Paint additives and water-based paint compositions

Abstract

A paint additive that provides excellent coating properties and storage stability, and an aqueous paint composition using the paint additive are provided. [Solution] According to the present invention, a paint additive is provided that contains a vinyl alcohol-based polymer having vinyl alcohol units and vinyl ester units, wherein the vinyl alcohol-based polymer has a degree of saponification of 70 mol% or more and a viscosity-average degree of polymerization of 1000 to 5000, and the ratio V1 / V2 of the viscosity value V1 at a shear rate of 0.1 / s to the viscosity value V2 at a shear rate of 1000 / s of a 4 mass% aqueous solution of the vinyl alcohol-based polymer is 10 or more.

Description

Technical Field

[0001] The present invention relates to an additive for paints containing a polyvinyl alcohol-based polymer, and an aqueous paint composition using the additive for paints.

Background Art

[0002] Paints are used in various applications such as for automobiles, buildings, ships, etc., and play roles such as protecting the object to be painted (preventing rust, anti-corrosion, etc.), improving aesthetics (providing gloss, improving smoothness, etc.), and imparting functions (preventing scratches, self-healing, etc.).

[0003] Paints usually contain resins, pigments, solvents, and additives, and exhibit the required properties by adjusting the types and amounts of these according to the purpose. In particular, by adjusting the types and amounts of additives, the properties of the paint can be changed. For example, when various viscosity characteristics are required for the paint according to the form of the object and the painting means, the viscosity characteristics of the paint can be adjusted by using a rheology control agent as an additive.

[0004] As the rheology control agent, for example, cellulose ether, urethane thickener, acrylic thickener, bentonite, silica particles, etc. are generally used. Patent Document 1 discloses a thickener containing a polyvinyl alcohol-based polymer that can be used in paints.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] However, conventional rheology control agents can cause problems such as dripping and sedimentation, especially in water-based paints. Furthermore, to improve coating properties, there is a need for rheology control agents that not only thicken paints but also possess good thixotropy.

[0007] This invention has been made in view of these circumstances, and provides a paint additive that can produce a paint with excellent coating properties and storage stability, and an aqueous paint composition using the paint additive.

[0008] As a result of diligent research to solve the above problems, the present inventors have found that the above problems can be solved when a polyvinyl alcohol-based polymer has a specific range of saponification degree and viscosity-average degree of polymerization, and when the thixotropy index (hereinafter also referred to as TI) of an aqueous solution of the polyvinyl alcohol-based polymer is greater than or equal to a predetermined value obtained by dividing the viscosity measured at a low shear rate by the viscosity measured at a high shear rate. This led to the completion of the present invention.

[0009] The following inventions are provided. [1] A paint additive containing a vinyl alcohol polymer having vinyl alcohol units and vinyl ester units, wherein the vinyl alcohol polymer has a degree of saponification of 70 mol% or more and a viscosity-average degree of polymerization of 1000 to 5000, and the ratio V1 / V2 of the viscosity value V1 at a shear rate of 0.1 / s to the viscosity value V2 at a shear rate of 1000 / s of a 4 mass% aqueous solution of the vinyl alcohol polymer is 10 or more. [2] The paint additive according to [1], wherein the degree of saponification of the vinyl alcohol polymer is 70 mol% to 99 mol%. [3] The paint additive according to [1] or [2], wherein the vinyl alcohol polymer has polyfunctional monomer units. [4] The paint additive according to any one of [1] to [3], wherein the polyfunctional monomer has a structure derived from an isocyanurate having two or more allyl groups. [5] The paint additive according to any one of [1] to [4], wherein the content of the polyfunctional monomer units is 0.001 mol% to 1.0 mol% when the total of the vinyl alcohol units and the vinyl ester units is 100 mol%. A water-based paint composition containing any one of the paint additives described in [6][1] to [5]. [7] The aqueous paint composition according to [6], wherein when the total amount of components other than the vinyl alcohol polymer contained in the aqueous paint composition is 100 parts by mass, the vinyl alcohol polymer is included in 0.1 parts by mass to 5 parts by mass. [Effects of the Invention]

[0010] The present invention provides a paint additive that can produce a paint with excellent coating properties and storage stability, and an aqueous paint composition using the paint additive. [Modes for carrying out the invention]

[0011] Embodiments of the present invention will be described below. The various features shown in the embodiments below can be combined with each other. Furthermore, each feature can constitute an invention independently. In addition, any element not specified in the claims in the embodiments below is an optional element and can be omitted. Any number of zeros (for example, one or two) may be added to the end of the numerical values ​​disclosed in the following description. For example, one or two zeros may be added after "1.4" to make it "1.40" or "1.400".

[0012] A paint additive according to one embodiment of the present invention can be used with acrylic paints, urethane paints, silicone paints, fluoropolymer paints, inorganic paints, etc., and is particularly suitable as an additive for water-based paints. The paint additive of this embodiment is a vinyl alcohol-based polymer having vinyl alcohol units and vinyl ester units, and contains a vinyl alcohol-based polymer whose degree of saponification, viscosity-average degree of polymerization, and thixotropy index of a 4% by mass aqueous solution have been adjusted. The paint additive may further contain, if necessary, pigment dispersants, coating agents, preservatives, antifouling agents, etc.

[0013] 1. Polyvinyl alcohol-based polymers The polyvinyl alcohol polymer (hereinafter also referred to as "PVA") used as an additive for paints according to one embodiment of the present invention is a vinyl alcohol polymer having vinyl alcohol units and vinyl ester units, having a degree of saponification of 70 mol% or more, a viscosity-average degree of polymerization of 1000 to 5000, and a ratio V1 / V2 of the viscosity value V1 at a shear rate of 0.1 / s to the viscosity value V2 at a shear rate of 1000 / s of a 4 mass% aqueous solution of the vinyl alcohol polymer of 1000 / s of 10 or more.

[0014] The PVA in question is a polymer obtained by saponifying a polymer obtained by polymerizing raw material monomers containing vinyl ester monomers. Preferably, the PVA is obtained by saponifying a copolymer of saponified vinyl ester monomers and other monomers (hereinafter also referred to as an "intermediate copolymer"). Some of the structural units (vinyl ester units) derived from the vinyl ester monomers contained in the homopolymer or intermediate copolymer undergo hydrolysis of the ester groups during saponification to become structural units (vinyl alcohol units) having hydroxyl groups.

[0015] Examples of vinyl ester monomers include vinyl acetate, vinyl propionate, vinyl valerate, vinyl caprate, vinyl laurate, vinyl stearate, vinyl benzoate, vinyl pivalate, etc., and these may be used individually or in combination of two or more. Preferably, the vinyl ester monomer contains vinyl acetate, and more preferably, the vinyl ester monomer is vinyl acetate.

[0016] Furthermore, other monomers copolymerizable with vinyl ester monomers may include polyfunctional monomers. These polyfunctional monomers are not particularly limited, and any compound having two or more polymerizable unsaturated bonds in its molecule can be used. Examples include divinyl ethers such as ethanediol divinyl ether, propanediol divinyl ether, butanediol divinyl ether, ethylene glycol divinyl ether, diethylene glycol divinyl ether, triethylene glycol divinyl ether, polyethylene glycol divinyl ether, propylene glycol divinyl ether, and polypropylene glycol divinyl ether; divinyl sulfonic acid compounds; and others.

[0017] Furthermore, polyfunctional monomers copolymerizable with vinyl ester monomers include diene compounds such as pentadiene, hexadiene, heptadiene, octadiene, nonadiene, and decadiene; diallyl ether compounds such as glycerin diallyl ether, diethylene glycol diallyl ether, ethylene glycol diallyl ether, triethylene glycol diallyl ether, polyethylene glycol diallyl ether, trimethylolpropane diallyl ether, and pentaerythritol diallyl ether; trialyl ether compounds such as glycerin triallyl ether, trimethylolpropane triallyl ether, and pentaerythritol triallyl ether; and pentaerythritol Other examples include tetraallyl ether compounds such as litol tetraallyl ether; monomers containing allyl ester groups such as diallyl phthalate, diallyl maleate, diallyl itaconate, diallyl terephthalate, and diallyl adipate; monomers containing allylamino groups such as diallylamine, diallylmethylamine, and diallylamine; monomers containing allylammonium groups such as diallylammonium salts like diallyldimethylammonium chloride; and polyfunctional monomers containing two or more allyl groups such as diallyl isocyanurate derivatives, triallyl isocyanurate, 1,3-diallylurea, triallyl phosphate, and diallyl disulfide.

[0018] Furthermore, examples of the polyfunctional monomer copolymerizable with the vinyl ester monomer include monomers having (meth)acrylic acid such as ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, glycerin di(meth)acrylate, glycerin tri(meth)acrylate, pentaerythritol tri(meth)acrylate, trimethylolpropane tri(meth)acrylate, ditrimethylolpropane tetra(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol hexa(meth)acrylate, and tri(meth)acrylate of isocyanuric acid; monomers having (meth)acrylamide such as N,N'-methylenebis(meth)acrylamide and N,N'-ethylenebis(meth)acrylamide; aromatic monomers such as divinylbenzene and trivinylbenzene; monomers having a glycidyl group such as allyl glycidyl ether and glycidyl (meth)acrylate; and the like.

[0019] Among these polyfunctional monomers, from the viewpoint of reactivity with the vinyl ester monomer, an allyl cyanurate derivative having a carbonyl group or an amide group in the molecule and having two or more allyl groups is preferable. Specifically, the use of triallyl isocyanurate or allyl methacrylate is preferable. Particularly, from the viewpoints such as resistance to decomposition in the saponification reaction, the use of a diallyl isocyanurate derivative or triallyl isocyanurate is preferable. [[ID=**5**]] [[ID=**6**]]

[0020] [[ID=**7**]] [[ID=**8**]]The diallyl isocyanurate derivative is preferably a compound represented by the following formula (1) (hereinafter, also referred to as "Compound A"). [[ID=**9**]] [[ID=**10**]]

[0021] [[ID=**11**]] [[ID=**12**]] [[ID=**13**]]

Chemical formula

[0022] [[ID=**19**]] In formula (1) above, R is a linear, branched, or cyclic alkyl group having 1 to 18 carbon atoms. R is preferably a linear or branched alkyl group, and more preferably a linear alkyl group. The number of carbon atoms in R is preferably 1 to 18, more preferably 1 to 16, and even more preferably 1 to 14. Specifically, the number of carbon atoms in R may be, for example, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, or 18, and may be within the range of any two of the values ​​exemplified here. Specific examples of linear alkyl group R include methyl group, ethyl group, propyl group, butyl group, pentyl group, hexyl group, heptyl group, octyl group, nonyl group, decyl group, undecyl group, dodecyl group, tridecyl group, tetradecyl group, pentadecyl group, hexadecyl group, heptadecyl group, octadecyl group, and the like, with methyl group or tetradecyl group being preferred.

[0023] Compound A, represented by formula (1) above, may be used alone or in combination of two or more compounds. Preferably, compound A comprises one or more compounds in which R is selected from a methyl group and a tetradecyl group, and more preferably, compound A is a compound in which R is a methyl group or a tetradecyl group.

[0024] The polyvinyl alcohol polymer contains, when the total amount of vinyl alcohol units and vinyl ester units contained in the polyvinyl alcohol polymer is set to 100 mol%, it preferably contains 0.001 to 1.0 mol%, more preferably 0.01 to 0.5 mol%, and even more preferably 0.03 to 0.3 mol% of polyfunctional monomer units. The content of polyfunctional monomer units in the polyvinyl alcohol polymer (the degree of modification of the polyvinyl alcohol polymer) is specifically, for example, 0.001, 0.01, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.10, 0.11, 0.12, 0.13, 0.14, 0.15, 0.16, 0.17, 0.18, 0.19, 0.20, 0.21, 0.22, 0.23, 0.24, 0.25, 0.26, 0.27, 0.28, 0.29, 0.30, 0.35, 0.40, 0.45, 0.50, and 1.0 mol%, and may also be within the range of any two of the values ​​exemplified here.

[0025] The content of polyfunctional monomer units in polyvinyl alcohol-based polymers (the degree of modification of the polyvinyl alcohol-based polymer) can be calculated, for example, based on the results of NMR measurements or trace nitrogen quantification. A calculation method based on NMR measurements using diallylmethyl isocyanurate and diallyltetradecyl isocyanurate is specifically described in the examples below.

[0026] The polyvinyl alcohol polymer preferably contains 90 to 100 mol%, more preferably 95 to 100 mol%, and even more preferably 99 to 100 mol%, of structural units derived from vinyl ester monomers (vinyl alcohol units and vinyl ester units) and structural units derived from polyfunctional monomers in total per 100 mol% of the constituent units contained in the polyvinyl alcohol polymer. Specifically, the total content of structural units derived from vinyl ester monomers and structural units derived from polyfunctional monomers in per 100 mol% of the constituent units contained in the polyvinyl alcohol polymer is, for example, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 99.5, 99.9, and 100 mol%, and may be within the range of any two of the values ​​exemplified here.

[0027] The intermediate copolymer may be further copolymerized with other monomers copolymerizable with vinyl ester monomers and polyfunctional monomers, to the extent that the effects of the present invention are not impaired. Other monomers include, for example, α-olefin monomers such as ethylene and propylene; alkyl (meth)acrylate monomers such as methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate; unsaturated amide monomers such as (meth)acrylamide and N-methylolacrylamide; unsaturated carboxylic acid monomers such as (meth)acrylic acid, crotonic acid, maleic acid, itaconic acid, and fumaric acid; and alkyl (methyl, ethyl, propylene) unsaturated carboxylic acids. Examples include ester monomers (such as glycidyl ether); anhydrides of unsaturated carboxylic acids such as maleic anhydride; salts of unsaturated carboxylic acids with sodium, potassium, ammonium, etc.; glycidyl group-containing monomers such as allyl glycidyl ether and glycidyl (meth)acrylate; sulfonic acid group-containing monomers or salts thereof such as 2-acrylamido-2-methylpropanesulfonic acid; phosphate group-containing monomers such as acid phosphooxyethyl methacrylate and acid phosphooxypropyl methacrylate; alkyl vinyl ether monomers; and so on.

[0028] The viscosity-average degree of polymerization of the polyvinyl alcohol-based polymer is preferably 1000 to 5000. If the viscosity-average degree of polymerization is too low, the storage stability of the paint may not be sufficient. If the viscosity-average degree of polymerization is too high, the viscosity of the aqueous solution may become high. Also, if the viscosity-average degree of polymerization is too high, the viscosity of the paint composition may become high, and the coatability may deteriorate. Specifically, the viscosity-average degree of polymerization is, for example, 1000, 1200, 1400, 1600, 1800, 2000, 2200, 2400, 2600, 2800, 3000, 3200, 3400, 3600, 3800, 4000, 4500, and 5000, and may also be within the range of any two of the values ​​exemplified here.

[0029] The "viscosity-average degree of polymerization" is a value calculated from the intrinsic viscosity [η] (g / dL) measured at 30°C using an Ostwald viscometer with deionized water as the solvent, in accordance with JIS K 6726:1994 "3.7 Average degree of polymerization," using the following formula (A). log(P) = 1.613 × log([η] × 10 4 / 8.29) ···(A) Here, P represents the viscosity-average degree of polymerization.

[0030] The degree of saponification of the polyvinyl alcohol polymer is preferably 70 mol% or higher, and may be, for example, 70 mol% to 99.9 mol%, or 70 mol% to 99 mol%. When this range is met, the hydrophobicity of the remaining ester groups and the action of intermolecular hydrogen bonding of the polyvinyl alcohol polymer are within a favorable range, resulting in good thixotropy. Specifically, the degree of saponification may be, for example, 70, 75, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 99.9 mol%, and may be within the range of any two of the values ​​exemplified here.

[0031] The "degree of saponification" can be calculated by measuring it in accordance with JIS K 6726:1994 "3.5 Degree of Saponification".

[0032] Polyvinyl alcohol-based polymers are preferred if they have high thixotropy when dissolved in aqueous solution. Thixotropy is the property of having relatively high viscosity and low fluidity when no external force is applied, but relatively low viscosity and good fluidity when an external force such as shear stress is applied. In this specification, the value obtained by dividing the viscosity measured at a low shear rate by the viscosity measured at a high shear rate is used as an indicator of thixotropy. Specifically, when a polyvinyl alcohol-based polymer is dissolved in a 4% by mass aqueous solution, the ratio V1 / V2 of the viscosity value V1 at a shear rate of 0.1 / s and the viscosity value V2 at a shear rate of 1000 / s at room temperature (23℃±2℃) is used as an indicator of thixotropy.

[0033] The polyvinyl alcohol polymer preferably has a V1 / V2 ratio of 10 or higher, and more preferably 11 or higher. When the polyvinyl alcohol polymer is used as a paint additive, the higher the V1 / V2 value, the higher the paint's thixotropy, resulting in low viscosity during application and high viscosity after application and during storage, thus providing excellent coatability and storage stability. There is no upper limit to the V1 / V2 ratio, but in practice, it is considered to be around 15.

[0034] The polyvinyl alcohol-based polymer preferably has a viscosity value V1 of 50 mPa·s or higher, and more preferably 100 mPa·s or higher, at room temperature (23°C ± 2°C) and a shear rate of 0.1 / s in a 4% by mass aqueous solution. A higher V1 may result in higher thixotropy of the coating. While there is no particular upper limit to V1, it is realistically considered to be around 1500.

[0035] The polyvinyl alcohol-based polymer preferably has a viscosity value V2 of 5 to 150 mPa·s, more preferably 10 to 20 mPa·s, at a shear rate of 1000 / s at room temperature (23℃ ± 2℃) in a 4% by mass aqueous solution. Specifically, V2 can be, for example, 5, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 30, 40, 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, or 150 mPa·s, and may also be within the range of any two of the values ​​exemplified here. If the value of V2 is too high, the coating properties will deteriorate. Also, if the value of V2 is high, the V1 / V2 value will decrease, which may result in lower thixotropy of the paint.

[0036] <Method for producing polyvinyl alcohol-based polymers> The method for producing polyvinyl alcohol-based polymers is not particularly limited, but may include, for example, a polymerization step and a saponification step.

[0037] In the polymerization step, the raw material monomers containing vinyl ester monomers are polymerized to obtain a homopolymer. Alternatively, the raw material monomers containing vinyl ester monomers and other monomers may be polymerized to obtain an intermediate copolymer. The polymerization method for the homopolymer or intermediate copolymer is not particularly limited, but known polymerization methods such as solution polymerization, suspension polymerization, and bulk polymerization can be used. Solution polymerization in alcohol is preferred because it is easy to operate and the same solvent as the saponification step can be used. Methanol is particularly preferred as the alcohol.

[0038] The amount of alcohol added may be, for example, 30.0 to 80.0 parts by mass, preferably 40.0 to 70.0 parts by mass, per 100 parts by mass of vinyl ester monomer.

[0039] Furthermore, if the raw material monomer contains a polyfunctional monomer, the amount of polyfunctional monomer added may be, for example, 0.05 to 0.40 parts by mass, preferably 0.10 to 0.25 parts by mass, per 100 parts by mass of vinyl ester monomer.

[0040] Furthermore, the amount of vinyl ester monomer added relative to 100% by mass of the total amount of raw material monomers may be, for example, 95.0 to 99.9% by mass, preferably 99.0 to 99.5% by mass, and more preferably 99.6 to 99.0% by mass.

[0041] Furthermore, the conversion rate of the vinyl ester monomer may be, for example, 40.0 to 70.0%, and preferably 50.0 to 60.0%.

[0042] Furthermore, polymerization initiators can be used in polymerization reactions. Polymerization initiators are not particularly limited, but for example, azo compounds such as azobisisobutyronitrile, azobis-2,4-dimethylvaleronitrile, azobis(4-methoxy-2,4-dimethylvaleronitrile), azobisdimethylvaleronitrile, and azobismethoxyvaleronitrile; peroxides such as acetyl peroxide, benzoyl peroxide, lauroyl peroxide, acetylcyclohexylsulfonyl peroxide, and 2,4,4-trimethylpentyl-2-peroxyphenoxyacetate; peroxycarbonate compounds such as di-n-propyl peroxydicarbonate, diisopropyl peroxydicarbonate, di-2-ethylhexyl peroxydicarbonate, and diethoxyethyl peroxydicarbonate; and perester compounds such as t-butyl peroxyneodecanate, α-cumyl peroxyneodecanate, and t-butyl peroxyneodecanate can be used alone or in combination.

[0043] In the saponification process, the intermediate copolymer is saponified to obtain a saponified product. The method for saponifying the intermediate copolymer is not particularly limited, but for example, a simple and preferred method is to dissolve the intermediate copolymer in alcohol and saponify it with an alkali (e.g., sodium hydroxide). The alcohol used is not particularly limited, but examples include methanol, ethanol, and butanol. Among these, methanol is preferred because the solvent can be easily recovered and reused, thus reducing manufacturing costs. The saponification process may include a neutralization step with acetic acid or the like. In one example, when alkali is added to a methanol solution of the intermediate copolymer, the paste becomes gel-like as saponification progresses. This gel-like substance (which may also be a block of gel-like substance) is crushed with a cutter, neutralized with acetic acid, washed, and dried (solvent removal step described later) to obtain granular particles. These granular particles can be crushed (crushing step and classification step described later) to obtain a powder.

[0044] A method for producing a polyvinyl alcohol-based polymer may further include a solvent removal step. In the solvent removal step, the solvent can be removed, for example, by heating and drying.

[0045] When an aqueous paint composition contains 0.1 to 5 parts by mass of polyvinyl alcohol polymer, 30 to 80 parts by mass of acrylic resin, 5 to 40 parts by mass of titanium dioxide, and 5 to 30 parts by mass of water, per 100 parts by mass of the total components other than the polyvinyl alcohol polymer in the aqueous paint composition (more specifically, for example, when an aqueous paint composition contains 2 parts by mass of polyvinyl alcohol polymer, 60 parts by mass of acrylic resin, 20 parts by mass of titanium dioxide, and 10 parts by mass of water, per 100 parts by mass of the total components other than the polyvinyl alcohol polymer in the aqueous paint composition), the ratio V1 / V2 of the viscosity value V1 at a shear rate of 0.1 / s to the viscosity value V2 at a shear rate of 1000 / s at room temperature (23℃±2℃) is preferably 1000 or more, and more preferably 1200 or more. The upper limit of V1 / V2 is not particularly limited, but in reality, it is considered to be around 2000.

[0046] When an aqueous paint composition is prepared containing 0.1 to 5 parts by mass of polyvinyl alcohol polymer, 30 to 80 parts by mass of acrylic resin, 5 to 40 parts by mass of titanium dioxide, and 5 to 30 parts by mass of water, per 100 parts by mass of the total components other than the polyvinyl alcohol polymer in the aqueous paint composition (more specifically, for example, when an aqueous paint composition is prepared containing 2 parts by mass of polyvinyl alcohol polymer, 60 parts by mass of acrylic resin, 20 parts by mass of titanium dioxide, and 10 parts by mass of water, per 100 parts by mass of the total components other than the polyvinyl alcohol polymer in the aqueous paint composition), the viscosity value V1 at room temperature (23°C ± 2°C) and a shear rate of 0.1 / s is preferably 100,000 mPa·s or more, and more preferably 120,000 mPa·s or more. The upper limit of V1 is not particularly limited, but in reality, it is considered to be around 450,000.

[0047] When the aqueous paint composition contains 0.1 to 5 parts by mass of polyvinyl alcohol polymer, 30 to 80 parts by mass of acrylic resin, 5 to 40 parts by mass of titanium dioxide, and 5 to 30 parts by mass of water, per 100 parts by mass of the total components other than the polyvinyl alcohol polymer in the aqueous paint composition (more specifically, for example, when the aqueous paint composition contains 2 parts by mass of polyvinyl alcohol polymer, 60 parts by mass of acrylic resin, 20 parts by mass of titanium dioxide, and 10 parts by mass of water, per 100 parts by mass of the total components other than the polyvinyl alcohol polymer in the aqueous paint composition), the viscosity value V2 at a shear rate of 1000 / s at room temperature (23℃±2℃) is preferably 50 to 300 mPa·s, and more preferably 110 to 200 mPa·s. The V2 values ​​are specifically, for example, 50, 100, 110, 120, 130, 140, 150, 160, 170, 180, 190, 200, 250, and 300 mPa·s, and may also be within the range of any two of the values ​​exemplified here.

[0048] When the aqueous paint composition contains 0.1 to 5 parts by mass of polyvinyl alcohol polymer, 30 to 80 parts by mass of acrylic resin, 5 to 40 parts by mass of titanium dioxide, and 5 to 30 parts by mass of water, per 100 parts by mass of the total components other than the polyvinyl alcohol polymer in the aqueous paint composition (more specifically, for example, when the aqueous paint composition contains 2 parts by mass of polyvinyl alcohol polymer, 60 parts by mass of acrylic resin, 20 parts by mass of titanium dioxide, and 10 parts by mass of water, per 100 parts by mass of the total components other than the polyvinyl alcohol polymer in the aqueous paint composition), the sedimentation separation rate after 12 weeks is preferably 2% or less. Specifically, the sedimentation separation rate may be, for example, 0, 0.2, 0.4, 0.6, 0.8, 1.0, 1.5, or 2.0%, and may be within the range of any two of the values ​​exemplified here.

[0049] When the aqueous paint composition contains 0.1 to 5 parts by mass of polyvinyl alcohol polymer, 30 to 80 parts by mass of acrylic resin, 5 to 40 parts by mass of titanium dioxide, and 5 to 30 parts by mass of water, per 100 parts by mass of the total components other than the polyvinyl alcohol polymer in the aqueous paint composition (more specifically, for example, when the aqueous paint composition contains 2 parts by mass of polyvinyl alcohol polymer, 60 parts by mass of acrylic resin, 20 parts by mass of titanium dioxide, and 10 parts by mass of water, per 100 parts by mass of the total components other than the polyvinyl alcohol polymer in the aqueous paint composition), it is preferable that the aqueous paint composition does not exhibit sagging (flow of the paint film) as measured according to the measurement method described in JIS-K-5551:2018 (7.10 Sagging). Specifically, when the aqueous paint composition is applied to a glass plate and the glass plate is propped up at an angle of 80 to 90°, it is preferable that no sagging of the paint film occurs 3 minutes after the glass plate is propped up.

[0050] When the aqueous paint composition contains 0.1 to 5 parts by mass of polyvinyl alcohol polymer, 30 to 80 parts by mass of acrylic resin, 5 to 40 parts by mass of titanium dioxide, and 5 to 30 parts by mass of water, per 100 parts by mass of the total components other than the polyvinyl alcohol polymer in the aqueous paint composition (more specifically, for example, when the aqueous paint composition contains 2 parts by mass of polyvinyl alcohol polymer, 60 parts by mass of acrylic resin, 20 parts by mass of titanium dioxide, and 10 parts by mass of water, per 100 parts by mass of the total components other than the polyvinyl alcohol polymer in the aqueous paint composition), it is preferable that no cracking, blistering, or peeling of the test piece is observed when the aqueous paint composition is coated to a film thickness of 25 to 30 μm and the resulting test piece is immersed in water for 14 days in accordance with the method described in JIS-K-5600-6-1:2016.

[0051] 2. Water-based paint composition An aqueous coating composition according to one embodiment of the present invention may contain the polyvinyl alcohol-based polymer. The aqueous coating composition is, for example, a composition comprising water, a resin, a pigment, and further comprising the polyvinyl alcohol-based polymer. An aqueous coating composition according to one embodiment may also contain the paint additive. The aqueous coating composition is, for example, a composition comprising water, a resin, a pigment, and the paint additive.

[0052] When the total amount of components other than the polyvinyl alcohol polymer in the aqueous paint composition is 100 parts by mass, the amount of polyvinyl alcohol polymer added is preferably 0.1 to 5 parts by mass, and more preferably 0.5 to 3 parts by mass. Specifically, the amount added is, for example, 0.10, 0.15, 0.16, 0.17, 0.18, 0.19, 0.20, 0.21, 0.22, 0.23, 0.24, 0.25, 0.30, 0.35, 0.40, 0.50, 1.0, 2.0, 3.0, 4.0, 5.0, and may be within the range of any two of the values ​​exemplified here. Within the above-mentioned range of additive amounts, it is possible to impart good thixotropy to the paint without impairing the dispersibility of the water-based paint, thereby improving its coatability and storage stability.

[0053] The water-based paint composition may contain other additives as long as they do not impair the effects of the present invention.

[0054] <Method for manufacturing aqueous paint compositions> An aqueous paint composition according to one embodiment of the present invention can be prepared, for example, by adding an aqueous resin, a pigment, and the polyvinyl alcohol-based polymer or paint additive to water, and then dispersing and mixing them using a bead mill, homogenizer, film mixer, etc. The method of adding the polyvinyl alcohol-based polymer or paint additive to the aqueous paint composition is not particularly limited. The paint additive of the present invention may be added to the aqueous paint as an aqueous solution, or it may be added in pellet or powder form.

[0055] <Water> The water used in this invention is preferably conventionally used water, such as ion-exchanged water, distilled water, or ultrapure water, which is free of impurities, but is not particularly limited. When the total amount of components other than the vinyl alcohol polymer contained in the aqueous coating composition is 100 parts by mass, the amount of water is preferably 5 to 30 parts by mass, specifically, for example, 5, 10, 15, 20, 25, or 30 parts by mass, and may be within the range of any two of the values ​​exemplified here.

[0056] <Resin> The aqueous resin used in the present invention is not particularly limited as long as it can disperse pigments, and resins having forms such as water-soluble, dispersion, emulsion, or microgel can be used. Specifically, examples of aqueous resins include acrylic resins, alkyd resins, polyester resins, polyurethane resins, acrylic urethane resins, silicone resins, blocked isocyanates, fluororesins, epoxy resins, epoxy acrylate resins, phenolic resins, melamine resins, vinyl resins, polyamide resins, cellulose resins, and the like. From the viewpoint of cost, acrylic resins and the like can be preferably used. From the viewpoint of paintability and stability, fluororesins and the like can be preferably used. Furthermore, the aqueous resin used in the aqueous coating composition of the present invention also includes compounds that can potentially form resins by polymerization or crosslinking, so-called monomers and oligomers.

[0057] When the total amount of components other than the polyvinyl alcohol polymer in the aqueous coating composition is 100 parts by mass, the amount of resin is preferably 30 to 80 parts by mass. Specifically, the amount of resin may be, for example, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, or 80 parts by mass, and may be within the range of any two of the values ​​exemplified here.

[0058] <Pigments> The types of pigments used in this invention are not particularly limited, and coloring pigments, white pigments, extender pigments, rust-preventive paints, etc., can be used. Specific examples of pigments include coloring pigments such as carbon black, lead yellow, molybdenum red, red iron oxide, yellow iron oxide, titanium dioxide, iron black, yellow ochre, sienna, amber, green earth, Mars violet, cadmium yellow, cadmium red, cadmium red, cadmium yellow, ultramarine, and Prussian blue; white pigments such as titanium dioxide, ultrafine titanium dioxide, lead white, basic lead sulfate, basic lead silicate, zinc oxide, zinc sulfide, antimony trioxide, and calcium composites; extender pigments such as calcium carbonate, barium sulfate, alumina white, silica, diatomaceous earth, kaolin, talc, organic bentonite, and white carbon; and rust-preventive paints such as zinc chromate, red zinc, and zinc phosphate.

[0059] When the total amount of components other than the polyvinyl alcohol polymer in the aqueous paint composition is 100 parts by mass, the amount of pigment is preferably 5 to 40 parts by mass. Specifically, the amount of pigment may be, for example, 5, 10, 15, 20, 25, 30, 35, or 40 parts by mass, and may be within the range of any two of the values ​​exemplified here.

[0060] <Other additives> Furthermore, the aqueous colorant composition of the present invention may optionally further contain conventional additives such as pigment dispersants, coating agents, preservatives, antifouling agents, rust inhibitors, surfactants, wetting agents, defoaming agents, leveling agents, anti-coagulation agents, pH adjusters, and flexibility-imparting agents.

[0061] <Thixotropy of paints> The aqueous coating composition according to the present invention preferably has a ratio V1 / V2 of viscosity value V1 at a shear rate of 0.1 / s and viscosity value V2 at a shear rate of 1000 / s at room temperature (23℃±2℃) of 1000 or more, and more preferably 1200 or more. The upper limit of V1 / V2 is not particularly limited, but in reality, it is considered to be around 2000.

[0062] The aqueous coating composition according to the present invention preferably has a viscosity value V1 of 100,000 mPa·s or more at room temperature (23℃ ± 2℃) and a shear rate of 0.1 / s, and more preferably 120,000 mPa·s or more. The upper limit of V1 is not particularly limited, but in reality, it is considered to be around 450,000.

[0063] The aqueous coating composition according to the present invention preferably has a viscosity value V2 of 50 to 300 mPa·s at a shear rate of 1000 / s at room temperature (23℃ ± 2℃), and more preferably 110 to 200 mPa·s. Specifically, the value of V2 may be, for example, 50, 100, 110, 120, 130, 140, 150, 160, 170, 180, 190, 200, 250, or 300 mPa·s, and may be within the range of any two of the values ​​exemplified here.

[0064] <Sedimentation separation degree> The aqueous coating composition according to the present invention preferably has a sedimentation separation rate of 2% or less after 12 weeks. Specifically, the sedimentation separation rate may be, for example, 0, 0.2, 0.4, 0.6, 0.8, 1.0, 1.5, or 2.0%, and may be within the range of any two of the values ​​exemplified herein.

[0065] <Sagging> The aqueous coating composition according to the present invention preferably exhibits no sagging of the coating film within 3 minutes after the glass plate is placed upright, following the measurement method described in JIS-K-5551:2018 (7.10 Sagging). Coatings with good thixotropy become highly viscous after application, making them less prone to sagging. The time from placing the glass plate upright until sagging of the coating film occurs is preferably 180 seconds (3 minutes) or more, more preferably 200 seconds or more, and even more preferably 300 seconds or more.

[0066] <Water resistance of the coating> In the present invention, it is preferable that when the aqueous coating composition is applied to a film thickness of 25 to 30 μm and the resulting test piece is immersed in water for 14 days in accordance with the method described in JIS-K-5600-6-1:2016, no cracking, blistering, or peeling of the test piece is observed.

[0067] The thixotropy, sedimentation separation, sagging, and water resistance of the above-mentioned aqueous paint composition can be adjusted by controlling the thixotropy of the aqueous solution of the polyvinyl alcohol polymer, depending on the degree of polymerization, degree of saponification, amount of modification, and type of vinyl ester monomer and polyfunctional monomer, and further by adjusting the amount of polyvinyl alcohol polymer added to the aqueous paint.

[0068] 3.Use The above-mentioned polyvinyl alcohol polymer or paint additive is used as an additive to paints used when painting structures such as buildings and structures, vehicles (automobiles, etc.), furniture, fixtures, electronic equipment, etc. Furthermore, the above-mentioned aqueous paint composition containing the above-mentioned polyvinyl alcohol polymer or paint additive is used as an aqueous paint for painting structures such as buildings and structures, vehicles (automobiles, etc.), furniture, fixtures, electronic equipment, etc. [Examples]

[0069] The present invention will be described in more detail below with reference to examples. These are all illustrative examples and do not limit the scope of the present invention.

[0070] <Preparation of polyvinyl alcohol-based polymers> [Example 1, Example 2, Example 9] In a polymerization vessel equipped with a reflux condenser, dropping funnel, and stirrer, 100 parts by mass of vinyl acetate, 0.16 parts by mass of triallyl isocyanurate (TAIC, manufactured by Shinryo Co., Ltd.), 67 parts by mass of methanol as a solvent, and 0.003 parts by mass of di-n-propyl peroxydicarbonate (Perloyl NPP, manufactured by Nippon Oil & Fats Co., Ltd.) as a polymerization initiator were charged, and polymerization was carried out below the boiling point for 8 hours with stirring under a nitrogen atmosphere. After the reaction was stopped, unreacted vinyl acetate was removed from the polymerization system. A methanol solution of the vinyl acetate polymer (intermediate copolymer) was obtained.

[0071] A methanol solution of sodium hydroxide (calculated as 0.008 moles of sodium hydroxide relative to the vinyl acetate-derived structural units) was added to the methanol solution of the vinyl acetate polymer obtained above, and a saponification reaction was carried out at 45°C for 45 minutes. The resulting reaction solution was heated and dried to obtain a polyvinyl alcohol-based polymer with a degree of saponification of 88 mol%.

[0072] The dried polyvinyl alcohol-based polymer was pulverized using an ACM pulverizer (manufactured by Hosokawa Micron Corporation) and then classified.

[0073] [Example 3] In a polymerization vessel equipped with a reflux condenser, dropping funnel, and stirrer, 100 parts by mass of vinyl acetate, 0.16 parts by mass of triallyl isocyanurate (TAIC, manufactured by Shinryo Co., Ltd.), 67 parts by mass of methanol as a solvent, and 0.004 parts by mass of di-n-propyl peroxydicarbonate (Perloyl NPP, manufactured by Nippon Oil & Fats Co., Ltd.) as a polymerization initiator were charged, and polymerization was carried out below the boiling point for 2 hours under a nitrogen atmosphere with stirring. After the reaction was stopped, unreacted vinyl acetate was removed from the polymerization system. A methanol solution of the vinyl acetate polymer (intermediate copolymer) was obtained.

[0074] A methanol solution of sodium hydroxide (calculated as 0.005 moles of sodium hydroxide relative to the structural units derived from vinyl acetate) was added to the methanol solution of the vinyl acetate polymer obtained above, and a saponification reaction was carried out at 45°C for 45 minutes. The resulting reaction solution was heated and dried to obtain a polyvinyl alcohol polymer with a degree of saponification of 80 mol%. The polyvinyl alcohol polymer obtained by drying in the same manner as in Example 1 was pulverized and classified.

[0075] [Example 4] A polyvinyl alcohol polymer was obtained in the same manner as in Example 1, except that the degree of saponification of the polyvinyl alcohol polymer was changed to 99 mol% using a methanol solution of the vinyl acetate polymer from Example 1. The polyvinyl alcohol polymer obtained by drying in the same manner as in Example 1 was then pulverized and classified.

[0076] [Example 5] A polyvinyl alcohol polymer was obtained in the same manner as in Example 1, except that the degree of saponification of the polyvinyl alcohol polymer was changed to 99.9 mol% using a methanol solution of the vinyl acetate polymer from Example 1. The polyvinyl alcohol polymer obtained by drying in the same manner as in Example 1 was then pulverized and classified.

[0077] [Example 6] In a polymerization vessel equipped with a reflux condenser, dropping funnel, and stirrer, 100 parts by mass of vinyl acetate, 0.33 parts by mass of triallyl isocyanurate (TAIC, manufactured by Shinryo Co., Ltd.), 150 parts by mass of methanol as a solvent, and 0.01 parts by mass of di-n-propyl peroxydicarbonate (Perloyl NPP, manufactured by Nippon Oil & Fats Co., Ltd.) as a polymerization initiator were charged, and polymerization was carried out below the boiling point for 8 hours while stirring under a nitrogen atmosphere. After the reaction was stopped, unreacted vinyl acetate was removed from the polymerization system. A methanol solution of the vinyl acetate polymer (intermediate copolymer) was obtained.

[0078] A methanol solution of sodium hydroxide (calculated as 0.005 moles of sodium hydroxide relative to the structural units derived from vinyl acetate) was added to the methanol solution of the vinyl acetate polymer obtained above, and a saponification reaction was carried out at 45°C for 45 minutes. The resulting reaction solution was heated and dried to obtain a polyvinyl alcohol polymer with a degree of saponification of 80 mol%. The polyvinyl alcohol polymer obtained by drying in the same manner as in Example 1 was pulverized and classified.

[0079] [Example 7] In a polymerization vessel equipped with a reflux condenser, dropping funnel, and stirrer, 100 parts by mass of vinyl acetate, 0.16 parts by mass of triallyl isocyanurate (TAIC, manufactured by Shinryo Co., Ltd.), 33.3 parts by mass of methanol as a solvent, and 0.007 parts by mass of di-n-propyl peroxydicarbonate (Perloyl NPP, manufactured by Nippon Oil & Fats Co., Ltd.) as a polymerization initiator were charged, and polymerization was carried out below the boiling point for 7 hours while stirring under a nitrogen atmosphere. After the reaction was stopped, unreacted vinyl acetate was removed from the polymerization system. A methanol solution of the vinyl acetate polymer (intermediate copolymer) was obtained.

[0080] A methanol solution of sodium hydroxide (calculated as 0.007 moles of sodium hydroxide relative to the structural units derived from vinyl acetate) was added to the methanol solution of the vinyl acetate polymer obtained above, and a saponification reaction was carried out at 45°C for 45 minutes. The resulting reaction solution was heated and dried to obtain a polyvinyl alcohol polymer with a degree of saponification of 88 mol%. The polyvinyl alcohol polymer obtained by drying in the same manner as in Example 1 was pulverized and classified.

[0081] [Example 8] In a polymerization vessel equipped with a reflux condenser, dropping funnel, and stirrer, 100 parts by mass of vinyl acetate, 0.09 parts by mass of triallyl isocyanurate (TAIC, manufactured by Shinryo Co., Ltd.), 50 parts by mass of methanol as a solvent, and 0.005 parts by mass of di-n-propyl peroxydicarbonate (Perloyl NPP, manufactured by Nippon Oil & Fats Co., Ltd.) as a polymerization initiator were charged, and polymerization was carried out below the boiling point for 5 hours under a nitrogen atmosphere with stirring. After the reaction was stopped, unreacted vinyl acetate was removed from the polymerization system. A methanol solution of the vinyl acetate polymer (intermediate copolymer) was obtained.

[0082] A methanol solution of sodium hydroxide (calculated as 0.007 moles of sodium hydroxide relative to the structural units derived from vinyl acetate) was added to the methanol solution of the vinyl acetate polymer obtained above, and a saponification reaction was carried out at 45°C for 45 minutes. The resulting reaction solution was heated and dried to obtain a polyvinyl alcohol polymer with a degree of saponification of 88 mol%. The polyvinyl alcohol polymer obtained by drying in the same manner as in Example 1 was pulverized and classified.

[0083] [Example 10] In a polymerization vessel equipped with a reflux condenser, dropping funnel, and stirrer, 100 parts by mass of vinyl acetate, 0.22 parts by mass of diallylmethyl isocyanurate (MeDAIC, manufactured by Shikoku Chemicals Co., Ltd.), 66.7 parts by mass of methanol as a solvent, and 0.005 parts by mass of di-n-propyl peroxydicarbonate (Perloyl NPP, manufactured by Nippon Oil & Fats Co., Ltd.) as a polymerization initiator were charged. Polymerization was carried out below the boiling point for 8 hours under a nitrogen atmosphere with stirring (conversion rate of vinyl acetate: 57%). After the reaction was stopped, unreacted vinyl acetate was removed from the polymerization system. A methanol solution of the vinyl acetate polymer (intermediate copolymer) was obtained.

[0084] A methanol solution of sodium hydroxide (calculated as 0.007 moles of sodium hydroxide relative to the structural units derived from vinyl acetate) was added to the methanol solution of the vinyl acetate polymer obtained above, and a saponification reaction was carried out at 45°C for 45 minutes. The resulting reaction solution was heated and dried to obtain a polyvinyl alcohol polymer with a degree of saponification of 88 mol%. The polyvinyl alcohol polymer obtained by drying in the same manner as in Example 1 was pulverized and classified.

[0085] [Example 11] In a polymerization vessel equipped with a reflux condenser, dropping funnel, and stirrer, 100 parts by mass of vinyl acetate, 0.37 parts by mass of diallyltetradecyl isocyanurate (LDAIC, manufactured by Shikoku Chemicals Co., Ltd.), 42.9 parts by mass of methanol as a solvent, and 0.01 parts by mass of di-n-propyl peroxydicarbonate (Perloyl NPP, manufactured by Nippon Oil & Fats Co., Ltd.) as a polymerization initiator were charged. Polymerization was carried out below the boiling point for 4 hours under a nitrogen atmosphere with stirring (conversion rate of vinyl acetate: 57%). After the reaction was stopped, unreacted vinyl acetate was removed from the polymerization system. A methanol solution of the vinyl acetate polymer (intermediate copolymer) was obtained.

[0086] A methanol solution of sodium hydroxide (calculated as 0.007 moles of sodium hydroxide relative to the structural units derived from vinyl acetate) was added to the methanol solution of the vinyl acetate polymer obtained above, and a saponification reaction was carried out at 45°C for 45 minutes. The resulting reaction solution was heated and dried to obtain a polyvinyl alcohol polymer with a degree of saponification of 88 mol%. The polyvinyl alcohol polymer obtained by drying in the same manner as in Example 1 was pulverized and classified.

[0087] [Comparative Example 1] In a polymerization vessel equipped with a reflux condenser, dropping funnel, and stirrer, 100 parts by mass of vinyl acetate, 0.16 parts by mass of triallyl isocyanurate (TAIC, manufactured by Shinryo Co., Ltd.), 150 parts by mass of methanol as a solvent, and 0.01 parts by mass of di-n-propyl peroxydicarbonate (Perloyl NPP, manufactured by Nippon Oil & Fats Co., Ltd.) as a polymerization initiator were charged, and polymerization was carried out below the boiling point for 8 hours while stirring under a nitrogen atmosphere. After the reaction was stopped, unreacted vinyl acetate was removed from the polymerization system. A methanol solution of the vinyl acetate polymer (intermediate copolymer) was obtained.

[0088] A methanol solution of sodium hydroxide (calculated as 0.007 moles of sodium hydroxide relative to the structural units derived from vinyl acetate) was added to the methanol solution of the vinyl acetate polymer obtained above, and a saponification reaction was carried out at 45°C for 45 minutes. The resulting reaction solution was heated and dried to obtain a polyvinyl alcohol polymer with a degree of saponification of 88 mol%. The polyvinyl alcohol polymer obtained by drying in the same manner as in Example 1 was pulverized and classified.

[0089] [Comparative Example 2] In a polymerization vessel equipped with a reflux condenser, dropping funnel, and stirrer, 100 parts by mass of vinyl acetate, 0.16 parts by mass of triallyl isocyanurate (TAIC, manufactured by Shinryo Co., Ltd.), 15 parts by mass of methanol as a solvent, and 0.003 parts by mass of di-n-propyl peroxydicarbonate (Perloyl NPP, manufactured by Nippon Oil & Fats Co., Ltd.) as a polymerization initiator were charged, and polymerization was carried out below the boiling point for 8 hours while stirring under a nitrogen atmosphere. After the reaction was stopped, unreacted vinyl acetate was removed from the polymerization system. A methanol solution of the vinyl acetate polymer (intermediate copolymer) was obtained.

[0090] A methanol solution of sodium hydroxide (calculated as 0.007 moles of sodium hydroxide relative to the structural units derived from vinyl acetate) was added to the methanol solution of the vinyl acetate polymer obtained above, and a saponification reaction was carried out at 45°C for 45 minutes. The resulting reaction solution was heated and dried to obtain a polyvinyl alcohol polymer with a degree of saponification of 88 mol%. The polyvinyl alcohol polymer obtained by drying in the same manner as in Example 1 was pulverized and classified.

[0091] [Comparative Example 3] A polyvinyl alcohol polymer was obtained in the same manner as in Example 1, except that the degree of saponification of the polyvinyl alcohol polymer was changed to 65 mol% using a methanol solution of the vinyl acetate polymer from Example 1. The polyvinyl alcohol polymer obtained by drying in the same manner as in Example 1 was then pulverized and classified.

[0092] [Comparative Example 4] In a polymerization vessel equipped with a reflux condenser, dropping funnel, and stirrer, 100 parts by mass of vinyl acetate, 5 parts by mass of methanol as a solvent, and 0.003 parts by mass of di-n-propyl peroxydicarbonate (perloyl NPP, manufactured by Nippon Oil & Fats Co., Ltd.) as a polymerization initiator were charged, and polymerization was carried out below the boiling point for 4 hours under a nitrogen atmosphere with stirring. After the reaction was stopped, unreacted vinyl acetate was removed from the polymerization system. A methanol solution of the vinyl acetate polymer (intermediate copolymer) was obtained.

[0093] A methanol solution of sodium hydroxide (calculated as 0.007 moles of sodium hydroxide relative to the structural units derived from vinyl acetate) was added to the methanol solution of the vinyl acetate polymer obtained above, and a saponification reaction was carried out at 45°C for 45 minutes. The resulting reaction solution was heated and dried to obtain a polyvinyl alcohol polymer with a degree of saponification of 40 mol%. The polyvinyl alcohol polymer obtained by drying in the same manner as in Example 1 was pulverized and classified.

[0094] <Measurement and Evaluation> The physical properties and characteristics of the polyvinyl alcohol-based polymers (PVA) obtained in each example and comparative example were measured. The results are shown in Table 1.

[0095] [Table 1]

[0096] [Viscosity average degree of polymerization] For the PVAs in the examples and comparative examples obtained above, the viscosity-average degree of polymerization was calculated from the intrinsic viscosity [η] (g / dL) measured at 30°C using an Ostwald viscometer with deionized water as the solvent, in accordance with JIS K 6726:1994 "3.7 Average degree of polymerization," using the following formula (A). P represents the viscosity-average degree of polymerization. log(P) = 1.613 × log([η] × 10 4 / 8.29) ···(A)

[0097] [Degree of saponification] The degree of saponification of the PVA obtained in the above examples and comparative examples was measured in accordance with JIS K 6726:1994 "3.5 Degree of Saponification". Specifically, the degree of saponification was determined by back titration using N / 10 sulfuric acid as specified in JIS K 8951:2006 and N / 10 sodium hydroxide solution as specified in JIS K 8576:2019.

[0098] [Amount of denaturation] For the PVA obtained above in Examples 1-8 and Comparative Examples 1-3 using triallyl isocyanurate, the degree of denaturation was calculated using the trace total nitrogen analyzer "TN-2100H" (manufactured by Nitto Seikou Analytech Co., Ltd.) (for detailed methods, please refer to International Publication No. 2023 / 238674).

[0099] Furthermore, the amount of modification (mol%) of the PVA in Example 9, which used diallylmethyl isocyanurate, and in Example 10, which used diallyltetradecyl isocyanurate, was calculated using the following method. The amount of denaturation is calculated using fully saponified PVA. 1The composition was determined by 1H-NMR analysis. Fully saponified PVA was prepared by the following procedure: After removing unreacted vinyl acetate from the polymerization system, the methanol solution of the vinyl acetate polymer (intermediate copolymer) was dried in a dryer. 12 g of the dried sample and 388 g of methanol were added to a flask and dissolved at 40°C for 1 hour. Then, 20 mL of 10% NaOH methanol solution was added and the mixture was reacted at 40°C for 1 hour. Subsequently, 3 mL of acetic acid was added for neutralization, the mixture was filtered, and the residue, which mainly consisted of PVA, was washed by Soxhlet extraction using methanol to obtain fully saponified PVA. The obtained fully saponified PVA was dried in a drying oven at 90°C for 1 hour. The dried PVA was dissolved in heavy water, and NMR (ECX-400, manufactured by JEOL Ltd.) was used under the conditions of a measurement temperature of 80°C and 128 cumulative measurements. 1 1H-NMR spectra were obtained. (Diallylmethylisocyanurate) From the obtained spectrum, the integral value of the peak originating from the methyl group on the nitrogen atom (3.2-3.4 ppm) was taken as a, and the integral value of the peak originating from the methylene group not adjacent to the hydroxyl group of the vinyl alcohol unit and the methylene group not adjacent to the ester group of the vinyl ester monomer unit (1.3-2 ppm) was taken as b. The amount of modification of PVA (copolymerization amount of triallylmethyl isocyanurate in PVA) X (mol%) was calculated from the following formula (B). (Diallyltetradecylisocyanurate) From the obtained spectrum, the integral value of the peak (0.7-0.9 ppm) originating from the methyl group at the end of the tetradecyl group on the nitrogen atom was taken as a, and the integral value of the peak (1.3-2 ppm) originating from the methylene group not adjacent to the hydroxyl group of the vinyl alcohol unit and the methylene group not adjacent to the ester group of the vinyl ester monomer unit was taken as b. The copolymerization amount X (mol%) of diallyltetradecyl isocyanurate in PVA was calculated from the following formula (B). X=((1 / 3)a / (b / 2))×100 ···(B)

[0100] [Thixotropy index of PVA polymer aqueous solution] For the PVA samples obtained in the above-mentioned examples and comparative examples, 4% by mass aqueous solutions were prepared, and the viscosity was measured at room temperature (23°C ± 2°C) at shear rates of 0.1 / s and 1000 / s using a rheometer measuring device (Anton Paar MCR). A cone plate CP50-2 (diameter: 50 mm, angle 2°) was used. The value V1 / V2 obtained by dividing the viscosity V1 at a shear rate of 0.1 / s by the viscosity V2 at a shear rate of 1000 / s was defined as the thixotropy index (indicated as "viscosity ratio" in the table).

[0101] [Preparation of water-based paint composition] First, 10 parts by mass of water, 20 parts by mass of titanium dioxide (Teika Corporation, JR-901), 4 parts by mass of dispersant (BYK Corporation, DISPERBYK-102), and 30 parts by mass of acrylic resin emulsion (50% solids content, Japan Coating Resin Co., Ltd., Movinyl 7710) were weighed out and mixed in a bead mill to obtain a mixed solution. Next, to the mixed solution obtained above, 5 parts by mass of a coating agent (JNC Corporation, CS-12), 1 part by mass of a preservative (Yamato Chemical Industry Co., Ltd., Amolden FS-14D), and 30 parts by mass of an acrylic emulsion (50% solids content, Japan Coating Resin Co., Ltd., Movinyl 7710) were added and mixed using a bead mill. Furthermore, the PVA used in the above examples and comparative examples was added in the amounts shown in Table 1 as a rheology control agent and mixed using a bead mill. The physical properties of the obtained water-based paint were measured using the following method. The results are shown in Table 1.

[0102] [Thixotropy Index of Water-Based Paints] The viscosity of the aqueous paint compositions according to the above-mentioned examples and comparative examples was measured at room temperature (23°C ± 2°C) at shear rates of 0.1 / s and 1000 / s using a rheometer measuring device (Anton Paar MCR). A cone plate CP50-2 (diameter: 50 mm, angle 2°) was used. The value V1 / V2 obtained by dividing the viscosity V1 at a shear rate of 0.1 / s by the viscosity V2 at 1000 / s was defined as the thixotropy index (indicated as "viscosity ratio" in the table).

[0103] [Sedimentation separation degree] The aqueous paint compositions according to the above-mentioned examples and comparative examples were placed in a 100 mL colorimetric tube, and the volume of the supernatant of the aqueous paint composition after 12 weeks was measured by visually reading the scale on the 100 mL colorimetric tube.

[0104] [sagging] The aqueous paint compositions obtained in the above examples and comparative examples were evaluated for their sag properties according to the measurement method described in JIS-K-5551:2018 (7.10 Sag Properties). Specifically, the aqueous paint composition was applied to a glass plate (150 mm × 100 mm × 2 mm) to a thickness of 250 μm at room temperature (23 °C ± 2 °C) using a sag tester. The flow (sag) of the paint film was observed by standing the test piece vertically, and the sag property was evaluated by measuring the time from when the test piece was stood up until sag occurred. Sag was evaluated according to the following evaluation criteria. Note that if no sag occurred in the paint film for more than 300 seconds (5 minutes) after the test piece was stood up, the time is indicated as ">300". ○: No sagging of the coating occurs even after 180 seconds (3 minutes) or more have passed since the test specimen was placed upright. ×: The coating sagged less than 180 seconds (3 minutes) after the test specimen was placed upright.

[0105] [Water resistance of the coating] The aqueous paint compositions obtained in the above examples and comparative examples were evaluated for their water resistance according to the measurement method described in JIS-K-5600-6-1:2016. Specifically, the aqueous paint composition was diluted to 5% with clean water and applied using a brush at a rate of 0.12 kg / m². 2The coating was applied to a flexible substrate (150 mm × 70 mm × 4 mm) with a film thickness of 25-30 μm. The resulting test specimens were immersed in pure water at room temperature (23°C ± 2°C) for 14 days, and the presence or absence of cracks, blistering, and peeling was evaluated visually according to the following evaluation criteria. ○: No cracks, swelling, or peeling. ×: Cracks, swelling, or peeling present.

Claims

1. A paint additive containing a vinyl alcohol-based polymer having vinyl alcohol units and vinyl ester units, The vinyl alcohol-based polymer has a degree of saponification of 70 mol% or more and a viscosity-average degree of polymerization of 1000 to 5000. Viscosity value V of a 4% by mass aqueous solution of the vinyl alcohol polymer at a shear rate of 0.1 / s １ Viscosity value V at a shear rate of 1000 / s ２ Ratio V １ / V ２ A paint additive in which the value is 10 or higher.

2. The paint additive according to claim 1, wherein the degree of saponification of the vinyl alcohol-based polymer is 70 mol% to 99 mol%.

3. The paint additive according to claim 1, wherein the vinyl alcohol-based polymer has polyfunctional monomer units.

4. The paint additive according to claim 1, wherein the polyfunctional monomer has a structure derived from an isocyanurate having two or more allyl groups.

5. The paint additive according to claim 1, wherein the content of the polyfunctional monomer units is 0.001 mol% to 1.0 mol% when the total of the vinyl alcohol units and the vinyl ester units is 100 mol%.

6. A water-based paint composition comprising the paint additive described in any one of claims 1 to 5.

7. A water-based paint composition, The aqueous paint composition according to claim 6, wherein when the total amount of components other than the vinyl alcohol polymer contained in the aqueous paint composition is 100 parts by mass, the aqueous paint composition contains 0.1 parts by mass to 5 parts by mass of the vinyl alcohol polymer.

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