Conjugated diene polymer latex and dip molded body

Abstract

The present invention provides a conjugated diene polymer latex which is obtained by copolymerizing a conjugated diene monomer (m-1), an α,β-ethylenically unsaturated nitrile monomer (m-2), a carboxyl-group-containing ethylenically unsaturated monomer (m-3), and a high Tg monomer (m-4), wherein the high Tg monomer (m-4) has a glass transition temperature (Tg) of higher than 10°C when in the form of a homopolymer, and is not any of the monomers (m-1) to (m-3).

Description

Latex and dip-molded products of conjugated diene polymers

[0001] The present invention relates to a latex of a conjugated diene polymer, and more particularly to a latex of a conjugated diene copolymer that can give a dip-molded article that is excellent in flexibility, wet grip property, abrasion resistance, and chemical solution permeation resistance.

[0002] Conventionally, protective gloves that have improved solvent resistance, gripping properties, abrasion resistance, etc. by covering fiber gloves with rubber, resin, etc. have been used for various purposes such as manufacturing work in factories, light work, construction work, agricultural work, etc.

[0003] Such protective gloves are required to have excellent mechanical strength such as abrasion resistance and durability, as well as excellent flexibility. Furthermore, since protective gloves may be used in wet conditions, they are also required to have excellent wet grip properties.

[0004] For example, Patent Document 1 describes a latex composition for dip molding, which is obtained by mixing a latex of a conjugated diene polymer (A) having a glass transition temperature of 10°C or lower and a latex of a polymer (B) having a glass transition temperature of more than 10°C.

[0005] Japanese Patent Application Laid-Open No. 2020-111097

[0006] The dip-molding latex composition described in Patent Document 1 can provide a dip-molded article that is excellent in abrasion resistance and wet grip property when water or oil is attached. However, through intensive studies, the present inventors have found that there is room for improvement in the chemical liquid permeation resistance of the dip-molded article obtained by the technique of Patent Document 1.

[0007] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a latex of a conjugated diene copolymer which can give a dip-molded article having excellent flexibility, wet grip property, abrasion resistance, and chemical solution permeation resistance.

[0008] As a result of intensive research to solve the above-mentioned problems, the present inventors have found that the above-mentioned problems can be solved by a latex of a conjugated diene copolymer obtained by copolymerizing a conjugated diene monomer (m-1), an α,β-ethylenically unsaturated nitrile monomer (m-2), a carboxyl group-containing ethylenically unsaturated monomer (m-3), and a high Tg monomer (m-4) described below, and have thus completed the present invention.

[0009] That is, according to the present invention, there is provided a latex of a conjugated diene copolymer obtained by copolymerizing a conjugated diene monomer (m-1), an α,β-ethylenically unsaturated nitrile monomer (m-2), a carboxyl group-containing ethylenically unsaturated monomer (m-3), and a high Tg monomer (m-4), wherein the high Tg monomer (m-4) is a monomer having a glass transition temperature (Tg) of more than 10°C when made into a homopolymer, and the high Tg monomer (m-4) is a monomer other than the conjugated diene monomer (m-1), the α,β-ethylenically unsaturated nitrile monomer (m-2), and the carboxyl group-containing ethylenically unsaturated monomer (m-3).

[0010] In the conjugated diene copolymer latex of the present invention, it is more preferable that the ratio of units of the conjugated diene monomer (m-1) is 20 to 70 wt%, the ratio of units of the α,β-ethylenically unsaturated nitrile monomer (m-2) is 10 to 50 wt%, the ratio of units of the carboxyl group-containing ethylenically unsaturated monomer (m-3) is 0.1 to 10 wt%, and the ratio of units of the high Tg monomer (m-4) is 3 to 30 wt%, based on the entire polymer components in the conjugated diene copolymer latex. In the conjugated diene copolymer latex of the present invention, it is more preferable that the conjugated diene monomer (m-1) is 1,3-butadiene or isoprene. In the conjugated diene copolymer latex of the present invention, it is more preferable that the high Tg monomer (m-4) is an aromatic vinyl monomer. The conjugated diene copolymer latex of the present invention more preferably contains two or more anionic surfactants. The conjugated diene copolymer latex of the present invention is preferably formed by dispersing aggregate particles aggregated by a water-soluble polymer in water. The conjugated diene copolymer latex of the present invention preferably has a sedimentation velocity of 1.6 μm / s or more, measured using a centrifugal sedimentation particle size distribution analyzer under conditions of a rotation speed of 4000 rpm, a centrifugal acceleration of 2300 G, and a measurement time of 50 minutes. The conjugated diene copolymer latex of the present invention is more preferably a latex composition for dip molding.

[0011] The present invention also provides a dip-molded article made using the latex of the conjugated diene copolymer. Furthermore, the present invention also provides a dip-molded article made by immersing a substrate in the latex of the conjugated diene copolymer. In the dip-molded article of the present invention, the substrate is preferably a fibrous substrate.

[0012] According to the present invention, it is possible to provide a latex of a conjugated diene copolymer which can give a dip-molded article having excellent flexibility, wet grip properties, abrasion resistance, and resistance to chemical permeation.

[0013] <Latex of Conjugated Diene Copolymer> The latex of the conjugated diene copolymer of the present invention is obtained by copolymerizing a conjugated diene monomer (m-1), an α,β-ethylenically unsaturated nitrile monomer (m-2), a carboxyl group-containing ethylenically unsaturated monomer (m-3), and a high Tg monomer (m-4) described later.

[0014] The latex of the conjugated diene copolymer of the present invention is obtained by copolymerizing at least the above four types of monomers, and therefore can provide a dip-molded article having excellent flexibility, wet grip properties, abrasion resistance, and chemical permeation resistance.

[0015] On the other hand, for example, a dip-molded article excellent in flexibility, wet grip properties, abrasion resistance, and chemical permeation resistance cannot be obtained using a latex of a conjugated diene copolymer obtained without using the high Tg monomer (m-4). Furthermore, for example, a dip-molded article excellent in flexibility, wet grip properties, abrasion resistance, and chemical permeation resistance cannot be obtained using a latex obtained by mixing a latex of a copolymer obtained by copolymerizing a conjugated diene monomer (m-1), an α,β-ethylenically unsaturated nitrile monomer (m-2), and a carboxyl group-containing ethylenically unsaturated monomer (m-3) with a latex of a homopolymer of the high Tg monomer (m-4) obtained by copolymerizing the high Tg monomer (m-4).

[0016] The conjugated diene monomer (m-1) is not particularly limited, but is preferably a conjugated diene monomer having 4 to 6 carbon atoms such as 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, or chloroprene, more preferably 1,3-butadiene or isoprene, and particularly preferably 1,3-butadiene. These conjugated diene monomers (m-1) may be used alone or in combination of two or more.

[0017] The α,β-ethylenically unsaturated nitrile monomer (m-2) is not particularly limited, but it is preferable to use an ethylenically unsaturated compound having a nitrile group and preferably having 3 to 18 carbon atoms. Examples of such an α,β-ethylenically unsaturated nitrile monomer (m-2) include acrylonitrile, methacrylonitrile, and halogen-substituted acrylonitrile, and among these, acrylonitrile is particularly preferred. These α,β-ethylenically unsaturated nitrile monomers (m-2) may be used alone or in combination of two or more.

[0018] The carboxyl group-containing ethylenically unsaturated monomer (m-3) is not particularly limited, and examples thereof include ethylenically unsaturated monocarboxylic acids such as acrylic acid, methacrylic acid, and crotonic acid; ethylenically unsaturated polycarboxylic acids and anhydrides thereof such as fumaric acid, maleic acid, itaconic acid, maleic anhydride, and itaconic anhydride; and partially esterified ethylenically unsaturated polycarboxylic acids such as methyl maleate and methyl itaconate. These monomers can also be used as alkali metal salts or ammonium salts. Among these, ethylenically unsaturated monocarboxylic acids and ethylenically unsaturated polycarboxylic acids are preferred, with acrylic acid, methacrylic acid, fumaric acid, and maleic acid being more preferred, acrylic acid and methacrylic acid being even more preferred, and methacrylic acid being particularly preferred. These carboxyl group-containing ethylenically unsaturated monomers (m-3) may be used alone or in combination of two or more.

[0019] The high Tg monomer (m-4) used in the present invention is a monomer that, when made into a homopolymer, has a glass transition temperature (Tg) of more than 10° C., and is a monomer other than the conjugated diene monomer (m-1), the α,β-ethylenically unsaturated nitrile monomer (m-2), and the carboxyl group-containing ethylenically unsaturated monomer (m-3). In the present invention, the "glass transition temperature (Tg) when made into a homopolymer" means the glass transition temperature (Tg) when made into a homopolymer having a molecular weight of 50,000 or more.

[0020] Such high Tg monomer (m-4) is not particularly limited, but examples thereof include aromatic vinyl monomers, monocarboxylic acid ester group-containing ethylenically unsaturated monomers, dicarboxylic acid diester group-containing ethylenically unsaturated monomers, vinyl acetate, vinyl chloride, tetrafluoroethylene, etc. These high Tg monomers (m-4) may be used alone or in combination of two or more.

[0021] The aromatic vinyl monomer as the high Tg monomer (m-4) is not particularly limited as long as it has a glass transition temperature (Tg) of more than 10°C when made into a homopolymer, and examples thereof include styrene and alkylstyrene, and among these, styrene is preferred.

[0022] The monocarboxylic acid ester group-containing ethylenically unsaturated monomer as the high Tg monomer (m-4) is not particularly limited as long as it has a glass transition temperature (Tg) of more than 10°C when made into a homopolymer, and examples thereof include methacrylic acid esters such as methyl methacrylate, ethyl methacrylate, and n-butyl methacrylate. Among these, methacrylic acid esters are preferred, and methyl methacrylate is more preferred.

[0023] The dicarboxylic acid diester group-containing ethylenically unsaturated monomer as the high Tg monomer (m-4) is not particularly limited as long as it has a glass transition temperature (Tg) of more than 10°C when made into a homopolymer, and examples thereof include maleic acid diesters such as dimethyl maleate; itaconic acid diesters such as methyl itaconate; and the like.

[0024] The glass transition temperature (Tg) of the high Tg monomer (m-4) when made into a homopolymer is not particularly limited as long as it is more than 10° C., but is preferably 30° C. or higher, and more preferably 60° C. or higher. Examples of the high Tg monomer (m-4) that has a glass transition temperature (Tg) of 60° C. or higher when made into a homopolymer include styrene, methylstyrene, methyl methacrylate, vinyl chloride, and tetrafluoroethylene.

[0025] As the high Tg monomer (m-4), an aromatic vinyl monomer, a monocarboxylic acid ester group-containing ethylenically unsaturated monomer, and vinyl chloride are preferred, an aromatic vinyl monomer and a methacrylic acid ester are more preferred, an aromatic vinyl monomer and methyl methacrylate are further preferred, and styrene is particularly preferred.

[0026] The conjugated diene copolymer used in the present invention may be obtained by copolymerizing a conjugated diene monomer (m-1), an α,β-ethylenically unsaturated nitrile monomer (m-2), a carboxyl group-containing ethylenically unsaturated monomer (m-3), a high Tg monomer (m-4), and other ethylenically unsaturated monomers copolymerizable with these.

[0027] Such other ethylenically unsaturated monomers are not particularly limited, but include those not corresponding to the high Tg monomer (m-4) among acrylic acid ester monomers, sulfonic acid group-containing ethylenically unsaturated monomers, phosphoric acid group-containing ethylenically unsaturated monomers, etc. These monomers may be used alone or in combination of two or more.

[0028] Examples of such acrylate monomers include ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, sec-butyl acrylate, tert-butyl acrylate, n-pentyl acrylate, sec-pentyl acrylate, isopentyl acrylate, neopentyl acrylate, n-hexyl acrylate, isohexyl acrylate, neohexyl acrylate, sec-hexyl acrylate, and tert-hexyl acrylate, and among these, ethyl acrylate is preferred.

[0029] The sulfonic acid group-containing ethylenically unsaturated monomer and the phosphoric acid group-containing ethylenically unsaturated monomer may be used in the form of an alkali metal salt or an ammonium salt, and one type may be used alone or two or more types may be used in combination.

[0030] The bonding mode of each monomer in the conjugated diene copolymer used in the present invention can be various bonding modes, such as block, tapered, and random. Furthermore, the latex of the conjugated diene copolymer of the present invention may contain two or more conjugated diene copolymers having different bonding modes. It is desirable that the latex of the conjugated diene copolymer of the present invention contains at least a random conjugated diene copolymer.

[0031] The ratio of the conjugated diene monomer (m-1) units to the entire polymer components in the latex of the conjugated diene copolymer of the present invention is not particularly limited, but is preferably 10 to 86.9 wt %, more preferably 20 to 80 wt %, even more preferably 30 to 73 wt %, particularly preferably 36.5 to 70 wt %, and most preferably 43 to 65 wt %. For example, the ratio of the conjugated diene monomer (m-1) units may be 20 to 70 wt %. When the ratio of the conjugated diene monomer (m-1) units is within the above range, the resulting dip-molded article will have an even better balance of flexibility, wet grip properties, abrasion resistance, and chemical permeation resistance.

[0032] The ratio of the α,β-ethylenically unsaturated nitrile monomer (m-2) units to the entire polymer components in the latex of the conjugated diene copolymer of the present invention is not particularly limited, but is preferably 10 to 50 wt %, more preferably 15 to 45 wt %, even more preferably 20 to 40 wt %, particularly preferably 21.5 to 38 wt %, and most preferably 25 to 35 wt %. When the ratio of the α,β-ethylenically unsaturated nitrile monomer (m-2) units is within the above range, the resulting dip-molded article will have an even better balance of flexibility, wet grip properties, abrasion resistance, and chemical permeation resistance.

[0033] The ratio of the carboxyl group-containing ethylenically unsaturated monomer (m-3) units to the entire polymer components in the latex of the conjugated diene copolymer of the present invention is not particularly limited, but is preferably 0.1 to 10 wt%, more preferably 0.5 to 9 wt%, even more preferably 1 to 8 wt%, particularly preferably 1.5 to 7.5 wt%, and most preferably 2 to 7 wt%. When the ratio of the carboxyl group-containing ethylenically unsaturated monomer (m-3) units is within the above range, the resulting dip-molded article will have an even better balance of flexibility, wet grip properties, abrasion resistance, and chemical permeation resistance.

[0034] The ratio of the high Tg monomer (m-4) units to the entire polymer components in the latex of the conjugated diene copolymer of the present invention is not particularly limited, but is preferably 3 to 30 wt%, more preferably 4.5 to 26 wt%, even more preferably 6 to 22 wt%, particularly preferably 7 to 18 wt%, and most preferably 8 to 15 wt%. When the ratio of the high Tg monomer (m-4) units is within the above range, the resulting dip-molded article has an even better balance of flexibility, wet grip properties, abrasion resistance, and chemical permeation resistance.

[0035] The weight ratio of the abundance ratio of the units of the carboxyl group-containing ethylenically unsaturated monomer (m-3) to the abundance ratio of the units of the high Tg monomer (m-4) (abundance ratio of the carboxyl group-containing ethylenically unsaturated monomer (m-3):abundance ratio of the high Tg monomer (m-4)) in the entire polymer components in the latex of the conjugated diene copolymer of the present invention is preferably 1:0.1 to 1:30, more preferably 1:0.5 to 1:25, even more preferably 1:0.5 to 1:5, and particularly preferably 1:1 to 1:3, from the viewpoint of making the effects of the present invention more pronounced.

[0036] The ratio of the units of the other ethylenically unsaturated monomers in the entire polymer components in the latex of the conjugated diene copolymer of the present invention is not particularly limited, but is preferably 0 to 20% by weight, more preferably 0 to 10% by weight, and even more preferably 0 to 5% by weight.

[0037] The ratio of the units of each monomer in the entire polymer component of the latex of the conjugated diene copolymer of the present invention is, for example, １ The ratio of each monomer unit can be calculated from the amount of each monomer used in producing the latex of the conjugated diene copolymer.

[0038] The latex of the conjugated diene copolymer of the present invention may contain two or more conjugated diene copolymers having different contents of each monomer unit. For example, the latex of the conjugated diene copolymer of the present invention may contain a conjugated diene copolymer having a low content of the high Tg monomer (m-4) (preferably 10% by weight or less) and a conjugated diene copolymer having a high content of the high Tg monomer (m-4) (preferably more than 10% by weight).

[0039] The latex of the conjugated diene copolymer of the present invention may contain other polymers in addition to the conjugated diene copolymer used in the present invention described above. The other polymers may be any polymers that do not contain any one or more monomers selected from the group consisting of the conjugated diene monomer (m-1), the α,β-ethylenically unsaturated nitrile monomer (m-2), the carboxyl group-containing ethylenically unsaturated monomer (m-3), and the high Tg monomer (m-4). The other polymers are not particularly limited, but examples thereof include polymers obtained by polymerizing one to three monomers selected from the group consisting of the conjugated diene monomer (m-1), the α,β-ethylenically unsaturated nitrile monomer (m-2), the carboxyl group-containing ethylenically unsaturated monomer (m-3), and the high Tg monomer (m-4) with other ethylenically unsaturated monomers used as needed.

[0040] The content of the above-mentioned other polymers in the latex of the conjugated diene copolymer of the present invention is not particularly limited as long as it is within a range that does not impair the effects of the present invention, but it is preferably 0 to 100 parts by weight, more preferably 0 to 50 parts by weight, still more preferably 0 to 20 parts by weight, and particularly preferably 0 to 10 parts by weight, relative to 100 parts by weight of the conjugated diene copolymer used in the present invention.

[0041] The glass transition temperature (Tg) of the polymer component constituting the latex of the conjugated diene copolymer of the present invention is not particularly limited, but is preferably from -40 to 0°C, more preferably from -30 to -5°C.

[0042] The volume average primary particle diameter of the polymer particles constituting the latex (latex composition) of the conjugated diene copolymer of the present invention is preferably 30 to 250 nm, more preferably 30 to 200 nm, and even more preferably 50 to 180 nm. The volume average primary particle diameter of the polymer particles constituting the latex of the conjugated diene copolymer of the present invention can be measured, for example, using a light scattering diffraction particle measuring device.

[0043] The latex of the conjugated diene copolymer of the present invention is prepared by dispersing a polymer component containing a conjugated diene copolymer in water. The content of the polymer component in the latex of the conjugated diene copolymer of the present invention is not particularly limited, but is preferably 20 to 65 wt %, more preferably 30 to 60 wt %, and even more preferably 35 to 55 wt %, based on 100 parts by weight of the total weight of the polymer component and water. By setting the content of the polymer component within the above range, the transport efficiency of the latex of the conjugated diene copolymer can be improved, and the viscosity of the latex of the conjugated diene copolymer becomes appropriate, thereby improving the handleability of the latex of the conjugated diene copolymer.

[0044] The latex of the conjugated diene copolymer of the present invention preferably contains a surfactant in addition to the conjugated diene copolymer used in the present invention and water. The surfactant is not particularly limited, but examples thereof include anionic surfactants, nonionic surfactants, cationic surfactants, and amphoteric surfactants, with anionic surfactants being preferred. These surfactants may be used alone or in combination of two or more. The latex of the conjugated diene copolymer of the present invention preferably contains two or more anionic surfactants.

[0045] The anionic surfactant is not particularly limited, but examples thereof include a compound (a) having one anionic group and an aromatic ring, a compound (b1) having two or more anionic groups and a benzene ring, and a compound (b2) having one anionic group and no aromatic ring.

[0046] The compound (a) having one anionic group and an aromatic ring (hereinafter referred to as "compound (a)" where appropriate) is a compound having only one anionic group and an aromatic ring.

[0047] The anionic group contained in the compound (a) may be a carboxylic acid group (—COOH), a carboxylic acid salt group (—COOX), a sulfonic acid group (—SO ３ H), sulfonate group (-SO ３ X), sulfate ester group (-OSO ３ H), sulfate ester group (-OSO ３ X), phosphate group (-OP(=O)(OH) ２ ), phosphate group (-OP(=O)(OH)(OX) or -OP(=O)(OX) ２ ) and the like. In the formula, X is an atom or molecule constituting a cation. Examples of X include metal atoms such as lithium, sodium, potassium, calcium, magnesium, and aluminum, and ammonium, with sodium, potassium, and ammonium being preferred, and sodium being more preferred. The anionic group possessed by compound (a) is preferably a sulfonate group or a sulfate ester group, more preferably a sulfonate group, and a sodium sulfonate group (—SO ３That is, compound (a) is preferably a sulfonate or a sulfate salt, more preferably a sulfonate salt, and even more preferably a sodium sulfonate salt.

[0048] The aromatic ring contained in compound (a) may be any ring having aromaticity, and is not particularly limited, but examples thereof include non-condensed aromatic rings such as benzene rings and condensed aromatic rings such as naphthalene rings. Compound (a) preferably has a non-condensed aromatic ring, and the number of non-condensed aromatic rings in compound (a) is not particularly limited, but is preferably 1. The non-condensed aromatic ring contained in compound (a) is preferably a benzene ring, and the number of benzene rings in compound (a) is not particularly limited, but is preferably 1.

[0049] The compound (a) preferably has an alkyl group. When the compound (a) has an alkyl group, the alkyl group in the compound (a) preferably has 8 to 16 carbon atoms, and more preferably has 10 to 14 carbon atoms.

[0050] Examples of the compound (a) include alkylbenzene sulfonates such as sodium decylbenzene sulfonate, potassium decylbenzene sulfonate, sodium undecylbenzene sulfonate, potassium undecylbenzene sulfonate, sodium dodecylbenzene sulfonate, potassium dodecylbenzene sulfonate, sodium tridecylbenzene sulfonate, potassium tridecylbenzene sulfonate, sodium tetradecylbenzene sulfonate, and potassium tetradecylbenzene sulfonate. Among these, from the viewpoint of making the effects of the present invention more pronounced, alkylbenzene sulfonates are preferred, sodium alkylbenzene sulfonate is more preferred, and sodium dodecylbenzene sulfonate is even more preferred. Compound (a) may be used alone or in combination of two or more types.

[0051] The molecular weight of the compound (a) is preferably 100 to 600, more preferably 200 to 500, and even more preferably 300 to 400, from the viewpoint of making the effects of the present invention more pronounced.

[0052] The number of anionic groups in compound (b1) having two or more anionic groups and a benzene ring (hereinafter referred to as "compound (b1)" as appropriate) is not particularly limited as long as it is two or more, but it is preferably two.

[0053] Examples of the anionic group contained in the compound (b1) include the same anionic groups as those contained in the compound (a). The anionic group contained in the compound (b1) is preferably a sulfonate group or a sulfate ester group, more preferably a sulfonate group, and more preferably a sodium sulfonate group (—SO ３ Na) is more preferred. That is, compound (b1) is preferably a sulfonate or a sulfate ester salt, more preferably a sulfonate, and even more preferably a sodium sulfonate salt. The two or more anionic groups contained in compound (b1) may be the same or different, but are preferably the same.

[0054] Compound (b1) has a benzene ring. The number of benzene rings in compound (b1) is not particularly limited, but is preferably two or more, and more preferably two. Compound (b1) may have an aromatic ring other than a benzene ring. Examples of aromatic rings other than a benzene ring include non-fused aromatic rings containing heteroatoms and fused aromatic rings such as naphthalene rings. The number of aromatic rings other than a benzene ring in compound (b1) is preferably two or less, more preferably one or less, and even more preferably zero. That is, compound (b1) preferably does not have any aromatic rings other than a benzene ring.

[0055] The compound (b1) preferably has an ether bond, and more preferably has a diphenyl ether structure.

[0056] The compound (b1) preferably has an alkyl group. When the compound (b1) has an alkyl group, the alkyl group in the compound (b1) preferably has 8 to 16 carbon atoms, and more preferably has 10 to 14 carbon atoms.

[0057] Examples of the compound (b1) include alkyl diphenyl ether disulfonates such as disodium alkyl diphenyl ether disulfonate, dipotassium alkyl diphenyl ether disulfonate, and diammonium alkyl diphenyl ether disulfonate, and among these, from the viewpoint of making the effects of the present invention more pronounced, disodium alkyl diphenyl ether disulfonate is preferred, more preferably disodium alkyl diphenyl ether disulfonate having an alkyl group with 8 to 16 carbon atoms, and even more preferably disodium alkyl diphenyl ether disulfonate having an alkyl group with 10 to 14 carbon atoms. Compound (b1) may be used alone or in combination of two or more types.

[0058] The molecular weight of the compound (b1) is preferably from 100 to 1,000, more preferably from 200 to 850, even more preferably from 300 to 750, and particularly preferably from 400 to 650, from the viewpoint of making the effects of the present invention more pronounced.

[0059] The compound (b2) having one anionic group and no aromatic ring (hereinafter referred to as "compound (b2)" where appropriate) is a compound having only one anionic group and no aromatic ring.

[0060] Examples of the anionic group contained in the compound (b2) include the same anionic groups as those contained in the compound (a). The anionic group contained in the compound (b2) is preferably a sulfonate group or a sulfate ester group, more preferably a sulfate ester group, and more preferably a sodium sulfate group (-OSO ３ That is, the compound (b2) is preferably a sulfonate or a sulfate ester salt, more preferably a sulfate ester salt, and further preferably a sodium sulfate ester salt.

[0061] The compound (b2) preferably has an alkyl group. When the compound (b2) has an alkyl group, the alkyl group in the compound (b2) preferably has 8 to 16 carbon atoms, and more preferably has 10 to 14 carbon atoms.

[0062] Examples of the compound (b2) include fatty acid salts such as sodium laurate, potassium myristate, sodium palmitate, potassium oleate, sodium linolenate, and sodium rosinate; alkyl sulfosuccinates such as sodium di(2-ethylhexyl)sulfosuccinate, potassium di(2-ethylhexyl)sulfosuccinate, and sodium dioctyl sulfosuccinate; sodium octyl sulfate, potassium octyl sulfate, sodium decyl sulfate, potassium decyl sulfate, sodium undecyl sulfate, potassium undecyl sulfate, sodium dodecyl sulfate (sodium lauryl sulfate), and potassium dodecyl sulfate (lauryl sulfate).

[0043] Examples of the alkyl ester salt include alkyl sulfates such as sodium tetradecyl sulfate, potassium tetradecyl sulfate, sodium hexadecyl sulfate, and potassium hexadecyl sulfate; polyoxyethylene alkyl ether sulfates such as sodium polyoxyethylene lauryl ether sulfate and potassium polyoxyethylene lauryl ether sulfate; and monoalkyl phosphates such as sodium lauryl phosphate and potassium lauryl phosphate. Among these, from the viewpoint of making the effects of the present invention more pronounced, alkyl sulfates are preferred, sodium alkyl sulfate is preferred, and sodium lauryl sulfate is more preferred.

[0063] The molecular weight of the compound (b2) is preferably from 100 to 600, more preferably from 200 to 450, and even more preferably from 250 to 350, from the viewpoint that the effects of the present invention become more pronounced.

[0064] The anionic surfactant is not particularly limited to the compounds described above, and for example, a sodium salt of a β-naphthalenesulfonic acid formalin condensate can also be used. The anionic surfactant may be used alone or in combination of two or more.

[0065] From the viewpoint of making the effects of the present invention more pronounced, the latex of the conjugated diene copolymer of the present invention preferably contains at least one selected from compound (a), compound (b1) and compound (b2) as an anionic surfactant, and more preferably contains at least one selected from compound (b1) and compound (b2). Also, from the viewpoint of further improving the wet grip property and abrasion resistance of the obtained dip-molded article, it is more preferable to contain at least compound (a) and compound (b1) or compound (b2), and particularly preferable to contain at least compound (a) and compound (b1).

[0066] The content of the surfactant in the latex of the conjugated diene copolymer of the present invention is not particularly limited, but is preferably 0.1 to 15.0 parts by weight, more preferably 0.5 to 10.0 parts by weight, still more preferably 0.8 to 7.4 parts by weight, and particularly preferably 1.0 to 6.5 parts by weight, relative to 100 parts by weight of the polymer component contained in the latex of the conjugated diene copolymer.

[0067] When the latex of the conjugated diene copolymer of the present invention contains the compound (a), the content of the compound (a) is not particularly limited, but from the viewpoint of making the effects of the present invention more remarkable, the content of the compound (a) is preferably 0.1 to 5.0 parts by weight, more preferably 0.5 to 3.0 parts by weight, still more preferably 0.8 to 2.4 parts by weight, and particularly preferably 1.0 to 2.0 parts by weight, relative to 100 parts by weight of the polymer component contained in the latex of the conjugated diene copolymer.

[0068] When the latex of the conjugated diene copolymer of the present invention contains the compound (b1), the content of the compound (b1) is preferably 0.1 to 10.0 parts by weight, more preferably 0.5 to 7.0 parts by weight, still more preferably 1.0 to 5.0 parts by weight, and particularly preferably 1.2 to 4.5 parts by weight, relative to 100 parts by weight of the polymer component contained in the latex of the conjugated diene copolymer, from the viewpoint that the effects of the present invention become more remarkable.

[0069] When the latex of the conjugated diene copolymer of the present invention contains the compound (b2), the content of the compound (b2) is preferably 0.1 to 10.0 parts by weight, more preferably 0.5 to 7.0 parts by weight, still more preferably 1.0 to 5.0 parts by weight, and particularly preferably 1.2 to 4.5 parts by weight, relative to 100 parts by weight of the polymer component contained in the latex of the conjugated diene copolymer, from the viewpoint that the effects of the present invention become more remarkable.

[0070] When the latex of the conjugated diene copolymer of the present invention contains at least one of the compound (b1) and the compound (b2), the total content of the compound (b1) and the compound (b2) is preferably 0.1 to 10.0 parts by weight, more preferably 0.5 to 7.0 parts by weight, still more preferably 1.0 to 5.0 parts by weight, and particularly preferably 1.2 to 4.5 parts by weight, relative to 100 parts by weight of the polymer components contained in the latex of the conjugated diene copolymer, from the viewpoint that the effects of the present invention become more remarkable.

[0071] When the latex of the conjugated diene copolymer of the present invention contains the compound (a) and the compound (b1) or the compound (b2), the weight ratio of the content of the compound (a) to the total content of the compound (b1) and the compound (b2) (weight of the compound (a): total weight of the compound (b1) and the compound (b2)) is preferably 5:95 to 95:5, more preferably 10:90 to 90:10, even more preferably 15:85 to 80:20, and particularly preferably 20:80 to 70:30, from the viewpoint of making the effects of the present invention more pronounced.

[0072] The content of each surfactant in the latex of the conjugated diene copolymer of the present invention can be calculated from the amount of each surfactant used in producing the latex of the conjugated diene copolymer.

[0073] (Latex Composition) The latex of the conjugated diene copolymer of the present invention may be a latex composition further containing various compounding agents such as a crosslinking agent, or may be a latex composition for dip molding used for producing a dip-molded article.

[0074] The crosslinking agent is not particularly limited, but sulfur-based crosslinking agents are preferred, and examples thereof include sulfur such as powdered sulfur, sulfur flowers, precipitated sulfur, colloidal sulfur, surface-treated sulfur, and insoluble sulfur; sulfur-containing compounds such as sulfur chloride, sulfur dichloride, morpholine disulfide, alkylphenol disulfide, dibenzothiazyl disulfide, caprolactam disulfide, phosphorus-containing polysulfide, and polymeric polysulfides; and sulfur-donating compounds such as tetramethylthiuram disulfide, dimethyldithiocarbamate selenium, and 2-(4'-morpholinodithio)benzothiazole. These crosslinking agents may be used alone or in combination of two or more.

[0075] The content of the crosslinking agent is preferably 0.01 to 5 parts by weight, more preferably 0.05 to 3 parts by weight, and even more preferably 0.1 to 2 parts by weight, based on 100 parts by weight of the polymer component contained in the latex composition.

[0076] Furthermore, the latex composition of the present invention preferably further contains a crosslinking accelerator (vulcanization accelerator) and zinc oxide in addition to the crosslinking agent.

[0077] The crosslinking accelerator (vulcanization accelerator) is not particularly limited, but examples thereof include dithiocarbamic acids such as diethyldithiocarbamic acid, dibutyldithiocarbamic acid, di-2-ethylhexyldithiocarbamic acid, dicyclohexyldithiocarbamic acid, diphenyldithiocarbamic acid, and dibenzyldithiocarbamic acid, and zinc salts thereof; 2-mercaptobenzothiazole, 2-mercaptobenzothiazole zinc, 2-mercaptothiazoline, dibenzothiazyl disulfide, and 2-(2,4-dinitrophenylthio)benzo Examples of crosslinking accelerators include thiazole, 2-(N,N-diethylthiocarbamoylthio)benzothiazole, 2-(2,6-dimethyl-4-morpholinothio)benzothiazole, 2-(4'-morpholinodithio)benzothiazole, 4-morpholinyl-2-benzothiazyl disulfide, and 1,3-bis(2-benzothiazylmercaptomethyl)urea. Of these, zinc diethyldithiocarbamate, zinc dibutyldithiocarbamate, 2-mercaptobenzothiazole, and zinc 2-mercaptobenzothiazole are preferred. These crosslinking accelerators may be used alone or in combination of two or more.

[0078] The content of the crosslinking accelerator is preferably 0.1 to 10 parts by weight, more preferably 0.5 to 5 parts by weight, based on 100 parts by weight of the polymer components contained in the latex composition. The content of zinc oxide is preferably 0.1 to 10 parts by weight, more preferably 0.5 to 5 parts by weight, based on 100 parts by weight of the polymer components contained in the latex composition.

[0079] The latex of the conjugated diene copolymer of the present invention preferably further contains a water-soluble polymer.

[0080] Examples of water-soluble polymers include vinyl compounds such as polyvinyl alcohol and polyvinylpyrrolidone; cellulose derivatives and salts thereof such as hydroxyethyl cellulose, hydroxypropyl cellulose, and carboxymethyl cellulose; polycarboxylic acid compounds and salts thereof such as polyacrylic acid; and polyoxyethylene derivatives such as polyethylene glycol ether. Preferred water-soluble polymers include cellulose derivatives and salts thereof, polycarboxylic acid compounds and sodium salts thereof, more preferred are cellulose derivatives and salts thereof, and particularly preferred are carboxymethyl cellulose and sodium salts thereof. The weight-average molecular weight (Mw) of the water-soluble polymer is not particularly limited, but is preferably 100 or more, more preferably 1,000 or more, and is preferably 5,000,000 or less, and more preferably 3,000,000 or less. The content of the water-soluble polymer is preferably 0.01 to 10 parts by weight, more preferably 0.1 to 5 parts by weight, per 100 parts by weight of the polymer component contained in the conjugated diene copolymer latex.

[0081] When the conjugated diene copolymer latex of the present invention contains a water-soluble polymer, the conjugated diene copolymer latex of the present invention is preferably a latex in which aggregate particles formed by aggregation with the water-soluble polymer are dispersed in water. The method for dispersing the conjugated diene copolymer latex of the present invention in which aggregate particles formed by aggregation with the water-soluble polymer are dispersed in water is not particularly limited, but a method using a water-soluble polymer having the above-mentioned preferred weight-average molecular weight (Mw) or a method in which the content of the water-soluble polymer is within the above-mentioned preferred range is preferred. Here, the volume-average particle diameter (secondary particle diameter) of the aggregate particles formed by aggregation with the water-soluble polymer is preferably 1.5 μm or more, more preferably 5 μm or more. The volume-average particle diameter of the aggregate particles formed by aggregation with the water-soluble polymer can be measured using an optical microscope.

[0082] The latex of the conjugated diene copolymer of the present invention may contain fillers such as carbon black, silica, calcium carbonate, aluminum silicate, magnesium silicate, calcium silicate, magnesium oxide, zinc (meth)acrylate, magnesium (meth)acrylate, titanium oxide, etc. The latex of the conjugated diene copolymer of the present invention may contain predetermined amounts of other additives, such as antioxidants, antioxidants, preservatives, antibacterial agents, wetting agents, dispersants, pigments, dyes, reinforcing agents, and pH adjusters, as needed.

[0083] The solids concentration of the latex of the conjugated diene copolymer of the present invention is preferably 20 to 65% by weight, more preferably 30 to 60% by weight, and even more preferably 35 to 55% by weight. By setting the solids concentration of the latex of the conjugated diene copolymer within the above range, the transport efficiency of the latex of the conjugated diene copolymer can be improved, and the viscosity of the latex of the conjugated diene copolymer becomes appropriate, thereby improving the handleability of the latex of the conjugated diene copolymer.

[0084] The solid content concentration of the latex of the conjugated diene copolymer of the present invention can be adjusted to the above range by, for example, a concentration treatment or a dilution treatment, which will be described later. Among these, the concentration treatment is preferred from the viewpoint of productivity.

[0085] The pH of the latex of the conjugated diene copolymer of the present invention is preferably 5 to 13, more preferably 7 to 10, and even more preferably 7.5 to 9. By setting the pH of the latex of the conjugated diene copolymer within the above range, the mechanical stability is improved, and the generation of coarse aggregates during the transfer of the latex of the conjugated diene copolymer can be suppressed, and the viscosity of the latex of the conjugated diene copolymer becomes appropriate, thereby improving the handleability of the latex of the conjugated diene copolymer.

[0086] The sedimentation velocity of the conjugated diene copolymer latex of the present invention, measured using a centrifugal sedimentation particle size distribution analyzer under conditions of a rotation speed of 4000 rpm, a centrifugal acceleration of 2300 G, and a measurement time of 50 minutes, is preferably 1.6 μm / s or more, more preferably 2.0 μm / s or more, and even more preferably 3.0 μm / s or more. Furthermore, when even better wet grip performance is required, the sedimentation velocity is particularly preferably 3.7 μm / s or more, and most preferably 4.0 μm / s or more. A preferred method for adjusting the sedimentation velocity within the above range is, for example, to incorporate a water-soluble polymer into the conjugated diene copolymer latex and to adjust the type, weight-average molecular weight (Mw), and content of the water-soluble polymer. In addition to this method, more preferred methods include adjusting the abundance ratio of each monomer unit in the entire polymer component of the conjugated diene copolymer latex within the above-mentioned preferred range, or adjusting the solids concentration of the conjugated diene copolymer latex within the above-mentioned preferred range. The upper limit of the sedimentation velocity is not particularly limited, but is usually 70 μm / s or less, and preferably 40 μm / s or less.

[0087] <Method for producing latex of conjugated diene copolymer> The latex of the conjugated diene copolymer of the present invention can be obtained, for example, by emulsion polymerization of a monomer mixture containing the above-mentioned monomers. During emulsion polymerization, polymerization secondary materials such as an emulsifier, a polymerization initiator, and a molecular weight modifier can be used.

[0088] The emulsifier used in emulsion polymerization is not particularly limited, but examples thereof include anionic surfactants, nonionic surfactants, cationic surfactants, and amphoteric surfactants, with anionic surfactants being preferred.

[0089] Specific examples of the anionic surfactant used in emulsion polymerization include those mentioned above as the anionic surfactants that can be contained in the latex of the conjugated diene copolymer of the present invention, and the same applies to suitable ones. By using an anionic surfactant as an emulsifier used in emulsion polymerization, the latex of the conjugated diene copolymer of the present invention can contain the anionic surfactant.

[0090] The amount of the emulsifier used in emulsion polymerization is preferably 0.5 to 10 parts by weight, more preferably 1 to 8 parts by weight, based on 100 parts by weight of the total monomers used.

[0091] The polymerization initiator is not particularly limited, but a radical initiator is preferable. Examples of the radical initiator include, but are not particularly limited to, inorganic peroxides such as sodium persulfate, potassium persulfate, ammonium persulfate, potassium perphosphate, and hydrogen peroxide; organic peroxides such as t-butyl peroxide, cumene hydroperoxide, p-menthane hydroperoxide, di-t-butyl peroxide, t-butylcumyl peroxide, acetyl peroxide, isobutyryl peroxide, octanoyl peroxide, dibenzoyl peroxide, 3,5,5-trimethylhexanoyl peroxide, and t-butylperoxyisobutyrate; and azo compounds such as azobisisobutyronitrile, azobis-2,4-dimethylvaleronitrile, azobiscyclohexanecarbonitrile, and methyl azobisisobutyrate. Among these, inorganic peroxides or organic peroxides are preferable, inorganic peroxides are more preferable, and persulfates are particularly preferable. These polymerization initiators may be used alone or in combination of two or more.

[0092] The amount of the polymerization initiator used is preferably 0.01 to 2 parts by weight, more preferably 0.05 to 1.5 parts by weight, based on 100 parts by weight of the total monomers used.

[0093] The molecular weight modifier is not particularly limited, but examples thereof include α-methylstyrene dimer; mercaptans such as t-dodecyl mercaptan, n-dodecyl mercaptan, and octyl mercaptan; halogenated hydrocarbons such as carbon tetrachloride, methylene chloride, and methylene bromide; and sulfur-containing compounds such as tetraethylthiuram disulfide, dipentamethylenethiuram disulfide, and diisopropylxanthogen disulfide; and among these, mercaptans are preferred, with t-dodecyl mercaptan being more preferred. These molecular weight modifiers may be used alone or in combination of two or more.

[0094] The amount of the molecular weight modifier used varies depending on the type, but is preferably 0.1 to 1.5 parts by weight, more preferably 0.2 to 1.0 part by weight, per 100 parts by weight of the total monomers used.

[0095] The emulsion polymerization is usually carried out in water, and the amount of water used is preferably 80 to 500 parts by weight, more preferably 100 to 200 parts by weight, per 100 parts by weight of the total monomers used.

[0096] In emulsion polymerization, if necessary, other polymerization secondary materials may be used, such as a chelating agent, a dispersant, a pH adjuster, an oxygen scavenger, a particle size adjuster, etc., and the type and amount of these materials are not particularly limited.

[0097] Examples of methods for adding the monomers include adding the monomers to be used all at once to a reaction vessel, adding them continuously or intermittently as the polymerization progresses, and adding a portion of the monomers and reacting them to a specific conversion rate, followed by adding the remaining monomers continuously or intermittently to polymerize them. Any of these methods may be used. When the monomers are mixed and added continuously or intermittently, the composition of the mixture may be constant or may be varied. Furthermore, the various monomers to be used may be mixed in advance and then added to the reaction vessel, or each monomer may be added separately to the reaction vessel.

[0098] For example, polymerization may be initiated in a reaction vessel with no high Tg monomer (m-4) or with only a portion of the high Tg monomer (m-4) added, and the reaction may be continued until a specific conversion is reached, after which the remaining high Tg monomer (m-4) may be added continuously or intermittently to carry out polymerization. By such a method, the latex of the conjugated diene copolymer of the present invention can be one containing a conjugated diene copolymer having a low content of the high Tg monomer (m-4) (preferably 10% by weight or less) and a conjugated diene copolymer having a high content of the high Tg monomer (m-4) (preferably more than 10% by weight).

[0099] The polymerization temperature during emulsion polymerization is not particularly limited, but is usually 0 to 95° C., preferably 10 to 90° C., and more preferably 30 to 90° C. The polymerization time is not particularly limited, but is usually about 5 to 40 hours.

[0100] After the polymerization reaction is terminated, if desired, the unreacted monomer may be removed and the solid content concentration and pH may be adjusted.

[0101] Furthermore, various compounding agents such as a surfactant and a crosslinking agent may be added as needed to the latex of the conjugated diene copolymer obtained by the above production method. For example, by mixing various compounding agents such as a crosslinking agent with the latex of the conjugated diene copolymer obtained by the above production method, a latex composition can be produced as the latex of the conjugated diene copolymer.

[0102] The latex (latex composition) of the conjugated diene copolymer of the present invention may be obtained through a concentration treatment or a dilution treatment. The latex (latex composition) of the conjugated diene copolymer of the present invention is preferably obtained through a concentration treatment. The concentration treatment method is not particularly limited, but examples thereof include vacuum distillation, atmospheric distillation, centrifugation, membrane concentration, etc. Among these, a concentration method accompanied by heating is preferred, and vacuum distillation accompanied by heating is more preferred.

[0103] In the concentration method involving heating, the heating temperature is preferably 50° C. to 100° C. In the distillation under reduced pressure, the pressure is preferably 20 kPa to 90 kPa.

[0104] <Dip-molded article> The dip-molded article of the present invention is a molded article made using the latex of the conjugated diene copolymer of the present invention described above. The dip-molded article of the present invention may also be a molded article made using the latex composition described above as the latex of the conjugated diene copolymer. Since the dip-molded article of the present invention is obtained using the latex of the conjugated diene copolymer of the present invention described above, it has excellent resistance to chemical permeation and a good balance of wet grip properties and flexibility.

[0105] The dip-molded article of the present invention may be a film-molded article made of the latex of a conjugated diene copolymer obtained by immersing a dip-molding mold in the latex of the conjugated diene copolymer of the present invention described above, or may be a laminate of a substrate and a polymer layer made of the latex of a conjugated diene copolymer obtained by immersing a substrate in the latex of a conjugated diene copolymer. Hereinafter, a case where the dip-molded article of the present invention is a laminate of a substrate and a polymer layer made of the latex of a conjugated diene copolymer will be described as an example, but the present invention is not limited to such an embodiment.

[0106] The substrate is not particularly limited, but when the dip-molded article of the present invention is used as a protective glove, a fibrous substrate can be suitably used. The fibrous substrate is not particularly limited, but for example, a glove made by weaving a twisted monofilament yarn can be used. The fibers constituting the fibrous substrate are not particularly limited, but natural fibers such as cotton, wool, linen, and sheep's wool, and synthetic fibers such as polyester, polyurethane, acrylic, and nylon can be used as materials. The average thickness of the fibrous substrate is preferably 50 to 3,000 μm, more preferably 100 to 2,000 μm.

[0107] The dip-molded article of the present invention can be produced, for example, by immersing a substrate in the latex of the conjugated diene copolymer of the present invention to form a polymer layer made of the latex of the conjugated diene copolymer on the substrate. The dip-molded article of the present invention can also be produced by using the above-mentioned latex composition as the latex of the conjugated diene copolymer.

[0108] When the substrate is immersed in the latex of the conjugated diene copolymer, it is preferable to immerse the substrate in the latex of the conjugated diene copolymer in a state in which the substrate is previously placed on a molding die having a desired shape.

[0109] The mold for covering the substrate is not particularly limited, and various materials such as porcelain, glass, metal, and plastic can be used. The shape of the mold may be a desired shape according to the shape of the final product. For example, when the dip-molded article of the present invention is used as a protective glove, it is preferable to use various types of molds for gloves, such as molds having a shape from the wrist to the fingertips, as the mold for covering the substrate.

[0110] Furthermore, before immersing the substrate in the latex of the conjugated diene copolymer, it is preferable to first immerse the substrate in a coagulant solution to adhere the coagulant solution to the substrate. In this case, it is preferable to immerse the substrate in the coagulant solution while the substrate is first placed over a mold of the desired shape. Examples of molds of the desired shape include those described above. Furthermore, after adhering the coagulant solution to the substrate, it is preferable to remove the solvent contained in the coagulant solution by drying. The drying temperature is not particularly limited and may be selected depending on the solvent used, but is preferably 10 to 80°C, more preferably 15 to 70°C. The drying time is not particularly limited, but is preferably 600 to 1 second, more preferably 300 to 5 seconds.

[0111] Next, the substrate with the coagulant solution attached is placed over a molding die of a desired shape and immersed in the latex of a conjugated diene copolymer, thereby coagulating the latex of the conjugated diene copolymer and adhering a polymer layer made of the latex of the conjugated diene copolymer onto the substrate.

[0112] After the substrate is immersed in the latex of the conjugated diene copolymer, it is preferable to dry it. The drying temperature is not particularly limited, but is preferably 10 to 80° C., more preferably 15 to 80° C. The drying time is not particularly limited, but is preferably 120 minutes to 5 seconds, more preferably 60 minutes to 10 seconds.

[0113] In addition, when a latex of a conjugated diene copolymer containing a crosslinking agent (latex composition) is used, the latex of a conjugated diene copolymer may be aged in advance (also referred to as pre-vulcanization).

[0114] The temperature conditions for aging are not particularly limited, but are preferably 20 to 50° C. Furthermore, the aging time is preferably 4 hours or more and 120 hours or less, more preferably 24 hours or more and 72 hours or less, from the viewpoint of preventing peeling between the substrate and the polymer layer and improving the mechanical properties of the polymer layer.

[0115] Next, it is preferable to heat the latex of the conjugated diene copolymer attached to the substrate, thereby crosslinking the polymer components contained in the latex of the conjugated diene copolymer.

[0116] The heating temperature for crosslinking is preferably 60 to 160°C, more preferably 80 to 150°C. By setting the heating temperature within the above range, the time required for the crosslinking reaction can be shortened, thereby improving the productivity of dip-molded articles, and oxidative degradation of the polymer component due to excessive heating can be suppressed, thereby improving the physical properties of the obtained dip-molded articles. The heating time for crosslinking can be appropriately selected depending on the heating temperature, but is usually 5 to 120 minutes.

[0117] It is preferable to remove water-soluble impurities (such as emulsifiers, water-soluble polymers, and coagulants) from the polymer layer of the dip-molded article obtained in this manner, by immersing the polymer layer formed on the substrate in warm water at 20 to 80°C for about 0.5 to 60 minutes, as necessary.

[0118] After immersion in warm water, drying may be further performed. The drying temperature and drying time at this time are not particularly limited, but may be the same as the drying temperature and drying time in the drying step after immersion in the latex of the conjugated diene copolymer described above.

[0119] Then, after forming a polymer layer on the substrate while the substrate is placed over the mold as described above, the dip-molded article can be obtained by removing the substrate from the mold (or demolding). Methods for removing the substrate from the mold include peeling it off by hand, or by using water pressure or compressed air.

[0120] Before or after detaching the dip-molded article from the mold, it may be subjected to a further heat treatment (post-crosslinking step) at a temperature of 60 to 120° C. for 10 to 120 minutes. After detaching the dip-molded article from the mold, a surface treatment layer may be formed on the inner and / or outer surfaces of the dip-molded article by a chlorination treatment, a coating treatment, or the like.

[0121] As a method for obtaining a dip-molded article, a method of foaming a latex for dip-molding other than the latex of the conjugated diene copolymer of the present invention and dip-molding the foamed article may be considered. However, such a method may result in a dip-molded article having poor wet grip properties and poor flexibility.

[0122] Another possible method for obtaining a dip-molded article is to form a dip layer using a dip-molding latex other than the latex of the conjugated diene copolymer of the present invention, then adhere a water-soluble metal salt to the surface of the dip layer, and, if necessary, dry, crosslink, or the like, and then wash off the water-soluble metal salt adhered to the surface. However, such a method may result in the obtained dip-molded article having poor flexibility or poor resistance to chemical permeation. Furthermore, there is also a risk that components derived from the water-soluble metal salt (e.g., metal components) may remain on the surface of the dip-molded article.

[0123] In addition, these methods require a foaming step, a step of adhering a water-soluble metal salt, and a step of washing away the water-soluble metal salt, which may reduce the production efficiency of dip-molded articles.

[0124] By using the latex of the conjugated diene copolymer of the present invention, it is possible to obtain the dip-molded article of the present invention, which has excellent resistance to chemical permeation and a well-balanced wet grip property and flexibility, without undergoing a foaming process, a process of adhering a water-soluble metal salt, and a process of washing away the water-soluble metal salt. Furthermore, by using the latex of the conjugated diene copolymer of the present invention, it is possible to obtain the dip-molded article of the present invention, which has excellent resistance to chemical permeation and a well-balanced wet grip property and flexibility, without undergoing a process of adding other polymers. Therefore, by using the latex of the conjugated diene copolymer of the present invention, it is possible to produce the dip-molded article of the present invention with high production efficiency while reducing components derived from water-soluble metal salts (e.g., metal components) on the surface of the dip-molded article.

[0125] In the dip-molded article of the present invention, the polymer layer made of the latex of the conjugated diene copolymer of the present invention has a thickness of preferably 0.05 to 1.0 mm, more preferably 0.06 to 0.8 mm, and even more preferably 0.07 to 0.7 mm.

[0126] Furthermore, when the dip-formed article of the present invention includes a substrate and a polymer layer, the thickness of the laminate including the substrate and the polymer layer is preferably 0.1 to 10 mm, more preferably 0.4 to 2.0 mm, and even more preferably 0.5 to 1.1 mm.

[0127] The dip-molded article of the present invention is excellent in flexibility, wet grip property, abrasion resistance, and chemical permeation resistance, and can be suitably used, for example, for glove applications, particularly for protective gloves. While the above description exemplifies the case where the dip-molded article of the present invention is a laminate of a substrate and a polymer layer comprising the latex of the conjugated diene copolymer of the present invention, as mentioned above, the present invention is not limited to such an embodiment, and it is of course also possible to form a film-molded article comprising the latex of the conjugated diene copolymer of the present invention by immersing a dip-molding mold in the latex of the conjugated diene copolymer of the present invention.

[0128]

[0013] Incidentally, gloves made of only a polymer layer without a substrate are thin and therefore rarely have a problem with wet gripping property. On the other hand, gloves made of a laminate of a substrate and a polymer layer have a particular problem that the thickness of the glove (the total thickness of the laminate of the substrate and the polymer layer) tends to be large and the wet gripping property tends to be insufficient. By using the latex of the conjugated diene copolymer of the present invention, gloves made of a laminate of a substrate and a polymer layer made of the latex of the conjugated diene copolymer of the present invention can be made excellent in flexibility, wet gripping property, abrasion resistance, and chemical permeation resistance.

[0129] The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited to these examples. Note that "parts" and "%" are by weight unless otherwise specified. Various measurements were carried out according to the following methods.

[0130] <Solid content concentration> 2 g of sample (weight: X2) was weighed out onto an aluminum dish (weight: X1) and dried in a hot air dryer at 105°C for 2 hours. After cooling in a desiccator, the sample was weighed together with the aluminum dish (weight: X3) and the solid content concentration was calculated according to the following formula: Solid content concentration (wt%) = (X3 - X1) x 100 / X2

[0131] <Ratio of each monomer unit in the entire polymer components in the latex of conjugated diene copolymer> The ratio of each monomer unit in the entire polymer components in the latex of conjugated diene copolymer was calculated from the amount of each monomer used in producing the latex of conjugated diene copolymer.

[0132] <Presence or Absence of Aggregate Particles Aggregated by Carboxymethyl Cellulose> The dip-molding latex composition was observed using a digital microscope (manufactured by Keyence Corporation, product name "VHX-500") to determine whether aggregate particles were formed.

[0133] <Sedimentation Rate> The sedimentation rate of each dip-molding latex composition was measured using a centrifugal sedimentation particle size distribution analyzer (manufactured by LUM Corporation, product name "Lumisizer") under conditions of a rotation speed of 4000 rpm, a centrifugal acceleration of 2300 G, and a measurement time of 50 minutes.

[0134] <Productivity of dip molding latex composition> The productivity of the dip molding latex composition was evaluated according to the following criteria: A: The dip molding latex composition was obtained using only one type of polymer latex B: The dip molding latex composition was obtained using two types of polymer latex C: The dip molding latex composition was obtained using three or more types of polymer latex It can be determined that the more the dip molding latex composition is obtained using fewer types of polymer latex, the more excellent the productivity of the dip molding latex composition.

[0135] <Flexibility of Protective Gloves> The flexibility of the protective gloves was evaluated by a sensory test. Specifically, the following commercially available protective gloves A and B were prepared as control samples and evaluated according to the following procedure. Protective glove A: A dip-molded product (laminate) having a substrate and a polymer layer, obtained without undergoing a process of foaming the polymer layer or a surface treatment process after forming the dip layer. Protective glove A has excellent flexibility but no wet gripping ability. Protective glove B: A dip-molded product (laminate) having a substrate and a polymer layer, obtained through a surface treatment process after forming the dip layer. Protective glove B has relatively high wet gripping ability. Two subjects used the protective gloves obtained in the Examples and Comparative Examples, Protective Glove A, and Protective Glove B, and judged whether the flexibility of the protective gloves obtained in the Examples and Comparative Examples was better, equal to, or worse than that of Protective Glove A and Protective Glove B, and scored them based on the following criteria. The flexibility of the protective gloves was then evaluated by averaging the scores of the two subjects. 5 Has better flexibility than protective glove A 4 Has flexibility equivalent to protective glove A 3 Has flexibility intermediate between the flexibility of protective glove A and protective glove B 2 Has flexibility equivalent to protective glove B 1 Has flexibility inferior to protective glove B The higher the value, the better the flexibility is judged to be.

[0136] <Wet Grip Property of Protective Gloves> The protective gloves obtained in each Example and Comparative Example were washed with running water for 3 minutes to prepare protective gloves for wet grip property testing. Metal molds with different weights ranging from 0.5 kg to 15.0 kg in 0.5 kg increments were prepared. Three workers were then asked to wear protective gloves and lift the dry metal molds in order of weight, starting with the lightest, and the maximum weight (W1 (kg)) that they could lift was determined for each of the three workers. Next, test oil IRM903 was applied to the metal molds. The three workers were then asked to wear protective gloves and lift the metal molds with test oil IRM903 applied in order of weight, starting with the lightest, and the maximum weight (W2 (kg)) that they could lift was determined for each of the three workers. The scores calculated for each of the three workers using the following formula were then arithmetically averaged to calculate an average score for evaluation. The higher the score, the greater the maximum weight that could be lifted, and the better the wet grip property. (Score) = 100 x W2 (kg) / W1 (kg)

[0137] <Abrasion Resistance of Protective Gloves> Abrasion tests were conducted in accordance with the method described in EN388 using a Martindale abrasion tester (product name "STM633", manufactured by SATRA). Specifically, the protective gloves were repeatedly rubbed while applying a predetermined load, and the number of rubs until breakage was obtained. The number of rubs until breakage was evaluated and categorized into levels from LEVEL 0 to LEVEL 4. LEVEL 4: Number of revolutions 8,000 or more LEVEL 3: Number of revolutions 2,000 or more but less than 8,000 LEVEL 2: Number of revolutions 500 or more but less than 2,000 LEVEL 1: Number of revolutions 100 or more but less than 500 LEVEL 0: Number of revolutions less than 100 It can be said that the higher the level, the more excellent the abrasion resistance.

[0138] <Resistance to Chemical Liquid Permeation of Protective Gloves> The amount of oil permeation through protective gloves was measured using the following procedure. (1) A portion of the index finger was cut out from a protective glove (laminate) to obtain a finger-shaped test piece. (2) Test oil IRM903 was placed in an aluminum cup. (3) Filter paper (weight: W1) was placed inside the test piece, and the inner surface of the portion of the test piece corresponding to the finger pad (a portion with an area of ​​approximately 2 to 5 cm2) was brought into close contact with the filter paper. (4) The test piece containing the filter paper was placed in the aluminum cup containing the test oil IRM903, and the outer surface of the portion corresponding to the finger pad (the portion where the filter paper was brought into close contact in (3)) was brought into contact with the test oil IRM903. (5) After leaving it to stand for 24 hours, the filter paper was removed from the test piece, and the weight of the filter paper after the test (W2) was measured. (6) The amount of test oil IRM903 permeating through the test piece (W2 - W2) was calculated. (7) The middle finger, ring finger, and little finger portions of the protective glove (laminate) were cut out, respectively, to obtain three more test pieces. The amount of test oil IRM903 that had permeated through each of the obtained test pieces was determined in the same manner as above. (8) The average amount of test oil IRM903 that had permeated through the test pieces for a total of four test pieces was determined and used as the oil permeation amount of the protective glove. It can be determined that the smaller the oil permeation amount, the better the oil permeation resistance and chemical permeation resistance.

[0139] Example 1 (Production of Conjugated Diene Copolymer Latex (A-1)) A polymerization reactor was charged with 52.2 parts of 1,3-butadiene as the conjugated diene monomer (m-1), 22.8 parts of acrylonitrile as the α,β-ethylenically unsaturated nitrile monomer (m-2), 5 parts of methacrylic acid as the carboxyl group-containing ethylenically unsaturated monomer (m-3), 1.41 parts of sodium dodecylbenzenesulfonate (compound (a)), 3 parts of sodium alkyldiphenyl ether disulfonate (compound (b1)), 0.5 parts of β-naphthalenesulfonic acid formalin condensate sodium salt, 0.7 parts of t-dodecyl mercaptan, 132 parts of ion-exchanged water, 0.3 parts of potassium persulfate, and 0.05 parts of ethylenediaminetetraacetic acid sodium salt, and polymerization was carried out while maintaining the polymerization temperature at 30 to 40°C. Next, when the polymerization conversion rate reached 50% by weight based on the total amount of monomers charged into the polymerization reactor, 10 parts of acrylonitrile were further charged into the polymerization reactor, and the polymerization was continued while maintaining the polymerization temperature at 30 to 40°C. Furthermore, when the polymerization conversion rate reached 90% by weight based on the total amount of monomers charged into the polymerization reactor, 10 parts of styrene as a high Tg monomer (m-4) were further charged into the polymerization reactor, and the polymerization was continued while maintaining the polymerization temperature at 30 to 40°C. Then, the reaction was continued until the polymerization conversion rate reached 96% by weight based on the total amount of monomers charged into the polymerization reactor, thereby obtaining a polymerization solution. Then, by adjusting the pH and solid content concentration, a conjugated diene copolymer latex (A-1) having a solid content concentration of 40% by weight and a pH of 8 was obtained. The content of each anionic surfactant in the obtained latex (A-1) of conjugated diene copolymer per 100 parts by weight of the polymer component was approximately the same as the amount of each anionic surfactant used per 100 parts by weight of the monomer used in the polymerization. A portion of the obtained latex (A-1) of conjugated diene copolymer was sampled, and the abundance ratio of each monomer unit in the entire polymer component in the latex (A-1) of conjugated diene copolymer was determined by the above-mentioned method. The results are shown in Table 1.

[0140] (Preparation of aqueous dispersion of colloidal sulfur) 1.0 part of colloidal sulfur (manufactured by Hosoi Chemical Industry Co., Ltd.), 0.5 part of a dispersant (manufactured by Kao Corporation, trade name "Demol N"), 0.0015 part of a 5 wt % aqueous potassium hydroxide solution (manufactured by Wako Pure Chemical Industries, Ltd.), and 1.0 part of water were pulverized and stirred in a ball mill for 48 hours to prepare an aqueous dispersion of colloidal sulfur with a solids concentration of 50 wt %.

[0141] (Preparation of aqueous dispersion of zinc dibutyldithiocarbamate, aqueous dispersion of zinc oxide, and aqueous dispersion of titanium oxide) An aqueous dispersion of zinc dibutyldithiocarbamate having a solids concentration of 50 wt %, an aqueous dispersion of zinc oxide having a solids concentration of 50 wt %, and an aqueous dispersion of titanium oxide having a solids concentration of 50 wt % were prepared in the same manner as above, except that zinc dibutyldithiocarbamate (manufactured by Ouchi Shinko Chemical Industry Co., Ltd.), zinc oxide (manufactured by Seido Chemical Industry Co., Ltd.), and titanium oxide, respectively, were used instead of colloidal sulfur.

[0142] (Preparation of dip molding latex composition) The aqueous dispersions of each compounding ingredient prepared above were added to the latex mixture so that, based on the solid content, 1.0 part of colloidal sulfur, 1.0 part of zinc dibutyldithiocarbamate, 1.5 parts of zinc oxide, and 3.0 parts of titanium oxide were added per 100 parts of the polymer component in the conjugated diene copolymer latex (A-1). When adding the aqueous dispersions of each compounding ingredient, a predetermined amount was slowly added while the latex mixture was being stirred. After the compounding ingredients were uniformly mixed, carboxymethyl cellulose (manufactured by Daicel Corporation, trade name "Daicel 2200", weight average molecular weight: 550,000) was added as a water-soluble polymer until the viscosity reached 3,000 cps, to obtain a dip molding latex composition with a solid content of 40% by weight. The obtained latex composition for dip molding was measured and evaluated for the presence or absence of aggregate particles aggregated by carboxymethyl cellulose, the settling rate, and the productivity of the latex composition for dip molding according to the above-mentioned methods. The results are shown in Table 1.

[0143] (Preparation of Coagulant Solution) A coagulant solution was prepared by dissolving calcium nitrate as a coagulant in methanol at a ratio of 2.0 wt %.

[0144] (Production of Protective Gloves) First, the dip-molding latex composition obtained above was aged (also referred to as pre-vulcanization) at 30°C for 48 hours. Next, a ceramic glove mold covered with a glove-shaped fiber substrate (material: nylon, linear density: 300 denier, gauge: 13 gauge, thickness: 0.8 mm) was immersed in the coagulant solution prepared above for 5 seconds, removed from the coagulant solution, and dried at 30°C for 1 minute. The ceramic glove mold was then immersed in the aged dip-molding latex composition for 5 seconds, removed from the aged dip-molding latex composition, and dried at 25°C for 20 minutes to form a dip layer on the fiber substrate. The ceramic glove mold with the dip layer formed thereon was then heat-treated at 110°C for 30 minutes to crosslink the polymer in the dip layer, forming a polymer layer. Next, the fiber substrate with the polymer layer formed thereon was peeled off from the ceramic glove mold to obtain a protective glove (dip-molded product). The thickness of the polymer layer in the obtained protective glove was 0.15 mm, and the thickness of the protective glove (the total thickness of the laminate including the substrate and the polymer layer) was 1.0 mm. The obtained protective glove was evaluated for flexibility, wet grip property, abrasion resistance, and chemical permeation resistance. The results are shown in Table 1.

[0145] Examples 2 to 6, Comparative Examples 1 and 2 Conjugated diene copolymer latexes (A-2) to (A-8) having a solids concentration of 40% by weight and a pH of 8 were obtained in the same manner as in Example 1, except that the timing, type, and amount of each monomer used, and the type and amount of each anionic surfactant were changed as shown in Table 1. The content of each anionic surfactant per 100 parts by weight of the polymer component in the obtained conjugated diene copolymer latexes (A-2) to (A-8) was approximately the same as the amount of each anionic surfactant used per 100 parts by weight of the monomer used in the polymerization. Protective gloves (dip-molded articles) were obtained in the same manner as in Example 1, except that the conjugated diene copolymer latexes (A-2) to (A-8) obtained above were used instead of the conjugated diene copolymer latex (A-1). The thickness of the polymer layer in the obtained protective gloves was 0.15 mm, and the thickness of the protective gloves (thickness of the entire laminate including the substrate and the polymer layer) was 1.0 mm. The conjugated diene copolymer latexes (A-2) to (A-8), the dip-molding latex composition, and the protective gloves (dip-molded articles) were measured and evaluated in the same manner as in Example 1. The results are shown in Table 1.

[0146] Comparative Example 3 A latex (A-9) of a conjugated diene copolymer having a solid content of 40% by weight and a pH of 8 was obtained in the same manner as in Example 1, except that the types and amounts of the monomers used at the start of polymerization, the types and amounts of the monomers added during polymerization, and the amount of anionic surfactant were changed as shown in Table 1. The contents of the anionic surfactants per 100 parts by weight of the polymer component in the obtained latex (A-9) of a conjugated diene copolymer were approximately the same as the amounts of the anionic surfactants used per 100 parts by weight of the monomers used in the polymerization.

[0147] The conjugated diene copolymer latex (A-9) obtained above and a polystyrene resin latex (the glass transition temperature (Tg) of the polystyrene resin was 85°C, the weight average particle diameter of the polystyrene resin particles was 300 nm, and the surface tension of the polystyrene resin latex at 25°C was 43 mN / m) were mixed in a weight ratio such that the amount of polystyrene resin in the polystyrene resin latex was 30 parts relative to 70 parts of the polymer components in the conjugated diene copolymer latex (A-9), thereby obtaining a latex mixture. Protective gloves (dip-molded articles) were obtained in the same manner as in Example 1, except that the latex mixture obtained above was used instead of the conjugated diene copolymer latex (A-1). The thickness of the polymer layer in each of the obtained protective gloves was 0.15 mm, and the thickness of the protective glove (the thickness of the entire laminate including the substrate and the polymer layer) was 1.0 mm. The conjugated diene copolymer latex (A-8) and the protective glove (dip-molded product) were measured and evaluated in the same manner as in Example 1. The results are shown in Table 1.

[0148]

[0149] As shown in Table 1, when a latex of a conjugated diene copolymer obtained by copolymerizing a conjugated diene monomer (m-1), an α,β-ethylenically unsaturated nitrile monomer (m-2), a carboxyl group-containing ethylenically unsaturated monomer (m-3), and a high Tg monomer (m-4) was used, the resulting dip-molded article had excellent flexibility, wet grip properties, abrasion resistance, and chemical solution permeation resistance (Examples 1 to 6).

[0150] On the other hand, when the latex of the conjugated diene copolymer was obtained without using the high Tg monomer (m-4), the obtained dip-molded article had poor wet grip properties (Comparative Examples 1 and 2).

[0151] Furthermore, when a latex mixture obtained by mixing a latex of a copolymer obtained by copolymerizing a conjugated diene monomer (m-1), an α,β-ethylenically unsaturated nitrile monomer (m-2), and a carboxyl group-containing ethylenically unsaturated monomer (m-3) with a latex of a homopolymer of a high Tg monomer (m-4) obtained by copolymerizing a high Tg monomer (m-4) was used, the dip-molded article obtained had poor resistance to chemical liquid permeation (Comparative Example 3).

Claims

1. A latex of a conjugated diene copolymer obtained by copolymerizing a conjugated diene monomer (m-1), an α,β-ethylenically unsaturated nitrile monomer (m-2), a carboxyl group-containing ethylenically unsaturated monomer (m-3), and a high Tg monomer (m-4), The high Tg monomer (m-4) is a monomer that, when made into a homopolymer, gives a glass transition temperature (Tg) of more than 10°C, and is a monomer other than the conjugated diene monomer (m-1), the α,β-ethylenically unsaturated nitrile monomer (m-2), and the carboxyl group-containing ethylenically unsaturated monomer (m-3).

2. 2. The latex of a conjugated diene copolymer according to claim 1, wherein, in the entire polymer components in the latex of the conjugated diene copolymer, an abundance ratio of units of the conjugated diene monomer (m-1) is 20 to 70% by weight, an abundance ratio of units of the α,β-ethylenically unsaturated nitrile monomer (m-2) is 10 to 50% by weight, an abundance ratio of units of the carboxyl group-containing ethylenically unsaturated monomer (m-3) is 0.1 to 10% by weight, and an abundance ratio of units of the high Tg monomer (m-4) is 3 to 30% by weight.

3. 3. The latex of a conjugated diene copolymer according to claim 1, wherein the conjugated diene monomer (m-1) is 1,3-butadiene or isoprene.

4. 3. The latex of conjugated diene copolymer according to claim 1, wherein the high Tg monomer (m-4) is an aromatic vinyl monomer.

5. 3. The latex of the conjugated diene copolymer according to claim 1, further comprising two or more anionic surfactants.

6. 3. The conjugated diene copolymer latex according to claim 1, wherein the aggregate particles are dispersed in water and are formed by aggregating with the water-soluble polymer.

7. 3. The latex of conjugated diene copolymer according to claim 1 or 2, which has a sedimentation velocity of 1.6 μm / s or more when measured using a centrifugal sedimentation particle size distribution analyzer under conditions of a rotation speed of 4000 rpm, a centrifugal acceleration of 2300 G, and a measurement time of 50 minutes.

8. 3. The latex of the conjugated diene copolymer according to claim 1, which is a latex composition for dip molding.

9. A dip-molded article obtained by using the latex of the conjugated diene copolymer according to claim 1 or 2.

10. A dip-molded article obtained by immersing a substrate in the latex of the conjugated diene copolymer according to claim 1 or 2.

11. The dip-formed article according to claim 10, wherein the substrate is a fibrous substrate.