CN116917401A - Latex composition for foam rubber and foam rubber - Google Patents

Abstract

The invention provides a latex composition for foam rubber, which contains a copolymer rubber latex, a nitroxyl radical compound and a thiazoline compound. The copolymer rubber latex contains 30 to 60% by weight of cyano-containing ethylenically unsaturated The solid content concentration of the latex composition for foam rubber is 55 to 75% by weight.

Description

Latex composition for foam rubber and foam rubber

Technical field

The present invention relates to a latex composition for foam rubber and foam rubber. More specifically, it relates to a foam rubber that is excellent in oil resistance, has a soft touch, and appropriately suppresses discoloration, deterioration and the generation of odor during repeated use. A latex composition for foam rubber, and a foam rubber obtained using such a latex composition for foam rubber.

Background technique

Foam rubber (rubber foam) produced using polymer rubber latex is used in various applications such as mattresses, cosmetic sponges (powder puffs), rollers, and impact absorbers. In the use of foam rubber, especially as a powder puff, it is required to have good oil resistance against cosmetics and a soft touch.

From the viewpoint of being able to impart good oil resistance to cosmetics, for example, Patent Document 1 proposes a copolymer rubber latex for foam rubber as a material for forming foam rubber suitable for a powder puff as a cosmetic sponge. It is characterized in that it is composed of 45-60% by weight of cyano group-containing ethylenically unsaturated monomer, 15-52% by weight of 1,3-butadiene, 3-40% by weight of isoprene and 0-30% by weight. The copolymer rubber latex is a copolymer rubber latex obtained by emulsion polymerization of a monomer mixture composed of other ethylenically unsaturated monomers that can be copolymerized with them, and the gel content of the copolymer rubber is 65% by weight or less.

existing technical documents

patent documents

Patent Document 1: Japanese Patent No. 5186992.

Contents of the invention

Invent the problem to be solved

According to the technology of the above-mentioned Patent Document 1, foam rubber with excellent oil resistance and soft touch can be obtained. However, there are problems such as discoloration, deterioration, and odor generation when used repeatedly.

The present invention was made in view of such actual circumstances, and an object of the present invention is to provide a foam that is excellent in oil resistance, has a soft touch, and appropriately suppresses discoloration, deterioration, and generation of odor during repeated use. A rubber latex composition for foam rubber, and a foam rubber obtained using such a latex composition for foam rubber.

solutions to problems

The present inventors conducted in-depth studies to solve the above problems and found that by blending a copolymer rubber latex containing a cyano group-containing ethylenically unsaturated monomer unit and an aliphatic conjugated diene-based monomer unit in a predetermined ratio, Based on the finding that a latex composition containing a nitroxyl radical compound and a thiazoline compound and having a solid content concentration within a predetermined range can solve the above problems, the present invention was completed.

That is, according to the present invention, it is possible to provide a latex composition for foam rubber, which contains a copolymer rubber latex, a nitroxyl radical compound, and a thiazoline compound, and the copolymer rubber latex contains 30 to 60% by weight of cyano group-containing compounds. The solid content concentration of the latex composition for foam rubber is 55 to 75% by weight.

In the latex composition for foam rubber of the present invention, it is preferable that the content of the nitroxyl radical compound is 100 to 10000 ppm by weight.

In the latex composition for foam rubber of the present invention, the content of the thiazoline compound is preferably 10 to 1000 ppm by weight.

In the latex composition for foam rubber of the present invention, it is preferable that the nitroxyl radical compound is 2,2,6,6-tetramethylpiperidin-1-oxyl radical (TEMPO).

In the latex composition for foam rubber of the present invention, it is preferable that the thiazoline compound is 2-methyl-4-isothiazolin-3-one (MIT) or 1,2-benzisothiazolin-3-one. (BIT).

The latex composition for foam rubber of the present invention preferably has a solid content concentration of 60 to 70% by weight.

The latex composition for foam rubber of the present invention preferably has a solid content concentration of 63 to 69% by weight.

The latex composition for foam rubber of the present invention preferably has a solid content concentration of 64.5 to 67.5% by weight.

Furthermore, according to the present invention, it is possible to provide foam rubber obtained using the above-mentioned latex composition for foam rubber.

Invention effect

According to the present invention, it is possible to provide a latex composition for foam rubber that can form a foam rubber that is excellent in oil resistance, has a soft touch, and appropriately suppresses discoloration, deterioration, and generation of odor during repeated use, and uses such a latex composition. Foam rubber obtained from a latex composition.

Detailed ways

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

＜Copolymer rubber latex＞

The copolymer rubber latex used in the present invention is a copolymer rubber latex containing 30 to 60% by weight of cyano-containing ethylenically unsaturated monomer units and 40 to 70% by weight of aliphatic conjugated diene monomer units. , more specifically, 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 can be obtained by combining, for example, a cyano group-containing ethylenically unsaturated monomer, an aliphatic conjugated diene-based monomer, and other ethylenically unsaturated monomers that can be copolymerized with them if necessary. The monomer mixture is obtained by emulsion polymerization.

Examples of the cyano group-containing unsaturated monomer 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. In the copolymer rubber constituting the copolymer rubber latex, the content of the cyano group-containing unsaturated monomer units in all monomer units is 30 to 60% by weight, preferably 35 to 55% by weight, and more preferably 40 to 50% by weight. %. When the content of the cyano group-containing ethylenically unsaturated monomer unit is too small, the oil resistance of the foam rubber obtained becomes insufficient. On the other hand, when it is too large, the texture of the foam rubber obtained becomes hard and the touch against the skin becomes poor.

Examples of aliphatic conjugated diene monomers include 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, and 2-ethyl-1. 3-butadiene, 1,3-pentadiene and chloroprene, etc. 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. In the copolymer rubber constituting the copolymer rubber latex, the content of aliphatic conjugated diene monomer units in all monomer units is 40 to 70% by weight, preferably 45 to 65% by weight, and more preferably 50 to 50% by weight. 60% by weight. When the content of the aliphatic conjugated diene monomer unit is too small, the obtained foam rubber becomes hard. On the other hand, when it is too large, the oil resistance of the obtained foam rubber becomes insufficient.

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

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

Examples of other ethylenically unsaturated monomers that can be copolymerized include: (meth)acrylic acid, maleic acid (anhydride), fumaric acid, itaconic acid and other ethylenically unsaturated carboxylic acids; (meth)acrylic acid Methyl ester, ethyl (meth)acrylate, butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, lauryl (meth)acrylate, monomethyl maleate or di-maleate Methyl ester, monoethyl fumarate or diethyl fumarate, mono-n-butyl fumarate or di-n-butyl fumarate, mono-n-butyl itaconate or di-n-butyl itaconate, etc. Monoalkyl esters or dialkyl esters of ethylenically unsaturated carboxylic acids; alkoxy groups of the above ethylenically unsaturated carboxylic acids such as methoxy acrylate, ethoxy acrylate, methoxyethoxyethyl acrylate, etc. Alkyl esters; (meth)acrylates with hydroxyalkyl groups such as 2-hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, hydroxybutyl (meth)acrylate, etc.; (meth)acrylic acid Glycidyl ester; (meth)acrylamide, N-hydroxymethyl(meth)acrylamide, N-butoxymethyl(meth)acrylamide and other (meth)acrylamide and their derivatives; dimethyl Acrylates with amino groups such as methylaminomethacrylate and diethylaminomethacrylate; aromatic vinyl monomers such as styrene, α-methylstyrene, vinyltoluene, and chlorostyrene; ethylene, propylene and other α-olefins; non-conjugated diene monomers such as dicyclopentadiene, vinylnorbornene, etc. These monomers can be used alone or in combination of two or more types.

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

In addition, the gel content of the copolymer rubber constituting the copolymer rubber latex used in the present invention is not particularly limited, but from the viewpoint of further improving the strength and flexibility of the obtained foam rubber, it is preferably 5 to 80% by weight, more preferably 5 to 80% by weight. Preferably it is 10-75 weight%, More preferably, it is 20-70 weight%. In addition, the gel content can be determined as follows: obtain a film of the copolymer rubber, immerse the film in methyl ethyl ketone for 48 hours in a constant temperature and humidity chamber at a temperature of 23° C. and a humidity of 50%, and measure the amount of methyl ethyl ketone that is insoluble in the methyl ethyl ketone at this time. The weight of the component is thus determined as the amount of the component insoluble in methyl ethyl ketone. 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 common emulsion polymerization method.

Polymerization reagents such as emulsifiers (surfactants), polymerization initiators, chelating agents, oxygen scavengers, and molecular weight regulators used in emulsion polymerization can use various conventionally known reagents and are not particularly limited.

As the emulsifier, anionic and/or non-ionic emulsifiers are generally used. 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, potassium hydrogenated rosinate, and sodium hydrogenated rosinate. Resinates such as sodium dodecylbenzenesulfonate and alkylbenzene sulfonates such as sodium dodecylbenzene sulfonate, etc. 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 usage amount of the emulsifier is preferably 0.5 to 5 parts by weight relative to 100 parts by weight of all monomers used in the polymerization.

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

Examples of the molecular weight regulator include n-hexyl mercaptan, n-octyl mercaptan, tert-octyl mercaptan, n-dodecyl mercaptan, tert-dodecyl mercaptan, n-stearyl mercaptan, etc. Alkyl mercaptans; xanthate compounds such as dimethyl xanthogen disulfide and diisopropyl xanthate disulfide; tetramethylthiuram disulfide, tetraethylthiuram disulfide, Thiuram compounds such as tetramethylthiuram monosulfide; phenol compounds such as 2,6-di-tert-butyl-4-methylphenol, styrenated phenol; allyl compounds such as allyl alcohol; Halogenated hydrocarbon compounds such as methyl chloride, dibromomethane, carbon tetrabromide; α-benzyloxystyrene, α-benzyloxyacrylonitrile, α-benzyloxyacrylamide, triphenylethane, penta Phenylethane, acrolein, methacrolein, thioglycolic acid, thiomalic acid, 2-ethylhexyl thioglycolate, α-methylstyrene dimer, terpinene, etc. These can be used individually by 1 type or in combination of 2 or more types. The usage amount of the molecular weight regulator 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 based on 100 parts by weight of all monomers used in the polymerization.

The emulsion polymerization reaction may be either a continuous type or a batch type, and the polymerization time and the like are not particularly limited. The method of adding the monomer is not particularly limited, and for example, a one-time addition method, a batch addition method, etc. can be used. From the viewpoint of further improving the balance between the oil resistance and softness of the obtained foam rubber, polymerization can be preferably used. A method in which a part of the aliphatic conjugated diene monomer used is added to a reactor to continue polymerization after initiating the polymerization reaction. At this time, it is preferable to add a part of the cyano group-containing ethylenically unsaturated monomer and the aliphatic conjugated diene monomer into the reactor, and after initiating the polymerization reaction, the polymerization reaction rate in the reactor reaches 20 to 65 %, the remaining part of the aliphatic conjugated diene monomer is added to the reactor at once or in batches, and the polymerization reaction is further continued.

The polymerization conversion rate when the polymerization is terminated is not particularly limited, but is preferably 70 to 95% by weight, and more preferably 75 to 90% by weight. By setting the polymerization conversion rate within the above range, the gel content can be brought into a preferred range and productivity can be improved. In addition, the polymerization temperature is not particularly limited, but is preferably 0 to 50°C, and more preferably 3 to 40°C.

After polymerization, if necessary, after removing unreacted monomers, it is preferable to perform a particle size increasing treatment by a known method. The particle size increasing treatment can increase the solid content concentration of the copolymer rubber latex to a level suitable for foam rubber. range of use.

Examples of the particle size increasing treatment include: terminating the reaction during polymerization and vigorously stirring; and after completion of polymerization, adding aliphatic conjugated diene monomer, toluene, etc. as a solvent and vigorously stirring. Methods; methods such as adding particle size increasing agents such as carboxyl group-containing polymer latex to copolymer rubber latex and stirring.

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

In addition, the viscosity of the copolymer rubber latex used in the present invention is preferably 1000 cps or less, more preferably 100 to 800 cps, and still more preferably 200 to 500 cps. By setting the viscosity of the copolymer rubber latex within the above range, handleability and foamability can be highly balanced. In addition, the viscosity of the copolymer rubber latex can be measured using a B-type viscometer at a temperature of 25°C and a rotation speed of 60 rpm. The copolymer rubber latex of the present invention only needs to have a viscosity at 25° C. within the above range at a solid concentration (for example, a solid concentration actually used) of 65% by weight to 67% by weight. %, the viscosity at 25°C is within the above range. At this time, when the solid content concentration of the latex composition is less than 65% by weight, the above-mentioned viscosity measurement can be performed after adjusting the solid content concentration by performing a concentration operation by vacuum distillation, normal pressure distillation, centrifugation, membrane concentration, etc. , when the solid content concentration of the latex composition is greater than 67% by weight, the above-mentioned viscosity measurement can be performed after adjusting the solid content concentration by adding water for dilution.

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

＜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, and the solid content concentration of the latex composition for foam rubber is 55 to 75% by weight. scope.

According to the present invention, by combining a nitroxyl radical compound and a thiazoline compound in the copolymer rubber latex, the resulting foam rubber can have excellent oil resistance and soft touch, and can appropriately suppress deterioration during repeated use. Discoloration, deterioration and development of odor.

The nitroxyl radical compound is a compound that functions as a stabilizer in the latex composition for foam rubber of the present invention. The nitroxyl radical compound is not particularly limited as long as it has a nitroxyl radical structure. Examples include 2,2,6,6-tetramethylpiperidin-1-oxyl radical (TEMPO) and 4-hydroxy-2,2,6,6-tetramethyl-1-piperidinyloxyl radical. (4H-TEMPO), 2-azaadamantane-N-oxygen radical (AZADO), 1-methyl-2-azaadamantane-N-oxygen radical (1-Me-AZADO) or 9-nitrogen Heterobicyclo[3.3.1]nonane-N-oxyl radical (ABNO), etc. These can be used individually by 1 type or in combination of 2 or more types. Among these, 2,2,6,6-tetramethylpiperidin-1-oxyl radical (TEMPO) and 4-hydroxy-2,2,6,6-tetramethyl-1-piperidinyloxy are preferred. radical (4H-TEMPO), more preferably 2,2,6,6-tetramethylpiperidin-1-oxyl radical (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, more preferably 500 to 5,000 ppm by weight, and still more preferably It is 500 to 2,500 ppm by weight, 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, it is possible to more appropriately suppress discoloration, deterioration, and generation of odor when the obtained foam rubber is repeatedly used.

The thiazoline compound is not particularly limited as long as it has a thiazoline structure. Examples thereof include an isothiazoline compound represented by the following general formula (1) and an isothiazoline compound represented by the following general formula (2). Benzisothiazoline compounds, etc.

[Chemical formula 1]

In the above general formula (1), R ¹ represents a hydrogen atom or an organic group which may have a substituent, and R ² and R ³ each independently represent a hydrogen atom, a halogen atom or an organic group which may have a substituent. When R ¹ , R ² , and R ³ are hydrocarbon groups, they may have a chain carbon skeleton such as a linear or branched chain, a cyclic carbon skeleton, or a halogen atom, an alkoxy group, or a dihydrocarbon group. Alkylamino, acyl, alkoxycarbonyl and other substituents. In addition, the number of carbon atoms of the hydrocarbon group is preferably 1 to 12, more preferably 1 to 10, and particularly preferably 1 to 8. Specific examples of such hydrocarbon groups include methyl, ethyl, propyl, isopropyl, butyl, hexyl, cyclohexyl, octyl, 2-ethylhexyl, and the like.

[Chemical formula 2]

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

Specific examples of the isothiazoline compound represented by the general formula (1) include 2-methyl-4-isothiazolin-3-one (MIT) and 2-n-octyl-4-isothiazole. Lin-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, etc. Specific examples of the benzisothiazoline compound represented by the general formula (2) include 1,2-benzisothiazolin-3-one (BIT) and N-n-butyl-1 ,2-benzisothiazolin-3-one, etc. Among these, 2-methyl-4-isothiazolin-3-one (MIT) is preferred from the viewpoint that it can further enhance the effect of suppressing discoloration, deterioration, and odor generation of the obtained foam rubber during repeated use. , 1,2-benzisothiazolin-3-one (BIT), more preferably 1,2-benzisothiazolin-3-one (BIT).

The content of the thiazoline compound in the latex composition for foam rubber of the present invention is not particularly limited, but is preferably 10 to 1000 ppm by weight, more preferably 10 to 500 ppm by weight, still more preferably 50 to 450 ppm by weight, and still more preferably It is 80 to 400 ppm by weight, very preferably 100 to 400 ppm by weight, particularly preferably 100 to 250 ppm by weight, and most preferably 100 to 150 ppm by weight. By setting the content of the thiazoline 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 content of the nitroxyl radical compound and the thiazoline compound in the latex composition for foam rubber of the present invention only needs to be within the above range, so as to further improve the ability to suppress discoloration, deterioration and odor of the obtained foam rubber during repeated use. From the viewpoint of the effect produced, it is preferable that their content is in the range of 1:1 to 30:1 in terms of the weight ratio of "nitroxyl radical compound:thiazoline compound", and more preferably 5:1 to 20:1. The range is more preferably in the range of 8:1 to 12:1.

In addition, the latex composition for foam rubber of the present invention may further contain a vulcanizing agent. As the vulcanizing agent, vulcanizing agents commonly used in the production of foam rubber can be used, and examples thereof include sulfur such as sulfur powder, sublimated sulfur, precipitated sulfur, colloidal sulfur, surface-treated sulfur, and insoluble sulfur; sulfur chloride, dichloride Sulfur, morpholine disulfide, alkylphenol disulfide, 1,1'-dithiobiscaprolactam, phosphorus-containing polysulfide, polymer polysulfide, 2-(4'-morpholinodithio) Sulfur compounds such as benzothiazole. Among these, sulfur can be preferably used. One type of vulcanizing agent can be used alone, or two or more types can be used in combination.

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

The latex composition for foam rubber of the present invention may further contain a vulcanization accelerator. As the vulcanization accelerator, vulcanization accelerators commonly used in the production of foam rubber can be used, and examples thereof include diethyldithiocarbamic acid, dibutyldithiocarbamic acid, and di-2-ethylhexyl Dithiocarbamates such as dithiocarbamates, dicyclohexyldithiocarbamates, diphenyldithiocarbamates, and dibenzyldithiocarbamates and their zinc salts; 2-mercaptobenzo Thiazole, 2-mercaptobenzothiazole zinc, 2-mercaptothiazoline, dibenzothiazole disulfide, 2-(2,4-dinitrophenylthio)benzothiazole, 2-(N,N-di Ethylthiocarbamoylthio)benzothiazole, 2-(2,6-dimethyl-4-morpholinothio)benzothiazole, 2-(4'-morpholinodithio) Benzothiazole, 4-morpholinyl-2-benzothiazole disulfide, 1,3-bis(2-benzothiazolylmercaptomethyl)urea, etc. One type of vulcanization accelerator can be used alone, or two or more types can be used in combination.

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

Furthermore, the latex composition for foam rubber 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. It is preferably 0.1 to 5 parts by weight, and more preferably 0.2 to 2 parts by weight relative to 100 parts by weight of the rubber component in the latex composition for foam rubber. parts by weight.

The preparation method of the latex composition for foam rubber of the present invention is not particularly limited, and examples thereof include mixing a nitroxyl radical compound and a thiazoline-based compound into a copolymer rubber latex, and using a vulcanizing agent, a vulcanizing accelerator, and an oxidizing agent as necessary. Methods of various compounding agents such as zinc, etc. On the other hand, the nitroxyl radical compound functions as a stabilizer and therefore also functions as a polymerization terminator and polymerization inhibitor for terminating the polymerization reaction. Therefore, for some of the nitroxyl radical compounds, That is, when a copolymer rubber latex is obtained by emulsion polymerization, it can be blended as a polymerization terminator for terminating the polymerization reaction. In addition, at this time, some of the nitroxyl radical compounds may exist in a state of being bonded to the terminal end of the copolymer rubber constituting the copolymer rubber latex. In addition, compounding agents other than the copolymer rubber latex and the nitroxyl radical compound may be added in the form of an aqueous dispersion or aqueous solution containing them.

In addition, the latex composition for foam rubber of the present invention may also contain, for example: anti-aging agents; colorants; bubble stabilizers; dispersants such as NASF (sodium salt of naphthalene sulfonate formaldehyde condensate); polyacrylic acid and its sodium salt, seaweed Thickeners such as sodium sulfate and polyvinyl alcohol; aliphatic alkaline soaps such as potassium oleate; sulfates of higher alcohols such as sodium lauryl sulfate; surfactants as foaming agents, etc.

The solid content concentration of the latex composition for foam rubber of the present invention is in the range of 55 to 75% by weight, preferably in the range of 60 to 70% by weight, more preferably in the range of 63 to 69% by weight, and even more preferably in the range of 64.5 to 67.5% by weight. %, particularly preferably in the range of 65 to 67% by weight. When the solid content concentration is too low, rough foam will be generated when the foam rubber is obtained, and the appearance of the obtained foam rubber will deteriorate. When the solid content concentration is increased above the above range, productivity will decrease. The solid content concentration can be adjusted, for example, by adjusting the solid content concentration of the copolymer rubber latex used, the amount of the compounding agent, and the like.

＜Foam rubber＞

The foam rubber of the present invention is obtained by using the latex composition for foam rubber of the present invention described above.

Specifically, the foam rubber of the present invention can be obtained by foaming and solidifying the latex composition for foam rubber of the present invention described above, and vulcanizing it as necessary.

Foaming of latex compositions for foam rubber usually uses air, but carbonates such as ammonium carbonate and sodium bicarbonate; azo compounds such as azodicarboxylic acid amide and azobisisobutyronitrile; benzene sulfonyl hydrazide, etc. A substance that produces gas. When air is used, the copolymer rubber latex is stirred and air is drawn in to cause foaming. At this time, for example, an Oakes foaming machine, an ultrasonic foaming machine, etc. are used.

It is foamed to a predetermined expansion ratio, and then the foamed latex composition is solidified in order to fix the foamed state. The coagulation method is not particularly limited as long as it can gel and solidify the latex composition for foam rubber, and any conventionally known method can be used. For example, a fluorosilicic acid compound such as sodium hexafluorosilicate, potassium hexafluorosilicate (sodium fluorosilicate, potassium fluorosilicate), and sodium titanium fluorosilicate is added to the foamed latex composition for foam rubber as a coagulation agent. The Dunlop method (normal temperature coagulation method) of the agent; adding heat-sensitive coagulation such as organopolysiloxane, polyvinyl methyl ether, zinc ammonium sulfate complex salt, etc. to the foamed latex composition for foam rubber Heat-sensitive coagulation method of agent; freeze coagulation method, etc. The usage amount of the coagulant is not particularly limited, but is usually about 0.5 to 10 parts by weight relative to 100 parts by weight of the latex composition for foam rubber (solid content).

Then, the foamed rubber latex composition can be obtained by transferring the foamed latex composition for foam rubber to a mold of a predetermined shape in a state where the coagulant is added but still fluid, and solidified. In addition, after solidification, heating may be performed in order to vulcanize the foam rubber. The conditions for vulcanization can preferably be set to a condition in which heat treatment is performed at a temperature of 100 to 160°C, preferably for 15 to 120 minutes.

The obtained foam rubber is preferably cleaned after being taken out from the mold. The cleaning method is not particularly limited. For example, a cleaning method may be performed using a cleaning machine or the like, using water at about 20° C. to 70° C., and stirring for about 5 to 15 minutes. After washing, it is preferable to remove water and dry the foam rubber 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 powder puff (cosmetic sponge) or the like by, for example, cutting it into a predetermined thickness and cutting it into a predetermined shape, and then polishing the side surfaces with a rotating grindstone or the like.

The foam rubber of the present invention is obtained using the latex composition for foam rubber of the present invention described above. Therefore, it has excellent oil resistance, has a soft touch, and appropriately suppresses discoloration, deterioration and odor generation during repeated use, and is suitable as Powder puff (makeup sponge). In addition to powder puffs (cosmetic sponges), it can be suitably used for various applications such as mattresses, rollers, and impact absorbers.

Example

Hereinafter, the present invention will be described in detail using examples, but the present invention is not limited to these examples. In addition, the following "parts" are based on weight unless otherwise specified. In addition, various physical properties were measured as follows.

<Solid content concentration of copolymer rubber latex and foam rubber latex composition>

Accurately weigh 2 g of the sample (weight: X2) in an aluminum pan (weight: X1), and dry it in a hot air dryer at 105°C for 2 hours. Next, after cooling in a desiccator, the weight was measured together with the aluminum pan (weight: X3), and the solid content concentration was calculated based on the following formula.

Solid content concentration (weight%)=(X3-Xl)×l00/X2

<Viscosity of copolymer rubber latex>

The viscosity of the copolymer rubber latex was measured using a B-type viscometer at a temperature of 25°C and a rotation speed of 60 rpm.

＜Odor of copolymer rubber latex＞

After adding 50 mL of copolymer rubber latex to a sealable 100 mL container and leaving it at 25° C. for 24 hours, five people checked the odor during opening and closing. Judgment is carried out based on the following criteria.

A: None of the five people felt the rancid smell.

B: 1 to 4 out of 5 people felt a rancid smell.

C: 5 out of 5 people felt the rancid smell.

＜Oil resistance of foam rubber＞

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

＜Type F hardness of foam rubber＞

The hardness of the foam rubber was measured using an ASKER rubber hardness meter F type (manufactured by Polymer Instruments Co., Ltd.). The lower the value, the softer the foam rubber is, and it can be judged that the skin feels better.

＜Discoloration, deterioration, and odor of foam rubber due to repeated use＞

A test piece was obtained by punching a disk-shaped foam rubber with a thickness of 0.8 cm into a circle with a diameter of about 38 mm, and the obtained test piece was repeatedly used. As a repeated use operation, first, the test piece was immersed in silicone oil (decamethylcyclopentasiloxane), washed with water using a kitchen neutral detergent, and air-dried at room temperature for 24 hours. First, this operation was repeated 10 times, and then left at 25°C for 10 days to obtain a test piece after repeated use. The test pieces after repeated use were used to evaluate discoloration, deterioration and odor during repeated use.

(discoloration due to repeated use)

Regarding discoloration during repeated use, five people visually confirmed the test pieces before and after repeated use, compared with the sample before repeated use, and judged according to the following standards.

A: No obvious discoloration was seen in any of the 5 people.

B: 1 to 4 people felt discoloration.

C: All 5 people clearly felt a brownish discoloration.

(Deterioration due to repeated use)

Deterioration during repeated use was confirmed through tactile evaluation by five people who actually touched it with their hands, and the judgment was made based on the following standards.

A: None of the five people felt any obvious changes in touch.

B: 1 to 4 people felt the change in touch.

C: All 5 people clearly felt a hard and dry touch.

(Smell due to 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. The odor after leaving was confirmed by five people and judged according to the following standards.

A: All 5 people couldn’t feel the odor at all.

B: 1 to 4 people felt a slight odor.

C: All 5 people clearly felt the odor.

<Example 1>

(Preparation of copolymer rubber latex)

In the pressure-resistant reaction vessel, add 200 parts of ion-exchange water, 1.5 parts of potassium oleate, 35 parts of acrylonitrile, 0.5 parts of tert-dodecyl mercaptan, 0.03 parts of sodium formaldehyde sulfoxylate, 0.003 parts of ferrous sulfate and 0.008 parts of sodium ethylenediaminetetraacetate. After sufficient degassing, add 45 parts of 1,3-butadiene. 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. Then, when the polymerization conversion rate reaches 40%, 10 parts of 1,3-butadiene is added to continue the polymerization reaction. Furthermore, 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 reaches 80%, 2,2,6,6-tetramethylpiperidin-1-oxyl radical (TEMPO) is added in the form of an aqueous dispersion to terminate the polymerization reaction. In addition, the usage amount of 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO) was set to an amount of 2000 ppm by weight in the finally obtained latex composition for foam rubber. Then, after removing the unreacted monomer, 80 parts of 1,3-butadiene was added to adjust the temperature in the system to 15°C, and stirred at 1000 rpm for 5 hours using a paddle-type stirring blade to increase the particle size. deal with. Next, 1,3-butadiene was removed and then concentrated to obtain a copolymer rubber latex with a solid content concentration of 67% by weight. The obtained copolymer rubber latex had a pH of 11.3 and a viscosity (B-type viscosity) of 280 cps. In addition, the composition and the amount of the monomer units contained in the copolymer rubber constituting the copolymer rubber latex are substantially the same (the same applies to Examples 2 to 5 and Comparative Examples 1 to 5 described later).

(Preparation of latex composition for foam rubber)

Then, 4 parts of a vulcanization-based aqueous dispersion (colloidal sulfur/dithiocarbamate-based vulcanization accelerator NOCCELER EZ (Ouchi Hoshiki Chemical Industry) was added to 100 parts of the solid content of the copolymer rubber latex obtained above Co., Ltd.)/thiazole-based vulcanization accelerator NOCCELER MZ (manufactured by Ouchi Shinko Chemical Industry Co., Ltd.) = 2/1/1 (weight ratio): solid content concentration 50% by weight), 3 parts of zinc oxide aqueous dispersion ( Solid content concentration: 50% by weight), 1 part of air bubble stabilizer (Torimen base: manufactured by Crompton Corp), and 1,2-benzisothiazolin-3-one (BIT), and fully disperse them to obtain a solid content concentration It is a 67% by weight copolymer latex composition for foam rubber. In addition, the addition amount of 1,2-benzisothiazolin-3-one (BIT) was set to an amount of 100 ppm by weight in the copolymer latex composition for foam rubber.

(Manufacturing of foam rubber)

Then, the copolymer latex composition for foam rubber obtained above was stirred using a vertical mixer (ESM945 manufactured by Electrolux Corporation), and after foaming to about 5 times the volume, 1.5 parts of sodium fluorosilicate aqueous dispersion (solid component concentration: 20% by weight), and further stirred for 1 minute to obtain a foamed product. Next, the obtained foam was poured into a mold for molding (diameter 7 cm, height 8 cm), solidified, and then vulcanized at 110° C. for 1 hour to obtain foam rubber. Wash the foam rubber taken out from the mold with hot water at 40°C for 10 minutes, dry it in an oven at 60°C for 4 hours, and then cut it into a disc shape with a thickness of 0.8cm to obtain a disc-shaped foam rubber. Follow the above steps According to the method, oil resistance, F-type hardness, discoloration, deterioration and odor during repeated use were measured and evaluated. The results are shown in Table 1.

<Example 2>

The usage amount of acrylonitrile was changed to 45 parts, the amount of 1,3-butadiene used in polymerization initiation was changed to 35 parts, and 2,2,6,6-tetramethylpiperidine-1-oxo Except that the usage amount of free radicals (TEMPO) was set to 1000 ppm by weight in the finally obtained latex composition for foam rubber, the same operation was performed as in Example 1 to prepare a solid content concentration of 65 wt%. Copolymer rubber latex. The pH and viscosity (type B viscosity) of the obtained copolymer rubber latex are shown in Table 1.

Then, except using the copolymer rubber latex obtained above, preparation of a latex composition for foam rubber (solid content concentration: 65% by weight) and production of foam rubber were carried out in the same manner as in Example 1, and evaluation was performed in the same manner. The results are shown in Table 1.

<Example 3>

A solid component was prepared in the same manner as in Example 2 except that the amount of 1,3-butadiene used at the time of polymerization initiation was changed to 30 parts and 5 parts of isoprene was further blended at the time of polymerization initiation. Copolymer rubber latex with a concentration of 67% by weight. The pH and viscosity (type B viscosity) of the obtained copolymer rubber latex are shown in Table 1.

Then, except using the copolymer rubber latex obtained above, preparation of a latex composition for foam rubber (solid content concentration 67% by weight) and production of foam rubber were carried out in the same manner as in Example 1, and evaluation was performed in the same manner. The results are shown in Table 1.

<Example 4>

In addition, the usage amount of 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO) is set to 500 ppm by weight in the finally obtained latex composition for foam rubber. , the same operation as in Example 2 was performed to prepare a copolymer rubber latex with a solid content concentration of 65% by weight. The pH and viscosity (type B viscosity) of the obtained copolymer rubber latex are shown in Table 1.

Then, except using the copolymer rubber latex obtained above, preparation of a latex composition for foam rubber (solid content concentration: 65% by weight) and production of foam rubber were carried out in the same manner as in Example 1, and evaluation was performed in the same manner. The results are shown in Table 1.

<Example 5>

The copolymer rubber latex obtained in the same manner as in Example 2 was used, but the same amount of 2-methyl-4-isothiazolin-3-one (MIT) was used instead of 1,2-benzisothiazolin- Except for 3-ketone (BIT), the preparation of a latex composition for foam rubber (solid content concentration 65% by weight) and the production of foam rubber were carried out in the same manner as in Example 2, and evaluation was performed in the same manner. The results are shown in Table 1.

＜Comparative example 1＞

The usage amount of acrylonitrile was changed to 47 parts, the amount of 1,3-butadiene used during polymerization initiation was changed to 18 parts, and 15 parts of isoprene was added during polymerization initiation, and diethyl was used. The aqueous dispersion of hydroxylamine (HAS) was used instead of the aqueous dispersion of 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO). The operation was carried out in the same manner as in Example 1. A copolymer rubber latex having a solid content concentration of 65% by weight was prepared. In addition, the usage amount of diethylhydroxylamine (HAS) was set to an amount of 2000 ppm by weight in the finally obtained latex composition for foam rubber. In addition, the pH and viscosity (type B viscosity) of the obtained copolymer rubber latex are shown in Table 1.

Then, except using the copolymer rubber latex obtained above, preparation of a latex composition for foam rubber (solid content concentration: 65% by weight) and production of foam rubber were carried out in the same manner as in Example 1, and evaluation was performed in the same manner. The results are shown in Table 1.

＜Comparative example 2＞

The same procedure as Example 2 was performed except that the aqueous dispersion of diethylhydroxylamine (HAS) was used instead of the aqueous dispersion of 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO). By operation, a copolymer rubber latex with a solid content concentration of 65% by weight was prepared. In addition, the usage amount of diethylhydroxylamine (HAS) was set to an amount of 2000 ppm by weight in the finally obtained latex composition for foam rubber. In addition, the pH and viscosity (type B viscosity) of the obtained copolymer rubber latex are shown in Table 1.

Then, except using the copolymer rubber latex obtained above, preparation of a latex composition for foam rubber (solid content concentration: 65% by weight) and production of foam rubber were carried out in the same manner as in Example 1, and evaluation was performed in the same manner. The results are shown in Table 1.

＜Comparative Example 3＞

Except not using 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO), the same procedure as in Example 2 was performed to prepare a copolymer rubber latex with a solid content concentration of 65% by weight. . In addition, in Comparative Example 3, no polymerization terminator for emulsion polymerization was used. The pH and viscosity (type B viscosity) of the obtained copolymer rubber latex are shown in Table 1.

Then, except using the copolymer rubber latex obtained above, preparation of a latex composition for foam rubber (solid content concentration: 66% by weight) and production of foam rubber were carried out in the same manner as in Example 1, and evaluation was performed in the same manner. The results are shown in Table 1.

＜Comparative Example 4＞

Foam rubber was performed 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. Evaluation was performed in the same manner as in the preparation of the latex composition (solid content concentration: 65% by weight) and the production of foam rubber. The results are shown in Table 1.

＜Comparative Example 5＞

Except that the usage amount of acrylonitrile was changed to 20 parts and the amount of 1,3-butadiene used in polymerization initiation was changed to 55 parts, the same operation was performed as in Example 3 to prepare a solid content concentration of 65 parts by weight. % copolymer rubber latex. The pH and viscosity (type B viscosity) of the obtained copolymer rubber latex are shown in Table 1.

Then, except using the copolymer rubber latex obtained above, preparation of a latex composition for foam rubber (solid content concentration: 65% by weight) and production of foam rubber were carried out in the same manner as in Example 1, and evaluation was performed in the same manner. The results are shown in Table 1.

[Table 1]

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, nitroxyl The foam rubber obtained from a latex composition for foam rubber having a radical compound, a thiazoline compound, and a solid content concentration of 55 to 75% by weight has excellent oil resistance, has a soft touch, and appropriately suppresses deterioration during repeated use. Discoloration, deterioration and generation of odor (Examples 1 to 5).

On the other hand, when diethylhydroxylamine (HAS) is used instead of the nitroxyl radical compound, although 1,2-benzisothiazolin-3-one (BIT) is contained as a thiazoline compound, The obtained foam rubber generates an odor when used repeatedly (Comparative Examples 1 and 2).

When the nitroxyl radical compound is not used, the obtained foam rubber undergoes discoloration and deterioration during repeated use, and the inhibitory effect on the generation of odor during repeated use is insufficient (Comparative Example 3).

In addition, when a nitroxyl radical compound was contained but no thiazoline compound was contained, the resulting foam rubber produced an odor when repeatedly used (Comparative Example 4).

Furthermore, when the composition of the copolymer rubber constituting the copolymer rubber latex is outside the range specified by the present invention, the resulting foam rubber has poor oil resistance and low F-type hardness, and cannot obtain a soft touch (Comparative Example 5).

Claims (9)

1. A latex composition for foam rubber comprising a copolymer rubber latex, a nitroxyl radical compound and a thiazoline compound,

the copolymer rubber latex contains 30 to 60% by weight of a cyano-containing ethylenically unsaturated monomer unit and 40 to 70% by weight of an aliphatic conjugated diene monomer unit,

the solid content concentration of the latex composition for foam rubber is 55-75 wt%.

2. The latex composition for foamed rubber according to claim 1, wherein the nitroxyl radical compound is contained in an amount of 100 to 10000 ppm by weight.

3. The latex composition for foamed rubber according to claim 1 or 2, wherein the thiazoline compound is contained in an amount of 10 to 1000 ppm by weight.

4. A latex composition for foam rubber according to any one of claims 1 to 3, wherein the nitroxyl radical compound is 2, 6-tetramethylpiperidin-1-oxyl (TEMPO).

5. The latex composition for foam rubber according to any one of claims 1 to 4, wherein the thiazoline-based compound is 2-methyl-4-isothiazolin-3-one (MIT) or 1, 2-benzisothiazolin-3-one (BIT).

6. The latex composition for foamed rubber according to any one of claims 1 to 5, wherein the solid content concentration of the latex composition for foamed rubber is 60 to 70% by weight.

7. The latex composition for foamed rubber according to any one of claims 1 to 6, wherein the solid content concentration of the latex composition for foamed rubber is 63 to 69% by weight.

8. The latex composition for foamed rubber according to any one of claims 1 to 7, wherein the solid content concentration of the latex composition for foamed rubber is 64.5 to 67.5% by weight.

9. A foam rubber obtained by using the latex composition for a foam rubber according to any one of claims 1 to 8.