JP2019183119A - Copolymer latex for foam molding - Google Patents

Abstract

To provide a copolymer latex for foam molding capable of suppressing cracking or uneven distribution of air bubbles during foam molding, and reducing molding failure rate.SOLUTION: There is provided a copolymer latex for cosmetic puff consisting of 30 to 80 mass% of a structural unit derived from a conjugate diene monomer, 20 to 50 mass% of a structural unit derived from a vinyl cyanide monomer, and 0 to 20 mass% of other structural unit, and satisfying following conditions (1) and (2). (1) Volume average particle diameter of particles with particle diameter of 0.5 μm or more is 0.7 to 2.0 μm. (2) Volume ratio of particle diameter of 0.5 μm or more is 10% or more.SELECTED DRAWING: None

Description

  The present invention relates to a copolymer latex for foam molding that can suppress cracks and uneven distribution of bubbles during foam molding and reduce the molding defect rate.

  Foam moldings molded from copolymer latex as a raw material through a foaming process, gelation process, vulcanization process, washing process, and drying process are various shock absorbing materials, sound insulating materials, sound absorbing materials, oil-drawing materials, It is used for various purposes as a sponge core material for mattresses and cushions, and a puff for makeup.

Among them, cosmetic puffs are required to reduce the defective rate during puff molding in addition to the balance between elasticity, texture, and oil resistance. Although there are some defects during puff molding, cracks in the puff and uneven distribution of bubbles in which bubbles do not exist uniformly in the center and the outer layer can be mentioned.
Patent Documents 1 and 2 propose a method for improving the texture and feel of the foamed molded product, but it is still insufficient for suppressing cracks and uneven distribution of bubbles.

JP-A-6-32942

Japanese Patent Laid-Open No. 11-263846

  An object of the present invention is to provide a copolymer latex for foam molding in which cracking and bubble uneven distribution during foam molding are suppressed, and the molding defect rate can be lowered.

  As a result of intensive studies, the present inventors have found that the problem can be solved by regulating the copolymer latex to a specific particle size distribution, and have completed the present invention.

That is, the present invention includes the following [1] to [3].
[1] It consists of 30 to 80% by mass of structural units derived from conjugated diene monomers, 20 to 50% by mass of structural units derived from vinyl cyanide monomers, and 0 to 20% by mass of other structural units. A copolymer latex for foam molding characterized by satisfying the following conditions (1) and (2).
(1) The volume average particle size of particles having a particle size of 0.5 μm or more is 0.7 to 2.0 μm.
(2) The volume ratio with a particle size of 0.5 μm or more is 10% or more.
[2] The copolymer latex for foam molding according to [1], wherein the volume average particle diameter of particles having a particle diameter of 0.5 μm or more is 0.7 to 1.5 μm.
[3] The copolymer latex for foam molding according to any one of [1] to [2], wherein a volume ratio of a particle size of 0.5 μm or more is 10% or more and 30% or less.

  ADVANTAGE OF THE INVENTION According to this invention, the copolymerization latex for foam molding by which the crack at the time of foam molding and the uneven distribution of a bubble are suppressed can be obtained. Therefore, the defective rate of the foam molded body is low, and productivity can be improved.

The present invention is described in detail below.
The foamed copolymer latex of the present invention includes a structural unit derived from a conjugated diene monomer, a structural unit derived from a vinyl cyanide monomer, and other structural units.

  The structural unit derived from a conjugated diene monomer is a structural unit formed by polymerizing a conjugated diene monomer. Conjugated diene monomers include 1,3-butadiene, 2-methyl-1,3-butadiene, 2,3-dimethyl-1,3-butadiene, 2-chloro-1,3-butadiene, substituted straight chain Conjugated pentadienes, substituted and side chain conjugated hexadienes and the like can be mentioned, and these can be used alone or in combination. In particular, the use of 1,3-butadiene is preferred.

  The structural unit derived from a vinyl cyanide monomer is a structural unit formed by polymerization of a vinyl cyanide monomer. Examples of the vinyl cyanide monomer include monomers such as acrylonitrile, methacrylonitrile, α-chloroacrylonitrile, α-ethylacrylonitrile. These can be used alone or in combination of two or more. The use of acrylonitrile or methacrylonitrile is particularly preferable.

  Examples of monomers corresponding to other structural units include alkenyl aromatic monomers, unsaturated carboxylic acid alkyl ester monomers, ethylenically unsaturated carboxylic acid monomers, and unsaturated compounds containing hydroxyalkyl groups. Examples thereof include a monomer, an unsaturated carboxylic acid amide monomer, and a polyfunctional ethylenically unsaturated monomer containing two or more unsaturated double bonds.

  Examples of the alkenyl aromatic monomer include styrene, α-methylstyrene, methyl-α-methylstyrene, vinyltoluene and the like. These can be used alone or in combination of two or more. In particular, use of styrene is preferable.

  Unsaturated carboxylic acid alkyl ester monomers include methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, butyl acrylate, glycidyl methacrylate, dimethyl fumarate, diethyl fumarate, dimethyl maleate, diethyl maleate, dimethyl itaconate , Monomethyl fumarate, monoethyl fumarate, 2-ethylhexyl acrylate and the like. These can be used alone or in combination of two or more. In particular, the use of methyl methacrylate is preferred.

  Examples of the ethylenically unsaturated carboxylic acid monomer include monobasic acids or dibasic acids (anhydrides) such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, fumaric acid, and itaconic acid. Or 2 or more types can be used.

  Examples of unsaturated monomers containing a hydroxyalkyl group include β-hydroxyethyl acrylate, β-hydroxyethyl methacrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate, hydroxybutyl acrylate, hydroxybutyl methacrylate, and 3-chloro-2-hydroxypropyl. Examples include methacrylate, di- (ethylene glycol) maleate, di- (ethylene glycol) itaconate, 2-hydroxyethyl maleate, bis (2-hydroxyethyl) maleate, 2-hydroxyethyl methyl fumarate and the like. These can be used alone or in combination of two or more.

  Examples of unsaturated carboxylic acid amide monomers include acrylamide, methacrylamide, N-methylol acrylamide, N-methylol methacrylamide, N, N-dimethylacrylamide and the like. These can be used alone or in combination of two or more.

  Polyfunctional ethylenically unsaturated monomers containing two or more unsaturated double bonds include allyl methacrylate; ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, etc. Polyethylene glycol di (meth) acrylate; divinyl compounds such as divinylbenzene, and the like. These can be used alone or in combination of two or more.

  In addition to the above monomers, any of the monomers used in ordinary emulsion polymerization, such as ethylene, propylene, vinyl acetate, vinyl propionate, vinyl chloride, vinylidene chloride, can be used.

  The structural unit constituting the foam molding copolymer latex of the present invention is 30 to 80% by mass of a structural unit derived from a conjugated diene monomer, and 20 to 50% by mass of a structural unit derived from a vinyl cyanide monomer. %, And other structural units 0 to 20% by mass.

  The structural unit derived from the conjugated diene monomer is 30 to 80% by mass, preferably 35 to 80% by mass, and more preferably 40 to 75% by mass. By being the said range, the feel of a foaming molding is good and the stability of the latex in a concentration process can be maintained.

  The structural unit derived from the vinyl cyanide monomer is 20 to 50% by mass, preferably 20 to 45% by mass, and more preferably 25 to 45% by mass. By being the said range, oil resistance is fully exhibited and the texture of a foaming molding is not impaired.

  Other structural units are 0-20 mass%, and 0-15 mass% is more preferable. By being in the above range, it is possible to balance texture and oil resistance.

  The copolymer latex of the present invention is not particularly limited, but can be obtained by, for example, an emulsion polymerization method.

  When performing emulsion polymerization, in addition to the above monomers, an emulsifier (surfactant), a polymerization initiator, and a chain transfer agent, a reducing agent, and the like can be blended as necessary.

  Examples of emulsifiers (surfactants) include sulfates of higher alcohols, alkylbenzene sulfonates, alkyl diphenyl ether sulfonates, aliphatic sulfonates, aliphatic carboxylates, and sulfates of nonionic surfactants. One type or two or more types of nonionic emulsifiers such as anionic emulsifiers such as salts, and alkyl ester type, alkyl phenyl ether type, and alkyl ether type of polyethylene glycol can be used. In particular, the use of sodium salt of rosin acid salt, fatty acid soap or naphthalenesulfonic acid formalin condensate is preferable. Although the usage-amount of an emulsifier is not restrict | limited in particular, Usually, it is the range of 1-5 mass parts with respect to 100 mass parts of all the monomers.

  Examples of the polymerization initiator include water-soluble polymerization initiators such as lithium persulfate, potassium persulfate, sodium persulfate, and ammonium persulfate; cumene hydroperoxide, benzoyl peroxide, t-butyl hydroperoxide, acetyl peroxide And oil-soluble polymerization initiators such as diisopropylbenzene hydroperoxide and 1,1,3,3-tetramethylbutyl hydroperoxide. These can be used alone or in combination of two or more. In particular, it is preferable to select from potassium persulfate, sodium persulfate, cumene hydroperoxide, and t-butyl hydroperoxide. Although the usage-amount of a polymerization initiator is not restrict | limited in particular, Usually, it is the range of 0.05-2 mass parts with respect to 100 mass parts of all the monomers.

  Examples of chain transfer agents include alkyl mercaptans such as n-hexyl mercaptan, n-octyl mercaptan, t-octyl mercaptan, n-dodecyl mercaptan, t-dodecyl mercaptan, and n-stearyl mercaptan; dimethylxanthogen disulfide, and diisopropyl Xanthogen compounds such as xanthogen disulfide; thiuram compounds such as tetramethylthiuram disulfide, tetraethylthiuram disulfide, and tetramethylthiuram monosulfide; 2,6-di-t-butyl-4-methylphenol, and styrenated phenols Phenolic compounds; allyl compounds such as allyl alcohol; halogenated hydrocarbon compounds such as dichloromethane, dibromomethane, and carbon tetrabromide; α- Vinyl ethers such as benzyloxystyrene, α-benzyloxyacrylonitrile, and α-benzyloxyacrylamide; triphenylethane, pentaphenylethane, acrolein, methacrolein, thioglycolic acid, thiomalic acid, 2-ethylhexylthioglycolate, terpinolene, And chain transfer agents such as α-methylstyrene dimer. These can be used alone or in combination of two or more. Although the usage-amount of a chain transfer agent is not restrict | limited in particular, Usually, it is the range of 0-5 mass parts with respect to 100 mass parts of all monomers.

  Examples of the reducing agent include reducing sugars such as dextrose and saccharose; amines such as dimethylaniline and triethanolamine; carboxylic acids such as L-ascorbic acid, erythorbic acid, tartaric acid, and citric acid and salts thereof; Examples thereof include salts, bisulfites, pyrosulfites, nithionates, nithionates, thiosulfates, formaldehyde sulfonates, and benzaldehyde sulfonates. In particular, it is preferable to select from L-ascorbic acid and erythorbic acid. The amount of the reducing agent used can be appropriately adjusted in consideration of combinations of other additives.

  In addition, the emulsion polymerization includes saturated hydrocarbons such as pentane, hexane, heptane, octane, cyclohexane, cycloheptane, etc .; Saturated hydrocarbons; hydrocarbon compounds such as aromatic hydrocarbons such as benzene, toluene and xylene can be used. In particular, cyclohexene and toluene, which have a moderately low boiling point and can be easily recovered and reused by steam distillation after the completion of polymerization, are preferred.

Furthermore, known additives such as oxygen scavengers, chelating agents, and dispersants may be used as necessary, and these types and amounts are not particularly limited, and appropriate amounts can be used as appropriate. Furthermore, known additives such as antifoaming agents, anti-aging agents, antiseptics, antibacterial agents, flame retardants, and UV absorbers may be used. I can do it.
Further, the copolymer latex of the present invention can be appropriately blended with other latexes depending on the purpose of use.

  The temperature during emulsion polymerization is preferably set in the range of 5 to 100 ° C., more preferably in the range of 10 to 85 ° C., from the viewpoint of safety in the tank and productivity in consideration of safety.

  Examples of the method for adding the monomer component and other components during the emulsion polymerization include a batch addition method, a divided addition method, a continuous addition method, and a power feed method. Among them, it is preferable to employ a continuous addition method (hereinafter sometimes referred to as “continuous addition”). Further, the attachment may be performed a plurality of times.

  About the reaction time of emulsion polymerization, it is preferable to set it as 5 to 60 hours from a viewpoint of productivity, for example, and it is more preferable to set it as 10 to 50 hours.

  In addition, the emulsion polymerization is preferably terminated after confirming that the polymer conversion rate has exceeded 90%. In this way, a copolymer latex is obtained.

  From the viewpoint of dispersion stability, the obtained copolymer latex is preferably adjusted to pH 8 to 13 and adjusted to 9 to 12 with ammonia, potassium hydroxide, sodium hydroxide or the like. More preferred.

  Moreover, it is preferable that the unreacted monomer and other low boiling point compounds are removed from the obtained copolymer latex by a method such as steam distillation.

  The solid content concentration of the copolymer latex of the present invention is preferably 50% by weight or more.

The copolymer latex of the present invention must satisfy the following (1) and (2) as the definition of the particle size distribution.
(1) The volume average particle size of particles having a particle size of 0.5 μm or more is 0.7 to 2.0 μm.
(2) The volume ratio with a particle size of 0.5 μm or more is 10% or more.

  In the copolymer latex of the present invention, (1) the volume average particle diameter of particles having a particle diameter of 0.5 μm or more is 0.7 to 2.0 μm, and preferably 0.7 to 1.5 μm.

  In the copolymer latex of the present invention, (2) the volume ratio of the particle diameter of 0.5 μm or more is 10% or more, and preferably 10% or more and 30% or less. When (1) is less than the above lower limit, if the solid content concentration of the copolymer latex suitable for obtaining a fine foamed molded product is increased, the viscosity becomes high and handling becomes difficult, and the low solid content taking viscosity into consideration. When foam molding is performed at a partial concentration, there is a problem that molding defects frequently occur. If (1) exceeds the above upper limit, foam molding is possible, but there is a problem that cracks occur during foam molding, and the bubbles in the center and outer layer portions of the foam molded body become non-uniform. When (2) is less than the above lower limit, it is difficult to generate fine bubbles during molding, and there is a problem that even if foam molding can be performed, cracking and non-uniformity of bubbles cannot be suppressed. When (1) and (2) are within the above ranges, cracks during foam molding do not occur, and the bubbles in the center of the foam molded body and the outer layer are uniform, so that the uneven distribution of bubbles can be suppressed.

  Examples of the method for adjusting the particle size distributions (1) to (2) include, for example, polymerization conditions such as increase / decrease in the amount of emulsifier during polymerization, polymerization temperature and monomer addition method, and particle size enlargement treatment shown below. The amount can be adjusted by various methods such as the amount of the particle thickening agent, the degree of swelling and stirring conditions, the amount of emulsifier and the solid content, and the ratio of the particles before enlargement to the enlarged particles.

The method for enlarging the particle size of the copolymer latex is not particularly limited. For example, a method of forcibly stirring by adding a particle size thickening agent such as a carboxyl group-containing copolymer particle (generally a chemical agglomeration method and A method in which the reaction is stopped in the middle of the polymerization and the particles swell with the monomer and are forcibly stirred in a state where they are easily fused to each other. Add a monomer, solvent such as toluene, cyclohexene, etc., and forcibly stir the particles in a state where they are swollen and easily fused together, and use a Menton-Gorin homogenizer to warm the copolymer latex. And a method of enlarging by applying high shear by spraying from a nozzle at a constant pressure (hereinafter referred to as warming and pressure enlargement method).
As a method for enlarging the particle size of the copolymer latex, preferably, a heating and pressurizing method is employed. In the warming and pressure enlargement method, preferably, an emulsion such as an unsaturated fatty acid salt (such as potassium oleate) or a particle size adjusting agent is added to the copolymer latex obtained by emulsion polymerization, and then high shear is applied. give.
The addition amount of the emulsifier or the particle size adjusting agent is adjusted from the particle size of the copolymer latex before the enlargement treatment, the amount of the emulsifier already contained, the solid content, and the like to obtain a desired particle size.
Moreover, the pressure in the heating and pressurizing enlargement method affects the selection of equipment, the allowable width of the processing amount, the particle diameter, and the success or failure of enlargement, for example, 2.5 × 10 ⁷ Pa or more, preferably 4. It is 0 × 10 ⁷ Pa or more, for example, 6.0 × 10 ⁷ Pa or less.
The copolymer latex for foam molding includes a copolymer latex (first copolymer latex) obtained by emulsion polymerization, and a copolymer whose particle size is enlarged by the above-described particle size enlargement method. Latex (second copolymer latex) may be included. The second copolymer latex may be obtained by the above-described particle size enlargement method using the first copolymer latex as a raw material. In other words, the first copolymer latex and the second copolymer latex may be composed of the same structural unit, and the mass ratio of each structural unit may be the same.
The first copolymer latex and the second copolymer latex have a particle size distribution of the foam molding copolymer latex, and the volume average particle size of particles having a particle size of 0.5 μm or more is 0.7 to The mixture is mixed so that the volume ratio is 2.0 μm and the volume ratio of the particle diameter is 0.5 μm or more is 10% or more.
For example, the mixing ratio of the first copolymer latex and the second copolymer latex (first copolymer latex / second copolymer latex) is 20/80.

  There is no limitation in particular in the manufacturing method of the foaming molding using the copolymer latex of this invention, A well-known method can be used. Usually, it consists of a process of adding a vulcanizing agent and an auxiliary agent, a foaming process, a gelling process, a vulcanizing process, a water washing process, and a drying process. In the step of adding a vulcanizing agent and an auxiliary agent, an auxiliary agent such as a vulcanizing agent, a vulcanization accelerator, and an anti-aging agent, a thickener, a water retention agent, and a coloring agent are added as necessary. The vulcanizing agent is not particularly limited. For example, sulfur or colloidal sulfur obtained by emulsifying and dispersing it is used. Vulcanization aids and vulcanization accelerators are not particularly limited. Examples of vulcanization aids include zinc white, and examples of vulcanization accelerators include dithiocarbamate accelerators such as zinc diethyldithiocarbamate, 2-mercapto. Examples include thiazole accelerators such as benzothiazole and its zinc salt and dibenzothiazyl disulfide.

  There is no particular limitation on the amount of each of the above-mentioned additives added to 100 parts by mass in terms of solid content of the copolymer latex when producing the foamed molded product, but for example, sulfur 0.3 to 10 parts by weight, zinc white 0 It is common to use in the range of 0.5-10 parts by weight and vulcanization accelerator 0.2-5 parts by weight. Moreover, you may add auxiliary agents, such as various anti-aging agents, a thickener, a water retention agent, and a coloring agent, as an auxiliary agent in the range which does not prevent the effect of this invention.

  A known method can be used as the foaming method in the foaming step, and there is no particular limitation. Examples of the foaming method include a forced foaming method in which air or a gas generating substance is used alone or in combination, and mixed by various methods. As the forced foaming device, for example, an Oaks foaming machine, an ultrasonic foaming machine or the like can be used.

  A known method can be used as the gelation method in the gelation step, and there is no particular limitation. Examples of the gelation method include a heat-sensitive coagulation method using an organopolysiloxane and a freezing coagulation method in which the temperature is rapidly lowered. As a gelling agent, sodium silicofluoride, potassium silicofluoride, titanium sodium silicofluoride, etc. The normal temperature coagulation method (Dunlop method) in which the silicon fluoride compound is added to the foamed copolymer latex is considered to be most effective.

  Various conditions in the vulcanization step after gelation are not particularly limited, and a good-quality foam molded article can be obtained by vulcanization at a temperature of about 100 to 150 ° C. for about 10 to 100 minutes. In addition, although there are no particular restrictions on the conditions of the water washing step and the drying step, it is washed with water or hot water at 25 to 60 ° C. for about 5 to 20 minutes, and then the water is removed by a method such as a centrifugal separation method. It is preferable to dry at about 40 to 120 ° C. so that the texture of the foamed molded product can be maintained.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated further more concretely, this invention is not limited to these Examples, unless the summary is exceeded. In the examples, parts and percentages indicating percentages are based on weight unless otherwise specified.

Method of measuring number average particle diameter, volume average particle diameter, volume ratio of particles of copolymer latex of 0.5 μm or more Number average particle diameter, volume average particle diameter, volume of particles of 0.5 μm or more of copolymer latex For the measurement of the ratio, a number counting type particle size distribution measuring device “Accusizer 780APS” manufactured by ParticleSizing Systems was used. As a carrier, a 0.1% sodium dodecylbenzenesulfonate aqueous solution from which particles of 0.5 μm or more were removed with a filter was used, and the sample was diluted 1000 times with the carrier and measured.

Preparation of copolymer latex a (polymerization step)
In a pressure-resistant polymerization reactor, 65 parts of butadiene, 35 parts of acrylonitrile, 0.6 parts of t-dodecyl mercaptan, 0.5 parts of potassium oleate, 0.5 parts of sodium salt of formalin naphthalene sulfonate, ethylenediaminetetraacetic acid Charge 0.01 parts of tetrasodium salt, 0.001 part of ferrous sulfate and 110 parts of pure water, add 0.1 part of cumene hydroperoxide and 0.2 part of sodium formaldehydesulfonate, and the temperature in the tank is 10 ° C. The reaction was started. Next, when the polymerization conversion reached 25%, 0.5 part of potassium oleate, 0.03 part of sodium formaldehydesulfonate, and 5 parts of pure water were added. Next, when the polymerization conversion reached 50%, 0.5 part of potassium oleate, 0.03 part of sodium formaldehydesulfonate, and 5 parts of pure water were added. Next, when the polymerization conversion reached 75%, 0.03 part of sodium formaldehydesulfonate and 5 parts of pure water were added. When the polymerization conversion rate reached 95% or more, diethylhydroxyamine was added as a polymerization terminator, and then 0.5 parts of potassium oleate and 5 parts of pure water were added to complete the polymerization. Next, copolymer latex a was obtained by removing residual butadiene by steam distillation.
The copolymer latex a had a solid content concentration of 42% and an average particle size of 0.12 μm. The average particle size was measured with FRAR-1000 (manufactured by Otsuka Electronics).

Production of particle-enlarged latex A1 (enlargement process)
After adding 0.40 part of potassium oleate to 100 parts of copolymer latex a (in terms of solid content), using a Manton-Gaulin homogenizer, a temperature of 40 ° C. and a pressure of 2.5 × 10 ⁷ A particle enlarged latex A1 was obtained by carrying out a particle size enlargement treatment by the heating and pressure enlargement method under the condition of Pa.

Production of particle-enlarged latex A2 (enlargement process)
A particle enlarged latex A2 was obtained by carrying out a particle size enlargement treatment under the same conditions as the particle enlarged latex A1, except that the pressure of the heated pressure enlargement method was 4.0 × 10 ⁷ Pa.

Production of particle enlarged latex A3 (enlargement process)
A particle enlarged latex A3 was obtained by carrying out a particle diameter enlargement treatment under the same conditions as the particle enlarged latex A2 except that the amount of potassium oleate added was 0.55 part.

Production of particle enlarged latex A4 (enlargement process)
A particle enlarged latex A4 was obtained by carrying out a particle size enlargement treatment under the same conditions as the particle enlarged latex A2 except that the amount of potassium oleate added was 0.60 part.

Production of particle enlarged latex A5 (enlargement process)
A particle enlarged latex A5 was obtained by carrying out a particle size enlargement treatment under the same conditions as the particle enlarged latex A2 except that the amount of potassium oleate added was 0.65 part.

Preparation of copolymer latex B (mixing process)
Copolymer latex a and particle-enlarged latex A1 are mixed at a ratio of 30:70 (solid content conversion), and 0.5 parts of potassium oleate and potassium rosinate with respect to 100 parts of the mixture (solid content conversion) After adding 0.8 part, copolymer latex B was obtained by concentrating. The solid content concentration was 68%, the number average particle diameter of particles of 0.5 μm or more was 1.3 μm, the volume average particle diameter was 7.7 μm, and the volume ratio was 62%.

Preparation of copolymer latex C (mixing process)
Copolymer latex C was obtained by concentrating the copolymer latex a and the copolymer latex A2 in the same condition as the copolymer latex B except that the copolymer latex A2 was mixed at a ratio of 30:70 (in terms of solid content). . The solid content concentration was 68%, the number average particle diameter of particles of 0.5 μm or more was 1.0 μm, the volume average particle diameter was 2.7 μm, and the volume ratio was 44%.

Preparation of copolymer latex D (mixing process)
Copolymer latex D was obtained by concentrating under the same conditions as copolymer latex B except that copolymer latex a and copolymer latex A3 were mixed at a ratio of 20:80 (in terms of solid content). . The solid content concentration was 68%, the number average particle size of particles of 0.5 μm or more was 0.8 μm, the volume average particle size was 1.5 μm, and the volume ratio was 27%.

Preparation of copolymer latex E (mixing process)
Copolymer latex E was obtained by concentrating under the same conditions as copolymer latex B except that copolymer latex a and copolymer latex A4 were mixed at a ratio of 20:80 (in terms of solid content). . The solid content concentration was 68%, the number average particle diameter of particles of 0.5 μm or more was 0.7 μm, the volume average particle diameter was 1.0 μm, and the volume ratio was 14%.

Preparation of copolymer latex F (mixing process)
Copolymer latex F was obtained by concentrating under the same conditions as copolymer latex B except that copolymer latex a and copolymer latex A5 were mixed at a ratio of 20:80 (in terms of solid content). . The solid content concentration was 55%, the number average particle size of particles of 0.5 μm or more was 0.6 μm, the volume average particle size was 0.7 μm, and the volume ratio was 7%.

<Examples 1-2 and Comparative Examples 1-3>
Production of Foam Molded Body 100 parts of each of the above copolymer latexes B to F in terms of solid content is 1.2 parts of colloidal sulfur as a vulcanizing agent and 2-mercaptobenzothiazole zinc salt as a vulcanizing accelerator Chemical Industry Co., Ltd. Noxeller MZ (0.8 parts), Diethyldithiocarbamate Zinc (Ouchi Shinsei Chemical Co., Ltd. Noxeller EZ) 0.2 parts, Trimen Base 1.0 parts as a foam stabilizer Mix evenly. After curing for 2 hours in a constant temperature room at 27 ° C., 2.5 parts of zinc white is added, and the mixture is forcibly stirred using a biaxial hand mixer and foamed 5 times in volume. Then, 2.5 parts of sodium silicofluoride slurry was added, and stirring was continued for 30 seconds at room temperature. After pouring into a mold (length x width x height 5 cm x 5 cm x 10 cm) and gelling It was vulcanized with 110 ° C. pressurized steam for 30 minutes. Then, it took out from the mold and obtained the foaming molding. The following evaluation was performed about the obtained foaming molding.

Evaluation of Foam Molded Body The foam molded body obtained above was sliced to a thickness of 1 cm in the height direction, and five samples were cut out as evaluation samples. Thereafter, cracks and bubble uniformity were inspected for each sample, and the most common state among the five samples was determined as follows.
X: Cracks occur between the center portion and the outer layer portion of the molded product, and bubbles in the center portion and the outer layer portion are not uniform.
○: There is no crack between the center part and the outer layer part of the molded product, but the air bubbles in the center part and the outer layer part are slightly uneven.
A: There is no crack between the center portion and the outer layer portion of the molded product, and the air bubbles in the center portion and the outer layer portion are uniform.

  As described above, according to the present invention, it is possible to provide a copolymer latex for foam molding that can suppress cracks and uneven distribution of bubbles during foam molding and can reduce the molding defect rate.

Claims (5)

It consists of 30 to 80% by mass of structural units derived from conjugated diene monomers, 20 to 50% by mass of structural units derived from vinyl cyanide monomers, and 0 to 20% by mass of other structural units. 1. A foamed copolymer latex characterized by satisfying 1) and (2).
(1) The volume average particle size of particles having a particle size of 0.5 μm or more is 0.7 to 2.0 μm.
(2) The volume ratio with a particle size of 0.5 μm or more is 10% or more.   The copolymer latex for foam molding according to claim 1, wherein the volume average particle size of particles having a particle size of 0.5 µm or more is 0.7 to 1.5 µm.   The copolymer latex for foam molding according to any one of claims 1 to 2, wherein a volume ratio of a particle size of 0.5 µm or more is 10% or more and 30% or less. A first copolymer comprising 30 to 80% by mass of structural units derived from a conjugated diene monomer, 20 to 50% by mass of structural units derived from a vinyl cyanide monomer, and 0 to 20% by mass of other structural units. A polymer latex;
The copolymer latex for foam molding according to any one of claims 1 to 3, wherein the first copolymer latex includes a second copolymer latex that is enlarged. A first copolymer comprising 30 to 80% by mass of structural units derived from a conjugated diene monomer, 20 to 50% by mass of structural units derived from a vinyl cyanide monomer, and 0 to 20% by mass of other structural units. A polymerization step of obtaining a polymer latex by emulsion polymerization;
An enlargement step of enlarging the particle size of the first copolymer latex to obtain a second copolymer latex having a particle size larger than that of the first copolymer latex;
In the first copolymer latex and the second copolymer latex, the volume average particle diameter of particles having a particle diameter of 0.5 μm or more is 0.7 to 2.0 μm, and the particle diameter is 0.5 μm. A method for producing a foam molding copolymer latex, comprising: a mixing step of obtaining a foam molding copolymer latex by mixing so that the volume ratio is 10% or more.