WO2019151020A1 - Foam rubber latex - Google Patents

Abstract

Provided is a foam rubber latex containing particles of a nitrile group-containing conjugated diene-based copolymer, wherein: the nitrile group-containing conjugated diene-based copolymer contains an ethylenically unsaturated nitrile monomer unit and a conjugated diene monomer unit; the content ratio of the ethylenically unsaturated nitrile monomer unit is 40-60 weight%; and the volume cumulative particle size d10 of the particles in a volume-based particle size distribution is 130 nm or greater.

Description

Latex for foam rubber

The present invention relates to a latex for foam rubber used in the production of foam rubber.

Foam rubber (rubber foam) manufactured using latex for foam rubber is used for various purposes as a mattress, puff (cosmetic sponge), roll, impact absorber and the like. Among such foam rubber applications, particularly foam rubber used for puffs is required to have good oil resistance and a soft feel.

For example, Patent Document 1 discloses that 30 to 45% by weight of a cyano group-containing ethylenically unsaturated monomer unit (a1), 55 to 70% by weight of a conjugated diene monomer unit (a2), and a cyano group-containing ethylenically unsaturated monomer unit (a2). A latex (A) of a copolymer (a) comprising 0 to 15% by weight of a unit (a3) of another ethylenically unsaturated monomer copolymerizable with a saturated monomer and a conjugated diene monomer, and cyano 45 to 65% by weight of group-containing ethylenically unsaturated monomer unit (b1), 35 to 55% by weight of conjugated diene monomer unit (b2), and cyano group-containing ethylenically unsaturated monomer and conjugated diene monomer Latex (B) of copolymer (b) comprising 0 to 20% by weight of other ethylenically unsaturated monomer units (b3) copolymerizable with the polymer (provided that cyano group-containing ethylenically unsaturated monomer) The amount of the body unit (b1) is cyano group-containing ethyl The amount of the unsaturated unsaturated monomer unit (a1) is 5% by weight or more). The weight ratio of the copolymer (a) to the copolymer (b) ((copolymer (a) / copolymer There is disclosed a copolymer rubber latex composition for foam rubber obtained by mixing the polymer (b)) at a ratio of 20/80 to 80/20.

International Publication No. 2009/145209

However, there is a need for a technique for further improving handling properties and moldability, and further improving the swelling resistance of the resulting foam rubber to cosmetics and the wear resistance when the cosmetics are included.

The present invention has been made in view of such a situation, and is excellent in handling property and moldability, and can produce a foam rubber that hardly deforms even when it contains a cosmetic and has little wear. An object is to provide a latex for foam rubber.

As a result of earnest research to achieve the above object, the present inventors have used particles of a nitrile group-containing conjugated diene copolymer containing a relatively large amount of ethylenically unsaturated nitrile monomer units, and The inventors have found that the above object can be achieved by appropriately adjusting the volume cumulative particle diameter d10 of the particles, and have completed the present invention.

That is, according to the present invention, a latex for foam rubber containing particles of a nitrile group-containing conjugated diene copolymer, wherein the nitrile group-containing conjugated diene copolymer is an ethylenically unsaturated nitrile monomer Units and a conjugated diene monomer unit, the content of the ethylenically unsaturated nitrile monomer unit is 40 to 60% by weight, and the volume cumulative particle diameter d10 in the volume-based particle size distribution of the particles However, a latex for foam rubber having a thickness of 130 nm or more is provided.

In the latex for foam rubber of the present invention, the content of the ethylenically unsaturated nitrile monomer unit is preferably 45 to 55% by weight.
In the latex for foam rubber of the present invention, the volume cumulative particle size d50 in the volume-based particle size distribution of the particles is preferably 420 to 1500 nm.
The latex for foam rubber of the present invention preferably has a solid content concentration of 60% by mass or more.
The latex for foam rubber of the present invention preferably has a viscosity of 3200 mPa · s or less when measured using a B-type viscometer under conditions of a temperature of 25 ° C., a rotation speed of 60 rpm, and a rotation time of 60 seconds.
It is preferable that the latex for foam rubber of the present invention further contains a crosslinking agent.
Moreover, according to this invention, the foam rubber obtained from said latex for foam rubber is provided.

According to the present invention, it is possible to provide a latex for foam rubber that is excellent in handling properties and moldability, and that is capable of producing a foam rubber that is less likely to be deformed even when a cosmetic is included, and that has little wear.

<Latex for foam rubber>
The latex for foam rubber of the present invention contains particles of a nitrile group-containing conjugated diene copolymer.

Nitrile group-containing conjugated diene copolymer A nitrile group-containing conjugated diene copolymer is a copolymer containing an ethylenically unsaturated nitrile monomer unit and a conjugated diene monomer unit, in addition to these, Other ethylenically unsaturated monomer units formed by ethylenically unsaturated nitrile monomers and other ethylenically unsaturated monomers copolymerizable with conjugated diene monomers, used as necessary You may contain.

The ethylenically unsaturated nitrile monomer is not particularly limited as long as it is an ethylenically unsaturated monomer containing a nitrile group. For example, acrylonitrile, methacrylonitrile, fumaronitrile, α-chloroacrylonitrile, α-cyanoethylacrylonitrile Etc. Of these, acrylonitrile and methacrylonitrile are preferable, and acrylonitrile is more preferable. These ethylenically unsaturated nitrile monomers can be used alone or in combination of two or more.

In the nitrile group-containing conjugated diene copolymer, the content of the ethylenically unsaturated nitrile monomer unit formed by the ethylenically unsaturated nitrile monomer is 40 to 60% by weight, preferably 45 to 55% by weight. By making the content ratio of the ethylenically unsaturated nitrile monomer unit in the above range, excellent handling properties and moldability can be obtained, and the resulting foam rubber is hard to be deformed and worn even when cosmetics are included. Can be reduced. If the content ratio of the ethylenically unsaturated nitrile monomer unit is too small, the foam rubber obtained is easily deformed and easily worn when it contains a cosmetic. When there is too much content rate of an ethylenically unsaturated nitrile monomer unit, the foam rubber obtained will become hard too much and a touch feeling will deteriorate easily.

Examples of the conjugated diene monomer include 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, 2-ethyl-1,3-butadiene, 1,3-pentadiene and chloroprene. It is done. Of these, 1,3-butadiene and isoprene are preferable. These conjugated diene monomers can be used alone or in combination of two or more.

The content ratio of the conjugated diene monomer unit formed by the conjugated diene monomer in the nitrile group-containing conjugated diene copolymer is preferably 40 to less than 60% by weight, more preferably 45 to 55% by weight. %. By making the content ratio of the conjugated diene monomer unit within the above range, more excellent handling properties and moldability can be obtained, and the resulting foam rubber is less likely to be deformed and more worn even when cosmetics are included. Can be reduced.

Examples of other ethylenically unsaturated monomers copolymerizable with ethylenically unsaturated nitrile monomers and conjugated diene monomers include (meth) acrylic acid, (anhydrous) maleic acid, fumaric acid, itaconic acid Ethylenically unsaturated carboxylic acids such as methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, lauryl (meth) acrylate, mono- or dimethyl maleate, mono-fumaric acid Or mono- or dialkyl ester of ethylenically unsaturated carboxylic acid such as diethyl, mono or di-n-butyl fumarate, mono- or di-n-butyl itaconic acid; ethylenic such as methoxy acrylate, ethoxy acrylate, methoxy ethoxy ethyl acrylate Unsaturated carboxylic acid Xyalkyl ester; (meth) acrylate having a hydroxyalkyl group such as 2-hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, hydroxybutyl (meth) acrylate, etc .; glycidyl (meth) acrylate; (meth) acrylamide, N -(Meth) acrylic acid amides and derivatives thereof such as methylol (meth) acrylamide and N-butoxymethyl (meth) acrylamide; acrylates having amino groups such as dimethylaminomethyl acrylate and diethylaminomethyl acrylate; styrene, α-methylstyrene, Aromatic vinyl monomers such as vinyl toluene and chlorostyrene; α-olefins such as ethylene and propylene; non-conjugated diene monomers such as dicyclopentadiene and vinyl norbornene Rukoto can. These monomers can be used alone or in combination of two or more. In the nitrile group-containing conjugated diene copolymer, the content of other monomer units formed by other ethylenically unsaturated monomers is preferably 40% by weight or less, more preferably 30% by weight. % Or less, more preferably 20% by weight or less. By making the content ratio of other monomer units in the above range, more excellent handling properties and moldability can be obtained, and the resulting foam rubber is more resistant to deformation and more worn even when cosmetics are included. Can be reduced.

The particles contained in the latex for foam rubber have a volume cumulative particle diameter d10 (particle diameter at which the cumulative volume calculated from the small diameter side in the volume-based particle diameter distribution is 10%) is 130 nm or more, preferably 140 nm or more, More preferably, it is 150 nm or more and may be 250 nm or less. By setting the volume cumulative particle diameter d10 of the particles within the above range, excellent handling properties and moldability can be obtained, and the foam rubber obtained is hardly deformed even when cosmetics are included, and wear is low. be able to. When the volume cumulative particle size d10 is too small, the latex for foam rubber is inferior in handling property and moldability.

Further, the particles contained in the latex for foam rubber have a volume cumulative particle size d50 (particle size at which the cumulative volume is 50% in the volume-based particle size distribution), preferably 420 to 1500 nm, more preferably 460 to 1250 nm, More preferably, it is 500 to 1000 nm. By setting the volume cumulative particle size d50 in the above range, more excellent handling properties and moldability can be obtained, and the foam rubber obtained is less likely to be deformed even when cosmetics are included, and has less wear. can do.

The solid content concentration of the latex for foam rubber is preferably 50 to 70% by weight or more, more preferably 57% by weight or more, and further preferably 60% by weight or more. By making the solid content concentration within the above range, more excellent handling properties and moldability can be obtained, and the foam rubber obtained should be more resistant to deformation and less wear even when cosmetics are included. Can do. The method of controlling the solid content concentration of the foam rubber latex within the above range is not particularly limited, and examples thereof include a method of concentrating the foam rubber latex so as to have a desired solid content concentration. .

The viscosity of the latex for foam rubber is preferably 3200 mPa · s or less, more preferably 100 to 100, when measured using a B-type viscometer under the conditions of a temperature of 25 ° C., a rotation speed of 60 rpm, and a rotation time of 60 seconds. 2500 mPa · s, more preferably 130 to 2000 mPa · s. By setting the viscosity within the above range, more excellent handling properties and moldability can be obtained, and the foam rubber obtained can be made more resistant to deformation and less worn even when cosmetics are included. .

The latex for foam rubber is obtained by, for example, copolymerizing a monomer constituting the nitrile group-containing conjugated diene copolymer contained in the latex for foam rubber by an emulsion polymerization method. It can be manufactured by a process for adjusting the cumulative particle size, a manufacturing method for concentration, and the like.

A conventionally known method can be employed as the emulsion polymerization method. For example, when emulsion polymerization is carried out on a monomer mixture containing the above-mentioned monomers, emulsifiers (surfactants), polymerization initiators, chelating agents, oxygen scavengers, molecular weight regulators, etc., which are usually used. The polymerization auxiliary material can be used. The method for adding these polymerization auxiliary materials is not particularly limited, and any method such as an initial batch addition method, a divided addition method, or a continuous addition method may be used.

The emulsifier is not particularly limited, and examples thereof include an anionic emulsifier and a nonionic emulsifier. Examples of the anionic emulsifier include fatty acid salts such as potassium beef tallow fatty acid, partially hydrogenated beef tallow fatty acid potassium, potassium oleate, sodium oleate; potassium rosinate, sodium rosinate, hydrogenated potassium rosinate, and hydrogenated sodium rosinate Resin acid salts such as alkylbenzene sulfonates such as sodium dodecylbenzene sulfonate. Examples of nonionic emulsifiers include polyethylene glycol ester type and pluronic type emulsifiers such as block copolymers of ethylene oxide and propylene oxide. Among these, anionic emulsifiers are preferable, fatty acid salts are more preferable, and potassium oleate and sodium oleate are particularly preferable. Moreover, these emulsifiers can be used individually or in combination of 2 or more types. The amount of the emulsifier used is preferably 0.5 to 5 parts by weight with respect to 100 parts by weight of the monomer mixture.

The polymerization initiator is not particularly limited, and examples thereof include inorganic peroxides such as sodium persulfate, potassium persulfate, ammonium persulfate, potassium perphosphate, and hydrogen peroxide; diisopropylbenzene hydroperoxide, cumene hydroperoxide, t-butyl hydroperoxide, 1,1,3,3-tetramethylbutyl hydroperoxide, 2,5-dimethylhexane-2,5-dihydroperoxide, di-t-butyl peroxide, di-α- Organic peroxides such as cumyl peroxide, acetyl peroxide, isobutyryl peroxide, benzoyl peroxide, octanoyl peroxide, 3,5,5-trimethylhexanoyl peroxide; azobisisobutyronitrile, azobis-2 , 4-Dimethyl Reronitoriru, azo compounds such as azobis methyl butyrate; and the like. These polymerization initiators can be used alone or in combination of two or more. The amount of the polymerization initiator used is preferably 0.01 to 10 parts by weight, more preferably 0.01 to 2 parts by weight with respect to 100 parts by weight of the monomer mixture.

Also, the peroxide initiator can be used as a redox polymerization initiator in combination with a reducing agent. Although it does not specifically limit as this reducing agent, Compounds containing metal ions in a reduced state such as ferrous sulfate and cuprous naphthenate; Sulfurous compounds such as sodium formaldehyde sulfoxylate; Sodium methanesulfonate and the like Sulphonic acid compounds; amine compounds such as dimethylaniline; and the like. These reducing agents can be used alone or in combination of two or more. The amount of the reducing agent used is preferably 3 to 1000 parts by weight with respect to 100 parts by weight of the peroxide.

Examples of the molecular weight regulator include alkyl mercaptans such as n-hexyl mercaptan, n-octyl mercaptan, t-octyl mercaptan, n-dodecyl mercaptan, t-dodecyl mercaptan, n-stearyl mercaptan; dimethylxanthogen disulfide, diisopropylxanthogendi Xanthogen compounds such as sulfide; thiuram compounds such as tetramethylthiuram disulfide, tetraethylthiuram disulfide, tetramethylthiuram monosulfide; phenolic compounds such as 2,6-di-t-butyl-4-methylphenol and styrenated phenol; Allyl compounds such as allyl alcohol; halogenated hydrocarbon compounds such as dichloromethane, dibromomethane and carbon tetrabromide; α-benzyloxystyrene, α- Examples thereof include benzyloxyacrylonitrile, α-benzyloxyacrylamide, triphenylethane, pentaphenylethane, acrolein, methacrolein, thioglycolic acid, thiomalic acid, 2-ethylhexyl thioglycolate, α-methylstyrene dimer, and terpinolene. These molecular weight modifiers can be used alone or in combination of two or more. The amount of the molecular weight modifier used is preferably 0.1 to 3 parts by weight, more preferably 0.2 to 2 parts by weight, and particularly preferably 0.3 to 1.5 parts by weight with respect to 100 parts by weight of the monomer mixture. Part.

The amount of water used for emulsion polymerization is preferably from 80 to 600 parts by weight, particularly preferably from 100 to 300 parts by weight, based on 100 parts by weight of the total monomers used.

The emulsion polymerization reaction may be either a continuous type or a batch type, and the polymerization time is not particularly limited. Examples of the monomer addition method include a method of adding monomers to be used in a reaction vessel all at once, a method of adding continuously or intermittently as the polymerization proceeds, and a part of the monomer is added. And a method in which the remaining monomer is continuously or intermittently added and polymerized, and any method may be employed. When the monomers are mixed and added continuously or intermittently, the composition of the mixture may be constant or may be changed. Each monomer may be added to the reaction vessel after previously mixing various monomers to be used, or may be added separately to the reaction vessel. In the case of using a method in which a part of the monomer is added to the reaction vessel and the polymerization is continued after the polymerization reaction is started, for example, a part of the ethylenically unsaturated nitrile monomer and the conjugated diene monomer. After the polymerization reaction is started, the remainder of the conjugated diene monomer is added to the reaction vessel in a batch or divided manner while the polymerization reaction rate in the reaction vessel is 20 to 65%. Further, a method of continuing the polymerization reaction can be mentioned. In this case, the proportion of the conjugated diene monomer added after the polymerization reaction is started is preferably 20 to 60% by weight based on the total amount of the conjugated diene monomer used for the polymerization.

Furthermore, when carrying out emulsion polymerization, polymerization auxiliary materials such as chelating agents, dispersants, pH adjusters, oxygen scavengers and particle size adjusters can be used as necessary. There is no particular limitation.

As described above, the monomer mixture is emulsion-polymerized, and when the predetermined polymerization conversion rate is reached, the polymerization reaction is stopped by cooling the polymerization system or adding a polymerization terminator. The polymerization conversion rate when the polymerization is stopped is not particularly limited, but is preferably 70% or more, more preferably 80% or more, and further preferably 90% or more. If the polymerization conversion is too low, productivity tends to decrease. The polymerization temperature is not particularly limited, but is preferably 0 to 50 ° C, more preferably 2 to 35 ° C.

The polymerization terminator is not particularly limited. For example, hydroxylamine, hydroxyamine sulfate, diethylhydroxylamine, hydroxyaminesulfonic acid and its alkali metal salt, sodium dimethyldithiocarbamate, hydroquinone derivative, catechol derivative, and hydroxydimethyl Examples thereof include aromatic hydroxydithiocarboxylic acids such as benzenethiocarboxylic acid, hydroxydiethylbenzenedithiocarboxylic acid, hydroxydibutylbenzenedithiocarboxylic acid, and alkali metal salts thereof. The amount of the polymerization terminator used is preferably 0.05 to 2 parts by weight with respect to 100 parts by weight of the monomer mixture.

The emulsion can be obtained by carrying out the polymerization reaction as described above. In addition, after stopping a polymerization reaction and obtaining an emulsion, you may remove an unreacted monomer from an emulsion as needed.

After stopping the polymerization reaction, the volume cumulative particle diameter d10 and the volume cumulative particle diameter d50 are further adjusted by adjusting the volume cumulative particle diameter of the nitrile group-containing conjugated diene copolymer particles contained in the obtained emulsion. Can be adjusted within the above range.

As a method for adjusting the volume cumulative particle size, (i) a method of enlarging particles by bringing the particles in the emulsion together, a method of performing a particle size enlargement treatment, and (ii) particles contained in the emulsion. After coagulating to obtain a coagulated product, the coagulated product is dissolved in an organic solvent to obtain a solution, and then the obtained solution is emulsified in water in the presence of a surfactant, and the organic solvent is removed if necessary. (Iii) a method of mixing two or more emulsions having different volume cumulative particle diameters, and the like.

In the method (i), the particle size enlargement method is not particularly limited. For example, (1) a conjugated diene compound such as 1,3-butadiene, toluene and the like after the polymerization is completed And (2) a method of adding a particle size thickening agent such as carboxyl group-containing polymer latex to the emulsion and stirring vigorously.

When the particle size enlargement treatment is performed by the method (1), the amount of the solvent added is preferably 30 to 300 weights with respect to 100 parts by weight of the nitrile group-containing conjugated diene copolymer in the emulsion. Part. In addition, when the particle size enlargement treatment is performed by the method of (1) above, the stirring conditions are not particularly limited. For example, the rotation speed is preferably set using a stirring device such as a paddle type stirring blade. Is 50 to 2,500 rpm, and the stirring time is preferably 0.5 to 12.0 hours.

In addition, when performing particle size enlargement treatment, an antifoaming agent is added to the emulsion from the viewpoint of suppressing foaming associated with stirring, and the particle size enlargement treatment is performed in the presence of the antifoaming agent. Is preferred.

In addition, after obtaining the latex for foam rubber by performing the particle size enlargement treatment, it is preferable to adjust the solid content concentration of the latex for foam rubber by performing a concentration treatment on the latex for foam rubber. The method for the concentration treatment is not particularly limited, and examples thereof include methods such as vacuum distillation, atmospheric distillation, centrifugation, and membrane concentration. Among these, vacuum distillation is preferable.

When the latex for foam rubber is concentrated by distillation under reduced pressure, the concentration (gauge pressure) is preferably 0.0 MPa to −0.1 MPa, more preferably −0.05 MPa to −0. 099 MPa, and the temperature is preferably 30 to 100 ° C., more preferably 40 to 95 ° C.

In performing the concentration treatment, it is preferable to add an antifoaming agent to the latex for foam rubber and perform the concentration treatment in the presence of the antifoaming agent from the viewpoint of suppressing foaming during concentration.

The antifoaming agent used at the time of the particle size enlargement treatment and the concentration treatment is not particularly limited. For example, an oil-based antifoaming agent, a mineral oil-based antifoaming agent such as a modified hydrocarbon oil based on mineral oil, Examples include silicone-based antifoaming agents such as silicone oil, polymer-based antifoaming agents, and among these, mineral oil-based antifoaming agents and silicone-based antifoaming agents are preferable. These antifoaming agents can be used alone or in combination of two or more. In addition, an antifoamer may be added only at the time of any one process among a particle size enlargement process and a concentration process, and at the time of both processes, the same antifoamer or a different antifoamer, Each may be added, but at least by adding an antifoaming agent when performing the particle size enlargement treatment, not only in the particle size enlargement treatment, but also in the concentration treatment performed after the particle size enlargement treatment, It is preferable because foaming can be suppressed by the antifoaming agent.

The total amount of the antifoaming agent added at the time of the particle size enlargement treatment and the concentration treatment is preferably about 0.1 part by weight with respect to 100 parts by weight of the nitrile group-containing conjugated diene copolymer in the obtained foam rubber latex. The amount is 001 to 1.0 part by weight, more preferably 0.005 to 0.8 part by weight, still more preferably 0.005 to 0.6 part by weight. When the addition amount of the antifoaming agent is less than 0.001 part by weight, when the particle size enlargement treatment is performed, foaming becomes intense, the particle size enlargement is not appropriately performed, and a desired particle size distribution is obtained. There is a risk that foaming will become intense and the productivity of latex for foam rubber may be reduced when concentration treatment is performed. On the other hand, if the addition amount of the antifoaming agent is more than 1.0 part by weight, the content of the antifoaming agent in the finally obtained latex for foam rubber becomes too much, and the resulting foam rubber Young The rate will be too low and the elasticity will be inferior.

In the method (ii), examples of a method for solidifying the particles contained in the emulsion include, for example, a method of mixing an emulsion and a water-soluble organic solvent, a method of mixing an emulsion and an acid, and an emulsion and a salt. And a method of mixing them.

As the water-soluble organic solvent, it is more preferable to select a solvent that does not dissolve the polymer in the latex. Examples of such an organic solvent include methanol, ethanol, isopropyl alcohol, ethylene glycol, and the like. Examples of the acid include acetic acid, formic acid, phosphoric acid, hydrochloric acid and the like. Examples of the salt include calcium chloride, sodium chloride, aluminum sulfate, potassium chloride and the like.

Examples of the organic solvent used in the method (ii) include aromatic hydrocarbon solvents such as benzene, toluene, and xylene; alicyclic hydrocarbon solvents such as cyclopentane, cyclopentene, cyclohexane, and cyclohexene; pentane, hexane, heptane, and the like. Aliphatic hydrocarbon solvents: halogenated hydrocarbon solvents such as methylene chloride, chloroform, ethylene dichloride; acetone, methyl ethyl ketone, diethyl ketone, diisopropyl ketone, methyl isobutyl ketone, methyl hexyl ketone, diisobutyl ketone, butyraldehyde, propyl acetate, Ketone solvents such as butyl acetate and amyl acetate; ester solvents such as ethyl propionate, ethyl isobutyrate and butyl butyrate; dimethyl ether, dihexyl ether, ethylene glycol Dimethyl ether, ethers such as ethylene glycol diethyl ether solvent; and the like.

In the method (ii), an emulsifier and a disperser can be used to emulsify the obtained solution in water in the presence of a surfactant. Further, the method for adding the surfactant is not particularly limited, and it may be added to the solution in advance, or may be added to the solution during the emulsification operation, or may be added all at once or dividedly. May be.

Examples of the emulsifier include a batch type emulsifier such as a trade name: homogenizer (manufactured by IKA), a trade name: polytron (manufactured by Kinematica), and a trade name: TK auto homomixer (manufactured by Tokushu Kika Kogyo Co., Ltd.); Name: TK Pipeline Homomixer (manufactured by Koki Kogyo Kogyo Co., Ltd.), Product Name: Colloid Mill (made by Shinko Pantech Co., Ltd.), Product Name: Thrasher (manufactured by Nihon Coke Kogyo Co., Ltd.), Product Name: Trigonal Wet Fine Crusher ( Product name: Cavitron (manufactured by Eurotech), product name: Milder (manufactured by Taiheiyo Kiko Co., Ltd.), product name: Fine Flow Mill (manufactured by Taiheiyo Kiko Co., Ltd.), etc. Name: Microfluidizer (manufactured by Mizuho Kogyo Co., Ltd.), Product name: Nanomizer (manufactured by Nanomizer Co., Ltd.), Product name: APV Gaurin (manufactured by Gaulin Co., Ltd.), etc .; Membrane Membrane emulsifiers such as chemical generators (manufactured by Chilling Industries Co., Ltd.); Product name: Vibrating emulsifiers such as Vibro mixers (manufactured by Chilling Industries Co., Ltd.); Machine; and the like. The conditions for the emulsification operation by the emulsifier are not particularly limited, and the processing temperature, processing time, etc. may be appropriately selected so as to obtain a desired dispersion state. Further, by adjusting the stirring speed, the shearing force to be applied can be adjusted, and the volume cumulative particle size can be adjusted to a desired range.

(Ii) Examples of the surfactant used in the method (ii) include anionic emulsifiers and nonionic emulsifiers. Examples of the anionic emulsifier include fatty acid salts such as potassium beef tallow fatty acid, partially hydrogenated beef tallow fatty acid potassium, potassium oleate, sodium oleate; potassium rosinate, sodium rosinate, hydrogenated potassium rosinate, and hydrogenated sodium rosinate Resin acid salts such as alkylbenzene sulfonates such as sodium dodecylbenzene sulfonate. Examples of nonionic emulsifiers include polyethylene glycol ester type and pluronic type emulsifiers such as block copolymers of ethylene oxide and propylene oxide. Among these, anionic emulsifiers are preferable, and fatty acid salts and alkylbenzene sulfonates are more preferable. The amount of the surfactant used is preferably 0.5 to 50 parts by weight, more preferably 0.5 to 30 parts by weight, and further preferably 5 to 25 parts by weight with respect to 100 parts by weight of the particles. By appropriately adjusting the amount of the surfactant used, the volume cumulative particle size can be adjusted to a desired range.

In the method (ii), examples of the method for removing the organic solvent include methods such as vacuum distillation, atmospheric distillation, steam distillation, and centrifugation.

In the method (iii), two or more emulsions may be mixed so as to obtain a desired volume cumulative particle diameter, and the mixing method is not particularly limited. The combination of the emulsions is not limited. For example, two emulsions having different volume cumulative particle sizes obtained by the method (i) may be mixed, or the volume cumulative particles obtained by the method (ii) Two emulsions having different diameters may be mixed. Moreover, the emulsion obtained by polymerization and the emulsion obtained by the method (i) and / or (ii) may be mixed by a known method, or obtained by the method (i). You may mix an emulsion and the emulsion obtained by the method of (ii).

<Latex composition for foam rubber>
As the latex for foam rubber, it is preferable to use a latex containing a compounding agent such as a crosslinking agent. That is, it is preferably used as a latex composition for foam rubber.

Examples of crosslinking agents include sulfur such as powdered sulfur, sulfur white, precipitated sulfur, colloidal sulfur, surface-treated sulfur, insoluble sulfur, etc .; sulfur chloride, sulfur dichloride, morpholine disulfide, alkylphenol disulfide, N, N′-dithio And sulfur-containing compounds such as bis (hexahydro-2H-azepinone-2), phosphorus-containing polysulfides, polymer polysulfides, and 2- (4′-morpholino · dithio) benzothiazole. Among these, sulfur can be preferably used. A crosslinking agent can be used individually by 1 type or in combination of 2 or more types.

The content of the crosslinking agent is not particularly limited, but is preferably 0.1 to 10 parts by weight, more preferably 0.2 parts per 100 parts by weight of the nitrile group-containing conjugated diene copolymer in the latex for foam rubber. ~ 3 parts by weight. By making content of a crosslinking agent into the said range, the intensity | strength of the foam rubber obtained can be raised more.

Moreover, it is preferable that the latex for foam rubber used by this invention contains a crosslinking accelerator further.
As the crosslinking accelerator, those usually used in the production of foam rubber can be used, such as diethyldithiocarbamic acid, dibutyldithiocarbamic acid, di-2-ethylhexyldithiocarbamic acid, dicyclohexyldithiocarbamic acid, diphenyldithiocarbamic acid, dibenzyldithiocarbamic acid and the like. Dithiocarbamic acids and zinc salts thereof; 2-mercaptobenzothiazole, 2-mercaptobenzothiazole zinc, 2-mercaptothiazoline, dibenzothiazyl disulfide, 2- (2,4-dinitrophenylthio) benzothiazole, 2- ( 2,6-dimethyl-4-morpholinothio) benzothiazole, 4-morpholinyl-2-benzothiazyl disulfide, 1,3-bis (2-benzothiazyl mercapto Chill) including urea and the like, but zinc diethyldithiocarbamate, zinc dibutyldithiocarbamate, 2-mercaptobenzothiazole zinc is preferred. A crosslinking accelerator can be used individually by 1 type or in combination of 2 or more types.

The content of the crosslinking accelerator is preferably 0.1 to 5 parts by weight, more preferably 0.2 to 4 parts by weight based on 100 parts by weight of the nitrile group-containing conjugated diene copolymer in the latex for foam rubber. Parts by weight. By making content of a crosslinking accelerator into the said range, the intensity | strength of the foam rubber obtained can be raised more.

Furthermore, the latex for foam rubber used in the present invention preferably contains zinc oxide.
The content of zinc oxide is not particularly limited, but is preferably 0.5 to 10 parts by weight, more preferably 0.5 parts per 100 parts by weight of the nitrile group-containing conjugated diene copolymer in the latex for foam rubber. ~ 8 parts by weight. By making content of zinc oxide into the said range, the intensity | strength of the foam rubber obtained can be raised more, making emulsification stability favorable.

The latex for foam rubber used in the present invention further includes an anti-aging agent, a colorant, a foam stabilizer and the like, and a dispersant for stably dispersing the above-mentioned various compounding agents in the latex (for example, NASF (naphthalene sulfone). Acid formalin condensate sodium salt)), thickener (for example, polyacrylic acid and its sodium salt, sodium alginate, polyvinyl alcohol, etc.), surfactant as foaming agent (for example, fat such as potassium oleate) Group alkali soaps, sulfates of higher alcohols such as sodium dodecyl sulfate, etc.) can be blended as required.

The method of mixing various compounding agents with the latex for foam rubber is not particularly limited. For example, after obtaining the latex for foam rubber as described above, the foam is formed using a dispersing machine such as a ball mill, a kneader, or a disper. After preparing an aqueous dispersion of compounding ingredients other than foam rubber latex using a method of mixing various compounding agents blended into the rubber latex as necessary, or the above-mentioned disperser, the aqueous dispersion And the like, and the like are mixed with latex for foam rubber.

<Form rubber>
Foam rubber can be obtained by foaming and coagulating the above-described latex for foam rubber at a desired foaming ratio. Although air is usually used for foaming, carbonates such as ammonium carbonate and sodium bicarbonate; azo compounds such as azodicarboxylic acid amide and azobisisobutyronitrile; and gas generating substances such as benzenesulfonyl hydrazide can also be used. In the case of using air, the foam rubber latex can be stirred and foamed by entraining air. At this time, for example, an Oaks foaming machine, an ultrasonic foaming machine, a stand mixer, or the like can be used.

After foaming the foam rubber latex, the foam rubber latex is coagulated in order to fix the foamed state. Any coagulation method may be used as long as the latex can be gelled and solidified, and a conventionally known method can be used. For example, sodium hexafluorosilicate (sodium silicofluoride), potassium hexafluorosilicate (silica Dunlop method (room temperature coagulation method) in which room temperature coagulant such as potassium fluoride), silicon fluoride compound such as titanium silicofluoride is added to foamed latex for foam rubber (organopolysiloxane, polyvinyl methyl ether, sulfuric acid) A heat-sensitive coagulation method in which a heat-sensitive coagulant such as zinc ammonium complex salt is added to foamed latex for foam rubber; a freeze coagulation method or the like is used. The amount of the coagulant such as the room temperature coagulant and the heat-sensitive coagulant is not particularly limited, but is preferably 0.1 to 10 with respect to 100 parts by weight of the nitrile group-containing conjugated diene copolymer in the latex for foam rubber. Part by weight, more preferably 0.5-8.

Then, after the foam rubber latex is added with a coagulant, it is transferred to a mold having a desired shape and coagulated to obtain a foam rubber. When a crosslinking agent is blended in the latex for foam rubber, it is preferable to crosslink by heating after coagulation. The crosslinking conditions may be such that a heat treatment is preferably performed at a temperature of 100 to 160 ° C., preferably 15 to 120 minutes.

The obtained foam rubber is preferably washed after being taken out of the mold. The washing method is not particularly limited, and examples thereof include a washing method using a washing machine or the like and stirring with water at about 20 to 70 ° C. for about 5 to 15 minutes. After washing, draining and drying at a temperature of about 30 to 90 ° C. are preferred so as not to impair the texture of the foam rubber. The foam rubber thus obtained can be used as a puff (cosmetic sponge) or the like by, for example, slicing to a predetermined thickness, cutting into a predetermined shape, and polishing the side surface with a rotating grindstone or the like. it can.

The foam rubber obtained using the latex for foam rubber of the present invention can be suitably used for various uses such as mattresses, puffs (cosmetic sponges), rolls, impact absorbers and the like. In particular, the foam rubber obtained using the latex for foam rubber of the present invention is not easily deformed even when a liquid cosmetic containing an ultraviolet absorber such as octyl paramethoxycinnamate (ethylhexyl methoxycinnamate) is included. Since it is less worn, it can be suitably used as a puff (cosmetic sponge) impregnated with liquid cosmetics.

Hereinafter, the present invention will be specifically described with reference to examples and comparative examples. In the following, “parts” are based on weight unless otherwise specified. The test and evaluation were as follows.

The content ratio of the ethylenically unsaturated nitrile monomer unit was calculated by measuring the nitrogen content in the nitrile group-containing conjugated diene copolymer by Kjeldahl method according to JIS K6384.

Cumulative volume particle diameter light scattering diffraction particle size analyzer (Model "LS-13320", manufactured by Beckman Coulter, Inc.) was used to measure particle size distribution based on volume of the latex foam rubber. Based on the obtained volume-based particle size distribution, a volume cumulative particle size d10 and a volume cumulative particle size d50 were determined.

A 2 g sample was precisely weighed (weight: X2) in a solid content aluminum dish (weight: X1) and dried in a hot air drier at 105 ° C. for 2 hours. Subsequently, after cooling in a desiccator, the weight of the aluminum pan was measured (weight: X3), and the solid content concentration was calculated according to the following formula.
Solid content concentration (% by weight) = (X3−X1) × 100 / X2

The viscosity of the latex for viscosity foam rubber was measured using a viscometer (BII type viscometer (model name: BLII), manufactured by Toki Sangyo Co., Ltd.) under the conditions of a temperature of 25 ° C., a rotation speed of 60 rpm, and a rotation time of 60 seconds.

100g of latex for handling rubber foam is filtered through an 80 mesh wire mesh (200cm ² ), and the amount of filtration (the amount of latex that has passed through the wire mesh) is measured when filtered for 5 minutes without applying pressure. The evaluation was based on the following criteria. A large amount of filtration means that the latex is excellent in handling properties (transferability of the latex and handling properties at the time of mixing the additive).
A: The filtration amount was more than 90 g.
B: The amount of filtration was 20 to 90 g.
C: The filtration amount was less than 20 g.

Conditions such as moldability foaming and vulcanization were observed and evaluated according to the following criteria.
A: Moldable B-1: Molded but shrunk during vulcanization.
B-2: Although formed, it was difficult to foam.
C: Not moldable

Difficult to deform when foam rubber contains liquid cosmetic Foam rubber is punched into a cylindrical shape with a diameter of 3.3 cm and a thickness of 0.8 cm, and liquid cosmetic (ANESSA (registered trademark) Perfect UV Aqua Booster, The ratio of foam rubber diameter after immersion to the diameter of foam rubber before immersion (swelling rate (%) = (diameter of foam rubber after immersion)) / (immersion) The previous foam rubber diameter) × 100) was calculated and evaluated according to the following criteria.
A: The swelling rate was less than 110%.
B: The swelling rate was 110 to 115%.
C: The swelling rate was over 115%.

When the foam rubber contains a liquid cosmetic, the abrasion-resistant foam rubber is immersed in a liquid cosmetic (ANESSA (registered trademark) Perfect UV Aqua Booster, manufactured by Shiseido Co., Ltd.), and a Martindale abrasion tester (STM633, SATRA). Was used to measure wear loss at a test temperature of 23 ° C., a load of 9 kPa, and a polishing wheel rotation speed of 1000 times, and evaluated according to the following criteria.
A: Abrasion loss was less than 30%.
B: Wear loss was 30 to 35%.
C: Wear loss was more than 35%.

Example 1
Production of latex In a pressure-resistant reaction vessel, 200 parts of water, 1.5 parts of potassium oleate, 55 parts of acrylonitrile, 0.5 part of t-dodecyl mercaptan, 0.03 part of sodium formaldehyde sulfoxylate, 0. 003 parts, 0.008 part of ethylenediaminetetraacetic acid / sodium were added and thoroughly deaerated, and then 25 parts of 1,3-butadiene was added.

Next, 0.05 part of cumene hydroperoxide was added as a polymerization initiator, and emulsion polymerization was started at a reaction temperature of 5 ° C. When the polymerization conversion rate reached 40%, 10 parts of 1,3-butadiene was added and the polymerization reaction was continued. Further, when the polymerization conversion rate reached 60%, 10 parts of 1,3-butadiene was added and the polymerization reaction was continued. When the polymerization conversion rate reached 80%, a polymerization terminator solution consisting of 0.25 part of diethylhydroxylamine and 5 parts of water was added to stop the polymerization reaction to obtain an emulsion.

Next, 80 parts of 1,3-butadiene as a solvent is added to the emulsion, the temperature in the system is set to 15 ° C., and the rotational speed is 1,000 rpm and the stirring time is 5 hours using a paddle type stirring blade. The particle size was enlarged by vigorous stirring. Next, 1,3-butadiene was removed, and then a concentration treatment was performed at 70 ° C. under a reduced pressure condition of −0.05 MPa (gauge pressure) to obtain a latex. Then, according to the above method, the obtained latex was measured for the content ratio of ethylenically unsaturated nitrile monomer units, the volume cumulative particle size and the viscosity of the latex (solid content concentration 65% by weight), and the handling property of the latex. Evaluated. The results are shown in Table 1.

Preparation of latex composition For 100 parts of nitrile group-containing conjugated diene copolymer in latex, vulcanized aqueous dispersion (colloidal sulfur / dithiocarbamate vulcanization accelerator Noxeller EZ (Ouchi Shinsei Chemical Industry Co., Ltd.) Manufactured) / thiazole vulcanization accelerator Noxeller MZ (manufactured by Ouchi Shinsei Chemical Co., Ltd.) = 2/1/1 (weight ratio), solid content concentration 50%), 4 parts, zinc oxide aqueous dispersion (solid content concentration 50) %) 3 parts and 1 part of a bubble stabilizer (Trimenbase: manufactured by Crompton Corp) were added and dispersed sufficiently to obtain a latex composition.

Production of foam rubber The latex composition was stirred using a stand mixer (model “ESM945”, manufactured by Electrolux Co., Ltd.) and foamed to a volume of about 5 times. (Partial concentration 20%) 1.5 parts was added, and the mixture was further stirred for 1 minute to obtain a foam.

Next, the obtained foamed product was poured into a molding mold (diameter 7 cm, height 8 cm), solidified, and then vulcanized by heating at 110 ° C. for 1 hour, and then taken out from the mold to 40 ° C. This was washed with water for 10 minutes, further dried in an oven at 60 ° C. for 4 hours, and cut to a thickness of 0.8 cm in the height direction to obtain a disk-like foam rubber. About the obtained foam rubber, according to the above-mentioned method, it was difficult to deform when the foam rubber contained the liquid cosmetic, and the abrasion resistance when the foam rubber contained the liquid cosmetic was evaluated. Moreover, the state from foaming to completion of vulcanization was confirmed, and formability was confirmed according to the above method. The results are shown in Table 1.

Example 2
An emulsion was obtained in the same manner as in Example 1. 3000 parts of methanol was prepared, and the obtained emulsion was dropped therein to solidify the nitrile group-containing conjugated diene copolymer to obtain crumb. Subsequently, the obtained crumb was washed with water and dried under reduced pressure at 50 ° C. to obtain a nitrile group-containing conjugated diene copolymer.

Next, the resulting nitrile group-containing conjugated diene copolymer is mixed with methyl isobutyl ketone, dissolved by raising the temperature to 60 ° C. with stirring, and a solution of the nitrile group-containing conjugated diene copolymer. Got.
On the other hand, potassium oleate and water were mixed to obtain an aqueous emulsifier solution having a concentration of 1.0% by weight.
Next, the product name: Multiline Mixer MS26-MMR-5.5L (Satake Chemical Co., Ltd.) is used so that the weight ratio of the solution of the nitrile group-containing conjugated diene copolymer and the aqueous emulsifier solution is 1: 1. Using a trade name: Milder MDN310 (manufactured by Taiheiyo Kiko Co., Ltd.) and mixing and emulsifying at 1500 rpm to obtain an emulsion.

Next, the emulsion was heated to 80 ° C. under a reduced pressure of −0.01 to −0.09 MPa (gauge pressure), and methyl isobutyl ketone was distilled off to obtain a latex. Next, concentration treatment was performed at 70 ° C. under a reduced pressure condition of −0.05 MPa (gauge pressure) to obtain a latex. And about the obtained latex, according to the said method, the content rate of an ethylenically unsaturated nitrile monomer unit, a volume cumulative particle diameter, and the viscosity (solid content concentration of 64 weight%) of latex are measured, Latex handling property Evaluated. The results are shown in Table 1.

Further, a latex composition and foam rubber were obtained in the same manner as in Example 1, and evaluated in the same manner as in Example 1. The results are shown in Table 1.

Comparative Example 1
In a pressure-resistant reaction vessel, 200 parts of water, 1.5 parts of potassium oleate, 38 parts of acrylonitrile, 0.5 part of t-dodecyl mercaptan, 0.03 part of sodium formaldehyde sulfoxylate, 0.003 part of ferrous sulfate, Ethylenediaminetetraacetic acid / sodium (0.008 parts) was added and thoroughly deaerated, and then 45 parts of 1,3-butadiene and 17 parts of isoprene were added.
Subsequently, 0.05 part of cumene hydroperoxide was added as a polymerization initiator, and emulsion polymerization was started at a reaction temperature of 5 ° C. When the polymerization conversion reached 95%, a polymerization terminator solution consisting of 0.25 part of diethylhydroxylamine and 5 parts of water was added to stop the polymerization reaction to obtain an emulsion. Next, in the same manner as in Example 1, a particle size enlargement treatment and a concentration treatment were performed to obtain a latex. Then, the content of the ethylenically unsaturated nitrile monomer unit, the volume cumulative particle size and the viscosity of the latex (solid content concentration 65% by weight) are measured for the obtained latex according to the above method, and the handling property of the latex is measured. Evaluated. The results are shown in Table 1.

Further, a latex composition and foam rubber were obtained in the same manner as in Example 1, and evaluated in the same manner as in Example 1. The results are shown in Table 1.

Example 3
The latex obtained in Example 2 and the latex obtained in Comparative Example 1 were mixed so that the nitrile group-containing conjugated diene copolymer contained in each latex was 1: 1 by weight. A latex was obtained. Then, the content of the ethylenically unsaturated nitrile monomer unit, the volume cumulative particle size and the viscosity of the latex (solid content concentration 65% by weight) are measured for the obtained latex according to the above method, and the handling property of the latex is measured. Evaluated. The results are shown in Table 1.

Further, a latex composition and foam rubber were obtained in the same manner as in Example 1, and evaluated in the same manner as in Example 1. The results are shown in Table 1.

Example 4
By adding water to the latex obtained in Example 2, the solid content concentration was adjusted to 55% by weight. Then, the content of the ethylenically unsaturated nitrile monomer unit, the volume cumulative particle size, and the latex viscosity (solid content concentration 55% by weight) are measured for the obtained latex according to the above method, and the handling property of the latex is measured. Evaluated. The results are shown in Table 1.

Further, a latex composition and foam rubber were obtained in the same manner as in Example 1, and evaluated in the same manner as in Example 1. The results are shown in Table 1.

Comparative Example 2
In a pressure-resistant reaction vessel, water 200 parts, potassium oleate 1.5 parts, acrylonitrile 60 parts, t-dodecyl mercaptan 0.6 parts, sodium formaldehyde sulfoxylate 0.03 parts, ferrous sulfate 0.003 parts, After adding 0.008 part of ethylenediaminetetraacetic acid / sodium and thoroughly degassing, 20 parts of 1,3-butadiene was added.

Next, 0.05 part of cumene hydroperoxide was added as a polymerization initiator, and emulsion polymerization was started at a reaction temperature of 5 ° C. When the polymerization conversion rate reached 40%, 10 parts of 1,3-butadiene was added and the polymerization reaction was continued. Further, when the polymerization conversion rate reached 60%, 10 parts of 1,3-butadiene was added and the polymerization reaction was continued. When the polymerization conversion rate reached 80%, a polymerization terminator solution consisting of 0.25 part of diethylhydroxylamine and 5 parts of water was added to stop the polymerization reaction to obtain an emulsion.

Thereafter, after the unreacted monomer was removed from the obtained emulsion, the content ratio of the ethylenically unsaturated nitrile monomer unit and the volume cumulative particle diameter were measured according to the above-described method. Thereafter, concentration was performed to obtain a latex having a solid content concentration of 63%. And the handling property of latex was evaluated. The results are shown in Table 1. In addition, although it was going to measure the viscosity (solid content concentration 63 weight%) of latex, the viscosity was too high and could not be measured.

Further, a latex composition was obtained in the same manner as in Example 1, and an attempt was made to mold a foam rubber. However, the viscosity was too high to be molded.

Comparative Example 3
In a pressure-resistant reaction vessel, water 200 parts, potassium oleate 1.5 parts, acrylonitrile 40 parts, t-dodecyl mercaptan 0.5 parts, sodium formaldehyde sulfoxylate 0.03 parts, ferrous sulfate 0.003 parts, After adding 0.008 part of ethylenediaminetetraacetic acid / sodium and thoroughly degassing, 60 parts of 1,3-butadiene was added.

Next, 0.05 part of cumene hydroperoxide was added as a polymerization initiator, and emulsion polymerization was started at a reaction temperature of 5 ° C. When the polymerization conversion rate reached 95%, a polymerization terminator solution consisting of 0.25 part of diethylhydroxylamine and 5 parts of water was added to stop the polymerization reaction to obtain an emulsion.

Then, after removing unreacted monomers from the obtained emulsion, 80 parts of 1,3-butadiene as a solvent was added, the temperature inside the system was set to 15 ° C., and 1 using a paddle type stirring blade. The mixture was stirred at a rotational speed of 1,000 rpm for 5 hours to carry out a particle size enlargement treatment. Next, 1,3-butadiene was removed and then concentrated to obtain a latex having a solid content concentration of 63%.

The latex obtained in the above and the latex obtained in Comparative Example 2 were mixed so that the nitrile group-containing conjugated diene copolymer contained in each latex was 1: 1 by weight, and the latex was mixed. Got. Then, the content of the ethylenically unsaturated nitrile monomer unit, the volume cumulative particle size and the viscosity of the latex (solid content concentration 63 wt%) are measured for the obtained latex according to the above method, and the handling property of the latex is measured. Evaluated. The results are shown in Table 1.

Further, a latex composition and foam rubber were obtained in the same manner as in Example 1, and evaluated in the same manner as in Example 1. The results are shown in Table 1.

Comparative Example 4
A latex was obtained in the same manner as in Example 2 except that the concentration of the aqueous emulsifier solution used was changed to 4.0% by weight, and the rotational speed of the trade name: Milder MDN310 (manufactured by Taiheiyo Kiko) was changed to 5000 rpm. . Then, the content of the ethylenically unsaturated nitrile monomer unit, the volume cumulative particle size and the viscosity of the latex (solid content concentration 65% by weight) are measured for the obtained latex according to the above method, and the handling property of the latex is measured. Evaluated. The results are shown in Table 1.

Further, a latex composition and foam rubber were obtained in the same manner as in Example 1, and evaluated in the same manner as in Example 1. The results are shown in Table 1.

As shown in Table 1, nitrile group-containing conjugated diene copolymer particles having an ethylenically unsaturated nitrile monomer unit content of 40 to 60% by weight, the volume accumulation in a volume-based particle size distribution A latex for foam rubber containing particles having a particle size d10 of 130 nm or more is excellent in handling properties and moldability, and produces a foam rubber that is not easily deformed even when cosmetics are included and has little wear. (Examples 1 to 4). Further, when the solid content concentration of the latex for foam rubber was 60% by weight or more, the latex for foam rubber was further excellent in moldability (Examples 1 to 3).

On the other hand, the ethylenically unsaturated nitrile monomer unit in the nitrile group-containing conjugated diene copolymer contained in the latex for foam rubber, such as the latex disclosed in Production Example 1 of International Publication No. 2009/145209 When the content ratio is less than 40% by weight, it was difficult to produce a foam rubber with little wear even when a cosmetic was included (Comparative Example 1).
Also, foam rubber containing particles having a volume cumulative particle size d10 in a volume-based particle size distribution of less than 130 nm, as in the latex disclosed in Production Example 4 and Example 4 of International Publication No. 2009 / 145,094 The latex for use was inferior in moldability, and even when a cosmetic material was included, it was difficult to deform and it was not possible to produce a foam rubber with little wear (Comparative Examples 2 to 4).

Claims (7)

A latex for foam rubber containing particles of a nitrile group-containing conjugated diene copolymer,
The nitrile group-containing conjugated diene copolymer contains an ethylenically unsaturated nitrile monomer unit and a conjugated diene monomer unit, and the content ratio of the ethylenically unsaturated nitrile monomer unit is 40-60. % By weight
A latex for foam rubber, wherein a volume cumulative particle size d10 in a volume-based particle size distribution of the particles is 130 nm or more. The latex for foam rubber according to claim 1, wherein the content of the ethylenically unsaturated nitrile monomer unit is 45 to 55 wt%. The latex for foam rubber according to claim 1 or 2, wherein a volume cumulative particle size d50 in a volume-based particle size distribution of the particles is 420 to 1500 nm. The latex for foam rubber according to any one of claims 1 to 3, wherein the solid content concentration is 60% by weight or more. The foam rubber according to any one of claims 1 to 4, having a viscosity of 3200 mPa · s or less when measured using a B-type viscometer under conditions of a temperature of 25 ° C, a rotation speed of 60 rpm, and a rotation time of 60 seconds. latex. The latex for foam rubber according to any one of claims 1 to 5, further comprising a crosslinking agent. Foam rubber obtained from the latex for foam rubber according to any one of claims 1 to 6.