaturated nitrile include the same ones as those exemplified as the α,β-unsaturated nitrile in the other repeating units in the above-mentioned polymer (Pa).

[0053] Examples of the carbonyl group-containing compound include the same ones as those exemplified as the carbonyl group-containing compound in the other repeating units in the above-mentioned polymer (Pa).

[0054] Examples of the conjugated diene include the same ones as those exemplified as the conjugated diene in the other repeating units in the above-mentioned polymer (Pa).

[0055] Examples of the aromatic vinyl compound include the same ones as those exemplified as the aromatic vinyl compound in the other repeating units in the above-mentioned polymer (Pa).

[0056] Examples of the vinyl ether include the same ones as those exemplified as the vinyl ether in the other repeating units in the above-mentioned polymer (Pa).

[0057] Examples of the allyl ether include the same ones as those exemplified as the allyl ether in the other repeating units in the above-mentioned polymer (Pa).

[0058] Examples of the polymerizable group-containing alkoxysilane include the same ones as those exemplified as the polymerizable group-containing alkoxysilane in the above-mentioned polymer (Pa).

[0059] Examples of the unsaturated carboxylic acid ester include the alkyl ester of the above-mentioned unsaturated carboxylic acid, the hydroxyalkyl ester of the above-mentioned unsaturated carboxylic acid, and the like.

[0060] When the polymer (Pb) has other repeating units, the lower limit of the content ratio of this repeating unit is preferably 0% by mass and more preferably 10% by mass with respect to all the repeating units constituting the polymer (Pb). The upper limit of the above content ratio is preferably 30% by mass and more preferably 20% by mass.

[0061] [Physical properties of [A] particles] (Average particle diameter) The lower limit of the average particle diameter of [A] particles is preferably 30 nm, more preferably 50 nm, and even more preferably 80 nm. The upper limit of the above average particle diameter is preferably 6,000 nm. When the average particle diameter of [A] particles is within the above range, a dense coating film can be formed when film formation is carried out.

[0062] In addition, when the average particle diameter of [A] particles is 500 nm or more (hereinafter, also referred to as "large particle diameter"), a coating film with further reduced gloss can be formed. The lower limit of the average particle diameter of [A] particles with a large particle diameter is 500 nm or more, and 550 nm is preferable. The upper limit of the above average particle diameter is preferably 6,000 nm, more preferably 5,000 nm, and even more preferably 4,000 nm. When the average particle diameter of [A] particles with a large particle diameter is within the above range, a coating film with even further reduced gloss can be formed.

[0063] When [A] particles have a large particle diameter, the above-mentioned polymer (Pa) preferably further has a repeating unit derived from a crosslinkable monomer. In this case, a coating film with even further reduced gloss can be formed. Note that the "crosslinkable monomer" refers to a compound having at least two ethylenically unsaturated groups.

[0064] Examples of the crosslinkable monomer include allyl methacrylate, allyl acrylate, triallyl cyanurate, triallyl isocyanurate, diallyl phthalate, diallyl maleate, divinyl adipate, divinyl benzene, ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, triethylene glycol dimethacrylate, trimethylolpropane trimethacrylate, pentaerythritol tetramethacrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, ditrimethylolpropane tetra(meth)acrylate, dipentaerythritol hexa(meth)acrylate, dipropylene glycol dimethacrylate, divinyl benzene, and their acrylates. Among these, allyl methacrylate, triallyl isocyanurate, or ethylene glycol dimethacrylate is preferable, and allyl methacrylate is more preferable. The polymer (Pa) can have repeating units derived from one or more crosslinkable monomers.

[0065] The lower limit of the content ratio of the repeating unit derived from the crosslinkable monomer is preferably 0.01% by mass, more preferably 0.1% by mass, based on all the repeating units constituting the polymer (Pa). The upper limit of the above content ratio is preferably 10% by mass, more preferably 5% by mass.

[0066] In this specification, the average particle diameter of the [A] particles is the value of the particle diameter (D50) at which the cumulative frequency of the number of particles becomes 50% when the particle size distribution is measured using a particle size distribution measuring device based on the light scattering method. Examples of such a particle size distribution measuring device include "FPAR-1000" of Otsuka Electronics Co., Ltd. The particle size distribution measuring device is not limited to evaluating only the primary particles of the [A] particles, but can also evaluate the secondary particles formed by the aggregation of the primary particles. Therefore, the particle size distribution measured by these particle size distribution measuring devices can be used as an index of the dispersion state of the [A] particles contained in the coating composition.

[0067] (Endothermic peak temperature) [A] particles preferably have at least one endothermic peak in the temperature range of -50°C or higher and +95°C or lower when measured by differential scanning calorimetry (DSC) in accordance with JIS K7121. It is more preferable that one of the endothermic peaks of [A] particles is in the range of -30°C or higher and +95°C or lower, and even more preferable that it is in the range of -20°C or higher and +95°C or lower. When the temperature of one of the endothermic peaks of [A] particles is within the above range, [A] particles can impart better flexibility and adhesiveness to the coating film.

[0068] Also, when [A] particles are measured by differential scanning calorimetry (DSC) in accordance with JIS K7121, it is preferable that in addition to the above-mentioned endothermic peak, one or more endothermic peaks are observed in the temperature range of higher than 90°C and 150°C or lower.

[0069] (Tetrahydrofuran (THF) insoluble content) The THF insoluble content of [A] particles is preferably 50% by mass or more, and more preferably 60% by mass or more. The THF insoluble content serves as an index for the solvent resistance of the resulting coating film. For this reason, by setting the THF insoluble content within the above range, even when an organic solvent-based coating film is further laminated on the coating film formed using the coating composition, elution of the polymer into the organic solvent-based coating film can be suppressed, which is considered preferable. Also, the THF insoluble content can be one of the indices for the durability of the resulting coating film. For this reason, it is considered that the durability is improved by setting the THF insoluble content within the above range.

[0070] In addition, when [A] particles have a large particle size, the THF insoluble content of [A] particles is preferably 60% by mass or more, more preferably 70% by mass or more, and even more preferably 80% by mass or more. By setting the THF insoluble content within the above range, a coating film with even lower gloss can be formed.

[0071] [Synthesis method of [A] particles] [A] particles can be produced, for example, by emulsion-polymerizing a predetermined monomer according to a known method to form a polymer (Pa). The synthesis method of [A] particles is not particularly limited as long as the repeating unit of the polymer (Pa) has the above-described configuration. For example, it can be easily synthesized by a known emulsion polymerization process or by appropriately combining them, and can be synthesized, for example, by the method described in International Publication No. 2014 / 112252.

[0072] When the [A] particles contain a polymer (Pb), for example, a polymer (Pb) having a repeating unit derived from a fluorine-containing ethylenic monomer is formed by a known method. Then, a monomer for forming the polymer (Pa) is added to the polymer (Pb), and after absorbing the monomer into the mesh structure of the polymer (Pb) particles, it can also be synthesized by polymerizing the monomer absorbed in the mesh structure of the polymer (Pb) to form the polymer (Pa).

[0073] When the [A] particles have a large particle size, the large-sized [A] particles can be produced by adding [C] PVA, which will be described later, when emulsion-polymerizing a predetermined monomer according to a known method.

[0074] <[B] Liquid medium> [B] As the liquid medium, an aqueous medium containing water is preferred. This aqueous medium can contain a non-aqueous medium other than water. From the viewpoint of improving the coatability of the coating composition, it can contain a non-aqueous medium having a standard boiling point of 60°C or higher and 350°C or lower. Specific examples of such non-aqueous media include, for example, amides such as N-methylpyrrolidone, dimethylformamide, N,N-dimethylacetamide; hydrocarbons such as toluene, xylene, n-dodecane, tetralin; alcohols such as methanol, ethanol, isopropyl alcohol, n-butyl alcohol, isobutyl alcohol, t-butyl alcohol, ethylene glycol, glycerin, propylene glycol, 2-ethyl-1-hexanol, 1-nonanol, lauryl alcohol; ketones such as methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, phorone, acetophenone, isophorone; esters such as ethyl acetate, butyl acetate, benzyl acetate, isopentyl butyrate, methyl lactate, ethyl lactate, butyl lactate; amines such as o-toluidine, m-toluidine, p-toluidine; lactones such as γ-butyrolactone, δ-valerolactone; sulfoxides such as dimethyl sulfoxide, and sulfone compounds such as sulfolane.

[0075] [B] When the liquid medium contains water and a non-aqueous medium other than water, the lower limit of the water content in the [B] liquid medium is preferably 80% by mass, more preferably 90% by mass. By using an aqueous medium as the [B] liquid medium, the coating composition has a lower impact on the environment and higher safety for handling workers.

[0076] <[C]PVA> The coating composition preferably contains [C] PVA. In this case, the stain removability and low glossiness of the coating film formed by the coating composition can be further improved.

[0077] In the coating composition, [C]PVA may be added as polyvinyl alcohol used as an emulsifier during the synthesis of [A] particles, or may be polyvinyl alcohol added after the synthesis of [A] particles, or may be both. When the [A] particles have a large particle size, it is preferable that [C]PVA is added at least as polyvinyl alcohol used as an emulsifier during the synthesis of [A] particles.

[0078] [C]PVA is not particularly limited as long as it is a polymer obtained by saponifying a polyvinyl ester obtained by polymerizing a vinyl ester compound such as vinyl acetate, and known polyvinyl alcohol can be used. Further, modified polyvinyl alcohol may be used. Examples of the modified polyvinyl alcohol include carboxylic acid-modified polyvinyl alcohol, acetoxy-modified polyvinyl alcohol, and silanol-modified polyvinyl alcohol.

[0079] The lower limit of the saponification degree of polyvinyl alcohol is preferably 70 mol%, more preferably 80 mol%. The saponification degree refers to a value measured in accordance with JIS-K-6726 (1994).

[0080] Examples of commercially available polyvinyl alcohol include "Poval 5-88", "25-88KL", "25-98R" of Kuraray Co., Ltd., "Gosenol GL-03", "Gosenex Z-200" of Mitsubishi Chemical Corporation, and the like.

[0081] When the coating composition contains [C]PVA, the lower limit of the content of [C]PVA is preferably 1 part by mass, more preferably 10 parts by mass, and still more preferably 15 parts by mass with respect to 100 parts by mass of [A] particles. The upper limit of the above content is preferably 300 parts by mass, more preferably 200 parts by mass, and still more preferably 150 parts by mass with respect to 100 parts by mass of [A] particles. When the content of [C]PVA is within the above range, the stain resistance of the coating film formed by the coating composition can be further improved.

[0082] <[D] Crosslinking agent> The coating composition can contain a [D] crosslinking agent. By containing the [D] crosslinking agent in the coating composition, the coating film can be densified by crosslinking and water resistance can be imparted. As the [D] crosslinking agent, it is preferably dissolved in a [B] liquid medium.

[0083] Examples of the [D] crosslinking agent include hydrazine derivatives, carbodiimide compounds, isocyanate compounds, amino compounds, epoxy compounds, alkoxysilyl group-containing compounds, metal-based crosslinking agents, oxazoline compounds, acid anhydrides, aziridine compounds, and the like.

[0084] Examples of the hydrazine derivative include compounds having at least two hydrazino groups. The lower limit of the content of the hydrazine derivative is preferably 0.02 mol, more preferably 0.2 mol, per 1 mol of the carbonyl group contained in the [A] polymer particles. The upper limit of the above content is preferably 1.1 mol, more preferably 1.0 mol. If the content of the hydrazine derivative is less than 0.02 mol or exceeds 1.1 mol per 1 mol of the carbonyl group contained in the [A] particles, the water resistance and solvent resistance of the formed coating film may be insufficient.

[0085] Examples of hydrazine derivatives having at least two hydrazino groups include dicarboxylic acid dihydrazides having 2 to 10 carbon atoms, preferably 4 to 6 carbon atoms, such as oxalic acid dihydrazide, malonic acid dihydrazide, succinic acid dihydrazide, glutaric acid dihydrazide, adipic acid dihydrazide, isophthalic acid dihydrazide, sebacic acid dihydrazide, maleic acid dihydrazide, fumaric acid dihydrazide, itaconic acid dihydrazide, etc., and aliphatic water-soluble dihydrazines having 2 to 4 carbon atoms, such as ethylene-1,2-dihydrazine, propylene-1,3-dihydrazine, butylene-1,4-dihydrazine. Among these, adipic acid dihydrazide is preferred. When the water in the composition scatters due to drying, the hydrazine derivative has the effect of reacting the carbonyl group of the polymer with the hydrazino group in the hydrazine derivative to form a film with a network structure. Usually, no catalyst is used for this cross-linking reaction, but if necessary, water-soluble metal salts such as zinc sulfate, manganese sulfate, cobalt sulfate, etc. can be used as catalysts.

[0086] Examples of commercially available carbodiimide compounds include, for example, "Carbodilite E-02", "E-03A", "E-04", "E-05", "V-02", "SV-02", "V-02-L2", "V-04", "V-10", etc. of Nisshinbo Chemical Co., Ltd. Among these, "Carbodilite V-02-L2", "V-02" or "E-05" is preferred.

[0087] Specific examples of isocyanate compounds include, for example, 2,4-tolylene diisocyanate, diphenylmethane-4,4'-diisocyanate, xylylene diisocyanate, isophorone diisocyanate, lysine methyl ester diisocyanate, methylcyclohexyl diisocyanate, trimethylhexamethylene diisocyanate, hexamethylene diisocyanate, n-pentane-1,4-diisocyanate, trimers of these, adducts and biuret compounds of these, polymers of these having two or more isocyanate groups, lysine triisocyanate, blocked isocyanates, etc.

[0088] Specific examples of the amino compound include, for example, melamine resin, urea resin, guanamine resin, amine adduct, polyamide, and other amino acid-based substances (for example, "AC454" of Tosoh Corporation, etc.).

[0089] Specific examples of the epoxy compound include, for example, epoxy resin, epoxy-modified silane coupling agent, etc.

[0090] Specific examples of the alkoxysilyl group-containing compound include, for example, methyltrimethoxysilane, methyltriethoxysilane, phenyltrimethoxysilane, 3-trimethoxysilylpropyl succinic anhydride, 3-isocyanatopropyltriethoxysilane, tris-(trimethoxysilylpropyl) isocyanurate, etc.

[0091] Specific examples of the metal-based crosslinking agent include, for example, organic titanium compounds such as titanium lactate, and zirconium compounds such as ammonium zirconium carbonate, etc. Commercially available products of titanium lactate include, for example, "Organix TC-310" of Matsumoto Fine Chemical Co., Ltd., etc. Commercially available products of ammonium zirconium carbonate include, for example, "AZ Coat 5800MT" of San Nopco Ltd., etc.

[0092] When the coating composition contains the [D] crosslinking agent, the lower limit of the content of the [D] crosslinking agent is preferably 0.1 part by mass, more preferably 1 part by mass, based on 100 parts by mass of the [A] particles. The upper limit of the above content is preferably 20 parts by mass, more preferably 10 parts by mass.

[0093] Examples of the method for adding the [D] crosslinking agent include, for example, a method of adding a composition in which the [D] crosslinking agent is dissolved or dispersed in water, a method of adding a composition in which the [D] crosslinking agent is dissolved in a small amount of water-soluble organic solvent, a method of directly adding the [D] crosslinking agent to the composition, etc.

[0094] <Other optional components> The coating composition may contain, if necessary, other optional components in addition to [A] particles, [B] liquid medium, [C] PVA, and [D] crosslinking agent. Examples of other optional components include matting agents, aqueous urethane resins, fillers, surface treatment agents, weather resistance improvers, thickeners, defoamers, film-forming aids, antifreeze agents, pH adjusters, wetting improvers, pigments, and the like. Commercially available products can also be used. The coating composition can contain one or more other optional components.

[0095] Examples of methods for adding other optional components include adding a composition in which other optional components are dissolved or dispersed in water to the composition, adding a composition in which other optional components are dissolved in a small amount of water-soluble organic solvent to the composition, directly adding other optional components to the composition, and adding other optional components to the polymerization system when synthesizing the polymer (Pa) constituting [A] particles.

[0096] [Method for Preparing Coating Composition] The coating composition can be prepared, for example, by preparing a dispersion of [B] liquid medium containing [A] particles, and mixing this dispersion with a suspension of [C] PVA and [D] crosslinking agent in [B] liquid medium, and other optional components as necessary. The lower limit of the solid content concentration of the coating composition is preferably 1% by mass, more preferably 10% by mass, and even more preferably 30% by mass. The upper limit of the solid content concentration is preferably 80% by mass, more preferably 70% by mass, and even more preferably 60% by mass.

Examples

[0097] Hereinafter, the present invention will be specifically described based on examples, but the present invention is not limited to these examples at all.

[0098] [Synthesis of [A] Particles] Abbreviations of each component used for the synthesis of [A] particles are shown below. MMA: Methyl methacrylate EHA: 2-Ethylhexyl acrylate BA: Butyl acrylate BMA: Butyl methacrylate LA: Lauryl acrylate HEMA: 2-Hydroxyethyl methacrylate CHMA: Cyclohexyl methacrylate PEGMA: Polyethylene glycol methacrylate (「PE-200」 of NOF Corporation, average number of added oxyethylene moles: 4.5) PMPMA: 1,2,2,6,6-Pentamethyl-4-piperidyl methacrylate (「LA-82」 of ADEKA Corporation) MAPS: 3-(Trimethoxysilyl)propyl methacrylate DAAM: Diacetone acrylamide AA: Acrylic acid MAA: Methacrylic acid AN: Acrylonitrile AMA: Allyl methacrylate VDF: Vinylidene fluoride TFE: Tetrafluoroethylene HFP: Hexafluoropropylene

[0099] [Synthesis Example 1] Synthesis of Particles (S1) 60 parts by mass of methyl methacrylate (MMA), 30 parts by mass of 2-ethylhexyl acrylate (EHA), 2 parts by mass of cyclohexyl methacrylate (CHMA), 5 parts by mass of methacrylic acid (MAA), 1 part by mass of acrylonitrile (AN), 1 part by mass of polyethylene glycol methacrylate (PEGMA), 1 part by mass of 1,2,2,6,6-pentamethyl-4-piperidyl methacrylate (PMPMA), 2 parts by mass of an emulsifier (“ADEKA Riasol SR10” of ADEKA Corporation), 1 part by mass of sodium dodecylbenzenesulfonate, and 80 parts by mass of water were mixed in a reaction vessel and stirred well to prepare a monomer emulsion. Then, the temperature of a separable flask was started to be raised in a water bath. When the internal temperature of this separable flask reached 50°C, 0.3 part by mass of ammonium persulfate as a polymerization initiator was added. When the internal temperature of the separable flask reached 75°C, the addition of the above monomer emulsion was started, and the monomer emulsion was slowly added over 2 hours while maintaining the internal temperature of the separable flask at 75°C. Then, the internal temperature of the separable flask was raised to 85°C and this temperature was maintained for 1 hour to carry out a polymerization reaction to polymerize a polymer (Pa-1). Then, the separable flask was cooled to stop the reaction, ammonia water was added to adjust the pH to 7.6, water was added to adjust the solid content concentration, and an aqueous dispersion containing 46% by mass of particles (S1) was obtained.

[0100] [Synthesis Example 2] Synthesis of Particles (S2) 51 parts by mass of methyl methacrylate (MMA), 46 parts by mass of 2-ethylhexyl acrylate (EHA), 3 parts by mass of methacrylic acid (MAA), 5 parts by mass of an emulsifier ("Poval 5-88" of Kuraray Co., Ltd.), and 20 parts by volume of water were mixed in a reaction vessel and stirred well to prepare a monomer emulsion. 45 parts by mass of water was charged into a separable flask. After thoroughly purging the inside of this separable flask with nitrogen, the temperature was started to be raised in a water bath, and when the internal temperature of the separable flask reached 82°C, 0.03 part by mass of ammonium persulfate as a polymerization initiator was added. One minute after the addition of the polymerization initiator, the addition of the above monomer emulsion was started, and the monomer emulsion was slowly added over 4 hours while maintaining the internal temperature of the separable flask at 82°C. At that time, 0.02 part of ammonium persulfate was additionally added every hour. Thereafter, the internal temperature of the separable flask was maintained at 82°C for 3 hours to carry out a polymerization reaction, and a polymer (Pa-2) was polymerized. Thereafter, the separable flask was cooled to stop the reaction, ammonia water was added to adjust the pH to 5.0, water was added to adjust the solid content concentration, and an aqueous dispersion containing 46% by mass of particles (S2) was obtained.

[0101] [Synthesis Example 3] Synthesis of Particles (S3) A polymer (Pa-3) was synthesized in the same manner as in Synthesis Example 2 except that monomers of the types and amounts shown in Table 1 below were used, and an aqueous dispersion containing 46% by mass of particles (S3) was obtained.

[0102] [Synthesis Example 4] Synthesis of Particles (S4) 51 parts by mass of methyl methacrylate (MMA), 46 parts by mass of 2-ethylhexyl acrylate (EHA), 3 parts by mass of methacrylic acid (MAA), 5 parts by mass of an emulsifier ("Poval 5-88" manufactured by Kuraray Co., Ltd.), and 20 parts by volume of water were mixed in a reaction vessel and stirred well to prepare a monomer emulsion. 11 parts by mass of an aqueous dispersion (5 parts by mass of polymer (Pa-2)) containing particles (S2) of the polymer (Pa-2) obtained in Synthesis Example 2 and 45 parts by mass of water were charged into a separable flask. After sufficiently purging the inside of this separable flask with nitrogen, the temperature was started to be raised in a water bath. When the internal temperature of the separable flask reached 82°C, 0.03 part by mass of ammonium persulfate as a polymerization initiator was added. One minute after the addition of the polymerization initiator, the addition of the above monomer emulsion was started, and the monomer emulsion was slowly added over 4 hours while maintaining the internal temperature of the separable flask at 82°C. At that time, 0.02 part of ammonium persulfate was additionally added every hour. Thereafter, the internal temperature of the separable flask was maintained at 82°C for 3 hours to carry out a polymerization reaction to polymerize the polymer (Pa-4). Thereafter, the separable flask was cooled to stop the reaction, ammonia water was added to adjust the pH to 5.0, water was added to adjust the solid content concentration, and an aqueous dispersion containing 46% by mass of particles (S4) was obtained.

[0103] [Synthesis Example 5] Synthesis of Particles (S5) A polymer (Pa-5) was synthesized in the same manner as in Synthesis Example 4 except that monomers of the types and amounts shown in Table 1 below were used, and an aqueous dispersion containing 46% by mass of particles (S5) was obtained.

[0104] [Synthesis Example 6] Synthesis of Particles (S6) After sufficiently purging the inside of an autoclave with an internal volume of about 6 L equipped with an electromagnetic stirrer with nitrogen, 2.5 L of deoxygenated pure water and 25 g of ammonium perfluorodecanoate as an emulsifier were charged, and the temperature was raised to 60°C while stirring at 350 rpm. Next, a mixed gas composed of 720 parts by mass of vinylidene fluoride (VDF) and 180 parts by mass of hexafluoropropylene (HFP) as monomers was added until the internal pressure reached 20 kg / cm 2Charged until reaching [the specified condition]. 25 g of a Freon 113 solution containing 20% by mass of diisopropyl peroxydicarbonate as a polymerization initiator was injected using nitrogen gas to initiate polymerization. During the polymerization, a mixed gas composed of 720 parts by mass of VDF and 180 parts by mass of HFP was sequentially injected so that the internal pressure was maintained at 20 kg / cm 2 and the pressure was maintained at 20 kg / cm 2 . Also, since the polymerization rate decreased as the polymerization progressed, after 3 hours, the same amount of the same polymerization initiator solution was injected using nitrogen gas, and the reaction was continued for another 3 hours. Then, while cooling the reaction solution, stirring was stopped, and after releasing the unreacted monomers, the reaction was stopped to obtain an aqueous dispersion containing 40% by mass of fine particles of the polymer (Pb-1). Regarding the obtained polymer (Pb-1), 19 as a result of analysis by F-NMR, the mass composition ratio of each monomer was VDF / HFP = 720 / 180.

[0105] After sufficiently replacing the inside of the separable flask with nitrogen, 2250 parts by mass of an aqueous dispersion containing fine particles of the polymer (Pb-1) obtained in the above process (900 parts by mass of the polymer (Pb-1)), 1 part by mass of sodium polyoxyethylene dodecyl ether sulfate, and 100 parts by mass of water were charged. In a separate container, 30 parts by mass of methyl methacrylate (MMA), 49 parts by mass of 2-ethylhexyl acrylate (EHA), 5 parts by mass of cyclohexyl methacrylate (CHMA), 1 part by mass of 1,2,2,6,6-pentamethyl-4-piperidyl methacrylate (PMPMA), 1 part by mass of 3-(trimethoxysilyl)propyl methacrylate (MAPS), 5 parts by mass of diacetone acrylamide (DAAM), 2 parts by mass of acrylic acid (AA), 2 parts by mass of methacrylic acid (MAA), 5 parts by mass of acrylonitrile (AN), 1 part by mass of 2-ethylhexyl thioglycolate, 2 parts by mass of an emulsifier ("ADEKA SOAP SR10" manufactured by ADEKA Corporation), and 80 parts by mass of water were mixed with respect to 900 parts by mass of the polymer (Pb-1) contained in this aqueous dispersion, and stirred well to prepare a monomer emulsion. Then, the temperature of the separable flask was started to be raised in a water bath, and when the internal temperature of the separable flask reached 50°C, 0.5 part by mass of ammonium persulfate as a polymerization initiator was added. When the internal temperature of the separable flask reached 75°C, the addition of the above-prepared monomer emulsion was started, and the monomer emulsion was slowly added over 2 hours while maintaining the internal temperature of the separable flask at 75°C. Then, the internal temperature of the separable flask was raised to 85°C, and this temperature was maintained for 1 hour to carry out a polymerization reaction to polymerize the polymer (Pa-6). Then, the separable flask was cooled to stop the reaction, ammonia water was added to adjust the pH to 7.6, water was added to adjust the solid content concentration, and an aqueous dispersion containing 46% by mass of the particles (S6) was obtained.

[0106] [Synthesis Examples 7 and 8] Synthesis of Particles (S7) and Particles (S8) An aqueous dispersion containing 46% by mass of the particles (S7) and an aqueous dispersion containing 46% by mass of the particles (S8) were obtained in the same manner as in Synthesis Example 6, except that monomers of the types and amounts shown in Table 1 below were used.

[0107] <[Physical Properties of Particles]> Regarding the synthesized [A] particles, the average particle diameter, endothermic peak temperature, and THF-insoluble content were measured by the following methods. The results are shown in Table 1 below.

[0108] [Average particle diameter] Regarding the aqueous dispersion, the particle size distribution was measured using a particle size distribution measuring device (「FPAR-1000」manufactured by Otsuka Electronics Co., Ltd.) based on the dynamic light scattering method, and the average particle diameter (D50) was determined from the particle size distribution.

[0109] [Endothermic peak temperature] Regarding the aqueous dispersion, it was measured by a differential scanning calorimeter (DSC), and an endothermic peak was observed.

[0110] [THF-insoluble content] Approximately 10 g of the obtained aqueous dispersion was weighed into a petri dish made of Teflon (registered trademark) with a diameter of 8 cm and dried at 120°C for 1 hour to form a film. 1 g of the obtained film was immersed in 400 mL of tetrahydrofuran (THF) and shaken at 50°C for 3 hours. Then, the THF phase was filtered through a 300-mesh wire mesh to separate the insoluble matter, and the THF-insoluble content (%) was determined by the following formula from the measured value of the mass (Y (g)) of the residue obtained by evaporating and removing the THF solvent from the THF phase. THF-insoluble content (%) = ((1 - Y) / 1) × 100

[0111] In Table 1 below, “-” indicates that the corresponding component was not used.

[0112]

Table 1

[0113] <Preparation of Coating Composition and Formation of Coating Film> Each component other than the [A] particles used in the preparation of the coating composition is shown below.

[0114] [[C] PVA] (C-1): Polyvinyl alcohol ("Poval 5-88" of Kuraray Co., Ltd. (saponification degree 87%)) (C-2): Carboxylic acid-modified polyvinyl alcohol ("Poval 25-88KL" of Kuraray Co., Ltd.) (C-3): Acetoxy-modified polyvinyl alcohol ("Gosenex Z-200" of Mitsubishi Chemical Corporation) (C-4): Silanol-modified polyvinyl alcohol ("25-98R" of Kuraray Co., Ltd.)

[0115] [[D] Crosslinking agent] (D-1): Adipic acid dihydrazide of Otsuka Chemical Co., Ltd. (D-2): "Carbodilite E-05" of Nisshinbo Chemicals, Inc. (D-3): "KBM9659" of Shin-Etsu Chemical Co., Ltd.

[0116] [Other components] Waterborne urethane resin: "Superflex 460" of Dai-ichi Kogyo Seiyaku Co., Ltd.

[0117] [Example 1-1] Preparation of coating composition (T1) and formation of coating film [A] 213 parts by mass of an aqueous dispersion containing particles (S1) as particles (containing 100 parts by mass of particles (S1)), 25 parts by mass of an aqueous dispersion of (D-2) as [D] crosslinking agent (containing 10 parts by mass of solid content), 2 parts by mass of texanol ("CS-12" of JNC Corporation) as a film-forming aid, 2 parts by mass of ethyl carbitol, and 1 part by mass of butyl cellosolve were added and stirred at 300 rpm to prepare a coating composition (T1). The coating composition (T1) was applied to the surface of urethane synthetic leather using a bar coater so that the dry film thickness was 2 to 20 μm, and dried at 120°C for 2 minutes to form a coating film.

[0118] [Examples 1-2 to 1-16 and Comparative Examples 1-1 to 1-4] Coating compositions (T2) to (T16) and (CT1) to (CT4) were prepared and coating films were formed in the same manner as in Example 1-1 except that each component of the type and amount shown in Table 2 below was used.

[0119] <Evaluation> For the above-formed coating film, the stain resistance, stain removability, and glossiness were evaluated according to the following methods. The results are shown in Table 2 below. In Table 2 below, "-" indicates that the corresponding component was not used.

[0120] [Stain Resistance (1)] The coating film was set on the curved surface of a shaking friction fastness tester ("RT-300" manufactured by Dai-ichi Kagaku Seiki Co., Ltd.), and a contamination friction test of 500 reciprocations was performed using a friction element with a contamination cloth (EMPA#128 / 1) and a weight of 1300 g attached. The Lab values before and after the contamination friction test were measured with a handy color difference meter ("CM-700d" manufactured by Konica Minolta, Inc.), and the color difference ΔE was calculated. The stain resistance was evaluated as "A" (extremely good) when ΔE was less than 25, "B" (good) when 25 or more and less than 30, "C" (fairly good) when 30 or more and less than 40, "D" (poor) when 40 or more and less than 50, and "E" (extremely poor) when 50 or more.

[0121] [Stain Removability (1)] After the contamination friction test in the above "Stain Resistance (1)" test, the coating film was wiped with water by hand using a wet Benkot, and the end point was set when no contamination remained on the Benkot side. The Lab value after water wiping was measured in the same manner as the method used in the above "Stain Resistance (1)" test, and the color difference ΔE was calculated using the Lab value before the contamination friction test. The stain removability was evaluated as "A" (extremely good) when ΔE was less than 25, "B" (very good) when 25 or more and less than 30, "C" (good) when 30 or more and less than 40, "D" (poor) when 40 or more and less than 50, and "E" (extremely poor) when 50 or more.

[0122] [Glossiness] Regarding the coating film before conducting the test of the above "soil resistance (1)", the 60° gloss was measured using a gloss meter ("micro-TRI-gloss" by BYK). The lower the numerical value of the 60° gloss, the lower the gloss. The glossiness was evaluated as "A" (extremely good) when the 60° gloss was less than 5, "B" (very good) when it was 5 or more and less than 10, "C" (good) when it was 10 or more and less than 20, "D" (poor) when it was 20 or more and less than 25, and "E" (extremely poor) when it was 25 or more.

[0123]

Table 2

[0124] From the results in Table 2, it became clear that the coating film formed by the coating composition of the examples was superior in soil resistance and soil removability compared to the coating film formed by the coating composition of the comparative examples. Therefore, according to the said coating composition, a coating film excellent in soil resistance and soil removability can be formed on leather.

[0125] [Examples 2-1 to 2-16 and Comparative Examples 2-1 to 2-4] Regarding the coating films for which the results of the above glossiness test were not an "A" evaluation (60° gloss less than 5), coating compositions were prepared by gradually increasing and adding 1 part by mass of a matting agent ("ACEMATT TS100" by Evonik) to 100 parts by mass of the corresponding coating composition that formed the coating film, and then coating films were formed. By evaluating the glossiness of each coating film, the amount of the matting agent required for the glossiness to be an "A" evaluation was determined. The results are shown in Table 3 below. For Examples 2-15 and 2-16, since the results of the glossiness test were an "A" evaluation in Examples 1-15 and 1-16, the above operation was not performed. Therefore, for these examples, the amount of the matting agent is described as "0" in Table 3 below.

[0126] The matting agents in the amounts determined in the above tests were added to the coating compositions (T1) to (T14) and (CT1) to (CT4) to prepare coating compositions (T1') to (T14') and (CT1') to (CT4').

[0127] Next, coating films were formed using the coating compositions (T1') to (T14'), (T15), (T16) and (CT1') to (CT4').

[0128] <Evaluation> For the above-formed coating films, the stain resistance and stain removability were evaluated according to the following method. The results are shown in Table 3 below.

[0129] [Stain resistance (2)] The color difference ΔE was calculated in the same manner as in the above test for "stain resistance (1)". The evaluation criteria for stain resistance in this test were as follows: "A" (extremely good) when ΔE was less than 25, "B" (very good) when 25 or more and less than 30, "C + "(good) when 30 or more and less than 35, "C" (fairly good) when 35 or more and less than 40, "D" (poor) when 40 or more and less than 50, and "E" (extremely poor) when 50 or more.

[0130] [Stain removability (2)] The color difference ΔE was calculated and the stain resistance was evaluated in the same manner as in the above test for "stain removability (1)", except that the coating film after the contamination friction test in the above test for "stain resistance (2)" was used.

[0131]

Table 3

[0132] From the results in Table 3, it was revealed that the coating compositions of the examples required less matting agent amount to reduce the glossiness as compared with the coating compositions of the comparative examples. Also, it was revealed that the coating films formed from the coating compositions of the examples had good stain resistance and stain removability even when a matting agent was blended.

[0133] In addition, in Examples 2-11 to 2-14, it was revealed that the addition amount of the matting agent could be reduced, and a coating film excellent in stain resistance and stain removability could be formed.

[0134] Furthermore, in Examples 2-15 and 2-16, it was revealed that a coating film having low gloss and being further excellent in stain resistance and stain removability could be formed even without adding a matting agent.

Claims

1. Particles containing a first polymer having a repeating unit derived from an unsaturated carboxylic acid ester, polyvinyl alcohol, and a liquid medium are contained, and the leather coating composition has an average particle diameter of the above particles of 500 nm or more and 6000 nm or less.

2. The leather coating composition according to Claim 1, wherein the content of the polyvinyl alcohol is 1 part by mass or more and 300 parts by mass or less with respect to 100 parts by mass of the above particles.

3. The leather coating composition according to Claim 1 or Claim 2, wherein the first polymer further has a repeating unit derived from a crosslinkable monomer.

4. The leather coating composition according to any one of Claims 1 to 3, wherein the THF-insoluble content of the above particles is 60% by mass or more.

5. The leather coating composition according to any one of Claims 1 to 4, wherein the above particles further contain a second polymer having a repeating unit derived from a fluorine-containing ethylenic monomer in the same particle.

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