JP7133302B2 - Method for producing N-vinyllactam polymer - Google Patents

Description

The present invention relates to a method for producing an N-vinyllactam polymer. More particularly, it relates to a method for producing an N-vinyllactam polymer useful for hollow fiber membranes such as artificial dialysis membranes.

N-vinyllactam polymers such as polyvinylpyrrolidone and vinylpyrrolidone copolymers, which are typical cyclic amide group-containing polymers, have advantages such as biocompatibility, safety, and hydrophilicity, and are therefore used as pharmaceuticals. , cosmetics, fiber modifiers, adhesives, paints, dispersants, dye solubilizers, inks, and electronic parts.
For example, in Patent Document 1, when a 2 wt % aqueous solution containing polyvinylpyrrolidone having a K value of 50 or more and 120 or less is filtered through a membrane filter having a pore size of 1.2 μm, the content of insoluble matter remaining on the filter is is 70 ppm or less.

Japanese Patent No. 5121470

As described above, Patent Document 1 discloses a polyvinylpyrrolidone powder composition having an insoluble content within a specific range, and discloses that the composition is used for various purposes. However, in applications such as artificial dialysis membranes, it is required to suppress gel formation among insolubles at a higher level. Conventional production methods are not sufficient in reducing gel formation, and there is room for improvement.

An object of the present invention is to provide a method for producing an N-vinyllactam polymer capable of sufficiently reducing gel formation.

The present inventors conducted various studies on a method for producing an N-vinyllactam polymer capable of sufficiently reducing gel formation, and found that a monomer component containing an N-vinyllactam monomer was used to initiate polymerization. In a production method comprising a step of polymerizing using an agent and a step of drying the polymer obtained in the polymerization step, from the start of the polymerization step to before the drying step, the monomer component and / or the polymer It was found that gel formation can be suppressed by setting the total time for which the temperature in the system including coalescence is 93° C. or higher to 90 minutes or longer. Specifically, the present inventors found that in the method for producing an N-vinyl lactam polymer, the drying step is carried out at a high temperature, and if the polymerization initiator remains in the drying step, radicals are generated from the remaining polymerization initiator. We found that it promotes gel formation. Then, as described above, from the start of the polymerization step to before the drying step, the total time during which the temperature in the system is 93 ° C. or higher is set to 90 minutes or more, so that the polymerization initiator can be added before the drying step. It has been found that the residual amount of is sufficiently reduced and the formation of gel is suppressed. In this way, the inventors have conceived that the above problems can be solved admirably, and arrived at the present invention.

That is, the present invention is a method for producing an N-vinyllactam polymer, the production method comprising a step of polymerizing a monomer component containing an N-vinyllactam monomer using a polymerization initiator. and a step of drying the polymer obtained in the polymerization step, and the temperature in the system containing the monomer component and / or polymer is 93 ° C. between the start of the polymerization step and before the drying step. It is a method for producing an N-vinyl lactam polymer, wherein the total time of the above is 90 minutes or more.

In the polymerization step, the temperature in the reaction system is preferably 40 to 80° C. when the polymerization initiator is added.
The amount of the polymerization initiator used is preferably 0.07 to 0.7% by mass with respect to 100% by mass of the total monomers.
The polymerization initiator is preferably an azo compound.
The drying step is preferably performed by a drum dryer method.

The present invention also provides a composition containing an N-vinyllactam polymer, wherein the total number of gel particles having a diameter of 2 μm or more and less than 10 μm per 0.1 g of the N-vinyllactam polymer is 1200. It is also an N-vinyl lactam polymer-containing composition having a number of 1 or less.
The N-vinyllactam polymer preferably has a K value of 60 to 100 according to the Fikentscher method.

The method for producing an N-vinyllactam polymer of the present invention has the above-described configuration, and can sufficiently suppress the formation of gel (gel particles) in the resulting N-vinyllactam polymer. It can be suitably used for films and the like.

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 without changing the gist of the present invention. In addition, the form which combined 2 or 3 or more of each preferable form of this invention described below also corresponds to the preferable form of this invention.

The method for producing an N-vinyllactam polymer of the present invention comprises a step of polymerizing a monomer component containing an N-vinyllactam monomer using a polymerization initiator (hereinafter also referred to as a polymerization step); a step of drying the polymer obtained in the polymerization step (hereinafter also referred to as a drying step), and from the start of the polymerization step to before the drying step, a system containing a monomer component and / or a polymer The total time during which the internal temperature is 93°C or higher is 90 minutes or longer.
The time during which the temperature in the system containing the monomer component and/or polymer is 93° C. or higher is 90 minutes or longer in total from the start of the polymerization step to the drying step, even if it is continuous. It can be intermittent.
By setting the temperature in the system to 93° C. or higher, the amount of residual initiator can be reduced, and the number of gels generated in the drying process can be reduced.
The total time is preferably 120 minutes or longer, more preferably 150 minutes or longer, still more preferably 180 minutes or longer, and particularly preferably 210 minutes or longer. Moreover, it is usually preferable that the time is 420 minutes or less.
The temperature in the system containing the monomer component and/or polymer is preferably 94 to 100°C, more preferably 95 to 100°C.
In the present invention, the "time point at which the polymerization step is started" refers to the time point at which both at least a portion of the monomer components and at least a portion of the initiator are added to the reaction system (reactor). "End of process" shall refer to the end of the polymerization reaction.

The polymerization step is characterized by polymerizing the monomer components using a polymerization initiator.
The polymerization initiator is not particularly limited, but hydrogen peroxide, peroxides such as 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(2,4-dimethylvaleronitrile) ), 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-imidazolin-2-yl)propane]disulfate hydrate, 2,2′-azobis(1-imino-1-pyrrolidino-2-methylpropane) dihydrochloride, 2,2′-azobis[N-( 2-carboxyethyl)-2-methylpropionamidine]n hydrate, 2,2′-azobis[2-methyl-N-(2-hydroxyethyl)propionamide] and other azo compounds; benzoyl peroxide, peroxide Organic peroxides such as lauroyl oxide, peracetic acid, di-t-butyl peroxide, and cumene hydroperoxide; ascorbic acid and hydrogen peroxide, sodium sulfoxylate and t-butyl hydroperoxide, persulfates and metal salts, etc. and a redox initiator that generates radicals by combining an oxidizing agent and a reducing agent. Among these polymerization initiators, hydrogen peroxide, persulfates and azo compounds are preferred, and azo compounds are more preferred.
Since the azo compound has a decomposition rate within a suitable range at 93 to 100° C., it is possible to sufficiently suppress the remaining amount of the polymerization initiator before the drying step. The 10-hour half-life temperature (in water or toluene) of the azo compound is preferably 40 to 90°C. It is more preferably 50 to 70°C.
The residual amount of the polymerization initiator is so small that it cannot be quantified. can be approximated.

Among the above azo compounds, 2,2′-azobis[2-(2-imidazolin-2-yl)propane], 2,2′-azobis[N-(2-carboxyethyl)-2-methylpropionamidine] hydrate, dimethyl 2,2'-azobis(2-methylpropionate), 2,2'-azobis(isobutyronitrile), 2,2'-azobis(2-methylbutyronitrile), 2, 2′-Azobis[N-(2-carboxyethyl)-2-methylpropionamidine]hydrate and 2,2′-azobis(2,4-dimethylvaleronitrile) are more preferred. Since these compounds are highly safe, the resulting N-vinyllactam polymer can be suitably used for medical applications such as artificial dialysis membranes. These polymerization initiators may be used alone or in the form of a mixture of two or more.

The amount of the polymerization initiator used is preferably 0.07 to 0.7% by mass with respect to 100% by mass of the total monomers. Thereby, the residual amount of the polymerization initiator can be sufficiently reduced before the drying step. The amount of the polymerization initiator used is more preferably 0.08 to 0.5% by mass, still more preferably 0.09 to 0.4% by mass, and particularly preferably 0.1 to 0.3% by mass. be.

The method of adding the polymerization initiator to the reaction system may be a method of adding all at once or a method of adding sequentially, but the method of adding all at once is preferred. As a result, the remaining amount of the polymerization initiator can be sufficiently reduced before the drying step, and the K value according to the Fikentscher method can be set in a range suitable for use as an artificial dialysis membrane.

In the above production method, the total time during which the temperature in the system containing the monomer component and/or polymer is 93 ° C. or higher from the start of the polymerization step to before the drying step is 90 minutes or more. However, it is preferable that the temperature in the reaction system is 40 to 80° C. when the polymerization initiator is added.
Thereby, the K value of the polymer can be more sufficiently controlled, and the residual amount of the polymerization initiator can be more sufficiently reduced before the drying step. The temperature in the reaction system during the addition of the polymerization initiator is more preferably 50 to 80°C, still more preferably 60 to 80°C.

In the above production method, the total time during which the temperature in the system containing the monomer component and/or polymer is 93 ° C. or higher from the start of the polymerization step to before the drying step is 90 minutes or more. However, the polymerization temperature in the polymerization step is preferably 50-100°C, more preferably 60-100°C.

In the above polymerization step, when a solvent is used, examples of the solvent include one or more selected from alcohols such as water, methyl alcohol, ethyl alcohol, isopropyl alcohol, n-butyl alcohol and diethylene glycol. . Water is preferred as the solvent.

In the polymerization step, the pH during polymerization (that is, the pH of the polymerization solution used for polymerization) is preferably 4 or more, more preferably 6 or more, from the viewpoint of sufficiently suppressing impurities or by-products. Moreover, 11 or less are preferable.

In the polymerization step, the pressure in the reaction system may be under normal pressure (atmospheric pressure), under reduced pressure, or under increased pressure. It is preferable to seal the inside of the system and perform the reaction under pressure. Moreover, it is preferable to carry out under normal pressure (atmospheric pressure) in terms of equipment such as a pressurizing device, a decompressing device, a pressure-resistant reaction vessel, and piping.
The atmosphere in the reaction system may be an air atmosphere, but is preferably an inert atmosphere. A polymerization step is preferably carried out.

The monomer component used in the polymerization step includes an N-vinyllactam monomer.
The N-vinyllactam-based monomer is not particularly limited as long as it is a monomer having an N-vinyllactam structure, but the following formula (1);

(Wherein, R ¹ , R ² , R ³ and R ⁴ are the same or different and represent a hydrogen atom or an alkyl group having 1 to 10 carbon atoms. x represents an integer of 0 to 4. y represents represents an integer of 1 to 3.) is preferred.
The number of carbon atoms in the alkyl group for R ¹ to R ⁴ is preferably 1 to 6, more preferably 1 to 4. More preferably, the alkyl group is a methyl group or an ethyl group, and particularly preferably a methyl group.
R ¹ to R ³ are preferably hydrogen atoms. ^R4 is preferably a hydrogen atom or a methyl group, more preferably a hydrogen atom.
x is preferably an integer of 0 to 2, more preferably an integer of 0 to 1, and most preferably 0.
y is preferably 1 or 2, more preferably 1.

Examples of compounds represented by the above formula (1) include N-vinylpyrrolidone, N-vinyl-5-methylpyrrolidone, N-vinylpiperidone, N-vinylcaprolactam, 1-(2-propenyl)-2-pyrrolidone, and the like. and can be used alone or in combination of two or more. As the N-vinyllactam, an unsaturated monomer having a pyrrolidone ring is preferred. More preferred is N-vinylpyrrolidone.

The above monomer component may contain other monomers than the N-vinyllactam monomer.
The other monomer is not particularly limited as long as it is a compound that can be copolymerized with an N-vinyllactam monomer, has no lactam structure, and has one ethylenically unsaturated hydrocarbon group. (i) unsaturated monocarboxylic acids such as acrylic acid and methacrylic acid and salts thereof; (ii) unsaturated dicarboxylic acids such as fumaric acid, maleic acid, methyleneglutaric acid and itaconic acid and salts thereof (monosalts); (iii) unsaturated sulfonic acids such as 3-allyloxy-2-hydroxypropanesulfonic acid, (meth)allylsulfonic acid, isoprenesulfonic acid and salts thereof; (iv) Hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, 3-(meth)allyloxy-1,2-dihydroxypropane, (meth)allyl alcohol, isoprenol and other unsaturated alcohols and alkylenes obtained by adding alkylene oxide to the hydroxyl groups of these Oxide adduct; (v) (meth)acrylic acid esters such as methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, and cyclohexyl (meth)acrylate; (vi) (meth) N-substituted or unsubstituted (meth)acrylamides such as acrylamide, N-monomethyl(meth)acrylamide, N-monoethyl(meth)acrylamide, N,N-dimethyl(meth)acrylamide; (vii) styrene, indene, vinylaniline, etc. (viii) alkenes such as ethylene, propylene, butadiene, isobutylene and octene; (ix) vinyl carboxylates such as vinyl acetate and vinyl propionate; (x) N,N-dimethylaminoethyl Unsaturated amines such as (meth)acrylates, N,N-dimethylaminoethyl (meth)acrylamide, vinylpyridine, vinylimidazole and salts thereof or quaternized products thereof; (xi) vinylformamide, vinylacetamide, vinyloxazolidone, etc. (xii) unsaturated anhydrides such as maleic anhydride and itaconic anhydride; (xiii) vinyl ethylene carbonate and derivatives thereof; (xiv) ethyl (meth)acrylate-2-sulfonate and derivatives thereof; (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 use only 1 type and may use 2 or more types together.
Examples of the salts in (i) to (iii) and (x) are metal salts, ammonium salts, organic amine salts, and the like. The alkylene oxide in (iv) is exemplified by ethylene oxide, propylene oxide and the like, preferably an alkylene oxide having 1 to 20 carbon atoms, more preferably an alkylene oxide having 1 to 4 carbon atoms. The number of moles of the alkylene oxide to be added in (iv) is preferably 0 to 50 mol, more preferably 0 to 20 mol, per 1 mol of the compound (iv).

As the above other monomers, monomers having 2 to 20 carbon atoms are preferable. A monomer having 2 to 15 carbon atoms is more preferred, and a monomer having 2 to 10 carbon atoms is even more preferred. In addition, when the other monomer is an alkylene oxide adduct, the number of carbon atoms in the structural portion other than the alkylene oxide structural portion preferably has these values.

The proportion of the N-vinyl lactam monomer contained in the above monomer component is preferably 50 to 100 mol % with respect to 100 mol % of the total monomer component. More preferably 60 to 100 mol%, still more preferably 70 to 100 mol%, still more preferably 80 to 100 mol%, particularly preferably 90 to 100 mol%, most preferably 100 mol% is.

The ratio of other monomers contained in the above monomer component is preferably 0 to 50 mol% with respect to 100 mol% of the total monomer component. More preferably 0 to 40 mol%, still more preferably 0 to 30 mol%, still more preferably 0 to 20 mol%, particularly preferably 0 to 10 mol%, most preferably 0 mol% is.

In the above production method, the total time during which the system containing the monomer component and/or the polymer is at a temperature of 93 ° C. or higher from the end of the addition of the polymerization initiator to the drying step is 60 to 420 minutes. Preferably. Thereby, the residual amount of the polymerization initiator can be reduced more efficiently.
More preferably 90 to 420 minutes, even more preferably 150 to 360 minutes, still more preferably 180 to 300 minutes.

The production method of the present invention preferably includes an aging step (meaning a step of keeping the polymer under heating/heat-retaining conditions after polymerization) for the purpose of reducing the amount of monomers. The polymerization process of the present invention, as described above, starts when both at least part of the monomer components and at least part of the initiator are added into the reaction system (reactor). After the start of the polymerization step (polymerization reaction), the temperature in the reaction system rises due to the heat of polymerization, and after reaching the maximum temperature, the temperature falls. After that, the temperature of the heat medium such as the jacket temperature is increased, and the time when the temperature in the reaction system stops falling is defined as the start time of the aging process.
As described above, the polymerization step in the production method of the present invention ends at the end of the polymerization reaction, so the aging step is included in the polymerization step as long as the polymerization reaction continues.
The aging time is not particularly limited, but preferably 30 minutes to 5 hours, more preferably 1 to 3 hours. In the aging step, the temperature in the system may not always be constant, but the total time during which the temperature in the system containing the polymer is 93° C. or higher is preferably 30 minutes to 5 hours. Thereby, the remaining amount of the polymerization initiator can be sufficiently reduced before the drying step.

The production method of the present invention preferably includes a step of adding an organic acid to the obtained polymer (polymer). This makes it possible to reduce the amount of N-vinyllactam monomers remaining in the polymer.
The timing of performing the step of adding the organic acid is not particularly limited as long as it is after the start of the polymerization step and before the drying step, but it is preferably after the start of the aging step.
As described above, the polymerization step in the production method of the present invention ends at the end of the polymerization reaction, so as long as the polymerization reaction is in progress, the addition step of the organic acid is also included in the polymerization step. Become.
Examples of the organic acid include, but are not limited to, organic compounds having an acid group such as a carboxyl group, a sulfonic acid group, a phosphonic acid group, a sulfuric acid group, and a phosphoric acid group. 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, laurylsulfuric acid and the like. .

The amount of the organic acid to be used is not particularly limited, but is preferably 0.01 to 3% by mass with respect to 100% by mass of the N-vinyllactam 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-vinyllactam monomer remaining in the resulting polymer. The amount of the organic acid used is more preferably 0.03 to 1% by mass, still more preferably 0.05 to 0.5% 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 a neutralized product of the organic acid and the base added mainly in the neutralization step described later.

When the organic acid is added to an N-vinyllactam polymer that may contain an N-vinyllactam monomer, the reaction time between the organic acid and the N-vinyllactam monomer is not particularly limited. is preferably 10 minutes to 3 hours. More preferably, it is 30 minutes to 2 hours.
Although the reaction temperature between the organic acid and the N-vinyllactam monomer is not particularly limited, it is preferably 93° C. or higher. Thereby, the residual amounts of the polymerization initiator and the N-vinyllactam-based monomer can be sufficiently reduced. That is, it is also one of preferred embodiments of the present invention to perform the organic acid addition step at 93° C. or higher. More preferably, the temperature in the reaction system is 93° C. or higher for 30 to 100% of the 100% of the time from the start of addition of the organic acid to the addition of the base described later. More preferably, the temperature in the reaction system is kept at 93° C. or higher throughout the period from the start of addition of the organic acid to the addition of the base.
The reaction temperature between the organic acid and the N-vinyllactam monomer is more preferably 94 to 100°C, still more preferably 95 to 100°C.

When the production method of the present invention includes the organic acid addition step, it preferably includes a neutralization step after the organic acid addition step. Although the neutralization method is not particularly limited, it is preferable to add a base after reacting the N-vinyllactam monomer with the organic acid. The above base is not particularly limited, but for example, ammonia; aliphatic amines such as monoethanolamine, diethanolamine and triethanolamine; aromatic amines such as aniline; alkali metal hydroxides such as sodium hydroxide and potassium hydroxide etc. These may use only 1 type and may use 2 or more types together. Among these, ammonia, aliphatic amines and hydroxides of alkali metals are preferred, ammonia, monoethanolamine, diethanolamine, sodium hydroxide and potassium hydroxide are more preferred, and diethanolamine is even more preferred.

The production method preferably includes a step of adding an antioxidant to the polymer obtained in the polymerization step before the drying step. This prevents the generation of radicals from the residual polymerization initiator in the drying step and/or stops the chain reaction of the radicals generated from the residual initiator, thereby more sufficiently suppressing gel formation. The step of adding the antioxidant is not particularly limited as long as it is performed before the drying step, and may be performed during the polymerization reaction or after the polymerization reaction. When it contains, it is preferable to include the step of adding an antioxidant after the neutralization step.
The antioxidant is not particularly limited as long as it suppresses the generation of radicals in the drying process, and the antioxidant includes antioxidants, reducing agents, and the like.
Examples of the antioxidant include sodium salicylate, 2,4-dihydroxybenzophenone, 2,6-di-t-butyl-p-cresol, butylated hydroxyanisole (butylated hydroxyanisole), 2,6-di-t -butyl-4-methylphenol, 2,6-di-t-butyl-4-ethylphenol, stearyl-β-(3,5-di-t-butyl-4-hydroxyphenyl)propionate, 3,4,5 - phenolic antioxidants such as trihydroxybenzoic acid propyl ester, hydroquinone, catechol, dibutylhydroxytoluene; ethyl-6-t-butylphenol), 4,4'-thiobis(3-methyl-6-t-butylphenol), 4,4'-butylidenebis(3-methyl-6-t-butylphenol), 3,9-bis [1,1-dimethyl-2-[β-(3-t-butyl-4-hydroxy-5-methylphenyl)propionyloxy]ethyl]-2,4,8,10-tetraoxaspiro[5,5] Bisphenol antioxidants such as undecane, 4,4′-(2,3-dimethyltetramethylene) dipyrocatechol; 1,1,3-tris(2-methyl-4-hydroxy-5-t-butylphenyl) butane, 1,3,5-trimethyl-2,4,6-tris(3,5-di-t-butyl-4-hydroxybenzyl)benzene, tetrakis[methylene-3-(3′,5′-di- t-butyl-4′-hydroxyphenyl)propionate]methane, bis[3,3′-bis(4′-hydroxy-3′-t-butylphenyl)butyric acid] glycol ester, 1,3,5-tris(3 ',5'-di-t-butyl-4'-hydroxybenzyl)-s-triazine-2,4,6-(1H,3H,5H)trione, polymeric phenolic antioxidants such as tocopherols;

Dilauryl-3,3'-thiodipropionate, dimyristyl-3,3'-thiodipropionate, distearyl-3,3'-thiodipropionate, 2-mercaptobenzimidazole, tetrakismethylene-3-(laurylthio ) Propionate methane, sulfur-based antioxidants such as stearylthiopropylamide; -butylphenylditridecyl)phosphite, cyclic neopentanetetraylbis(octadecyl)phosphite, tris(nonylphenyl)phosphite, tris(mono and/or dinonylphenyl)phosphite, diisodecylpentaerythritol diphosphite, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, 10-(3,5-di-t-butyl-4-hydroxybenzyl)-9,10-dihydro-9-oxa-10 -phosphaphenanthrene-10-oxide, 10-decyloxy-9,10-dihydro-9-oxa-10-phosphaphenanthrene, tris(2,4-di-t-butylphenyl)phosphite, cyclic neopentanetetra ylbis(2,6-di-t-butyl-4-methylphenyl)phosphite, 2,2-methylenebis(4,6-di-t-butylphenyl)octylphosphite, distearylpentaerythritol diphosphite, Phosphorus antioxidants such as di(2,4-di-t-butylphenyl)phosphite, tetrakis(2,4-di-t-butylphenyl)-4,4-biphenylene phosphite; erythorbic acid, erythorbic acid alcohol-based antioxidants such as sodium and isopropyl citrate; , N'-diphenyl-p-phenylenediamine and other amine antioxidants; 4-benzoyloxy-2,2,6,6-tetramethylpiperidine, bis(2,2,6,6-tetramethyl-4- piperidinyl) sebacate, bis (1-octyloxy-2,2,6,6-tetramethyl-4-piperidinyl) sebacate, bis (1,2,2,6,6-pentamethyl-4- piperidinyl) sebacate, dimethyl-1-(2-hydroxyethyl)-4-hydroxy-2,2,6,6-tetramethylpiperidine succinate and its condensates, 8-acetyl-3-dodecyl-7,7,9 ,9-tetramethyl-1,3,8-triazaspiro[4,5]decane-2,4-dione and other hindered amine antioxidants; benzotriazole, methylbenzotriazole potassium salt and other triazole antioxidants; vitamins A, vitamin C, vitamin E, vitamins such as vitamin Q, and the like.

The antioxidant preferably has a solubility of 30 g or more in 100 g of N-methylpyrrolidone at 25°C. When the N-vinyllactam polymer is used for the artificial dialysis membrane, the polymer is dissolved in a solvent and spun. If the solubility in N-methylpyrrolidone is within the above range, it is possible to suppress the insoluble matter of the antioxidant from remaining as an impurity, and it is possible to sufficiently reduce the residue on ignition, so that the obtained N-vinyl lactam The system polymer can be preferably used for applications such as artificial dialysis membranes. The ignition residue can be measured by the method described later.
The solubility of the antioxidant in 100 g of N-methylpyrrolidone at 25° C. is more preferably 35 g or more, still more preferably 40 g or more, even more preferably 45 g or more, and particularly preferably 50 g or more.
From the viewpoint of the solubility of the antioxidant in N-methylpyrrolidone, the antioxidant preferably does not contain a salt such as a sodium salt. As a result, the residue on ignition of the N-vinyllactam polymer can be suppressed more sufficiently.

Antioxidants having solubility in N-methylpyrrolidone within the above range include, for example, the above vitamins, dibutylhydroxytoluene, butylhydroxyanisole, benzotriazole, 2-mercaptobenzimidazole, N,N'-di-sec- Butyl-p-phenylenediamine may be mentioned.
As the antioxidant, vitamins, dibutylhydroxytoluene, and N,N'-di-sec-butyl-p-phenylenediamine are preferable from the viewpoint of safety. Vitamin E is more preferred.

The amount of the antioxidant added is not particularly limited, but is preferably 50 to 3000 mg/kg based on the mass of the N-vinyllactam polymer. As a result, the generation of radicals in the drying step can be more sufficiently suppressed, and the remaining of the antioxidant as an impurity can be sufficiently suppressed. More preferably 80 to 2500 mg/kg, still more preferably 100 to 2000 mg/kg.

The production method preferably includes a step of filtering the polymer obtained in the polymerization step before the drying step. This makes it possible to more sufficiently remove insoluble matter in the polymer. The method of the filtration step is not particularly limited, but it is preferable to filter the polymer (polymer solution) obtained in the polymerization step as it is or after diluting it to an appropriate concentration using a filter. The pore size of the filter used for filtration is preferably 2 μm or more and 100 μm or less, more preferably 4 μm or more and 50 μm or less.

The production method includes a step of drying the polymer obtained in the polymerization step. Although the method of the drying step is not particularly limited, it is preferable to dry the polymer (polymer solution) using a heated surface contact dryer. The drying temperature and time are not particularly limited, and may be appropriately adjusted according to the amount of the polymer solution and the like. ℃ or less. The drying time is preferably within 1 hour, more preferably within 30 minutes, and even more preferably within 10 minutes.
Examples of heating surface contact type dryers include drum dryers, belt dryers, disk dryers, and the like. Among them, a drum dryer is preferable because it is excellent in thermal efficiency, rapidity, and continuous operability. That is, it is one of preferred embodiments of the present invention to carry out the drying step by the drum dryer method.
Examples of the drum dryer include, but are not particularly limited to, a single drum dryer, a double drum dryer, and a twin drum dryer.

The production method preferably includes a step of pulverizing the polymer after the drying step.
Pulverization of the above polymer may be carried out by a commonly used method, for example, a dry coarse pulverization method using a pin mill or hammer mill; a dry fine pulverization method using a jet mill, roller mill, ball mill, micron mill or the like; be done. The pulverization conditions are not particularly limited, and may be appropriately set so as to obtain the desired particle size according to the use of the polymer.

The present invention also provides a composition containing an N-vinyllactam polymer, wherein the total number of gel particles having a diameter of 2 μm or more and less than 10 μm per 0.1 g of the N-vinyllactam polymer is 1200. It is also an N-vinyl lactam polymer-containing composition having a number of 1 or less.
The method for producing the N-vinyllactam polymer-containing composition is not particularly limited, but it can be produced by the method for producing an N-vinyllactam polymer of the present invention.
The number of gel particles can be measured by the method described in Examples.
The total number of the gel particles is preferably 1000 or less, more preferably 800 or less, even more preferably 500 or less, still more preferably 300 or less.

The N-vinyllactam polymer preferably has a K value of 60 to 100 according to the Fikentscher method. As a result, the N-vinyllactam polymer can be used more preferably in artificial dialysis membranes and the like. The K value is more preferably 65-95, still more preferably 70-95.

The K value according to the Fikentscher method can be obtained by the following measuring method.
If the K value is less than 20, measure the viscosity of a 5% (g/100ml) solution, and if the K value is 20 or more, measure the viscosity of a 1% (g/100ml) solution.
The sample concentration is converted to dry matter.
When the K value is 20 or more, accurately weigh 1.0 g of the sample, put it in a 100 ml volumetric flask, add distilled water at room temperature, dissolve completely while shaking, and add distilled water to make exactly 100 ml. do. After leaving this sample solution in a constant temperature bath (25±0.2° C.) for 30 minutes, the viscosity is measured using an Ubbelohde viscometer. The time for the solution to flow between the two marked lines (solution flow time) is measured. Measure several times and take the average value. Distilled water is also measured in order to determine the relative viscosity (flow time of water). The two resulting flow times are corrected based on the Hagenbach-Couette correction. If the K value is less than 20, the flow time of the solution is determined in the same manner as above, except that the mass of the sample is 5.0 g.
From the flow times of the solution and water thus measured, the K value is calculated by the following formula.

In the above formula, Z represents the relative viscosity (ηrel) of the solution of concentration C. C is concentration (%: g/100 ml).
Relative viscosity ηrel is obtained by the following equation.
ηrel = (flow time of solution)/(flow time of water)

The composition containing the N-vinyllactam polymer preferably has a solubility of 30 g or more in 100 g of N-methylpyrrolidone at 25°C. When an N-vinyllactam polymer is used for an artificial dialysis membrane, the polymer is dissolved in a solvent and spun, so if the solubility in N-methylpyrrolidone is within the above range, it is more suitable for applications such as an artificial dialysis membrane. be able to. More preferably, the solubility is 40 g or more, and still more preferably 50 g or more.

The composition preferably has a residue on ignition of 200 mg/kg or less based on the mass of the N-vinyllactam polymer. The residue on ignition may remain as an insoluble matter when the polymer is dissolved in a solvent and spun, but if the residue on ignition is within the above range, the insoluble matter can be sufficiently reduced, The resulting N-vinyllactam polymer can be preferably used for applications such as artificial dialysis membranes.
It is more preferably 150 mg/kg or less, still more preferably 100 mg/kg or less.
The residue on ignition can be measured according to the Japanese Pharmacopoeia 16th Edition General Tests 2.44 Test Method for Residue on Ignition.

EXAMPLES The present invention will be described in more detail with reference to examples below, but the present invention is not limited only to these examples. Unless otherwise specified, "part" means "mass part" and "%" means "mass %".

<Measurement of number of gel particles>
Dilute the N-vinyllactam polymer with ultrapure water so that the solid content of the N-vinyllactam polymer becomes 1% (concentration on a dry matter basis), and place in a 100 ml mayonnaise bottle on a rotary shaker. was dissolved using The amount of gel in 10 ml of the prepared 1% N-vinyllactam polymer aqueous solution was measured under the following conditions.
Measuring device: Particle Measuring Systems APSS-2000 (manufactured by Spectris Co., Ltd.)
One measurement volume: 10ml
Number of measurements: 5 times (the average of 5 times was taken as the measured value)
Measured particle diameter: 2 μm or more and less than 10 μm (total number of particles of 2 to 3, 3 to 5, 5 to 10 μm)

<Measurement of solid content of N-vinyl lactam polymer>
About 1 g of the crosslinked polymer (mass W2 (g)) is weighed into a weighing can (mass W1 (g)) having a bottom diameter of about 5 cm, left to stand for 1 hour in a windless dryer at 150 ° C., and dried. let me The mass (W3 (g)) of the weighing can after drying and the crosslinked polymer was measured, and the solid content was obtained from the following formula.
Solid content (% by mass) = ((W3 (g) - W1 (g)) / W2 (g)) x 100

<Example 1 and Comparative Example 1>
Polyvinylpyrrolidone was produced as follows, and the number of gel particles and the residue on ignition were measured. Table 1 shows the results.
160 parts of N-vinylpyrrolidone (manufactured by Nippon Shokubai Co., Ltd., hereinafter also referred to as VP) in a 1 L reactor (SUS304) equipped with a Maxblend stirring blade (SUS304), a thermometer, a reflux tube, and a jacket, 636 parts of deionized water was charged, and 0.02 part of diethanolamine was added to adjust the pH of the aqueous monomer solution to 8.3. While stirring the aqueous monomer solution at 250 rpm, nitrogen substitution was performed at 200 ml/min for 30 minutes to remove dissolved oxygen. Next, while introducing nitrogen at 30 ml/min and stirring at 250 rpm, the reactor was heated to an internal temperature of 75°C. After the liquid temperature was stabilized at 75° C., 0.38 parts of 2,2′-azobis(2-methylbutyronitrile) (hereinafter also referred to as “V-59”) was dissolved in 3.5 parts of isopropanol for polymerization. An initiator solution was added to initiate polymerization. After the polymerization initiator solution was added, the reaction was carried out with the jacket temperature adjusted to match the inner temperature (inner temperature +0.3 to 2° C.) from the time when an increase in the inner temperature due to the polymerization reaction was observed. After 14 minutes from the addition of the polymerization initiator solution, the internal temperature reached 93° C., the temperature further increased, and after the internal temperature reached the maximum temperature, the temperature was observed to drop. After that, in Example 1, the inner temperature was maintained at 95° C. by adjusting the jacket temperature. In Comparative Example 1, the temperature decreased to 93°C 68 minutes after the addition of the polymerization initiator solution, and then the inner temperature was maintained at 90°C by adjusting the jacket temperature.
After continuing the reaction for 3 hours after adding the polymerization initiator solution, an acid aqueous solution obtained by dissolving 0.14 parts of malonic acid in 1.3 parts of deionized water was added to adjust the reaction solution to pH 4 or less, The internal temperature was maintained at 95° C. in Example 1 and at 90° C. in Comparative Example 1 for 90 minutes.
Then, an alkaline aqueous solution obtained by dissolving 0.24 parts of diethanolamine in 2.2 parts of deionized water was added to adjust the pH of the reaction solution to 6 to 7. The internal temperature was maintained at °C for 30 minutes. After that, the inner temperature of the reactor decreased as the jacket temperature was decreased, and in Example 1, the temperature passed 93°C 302 minutes after the addition of the polymerization initiator solution. An aqueous polymer solution containing about 20% polyvinylpyrrolidone was thus obtained.

The polyvinylpyrrolidone aqueous solution obtained in the above polymerization step was dried with a heated surface contact dryer. A drum dryer having a rotating drum (manufactured by Katsuragi Industry Co., Ltd.) was used as the heating surface contact type dryer. A feed roll was attached to the drum dryer, and the polymer solution was supplied to the feed roll. The supply amount was adjusted so that the amount of the polymer solution remaining between the feed roll and the rotating drum was constant. Steam was introduced into the rotating drum to bring the temperature of the heat transfer surface of the drum to 140°C. Further, the rotary drum was rotated at a constant speed so as to make one revolution in 40 seconds, and the feed roll was rotated so that the peripheral speed of the outer peripheral portion of the feed roll was equal to the peripheral speed of the outer peripheral portion of the rotary drum.
A sheet-like dried polyvinylpyrrolidone product was obtained by scraping off the dried product with a scraper located at a position rotated for 20 to 30 seconds from the supply portion of the polymer solution in the rotating drum. The obtained dried sheet material was pulverized with a mixer to obtain powdery polyvinylpyrrolidone.

Using the obtained powdery polyvinylpyrrolidone, the number of gel particles per 0.1 g of the N-vinyllactam polymer was measured.
Furthermore, the residue on ignition of the obtained powdery polyvinylpyrrolidone was measured according to the Japanese Pharmacopoeia 16th Edition General Tests 2.44 Test Method for Residue on Ignition.

Claims (9)

A method for producing an N-vinyl lactam polymer, comprising:
The production method includes a step of polymerizing a monomer component containing an N-vinyllactam monomer using a polymerization initiator and a step of drying the polymer obtained in the polymerization step,
The total time during which the temperature in the system containing the monomer component and/or the polymer is 93° C. or higher from the start of the polymerization step to the drying step is 90 minutes or more,
In the polymerization step, the temperature in the reaction system at the time of addition of the polymerization initiator is 60 to 80 ° C.,
A method for producing an N-vinyllactam polymer, wherein the drying step is performed by a drum dryer method. The production of the N-vinyl lactam polymer according to claim 1, wherein the amount of the polymerization initiator used is 0.07 to 0.7% by mass based on 100% by mass of the total monomers. Method. 3. The method for producing an N-vinyllactam polymer according to claim 1, wherein the polymerization initiator is an azo compound. The method for producing an N-vinyllactam polymer according to claim 3, wherein the azo compound has a 10-hour half-life temperature of 40 to 90°C. The method for producing an N-vinyllactam polymer according to any one of claims 1 to 4, wherein water is used in the polymerization step. The N-vinyllactam polymer according to any one of claims 1 to 5, wherein the method for producing the N-vinyllactam polymer includes a step of adding an organic acid to the obtained polymer. manufacturing method. 7. Any one of claims 1 to 6, wherein the amount of the organic acid used is 0.01 to 3% by mass with respect to 100% by mass of the N-vinyllactam monomer used in the polymerization step. A method for producing the described N-vinyllactam polymer. The method for producing an N-vinyllactam polymer according to any one of claims 1 to 7, wherein the polymerization temperature in the polymerization step is 60 to 100°C. 9. The method for producing an N-vinyllactam polymer according to any one of claims 1 to 8, wherein the pH during polymerization in the polymerization step is 4 or higher.