JPWO2009145009A1 - Copolymer latex composition for foam rubber, copolymer latex composition for vulcanizable foam rubber, and foam rubber - Google Patents

Abstract

The copolymer rubber latex composition for foam rubber of the present invention has a cyano group-containing ethylenically unsaturated monomer unit (a1) of 30 to 45% by weight, a conjugated diene monomer unit (a2) of 55 to 70% by weight, And a copolymer (a) comprising 0 to 15% by weight of a unit (a3) of another ethylenically unsaturated monomer copolymerizable with a cyano group-containing ethylenically unsaturated monomer and a conjugated diene monomer. Latex (A), cyano group-containing ethylenically unsaturated monomer unit (b1) 45 to 65% by weight, conjugated diene monomer unit (b2) 35 to 55% by weight, and cyano group-containing ethylenically unsaturated monomer unit Latex (B) of copolymer (b) comprising 0 to 20% by weight of a unit of monomer and other ethylenically unsaturated monomer copolymerizable with conjugated diene monomer (provided that cyano group Containing ethylenically unsaturated monomer unit (b ) Is greater than the amount of the cyano group-containing ethylenically unsaturated monomer unit (a1) by at least 5% by weight), and the weight ratio of the copolymer (a) to the copolymer (b) (( Copolymer (a) / copolymer (b)), which is obtained by mixing at a ratio of 20/80 to 80/20.

Description

  The present invention provides a foam rubber suitable as a cosmetic sponge (puff) having excellent oil resistance and a soft touch, a vulcanizable foam rubber copolymer rubber latex composition for the foam rubber, and a foam rubber The present invention relates to a copolymer rubber latex composition.

  Foam rubber (rubber foam) produced using a polymer rubber latex is used in various applications as a mattress, puff, roll, impact absorber and the like. Among the applications of foam rubber, especially for puffs, there is a demand for sponges that have good oil resistance to cosmetics and have a soft feel.

Patent Document 1 discloses an acrylonitrile-butadiene copolymer rubber (NBR) latex that imparts oil resistance to a puff.
Patent Document 2 discloses 15 to 45% by weight of a cyano group-containing ethylenically unsaturated monomer, 55 to 85% by weight of a conjugated diene monomer, and 0 to 30 ethylenically unsaturated monomers copolymerizable therewith. It is a copolymer rubber latex obtained by emulsion polymerization of a monomer mixture consisting of wt%, the microstructure of the conjugated diene monomer unit is in a specific range, and the gel content is 20 to 65 wt% A copolymer rubber latex for foam rubber containing a copolymer rubber in the range is disclosed.
Patent Document 3 includes 10 to 50% by weight of a cyanated vinyl monomer, 50 to 90% by weight of an aliphatic conjugated diene monomer, and 0 to 20% by weight of another monomer copolymerizable therewith. A copolymer latex obtained by emulsion polymerization of a monomer mixture and having a solid content concentration of 60% or more and a Mooney viscosity of 60 to 150 is disclosed.
Patent Document 4 discloses a puff using a mixture of an NBR latex and an EPDM latex in which the ratio of EPDM is specified, which is suitable for a powder cosmetic containing a polar oil.

JP-A-6-14811 JP-A-11-263847 JP 2006-181051 A JP 2007-89965 A

In recent years, as disclosed in Patent Document 4, the puff has been required to have excellent oil resistance, as compared with the conventional case. In order to improve oil resistance in the NBR latex, it is usually performed to increase the amount of a cyano group-containing ethylenically unsaturated monomer typified by acrylonitrile. However, according to the study by the present inventors, it is possible to improve the oil resistance by increasing the amount of the cyano group-containing ethylenically unsaturated monomer. It was found that it was difficult to satisfy the characteristics required as a puff.
In view of the above circumstances, the present inventors have intensively studied to provide a foam rubber suitable as a puff having good oil resistance and a soft feel. As a result, by using two types of latexes of a copolymer containing a specific amount of a cyano group-containing ethylenically unsaturated monomer unit, by using a copolymer rubber latex composition obtained by mixing them in a specific range, The present inventors have found that the object of the present invention is achieved, and have completed the present invention based on this finding.

  The present invention relates to a cyano group-containing ethylenically unsaturated monomer unit (a1) 30 to 45% by weight, a conjugated diene monomer unit (a2) 55 to 70% by weight, and a cyano group-containing ethylenically unsaturated monomer. And latex (A) of copolymer (a) comprising 0 to 15% by weight of unit (a3) of other ethylenically unsaturated monomer copolymerizable with conjugated diene monomer, and cyano group-containing ethylenic monomer Copolymerized with 45 to 65% by weight of unsaturated monomer unit (b1), 35 to 55% by weight of conjugated diene monomer unit (b2), and cyano group-containing ethylenically unsaturated monomer and conjugated diene monomer Possible other ethylenically unsaturated monomer unit (b3) latex (B) of copolymer (b) consisting of 0 to 20% by weight (provided that cyano group-containing ethylenically unsaturated monomer unit (b1) ) Amount of cyano group-containing ethylenically unsaturated monomer Greater than the amount of the unit (a1) by weight ratio of the copolymer (a) to the copolymer (b) ((copolymer (a) / copolymer (b)). , 20/80 to 80/20, a rubber copolymer composition for foam rubber.

In a preferred embodiment of the present invention, the cyano group-containing ethylenically unsaturated monomer unit (a1) is an acrylonitrile unit, and the conjugated diene monomer unit (a2) is a 1,3-butadiene unit and an isoprene unit. is there.
The preferred weight ratio of the 1,3-butadiene unit and the isoprene unit is in the range of 5/5 to 9/1.
The preferred gel content of the copolymer (a) is 65% by weight or less.
Preferably, the cyano group-containing ethylenically unsaturated monomer unit (b1) is an acrylonitrile unit, and the conjugated diene monomer unit (b2) is a 1,3-butadiene unit.
The preferable gel content of the copolymer (b) is 35% by weight or less.

  The present invention provides a copolymer rubber latex composition for a vulcanizable foam rubber comprising the copolymer rubber latex composition for a foam rubber and a vulcanizing agent. A preferred vulcanizing agent is sulfur. Preferably, the copolymer rubber latex composition for vulcanizable foam rubber of the present invention contains a vulcanization aid and a vulcanization accelerator. A preferred vulcanization aid is zinc oxide, and preferred vulcanization accelerators are thiazole vulcanization accelerators and dithiocarbamate vulcanization accelerators.

  Furthermore, the present invention provides a foam rubber obtained by foaming, coagulating and vulcanizing the copolymer rubber latex composition for vulcanizable foam rubber.

  The foam rubber of the present invention has excellent oil resistance and a good texture, and is particularly suitable for puffs.

  The copolymer rubber latex composition for foam rubber of the present invention comprises a specific copolymer (a) latex (A) and a specific copolymer (b) latex (B) at a specific ratio. It is a mixture.

Latex (A)
Latex (A) used in the present invention comprises 30 to 45% by weight of cyano group-containing ethylenically unsaturated monomer unit (a1), 55 to 70% by weight of conjugated diene monomer unit (a2), and cyano group-containing ethylene. It is a latex of a copolymer (a) composed of 0 to 15% by weight of units (a3) of other ethylenically unsaturated monomers copolymerizable with a polymerizable unsaturated monomer and a conjugated diene monomer.

Examples of the cyano group-containing ethylenically unsaturated monomer constituting the cyano group-containing ethylenically unsaturated monomer unit (a1) include acrylonitrile, methacrylonitrile, α-chloroacrylonitrile, α-cyanoethyl acrylate, and the like. It is done. These can be used alone or in combination of two or more. Particularly preferred are acrylonitrile and methacrylonitrile.
The content of the cyano group-containing ethylenically unsaturated monomer unit (a1) in the copolymer (a) is 30 to 45% by weight, preferably 35 to 40% by weight. If this amount is small, the oil resistance is insufficient, while if it is large, the puff feel becomes hard and the texture becomes poor.

Examples of the conjugated diene monomer constituting the conjugated diene monomer unit (a2) include 1,3-butadiene, isoprene (2-methyl-1,3-butadiene), 2,3-dimethyl-1,3. -Butadiene, 2-ethyl-1,3-butadiene, 1,3-pentadiene and the like. These can be used alone or in combination of two or more. Among these, 1,3-butadiene and isoprene are preferable.
The content of the conjugated diene monomer unit (a2) in the copolymer (a) is 55 to 70% by weight, preferably 60 to 65% by weight. If this amount is small, the puff feel will be hard and the texture will be poor, and conversely if it is large, the oil resistance will be insufficient.
The conjugated diene monomer unit (a2) preferably contains a 1,3-butadiene unit and an isoprene unit in terms of being excellent in the balance between puff texture and oil resistance, and the weight ratio thereof is 1,3- The butadiene unit / isoprene unit is preferably in the range of 5/5 to 9/1.

As other ethylenically unsaturated monomers constituting the unit (a3) of other ethylenically unsaturated monomers copolymerizable with cyano group-containing ethylenically unsaturated monomers and conjugated diene monomers, For example, (meth) acrylic acid, (anhydrous) maleic acid, fumaric acid, itaconic acid and other ethylenically unsaturated carboxylic acids; methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, 2-ethylhexyl ( Ethylenically unsaturated carboxylic acids such as (meth) acrylate, lauryl (meth) acrylate, mono or dimethyl maleate, mono or diethyl fumarate, mono or di-n-butyl fumarate, mono- or di-n-butyl itaconic acid Mono- or dialkyl esters of methoxy acrylate, ethoxy acrylate, methoxyethoxy ethyl Alkoxyalkyl esters of ethylenically unsaturated carboxylic acids such as acrylate; (meth) acrylates having a hydroxyalkyl group such as 2-hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, hydroxybutyl (meth) acrylate; glycidyl (Meth) acrylate; (meth) acrylamide, N-methylol (meth) acrylamide, (meth) acrylic amide and derivatives thereof such as N-butoxymethyl (meth) acrylamide; amino groups such as dimethylaminomethyl acrylate and diethylaminomethyl acrylate An acrylate having an aromatic vinyl monomer such as styrene, α-methylstyrene, vinyltoluene and chlorostyrene; an α-olefin such as ethylene and propylene; Include non-conjugated diene monomers such as vinyl norbornene. These monomers can be used alone or in combination of two or more.
The content of other ethylenically unsaturated monomer units (a3) in the copolymer (a) is 15% by weight or less, preferably 10% by weight or less, more preferably 0% by weight. When the content is large, the balance of characteristics required as a puff deteriorates.

The gel content of the copolymer (a) is preferably 65% by weight or less, more preferably 10 to 65% by weight, and particularly preferably 30 to 60% by weight. When the gel content is in the above range, a foam rubber excellent in flexibility can be obtained while maintaining the strength. If the strength of the foam rubber is too low, chipping may occur when a cosmetic material or the like is scraped off as a puff.
In addition, gel content is defined by the methyl ethyl ketone insoluble matter mentioned later.

Such a latex (A) can be obtained by a usual emulsion polymerization technique, and the gel content can be adjusted by the polymerization temperature, the polymerization conversion rate, the amount of molecular weight regulator used, and the like.
As the polymerization agent such as an emulsifier (surfactant), a polymerization initiator, a chelating agent, an oxygen scavenger and a molecular weight modifier used for emulsion polymerization, conventionally known respective agents can be used and are not particularly limited.
For example, as the emulsifier, an anionic and / or nonionic (nonionic) emulsifier is usually used. The emulsifier is usually used in the range of 0.5 to 5 parts by weight with respect to 100 parts by weight of the total monomers.

  Examples of the anionic emulsifier include fatty acid salts such as potassium beef tallow fatty acid, partially hydrogenated beef tallow fatty acid potassium, potassium oleate, and sodium oleate; potassium rosinate, sodium rosinate, hydrogenated potassium rosinate, and hydrogenated sodium rosinate Resin acid salts such as alkylbenzene sulfonates such as sodium dodecylbenzene sulfonate. Examples of the nonionic emulsifier include a polyethylene glycol ester type, a polyethylene glycol ester type, and a pluronic type emulsifier such as a block copolymer of ethylene oxide and propylene oxide.

  Examples of the polymerization initiator include pyrolytic 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; redox initiators composed of these and reducing agents such as divalent iron ions It is done. Of these, redox initiators are preferred. The amount of these initiators used is usually in the range of 0.01 to 10 parts by weight with respect to 100 parts by weight of the total monomers.

Examples of the molecular weight regulator include alkyl mercaptans such as n-hexyl mercaptan, n-octyl mercaptan, t-octyl mercaptan, n-dodecyl mercaptan, t-dodecyl mercaptan, n-stearyl mercaptan; dimethylxanthogen disulfide, diisopropylxanthogendi Xanthogen compounds such as sulfide; thiuram compounds such as tetramethylthiuram disulfide, tetraethylthiuram disulfide 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-ben Examples include diloxyacrylonitrile, α-benzyloxyacrylamide, triphenylethane, pentaphenylethane, acrolein, methacrolein, thioglycolic acid, thiomalic acid, 2-ethylhexyl thioglycolate, α-methylstyrene dimer, terpinolene, and the like. 1 type, or 2 or more types can be used.
The amount of the molecular weight modifier used is preferably 0.1 to 3 parts by weight, more preferably 0.2 to 2 parts by weight, and particularly preferably 0.3 to 1.5 parts by weight with respect to 100 parts by weight of the total monomers. Part. If the amount used is small, the gel content tends to be high, whereas if it is too large, the strength of the foam rubber tends to decrease.

The emulsion polymerization reaction may be either a continuous type or a batch type, and the polymerization time is not particularly limited.
The method for adding the monomer is not particularly limited, and for example, a batch addition method, a divided addition method, or the like can be used.

The polymerization conversion rate when the polymerization is stopped is not particularly limited, but is preferably 90% by weight or more, more preferably 93% by weight or more. If the polymerization conversion is too low, productivity tends to decrease.
Although superposition | polymerization temperature is not specifically limited, Preferably it is 0-50 degreeC, More preferably, it is 5-35 degreeC.
After the polymerization, if necessary, after removing the unreacted monomer, it is preferable to perform a particle size enlargement treatment by a known method. By performing this particle size enlargement treatment, the solid content concentration of the latex (A) can be increased to a range suitable for foam rubber.

Examples of the method for enlarging the particle size include a method in which the reaction is stopped in the middle of the polymerization and strongly stirred; a method in which a conjugated diene monomer such as butadiene, toluene, or the like is added as a solvent after the polymerization is completed; Examples thereof include a method in which a particle size thickening agent such as a polymer latex is added to the copolymer latex and stirred.
After the particle size enlargement treatment, the solid content concentration is adjusted to an optimum range by a concentration operation. The solid content concentration of the latex (A) is preferably in the range of 55 to 75% by weight, and preferably in the range of 60 to 70% by weight. If the solid content concentration is too low, bubble roughness tends to occur and the appearance tends to deteriorate, and it is difficult to increase the solid content concentration beyond the above range.
The weight average particle diameter of the copolymer (a) particles is also not particularly limited, but is usually about 300 to 3000 nm, preferably about 400 to 2000 nm.

Latex (B)
The latex (B) used in the present invention comprises 45 to 65% by weight of cyano group-containing ethylenically unsaturated monomer unit (b1), 35 to 55% by weight of conjugated diene monomer unit (b2), and cyano group-containing ethylene. It is a latex of a copolymer (b) composed of 0 to 15% by weight of a unit (b3) of another ethylenically unsaturated monomer copolymerizable with a polymerizable unsaturated monomer and a conjugated diene monomer. However, the amount of the cyano group-containing ethylenically unsaturated monomer unit (b1) is 5% by weight or more larger than the amount of the cyano group-containing ethylenically unsaturated monomer unit (a1).

Examples of the cyano group-containing ethylenically unsaturated monomer constituting the cyano group-containing ethylenically unsaturated monomer unit (b1) include acrylonitrile, methacrylonitrile, α-chloroacrylonitrile, α-cyanoethyl acrylate, and the like. It is done. These can be used alone or in combination of two or more. Particularly preferred are acrylonitrile and methacrylonitrile.
The content of the cyano group-containing ethylenically unsaturated monomer unit (b1) in the copolymer (b) is 45 to 65% by weight, preferably 47 to 60% by weight. If this amount is small, the oil resistance is insufficient, while if it is large, the puff feel becomes hard and the texture becomes poor.

Examples of the conjugated diene monomer constituting the conjugated diene monomer unit (b2) include 1,3-butadiene, isoprene (2-methyl-1,3-butadiene), 2,3-dimethyl-1,3. -Butadiene, 2-ethyl-1,3-butadiene, 1,3-pentadiene and the like. These can be used alone or in combination of two or more. Among these, 1,3-butadiene and isoprene are preferable.
The content of the conjugated diene monomer unit (b2) in the copolymer (b) is 35 to 55% by weight, preferably 40 to 53% by weight. If this amount is small, the puff feel will be hard and the texture will be poor, and conversely if it is large, the oil resistance will be insufficient.

As other ethylenically unsaturated monomers constituting the unit (b3) of other ethylenically unsaturated monomers copolymerizable with cyano group-containing ethylenically unsaturated monomers and conjugated diene monomers, For example, (meth) acrylic acid, (anhydrous) maleic acid, fumaric acid, itaconic acid and other ethylenically unsaturated carboxylic acids; methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, 2-ethylhexyl ( Ethylenically unsaturated carboxylic acids such as (meth) acrylate, lauryl (meth) acrylate, mono or dimethyl maleate, mono or diethyl fumarate, mono or di-n-butyl fumarate, mono- or di-n-butyl itaconic acid Mono- or dialkyl esters of methoxy acrylate, ethoxy acrylate, methoxyethoxy ethyl Alkoxyalkyl esters of ethylenically unsaturated carboxylic acids such as acrylate; (meth) acrylates having a hydroxyalkyl group such as 2-hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, hydroxybutyl (meth) acrylate; glycidyl (Meth) acrylate; (meth) acrylamide, N-methylol (meth) acrylamide, (meth) acrylic amide and derivatives thereof such as N-butoxymethyl (meth) acrylamide; amino groups such as dimethylaminomethyl acrylate and diethylaminomethyl acrylate An acrylate having an aromatic vinyl monomer such as styrene, α-methylstyrene, vinyltoluene and chlorostyrene; an α-olefin such as ethylene and propylene; Include non-conjugated diene monomers such as vinyl norbornene. These monomers can be used alone or in combination of two or more.
The content of other ethylenically unsaturated monomer units (b3) in the copolymer (b) is 20% by weight or less, preferably 10% by weight or less, more preferably 0% by weight. When the content is large, the balance of characteristics required as a puff deteriorates.

The gel content of the copolymer (b) is preferably 35% by weight or less, more preferably 0 to 35% by weight, and particularly preferably 0 to 30% by weight. When the gel content is in the above range, a foam rubber that is superior in balance between oil resistance and flexibility can be obtained. If the gel content is too high, flexibility may be impaired.
In addition, gel content is defined by the methyl ethyl ketone insoluble matter mentioned later.

Such a latex (B) can be obtained by an ordinary emulsion polymerization method, and the gel content depends on the polymerization temperature, the polymerization conversion rate, the monomer addition method, the amount of use of the molecular weight regulator, and the like. Can be adjusted.
As the polymerization agent such as an emulsifier (surfactant), a polymerization initiator, a chelating agent, an oxygen scavenger and a molecular weight modifier used for emulsion polymerization, conventionally known respective agents can be used and are not particularly limited. For example, as the emulsifier, an anionic and / or nonionic (nonionic) emulsifier is usually used. The emulsifier is usually used in the range of 0.5 to 5 parts by weight with respect to 100 parts by weight of the total monomers.

  Examples of the anionic emulsifier include fatty acid salts such as potassium beef tallow fatty acid, partially hydrogenated beef tallow fatty acid potassium, potassium oleate, and sodium oleate; potassium rosinate, sodium rosinate, hydrogenated potassium rosinate, and hydrogenated sodium rosinate Resin acid salts such as alkylbenzene sulfonates such as sodium dodecylbenzene sulfonate. Examples of the nonionic emulsifier include a polyethylene glycol ester type, a polyethylene glycol ester type, and a pluronic type emulsifier such as a block copolymer of ethylene oxide and propylene oxide.

  Examples of the polymerization initiator include pyrolytic 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; redox initiators composed of these and reducing agents such as divalent iron ions It is done. Of these, redox initiators are preferred. The amount of these initiators used is usually in the range of 0.01 to 10 parts by weight with respect to 100 parts by weight of the total monomers.

Examples of the molecular weight regulator include alkyl mercaptans such as n-hexyl mercaptan, n-octyl mercaptan, t-octyl mercaptan, n-dodecyl mercaptan, t-dodecyl mercaptan, n-stearyl mercaptan; dimethylxanthogen disulfide, diisopropylxanthogendi Xanthogen compounds such as sulfide; thiuram compounds such as tetramethylthiuram disulfide, tetraethylthiuram disulfide 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-ben Examples include diloxyacrylonitrile, α-benzyloxyacrylamide, triphenylethane, pentaphenylethane, acrolein, methacrolein, thioglycolic acid, thiomalic acid, 2-ethylhexyl thioglycolate, α-methylstyrene dimer, terpinolene, and the like. 1 type, or 2 or more types can be used.
The amount of the molecular weight modifier used is preferably 0.1 to 3 parts by weight, more preferably 0.2 to 2 parts by weight, and particularly preferably 0.3 to 1.5 parts by weight with respect to 100 parts by weight of the total monomers. Part. If the amount used is small, the gel content tends to be high, whereas if it is too large, the strength of the foam rubber tends to decrease.

The emulsion polymerization reaction may be either a continuous type or a batch type, and the polymerization time is not particularly limited.
The method for adding the monomer is not particularly limited, and for example, a batch addition method, a divided addition method, or the like can be used. A method in which a part of the conjugated diene monomer used for the polymerization is added to the reactor after the polymerization reaction is continued and the polymerization is continued is preferable because the foam rubber obtained is excellent in the balance between oil resistance and flexibility. Can be adopted.
In this case, after adding the cyano group-containing ethylenically unsaturated monomer and a part of the conjugated diene monomer to the reactor and starting the polymerization reaction, the polymerization reaction rate in the reactor is 20 to 65%. In the meantime, it is preferable to add the remainder of the conjugated diene monomer all at once or in a divided manner to the reactor and further continue the polymerization reaction. The ratio of the conjugated diene monomer added after the start of the polymerization reaction is 20 to 60% by weight of the total amount of the conjugated diene monomer used for the polymerization. The monomer composition used in this case is 50 to 70% by weight of a cyano group-containing ethylenically unsaturated monomer and 30 to 5 conjugated diene monomer.
It is preferably in the range of 0% by weight.

The polymerization conversion rate when the polymerization is stopped is not particularly limited, but is preferably 70 to 90% by weight, and more preferably 75 to 85% by weight. If this polymerization conversion rate is too low, productivity tends to decrease. On the other hand, if it is too high, the composition distribution of the polymer spreads and the flexibility of the foam rubber may be impaired.
Although superposition | polymerization temperature is not specifically limited, Preferably it is 0-50 degreeC, More preferably, it is 5-35 degreeC. If the polymerization temperature is too high, the gel content tends to increase.
After the polymerization, if necessary, after removing the unreacted monomer, a particle size enlargement treatment may be performed by a known method. By performing this particle size enlargement treatment, the solid content concentration of the latex (B) can be increased to a range suitable for foam rubber. As the particle size enlargement method, the method described in the latex (A) can be employed.

Copolymer rubber latex composition for foam rubber The copolymer rubber latex composition for foam rubber of the present invention comprises the latex (A) and the latex (B) which are copolymerized with the copolymer (a). The weight ratio of the polymer (b) ((copolymer (a) / copolymer (b)) is mixed at a ratio of 20/80 to 80/20.
The mixing ratio of the latex (A) and the latex (B) is a weight ratio of the copolymer (a) to the copolymer (b) ((copolymer (a) / copolymer (b)). 80 to 80/20, preferably 40/60 to 70/30 When the ratio of the copolymer (a) is small, the foam rubber is inferior in flexibility, and conversely when it is large, the oil resistance is inferior.

  The total amount of the copolymer (a) and the copolymer (b) is preferably 90% by weight or more with respect to the total polymer in the copolymer rubber latex composition for foam rubber of the present invention. More preferably, it is 95% by weight or more. If this ratio is too small, the balance of characteristics required as a puff tends to deteriorate.

  The amount of all cyano group-containing ethylenically unsaturated monomer units contained with respect to all polymers in the foam rubber copolymer rubber latex composition of the present invention may be in the range of 40 to 45% by weight. preferable. When this amount is in the above range, an excellent foam rubber can be obtained due to a balance between oil resistance and flexibility.

The solid content concentration of the copolymer rubber latex composition for foam rubber of the present invention is preferably in the range of 55 to 75% by weight, and preferably in the range of 60 to 70% by weight. If the solid content concentration is too low, bubble roughness tends to occur and the appearance tends to deteriorate, and it is difficult to increase the solid content concentration beyond the above range.
In order to adjust the solid content concentration within the above range, it is preferable to subject the latex (A) and / or latex (B) to the aforementioned particle size enlargement treatment in advance. Of course, after the latex (A) after polymerization and the latex (B) after polymerization are mixed, the latex mixture can be subjected to particle size enlargement treatment.

Copolymer latex composition for vulcanizable foam rubber The copolymer latex composition for vulcanizable foam rubber of the present invention comprises the above-described copolymer rubber latex composition for foam rubber and a vulcanizing agent. .
As the vulcanizing agent, any vulcanizing system used for producing ordinary foam rubber using a polymer rubber latex can be used, and is not particularly limited. As the vulcanization system, for example, sulfur as a vulcanizing agent, particularly colloidal sulfur, zinc oxide / various vulcanization accelerators as a vulcanization aid are used. Examples of the vulcanization accelerator include 2-mercaptobenzothiazole and its zinc salt, a thiazole accelerator such as dibenzothiazyl disulfide, and a dithiocarbamate accelerator such as zinc diethyldithiocarbamate. The amount of these vulcanizing agents and vulcanizing aids used is not particularly limited, but usually 0.1 to 10 parts by weight of sulfur and 0. 10% of zinc oxide with respect to 100 parts by weight of the copolymer rubber latex (solid content). About 5 to 10 parts by weight and about 0.1 to 5 parts by weight of the vulcanization accelerator. These usage amounts are determined so as to satisfy the required performance of the foam rubber.

  Examples of the compounding agent used as necessary include an anti-aging agent, a colorant, a foam stabilizer and the like, and a dispersant for stably dispersing the above-mentioned various compounding agents in the latex, for example, NASF (naphthalenesulfonic acid). Sodium salt of formalin condensate), etc .; thickeners such as polyacrylic acid and sodium salts thereof, sodium alginate, polyvinyl alcohol, etc .; surfactants as foaming agents such as aliphatic alkali soaps such as potassium oleate A necessary effective amount of sulfate of higher alcohol such as sodium dodecyl sulfate can be used. The following coagulants are used.

Foam rubber The foam rubber of the present invention can be obtained by foaming, coagulating and vulcanizing the copolymer rubber latex composition for vulcanizable foam rubber.
Although air is usually used for foaming, carbonates such as ammonium carbonate and sodium bicarbonate; azo compounds such as azodicarboxylic acid amide and azobisisobutyronitrile; and gas generating substances such as benzenesulfonyl hydrazide can also be used. In the case of using air, the copolymer rubber latex is agitated, and air is entrained and foamed. At this time, for example, an Oaks foaming machine, an ultrasonic foaming machine or the like is used.
Foaming is performed at a predetermined foaming ratio, and then the foamed latex composition is coagulated in order to fix the foamed state. The coagulation method is not particularly limited as long as the latex can be gelled and solidified, and any conventionally known method can be used. For example, the Dunlop method (room temperature coagulation method) added to the latex composition obtained by foaming a silicon fluoride compound such as sodium hexafluorosilicate, potassium (sodium fluorosilicate, potassium) and titanium silicofluoride as a coagulant ); A thermal coagulation method in which a thermal coagulant such as organopolysiloxane, polyvinyl methyl ether, zinc ammonium sulfate complex salt or the like is added to the foamed latex composition; a freeze coagulation method or the like is used. Although the usage-amount of a coagulant is not specifically limited, Usually, it is about 0.5-10 weight part with respect to 100 weight part of this latex composition (solid content).

  By transferring the foamed latex composition still having fluidity to which a coagulant has been added to a mold having a predetermined shape and coagulating, for example, by vulcanizing at a temperature of about 100 to 160 ° C. for about 15 to 60 minutes. Foam rubber is obtained. The foam rubber is taken out from the mold and washed with stirring at about 20 to 70 ° C. for about 5 to 15 minutes using, for example, a washing machine. After washing, drain water and dry at a temperature of about 30 to 90 ° C. so as not to impair the texture of the foam rubber. For example, the foam rubber thus obtained is sliced to a predetermined thickness, cut into a predetermined shape, and then the side surface is polished with a rotating grindstone to produce a cosmetic sponge, that is, a puff.

  The foam rubber of the present invention has excellent oil resistance and a good texture, and is particularly suitable for puffs. The oil resistance (according to the method described in Examples) of the foam rubber of the present invention is preferably 40% or less. The texture of the foam rubber of the present invention is related to the hardness (Asker F-type hardness). The lower the hardness is, the softer it is, and the preferable hardness is 65 (degrees) or less, more preferably 60 (degrees) or less. is there.

Next, the present invention will be described more specifically with reference to examples and comparative examples. Parts and% in the following examples are based on weight unless otherwise specified.
The evaluation method is shown below.

(1) Composition of copolymer After a copolymer latex was added to a large amount of methanol and coagulated, the taken-out coagulated product was sufficiently washed with water. This solid was vacuum-dried and measured as follows.
According to JIS K6384, the nitrogen content in the copolymer was measured by the Kjeldahl method, and the acrylonitrile unit amount of the copolymer was determined therefrom.
The ratio of the 1,3-butadiene unit amount and the isoprene unit amount was determined as follows. About 1 mg of the copolymer is wrapped in pyrofoil 590 (manufactured by Nihon Analytical Industrial Co., Ltd.), heated at 590 ° C. for 7 seconds to be gasified, and subjected to gas chromatography analysis (conditions are shown below). Asked. In the measurement, a calibration curve prepared by analyzing a sample having a known 1,3-butadiene unit amount and isoprene unit amount was used.
Gas chromatography: GC-14A (manufactured by Shimadzu Corporation)
Column: TC-1701 (manufactured by GL Sciences)
Temperature increase rate: 10 ° C / min Temperature range: 50-200 ° C

(2) Measurement of methyl ethyl ketone insoluble matter (%) Copolymer latex was poured on a horizontally maintained glass plate and dried in a constant temperature and humidity chamber at a temperature of 23 ° C. and a humidity of 50% for 48 hours. A 0.5 mm dry film was prepared. A part of this was cut into a strip of about 2 mm × 2 mm, weighed about 0.25 g, placed in an 80 mesh wire net, and the weight of the test film was precisely weighed (WB). The wire mesh containing the test film is immersed in a beaker containing 80 ml of methyl ethyl ketone and left to stand for 48 hours in the temperature and humidity chamber. Thereafter, the wire mesh was taken out, dried, and precisely weighed to determine the weight (WA) of components insoluble in methyl ethyl ketone. From these, the methyl ethyl ketone insoluble matter is determined based on the following formula.
Methyl ethyl ketone insoluble matter (%) = (WA / WB) × 100

(3) Density of foam rubber A plate-like foam rubber having a thickness of 0.8 cm is punched into a circle having a diameter of about 38 mm, its weight is measured, and the density (g / cm ³ ) is obtained from the volume and weight of the test piece. .
(4) F hardness of foam rubber The hardness (degree) of foam rubber was measured using an Asker rubber hardness meter F type (manufactured by Kobunshi Keiki Co., Ltd.). The lower the value, the softer the foam rubber and the better the touch.
(5) Oil resistance of foam rubber A test piece obtained by punching a plate-like foam rubber having a thickness of 0.8 cm into a circle having a diameter of about 38 mm is immersed in 100 ml of toluene at 23 ° C. for 1 hour. Thereafter, the test piece was taken out, the diameter was measured, and the linear expansion degree (%) was determined by the following formula.
Linear expansion (%) = [(L′−L) / L] × 100
(L: Diameter before immersion L ′: Diameter after immersion)
The smaller the value of the linear expansion, the better the oil resistance of the foam rubber.

(6) Texture of foam rubber The texture of foam rubber was sensuously inspected, and two-stage evaluation was performed.
G: Soft texture and excellent elasticity.
N: The texture is hard and the elasticity is insufficient.
(7) Appearance of foam rubber The uniformity of foam rubber foam was visually observed and evaluated in two stages.
G: Uniform.
N: Uneven portions are conspicuous.

Production Example 1
Production of copolymer latex A1 In a pressure-resistant reaction vessel, 200 parts of water, 1.5 parts of potassium oleate, 38 parts of acrylonitrile, 0.5 part of t-dodecyl mercaptan, 0.03 part of sodium formaldehyde sulfoxylate, sulfuric acid After adding 0.003 part of ferrous iron and 0.008 part of ethylenediaminetetraacetic acid / natrium, and sufficiently degassing, 45 parts of 1,3-butadiene and 17 parts of isoprene were added.
Subsequently, 0.05 part of cumene hydroperoxide was added as a polymerization initiator, and emulsion polymerization was started at a reaction temperature of 5 ° C.
When the polymerization conversion rate reached 95%, a polymerization stopper solution consisting of 0.25 part of diethylhydroxyamine and 5 parts of water was added to stop the polymerization reaction.
After removing the unreacted monomer, 80 parts of 1,3-butadiene was added, the temperature in the system was set to 15 ° C., and the mixture was stirred for 5 hours at a rotation speed of 1,000 rpm using a paddle type stirring blade. The particle size enlargement process was performed. Subsequently, 1,3-butadiene was removed and then concentrated to obtain a copolymer latex A1 having a solid content concentration of 65%.
The copolymer composition and methyl ethyl ketone insoluble matter of copolymer latex A1 were measured, and the results are shown in Table 1.

Production Examples 2 and 3
Copolymer latexes A2 and A3 were obtained in the same manner as in Production Example 1 except that the monomer composition shown in Table 1 was changed. Their copolymer composition and methyl ethyl ketone insoluble matter were measured, and the results are shown in Table 1.

Production Example 4
Production of copolymer latex B1 In a pressure resistant reactor, 200 parts of water, 1.5 parts of potassium oleate, 60 parts of acrylonitrile, 0.6 parts of t-dodecyl mercaptan, 0.03 part of sodium formaldehyde sulfoxylate, sulfuric acid After adding 0.003 part of ferrous iron and 0.008 part of ethylenediaminetetraacetic acid / natrium, sufficiently deaerated, 20 parts of 1,3-butadiene was added.
Subsequently, 0.05 part of cumene hydroperoxide was added as a polymerization initiator, and emulsion polymerization was started at a reaction temperature of 5 ° C.
When the polymerization conversion rate reached 40%, 10 parts of 1,3-butadiene was added and the polymerization reaction was continued. 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 reached 80%, a polymerization stopper solution consisting of 0.25 part of diethylhydroxyamine and 5 parts of water was added to stop the polymerization reaction.
After removing the unreacted monomer, concentration was performed to obtain a copolymer latex B1 having a solid content concentration of 52%.
The copolymer composition and methyl ethyl ketone insoluble matter of copolymer latex B1 were measured, and the results are shown in Table 1.

Example 1
Copolymer latex A1 and copolymer latex B1 were mixed so that the ratio of the copolymer contained in each latex was 70 parts and 30 parts. The obtained mixture was concentrated to prepare a copolymer latex composition having a solid content concentration of 63%.

Preparation of foam rubber For 100 parts of solid content of the copolymer latex composition, a vulcanized aqueous dispersion (colloidal sulfur / dithiocarbamate vulcanization accelerator Noxeller EZ (manufactured by Ouchi Shinsei Chemical Co., Ltd.) / Thiazole vulcanization accelerator Noxeller MZ (manufactured by Ouchi Shinsei Chemical Co., Ltd.) = 2/1/1 (weight ratio): solid content concentration 50%) 4 parts, zinc oxide aqueous dispersion (solid content concentration 50% 3 parts and 1 part of a bubble stabilizer (trimene base: manufactured by Crompton Corp) were added and sufficiently dispersed to obtain a copolymer latex composition for vulcanizable foam rubber.
The latex composition was stirred using a stand mixer (ESM945 manufactured by Electrolux Co., Ltd.) and foamed to a volume of about 5 times, and then an aqueous dispersion of sodium silicofluoride (solid content concentration 20%). 5 parts were added and further stirred for 1 minute.
The foamed product was poured into a molding form (diameter 7 cm, height 8 cm), solidified, and then vulcanized at 110 ° C. for 1 hour to obtain a foam rubber.
The foam rubber taken out 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 a disk shape so that the thickness was 0.8 cm in the length direction.
The properties of the foam rubber were measured and the results are shown in Table 2.

Examples 2, 3, 5 and Comparative Examples 1 and 2
A copolymer latex composition was obtained in the same manner as in Example 1 except that the mixing ratio was changed as shown in Table 2. A foam rubber was obtained in the same manner as in Example 1 except that the obtained copolymer latex composition was used. The properties of the foam rubber were measured and the results are shown in Table 2.

Example 4
A copolymer latex composition was obtained in the same manner as in Example 1 except that the copolymer latex A2 was used instead of the copolymer latex A1. A foam rubber was obtained in the same manner as in Example 1 except that the obtained copolymer latex composition was used. The properties of the foam rubber were measured and the results are shown in Table 2.

Comparative Example 3
A copolymer latex composition was obtained in the same manner as in Example 1 except that the copolymer latex A3 was used instead of the copolymer latex A1. A foam rubber was obtained in the same manner as in Example 1 except that the obtained copolymer latex composition was used. The properties of the foam rubber were measured and the results are shown in Table 2.

From the results in Table 2, the following can be understood.
The foam rubber of Comparative Example 1 having a large proportion of the copolymer latex A1 is relatively excellent in flexibility but inferior in oil resistance.
The foam rubber of Comparative Example 2 with a small ratio of the copolymer latex A1 is excellent in oil resistance, but is inferior in flexibility and deteriorated in appearance.
The foam rubber of Comparative Example 3 using the copolymer latex A3 with a small amount of acrylonitrile units is excellent in flexibility but inferior in oil resistance.
Compared to these comparative examples, the foam rubbers of Examples 1 to 5 are foam rubbers that are suitable as a cosmetic sponge (puff) having excellent oil resistance, low hardness, and soft touch.

  The foam rubber of the present invention has excellent oil resistance and a good texture, and is particularly suitable for puffs.

Claims (11)

Cyano group-containing ethylenically unsaturated monomer unit (a1) 30 to 45% by weight, conjugated diene monomer unit (a2) 55 to 70% by weight, and cyano group-containing ethylenically unsaturated monomer unit and conjugated diene unit A latex (A) of a copolymer (a) composed of 0 to 15% by weight of another ethylenically unsaturated monomer unit (a3) copolymerizable with the monomer, and a cyano group-containing ethylenically unsaturated monomer 45 to 65% by weight of the body unit (b1), 35 to 55% by weight of the conjugated diene monomer unit (b2), and other copolymerizable with the cyano group-containing ethylenically unsaturated monomer and conjugated diene monomer Latex (B) of copolymer (b) comprising 0 to 20% by weight of ethylenically unsaturated monomer unit (b3) (however, the amount of cyano group-containing ethylenically unsaturated monomer unit (b1) is , A cyano group-containing ethylenically unsaturated monomer unit (a1 5% by weight or more than the amount of the polymer (a) by weight ratio of the copolymer (a) to the copolymer (b) ((copolymer (a) / copolymer (b)) A copolymer rubber latex composition for foam rubber formed by mixing at a ratio of ˜80 / 20. The foam according to claim 1, wherein the cyano group-containing ethylenically unsaturated monomer unit (a1) is an acrylonitrile unit, and the conjugated diene monomer unit (a2) is a 1,3-butadiene unit and an isoprene unit. Copolymer rubber latex composition for rubber. The copolymer rubber latex composition for foam rubber according to claim 2, wherein the weight ratio of 1,3-butadiene units to isoprene units is in the range of 5/5 to 9/1. The copolymer rubber latex composition for foam rubber according to any one of claims 1 to 3, wherein the gel content of the copolymer (a) is 65% by weight or less. The cyano group-containing ethylenically unsaturated monomer unit (b1) is an acrylonitrile unit, and the conjugated diene monomer unit (b2) is a 1,3-butadiene unit. The copolymer rubber latex composition for foam rubber described. The copolymer rubber latex composition for foam rubber according to any one of claims 1 to 5, wherein the gel content of the copolymer (b) is 35% by weight or less. A copolymer rubber latex composition for a vulcanizable foam rubber comprising the copolymer rubber latex composition for a foam rubber according to any one of claims 1 to 6 and a vulcanizing agent. The copolymer rubber latex composition for vulcanizable foam rubber according to claim 7, wherein the vulcanizing agent is sulfur. The vulcanizable foam rubber copolymer rubber latex composition according to claim 7 or 8, further comprising a vulcanization aid and a vulcanization accelerator. The copolymer rubber latex composition for vulcanizable foam rubber according to claim 9, wherein the vulcanization aid is zinc oxide, and the vulcanization accelerator is a thiazole vulcanization accelerator and a dithiocarbamate vulcanization accelerator. . A foam rubber obtained by foaming, coagulating and vulcanizing the copolymer rubber latex composition for a vulcanizable foam rubber according to any one of claims 7 to 10.