WO2010098008A1 - Composition for dip forming, and dip-formed articles - Google Patents

Abstract

A composition for dip forming, which comprises a synthetic polyisoprene latex, a sulfur-containing vulcanizing agent, zinc oxide, a vulcanization accelerator, and a dispersant, said dispersant being either a salt of an olefinic compound/ ethylenically unsaturated dicarboxylic acid copolymer having a weight-average molecular weight of 1,000 to 150,000 and/or a salt of an olefinic compound/ethylenically unsaturated dicarboxylic monoester copolymer having a weight-average molecular weight of 1,000 to 150,000.

Description

DIP MOLDING COMPOSITION AND DIP MOLDED BODY

The present invention suppresses the formation of coarse agglomerates during aging, and is excellent in tensile strength even if the aging period is not lengthened, and also excellent in safety when used in contact with the human body. The present invention relates to a dip-molding composition that gives a dip-molded body and a dip-molded body formed by molding the dip-molding composition.

Conventionally, a dip-molded product is known which is dip-molded with a dip molding composition containing natural latex and used in contact with a human body such as a nipple, balloon, glove, balloon, and sack. However, since natural latex contains a protein that causes allergic symptoms in the human body, there are cases in which there is a problem as a dip-molded body that is in direct contact with a biological mucous membrane or organ.

Therefore, studies have been made on using synthetic acrylonitrile-butadiene copolymer rubber and polyisoprene latex.

For example, Patent Document 1 discloses a dip molding composition in which a latex of acrylonitrile-butadiene copolymer rubber containing an ethylenically unsaturated acid monomer unit is blended with a vulcanization accelerator composed of sulfur, zinc oxide and a thiazole compound. A dip-molded body obtained by dip-molding a product is disclosed. Although the dip-molded body of Patent Document 1 does not contain a protein that causes allergic symptoms in the human body, it has a high stress at 300% elongation and is not satisfactory in terms of flexibility.

Further, Patent Document 2 discloses a dip molding composition in which sulfur, zinc oxide, a specific vulcanization accelerator and a dispersant are blended with a synthetic polyisoprene latex, and such a dip molding composition is disclosed as follows. It gives a dip-molded body that is flexible and excellent in tensile strength. As the dispersant used here, an anionic surfactant such as sodium lauryl sulfate, an alkaline earth metal salt of casein, and the like are disclosed, and the latter can be preferably used. However, casein is a kind of protein and there is a concern that it causes allergic symptoms in the human body.

Moreover, the composition for dip molding containing the latex of synthetic polyisoprene is usually aged for a suitable period (sometimes referred to as pre-vulcanization) so as to maintain the tensile strength of the resulting dip-molded article stably high. )) And then subjected to dip molding. However, in the case where sodium lauryl sulfate is used as a dispersant instead of the alkaline earth metal salt of casein, and when the alkaline earth metal salt of casein is not blended, the dip obtained without increasing the aging period There exists a problem in which the tensile strength of a molded object is inferior. Furthermore, in the case where a dispersant is not blended, the dispersion stability of the synthetic polyisoprene latex decreases, and coarse agglomerates are produced during aging, making it difficult to use for dip molding. is there.

Japanese Patent Publication “Japanese Patent Laid-Open No. 2003-246891 (published on September 5, 2003)” Japanese Patent Gazette “Special Table 2004-532752 (published on Oct. 28, 2004)”

The problem to be solved by the present invention is to suppress the formation of coarse agglomerates during aging, and also has excellent tensile strength without increasing the aging period and is used in contact with the human body. Another object of the present invention is to provide a dip-molding composition that provides a dip-molded article with excellent safety.

In order to solve the above problems, the inventors of the present invention, as a dispersant to be blended in a dip molding composition containing a synthetic polyisoprene latex, a sulfur vulcanizing agent, zinc oxide and a vulcanization accelerator, has a weight average. The inventors have found that the above problems can be solved by selecting a salt of a styrene-maleic acid polymer or a styrene-maleic acid monoester polymer having a molecular weight in a specific range, and the present invention has been completed.

Thus, according to the present invention, a dip-molding composition containing a synthetic polyisoprene latex, a sulfur-based vulcanizing agent, zinc oxide, a vulcanization accelerator and a dispersing agent, wherein the dispersing agent has a weight average molecular weight of 1. Olefin compound having a molecular weight of 1,000 to 150,000 and / or an ethylenically unsaturated dicarboxylic acid polymer salt and / or an olefin compound having a weight average molecular weight of 1,000 to 150,000 and an ethylenically unsaturated dicarboxylic acid monoester polymer A dip-forming composition characterized in that it is a salt of

Further, according to the present invention, there is provided a dip-molded body obtained by dip-molding the above dip-molding composition.

The dip-forming composition of the present invention is excellent in tensile strength and used in contact with the human body while suppressing the formation of coarse aggregates during aging and without extending the aging period. In addition, a dip-molded body having excellent safety is provided.

The dip molding composition of the present invention contains a synthetic polyisoprene latex, a sulfur vulcanizing agent, zinc oxide, a vulcanization accelerator and a specific dispersant.

The synthetic polyisoprene latex used in the present invention is a synthetic polyisoprene latex obtained by polymerizing isoprene.

The synthetic polyisoprene may be obtained by copolymerizing a small amount of another ethylenically unsaturated monomer copolymerizable with isoprene. The content of isoprene units in the synthetic polyisoprene is preferably 70% by mass or more, more preferably 90% by mass or more, and particularly preferably 95% by mass or more. The synthetic polyisoprene is most preferably a homopolymer of isoprene from the viewpoint of obtaining a dip-molded product that is flexible and excellent in tensile strength.

Examples of other ethylenically unsaturated monomers copolymerizable with isoprene include conjugated diene monomers other than isoprene such as butadiene, chloroprene and 1,3-pentadiene; acrylonitrile, methacrylonitrile, fumaronitrile, α- Ethylenically unsaturated nitrile monomers such as chloroacrylonitrile; vinyl aromatic monomers such as styrene and alkylstyrene; methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, (meth) Examples thereof include ethylenically unsaturated carboxylic acid ester monomers such as 2-ethylhexyl acrylate; crosslinkable monomers such as divinylbenzene, diethylene glycol di (meth) acrylate, and pentaerythritol (meth) acrylate.

Other ethylenically unsaturated monomers copolymerizable with isoprene can be used alone or in combination of two or more.

There are four types of isoprene units in the synthetic polyisoprene, which are cis bond units, trans bond units, 1,2-vinyl bond units, and 3,4-vinyl bond units, depending on the bond state of isoprene. From the viewpoint of excellent tensile strength of the dip-molded product, the ratio of the cis bond unit in the isoprene unit in the synthetic polyisoprene is preferably 70% by mass or more, more preferably 90% by mass or more, and particularly preferably 95% by mass or more. is there.

The average molecular weight of the synthetic polyisoprene is a weight average molecular weight in terms of standard polystyrene by gel permeation chromatography analysis, preferably 500,000 to 5,000,000, more preferably 800,000 to 3,000,000. It is. When the average molecular weight of the synthetic polyisoprene is 500,000 or more, the tensile strength of the dip-molded product is improved, and when it is 5,000,000 or less, the synthetic polyisoprene latex tends to be easily produced.

As a method for producing the synthetic polyisoprene latex used in the present invention, for example, (1) a synthetic polyisoprene solution dissolved in an organic solvent is emulsified in water in the presence of a surfactant, and the organic solvent is removed if necessary. (2) Isoprene alone or a mixture of isoprene and an ethylenically unsaturated monomer copolymerizable therewith is emulsion-polymerized or suspension-polymerized to produce a synthetic polyisoprene latex directly. A method for producing isoprene latex is mentioned.

Synthetic polyisoprene having a high proportion of cis-bond units in isoprene units can be used, and the production method (1) is preferable because a dip-molded article having excellent tensile strength can be obtained.

Synthetic polyisoprene is a solution of isoprene in an inert polymerization solvent using, for example, a Ziegler polymerization catalyst composed of trialkylaluminum-titanium tetrachloride or an alkyllithium polymerization catalyst such as n-butyllithium or sec-butyllithium. It can be obtained by polymerization. The obtained synthetic polyisoprene polymerization solution can be used as it is, or after the solid synthetic polyisoprene is taken out from the polymerization solution, the solid synthetic polyisoprene can be dissolved in an organic solvent and used.

Also, commercially available solid synthetic polyisoprene can be used.

Examples of the organic solvent used in the above production method (1) include aromatic hydrocarbon solvents such as benzene, toluene and xylene; alicyclic hydrocarbon solvents such as cyclopentane, cyclopentene and cyclohexane; pentane, hexane and heptane. Aliphatic hydrocarbon solvents such as methylene chloride, chloroform, ethylene dichloride and the like; and the like. Of these, aromatic hydrocarbon solvents and alicyclic hydrocarbon solvents are preferable, and alicyclic hydrocarbon solvents are particularly preferable.

The amount of the organic solvent used is, for example, 2,000 parts by mass or less, preferably 20 to 1,500 parts by mass, more preferably 50 to 1,000 parts by mass with respect to 100 parts by mass of the synthetic polyisoprene. .

Examples of the surfactant include nonionic surfactants such as polyoxyethylene alkyl ether, polyoxyethylene alkylphenol ether, polyoxyethylene alkyl ester, polyoxyethylene sorbitan alkyl ester; myristic acid, palmitic acid, oleic acid, Salts of fatty acids such as linolenic acid, anionic surfactants such as alkylbenzene sulfonates such as sodium dodecylbenzenesulfonate, higher alcohol sulfates and alkylsulfosuccinates; alkyltrimethylammonium chloride, dialkylammonium chloride, benzylammonium chloride And other cationic surfactants. Copolymerizable surfactants such as sulfoesters of α, β-unsaturated carboxylic acids, sulfate esters of α, β-unsaturated carboxylic acids, and sulfoalkylaryl ethers can also be used. Of these, anionic surfactants are preferred. These surfactants can be used alone or in combination of two or more.

The amount of the surfactant used is preferably 0.5 to 50 parts by mass, more preferably 0.5 to 20 parts by mass with respect to 100 parts by mass of the synthetic polyisoprene. If it is 0.5 parts by mass or more, sufficient latex stability can be obtained, and if it is 50 parts by mass or less, it is economically advantageous, and it is difficult to foam, resulting in foaming during dip molding. The problem can be suppressed.

An apparatus for emulsifying an organic solvent solution of synthetic polyisoprene in water in the presence of a surfactant is not particularly limited as long as it is generally commercially available as an emulsifier or a disperser.

The method for adding the surfactant is not particularly limited, and it may be added in advance to an organic solvent solution of water and / or synthetic polyisoprene, or may be added to the emulsion during the emulsification operation. It may be added all at once or dividedly.

Examples of the emulsifier include batch type emulsifiers such as a homogenizer (manufactured by IKA), polytron (manufactured by Kinematica), and TK auto homomixer (manufactured by Special Machine Industries); TK pipeline homo mixer (special machine industry) Co., Ltd.), colloid mill (manufactured by Shinko Pantech Co., Ltd.), thrasher, trigonal wet pulverizer (manufactured by Mitsui Miike Chemical Co., Ltd.), Cavitron (manufactured by Eurotech Co., Ltd.), milder, fine flow mill (manufactured by Taiheiyo Kiko Co., Ltd.) Continuous emulsifiers; high-pressure emulsifiers such as microfluidizer (manufactured by Mizuho Kogyo), nanomizer (manufactured by Nanomizer), APV Gaurin (manufactured by Gaurin); Machine: Vibratory emulsifier such as Vibro mixer (manufactured by Chilling Industries Co., Ltd.); Ultrasonic emulsifier such as ultrasonic homogenizer (manufactured by Branson) And the like.

The conditions for the emulsification operation are not particularly limited, and a processing temperature, a processing time, and the like are appropriately selected so that a desired dispersion state is obtained.

Usually, the organic solvent is removed from the emulsion obtained through the emulsification operation to obtain a synthetic polyisoprene 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 the like can be employed.

Furthermore, if necessary, in order to increase the solid content concentration of the synthetic polyisoprene latex, a concentration operation may be performed by employing a method such as vacuum distillation, atmospheric distillation, centrifugation, membrane concentration or the like.

The solid content concentration of the synthetic polyisoprene latex is preferably 30 to 70% by mass, more preferably 40 to 70% by mass. If the solid content concentration is 30% by mass or more, the synthetic polyisoprene latex can be prevented from separating when the synthetic polyisoprene latex is stored, and if it is 70% by mass or less, the synthetic polyisoprene particles are aggregated. And generation of coarse aggregates can be suppressed.

The volume average particle diameter of the synthetic polyisoprene particles in the synthetic polyisoprene latex is preferably 0.05 to 3 μm, more preferably 0.2 to 2 μm. If the volume average particle diameter is 0.05 μm or more, the latex viscosity is not too high and handling is easy, and if it is 3 μm or less, a film is formed on the latex surface when the synthetic polyisoprene latex is stored. Can be suppressed, and handling becomes easy.

To the synthetic polyisoprene latex, additives such as a pH adjuster, an antifoaming agent, a preservative, a crosslinking agent, a chelating agent, an oxygen scavenger, and a dispersing agent may be blended within a range not impairing the effects of the present invention. it can. Examples of the pH adjuster include alkali metal hydroxides such as sodium hydroxide and potassium hydroxide; alkali metal carbonates such as sodium carbonate and potassium carbonate; alkali metal hydrogen carbonates such as sodium bicarbonate; ammonia An organic amine compound such as trimethylammonium or triethanolamine. Of these, alkali metal hydroxides or ammonia are preferably used.

The dip molding composition of the present invention contains a sulfur-based vulcanizing agent.

Examples of sulfur vulcanizing agents include powdered sulfur, sulfur white, precipitated sulfur, colloidal sulfur, surface-treated sulfur, insoluble sulfur, and the like; sulfur chloride, sulfur dichloride, morpholine disulfide, alkylphenol disulfide, N, N And sulfur-containing compounds such as' -dithio-bis (hexahydro-2H-azepinone-2), phosphorus-containing polysulfides, polymer polysulfides, and 2- (4'-morpholinodithio) benzothiazole. Of these, sulfur is preferably used.

The amount of the sulfur vulcanizing agent used is not particularly limited, but is preferably 0.1 to 10 parts by mass, more preferably 0.2 to 3 parts by mass with respect to 100 parts by mass of the synthetic polyisoprene. When the content is 0.1 to 10 parts by mass, the tensile strength of the dip-molded product can be improved.

The dip molding composition of the present invention contains zinc oxide.

The amount of zinc oxide used is not particularly limited, but is preferably 0.1 to 5 parts by mass, more preferably 0.2 to 2 parts by mass with respect to 100 parts by mass of the synthetic polyisoprene. By being 0.1 parts by mass or more, the tensile strength of the dip-molded product can be improved, and by being 5 parts by mass or less, the stability of the synthetic polyisoprene particles in the dip-molding composition is improved. Thus, the generation of coarse aggregates can be suppressed.

The dip molding composition of the present invention contains a vulcanization accelerator.

As the vulcanization accelerator, those usually used in dip molding can be used. For example, diethyldithiocarbamic acid, dibutyldithiocarbamic acid, di-2-ethylhexyldithiocarbamic acid, dicyclohexyldithiocarbamic acid, diphenyldithiocarbamic acid, dibenzyldithiocarbamic acid Dithiocarbamic acids and zinc salts thereof; 2-mercaptobenzothiazole, 2-mercaptobenzothiazole zinc, 2-mercaptothiazoline, dibenzothiazyl disulfide, 2- (2,4-dinitrophenylthio) benzothiazole, 2- (N , N-diethylthio-carbylthio) benzothiazole, 2- (2,6-dimethyl-4-morpholinothio) benzothiazole, 2- (4'-morpholino-dithio) benzothia Lumpur, 4-morpholinyl-2-benzothiazyl disulfide, 1,3-bis (2-benzothiazyl mercaptomethyl) such as urea and the like. Of these, zinc diethyldithiocarbamate, 2-mercaptobenzothiazole, and zinc 2-mercaptobenzothiazole are preferable. These vulcanization accelerators can be used alone or in combination of two or more.

The amount of the vulcanization accelerator used is preferably 0.05 to 5 parts by mass, more preferably 0.1 to 2 parts by mass with respect to 100 parts by mass of the synthetic polyisoprene. If it is 0.05 part by mass or more, the tensile strength of the dip-molded product does not decrease, and a suitable tensile strength can be obtained. Moreover, it can prevent that the elongation of a dip molded object falls that it is 5 mass parts or less, and can be set as suitable tensile strength.

The dip molding composition of the present invention contains a specific dispersant.

The dispersant used in the present invention includes an olefin compound having a weight average molecular weight of 1,000 to 150,000 and an ethylenically unsaturated dicarboxylic acid polymer salt and an olefin compound having a weight average molecular weight of 1,000 to 150,000. -At least one of the salts of the ethylenically unsaturated dicarboxylic acid monoester polymer.

The olefin compound forming the olefin compound-ethylenically unsaturated dicarboxylic acid polymer and the olefin compound-ethylenically unsaturated dicarboxylic acid monoester polymer is not particularly limited as long as it is a hydrocarbon compound having a carbon-carbon unsaturated bond. Α-olefins such as ethylene, propylene, 1-butene, 1-pentene, 1-hexene; cyclomonoolefins such as cyclobutene, cyclopentene, cyclohexene; 1,3-butadiene, isoprene, 1,3-pentadiene, cyclo Conjugated dienes such as pentadiene; vinyl aromatic hydrocarbons such as styrene, methylstyrene, ethylstyrene, and α-methylstyrene. Among these, vinyl aromatic hydrocarbons are preferable and styrene is more preferable because of excellent dispersion stabilization effect.

These olefin compounds can be used alone or in combination of two or more.

Examples of the ethylenically unsaturated dicarboxylic acid that forms the olefin compound-ethylenically unsaturated dicarboxylic acid polymer include fumaric acid, maleic acid, itaconic acid, citraconic acid, and the like. Since it forms a carboxyl group, ethylenically unsaturated dicarboxylic anhydrides such as maleic anhydride, itaconic anhydride, and citraconic anhydride can also be used. Of course, ammonium fumarate, sodium fumarate, maleic acid ammonium salt, maleic acid sodium salt, itaconic acid ammonium salt, citraconic acid ammonium salt, etc. which have previously formed a salt structure can also be used.

These ethylenically unsaturated dicarboxylic acids can be used alone or in combination of two or more.

Examples of the ethylenically unsaturated dicarboxylic acid monoester forming the olefin compound-ethylenically unsaturated dicarboxylic acid monoester polymer include monomethyl fumarate, monoethyl fumarate, monopropyl fumarate, monobutyl fumarate, monopentyl fumarate , Monomethyl maleate, monoethyl maleate, monopropyl maleate, monobutyl maleate, monopentyl maleate, monomethyl itaconate, monoethyl itaconate, monopropyl itaconate, monobutyl itaconate, monomethyl citraconic acid, monoethyl citraconic acid, citraconic acid Examples thereof include monopropyl and monobutyl citraconic acid. In addition, these ethylenically unsaturated dicarboxylic acid monoesters can be neutralized with a base in advance and used in a salt structure state.

These ethylenically unsaturated dicarboxylic acid monoesters can be used alone or in combination of two or more.

In addition, after forming a polymer of an olefin compound and an ethylenically unsaturated dicarboxylic acid anhydride, a corresponding alcohol such as methanol, ethanol, propanol, butanol is reacted with the dicarboxylic acid anhydride group in the polymer, It can also be converted to a monoester structure of dicarboxylic acid.

In the olefin compound-ethylenically unsaturated dicarboxylic acid polymer, the molar ratio between the unit derived from the olefin compound and the unit derived from the ethylenically unsaturated dicarboxylic acid is preferably 30:70 to 80:20, more preferably 40. : 60 to 75:25. Within this range, the dispersion stabilizing effect is superior.

In the olefin compound-ethylenically unsaturated dicarboxylic acid monoester polymer, the molar ratio between the unit derived from the olefin compound and the unit derived from the ethylenically unsaturated dicarboxylic acid monoester is preferably 30:70 to 80:20, More preferably, it is 40:60 to 75:25. Within this range, the dispersion stabilizing effect is superior.

The weight average molecular weights of the olefin compound-ethylenically unsaturated dicarboxylic acid polymer and the olefin compound-ethylenically unsaturated dicarboxylic acid monoester polymer are both 1,000 to 150,000, and 3,000 to 120,000. Is preferably in the range of 3,000 to 100,000, more preferably in the range of 3,000 to 100,000, and still more preferably in the range of 3,000 to 90,000. Even if the weight average molecular weight is low or high, the storage stability of the resulting dip-forming composition is poor.

The salt of the olefin compound-ethylenically unsaturated dicarboxylic acid polymer is converted to a salt structure by reacting with a base to neutralize the carboxyl group when the salt structure ethylenically unsaturated dicarboxylic acid is not used. Obtained.

Although it does not specifically limit as a base, Alkali metal hydroxides, such as sodium hydroxide and potassium hydroxide; Alkali metal carbonates, such as sodium carbonate and potassium carbonate; Alkali metal hydrogen carbonates, such as sodium hydrogencarbonate; Ammonia: Organic amine compounds such as trimethylammonium and triethanolamine. Of these, ammonia is preferably used.

The reaction rate of the neutralization reaction is preferably 70% or more, more preferably 80% or more, and complete neutralization is particularly preferable.

The salt of the olefin compound-ethylenically unsaturated dicarboxylic acid monoester polymer is obtained by reacting with a base to neutralize the carboxyl group when the salted ethylenically unsaturated dicarboxylic acid monoester is not used. Obtained by converting to structure.

The base used and the neutralization reaction rate are the same as described above.

The olefin compound-ethylenically unsaturated dicarboxylic acid polymer and the olefin compound-ethylenically unsaturated dicarboxylic acid monoester polymer can each be produced by conventional methods.

Mix the above-mentioned olefin compound, ethylenically unsaturated dicarboxylic acid and ethylenically unsaturated dicarboxylic acid monoester in desired ratio, organic peroxide such as benzoyl peroxide and cumene hydroperoxide, azobisisobutyronitrile, etc. This azo compound can be used as a polymerization initiator for polymerization.

The molecular weight of the polymer can be adjusted by adjusting the concentration of the polymerization initiator and the polymerization temperature, or adding an appropriate amount of a thiol compound or an alcohol compound that functions as a molecular weight regulator.

Commercial products can also be used for the olefin compound-ethylenically unsaturated dicarboxylic acid polymer, the olefin compound-ethylenically unsaturated dicarboxylic acid monoester polymer, and salts thereof.

The total amount of the olefin compound-ethylenically unsaturated dicarboxylic acid polymer salt and the olefin compound-ethylenically unsaturated dicarboxylic acid monoester polymer salt used is preferably 100 parts by mass of the synthetic polyisoprene. The amount is 0.1 to 10 parts by mass, and more preferably 0.5 to 3 parts by mass. By being 0.1 parts by mass or more, the storage stability of the dip molding composition is improved, and by being 10 parts by mass or less, foaming of the dip molding composition is suppressed, and a pinhole is formed in the dip molding. Can be prevented.

Since the salt of the olefin compound-ethylenically unsaturated dicarboxylic acid polymer and the salt of the olefin compound-ethylenically unsaturated dicarboxylic acid monoester polymer form a salt structure, they are easily dissolved in water and in an aqueous solution state. It can be handled. The concentration is not particularly limited, but is, for example, 5 to 45% by mass.

The dip molding composition of the present invention further requires a reinforcing agent such as carbon black, silica and talc; a filler such as calcium carbonate and clay; an anti-aging agent; an ultraviolet absorber; and a compounding agent such as a plasticizer. It can be blended accordingly.

Antiaging 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 such as reaction products; 2,2′-thiobis- (4-methyl-6-tert-butylphenol), 4,4′-thio Bis- (6-t-butyl-o-cresol), 2,6-di-t-butyl-4- (4,6-bis (octylthio) -1,3,5-triazin-2-ylamino) phenol, etc. Thiobisphenol antioxidants; phosphite antioxidants such as tris (nonylphenyl) phosphite, diphenylisodecyl phosphite, tetraphenyldipropylene glycol diphosphite; sulfur ester aging such as dilauryl thiodipropionate Inhibitors: phenyl-α-naphthylamine, phenyl-β-naphthylamine, p- (p-toluenesulfonylamide) -diphenylamine, 4,4 '-(α, α-dimethylbenzyl) diphenylamine, N, N-diphenyl-p- Phenylenediamine, N-isopropyl-N'-phenyl-p-pheny Amine-based anti-aging agents such as diamine and butyraldehyde-aniline condensates; quinoline anti-aging agents such as 6-ethoxy-2,2,4-trimethyl-1,2-dihydroquinoline; 2,5-di- (t -Amil) Hydroquinone anti-aging agents such as hydroquinone; These anti-aging agents can be used alone or in combination of two or more.

The amount of the anti-aging agent used is preferably 0.05 to 10 parts by mass, more preferably 0.1 to 5 parts by mass with respect to 100 parts by mass of the synthetic polyisoprene. If it is 0.05 mass part or more, a vulcanization reaction can fully be advanced. Moreover, if it is 10 mass parts or less, it is economically advantageous and the dip molded object of sufficient tensile strength can be obtained.

The method for preparing the dip molding composition is not particularly limited. As the adjustment method, using a dispersing machine such as a ball mill, a kneader, or a disper, a synthetic polyisoprene latex is blended with a sulfur-based vulcanizing agent, zinc oxide, a vulcanization accelerator and the above-described dispersing agent, and if necessary. After preparing an aqueous dispersion of the desired compounding ingredients other than the synthetic polyisoprene latex using the above-mentioned disperser or a method of mixing other compounding agents, the aqueous dispersion is mixed with the synthetic polyisoprene latex. The method of doing is mentioned. It is also possible to add other compounding agents after previously mixing the above-mentioned dispersant with the synthetic polyisoprene latex.

The pH of the dip molding composition is preferably 7 or more, more preferably in the range of pH 8-12.

The solid content concentration of the dip molding composition is, for example, in the range of 15 to 65% by mass.

The dip molding composition of the present invention is preferably aged (also referred to as pre-vulcanization) before being subjected to dip molding.

The pre-curing time is not particularly limited and depends on the pre-curing temperature, but is preferably 1 to 14 days, and more preferably 1 to 7 days. By setting the duration to 1 to 14 days, a dip-molded product having a suitable tensile strength can be obtained.

The pre-vulcanization temperature is preferably 20 to 40 ° C.

After pre-vulcanization, it is preferably stored at a temperature of 10 to 25 ° C. until it is used for dip molding. By setting the temperature to 10 to 25 ° C., a dip-molded product having a suitable tensile strength can be obtained.

The dip-molded product of the present invention is obtained by dip-molding the dip-molding composition of the present invention.

Dip molding is a method in which a mold is immersed in a dip molding composition, the composition is deposited on the surface of the mold, the mold is then lifted from the composition, and the composition deposited on the mold surface is dried. is there. The mold prior to being immersed in the dip molding composition can be preheated. A coagulant can be used as necessary before the mold is immersed in the dip molding composition or after the mold is pulled up from the dip molding composition. Specific examples of the method of using the coagulant include a method in which a mold before dipping in a dip molding composition is immersed in a coagulant solution to attach the coagulant to the mold (anode coagulation dipping method), a dip molding composition This is a method of immersing the mold in which the material is deposited in a coagulant solution (Teag adhesion dipping method).

An anode coagulation dipping method is preferred in that a dip-formed body with little thickness unevenness can be obtained.

Specific examples of coagulants 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; acetates such as barium acetate, calcium acetate, and zinc acetate Water-soluble polyvalent metal salts such as calcium sulfate, magnesium sulfate, and 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, and are preferably used in the form of an aqueous solution. This aqueous solution may further contain a water-soluble organic solvent such as methyl alcohol and ethyl alcohol, and 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 mass, more preferably 15 to 30% by mass.

After the mold is lifted from the dip molding composition, for example, the deposit formed on the mold is dried by heating. Drying conditions are appropriately selected.

Next, the deposit formed on the mold is vulcanized by heating.

The heating conditions during vulcanization are not particularly limited, but are preferably 60 to 150 ° C., more preferably 100 to 130 ° C., and preferably 10 to 120 minutes.

The method of heating is not particularly limited, and there are a method of heating with warm air in an oven, a method of heating by irradiating infrared rays, and the like.

Preferably, the mold is washed with water or warm water to remove water-soluble impurities (eg, excess surfactant, coagulant) before or after heating the mold on which the dip molding composition has been deposited. .

The dip-formed body after vulcanization is desorbed from the mold. Specific examples of the desorption method include a method of peeling from a mold by hand, a method of peeling by water pressure or compressed air pressure. If the dip-molded product being formed has sufficient strength against desorption, it may be desorbed in the middle step and then the subsequent processing may be continued.

When the dip-molded body is a glove, in order to prevent the dip-molded bodies from sticking to the contact surface and improve slipping during attachment and detachment, organic fine particles such as talc and calcium carbonate or starch particles are used as gloves. It may be dispersed 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.

Hereinafter, the present invention will be described in detail by way of examples, but the present invention is not limited to these examples. In the following, “%” and “part” are based on mass unless otherwise specified.

Various physical properties were measured as follows.
(1) Weight average molecular weight of synthetic polyisoprene Synthetic polyisoprene latex was dissolved in tetrahydrofuran so that the solid content concentration was 0.1% by mass. This solution was subjected to gel permeation chromatography analysis and calculated as a weight average molecular weight in terms of standard polystyrene.
(2) Amount of cis bond unit of synthetic polyisoprene Methanol was added to the synthetic polyisoprene latex and coagulated. The obtained coagulated product is dried and then analyzed by 1H-NMR, and expressed as a ratio of cis bond units to all isoprene units in the synthetic polyisoprene.
(3) Volume average particle diameter of synthetic polyisoprene latex The volume average particle diameter was determined using a light scattering diffraction particle measuring device (Coulter LS-230).
(4) Tensile Strength of Dip Molded Body The tensile strength of the dip molded body was measured based on ASTM D412. The dip-formed film was punched with a dumbbell (Die-C) to prepare a test piece for measuring tensile strength. The test piece was pulled at a tensile speed of 500 mm / min with a Tensilon universal testing machine (RTC-1225A manufactured by Orientec Co., Ltd.), and the tensile strength (unit: MPa) immediately before breaking was measured.
(5) Storage stability of dip molding composition The obtained dip molding composition was stored in a thermostatic bath at 30 ° C for 7 days. Thereafter, the dip-forming composition was passed through a 100-mesh wire mesh, and the dry mass of the aggregate remaining on the wire mesh was measured. It shows as a percentage of the total solid content in the dip molding composition of the dried aggregate. A large value indicates that the dip molding composition is inferior in storage stability.

(Production Example 1)
Synthetic polyisoprene (manufactured by Nippon Zeon Co., Ltd .: NIPOL IR2200L) was dissolved in cyclohexane to prepare a cyclohexane solution of polyisoprene having a solid content concentration of 10% by mass. The cyclohexane solution and a sodium dodecylbenzenesulfonate aqueous solution having a solid content concentration of 1.5% by mass were mixed at a mass ratio of 1: 1 and stirred. This operation was performed 10 times with a rotor-stator type emulsifier (Milk 307 manufactured by Taiheiyo Kiko Co., Ltd.) to obtain an emulsion. Cyclohexane is distilled off from the emulsion at 80 ° C. under a reduced pressure of −0.01 to −0.09 MPa, and then centrifuged with a continuous centrifuge (SGR509 manufactured by Alfa Laval) to obtain a solid concentration of 57 mass. % Synthetic polyisoprene latex was obtained. The volume average particle diameter of this synthetic polyisoprene latex was 1.0 μm. The weight average molecular weight of the synthetic polyisoprene was about 1,600,000, and the ratio of cis bond units was 98% by mass.

Example 1
While stirring the synthetic polyisoprene latex obtained in Production Example 1, an aqueous solution of ammonium salt (dispersant A) of styrene-maleic acid mono-n-butyl ester polymer (Arakawa Chemical Industries, Ltd .: Alastor 703S) An amount corresponding to 0.75 parts by mass in terms of solid content was added to 100 parts by mass of the solid content of the latex. Next, while stirring the obtained mixture, 1.5 parts by weight of zinc oxide, 1.5 parts by weight of sulfur, an anti-aging agent (made by Goodyear) in terms of solid content with respect to 100 parts by weight of synthetic polyisoprene in the mixture. Wingstay L) 2 parts by weight, 0.125 parts by weight of zinc diethyldithiocarbamate, 0.3 parts by weight of mercaptobenzothiazole zinc salt, after adding an aqueous dispersion of each compounding agent, and then adding an aqueous potassium hydroxide solution Thus, a dip molding composition having a pH adjusted to 10.5 was obtained. This was stored at 30 ° C. in a thermostatic bath.

(Dip molding)
A glass mold (diameter of about 5 cm, crushed portion length of about 15 cm) whose surface has been ground is washed, preheated in an oven at 70 ° C., then 16% by mass of calcium nitrate and 0.05% by mass of polyoxyethylene It was immersed in a coagulant aqueous solution made of lauryl ether (Emulgen 109P manufactured by Kao Corporation) for 5 seconds and taken out. The glass mold coated with the coagulant was then dried in an oven at 70 ° C. Thereafter, the glass mold coated with the coagulant was taken out from the oven, dipped in the dip molding composition for 10 seconds, taken out, and dried at room temperature for 60 minutes. The film-coated mold was placed in an oven, heated from 50 ° C. to 60 ° C. for 25 minutes and pre-dried, and then placed in a 70 ° C. oven for 10 minutes for further drying. The mold was immersed in warm water at 60 ° C. for 2 minutes and then air-dried at room temperature for 10 minutes. Thereafter, the mold coated with the film was placed in an oven and vulcanized at 100 ° C. for 60 minutes. The mold covered with the vulcanized film was cooled to room temperature, talc was sprayed, and then the film was peeled from the glass mold. The tensile strength of the obtained film was measured, and the results are shown in Table 1.

(Aging change of dip molding composition)
The dip-forming composition was stored at 30 ° C., and the dip-forming was performed every day to obtain a dip-formed body over time. The tensile strength of the obtained dip-molded product was measured, and the tensile strength of the dip-molded product obtained on the third day, the number of days when the tensile strength becomes maximum, and the tensile strength at that time are shown in Table 1.

(Example 2)
In place of Dispersant A, styrene-maleic acid mono-sec-butyl ester-maleic acid monomethyl ester polymer (manufactured by Hercules: Scriptset 550; the molar ratio of maleic acid mono-sec-butyl ester to maleic acid monomethyl ester is 2: 1) using an aqueous ammonium salt solution obtained by neutralizing 100% with aqueous ammonia as the dispersant B, and the blending amount thereof is 100 parts by mass of the solid content of the synthetic isoprene latex. This was performed in the same manner as in Example 1 except that the amount was changed to an amount corresponding to 1 part by mass in terms of solid content.

Evaluation results are shown in Table 1.

(Example 3)
Instead of the dispersant A, an aqueous ammonium salt solution obtained by neutralizing 100% of a styrene-maleic anhydride polymer (manufactured by Yoshitsumi Fujii Co., Ltd .: SMA-1000P) with aqueous ammonia is used as the dispersant C. The same procedure as in Example 1 was performed except that it was used.

Evaluation results are shown in Table 1.

(Comparative Example 1)
The same procedure as in Example 1 was performed except that the dispersant A was not added.

Evaluation results are shown in Table 1.

(Comparative Example 2)
Example of Example except that an aqueous ammonium salt solution obtained by neutralizing 100% of styrene-maleic anhydride polymer (manufactured by Hercules: Scriptset 520) with ammonia water instead of the dispersant A was used as the dispersant D. 1 was performed.

Evaluation results are shown in Table 1. However, since the whole composition for dip molding became agglomerated on the fourth day of storage, the subsequent evaluation was not performed.

(Comparative Example 3)
The same procedure as in Example 1 was performed except that sodium lauryl sulfate was used in place of Dispersant A.

Evaluation results are shown in Table 1.

In addition, the characteristic of the used dispersing agent is shown below.
[Dispersant A]: Ammonium salt of styrene-maleic acid mono-n-butyl ester polymer (Arakawa Chemical Industries, Ltd .; Alastor 703S)
Weight average molecular weight of styrene-maleic acid mono-n-butyl ester polymer = 13,800
[Dispersant B]: Ammonium salt of styrene-maleic acid mono-sec-butyl ester-maleic acid monomethyl ester polymer (manufactured by Hercules: Scripset 550) Styrene-maleic acid mono-sec-butyl ester-maleic acid monomethyl ester polymer Weight average molecular weight = 84,700
The molar ratio of maleic acid mono-sec-butyl ester to maleic acid monomethyl ester is 2: 1.
[Dispersant C]: Ammonium salt of styrene-maleic anhydride polymer (manufactured by Yoshitsumi Fujii Co., Ltd .: SMA-1000P) Weight average molecular weight of styrene-maleic anhydride polymer = 5,900
[Dispersant D]: Ammonium salt of styrene-maleic anhydride polymer (manufactured by Hercules: Scriptset 520) Weight average molecular weight of styrene-maleic anhydride polymer = 220,000
(Measurement of weight average molecular weight of dispersant)
Dispersant A was dropped into a 1% by mass hydrochloric acid aqueous solution, and the precipitate was thoroughly washed with ion-exchanged water, then dried and subjected to measurement.

Dispersants B to D were subjected to measurement as they were commercially available.

The molecular weight was measured by gel permeation chromatography using tetrahydrofuran as an eluent and TSKgel-SuperHZM-M manufactured by Tosoh Corporation as a column, and calculated as a weight average molecular weight in terms of standard polystyrene. For measurement of the dispersant D, TSKgel-SuperHM-H manufactured by Tosoh Corporation was used as a column.

Table 1 shows the following.

In the dip molding composition of Comparative Example 1 in which no dispersant was added, aggregates were formed, the storage stability was poor, the tensile strength on the third day was low, and the period until reaching the maximum tensile strength was long. .

The composition for dip molding of Comparative Example 2 using Dispersant D in which the weight average molecular weight of the dispersant is larger than the range of the present invention was inferior in storage stability and had a low tensile strength on the third day.

Although the dip molding composition of Comparative Example 3 to which sodium lauryl sulfate was added had good storage stability, the tensile strength on the third day was low and the period until reaching the maximum tensile strength was long.

In contrast to these comparative examples, the dip molding compositions of Examples 1 to 3, which are within the scope of the present invention, also have good storage stability, high tensile strength on the third day, and until the maximum tensile strength is reached. The period of was short.

The dip molding composition according to the present invention forms at least one of the salt of the olefin compound-ethylenically unsaturated dicarboxylic acid polymer and the salt of the olefin compound-ethylenically unsaturated dicarboxylic acid monoester polymer. More preferably, the olefin compound is styrene.

In the dip molding composition according to the present invention, the olefin compound-ethylenically unsaturated dicarboxylic acid polymer salt is more preferably a styrene-maleic acid polymer salt.

In the dip molding composition according to the present invention, the olefin compound-ethylenically unsaturated dicarboxylic acid monoester polymer is more preferably a styrene-maleic acid monoester polymer salt.

In the dip molding composition according to the present invention, at least one of the olefin compound-ethylenically unsaturated dicarboxylic acid polymer salt and the olefin compound-ethylenically unsaturated dicarboxylic acid monoester polymer salt is ammonium. More preferably, it is a salt.

Further, in the dip molding composition according to the present invention, the weight average molecular weight of the dispersant is more preferably 5,900 or more and 84,700 or less.

In the dip molding composition according to the present invention, the amount of the dispersant is more preferably 0.1 to 10 parts by mass with respect to 100 parts by mass of the synthetic polyisoprene latex.

In the dip molding composition according to the present invention, the synthetic polyisoprene forming the synthetic polyisoprene latex is more preferably a homopolymer of isoprene.

In the dip molding composition according to the present invention, the synthetic polyisoprene latex is produced by emulsifying a synthetic polyisoprene solution dissolved in an organic solvent in water in the presence of a surfactant. It is more preferable.

A molded product obtained by dip-molding the dip-forming composition of the present invention is a medical article such as a nipple for baby bottles, a dropper, a tube, a water pillow, a balloon sac, a catheter, and a condom; a toy such as a balloon, a doll, and a ball; It is suitable for industrial articles such as pressure forming bags and gas storage bags; surgical, diagnostic, household, agricultural, fishery and industrial gloves; finger sacks and the like.

Claims (10)

1. A composition for dip molding comprising a synthetic polyisoprene latex, a sulfur-based vulcanizing agent, zinc oxide, a vulcanization accelerator and a dispersing agent, wherein the dispersing agent has a weight average molecular weight of 1,000 to 150,000. It is at least one of a salt of an olefin compound-ethylenically unsaturated dicarboxylic acid polymer and a salt of an olefin compound-ethylenically unsaturated dicarboxylic acid monoester polymer having a weight average molecular weight of 1,000 to 150,000. A composition for dip molding characterized by the above.
2. 2. The dip according to claim 1, wherein the olefin compound forming at least one of the olefin compound-ethylenically unsaturated dicarboxylic acid polymer salt and the olefin compound-ethylenically unsaturated dicarboxylic acid monoester polymer salt is styrene. Molding composition.
3. 3. The dip molding composition according to claim 1, wherein the salt of the olefin compound-ethylenically unsaturated dicarboxylic acid polymer is a salt of a styrene-maleic acid polymer.
4. The dip molding composition according to any one of claims 1 to 3, wherein the olefin compound-ethylenically unsaturated dicarboxylic acid monoester polymer is a salt of a styrene-maleic acid monoester polymer.
5. 5. At least one of the salt of the olefin compound-ethylenically unsaturated dicarboxylic acid polymer and the salt of the olefin compound-ethylenically unsaturated dicarboxylic acid monoester polymer is an ammonium salt. The composition for dip molding as described in 2.
6. The dip molding composition according to any one of claims 1 to 5, wherein the dispersant has a weight average molecular weight of 5,900 or more and 84,700 or less.
7. The dip molding composition according to any one of claims 1 to 6, wherein the amount of the dispersant is 0.1 to 10 parts by mass with respect to 100 parts by mass of the synthetic polyisoprene latex.
8. The dip molding composition according to any one of claims 1 to 7, wherein the synthetic polyisoprene forming the synthetic polyisoprene latex is a homopolymer of isoprene.
9. 9. The synthetic polyisoprene latex is produced by emulsifying a synthetic polyisoprene solution dissolved in an organic solvent in water in the presence of a surfactant. Dip molding composition.
10. A dip-molded product obtained by dip-molding the dip-molding composition according to any one of claims 1 to 9.