JP2016160365A - Manufacturing method of synthetic isoprene polymer latex, synthetic isoprene polymer latex, composition for dip molding and dip molded body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method of a synthetic isoprene polymer latex capable of providing a dip molded body capable of obtaining high centrifugal separation yield and excellent in tensile strength.SOLUTION: A manufacturing method of a synthetic isoprene polymer latex by dissolving a synthetic isoprene polymer having weight average molecular weight (Mw) of 100,000 to 3,000,000 obtained by solution polymerization using an alkyl lithium polymerization catalyst in a hydrocarbon-based solvent having 5 o 8 carbon atoms and having viscosity measured at 25°C by a Brookfield viscometer of 100 to 70,000 mPa s includes an emulsification process of emulsifying the synthetic isoprene polymer solution to obtain an emulsified article, a desolvation process for desolvating the hydrocarbon-based solvent from the emulsified article and a centrifugal separation process for centrifugal separating the emulsified article desolvated in the desolvation process.SELECTED DRAWING: None

Description

  The present invention relates to a method for producing a synthetic isoprene polymer latex, a synthetic isoprene polymer latex, a dip-molding composition, and a dip-molded product. More specifically, a method for producing a synthetic isoprene polymer latex in which a polymer solution having a viscosity within a predetermined range is emulsified in the presence of a surfactant, desolvated, and centrifuged to obtain a synthetic isoprene polymer latex. The present invention relates to a synthetic isoprene polymer latex obtained by a production method, a dip molding composition containing the latex, and a dip molding obtained by dip molding the dip molding composition.

  Conventionally, it is known that a dip molding composition containing a latex of natural rubber is dip-molded to obtain a dip-molded body used in contact with a human body such as a nipple, a balloon, a glove, a balloon, and a sack. Yes. However, since natural rubber 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 product that is in direct contact with a living mucous membrane or an organ. For this reason, the demand for dip-molded bodies using latex of synthetic isoprene polymer rubber is rapidly increasing, and in order to meet the increasing demand year by year, it is required to improve the productivity of synthetic isoprene polymer latex. It was.

  As a method for improving productivity, there is a method of using a polymer solution obtained by dissolving a synthetic isoprene polymer, which is a raw material of a synthetic isoprene polymer latex, in a solvent while increasing the concentration. The polymer solution had a high viscosity, making it difficult to transport this solution. In addition, when emulsification operation is performed on a high concentration polymer solution, the particle size of the latex obtained after emulsification tends to increase, and concentration is performed using a centrifuge to increase the solid content concentration of the latex. In some cases, it was excessively concentrated and aggregated. For this reason, productivity may be reduced due to a decrease in centrifugal separation yield.

In addition, since surgical gloves require high tensile strength to prevent infection by doctors and nurses, it is necessary to design a large molecular weight of the synthetic isoprene polymer that is the base material of the gloves. However, when the molecular weight is increased, the viscosity of the polymer solution is rapidly increased, so that it is difficult to transfer the polymer solution to the pipe.
Therefore, it has been difficult to achieve both improvement in latex productivity and improvement in tensile strength of surgical gloves.

  Patent Document 1 discloses a method for producing a synthetic isoprene polymer latex. However, there is no specific explanation for the viscosity of the polymer solution, the solid content concentration, the particle size of the latex, and the centrifugation yield, and it is compatible with improving the productivity of the latex and obtaining a dip-molded body having excellent tensile strength. There was no mention of how to do it.

Special table 2009-553301 gazette

  An object of this invention is to provide the manufacturing method of the synthetic isoprene polymer latex which can obtain the high centrifugation yield and can obtain the dip-molding body excellent in tensile strength. It is another object of the present invention to provide a synthetic isoprene polymer latex obtained by this method, a dip molding composition containing the latex, and a dip molding obtained by dip molding the dip molding composition.

  As a result of earnest research to solve the above problems, the present inventors have used a synthetic isoprene polymer having a weight average molecular weight within a predetermined range, and by controlling the viscosity of the resulting polymer solution within a predetermined range, The inventors have found that the object can be achieved and have completed the present invention.

That is, according to the present invention,
(1) A synthetic isoprene polymer having a weight average molecular weight (Mw) of 100,000 to 3,000,000 obtained by solution polymerization using an alkyl lithium polymerization catalyst is dissolved in a hydrocarbon solvent having 5 to 8 carbon atoms. An emulsification step of emulsifying the synthetic isoprene polymer solution obtained by emulsifying the synthetic isoprene polymer solution having a viscosity of 100 to 70,000 mPa · s measured at 25 ° C. with a Brookfield viscometer; A method for producing a synthetic isoprene polymer latex comprising a desolvation step of desolvating the hydrocarbon solvent from the emulsion, and a centrifugation step of centrifuging the emulsion that has been desolvated in the desolvation step ,
(2) In the method according to (1), a synthetic isoprene polymer latex obtained by using a synthetic isoprene polymer having a cis bond unit (1,4-cis structure) content of 70% or more,
(3) Synthetic isoprene polymer latex obtained by the method according to (1), wherein the solid content concentration is 40% or more and the average particle size is 0.6 to 3.0 μm. ,
(4) A composition for dip molding comprising the synthetic isoprene polymer latex according to (2) or (3), sulfur, and a vulcanization accelerator,
(5) A dip-molded body obtained by dip-molding the dip-molding composition described in (4) is provided.

  ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of the synthetic isoprene polymer latex which can obtain a high centrifugation yield and can obtain the dip-molding body excellent in tensile strength is provided.

  Hereinafter, the manufacturing method of the synthetic isoprene polymer latex of this invention is demonstrated. The method for producing a synthetic isoprene polymer latex of the present invention comprises a synthetic isoprene polymer having a weight average molecular weight (Mw) of 100,000 to 3,000,000 obtained by solution polymerization using an alkyllithium polymerization catalyst. A synthetic isoprene polymer solution dissolved in a hydrocarbon solvent of 5 to 8 and having a viscosity of 100 to 70,000 mPa · s measured at 25 ° C. with a Brookfield viscometer. An emulsification step of emulsifying to obtain an emulsion, a desolvation step of desolvating the hydrocarbon solvent from the emulsion, and a centrifugation step of centrifuging the emulsion that has been desolvated in the desolvation step; including.

(Synthetic isoprene polymer)
The synthetic isoprene polymer used in the present invention is obtained by polymerizing isoprene by solution polymerization using an alkyl lithium polymerization catalyst.

  The synthetic isoprene polymer may be a copolymer of another ethylenically unsaturated monomer copolymerizable with isoprene. The content of isoprene units in the synthetic isoprene polymer is flexible, and it is easy to obtain a dip-molded product excellent in tensile strength. Therefore, it is preferably 70% by weight or more, more preferably 90%, based on all monomer units. % By weight or more, more preferably 95% by weight or more, particularly preferably 100% by weight (homopolymer of isoprene).

  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) And ethylenically unsaturated carboxylic acid ester monomers such as acrylic acid-2-ethylhexyl; and crosslinkable monomers such as divinylbenzene, diethylene glycol di (meth) acrylate, and pentaerythritol (meth) acrylate. In addition, the other ethylenically unsaturated monomer copolymerizable with these isoprenes may be used individually by 1 type, and may use multiple types together.

  The isoprene unit in the synthetic isoprene polymer includes a cis bond unit (1,4-cis structure), a trans bond unit (1,4-trans structure), a 1,2-vinyl bond unit, 3 depending on the bond state of isoprene. There are four types of 4-vinyl bond units.

  From the viewpoint of improving the tensile strength of the dip-molded product, the content of cis-bond units (1,4-cis structure) in the isoprene units contained in the synthetic isoprene polymer is preferably relative to the total isoprene units. It is 70% by weight or more, more preferably 75% by weight or more.

  The weight average molecular weight of the synthetic isoprene polymer used in the present invention is 100,000 to 3,000,000, preferably 200,000 to 2,500,000 in terms of standard polystyrene by gel permeation chromatography analysis. Particularly preferred is 300,000 to 2,000,000. It is. If the weight average molecular weight of the synthetic isoprene polymer is too small, the tensile strength of the resulting dip-molded product tends to decrease, and conversely if too large, the synthetic isoprene polymer latex tends to be difficult to produce. In addition, the viscosity of the synthetic isoprene polymer solution tends to be high, and piping transportation tends to be difficult.

  In addition, the molecular weight distribution of the synthetic isoprene polymer used in the present invention is the ratio (Mw / Mw) of the weight average molecular weight (Mw) and the number average molecular weight (Mn) measured as a value in terms of polystyrene by gel permeation chromatography. Mn) is preferably 1.0 to 2.2.

Moreover, the polymer Mooney viscosity [ML1 _{+ 4} , 100 degreeC] of a synthetic isoprene polymer is 50-80, Preferably it is 60-80, Most preferably, it is 70-80.

  The synthetic isoprene polymer used in the present invention can be obtained by solution polymerization of isoprene in an inert polymerization solvent using an alkyl lithium polymerization catalyst. Examples of the alkyl lithium polymerization catalyst include n-butyl lithium and sec-butyl lithium, and it is more preferable to use n-butyl lithium.

  In the present invention, it is preferable to use a polymerization accelerator in addition to the polymerization catalyst in the polymerization of the synthetic isoprene polymer. As the polymerization accelerator, tetramethylethylenediamine (TMEDA), hexamethylphosphoramide (HMPA), N, N′-dimethylpropyleneurea (DMPU), dimethylsulfoxide (DMSO), or the like can be used. Among these, it is preferable to use TMEDA.

  In addition, after synthesizing the synthetic isoprene polymer, impurities such as a polymerization catalyst residue remaining in the polymer solution may be removed. Moreover, you may add the anti-aging agent mentioned later to the solution during superposition | polymerization or after superposition | polymerization.

  The synthetic isoprene polymer solution used in the present invention is obtained by dissolving a synthetic isoprene polymer in a hydrocarbon solvent having 5 to 8 carbon atoms. In addition, what was mentioned above can be used as a synthetic isoprene polymer.

Examples of the hydrocarbon solvent having 5 to 8 carbon atoms include aromatic hydrocarbon solvents such as benzene, toluene and xylene; alicyclic hydrocarbon solvents such as cyclopentane, cyclopentene, cyclohexane and cyclohexene; 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, alicyclic hydrocarbon solvents, and aliphatic hydrocarbon solvents are preferable, and cyclohexane, toluene, n-hexane, and pentane are particularly preferable.
In addition, the usage-amount of a hydrocarbon type solvent becomes like this. Preferably it is 2,000 weight part or less with respect to 100 weight part of synthetic isoprene polymers, More preferably, it is 20-1,500 weight part.

  The viscosity of the synthetic isoprene polymer solution used in the present invention is 100 to 70,000 mPa · s, preferably 1,000 to 30,000 mPa · s, and more preferably 5,000 to 20,000 mPa · s. If the viscosity of the synthetic isoprene polymer solution is too high or too low, the centrifugal separation yield of the latex tends to deteriorate. Moreover, when the viscosity of the synthetic isoprene polymer solution is too high, the transfer tends to be difficult. The viscosity is a value measured at 25 ° C. with a Brookfield viscometer (hereinafter sometimes referred to as “B-type viscometer”).

  The solid content concentration of the synthetic isoprene polymer solution used in the present invention is not particularly limited, but is preferably 5 to 50% by weight, more preferably 10 to 40% by weight. If the solid concentration is too high or too low, the latex centrifuge yield tends to deteriorate.

  As a method for preparing a synthetic isoprene polymer solution, for example, a method in which the above-mentioned hydrocarbon solvent is used as a solvent during solution polymerization, and a polymer solution of a synthetic isoprene polymer obtained by solution polymerization is used as it is, the polymer solution The solid synthetic isoprene polymer is taken out from the solution, and then the solid synthetic isoprene polymer is dissolved in a hydrocarbon solvent and used. Polymerization of the synthetic isoprene polymer obtained by solution polymerization A method using the solution as it is is preferred.

(Emulsification process)
In the emulsification step of the present invention, the synthetic isoprene polymer solution is emulsified in water in the presence of a surfactant to obtain an emulsion.

  Examples of the surfactant include nonionic surfactants such as polyoxyethylene alkyl ether, polyoxyethylene alkylphenol ether, polyoxyethylene alkyl ester, polyoxyethylene sorbitan alkyl ester; lauric acid, myristic acid, palmitic acid, Anionic surfactants such as sodium or potassium salts of fatty acids such as oleic acid, linolenic acid, rosin acid, alkylbenzene sulfonates such as sodium dodecylbenzene sulfonate, higher alcohol sulfates, alkyl sulfosuccinates; alkyl trimethyl ammonium Cationic surfactants such as chloride, dialkyldimethylammonium chloride, alkylbenzyldimethylammonium chloride; sulfates of α, β-unsaturated carboxylic acids Copolymerizable surfactants such as phosphate esters, sulfate esters of α, β-unsaturated carboxylic acids, sulfoalkylaryl ethers, and the like. Anionic surfactants are preferred, such as sodium rosinate and rosin acid. Potassium and sodium dodecylbenzenesulfonate are particularly preferred. In addition, these surfactants may be used individually by 1 type, and may use 2 or more types together.

  The amount of the surfactant used is preferably 0.5 to 50 parts by weight, more preferably 0.5 to 30 parts by weight with respect to 100 parts by weight of the synthetic isoprene polymer. If the amount is too small, the stability of the latex tends to be inferior. On the other hand, if the amount is too large, foaming tends to occur and problems may occur during dip molding.

  The amount of water used in the emulsification step is preferably 50 to 5,000 parts by weight, more preferably 100 to 3,000 parts by weight with respect to 100 parts by weight of the synthetic isoprene polymer.

  Examples of the water used include hard water, soft water, ion exchange water, distilled water, and zeolite water. Moreover, you may use together the polar solvent represented by alcohol, such as methanol, with water.

  An apparatus for emulsifying the synthetic isoprene polymer solution 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 may be added to water and / or a synthetic isoprene polymer solution in advance, 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 a batch type emulsifier such as trade name: homogenizer (manufactured by IKA), trade name: polytron (manufactured by Kinematica), trade name: TK auto homomixer (manufactured by Tokushu Kika Kogyo Co., Ltd.), etc. Name: TK Pipeline Homomixer (manufactured by Koki Kogyo Kogyo Co., Ltd.), Product Name: Colloid Mill (made by Shinko Pantech Co., Ltd.), Product Name: Thrasher (manufactured by Nihon Coke Kogyo Co., Ltd.), Product Name: Trigonal Wet Fine Crusher ( Product name: Cavitron (manufactured by Eurotech), product name: Milder (manufactured by Taiheiyo Kiko Co., Ltd.), product name: Fine Flow Mill (manufactured by Taiheiyo Kiko Co., Ltd.), etc. Name: Microfluidizer (manufactured by Mizuho Kogyo Co., Ltd.), Product name: Nanomizer (manufactured by Nanomizer Co., Ltd.), Product name: APV Gaurin (manufactured by Gaulin Co., Ltd.), etc .; Membrane emulsifiers such as chemical generators (manufactured by Chilling Industries Co., Ltd.); Product name: Vibrating emulsifiers such as Vibro mixers (manufactured by Chilling Industries Co., Ltd.); Machine; and the like. In addition, the conditions of the emulsification operation by the emulsification apparatus are not particularly limited, and the treatment temperature, the treatment time, and the like may be appropriately selected so as to obtain a desired dispersion state.

(Desolvation process)
In the desolvation step of the present invention, the hydrocarbon solvent is removed from the emulsion obtained through the emulsification step to obtain a synthetic isoprene polymer latex. As a method for removing the hydrocarbon solvent from the emulsion, a method such as vacuum distillation, atmospheric distillation, steam distillation, and centrifugal separation can be employed. Distillation and atmospheric distillation are preferred. As for the temperature of vacuum distillation and atmospheric distillation, 50-100 degreeC is preferable. The pressure of vacuum distillation is preferably −50 to −1 kPa (gauge pressure).
In addition, you may perform operation which removes an aggregate before and after a solvent removal process.

(Centrifugation process)
In the centrifugation step of the present invention, a synthetic isoprene polymer latex having a high solid content is obtained by subjecting the synthetic isoprene polymer latex obtained through the solvent removal step to a concentration operation by centrifugation.

  In the centrifugation step, the synthetic isoprene polymer latex obtained through the solvent removal step is centrifuged for concentration to obtain a synthetic isoprene polymer latex concentrated as a light liquid and synthesized as a heavy liquid. It is preferable to obtain a waste liquid containing an isoprene polymer and a surfactant.

  Centrifugation uses, for example, a centrifugal separator, preferably having a centrifugal force of 2,000 to 5,000 G, and a solid content concentration of the synthetic isoprene polymer latex obtained through the solvent removal step, preferably 2 to 15% by weight. The back pressure (gauge pressure) of the centrifuge can be preferably set to 0.03 to 1.6 MPa. Moreover, when using a continuous centrifuge, as for the flow rate sent to a continuous centrifuge, 500-2,000 Kg / hr is preferable.

  The centrifuge is not particularly limited. For example, a continuous centrifuge such as a trade name “SRG610” (manufactured by Alfa Laval Co., Ltd.), or a papillary centrifuge such as a trade name “H-2000B” (manufactured by Kokusan Co., Ltd.). However, a continuous centrifuge is preferable because of its high processing capacity.

  The centrifugation yield in the centrifugation step is preferably 75% or more, more preferably 85% or more.

  The solid content concentration of the synthetic isoprene polymer latex obtained through the centrifugation step is preferably 40% by weight or more, more preferably 40 to 70% by weight, and still more preferably 50 to 70% by weight. If the solid content concentration is too low, there is a concern that the synthetic isoprene polymer particles may be separated when the synthetic isoprene polymer latex is stored. Conversely, if the solid content concentration is too high, the synthetic isoprene polymer particles are aggregated to form coarse aggregates. May occur.

  The average particle diameter of latex particles (synthetic isoprene polymer particles) in the synthetic isoprene polymer latex is preferably 0.6 to 3.0 μm, more preferably 0.8 to 2.0 μm. If this average particle diameter is too small, the latex viscosity may become too high, making it difficult to handle. In addition, the centrifugal separation yield of latex tends to deteriorate. If the average particle size is too large, a film may be formed on the latex surface when the synthetic isoprene polymer latex is stored.

  The average particle diameter of latex particles is a volume average particle diameter calculated by measuring with a laser diffraction particle size distribution analyzer (for example, SALD-2200; manufactured by Shimadzu Corporation).

The conductivity of the synthetic isoprene polymer latex is preferably 0.5 mS / cm to 2.0 mS / cm. When the conductivity is less than 0.5 mS / cm, a large amount of aggregates may be generated during emulsification or concentration. In addition, when the electrical conductivity exceeds 2.0 mS / cm, foaming becomes severe at the time of solvent removal, foaming is severe when the composition for dip molding is transferred or blended, and pinholes are formed in the resulting dip molded body. Defects may occur.
The conductivity is a value measured at a measurement temperature of 25 ° C. using a conductivity meter (trade name: SG78-FK2) manufactured by METLER TOLEDO.

  The total content of the alicyclic hydrocarbon solvent, the aliphatic hydrocarbon solvent and the aromatic hydrocarbon solvent in the synthetic isoprene polymer latex is preferably 500 ppm by weight or less. In addition, cyclohexane is preferable as the alicyclic hydrocarbon solvent, normal pentane is preferable as the aliphatic hydrocarbon solvent, and toluene is preferable as the aromatic hydrocarbon solvent. If the total content of the alicyclic hydrocarbon solvent, aliphatic hydrocarbon solvent and aromatic hydrocarbon solvent, especially the total content of cyclohexane, pentane and toluene, is too high, the odor of the composition for dip molding tends to be tight. is there.

  The total content of the hydrocarbon solvent can be measured by a generally usable measuring method such as a gas chromatography method.

  In addition, the synthetic isoprene polymer tex usually contains a pH adjuster, antifoaming agent, preservative, crosslinking agent, chelating agent, oxygen scavenger, dispersant, anti-aging agent, etc. An agent may be blended.

  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 trimethylamine or triethanolamine; an alkali metal hydroxide or ammonia is preferred.

(Dip molding composition)
The dip molding composition of the present invention preferably comprises the synthetic isoprene polymer latex, a vulcanizing agent, and a vulcanization accelerator. Moreover, the other component may be included as needed.

(Vulcanizing agent)
Examples of the vulcanizing agent include sulfur such as powdered sulfur, sulfur white, precipitated sulfur, colloidal sulfur, surface-treated sulfur, insoluble sulfur, etc .; sulfur chloride, sulfur dichloride, morpholine disulfide, alkylphenol disulfide, N, N′— Sulfur-containing compounds such as dithio-bis (hexahydro-2H-azepinone-2), phosphorus-containing polysulfide, polymer polysulfide, 2- (4′-morpholinodithio) benzothiazole, and the like can be used. In the present invention, sulfur can be preferably used. These vulcanizing agents may be used alone or in combination of two or more.

  Although the usage-amount of a vulcanizing agent is not specifically limited, Preferably it is 0.1-10 weight part with respect to 100 weight part of synthetic isoprene polymers, More preferably, it is 0.2-3 weight part. If the amount is too small or too large, the tensile strength of the dip-molded product tends to decrease.

(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 and the like. Dithiocarbamic acids and their zinc salts; 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) benzothiazo And 4-morpholinyl-2-benzothiazyl disulfide, 1,3-bis (2-benzothiazyl mercaptomethyl) urea, etc., but zinc diethyldithiocarbamate, 2-mercaptobenzothiazole, and 2-mercaptobenzothiazole zinc preferable. These vulcanization accelerators may 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 weight, more preferably 0.1 to 2 parts by weight with respect to 100 parts by weight of the synthetic isoprene polymer. If this amount is small, the tensile strength of the dip-molded product may decrease. On the other hand, if this amount is excessive, the elongation and tensile strength of the dip-formed product may be lowered.

(Other ingredients)
(Zinc oxide)
The dip molding composition preferably further contains zinc oxide. The content of zinc oxide is not particularly limited, but is preferably 0.1 to 5 parts by weight, more preferably 0.2 to 2 parts by weight with respect to 100 parts by weight of the synthetic isoprene polymer. If this amount is too small, the tensile strength of the dip-molded product tends to decrease. Conversely, if it is too large, the stability of the isoprene polymer particles in the dip-molding composition decreases and coarse aggregates are generated. There is a case.

(Dispersant)
The dip molding composition may contain a dispersant as necessary, and examples of the dispersant include sodium lauric acid, myristic acid, palmitic acid, oleic acid, linolenic acid and rosinic acid, Examples include potassium salts and anionic surfactants such as alkylbenzene sulfonates such as sodium dodecylbenzenesulfonate, higher alcohol sulfates, and alkylsulfosuccinates. Sodium dodecylbenzenesulfonate is particularly preferable. In addition, these surfactants may be used individually by 1 type, and may use 2 or more types together.

  The amount of the dispersant used is preferably 0.01 to 5 parts by weight and more preferably 0.05 to 3 parts by weight with respect to 100 parts by weight of the synthetic isoprene polymer. If this amount is small, the blending stability of the dip-forming composition may be reduced, or aggregates may increase during pre-vulcanization. On the other hand, if this amount is excessive, the dip-forming composition tends to foam and pinholes are likely to occur.

(Combination agent)
The dip molding composition further includes an anti-aging agent; a reinforcing agent such as carbon black, silica and talc; a filler such as calcium carbonate and clay; an ultraviolet absorber; a plasticizer; Can be blended.

  Anti-aging agents include 2,6-di-4-methylphenol, 2,6-di-t-butylphenol, butylhydroxyanisole, 2,6-di-t-butyl-α-dimethylamino-p-cresol, Octadecyl-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate, styrenated phenol, 2,2′-methylene-bis (6-α-methyl-benzyl-p-cresol), 4, Butylation of 4'-methylenebis (2,6-di-tert-butylphenol), 2,2'-methylene-bis (4-methyl-6-tert-butylphenol), alkylated bisphenol, p-cresol and dicyclopentadiene Phenol-based antioxidants containing no sulfur atom, such as reaction products; 2,2′-thiobis- (4-methyl-6-tert-butylphenol) ), 4,4′-thiobis- (6-tert-butyl-o-cresol), 2,6-di-tert-butyl-4- (4,6-bis (octylthio) -1,3,5-triazine Thiobisphenol-based antioxidants such as 2-ylamino) phenol; phosphite-based antioxidants such as tris (nonylphenyl) phosphite, diphenylisodecyl phosphite, tetraphenyldipropylene glycol diphosphite; thiodipropionic acid Sulfur ester type antioxidants such as dilauryl; phenyl-α-naphthylamine, phenyl-β-naphthylamine, p- (p-toluenesulfonylamido) -diphenylamine, 4,4 ′-(α, α-dimethylbenzyl) diphenylamine, N , N-Diphenyl-p-phenylenediamine, N-isopropyl-N′-F Amine-based antioxidants such as nyl-p-phenylenediamine and butyraldehyde-aniline condensates; quinoline antioxidants such as 6-ethoxy-2,2,4-trimethyl-1,2-dihydroquinoline; -Hydroquinone anti-aging agents such as di- (t-amyl) hydroquinone; These anti-aging agents may 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 weight, more preferably 0.1 to 5 parts by weight with respect to 100 parts by weight of the synthetic isoprene polymer. If this amount is too small, the synthetic isoprene polymer may deteriorate. Moreover, when there is too much this quantity, the tensile strength of a dip molded object may fall.

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, a disper, etc., a latex of a synthetic isoprene polymer, a vulcanizing agent, a vulcanization accelerator, and zinc oxide blended as necessary, and aging prevention After preparing an aqueous dispersion of a desired compounding component other than a synthetic isoprene polymer latex using a method of mixing other compounding agents such as an agent or the above-mentioned disperser in advance, the aqueous dispersion is synthesized with synthetic isoprene. The method of mixing with the latex of a polymer is mentioned. In addition, after the above-mentioned dispersant is mixed in advance with the latex of the synthetic isoprene polymer, other compounding agents such as a vulcanizing agent, a vulcanization accelerator, and an anti-aging agent can be added.
The pH of the dip molding composition is preferably 7 or more, more preferably in the range of pH 8-12.
Moreover, the solid content concentration of the dip molding composition is, for example, in the range of 15 to 65% by weight.

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

  The time for the pre-vulcanization is not particularly limited and depends on the pre-vulcanization temperature, but is preferably 1 to 14 days, and more preferably 1 to 7 days. If this time is too short or too long, the tensile strength of the resulting dip-formed product tends to decrease.

  After pre-vulcanization, it is preferably stored at a temperature of 10 ° C. to 30 ° C. until it is used for dip molding. When stored at a high temperature, the tensile strength of the resulting dip-molded product tends to decrease.

(Dip molded body)
The dip-molded body of the present invention can be 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 before dipping in the dip molding composition may 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). Among these, the anode coagulation dipping method is preferable 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 weight, more preferably 8 to 30% by weight.

  After the mold is lifted from the dip molding composition, for example, the deposit formed on the mold is dried by heating. Drying conditions can be selected as appropriate.

  Subsequently, the deposit formed on the mold is vulcanized by heating. The heating conditions at the time of 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 heating method is not particularly limited, and examples thereof include a method of heating with warm air in an oven and a method of heating by irradiating infrared rays.

  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.

  EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not limited to these Examples. The following “%” and “part” are based on weight unless otherwise specified. Various physical properties were measured as follows.

The weight average molecular weight synthetic isoprene polymer latex was dissolved in tetrahydrofuran so that the solid content concentration was 0.04% by weight. This solution was subjected to gel permeation chromatography analysis and calculated as a weight average molecular weight in terms of standard polystyrene.

Content of cis-bond units (1,4-cis structure) Methanol was added to the synthetic isoprene polymer latex obtained in the examples and comparative examples to coagulate. The obtained solidified product was dried and analyzed by ¹ H-NMR to show the content of cis-bond units (1,4-cis structure) relative to all isoprene units in the synthetic isoprene polymer.

The solid content concentration of the solid content synthetic isoprene polymer solution, the latex before centrifugation and the latex after centrifugation was precisely weighed in an aluminum dish (weight: X1) whose weight was measured in advance (weight: X2). This was dried with a dryer at 105 ° C. for 2 hours and cooled in a desiccator, and then the weight of the entire aluminum pan was measured (weight: X3), and determined by the following formula. In addition, the solid content concentration of the latex before centrifugation was used for calculation of the centrifugation yield mentioned later.
Solid content concentration (% by weight) = [(X3−X1) / X2] × 100

Synthetic isoprene polymer solution viscosity In the examples and comparative examples, the viscosity of the synthetic isoprene polymer solution was measured at 25 ° C using a B-type viscometer (Brookfield viscometer, model BH, manufactured by Tokyo Keiki Co., Ltd.). did.
Specifically, 200 ml of the synthetic isoprene polymer solution was placed in a glass beaker having a capacity of 300 ml, and the viscosity was measured by immersing the rotor in this solution up to the line marked on the rotor.

Average particle diameter The volume average particle diameter of the latex particles obtained in the examples and comparative examples was measured using a laser diffraction particle size distribution analyzer (SALD-2200, manufactured by Shimadzu Corporation).

Centrifugal Yield Synthetic isoprene polymer latex (weight: weight): Centrifuge (H-2000B, manufactured by Kokusan Co., Ltd.) and rotor MN X4) was added, the temperature was set to 20 ° C., and centrifugation was performed at a rotation speed of 3500 rpm for 30 minutes. After the rotation stopped, a light liquid (weight: X5) was scraped from the centrifuge tube, and the centrifugal separation yield was calculated from the following formula.
Centrifugal yield (%) = [(X5 × latex solid content after centrifugation) / (X4 × latex solid content before centrifugation)] × 100

Tensile strength and elongation at break of the dip-formed product The tensile strength and elongation at break of the dip-formed product were measured based on ASTM D412. Specifically, the dip-molded film was punched with a dumbbell (Die-C: manufactured by Dumbbell) 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 and the elongation (unit:%) immediately before breaking were measured. And tensile strength and elongation at break, respectively.

Example 1
(Production of synthetic isoprene polymer)
In a dried and nitrogen-substituted autoclave with stirring, 1150 parts of cyclohexane, 100 parts of isoprene and 0.0070 part of tetramethylethylenediamine (hereinafter sometimes referred to as “TMEDA”) were charged. The temperature in the autoclave was adjusted to 60 ° C., and 0.013 part of a 15 wt% hexane catalyst solution of n-butyllithium was added and stirred for 1 hour while stirring. The polymerization reaction rate was 99%. 0.0031 parts of methanol was added as a polymerization terminator to the resulting synthetic isoprene polymer solution (hereinafter sometimes referred to as “polymer solution”) to stop the reaction. The obtained synthetic isoprene polymer had a weight average molecular weight (Mw) of 400,000, Mw / Mn = 1.1, and a cis bond unit (1,4-cis structure) content of 75%. The polymer solution had a solid content concentration of 8.0% and a Brookfield viscosity of 200 mPa · s.

(Production of synthetic isoprene polymer latex)
A total amount of 1250 parts of this synthetic isoprene polymer in cyclohexane solution (100 parts of synthetic isoprene polymer, 1150 parts of cyclohexane) and 0.8% by weight of “Longis N-18” (manufactured by Arakawa Chemical Co., Ltd.) 1250 parts of an aqueous activator solution was prepared.

  The total amount of the cyclohexane solution of the synthetic isoprene polymer and the total amount of the surfactant aqueous solution were placed in a SUS304 container and mixed by stirring. Subsequently, the homogenizer (trade name “Milder MDN-303V”, Taiheiyo Kiko ( Emulsified dispersion treatment was performed by the company), and the emulsified mixed liquid was obtained.

  Next, cyclohexane was distilled off from the emulsified liquid mixture in a solvent removal tank to obtain a synthetic isoprene polymer latex. And the aggregate in the synthetic isoprene polymer latex was removed using a 200 mesh stainless steel wire mesh.

  Next, the rotor MN was set in a cooling centrifuge (model “H-2000B”, manufactured by Kokusan Co., Ltd.), and the obtained latex was put in a centrifuge tube having a capacity of 500 ml. This was centrifuged for 30 minutes at a set temperature of 20 ° C. and a rotation speed of 3500 rpm. Immediately after the rotation stopped, the light liquid was scraped from the centrifuge tube to obtain the synthetic isoprene polymer latex of Example 1. Aggregates were not seen and the centrifugation yield was 91%. The resulting synthetic isoprene polymer latex had a solid content concentration of 66% and an average particle size of 2.06 μm.

(Preparation of dip molding composition)
While stirring the resultant synthetic isoprene polymer latex, sodium dodecylbenzenesulfonate having a concentration of 10% by weight was added to 100 parts of the synthetic isoprene polymer so as to be 1 part in terms of solid content. Then, while stirring the obtained mixture, 1.5 parts of zinc oxide, 1.5 parts of sulfur, an antioxidant (trade name: Wingstay) in terms of solid content with respect to 100 parts of the synthetic isoprene polymer in the mixture. L, manufactured by Goodyear) 3 parts, 0.3 parts zinc diethyldithiocarbamate, 0.5 parts zinc dibutyldithiocarbamate, 0.7 parts zinc mercaptobenzothiazole zinc were added to each component. Thereafter, an aqueous potassium hydroxide solution was added to obtain a dip molding composition having a pH adjusted to 10.5.
Thereafter, the obtained dip molding composition was aged in a constant temperature water bath adjusted to 30 ° C. for 48 hours.

(Manufacture of dip-molded bodies)
A commercially available ceramic hand mold (manufactured by Shinko Co., Ltd.) was washed and preheated in an oven at 70 ° C., and then 18 wt% calcium nitrate and 0.05 wt% polyoxyethylene lauryl ether (trade name: Emulgen 109P) The product was immersed in a coagulant solution made of Kao Corporation for 5 seconds and taken out. Next, the hand mold coated with the coagulant was dried in an oven at 70 ° C. for 30 minutes or more.

  Thereafter, the hand mold coated with the coagulant was taken out of the oven and immersed in the dip molding composition for 10 seconds. Then, after air-drying for 10 minutes at room temperature, this hand mold was immersed in 60 degreeC warm water for 5 minutes. Further, after being placed in an oven at 130 ° C. and vulcanized for 30 minutes, it was cooled to room temperature, sprayed with talc, and then peeled off from the hand mold. Table 1 shows the measurement results of the tensile strength and elongation at break of the obtained dip-molded body.

Example 2
In the production of the synthetic isoprene polymer, polymerization was carried out in the same manner as in Example 1 except that TMEDA was not used and the amount of the n-butyllithium 15 wt% hexane catalyst solution was changed to 0.0057 parts. A synthetic isoprene polymer having an average molecular weight (Mw) of 900,000, Mw / Mn = 1.2, and a cis bond unit (1,4-cis structure) content of 84% was obtained. The polymer solution had a solid content concentration of 8.0% and a Brookfield viscosity of 6,000 mPa · s.

  Further, except that the synthetic isoprene polymer obtained in Example 2 was used, the production of the synthetic isoprene polymer latex, the preparation of the composition for dip molding, and the production of the dip molded body were carried out in the same manner as in Example 1. went. Using the obtained synthetic isoprene polymer latex, the centrifugation yield was calculated and the average particle size of the latex was measured in the same manner as in Example 1. Furthermore, tensile strength and elongation at break were evaluated using the obtained dip-molded body.

Example 3
In the production of the synthetic isoprene polymer, the same as Example 1 except that the amount of TMEDA was changed to 0.00012 part and the amount of n-butyllithium 15 wt% hexane catalyst solution was changed to 0.0053 part. Polymerization was carried out to obtain a synthetic isoprene polymer having a weight average molecular weight (Mw) of 1,200,000, Mw / Mn = 1.2, and a cis bond unit (1,4-cis structure) content of 85%. The polymer solution had a solid content concentration of 8.0% and a Brookfield viscosity of 12,000 mPa · s.

  Further, except that the synthetic isoprene polymer obtained in Example 3 was used, the production of the synthetic isoprene polymer latex, the preparation of the dip-molding composition, and the production of the dip-molded body were performed in the same manner as in Example 1. went. Using the obtained synthetic isoprene polymer latex, the centrifugation yield was calculated and the average particle size of the latex was measured in the same manner as in Example 1. Furthermore, tensile strength and elongation at break were evaluated using the obtained dip-molded body.

Example 4
In the production of the synthetic isoprene polymer, the same as Example 1 except that the amount of TMEDA was changed to 0.00024 part and the amount of n-butyllithium 15 wt% hexane catalyst solution was changed to 0.0053 part. Polymerization was performed to obtain a synthetic isoprene polymer having a weight average molecular weight (Mw) of 154,000, Mw / Mn = 1.4, and a cis bond unit (1,4-cis structure) content of 85%. The polymer solution had a solid content concentration of 8.0% and a Brookfield viscosity of 18,000 mPa · s.

  Further, except that the synthetic isoprene polymer obtained in Example 4 was used, the production of the synthetic isoprene polymer latex, the preparation of the dip-molding composition, and the production of the dip-molded body were performed in the same manner as in Example 1. went. Using the obtained synthetic isoprene polymer latex, the centrifugation yield was calculated and the average particle size of the latex was measured in the same manner as in Example 1. Furthermore, tensile strength and elongation at break were evaluated using the obtained dip-molded body.

Example 5
In the production of the synthetic isoprene polymer, the same as Example 1 except that the amount of TMEDA was changed to 0.00041 parts and the amount of n-butyllithium 15 wt% hexane catalyst solution was changed to 0.0047 parts. Polymerization was carried out to obtain a synthetic isoprene polymer having a weight average molecular weight (Mw) of 2.4 million, Mw / Mn = 1.5, and a cis bond unit (1,4-cis structure) content of 87%. The polymer solution had a solid content concentration of 8.0% and a Brookfield viscosity of 30,000 mPa · s.

  Further, except that the synthetic isoprene polymer obtained in Example 5 was used, the production of the synthetic isoprene polymer latex, the preparation of the composition for dip molding, and the production of the dip molded body were carried out in the same manner as in Example 1. went. Using the obtained synthetic isoprene polymer latex, the centrifugation yield was calculated and the average particle size of the latex was measured in the same manner as in Example 1. Furthermore, tensile strength and elongation at break were evaluated using the obtained dip-molded body.

Comparative Example 1
In the production of the synthetic isoprene polymer, the same as Example 1 except that the amount of TMEDA was changed to 0.0140 parts and the amount of n-butyllithium 15 wt% hexane catalyst solution was changed to 0.026 parts. Polymerization was carried out to obtain a synthetic isoprene polymer having a weight average molecular weight (Mw) of 50,000, Mw / Mn = 1.0, and a cis bond unit (1,4-cis structure) content of 72%. The polymer solution had a solid content concentration of 8.0% and a Brookfield viscosity of 50 mPa · s.

  Further, except that the synthetic isoprene polymer obtained in Comparative Example 1 was used, the production of the synthetic isoprene polymer latex, the preparation of the composition for dip molding, and the production of the dip molded body were carried out in the same manner as in Example 1. went. Using the obtained synthetic isoprene polymer latex, the centrifugation yield was calculated and the average particle size of the latex was measured in the same manner as in Example 1. The obtained dip-formed product could not be evaluated for tensile strength and elongation at break because of poor film formation.

Comparative Example 2
In the production of the synthetic isoprene polymer, the same as Example 1 except that the amount of TMEDA was changed to 0.00025 parts and the amount of n-butyllithium 15 wt% hexane catalyst solution was changed to 0.0047 parts. Polymerization was carried out to obtain a synthetic isoprene polymer having a weight average molecular weight (Mw) of 4 million, Mw / Mn = 1.9, and a cis bond unit (1,4-cis structure) content of 90%. The polymer solution had a solid content concentration of 8.0% and a Brookfield viscosity of 100,000 mPa · s.

  Further, except that the synthetic isoprene polymer obtained in Comparative Example 2 was used, the production of the synthetic isoprene polymer latex, the preparation of the composition for dip molding, and the production of the dip molded body were carried out in the same manner as in Example 1. went. Using the obtained synthetic isoprene polymer latex, the centrifugation yield was calculated and the average particle size of the latex was measured in the same manner as in Example 1. In addition, since the viscosity was too high and the transfer took a long time, a dip-molded product could not be obtained within a predetermined time.

Comparative Example 3
In the production of the synthetic isoprene polymer, polymerization was carried out in the same manner as in Example 3. The weight average molecular weight (Mw) was 1.2 million, Mw / Mn = 1.2, and the content of cis bond units (1,4-cis structure) was 85. % Synthetic isoprene polymer was obtained. Using the obtained synthetic isoprene polymer, a polymer solution (12.5 parts of synthetic isoprene polymer, 1237.5 parts of cyclohexane) was prepared. The obtained polymer solution had a solid content concentration of 1.0% and a Brookfield viscosity of 70 mPa · s.

  Further, the synthetic isoprene polymer latex was prepared in the same manner as in Example 1 except that 1250 parts of the total amount of the polymer solution obtained in Comparative Example 3 (12.5 parts of synthetic isoprene polymer and 1237.5 parts of cyclohexane) was used. Production, preparation of a composition for dip molding, and production of a dip-molded body were carried out. Using the obtained synthetic isoprene polymer latex, the centrifugation yield was calculated and the average particle size of the latex was measured in the same manner as in Example 1. Furthermore, tensile strength and elongation at break were evaluated using the obtained dip-molded body.

  As shown in Table 1, a synthetic isoprene polymer having a weight average molecular weight (Mw) of 100,000 to 3,000,000 obtained by solution polymerization using an alkyl lithium polymerization catalyst is converted to a hydrocarbon having 5 to 8 carbon atoms. A synthetic isoprene polymer solution dissolved in a system solvent, which is emulsified with a synthetic isoprene polymer solution having a viscosity of 100 to 70,000 mPa · s measured at 25 ° C. with a Brookfield viscometer to obtain an emulsion Synthetic isoprene polymer latex comprising an emulsification step, a desolvation step for desolvating the hydrocarbon solvent from the emulsion, and a centrifugation step for centrifuging the emulsion that has been desolvated in the desolvation step According to this production method, the centrifugation yield of the obtained synthetic isoprene polymer latex is good, and Tensile strength and elongation at break of the dip molded product produced using the latex was good (Examples 1-5).

On the other hand, when a synthetic isoprene polymer having a weight average molecular weight (MW) of less than 100,000 was used, a dip-molded product produced using the obtained latex could not be evaluated due to poor film formation (Comparative Example 1). .
Further, when a synthetic isoprene polymer having a weight average molecular weight (MW) greater than 3,000,000 was used, the viscosity was too high, and it took too much time to transfer, and a dip-formed product was not obtained within a predetermined time. Moreover, the centrifugation yield of the obtained synthetic isoprene polymer latex was low (Comparative Example 2).
Moreover, when the solid content concentration of the synthetic isoprene polymer solution used was too low, the centrifugation yield of the obtained synthetic isoprene polymer latex was low (Comparative Example 3).

Claims (5)

A synthetic isoprene polymer having a weight average molecular weight (Mw) of 100,000 to 3,000,000 obtained by solution polymerization using an alkyl lithium polymerization catalyst is dissolved in a hydrocarbon solvent having 5 to 8 carbon atoms. An emulsifying step of emulsifying the synthetic isoprene polymer solution, wherein the synthetic isoprene polymer solution having a viscosity measured at 25 ° C. by a Brookfield viscometer of 100 to 70,000 mPa · s is emulsified;
A desolvation step of desolvating the hydrocarbon solvent from the emulsion,
A method for producing a synthetic isoprene polymer latex comprising a centrifugation step of centrifuging the emulsion that has been desolvated in the solvent removal step.   The synthetic isoprene polymer latex obtained by using the synthetic isoprene polymer having a cis bond unit (1,4-cis structure) content of 70% or more in the method according to claim 1.   A synthetic isoprene polymer latex obtained by the method according to claim 1, wherein the solid content concentration is 40% or more and the average particle size is 0.6 to 3.0 μm.   A composition for dip molding comprising the synthetic isoprene polymer latex according to claim 2 or 3, sulfur, and a vulcanization accelerator.   A dip-molded product obtained by dip-molding the dip-molding composition according to claim 4.