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

N-vinyl lactam copolymer and composition

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

[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 carbon material dispersant is characterized by using a copolymer containing acrylonitrile and N-vinylpyrrolidone (see Patent Document 2). Furthermore, a carbon nanotube dispersion for electrodes has been reported that is characterized by using carbon nanotubes, polyvinylpyrrolidone, N-methyl-2-pyrrolidone, and an amine-based compound (see Patent Document 3).

[0004] JP 2018-170218 A JP 2016-65142 A Japanese Patent No. 6531926 A

[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 retain excellent carbon dispersibility and solubility in water while exhibiting little elution into carbonate-based electrolyte solvents.

[0007] As a result of extensive 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, etc.: [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 units (A) derived from a salt of an acid group-containing monomer are structural units (A1) derived from a salt of a carboxyl group-containing monomer and / or structural units (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, based on 100% by mass of the total amount of the structural units (A) and (B). [4] The N-vinyl lactam copolymer according to any 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, based on 100% by mass of the total amount of the structural units (A) and (B). [5] The N-vinyl lactam copolymer according to any of [1] to [4] above, which has a solubility in water of 1% by mass or more. [6] The N-vinyl lactam copolymer according to any 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 [1] to [6] above, having 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 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, further comprising N-methyl-2-pyrrolidone and / or water.

[12] The composition according to

[10] or

[11] above, wherein the carbon material is one or more selected from the group consisting of carbon black, carbon nanofibers, and carbon nanotubes.

[13] The composition according to any one of

[10] to

[12] 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.

[14] The composition according to any one of

[10] to

[13] 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.

[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 comprising a salt of an acid group-containing monomer and an N-vinyl lactam monomer.

[0009] According to the present disclosure, it is possible to provide an N-vinyl lactam copolymer and composition that retain excellent carbon dispersibility and solubility in water while exhibiting little elution into carbonate-based electrolyte solvents.

[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% 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, 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 solubility in water while exhibiting low elution into carbonate-based electrolyte solvents. Furthermore, conventional polymers disclosed in Patent Documents 1 to 3, etc., have problems such as 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 increased amounts 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 a favorable balance between the electrostatic repulsion due to the salt of the acid group and the adsorptivity to carbon due to the N-vinyl lactam, and therefore has excellent dispersibility for 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, and a phosphate group. Preferred examples of the acid group include a carboxyl group and 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 phosphate 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-methylene glutaric 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. 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, 2-((meth)acryloyloxy)ethanesulfonic acid, etc. Among these, 2-acrylamido-2-methyl-1-propanesulfonic acid, 2-hydroxy-3-allyloxypropanesulfonic acid, 2-sulfoethyl methacrylic acid, vinylsulfonic acid, and p-styrenesulfonic acid are preferred, and 2-acrylamido-2-methyl-1-propanesulfonic acid is more preferred.

[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] In one preferred embodiment of the present invention, the N-vinyl lactam copolymer of the present disclosure has structural units derived from a (meth)acrylate salt as the salt of a carboxyl group-containing monomer. In this case, acrylic acid and / or methacrylic acid can be used as the 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. Alternatively, an unneutralized acid group-containing monomer may be used, and a neutralization treatment may be performed 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 reduces 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 is converted into a single bond. When the structural unit (A) is a structural unit derived from a (meth)acrylate, a structural unit obtained by performing a polymerization reaction using a monomer such as acrylamide or acrylonitrile, followed by hydrolysis and then converting the resulting product into a carboxylate by a neutralization reaction or the like 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, which is preferable.

[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 on the salt, as long as it is one or more 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 salt is preferably an alkali metal salt, an alkaline earth metal salt, or an ammonium salt. More preferably, it is an alkali metal salt or an ammonium salt, and even more preferably, it is a lithium salt, a sodium salt, a potassium salt, or an ammonium salt. Particularly preferably, it is a lithium salt or a sodium salt. When the salt is the above-mentioned salt, the N-vinyl lactam copolymer of the present disclosure has a good withstand voltage and the generation of volatile substances is suppressed, so that it 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] (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. However, an asterisk represents an atom contained in another structural unit of the same type or a different type to which the structural unit represented by general formula (1) is bonded.)

[0028] R in the general formula (1) １is 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. More preferably, it is 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 monomer described above, it exhibits excellent effects in terms of being able to more sufficiently reduce the amount of impurities and more sufficiently prevent the battery performance from being impaired by 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 a 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 in the N-vinyl lactam copolymer of the present disclosure as the structural unit (B) by polymerization of the N-vinyl lactam monomer. In other words, the N-vinyl lactam monomer is a precursor of the structural unit derived from the 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 preferred 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. When the total amount of the structural units (A) and (B) is taken as 100% by mass, the content of the structural unit (A) is 30% by mass or less. When the content of the structural unit (A) is within the aforementioned range, dissolution 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. When the content of the structural unit (A) is within the aforementioned range, dissolution into the electrolyte solvent can be more sufficiently suppressed, and the dispersibility of the carbon material can be improved. Furthermore, 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 0.1 to 30% by mass, more preferably 1 to 25% by mass, even more preferably 1.5 to 20% by mass, and particularly preferably 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. A content of the structural unit (A) within the above range is preferred 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 the total content of the structural unit (A) and the structural units derived from the acid group-containing monomer is preferably 30% by mass or less. The total content of the structural unit (A) and the structural units derived from the 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. The total content of the structural unit (A) and the structural units derived from the 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 units 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 units derived from the acid-type acid group-containing monomer may be 12 mass% or less, less than 10 mass%, or 5 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 serve 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 alkoxyalkyl (meth)acrylates such as dimethylaminoethyl (meth)acrylate; 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, 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, monoalkoxy polyalkylene 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 preferred in that they can impart adsorptivity to carbon and improve the 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 oxide. Furthermore, when the polyalkylene glycol is an adduct of two or more types of alkylene oxide, the adduct may be in any form, such as random addition, block addition, or alternating addition. The oxyalkylene groups in the polyalkylene glycol chain preferably 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 aspect, 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% by mass of structural units derived from a polyalkylene glycol chain-containing monomer, relative to 100% by 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 polyalkylene glycol chain-containing monomer is more preferably 1 to 30% by mass, even more preferably 5 to 25% by mass, and particularly preferably 10 to 25% by mass.

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

[0042] The N-vinyl lactam copolymer of the present disclosure may contain 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), a phosphorous acid (salt) group (meaning a phosphorous acid group or a phosphite group), and the like. 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, with metal salts being preferred. Metal salts include, for example, 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 base thereof, it is possible to convert the desired acid or metal salt, for example, by forming a hypophosphite (salt) group and / or a phosphite (salt) group in the main chain of the polymer and then adding an acid or base. Similarly, conversion is also possible 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 carried out 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 at its terminal, such as an aldehyde group, a carboxyl group, a hydroxyl group, an amino group, etc. When the N-vinyl lactam copolymer of the present disclosure has a structural unit derived from vinylpyrrolidone at its terminal, it is preferably a copolymer represented by the following general formula (2):

[0047] (In the formula, 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, as described below, 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.

[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. It is 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 within the aforementioned range, it is preferable in that it has excellent dispersibility of carbon materials and can suppress thickening of carbon material dispersions. The weight-average molecular weight of the lactam group-containing copolymer of the present disclosure is measured 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. Preferably, it is 55 or less, and more preferably 50 or less. A K value within the above-mentioned range is preferred in that it can suppress thickening of the carbon material dispersion. 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. More preferably, it is 23 or more, and even more preferably 25 or more. A K value within the above-mentioned range is preferred in that it provides excellent dispersibility of the carbon material. Note that the K value of the lactam group-containing copolymer of the present disclosure as 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 in N-methyl-2-pyrrolidone of 1% by mass or more. 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. The solubility is preferably 1.2% by mass or more, more preferably 1.5% by mass or more, and even more 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 in the above-mentioned range, it can be used as a carbon material dispersant in N-methyl-2-pyrrolidone, and is therefore 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 solubility in water of 1% by mass or more. A solubility in water of 1% by mass or more 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. The solubility 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 N-vinyl lactam copolymer of the present disclosure has a solubility in water within the above-mentioned range, it can be used as a carbon material dispersant in water, and is therefore preferred 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. The solubility 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, even 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 prepared using the N-vinyl lactam copolymer of the present disclosure as a battery material and the resulting electrode is incorporated into a cell using a nonaqueous electrolyte, it is preferable that the amount of dissolution and elution in the nonaqueous electrolyte is small. The nonaqueous electrolyte 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, and any solvent commonly used in batteries can be used as the electrolyte solvent. A suitable nonaqueous electrolyte is 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. An organic solvent with a low water content is more preferable.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 erythritan 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, and 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; 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 in a carbonate-based electrolyte solvent of 1% by mass or less, 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. The solubility in a mixed solvent of ethylene carbonate / ethyl methyl carbonate = 3 / 7 (mass ratio) is preferably 0.09 mass % or less. It is more preferably 0.07 mass % or less, even more preferably 0.05 mass % or less, and particularly preferably 0.02 mass % or less. Having 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) within the above-mentioned range is preferable in that it can more sufficiently prevent the N-vinyl lactam copolymer of the present disclosure from leaching from the electrode into the electrolyte solvent, thereby thickening 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. Preferred forms of the N-vinyl lactam copolymer contained in the composition of the present disclosure are 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, and specific examples thereof include carbon black (e.g., ketjen black, acetylene black, etc.), graphite, carbon nanotubes (e.g., single-walled carbon nanotubes, multi-walled carbon nanotubes, etc.), carbon fibers (e.g., vapor-grown carbon fibers, etc.), and metal powder materials.

[0060] <Carbon Nanotubes> Examples of carbon nanotubes (hereinafter referred to as CNTs) among the carbon materials 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. Carbon nanotubes are nanocarbon materials in which the graphene sheet is rolled into a cylindrical shape. Types of carbon nanotubes include single-walled carbon nanotubes (SWNTs) consisting of only a single layer and multi-walled carbon nanotubes (MWNTs) in which carbon nanotubes are stacked concentrically. There are no limitations on the shape, size, or production method of the carbon nanotubes, and known nanotubes can be used. Mixtures of these nanotubes are also acceptable. 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 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 CNT, the content of impurities contained in the CNT 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 battery performance and further improves battery performance.

[0063] <Solvent> The composition of the present disclosure may optionally contain a solvent capable of dissolving the N-vinyl lactam copolymer of the present disclosure and further dispersing the carbon material. Examples of the solvent that can be used include 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 readily 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 the burden on the environment, it is particularly preferable to use water alone, but it is preferable to use a hydrophilic organic solvent mixed with water to improve the wettability of the nanocarbon material (carbon nanotubes) during dispersion, to make it easier to disintegrate the nanocarbon material in an aggregated state, 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 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%, when the total amount of the composition of the present disclosure is taken as 100 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 for producing 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 method for producing a composition into a carbon material dispersion, including a dispersion 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 method for producing 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 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, relative to 100% by mass of the carbon material dispersion. 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 can be determined 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 an ultrasonic homogenizer, a vibration mill, a jet mill, a ball mill, a bead mill, a sand mill, a roll mill, a homogenizer, a high-pressure homogenizer, an ultrasonic device, an attritor, a dissolver, and a paint shaker. In the dispersion process, dispersion using ultrasonic dispersion, a bead mill dispersion, an emulsifier, or the like is 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] <Method for Confirming Dispersion State> In addition to visual inspection, the dispersibility of the carbon material in the carbon material dispersion of the present disclosure can be confirmed 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. Then, the mixture is centrifuged to separate and precipitate any undispersed carbon material. 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 based on the concentration of the resulting dispersion and by comparing the concentration of the dispersion with the amount of the dispersion. Alternatively, the dispersion of the composition of the present disclosure after centrifugation can be left standing for a long period of time to confirm 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, it is possible to obtain carbon material-dispersed resin compositions in various forms. As the resin composition, a conventionally known resin composition can be used. Specifically, a resin composition containing a resin such as an acrylic resin, a styrene resin, an olefin resin, a vinyl ether resin, a vinyl alcohol resin, a polyester resin, a polyurethane resin, a polyamide resin, a polycarbonate resin, a polyimide resin, an epoxy resin, a melamine resin, a phenolic resin, or a silicone resin 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 according to the present disclosure includes a polymerization step of polymerizing raw material monomers. The 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, also constitutes the present invention.

[0074] <Monomer Components> As described above, 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. The monomer corresponding to the structural unit (A) can be represented as monomer (A). The monomer corresponding to the structural unit (B) can be represented as monomer (B). The monomers (A) and (B) are as described above, and the same applies to preferred embodiments. As described above, 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, 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 represented 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 essentially comprise the monomer (A) and the monomer (B). When the total amount of the monomers (A) and (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-mentioned 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 100% by mass of the total amount of the monomers (A) and (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 use ratio of the monomer (A) in the above-mentioned range is preferable in that dissolution in the electrolyte solvent can be suppressed. In one embodiment, the content of the monomer (A) may be 12 mass% or less, less than 10 mass%, or 5 mass% or less. The content of the monomer (A) in the above-mentioned range is preferable in that solubility in N-methyl-2-pyrrolidone is good.

[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, based on the total amount of the monomer (A), the monomer (B), and the other monomer (E) being 100% by mass. More preferably, it is 30% by mass or less, even more preferably 20% by mass or less, and even more preferably 10% by mass or less. In one aspect, 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 considered to be the corresponding amino group (in amine equivalent) for the calculation. 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> When polymerizing the monomer, it is preferable to use a radical polymerization initiator. 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 an N-vinyl lactam polymer 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 Preferred are 2,2'-azobis(2,4-dimethylvaleronitrile), 2,2'-azobis(2-methylbutyronitrile), and dimethyl 2,2'-azobis(2-methylpropionate), with 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 being more preferred, and 2,2'-azobis-2-amidinopropane dihydrochloride being the most preferred. Furthermore, azo polymerization initiators having a carboxyl group (such as 2,2'-azobis[N-(2-carboxyethyl)-2-methylpropionamidine]) can adversely affect coloration, so when used optionally, it is preferred to use as little as possible, and it is even more preferred 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 having a 10-hour half-life temperature of 30°C or higher and 180°C or lower are preferred, and those having 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 selected from the azo polymerization initiators and the organic peroxides, although other radical polymerization initiators may 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 polymerization initiator and / or hydrogen peroxide. Hydrogen peroxide is preferred because it facilitates lowering the molecular weight without the need for a chain transfer agent such as a phosphorus compound. By lowering the molecular weight of the N-vinyl lactam copolymer, further improvement in dispersion performance can be expected.

[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 relative to the total monomer components. It is more preferably 0.5% by mass to 4% by mass, and even more preferably 1% by mass to 3% by mass. When the amount of the radical polymerization initiator used is within the above-mentioned range, it is preferred in that it tends to be easier to adjust the molecular weight of the polymer, the amount of impurities is small, and coloration during heating tends to be further 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 monomers used. This allows the polymerization reaction rate to be within a more favorable range. Furthermore, by using 1.0% by mass or more of hydrogen peroxide relative to 100% by mass of the total monomers used, the stability over time of the resulting polymer solution is improved. Furthermore, by using 4.0% by mass or less of hydrogen peroxide, 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, to adjust the molecular weight of the N-vinyl lactam copolymer of the present disclosure, although this is not limited thereto. 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; phosphorous acid, phosphites, hypophosphorous acid, hypophosphites, and hydrates thereof; and lower oxides and salts thereof, such as sulfurous acid, hydrogen sulfite, dithionous acid, metabisulfite, and bisulfite salts (including compounds that dissolve in water to generate bisulfite). 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 makes it possible to efficiently introduce a substituent containing a phosphorus atom into the N-vinyl lactam copolymer of the present disclosure. Furthermore, the molecular weight can be efficiently reduced. Unless otherwise specified, examples of the phosphorus atom-containing compound and preferred embodiments thereof include hypophosphorous acid (salt), phosphorous acid (salt), phosphoric acid (salt), hypophosphite ester, phosphite ester, and phosphate ester. Due to their high chain transfer efficiency, hypophosphorous acid (salt), phosphorous acid (salt), and hypophosphite ester are preferred, and hypophosphorous acid (salt) is more preferred. When a phosphorus atom-containing compound is used, one type 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, and 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 hydrogensulfite; 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 Compound> 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 ３Among the heavy metals, iron and / or copper are preferred, and the reducing compound is Mohr's salt (Fe(NH ４ ) ２ (SO ４ ) ２ ・6H ２ Heavy metal salts such as 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 also be used.

[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 fall within a suitable range. The amount of the metal ions is also preferably 0.001 to 0.35 mmol%, more preferably 0.001 to 0.21 mmol%, 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. However, it is preferable not to use them in special industrial applications such as the production of hollow fiber membranes or in 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 purposes such as 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 progress of the polymerization reaction is further accelerated compared to when ammonia and / or an amine compound are not present. They can also function as a basic pH adjuster. Note that 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 it may be used 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 early stage of polymerization, or may be gradually added to the reaction vessel during polymerization.

[0094] Any appropriate amine compound can be used as the amine compound. Specific examples include primary amines, secondary amines, and tertiary amines. Only one type of amine may be used, or two or more types may be used.

[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. Examples of the secondary amine include 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. Of these secondary amines, dialkanolamines and dialkylamines are preferred, with dialkanolamines being more preferred, and 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 ammonia and an amine compound are used, the total amount of both used is preferably 0.01 part by mass or more, and more preferably 0.02 to 1 part by mass, per 100 parts by mass of N-vinyl lactam. Within the above-mentioned range, the reaction rate tends to be improved, 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 the amount used is not particularly limited, but is preferably 0.1 to 3.0% by mass, more preferably 0.15 to 2.0% by mass, and even more preferably 0.2 to 1.0% by mass, relative to 100% by mass of the total amount of monomers used.

[0100] When a copper salt is used as the heavy metal salt and ammonia is further used, an ammine complex salt of copper may be formed. Examples of the ammine complex salt of copper include diamine copper salt ([Cu(NH ３ ) ２ ] ２ SO ４ ・H ２ O, [Cu(NH ３ ) ２ ]Cl, etc.), tetraammine copper salts ([Cu(NH ３ ) ４ ]SO ４ ・H ２ O, [Cu(NH ３ ) ４ ]Cl ２When 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 add a copper salt such as copper sulfate, copper chloride, copper nitrate, or copper acetate and ammonia to the reactor to form the copper ammine complex salt.

[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 solvents 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. Water is more preferred. 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 nonvolatile matter 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. Furthermore, the temperature during polymerization may be 70°C or higher, 75 to 110°C, or 80 to 105°C. The temperature during polymerization does not need to be kept constant throughout the progress of the polymerization reaction. For example, polymerization may be started from room temperature, the temperature may be raised to a set temperature over an appropriate temperature rise time or rate, and then the set temperature may 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 more, more preferably 6 or more, and is preferably 11 or less, 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 pressurizing device, a decompressor, 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 is preferably an inert atmosphere, and 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 becomes longer, the coloring of the polymerization liquid tends to become greater. After the polymerization is completed, an aging step (a step of maintaining the polymerization liquid under heating and heat-retaining conditions after polymerization) may be provided 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 further 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 Acid> In the present disclosure, after completion of the polymerization reaction, 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. As a result, the remaining N-vinyl lactam is 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 by the acid to 2-pyrrolidone.

[0110] Preferred organic acids that can be used to reduce the amount of residual monomers are carboxylic acids having a boiling point (e.g., 100°C or higher) higher than the reaction liquid temperature when the organic acid is added, 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 according to 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 according to 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, inhibits coloration during heating, and tends to suppress odor. Furthermore, since residual monomers are likely to dissolve in the electrolyte solvent and inhibit battery performance, reducing the amount of residual monomer is preferred in that it sufficiently inhibits the inhibition of battery performance.

[0113] <Amount of Monomer-Derived Impurities> The method for producing an N-vinyl lactam copolymer according to the present disclosure is preferred because it enables the amount of monomer-derived impurities to be reduced. For example, if the monomer is N-vinyl-2-pyrrolidone, the monomer-derived impurity is 2-pyrrolidone. The amount of monomer-derived impurities is preferably 50,000 ppm or less relative to the obtained N-vinyl lactam polymer according to 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. Having the amount of monomer-derived impurities within the above-described range is preferred in that coloration during heating and odors tend to be suppressed. Furthermore, since impurities are easily dissolved in electrolyte solvents and may impair battery performance, reducing the amount of impurities is preferred in that this impairment of battery performance can be sufficiently suppressed. 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 Step> 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 or the like and includes a pulverization step. Drying and pulverization may be carried out by a known general method, and for example, powder can be obtained by 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 Steps> 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 treatment is carried out by adding the cation exchange resin 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 cation exchange resin, and then filtering the resulting suspension. 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] [Uses of N-vinyl lactam copolymer] 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 semiconductor cleaning agent, 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 a paint composition, a surface treatment agent, a resin modifier, a binder for an inorganic substance, a ceramic binder, an additive for an inorganic composition, a fiber treatment agent, and an additive for a functional fiber.

[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] Each evaluation of the polymer was carried out by the following method. <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 left to stand in a constant temperature dryer at 150°C for 1 hour to dry. After drying, the mass (W3 (g)) of the weighing can + polymer 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> Deionized water was added to the polymer to dilute it 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 measure the relative viscosity, the same measurement was also taken for deionized water. The two obtained flow times were corrected based on the Hagenbach-Couette correction.

[0120] In the above formula, Z is the relative viscosity (ηrel) of a solution of concentration C, and C is the concentration (%: g / 100 ml). The relative viscosity ηrel was obtained by the following formula.

[0121]

[0122] <Measurement of Weight-Average Molecular Weight (Mw) of Polymer> The weight-average molecular weight of the copolymer was measured and determined by gel permeation chromatography (GPC) under the following conditions: Apparatus: Alliance HPLC system manufactured by Waters Detector: RI Column: TSKgel α-M (2 columns), TSKgel α manufactured by Tosoh Column temperature: 40°C Flow rate: 0.6 ml / 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 Analysis of N-Vinylpyrrolidone and 2-Pyrrolidone in Polymer> Quantitative analysis was performed by liquid chromatography under the following conditions: Apparatus: Shiseido "NANOSPACE SI-2" (UV / VIS detector used) Column: Osaka Soda "CAPCELLPAK C18 UG120 (inner diameter 1.5 mm, length 250 mm)", 40°C Eluent: LC-grade methanol (manufactured by Wako Pure Chemical Industries, Ltd.) / ultrapure water = 1 / 24 (mass ratio), with 0.04 mass% sodium 1-heptanesulfonate added Flow rate: 100 μL / min

[0125] <Quantitative Analysis of Salt of Acid Group-Containing Monomer in Polymer> Quantitative analysis was carried out by liquid chromatography under the following conditions: Apparatus: Alliance HPLC system manufactured by Waters Column: Shodex RS pack DE-413L, Shodex RS pack DE-G manufactured by Showa Denko K.K., 40°C Eluent: 0.1% aqueous phosphoric acid solution Flow rate: 1 mL / min

[0126] <Evaluation of Solubility of Polymer 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: ◯: The solution was transparent and no insoluble matter was observed; ×: Insoluble matter was observed and / or the solution was opaque.

[0127] <Evaluation of Solubility of Polymer 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 and standing for 24 hours, the solution was visually observed and evaluated according to the following criteria: ◯: The solution was transparent and no insoluble matter was observed; ×: Insoluble matter was observed and / or the solution was 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 ROLLER 10 Digital, 80 rpm). Thereafter, the viscosity of the electrolyte was compared before and after the addition of the polymer. In addition, the supernatant was diluted 2-fold with N,N-dimethylformamide, and the viscosity was measured using gel permeation chromatography (GPC) under the following conditions. Apparatus: HLC-8320GPC manufactured by Tosoh Detector: RI Column: Shodex KD-806M (2 columns), KD-G 4A manufactured by Showa Denko K.K. Column temperature: 40°C Flow rate: 0.8 ml / 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 (diluted 2-fold) 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 the electrolyte, calculated from the amount added The solubility of the polymer in the electrolyte was determined using the following formula: Solubility (%) = 0.1 × Elution rate (%) When the elution rate was 100%, the solubility was determined to be 0.1% or more.

[0129] (Production Example 1: Production of Polymer A) 420 parts of deionized water were charged into a 1 L reactor (made of SUS304) equipped with a Maxblend type stirring blade (made of SUS304), a thermometer, a reflux condenser, and a jacket. While stirring this deionized water at 250 rpm, nitrogen substitution was performed at 200 ml / min for 30 minutes to remove dissolved oxygen. Next, nitrogen introduction was 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 mass 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 mass 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, respectively, to initiate polymerization. After the 120-minute dropwise addition of the 4% by mass aqueous solution of AA-Li was completed, followed by the dropwise addition of 4.6 parts over 30 minutes. Furthermore, after the 120-minute dropwise addition of the 10% by mass aqueous solution of V-50 was completed, 30 minutes later, 1.8 parts was added all at once. The temperature was maintained at 80°C for 240 minutes from the start of dropwise addition to obtain an NVP / AA-Li copolymer solution. The obtained NVP / AA-Li copolymer solution was dried in vacuo at 110°C, then pulverized to pass through a JIS standard sieve with a mesh size of 500 µm, and the powder was further dried in vacuo at 110°C to obtain an NVP / AA-Li copolymer (powder).

[0130] (Production Example 2: Production of Polymer B) A 1 L reactor equipped with a Maxblend-type stirring blade, a thermometer, a reflux condenser, and a 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 temperature increase of this solution were carried out 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 mass 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 mass 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 4% by mass aqueous solution of AA-Na was completed, 4.1 parts was then added dropwise over 30 minutes. Furthermore, 1.4 parts of a 10% by mass aqueous solution of V-50 was added all at once 30 minutes after the completion of 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-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 temperature increase of this solution were carried out 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 (acrylic acid manufactured by Nippon Shokubai, neutralized with aqueous ammonia; 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 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) 311 parts of deionized water were charged into a 1 L reactor equipped with a Maxblend-type stirring blade, a thermometer, a reflux condenser, and a jacket. Nitrogen substitution and temperature increase of this solution were carried out 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 mass aqueous solution of AA-NH3, 79.2 parts of a 10% by mass 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 mass 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 mass aqueous solution of AA-NH3 and the 10% by mass aqueous solution of MEA was completed, 4.2 parts each were added dropwise over 30 minutes. Furthermore, 1.7 parts of a 10% by mass aqueous solution of V-50 was added all at once 30 minutes after the completion of 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 L reactor (made of 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 copper sulfate solution (the amount of copper sulfate relative to NVP+AA-Na was 0.4 ppm) and 230.8 parts of deionized water. While stirring at 250 rpm, nitrogen substitution was carried out at 200 ml / min for 30 minutes to remove dissolved oxygen. Next, nitrogen introduction was increased to 30 ml / min, and the reactor was heated while stirring at 250 rpm until the internal temperature reached 60°C. Next, while maintaining the temperature at 60°C, 444.4 parts of a 90% aqueous NVP solution (400 parts of NVP diluted with 44.4 parts of deionized water), 179.6 parts of a 4% aqueous AA-Na solution (19.8 parts of a 37% aqueous AA-Na solution diluted with 163.5 parts of deionized water), 28.1 parts of a 15% aqueous hydrogen peroxide solution (16.1 parts of a 35% aqueous 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% aqueous ammonia solution (2.4 parts of a 28% aqueous ammonia 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 sequential 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 (the amount of ammonia relative to the NVP + AA-Na was 0.05%) were added dropwise over 30 minutes. 240 minutes after the start of the NVP addition, the temperature was raised to 80°C, and 4.8 parts of a 15% aqueous hydrogen peroxide solution (the amount of hydrogen peroxide relative to the NVP + AA-Na was 0.18%) was added dropwise over 30 minutes. Next, 330 minutes after the start of the NVP addition, 4.8 parts of a 15% aqueous hydrogen peroxide solution (the amount of hydrogen peroxide relative to the NVP was 0.18%) was added dropwise over 30 minutes, and the temperature 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 copper sulfate aqueous solution and deionized water were charged into a Max Blend-type agitator, 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% NVP aqueous solution, 165.0 parts of a 4% AA-Na aqueous solution, 38.8 parts of a 25% hydrogen peroxide solution (amount of hydrogen peroxide relative to NVP + AA-Na: 2.4%), and 21.1 parts of a 3% aqueous ammonia solution (amount of ammonia relative to NVP + AA-Na: 0.16%) were added dropwise separately over 180 minutes. After the sequential dropwise addition of the raw materials was completed, 18.3 parts of a 4% AA-Na aqueous 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% aqueous hydrogen peroxide (the amount of hydrogen peroxide relative to the NVP + AA-Na was 0.21%) was added dropwise over 30 minutes. Next, 330 minutes after the start of the dropwise addition of NVP, 3.4 parts of 25% aqueous hydrogen peroxide (the amount of hydrogen peroxide relative to the NVP + AA-Na was 0.21%) was added dropwise over 30 minutes, and the temperature 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 Maxblend 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 nitrogen substitution and heating of this solution were carried out in the same manner as in Production Example 5. After the liquid temperature was stabilized at 60°C, 388.9 parts of a 90% aqueous NVP solution, 23.5 parts of a 25% aqueous hydrogen peroxide solution (1.4% hydrogen peroxide relative to the monomer), and 21.8 parts of a 3% aqueous ammonia solution (0.16% ammonia relative to the monomer) were added dropwise over 180 minutes, respectively, and 259.7 parts of an aqueous AA-Na / PEGMA(9) solution (20.5 parts of a 37% aqueous AA-Na 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 completion of the sequential dropwise addition of NVP, 9.1 parts of a 3% aqueous ammonia solution (0.06% ammonia relative to the monomer) 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 (amount of hydrogen peroxide relative to the monomer: 0.12%) were added dropwise over 30 minutes. Next, 330 minutes after the start of the NVP addition, 2.1 parts of a 25% hydrogen peroxide solution (amount of hydrogen peroxide relative to the monomer: 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 an 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 copper sulfate solution (the amount of copper sulfate relative to the monomer was 0.4 ppm) and 245.2 parts of deionized water. The nitrogen substitution and temperature increase 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 NVP solution, 231.7 parts of an aqueous AA-Na / PEGMA (9) solution (21.1 parts of a 37% aqueous AA-Na solution and 64.9 parts of PEGMA (9) diluted with 186.6 parts of deionized water), 25.3 parts of a 15% aqueous hydrogen peroxide solution (the amount of hydrogen peroxide relative to the monomer was 0.88%), and 22.4 parts of a 3% aqueous ammonia 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, 40.9 parts of an AA-Na / PEGMA (9) aqueous solution was added dropwise over 90 minutes, and 9.3 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 2.2 parts of a 15% aqueous 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 a 15% aqueous hydrogen peroxide solution (amount of hydrogen peroxide relative to the monomer: 0.08%) was added dropwise over 30 minutes, and the temperature 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 in 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 nitrogen substitution and heating of this solution were carried out in the same manner 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 (amount of hydrogen peroxide relative to the monomer: 1.4%), and 19.8 parts of a 3% aqueous ammonia solution (amount of ammonia relative to the monomer: 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 AA-Na / PEGMA(13) aqueous solution were added dropwise over 90 minutes, and 8.3 parts of a 3% aqueous ammonia solution (amount of ammonia relative to the monomer: 0.06%) were added dropwise over 30 minutes. 240 minutes after the start of the NVP addition, 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% aqueous hydrogen peroxide (amount of hydrogen peroxide relative to the monomer: 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 vacuum-dried to obtain an NVP / AA-Na / PEGMA (13) copolymer (dried product).

[0138] Polymer J: Polyvinylpyrrolidone K-30 (manufactured by 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) Production Example 1 was repeated except that the copolymerization ratio of NVP / AA-Li was changed to 76 / 24, to obtain an NVP / AA-Li copolymer (powder).

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

[0141] (Examples 1 to 9, Comparative Examples 1 to 4) For polymers A to M, the K value, weight average molecular weight (Mw), pH, amounts of N-vinylpyrrolidone and 2-pyrrolidone, and amounts of (meth)acrylate were measured using the methods described above. Furthermore, evaluation of solubility in NMP, deionized water, and an electrolyte solution (ethylene carbonate / ethyl methyl carbonate = 3 / 7 (weight ratio)) was also performed using the methods described above. Furthermore, for polymers J and K, the following additional evaluation was also performed. <Evaluation 2 of Solubility of Polymer in Electrolyte Solution: Ethylene Carbonate / Ethyl Methyl Carbonate = 3 / 7 (weight ratio) Mixed Solvent> The same evaluation as for the evaluation of solubility of polymer in the electrolyte solution mixed solvent was performed, 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 determined to be 100% for both polymers J and K. In other words, the solubility was confirmed to be 1.2% or more for both J and K. The results are shown in Tables 1 and 2.

[0142]

[0143]

[0144] From the above results, it was revealed 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 copolymer of the present invention (Examples 1 to 9) maintains its solubility in NMP and water while reducing elution into the electrolyte and suppressing the increase in the viscosity of the electrolyte. It is believed that the increase in the viscosity of the electrolyte solvent, for example, in the case of battery applications, may impair battery performance. Furthermore, when the copolymerization ratio of the AA salt is increased to more than 15% by mass (Comparative Examples 3 and 4), the copolymer does not dissolve in the electrolyte, but loses solubility in NMP, which makes it inconvenient to use NMP as the solvent (e.g., when blended into a positive electrode slurry for battery applications). Furthermore, the copolymers of Comparative Examples 3 and 4 have a K value greater than 60, and although they are soluble in water, an increase in the viscosity of water is observed, which is inconvenient.

[0145] (Examples 10 to 29, Comparative Examples 5 to 22) 80 g of deionized water or NMP and 0.5% by mass 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, manufactured by Showa Denko K.K. Multi-walled carbon nanotubes with a fiber diameter of approximately 150 nm and a fiber length 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), and then allowed to stand for 1 day, after which the dispersion stability was evaluated visually. Comparative Examples 5 to 6 and 14 to 15 were evaluated in the same manner without adding a polymer. The evaluation criteria are as follows: ◯: The supernatant was black and the background could not be seen through. ×: The supernatant was nearly transparent and the background could be seen through. 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]

[0147]

[0148]

[0149]

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

[0151] (Examples 30-31, Comparative Example 23) 0.2 g (0.5% by mass) of polymers B and G were weighed out into a 50 ml screw tube, and deionized water was added to bring the total weight to 40 g. The polymer aqueous 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 "CNT") was added to the polymer aqueous solution and stirred for 24 hours or more (magnetic stirrer stirring speed: scale 5). The CNT species used were as follows: CNT-2: K-Nanos300T, manufactured by Kumho Petrochemical. Fiber diameter: multi-walled carbon nanotubes with a diameter of 10-15 nm. The solution was then allowed to stand, and the dispersion stability after a certain period of time was evaluated visually. Comparative Example 23 was evaluated in the same manner, but 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 standing was continued and the state was observed 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 dispersion stability.

[0152] (Example 32, Comparative Example 24) 0.02 g (0.05% by mass) of polymer G (Example 32) and polymer J (Comparative Example 24) were weighed out 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), and it was confirmed that the polymer had dissolved. Next, 0.02 g (0.05% by mass) of carbon nanotubes (hereinafter also referred to as "CNT") was added to the aqueous polymer solution and stirred for 24 hours or more (magnetic stirrer stirring speed: scale 5). The CNT species used were as follows: CNT-2: K-Nanos300T, manufactured by Kumho Petrochemical. Fiber diameter: multi-walled carbon nanotubes with a diameter of 10-15 nm. The solution was then allowed to stand, and the dispersion stability after 5 hours was evaluated visually. In Comparative Example 24, the supernatant was nearly transparent, but the background was not visible (two-layer separation was confirmed), while in Example 32, in which Polymer G was added, the supernatant was black, and the background was not visible (uniform dispersion) and it was confirmed that the dispersant of the present invention maintained good dispersion stability even when the amount of dispersant was reduced.

[0153] (Production Examples 12 to 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 polymers B, E, J, N, O, and P was evaluated using the following method. 0.38 g (0.75%) of polymer in terms of solid content, 2.5 g (5%) of CNT-2, and 47.1 g of deionized water were weighed out. After stirring for 10 minutes at 2000 rpm using a planetary centrifugal mixer, the mixture was dispersed for 20 minutes using an ultrasonic homogenizer while cooling. After allowing to stand for 3 days, the viscosity was measured using an E-type viscometer. Spindle 51, rotation speed 0.5 to 250 rpm. The results are shown in Tables 7 and 8.

[0155]

[0156]

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

[0158] (Production Examples 15 and 16: Production of Polymers Q and R) An NVP / AA-Na copolymer (powder) (polymer Q) was 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 85 / 15 and the amount of hydrogen peroxide used was reduced to 64% relative to 100% the amount used in polymer F. 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 to polymer F was changed to 80 / 20 and the amount of hydrogen peroxide used was increased to 147% relative to 100% the amount used in polymer F.

[0159] (Production Example 17: Production of Polymer S) A 1 L reactor (made of 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 copper sulfate solution (the amount of copper sulfate relative to NVP+AMPS-Na was 0.4 ppm) and 263.7 parts of deionized water. While stirring at 250 rpm, nitrogen substitution was carried out at 200 ml / min for 30 minutes to remove dissolved oxygen. Next, nitrogen introduction was increased to 30 ml / min, and the reactor was heated while stirring at 250 rpm until the internal temperature reached 60°C. After the liquid temperature was stabilized at 60°C, 477.8 parts of a 90% aqueous NVP solution, 135.4 parts of a 30% aqueous AMPS-Na (2-acrylamido-2-methyl-1-propanesulfonate sodium) solution, 33.3 parts of a 20% aqueous hydrogen peroxide solution (the amount of hydrogen peroxide relative to the NVP + AMPS-Na was 1.4%), and 24.7 parts of a 3% aqueous ammonia solution (the amount of ammonia relative to the NVP + AMPS-Na was 0.16%) were each added dropwise over 180 minutes. After completion of the sequential dropwise addition of the raw materials, 23.9 parts of a 30% aqueous AMPS-Na solution were added dropwise over 90 minutes, and 10.3 parts of a 3% aqueous ammonia solution (the amount of ammonia relative to the NVP + AMPS-Na was 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 2.9 parts of 20% aqueous hydrogen peroxide (the amount of hydrogen peroxide relative to the NVP+AMPS-Na was 0.12%) was added dropwise over 30 minutes. Then, 330 minutes after the start of the dropwise addition of NVP, 2.9 parts of 20% aqueous hydrogen peroxide (the amount of hydrogen peroxide relative to the NVP+AMPS-Na was 0.12%) was added dropwise over 30 minutes, and the temperature was maintained at 80°C for another hour to obtain an NVP / AMPS-Na copolymer solution.

[0160] (Production Example 18: Production of Polymer T) A 1 L reactor (made of 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 copper sulfate solution (the amount of copper sulfate relative to NVP+AMPS-Na was 0.4 ppm) and 242.5 parts of deionized water. While stirring at 250 rpm, nitrogen substitution was carried out at 200 ml / min for 30 minutes to remove dissolved oxygen. Next, nitrogen introduction was increased to 30 ml / min, and the reactor was heated while stirring at 250 rpm until the internal temperature reached 60°C. 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% aqueous ammonia solution (the amount of ammonia relative to the NVP + AMPS-Na was 0.16%) were each added dropwise over 180 minutes. After the sequential dropwise addition of the raw materials was completed, 43.3 parts of a 45% AMPS-Na aqueous solution were added dropwise over 90 minutes, and 9.9 parts of a 3% aqueous ammonia solution (the amount of ammonia relative to the NVP + AMPS-Na was 0.06%) were added dropwise over 30 minutes. 240 minutes after the start of the NVP addition, the temperature was raised to 80°C, and 2.5 parts of a 25% aqueous hydrogen peroxide solution (the amount of hydrogen peroxide relative to the NVP + AMPS-Na was 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% aqueous hydrogen peroxide (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 L reactor (made of 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 copper sulfate solution (the amount of copper sulfate relative to NVP + AA-Na + AN was 0.4 ppm) and 182.5 parts of deionized water. While stirring at 250 rpm, nitrogen substitution was carried out at 200 ml / min for 30 minutes to remove dissolved oxygen. Next, nitrogen introduction was increased to 30 ml / min, and the reactor was heated while stirring at 250 rpm until the internal temperature reached 60°C. After stabilizing the liquid temperature at 60°C, a solution of 380.0 parts NVP, 27.4 parts acrylonitrile (hereinafter also referred to as "AN"), and 42.2 parts deionized water, 195.2 parts of a 20% aqueous AA-Na solution, 43.4 parts of a 25% aqueous hydrogen peroxide solution (the amount of hydrogen peroxide relative to the NVP + AA-Na + AN was 2.4%), and 23.6 parts of a 3% aqueous ammonia solution (the amount of ammonia relative to the NVP + AA-Na + AN was 0.16%) were each added dropwise over 180 minutes. After completion of the sequential dropwise addition of the raw materials, 48.8 parts of a 20% aqueous AA-Na solution were added dropwise over 90 minutes, and 9.8 parts of a 3% aqueous ammonia solution (the amount of ammonia relative to the NVP + AA-Na + AN was 0.06%) were added dropwise over 30 minutes. 240 minutes after the start of the NVP addition, the temperature was raised to 80°C, and 3.8 parts of 25% aqueous hydrogen peroxide (0.21% of the amount of hydrogen peroxide relative to NVP + AA-Na + AN) was added dropwise over 30 minutes. Next, 330 minutes after the start of the NVP addition, 3.8 parts of 25% aqueous hydrogen peroxide (0.21% of the amount of hydrogen peroxide relative to NVP + AA-Na + AN) was added dropwise over 30 minutes, and the temperature was maintained at 80°C for an additional 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 using the following method. 0.5 g (1.0%) of polymer, calculated as solids, 3.0 g (6%) of CNT-2, and 46.5 g of deionized water were weighed out. After stirring for 10 minutes at 2000 rpm using a planetary centrifugal mixer, dispersion treatment was carried out for 20 minutes using an ultrasonic homogenizer while cooling. The viscosity was measured using an E-type viscometer immediately after dispersion treatment and after leaving to stand at 50°C for 1 day. Spindle 51, rotation speed 0.5 to 250 rpm. The results are shown in Table 9.

[0163]

[0164] Although carbon dispersibility was good even when AA-Na was replaced with AMPS-Na, dispersion stability was better with AA-Na. Furthermore, copolymerization of AN as the 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 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. The N-vinyl lactam copolymer according to claim 1, 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.

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 units (A) and (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 mass% or less relative to 100 mass% of the total amount of the structural units (A) and (B).

5. The N-vinyl lactam copolymer according to claim 1 or 2, 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 1 or 2.

9. The N-vinyl lactam copolymer according to claim 1 or 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. 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.