JP2017110148A - Manufacturing method of spherical hydrophilic resin - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide further improvement of a spherical hydrophilic resin in uniformity of a shape or particle diameter size, further smoothness of a surface because a rod-like hydrophilic resin is formed partially.SOLUTION: There is provided a spherical hydrophilic resin obtained by a manufacturing method for manufacturing a spherical hydrophilic resin (B) by melting and mixing a polyvinyl alcohol-based resin (a) and a hydrophilic resin (b), wherein a contact angle when making a film from the polyvinyl alcohol-based resin (a) is 20 to 80°.SELECTED DRAWING: None

Description

  The present invention relates to a method for producing a spherical hydrophilic resin, and more specifically, the spherical hydrophilic resin has excellent shape uniformity and surface smoothness, and further has a filler, a cosmetic member, a toner, a ceramic pore forming material, a light The present invention relates to a method for producing a spherical hydrophilic resin having an appropriate particle size that is not too fine but not too large, which is optimal for uses such as a diffusing agent and a matting agent.

  Conventionally, resin fine particles have been used for applications such as fillers, cosmetic members, toners, ceramic pore forming materials, light diffusing agents, matting agents, and the like. A precipitation method and the like are known. However, in the pulverization method, it takes time and energy to form fine particles, and the shape of the particles is not constant, and further, the particle size distribution is widened. In the polymerization method, In order to obtain uniform fine particles, it is necessary to finely control the polymerization conditions, and the polymerization method and its process management are complicated. In addition, the precipitation method has drawbacks such that the precipitated fine particles are likely to aggregate and that good fine particles cannot be easily obtained. Further, in these methods, it is a problem that it is difficult to make the resin spherical.

  Therefore, in order to solve these problems, a method for obtaining a spherical resin by mixing and kneading a water-soluble resin that can be melt-molded within a specific viscosity range and a thermoplastic resin (for example, see Patent Document 1). .) Has been proposed.

JP 09-165457 A

  However, in the disclosed technique disclosed in Patent Document 1, a part of the rod-shaped hydrophilic resin may be formed in the obtained spherical hydrophilic resin, and the shape uniformity, particle size, and surface Further improvement in the smoothness and the like was demanded.

  Therefore, the present invention has an object of providing a spherical hydrophilic resin that is excellent in uniformity of the shape and surface smoothness of the spherical hydrophilic resin and further has an appropriate particle size. It is.

  However, as a result of intensive studies in view of such circumstances, the present inventors have found that polyvinyl alcohol resin (a) and hydrophilic resin (b) are melt-kneaded to produce spherical hydrophilic resin (B). By selecting and using a more hydrophilic resin among alcohol-based resins, the spherical hydrophilic resin has excellent shape uniformity and surface smoothness, and has an appropriate particle size that is not too small and not too small. It was found that a spherical hydrophilic resin can be obtained, and the present invention was completed.

  That is, the gist of the present invention is that a polyvinyl alcohol resin (a) and a hydrophilic resin (b) are melt-kneaded to produce a spherical hydrophilic resin (B). The present invention relates to a method for producing a spherical hydrophilic resin, wherein the contact angle is 20 to 80 °.

  According to the production method of the present invention, a spherical hydrophilic resin having an appropriate particle size and excellent particle shape uniformity can be obtained, and the obtained spherical hydrophilic resin is particularly suitable for cosmetic members and the like. Useful.

Hereinafter, the present invention will be specifically described.
The polyvinyl alcohol-based resin used in the present invention (hereinafter, polyvinyl alcohol-based resin is abbreviated as PVA-based resin) (a) has a water contact angle of 20 to 80 ° when formed into a film, The angle is preferably 25 to 80 °, more preferably 30 to 75 °, and particularly preferably 30 to 70 °. If the contact angle of water is too small, there will be a problem of lowering productivity and cost when producing such a resin, and if too large, the particle size will not be appropriate or the uniformity of the particle shape will be impaired. Or
In the present invention, the contact angle is measured by the following method.
A 5% by weight aqueous solution of the PVA resin (a) is poured into a 10 cm × 10 cm mold and dried in an environment of 23 ° C. and 50% RH for 2 days to produce a film having a thickness of 60 μm. And the contact angle of the obtained film is measured in the following procedures using the Kyowa Interface Science Co., Ltd. solid-liquid interface analyzer in the environment of 23 degreeC and 50% RH.
(1) Place the prepared film horizontally on the sample stage of the apparatus. (2) Drop 0.2 ml of purified water on the film surface to form water droplets. (3) Measure the angle between the water droplet and the film surface.
The said measurement is performed 10 times and let the average value be a contact angle of a PVA type | system | group (a) film.

  As the PVA-based resin (a), any unmodified PVA or modified PVA-based resin can be used as long as the above contact angle is satisfied.

  The degree of saponification (measured in accordance with JIS K 6726) of the PVA-based resin (a) is preferably 50 to 100 mol%, more preferably 80 to 100 mol%, particularly 90 to 100 mol%, especially Is preferably 98 to 100 mol%. If the degree of saponification is too low, it tends to be difficult to dissolve in water.

  Further, the weight average polymerization degree (measured in accordance with JIS K 6726) of the PVA resin (a) is preferably 150 to 3000, more preferably 200 to 1000, and particularly preferably 250 to 600. If the weight average degree of polymerization is too low, the production efficiency in the production process tends to be low, and if it is too high, the viscosity at the time of melting becomes high, the load is excessively applied to the apparatus, and the melt moldability tends to be low.

  Further, the PVA-based resin (a) preferably has a melt flow rate (hereinafter, abbreviated as MFR) at a temperature of 210 ° C. and a load of 2160 g of 1 to 150 g / 10 minutes, and more preferably 20 It is preferable that it is -130g / 10min. If the MFR is too low, the load on the melt molding apparatus increases, and the moldability and productivity tend to decrease. Conversely, if the MFR is too high, the strand moldability tends to decrease.

Moreover, when using modified PVA-type resin as PVA-type resin (a), there exist copolymerization modification PVA and post-modification PVA, for example. The amount of modification varies depending on the nature of the modifying group, but is usually 1 to 30 mol%, preferably 1 to 20 mol%, more preferably 1 to 10 mol%.
The copolymer-modified PVA can be produced by copolymerizing vinyl acetate and another unsaturated monomer copolymerizable with vinyl acetate, and then saponifying.

  Examples of the other unsaturated monomer include olefins such as ethylene, propylene, isobutylene, α-octene, α-dodecene, α-octadecene, 3-buten-1-ol, and 4-penten-1-ol. Derivatives such as hydroxy group-containing α-olefins such as 5-hexen-1-ol and acylated products thereof, and unsaturated such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, maleic anhydride, itaconic acid, undecylenic acid, etc. Acids, salts thereof, monoesters or dialkyl esters, nitriles such as acrylonitrile and methacrylonitrile, amides such as diacetone acrylamide, acrylamide and methacrylamide, olefin sulfones such as ethylene sulfonic acid, allyl sulfonic acid and methallyl sulfonic acid Acids or their salts, al Ruvinyl ethers, dimethylallyl vinyl ketone, N-vinyl pyrrolidone, vinyl chloride, vinyl ethylene carbonate, 2,2-dialkyl-4-vinyl-1,3-dioxolane, glycerol monoallyl ether, 3,4-diacetoxy-1- Examples thereof include vinyl compounds such as butene, substituted vinyl acetates such as isopropenyl acetate and 1-methoxyvinyl acetate, vinylidene chloride, 1,4-diacetoxy-2-butene and vinylene carbonate.

  Moreover, PVA-type resin which has a primary hydroxyl group in a side chain can also be used as copolymerization modification PVA. The number of primary hydroxyl groups is usually 1 to 5, preferably 1 to 2, and particularly preferably 1. It is also preferable to have a secondary hydroxyl group in addition to the primary hydroxyl group. Examples thereof include a PVA resin (a1) having a 1,2 diol structure in the side chain and a PVA resin having a hydroxyalkyl group in the side chain.

  Next, the post-modified PVA can be produced by post-modifying unmodified PVA. Examples of the post-modification method include a method of converting unmodified PVA into acetoacetate ester, acetalization, urethanization, etherification, and phosphate esterification.

In the present invention, among the above modified PVA resins, a PVA resin containing a hydrophilic modifying group is preferable, particularly in terms of melt moldability and affinity with the hydrophilic resin (b). PVA resin having a primary hydroxyl group in the chain, particularly PVA resin (a1) having a 1,2-diol structure in the side chain, and sulfonic acid-modified PVA resin (a2) are particularly preferable.
Hereinafter, the PVA resin (a1) having a 1,2-diol structure in the side chain and the sulfonic acid-modified PVA resin (a2) will be described in detail.

[PVA resin having a 1,2-diol structure in the side chain (a1)]
The content of the structural unit having a 1,2-diol structure in the side chain in the PVA resin (a1) having a 1,2-diol structure in the side chain is 1 to 20 mol%, particularly 1.5 to 10 mol%. Furthermore, it is preferably 3 to 8 mol%. If the content is too low, the melting point becomes high, so that the molding temperature must be increased, insoluble matter tends to be generated due to thermal degradation, and water solubility tends to be lowered. On the other hand, if it is too high, the improvement of melt moldability and water solubility will reach its peak, and the productivity tends to decrease.

  The degree of saponification (measured according to JIS K 6726) when using a PVA resin (a1) having a 1,2-diol structure in the side chain is preferably 50 to 100 mol%, more preferably 60 to 100 mol. % Is preferable, and 70 to 100 mol% is particularly preferable. If the degree of saponification is too low, the thermal stability at the time of melt molding tends to decrease, or the odor of acetic acid tends to increase.

  The average degree of polymerization (measured according to JIS K 6726) of the PVA resin (a1) having a 1,2-diol structure in the side chain is usually 150 to 3000, preferably 200 to 1000, particularly preferably 250. ~ 600. If the degree of polymerization is too low, the production efficiency in the production process tends to be low, and if it is too high, the viscosity at the time of melting becomes high, the load is excessively applied to the apparatus, and the melt moldability tends to be low.

  Furthermore, the MFR of the PVA resin (a1) having a 1,2-diol structure in the side chain at 210 ° C. and a load of 2160 g is preferably 1 to 150 g / 10 minutes, and more preferably 20 to 100 g / 10 minutes. More preferably, it is 30-50 g / 10min. If the MFR is too small, the load on the melt molding apparatus increases, and the moldability and productivity tend to decrease. Conversely, if the MFR is too large, the strand moldability tends to decrease.

The PVA resin (a1) having a 1,2-diol structure in the side chain has a structural unit represented by the following general formula (1), and R ¹ , R ² and R ³ in the general formula (1) are: Each independently represents a hydrogen atom or an organic group, X represents a single bond or a bonded chain, and R ⁴ , R ⁵ and R ⁶ each independently represent a hydrogen atom or an organic group.

In particular, it is preferable that R ^{1 to} R ³ and R ^{4 to} R ⁶ in the structural unit represented by the general formula (1) are all hydrogen atoms and X is a single bond, which is represented by the following formula (2). A PVA resin (a1) having a structural unit and having a 1,2-diol structure in the side chain is suitably used.

In addition, R ^{1 to} R ³ and R ^{4 to} R ⁶ in the structural unit represented by the general formula (1) may be organic groups as long as the resin properties are not significantly impaired. Examples of the organic group include alkyl groups having 1 to 4 carbon atoms such as a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, and a tert-butyl group. The group may have a functional group such as a halogen group, a hydroxyl group, an ester group, a carboxylic acid group, or a sulfonic acid group, if necessary.

Further, X in the structural unit represented by the general formula (1) is preferably a single bond from the viewpoint of thermal stability or stability under high temperature or acidic conditions. A binding chain may be used as long as it does not inhibit the above. Examples of such a linking chain include hydrocarbons such as alkylene, alkenylene, alkynylene, phenylene and naphthylene (these hydrocarbons may be substituted with halogen such as fluorine, chlorine and bromine), and -O. _{-, - (CH 2 O)} m -, - (OCH 2) m -, - (CH 2 O) mCH 2 -, - CO -, - COCO -, - CO (CH 2) mCO -, - CO (C ₆ H ₄ ) CO—, —S—, —CS—, —SO—, —SO ₂ —, —NR—, —CONR—, —NRCO—, —CSNR—, —NRCS—, —NRNR—, —HPO 4 _{-, - Si (OR) 2} -, - OSi (OR) 2 -, - OSi (OR) 2 O -, - Ti (OR) 2 -, - OTi (OR) 2 -, - OTi (OR) 2 O -, -Al (OR)-, -OAl (OR)-, -OAl (OR) O-, etc. Is an optional substituent each independently, preferably a hydrogen atom or an alkyl group having 1 to 12 carbon atoms, and m can be mentioned a natural number.). Among these, alkylene having 6 or less carbon atoms, particularly methylene, or —CH ₂ OCH ₂ — is preferable from the viewpoint of stability during production or use.

  Examples of the method for producing a PVA resin (a1) having a 1,2-diol structure in the side chain used in the present invention include (i) a vinyl ester monomer and a compound represented by the following general formula (3). A method of saponifying a copolymer, (ii) a method of saponifying and decarboxylating a copolymer of a vinyl ester monomer and a compound represented by the following general formula (4), and (iii) a vinyl ester monomer And a method of saponifying and deketalizing a copolymer of a compound represented by the following general formula (5) is preferably used.

In the general formulas (3), (4) and (5), R ¹ , R ² , R ³ , X, R ⁴ , R ⁵ and R ⁶ are all the same as in the case of the general formula (1). . R ⁷ and R ⁸ are each independently a hydrogen atom or R ⁹ —CO— (wherein R ⁹ is an alkyl group having 1 to 4 carbon atoms).
R ¹⁰ and R ¹¹ are each independently a hydrogen atom or an alkyl group having 1 to 4 carbon atoms.

For the methods (i), (ii) and (iii), for example, the method described in JP-A-2006-95825 can be used.
Of these, it is preferable to use 3,4-diasiloxy-1-butene as the compound represented by the general formula (3) in the method (i) from the viewpoint of excellent copolymerization reactivity and industrial handleability. In particular, 3,4-diacetoxy-1-butene is preferably used.
In addition, the reactive ratio (r) of each monomer when vinyl acetate is used as a vinyl ester monomer and 3,4-diacetoxy-1-butene is copolymerized is r (vinyl acetate) = 0.710. , R (3,4-diacetoxy-1-butene) = 0.701, which is an example of a compound represented by the general formula (4) used in the method (ii) in the case of vinyl ethylene carbonate. Compared with r (vinyl acetate) = 0.85 and r (vinyl ethylene carbonate) = 5.4, 3,4-diacetoxy-1-butene is excellent in copolymerization reactivity with vinyl acetate. It is shown.

  The chain transfer constant (Cx) of 3,4-diacetoxy-1-butene is Cx (3,4-diacetoxy-1-butene) = 0.003 (65 ° C.), which is the Cx of vinyl ethylene carbonate. (Vinylethylene carbonate) = 0.005 (65 ° C.) and 2,2-dimethyl-4-vinyl-1,3 which is an example of a compound represented by the general formula (5) used in the method (iii) -Compared to Cx (2,2-dimethyl-4-vinyl-1,3-dioxolane) = 0.023 (65 ° C) of dioxolane, the degree of polymerization tends to increase, and it is difficult to cause a decrease in polymerization rate. It is shown.

  In addition, such 3,4-diacetoxy-1-butene is a by-product generated when saponifying the copolymer, and a by-product generated during the saponification from a structural unit derived from vinyl acetate frequently used as a vinyl ester monomer. It is an industrially significant advantage that it is the same as the resulting compound, and it is not necessary to provide any special equipment or process for the subsequent treatment or solvent recovery system, and conventional equipment can be used.

The 3,4-diacetoxy-1-butene described above is an epoxy butene derivative described in, for example, International Publication No. 2000/24702, U.S. Pat. No. 5,562,086, U.S. Pat. No. 6,072,079. It can be produced by a synthesis method passing through or a reaction of isomerizing 1,4-diacetoxy-1-butene, which is an intermediate product in the production process of 1,4-butanediol, using a metal catalyst such as palladium chloride.
At the reagent level, Across products can be obtained from the market.

If the PVA resin obtained by the method (ii) or (iii) is insufficiently decarboxylated or deacetalized, a carbonate ring or an acetal ring remains in the side chain, The PVA resin may be cross-linked by such a cyclic group to generate a gel-like product.
Therefore, also from this point, the PVA resin obtained by the method (i) is preferably used in the present invention.

In addition, although the content rate of the structural unit represented by General formula (1) in PVA-type resin (a1) which has a 1, 2- diol structure in a side chain completely saponified PVA-type resin (a1), It can be determined from ¹ H-NMR spectrum (solvent: DMSO-d6, internal standard: tetramethylsilane). Specifically, it is calculated from a peak area derived from a hydroxyl group proton, a methine proton and a methylene proton, a methylene proton of a main chain, a proton of a hydroxyl group linked to the main chain, etc. in the structural unit represented by the general formula (2). Can do.

Next, the sulfonic acid-modified PVA resin (a2) will be described.
[Sulfonic acid-modified PVA resin (a2)]
The sulfonic acid group content of the sulfonic acid-modified PVA resin (a2) is 0.1 to 20 mol%, particularly 1 to 10 mol%, and more preferably 1.5 to 5 mol%. If the content is too low, the melting point becomes high, so that the molding temperature must be increased, insoluble matter tends to be generated due to thermal degradation, and water solubility tends to be lowered. On the other hand, if it is too high, the improvement of melt moldability and water solubility will reach its peak, and the productivity tends to decrease.

  The saponification degree (measured in accordance with JIS K 6726) when the sulfonic acid-modified PVA resin (a2) is used is preferably 50 to 100 mol%, more preferably 60 to 100 mol%, and particularly preferably 70. ˜100 mol%. If the degree of saponification is too low, the thermal stability at the time of melt molding tends to decrease, or the odor of acetic acid tends to increase.

  Moreover, the average degree of polymerization (measured according to JIS K 6726) of the sulfonic acid-modified PVA resin (a2) is usually 150 to 3000, preferably 200 to 1000, and particularly preferably 230 to 600. If the degree of polymerization is too low, the production efficiency in the production process tends to be low, and if it is too high, the viscosity at the time of melting becomes high, the load is excessively applied to the apparatus, and the melt moldability tends to be low.

  Further, the MFR of the sulfonic acid-modified PVA resin (a2) at 210 ° C. and a load of 2160 g is usually 1 to 150 g / 10 minutes, preferably 50140 g / 10 minutes, particularly preferably 100 to 130 g / 10. Minutes. If the MFR is too small, the load on the melt molding apparatus increases, and the moldability and productivity tend to decrease. Conversely, if the MFR is too large, the strand moldability tends to decrease.

The sulfonic acid-modified PVA resin (a2) can be generally obtained by copolymerizing a vinyl ester monomer and a sulfonic acid group-containing monomer and saponifying the obtained polymer.
Such vinyl ester monomers include vinyl formate, vinyl acetate, vinyl propionate, vinyl valelate, vinyl butyrate, vinyl isobutyrate, vinyl pivalate, vinyl caprate, vinyl laurate, vinyl stearate, vinyl benzoate. And vinyl versatate. Of these, vinyl acetate is preferably used from the economical viewpoint.

  Examples of the sulfonic acid group-containing monomer include (a) an olefin sulfonic acid represented by the following general formula (6), and (b) a sulfoalkyl maleate represented by the following general formulas (7) and (8). (C) sulfoalkyl (meth) acrylamide represented by the following general formula (9), (10), (11), (d) sulfoalkyl (meth) acrylate represented by the following general formula (12), etc. Can be mentioned.

上記一般式（６）において、Ｒは炭素数１〜４のアルキレン基を示し、Ｍは水素原子又はアルカリ金属又はアンモニウム基を示す。

上記一般式（７）、（８）において、Ｒ¹²は炭素数１〜３のアルキル基、ｎは２〜４の整数、Ｍは水素原子又はアルカリ金属又はアンモニウム基を示す。

In the general formula (6), R represents an alkylene group having 1 to 4 carbon atoms, and M represents a hydrogen atom, an alkali metal, or an ammonium group.

In the general formulas (7) and (8), R ¹² represents an alkyl group having 1 to 3 carbon atoms, n represents an integer of 2 to 4, and M represents a hydrogen atom, an alkali metal, or an ammonium group.

上記一般式（９）、（１０）、（１１）において、Ｒ¹³、Ｒ¹⁴、Ｒ¹⁵、Ｒ¹⁷、Ｒ¹⁸、Ｒ¹⁹、Ｒ²⁰は水素又は炭素数１〜３のアルキル基を示し、Ｒ¹⁶は炭素数１〜３のアルキル基、ｎは２〜４の整数、Ｍは水素原子又はアルカリ金属又はアンモニウム基を示す。

上記一般式（１２）、Ｒ²¹は水素又は炭素数１〜３のアルキル基を示し、ｎは２〜４の整数、Ｍは水素原子又はアルカリ金属又はアンモニウム基を示す。

In the general formulas (9), (10), and (11), R ¹³ , R ¹⁴ , R ¹⁵ , R ¹⁷ , R ¹⁸ , R ¹⁹ , and R ²⁰ represent hydrogen or an alkyl group having 1 to 3 carbon atoms, R ¹⁶ represents an alkyl group having 1 to 3 carbon atoms, n represents an integer of 2 to 4, and M represents a hydrogen atom, an alkali metal, or an ammonium group.

In the general formula (12), R ²¹ represents hydrogen or an alkyl group having 1 to 3 carbon atoms, n represents an integer of 2 to 4, and M represents a hydrogen atom, an alkali metal, or an ammonium group.

Specific examples of the olefin sulfonic acid include olefin sulfonic acids such as vinyl sulfonic acid, allyl sulfonic acid, and methallyl sulfonic acid, or salts thereof.
Specific examples of the sulfoalkyl malate include sodium sulfopropyl 2-ethylhexyl malate, sodium sulfopropyl 2-ethylhexyl malate, sodium sulfopropyl tridecyl malate, sodium sulfopropyl eicosyl malate, and the like. It is done.
Specific examples of the sulfoalkyl (meth) acrylamide include sodium sulfomethyl acrylamide, sodium sulfo t-butyl acrylamide, sodium sulfo S-butyl acrylamide, sodium sulfo t-butyl methacrylamide and the like.
Furthermore, specific examples of the sulfoalkyl (meth) acrylate include sodium sulfoethyl acrylate.
When introducing by copolymerization, olefin sulfonic acid or a salt thereof is preferably used among the sulfonic acid group-containing unsaturated monomers.

The method for copolymerizing the vinyl ester monomer and the sulfonic acid group-containing monomer is not particularly limited, and is a known method such as bulk polymerization, solution polymerization, suspension polymerization, dispersion polymerization, or emulsion polymerization. In general, solution polymerization is performed.
The method for charging the monomer component at the time of copolymerization is not particularly limited, and any method such as batch charging, split charging, continuous charging, etc. may be employed.
Examples of the solvent used in such copolymerization include usually lower alcohols such as methanol, ethanol, isopropyl alcohol, n-propanol and butanol, and ketones such as acetone and methyl ethyl ketone, and industrially preferred is methanol. used.
The amount of the solvent used may be appropriately selected in consideration of the chain transfer constant of the solvent in accordance with the degree of polymerization of the target copolymer. For example, when the solvent is methanol, S (solvent) / M ( Monomer) = 0.01 to 10 (mass ratio), preferably 0.05 to 3 (mass ratio).

For the copolymerization, a polymerization catalyst is used. Examples of the polymerization catalyst include known radical polymerization catalysts such as azobisisobutyronitrile, acetyl peroxide, benzoyl peroxide, lauryl peroxide, azobisdimethylvaleronitrile, azo And low temperature active radical polymerization catalysts such as bismethoxydimethylvaleronitrile. The amount of the polymerization catalyst used varies depending on the type of catalyst and cannot be determined unconditionally, but is arbitrarily selected according to the polymerization rate. For example, when azoisobutyronitrile or acetyl peroxide is used, 0.01 to 1.0 mol% is preferable with respect to the vinyl ester monomer, and 0.02 to 0.5 mol% is particularly preferable.
Moreover, the reaction temperature of a copolymerization reaction is performed at about 30 degreeC-a boiling point by the solvent and pressure to be used, More specifically, it is 35-150 degreeC, Preferably it is carried out in 40-75 degreeC.

The resulting copolymer is then saponified. Such saponification is carried out by dissolving the copolymer obtained above in an alcohol or hydrous alcohol and using an alkali catalyst or an acid catalyst.
Examples of the alcohol include methanol, ethanol, propanol, tert-butanol and the like, and methanol is particularly preferably used. The concentration of the copolymer in the alcohol is appropriately selected depending on the viscosity of the system, but is usually selected from the range of 10 to 60% by weight. Examples of the catalyst used for saponification include alkali catalysts such as alkali metal hydroxides and alcoholates such as sodium hydroxide, potassium hydroxide, sodium methylate, sodium ethylate, potassium methylate and lithium methylate; Acid catalysts such as sulfuric acid, hydrochloric acid, nitric acid, metasulfonic acid, zeolite, and cation exchange resin are listed.

The amount of the saponification catalyst used is appropriately selected depending on the saponification method, the target degree of saponification, and the like. Usually, when an alkali catalyst is used, the vinyl ester monomer and the general formula (6) to A ratio of 0.1 to 30 mmol, preferably 2 to 15 mmol, is appropriate for 1 mol of the total amount of the compound represented by (12).
The reaction temperature for the saponification reaction is not particularly limited, but is preferably 10 to 60 ° C (particularly 20 to 50 ° C).

Next, the hydrophilic resin (b) used in the present invention will be described.
[Hydrophilic resin (b)]
The hydrophilic resin (b) may be any resin having hydrophilicity, and examples thereof include polyester resins, polyamide resins, acrylic resins, vinyl alcohol resins, and the like, and the degree of hydrophilicity is controlled among them. A vinyl alcohol resin is preferable in terms of the point, and an ethylene-vinyl acetate copolymer saponified product is particularly preferable in terms of excellent melt moldability.

  Examples of the polyester-based resin include polyethylene terephthalate, polybutylene adipate, polybutylene terephthalate, poly (ethylene-2,6-naphthalate), polyethylene adipate, polyethylene isophthalate, polyethylene terephthalate / polyethylene adipate copolymer, polybutylene terephthalate / Polybutylene adipate copolymer, polybutylene terephthalate / polytetramethylene glycol copolymer, polyethylene terephthalate / polytetramethylene glycol copolymer, polybutylene terephthalate / polycaprolactone copolymer, polyethylene terephthalate / polycaprolactone copolymer, etc. Used.

  Examples of polyamide-based resins include homopolyamides and copolyamides. Examples of homopolyamides include polycapramide (nylon 6), poly-ω-aminoheptanoic acid (nylon 7), poly-ω-aminononanoic acid (nylon 9), and polyounde. Canamide (nylon 11), polylaurin lactam (nylon 12), polyethylenediamine adipamide (nylon 2, 6), polytetramethylene adipamide (nylon 4, 6), polyhexamethylene adipamide (nylon 6, 6), polyhexamethylene sepacamide (nylon 6,10), polyhexamethylene dodecamide (nylon 6,12), polyoctamethylene adipamide (nylon 8,6), polydecamethylene adipamide (nylon 10) , 6), polydodecamethylene sepacamide (nylon 10, 8), etc. Examples of copolyamides include caprolactam / laurin lactam copolymer, caprolactam / hexamethylene diammonium adipate copolymer, caprolactam / laurin lactam copolymer, laurin lactam / hexamethylene diammonium adipate copolymer, hexamethylene di Ammonium adipate / hexamethylene diammonium separate copolymer, ethylene diammonium adipate / hexamethylene diammonium adipate copolymer, caprolactam / hexamethylene diammonium adipate / hexamethylene diammonium separate copolymer, terephthalic acid / isophthalic acid / Hexamethylenediamine copolymer (amorphous nylon), m-xylylene adipamide, etc., preferably terephthalic acid / isoform Luric acid / hexamethylenediamine copolymer (amorphous nylon), m-xylylene adipamide, polyhexamethylene dodecamide (nylon 6,12), caprolactam / hexamethylene diammonium adipate copolymer, caprolactam / laurin A lactam copolymer is used.

Examples of acrylic resins include 2-hydroxyethyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 5-hydroxypentyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate, 8-hydroxyoctyl (meth) acrylate, and the like. Hydroxyalkyl esters of acrylic acid, caprolactone-modified monomers such as caprolactone-modified 2-hydroxyethyl (meth) acrylate, oxyalkylene-modified monomers such as diethylene glycol (meth) acrylate and polyethylene glycol (meth) acrylate, 2-acryloyloxyethyl-2 -Hydroxyethylphthalic acid, 2-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, 3-chloro 2-hydroxypropyl (me ) Acrylate, 2,2-dimethyl 2-hydroxyethyl (meth) acrylate, 2-ethoxyethyl acrylate, 2-methoxyethyl acrylate, 3-methoxybutyl acrylate, ethyl carbitol acrylate, 2-butoxyethyl acrylate, glycidyl methacrylate, allyl Glycidyl group-containing monomers such as glycidyl methacrylate, acrylamide, methacrylamide,
A homopolymer such as (meth) acrylic acid, crotonic acid, maleic acid, maleic anhydride, fumaric acid, citraconic acid, glutaconic acid, itaconic acid, or a copolymer obtained by combining these is used.

  In the present invention, the MFR of the hydrophilic resin (b) at 210 ° C. and a load of 2160 g is usually 0.5 to 100 g / 10 min. If the MFR is too small, the melt viscosity becomes too high and melt extrusion becomes difficult, and the load on the melt molding apparatus increases, so that the moldability and productivity tend to decrease. There is a tendency for the formability of the to decrease.

Next, the saponified ethylene-vinyl acetate copolymer (b1), which is a preferred embodiment of the hydrophilic resin (b), will be described.
[Saponified ethylene-vinyl acetate copolymer (b1)]
The saponified ethylene-vinyl acetate copolymer (b1) is a resin obtained by saponifying a copolymer of ethylene and a vinyl ester monomer (ethylene-vinyl ester copolymer), It is a water-insoluble thermoplastic resin. The polymerization method can also be carried out using any known polymerization method such as solution polymerization, suspension polymerization, and emulsion polymerization. Generally, solution polymerization using a lower alcohol such as methanol as a solvent is used. Saponification of the obtained ethylene-vinyl ester copolymer can also be performed by a known method. The saponified ethylene-vinyl acetate copolymer (b1) produced in this manner mainly comprises ethylene-derived structural units and vinyl alcohol structural units, and in some cases, a slight amount of vinyl ester remaining without being saponified. Includes structural units.

  As the vinyl ester monomer, vinyl acetate is typically used because it is easily available from the market and has good impurity treatment efficiency during production. Examples of other vinyl ester monomers include vinyl formate, vinyl propionate, vinyl valelate, vinyl butyrate, vinyl isobutyrate, vinyl pivalate, vinyl caprate, vinyl laurate, vinyl stearate, vinyl versatate, etc. Examples include aliphatic vinyl esters, aromatic vinyl esters such as vinyl benzoate, and the like. Usually, aliphatic vinyl esters having 3 to 20 carbon atoms, preferably 4 to 10 carbon atoms, and particularly preferably 4 to 7 carbon atoms are used. Can do. These are usually used alone, but a plurality of them may be used simultaneously as necessary.

  The saponification degree of the vinyl ester component in the saponified ethylene-vinyl acetate copolymer (b1) is JIS K6726 (however, the saponified ethylene-vinyl acetate copolymer (B1) is uniformly dissolved in water / methanol solvent) The measured value is usually from 90 to 100 mol%, preferably from 95 to 100 mol%, particularly preferably from 99 to 100 mol%. When the degree of saponification is too low, gas barrier properties, thermal stability, moisture resistance and the like tend to decrease.

  The saponified ethylene-vinyl acetate copolymer (b1) used in the present invention is derived from the following comonomer in addition to ethylene structural units and vinyl alcohol structural units (including unsaponified vinyl ester structural units). A structural unit may be further included. Examples of the comonomer include α-olefins such as propylene, isobutene, α-octene, α-dodecene, α-octadecene; 3-buten-1-ol, 4-penten-1-ol, 3-butene-1, Hydroxyl group-containing α-olefins such as 2-diols and hydroxy group-containing α-olefin derivatives such as esterified products and acylated products thereof; unsaturated carboxylic acids or salts thereof, partial alkyl esters, fully alkyl esters, nitriles, amides or anhydrous Unsaturated sulfonic acid or its salt; Vinyl silane compound; Vinyl chloride; Styrene.

  Further, “post-modified” saponified ethylene-vinyl acetate copolymers such as urethanization, acetalization, cyanoethylation, and oxyalkyleneation can also be used.

  Further, the MFR of the saponified ethylene-vinyl acetate copolymer (b1) at 210 ° C. and a load of 2160 g is usually 0.5 to 100 g / 10 minutes, and particularly preferably 1 to 20 g / 10 minutes. Furthermore, it is preferable that it is 3-15 g / 10min. If the MFR is too small, the melt viscosity becomes too high and melt extrusion becomes difficult, and the load on the melt molding apparatus increases, so that the moldability and productivity tend to decrease. There is a tendency for the formability of the to decrease.

[Method for producing spherical hydrophilic resin (B)]
The method for producing the spherical hydrophilic resin (B) according to the present invention is obtained by melt-kneading the PVA resin (a) and the hydrophilic resin (b), and removing the PVA resin (a) by washing with water. This is a method for producing (B).

  In the present invention, the mixing weight ratio of the PVA resin (a) and the hydrophilic resin (b) is 1 to 100 parts by weight of the hydrophilic resin (b) with respect to 100 parts by weight of the PVA resin (a). The amount is preferably 3 to 70 parts by weight, more preferably 5 to 60 parts by weight. If the content of the hydrophilic resin (b) is too small, the productivity of the spherical hydrophilic resin is lowered and becomes impractical. Conversely, if the content of the hydrophilic resin (b) is too large, the hydrophilic resin ( b) tends to be a matrix.

  Moreover, it is preferable that the difference of MFR (210 degreeC, load 2160g) of PVA-type resin (a) and hydrophilic resin (b) is 20-150, and it is 20-120 especially. Further, when the PVA resin (a) is a PVA resin (a1) having a 1,2-diol structure in the side chain, it is particularly preferably 25 to 100, more preferably 27 to 50, and the sulfonic acid-modified PVA resin ( In the case of a2), 40 to 120, more preferably 80 to 118 are particularly preferable. If the MFR difference is too small, the particle size of the spherical hydrophilic resin tends to be too fine, and if it is too large, the particle size of the spherical hydrophilic resin tends to be too large, or the melt extrusion moldability tends to decrease.

  In the present invention, when the hydrophilic resin (b) is a saponified ethylene-vinyl acetate copolymer (b1) in particular, the PVA resin (a ) And the saponification degree of the ethylene-vinyl acetate copolymer saponified product (B1) is preferably 25 mol% or less, particularly preferably 20 mol% or less, and more preferably 15 mol% or less. .

  In this invention, you may mix | blend various additives other than said PVA-type resin (a) and hydrophilic resin (b). Examples of such additives include plasticizers, heat stabilizers, light stabilizers, ultraviolet absorbers, antioxidants, pigments, colorants, various inorganic fine particles, various fillers, antistatic agents, mold release agents, lubricants, Examples include fragrances, crystal nucleating agents, flame retardants, foaming agents, softening agents, preservatives, antibacterial agents, antiblocking agents, and surfactants.

Next, the steps of the production method of the present invention will be described.
A mixture of the PVA resin (a) and the hydrophilic resin (b) obtained by dry blending, melt kneading, or the like is set at a cylinder temperature of 180 to 220 ° C. and a head temperature of about 180 to 220 ° C. using a twin screw extruder. It is melt-molded under conditions to obtain a molded product. In addition, the cylinder temperature here represents the highest temperature among the temperatures of each column of the cylinder. The shape of the molded product is not particularly limited, and may be any shape such as a strand shape, a pellet shape, or a film shape. A pellet shape is preferable in consideration of the efficiency of the subsequent removal treatment of the PVA resin (a).

Next, the obtained molded product is brought into contact with water in a (warm) water bath of about 10 to 90 ° C. (preferably 20 to 80 ° C.) to elute the PVA resin (a) component in the molded product.
The contact time between the molded product and the (warm) water in the (warm) water bath is generally determined by the mixed composition of PVA resin (a) and hydrophilic resin (b), film thickness, pellet shape, and the like. Although it cannot be stated, it is usually preferably 1 to 300 minutes, more preferably 5 to 200 minutes.

  Thus, although a spherical hydrophilic resin is obtained, according to the present invention, the average particle size is 0.5 to 5 μm, preferably 0.8 to 4.5 μm, more preferably 1.0 to 4.0 μm. It is possible to obtain a spherical hydrophilic resin with a spherical hydrophilic resin having a particle size and excellent shape uniformity and surface smoothness. For example, hydrophilic resin fillers, cosmetic members, toners, ceramic pores It can be widely used for forming materials, light diffusing agents, matting agents and the like.

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the following examples unless it exceeds the gist.
In the examples, “parts” and “%” mean weight basis.
In the examples, MFR is a value measured using a melt indexer F-F01 manufactured by Toyo Seiki Seisakusho under the conditions of a temperature of 210 ° C. and a load of 2160 g.

Example 1
[Preparation of PVA resin (a1-1) having 1,2-diol structure in side chain]
First, 1000 parts of vinyl acetate, 160 parts of 3,4-diacetoxy-1-butene (8 mol% to charged vinyl acetate), 300 parts of methanol, 0.26 mol% of azobisisobutyronitrile (AIBN) (to charged acetic acid) Vinyl).
Next, a reactor equipped with a reflux condenser, a dropping funnel, and a stirrer was charged with all of methanol and AIBN, and 50% of vinyl acetate and 3,4-diacetoxy-1-butene. The temperature was raised to initiate the polymerization. Further, the remainder (50%) of vinyl acetate and 3,4-diacetoxy-1-butene was added dropwise over 8 hours. When the polymerization rate of vinyl acetate reached 90%, a predetermined amount of m-dinitrobenzene was added. The polymerization was terminated, and subsequently, distillation was performed while blowing methanol vapor to remove unreacted vinyl acetate monomer out of the system to obtain a methanol solution of the copolymer.

  Next, the methanol solution was adjusted to a concentration of 50% and charged into a kneader. While maintaining the solution temperature at 35 ° C., a methanol solution containing 2% sodium in sodium hydroxide was converted into a vinyl acetate structural unit in the copolymer and Saponification was carried out by adding 5.0 mmol per 1 mol of the total amount of 3,4-diacetoxy-1-butene structural units. After confirming the increase in viscosity, a sodium solution containing 2% of sodium hydroxide in a methanol solution was 7 mmol per 1 mol of the total amount of vinyl acetate structural unit and 3,4-diacetoxy-1-butene structural unit in the copolymer. Saponification was carried out at a ratio of When saponification progressed as saponification progressed and became particulate, 0.8 equivalent of sodium hydroxide was added to neutralizing acetic acid, filtered, washed thoroughly with methanol, and heated in a hot air dryer The PVA resin (a1-1) having a 1,2-diol structural unit in the side chain was obtained.

The degree of saponification of the PVA resin (a1-1) having a 1,2-diol structural unit in the obtained side chain is due to hydrolysis of the residual vinyl acetate structural unit and 3,4-diacetoxy-1-butene structural unit. It was 99 mol% when it analyzed by the alkali consumption required, and the weight average molecular weight was 300 when measured according to JISK6726. The content of the side chain 1,2-diol structural unit was 8 mol% when calculated by measurement with ¹ H-NMR (internal standard substance; tetramethylsilane). Moreover, it was 42 g / 10min when MFR was measured according to JISK7210.

[Measurement of contact angle of film made of PVA resin (a)]
A 5% aqueous solution of the PVA resin (a1-1) obtained above was poured into a 10 cm × 10 cm mold and dried in an environment of 23 ° C. and 50% RH for 2 days to produce a film having a thickness of 60 μm. . And the contact angle of the obtained film was measured in the following procedures using the Kyowa Interface Science Co., Ltd. solid-liquid interface analyzer in the environment of 23 degreeC and 50% RH.
(1) Place the prepared film horizontally on the sample stage of the apparatus.
(2) 0.2 ml of purified water is dropped on the film surface to form water droplets.
(3) The angle formed by the water droplet and the film surface is measured.
The said measurement was performed 10 times and the average value was made into the contact angle of a PVA-type film.
The results are shown in Table 1.

[Preparation of Pellet Containing PVA Resin (a) and Saponified Ethylene-Vinyl Acetate Copolymer (b1))
90 parts of PVA resin (a1-1) obtained above, ethylene content 44 mol%, saponification 99 mol%, MFR 12 g / 10 min (difference in MFR between PVA resin (a1-1) 30 ) 10 parts of ethylene-vinyl acetate copolymer saponified product (b1-1) is formed into a strand under the following conditions using a twin screw extruder (Technobel KZW15-60). And pelletized.
Extruder: 15 mmφ L / D = 60 manufactured by Technobel
Extrusion temperature (° C.): C1 / C2 / C3 / C4 / C5 / C6 / C7 / C8 / D = 90/150/210/210/210/210/210/200/200
Rotation speed: 200rpm
Discharge rate: 1.5kg / h

[Production of spherical hydrophilic resin (B)]
The pellets obtained above are immersed and stirred in a water bath at room temperature for about 1 hour to elute the PVA resin (a1-1) to obtain a saponified ethylene-vinyl acetate copolymer (B) spherical resin. It was.

[Evaluation of average particle diameter of spherical hydrophilic resin (B)]
Using a scanning electron microscope (manufactured by JEOL Ltd., JSM-6060LA), the spherical hydrophilic resin (B) is photographed, a sphere is randomly selected, the particle size is measured, and the average particle size of the measured sphere is calculated. did.
The results are shown in Table 1.

[Evaluation of shape uniformity of spherical hydrophilic resin (B)]
The molded state of the spherical hydrophilic resin (B) obtained above was visually observed and evaluated according to the following criteria.
A: Almost no rod-shaped moldings were observed B: Some rod-shaped moldings were observed C: Many rod-shaped moldings were observed

[Evaluation of surface state of spherical hydrophilic resin (B)]
The surface state of the spherical hydrophilic resin (B) obtained above was visually observed and evaluated according to the following criteria.
A: The surface was smooth B: Some rough parts were seen on the surface C: Many rough parts were seen on the surface

Example 2
In Example 1, as the hydrophilic resin (b), ethylene having an ethylene content of 29 mol%, a saponification degree of 99.5 mol%, an MFR of 8 g / 10 min (an MFR difference of 34 from the PVA resin (a1-1)) was A vinyl acetate copolymer saponified product (b1-2) was used in the same manner except that the extrusion temperature was changed as follows to obtain a spherical hydrophilic resin (B), and the same evaluation was performed.
Extrusion temperature (° C.): C1 / C2 / C3 / C4 / C5 / C6 / C7 / C8 / D = 90/150/220/220/220/220/220/210/210 The results are shown in Table 1.

Example 3
In Example 2, the content of the PVA resin (a1-1) and the saponified ethylene-vinyl acetate copolymer (b1-2) was (a1-1) / (b1-2) = 100/43 (weight) Ratio) was carried out in the same manner except that the mixture was melt-mixed to obtain a spherical hydrophilic resin (B), and the same evaluation was performed.
The results are shown in Table 1.

Example 4
In Example 1, ethylene-vinyl acetate having an ethylene content of 44 mol%, a saponification degree of 99 mol%, and an MFR of 3 g / 10 min (MFR difference of 39 from PVA resin (a1-1)) as the hydrophilic resin (b) A spherical hydrophilic resin (B) was obtained in the same manner except that the saponified copolymer (b1-3) was used, and the same evaluation was performed.
The results are shown in Table 1.

Example 5
In Example 2, ethylene-vinyl acetate having an ethylene content of 29 mol%, a saponification degree of 99 mol%, and an MFR of 4 g / 10 min (an MFR difference of 38 from the PVA resin (a1-1)) as the hydrophilic resin (b) A spherical hydrophilic resin (B) was obtained in the same manner except that the saponified copolymer (b1-4) was used, and the same evaluation was performed.
The results are shown in Table 1.

Example 6
In Example 1, sulfonic acid-modified PVA resin (a2-1) as PVA-based resin (a) (saponification degree 99 mol%, average polymerization degree 260, sulfonic acid group content 2 mol%, contact in the case of film) An ethylene content of 44 mol% as a hydrophilic resin (b), a saponification degree of 99 mol%, an MFR difference of 3 g / 10 min with the PVA resin (a1-1) 115) ethylene-acetic acid Spherical hydrophilic resin (B) was obtained in the same manner as in Example 1 except that the saponified vinyl copolymer (b1-3) was used and the extrusion temperature was changed as follows, and the same evaluation was performed. . The results are shown in Table 1.
Extrusion temperature (° C.): C1 / C2 / C3 / C4 / C5 / C6 / C7 / C8 / D = 90/150/220/220/220/220/220/210/210

Comparative Example 1
In Example 1, the PVA resin (a) has an oxyalkylene group content of 1 mol%, a saponification degree of 93 mol%, an average degree of polymerization of 550, MFR of 3 g / 10 min, and a contact angle of 112 ° when formed into a film. Using a certain oxyalkylene group-containing PVA resin, as the hydrophilic resin (b), an ethylene-vinyl acetate copolymer saponified product (b1) having an ethylene content of 29 mol%, a saponification degree of 99 mol%, and an MFR of 4 g / 10 min. -4) (MFR difference with PVA resin (a) (b) -1), that the extrusion temperature was as follows, and the pellet was immersed in a hot water bath at 80 ° C. for about 1 hour. A spherical hydrophilic resin was obtained in the same manner except that (a) the PVA-based resin was eluted by stirring, and the same evaluation was performed. The results are shown in Table 1.
Extrusion temperature (° C.): C1 / C2 / C3 / C4 / C5 / C6 / C7 / C8 / D = 90/150/220/220/220/220/220/210/210

Comparative Example 2
In Comparative Example 1, unmodified PVA having a saponification degree of 88 mol%, an average polymerization degree of 300, MFR of 20 g / 10 min, and a contact angle of 83 ° when formed into a film was used as the PVA-based resin (a). b) An ethylene-vinyl acetate copolymer saponified product having an ethylene content of 44 mol%, a saponification degree of 99 mol%, and an MFR of 3 g / 10 min (MFR difference of 17 from PVA) was used. A spherical hydrophilic resin was obtained in the same manner as described above, and the same evaluation was performed. The results are shown in Table 1.
Extrusion temperature (° C.): C1 / C2 / C3 / C4 / C5 / C6 / C7 / C8 / D = 90/150/210/210/210/210/210/200/200

The spherical hydrophilic resins of Examples 1 to 6 produced by the production method of the present invention are particles having an appropriate particle diameter, and further, there is little mixing of rod-shaped molded products, excellent shape uniformity, and smooth surface. It was excellent in properties.
On the other hand, in Comparative Examples 1 and 2 having a large contact angle when a PVA resin film was used, the particle size was too large or too small, and the shape uniformity and surface smoothness were inferior.

  In the present invention, it is possible to obtain a spherical hydrophilic resin with a spherical particle size resin having a suitable particle size and excellent shape uniformity and surface smoothness, and the obtained spherical hydrophilic resin is filled. It can be widely used for applications such as agents, cosmetic members, toners, ceramic pore forming materials, light diffusing agents, and matting agents.

Claims (9)

In the method of melt-kneading the polyvinyl alcohol resin (a) and the hydrophilic resin (b) to produce the spherical hydrophilic resin (B), the contact angle when the polyvinyl alcohol resin (a) is made into a film is 20 to 20%. A method for producing a spherical hydrophilic resin (B), which is 80 °. The spherical hydrophilic resin (B) according to claim 1, wherein the difference in melt flow rate (210 ° C, load 2160 g) between the polyvinyl alcohol resin (a) and the hydrophilic resin (b) is 20 to 150. Manufacturing method. The method for producing a spherical hydrophilic resin (B) according to claim 1 or 2, wherein 1 to 100 parts by weight of the hydrophilic resin (b) is mixed with 100 parts by weight of the polyvinyl alcohol resin (a). . The method for producing a spherical hydrophilic resin (B) according to any one of claims 1 to 3, wherein the polyvinyl alcohol resin (a) is a polyvinyl alcohol resin containing a hydrophilic modifying group. The method for producing a spherical hydrophilic resin (B) according to any one of claims 1 to 4, wherein the polyvinyl alcohol resin (a) is a polyvinyl alcohol resin having a primary hydroxyl group in a side chain. The spherical hydrophilic resin (B) according to any one of claims 1 to 5, wherein the polyvinyl alcohol resin (a) is a polyvinyl alcohol resin (a1) having a 1,2-diol structure in the side chain. Production method. The method for producing a spherical hydrophilic resin (B) according to any one of claims 1 to 4, wherein the polyvinyl alcohol resin (a) is a sulfonic acid-modified polyvinyl alcohol resin (a2). The method for producing a spherical hydrophilic resin (B) according to any one of claims 1 to 7, wherein the hydrophilic resin (b) is a saponified ethylene-vinyl acetate copolymer (B1). The spherical hydrophilic resin (B) according to claim 8, wherein the difference in saponification degree between the polyvinyl alcohol resin (a) and the saponified ethylene-vinyl acetate copolymer (B1) is 25 mol% or less. ) Manufacturing method.