(METH)acrylic copolymer and antifouling coating composition

Abstract

To provide an antifouling coating composition capable of forming a coating film having a suitable degree of consumption to exhibit a long-term antifouling effect and a polymer suitable for obtaining the antifouling coating composition.SOLUTION: There is provided a (meth)acrylic copolymer having a weight average molecular weight of 1000 to 4000, which comprises a structural unit derived from a monomer (a) having at least one structure of -CO-O-M-O-CO- and -CO-O-M-R0 [R0 is a monovalent organic acid residue, M is a divalent metal atom] and a structural unit derived from a monomer (b) copolymerizable with the monomer (a), wherein the content of the metal atom M is 6.0 mass% or more and the total solubility parameter (SP value) of the monomer (b) is 20.7 (J / cm3)1 / 2 or more.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a (meth)acrylic copolymer and an antifouling coating composition containing the (meth)acrylic copolymer. [Background technology]

[0002] BACKGROUND ART It is known that marine structures and ships are coated with antifouling paints in order to prevent the adhesion of marine organisms, which cause corrosion of parts in contact with seawater and a decrease in sailing speed. Self-polishing antifouling paints are known as antifouling paints. Self-polishing antifouling paints typically contain a hydrolyzable resin and an antifouling agent. The coating film obtained from this antifouling paint exhibits a long-lasting antifouling effect by gradually dissolving the coating surface in seawater, resulting in surface renewal (self-polishing). This allows the antifouling components to be constantly exposed on the coating surface.

[0003] As a self-polishing antifouling paint, for example, the following resin compositions containing metal-containing polymers have been proposed. Such resin compositions are formulated with antifouling agents and the like to form antifouling paints. The metal-containing polymers contained in these resin compositions are hydrolyzable, and coating films containing them exhibit self-polishing properties.

[0004] Furthermore, in recent years, there has been a demand for a reduction in volatile organic compounds (hereinafter also referred to as "VOCs") due to their impact on the environment, etc. "VOCs" generally refer to organic compounds that easily volatilize at normal temperature and pressure (volatile organic compounds).

[0005] (1) A metal-containing copolymer for antifouling paint obtained by polymerizing a mixture of a metal-containing polymerizable monomer and a monomer containing a polymerizable monomer copolymerizable therewith at 110°C or higher in a pressurized vessel under pressure so as not to reflux water (Patent Document 1). (2) A metal-containing copolymer for antifouling paints having a molecular weight of 1000-5000 obtained by copolymerizing a mixture of a metal-containing polymerizable monomer and a monomer containing a polymerizable monomer copolymerizable therewith (Patent Document 2). (3) A metal-containing copolymer for antifouling coatings, which contains a metal and comprises a structural unit derived from a polymerizable monomer having an alicyclic functional group (Patent Document 3).

[0006] However, the coating film formed from the antifouling paint using the resin composition of Patent Documents 1 and 2 did not have sufficient coating film performance. Specifically, the solubility (also called consumption rate) was not high enough, and the consumption of the coating film was not appropriate, so the antifouling effect of the coating film was not necessarily sufficient. The resin composition of Patent Document 3 has a low glass transition temperature (Tg), and therefore does not have sufficient resistance to wood blocks when forming an antifouling coating. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Laid-Open No. 2011-16958 [Patent Document 2] International Publication No. 2014 / 189069 [Patent Document 3] Japanese Patent Application Laid-Open No. 2002-241676 Summary of the Invention [Problem to be solved by the invention]

[0008] To lower the viscosity of an antifouling coating, for example, by lowering the molecular weight of the resin, which is a coating film-forming component, the viscosity of the composition can be reduced even with a small amount of organic solvent. However, in this case, the initial wear rate of the coating film tends to be excessively fast, and the rate of wear thereafter tends to slow down, making it difficult to obtain stable antifouling properties over the long term. Thus, there is a trade-off between lowering the viscosity of an antifouling coating composition and achieving good wear rate of the antifouling coating film, and an antifouling coating composition that can achieve both of these has been desired.

[0009] An object of the present invention is to provide an antifouling coating composition that can form a coating film having an appropriate wear level to exhibit a long-term antifouling effect and that can keep the viscosity low, and a polymer that is suitable for obtaining the antifouling coating composition. [Means for solving the problem]

[0010] The present invention has the following aspects. [1] A (meth)acrylic copolymer (A) comprising a structural unit derived from a monomer (a) containing a metal atom M and a structural unit derived from a monomer (b) copolymerizable with the monomer (a), The monomer (a) has at least one of a structure represented by the following formula (I) and a structure represented by the following formula (II), the content of the metal atom M is 6.0% by mass or more relative to all structural units of the (meth)acrylic copolymer (A); The total solubility parameter (SP value) of the monomer (b) is 20.7 (J / cm 3 ) 1 / 2 That's all, The (meth)acrylic copolymer (A) has a weight average molecular weight of 1,000 to 4,000. -CO-OMO-CO- (I) -CO-OMR 0 (II) [In the formula, R 0 represents a monovalent organic acid residue, and M represents a divalent metal atom. [2] The (meth)acrylic copolymer according to [1], wherein the (meth)acrylic copolymer (A) has an acid value of 98 mgKOH / g or more. [3] The (meth)acrylic copolymer (A) has a coating hardness of 4.9 N / mm 2 The (meth)acrylic copolymer according to [1] or [2] above. [4] The (meth)acrylic copolymer according to any one of [1] to [3], wherein a 55% by mass solids solution containing the (meth)acrylic copolymer (A) as a solid content has a Gardner viscosity of Z3 or less at 25°C. [5] An antifouling coating composition comprising the (meth)acrylic copolymer (A) according to any one of the above [1] to [4]. [6] The antifouling coating composition according to [5], further comprising an antifouling agent. [7] The antifouling coating composition according to [6], wherein the antifouling agent comprises one or more selected from the group consisting of cuprous oxide, 4-bromo-2-(4-chlorophenyl)-5-(trifluoromethyl)-1H-pyrrole-3-carbonitrile, pyridine-triphenylborane, zinc pyrithione, copper pyrithione, and medetomidine. [8] The antifouling coating composition according to any one of [5] to [7], which contains a thermoplastic resin other than the (meth)acrylic copolymer (A). [9] The antifouling coating composition according to any one of [5] to [8], which contains a solid content of 72 mass % or more.

[10] The antifouling coating composition according to any one of [5] to [9], which has a viscosity of 5 Pa·s or less at 25°C as measured with a Brookfield viscometer when the solid content is 71% by mass. [Effects of the Invention]

[0011] According to the present invention, it is possible to provide an antifouling coating composition that can form a coating film having an appropriate degree of wear to exhibit a long-term antifouling effect and that can keep the viscosity low, and a polymer that is suitable for obtaining the antifouling coating composition. DETAILED DESCRIPTION OF THE INVENTION

[0012] Preferred embodiments of the present invention will be described below, but the present invention is not limited to these embodiments.

[0013] The following definitions of terms apply throughout the specification and claims. In this specification, "(meth)acrylate" is a general term for acrylate and methacrylate, "(meth)acrylic acid" is a general term for acrylic acid and methacrylic acid, "(meth)acryloyl group" is a general term for acryloyl group and methacryloyl group, "(meth)acrylonitrile" is a general term for acrylonitrile and methacrylonitrile, and "(meth)acrylamide" is a general term for acrylamide and methacrylamide. The term "(meth)acrylic copolymer" refers to a copolymer in which at least some of the constituent units are derived from a (meth)acrylic monomer. The (meth)acrylic copolymer may further contain constituent units derived from a monomer other than the (meth)acrylic monomer (for example, a vinyl monomer such as styrene). "(Meth)acrylic monomer" means a monomer having a (meth)acryloyl group. The term "structural unit" is a general term for an atomic group derived from one molecule of a monomer that is formed directly by polymerizing the monomer, and an atomic group obtained by chemically converting a part of the above atomic group.

[0014] In this specification, the solid content is measured by the following method. The measurement sample is dried at 105°C for 2 hours, and the heating residue is calculated from the mass before drying and the mass after drying using the following formula, and this value is taken as the solid content. Heating residue (mass%) = mass after drying / mass before drying x 100

[0015] In this specification, the weight average molecular weight (Mw) and number average molecular weight (Mn) of a polymer are polystyrene-equivalent molecular weights measured by gel permeation chromatography (GPC).

[0016] In this specification, the coating hardness is the coating hardness (Martens hardness) measured by the measurement method described below.

[0017] In this specification, the Gardner viscosity is measured by a method conforming to the measurement method specified in JIS K 5600-2-2:1999.

[0018] (Meth)acrylic copolymer (A) The (meth)acrylic copolymer (A) of this embodiment is composed of structural units derived from the monomer (a) and structural units derived from the monomer (b).

[0019] [Monomer (a)] The monomer (a) has at least one of a structure (I) represented by the following formula (I) and a structure (II) represented by the following formula (II). 0 represents a monovalent organic acid residue, and M represents a divalent metal atom. -CO-OMO-CO- (I) -CO-OMR 0 (II)

[0020] The structural unit derived from the monomer (a) has a carboxylate that forms an ionic bond with the divalent metal atom represented by M, and therefore contributes to the development of self-polishing properties. As the divalent metal atom represented by M, Zn, Cu, Mg or Ca is preferred, and Zn or Cu is more preferred, in terms of improving the water resistance of the coating film.

[0021] As a structural unit derived from the monomer (a) having the structure (I) (hereinafter also referred to as "monomer (aI)"), a structural unit (U1) represented by the following formula (1) is preferred. As the structural unit derived from the monomer (a) having the structure (II) (hereinafter also referred to as "monomer (a-II)"), the structural unit (U2) represented by the following formula (2) is preferred. The (meth)acrylic copolymer (A) preferably contains at least one unit selected from the group consisting of the structural unit (U1) and the structural unit (U2).

[0022] [ka]

[0023] In the formula, R 1 ~R 3 each independently represents a hydrogen atom or a methyl group, R32 represents an organic acid residue, and M represents a divalent metal atom.

[0024] Examples of monomer (aI) having structure (I) include zinc acrylate [(CH2=CHCOO)2Zn], zinc methacrylate [(CH2=C(CH3)COO)2Zn], copper acrylate [(CH2=CHCOO)2Cu], copper methacrylate [(CH2=C(CH3)COO)2Cu], magnesium acrylate [(CH2=CHCOO)2Mg], magnesium methacrylate [(CH2=C(CH3)COO)2Mg], calcium acrylate [(CH2=CHCOO)2Ca], calcium methacrylate [(CH2=C(CH3)COO)2Ca], and the like. In particular, zinc (meth)acrylate and copper (meth)acrylate are preferred from the viewpoint of water resistance of the coating film containing the (meth)acrylic copolymer (A). Any one of these may be used alone, or two or more may be used in combination.

[0025] R 0 or R 32 The organic acid residue represented by is the portion remaining after removing one proton from an organic acid (for example, the portion remaining after removing the proton from the carboxyl group of an organic carboxylic acid). The atom to which the removed proton was bonded in the remaining portion of the organic acid is ionic bonded to a divalent metal atom represented by M. The organic acid is preferably a carboxylic acid, and examples thereof include monocarboxylic acids such as monochloroacetic acid, monofluoroacetic acid, acetic acid, propionic acid, octylic acid, versatic acid, isostearic acid, palmitic acid, cresotic acid, α-naphthoic acid, β-naphthoic acid, benzoic acid, 2,4,5-trichlorophenoxyacetic acid, 2,4-dichlorophenoxyacetic acid, quinolinecarboxylic acid, nitrobenzoic acid, nitronaphthalenecarboxylic acid, pyruvic acid, naphthenic acid, abietic acid, and hydrogenated abietic acid. Of these, fatty acids (aliphatic monocarboxylic acids) having 1 to 20 carbon atoms are preferred, as they provide a highly durable coating film that can prevent cracking and peeling over a long period of time.

[0026] Examples of the monomer (a-II) having the structure (II) include the following compounds: Metal monochloroacetate (meth)acrylates such as magnesium monochloroacetate (meth)acrylate, calcium monochloroacetate (meth)acrylate, zinc monochloroacetate (meth)acrylate, and copper monochloroacetate (meth)acrylate; monofluoroacetate metal (meth)acrylates such as magnesium monofluoroacetate (meth)acrylate, calcium monofluoroacetate (meth)acrylate, zinc monofluoroacetate (meth)acrylate, and copper monofluoroacetate (meth)acrylate; metal acetate (meth)acrylates such as magnesium acetate (meth)acrylate, calcium acetate (meth)acrylate, zinc acetate (meth)acrylate, and copper acetate (meth)acrylate; metal propionate (meth)acrylates such as magnesium propionate (meth)acrylate, calcium propionate (meth)acrylate, zinc propionate (meth)acrylate, and copper propionate (meth)acrylate; Metal octylate (meth)acrylates such as magnesium octylate (meth)acrylate, calcium octylate (meth)acrylate, zinc octylate (meth)acrylate, and copper octylate (meth)acrylate; metal versatate (meth)acrylates such as magnesium versatate (meth)acrylate, calcium versatate (meth)acrylate, zinc versatate (meth)acrylate, and copper versatate (meth)acrylate; metal (meth)acrylate isostearate such as magnesium (meth)acrylate isostearate, calcium (meth)acrylate isostearate, zinc (meth)acrylate isostearate, and copper (meth)acrylate isostearate; metal palmitate (meth)acrylates such as magnesium palmitate (meth)acrylate, calcium palmitate (meth)acrylate, zinc palmitate (meth)acrylate, and copper palmitate (meth)acrylate; cresotonic acid metal (meth)acrylates such as magnesium cresotonic acid (meth)acrylate, calcium cresotonic acid (meth)acrylate, zinc cresotonic acid (meth)acrylate, and copper cresotonic acid (meth)acrylate; α-naphthoic acid metal (meth)acrylates such as α-naphthoic acid magnesium (meth)acrylate, α-naphthoic acid calcium (meth)acrylate, α-naphthoic acid zinc (meth)acrylate, and α-naphthoic acid copper (meth)acrylate; β-naphthoic acid metal (meth)acrylates such as β-naphthoic acid magnesium (meth)acrylate, β-naphthoic acid calcium (meth)acrylate, β-naphthoic acid zinc (meth)acrylate, and β-naphthoic acid copper (meth)acrylate; metal benzoate (meth)acrylates such as magnesium benzoate (meth)acrylate, calcium benzoate (meth)acrylate, zinc benzoate (meth)acrylate, and copper benzoate (meth)acrylate; 2,4,5-trichlorophenoxyacetic acid metal (meth)acrylates such as 2,4,5-trichlorophenoxyacetic acid magnesium (meth)acrylate, 2,4,5-trichlorophenoxyacetic acid calcium (meth)acrylate, 2,4,5-trichlorophenoxyacetic acid zinc (meth)acrylate, and 2,4,5-trichlorophenoxyacetic acid copper (meth)acrylate; 2,4-dichlorophenoxyacetic acid metal (meth)acrylates such as 2,4-dichlorophenoxyacetic acid magnesium (meth)acrylate, 2,4-dichlorophenoxyacetic acid calcium (meth)acrylate, 2,4-dichlorophenoxyacetic acid zinc (meth)acrylate, and 2,4-dichlorophenoxyacetic acid copper (meth)acrylate; metal quinoline carboxylate (meth)acrylates such as magnesium quinoline carboxylate (meth)acrylate, calcium quinoline carboxylate (meth)acrylate, zinc quinoline carboxylate (meth)acrylate, and copper quinoline carboxylate (meth)acrylate; Metal nitrobenzoate (meth)acrylates such as magnesium nitrobenzoate (meth)acrylate, calcium nitrobenzoate (meth)acrylate, zinc nitrobenzoate (meth)acrylate, and copper nitrobenzoate (meth)acrylate; metal nitronaphthalene carboxylate (meth)acrylates such as magnesium nitronaphthalene carboxylate, calcium nitronaphthalene carboxylate, zinc nitronaphthalene carboxylate, and copper nitronaphthalene carboxylate; Metal pyruvate (meth)acrylates such as magnesium pyruvate (meth)acrylate, calcium pyruvate (meth)acrylate, zinc pyruvate (meth)acrylate, and copper pyruvate (meth)acrylate. Any one of these may be used alone, or two or more may be used in combination.

[0027] The (meth)acrylic copolymer (A) may have both the structural unit (U1) and the structural unit (U2). When the (meth)acrylic copolymer (A) contains both the structural unit (U1) and the structural unit (U2), the ratio (molar ratio) of the structural unit (U1) to the structural unit (U2) in the (meth)acrylic copolymer (A), (U1) / (U2), is preferably 10 / 90 to 90 / 10, more preferably 20 / 80 to 80 / 20, and even more preferably 30 / 70 to 70 / 30. If this ratio is less than the upper limit, the viscosity of the polymer composition containing the (meth)acrylic copolymer (A) tends to decrease, whereas if it is more than the lower limit, the self-polishing properties of the coating film tend to be maintained for a long period of time.

[0028] [Method for producing monomer (a)] The monomer (a) may be a monomer produced by a known method or may be a commercially available monomer. Monomer (aI) can be obtained, for example, by reacting an inorganic metal compound containing a metal element corresponding to M in formula (I) with a carboxylic acid-containing polymerizable monomer such as (meth)acrylic acid in a diluent such as a solvent or a reactive diluent having a polymerizable unsaturated group such as an ethylenically unsaturated monomer. The mixture containing monomer (aI) obtained by this method has excellent compatibility with solvents and other monomers, and polymerization can be easily carried out. The reaction to obtain the monomer (aI) is preferably carried out in the presence of water, and the content of water in the reaction product is preferably in the range of 0.01 to 30% by mass. Examples of the inorganic metal compounds include oxides, hydroxides, chlorides, etc. of metals selected from Zn, Cu, Mg, and Ca.

[0029] The monomer (a-II) is, for example, a polymerizable compound containing an inorganic metal compound containing a metal element corresponding to M in the formula (II), a carboxylic acid-containing polymerizable monomer such as (meth)acrylic acid, and an organic acid residue R 0 and an organic acid corresponding to the above in a diluent such as a solvent or a reactive diluent having a polymerizable unsaturated group such as an ethylenically unsaturated monomer. Examples of the inorganic metal compound include the same inorganic metal compounds as those used to obtain the monomer (aI).

[0030] The monomer mixture containing the monomer (aI) and the monomer (a-II) is an inorganic metal compound containing a metal element corresponding to M in the formula (I) and the formula (II), a carboxylic acid-containing polymerizable monomer such as (meth)acrylic acid, and an organic acid residue R in the formula (II). 0 and an organic acid corresponding to the above in a diluent such as a solvent or a reactive diluent having a polymerizable unsaturated group such as an ethylenically unsaturated monomer. In this case, the organic acid residue R in formula (II) 0 The amount of the organic acid corresponding to the above is preferably 0.01 to 3 times by mole, more preferably 0.01 to 0.95 times by mole, and even more preferably 0.1 to 0.7 times by mole, relative to the amount of the inorganic metal compound. The organic acid residue R in formula (II) 0When the amount of organic acid used corresponding to the above is equal to or greater than the lower limit, precipitation of solids is suppressed in the production process of a monomer mixture containing monomer (aI) and monomer (a-II), and the self-polishing property and crack resistance of the resulting coating film become better, whereas when the amount is equal to or less than the upper limit, the antifouling property of the resulting coating film tends to be maintained for a longer period of time.

[0031] [Monomer (b)] The monomer (b) is not particularly limited as long as it is a monomer copolymerizable with the monomer (a). Monomer (b) may be one type or two or more types. The total Sp value of the monomer (b) is 20.7 (J / cm 3 ) 1 / 2 The value is selected so that the value is equal to or greater than the above. When the total SP value of the monomers (b) is equal to or greater than the lower limit, the antifouling property is excellent. The upper limit of the SP value is not particularly limited, but from the viewpoint of maintaining the antifouling property for a long period of time, it is preferred that the SP value is 22.4 (J / cm 3 ) 1 / 2 Preferably, 21.57 (J / cm 3 ) 1 / 2 The following is more preferred:

[0032] Examples of the monomer (b) include the following compounds: Substituted or unsubstituted alkyl (meth)acrylates [for example, methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, i-propyl (meth)acrylate, n-butyl (meth)acrylate, i-butyl (meth)acrylate, t-butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, lauryl (meth)acrylate, stearyl (meth)acrylate, behenyl (meth)acrylate, 1-methyl-2-methoxyethyl (meth)acrylate, 2-methoxyethyl (meth)acrylate, 3-methoxybutyl (meth)acrylate, 3-methyl-3-methoxybutyl (meth)acrylate], substituted or unsubstituted aralkyl (meth)acrylates [for example, , benzyl (meth)acrylate, m-methoxyphenylethyl (meth)acrylate, p-methoxyphenylethyl (meth)acrylate], substituted or unsubstituted aryl (meth)acrylates [for example, phenyl (meth)acrylate, m-methoxyphenyl (meth)acrylate, p-methoxyphenyl (meth)acrylate, o-methoxyphenylethyl (meth)acrylate], substituted or unsubstituted alicyclic (meth)acrylates [for example, isobornyl (meth)acrylate, cyclohexyl (meth)acrylate, trifluoroethyl (meth)acrylate, perfluorooctyl (meth)acrylate, perfluorocyclohexyl (meth)acrylate], and other hydrophobic group-containing (meth)acrylic acid ester monomers; Oxyethylene group-containing (meth)acrylic acid ester monomers such as 2-methoxyethyl (meth)acrylate, 2-ethoxyethyl (meth)acrylate, 2-butoxyethyl (meth)acrylate, butoxydiethylene glycol (meth)acrylate, methoxytriethylene glycol (meth)acrylate, methoxypolyethylene glycol (meth)acrylate, phenoxyethyl (meth)acrylate, and 2-(2-ethylhexaoxy)ethyl (meth)acrylate; hydroxyl group-containing (meth)acrylic acid ester monomers such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, and glycerol (meth)acrylate; Terminally alkoxyallylated polyether monomers such as methoxy polyethylene glycol allyl ether, methoxy polypropylene glycol allyl ether, butoxy polyethylene glycol allyl ether, butoxy polypropylene glycol allyl ether, methoxy polyethylene glycol-polypropylene glycol allyl ether, and butoxy polyethylene glycol-polypropylene glycol allyl ether; Epoxy group-containing vinyl monomers such as glycidyl (meth)acrylate, α-ethyl glycidyl acrylate, and 3,4-epoxybutyl (meth)acrylate; primary or secondary amino group-containing vinyl monomers such as butylaminoethyl (meth)acrylate and (meth)acrylamide; tertiary amino group-containing vinyl monomers such as dimethylaminoethyl (meth)acrylate, diethylaminoethyl (meth)acrylate, dimethylaminopropyl (meth)acrylate, dimethylaminobutyl (meth)acrylate, dibutylaminoethyl (meth)acrylate, dimethylaminoethyl (meth)acrylamide, and dimethylaminopropyl (meth)acrylamide; Heterocyclic basic monomers such as vinylpyrrolidone, vinylpyridine, and vinylcarbazole; Trimethylsilyl (meth)acrylate, triethylsilyl (meth)acrylate, tri-n-propylsilyl (meth)acrylate, tri-n-butylsilyl (meth)acrylate, tri-n-amylsilyl (meth)acrylate, tri-n-hexylsilyl (meth)acrylate, tri-n-octylsilyl (meth)acrylate, tri-n-dodecylsilyl (meth)acrylate, triphenylsilyl (meth)acrylate, tri-p-methylphenylsilyl (meth)acrylate, tribenzylsilyl (meth)acrylate, triisopropylsilyl (meth)acrylate, triisobutylsilyl (meth)acrylate, tri-s-butylsilyl (meth)acrylate, tri-2-methylisopropylsilyl (meth)acrylate, tri-t-butylsilyl (meth)acrylate, ethyldimethylsilyl (meth)acrylate, n-butyldimethylsilyl (meth) Organosilyl group-containing vinyl monomers such as acrylate, diisopropyl-n-butylsilyl (meth)acrylate, n-octyldi-n-butylsilyl (meth)acrylate, diisopropylstearylsilyl (meth)acrylate, dicyclohexylphenylsilyl (meth)acrylate, t-butyldiphenylsilyl (meth)acrylate, lauryldiphenylsilyl (meth)acrylate, triisopropylsilylmethyl maleate, triisopropylsilylamyl maleate, tri-n-butylsilyl-n-butyl maleate, t-butyldiphenylsilyl methyl maleate, t-butyldiphenylsilyl-n-butyl maleate, triisopropylsilylmethyl fumarate, triisopropylsilylamyl fumarate, tri-n-butylsilyl-n-butyl fumarate, t-butyldiphenylsilyl methyl fumarate, and t-butyldiphenylsilyl-n-butyl fumarate; Vinyl monomers containing an acid anhydride group, such as maleic anhydride and itaconic anhydride; Methacrylic acid, acrylic acid, crotonic acid, vinylbenzoic acid, fumaric acid, itaconic acid, maleic acid, citraconic acid, monomethyl maleate, monoethyl maleate, monobutyl maleate, monooctyl maleate, monomethyl itaconate, monoethyl itaconate, monobutyl itaconate, monooctyl itaconate, monomethyl fumarate, monoethyl fumarate, monobutyl fumarate, monooctyl fumarate, monoethyl citraconic acid, monohydroxyethyl tetrahydrophthalate (meth)acrylate, tetrahydrophthalic acid Carboxy group-containing ethylenically unsaturated monomers such as monohydroxypropyl phthalate (meth)acrylate, monohydroxybutyl tetrahydrophthalate (meth)acrylate, monohydroxyethyl phthalate (meth)acrylate, monohydroxypropyl phthalate (meth)acrylate, monohydroxyethyl succinate (meth)acrylate, monohydroxypropyl succinate (meth)acrylate, monohydroxyethyl maleate (meth)acrylate, and monohydroxypropyl maleate (meth)acrylate; unsaturated dicarboxylic acid diester monomers such as dimethyl maleate, dibutyl maleate, dimethyl fumarate, dibutyl fumarate, dibutyl itaconate, and diperfluorocyclohexyl fumarate; Cyano group-containing vinyl monomers such as acrylonitrile and methacrylonitrile; vinyl ether monomers such as alkyl vinyl ethers [e.g., ethyl vinyl ether, propyl vinyl ether, butyl vinyl ether, hexyl vinyl ether, 2-ethylhexyl vinyl ether, etc.] and cycloalkyl vinyl ethers [e.g., cyclohexyl vinyl ether, etc.]; vinyl ester monomers such as vinyl acetate, vinyl propionate, vinyl butyrate, and vinyl benzoate; Aromatic vinyl monomers such as styrene, vinyl toluene, and α-methyl styrene; Halogenated olefins such as vinyl chloride, vinylidene chloride, vinyl fluoride, vinylidene fluoride, and chlorotrifluoroethylene; Polyfunctional monomers such as ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, 1,4-butanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, 1,10-decanediol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol hexa(meth)acrylate, allyl methacrylate, triallyl cyanurate, diallyl maleate, and polypropylene glycol diallyl ether.

[0033] In particular, a monofunctional monomer having one ethylenically unsaturated bond is preferred, since this makes it easier to obtain a (meth)acrylic copolymer (A) with a low viscosity even when the solid content is high. One or more of these can be selected and used so as to obtain the desired Sp value.

[0034] In addition, since this improves the block resistance, it is preferable that the monomer (b) contains a monomer (b1) having a Tg of 50° C. or higher. The content of the structural units derived from the monomer (b1) is preferably 10 to 50 mass% relative to the total mass (100 mass%) of the structural units derived from the monomer (b). Here, good resistance to wood blocks means that when a hard substrate such as a wood block comes into contact with the coating film, no marks are left.

[0035] Examples of the monomer (b1) having a Tg of 50° C. or higher include the following compounds: hydrophobic group-containing methacrylic acid ester monomers such as substituted or unsubstituted alkyl methacrylates [e.g., methyl methacrylate, ethyl methacrylate, i-butyl methacrylate, t-butyl methacrylate], benzyl methacrylate, phenyl methacrylate, substituted or unsubstituted alicyclic (meth)acrylates [e.g., isobornyl methacrylate, cyclohexyl methacrylate, isobornyl acrylate], perfluorooctyl methacrylate, and perfluorocyclohexyl methacrylate; Hydroxyl group-containing (meth)acrylic acid ester monomers such as 2-hydroxyethyl methacrylate and 2-hydroxypropyl methacrylate; styrene; and the like, monomers described in POLYMER HANDBOOK, FOURTH EDITION (J. Brandrup et al.) can be used.

[0036] [Content] The content of the metal atom M derived from the monomer (a) relative to all constituent units of the (meth)acrylic copolymer (A) is 6.0 mass% or more, preferably 6.3 mass% or more, more preferably 7.0 mass% or more, and even more preferably 7.4 mass% or more. When the content of the metal atom M is equal to or more than the lower limit, the coating film containing the (meth)acrylic copolymer (A) has excellent wear resistance and static soiling resistance.

[0037] The content of the structural units derived from the monomer (a) relative to all structural units of the (meth)acrylic copolymer (A) is preferably 1 to 40 mass%, more preferably 5 to 30 mass%, and the total content of the structural units derived from the monomer (a) and the structural units derived from the monomer (b) relative to all structural units of the (meth)acrylic copolymer (A) is 100 mass%. When the content of the structural units derived from the monomer (a) is equal to or greater than the lower limit, the long-term self-polishing property of the coating film containing the (meth)acrylic copolymer (A) is superior. When the content is equal to or less than the upper limit, the storage stability of the antifouling coating composition, the adhesion of the coating film formed, the water resistance in seawater, and the balance between hardness and crack resistance tend to be improved. The content (mass %) of each structural unit in the (meth)acrylic copolymer (A) can be measured by known methods such as gas chromatography, high performance liquid chromatography, and nuclear magnetic resonance spectroscopy.

[0038] The combined content of the structural units (U1) and (U2) relative to the total mass of the structural units derived from the monomer (a) is preferably 50% by mass or more, more preferably 80% by mass or more, and may be 100% by mass. When the total content of the structural units (U1) and (U2) is at least the above lower limit, the long-term self-polishing properties of the coating film containing the (meth)acrylic copolymer (A) will be even better.

[0039] [Characteristics of (meth)acrylic copolymer (A)] [Molecular weight] The weight average molecular weight (Mw) of the (meth)acrylic copolymer (A) is 1,000 to 4,000, and preferably 2,000 to 3,500. When the weight-average molecular weight of the (meth)acrylic copolymer (A) is equal to or less than the upper limit, it is easy to obtain an antifouling coating composition with a low viscosity even when the solid content is high. Therefore, it is easy to obtain an antifouling coating composition or an antifouling coating composition with a high coating solid content and a low amount of VOCs, which are required to be reduced in solvents due to their impact on the environment, etc. Furthermore, when the weight-average molecular weight of the (meth)acrylic copolymer (A) is equal to or less than the upper limit, the coating film formed has excellent antifouling properties. When the weight average molecular weight of the (meth)acrylic copolymer (A) is at least the lower limit, the hardness and durability of the coating film that is formed are superior.

[0040] The number average molecular weight (Mn) of the (meth)acrylic copolymer (A) is preferably from 500 to 2,500, more preferably from 750 to 2,000. The polydispersity (Mw / Mn) of the (meth)acrylic copolymer (A) is preferably from 1.5 to 5.0, more preferably from 2.2 to 3.0.

[0041] [Acid value] The acid value of the (meth)acrylic copolymer (A) is preferably 98 mgKOH / g or more, more preferably 107 mgKOH / g or more, and is preferably 200 mgKOH / g or less, more preferably 150 mgKOH / g or less. When the acid value of the (meth)acrylic copolymer (A) is equal to or greater than the lower limit, an optimum degree of wear tends to be obtained, and when it is equal to or less than the upper limit, water resistance tends to be good.

[0042] [Viscosity (Gardner viscosity)] The Gardner viscosity of a resin solution having a solid content of 55 mass % in which the (meth)acrylic copolymer (A) is the solid content is preferably Z3 or less at 25° C. The Gardner viscosity is preferably Z1 or less, and more preferably X or less. When the Gardner viscosity of the (meth)acrylic copolymer (A) is equal to or lower than the upper limit, the amount of dilution solvent required when preparing the coating material is small, and an antifouling coating material composition with a low VOC content is easily obtained. The lower limit of the Gardner viscosity is not particularly limited, but is preferably D or higher in terms of preventing paint sagging during application.

[0043] [Coating film hardness (Martens hardness)] The coating hardness (Martens hardness) of the (meth)acrylic copolymer (A) is 4.9 N / mm 2 More than 5.4N / mm is preferable. 2 More preferably, 5.8N / mm 2 The above is even more preferable. When the coating film hardness (Martens hardness) of the (meth)acrylic copolymer (A) is at least the lower limit, a coating film having excellent coating film hardness and coating film physical properties and an appropriate wear degree for exhibiting a long-term antifouling effect can be formed. When the coating film hardness is at most the upper limit, crack resistance tends to be good.

[0044] [Method for producing (meth)acrylic copolymer (A)] (Method for producing (meth)acrylic copolymer (A)) Examples of methods for producing the (meth)acrylic copolymer (A) include known methods including the following Method 1 and Method 2. (Method 1) A method of copolymerizing a mixture of a monomer (a) containing a metal atom M and a monomer (b). (Method 2) A method of introducing a metal atom M into a precursor polymer (A') obtained by copolymerizing a mixture of a precursor monomer (a') having a carboxy group and a monomer (b). As a method of introducing the metal atom M, for example, a method of reacting the carboxy group of the precursor polymer (A') with a metal oxide such as zinc oxide can be used.

[0045] Known polymerization methods such as solution polymerization, suspension polymerization, bulk polymerization, emulsion polymerization, etc. can be applied to Method 1 and Method 2. Solution polymerization may be preferable in terms of productivity and coating performance.

[0046] In particular, it is preferable to produce the (meth)acrylic copolymer (A) by Method 1, since the antifouling coating composition containing the (meth)acrylic copolymer (A) has excellent storage stability and the antifouling coating film can maintain stable self-polishing properties for a long period of time.

[0047] (solvent) Examples of the solvent used in producing the (meth)acrylic copolymer (A) include those exemplified below as the solvent (S) that can be contained in the antifouling coating composition. Note that it is preferable to contain an alcohol, as this improves the stability during production of the (meth)acrylic copolymer (A).

[0048] In producing the (meth)acrylic copolymer (A), the copolymerization reaction may be carried out by a known method using a known polymerization initiator. For example, a method may be used in which a monomer mixture consisting of the monomer (aI) and / or the monomer (a-II) and the monomer (b) is reacted in a solvent in the presence of a radical polymerization initiator at a reaction temperature of 60 to 180°C for 2 to 14 hours. In this case, a chain transfer agent may be used as necessary.

[0049] Known radical polymerization initiators can be used, including, for example, azo compounds such as 2,2'-azobisisobutyronitrile, 2,2'-azobis(2-methylbutyronitrile), and 2,2'-azobis(2,4-dimethylvaleronitrile); and organic peroxides such as lauryl peroxide, benzoyl peroxide, cumene hydroperoxide, lauryl peroxide, di-t-butyl peroxide, t-butylperoxy-2-ethylhexanoate, and t-butyl peroctoate. The content of the polymerization initiator is not particularly limited and can be set appropriately.

[0050] Known chain transfer agents can be used, including, for example, mercaptans such as n-dodecyl mercaptan, cobalt chain transfer agents, thioglycolic acid esters such as octyl thioglycolate, α-methylstyrene dimer, and terpinolene. The content of the chain transfer agent is not particularly limited and can be set appropriately.

[0051] A monomer mixture consisting of monomer (a) and monomer (b) is reacted in a solvent in the presence of a radical polymerization initiator at a reaction temperature of 60 to 180°C for 2 to 14 hours to obtain a liquid resin composition containing a (meth)acrylic copolymer (A). If the solid content relative to the total mass of the resulting resin composition is too low, the viscosity will be too high, resulting in a solution with no fluidity after polymerization and making it difficult to remove. If the solid content is too high, it will be difficult to reduce the VOC of the paint when it is made into a paint. The solid content can be set within a range that does not cause these problems. For example, 47 to 70 mass% is preferable, and 50 to 60 mass% is more preferable.

[0052] <Antifouling coating composition> The antifouling coating composition of this embodiment contains the (meth)acrylic copolymer (A) of this embodiment described above, and may optionally contain an antifouling agent (F), a thermoplastic resin other than the (meth)acrylic copolymer (A), a solvent (S), and other optional components.

[0053] [Anti-fouling agent (F)] The antifouling coating composition preferably further contains an antifouling agent (F). The antifouling agent (F) includes inorganic antifouling agents, organic antifouling agents, etc., and one or more of them can be appropriately selected and used depending on the required performance. Examples include copper-based antifouling agents such as cuprous oxide, copper thiocyanate, and copper powder, compounds of other metals (lead, zinc, nickel, etc.), amine derivatives such as diphenylamine, nitrile compounds, benzothiazole compounds, maleimide compounds, and pyridine compounds such as zinc pyrithione and copper pyrithione.

[0054] More specifically, examples of the antifouling agent (F) include 4-bromo-2-(4-chlorophenyl)-5-(trifluoromethyl)-1H-pyrrole-3-carbonitrile, manganese ethylenebisdithiocarbamate, zinc dimethyldithiocarbamate, 2-methylthio-4-t-butylamino-6-cyclopropylamino-s-triazine, 2,4,5,6-tetrachloroisophthalonitrile, N,N-dimethyldichlorophenylurea, zinc ethylenebisdithiocarbamate, copper rhodanide, 4,5-dichloro-2-n-octyl-3(2H)-isothiazolone, N-(fluorodichloromethylthio)phthalimide, N,N'-dimethyl-N'-phenyl-(N-fluorodichloro ... (methylthio)sulfamide, 2-pyridinethiol-1-oxide zinc salt (pyrithione zinc), 2-pyridinethiol-1-oxide copper salt (pyrithione copper), tetramethylthiuram disulfide, Cu-10%Ni solid solution alloy, 2,4,6-trichlorophenylmaleimide 2,3,5,6-tetrachloro-4-(methylsulfonyl)pyridine, 3-iodo-2-propynyl butylcarbamate, diiodomethyl para-trisulfone, bisdimethyldithiocarbamoylzinc ethylene bisdithiocarbamate, phenyl(bispyridyl)bismuth dichloride, 2-(4-thiazolyl)-benzimidazole, medetomidine, pyridine-triphenylborane, and the like.

[0055] In terms of good antifouling performance, it is preferable to contain at least one selected from the group consisting of cuprous oxide, 4-bromo-2-(4-chlorophenyl)-5-(trifluoromethyl)-1H-pyrrole-3-carbonitrile, pyridine-triphenylborane, zinc pyrithione, copper pyrithione, and medetomidine.

[0056] Furthermore, at least two selected from the group consisting of cuprous oxide, 4-bromo-2-(4-chlorophenyl)-5-(trifluoromethyl)-1H-pyrrole-3-carbonitrile, zinc pyrithione, copper pyrithione, and medetomidine may be combined.

[0057] [Thermoplastic resin other than the (meth)acrylic copolymer (A)] The other thermoplastic resins than the (meth)acrylic copolymer (A) are thermoplastic resins that have neither the structure (I) nor the structure (II).

[0058] When the antifouling coating composition contains a thermoplastic resin in addition to the acrylic copolymer (A), the coating film properties such as crack resistance and water resistance are improved. Other thermoplastic resins include, for example: Chlorinated paraffin; chlorinated polyolefins such as chlorinated rubber, chlorinated polyethylene, and chlorinated polypropylene; polyvinyl ether; polypropylene sebacate; partially hydrogenated terphenyl; polyvinyl acetate; poly(meth)acrylic acid alkyl esters such as methyl (meth)acrylate copolymers, ethyl (meth)acrylate copolymers, propyl (meth)acrylate copolymers, butyl (meth)acrylate copolymers, and cyclohexyl (meth)acrylate copolymers; polyether polyols; alkyd resins; polyester resins; vinyl chloride resins such as vinyl chloride-vinyl acetate copolymers, vinyl chloride-vinyl propionate copolymers, vinyl chloride-isobutyl vinyl ether copolymers, vinyl chloride-isopropyl vinyl ether copolymers, and vinyl chloride-ethyl vinyl ether copolymers; silicone oils; waxes; oils and fats that are solid at room temperature other than wax, oils and fats that are liquid at room temperature such as castor oil, and refined products thereof; petrolatum; liquid paraffin; rosin, hydrogenated rosin, naphthenic acid, fatty acids, and their divalent metal salts; etc. Examples of waxes include waxes derived from animals such as beeswax; waxes derived from plants; semi-synthetic waxes such as amide waxes; and synthetic waxes such as polyethylene oxide waxes. Among the above, chlorinated paraffin, wax, polyvinyl ether, polyether polyol, rosin, and vinyl chloride-isobutyl vinyl ether copolymer are preferred, and chlorinated paraffin, amide wax, oxidized polyethylene wax, polyvinyl ether, rosin, and vinyl chloride-isobutyl vinyl ether copolymer are particularly preferred. These thermoplastic resins may be used alone or in combination of two or more.

[0059] Solvent The antifouling coating composition may further contain a solvent (S). The solvent (S) is not particularly limited as long as it can dissolve the (meth)acrylic copolymer (A). Examples of the solvent include monohydric alcohols such as methanol, ethanol, isopropanol, n-butanol, and propylene glycol monomethyl ether; polyhydric alcohols such as ethylene glycol and 1,2-propylene glycol; ketones such as acetone, methyl ethyl ketone, and acetylacetone; ethers such as methyl ethyl ether and dioxane; glycol ethers such as ethylene glycol monoethyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol mono-n-propyl ether, ethylene glycol dimethyl ether, diethylene glycol monomethyl ether, diethylene glycol dimethyl ether, and dipropylene glycol monopropyl ether; glycol acetates such as ethylene glycol monoacetate, ethylene glycol diacetate, and ethylene glycol monomethyl ether acetate; aliphatic hydrocarbons such as n-pentane and n-hexane; and aromatic hydrocarbons such as toluene, xylene, and solvent naphtha. These may be used alone or in combination of two or more.

[0060] [Other optional ingredients] Other optional components may include silicon compounds such as dimethylpolysiloxane and silicone oil, and fluorine-containing compounds such as fluorinated hydrocarbons, for the purpose of imparting lubricity to the coating surface and preventing the adhesion of organisms. Furthermore, various pigments, antifoaming agents, pigment dispersants, leveling agents, anti-sagging agents, matting agents, ultraviolet absorbers, antioxidants, heat resistance improvers, slip agents, preservatives, plasticizers, viscosity control agents, etc. may also be contained.

[0061] [Content] The total solid content (paint solid content) relative to the total mass of the antifouling coating composition is preferably 72 mass % or more, more preferably 72 to 90 mass %, and even more preferably 74 to 80 mass %. If the paint solids content is equal to or greater than the lower limit, the VOC of the paint can be reduced, and if it is equal to or less than the upper limit, the paint viscosity will be suitable for application. In this specification, the solid content of the paint is a value measured by the same method as that for the solid content of the antifouling paint composition.

[0062] The total content of components other than the (meth)acrylic copolymer (A) (the antifouling agent (F), other thermoplastic resins, and other optional components) contained in the solid content of the antifouling coating composition is not particularly limited, but is preferably 50 to 400 parts by mass, more preferably 100 to 350 parts by mass, per 100 parts by mass of the (meth)acrylic copolymer (A).

[0063] When the antifouling coating composition contains an antifouling agent (F), the content of the antifouling agent (F) is not particularly limited, but is preferably 10 to 200 parts by mass, more preferably 50 to 150 parts by mass, per 100 parts by mass of the (meth)acrylic copolymer (A). When the content of the antifouling agent (F) in the antifouling coating composition is equal to or greater than the lower limit, the antifouling effect of the coating film formed is superior, and when it is equal to or less than the upper limit, the coating film properties are superior.

[0064] When the antifouling coating composition contains another thermoplastic resin, the content of the other thermoplastic resin is not particularly limited, but is preferably 0.1 to 50 parts by mass, more preferably 0.1 to 10 parts by mass, per 100 parts by mass of the (meth)acrylic copolymer (A). If the content of the thermoplastic resin in the antifouling coating composition is at least the lower limit, the coating film properties such as crack resistance and water resistance will be better, and if it is at most the upper limit, the hydrolysis resistance will be better.

[0065] [Physical Properties] [B-type viscosity of antifouling coating composition] The viscosity of the antifouling coating composition measured with a Brookfield viscometer at 25°C (also referred to as Brookfield viscosity) is preferably 0.5 to 10 Pa·s, more preferably 0.75 to 7.5 Pa·s, and more preferably 1 to 5 Pa·s. When the Brookfield viscosity of the antifouling coating composition is at least the lower limit and at most the upper limit, the coating properties are good.

[0066] The viscosity of the antifouling coating composition can be adjusted by the viscosity of the (meth)acrylic copolymer (A) or the resin composition containing the (meth)acrylic copolymer (A), the amount of solvent added, and the like. For example, when the total solid content (paint solid content) relative to the total mass of the antifouling coating composition is 71 mass %, the Brookfield viscosity is preferably 5 Pa·s or less.

[0067] [Method of manufacturing antifouling coating composition] The antifouling coating composition of the present invention can be prepared by further adding an antifouling agent (F), other components (Z-2), and a solvent (S) to the antifouling coating composition of the present invention, if necessary, and mixing them.

[0068] <Use of antifouling coating composition> The antifouling coating composition of this embodiment can be used to form a coating film (antifouling coating film) on the surface of a substrate such as a ship, various fishing nets, port facilities, oil fences, bridges, underwater structures such as an undersea base, etc. A coating film using the antifouling coating composition of this embodiment can be formed on the surface of a substrate directly or via an undercoat film. The undercoat film can be formed using a wash primer, a primer such as a chlorinated rubber or epoxy primer, an intermediate paint, or the like.

[0069] <Coating film> [Method of manufacturing antifouling coating film] The coating film can be formed by a known method, for example, by applying the antifouling coating composition to the surface of a substrate or onto a base coating film on the substrate by means of brush coating, spray coating, roller coating, immersion coating, or the like, and then drying to form a coating film. The amount of antifouling coating composition to be applied can generally be set to an amount that will result in a dry coating film thickness (dry film thickness) of 10 to 400 μm. The coating film can usually be dried at room temperature, and may be dried by heating as required.

[0070] <Action and effect> The antifouling coating film of this embodiment contains a (meth)acrylic copolymer (A). The (meth)acrylic copolymer (A) exhibits self-polishing properties due to its Structure I or Structure II (a structure having a carboxylate ionically bonded to a metal atom M). That is, when a coating film obtained from the antifouling coating composition of the present invention comes into contact with seawater, Structure I or Structure II is hydrolyzed to generate a carboxyl group, causing the coating film to dissolve in seawater. Therefore, the surface of the coating film gradually dissolves (wears) when it comes into contact with seawater, resulting in surface renewal (self-polishing). In particular, when the antifouling coating film contains an antifouling agent, the agent is always exposed on the surface of the coating film, and an excellent antifouling effect is exhibited for a long period of time. Furthermore, this coating film has excellent hardness and water resistance, and is less susceptible to damage or peeling that would reduce the antifouling effect. Furthermore, the degree of wear can be adjusted to an optimum level so that the excellent antifouling effect can be stably maintained over a long period of time.

[0071] According to this embodiment, for example, an antifouling coating film can be obtained that exhibits a degree of wear of 5 to 50 μm / M in the coating wear test (3 months) described in the Examples below. If the degree of wear is 5 μm / M or more, sufficient self-polishing properties can be obtained. If the degree of wear is 50 μm / M or less, good long-term antifouling properties can be obtained.

[0072] Furthermore, since the (meth)acrylic copolymer (A) has a low viscosity, the antifouling coating composition of this embodiment can be produced without adding a solvent during production of the antifouling coating composition, and the antifouling coating composition can be well mixed with the antifouling agent or the like without adding a solvent or even with only a small amount of solvent added. Therefore, an antifouling coating composition with a low VOC content can be produced. [Example]

[0073] The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited to these examples. In the examples, "parts" means "parts by mass."

[0074] <Measurement and evaluation methods> (Solid content (heated residue)) 0.50 g of sample (resin composition or coating composition) was weighed into an aluminum dish, and 3 mL of toluene was added with a dropper and spread evenly across the bottom of the dish for pre-drying. Pre-drying is a process in which the sample is spread over the entire dish to facilitate the evaporation of the solvent during main drying. In pre-drying, the sample and toluene were heated and dissolved in a water bath at 70-80°C, and then evaporated to dryness. After pre-drying, main drying was carried out for 2 hours in a hot air dryer at 105°C. The solid content (heating residue) was calculated from the mass of the sample before pre-drying (mass before drying) and the mass after main drying (mass after drying) using the following formula. Solid content (mass%) = mass after drying (g) / mass before drying (g) × 100

[0075] (Weight average molecular weight (Mw), number average molecular weight (Mn)) The weight-average molecular weight (Mw) and number-average molecular weight (Mn) of the polymer were measured using gel permeation chromatography (GPC) (Tosoh Corporation, HLC-8220) with DMF (N,N-dimethylformamide) as the eluent. The columns used were TSKgel α-M (Tosoh Corporation, 7.8 mm × 30 cm) and TSKguard column α (Tosoh Corporation, 6.0 mm × 4 cm). A calibration curve was prepared using F288 / F1 / F28 / F80 / F40 / F20 / F2 / A1000 (Tosoh Corporation, standard polystyrene) and styrene monomer.

[0076] (Solubility parameter (SP value)) The total solubility parameter (SP value) of the monomer (b) was determined by the following method. The solubility parameters were calculated using the Fedors method described in "Solubility Parameter Application Case Studies" published by Johokko Co., Ltd. The calculation results were MMA (SP value 20.32), EA (SP value 20.87), and MTA (SP value 20.78).

[0077] (acid number) The acid value of the (meth)acrylic copolymer (A) was calculated as follows. The resin composition obtained in each manufacturing example was used as the measurement sample. Approximately 0.5 g of the measurement sample was accurately weighed into a beaker (A (g)), and 50 mL of a toluene / 95% ethanol solution was added. A few drops of phenolphthalein were added, and the sample was titrated with a 0.5 M potassium hydroxide solution (titer = B (mL), titer of the potassium hydroxide solution = f). A blank measurement was performed in the same manner (titer = C (mL)), and the titer was calculated according to the following formula. Acid value (mgKOH / g) = {(BC) × 0.2 × 56.11 × f} / A / solids

[0078] (Gardner viscosity) The resin composition obtained in each production example was used as a measurement sample. A measurement sample was placed in a dried Gardner bubble viscosity tube (hereinafter simply referred to as "viscosity tube") up to the indicator line and then plugged with a cork. The viscosity tube containing the sample was immersed vertically in a thermostatic water bath adjusted to a specified temperature (25.0±0.5°C) for at least 2 hours to keep the sample at a constant temperature. The viscosity tube containing the sample and the reference tube were simultaneously rotated 180°, and the viscosity (Gardner viscosity) was determined by comparing the bubble rise rate of the sample with that of the reference tube.

[0079] (Coating film hardness) The resin compositions obtained in each production example were used as measurement samples. The measurement samples were applied to glass substrates using a 500 μm applicator so that the dry film thickness was 80 to 150 μm, and the coating was dried at 25°C for one week to obtain test panels with coating films. The coating film hardness (Martens hardness) of the test panels was measured at 25°C using an ultra-microhardness tester (manufactured by Fisher Instruments, product name: HM2000). The measurement conditions were: dQRST(F) / dt = constant, F (test force) = 10 mN / 10 seconds, C (maximum load creep time) = 5 seconds, maximum indentation load = 10 mN, maximum indentation depth = 6 μm. The coating hardness (Martens hardness) was measured at three different points on the coating of the test plate, and the average value was taken as the hardness of the coating.

[0080] (B type viscosity) The coating composition obtained in each example was used as a measurement sample, and the Brookfield viscosity was measured by the following method. The measurement sample was stored at 25°C for 2 hours and then measured using a Brookfield viscometer.

[0081] (Paint film wear test) The coating composition obtained in each example was used as a measurement sample, and the degree of wear was measured by the following method. The measurement sample was applied to a 50 mm x 50 mm x 2 mm (thickness) hard vinyl chloride plate with an applicator to a dry film thickness of 120 μm, and then dried to form a coating film, obtaining a test plate. This test plate was attached to a rotating drum placed in seawater and rotated at a peripheral speed of 7.7 m / s (15 knots). This condition was maintained for three months, and the coating film thickness (μm) three months after installation was measured. From the measured film thickness, the consumed film thickness after three months (120 μm - measured film thickness) was calculated, and this value was used as the consumption rate. The consumption rate is preferably within the range of 5 to 50 μm / M.

[0082] (Static stain resistance) The coating composition obtained in each example was used as a measurement sample, and the static antifouling properties were evaluated by the following method. The test sample was applied with a brush to a sandblasted steel plate that had previously been coated with an anti-rust paint so that the dry film thickness was 200 to 300 μm, and then dried to form a coating film to obtain a test plate. After leaving this test plate in the sea for 3 months, the ratio of the area where marine organisms had attached to the total area of ​​the coating (the area of ​​marine organism attachment) was measured, and the static antifouling properties were evaluated according to the following criteria. ◎: The area of ​​adhesion of marine organisms is less than 10%. ○: The area of ​​adhesion of marine organisms is more than 10% but less than 20%. △: The area of ​​adhesion of marine organisms is more than 20% but less than 40%. ×: Area of ​​adhesion of marine organisms exceeds 40%.

[0083] (Materials used) PGM: propylene glycol methyl ether. Monomer (M1): A metal atom-containing monomer mixture synthesized in Production Example M1 described below. MMA: Methyl methacrylate EA: Ethyl acrylate MTA: 2-Methoxyethyl acrylate AIBN: 2,2'-azobisisobutyronitrile AMBN: 2,2'-azobis(2-methylbutyronitrile) Perbutyl D: Di-t-butyl peroxide Nofumer MSD: Product name, manufactured by NOF Corporation, α-methylstyrene dimer

[0084] [Manufacturing example M1] A reaction vessel equipped with a stirrer, a temperature regulator, and a dropping funnel was charged with 85.4 parts of PGM and 40.7 parts of zinc oxide, and the mixture was heated to 75°C with stirring. Subsequently, a mixture of 43.1 parts of methacrylic acid, 36.1 parts of acrylic acid, and 5 parts of water was added dropwise from the dropping funnel at a constant rate over 3 hours. After stirring for an additional 2 hours, 36 parts of PGM was added to obtain a transparent metal atom-containing monomer mixture (monomer (M1)) with a solids content of 44.8% by mass. Monomer (M1) includes (CH2=CHCOO)2Zn, (CH2=C(CH3)COO)2Zn, and (CH2=CHCOO)Zn(OCOC(CH3)=CH2). The metal content relative to the solid content of the monomer (M1) was 29.5 mass %.

[0085] [Production Example 1: Production of Resin Composition A-1 Containing (Meth)acrylic Copolymer A-1] A (meth)acrylic copolymer A-1 was synthesized according to the formulation shown in Table 1 (unit: parts by mass). That is, 15 parts of PGM, 30 parts of xylene, and 4 parts of ethyl acrylate were charged into an autoclave capable of pressure polymerization equipped with a condenser, a thermometer, a dropping tank, and a stirrer, and the mixture was pressurized to 350 kPa with stirring and heated to 150° C. Subsequently, a mixture consisting of 30 parts of methyl methacrylate, 62.4 parts of ethyl acrylate, 52.4 parts (23.6 parts in terms of solids content) of the monomer (M1) produced in Production Example M1, 1.2 parts of a chain transfer agent (NOFMER MSD manufactured by NOF CORPORATION), 1.0 part of AIBN, 7 parts of AMBN, and 2.5 parts of Perbutyl D was added dropwise from the dropping tank at a constant rate over 3 hours. After the dropwise addition was completed, the temperature was lowered to 110°C over 30 minutes, and 0.5 parts of t-butyl peroctoate and 3.2 parts of xylene were added dropwise over 30 minutes. After stirring for another 1 hour and 30 minutes, 7 parts of xylene was added and the mixture was filtered through a 300 mesh filter, yielding a pale yellow, transparent resin composition (A-1) with a heating residue (solid content) of 57.3% and no insoluble matter, having a Gardner viscosity of U+. The items shown in Table 1 were measured using the above methods, and the results are shown in the table (the same applies hereinafter). The content of zinc atoms (unit: mass %) relative to the total mass (solid content) of the monomers was determined and taken as the metal content relative to all structural units of the (meth)acrylic copolymer. In Table 1, the values ​​shown in the columns for monomer, initiator, and chain transfer agent indicate the amount (parts) charged, and the value shown in the column for monomer (M1) indicates the amount (parts) charged in solid content.

[0086] [Manufacturing Examples 2 to 10] Resin compositions A-2 to A-10 containing acrylic copolymers A-2 to A-10, respectively, were produced in the same manner as in Production Example 1, except that the types and amounts of monomers and initiators were as shown in Table 1, and the amount of solvent initially charged to the reaction vessel and the amount of xylene after the dropwise addition were adjusted according to the respective solid contents.

[0087] [Table 1]

[0088] [Examples 1 to 8, Comparative Examples 1 and 2] In this example, antifouling coating compositions were prepared using the resin compositions A-1 to A-10 obtained in Production Examples 1 to 10. That is, each component was charged in the formulation (unit: parts by mass) shown in Table 2, glass beads were added, and the mixture was pre-mixed with a stirring rod, and the pigment was dispersed using a rocking shaker to obtain an antifouling coating composition. The antifouling coating compositions obtained in each example were evaluated for B-type viscosity and coating film performance (wear and static antifouling properties) using the methods described above. The evaluation results are shown in Table 2.

[0089] [Table 2]

[0090] As shown in Tables 1 and 2, the antifouling coating compositions of Examples 1 to 8 had low viscosities, had appropriate wear levels to achieve long-term antifouling effects, and were excellent in long-term static antifouling properties. On the other hand, the antifouling coating composition of Comparative Example 1, in which the weight-average molecular weight of the (meth)acrylic copolymer (A) exceeded 4000, had a high B-type viscosity. The coating film performance (wear rate, static antifouling property) of Comparative Example 2, in which the metal content was less than 6.0 mass%, was poor.

Claims

1. A (meth)acrylic copolymer (A) comprising a structural unit derived from a monomer (a) containing a metal atom M and a structural unit derived from a monomer (b) copolymerizable with the monomer (a), The monomer (a) has at least one of a structure represented by the following formula (I) and a structure represented by the following formula (II): the content of the metal atom M is 6.0% by mass or more relative to all structural units of the (meth)acrylic copolymer (A), The total solubility parameter (SP value) of the monomer (b) is 20.7 (J / cm ３ ) １／２ That's all, The (meth)acrylic copolymer (A) has a weight average molecular weight of 1,000 to 4,000. -CO-O-M-O-CO-...(I) ----O-M-R ０ ・・・(--) [In the formula, R ０ represents a monovalent organic acid residue, and M represents a divalent metal atom.

2. The (meth)acrylic copolymer according to claim 1, wherein the (meth)acrylic copolymer (A) has an acid value of 98 mg KOH / g or more.

3. The (meth)acrylic copolymer (A) has a coating hardness of 4.9 N / mm ２ The (meth)acrylic copolymer according to claim 1 , wherein the (meth)acrylic copolymer is any of the above.

4. The (meth)acrylic copolymer according to claim 1, wherein a 55% by mass solids solution containing the (meth)acrylic copolymer (A) as a solid content has a Gardner viscosity at 25°C of Z3 or less.

5. An antifouling coating composition comprising the (meth)acrylic copolymer (A) according to any one of claims 1 to 4.

6. The antifouling coating composition of claim 5 further comprising an antifouling agent.

7. The antifouling coating composition according to claim 6, wherein the antifouling agent comprises at least one selected from the group consisting of cuprous oxide, 4-bromo-2-(4-chlorophenyl)-5-(trifluoromethyl)-1H-pyrrole-3-carbonitrile, pyridine-triphenylborane, zinc pyrithione, copper pyrithione, and medetomidine.

8. The antifouling coating composition according to claim 5, further comprising a thermoplastic resin other than the (meth)acrylic copolymer (A).

9. The antifouling coating composition according to claim 5, which contains a solid content of 72 mass % or more.

10. 6. The antifouling coating composition according to claim 5, which has a viscosity of 5 Pa·s or less at 25°C as measured with a Brookfield viscometer when the solids content is 71% by mass.

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