WO2021054242A1

WO2021054242A1 - Latex composition, film-formed article, and dip-molded article

Info

Publication number: WO2021054242A1
Application number: PCT/JP2020/034314
Authority: WO
Inventors: 友哉谷山; 実紗林
Original assignee: 日本ゼオン株式会社
Priority date: 2019-09-20
Filing date: 2020-09-10
Publication date: 2021-03-25
Also published as: JPWO2021054242A1

Abstract

Provided is a latex composition that contains a carboxy-modified polymer latex and a xanthate compound, wherein the swelling index (SI) of the carboxy-modified polymer latex is 120-190%.

Description

Latex composition, film moldings and dip moldings

The present invention relates to a latex composition, a film molded product and a dip molded product, and more specifically, it is possible to suppress the occurrence of symptoms of delayed type allergy (Type IV) in addition to immediate type allergy (Type I), and tear strength. It is possible to provide a film molded product such as a dip molded product having a high quality and a flexible texture, and further, when obtaining a film molded product such as such a dip molded product, the aging (pre-vulcanization) time can be shortened. The present invention relates to a latex composition capable of producing a film molded product such as a dip molded product with high productivity, and a film molded product and a dip molded product obtained by using such a latex composition.

Conventionally, it is known that a latex composition containing a latex of natural rubber is dip-molded to obtain a dip-molded body that is used in contact with the human body such as a nipple, a balloon, a glove, a balloon, and a sack. However, since the latex of natural rubber contains a protein that causes the symptoms of immediate allergy (Type I) in the human body, there may be a problem as a dip molded product that comes into direct contact with the biological mucous membrane or organs. Therefore, studies have been conducted on using synthetic rubber latex instead of natural rubber latex.

For example, Patent Document 1 discloses a latex composition obtained by blending zinc oxide, sulfur, and a vulcanization accelerator with a latex of synthetic polyisoprene, which is a synthetic rubber, as a composition for dip molding. However, while the technique of Patent Document 1 can prevent the occurrence of immediate allergy (Type I) due to a protein derived from natural rubber, the dithiocarbamate system contained in the dip molded product when it is used as a dip molded product. Due to the vulcanization accelerator or thiazole-based vulcanization accelerator, when it comes into contact with the human body, it may cause allergic symptoms of delayed type allergy (Type IV). Further, in the technique of Patent Document 1, there is a problem that aging (pre-vulcanization) takes a relatively long time in order to obtain a dip molded article having sufficient mechanical strength, and from the viewpoint of improving productivity. There has been a demand for a latex composition capable of producing a dip molded product having sufficient mechanical strength even with a relatively short aging time.

International Publication No. 2014/12954

The present invention has been made in view of such an actual situation, and can suppress the occurrence of symptoms of delayed type allergy (Type IV) in addition to immediate type allergy (Type I), has high tear strength, and is flexible. It is possible to give a film molded product such as a dip molded product having a good texture, and further, when obtaining a film molded product such as such a dip molded product, the aging (pre-vulcanization) time can be shortened. It is an object of the present invention to provide a latex composition capable of producing a film molded product such as a dip molded product with high productivity, and a film molded product and a dip molded product obtained by using such a latex composition.

As a result of diligent studies to achieve the above object, the present inventors have added a xanthogen compound to the latex of the carboxy-modified polymer, and the swell index (SI) is 120 as the latex of the carboxy-modified polymer. It has been found that the above object can be achieved by using a polymer in the range of about 190%, and the present invention has been completed.

That is, according to the present invention, it is a latex composition containing a latex of a carboxy-modified polymer and a xanthate compound.
A latex composition having a latex swell index (SI) of 120 to 190% of the carboxy-modified polymer is provided.

In the latex composition of the present invention, the modification rate of the carboxy-modified polymer by a carboxyl group is a molar ratio calculated by (number of carboxyl groups / total number of monomer units of the carboxy-modified polymer) × 100. It is preferably 01 to 10 mol%.
In the latex composition of the present invention, the carboxy-modified polymer modifies synthetic polyisoprene, styrene-isoprene-styrene block copolymer, or natural rubber from which proteins have been removed with a monomer having a carboxyl group. It is preferably obtained.
The latex composition of the present invention preferably further contains a sulfur-based vulcanizing agent.
In the latex composition of the present invention, the toluene-insoluble content of the latex of the carboxy-modified polymer is preferably 55 to 85% by weight.
In the latex composition of the present invention, the xanthogen compound preferably has a volume average particle diameter in the range of 0.001 to 9 μm and a 95% volume cumulative diameter (D95) in the range of 0.1 to 43 μm.

Further, according to the present invention, a film molded product made of the latex composition of the present invention is provided.
Alternatively, according to the present invention, there is provided a dip molded body obtained by dip molding the latex composition of the present invention.

According to the present invention, it is possible to suppress the occurrence of symptoms of delayed type allergy (Type IV) in addition to immediate type allergy (Type I), and film molding of a dip molded body or the like having high tear strength and a flexible texture. A body can be given, and when a film molded product such as a dip molded product is obtained, the aging (pre-vulcanization) time can be shortened, and a film such as a dip molded product can be obtained with high productivity. It is possible to provide a latex composition capable of producing a molded product, and a film molded product and a dip molded product obtained by using such a latex composition.

<Latex composition>
The latex composition of the present invention is a latex composition containing a latex of a carboxy-modified polymer and a xanthate compound.
As the latex of the carboxy-modified polymer, one having a swell index (SI) in the range of 120 to 190% is used.

The latex of the carboxy-modified polymer used in the present invention may be a latex of a polymer in which a carboxy group has been introduced, and is not particularly limited, but a conjugated diene-based polymer or a natural rubber from which a protein has been removed is used as a carboxyl group. It is preferable that the latex is a carboxy-modified polymer obtained by modifying with a monomer having.

<Conjugated diene polymer>
The conjugated diene-based polymer is not particularly limited, and examples thereof include synthetic polyisoprene, styrene-isoprene-styrene block copolymer (SIS), and a nitrile group-containing conjugated diene-based copolymer. Among these, those containing isoprene units such as synthetic polyisoprene and SIS are preferable, and synthetic polyisoprene is particularly preferable.

When synthetic polyisoprene is used as the conjugated diene-based polymer, the synthetic polyisoprene may be a homopolymer of isoprene, or may be a copolymer of isoprene and another ethylenically unsaturated monomer copolymerizable with isoprene. It may be a polymer. The content of the isoprene unit in the synthetic polyisoprene is preferably 70% by weight or more with respect to all the monomer units because it is easy to obtain a film molded body such as a dip molded body which is flexible and has excellent tear strength. It is more preferably 90% by weight or more, further preferably 95% by weight or more, and particularly preferably 100% by weight (isoprene homopolymer).

Other ethylenically unsaturated monomers copolymerizable with isoprene include conjugated diene monomers other than isoprene, such as butadiene, chloroprene, 1,3-pentadiene; acrylonitrile, methacrylonitrile, fumaronitrile, α-. Ethylene unsaturated nitrile monomers such as chloroacrylonitrile; vinyl aromatic monomers such as styrene and alkylstyrene; methyl (meth) acrylate (meaning "methyl acrylate and / or methyl methacrylate" and below. , (Meta) ethyl acrylate, etc.), Ethylene unsaturated styrene ester monomer such as (meth) acrylate, butyl (meth) acrylate, -2-ethylhexyl (meth) acrylate; etc. Can be mentioned. The other ethylenically unsaturated monomers copolymerizable with these isoprene may be used alone or in combination of two or more.

Synthetic polyisoprene is prepared in an inert polymerization solvent using a conventionally known method, for example, a Cheegler-based polymerization catalyst composed of trialkylaluminum-titanium tetrachloride or an alkyllithium polymerization catalyst such as n-butyllithium or sec-butyllithium. , Isoprene and other copolymerizable ethylenically unsaturated monomers used as needed can be obtained by solution polymerization. The polymer solution of synthetic polyisoprene obtained by solution polymerization may be used as it is for the production of synthetic polyisoprene latex, but after taking out solid synthetic polyisoprene from the polymer solution, it is dissolved in an organic solvent. It can also be used in the production of synthetic polyisoprene latex. The synthetic polyisoprene latex can be used for producing the latex of the carboxy-modified polymer used in the present invention, as will be described later.
When a polymer solution of synthetic polyisoprene is obtained by the method described above, impurities such as the residue of the polymerization catalyst remaining in the polymer solution may be removed. Further, an anti-aging agent described later may be added to the solution during or after the polymerization. Alternatively, a commercially available solid synthetic polyisoprene can be used.

There are four types of isoprene units in synthetic polyisoprene, cis-binding units, trans-binding units, 1,2-vinyl-binding units, and 3,4-vinyl-binding units, depending on the isoprene binding state. From the viewpoint of improving the tear strength of the obtained film molded product such as a dip molded product, the content ratio of the cis bond unit in the isoprene unit contained in the synthetic polyisoprene is preferably 70% by weight or more with respect to the total isoprene unit. It is more preferably 90% by weight or more, still more preferably 95% by weight or more.

The weight average molecular weight of the synthetic polyisoprene is preferably 10,000 to 5,000,000, more preferably 500,000 to 5,000,000, more preferably 500,000 to 5,000,000, in terms of standard polystyrene by gel permeation chromatography analysis. Is between 800,000 and 3,000,000. By setting the weight average molecular weight of the synthetic polyisoprene in the above range, the tear strength of the film molded product such as a dip molded product is improved, and the synthetic polyisoprene latex tends to be easily produced.

The polymer Mooney viscosity (ML1 + 4, 100 ° C.) of the synthetic polyisoprene is preferably 50 to 80, more preferably 60 to 80, and even more preferably 70 to 80.

As a method for obtaining a synthetic polyisoprene latex, for example, (1) a solution or a fine suspension of synthetic polyisoprene dissolved or finely dispersed in an organic solvent is emulsified in water in the presence of an anionic surfactant. Then, if necessary, a method for producing a synthetic polyisoprene latex by removing an organic solvent, (2) isoprene alone or a mixture of isoprene and an ethylenically unsaturated monomer copolymerizable therewith, anionic surfactant A method of directly producing a synthetic polyisoprene latex by emulsification polymerization or suspension polymerization in the presence of an agent can be mentioned, but synthetic polyisoprene having a high ratio of cis-bonding units in isoprene units can be used. The production method (1) above is preferable from the viewpoint that a film-formed body such as a dip-formed body having excellent mechanical properties such as tear strength can be easily obtained.

Examples of the organic solvent used in the production method (1) above include aromatic hydrocarbon solvents such as benzene, toluene and xylene; alicyclic hydrocarbon solvents such as cyclopentane, cyclopentene, cyclohexane and cyclohexene; pentane, hexane and the like. An aliphatic hydrocarbon solvent such as heptane; a halogenated hydrocarbon solvent such as methylene chloride, chloroform and ethylene dichloride; and the like can be mentioned. Of these, an alicyclic hydrocarbon solvent is preferable, and cyclohexane is particularly preferable.

The amount of the organic solvent used is preferably 2,000 parts by weight or less, more preferably 20 to 1,500 parts by weight, and further preferably 500 to 1,500 parts by weight with respect to 100 parts by weight of the synthetic polyisoprene. is there.

Examples of the anionic surfactant used in the production method (1) above include fatty acid salts such as sodium laurate, potassium myristate, sodium palmitate, potassium oleate, sodium linolenate, and sodium loginate; dodecylbenzene sulfone. Alkylbenzene sulfonates such as sodium acid, potassium dodecylbenzene sulfonate, sodium decylbenzene sulfonate, potassium decylbenzene sulfonate, sodium cetylbenzenesulfonate, potassium cetylbenzenesulfonate; sodium di (2-ethylhexyl) sulfosuccinate, di (2-Ethylhexyl) Alkyl sulfosuccinates such as potassium sulfosuccinate and sodium dioctyl sulfosuccinate; alkyl sulfates such as sodium lauryl sulfate and potassium lauryl sulfate; sodium polyoxyethylene lauryl ether sulfate, potassium polyoxyethylene lauryl ether sulfate, etc. Polyoxyethylene alkyl ether sulfate ester salt; monoalkyl phosphate such as sodium lauryl phosphate and potassium lauryl phosphate; and the like.

Among these anionic surfactants, fatty acid salts, alkylbenzene sulfonates, alkyl sulfosuccinates, alkyl sulfates and polyoxyethylene alkyl ether sulfates are preferable, and fatty acid salts and alkylbenzene sulfonates are particularly preferable.

In addition, a trace amount of the polymerization catalyst (particularly aluminum and fatty acid) derived from synthetic polyisoprene can be removed more efficiently, and the generation of agglomerates during the production of the latex composition is suppressed. Therefore, alkylbenzene is used. It is preferable to use at least one selected from the group consisting of sulfonates, alkyl sulfosuccinates, alkyl sulfates and polyoxyethylene alkyl ether sulfates in combination with fatty acid salts, preferably with alkylbenzene sulfonates. , It is particularly preferable to use it in combination with a fatty acid salt. Here, as the fatty acid salt, sodium loginate and potassium loginate are preferable, and as the alkylbenzene sulfonate, sodium dodecylbenzene sulfonate and potassium dodecylbenzene sulfonate are preferable. In addition, these surfactants may be used alone or in combination of two or more.

As described above, at least one selected from the group consisting of alkylbenzene sulfonates, alkylsulfosuccinates, alkylsulfate salts and polyoxyethylene alkylether sulfates should be used in combination with fatty acid salts. The resulting latex contains at least one selected from alkylbenzene sulfonates, alkyl sulfosuccinates, alkyl sulfates and polyoxyethylene alkyl ether sulfates, and fatty acid salts. ..

Further, in the production method of (1) above, a surfactant other than the anionic surfactant may be used in combination, and the surfactant other than the anionic surfactant may be α, β-non. Examples thereof include copolymerizable surfactants such as sulfoesters of saturated carboxylic acids, sulfate esters of α, β-unsaturated carboxylic acids, and sulfoalkylaryl ethers.

Further, polyoxyethylene alkyl ether, polyoxyethylene alkyl phenol ether, polyoxyethylene alkyl ester, polyoxyethylene sorbitan alkyl ester, etc., as long as they do not inhibit coagulation by the coagulant used for molding such as dip molding. Nonionic surfactants may also be used in combination.

The amount of the anionic surfactant used in the production method (1) is preferably 0.1 to 50 parts by weight, more preferably 0.5 to 30 parts by weight, based on 100 parts by weight of the synthetic polyisoprene. is there. When two or more kinds of surfactants are used, it is preferable that the total amount of these surfactants used is in the above range. That is, for example, when at least one selected from alkylbenzene sulfonate, alkylsulfosuccinate, alkylsulfate ester salt and polyoxyethylene alkyl ether sulfate ester salt is used in combination with a fatty acid salt, these It is preferable that the total amount used is in the above range. If the amount of the anionic surfactant used is too small, a large amount of agglomerates may be generated during emulsification. May occur.

In addition, when at least one selected from alkylbenzene sulfonate, alkylsulfosuccinate, alkylsulfate ester salt and polyoxyethylene alkylether sulfate ester salt is used in combination as the anionic surfactant, and the fatty acid salt is used in combination. In the above, the ratio of these to be used is the surface activity of at least one selected from "fatty acid salt": "alkylbenzene sulfonate, alkylsulfosuccinate, alkylsulfate ester salt and polyoxyethylene alkylether sulfate ester salt". The weight ratio of "total of agents" is preferably in the range of 1: 1 to 10: 1, more preferably in the range of 1: 1 to 7: 1. Too much of the surfactant selected from alkylbenzene sulfonates, alkyl sulfosuccinates, alkyl sulfates and polyoxyethylene alkyl ether sulfates will result in the handling of synthetic polyisoprenes. Foaming may become intense, which requires operations such as standing for a long time and adding an antifoaming agent, which may lead to deterioration of workability and cost increase.

The amount of water used in the production method (1) is preferably 10 to 1,000 parts by weight, more preferably 30 to 500 parts by weight, most preferably 30 parts by weight, based on 100 parts by weight of the organic solvent solution of synthetic polyisoprene. Is 50 to 100 parts by weight. Examples of the type of water used include hard water, soft water, ion-exchanged water, distilled water, zeolite water and the like, and soft water, ion-exchanged water and distilled water are preferable.

An apparatus for emulsifying a solution or microsuspension of synthetic polyisoprene dissolved or finely dispersed in an organic solvent in water in the presence of an anionic surfactant may be a commercially available emulsifier or disperser. It can be used without particular limitation. The method of adding the anionic surfactant to the synthetic polyisoprene solution or microsuspension is not particularly limited, and it is previously added to water, the synthetic polyisoprene solution or the microsuspension, or both. It may be added, may be added to the emulsified solution during the emulsification operation, may be added all at once, or may be added in portions.

Examples of the emulsifying device include batch emulsification such as the product name "Homogenizer" (manufactured by IKA), the product name "Polytron" (manufactured by Kinematica), and the product name "TK Auto Homo Mixer" (manufactured by Tokushu Kika Kogyo Co., Ltd.). Machine; Product name "TK Pipeline Homo Mixer" (manufactured by Tokushu Kagaku Kogyo Co., Ltd.), Product name "Coloid Mill" (manufactured by Shinko Pantech Co., Ltd.) Trigonal wet pulverizer (Mitsui Miike Kakoki Co., Ltd.), product name "Cavitron" (Eurotech Co., Ltd.), product name "Milder" (Pacific Kiko Co., Ltd.), product name "Fine Flow Mill" (Pacific Kiko Co., Ltd.) Continuous emulsifiers such as (manufactured by); high-pressure emulsifiers such as product name "Microfluidizer" (manufactured by Mizuho Kogyo Co., Ltd.), product name "Nammizer" (manufactured by Nanomizer Co., Ltd.) Membrane emulsifiers such as the product name "Membrane Emulsifier" (manufactured by Cooling Industry Co., Ltd.); Vibration type emulsifying machines such as the product name "Vibro Mixer" (manufactured by Cooling Industry Co., Ltd.); Product name "Ultrasonic Homogenizer" (Branson) An ultrasonic emulsifier such as (manufactured by the company); etc. The conditions for the emulsification operation by the emulsification device are not particularly limited, and the treatment temperature, treatment time, and the like may be appropriately selected so as to obtain a desired dispersed state.

In the production method (1) above, it is desirable to remove the organic solvent from the emulsion obtained through the emulsification operation.
As a method for removing the organic solvent from the emulsion, a method in which the content of the organic solvent (preferably alicyclic hydrocarbon solvent) in the obtained synthetic polyisoprene latex can be 500% by weight ppm or less is preferable. For example, methods such as vacuum distillation, atmospheric distillation, steam distillation, and centrifugation can be adopted.

In the method (1) above, it is desirable to remove the organic solvent from the emulsion obtained through the emulsification operation to obtain a synthetic polyisoprene latex. In the method for removing the organic solvent from the emulsion, the total content of the alicyclic hydrocarbon solvent and the aromatic hydrocarbon solvent as the organic solvent in the obtained synthetic polyisoprene latex can be 500% by weight ppm or less. Such a method is not particularly limited, and methods such as vacuum distillation, atmospheric distillation, steam distillation, and centrifugation can be adopted.

Further, after removing the organic solvent, if necessary, in order to increase the solid content concentration of the synthetic polyisoprene latex, a concentration operation may be performed by a method such as vacuum distillation, atmospheric distillation, centrifugation, membrane concentration, or the like. In particular, it is preferable to perform centrifugation from the viewpoint that the solid content concentration of the synthetic polyisoprene latex can be increased and the residual amount of the surfactant in the synthetic polyisoprene latex can be reduced.

Centrifugation uses, for example, a continuous centrifuge to centrifuge the centrifugal force, preferably 100 to 10,000 G, and the solid content concentration of the synthetic polyisoprene latex before centrifugation, preferably 2 to 15% by weight. The flow velocity to be fed into the machine is preferably 500 to 1700 kg / hr, and the back pressure (gauge pressure) of the centrifuge is preferably 0.03 to 1.6 MPa. As a liquid, a synthetic polyisoprene latex can be obtained. As a result, the residual amount of the surfactant in the synthetic polyisoprene latex can be reduced.

The solid content concentration of the synthetic polyisoprene latex is preferably 30 to 70% by weight, more preferably 40 to 70% by weight. If the solid content concentration is too low, the solid content concentration of the latex composition described later becomes low, so that the film thickness of the dip molded product described later becomes thin and it becomes easy to tear. On the contrary, if the solid content concentration is too high, the viscosity of the synthetic polyisoprene latex becomes high, which may make it difficult to transfer the synthetic polyisoprene latex or stir it in the compounding tank.

The volume average particle size of the synthetic polyisoprene latex is preferably 0.1 to 10 μm, more preferably 0.5 to 3 μm, and even more preferably 0.5 to 2.0 μm. By setting the volume average particle size in the above range, the latex viscosity becomes appropriate and easy to handle, and it is possible to suppress the formation of a film on the latex surface when the synthetic polyisoprene latex is stored.

In addition, synthetic polyisoprene latex contains additives such as pH adjusters, defoamers, preservatives, cross-linking agents, chelating agents, oxygen trapping agents, dispersants, and antiaging agents, which are usually blended in the field of latex. It may be blended.
Examples of the pH adjuster include hydroxides of alkali metals such as sodium hydroxide and potassium hydroxide; alkali metal carbonates such as sodium carbonate and potassium carbonate; alkali metal bicarbonates such as sodium hydrogen carbonate; ammonia. ; Organic amine compounds such as trimethylamine and triethanolamine; and the like; but alkali metal hydroxides or ammonia are preferable.

Further, as the conjugated diene-based polymer, as described above, a styrene-isoprene-styrene block copolymer (SIS) can also be used. In SIS, "S" represents a styrene block and "I" represents an isoprene block.

SIS can be obtained by block copolymerization of isoprene and styrene in an inert polymerization solvent using a conventionally known method, for example, an active organometallic such as n-butyllithium as an initiator. The obtained SIS polymer solution may be used as it is in the production of SIS latex, but after taking out the solid SIS from the polymer solution, the solid SIS is dissolved in an organic solvent to SIS. It can also be used in the production of latex. As will be described later, the SIS latex can be used for producing the latex of the carboxy-modified polymer used in the present invention. The method for producing SIS latex is not particularly limited, but a SIS solution or fine suspension dissolved or finely dispersed in an organic solvent is emulsified in water in the presence of a surfactant, and the organic solvent is removed if necessary. The method for producing the SIS latex is preferable.
At this time, impurities such as the residue of the polymerization catalyst remaining in the polymer solution after the synthesis may be removed. Further, an anti-aging agent described later may be added to the solution during or after the polymerization. Alternatively, a commercially available solid SIS can be used.

As the organic solvent, the same solvent as in the case of the synthetic polyisoprene can be used, and an aromatic hydrocarbon solvent and an alicyclic hydrocarbon solvent are preferable, and cyclohexane and toluene are particularly preferable.
The amount of the organic solvent used is usually 50 to 2,000 parts by weight, preferably 80 to 1,000 parts by weight, more preferably 100 to 500 parts by weight, still more preferably 150 to 300 parts by weight, based on 100 parts by weight of SIS. It is a part by weight.

As the surfactant, the same one as in the case of the above synthetic polyisoprene can be exemplified, an anionic surfactant is preferable, and sodium rosinate and sodium dodecylbenzenesulfonate are particularly preferable.

The amount of the surfactant used is preferably 0.1 to 50 parts by weight, more preferably 0.5 to 30 parts by weight, based on 100 parts by weight of SIS. By setting the amount of the surfactant used within the above range, it is possible to appropriately improve the stability of the latex while effectively suppressing the occurrence of problems during dip molding.

The amount of water used in the above-mentioned method for producing SIS latex is preferably 10 to 1,000 parts by weight, more preferably 30 to 500 parts by weight, and most preferably 50 parts by weight with respect to 100 parts by weight of the organic solvent solution of SIS. ~ 100 parts by weight. Examples of the type of water used include hard water, soft water, ion-exchanged water, distilled water, and zeolite water. Further, a polar solvent typified by alcohol such as methanol may be used in combination with water.

An apparatus for emulsifying an organic solvent solution or fine suspension of SIS in water in the presence of a surfactant can be exemplified as the same as in the case of the above synthetic polyisoprene. The method of adding the surfactant is not particularly limited, and the surfactant may be added to water, an organic solvent solution of SIS, a fine suspension, or both in advance, or during the emulsification operation. In addition, it may be added to the emulsion, may be added all at once, or may be added separately.

In the above-mentioned method for producing SIS latex, it is preferable to remove the organic solvent from the emulsion obtained through the emulsification operation to obtain SIS latex. The method for removing the organic solvent from the emulsion is not particularly limited, and methods such as vacuum distillation, atmospheric distillation, steam distillation, and centrifugation can be adopted.

Further, after removing the organic solvent, if necessary, in order to increase the solid content concentration of the SIS latex, a concentration operation may be performed by a method such as vacuum distillation, atmospheric distillation, centrifugation, or membrane concentration.

The solid content concentration of the SIS latex is preferably 30 to 70% by weight, more preferably 50 to 70% by weight. If the solid content concentration is too low, the solid content concentration of the latex composition described later becomes low, so that the film thickness of the dip molded product becomes thin and it becomes easy to tear. On the contrary, if the solid content concentration is too high, the viscosity of the SIS latex becomes high, and it becomes difficult to transfer the SIS latex by piping or to stir it in the compounding tank.

In addition, SIS latex contains additives such as pH adjusters, antifoaming agents, preservatives, cross-linking agents, chelating agents, oxygen scavengers, dispersants, and anti-aging agents, which are usually blended in the field of latex. You may. As the pH adjuster, the same as in the case of the above synthetic polyisoprene can be exemplified, and alkali metal hydroxide or ammonia is preferable.

The content of the styrene unit in the styrene block in the SIS contained in the SIS latex thus obtained is preferably 70 to 100% by weight, more preferably 70 to 100% by weight, based on all the monomer units constituting the styrene block. It is 90 to 100% by weight, more preferably 100% by weight.
The content of the isoprene unit in the isoprene block in the SIS is preferably 70 to 100% by weight, more preferably 90 to 100% by weight, still more preferably 100, based on all the monomer units constituting the isoprene unit. By weight%.
The content ratio of the styrene unit and the isoprene unit in the SIS is a weight ratio of "styrene unit: isoprene unit", which is usually 1:99 to 90:10, preferably 3:97 to 70:30, and more preferably 5. : 95 to 50:50, more preferably 10:90 to 30:70.

The weight average molecular weight of SIS is preferably 10,000 to 1,000,000, more preferably 50,000 to 500,000, still more preferably 100,000 in terms of standard polystyrene by gel permeation chromatography analysis. ~ 300,000. By setting the weight average molecular weight of SIS in the above range, the balance between tear strength and flexibility of a film molded product such as a dip molded product is improved, and SIS latex tends to be easily produced.

The volume average particle size of the latex particles (SIS particles) in the SIS latex is preferably 0.1 to 10 μm, more preferably 0.5 to 3 μm, and even more preferably 0.5 to 2.0 μm. By setting the volume average particle size of the latex particles in the above range, the latex viscosity becomes appropriate and easy to handle, and it is possible to suppress the formation of a film on the latex surface when the SIS latex is stored.

Further, as the conjugated diene-based polymer, as described above, a nitrile group-containing conjugated diene-based copolymer can also be used.

The nitrile group-containing conjugated diene-based copolymer is a copolymer obtained by copolymerizing an ethylenically unsaturated nitrile monomer with a conjugated diene monomer, and in addition to these, these are used as needed. It may be a copolymer obtained by copolymerizing another ethylenically unsaturated monomer copolymerizable with.

Examples of the conjugated diene monomer include 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, 2-ethyl-1,3-butadiene, 1,3-pentadiene and chloroprene. Be done. Among these, 1,3-butadiene and isoprene are preferable, and 1,3-butadiene is more preferable. These conjugated diene monomers can be used alone or in combination of two or more. The content ratio of the conjugated diene monomer unit formed by the conjugated diene monomer in the nitrile group-containing conjugated diene-based copolymer is preferably 56 to 78% by weight, more preferably 56 to 73% by weight. , More preferably 56 to 68% by weight. By setting the content of the conjugated diene monomer unit in the above range, the obtained film-molded product such as a dip-molded product can be made more excellent in texture while having sufficient tear strength.

The ethylenically unsaturated nitrile monomer is not particularly limited as long as it is an ethylenically unsaturated monomer containing a nitrile group, and for example, acrylonitrile, methacrylonitrile, fumaronitrile, α-chloroacrylonitrile, α-cyanoethylacrylonitrile. And so on. Of these, acrylonitrile and methacrylonitrile are preferable, and acrylonitrile is more preferable. These ethylenically unsaturated nitrile monomers can be used alone or in combination of two or more. The content ratio of the ethylenically unsaturated nitrile monomer unit formed of the ethylenically unsaturated nitrile monomer in the nitrile group-containing conjugated diene-based copolymer is preferably 20 to 40% by weight, more preferably 20 to 40% by weight. Is 25 to 40% by weight, more preferably 30 to 40% by weight. By setting the content of the ethylenically unsaturated nitrile monomer unit in the above range, it is possible to make the obtained film molded product such as a dip molded product more excellent in texture while having sufficient tear strength. it can.

Other ethylenically unsaturated monomers copolymerizable with the conjugated diene monomer and the ethylenically unsaturated nitrile monomer include, for example, ethylenically unsaturated, which is an ethylenically unsaturated monomer containing a carboxyl group. Saturated carboxylic acid monomer; Vinyl aromatic monomer such as styrene, alkylstyrene, vinylnaphthalene; Fluoroalkylvinyl ether such as fluoroethyl vinyl ether; (meth) acrylamide, N-methylol (meth) acrylamide, N, N-dimethylol Ethylene unsaturated amide monomers such as (meth) acrylamide, N-methoxymethyl (meth) acrylamide, N-propoxymethyl (meth) acrylamide; methyl (meth) acrylate, ethyl (meth) acrylate, (meth) Butyl acrylate, -2-ethylhexyl (meth) acrylate, trifluoroethyl (meth) acrylate, tetrafluoropropyl (meth) acrylate, dibutyl maleate, dibutyl fumarate, diethyl maleate, methoxy (meth) acrylate Methyl, ethoxyethyl (meth) acrylate, methoxyethoxyethyl (meth) acrylate, cyanomethyl (meth) acrylate, -2-cyanoethyl (meth) acrylate, -1-cyanopropyl (meth) acrylate, (meth) -2-Acrylic acid-6-cyanohexyl, (meth) acrylate-3-cyanopropyl, (meth) hydroxyethyl acrylate, (meth) hydroxypropyl acrylate, glycidyl (meth) acrylate, dimethylaminoethyl (meth) ) Ethylene unsaturated carboxylic acid ester monomer such as acrylate; divinylbenzene, polyethylene glycol di (meth) acrylate, polypropylene glycol di (meth) acrylate, trimethylpropanthry (meth) acrylate, pentaerythritol (meth) acrylate, etc. Crosslinkable monomer; and the like. These ethylenically unsaturated monomers can be used alone or in combination of two or more.

The ethylenically unsaturated carboxylic acid monomer is not particularly limited as long as it is an ethylenically unsaturated monomer containing a carboxyl group, but for example, a single amount of an ethylenically unsaturated monocarboxylic acid such as acrylic acid or methacrylic acid. Body; Esterically unsaturated polycarboxylic acid monomer such as itaconic acid, maleic acid, fumaric acid; Ethyl unsaturated polycarboxylic acid anhydride such as maleic anhydride, citraconic anhydride; monobutyl fumarate, maleic acid Examples thereof include ethylenically unsaturated polyvalent carboxylic acid partial ester monomers such as monobutyl and mono-2-hydroxypropyl maleate. Among these, ethylenically unsaturated monocarboxylic acid is preferable, and methacrylic acid is particularly preferable. These ethylenically unsaturated carboxylic acid monomers can also be used as alkali metal salts or ammonium salts. Further, the ethylenically unsaturated carboxylic acid monomer can be used alone or in combination of two or more. The content ratio of the ethylenically unsaturated carboxylic acid monomer unit formed by the ethylenically unsaturated carboxylic acid monomer in the nitrile group-containing conjugated diene-based copolymer is preferably 2 to 5% by weight. It is more preferably 2 to 4.5% by weight, still more preferably 2.5 to 4.5% by weight. By setting the content of the ethylenically unsaturated carboxylic acid monomer unit in the above range, the obtained film molded product such as a dip molded product should have a sufficient tear strength and a better texture. Can be done.

The content ratio of the other monomer unit formed by the other ethylenically unsaturated monomer in the nitrile group-containing conjugated diene-based copolymer is preferably 10% by weight or less, more preferably 5% by weight. % Or less, more preferably 3% by weight or less.

The nitrile group-containing conjugated diene-based copolymer can be obtained by copolymerizing a monomer mixture containing the above-mentioned monomer, and a method of copolymerizing by emulsion polymerization is preferable. As the emulsion polymerization method, a conventionally known method can be adopted.

When emulsion-polymerizing a monomer mixture containing the above-mentioned monomer, commonly used polymerization auxiliary materials such as an emulsifier, a polymerization initiator, and a molecular weight modifier can be used. The method of adding these polymerization auxiliary materials is not particularly limited, and any method such as an initial batch addition method, a split addition method, or a continuous addition method may be used.

The emulsifier is not particularly limited, but is, for example, a nonionic emulsifier such as polyoxyethylene alkyl ether, polyoxyethylene alkyl phenol ether, polyoxyethylene alkyl ester, polyoxyethylene sorbitan alkyl ester; potassium dodecylbenzenesulfonate, dodecylbenzene. Anionic emulsifiers such as alkylbenzene sulfonates such as sodium sulfonate, higher alcohol sulfates, alkyl sulfosuccinates; cationic emulsifiers such as alkyltrimethylammonium chloride, dialkylammonium chloride, benzylammonium chloride; α, β-unsaturated Examples thereof include sulfoesters of carboxylic acids, sulfate esters of α, β-unsaturated carboxylic acids, copolymerizable emulsifiers such as sulfoalkylaryl ethers, and the like. Among them, an anionic emulsifier is preferable, alkylbenzene sulfonate is more preferable, and potassium dodecylbenzene sulfonate and sodium dodecylbenzene sulfonate are particularly preferable. These emulsifiers can be used alone or in combination of two or more. The amount of the emulsifier used is preferably 0.1 to 10 parts by weight with respect to 100 parts by weight of the monomer mixture.

The polymerization initiator is not particularly limited, and is, for example, an inorganic peroxide such as sodium persulfate, potassium persulfate, ammonium persulfate, potassium perphosphate, hydrogen peroxide; diisopropylbenzene hydroperoxide, cumene hydroperoxide, etc. t-Butylhydroperoxide, 1,1,3,3-tetramethylbutylhydroperoxide, 2,5-dimethylhexane-2,5-dihydroperoxide, di-t-butyl peroxide, di-α- Organic peroxides such as cumyl peroxide, acetyl peroxide, isobutyryl peroxide, benzoyl peroxide; azo compounds such as azobisisobutyronitrile, azobis-2,4-dimethylvaleronitrile, methyl azobisisobutyrate; etc. Can be mentioned. These polymerization initiators can be used alone or in combination of two or more. The amount of the polymerization initiator used is preferably 0.01 to 10 parts by weight, more preferably 0.01 to 2 parts by weight, based on 100 parts by weight of the monomer mixture.

In addition, the peroxide initiator can be used as a redox-based polymerization initiator in combination with a reducing agent. The reducing agent is not particularly limited, but is a compound containing a metal ion in a reduced state such as ferrous sulfate and ferrous naphthenate; a sulfonic acid compound such as sodium methanesulfonate; an amine compound such as dimethylaniline. ; And so on. These reducing agents can be used alone or in combination of two or more. The amount of the reducing agent used is preferably 3 to 1000 parts by weight with respect to 100 parts by weight of the peroxide.

The amount of water used for emulsion polymerization is preferably 80 to 600 parts by weight, particularly preferably 100 to 200 parts by weight, based on 100 parts by weight of all the monomers used.

Examples of the method for adding the monomer include a method of collectively adding the monomers used in the reaction vessel, a method of continuously or intermittently adding the monomers as the polymerization progresses, and a method of adding a part of the monomers. Then, the reaction is carried out to a specific conversion rate, and then the remaining monomer is continuously or intermittently added to polymerize, and any of these methods may be adopted. When the monomers are mixed and added continuously or intermittently, the composition of the mixture may be constant or variable. Further, each monomer may be added to the reaction vessel after mixing various monomers to be used in advance, or may be added to the reaction vessel separately.

Further, if necessary, polymerization auxiliary materials such as a chelating agent, a dispersant, a pH adjusting agent, an oxygen scavenger, and a particle size adjusting agent can be used, and these are not particularly limited in terms of type and amount used.

The polymerization temperature at the time of performing emulsion polymerization is not particularly limited, but is usually 3 to 95 ° C, preferably 5 to 60 ° C. The polymerization time is about 5 to 40 hours.

As described above, the monomer mixture is emulsion-polymerized, and when the predetermined polymerization conversion rate is reached, the polymerization system is cooled or a polymerization inhibitor is added to stop the polymerization reaction. The polymerization conversion rate when the polymerization reaction is stopped is preferably 90% by weight or more, more preferably 93% by weight or more.

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

After stopping the polymerization reaction, if desired, the unreacted monomer is removed and the solid content concentration and pH are adjusted to obtain a latex of a nitrile group-containing conjugated diene-based copolymer.

Further, an antiaging agent, a preservative, an antibacterial agent, a dispersant and the like may be appropriately added to the latex of the nitrile group-containing conjugated diene copolymer, if necessary.

The number average particle size of the latex of the nitrile group-containing conjugated diene copolymer is preferably 60 to 300 nm, more preferably 80 to 150 nm. The particle size can be adjusted to a desired value by a method such as adjusting the amount of the emulsifier and the polymerization initiator used.

As the conjugated diene polymer used in the present invention, as described above, synthetic polyisoprene, styrene-isoprene-styrene block copolymer (SIS), nitrile group-containing conjugated diene polymer and the like can be used. , Butadiene polymer, styrene-butadiene copolymer and the like may be used.

The butadiene polymer may be a homopolymer of 1,3-butadiene as a conjugated diene monomer, or another ethylenically non-polymerizable copolymer with 1,3-butadiene as a conjugated diene monomer. It may be a copolymer obtained by copolymerizing with a saturated monomer.

The styrene-butadiene copolymer is a copolymer obtained by copolymerizing 1,3-butadiene as a conjugated diene monomer with styrene, and in addition to these, it is used as needed. It may be a copolymer obtained by copolymerizing another copolymerizable ethylenically unsaturated monomer.

Further, as the polymer latex for obtaining the latex of the carboxy-modified polymer used in the present invention, in addition to the latex of the conjugated diene-based polymer described above, a latex of natural rubber (deproteinized natural rubber) from which proteins have been removed is used. You can also do it. As the latex of deproteinized natural rubber, known methods such as a method of decomposing a protein in a natural rubber latex with a proteolytic enzyme or a surfactant and removing the produced decomposition product by washing or centrifugation are known. What is known as so-called "deproteinized natural rubber latex" obtained by the protein removal method can be used.
Further, as the latex of the deproteinized natural rubber, it is preferable to use one adjusted to the solid content concentration in the same range as the solid content concentration of the latex of the conjugated diene polymer described above, and it is prepared by adding the same additive. You may use the one that has been prepared.

<Latex of carboxy-modified polymer>
The carboxy-modified polymer constituting the latex of the carboxy-modified polymer used in the present invention can be obtained by modifying the above-mentioned conjugated diene-based polymer or deproteinized natural rubber with a monomer having a carboxyl group. Alternatively, when a polymer containing an ethylenically unsaturated carboxylic acid monomer unit is used as the conjugated diene polymer, the conjugated diene polymer is modified with a monomer having a carboxyl group. The conjugated diene polymer can be used as it is as a carboxy-modified polymer.

The method for modifying the conjugated diene-based polymer or deproteinized natural rubber with a monomer having a carboxyl group is not particularly limited, but for example, the conjugated diene-based polymer or deproteinized natural rubber is simply a simple compound having a carboxyl group. Examples thereof include a method of graft-polymerizing a dimer in an aqueous phase. The method for graft-polymerizing a monomer having a carboxyl group in an aqueous phase is not particularly limited, and a conventionally known method may be used. For example, a conjugated diene polymer or a latex of a deproteinized natural rubber may be used. After adding the monomer having a carboxyl group and the organic peroxide, a method of reacting the monomer having a carboxyl group with the conjugated diene polymer or the deproteinized natural rubber in the aqueous phase is preferable.

The organic peroxide is not particularly limited, but for example, diisopropylbenzene hydroperoxide, cumene hydroperoxide, t-butyl hydroperoxide, 1,1,3,3-tetramethylbutyl hydroperoxide, di-t. -Butyl peroxide, isobutylyl peroxide, benzoyl peroxide and the like can be mentioned, but 1,1,3,3-tetramethylbutylhydroperoxide is particularly preferable from the viewpoint of improving the mechanical strength of the obtained dip molded product. .. These organic peroxides may be used alone or in combination of two or more.

The amount of the organic peroxide added is not particularly limited, but is preferably 0.01 to 3 parts by weight, more preferably 0. parts by weight, based on 100 parts by weight of the conjugated diene polymer or deproteinized natural rubber contained in the latex. 1 to 1 part by weight.

In addition, the organic peroxide can be used as a redox-based polymerization initiator in combination with a reducing agent. The reducing agent is not particularly limited, but for example, a compound containing a metal ion in a reduced state such as ferrous sulfate and ferrous naphthenate; a sulfonic acid compound such as sodium methanesulfonate; an amine such as dimethylaniline. Compounds; sodium formaldehyde sulfoxylate; and the like. These reducing agents may be used alone or in combination of two or more.

The amount of the reducing agent added is not particularly limited, but is preferably 0.01 to 1 part by weight, more preferably 0.2 to 0.85 parts by weight, based on 1 part by weight of the organic peroxide. ..

The method of adding the organic peroxide and the reducing agent is not particularly limited, and known addition methods such as batch addition, divided addition, and continuous addition can be used, respectively.

When reacting a monomer having a carboxyl group with a conjugated diene polymer or a deproteinized natural rubber, it is preferable to carry out the reaction in the presence of a dispersant.

The dispersant is not particularly limited, but is not particularly limited, such as a derivative of aromatic sulfonic acid, a fatty acid salt, an alkylbenzene sulfonate, an alkylsulfosuccinate, an alkylsulfate ester salt, a polyoxyethylene alkyl ether sulfate ester salt, a monoalkyl phosphate salt, and the like. Anionic surfactants are preferred, and aromatic sulfonic acid derivatives are more preferred. The dispersants may be used alone or in combination of two or more.

The derivative of the aromatic sulfonic acid is not particularly limited, but a compound represented by the following general formula (1) is preferable.

(In the above general formula (1), R ¹ and R ² are independently hydrogen atoms or arbitrary organic groups, and R ¹ and R ² may be bonded to each other to form a ring structure. .)

When the R ¹ and R ² are not bonded to each other, as the organic group can be an R ¹ and R ^2, but not limited to, methyl group, ethyl group, n- propyl group, an isopropyl group, n- butyl group, an isobutyl group , Se-butyl group, t-butyl group, n-pentyl group, n-hexyl group, n-heptyl group, n-octyl group, n-nonyl group, n-decyl group and other alkyl groups having 1 to 30 carbon atoms. Cycloalkyl group having 3 to 30 carbon atoms such as cyclopropyl group, cyclopentyl group, cyclohexyl group, cycloheptyl group and cyclooctyl group; aryl having 6 to 30 carbon atoms such as phenyl group, biphenyl group, naphthyl group and anthranyl group Group: methoxy group, ethoxy group, n-propoxy group, isopropoxy group, n-butoxy group, isobutoxy group, sec-butoxy group, t-butoxy group, n-pentyloxy group, n-hexyloxy group, phenoxy group, etc. An alkoxy group having 1 to 30 carbon atoms; and the like. In addition, these organic groups may have a substituent, and the position of the substituent can be any position.

When R ¹ and R ² are bonded to each other to form a ring structure, the ring structure is not particularly limited, but an aromatic compound is preferable, and an aromatic compound having a benzene ring such as benzene or naphthalene is used. More preferably, naphthalene is particularly preferable. In addition, these ring structures may have a substituent, and the position of the substituent can be any position.

In the present invention, as the derivative of the aromatic sulfonic acid, among the compounds represented by the above general formula (1), as particularly preferable ones, R ¹ and R ² are bonded to each other to form a ring structure. Examples thereof include those having a benzene ring structure in the above general formula (1). More specifically, it is preferable to use a compound having a structure represented by the following general formula (2).

(In the above general formula (2), R ³ is a divalent hydrocarbon group which may have a substituent.)

In the above general formula (2), R ³ may be a divalent hydrocarbon group which may have a substituent, and is not particularly limited, but an alkylene group having 1 to 10 carbon atoms is preferable, and a methylene group is preferable. Is particularly preferable.

Further, the derivative of the aromatic sulfonic acid preferably has the structure represented by the general formula (2) repeatedly, and the number of repeating units of the structure represented by the general formula (2) is not particularly limited. However, the number is preferably 10 to 100, more preferably 20 to 50.

The weight average molecular weight of the aromatic sulfonic acid derivative is preferably 500 to 100,000, more preferably 3,000 to 50,000, and even more preferably 5,000 to 30,000.

The amount of the dispersant added is not particularly limited, but from the viewpoint that the generation of agglomerates can be more effectively suppressed even when the solid content concentration of the latex of the conjugated diene polymer or the deproteinized natural rubber is increased. Therefore, it is preferably 0.01 to 10 parts by weight, more preferably 0.1 to 5 parts by weight, based on 100 parts by weight of the conjugated diene polymer or deproteinized natural rubber contained in the latex.

The method of adding the dispersant to the latex of the conjugated diene polymer or the deproteinized natural rubber is not particularly limited, and known addition methods such as batch addition, divided addition, and continuous addition can be adopted. Further, the dispersant may be added directly to the latex, or an aqueous solution of the dispersant may be prepared in advance and the prepared aqueous solution of the dispersant may be added to the latex.

The reaction temperature (denaturation reaction temperature) at the time of reacting the conjugated diene polymer or the deproteinized natural rubber with the monomer having a carboxyl group is not particularly limited, but is preferably 15 to 80 ° C., more preferably 15 to 50 ° C. ° C., more preferably 18-35 ° C. The reaction time (denaturation reaction temperature) when reacting the monomer having a carboxyl group may be appropriately set according to the above reaction temperature, but is preferably 30 to 300 minutes, more preferably 45 to 80 minutes. ..

The solid content concentration of the latex of the conjugated diene polymer or the deproteinized natural rubber when reacting the monomer having a carboxyl group is not particularly limited, but is preferably 5 to 60% by weight, more preferably 10 to 40% by weight. It is% by weight.

Examples of the monomer having a carboxyl group include ethylenically unsaturated monocarboxylic acid monomers such as acrylic acid and methacrylic acid; and ethylenically unsaturated polyvalents such as itaconic acid, maleic acid, fumaric acid, and butentricarboxylic acid. Carboxylic acid monomer; Partial ester monomer of ethylenically unsaturated polyvalent carboxylic acid such as monobutyl fumarate, monobutyl maleate, mono2-hydroxypropyl maleate; polyvalent carboxylic acid such as maleic anhydride and citraconic anhydride Acid anhydride; etc. can be mentioned, but since the effect of the present invention becomes more remarkable, an ethylenically unsaturated monocarboxylic acid monomer is preferable, acrylic acid and methacrylic acid are more preferable, and methacrylic acid is preferable. Especially preferable. It should be noted that these monomers may be used alone or in combination of two or more.
Further, the above-mentioned carboxyl group includes those which are salts with alkali metals, ammonia and the like.

The amount of the monomer having a carboxyl group to be used is preferably 0.01 parts by weight to 100 parts by weight, more preferably 0.01 parts by weight or more, based on 100 parts by weight of the conjugated diene polymer or the deproteinized natural rubber. It is 40 parts by weight, more preferably 0.5 parts by weight to 20 parts by weight, and particularly preferably 1.5 to 4.5 parts by weight. By setting the amount of the monomer having a carboxyl group in the above range, the viscosity of the obtained latex composition becomes more appropriate, the transfer becomes easier, and the dip formed by using the obtained latex composition. The tear strength of a film molded product such as a molded product is further improved.

The method of adding the monomer having a carboxyl group to the latex is not particularly limited, and known addition methods such as batch addition, divided addition, and continuous addition can be adopted.

Further, after reacting a conjugated diene polymer or a deproteinized natural rubber with a monomer having a carboxyl group, the latex after the reaction may be post-heated, if necessary. By performing post-heating, the denaturation reaction by the monomer having a carboxyl group can be further advanced. The temperature of the post-heating is not particularly limited, but is the same as or higher than the reaction temperature (modification reaction temperature) when reacting the above-mentioned conjugated diene polymer or deproteinized natural rubber with a monomer having a carboxyl group. The specific post-heating temperature is preferably 20 to 85 ° C, more preferably 23 to 60 ° C, and even more preferably 20 to 45 ° C. The post-heating time may be appropriately set according to the post-heating temperature, but is preferably 30 to 300 minutes, more preferably 45 to 80 minutes.

The modification rate of the carboxy-modified polymer by the monomer having a carboxyl group may be appropriately controlled according to the intended use of the obtained latex composition, but is preferably 0.01 to 10 mol%, more preferably 0. It is 1 to 5 mol%, more preferably 0.2 to 0.8 mol%, and particularly preferably 0.3 to 0.7 mol%. The denaturation rate is represented by the following formula (i).
Degeneration rate (mol%) = (X / Y) x 100 ... (i)
In the above formula (i), X represents the number of carboxyl groups in the carboxy-modified polymer, and Y represents the total number of monomer units of the carboxy-modified polymer. X can be determined by measuring the carboxy-modified polymer by ^{1 H-NMR.} Further, Y is (weight average molecular weight (Mw) of the carboxy-modified polymer) / (average molecular weight of the monomers (average molecular weight of the monomer mixture) according to the content ratio of each monomer unit constituting the carboxy-modified polymer). It can be obtained by calculation.

The conversion rate of the graft polymerization is preferably 95% by weight or more, more preferably 97% by weight or more. By setting the conversion rate of the graft polymerization within the above range, the tear strength of the obtained film molded product such as a dip molded product is further improved.

Additives such as pH adjusters, antifoaming agents, preservatives, chelating agents, oxygen scavengers, dispersants, and antiaging agents, which are usually blended in the latex of the carboxy-modified polymer used in the present invention. May be blended.

Examples of the pH adjuster include hydroxides of alkali metals such as sodium hydroxide and potassium hydroxide; alkali metal carbonates such as sodium carbonate and potassium carbonate; alkali metal bicarbonates such as sodium hydrogen carbonate; ammonia. ; Organic amine compounds such as trimethylamine and triethanolamine; etc., but alkali metal hydroxides or ammonia are preferable.

Further, after graft polymerization, if necessary, in order to increase the solid content concentration of the latex of the carboxy-modified polymer, a concentration operation may be performed by a method such as vacuum distillation, atmospheric distillation, centrifugation, or membrane concentration. Centrifugation is preferable from the viewpoint that the residual amount of the anionic surfactant in the latex of the carboxy-modified polymer can be adjusted.

When the latex of the carboxy-modified polymer after graft polymerization is centrifuged, it is preferable to add a pH adjuster in advance to set the pH of the latex to 7 or more in order to improve the mechanical stability of the latex. Is more preferably set to 9 or more. When the pH of the latex is adjusted, the carboxyl group introduced by denaturation may be in a salt state.

The solid content concentration of the latex of the carboxy-modified polymer is preferably 30 to 70% by weight, more preferably 40 to 70% by weight. By setting the solid content concentration in the above range, the generation of agglomerates in the latex can be more effectively suppressed, and the separation of polymer particles when the latex is stored can be more effectively suppressed.

The content ratio of the monomer unit having a carboxyl group in the carboxy-modified polymer is preferably 0.01 to 50% by weight, more preferably 0.5 to 40% by weight, based on all the monomer units. , More preferably 1 to 30% by weight, and particularly preferably 1 to 15% by weight. By setting the content ratio of the monomer unit having a carboxyl group in the above range, the mechanical stability of the obtained latex composition is further improved, and further, the dip molded product formed by using the obtained latex composition. Flexibility and tear strength are further improved.

Further, in the present invention, a latex having a swell index (SI) of 120 to 190% is used as the latex of the carboxy-modified polymer. According to the present invention, when a film molded product such as a dip molded product is obtained by using a latex of a carboxy-modified polymer having a swell index (SI) in such a range in combination with a xanthogen compound, The obtained film molded product such as a dip molded product can suppress the occurrence of delayed type allergy (Type IV) in addition to immediate type allergy (Type I), has high tear strength, and has a flexible texture. Furthermore, when obtaining a film molded product such as a dip molded product, the aging (pre-vulcanization) time can be shortened, and a film such as a dip molded product can be obtained with high productivity. It is possible to manufacture a molded product.

The swell index (SI) of the latex of the carboxy-modified polymer is obtained by forming the latex of the carboxy-modified polymer into a film, and immersing the obtained film of the carboxy-modified polymer in toluene at 25 ° C. for 1 hour before and after immersion in toluene. It can be obtained by measuring the width of the film and measuring the linear swelling rate. Specifically, the swell index (SI) can be obtained according to the following formula.
Swell index (SI) [%] = [{(width of film after immersion in toluene)-(width of film before immersion in toluene)} / (width of film before immersion in toluene)] × 100

As a method for producing a film for measurement for measuring the swell index (SI) of the latex of the carboxy-modified polymer, for example, the following dip method can be adopted.
That is, in the dip method, first, an acid or an alkali is added to the latex of the carboxy-modified polymer to adjust the pH to 8.2. Then, a ceramic mold with a ground surface was prepared, washed, preheated in an oven at 70 ° C. for 30 minutes, and then 18% by weight of calcium nitrate and 0.05% by weight of polyoxy. A preheated ceramic mold is immersed in an aqueous coagulant containing ethylene lauryl ether (trade name "Emargen 109P", manufactured by Kao Corporation) for 5 seconds. Then, the ceramic mold is taken out from the coagulant aqueous solution, and the ceramic mold coated with the coagulant is dried in an oven at 70 ° C. for 20 minutes. Next, the ceramic mold coated with the coagulant was taken out from the oven, and the removed ceramic mold was placed in the latex of the carboxy-modified polymer adjusted to pH = 8.2 at 25 ° C. for 10 seconds. A film for measurement is taken out after being immersed under the conditions, and a ceramic mold coated with a latex of a carboxy-modified polymer is immersed in warm water at 60 ° C. for 5 minutes and then dried at room temperature for 6 hours. Obtain a ceramic mold coated with. Then, after spraying talc on this, the film for measurement can be obtained by peeling the film for measurement from the ceramic molding die. The thickness of the film for measurement is not particularly limited, but is preferably about 0.2 mm.

In the present invention, the swell index (SI) of the latex of the carboxy-modified polymer may be 120 to 190%, but tearing occurs when the aging (pre-vulcanization) time is as short as 24 hours, for example. From the viewpoint of making the strength stability more excellent, the swell index (SI) is preferably 127 to 165%, more preferably 130 to 160%, and further preferably 140 to 160%. When a latex having a swell index (SI) of less than 120% or more than 190% is used as the latex of the carboxy-modified polymer, aging (pre-vulcanization) is performed in order to obtain sufficient mechanical strength such as tear strength. It takes a long time, which makes it less productive.

The method for adjusting the swell index (SI) of the latex of the carboxy-modified polymer is not particularly limited, but for example, a conjugated diene polymer or a monomer having a carboxyl group is reacted with a deproteinized natural rubber. A method of adjusting the reaction temperature (denaturation reaction temperature) and the reaction time (denaturation reaction time) at the time of aging, a method of selecting the presence or absence of post-heating of the polymer after the reaction, and post-heating of the polymer after the reaction. A method of adjusting the post-heating temperature and the post-heating time, a method of adjusting the type and amount of the monomer having a carboxyl group used in the modification reaction, and a method of combining with an organic peroxide in the modification reaction. Examples thereof include a method of adjusting the type and amount of the reducing agent used, and it is desirable to appropriately combine and adjust these.

Further, the latex of the carboxy-modified polymer used in the present invention preferably has a swell index (SI) in the above range and a toluene insoluble content of 55 to 85% by weight, preferably 60 to 80% by weight. It is more preferably%, and further preferably 65 to 80% by weight. When the amount of toluene insoluble is in the above range, the action and effect of the present invention can be made even more remarkable.

The toluene-insoluble content of the latex of the carboxy-modified polymer can be measured by the following method.
That is, first, an acid or an alkali is added to the latex of the carboxy-modified polymer to adjust the pH to 8.2. Then, the latex of the carboxy-modified polymer adjusted to pH = 8.2 is cast on a glass plate having a smooth surface, and then dried at 25 ° C. for 120 hours for measurement by the casting method. You can get the film. The thickness of the film for measurement is not particularly limited, but is preferably about 0.2 mm. Then, the weight of the film for measurement thus obtained (this weight is referred to as "W1") is measured, and then the film is immersed in toluene at 25 ° C. for 24 hours. The soaked film is then dried at 100 ° C. for 24 hours to remove toluene. Then, the weight (this weight is referred to as "W2") of the film after removing toluene is measured, and the amount of toluene insoluble can be measured from the measurement results of these weights according to the following formula.
Toluene insoluble amount [% by weight] = (W2 / W1) × 100
The method for adjusting the toluene insoluble amount of the latex of the carboxy-modified polymer to the above range is not particularly limited, but for example, a conjugated diene polymer or a deproteinized natural rubber is reacted with a monomer having a carboxyl group. A method of adjusting the reaction temperature (denaturation reaction temperature) and reaction time (denaturation reaction time), a method of selecting the presence or absence of post-heating of the polymer after the reaction, and a method of post-heating the latex after the reaction. A method of adjusting the post-heating temperature and post-heating time of the squeezing, a method of adjusting the type and amount of the monomer having a carboxyl group used in the denaturation reaction, and further, in the denaturation reaction, in combination with an organic peroxide. Examples thereof include a method of adjusting the type of reducing agent to be used and the amount of the reducing agent used, and it is desirable to appropriately combine and adjust these.

Further, the latex of the carboxy-modified polymer used in the present invention preferably has a swell index (SI) in the above range and a swelling rate with respect to THF of 5 to 40 times, preferably 10 to 35 times. It is more preferable that there is, and it is further preferable that it is 10 to 30 times. When the swelling rate with respect to THF is in the above range, the action and effect of the present invention can be made even more remarkable.

The swelling rate of the latex of the carboxy-modified polymer with respect to THF can be measured by the following method.
That is, first, a film for measurement was obtained by a casting method in the same manner as in the case of the above-mentioned measurement of the amount of toluene insoluble, and the obtained film for measurement was placed in tetrahydrofuran (THF) at 25 ° C. at 24 ° C. The film was soaked for a long time, the soaked film was pulled up, and the weight (weight A) was immediately measured. Then, the dipped film is dried at 100 ° C. for 24 hours, and the dry weight (weight B) of the film is measured. Then, based on the measurement result, the swelling rate with respect to THF can be obtained according to the following formula.
Swelling rate (times) with respect to THF = B / A

Further, the latex of the carboxy-modified polymer used in the present invention preferably has a swell index (SI) in the above range and a THF insoluble content of 80 to 100% by weight, preferably 83 to 99% by weight. It is more preferably%, and further preferably 85 to 98% by weight. When the amount of THF insoluble is in the above range, the action and effect of the present invention can be made even more remarkable.

The THF-insoluble content of the latex of the carboxy-modified polymer can be measured by the following method.
That is, first, in the same manner as in the case of the above-mentioned measurement of the amount of toluene insoluble, a film for measurement is obtained by the casting method, and the weight of the obtained film for measurement (this weight is referred to as "W3"). After measuring, the film is immersed in tetrahydrofuran (THF) at 25 ° C. for 24 hours. The soaked film is then dried at 100 ° C. for 24 hours to remove THF. Then, the weight (this weight is referred to as "W4") of the film after removing THF is measured, and the amount of THF insoluble can be measured from the measurement results of these weights according to the following formula.
THF insoluble amount [% by weight] = (W4 / W3) × 100

<Xanthate compound>
The latex composition of the present invention contains a xanthate compound in addition to the latex of the carboxy-modified polymer described above.

The xanthate compound used in the present invention can act as a vulcanization accelerator when used in combination with a sulfur-based vulcanization agent, for example. That is, when a sulfur-based vulcanizing agent is blended in the latex composition and the carboxy-modified polymer in the latex composition is vulcanized with the sulfur-based vulcanizing agent to obtain a film molded body such as a dip molded body. The xanthogen compound acts as a vulcanization accelerator. In addition, the xanthogen compound acts as a vulcanization accelerator on a latex composition containing a sulfur-based vulcanizing agent, and after vulcanization is performed, alcohol and disulfide are generated by heat applied during vulcanization. It is decomposed into carbon and the like. For example, a xanthate compound is decomposed into alcohol, carbon disulfide, etc. by the heat applied when producing a film-formed body (heat of about 100 to 130 ° C. when vulcanizing a carboxy-modified polymer), and further decomposed. The components (alcohol, carbon disulfide, etc.) produced by the above volatilize. Thereby, the residual amount of the xanthate compound can be reduced in the obtained film molded product. According to the present invention, a vulcanization accelerator (for example, a dithiocarbamate-based vulcanization accelerator, a thiazole-based vulcanization accelerator, etc.) that has conventionally caused the occurrence of delayed type allergy (Type IV) symptoms is used. However, the xanthate compound can be used as a vulcanization accelerator, whereby the residual amount of the xanthate compound in the obtained film-molded product such as a dip-molded product can be reduced, so that the obtained film-molded product is delayed. It is possible to suppress the occurrence of symptoms of type allergy (Type IV). Moreover, since the latex composition of the present invention uses a synthetic rubber such as a conjugated diene polymer or a carboxy-modified polymer using a deproteinized natural rubber, the obtained film-formed product is included in the natural rubber. It is also possible to suppress the occurrence of symptoms of immediate type allergy (Type I) caused by the protein.

The xanthogen compound used in the present invention is not particularly limited, and examples thereof include xanthate acid and xanthogenate.

The xanthogenate may be a salt compound having a xanthate structure, and is not particularly limited, but is preferably a metal salt of xanthate, and among them, the general formula (ROC (= S) S) xZ. (Here, R is a linear or branched hydrocarbon, Z is a metal atom. X is a number corresponding to the valence of Z, and is usually 1 to 4, preferably 2 to 4, particularly preferably 2. The compound represented by) is preferable. Further, among the metal salts of xanthate, the zinc salt of xanthate is more preferable.

The xanthogenate represented by the above general formula (ROC (= S) S) xZ is not particularly limited, and is, for example, zinc dimethylxanthate, zinc diethylxanthogenate, zinc dipropylxanthate, diisopropylxanthate. Zinc, Zinc dibutylxanthate, Zinc dipentylxanthate, Zinc dihexylxanthate, Zinc diheptylxanthate, Zinc dioctylxanthate, Zinc di (2-ethylhexyl) xanthate, Zinc didecylxanthate, Zinc didodecylxanthate, Potassium dimethylxanthate, potassium ethylxanthate, potassium propylxanthate, potassium isopropylxanthate, potassium butylxanthate, potassium pentylxanthate, potassium hexylxanthate, potassium heptylxanthate, potassium octylxanthate, 2-ethylhexanthate Potassium, potassium decylxanthate, potassium dodecylxanthate, sodium methylxanthate, sodium ethylxanthate, sodium propylxanthate, sodium isopropylxanthate, sodium butylxanthate, sodium pentylxanthate, sodium hexylxanthate, heptylxanthate Examples thereof include sodium, sodium octylxanthate, sodium 2-ethylhexanthate, sodium decylxanthate, and sodium dodecylxanthate. Among these, isopropylxanthogenates and butylxanthogenates may be used, and xanthogenates having x of 2 or more in the above general formula (ROC (= S) S) xZ are preferable, and diisopropylxanthogenates. , Dibutylxanthogenates are more preferable, zinc diisopropylxanthogenate and zinc dibutylxanthogenate are further preferable, and zinc diisopropylxanthogenate is particularly preferable. These xanthogenates may be used alone or in combination of two or more.

Note that these xanthogen compounds may be used alone or in combination of two or more.

Further, in the present invention, it is preferable to disperse the xanthogen compound in the latex composition in the form of particles or powder, and the volume average particle size of the xanthogen compound dispersed in the latex composition is 0.001. The range is preferably in the range of ~ 9 μm. By setting the volume average particle size of the xanthogen compound dispersed in the latex composition in the range of 0.001 to 9 μm, the obtained film-molded product such as a dip-molded product has higher tear strength and stability of tear strength. It can be said that the pinholes are more excellent and the occurrence of pinholes is effectively suppressed.

The volume average particle size of the xanthate compound dispersed in the latex composition is preferably in the range of 0.001 to 9 μm, more preferably in the range of 0.05 to 9 μm, and further preferably in the range of 0.05 to 7 μm. The range, even more preferably the range of 0.07 to 5 μm, particularly preferably the range of 1 to 4 μm. By setting the volume average particle size of the xanthate compound dispersed in the latex composition within the above range, the effect of improving the tear strength and the stability of the tear strength can be further enhanced.

Further, in the present invention, the volume average particle size of the xantogen compound dispersed in the latex composition is preferably in the above range, but the 95% volume cumulative diameter (D95) of the xantogen compound is in the range of 0.1 to 43 μm. It is preferably in the range of 0.1 to 40 μm, more preferably 0.1 to 35 μm, still more preferably 0.1 to 20 μm, and particularly preferably 5 to 18 μm. By setting the 95% volume cumulative diameter (D95) in the above range, the effect of improving the tear strength and the stability of the tear strength can be further enhanced. The volume average particle diameter and the 95% volume cumulative diameter (D95) of the xantogen compound can be measured using, for example, a laser diffraction / scattering type particle size distribution meter.

It should be noted that these xanthogen compounds may be contained alone in the latex composition of the present invention, but it is preferable that two or more of them are contained. For example, when xanthogenic acid is blended in a latex composition, a part of the blended xanthate acid is present in the form of xanthate salt due to the action of a typical metal compound described later, and as a result, the latex composition. May contain two or more xanthogen compounds. Alternatively, when the latex composition contains sulfur as a sulfur-based vulcanizer or the like, the xanthogenic acid blended in the latex composition exists in the form of xanthogen disulfide or xanthogen polysulfide due to the action of sulfur. You may. Similarly, when the latex composition is blended with xanthate, xanthogen disulfide or xanthogen polysulfide, these are any of xanthate acid, xanthogenate, xanthogen disulfide and xanthogen polysulfide, respectively. It may exist in the form of.

The content ratio of the xanthogen compound in the latex composition of the present invention (when a plurality of xanthogen compounds are contained in the latex composition, the total content ratio) is 100 parts by weight of the carboxy-modified polymer contained in the latex. On the other hand, it is preferably 0.01 to 10 parts by weight, more preferably 0.1 to 7 parts by weight, and further preferably 0.5 to 5 parts by weight. By setting the content ratio of the xanthogen compound in the above range, it is possible to further improve the tear strength of the obtained membrane molded product such as a dip molded product while suppressing the occurrence of the symptoms of delayed type allergy (Type IV). ..

Further, in the present invention, when a xanthate compound is added to the latex of a carboxy-modified polymer to prepare a latex composition, the xanthate compound is dispersed in water or alcohol to obtain a xanthate compound dispersion. , It is preferable to add in the form of a xanthate compound dispersion. In this case, it is preferable that the volume average particle size of the xantogen compound in the xantogen compound dispersion is within the above range, and in addition to the volume average particle size, the 95% volume cumulative diameter (D95) is also within the above range. It is preferable to do so.

The content ratio of the xanthate compound in the xanthate compound dispersion is preferably 1 to 60% by weight, more preferably 10 to 50% by weight, still more preferably 30 to 50% by weight, based on the entire xanthate compound dispersion. Is. By setting the content ratio of the xanthate compound in the above range, the xanthate compound dispersion can be made more excellent in storage stability.

Further, the xanthate compound dispersion preferably further contains a nonionic surfactant and / or a nonionic anionic surfactant in addition to the xanthate compound described above.

By dispersing the above-mentioned xanthogen compound in water or alcohol together with a nonionic surfactant and / or a nonionic anionic surfactant, the xanthogen compound can be better dispersed, whereby xanthogen can be better dispersed. The effect of the compound as a vulcanization accelerator can be further enhanced, whereby the vulcanization time (particularly, aging (pre-vulcanization)) in obtaining a vulcanized product of a polymer such as a conjugated diene-based polymer can be obtained. The time required) can be shortened, and productivity can be improved. In the present invention, it is preferable to use at least one of a nonionic surfactant and a nonionic anionic surfactant, and it is more preferable to use a nonionic surfactant.

The nonionic surfactant may be a nonionic surfactant, and is not particularly limited. For example, polyoxyalkylene glycol, polyoxyalkylene alkyl ether, polyoxyalkylene alkyl phenyl ether, or polyoxyethylene styrene. Examples thereof include phenyl ether, polyoxyethylene (hardened) castor oil, polyoxyethylene alkylamine, and fatty acid alkanolamide.

Examples of the polyoxyalkylene glycol include polyoxypropylene glycol ethylene oxide adducts such as polyoxyethylene glycol, polyoxypropylene glycol, and polyoxyethylene polyoxypropylene glycol.

Examples of the polyoxyalkylene alkyl ether include linear or branched chain ethers to which 1 to 50 (preferably 1 to 10) propylene oxide and / or ethylene oxide are added. Among these, linear or branched ethers to which 1 to 50 propylene oxides (preferably 1 to 10) have been added, and direct chains to which 1 to 50 ethylene oxides (preferably 1 to 10) have been added. Chain-shaped or branched-chain ethers, linear or branched-chain ethers in which a total of 2 to 50 (preferably 2 to 10) blocks of ethylene oxide and propylene oxide are added or randomly added, and the like are polyoxyethylene. Dodecyl ether, polyoxyethylene lauryl ether and the like can be mentioned.

Examples of the polyoxyalkylene alkyl phenyl ether include compounds in which 1 to 50 (preferably 1 to 10) propylene oxide and / or ethylene oxide are added to the alkyl phenol.
Examples of the polyoxyethylene styrenated phenyl ether include ethylene oxide adducts of (mono, di, tri) styrenated phenol, and among these, polyoxyethylene di, which is an ethylene oxide adduct of distyrene phenol. Styrylated phenyl ether is preferred.

Examples of the polyoxyethylene (hardened) castor oil include castor oil or an ethylene oxide adduct of hardened castor oil.
Examples of the fatty acid alkanolamide include lauric acid diethanolamide, palmitic acid diethanolamide, myristic acid diethanolamide, stearic acid diethanolamide, oleic acid diethanolamide, palm oil fatty acid diethanolamide, and coconut oil fatty acid diethanolamide.

Among the nonionic surfactants, a nonionic surfactant having a polyoxyalkylene structure is preferable, a nonionic surfactant having a polyoxyethylene structure is more preferable, and a hydrocarbylated ether of polyoxyethylene is more preferable. , Polyoxyalkylene alkyl ethers and polyoxyethylene distyrene phenyl ethers are more preferred, and polyoxyethylene distyrene phenyl ethers are particularly preferred. The nonionic surfactant may be used alone or in combination of two or more.

Further, the nonionic anionic surfactant is an anionic surfactant (that is, a substance that dissociates ions in an aqueous solution and exhibits surface activity in the anionic portion), and is nonionic in its molecular main chain. It is not particularly limited as long as it has a segment that acts as a surfactant of, for example, a polyalkylene oxide chain.

Examples of such nonionic anionic surfactants include compounds represented by the following general formula (3).
R ^4- O- (CR ⁵ R ⁶ CR ⁷ R ⁸ ) n-SO ₃ M (3)
(In the above general formula (3), R ⁴ is an aryl group having 6 to 14 carbon atoms which may be substituted with an alkyl group having 6 to 16 carbon atoms or an alkyl group having 1 to 25 carbon atoms, R ⁵ to R ⁸ is a group independently selected from the group consisting of hydrogen and methyl groups, M is an alkali metal atom or ammonium ion, and n is 3 to 40.)

Specific examples of nonionic anionic surfactants include polyoxyethylene such as polyoxyethylene lauryl ether sulfate, polyoxyethylene cetyl ether sulfate, polyoxyethylene stearyl ether sulfate, and polyoxyethylene oleyl ether sulfate. Alkyl ether sulfate; polyoxyethylene aryl phenyl ether sulfate such as polyoxyethylene nonylphenyl ether sulfate, polyoxyethylene octylphenyl ether sulfate, polyoxyethylene distyryl ether sulfate; and the like.

Among the nonionic anionic surfactants, the nonionic anionic surfactant having a polyoxyalkylene structure is preferable, and the nonionic anionic surfactant having a polyoxyethylene structure is more preferable. The nonionic anionic surfactant may be used alone or in combination of two or more.

The content of the nonionic surfactant and / or the nonionic anionic surfactant in the xanthogen compound dispersion is not particularly limited, but is preferably 0.1 to 30 parts by weight based on 100 parts by weight of the xanthogen compound. Parts, more preferably 1 to 20 parts by weight, still more preferably 4 to 15 parts by weight, and particularly preferably 5.5 to 9.5 parts by weight. By setting the content of the nonionic surfactant and / or the nonionic anionic surfactant in the above range, the dispersibility of the xanthate compound in the xanthate compound dispersion can be further enhanced.

The method for preparing the xanthogen compound dispersion is not particularly limited, but is limited to a xanthogen compound, a nonionic surfactant and / or a nonionic anionic surfactant used as needed, and water or alcohol (for example, methanol). , Ethanol, propanol and at least one selected from butanol), and then the obtained mixed solution is crushed, and in particular, the xanthogen compound is prepared by adjusting the crushing conditions. It is preferable that the volume average particle diameter of the above range is in the above range. Here, the crushing treatment may be any treatment that can alleviate the crushing and aggregation of the xanthate compound contained in the dispersion, and is not particularly limited, but for example, shearing action or grinding. Examples thereof include a method using a known crusher, such as a method using a crusher utilizing the action and a method using a stirring type crusher. Specifically, a crushing device such as a roll mill, a hammer mill, a vibration mill, a jet mill, a ball mill, a planetary ball mill, a bead mill, a sand mill, or a three-roll mill can be used. Among these, a method of performing the crushing treatment using a ball mill, a planetary ball mill, or a bead mill is preferable from the viewpoint that the volume average particle size of the xanthogen compound in the dispersion can be preferably controlled.

For example, when the crushing process is performed using a ball mill, a medium having a media size of preferably φ5 to φ50 mm, more preferably φ10 to φ35 mm is used, and the rotation speed is preferably 10 to 300 rpm. It is preferable to carry out the crushing treatment under the conditions of more preferably 10 to 100 rpm and a treatment time of preferably 24 to 120 hours, more preferably 24 to 72 hours. When the crushing process is performed using a planetary ball mill, a medium having a media size of preferably φ0.1 to φ5 mm, more preferably φ0.3 to φ3 mm is used, and the rotation speed is high. It is preferable to carry out the crushing treatment under the conditions of preferably 100 to 1000 rpm, more preferably 100 to 500 rpm, and a treatment time of preferably 0.25 to 5 hours, more preferably 0.25 to 3 hours. is there. Further, when the crushing treatment is performed using a bead mill, a medium having a media size of preferably φ0.1 to φ3 mm, more preferably φ0.1 to φ1 mm is used, and the rotation speed is preferably high. Is preferably 1000 to 10000 rpm, more preferably 1000 to 5000 rpm, and the treatment time is preferably 0.25 to 5 hours, more preferably 0.25 to 3 hours.

In the present invention, in the latex composition, in addition to the xanthogen compound, a compound conventionally used as a vulcanization accelerator, specifically, sulfur which causes symptoms of delayed type allergy (Type IV). A vulcanization accelerator containing (for example, dithiocarbamate-based vulcanization accelerator, thiazole-based vulcanization accelerator, etc.), and a film-formed body such as a dip-formed body obtained after acting as a vulcanization accelerator. It is preferable that the compound that remains in the vulcanization is substantially not contained.

In the latex composition of the present invention, the method for blending the xanthogen compound may be any method as long as it is a method in which the latex of the carboxy-modified polymer and the xantogen compound are finally mixed, and is not particularly limited. After obtaining the latex of the carboxy-modified polymer, a method of blending the xanthogen compound with the latex of the carboxy-modified polymer, or adding the xanthogen compound to a solution or fine suspension of the carboxy-modified polymer dissolved or finely dispersed in an organic solvent in advance. After blending, a solution or microsuspension of the carboxy-modified polymer containing the xanthogen compound is emulsified in water, and if necessary, the organic solvent is removed to remove the latex of the carboxy-modified polymer containing the xanthogen compound. And so on. Among these, from the viewpoint that the xanthogen compound is easily dissolved and the xanthogen compound is more easily blended, a method of blending the xanthogen compound with the latex of the carboxy-modified polymer after obtaining the latex of the carboxy-modified polymer is used. preferable.

<Other ingredients>
The latex composition of the present invention may contain the above-mentioned latex of the carboxy-modified polymer and the xanthate compound, but it is preferable that the latex composition further contains a sulfur-based vulcanizing agent.
Examples of the sulfur-based sulfurizing agent include sulfur powder, sulfur flower, precipitated sulfur, colloidal sulfur, surface-treated sulfur, and insoluble sulfur; sulfur chloride, sulfur dichloride, morpholin disulfide, alkylphenol disulfide, and caprolactam disulfide (N). , N'-dithio-bis (hexahydro-2H-azepinone-2)), phosphorus-containing polysulfide, high molecular weight polysulfide, 2- (4'-morpholinodithio) benzothiazole and other sulfur-containing compounds. Of these, sulfur can be preferably used. The cross-linking agent may be used alone or in combination of two or more.

The content of the sulfur-based vulcanizing agent is not particularly limited, but is preferably 0.1 to 10 parts by weight, more preferably 0.2 to 3 parts by weight, based on 100 parts by weight of the carboxy-modified polymer. By setting the content of the sulfur-based vulcanizing agent in the above range, the tear strength can be further increased while suppressing the occurrence of the symptoms of delayed type allergy (Type IV) in the obtained film molded body such as a dip molded body. Can be done.

In addition, the latex composition of the present invention further contains a cross-linking accelerator as long as the occurrence of delayed allergy (Type IV) symptoms can be suppressed in the obtained film molded product such as a dip molded product. May be good.
As the cross-linking accelerator, those usually used in dip molding can be used, for example, dithiocarbamines such as diethyldithiocarbamic acid, dibutyldithiocarbamic acid, di-2-ethylhexyldithiocarbamic acid, dicyclohexyldithiocarbamic acid, diphenyldithiocarbamic acid, and dibenzyldithiocarbamic acid. Acids and their zinc salts; 2-mercaptobenzothiazole, 2-mercaptobenzothiazole zinc, 2-mercaptothiazolin, dibenzothiazyl disulfide, 2- (2,4-dinitrophenylthio) benzothiazole, 2- (N, N-dithiocarbamoylthio) benzothiazole, 2- (2,6-dimethyl-4-morpholinothio) benzothiazole, 2- (4'-morpholino dithio) benzothiazole, 4-morpholinyl-2-benzothiadyl disulfide, Examples thereof include 1,3-bis (2-benzothiadyl mercaptomethyl) urea, but zinc diethyldithiocarbamate, zinc 2dibutyldithiocarbamate, and zinc 2-mercaptobenzothiazole are preferable. The cross-linking accelerator may be used alone or in combination of two or more.

Further, the latex composition of the present invention preferably contains a typical metal compound other than an oxide, and by containing a typical metal compound other than an oxide, a film molding such as a dip molded product obtained can be formed. The tear strength of the body can be further increased.

Typical metals constituting the main group metal compound used in the present invention include Group 1 elements, Group 2 elements, Group 12 elements, Group 13 elements, Group 14 elements, Group 15 elements, Group 16 elements, and the like. At least one element selected from the group consisting of Group 17 elements and Group 18 elements can be used, and among them, Group 2 elements, Group 12 elements, Group 13 elements, and Group 14 elements are used. Preferably, zinc, magnesium, calcium, aluminum and lead are more preferred, zinc, magnesium and calcium are even more preferred, and zinc is particularly preferred.

The typical metal compound used in the present invention may be a compound containing the above-mentioned typical metal other than an oxide, and is not particularly limited, but the tear strength of the obtained film-formed body such as a dip-shaped body is higher. From the viewpoint of improvement, a compound containing at least one carbon is preferable, a carbonate, a hydrogen carbonate, a hydroxide, and an organic metal compound are more preferable, and a carbonate, a hydrogen carbonate, and an organic metal compound are further preferable. Among these, inorganic salts such as carbonates and hydrogen carbonates are particularly preferable from the viewpoint of excellent stability of the compound itself and excellent availability. These typical metal compounds may be used alone or in combination of two or more.

As described above, the typical metal compound used in the present invention may be a compound other than an oxide, and such an oxide may be, for example, zinc oxide, magnesium oxide, calcium oxide, or lead oxide. , Tin oxide, and aluminum oxide.

The content ratio of the typical metal compound in the latex composition of the present invention is preferably 0.01 to 10 parts by weight, more preferably 0.1 to 5 parts by weight, based on 100 parts by weight of the carboxy-modified polymer contained in the latex. It is by weight, more preferably 1 to 3 parts by weight. By setting the content ratio of the main group compound in the above range, the tear strength of the obtained film molded product such as a dip molded product can be further improved.

Further, the latex composition of the present invention further contains an antiaging agent; a dispersant; a reinforcing agent such as carbon black, silica and talc; a filler such as calcium carbonate and clay; an ultraviolet absorber; a plasticizer; and the like. The agent can be blended as needed.

Anti-aging agents include 2,6-di-4-methylphenol, 2,6-di-t-butylphenol, butylhydroxyanisole, 2,6-di-t-butyl-α-dimethylamino-p-cresol, Octadecyl-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate, styrenated phenol, 2,2'-methylene-bis (6-α-methyl-benzyl-p-cresol), 4, Butylation of 4'-methylenebis (2,6-di-t-butylphenol), 2,2'-methylene-bis (4-methyl-6-t-butylphenol), alkylated bisphenol, p-cresol and dicyclopentadiene Phenolic antioxidants that do not contain sulfur atoms such as reaction products; 2,2'-thiobis- (4-methyl-6-t-butylphenol), 4,4'-thiobis- (6-t-butyl-) O-cresol), 2,6-di-t-butyl-4- (4,6-bis (octylthio) -1,3,5-triazine-2-ylamino) phenol and other thiobisphenolic antioxidants; Tris (Nonylphenyl) phosphite, diphenylisodecylphosphite, tetraphenyldipropylene glycol / diphosphite and other phosphite-based anti-aging agents; sulfur ester-based anti-aging agents such as dilauryl thiodipropionate; phenyl-α-naphthylamine, Phenyl-β-naphthylamine, p- (p-toluenesulfonylamide) -diphenylamine, 4,4'-(α, α-dimethylbenzyl) diphenylamine, N, N-diphenyl-p-phenylenediamine, N-isopropyl-N' -Amine-based anti-aging agents such as phenyl-p-phenylenediamine, butylaldehyde-aniline condensate; quinoline-based anti-aging agents such as 6-ethoxy-2,2,4-trimethyl-1,2-dihydroquinolin; 2, Hydroquinone-based anti-aging agents such as 5-di (t-amyl) hydroquinone; and the like. These antioxidants can be used alone or in combination of two or more.

The content of the anti-aging agent is preferably 0.05 to 10 parts by weight, more preferably 0.1 to 5 parts by weight, based on 100 parts by weight of the carboxy-modified polymer.

The method for mixing various compounding agents with the latex composition of the present invention is not particularly limited, but for example, as described above, a latex composition containing a latex of a carboxy-modified polymer, a xanthogen compound, and a typical metal compound can be used. After obtaining the latex composition, a method of mixing various compounding agents to be blended with the latex composition using a disperser such as a ball mill, a kneader, or a disper, or using the above disperser, a carboxy-modified polymer. Examples thereof include a method of preparing an aqueous dispersion of a compounding component other than the latex of the above, and then mixing the aqueous dispersion with the latex of the carboxy-modified polymer.

The solid content concentration of the latex composition of the present invention is preferably 10 to 60% by weight, more preferably 10 to 55% by weight.

When the latex composition of the present invention contains a sulfur-based vulcanizing agent, it is aged before being subjected to dip molding from the viewpoint of further enhancing the mechanical properties of the obtained film molded product such as the dip molded product. Pre-vulcanization) is preferable. It is preferable to carry out aging (pre-vulcanization). The aging (pre-vulcanization) time is not particularly limited, but is preferably 6 to 42 hours, more preferably 12 to 38 hours, and even more preferably 18 to 36 hours. According to the latex composition of the present invention, even when the aging (pre-vulcanization) time is relatively short as described above, a film molded product such as a dip molded product having sufficiently excellent mechanical properties such as tear strength can be obtained. This makes it possible to shorten the time required for aging (pre-vulcanization) and further improve the production efficiency. The temperature of the pre-vulcanization is not particularly limited, but is preferably 20 to 40 ° C, more preferably 20 to 30 ° C.

<Membrane molded product>
The film molded product of the present invention is a film-shaped molded product made of the latex composition of the present invention. The film thickness of the film molded product of the present invention is preferably 0.03 to 0.50 mm, more preferably 0.05 to 0.40 mm, and particularly preferably 0.08 to 0.30 mm.

The film molded product of the present invention is not particularly limited, but a dip molded product obtained by dip molding the latex composition of the present invention is preferable. Dip molding is a method in which a mold is dipped in a latex composition, the composition is deposited on the surface of the mold, then the mold is pulled up from the composition, and then the composition deposited on the surface of the mold is dried. is there. The mold before being immersed in the latex composition may be preheated. Further, a coagulant can be used if necessary before immersing the mold in the latex composition or after pulling the mold out of the latex composition.

Specific examples of the method of using the coagulant include a method of immersing the mold before being immersed in the latex composition in a solution of the coagulant to attach the coagulant to the mold (anode adhesion immersion method), and depositing the latex composition. There is a method of immersing the formed mold in a coagulant solution (Teeg adhesion immersion method), but the anode adhesion immersion method is preferable in that a dip molded product having less uneven thickness can be obtained.

Specific examples of the coagulant include metal halides such as barium chloride, calcium chloride, magnesium chloride, zinc chloride and aluminum chloride; nitrates such as barium nitrate, calcium nitrate and zinc nitrate; acetic acid such as barium acetate, calcium acetate and zinc acetate. Salts; water-soluble polyvalent metal salts such as calcium sulfate, magnesium sulfate, sulfates such as aluminum sulfate; Of these, calcium salts are preferable, and calcium nitrate is more preferable. These water-soluble polyvalent metal salts can be used alone or in combination of two or more.

The coagulant can usually be used as a solution of water, alcohol, or a mixture thereof, and is preferably used in the state of an aqueous solution. This aqueous solution may further contain a water-soluble organic solvent such as methanol or ethanol or a nonionic surfactant. The concentration of the coagulant varies depending on the type of the water-soluble polyvalent metal salt, but is preferably 5 to 50% by weight, more preferably 10 to 30% by weight.

After pulling the mold out of the latex composition, it is usually heated to dry the deposits formed on the mold. The drying conditions may be appropriately selected.

When the latex composition contains a cross-linking agent, the obtained dip-molded layer is usually heat-treated and cross-linked. Before the heat treatment, water-soluble impurities (for example, excess emulsifier, coagulant, etc.) may be removed by immersing in water, preferably warm water at 30 to 70 ° C. for about 1 to 60 minutes. The operation for removing water-soluble impurities may be performed after the dip molding layer has been heat-treated, but it is preferably performed before the heat treatment because the water-soluble impurities can be removed more efficiently.

Crosslinking of the dip molded layer is usually carried out by subjecting the dip molded layer to a heat treatment at a temperature of 80 to 150 ° C., preferably for 10 to 130 minutes. As a heating method, a method of external heating by infrared rays or heated air or internal heating by high frequency can be adopted. Of these, external heating with heated air is preferable.

Then, by desorbing the dip molding layer from the dip molding mold, a dip molded body can be obtained as a film-shaped film molded body. As a desorption method, a method of manually peeling from the molding mold or a method of peeling by water pressure or compressed air pressure can be adopted. After desorption, heat treatment may be further performed at a temperature of 60 to 120 ° C. for 10 to 120 minutes.
In addition to the method of dip molding the latex composition of the present invention described above, the film-molded article of the present invention is a method capable of molding the latex composition of the present invention into a film (for example, a coating method, etc.). ), It may be obtained by any method.

Since the film molded product of the present invention including the dip molded product of the present invention is obtained by using the latex composition of the present invention described above, it suppresses the occurrence of the symptoms of delayed type allergy (Type IV) while suppressing the occurrence of the symptoms. It is also excellent in tear strength, and can be particularly preferably used as a glove, for example. When the film-molded body is a glove, in order to prevent adhesion between the film-molded bodies on the contact surface and to improve slippage during attachment / detachment, gloves are made of inorganic fine particles such as talc and calcium carbonate or organic fine particles such as starch particles. It may be sprayed on the surface, an elastomer layer containing fine particles may be formed on the surface of the glove, or the surface layer of the glove may be chlorinated.

In addition to the gloves, the film-molded article of the present invention, including the dip-molded article of the present invention, includes medical supplies such as baby bottle nipples, droppers, tubes, water pillows, balloon sack, catheters, and condoms; balloons, dolls, etc. , Balls and other toys; industrial products such as pressure molding bags and gas storage bags; can also be used for finger cots and the like.

Hereinafter, the present invention will be described in detail by way of examples, but the present invention is not limited to these examples. Unless otherwise specified, the following "parts" are based on weight. Various physical properties were measured as follows.

<Solid content concentration>
2 g of the sample was precisely weighed on an aluminum plate (weight: X1) (weight: X2), and this was dried in a hot air dryer at 105 ° C. for 2 hours. Then, after cooling in the desiccator, the weight of each aluminum dish was measured (weight: X3), and the solid content concentration was calculated according to the following formula.
Solid content concentration (% by weight) = (X3-X1) x 100 / X2

<Denaturation rate>
The number of carboxyl groups in the carboxy-modified polymer was determined by measuring the carboxy-modified polymer constituting the latex of the carboxy-modified polymer by ^{1 H-NMR.} Then, based on the determined number of carboxyl groups, the modification rate by the carboxyl group-containing compound was determined according to the following formula (i).
Degeneration rate (mol%) = (X / Y) x 100 ... (i)
In the above formula (i), X is the number of carboxyl groups in the carboxy-modified polymer, and Y is the total number of monomer units of the carboxy-modified polymer ((weight average molecular weight (Mw) of the carboxy-modified polymer)). / (The average molecular weight of the monomers (the average molecular weight of the monomer mixture) according to the content ratio of each monomer unit constituting the carboxy-modified polymer) is represented.

<Swell Index (SI)>
Potassium hydroxide was added to the latex of the carboxy-modified polymer to adjust the pH to 8.2. Then, a ceramic mold with a ground surface was prepared, washed, preheated in an oven at 70 ° C. for 60 minutes, and then 18% by weight of calcium nitrate and 0.05% by weight of polyoxy. A preheated ceramic mold was immersed in an aqueous coagulant containing ethylene lauryl ether (trade name "Emargen 109P", manufactured by Kao Corporation) for 5 seconds. Then, the ceramic mold was taken out from the coagulant aqueous solution, and the ceramic mold coated with the coagulant was dried in an oven at 70 ° C. for 20 minutes. Next, the ceramic mold coated with the coagulant was taken out from the oven, and the removed ceramic mold was placed in the latex of the carboxy-modified polymer adjusted to pH = 8.2 at 25 ° C. for 10 seconds. A film for measurement is taken out after being immersed under the conditions, and a ceramic mold coated with a latex of a carboxy-modified polymer is immersed in warm water at 60 ° C. for 2 minutes and then dried at room temperature for 6 hours. A ceramic mold coated with was obtained. Then, after spraying talc on this, the obtained film was peeled off from a ceramic molding die to obtain a dip film having a thickness of 0.2 mm. Then, a test film having a diameter of 25 mm was cut out from the obtained dip film, and the obtained test film was immersed in toluene at 25 ° C. for 1 hour, and the width of the test piece before and after immersion in toluene was measured. The swell index (SI) was calculated according to the following formula.
Swell index (SI) [%] = [{(width of film after immersion in toluene)-(width of film before immersion in toluene)} / (width of film before immersion in toluene)] × 100

<Toluene insoluble amount>
Potassium hydroxide was added to the latex of the carboxy-modified polymer to adjust the pH to 8.2. Then, the latex of the carboxy-modified polymer adjusted to pH = 8.2 was cast on a glass plate having a smooth surface, and then dried at 25 ° C. for 120 hours to obtain a cast film. Then, 0.2 to 0.3 g of a sample is measured from the obtained cast film (this weight is referred to as "W1"), placed in an 80 mesh wire mesh basket, and placed in toluene at 25 ° C. for 24 hours. Soaked. Then, the film remaining in the wire mesh cage was dried under reduced pressure at 100 ° C. for 24 hours to remove toluene. Then, the weight (this weight is referred to as "W2") of the film after removing toluene was measured, and the amount of toluene insoluble was measured from the measurement results of these weights according to the following formula.
Toluene insoluble amount [% by weight] = (W2 / W1) × 100

<Swelling rate with respect to THF>
A cast film was obtained by the same method as the above-mentioned "insoluble amount of toluene". The obtained cast film for measurement was immersed in tetrahydrofuran (THF) at 25 ° C. for 24 hours, the immersed film was pulled up, and the weight (weight A) was immediately measured. Then, the dipped film was dried at 100 ° C. for 24 hours, and the dry weight (weight B) of the film was measured. Then, based on the measurement result, the swelling rate with respect to THF was determined according to the following formula.
Swelling rate (times) with respect to THF = B / A

<Tetrahydrofuran insoluble amount>
A cast film was obtained by the same method as the above-mentioned "insoluble amount of toluene". A sample of 0.2 to 0.3 g is measured from the obtained cast film (this weight is referred to as “W3”), placed in an 80 mesh wire mesh basket, and immersed in toluene at 25 ° C. for 24 hours. I let you. Then, the film remaining in the wire mesh cage was dried under reduced pressure at 100 ° C. for 24 hours to remove THF. Then, the weight (this weight is referred to as "W4") of the film after removing toluene was measured, and the amount of THF insoluble was measured from the measurement results of these weights according to the following formula.
THF insoluble amount [% by weight] = (W4 / W3) × 100

<Patch test>
A test piece obtained by cutting a film-shaped dip molded product having a film thickness of about 0.2 mm into a size of 10 × 10 mm was attached to each of the arms of 10 subjects. Then, 48 hours later, by observing the pasted portion, the presence or absence of allergic symptoms of delayed type allergy (Type IV) was confirmed and evaluated according to the following criteria.
The patch test was performed on a dip molded product having an aging (pre-vulcanization) time of 24 hours.
A: All subjects had no allergic symptoms.
B: Allergic symptoms were observed in some subjects.

<Tear strength of dip molded product>
Based on ASTM D624-00, the dip molded product was left in a constant temperature and humidity chamber at 23 ° C. and 50% relative humidity for 24 hours or more, and then punched and torn with a dumbbell (trade name "Die C", manufactured by Dumbbell). A test piece for strength measurement was prepared. The test piece was pulled by a Tencilon universal testing machine (trade name "RTG-1210", manufactured by A & D Co., Ltd.) at a tensile speed of 500 mm / min, and the tear strength (unit: N / mm) was measured. The measurement was performed on 5 test pieces, and the median value among the measured values of the tear strength of the 5 test pieces (that is, the test piece showing the third largest value among the 5 test pieces). (Value of tear strength) was adopted as the value of tear strength.
The tear strength of the dip molded product was measured for a dip molded product having an aging (pre-vulcanization) time of 24 hours and a dip molded product having an aging (pre-vulcanization) time of 48 hours.

<500% tensile stress of dip molded product>
Based on ASTM D412, the dip molded product was punched with a dumbbell (trade name "Super Dumbbell (model: SDKM-100C)", manufactured by Dumbbell Co., Ltd.) to prepare a test piece. The test piece was measured for tensile stress (unit: MPa) when the tensile speed was 500 mm / min and the elongation rate was 500% with a Tencilon universal testing machine (trade name "RTG-1210", manufactured by A & D Co., Ltd.). The smaller the tensile stress at 500%, the more flexible the dip molded product becomes, which is preferable.
The 500% tensile stress of the dip molded product was measured for the dip molded product having an aging (pre-vulcanization) time of 24 hours and the dip molded product having an aging (pre-vulcanization) time of 48 hours.

<Example 1>
(Manufacture of Latex of Carboxy-modified Synthetic Polyisoprene (A-1))
Synthetic polyisoprene having a weight average molecular weight of 1,300,000 (trade name "NIPOL IR2200L", manufactured by Nippon Zeon Co., Ltd., homopolymer of isoprene, cis bond unit amount 98% by weight) is mixed with cyclohexane and stirred. The temperature was raised to 60 ° C. to dissolve the mixture, and a cyclohexane solution (a) of synthetic polyisoprene having a viscosity of 12,000 mPa · s measured by a B-type viscosity meter was prepared (solid content concentration: 8% by weight).

On the other hand, 20 parts of sodium rosinate was added to water, the temperature was raised to 60 ° C. and dissolved to prepare an aqueous anionic surfactant solution (b) having a concentration of 1.5% by weight.

Next, the cyclohexane solution (a) and the anionic surfactant aqueous solution (b) are mixed in a mixer (trade name "Multiline Mixer MS26-MMR-5" so as to have a weight ratio of 1: 1.5. .5L ”, manufactured by Satake Kagaku Kikai Kogyo Co., Ltd.), and then mixed and emulsified using an emulsifying device (trade name“ Milder MDN310 ”, manufactured by Pacific Kiko Co., Ltd.) at a rotation speed of 4100 rpm to emulsify. Liquid (c) was obtained. At that time, the total feed flow velocity of the cyclohexane solution (a) and the anionic surfactant aqueous solution (b) was 2,000 kg / hr, the temperature was 60 ° C., and the back pressure (gauge pressure) was 0.5 MPa.

Next, the emulsion (c) was heated to 80 ° C. under a reduced pressure of −0.01 to −0.09 MPa (gauge pressure), cyclohexane was distilled off, and an aqueous dispersion (d) of synthetic polyisoprene was added. Obtained. At that time, an antifoaming agent (trade name "SM5515", manufactured by Toray Dow Corning Co., Ltd.) was continuously added while spraying so as to have an amount of 300 ppm by weight with respect to the synthetic polyisoprene in the emulsion (c). .. When distilling off cyclohexane, the emulsion (c) is adjusted to be 70% by volume or less of the volume of the tank, and a three-stage inclined paddle blade is used as the stirring blade, and the mixture is slowly stirred at 60 rpm. Was carried out.

Then, after the distillation of cyclohexane is completed, the obtained aqueous dispersion (d) of synthetic polyisoprene is used in a continuous centrifuge (trade name "SRG510", manufactured by Alfa Laval) from 4,000 to Centrifugation at 5,000 G gave a latex (e) of synthetic polyisoprene as a light liquid. The conditions for centrifugation are as follows: the solid content concentration of the aqueous dispersion (d) before centrifugation is 10% by weight, the flow velocity during continuous centrifugation is 1300 kg / hr, and the back pressure (gauge pressure) of the centrifuge is 1. It was set to 5 MPa. The obtained synthetic polyisoprene latex (e) had a solid content concentration of 60% by weight.

Next, 130 parts of distilled water was added to 100 parts of the synthetic polyisoprene in the latex (e) of the obtained synthetic polyisoprene to dilute it. Then, in the latex (e) of synthetic polyisoprene, a sodium salt of β-naphthalene sulfonic acid formalin condensate as a dispersant for 100 parts of synthetic polyisoprene (trade name "Demor T-45", manufactured by Kao Co., Ltd.). 0.8 part was diluted with 4 parts of distilled water to 100 parts of synthetic polyisoprene and added over 5 minutes. Next, the latex (e) of synthetic polyisoprene to which a dispersant was added was charged into a reaction vessel equipped with a stirrer substituted with nitrogen, and the temperature was heated to 30 ° C. while stirring. Further, using another container, 3 parts of methacrylic acid as a carboxyl group-containing compound and 16 parts of distilled water were mixed to prepare a diluted methacrylic acid solution. This diluted methacrylic acid solution was added to the reaction vessel kept at a temperature of 20 ° C. over 30 minutes.

Furthermore, using another container, 7 parts of distilled water, 0.32 parts of sodium formaldehyde sulfoxylate (trade name "SFS", manufactured by Mitsubishi Gas Chemical Company), ferrous sulfate (trade name "Frost Fe", Chubu Killest) A solution (f) consisting of 0.01 parts was prepared. After transferring this solution (f) into a reaction vessel, 0.5 part of 1,1,3,3-tetramethylbutylhydroperoxide (trade name "Perocta H", manufactured by Nippon Oil & Fats Co., Ltd.) is added and 20 parts are added. After reacting at ° C. for 1 hour, the mixture was concentrated in a centrifuge to obtain a latex of carboxy-modified synthetic polyisoprene (A-1). When the modification rate of the obtained carboxy-modified synthetic polyisoprene (A-1) latex was measured according to the above method, the modification rate was 0.5 mol%.

Then, using the obtained latex of carboxy-modified synthetic polyisoprene (A-1), the swell index (SI), the amount of toluene insoluble, the swelling rate with respect to THF, and the amount of THF insoluble were measured. The results are shown in Table 1.

(Preparation of xanthate compound dispersion)
Zinc diisopropylxanthogenate as a xanthogen compound (trade name "Noxeller ZIX", manufactured by Ouchi Shinko Kagaku Kogyo Co., Ltd., volume average particle diameter: 14 μm, 95% volume cumulative diameter (D95): 55 μm), 2 parts, nonionic surfactant 0.15 parts of polyoxyethylene distyrene phenyl ether (trade name "Emargen A-60", manufactured by Kao Co., Ltd.) and 4.5 parts of water as an agent, ball mill (trade name "porcelain ball mill", Nikko) A xanthogen compound dispersion was obtained by crushing the mixture by mixing with (manufactured by Kagaku Co., Ltd.). As the mixing conditions by the ball mill, ceramic porcelain balls of φ10 mm to φ35 mm (a mixture of φ10 mm, φ15 mm, φ20 mm, φ25 mm, φ30 mm and φ35 mm ceramic porcelain balls) were used, and the mixing conditions were set at 50 rpm for 72 hours. .. In addition, the volume average particle size and 95% volume cumulative diameter (D95) of zinc diisopropylxanthogenate in the obtained xanthogen compound dispersion were measured by a laser diffraction scattering type particle size distribution meter (trade name "SALD-2300", Shimadzu Co., Ltd.). As a result of measurement using (manufactured by Mfg. Co., Ltd.), the volume average particle size of zinc diisopropylxanthogenate was 3 μm, and the 95% volume cumulative diameter (D95) was 16 μm.

(Preparation of latex composition)
First, a styrene-maleic acid mono-sec-butyl ester-maleic acid monomethyl ester polymer (trade name "Scripest550", manufactured by Hercules) is 100% neutralized with sodium hydroxide to neutralize the carboxyl groups in the polymer. An aqueous sodium salt solution (concentration: 10% by weight) was prepared. Then, this aqueous sodium salt solution was added to the latex of the carboxy-modified synthetic polyisoprene (A-1) obtained above with respect to 100 parts of the carboxy-modified synthetic polyisoprene (A-1) in terms of solid content of 0.8. Addition was made in portions to obtain a mixture.

Then, while stirring the obtained mixture, 6.65 parts of the xanthogen compound dispersion prepared above (in terms of zinc diisopropylxanthogenate) was added to 100 parts of the carboxy-modified synthetic polyisoprene (A-1) in the mixture. 2 parts) was added.

Next, in terms of solid content, each compounding agent has 1.5 parts of zinc oxide as an activator, 1.0 part of sulfur, and 2 parts of an antiaging agent (trade name "Wingstay L", manufactured by Goodyear Tire and Rubber Co., Ltd.). The aqueous dispersion of the above was added to obtain a latex composition. Then, the obtained latex composition was divided into two, one of which was aged for 24 hours (pre-vulcanization) in a constant temperature water bath adjusted to 25 ° C., and the other was a constant temperature water tank adjusted to 25 ° C. By carrying out aging (pre-vulcanization) for 48 hours, a 24-hour aged latex composition and a 48-hour aged latex composition were obtained.

(Manufacturing of dip molded body)
After washing a commercially available ceramic hand mold (manufactured by Shinko Co., Ltd.) and preheating it in an oven at 70 ° C., 18% by weight of calcium nitrate and 0.05% by weight of polyoxyethylene lauryl ether (trade name "Emargen 109P") , Manufactured by Kao Corporation) was immersed in the coagulant aqueous solution for 5 seconds and taken out from the coagulant aqueous solution. Next, the hand mold was dried in an oven at 70 ° C. for 30 minutes or more to attach a coagulant to the hand mold, and the hand mold was covered with the coagulant.

Then, the hand mold coated with the coagulant was taken out from the oven and immersed in the 24-hour aged latex composition obtained above for 10 seconds. Next, the hand mold was air-dried at room temperature for 10 minutes and then immersed in warm water at 60 ° C. for 5 minutes to elute water-soluble impurities to form a dip molding layer on the hand mold. Then, the dip molded layer formed in the hand mold is vulcanized by heating it in an oven at a temperature of 130 ° C. for 30 minutes, cooled to room temperature, sprayed with talc, and then peeled off from the hand mold. , A glove-shaped dip molded product (aged for 24 hours) was obtained. Further, a glove-shaped dip molded article (48-hour aged product) was obtained in the same manner as described above except that the 48-hour aged latex composition was used instead of the 24-hour aged latex composition. Then, using the obtained dip molded products (24-hour aged product and 48-hour aged product), the tear strength and 500% tensile stress were measured and a patch test was performed according to the above method. The results are shown in Table 1.

In Example 1, the tear strength of the dip molded product (aged for 24 hours) was measured for five test pieces according to the above method, and as a result, the measured value of the tear strength was the median value. The ratio of the test pieces in the range of ± 10% is 70% or more (that is, the measured value of the tear strength among the five test pieces is in the range of ± 10% with respect to the median value. The number of test pieces was 4 or more), and the stability of tear strength was excellent.

<Example 2>
(Manufacture of Latex of Carboxy-modified Synthetic Polyisoprene (A-2))
In the same manner as in Example 1, the amount of sodium formaldehyde sulfoxylate used was changed from 0.32 part to 0.30 part when the modification reaction with methacrylic acid was performed after obtaining the latex (e) of synthetic polyisoprene. The reaction temperature (modification reaction temperature) when the modification reaction with methacrylic acid is changed is changed from 20 ° C. to 30 ° C., and the modification reaction is performed under the conditions of 30 ° C. for 1 hour, and then after the modification reaction. A latex of carboxy-modified synthetic polyisoprene (A-2) was obtained in the same manner as in Example 1 except that the latex was further post-heated at 40 ° C. for 1 hour. When the modification rate of the obtained carboxy-modified synthetic polyisoprene (A-2) latex was measured according to the above method, the modification rate was 0.5 mol%.
Then, using the obtained latex of carboxy-modified synthetic polyisoprene (A-2), the swell index (SI), the amount of toluene insoluble, the swelling rate with respect to THF, and the amount of THF insoluble were measured. The results are shown in Table 1.

(Preparation of latex composition, production of dip molded product)
A 24-hour aged latex composition, a 48-hour aged latex composition, and a dip in the same manner as in Example 1 except that the latex of the carboxy-modified synthetic polyisoprene (A-2) obtained above was used. Molds (24-hour aged product and 48-hour aged product) were obtained and evaluated in the same manner. The results are shown in Table 1.
In Example 2, the tear strength of the dip molded product (aged for 24 hours) was measured for five test pieces according to the above method, and as a result, the measured value of the tear strength was the median value. The proportion of test pieces in the range of ± 10% is less than 70% (that is, the measured tear strength of the five test pieces is in the range of ± 10% of the median. The number of test pieces was 3 or less).

<Example 3>
(Manufacture of Latex of Carboxy-modified Synthetic Polyisoprene (A-3))
In the same manner as in Example 1, the amount of sodium formaldehyde sulfoxylate used was changed from 0.32 part to 0.25 part when the modification reaction with methacrylic acid was carried out after obtaining the latex (e) of synthetic polyisoprene. The carboxy-modified synthetic polyisoprene (A-3) was prepared in the same manner as in Example 1 except that the reaction temperature (modification reaction temperature) when performing the modification reaction with methacrylic acid was changed from 20 ° C. to 30 ° C. Obtained latex. When the modification rate of the obtained carboxy-modified synthetic polyisoprene (A-3) latex was measured according to the above method, the modification rate was 0.5 mol%.
Then, using the obtained latex of carboxy-modified synthetic polyisoprene (A-3), the swell index (SI), the amount of toluene insoluble, the swelling rate with respect to THF, and the amount of THF insoluble were measured. The results are shown in Table 1.

(Preparation of latex composition, production of dip molded product)
A 24-hour aged latex composition, a 48-hour aged latex composition, and a dip in the same manner as in Example 1 except that the latex of the carboxy-modified synthetic polyisoprene (A-3) obtained above was used. Molds (24-hour aged product and 48-hour aged product) were obtained and evaluated in the same manner. The results are shown in Table 1.
In Example 3, the tear strength of the dip molded product (aged for 24 hours) was measured for five test pieces according to the above method, and as a result, the measured value of the tear strength was the median value. The ratio of the test pieces in the range of ± 10% is 70% or more (that is, the measured value of the tear strength among the five test pieces is in the range of ± 10% with respect to the median value. The number of test pieces was 4 or more), and the stability of tear strength was excellent.

<Example 4>
(Manufacture of Latex of Carboxy-modified Synthetic Polyisoprene (A-4))
In the same manner as in Example 1, the amount of sodium formaldehyde sulfoxylate used was changed from 0.32 part to 0.20 part when the modification reaction with methacrylic acid was performed after obtaining the latex (e) of synthetic polyisoprene. The reaction temperature (modification reaction temperature) when the modification reaction with methacrylic acid is changed is changed from 20 ° C. to 30 ° C., and the modification reaction is performed under the conditions of 30 ° C. for 1 hour, and then after the modification reaction. A latex of carboxy-modified synthetic polyisoprene (A-4) was obtained in the same manner as in Example 1 except that the latex was further post-heated at 30 ° C. for 1 hour. When the modification rate of the obtained carboxy-modified synthetic polyisoprene (A-4) latex was measured according to the above method, the modification rate was 0.5 mol%.
Then, using the obtained latex of carboxy-modified synthetic polyisoprene (A-4), the swell index (SI), the amount of toluene insoluble, the swelling rate with respect to THF, and the amount of THF insoluble were measured. The results are shown in Table 1.

(Preparation of latex composition, production of dip molded product)
A 24-hour aged latex composition, a 48-hour aged latex composition, and a dip in the same manner as in Example 1 except that the latex of the carboxy-modified synthetic polyisoprene (A-4) obtained above was used. Molds (24-hour aged product and 48-hour aged product) were obtained and evaluated in the same manner. The results are shown in Table 1.
In Example 4, the tear strength of the dip molded product (aged for 24 hours) was measured for five test pieces according to the above method, and as a result, the measured value of the tear strength was the median value. The proportion of test pieces in the range of ± 10% is less than 70% (that is, the measured tear strength of the five test pieces is in the range of ± 10% of the median. The number of test pieces was 3 or less).

<Example 5>
(Manufacture of Latex of Carboxy-modified Synthetic Polyisoprene (A-5))
In the same manner as in Example 1, the amount of sodium formaldehyde sulfoxylate used was changed from 0.32 part to 0.40 part when the modification reaction with methacrylic acid was carried out after obtaining the latex (e) of synthetic polyisoprene. A latex of carboxy-modified synthetic polyisoprene (A-5) was obtained in the same manner as in Example 1 except for the modification. When the modification rate of the obtained carboxy-modified synthetic polyisoprene (A-5) latex was measured according to the above method, the modification rate was 0.5 mol%.
Then, using the obtained latex of carboxy-modified synthetic polyisoprene (A-5), the swell index (SI), the amount of toluene insoluble, the swelling rate with respect to THF, and the amount of THF insoluble were measured. The results are shown in Table 1.

(Preparation of latex composition, production of dip molded product)
A 24-hour aged latex composition, a 48-hour aged latex composition, and a dip in the same manner as in Example 1 except that the latex of the carboxy-modified synthetic polyisoprene (A-5) obtained above was used. Molds (24-hour aged product and 48-hour aged product) were obtained and evaluated in the same manner. The results are shown in Table 1.
In Example 5, the tear strength of the dip molded product (aged for 24 hours) was measured for five test pieces according to the above method, and as a result, the measured value of the tear strength was the median value. The ratio of the test pieces in the range of ± 10% is 70% or more (that is, the measured value of the tear strength among the five test pieces is in the range of ± 10% with respect to the median value. The number of test pieces was 4 or more), and the stability of tear strength was excellent.

<Comparative example 1>
(Manufacture of Latex of Carboxy-modified Synthetic Polyisoprene (A-6))
In the same manner as in Example 1, the amount of sodium formaldehyde sulfoxylate used was changed from 0.32 part to 0.15 part when the modification reaction with methacrylic acid was performed after obtaining the latex (e) of synthetic polyisoprene. The reaction temperature (modification reaction temperature) when the modification reaction with methacrylic acid is changed is changed from 20 ° C. to 30 ° C., and the modification reaction is performed under the conditions of 30 ° C. for 1 hour, and then after the modification reaction. A latex of carboxy-modified synthetic polyisoprene (A-6) was obtained in the same manner as in Example 1 except that the latex was further post-heated at 30 ° C. for 1 hour. When the modification rate of the obtained carboxy-modified synthetic polyisoprene (A-6) latex was measured according to the above method, the modification rate was 0.5 mol%.
Then, using the obtained latex of carboxy-modified synthetic polyisoprene (A-6), the swell index (SI), the amount of toluene insoluble, the swelling rate with respect to THF, and the amount of THF insoluble were measured. The results are shown in Table 1.

(Preparation of latex composition, production of dip molded product)
A 24-hour aged latex composition, a 48-hour aged latex composition, and a dip in the same manner as in Example 1 except that the latex of the carboxy-modified synthetic polyisoprene (A-6) obtained above was used. Molds (24-hour aged product and 48-hour aged product) were obtained and evaluated in the same manner. The results are shown in Table 1.

<Comparative example 2>
(Manufacture of Latex of Carboxy-modified Synthetic Polyisoprene (A-7))
In the same manner as in Example 1, the reaction temperature (denaturation reaction temperature) when performing the modification reaction with methacrylic acid after obtaining the latex (e) of synthetic polyisoprene was changed from 20 ° C. to 40 ° C. A latex of carboxy-modified synthetic polyisoprene (A-7) was obtained in the same manner as in Example 1. When the modification rate of the obtained carboxy-modified synthetic polyisoprene (A-7) latex was measured according to the above method, the modification rate was 0.5 mol%.
Then, using the obtained latex of carboxy-modified synthetic polyisoprene (A-7), the swell index (SI), the amount of toluene insoluble, the swelling rate with respect to THF, and the amount of THF insoluble were measured. The results are shown in Table 1.

(Preparation of latex composition, production of dip molded product)
A 24-hour aged latex composition, a 48-hour aged latex composition, and a dip in the same manner as in Example 1 except that the latex of the carboxy-modified synthetic polyisoprene (A-7) obtained above was used. Molds (24-hour aged product and 48-hour aged product) were obtained and evaluated in the same manner. The results are shown in Table 1.

As shown in Table 1, a latex having a swell index (SI) in the range of 120 to 190% is used as the latex of the carboxy-modified polymer, and a latex composition obtained by blending the xanthogen compound with the latex is used. For example, it provides a dip molded product in which the occurrence of delayed type allergy (Type IV) symptoms is effectively suppressed, and the obtained dip molded product has sufficient tear strength and further has a flexible texture. In particular, even if the aging is shortened to 24 hours, sufficient tear strength can be achieved, so that the time required for aging (pre-vulcanization) can be shortened and the productivity is excellent. Can be confirmed (Examples 1 to 5).

On the other hand, when a latex having a swell index (SI) of less than 120% or a swell index (SI) of more than 190% is used as the latex of the carboxy-modified polymer, the obtained dip molded product is torn after a aging time of 24 hours. In order for the strength to be low and the tear strength to be sufficient, it was necessary to increase the aging time to 48 hours (Comparative Examples 1 and 2).

Claims

A latex composition containing a latex of a carboxy-modified polymer and a xanthate compound.
A latex composition in which the latex swell index (SI) of the carboxy-modified polymer is 120 to 190%.
A claim that the modification rate of the carboxy-modified polymer by a carboxyl group is 0.01 to 10 mol% in a molar ratio calculated by (number of carboxyl groups / total number of monomer units of the carboxy-modified polymer) × 100. Item 2. The latex composition according to Item 1.
Claim 1 is the carboxy-modified polymer obtained by modifying synthetic polyisoprene, styrene-isoprene-styrene block copolymer, or natural rubber from which proteins have been removed with a monomer having a carboxyl group. Or the latex composition according to 2.
The latex composition according to any one of claims 1 to 3, further containing a sulfur-based vulcanizing agent.
The latex composition according to any one of claims 1 to 4, wherein the toluene-insoluble content of the latex of the carboxy-modified polymer is 55 to 85% by weight.
The latex according to any one of claims 1 to 5, wherein the xanthogen compound has a volume average particle diameter in the range of 0.001 to 9 μm and a 95% volume cumulative diameter (D95) in the range of 0.1 to 43 μm. Composition.
A film molded product made of the latex composition according to any one of claims 1 to 6.
A dip molded product obtained by dip molding the latex composition according to any one of claims 1 to 6.