JP7668663B2 - Binder - Google Patents

Description

The present invention relates to a binder.

It has been known that the strength and other properties of fibers can be improved by attaching a binder to the fibers, and binders that combine polyacrylic acid-based polymers with inorganic salts have been used (for example, Patent Documents 1 and 2).

Japanese Patent Application Publication No. 11-158773 Japanese Unexamined Patent Publication No. 6-184285

Conventional binders that combine polyacrylic acid-based polymers and inorganic salts have the problem of not being able to sufficiently increase fiber strength.

Therefore, the present invention aims to provide a binder that has strength, high elongation, and high toughness.

The present inventors have conducted various studies to achieve the above object and have come up with the present invention. That is, the present disclosure relates to a binder comprising a polymer having a structural unit derived from the following general formula (1) and one or more compounds selected from the group consisting of a polyfunctional aziridine compound, a polyfunctional oxazoline compound, a polyfunctional epoxy compound, and a polyfunctional isocyanate compound.

(In general formula (1), R ¹ represents an alkyl group having 1 to 4 carbon atoms, a hydrogen atom, an alkali metal atom, an alkaline earth metal atom, or ammonium.)

The binder disclosed herein has high strength and can also exhibit the functionality of being highly ductile. This makes it possible to apply it to a variety of fields, including fibers, processed fiber products, paper, films, and electronic information materials.

The present invention will be described in detail below. Note that a combination of two or more of the individual preferred embodiments of the present invention described below is also a preferred embodiment of the present invention.

Binders of the present disclosure
<Structural unit represented by general formula (1)>
The binder of the present disclosure contains a polymer (hereinafter also referred to as the “polymer of the present disclosure”), and the polymer (hereinafter also referred to as the RHMA-based polymer) contains a structural unit derived from the following general formula (1).

(In general formula (1), R ¹ represents an alkyl group having 1 to 4 carbon atoms, a hydrogen atom, an alkali metal atom, an alkaline earth metal atom, or ammonium.)
The alkyl group having 1 to 4 carbon atoms represented by R ¹ is preferably an alkyl group having 1 to 2 carbon atoms, and more preferably an alkyl group having 1 carbon atom (methyl group).

The alkali metal atom represented by ^R1 is preferably lithium, sodium or potassium, more preferably sodium or potassium, and even more preferably sodium.

The alkaline earth metal atom represented by ^R1 includes calcium, magnesium, and the like.

The ammonium represented by ^R1 is not limited to NH4 ⁺ , but is defined to include organic ammonium. Examples of organic ammonium include quaternary ammonium such as tetraalkylammonium such as tetramethylammonium and tetrabutylammonium; and ammonium (primary to tertiary ammonium) formed by protonating an amine. ^R1 is preferably an ammonium formed by protonating ammonia or an amine. Examples of the amine include trialkylamines (preferably _triC1-10 alkylamines) such as trimethylamine, triethylamine, and tributylamine; and hydroxyalkylamines (preferably di- or tri( _hydroxyC1-10 alkyl)amines) such as diethanolamine and triethanolamine, with hydroxyalkylamines being preferred.

The structural unit represented by the above general formula (1) may be formed by a polymerization reaction of a monomer represented by the following general formula (2), but may also be formed by other methods. For example, a monomer in which R ¹ in the general formula (2) is an alkyl group having 1 to ⁴ carbon atoms may be polymerized and hydrolyzed to form a structural unit of an alkali metal, a structural unit of an alkaline earth metal, or an ammonium structural unit in the above general formula (1).

(In general formula (2), R ¹ represents an alkyl group having 1 to 4 carbon atoms, a hydrogen atom, an alkali metal atom, an alkaline earth metal atom, or ammonium.)
In the above general formula (2), R ¹ may be one type or two or more types. When R ¹ is two or more types, it may be formed by polymerizing two or more types of monomers represented by the above general formula (2), or it may be formed by polymerizing a monomer represented by the above general formula (2) in which R ¹ is an alkyl group having 1 to 4 carbon atoms, and then partially hydrolyzing the ester group or hydrolyzing it with two or more types of basic substances.

The polymer of the present disclosure preferably contains 30% by mass or more of the structural unit represented by the above general formula (1), more preferably 40% by mass or more, even more preferably 45% by mass or more, and even more preferably 50% by mass or more. On the other hand, the polymer of the present disclosure preferably contains 99.9% by mass or less of the structural unit represented by the above general formula (1), more preferably 99% by mass or less, even more preferably 97% by mass or less, and most preferably 95% by mass or less. By containing the structural unit in the above range, the pH, hydrophilicity, etc. can be adjusted, so that the binder of the present disclosure tends to have high strength and large elongation.

The polymer of the present disclosure may have a multilayer structure, for example a core-shell structure consisting of a core portion and a shell portion provided on the surface of the core portion.

<Structural units derived from other monomers>
The polymer of the present disclosure may contain one or more structural units derived from a monomer other than the structural unit represented by the above general formula (1) (hereinafter also referred to as "structural units derived from other monomers"). That is, the polymer may contain one or more structural units derived from a monomer other than the monomer represented by the above general formula (2) (hereinafter also referred to as "other monomers").

The structural unit derived from the other monomer can be formed, for example, by radical polymerization of the other monomer. Note that the structural unit derived from the other monomer may have the same structure as the structure in which the carbon-carbon double bond of the other monomer is replaced with a carbon-carbon single bond, and is not limited to the structural unit formed by polymerization of the other monomer, and may be, for example, a structural unit formed by a reaction after polymerization.

Other monomers are not particularly limited and include (meth)acrylic monomers such as methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, t-butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, and lauryl (meth)acrylate; styrene monomers such as styrene, α-methylstyrene, p-methylstyrene, tert-butylstyrene, chlorostyrene, and vinyltoluene; (meth) Carboxyl group-containing monomers such as acrylic acid, maleic acid, fumaric acid, crotonic acid, itaconic acid, and maleic anhydride; silane group-containing monomers such as vinyltrimethoxysilane, vinyltriethoxysilane, vinyltri(methoxyethoxy)silane, γ-(meth)acryloyloxypropyltrimethoxysilane, 2-styrylethyltrimethoxysilane, vinyltrichlorosilane, γ-(meth)acryloyloxypropylhydroxysilane, and γ-(meth)acryloyloxypropylmethylhydroxysilane; hydroxyl group-containing monomers such as 1-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate; nitrogen atom-containing monomers such as (meth)acrylamide, N,N-dimethyl (meth)acrylamide, dimethylaminoethyl (meth)acrylamide, N-vinylpyrrolidone, and (meth)acrylonitrile; ethylene glycol methoxy (meth)acrylate, Examples include oxo group-containing monomers such as diethylene glycol methoxy (meth)acrylate; fluorine atom-containing monomers such as trifluoroethyl (meth)acrylate, tetrafluoropropyl (meth)acrylate, and octafluoropentyl (meth)acrylate; light stabilizing monomers such as 2,2,6,6-tetramethylpiperidine-4-(meth)acrylate; ultraviolet absorbing monomers such as benzotriazole-based ultraviolet absorbing monomers and benzophenone-based ultraviolet absorbing monomers; and polyfunctional ethylenically unsaturated monomers.

As the polyfunctional ethylenically unsaturated monomer, one or more types can be used, and it is preferable that the polyfunctional ethylenically unsaturated monomer is a non-hydrolyzable monomer. In addition, as described later, hydrolysis can be performed by adding a basic aqueous solution such as an aqueous sodium hydroxide solution, an aqueous diethanolamine solution, an aqueous ammonia solution, or an aqueous cyclohexylamine solution to the polymer used in the present invention, so it is more preferable that the non-hydrolyzable monomer has resistance to basic hydrolysis. The non-hydrolyzable monomer is preferably a polyfunctional monomer (hydrocarbon) composed only of carbon atoms and hydrogen atoms, and may have an ether bond as necessary. In this specification, the polyfunctional monomer as a hydrocarbon that may have an ether bond is referred to as a hydrocarbon-based crosslinking agent that may have an ether bond. The hydrocarbon-based crosslinking agent that may have an ether bond preferably has two or more ethylenically unsaturated bonds, and more preferably has two ethylenically unsaturated bonds. Specific examples of hydrocarbon-based crosslinking agents that may have an ether bond include divinylbenzene, 1,3-butadiene, trivinylbenzene, divinylnaphthalene, trivinylcyclohexane, divinyl ether, diallyl ether, and polyvalent methacrylic acid esters. Divinylbenzene, 1,3-butadiene, diallyl ether, and polyvalent methacrylic acid esters are preferred, and divinylbenzene and polyvalent methacrylic acid esters are more preferred.

Examples of diallyl ethers include dialkylene glycol diallyl ethers such as diethylene glycol diallyl ether, dipropylene glycol diallyl ether, and dibutylene glycol diallyl ether; and polyalkylene glycol diallyl ethers such as polyethylene glycol diallyl ether, polypropylene glycol diallyl ether, and polybutylene glycol diallyl ether. Examples of polyvalent methacrylic acid esters include ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, triethylene glycol dimethacrylate, tetraethylene glycol dimethacrylate, polyethylene glycol dimethacrylate, 1,3-butanediol dimethacrylate, 1,4-butanediol dimethacrylate, 1,6-hexanediol dimethacrylate, 1,9-nonanediol dimethacrylate, neopentyl glycol dimethacrylate, dipropylene glycol dimethacrylate, polypropylene glycol dimethacrylate, trimethylolpropane trimethacrylate, pentaerythritol trimethacrylate, pentaerythritol tetramethacrylate, dipentaerythritol hexamethacrylate, and methacryl-modified polydimethylsiloxane.

The polymer of the present disclosure may contain crosslinkable units such as structural units derived from polyfunctional ethylenically unsaturated monomers. The structural units derived from polyfunctional ethylenically unsaturated monomers are preferably 30% by mass or less, more preferably 20% by mass or less, and even more preferably 10% by mass or less, of the total monomer units (100% by mass), and may be 0% by mass (not including monomer units derived from polyfunctional ethylenically unsaturated monomers). If crosslinked, the polymer will retain its particle shape even after hydrolysis, but if the degree of crosslinking increases, flexibility will be lost, adhesion to fibers, etc. will be poor, and the contact area between the binder and fibers, etc. may be reduced.

The polymer of the present disclosure may have a particle shape (hereinafter, also referred to as "polymer particles of the present disclosure"). The preferred particle size of the polymer particles of the present disclosure is preferably a volume average particle size of 10 nm to 10 μm, more preferably 50 nm to 5 μm, even more preferably 100 nm to 1 μm, and particularly preferably 150 to 850 nm. The volume average particle size of the polymer of the present disclosure can be measured, for example, by a dynamic light scattering method.
The polymer of the present disclosure may have a multilayer structure, for example, a core-shell structure composed of a core portion and a shell portion provided on the surface of the core portion.

The polymer of the present disclosure may be a core-shell particle composed of a core portion and a shell portion provided on the surface thereof. In the case of a core-shell particle, it is preferable that the shell portion contains a structural unit represented by the above general formula (1). On the other hand, it is preferable that the core portion contains a monomer unit derived from a monofunctional (meth)acrylic monomer. As the monofunctional (meth)acrylic monomer, an alkyl ester of (meth)acrylic acid having 1 to 12 carbon atoms is preferable, and an alkyl ester of (meth)acrylic acid having 1 to 4 carbon atoms is more preferable. As the monofunctional (meth)acrylic monomer, for example, methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, t-butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, lauryl (meth)acrylate, etc. can be mentioned, and one or more kinds can be used. The core portion preferably contains 50% by mass or more of monomer units derived from monofunctional (meth)acrylic monomers, more preferably 70% by mass or more, even more preferably 90% by mass or more, and particularly preferably 100% by mass. The core portion may or may not contain a structural unit represented by the above general formula (1) and a structural unit derived from a polyfunctional ethylenically unsaturated monomer.

The core part may contain a monomer other than the monofunctional (meth)acrylic monomer, and examples of the monomer other than the monofunctional (meth)acrylic monomer include monofunctional styrene monomers. Examples of the styrene monomer include alkylstyrenes such as styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, α-methylstyrene, ethylvinylbenzene, and p-t-butylstyrene; and styrene monofunctional monomers such as halogen-containing styrenes such as o-chlorostyrene, m-chlorostyrene, and p-chlorostyrene. Each of these monomers may be used alone, or two or more of them may be used in combination.

<Polyfunctional aziridine compound>
This refers to a compound having one or more oxazoline groups in one molecule, and further having the functional group and one or more reactive functional groups, such as a carboxy group, a (meth)acryloyl group, an amino group, a hydroxy group, an aromatic hydroxy group, a thiol group, an aromatic thiol group, an aziridine group, an oxazoline group, an epoxy group, an isocyanate group, a carbodiimide group, etc.

Examples of polyfunctional aziridine compounds include N,N'-diphenylmethane-4,4'-bis(1-aziridinecarboxite), N,N'-toluene-2,4-bis(1-aziridinecarboxite), bisisophthaloyl-1-(2-methylaziridine), tri-1-aziridinylphosphine oxide, N,N'-hexamethylene-1,6-bis(1-aziridinecarboxite), trimethylolpropane-tri-β-aziridinyl propionate, tetramethylolmethane-tri-β-aziridinyl propionate, tris-2,4,6-(1-aziridinyl)-1,3,5-triazine, trimethylolpropane tris[3-(1-aziridinyl)propionate], trimethylolpropane tris[3-(1 -aziridinyl)butyrate], trimethylolpropane tris[3-(1-(2-methyl)aziridinyl)propionate], trimethylolpropane tris[3-(1-aziridinyl)-2-methylpropionate], 2,2'-bishydroxymethylbutanol tris[3-(1-aziridinyl)propionate], pentaerythritol tetra[3-(1-aziridinyl)propionate], diphenylmethane-4,4-bis-N,N'-ethyleneurea, 1,6-hexamethylene bis-N,N'-ethyleneurea, 2,4,6-(triethyleneimino)-Syn-triazine, bis[1-(2-ethyl)aziridinyl]benzene-1,3-carboxylic acid amide, aziridine group-containing polymers, etc.

<Polyfunctional oxazoline compound>
This refers to a compound having one or more oxazoline groups in one molecule, and further having the functional group and one or more reactive functional groups, such as a carboxy group, a (meth)acryloyl group, an amino group, a hydroxy group, an aromatic hydroxy group, a thiol group, an aromatic thiol group, an aziridine group, an oxazoline group, an epoxy group, an isocyanate group, a carbodiimide group, etc.

Polyfunctional oxazoline compounds include 2'-methylenebis(2-oxazoline), 2,2'-ethylenebis(2-oxazoline), 2,2'-ethylenebis(4-methyl-2-oxazoline), 2,2'-propylenebis(2-oxazoline), 2,2'-tetramethylenebis(2-oxazoline), 2,2'-hexamethylenebis(2-oxazoline), 2,2'-octamethylenebis(2-oxazoline), 2,2'-p-phenylenebis(2-oxazoline), 2,2'-p-phenylenebis(4,4'-dimethyl-2-oxazoline), 2,2'-p-phenylenebis(4-methyl-2-oxazoline), 2,2'-p-phenylenebis(4-phenyl-2-oxazoline), oxazoline), 2,2'-m-phenylene bis(2-oxazoline), 2,2'-m-phenylene bis(4-methyl-2-oxazoline), 2,2'-m-phenylene bis(4,4'-dimethyl-2-oxazoline), 2,2'-m-phenylene bis(4-phenylene bis-2-oxazoline), 2,2'-o-phenylene bis(2-oxazoline), 2,2'-o-phenylene bis(4-methyl-2-oxazoline), 2,2'-bis(2-oxazoline), 2,2'-bis(4-methyl-2-oxazoline), 2,2'-bis(4-ethyl-2-oxazoline), 2,2'-bis(4-phenyl-2-oxazoline), and oxazoline group-containing polymers.

<Polyfunctional epoxy compound>
This refers to a compound having one or more epoxy groups in one molecule, and further having the functional group and one or more reactive functional groups, such as a carboxy group, a (meth)acryloyl group, an amino group, a hydroxy group, an aromatic hydroxy group, a thiol group, an aromatic thiol group, an aziridine group, an oxazoline group, an epoxy group, an isocyanate group, a carbodiimide group, etc.

Examples of polyfunctional epoxy compounds include aromatic epoxy compounds, aliphatic epoxy compounds, alicyclic epoxy compounds, and hydrogenated epoxy compounds. Preferred are alicyclic epoxy compounds and aliphatic epoxy compounds, and more preferred are alicyclic glycidyl ether compounds and aliphatic glycidyl ether compounds.

Examples of alicyclic glycidyl ether compounds include dicyclopentadiene dimethanol diglycidyl ether, adamantane dimethanol diglycidyl ether, 1,2-bis(glycidyloxy)cyclohexane, 1,3-bis(glycidyloxy)cyclohexane, 1,4-bis(glycidyloxy)cyclohexane, 1,4-bis(glycidyloxy)decalin, 1,6-bis(glycidyloxy)decalin, 1,4-bis(glycidyloxymethyl)cyclohexane, 1,4-bis(glycidyloxybutyl)cyclohexane, 1,2-cyclohexanedicarboxylic acid diglycidyl ester, 1,4-cyclohexanedicarboxylic acid diglycidyl ester, and 1,3,5-cyclohexanetricarboxylic acid triglycidyl ester.

Examples of aliphatic glycidyl ether compounds include diglycidyl ether of ethylene glycol, diglycidyl ether of propylene glycol, diglycidyl ether of 1,4-butanediol, diglycidyl ether of cyclohexanedimethanol, diglycidyl ether of glycerin or triglycidyl ether of trimethylolpropane, tetraglycidyl ether of pentaerythritol, diglycidyl ether of dodecahydrobisphenol A, etc.

Commercially available products include, for example, sorbitol polyglycidyl ether (e.g., "Denacol EX-612", "Denacol EX-614", and "Denacol EX-622", manufactured by Nagase ChemteX Corporation), glycerol polyglycidyl ether (e.g., "Denacol EX-314", manufactured by Nagase ChemteX Corporation), diglycerol polyglycidyl ether (e.g., "Denacol EX-421", manufactured by Nagase ChemteX Corporation), polyglycerol polyglycidyl ether (e.g., "Denacol EX-421", manufactured by Nagase ChemteX Corporation), and polyglycerol polyglycidyl ether (e.g., "Denacol EX-421", manufactured by Nagase ChemteX Corporation). ether (e.g., "Denacol EX-521", manufactured by Nagase ChemteX Corporation), pentaerythritol polyglycidyl ether (e.g., "Denacol EX-411", manufactured by Nagase ChemteX Corporation), trimethylolpropane polyglycidyl ether (e.g., "Denacol EX-321", manufactured by Nagase ChemteX Corporation), neopentyl glycol diglycidyl ether (e.g., "Denacol EX-211", manufactured by Nagase ChemteX Corporation), 1,6 -Hexanediol diglycidyl ether (e.g., "Denacol EX-212", manufactured by Nagase ChemteX Corporation), ethylene glycol diglycidyl ether (e.g., "Denacol EX-811", manufactured by Nagase ChemteX Corporation), diethylene glycol diglycidyl ether (e.g., "Denacol EX-851", manufactured by Nagase ChemteX Corporation), polyethylene glycol diglycidyl ether (e.g., "Denacol EX-821", "Denacol EX -830", "Denacol EX-832", "Denacol EX-841", "Denacol EX-861", manufactured by Nagase ChemteX Corporation), propylene glycol diglycidyl ether (e.g., "Denacol EX-911", manufactured by Nagase ChemteX Corporation), polypropylene glycol diglycidyl ether (e.g., "Denacol EX-941", "Denacol EX-920", "Denacol EX-931", manufactured by Nagase ChemteX Corporation), etc.

<Polyfunctional isocyanate compound>
This refers to a compound having one or more isocyanate groups in one molecule, and further having the functional group and one or more reactive functional groups, such as a carboxy group, a (meth)acryloyl group, an amino group, a hydroxy group, an aromatic hydroxy group, a thiol group, an aromatic thiol group, an aziridine group, an oxazoline group, an epoxy group, an isocyanate group, a carbodiimide group, etc.

Examples of polyfunctional isocyanate compounds include diisocyanate compounds such as aromatic diisocyanate compounds, alicyclic diisocyanate compounds, and aliphatic diisocyanate compounds; adduct polyisocyanate compounds; biuret polyisocyanate compounds; and polyisocyanate compounds having an isocyanurate ring. Preferred are aromatic diisocyanate compounds, alicyclic diisocyanate compounds, and aliphatic diisocyanate compounds.

Examples of aromatic diisocyanate compounds include tolylene diisocyanate, 2,2'-diphenylmethane diisocyanate, 2,4'-diphenylmethane diisocyanate, 4,4'-diphenylmethane diisocyanate, 4,4'-diphenyldimethylmethane diisocyanate, 4,4'-dibenzyl diisocyanate, 1,5-naphthylene diisocyanate, xylylene diisocyanate, 1,3-phenylene diisocyanate, and 1,4-phenylene diisocyanate.

Alicyclic diisocyanate compounds include isophorone diisocyanate, hydrogenated xylylene diisocyanate, 4,4'-cyclohexylmethane diisocyanate, 1,4-cyclohexane diisocyanate, methylcyclohexylene diisocyanate, 1,3-bis(isocyanatemethyl)cyclohexane, etc.

Examples of aliphatic diisocyanate compounds include tetramethylene diisocyanate, dodecamethylene diisocyanate, 1,4-butane diisocyanate, hexamethylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, 2,4,4-trimethylhexamethylene diisocyanate, lysine diisocyanate, 2-methylpentane-1,5-diisocyanate, and 3-methylpentane-1,5-diisocyanate.

From the viewpoint of stability, the polyfunctional isocyanate compound is preferably a blocked isocyanate in which the isocyanate group is inactivated by reacting it with a masking agent having active hydrogen. For example, commercially available products include DM-6400, Meikanate DM-3031CONC, Meikanate DM-35HC, Meikanate TP-10, Meikanate CX, SU-268A, NBP-8730, NBP-211 [manufactured by Meisei Chemical Industry Co., Ltd.], Elastron BN-69, BN-77, BN-27, BN-11, BN-44, BN-04, BN-08, E-37, H-3-DF, H-15, BAP, NEW BAP, F-29, W-11P, MF-25K [manufactured by Daiichi Kogyo Seiyaku Co., Ltd.], Takenate WB-700, WB-770, WB-920 [manufactured by Mitsui Chemicals Polyurethanes Co., Ltd.], Karenz MOI-BM, MOI-BP [manufactured by Showa Denko K.K.], Duranate MF-K60B, SBN-70D, MF-B60B, MF-B90B, 17B-60P, TPA-B80B, TPA-B80E, E402-B80B [manufactured by Asahi Kasei Chemicals Co., Ltd.], BI-7950, BI-7951, BI-7960, BI-7961, BI-7963, BI-7982, BI-7991, BI-7992 [Ba xenden Co., Ltd.], IPDI-B1065, IPDI-B1530, IPDI-BF1540 [manufactured by HULS Co., Ltd.], Burnock B7-887-60, B3-867, DB980K [manufactured by Dainippon Ink Co., Ltd.], Desmodur BL1100/1, Sumidur BL3175, Desmodur BL3272MPA, Desmodur BL3475BA/SN, Desmodur BL3575/1MPA/SN [manufactured by Sumitomo Bayer Urethane Co., Ltd.], and 3-(3,4-dichlorophenyl)-1,1-dimethylurea "DCMU" [manufactured by Hodogaya Chemical Co., Ltd.].

In addition to the structural unit represented by the general formula (1) above, the polymer of the present disclosure may contain one or more structural units derived from one or more compounds selected from the group consisting of polyfunctional aziridine compounds, polyfunctional oxazoline compounds, polyfunctional epoxy compounds, and polyfunctional isocyanate compounds (hereinafter also referred to as "structural units derived from polyfunctional compounds").

The polymer of the present disclosure preferably contains 1% by mass or more, more preferably 5% by mass or more, and even more preferably 10% by mass or more of structural units derived from one or more compounds selected from the group consisting of polyfunctional aziridine compounds, polyfunctional oxazoline compounds, polyfunctional epoxy compounds, and polyfunctional isocyanate compounds. On the other hand, the polymer of the present disclosure preferably contains 50% by mass or less, more preferably 40% by mass or less, and even more preferably 30% by mass or less of structural units derived from one or more compounds selected from the group consisting of polyfunctional aziridine compounds, polyfunctional oxazoline compounds, polyfunctional epoxy compounds, and polyfunctional isocyanate compounds. By including the structural units in the above range, the polymer tends to have high strength and high elongation.

The binder of the present disclosure preferably contains 0.5% by mass or more, more preferably 5% by mass or more, and even more preferably 10% by mass or more of structural units derived from one or more compounds selected from the group consisting of polyfunctional aziridine compounds, polyfunctional oxazoline compounds, polyfunctional epoxy compounds, and polyfunctional isocyanate compounds. On the other hand, the polymer of the present disclosure preferably contains 50% by mass or less, more preferably 40% by mass or less, and even more preferably 30% by mass or less of structural units derived from one or more compounds selected from the group consisting of polyfunctional aziridine compounds, polyfunctional oxazoline compounds, polyfunctional epoxy compounds, and polyfunctional isocyanate compounds. By including them in the above range, high toughness tends to be exhibited.

[Method of manufacturing the binder of the present disclosure]
<Polymerization method>
The RHMA polymer is obtained by polymerizing at least one monomer represented by the above formula (2) in which R1 is an alkyl group having 1 to 4 carbon atoms (hereinafter referred to as hydroxymethyl acrylic acid ester) in an aqueous solvent, and, if necessary, partially or completely hydrolyzing the monomer to convert a part or all of the portion corresponding to R1 into a hydrogen atom, an alkali metal atom, an alkaline earth metal atom, ammonium, or the like. The hydroxymethyl acrylic acid ester may be polymerized together with other monomers (hereinafter, these may be collectively referred to as "raw monomer components"). When hydroxymethyl acrylic acid ester is used as a raw monomer, the product can be made into a particulate form even when polymerized in an aqueous solvent.

Polymerization methods include suspension polymerization, emulsion polymerization, dispersion polymerization, etc. Among them, emulsion polymerization is preferred in which the raw material monomer components are dispersed in a reaction solvent in the presence of an emulsifier to carry out a (radical) polymerization reaction. Specifically, the method for producing the polymer of the present invention preferably includes emulsion polymerization in which at least one monomer represented by the above formula (2) is dispersed in an aqueous solvent in the presence of an emulsifier to carry out a polymerization reaction. The emulsion polymerization may be carried out in only one stage or in multiple stages.

The emulsifier may be one or more than one type, and may be a non-reactive surfactant or a reactive surfactant having a radically polymerizable group in its structure.

Non-reactive surfactants include anionic and nonionic surfactants. Examples of anionic surfactants include fatty acid salts, alkyl (aryl) sulfonates, alkyl sulfate ester salts, and polyoxyethylene alkyl (phenyl) ether sulfate salts. Examples of nonionic surfactants include polyoxyethylene alkyl (phenyl) ethers, polyoxyethylene sorbitan fatty acid esters, polyoxyethylene fatty acid esters, and polyoxyethylene polyoxypropylene block polymers.

Reactive surfactants include anionic and nonionic surfactants. Anionic reactive surfactants include, but are not limited to, ether sulfate reactive surfactants and phosphate ester reactive surfactants.

The amount of emulsifier is preferably 0.05 parts by mass or more, more preferably 0.1 parts by mass or more, and even more preferably 0.3 parts by mass or more, per 100 parts by mass of the total raw material monomer components, and is preferably 20 parts by mass or less, more preferably 10 parts by mass or less, even more preferably 5 parts by mass or less, and particularly preferably 3 parts by mass or less.

In the present disclosure, the aqueous solvent may be water alone or a mixed solvent of water and a water-miscible organic solvent, but water alone is preferred. The aqueous solvent typically refers to a solvent containing more than 50% by volume of water. As the water, ion-exchanged water (deionized water), distilled water, pure water, etc. can be used. As the water-miscible organic solvent, an organic solvent (such as a lower alcohol) that can be mixed uniformly with water can be used. From the viewpoint of minimizing the amount of organic solvent remaining in the polymer, an aqueous solvent in which 80% by volume or more of the aqueous solvent is water is preferred, an aqueous solvent in which 90% by volume or more of the aqueous solvent is water is more preferred, an aqueous solvent in which 95% by volume or more of the aqueous solvent is water is even more preferred, an aqueous solvent substantially composed of water (an aqueous solvent in which 99.5% by volume or more of water) is particularly preferred, and water alone is most preferred.

When polymerizing the raw material monomer components, for example, a polymerization initiator, irradiation with ultraviolet rays or radiation, application of heat, or other means are used. It is preferable to use a polymerization initiator, and from the viewpoint of efficiently reacting the raw material monomer components and sufficiently reducing the amount of remaining monomer, a polymerization initiator that combines an oxidizing agent and a reducing agent (redox type polymerization initiator) is preferable.

The hydrolysis of the polymer of the present disclosure can be carried out by adding a basic aqueous solution such as an aqueous sodium hydroxide solution, an aqueous calcium hydroxide solution, an aqueous ammonia solution, or an aqueous cyclohexylamine solution. In addition, partial or complete neutralization can be carried out by adding an appropriate amount of acid to the hydrolysis liquid. By carrying out hydrolysis and neutralization, the group corresponding to R1 in the above general formula (1) can be converted to a hydrogen atom, an alkali metal atom, an alkali metal atom, or ammonium. By adjusting the amount of acid or base used during polymerization, hydrolysis, and neutralization, or by adjusting the proportion of monomer units in which R1 is a hydrogen atom, the pH and hydrophilicity of the polymer can be adjusted, which tends to improve the operability as a binder and the ease of uniform dispersion in the binder.

<Water Dispersion>
The binder in which the polymer is dispersed in water (aqueous dispersion) by dispersing the polymer in water as described above is also included in the scope of the present invention. The polymer in the aqueous dispersion has a hydroxymethyl group and is excellent in hydrophilicity. The polymer has good dispersibility in water, has high storage stability as a dispersion, and can be easily hydrolyzed. When hydrolysis and subsequent neutralization are performed as necessary, hydrolysis can be performed by adding a basic aqueous solution such as an aqueous sodium hydroxide solution, an aqueous ammonia solution, an aqueous diethanolamine solution, or an aqueous cyclohexylamine solution to the polymer contained in the aqueous dispersion. Furthermore, partial or complete neutralization can be performed by adding an appropriate acid to the hydrolysis liquid. By performing hydrolysis and neutralization, the group corresponding to R1 in the above general formula (1) can be made into a hydrogen atom, an alkali metal atom, an alkaline earth metal atom, or ammonium. The volume average particle size of the polymer can be easily adjusted by adjusting the amount of acid or base used during polymerization, hydrolysis, and neutralization, or by adjusting the ratio of monomer units in which R1 is a hydrogen atom, so that the binder can be used in a wide range of applications.

The aqueous dispersion preferably contains 5% by mass or more of the polymer, more preferably 10% by mass or more, and preferably 100% by mass or less, more preferably 50% by mass or less.

The volume average particle diameter of the polymer contained in the aqueous dispersion is preferably 10 nm to 10 μm, more preferably 50 nm to 5 μm, even more preferably 100 nm to 1 μm, and particularly preferably 150 to 850 nm. The volume average particle diameter of the polymer contained in the aqueous dispersion was measured by dynamic light scattering.

[Uses of the binder of the present disclosure]
The use of the binder used in the present invention is not limited. Because of its functionality of achieving both tensile strength and elongation, it can be applied to various fields such as fibers, processed fiber products, nonwoven fabrics, sheets, paper, binders, paints, adhesives, thickeners, thermoplastic resins, thermosetting resins, various films, electronic information materials, catalyst carriers, heat insulating materials, and low reflection materials.

[Synthesis of polymer]
<Production Example 1>
In a stainless steel reaction kettle equipped with a stirrer, a thermometer and a cooling tube, 804.8 parts by mass of deionized water and 0.72 parts by mass of anionic reactive surfactant ADEKA REASOAP SR-20 (active ingredient 100% by mass, manufactured by ADEKA Corporation) mainly composed of ether sulfate type ammonium salt diluted with ion-exchanged water to 25.0% by mass of active ingredient (hereinafter referred to as "SR-20 (active ingredient 25.0% by mass)") were added, and the internal temperature was raised to 75 ° C. and maintained at the same temperature. 67.5 parts by mass of methyl methacrylate (hereinafter referred to as "MMA"), 67.5 parts by mass of n-butyl acrylate (hereinafter referred to as "BA"), 11.0 parts by mass of SR-20 (active ingredient 25.0% by mass), and 124.0 parts by mass of deionized water were added to the dropping funnel A to prepare a dropping pre-emulsion A in the dropping funnel. 135.0 parts by mass of methyl 2-hydroxymethylacrylate (hereinafter referred to as "RHMA"), 15.0 parts by mass of divinylbenzene (manufactured by Nippon Steel Chemical & Material Co., Ltd., divinylbenzene purity 81%, hereinafter referred to as "DVB810"), 12.3 parts by mass of SR-20 (active ingredient 25.0% by mass), 0.27 parts by mass of aqueous ammonia (concentration 28% by mass), and 137.5 parts by mass of deionized water were charged into the dropping funnel B to prepare a dropping pre-emulsion B in the dropping funnel. 320 parts by mass of aqueous hydrogen peroxide (concentration 0.61% by mass) was charged into the dropping funnel C. 320 parts by mass of an aqueous L-ascorbic acid solution (concentration 0.92% by mass) was charged into the dropping funnel D.

Next, after replacing the inside of the reaction vessel with nitrogen gas, 15.0 parts by mass of a mixed monomer composition of 7.5 parts by mass of MMA and 7.5 parts by mass of BA, 20 parts by mass of hydrogen peroxide (concentration 0.25% by mass), and 20 parts by mass of an aqueous L-ascorbic acid solution (concentration 0.38% by mass) were added to the reaction vessel to carry out an initial polymerization reaction. Next, pre-emulsion A for dropping was dropped from dropping funnel A for 60 minutes, pre-emulsion B for dropping from dropping funnel B for 180 minutes, hydrogen peroxide from dropping funnel C for 240 minutes, and an aqueous L-ascorbic acid solution from dropping funnel D for 240 minutes. Dropping of pre-emulsion B for dropping was started immediately after the dropping of pre-emulsion A for dropping was completed.

After the dropwise addition was completed, the internal temperature of the reaction vessel was maintained at 75° C. and the reaction solution was aged at the same temperature for 2 hours, and then cooled to obtain a polymer particle dispersion in which the polymer particles were dispersed.
280.0 parts by mass of the polymer particle water dispersion obtained above and 23.6 parts by mass of an aqueous sodium hydroxide solution (concentration 20.0% by mass) as a basic aqueous solution were mixed and stirred overnight at 25° C. to obtain an aqueous polymer particle dispersion (1a) in which partially hydrolyzed polymer particles (1) were dispersed. At this time, the ratio of the mole number of sodium hydroxide added to the mole number of RHMA in the aqueous polymer particle dispersion was 75%. The volume average particle diameter was 339 nm.

<Production Example 2>
Except for changing the basic aqueous solution during hydrolysis to 8.0 parts by mass of an aqueous ammonia solution (concentration 25.0% by mass) in Production Example 1, polymer particles (2) and a polymer particle aqueous dispersion (2a) in which the polymer particles (2) are dispersed were obtained in the same manner as in Production Example 1. At this time, the ratio of the number of moles of ammonia added to the number of moles of RHMA in the polymer particle aqueous dispersion was 75%. The volume average particle diameter was 391 nm.

<Production Example 3>
In a stainless steel reaction kettle equipped with a stirrer, a thermometer, and a cooling tube, 836.8 parts by mass of deionized water and 3.84 parts by mass of SR-20 (active ingredient 25.0% by mass) were added, and the internal temperature was raised to 75°C and maintained at the same temperature. 80.0 parts by mass of RHMA, 48.0 parts by mass of BA, and 32.0 parts by mass of 2-[(3,5-dimethylpyrazolyl)carbonylamino]ethyl methacrylate (manufactured by Showa Denko KK, Karenz MOI-BM, hereinafter referred to as "MOI-BM") were added to the dropping funnel A to prepare a mixed monomer composition for dropping in the dropping funnel. 100 parts by mass of hydrogen peroxide solution (concentration 1.07% by mass) was added to the dropping funnel B. 100 parts by mass of an aqueous L-ascorbic acid solution (concentration 1.60% by mass) was added to the dropping funnel C. Into a dropping funnel D, 12.2 parts by mass of SR-20 (active ingredient 25.0% by mass), 0.36 parts by mass of an aqueous ammonia solution (concentration 28% by mass), and 87.4 parts by mass of deionized water were charged to prepare an aqueous emulsifier solution in the dropping funnel.
Next, after replacing the inside of the reaction vessel with nitrogen gas, 40.0 parts by mass of a mixed monomer composition of 20.0 parts by mass of RHMA, 12.0 parts by mass of BA, and 8.0 parts by mass of MOI-BM, 20 parts by mass of hydrogen peroxide (concentration 1.34% by mass), and 20 parts by mass of an aqueous L-ascorbic acid solution (concentration 2.00% by mass) were added to the reaction vessel to carry out an initial polymerization reaction. Subsequently, the mixed monomer for dropping was dropped from the dropping funnel A for 240 minutes, the hydrogen peroxide solution from the dropping funnel B for 240 minutes, the aqueous L-ascorbic acid solution from the dropping funnel C for 240 minutes, and the aqueous emulsifier solution from the dropping funnel D for 240 minutes.
After the dropwise addition was completed, the internal temperature of the reaction vessel was maintained at 75° C. and the reaction solution was aged at the same temperature for 2 hours, and then cooled to obtain a polymer particle dispersion in which the polymer particles were dispersed.
280.0 parts by mass of the polymer particle water dispersion obtained above and 26.2 parts by mass of an aqueous sodium hydroxide solution (concentration 20.0% by mass) as a basic aqueous solution were mixed and stirred overnight at 25°C to obtain an aqueous polymer particle dispersion (3a) in which a mixture (3) of partially hydrolyzed polymer particles and a partially hydrolyzed water-soluble polymer was dispersed. At this time, the ratio of the moles of sodium hydroxide added to the moles of RHMA in the aqueous polymer particle dispersion was 75%. The volume average particle diameter was 665 nm.

<Production Example 4>
In the same manner as in Production Example 3, except that the basic aqueous solution during hydrolysis was changed to 8.9 parts by mass of an aqueous ammonia solution (concentration 25.0% by mass), a mixture (4) of partially hydrolyzed polymer particles and a polymer that was partially hydrolyzed and water-soluble, and a polymer particle water dispersion (4a) in which the mixture (4) was dispersed were obtained. At this time, the ratio of the number of moles of ammonia added to the number of moles of RHMA in the polymer particle water dispersion was 75%. The volume average particle diameter was 130 nm.

<Production Example 5>
Deionized water was added to polyacrylic acid (average molecular weight: about 5,000) manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., and dissolved to a concentration of 5% by mass. A 10% by mass aqueous solution of sodium hydroxide was added to the resulting aqueous solution of polyacrylic acid so that the sodium hydroxide was 25 mol% relative to the carboxyl groups of polyacrylic acid, and the mixture was stirred overnight at 25° C. to obtain an aqueous solution of partially neutralized polyacrylic acid.

<Production Example 6>
A 0.5-liter glass separable flask equipped with a reflux condenser, a stirrer, and a thermometer was charged with 200.3 g of deionized water (initial charge), and the temperature was raised to the boiling point under stirring. Next, 118.9 g (1.32 mol) of 80% acrylic acid (hereinafter referred to as "80% AA") was added dropwise from the tip nozzle through separate supply paths at two supply rates, 180 minutes for 180, 102.1 g (0.88 mol) of 2-hydroxyethyl acrylate (hereinafter referred to as "HEA") for 180, 34.1 g of 5% sodium persulfate (hereinafter referred to as "NaPS") for 195, and 13.0 g of 15% sodium hypophosphite (hereinafter referred to as "SHP") for 18 minutes, followed by 52.0 g for 162 minutes, into the polymerization reaction system in a boiling reflux state under stirring. The dropping of each component was carried out continuously at a constant dropping rate except for 15% SHP. After the dropping of 80% AA was completed, the reaction solution was kept at the boiling point reflux state (aging) for another 30 minutes. The solid content of the obtained polymer aqueous solution was 40.9%, and the weight average molecular weight (Mw) was 4900.
280.0 parts by mass of the acrylic acid-based copolymer aqueous solution obtained above and 47.7 parts by mass of an aqueous sodium hydroxide solution (concentration: 20% by mass) as a basic aqueous solution were mixed and stirred overnight at 25° C. to obtain a partially neutralized polyacrylic acid-based copolymer (X). At this time, the ratio of the number of moles of sodium hydroxide added to the number of moles of acrylic acid in the aqueous acrylic acid-based copolymer solution was 25%.

<Volume average particle size>
The fine particle dispersion was diluted with ion-exchanged water and measured using a light scattering particle size distribution measuring device (Spectris's "Zetasizer Ultra") to determine the volume average particle size (nm) of the fine particles by dynamic light scattering.
<Weight average molecular weight>
The weight average molecular weight (Mw) was measured under the following conditions.
Apparatus: Tosoh HLC-8320GPC
Detector: RI
Column: Tosoh TSK-GEL G3000PWXL
Column temperature: 35°C
Flow rate: 0.5ml/min
Calibration curve: Polysodium acetate standard manufactured by Sowa Science Co., Ltd.
Eluent: A mixture of sodium dihydrogen phosphate dodecahydrate/disodium hydrogen phosphate dihydrate (34.5 g/46.2 g) diluted with pure water to 5,000 g.

<Tensile strength>
A tensile test was performed using a tensile tester ("AUTOGRAPH AG-1kNXPlus" manufactured by Shimadzu Corporation) by clamping the test piece between clamps so that the test length was 180 mm, at a speed of 20 mm/min.

The tensile strength was calculated from the maximum test force at the time when the test piece broke according to the following formula.

The elongation was calculated from the displacement at the time when the test piece broke according to the following formula.

<Reference Example 1>
A piece of calligraphy paper (Yuki no Ko calligraphy paper, manufactured by Maruai Co., Ltd., thickness 50 μm) was cut into a piece having a width of 15 mm and a length of 250 mm to prepare test piece 0. The above-mentioned tensile strength was measured for test piece 0. The measurement results are shown in Table 1.
Example 1
The polymer particle dispersion (1a) obtained in Production Example 1 was diluted with ion-exchanged water so that the concentration of the polymer particles was 1% by mass. Then, the aqueous polyisocyanate crosslinking agent Elastron BN-69 (manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) was added so that the concentration was 20% by mass relative to the polymer particles, and the mixture was thoroughly stirred. The obtained liquid was spread in a tray, and a Japanese writing paper (Yuki no Ko Japanese writing paper, film thickness 50 μm, manufactured by Maruai Co., Ltd.) sandwiched between a stainless steel mesh guide with a mesh size of 500 μm was gently immersed therein. After immersion for 1 minute, the filter paper was pulled up together with the stainless steel mesh guide, and the diluted liquid was drained until it no longer dripped. The stainless steel mesh guide was dried at 150 ° C. for 15 minutes in a constant temperature incubator (manufactured by Yamato Scientific Co., Ltd. "DNF400"). Thereafter, the stainless steel mesh guide was removed, and the filter paper was cut into a width of 15 mm and a length of 250 mm to prepare a test piece 1.
The above-mentioned tensile test was carried out on the test piece 1. The strength improvement effect and the elongation improvement effect due to the application of the binder were calculated based on the following formula. The calculation results are shown in Table 1.

<Examples 2 to 9, Comparative Examples 1 to 9>
The tensile strength and elongation were measured in the same manner as in Example 1, except that the microparticle dispersions of Production Examples 2 to 4, the water-soluble polymer aqueous solutions of Production Examples 5 and 6, the aqueous polyisocyanate crosslinking agent Elastron BN-69 (manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.), and the special epoxy compound Denacol EX-614B (manufactured by Nagase ChemteX Corporation) were used instead of the microparticle dispersion (1a) obtained in Production Example 1. The measurement results are shown in Table 1. The strength improvement effect and elongation improvement effect were also calculated in the same manner as in Example 1, and the calculation results are shown in Table 1.

The results in Table 1 make it clear that the binder disclosed herein exhibits a function that combines high strength and elongation.

Claims (5)

A binder for bonding fibers, processed fiber products, or nonwoven fabrics, comprising a polymer having a structural unit derived from the following general formula (1) and one or more compounds selected from the group consisting of polyfunctional aziridine compounds, polyfunctional oxazoline compounds, polyfunctional epoxy compounds, and polyfunctional isocyanate compounds:

(In general formula (1), R1 represents an alkyl group having 1 to 4 carbon atoms, a hydrogen atom, an alkali metal atom, an alkaline earth metal atom, or ammonium.) A polymer for a binder, comprising a polymer having a structural unit derived from the following general formula (1), and a structural unit derived from one or more compounds selected from the group consisting of a polyfunctional aziridine compound, a polyfunctional oxazoline compound, a polyfunctional epoxy compound, and a polyfunctional isocyanate compound:

(In general formula (1), R1 represents an alkyl group having 1 to 4 carbon atoms, a hydrogen atom, an alkali metal atom, an alkaline earth metal atom, or ammonium.) A binder comprising the binder polymer according to claim 2 and one or more compounds selected from the group consisting of polyfunctional aziridine compounds, polyfunctional oxazoline compounds, polyfunctional epoxy compounds, and polyfunctional isocyanate compounds. 4. The binder according to claim 1, wherein the polyfunctional epoxy compound is a polyfunctional glycidyl ether compound. 4. The binder according to claim 1, wherein the polyfunctional isocyanate compound is a blocked isocyanate compound.