阅读说明：本技术 改性乙烯醇类聚合物粒子的制造方法和由该制造方法得到的粒子 (Process for producing modified vinyl alcohol polymer particles and particles obtained by the process ) 是由 立花祐贵 天野雄介 清水由贵 前川一彦 于 2020-03-12 设计创作，主要内容包括：一种改性乙烯醇类聚合物粒子的制造方法,其是将含有不饱和羧酸、酸催化剂和水的混合介质与乙烯醇类聚合物粒子混合的改性乙烯醇类聚合物粒子的制造方法,其中,将所述混合介质与所述乙烯醇类聚合物粒子混合,使所述不饱和羧酸与所述乙烯醇类聚合物反应,由此得到包含下述式(2)所示的乙烯酯单元、乙烯醇单元相对于全部结构单元的含量为95～99.99摩尔％并且平均粒径为50～2000μm的改性乙烯醇类聚合物粒子。该制造方法没有来自反应时使用的液体介质等的硫成分残留的问题,而且能够在维持粒子形状的状态下对乙烯醇类聚合物粒子进行改性,因而不需要使聚合物在大量的不良溶剂中析出的步骤,因此简便且在经济上也优良。(A method for producing modified vinyl alcohol polymer particles, which comprises mixing a mixing medium containing an unsaturated carboxylic acid, an acid catalyst and water with vinyl alcohol polymer particles, wherein the mixing medium is mixed with the vinyl alcohol polymer particles, and the unsaturated carboxylic acid is reacted with the vinyl alcohol polymer to obtain modified vinyl alcohol polymer particles comprising vinyl ester units represented by the following formula (2), the content of the vinyl alcohol units relative to the total structural units being 95 to 99.99 mol%, and the average particle diameter being 50 to 2000 [ mu ] m. The method does not have the problem of sulfur component residue from liquid medium used in reaction, and can maintain the particle shape of the polyvinyl alcoholSince the polymer-like particles are modified, a step of precipitating the polymer in a large amount of a poor solvent is not required, and hence the polymer-like particles are simple and excellent in economical efficiency.)

1. A process for producing modified vinyl alcohol polymer particles, which comprises mixing vinyl alcohol polymer particles with a medium containing an unsaturated carboxylic acid, an acid catalyst and water, wherein,

the unsaturated carboxylic acid is represented by the following formula (1),

mixing the vinyl alcohol polymer particles with the mixing medium, and reacting the vinyl alcohol polymer particles with the unsaturated carboxylic acid to obtain modified vinyl alcohol polymer particles having a vinyl ester unit represented by the following formula (2), a content of the vinyl alcohol unit based on the total structural units of 95 to 99.99 mol%, and an average particle diameter of 50 to 2000 [ mu ] m,

in the formula (1), X represents a carbon-carbon bond or a divalent saturated hydrocarbon group which may have a branched structure and has 1 to 10 carbon atoms, Y represents a hydrogen atom or a saturated hydrocarbon group which may have a branched structure and has 1 to 6 carbon atoms, Z represents a hydrogen atom or a methyl group,

x, Y, Z in the formula (2) has the same meaning as in the formula (1).

2. The production process according to claim 1, wherein the modified vinyl alcohol polymer particles have a specific surface area of 0.01 to 1.0m²/g。

3. The production method according to claim 1 or 2, wherein the water content in the mixed medium is 1 to 30 mass%.

4. The production process according to any one of claims 1 to 3, wherein the mixed medium further contains acetic acid.

5. The production method according to any one of claims 1 to 4, wherein Y is a hydrogen atom.

6. The production method according to any one of claims 1 to 5, wherein X is a carbon-carbon bond.

7. The production method according to any one of claims 1 to 6, wherein the modified vinyl alcohol polymer particles are further washed.

8. A modified vinyl alcohol polymer particle comprising a vinyl ester unit represented by the following formula (2),

the content of the vinyl alcohol unit is 95 to 99.99 mol% with respect to the total structural units, the content of the sulfur component is 0.01 to 20000ppm, the average particle diameter is 50 to 2000 μm,

in the formula (2), X represents a carbon-carbon bond or a divalent saturated hydrocarbon group which may have a branched structure and has 1 to 10 carbon atoms, Y represents a hydrogen atom or a saturated hydrocarbon group which may have a branched structure and has 1 to 6 carbon atoms, and Z represents a hydrogen atom or a methyl group.

9. The particle according to claim 8, wherein a proportion of a vinyl ester unit present in a triad or more in the modified vinyl alcohol polymer to the total vinyl ester units is 10 mol% or less.

10. The particle of claim 8 or 9, wherein the Yellowness Index (YI) is 50 or less as measured by ASTM D1925.

11. The particle according to any one of claims 8 to 10, wherein the content of the vinyl ester unit represented by the formula (2) is 0.01 to 5 mol% with respect to the entire structural units.

12. Particles according to any one of claims 8 to 11 wherein Y is a hydrogen atom.

13. The particle of any of claims 8-12, wherein X is a carbon-carbon bond.

Technical Field

The present invention relates to a method for producing modified vinyl alcohol polymer particles having an unsaturated hydrocarbon group in a side chain, and particles obtained by the production method.

Background

Vinyl alcohol polymers represented by polyvinyl alcohol are excellent in interfacial properties and strength properties as crystalline water-soluble polymers having a small number, and are used for paper processing, fiber processing, emulsion stabilizers, and the like. Vinyl alcohol Polymer gels obtained by crosslinking vinyl alcohol polymers by various methods have been used for Super Absorbent resins (Super Absorbent polymers), contact lenses, fillers for aqueous/organic solvent SEC columns, and the like, because of their hydrophilicity and safety. In particular, a vinyl alcohol polymer having a vinyl alcohol unit content of 95 mol% or more exhibits high hydrophilicity as a column filler, and a film or fiber obtained by using an aqueous solution of such a vinyl alcohol polymer has excellent strength. In addition, in order to improve specific functions, attempts have been made to introduce functional groups and the like into vinyl alcohol polymers, and various modified vinyl alcohol copolymers have been developed.

Among these, a modified vinyl alcohol polymer having an unsaturated hydrocarbon group introduced into a side chain can be cross-linked by irradiation with high-energy rays to resist hydration, modified by graft polymerization, and the like. As a method for introducing an unsaturated hydrocarbon group into a side chain, a method of reacting a hydroxyl group of a vinyl alcohol polymer with various compounds is common. For example, patent document 1 discloses a method for synthesizing an unsaturated hydrocarbon group-containing vinyl alcohol polymer by acetalization using an aldehyde having an unsaturated hydrocarbon group. Patent document 2 discloses a method for synthesizing an unsaturated hydrocarbon group-containing vinyl alcohol polymer by etherification using an epoxy compound having an unsaturated hydrocarbon group. However, since compounds having mutagenicity are considered to exist among aldehyde and epoxy compounds, a method not using these compounds is required.

On the other hand, there is also disclosed a method for synthesizing an unsaturated hydrocarbon group-containing vinyl alcohol polymer by esterification using an unsaturated carboxylic acid or an unsaturated carboxylic acid ester which is highly safe. For example, patent documents 3 and 4 disclose the following methods: the modified vinyl alcohol polymer is obtained by dissolving a vinyl alcohol polymer in dimethyl sulfoxide (DMSO), then performing transesterification using an unsaturated carboxylic acid ester, and then precipitating the product in a poor solvent. Patent document 5 describes the following method: a vinyl alcohol polymer is dissolved in water and then esterified using an unsaturated carboxylic acid and an acid catalyst, thereby producing a solution containing a modified vinyl alcohol polymer. Non-patent document 1 discloses the following method: the modified vinyl alcohol polymer is obtained by dissolving a vinyl alcohol polymer in water, esterifying the resultant with an unsaturated carboxylic acid, acetic acid and an acid catalyst, and precipitating the esterified product in a poor solvent.

Documents of the prior art

Patent document

Patent document 1: japanese laid-open patent publication No. 2009-108305

Patent document 2: japanese patent laid-open publication No. 2003-231715

Patent document 3: WO2018/124015 publication

Patent document 4: WO2018/124014 publication

Patent document 5: japanese laid-open patent publication No. 2007-321099

Non-patent document

Non-patent document 1: journal of polymer Science (Journal of polymer Science): edition A: polymer Chemistry 1997, volume 35, pages 3603-3611

Disclosure of Invention

Problems to be solved by the invention

However, the production methods of modified vinyl alcohol polymers described in patent documents 3 and 4 are extremely complicated and economically disadvantageous in that the transesterification reaction is carried out in a state where the vinyl alcohol polymer is dissolved in DMSO, and the polymer needs to be precipitated in a large amount of a poor solvent after the reaction in order to separate the modified vinyl alcohol polymer. It has also been found that when a polymer is precipitated by such a method, it is difficult to control the particle shape, and when the obtained polymer is used as a filler for a column, problems such as poor liquid permeation are caused.

In addition, the present inventors have clarified the following problems: DMSO has a very high affinity with the vinyl alcohol polymer, and is likely to remain in the resin even when precipitated in a poor solvent. Therefore, when the obtained vinyl alcohol polymer is used as a filler for a column, there is a problem that a sulfur component is eluted with time to cause contamination. Further, when the modified vinyl alcohol polymers obtained by the production methods described in patent documents 3 and 4 are stored as an aqueous solution, there is a problem that odor due to residual sulfur components is conspicuous.

In the methods for producing modified vinyl alcohol polymers described in patent document 5 and non-patent document 1, since the reaction is carried out using water as a solvent instead of DMSO, the problem of the residual sulfur component can be solved, but in order to isolate the modified vinyl alcohol polymer, it is necessary to precipitate the polymer in a large amount of a poor solvent after the reaction, which is extremely complicated and economically disadvantageous. It has also been found that when a polymer is precipitated by such a method, it is difficult to control the particle shape, and when the obtained polymer is used as a filler for a column, problems such as poor liquid permeation are caused. Patent document 5 discloses only a solution containing a modified vinyl alcohol polymer, and does not disclose a particle shape at all.

The present invention has been made to solve the above problems, and an object thereof is to provide a method for producing modified vinyl alcohol polymer particles having an unsaturated hydrocarbon group, which is capable of controlling the particle shape and is excellent in cost. Further, it is an object of the present invention to provide modified vinyl alcohol polymer particles having an unsaturated hydrocarbon group, which have a small sulfur content and an average particle diameter within a predetermined range.

Means for solving the problems

The present inventors have conducted intensive studies to solve the above problems, and as a result, have found the following. That is, it has been found that when a mixed medium containing an unsaturated carboxylic acid, an acid catalyst and water is mixed with vinyl alcohol polymer particles to carry out a reaction between the unsaturated carboxylic acid and the vinyl alcohol polymer particles, it is not necessary to deposit a large amount of a poor solvent in the separation of a reaction product, and the particle shape of the obtained modified vinyl alcohol polymer can be controlled. Further, it has been found that the odor when the modified vinyl alcohol polymer particles are used as an aqueous solution is reduced by reducing the content of the sulfur component. Further, the present inventors have found that the problems of liquid permeability and contamination when modified vinyl alcohol polymer particles are used as a filler for a column can be solved by setting the average particle diameter of the modified vinyl alcohol polymer particles to a specific range and reducing the content of a sulfur component, and have completed the present invention.

Specifically, the above problems can be solved by providing a method for producing modified vinyl alcohol polymer particles by mixing vinyl alcohol polymer particles with a mixed medium containing an unsaturated carboxylic acid, an acid catalyst and water, wherein the unsaturated carboxylic acid is represented by the following formula (1), and the modified vinyl alcohol polymer particles are obtained by mixing the mixed medium with the vinyl alcohol polymer particles and reacting the unsaturated carboxylic acid with the vinyl alcohol polymer particles, and contain a vinyl ester unit represented by the following formula (2), wherein the content of the vinyl alcohol unit is 95 to 99.99 mol% with respect to the total structural units, and the average particle diameter is 50 to 2000 μm.

[ in the formula (1), X represents a carbon-carbon bond or a divalent saturated hydrocarbon group which may have a branched structure and has 1 to 10 carbon atoms, Y represents a hydrogen atom or a saturated hydrocarbon group which may have a branched structure and has 1 to 6 carbon atoms, and Z represents a hydrogen atom or a methyl group. ]

[ X, Y, Z in the formula (2) has the same meaning as in the formula (1). ]

In this case, the specific surface area of the modified vinyl alcohol polymer particles is preferably 0.01 to 1.0m²(ii) in terms of/g. The content of water in the mixed medium is preferably 1 to 30% by mass. Preferably, the mixed medium further contains acetic acid. It is also preferred that Y is a hydrogen atom. It is also preferred that X is a carbon-carbon bond.

In the above production method, it is preferable that the modified vinyl alcohol polymer particles are further washed.

The above problem can also be solved by providing modified vinyl alcohol polymer particles comprising a vinyl ester unit represented by the following formula (2), wherein the content of the vinyl alcohol unit is 95 to 99.99 mol% with respect to the total structural units, the content of the sulfur component is 0.01 to 20000ppm, and the average particle diameter is 50 to 2000 [ mu ] m.

[ in the formula (2), X represents a carbon-carbon bond or a divalent saturated hydrocarbon group which may have a branched structure and has 1 to 10 carbon atoms, Y represents a hydrogen atom or a saturated hydrocarbon group which may have a branched structure and has 1 to 6 carbon atoms, and Z represents a hydrogen atom or a methyl group. ]

In this case, the proportion of the vinyl ester units present in triads or more in the modified vinyl alcohol polymer is preferably 10 mol% or less with respect to the total vinyl ester units. The modified vinyl alcohol polymer particles preferably have a Yellowness Index (YI) of 50 or less as measured by ASTM D1925. The content of the vinyl ester unit represented by the formula (2) in the modified vinyl alcohol polymer particles is preferably 0.01 to 5 mol% based on the total structural units. It is also preferred that Y is a hydrogen atom. It is also preferred that X is a carbon-carbon bond.

Effects of the invention

The method for producing modified vinyl alcohol polymer particles of the present invention is free from the problem of residual sulfur components derived from a liquid medium or the like used in the reaction, and can modify vinyl alcohol polymer particles while maintaining the particle shape, and therefore, a step of precipitating a polymer into a large amount of a poor solvent is not required, and the method is simple and economically excellent. Further, the modified vinyl alcohol polymer particles of the present invention have a small sulfur content, excellent high-energy ray reactivity, and an average particle diameter within a predetermined range, and therefore are suitably used as a column filler or the like. In addition, when producing a film or a fiber, the modified vinyl alcohol polymer particles of the present invention have little odor when used as an aqueous solution.

Detailed Description

The present invention is a method for producing modified vinyl alcohol polymer particles, wherein a mixed medium containing an unsaturated carboxylic acid, an acid catalyst and water is mixed with vinyl alcohol polymer particles, wherein the unsaturated carboxylic acid is represented by the following formula (1), the mixed medium is mixed with the vinyl alcohol polymer particles, and the unsaturated carboxylic acid is reacted with the vinyl alcohol polymer particles, thereby obtaining modified vinyl alcohol polymer particles containing a vinyl ester unit represented by the following formula (2), the content of the vinyl alcohol unit relative to the total structural units being 95 to 99.99 mol%, and the average particle diameter being 50 to 2000 [ mu ] m.

[ in the formula (1), X represents a carbon-carbon bond or a divalent saturated hydrocarbon group which may have a branched structure and has 1 to 10 carbon atoms, Y represents a hydrogen atom or a saturated hydrocarbon group which may have a branched structure and has 1 to 6 carbon atoms, and Z represents a hydrogen atom or a methyl group. ]

[ X, Y, Z in the formula (2) has the same meaning as in the formula (1). ]

In the production method of the present invention, the unsaturated carboxylic acid to be reacted with the vinyl alcohol polymer particles is represented by formula (1). X in the formula (1) represents a carbon-carbon bond or a divalent saturated hydrocarbon group having 1 to 10 carbon atoms and having a branched structure. From the viewpoint of high energy ray reactivity, X is preferably a carbon-carbon bond. Specific examples of the unsaturated carboxylic acid in which X is a carbon-carbon bond include methacrylic acid, acrylic acid, crotonic acid, and the like.

The number of carbon atoms of the saturated hydrocarbon group used as X is 1 to 10. When the number of carbon atoms exceeds 10, the water solubility is poor. The number of carbon atoms is preferably 5 or less, more preferably 3 or less, and still more preferably 2 or less.

As the divalent saturated hydrocarbon group used as X, there can be mentioned: alkylene, cycloalkylene, and the like. Examples of the alkylene group include: methylene, ethylene, propylene, butylene, pentylene, hexylene, heptylene, octylene, nonylene, decylene, and the like. Examples of the cycloalkylene group include: cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, and the like. The alkylene group and cycloalkylene group used as X may have an alkyl group such as a methyl group or an ethyl group as a branched structure.

Y in the formula (1) represents a hydrogen atom or a saturated hydrocarbon group which has 1-6 carbon atoms and may have a branched structure. Y is preferably a hydrogen atom.

The number of carbon atoms of the saturated hydrocarbon group used as Y is 1 to 6. When the number of carbon atoms exceeds 6, the water solubility may be deteriorated. The number of carbon atoms is preferably 5 or less, more preferably 3 or less, and still more preferably 2 or less.

Examples of the saturated hydrocarbon group used as Y include an alkyl group and a cycloalkyl group. Examples of the alkyl group include: methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, tert-butyl, pentyl, isopentyl, neopentyl, hexyl and the like. Examples of the cycloalkyl group include cyclopropyl, cyclobutyl, cyclopentyl, and cyclohexyl. The alkyl group and the cycloalkyl group used as Y may have an alkyl group such as a methyl group or an ethyl group as a branched structure.

Specific examples of the unsaturated carboxylic acid represented by the formula (1) include: methacrylic acid, acrylic acid, crotonic acid, 3-methyl-3-butenoic acid, 4-pentenoic acid, 2-methyl-4-pentenoic acid, 5-hexenoic acid, 3-dimethyl-4-pentenoic acid, 7-octenoic acid, trans-3-pentenoic acid, trans-4-decenoic acid, 10-undecenoic acid and the like. Among them, methacrylic acid, acrylic acid, 4-pentenoic acid and 10-undecenoic acid are preferable from the viewpoint of industrial availability and reactivity.

In the production method of the present invention, an acid catalyst is used as a catalyst for the reaction of the unsaturated carboxylic acid and the vinyl alcohol polymer particles. This promotes the reaction between the unsaturated carboxylic acid and the vinyl alcohol polymer particles. The acid catalyst may be any catalyst that catalyzes the dehydration esterification reaction of the unsaturated carboxylic acid represented by the formula (1) with the hydroxyl group of the vinyl alcohol polymer particles, and any of an organic acid and an inorganic acid may be used. Examples of the organic acid include methanesulfonic acid, benzenesulfonic acid, trifluoromethanesulfonic acid and p-toluenesulfonic acid, and examples of the inorganic acid include sulfuric acid, hydrochloric acid and nitric acid. Among them, methanesulfonic acid, p-toluenesulfonic acid and sulfuric acid are preferable, and p-toluenesulfonic acid is particularly preferable.

The saponification degree of the vinyl alcohol polymer constituting the vinyl alcohol polymer particles used in the present invention is preferably 95 to 99.99 mol%. The viscosity average degree of polymerization of the vinyl alcohol polymer is preferably 100 to 5000, and more preferably 200 to 4000. When the viscosity average degree of polymerization is less than 100, the mechanical strength of the resulting modified vinyl alcohol polymer may be lowered. On the other hand, when the viscosity average polymerization degree exceeds 5000, it may become difficult to industrially produce vinyl alcohol polymer particles. The degree of saponification and the degree of viscosity-average polymerization of the vinyl alcohol polymer were measured according to JIS K6726.

The vinyl alcohol units in the vinyl alcohol polymer can be derived from the vinyl ester units by hydrolysis, alcoholysis, or the like. Therefore, depending on the conditions for converting the vinyl ester unit into the vinyl alcohol unit, the vinyl ester unit may remain in the vinyl alcohol polymer.

Examples of the vinyl ester of the above-mentioned vinyl ester unit include: vinyl formate, vinyl acetate, vinyl propionate, vinyl butyrate, vinyl isobutyrate, vinyl pivalate, vinyl versatate, vinyl caproate, vinyl caprylate, vinyl laurate, vinyl palmitate, vinyl stearate, vinyl oleate, vinyl benzoate, and the like, and among them, vinyl acetate is preferable from an industrial viewpoint.

The vinyl alcohol polymer may contain other monomer units than the vinyl alcohol unit and the vinyl ester unit as long as the effect of the present invention is not hindered. Examples of such other monomer units include monomer units derived from an ethylenically unsaturated monomer copolymerizable with the vinyl ester. Examples of such ethylenically unsaturated monomers include: α -olefins such as ethylene, propylene, n-butene, isobutylene and 1-hexene; acrylic acid and salts thereof; acrylic esters such as methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, tert-butyl acrylate, 2-ethylhexyl acrylate, dodecyl acrylate, and octadecyl acrylate; methacrylic acid and salts thereof; methacrylates such as methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, tert-butyl methacrylate, 2-ethylhexyl methacrylate, dodecyl methacrylate, and octadecyl methacrylate; acrylamide, N-methacrylamide, N-ethylacrylamide, N-dimethylacrylamide, diacetoneacrylamide, acrylamidopropanesulfonic acid and salts thereof, acrylamidopropyldimethylamine and salts thereof (e.g., quaternary salts); methacrylamide, N-methylmethacrylamide, N-ethylmethacrylamide, methacrylamidopropanesulfonic acid and salts thereof, methacrylamidopropyldimethylamine and salts thereof (e.g. quaternary salts); vinyl ethers such as methyl vinyl ether, ethyl vinyl ether, n-propyl vinyl ether, isopropyl vinyl ether, n-butyl vinyl ether, isobutyl vinyl ether, tert-butyl vinyl ether, dodecyl vinyl ether, stearyl vinyl ether, and 2, 3-diacetoxy-1-vinyloxypropane; vinyl cyanides such as acrylonitrile and methacrylonitrile; vinyl halides such as vinyl chloride and vinyl fluoride; vinylidene halides such as vinylidene chloride and vinylidene fluoride; allyl compounds such as allyl acetate, 2, 3-diacetoxy-1-allyloxypropane, and allyl chloride; unsaturated dicarboxylic acids such as maleic acid, itaconic acid, and fumaric acid, and salts or esters thereof; vinyl silyl compounds such as vinyltrimethoxysilane; isopropenyl acetate, and the like.

The content of the monomer unit other than the vinyl alcohol unit and the vinyl ester unit in the vinyl alcohol polymer is usually 10 mol% or less, preferably 5 mol% or less, and more preferably 1 mol% or less.

The average particle diameter of the vinyl alcohol polymer particles used in the present invention is preferably 50 to 2000. mu.m. When the average particle diameter is less than 50 μm, the liquid permeability may be insufficient when the obtained modified vinyl alcohol-based polymer particles are used as a filler for a column. The average particle diameter is more preferably 100 μm or more, still more preferably 200 μm or more, particularly preferably 300 μm or more, and most preferably 500 μm or more. On the other hand, when the average particle diameter exceeds 2000. mu.m, the reaction may not proceed uniformly inside and outside the particles. The average particle diameter is more preferably 900 μm or less, and still more preferably 800 μm or less.

The modified vinyl alcohol polymer particles are obtained by mixing a mixing medium containing an unsaturated carboxylic acid represented by the formula (1), the acid catalyst and water with vinyl alcohol polymer particles to react the unsaturated carboxylic acid with the vinyl alcohol polymer particles. In this manner, by reacting the vinyl alcohol polymer particles with the unsaturated carboxylic acid, that is, by carrying out the reaction while maintaining the particle shape of the vinyl alcohol polymer particles as a raw material, it is not necessary to deposit the vinyl alcohol polymer particles in a large amount of a poor solvent during the separation of the reaction product, and the particle shape of the modified vinyl alcohol polymer particles can be controlled. Further, there is no problem that sulfur components derived from a liquid medium or the like used in the reaction remain in the modified vinyl alcohol-based polymer particles. In addition, in the obtained modified vinyl alcohol polymer particles, since the proportion of vinyl ester units present in triads or more is reduced, the viscosity stability is improved in the case of an aqueous solution. As a method for reacting the unsaturated carboxylic acid with the vinyl alcohol polymer particles, the following method is preferred: the vinyl alcohol polymer particles are dispersed in the mixing medium by mixing the mixing medium with the vinyl alcohol polymer particles, and the unsaturated carboxylic acid is reacted with the vinyl alcohol polymer particles. Specifically, the following methods can be cited: the unsaturated carboxylic acid is reacted with the vinyl alcohol polymer particles by mixing the mixing medium with the vinyl alcohol polymer particles to prepare a slurry or a dispersion. Further, the following methods may be mentioned: the unsaturated carboxylic acid is reacted with the vinyl alcohol polymer particles by uniformly mixing the mixing medium with the vinyl alcohol polymer particles.

The mixing method of the mixing medium and the vinyl alcohol polymer particles is not particularly limited as long as the both can be uniformly mixed. Specifically, there may be mentioned: (1) a method of preparing the mixed medium and then mixing the mixed medium with the vinyl alcohol polymer particles; (2) a method of mixing the vinyl alcohol polymer with a part of the components of the mixed medium and then mixing the resulting mixture with the remaining components of the mixed medium; (3) and (1) a method of simultaneously mixing the components of the mixing medium with the vinyl alcohol polymer particles.

The mass ratio of the vinyl alcohol polymer particles to the mixed medium [ polymer particles/mixed medium ] when the mixed medium is mixed with vinyl alcohol polymer particles is preferably 3/97 to 90/10. In the case where the mass ratio [ polymer particles/mixing medium ] is less than 3/97, the reactivity may be significantly reduced. The mass ratio [ polymer particles/mixing medium ] is more preferably 10/90 or more. On the other hand, when the mass ratio [ polymer particles/mixing medium ] exceeds 90/10, the mixing medium may not be uniformly mixed with the vinyl alcohol-based polymer particles, and the reactivity may be significantly lowered. The mass ratio [ polymer particles/mixing medium ] is more preferably 80/20 or less, and still more preferably 50/50 or less.

The content of water in the mixed medium is preferably 1 to 30% by mass. When the water content is less than 1% by mass, the resulting modified vinyl alcohol polymer particles may be easily colored. The content of water is more preferably 3% by mass or more, still more preferably 5% by mass or more, and particularly preferably 8% by mass or more. On the other hand, when the water content exceeds 30% by mass, the vinyl alcohol polymer is dissolved during the reaction, and there is a possibility that it is difficult to modify the vinyl alcohol polymer particles while maintaining the particle shape. The content of water is more preferably 20% by mass or less, and still more preferably 18% by mass or less.

The amount of the acid catalyst added when the unsaturated carboxylic acid is reacted with the vinyl alcohol polymer particles is preferably 0.0001 to 0.1 mol per 1 mol of hydroxyl groups in the vinyl alcohol polymer. The amount of addition is more preferably 0.0005 mol or more. On the other hand, the amount of addition is more preferably 0.08 mol or less.

The content of the unsaturated carboxylic acid in the mixed medium is preferably 5 to 2000 parts by mass per 100 parts by mass of the vinyl alcohol polymer particles. When the amount of the unsaturated carboxylic acid added is less than 5 parts by mass, the reactivity may be lowered. The content of the unsaturated carboxylic acid is more preferably 10 parts by mass or more, still more preferably 20 parts by mass or more, and particularly preferably 30 parts by mass or more. On the other hand, when the content of the unsaturated carboxylic acid exceeds 2000 parts by mass, the unreacted unsaturated carboxylic acid may increase, thereby increasing the cost. The content of the unsaturated carboxylic acid is more preferably 1500 parts by mass or less, still more preferably 1000 parts by mass or less, and particularly preferably 700 parts by mass or less.

From the viewpoint of controlling the content of the vinyl acetate unit in the modified vinyl alcohol polymer, the mixed medium preferably further contains acetic acid. The content of acetic acid in the mixed medium is preferably 1 to 1000 parts by mass with respect to 100 parts by mass of water in the mixed medium. The content of acetic acid is more preferably 5 parts by mass or more, and still more preferably 10 parts by mass or more. On the other hand, the content of acetic acid is more preferably 800 parts by mass or less, and still more preferably 600 parts by mass or less.

The above-mentioned mixing medium may contain other additives than the unsaturated carboxylic acid represented by the formula (1), the above-mentioned acid catalyst, water and acetic acid. Examples of the other additives include surfactants and organic solvents. Examples of the surfactant include: nonionic surfactants such as polyoxyethylene-alkyl ether type, polyoxyethylene-alkylphenol type, polyoxyethylene-polyol ester type, esters of polyhydric alcohols with fatty acids, and oxyethylene-oxypropylene block polymers; anionic surfactants such as higher alcohol sulfates, higher fatty acid alkali salts, polyoxyethylene alkylphenol ether sulfates, alkylbenzene sulfonates, naphthalenesulfonate formalin condensates, alkyldiphenylether sulfonates, dialkyl sulfosuccinates, and higher alcohol phosphate salts, and reactive surfactants. Examples of the organic solvent include: alcohols such as methanol, ethanol, propanol, and butanol; aliphatic or alicyclic hydrocarbons such as n-hexane, n-pentane and cyclohexane; aromatic hydrocarbons such as benzene and toluene; nitriles such as acetonitrile and benzonitrile; diethyl ether, diphenyl ether, anisole, 1, 2-dimethoxyethane, 1, 4-bisEthers such as alkanes; ketones such as acetone, methyl ethyl ketone, methyl isopropyl ketone, and methyl isobutyl ketone; and esters such as methyl acetate, ethyl acetate, and ethyl propionate. Examples of other additives include ultraviolet absorbers, light stabilizers, antioxidants, plasticizers, and defoaming agents. The content of the other additives in the above-mentioned mixed medium is preferably 50% by mass or less, and more preferably 35% by mass or less. In addition, the mixed medium preferably does not contain a sulfur-containing liquid medium.

The temperature at which the unsaturated carboxylic acid and the vinyl alcohol polymer particles are reacted is preferably 10 to 120 ℃. The temperature is more preferably 30 ℃ or higher, and still more preferably 50 ℃ or higher. On the other hand, the temperature is more preferably 100 ℃ or lower, and still more preferably 90 ℃ or lower. The reaction time for reacting the unsaturated carboxylic acid with the vinyl alcohol polymer particles is usually 0.5 to 72 hours.

It is preferable to further clean the modified vinyl alcohol polymer particles after the reaction. As a specific cleaning method, a method of cleaning the particles with a solvent can be cited. Specifically, there may be mentioned a method of immersing the particles in a solvent and then removing the liquid, a method of cleaning the particles by bringing the solvent into contact with the particles while circulating the solvent in a cleaning tower, a method of spraying the cleaning solvent while fluidizing the particles, and the like. Examples of the solvent to be used include: alcohols such as methanol, ethanol, propanol, and butanol; aliphatic or alicyclic hydrocarbons such as n-hexane, n-pentane and cyclohexane; aromatic hydrocarbons such as benzene and toluene; nitriles such as acetonitrile and benzonitrile; diethyl ether, diphenyl ether, anisole, 1, 2-dimethoxyethane, 1, 4-bisEthers such as alkanes; ketones such as acetone, methyl ethyl ketone, methyl isopropyl ketone, and methyl isobutyl ketone; and esters such as methyl acetate, ethyl acetate, and ethyl propionate. Among them, alcohols, ethers, ketones, and esters are more preferable, methanol, ethanol, propanol, diethyl ether, 1, 2-dimethoxyethane, acetone, methyl ethyl ketone, methyl acetate, and ethyl acetate are further preferable, and methanol, propanol, acetone, methyl ethyl ketone, methyl acetate, and ethyl acetate are particularly preferable. These organic solvents may be used alone, or two or more of them may be used in combination.

It is preferable that the modified vinyl alcohol polymer particles after the reaction are washed if necessary and then dried. In this case, the drying temperature is usually 20 to 150 ℃ and the drying time is usually 1 to 72 hours. The modified vinyl alcohol polymer particles may be dried under atmospheric pressure or under reduced pressure.

The average particle diameter of the modified vinyl alcohol polymer particles thus obtained needs to be 50 to 2000 μm. The modified vinyl alcohol polymer particles having such an average particle diameter are excellent in liquid permeability and the like when used as a column filler. Further, according to the production method of the present invention, since the shape of the modified vinyl alcohol polymer particles can be easily controlled, the modified vinyl alcohol polymer particles having such an average particle diameter can be easily produced. When the average particle diameter is less than 50 μm, the liquid permeability is insufficient when the obtained modified vinyl alcohol polymer particles are used as a filler for a column. The average particle diameter is preferably 100 μm or more, more preferably 200 μm or more, further preferably 300 μm or more, and particularly preferably 500 μm or more. On the other hand, when the average particle diameter exceeds 2000. mu.m, the reaction does not proceed uniformly inside and outside the modified vinyl alcohol polymer particles when the modified vinyl alcohol polymer particles are produced. The average particle diameter is preferably 900 μm or less, more preferably 800 μm or less.

The specific surface area of the obtained modified vinyl alcohol polymer particles is preferably 0.01 to 1.0m²(ii) in terms of/g. The specific surface area is less than 0.01m²When used as a column packing material,/g, the separation performance may be deteriorated. The specific surface area is more preferably 0.1m²More than g. On the other hand, the specific surface area is more than 1.0m²In the case of using the solid particles as a column packing material,/g, the particles may be compacted and poor filtration may occur.

In the modified vinyl alcohol polymer particles obtained, the proportion of the vinyl ester units present in triads or more to the total vinyl ester units is preferably 10 mol% or less from the viewpoint of improving viscosity stability when prepared as an aqueous solution. The above ratio is more preferably 9 mol% or less, still more preferably 8 mol% or less, and particularly preferably 7 mol% or less. On the other hand, the proportion of the vinyl ester unit present in the triad or more is usually 0.1 mol% or more. The proportion of the vinyl ester units present in triads or more may be determined by the use described in the examples below¹H-NMR measurement method.

The content of the vinyl alcohol unit in the obtained modified vinyl alcohol polymer needs to be 95 to 99.99 mol% with respect to the total structural units. When the content of the vinyl alcohol unit is less than 95 mol%, the crystallinity of the modified vinyl alcohol polymer is significantly reduced, and the mechanical strength may be reduced. The content of the vinyl alcohol unit is more preferably 95.5 mol% or more. On the other hand, when the content of the vinyl alcohol unit exceeds 99.99 mol%, it may be difficult to industrially produce the modified vinyl alcohol polymer. The content of the vinyl alcohol unit is preferably 99.9 mol% or less.

The content of the vinyl ester unit represented by the formula (2) in the obtained modified vinyl alcohol polymer particles is preferably 0.01 to 5 mol% based on the total structural units. When the content of the vinyl ester unit is less than 0.01 mol%, the crosslinking reaction may not sufficiently proceed when the crosslinking reaction of the modified vinyl alcohol polymer particles proceeds. The content of the vinyl ester unit is more preferably 0.05 mol% or more, still more preferably 0.3 mol% or more, and particularly preferably 0.5 mol% or more. On the other hand, when the content of the vinyl ester unit exceeds 5 mol%, the water solubility of the modified vinyl alcohol polymer particles may be deteriorated. The content of the vinyl ester unit represented by the formula (2) can be determined by the use described in the examples described later¹H-NMR measurement method.

The modified vinyl alcohol polymer particles obtained may contain other monomer units than the vinyl alcohol unit and the vinyl ester unit as long as the effect of the present invention is not hindered. Examples of such other monomer units include the monomer units described above as monomer units other than the vinyl alcohol unit and the vinyl ester unit contained in the vinyl alcohol polymer particles used for producing the modified vinyl alcohol polymer particles. The content of the monomer unit other than the vinyl alcohol unit and the vinyl ester unit in the modified vinyl alcohol-based polymer particles is usually 10 mol% or less, preferably 5 mol% or less, and more preferably 1 mol% or less.

The viscosity average degree of polymerization of the obtained modified vinyl alcohol polymer particles is preferably 100 to 5000, and more preferably 200 to 4000. When the viscosity average degree of polymerization is less than 100, the mechanical strength of the resulting modified vinyl alcohol polymer particles may be lowered. On the other hand, when the viscosity average polymerization degree exceeds 5000, it may become difficult to industrially produce vinyl alcohol polymer particles. The viscosity average polymerization degree of the modified vinyl alcohol polymer particles is measured in accordance with JIS K6726.

The content of the sulfur component in the obtained modified vinyl alcohol polymer particles is preferably 0.01 to 20000 ppm. Such modified vinyl alcohol polymer particles having a small sulfur content are less likely to cause contamination due to elution of the sulfur component when used as a filler for a column. Further, when the modified vinyl alcohol polymer particles are prepared into an aqueous solution, the odor is reduced. The content of the sulfur component is more preferably 10000ppm or less, still more preferably 5000ppm or less, and particularly preferably 3000ppm or less. On the other hand, when the sulfur content is less than 0 to 01ppm, it may be difficult to industrially produce the modified vinyl alcohol polymer particles. The content of the sulfur component is more preferably 0.1ppm or more, and still more preferably 1ppm or more.

The Yellowness Index (YI) of the obtained modified vinyl alcohol polymer particles measured according to ASTM D1925 is preferably 50 or less. By using such modified vinyl alcohol polymer particles, molded articles such as films and fibers having good appearance can be obtained. In addition, when modified vinyl alcohol polymer particles having a good hue are used as a filler for the column, the deterioration of the column can be judged by using the change in hue as an index. YI is more preferably 40 or less, still more preferably 30 or less, and particularly preferably 20 or less.

The modified vinyl alcohol polymer particles of the present invention are modified vinyl alcohol polymer particles comprising a vinyl ester unit represented by the following formula (2), wherein the content of the vinyl alcohol unit is 95 to 99.99 mol% with respect to the total structural units, the content of the sulfur component is 0.01 to 20000ppm, and the average particle diameter is 50 to 2000 [ mu ] m.

[ in the formula (2), X represents a carbon-carbon bond or a divalent saturated hydrocarbon group which may have a branched structure and has 1 to 10 carbon atoms, Y represents a hydrogen atom or a saturated hydrocarbon group which may have a branched structure and has 1 to 6 carbon atoms, and Z represents a hydrogen atom or a methyl group. ]

The vinyl ester unit represented by formula (2) in the modified vinyl alcohol polymer particles of the present invention is the same as the vinyl ester unit represented by formula (2) in the modified vinyl alcohol polymer particles obtained by the above-mentioned production method.

The proportion of the vinyl ester unit present in triads or more in the modified vinyl alcohol polymer particles of the present invention to the total vinyl ester units is preferably 10 mol% or less. The modified vinyl alcohol polymer particles preferably have a Yellowness Index (YI) of 50 or less as measured by ASTM D1925. The content of the vinyl ester unit represented by the formula (2) in the modified vinyl alcohol polymer particles is preferably 0.01 to 5 mol% based on the total structural units.

Such modified vinyl alcohol polymer particles have a small sulfur content, excellent high-energy ray reactivity, and an average particle diameter within a predetermined range, and are therefore suitable for use as a column filler. The modified vinyl alcohol polymer particles of the present invention have good hue, high viscosity stability when prepared as an aqueous solution, and little odor, and are therefore also suitable for use in molded articles such as films and fibers. The modified vinyl alcohol polymer particles of the present invention having an average particle diameter within a predetermined range can be efficiently transported, and therefore, cost reduction can be expected. Further, in the modified vinyl alcohol polymer particles of the present invention, since the content of the fine sulfur-containing powder is small, it is possible to prevent health damage to operators due to the attraction thereof.

[ examples ]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples at all. In the examples and comparative examples, "%" and "part(s)" represent "% by mass" and "part(s) by mass", respectively, unless otherwise specified.

[ calculation of the content of vinyl alcohol units ]

Modified vinyl alcohol Polymer particles were measured at room temperature using a nuclear magnetic resonance device "LAMBDA 500" manufactured by Japan electronic Co., Ltd, using a DMSO-d6 solvent¹H-NMR was carried out to calculate the vinyl alcohol unit content of the polymer particles from the integrated value of the peak (3.4 to 4.0ppm) ascribed to the methine proton bonded to the hydroxyl group and the integrated value of the peak (4.7 to 5.3ppm) ascribed to the methine proton of the vinylester group.

[ calculation of modification ratio ]

Modified vinyl alcohol Polymer particles were measured at room temperature using a nuclear magnetic resonance device "LAMBDA 500" manufactured by Japan electronic Co., Ltd¹H-NMR was carried out to calculate the modification ratio of the polymer particles [ the content (mol%) of the vinyl ester unit represented by the above formula (2) based on the total structural units ] from the integrated value of the peak (5.0 to 7.5ppm) ascribed to the proton of the olefin]. For example, in example 1, the modification rate was calculated from the integrated values of the peaks ascribed to olefin protons appearing at 5.6ppm and 6.0 ppm.

[ calculation of the proportion of vinyl ester groups present in triads or more ]

Modified vinyl alcohol Polymer particles were measured at 80 ℃ with a DMSO-d6 solvent using a nuclear magnetic resonance device "LAMBDA 500" manufactured by Japan electronic Co., Ltd¹H-NMR. The proportion of vinyl ester groups present in triads relative to all vinyl ester units is calculated from the integrated values of (a)4.7 to 4.9ppm (methine proton in the middle of the hydroxy-vinylester-hydroxy group), (b)4.9 to 5.05ppm (methine proton in the middle of the hydroxy-vinylester-vinyl ester group), and (c)5.05 to 5.25ppm (methine proton in the middle of the vinylester triads) according to the following formula.

The ratio of vinyl ester groups present in triads or more (%) - (c)/{ (a) + (b) + (c) } × 100

[ measurement of average particle diameter ]

The modified vinyl alcohol polymer particles were dispersed in methanol, and the volume average particle diameter (μm) was measured using a laser diffraction device "LA-950V 2" manufactured by horiba, Ltd.

[ measurement of specific surface area ]

The specific surface area (m) of the modified vinyl alcohol polymer particles was determined by the BET single-point method using nitrogen adsorption using a specific surface area measuring apparatus "MONOSORB" manufactured by ュアサアイオニクス K²/g)。

[ measurement of hue (yellow index; YI) ]

YI (ASTM D1925) of the modified vinyl alcohol polymer particles obtained in examples or comparative examples was measured by the following method using a spectrocolorimeter "CM-8500D" manufactured by Konika Mingta corporation (light source: D65, CM-A120 white calibration plate, SCE was measured by regular reflection using a CM-A126 petri dish set, and diameter. phi.30 mm was measured). 5g of the sample was added to the petri dish, the side was lightly tapped without compacting the powder, and the petri dish was shaken to uniformly spread the powder. In this state, a total of 10 measurements (each measurement after shaking the culture dish) were performed, and the average value was defined as the YI of the polymer particles.

[ evaluation of photosensitivity ]

To an aqueous solution (concentration: 5 mass%) in which the modified vinyl alcohol polymer particles obtained in examples or comparative examples were dissolved, 2-hydroxy-4' - (2-hydroxyethoxy) -2-methylpropiophenone as a photoinitiator was added in an amount of 1 part by mass per 100 parts by mass of the particles, and then the particles were dissolved to prepare a coating solution. The coating solution was cast into a 15cm × 15cm frame prepared by folding the edge of a polyethylene terephthalate film, and the solvent was sufficiently volatilized at room temperature and atmospheric pressure to obtain a film having a thickness of about 100 μm. Here at 10J/cm²The film for evaluation was produced by irradiating ultraviolet light at the intensity of (2), and the mass was measured (W2). The obtained film for evaluation was immersed in boiling water for 1 hour, taken out of the water, vacuum-dried at 40 ℃ for 12 hours, and then measured for mass (W1). From the obtained mass (W1) and the mass (W2) of the film before immersion, the dissolution rate under boiling conditions was calculated according to the following formula, and this dissolution rate was used as an index of photosensitivity (lower dissolution rate indicates higher photosensitivity). In the case where the evaluation film dissolved during immersion in water, the evaluation was ""could not be measured" is shown as "-" in Table 1.

The dissolution rate (mass%) was 100 × ([ W2] - [ W1])/[ W2]

[ viscosity stability ]

The viscosity η immediately after preparation of an aqueous solution (concentration: 15% by mass) in which the particles obtained in examples or comparative examples were dissolved was measured using a viscometer "LVDV-2 + PRO" manufactured by Brookfield₀And viscosity eta after 7 days of preparation₇Then calculating the viscosity ratio eta₇/η₀The viscosity stability was evaluated according to the following criteria. Viscosity ratio eta₇/η₀The larger the value of (A) is, the larger the increase in the viscosity of the solution is, the poorer the viscosity stability is.

A：η₇/η₀Less than 1.3

B：η₇/η₀Is 1.3 or more and less than 1.6

C：η₇/η₀Is more than 1.6

[ evaluation of liquid permeability ]

The modified vinyl alcohol polymer particles obtained in examples or comparative examples were irradiated with 150kGy of electron beam to crosslink and resist hydration. 100 parts by mass of the crosslinked modified vinyl alcohol polymer particles were packed in a column (glass filter having an inner diameter of 50mm and an opening diameter of 40 to 50 μm and having a cock). 130 parts by mass of a methanol/water mixture (9/1 mass ratio) was charged therein, and then the cock was opened to start filtration. The filtrate was collected, and the time when 90% (i.e., 117 parts by mass) of the added mixed solution was collected as the filtrate was referred to as "filtration completion", and the liquid permeability was evaluated from the time required from the start of filtration to the completion of filtration.

A: case where the filtering ends in less than 150 seconds

B: ending at 150 seconds or more and less than 300 seconds

C: in the case where 300 seconds or more are required until the end of filtration

[ evaluation of the content of the Sulfur component ]

The modified vinyl alcohol polymer particles obtained in examples or comparative examples were dried at 80 ℃ for 12 hours, and then the content of the sulfur component in the modified vinyl alcohol polymer particles was measured using an organic element analyzer 2400II manufactured by perkin elmer.

[ example 1]

482.0 parts by mass of methacrylic acid, 85.1 parts by mass of ion-exchanged water, 1.3 parts by mass of p-methoxyphenol, and 4.5 parts by mass of 47% sulfuric acid were sequentially charged into a reactor equipped with a stirrer, a reflux tube, and an addition port, 100 parts by mass of a commercially available polyvinyl alcohol resin (degree of viscosity-average polymerization 500, degree of saponification 98.5 mol%, average particle diameter 723 μm) was added while stirring at room temperature, and the temperature was raised to 80 ℃ while stirring, and the reaction was carried out for 5 hours in a slurry state. Then, the mixture was cooled to room temperature, the contents were filtered, the modified vinyl alcohol polymer was recovered, washed with a large amount of methanol, and dried at 40 ℃ and 1.3Pa for 20 hours, thereby obtaining target particles. The results of structural analysis and physical property evaluation of the obtained modified vinyl alcohol polymer particles are shown in table 1.

[ example 2]

To a reactor equipped with a stirrer, a reflux tube and an addition port, 510.3 parts by mass of 4-pentenoic acid, 56.7 parts by mass of ion-exchanged water, 1.3 parts by mass of p-methoxyphenol and 4.2 parts by mass of p-toluenesulfonic acid monohydrate were sequentially charged, 100 parts by mass of a commercially available polyvinyl alcohol resin (degree of viscosity-average polymerization 1700, degree of saponification 98.5 mol%, average particle diameter 698 μm) was added while stirring at room temperature, and the temperature was raised to 60 ℃ while stirring, and the mixture was reacted for 3 hours in a slurry state. Then, the post-treatment was performed in the same manner as in example 1 to obtain target particles. The results of structural analysis and physical property evaluation of the obtained modified vinyl alcohol polymer particles are shown in table 1.

The obtained modified vinyl alcohol polymer particles were processed¹As a result of H-NMR measurement, the ratio of vinyl ester groups present in triads or more cannot be calculated because the peak of the proton attributed to the olefin in the unsaturated hydrocarbon group and the peak of the proton attributed to the methine group in the vinyl ester group overlap. Therefore, the modified vinyl alcohol polymer particles (the content of the modified vinyl alcohol polymer: 5% by mass) were dissolved in water, and 1 mol of the modified vinyl alcohol polymer particles was added to 1 mol of the olefinFurther, 2-hydroxy-4' - (2-hydroxyethoxy) -2-methylpropiophenone was added as a photoinitiator in an amount of 1 mole based on 1 mole of propanethiol. At a rate of 3000mJ/cm²The thus prepared solution was irradiated with ultraviolet rays at an intensity of (1). Adding the obtained solution into a large amount of methanol to precipitate polymer particles, and passing through¹As a result of analyzing the particles by H-NMR, the olefin proton peak disappears due to the addition of thiol, and therefore the proportion of vinyl ester groups present in triads or more can be calculated.

[ example 3]

To a reactor equipped with a stirrer, a reflux tube and an addition port, 454.2 parts by mass of methacrylic acid, 5.7 parts by mass of acetic acid, 56.7 parts by mass of ion-exchanged water, 1.3 parts by mass of p-methoxyphenol and 4.2 parts by mass of p-toluenesulfonic acid monohydrate were sequentially charged, 100 parts by mass of a commercially available polyvinyl alcohol resin (degree of viscosity-average polymerization 1700, degree of saponification 99.5 mol%, average particle diameter 128 μm) was added while stirring at room temperature, and the temperature was raised to 90 ℃ while stirring, and the mixture was reacted in a slurry state for 3 hours. Then, the post-treatment was performed in the same manner as in example 1 to obtain target particles. The results of structural analysis and physical property evaluation of the obtained modified vinyl alcohol polymer particles are shown in table 1.

[ example 4]

Into a reactor equipped with a stirrer, a reflux tube and an addition port, 510.3 parts by mass of methacrylic acid, 28.4 parts by mass of acetic acid, 28.4 parts by mass of ion-exchanged water, 1.3 parts by mass of p-methoxyphenol and 8.1 parts by mass of p-toluenesulfonic acid monohydrate were sequentially charged, 100 parts by mass of a commercially available polyvinyl alcohol resin (degree of viscosity average polymerization 1700, degree of saponification 95 mol%, average particle diameter 730 μm) was added while stirring at room temperature, and the temperature was raised to 65 ℃ while stirring, and the reaction was carried out for 5 hours in a slurry state. Then, the post-treatment was performed in the same manner as in example 1 to obtain target particles. The results of structural analysis and physical property evaluation of the obtained modified vinyl alcohol polymer particles are shown in table 1.

[ example 5]

Into a reactor equipped with a stirrer, a reflux tube and an addition port, 493.3 parts by mass of acrylic acid, 17.0 parts by mass of acetic acid, 56.7 parts by mass of ion-exchanged water, 1.3 parts by mass of p-methoxyphenol and 4.2 parts by mass of p-toluenesulfonic acid monohydrate were sequentially charged, 100 parts by mass of a commercially available polyvinyl alcohol resin (having a viscosity polymerization degree of 1000, a saponification degree of 98.5 mol% and an average particle diameter of 725 μm) was added while stirring at room temperature, and the temperature was raised to 65 ℃ while stirring, and the mixture was reacted for 5 hours in a slurry state. Then, the post-treatment was performed in the same manner as in example 1 to obtain target particles. The results of structural analysis and physical property evaluation of the obtained modified vinyl alcohol polymer particles are shown in table 1.

[ example 6]

100 parts by mass of a commercially available polyvinyl alcohol resin (degree of viscosity-average polymerization of 1700, degree of saponification of 98.5 mol%, average particle diameter of 698 μm) was charged into a reactor equipped with a stirrer, a reflux tube, and an addition port, and a mixed solution of 58.0 parts by mass of methacrylic acid, 2.0 parts by mass of acetic acid, 6.7 parts by mass of ion-exchanged water, 0.3 parts by mass of p-methoxyphenol, and 12.6 parts by mass of p-toluenesulfonic acid monohydrate, which had been previously mixed, was added in small amounts at a time while stirring at room temperature. The mixture was stirred sufficiently to uniformly mix the entire mixture with the polyvinyl alcohol resin, and then the temperature was raised to 70 ℃ while stirring, and the reaction was carried out for 5 hours in a powder state. Then, the powder was washed with a large amount of methanol and then dried at 40 ℃ under 1.3Pa for 12 hours, thereby obtaining target particles. The results of structural analysis and physical property evaluation of the obtained modified vinyl alcohol polymer particles are shown in table 1.

[ example 7]

564.2 parts by mass of methacrylic acid, 2.8 parts by mass of ion-exchanged water, 1.3 parts by mass of p-methoxyphenol, and 4.2 parts by mass of p-toluenesulfonic acid monohydrate were sequentially charged into a reactor equipped with a stirrer, a reflux tube, and an addition port, 100 parts by mass of a commercially available polyvinyl alcohol resin (viscosity average degree of polymerization 500, degree of saponification 98.5 mol%, average particle diameter 720 μm) was added while stirring at room temperature, and the temperature was raised to 80 ℃ while stirring, and the reaction was carried out for 5 hours in a slurry state. Then, the post-treatment was performed in the same manner as in example 1 to obtain target particles. The results of structural analysis and physical property evaluation of the obtained modified vinyl alcohol polymer particles are shown in table 1.

Comparative example 1

A commercially available polyvinyl alcohol resin (degree of viscosity-average polymerization 1700, degree of saponification 98.5 mol%, average particle diameter 698 μm) was evaluated. The results of structural analysis and physical property evaluation are shown in table 1.

Comparative example 2

A reactor equipped with a stirrer, a reflux tube and an addition port was charged with 400.0 parts by mass of dimethyl sulfoxide and 100 parts by mass of a commercially available polyvinyl alcohol resin (degree of viscosity average polymerization 1700, degree of saponification 98.5 mol%, average particle diameter 698 μm) which had been vacuum-dried at 80 ℃ for 24 hours, and heated to 100 ℃ while stirring to obtain a homogeneous solution. To the solution were added 33.4 parts by mass of methyl methacrylate and 1.1 parts by mass of phenothiazine, and the mixture was stirred until uniform. To the resulting solution was added 1.9 parts by mass of sodium acetate as a transesterification catalyst, reacted for 5 hours, and then naturally cooled to room temperature. DMSO was added to the reaction solution to dilute the reaction solution, and the resulting solution was added dropwise to methanol to isolate a polymer, which was then dried at 40 ℃ under 1.3Pa for 12 hours. The results of structural analysis and physical property evaluation of the obtained modified vinyl alcohol polymer particles are shown in table 1.

Comparative example 3

A reactor equipped with a stirrer, a reflux tube and an addition port was charged with 400.0 parts by mass of dimethyl sulfoxide and 100 parts by mass of a commercially available polyvinyl alcohol resin (degree of viscosity-average polymerization: 500, degree of saponification: 98.5 mol%, average particle diameter: 723 μm) which had been vacuum-dried at 80 ℃ for 24 hours, and the temperature was raised to 100 ℃ while stirring, thereby obtaining a homogeneous solution. To the solution, 40.0 parts by mass of methyl 3, 3-dimethylpentenoate (MPM) was added, and the mixture was stirred until uniform. To the resulting solution, 0.4 part by mass of tetramethylammonium methyl carbonate as a transesterification catalyst was added, reacted for 5 hours, and then naturally cooled to room temperature. DMSO was added to the reaction solution to dilute the reaction solution, and the resulting solution was added dropwise to methanol to isolate a polymer, which was then dried at 40 ℃ under 1.3Pa for 12 hours. The results of structural analysis and physical property evaluation of the obtained modified vinyl alcohol polymer particles are shown in table 1.

Comparative example 4

288.0 parts by mass of ion-exchanged water was put into a reactor equipped with a stirrer, a reflux tube and an addition port, 100 parts by mass of a commercially available polyvinyl alcohol resin (degree of viscosity-average polymerization 500, degree of saponification 98.5 mol%, average particle diameter 723 μm) was added while stirring, the temperature was raised to 95 ℃ and the mixture was heated and stirred for 3 hours to obtain a homogeneous solution. The solution was cooled to room temperature, 558.0 parts by mass of methacrylic acid, 2 parts by mass of p-methoxyphenol and 27.0 parts by mass of a 36% aqueous acid solution were sequentially added while stirring, and the mixture was heated to 80 ℃ while stirring to react in a uniform solution state for 2 hours, followed by cooling to room temperature. The resulting solution was diluted, and a large amount of methanol was added to a strongly stirred place in small amounts to precipitate modified vinyl alcohol polymer fine particles. The precipitate was collected, washed with a large amount of methanol, and dried at 40 ℃ under 1.3Pa for 12 hours to obtain target fine particles. The results of structural analysis and physical property evaluation of the obtained modified vinyl alcohol polymer particles are shown in table 1.

As is clear from examples 1 to 7, in the production method of the present invention, since the modified vinyl alcohol polymer particles are directly modified in the form of particles, the modified vinyl alcohol polymer particles can be easily separated without performing an operation of precipitating the reaction product in a poor solvent. The modified vinyl alcohol polymer particles of the present invention exhibit high viscosity stability in the case of an aqueous solution, and have little odor due to a sulfur component. In addition, the modified vinyl alcohol polymer particles have excellent high-energy ray reactivity, and have excellent liquid permeability when used as a column filler after crosslinking. In addition, in the production method of the present invention, since DMSO is not used, contamination of sulfur components can be suppressed.

In the case of performing the reaction by dissolving vinyl alcohol polymer particles in a solvent as in comparative examples 2 to 4, in order to separate the modified vinyl alcohol polymer particles as a reaction product, it is necessary to precipitate the particles in a poor solvent, which is not only complicated in operation but also difficult in controlling the particle shape. In addition, the unmodified vinyl alcohol polymer particles of comparative example 1 did not exhibit photosensitivity. The vinyl alcohol polymer particles of comparative examples 1 and 2 in which the proportion of vinyl ester groups present in triads or more exceeds 10% had low viscosity stability when prepared into an aqueous solution. As in comparative examples 2 to 4, the modified vinyl alcohol polymer particles obtained by the reaction in the state where the vinyl alcohol polymer particles are dissolved had an average particle diameter of less than 50 μm and poor liquid permeability. When DMSO is used in the reaction as in comparative examples 2 and 3, the content of the sulfur component in the modified vinyl alcohol polymer particles is extremely large.

[ example 8]

The modified vinyl alcohol polymer particles obtained in example 6 were evaluated as a column filler. The particles were irradiated with 150kGy of electron beam to crosslink and resist hydration. 100 parts by mass of the crosslinked modified vinyl alcohol polymer particles were packed in a column (glass filter having an inner diameter of 50mm and an opening diameter of 40 to 50 μm with a cock) and 1000 parts by mass of super-dehydrated methanol as an eluent was passed therethrough to wet the polymer particles. The super-dehydrated methanol containing 5 mass% of ion-exchanged water was adsorbed on the polymer particles on the upper part of the column, and then 100 parts by mass of the super-dehydrated methanol as an eluent was passed therethrough. Liquid is recovered from the column outlet for analysis.

During the above test, good liquid permeability was maintained. By passing¹The H-NMR analysis of the recovered solution confirmed that: since the recovered solution does not contain water, water is retained in the modified vinyl alcohol polymer particles. Further, the recovered solution was subjected to elemental analysis, and as a result, the sulfur content in the recovered solution was 18 ppm.