JPH0623210B2 - Polyvinyl alcohol-based polymer, method for producing the same, and paper surface sizing agent and dispersion stabilizer comprising the polymer - Google Patents

Description

TECHNICAL FIELD The present invention relates to a novel polyvinyl alcohol-based polymer having a specific ethylenically unsaturated dicarboxylic acid monoester unit introduced therein, a method for producing the same, and a paper made from the polyvinyl alcohol-based polymer. It relates to surface sizing agents and dispersion stabilizers.

Conventional technology Polyvinyl alcohol is a paper surface sizing agent,
It is widely used as a dispersion stabilizer used in emulsion or suspension polymerization of vinyl compounds, but polyvinyl alcohol obtained by simply saponifying polyvinyl acetate is often unsatisfactory in quality.

Therefore, attempts have been made to copolymerize and modify polyvinyl alcohol using various monomers, for example, a method for copolymerizing and modifying an ethylenically unsaturated carboxylic acid-based monomer, a method for copolymerizing and modifying an alkyl vinyl ether, and an α-olefin. There have been proposed methods such as a method of copolymerization modification with a method, a method of copolymerization modification with a saturated branched fatty acid vinyl, and a method combining these.

Among them, the one in which an ethylenically unsaturated carboxylic acid-based monomer is introduced into polyvinyl alcohol is widely used as a paper surface sizing agent, and the one in which a hydrophobic group and a carboxyl group are introduced into polyvinyl alcohol is a surface active agent. Since it can be expected to function as an agent, it is of interest as a stabilizer used during emulsion polymerization or suspension polymerization of vinyl compounds.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention However, the surface sizing agent for paper in which an ethylenically unsaturated carboxylic acid-based monomer is introduced into polyvinyl alcohol shows good results as compared with polyvinyl alcohol in which it is not introduced. It is desired to further improve air quality and oil absorption.

In addition, when introducing a hydrophobic group into polyvinyl alcohol, increasing the amount of the hydrophobic group introduced decreases the solubility of the polymer in water, making it useable as a dispersion stabilizer and other intended uses. It may not be possible.

The inventors of the present invention have introduced various types of monoalkyl esters of ethylenically unsaturated dicarboxylic acids, the alkyl groups of which are alkyl esters of primary alcohols, in order to introduce a hydrophobic group and a carboxyl group into polyvinyl alcohol. Was attempted to be copolymerized with vinyl acetate and then subjected to saponification, but this product could not serve the purpose of introducing a hydrophobic group because the alkyl group was easily eliminated during the saponification reaction to become a carboxyl group or a lactone.

The present invention provides a novel polyvinyl alcohol-based polymer by copolymerization and saponification using a specific ethylenically unsaturated dicarboxylic acid monoalkyl ester having a secondary or tertiary alkyl group as a modifying component. It was reached as a result of intensive research to find its application.

Means for Solving Problems Polyvinyl alcohol-based polymer The polyvinyl alcohol-based polymer of the present invention has the formula It has a repeating unit represented by.

Of the above formulas, the first repeating unit is an ethylenically unsaturated dicarboxylic acid monoester unit (A), the second repeating unit is a vinyl alcohol unit (B), 3
The second repeating unit is a vinyl acetate unit (C).

Ethylenically unsaturated dicarboxylic acid monoester unit (A)
One of the two carboxyl groups of To form an ester. Here, R ₁ is hydrogen, an alkyl group or an aryl group, and R ₂ and R ₃ are an alkyl group or an aryl group, so the group represented by the above formula is secondary or tertiary. Examples of the alkyl group include an alkyl group having about 1 to 10 carbon atoms (in particular, an alkyl group having 1 to 8 carbon atoms) and a cycloalkyl group,
Examples of the aryl group include a phenyl group, a substituted phenyl group and a benzyl group.

Vinyl alcohol unit (B) is vinyl acetate unit (C)
Is introduced into the polymer and then the vinyl acetate unit (C) is saponified. When the saponification is completed, the vinyl acetate unit (C) in the polymer will disappear.

The ratio of each unit of the polymer is determined as follows from a practical viewpoint.

That is, the ratio of the ethylenically unsaturated dicarboxylic acid monoester unit (A) in the polymer is 0.2 to 20 mol%, and the total ratio of the vinyl alcohol unit (B) and the vinyl acetate unit (C) in the polymer is The ratio of the vinyl alcohol units (B) to the total amount of the remaining vinyl alcohol units (B) and vinyl acetate units (C)
The ratio of each unit is set so as to be 10 to 100 mol%, preferably 65 to 99.5 mol%.

If the proportion of each unit is selected as described above, a suitable hydrophobic group and hydrophilic group are introduced into the polymer, and the surface sizing agent of paper described later, used during emulsion polymerization or suspension polymerization of polymerizable monomers A dispersion stabilizer and a polymer suitable for other purposes can be obtained.

Method for producing polyvinyl alcohol-based polymer The above-mentioned polyvinyl alcohol-based polymer has the formula (However, COOM, R ₁ , R ₂ , and R ₃ are as described above), the ethylenically unsaturated dicarboxylic acid monoester (a) is copolymerized with vinyl acetate (c), and then saponified. It is manufactured by

Examples of the ethylenically unsaturated dicarboxylic acid monoester (a) include maleic acid monoester, fumaric acid monoester, itaconic acid monoester, citraconic acid monoester, and the like.
An ethylenically unsaturated dicarboxylic acid such as maleic anhydride, fumaric acid, itaconic acid, itaconic anhydride, citraconic acid, citraconic anhydride or an anhydride thereof or an acid halide thereof is represented by the formula: (R ₁ , R ₂ and R ₃ are the same as above) with or without a catalyst or a suitable catalyst (sulfuric acid, hydrochloric acid, phosphoric acid,
It is obtained by reacting in the presence of a protic acid such as p-toluenesulfonic acid).

Such alcohols include dimethyl carbinol,
Diethyl carbinol, methyl ethyl carbinol, di-n-propyl carbinol, diisopropyl carbinol, methyl n-propyl carbinol, methyl isopropyl carbinol, ethyl n-propyl carbinol,
Secondary alcohols such as ethyl isopropyl carbinol, dibutyl carbinol, diamyl carbinol, methylhexyl carbinol, dihexyl carbinol, dioctyl carbinol, dicyclohexyl carbinol, dibenzyl carbinol, diphenyl carbinol, trimethyl carbinol, triethyl. Tertiary alcohols such as carbinol, methyldiethylcarbinol and dimethylethylcarbinol are exemplified, and the secondary alcohol is particularly preferable from the viewpoint of easy availability.

In addition to the above-mentioned ethylenically unsaturated dicarboxylic acid monoester (a) and vinyl acetate (c), other copolymerizable monomer components such as ethylenically unsaturated monocarboxylic acid may be used as long as the gist of the present invention is not impaired. Acids (acrylic acid, methacrylic acid, crotonic acid, etc.) or their esters, ethylenically unsaturated dicarboxylic acids (maleic acid, fumaric acid, itaconic acid, citraconic acid, etc.) or their diesters or anhydrides, vinyl esters other than vinyl acetate ( Vinyl propionate, vinyl laurate, vinyl stearate, vinyl versatate, etc.), amide monomers (acrylamide, methacrylamide, etc.), nitrile monomers (acrylonitrile, methacrylonitrile, etc.), α-olefins, vinyl ethers, allyl compounds ( Allyl sulfonate sodium , Potassium allyl sulfonate, diallyl methyl ammonium halide and the like) may be a small amount copolymerization and the like.

Ethylenically unsaturated dicarboxylic acid monoester (a) and vinyl acetate (c) (or these and other monomer components)
The copolymerization reaction of can be carried out in the absence of a solvent, but usually a suitable solvent, particularly methanol, ethanol,
It is carried out in the presence of a lower alcohol such as propanol or butanol, especially methanol. Each component may be charged all at once for polymerization, or the reaction may be allowed to proceed while charging intermittently or sequentially.

As the polymerization catalyst, usual radical polymerization catalysts such as azoisobutyronitrile, benzoyl peroxide and acetyl peroxide are used.

The reaction temperature is often about 58 to 65 ° C.

After the completion of the polymerization reaction, the residual monomer is expelled if necessary, and then the system is mixed with a solvent (alcohol, ketone,
In the presence of an alkali catalyst such as alkali hydroxide or alkali metal alcoholate or an acid catalyst such as an inorganic acid, the saponification reaction is carried out at room temperature or under heating (about 20 to 50 ° C) in a state of being adjusted to a solvent such as benzene. Carry out. The saponification product precipitates as the saponification reaction proceeds, but depending on the degree of saponification and the type of solvent used, the saponification product may not precipitate. After completion of the saponification, the saponification reaction product is pulverized if necessary, neutralized if necessary, washed with alcohol or the like, and then dried to obtain the intended polyvinyl alcohol-based polymer. By this saponification reaction, the vinyl acetate unit (C) introduced into the polymer becomes the vinyl alcohol unit (B). In addition, the carboxyl group of the ethylenically unsaturated dicarboxylic acid monoester unit (A) introduced into the polymer, which is not esterified, becomes a free carboxyl group depending on the type of catalyst used, neutralization conditions, washing conditions, etc. There are cases where it becomes, and cases where it becomes its salt.

In this case, when the ratio of the vinyl alcohol unit (B) to the total amount of the vinyl alcohol unit (B) and the vinyl acetate unit (C) becomes close to 100 mol%, that is, when the saponification proceeds almost completely, ethylenic Since a part of the —CR ₁ R ₂ R ₃ group in the unsaturated dicarboxylic acid monoester unit (A) tends to be eliminated as the corresponding alcohol, the vinyl alcohol unit (B) and the vinyl acetate unit (C) are separated from each other. Vinyl alcohol unit (B) to the total amount
It is desirable to keep the ratio of 99.5 mol% or less. A particularly preferred range is 65 to 99 mol%.

Use of Polyvinyl Alcohol-Based Polymer as Paper Processing Agent, Especially Paper Surface Sizing Agent The polyvinyl alcohol-based polymer obtained above is particularly useful as a paper surface sizing agent. That is, when an aqueous solution of this polyvinyl alcohol-based polymer is applied to paper and surface sizing is performed, the air permeability and oil absorption are remarkably higher than those of a carboxyl group-modified polyvinyl alcohol or the like which has been generally used for this purpose. It is excellent.

When the above-mentioned polyvinyl alcohol-based polymer is used as a surface sizing agent for paper, it is generally used by dissolving it in water, but it can also be used in a solvent system. The type of solvent is appropriately selected according to the amount of modification, the degree of saponification, and other physical properties of the resin.

The sizing agent is prepared by mixing the polyvinyl alcohol-based polymer with a solvent.

The concentration of the polymer in the sizing agent may be appropriately adjusted according to the purpose, but in consideration of workability and the like, it is usually selected from the range of about 1 to 20% by weight.

As the sizing agent, if necessary, glyoxal, a waterproofing agent such as urea resin, an antifoaming agent, a release agent, a surfactant, a preservative,
Known additives such as insect repellents, rust preventives and thickeners may be added, and other conventionally known paper sizing agents such as polyvinyl alcohol, starch, carboxymethyl cellulose, acrylic latex, SBR latex and the like. Can be mixed.

As the paper on which the sizing agent is coated, for example, a paper board such as a Manila ball, a white ball, a liner, a printing paper such as a general high-quality paper, a gravure paper, and the like are preferably used, but the paper is not limited thereto.

In coating the paper with the sizing agent, any known method such as a size press coating, a roll coater method, an ear doctor method or a blade coating method may be employed. And
The coating amount of the sizing agent is preferably such that the polyvinyl alcohol-based polymer of the present invention has a solid content of 0.1 to 5 g / m ² , and particularly preferably 0.5 to 3 g / m ² . Of course, the method is not limited to such a method, and an internal sizing method in which a sizing agent is added to the pulp dispersion liquid to make paper, or a method in which a powdery or fibrous sizing agent is mixed into the paper can be used.

The sizing agent of the present invention is mainly used as a clear coating agent as described above, but it can also be suitably used as a binder for pigment coating. As the pigment, clay, calcium carbonate, kaolin, diatomaceous earth,
Known pigments such as titanium oxide and satin white are used.

Use of Polyvinyl Alcohol-Based Polymer as Dispersion Stabilizer The polyvinyl alcohol-based polymer obtained above has a carboxyl group and a hydrophobic group simultaneously introduced into the polymer by the ethylenically unsaturated dicarboxylic acid monoester unit (A). Since it has surface-active ability, it is also useful as a dispersion stabilizer used for emulsification or suspension. This dispersion stabilizer is superior to conventional polyvinyl alcohol-based dispersion stabilizers and other dispersion stabilizers. It has the property.
Especially when it is used as an emulsifier, its effects are dramatically improved in storage stability, dilution stability, freeze-thaw stability, etc. of the emulsion, and when it is used as a suspending agent, for example, polyvinyl chloride resin particles Particle size distribution, plasticizer absorbability, porosity, etc. are significantly improved.

The most industrially useful application of the dispersion stabilizer is an emulsifier during emulsion polymerization or a suspending agent during suspension polymerization.

Even when it is used for such an application, it becomes water-soluble or water-insoluble depending on the amount of the hydrophobic group and the hydrophilic group in the ethylenically unsaturated dicarboxylic acid monoester unit (A) and the content of the vinyl alcohol unit (B). However, any of them can be used as a dispersion stabilizer. That is, when the polymer of the present invention in the water-soluble range is used for the polymerization in an aqueous medium, it can be used alone or in combination with other water-soluble polymer substances if necessary. it can. On the other hand, when it is polymerized by itself using a polymer in the water-insoluble range, it may be combined with another water-soluble polymer or a copolymerization component capable of imparting hydrophilicity, such as acrylic acid or methacrylic acid. It is also possible to further copolymerize an alkali metal salt or ammonium salt of an ethylenically unsaturated carboxylic acid such as an acid or maleic acid to convert it into water-soluble and use it.

Typical examples of the water-soluble polymer that can be combined are polyvinyl alcohol having an average saponification degree of 60 to 100 mol% and an average degree of polymerization of 100 to 3000, or a derivative thereof. Examples of the polyvinyl alcohol derivative include carbonyl group-containing polyvinyl alcohol, polyvinyl alcohol formal compound, acetal compound, butyral compound, urethane compound, sulfonic acid, and ester compound with carboxylic acid. further,
Examples of the saponified product of a vinyl ester and a copolymer of the vinyl ester and a monomer copolymerizable therewith include, as the monomer,
Ethylene, propylene, isobutylene, α-octene,
Olefins such as α-dodecene and α-octadecene, unsaturated acids such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, maleic anhydride, and itaconic acid, or salts thereof or mono- or dialkyl esters, acrylonitrile, methacrylonitrile, etc. , Amides such as acrylamide and methacrylamide, olefin sulfonic acids such as ethylene sulfonic acid, allyl sulfonic acid and methallyl sulfonic acid or salts thereof, alkyl vinyl ethers, vinyl ketone, N-vinyl pyrrolidone, vinyl chloride, vinylidene chloride Etc.

Examples of the water-soluble polymer that can be combined include various other cellulose polymers such as alkyl cellulose, hydroxyalkyl cellulose, and carboxyalkyl cellulose, starch, tragacanth, pectin, gray, alginic acid or a salt thereof, gelatin, polyvinylpyrrolidone, Polyacrylic acid or its salt, polymethacrylic acid or its salt, polyacrylamide, polymethacrylamide, vinyl acetate and maleic acid, maleic anhydride, acrylic acid, methacrylic acid, itaconic acid, fumaric acid, crotonic acid and other unsaturated acids And copolymers of styrene and the above unsaturated acids, copolymers of vinyl ether and the above unsaturated acids, and salts or esters of these copolymers.

In carrying out emulsion polymerization, any ordinary emulsion polymerization method such as heating and stirring may be carried out by temporarily or continuously adding a polymerizable monomer in the presence of water, a dispersion stabilizer and a polymerization catalyst. The amount of the dispersion stabilizer to be used varies somewhat depending on the type, the required resin content of the emulsion, etc., but is usually selected from the range of about 1 to 8% by weight based on the whole emulsion polymerization reaction system. As the polymerization catalyst, usually potassium persulfate, ammonium persulfate, etc., alone or in combination with acidic sodium sulfite,
Further, redox catalysts such as hydrogen peroxide-tartaric acid, hydrogen peroxide-iron salt, hydrogen peroxide-ascorbic acid-iron salt, hydrogen peroxide-Rongalit-iron salt are used. The polymerization temperature is selected from the range of 30 to 80 ° C.

Further, the above emulsifier can be used not only alone but also in combination with various water-soluble polymers as described above. Furthermore, polyoxyethylene alkyl ether type, polyoxyethylene alkylphenol type, polyoxyethylene polyhydric alcohol ester type, ester of polyhydric alcohol and fatty acid, nonionic surfactant such as oxyethylene / oxypropylene block polymer, higher alcohol Anion interface of sulfate, higher fatty acid alkali salt, polyoxyethylene alkylphenol ether sulfate, alkylbenzene sulfonate, naphthalene sulfonate formalin condensate, alkyl diphenyl ether sulfonate, dialkyl sulfosuccinate, higher alcohol phosphate ester salt, etc. An activator can also be used in combination. When the emulsifier and the surfactant are used in combination, the mixing ratio is appropriately polymer / surfactant = 20/1/1 to 1/20 (weight ratio). These do not necessarily have to be mixed and used, and any method such as using one component at the initial stage of polymerization and adding another component during the polymerization is possible. Furthermore, plasticizers such as phthalates and phosphates, sodium carbonate,
A pH adjusting agent such as sodium acetate or sodium phosphate may also be used in combination.

Examples of the polymerizable monomer to be emulsion-polymerized include ethylenically unsaturated monomers and butadiene-based monomers. As the ethylenically unsaturated monomer, vinyl acetate,
Acrylic acid ester, methacrylic acid ester, vinyl chloride, vinylidene chloride, acrylonitrile, styrene, ethylene and the like can be mentioned, and homopolymerization or copolymerization thereof can be carried out.

Among other things, when homopolymerizing or copolymerizing acrylic monomers such as acrylic acid ester or methacrylic acid ester, an emulsion with particularly good mechanical stability, leaving stability, pigment miscibility, etc. can be obtained. The case of polymerization is particularly important.

As the butadiene-based monomer, butadiene-1,3,3
There are 2-methylbutadiene-1,3,2,3-dimethylbutadiene-1,3, 2-chlorobutadiene-1,3 and the like, and these are used alone or mixed with an ethylenically unsaturated monomer. Among these, butadiene-
1,3 and styrene and (meth) acrylic acid, butadiene 1,3 and acrylonitrile, butadiene-1,3 and acrylonitrile and styrene, butadiene-1,3 and acrylonitrile and (meth) acrylic ester, butadiene-1,3 and It is advantageous to carry out the polymerization with a combination of methyl methacrylate, butadiene-1,3, methyl methacrylate and (meth) acrylic acid.

In suspension polymerization, usually, a dispersion stabilizer is added to an aqueous medium to disperse a vinyl-based monomer, and the polymerization is performed in the presence of an oil-soluble catalyst. The dispersion stabilizer is added to the aqueous medium as a powder or in the form of a solution. The amount used is usually 0.005 to 5% by weight based on the weight of the monomer. When added as a solution, make an aqueous solution or alcohol,
It is added as a solution in an organic solvent such as a ketone or ester. The dispersion stabilizer may be charged all at once at the beginning of the polymerization or may be charged separately during the polymerization.

The catalyst used may be any oil-soluble catalyst, for example, benzoyl peroxide, lauroyl peroxide, diisopropyl peroxydicarbonate, α, α′-azobisisobutyronitrile, α, α ′.
-Azobis-2,4-dimethylvaleronitrile, acetylcyclohexylsulfonyl peroxide or mixtures thereof are used.

The polymerization temperature is selected from the range of 30 to 70 ° C.

It is also possible to appropriately use various kinds of surfactants or inorganic dispersants as an auxiliary agent during the polymerization.

As a monomer to be subjected to suspension polymerization, not only vinyl chloride homopolymerization but also a monomer copolymerizable therewith,
For example, vinylidene halide, vinyl ether, vinyl acetate, vinyl benzoate, acrylic acid, methacrylic acid,
Maleic acid or its anhydride, ethylene, propylene,
It is also suitable as a copolymer with styrene and the like, and can be used not only for vinyl chloride but also for suspension polymerization of any vinyl compound such as styrene, methacrylic acid ester and vinyl acetate.

Further, in the dispersion stabilizer of the present invention, various nonionic or anionic surfactants are used alone or mixed as an emulsifier in an aqueous medium, or emulsion polymerization of a polymerizable monomer is performed using various water-soluble protective colloids. By adding the above-mentioned dispersion stabilizer to the produced aqueous emulsion, the standing stabilizer, freeze-thaw stability, dilution stability and the like can be remarkably improved.

Further, the dispersion stabilizer of the present invention is also useful in producing an emulsion by the post-emulsification method. In this case, the dispersion stabilizer may be dissolved in water and the solution or molten resin may be dropped and stirred therein, or the dispersion stabilizer aqueous solution may be dropped and stirred into the molten resin. No measures such as heating are required for emulsification, but if necessary, it may be heated to about 45 to 85 ° C.
There is no particular limitation on the substance to be emulsified, epoxy resin, urethane resin, urea-formaldehyde precondensate, phenol-formaldehyde precondensate, alkyd resin,
Ketene dimer, rosin, silicone resin, wax,
Examples include polypropylene, polyethylene and asphalt. If necessary, polyoxyethylene alkyl ether type, polyoxyethylene alkylphenol type,
Various surfactants used in the above-mentioned emulsion polymerization can be used in combination, including a nonionic surfactant such as a polyhydric alcohol ester type or a cationic surfactant such as a higher alkylamine salt. It is also possible to mix these surfactants in the object to be emulsified.
Furthermore, plasticizers such as phthalates and phosphates,
A pH adjusting agent such as sodium carbonate, sodium acetate or sodium phosphate can also be used in combination.

To the emulsion thus obtained, it is possible to add other water-soluble polymer substances as described above for the purpose of increasing the viscosity. The addition amount is usually in the range of 5 to 500% by weight in terms of solid content with respect to the emulsion.

Further, a cross-linking agent, a water-proofing agent, a pigment, a dispersant, an antifoaming agent, an oil agent and the like may be appropriately mixed with the emulsion, if necessary.

The obtained emulsion is useful as a paper processing agent, an adhesive, a paint, a fiber processing agent, cosmetics, a civil engineering building material, and the like.

Use of polyvinyl alcohol-based polymer The polyvinyl alcohol-based polymer obtained above is a surface sizing agent for paper, a dispersion stabilizer used during emulsion polymerization or suspension polymerization of a polymerizable monomer, and conventionally polyvinyl alcohol is used. It can be used for various purposes.

The applications are summarized as follows.

(1) Coating materials Clear coating agents for paper, pigment coating agents for paper, internal sizing agents for paper, sizing agents for textile products, warp lake agents, textile processing agents, leather finishing agents, paints, anti-fog agents, miles (2) Dispersion stabilizer-related pigment dispersion stabilizers for paints, India ink, watercolor colors, adhesives, etc.
Emulsifiers for emulsion polymerization of ethylenically unsaturated monomers and butadiene-based monomers, vinyl chloride, vinylidene chloride, styrene, acrylic ester, methacrylic acid ester, dispersion stabilizers for suspension polymerization of various vinyl monomers such as vinyl acetate, polyolefin, polyester Hydrophobic resin such as resin,
Post-emulsifier for epoxy resin, paraffin, bitumen, etc. (3) Related to moldings Fiber, film, sheet, pipe, tube, leak-proof film,
Water-soluble fibers for provisional coatings and chemical lace (4) Adhesives Adhesives for wood, paper, aluminum foil, plastics, etc., rewetting agents, binders for non-woven fabrics, fibrous binders,
Binder for manufacturing various building materials such as gypsum board and fiber board, binder for various powder granulation, additive for cement and mortar,
Hot-melt type adhesive, dye fixing agent, amino resin adhesive improver (5) Hydrophobic resin blending agent Addition for antistatic agent and hydrophilicity-imparting agent of hydrophobic resin, composite fiber, film and other molded articles Agent (6) Thickener-related Thickener for various emulsions (7) Flocculant-related Flocculant for suspended solids and dissolved in water, wax slurry improver for pulp slurry (8) Soil improver (9) Photosensitizer, Electrosensitive agent (10) Ion exchange resin, ion exchange membrane (11) Chelating resin (12) Cosmetics such as hair spray, setting lotion, etc. (13) Plating bath aid, rust preventive agent In the polymer of the present invention, The dicarboxylic acid monoester unit (A) plays a role of simultaneously introducing a hydrophobic group and a carboxyl group into the polymer, and the vinyl alcohol group (B) and the vinyl ester group (C) form a polymer skeleton. It also plays a role in controlling water solubility and adhesiveness. The combination of each of these units results in an optimal polymer structure for paper surface sizing agents, dispersion stabilizers, and other purposes.

EXAMPLES Next, the present invention will be further described with reference to examples.

Hereinafter, “parts” and “%” are based on weight unless otherwise specified.

Production of Polyvinyl Alcohol-based Polymer Production Example 1 98 parts of maleic anhydride, 172 parts of di-n-amylcarbinol and 0.2 part of sulfuric acid were charged into a flask and stirred under agitation of 80 parts.
The reaction was carried out at 6 ° C for 6 hours. The charged molar ratio of maleic anhydride and di-n-amyl carbinol is 1: 1. After completion of the reaction, by recrystallizing the reaction product, the formula A compound (a) represented by 100% reaction rate,
The yield was 85%.

A polymerization vessel was charged with 456 parts of vinyl acetate (c) and 91 parts of methanol, and the temperature was raised under a nitrogen stream while stirring the system.
When the temperature reached ℃, azoisobutyronitrile was added in an amount of 0.088 mol% to vinyl acetate (c). Thereafter, at this temperature, 56 parts of a 50% methanol solution of the compound (a) obtained above was added to 6 parts.
Polymerization is carried out while dripping over a period of time
The polymerization reaction was continued for 30 minutes. The polymerization rate of vinyl acetate (c) was 66.9, and the polymerization rate of compound (a) was almost 100%.

After completion of the reaction, methanol vapor was blown into the reaction solution to remove unreacted monomers, and a methanol solution of the copolymer was obtained.

This solution was diluted with methanol to adjust the concentration to 40%, charged into a kneader, and neutralized by adding sodium hydroxide while keeping the solution temperature at 35 ° C. 20 mmol of sodium hydroxide was further added to the vinyl acetate unit in the polymer and kneaded. As the saponification reaction progressed, a saponified product was deposited and finally became a slurry. This slurry was filtered, washed well with methanol, and dried in a hot air drier to obtain a white powdery polyvinyl alcohol polymer.

The obtained polymer was extracted and washed with methanol using a Soxhlet extractor, and the degree of modification with the compound (a) was measured by NMR.
As a result of analysis by the above method, the degree of denaturation was found to be 2.4 mol%. As a result of IR analysis of the saponification degree of the vinyl acetate unit, it was found that the saponification degree was 93 mol%. The viscosity of a 4% aqueous solution of this polymer measured by a B-type viscometer was 30 cps / 20 ° C.

Production Examples 2-6, Comparative Examples 1-2 Under the conditions shown in Table 1, production of ethylenically unsaturated dicarboxylic acid monoesters, copolymerization of the obtained monoesters with vinyl acetate, copolymers obtained Was saponified.

The conditions and results are shown in Table 1. The case of Production Example 1 is shown again in this table.

In addition, among the polyvinyl alcohol-based polymers obtained by the above Production Examples, IR spectra of Production Examples 1 to 3 are shown in FIGS. 1 to 3 and NMR spectra are shown in FIGS. 4 to 6, respectively.

The attributions of the IR spectrum and the NMR spectrum of the polyvinyl alcohol-based polymers obtained in the above Production Examples 1 to 3 are shown below.

Polyvinyl alcohol-based polymer obtained in Production Example 1 (FIGS. 1 and 4) Polyvinyl alcohol-based polymer obtained in Production Example 2 (FIGS. 2 and 5) Polyvinyl alcohol-based polymer obtained in Production Example 3 (FIGS. 3 and 6) Paper Surface Sizing Agents Sizing Examples 1 to 3 In order to check the suitability of the polyvinyl alcohol-based polymers obtained by the above Production Examples as paper surface sizing agents, the polymers obtained in Production Examples 1 to 3 respectively are used. Surface sizing was performed on wood free paper having a basis weight of 60 g / m ² using a 4% aqueous solution. As a device, a size press manufactured by Kumagai Riki Co., Ltd. was used, and drying was performed at 110 ° C. for 1 minute.

Table 2 shows the measurement results of the oil absorption, air permeability, and Steckigt size of the coated paper.

Comparative Examples 1 to 3 As a comparative example, the polymer produced in Comparative Example 1 described above (Comparative Example 1), and a saponified product of a maleic acid monomethyl ester-vinyl acetate copolymer which is widely used as a surface sizing agent for conventional paper ( Degree of modification 3 mol%, degree of saponification 93 mol%, almost all methyl ester was removed during the saponification reaction (Comparative Example 2), saponified vinyl versatate-maleic acid-vinyl acetate copolymer (modified The degree of vinyl versatate is 2.7 mol%, maleic acid is 2.7 mol%, and saponification degree is 92.
The same test was performed for (mol%) (Control Example 3).
The results are also shown in Table 2.

From Table 2 as well, the polyvinyl alcohol-based polymer of the present invention not only has a good surface sizing property, but also has significantly improved oil absorption and air permeability as compared with conventional paper surface sizing agents. I understand.

Emulsification Stabilizer Appropriate Emulsifier Examples 1 to 3 In order to check the suitability of polyvinyl alcohol-based polymers as dispersion stabilizers, the above Production Examples 1 to 3 are respectively performed.
Emulsion polymerization of butyl acrylate was carried out as described below using the polymer obtained in 1.

A glass polymerization vessel having a volume of 500 cc equipped with a reflux condenser, a dropping funnel, a thermometer and a stirrer was used.
50 parts and 5 parts of 10% aqueous solution of dibasic sodium phosphate as a pH adjuster were added, and the internal temperature was adjusted to 6 while rotating at a speed of 200 rpm.
The temperature was raised to 5 ° C.

Then 9 parts butyl acrylate and 4% potassium persulfate
1.25 parts of the aqueous solution was added to start emulsion polymerization. Initial polymerization
It was carried out for 35 minutes, then 81 parts of butyl acrylate was continuously added dropwise over 4 hours while adjusting the internal temperature of the polymerization vessel to 70 ° C., and 5 parts of 4% aqueous solution of potassium persulfate was divided into 2 parts. Preparation and emulsion polymerization were continued. The internal temperature was kept at 75 ° C., the aging reaction was carried out for 1 hour, and then the residual monomer was expelled to obtain an emulsion of polybutyl acrylate.

Table 3 shows the measurement results of various properties of the obtained emulsion.

Control Example 4 2.7 g of a nonionic surfactant (Nissan Nonion p-230 manufactured by NOF CORPORATION) and an anionic surfactant (Nissan Trucks H-4 manufactured by NOF CORPORATION) were used instead of the suspension agent.
5) An experiment was conducted in the same manner as in Emulsifier Examples 1 to 3 except that 0.8 g was used in combination.

The results are also shown in Table 3.

Table 3 also shows that the polyvinyl alcohol-based polymer of the present invention has remarkably improved leaving stability, freeze-thaw stability, and dilution stability as compared with conventional emulsifiers.

Suspension Stability Suitability Suspension Agent Examples 1 to 3 To examine suitability of polyvinyl alcohol-based polymers as dispersion stabilizers, the polymers obtained in the above Production Examples 1 to 3 are used for vinyl chloride as described below. Was subjected to suspension polymerization.

An autoclave equipped with a stirrer was charged with 100 parts of vinyl chloride monomer, 150 parts of water, 0.1 part of a dispersion stabilizer consisting of the above polymer, 0.1 part of lauroyl peroxide and 0.2 part of lauroyl peroxide, and the suspension was stirred at a rotation speed of 400 rpm at a temperature of 60 ° C. Suspension polymerization was performed.

The performance of the obtained polyvinyl chloride particles is shown in Table 4.

Control Example 5 An experiment was conducted in the same manner as in Suspension Agent Examples 1 to 3 except that partially saponified polyvinyl alcohol (saponification degree of vinyl acetate component: 80.5 mol%) which was generally used as a dispersion stabilizer for vinyl chloride was used. went. The results are also shown in Table 4.

It can be seen from Table 4 that the polyvinyl alcohol-based polymer of the present invention has remarkably improved porosity, particle size distribution and plasticizer absorbability as compared with the conventional dispersion stabilizer.

Effects of the Invention In the polyvinyl alcohol-based polymer of the present invention,
Since the dicarboxylic acid monoester unit (A) is introduced into the polymer, the polymer has both a hydrophobic group and a carboxyl group, and when this polymer is used as a paper surface sizing agent, Compared to surface sizing agents, the air permeability and oil absorption are remarkably excellent, and when this polymer is used as a dispersion stabilizer during emulsion polymerization or suspension polymerization of vinyl compounds, it is a conventional dispersion stabilizer. The dispersion stabilizing effect is much better than the above.

In addition to these applications, a wide range of applications can be expected.

[Brief description of drawings]

1 to 3 are IR spectra of the polyvinyl alcohol-based polymers obtained in Production Examples 1 to 3, and FIGS. 4 to 6 are NMR spectra of the polyvinyl alcohol-based polymers obtained in Production Examples 1 to 3, respectively.

Claims (6)

[Claims] 1. A formula A polyvinyl alcohol polymer having a repeating unit represented by: 2. The polyvinyl alcohol polymer according to claim 1, wherein 100q / (q + r) = 65-99.5. 3. A formula (However, COOM is free COOH or a salt thereof, R ₁ is hydrogen, an alkyl group or an aryl group, and R ₂ and R ₃ are an alkyl group or an aryl group) and an ethylenically unsaturated dicarboxylic acid monoester (a) After copolymerizing with vinyl acetate (c), this is saponified and the formula A method for producing a polyvinyl alcohol-based polymer, which comprises obtaining a polyvinyl alcohol-based polymer having a repeating unit represented by: 4. A formula A surface sizing agent for paper comprising a polyvinyl alcohol-based polymer having a repeating unit represented by: 5. A formula A dispersion stabilizer comprising a polyvinyl alcohol-based polymer having a repeating unit represented by: 6. The dispersion stabilizer according to claim 5, which is used during emulsion polymerization or suspension polymerization of a polymerizable monomer.