JP2019157000A - Aqueous binder - Google Patents

Abstract

To provide an aqueous binder high in binding force or adhesive force and excellent in production stability, storage stability, and solvent resistance to a highly polar organic solvent.SOLUTION: An aqueous binder (C) contains: an aqueous dispersion of a polymer (A) containing a (meth)acrylate unit and a polyfunctional compound unit; and an aqueous dispersion of a polymer (B) containing a (meth)acrylate unit and an α,β-unsaturated carboxylic acid unit. Preferably, the aqueous dispersion of the polymer (A) and the aqueous dispersion of the polymer (B) have a volume average particle diameter of 50-250 nm, and the aqueous binder (C) has a volume average particle diameter of 60-500 nm. Preferably, the polymer (A) has a content of the α,β-unsaturated carboxylic acid unit of less than 7 mass%, and the polymer (B) has a content of the α,β-unsaturated carboxylic acid unit of 7-30 mass%.SELECTED DRAWING: None

Description

  The present invention relates to an aqueous binder. More specifically, the present invention relates to a water-based (meth) acrylic binder having high binding force or adhesive strength and excellent manufacturing stability and storage stability.

  When processing pigments, ceramics, non-woven fabrics, fibers, leather, paper, inks, metals, toners, etc., styrene-butadiene copolymers, polyvinylidene fluoride, polyolefins, polyesters as excipients, binders or adhesives Resin components such as poly (meth) acrylic acid esters are used as binders. For example, polyesters and polyacrylates are used as binders for inks and pigments in the paint and coating fields, and in the field of power storage devices such as lithium ion secondary batteries, electrode sheet active materials, conductive assistants, and current collectors are mutually connected. Styrene-butadiene copolymers, polyvinylidene fluoride, polyolefins, and polyacrylic esters are used for binders and binders for binding. In addition, ethylene-acrylic acid copolymers and polyacrylic acid esters are used as primers and binders for various substrates such as aluminum foil.

  In recent years, due to increasing demands for environmental problems, work environment improvements, and safety improvements, water-based binders in which resin components are dispersed in water instead of organic solvents are required in these fields.

  As such an aqueous binder, an aqueous binder using a poly (meth) acrylic acid ester has been extensively studied, and many techniques for improving its binding property have been reported. Among them, introduction of an acid group is effective, and a copolymer of a poly (meth) acrylic acid ester and an α, β-unsaturated carboxylic acid has been reported (for example, Patent Documents 1 to 3).

JP 2012-214694 A JP 2009-91508 A JP 2009-79119 A

  However, introduction of an acid group tends to deteriorate the production stability and storage stability of the aqueous binder, which may cause a change in the viscosity of the aqueous binder, and may further generate aggregates. In addition, the solvent resistance to highly polar organic solvents such as dimethyl carbonate also tends to decrease.

  The present invention solves the above-described problems, and is an aqueous binder that has high binding force or adhesive strength, excellent manufacturing stability and storage stability, and excellent solvent resistance against highly polar organic solvents. The purpose is to provide.

  As a result of intensive studies to solve the above problems, the present inventor has obtained an aqueous dispersion of a crosslinkable polymer (A) containing a (meth) acrylic acid ester unit and a polyfunctional compound unit, and (meth) acrylic. An aqueous binder (C) containing an aqueous dispersion of a non-crosslinkable polymer (B) containing an acid ester unit and an α, β-unsaturated carboxylic acid unit exhibits a high binding force or adhesive force and is produced. It was found that the stability, storage stability, and solvent resistance were excellent, and the present invention was completed.

  That is, the gist of the present invention is as follows.

[1] An aqueous dispersion of a polymer (A) containing a (meth) acrylic acid ester unit and a polyfunctional compound unit, and a polymer containing a (meth) acrylic acid ester unit and an α, β-unsaturated carboxylic acid unit ( An aqueous binder (C) comprising an aqueous dispersion of B).

[2] The aqueous binder (C) according to [1], which is a mixture of an aqueous dispersion of the polymer (A) and an aqueous dispersion of the polymer (B).

[3] The volume average particle size of the aqueous dispersion of the polymer (A) is 50 to 250 nm, the volume average particle size of the aqueous dispersion of the polymer (B) is 50 to 250 nm, and the aqueous binder. The aqueous binder (C) according to [1] or [2], wherein the volume average particle diameter of (C) is 60 to 500 nm.

[4] In the polymer (A), the content of α, β-unsaturated carboxylic acid units is 7% by mass with respect to a total of 100% by mass of all monomer units constituting the polymer (A). The content of the α, β-unsaturated carboxylic acid unit in the polymer (B) is 7 with respect to a total of 100% by mass of all the monomer units constituting the polymer (B). The aqueous binder (C) according to any one of [1] to [3], which is ˜30% by mass.

[5] The aqueous binder (C) according to any one of [1] to [4], wherein the α, β-unsaturated carboxylic acid is (meth) acrylic acid.

[6] The content of the polyfunctional compound unit of the polymer (A) is 0.01 to 5% by mass with respect to a total of 100% by mass of all monomer units constituting the polymer (A). The aqueous binder (C) according to any one of [1] to [5], wherein the polymer (B) does not contain a polyfunctional compound unit.

[7] The content of the polymer (A) is 50 to 99 parts by mass with respect to a total of 100 parts by mass of the polymer (A) and the polymer (B), and the content of the polymer (B) is 1. The aqueous binder (C) according to any one of [1] to [6], which is ˜50 parts by mass.

  ADVANTAGE OF THE INVENTION According to this invention, the water-based binder which has high binding force or adhesive force, and is excellent also in manufacturing stability, storage stability, and solvent resistance with respect to a highly polar organic solvent can be provided.

  In the aqueous binder (C) of the present invention containing the polymer (A) and the polymer (B), the polymer (A) contains a polyfunctional compound unit, so that it is appropriately crosslinked to maintain the particle shape. Since the compound (B) does not contain a polyfunctional compound unit, it is combined with the particle surface of the polymer (A) at the time of mixing or coating. For this reason, the improvement effect of the binding property or the adhesive force by the acid group of the α, β-unsaturated carboxylic acid unit of the polymer (B) is easily exhibited. Furthermore, since both of the polymer (A) and the polymer (B) contain a (meth) acrylic acid ester unit and are easily compatible with each other and easily combined, the aqueous binder (C) and the base material It has excellent binding power or adhesive strength and excellent solvent resistance. Further, since the total amount of α, β-unsaturated carboxylic acid units in the aqueous binder (C) is small, the production stability, storage stability, and solvent resistance are excellent.

  The aqueous binder of the present invention can be used as an excipient, binder, or adhesive for pigments, ceramics, non-woven fabrics, fibers, leather, paper, ink, metal, toner, and the like.

  Hereinafter, embodiments of the present invention will be described in detail.

In the present specification, “unit” means a structural portion derived from a compound (monomer) before polymerization contained in a polymer. For example, “(meth) acrylic acid ester unit” means “( It means “a structural portion derived from a (meth) acrylic acid ester and contained in a polymer”.
Further, the content of the monomer unit of each polymer corresponds to the amount of the monomer used in the production of the polymer.
In the present specification, “(meth) acryl” means one or both of “acryl” and “methacryl”.

  The aqueous binder (C) of the present invention comprises an aqueous dispersion of a polymer (A) containing a (meth) acrylate unit and a polyfunctional compound unit, a (meth) acrylate unit and an α, β-unsaturated carboxylic acid. A water dispersion of a polymer (B) containing an acid unit, for example, mixing a water dispersion of a polymer (A) and a water dispersion of a polymer (B), respectively, produced. Preferably, it is manufactured by adding the aqueous dispersion of the polymer (B) while stirring the aqueous dispersion of the polymer (A).

[Polymer (A)]
The polymer (A) in the present invention (hereinafter sometimes referred to as “the polymer (A) of the present invention”) is usually a (meth) acrylic acid ester and a polyfunctional compound and others used as necessary. Can be obtained by radical polymerization of a copolymerizable monomer (hereinafter sometimes referred to as “other monomer”).

  The (meth) acrylic acid ester used for the production of the polymer (A) of the present invention has a (meth) acrylic acid alkyl ester having an alkyl group, a phenyl group, an aromatic hydrocarbon group such as a benzyl group (meth). Preferable examples include acrylic acid aryl esters. In addition, the alkyl group and aryl group of (meth) acrylic acid alkyl ester and (meth) acrylic acid aryl ester are hydroxyl groups, epoxy groups, isocyanate groups, halogen atoms, as long as they are other than acid groups such as carboxyl groups and sulfoxyl groups. It may be substituted with a substituent such as

  Examples of (meth) acrylic acid esters include methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, i-propyl (meth) acrylate, and (meth) acrylic acid n-. Butyl, i-butyl (meth) acrylate, t-butyl (meth) acrylate, amyl (meth) acrylate, isoamyl (meth) acrylate, octyl (meth) acrylate, 2-ethylhexyl (meth) acrylate , Decyl (meth) acrylate, lauryl (meth) acrylate, stearyl (meth) acrylate, lauryl (meth) acrylate, cyclohexyl (meth) acrylate, pentyl (meth) acrylate, phenyl (meth) acrylate, Benzyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, 2- (meth) acrylic acid 2- Preferred examples include droxypropyl, glycidyl (meth) acrylate, 2-acryloyloxyethyl isocyanate, 2-methacryloyloxyethyl isocyanate, and among these, ethyl acrylate, n-butyl acrylate, acrylic acid A (meth) acrylic acid alkyl ester having 1 to 10 carbon atoms of an alkyl group such as -2-ethylhexyl is preferred.

  These (meth) acrylic acid esters may be used alone or in combination of two or more.

  The content of the (meth) acrylic acid ester unit contained in the polymer (A) is the (meth) acrylic acid ester unit, the polyfunctional compound unit which is the total monomer unit in the polymer (A), and as necessary. It is preferably 50 to 99.99% by mass and more preferably 70 to 99.99% by mass with respect to a total of 100% by mass of other monomer units contained. When the content of the (meth) acrylic acid ester unit in the polymer (A) is within the above range, the binding property or adhesive strength of the obtained aqueous binder (C) is excellent.

  The polyfunctional compound used for the production of the polymer (A) of the present invention has two or more carbon atom-carbon atom double bonds in the molecule, and is not limited thereto. Benzene, allyl (meth) acrylate, ethylene glycol di (meth) acrylate, propylene glycol di (meth) acrylate, 1,3-butylene di (meth) acrylate, 1,4-butylene glycol di (meth) acrylate, tetraethylene glycol di Preferable examples include (meth) acrylate, tetradecaethylene glycol di (meth) acrylate, triallyl cyanurate, triallyl isocyanurate, pentaerythritol triallyl ether, pentaerythritol tetra (meth) acrylate and the like. Of these, (meth) acrylate polyfunctional compounds such as allyl (meth) acrylate and 1,3-butylene (meth) acrylate are particularly preferable.

  These polyfunctional compounds may be used individually by 1 type, and may be used in combination of 2 or more type.

  The content of the polyfunctional compound unit contained in the polymer (A) includes (meth) acrylic acid ester units, polyfunctional compound units, which are all monomer units in the polymer (A), and if necessary. Preferably it is 0.01-5 mass% with respect to a total of 100 mass% of another monomer unit, More preferably, it is 0.03-3 mass%. When the content of the polyfunctional compound unit in the polymer (A) is within the above range, it is possible to maintain the particle shape while having an appropriate degree of crosslinking and being flexible. ) Is improved in binding property or adhesive strength and solvent resistance.

  The polymer (A) of the present invention may further contain other copolymerizable monomer units capable of radical polymerization in addition to the (meth) acrylic acid ester unit and the polyfunctional compound unit. Examples of other monomers include, but are not limited to, aromatic vinyl, vinyl cyanide, conjugated diene, maleimide, glycidyl methacrylate, and the like, which are required for the aqueous binder (C). Can be selected according to the performance to be used.

  Examples of the aromatic vinyl include styrene, α-methylstyrene, o-, m-, p-methylstyrene, ethylstyrene, 1,1-diphenylstyrene, N, N-diethyl-p-aminostyrene, N, N. -Diethyl-p-aminomethylstyrene, vinylpyridine, vinylxylene, monochlorostyrene, dichlorostyrene, monobromostyrene, dibromostyrene, tribromostyrene, fluorostyrene, pt-butylstyrene, vinylnaphthalene and the like are preferable. In particular, styrene is preferred. Aromatic vinyl may be used individually by 1 type, and may be used in combination of 2 or more type.

  Preferable examples of vinyl cyanide include acrylonitrile and methacrylonitrile. A vinyl cyanide may be used individually by 1 type, and may be used in combination of 2 or more type. By including a vinyl cyanide unit in the polymer (A), the solvent resistance is improved.

  Examples of the conjugated diene include 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, 2-methyl-1,3-pentadiene, 1,3-pentadiene, 1,3-hexadiene, 4,5-diethyl-1,3-octadiene, chloroprene and the like are preferable, and 1,3-butadiene and isoprene are particularly preferable. A conjugated diene may be used individually by 1 type, and may be used in combination of 2 or more type.

  Preferred examples of maleimide include N-phenylmaleimide, N-cyclohexylmaleimide, Nn-butylmaleimide, Nt-butylmaleimide, and the like. A maleimide may be used individually by 1 type and may be used in combination of 2 or more type.

  The content of other monomer units contained in the polymer (A) is the (meth) acrylic acid ester unit, polyfunctional compound unit, and as required, all monomer units in the polymer (A). Preferably it is 0-49.99 mass% with respect to a total of 100 mass% of the other monomer unit contained, More preferably, it is 0-30 mass%. When the content of the other monomer units in the polymer (A) is not more than the above upper limit, the binding property or adhesive strength of the resulting aqueous binder (C) is excellent.

In addition, you may contain the (alpha), (beta)-unsaturated carboxylic acid unit which comprises the below-mentioned polymer (B) as another monomer unit contained in the polymer (A) of this invention. However, in this case, the content of the α, β-unsaturated carboxylic acid unit in the polymer (A) is the (meth) acrylic acid ester unit, polyfunctional, which is the total monomer unit in the polymer (A). Preferably it is less than 7 mass%, More preferably, it is less than 5 mass% with respect to a total of 100 mass% of a compound unit and the other monomer unit contained as needed. When the content of the α, β-unsaturated carboxylic acid unit in the polymer (A) exceeds the above upper limit, the resulting aqueous binder (C) is inferior in production stability, storage stability, and solvent resistance. .
The polymer (A) of the present invention preferably does not contain an α, β-unsaturated carboxylic acid unit.

  Preferred examples of the method for producing the polymer (A) include emulsion polymerization, miniemulsion polymerization, suspension polymerization, bulk polymerization and the like, and an aqueous dispersion of the polymer (A) is obtained at the time of production. From the viewpoint of easy control, emulsion polymerization and miniemulsion polymerization are preferred.

  For example, a method for obtaining an aqueous dispersion of the polymer (A) by emulsion polymerization is not particularly limited, but a (meth) acrylic acid ester, a polyfunctional compound, and a compound as necessary are used in an aqueous solvent in which an emulsifier is dispersed. A method of performing polymerization by adding another monomer and a radical initiator and heating is preferable. The addition method of an emulsifier, a radical initiator, a (meth) acrylic acid ester, a polyfunctional compound, and other monomers is not particularly limited, and may be any one of batch, divided, and continuous.

  Examples of the emulsifier used in the emulsion polymerization include anionic surfactants, nonionic surfactants, amphoteric surfactants, and the like. For example, higher alcohol sulfates, alkylbenzene sulfonates, fatty acid sulfonates, phosphates. Anionic surfactants such as systems (for example, monoglyceride ammonium phosphate), fatty acid salts (for example, dipotassium alkenyl succinate), amino acid derivative salts, ordinary polyethylene glycol alkyl ester type, alkyl ether type, alkyl phenyl ether type, etc. A nonionic surfactant having a carboxylate, sulfate ester salt, sulfonate salt, phosphate ester salt and the like in the anion portion and an amphoteric surfactant having an amine salt, a quaternary ammonium salt and the like in the cation portion Preferably mentioned. These may be used alone or in combination of two or more.

  The addition amount of the emulsifier used in the emulsion polymerization is usually 0.001 to 5 parts by mass with respect to a total of 100 parts by mass of the (meth) acrylic acid ester, the polyfunctional compound, and other monomers used as necessary. Preferably it is 0.005-3 mass parts. It is easy to control the volume average particle diameter of a polymer (A) to 50-250 nm as the addition amount of an emulsifier is the said range.

  Known radical initiators used for emulsion polymerization can be used, for example, azo polymerization initiators, photopolymerization initiators, inorganic peroxides, organic peroxides, organic peroxides, transition metals, and reducing agents. Preferred examples include a combined redox initiator. Of these, azo polymerization initiators, inorganic peroxides, organic peroxides, and redox initiators that can initiate polymerization by heating are preferred. These may be used alone or in combination of two or more.

  Examples of the azo polymerization initiator include 2,2′-azobis (4-methoxy-2,4-dimethylvaleronitrile), 2,2′-azobis (2,4-dimethylvaleronitrile), and 2,2′-. Azobisisobutyronitrile, 2,2′-azobis (2-methylbutyronitrile), 1,1′-azobis (cyclohexane-1-carbonitrile), 1-[(1-cyano-1-methylethyl) Azo] formamide, 4,4′-azobis (4-cyanovaleric acid), dimethyl 2,2′-azobis (2-methylpropionate), dimethyl 1,1′-azobis (1-cyclohexanecarboxylate) 2,2′-azobis [2-methyl-N- (2-hydroxyethyl) propionamide], 2,2′-azobis (N-butyl-2-methylpropionamide) 2,2′-azobis (N-cyclohexyl-2-methylpropionamide), 2,2′-azobis [2- (2-imidazolin-2-yl) propane], 2,2′-azobis (2,4 , 4-trimethylpentane) and the like.

  Examples of inorganic peroxides include potassium persulfate, sodium persulfate, ammonium persulfate, and hydrogen peroxide.

  Examples of the organic peroxide include peroxyester compounds, and specific examples thereof include α, α′-bis (neodecanoylperoxy) diisopropylbenzene, cumylperoxyneodecanoate, 1,1,3, 3-tetramethylbutylperoxyneodecanoate, 1-cyclohexyl-1-methylethylperoxyneodecanoate, t-hexylperoxyneodecanoate, t-butylperoxyneodecanoate, t-hexylperoxypivalate, t-butylperoxypivalate, 1,1,3,3-tetramethylbutylperoxy-2-ethylhexanoate, 2,5-dimethyl-2,5-bis (2-ethylhexanoylperoxy) hexane, 1- Cyclohexyl-1-methylethylperoxy-2-ethylhexano , T-hexylperoxy 2-hexylhexanoate, t-butylperoxy 2-hexylhexanoate, t-butylperoxyisobutyrate, t-hexylperoxyisopropylmonocarbonate, t-butylperoxymaleic acid, t- Butyl peroxy 3,5,5-trimethylhexanoate, t-butyl peroxylaurate, 2,5-dimethyl-2,5-bis (m-toluoyl peroxy) hexane, t-butyl peroxyisopropyl monocarbonate, t- Butylperoxy 2-ethylhexyl monocarbonate, t-hexylperoxybenzoate, 2,5-dimethyl-2,5-bis (benzoylperoxy) hexane, t-butylperoxyacetate, t-butylperoxy-m-toluoyl Nzoate, t-butylperoxybenzoate, bis (t-butylperoxy) isophthalate, 1,1-bis (t-hexylperoxy) 3,3,5-trimethylcyclohexane, 1,1-bis (t-hexylperoxy) cyclohexane 1,1-bis (t-butylperoxy) 3,3,5-trimethylcyclohexane, 1,1-bis (t-butylperoxy) cyclohexane, 1,1-bis (t-butylperoxy) cyclododecane, 2, 2-bis (t-butylperoxy) butane, n-butyl 4,4-bis (t-butylperoxy) valerate, 2,2-bis (4,4-di-t-butylperoxycyclohexyl) propane, α, α '-Bis (t-butyl peroxide) diisopropylbenzene, dicumyl peroxide, 2,5- Methyl-2,5-bis (t-butylperoxy) hexane, t-butylcumyl peroxide, di-t-butyl peroxide, cumene hydroperoxide, diisopropylbenzene hydroperoxide, t-butyl hydroperoxide, benzoyl peroxide, lauroylper Oxide, dimethylbis (t-butylperoxy) hexyne-3, bis (t-butylperoxyisopropyl) benzene, bis (t-butylperoxy) trimethylcyclohexane, butyl-bis (t-butylperoxy) valerate, 2 Preferred examples include t-butyl ethylhexaneperoxy acid, dibenzoyl peroxide, paramentane hydroperoxide, and t-butyl peroxybenzoate.

  As the redox initiator, a combination of an organic peroxide, ferrous sulfate, a chelating agent and a reducing agent is preferable. For example, cumene hydroperoxide, ferrous sulfate, sodium pyrophosphate and dextrose, t-butyl hydroperoxide, sodium formaldehyde human sulfoxylate, ferrous sulfate heptahydrate, ethylenediaminetetraacetic acid diacetate Suitable examples include those composed of sodium.

  The addition amount of the radical initiator is usually 5 parts by mass or less, preferably 3 parts by mass with respect to a total of 100 parts by mass of (meth) acrylic acid ester, polyfunctional compound, and other monomers used as necessary. Hereinafter, it is 0.001-3 mass parts, for example.

You may add a chain transfer agent as needed at the time of manufacture of a polymer (A). As chain transfer agents, mercaptans (octyl mercaptan, n- or t-dodecyl mercaptan, n-hexadecyl mercaptan, n- or t-tetradecyl mercaptan, etc.), allyl compounds (allylsulfonic acid, methallylsulfonic acid, these) Sodium salts, etc.), α-methylstyrene dimers, and the like, and mercaptans are preferred from the viewpoint of easy adjustment of the molecular weight. A chain transfer agent may be used individually by 1 type, and may be used in combination of 2 or more type.
The method for adding the chain transfer agent may be any of batch, split, and continuous.

  The addition amount of the chain transfer agent is usually 2.0 parts by mass or less, for example, about 0.1 parts by mass with respect to 100 parts by mass in total of the (meth) acrylic acid ester, the polyfunctional compound, and other monomers used as necessary. 01-2.0 mass parts is preferable.

  The emulsion polymerization is preferably performed in an aqueous reaction solvent having a solid content concentration of about 5 to 50% by mass. According to such a reaction, the polymer (A) containing about 5 to 49% by mass of the polymer (A). An aqueous dispersion can be obtained.

  The volume average particle size of the aqueous dispersion of the polymer (A) (volume average particle size of the dispersed particles of the polymer (A) in the aqueous dispersion of the polymer (A)) is preferably 50 to 250 nm, more preferably. Is 70-200 nm. When the volume average particle diameter of the aqueous dispersion of the polymer (A) is within the above range, the volume average particle diameter of the obtained aqueous binder (C) is preferably controlled to 60 to 500 nm.

  The method for setting the volume average particle diameter of the aqueous dispersion of the polymer (A) in the above range is not particularly limited, and a known method can be used. For example, if the amount of the emulsifier is decreased, the volume average particle is reduced. The diameter increases, and the volume average particle diameter tends to decrease if the amount of the emulsifier added is increased. In addition, there are a method of seed polymerization, a method of adding seed particles to emulsion polymerization, and the like.

  The volume average particle size of the aqueous dispersion of the polymer (A), the volume average particle size of the aqueous dispersion of the polymer (B) described later, and the volume average particle size of the aqueous binder (C) of the present invention are described later. It is measured by the method described in the example section.

  The degree of crosslinking of the polymer (A) can be indicated by the gel content (insoluble content) when dissolved in acetone. The gel content of the polymer (A) is preferably 40 to 100% by mass, more preferably 70 to 99% by mass. When the gel content of the polymer (A) is within the above range, the resulting water-based binder (C) has good solvent resistance, binding power and adhesive strength.

The gel content rate of a polymer (A) is calculated | required with the following method.
The aqueous dispersion of the polymer (A) is dropped into a methanol / sulfuric acid solution to solidify, washed with methanol, and dried to obtain the polymer (A). The obtained polymer (A) is weighed, and 40 times the amount of acetone is added to swell for 24 hours. Then, after separating into an acetone soluble part and an insoluble part with a centrifuge, an insoluble part is dried. The gel content is calculated by the following formula 1 from the weight of the weighed polymer (A) and the dried insoluble matter.
Gel content rate = W / P × 100 (Formula 1)
P: Mass of the weighed polymer (A) W: Mass after drying of insoluble acetone

[Polymer (B)]
The polymer (B) in the present invention (hereinafter sometimes referred to as “the polymer (B) of the present invention”) is a (meth) acrylic acid ester and an α, β-unsaturated carboxylic acid, and if necessary. It can be obtained by radical polymerization of other copolymerizable monomers (other monomers) used.

  The (meth) acrylic acid ester used for the production of the polymer (B) of the present invention can be the same as that described above as the one used for the production of the polymer (A). It is the same. (Meth) acrylic acid esters may be used alone or in combination of two or more.

  The content of the (meth) acrylic acid ester unit contained in the polymer (B) is the (meth) acrylic acid ester unit, α, β-unsaturated carboxylic acid which is the total monomer unit in the polymer (B). Preferably it is 50-93 mass%, More preferably, it is 50-90 mass%, More preferably, it is 80-90 mass% with respect to a total of 100 mass% of a unit and the other monomer unit contained as needed. When the content of the (meth) acrylic acid ester unit in the polymer (B) is within the above range, the compatibility of the polymer (A) and the polymer (B) is improved, and the resulting aqueous binder (C) It has excellent binding properties and adhesive strength.

  The α, β-unsaturated carboxylic acid used in the production of the polymer (B) of the present invention has one or more carboxyl groups in the molecule. For example, (meth) acrylic acid, crotonic acid, maleic acid , Fumaric acid, itaconic acid and the like. Of these, α, β-unsaturated carboxylic acid is (from the viewpoint of ease of complexation of a part or all of the polymer (A) and the polymer (B) in the aqueous binder (C) ( (Meth) acrylic acid is preferred. These α, β-unsaturated carboxylic acids may be used alone or in combination of two or more.

  The content of the α, β-unsaturated carboxylic acid unit contained in the polymer (B) is (meth) acrylic acid ester unit, α, β-unsaturated which is the total monomer unit in the polymer (B). It is preferably 7 to 30% by mass, more preferably 10 to 30% by mass, and further preferably 10 to 20% by mass with respect to the total of 100% by mass of the carboxylic acid unit and other monomer units included as necessary. is there. When the content of the α, β-unsaturated carboxylic acid unit in the polymer (B) is 7% by mass or more, the resulting aqueous binder (C) has excellent binding properties and adhesive strength, and is 30% by mass. When it is below, aggregates and the like are less likely to be produced during the production of the polymer (B) and the aqueous binder (C), the production stability is excellent, and the viscosity change and aggregates are preserved even if the aqueous binder (C) is stored for a long time. Since generation | occurrence | production of is suppressed, it becomes the thing excellent also in the storage stability.

  The polymer (B) of the present invention may further contain other copolymerizable monomers capable of radical polymerization in addition to the (meth) acrylic acid ester unit and the α, β-unsaturated carboxylic acid unit. it can. As another monomer, the thing similar to what was used for manufacture of a polymer (A) can be used, It can select and use according to the performance calculated | required by an aqueous | water-based binder (C).

  The content of the other monomer units contained in the polymer (B) is (meth) acrylic acid ester units, α, β-unsaturated carboxylic acid units which are all monomer units in the polymer (B). And it is 0-45 mass% preferably with respect to the total of 100 mass% of the other monomer unit contained as needed. When the content of other monomer units in the polymer (B) is not more than the above upper limit, the binding property or adhesive strength of the resulting aqueous binder (C) is excellent.

  When the polymer (B) contains a polyfunctional compound unit, the binding force or adhesive strength of the resulting aqueous binder (C) is lowered, so the polymer (B) may not contain a polyfunctional compound unit. preferable.

  Examples of the method for producing the polymer (B) include emulsion polymerization, miniemulsion polymerization, suspension polymerization, bulk polymerization, and the like. An aqueous dispersion of the polymer (B) is obtained at the time of production, and the particle diameter is also controlled. Since it is easy, emulsion polymerization and miniemulsion polymerization are preferable.

  For example, a method for obtaining an aqueous dispersion of the polymer (B) by emulsion polymerization is not particularly limited, but an acrylate ester is dispersed in an aqueous solvent in which an emulsifier is dispersed, as in the above-described method for producing the polymer (A). , [Alpha], [beta] -unsaturated carboxylic acid, other monomers used as necessary and a radical initiator, and a method of performing polymerization by heating. The method for adding the emulsifier, radical initiator, (meth) acrylic acid ester, α, β-unsaturated carboxylic acid, and other monomers is not particularly limited, and may be any of batch, split, and continuous.

  The emulsifier, radical initiator and chain transfer agent used as necessary when the polymer (B) is produced by emulsion polymerization are the same as those described above for use in the production of the polymer (A). Can be used, and the amount of addition can also be used in the same range.

  In addition, the emulsion polymerization of the polymer (B) is preferably performed in an aqueous reaction solvent having a solid content concentration of about 5 to 50% by mass. According to such a reaction, the polymer (B) is converted to 5 to 49%. An aqueous dispersion of the polymer (B) containing about mass% can be obtained.

  The volume average particle diameter of the aqueous dispersion of the polymer (B) (volume average particle diameter of the dispersed particles of the polymer (B) in the aqueous dispersion of the polymer (B)) is preferably 50 to 250 nm, more preferably. Is 70-200 nm. When the volume average particle diameter of the polymer (B) is within the above range, the volume average particle diameter of the obtained aqueous binder (C) is preferably easily controlled to 60 to 500 nm.

  The method for setting the volume average particle diameter of the aqueous dispersion of the polymer (B) in the above range is not particularly limited, and a known method can be used. For example, if the amount of the emulsifier is decreased, the volume average particle is reduced. The diameter increases, and the volume average particle diameter tends to decrease if the amount of the emulsifier added is increased. In addition, there are a method of seed polymerization, a method of adding seed particles to emulsion polymerization, and the like.

[Water-based binder (C)]
The aqueous binder (C) of the present invention includes an aqueous dispersion of the polymer (A) and an aqueous dispersion of the polymer (B). The polymer (A) and the polymer (A) in the aqueous binder (C) Part or all of B) may be combined.

  The content of the polymer (A) in the aqueous binder (C) of the present invention is preferably 50 to 99 parts by mass, more preferably 70 to 100 parts by mass in total of the polymer (A) and the polymer (B). -99 mass parts, More preferably, it is 85-97 mass parts. When the content of the polymer (A) is not less than the lower limit of the above range, the acid groups in the aqueous binder (C) are reduced, so that the production stability and storage stability are improved and are not more than the upper limit of the above range. And the polymer (B) can be combined on the surface of the polymer (A), and the binding property or the adhesive force is improved. Moreover, solvent resistance will also become it favorable that content of a polymer (A) is below the upper limit of the said range.

  The content of the polymer (B) in the aqueous binder (C) of the present invention is preferably 1 to 50 parts by mass, more preferably 1 with respect to 100 parts by mass in total of the polymer (A) and the polymer (B). -30 mass parts, More preferably, it is 3-15 mass parts. When the content of the polymer (B) is not less than the lower limit of the above range, the polymer (B) can be composited on the surface of the polymer (A), and the binding property or adhesive force becomes good, and is not more than the upper limit of the above range. And since the acid group in an aqueous binder (C) decreases, manufacturing stability and storage stability become favorable. Moreover, solvent resistance will also become favorable that content of a polymer (B) is more than the minimum of the said range.

  The aqueous binder (C) of the present invention is produced by mixing an aqueous dispersion of the polymer (A) and an aqueous dispersion of the polymer (B), and the mixing method is not particularly limited. A method of adding the aqueous dispersion of the polymer (B) while stirring the aqueous dispersion of (A) is preferred. Moreover, you may add the aqueous solution of a condensed acid salt to this mixed system as needed.

  The condensed acid salt used here is a salt of a condensed acid and an alkali metal or alkaline earth metal. The condensed acid is an acid having a polynuclear structure in which an oxo acid is condensed, and examples thereof include polyphosphoric acid (such as pyrophosphoric acid) and polysilicic acid. Although not limited thereto, sodium pyrophosphate or potassium pyrophosphate is preferred as the condensed acid salt.

  The addition amount of the condensed acid salt is usually 0 to 10% by mass, preferably 0.01 to 2 parts by mass with respect to 100 parts by mass in total of the polymer (A) and the polymer (B). When the addition amount of the condensed acid salt is in the above range, the volume average particle diameter of the obtained aqueous binder (C) can be easily controlled to 60 to 500 nm, which is preferable.

  The volume average particle diameter of the aqueous binder (C) of the present invention (the volume average particle diameter of the dispersed particles of the polymer (A), the polymer (B) and these composites in the aqueous binder (C)) is preferably It is 60-500 nm, More preferably, it is 80-300 nm, More preferably, it is 100-250 nm. When the volume average particle diameter of the aqueous binder (C) is not less than the lower limit of the above range, the viscosity of the aqueous binder (C) is preferably not easily increased, and it is easy to apply. Adhesive force is good and preferable.

  The volume average particle diameter of the water-based binder (C) is the volume average particle diameter of the aqueous dispersion of the polymer (A), the volume average particle diameter of the aqueous dispersion of the polymer (B), α of the polymer (B), The volume average particle of the aqueous dispersion of the polymer (A) can be controlled by the content of the β-unsaturated carboxylic acid unit, the added amount of the aqueous dispersion of the polymer (B), and the added amount of the condensed acid salt. As the diameter and / or the volume average particle size of the aqueous dispersion of the polymer (B) increases, the content of the α, β-unsaturated carboxylic acid unit in the polymer (B), the aqueous dispersion of the polymer (B) The volume average particle diameter of the water-based binder (C) tends to increase as the amount of the additive and the amount of the condensed acid salt increase.

  The aqueous binder (C) of the present invention may contain additives known in the art as necessary, such as viscosity modifiers, dispersants, stabilizers, storage stabilizers, and antifoaming agents. .

  The aqueous binder (C) of the present invention preferably contains the polymer (A) and the polymer (B) at a total concentration of 5 to 50% by mass from the viewpoint of adhesive strength and storage stability. It is preferable that the whole solid density | concentration which added the additive of 5 to 5 mass%.

  The aqueous binder of the present invention can be suitably used as an excipient, binder, or adhesive for pigments, ceramics, non-woven fabrics, fibers, leather, paper, ink, metal, toner, and the like.

  Hereinafter, the present invention will be described more specifically with reference to production examples, examples, and comparative examples. However, the present invention is not limited to the following examples unless it exceeds the gist.

[Evaluation of physical properties and characteristics]
Evaluation methods of physical properties and characteristics in the following examples and comparative examples are as follows.

<Volume average particle diameter>
The volume average particle diameter of the aqueous dispersion of the polymer (A), the aqueous dispersion of the polymer (B), and the aqueous binder (C) was measured using pure water as a measurement solvent, and Microtrac (“Nanotrack 150 manufactured by Nikkiso Co., Ltd.) was used. )).

<Gel content>
The gel content of the polymer (A) was determined by the above-described formula 1.

<Production stability of aqueous binder (C)>
After producing the aqueous binder (C), it is filtered through a 200-mesh wire mesh, the agglomerates remaining on the 200-mesh wire mesh are dried and weighed, and evaluated as the rate of occurrence of the agglomerates relative to the solid content of the aqueous binder (C). did. The smaller the incidence, the better the production stability.

<Storage stability of aqueous binder (C)>
A water-based binder (C) 100 g (as a solid content) was put in a plastic container and stored in a refrigerator set at 5 ° C. for 1 month. After storage, the condition was visually confirmed and evaluated according to the following criteria.
(Double-circle): There is no agglomerate and sediment and there is no change in the storage period.
○: Slight aggregates are observed, but there is no sediment.
Δ: Sediment is slightly seen.
X: A sediment is seen.

<Binding power of water-based binder (C)>
The aqueous binder (C) was applied to an aluminum foil using an applicator (film thickness: 25 μm) and dried at 70 ° C. for 30 minutes. After drying, a cellophane tape is applied to the surface, and a 90 ° peel test is performed by pulling the cellophane tape using a tensile tester to determine the adhesion peel strength (metal adhesion) between the dried aqueous binder (C) and the aluminum foil. The binding force was evaluated by measuring. The greater the metal adhesion, the better the binding force.

<Solvent resistance of aqueous binder (C)>
The water-based binder (C) was dried at 70 ° C. for 24 hours, and then vacuum-dried at room temperature for 24 hours to prepare a dried film-like water-based binder (C). The weight of the obtained dried product is defined as W1. This dried product was immersed in dimethyl carbonate (DMC) at 60 ° C. for 6 hours, then filtered through a 200 mesh wire net, and the residue was vacuum dried at room temperature for 24 hours. Let the weight of the residue after vacuum drying be W2.
DMC insoluble matter (%) was calculated by the formula (W2 / W1 × 100). The more insoluble in DMC, the better the solvent resistance.

[Production Example 1: Production of polymer (A-1)]
In a reaction vessel equipped with a reagent injection vessel, a condenser, a jacket heater and a stirring device, 130 parts by mass of deionized water, 0.4 parts by mass of dipotassium alkenyl succinate (Latemul ASK manufactured by Kao Corporation), n-acrylic acid Charge 52.5 parts by weight of butyl, 17.5 parts by weight of 2-ethylhexyl acrylate, 0.07 part by weight of 1,3-butylene glycol dimethacrylate, 0.05 part by weight of t-butyl hydroperoxide, and replace with nitrogen while stirring. Went. After raising the internal temperature to 55 ° C, 0.09 parts by mass of sodium formaldehyde sulfoxylate, 0.00015 parts by mass of ferrous sulfate heptahydrate, 0.00045 parts by mass of disodium ethylenediaminetetraacetate, 10 parts by mass of deionized water An aqueous solution consisting of was added to initiate the polymerization. After the polymerization exotherm was confirmed, the internal temperature was set to 70 ° C., and the reaction was carried out for 1 hour.

  Next, 0.1 parts by mass of dipotassium alkenyl succinate, 0.04 parts by mass of sodium formaldehyde sulfoxylate, 0.002 parts by mass of ferrous sulfate heptahydrate, 0.006 parts by mass of disodium ethylenediaminetetraacetate and deionized water After adding an aqueous solution consisting of 10 parts by mass, at 70 ° C., 22.5 parts by mass of n-butyl acrylate, 7.5 parts by mass of 2-ethylhexyl acrylate, 0.03 parts by mass of 1,3-butylene glycol dimethacrylate, A mixture of 0.03 parts by mass of t-butyl hydroperoxide was added dropwise over 2 hours. After completion of dropping, the mixture was further reacted at 70 ° C. for 1 hour to obtain an aqueous dispersion of the polymer (A-1).

  The aqueous dispersion of the polymer (A-1) had a volume average particle size of 131 nm, a gel content of 89% by mass, and a solid content of 39% by mass.

[Production Example 2: Production of polymer (A-2)]
The reaction vessel was charged with 52.5 parts by mass of n-butyl acrylate and 17.5 parts by mass of 2-ethylhexyl acrylate, and 70 parts by mass of n-butyl acrylate. The polymerization was carried out under the same reaction conditions as in Production Example 1 except that 7.5 parts by mass of 2-ethylhexyl acrylate was changed to 30 parts by mass of n-butyl acrylate, and an aqueous dispersion of the polymer (A-2) was obtained. Obtained.
The aqueous dispersion of the polymer (A-2) had a volume average particle size of 122 nm, a gel content of 87% by mass, and a solid content of 39% by mass.

[Production Example 3: Production of polymer (A-3)]
0.07 parts by mass of 1,3-butylene glycol dimethacrylate charged in the reaction vessel was 0.5 parts by mass of allyl methacrylate, and 0.03 parts by mass of 1,3-butylene glycol dimethacrylate was added dropwise. Polymerization was performed under the same reaction conditions as in Production Example 1 except that the amount was 3 parts by mass to obtain an aqueous dispersion of the polymer (A-3).
The aqueous dispersion of the polymer (A-3) had a volume average particle size of 132 nm, a gel content of 97% by mass, and a solid content of 39% by mass.

[Production Example 4: Production of polymer (A-4)]
52.5 parts by mass of n-butyl acrylate and 17.5 parts by mass of 2-ethylhexyl acrylate prepared in the reaction vessel were 47.25 parts by mass of n-butyl acrylate, 15.75 parts by mass of 2-ethylhexyl acrylate, acrylonitrile. 7 parts by mass, and dropped 22.5 parts by mass of n-butyl acrylate, 7.5 parts by mass of 2-ethylhexyl acrylate, 20.25 parts by mass of n-butyl acrylate, and 6.75 hexyl acrylate. Polymerization was carried out under the same reaction conditions as in Production Example 1, except that the content was 3 parts by mass and 3 parts by mass of acrylonitrile, to obtain an aqueous dispersion of polymer (A-4).
The aqueous dispersion of the polymer (A-4) had a volume average particle size of 130 nm, a gel content of 92% by mass, and a solid content of 39% by mass.

[Production Example 5: Production of polymer (A′-1)]
The reaction conditions were the same as in Production Example 2 except that 0.07 parts by mass of 1,3-butylene glycol dimethacrylate charged in the reaction vessel and 0.03 parts by mass of 1,3-butylene glycol dimethacrylate that had been added dropwise were not used. Polymerization was performed to obtain an aqueous dispersion of the polymer (A′-1).
The aqueous dispersion of the polymer (A′-1) had a volume average particle size of 119 nm, a gel content of 8% by mass, and a solid content of 39% by mass.

  The raw materials used and physical properties of the polymers (A-1) to (A-4) and (A′-1) are summarized in Table 1 below.

[Production Example 6: Production of polymer (B-1)]
In a reaction vessel equipped with a reagent injection vessel, a condenser tube, a jacket heater and a stirrer, 200 parts by mass of deionized water, 2 parts by mass of potassium oleate, 4 parts by mass of sodium dioctylsulfosuccinate, sodium formaldehyde sulfoxylate 0. 3 parts by mass, 0.003 parts by mass of ferrous sulfate heptahydrate and 0.009 parts by mass of disodium ethylenediaminetetraacetate were charged, and nitrogen substitution was performed while stirring. After raising the temperature to 60 ° C., a mixture of 82 parts by mass of n-butyl acrylate, 18 parts by mass of methacrylic acid, and 0.5 parts by mass of cumene hydroperoxide was added dropwise over 120 minutes. Furthermore, the aqueous dispersion of the polymer (B-1) was obtained by making it react at 60 degreeC for 2 hours.
The aqueous dispersion of the polymer (B-1) had a volume average particle size of 115 nm and a solid content of 33% by mass.

[Production Example 7: Production of polymer (B-2)]
Polymerization was carried out under the same reaction conditions as in Production Example 6 except that 82 parts by mass of dropped n-butyl acrylate and 18 parts by mass of methacrylic acid were changed to 88 parts by mass of n-butyl acrylate and 12 parts by mass of methacrylic acid. An aqueous dispersion of the union (B-2) was obtained.
The aqueous dispersion of the polymer (B-2) had a volume average particle size of 92 nm and a solid content of 33% by mass.

  The raw materials and physical properties of the polymers (B-1) and (B-2) are summarized in Table 2 below.

[Example 1: Production of aqueous binder (C-1)]
While stirring 92 parts by mass (in terms of solid content) of the aqueous dispersion of polymer (A-1) at 60 ° C., 0.15 parts by mass of 4% sodium pyrophosphate aqueous solution (in terms of solid content) was added as a condensed acid salt. Then, 8 parts by mass (converted to solid content) of the polymer (B-1) was added and stirred for 30 minutes to obtain an aqueous binder (C-1). The obtained aqueous binder (C-1) was filtered through a 200-mesh wire mesh to remove aggregates.
The volume average particle diameter of the water-based binder (C-1) was 153 nm, the solid content was 37.9% by mass, and the aggregate remaining in the 200-mesh wire net was 0.10% by mass.
Table 4 shows the evaluation results of the obtained aqueous binder (C-1).

[Examples 2 to 6, 8 to 11, Comparative Examples 3 and 6: aqueous binders (C-2) to (C-6), (C-8) to (C-11), (C-14), ( Production of C′-3)]
Aqueous binders (C-2) to (C-) as in Example 1 except that the types and blending amounts of the polymer (A), the polymer (B) and the sodium polyphosphate were as shown in Tables 4 and 5. 6), (C-8) to (C-11), (C-14), and (C′-3) were obtained.
Volume average particle diameters of obtained water-based binders (C-2) to (C-6), (C-8) to (C-11), (C-14), and (C′-3) and a 200 mesh wire mesh Tables 4 and 5 show the amount of the remaining aggregates and other evaluation results.

[Example 7: Production of aqueous binder (C-7)]
While stirring 92 parts by mass (solid content conversion) of polymer (A-2) at 60 ° C., 8 parts by mass of polymer (B-1) (solid content conversion) is added and stirred for 30 minutes. An aqueous binder (C-7) was obtained. The obtained aqueous binder (C-7) was filtered through a 200-mesh wire net to remove aggregates.
The volume average particle size of the water-based binder (C-7) was 132 nm, the solid content was 37.9% by mass, and the aggregate remaining in the 200-mesh wire mesh was 0.04% by mass.
Table 4 shows the evaluation results of the obtained aqueous binder (C-7).

[Comparative Examples 1, 2, 7: Production of water-based binders (C-12), (C-13), (C-15)]
The aqueous dispersion of the polymer (A-1), the aqueous dispersion of the polymer (A-2), and the aqueous dispersion of the polymer (B-1) were respectively converted into an aqueous binder (C-12) and an aqueous binder (C -13), evaluated as an aqueous binder (C-15), and the results are shown in Table 5.

[Comparative Example 4: Production of aqueous binder (C′-1)]
In a reaction vessel equipped with a reagent injection vessel, a cooling tube, a jacket heater and a stirring device, 130 parts by mass of deionized water, 0.4 parts by mass of sodium dodecylbenzenesulfonate, 67.9 parts by mass of n-butyl acrylate, 2.1 parts by mass of acrylic acid, 0.07 parts by mass of 1,3-butylene glycol dimethacrylate and 0.05 parts by mass of t-butyl hydroperoxide were charged, and nitrogen substitution was performed while stirring. After raising the internal temperature to 55 ° C, 0.09 parts by mass of sodium formaldehyde sulfoxylate, 0.00015 parts by mass of ferrous sulfate heptahydrate, 0.00045 parts by mass of disodium ethylenediaminetetraacetate, 10 parts by mass of deionized water An aqueous solution consisting of was added to initiate the polymerization. After the polymerization exotherm was confirmed, the internal temperature was set to 70 ° C., and the reaction was carried out for 1 hour.

  Next, 0.1 parts by mass of sodium dodecylbenzenesulfonate, 0.04 parts by mass of sodium formaldehyde sulfoxylate, 0.002 parts by mass of ferrous sulfate heptahydrate, 0.006 parts by mass of disodium ethylenediaminetetraacetate and deionization After adding an aqueous solution consisting of 10 parts by weight of water, 29.1 parts by weight of n-butyl acrylate, 0.9 parts by weight of acrylic acid, 0.03 parts by weight of 1,3-butylene glycol dimethacrylate, t- A mixture of 0.03 parts by weight of butyl hydroperoxide was added dropwise over 2 hours. After completion of dropping, the mixture was further reacted at 70 ° C. for 1 hour to obtain an aqueous dispersion of the polymer (C′-1). The obtained aqueous dispersion of the polymer (C′-1) was filtered through a 200-mesh wire mesh to remove aggregates, and evaluated as an aqueous binder (C′-1).

The volume average particle diameter of the water-based binder (C′-1) was 86 nm, the solid content was 38.5% by mass, and the aggregate remaining in the 200-mesh wire mesh was 0.32% by mass.
Table 5 shows the evaluation results of the obtained aqueous binder (C′-1).

[Comparative Example 5: Production of aqueous binder (C′-2)]
Acrylic acid prepared by dropping 67.9 parts by mass of n-butyl acrylate and 2.1 parts by mass of acrylic acid into 66.5 parts by mass of acrylic acid and 3.5 parts by mass of acrylic acid. Polymerization was carried out under the same reaction conditions as in Comparative Example 4 except that 29.1 parts by weight of n-butyl and 0.9 parts by weight of acrylic acid were changed to 28.5 parts by weight of n-butyl acrylate and 1.5 parts by weight of acrylic acid. Then, an aqueous dispersion of the polymer (C′-2) was obtained, and the aggregate was removed to evaluate as an aqueous binder (C′-2).

The volume average particle diameter of the water-based binder (C′-2) was 88 nm, the solid content was 38% by mass, and the aggregate remaining in the 200 mesh wire net was 0.54% by mass.
Table 5 shows the evaluation results of the obtained aqueous binder (C′-2).

  The raw materials and physical properties of the polymers (C′-1) and (C′-2) are summarized in Table 3 below.

  As shown in Examples 1 to 11 in Table 4, according to the present invention, it is possible to provide an aqueous binder having high binding force or adhesive force and excellent manufacturing stability, storage stability, and solvent resistance.

  As shown in Table 5, Comparative Examples 1 and 2 are inferior in binding force because they do not contain the polymer (B), and Comparative Example 3 is inferior in binding force and solvent resistance because the polymer (A) does not contain a polyfunctional compound unit. Inferior to sex. As shown in Comparative Examples 4 and 5, in the copolymer of acrylic acid ester, polyfunctional compound, and α, β-unsaturated carboxylic acid, the binding force increases as the amount of α, β-unsaturated carboxylic acid added increases. Although improved, the production stability, storage stability, and solvent resistance are poor. Even if it uses combining a polymer (A) and the polymer (C'-2) which contains a polyfunctional compound unit with an alpha, beta-unsaturated carboxylic acid unit like the comparative example 6, sufficient binding force is used. Cannot be obtained. Since Comparative Example 7 does not contain the polymer (A), the production stability, storage stability, and solvent resistance are poor.

Claims (7)

  An aqueous dispersion of a polymer (A) containing a (meth) acrylic acid ester unit and a polyfunctional compound unit, and a polymer (B) containing a (meth) acrylic acid ester unit and an α, β-unsaturated carboxylic acid unit An aqueous binder (C) containing an aqueous dispersion.   The aqueous binder (C) according to claim 1, wherein the aqueous binder (C) is a mixture of the aqueous dispersion of the polymer (A) and the aqueous dispersion of the polymer (B).   The volume average particle size of the aqueous dispersion of the polymer (A) is 50 to 250 nm, the volume average particle size of the aqueous dispersion of the polymer (B) is 50 to 250 nm, and the aqueous binder (C) The water-based binder (C) according to claim 1 or 2, wherein the volume average particle diameter of the water-based binder (C) is 60 to 500 nm. In the polymer (A), the content of α, β-unsaturated carboxylic acid units is less than 7% by mass with respect to 100% by mass in total of all monomer units constituting the polymer (A). ,
In the polymer (B), the content of α, β-unsaturated carboxylic acid units is 7 to 30% by mass with respect to 100% by mass in total of all monomer units constituting the polymer (B). The aqueous binder (C) according to any one of claims 1 to 3, wherein the aqueous binder (C) is.   The aqueous binder (C) according to any one of claims 1 to 4, wherein the α, β-unsaturated carboxylic acid is (meth) acrylic acid.   Content of the polyfunctional compound unit of the polymer (A) is 0.01 to 5% by mass with respect to 100% by mass in total of all monomer units constituting the polymer (A), and the weight The aqueous binder (C) according to any one of claims 1 to 5, wherein the combined body (B) does not contain a polyfunctional compound unit.   The content of the polymer (A) is 50 to 99 parts by mass with respect to a total of 100 parts by mass of the polymer (A) and the polymer (B), and the content of the polymer (B) is 1 to 50 parts by mass. The aqueous binder (C) according to any one of claims 1 to 6, wherein the aqueous binder (C) is a part.