N-vinyl lactam copolymer and composition

Abstract

The purpose of the present invention is to provide an N-vinyl lactam copolymer and composition that have little elution into carbonate electrolyte solvents while maintaining excellent carbon dispersion ability and solubility in water. The present invention is an N-vinyl lactam copolymer that has a structural unit (A) derived from a salt of an acid group-containing monomer and a structural unit (B) derived from an N-vinyl lactam monomer, in which, when the total amount of structural units (A) and structural units (B) is taken as 100 mass%, the content of structural units (A) is 30 mass% or less, the weight average molecular weight is from 1,000 to 100,000, and the K value by the Fikentscher method is 12-60.

Description

[Technical Field]

[0001] The present disclosure relates to N-vinyl lactam copolymers and compositions. [Background technology]

[0002] N-vinyl lactam polymers, such as polyvinylpyrrolidone, are water-soluble and safe functional polymers that are used in a wide range of fields, including cosmetics, pharmaceutical and agricultural intermediates, food additives, photosensitive electronic materials, tackifiers, various specialized industrial applications (e.g., hollow fiber membrane production), and battery materials.

[0003] It has been reported that a battery positive electrode paste is characterized by using a copolymer of stearyl methacrylate, methoxypolyethylene glycol methacrylate, and methacrylamide (see Patent Document 1). It has also been reported that a copolymer containing acrylonitrile and N-vinylpyrrolidone is used as a dispersant for carbon materials (see Patent Document 2). Furthermore, a carbon nanotube dispersion liquid for electrodes, which is characterized by using carbon nanotubes, polyvinylpyrrolidone, N-methyl-2-pyrrolidone, and an amine compound, has been reported (see Patent Document 3). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2018-170218 [Patent Document 2] Japanese Patent Application Laid-Open No. 2016-65142 [Patent Document 3] Patent No. 6531926 Summary of the Invention [Problem to be solved by the invention]

[0005] However, although polyvinylpyrrolidone has excellent carbon dispersion ability, it has the problem of eluting into the carbonate-based electrolyte solvent of the battery, thereby impairing battery performance. Furthermore, although the copolymers described in these patent documents can suppress elution into the electrolyte solvent, they have the problem of low solubility in water, and can only be used as a positive electrode material.

[0006] Therefore, an object of the present disclosure is to provide an N-vinyl lactam copolymer and composition that exhibits low elution into carbonate-based electrolyte solvents while maintaining excellent carbon dispersibility and solubility in water. [Means for solving the problem]

[0007] As a result of intensive research, the present inventors have found that by using predetermined components as monomers constituting an N-vinyl lactam copolymer and by setting the composition ratio thereof within a predetermined range, it is possible to reduce elution into the electrolyte solvent while maintaining excellent carbon dispersibility and solubility in water. They have thus come to the conclusion that the above-mentioned problems can be solved beautifully, and have arrived at the present invention.

[0008] The present invention includes the following N-vinyl lactam copolymers and the like. [1] An N-vinyl lactam copolymer having structural units (A) derived from a salt of an acid group-containing monomer and structural units (B) derived from an N-vinyl lactam monomer, wherein the content of structural units (A) is 30% by mass or less when the total amount of structural units (A) and structural units (B) is taken as 100% by mass, the weight-average molecular weight is 1,000 or more and 100,000 or less, and the K value measured by the Fikentscher method is 12 to 60. [2] The N-vinyl lactam copolymer according to [1] above, wherein the structural unit (A) derived from a salt of an acid group-containing monomer is a structural unit (A1) derived from a salt of a carboxyl group-containing monomer and / or a structural unit (A2) derived from a salt of a sulfonic acid group-containing monomer. [3] The N-vinyl lactam copolymer according to [1] or [2] above, wherein when the structural unit (A) contains the structural unit (A1), the content of the structural unit (A1) is 15% by mass or less relative to 100% by mass of the total amount of the structural unit (A) and the structural unit (B). [4] The N-vinyl lactam copolymer according to any one of [1] to [3] above, wherein when the structural unit (A) contains the structural unit (A2), the content of the structural unit (A2) is 30% by mass or less relative to 100% by mass of the total amount of the structural unit (A) and the structural unit (B). [5] The N-vinyl lactam copolymer according to any one of the above [1] to [4], which has a solubility in water of 1% by mass or more. [6] The N-vinyl lactam copolymer according to any one of [1] to [5] above, which has a solubility in an electrolyte solvent of 1% by mass or less. [7] The N-vinyl lactam copolymer according to any one of the above [1] to [6], which has a weight average molecular weight of 5,000 or more and 100,000 or less. [8] The N-vinyl lactam copolymer according to any one of [1] to [7] above, wherein the structural unit (A1) derived from a salt of a carboxyl group-containing monomer is a structural unit derived from at least one selected from the group consisting of lithium acrylate, sodium acrylate, potassium acrylate, and ammonium acrylate. [9] The N-vinyl lactam copolymer according to any one of [1] to [8] above, wherein the structural unit (A2) derived from a salt of a sulfonic acid group-containing monomer is a structural unit derived from at least one selected from the group consisting of 2-acrylamido-2-methyl-1-propanesulfonic acid (sodium, lithium, potassium, ammonium), 2-hydroxy-3-allyloxypropanesulfonic acid (sodium, lithium, potassium, ammonium), 2-sulfoethylmethacrylic acid (sodium, lithium, potassium, ammonium), vinylsulfonic acid (sodium, lithium, potassium, ammonium), and p-styrenesulfonic acid (sodium, lithium, potassium, ammonium).

[10] A composition comprising an N-vinyl lactam copolymer having structural units (A) derived from a salt of an acid group-containing monomer and structural units (B) derived from an N-vinyl lactam monomer, and a carbon material.

[11] The composition according to

[10] above, which contains N-methyl-2-pyrrolidone and / or water.

[12] The composition according to

[10] or

[11] above, wherein the carbon material is at least one selected from carbon black, carbon nanofibers, and carbon nanotubes.

[13] The composition according to any one of the above

[10] to

[12] , wherein the structural unit (A) derived from the salt of an acid group-containing monomer is a structural unit (A1) derived from the salt of a carboxyl group-containing monomer and / or a structural unit (A2) derived from the salt of a sulfonic acid group-containing monomer.

[14] The composition according to any one of the above

[10] to

[13] , wherein the structural unit (A) derived from a salt of an acid group-containing monomer is a structural unit (A1) derived from a salt of a carboxyl group-containing monomer.

[15] A method for producing the N-vinyl lactam copolymer according to any one of [1] to [9] above, the method comprising a step of polymerizing a monomer component containing a salt of an acid group-containing monomer and an N-vinyl lactam monomer. [Effects of the Invention]

[0009] According to the present disclosure, it is possible to provide an N-vinyl lactam copolymer and composition that exhibits low elution into carbonate-based electrolyte solvents while maintaining excellent carbon dispersibility and solubility in water. DETAILED DESCRIPTION OF THE INVENTION

[0010]

[0023] The following detailed description of preferred embodiments of the present disclosure is merely exemplary in nature and is in no way intended to limit the present disclosure, its application, or its uses.

[0011] In the following description, unless otherwise specified, "%" means "% by mass", "parts" means "parts by mass", and the range "A to B" means A or more and B or less. In addition, in this disclosure, "(meth)acrylate" means "acrylate" or "methacrylate", and "(meth)acrylic" means "acrylic" or "methacrylic".

[0012] [N-vinyl lactam copolymer] The N-vinyl lactam copolymer of the present disclosure has a structural unit (A) derived from a salt of an acid group-containing monomer and a structural unit (B) derived from an N-vinyl lactam monomer, and when the total amount of the structural units (A) and (B) is taken as 100 mass%, the content of the structural unit (A) is 30 mass% or less, the weight average molecular weight is 1,000 or more and 100,000 or less, and the K value measured by the Fikentscher method is 12 to 60. As a result, the N-vinyl lactam copolymer of the present disclosure maintains its solubility in water while exhibiting minimal elution in carbonate-based electrolyte solvents. Furthermore, conventional polymers disclosed in Patent Documents 1 to 3, etc., have the problem of insufficient dispersibility in dispersions of carbon materials used as positive electrode materials, and there is also the risk of battery performance being impaired due to the high amount of impurities such as residual monomers. In contrast, the N-vinyl lactam copolymer has a reduced amount of impurities such as residual monomers, and also has an excellent balance between the electrostatic repulsion of the acid group salt and the adsorption of N-vinyl lactam to carbon, resulting in excellent dispersibility of carbon materials.

[0013] The acid group-containing monomer (the precursor of the salt of the acid group-containing monomer) may be any compound having an acid group and an ethylenically unsaturated hydrocarbon group. The acid group is not particularly limited, but examples thereof include a carboxyl group, a sulfonic acid group, a phosphoric acid group, etc. The acid group is preferably a carboxyl group or a sulfonic acid group. Examples of the acid group-containing monomer include a carboxyl group-containing monomer, a sulfonic acid group-containing monomer, and a phosphoric acid group-containing monomer.

[0014] The carboxyl group-containing monomer is not particularly limited as long as it has a carboxyl group and an ethylenically unsaturated hydrocarbon group, and examples thereof include unsaturated monocarboxylic acid monomers such as (meth)acrylic acid, crotonic acid, tiglic acid, 3-methylcrotonic acid, 2-methyl-2-pentenoic acid, and itaconic acid, and unsaturated dicarboxylic acid monomers such as maleic acid, itaconic acid, mesaconic acid, citraconic acid, fumaric acid, and 2-methyleneglutaric acid. Of these, (meth)acrylic acid and maleic acid are preferred, and (meth)acrylic acid is more preferred.

[0015] The sulfonic acid group-containing monomer is not particularly limited as long as it has a sulfonic acid group and an ethylenically unsaturated hydrocarbon group, and examples thereof include 2-acrylamido-2-methyl-1-propanesulfonic acid, 2-hydroxy-3-allyloxypropanesulfonic acid, 2-sulfoethylmethacrylic acid, p-styrenesulfonic acid, 2-(meth)allyloxyethylenesulfonic acid, α-methyl-p-styrenesulfonic acid, vinylsulfonic acid, vinylsulfamic acid, (meth)allyl sulfonic acid, and isoprene. Examples of suitable acrylic acid include sulfonic acid, 4-(allyloxy)benzenesulfonic acid, 1-methyl-2-propene-1-sulfonic acid, 1,1-dimethyl-2-propene-1-sulfonic acid, 3-butene-1-sulfonic acid, 1-butene-3-sulfonic acid, 2-acrylamido-1-methylpropanesulfonic acid, 2-acrylamidopropanesulfonic acid, 2-acrylamido-n-butanesulfonic acid, 2-acrylamido-2-phenylpropanesulfonic acid, and 2-((meth)acryloyloxy)ethanesulfonic acid. Among these, preferred are 2-acrylamido-2-methyl-1-propanesulfonic acid, 2-hydroxy-3-allyloxypropanesulfonic acid, 2-sulfoethylmethacrylic acid, vinylsulfonic acid, and p-styrenesulfonic acid, and more preferred is 2-acrylamido-2-methyl-1-propanesulfonic acid.

[0016] The phosphate group-containing monomer is not particularly limited as long as it has a phosphate group and an ethylenically unsaturated hydrocarbon group, and examples thereof include (meth)acryloyloxyalkyl phosphate esters such as (meth)acryloyloxyethyl phosphate and (meth)acryloyloxyisopropyl phosphate; and alkenyl phosphate esters such as vinyl phosphate, allyl phosphate, propenyl phosphate, isopropenyl phosphate, butenyl phosphate, pentenyl phosphate, octenyl phosphate, decenyl phosphate, and dodecenyl phosphate.

[0017] The N-vinyl lactam copolymer of the present disclosure preferably has a structural unit (A1) derived from a salt of a carboxyl group-containing monomer and / or a structural unit (A2) derived from a salt of a sulfonic acid group-containing monomer, and more preferably has the structural unit (A1).

[0018] A preferred embodiment of the present invention is an N-vinyl lactam copolymer having a structural unit derived from a (meth)acrylate salt as a salt of a carboxyl group-containing monomer. In this case, acrylic acid and / or methacrylic acid can be used as a precursor (monomer) before polymerization, and the acrylic acid and / or methacrylic acid in the obtained N-vinyl lactam copolymer should be in the form of a carboxylic acid salt, without containing an acid form.

[0019] The method for producing the N-vinyl lactam copolymer of the present disclosure is not particularly limited, and a salt of an acid group-containing monomer such as a (meth)acrylate may be used as the monomer component, or an unneutralized acid group-containing monomer may be used and neutralized after the polymerization reaction to form a neutralized salt. It is preferable to use a salt of an acid group-containing monomer such as a (meth)acrylate as the monomer component, since this allows for a reduction in the amount of impurities such as residual monomers. The structural unit (A) derived from the salt of the acid group-containing monomer has the same structure as the structural unit in which the polymerizable carbon-carbon double bond group of the salt of the acid group-containing monomer becomes a single bond. When the structural unit (A) is a structural unit derived from a (meth)acrylate salt, a case in which a monomer such as acrylamide or acrylonitrile is subjected to a polymerization reaction, followed by hydrolysis and then a neutralization reaction to convert the resulting product into a carboxylate is also included in the structural unit (A) of the present disclosure.

[0020] The (meth)acrylic acid is not particularly limited as long as it is at least one selected from acrylic acid and methacrylic acid. Acrylic acid is preferred. If the structural unit derived from a (meth)acrylate salt is a structural unit derived from an acrylate salt, the N-vinyl lactam copolymer of the present disclosure can be more sufficiently reduced in the amount of residual monomer contained therein, and the solubility in water and electrolyte solvents can be adjusted as designed.

[0021] The N-vinyl lactam copolymer of the present disclosure has a structural unit (A) derived from a salt of an acid group-containing monomer, and examples of the salt include alkali metal salts, alkaline earth metal salts, ammonium salts, organic ammonium salts, organic amine salts, etc. There are no particular limitations as long as the salt is at least one selected from these salts.

[0022] Examples of alkali metal salts include lithium salts, sodium salts, potassium salts, etc. Examples of alkaline earth metal salts include calcium salts, magnesium salts, etc.

[0023] Examples of organic ammonium salts include methylammonium salts, ethylammonium salts, dimethylammonium salts, diethylammonium salts, trimethylammonium salts, and triethylammonium salts.

[0024] Examples of organic amine salts include alkanolamine salts such as ethanolamine salts, diethanolamine salts, triethanolamine salts, monoisopropanolamine salts, diisopropanolamine salts, triisopropanolamine salts, hydroxyethyldiisopropanolamine salts, dihydroxyethylisopropanolamine salts, tetrakis(2-hydroxypropyl)ethylenediamine, and pentakis(2-hydroxypropyl)diethylenetriamine. Among these, preferred are diethanolamine salts, diisopropanolamine salts, triisopropanolamine salts, hydroxyethyldiisopropanolamine salts, tetrakis(2-hydroxypropyl)ethylenediamine salts, and pentakis(2-hydroxypropyl)diethylenetriamine salts, and more preferred are diethanolamine salts, triisopropanolamine salts, and hydroxyethyldiisopropanolamine salts.

[0025] The salts are preferably alkali metal salts, alkaline earth metal salts, and ammonium salts, more preferably alkali metal salts and ammonium salts, and even more preferably lithium salts, sodium salts, potassium salts, and ammonium salts. Particularly preferred are lithium salts and sodium salts. When the salt is the above-mentioned salt, the N-vinyl lactam copolymer of the present disclosure has a good withstand voltage and suppresses the generation of volatile substances, which is preferable from the viewpoint of more sufficiently suppressing the impairment of battery performance.

[0026] The structural unit derived from the (meth)acrylate salt can be represented by the following general formula (1).

[0027] [ka] (In general formula (1), R 1 represents one or more selected from a metal atom, an ammonium salt, an organic ammonium salt, and an organic amine salt. 2 is a hydrogen atom or a methyl group. Here, the asterisk represents an atom contained in another structural unit of the same or different type to which the structural unit represented by general formula (1) is bonded.)

[0028] R in the general formula (1) 1 is not particularly limited as long as it is at least one selected from a metal atom, an ammonium salt, an organic ammonium salt, and an organic amine salt, and the preferred forms are the same as those described above for the salts. 2 is not particularly limited as long as it is a hydrogen atom and / or a methyl group, and the preferred forms are as described above.

[0029] Another preferred embodiment of the structural unit derived from the (meth)acrylate salt is a structural unit derived from at least one selected from the group consisting of lithium acrylate, sodium acrylate, potassium acrylate, and ammonium acrylate, and more preferably at least one selected from lithium acrylate and sodium acrylate. When the structural unit derived from the (meth)acrylate salt is a structural unit derived from the above-mentioned monomer, the amount of impurities can be more sufficiently reduced, and an excellent effect can be exhibited in terms of more sufficiently suppressing the impairment of battery performance due to impurities.

[0030] An embodiment in which the N-vinyl lactam copolymer of the present disclosure has a structural unit (A2) derived from a salt of a sulfonic acid group-containing monomer is also one of the preferred embodiments of the present invention. The structural unit (A2) derived from a salt of the sulfonic acid group-containing monomer is preferably a structural unit derived from at least one selected from the group consisting of 2-acrylamido-2-methyl-1-propanesulfonic acid (sodium, lithium, potassium, ammonium), 2-hydroxy-3-allyloxypropanesulfonic acid (sodium, lithium, potassium, ammonium), 2-sulfoethylmethacrylic acid (sodium, lithium, potassium, ammonium), vinylsulfonic acid (sodium, lithium, potassium, ammonium), and p-styrenesulfonic acid (sodium, lithium, potassium, ammonium). More preferably, it is a structural unit derived from 2-acrylamido-2-methyl-1-propanesulfonic acid (sodium, lithium, potassium, ammonium).

[0031] The structural unit (B) derived from the N-vinyl lactam monomer is not particularly limited as long as the structural unit derived from the monomer is contained as the structural unit (B) in the N-vinyl lactam copolymer of the present disclosure by polymerization of the N-vinyl lactam monomer. In other words, an N-vinyl lactam monomer is a precursor of a structural unit derived from an N-vinyl lactam monomer. The N-vinyl lactam monomer is a monomer having a cyclic lactam ring, and examples thereof include N-vinyl-2-pyrrolidone, N-vinylcaprolactam, N-vinyl-4-butylpyrrolidone, N-vinyl-4-propylpyrrolidone, N-vinyl-4-ethylpyrrolidone, N-vinyl-4-methylpyrrolidone, N-vinyl-4-methyl-5-ethylpyrrolidone, N-vinyl-4-methyl-5-propylpyrrolidone, N-vinyl-5-methyl-5-ethylpyrrolidone, N-vinyl-5-propylpyrrolidone, N-vinyl-5-butylpyrrolidone, N-vinyl-4-methylcaprolactam, N-vinyl-6-methylcaprolactam, N-vinyl-6-propylcaprolactam, and N-vinyl-7-butylcaprolactam. Among these, N-vinyl-2-pyrrolidone and / or N-vinylcaprolactam are preferably used because they have good polymerizability, and the resulting polymer has good color stability at high temperatures and good solubility in solvents. Note that the N-vinyl lactam monomers can be used alone or in combination of two or more.

[0032] The N-vinyl lactam copolymer of the present disclosure essentially comprises a structural unit (A) derived from a salt of an acid group-containing monomer and a structural unit (B) derived from an N-vinyl lactam monomer, and the content of the structural unit (A) is 30% by mass or less when the total amount of the structural units (A) and (B) is taken as 100% by mass. When the content of the structural unit (A) is within the above-mentioned range, leaching into the electrolyte solvent can be suppressed, and the dispersibility of the carbon material can be improved. Furthermore, the content of the structural unit (A) is preferably 0.1% by mass or more, more preferably 1% by mass or more, and even more preferably 1.5% by mass or more. If the content of the structural unit (A) is within the above range, dissolution in the electrolyte solvent can be more sufficiently suppressed, which is preferable in that the dispersibility of the carbon material is improved. The content of the structural unit (A) is preferably 25% by mass or less, more preferably 20% by mass or less, and even more preferably 15% by mass or less. The content of the structural unit (A) is preferably from 0.1 to 30% by mass, more preferably from 1 to 25% by mass, even more preferably from 1.5 to 20% by mass, and particularly preferably from 2 to 15% by mass. In one embodiment, the content of the structural unit (A) may be 12% by mass or less, less than 10% by mass, or 5% by mass or less. The content of the structural unit (A) within the above range is preferable in terms of good solubility in N-methyl-2-pyrrolidone.

[0033] When the N-vinyl lactam copolymer of the present disclosure has the structural unit (A1), the content of the structural unit (A1) is preferably 0.1 to 15 mass%, more preferably 1 to 13 mass%, and even more preferably 1.5 to 10 mass%, relative to 100 mass% of the total amount of the structural units (A) and (B).

[0034] When the N-vinyl lactam copolymer of the present disclosure has the structural unit (A2), the content of the structural unit (A2) is preferably 5 to 30 mass%, more preferably 8 to 25 mass%, and even more preferably 10 to 22 mass%, relative to 100 mass% of the total amount of the structural units (A) and (B).

[0035] Furthermore, when the total amount of the structural unit (A) and the structural unit (B) is taken as 100% by mass, the content of the structural unit (A) derived from the salt of the acid group-containing monomer may be 30% by mass or less, but it is preferable that the total content of the structural unit (A) and the structural unit derived from the acid type acid group-containing monomer is 30% by mass or less. Furthermore, the total content of the structural unit (A) and the structural unit derived from the acid type acid group-containing monomer is preferably 0.1% by mass or more, more preferably 1% by mass or more, and even more preferably 1.5% by mass or more. Furthermore, the total content of the structural unit (A) and the structural unit derived from the acid type acid group-containing monomer is more preferably 25% by mass or less, even more preferably 20% by mass or less, and particularly preferably 15% by mass or less. The total content of the structural unit (A) and the structural unit derived from the acid type acid group-containing monomer is preferably 0.1 to 30 mass%, more preferably 1 to 25 mass%, even more preferably 1.5 to 20 mass%, and particularly preferably 2 to 15 mass%. In one embodiment, the total content of the structural unit (A) and the structural unit derived from the acid type acid group-containing monomer may be 12% by mass or less, less than 10% by mass, or 5% by mass or less.

[0036] The content of the structural unit (B) in the N-vinyl lactam copolymer of the present disclosure is 70% by mass or more, preferably 70 to 99.9% by mass, more preferably 75 to 99% by mass, even more preferably 80 to 98.5% by mass, and particularly preferably 85 to 98% by mass, based on 100% by mass of the total amount of the structural units (A) and (B).

[0037] The N-vinyl lactam copolymer of the present disclosure is not particularly limited as long as it essentially contains the structural unit (A) derived from a salt of an acid group-containing monomer and the structural unit (B) derived from an N-vinyl lactam monomer, but may also contain a structural unit (E) derived from another monomer. Specific examples of monomers that can be used as precursors for structural units derived from other monomers include acid-type carboxyl group-containing monomers (excluding salts of carboxyl group-containing monomers) such as (meth)acrylic acid, maleic acid, fumaric acid, itaconic acid, crotonic acid, and 2-methylene glutaric acid; hydroxyl group-containing alkyl (meth)acrylates such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, and α-hydroxymethylethyl (meth)acrylate; alkyl (meth)acrylates that are esters of alkyl groups having 1 to 18 carbon atoms of (meth)acrylic acid, such as methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, cyclohexyl (meth)acrylate, lauryl (meth)acrylate, and stearyl (meth)acrylate; and ) acrylate and other alkoxyalkyl (meth)acrylates; amino group-containing acrylates such as dimethylaminoethyl (meth)acrylate or its quaternized derivatives; amide group-containing monomers such as (meth)acrylamide, dimethylacrylamide, isopropylacrylamide; vinyl esters such as vinyl acetate; alkenes such as ethylene and propylene; aromatic vinyl monomers such as styrene; maleimide derivatives such as maleimide, phenylmaleimide, and cyclohexylmaleimide; (meth)acrylamide Nitrile group-containing vinyl monomers such as acrylonitrile; monomers having an acid type sulfonic acid group such as 3-allyloxy-2-hydroxypropanesulfonic acid, 2-acrylamido-2-methylpropanesulfonic acid, styrenesulfonic acid, and vinylsulfonic acid (excluding salts of sulfonic acid group-containing monomers), vinylphosphonic acid, (meth)allylphosphonic acid, and other monomers having an acid type phosphonic acid group (excluding salts of phosphoric acid group-containing monomers); aldehyde group-containing vinyl monomers such as (meth)acrolein;Examples of suitable monomers include alkyl vinyl ethers such as methyl vinyl ether, ethyl vinyl ether, and butyl vinyl ether; other functional group-containing monomers such as vinyl chloride, vinylidene chloride, and allyl alcohol; and polyalkylene glycol chain-containing monomers such as polyalkylene glycol (meth)acrylate, monoalkoxypolyalkylene glycol (meth)acrylate, vinyl alcohol, (meth)allyl alcohol, and isoprenol, which are unsaturated alcohols to which 1 to 300 moles of alkylene oxide have been added. These other monomers may be used alone or in combination of two or more. The terms "salts" for carboxylates, sulfonates, and phosphonates are the same as those for the salts described above. The same also applies to preferred embodiments. As the structural unit (E) derived from other monomers, polyalkylene glycol chain-containing monomers are preferred because they can impart steric repulsion properties and improve the dispersion stability of carbon materials in low-concentration systems. Nitrile group-containing vinyl monomers such as (meth)acrylonitrile and amino group-containing acrylates are also preferred in that they can impart adsorptivity to carbon and improve carbon dispersion stability in high-concentration systems.

[0038] The average number of moles of alkylene oxide added in the polyalkylene glycol chain-containing monomer is not particularly limited, but is preferably 1 to 100, more preferably 1 to 50, even more preferably 1 to 30, and particularly preferably 1 to 20. Examples of the alkylene oxide include oxyethylene, oxypropylene, oxybutylene, oxyisobutylene, oxy-2,3-butylene, oxystyrene, and oxyalkylenes having 2 to 10 carbon atoms. More preferred are alkylene oxides having 2 to 4 carbon atoms, such as oxyethylene, oxypropylene, and oxybutylene, and even more preferred are oxyethylene and oxypropylene. The oxyalkylene group represented by AO is not limited to groups formed by an addition reaction of alkylene oxides. Furthermore, when the polyalkylene glycol is an adduct of two or more types of alkylene oxides, it may be in any form, such as random addition, block addition, or alternating addition. It is preferable that the oxyalkylene groups in the polyalkylene glycol chain contain oxyethylene groups as an essential component, more preferably 50 mol % or more of oxyethylene groups, and even more preferably 90 mol % or more of oxyethylene groups.

[0039] When the N-vinyl lactam copolymer of the present disclosure contains the other structural unit (E), the content of the structural unit (E) is preferably 50% by mass or less, more preferably 30% by mass or less, even more preferably 20% by mass or less, and even more preferably 10% by mass or less, when the total amount of the structural unit (A), the structural unit (B), and the other structural unit (E) is taken as 100% by mass. In one embodiment, the content of the monomer (E) is preferably 5% by mass or less, more preferably 2% by mass or less, and particularly preferably 0% by mass.

[0040] In one preferred embodiment of the present invention, the N-vinyl lactam copolymer of the present disclosure contains 0.1 to 30 mass% of structural units derived from a polyalkylene glycol chain-containing monomer, relative to 100 mass% of the total amount of the structural units (A), (B), and other structural units (E). The content of the structural units derived from a polyalkylene glycol chain-containing monomer is more preferably 1 to 30 mass%, even more preferably 5 to 25 mass%, and particularly preferably 10 to 25 mass%.

[0041] In one preferred embodiment of the present invention, the N-vinyl lactam copolymer of the present disclosure contains 0.1 to 30 mass% of structural units derived from a nitrile group-containing vinyl monomer such as (meth)acrylonitrile, relative to 100 mass% of the total amount of the structural units (A), (B), and other structural units (E). The content of the structural units derived from the nitrile group-containing vinyl monomer is more preferably 1 to 25 mass%, even more preferably 3 to 20 mass%, and particularly preferably 5 to 15 mass%.

[0042] The N-vinyl lactam copolymer of the present disclosure may have a phosphorus atom. The phosphorus atom can be introduced into the main chain of the N-vinyl lactam copolymer of the present disclosure, for example, by using a phosphorus compound such as hypophosphorous acid (salt) as a reducing agent during production of the N-vinyl lactam copolymer of the present disclosure, as described below.

[0043] The phosphorus atom may be contained in the N-vinyl lactam copolymer as a structural unit containing a phosphorus atom. Having a structural unit containing a phosphorus atom in the main chain makes it possible to reduce discoloration (yellowing) of the N-vinyl lactam copolymer when heated. Examples of the structural unit containing phosphorus in the main chain include a hypophosphorous acid (salt) group (meaning a hypophosphorous acid group or a hypophosphite group) and a phosphorous acid (salt) group (meaning a phosphorous acid group or a phosphite group), and at least one selected from the group consisting of these is preferred. More specifically, examples include a phosphonic acid (salt) group and a phosphinic acid (salt) group. Among these, a phosphinic acid (salt) group is preferred. That is, the N-vinyl lactam copolymer of the present disclosure may have a phosphinic acid (salt) group in the main chain.

[0044] Examples of the salt include metal salts, ammonium salts, and organic amine salts, and metal salts are preferred. Examples of the metal salt include alkali metal salts such as lithium salts, sodium salts, and potassium salts; alkaline earth metal salts such as calcium salts and magnesium salts; and transition metal salts, with alkali metal salts being preferred. When the structural unit containing a phosphorus atom is a structural unit consisting of a hypophosphite group, a phosphite group, or a metal salt thereof, it is possible to convert the hypophosphite (salt) group and / or the phosphite (salt) group into the desired acid or metal salt by adding an acid or base, for example, after forming the hypophosphite (salt) group and / or the phosphite (salt) group in the main chain of the polymer. Similarly, the conversion can also be performed by treatment with an ion exchange resin or the like.

[0045] In the N-vinyl lactam copolymer of the present disclosure having a structural unit containing a phosphorus atom in the main chain, the content of the structural unit containing a phosphorus atom in the main chain is preferably 0.01% by mass or more, more preferably 0.05% by mass or more, and even more preferably 0.1% by mass or more, relative to the total mass of the N-vinyl lactam copolymer of the present disclosure (100% by mass). It is also preferably 10% by mass or less, more preferably 7% by mass or less, and even more preferably 6% by mass or less. When calculating the mass% of the structural unit containing phosphorus in the main chain relative to the total mass of the N-vinyl lactam copolymer of the present disclosure, the calculation is also performed in acid or amine terms, if applicable, as described above. The phosphorus atom or the structural unit containing a phosphorus atom introduced into the main chain of the N-vinyl lactam copolymer of the present disclosure may be, for example, 31 It can be measured by P-NMR analysis.

[0046] The N-vinyl lactam copolymer of the present disclosure may have a functional group such as an aldehyde group, a carboxyl group, a hydroxyl group, or an amino group at its terminal. When the N-vinyl lactam copolymer of the present disclosure has a structural unit derived from vinylpyrrolidone at its terminal, it is represented by the following general formula (2):

[0047] [ka] (wherein Z represents an aldehyde group, a carboxyl group, a hydroxyl group, or an amino group-containing group; the asterisk represents an atom contained in another structural unit to which the vinylpyrrolidone-derived structural unit is bonded). The structure represented by the above general formula (2) can be introduced, for example, by using hydrogen peroxide as a polymerization initiator and a base such as ammonia as a pH adjuster during the production of the N-vinyl lactam copolymer of the present disclosure, as described below.

[0048] The phosphorus atom in the copolymer can be introduced, for example, by using a phosphorus compound such as hypophosphorous acid (salt) as a reducing agent during the production of the N-vinyl lactam copolymer of the present disclosure, as described below. However, when it is difficult to obtain a phosphorus compound, it is preferable that the N-vinyl lactam copolymer of the present disclosure has a structure represented by the above general formula (2).

[0049] The weight average molecular weight of the N-vinyl lactam copolymer of the present disclosure is not particularly limited as long as it is 1,000 to 100,000, preferably 3,000 to 90,000, more preferably 5,000 to 80,000, even more preferably 7,000 to 70,000, particularly preferably 8,000 to 60,000, and most preferably 10,000 to 50,000. When the weight average molecular weight of the N-vinyl lactam copolymer of the present disclosure is in the above-mentioned range, it is preferable in that it has excellent dispersibility of carbon materials and can suppress thickening of the carbon material dispersion liquid. The weight average molecular weight of the lactam group-containing copolymer of the present disclosure is determined by the method described in the Examples below.

[0050] The N-vinyl lactam copolymer of the present disclosure has a K value of 12 to 60 or less, as measured by the Fikentscher method. It is preferably 55 or less, and more preferably 50 or less. A K value within the above-mentioned range is preferred in that thickening of the carbon material dispersion can be suppressed. Furthermore, the N-vinyl lactam copolymer of the present disclosure preferably has a K value of 20 or more, as measured by the Fikentscher method. It is more preferably 23 or more, and even more preferably 25 or more. A K value within the above-mentioned range is preferred in that excellent dispersibility of the carbon material is achieved. The K value of the lactam group-containing copolymer of the present disclosure measured by the Fikentscher method is a value measured by the method described in the Examples below.

[0051] The N-vinyl lactam copolymer of the present disclosure preferably has a solubility of 1% by mass or more in N-methyl-2-pyrrolidone. A solubility of 1% by mass or more in N-methyl-2-pyrrolidone means that 1 g or more of the N-vinyl lactam copolymer of the present disclosure dissolves in 100 g of N-methyl-2-pyrrolidone at 25°C and atmospheric pressure. It is preferably 1.2% by mass or more, more preferably 1.5% by mass or more, and further preferably 2% by mass or more. When the solubility of the N-vinyl lactam copolymer of the present disclosure in N-methyl-2-pyrrolidone is within the above-mentioned range, it can be used as a carbon material dispersant in N-methyl-2-pyrrolidone, which is preferable in that it can be used, for example, as a carbon material dispersant in a positive electrode paste for a battery.

[0052] The N-vinyl lactam copolymer of the present disclosure preferably has a water solubility of 1% by mass or more, which means that 1 g or more of the N-vinyl lactam copolymer of the present disclosure dissolves in 100 g of water at 25°C and atmospheric pressure. It is more preferably 3% by mass or more, even more preferably 5% by mass or more, and particularly preferably 10% by mass or more. When the solubility in water of the N-vinyl lactam copolymer of the present disclosure is within the above-mentioned range, it can be used as a carbon material dispersant in water, which is preferable in that it can be used, for example, as a carbon material dispersant in a negative electrode paste for a battery.

[0053] The N-vinyl lactam copolymer of the present disclosure preferably has a solubility of 1% by mass or less in an electrolyte solvent. A solubility of 1% by mass or less in an electrolyte solvent means that only 1 g or less of the N-vinyl lactam copolymer of the present disclosure dissolves in 100 g of the electrolyte solvent at 25°C and atmospheric pressure. It is more preferably 0.5% by mass or less, even more preferably 0.09% by mass or less, even more preferably 0.07% by mass or less, still more preferably 0.05% by mass or less, and particularly preferably 0.02% by mass or less.

[0054] When a positive electrode or a negative electrode is produced using the N-vinyl lactam copolymer of the present disclosure as a battery material and is incorporated into a cell using a non-aqueous electrolyte, it is preferable that the amount of dissolution and elution in the non-aqueous electrolyte is small. The nonaqueous electrolyte solution contains an electrolyte solvent. The electrolyte solvent is not particularly limited as long as it can dissolve and disperse electrolyte salts such as various Li salts. Any solvent generally used in batteries can be used as the electrolyte solvent. The nonaqueous electrolyte is preferably a solvent that has a high dielectric constant, high solubility for the electrolyte salt, a boiling point of 60° C. or higher, and a wide electrochemical stability range, and more preferably an organic solvent with a low water content. Examples of such organic solvents include ether solvents such as ethylene glycol dimethyl ether, ethylene glycol diethyl ether, tetrahydrofuran, 2-methyltetrahydrofuran, 2,6-dimethyltetrahydrofuran, tetrahydropyran, crown ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, 1,4-dioxane, and 1,3-dioxolane; chain carbonate ester (carbonate) solvents such as dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, diphenyl carbonate, and methyl phenyl carbonate; saturated cyclic carbonate ester (carbonate) solvents such as ethylene carbonate, propylene carbonate, 2,3-dimethyl ethylene carbonate, 1,2-butylene carbonate, and erythrityl carbonate; cyclic carbonate ester (carbonate) solvents having an unsaturated bond such as vinylene carbonate, methyl vinylene carbonate, ethyl vinylene carbonate, 2-vinyl ethylene carbonate, and phenyl ethylene carbonate; fluoroethylene carbonate, 4,5-difluoroethylene carbonate, and the like. Fluorine-containing cyclic carbonate solvents such as carbonate and trifluoropropylene carbonate; aromatic carboxylic acid ester solvents such as methyl benzoate and ethyl benzoate; lactone solvents such as γ-butyrolactone, γ-valerolactone, δ-valerolactone; phosphate ester solvents such as trimethyl phosphate, ethyl dimethyl phosphate, diethyl methyl phosphate, and triethyl phosphate; acetonitrile, propionitrile, methoxypropionitrile, glutaronitrile, adiponitrile, 2-methylglutaronitrile Examples of suitable solvents include nitrile solvents such as tolyl, valeronitrile, butyronitrile, and isobutyronitrile; sulfur compound solvents such as dimethyl sulfone, ethyl methyl sulfone, diethyl sulfone, sulfolane, 3-methyl sulfolane, and 2,4-dimethyl sulfolane; aromatic nitrile solvents such as benzonitrile and tolunitrile; and nitromethane, 1,3-dimethyl-2-imidazolidinone, 1,3-dimethyl-3,4,5,6-tetrahydro-2(1H)-pyrimidinone, and 3-methyl-2-oxazolidinone.These solvents may be used alone or in combination of two or more.

[0055] Among the electrolyte solvents, carbonate solvents such as chain carbonate ester solvents and cyclic carbonate ester solvents, lactone solvents, and ether solvents are preferred, with dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, ethylene carbonate, propylene carbonate, γ-butyrolactone, γ-valerolactone, and the like being more preferred, and carbonate solvents such as dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, ethylene carbonate, and propylene carbonate being even more preferred.

[0056] The N-vinyl lactam copolymer of the present disclosure preferably has a solubility of 1 mass % or less in a carbonate-based electrolyte solvent. It is more preferably 0.5% by mass or less, even more preferably 0.09% by mass or less, even more preferably 0.07% by mass or less, particularly preferably 0.05% by mass or less, and most preferably 0.02% by mass or less.

[0057] The N-vinyl lactam copolymer of the present disclosure preferably has low solubility in a mixed solvent of ethylene carbonate / ethyl methyl carbonate among the carbonate-based electrolyte solvents, and preferably has a solubility of 0.09 mass % or less in a mixed solvent of ethylene carbonate / ethyl methyl carbonate = 3 / 7 (mass ratio). It is more preferably 0.07% by mass or less, even more preferably 0.05% by mass or less, and particularly preferably 0.02% by mass or less. It is preferable that the solubility of the N-vinyl lactam copolymer of the present disclosure in a mixed solvent of ethylene carbonate / ethyl methyl carbonate = 3 / 7 (mass ratio) is within the above-mentioned range, since it is possible to more sufficiently prevent the N-vinyl lactam copolymer of the present disclosure from leaching from the electrode into the electrolyte solvent, thereby increasing the viscosity of the electrolyte solvent or inhibiting battery performance.

[0058] [Composition] The composition of the present disclosure is not particularly limited as long as it contains an N-vinyl lactam copolymer having structural units (A) derived from a salt of an acid group-containing monomer and structural units (B) derived from an N-vinyl lactam monomer, and a carbon material. The preferred form of the N-vinyl lactam copolymer contained in the composition of the present disclosure is as described above.

[0059] The carbon material of the present disclosure is conductive carbon mainly used for the positive electrode or negative electrode of a battery. Specific examples include carbon black (e.g., ketjen black, acetylene black), graphite, carbon nanotubes (e.g., single-walled carbon nanotubes, multi-walled carbon nanotubes), carbon fibers (e.g., vapor-grown carbon fibers), and metal powder materials.

[0060] <Carbon nanotubes> Among the carbon materials, carbon nanotubes (hereinafter referred to as CNTs) include carbon nanotubes, carbon nanohorns, and nanographenes. Nanocarbon materials are nanosized substances consisting of a single layer (graphene sheet) of a six-membered ring graphite structure formed by covalent bonds between carbon atoms, and carbon nanotubes are nanocarbon materials in which the graphene sheet is rolled into a cylindrical shape. Types include single-walled carbon nanotubes (SWNTs) consisting of only one layer, and multi-walled carbon nanotubes (MWNTs) with a structure in which carbon nanotubes are stacked concentrically. There are no limitations on the shape, size, or production method, and known products can be used. Mixtures of these may also be used. The length of the carbon nanotubes is not particularly limited, but is preferably 0.5 μm or more, more preferably 1 μm or more, from the viewpoint of electrical conductivity, and is preferably 30 μm or less from the viewpoint of dispersibility.

[0061] From the viewpoint of achieving a high concentration of the effective components of the CNTs, the content of impurities contained in the CNTs is preferably 40% by mass or less, more preferably 30% by mass or less, even more preferably 20% by mass or less, particularly preferably 10% by mass or less, and most preferably substantially 0% by mass.

[0062] The carbon material contained in the composition of the present disclosure is preferably one or more selected from carbon black, carbon nanofibers, and carbon nanotubes. If the carbon material contained in the composition of the present disclosure is the above-mentioned carbon material, it is preferable in that it does not adversely affect the battery performance and further improves the battery performance.

[0063] <Solvent> The composition of the present disclosure may contain, as necessary, a solvent that can dissolve the N-vinyl lactam copolymer of the present disclosure and further disperse the carbon material. The solvent may be water, a water-soluble solvent, an organic solvent, or a mixture thereof. Examples include water, an acidic aqueous solution, an alkaline aqueous solution, alcohol, ether, petroleum ether, glycol ether, cellosolve, benzene, ethyl acetate, chloroform, ketone, acetone, toluene, and N-methyl-2-pyrrolidone. Among these, N-methyl-2-pyrrolidone and / or water are preferred because they easily dissolve the N-vinyl lactam copolymer of the present disclosure and other components such as binder components, thereby improving the dispersibility of the carbon material.

[0064] The alcohol is preferably a monohydric alcohol, more preferably a monohydric alcohol having 1 to 5 carbon atoms, and even more preferably a monohydric alcohol having 2 to 4 carbon atoms, and may be linear or branched. Examples of such alcohols include methanol, ethanol, isopropyl alcohol, butanol, etc., with ethanol and isopropyl alcohol being more preferred, and isopropyl alcohol being even more preferred. Considering ease of handling and environmental impact, it is particularly preferable to use water alone, but it is also preferable to use a hydrophilic organic solvent mixed with water in order to improve the wettability of the nanocarbon material (carbon nanotubes) during dispersion, to make it easier to break up aggregated nanocarbon materials, and to aid in the dispersion of the nanocarbon material. The hydrophilic organic solvent is a solvent that is compatible with water when mixed with it, and specific examples thereof include methanol, ethanol, propanol, isopropanol, butanol, pentanol, ethanediol, propanediol, butanediol, glycerin, trimethylolpropane, pentaerythritol, diethylene glycol, dipropylene glycol, triethylene glycol, ethylene glycol monobutyl ether, propylene glycol monomethyl ether, propylene glycol monopropyl ether, diethylene glycol monobutyl ether, diethylene glycol dimethyl ether, acetone, tetrahydrofuran, N-methyl-2-pyrrolidone, N,N-dimethylformamide, dimethyl sulfoxide, etc. These hydrophilic organic solvents can be used alone or in combination.

[0065] The content of the solvent in the composition of the present disclosure may be appropriately set depending on the purpose and application and is not particularly limited, but when the total amount of the composition of the present disclosure is taken as 100 mass%, the content is preferably 1 to 99.9 mass%, more preferably 10 to 99.5 mass%, even more preferably 30 to 99 mass%, and particularly preferably 50 to 98.5 mass%.

[0066] The content of the N-vinyl lactam copolymer of the present disclosure contained in the composition of the present disclosure is preferably 0.1% by mass or more, more preferably 0.2% by mass or more, and even more preferably 0.5% by mass or more, relative to 100% by mass of the composition of the present disclosure, from the viewpoint of dispersibility of the carbon material, and is preferably 50% by mass or less, more preferably 40% by mass or less, and even more preferably 30% by mass or less, from the viewpoint of dispersibility.

[0067] <Method of manufacturing carbon material dispersion> The composition of the present disclosure can also be made into a carbon material dispersion. For example, it can be produced by blending the N-vinyl lactam copolymer of the present disclosure, the carbon material, and the solvent using a known method. Therefore, in one aspect, the present disclosure relates to a production method for producing a carbon material dispersion from a composition, the method including a dispersing step of mixing the N-vinyl lactam copolymer of the present disclosure, the carbon material, and the solvent, and dispersing the carbon material in a liquid medium. The production method for a carbon material dispersion of the present disclosure makes it possible to produce a carbon material dispersion with excellent dispersibility. The carbon material and solvent used in the dispersion production method of the present disclosure can be the same as the components contained in the composition of the present disclosure described above.

[0068] From the viewpoint of ease of handling, the content of the N-vinyl lactam copolymer of the present disclosure relative to 100% by mass of the carbon material dispersion is preferably 0.1% by mass or more and 20% by mass or less, more preferably 0.1% by mass or more and 10% by mass or less, and even more preferably 0.3% by mass or more and 5% by mass or less. The content of the N-vinyl lactam copolymer of the present disclosure in the carbon material dispersion can be determined, for example, from the amount of raw materials charged, or by filtering the carbon materials and measuring the amount of solids in the solution.

[0069] In the dispersion production process, the carbon material dispersion can be produced using a common mixer / disperser used in paint production. Examples of the mixer / disperser include at least one selected from ultrasonic homogenizers, vibration mills, jet mills, ball mills, bead mills, sand mills, roll mills, homogenizers, high-pressure homogenizers, ultrasonic devices, attritors, dissolvers, and paint shakers. In the dispersion process, ultrasonic dispersion, bead mill dispersion, emulsifiers, and the like are preferred from the viewpoint of improving dispersibility. The carbon material used for dispersion may be in a dry state or may contain a liquid medium. In the dispersion process, the preferred amounts of each component may be the same as the preferred proportions of the composition of the present disclosure described above.

[0070] <How to check the dispersion state> The dispersibility of the carbon material in the carbon material dispersion of the present disclosure can be confirmed not only by visual inspection but also by measuring the absorbance of the dispersion containing the carbon material using a spectrophotometer, as described below. First, several samples of dispersions containing a known, extremely low concentration of carbon material are prepared, and the absorbance at a specific wavelength is measured to create a calibration curve of absorbance versus concentration. Next, the carbon material, the solvent, and the N-vinyl lactam copolymer of the present disclosure are mixed and dispersed using a predetermined dispersion method. The mixture is then centrifuged to separate any remaining undispersed carbon material by settling. The supernatant is diluted to a concentration at which absorbance can be measured, and the absorbance is measured. The concentration is calculated from the calibration curve. Dispersibility can be evaluated by comparing the concentration of the resulting dispersion and the amount of the dispersion with that of the starting material. Alternatively, the dispersion of the composition of the present disclosure can be left to stand for an extended period of time after centrifugation to check for the presence or absence of aggregates.

[0071] <Carbon nanotube-dispersed resin composition> By adding a resin composition other than the N-vinyl lactam copolymer of the present disclosure to the carbon material dispersion liquid of the present disclosure, various forms of carbon material-dispersed resin compositions can be obtained. As the resin composition, a conventionally known resin composition can be used. Specifically, resin compositions containing resins such as acrylic resins, styrene resins, olefin resins, vinyl ether resins, vinyl alcohol resins, polyester resins, polyurethane resins, polyamide resins, polycarbonate resins, polyimide resins, epoxy resins, melamine resins, phenolic resins, and silicone resins can be used. The form of the resin may be a resin solid or a resin solution. A mixture of multiple resins may also be used.

[0072] The carbon material-dispersed resin composition of the present disclosure can be used as a paint, ink, plastic, or the like in which carbon materials are dispersed, and is expected to be used as a conductive material as well as an antistatic material. A paint or ink in which carbon materials are dispersed can be produced by adding a separate resin composition to the carbon material dispersion of the present disclosure to form a paint or ink composition, or by adding a carbon material dispersion to a commercially available paint or ink. Furthermore, a plastic in which carbon materials are dispersed can be produced by mixing a molten plastic with the carbon material dispersion of the present disclosure and then removing the solvent, or by adding a finely powdered plastic with the carbon material dispersion of the present disclosure and then removing the solvent or precipitating the carbon materials.

[0073] [Method for producing N-vinyl lactam copolymer] The method for producing an N-vinyl lactam copolymer of the present disclosure includes a polymerization step of polymerizing raw material monomers. The present invention also includes a method for producing an N-vinyl lactam copolymer, which includes a step of polymerizing a monomer component containing a salt of an acid group-containing monomer and an N-vinyl lactam monomer.

[0074] <Monomer component> As described above, the N-vinyl lactam copolymer of the present disclosure essentially comprises the structural unit (A) derived from a salt of an acid group-containing monomer and the structural unit (B) derived from an N-vinyl lactam monomer. The monomer corresponding to the structural unit (A) can be represented as monomer (A), and the monomer corresponding to the structural unit (B) can be represented as monomer (B). The monomer (A) and the monomer (B) are as described above, and the preferred embodiments are also the same. As described above, the N-vinyl lactam copolymer of the present disclosure essentially contains the structural unit (A) derived from a salt of an acid group-containing monomer and the structural unit (B) derived from an N-vinyl lactam monomer, but may also contain a structural unit (E) derived from another monomer. The monomer corresponding to the structural unit derived from another monomer can be referred to as monomer (E). The monomer (E) is as described above.

[0075] The monomers used in the polymerization step of the N-vinyl lactam copolymer of the present disclosure are the monomer (A) and the monomer (B), and when the total amount of the monomer (A) and the monomer (B) is taken as 100% by mass, the content (amount used) of the monomer (A) is 30% by mass or less. The content of the monomer (A) within the above range is preferable in terms of good dispersibility of the carbon material and good solubility in N-methyl-2-pyrrolidone. The amount of the monomer (A) used is preferably 25% by mass or less, more preferably 20% by mass or less, and even more preferably 15% by mass or less. Furthermore, the content of the monomer (A) relative to the total amount (100% by mass) of the monomer (A) and the monomer (B) is preferably 0.1% by mass or more, more preferably 1% by mass or more, and even more preferably 1.5% by mass or more. The proportion of the monomer (A) used within the above range is preferable in that dissolution into the electrolyte solvent can be suppressed. In one embodiment, the content of the monomer (A) may be 12% by mass or less, less than 10% by mass, or 5% by mass or less. The content of the monomer (A) within the above range is preferable in terms of good solubility in N-methyl-2-pyrrolidone.

[0076] The monomer used in the polymerization step of the N-vinyl lactam copolymer of the present disclosure may be a monomer (E) other than the monomer (A) and the monomer (B). When the other monomer (E) is used, the amount of the monomer (E) used is preferably 50% by mass or less, more preferably 30% by mass or less, even more preferably 20% by mass or less, and even more preferably 10% by mass or less, relative to the total amount of the monomer (A), the monomer (B), and the other monomer (E) being 100% by mass. In one embodiment, the content of the monomer (E) is preferably 5% by mass or less, more preferably 2% by mass or less, and particularly preferably 0% by mass.

[0077] When calculating the proportion of other monomers, etc. used in the total monomer components, if the other monomers have a salt of an amino group, the salt of the amino group is calculated as the corresponding amino group (amine equivalent). When calculating the structures, etc. derived from other monomers relative to the structural units derived from all monomer components, and when calculating the structural units derived from other monomers relative to the total mass of the N-vinyl lactam copolymer of the present disclosure, the calculation is similarly performed in amine equivalent, if applicable.

[0078] <Radical polymerization initiator> It is preferable to use a radical polymerization initiator when polymerizing the monomer. In the production method of the present disclosure, particularly in the polymerization step, it is preferable to use an azo polymerization initiator, hydrogen peroxide, and / or an organic peroxide as the radical polymerization initiator. The azo polymerization initiator refers to a compound that has an azo bond and generates radicals by heat or the like.

[0079] Examples of azo-based polymerization initiators that can be used in the present disclosure include, but are not limited to, 2,2′-azobis-2-amidinopropane dihydrochloride, 2,2′-bis(2-imidazolin-2-yl)[2,2′-azobispropane] dihydrochloride, 2,2′-bis(2-imidazolin-2-yl)[2,2′-azobispropane] disulfate, 2,2′-azobis[2-(2-imidazolin-2-yl)propane] disulfate dihydrate, 2,2′-azobis-(propane-2-carboxamidine) dihydrochloride, 2,2′-azobis[N-(2-carboxyethyl)-2-methylpropionamidine], 2,2′-azobis{2-[1-(2-hydroxyethyl)-2-imidazolin-2-yl]propane} dihydrochloride, 2,2′-azobis Examples include 2,2'-azobis[2-(2-imidazolin-2-yl)propane], 2,2'-azobis(1-imino-1-pyrrolidino-2-methylpropane) dihydrochloride, 2,2'-azobis{2-methyl-N-[1,1-bis(hydroxymethyl)-2-hydroxyethyl]propionamide}, 2,2'-azobis[N-(2-hydroxyethyl)-2-methylpropanamide], 4,4'-azobis-4-cyanovaleric acid, azobisisobutyronitrile, 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile), 2,2'-azobis(2,4-dimethylvaleronitrile), 2,2'-azobis(2-methylbutyronitrile), and dimethyl 2,2'-azobis(2-methylpropionate). Among these, those having a 10-hour half-life temperature of 30°C or higher and 90°C or lower are preferred, and those having a 10-hour half-life temperature of 40°C or higher and 70°C or lower are more preferred, because they tend to enable efficient production of N-vinyl lactam polymers and because the color tone of the resulting polymer at high temperatures tends to be good.Specifically, 2,2'-azobis-2-amidinopropane dihydrochloride, 2,2'-bis(2-imidazolin-2-yl)[2,2'-azobispropane] dihydrochloride, 2,2'-bis(2-imidazolin-2-yl)[2,2'-azobispropane] disulfate, 2,2'-azobis[2-(2-imidazolin-2-yl)propane] disulfate dihydrate, 2,2'-azobis-(propane-2-carboxamidine) dihydrochloride, 2,2'-azobis[2-(2-imidazolin-2-yl)propane], azobisisobutyronitride

[0033] Preferred are 2,2'-azobis(2,4-dimethylvaleronitrile), 2,2'-azobis(2-methylbutyronitrile), and dimethyl 2,2'-azobis(2-methylpropionate), more preferred are 2,2'-azobis-2-amidinopropane dihydrochloride, 2,2'-bis(2-imidazolin-2-yl)[2,2'-azobispropane] dihydrochloride, and 2,2'-azobis[2-(2-imidazolin-2-yl)propane]disulfate dihydrate, and most preferred is 2,2'-azobis-2-amidinopropane dihydrochloride. Furthermore, azo polymerization initiators having a carboxyl group (such as 2,2'-azobis[N-(2-carboxyethyl)-2-methylpropionamidine]) may have an adverse effect on coloring, so if used as desired, it is preferable to use as little of them as possible, and it is even more preferable not to use them at all.

[0080] Examples of organic peroxides that can be used in the present disclosure include alkyl hydroperoxides such as tertiary butyl hydroperoxide, ditertiary butyl peroxide, cumene hydroperoxide, tertiary hexyl hydroperoxide, and p-menthane hydroperoxide; tertiary butyl peroxyacetate, disuccinoyl peroxide, and peracetic acid. Among these organic peroxides, those with a 10-hour half-life temperature of 30°C or higher and 180°C or lower are preferred, and those with a 10-hour half-life temperature of 40°C or higher and 170°C or lower are more preferred.

[0081] The radical polymerization initiator used in the production method of the present disclosure, particularly in the polymerization step, preferably comprises one or more of the azo polymerization initiators and organic peroxides, but other radical polymerization initiators may also be used in combination. Examples of such initiators include persulfates such as sodium persulfate, potassium persulfate, and ammonium persulfate, and hydrogen peroxide. The radical polymerization initiator used in the present invention is preferably the azo-based polymerization initiator and / or hydrogen peroxide. Hydrogen peroxide is preferred because it can easily reduce the molecular weight without using a chain transfer agent such as a phosphorus compound. By reducing the molecular weight of the N-vinyl lactam copolymer, it is expected that the dispersion performance will be further improved.

[0082] Unless otherwise specified, the amount of the radical polymerization initiator used (the total amount when multiple types are used) is preferably 0.1% by mass to 5% by mass, more preferably 0.5% by mass to 4% by mass, and even more preferably 1% by mass to 3% by mass, based on the total amount of the monomer components. When the amount of the radical polymerization initiator used is within the above range, it is preferable in that the molecular weight of the polymer tends to be easily adjusted, the amount of impurities tends to be small, and coloring during heating tends to be more suppressed.

[0083] The method of adding the polymerization initiator to the reaction system (polymerization vessel) is not particularly limited, but it is preferable to add the polymerization initiator continuously or stepwise. When the polymerization initiator is added continuously, the dropwise addition rate may be changed.

[0084] The polymerization initiator may be added as it is without being dissolved in a solvent, but it is preferable to add it to the reaction system (polymerization vessel) after dissolving it in a solvent described below.

[0085] When hydrogen peroxide is used as a radical polymerization initiator in the above production method, its amount is not particularly limited, but is preferably 1.0 to 4.0% by mass relative to 100% by mass of the total amount of monomers used. This allows the polymerization reaction rate to be within a more suitable range. Furthermore, by using hydrogen peroxide in an amount of 1.0% by mass or more relative to 100% by mass of the total amount of monomers used, the stability over time of the resulting polymer solution is improved. Furthermore, by using hydrogen peroxide in an amount of 4.0% by mass or less, the amount of 2-pyrrolidone produced as a by-product can be sufficiently reduced, allowing the polymer to exhibit its full performance. The amount of hydrogen peroxide used is preferably 1.2 to 3.9% by mass, more preferably 1.5 to 3.8% by mass, and even more preferably 2.0 to 3.7% by mass.

[0086] <Reducing agent> In the production method of the present disclosure, particularly in the polymerization step, a reducing agent may be used, for example, but not limited to, to adjust the molecular weight of the N-vinyl lactam copolymer of the present disclosure. Usable reducing agents include, but are not limited to, thiol compounds such as mercaptoethanol, thioglycerol, thioglycolic acid, 2-mercaptopropionic acid, 3-mercaptopropionic acid, thiomalic acid, octyl thioglycolate, octyl 3-mercaptopropionate, 2-mercaptoethanesulfonic acid, n-dodecyl mercaptan, octyl mercaptan, and butyl thioglycolate; halides such as carbon tetrachloride, methylene chloride, bromoform, and bromotrichloroethane; hydroxyl-containing compounds other than the above alcohol compounds; lower oxides and salts thereof such as phosphorous acid, phosphites, hypophosphorous acid, hypophosphites, and hydrates thereof; and bisulfites (including compounds that dissolve in water to generate bisulfites) such as sulfurous acid, hydrogen sulfite, dithionous acid, metabisulfite, and their salts. These salts include metal salts such as sodium, ammonium salts, or organic amine salts. Two or more of the above reducing agents may be used. It is preferable to reduce the amount of metal salts such as sodium salts as much as possible when the composition is used in special industrial applications such as the production of hollow fiber membranes or in electrical materials applications such as semiconductor cleaning.

[0087] <Chain transfer agent> The polymerization step may be carried out in the presence of a phosphorus atom-containing compound. Chain transfer to the phosphorus atom-containing compound enables efficient introduction of a phosphorus atom-containing substituent into the N-vinyl lactam copolymer of the present disclosure. Furthermore, the molecular weight can be efficiently reduced. Examples of phosphorus atom-containing compounds and preferred embodiments thereof include hypophosphorous acid (salts), phosphorous acid (salts), phosphoric acid (salts), hypophosphite esters, phosphite esters, and phosphate esters, unless otherwise specified. Because of their high chain transfer efficiency, hypophosphorous acid (salts), phosphorous acid (salts), and hypophosphite esters are preferred, and hypophosphorous acid (salts) is more preferred. When a phosphorus atom-containing compound is used, one type may be used, or two or more types may be used.

[0088] In the polymerization step, the amount of the phosphorus atom-containing compound used is preferably 0.1 g or more and 5 g or less, more preferably 0.3 g or more and 1 g or less, per mole of the amount of the monomer (total monomers) used. When the phosphorus atom-containing compound is a salt, the mass of the salt is calculated based on the mass of the corresponding acid. For example, when the compound is sodium hypophosphite, the mass is calculated based on the mass of the corresponding acid, hypophosphorous acid.

[0089] In the polymerization step, if desired, a chain transfer agent other than the phosphorus atom-containing compound (hereinafter also referred to as "other chain transfer agent") can be used. Examples of other chain transfer agents include thiol-based chain transfer agents such as mercaptoethanol and mercaptopropionic acid; halides such as carbon tetrachloride and methylene chloride; secondary alcohols such as isopropyl alcohol and glycerin; sulfites (salts) such as sodium sulfite; bisulfites (salts) such as sodium hydrogen sulfite; dithionites (salts) such as sodium dithionite; and pyrosulfites (salts) such as potassium pyrosulfite. When using the other chain transfer agents, they may be used alone or in combination of two or more.

[0090] <Reducing compounds> In the production method of the present disclosure, particularly in the polymerization step, a heavy metal ion (or a heavy metal salt) may be used as a reducing compound that acts as a decomposition catalyst for the polymerization initiator. In the present invention, a heavy metal is defined as a compound having a specific gravity of 4 g / cm 3 Among heavy metals, iron and / or copper are preferred, and heavy metal salts such as Mohr's salt (Fe(NH4)2(SO4)2·6H2O), ferrous sulfate heptahydrate, ferrous chloride, ferric chloride, copper(I) sulfate and / or its hydrate, copper(II) sulfate and / or its hydrate, and copper(II) chloride and / or its hydrate may be used as the reducing compound.

[0091] The amount of the heavy metal compound used is not particularly limited, but the amount of metal ions is preferably 0.01 to 10 ppm by mass relative to the monomer component. That is, the amount of the heavy metal compound used, converted into the amount of metal ions, is preferably 0.01 to 10 ppm by mass relative to the monomer component. The amount of metal ions is more preferably 0.01 to 5 ppm by mass. This allows the decomposition rate of hydrogen peroxide to be within a suitable range. The amount of the metal ions is preferably 0.001 to 0.35 millimol %, and more preferably 0.001 to 0.21 millimol %, relative to the monomer component.

[0092] When the heavy metal ions are used, they can be used in a range of, for example, 0.1 to 10 ppm, but it is preferable not to use them when they are used for special industrial applications such as hollow fiber membrane production or electrical material applications such as semiconductor cleaning.

[0093] <Other additives> In the production method of the present disclosure, particularly in the polymerization step, ammonia and / or an amine compound may be used for the purposes of accelerating the polymerization reaction and preventing hydrolysis of the N-vinyl lactam. Ammonia and / or an amine compound function as a co-catalyst in the polymerization reaction. That is, when ammonia and / or an amine compound are present in the reaction system, the polymerization reaction proceeds more rapidly than when they are not present. They can also function as a basic pH adjuster. Ammonia causes odor and also affects coloration, so it is preferable to use a limited amount. When ammonia is used, it may be used as a gaseous element at room temperature or as an aqueous solution (ammonia water). The addition of ammonia and / or an amine compound can be carried out by any appropriate method. For example, the ammonia and / or the amine compound may be charged into the reaction vessel from the beginning of the polymerization, or may be gradually added to the reaction vessel during the polymerization.

[0094] Any appropriate amine compound can be used as the amine compound. Specific examples include primary amines, secondary amines, and tertiary amines. The amines may be used alone or in combination of two or more.

[0095] Examples of the primary amine include monoethanolamine, allylamine, isopropylamine, diaminopropylamine, ethylamine, 2-ethylhexylamine, 3-(2-ethylhexyloxy)propylamine, 3-ethoxypropylamine, 3-(diethylamino)propylamine, 3-(dibutylamino)propylamine, tetramethylethylenediamine, t-butylamine, sec-butylamine, propylamine, 3-(methylamino)propylamine, 3-(dimethylamino)propylamine, and 3-methoxypropylamine. The primary amines may be used alone or in combination of two or more.

[0096] Examples of the secondary amine include aliphatic secondary amines such as dimethylamine, diethylamine, dipropylamine, diisopropylamine, N-methylethylamine, N-methylpropylamine, N-methylisopropylamine, N-methylbutylamine, N-methylisobutylamine, N-methylcyclohexylamine, N-ethylpropylamine, N-ethylisopropylamine, N-ethylbutylamine, N-ethylisobutylamine, N-ethylcyclohexylamine, N-methylvinylamine, and N-methylallylamine; N-methylethylenediamine, N-ethylethylenediamine, N,N'-dimethylethylenediamine, N,N'-diethylethylenediamine, N-methyltrimethylenediamine, N-ethyltrimethylenediamine, and N,N'-dimethyltrimethylenediamine. Aliphatic diamines and triamines such as amine, N,N'-diethyltrimethylenediamine, diethylenetriamine, and dipropylenetriamine; aromatic amines such as N-methylbenzylamine, N-ethylbenzylamine, N-methylphenethylamine, and N-ethylphenethylamine; monoalkanolamines such as N-methylethanolamine, N-ethylethanolamine, N-propylethanolamine, N-isopropylethanolamine, N-butylethanolamine, and N-isobutylethanolamine; dialkanolamines such as diethanolamine, dipropanolamine, diisopropanolamine, and dibutanolamine; and cyclic amines such as pyrrolidine, piperidine, piperazine, N-methylpiperazine, N-ethylpiperazine, morpholine, and thiomorpholine. The secondary amines may be used alone or in combination of two or more. Among these secondary amines, dialkanolamines and dialkylamines are preferred, and dialkanolamines are more preferred, with diethanolamine being particularly preferred.

[0097] Examples of the tertiary amine include trialkanolamines such as trimethylamine, triethylamine, tripropylamine, triisopropylamine, triethanolamine, tripropanolamine, triisopropanolamine, and tributanolamine. The tertiary amines may be used alone or in combination of two or more. Among these tertiary amines, trialkanolamines are preferred, and triethanolamine is particularly preferred.

[0098] When the ammonia and amine compound are used, the total amount of both used is preferably 0.01 part by mass or more, more preferably 0.02 to 1 part by mass, per 100 parts by mass of N-vinyl lactam. Within the above range, the reaction rate tends to improve, and the effect of suppressing hydrolysis and coloration of N-vinyl lactam that accompanies a decrease in pH during the reaction can be obtained.

[0099] When hydrogen peroxide is used as a polymerization initiator, it is preferable to use ammonia, and although there are no particular restrictions on the amount used, it is preferably 0.1 to 3.0 mass %, more preferably 0.15 to 2.0 mass %, and even more preferably 0.2 to 1.0 mass %, relative to 100 mass % of the total amount of monomers used.

[0100] When a copper salt is used as the heavy metal salt and ammonia is also used, an ammine copper complex salt may be formed. Examples of the ammine copper complex salt include diamine copper salts ([Cu(NH3)2]2SO4·H2O, [Cu(NH3)2]Cl, etc.) and tetraamine copper salts ([Cu(NH3)4]SO4·H2O, [Cu(NH3)4]Cl, etc.). When a copper ammine complex salt is used as the heavy metal salt, the copper ammine complex salt may be added to the reactor, but it is preferable to form the copper ammine complex salt by adding a copper salt such as copper sulfate, copper chloride, copper nitrate, or copper acetate and ammonia to the reactor.

[0101] When hydrogen peroxide and ammonia are used in the production of the N-vinyl lactam copolymer of the present invention, ammonia and hydrogen peroxide may be further added after the addition of the monomer components is completed. The amounts of ammonia and hydrogen peroxide used after the addition of the monomer components are preferably 0 to 0.3% by mass and 0.2 to 2.5% by mass, respectively, relative to 100% by mass of the total amount of monomers used.

[0102] <Polymerization solvent> The polymerization step is preferably carried out in the presence of a solvent. Examples of the solvent include one or more selected from alcohols such as water, methyl alcohol, ethyl alcohol, isopropyl alcohol (2-propanol), n-butyl alcohol, and diethylene glycol. Preferred solvents are water and isopropyl alcohol, and more preferred is water. The amount of solvent used is preferably 40 to 1000% by mass relative to 100% by mass of the monomer.

[0103] The polymerization step is preferably carried out so that the solid content concentration (concentration of non-volatile content in the solution) after completion of the polymerization is 10 to 80 mass %, more preferably 15 to 70 mass %, and even more preferably 20 to 60 mass %, relative to 100 mass % of the polymerization solution.

[0104] <Other polymerization conditions> The temperature during polymerization is preferably 50° C. or higher, more preferably 55 to 100° C., and even more preferably 60 to 90° C. If the temperature during polymerization is within the above range, the amount of residual monomer components tends to be reduced, and the dispersibility of the polymer tends to be improved. The temperature during polymerization may be 70°C or higher, 75 to 110°C, or 80 to 105°C. It is not necessary to maintain the temperature during polymerization at a constant value during the progress of the polymerization reaction. For example, the polymerization may be started from room temperature, the temperature may be raised to a set temperature for an appropriate temperature rise time or at an appropriate temperature rise rate, and the set temperature may then be maintained. Alternatively, the polymerization temperature may be varied (raised or lowered) over time during the progress of the polymerization reaction depending on the method of dropping the monomer components, initiator, etc.

[0105] The pH during polymerization is preferably 5 or higher, more preferably 6 or higher, and preferably 11 or lower, from the viewpoint of suppressing the generation of impurities or by-products.

[0106] The pressure in the reaction system may be normal pressure (atmospheric pressure), reduced pressure, or increased pressure, but from the viewpoint of the molecular weight of the resulting polymer, it is preferable to carry out the reaction at normal pressure or by sealing the reaction system and carrying out the reaction under increased pressure. Furthermore, from the viewpoint of equipment such as a pressure device, a pressure-reducing device, a pressure-resistant reaction vessel, and piping, it is preferable to carry out the reaction at normal pressure (atmospheric pressure). The atmosphere in the reaction system may be an air atmosphere, but an inert atmosphere is preferable; for example, it is preferable to replace the atmosphere in the system with an inert gas such as nitrogen before the start of polymerization.

[0107] The polymerization time is preferably 30 minutes or more and 5 hours or less. As the polymerization time increases, the color of the polymerization liquid tends to become more pronounced. After the polymerization is completed, an aging step (a step of maintaining the polymerization liquid under heated and warm conditions after polymerization) may be performed for the purpose of reducing the amount of monomer remaining in the polymerization liquid. The aging time is usually 1 minute or more and 4 hours or less. It is preferable to add a polymerization initiator (booster) during the aging time, as this can reduce the amount of monomer remaining in the polymerization liquid.

[0108] In the latter stage of polymerization, it is preferable to finish adding the initiator at the same time as or later than the monomer addition, since this makes it possible to reduce the amount of monomer remaining in the polymerization solution.

[0109] <Addition of organic acids> In the present disclosure, after the polymerization reaction is completed, an organic acid or an aqueous solution thereof may be added to the reaction solution (hereinafter also referred to as an organic acid addition step). In this case, it is preferable to maintain the reaction temperature during the polymerization reaction. This allows the remaining N-vinyl lactam to be hydrolyzed by the acid, thereby reducing the amount of unreacted monomer (i.e., the amount of monomer remaining in the reaction solution). For example, if the monomer is N-vinyl-2-pyrrolidone, it is hydrolyzed to 2-pyrrolidone by the acid.

[0110] Preferred organic acids that can be used to reduce the amount of residual monomers are carboxylic acids having a boiling point higher than the reaction liquid temperature when the organic acid is added (for example, 100°C or higher), and specific examples include formic acid, acetic acid, propionic acid, oxalic acid, malonic acid, succinic acid, aspartic acid, citric acid, glutamic acid, fumaric acid, malic acid, maleic acid, phthalic acid, trimellitic acid, pyromellitic acid, etc. These organic acids may be used alone or in combination of two or more.

[0111] The amount of organic acid used may be adjusted appropriately depending on the amount of N-vinyl lactam used in the polymerization reaction, and is not particularly limited, but may be, for example, such that the pH of the reaction solution after polymerization is preferably 5 or less, more preferably 3 or more and 4 or less. Specifically, the amount of organic acid used is preferably 100 ppm or more and 30,000 ppm or less, more preferably 500 ppm or more and 20,000 ppm or less, relative to the amount of N-vinyl lactam used.

[0112] <Residual monomer amount> The method for producing an N-vinyl lactam copolymer of the present disclosure is preferred because it allows for a reduction in the amount of unreacted remaining monomer. The amount of residual monomer is preferably 200 ppm or less relative to the obtained N-vinyl lactam polymer of the present disclosure. It is more preferably 100 ppm or less, even more preferably 50 ppm or less, and particularly preferably 10 ppm or less. A residual monomer amount within the above-mentioned range is preferred in that it reduces the amount of impurities, suppresses coloration during heating, and tends to suppress odor. Furthermore, since residual monomers are easily soluble in electrolyte solvents and may impair battery performance, reducing the amount of residual monomer is preferred in that it sufficiently prevents the impairment of battery performance.

[0113] <Amount of impurities derived from monomers> The method for producing an N-vinyl lactam copolymer of the present disclosure is preferred because it allows for a reduction in the amount of impurities derived from the monomer. For example, if the monomer is N-vinyl-2-pyrrolidone, the impurity derived from the monomer is 2-pyrrolidone. The amount of impurities derived from the monomer is preferably 50,000 ppm or less relative to the obtained N-vinyl lactam polymer of the present disclosure. It is more preferably 30,000 ppm or less, even more preferably 20,000 ppm or less, and particularly preferably 15,000 ppm or less. A monomer-derived impurity amount within the above-mentioned range is preferred because it tends to suppress coloration during heating and odor. Furthermore, since impurities are easily dissolved in electrolyte solvents and may impair battery performance, reducing the amount of impurities is preferred because it sufficiently prevents the impairment of battery performance. In one embodiment, the amount of impurities derived from monomers may be 5000 ppm or less, 3000 ppm or less, 2000 ppm or less, or 1500 ppm or less.

[0114] <Drying process> To obtain an N-vinyl lactam copolymer from the N-vinyl lactam copolymer solution obtained in the polymerization step, a drying step may be carried out. The drying step is a step of powdering, etc., and includes a pulverization step. Drying and pulverization may be carried out by a known general method, and powder can be obtained by, for example, spray drying, freeze drying, fluidized bed drying, drum drying, belt drying, etc. When drying by heating under normal pressure, the drying temperature is preferably about 100 to 250°C and the drying time is preferably about 0.2 to 180 minutes. When drying under reduced pressure, the drying temperature may be appropriately selected depending on the degree of reduced pressure. When drying an N-vinyl lactam copolymer solution having a K value of 60 or less, spray drying is preferred.

[0115] <Other processes> The production method of the present disclosure requires a polymerization step and may optionally include the organic acid addition step, drying step, etc., but may also optionally include other steps. For example, it may include a purification step, a desalting step, a concentration step, a dilution step, a pH adjustment step, etc. The color tone of the resulting N-vinyl lactam copolymer solution can be improved by treating the reaction solution (polymerization solution) with a cation exchange resin. The cation exchange resin treatment step can be carried out during polymerization (concurrently with the polymerization step) or after polymerization. The treatment with a cation exchange resin during the polymerization reaction can be carried out by any appropriate method. Preferably, the cation exchange resin is added to a reaction vessel in which the polymerization reaction of the monomer components is being carried out. Specific examples include a method in which the cation exchange resin is added to a reaction vessel in which the polymerization reaction is being carried out, finely suspending the resin, and then filtering the resulting mixture. The treatment time with the cation exchange resin can be any appropriate time. It is preferably 1 minute to 24 hours, more preferably 3 minutes to 12 hours, and even more preferably 5 minutes to 2 hours. The manufacturing method of the present disclosure may include none of the other steps described above, or may include one or more of them.

[0116] [Applications of N-vinyl lactam copolymers] The N-vinyl lactam copolymer of the present disclosure and / or the composition of the present invention can be used in a variety of applications, including, but not limited to, a hollow fiber membrane production aid, a cleaning agent for semiconductors, an additive for adhesives and pressure-sensitive adhesives, an aid for producing electronic components, a detergent additive, an additive for cosmetics, a thickener, an ink additive, a pigment dispersant, a dispersant for positive and negative electrode materials for batteries, a dispersant for inorganic particles, an additive for paint compositions, a surface treatment agent, a resin modifier, a binder for inorganic substances, a ceramic binder, an additive for inorganic compositions, a fiber treatment agent, and an additive for functional fibers. [Example]

[0117] 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, "parts" means "parts by mass" and "%" means "% by mass."

[0118] The polymer was evaluated by the following methods. <Measurement of polymer solid content> 1 g of polymer (mass W2 (g)) was weighed into a weighing can (mass W1 (g)) with a bottom diameter of approximately 5 cm, and then left to dry in a constant temperature dryer at 150°C for 1 hour. The mass of the weighing can and polymer after drying (W3 (g)) was measured, and the solid content was calculated using the following formula. Solid content (mass%) = ((W3(g)-W1(g)) / W2(g))×100

[0119] <Measurement of K value of polymer> The polymer was diluted with deionized water to a concentration of 1% by mass in terms of solid content, and the viscosity of the solution was measured using an Ubbelohde viscometer at 25±0.2°C. The time it took for the solution to flow between two marked lines was measured. Several measurements were taken and the average value was calculated. To determine the relative viscosity, the same measurement was also taken with deionized water. The two obtained flow times were corrected based on the Hagenbach-Couette correction.

[0120]

number

[0121]

number

[0122] <Measurement of polymer weight average molecular weight (Mw)> The weight average molecular weight of the copolymer was determined by measurement using gel permeation chromatography (GPC) under the following conditions. Equipment: Waters Alliance HPLC system Detector: RI Columns: Tosoh TSKgel α-M (2 columns), TSKgel α Column temperature: 40℃ Flow rate: 0.6ml / min Calibration curve: Polyethylene Oxide Standards Eluent: Ion-exchanged water / acetonitrile 84 / 16 (containing 1.4% sodium nitrate)

[0123] <Measurement of pH of polymer> Deionized water was added to the polymer to dilute it to a concentration of 5% by mass in terms of solid content, and the pH of the solution was measured.

[0124] <Quantitative determination of N-vinylpyrrolidone and 2-pyrrolidone in polymers> Quantitative analysis was carried out by liquid chromatography under the following conditions. Equipment: Shiseido "NANOSPACE SI-2" (using UV / VIS detector) Column: Osaka Soda "CAPCELLPAK C18 UG120 (inner diameter 1.5 mm, length 250 mm)", 40°C Eluent: LC-grade methanol (Wako Pure Chemical Industries, Ltd.) / ultrapure water = 1 / 24 (mass ratio), with 0.04 mass% sodium 1-heptanesulfonate added Flow rate: 100μL / min

[0125] <Quantitative determination of salts of acid group-containing monomers in polymers> Quantitative analysis was carried out by liquid chromatography under the following conditions. Equipment: Waters Alliance HPLC system Column: Shodex RS pak DE-413L, Shodex RS pak DE-G, manufactured by Showa Denko K.K., 40°C Eluent: 0.1% phosphoric acid aqueous solution Flow rate: 1mL / min

[0126] <Evaluation of polymer solubility in N-methyl-2-pyrrolidone> N-methyl-2-pyrrolidone (hereinafter also referred to as "NMP") was added to the polymer so that the concentration was 1% by mass in terms of solid content. After thorough stirring and standing for 24 hours, the solution was visually observed and evaluated according to the following criteria. 〇: The solution is clear and no insoluble matter is observed ×: Insoluble matter is observed and / or the solution is opaque

[0127] <Evaluation of polymer solubility in deionized water> Deionized water was added to the polymer so that the concentration was 1% by mass in terms of solid content. After thorough stirring, the solution was left to stand for 24 hours, and then visually observed and evaluated according to the following criteria. 〇: The solution is clear and no insoluble matter is observed ×: Insoluble matter is observed and / or the solution is opaque

[0128] <Evaluation of solubility of polymer electrolyte in a mixed solvent of ethylene carbonate / ethyl methyl carbonate = 3 / 7 (weight ratio)> A mixed solvent of ethylene carbonate / ethyl methyl carbonate = 3 / 7 (weight ratio) was added to the polymer to a concentration of 0.1 mass% in terms of solid content, and the mixture was stirred for 1 hour using a shaker (IKA ROLLER10 digital, 80 rpm). The viscosity of the electrolyte was then compared before and after adding the polymer. The supernatant was also diluted 2-fold with N,N-dimethylformamide and measured using gel permeation chromatography (GPC) under the following conditions. Equipment: Tosoh HLC-8320GPC Detector: RI Column: Showa Denko KD-806M (2 columns), KD-G 4A Column temperature: 40℃ Flow rate: 0.8ml / min Calibration curve: Polystyrene Standards Eluent: N,N-dimethylformamide (containing 0.1% LiBr) A calibration curve was drawn using polyvinylpyrrolidone K-30 (manufactured by Nippon Shokubai), and the polymer concentration (W4 (ppm)) in the supernatant (2-fold diluted) was quantified. The elution rate of the polymer into the electrolyte (ethylene carbonate / ethyl methyl carbonate = 3 / 7 (weight ratio)) was calculated using the following formula. Elution rate (%)=W4(ppm)×2 / W5(ppm)×100 W5 (ppm): Concentration of polymer in electrolyte, calculated from the amount added The solubility of the polymer in the electrolyte solution was calculated using the following formula. Solubility (%) = 0.1 x dissolution rate (%) When the dissolution rate was 100%, the solubility was judged to be 0.1% or more.

[0129] (Production Example 1: Production of Polymer A) A 1 L reactor (SUS304) equipped with a Maxblend-type stirring blade (SUS304), a thermometer, a reflux condenser, and a jacket was charged with 420 parts of deionized water. While stirring the deionized water at 250 rpm, nitrogen substitution was performed at 200 ml / min for 30 minutes to remove dissolved oxygen. The nitrogen introduction rate was then increased to 30 ml / min, and the reactor was heated to an internal temperature of 80°C while stirring at 250 rpm. After stabilizing the liquid temperature at 80°C, 180 parts of N-vinylpyrrolidone (manufactured by Nippon Shokubai, hereinafter also referred to as "NVP"), 87.2 parts of a 4% by weight aqueous solution of lithium acrylate (manufactured by Nippon Shokubai, acrylic acid neutralized with lithium hydroxide, hereinafter also referred to as "AA-Li"), and 45.9 parts of a 10% by weight aqueous solution of 2,2'-azobis(2-methylpropionamidine) dihydrochloride (manufactured by Fujifilm Wako Pure Chemical Industries, hereinafter also referred to as "V-50") as a polymerization initiator were added dropwise over 120 minutes to initiate polymerization. After the 120-minute dropwise addition of the 4% by weight aqueous solution of AA-Li was completed, 4.6 parts was added dropwise over 30 minutes. Furthermore, 30 minutes after the 120-minute dropwise addition, 1.8 parts of the 10% by weight aqueous solution of V-50 was added all at once. The temperature was maintained at 80°C for 240 minutes from the start of the dropwise addition to obtain an NVP / AA-Li copolymer solution. The obtained NVP / AA-Li copolymer solution was dried in vacuum at 110°C, then pulverized until it passed through a JIS standard sieve with a mesh size of 500 μm, and the powder was further dried in vacuum at 110°C to obtain the NVP / AA-Li copolymer (powder).

[0130] (Production Example 2: Production of Polymer B) A 1-L reactor equipped with a Maxblend-type stirring blade, thermometer, reflux condenser, and jacket was charged with 1.28 parts of sodium hypophosphite monohydrate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) and 438 parts of deionized water. Nitrogen substitution and heating of this solution were performed as in Production Example 1. After the liquid temperature was stabilized at 80°C, 180 parts of NVP, 78.3 parts of a 4% by weight aqueous solution of sodium acrylate (manufactured by Nippon Shokubai; acrylic acid neutralized with sodium hydroxide, hereinafter also referred to as "AA-Na"), and 34.8 parts of a 10% by weight aqueous solution of V-50 as a polymerization initiator were added dropwise over 120 minutes to initiate polymerization. After the 120-minute dropwise addition of the 4% by weight aqueous solution of AA-Na was completed, 4.1 parts were added dropwise over 30 minutes. Furthermore, 30 minutes after the 120-minute dropwise addition, 1.4 parts of the 10% by weight aqueous solution of V-50 was added all at once. The temperature was maintained at 80°C for 240 minutes from the start of the dropwise addition to obtain an NVP / AA-Na copolymer solution. The obtained NVP / AA-Na copolymer solution was dried and pulverized in the same manner as in Production Example 1 to obtain an NVP / AA-Na copolymer (powder).

[0131] (Production Example 3: Production of Polymer C) A 1-L reactor equipped with a Maxblend-type stirring blade, a thermometer, a reflux condenser, and a jacket was charged with 1.33 parts of sodium hypophosphite monohydrate and 449 parts of deionized water. Nitrogen substitution and heating of this solution were performed as in Production Example 1. After the liquid temperature was stabilized at 80°C, 180 parts of NVP, 90 parts of a 10% by weight aqueous solution of ammonium acrylate (Nippon Shokubai Co., Ltd., acrylic acid neutralized with ammonia water; hereinafter, also referred to as "AA-NH3"), and 36 parts of a 10% by weight aqueous solution of V-50 as a polymerization initiator were each added dropwise over 120 minutes to initiate polymerization. After the 120-minute dropwise addition of the 10% by weight aqueous solution of AA-NH3 was completed, 4.8 parts were added dropwise over 30 minutes. Furthermore, 30 minutes after the 120-minute dropwise addition, 1.4 parts of the 10% by weight aqueous solution of V-50 was added all at once. The temperature was maintained at 80°C for 240 minutes from the start of the dropwise addition to obtain an NVP / AA-NH3 copolymer solution. The obtained NVP / AA-NH3 copolymer solution was dried and pulverized in the same manner as in Production Example 1 to obtain an NVP / AA-NH3 copolymer (powder).

[0132] (Production Example 4: Production of Polymer D) A 1-L reactor equipped with a Maxblend-type stirring blade, a thermometer, a reflux condenser, and a jacket was charged with 311 parts of deionized water. Nitrogen substitution and temperature elevation of this solution were performed as in Production Example 1. After the liquid temperature was stabilized at 80°C, 150 parts of NVP, 79.2 parts of a 10% by weight aqueous solution of AA-NH3, 79.2 parts of a 10% by weight aqueous solution of 2-methoxyethyl acrylate (manufactured by Fujifilm Wako Pure Chemical Industries, hereinafter also referred to as "MEA"), and 41.7 parts of a 10% by weight aqueous solution of V-50 as a polymerization initiator were each added dropwise over 120 minutes to initiate polymerization. After the 120-minute dropwise addition, 4.2 parts each of the 10% by weight aqueous solution of AA-NH3 and the 10% by weight aqueous solution of MEA were added dropwise over 30 minutes. Furthermore, 1.7 parts of the 10% by weight aqueous solution of V-50 was added all at once 30 minutes after the 120-minute dropwise addition. The temperature was maintained at 80°C for 240 minutes from the start of the dropwise addition to obtain an NVP / AA-NH3 / MEA copolymer solution. The obtained NVP / AA-NH3 / MEA copolymer solution was dried and pulverized in the same manner as in Production Example 1 to obtain an NVP / AA-NH3 / MEA copolymer (powder).

[0133] (Production Example 5: Production of Polymer E) A 1-liter reactor (SUS304) equipped with a Maxblend-type stirring blade (made of SUS304), a thermometer, a reflux condenser, and a jacket was charged with 0.33 parts of a 0.05% aqueous solution of copper sulfate (0.4 ppm of copper sulfate relative to NVP+AA-Na) and 230.8 parts of deionized water. While stirring at 250 rpm, the mixture was purged with nitrogen at 200 mL / min for 30 minutes to remove dissolved oxygen. The nitrogen introduction rate was then increased to 30 mL / min, and the reactor was heated to an internal temperature of 60°C while stirring at 250 rpm. Next, while maintaining the temperature at 60°C, 444.4 parts of a 90% NVP aqueous solution (400 parts of NVP diluted with 44.4 parts of deionized water), 179.6 parts of a 4% AA-Na aqueous solution (19.8 parts of a 37% AA-Na aqueous solution diluted with 163.5 parts of deionized water), 28.1 parts of a 15% hydrogen peroxide solution (16.1 parts of a 35% hydrogen peroxide solution (manufactured by Tokyo Chemical Industry Co., Ltd.) diluted with 21.5 parts of deionized water) (the amount of hydrogen peroxide relative to NVP+AA-Na was 1.0%), and 16.0 parts of a 3% ammonia aqueous solution (2.4 parts of a 28% ammonia aqueous solution (manufactured by Wako Pure Chemical Industries, Ltd.) diluted with 20.2 parts of deionized water) (the amount of ammonia relative to NVP+AA-Na was 0.12%) were separately added dropwise over 180 minutes. After the successive dropwise addition of the raw materials was completed, 3.7 parts of a 4% aqueous AA-Na solution and 6.7 parts of a 3% aqueous ammonia solution (amount of ammonia relative to NVP+AA-Na: 0.05%) were added dropwise over 30 minutes. 240 minutes after the start of the dropwise addition of NVP, the temperature was raised to 80°C, and 4.8 parts of 15% hydrogen peroxide solution (amount of hydrogen peroxide relative to NVP+AA-Na: 0.18%) was added dropwise over 30 minutes. Next, 330 minutes after the start of the NVP dropwise addition, 4.8 parts of 15% hydrogen peroxide solution (the amount of hydrogen peroxide relative to NVP was 0.18%) was added dropwise over 30 minutes, and the mixture was further maintained at 80°C for 1 hour to obtain an NVP / AA-Na copolymer solution. The obtained NVP / AA-Na copolymer solution was spray-dried to obtain an NVP / AA-Na copolymer (powder).

[0134] (Production Example 6: Production of Polymer F) A Max Blend-type stirring blade was charged with an aqueous copper sulfate solution and deionized water, and the process from nitrogen substitution to heating was carried out as in Production Example 5. After the liquid temperature was stabilized at 60°C, 444.4 parts of a 90% aqueous NVP solution, 165.0 parts of a 4% aqueous AA-Na solution, 38.8 parts of a 25% aqueous hydrogen peroxide solution (the amount of hydrogen peroxide relative to the NVP + AA-Na was 2.4%), and 21.1 parts of a 3% aqueous ammonia solution (the amount of ammonia relative to the NVP + AA-Na was 0.16%) were added dropwise separately over 180 minutes. After the successive dropwise addition of the raw materials was completed, 18.3 parts of a 4% aqueous AA-Na solution and 8.8 parts of a 3% aqueous ammonia solution (amount of ammonia relative to NVP+AA-Na: 0.06%) were added dropwise over 30 minutes. 240 minutes after the start of the dropwise addition of NVP, the temperature was raised to 80°C, and 3.4 parts of 25% hydrogen peroxide solution (amount of hydrogen peroxide relative to NVP+AA-Na: 0.21%) was added dropwise over 30 minutes. Next, 330 minutes after the start of the NVP dropwise addition, 3.4 parts of 25% hydrogen peroxide solution (the amount of hydrogen peroxide relative to NVP + AA-Na was 0.21%) was added dropwise over 30 minutes, and the mixture was further maintained at 80°C for 1 hour to obtain an NVP / AA-Na copolymer solution. The obtained NVP / AA-Na copolymer solution was spray-dried to obtain an NVP / AA-Na copolymer (powder).

[0135] (Production Example 7: Production of Polymer G) A 1 L reactor equipped with a Max Blend type stirring blade, a thermometer, a reflux condenser, and a jacket was charged with 0.34 parts of a 0.05% aqueous solution of copper sulfate (the amount of copper sulfate relative to the monomer was 0.4 ppm) and 230.4 parts of deionized water. The solution was purged with nitrogen and heated as in Production Example 5. After the liquid temperature was stabilized at 60°C, 388.9 parts of a 90% NVP aqueous solution, 23.5 parts of a 25% hydrogen peroxide solution (the amount of hydrogen peroxide relative to the monomer was 1.4%), and 21.8 parts of a 3% aqueous ammonia solution (the amount of ammonia relative to the monomer was 0.16%) were added dropwise over 180 minutes, respectively, and 259.7 parts of an AA-Na / PEGMA (9) aqueous solution (20.5 parts of a 37% AA-Na aqueous solution, 63.1 parts of polyethylene glycol monomethyl ether acrylate (n = approximately 9) (manufactured by Tokyo Chemical Industry Co., Ltd.; hereinafter, also referred to as "PEGMA (9)") diluted with 181.5 parts of deionized water) were added dropwise over 240 minutes. After the sequential dropwise addition of NVP was completed, 9.1 parts of a 3% aqueous ammonia solution (amount of ammonia relative to the monomer: 0.06%) was added dropwise over 30 minutes. 240 minutes after the start of the NVP addition, the temperature was raised to 80°C, and 5.3 parts of an aqueous AA-Na / PEGMA (9) solution and 2.1 parts of a 25% hydrogen peroxide solution (the amount of hydrogen peroxide relative to the monomer was 0.12%) were added dropwise separately over 30 minutes. Next, 330 minutes after the start of the NVP addition, 2.1 parts of 25% hydrogen peroxide solution (the amount of hydrogen peroxide relative to the monomer was 0.12%) was added dropwise over 30 minutes, and the mixture was further maintained at 80°C for 1 hour to obtain an NVP / AA-Na / PEGMA (9) copolymer solution. The obtained NVP / AA-Na / PEGMA (9) copolymer solution was spray-dried to obtain NVP / AA-Na / PEGMA (9) copolymer (dried product).

[0136] (Production Example 8: Production of Polymer H) A 1 L reactor equipped with a Maxblend-type stirring blade, a thermometer, a reflux condenser, and a jacket was charged with 0.35 parts of a 0.05% aqueous solution of copper sulfate (the amount of copper sulfate relative to the monomer was 0.4 ppm) and 245.2 parts of deionized water. The nitrogen substitution and heating of this solution were carried out as in Production Example 5. After the liquid temperature was stabilized at 60 ° C, 400.0 parts of a 90% aqueous solution of NVP, 231.7 parts of an aqueous solution of AA-Na / PEGMA (9) (21.1 parts of a 37% aqueous solution of AA-Na and 64.9 parts of PEGMA (9) diluted with 186.6 parts of deionized water), 25.3 parts of a 15% aqueous solution of hydrogen peroxide (the amount of hydrogen peroxide relative to the monomer was 0.88%), and 22.4 parts of a 3% aqueous solution of ammonia (the amount of ammonia relative to the monomer was 0.16%) were added dropwise separately over 180 minutes. After the sequential dropwise addition of the raw materials was completed, 40.9 parts of an aqueous solution of AA-Na / PEGMA (9) was added dropwise over 90 minutes, and 9.3 parts of a 3% aqueous solution of ammonia (amount of ammonia relative to the monomer: 0.06%) was added dropwise over 30 minutes. 240 minutes after the start of the dropwise addition of NVP, the temperature was raised to 80° C., and 2.2 parts of 15% hydrogen peroxide solution (amount of hydrogen peroxide relative to the monomer: 0.08%) was added dropwise over 30 minutes. Next, 330 minutes after the start of the NVP addition, 2.2 parts of 15% hydrogen peroxide solution (the amount of hydrogen peroxide relative to the monomer was 0.08%) was added dropwise over 30 minutes, and the mixture was further maintained at 80°C for 1 hour to obtain an NVP / AA-Na / PEGMA (9) copolymer solution. The obtained NVP / AA-Na / PEGMA (9) copolymer solution was dried under vacuum to obtain NVP / AA-Na / PEGMA (9) copolymer (dried product).

[0137] (Production Example 9: Production of Polymer I) A 1 L reactor equipped with a Maxblend-type stirring blade, a thermometer, a reflux condenser, and a jacket was charged with 0.31 parts of a 0.05% aqueous solution of copper sulfate (the amount of copper sulfate relative to the monomer was 0.4 ppm) and 216.8 parts of deionized water. The solution was purged with nitrogen and heated as in Production Example 5. After the liquid temperature was stabilized at 60°C, 311.1 parts of a 90% NVP aqueous solution, 330.2 parts of an AA-Na / PEGMA (13) aqueous solution (18.6 parts of a 37% AA-Na aqueous solution, 95.6 parts of polyethylene glycol monomethyl ether acrylate (n = approximately 13) (manufactured by Tokyo Chemical Industry Co., Ltd.; hereinafter, also referred to as "PEGMA (13)") diluted with 274.3 parts of deionized water), 21.3 parts of a 25% hydrogen peroxide solution (the amount of hydrogen peroxide relative to the monomer was 1.4%), and 19.8 parts of a 3% ammonia aqueous solution (the amount of ammonia relative to the monomer was 0.16%) were separately added dropwise over 180 minutes. After the sequential dropwise addition of the raw materials was completed, 58.3 parts of an aqueous solution of AA-Na / PEGMA (13) was added dropwise over 90 minutes, and 8.3 parts of a 3% aqueous solution of ammonia (amount of ammonia relative to the monomer: 0.06%) was added dropwise over 30 minutes. 240 minutes after the start of the dropwise addition of NVP, the temperature was raised to 80° C., and 1.9 parts of 25% aqueous hydrogen peroxide (amount of hydrogen peroxide relative to the monomer: 0.12%) was added dropwise over 30 minutes. Next, 330 minutes after the start of the NVP addition, 1.9 parts of 25% hydrogen peroxide solution (the amount of hydrogen peroxide relative to the monomer was 0.12%) was added dropwise over 30 minutes, and the mixture was further maintained at 80°C for 1 hour to obtain an NVP / AA-Na / PEGMA (13) copolymer solution. The obtained NVP / AA-Na / PEGMA (13) copolymer solution was dried under vacuum to obtain NVP / AA-Na / PEGMA (13) copolymer (dried product).

[0138] Polymer J: Polyvinylpyrrolidone K-30 (Nippon Shokubai) Polymer K: Polyvinylpyrrolidone (manufactured by Aldrich, product name: PVP-360, average mol wt 360,000)

[0139] (Production Example 10: Production of Polymer L) An NVP / AA-Li copolymer (powder) was obtained in the same manner as in Production Example 1, except that the copolymerization ratio of NVP / AA-Li was changed to 76 / 24.

[0140] (Production Example 11: Production of Polymer M) An NVP / AA-NH3 copolymer (powder) was obtained in the same manner as in Production Example 1, except that AA-Li was changed to AA-NH3 and the copolymerization ratio of NVP / AA-NH3 was changed to 80 / 20.

[0141] (Examples 1 to 9, Comparative Examples 1 to 4) The K value, weight-average molecular weight (Mw), pH, amounts of N-vinylpyrrolidone and 2-pyrrolidone, and amounts of (meth)acrylate were measured for polymers A to M. The solubility in NMP, deionized water, and an electrolyte (ethylene carbonate / ethyl methyl carbonate = 3 / 7 (weight ratio)) was also evaluated by the same methods as above. Furthermore, for polymers J and K, the following additional evaluations were carried out. <Evaluation of Solubility of Polymer in Electrolyte: Ethylene Carbonate / Ethyl Methyl Carbonate = 3 / 7 (Weight Ratio) Mixed Solvent 2> The same procedure as in the evaluation of the solubility of polymers in mixed solvents of electrolyte solutions was carried out, except that a mixed solvent of ethylene carbonate / ethyl methyl carbonate = 3 / 7 (weight ratio) was added to polymers J and K so that the concentration was 1.2 mass% in terms of solid content. The elution rates of the copolymers in the electrolyte (ethylene carbonate / ethyl methyl carbonate = 3 / 7 (weight ratio)) were calculated to be 100% for both polymers J and K. In other words, the solubility of both J and K was confirmed to be 1.2% or more. The results are shown in Tables 1 and 2.

[0142] [Table 1]

[0143] [Table 2]

[0144] The above results demonstrate that polyvinylpyrrolidone (Comparative Examples 1 and 2) dissolves in NMP and water and dissolves in the electrolyte at a concentration of 1.2% or more, resulting in an increase in the viscosity of the electrolyte. However, the NVP / AA salt copolymers of the present invention (Examples 1 to 9) maintain their solubility in NMP and water while reducing elution into the electrolyte and suppressing the increase in the viscosity of the electrolyte. The increase in the viscosity of the electrolyte solvent may impair battery performance, for example, in battery applications. Furthermore, when the copolymerization ratio of the AA salt is greater than 15% by mass (Comparative Examples 3 and 4), the copolymer is insoluble in the electrolyte, but loses solubility in NMP. This makes it unsuitable for use in NMP as a solvent (e.g., in a positive electrode slurry for battery applications), which is undesirable. Furthermore, the copolymers of Comparative Examples 3 and 4 have K values ​​greater than 60, meaning they are soluble in water, but increase the viscosity of the water, which is undesirable.

[0145] (Examples 10 to 29, Comparative Examples 5 to 22) 80 g of deionized water or NMP and 0.5% by mass of each of Polymers A to M were added to a 110 ml screw tube and stirred with a stirrer tip (2.5 cm). 0.05% by mass of carbon nanotubes (VGCF-H (registered trademark, Showa Denko K.K., multi-walled carbon nanotubes with fiber diameters of approximately 150 nm and fiber lengths of 10 to 20 μm, hereinafter also referred to as "CNT") or carbon black (Mitsubishi Carbon Black #10, hereinafter also referred to as "CB") was added to the polymer solution and stirred for 1 minute (magnetic stirrer stirring speed: HIGH, scale 9). After allowing to stand for 1 day, the dispersion stability was evaluated visually. Comparative Examples 5 to 6 and 14 to 15 were evaluated in the same manner without adding any polymer. The evaluation criteria are as follows: 〇: The supernatant is black and you can't see through to the background ×: The supernatant is almost transparent and the background is visible The results for the CNT dispersion are shown in Tables 3 and 4, and the results for the CB dispersion are shown in Tables 5 and 6.

[0146] [Table 3]

[0147] [Table 4]

[0148] [Table 5]

[0149] [Table 6]

[0150] From the above results, when no polymer was added (Comparative Examples 5, 6, 14, and 15), the CNTs and CB settled or floated within one day, resulting in a nearly transparent solution. However, when using the NVP / AA salt copolymer of the present invention (Examples 10 to 29) and low-molecular-weight polyvinylpyrrolidone (Comparative Examples 7, 8, 16, and 17), the CNTs and CB remained well dispersed even after one day. On the other hand, when using high-molecular-weight polyvinylpyrrolidone (Comparative Examples 9 and 18), the CNTs and CB could not be maintained in a dispersed state after one day. When the CB and CNT concentrations were low, as in the present dispersion, low-molecular-weight polyvinylpyrrolidone and the N-vinyl lactam copolymer of the present disclosure were found to be better. Furthermore, because polymers L to M were not soluble in NMP at 1%, they did not contribute to the dispersibility of CNTs and CB in NMP (Comparative Examples 11, 13, 20, and 22). It was also revealed that polymers L to M did not contribute to the dispersibility of CNT and CB in water (Comparative Examples 10, 12, 19, and 21). Furthermore, when the mixture was allowed to stand and the state of the mixture was checked after 268 hours, it was confirmed that polymers G to I had better dispersibility than the others. This is thought to be due to the steric repulsion effect of PEGMA copolymerized as the third component, which further improved dispersion stability.

[0151] (Examples 30 to 31, Comparative Example 23) Polymers B and G were each weighed out in an amount of 0.2 g (0.5% by mass) in terms of solid content into a 50 ml screw tube, and deionized water was added to bring the total weight to 40 g. The aqueous polymer solution was stirred with a stirrer tip (2.5 cm) to confirm that the polymer had dissolved. Next, 0.02 g (0.05% by mass) of carbon nanotubes (hereinafter also referred to as "CNTs") was added to the aqueous polymer solution, and the solution was stirred for 24 hours or more (magnetic stirrer stirring speed: scale 5). The CNT types used are as follows: CNT-2: K-Nanos300T, manufactured by Kumho Petrochemical. Fiber diameter: 10-15nm multi-walled carbon nanotubes The mixture was then allowed to stand, and the dispersion stability was evaluated visually after a certain period of time had passed. Comparative Example 23 was evaluated in the same manner without adding any polymer. In Comparative Example 23, when no polymer was added, after 1 minute of standing, the supernatant was nearly transparent and the background was visible (most of it had settled), indicating a poor result. In contrast, in Examples 30 and 31, in which polymers B and G were added, the supernatant remained black and the background was not visible (uniformly dispersed) even after 1 week (168 hours). Furthermore, when the mixture was allowed to stand and the state was checked after 336 hours, it was confirmed that polymer G had better dispersibility than polymer B. It is believed that the steric repulsion effect of PEGMA copolymerized as the third component further improved the dispersion stability.

[0152] (Example 32, Comparative Example 24) Polymer G (Example 32) and Polymer J (Comparative Example 24) were weighed out in an amount of 0.02 g (0.05% by mass) in terms of solid content into a 50 ml screw tube, and deionized water was added to bring the total weight to 40 g. The aqueous polymer solution was stirred with a stirrer tip (2.5 cm) to confirm that the polymer had dissolved. Next, 0.02 g (0.05% by mass) of carbon nanotubes (hereinafter also referred to as "CNTs") were added to the aqueous polymer solution, and the solution was stirred for 24 hours or more (magnetic stirrer stirring speed: scale 5). The CNT types used are as follows: CNT-2: K-Nanos300T, manufactured by Kumho Petrochemical. Fiber diameter: 10-15nm multi-walled carbon nanotubes The mixture was then allowed to stand, and the dispersion stability was evaluated visually after 5 hours had passed. In Comparative Example 24, the supernatant was nearly transparent, but the background was not visible (two-layer separation was confirmed), as shown by △, whereas in Example 32, in which Polymer G was added, the supernatant was black, and the background was not visible (uniform dispersion) as shown by ◯. It was confirmed that the newly developed dispersant maintains good dispersion stability even when the amount of dispersant is reduced.

[0153] (Examples 12-14) NVP / AA-Na copolymers (powder) (polymers N, O, P) were obtained in the same manner as in Production Example 6, except that the copolymerization ratio of NVP / AA-Na to polymer F was changed to 95 / 5, 90 / 10, and 85 / 15.

[0154] (Examples 33 to 38, Comparative Example 25) The dispersibility of the polymers B, E, J, N, O, and P was evaluated by the following method. 0.38 g (0.75%) of the polymer (solid content), 2.5 g (5%) of CNT-2, and 47.1 g of deionized water were weighed out. After stirring at 2000 rpm for 10 minutes using a planetary centrifugal mixer, the mixture was dispersed in an ultrasonic homogenizer for 20 minutes while cooling. After standing for 3 days, the viscosity was measured using an E-type viscometer. Spindle 51, rotation speed 0.5~250rpm The results are shown in Tables 7 and 8.

[0155] [Table 7]

[0156] [Table 8]

[0157] The results in Table 8 show that by using a hydrogen peroxide-based initiator (Example 38) when producing a polymer, the viscosity can be reduced even for high molecular weight polymers, i.e., the dispersion (stability) is improved.

[0158] (Production Examples 15 and 16: Production of Polymers Q and R) The procedure of Production Example 6 was repeated, except that the copolymerization ratio of NVP / AA-Na in Polymer F was changed to 85 / 15 and the amount of hydrogen peroxide used was reduced to 64% relative to the amount used in Polymer F (100%), to obtain an NVP / AA-Na copolymer (powder) (Polymer Q). An NVP / AA-Na copolymer (powder) (Polymer R) was obtained in the same manner as in Production Example 6, except that the copolymerization ratio of NVP / AA-Na in Polymer F was changed to 80 / 20 and the amount of hydrogen peroxide used was increased to 147% of the amount used in Polymer F (100%).

[0159] (Production Example 17: Production of Polymer S) A 1-liter reactor (SUS304) equipped with a Maxblend-type stirring blade (made of SUS304), a thermometer, a reflux condenser, and a jacket was charged with 0.38 parts of a 0.05% aqueous solution of copper sulfate (0.4 ppm of copper sulfate relative to NVP + AMPS-Na) and 263.7 parts of deionized water. While stirring at 250 rpm, the mixture was purged with nitrogen at 200 mL / min for 30 minutes to remove dissolved oxygen. The nitrogen introduction rate was then increased to 30 mL / min, and the reactor was heated to an internal temperature of 60°C while stirring at 250 rpm. After the liquid temperature was stabilized at 60°C, 477.8 parts of a 90% NVP aqueous solution, 135.4 parts of a 30% AMPS-Na (2-acrylamido-2-methyl-1-propanesulfonate sodium) aqueous solution, 33.3 parts of a 20% hydrogen peroxide solution (the amount of hydrogen peroxide relative to the NVP+AMPS-Na was 1.4%), and 24.7 parts of a 3% ammonia aqueous solution (the amount of ammonia relative to the NVP+AMPS-Na was 0.16%) were added dropwise separately over 180 minutes. After the sequential dropwise addition of the raw materials was completed, 23.9 parts of a 30% aqueous AMPS-Na solution was added dropwise over 90 minutes, and 10.3 parts of a 3% aqueous ammonia solution (amount of ammonia relative to NVP+AMPS-Na: 0.06%) was added dropwise over 30 minutes. 240 minutes after the start of the dropwise addition of NVP, the temperature was raised to 80°C, and 2.9 parts of 20% hydrogen peroxide solution (amount of hydrogen peroxide relative to NVP+AMPS-Na: 0.12%) was added dropwise over 30 minutes. Next, 330 minutes after the start of the dropwise addition of NVP, 2.9 parts of 20% hydrogen peroxide solution (the amount of hydrogen peroxide relative to NVP + AMPS-Na was 0.12%) was added dropwise over 30 minutes, and the mixture was further maintained at 80°C for 1 hour to obtain an NVP / AMPS-Na copolymer solution.

[0160] (Production Example 18: Production of Polymer T) A 1-liter reactor (SUS304) equipped with a Maxblend-type stirring blade (made of SUS304), a thermometer, a reflux condenser, and a jacket was charged with 0.37 parts of a 0.05% aqueous solution of copper sulfate (0.4 ppm of copper sulfate relative to NVP + AMPS-Na) and 242.5 parts of deionized water. While stirring at 250 rpm, the mixture was purged with nitrogen at 200 mL / min for 30 minutes to remove dissolved oxygen. The nitrogen introduction rate was then increased to 30 mL / min, and the reactor was heated to an internal temperature of 60°C while stirring at 250 rpm. After the liquid temperature was stabilized at 60°C, 400.0 parts of a 90% NVP aqueous solution, 173.3 parts of a 45% AMPS-Na aqueous solution, 28.0 parts of a 25% hydrogen peroxide solution (the amount of hydrogen peroxide relative to the NVP+AMPS-Na was 1.5%), and 23.7 parts of a 3% ammonia aqueous solution (the amount of ammonia relative to the NVP+AMPS-Na was 0.16%) were added dropwise separately over 180 minutes. After the sequential dropwise addition of the raw materials was completed, 43.3 parts of a 45% aqueous AMPS-Na solution was added dropwise over 90 minutes, and 9.9 parts of a 3% aqueous ammonia solution (amount of ammonia relative to NVP+AMPS-Na: 0.06%) was added dropwise over 30 minutes. 240 minutes after the start of the dropwise addition of NVP, the temperature was raised to 80°C, and 2.5 parts of 25% hydrogen peroxide solution (amount of hydrogen peroxide relative to NVP+AMPS-Na: 0.14%) was added dropwise over 20 minutes. Next, 330 minutes after the start of the dropwise addition of NVP, 2.5 parts of 25% hydrogen peroxide solution (the amount of hydrogen peroxide relative to NVP + AMPS-Na was 0.14%) was added dropwise over 20 minutes, and the mixture was further maintained at 80°C for 1 hour to obtain an NVP / AMPS-Na copolymer solution.

[0161] (Production Example 19: Production of Polymer U) A 1-liter reactor (SUS304) equipped with a Maxblend-type stirring blade (made of SUS304), a thermometer, a reflux condenser, and a jacket was charged with 0.36 parts of a 0.05% aqueous solution of copper sulfate (0.4 ppm of copper sulfate relative to NVP + AA-Na + AN) and 182.5 parts of deionized water. While stirring at 250 rpm, the mixture was purged with nitrogen at 200 mL / min for 30 minutes to remove dissolved oxygen. The nitrogen introduction rate was then increased to 30 mL / min, and the reactor was heated to an internal temperature of 60°C while stirring at 250 rpm. After the liquid temperature was stabilized at 60°C, a solution of 380.0 parts NVP + 27.4 parts acrylonitrile (hereinafter also referred to as "AN") + 42.2 parts deionized water, 195.2 parts of 20% AA-Na aqueous solution, 43.4 parts of 25% hydrogen peroxide solution (the amount of hydrogen peroxide relative to NVP + AA-Na + AN is 2.4%), and 23.6 parts of 3% ammonia aqueous solution (the amount of ammonia relative to NVP + AA-Na + AN is 0.16%) were added dropwise separately over 180 minutes. After the sequential dropwise addition of the raw materials was completed, 48.8 parts of a 20% aqueous AA-Na solution was added dropwise over 90 minutes, and 9.8 parts of a 3% aqueous ammonia solution (amount of ammonia relative to NVP+AA-Na+AN: 0.06%) was added dropwise over 30 minutes. 240 minutes after the start of the dropwise addition of NVP, the temperature was raised to 80°C, and 3.8 parts of 25% hydrogen peroxide solution (amount of hydrogen peroxide relative to NVP+AA-Na+AN: 0.21%) was added dropwise over 30 minutes. Next, 330 minutes after the start of the NVP addition, 3.8 parts of 25% hydrogen peroxide solution (the amount of hydrogen peroxide relative to NVP + AA-Na + AN was 0.21%) was added dropwise over 30 minutes, and the mixture was further maintained at 80°C for 1 hour to obtain an NVP / AA-Na / AN copolymer solution.

[0162] (Examples 39 to 45, Comparative Example 26) The dispersibility of polymers O, P, Q, R, S, T, U, and J was evaluated by the following method. 0.5 g (1.0%) of the polymer (solid content), 3.0 g (6%) of CNT-2, and 46.5 g of deionized water were weighed out. After stirring at 2000 rpm for 10 minutes using a planetary centrifugal mixer, the mixture was dispersed in an ultrasonic homogenizer for 20 minutes while cooling. The viscosity was measured immediately after dispersion treatment and after standing at 50°C for 1 day using an E-type viscometer. Spindle 51, rotation speed 0.5~250rpm The results are shown in Table 9.

[0163] [Table 9]

[0164] Although carbon dispersion was good when AA-Na was replaced with AMPS-Na, dispersion stability was better with AA-Na. Furthermore, copolymerization of AN as a third component tended to improve dispersion stability.

Claims

1. A structural unit (A) derived from a salt of an acid group-containing monomer, and having a structural unit (B) derived from an N-vinyl lactam monomer, When the total amount of the structural units (A) and (B) is 100% by mass, The content of the structural unit (A) is 30% by mass or less, The weight average molecular weight is 1,000 or more and 100,000 or less, The K value according to the Fikentscher method is 12 to 60, The N-vinyl lactam copolymer, wherein the N-vinyl lactam monomer is N-vinyl-2-pyrrolidone.

2. 2. The N-vinyl lactam copolymer according to claim 1, wherein the structural unit (A) derived from a salt of an acid group-containing monomer is a structural unit (A1) derived from a salt of a carboxyl group-containing monomer and / or a structural unit (A2) derived from a salt of a sulfonic acid group-containing monomer.

3. 3. The N-vinyl lactam copolymer according to claim 2, wherein when the structural unit (A) contains the structural unit (A1), the content of the structural unit (A1) is 15% by mass or less relative to 100% by mass of the total amount of the structural unit (A) and the structural unit (B).

4. 3. The N-vinyl lactam copolymer according to claim 2, wherein when the structural unit (A) contains the structural unit (A2), the content of the structural unit (A2) is 30% by mass or less relative to 100% by mass of the total amount of the structural unit (A) and the structural unit (B).

5. 3. The N-vinyl lactam copolymer according to claim 1, which has a solubility in water of 1% by mass or more.

6. 3. The N-vinyl lactam copolymer according to claim 1, which has a solubility in an electrolyte solvent of 1% by mass or less.

7. The weight average molecular weight is 5,000 or more and 100,000 or less. The N-vinyl lactam copolymer according to claim 1 or 2.

8. The structural unit (A1) derived from a salt of a carboxyl group-containing monomer is a structural unit derived from at least one selected from the group consisting of lithium acrylate, sodium acrylate, potassium acrylate, and ammonium acrylate; The N-vinyl lactam copolymer according to claim 2.

9. The N-vinyl lactam copolymer according to claim 2, wherein the structural unit (A2) derived from a salt of a sulfonic acid group-containing monomer is a structural unit derived from at least one selected from the group consisting of 2-acrylamido-2-methyl-1-propanesulfonic acid (sodium, lithium, potassium, ammonium), 2-hydroxy-3-allyloxypropanesulfonic acid (sodium, lithium, potassium, ammonium), 2-sulfoethylmethacrylic acid (sodium, lithium, potassium, ammonium), vinylsulfonic acid (sodium, lithium, potassium, ammonium), and p-styrenesulfonic acid (sodium, lithium, potassium, ammonium).

10. The N-vinyl lactam copolymer according to claim 1 A composition comprising a carbon material.

11. Contains N-methyl-2-pyrrolidone and / or water The composition of claim 10.

12. 12. The composition according to claim 10, wherein the carbon material is at least one selected from the group consisting of carbon black, carbon nanofibers, and carbon nanotubes.

13. 12. The composition according to claim 10 or 11, wherein the structural unit (A) derived from the salt of an acid group-containing monomer is a structural unit (A1) derived from the salt of a carboxyl group-containing monomer and / or a structural unit (A2) derived from the salt of a sulfonic acid group-containing monomer.

14. The composition according to claim 10 or 11, wherein the structural unit (A) derived from a salt of an acid group-containing monomer is a structural unit (A1) derived from a salt of a carboxyl group-containing monomer.

15. A method for producing the N-vinyl lactam copolymer according to claim 1 or 2, comprising a step of polymerizing a monomer component containing a salt of an acid group-containing monomer and an N-vinyl lactam monomer.

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