JP7156030B2 - synthetic polyisoprene latex - Google Patents

Description

The present invention provides a synthetic polyisoprene latex capable of effectively suppressing odor, excellent in tensile strength and elongation, and capable of providing a film molded article such as a dip molded article having a soft feel, and such a synthetic polyisoprene latex. The present invention relates to a latex composition, film molded article and packaging structure using synthetic polyisoprene latex.

BACKGROUND ART Conventionally, there has been known a film formed article obtained by forming a latex composition containing natural rubber latex into a film. For example, the film-formed article is obtained by dip-molding a latex composition containing natural rubber latex, and dip-formed articles used in contact with the human body, such as nipples, balloons, gloves, balloons, and sacks, are known. It is However, since natural rubber latex contains proteins that cause allergic symptoms in the human body, there are cases in which it is problematic as a dip-molded article that comes into direct contact with living mucous membranes or organs. Therefore, the use of synthetic rubber latex instead of natural rubber latex has been investigated.

For example, Patent Document 1 discloses a synthetic polyisoprene latex obtained by using a rosinate as a surfactant as a latex used for dip molding. However, the dip-molded article obtained using the synthetic polyisoprene latex disclosed in Patent Document 1 has a problem that it has a strong odor. A synthetic rubber latex that can be

Japanese Patent Publication No. 2009-531497

The present invention has been made in view of such circumstances, and provides a film molded article such as a dip molded article which is effectively suppressed in odor, is excellent in tensile strength and elongation, and has a soft texture. It is an object of the present invention to provide a synthetic polyisoprene latex capable of

As a result of intensive studies to achieve the above object, the present inventors found that by setting the amount of tall rosin-based surfactant contained in the synthetic polyisoprene latex to a specific range, such a synthetic polyisoprene It was found that a film molded article such as a dip molded article obtained using latex effectively suppresses odor, is excellent in tensile strength and elongation, and also has a soft texture, and the present invention was established. I came to complete it.

That is, according to the present invention, there is provided a synthetic polyisoprene latex containing 0.3 to 1.5 parts by weight of a tall rosin-based surfactant with respect to 100 parts by weight of synthetic polyisoprene.
In the synthetic polyisoprene latex of the present invention, the synthetic polyisoprene is preferably polymerized by anionic polymerization.
In the synthetic polyisoprene latex of the present invention, the content of the tall rosin-based surfactant is preferably 0.3 to 1.3 parts by weight with respect to 100 parts by weight of the synthetic polyisoprene.

Further, according to the present invention, there is provided a method for producing the synthetic polyisoprene latex, wherein a polymer solution of synthetic polyisoprene polymerized by anionic polymerization is emulsified in water in the presence of a tall rosin surfactant. A method for making a synthetic polyisoprene latex is provided comprising a process.
In the method for producing a synthetic polyisoprene latex of the present invention, the polymer solution preferably contains an organic solvent.
The method for producing a synthetic polyisoprene latex of the present invention preferably further comprises a step of removing the organic solvent from the emulsion obtained by the step of emulsifying in water.

According to the present invention, there is provided a latex composition containing the synthetic polyisoprene latex described above and a vulcanizing agent and/or a vulcanization accelerator.

Further, according to the present invention, there is provided a film molded article comprising the above latex composition.
Furthermore, according to the present invention, at least a portion of the first sheet substrate and at least a portion of the second sheet substrate are adhesively laminated with a coating film made of the above synthetic polyisoprene latex, A packaging structure is provided that can accommodate an item to be packaged between the first sheet substrate and the second sheet substrate.

According to the present invention, there is provided a synthetic polyisoprene latex which is effectively suppressed in odor, excellent in tensile strength and elongation, and capable of giving a film molded article such as a dip molded article having a soft touch. can be done.

Synthetic Polyisoprene Latex The synthetic polyisoprene latex of the present invention is a latex of synthetic polyisoprene. It contains at a ratio of

The synthetic polyisoprene latex of the present invention contains 0.3 to 1.5 parts by weight of tall rosin surfactant per 100 parts by weight of synthetic polyisoprene. In the case of the film molded product of (1), the resulting film molded product such as a dip molded product can effectively suppress odor, have excellent tensile strength and elongation, and have a flexible texture. It is. The content of the tall rosin surfactant is preferably 0.3 to 1.3 parts by weight, more preferably 0.3 to 1.1 parts by weight. If the content of the tall rosin-based surfactant is too low, synthetic polyisoprene aggregates (coagulum) tend to occur, resulting in a latex having poor mechanical stability. On the other hand, if the content of the tall rosin-based surfactant is too high, the odor of the resulting film-formed article such as a dip-formed article is deteriorated.

The synthetic polyisoprene contained in the synthetic polyisoprene latex of the present invention may be a homopolymer of isoprene or a copolymer of isoprene and other ethylenically unsaturated monomers copolymerizable therewith. There may be. The content of the isoprene units in the synthetic polyisoprene is preferably 70% by weight or more based on the total monomer units, since it is easy to obtain a film molded product such as a dip molded product that is flexible and has excellent tensile strength. More preferably 90% by weight or more, still more preferably 95% by weight or more, and particularly preferably 100% by weight (isoprene homopolymer).

Other ethylenically unsaturated monomers copolymerizable with isoprene include conjugated diene monomers other than isoprene such as butadiene, chloroprene, 1,3-pentadiene; acrylonitrile, methacrylonitrile, fumaronitrile, α- ethylenically unsaturated nitrile monomers such as chloroacrylonitrile; vinyl aromatic monomers such as styrene and alkylstyrene; methyl (meth)acrylate (meaning "methyl acrylate and/or methyl methacrylate"; hereinafter , Ethyl (meth)acrylate, etc.), ethylenically unsaturated carboxylic acid ester monomers such as ethyl (meth)acrylate, butyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate; is mentioned. These other ethylenically unsaturated monomers copolymerizable with isoprene may be used singly or in combination.

Synthetic polyisoprene may be polymerized by any method such as a conventionally known method, coordination polymerization or anionic polymerization. A preferred method is to obtain a synthetic polyisoprene polymer solution by solution polymerization of isoprene and optionally other copolymerizable ethylenically unsaturated monomers in an inert polymerization solvent. be. The Ziegler-based polymerization catalyst is not particularly limited, and a known one can be used. For example, titanium tetrachloride is reduced with an organoaluminum compound and further treated with various electron donors and electron acceptors. a catalyst system combining a titanium trichloride composition and an organoaluminum compound, and a supported catalyst system in which titanium tetrachloride and various electron donors are brought into contact with magnesium halide. Among these, titanium tetrachloride and Catalyst systems using organoaluminum compounds are preferred, with titanium tetrachloride and trialkylaluminum catalyst systems being particularly preferred.

In the case of anionic polymerization, isoprene and, if necessary, other copolymerizable ethylenically unsaturated monomers are mixed in an inert polymerization solvent using an organic alkali metal catalyst. A preferred method is to obtain a polymer solution of synthetic polyisoprene by solution polymerization. By using an organic alkali metal catalyst as a polymerization catalyst for anionic polymerization, anionic polymerization can proceed with high living properties, so that synthetic polyisoprene with a high weight-average molecular weight can be obtained at a high yield. Therefore, it is preferable. The organic alkali metal catalyst is not particularly limited, and known ones can be used. Monolithium compounds; organic polyvalent lithium such as dilithiomethane, 1,4-dilithiobutane, 1,4-dilithio-2-ethylcyclohexane, 1,3,5-trilithiobenzene, 1,3,5-tris(lithiomethyl)benzene compounds; organic sodium compounds such as sodium naphthalene; organic lithium compounds such as potassium naphthalene; Among these, it is preferable to use an organic monolithium compound, and it is more preferable to use n-butyllithium. These organic alkali metal catalysts may be used alone or in combination of two or more.

Examples of the polymerization solvent used for polymerization include organic solvents, such as aromatic hydrocarbon solvents such as benzene, toluene and xylene; alicyclic hydrocarbon solvents such as cyclopentane, cyclopentene, cyclohexane and cyclohexene; Aliphatic hydrocarbon solvents such as butane, pentane, hexane and heptane; halogenated hydrocarbon solvents such as methylene chloride, chloroform and ethylene dichloride; Among these, aliphatic hydrocarbon solvents are preferred, butane, hexane and pentane are more preferred, hexane is still more preferred, and normal hexane is particularly preferred.

There are four types of isoprene units in synthetic polyisoprene, ie, cis bond units, trans bond units, 1,2-vinyl bond units, and 3,4-vinyl bond units, depending on the bonding state of isoprene. From the viewpoint of improving the tensile strength of the obtained 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% by weight, based on the total isoprene units. % or more, more preferably 95% by weight or more.

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

The polymer Mooney viscosity (ML ₁₊₄ , 100° C.) of the synthetic polyisoprene is preferably 50-80, more preferably 60-80, even more preferably 70-80.

The synthetic polyisoprene latex of the present invention can be obtained, for example, by the following method using the synthetic polyisoprene polymer solution obtained by the above-described coordination polymerization or anionic polymerization. That is, (1) from a polymer solution of synthetic polyisoprene obtained by coordination polymerization or anionic polymerization, synthetic polyisoprene once solidified is dissolved or finely dispersed in an organic solvent to obtain a polymer solution of synthetic polyisoprene. A method of producing a synthetic polyisoprene latex by obtaining a (solution or fine suspension) and emulsifying a synthetic polyisoprene polymer solution in water in the presence of a tall rosin-based surfactant as an emulsifier, ( 2) Synthetic polyisoprene latex by directly emulsifying a synthetic polyisoprene polymer solution obtained by coordination polymerization or anionic polymerization in water in the presence of a tall rosin-based surfactant as an emulsifier without coagulation. A method for producing the Either of the above methods (1) and (2) may be adopted, but when synthetic polyisoprene obtained by anionic polymerization is used, the heat history due to coagulation etc. can be reduced, thereby resulting in dip molding. The above method (2) is preferable from the viewpoint that a film molded article such as a body can be made more excellent in tensile strength and elongation.

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

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

In the present invention, in both methods (1) and (2) above, a tall rosin-based surfactant is used as an emulsifier for emulsifying the synthetic polyisoprene. , By using a tall rosin-based surfactant, it is possible to suppress foaming when removing the organic solvent in the subsequent step, and further suppress the generation of aggregates (coagulum) of the resulting synthetic polyisoprene. It is possible to improve the mechanical stability of the latex. Furthermore, a tall rosin-based surfactant is used, and the content in the finally obtained synthetic polyisoprene latex is 0.3 to 1.5 parts by weight per 100 parts by weight of the synthetic polyisoprene. By controlling the ratio to , the resulting film molded article such as a dip molded article can effectively suppress odor and have excellent tensile strength and elongation.

The tall rosin-based surfactant may be a tall rosin obtained by rectification of crude tall oil or a derivative of such a tall rosin as a raw material. Chlorinated metal salts of tall rosin such as sodium tall rosinate, disproportionated tall rosin disproportionated by using a disproportionation catalyst such as an iodine-based catalyst, and resin acids constituting disproportionation tall rosin Metal salts of disproportionated tall rosin such as disproportionated sodium tall rosinate and the like are included. As tall rosin, 33 to 48% by weight of abietic acid, 2 to 8% by weight of neoabietic acid, 10 to 20% by weight of parastric acid, 3 to 8% by weight of pimaric acid, 4 to 10% by weight of isopimaric acid, and hydro Those containing 15 to 25% by weight of abietic acid are preferred. In the disproportionated tall rosin, at least part of abietic acid, neoabietic acid, and parastric acid among the above components is converted to dehydroabietic acid by a disproportionation reaction.

The amount of the tall rosin-based surfactant used as an emulsifier when emulsifying the synthetic polyisoprene is preferably 1 to 15 parts by weight, more preferably 3 to 12 parts by weight, based on 100 parts by weight of the synthetic polyisoprene. More preferably 5 to 10 parts by weight. If the amount of the tall rosin-based surfactant used is too small, emulsification will be insufficient. The content of the surfactant becomes too large, and the odor becomes worse.

The amount of water used when emulsifying the synthetic polyisoprene is preferably 10 to 200 parts by weight, more preferably 30 to 100 parts by weight, and most preferably 50 parts by weight with respect to 100 parts by weight of the synthetic polyisoprene polymer solution. ~70 parts by weight. Types of water to be used include hard water, soft water, ion-exchanged water, distilled water, zeolite water, etc. Soft water, ion-exchanged water and distilled water are preferred. If the amount of water used is too small, emulsification will be insufficient, while if it is too large, the productivity will decrease.

When a synthetic polyisoprene polymer solution is emulsified in water in the presence of a tall rosin-based surfactant as an emulsifier, an emulsifier that is generally commercially available as an emulsifier or disperser can be used without particular limitation. The method of adding the tall rosin-based surfactant to the synthetic polyisoprene polymer solution is not particularly limited. It may be added to the emulsified liquid during the emulsification operation, may be added all at once, or may be added in portions.

Examples of emulsifying devices include batch-type emulsifiers such as the trade name "Homogenizer" (manufactured by IKA), the trade name "Polytron" (manufactured by Kinematica), and the trade name "TK Auto Homomixer" (manufactured by Tokushu Kika Kogyo Co., Ltd.). Machine; trade name "TK Pipeline Homo Mixer" (manufactured by Tokushu Kika Kogyo Co., Ltd.), trade name "Colloid Mill" (manufactured by Shinko Pantec Co., Ltd.), trade name "Slasher" (manufactured by Nippon Coke Kogyo Co., Ltd.), trade name " Trigonal wet pulverizer” (manufactured by Mitsui Miike Kakoki Co., Ltd.), trade name “Cavitron” (manufactured by Eurotech), trade name “Milder” (manufactured by Taiheiyo Kiko Co., Ltd.), trade name “Fine Flow Mill” (Taiheiyo Kiko Co., Ltd.) (manufactured by Mizuho Kogyo Co., Ltd.), trade name "Nanomizer" (manufactured by Nanomizer Co., Ltd.), trade name "APV Gaulin" (manufactured by Gaulin Co., Ltd.), etc. Membrane emulsifiers such as the trade name "Membrane Emulsifier" (manufactured by Reika Kogyo Co., Ltd.); Vibratory emulsifiers such as the trade name "Vibro Mixer" (manufactured by Reika Kogyo Co., Ltd.); Trade name "Ultrasonic Homogenizer" (Branson An ultrasonic emulsifier such as (manufactured by Co., Ltd.) can be used. The conditions for the emulsification operation by the emulsifying device are not particularly limited, and the treatment temperature, treatment time, etc. may be appropriately selected so as to obtain a desired dispersed state.

It is also desirable to remove the organic solvent from the emulsion obtained by emulsifying the synthetic polyisoprene polymer solution in water in the presence of a tall rosin surfactant as an emulsifier. As a method for removing the organic solvent from the emulsion, a method capable of reducing the content of the organic solvent (preferably an aliphatic hydrocarbon solvent) in the emulsion to 500 ppm by weight or less is preferable. Methods such as atmospheric distillation, steam distillation, and centrifugal separation can be employed, but among these, vacuum distillation is preferred from the viewpoint that the organic solvent can be removed appropriately and efficiently.

Additives such as pH adjusters, antifoaming agents, preservatives, chelating agents, oxygen scavengers, dispersants, anti-aging agents, etc., are added to the emulsion after removing the organic solvent. You may Examples of pH adjusters include alkali metal hydroxides such as sodium hydroxide and potassium hydroxide; alkali metal carbonates such as sodium carbonate and potassium carbonate; alkali metal hydrogencarbonates such as sodium hydrogencarbonate; organic amine compounds such as trimethylamine and triethanolamine; and the like, but alkali metal hydroxides and ammonia are preferred.

In addition, after removing the organic solvent, it is desirable to carry out a concentration operation by a method such as vacuum distillation, normal pressure distillation, centrifugation, membrane concentration, etc., as necessary, in order to increase the solid content concentration in the synthetic polyisoprene latex. In particular, centrifugation is preferred because it can increase the solid content concentration in the synthetic polyisoprene latex and adjust the content of the tall rosin-based surfactant in the synthetic polyisoprene latex.

Centrifugation can be performed using, for example, a continuous centrifuge or a batch centrifuge, but from the viewpoint of excellent productivity of the synthetic polyisoprene latex, it is preferable to use a continuous centrifuge. When the emulsion is concentrated by centrifugation, the synthetic polyisoprene latex can be obtained as a light liquid that is a part of the dispersed liquid after centrifugation. Therefore, according to centrifugation, the residual liquid after removing the synthetic polyisoprene latex as the light liquid contains the desired amount of tall rosin-based surfactant to be removed. It is possible to appropriately adjust the content of the tall rosin-based surfactant in the synthetic polyisoprene latex.

The conditions for centrifugation are not particularly limited, and the content of the tall rosin-based surfactant in the finally obtained synthetic polyisoprene latex is 0 per 100 parts by weight of the synthetic polyisoprene contained in the latex. .3 to 1.5 parts by weight. For example, the solid content concentration of the emulsion used for centrifugation (emulsion before centrifugation) is preferably 5 to 11% by weight, more preferably 7 to 10.7% by weight, and still more preferably 9 to 10.5% by weight. %. By setting the solid content concentration of the emulsion before centrifugation within the above range, it is possible to prevent aggregation of synthetic polyisoprene or the like during centrifugation, thereby improving the mechanical stability of the emulsion. is preferable because the amount of the tall rosin-based surfactant in the finally obtained synthetic polyisoprene latex can be appropriately adjusted to the desired amount. When centrifuging, the emulsion from which the organic solvent has been removed may be used as it is, or may be used after adjusting the solid content concentration.

As for the conditions for centrifugation, when a continuous centrifuge is used, the centrifugal acceleration is preferably 5,000 to 11,000 G, more preferably 6,000 to 10,000 G, further preferably is 7,000 to 9,500 G, and the feed amount of the emulsified liquid to the continuous centrifuge is preferably 0.5 to 1.5 m ³ /hour, more preferably 0.7 to 1.45 m ³ /hour. , more preferably 0.9 to 1.4 m ³ /hour, the residence time in the continuous centrifuge is preferably 2.0 to 4.0 minutes, more preferably 2.5 to 3.0 minutes, Further, the back pressure (gauge pressure) of the centrifuge is preferably 0.03 to 1.6 MPa. By setting the conditions for centrifugation as described above, it is possible to prevent aggregation of synthetic polyisoprene or the like during centrifugation. It is preferable because the amount of the tall rosin-based surfactant in the synthetic polyisoprene latex obtained can be appropriately adjusted to the desired amount.

In the above, an example of the conditions for obtaining the synthetic polyisoprene latex of the present invention containing 0.3 to 1.5 parts by weight of the tall rosin-based surfactant with respect to 100 parts by weight of the synthetic polyisoprene. was exemplified, but it is not particularly limited to such conditions. In particular, the amount of the tall rosin-based surfactant in the synthetic polyisoprene latex of the present invention is mainly determined by the amount of the tall rosin-based surfactant used when emulsifying the synthetic polyisoprene polymer solution in water, centrifugation, It can be adjusted by appropriately combining the solid content concentration of the previous emulsion and the conditions for centrifugation. Each condition may be appropriately adjusted so that the amount of the surfactant falls within the range specified by the present invention. For example, when the amount of tall rosin surfactant used for emulsifying a synthetic polyisoprene polymer solution in water is relatively small, the amount of tall rosin surfactant to be removed by centrifugation is relatively small. Therefore, it may be possible to make the centrifugal acceleration in the continuous centrifuge larger than the above range or to increase the feed amount of the emulsified liquid to the continuous centrifuge.

Latex Composition The latex composition of the present invention is obtained by blending the synthetic polyisoprene latex of the present invention with a vulcanizing agent and/or a vulcanization accelerator.

Examples of vulcanizing agents include sulfur such as powdered sulfur, sulfur flowers, precipitated sulfur, colloidal sulfur, surface-treated sulfur, and insoluble sulfur; sulfur chloride, sulfur dichloride, morpholine disulfide, alkylphenol disulfide, N,N'- Sulfur-containing compounds such as dithio-bis(hexahydro-2H-azepinone-2), phosphorus-containing polysulfides, polymeric polysulfides, and 2-(4′-morpholinodithio)benzothiazole can be mentioned. Among these, sulfur can be preferably used. A vulcanizing agent can be used individually by 1 type or in combination of 2 or more types.

The content of the vulcanizing agent is not particularly limited, but is preferably 0.1 to 10 parts by weight, more preferably 0.2 to 3 parts by weight, based on 100 parts by weight of the synthetic polyisoprene contained in the latex. . By setting the content of the vulcanizing agent within the above range, it is possible to further increase the tensile strength of the resulting film-formed article such as a dip-formed article.

As the vulcanization accelerator, those commonly used in the method of obtaining a film molded article such as dip molding can be used. acids, dithiocarbamic acids such as dibenzyldithiocarbamic acid and zinc salts thereof; ) benzothiazole, 2-(N,N-diethylthio-carbylthio)benzothiazole, 2-(2,6-dimethyl-4-morpholinothio)benzothiazole, 2-(4'-morpholino-dithio)benzothiazole, 4- morphonylyl-2-benzothiazyl disulfide, 1,3-bis(2-benzothiazyl-mercaptomethyl)urea and the like, but zinc diethyldithiocarbamate, zinc 2-dibutyldithiocarbamate and zinc 2-mercaptobenzothiazole are preferred. A vulcanization accelerator can be used individually by 1 type or in combination of 2 or more types.

The content of the vulcanization accelerator is preferably 0.05 to 5 parts by weight, more preferably 0.1 to 2 parts by weight, per 100 parts by weight of the synthetic polyisoprene contained in the latex. By setting the content of the vulcanization accelerator within the above range, it is possible to further increase the tensile strength of the obtained film-formed article such as a dip-formed article.

Moreover, the latex composition of the present invention preferably further contains an anti-aging agent. Antiaging agents include 2,6-di-4-methylphenol, 2,6-di-t-butylphenol, butylhydroxyanisole, 2,6-di-t-butyl-α-dimethylamino-p-cresol, octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate, styrenated phenol, 2,2′-methylene-bis(6-α-methyl-benzyl-p-cresol), 4, 4′-methylenebis(2,6-di-t-butylphenol), 2,2′-methylene-bis(4-methyl-6-t-butylphenol), alkylated bisphenols, butylation of p-cresol and dicyclopentadiene Phenolic antioxidants containing no sulfur atoms such as reaction products; 2,2'-thiobis-(4-methyl-6-t-butylphenol), 4,4'-thiobis-(6-t-butyl- o-cresol), 2,6-di-t-butyl-4-(4,6-bis(octylthio)-1,3,5-triazin-2-ylamino)phenol and other thiobisphenol antioxidants; (nonylphenyl) phosphite, diphenylisodecyl phosphite, tetraphenyldipropylene glycol diphosphite and other phosphite ester antioxidants; sulfur ester antioxidants such as dilauryl thiodipropionate; phenyl-α-naphthylamine, Phenyl-β-naphthylamine, p-(p-toluenesulfonylamido)-diphenylamine, 4,4′-(α,α-dimethylbenzyl)diphenylamine, N,N-diphenyl-p-phenylenediamine, N-isopropyl-N′ -amine antioxidants such as phenyl-p-phenylenediamine and butyraldehyde-aniline condensates; quinoline antioxidants such as 6-ethoxy-2,2,4-trimethyl-1,2-dihydroquinoline;2, hydroquinone anti-aging agents such as 5-di-(t-amyl) hydroquinone; These antioxidants may be used singly or in combination of two or more. Among these, phenol-based anti-aging agents are preferable, and phenol-based anti-aging agents containing no sulfur atom are more preferable because they have a small effect of inhibiting the vulcanization reaction and have a high antioxidant effect.

The content of the antioxidant is preferably 0.1 to 10 parts by weight, more preferably 1 to 7 parts by weight, and still more preferably 3 to 6 parts by weight, based on 100 parts by weight of the synthetic polyisoprene contained in the latex. is. By setting the content of the anti-aging agent within this range, a sufficient anti-oxidation effect can be obtained without inhibiting the vulcanization reaction during vulcanization, which is preferable.

Moreover, the latex composition of the present invention 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, based on 100 parts by weight of the synthetic polyisoprene contained in the latex. By setting the content of zinc oxide within the above range, it is possible to improve the emulsion stability and further increase the tensile strength of the resulting film-formed article such as a dip-formed article.

The latex composition of the present invention further contains compounding agents such as dispersants; reinforcing agents such as carbon black, silica and talc; fillers such as calcium carbonate and clay; UV absorbers; can be compounded.

The method for preparing the latex composition of the present invention is not particularly limited. After preparing an aqueous dispersion of ingredients other than synthetic polyisoprene latex using a method of mixing various compounding agents such as anti-aging agents that are blended as necessary, or using such a disperser, the aqueous dispersion is prepared. A method of mixing the liquid with synthetic polyisoprene latex and the like can be mentioned.

The latex composition of the present invention preferably has a pH of 7 or higher, more preferably in the range of 7-13, and even more preferably in the range of 8-12. Also, the solid content concentration of the latex composition is preferably in the range of 15 to 65% by weight.

The latex composition of the present invention is preferably aged (pre-crosslinked) before being subjected to molding such as dip molding from the viewpoint of further enhancing the mechanical properties of the resulting film molded article such as dip molded article. The pre-crosslinking time is not particularly limited and depends on the pre-crosslinking temperature, but is preferably 1 to 14 days, more preferably 1 to 7 days. The pre-crosslinking temperature is preferably 20 to 40°C.
After pre-crosslinking, it is preferably stored at a temperature of 10 to 30° C. until it is subjected to molding such as dip molding. If stored at a high temperature, the tensile strength of the resulting film-formed article such as a dip-formed article may decrease.

Film molded article The film molded article of the present invention is a film-like molded article made of the latex composition of the present invention. The film thickness of the film molded product of the present invention is preferably 0.03 to 0.50 mm, more preferably 0.05 to 0.40 mm, particularly preferably 0.08 to 0.30 mm.

Although the film molded article of the present invention is not particularly limited, it is preferably a dip molded article obtained by dip molding the latex composition of the present invention. Dip molding is a method in which a mold is immersed in a latex 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 surface of the mold is dried. be. The mold may be preheated before being immersed in the latex composition. A coagulant can also be used, if desired, before the mold is dipped into the latex composition or after the mold is lifted from the latex composition.

Specific examples of the method of using the coagulant include a method of immersing the mold before being immersed in the latex composition in a coagulant solution to adhere the coagulant to the mold (anodic coagulant dipping method), and a method of depositing the latex composition. Although there is a method of immersing the molded mold in a coagulant solution (Teeg adhesion dipping method), the anodic adhesion dipping method is preferable in that a dip molded article with little unevenness in thickness 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; acetic acid such as barium acetate, calcium acetate and zinc acetate; salts; sulfates such as calcium sulfate, magnesium sulfate, and aluminum sulfate; water-soluble polyvalent metal salts such as; Among them, calcium salts are preferred, and calcium nitrate is more preferred. These water-soluble polyvalent metal salts can be used alone or in combination of two or more.

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

After the mold is withdrawn from the latex composition, it is usually heated to dry the deposit formed on the mold. Drying conditions may be appropriately selected.

Heating is then applied to crosslink the deposit formed on the mold.
The heating conditions for cross-linking are not particularly limited, but the heating temperature is preferably 60 to 150° C., more preferably 100 to 130° C., and the heating time is preferably 10 to 120 minutes.
The heating method is not particularly limited, but includes a method of heating with hot air in an oven, a method of heating by irradiating infrared rays, and the like.

Also, before or after heating the latex composition-deposited mold, the mold can be washed with water or hot water to remove water-soluble impurities (e.g., excess surfactant and coagulant). preferable. The hot water to be used is preferably 40°C to 80°C, more preferably 50°C to 70°C.

The dip molded article after cross-linking is removed from the mold. Specific examples of the detachment method include a method of manually peeling from the mold, a method of peeling by water pressure or compressed air pressure, and the like. If the dip-molded article in the middle of cross-linking has sufficient strength against detachment, it may be detached in the middle of cross-linking, and the subsequent cross-linking may be continued.

The film molded article of the present invention and the dip molded article, which is one aspect thereof, are obtained using the above-described latex of the present invention, and therefore are excellent in tensile strength and elongation, and are particularly suitable for gloves, for example. can be used for In the case where the membrane molded article is a glove, the glove is coated with inorganic fine particles such as talc or calcium carbonate or organic fine particles such as starch particles in order to prevent the contact surfaces of the membrane compacts from sticking to each other and to improve the slippage when putting on and taking off the gloves. It may be sprayed on the surface, an elastomer layer containing fine particles may be formed on the glove surface, or the surface layer of the glove may be chlorinated.

In addition to the above-mentioned gloves, the film molded article of the present invention and the dip molded article which is one aspect thereof can also be used for nursing bottle nipples, droppers, tubes, water pillows, balloon sacks, catheters, condoms, and other medical supplies; balloons; , dolls, balls and other toys; industrial products such as pressure molding bags and gas storage bags; finger cots and the like.

Packaging structure The packaging structure of the present invention is formed by adhesively laminating the first sheet base material and the second sheet base material coated with the synthetic polyisoprene latex of the present invention described above, and is capable of accommodating an item to be packaged. Show structure. Specifically, in the packaging structure of the present invention, the first sheet base material and the second sheet base material are arranged such that the surfaces coated with the synthetic polyisoprene latex (latex-coated surfaces) face each other. If necessary, the article to be packaged is sandwiched and pressed while the latex-coated surfaces of the first sheet base material and the second sheet base material are in contact with each other, thereby separating the first sheet base material and the second sheet base material. The sheet base material is adhered to each other, thereby forming a structure capable of packaging an object to be packaged. The items to be packaged are not particularly limited, but include, for example, various items to be packaged that are desired to be sterilized, such as medical products such as bandages. The first sheet base material and the second sheet base material are not particularly limited, but examples include paper materials such as glassine paper, high-density polyethylene nonwoven fabric, polyolefin film, polyester film, etc. A paper material is preferable, and glassine paper is particularly preferable, because it is easy to handle (it has an appropriate degree of bending easiness) and it is inexpensive.

EXAMPLES The present invention will be described in more detail below with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples. In the following, "parts" are by weight unless otherwise specified. Physical properties and properties are tested or evaluated as follows.

Weight average molecular weight (Mw)
The synthetic polyisoprene contained in the polymer solution was diluted with tetrahydrofuran so that the solid content concentration was 0.1% by weight. Average molecular weight (Mw) was calculated.

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

Content ratio of disproportionated tall sodium rosinate and disproportionated gum sodium rosinate To 0.1 g of polyisoprene latex, 2 ml of water was added and diluted to 10 ml with acetonitrile. The resulting liquid was shaken well to solidify the rubber. The aqueous layer was then filtered through a 0.2 μm disc filter. This liquid was analyzed by high-performance liquid chromatography to calculate the content ratio (unit: parts by weight) of disproportionated sodium tall rosinate and disproportionated sodium gum rosinate with respect to 100 parts of synthetic polyisoprene.

A film-like dip-molded article having an odor film thickness of about 0.2 mm was evaluated for odor according to the following criteria.
A: No odor is felt at all.
B: Slight odor, but not unpleasant.
C: Odor is clearly sensed.
D: A strong odor is sensed, which is unpleasant.

Carbon disulfide content and carbonyl sulfide content Measurement of the carbon disulfide content and carbonyl sulfide content of a film-shaped dip molded product with a thickness of about 0.2 mm using a triple quadrupole gas chromatograph mass spectrometer. did Specifically, the area (Area) of the peak corresponding to carbon disulfide detected by triple quadrupole gas chromatograph mass spectrometry and the area (Area) of the peak corresponding to carbonyl sulfide are converted to 1 g of sample. The obtained values were obtained as the amount of carbon disulfide and the amount of carbonyl sulfide (unit: Area/g). Since carbon disulfide and carbonyl sulfide cause odor, it can be judged that the larger the amount of carbon disulfide and the amount of carbonyl sulfide (unit: Area/g), the stronger the odor.

Based on the tensile strength, elongation at break (tensile elongation), and 500% tensile stress ASTM D412 of the dip-molded body, a film-shaped dip-molded body having a thickness of about 0.2 mm was used as a dumbbell (trade name: "Super Dumbbell (model : SDMK-100C)”, manufactured by Dumbbell) to prepare a test piece for tensile strength measurement. The test piece is pulled at a tensile speed of 500 mm / min with a Tensilon universal testing machine (trade name "RTG-1210", manufactured by Orientec Co., Ltd.), tensile strength immediately before breakage (unit: MPa), elongation immediately before breakage (unit: % ) and the tensile stress (unit: MPa) at an elongation of 500%. Incidentally, the higher the tensile strength and the elongation at break, the better. Also, the smaller the tensile stress at 500%, the better the flexibility of the dip-molded article, which is preferable.

Example 1
(Production of polymer solution of synthetic polyisoprene (a-1))
1150 parts of normal hexane and 100 parts of isoprene were charged into a dried and nitrogen-purged agitated autoclave. Next, the temperature in the autoclave is set to 60° C., 0.006 part of n-butyllithium is added with stirring and reacted for 2 hours, and then 0.05 part of methanol is added as a polymerization terminator to stop the reaction. A normal hexane solution of synthetic polyisoprene (a-1) was obtained. The weight average molecular weight of synthetic polyisoprene (a-1) in the normal hexane solution was 3,520,000.

(Production of synthetic polyisoprene latex (A-1))
Next, 1250 parts of the normal hexane solution of the obtained synthetic polyisoprene (a-1) was heated to 60°C, and 1250 parts of an aqueous solution of disproportionated sodium tall rosinate having a concentration of 1.0% by weight heated to 60°C, The flow rate was adjusted so that the weight ratio was 1:1, mixing was performed using a line mixer, and then an emulsion was obtained using a homogenizer.

Further, the emulsified liquid obtained above was heated to 80° C. under reduced pressure to distill off normal hexane, thereby obtaining an aqueous dispersion of synthetic polyisoprene (a-1). After adjusting the resulting water dispersion to a solid content concentration of 10.3% by weight, the water dispersion liquid with the adjusted solid content concentration is subjected to a closed disk type continuous centrifuge (product name “SGR509”, manufactured by Alfa Laval ) at a flow rate of 1.0 m ³ / hour (condition of 3.0 minutes when converted to residence time), centrifuged at a centrifugal acceleration of 9,000 G, and synthetic polyisoprene latex ( A-1) was obtained. The content of disproportionated sodium tall rosinate in the obtained synthetic polyisoprene latex (A-1) was measured and found to be 0.8 parts per 100 parts of synthetic polyisoprene.

(Preparation of latex composition)
While stirring the synthetic polyisoprene latex (A-1) obtained above, the compounding amount in terms of solid content is 1 part per 100 parts of the synthetic polyisoprene in the synthetic polyisoprene latex (A-1). Sodium dodecylbenzenesulfonate with a concentration of 10% by weight was added so as to obtain a Then, while stirring the obtained mixture, 1.5 parts of zinc oxide, 1.5 parts of sulfur, and an antioxidant (trade name “Wingstay L", manufactured by Goodyear), 0.3 parts of zinc diethyldithiocarbamate, 0.5 parts of zinc dibutyldithiocarbamate, and 0.7 parts of zinc mercaptobenzothiazole. After the addition, an aqueous potassium hydroxide solution was added to obtain a latex composition adjusted to pH 10.5. After that, the resulting latex composition was aged for 48 hours in a constant temperature water bath adjusted to 30°C.

(Manufacturing of dip molded body)
Ground-surfaced glass molds (approximately 5 cm in diameter and approximately 15 cm of grind length) were cleaned and preheated in an oven at 70° C. before being treated with 18% by weight calcium nitrate and 0.05% by weight polyoxyethylene. It was immersed in an aqueous coagulant solution containing lauryl ether (trade name “Emulgen 109P”, manufactured by Kao Corporation) for 5 seconds and then taken out. The coagulant-coated glass mold was then dried in an oven at 70° C. for 30 minutes or more.

After that, the coagulant-coated glass mold is removed from the oven, the latex composition obtained above is adjusted to 25° C., immersed in the latex composition for 10 seconds, then removed, and then at room temperature for 60 minutes. Air-drying yielded a film-coated glass mold. Then, the glass mold coated with the film was immersed in hot water at 60° C. for 2 minutes, and then air-dried at room temperature for 30 minutes. After that, the glass mold covered with the film was placed in an oven at 120 ° C. for 20 minutes to vulcanize, cooled to room temperature, sprinkled with talc, and then peeled off the film from the glass mold to obtain a dip molded body. got Then, using the obtained dip-molded body, odor, amount of carbon disulfide, amount of carbonyl sulfide, tensile strength, elongation at break, and 500% tensile stress were measured according to the above methods. Table 1 shows the results.

Example 2
(Production of synthetic polyisoprene latex (A-2))
The flow rate when continuously feeding the water dispersion with the adjusted solid content concentration to the continuous centrifuge is from 1.0 m ³ / hour to 1.3 m ³ / hour (converted to residence time, 2.3 minutes A synthetic polyisoprene latex (A-2) was obtained in the same manner as in Example 1, except that the conditions were changed. The content of disproportionated sodium tall rosinate in the obtained synthetic polyisoprene latex (A-2) was measured and found to be 1.3 parts per 100 parts of synthetic polyisoprene.

(Preparation of latex composition, manufacture of dip molded product)
Then, a latex composition was prepared and a dip-molded body was produced in the same manner as in Example 1, except that the synthetic polyisoprene latex (A-2) obtained above was used, and evaluation was performed in the same manner. gone. Table 1 shows the results.

Example 3
(Production of synthetic polyisoprene latex (A-3))
A normal hexane solution of the synthetic polyisoprene (a-1) obtained in the same manner as in Production Example 1 was coagulated in methanol, and then the obtained coagulate was vacuum-dried at 70° C. for 12 hours to obtain a solid state. of synthetic polyisoprene (a-1) was obtained. Next, the obtained solid synthetic polyisoprene (a-1) is redissolved in normal hexane to obtain a normal hexane solution of the synthetic polyisoprene (a-1) having a solid concentration of 8% by weight. Synthetic polyisoprene was obtained by preparing an emulsified liquid, distilling off normal hexane, and centrifuging in the same manner as in Example 2, except that the normal hexane solution of the obtained synthetic polyisoprene (a-1) was used. A latex (A-3) was obtained. The content of disproportionated sodium tall rosinate in the obtained synthetic polyisoprene latex (A-3) was measured and found to be 1.3 parts per 100 parts of synthetic polyisoprene.

(Preparation of latex composition, manufacture of dip molded product)
Then, a latex composition was prepared and a dip-molded article was produced in the same manner as in Example 1, except that the synthetic polyisoprene latex (A-3) obtained above was used, and evaluation was performed in the same manner. gone. Table 1 shows the results.

Example 4
(Production of polymer solution of synthetic polyisoprene (a-2))
1150 parts of normal hexane and 100 parts of isoprene were charged into a dried and nitrogen-purged agitated autoclave. Next, the temperature in the autoclave is set to 30° C., and 0.03 parts of titanium tetrachloride, 0.03 parts of triisobutylaluminum, and 0.005 parts of normal butyl ether are added with stirring and reacted for 2 hours, followed by a polymerization terminator. 0.05 part of methanol was added as a solution to stop the reaction, and a normal hexane solution of synthetic polyisoprene (a-2) was obtained. The weight average molecular weight of synthetic polyisoprene (a-2) in the normal hexane solution was 1,860,000.

(Production of synthetic polyisoprene latex (A-4))
The normal hexane solution of the synthetic polyisoprene (a-2) obtained above was coagulated in methanol, and the resulting coagulate was vacuum-dried at 70° C. for 12 hours to obtain a solid synthetic polyisoprene. (a-2) was obtained. Next, the obtained solid synthetic polyisoprene (a-2) was redissolved in normal hexane to obtain a normal hexane solution of synthetic polyisoprene (a-2) having a solid content concentration of 8% by weight. Then, preparation of an emulsified liquid, distillation of normal hexane, and centrifugation were carried out in the same manner as in Example 2, except that the normal hexane solution of the synthetic polyisoprene (a-2) obtained by redissolution was used. to obtain a synthetic polyisoprene latex (A-4). The content of disproportionated sodium tall rosinate in the obtained synthetic polyisoprene latex (A-4) was measured and found to be 1.3 parts per 100 parts of synthetic polyisoprene.

(Preparation of latex composition, manufacture of dip molded product)
Then, a latex composition was prepared and a dip-molded body was produced in the same manner as in Example 1, except that the synthetic polyisoprene latex (A-4) obtained above was used, and evaluation was performed in the same manner. gone. Table 1 shows the results.

Comparative example 1
(Production of synthetic polyisoprene latex (A-5))
The solid content concentration of the aqueous dispersion of synthetic polyisoprene (a-1) to be centrifuged was changed to 11.5% by weight, and the flow rate when continuously fed to the continuous centrifuge was 1.0 m. Synthetic polyisoprene latex (A-5) was obtained in the same manner as in Example 1, except that the flow rate was changed from 3 m ³ /h to 1.6 m ³ /h (1.9 minutes in terms of residence time). The content of disproportionated sodium tall rosinate in the obtained synthetic polyisoprene latex (A-5) was measured and found to be 1.7 parts per 100 parts of synthetic polyisoprene.

(Preparation of latex composition, manufacture of dip molded product)
Then, a latex composition was prepared and a dip-molded article was produced in the same manner as in Example 1, except that the synthetic polyisoprene latex (A-5) obtained above was used, and evaluation was performed in the same manner. gone. Table 1 shows the results.

Comparative example 2
(Production of synthetic polyisoprene latex (A-6))
The solid content concentration of the aqueous dispersion of synthetic polyisoprene (a-1) to be centrifuged was changed to 11.5% by weight, and the flow rate when continuously fed to the continuous centrifuge was 1.0 m. A synthetic polyisoprene latex (A-6) was obtained in the same manner as in Example 1, except that the flow rate was changed from ³ /h to 1.3 m ³ /h and the centrifugal acceleration was changed to 12,000G. The content of disproportionated sodium tall rosinate in the obtained synthetic polyisoprene latex (A-6) was measured and found to be 0.2 parts per 100 parts of synthetic polyisoprene.

A latex composition was prepared in the same manner as in Example 1, except that the synthetic polyisoprene latex (A-6) obtained above was used. However, it was not possible to prepare a latex composition, and furthermore, it was not possible to produce a dip-molded product.

Comparative example 3
(Production of synthetic polyisoprene latex (A-7))
A synthetic polymer was prepared in the same manner as in Example 2, except that an aqueous solution of sodium disproportionated gum rosinate (trade name "Londis K-25", manufactured by Arakawa Chemical Industries, Ltd.) having a concentration of 1.0% by weight was used as the emulsifier. An isoprene latex (A-7) was obtained. The content of disproportionated gum sodium rosinate in the obtained synthetic polyisoprene latex (A-7) was measured and found to be 1.3 parts per 100 parts of synthetic polyisoprene.

(Preparation of latex composition, manufacture of dip molded product)
Then, a latex composition was prepared and a dip-molded body was produced in the same manner as in Example 1, except that the synthetic polyisoprene latex (A-7) obtained above was used, and evaluation was performed in the same manner. gone. Table 1 shows the results.

（＊１）合成ポリイソプレン１００部に対する含有量

(*1) Content per 100 parts of synthetic polyisoprene

From Table 1, a dip as one embodiment of a film molded product obtained using a synthetic polyisoprene latex containing 0.3 to 1.5 parts of a tall rosin-based surfactant with respect to 100 parts of synthetic polyisoprene. The molded articles had an effectively suppressed odor, excellent tensile strength and elongation, and had a soft texture (low 500% tensile stress) (Examples 1 to 4).

On the other hand, when the amount of the tall rosin-based surfactant in the synthetic polyisoprene latex was too large, the resulting dip-molded article had a strong odor and was inferior in tensile strength (Comparative Example 1).
Further, when the amount of the tall rosin-based surfactant in the synthetic polyisoprene latex was too small, the synthetic polyisoprene agglomerated remarkably, resulting in extremely poor latex stability (Comparative Example 2).
Furthermore, when disproportionated sodium gum rosinate was used as an emulsifier, the resulting dip molded product had a strong odor (Comparative Example 3).

Claims (9)

Containing 0.3 to 1.5 parts by weight of a tall rosin-based surfactant with respect to 100 parts by weight of synthetic polyisoprene ,
A synthetic polyisoprene latex wherein the tall rosin-based surfactant is a metal salt of disproportionated tall rosin . The synthetic polyisoprene latex according to Claim 1, wherein the synthetic polyisoprene is polymerized by anionic polymerization. 3. The synthetic polyisoprene latex according to claim 1, wherein the content of said tall rosin-based surfactant is in a proportion of 0.3 to 1.3 parts by weight with respect to 100 parts by weight of said synthetic polyisoprene. A method for producing the synthetic polyisoprene latex according to any one of claims 1 to 3,
A method for producing a synthetic polyisoprene latex comprising a step of emulsifying a polymer solution of synthetic polyisoprene polymerized by anionic polymerization in water in the presence of a tall rosin surfactant. 5. The method for producing a synthetic polyisoprene latex according to claim 4, wherein the polymer solution contains an organic solvent. The method for producing a synthetic polyisoprene latex according to claim 5, further comprising a step of removing the organic solvent from the emulsion obtained by the step of emulsifying in water. A latex composition containing the synthetic polyisoprene latex according to any one of claims 1 to 3 and a vulcanizing agent and/or a vulcanization accelerator. A molded film made of the latex composition according to claim 7 . At least part of the first sheet substrate and at least part of the second sheet substrate are adhesively laminated with a coating film made of the synthetic polyisoprene latex according to any one of claims 1 to 3, A packaging structure capable of accommodating an object to be packaged between the first sheet base material and the second sheet base material.