JPWO2016088576A1 - Synthetic polyisoprene latex for dip molding, dip molding composition and dip molded body - Google Patents

Abstract

The total amount of Al content and Ti content is 500 ppm or less, and the antifoaming agent content is 500 ppm or less.

Description

  The present invention relates to a dip-molding synthetic polyisoprene latex, a dip-molding composition, and a dip-molded body. More specifically, the present invention relates to a dip-molded body in which agglomerates are less generated with respect to mechanical shearing force such as transfer by a pump or agitation in a tank and the like, and no repellency is generated during dip-molded body production.

  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. Therefore, studies have been made on using synthetic polyisoprene instead of natural rubber.

  For example, Patent Document 1 discloses a dip molding composition that gives a dip molded article having excellent strength as a dip molding composition containing synthetic polyisoprene. However, when a dip-molded body obtained using synthetic polyisoprene is used as a glove or the like, required characteristics have become severe, and further improvement has been demanded in addition to strength.

  Synthetic polyisoprene latex is weak against mechanical shearing force and has problems such as generation of aggregates during transfer by a pump. In addition to clogging the piping during pump transfer, the agglomerates can cause poor appearance and pinholes when attached to the surface of the dip-molded body, so it has been necessary to remove them frequently. Since pipe cleaning and an increase in defective rate also lead to an increase in cost, a synthetic polyisoprene latex that is resistant to mechanical shearing force has been demanded. As a method of strengthening mechanical shearing force, there is a method of increasing the amount of surfactant as in Patent Document 1, but since foam causes pinholes, it is necessary to add a large amount of antifoaming agent. .

  Synthetic polyisoprene latex is known to be produced by dissolving synthetic polyisoprene in a solvent, emulsifying it together with a surfactant, and then removing the solvent. In this method, since the surfactant foams during solvent removal, it is common to add an antifoaming agent, and a large amount of antifoaming agent has been used to shorten the operation time.

  Thus, when using a large amount of surfactant, it is necessary to use a large amount of antifoaming agent. Therefore, repellency due to the antifoaming agent was generated on the surface of the dip-molded product, and the defect rate was high.

  Further, according to the study of the present inventor, in the presence of Ti and Al derived from Ziegler-based polymerization catalyst etc., the mechanism is not clear, but synthetic polyisoprene latex added with a lot of antifoaming agent is mechanical. It has been found that there is a tendency that aggregates are easily generated by shearing force. For this reason, although it is necessary to reduce the usage-amount of an antifoamer as much as possible, it was difficult to reduce an antifoamer for said reason.

  Under such circumstances, there has been a demand for a synthetic polyisoprene latex that can provide a dip-molded body that has high stability against mechanical shearing force and has no repellency.

International Publication No. 2013/099501

  The present invention relates to a dip-molding synthetic polyisoprene latex that gives a dip-molded body having high stability against mechanical shearing force, and a dip-molding composition using the dip-molding synthetic polyisoprene latex. And it aims at providing a dip molding.

  As a result of diligent research to solve the above problems, the present inventors have found that the total amount of Al content and Ti content is 500 ppm or less, and the antifoaming agent content is 500 ppm or less. The present inventors have found that latex can achieve the above object and have completed the present invention.

That is, according to the present invention,
(1) A synthetic polyisoprene latex for dip molding having a total amount of Al content and Ti content of 500 ppm or less and an antifoaming agent content of 500 ppm or less,
(2) The synthetic polyisoprene latex for dip molding according to (1), wherein the total amount of the Al content and the Ti content is 200 ppm or less,
(3) The synthetic polyisoprene latex for dip molding according to (1) or (2), wherein the antifoaming agent content is 80 ppm or less,
(4) For dip molding according to any one of (1) to (3), the content ratio of cis-bond units in the isoprene units contained in the synthetic polyisoprene is 90% by weight or more based on the total isoprene units. Synthetic polyisoprene latex,
(5) A composition for dip molding comprising the synthetic polyisoprene latex for dip molding according to any one of (1) to (4), a sulfur vulcanizing agent and a vulcanization accelerator,
(6) A dip-molded body obtained by dip-molding the dip-molding composition described in (5) is provided.

  ADVANTAGE OF THE INVENTION According to this invention, the synthetic polyisoprene latex for dip molding which gives the dip molding which has high stability with respect to a mechanical shear force, and there is no repellency, For dip molding using this synthetic polyisoprene latex for dip molding Compositions and dip compacts are provided.

  The synthetic polyisoprene latex for dip molding according to the present invention will be described below. The synthetic polyisoprene latex for dip molding of the present invention has a total amount of Al content and Ti content of 500 ppm or less and an antifoaming agent content of 500 ppm or less.

(Synthetic polyisoprene latex)
The synthetic polyisoprene latex for dip molding of the present invention is a latex of synthetic polyisoprene obtained by polymerizing isoprene.

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

  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.

  As the isoprene units in the synthetic polyisoprene, there are four types of 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 improving the tensile strength of the dip-molded product, the content of cis-bond units in the isoprene units contained in the synthetic polyisoprene is preferably 70% by weight or more, more preferably 90%, based on the total isoprene units. % By weight or more, particularly preferably 95% by weight or more.

  The weight average molecular weight of the synthetic polyisoprene is 10,000 to 5,000,000, preferably 500,000 to 5,000,000, particularly preferably 800,000 in terms of standard polystyrene by gel permeation chromatography analysis. 000 to 3,000,000. If the weight average molecular weight of the synthetic polyisoprene is too small, the tensile strength of the dip-molded product tends to decrease. Conversely, if it is too large, the synthetic polyisoprene latex tends to be difficult to produce.

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

  The volume average particle diameter of latex particles (synthetic polyisoprene particles) in the synthetic polyisoprene latex is preferably 0.5 to 10 μm, more preferably 0.5 to 3 μm, and particularly preferably 0.5 to 2 μm. . If the volume average particle size is too small, the latex viscosity may become too high and difficult to handle. Conversely, if the volume average particle size is too large, a film may be formed on the latex surface when the synthetic polyisoprene latex is stored. .

The electrical conductivity of the synthetic polyisoprene latex is preferably 0.6 mS / cm to 2.0 mS / cm. If the conductivity is too small, a large amount of aggregates may be generated during emulsification or concentration. Further, if the electrical conductivity is too high, foaming becomes violent at the time of solvent removal, foaming is severe when the composition for dip molding is transferred or blended, and defects such as pinholes may be left on the glove.
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 content of the alicyclic hydrocarbon solvent in the synthetic polyisoprene latex is preferably 500 ppm by weight or less. Moreover, cyclohexane is preferable as the alicyclic hydrocarbon solvent. When there is too much content of an alicyclic hydrocarbon solvent, there exists a tendency for the odor of the composition for dip molding to become tight.

  Here, the alicyclic hydrocarbon solvent is an organic solvent for dissolving or finely dispersing synthetic polyisoprene, which will be described later, when producing synthetic polyisoprene latex.

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

  As a method for producing a synthetic polyisoprene latex, for example, (1) a solution or fine suspension of a synthetic polyisoprene dissolved or finely dispersed in an organic solvent is emulsified in water in the presence of a surfactant, and if necessary, A method for producing a synthetic polyisoprene latex by removing an organic solvent, (2) emulsion polymerization or suspension polymerization of isoprene alone or a mixture of ethylenically unsaturated monomers copolymerizable with isoprene, A method of directly producing a synthetic polyisoprene latex is mentioned, but a synthetic polyisoprene having a high ratio of cis bond units in the isoprene unit can be used, and a dip molded article having excellent tensile strength can be obtained. The production method (1) is preferred.

  Synthetic polyisoprene is produced in an inert polymerization solvent using a conventionally known method, for example, a Ziegler polymerization catalyst comprising trialkylaluminum-titanium tetrachloride or an alkyllithium polymerization catalyst such as n-butyllithium or sec-butyllithium. It can be obtained by solution polymerization of isoprene. Among these, from the viewpoint of increasing the content ratio of the cis bond unit in the isoprene unit, it is preferable to use a Ziegler polymerization catalyst in the present invention. The obtained polymer solution of synthetic polyisoprene may be used as it is, but after the solid synthetic polyisoprene is taken out from the polymer solution, the solid synthetic polyisoprene is dissolved in an organic solvent and used. You can also.

At this time, after synthesizing the polyisoprene, impurities such as a residue of the polymerization catalyst 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.
Commercially available solid synthetic polyisoprene may also be used.

  Examples of the organic solvent used in the production method (1) include aromatic hydrocarbon solvents such as benzene, toluene and xylene; alicyclic hydrocarbon solvents such as cyclopentane, cyclopentene, cyclohexane and cyclohexene; pentane, hexane, And aliphatic hydrocarbon solvents such as heptane; halogenated hydrocarbon solvents such as methylene chloride, chloroform and ethylene dichloride; Of these, aromatic hydrocarbon solvents and alicyclic hydrocarbon solvents are preferred, with cyclohexane and toluene being particularly preferred.

  In addition, the usage-amount of an organic solvent becomes like this. Preferably it is 2,000 weight part or less with respect to 100 weight part of synthetic polyisoprenes, More preferably, it is 20-1,500 weight part.

  Examples of the surfactant used in the production method of (1) above include nonionic surfactants such as polyoxyethylene alkyl ether, polyoxyethylene alkyl phenol ether, polyoxyethylene alkyl ester, polyoxyethylene sorbitan alkyl ester; Sodium or potassium salts of fatty acids such as lauric acid, myristic acid, palmitic acid, oleic acid, linolenic acid, rosin acid, alkylbenzene sulfonates such as sodium dodecylbenzene sulfonate, higher alcohol sulfates, alkyl sulfosuccinates, etc. Anionic surfactants; cationic surfactants such as alkyltrimethylammonium chloride, dialkyldimethylammonium chloride, alkylbenzyldimethylammonium chloride; , Β-unsaturated carboxylic acid sulfoesters, α, β-unsaturated carboxylic acid sulfate esters, sulfoalkylaryl ethers and the like, and the like, and anionic surfactants are preferred. Particularly preferred are sodium rosinate and sodium dodecylbenzene sulfonate. 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 polyisoprene. 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 production method (1) is preferably 50 to 5,000 parts by weight, more preferably 100 to 3,000 parts by weight, based on 100 parts by weight of the synthetic polyisoprene.

  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 an organic solvent solution or fine suspension 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 addition method of the surfactant is not particularly limited, and the emulsified liquid may be added during the emulsification operation even if it is added to the organic solvent solution or fine suspension of water and / or synthetic polyisoprene in advance. It may be added in a batch, or 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 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.

  In the method (1), it is preferable to obtain a synthetic polyisoprene latex by removing the organic solvent from the emulsion obtained through the emulsification operation. The method for removing the organic solvent from the emulsion is not particularly limited, and methods such as vacuum distillation, atmospheric distillation, steam distillation, and centrifugation can be employed.

  In the operation of removing the organic solvent, an antifoaming agent is used to suppress foaming caused by the surfactant. Examples of antifoaming agents include mineral oil antifoaming agents, silicone antifoaming agents, and polymer antifoaming agents. Among these, silicone-based antifoaming agents such as silicone oil can be preferably used. The amount of the antifoaming agent is preferably 100 to 2000 ppm with respect to 100 parts by weight of the synthetic polyisoprene, although it depends on the amount of the surfactant used. If this amount is too large, repellency is likely to occur on the surface of the resulting dip-formed body.

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

  The solid content concentration of the synthetic polyisoprene latex is preferably 30 to 70% by weight, more preferably 40 to 70% by weight. If the solid content concentration is too low, the solid content concentration of the dip-molding composition becomes low, and the film thickness of the dip-molded product becomes thin and easily broken. On the other hand, if it is too high, the viscosity of the synthetic polyisoprene latex will be high, and it will be difficult to transfer it by piping or to stir in the preparation tank.

  Synthetic polyisoprene latex is blended with additives such as pH adjusters, preservatives, cross-linking agents, chelating agents, oxygen scavengers, dispersants and anti-aging agents that are usually blended in the latex field. Also good.

  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.

  In the present invention, Al and Ti are removed from the synthetic polyisoprene. A method for performing the removal operation is not particularly limited, but a method of washing the synthetic polyisoprene with a strong alkali is preferable. As the strong alkali, an aqueous NaOH solution of 10% or more is preferable.

  The total amount of Al content and Ti content in the synthetic polyisoprene latex thus obtained is 500 ppm or less, preferably 200 ppm or less, and the content of the antifoaming agent is 500 ppm or less, preferably 80 ppm or less. In addition, the total amount of Al content and Ti content and the content of the antifoaming agent are ratios (ppm) expressed on a weight basis. By setting this amount within the above range, the mechanical stability of the latex, the shortening of the prevulcanization time, and the tensile strength of the dip-formed product during a specific aging period tend to be improved.

(Dip molding composition)
The dip molding composition of the present invention comprises the above-described synthetic polyisoprene latex, a vulcanizing agent, and a vulcanization accelerator.

(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. Of these, sulfur is 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 polyisoprenes, More preferably, it is 0.2-3 weight part. By setting this amount within the above range, the tensile strength of the dip-formed product tends to be improved.

(Vulcanization accelerator)
As the vulcanization accelerator, those usually used in dip molding can be used. 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, and the like. 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 polyisoprene. By setting this amount within the above range, the tensile strength of the dip-molded product and the elongation immediately before breakage are improved.

(Other ingredients)
(Zinc oxide)
The dip molding composition of the present invention preferably further contains zinc oxide. Although content of zinc oxide is not specifically limited, Preferably it is 0.1-5 weight part with respect to 100 weight part of synthetic polyisoprenes, More preferably, it is 0.2-2 weight part. By setting this amount within the above range, the tensile strength of the dip-molded product is improved, the stability of the synthetic polyisoprene particles is improved, and the generation of aggregates can be suppressed.

(Dispersant)
The dip molding composition of the present invention may contain a dispersant as necessary. Examples of the dispersant include fatty acids such as lauric acid, myristic acid, palmitic acid, oleic acid, linolenic acid, and rosin acid. And anionic surfactants such as alkyl alcohol sulfonates such as sodium dodecylbenzene sulfonate, higher alcohol sulfates and alkyl sulfosuccinates, sodium dodecyl benzene sulfonate 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, more preferably 0.05 to 3 parts by weight with respect to 100 parts by weight of the synthetic polyisoprene. By setting this amount within the above range, the blending stability of the dip molding composition can be improved, foaming can be prevented, and pinholes can be prevented from being generated.

(Combination agent)
The dip molding composition of the present invention further requires a compounding agent such as 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; It can be blended according to.

  Anti-aging agents include 2,6-di-4-methylphenol, 2,6-di-t-butylphenol, butylhydroxyanisole, 2,6-di-t-butyl-α-dimethylamino-p-cresol, Octadecyl-3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate, styrenated phenol, 2,2′-methylene-bis (6-α-methyl-benzyl-p-cresol), 4, Butylation of 4'-methylenebis (2,6-di-t-butylphenol), 2,2'-methylene-bis (4-methyl-6-t-butylphenol), alkylated bisphenol, p-cresol and dicyclopentadiene 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-2 -Thiobisphenol-based antioxidants such as ylamino) phenol; phosphite-based antioxidants such as tris (nonylphenyl) phosphite, diphenylisodecyl phosphite, tetraphenyldipropylene glycol diphosphite; dilauryl thiodipropionate, etc. Sulfur ester anti-aging agent of: phenyl-α-naphthylamine, phenyl-β-naphthylamine, p- (p-toluenesulfonylamido) -diphenylamine, 4,4 ′-(α, α-dimethylbenzyl) diphenylamine, N, N -Diphenyl-p-phenylenediamine, N-isopropyl-N'-phenyl- -Amine-based antioxidants such as phenylenediamine and butyraldehyde-aniline condensates; Quinoline-based antioxidants such as 6-ethoxy-2,2,4-trimethyl-1,2-dihydroquinoline; 2,5-di- Hydroquinone anti-aging agents such as (t-amyl) hydroquinone; and the like. 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 polyisoprene. By making this amount into the above range, the deterioration of the synthetic polyisoprene is suppressed and the tensile strength of the dip-formed product is improved.

The method for preparing the dip molding composition is not particularly limited. As the preparation method, using a dispersing machine such as a ball mill, a kneader, or a disper, the latex of the synthetic polyisoprene is blended with a vulcanizing agent, a vulcanization accelerator, zinc oxide, the above-described dispersing agent, and if necessary. After preparing an aqueous dispersion of desired compounding ingredients other than latex of synthetic polyisoprene using a method of mixing other compounding agents such as anti-aging agents and the above-mentioned disperser in advance, the aqueous dispersion is synthesized. The method of mixing with the latex of polyisoprene is mentioned. Further, after the above-mentioned dispersant is mixed in advance with the latex of synthetic polyisoprene, 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.

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

The time for pre-vulcanization is not particularly limited and depends on the pre-vulcanization temperature, but is preferably 1 to 14 days, more preferably from the viewpoint of obtaining a dip-molded body having suitable tensile strength. 1-7 days.
The pre-vulcanization temperature is preferably 20 to 40 ° C. By setting the pre-vulcanization temperature within the above range, both the storage period and the production rate can be achieved.

  From the viewpoint of obtaining a dip-molded body having a suitable tensile strength, it is preferably stored at 10 to 25 ° C. until it is subjected to dip molding after pre-vulcanization.

(Dip molded body)
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 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).
An anode coagulation dipping method is preferred in that a dip-formed product 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 are appropriately selected.
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.
In Examples and Comparative Examples, physical properties were measured and evaluated as follows.

(Weight average molecular weight)
The synthetic polyisoprene latex obtained in Examples and Comparative Examples was dissolved in tetrahydrofuran so that the solid content concentration was 0.1% by weight. This solution was subjected to gel permeation chromatography analysis and calculated as the weight average molecular weight of the synthetic polyisoprene in terms of standard polystyrene.

(Cis bond unit amount)
Methanol was added to the synthetic polyisoprene 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 ratio of cis-bond units to all isoprene units in the synthetic polyisoprene.

(Al content)
Using ICP-AES (manufactured by SIS Nanotechnology), the internal standard calibration curve method was used for the measurement according to the following procedure.
(1) A sample was weighed in a platinum crucible. A platinum crucible for blank tests was also prepared.
(2) Heated gradually on the heater. (The same operation was performed for the platinum crucible for the blank test.)
(3) When no more smoke was generated, it was ignited with a burner, covered, and incinerated in an electric furnace at 550 ° C.
(4) Nitric acid and ultrapure water were added after cooling.
(5) After heating, it was transferred to a plastic container and the volume was adjusted.
(6) It diluted suitably and measured by ICP-AES.

(Ti content)
Using ICP-AES (manufactured by SIS Nanotechnology), the internal standard calibration curve method was used for the measurement according to the following procedure.
(1) The sample was weighed into a volumetric flask. A volumetric flask for a blank test was prepared.
(2) Wet decomposition with sulfuric acid and nitric acid. (The same operation was performed for the blank test flask.)
(3) After constant volume, it was diluted appropriately and measured by ICP-AES.

(Total amount of Al content and Ti content)
The total amount of Al content and Ti content measured as described above was determined and used as the total amount of Al content and Ti content.

(Defoamer content)
-Preparation of calibration curve The antifoaming agent was dried and then dissolved in carbon tetrachloride. A predetermined amount was collected from this and dissolved in 1 mL of TMS-free chloroform to prepare a standard sample for the calibration curve. Using this, H-NMR measurement was performed to prepare a calibration curve.
-Content measurement (1) The latex was freeze-dried and then Soxhlet extracted with acetone.
(2) After the extract was dissolved in 1 mL of TMS-free chloroform, H-NMR measurement was performed, and the content was determined based on a calibration curve.

(Mechanical stability test)
The test was conducted according to the method described in “Determination of Mechanical Stability” of ASTM D1417-10. The stainless steel disc used was a stainless steel disc having a diameter of 20.83 ± 0.03 mm described in “Mechanical Stability” of ASTM D1076-19.

(Presence or absence of repelling during dipping)
The occurrence state of cissing on the surface of the dip-molded body obtained in the examples and comparative examples was visually determined.

(Tensile strength of dip-molded body and elongation just before breaking)
The tensile strength of the dip-molded body was measured based on ASTM D412.
The dip-formed film was punched with a dumbbell (SDMK-100C: dumbbell) to produce a test piece for measuring tensile strength. The test piece was pulled with a Tensilon universal testing machine (trade name “RTG-1210”, manufactured by A & D Co., Ltd.) at a pulling speed of 500 mm / min, tensile strength immediately before break (unit: MPa), elongation just before break (unit: :%).

Example 1
Synthetic polyisoprene having a weight average molecular weight of 1,300,000 (trade name “IR2200L”, manufactured by Nippon Zeon Co., Ltd., isoprene homopolymer, cis bond unit amount 98%) is mixed with a high-speed grinder (form: SH- 016, Plako Co., Ltd.) to obtain small pieces of 3 cm or less. The small pieces were put into a stirring citric acid methanol solution (citric acid 25%) and washed for 12 hours while changing the citric acid methanol solution every 3 hours. Thereafter, the small piece was washed with 20% NaOH aqueous solution and further washed with distilled water. The small piece after washing was dried in a vacuum dryer.

  100 parts of this synthetic polyisoprene was dissolved in 1150 parts of cyclohexane (manufactured by Wako Pure Chemical Industries, Ltd.) to obtain a cyclohexane solution (b1) of synthetic polyisoprene. Next, sodium rosinate (trade name “Longis N-18”, manufactured by Arakawa Chemical Co., Ltd.) 1% by weight and sodium dodecylbenzenesulfonate (trade name “Neoperex G-15”, manufactured by Kao Corporation) 1245 parts of a surfactant aqueous solution (a1) containing 0.5% by weight and containing no synthetic polyisoprene was prepared.

  Then, the total amount of the cyclohexane solution (b1) of the synthetic polyisoprene and the total amount of the surfactant aqueous solution (a1) were placed in a container made of SUS304 and mixed by stirring. Subsequently, a homogenizer (trade name “Milder MDN- 303V "(manufactured by Taiheiyo Kiko Co., Ltd.) to obtain an emulsified mixed liquid (c1).

  Next, an antifoaming agent (trade name “SM5515” manufactured by Toray Dow Corning Co., Ltd.) is added to 400 ppm with respect to 100 parts of the synthetic polyisoprene, and the emulsified mixed liquid (c1) is added in the solvent removal tank. Then, cyclohexane was distilled off to obtain a synthetic polyisoprene latex (e1). And the aggregate in synthetic polyisoprene latex (e1) was removed using the 200 mesh stainless steel metal-mesh.

Next, the synthetic polyisoprene latex (e1) after the removal of the aggregates was centrifuged with a closed disk type continuous centrifuge (SGR509 manufactured by Alfa Laval) under the conditions of 9000 G and a flow rate of 1600 L / hr. . As a result, the synthetic polyisoprene latex of Example 1 having a solid content concentration of 61%, an Al content of 50 ppm, a Ti content of 80 ppm (that is, a total amount of Al content and Ti content of 130 ppm) and an antifoaming agent content of 30 ppm was obtained. Obtained. When the centrifuge bowl was opened and the disc opened, almost no agglomerates were seen.
Moreover, the resistance (mechanical stability test) with respect to the mechanical shear force of the obtained synthetic polyisoprene latex was measured. The results are shown in Table 1.

(Dip molding composition)
While stirring the synthetic polyisoprene latex, sodium dodecylbenzenesulfonate having a concentration of 10% by weight was added to 100 parts of the synthetic polyisoprene so as to be 1 part in terms of solid content. And while stirring the obtained mixture, 1.5 parts of zinc oxide, 1.5 parts of sulfur and an antioxidant (trade name: Wingstay L) in terms of solid content with respect to 100 parts of synthetic polyisoprene in the mixture. 2 parts, zinc diethyldithiocarbamate 0.3 parts, zinc dibutyldithiocarbamate 0.5 parts, zinc 2-mercaptobenzothiazole zinc 0.7 parts After that, 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.

(Dip molded body)
After washing a commercially available ceramic hand mold (manufactured by Shinko Co., Ltd.) and preheating in an oven at 70 ° C., 18 wt% calcium nitrate and 0.05 wt% polyoxyethylene lauryl ether (trade name: It was immersed in a coagulant aqueous solution made of Emulgen 109P (manufactured by 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. Thereafter, the hand mold covered with the film-like synthetic polyisoprene was placed in an oven at 130 ° C. and vulcanized for 30 minutes.

  The hand mold covered with the vulcanized film was cooled to room temperature, visually checked for the presence of repelling, and then talc was sprayed before peeling from the hand mold. Table 1 shows the measurement results of the tensile strength and elongation immediately before breakage of the obtained dip-molded body.

(Example 2)
Synthetic polyisoprene having a weight average molecular weight of 1,300,000 (trade name “IR2200L”, manufactured by Nippon Zeon Co., Ltd., isoprene homopolymer, cis bond unit amount 98%) is mixed with a high-speed grinder (form: SH- 016, Plako Co., Ltd.) to obtain small pieces of 3 cm or less. A dip-molded article was produced and evaluated in the same manner as in Example 1 except that the washing time of the small piece of citric acid with the methanol solution was stopped at 6 hours. The results are shown in Table 1.

(Example 3)
A synthetic polyisoprene latex was obtained in the same manner as in Example 1 except that the amount of the antifoaming agent used before removing the solvent was increased to 1500 ppm with respect to 100 parts of the synthetic polyisoprene. The antifoaming agent content of the synthetic polyisoprene latex after this centrifugation was 100 ppm. Using this latex, a dip-formed product was produced and evaluated in the same manner as in Example 1. The results are shown in Table 1.

(Comparative Example 1)
Synthetic polyisoprene having a weight average molecular weight of 1,300,000 (trade name “IR2200L”, manufactured by Nippon Zeon Co., Ltd., isoprene homopolymer, cis bond unit amount 98%) is mixed with a high-speed grinder (form: SH- 016, Plako Co., Ltd.) to obtain small pieces of 3 cm or less. 100 parts of this synthetic polyisoprene was dissolved in 1150 parts of cyclohexane (manufactured by Wako Pure Chemical Industries, Ltd.) without washing to obtain a cyclohexane solution (b1) of synthetic polyisoprene. Next, sodium rosinate (trade name “Longis N-18”, manufactured by Arakawa Chemical Co., Ltd.) 1% by weight and sodium dodecylbenzenesulfonate (trade name “Neopelex G-15”, manufactured by Kao Corporation) 1245 parts of a surfactant aqueous solution (a1) containing 0.5% by weight and containing no synthetic polyisoprene was prepared.

  Then, the total amount of the cyclohexane solution (b1) of the synthetic polyisoprene and the total amount of the surfactant aqueous solution (a1) were placed in a container made of SUS304 and mixed by stirring. Subsequently, a homogenizer (trade name “Milder MDN- 303V "(manufactured by Taiheiyo Kiko Co., Ltd.) to obtain an emulsified mixed liquid (c1).

  Next, an antifoaming agent (trade name “SM5515” manufactured by Toray Dow Corning Co., Ltd.) is added to 400 ppm with respect to 100 parts of the synthetic polyisoprene, and the emulsified mixed liquid (c1) is added in the solvent removal tank. Then, cyclohexane was distilled off to obtain a synthetic polyisoprene latex (e1).

  Then, without using a closed disk type continuous centrifuge, using an evaporator, it was concentrated at 80 ° C. to a solid content concentration of 61%, an Al content of 150 ppm, a Ti content of 380 ppm, and an antifoaming agent content of 30 ppm. A synthetic polyisoprene latex was obtained. Using this latex, a dip-molded product was produced and evaluated in the same manner as in Example 1. The results are shown in Table 1.

(Comparative Example 2)
After obtaining a synthetic polyisoprene latex in the same manner as in Example 1, the antifoaming agent (trade name “SM5515”: so that the antifoaming agent content (total) becomes 800 ppm in the synthetic polyisoprene latex after centrifugation. Toray Dow Corning) was added. In the same manner as in Example 1, a dip-molded body was produced and evaluated in the same manner. The results are shown in Table 1.

(Comparative Example 3)
In the same manner as in Comparative Example 1, after obtaining a synthetic polyisoprene latex, an antifoaming agent (trade name “SM5515”) was added so that the content (total) of the antifoaming agent was 800 ppm in the synthetic polyisoprene latex after the evaporator concentration. : Toray Dow Corning) was added. In the same manner as in Example 1, a dip-molded body was produced and evaluated. The results are shown in Table 1.

  In Examples 1 to 3, all had high mechanical stability, and no repellency was observed in the dip-molded body. Further, a dip-molded product having high tensile strength and high elongation at break was obtained.

  On the other hand, in Comparative Example 1 in which the total amount of Al content and Ti content is 500 ppm or more, the mechanical stability of the latex was low. The tensile strength and elongation at break of the dip-molded body produced using this latex were low.

  Further, in Comparative Example 2 having a large antifoaming agent content, the mechanical stability of the latex was low. In the dip-molded body produced using this latex, a lot of repellency was generated on the surface, the appearance was poor, and the tensile strength and elongation at break of the dip-molded body were low.

  Furthermore, in Comparative Example 3 in which the total amount of Al content and Ti content was 500 ppm or more and the antifoaming agent content was 500 ppm or more, the generation of aggregates was the most in the mechanical stability test. . Moreover, there were many repellency in the surface of the dip molded object produced using this latex. Moreover, this dip-molded body had the lowest tensile strength among the examples and comparative examples.

Claims (6)

  A synthetic polyisoprene latex for dip molding in which the total amount of Al content and Ti content is 500 ppm or less and the antifoaming agent content is 500 ppm or less.   The synthetic polyisoprene latex for dip molding according to claim 1, wherein a total amount of the Al content and the Ti content is 200 ppm or less.   The synthetic polyisoprene latex for dip molding according to claim 1 or 2, wherein the antifoaming agent content is 80 ppm or less.   The synthetic polyisoprene latex for dip molding according to any one of claims 1 to 3, wherein a content ratio of cis-bond units in isoprene units contained in the synthetic polyisoprene is 90% by weight or more based on all isoprene units.   A composition for dip molding comprising the synthetic polyisoprene latex for dip molding according to any one of claims 1 to 4, a sulfur vulcanizing agent and a vulcanization accelerator.   A dip-molded product obtained by dip-molding the dip-molding composition according to claim 5.