WO2021215381A1 - Method for producing carboxyl group-containing crosslinked polymer or salt thereof - Google Patents

Abstract

The present invention provides a method for producing a carboxyl group-containing crosslinked polymer or a salt thereof, by which it is possible to achieve a balance between the coatability and the coating film performance of a composition that contains this crosslinked polymer or a salt thereof.　This method for producing a carboxyl group-containing crosslinked polymer or a salt thereof includes a step for polymerizing monomer components including an ethylenically unsaturated carboxylic acid monomer by means of precipitation polymerization or dispersion polymerization in the presence of an exchange chain transfer mechanism type control agent. The exchange chain transfer mechanism type control agent is a polymer having a living radical polymerization active unit derived from an exchange chain transfer mechanism with one or more vinyl-based monomer polymer chains, and/or a polymer other than said polymer.

Description

Method for producing a carboxyl group-containing crosslinked polymer or a salt thereof

The present invention relates to a method for producing a carboxyl group-containing crosslinked polymer or a salt thereof.

Carboxyl group-containing polymers are used in various applications such as thickeners and viscosity modifiers for cosmetics, binders for non-aqueous electrolyte secondary battery electrodes, sedimentation inhibitors for pigments, and dispersion stabilizers for metal powders. ing.
Among these uses, as a thickener for cosmetics, when the carboxyl group-containing polymer is linear, it has a spinnability and feels sticky, but as the degree of cross-linking is increased, the spinnability becomes higher. It has the characteristic that it decreases and you can feel the freshness. Therefore, in cosmetics that do not require spinnability and require freshness, a carboxyl group-containing crosslinked polymer is often used because of the advantage that high viscosity can be obtained with a small amount of use. Further, as a binder for a lithium ion secondary battery electrode, a carboxyl group-containing crosslinked polymer is often used because of the advantages of being able to impart good binding properties and cycle characteristics.

Here, as a method for producing the carboxyl group-containing crosslinked polymer, various methods such as a precipitation polymerization method and a dispersion polymerization method are known.

The precipitation polymerization method is a polymerization method in which a polymerizable monomer is dissolved in a solvent, but the obtained polymer is insoluble in a solvent and precipitates to obtain a crosslinked polymer, and particles having a size of several μm to several hundreds of μm are generally obtained. .. For example, in Patent Document 1, as a carboxyl group-containing crosslinked polymer, a microcrosslinked acrylic acid-based polymer is produced by precipitation polymerization, and an attempt is made to use it as a binder for a lithium ion secondary battery electrode.

The dispersion polymerization method is a method of obtaining a crosslinked polymer as primary particles by using a dispersion stabilizer or the like for precipitation polymerization, depending on the type and amount of the polymerizable monomer, solvent, and dispersion stabilizer. This is a polymerization method capable of controlling the particle size of the produced fine particles, and is suitable for obtaining particles having a size of submicron to several μm. For example, in Patent Document 2, as a carboxyl group-containing crosslinked polymer, a microcrosslinked acrylic acid-based polymer is produced by dispersion polymerization, and an attempt is made to use it as a binder for a lithium ion secondary battery electrode.

International Publication No. 2014/060407 International Publication No. 2017/073589

However, according to the studies by the inventors, the precipitation polymerization method and the dispersed weight described in Patent Documents 1 and 2 are used as a binder for particles in the slurry (for example, a binder for the active material in the lithium ion secondary battery electrode slurry). When a legally produced microcrosslinked acrylic acid-based polymer is used, the micro-crosslinking of the acrylic acid-based polymer can enhance the binding property between the particles in the slurry, while the polymer. Since the spread in water increases and the viscosity increases significantly even with a small amount of addition, there is a limit to the reduction of the slurry viscosity, and both coatability and coating performance (for example, cycle characteristics of a lithium ion secondary battery) can be achieved. There was a problem.

The present invention has been made in view of such circumstances, and an object of the present invention is to achieve both coatability and coating performance of a composition containing a carboxyl group-containing crosslinked polymer or a salt thereof. The present invention provides a method for producing a crosslinked polymer or a salt thereof.

As a result of diligent studies to solve the above problems, the present inventors have conducted precipitation polymerization or dispersion polymerization in the presence of an exchange chain transfer mechanism type control agent to carry out a monomer containing an ethylenically unsaturated carboxylic acid monomer. By using a carboxyl group-containing crosslinked polymer or a salt thereof obtained by a production method including a step of polymerizing the components, the coating property of the crosslinked polymer or the composition containing the salt thereof is ensured and excellent. The present invention has been completed by finding that the coating performance can be exhibited.

The present invention is as follows.
[1] A method for producing a carboxyl group-containing crosslinked polymer or a salt thereof, which comprises a single amount containing an ethylenically unsaturated carboxylic acid monomer by precipitation polymerization or dispersion polymerization in the presence of an exchange chain transfer mechanism type control agent. A polymer comprising a step of polymerizing a body component, wherein the exchange chain transfer mechanism type control agent has a polymer chain of one or more kinds of vinyl-based monomers and a living radical polymerization active unit by the exchange chain transfer mechanism. And / or a production method which is an exchange chain transfer mechanism type control agent other than the polymer.
[2] The production method according to [1], wherein the exchange chain transfer mechanism type control agent is a reversible addition-cleaving type chain transfer agent (RAFT agent).
[3] The production method according to [2], wherein the reversible addition-cleaving chain transfer agent has a trithiocarbonate group in the molecule.
[4] The amount of the exchange chain transfer mechanism type control agent used is 0.0001 to 0.50 mol% with respect to the total amount of the monomer components containing the ethylenically unsaturated carboxylic acid monomer [1]. The manufacturing method according to any one of [3].
[5] The production according to any one of [1] to [4], wherein the monomer component contains 50% by mass or more and 100% by mass or less of an ethylenically unsaturated carboxylic acid monomer with respect to the total amount thereof. Method.
[6] The crosslinked polymer is crosslinked with a crosslinkable monomer, and the amount of the crosslinkable monomer used is 0.1 mass by mass with respect to 100 parts by mass of the total amount of the non-crosslinkable monomer. The production method according to any one of [1] to [5], wherein the amount is equal to or more than 2.0 parts by mass or less.
[7] The crosslinked polymer or a salt thereof is neutralized to a degree of neutralization of 80 to 100 mol%, and then the particle size measured in an aqueous medium is 0.1 μm or more and 5.0 μm or less in terms of volume-based median diameter. The production method according to any one of [1] to [6].
[8] The production method according to any one of [1] to [7], wherein the crosslinked polymer or a salt thereof has a water swelling degree of 20 or more and 80 or less at pH 8.

According to the carboxyl group-containing crosslinked polymer or a salt thereof obtained by the production method of the present invention, it is possible to achieve both the coatability and the coating film performance of the composition containing the crosslinked polymer or the salt thereof.

It is a figure which shows the apparatus used for measuring the water swelling degree of a crosslinked polymer or a salt thereof.

In the present invention, a carboxyl group-containing crosslinked polymer (hereinafter, "" This is a production method comprising a step of producing (also referred to as "the present crosslinked polymer") or a salt thereof.

Hereinafter, the present invention will be described in detail.
In addition, in this specification, "(meth) acrylic" means acrylic and / or methacrylic, and "(meth) acrylate" means acrylate and / or methacrylate. Further, the “(meth) acryloyl group” means an acryloyl group and / or a methacryloyl group.

1. 1. Structural unit of this crosslinked polymer <Structural unit derived from ethylenically unsaturated carboxylic acid monomer>
The crosslinked polymer has a structural unit derived from an ethylenically unsaturated carboxylic acid monomer (hereinafter, also referred to as “component (a)”), and is a single amount containing an ethylenically unsaturated carboxylic acid monomer. The body component can be introduced into the polymer by precipitation polymerization or dispersion polymerization. Since the crosslinked polymer has a carboxyl group by having such a structural unit, the adhesiveness to the substrate is improved and water swelling property is imparted. Therefore, the composition containing the crosslinked polymer or a salt thereof. The stability of the product (hereinafter, also referred to as “the present composition”) can be enhanced. In particular, in lithium ion secondary battery applications, the adhesiveness to the current collector, which is the base material, is improved, and the lithium ion desolvation effect and ionic conductivity are excellent, so the resistance is small and the high rate characteristics are excellent. An electrode is obtained.

Examples of the ethylenically unsaturated carboxylic acid monomer include (meth) acrylic acid, itaconic acid, crotonic acid, maleic acid, fumaric acid; and (meth) acrylamide alkyl such as (meth) acrylamide hexane acid and (meth) acrylamide dodecanoic acid. Carboxylic acid; ethylenically unsaturated monomers having carboxyl groups such as monohydroxyethyl succinate (meth) acrylate, ω-carboxy-caprolactone mono (meth) acrylate, β-carboxyethyl (meth) acrylate, or (partial) thereof. ) Alkali neutralized products may be mentioned, and one of these may be used alone, or two or more thereof may be used in combination. Among the above, a compound having an acryloyl group as a polymerizable functional group is preferable, and particularly preferably Acrylic acid. When acrylic acid is used as the ethylenically unsaturated carboxylic acid monomer, a polymer having a high carboxyl group content can be obtained.

The content of the component (a) in the present crosslinked polymer is not particularly limited, but may be, for example, 10% by mass or more and 100% by mass or less with respect to all the structural units of the present crosslinked polymer. By containing the component (a) in such a range, excellent adhesiveness to the base material can be easily ensured. The lower limit is, for example, 20% by mass or more, for example, 30% by mass or more, and for example, 40% by mass or more. When the lower limit is 50% by mass or more, the dispersion stability of the present composition becomes good and a higher binding force can be obtained, which is preferable, and it may be 60% by mass or more, or 70% by mass or more. It may be 80% by mass or more. Further, the upper limit is, for example, 99.9% by mass or less, for example, 99.5% by mass or less, for example, 99% by mass or less, for example, 98% by mass or less, and for example, 95% by mass. It is less than or equal to, for example, 90% by mass or less, and for example, 80% by mass or less. The range may be a range in which such a lower limit and an upper limit are appropriately combined, and is, for example, 10% by mass or more and 100% by mass or less, and for example, 50% by mass or more and 100% by mass or less, and for example. It can be 50% by mass or more and 99.9% by mass or less, and can be, for example, 50% by mass or more and 99% by mass or less, and can be, for example, 50% by mass or more and 98% by mass or less.

<Other structural units>
In addition to the component (a), the crosslinked polymer may contain a structural unit derived from another ethylenically unsaturated monomer copolymerizable with the component (hereinafter, also referred to as “component (b)”). can. The component (b) includes, for example, an ethylenically unsaturated monomer compound having an anionic group other than a carboxyl group such as a sulfonic acid group and a phosphoric acid group, or a nonionic ethylenically unsaturated monomer. The structural unit from which it is derived can be mentioned. These structural units are ethylenically unsaturated monomer compounds having anionic groups other than carboxyl groups such as sulfonic acid groups and phosphoric acid groups, or monomers containing nonionic ethylenically unsaturated monomers. Can be introduced by copolymerizing.

The ratio of the component (b) can be 0% by mass or more and 90% by mass or less with respect to all the structural units of the present crosslinked polymer. The ratio of the component (b) may be 1% by mass or more and 60% by mass or less, 2% by mass or more and 50% by mass or less, and 5% by mass or more and 40% by mass or less. It may be 10% by mass or more and 30% by mass or less. Further, particularly in the use of a lithium ion secondary battery, when the component (b) is contained in an amount of 1% by mass or more based on all the structural units of the crosslinked polymer, the affinity for the electrolytic solution is improved, so that the lithium ion conductivity is improved. Can also be expected to improve.

As the component (b), among the above, structural units derived from nonionic ethylenically unsaturated monomers are preferable from the viewpoint of obtaining a coating film having good bending resistance, and nonionic ethylenically unsaturated. Examples of the saturated monomer include (meth) acrylamide and its derivatives, a nitrile group-containing ethylenically unsaturated monomer, an alicyclic structure-containing ethylenically unsaturated monomer, a hydroxyl group-containing ethylenically unsaturated monomer, and the like. Be done.

Examples of the (meth) acrylamide derivative include N-alkyl (meth) acrylamide compounds such as isopropyl (meth) acrylamide and t-butyl (meth) acrylamide; Nn-butoxymethyl (meth) acrylamide and N-isobutoxymethyl. N-alkoxyalkyl (meth) acrylamide compounds such as (meth) acrylamide; N, N-dialkyl (meth) acrylamide compounds such as dimethyl (meth) acrylamide and diethyl (meth) acrylamide include one of them. It may be used alone or in combination of two or more.

Examples of the nitrile group-containing ethylenically unsaturated monomer include (meth) achlorinitrile; (meth) cyanomethyl acrylate, (meth) cyanoethyl acrylate and other (meth) acrylate cyanoalkyl ester compounds; 4-cyanostyrene. , 4-Cyano-α-methylstyrene and other unsaturated aromatic compounds containing cyano groups; examples thereof include vinylidene cyanide, and one of these may be used alone or in combination of two or more. You may use it. Among the above, acrylonitrile is preferable because it has a high nitrile group content.

Examples of the alicyclic structure-containing ethylenically unsaturated monomer include cyclopentyl (meth) acrylate, cyclohexyl (meth) acrylate, methylcyclohexyl (meth) acrylate, t-butylcyclohexyl (meth) acrylate, and (meth). ) Cyclodecyl acrylate and cyclododecyl (meth) acrylate and other aliphatic substituents may have (meth) cycloalkyl acrylate; isobornyl (meth) acrylate, adamantyl (meth) acrylate, (meth). ) Dicyclopentenyl acrylate, dicyclopentenyloxyethyl (meth) acrylate, dicyclopentanyl (meth) acrylate, and cyclohexanedimethanol mono (meth) acrylate and cyclodecanedimethanol mono (meth) acrylate, etc. Cycloalkyl polyalcohol mono (meth) acrylate and the like can be mentioned, and one of these may be used alone, or two or more thereof may be used in combination.

Examples of the hydroxyl group-containing ethylenically unsaturated monomer include hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, and hydroxybutyl (meth) acrylate, and one of these is used alone. It may be used in combination, or two or more kinds may be used in combination.

The crosslinked polymer or a salt thereof is excellent in binding properties to particles in the slurry, and thus contains (meth) acrylamide and its derivatives, a nitrile group-containing ethylenically unsaturated monomer, and an alicyclic structure-containing ethylenic property. It preferably contains structural units derived from unsaturated monomers and the like.
Further, particularly in the application of a lithium ion secondary battery, when a structural unit derived from a hydrophobic ethylenically unsaturated monomer having a solubility in water of 1 g / 100 ml or less is introduced as the component (b), an electrode is used. It can exert a strong interaction with the material and can exhibit good binding property to the active material. As a result, a solid and well-integrated electrode mixture layer can be obtained. Therefore, the above-mentioned "hydrophobic ethylenically unsaturated monomer having a solubility in water of 1 g / 100 ml or less" is particularly selected. An alicyclic structure-containing ethylenically unsaturated monomer is preferable.
Further, particularly in the application of a lithium ion secondary battery, the structural unit derived from the hydroxyl group-containing ethylenically unsaturated monomer may be contained as the component (b) in that the cycle characteristics of the obtained secondary battery are improved. Preferably, the structural unit is preferably contained in an amount of 0.5% by mass or more and 70% by mass or less, more preferably 2.0% by mass or more and 50% by mass or less, and 10.0% by mass or more and 50% by mass or less. It is more preferable to include it.

Further, as the other nonionic ethylenically unsaturated monomer, for example, (meth) acrylic acid ester may be used. Examples of the (meth) acrylic acid ester include (meth) methyl acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, isobutyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, and the like. Meta) Acrylic acid alkyl ester compound;
Aromatic (meth) acrylic acid ester compounds such as (meth) phenyl acrylate, (meth) phenylmethyl acrylate, and (meth) phenylethyl acrylate;
Examples thereof include (meth) acrylic acid alkoxyalkyl ester compounds such as 2-methoxyethyl (meth) acrylic acid and 2-ethoxyethyl (meth) acrylic acid, and one of these may be used alone. Two or more types may be used in combination.

From the viewpoint of adhesion to particles in the slurry and coating film performance, an aromatic (meth) acrylic acid ester compound can be preferably used. Compounds having an ether bond, such as (meth) acrylic acid alkoxyalkyl esters such as 2-methoxyethyl (meth) acrylate and 2-ethoxyethyl (meth) acrylate, from the viewpoint of further improving lithium ion conductivity and high-rate characteristics. Is preferable, and 2-methoxyethyl (meth) acrylate is more preferable.

Among the nonionic ethylenically unsaturated monomers, a compound having an acryloyl group is obtained in that a polymer having a long primary chain length can be obtained due to its high polymerization rate and the adhesive strength of this crosslinked polymer is improved. preferable. Further, as the nonionic ethylenically unsaturated monomer, a compound having a glass transition temperature (Tg) of a homopolymer of 0 ° C. or less is preferable in terms of improving the bending resistance of the obtained coating film.

The crosslinked polymer may be in the form of a salt in which some or all of the carboxyl groups contained in the polymer are neutralized. The type of salt is not particularly limited, but alkali metal salts such as lithium salt, sodium salt and potassium salt; alkaline earth metal salts such as calcium salt and barium salt; other metal salts such as magnesium salt and aluminum salt; ammonium. Examples thereof include salts and organic amine salts. In particular, in lithium ion secondary battery applications, alkali metal salts and magnesium salts are preferable, and alkali metal salts are more preferable, from the viewpoint that adverse effects on battery characteristics are unlikely to occur.

The present crosslinked polymer is a crosslinked polymer having a crosslinked structure. The cross-linking method in the present cross-linked polymer is not particularly limited, and examples thereof include the following methods.
1) Copolymerization of crosslinkable monomers 2) Utilizing chain transfer to polymer chains during radical polymerization 3) After synthesizing a polymer having a reactive functional group, post-crosslinking is performed by adding a crosslinking agent as necessary. When the crosslinked polymer has a crosslinked structure, the crosslinked polymer or a salt thereof can have excellent adhesive strength. Among the above, the method by copolymerization of crosslinkable monomers is preferable because the operation is simple and the degree of crosslinking can be easily controlled.

<Crosslinkable monomer>
Examples of the crosslinkable monomer include a polyfunctional polymerizable monomer having two or more polymerizable unsaturated groups, a monomer having a self-crosslinkable crosslinkable functional group such as a hydrolyzable silyl group, and the like. Can be mentioned.

The polyfunctional polymerizable monomer is a compound having two or more polymerizable functional groups such as a (meth) acryloyl group and an alkenyl group in the molecule, and is a polyfunctional (meth) acrylate compound, a polyfunctional alkenyl compound, ( Meta) Examples thereof include compounds having both an acryloyl group and an alkenyl group. These compounds may be used alone or in combination of two or more. Among these, a polyfunctional alkenyl compound is preferable because a uniform crosslinked structure can be easily obtained, and a polyfunctional allyl ether compound having two or more allyl ether groups in the molecule is particularly preferable.

Examples of the polyfunctional (meth) acrylate compound include ethylene glycol di (meth) acrylate, propylene glycol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, polyethylene glycol di (meth) acrylate, and polypropylene glycol di (meth) acrylate. Di (meth) acrylates of dihydric alcohols such as meta) acrylate; trimethylol propantri (meth) acrylate, tri (meth) acrylate of trimethyl propanethylene oxide modified product, glycerin tri (meth) acrylate, pentaerythritol tri (meth) Tri (meth) acrylates of trivalent or higher polyhydric alcohols such as meta) acrylates and pentaerythritol tetra (meth) acrylates, poly (meth) acrylates such as tetra (meth) acrylates; Bisamides and the like can be mentioned.

Examples of the polyfunctional alkenyl compound include polyfunctional allyl ether compounds such as trimethylolpropanediallyl ether, trimethylolpropanetriallyl ether, pentaerythritol diallyl ether, pentaerythritol triallyl ether, tetraallyloxyethane, and polyallyl saccharose; diallyl phthalate and the like. Polyfunctional allyl compound; Examples thereof include polyfunctional vinyl compounds such as divinylbenzene.

Compounds having both (meth) acryloyl group and alkenyl group include allyl (meth) acrylate, isopropenyl (meth) acrylate, butenyl (meth) acrylate, pentenyl (meth) acrylate, and (meth) acrylate. 2- (2-Vinyloxyethoxy) ethyl and the like can be mentioned.

Specific examples of the monomer having a self-crosslinkable crosslinkable functional group include a hydrolyzable silyl group-containing vinyl monomer, N-methylol (meth) acrylamide, N-methoxyalkyl (meth) acrylate and the like. Can be mentioned. These compounds can be used alone or in combination of two or more.

The hydrolyzable silyl group-containing vinyl monomer is not particularly limited as long as it is a vinyl monomer having at least one hydrolyzable silyl group. For example, vinyl silanes such as vinyl trimethoxysilane, vinyl triethoxysilane, vinyl methyl dimethoxysilane, vinyl dimethyl methoxysilanen; silyl such as trimethoxysilylpropyl acrylate, triethoxysilylpropyl acrylate, methyldimethoxysilylpropyl acrylate and the like. Group-containing acrylic acid esters; silyl group-containing methacrylate esters such as trimethoxysilylpropyl methacrylate, triethoxysilylpropyl methacrylate, methyldimethoxysilylpropyl methacrylate, dimethylmethoxysilylpropyl methacrylate; trimethoxysilylpropyl vinyl ether and the like. Cyril group-containing vinyl ethers; Examples thereof include silyl group-containing vinyl esters such as trimethoxysilyl undecanoate vinyl.

When the present crosslinked polymer is crosslinked with a crosslinkable monomer, the amount of the crosslinkable monomer used is the total amount of monomers other than the crosslinkable monomer (non-crosslinkable monomer). It is preferably 0.05 parts by mass or more and 5.0 parts by mass or less, more preferably 0.1 parts by mass or more and 5.0 parts by mass or less, and further preferably 0.2 parts by mass or more with respect to 100 parts by mass. It is 4.0 parts by mass or less, more preferably 0.3 parts by mass or more and 3.0 parts by mass or less. When the amount of the crosslinkable monomer used is 0.05 parts by mass or more, it is preferable in that the adhesive strength and the stability of the present composition become better. If it is 5.0 parts by mass or less, the stability of precipitation polymerization or dispersion polymerization tends to be high.
Similarly, the amount of the crosslinkable monomer used may be 0.02 to 1.7 mol% with respect to the total amount of the monomers other than the crosslinkable monomer (non-crosslinkable monomer). It is preferably 0.10 to 1.0 mol%, more preferably 0.10 to 1.0 mol%.

2. Method for Producing the Crosslinked Polymer The crosslinked polymer is a monomer component containing the above ethylenically unsaturated carboxylic acid monomer in the presence of an exchange chain transfer mechanism type control agent (hereinafter, also referred to as “the present monomer”). It is obtained by precipitation polymerization or dispersion polymerization.
Here, precipitation polymerization is a method for producing a polymer by carrying out a polymerization reaction in a solvent that dissolves a monomer as a raw material but does not substantially dissolve the polymer to be produced. As the polymerization progresses, the polymer particles become larger due to aggregation and growth, and a dispersion liquid of the polymer particles in which the primary particles of several tens of nm to several hundreds nm are secondarily aggregated to several μm to several tens of μm can be obtained. Dispersion stabilizers can also be used to control the particle size of the polymer.
The secondary aggregation can also be suppressed by selecting a dispersion stabilizer, a polymerization solvent, or the like. In general, precipitation polymerization in which secondary agglutination is suppressed is also called dispersion polymerization.

Regarding the exchange chain transfer mechanism type control agent The exchange chain transfer mechanism type control agent according to the present invention includes a control agent (hereinafter, also referred to as “RAFT agent”) in the reversible addition-cleaving chain transfer polymerization method (RAFT method). In the iodine transfer polymerization method, the control agent in the polymerization method using an organic tellurium compound (TERP method), the control agent in the polymerization method using an organic antimony compound (SBRP method), and the polymerization method using an organic bismuth compound (BIRP method). Control agents and the like can be mentioned. As the exchange chain transfer mechanism type control agent, a polymer having a polymer chain of one or more kinds of vinyl-based monomers and a living radical polymerization active unit by the exchange chain transfer mechanism (hereinafter, simply "the first polymer"). A control agent other than the polymer can be used, which will be described in detail in paragraphs [0052] to [0078] described later. The first polymer and the control agent other than the polymer may be used alone or in combination.
Precipitation polymerization or dispersion polymerization of this monomer in the presence of an exchange chain transfer mechanism type control agent shortens the primary chain length, and the same chain length forms a uniform crosslinked structure. It is possible to increase the degree of water swelling of the polymer. Along with this, it is presumed that good coatability and excellent coating film performance can be achieved at the same time by reducing the viscosity of the composition.
Among these, the RAFT agent and the control agent in the iodine transfer polymerization method are preferable, and the RAFT agent is more preferable, because the crosslinked structure of the present crosslinked polymer can be made more uniform.

RAFT agents include a first polymer having a living radical polymerization active unit by a reversible addition-cleavage chain transfer method (detailed below) and / or a RAFT agent (dithioester) other than the first polymer. Compounds, xanthate compounds, trithiocarbonate compounds, dithiocarbamate compounds, etc.) can be used.
Specific examples of the RAFT agent other than the first polymer include 2-cyano-2-propylbenzodithioate, 2-phenyl-2-propylbenzodithioate, trithiocarbonate, and 2-cyano-. 2-propyldodecyltrithiocarbonate, 2- (dodecylthiocarbonothio oil thio) propionic acid, 3-((1-carboxyethylthio) carbonothio oil thio)) propionic acid, 2- (dodecylthio carbonothio oil thio) Methyl 2-methylpropanoate, 1,4-bis (n-dodecylsulfanylthiocarbonylsulfanylmethyl) benzene, dibenzyltrithiocarbonate, distyryltrithiocarbonate, dicumyltrithiocarbonate, cyanomethyl-N-methyl-N- Examples thereof include phenyldithiocarbamate.
Among the RAFT agents, those having trithiocarbonate in the molecule are particularly preferable in that the crosslinked structure of the present crosslinked polymer can be made more uniform.

As the control agent in the iodine transfer polymerization method, a first polymer having a living radical active unit by the iodine transfer polymerization method (detailed later) and / or a control agent other than the first polymer shall be used. Can be done.
Specific examples of the control agent other than the first polymer include alkyl groups such as methyl iodide, methylene iodide, iodoform, carbon tetraiodide, 1-phenylethyl iodide, and benzyl iodide. Pafluoroalkyl perfluoroalkyl iodide having 1 to 20 carbon atoms, ethyl 2-iodopropionate, methyl 2-iodoisobutyrate, ethyl 2-iodoisobutyrate, ethyl 2-iodo-2-phenylacetate, bis (2-iodine) Examples thereof include -2-phenylacetic acid) ethylene glycol, bis (2-iodoisobutyric acid) ethylene glycol, 1,5-diiodo-2,4-dimethylbenzene, and 2-iodopropionitrile.

The exchange chain transfer mechanism type control agent may be a monofunctional one having one active site, or a bifunctional or more agent having two or more active sites. A bifunctional or higher exchange chain transfer mechanism type control agent is one in which a polymer chain is extended in a bidirectional or higher direction. From the viewpoint of producing the present crosslinked polymer, it may be preferable to use a bifunctional or trifunctional or higher exchange chain transfer mechanism type control agent.

The amount of the exchange chain transfer mechanism type control agent used is 0.0001 to 0.50 mol% with respect to the total amount of the present monomer in that the crosslinked structure of the crosslinked polymer can be made more uniform. It is more preferable, it is more preferably 0.0001 to 0.40 mol%, further preferably 0.0001 to 0.30 mol%, and more preferably 0.0002 to 0.30 mol%. More preferred.

As the polymerization initiator used together with the exchange chain transfer mechanism type control agent, known polymerization initiators such as azo compounds, organic peroxides, and inorganic peroxides can be used, but are not particularly limited. The conditions of use can be adjusted by known methods such as heat initiation, redox initiation with a reducing agent, and UV initiation so that the amount of radicals generated is appropriate. In order to obtain the present crosslinked polymer having a long primary chain length, it is preferable to set the conditions so that the amount of radicals generated is smaller within the allowable range of the production time.
Among the above-mentioned polymerization initiators, an azo compound is preferable because it is easy to handle for safety and side reactions during radical polymerization are unlikely to occur. Specific examples of the above azo compounds include 2,2'-azobisisobutyronitrile, 2,2'-azobis (2,4-dimethylvaleronitrile), and 2,2'-azobis (4-methoxy-2, 4-Dimethylvaleronitrile), dimethyl-2,2'-azobis (2-methylpropionate), 2,2'-azobis (2-methylbutyronitrile), 1,1'-azobis (cyclohexane-1-) Carbonitrile), 2,2'-azobis [N- (2-propenyl) -2-methylpropionamide], 2,2'-azobis (N-butyl-2-methylpropionamide) and the like. Only one kind of the radical polymerization initiator may be used, or two or more kinds thereof may be used in combination.

The preferable amount of the polymerization initiator used is, for example, 0.001 to 2 parts by mass and, for example, 0.005 to 1 part by mass, when the total amount of the monomer components used is 100 parts by mass. Further, for example, it is 0.01 to 0.1 parts by mass. When the amount of the polymerization initiator used is 0.001 part by mass or more, the polymerization reaction can be stably carried out, and when it is 2 parts by mass or less, a polymer having a long primary chain length can be easily obtained.
The proportion of the polymerization initiator used is not particularly limited, but the amount of the polymerization initiator used per 1 mol of the exchange chain transfer mechanism type control agent is 0.5 mol from the viewpoint that the crosslinked structure of the present crosslinked polymer can be made uniform. It is preferably less than or equal to 0.2 mol or less. Further, from the viewpoint of stably performing the polymerization reaction, the lower limit of the amount of the polymerization initiator used with respect to 1 mol of the exchange chain transfer mechanism type control agent is 0.001 mol. Therefore, the amount of the polymerization initiator used with respect to 1 mol of the exchange chain transfer mechanism type control agent is preferably in the range of 0.001 mol or more and 0.5 mol or less, and more preferably in the range of 0.005 mol or more and 0.2 mol or less.

As the polymerization solvent, a solvent selected from water, various organic solvents and the like can be used in consideration of the type of monomer used and the like. In order to obtain a polymer having a longer primary chain length, it is preferable to use a solvent having a small chain transfer constant.
Specific examples of the polymerization solvent include water-soluble solvents such as methanol, t-butyl alcohol, acetone, methyl ethyl ketone, acetonitrile and tetrahydrofuran, as well as benzene, ethyl acetate, dichloroethane, n-hexane, cyclohexane and n-heptane. , One of these can be used alone or in combination of two or more. Alternatively, it may be used as a mixed solvent of these and water. In the present invention, the water-soluble solvent refers to a solvent having a solubility in water at 20 ° C. of more than 10 g / 100 ml.
Of the above, the formation of coarse particles and adhesion to the reactor are small and the polymerization stability is good, and the precipitated crosslinked polymer is difficult to secondary agglomerate (or even if secondary agglomeration occurs, it dissolves in the aqueous medium. Methyl ethyl ketone and acetonitrile are preferable because they are easy to use), a polymer having a small chain transfer constant and a large degree of polymerization (primary chain length) can be obtained, and the operation is easy during the step neutralization described later. ..

Similarly, in order to allow the neutralization reaction to proceed stably and quickly in the process neutralization, it is preferable to add a small amount of a highly polar solvent to the polymerization solvent. Such highly polar solvents preferably include water and methanol. The amount of the highly polar solvent used is preferably 0.05 to 20.0% by mass, more preferably 0.1 to 10.0% by mass, still more preferably 0.1 to 5% by mass based on the total mass of the medium. It is 0.0% by mass, more preferably 0.1 to 1.0% by mass. When the proportion of the highly polar solvent is 0.05% by mass or more, the effect on the neutralization reaction is recognized, and when it is 20.0% by mass or less, no adverse effect on the polymerization reaction is observed. Further, in the polymerization of highly hydrophilic ethylenically unsaturated carboxylic acid monomer such as acrylic acid, the polymerization rate is improved when a highly polar solvent is added, and it becomes easy to obtain a polymer having a long primary chain length. Among the highly polar solvents, water is particularly preferable because it has a large effect of improving the polymerization rate.

The reaction temperature during the polymerization reaction in the presence of the exchange chain transfer mechanism type controller is preferably 30 ° C. or higher and 120 ° C. or lower, more preferably 40 ° C. or higher and 110 ° C. or lower, and further preferably 50 ° C. or higher and 100 ° C. or higher. It is below ° C. When the reaction temperature is 30 ° C. or higher, the polymerization reaction can proceed smoothly. On the other hand, when the reaction temperature is 120 ° C. or lower, side reactions can be suppressed and restrictions on the initiators and solvents that can be used are relaxed.

The crosslinked polymer dispersion obtained through the polymerization step can be obtained in a powder state by subjecting the dispersion to a reduced pressure and / or heat treatment in the drying step and distilling off the solvent. At this time, for the purpose of removing the unreacted monomer (and its salt) before the drying step, following the polymerization step, a solid-liquid separation step such as centrifugation and filtration, an organic solvent or an organic solvent / water. It is preferable to include a cleaning step using a mixed solvent.
When the above cleaning step is provided, even when the crosslinked polymer is secondarily agglutinated, it is easily unraveled at the time of use, and the remaining unreacted monomer is removed, so that the coating film performance is also good. Is shown.

In the production method of the present invention, when an unneutralized or partially neutralized salt is used as the ethylenically unsaturated carboxylic acid monomer, an alkaline compound is added to the dispersion of the crosslinked polymer obtained in the polymerization step to add weight. After neutralizing the coalescence (hereinafter, also referred to as "step neutralization"), the solvent may be removed in a drying step. Further, after obtaining the powder of the crosslinked polymer in an unneutralized or partially neutralized salt state, an alkaline compound is added when preparing the slurry composition to neutralize the polymer (hereinafter, "post-neutralization"). It may also be called). Of the above, process neutralization is preferable because the secondary aggregates tend to be easily disintegrated.

Here, as the exchange chain transfer mechanism type control agent, as described above, a polymerized chain (hereinafter, also simply referred to as “first monomer”) of one kind or two or more kinds of vinyl-based monomers (hereinafter, also simply referred to as “first monomer”) ( Hereinafter, a polymer (first polymer) having a living radical polymerization active unit by an exchange chain transfer mechanism and a “first polymer chain”) can be used.

In producing the present crosslinked polymer by polymerizing the present monomer in the presence of the first polymer, the first polymer is used as a starting point for the polymerization of the present monomer and the polymerization of the crosslinked polymer. The present crosslinked polymer, which can be used as a dispersion stabilizer in a solvent and has a polymer chain having a structural unit derived from the present monomer bonded to the polymer chain of the first polymer, is obtained as dispersed fine particles. Can be done. By doing so, the polymerization stability, that is, the aggregation of the present crosslinked polymer during the polymerization step is suppressed, the generation of coarse aggregated particles is suppressed, the particle size is small, and the particle size distribution is narrow. You can get coalescence.

In order to make the first polymer function as a dispersion stabilizer in producing the present crosslinked polymer by polymerizing the present monomer in the presence of the first polymer, for example, the first polymer is used. , 0.3 parts by mass or more and 50 parts by mass or less can be used with respect to 100 parts by mass of the total mass of this monomer. By using it in such a range, it is possible to produce the present crosslinked polymer mainly containing the present monomer while allowing the first polymer to function as a dispersion stabilizer. Further, if the amount of the first polymer is less than 0.3 parts by mass, it is difficult to obtain a sufficient dispersion stabilizing effect, and the particle size of the crosslinked polymer tends to exceed 0.3 μm, even if it exceeds 50 parts by mass. This is because it is difficult to improve the functionality as a dispersion stabilizer, and the effect of reducing the particle size of the crosslinked polymer is also reduced.

The first polymer can be used with respect to 100 parts by mass of the total mass of the present monomer, for example, 0.5 parts by mass or more, and for example, 1 part by mass or more. Further, the first polymer can be used, for example, 40 parts by mass or less, for example, 30 parts by mass or less, and for example, 20 parts by mass or less. The range of the amount of the first polymer used with respect to 100 parts by mass of the total mass of the present monomer can be set by appropriately combining the above upper limit and lower limit.

Method for Producing First Polymer By polymerizing a monomer composition containing the first monomer in the presence of a known exchange chain transfer mechanism type control agent, a structural unit derived from the first monomer It is possible to obtain a first polymer having a first polymer chain having the above and a living polymerization active unit by an exchange chain transfer mechanism.

The polymerization conditions for producing the first polymer are well known to those skilled in the art, and examples of the polymerization process include various processes such as bulk polymerization, solution polymerization, suspension polymerization and emulsion polymerization. Considering that it is a polymerization starting point in the production of coalescence and that it functions as a dispersion stabilizer, solution polymerization can be used, for example. Further, the polymerization conditions such as the type of the exchange chain transfer mechanism control agent, the type and amount of the polymerization initiator, the polymerization solvent, and the reaction temperature are described in the above paragraphs [0040] to [0043] and [0045] to [0049]. The amount of the exchange chain transfer mechanism control agent used is appropriately adjusted according to the number average molecular weight (Mn) of the target first polymer.
As the exchange chain transfer mechanism control agent, a RAFT agent and a control agent in the iodine transfer polymerization method are preferable in that the molecular weight distribution of the first polymer can be reduced.
Further, the concentration at the time of producing the first polymer is not particularly limited with respect to the total mass of the amount charged such as the polymerization solvent and the first monomer, but is, for example, 10% by mass or more and 80% by mass. % Or less, for example, 15% by mass or more and 70% by mass or less, and for example, 20% by mass or more and 70% by mass or less.

Typically, when a monofunctional exchange chain transfer mechanism type control agent is used, a living polymerization active unit is provided at the end of the first polymerization chain, and the exchange chain transfer mechanism type having two or more functionalitys is used. When a control agent is used, it is branched in two or more directions with the living polymerization active unit as a base point, and each of them is provided with a first polymerization chain. In any of the embodiments, when another polymerized chain is provided, the other polymerized chain is directly bonded to the living polymerization active unit, and the first polymerization is carried out more distally to the living polymerization active unit. The first polymerized chain is bonded to the distal end of the other polymerized chain so that the chain is provided.

The first polymer may also include two or more types of first polymerized chains. For example, after performing living radical polymerization or the like using one or more first monomers of a certain composition, one or more first monomers of another composition are used. By carrying out living radical polymerization or the like, a first polymer having a first polymerization chain (block) having a structural unit derived from the first monomer having a different composition can be obtained.

The number average molecular weight (Mn) of the first polymer is not particularly limited, but is, for example, 3,000 or more, for example, 5,000 or more, and for example, 7,000 or more. Also, for example, 8,000 or more, and for example, 10,000 or more. Further, the Mn is 50,000 or less, for example, 30,000 or less, and for example, 25,000 or less, and for example, 20,000 or less, and for example, 15,000 or less. And, for example, 14,000 or less, and for example, 12,000 or less. The range of Mn can be set by appropriately combining the above-mentioned lower limit and upper limit, and is, for example, 5,000 or more and 25,000 or less, and for example, 10,000 or more and 25,000 or less. For example, it is 10,000 or more and 15,000 or less, and for example, 10,000 or more and 14,000 or less.

The weight average molecular weight (Mw) of the first polymer is not particularly limited, but is, for example, 5,000 or more, for example, 7,000 or more, and for example, 9,000 or more. Also, for example, 10,000 or more, for example, 13,000 or more, and for example, 15,000 or more. Further, the Mw is 60,000 or less, for example, 55,000 or less, and for example, 50,000 or less, and for example, 45,000 or less, and for example, 40,000 or less. And, for example, 36,000 or less, and for example, 35,000 or less, and for example, 30,000 or less, and for example, 25,000 or less. The range of Mw can be set by appropriately combining the above-mentioned lower limit and upper limit, and is, for example, 1,000 or more and 40,000 or less, and for example, 10,000 or more and 35,000 or less. For example, it is 10,000 or more and 30,000 or less, and for example, 15,000 or more and 25,000 or less.

Both Mw and Mn of the first polymer can be measured by gel permeation chromatography using polystyrene as a standard substance. As for the details of the chromatography conditions, the conditions disclosed in the subsequent examples can be adopted.

The molecular weight distribution (Mw / Mn) of the first polymer is not particularly limited, but is, for example, 2.5 or less, for example, 2.4 or less, and for example, 2.3 or less. Yes, for example 2.0 or less, and for example 1.6 or less, and for example 1.5 or less, and for example 1.4 or less, and for example 1.3 or less. be. Further, the molecular weight distribution is, for example, 1.1 or more, for example, 1.2 or more, and for example, 1.3 or more, and for example, 1.4 or more, and for example, 1.5 or more. Is. The range of the molecular weight distribution can be set by appropriately combining the above-mentioned lower limit and upper limit. For example, 1.1 or more and 2.5 or less, for example, 1.1 or more and 2.4 or less, and for example, 1 It can be 1 or more and 2.3 or less, and for example, 1.1 or more and 2.0 or less.

The smaller the molecular weight distribution of the first polymer, the smaller the particle size of the obtained crosslinked polymer tends to be. The molecular weight distribution is preferably 2.4 or less, and in order to obtain the present crosslinked polymer having a smaller particle size, it is preferably 1.7 or less, and more preferably 1. It is 6 or less, and more preferably 1.4 or less.

<First monomer>
Examples of the first monomer include styrenes, (meth) acrylonitrile compounds, maleimide compounds, unsaturated acid anhydrides and unsaturated carboxylic acid compounds. One or a combination of two or more of these can be used.

Styrenes include styrene and its derivatives. Specific compounds include styrene, α-methylstyrene, β-methylstyrene, vinyltoluene, vinylxylene, vinylnaphthalene, o-methylstyrene, m-methylstyrene, p-methylstyrene, o-ethylstyrene, and m-. Ethylstyrene, p-ethylstyrene, pn-butylstyrene, p-isobutylstyrene, pt-butylstyrene, o-methoxystyrene, m-methoxystyrene, p-methoxystyrene, o-chloromethylstyrene, p- Examples thereof include chloromethylstyrene, o-chlorostyrene, p-chlorostyrene, o-hydroxystyrene, m-hydroxystyrene, p-hydroxystyrene, divinylbenzene, etc., and one or more of these may be used. can. Among these, styrene, o-methoxystyrene, m-methoxystyrene, p-methoxystyrene, o-hydroxystyrene, m-hydroxystyrene, and p-hydroxystyrene are preferable from the viewpoint of polymerizable property.

Examples of the (meth) acrylonitrile compound include (meth) acrylonitrile, acrylonitrile, α-methylacrylonitrile, and the like. For example, acrylonitrile is used.

As the maleimide compound, the maleimide compound includes a maleimide and an N-substituted maleimide compound. Specific examples of the N-substituted maleimide compound include N-methylmaleimide, N-ethylmaleimide, Nn-propylmaleimide, N-isopropylmaleimide, Nn-butylmaleimide, N-isobutylmaleimide, and N-tert-butyl. N-alkyl-substituted maleimide compounds such as maleimide, N-pentylmaleimide, N-hexylmaleimide, N-heptylmaleimide, N-octylmaleimide, N-laurylmaleimide, N-stearylmaleimide; N-cyclopentylmaleimide, N-cyclohexylmaleimide, etc. N-Cycloalkyl-substituted maleimide compounds; N-phenylmaleimide, N- (4-hydroxyphenyl) maleimide, N- (4-acetylphenyl) maleimide, N- (4-methoxyphenyl) maleimide, N- (4-ethoxy) Examples thereof include N-aryl-substituted maleimide compounds such as phenyl) maleimide, N- (4-chlorophenyl) maleimide, N- (4-bromophenyl) maleimide, and N-benzylmaleimide, and one or more of these. Can be used. For example, N-phenylmaleimide is used.

Further, examples of the unsaturated acid anhydride include maleic anhydride, itaconic anhydride, citraconic anhydride and the like, and one or more of these can be used.

Examples of unsaturated carboxylic acid compounds include (meth) acrylic acid, maleic acid, fumaric acid, itaconic acid, crotonic acid, citraconic acid, silicic acid, maleic acid, fumaric acid, itaconic acid, citraconic acid, maleic anhydride, and anhydrous. Examples thereof include unsaturated dicarboxylic acids such as itaconic acid and citraconic anhydride, and monoalkyl esters of unsaturated dicarboxylic acids, and one or more of them can be used.

Among these, the first monomer preferably contains, for example, at least styrenes. This is because styrenes are easy to carry out in the living room and can impart appropriate hydrophobicity and affinity to organic solvents. It is possible to impart hydrophobicity or affinity to an organic solvent to the first polymerized chain. By doing so, for example, when a crosslinked polymer is produced by a dispersion polymerization method in a polar organic solvent, the first polymer tends to be present on the surface layer of the crosslinked polymer, and the crosslinked polymer is produced. Dispersion stability is improved.

Styrene is, for example, 20% by mass or more of the total mass of the first monomer. This is because if the content is 20% by mass or more, the living polymerization is facilitated, and an appropriate hydrophobicity and an affinity for an organic solvent can be appropriately imparted. Further, for example, it is 30% by mass or more, and for example, 35% by mass or more, and for example, 40% by mass or more, and for example, 50% by mass or more, and for example, 60% by mass or more. Further, for example, it is 65% by mass or more, for example, 70% by mass or more, and for example, 75% by mass or more. Further, the styrenes are 100% by mass or less of the total mass, and are, for example, 95% by mass or less, and are, for example, 90% by mass or less, and are, for example, 85% by mass or less, and are, for example,. It is 80% by mass or less, and for example, 75% by mass or less. The range of the styrenes with respect to the total mass can be set by appropriately combining the above-mentioned lower limit and upper limit, and is, for example, 20% by mass or more and 95% by mass or less, and for example, 30% by mass or more and 75% by mass or more. And, for example, 35% by mass or more and 85% by mass or less.

The (meth) acrylonitrile compound, maleimide compound, acid anhydride and unsaturated carboxylic acid compound can be used alone, and it is preferable to use one or more of these four types in combination with styrenes. This is because all of these four types can maintain, regulate or impart the hydrophobicity or organic solvent affinity of the first polymerized chain. Among them, one or more of (meth) acrylonitrile compounds such as acrylonitrile, maleimide compounds such as N-phenylmaleimide, and acid anhydrides. Of these, a combination of styrene and acrylonitrile, styrene and N-phenylmaleimide and the like is preferable. The unsaturated carboxylic acid compound is preferable in that the polarity of the first polymer can be easily changed.

When used in combination with styrenes, the total amount of these one or more first monomers other than styrenes is the first monomer for polymerizing the first polymerized chain (first). It is, for example, 20% by mass or more of the total mass of the first monomer unit of the polymerized chain). Further, for example, it is 25% by mass or more, and for example, 30% by mass or more, and for example, 35% by mass or more, and for example, 40% by mass or more, and for example, 50% by mass or more. Further, for example, it is 60% by mass or more. The (meth) acrylonitrile compound is 80% by mass or less of the total mass, and is, for example, 75% by mass or less, and is, for example, 70% by mass or less, and is, for example, 65% by mass or less. Further, for example, it is 60% by mass or less, for example, 55% by mass or less, and for example, 50% by mass or less. The range of the styrenes with respect to the total mass can be set by appropriately combining the above lower limit and upper limit, and is, for example, 20% by mass or more and 65% by mass or less, and for example, 25% by mass or more and 50% by mass or more. It is as follows.

<First polymerized chain>
The first polymerized chain may be a polymerized chain containing only the first monomer described above, but if necessary, other vinyl-based monomers other than the above may be used as the first monomer. be able to. For example, known vinyl-based monomers such as (meth) acrylic acid esters such as (meth) acrylic acid and alkyl (meth) acrylic acid can be used.
It should be noted that these other monomers are, for example, 10% by mass or less, for example, 5% by mass or less, for example, 3% by mass or less, or, for example, the total mass of the monomers constituting the first polymerized chain. 1, 1% by mass or less, and for example, 0.5% by mass or less.

Further, the first polymer may include a block (another polymer chain) different from that of the first polymer chain. Such other polymerized chains may be added, for example, in another synthetic step after the formation of the first polymerized chain. In this case, a radical polymerization initiator and another vinyl-based monomer are continuously or newly supplied to the first polymer having the first polymer chain to have a composition different from that of the first polymer chain. It is possible to obtain a first polymer having another polymer chain (block) composed of units derived from a monomer other than the first monomer. By being provided so as to be directly linked to the living radical active unit, which will be described later, and to be linked to the first polymerized chain, a part of the monomer common to the present monomer used in the present crosslinked polymer can be partially linked in advance. It can be provided in the first polymer.

<Living radical polymerization active unit>
Since the first polymer has a living radical polymerization active unit by an exchange chain transfer mechanism, it can be used as a solubility or dispersion stabilizer in the polymerization solvent of the first polymer in the precipitation polymerization or dispersion polymerization of this monomer. Various monomers can be selected for the function of.

As the exchange chain transfer mechanism of the living radical polymerization active unit in the first polymer, a reversible addition-cleavage chain transfer polymerization method (RAFT method), an iodine transfer polymerization method, a polymerization method using an organic tellurium compound (TERP method), and the like. Examples thereof include a polymerization method using an organic antimony compound (SBRP method) and a polymerization method using an organic bismuth compound (BIRP method). Among these, the RAFT method and the iodine transfer polymerization method are preferable, and the RAFT method is more preferable, because the particle size of the crosslinked polymer can be reduced.

3. 3. Characteristics of the present crosslinked polymer <Aqueous viscosity of the present crosslinked polymer>
The crosslinked polymer or a salt thereof preferably has a viscosity of 100 mPa · s or more in a 2% by mass aqueous solution thereof. When the viscosity of the 2% by mass aqueous solution is 100 mPa · s or more, the composition containing the crosslinked polymer has high storage stability and can exhibit excellent adhesive strength. The viscosity of the 2 mass% concentration aqueous solution may be 1,000 mPa · s or more, 10,000 mPa · s or more, or 50,000 mPa · s or more. It is obtained by uniformly dissolving or dispersing the present crosslinked polymer or a salt thereof in an amount to be a concentration in water, and then measuring the B-type viscosity (25 ° C.) at 12 rpm according to the method described in Examples.

This crosslinked polymer absorbs water and becomes swollen in water. In general, when the crosslinked polymer has an appropriate degree of crosslinkage, the larger the amount of hydrophilic groups contained in the crosslinked polymer, the easier it is for the crosslinked polymer to absorb water and swell. Regarding the degree of cross-linking, the lower the degree of cross-linking, the easier it is for the cross-linked polymer to swell. However, even if the number of cross-linking points is the same, the larger the molecular weight (primary chain length), the more cross-linking points that contribute to the formation of the three-dimensional network, so that the cross-linked polymer is less likely to swell. Therefore, the viscosity of the crosslinked polymer aqueous solution can be adjusted by adjusting the amount of hydrophilic groups of the crosslinked polymer, the number of crosslinked points, the primary chain length, and the like. At this time, the number of the cross-linking points can be adjusted by, for example, the amount of the cross-linking monomer used, the chain transfer reaction to the polymer chain, the post-crosslinking reaction, and the like. Further, the primary chain length of the polymer can be adjusted by setting conditions related to the amount of radicals generated such as the initiator and the polymerization temperature, and selecting the polymerization solvent in consideration of chain transfer and the like.

<Particle size of this crosslinked polymer>
In the present composition, the crosslinked polymer does not exist as a mass (secondary agglomerate) having a large particle size, but is well dispersed as water-swelled particles having an appropriate particle size. Is preferable because it can exhibit good adhesive strength.

In this crosslinked polymer, the particle size (water-swelling particle size) when a crosslinked polymer having a degree of neutralization based on a carboxyl group of 80 to 100 mol% is dispersed in water is a volume-based median diameter. It is preferably in the range of 0.1 μm or more and 5.0 μm or less. The more preferable range of the particle size is 0.1 μm or more and 4.0 μm or less, the more preferable range is 0.1 μm or more and 3.0 μm or less, and the more preferable range is 0.2 μm or more and 3.0 μm or less. Yes, and even more preferable ranges are 0.3 μm or more and 3.0 μm or less. When the particle size is in the range of 0.1 μm or more and 5.0 μm or less, the composition is uniformly present in a suitable size in the present composition, so that the present composition is highly stable and exhibits excellent adhesive strength. It becomes possible. If the particle size exceeds 5.0 μm, the adhesive strength may be insufficient as described above. In addition, there is a risk that the coatability will be insufficient because it is difficult to obtain a smooth coated surface. On the other hand, when the particle size is less than 0.1 μm, there is concern from the viewpoint of stable manufacturability.

In the present crosslinked polymer, acid groups such as a carboxyl group derived from an ethylenically unsaturated carboxylic acid monomer are neutralized so that the degree of neutralization is 20 mol% or more in the present composition, and the mode of the salt is It is preferable to use as. The degree of neutralization is more preferably 50 mol% or more, further preferably 70 mol% or more, still more preferably 75 mol% or more, still more preferably 80 mol% or more, and particularly preferably. It is 85 mol% or more. The upper limit of the degree of neutralization is 100 mol%, and may be 98 mol% or 95 mol%. The range of the degree of neutralization may be appropriately combined with the above lower limit value and upper limit value, and may be, for example, 50 mol% or more and 100 mol% or less, or 75 mol% or more and 100 mol% or less. , 80 mol% or more and 100 mol% or less. When the degree of neutralization is 20 mol% or more, the water swelling property is good and the dispersion stabilizing effect is easily obtained, which is preferable. In the present specification, the degree of neutralization can be calculated by calculation from the charged values of a monomer having an acid group such as a carboxyl group and a neutralizing agent used for neutralization. The degree of neutralization was determined by measuring the IR of the crosslinked polymer or a salt thereof after drying the crosslinked polymer or a salt thereof at 80 ° C. for 3 hours under reduced pressure, and measuring the peak derived from the C = O group of the carboxylic acid and the C = of the carboxylate. It can be confirmed from the intensity ratio of the peak derived from the O group.

<Water swelling degree of this crosslinked polymer>
In this specification, the water swelling degree is the weight of the dry present crosslinked polymer "(W _{A) g",} and the amount of water absorbed the crosslinked polymer upon saturation swelling with water "(W _B ) G ”, it is calculated based on the following formula.
(Water swelling _{degree) = {(W A) +} (W B)} / (W A)

The crosslinked polymer or a salt thereof preferably has a water swelling degree of 20 or more and 80 or less at pH 8. When the degree of water swelling is within the above range, the crosslinked polymer or a salt thereof swells appropriately in an aqueous medium, so that a sufficient adhesion area to the particles in the slurry and the substrate is secured when forming the coating film. It becomes possible to do so, and the binding property tends to be good. The degree of water swelling may be, for example, 21 or more, 23 or more, 25 or more, 27 or more, or 30 or more. When the degree of water swelling is 20 or more, the crosslinked polymer or a salt thereof spreads on the surface of the particles or the base material in the slurry, and a sufficient adhesive area can be secured, so that good binding property can be obtained. The upper limit of the degree of water swelling at pH 8 may be 75 or less, 70 or less, 65 or less, 60 or less, or 55 or less. If the degree of water swelling exceeds 80, the viscosity of the present composition tends to increase, and as a result of insufficient uniformity of the mixture layer, sufficient binding force may not be obtained. In addition, the coatability of the present composition may decrease. The range of the degree of water swelling at pH 8 can be set by appropriately combining the above upper limit value and lower limit value, and is, for example, 23 or more and 70 or less, and for example, 25 or more and 65 or less, and for example, 25. It is 55 or less.
The degree of water swelling at pH 8 can be obtained by measuring the degree of swelling of the crosslinked polymer or a salt thereof in water at pH 8. As the water having a pH of 8, for example, ion-exchanged water can be used, and the pH value may be adjusted by using an appropriate acid or alkali, a buffer solution or the like, if necessary. The pH at the time of measurement is, for example, in the range of 8.0 ± 0.5, preferably in the range of 8.0 ± 0.3, more preferably in the range of 8.0 ± 0.2, and further. It is preferably in the range of 8.0 ± 0.1.

A person skilled in the art can adjust the degree of water swelling by controlling the composition and structure of the crosslinked polymer. For example, the degree of water swelling can be increased by introducing an acidic functional group or a highly hydrophilic structural unit into the crosslinked polymer. Further, by lowering the degree of cross-linking of the cross-linked polymer, the degree of water swelling is usually increased.

Hereinafter, the present invention will be specifically described based on Examples. The present invention is not limited to these examples. In the following, "parts" and "%" mean parts by mass and% by mass unless otherwise specified.

<< Evaluation of carboxyl group-containing crosslinked polymer (salt) >>
(Water swelling degree at pH 8)
The degree of water swelling at pH 8 was measured by the following method. The measuring device is shown in FIG.
The measuring device is composed of <1> to <3> in FIG.
<1> It is composed of a burette 1, a pinch cock 2, a silicon tube 3 and a polytetrafluoroethylene tube 4 having a branch tube for venting air.
<2> A support cylinder 8 having a large number of holes on the bottom surface is installed on the funnel 5, and a filter paper 10 for an apparatus is installed on the support cylinder 8.
<3> The crosslinked polymer sample 6 (measurement sample) is sandwiched between two sample fixing filter papers 7, and the sample fixing filter paper is fixed by the adhesive tape 9. All the filter papers used are ADVANTEC No. 2. The inner diameter is 55 mm.
<1> and <2> are connected by a silicon tube 3.
Further, the heights of the funnel 5 and the support cylinder 8 are fixed with respect to the burette 1, and the lower end of the polytetrafluoroethylene tube 4 installed inside the burette branch pipe and the bottom surface of the support cylinder 8 are at the same height. (Dotted line in FIG. 1).

The measuring method will be described below.
The pinch cock 2 in <1> is removed, ion-exchanged water is poured from the upper part of the burette 1 through the silicon tube 3, and the burette 1 to the filter paper 10 for the device are filled with the ion-exchanged water 12. Next, the pinch cock 2 is closed, and air is removed from the polytetrafluoroethylene tube 4 connected to the burette branch pipe with a rubber stopper. In this way, the ion-exchanged water 12 is continuously supplied from the burette 1 to the filter paper 10 for the apparatus.
Next, after removing the excess ion-exchanged water 12 oozing from the filter paper 10 for the device, the reading (a) of the scale of the burette 1 is recorded.
Weigh 0.1 to 0.2 g of the dry powder of the measurement sample, and place it evenly on the center of the sample fixing filter paper 7 as shown in <3>. The sample is sandwiched between another filter paper, and the two filter papers are fastened with the adhesive tape 9 to fix the sample. The filter paper on which the sample is fixed is placed on the device filter paper 10 shown in <2>.
Next, the reading (b) of the scale of the burette 1 is recorded 30 minutes after the lid 11 is placed on the filter paper 10 for the device.
The total (c) of the water absorption of the measurement sample and the water absorption of the two sample fixing filter papers 7 is obtained by (ab). By the same operation, the water absorption amount (d) of only the two filter papers 7 containing no crosslinked polymer sample is measured.
The above operation was performed, and the degree of water swelling was calculated from the following formula. As the solid content used in the calculation, the value measured by the method described later was used.
Water swelling degree = {dry weight of measurement sample (g) + (cd)} / {dry weight of measurement sample (g)}
However, the dry weight (g) of the measurement sample = the weight (g) of the measurement sample × (solid content (%) ÷ 100)

Here, the method for measuring the solid content will be described below.
Approximately 0.5 g of the sample is collected in a weighing bottle [weight of the weighing bottle = B (g)] whose weight has been measured in advance, and the entire weighing bottle is accurately weighed [W ₀ (g)]. The sample was placed in a windless dryer together with the weighing bottle, dried at 155 ° C. for 45 minutes, and the weight at that time was measured together with the weighing bottle [W ₁ (g)], and the solid content was determined by the following formula.
Solid content (%) = (W _1- B) / (W _0- B) x 100

(Measurement of particle size (water-swelling particle size) in water medium)
0.25 g of the carboxyl group-containing crosslinked polymer salt powder and 49.75 g of ion-exchanged water were weighed in a 100 cc container and set in a rotating / revolving stirrer (Awatori Rentaro AR-250, manufactured by Shinky). Next, stirring (rotation speed 2,000 rpm / revolution speed 800 rpm, 7 minutes) and defoaming (rotation speed 2,200 rpm / revolution speed 60 rpm, 1 minute) are performed, and the carboxyl group-containing crosslinked polymer salt swells in water. A hydrogel in a state of being prepared was prepared.
Next, the particle size distribution of the hydrogel was measured with a laser diffraction / scattering particle size distribution meter (Microtrack MT-3300EXII, manufactured by Microtrac Bell) using ion-exchanged water as a dispersion medium. When an amount of hydrogel capable of obtaining an appropriate scattered light intensity was added to the place where an excessive amount of dispersion medium was circulated with respect to the hydrogel, the particle size distribution shape measured after several minutes became stable. As soon as the stability was confirmed, the particle size distribution was measured to obtain a volume-based median diameter (D50) as a representative value of the particle size.

(Measurement of viscosity of 2% by mass aqueous solution)
2.0 parts of the carboxyl group-containing crosslinked polymer salt powder and 98 parts of the ion-exchanged water were weighed in a container and set in a rotating / revolving stirrer (Awatori Rentaro AR-250, manufactured by Shinky). Next, stirring (rotation speed 2,000 rpm / revolution speed 800 rpm, 7 minutes) and defoaming (rotation speed 2,200 rpm / revolution speed 60 rpm, 1 minute) were repeated until there were no unswelled powdery parts, and carboxyl group-containing cross-linking was performed. A hydrogel fine particle dispersion in which the polymer salt was swollen in water was prepared. After adjusting each of the obtained hydrogel fine particle dispersions to 25 ° C. ± 1 ° C., the viscosity at a rotor speed of 12 rpm was measured using a B-type viscometer (TVB-10 manufactured by Toki Sangyo Co., Ltd.).

≪Synthesis of the first polymer≫
(Polymer 1)
2.0 parts of RAFT agent (dibenzyltrithiocarbonate: DBTTC), 2,2'-azobis (2-methylbutylonitrile) (2-methylbutylonitrile) in a reactor equipped with a stirrer, thermometer, reflux condenser and nitrogen introduction tube. Japan Finechem Co., Ltd., trade name "ABN-E") 0.410 parts, styrene (St) 75 parts, acrylonitrile (AN) 25 parts, and anisole 67 parts were charged, sufficiently degassed by nitrogen bubbling, and at 80 ° C. Polymerization was started in a constant temperature bath. After 4 hours, the reaction was stopped by cooling to room temperature. The above polymerization solution was reprecipitated and purified from methanol / water = 90/10 (vоl%) and vacuum dried to obtain a polymer 1. As a result of the test by gas chromatography, the reaction rate of the obtained polymer 1 was 72%. The molecular weight of the polymer 1 was Mn11,900, Mw15,500, and Mw / Mn was 1.30. Styrene and acrylonitrile correspond to the first monomer.

(Method for measuring the molecular weight of the first polymer)
The molecular weight of the first polymer was measured by gel permeation chromatography (GPC). That is, a polystyrene-equivalent number average molecular weight (Mn) and a weight average molecular weight (Mw) were obtained by THF-based GPC. Moreover, the molecular weight distribution (Mw / Mn) was calculated from the obtained values. The GPC was performed under the following conditions.

Column: Tosoh TSKgel SuperMultipore HZ-M x 4 Solvent: Tetrahydrofuran Temperature: 40 ° C
Detector: RI
Flow velocity: 600 μL / min

<< Production of crosslinked polymer salt containing carboxyl group >>
(Example 1: Production of crosslinked polymer salt R-1 containing a carboxyl group)
A reactor equipped with a stirring blade, a thermometer, a reflux condenser and a nitrogen introduction tube was used for the polymerization.
In the reactor, 567 parts of acetonitrile, 2.20 parts of ion-exchanged water, 100 parts of acrylic acid (hereinafter referred to as "AA"), 0.001 part of DBTTC, trimethylolpropane diallyl ether (manufactured by Daiso, trade name "Neoallyl T"). -20 ") 0.90 parts and 1.0 mol% of triethylamine with respect to the above AA were charged. After sufficiently replacing the inside of the reactor with nitrogen, the inside temperature was raised to 55 ° C. by heating. After confirming that the internal temperature was stable at 55 ° C., 2,2'-azobis (2,4-dimethylvaleronitrile) (manufactured by Wako Pure Chemical Industries, Ltd., trade name "V-65") 0 as a polymerization initiator. When .040 parts were added, white turbidity was observed in the reaction solution, and this point was set as the polymerization initiation point. The monomer concentration was calculated to be 15.0%. Cooling of the reaction solution is started 12 hours after the polymerization start point, and after the internal temperature is lowered to 25 ° C., _{a powder of lithium hydroxide / monohydrate (hereinafter referred to as “LiOH / H 2} O”) is used. 52.4 parts were added. After the addition, stirring was continued at room temperature for 12 hours to obtain a slurry-like polymerization reaction solution in which particles of the carboxyl group-containing polymer salt R-1 (Li salt, neutralization degree 90 mol%) were dispersed in a medium.

The obtained polymerization reaction solution was centrifuged to settle the polymer particles, and then the supernatant was removed. Then, after redispersing the precipitate in acetonitrile having the same weight as the polymerization reaction solution, the washing operation of precipitating the polymer particles by centrifugation to remove the supernatant was repeated twice. The precipitate was recovered and dried at 80 ° C. for 3 hours under reduced pressure conditions to remove volatile components to obtain a powder of the carboxyl group-containing polymer salt R-1. Since the carboxyl group-containing polymer salt R-1 has hygroscopicity, it was stored in a container having a water vapor barrier property. The powder of the carboxyl group-containing polymer salt R-1 was measured by IR, and the degree of neutralization was determined from the intensity ratio of the peak derived from the C = O group of the carboxylic acid and the peak derived from the C = O of the carboxylic acid Li. , 90 mol% equal to the calculated value from the preparation. The degree of water swelling was 36.4, the particle size in the aqueous medium was 1.72 μm, and the viscosity of the 2% by mass aqueous solution was 9,110 mPa · s.

(Examples 2 to 15 and Comparative Examples 1 to 2: Production of carboxyl group-containing crosslinked polymer salts R-2 to R-17)
The same operation as in Production Example 1 was carried out except that the amounts of the monomer, the crosslinkable monomer and the neutralizing agent were as shown in Table 1, and the carboxyl group-containing crosslinked polymer salts R-2 to R were carried out. A polymerization reaction solution containing -17 was obtained.
Next, the same operations as in Production Example 1 were carried out for each polymerization reaction solution to obtain powdery carboxyl group-containing crosslinked polymer salts R-2 to R-17. Each carboxyl group-containing crosslinked polymer salt was sealed and stored in a container having a water vapor barrier property. Table 1 shows the degree of water swelling of R-2 to R-17, the particle size in the aqueous medium, and the viscosity of the 2% by mass aqueous solution. Incidentally, the particle diameter in an aqueous medium of R-3 (degree of neutralization 70 mol%) was measured after adjusting the neutralization degree of 90 mol% by LiOH · _{H 2} O.

Details of the compounds used in Table 1 are shown below.
AA: Acrylic acid IBXA: Isobornyl acrylate BM1430: 2- (Dodecylthiocarbonothio oilthio) Propionic acid IBME: 2-Methyl iodoisobutyrate T-20: Trimethylolpropane diallyl ether (manufactured by Daiso, trade name "Neoallyl T-" 20 "))
P-30: Pentaerythritol triallyl ether (manufactured by Daiso, trade name "Neoallyl P-30")
TEA: Triethylamine AcN: Acetonitrile V-65: 2,2'-azobis (2,4-dimethylvaleronitrile) (manufactured by Wako Pure Chemical Industries, Ltd.)
LiOH ・ H ₂ O: Lithium hydroxide ・ Monohydrate Na ₂ CO ₃ : Sodium carbonate K ₂ CO ₃ : Potassium carbonate

<< Evaluation of composition containing carboxyl group-containing crosslinked polymer salt >>
(Example 1: Evaluation of composition containing carboxyl group-containing crosslinked polymer salt R-1)
<Preparation of slurry composition>
Prepare a SiOx (0.8 <x <1.2) surface coated with 10% carbon by the CVD method (hereinafter referred to as "Si-based active material"), and prepare artificial graphite and Si-based active material. The mixture was used as the active material. As the binder, a mixture of the present crosslinked polymer salt R-1, styrene-butadiene rubber (SBR) -based latex, and carboxymethyl cellulose (CMC) was used.
Artificial graphite: Si-based active material: R-1: SBR: CMC = 90: 10: 1.0: 1.0: using water as a diluting solvent so that the solid content concentration of the slurry composition is 50% by mass. With a mass ratio of 1.0 (solid content), T.I. K. A slurry composition was prepared by mixing with a hibis mix for 2 hours. The viscosity of the slurry composition was 3,670 mPa · s, which was a sufficiently low value.
An electrode was prepared using the obtained slurry composition, and its coatability and coating film performance were evaluated. The specific procedure and evaluation method are shown below.

(Slurry composition coatability)
The above slurry composition was applied to both sides of a copper foil (thickness: 20 μm) and dried to form a mixture layer. Then, after rolling so that the thickness of the mixture layer was 27 μm and the packing density was 1.3 g / cm ³ , the negative electrode electrode plate was obtained by punching 3 cm square.
The coatability of the slurry composition in the production of the negative electrode electrode plate was evaluated based on the following criteria, and was evaluated as “⊚”.
<Evaluation criteria>
⊚: No abnormal appearance such as streaks or bumps is observed on the surface.
〇: Slight abnormalities in appearance such as streaks and bumps are observed on the surface.
Δ: Some appearance abnormalities such as streaks and bumps are observed on the surface.
X: Appearance abnormalities such as streaks and bumps are noticeably observed on the surface.

<Manufacturing of lithium ion secondary battery>
In N-methylpyrrolidone (NMP) solvent, 100 parts of lithium iron phosphate (LFP) as the positive electrode active material, 0.2 parts of carbon nanotubes as the conductive agent, 2 parts of Ketjen black, and vapor layer carbon fiber (VGCF). ) 0.6 part was mixed and added, and polyvinylidene fluoride (PVDF) was mixed as a binder for the electrode composition to prepare a composition for a positive electrode. A mixture layer was formed by applying the positive electrode composition to an aluminum current collector (thickness: 15 μm) and drying it. Then, after rolling so that the thickness of the mixture layer was 88 μm and the packing density was 3.1 g / cm ³ , the mixture was punched 3 cm square to obtain a positive electrode plate.
Using the positive electrode plate, the negative electrode plate, and the separator, a lithium ion secondary battery of a laminated cell was produced. _{As the electrolytic solution, one in which LiPF 6} was dissolved at a concentration of 1.0 mol / liter in a mixed solvent containing ethylene carbonate (EC) and ethyl methyl carbonate (DEC) at a volume ratio of 25:75 was used.

(Coating film performance)
In this example, the performance of the coating film obtained from the above slurry composition was evaluated by measuring the cycle characteristics of the lithium ion secondary battery.
The lithium-ion secondary battery of the laminated cell produced by the above procedure is charged / discharged at a charge / discharge rate of 0.2 C under the condition of 2.7 to 3.4 V by CC discharge, and the initial capacity is increased. C0 was measured. Further, charging and discharging were repeated in an environment of 25 ° C., and the capacity C50 after 50 cycles was measured. The cycle characteristic (ΔC) calculated by the following formula was 91.8%, and the cycle characteristic based on the following criteria was evaluated as “◯”. The higher the value of ΔC, the better the cycle characteristics.
ΔC = C50 / C0 × 100 (%)
<Evaluation criteria>
⊚: Charge / discharge capacity retention rate is 95.0% or more 〇: Charge / discharge capacity retention rate is 90.0% or more and less than 95.0% Δ: Charge / discharge capacity retention rate is 85.0% or more and less than 90.0% × : Charge / discharge capacity retention rate is less than 85.0%

(Examples 2 to 15 and Comparative Examples 1 to 2: Evaluation of a composition containing carboxyl group-containing crosslinked polymer salts R-2 to R-17)
A slurry composition was prepared by performing the same operation as in Example 1 except that the carboxyl group-containing crosslinked polymer salt was as shown in Table 1, and the viscosity of the composition was measured. In addition, the coatability of the composition and the cycle characteristics of the secondary battery obtained by using the composition were evaluated. The results are shown in Table 1.

≪Evaluation result≫
As is clear from the results of Examples 1 to 15, all the slurry compositions containing the crosslinked polymer salt obtained by the production method of the present invention have good coatability and a coating film of the composition. The performance (in this example, the cycle characteristics of the secondary battery provided with the electrodes obtained by using the composition) was also excellent. Among these, when the water swelling degree and the particle size in the aqueous medium are the same (Examples 2, 12, and 13), as an exchange chain transfer mechanism type control agent, in reversible addition cleavage type chain transfer polymerization. The case where the control agent was used (Examples 2 and 12) was superior to the case where the iodine transfer polymerization control agent was used (Example 13) (in this example, the charge / discharge capacity was maintained). High rate and excellent cycle characteristics).
On the other hand, in the case of a slurry composition containing a crosslinked polymer produced without using an exchange chain transfer mechanism type controller, either the coating film performance (cycle characteristics of the secondary battery) or the coatability is significantly inferior. (Comparative Examples 1 and 2).

Since the composition containing the carboxyl group-containing crosslinked polymer or a salt thereof obtained by the production method of the present invention is excellent in both coatability and coating performance, it is a thickener for cosmetics, a viscosity modifier, and non-water. It is expected to be applied to various applications such as binders for electrolyte secondary battery electrodes, sedimentation inhibitors for pigments, and dispersion stabilizers for metal powders.

Claims (8)

1. A method for producing a carboxyl group-containing crosslinked polymer or a salt thereof.
   A step of polymerizing a monomer component containing an ethylenically unsaturated carboxylic acid monomer by precipitation polymerization or dispersion polymerization in the presence of an exchange chain transfer mechanism type control agent is provided.
   The exchange chain transfer mechanism type control agent is a polymer having one or more types of vinyl monomer polymer chains and a living radical polymerization active unit by the exchange chain transfer mechanism, and / or other than the polymer. A manufacturing method that is an exchange chain transfer mechanism type control agent.
2. The production method according to claim 1, wherein the exchange chain transfer mechanism type control agent is a reversible addition-cleaving type chain transfer agent (RAFT agent).
3. The production method according to claim 2, wherein the reversible addition-cleaving chain transfer agent has a trithiocarbonate group in the molecule.
4. Claims 1 to 3 in which the amount of the exchange chain transfer mechanism type control agent used is 0.0001 to 0.50 mol% with respect to the total amount of the monomer components containing the ethylenically unsaturated carboxylic acid monomer. The production method according to any one of the above.
5. The production method according to any one of claims 1 to 4, wherein the monomer component contains 50% by mass or more and 100% by mass or less of an ethylenically unsaturated carboxylic acid monomer with respect to the total amount thereof.
6. The crosslinked polymer is crosslinked with a crosslinkable monomer, and the amount of the crosslinkable monomer used is 0.1 part by mass or more with respect to 100 parts by mass of the total amount of the non-crosslinkable monomer. The production method according to any one of claims 1 to 5, wherein the amount is 0.0 parts by mass or less.
7. The crosslinked polymer or a salt thereof is neutralized to a degree of neutralization of 80 to 100 mol%, and then the particle size measured in an aqueous medium is 0.1 μm or more and 5.0 μm or less in terms of volume-based median diameter. The production method according to any one of claims 1 to 6.
8. The production method according to any one of claims 1 to 7, wherein the crosslinked polymer or a salt thereof has a water swelling degree of 20 or more and 80 or less at pH 8.

Images