JP2014101504A - Vinyl acetate-maleate ester copolymer, its manufacturing method and coating for wood - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a vinyl acetate-maleate ester copolymer excellent in workability and weather resistance when used as a coating for wood, and its manufacturing method.SOLUTION: A vinyl acetate-maleate ester copolymer is obtained by emulsion polymerization of vinyl acetate and maleate ester in the presence of partially saponificated polyvinyl alcohol and glycol represented by the formula (1) and having 4 to 7 carbon atoms. (1), where R, R, Rand Rrepresent each independently a hydrogen atom or a monovalent hydrocarbon group.

Description

  The present invention relates to a vinyl acetate-maleic acid ester copolymer, a production method thereof, and a wood coating material using the same.

  Conventionally, vinyl acetate emulsions obtained by polymerizing vinyl acetate as a monomer are used for coatings in the construction and building materials field, adhesives for woodworking, plastic processing, paper processing, etc. It is used for various applications such as admixtures.

  However, since this vinyl acetate emulsion generally has a high viscosity, it is difficult to apply as a paint to an object to be applied such as a building material, resulting in poor workability.

  Then, the method of manufacturing the vinyl acetate type emulsion for improving this workability | operativity is proposed (refer patent document 1).

  In Patent Document 1, in the case of emulsion polymerization of a vinyl ester monomer in the presence of 3-methoxy-3-methyl-1-butanol using a vinyl alcohol polymer as a dispersant, A method for producing a vinyl acetate copolymer emulsion by adding 3-methoxy-3-methyl-1-butanol simultaneously with the addition is disclosed.

JP 2011-132270 A

  By the way, when the vinyl acetate emulsion of Patent Document 1 is used for an outdoor paint such as an outer wall of a building, the coating film obtained by drying the paint has its surface exposed to the outdoor environment for a long time. Phenomenon (blister) that partly swells occurs. Blisters can damage the appearance of the coating film or cause the coating film to peel off. Therefore, the paint obtained from Patent Document 1 is inferior in weather resistance.

  Accordingly, an object of the present invention is to provide a vinyl acetate polymer having good workability and weather resistance and a method for producing the same.

  The present inventor has intensively studied the above problems, and by performing emulsion polymerization of vinyl acetate and maleate in the presence of partially saponified polyvinyl alcohol and a specific glycol, workability is good and weather resistance is good. The inventors have found that an improved vinyl acetate-maleic acid ester copolymer can be obtained, and have completed the present invention.

That is, the present invention
(1) It is obtained by emulsion polymerization of vinyl acetate and maleate in the presence of partially saponified polyvinyl alcohol and glycol having the carbon number of 4 or more and 7 or less represented by the following formula (1). Vinyl acetate-maleic acid ester copolymer, characterized by

(Wherein R ¹ , R ² , R ³ and R ⁴ each independently represents a hydrogen atom or a monovalent hydrocarbon group.)
(2) The vinyl acetate-maleic acid ester copolymer according to (1) above, wherein the vinyl acetate-maleic acid ester copolymer has a weight average molecular weight of 200,000 or more,
(3) Wood paint (4) partially saponified polyvinyl alcohol, characterized by containing the vinyl acetate-maleic acid ester copolymer described in (1) or (2) above, and the following formula (1) A vinyl acetate-maleic acid ester copolymer, comprising the step of emulsion polymerization of vinyl acetate and maleic acid ester in the presence of glycol having 4 to 7 carbon atoms Method.

(Wherein R ¹ , R ² , R ³ and R ⁴ each independently represents a hydrogen atom or a monovalent hydrocarbon group.)
It is.

  According to the vinyl acetate-maleic acid ester copolymer of the present invention, it is possible to achieve a low viscosity of the coating material containing the vinyl acetate-maleic acid ester copolymer. Therefore, it becomes easy to apply the coating material to an object to be coated, and workability is good.

  Moreover, even if the coating film obtained by applying and drying the coating material on an object to be coated is exposed to the outdoors for a long time, the generation of blisters is suppressed. Therefore, the weather resistance is good.

  According to the wood coating material of the present invention, since it contains the vinyl acetate-maleic acid ester copolymer of the present invention, it can be suitably used as a wood protective material having good workability and weather resistance.

  According to the method for producing a vinyl acetate-maleic acid ester copolymer of the present invention, a vinyl acetate-maleic acid ester copolymer having good workability and weather resistance can be produced.

FIG. 1 shows an example of a tensile test profile obtained by the tensile test of the example (a mode in which the stress increases linearly). FIG. 2 shows an example of a tensile test profile obtained in the tensile test of the example (a mode in which the stress is constant). FIG. 3 shows an example of the tensile test profile obtained in the tensile test of the example (embodiment showing the yield point).

  The vinyl acetate-maleic acid ester copolymer of the present invention is vinyl acetate and maleic acid in the presence of partially saponified polyvinyl alcohol and a glycol represented by the following formula (1) having 4 to 7 carbon atoms. It is obtained by emulsion polymerization with an ester.

  Partially saponified polyvinyl alcohol is a dispersant compounded as a protective colloid during emulsion polymerization. For example, a polyvinyl acetate polymer obtained by polymerizing a vinyl monomer containing vinyl acetate as a main component is obtained by a known method. It can be obtained by saponification.

  The degree of saponification of partially saponified polyvinyl alcohol is, for example, 70 mol% or more, preferably 80 mol% or more, and for example, 95 mol% or less, preferably 90 mol% or less.

  When the degree of saponification of the partially saponified polyvinyl alcohol is less than 70 mol%, the water solubility is lowered and emulsion polymerization may not be possible. On the other hand, when the degree of saponification exceeds 95 mol%, the surface activity is lowered, the particle size is increased, and emulsion polymerization may not be performed.

  The saponification degree can be measured based on, for example, the integrated value of the NMR spectrum, the hydroxyl value, and the like.

  The average degree of polymerization of the partially saponified polyvinyl alcohol is, for example, 100 or more, preferably 500 or more, and for example, 8000 or less, preferably 2500 or less. When the average degree of polymerization is in the above range, the partially saponified polyvinyl alcohol can further exhibit the function as a protective colloid.

  The average degree of polymerization of partially saponified polyvinyl alcohol can be measured based on, for example, gel permeation chromatography (GPC), melt viscosity, aqueous solution viscosity, and the like.

  The partially saponified polyvinyl alcohol has a viscosity at 20 ° C. of a 4% aqueous solution of, for example, 3 mPa · sec or more, preferably 5 mPa · sec or more, and for example, 100 mPa · sec or less, preferably 50 mPa · sec or less. is there.

  The viscosity of partially saponified polyvinyl alcohol can be measured at 20 ° C. using a 4% aqueous solution with a B-type viscometer (rotor No. 1 or L adapter).

  Specific examples of the partially saponified polyvinyl alcohol include PVA-205, PVA-217, and PVA-224 manufactured by Kuraray.

  Glycol is represented by the following formula (1).

R ¹ , R ² , R ³ and R ⁴ each independently represent a hydrogen atom or a monovalent hydrocarbon group.

  The monovalent hydrocarbon group has, for example, a carbon number of 1 such as methyl group, ethyl group, n-propyl group, iso-propyl group, n-butyl group, iso-butyl group, sec-butyl group, and tert-butyl group. -4 alkyl groups are mentioned.

Preferably, at least one of R ¹ , R ² , R ³ and R ⁴ is a hydrogen atom, and the remainder is a monovalent hydrocarbon group. More preferably, one or two of R ¹ , R ² , R ³ and R ⁴ are hydrogen atoms, and the rest are monovalent hydrocarbon groups.

  The number of carbon atoms of the glycol is 4 or more, preferably 5 or more, and 7 or less, preferably 6 or less.

  Specific examples of the glycol include 1,3-butanediol, 1,3-pentanediol, 3-methyl-1,3-butanediol, 2,4-pentanediol, 1,3-hexanediol, 2, 4-hexanediol, 3-methyl-1,3-pentanediol, 4-methyl-1,3-pentanediol, 2-methyl-2,4-pentanediol, 1,3-heptanediol, 2,4- Heptanediol, 3,5-heptanediol, 3-methyl-1,3-hexanediol, 4-methyl-1,3-hexanediol, 5-methyl-1,3-hexanediol, 3-ethyl-1,3 -Pentanediol, 3,4-dimethyl-1,3-pentanediol, 2-methyl-2,4-hexanediol, 4-methyl-2,4-hexanediol, 5-methyl Le-2,4-hexanediol, etc. 2,4-dimethyl-2,4-pentanediol.

  These glycols can be used alone or in combination of two or more.

  Of these, 2-methyl-2,4-pentanediol and 2,4-hexanediol are preferable, and 2-methyl-2,4-pentanediol is more preferable.

  By using such a glycol, the viscosity of a copolymer emulsion (described later) can be reduced, and workability can be improved. In addition, the molecular weight of the vinyl acetate-maleic acid ester copolymer can be sufficiently increased, and the particle diameter can be reduced, so that the weather resistance of the vinyl acetate-maleic acid ester copolymer is excellent, and the copolymer emulsion Storage stability can be improved.

  Examples of maleates include maleic acid C1-18 monoalkyl esters such as methyl maleate, ethyl maleate, propyl maleate, butyl maleate, octyl maleate, dodecyl maleate, lauryl maleate and stearyl maleate ( Preferably, maleic acid C2-6 monoalkyl esters) such as dimethyl maleate, diethyl maleate, dipropyl maleate, dibutyl maleate, dioctyl maleate, didodecyl maleate, dilauryl maleate, etc. 18 alkyl) ester (preferably maleic acid di (C2-6alkyl) ester), for example, 1-benzyl-4-methyl maleate and the like.

  Maleate esters can be used alone or in combination of two or more.

  The maleate ester is preferably a dialkyl maleate, more preferably dibutyl maleate, dipropyl maleate, and particularly preferably dibutyl maleate.

  In the present invention, vinyl acetate and maleic acid ester are used in combination as a copolymer monomer. By using vinyl acetate, the resulting vinyl acetate-maleic acid ester copolymer has good adhesion to wood. Moreover, by using maleic acid ester, the hydrolysis resistance of the vinyl acetate-maleic acid ester copolymer can be improved, and the weather resistance of the coating film can be further improved. Moreover, by lowering the glass transition temperature of the vinyl acetate-maleic acid ester copolymer, it is possible to impart film forming properties to the copolymer emulsion and to improve the crack resistance of the coating film.

  In the present invention, in addition to vinyl acetate and maleic acid ester, other copolymerizable monomers can be copolymerized within a range not impairing the effects of the present invention.

  Examples of such copolymerizable monomers include ethylenically unsaturated monomers and diene monomers.

  Examples of the ethylenically unsaturated monomer include vinyl esters such as vinyl propionate and VeoVa10 (neodecanoic acid ethenyl ester), for example, olefins such as ethylene, propylene, and isobutylene, such as vinyl chloride, vinyl fluoride, vinyl bromide, Halogenated olefins such as vinylidene chloride and vinylidene fluoride, for example, unsaturated carboxylic acids such as (meth) acrylic acid, fumaric acid, itaconic acid, such as methyl (meth) acrylate, ethyl (meth) acrylate, (meth ) (Meth) acrylate esters such as butyl acrylate, 2-ethylhexyl (meth) acrylate, dodecyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, such as dimethylaminoethyl (meth) acrylate and Quaternized compounds, for example (me ) Acrylamide, N- methylolacrylamide, N, N'-dimethyl acrylamide, such as acrylamide-2-methylpropanesulfonic acid and salts thereof (meth) acrylamide monomer include, for example, (meth) acrylonitrile.

  Examples of the diene monomer include butadiene, isoprene, chloroprene and the like.

  These can be used alone or in combination of two or more.

  And in order to produce the vinyl acetate-maleic acid ester polymer of the present invention, in the presence of partially saponified polyvinyl alcohol and glycol represented by the above general formula (1) and having 4 to 7 carbon atoms. , Vinyl acetate and maleate ester, and, if necessary, the above copolymerizable monomers (hereinafter collectively referred to as monomer components) are emulsion-polymerized. Emulsion polymerization can be carried out by known methods and conditions except that the above components are used. For example, a monomer component and a glycol-containing hydrophobic solution are added to an aqueous solution (PVA aqueous solution) containing partially saponified polyvinyl alcohol, and the monomer component is polymerized by adding a polymerization initiator and heat while stirring. An emulsion (copolymer emulsion) containing a vinyl acetate-maleic acid ester copolymer can be obtained.

  Specifically, first, the monomer component and the glycol are mixed and stirred to prepare a uniform hydrophobic solution.

  The mixing ratio of vinyl acetate and maleic acid ester (vinyl acetate / maleic acid ester) is 85/15 to 40/60 by mass ratio, preferably 75/25 to 50/50, more preferably 70. / 30 to 55/45.

  By setting the blending ratio in the above range, the glass transition temperature of the resulting vinyl acetate-maleic acid ester copolymer can be lowered, and the hydrolysis resistance can be further improved. Furthermore, when used as a vehicle for wood paints, it is possible to form a coating film excellent in weather resistance and adhesion, and to adjust the hardness of the coating film to an appropriate range.

  The blending ratio of glycol is, for example, 0.5 parts by mass or more, preferably 1 part by mass or more, more preferably 2 parts by mass, with respect to 100 parts by mass of the total amount of vinyl acetate and maleate. For example, it is 30 parts by mass or less, preferably 20 parts by mass or less, and more preferably 10 parts by mass or less.

  By making a mixture ratio 0.5 mass part or more, workability | operativity of the copolymer emulsion obtained can be made still more favorable. On the other hand, when the blending ratio is 30 parts by mass or less, the molecular weight can sufficiently maintain the weather resistance.

  In the case of blending other copolymerizable monomers, the blending ratio is, for example, 10 parts by mass or less, preferably 5 parts by mass or less with respect to 100 parts by mass of the total amount of vinyl acetate and maleate. is there.

  Next, an aqueous PVA solution is prepared.

  Preparation of the PVA aqueous solution is, for example, by adding and dispersing partially saponified polyvinyl alcohol under stirring of cold water at 25 ° C. or less, heating it to 60-90 ° C. and dissolving it, and dissolving the partially saponified polyvinyl alcohol in water. After confirming this, it is carried out by cooling to room temperature.

 The concentration of the partially saponified polyvinyl alcohol in the PVA aqueous solution is, for example, 2% by mass or more, preferably 4% by mass or more, and for example, 40% by mass or less, preferably 30% by mass or less.

  In addition, the PVA aqueous solution can be premixed with a buffering electrolyte from the viewpoint of suppressing the hydrolysis of the vinyl acetate-maleic acid ester copolymer obtained during the polymerization reaction and the polymerization reaction (before Addition). In addition, the electrolyte can be continuously supplied into the reaction liquid obtained by mixing an aqueous PVA solution and a hydrophobic solution and emulsion polymerization (addition in the middle).

  Examples of the electrolyte include sodium acetate, sodium phosphate, sodium carbonate, sodium bicarbonate, and the like, and preferably sodium acetate.

  The blending ratio of the electrolyte is, for example, 0.01 parts by mass or more, preferably 0.1 parts by mass or more, and for example, 1 part by mass or less, preferably 0.1 parts by mass with respect to 100 parts by mass of the monomer component. 5 parts by mass or less.

  Subsequently, after mixing a hydrophobic solution with PVA aqueous solution, it heats up, stirring.

  The mixing ratio of the PVA aqueous solution and the hydrophobic solution is, for example, 0.5 parts by mass or more, preferably 1.0 parts by mass or more, more preferably 100 parts by mass of partially saponified polyvinyl alcohol with respect to 100 parts by mass of the monomer component. 2.0 parts by mass or more, for example, 20 parts by mass or less, preferably 10 parts by mass or less, and more preferably 8.0 parts by mass or less.

  Polymerization stability will become favorable in a compounding ratio being 0.5 mass part or more. On the other hand, when the blending ratio is 20 parts by mass or less, thickening of the reaction solution during the polymerization reaction can be suppressed. Furthermore, in particular, when the blending ratio is 2.0 parts by mass or more, the water vapor permeability of the coating film becomes good, so that the adhesiveness with wood becomes good. On the other hand, in particular, when the blending ratio is 8.0 parts by mass or less, the coating workability of the paint can be made a good viscosity.

  For stirring, for example, a stirrer that is usually used for a synthesis reaction, such as a saddle type, an anchor type, or a propeller type, is used. Preferably, a stirrer having a large diameter and / or cross-sectional area and used for a high viscosity liquid (for example, 1000 mPa · sec or more) is used.

  The stirring conditions are appropriately set, and the peripheral speed of the stirring blade is set to, for example, 10 m / min or more, preferably 20 m / min or more, and for example, 400 m / min or less, preferably 200 m / min or less.

  The heating temperature is, for example, 30 ° C. or more, preferably 40 ° C. or more, more preferably 50 ° C. or more, further preferably 55 ° C. or more, and for example, 90 ° C. or less, preferably 80 ° C. or less. More preferably, it is 70 degrees C or less, More preferably, it is also 65 degrees C or less.

  By setting the heating temperature to 30 ° C. or higher, particularly 40 ° C. or higher, the polymerization initiator is decomposed and the polymerization is easily started. In addition, a sufficient polymerization rate can be obtained. On the other hand, by setting the heating temperature to 90 ° C. or lower, particularly 70 ° C. or lower, chain transfer of vinyl acetate-maleic ester copolymer radical to partially saponified polyvinyl alcohol, and vinyl acetate-maleic acid of partially saponified polyvinyl alcohol Since graft polymerization onto the ester copolymer is appropriately adjusted, the viscosity of the resulting copolymer emulsion can be further reduced, and workability can be further improved.

  In parallel with the heating, an inert gas such as nitrogen can be introduced into the atmosphere of the reaction vessel and / or the charged solution to facilitate the initiation of polymerization.

  Next, a polymerization initiator is added to the mixed liquid of the heated PVA aqueous solution and the hydrophobic solution. Thereby, a polymerization initiator decomposes | disassembles in a liquid mixture, a radical generate | occur | produces, a monomer component carries out radical polymerization by the radical, and a vinyl acetate-maleic acid ester copolymer is produced | generated.

  Examples of the polymerization initiator include polymerization initiators usually used in emulsion polymerization, preferably water-soluble polymerization initiators.

  Examples of the water-soluble polymerization initiator include 2,2′-azobis (2-methylpropionamidine) disulfate, 2,2′-azobis (2-methylpropionamidine) dihydrochloride, and 2,2′-azobis. (2-amidinopropane) dihydrochloride, 2,2′-azobis [N- (2-carboxyethyl) -2-methylpropionamidine] hydrate, 2,2′-azobis (N, N′-dimethylene) Isobutylamidine), 2,2′-azobis {2- [1- (2-hydroxyethyl) -2-imidazolin-2-yl] propane} dihydrochloride, 2,2′-azobis (1-imino-1- Pyrrolidino-2-methylpropane) dihydrochloride, 2,2′-azobis {2-methyl-N- [1,1-bis (hydroxymethyl) -2-hydroxyethyl] propionamide}, 2,2′-azo [2-methyl-N- (2-hydroxyethyl) propionamide], 2,2′-azobis [2- (2-imidazolin-2-yl) propane], 2,2′-azobis [2- (2 -Imidazolin-2-yl) propane] dihydrochloride, 2,2′-azobis [2- (2-imidazolin-2-yl) propane] disulfate dihydrate, such as peroxy Persulfate compounds such as potassium sulfate, sodium persulfate and ammonium persulfate, for example, water-soluble inorganic peroxides such as hydrogen peroxide, water-soluble organic peroxides such as tert-butyl peroxide and cumene peroxide, etc. Is mentioned. Further, as a water-soluble polymerization initiator, for example, a water-soluble polymerization initiator excluding a water-soluble azo compound, ascorbic acid, sodium bisulfite, sodium hyposulfite, sodium bisulfite, sodium sulfite, sodium hydroxymethanesulfinate (Longalite) ), Redox-based water-soluble polymerization initiators in combination with water-soluble reducing agents such as thiourea dioxide, sodium thiosulfate, tartaric acid, divalent iron salts, monovalent copper salts, and amines.

  From the viewpoint of facilitating the initiation of polymerization, a persulfate compound is preferable. Furthermore, from the viewpoint that an aqueous solution can be easily prepared, sodium persulfate and ammonium persulfate are more preferable.

  The polymerization initiators can be used alone or in combination of two or more.

  The blending ratio of the polymerization initiator is, for example, 0.01 parts by mass or more, preferably 0.1 parts by mass or more, and for example, 5 parts by mass or less, preferably 100 parts by mass of the monomer component. It is also 2 parts by mass or less.

  By setting the blending ratio of the polymerization initiator to 0.01 parts by mass or more, particularly 0.1 parts by mass or more, the monomer component can be efficiently emulsion polymerized. On the other hand, it can suppress that the molecular weight of the vinyl acetate maleic acid ester copolymer obtained falls too much by making a mixture ratio into 2 mass parts or less.

  In the present invention, the hydrophobic solution is preferably added to the aqueous PVA solution in two stages. That is, first, a part of the hydrophobic solution is added to the PVA solution, and then the emulsion polymerization reaction is started by a polymerization initiator and heating, and then the remaining hydrophobic solution is gradually added to the reaction solution. It can also be added. Thereby, intense heat generation at the start of the polymerization can be suppressed, the polymerization temperature can be appropriately controlled, and the monomer unit composition in the copolymer can be made to be uniform.

  The ratio (part by mass) of a part of the hydrophobic solution added first and the remaining hydrophobic solution added later is, for example, 1: 1 to 1:50, preferably 1:10 to 1 in the former: latter. : 20.

  The addition time of the remaining hydrophobic solution to the reaction solution is appropriately set according to the above ratio, and is, for example, 2 hours or more, preferably 4 hours or more, and for example, 12 hours or less, preferably Is 10 hours or less, more preferably 8 hours or less.

  The polymerization method is soap-free emulsion polymerization in which the polymerization reaction proceeds without adding an emulsifier because the partially saponified polyvinyl alcohol plays a role as a protective colloid. For example, an emulsifier can also be added.

  Examples of the emulsifier include emulsifiers commonly used in emulsion polymerization, and examples include anionic emulsifiers such as sodium dioctylsulfosuccinate, sodium dodecylbenzenesulfonate, sodium lauryl sulfate, sodium dodecyldiphenyletherdisulfonate, sodium nonyldiphenylethersulfonate. Examples thereof include nonionic emulsifiers such as polyoxyalkylene alkyl ethers, polyoxyalkylene alkyl aryl ethers, polyoxyalkylene aralkyl aryl ethers, polyoxyalkylene block copolymers, and polyoxyalkylene aryl ethers.

  In the present invention, a soap-free polymerization stabilized only with PVA is preferably employed. Thereby, the coating film containing a vinyl acetate-maleic acid ester copolymer can exhibit favorable water resistance and water vapor permeability.

  Thereby, the emulsion (copolymer emulsion) containing a vinyl acetate-maleic acid ester copolymer is obtained.

  The solid content (TSC) of the obtained copolymer emulsion is, for example, 45% by mass or more, preferably 48% by mass or more, more preferably 50% by mass or more, and for example, 60% by mass or less, preferably Is 55% by mass or less, more preferably 52% by mass or less.

  When the solid content is 45% by mass or more, the standing stability of the copolymer emulsion is good. On the other hand, when the solid content concentration is 60% by mass or less, an increase in the viscosity of the reaction solution at the time of emulsion polymerization can be suppressed, and a vinyl acetate-maleic acid ester copolymer can be easily produced.

  The viscosity of the copolymer emulsion is, for example, 0.5 Pa · sec or more, preferably 1.0 Pa · sec or more, more preferably 1.5 Pa · sec in a copolymer emulsion having a solid content of 50 to 51%. For example, it is 4.0 Pa · sec or less, preferably 3.0 Pa · sec or less, and more preferably 2.5 Pa · sec or less.

  The method for measuring the solid content will be described in detail in Examples.

  The viscosity is measured using a Brookfield M-type viscometer (rotor No. 3) under the conditions of 25 ° C. and 30 rpm.

  When the viscosity of the copolymer emulsion is within the above range, the workability of the coating obtained from the copolymer emulsion is improved.

  The pH of the copolymer emulsion is, for example, 3.0 or more, preferably 4.0 or more, and is, for example, 7.0 or less, preferably 6.0 or less.

  The minimum film forming temperature of the copolymer emulsion is, for example, 30 ° C. or lower, preferably 0 ° C. or lower.

  When the minimum film-forming temperature is in the above range, it can be suitably used as a vehicle for paints.

  The average particle size of the vinyl acetate-maleic ester copolymer dispersed in the copolymer emulsion is, for example, 0.1 μm or more, preferably 0.3 μm or more, more preferably 0.5 μm or more, Further, for example, it is 2.0 μm or less, preferably 1.3 μm or less, more preferably 1.0 μm or less, and still more preferably 0.8 μm or less. Even if the vinyl acetate-maleic acid ester copolymer of the present invention is a soap-free emulsion polymerization vinyl acetate-maleic acid ester copolymer, it is easily controlled to an average particle size in the above range. This is presumed that the glycol of the above formula (1) contributes to interface stabilization.

  The average particle diameter can be determined by a dynamic light scattering method.

  The weight average molecular weight of the vinyl acetate-maleic acid ester copolymer is, for example, 200,000 or more, preferably 250,000 or more, more preferably 300,000 or more, and, for example, 1,000,000 or less, preferably 60 10,000 or less, more preferably 500,000 or less.

  When the weight average molecular weight is in the above range, the copolymer can be prevented from being decomposed by ultraviolet rays, and the weather resistance of the coating film can be further improved.

  The degree of dispersion (weight average molecular weight / number average molecular weight) of the vinyl acetate-maleic acid ester copolymer is, for example, 1.0 or more, preferably 3.0 or more, and for example, 10.0 or less. Preferably, it is 7.0 or less.

  The weight average molecular weight and number average molecular weight (both are standard polystyrene equivalent values) of the vinyl acetate-maleic acid ester copolymer and the degree of dispersion thereof can be measured by gel permeation chromatography (GPC).

  The glass transition temperature of the vinyl acetate-maleic acid ester copolymer is, for example, 10 ° C. or less, preferably 0 ° C. or less, and for example, −40 ° C. or more.

  When the glass transition temperature is within the above range, the vinyl acetate-maleic acid ester copolymer exhibits an expansion / contraction function, and the coating film has good crack resistance.

  And according to the vinyl acetate-maleic acid ester copolymer of this invention, the viscosity reduction of the coating material containing the vinyl acetate-maleic acid ester copolymer can be achieved. Therefore, it becomes easy to apply the coating material to an object to be coated, and workability is good.

  Moreover, even if the coating film obtained by applying and drying the coating material on an object such as wood is exposed to the outdoors for a long time, the occurrence of blisters is suppressed. Therefore, the weather resistance is good.

  This is presumed to be achieved by the following mechanism. When the monomer components (vinyl acetate and maleate ester) undergo emulsion polymerization, the partially saponified polyvinyl alcohol serves as a protective colloid and part of the partially saponified polyvinyl alcohol is grafted onto the vinyl acetate-maleate ester copolymer. Polymerize to stabilize particles of vinyl acetate-maleic acid ester copolymer. At this time, if the partially saponified polyvinyl alcohol is excessively polymerized as a graft polymer on the copolymer, the hydrated layer constrained by the copolymer particles becomes enormous and the viscosity is increased. However, when the glycol is used in combination, the glycol has a skeleton common to a part of the PVA skeleton, and thus is chemically bonded to the vinyl acetate-maleic acid ester copolymer similarly to the partially saponified polyvinyl alcohol. . And since the said glycol is a moderate low molecule, the enlarging of the hydration layer which the particle | grains of the vinyl acetate-maleic acid ester copolymer obtained restrain is suppressed, As a result, low viscosity is achieved. It is guessed.

  In addition, this vinyl acetate-maleate ester copolymer has a tendency to polymerize alternately because the maleate ester monomer having a bulky structure has random copolymerizability with the vinyl acetate monomer, and is susceptible to hydrolysis. The vinyl acetate skeleton constitutes a polymer chain structure protected by a maleate skeleton. Therefore, it is guessed that it is excellent in weather resistance.

  On the other hand, wood exhausts and sucks water vapor by the humidity (moisture) in its environment. As a protective colloid, PVA graft-bonded or physically adsorbed to vinyl acetate-maleic acid ester copolymer particles exhibits water vapor permeability and exists in a lattice form in the coating film. Therefore, PVA can carry out this mass transfer of water vapor. Therefore, it is guessed that the coating film suitable for the wood coating material is formed.

  Moreover, the coating film obtained from the coating material containing the vinyl acetate-maleic acid ester copolymer of the present invention is excellent in elastic modulus (rigidity) at a low elongation of 0 to 100% in the tensile test, and stress until breakage. The occurrence of relaxation can be suppressed. Thereby, generation | occurrence | production of the blister in the repeated cycle of water absorption drying can be suppressed in long-term outdoor exposure.

  The coating material of the present invention contains the above-described vinyl acetate-maleic acid ester copolymer. Specifically, since the copolymer emulsion is contained in the paint as a paint vehicle, the workability and weather resistance are excellent.

  The paint of the present invention can be obtained, for example, by blending a copolymer emulsion and, if necessary, a filler into a copolymer emulsion.

  The blending ratio of the vinyl acetate-maleic acid ester copolymer in the paint is, for example, 5% by mass or more and 10% by mass or more, and for example, 50% by mass or less, and preferably 40% by mass or less.

  As the pigment, either an organic pigment or an inorganic pigment can be used.

  Examples of inorganic pigments include metal oxides such as titanium oxide (titania), zinc oxide (zinc white), yellow iron oxide, red iron oxide (bengal), black iron oxide (iron black), and chromium oxide (III). Chromate salts such as chrome yellow (yellow lead) and chrome vermilion (molybdenum red), sulfides such as litbon, cadmium yellow and cadmium red, metal complexes such as bitumen (pursian blue) and ultramarine blue (ultramarine blue) Examples thereof include carbon such as carbon black.

  Examples of organic pigments include First Yellow G (CI Pig Yellow 1), Isoindolinone Yellow R (CI Pig Yellow 110), Pyrazolone Orange (CI Pig Orange 13), and Naphthol Carmine FB (C.I. I. Pig Red 5), quinacridone magenta (C. I. Pig Red 122), quinacridone red (C. I. Pig Violet 19), dioxazine violet (C. I. Pig Violet 23), phthalocyanine blue R (C. I. Pig Blue 15) ), Phthalocyanine green (CI Pig Green 7), indanthrone blue (CI Pig Blue 60), and the like.

  The blending ratio of the pigment is, for example, 0.1% by mass or more, preferably 1% by mass or more, and for example, 20% by mass or less, preferably 10% by mass or less with respect to the paint.

  When the blending ratio of the pigment is within the above range, deterioration of the coating film due to ultraviolet rays can be suppressed.

  Examples of the filler include silica, mica, talc, stone powder, diatomaceous earth, clay, volcanic ash, coal ash, bentonite, graphite, carbon black, calcium carbonate, titanium oxide, alumina, aluminum powder, iron powder, molybdenum disulfide, and barium sulfate. Etc.

  The blending ratio of the filler is, for example, 1% by mass or more, preferably 5% by mass or more, and, for example, 50% by mass or less, preferably 30% by mass or less with respect to the paint.

  If necessary, pH adjusters, antifreeze agents, film-forming aids, dispersants, thickeners, antifoaming agents, surface conditioners, antibiotic activators (for example, antiseptics, fungicides, insecticides) Additives such as an agent, an algae repellent, and a repellent can also be contained.

  Although the content rate of these additives is suitably determined according to each additive, it is 0.01 mass% or more and 5 mass% or less, respectively with respect to a coating material. In addition, when it contains antibiotic active agent, the content rate of antibiotic active agent is 10 ppm or more and 5000 ppm or less with respect to a coating material, for example.

  Further, if necessary, water and an organic solvent can be added.

  The solid content concentration of the paint is, for example, 10% by mass or more, preferably 20% by mass or more, and for example, 80% by mass or less, preferably 70% by mass or less.

  The paint of the present invention has, for example, a viscosity at a solid content of 50% by mass of, for example, 0.1 Pa · sec or more, preferably 1.0 Pa · sec or more, more preferably 2.0 Pa · sec or more. For example, it is 5.0 Pa · sec or less, preferably 4.0 Pa · sec or less, and more preferably 3.0 Pa · sec or less.

  The viscosity is measured using a Brookfield M-type viscometer under the conditions of 25 ° C. and 30 rpm.

  The vinyl acetate-maleic acid ester copolymer of the present invention can be widely used for various known applications such as paints, adhesives and admixtures, and is preferably used as a paint.

  The paint of the present invention can be applied (or dipped) to various objects to be coated, and is preferably used for a wood paint. Specific examples of the objects to be coated include building materials such as floors, ceilings, window frames, inner walls, outer walls, and fences in buildings, and general industrial materials such as furniture. More preferably, it is used for a wood protective paint for exterior. Specific examples of such objects include window frames, inner walls, outer walls, and fences in buildings, as well as decks, lattices, play equipment, benches, exterior tables, chairs, and the like.

  Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples. However, the present invention is not limited to these examples. Moreover, the numerical value of the Example shown below can be substituted for the numerical value (namely, upper limit value or lower limit value) described in said embodiment.

  Details of the raw materials or measurement methods used in the examples and comparative examples shown in Tables 1 to 3 are described below.

PVA217: Trade name, partially saponified polyvinyl alcohol, degree of saponification: 87.0-89.0%, degree of polymerization: 1700, viscosity (4% aqueous solution, 20 ° C.): 22.0-27.0 mPa · sec, manufactured by Kuraray Co., Ltd. APS: ammonium persulfate, water-soluble polymerization initiator, manufactured by Wako Pure Chemical Industries, Ltd., reagent special grade SBS: sodium bisulfite, water-soluble reducing agent, manufactured by Wako Pure Chemical Industries, Ltd., reagent special grade Solid content (TSC) is ( It measured according to the procedure of 1)-(3).
(1) 1 g of the copolymer emulsion was precisely weighed and placed on an aluminum dish, and 1 mL of ion exchange water was added to widen the surface area of the copolymer emulsion.
(2) After volatilizing the volatile content of the copolymer emulsion in an air dryer (manufactured by Yamato Kagaku Co., Ltd.) at 105 ° C. for 3 hours, the aluminum plate is returned to room temperature in a desiccator. It was.
(3) The solid content on the aluminum pan was precisely weighed, and the solid content was determined from the following equation.

(Mass of accurately weighed solid content) / (Mass of precisely weighed copolymer emulsion) × 100%
The average particle size was measured by a dynamic light scattering method using a particle size analyzer FPAR-1000 (manufactured by Otsuka Electronics Co., Ltd.).

  The viscosity of the copolymer emulsion was measured using a Brookfield M-type viscometer (rotor No. 3) under the conditions of 25 ° C. and 30 rpm.

  The weight average molecular weight Mw and the degree of dispersion were measured by gel permeation chromatography under the following conditions.

Device: Alliance (Waters)
Sample: 0.1 mass / volume% orthodichlorobenzene (DCB) solution, injection volume 50 μl
Column: Stylagel (Waters)
Column temperature: 140 ° C
Eluent: DCB
Flow rate: 0.3 ml / min
Detector: Differential refractive index detector Standard substance: Polystyrene The insoluble matter of DCB was filtered through a 0.4 μm membrane filter, and the dry weight of the filtration residue was measured.

Example 1
In a 250 mL container, 132 g of vinyl acetate (hereinafter referred to as VAc), 88 g of dibutyl maleate (hereinafter referred to as DBM), and 17.6 g of 2-methyl-2,4-pentanediol (hereinafter referred to as 2MPD) were mixed and stirred. A homogeneous hydrophobic solution was prepared.

  In a 500 mL four-necked flask equipped with a stirrer, reflux condenser, thermometer and nitrogen inlet tube, 88.9 g of ion-exchanged water, 88 g of PVA217 (10%) aqueous solution, and 0.44 g of sodium acetate were blended. Prepared. Next, the four-necked flask was placed in a water bath, heated to 60 ° C. while stirring at a rotation speed of 200 rpm (peripheral speed 56.5 m / min) with a 9 cm diameter stirrer under a nitrogen stream, and then 60 ± 1 ° C. The internal temperature was controlled.

  14.3 g of the prepared hydrophobic solution was added to the 4-necked flask, and 10 minutes after the addition, 1.1 g of APS and 5.5 g of ion-exchanged water were added as equipment washing water.

  The reaction was continued for 10 minutes after confirming the start of the polymerization reaction of the emulsion polymerization by turning the charged liquid light blue.

  The remaining 223.3 g of the prepared hydrophobic solution was continuously fed to the polymerization reaction solution by a tubing pump over 6 hours and 30.8 g of an aqueous solution of sodium acetate (1%) over 7 hours. The temperature was raised to 70 ° C. from the 7th hour, the temperature was raised to 80 ° C. from the 8th hour, and ripening was carried out.

  This obtained the emulsion containing a vinyl acetate-dibutyl maleate copolymer.

Example 2
A hydrophobic solution was prepared in the same manner as in Example 1.

  In a four-necked flask, 78.4 g of ion-exchanged water, 88 g of PVA217 (10%) aqueous solution, and 0.44 g of sodium acetate were blended to prepare a PVA aqueous solution. Next, the four-necked flask was placed in a water bath, heated to 40 ° C. with stirring at a rotation speed of 200 rpm (peripheral speed 56.5 m / min) with a 9 cm diameter stirrer under a nitrogen stream, and then 40 ± 1 ° C. The internal temperature was controlled.

  14.3 g of the prepared hydrophobic solution was added to the 4-necked flask, and 4.4 g of an APS (5%) aqueous solution and 2.2 g of an SBS (5%) aqueous solution were added 10 minutes after the addition.

  The reaction was continued for 10 minutes after confirming the start of the polymerization reaction of the emulsion polymerization by turning the charged liquid light blue.

  The remaining 223.3 g of the prepared hydrophobic solution was 10 hours, 22 g of APS (5%) aqueous solution 12 g, and 12 g of sodium acetate (2.8%) aqueous solution 11 g and SBS (5%) aqueous solution 11 g 12 hours. Then, the polymerization reaction solution was continuously fed by a tubing pump. The temperature was raised to 50 ° C. from the 14th hour, the temperature was raised to 60 ° C. from the 15th hour, and ripening was performed.

  This obtained the emulsion containing a vinyl acetate-dibutyl maleate copolymer.

Example 3
A hydrophobic solution was prepared in the same manner as in Example 1.

  In a 4-neck flask, 79.1 g of ion-exchanged water, 88 g of PVA217 (10%) aqueous solution, and 0.44 g of sodium acetate were blended to prepare a PVA aqueous solution. Next, the four-necked flask was placed in a water bath, heated to 80 ° C. with stirring at a rotation speed of 200 rpm (peripheral speed 56.5 m / min) with a 9 cm diameter stirrer under a nitrogen stream, and then 80 ± 1 ° C. The internal temperature was controlled.

  14.3 g of the prepared hydrophobic solution was added to the 4-necked flask, and 0.044 g of APS and 5.5 g of ion-exchanged water were added as equipment washing water 10 minutes after the addition.

  The reaction was continued for 10 minutes after confirming the start of the polymerization reaction of the emulsion polymerization by turning the charged liquid light blue.

  The remaining 223.3 g of the prepared hydrophobic solution was continued for 4.5 hours, and a solution prepared by dissolving 0.31 g of sodium acetate in 44 g of an APS (0.5%) aqueous solution was continued for 5 hours with a tubing pump. Feeded. The temperature was raised to 90 ° C. from the 5th hour and ripening was carried out, and the reaction was terminated by cooling to 40 ° C. or less from the 6th hour.

  This obtained the emulsion containing a vinyl acetate-dibutyl maleate copolymer.

Example 4
In a 500 mL container, 264 g of VAc, 176 g of DBM, and 26.4 g of 2MPD were blended and stirred to prepare a uniform hydrophobic solution.

  A 1000 mL four-necked flask equipped with a stirrer, reflux condenser, thermometer and nitrogen inlet tube is mixed with 115.7 g of ion exchange water, 264 g of PVA217 (10%) aqueous solution and 0.88 g of sodium acetate, Prepared. Next, the four-necked flask was placed in a water bath, heated to 60 ° C. while stirring at a rotation speed of 200 rpm (peripheral speed 56.5 m / min) with a 9 cm diameter stirrer under a nitrogen stream, and then 60 ± 1 ° C. The internal temperature was controlled.

  28 g of the prepared hydrophobic solution was added to the 4-necked flask, and 10 minutes after the addition, 0.792 g of APS and 11 g of ion-exchanged water were added as equipment washing water.

  The reaction was continued for 10 minutes after confirming the start of the polymerization reaction of the emulsion polymerization by turning the charged liquid light blue.

  A solution in which 1.408 g of APS was dissolved in the remaining 438.4 g of the prepared hydrophobic solution and 61.6 g of an aqueous solution of sodium acetate (1%) was continuously fed to the polymerization reaction solution by a tubing pump over 6 hours. As the viscosity of the reaction solution increased, the stirring speed was gradually increased to 400 rpm. From 7 hours, the temperature was raised to 70 to 72 ° C., and the reaction was terminated by cooling to 40 ° C. or less from 8 hours.

  This obtained the emulsion containing a vinyl acetate-dibutyl maleate copolymer.

Example 5
Vinyl acetate in the same manner as in Example 4 except that 26.4 g of 2MPD was initially charged, the amount of monomer mixture charged at the start of polymerization was 26.4 g, and the hydrophobic solution in the continuous feed was 413.6 g of the monomer mixture. -An emulsion containing dibutyl maleate copolymer was obtained.

Example 6
Except for 17.6 g of 2MPD, 27.5 g of the charged hydrophobic solution at the start of polymerization, 124.5 g of ion-exchanged water, and 430.1 g of the continuous feed amount of the hydrophobic solution, the same as in Example 4. Thus, an emulsion containing a vinyl acetate-dibutyl maleate copolymer was obtained.

Example 7
2MPD 17.6g was charged first, the amount of monomer mixture at the start of polymerization was 26.4g, and the continuous feed hydrophobic solution was changed to 413.6g of monomer mixture. An emulsion containing a vinyl-dibutyl maleate copolymer was obtained.

Example 8
An emulsion containing vinyl acetate-dibutyl maleate copolymer was obtained in the same manner as in Example 6 except that the polymerization temperature was controlled to 70 ± 1 ° C.

Example 9
An emulsion containing vinyl acetate-dibutyl maleate copolymer was obtained in the same manner as in Example 6 except that the polymerization temperature was controlled at 65 ± 1 ° C.

Example 10
The internal temperature is controlled to 55 ± 1 ° C., and the charged ion exchange water is changed from 124.5 g to 111 g. At the start of polymerization, 0.158 g of SBS is added in addition to APS, and an aqueous solution of sodium acetate (1%) 61 In the same manner as in Example 6, except that 14.1 g of an SBS (2%) aqueous solution was continuously fed in parallel with continuous feeding of a solution obtained by dissolving 1.408 g of APS in .6 g, vinyl acetate-dibutyl maleate copolymer An emulsion containing coalesced was obtained.

Example 11
An emulsion containing a vinyl acetate-dibutyl maleate copolymer was obtained in the same manner as in Example 6 except that 286 g of VAc and 154 g of DBM in the hydrophobic solution were used.

Example 12
An emulsion containing a vinyl acetate-dibutyl maleate copolymer was obtained in the same manner as in Example 6 except that 242 g of VAc and 198 g of DBM in the hydrophobic solution were used.

Example 13
Contains vinyl acetate-dibutyl maleate copolymer in the same manner as in Example 6 except that the remaining 430.1 g of the prepared hydrophobic solution was continuously fed over 9 hours instead of continuously fed over 6 hours. An emulsion was obtained.

Comparative Example 1
Vinyl acetate-dibutyl maleate in the same manner as in Example 1 except that 2MPD was not blended in the hydrophobic solution and the blending amount of ion-exchanged water was changed from 88.9 g to 106.5 g in the PVA aqueous solution. An emulsion containing the copolymer was obtained.

Comparative Example 2
Vinyl acetate-dibutyl maleate copolymer in the same manner as in Example 1 except that 3-methoxy-3-methyl-1-butanol (trade name “Solfit”, manufactured by Kuraray Co., Ltd.) was used instead of 2MPD. An emulsion containing was obtained.

Comparative Example 3
An emulsion containing a vinyl acetate-dibutyl maleate copolymer was obtained in the same manner as in Example 1 except that 1,3-propylene glycol was used instead of 2MPD.

Manufacture of paints A stainless steel container was charged with 54.0 parts by weight of an emulsion (BMVAEm) containing a vinyl acetate-dibutyl maleate copolymer adjusted to a solid content of 50% and stirred with a disper according to the following formulation: Raw materials were added sequentially. The mixture was stirred until it was uniform, and filtered with a 60 mesh strainer to obtain a paint.

BMVAEm 54.0 parts by mass Ammonia water (25%) (pH adjuster) 0.1 parts by mass Texanol (film-forming aid) 1.5 parts by mass Propylene glycol (antifreezing agent) 1.5 parts by mass Acrylic dispersant 0.2 parts by weight Cellulosic thickener 0.3 parts by weight Silicone defoamer 0.1 parts by weight Acrylic surface conditioner 0.1 parts by weight Talc 3.0 parts by weight Calcium carbonate 8.5 parts by weight Barium sulfate 5.5 parts by mass Deionized water 15.2 parts by mass Pigmented water dispersion (50%) 10.0 parts by mass
Total 100.0 parts by mass (paint viscosity)
The viscosity of the paint prepared above was measured using a Brookfield M-type viscometer (rotor No. 3 or No. 4) under the conditions of 25 ° C. and 30 rpm. The results are shown in Table 4.

(Workability)
The paint prepared as described above was applied to a 150 mm × 70 mm × 10 mm square cedar board with a brush for aqueous coating so that the coating amount was 200 g / m ^2, and JIS K 5600- The test plate was dried for 7 days in the standard state described in 1-6 (temperature 23 ± 2 ° C., relative humidity 50 ± 5%).

  Regarding the brush workability (brush separation) at the time of painting, it was evaluated as ◯ when it was good, △ when it felt slightly heavy, felt heavy, and the brush eyes remained on the test plate The case was evaluated as x. The results are shown in Table 4.

(Weather resistance test (1 year))
The test plate was subjected to a one-year outdoor exposure test according to JIS K 5600-7-6 (outdoor exposure weather resistance test), and the surface state of the coating film was visually evaluated. At this time, the case where change was not able to be confirmed with the surface state at the time of an exposure test start and the surface state after one year was evaluated as (circle), and the case where generation | occurrence | production of blister was confirmed was evaluated as x. The results are shown in Table 4.

(Weather resistance test (2 years))
The test plate was subjected to an outdoor exposure test for 2 years in accordance with JIS K 5600-7-6 (outdoor exposure weather resistance test), and the surface state of the coating film was visually evaluated. At this time, when the change in the surface condition at the start of the exposure test and the surface condition after two years was not confirmed, it was evaluated as ◯, and when the occurrence of blisters was confirmed very slightly, it was evaluated as △. The case where occurrence of was clearly confirmed was evaluated as x. The results are shown in Table 4.

(Tensile test)
The coating material prepared above was poured into a release paper with a mold so that the thickness of the coating film after drying was 1 mm and dried to obtain a coating film. The obtained coating film was peeled off from the release paper with a mold, and the coating film was punched out in a dumbbell shape No. 2 defined in JIS K 6251, which was used as a test piece.

  In accordance with JIS A 6909 “Finish Finishing Coating Material”, a tensile test was carried out under the following conditions using three test pieces for each paint formulation using an autograph AGS-50NX manufactured by Shimadzu Corporation.

Measurement temperature 20 ° C, distance between chucks 20 mm, distance between marked lines 20 mm, tensile speed 200 mm / min Tensile test profiles showing elongation-stress curves obtained in the above tensile test were observed, and classified into 1 to 3 below. . The results are shown in Table 4.

  1: The stress increased linearly until the specimen was broken (see FIG. 1).

  2: The stress did not increase due to stress relaxation from the middle of the test piece to the time of rupture, and was constant (flat) (see FIG. 2).

  3: On the way to the break, the yield point was expressed by stress relaxation, and the stress at the time of breakage was smaller than the yield point stress (see FIG. 3).

(Minimum film forming temperature)
When the minimum film-forming temperature of the paint prepared above was measured using a simple film-forming temperature measuring device (manufactured by Imoto Seisakusho Co., Ltd.), the minimum film-forming temperature was 0 ° C. or less in all of the Examples and Comparative Examples. there were.

  In Tables 1 to 3, “%” indicates “% by mass” unless otherwise specified.

  Moreover, the mixing | blending ratio of the raw material in Table 1-Table 3 is computed by making the total amount of vinyl acetate and dibutyl maleate into 100 mass parts.

  The vinyl acetate-maleic acid ester copolymer of the present invention is used in various applications such as paints for various industrial products such as building materials, woodworking / plastic processing / paper processing adhesives, admixtures, etc. Can be used. In particular, it is used as a paint for wood protective materials, for example, on building materials such as floors, ceilings, window frames, inner walls, outer walls, and fences in buildings, such as furniture.

Claims (4)

It is obtained by emulsion polymerization of vinyl acetate and maleic acid ester in the presence of partially saponified polyvinyl alcohol and a glycol represented by the following formula (1) and having 4 to 7 carbon atoms. A vinyl acetate-maleic acid ester copolymer.

(Wherein R ¹ , R ² , R ³ and R ⁴ each independently represents a hydrogen atom or a monovalent hydrocarbon group.)   The vinyl acetate-maleic acid ester copolymer according to claim 1, wherein the vinyl acetate-maleic acid ester copolymer has a weight average molecular weight of 200,000 or more.   A wood coating material comprising the vinyl acetate-maleic acid ester copolymer according to claim 1 or 2. It comprises a step of emulsion polymerization of vinyl acetate and maleic acid ester in the presence of partially saponified polyvinyl alcohol and a glycol represented by the following formula (1) and having 4 to 7 carbon atoms. And a method for producing a vinyl acetate-maleic acid ester copolymer.

(Wherein R ¹ , R ² , R ³ and R ⁴ each independently represents a hydrogen atom or a monovalent hydrocarbon group.)

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