JP2020100738A - Method for producing modified polyisoprene latex - Google Patents

Abstract

To provide a method for producing modified polyisoprene latex, in which a modified polyisoprene latex having excellent handleability and capable of yielding a dip-formed product having a high tensile strength, can be produced with high productivity.SOLUTION: The method for producing modified polyisoprene latex is a method for producing modified polyisoprene latex in which a carboxyl group-containing compound is added to a polyisoprene latex and the polyisoprene and the carboxyl group-containing compound are reacted, and in which, as the polyisoprene latex, one having a volume average particle size of 700 nm or more and an electric conductivity of 1.5 mS/cm or less is used.SELECTED DRAWING: None

Description

TECHNICAL FIELD The present invention relates to a method for producing a modified polyisoprene latex capable of producing a modified polyisoprene latex capable of giving a dip-molded article having excellent handleability and high tensile strength with high productivity.

It is conventionally known that a latex composition containing a latex of natural rubber is dip-molded to obtain a dip-molded product which is used in contact with a human body such as a nipple, a balloon, a glove, a balloon and a sack. However, since the latex of natural rubber contains a protein that causes allergic symptoms in the human body, it may have a problem as a dip-molded product that comes into direct contact with a living mucous membrane or an organ. Therefore, studies have been conducted to remove proteins in the latex of natural rubber by purification or to use latex of synthetic rubber instead of natural rubber.

For example, Patent Document 1 discloses a method for producing a carboxy-modified synthetic isoprene polymer latex, which comprises a step of graft-polymerizing a monomer having a carboxyl group in a synthetic isoprene polymer in an aqueous phase. The carboxy-modified synthetic isoprene polymer latex contains at least one anionic surfactant, and the carboxy-modified synthetic isoprene polymer constituting the carboxy-modified synthetic isoprene polymer latex has a tetrahydrofuran insoluble content of 30% by weight or more. A method for producing a carboxy-modified synthetic isoprene polymer latex for dip molding is disclosed. However, in the technique of Patent Document 1, there are cases where aggregates are generated after the carboxy modification reaction, and there is room for improvement in productivity.

Japanese Patent No. 6206482

The present invention has been made in view of the above circumstances, excellent handling properties, and a modified polyisoprene latex that can provide a dip-molded article having high tensile strength, a modified polyisoprene latex that can be produced with high productivity. It aims at providing the manufacturing method of.

The present inventors, as a result of intensive studies to achieve the above objects, using a latex of polyisoprene having a specific volume average particle diameter and conductivity, by producing a latex of modified polyisoprene, The inventors have found that the above objects can be achieved, and completed the present invention.

That is, according to the present invention, a method for producing a latex of modified polyisoprene, which comprises adding a carboxyl group-containing compound to a latex of polyisoprene and reacting the polyisoprene and the carboxyl group-containing compound, wherein the polyisoprene is There is provided a method for producing a modified polyisoprene latex using a latex having a volume average particle size of 700 nm or more and an electric conductivity of 1.5 mS/cm or less.

In the present invention, it is preferable that the polyisoprene and the carboxyl group-containing compound are reacted in the presence of an anionic surfactant having a sulfonic acid group and a naphthalene structure.
In the present invention, the polyisoprene latex preferably has a solid content concentration of 20% by weight or more and less than 40% by weight.

Further, according to the present invention, there is provided a method for producing a latex composition, which comprises a step of adding a crosslinking agent to the modified polyisoprene latex obtained by the above production method.

Further, according to the present invention, there is provided a method for producing a dip-formed article, which comprises a step of dip-forming the latex composition obtained by the above-mentioned production method.

Further, according to the present invention, a method for producing an adhesive layer-forming substrate, comprising a step of forming an adhesive layer formed by using the modified polyisoprene latex obtained by the above-mentioned production method on the surface of the substrate. Will be provided.

ADVANTAGE OF THE INVENTION According to this invention, the modified polyisoprene latex which is excellent in handling property and which can provide a dip-molded article with high tensile strength is provided, and the manufacturing method of the modified polyisoprene latex which can be produced with high productivity is provided. can do.

The modified polyisoprene latex production method of the present invention comprises adding a carboxyl group-containing compound to a polyisoprene latex having a volume average particle diameter of 700 nm or more and an electric conductivity of 1.5 mS/cm or less, It is a production method of reacting isoprene with the carboxyl group-containing compound. The "conductivity" of the polyisoprene latex here means the conductivity measured in the polyisoprene latex having a solid content concentration of 30% by weight.

Polyisoprene Latex First, the polyisoprene latex used in the production method of the present invention will be described.
The latex of polyisoprene used in the production method of the present invention is not particularly limited, and a latex of synthetic polyisoprene or a latex of natural rubber from which proteins have been removed can be used. Latex is preferably used. In the production method of the present invention, a latex of polyisoprene and a carboxyl group-containing compound are reacted to produce a latex of modified polyisoprene. As the latex, one having a volume average particle diameter of 700 nm or more and an electric conductivity of 1.5 mS/cm or less is used.

Synthetic polyisoprene latex Synthetic polyisoprene contained in the synthetic polyisoprene latex may be a homopolymer of isoprene or may be copolymerized with isoprene and another ethylenically unsaturated monomer copolymerizable therewith. It may be one. The content of isoprene units in the synthetic polyisoprene is preferably 70% by weight or more, more preferably 90% by weight, based on the total monomer units, since a dip-molded product that is flexible and has excellent tensile strength can be easily obtained. % Or more, more preferably 95% by weight or more, and particularly preferably 100% by weight (isoprene homopolymer).

Other ethylenically unsaturated monomers copolymerizable with isoprene include, for example, 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 (means "methyl acrylate and/or methyl methacrylate"; , Ethyl (meth)acrylate, etc.), ethyl (meth)acrylate, butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, etc., ethylenically unsaturated carboxylic acid ester monomers; Are listed. These other ethylenically unsaturated monomers copolymerizable with isoprene may be used alone or in combination of two or more.

Synthetic polyisoprene can be prepared in an inert polymerization solvent using a conventionally known method, for example, a Ziegler-based polymerization catalyst composed of trialkylaluminum-titanium tetrachloride or an alkyllithium polymerization catalyst such as n-butyllithium or sec-butyllithium. , Isoprene, and other copolymerizable ethylenically unsaturated monomer used as necessary can be obtained by solution polymerization. The polymer solution of synthetic polyisoprene obtained by solution polymerization may be used as it is for the production of latex of synthetic polyisoprene, but after taking out solid synthetic polyisoprene from the polymer solution, it is dissolved in an organic solvent. Then, it can be used for the production of a latex of synthetic polyisoprene.
At this time, impurities such as the residue of the polymerization catalyst remaining in the polymer solution after the synthesis may be removed. Further, an anti-aging agent described below may be added to the solution during or after the polymerization. Alternatively, commercially available solid synthetic polyisoprene can be used.

There are four types of isoprene units in the synthetic polyisoprene, which are a cis bond unit, a trans bond unit, a 1,2-vinyl bond unit, and a 3,4-vinyl bond unit, depending on the bonding state of the isoprene. From the viewpoint of improving the tensile strength of the obtained dip molded product, the content ratio 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 further preferably, in terms of standard polystyrene by gel permeation chromatography analysis. Is 800,000 to 3,000,000. When the weight average molecular weight of the synthetic polyisoprene is within the above range, the tensile strength of the dip-formed product is improved and the latex of the synthetic polyisoprene tends to be easily produced.

Moreover, the polymer Mooney viscosity (ML1+4, 100° C.) of the synthetic polyisoprene is preferably 50 to 80, more preferably 60 to 80, and further preferably 70 to 80.

As a method for obtaining a latex of synthetic polyisoprene, for example, (1) a solution or fine suspension of synthetic polyisoprene dissolved or finely dispersed in an organic solvent is emulsified in water in the presence of a surfactant. A method of producing a latex of synthetic polyisoprene by optionally removing an organic solvent, (2) isoprene alone or a mixture of isoprene and an ethylenically unsaturated monomer copolymerizable therewith, In the presence, emulsion polymerization or suspension polymerization, directly, a method of producing a latex of synthetic polyisoprene, there may be mentioned, a synthetic polyisoprene having a high proportion of cis bond units in isoprene units can be used, The production method of (1) above is preferable from the viewpoint that a dip-formed product having excellent mechanical properties such as tensile strength can be easily obtained.

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

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

From the viewpoint of adjusting the conductivity of the latex of synthetic polyisoprene, it is preferable to use an ionic surfactant as the surfactant used in the above-mentioned production method (1), and among them, an anionic surfactant is more preferable. preferable. Examples of the anionic surfactant include fatty acid salts such as sodium laurate, potassium myristate, sodium palmitate, potassium oleate, sodium linolenate, and sodium rosinate; sodium dodecylbenzenesulfonate, potassium dodecylbenzenesulfonate, Alkylbenzenesulfonates such as sodium decylbenzenesulfonate, potassium decylbenzenesulfonate, sodium cetylbenzenesulfonate, potassium cetylbenzenesulfonate; sodium di(2-ethylhexyl)sulfosuccinate, potassium di(2-ethylhexyl)sulfosuccinate, Alkyl sulfosuccinates such as sodium dioctyl sulfosuccinate; Alkyl sulfate ester salts such as sodium lauryl sulfate and potassium lauryl sulfate; Polyoxyethylene alkyl ether sulfate salts such as sodium polyoxyethylene lauryl ether sulfate and potassium polyoxyethylene lauryl ether sulfate And monoalkyl phosphates such as sodium lauryl phosphate and potassium lauryl phosphate; and the like.

Among these anionic surfactants, fatty acid salts, alkylbenzene sulfonates, alkylsulfosuccinates, alkyl sulfate ester salts and polyoxyethylene alkyl ether sulfate ester salts are preferable, and fatty acid salts and alkylbenzene sulfonate salts are particularly preferable.

In addition, trace amount of the polymerization catalyst (particularly, aluminum and titanium) derived from the synthetic polyisoprene can be removed more efficiently, and the generation of aggregates is suppressed during the production of the latex composition. It is preferable to use a fatty acid salt in combination with at least one selected from the group consisting of a sulfonate, an alkylsulfosuccinate, an alkyl sulfate ester salt and a polyoxyethylene alkyl ether sulfate ester salt. It is particularly preferable to use a fatty acid salt in combination. Here, the fatty acid salt is preferably sodium rosinate and potassium rosinate, and the alkylbenzene sulfonate is preferably sodium dodecylbenzenesulfonate and potassium dodecylbenzenesulfonate. Further, these surfactants may be used alone or in combination of two or more.

As described above, the fatty acid salt is used in combination with at least one selected from the group consisting of alkyl benzene sulfonate, alkyl sulfosuccinate, alkyl sulfate ester salt and polyoxyethylene alkyl ether sulfate ester salt. The resulting latex contains a fatty acid salt and at least one selected from the group consisting of alkylbenzene sulfonate, alkylsulfosuccinate, alkyl sulfate ester salt and polyoxyethylene alkyl ether sulfate ester salt. ..

In the production method of (1) above, a surfactant other than the anionic surfactant may be used in combination, and as such a surfactant other than the anionic surfactant, α,β-insoluble Examples thereof include copolymerizable surfactants such as sulfoesters of saturated carboxylic acids, sulfate esters of α,β-unsaturated carboxylic acids, and sulfoalkylaryl ethers.

In addition, polyoxyethylene alkyl ether, polyoxyethylene alkylphenol ether, polyoxyethylene alkyl ester, polyoxyethylene sorbitan alkyl ester, etc. You may use together surfactant.

The amount of the surfactant used in the production method (1) is preferably 0.1 to 100 parts by weight, more preferably 0.5 to 80 parts by weight, and further preferably 100 parts by weight of the synthetic polyisoprene. Is 1 to 50 parts by weight. When two or more kinds of surfactants are used, the total amount of these used is preferably within the above range. That is, for example, when a fatty acid salt is used in combination with at least one selected from the group consisting of alkylbenzene sulfonate, alkylsulfosuccinate, alkyl sulfate ester salt and polyoxyethylene alkyl ether sulfate ester salt, It is preferable that the total amount used is within the above range. If the amount of the surfactant used is too small, a large amount of aggregates may be generated during emulsification. Conversely, if it is too large, foaming tends to occur, and pinholes may occur in the resulting dip-molded product. ..

When a fatty acid salt is used in combination with at least one selected from the group consisting of alkylbenzene sulfonate, alkylsulfosuccinate, alkyl sulfate ester salt and polyoxyethylene alkyl ether sulfate ester salt as an anionic surfactant. In addition, the ratio of these used is "fatty acid salt": "alkylbenzene sulfonate, alkyl sulfosuccinate, alkyl sulfate ester salt and polyoxyethylene alkyl ether sulfate ester salt at least one kind of surface active agent selected from The weight ratio of "total amount of agents" is preferably in the range of 1:1 to 10:1, more preferably in the range of 1:1 to 7:1. If the amount of at least one surfactant selected from the group consisting of alkyl benzene sulfonate, alkyl sulfosuccinate, alkyl sulfate ester salt and polyoxyethylene alkyl ether sulfate ester is too large, the synthetic polyisoprene is not easily handled. Foaming may become violent, which requires operations such as standing for a long time and addition of an antifoaming agent, which may lead to deterioration in workability and cost increase.

The amount of water used in the production method (1) is preferably 10 to 1,000 parts by weight, more preferably 30 to 500 parts by weight, and most preferably 100 parts by weight of the organic solvent solution of synthetic polyisoprene. Is 50 to 100. Examples of the type of water used include hard water, soft water, ion-exchanged water, distilled water, zeolite water and the like, and soft water, ion-exchanged water and distilled water are preferable.

An apparatus for emulsifying a solution or fine suspension of a synthetic polyisoprene dissolved or finely dispersed in an organic solvent in water in the presence of a surfactant is particularly preferable as long as it is commercially available as an emulsifier or a disperser. It can be used without limitation. The method of adding the surfactant to the solution or fine suspension of the synthetic polyisoprene is not particularly limited, and it is added to water or the solution or fine suspension of the synthetic polyisoprene in advance, or both. It may be added to the emulsion during the emulsification operation, may be added all at once, or may be added in portions.

Examples of the emulsifying device include batch type emulsifiers such as trade name "homogenizer" (manufactured by IKA), trade name "Polytron" (manufactured by Kinematica), trade name "TK Auto Homo Mixer" (manufactured by Tokushu Kika Kogyo). Machine: Product name "TK Pipeline Homo Mixer" (made by Tokushu Kika Kogyo Co., Ltd.), product name "Colloid Mill" (made by Shinko Pantec Co., Ltd.), product name "Slasher" (made by Nippon Coke Industry Co., Ltd.), product name " "Trigonal wet milling machine" (Mitsui Miike Kakoki Co., Ltd.), trade name "Cavitron" (Eurotec Co., Ltd.), trade name "Milder" (Pacific Kiko Co., Ltd.), trade name "Fine Flow Mill" (Pacific Kiko Co., Ltd.) High-pressure emulsifiers such as product name "Microfluidizer" (manufactured by Mizuho Industry Co., Ltd.), product name "Nanomizer" (manufactured by Nanomizer), product name "APV Gaulin" (manufactured by Gaulin), etc. Membrane emulsifiers such as trade name "Membrane emulsifier" (made by Refrigeration Industry Co., Ltd.); Vibratory emulsifiers such as trade name "Vibro Mixer" (made by Refrigeration Industry Co., Ltd.); Trade name "Ultrasonic homogenizer" (Branson Ultrasonic emulsifying machine (produced by the company); and the like. The conditions of the emulsification operation by the emulsification device are not particularly limited, and the treatment temperature, the treatment time, etc. may be appropriately selected so that the desired dispersion state is obtained.

In the production method (1), it is desirable to remove the organic solvent from the emulsion obtained through the emulsification operation.
As a method for removing the organic solvent from the emulsion, a method capable of adjusting the content of the organic solvent (preferably alicyclic hydrocarbon solvent) in the latex of the obtained synthetic polyisoprene to 500 ppm by weight or less is preferable. For example, methods such as vacuum distillation, atmospheric distillation, steam distillation, centrifugal separation and the like can be adopted.

In addition, after removing the organic solvent, if necessary, in order to increase the solid content concentration of the latex of synthetic polyisoprene, vacuum concentration, atmospheric distillation, centrifugal separation, concentration operation by a method such as membrane concentration may be performed. In particular, it is preferable to perform centrifugation from the viewpoint that the solid content concentration of the synthetic polyisoprene latex can be increased and the residual amount of the surfactant in the synthetic polyisoprene latex can be reduced.

Centrifugation is performed, for example, by using a continuous centrifuge to measure the centrifugal force, preferably 100 to 10,000 G, and the solid content concentration of the latex of the synthetic polyisoprene before centrifugation, preferably 2 to 15% by weight. The flow rate sent to the separator is preferably 500 to 1700 Kg/hr, and the back pressure (gauge pressure) of the centrifuge is preferably 0.03 to 1.6 MPa. A latex of synthetic polyisoprene can be obtained as a light liquid. And thereby, the residual amount of the surfactant in the latex of the synthetic polyisoprene can be reduced.

Further, after the concentration operation, water may be added, if necessary, in order to adjust the solid content concentration of the latex of synthetic polyisoprene. At this time, a surfactant may be further added. By adding water to the latex of synthetic isoprene, the solid content concentration in the latex of synthetic isoprene can be adjusted to a suitable range. The amount of water to be added is not particularly limited as long as the solid content concentration in the latex of synthetic isoprene falls within a suitable range described later. Examples of the type of water used include hard water, soft water, ion-exchanged water, distilled water, zeolite water and the like, and soft water, ion-exchanged water and distilled water are preferable.

Further, in the latex of synthetic polyisoprene, addition of a pH adjusting agent, an antifoaming agent, a preservative, a cross-linking agent, a chelating agent, an oxygen scavenger, a dispersant, an antiaging agent and the like, which are usually blended in the latex field, is added. You may mix an agent.
Examples of the pH adjusting agent 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 hydrogen carbonate; ammonia. Examples thereof include organic amine compounds such as trimethylamine and triethanolamine; and alkali metal hydroxides or ammonia are preferable.

In the production method of the present invention, as the polyisoprene latex, a natural rubber latex from which proteins have been removed can be used in addition to the synthetic polyisoprene latex described above. As the latex of natural rubber from which proteins have been removed, proteins in the natural rubber latex can be decomposed by a known protein removal method such as a method of decomposing proteins by proteolytic enzymes or surfactants and removing them by washing or centrifugation. What is known as a so-called "deproteinized natural rubber latex" can be used.

Method for producing modified polyisoprene latex The method for producing modified polyisoprene latex of the present invention is the above-mentioned polyisoprene latex, a carboxyl group-containing compound is added, and a carboxyl group-containing compound is reacted with polyisoprene contained in the latex. By doing so, a modified polyisoprene latex is obtained.

Then, in the present invention, in this case, as the latex of polyisoprene to be reacted with the carboxyl group-containing compound, one having a volume average particle diameter of 700 nm or more and an electric conductivity of 1.5 mS/cm or less is used. Thus, according to the present invention, a modified polyisoprene latex that is excellent in handling and can give a dip-molded article having high tensile strength can be produced with high productivity. The "conductivity" of the polyisoprene latex here means the conductivity measured in the polyisoprene latex having a solid content concentration of 30% by weight.

The volume average particle diameter of the latex of polyisoprene used in the present invention is preferably 720 to 1200 nm, more preferably 750 to 1100 nm. When the volume average particle size is too small, the productivity is lowered, and the latex of the modified polyisoprene obtained is inferior in handleability, and further, the latex of such modified polyisoprene is dip-molded. The obtained dip-formed product has poor tensile strength.

The conductivity of the latex of polyisoprene used in the present invention is preferably 0.5 to 1.4 mS/cm, more preferably 0.6 to 1.3 mS/cm. If the electrical conductivity is too high, the dip-molded product obtained by dip-molding the latex of the modified polyisoprene obtained will have poor tensile strength.

The method for adjusting the volume average particle diameter to the above range is not particularly limited, but for example, a solution or fine suspension of polyisoprene dissolved or finely dispersed in an organic solvent is emulsified in water in the presence of a surfactant. In the case of producing a latex of polyisoprene by the method of, the method of adjusting the mixing ratio of the synthetic polyisoprene and water during emulsification, the conditions of the emulsification operation (processing temperature, processing time, the rotation speed of the emulsifying device Etc.), a method of adjusting the type and amount of the anionic surfactant to be used, a method of adjusting the centrifugation conditions when performing the concentration operation by centrifugation, and the like. Further, the method of adjusting the conductivity in the above range is not particularly limited, but for example, a method of adjusting the type and amount of the anionic surfactant to be used, a solid content concentration of polyisoprene in the latex of polyisoprene, The method of adjusting etc. are mentioned.

The solid content concentration of the polyisoprene latex in the reaction with the carboxyl group-containing compound is preferably 20% by weight or more and less than 40% by weight, and more preferably 25 to 35% by weight. By setting the solid content concentration within the above range, it is possible to obtain a modified polyisoprene latex that is more excellent in handleability with higher productivity.

The carboxyl group-containing compound used in the present invention is not particularly limited as long as it is a compound capable of reacting with polyisoprene, and examples thereof include ethylenically unsaturated monocarboxylic acids such as acrylic acid and methacrylic acid; itaconic acid, maleic acid. Ethylenically unsaturated polycarboxylic acid such as fumaric acid; Ethylenically unsaturated polycarboxylic acid anhydride such as maleic anhydride and citraconic anhydride; monobutyl fumarate, monobutyl maleate, mono-2-hydroxypropyl maleate Ethylenically unsaturated polycarboxylic acid partial ester such as; and the like. Among these, ethylenically unsaturated monocarboxylic acid is preferable, and methacrylic acid is particularly preferable. These ethylenically unsaturated carboxylic acids can also be used as alkali metal salts or ammonium salts. The carboxyl group-containing compounds can be used alone or in combination of two or more.

The addition amount of the carboxyl group-containing compound, the viscosity of the latex of the modified polyisoprene obtained can be made moderate, and from the viewpoint that the tensile strength of the dip-molded product obtained is improved, it is included in the latex of polyisoprene. It is preferably 0.01 to 100 parts by weight, more preferably 0.01 to 40 parts by weight, and still more preferably 0.5 to 20 parts by weight with respect to 100 parts by weight of the polyisoprene.

The method for adding the carboxyl group-containing compound to the polyisoprene latex is not particularly limited, and known addition methods such as batch addition, divided addition, and continuous addition can be employed. The carboxyl group-containing compound may be directly added to the polyisoprene latex, or a solution or dispersion liquid of the carboxyl group-containing compound may be prepared in advance, and the prepared carboxyl group-containing compound solution or dispersion liquid may be added to the polyisoprene latex. It may be added to the latex.

The method for reacting the carboxyl group-containing compound with the polyisoprene contained in the latex is not particularly limited, and it is conventional in the reaction of modifying polyisoprene with the carboxyl group-containing compound, the reaction of graft-polymerizing the carboxyl group-containing compound with polyisoprene, etc. A known method may be used, for example, a carboxyl group-containing compound is added to polyisoprene in the presence of a redox catalyst obtained by adding a carboxyl group-containing compound to a latex of polyisoprene and combining an organic peroxide and a reducing agent. Is preferred.

（上記一般式（１）中、Ｒ^１およびＲ^２は、それぞれ独立して、水素原子または任意の有機基であり、Ｒ^１およびＲ^２は互いに結合して環構造を形成していてもよい。） Further, when reacting the carboxyl group-containing compound with the polyisoprene contained in the latex, a surfactant may be further added, and as the surfactant used at this time, an anionic surfactant is preferably used. be able to. As the anionic surfactant, the same ones as those exemplified as the anionic surfactant that can be used for producing the latex of the synthetic polyisoprene can be used. In addition to the exemplified ones, aromatic sulfone can be used. An acid derivative can also be used, and as the aromatic sulfonic acid derivative, a compound represented by the following general formula (1) is preferable.

(In the general formula (1), R ¹ and R ² are each independently a hydrogen atom or any organic group, and R ¹ and R ² may be bonded to each other to form a ring structure. .)

In the general formula (1), R ¹ and R ² are each independently a hydrogen atom or any organic group, and R ¹ and R ² may be bonded to each other to form a ring structure.

When R ¹ and R ² do not bond to each other, the organic group that can be R ¹ and R ² is not particularly limited, but is a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group. , Sec-butyl group, t-butyl group, n-pentyl group, n-hexyl group, n-heptyl group, n-octyl group, n-nonyl group, n-decyl group, and other alkyl groups having 1 to 30 carbon atoms A cycloalkyl group having 3 to 30 carbon atoms such as cyclopropyl group, cyclopentyl group, cyclohexyl group, cycloheptyl group, cyclooctyl group; aryl having 6 to 30 carbon atoms such as phenyl group, biphenyl group, naphthyl group, anthranyl group Group: methoxy group, ethoxy group, n-propoxy group, isopropoxy group, n-butoxy group, isobutoxy group, sec-butoxy group, t-butoxy group, n-pentyloxy group, n-hexyloxy group, phenoxy group, etc. An alkoxy group having 1 to 30 carbon atoms; and the like. In addition, these organic groups may have a substituent, and the position of the substituent can be any position.

When R ¹ and R ² are bonded to each other to form a ring structure, the ring structure is not particularly limited, but an aromatic compound is preferable, and an aromatic compound having a benzene ring such as benzene and naphthalene is preferable. More preferably, naphthalene is particularly preferable. In addition, these ring structures may have a substituent, and the position of the substituent may be any position.

（上記一般式（２）中、Ｒ^３は、置換基を有していてもよい２価の炭化水素基である。） In the present invention, as the aromatic sulfonic acid derivative used as the anionic surfactant, among the compounds represented by the general formula (1), it is preferable that R ¹ and R ² are bonded to each other to form a ring. Examples thereof include those that form a structure to form a benzene ring structure in the general formula (1). More specifically, it is preferable to use a compound having a structure having a sulfonic acid group and a naphthalene structure, that is, a structure represented by the following general formula (2). By using such a compound, the modified polyisoprene latex obtained is more excellent in the stability of the modification reaction.

(In the general formula (2), R ³ is a divalent hydrocarbon group which may have a substituent.)

In the general formula (2), R ³ is not particularly limited as long as it is a divalent hydrocarbon group which may have a substituent, and is preferably an alkylene group having 1 to 10 carbon atoms, and a methylene group. Is particularly preferable.

The aromatic sulfonic acid derivative used as the anionic surfactant preferably has the structure represented by the general formula (2) repeatedly, and the structure represented by the general formula (2) is repeated. The number of units is not particularly limited, but is preferably 10 to 100, more preferably 20 to 50.

As the anionic surfactant which is a compound having the structure represented by the general formula (2) repeatedly, a sodium salt of β-naphthalenesulfonic acid formalin condensate is preferable.

The amount of the surfactant used in the method for producing the modified polyisoprene latex is not particularly limited, but 100 parts by weight of the polyisoprene contained in the latex of the polyisoprene is included because the generation of aggregates can be further suppressed. On the other hand, it is preferably 0.01 to 20.0 parts by weight, more preferably 0.1 to 10.0 parts by weight. When two or more kinds of surfactants are used, the total amount of these used is preferably within the above range.

The method of adding the surfactant to the latex of polyisoprene is not particularly limited, and known addition methods such as batch addition, divided addition and continuous addition can be adopted. The surfactant may be directly added to the latex of polyisoprene, or an aqueous solution of the surfactant may be prepared in advance and the prepared aqueous solution of the surfactant may be added to the latex of polyisoprene.

The organic peroxide is not particularly limited, but for example, diisopropylbenzene hydroperoxide, cumene hydroperoxide, t-butyl hydroperoxide, 1,1,3,3-tetramethylbutyl hydroperoxide, di-t. -Butyl peroxide, isobutyryl peroxide, benzoyl peroxide and the like can be mentioned, but 1,1,3,3-tetramethylbutyl hydroperoxide is preferable from the viewpoint of improving the mechanical strength of the obtained dip-molded article. These organic peroxides may be used alone or in combination of two or more.

The addition amount of the organic peroxide is not particularly limited, but is preferably 0.01 to 3 parts by weight, more preferably 0.1 to 1 part by weight, relative to 100 parts by weight of polyisoprene contained in the latex of polyisoprene. Is.

Although the reducing agent is not particularly limited, for example, a compound containing a metal ion in a reduced state such as ferrous sulfate and cuprous naphthenate; a sulfonic acid compound such as sodium methanesulfonate; an amine such as dimethylaniline Compounds; and the like. These reducing agents may be used alone or in combination of two or more.

The addition amount of the reducing agent is not particularly limited, but is preferably 0.01 to 1 part by weight with respect to 1 part by weight of the organic peroxide.

The addition method of the organic peroxide and the reducing agent is not particularly limited, and known addition methods such as batch addition, divided addition, and continuous addition can be used.

The reaction temperature for reacting the carboxyl group-containing compound with polyisoprene is not particularly limited, but is preferably 5 to 70°C, more preferably 10 to 70°C. The reaction time for reacting the polyisoprene with the carboxyl group-containing compound is not particularly limited, but is preferably 5 to 600 minutes, more preferably 10 to 180 minutes.

The modification ratio of the monomer having a carboxyl group in the modified polyisoprene may be appropriately controlled according to the purpose of use of the latex obtained, but is preferably 0.01 to 10% by weight, more preferably 0.2 to 5%. %, more preferably 0.3 to 3% by weight, particularly preferably 0.4 to 2% by weight. The modification rate is represented by the following formula.
Denaturation rate (% by weight)=(X/Y)×100
In the above formula, X represents the weight of the monomer unit having a carboxyl group in the modified polyisoprene, and Y represents the weight of the modified polyisoprene. X is determined by performing ¹ H-NMR measurement on the modified polyisoprene and calculating from the result of ¹ H-NMR measurement, or by calculating the acid amount by neutralization titration and calculating from the calculated acid amount. be able to.

The modified polyisoprene latex in the present invention contains additives such as a pH adjuster, an antifoaming agent, an antiseptic, a chelating agent, an oxygen scavenger, a dispersant, and an antiaging agent, which are usually added in the latex field. You may mix.

Examples of the pH adjusting agent 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 hydrogen carbonate; ammonia. Examples thereof include organic amine compounds such as trimethylamine and triethanolamine; and alkali metal hydroxides or ammonia are preferable.

Further, after obtaining the modified polyisoprene latex as described above, if necessary, in order to increase the solid content concentration of the modified polyisoprene latex, vacuum distillation, atmospheric distillation, centrifugation, membrane concentration, etc. Although the concentration operation may be carried out by the method described above, centrifugation is preferable among these concentration operations from the viewpoint that the residual amount of the anionic surfactant in the modified polyisoprene latex can be adjusted.

When the modified polyisoprene latex is subjected to a centrifuge, it is preferable to add a pH adjusting agent in advance to adjust the latex pH to 7 or more in order to improve the mechanical stability of the modified polyisoprene latex. As the pH adjuster, hydroxides of alkali metals such as sodium hydroxide and potassium hydroxide or ammonia are preferable.
When the pH of the latex is adjusted, the carboxyl group in the modified polyisoprene may be in a salt state.

Centrifugation is carried out, for example, by using a continuous centrifuge, the centrifugal force is preferably 4,000 to 5,000 G, the flow rate fed into the centrifuge is preferably 500 to 2000 Kg/hr, and the back pressure of the centrifuge is set. The (gauge pressure) is preferably 0.03 to 1.6 MPa.

The modified polyisoprene latex according to the present invention has a solid content concentration of preferably 30 to 70% by weight, more preferably 40 to 70% by weight. By setting the solid content concentration in the above range, it is possible to prevent the polymer particles from being separated when the latex of the modified polyisoprene is stored, and the particles of the modified polyisoprene are aggregated and coarse. Generation of aggregates can also be suppressed.

The volume average particle size of the modified polyisoprene latex in the present invention is preferably 600 nm or more, more preferably 650 to 1100 nm. By setting the volume average particle diameter in the above range, the viscosity of the modified polyisoprene latex becomes more appropriate and becomes easier to handle when it is transferred by a pump, and the latex of the modified polyisoprene is stored when the latex is stored. It is possible to more effectively suppress the formation of a film on the surface.

Latex Composition The latex composition of the present invention is obtained by adding a crosslinking agent to the latex of the modified polyisoprene obtained by the above-mentioned production method of the present invention.

Examples of the cross-linking agent include sulfur such as powdered sulfur, sulfur flower, precipitated sulfur, colloidal sulfur, surface-treated sulfur and insoluble sulfur; sulfur chloride, sulfur dichloride, morpholine disulfide, alkylphenol disulfide, caprolactam disulfide (N, Examples thereof include sulfur-containing compounds such as N'-dithio-bis(hexahydro-2H-azepinone-2)), phosphorus-containing polysulfide, high molecular polysulfide, and 2-(4'-morpholino dithio)benzothiazole. Among these, sulfur can be preferably used. The crosslinking agent may be used alone or in combination of two or more.

The content of the cross-linking agent is not particularly limited, but is preferably 0.1 to 10 parts by weight, more preferably 0.2 to 3 parts by weight with respect to 100 parts by weight of the modified polyisoprene constituting the latex of the modified polyisoprene. Is. By setting the content of the cross-linking agent within the above range, the tensile strength of the obtained dip molded product can be further increased.

Further, the latex composition of the present invention preferably further contains a crosslinking accelerator.
As the cross-linking accelerator, those usually used in dip molding can be used, and examples thereof include xanthogenic acid, xanthogenic acid salt, xanthogenic disulfide (a compound in which two xanthogenic acids are bonded via a sulfur atom or the like), xanthogenic acid. Xanthogen compounds such as sulfides (compounds in which three or more xanthogenic acids are bonded via a sulfur atom or the like); diethyldithiocarbamic acid, dibutyldithiocarbamic acid, di-2-ethylhexyldithiocarbamic acid, dicyclohexyldithiocarbamic acid, diphenyldithiocarbamic acid, diphenyldithiocarbamic acid Dithiocarbamic acids such as benzyldithiocarbamic acid and zinc salts thereof; 2-mercaptobenzothiazole, 2-mercaptobenzothiazole zinc, 2-mercaptothiazoline, dibenzothiazyl disulfide, 2-(2,4-dinitrophenylthio)benzothiazole , 2-(N,N-diethylthiocarbaylthio)benzothiazole, 2-(2,6-dimethyl-4-morpholinothio)benzothiazole, 2-(4'-morpholinodithio)benzothiazole, 4-morphoniryl-2 -Benzothiazyl disulfide, 1,3-bis(2-benzothiazyl mercaptomethyl)urea and the like can be mentioned, but as a crosslinking accelerator used together when sulfur is used as a crosslinking agent, symptoms of delayed type allergy (Type IV) From the viewpoint of suppressing the generation of the above, a xanthogen compound is preferable, zinc diisopropylxanthogenate and zinc dibutylxanthogenate are more preferable, and zinc diisopropylxanthogenate is particularly preferable. The crosslinking accelerator may be used alone or in combination of two or more.

The content of the crosslinking accelerator 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 modified polyisoprene constituting the latex of the modified polyisoprene. .. By setting the content of the crosslinking accelerator within the above range, the tensile strength of the obtained dip-molded product can be further increased.

Further, 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 with respect to 100 parts by weight of modified polyisoprene constituting the latex of modified polyisoprene. Is. By setting the content of zinc oxide in the above range, it is possible to further improve the tensile strength of the obtained dip-molded article while improving the emulsion stability.

The latex composition of the present invention further contains a compounding agent such as an antioxidant, a dispersant; a reinforcing agent such as carbon black, silica, talc; a filler such as calcium carbonate and clay; an ultraviolet absorber; a plasticizer; It can be blended as needed.

The method for preparing the latex composition of the present invention is not particularly limited, but for example, using a dispersing machine such as a ball mill, a kneader, or a disper, a latex of the modified polyisoprene is mixed with a cross-linking agent, and if necessary, various types. A method of mixing the compounding agent, a method of mixing the aqueous dispersion with a latex of the modified polyisoprene after preparing an aqueous dispersion of the compounding ingredients other than the latex of the modified polyisoprene using the above-mentioned disperser, etc. Can be mentioned.

The latex composition of the present invention preferably has a pH of 7 or more, more preferably has a pH in the range of 7 to 13, and further preferably has a pH in the range of 8 to 12. 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 dip molding from the viewpoint of further enhancing the mechanical properties of the obtained dip molded article. The time for pre-crosslinking is not particularly limited and depends on the temperature of pre-crosslinking, but is preferably 1 to 14 days, more preferably 1 to 7 days. The temperature of pre-crosslinking is preferably 20 to 40°C.
After pre-crosslinking, it is preferable to store at a temperature of 10 to 30° C. until it is subjected to dip molding. If it is stored at a high temperature, the tensile strength of the obtained dip-molded product may decrease.

Dip-molded product The dip-molded product of the present invention is obtained by dip-molding the above-mentioned latex composition of the present invention. Dip molding is a method of immersing a mold in a latex composition, depositing the composition on the surface of the mold, then lifting the mold from the composition, and then drying the composition deposited on the surface of the mold. is there. The mold may be preheated before being immersed in the latex composition. In addition, a coagulant can be used if necessary before the mold is immersed in the latex composition or after the mold is pulled out of the latex composition.

Specific examples of the method of using the coagulant include a method in which the mold before being immersed in the latex composition is immersed in a solution of the coagulant to attach the coagulant to the mold (anode coagulation dipping method), and a latex composition is deposited. Although there is a method of immersing the formed mold in a coagulant solution (Teag coagulation dipping method), the anode coagulation dipping method is preferable from the viewpoint that a dip-formed body with less thickness unevenness can be obtained.

Specific examples of the coagulant 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; water-soluble polyvalent metal salts such as calcium sulfate, magnesium sulfate, and aluminum sulfate. Among them, calcium salt is preferable, and calcium nitrate is more preferable. These water-soluble polyvalent metal salts may 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 to 50% by weight, more preferably 10 to 30% by weight.

After withdrawing the mold from the latex composition, it is typically heated to dry the deposit formed on the mold. The drying conditions may be appropriately selected.

It is then heated to crosslink the deposit formed on the mold.
The heating conditions at the time of crosslinking are not particularly limited, but the heating temperature is 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 there are a method of heating with hot air in an oven, a method of irradiating with infrared rays and heating.

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

The dip-molded body after crosslinking is detached from the mold. Specific examples of the desorption method include a method of peeling from the mold by hand, a method of peeling with water pressure or compressed air pressure, and the like. As long as the dip-molded article during cross-linking has sufficient strength for desorption, it may be desorbed during cross-linking, and then the subsequent cross-linking may be continued.

Since the dip-molded article of the present invention is obtained by using the modified polyisoprene latex obtained by the production method of the present invention, the production amount per unit time (production efficiency) can be improved, and Since the amount of the waste solution at the time of concentrating the modified polyisoprene latex can be reduced, the load on the environment can be reduced. The dip-formed product according to the present invention can be used particularly suitably as a glove, for example. When the dip-molded body is a glove, in order to prevent the dip-molded bodies from adhering to each other at the contact surface and to improve the slippage during the attachment/detachment, the glove is made of inorganic particles such as talc and calcium carbonate or organic particles such as starch particles. It may be sprayed 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.

In addition to the above gloves, the dip-formed article of the present invention is a medical article such as a nipple for baby bottles, a dropper, a tube, a water pillow, a balloon sack, a catheter, a condom; a toy such as a balloon, a doll, a ball; It can also be used for industrial products such as molding bags and gas storage bags; finger cots and the like.

Adhesive Layer Forming Substrate The adhesive layer forming substrate of the present invention is obtained by forming an adhesive layer formed using the modified polyisoprene latex obtained by the production method of the present invention on the substrate surface. Is what you get.

The base material is not particularly limited, but a fiber base material can be used, for example. The type of fiber constituting the fiber base material is not particularly limited, and examples thereof include vinylon fiber, polyester fiber, nylon, polyamide fiber such as aramid (aromatic polyamide), glass fiber, cotton, rayon and the like. These can be appropriately selected according to the application. The shape of the fiber base material is not particularly limited, and examples thereof include staples, filaments, cords, ropes, woven fabrics (sailcloths, etc.), etc., and can be appropriately selected depending on the application. For example, the adhesive layer-forming substrate can be used as a substrate-rubber composite by adhering it to rubber via the adhesive layer. The base material-rubber composite is not particularly limited, but for example, a rubber toothed belt with a core using a cord-shaped fiber base material, a rubber using a base cloth-shaped fiber base material such as canvas. Examples include toothed belts.

The method for obtaining the base material-rubber composite is not particularly limited, but for example, an adhesive composition is attached to the base material by dipping treatment or the like to obtain a base material for forming an adhesive layer, and a base material for forming an adhesive layer. Is placed on rubber, and heating and pressurizing it. The pressurization can be performed using a compression (press) molding machine, a metal roll, an injection molding machine, or the like. The pressure applied is preferably 0.5 to 20 MPa, more preferably 2 to 10 MPa. The heating temperature is preferably 130 to 300°C, more preferably 150 to 250°C. The processing time of heating and pressurization is preferably 1 to 180 minutes, more preferably 5 to 120 minutes. By the method of heating and pressurizing, the molding of rubber and the bonding of the adhesive layer-forming base material and the rubber can be performed at the same time. In addition, it is preferable to form a mold for imparting a desired surface shape to the rubber of the target base material-rubber composite on the inner surface of the mold of the compressor used for pressurization or the surface of the roll.

Moreover, a base material-rubber-base material composite material can be mentioned as one aspect|mode of a base material-rubber composite material. The base material-rubber-base material composite can be formed, for example, by combining a base material (which may be a composite of two or more base materials) and a base material-rubber composite. Specifically, a core wire as a base material, rubber, and a base cloth as a base material are stacked (at this time, an adhesive composition is appropriately adhered to the core wire and the base cloth as an adhesive layer-forming base material). A base material-rubber-base material composite can be obtained by applying pressure while heating.

The base material-rubber composite obtained using the adhesive layer-forming base material of the present invention is excellent in mechanical strength, abrasion resistance and water resistance, and therefore, a flat belt, a V belt, a V ribbed belt, It can be suitably used as a belt such as a round belt, a square belt, and a toothed belt. In addition, the base material-rubber composite obtained by using the adhesive layer-forming base material in the present invention has excellent oil resistance and can be suitably used as an in-oil belt. Further, the base material-rubber composite obtained by using the adhesive layer-forming base material of the present invention can be suitably used for hoses, tubes, diaphragms and the like. Examples of the hose include a single-tube rubber hose, a multi-layer rubber hose, a braided type reinforcement hose, and a cloth wound type reinforcement hose. Examples of the diaphragm include a flat diaphragm and a rolling diaphragm.

The base material-rubber composite obtained using the adhesive layer-forming base material of the present invention can be used as an industrial product such as a seal or a rubber roll, in addition to the above-mentioned applications. Examples of the seal include a rotating part, a swinging part, a reciprocating part, and a fixed part seal. Examples of the moving part seal include an oil seal, a piston seal, a mechanical seal, a boot, a dust cover, a diaphragm, an accumulator and the like. Examples of the fixed portion seal include O-rings and various gaskets. Examples of rubber rolls include rolls that are parts of OA equipment such as printing equipment and copying equipment; fiber processing rolls such as spinning rolls and spinning draft rolls; iron making rolls such as bridle rolls, snubber rolls, and steering rolls; Can be mentioned.

Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples. In addition, the following "parts" are based on weight unless otherwise specified. The various physical properties were measured as follows.

2 g of the sample was precisely weighed (weight: X2) in a solid content aluminum dish (weight: X1), and dried in a hot air dryer at 105° C. for 2 hours. Then, 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 calculation formula.
Solid content concentration (% by weight)=(X3−X1)×100/X2

Volume average particle diameter The volume average particle diameter was determined using a laser diffraction type particle size distribution measuring device (trade name "SALD2200", manufactured by Shimadzu Corporation).

Modification reaction stability After producing a latex of modified polyisoprene in a reaction vessel equipped with a stirrer, visually observing the inside of the reaction vessel and evaluating the amount of aggregate attached to the reaction vessel and the stirrer based on the following criteria did. The smaller the amount of the attached agglomerates, the more excellent the stability of the modification reaction.
◯: No adhesion of aggregates was observed on either the reaction vessel or the stirrer, or adhesion of aggregates was observed on both the reaction vessel and the stirrer, but the amount of adhesion was slight.
X: Adhesion of aggregates was observed on both the reaction vessel and stirrer, or a large amount of aggregates was observed on both reaction vessel and stirrer.

The electrical conductivity was measured at 25° C. using an electrical conductivity meter (trade name “SG78-FK2”, manufactured by METTLER TOLEDO).

During the production of the centrifugable modified polyisoprene latex, 400 g of the polyisoprene latex immediately after the modification reaction (solid content concentration: 30% by weight) was used in a centrifuge (trade name "H-2000B", manufactured by Kokusan Co., Ltd.) Then, centrifugation was performed at 5,000 G. After that, 160 g of the light liquid obtained by centrifugation was collected and uniformly stirred, and then the solid content concentration was measured. The centrifuge time until the solid content concentration reaches 55% by weight or more is measured, and if the time is less than 1.25 hours, it is indicated as "○", and if it is 1.25 hours or more, it is indicated as "x", and the centrifugeability is Was evaluated. The shorter this time, the better the centrifugal separation property.

Handling property The handling property was evaluated as "O" when the viscosity of the modified polyisoprene latex measured using a B-type viscometer was less than 1000 mPas, and as "x" when it was 1000 mPas or more. The lower the viscosity, the better the handling property.

Based on the tensile strength STM D412 of the film-shaped dip-molded product, a film-shaped dip-molded product having a film thickness of about 0.2 mm was dumbbell (trade name "Super Dumbbell (model: SDMK-100C)", manufactured by Dumbbell ), the test piece for tensile strength measurement was produced. The test piece was pulled with a Tensilon universal tester (trade name "RTG-1210", manufactured by Orientec Co., Ltd.) at a pulling speed of 500 mm/min, and the tensile strength (unit: MPa) immediately before breaking was measured.

Example 1
Production of Latex of Synthetic Polyisoprene Synthetic polyisoprene having a weight average molecular weight of 1,300,000 (trade name "NIPOL IR2200L", manufactured by Nippon Zeon Co., isoprene homopolymer, cis bond unit amount 98%) was used as cyclohexane. After mixing and stirring, the temperature was raised to 60° C. and dissolved, and a cyclohexane solution (a) of polyisoprene having a viscosity of 12,000 mPa·s measured with a B-type viscometer was prepared (solid content concentration: 8 wt. %).

On the other hand, 20 parts of sodium rosinate and 10 parts of sodium dodecylbenzenesulfonate were added to water, and the temperature was raised to 60° C. to dissolve them, so that the concentration of sodium rosinate was 1.5 wt %, sodium dodecylbenzenesulfonate. An anionic surfactant aqueous solution (b1) having a concentration of 0.75% by weight was prepared.

Next, the cyclohexane solution (a) of the polyisoprene and the anionic surfactant aqueous solution (b) were mixed at a weight ratio of 1:1.5 by a mixer (trade name “Multiline Mixer MS26- MMR-5.5L", manufactured by Satake Chemical Machinery Co., Ltd.), and then mixed and emulsified at a rotation speed of 4100 rpm using an emulsifying device (trade name "Milder MDN310", manufactured by Taihei Kiki Co., Ltd.). To obtain an emulsion (c). At that time, the total feed flow rate of the cyclohexane solution (a) of polyisoprene and the anionic surfactant aqueous solution (b) was 2,000 kg/hr, the temperature was 60° C., and the back pressure (gauge pressure) was 0.5 MPa. And

Next, the emulsion (c) is heated to 80° C. under reduced pressure of −0.01 to −0.09 MPa (gauge pressure), cyclohexane is distilled off, and an aqueous dispersion (d1) of synthetic polyisoprene is obtained. Obtained. At that time, an antifoaming agent (trade name "SM5515", manufactured by Toray Dow Corning Co., Ltd.) was continuously added while spraying so that the amount of the synthetic polyisoprene in the emulsion (c) was 300 ppm by weight. .. When the cyclohexane is distilled off, the emulsion (c) is adjusted to 70% by volume or less of the volume of the tank, and a 3-stage inclined paddle blade is used as the stirring blade, and the mixture is slowly stirred at 60 rpm. Was carried out.

Then, after the distillation of cyclohexane is completed, the obtained synthetic polyisoprene aqueous dispersion (d1) is used in a continuous centrifuge (trade name “SRG510”, manufactured by Alfa Laval Co., Ltd.) at 4,000 to After centrifugation at 5,000 G, the light liquid obtained by centrifugation was obtained as an aqueous dispersion (d2) of synthetic polyisoprene. The heavy liquid obtained at the same time was transferred to another container and stored. The obtained synthetic polyisoprene aqueous dispersion (d2) had a solid content concentration of 56% by weight, a volume average particle diameter of 910 nm, a pH of 10, an electric conductivity of 0.93 mS/cm, and a B-type viscometer. The viscosity was 120 mPa·s. The conditions of the centrifugation were that the flow rate during continuous centrifugation was 1300 kg/hr and the back pressure (gauge pressure) of the centrifuge was 1.5 MPa. The obtained synthetic polyisoprene aqueous dispersion (d2) was diluted with 170 parts of distilled water to 100 parts of synthetic polyisoprene to obtain a synthetic polyisoprene latex (e1).

The obtained synthetic polyisoprene latex (e1) had a solid content concentration of 30% by weight, a volume average particle diameter of 910 nm, a pH of 10, and an electric conductivity of 0.70 mS/cm.

Production of latex of modified polyisoprene 1.1 parts of sodium salt of β-naphthalenesulfonic acid formalin condensate (trade name "Demol T-45", weight average molecular weight: 7,000, manufactured by Kao Corporation) was replaced with nitrogen. A reaction vessel equipped with a stirrer was charged. Then, 3 parts of methacrylic acid was added to the reaction vessel and stirred for 5 minutes. Next, 350 parts of the latex (e1) of the synthetic polyisoprene obtained above was added to the reaction vessel, and the mixture was stirred for 5 minutes.

Furthermore, using another container, 7 parts of distilled water, 0.32 parts of sodium formaldehyde sulfoxylate (trade name "SFS", manufactured by Mitsubishi Gas Chemical Co., Inc.), ferrous sulfate (trade name "Frost Fe", middle part Kirest) A solution (f) consisting of 0.01 part (manufactured by the company) was prepared. After this solution (f) was transferred into a reaction vessel, 0.5 part of 1,1,3,3-tetramethylbutyl hydroperoxide (trade name “Perocta H”, manufactured by NOF CORPORATION) was added to 30 The reaction was carried out at 0°C for 1 hour, and further at 30°C for 1 hour. At this time, the centrifugal property was evaluated according to the above method. The results are shown in Table 1.

After the reaction, sodium hydroxide was added to adjust the pH to 8, and this was then centrifuged at 4,000 to 5,000 G using a continuous centrifuge (trade name "SRG510", manufactured by Alfa Laval). (The flow rate is 1700 kg/hr, the back pressure (gauge pressure) of the centrifuge is 0.08 MPa), the solid content concentration is 56% by weight, the pH is 8, and the viscosity measured by the B-type viscometer is 380 mPa·s, A modified polyisoprene latex (g1) having a volume average particle diameter of 900 nm and an electric conductivity of 2.64 mS/cm was obtained. At this time, the stability of the denaturation reaction and the centrifuge were evaluated according to the method described above. The results are shown in Table 1.

Preparation of Latex Composition First, a styrene-maleic acid mono-sec-butyl ester-maleic acid monomethyl ester polymer (trade name "Scripset550", manufactured by Hercules) was prepared, and styrene-maleic acid mono-sec-butyl ester- was prepared. Sodium hydroxide was used to neutralize 100% of the carboxyl groups in the maleic acid monomethyl ester polymer to prepare a sodium salt aqueous solution (concentration: 10% by weight) as a dispersant (h). Then, the dispersant (h) was modified so as to be 0.8 parts in terms of solid content based on 100 parts of the modified polyisoprene in the modified polyisoprene latex (g1) obtained above. It was added to the latex of polyisoprene (g1).
Then, while stirring the obtained mixture, with respect to 100 parts of the modified polyisoprene in the mixture, in terms of solid content, 1.5 parts of zinc oxide, 1.5 parts of sulfur, an antioxidant (trade name "Wingstay L , Chukyo Yushi Co., Ltd.) and 2 parts of zinc diisopropylxanthogenate (crosslinking accelerator) were added to obtain a latex composition.
Then, the obtained latex composition was aged in a constant temperature bath at 25° C. for 48 hours.

Manufacture of a dip molded product A glass mold (diameter about 5 cm, scraping part length about 15 cm) whose surface has been ground is washed and preheated in an oven at 70° C., then 18% by weight calcium nitrate and 0.05% by weight. % Polyoxyethylene lauryl ether (trade name "Emulgen 109P", manufactured by Kao Corporation), immersed for 5 seconds in a coagulant aqueous solution, and taken out.
Then, the glass mold coated with the coagulant was dried in an oven at 70° C. for 30 minutes or more. Then, the glass mold coated with the coagulant is taken out of the oven, the latex composition obtained above is adjusted to 25° C., immersed in this latex composition for 10 seconds, taken out, and dried at room temperature for 60 minutes. Thus, a glass mold covered with a film was obtained. Then, the glass mold covered with the film was immersed in warm water at 60° C. for 2 minutes, and then air-dried at room temperature for 30 minutes. Then, the glass mold covered with the film was placed in an oven at 120° C. and vulcanized for 20 minutes. The glass mold covered with the vulcanized film was cooled to room temperature, sprinkled with talc, and then the film was peeled from the glass mold. Then, using the obtained film (dip molded body), the tensile strength was measured according to the above method. The results are shown in Table 1.

Example 2
In Example 1, the heavy liquid obtained at the same time as when the synthetic polyisoprene aqueous dispersion (d2) was obtained was subjected to 4, using a continuous centrifuge (trade name "SRG510", manufactured by Alfa Laval). By further centrifugation (second centrifugation) at 000 to 5,000 G, an aqueous dispersion (d3) of synthetic polyisoprene was obtained as a light liquid for the second centrifugation. The conditions for centrifugation (the conditions for the second centrifugation) were a flow rate during continuous centrifugation of 1300 kg/hr and a back pressure (gauge pressure) of the centrifuge of 1.5 MPa. The resulting synthetic polyisoprene aqueous dispersion (d3) was diluted with 150 parts of distilled water to 100 parts of synthetic polyisoprene to obtain a synthetic polyisoprene latex (e2). The obtained synthetic polyisoprene latex (e2) had a solid content concentration of 30% by weight, a volume average particle diameter of 535 nm, a pH of 10, and an electric conductivity of 1.05 mS/cm.
Then, the synthetic polyisoprene latex (e1) obtained in the same manner as in Example 1 and the synthetic polyisoprene latex (e2) obtained above were mixed in a weight ratio of the synthetic polyisoprene latex (e1). ): Synthetic polyisoprene latex (e2) = 1:1 to obtain a synthetic polyisoprene latex (e3). The obtained synthetic polyisoprene latex (e3) had a solid content concentration of 30% by weight, a volume average particle diameter of 765 nm, a pH of 10, and an electric conductivity of 0.98 mS/cm.
Then, a modified polyisoprene latex (g2) was produced by carrying out a modification reaction of the synthetic polyisoprene in the same manner as in Example 1 except that the obtained synthetic polyisoprene latex (e3) was used. Further, a latex composition and a dip molded article were produced in the same manner as in Example 1 except that the obtained modified polyisoprene latex (g2) was used, and the same evaluation was performed. The results are shown in Table 1.

Example 3
Synthetic polyisoprene aqueous dispersion (d2) obtained in the same manner as in Example 1 (100 parts, solid content equivalent), distilled water (155 parts) and surfactant aqueous solution (sodium dodecylbenzenesulfonate: rosin acid) 2.5 parts of potassium (1:2 concentration 15% by weight) (solid content conversion) was added to obtain a latex (e4) of synthetic polyisoprene. The obtained synthetic polyisoprene latex (e4) had a solid content concentration of 30% by weight, a volume average particle diameter of 920 nm, a pH of 10, and an electric conductivity of 1.28 mS/cm.
Then, a modified polyisoprene latex (g3) was produced by carrying out a modification reaction of the synthetic polyisoprene in the same manner as in Example 1 except that the obtained synthetic polyisoprene latex (e4) was used. Further, using the obtained modified polyisoprene (g3) latex, a latex composition and a dip-molded article were produced in the same manner as in Example 1 and evaluated in the same manner. The results are shown in Table 1.

Comparative Example 1
A synthetic polyisoprene latex (e2) obtained in the same manner as in Example 2 (solid content concentration: 30% by weight, volume average particle size: 535 nm, pH: 10, conductivity: 1.05 mS/cm) was used. A modified polyisoprene latex (g4) was produced by modifying the synthetic polyisoprene in the same manner as in Example 1 except for the above. Further, using the obtained modified polyisoprene latex (g4), a latex composition and a dip molded article were produced in the same manner as in Example 1 and evaluated in the same manner. The results are shown in Table 1.

Comparative example 2
140 parts of distilled water and an aqueous solution of a surfactant (sodium dodecylbenzenesulfonate: rosin acid) per 100 parts (solid content) of the aqueous dispersion (d2) of synthetic polyisoprene obtained in the same manner as in Example 1 5.0 parts of potassium (1:2 concentration 15% by weight) (solid content conversion) was added to obtain a latex (e5) of synthetic polyisoprene. The obtained synthetic polyisoprene latex (e5) had a solid content concentration of 30% by weight, a volume average particle diameter of 910 nm, a pH of 10, and an electric conductivity of 1.78 mS/cm.
Then, a modified polyisoprene latex (g5) was produced by carrying out a modification reaction of the synthetic polyisoprene in the same manner as in Example 1 except that the obtained synthetic polyisoprene latex (e5) was used. Further, using the obtained modified polyisoprene latex (g5), a latex composition and a dip molded product were produced in the same manner as in Example 1 and evaluated in the same manner. The results are shown in Table 1.

From Table 1, a carboxyl group-containing compound is added to a latex of polyisoprene having a volume average particle size of 700 nm or more and an electric conductivity of 1.5 mS/cm or less, and the polyisoprene and the carboxyl group-containing compound are reacted. When modified latex of modified polyisoprene is produced, the time required for centrifugation is short, and the viscosity of the modified latex of modified polyisoprene obtained is also low, which is excellent in productivity and handling. Furthermore, the films obtained by using such modified polyisoprene latex had excellent tensile strength (Examples 1 to 3).

On the other hand, when a modified polyisoprene latex is produced using a polyisoprene latex having a volume average particle size of less than 700 nm, it takes a long time to centrifuge and the viscosity of the obtained modified polyisoprene latex is low. Since it is also high, it is inferior in productivity and handling property, and further, the film obtained by using such a modified polyisoprene latex is inferior in tensile strength (Comparative Example 1).
Further, the film obtained using the modified polyisoprene latex produced using the latex of polyisoprene having an electric conductivity of more than 1.5 mS/cm was inferior in tensile strength (Comparative Example 2).

Claims (6)

A method for producing a latex of modified polyisoprene, which comprises adding a carboxyl group-containing compound to a latex of polyisoprene, and reacting the polyisoprene and the carboxyl group-containing compound,
A method for producing a latex of modified polyisoprene, wherein the latex of polyisoprene has a volume average particle diameter of 700 nm or more and an electric conductivity of 1.5 mS/cm or less. The method for producing a modified polyisoprene latex according to claim 1, wherein the reaction of the polyisoprene and the carboxyl group-containing compound is performed in the presence of an anionic surfactant having a sulfonic acid group and a naphthalene structure. The method for producing a modified polyisoprene latex according to claim 1 or 2, wherein a solid content concentration of the polyisoprene latex is 20% by weight or more and less than 40% by weight. A method for producing a latex composition, comprising a step of adding a crosslinking agent to the latex of modified polyisoprene obtained by the method according to any one of claims 1 to 3. A method for producing a dip-molded article, comprising a step of dip-molding the latex composition obtained by the production method according to claim 4. Production of an adhesive layer-forming substrate comprising a step of forming an adhesive layer formed on the surface of the substrate using the modified polyisoprene latex obtained by the production method according to claim 1. Method.