Method for producing N-vinyl lactam crosslinked polymer

Abstract

A method for producing an N-vinyl lactam crosslinked polymer is provided, which can suppress charging of powder in the production of the N-vinyl lactam crosslinked polymer. [Solution] A method for producing an N-vinyl lactam crosslinked polymer, the method comprising the steps of polymerizing a monomer component containing an N-vinyl lactam monomer and a crosslinkable monomer, adding a surfactant to the product obtained in the polymerization step, drying the product obtained after the surfactant addition step, and pulverizing and / or classifying the product obtained in the drying step, wherein the monomer component contains 50 mol % or more of an N-vinyl lactam monomer and 0.05 mol % or more of a crosslinkable monomer relative to 100 mol % of a non-crosslinkable monomer, and the surfactant is an ionic surfactant and / or a polyoxyalkylene glycol-type nonionic surfactant.

Description

[Technical Field]

[0001] The present invention relates to a method for producing an N-vinyl lactam crosslinked polymer, and more particularly to a method for producing an N-vinyl lactam crosslinked polymer useful for skin cosmetics, external skin preparations and hair cosmetics, writing instruments, ink absorbents for inkjet recording devices and the like, deodorants, fragrances, latent heat storage materials, etc. [Background technology]

[0002] Polymers having a lactam structure are used in a variety of applications because they are hydrophilic and highly safe for the human body and the environment. In particular, crosslinked polymers having a lactam structure are useful in applications for absorbing and retaining liquids such as water. Regarding such liquid-absorbent resins, for example, Patent Document 1 discloses an N-vinyllactam crosslinked polymer having structural units derived from N-vinyllactam and structural units derived from a crosslinking agent, characterized in that the N-vinyllactam crosslinked polymer has an ethanol absorption capacity of 3 to 40 g per gram of N-vinyllactam crosslinked polymer, the proportion (number) of particles having an aspect ratio of 1.15 to 10 as determined by a predetermined method is 10 to 100% relative to the total number of particles of the N-vinyllactam crosslinked polymer, and the water-soluble content is 35% by mass or less relative to 100% by mass of the total polymer. Furthermore, Patent Document 2 discloses a surfactant carrier having surfactant absorption capacity of 10 times or more.

[0003] However, water-absorbent resins such as polyacrylic acid are prone to become electrically charged, which poses a problem that the powder tends to adhere to the production line during pulverization and classification. To address this problem, a method using a surfactant is known as a method for preventing the powder from becoming electrically charged. Patent Document 3 also discloses a technology using a powder of an inorganic compound containing zinc or calcium as a constituent element. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2018 / 008759 [Patent Document 2] Japanese Patent Application Laid-Open No. 2017-113709 [Patent Document 3] Japanese Patent Application Publication No. 02-178332 Summary of the Invention [Problem to be solved by the invention]

[0005] As described above, various N-vinyl lactam crosslinked polymers have been disclosed in the past. Also, methods for preventing adhesion to production equipment due to electrostatic charge generated in the production of a water-absorbent resin have been disclosed in the past. However, the present inventors have found that the problem of adhesion due to electrostatic charge is greater in the production of nonionic N-vinyl lactam crosslinked polymers than in the production of ionic water-absorbent resins such as polyacrylic acid, and have found it necessary to improve this problem.

[0006] The present invention has been made in view of the above-mentioned current situation, and aims to provide a method for producing an N-vinyl lactam crosslinked polymer that can suppress the charging of powder in the production of the N-vinyl lactam crosslinked polymer. [Means for solving the problem]

[0007] The present inventors have conducted extensive research into methods for producing N-vinyl lactam crosslinked polymers and have found that the above-mentioned problems can be successfully solved by adding an ionic surfactant to a product obtained by polymerizing a monomer component containing a predetermined amount of an N-vinyl lactam monomer and a crosslinkable monomer, drying the product, and then pulverizing and / or classifying the product, thereby suppressing the charging of the powder during pulverization and / or classification, and thereby completing the present invention.

[0008] The present invention includes the following method for producing a crosslinked N-vinyl lactam polymer. [1] A method for producing an N-vinyl lactam crosslinked polymer, the method comprising the steps of: polymerizing a monomer component containing an N-vinyl lactam monomer and a crosslinkable monomer; adding a surfactant to the product obtained in the polymerization step; drying the product obtained after the surfactant addition step; and pulverizing and / or classifying the product obtained in the drying step, wherein the monomer component contains 50 mol % or more of an N-vinyl lactam monomer and 0.05 mol % or more of a crosslinkable monomer relative to 100 mol % of a non-crosslinkable monomer, and the surfactant is an ionic surfactant and / or a polyoxyalkylene glycol-type nonionic surfactant. [2] The method for producing an N-vinyl lactam crosslinked polymer according to [1] above, wherein the crosslinkable monomer comprises at least one selected from the group consisting of triallyl cyanurate, pentaerythritol (di-, tri-, tetra-)(meth)allyl ether, and triallyl isocyanurate. [3] The method for producing an N-vinyl lactam crosslinked polymer according to [1] or [2] above, wherein the ionic surfactant is an amphoteric surfactant. [4] The method for producing an N-vinyl lactam crosslinked polymer according to [3] above, wherein the amphoteric surfactant includes an alkyl betaine and / or an alkylamido betaine. [5] The method for producing an N-vinyl lactam crosslinked polymer according to any one of [1] to [4] above, wherein the polyoxyalkylene glycol nonionic surfactant is a polyoxyalkylene sorbitan fatty acid ester. [6] The method for producing an N-vinyl lactam crosslinked polymer according to any one of [1] to [5] above, wherein the amount of surfactant added in the surfactant addition step is 0.01 to 10 mass% relative to 100 mass% of the solid content of the product obtained in the polymerization step. [7] A composition comprising an N-vinyl lactam crosslinked polymer and a surfactant, wherein the N-vinyl lactam crosslinked polymer has structural units derived from an N-vinyl lactam monomer and structural units derived from a crosslinkable monomer, and the proportion of the structural units derived from the N-vinyl lactam monomer is 50 mol % or more and the proportion of the structural units derived from the crosslinkable monomer is 0.05 mol % or more relative to 100 mol % of the structural units derived from the non-crosslinkable monomer, and the surfactant is an ionic surfactant and / or a polyoxyalkylene glycol-type nonionic surfactant, and the content of the ionic surfactant is 10 mass % or less relative to 100 mass % of the solid content of the N-vinyl lactam crosslinked polymer. [8] The N-vinyl lactam crosslinked polymer-containing composition according to [7] above, wherein the crosslinkable monomer comprises at least one selected from the group consisting of triallyl cyanurate, pentaerythritol (di-, tri-, tetra-) (meth)allyl ether, and triallyl isocyanurate. [9] The N-vinyl lactam crosslinked polymer-containing composition according to the above [7] or [8], wherein the ionic surfactant is an amphoteric surfactant.

[10] The N-vinyl lactam crosslinked polymer-containing composition according to [9] above, wherein the amphoteric surfactant comprises an alkylbetaine and / or an alkylamidobetaine.

[11] The N-vinyl lactam crosslinked polymer-containing composition according to any one of [7] to

[10] , wherein the polyoxyalkylene glycol nonionic surfactant is a polyoxyalkylene sorbitan fatty acid ester.

[12] The composition containing an N-vinyl lactam crosslinked polymer according to any one of [7] to

[11] above, wherein the absolute value of the electrostatic charge measured by the following method is less than 21 nC. <Method for measuring electrostatic charge> 20 g of the composition containing the N-vinyl lactam crosslinked polymer is placed in a SUS container and shaken 100 times in an insulated state, after which the amount of electrostatic charge is measured by the Faraday cage method using a coulomb meter.

[13] The composition containing an N-vinyl lactam crosslinked polymer according to any one of [7] to

[12] above, wherein the average particle size (D50) of the N-vinyl lactam crosslinked polymer measured by a dry particle size distribution measuring device is in the range of 10 to 1000 μm. [Effects of the Invention]

[0009] The method for producing an N-vinyl lactam crosslinked polymer of the present invention has the above-mentioned configuration and can suppress charging of the powder during pulverization and / or classification, thereby enabling efficient production of an N-vinyl lactam crosslinked polymer, and the obtained N-vinyl lactam crosslinked polymer can be suitably used for various applications such as cosmetics, writing instruments, ink absorbents for inkjet recording devices and the like, deodorants, fragrances, and latent heat storage materials. DETAILED DESCRIPTION OF THE INVENTION

[0010] Preferred embodiments of the present invention will be specifically described below, but the present invention is not limited to the following description and can be appropriately modified and applied within the scope of the present invention. Note that combinations of two or more of the individual preferred embodiments of the present invention described below also fall within the scope of preferred embodiments of the present invention.

[0011] [Method for producing N-vinyl lactam crosslinked polymer] The method for producing a water absorbent resin of the present invention comprises the steps of: polymerizing a monomer component containing an N-vinyl lactam monomer and a crosslinkable monomer; adding a surfactant to a product obtained in the polymerization step; drying the product obtained after the surfactant addition step; and pulverizing and / or classifying the product obtained in the drying step, wherein the monomer component contains 50 mol % or more of an N-vinyl lactam monomer and 0.05 mol % or more of a crosslinkable monomer relative to 100 mol % of a non-crosslinkable monomer, and the surfactant is an ionic surfactant and / or a polyoxyalkylene glycol-type nonionic surfactant. Although nonionic N-vinyl lactam crosslinked polymers are more easily charged than ionic polyacrylic acid and the like, the use of the above-mentioned specific surfactants can sufficiently suppress the charging of the resin and sufficiently prevent the N-vinyl lactam crosslinked polymer (resin) from adhering to equipment during grinding and / or classification. By coating the resin surface with the above-mentioned specific surfactant, the surfactant on the resin surface adsorbs moisture in the air to form a conductive layer, reducing the electrostatic charge of the resin and thereby reducing the adhesion of the resin. Furthermore, the product obtained in the polymerization step is in a viscoelastic gel state and tends to adhere to drying nets and the like during drying, but in the production method of the present invention, by coating the resin surface with the above-mentioned predetermined surfactant, it is possible to prevent the gel-like product from adhering to drying nets and the like used in the drying step, which also enables efficient production of N-vinyl lactam crosslinked polymers.

[0012] (Polymerization process of monomer components) The polymerization step is not particularly limited as long as it involves polymerizing a monomer component containing 50 mol% or more of an N-vinyl lactam monomer and 0.05 mol% or more of a crosslinkable monomer relative to 100 mol% of a non-crosslinkable monomer, thereby producing a nonionic N-vinyl lactam crosslinked polymer. The proportion of the N-vinyl lactam monomer is preferably 50 to 100 mol%, more preferably 60 to 100 mol%, even more preferably 70 to 100 mol%, still more preferably 80 to 100 mol%, still more preferably 90 to 100 mol%, particularly preferably 95 to 100 mol%, and most preferably 100 mol%, relative to 100 mol% of the non-crosslinkable monomer.

[0013] The monomer component may contain 50 mol% or more of an N-vinyl lactam monomer as a non-crosslinkable monomer, and may contain other non-crosslinkable monomers other than the N-vinyl lactam monomer, the proportion of which may be 50 mol% or less relative to 100 mol% of the non-crosslinkable monomer. The proportion of other non-crosslinkable monomers is preferably 40 mol% or less, more preferably 30 mol% or less, even more preferably 20 mol% or less, still more preferably 10 mol% or less, particularly preferably 5 mol% or less, and most preferably 0 mol%.

[0014] The monomer component contains 0.05 mol % or more of a crosslinkable monomer, and the resulting resin can thereby exhibit excellent water absorbency. The proportion of the crosslinkable monomer is preferably 0.05 to 3.0 mol %, more preferably 0.06 to 2.0 mol %, even more preferably 0.08 to 1.0 mol %, and particularly preferably 0.1 to 0.75 mol %, relative to 100 mol % of the non-crosslinkable monomer.

[0015] The N-vinyl lactam monomer is not particularly limited as long as it is a non-crosslinkable monomer having an N-vinyl lactam structure, but is preferably a compound represented by the following formula (1).

[0016] [ka]

[0017] (In the formula, R 1 , R 2 , R 3 , R 4 are the same or different and represent a hydrogen atom or an alkyl group having 1 to 10 carbon atoms which may have a substituent. x represents an integer of 0 to 4. y represents an integer of 1 to 3.

[0018] Above R 1 ~R 4The alkyl group represented by the formula (I) is preferably an alkyl group having 1 to 6 carbon atoms, more preferably an alkyl group having 1 to 4 carbon atoms, further preferably a methyl group or an ethyl group, and particularly preferably a methyl group.

[0019] Examples of the substituent include ethylenically unsaturated hydrocarbon groups; carboxyl groups, sulfonic acid groups, and esters and salts thereof; and reactive functional groups capable of condensation reaction with a crosslinking agent, such as amino groups and hydroxyl groups.

[0020] Among them, the above R 1 , R 2 , R 3 is preferably a hydrogen atom. Above R 4 is preferably a hydrogen atom or a methyl group, more preferably a hydrogen atom.

[0021] In the above formula (1), x is preferably an integer of 0 to 2, more preferably an integer of 0 to 1, and even more preferably 0. y is preferably 1 or 2, and more preferably 1.

[0022] Specific examples of the compound represented by the formula (1) include N-vinylpyrrolidone, N-vinyl-5-methylpyrrolidone, N-vinylpiperidone, N-vinylcaprolactam, 1-(2-propenyl)-2-pyrrolidone, etc. Among these, N-vinylpyrrolidone is preferred.

[0023] The non-crosslinkable monomer other than the above-mentioned N-vinyl lactam monomer is not particularly limited as long as it is a compound that can be copolymerized with the N-vinyl lactam monomer, does not have a lactam structure, and has one ethylenically unsaturated hydrocarbon group. Examples of the non-crosslinkable monomer include: (i) unsaturated monocarboxylic acids such as acrylic acid and methacrylic acid, and salts thereof; (ii) unsaturated dicarboxylic acids such as fumaric acid, maleic acid, methylene glutaric acid, and itaconic acid, and salts thereof (either monosalts or disalts); (iii) 3-allyloxy-2-hydroxypropanesulfonic acid, (meth)allyl (iv) unsaturated sulfonic acids such as sulfonic acid and isoprenesulfonic acid and their salts; (iv) unsaturated alcohols such as hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, 3-(meth)allyloxy-1,2-dihydroxypropane, (meth)allyl alcohol, isoprenol and their alkylene oxide adducts in which alkylene oxide is added to the hydroxyl group; (v) (meth)acrylic acid esters such as methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, cyclohexyl (meth)acrylate; ( vi) N-substituted or unsubstituted (meth)acrylamides such as (meth)acrylamide, N-monomethyl(meth)acrylamide, N-monoethyl(meth)acrylamide, and N,N-dimethyl(meth)acrylamide; (vii) vinylaryl monomers such as styrene, indene, and vinylaniline; (viii) alkenes such as ethylene, propylene, butadiene, isobutylene, and octene; (ix) vinyl carboxylates such as vinyl acetate and vinyl propionate; (x) N,N-dimethylaminoethyl(meth)acrylate, N,N-dimethylaminoethyl (xi) unsaturated amines such as vinyl(meth)acrylamide, vinylpyridine, vinylimidazole, and salts or quaternized derivatives thereof; (xi) vinylamides such as vinylformamide, vinylacetamide, and vinyloxazolidone; (xii) unsaturated anhydrides such as maleic anhydride and itaconic anhydride; (xiii) vinyl ethylene carbonate and derivatives thereof; (xiv) ethyl (meth)acrylic acid-2-sulfonate and derivatives thereof; and (xv) vinyl ethers such as methyl vinyl ether, ethyl vinyl ether, and butyl vinyl ether. Among these, the above monomers (i) to (x) are preferred, and the above monomers (i), (v), (vi), (vii), (ix) and (x) are more preferred. These may be used alone or in combination of two or more. Examples of the salts in (i) to (iii) and (x) above include metal salts, ammonium salts, and organic amine salts. Examples of the alkylene oxide in (iv) above include ethylene oxide and propylene oxide, and alkylene oxides having 1 to 20 carbon atoms are preferred, and alkylene oxides having 1 to 4 carbon atoms are more preferred. The number of moles of alkylene oxide added in (iv) above is preferably 0 to 50 moles, and more preferably 0 to 20 moles, per mole of the compound in (iv) above.

[0024] The other non-crosslinkable monomer is preferably a monomer having 2 to 20 carbon atoms, more preferably a monomer having 2 to 15 carbon atoms, and even more preferably a monomer having 2 to 10 carbon atoms. When the other non-crosslinkable monomer is an alkylene oxide adduct, it is preferable that the number of carbon atoms in the structural moiety other than the alkylene oxide structural moiety is within these values.

[0025] The crosslinkable monomer may be any monomer having two or more polymerizable unsaturated groups, and examples thereof include crosslinkable monomers having a cyanuric acid skeleton such as triallyl cyanurate; N,N'-alkylenebis(meth)acrylamides having an alkylene group having 1 to 4 carbon atoms such as N,N'-methylenebis(meth)acrylamide; alkylenebis(N-vinylamides) having an alkylene group having 1 to 6 carbon atoms such as 1,4-butylenebis(N-vinylamide); (poly)ethylene glycol di(meth)acrylate, (poly)propylene ... (Poly)alkylene glycol di(meth)acrylates having an alkylene group having 1 to 4 carbon atoms, such as ethylene glycol di(meth)acrylate; trimethylolpropane (di, tri)(meth)acrylates which may be modified with an alkylene oxide having an alkylene group having 1 to 4 carbon atoms, such as trimethylolpropane tri(meth)acrylate, trimethylolpropane di(meth)acrylate, and ethylene oxide-modified trimethylolpropane tri(meth)acrylate; glycerin tri(meth)acrylate glycerin (di, tri) (meth)acrylates such as glycerin acrylate methacrylate; pentaerythritol (di, tri, tetra) (meth)acrylates such as pentaerythritol tetra(meth)acrylate; dipentaerythritol (di, tri, tetra, penta, hexa) (meth)acrylates such as dipentaerythritol hexa(meth)acrylate; pentaerythritol (di, tri, tetra) (meth)allyl ethers such as pentaerythritol tri(meth)allyl ether; Triallyl compounds having 9 to 20 carbon atoms, such as triallyl isocyanurate, triallyl phosphate, and triallylamine; diallyl compounds having 6 to 20 carbon atoms, such as diallyl carbonate and 1,3-bis(allyloxy)-2-propanol; (di, tri)vinyl compounds having 4 to 20 carbon atoms, such as divinyl ether, divinyl ketone, trivinylbenzene, divinylethylene urea, divinyltoluene, and divinylxylene; diisocyanates having 2 to 20 carbon atoms, such as tolylene diisocyanate and hexamethylene diisocyanate;Examples of such an allyl group include poly(meth)allyloxyalkane, N,N'-divinyl-2-imidazolidinone, N,N'-1,4-butylenebis(N-divinylacetamide), and (di-, tri-, tetra-, penta-, hexa-, hepta-, and octa-)allylsucrose. These may be used alone or in combination of two or more.

[0026] Among the above crosslinkable monomers, it is preferable to use a compound having two or more allyl groups, since the amount of remaining N-vinyl lactam and the soluble content (the non-crosslinked polymer content that dissolves in water) tend to decrease.Furthermore, it is also preferable that the crosslinkable monomer is nonionic. Preferred examples of the crosslinkable monomer include crosslinkable monomers having a cyanuric acid skeleton, pentaerythritol (di-, tri-, tetra-)(meth)allyl ether, triallyl isocyanurate, triallyl phosphate, triallylamine, diallyl carbonate, 1,3-bis(allyloxy)-2-propanol, divinylethyleneurea 1,4-butylenebis(N-vinylamide), and (di-, tri-, tetra-, penta-, hexa-, hepta-, octa-)allylsucrose. In one preferred embodiment of the present invention, the crosslinkable monomer is at least one selected from the group consisting of triallyl cyanurate, pentaerythritol (di-, tri-, tetra-)(meth)allyl ether, and triallyl isocyanurate.

[0027] The crosslinkable monomer is more preferably a crosslinkable monomer having a cyanuric acid skeleton. The crosslinkable monomer having a cyanuric acid skeleton is not particularly limited as long as it has a structure derived from cyanuric acid and at least two carbon-carbon double bonds, but is preferably a crosslinkable monomer having a structure represented by the following formula (2): [ka]

[0028] (In the formula, R 1 , R 2 , R 3are the same or different and represent a hydrogen atom or an alkyl group having 1 to 10 carbon atoms which may have a substituent. m are the same or different and represent an integer of 0 to 4. Above R 1 ~R 3 The number of carbon atoms in the alkyl group is preferably 1 to 6, more preferably 1 to 4. The alkyl group is more preferably a methyl group or an ethyl group, and particularly preferably a methyl group. Above R 1 ~R 3 The substituent in is not particularly limited, but examples thereof include ethylenically unsaturated hydrocarbon groups; carboxyl groups, sulfonic acid groups and esters and salts thereof; and reactive functional groups capable of condensation reacting with a crosslinking agent, such as amino groups and hydroxyl groups. R 1 ~R 3 is preferably a hydrogen atom. m is preferably 0, 1 or 2, and more preferably 1. The compound represented by the above formula (2) is preferably triallyl cyanurate.

[0029] In the polymerization step, the non-crosslinkable monomer and the crosslinkable monomer may be polymerized simultaneously, or the monomer component containing the non-crosslinkable monomer may be polymerized and then reacted with the crosslinkable monomer.

[0030] The polymerization method for the above-mentioned monomer components is not particularly limited, and for example, bulk polymerization, solution polymerization, suspension polymerization, reverse phase suspension polymerization, emulsion polymerization, reverse phase emulsion polymerization, precipitation polymerization, or cast polymerization, thin film polymerization, spray polymerization, etc. can be used. As the polymerization method, solution polymerization is preferred, and aqueous solution polymerization is more preferred. By performing solution polymerization, uneven crosslinking in the crosslinked polymer can be suppressed. The polymerization reaction may be carried out with or without stirring. The stirring method for carrying out the polymerization reaction is not particularly limited, but when a gel-like crosslinked polymer is produced, it is more preferable to use a double-arm kneader as a stirring device and stir while breaking the polymer into small particles by the shear force of the double-arm kneader. The polymerization step can be carried out either batchwise or continuously.

[0031] In the polymerization step, methods for initiating polymerization of the monomer component containing N-vinyl lactam include adding a polymerization initiator, irradiating with UV light, applying heat, and irradiating with light in the presence of a photoinitiator.

[0032] When a solvent is used in the polymerization step, examples of the solvent include one or more selected from alcohols such as water, methyl alcohol, ethyl alcohol, isopropyl alcohol, n-butyl alcohol, diethylene glycol, etc. From the viewpoint of safety of the resulting composition, it is preferable to use water as the solvent, and in this case, the solvent substitution step can be omitted, thereby improving productivity.

[0033] In the polymerization step, it is preferable to use a polymerization initiator when carrying out polymerization. Examples of the polymerization initiator include peroxides such as hydrogen peroxide and t-butyl hydroperoxide; persulfates such as sodium persulfate, potassium persulfate, and ammonium persulfate; dimethyl 2,2'-azobis(2-methylpropionate), 2,2'-azobis(isobutyronitrile), 2,2'-azobis(2-methylbutyronitrile), 2,2'-azobis(2-methylpropionamidine) dihydrochloride, 2,2'-azobis[N-(2-carboxyethyl)-2-methylpropionamidine] hydrate, 2,2'-azobis[2-(2-imidazolin-2-yl)propane], 2,2'-azobis[2-(2-imidazolin-2-yl)propane] dihydrochloride, 2,2'-azobis[2-(2-isopropyl ... Suitable initiators include azo compounds such as 2,2'-azobis(1-imino-1-pyrrolidino-2-methylpropane) disulfate hydrate, 2,2'-azobis[N-(2-carboxyethyl)-2-methylpropionamidine] hydrate, and 2,2'-azobis[2-methyl-N-(2-hydroxyethyl)propionamide]; organic peroxides such as benzoyl peroxide, lauroyl peroxide, peracetic acid, di-t-butyl peroxide, and cumene hydroperoxide; and redox initiators that generate radicals by combining an oxidizing agent and a reducing agent, such as ascorbic acid and hydrogen peroxide, sodium sulfoxylate and t-butyl hydroperoxide, and persulfates and metal salts. Among these polymerization initiators, hydrogen peroxide, persulfates, and azo compounds are preferred, with azo compounds being most preferred. Among these, 2,2'-azobis[2-(2-imidazolin-2-yl)propane]dihydrochloride, 2,2'-azobis[2-(2-imidazolin-2-yl)propane], 2,2'-azobis[2-(2-imidazolin-2-yl)propane]disulfate hydrate, 2,2'-azobis(2-methylpropionamidine)dihydrochloride, and 2,2'-azobis(2-methylbutyronitrile) are more preferred. These polymerization initiators may be used alone or in the form of a mixture of two or more.

[0034] The amount of the polymerization initiator used is preferably 0.1 g or more and 10 g or less per mole of the amount of monomer used (the total amount used of the N-vinyl lactam monomer, the non-crosslinkable monomer other than the N-vinyl lactam monomer, and the crosslinkable monomer). By using an amount of polymerization initiator of 0.1 g or more, the proportion of unreacted monomer contained in the obtained crosslinked polymer can be sufficiently reduced, and the amount of by-products derived from the unreacted monomer, such as the compound represented by formula (8) described below, can also be sufficiently suppressed. Furthermore, by using an amount of initiator of 10 g or less, the proportion of impurities contained in the obtained crosslinked polymer can be sufficiently reduced. Furthermore, by using an amount of initiator in such a ratio, coloration of the obtained crosslinked polymer can also be suppressed. That is, the present invention also encompasses a method for producing an N-vinyl lactam crosslinked polymer, in which a polymerization initiator is used in the polymerization step and the amount of the polymerization initiator used is 0.1 to 10 g per 1 mol of the monomer component. The amount of the polymerization initiator used is more preferably 0.1 g or more and 7 g or less, and even more preferably 0.1 g or more and 5 g or less.

[0035] Specific examples of suitable dispersants when reverse phase suspension polymerization is employed in the polymerization step include sorbitan fatty acid esters, sucrose fatty acid esters, glycerin fatty acid esters, polyglycerin fatty acid esters, cellulose esters such as ethyl cellulose and cellulose acetate, cellulose ethers, and carboxyl group-containing polymers such as α-olefin-maleic anhydride copolymers. These dispersants may be used alone or in an appropriate mixture of two or more. The hydrophobic organic solvent used when reverse phase suspension polymerization is employed is not particularly limited.

[0036] In the polymerization step, the atmosphere during polymerization is not particularly limited, but it is preferable to carry out the polymerization under an inert gas (nitrogen, argon, etc.) atmosphere. By carrying out the polymerization under an inert gas atmosphere, it is possible to improve the grinding efficiency of the obtained crosslinked polymer, reduce the proportion of unreacted monomers contained in the obtained crosslinked polymer, and shorten the reaction time between the organic acid and the crosslinked polymer when the organic acid is added to the crosslinked polymer.

[0037] In the polymerization step, the polymerization temperature is not particularly limited, but a relatively low temperature is preferred because it increases the molecular weight of the crosslinked polymer, and a temperature in the range of 20°C to 100°C is more preferred because it improves the polymerization rate. The reaction time may be appropriately set depending on the reaction temperature, the types (properties), combinations, and amounts of the monomer components, polymerization initiator, and solvent, etc., so that the polymerization reaction is completed.

[0038] The material of the reaction vessel in which the polymerization step is carried out is not particularly limited as long as it is capable of carrying out the polymerization step, but it is preferable to use a reaction vessel made of a material such as stainless steel. By carrying out the polymerization reaction using a reaction vessel made of such a material that easily transfers heat, the polymerization reaction can be sufficiently progressed, and the content of unreacted monomers (unsaturated monomers having a lactam structure, etc.) contained in the obtained crosslinked polymer can be reduced. It is also preferable to use a reaction vessel made of a material that does not allow iron to leach out, such as polypropylene. By using a reaction vessel made of such a material, the iron content in the resulting crosslinked polymer can be reduced.

[0039] After the polymerization reaction, an organic acid may be added to the resulting crosslinked polymer, which can reduce the amount of residual N-vinyl lactam monomer in the crosslinked polymer. The organic acid is not particularly limited, and examples thereof include organic compounds having an acid group such as a carboxyl group, a sulfonic acid group, a phosphonic acid group, a sulfate group, a phosphate group, etc. Examples of such organic acids include malonic acid, oxalic acid, succinic acid, aspartic acid, citric acid, glutamic acid, fumaric acid, malic acid, maleic acid, phthalic acid, trimellitic acid, pyromellitic acid, propionic acid, heptanoic acid, octanoic acid, glycolic acid, salicylic acid, lactic acid, L-ascorbic acid, benzoic acid, methanesulfonic acid, benzenesulfonic acid, laurylbenzenesulfonic acid, p-toluenesulfonic acid, benzenephosphonic acid, and lauryl sulfate.

[0040] The amount of the organic acid used is not particularly limited, but is preferably 0.01 to 5% by mass relative to 100% by mass of the N-vinyl lactam monomer charged in the polymerization step. When the amount of the organic acid used is within the above range, the amount of the organic acid (salt) can be reduced while reducing the amount of the N-vinyl lactam monomer remaining in the resulting polymer. The amount of the organic acid used is more preferably 0.05 to 3% by mass, and even more preferably 0.1 to 1% by mass. The organic acid (salt) refers to the organic acid and the salt of the organic acid, and the salt of the organic acid is mainly a neutralized product of the organic acid and a base added in the neutralization step described below.

[0041] When the organic acid is added to the crosslinked polymer, the reaction time between the organic acid and the crosslinked polymer is not particularly limited, but is preferably 10 minutes to 3 hours, and more preferably 30 minutes to 2 hours.

[0042] The method for producing the crosslinked polymer preferably includes a step of aging the crosslinked polymer after the polymerization reaction. By carrying out the aging step, the amount of residual N-vinyl lactam monomer can be reduced, and the amount of by-products derived from the residual N-vinyl lactam monomer, such as the compound represented by formula (8) described below, can also be reduced. The temperature in the aging step is not particularly limited, but is preferably 60 to 150°C. If the aging temperature is within the above range, the amount of residual N-vinyl lactam monomer can be more sufficiently reduced. It is more preferably 70 to 100°C. The aging time in the aging step is not particularly limited, but is preferably 10 minutes to 5 hours, and more preferably 30 minutes to 3 hours. When the method for producing the crosslinked polymer includes a step of adding an organic acid, the aging step is preferably carried out before the step of adding the organic acid.

[0043] In the polymerization step, a post-crosslinking step for forming the crosslinked structure may be carried out after the monomer components have been polymerized. Examples of methods for post-crosslinking (crosslinking after polymerization) in the post-crosslinking step include: (i) a method of irradiating the polymer obtained in the polymerization step with UV rays, gamma rays, or electron beams; (ii) a method of adding a reaction accelerator such as a condensing agent to the polymer obtained in the polymerization step to cause self-crosslinking; (iii) a method of applying heat to the polymer obtained in the polymerization step to cause self-crosslinking; (iv) a method of incorporating a radical generator into the polymer obtained in the polymerization step, and then applying heat to cause self-crosslinking; and (v) a method of incorporating a radical polymerizable crosslinking agent (crosslinkable monomer) and a radical polymerization initiator into the polymer obtained in the polymerization step, and then heating and / or irradiating with light.

[0044] In producing the crosslinked polymer of the present invention, when a crosslinked structure is formed by reacting a polymer obtained by polymerizing a monomer component containing a monomer having a reactive functional group with a crosslinking agent having multiple functional groups reactive with the reactive functional group, the amount of the crosslinking agent used is preferably an amount such that the functional groups possessed by the crosslinking agent account for 30 to 100 mol % relative to 100 mol % of the reactive functional groups possessed by the polymer (reactive functional groups reactive with the crosslinking agent). More preferably, it is 50 to 100 mol %. Using the crosslinking agent in such a ratio allows for the formation of a sufficient crosslinked structure and also reduces the amount of unreacted crosslinking agent remaining in the resulting crosslinked polymer.

[0045] The reaction accelerator used in the above method (ii) can be one or more of the following: acids such as sulfuric acid and phosphoric acid; bases such as sodium hydroxide and potassium hydroxide; and condensing agents such as N,N'-dicyclohexylcarbodiimide. The radical generator used in the above method (iv) may be the same as the polymerization initiator used in the above polymerization step. Among the polymerization initiators, peroxides such as hydrogen peroxide, t-butyl hydroperoxide, t-butyl peroxypivalate, octanoyl peroxide, succinic peroxide, t-hexylperoxy-2-ethylhexanoate, t-butylperoxy-2-ethylhexanoate, t-butylperoxyisobutyrate, and t-butylperoxymaleic acid are preferred.

[0046] In producing the crosslinked polymer of the present invention, when radicals are generated in a polymer and the polymer from which the radicals have been generated is reacted with a crosslinkable monomer to form a crosslinked structure, the amount of crosslinkable monomer used in the post-crosslinking step is preferably 0.1 to 50 mass% relative to 100 mass% of the polymer before the post-crosslinking step, and more preferably 1 to 30 mass%. Using the crosslinkable monomer in such a ratio makes it possible to form a sufficient crosslinked structure and also reduces the amount of unreacted crosslinkable monomer remaining in the resulting crosslinked polymer.

[0047] (Surfactant addition process) The surfactant addition step is a step of adding an ionic surfactant and / or a polyoxyalkylene glycol-type nonionic surfactant to the product obtained in the polymerization step. The total amount of the ionic surfactant and polyoxyalkylene glycol nonionic surfactant used is not particularly limited, but is preferably 0.01 to 10% by mass, more preferably 0.05 to 8% by mass, even more preferably 0.1 to 5% by mass, and particularly preferably 0.2 to 3% by mass, relative to 100% by mass of the solid content of the product obtained in the polymerization step. The solid content of the product obtained in the polymerization step (solid content of the crosslinked polymer) refers to a value measured by the following method. Approximately 1 g of cross-linked polymer (mass W2 (g)) is weighed into a weighing can (mass W1 (g)) with a bottom diameter of approximately 5 cm, and left to dry in a constant temperature dryer at 150°C for 1 hour. After drying, the mass of the weighing can and cross-linked polymer (W3 (g)) is measured, and the solid content is calculated using the following formula. Solid content (mass%) = ((W3(g)-W1(g)) / W2(g))×100

[0048] When an ionic surfactant is used in the surfactant addition step, the amount used is not particularly limited, but is preferably 0.01 to 10 mass %, more preferably 0.05 to 8 mass %, even more preferably 0.1 to 5 mass %, and particularly preferably 0.2 to 3 mass %, relative to 100 mass % of the solid content of the product obtained in the polymerization step.

[0049] When a polyoxyalkylene glycol-type nonionic surfactant is used in the surfactant addition step, the amount used is not particularly limited, but is preferably 0.01 to 10% by mass, more preferably 0.05 to 8% by mass, even more preferably 0.1 to 5% by mass, and particularly preferably 0.2 to 3% by mass, relative to 100% by mass of the solid content of the product obtained in the polymerization step.

[0050] Specific examples of the ionic surfactant include amphoteric surfactants (zwitterionic surfactants), anionic surfactants, and cationic surfactants. Among these, amphoteric surfactants and cationic surfactants are preferred, and amphoteric surfactants are more preferred.

[0051] The amphoteric surfactant is not particularly limited, but betaine surfactants are preferred. A betaine group is a group in which a cationic group (cationic moiety) and an anionic group (anionic moiety) are not adjacent to each other, and the substituent as a whole does not have an electric charge. The betaine surfactant may be any surfactant having a betaine group and a hydrophobic group, but is preferably a surfactant represented by the following formula (3):

[0052] [ka]

[0053] (In the formula, R 5 represents a hydrocarbon group having 8 to 20 carbon atoms which may have a hydroxyl group; W represents an organic group having a quaternary nitrogen; X represents NH, NR 6 , O or S, R 6 represents an alkyl group having 1 to 4 carbon atoms. Y represents COO, SO3, OPO(OR 7 )O or P(O)(OR 7 )O, R 7 is a hydrogen atom or an alkyl group having 1 to 4 carbon atoms. p and q are the same or different and are integers of 1 to 6. r and s are the same or different and are 0 or 1.

[0054] Above R 5 The hydrocarbon group is not particularly limited, and examples thereof include alkyl groups, alkenyl groups, alkynyl groups, aryl groups, and aralkyl groups.

[0055] Examples of the alkyl group include aliphatic alkyl groups such as n-octyl, n-nonyl, n-decyl, n-undecyl, n-dodecyl, n-tridecyl, n-tetradecyl, n-pentadecyl, n-hexadecyl, n-heptadecyl, n-octadecyl, n-nonadecyl, n-icosyl, 1,5-dimethylhexyl, t-octyl, branched nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl, stearyl, and icosyl; and alicyclic alkyl groups such as cyclooctyl, cyclohexylethyl, cyclohexylpropyl, cyclododecyl, adamantyl (C10), and cyclopentylpropyl.

[0056] Examples of the alkenyl group include an octenyl group, a nonenyl group, a decenyl group, a dodecenyl group, an octadecenyl group, and an icosenyl group. Examples of the alkynyl group include an octynyl group, a nonynyl group, a decynyl group, a dodecynyl group, an octadecynyl group, and an icosynyl group. Examples of the aryl group include a 2,3- or 2,4-xylyl group, a mesityl group, a naphthyl group, an anthryl group, a phenanthryl group, and a biphenylyl group. Examples of the aralkyl group include a phenethyl group, a phenylpropyl group, and a benzhydryl group.

[0057] The hydrocarbon group is preferably an alkyl group. More preferably, it is an n-octyl group, a sec-octyl group, a tert-octyl group, a 2-ethylhexyl group, a capryl group, a nonyl group, a decyl group, an undecyl group, a lauryl group, a tridecyl group, a myristyl group, a pentadecyl group, a cetyl group, a heptadecyl group, a stearyl group, or the like. From the viewpoint of gel dispersibility, R 5 As the alkyl group, a straight chain alkyl group is more preferred.

[0058] Also, R 5When the hydrocarbon group in has a hydroxyl group, it is preferably a hydroxyalkyl group, such as a 2-hydroxydecyl group, a 2-hydroxyundecyl group, a 2-hydroxylauryl group, a 2-hydroxytridecyl group, a 2-hydroxymyristyl group, a 2-hydroxypentadecyl group, a 2-hydroxycetyl group, a 2-hydroxyheptadecyl group, or a 2-hydroxystearyl group.

[0059] From the viewpoint of gel dispersibility, R 5 The hydrocarbon group preferably has 8 to 20 carbon atoms, more preferably 10 to 19 carbon atoms, and even more preferably 12 to 18 carbon atoms.

[0060] The W represents an organic group having a quaternary nitrogen. The above W is preferably represented by the following formula (4): -N + (R 8 )twenty four) (In the formula, R 8 are the same or different and represent a hydrocarbon group having 1 to 4 carbon atoms which may have a hydroxyl group, or a group represented by the following formula (5):

[0061] [ka]

[0062] (In the formula, R 9 are the same or different and represent a hydrocarbon group having 1 to 4 carbon atoms which may have a hydroxyl group. Above R 8 , R 9 Examples of the hydrocarbon group in include an alkyl group, an alkenyl group, and an alkynyl group, preferably an alkyl group, more preferably a methyl group, an ethyl group, a propyl group, or a butyl group, and particularly preferably a methyl group or an ethyl group. Above R 8 , R 9 The hydrocarbon group in may have a hydroxyl group. R 9is a hydroxyalkyl group is one of the preferred embodiments of the present invention.

[0063] The above W is preferably a group represented by formula (4). The above W is -N + The form of the group represented by (CH3)2- is a preferred embodiment of the present invention.

[0064] The above Y is COO, SO3, OPO(OR 7 )O or P(O)(OR 7 )O, R 7 is a hydrogen atom or an alkyl group having 1 to 4 carbon atoms. The above Y is preferably COO.

[0065] The above p and q are the same or different and are integers of 1 to 6. p is preferably 2 to 5, and more preferably 3. The above q is preferably 1 to 4, more preferably 1 to 2, and even more preferably 1.

[0066] The above r and s may be the same or different and each represents 0 or 1. The above embodiment in which r and s are 0 is a preferred embodiment of the present invention.

[0067] The above X is NH, NR 6 , O or S, R 6 represents an alkyl group having 1 to 4 carbon atoms. The above X is preferably NH.

[0068] The amphoteric surfactant is preferably a surfactant represented by the formula (3) above, where r=0, s=0, q=1 to 6, and R 5 is an alkyl group, W is -N + (R 8 )2-, alkylbetaine in which Y is COO, in the above formula (3), r=1, s=0, p=1 to 6, q=1 to 6, R 5 is an alkyl group, W is -N + (R 8)2-, an alkylamidobetaine where X is NH and Y is COO. In one preferred embodiment of the present invention, the amphoteric surfactant includes an alkylbetaine and / or an alkylamidobetaine. In the above formula (3), R 5 Preferably, X is an alkyl group, r is 0 or 1, and when r is 1, X is NH.

[0069] In the above formula (3), R 5 is an alkyl group, W is a group represented by formula (4), and R 8 is a methyl group, r and s are 0, q is 1, and Y is COO, which is a preferred embodiment of the present invention, and the chemical formula is 5 -N + (CH3)2-CH2COO - The compound is generally known as alkyldimethylaminoacetic acid betaine. Specific examples of alkyl dimethyl amino acetic acid betaine include capryl dimethyl amino acetic acid betaine, lauryl dimethyl amino acetic acid betaine, myristyl dimethyl amino acetic acid betaine, stearyl dimethyl amino acetic acid betaine, coconut oil alkyl dimethyl amino acetic acid betaine, etc. From the viewpoint of gel dispersibility and the physical properties of the water absorbent resin, capryl dimethyl amino acetic acid betaine, lauryl dimethyl amino acetic acid betaine or stearyl dimethyl amino acetic acid betaine, coconut oil alkyl dimethyl amino acetic acid betaine are preferred, and lauryl dimethyl amino acetic acid betaine and coconut oil alkyl dimethyl amino acetic acid betaine are more preferred.

[0070] Capryldimethylaminoacetic acid betaine is commercially available as "Amogen (registered trademark) HB-C" manufactured by Daiichi Kogyo Seiyaku Co., Ltd. Lauryldimethylaminoacetic acid betaine is commercially available as "Amhithol (registered trademark) 20BS" and "Amhithol (registered trademark) 24B" manufactured by Kao Corporation, "Nissan Anon (registered trademark) BL" and "Nissan Anon (registered trademark) BL-SF" manufactured by NOF Corporation, "Obazolin (registered trademark) LB" and "Obazolin (registered trademark) LB-SF" manufactured by Toho Chemical Industry Co., Ltd., "Rekabion (registered trademark) A-100" manufactured by New Japan Chemical Co., Ltd., "Amogen (registered trademark) K" and "Amogen (registered trademark) SH" manufactured by Daiichi Kogyo Seiyaku Co., Ltd. Stearyldimethylaminoacetic acid betaine is commercially available as "Amhithol (registered trademark) 86B" manufactured by Kao Corporation.

[0071] In the above formula (3), R 5 is an alkyl group, W is a group represented by formula (4), and R 4 is a methyl group, X is NH, r is 1, s is 0, p is 3, q ​​is 1, and Y is COO, the chemical formula is R 5 -CO-NH(CH2)3-N + (CH3)2-CH2COO - The general name of the compound is alkylamidopropyl betaine. Specific examples of alkylamidopropyl betaine include lauric acid amidopropyl betaine, coconut oil fatty acid amidopropyl betaine, palm kernel oil fatty acid amidopropyl betaine, etc. From the viewpoint of gel dispersibility and physical properties of the water-absorbing agent, lauric acid amidopropyl betaine or coconut oil fatty acid amidopropyl betaine is preferred, and lauric acid amidopropyl betaine is more preferred.

[0072] Lauryl amidopropyl betaine is commercially available as "Amphitol (registered trademark) 20AB" manufactured by Kao Corporation, "Rekabion (registered trademark) B-300" manufactured by New Japan Chemical Co., Ltd., "Amogen (registered trademark) LB-C" manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd., "Nissan Anon (registered trademark) BDL-SF" manufactured by NOF Corporation, etc. Furthermore, the coconut oil fatty acid amidopropyl betaine is commercially available as "Amphitol (registered trademark) 55AB" manufactured by Kao Corporation, "Obazoline (registered trademark) CAB30" manufactured by Toho Chemical Industry Co., Ltd., "Rekabion (registered trademark) B-200" manufactured by New Japan Chemical Co., Ltd., "Amogen (registered trademark) CB-H" manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd., etc.

[0073] In the above formula (3), R 5 is an alkyl group, W is a group represented by formula (4), and R 8 is a methyl group, r is 0, s is 1, q is 1, and Y is SO3, the chemical formula is R 5 -N + (CH3)2-CH2CH(OH)CH2SO3 - and the common name of the compound is alkylhydroxysulfobetaine. Specific examples of alkylhydroxysulfobetaines include laurylhydroxysulfobetaine. From the viewpoint of gel dispersibility and the physical properties of the water-absorbing agent, laurylhydroxysulfobetaine is preferred. The above-mentioned laurylhydroxysulfobetaine is commercially available as "Amphitol (registered trademark) 20HD" manufactured by Kao Corporation.

[0074] In the above formula (3), R 5 is an alkyl group, W is a group represented by formula (5), and R 5 When is a hydroxyethyl group, r and s are 0, q is 1, and Y is COO, a common name for the compound is alkylcarboxymethylhydroxyethylimidazolinium betaine. A specific example of alkylcarboxymethyl hydroxyethyl imidazolinium betaine is 2-alkyl-N-carboxymethyl-N-hydroxyethyl imidazolinium betaine. From the viewpoint of gel dispersibility and the physical properties of the water-absorbing agent, 2-alkyl-N-carboxymethyl-N-hydroxyethyl imidazolinium betaine is preferred. The 2-alkyl-N-carboxymethyl-N-hydroxyethyl imidazolinium betaine is commercially available as "Amphitol (registered trademark) 20YB" manufactured by Kao Corporation, "Nissan Anon (registered trademark) GLM-R-LV" manufactured by NOF Corporation, "Obazoline (registered trademark) 552" manufactured by Toho Chemical Industry Co., Ltd., etc.

[0075] The amphoteric surfactant is preferably alkyldimethylaminoacetic acid betaine or alkylamidopropyl betaine, more preferably lauryldimethylaminoacetic acid betaine, coconut oil alkyldimethylaminoacetic acid betaine or lauric acid amidopropyl betaine.

[0076] The anionic surfactant is not particularly limited as long as it has a hydrophobic group and a hydrophilic group that dissociates into anions, and examples thereof include alkyl or alkenyl sulfate ester salts; polyoxyalkylene alkyl or alkenyl ether sulfate ester salts having an oxyalkylene group; anionic surfactants having a sulfonate group; fatty acids or salts thereof, and sulfosuccinate esters.

[0077] More specific examples of the alkyl or alkenyl sulfate ester salts include alkyl sulfate ester salts in which the alkyl group has 10 to 18 carbon atoms, and alkenyl sulfate ester salts in which the alkenyl group has 10 to 18 carbon atoms.

[0078] More specific examples of the polyoxyalkylene alkyl or alkenyl ether sulfate salts having an oxyalkylene group include polyoxyalkylene alkyl ether sulfate salts having an alkyl group with 10 to 18 carbon atoms and an average number of added moles of alkylene oxide of 1 to 5, and polyoxyalkylene alkenyl ether sulfate salts having an alkenyl group with 10 to 18 carbon atoms and an average number of added moles of alkylene oxide of 1 to 5. Among these, polyoxyethylene alkyl ether sulfate salts having an average number of added moles of ethylene oxide of 1 to 3 are preferred, and polyoxyethylene alkyl ether sulfate salts having an alkyl group with 12 to 14 carbon atoms and an average number of added moles of ethylene oxide of 1 to 3 are more preferred, and sodium salts thereof are even more preferred.

[0079] More specific examples of the anionic surfactant having a sulfonate group include one or more anionic surfactants selected from alkylbenzenesulfonates having an alkyl group with 10 to 18 carbon atoms, alkenylbenzenesulfonates having an alkenyl group with 10 to 18 carbon atoms, alkanesulfonates having an alkyl group with 10 to 18 carbon atoms, α-olefinsulfonates having an α-olefin moiety with 10 to 18 carbon atoms, α-sulfofatty acid salts having a fatty acid moiety with 10 to 18 carbon atoms, α-sulfofatty acid lower alkyl ester salts having a fatty acid moiety with 10 to 18 carbon atoms and an ester moiety with 1 to 5 carbon atoms, and internal olefinsulfonates having 12 to 16 carbon atoms. Among these, alkylbenzenesulfonates having an alkyl group with 11 to 16 carbon atoms are preferred, and sodium alkylbenzenesulfonate having an alkyl group with 11 to 16 carbon atoms is more preferred.

[0080] The fatty acid or salt thereof may be a fatty acid or salt thereof having 10 to 20 carbon atoms. The fatty acid or salt thereof preferably has 12 to 18 carbon atoms, and more preferably has 14 to 18 carbon atoms.

[0081] The sulfosuccinate ester or salt thereof may be a sulfosuccinate ester or salt thereof having a hydrocarbon group having 5 to 18 carbon atoms.

[0082] The cationic surfactant is not particularly limited as long as it has a hydrophobic group and a hydrophilic group that dissociates into a cation, and examples thereof include quaternary ammonium salt type cationic surfactants. Examples of quaternary ammonium salt-type cationic surfactants include quaternary ammonium salts in which, of the four groups bonded to the nitrogen atom, one or two are hydrocarbon groups having 6 to 24 carbon atoms, and the remaining groups are hydrocarbon groups having 1 to 3 carbon atoms. The cationic surfactant includes a compound represented by the following formula (6):

[0083] [ka] (In the formula, R 10 is a chain hydrocarbon group having 8 to 24 carbon atoms, and R 11 is a chain hydrocarbon group having 8 to 24 carbon atoms, an alkyl group having 1 to 3 carbon atoms, or a hydroxyalkyl group having 1 to 3 carbon atoms, and R 12 and R 13 are the same or different and are an alkyl group having 1 to 3 carbon atoms or a hydroxyalkyl group having 1 to 3 carbon atoms, and Z - is an alkyl sulfate ion having 1 to 3 carbon atoms, or a halide ion.

[0084] In the above formula (6), R 10 The chain hydrocarbon group preferably has 9 to 20 carbon atoms, and more preferably 10 to 18 carbon atoms. R 11 is a chain hydrocarbon group having 8 to 24 carbon atoms, an alkyl group having 1 to 3 carbon atoms, or a hydroxyalkyl group having 1 to 3 carbon atoms or less, and R 11 The chain hydrocarbon group preferably has 10 to 18 carbon atoms. R 11 The chain hydrocarbon group R is preferably an alkyl group or an alkenyl group, more preferably an alkyl group. 12 , R 13 are the same or different and are a methyl group, an ethyl group, or a hydroxyalkyl group having 1 to 3 carbon atoms. R 10, R 11 Specific examples of the chain hydrocarbon group are octyl, nonyl, decyl, dodecyl, tetradecyl, hexadecyl, heptadecyl and octadecyl groups, with tetradecyl, hexadecyl, heptadecyl and octadecyl groups being preferred. Specific examples of the hydroxyalkyl group having 1 to 3 carbon atoms include a hydroxymethyl group, a hydroxyethyl group, and a hydroxypropyl group. Z - is CH3SO4 - , CH3CH2SO4 - , or a halide ion.

[0085] In the above formula (6), R 10 is an alkyl group having 8 to 24 carbon atoms, and R 11 ~R 13 In one preferred embodiment of the present invention, is an alkyl group having 1 to 3 carbon atoms.

[0086] Specific examples of the cationic surfactant include one or more compounds selected from trimethylstearylammonium salt, N-ethyl-N,N-dimethyltetradecylammonium salt, trimethylhexadecyl salt, N,N-dioctyl-N,N-dimethylammonium salt, N,N-dinonyl-N,N-dimethylammonium salt, N,N-didecyl-N,N-dimethylammonium salt, N,N-dioctyl-N-ethyl-N-methylammonium salt, N,N-dinonyl-N-ethyl-N-methylammonium salt, and N,N-didecyl-N-ethyl-N-methylammonium salt. Mono-long-chain ammonium salts and di-long-chain ammonium salts can also be used in combination. Among these, mono-long-chain ammonium salts such as trimethylstearylammonium salt are preferred. Counterions for these salts include, for example, CH3SO4 - , CH3CH2SO4 - or halide ions such as chloride ions.

[0087] The polyoxyalkylene glycol-type nonionic surfactant has a hydrophobic group and a polyoxyalkylene group as a hydrophilic group, and is not particularly limited as long as it is nonionic, but a compound having a structure derived from a polyhydric alcohol, a polyoxyalkylene group, and a hydrophobic group is preferred. Examples of the polyhydric alcohols include dihydric alcohols such as ethylene glycol, diethylene glycol, propylene glycol, and dipropylene glycol; glycerol (glycerin), 1,2,3-butanetriol, 1,2,4-butanetriol, 1,2,3-pentanetriol, 1,2,4-pentanetriol, 2-methyl-1,2,3-propanetriol, 2-methyl-2,3,4-butanetriol, 2-ethyl-1,2,3-butanetriol, 2,3,4-pentanetriol, 3-methylpentane-1,3,5-triol, 2,4-dimethyl-2,3,4-pentanetriol, 2,3,4-hexanetriol, 4-propyl-3,4,5-heptanetriol, and 1,3,5-cyclohexane. Examples of suitable alcohols include trihydric alcohols such as triol, pentamethylglycerin, trimethylolethane, and trimethylolpropane; tetrahydric alcohols such as tetramethylolmethane (pentaerythritol) and diglycerin; pentahydric alcohols such as arabitol, galactose, xylitol, glucose, fructose, mannose, allose, gulose, idose, and talose; hexahydric alcohols such as dipentaerythritol, sorbitol, mannitol, iditol, and inositol; heptahydric alcohols such as perseitol; polyhydric aliphatic alcohols such as octahydric alcohols such as sucrose, maltose, and lactose; and cyclic ether polyhydric alcohols obtained by dehydration of tetrahydric or higher alcohols such as sorbitan and sorbide. Among these, cyclic ether polyhydric alcohols are preferred, and sorbitan is more preferred.

[0088] The polyoxyalkylene group is not particularly limited as long as it has the same structure as that obtained by addition polymerization of an alkylene oxide. Examples of alkylene oxides include ethylene oxide, propylene oxide, butylene oxide, isobutylene oxide, 1-butene oxide, 2-butene oxide, and styrene oxide. The alkylene oxide preferably has 2 to 18 carbon atoms, more preferably 2 to 8 carbon atoms, and even more preferably 2 to 4 carbon atoms. The alkylene oxide is preferably ethylene oxide, propylene oxide or butylene oxide, more preferably ethylene oxide.

[0089] The average number of moles of oxyalkylene groups added in the polyoxyalkylene glycol nonionic surfactant is not particularly limited, but is preferably 1 to 100, more preferably 2 to 80, even more preferably 5 to 60, still more preferably 8 to 50, and particularly preferably 10 to 30.

[0090] The hydrophobic group may be any hydrophobic organic group, and examples thereof include hydrocarbon groups having 6 to 30 carbon atoms. Examples of the hydrocarbon group having 6 to 30 carbon atoms include an alkyl group, an alkenyl group, an alkynyl group, an aryl group, an aralkyl group, etc. The hydrophobic group is preferably an alkyl group or an alkenyl group.

[0091] The hydrophobic group preferably has 8 to 24 carbon atoms, more preferably 10 to 22 carbon atoms, and even more preferably 12 to 20 carbon atoms.

[0092] Examples of the alkyl group include an n-hexyl group, an n-heptyl group, an n-octyl group, an n-nonyl group, an n-decyl group, an n-undecyl group, an n-dodecyl group, an n-tridecyl group, an n-tetradecyl group, an n-pentadecyl group, an n-hexadecyl group, an n-heptadecyl group, an n-octadecyl group, an n-nonadecyl group, an n-icosyl group, a 1,3-dimethylbutyl group, a 3,3-dimethylbutyl group, a 2-ethylbutyl group, a 2-ethyl-2-methylpropyl group, a 1-methylheptyl group, a 2-ethylhexyl group, a 1-methyl ... aliphatic alkyl groups such as 5-dimethylhexyl, t-octyl, branched nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl, stearyl, and icosyl groups; and alicyclic alkyl groups such as cyclohexyl, cyclohexylmethyl, cycloheptyl, cyclooctyl, cyclohexylpropyl, cyclododecyl, norbornyl (C7), adamantyl (C10), and cyclopentylethyl groups.

[0093] Examples of the alkenyl group include a hexenyl group, a heptenyl group, an octenyl group, a nonenyl group, a decenyl group, a dodecenyl group, a pentadecenyl group, a hexadecenyl group, a heptadecenyl group, an octadecenyl group, and an icosenyl group. Examples of the alkynyl group include a hexynyl group, a heptynyl group, an octynyl group, a nonynyl group, a decynyl group, a dodecynyl group, an octadecynyl group, and an icosynyl group.

[0094] Examples of the aryl group include a phenyl group, an o-, m- or p-tolyl group, a 2,3- or 2,4-xylyl group, a mesityl group, a naphthyl group, an anthryl group, a phenanthryl group, and a biphenylyl group. Examples of the aralkyl group include a benzyl group, a phenethyl group, a phenylpropyl group, and a benzhydryl group.

[0095] The polyoxyalkylene glycol nonionic surfactant is represented by the following formula (7): (H-(OA 1 )k1 ) i -Z-((A 2 O) k2 -(CO) l -R 14 ) j (7) (In the formula, OA 1 and A 2 O may be the same or different and represent an oxyalkylene group. k1 and k2 represent the number of moles of oxyalkylene groups added and are numbers from 0 to 100. However, the total number of oxyalkylene groups present in formula (7), i.e., the sum of i k1s and j k2s, is 1 to 100. i and j may be the same or different and are numbers from 1 to 6. Z is a group derived from a polyhydric alcohol. l is 0 or 1. R 14 represents a hydrophobic group.

[0096] In the above formula (7), Z is a group derived from a polyhydric alcohol, and is a group obtained by abstracting a hydrogen atom from a hydroxyl group of the polyhydric alcohol. Specific examples and preferred forms of the polyhydric alcohol are as described above.

[0097] The above k1 and k2 are numbers from 0 to 100, and the total number of oxyalkylene groups present in formula (7) (the sum of i k1s and j k2s) is from 1 to 100. The preferred range of the total number of oxyalkylene groups present in formula (7) is the same as that described for the average number of moles of oxyalkylene groups added.

[0098] The above i and j are the same or different and are numbers from 1 to 6. The above i is preferably 1 to 5, more preferably 1 to 4, and even more preferably 1 to 3. j is preferably 1 to 3, more preferably 1 or 2, and even more preferably 1. The above l is 0 or 1. Preferably, l is 1.

[0099] Above R 14represents a hydrophobic group. Specific examples and preferred embodiments of the hydrophobic group are as described above. The above OA 1 and A 2 O may be the same or different and represents an oxyalkylene group. Specific examples and preferred embodiments of alkylene oxides forming the oxyalkylene group are as described above.

[0100] The polyoxyalkylene glycol type nonionic surfactant is preferably a compound obtained by adding an alkylene oxide to a polyhydric alcohol and then esterifying a fatty acid. The fatty acid is not particularly limited as long as it is a carboxylic acid having a hydrocarbon group having 6 to 30 carbon atoms, and examples thereof include saturated fatty acids such as enanthic acid, caprylic acid, 2-ethylhexanoic acid, pelargonic acid, capric acid, undecylic acid, lauric acid, tridecylic acid, myristic acid, pentadecylic acid, palmitic acid, margaric acid, stearic acid, nonadecylic acid, and arachidic acid; and monounsaturated fatty acids such as myristoleic acid, palmitoleic acid, sapienic acid, oleic acid, elaidic acid, vaccenic acid, gadoleic acid, eicosenoic acid (paulic acid), erucic acid, and nervonic acid. Examples of such fatty acids include diunsaturated fatty acids such as linoleic acid, eicosadienoic acid, and docosadienoic acid; triunsaturated fatty acids such as α-linolenic acid, γ-linolenic acid, pinolenic acid, eleostearic acid, mead acid, dihomo-γ-linolenic acid, and eicosatrienoic acid; tetraunsaturated fatty acids such as stearidonic acid, arachidonic acid, eicosatetraenoic acid, and adrenic acid; pentaunsaturated fatty acids such as bosseopentaenoic acid, eicosapentaenoic acid, docosapentaenoic acid, osbondo acid, sardine acid, and tetracosapentaenoic acid; and hexaunsaturated fatty acids such as docosahexaenoic acid and herring acid. Among these, saturated fatty acids and monounsaturated fatty acids are preferred, and monounsaturated fatty acids are more preferred.

[0101] The polyoxyalkylene glycol type nonionic surfactant is preferably a polyoxyalkylene sorbitan fatty acid ester, more preferably polyoxyethylene sorbitan monooleate.

[0102] The method for adding the surfactant in the surfactant addition step is not particularly limited, but it is preferable to add the surfactant while stirring the product obtained in the polymerization step. Specifically, for example, it is more preferable to use a double-arm kneader as the stirring device and stir the product obtained in the polymerization step while breaking it up by the shearing force of the double-arm kneader.

[0103] (drying process) The drying step is a step of drying the product obtained after the surfactant addition step. The drying method for the product in the drying step is not particularly limited, and can be carried out by a commonly used method such as a ventilation band dryer, a rotary ventilation dryer, an agitator dryer, a fluidized bed dryer, or a vibration fluidized bed dryer.

[0104] The drying temperature in the drying step is not particularly limited, but is preferably 100 to 250°C, more preferably 110 to 230°C, and even more preferably 120 to 200°C. The drying temperature is usually determined by the temperature of the heat medium. For example, in the case of hot air drying, it is the temperature of the hot air. However, in the case of microwave drying and other methods that cannot be determined by the temperature of the heat medium, the drying temperature is determined by the temperature of the product being dried. The drying temperature may be constant throughout the drying process or may be changed as appropriate during the drying process. Among these, hot air drying is more preferable. When hot air drying is used, the drying air flow rate is preferably in the range of 0.01 to 10 m / sec, more preferably 0.1 to 5 m / sec. The drying temperature is more preferably in the range of 110°C to 230°C, and even more preferably 120°C to 200°C. Drying may be performed at a constant temperature or by varying the temperature, but it is preferable that substantially all drying steps be performed within the above temperature range. The drying time in the drying step is preferably 30 to 300 minutes, more preferably 60 to 240 minutes, and even more preferably 90 to 180 minutes.

[0105] (Crushing and / or classification process) The pulverization and / or classification step is a step in which the product obtained in the drying step is pulverized and / or classified. The above production method preferably includes a pulverization step, which allows the average particle size and aspect ratio of the crosslinked polymer to be within a more suitable range. For example, roll-type crushers such as roll mills, hammer-type crushers such as hammer mills, impact crushers, cutter mills, turbo grinders, ball mills, pin mills, flash mills, and jet mills such as fluidized bed jet mills and target jet mills can be used. To crush the material to a smaller average particle size, it is more preferable to use a target jet mill. It is also preferable to use a roll mill, hammer-type crusher, impact crusher, pin mill, or jet mill to control the particle size distribution. To control the particle size distribution, it is more preferable to crush the material two or more times in succession, and even more preferable to crush the material three or more times in succession. When crushing is performed two or more times, the crushers may be the same or different, and crushers of different types may be used in combination. The pulverization method in the pulverization step is not particularly limited, and pulverization at room temperature or freeze-pulverization may be used. Because N-vinyl lactam crosslinked polymers are soft, freeze-pulverization is preferred. However, by using the target-type jet mill, the polymer can be pulverized more finely even at room temperature, and production costs can be reduced compared to freeze-pulverization. Furthermore, by using the target-type jet mill, the classification step can be omitted, further improving productivity.

[0106] When the classification step is carried out, it is preferable to carry out the classification step after the pulverization step. The classification may be performed using a sieve with a specific mesh size. The classifier used for classification with a sieve is not particularly limited, but examples thereof include a vibrating sieve (unbalanced weight-driven type, resonance type, vibration motor type, electromagnetic type, circular vibration type, etc.), an in-plane motion sieve (horizontal motion type, horizontal circular-linear motion type, three-dimensional circular motion type, etc.), a moving mesh sieve, a forced stirring type sieve, a mesh surface vibration type sieve, a wind-powered sieve, and an ultrasonic sieve, and preferably a vibrating sieve or an in-plane motion sieve.

[0107] [N-vinyl lactam crosslinked polymer-containing composition] The N-vinyllactam crosslinked polymer-containing composition of the present invention (hereinafter also referred to as the composition of the present invention) is a composition containing an N-vinyllactam crosslinked polymer and a surfactant, wherein the N-vinyllactam crosslinked polymer has structural units derived from an N-vinyllactam monomer and structural units derived from a crosslinkable monomer, and the proportion of the structural units derived from the N-vinyllactam monomer is 50 mol % or more and the proportion of the structural units derived from the crosslinkable monomer is 0.05 mol % or more relative to 100 mol % of the structural units derived from the non-crosslinkable monomer, and the surfactant is an ionic surfactant and / or a polyoxyalkylene glycol-type nonionic surfactant, and the content of the ionic surfactant is 10 mass % or less relative to 100 mass % of the solid content of the N-vinyllactam crosslinked polymer.

[0108] The content of the N-vinyl lactam crosslinked polymer in the composition of the present invention is not particularly limited, but is preferably 50 to 100% by mass, more preferably 60 to 100% by mass, and even more preferably 70 to 100% by mass, relative to 100% by mass of the composition.

[0109] The content of the ionic surfactant in the composition of the present invention is 10% by mass or less relative to 100% by mass of the solids content of the N-vinyl lactam crosslinked polymer. This sufficiently prevents the formation of lumps in the composition and also prevents the composition from becoming sticky. The content of the ionic surfactant is preferably 0.01 to 10% by mass, more preferably 0.05 to 8% by mass, even more preferably 0.1 to 5% by mass, and particularly preferably 0.2 to 3% by mass. Specific examples and preferred forms of the ionic surfactant are as described in the method for producing the N-vinyl lactam crosslinked polymer.

[0110] The total content of the ionic surfactant and polyoxyalkylene glycol-based nonionic surfactant in the composition of the present invention is not particularly limited as long as the content of the ionic surfactant is 10% by mass or less, but is preferably 0.01 to 10% by mass, more preferably 0.05 to 8% by mass, even more preferably 0.1 to 5% by mass, and particularly preferably 0.2 to 3% by mass, relative to 100% by mass of the solid content of the N-vinyl lactam crosslinked polymer.

[0111] When the composition of the present invention contains a polyoxyalkylene glycol-based nonionic surfactant, its content is not particularly limited, but is preferably 0.01 to 10% by mass, more preferably 0.05 to 8% by mass, even more preferably 0.1 to 5% by mass, and particularly preferably 0.2 to 3% by mass, relative to 100% by mass of the solid content of the N-vinyl lactam crosslinked polymer.

[0112] The composition of the present invention may contain other components in addition to the N-vinyl lactam crosslinked polymer and the ionic surfactant. The other components are not particularly limited, but examples thereof include water-soluble components (non-crosslinked polymer components that dissolve in water), polymerization initiator residues, residual monomers, polymerization by-products, moisture, etc., and the composition may contain one or more of these.

[0113] The N-vinyl lactam crosslinked polymer-containing composition contains, as a by-product during polymerization, a compound represented by the following formula (8):

[0114] [ka]

[0115] (In the formula, R 4represents a hydrogen atom or an alkyl group having 1 to 10 carbon atoms which may have a substituent. y represents an integer of 1 to 3. The composition may contain a compound represented by the formula (8), but the proportion of the compound is preferably 2% by mass or less relative to 100% by mass of the N-vinyl lactam crosslinked polymer. When the proportion of the compound represented by the formula (8) is 2% by mass or less, the odor and / or coloring of the composition can be sufficiently suppressed, and the composition can be suitably used as an air freshener. That is, the present invention also includes an N-vinyl lactam crosslinked polymer-containing composition in which the proportion of the compound represented by the above formula (8) is 2% by mass or less relative to 100% by mass of the N-vinyl lactam crosslinked polymer. The proportion of the compound represented by the above formula (8) is more preferably 1.5% by mass or less, and even more preferably 1% by mass or less. The proportion of the compound represented by the formula (8) in the composition can be measured by liquid chromatography. R in the above formula (8) 4 and y is R in the above formula (1). 4 and y.

[0116] The proportion of residual monomers such as N-vinyl lactam monomers in the composition is preferably 1000 ppm or less relative to 100% by mass of the N-vinyl lactam crosslinked polymer. If the proportion of residual monomers is within the above preferred range, the composition will be safer when used as an air freshener. The proportion of residual monomers is more preferably 500 ppm or less, and even more preferably 200 ppm or less. The proportion of the residual monomer in the composition can be measured by liquid chromatography.

[0117] The N-vinyl lactam crosslinked polymer-containing composition of the present invention contains an ionic surfactant in the above-mentioned ratio, so that it has low electrostatic charge and is sufficiently prevented from adhering to containers and the like. The composition of the present invention preferably has an absolute value of electrostatic charge of less than 21 nC as measured by the following method, more preferably less than 16 nC, and even more preferably less than 12 nC. <Method for measuring electrostatic charge> 20 g of the composition containing the N-vinyl lactam crosslinked polymer is placed in a SUS container and shaken 100 times in an insulated state, after which the amount of electrostatic charge is measured by the Faraday cage method using a coulomb meter.

[0118] (N-vinyl lactam crosslinked polymer) The N-vinyl lactam crosslinked polymer contained in the composition of the present invention (hereinafter also referred to as the crosslinked polymer of the present invention) has structural units derived from N-vinyl lactam monomers and structural units derived from crosslinkable monomers, and the proportion of the structural units derived from the N-vinyl lactam monomers is 50 mol % or more and the proportion of the structural units derived from the crosslinkable monomers is 0.05 mol % or more relative to 100 mol % of the structural units derived from non-crosslinkable monomers.

[0119] In the above-mentioned N-vinyl lactam crosslinked polymer, the proportion of structural units derived from N-vinyl lactam monomers is preferably 50 to 100 mol%, more preferably 60 to 100 mol%, even more preferably 70 to 100 mol%, still more preferably 80 to 100 mol%, still more preferably 90 to 100 mol%, particularly preferably 95 to 100 mol%, and most preferably 100 mol%, relative to 100 mol% of structural units derived from non-crosslinkable monomers. Specific examples and preferred forms of the N-vinyl lactam monomer are as described in the method for producing the N-vinyl lactam crosslinked polymer.

[0120] The N-vinyl lactam crosslinked polymer may have structural units derived from non-crosslinkable monomers other than N-vinyl lactam monomers, and the proportion thereof may be 50 mol% or less relative to 100 mol% of structural units derived from non-crosslinkable monomers, preferably 40 mol% or less, more preferably 30 mol% or less, even more preferably 20 mol% or less, still more preferably 10 mol% or less, particularly preferably 5 mol% or less, and most preferably 0 mol%.

[0121] In the N-vinyl lactam crosslinked polymer, the proportion of structural units derived from crosslinkable monomers is 0.05 mol % or more relative to 100 mol % of structural units derived from non-crosslinkable monomers. This gives the N-vinyl lactam crosslinked polymer excellent water absorption. The proportion of structural units derived from crosslinkable monomers is preferably 0.05 to 3.0 mol %, more preferably 0.06 to 2.0 mol %, even more preferably 0.08 to 1.0 mol %, and particularly preferably 0.1 to 0.75 mol %. Specific examples and preferred forms of the crosslinkable monomer are as described in the method for producing the N-vinyl lactam crosslinked polymer.

[0122] The crosslinked polymer of the present invention preferably has a water absorption capacity of 15 g or more (15 times or more) per gram of N-vinyl lactam crosslinked polymer, more preferably 18 g or more, and even more preferably 20 g or more. The crosslinked polymer of the present invention preferably has an oil absorption capacity of 3 g or more per 1 g of the crosslinked polymer, more preferably 5 g or more, even more preferably 10 g or more, still more preferably 15 g or more, and most preferably 20 g or more. The water and oil absorption capacity is a value calculated by "(weight of crosslinked polymer+amount of absorbed solution) / weight of crosslinked polymer".

[0123] The crosslinked polymer of the present invention preferably has a water-soluble content of 18% by mass or less relative to 100% by mass of the N-vinyl lactam crosslinked polymer. The water-soluble component is the non-crosslinked polymer component that dissolves in water. The crosslinked polymer of the present invention was stirred in approximately 100 times the amount of deionized water (electrical conductivity 10 μS / cm or less) at room temperature (23±2°C) and atmospheric pressure for 16 hours, and the amount of soluble components in the resulting solution was determined after filtration. If the water-soluble content is 18% by mass or less relative to 100% by mass of the N-vinyl lactam crosslinked polymer, gel crushing can be carried out more satisfactorily, and in this case, a kneader can be particularly suitably used. The present invention also includes an N-vinyl lactam crosslinked polymer having a water absorption capacity of 15 times or more and a water-soluble content of 18% by mass or less relative to 100% by mass of the N-vinyl lactam crosslinked polymer. The water-soluble content is more preferably 17% by mass or less, even more preferably 16% by mass or less, and even more preferably 15% by mass or less.

[0124] The N-vinyl lactam crosslinked polymer of the present invention preferably has an average particle size (D50) of 10 to 1000 μm. If the average particle size of the crosslinked polymer particles is 10 to 1000 μm, the liquid absorption rate of water and the like tends to be improved. Furthermore, if the average particle size is 10 μm or more, the water-soluble content in the crosslinked polymer can be more sufficiently reduced. The average particle size of the crosslinked polymer particles is more preferably 50 to 800 μm, and even more preferably 100 to 500 μm. The average particle size of the crosslinked polymer can be measured using a dry particle size distribution measuring device (Model: Mastersizer 3000 dry type, manufactured by the Malvern Division of Spectris Co., Ltd.).

[0125] In the N-vinyl lactam crosslinked polymer of the present invention, the proportion of particles having an aspect ratio of 1.15 to 10 is preferably 10 to 100% (number) of the total number of particles of the N-vinyl lactam crosslinked polymer. The proportion of particles having an aspect ratio of 1.15 to 10 is preferably 30 to 100% (number), more preferably 50 to 100% (number), even more preferably 70 to 100% (number), particularly preferably 90 to 100% (number), and most preferably 100% (number). The aspect ratio of the above particles is preferably 1.15 to 7, more preferably 1.15 to 5, even more preferably 1.2 to 5, and still more preferably 1.2 to 3. It is particularly preferably 1.25 to 3, and most preferably 1.25 to 2.5. The aspect ratio of the particles can be determined by measuring the major and minor axes of the primary particles of the N-vinyl lactam crosslinked product using a microscope (optical or electronic), and dividing the major axis by the minor axis to obtain the aspect ratio. Although the particles of the N-vinyl lactam crosslinked product may be aggregated, the aspect ratio is measured for the non-aggregated primary particles. When the primary particles overlap, only the non-overlapping particles are measured. The aspect ratio is calculated using image analysis particle size analysis software based on image data from an optical or electron microscope of the sample. Measurements can be made using image analysis particle size analysis software Mac-view ver.4 (manufactured by Mountec Co., Ltd.) or particle image analyzer Morphologi G3 (manufactured by the Malvern Division of Spectris Co., Ltd.), or similar image analysis software or image analyzer that operates on the same principle. The proportion of particles having an aspect ratio of 1.15 to 10 can be determined by measuring the aspect ratio of 100 or more randomly selected particles.

[0126] (Uses of the composition of the present invention) The N-vinyl lactam crosslinked product has excellent absorption capacity for water, oil, etc., and the composition of the present invention is sufficiently suppressed from becoming sticky or sticky, making it suitable for a variety of uses. The composition of the present invention can be used, for example, as a carrier for fragrance ingredients, deodorant ingredients, cosmetic ingredients, etc., a moisturizer, a thickener, a dispersant, a writing instrument, an ink absorbent, a latent heat storage material, etc. [Example]

[0127] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. Unless otherwise specified, "%" means "% by mass."

[0128] <Average particle size measurement method> The cumulative 50% value measured using a dry particle size distribution measuring device (Mastersizer 3000 dry type, manufactured by Spectris Co., Ltd., Malvern Division) was taken as the average particle size (D50). The measurement conditions are as follows: (Measurement conditions) Dry laser diffraction scattering method Dispersion pressure: 2 bar Particle refractive index: 1.52 Particle absorption rate: 0.01 Particle shape: non-spherical Solvent name: Air Measurement range: 0.1 to 3500 μm

[0129] [Manufacturing Example 1] A 10 L twin-arm kneader (Koike Iron Works Co., Ltd., Model LDS-50-0V) was charged with 1538.19 parts of N-vinylpyrrolidone (manufactured by Nippon Shokubai Co., Ltd., hereinafter also referred to as VP), 6.15 parts (0.18 mol % relative to VP) of triallyl cyanurate (CTA) as a crosslinkable monomer, and 3255.50 parts of deionized water. The mixture was then purged with nitrogen at a rate of 2 L / min for 30 minutes. The nitrogen introduction rate was then increased to 0.4 L / min, and the temperature was raised to 56 °C. After the liquid temperature stabilized at 56 °C, 35.82 parts (0.12 mol % relative to the total amount of VP and CTA) of an 11.2 wt % aqueous solution of 2,2'-azobis(2-methylpropionamidine) dihydrochloride (hereinafter also referred to as "V-50") was added as an initiator to initiate polymerization. Stirring was stopped immediately after the start of polymerization. When heat generation was observed, the bath temperature was raised to 80°C (the temperature increase took 26 minutes). Thereafter, the bath temperature was maintained at 80°C, and aging was carried out for 40 minutes, after which the polymerization was terminated. Stirring was then carried out for 4 minutes, and the resulting gel-like polymer (hydrogel) was crushed. Next, 52.15 g of a 30% aqueous solution of lauryldimethylaminoacetic acid betaine was added to the gel-like polymer, and after stirring for 6 minutes, the mixture was dried at 125°C for 130 minutes to obtain a dried crosslinked polymer. Next, the dried crosslinked polymer obtained was pulverized in a hammer mill to an average particle size (D50) of 200 to 400 μm, and a powdered crosslinked polymer was obtained.

[0130] [Manufacturing Examples 2 to 9] Polymerization was carried out in the same manner as in Production Example 1 above, and an additive selected from lauryldimethylaminoacetic acid betaine, lauric acid amidopropyl betaine, polyethylene glycol (average molecular weight approximately 600), trimethylstearylammonium chloride, and polyoxyethylene sorbitan monooleate was added in the same manner as in Production Example 1 above, or no additive was added. Next, drying and pulverization were carried out in the same manner as in Production Example 1 above, to obtain crosslinked polymers of Production Examples 2 to 9. The amounts of surfactants added in Production Examples 1 to 8 are as shown in Table 1 below.

[0131] [Table 1]

[0132] Test Example 1: Evaluation of antistatic properties The "antistatic properties" of the crosslinked polymers 1 to 9 produced in Production Examples 1 to 9 were evaluated by the following method. 20 g of the crosslinked polymer was placed in a SUS container and shaken 100 times in an insulated state, after which the amount of electrostatic charge was measured using a coulomb meter by the Faraday cage method. The antistatic properties were evaluated according to the following criteria. Judgment criteria Good: The absolute value of the electrostatic charge is less than 21 nC △ (fairly good): Absolute value of electrostatic charge is 21nC or more and less than 61nC × (Fail): The absolute value of the electrostatic charge is 61nC or more

[0133] [Test Example 2: Evaluation of anti-adhesion properties] The "anti-adhesion properties" of the crosslinked polymers 1 to 9 produced in Production Examples 1 to 9 were evaluated by the following method. The weight (W4 (g)) of the SUS container was measured, 20 g of cross-linked polymer was placed inside, and the container was shaken 100 times in an insulated state. The SUS container was turned upside down with the top lid open and struck 100 times to cause the powder inside to fall out. The weight (W5 (g)) of the SUS container with the powder attached was measured. The adhesion rate to the container was calculated according to the following formula: Adhesion rate to container (%): (W5(g)-W4(g)) / 20(g)×100 The adhesion prevention property was evaluated according to the following criteria. Judgment criteria Good (Good): Adhesion rate to container is less than 1% △ (fairly good): Adhesion rate to container is 1% or more but less than 5% × (Poor): Adhesion rate to container is 5% or more

[0134] [Test Example 3: Evaluation of stickiness] The "stickiness" of the crosslinked polymers 1 to 9 produced in Production Examples 1 to 9 was evaluated by the following method. The crosslinked polymer was picked up with a finger and rubbed with two fingers. Stickiness was evaluated according to the following criteria. Judgment criteria 〇 (Good): No stickiness △ (slightly good): Slight stickiness × (bad): Sticky

[0135] The results of evaluation of the crosslinked polymers 1 to 9 in the above Test Examples 1, 2 and 3 are shown in Table 2 below.

[0136] [Table 2]

[0137] The results in Table 2 above show that the crosslinked polymers of Examples 1 to 6 according to the present invention have better antistatic properties and improved antiadhesion properties than the crosslinked polymers of Comparative Examples 2 and 3. The crosslinked polymers of Examples 1 to 6 are also less sticky than Comparative Example 1. These results clearly show that the N-vinyl lactam crosslinked polymers according to the present invention, to which a specific surfactant has been added in a specific weight range, have improved antistatic properties and antiadhesion properties of the pulverized product, and are also free of stickiness.

Claims

1. A method for producing an N-vinyl lactam crosslinked polymer, comprising: The production method includes a step of polymerizing a monomer component including an N-vinyl lactam monomer and a crosslinkable monomer; adding a surfactant to the product obtained in the polymerization step; drying the product after the surfactant addition step; and grinding and / or classifying the product obtained in the drying step, the monomer component contains 50 mol % or more of an N-vinyl lactam monomer and 0.05 mol % or more of a crosslinkable monomer relative to 100 mol % of a non-crosslinkable monomer; The method for producing an N-vinyl lactam crosslinked polymer, wherein the surfactant is an ionic surfactant and / or a polyoxyalkylene glycol type nonionic surfactant.

2. The method for producing an N-vinyl lactam crosslinked polymer according to claim 1, wherein the crosslinkable monomer comprises at least one selected from the group consisting of triallyl cyanurate, pentaerythritol (di-, tri-, tetra-)(meth)allyl ether, and triallyl isocyanurate.

3. 3. The method for producing an N-vinyl lactam crosslinked polymer according to claim 1, wherein the ionic surfactant is an amphoteric surfactant.

4. The method for producing an N-vinyl lactam crosslinked polymer according to claim 3, wherein the amphoteric surfactant comprises an alkyl betaine and / or an alkylamido betaine.

5. 3. The method for producing an N-vinyl lactam crosslinked polymer according to claim 1, wherein the polyoxyalkylene glycol type nonionic surfactant is a polyoxyalkylene sorbitan fatty acid ester.

6. The method for producing an N-vinyl lactam crosslinked polymer according to claim 1 or 2, wherein the amount of surfactant added in the surfactant addition step is 0.01 to 10 mass% relative to 100 mass% of the solid content of the product obtained in the polymerization step.

7. A composition comprising an N-vinyl lactam crosslinked polymer and a surfactant, The N-vinyl lactam crosslinked polymer has a structural unit derived from an N-vinyl lactam monomer and a structural unit derived from a crosslinkable monomer, the proportion of structural units derived from the N-vinyl lactam monomer is 50 mol % or more and the proportion of structural units derived from the crosslinkable monomer is 0.05 mol % or more relative to 100 mol % of structural units derived from the non-crosslinkable monomer; The surfactant is an ionic surfactant and / or a polyoxyalkylene glycol-type nonionic surfactant, and the content of the ionic surfactant is 10% by mass or less relative to 100% by mass of the solid content of the N-vinyl lactam crosslinked polymer in the composition.

8. The N-vinyl lactam crosslinked polymer-containing composition according to claim 7, wherein the crosslinkable monomer comprises at least one selected from the group consisting of triallyl cyanurate, pentaerythritol (di-, tri-, tetra-) (meth) allyl ether, and triallyl isocyanurate.

9. 9. The N-vinyl lactam crosslinked polymer-containing composition according to claim 7, wherein the ionic surfactant is an amphoteric surfactant.

10. 10. The N-vinyl lactam crosslinked polymer-containing composition according to claim 9, wherein the amphoteric surfactant comprises an alkyl betaine and / or an alkylamido betaine.

11. 9. The N-vinyl lactam crosslinked polymer-containing composition according to claim 7, wherein the polyoxyalkylene glycol-type nonionic surfactant is a polyoxyalkylene sorbitan fatty acid ester.

12. 9. The N-vinyl lactam crosslinked polymer-containing composition according to claim 7, wherein the absolute value of the electrostatic charge measured by the following method is less than 21 nC. <Method for measuring electrostatic charge> 20 g of the composition containing an N-vinyl lactam crosslinked polymer is placed in an SUS container and shaken 100 times in an insulated state, after which the amount of electrostatic charge is measured by the Faraday cage method using a coulomb meter.

13. The N-vinyl lactam crosslinked polymer-containing composition according to claim 7 or 8, wherein the average particle size (D50) of the N-vinyl lactam crosslinked polymer measured by a dry particle size distribution measuring device is in the range of 10 to 1000 μm.

Images