JP7400187B2 - Dip molded body and its manufacturing method - Google Patents

Description

The present invention relates to a dip-molded article obtained by dip-molding a latex composition and a method for producing the same, and more particularly to a dip-molded article having high tensile strength, large elongation at break, a flexible texture, and a high stress retention rate. It relates to its manufacturing method.

Conventionally, latex compositions containing natural rubber latex, typified by natural rubber latex, have been used to form dip-molded bodies. As such dip-molded articles, dip-molded articles used in contact with the human body, such as nipples, balloons, gloves, balloons, sacks, etc., are known. However, since natural rubber latex contains proteins that cause allergic symptoms in the human body, it often has problems when used as dip-molded products, especially gloves, that come into direct contact with biological mucous membranes or organs. Therefore, consideration is being given to using synthetic rubber latex.

For example, Patent Document 1 describes 65 to 84.5 parts by weight of a conjugated diene monomer, 15 to 25 parts by weight of an ethylenically unsaturated nitrile monomer, and 0.5 to 10 parts by weight of an ethylenically unsaturated acid monomer. and a latex obtained by copolymerizing 100 parts by weight of a monomer mixture consisting of 0 to 19.5 parts by weight of other ethylenically unsaturated monomers copolymerizable with these, and blending sulfur with such a latex. A dip-molded product obtained by dip-molding a latex composition comprising: Although the dip-molded article described in Patent Document 1 has an excellent texture and sufficient tensile strength, its elongation at break and durability were not necessarily sufficient.

Further, Patent Document 2 discloses a rubber latex composition containing 3 to 30 parts by weight of phenyl alkylsulfonate based on 100 parts by weight of rubber, and gloves made of such a latex composition. Although the glove described in Patent Document 2 has excellent flexibility, it has poor texture and does not necessarily have a sufficient stress retention rate.

Japanese Patent Application Publication No. 2003-165814 Japanese Patent Application Publication No. 2002-309043

An object of the present invention is to provide a dip-molded article having high tensile strength, large elongation at break, flexible texture, and high stress retention, and a method for producing such a dip-molded article.

As a result of intensive research to solve the above problems, the present inventors have achieved the above object by controlling the content of calcium and the content of trivalent or higher valent metals contained in the dip-formed product within a predetermined range. We have discovered what can be achieved and have completed the present invention.

That is, according to the present invention, there is provided a dip-molded article obtained by dip-molding a latex composition containing a carboxyl group-containing rubber latex, wherein the content of calcium in the dip-molded article is 500 μg/g or less. , a dip-molded body having a content of trivalent or higher valent metal of 500 to 10,000 μg/g is provided.

In the dip-molded article of the present invention, the carboxyl group-containing rubber is preferably a carboxyl group-containing nitrile rubber.
In the dip-molded article of the present invention, it is preferable that the latex composition further contains a metal compound containing a trivalent or higher valent metal.
In the dip-molded article of the present invention, it is preferable that the latex composition further contains a heat-sensitive coagulant.

Further, according to the present invention, in the method for producing the above-mentioned dip-molded article, a heated dip-molding mold is brought into contact with a latex composition containing the latex of the carboxyl group-containing rubber. There is provided a method for producing a dip-molded article, which includes a step of forming a dip-molding layer on the surface of the dip-molding mold by thermally solidifying a product.

According to the present invention, it is possible to provide a dip-molded article having high tensile strength, large elongation at break, flexible texture, and high stress retention, and a method for producing such a dip-molded article.

The dip-molded article of the present invention is obtained by dip-molding a latex composition of carboxyl group-containing rubber, and the dip-molded article has a calcium content of 500 μg/g or less and a trivalent or higher metal content. It is 500 to 10,000 μg/g.

Latex Composition First, the latex composition used in the present invention will be explained.
The latex composition used in the present invention contains carboxyl group-containing rubber latex. The latex of the carboxyl group-containing rubber (hereinafter referred to as "carboxyl group-containing rubber (A)") may be any latex of rubber containing a carboxyl group, and is not particularly limited, but may include a conjugated diene monomer and ethylene. It is preferably a latex of carboxyl group-containing conjugated diene rubber obtained by copolymerizing unsaturated carboxylic acid monomers, such as carboxyl group-containing nitrile rubber (a1) and carboxyl group-containing styrene-butadiene rubber (a2). It is more preferable to use a latex of at least one type of rubber selected from the group consisting of conjugated diene rubber containing a carboxyl group (a3), and a latex of a nitrile rubber containing a carboxyl group (a1) is particularly preferable.

The latex of the carboxyl group-containing nitrile rubber (a1) is a copolymer obtained by copolymerizing an ethylenically unsaturated nitrile monomer in addition to a conjugated diene monomer and an ethylenically unsaturated carboxylic acid monomer. The latex may be a latex of a copolymer obtained by copolymerizing other ethylenically unsaturated monomers that are copolymerizable with these and used as needed.

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. It will be done. Among these, 1,3-butadiene is preferred. These conjugated diene monomers can be used alone or in combination of two or more. The content of conjugated diene monomer units formed by conjugated diene monomers in the carboxyl group-containing nitrile rubber (a1) is preferably 56 to 78% by weight, more preferably 56 to 73% by weight, More preferably 56 to 68% by weight, particularly preferably 56 to 67% by weight. By setting the content of the conjugated diene monomer unit within the above range, the dip molded product formed using the resulting latex composition has sufficient tensile strength, has excellent texture, and has increased elongation. It can be assumed that

The ethylenically unsaturated carboxylic acid monomer is not particularly limited as long as it is an ethylenically unsaturated monomer containing a carboxyl group, but examples include ethylenically unsaturated monocarboxylic acid monomers such as acrylic acid and methacrylic acid. Ethylenically unsaturated polycarboxylic acid monomers such as itaconic acid, maleic acid and fumaric acid; Ethylenically unsaturated polycarboxylic acid anhydrides such as maleic anhydride and citraconic anhydride; Monobutyl fumarate and maleic acid Examples include ethylenically unsaturated polycarboxylic acid partial ester monomers such as monobutyl and mono-2-hydroxypropyl maleate. Among these, ethylenically unsaturated monocarboxylic acids are preferred, and methacrylic acid is particularly preferred. These ethylenically unsaturated carboxylic acid monomers can also be used as alkali metal salts or ammonium salts. Further, the ethylenically unsaturated carboxylic acid monomers can be used alone or in combination of two or more. The content of ethylenically unsaturated carboxylic acid monomer units formed by ethylenically unsaturated carboxylic acid monomers in the carboxyl group-containing nitrile rubber (a1) is preferably 2 to 6.5% by weight. , more preferably 2 to 6% by weight, still more preferably 2 to 5% by weight, even more preferably 2 to 4.5% by weight, particularly preferably 2.5 to 4.5% by weight. By setting the content of the ethylenically unsaturated carboxylic acid monomer unit within the above range, the dip-molded product formed using the resulting latex composition has sufficient tensile strength and has excellent texture. The elongation can be further increased.

The ethylenically unsaturated nitrile monomer is not particularly limited as long as it is an ethylenically unsaturated monomer containing a nitrile group, but examples include acrylonitrile, methacrylonitrile, fumaronitrile, α-chloroacrylonitrile, α-cyanoethyl acrylonitrile. Examples include. Among them, acrylonitrile and methacrylonitrile are preferred, and acrylonitrile is more preferred. These ethylenically unsaturated nitrile monomers can be used alone or in combination of two or more. The content of ethylenically unsaturated nitrile monomer units formed by ethylenically unsaturated nitrile monomers in the carboxyl group-containing nitrile rubber (a1) is preferably 20 to 40% by weight, more preferably The amount is 25 to 40% by weight, more preferably 30 to 40% by weight, particularly preferably 30.5 to 40% by weight. By setting the content of the ethylenically unsaturated nitrile monomer unit within the above range, the dip molded product formed using the resulting latex composition has sufficient tensile strength, excellent texture, and elongation. can be further increased.

Other ethylenically unsaturated monomers that can be copolymerized with the conjugated diene monomer, ethylenically unsaturated carboxylic acid monomer, and ethylenically unsaturated nitrile monomer include, for example, styrene, alkylstyrene, and vinylnaphthalene. vinyl aromatic monomers such as; fluoroalkyl vinyl ethers such as fluoroethyl vinyl ether; (meth)acrylamide, N-methylol (meth)acrylamide, N,N-dimethylol (meth)acrylamide, N-methoxymethyl (meth)acrylamide, Ethylenically unsaturated amide monomers such as N-propoxymethyl (meth)acrylamide; methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, (meth)trifluoroethyl acrylate, tetrafluoropropyl (meth)acrylate, dibutyl maleate, dibutyl fumarate, diethyl maleate, methoxymethyl (meth)acrylate, ethoxyethyl (meth)acrylate, (meth)acrylic Methoxyethoxyethyl acid, cyanomethyl (meth)acrylate, 2-cyanoethyl (meth)acrylate, 1-cyanopropyl (meth)acrylate, 2-ethyl-6-cyanohexyl (meth)acrylate, (meth)acrylate ) Ethylenically unsaturated carboxylic acid ester monomers such as 3-cyanopropyl acrylate, hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, glycidyl (meth)acrylate, dimethylaminoethyl (meth)acrylate, etc. crosslinkable monomers such as divinylbenzene, polyethylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, and pentaerythritol (meth)acrylate; and the like. These ethylenically unsaturated monomers can be used alone or in combination of two or more.

The content of other monomer units formed by other ethylenically unsaturated monomers in the carboxyl group-containing nitrile rubber (a1) is preferably 10% by weight or less, more preferably 5% by weight. The content is preferably 3% by weight or less.

The latex of the carboxyl group-containing nitrile rubber (a1) can be obtained by copolymerizing a monomer mixture containing the above-mentioned monomers, but copolymerization by emulsion polymerization is preferred. As the emulsion polymerization method, conventionally known methods can be employed.

When emulsion polymerizing a monomer mixture containing the above-mentioned monomers, commonly used polymerization auxiliary materials such as an emulsifier, a polymerization initiator, and a molecular weight regulator 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 divided addition method, or a continuous addition method may be used.

Examples of emulsifiers include, but are not limited to, nonionic emulsifiers such as polyoxyethylene alkyl ether, polyoxyethylene alkylphenol ether, polyoxyethylene alkyl ester, and polyoxyethylene sorbitan alkyl ester; potassium dodecylbenzene sulfonate, dodecylbenzene. Anionic emulsifiers such as alkylbenzene sulfonates such as sodium sulfonate, higher alcohol sulfate ester salts, alkyl sulfosuccinates; cationic emulsifiers such as alkyltrimethylammonium chloride, dialkylammonium chloride, benzyl ammonium chloride; α,β-unsaturated Examples include copolymerizable emulsifiers such as sulfoesters of carboxylic acids, sulfate esters of α,β-unsaturated carboxylic acids, and sulfoalkylaryl ethers. Among these, anionic emulsifiers are preferred, alkylbenzenesulfonates are more preferred, and potassium dodecylbenzenesulfonate and sodium dodecylbenzenesulfonate are particularly preferred. These emulsifiers can be used alone or in combination of two or more. The amount of emulsifier used is preferably 0.1 to 10 parts by weight based on 100 parts by weight of the monomer mixture.

Examples of the polymerization initiator include, but are not limited to, inorganic peroxides such as sodium persulfate, potassium persulfate, ammonium persulfate, potassium perphosphate, and hydrogen peroxide; diisopropylbenzene hydroperoxide, cumene hydroperoxide, t-Butyl hydroperoxide, 1,1,3,3-tetramethylbutyl hydroperoxide, 2,5-dimethylhexane-2,5-dihydroperoxide, di-t-butyl peroxide, di-α- Organic peroxides such as cumyl peroxide, acetyl peroxide, isobutyryl peroxide, and benzoyl peroxide; azo compounds such as azobisisobutyronitrile, azobis-2,4-dimethylvaleronitrile, and methyl azobisisobutyrate; 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.

Further, a peroxide initiator can be used as a redox polymerization initiator in combination with a reducing agent. Examples of this reducing agent include, but are not limited to, compounds containing metal ions in a reduced state such as ferrous sulfate and cuprous naphthenate; sulfonic acid compounds such as sodium methanesulfonate; amine compounds such as dimethylaniline. ; etc. These reducing agents can be used alone or in combination of two or more. The amount of reducing agent used is preferably 3 to 1000 parts by weight per 100 parts by weight of peroxide.

The water used during emulsion polymerization is not particularly limited, but tap water or deionized water can be used, especially from the viewpoint of reducing the calcium content in the resulting dip molded product. It is more preferable to use deionized water.

The amount of water used in 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 the total monomers used.

Methods for adding monomers include, for example, adding the monomers used in the reaction vessel all at once, adding them continuously or intermittently as the polymerization progresses, and adding a portion of the monomers. Examples include a method in which the reaction is carried out to a specific conversion rate, and then the remaining monomers are added continuously or intermittently for polymerization, and any method may be employed. 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 the various monomers used in advance, or may be added to the reaction vessel separately.

Furthermore, polymerization auxiliary materials such as a chelating agent, a dispersing agent, a pH adjuster, an oxygen scavenger, and a particle size adjuster can be used as necessary, and these are not particularly limited in type or amount used.

The polymerization temperature during 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.

The monomer mixture is emulsion polymerized as described above, and when a predetermined polymerization conversion rate is reached, the polymerization reaction is stopped by cooling the polymerization system or adding a polymerization terminator. The polymerization conversion rate when stopping the polymerization reaction is preferably 90% by weight or more, more preferably 93% by weight or more.

Examples of polymerization terminators include, but are not limited to, hydroxylamine, hydroxyamine sulfate, diethylhydroxylamine, hydroxyamine sulfonic acid and its alkali metal salts, sodium dimethyldithiocarbamate, hydroquinone derivatives, catechol derivatives, and hydroxydimethyl. Examples include aromatic hydroxydithiocarboxylic acids such as benzenethiocarboxylic acid, hydroxydiethylbenzenedithiocarboxylic acid, and hydroxydibutylbenzenedithiocarboxylic acid, and their alkali metal salts. The amount of polymerization terminator used is preferably 0.05 to 2 parts by weight per 100 parts by weight of the monomer mixture.

After stopping the polymerization reaction, the latex of the carboxyl group-containing nitrile rubber (a1) can be obtained by removing unreacted monomers and adjusting the solid content concentration and pH, if desired.

Moreover, an anti-aging agent, a preservative, an antibacterial agent, a dispersant, etc. may be appropriately added to the latex of the carboxyl group-containing nitrile rubber (a1), if necessary.

The number average particle diameter of the latex of the carboxyl group-containing nitrile rubber (a1) is preferably 60 to 300 nm, more preferably 80 to 150 nm. The particle size can be adjusted to a desired value by adjusting the amounts of emulsifier and polymerization initiator used.

In addition, the latex of carboxyl group-containing styrene-butadiene rubber (a2) is obtained by copolymerizing styrene in addition to 1,3-butadiene as a conjugated diene monomer and an ethylenically unsaturated carboxylic acid monomer. A latex of a copolymer, which is obtained by copolymerizing other ethylenically unsaturated monomers that can be copolymerized with these, which are used as necessary in addition to these. Good too.

The content of butadiene units formed by 1,3-butadiene in the carboxyl group-containing styrene-butadiene rubber (a2) is preferably 56 to 78% by weight, more preferably 56 to 73% by weight, even more preferably is 56 to 68% by weight, particularly preferably 56 to 67% by weight. By setting the content of butadiene units within the above range, the dip-molded product formed using the resulting latex composition has sufficient tensile strength, excellent texture, and increased elongation. can do.

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, the same as the latex of the carboxyl group-containing nitrile rubber (a1) mentioned above. can be used. The content of ethylenically unsaturated carboxylic acid monomer units formed by ethylenically unsaturated carboxylic acid monomers in the carboxyl group-containing styrene-butadiene rubber (a2) is preferably 2 to 6.5% by weight. The amount is more preferably 2 to 6% by weight, still more preferably 2 to 5% by weight, even more preferably 2 to 4.5% by weight, particularly preferably 2.5 to 4.5% by weight. By setting the content of the ethylenically unsaturated carboxylic acid monomer unit within the above range, the dip-molded product formed using the resulting latex composition has sufficient tensile strength and has excellent texture. The elongation can be further increased.

The content of styrene units formed by styrene in the carboxyl group-containing styrene-butadiene rubber (a2) is preferably 20 to 40% by weight, more preferably 25 to 40% by weight, even more preferably 30 to 40% by weight. % by weight, particularly preferably from 30.5 to 40% by weight. By setting the content of styrene units within the above range, the dip-molded product formed using the resulting latex composition has sufficient tensile strength, excellent texture, and increased elongation. can do.

Examples of 1,3-butadiene as a conjugated diene monomer, ethylenically unsaturated carboxylic acid monomers, and other ethylenically unsaturated monomers copolymerizable with styrene include the above-mentioned carboxyl group-containing nitrile rubber. In addition to the same latex as (a1) (excluding styrene), isoprene, 2,3-dimethyl-1,3-butadiene, 2-ethyl-1,3-butadiene, 1,3-pentadiene and chloroprene Examples include conjugated diene monomers other than 1,3-butadiene such as 1,3-butadiene. The content of other monomer units formed by other ethylenically unsaturated monomers in the carboxyl group-containing styrene-butadiene rubber (a2) is preferably 10% by weight or less, more preferably 5% by weight or less. It is not more than 3% by weight, more preferably not more than 3% by weight.

The latex of the carboxyl group-containing styrene-butadiene rubber (a2) used in the present invention can be obtained by copolymerizing a monomer mixture containing the above-mentioned monomers, but copolymerization by emulsion polymerization is preferable. preferable. As for the emulsion polymerization method, polymerization may be carried out in the same manner as in the case of the carboxyl group-containing nitrile rubber (a1) using the same polymerization auxiliary materials.

Furthermore, anti-aging agents, preservatives, antibacterial agents, dispersants, etc. may be added to the latex of the carboxyl group-containing styrene-butadiene rubber (a2) used in the present invention, if necessary.

The number average particle diameter of the latex of the carboxyl group-containing styrene-butadiene rubber (a2) used in the present invention is preferably 60 to 300 nm, more preferably 80 to 150 nm. The particle size can be adjusted to a desired value by adjusting the amounts of emulsifier and polymerization initiator used.

Further, the latex of the carboxyl group-containing conjugated diene rubber (a3) is a latex of a copolymer obtained by copolymerizing a conjugated diene monomer and an ethylenically unsaturated carboxylic acid monomer, and in addition to these, It may also be a latex of a copolymer obtained by copolymerizing other ethylenically unsaturated monomers copolymerizable with these, which are used as necessary.

The content of conjugated diene monomer units formed by conjugated diene monomers in the carboxyl group-containing conjugated diene rubber (a3) is preferably 80 to 98% by weight, more preferably 90 to 98% by weight, More preferably, it is 95 to 97.5% by weight. By setting the content of the conjugated diene monomer unit within the above range, the dip molded product formed using the resulting latex composition has sufficient tensile strength, has excellent texture, and has increased elongation. It can be assumed that

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, the same as the latex of the carboxyl group-containing nitrile rubber (a1) mentioned above. can be used. The content ratio of the ethylenically unsaturated carboxylic acid monomer unit formed by the ethylenically unsaturated carboxylic acid monomer in the carboxyl group-containing conjugated diene rubber (a3) is preferably 2 to 10% by weight, and more Preferably 2 to 7.5% by weight, more preferably 2 to 6.5% by weight, even more preferably 2 to 6% by weight, particularly preferably 2 to 5% by weight, most preferably 2.5 to 5% by weight. Weight%. By setting the content of the ethylenically unsaturated carboxylic acid monomer unit within the above range, the dip-molded product formed using the resulting latex composition has sufficient tensile strength and has excellent texture. The elongation can be further increased.

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. As the conjugated diene monomer, any one of these may be used alone or two or more types may be used in combination.

Other ethylenically unsaturated monomers that can be copolymerized with the conjugated diene monomer and the ethylenically unsaturated carboxylic acid monomer include, for example, those similar to the latex of the carboxyl group-containing nitrile rubber (a1) mentioned above. can be mentioned. The content of other monomer units formed by other ethylenically unsaturated monomers in the carboxyl group-containing conjugated diene rubber (a3) is preferably 10% by weight or less, more preferably 5% by weight. The content is preferably 3% by weight or less.

The latex of the carboxyl group-containing conjugated diene rubber (a3) used in the present invention can be obtained by copolymerizing a monomer mixture containing the above-mentioned monomers, but copolymerization by emulsion polymerization is preferred. As for the emulsion polymerization method, polymerization may be carried out in the same manner as in the case of the carboxyl group-containing nitrile rubber (a1) using the same polymerization auxiliary materials.

Moreover, an anti-aging agent, a preservative, an antibacterial agent, a dispersant, etc. may be appropriately added to the latex of the carboxyl group-containing conjugated diene rubber (a3) used in the present invention, if necessary.

The number average particle diameter of the latex of the carboxyl group-containing conjugated diene rubber (a3) used in the present invention is preferably 60 to 300 nm, more preferably 80 to 150 nm. The particle size can be adjusted to a desired value by adjusting the amounts of emulsifier and polymerization initiator used.

Metal compound containing trivalent or higher valence metal (B)
In the present invention, from the viewpoint of keeping the content of trivalent or higher metals in the obtained dip molded product within the above-mentioned specific range, in addition to the latex of the carboxyl group-containing rubber (A) as a latex composition, The metal compound (B) containing a trivalent or higher valence metal is contained in the range of 0.1 to 1.5 parts by weight based on 100 parts by weight of the carboxyl group-containing rubber (A) contained in the latex. It is preferable to use In the latex composition used in the present invention, the metal compound (B) containing a trivalent or higher valence metal acts as a crosslinking agent.

In the present invention, it is preferable to use a metal compound (B) containing a trivalent or higher valent metal as a crosslinking agent instead of sulfur, which is commonly used as a crosslinking agent. Since it does not require sulfur-containing vulcanization accelerators, in addition to immediate-type allergies (Type I), delayed-type allergies (Type IV) caused by sulfur and sulfur-containing vulcanization accelerators can occur. ) can also be effectively suppressed.

In addition, according to the present invention, the content of a trivalent or higher metal in the obtained dip-formed product is reduced by adding the metal compound containing a trivalent or higher valent metal to the latex of the above-mentioned copolymer. The amount can be set within the above-mentioned specific range, and as a result, while maintaining sufficient tensile strength, it is possible to obtain excellent hand feel and further increase in elongation and stress retention.

The metal compound (B) containing a trivalent or higher valence metal may be any compound containing a trivalent or higher valence metal, and includes, but is not particularly limited to, an aluminum compound, a cobalt compound, a zirconium compound, a titanium compound, etc. Among these, aluminum compounds are preferred since they can better crosslink the carboxyl group-containing rubber (A) contained in the latex.

Examples of aluminum compounds include, but are not particularly limited to, aluminum oxide, aluminum chloride, aluminum hydroxide, aluminum nitrate, aluminum sulfate, aluminum metal, aluminum ammonium sulfate, aluminum bromide, aluminum fluoride, aluminum potassium sulfate, aluminum potassium sulfate, and aluminum sulfate. Examples include isopropoxide, sodium aluminate, potassium aluminate, sodium aluminum sulfite, and the like. In addition, these aluminum compounds can be used individually or in combination of 2 or more types. Among these, sodium aluminate is preferable because it can make the effects of the present invention more remarkable.

The content of the metal compound (B) containing a trivalent or higher valent metal in the latex composition used in the present invention is preferably 0.00 parts by weight based on 100 parts by weight of the carboxyl group-containing rubber (A) contained in the latex. 1 to 1.5 parts by weight, more preferably 0.1 to 1.25 parts by weight, even more preferably 0.1 to 1 parts by weight, particularly preferably 0.1 to 0.8 parts by weight. , most preferably 0.1 to 0.7 parts by weight. If the content of the metal compound containing a trivalent or higher valence metal is too small, crosslinking will be insufficient, and the dip molded product formed using the resulting latex composition may have poor tensile strength. On the other hand, if the content of the metal compound containing trivalent or higher valence metal is too high, the dip-molded product formed using the resulting latex composition will have low tensile strength, low elongation at break, and poor texture. There is a risk that this may occur.

Heat-sensitive coagulant (C)
Further, in the present invention, the latex composition contains a heat-sensitive coagulant (C) in addition to the latex of the carboxyl group-containing rubber (A) and the metal compound (B) containing a trivalent or higher valent metal. It is preferable to use one that is present. The heat-sensitive coagulant (C) has the effect of reducing the dispersion stability of the latex of the carboxyl group-containing rubber when heated to a temperature above a certain level, thereby causing the coagulation of the latex composition by heating. This makes it possible to

According to the present invention, a latex composition is dip-molded by containing a metal compound (B) containing a trivalent or higher valent metal in a specific ratio and further containing a heat-sensitive coagulant (C), and When making a molded product, it can be solidified without using a calcium-based coagulant that is normally used in dip molding, so dip molding can be performed while keeping the content of trivalent or higher metals in the dip molding within a specific range. It is possible to reduce the calcium concentration in the body, thereby making it possible to further improve the stress retention rate of the obtained dip-molded product.

The heat-sensitive coagulant (C) is not particularly limited as long as it has the effect of reducing the dispersion stability of latex when heated above a certain temperature, but examples include polyorganosiloxane, polyvinyl methyl ether, etc. , polyalkylene glycol, etc., among which polyorganosiloxane is preferred. The polyorganosiloxane used as the heat-sensitive coagulant (C) is preferably one modified with polyether, and more preferably polyether-modified silicone oil.

The content of the heat-sensitive coagulant (C) in the latex composition used in the present invention is preferably 0.01 to 10 parts by weight based on 100 parts by weight of the carboxyl group-containing rubber (A) contained in the latex. The amount is preferably 0.1 to 4 parts by weight, and even more preferably 0.5 to 2 parts by weight. If the content of the heat-sensitive coagulant (C) with respect to the carboxyl group-containing rubber (A) is too large, the latex composition may coagulate before dip molding. If the amount is too small, there is a risk that the dip-molded product may not be formed properly.

Alcoholic hydroxyl group-containing compound (D)
Furthermore, the latex composition used in the present invention contains, in addition to the latex of the carboxyl group-containing rubber (A), the metal compound (B) containing a trivalent or higher valent metal, and the heat-sensitive coagulant (C), a saccharide (d1 ), sugar alcohols (d2), hydroxy acids (d3) and hydroxy acid salts (d4).

By further containing the alcoholic hydroxyl group-containing compound (D), the stability as a latex composition can be further improved, and the resulting dip-molded product has high tensile strength, high elongation, and a flexible texture. In addition to having this, it can also have a high stress retention rate.

In particular, when using a metal compound (B) containing a metal with a valence of 3 or more as a crosslinking agent, an alcoholic hydroxyl group-containing compound (D) is blended with the metal compound (B) containing a metal with a valence of 3 or more. By doing so, it is possible to improve the dispersion state of the metal compound (B) containing a trivalent or higher valent metal in the latex composition, thereby improving the stability of the latex composition. Moreover, due to the action of the metal compound (B) containing a trivalent or higher valence metal and the alcoholic hydroxyl group-containing compound (D), the resulting dip molded product has a higher tensile strength. In addition to having a larger elongation at break and a softer feel, it can also have a higher stress retention rate.

The alcoholic hydroxyl group-containing compound (D) used in the present invention is at least one selected from saccharides (d1), sugar alcohols (d2), hydroxy acids (d3), and hydroxy acid salts (d4), and among these, , sugar alcohol (d2) and hydroxy acid salt (d4) from the viewpoint that the obtained membrane molded product such as a dip molded product can have a softer texture and a higher stress retention rate. It is preferable to use at least one selected from the following. In addition, when two or more types are used together as the alcoholic hydroxyl group-containing compound (D), at least one selected from saccharides (d1) and sugar alcohols (d2), a hydroxy acid (d3) and a hydroxy acid salt It is preferable to use in combination with at least one selected from (d4), and more preferably to use in combination with sugar alcohol (d2) and hydroxy acid salt (d4).

The saccharide (d1) is not particularly limited as long as it is a monosaccharide or a polysaccharide in which two or more monosaccharides are linked through a glycosidic bond, but examples thereof include erythrose, threatose, ribose, lyxose, xylose, arabinose, and allose. Monosaccharides such as , talose, gulose, altrose, galactose, idose, erythroulose, xylulose, ribulose, psicose, fructose, sorbose, tagatose; trehalose, maltose, isomaltose, cellobiose, gentiobiose, melibiose, lactose, sucrose, palatinose, etc. disaccharides; trisaccharides such as maltotriose, isomaltotriose, panose, cellotriose, manninotriose, solatriose, melezitose, planteose, gentianose, umbelliferose, lactosucrose, raffinose; maltotetraose, isomalt Homo-oligosaccharides such as tetraose; Tetrasaccharides such as stachyose, cellotetraose, scorodose, liquinose, and panose; Pentasaccharides such as maltopentaose and isomaltopentaose; Hexasaccharides such as maltohexaose and isomaltohexaose; etc. can be mentioned. These may be used alone or in combination of two or more.

The sugar alcohol (d2) may be any monosaccharide or polysaccharide sugar alcohol, and is not particularly limited, but includes, for example, tritol such as glycerin; tetritol such as erythritol, D-threitol, and L-threitol; D-arabinitol; Pentitols such as L-arabinitol, xylitol, ribitol, and pentaerythritol; Pentaerythritol; Hexitols such as sorbitol, D-iditol, galactitol, D-glucitol, and mannitol; Heptitol such as boremitol and perseitol; D-erythro-D- Octitol such as galacto-octitol; and the like. These may be used alone or in combination of two or more. Among these, hexitol, which is a sugar alcohol having 6 carbon atoms, is preferred, and sorbitol is more preferred.

The hydroxy acid (d3) may be any carboxylic acid having a hydroxyl group, and is not particularly limited. For example, glycolic acid, lactic acid, tartronic acid, glyceric acid, 2-hydroxybutyric acid, 3-hydroxybutyric acid, γ-hydroxy Aliphatic acids such as butyric acid, malic acid, 3-methylmalic acid, tartaric acid, citramalic acid, citric acid, isocitric acid, leucinic acid, mevalonic acid, pantoic acid, ricinoleic acid, ricinelaidic acid, cerebronic acid, quinic acid, shikimic acid, serine, etc. Hydroxy acids; salicylic acid, creosotic acid (homosalicylic acid, hydroxy(methyl)benzoic acid), vanillic acid, syringic acid, hydroxypropanoic acid, hydroxypentanoic acid, hydroxyhexanoic acid, hydroxyheptanoic acid, hydroxyoctanoic acid, hydroxynonanoic acid, Monomers such as hydroxydecanoic acid, hydroxyundecanoic acid, hydroxydododecanoic acid, hydroxytridecanoic acid, hydroxytetradecanoic acid, hydroxypentadecanoic acid, hydroxyheptadecanoic acid, hydroxyoctadecanoic acid, hydroxynonadecanoic acid, hydroxyicosanoic acid, ricinoleic acid, etc. Hydroxybenzoic acid derivatives, dihydroxybenzoic acid derivatives such as pyrocatechuic acid, resorcylic acid, protocatechuic acid, gentisic acid, orceric acid, trihydroxybenzoic acid derivatives such as gallic acid, phenylacetic acid derivatives such as mandelic acid, benzylic acid, atrolactic acid, etc. , aromatic hydroxy acids such as cinnamic acid and hydrocinnamic acid derivatives such as melilotic acid, fluoretic acid, coumaric acid, umbelic acid, caffeic acid, ferulic acid, and sinapinic acid. These may be used alone or in combination of two or more. Among these, aliphatic hydroxy acids are preferred, aliphatic α-hydroxy acids are more preferred, glycolic acid, lactic acid, tartronic acid, glyceric acid, malic acid, tartaric acid, and citric acid are even more preferred, and glycolic acid is particularly preferred.

The hydroxy acid salt (d4) may be any salt of a hydroxy acid, and is not particularly limited. Specific examples of the hydroxy acid (d3) include metal salts of hydroxy acids, such as sodium, potassium, etc. salts of alkali metals; salts of alkaline earth metals such as magnesium; As the hydroxy acid salt (d4), one type may be used alone, or two or more types may be used in combination. As the hydroxy acid salt (d4), an alkali metal salt of a hydroxy acid is preferable, and a sodium salt of a hydroxy acid is preferable. The hydroxy acid constituting the hydroxy acid salt (d4) is preferably an aliphatic hydroxy acid, more preferably an aliphatic α-hydroxy acid, such as glycolic acid, lactic acid, tartronic acid, glyceric acid, malic acid, tartaric acid, citric acid, etc. Acids are more preferred, and glycolic acid is particularly preferred. That is, sodium glycolate is particularly suitable as the hydroxy acid salt (d4).

The content of the alcoholic hydroxyl group-containing compound (D) in the latex composition used in the present invention is determined as follows: ):alcoholic hydroxyl group-containing compound (D)" weight ratio, preferably in the range of 1:0.1 to 1:50, more preferably in the range of 1:0.2 to 1:45. The amount is more preferably in the range of 1:0.3 to 1:30. By setting the content of the alcoholic hydroxyl group-containing compound (D) to the metal compound (B) containing a trivalent or higher valence metal within the above range, the effect of adding the alcoholic hydroxyl group-containing compound (D) can be further enhanced. .

The content of the alcoholic hydroxyl group-containing compound (D) may be such that the content of the metal compound (B) containing a trivalent or higher valence metal falls within the above range. The content per 100 parts by weight of rubber (A) is preferably 0.03 to 15 parts by weight, more preferably 0.05 to 10 parts by weight.

The latex composition used in the present invention includes, for example, a carboxyl group-containing rubber (A) latex, a metal compound (B) containing a trivalent or higher valent metal, which is used as necessary, and a heat-sensitive coagulant (C). It can be obtained by blending with the alcoholic hydroxyl group-containing compound (D). A method of blending a metal compound (B) containing a trivalent or higher valence metal, a heat-sensitive coagulant (C), and an alcoholic hydroxyl group-containing compound (D) into the latex of the carboxyl group-containing rubber (A), if necessary. Although not particularly limited, a metal compound containing a trivalent or higher valence metal (B), a heat-sensitive coagulant (C), and an alcoholic hydroxyl group-containing compound (D) may be used as necessary in the latex composition obtained. ) can be well dispersed, the heat-sensitive coagulant (C) is dissolved in water and added to the latex of the carboxyl group-containing rubber (A) in the form of an aqueous solution, and then added to the latex as necessary. It is preferable to add the metal compound (B) containing a trivalent or higher valence metal and the alcoholic hydroxyl group-containing compound (D) used in the form of an aqueous solution. Furthermore, in order to increase the stability of the solution when dissolving it, it is preferable to add a stabilizing agent such as a chelating agent or a buffering agent.

In addition, the latex composition used in the present invention includes the latex of the carboxyl group-containing rubber (A) described above, a metal compound containing a trivalent or higher valence metal (B), and a heat-sensitive coagulant (C), which are used as necessary. , and the alcoholic hydroxyl group-containing compound (D), if desired, surfactants, fillers, pH adjusters, thickeners, anti-aging agents, dispersants, pigments, fillers, softeners, etc. may be blended. You can.

Surfactants are not particularly limited, but include, for example, carboxylic acid-based, sulfonic acid-based, sulfuric acid ester-based, phosphate-based anionic surfactants, polyoxyalkylene ether-based, polyoxyalkylene ester-based, and polyhydric alcohols. Fatty acid ester type, sugar fatty acid ester type, alkyl polyglycoside type nonionic surfactants, alkylamine salt type, alkylamine derivative type and their quaternized products, and cationic surfactants such as imidazolinium salt type, etc. Can be mentioned. Among these, sulfate ester-based anionic surfactants and polyoxyalkylene ether-based nonionic surfactants are preferred, and sodium lauryl sulfate and polyoxyethylene nonylphenyl ether are more preferred. These surfactants can be used alone or in combination of two or more. The content of the surfactant in the latex composition is not particularly limited, but is preferably 0.01 to 10% by weight based on the solid content in the latex composition.

The solid content concentration of the latex composition used in the present invention is preferably 10 to 40% by weight, more preferably 15 to 35% by weight. Further, the pH of the latex composition used in the present invention is preferably 7.5 to 12.0, more preferably 8.0 to 11.5, and even more preferably 8.5 to 11.0.

Dip-molded body The dip-molded body of the present invention is obtained by dip-molding the latex composition described above, and has a calcium content of 500 μg/g or less, a trivalent or higher metal content of 500 to 10, 000μg/g.

The content of calcium in the dip-molded product of the present invention is 500 μg/g or less, preferably 300 μg/g or less, and more preferably 200 μg/g or less. The lower limit of the calcium content is not particularly limited, but considering the amount of calcium that is inevitably mixed, it is preferably 0.01 μg/g or more, more preferably 20 μg/g or more. If the content of calcium in the dip-molded article of the present invention is too high, the obtained dip-molded article will be inferior in feel, elongation, and stress retention.

Methods for keeping the calcium content in the dip-molded product of the present invention within the above range include, but are not particularly limited to, methods that employ processes that do not substantially use calcium or calcium-containing compounds, such as coagulation. When carrying out this process, instead of using a calcium-based coagulant, a method using a heat-sensitive coagulation method may be used. In addition, from the perspective of further reducing the calcium content in the dip-molded product, in addition to the method using the heat-sensitive coagulation method, when producing the latex of the carboxyl group-containing rubber contained in the latex composition used for dip-molding, , a method using ion-exchanged water, a method of washing the dip-molded layer formed by dip-molding with water before crosslinking, etc. may be combined.

In addition, the dip-molded product of the present invention has a calcium content of 500 μg/g or less, and a trivalent or higher metal content in the range of 500 to 10,000 μg/g, The content of the trivalent or higher valent metal in the dip-formed product of the present invention is preferably 1,000 to 8,000 μg/g, more preferably 1,500 to 6,000 μg/g. If the content of trivalent or higher metals in the dip-formed product of the present invention is too high, the resulting dip-formed product will have poor texture; if the content is too low, the resulting dip-formed product will have poor elongation at break. It is small and has a low stress retention rate. Note that examples of trivalent or higher-valent metals include aluminum, cobalt, zirconium, titanium, and the like. Note that the method for bringing the content of trivalent or higher valence metals in the dip-formed product of the present invention within the above range is not particularly limited, but may include the amount of the metal compound (B) containing the above-mentioned trivalent or higher metals. One example is a method of adjusting the Further, the dip-formed product of the present invention may have a content of trivalent or higher valent metals within the above range, but the content of aluminum among the trivalent or higher valent metals may be in the range of 500 to 10,000 μg/g. It is preferably in the range of 1,000 to 8,000 μg/g, even more preferably in the range of 1,500 to 6,000 μg/g.

The method for producing the dip-molded article of the present invention is not particularly limited, but from the viewpoint of reducing the calcium content in the dip-molded article as described above, a method of manufacturing by heat-sensitive coagulation is preferred. . In particular, by using a latex composition containing a heat-sensitive coagulant to form a dip-molded body, and producing a dip-molded body by heat-sensitive coagulation, it is possible to avoid the use of calcium-based coagulants normally used in dip molding. Accordingly, the content of calcium in the dip-molded article can be appropriately reduced.

Here, in dip molding, calcium-based coagulants are preferably used from the viewpoint of having excellent coagulation properties, thereby making it possible to obtain dip-formed products with high tensile strength and large elongation. If a coagulant is used, a considerable amount of the calcium-based coagulant will remain in the dip-formed body. On the other hand, the inventors of the present invention focused on the content of calcium and the content of trivalent or higher valent metals contained in the dip-formed body, and as a result, the calcium content was found to be 500 μg. If the amount exceeds /g, the crosslinking reaction by trivalent or higher metals (metal compounds containing trivalent or higher metals) will be partially inhibited. It has been found that by reducing the calcium content to 500 μg/g or less, crosslinking by trivalent or higher valence metals (metal compounds containing trivalent or higher metals) can proceed appropriately. It is. From this, according to the present invention, a dip-formed product can be made to have a high tensile strength, a large elongation at break, and a flexible texture, as well as a higher stress retention rate. It is possible.

In the heat-sensitive coagulation method, first, a heated dip molding mold is brought into contact with a latex composition containing carboxyl group-containing rubber latex to solidify the latex composition, and dip molding is performed on the surface of the dip molding mold. Preferably, a layer is formed. Note that the latex composition described above can be used as the latex composition containing the carboxyl group-containing rubber latex.

Specifically, in a method for producing a dip-molded article using a heat-sensitive coagulation method, a heated dip-molding mold is immersed in a latex composition, whereby the latex composition is transferred to the heated dip-molding mold. By contacting the latex composition, gelation and coagulation of the latex composition adhering to the surface of the dip molding mold proceed due to the heat of the dip molding mold, thereby forming a dip molding layer.

The dip molding mold used in the heat-sensitive solidification method is not particularly limited, but various materials such as porcelain, glass, metal, and plastic can be used. The shape of the dip molding mold may be a desired shape depending on the shape of the final product. For example, when the dip-molded product is used as a glove, it is preferable to use a dip-molding die for various gloves, such as a dip-molding die having a shape from the wrist to the fingertips.

When bringing the dip molding mold into contact with the latex composition, the dip molding mold is heated (also referred to as preheating) in advance, and the dip molding mold is brought into contact with the latex composition in a heated state. The temperature of the dip molding mold (also referred to as preheating temperature) during contact with the latex composition is preferably 30 to 100°C, more preferably 40 to 95°C, even more preferably 45 to 90°C, particularly preferably 50°C. -90°C, most preferably 55-90°C. By setting the preheating temperature of the dip molding mold within the above range, the temperature of the dip molding mold immediately before contact with the latex composition can be set within the following preferred range. The temperature of the dip molding mold immediately before contacting with the latex composition is preferably 25 to 100°C, more preferably 35 to 95°C, even more preferably 40 to 90°C, particularly preferably 45 to 90°C, and most preferably The temperature is 50-90°C. When forming a dip-molded body using a latex composition by a heat-sensitive coagulation method, if the temperature of the dip-molding mold immediately before contacting the latex composition is too high, the dip-molded body may not be formed properly. On the other hand, if the temperature of the dip-molding mold immediately before contacting the latex composition is too low, the latex composition may not solidify and a dip-molded article may not be formed.

Further, after bringing the dip molding mold into contact with the latex composition, it is preferable to dry the dip molding layer formed on the surface of the dip molding mold. The drying temperature in this case is not particularly limited, but is preferably 10 to 80°C, more preferably 15 to 80°C. Further, the drying time is not particularly limited, but is preferably 5 seconds to 120 minutes, more preferably 10 seconds to 60 minutes.

When the latex composition contains a crosslinking agent, the resulting dip-molded layer is usually crosslinked by heat treatment. In this case, when the latex composition contains a metal compound (B) containing a metal with a valence of 3 or more, the metal compound (B) containing a metal with a valence of 3 or more has a carboxyl group-containing rubber ( The process proceeds by reacting with the carboxyl group contained in A) to form a metal ion bond. Note that before heat treatment, the dip-formed layer is immersed in water, preferably warm water at 30 to 70°C, for about 1 to 60 minutes to remove water-soluble impurities (for example, excess emulsifier, calcium, etc.). You may. Although the operation for removing water-soluble impurities may be carried out after heat-treating the dip-formed layer, it is preferably carried out before heat-treating, since water-soluble impurities can be removed more efficiently.

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

Then, by removing the dip-molded layer from the dip-molding mold, a dip-molded body is obtained as a membrane-shaped membrane-shaped body. As a method for removing the mold, a method of peeling it off from the mold by hand or using water pressure or compressed air pressure can be adopted. Note that after demolding, heat treatment may be further performed at a temperature of 60 to 120° C. for 10 to 120 minutes.

The dip-molded product of the present invention obtained as described above has a calcium content of 500 μg/g or less and a trivalent or higher metal content of 500 to 10,000 μg/g, so it has a tensile strength. It has high strength, a large elongation at break, a flexible texture, and a high stress retention rate, and is also excellent in durability, and can be particularly suitably used as, for example, gloves. When the dip-formed objects are gloves, inorganic fine particles such as talc and calcium carbonate or organic fine particles such as starch particles are added to the gloves to prevent contact surfaces between the dip-formed objects from adhering to each other and to improve slippage when putting on and taking off the gloves. It may be sprayed on the surface of the glove, 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 above-mentioned gloves, the dip-molded product of the present invention can also be used for medical supplies such as nipples for baby bottles, droppers, tubes, water pillows, balloon sacks, catheters, and condoms; toys such as balloons, dolls, and balls; pressurized It can also be used for industrial products such as molding bags and gas storage bags; finger cots, etc.

Hereinafter, the present invention will be explained based on more detailed examples, but the present invention is not limited to these examples. In addition, in the following, "parts" are based on weight unless otherwise specified. In addition, the tests and evaluations were as follows.

Calcium concentration and aluminum concentration in the dip-formed body Calcium and aluminum in the dip-formed body were qualitatively and quantitatively determined by ICP-AES method. Note that SPS5000 (manufactured by SII Nano Technology) was used for the measurement. Furthermore, the amounts of calcium and aluminum ions in the dip-molded body were determined by ion chromatography using 0.01 g of the dip-molded body. Note that DX500 (manufactured by DIONEX) was used for the measurement.
From the measurement results of the ICP-AES method and the ion chromatography method, the concentration of calcium forming a salt with carboxyl groups in the dip-formed product, the concentration of aluminum (the amount of calcium (μg/ g) and the amount of aluminum (μg/g)) were determined.
Note that the detection limit value of calcium concentration in this measurement method is 20 μg/g. In addition, in the Examples and Comparative Examples, since no metal compounds containing trivalent or higher valent metals other than aluminum were used, the measured concentration of aluminum is considered to be approximately the same as the concentration of trivalent or higher valent metals. It will be done.

Tensile strength, elongation at break, stress at 500% elongation From the rubber gloves as dip molded bodies obtained in the Examples and Comparative Examples, a dumbbell (Die-C: manufactured by Dumbbell Co., Ltd.) was used in accordance with ASTM D-412. A dumbbell-shaped test piece was prepared. Next, the obtained test piece was pulled at a tensile speed of 500 mm/min, and the tensile strength at break, elongation at break, and stress at 500% elongation were measured. The higher the tensile strength and elongation at break, the better, and the lower the stress at 500% elongation, the softer the texture.

From the rubber gloves as dip molded bodies obtained in stress retention examples and comparative examples, dumbbell-shaped test pieces were prepared using dumbbells (Die-C: manufactured by Dumbbell Co., Ltd.) according to ASTM D-412. Then, tensile stress was applied to both ends of the test piece at a speed of 500 mm/min, and when the standard section of 25 mm of the test piece was stretched twice (100%), the extension was stopped and the tensile stress M ₁₀₀ (0) was applied. The tensile stress M ₁₀₀ (6) was also measured after 6 minutes had passed. The percentage of M ₁₀₀ (6) to M ₁₀₀ (0) (ie, the percentage of M ₁₀₀ (6)/M ₁₀₀ (0)) was defined as the stress retention rate. The higher the stress retention rate, the more preferable it is because it is less likely that the gloves will become loose (loose or sag) during use.

Production Example 1 (Production of latex of carboxyl group-containing nitrile rubber (A-1))
In a pressure-resistant polymerization reaction vessel equipped with a stirrer, 63 parts of 1,3-butadiene, 34 parts of acrylonitrile, 3 parts of methacrylic acid, 0.25 parts of t-dodecylmercaptan as a chain transfer agent, 132 parts of deionized water, and sodium dodecylbenzenesulfonate. 3 parts of sodium β-naphthalene sulfonate formalin condensate, 0.3 parts of potassium persulfate, and 0.005 parts of sodium ethylenediaminetetraacetate were charged, and the polymerization temperature was maintained at 37° C. to initiate polymerization. When the polymerization conversion rate reached 70%, the polymerization temperature was raised to 43°C, and the reaction was continued until the polymerization conversion rate reached 95%. After that, sodium dimethyldithiocarbamate was added as a polymerization terminator. The polymerization reaction was stopped by adding .1 part of the solution. After distilling off unreacted monomers under reduced pressure from the obtained copolymer latex, the solid content concentration and pH were adjusted, and a carboxyl group-containing nitrile rubber with a solid content concentration of 40% by weight and a pH of 8.0 was prepared. Latex (A-1) was obtained. The composition of the obtained carboxyl group-containing nitrile rubber (A-1) was 63% by weight of 1,3-butadiene units, 34% by weight of acrylonitrile units, and 3% by weight of methacrylic acid units.

Production Example 2 (Production of latex of carboxyl group-containing nitrile rubber (A-2))
A carboxyl group-containing nitrile with a solid content concentration of 40% by weight and a pH of 8.0 was prepared in the same manner as in Production Example 1, except that 132 parts of tap water (calcium concentration: 100 μg/g) was used instead of 132 parts of deionized water. A latex of rubber (A-2) was obtained. The composition of the obtained carboxyl group-containing nitrile rubber (A-2) was 63% by weight of 1,3-butadiene units, 34% by weight of acrylonitrile units, and 3% by weight of methacrylic acid units.

Example 1
Preparation of Latex Composition 250 parts of the latex of the carboxyl group-containing nitrile rubber (A-1) obtained in Production Example 1 (100 parts in terms of carboxyl group-containing nitrile rubber (A-1)) was added with 2.0 parts of sodium lauryl sulfate. 1 part, and 2.5 parts of polyoxyethylene nonylphenyl ether (product name "Emulgen 920", manufactured by Kao Corporation) were added and mixed. Next, 1.8 parts of a polyether-modified silicone oil aqueous solution (product name "TPA4380", manufactured by Momentive Performance Materials Japan, heat-sensitive coagulant) (0.6 parts in terms of polyether-modified silicone oil) was added to this mixed solution. After mixing, a mixed aqueous solution containing 0.2 parts of sodium aluminate, 0.4 parts of sorbitol, and 0.4 parts of sodium glycolate was added. Then, deionized water and a 5% by weight aqueous potassium hydroxide solution were added and mixed to obtain a latex composition with a solid content concentration of 30% by weight and a pH of 9.2.

Production of dip-molded object (gloves) A ceramic glove mold is heated to 70°C and immersed in the above latex composition for 5 seconds to thermally solidify to form a dip-molded layer on the glove mold. pulled out of the composition. After pulling it up, it was dried at a temperature of 70° C. for 10 minutes. After drying, the glove mold with the dip-molded layer formed thereon was immersed in warm water at 50° C. for 90 seconds to elute water-soluble impurities. Next, the glove mold with the dip-molded layer formed thereon is heat-treated at a temperature of 125°C for 25 minutes to crosslink the dip-molded layer, and the crosslinked dip-molded layer is peeled off from the glove mold to form a dip-molded article (rubber). gloves). Then, the obtained dip molded product (rubber gloves) was subjected to measurements of calcium concentration, aluminum concentration, tensile strength, elongation at break, stress at 500% elongation, and stress retention rate according to the above method. The results are shown in Table 1.

Example 2
When preparing the latex composition, a latex composition was prepared in the same manner as in Example 1, except that the amount of sodium aluminate used was changed from 0.2 parts to 0.4 parts. ) was manufactured and evaluated in the same manner. The results are shown in Table 1.

Example 3
When preparing the latex composition, a latex composition was prepared in the same manner as in Example 1, except that the amount of sodium aluminate used was changed from 0.2 parts to 0.6 parts. ) was manufactured and evaluated in the same manner. The results are shown in Table 1.

Example 4
When preparing a latex composition, instead of 250 parts of the latex of the carboxyl group-containing nitrile rubber (A-1) obtained in Production Example 1, the carboxyl group-containing nitrile rubber (A-2 ) A latex composition was prepared in the same manner as in Example 1, except that 250 parts of latex (100 parts in terms of carboxyl group-containing nitrile rubber (A-2)) was used; Gloves) were produced in the same manner as in Example 1, except that the step of immersing the glove mold with the dip-molded layer in hot water at 50°C for 90 seconds to elute water-soluble impurities was not performed. Dip molded products (rubber gloves) were manufactured and evaluated in the same manner. The results are shown in Table 1.

Example 5
When preparing the latex composition, the latex composition was prepared in the same manner as in Example 1, except that the pH of the latex composition was adjusted to 10.5, and the dip molded article (rubber gloves) was manufactured in the same manner. was evaluated. The results are shown in Table 1.

Comparative example 1
Preparation of latex composition A latex composition was obtained in the same manner as in Example 1, except that the polyether-modified silicone oil aqueous solution was not used.

Preparation of dip molded article (gloves) A coagulant aqueous solution was prepared by mixing 13 parts of calcium nitrate, 0.05 part of polyethylene glycol octylphenyl ether, which is a nonionic emulsifier, and 87 parts of deionized water. Next, a ceramic glove mold preheated to 70°C was immersed in this coagulant aqueous solution for 5 seconds, pulled up, and dried at a temperature of 70°C for 10 minutes to allow the coagulant to adhere to the glove mold. Ta. Then, the glove mold to which the coagulant was attached was immersed in the latex composition obtained above for 10 seconds at a temperature of 70°C, pulled up, and then immersed in warm water at 50°C for 90 seconds. Then, water-soluble impurities were eluted and a glove-shaped dip-molded layer was formed.
Next, the glove mold with the dip-molded layer formed thereon is heat-treated at a temperature of 125° C. for 25 minutes to crosslink the dip-molded layer, and the crosslinked dip-molded layer is peeled off from the glove mold to form a dip-molded article (rubber glove). I got it. Then, the obtained dip molded product (rubber gloves) was subjected to measurements of calcium and aluminum concentration, tensile strength, elongation at break, stress at 500% elongation, and stress retention rate according to the above method. The results are shown in Table 1.

Comparative example 2
When preparing the latex composition, a latex composition was prepared and a dip molded article (rubber gloves) was produced in the same manner as in Comparative Example 1, except that the pH was adjusted to 10.5, and evaluation was conducted in the same manner. Ta. The results are shown in Table 1.

As shown in Table 1, a dip-molded product obtained by dip-molding a latex composition containing a carboxyl group-containing rubber, the content of calcium is 500 μg/g or less, and the content of trivalent or higher metals is 500 μg/g or less. The dip-formed products with 500 to 10,000 μg/g had high tensile strength, large elongation at break, a flexible texture (low stress at 500% elongation), and high stress retention ( Examples 1-5).

On the other hand, dip-molded products with a calcium content exceeding 500 μg/g had low tensile strength, low elongation at break, and poor texture and stress retention (Comparative Examples 1 and 2).
Note that by comparing the results of Example 1 and Example 5 with the results of Comparative Example 1 and Comparative Example 2, the following can be confirmed. That is, when heat-sensitive coagulation is used instead of coagulation with calcium nitrate as in this example, even if the pH of the latex composition changes, the variation in the properties of the resulting dip-molded product can be suppressed to a small level ( The effect of pH fluctuations is small), so even if the pH fluctuates to some extent, desired characteristics can be obtained, and excellent production stability can be achieved.

Claims (4)

A dip-molded product obtained by dip-molding a latex composition containing carboxyl group-containing rubber latex , an aluminum compound , and a heat-sensitive coagulant ,
The dip-formed body has a calcium content of 500 μg/g or less and an aluminum content of 500 to 10,000 μg/g. The dip-molded article according to claim 1, wherein the carboxyl group-containing rubber is a carboxyl group-containing nitrile rubber. The dip-molded article according to claim 1 or 2, wherein the latex composition contains sodium aluminate as the aluminum compound. A method for producing a dip-molded article according to any one of claims 1 to 3 , comprising:
By bringing the heated dip molding mold into contact with the latex composition containing the latex of the carboxyl group-containing rubber , an aluminum compound, and a heat-sensitive coagulant , the latex composition is thermally coagulated, thereby forming the dip molding mold. A method for producing a dip-molded article, comprising a step of forming a dip-molding layer on the surface.