WO2022209827A1

WO2022209827A1 - Foam rubber latex composition and foam rubber

Info

Publication number: WO2022209827A1
Application number: PCT/JP2022/011392
Authority: WO
Inventors: 英和羽根田; 雅俊石葉
Original assignee: 日本ゼオン株式会社
Priority date: 2021-03-29
Filing date: 2022-03-14
Publication date: 2022-10-06
Also published as: CN116917401A; JPWO2022209827A1

Abstract

Provided is a foam rubber latex composition containing: a copolymeric rubber latex containing 30-60 wt% of a cyano group-containing ethylenically unsaturated monomer unit and 40-70 wt% of an aliphatic conjugated diene-based monomer unit; a nitroxyl radical compound; and a thiazoline-based compound, wherein the solid content concentration is 55-75 wt%.

Description

Latex composition for foam rubber and foam rubber

TECHNICAL FIELD The present invention relates to a latex composition for foam rubber and a foam rubber, and more particularly, it has excellent oil resistance, has a soft touch, and appropriately suppresses discoloration, deterioration, and odor generation during repeated use. The present invention relates to a foam rubber latex composition capable of providing foam rubber, and to a foam rubber obtained using such a foam rubber latex composition.

Foam rubber (rubber foam) manufactured using polymer rubber latex is used for various purposes such as mattresses, cosmetic sponges (puffs), rolls, and shock absorbers. Among the uses of foam rubber, particularly as a puff, there is a demand for foam rubber that has good oil resistance to cosmetics and a soft feel.

From the viewpoint of imparting good oil resistance to cosmetics, as a material for forming a foam rubber suitable for a puff as a cosmetic sponge, for example, in Patent Document 1, a cyano group-containing ethylenically unsaturated monomer 45-60% by weight, 15-52% by weight of 1,3-butadiene, 3-40% by weight of isoprene, and 0-30% by weight of other ethylenically unsaturated monomers copolymerizable therewith. A copolymer rubber latex for foam rubber has been proposed, which is a copolymer rubber latex obtained by emulsion polymerization of a mixture and characterized in that the gel content of the copolymer rubber is 65% by weight or less.

Japanese Patent No. 5186992

According to the technique of Patent Document 1, although a foam rubber having excellent oil resistance and a soft feel can be obtained, there are problems such as discoloration, deterioration, and odor when repeatedly used. .
The present invention has been made in view of such circumstances, and provides a foam rubber that has excellent oil resistance, has a soft feel, and is appropriately suppressed in discoloration, deterioration, and odor generation during repeated use. It is an object of the present invention to provide a latex composition for foam rubber which can be prepared and a foam rubber obtained using such a latex composition for foam rubber.

As a result of intensive studies aimed at solving the above problems, the present inventors have found a copolymer rubber containing a cyano group-containing ethylenically unsaturated monomer unit and an aliphatic conjugated diene-based monomer unit in a predetermined proportion. We have found that the above problems can be solved by a latex composition obtained by blending latex with a nitroxyl radical compound and a thiazoline-based compound and having a solid content concentration within a predetermined range. I have completed my invention.

That is, according to the present invention, a copolymer rubber latex containing 30 to 60% by weight of cyano group-containing ethylenically unsaturated monomer units and 40 to 70% by weight of aliphatic conjugated diene monomer units, A latex composition for foam rubber containing a nitroxyl radical compound and a thiazoline compound and having a solid content concentration of 55 to 75% by weight is provided.

In the latex composition for foam rubber of the present invention, the content of the nitroxyl radical compound is preferably 100 to 10,000 ppm by weight.
In the foam rubber latex composition of the present invention, the content of the thiazoline compound is preferably 10 to 1,000 ppm by weight.
In the foam rubber latex composition of the present invention, the nitroxyl radical compound is preferably 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO).
In the foam rubber latex composition of the present invention, the thiazoline compound is preferably 2-methyl-4-isothiazolin-3-one (MIT) or 1,2-benzisothiazolin-3-one (BIT). .
The foam rubber latex composition of the present invention preferably has a solid content concentration of 60 to 70% by weight.
The foam rubber latex composition of the present invention preferably has a solid content concentration of 63 to 69% by weight.
The foam rubber latex composition of the present invention preferably has a solid content concentration of 64.5 to 67.5% by weight.

Further, according to the present invention, there is provided a foam rubber obtained by using the above latex composition for foam rubber.

According to the present invention, there is provided a latex composition for foam rubber which is excellent in oil resistance, has a soft feel, and is capable of providing a foam rubber in which discoloration, deterioration and generation of odor during repeated use are appropriately suppressed. And a foam rubber obtained using such a latex composition for foam rubber can be provided.

The latex composition for foam rubber of the present invention is a copolymer rubber containing 30 to 60% by weight of cyano group-containing ethylenically unsaturated monomer units and 40 to 70% by weight of aliphatic conjugated diene monomer units. It contains latex, a nitroxyl radical compound and a thiazoline compound, and has a solid concentration of 55 to 75% by weight.

<Copolymer rubber latex>
The copolymer rubber latex used in the present invention is a copolymer rubber containing 30 to 60% by weight of cyano group-containing ethylenically unsaturated monomer units and 40 to 70% by weight of aliphatic conjugated diene monomer units. More specifically, it is a dispersion in which particles of copolymer rubber having such a monomer composition are dispersed in water.

The copolymer rubber latex used in the present invention includes, for example, a cyano group-containing ethylenically unsaturated monomer, an aliphatic conjugated diene-based monomer, and, if necessary, other polymers copolymerizable therewith. It can be obtained by emulsion polymerization of a monomer mixture containing an ethylenically unsaturated monomer.

Examples of cyano group-containing unsaturated monomers include acrylonitrile, methacrylonitrile, α-chloroacrylonitrile, α-cyanoethyl acrylate and the like. These can be used individually by 1 type or in combination of 2 or more types. Among these, acrylonitrile and methacrylonitrile are preferred, and acrylonitrile is more preferred. The content of the cyano group-containing unsaturated monomer units in the copolymer rubber constituting the copolymer rubber latex is 30 to 60% by weight, preferably 35 to 55% by weight, based on the total monomer units. %, more preferably 40 to 50% by weight. If the content of the cyano group-containing ethylenically unsaturated monomer unit is too small, the obtained foam rubber will have insufficient oil resistance, while if it is too large, the resulting foam rubber will have a hard hand and a rough texture. become worse.

Examples of aliphatic conjugated diene monomers include 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, 2-ethyl-1,3-butadiene, 1,3-pentadiene and chloroprene. mentioned. These can be used individually by 1 type or in combination of 2 or more types. Among these, 1,3-butadiene and isoprene are preferred, and 1,3-butadiene is more preferred. The content of the aliphatic conjugated diene monomer units in the copolymer rubber constituting the copolymer rubber latex is 40 to 70% by weight, preferably 45 to 65% by weight, based on the total monomer units. %, more preferably 50 to 60% by weight. If the content of the aliphatic conjugated diene-based monomer unit is too small, the resulting foam rubber will be hard, while if it is too large, the resulting foam rubber will have insufficient oil resistance.

As the aliphatic conjugated diene-based monomer, two or more types can be used in combination. For example, 1,3-butadiene and isoprene may be used in combination. From the viewpoint of more appropriately suppressing discoloration, deterioration, and generation of odor during repeated use, the content of isoprene units is preferably 30% by weight or less, and 20% by weight or less, based on the total monomer units. more preferably 2 to 10% by weight. In addition, the content ratio of 1,3-butadiene units and isoprene units is preferably 70:30 to 95:5, more preferably 80:20 in terms of weight ratio of 1,3-butadiene units:isoprene units. ~92:8.

In addition, the copolymer rubber constituting the copolymer rubber latex used in the present invention may optionally contain cyano group-containing ethylenically unsaturated monomer units and aliphatic conjugated diene monomer units in addition to , may contain units of other ethylenically unsaturated monomers copolymerizable with these monomers.

Other ethylenically unsaturated monomers that can be copolymerized include, for example, (meth)acrylic acid, (anhydride) maleic acid, fumaric acid, ethylenically unsaturated carboxylic acids such as itaconic acid; methyl (meth)acrylate; ethyl (meth)acrylate, butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, lauryl (meth)acrylate, mono- or dimethyl maleate, mono- or diethyl fumarate, mono- or di-n-butyl fumarate, itaconic acid mono- or di-alkyl esters of said ethylenically unsaturated carboxylic acids such as mono- or di-n-butyl; alkoxyalkyl esters of said ethylenically unsaturated carboxylic acids such as methoxyacrylate, ethoxyacrylate, methoxyethoxyethyl acrylate; 2-hydroxyethyl (Meth) acrylate, hydroxypropyl (meth) acrylate, hydroxybutyl (meth) acrylate having a hydroxyalkyl group; glycidyl (meth) acrylate; (meth) acrylamide, N-methylol (meth) acrylamide, N - (meth)acrylic acid amides such as butoxymethyl (meth)acrylamide and derivatives thereof; acrylates having an amino group such as dimethylaminomethyl acrylate and diethylaminomethyl acrylate; aromatics such as styrene, α-methylstyrene, vinyltoluene and chlorostyrene group vinyl monomers; α-olefins such as ethylene and propylene; non-conjugated diene monomers such as dicyclopentadiene and vinylnorbornene; These monomers can be used singly or in combination of two or more.

The content of other ethylenically unsaturated monomer units in the copolymer rubber constituting the copolymer rubber latex is preferably 10% by weight or less, more preferably 5% by weight or less.

The gel content of the copolymer rubber constituting the copolymer rubber latex used in the present invention is not particularly limited. 80% by weight, more preferably 10 to 75% by weight, and even more preferably 20 to 70% by weight. The gel content was obtained by obtaining a copolymer rubber film and immersing the film in methyl ethyl ketone for 48 hours in a constant temperature and humidity room at a temperature of 23° C. and a humidity of 50%. By measuring the weight of the insoluble component, the insoluble content of methyl ethyl ketone can be determined. The gel content of the copolymer rubber can be adjusted by appropriately adjusting the emulsion polymerization conditions.

The copolymer rubber latex used in the present invention can be produced by a normal emulsion polymerization technique.

Polymerization agents such as emulsifiers (surfactants), polymerization initiators, chelating agents, oxygen scavengers, and molecular weight modifiers used for emulsion polymerization can be conventionally known agents, and are not particularly limited.

Anionic and/or nonionic emulsifiers are usually used as emulsifiers. Examples of anionic emulsifiers include fatty acid salts such as potassium tallow fatty acid, potassium partially hydrogenated tallow fatty acid, potassium oleate, and sodium oleate; potassium rosinate, sodium rosinate, hydrogenated potassium rosinate, hydrogenated sodium rosinate; Alkylbenzenesulfonates such as sodium dodecylbenzenesulfonate and the like. Examples of nonionic emulsifiers include polyethylene glycol ester type, polyethylene glycol ester type, and pluronic type emulsifiers such as block copolymers of ethylene oxide and propylene oxide. These can be used individually by 1 type or in combination of 2 or more types. The amount of emulsifier to be used is preferably 0.5 to 5 parts by weight per 100 parts by weight of all the monomers used for polymerization.

Examples of polymerization initiators include thermal decomposition initiators such as persulfates such as potassium persulfate and ammonium persulfate; t-butyl hydroperoxide, cumene hydroperoxide, diisopropylbenzene hydroperoxide, octanoyl peroxide, Organic peroxides such as 3,5,5-trimethylhexanoyl peroxide; azo compounds such as azobisisobutyronitrile; and redox initiators comprising these and reducing agents such as divalent iron ions. be done. These can be used individually by 1 type or in combination of 2 or more types. Among these, redox initiators are preferred. The amount of polymerization initiator to be used is preferably 0.01 to 10 parts by weight per 100 parts by weight of all monomers used for polymerization.

Examples of molecular weight modifiers include alkylmercaptans such as n-hexylmercaptan, n-octylmercaptan, t-octylmercaptan, n-dodecylmercaptan, t-dodecylmercaptan and n-stearylmercaptan; xanthogen compounds such as sulfides; thiuram compounds such as tetramethylthiuram disulfide, tetraethylthiuram disulfide, and 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, carbon tetrabromide; α-benzyloxystyrene, α-benzyloxyacrylonitrile, α-benzyloxyacrylamide, triphenylethane, pentaphenylethane acrolein, methacrolein, thioglycolic acid, thiomalic acid, 2-ethylhexylthioglycolate, α-methylstyrene dimer, terpinolene and the like. These can be used individually by 1 type or in combination of 2 or more types. 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 part by weight with respect to 100 parts by weight of the total monomers used for polymerization. .5 parts by weight.

The emulsion polymerization reaction may be either continuous or batchwise, and the polymerization time is not particularly limited. The method of adding the monomer is not particularly limited, and for example, a batch addition method, a split addition method, or the like can be used, but the viewpoint is that the resulting foam rubber can have a better balance between oil resistance and flexibility. More preferably, a method of continuing the polymerization by adding a part of the aliphatic conjugated diene-based monomer used for the polymerization to the reactor after starting the polymerization reaction can be employed. In this case, the cyano group-containing ethylenically unsaturated monomer and part of the aliphatic conjugated diene monomer are added to the reactor to initiate the polymerization reaction, and the polymerization reaction rate in the reactor is 20. It is preferable to add the remainder of the aliphatic conjugated diene-based monomer in batches or in portions to the reactor and continue the polymerization reaction between 65% and 65%.

The polymerization conversion rate when stopping polymerization is not particularly limited, but is preferably 70 to 95% by weight, more preferably 75 to 90% by weight. By setting the polymerization conversion rate within the above range, it is possible to improve the productivity while keeping the gel content within a suitable range. Although the polymerization temperature is not particularly limited, it is preferably 0 to 50°C, more preferably 3 to 40°C.

After polymerization, if necessary, after removing unreacted monomers, it is preferable to apply a particle size enlarging treatment by a known method. , can be increased to a range suitable for foam rubber.

Examples of the particle size enlarging treatment include a method of stopping the reaction during polymerization and vigorously stirring; a method of adding an aliphatic conjugated diene monomer or toluene as a solvent after completion of polymerization and vigorously stirring; and a method of adding a particle size enlarging agent such as a contained polymer latex to a copolymer rubber latex and stirring.

After the particle size enlarging process, the solid content concentration is adjusted to the optimum range by the concentration operation. In the present invention, the solid content concentration of the copolymer rubber latex is preferably in the range of 55-75% by weight, more preferably in the range of 60-70% by weight.

Also, the viscosity of the copolymer rubber latex used in the present invention is preferably 1000 cps or less, more preferably 100 to 800 cps, still more preferably 200 to 500 cps. By setting the viscosity of the copolymer rubber latex within the above range, it is possible to achieve a high balance between handleability and foamability. The viscosity of the copolymer rubber latex can be measured using a Brookfield viscometer under conditions of a temperature of 25° C. and a rotational speed of 60 rpm. The copolymer rubber latex of the present invention may have a viscosity at 25° C. in the above range at a solid content concentration (for example, a solid content concentration actually used), but the solid content concentration is 65% to 67% by weight. %, the viscosity at 25° C. is preferably within the above range. In this case, when the solid content concentration of the latex composition is less than 65% by weight, concentration is performed by a method such as vacuum distillation, normal pressure distillation, centrifugation, membrane concentration, etc. to adjust the solid content concentration. When the solid content concentration of the latex composition exceeds 67% by weight, the above viscosity measurement can be performed after adjusting the solid content concentration by adding water for dilution.

The volume average particle size of the copolymer rubber contained in the copolymer rubber latex is not particularly limited, but is usually 300 to 3000 nm, preferably about 400 to 2000 nm. The volume average particle size can be measured using a laser diffraction particle size distribution analyzer. As a specific laser diffraction particle size distribution analyzer, there is a laser diffraction particle size distribution analyzer (model "LS-13320", manufactured by Beckman Coulter, Inc.).

<Latex composition for foam rubber>
The latex composition for foam rubber of the present invention is obtained by blending a nitroxyl radical compound and a thiazoline compound with the copolymer rubber latex described above, and has a solid content concentration in the range of 55 to 75% by weight. It is what was done.

According to the present invention, by blending a combination of a nitroxyl radical compound and a thiazoline-based compound with the copolymer rubber latex described above, the resulting foam rubber has excellent oil resistance and a soft feel. However, discoloration, deterioration and generation of odor during repeated use can be appropriately suppressed.

The nitroxyl radical compound is a compound that acts as a stabilizer in the foam rubber latex composition of the present invention, and the nitroxyl radical compound is not particularly limited as long as it has a nitroxyl radical structure. , for example, 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO), 4-hydroxy-2,2,6,6-tetramethyl-1-piperidinyloxy (4H-TEMPO), 2 - azaadamantane-N-oxyl (AZADO), 1-methyl-2-azaadamantane-N-oxyl (1-Me-AZADO) or 9-azabicyclo[3.3.1]nonane-N-oxyl (ABNO), etc. are mentioned. These can be used individually by 1 type or in combination of 2 or more types. Among these, 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO), 4-hydroxy-2,2,6,6-tetramethyl-1-piperidinyloxy (4H-TEMPO) Preferred is 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO).

The content of the nitroxyl radical compound in the latex composition for foam rubber of the present invention is not particularly limited, but is preferably 100 to 10,000 ppm by weight, more preferably 300 to 7,000 ppm by weight, and more preferably 300 to 7,000 ppm by weight. It is preferably 500 to 5,000 ppm by weight, more preferably 500 to 2,500 ppm by weight, still more preferably 500 to 2,000 ppm by weight, and particularly preferably 700 to 1,300 ppm by weight. By setting the content of the nitroxyl radical compound within the above range, discoloration, deterioration and generation of odor during repeated use of the obtained foam rubber can be more appropriately suppressed.

The thiazoline-based compound is not particularly limited as long as it is a compound having a thiazoline structure. compound and the like.

In general formula (1) above, R ¹ represents a hydrogen atom or an optionally substituted organic group, and R ² and R ³ each independently represent a hydrogen atom, a halogen atom, or a substituted Indicates an organic group which may have a group. When R ¹ , R ² and R ³ are hydrocarbon groups, they may have a chain carbon skeleton such as a straight or branched chain, or may have a cyclic carbon skeleton, or It may have a substituent such as a halogen atom, an alkoxyl group, a dialkylamino group, an acyl group, or an alkoxycarbonyl group. The number of carbon atoms in the hydrocarbon group is preferably 1-12, more preferably 1-10, and particularly preferably 1-8. Specific examples of such hydrocarbon groups include methyl, ethyl, propyl, isopropyl, butyl, hexyl, cyclohexyl, octyl and 2-ethylhexyl groups.

In general formula (2) above, R ⁴ represents a hydrogen atom or an optionally substituted organic group, and R ⁵ each independently represents a hydrogen atom or a substituent indicates a good organic group. When R ⁴ is a hydrocarbon group, it can be the same hydrocarbon group as the hydrocarbon group described in general formula (1) above. In addition, when R ⁵ is an organic group, the organic group includes an aliphatic group such as an alkyl group or a cycloalkyl group, or an aromatic group, and is preferably an aliphatic group. The number of carbon atoms in the alkyl group is preferably 1-12, more preferably 1-10, and particularly preferably 1-8. These alkyl groups and cycloalkyl groups may have substituents such as halogen atoms, alkoxyl groups, dialkylamino groups, acyl groups and alkoxycarbonyl groups. Specific examples of aliphatic groups include methyl, ethyl, propyl, isopropyl, butyl, hexyl, cyclohexyl, octyl and 2-ethylhexyl groups. In the above general formula (2), n represents an integer of 0-4.

Specific examples of the isothiazolin-based compounds represented by the general formula (1) include 2-methyl-4-isothiazolin-3-one (MIT), 2-n-octyl-4-isothiazolin-3-one, 4- chloro-2-n-octyl-4-isothiazolin-3-one, 5-chloro-2-methyl-4-isothiazolin-3-one, 5-chloro-2-n-octyl-4-isothiazolin-3-one and 4,5-dichloro-2-n-octyl-4-isothiazolin-3-one and the like. Further, specific examples of the benzisothiazoline compound represented by the general formula (2) include 1,2-benzisothiazolin-3-one (BIT) and Nn-butyl-1,2-benzisothiazoline-3 -on and the like. Among these, 2-methyl-4-isothiazolin-3-one (MIT), 1, and 2-methyl-4-isothiazolin-3-one (MIT) are preferred from the viewpoint of further enhancing the effect of suppressing discoloration, deterioration and generation of odor during repeated use of the resulting foam rubber. ,2-benzisothiazolin-3-one (BIT) is preferred, and 1,2-benzisothiazolin-3-one (BIT) is more preferred.

The content of the thiazoline-based compound in the foam rubber latex composition of the present invention is not particularly limited, but is preferably 10 to 1,000 ppm by weight, more preferably 10 to 500 ppm by weight, still more preferably 50 ppm by weight. ~450 ppm by weight, even more preferably 80 to 400 ppm by weight, even more preferably 100 to 400 ppm by weight, particularly preferably 100 to 250 ppm by weight, most preferably 100 to 150 ppm by weight. By setting the content of the thiazoline-based compound within the above range, discoloration, deterioration and generation of odor during repeated use of the resulting foam rubber can be more appropriately suppressed.

The contents of the nitroxyl radical compound and the thiazoline compound in the latex composition for foam rubber of the present invention may be within the above ranges, but the resulting foam rubber may be discolored, deteriorated, and odorous during repeated use. From the point of view that the inhibitory effect can be further enhanced, the content of these is preferably in the range of 1:1 to 30:1 in terms of the weight ratio of "nitroxyl radical compound: thiazoline compound", and 5: It is more preferably in the range of 1 to 20:1, more preferably in the range of 8:1 to 12:1.

In addition, the foam rubber latex composition of the present invention may further contain a vulcanizing agent. As the vulcanizing agent, those commonly used in the production of foam rubber can be used, for example, sulfur such as powdered sulfur, sulfur flower, precipitated sulfur, colloidal sulfur, surface-treated sulfur, insoluble sulfur; Morpholine disulfide, alkylphenol disulfide, N,N'-dithio-bis(hexahydro-2H-azepinone-2), phosphorus-containing polysulfide, polymeric polysulfide, sulfur such as 2-(4'-morpholinodithio)benzothiazole containing compounds. Among these, sulfur can be preferably used. A vulcanizing agent can be used individually by 1 type or in combination of 2 or more types.

The content of the vulcanizing agent in the latex composition for foam rubber of the present invention is not particularly limited, but is preferably 0.1 to 10 parts by weight with respect to 100 parts by weight of the rubber component in the latex composition for foam rubber. parts, more preferably 0.2 to 3 parts by weight. By setting the content of the vulcanizing agent within the above range, the strength of the obtained foam rubber can be further increased.

The foam rubber latex composition of the present invention may further contain a vulcanization accelerator. As vulcanization accelerators, those commonly used in the production of foam rubber can be used. dithiocarbamic acids and zinc salts thereof; 2-mercaptobenzothiazole, 2-mercaptobenzothiazole zinc, 2-mercaptothiazoline, dibenzothiazyl disulfide, 2-(2,4-dinitrophenylthio)benzothiazole, (N,N-diethylthiocarbylthio)benzothiazole, 2-(2,6-dimethyl-4-morpholinothio)benzothiazole, 2-(4'-morpholinodithio)benzothiazole, 4-morphonylyl-2-benzothiazyl disulfide, 1,3-bis(2-benzothiazyl-mercaptomethyl)urea and the like. A vulcanization accelerator can be used individually by 1 type or in combination of 2 or more types.

The content of the vulcanization accelerator in the latex composition for foam rubber of the present invention is not particularly limited, but is preferably 0.05 to 5 parts per 100 parts by weight of the rubber component in the latex composition for foam rubber. parts by weight, more preferably 0.1 to 2 parts by weight. By setting the amount of the vulcanization accelerator within the above range, the strength of the obtained foam rubber can be further increased.

In addition, the foam rubber latex composition of the present invention may further contain zinc oxide. The content of zinc oxide in the latex composition for foam rubber of the present invention is not particularly limited, but is preferably 0.1 to 5 parts by weight with respect to 100 parts by weight of the rubber component in the latex composition for foam rubber. , more preferably 0.2 to 2 parts by weight.

The method for preparing the latex composition for foam rubber of the present invention is not particularly limited. A method of mixing various compounding agents such as a sulfur accelerator and zinc oxide can be used. On the other hand, since the nitroxyl radical compound acts as a stabilizer, it also acts as a polymerization terminator or a polymerization inhibitor for terminating the polymerization reaction. Some of them may be blended as a polymerization terminator for terminating the polymerization reaction when obtaining a copolymer rubber latex by emulsion polymerization. In this case, part of the nitroxyl radical compound may be present in a state of being bound to the termination side terminal of the copolymer rubber constituting the copolymer rubber latex. In addition, the copolymer rubber latex and the compounding agents other than the nitroxyl radical compound may be added in the form of an aqueous dispersion or aqueous solution containing them.

Further, the latex composition for foam rubber of the present invention includes, for example, an antioxidant; a coloring agent; a foam stabilizer; a dispersant such as NASF (naphthalenesulfonic acid formalin condensate sodium salt); , sodium alginate, polyvinyl alcohol and other thickeners; aliphatic alkaline soaps such as potassium oleate, surfactants as foaming agents such as sulfates of higher alcohols such as sodium dodecyl sulfate; good.

The foam rubber latex composition of the present invention has a solid content concentration in the range of 55 to 75% by weight, preferably 60 to 70% by weight, more preferably 63 to 69% by weight, and still more preferably 64.5 to 67.5% by weight, particularly preferably 65 to 67% by weight. If the solid content concentration is too low, rough foam will occur when obtaining a foam rubber, resulting in a poor appearance of the resulting foam rubber. put away. The solid content concentration can be adjusted, for example, by adjusting the solid content concentration of the copolymer rubber latex used, the amount of compounding agents, and the like.

<Foam rubber>
The foam rubber of the present invention is obtained using the above-described latex composition for foam rubber of the present invention.
Specifically, the foam rubber of the present invention can be obtained by foaming the above latex composition for foam rubber of the present invention, coagulating it, and vulcanizing it if necessary.

Air is usually used for foaming latex compositions for foam rubber, and carbonates such as ammonium carbonate and sodium bicarbonate; azo compounds such as azodicarboxylic acid amide and azobisisobutyronitrile; gas generating substances such as benzenesulfonylhydrazide. can also be used. When air is used, the copolymer rubber latex is agitated and foamed by entraining the air. At this time, for example, an oak foaming machine, an ultrasonic foaming machine, or the like is used.

After foaming to a predetermined foaming ratio, the foamed latex composition is coagulated to fix the foamed state. The coagulation method is not particularly limited as long as it is a method capable of gelling and solidifying the foam rubber latex composition, and any conventionally known method can be used. For example, as a coagulant, a silicon fluoride compound such as sodium hexafluorosilicate, potassium hexafluorosilicate (sodium silicofluoride, potassium silicofluoride), titanium sodium silicofluoride, etc. is added to the foamed latex composition for foam rubber. Dunlop method (normal temperature coagulation method); heat-sensitive coagulation method in which a heat-sensitive coagulant such as organopolysiloxane, polyvinyl methyl ether, zinc ammonium sulfate complex is added to a foamed latex composition for foam rubber; be. The amount of the coagulant used is not particularly limited, but it is usually about 0.5 to 10 parts by weight with respect to 100 parts by weight of the foam rubber latex composition (solid content).

Then, the foam rubber can be obtained by transferring the foamed latex composition for foam rubber in a fluid state to which the coagulant has been added to a mold of a predetermined shape and solidifying it. In addition, after solidification, heating may be performed for vulcanization. The conditions for vulcanization are preferably conditions for heat treatment at a temperature of 100 to 160° C. for preferably 15 to 120 minutes.

It is preferable to wash the obtained foam rubber after removing it from the mold. The method of washing is not particularly limited, but for example, a method of washing with water of about 20 to 70° C. by stirring for about 5 to 15 minutes using a washing machine or the like can be mentioned. After washing, it is preferable to drain the water and dry at a temperature of about 30 to 90°C 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 it into a predetermined thickness, cutting it into a predetermined shape, and polishing the side surface with a rotating grindstone or the like. can.

Since the foam rubber of the present invention is obtained by using the above-described latex composition for foam rubber of the present invention, it has excellent oil resistance, has a soft feel, and discolors, deteriorates and smells during repeated use. generation is appropriately suppressed, and is suitable as a puff (cosmetic sponge). In addition to puffs (cosmetic sponges), it can also be suitably used for various applications such as mattresses, rolls, and shock absorbers.

Although the present invention will be described in detail below with reference to examples, the present invention is not limited to these examples. In addition, the following "parts" are by weight unless otherwise specified. Various physical properties were measured as follows.

<Solid Content Concentration of Copolymer Rubber Latex and Latex Composition for Foam Rubber>
2 g of the sample was accurately weighed (weight: X2) in an aluminum dish (weight: X1) and dried in a hot air dryer at 105°C for 2 hours. Next, after cooling in a desiccator, the weight of each aluminum dish was measured (weight: X3), and the solid content concentration was calculated according to the following formula.
Solid content concentration (% by weight) = (X3-X1) x 100/X2

<Viscosity of Copolymer Rubber Latex>
The viscosity of the copolymer rubber latex was measured at a temperature of 25° C. using a Brookfield viscometer at a rotation speed of 60 rpm.

<Odor of Copolymer Rubber Latex>
50 mL of the copolymer rubber latex was placed in a 100 mL container that can be sealed and left at 25° C. for 24 hours. Judgment was carried out according to the following criteria.
A: No putrid smell is felt by any of the five persons.
B: 1 to 4 out of 5 people felt putrid smell.
C: All 5 out of 5 people feel putrid smell.

<Oil resistance of foam rubber>
A test piece is obtained by punching a disk-shaped foam rubber having a thickness of 0.8 cm into a circle having a diameter of about 38 mm, and the obtained test piece is immersed in toluene at 23 ° C. for 24 hours. The ratio of the diameter of the test piece after immersion to the test piece (swelling rate (%)=(diameter of test piece after immersion)/(diameter of test piece before immersion)×100) was calculated. In addition, it can be judged that the lower the swelling rate, the better the oil resistance.

<F type hardness of foam rubber>
The hardness of the foam rubber was measured using an Asker rubber hardness meter F type (manufactured by Kobunshi Keiki Co., Ltd.). It can be judged that the lower the value, the softer the foam rubber and the better the touch.

<Discoloration, deterioration and odor during repeated use of foam rubber>
A disc-shaped foam rubber having a thickness of 0.8 cm was punched into a circle having a diameter of about 38 mm to obtain a test piece, and the obtained test piece was repeatedly used. As the repeated use operation, first, the test piece was immersed in silicone oil (decamethylcyclopentasiloxane), washed with a neutral kitchen detergent, and air-dried at room temperature for 24 hours. This operation was first repeated 10 times, and then left at 25° C. for 10 days to obtain a test piece after repeated use. Discoloration, deterioration, and odor during repeated use were evaluated using the test piece after repeated use.
(Discoloration after repeated use)
Regarding the discoloration during repeated use, the test pieces before and after repeated use were visually checked by 5 persons, and compared with the sample before repeated use, and judged according to the following criteria.
A: No clear discoloration was observed in any of the five persons.
B: 1 to 4 persons felt discoloration.
C: All 5 people clearly felt a dark brown discoloration.
(degradation during repeated use)
Deterioration during repeated use was confirmed by tactile evaluation by five persons who actually touched the material with their hands, and the evaluation was made according to the following criteria.
A: None of the five persons felt a clear tactile change.
B: 1 to 4 people felt a change in tactile sensation.
C: All 5 people felt a distinctly hard and crumbly tactile sensation.
(Odor during repeated use)
Regarding the odor during repeated use, each test piece was placed in a 100 mL container and left at room temperature for 24 hours.
A: None of the five feel any odor.
B: 1 to 4 people perceive a slight odor.
C: All 5 people clearly sense the odor.

<Example 1>
(Preparation of copolymer rubber latex)
200 parts of ion-exchanged water, 1.5 parts of potassium oleate, 35 parts of acrylonitrile, 0.5 parts of t-dodecyl mercaptan, 0.03 parts of sodium formaldehyde sulfoxylate, and 0.003 parts of ferrous sulfate are placed in a pressure-resistant reaction vessel. 0.008 part of ethylenediaminetetraacetic acid/sodium was added, and after sufficient degassing, 45 parts of 1,3-butadiene was added. Next, 0.05 parts of cumene hydroperoxide as a polymerization initiator and an appropriate amount of reducing agent were added to initiate emulsion polymerization at a reaction temperature of 5°C. When the polymerization conversion reached 40%, 10 parts of 1,3-butadiene was added to continue the polymerization reaction. Furthermore, when the polymerization conversion reached 60%, 10 parts of 1,3-butadiene was added to continue the polymerization reaction. When the polymerization conversion reached 80%, 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) was added in the form of an aqueous dispersion to terminate the polymerization reaction. The amount of 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) used was set to 2,000 ppm by weight in the final foam rubber latex composition. Then, after removing the unreacted monomer, 80 parts of 1,3-butadiene is added, the temperature in the system is set to 15° C., and the mixture is stirred for 5 hours at a rotation speed of 1,000 rpm using a paddle type stirring blade. Then, a grain size enlarging treatment was performed. Next, after removing 1,3-butadiene, concentration was carried out to obtain a copolymer rubber latex having a solid content concentration of 67% by weight. The resulting copolymer rubber latex had a pH of 11.3 and a viscosity (B type viscosity) of 280 cps. In addition, the composition of the monomer units contained in the copolymer rubber constituting the copolymer rubber latex was almost the same as the charged amount (also in Examples 2 to 5 and Comparative Examples 1 to 5 described later). Similarly.).

(Preparation of latex composition for foam rubber)
Then, with respect to 100 parts of the solid content of the copolymer rubber latex obtained above, a vulcanization-based aqueous dispersion (colloidal sulfur/dithiocarbamate-based vulcanization accelerator Noccellar EZ (Ouchi Shinko Kagaku Kogyo Co., Ltd. (manufactured by Ouchi Shinko Kagaku Kogyo Co., Ltd.) / thiazole-based vulcanization accelerator Noxceler MZ (manufactured by Ouchi Shinko Kagaku Kogyo Co., Ltd.) = 2/1/1 (weight ratio): solid content concentration 50% by weight) 4 parts, zinc oxide aqueous dispersion (solid content 3 parts (concentration weight 50%), 1 part foam stabilizer (trimene base: manufactured by Crompton Corp.), and 1,2-benzisothiazolin-3-one (BIT) were added and sufficiently dispersed to obtain a solid content concentration of 67% by weight. A copolymer latex composition for foam rubber was obtained. The amount of 1,2-benzisothiazolin-3-one (BIT) added was set to 100 ppm by weight in the copolymer latex composition for foam rubber.

(Manufacture of foam rubber)
Then, the copolymer latex composition for foam rubber obtained above is stirred using a stand mixer (ESM945 manufactured by Electrolux Co., Ltd.) and foamed so as to be about five times its volume, and then silicified. A foamed product was obtained by adding 1.5 parts of an aqueous soda dispersion (solid concentration: 20% by weight) and further stirring for 1 minute. Next, the resulting foam was poured into a mold (7 cm in diameter, 8 cm in height), solidified, and vulcanized at 110° C. for 1 hour to obtain a foam rubber. The foam rubber removed from the mold was washed with hot water at 40°C for 10 minutes, dried in an oven at 60°C for 4 hours, and then cut into discs with a thickness of 0.8 cm. A foam rubber was obtained, and oil resistance, F-type hardness, and discoloration, deterioration and odor during repeated use were measured and evaluated according to the above methods. Table 1 shows the results.

<Example 2>
The amount of acrylonitrile used was changed to 45 parts, the amount of 1,3-butadiene used at the start of polymerization was changed to 35 parts, and 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) A copolymer rubber having a solid content concentration of 65% by weight was prepared in the same manner as in Example 1, except that the amount used was adjusted to 1,000 ppm by weight in the final foam rubber latex composition. A latex was prepared. The pH and viscosity (B-type viscosity) of the obtained copolymer rubber latex were as shown in Table 1.
Then, in the same manner as in Example 1, except that the copolymer rubber latex obtained above was used, a latex composition for foam rubber (65% by weight of solid content) was prepared and a foam rubber was produced. performed and evaluated in the same way. Table 1 shows the results.

<Example 3>
In the same manner as in Example 2, except that the amount of 1,3-butadiene used at the start of polymerization was changed to 30 parts, and 5 parts of isoprene was further blended at the start of polymerization, a copolymer having a solid content concentration of 67% by weight was prepared. A coalesced rubber latex was prepared. The pH and viscosity (B-type viscosity) of the obtained copolymer rubber latex were as shown in Table 1.
Then, in the same manner as in Example 1, except that the copolymer rubber latex obtained above was used, a latex composition for foam rubber (67% by weight of solid content) was prepared and a foam rubber was produced. performed and evaluated in the same way. Table 1 shows the results.

<Example 4>
Example except that the amount of 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) used was 500 ppm by weight in the finally obtained foam rubber latex composition. A copolymer rubber latex having a solid concentration of 65% by weight was prepared in the same manner as in Example 2. The pH and viscosity (B-type viscosity) of the obtained copolymer rubber latex were as shown in Table 1.
Then, in the same manner as in Example 1, except that the copolymer rubber latex obtained above was used, a latex composition for foam rubber (65% by weight of solid content) was prepared and a foam rubber was produced. performed and evaluated in the same way. Table 1 shows the results.

<Example 5>
While using a copolymer rubber latex obtained in the same manner as in Example 2, instead of 1,2-benzisothiazolin-3-one (BIT), the same amount of 2-methyl-4-isothiazolin-3 A latex composition for foam rubber (solid concentration: 65% by weight) was prepared and foam rubber was produced in the same manner as in Example 2, except that MIT was used, and evaluated in the same manner. Table 1 shows the results.

<Comparative Example 1>
The amount of acrylonitrile used was changed to 47 parts, and the amount of 1,3-butadiene used at the start of polymerization was changed to 18 parts. ,6-Tetramethylpiperidine-1-oxyl (TEMPO) was replaced with an aqueous dispersion of diethylhydroxyamine (HAS) in the same manner as in Example 1, except that a solid content concentration of 65 wt. % copolymer rubber latex was prepared. The amount of diethylhydroxyamine (HAS) used was set to 2,000 ppm by weight in the finally obtained latex composition for foam rubber. The pH and viscosity (B-type viscosity) of the obtained copolymer rubber latex were as shown in Table 1.
Then, in the same manner as in Example 1, except that the copolymer rubber latex obtained above was used, a latex composition for foam rubber (65% by weight of solid content) was prepared and a foam rubber was produced. performed and evaluated in the same way. Table 1 shows the results.

<Comparative Example 2>
In the same manner as in Example 2, except that an aqueous dispersion of diethylhydroxyamine (HAS) was used instead of the aqueous dispersion of 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO). A copolymer rubber latex having a solids concentration of 65% by weight was prepared. The amount of diethylhydroxyamine (HAS) used was set to 2,000 ppm by weight in the finally obtained latex composition for foam rubber. The pH and viscosity (B-type viscosity) of the obtained copolymer rubber latex were as shown in Table 1.
Then, in the same manner as in Example 1, except that the copolymer rubber latex obtained above was used, a latex composition for foam rubber (65% by weight of solid content) was prepared and a foam rubber was produced. performed and evaluated in the same way. Table 1 shows the results.

<Comparative Example 3>
A copolymer rubber latex having a solid concentration of 65% by weight was prepared in the same manner as in Example 2, except that 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) was not used. In Comparative Example 3, no polymerization terminator for emulsion polymerization was used. The pH and viscosity (B-type viscosity) of the obtained copolymer rubber latex were as shown in Table 1.
Then, in the same manner as in Example 1 except that the copolymer rubber latex obtained above was used, a latex composition for foam rubber (66% by weight of solid content) was prepared and foam rubber was produced. performed and evaluated in the same way. Table 1 shows the results.

<Comparative Example 4>
In the same manner as in Example 2, except that the copolymer rubber latex obtained in the same manner as in Example 2 was used, and 1,2-benzisothiazolin-3-one (BIT) was not used, A latex composition for foam rubber (solid concentration: 65% by weight) was prepared, and foam rubber was produced and evaluated in the same manner. Table 1 shows the results.

<Comparative Example 5>
A copolymer rubber having a solid content concentration of 65% by weight was prepared in the same manner as in Example 3, except that the amount of acrylonitrile used was changed to 20 parts and the amount of 1,3-butadiene used at the start of polymerization was changed to 55 parts. A latex was prepared. The pH and viscosity (B-type viscosity) of the obtained copolymer rubber latex were as shown in Table 1.
Then, in the same manner as in Example 1, except that the copolymer rubber latex obtained above was used, a latex composition for foam rubber (65% by weight of solid content) was prepared and a foam rubber was produced. performed and evaluated in the same way. Table 1 shows the results.

As shown in Table 1, a copolymer rubber latex containing 30 to 60% by weight of cyano group-containing ethylenically unsaturated monomer units and 40 to 70% by weight of aliphatic conjugated diene monomer units; A foam rubber obtained by using a latex composition for foam rubber containing a xyl radical compound and a thiazoline-based compound and having a solid content concentration of 55 to 75% by weight has excellent oil resistance and a soft feel. Moreover, discoloration, deterioration and generation of odor during repeated use were appropriately suppressed (Examples 1 to 5).

On the other hand, when diethylhydroxyamine (HAS) is used instead of the nitroxyl radical compound, it contains 1,2-benzisothiazolin-3-one (BIT) as a thiazoline compound. The resulting foam rubber resulted in the generation of odor during repeated use (Comparative Examples 1 and 2).
When no nitroxyl radical compound was used, the obtained foam rubber was discolored and deteriorated during repeated use, and the effect of suppressing odor generation during repeated use was insufficient (Comparative Example 3). ).
Further, when the nitroxyl radical compound was contained but the thiazoline compound was not contained, the resulting foam rubber produced an odor during repeated use (Comparative Example 4).
Furthermore, if the composition of the copolymer rubber constituting the copolymer rubber latex is outside the range specified by the present invention, the resulting foam rubber will be inferior in oil resistance and will also have a low F-type hardness. A soft feel could not be obtained (Comparative Example 5).

Claims

a copolymer rubber latex containing 30 to 60% by weight of cyano group-containing ethylenically unsaturated monomer units and 40 to 70% by weight of aliphatic conjugated diene monomer units;
a nitroxyl radical compound;
containing a thiazoline-based compound,
A latex composition for foam rubber having a solid content concentration of 55 to 75% by weight.
The latex composition for foam rubber according to claim 1, wherein the content of the nitroxyl radical compound is 100 to 10,000 ppm by weight.
The latex composition for foam rubber according to claim 1 or 2, wherein the content of the thiazoline compound is 10 to 1,000 ppm by weight.
The latex composition for foam rubber according to any one of claims 1 to 3, wherein the nitroxyl radical compound is 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO).
The foam rubber according to any one of claims 1 to 4, wherein the thiazoline compound is 2-methyl-4-isothiazolin-3-one (MIT) or 1,2-benzisothiazolin-3-one (BIT). latex composition.
The latex composition for foam rubber according to any one of claims 1 to 5, which has a solid content concentration of 60 to 70% by weight.
The latex composition for foam rubber according to any one of claims 1 to 6, which has a solid content concentration of 63 to 69% by weight.
The latex composition for foam rubber according to any one of claims 1 to 7, which has a solid content concentration of 64.5 to 67.5% by weight.
A foam rubber obtained using the latex composition for foam rubber according to any one of claims 1 to 8.