JP2021116389A - Latex composition for dip molding and dip molding - Google Patents

Abstract

To provide a latex composition for dip molding that can suppress dripping during molding, and can provide a dip molding having excellent oil gripping properties.SOLUTION: A latex composition for dip molding contains a latex of a conjugated diene polymer (A) with a glass transition temperature of 10°C or lower, a latex of a polymer (B) with a glass transition temperature of higher than 10°C, and a thickener, and has a solid concentration of 42 wt.% or more and 55 wt.% or less.SELECTED DRAWING: None

Description

The present invention relates to a latex composition for dip molding, and more particularly to a latex composition for dip molding, which can suppress dripping during molding and can give a dip molded body having excellent oil grip.

Conventionally, solvent resistance, grip resistance, abrasion resistance, etc. have been improved by covering fiber gloves with rubber, resin, etc. in various applications such as manufacturing work, light work, construction work, and agricultural work in factories. Protective gloves are used.

Since such protective gloves are usually used in contact with the human body, they are required to have excellent mechanical strength such as abrasion resistance and durability, as well as excellent flexibility. Has been done.

For example, Patent Document 1 describes a coagulant solution adhering step of adhering a coagulant solution to a fiber base material, and a polymer latex is brought into contact with the fiber base material to which the coagulant solution is attached to coagulate the polymer. By providing a coagulation step of forming a polymer layer on the fiber substrate, 0.2 to 7.0% by weight of the metal salt as the coagulant as the coagulant solution in the solvent, and A method for producing a laminate using a product obtained by dissolving or dispersing 0.1 to 7.0% by weight of an organic acid is disclosed.

International Publication No. 2018/061868

According to the technique of Patent Document 1, a laminate having excellent flexibility and abrasion resistance and suitable for use in protective gloves can be obtained, but the grip performance (that is, oil grip property) when wet with oil can be obtained. There is room for improvement, and further improvement is required from the viewpoint that it can be suitably used even in applications where it is used wet with oil. Further, from the viewpoint of preventing molding defects and preventing contamination of manufacturing equipment, it is also required to suppress dripping during molding.

The present invention has been made in view of such an actual situation, and provides a latex composition for dip molding capable of suppressing dripping during molding and providing a dip molded body having excellent oil grip. With the goal. Another object of the present invention is to provide a dip molded product obtained by using such a latex composition for dip molding.

As a result of diligent research to solve the above problems, the present inventors have conducted a latex of a conjugated dip-based polymer (A) having a glass transition temperature of 10 ° C. or lower, and a polymer having a glass transition temperature of more than 10 ° C. According to the latex composition for dip molding, which contains the latex of B) and a thickener and has a solid content concentration of 42% by weight or more and 55% by weight or less, dripping during molding can be suppressed and oil grip property is obtained. It has been found that an excellent dip-molded article can be provided, and the present invention has been completed.

That is, according to the present invention, a latex of a conjugated diene polymer (A) having a glass transition temperature of 10 ° C. or lower, a latex of a polymer (B) having a glass transition temperature of more than 10 ° C., and a thickener. To provide a latex composition for dip molding, which contains and has a solid content concentration of 42% by weight or more and 55% by weight or less.

In the latex composition for dip molding of the present invention, the acid content of the thickener is preferably 2.5 mmol / g or less.
In the latex composition for dip molding of the present invention, the solid content concentration is preferably 43.5% by weight or more and 55% by weight or less.
In the latex composition for dip molding of the present invention, it is preferable that the conjugated diene polymer (A) is a nitrile group-containing conjugated diene polymer.
In the latex composition for dip molding of the present invention, the content of the conjugated diene polymer (A) in 100 parts by weight of the polymer component is preferably 40 parts by weight or more.
In the latex composition for dip molding of the present invention, the glass transition temperature of the polymer (B) is preferably 30 ° C. or higher, more preferably 50 ° C. or higher.
In the latex composition for dip molding of the present invention, it is preferable that the polymer (B) contains a monomer unit having a halogen atom.
In the latex composition for dip molding of the present invention, the polymer (B) is preferably a vinyl chloride resin.
In the latex composition for dip molding of the present invention, it is preferable that the vinyl chloride resin does not contain a plasticizer.
The latex composition for dip molding of the present invention preferably further contains a sulfur-based cross-linking agent.

Further, according to the present invention, there is provided a dip molded product using the above-mentioned latex composition for dip molding.
Further, according to the present invention, there is provided a dip molded body obtained by immersing the above-mentioned latex composition for dip molding in a base material.
In the dip molded product of the present invention, the film thickness of the polymer layer made of the latex composition for dip molding is preferably 0.05 to 1.0 mm.

According to the present invention, a dip molding latex composition capable of suppressing dripping during molding and providing a dip molded body having excellent oil grip properties, and such a dip molding latex composition can be used. The obtained dip molded article can be provided.

FIG. 1 is a diagram showing an example of a hydrochloric acid amount-electrical conductivity curve obtained when measuring the acid amount of a water-soluble polymer.

<Latex composition for dip molding>
The latex composition for dip molding of the present invention comprises a latex of a conjugated diene polymer (A) having a glass transition temperature of 10 ° C. or lower, a latex of a polymer (B) having a glass transition temperature of more than 10 ° C. It contains a thickener and has a solid content concentration of 42% by weight or more and 55% by weight or less.

A latex of a conjugated diene polymer (A) having a glass transition temperature of 10 ° C. or lower (hereinafter, appropriately referred to as “latex of a conjugated diene polymer (A)”) is formed, and the glass transition temperature is 10 ° C. Hereinafter, the conjugated diene polymer (A) (hereinafter, appropriately referred to as “conjugated diene polymer (A)”) may be a polymer having a unit derived from the conjugated diene monomer. , But not particularly limited, for example, nitrile rubber (NBR), natural rubber (NR), styrene-butadiene rubber (SBR), synthetic polyisoprene rubber (IR), polybutadiene rubber (BR), styrene-isoprene copolymer rubber, styrene. -Isoprene-styrene copolymerized rubber and the like can be mentioned. Among these, synthetic rubber is preferable from the viewpoint that the effect of the present invention becomes more remarkable, and a conjugated diene polymer containing a nitrile group such as NBR (hereinafter, appropriately referred to as “nitrile group-containing conjugated diene polymer”). ”) Is more preferable.

The nitrile group-containing conjugated diene polymer is not particularly limited, and for example, α, β-ethylenic unsaturated nitrile monomer, conjugated diene monomer, and copolymerizable copolymer used as required. A copolymer of other ethylenically unsaturated acid monomers can be used.

The α, β-ethylenically unsaturated nitrile monomer is not particularly limited, but an ethylenically unsaturated compound having a nitrile group and preferably having 3 to 18 carbon atoms can be used. Examples of such α, β-ethylenically unsaturated nitrile monomers include acrylonitrile, methacrylonitrile, and halogen-substituted acrylonitrile, and among these, acrylonitrile is particularly preferable. These α, β-ethylenically unsaturated nitrile monomers may be used alone or in combination of two or more.

The content ratio of the α, β-ethylenically unsaturated nitrile monomer unit in the nitrile group-containing conjugated diene polymer is preferably 10 to 45% by weight, more preferably 20 to 40% by weight, based on the total monomer units. It is% by weight, more preferably 25 to 40% by weight. By setting the content ratio of the α, β-ethylenically unsaturated nitrile monomer unit in the above range, the obtained dip molded product can be made excellent in solvent resistance.

As the conjugated diene monomer, a conjugated diene monomer having 4 to 6 carbon atoms such as 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, and chloroprene is preferable. , 1,3-butadiene and isoprene are more preferred, and 1,3-butadiene is particularly preferred. In addition, these conjugated diene monomers may be used individually by 1 type, and may be used in combination of 2 or more type.

The content ratio of the conjugated diene monomer unit in the nitrile group-containing conjugated diene polymer is preferably 40 to 80% by weight, more preferably 52 to 78% by weight, still more preferably 55, based on all the monomer units. ~ 75% by weight. By setting the content ratio of the conjugated diene monomer unit in the above range, the obtained dip molded product can be made excellent in flexibility.

Further, the nitrile group-containing conjugated diene polymer can be copolymerized with a monomer forming an α, β-ethylenic unsaturated nitrile monomer unit and a monomer forming a conjugated diene monomer unit. It may be copolymerized with other ethylenically unsaturated acid monomers.

The other copolymerizable ethylenically unsaturated acid monomer is not particularly limited, and for example, a carboxyl group-containing ethylenically unsaturated monomer or a monocarboxylic acid ester group-containing ethylenically unsaturated single amount. Examples thereof include a dicarboxylic acid diester group-containing ethylenically unsaturated monomer, a sulfonic acid group-containing ethylenically unsaturated monomer, and a phosphoric acid group-containing ethylenically unsaturated monomer.

The carboxyl group-containing ethylenically unsaturated monomer is not particularly limited, but is an ethylenically unsaturated monocarboxylic acid such as acrylic acid, methacrylic acid, and crotonic acid; fumaric acid, maleic acid, itaconic acid, maleic anhydride, and anhydrous. Examples thereof include ethylenically unsaturated polyvalent carboxylic acids such as itaconic acid and anhydrides thereof; partial esterified products of ethylenically unsaturated polyvalent carboxylic acids such as methyl maleate and methyl itaconic acid.

The monocarboxylic acid ester group-containing ethylenically unsaturated monomer is not particularly limited, and examples thereof include acrylic acid esters such as methyl acrylate; methacrylic acid esters such as methyl methacrylate; and crotonic acid esters such as methyl crotonate. Can be mentioned.

The dicarboxylic acid diester group-containing ethylenically unsaturated monomer is not particularly limited, and examples thereof include a maleic acid diester such as dimethyl maleate; an itaconic acid diester such as methyl itaconic acid; and the like.

The sulfonic acid group-containing ethylenically unsaturated monomer is not particularly limited, but is limited to vinyl sulfonic acid, methyl vinyl sulfonic acid, styrene sulfonic acid, (meth) allyl sulfonic acid, and ethyl (meth) acrylic acid-2-sulfonate. , 2-acrylamide-2-hydroxypropanesulfonic acid and the like.

The phosphoric acid group-containing ethylenically unsaturated monomer is not particularly limited, but is limited to propyl (meth) acrylic acid-3-chloro-2-phosphate, ethyl (meth) -2-phosphate, and 3-allyloxy. -2-Hydroxypropane phosphoric acid and the like can be mentioned.

These other copolymerizable ethylenically unsaturated acid monomers can be used as an alkali metal salt or an ammonium salt, or may be used alone or in combination of two or more. good. Among the other copolymerizable ethylenically unsaturated monomer, a carboxyl group-containing ethylenically unsaturated monomer is preferable, an ethylenically unsaturated monocarboxylic acid is more preferable, and acrylic acid and methacrylic acid are preferable. More preferably, methacrylic acid is particularly preferable.

When the nitrile group-containing conjugated diene polymer contains a unit of another copolymerizable ethylenically unsaturated acid monomer, the content of the other copolymerizable ethylenically unsaturated acid monomer unit The ratio is preferably 0.1 to 15% by weight, more preferably 1 to 10% by weight, still more preferably 2 to 8% by weight, based on all the monomer units.

The latex of the nitrile group-containing conjugated diene polymer can be obtained, for example, by emulsion polymerization of a monomer mixture containing the above-mentioned monomer. In emulsion polymerization, commonly used polymerization auxiliary materials such as emulsifiers, polymerization initiators, and molecular weight modifiers can be used.

The emulsifier used for emulsion polymerization is not particularly limited, and examples thereof include anionic surfactants, nonionic surfactants, cationic surfactants, and amphoteric surfactants, and anionic surfactants are used. preferable. Specific examples of anionic surfactants include fatty acid salts such as sodium laurate, potassium myristate, sodium palmitate, potassium oleate, sodium linolenate, and sodium rosinate; sodium dodecylbenzene sulfonate, potassium dodecylbenzene sulfonate. Alkylbenzene sulfonates such as sodium decylbenzene sulfonate, potassium decylbenzene sulfonate, sodium cetylbenzenesulfonate, potassium cetylbenzenesulfonate; sodium di (2-ethylhexyl) sulfosuccinate, potassium di (2-ethylhexyl) sulfosuccinate. Alkyl sulfosuccinates such as sodium dioctyl sulfosuccinate; alkyl sulfates such as sodium lauryl sulfate and potassium lauryl sulfate; polyoxyethylene alkyl ether sulfates such as sodium polyoxyethylene lauryl ether sulfate and potassium polyoxyethylene lauryl ether sulfate. Salts; monoalkyl phosphates such as sodium lauryl phosphate and potassium lauryl phosphate; and the like.
The amount of the emulsifier used for emulsion polymerization is preferably 0.5 to 10 parts by weight, more preferably 1 to 8 parts by weight, based on 100 parts by weight of all the monomers used.

The polymerization initiator is not particularly limited, but a radical initiator is preferable. The radical initiator is not particularly limited, and is, for example, an inorganic peroxide such as sodium persulfate, potassium persulfate, ammonium persulfate, potassium perphosphate, hydrogen peroxide; t-butyl peroxide, cumene hydroperoxide, etc. p-menthane hydroperoxide, di-t-butyl peroxide, t-butylcumyl peroxide, acetyl peroxide, isobutyryl peroxide, octanoyl peroxide, dibenzoyl peroxide, 3,5,5-trimethylhexanoyl Organic peroxides such as peroxide and t-butylperoxyisobutyrate; azo compounds such as azobisisobutyronitrile, azobis-2,4-dimethylvaleronitrile, azobiscyclohexanecarbonitrile, methyl azobisisobutyrate; etc. Among these, inorganic peroxides or organic peroxides are preferable, inorganic peroxides are more preferable, and persulfates are particularly preferable. These polymerization initiators may be used alone or in combination of two or more.
The amount of the polymerization initiator used is preferably 0.01 to 2 parts by weight, more preferably 0.05 to 1.5 parts by weight, based on 100 parts by weight of all the monomers used.

The molecular weight modifier is not particularly limited, and is, for example, α-methylstyrene dimer; mercaptans such as t-dodecyl mercaptan, n-dodecyl mercaptan, and octyl mercaptan; halogenation of carbon tetrachloride, methylene chloride, methylene bromide, and the like. Hydrocarbons; sulfur-containing compounds such as tetraethylthiolam diesulfide, dipentamethylene thiolum diesulfide, and diisopropylxanthogen disulfide; among these, mercaptans are preferable, and t-dodecyl mercaptan is more preferable. These molecular weight adjusting agents may be used alone or in combination of two or more.
The amount of the molecular weight adjusting agent used varies depending on the type, but is preferably 0.1 to 1.5 parts by weight, more preferably 0.2 to 1.0 parts by weight, based on 100 parts by weight of all the monomers used. It is a department.

Emulsion polymerization is usually carried out in water. The amount of water used is preferably 80 to 500 parts by weight, more preferably 100 to 200 parts by weight, based on 100 parts by weight of all the monomers used.

In the emulsion polymerization, if necessary, a polymerization auxiliary material other than the above may be further used. Examples of the polymerization auxiliary material include a chelating agent, a dispersant, a pH adjusting agent, an oxygen scavenger, a particle size adjusting agent, and the like, and the type and amount of these are not particularly limited.

Examples of the method for adding the monomer include a method of collectively adding the monomers used in the reaction vessel, a method of continuously or intermittently adding the monomers as the polymerization progresses, and a method of adding a part of the monomers. Then, the reaction is carried out to a specific conversion rate, and then the remaining monomer is continuously or intermittently added to polymerize, and any of these methods may be adopted. When the monomers are mixed and added continuously or intermittently, the composition of the mixture may be constant or varied.
Further, each monomer may be added to the reaction vessel after mixing various monomers to be used in advance, or may be added to the reaction vessel separately.

The polymerization temperature at the time of emulsion polymerization is not particularly limited, but is usually 0 to 95 ° C, preferably 5 to 70 ° C. The polymerization time is not particularly limited, but is usually about 5 to 40 hours.

After terminating the polymerization reaction, if desired, the unreacted monomer may be removed to adjust the solid content concentration and pH.

The glass transition temperature of the conjugated diene polymer (A) constituting the latex of the conjugated diene polymer (A) is 10 ° C. or lower, preferably 45 to -10 ° C., more preferably -40 to −. It is 10 ° C. If the glass transition temperature of the conjugated diene polymer (A) is too high, the obtained dip molded product will be inferior in oil grip. The method for setting the glass transition temperature of the conjugated diene polymer (A) in the above range is not particularly limited, but for example, the content ratio of each monomer constituting the conjugated diene polymer (A) is contained. Is included in the above-mentioned range.

The volume average particle size of the particles of the conjugated diene polymer (A) constituting the latex of the conjugated diene polymer (A) is preferably 30 to 1000 nm, more preferably 50 to 500 nm, and further preferably 70 to 70. It is 200 nm. By setting the volume average particle diameter of the particles of the conjugated diene polymer (A) in the above range, the glass transition temperature in the conjugated diene polymer (A) exceeds 10 ° C. in the obtained dip molded product. A polymer (B) can be finely dispersed, which can enhance wear resistance.

Further, from the viewpoint that the surface tension of the latex composition for dip molding is within a suitable range described later, the surface tension of the latex of the conjugated diene polymer (A) at 25 ° C. is preferably 28 to 72 mN / m. It is more preferably 29 to 65 mN / m, and even more preferably 30 to 60 mN / m. The surface tension of the latex of the conjugated diene polymer (A) is a method for adjusting the amount of the emulsifier used for emulsion polymerization, and the surface tension of the latex of the conjugated diene polymer (A) is the same as that of the conjugated diene polymer (A) constituting the latex of the conjugated diene polymer (A). It can be adjusted by a method of adjusting the volume average particle diameter of the particles.

Further, a weight having a glass transition temperature of more than 10 ° C. constituting a latex of the polymer (B) having a glass transition temperature of more than 10 ° C. (hereinafter, appropriately referred to as “latex of the polymer (B)”). The coalescence (B) (hereinafter, appropriately referred to as “polymer (B)”) is not particularly limited, and any polymer having a glass transition temperature of more than 10 ° C. may be used, but the obtained dip molding can be obtained. From the viewpoint of the oil grip property of the body, chemical permeability, and oil resistance during continuous use, a polymer containing a monomer unit having a halogen atom is preferable.

The halogen atom is not particularly limited, but for example, a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom are preferable. Among these, chlorine atoms are preferable from the viewpoint of oil grip property, chemical permeability, and oil resistance during continuous use of the obtained dip molded product. That is, as the polymer (B), a polymer containing a monomer unit having a chlorine atom is more preferable.

The monomer having a halogen atom that forms a monomer unit having a halogen atom is not particularly limited, and is not particularly limited, for example, an unsaturated alkyl halide, an unsaturated alcohol ester of a halogen-containing saturated carboxylic acid, and (meth) acrylic. Acid haloalkyl ester, (meth) acrylic acid haloacyloxyalkyl ester, (meth) acrylic acid (haloacetylcarbamoyloxy) alkyl ester, halogen-containing unsaturated ether, halogen-containing unsaturated ketone, halomethyl group-containing aromatic vinyl compound, halogen-containing Examples include unsaturated amides and haloacetyl group-containing unsaturated monomers. Among these, unsaturated alkyl halides are preferably used, vinyl chloride is more preferable, and polymers are preferable, from the viewpoints of oil grip property, chemical permeability resistance, and oil resistance during continuous use of the obtained dip molded product. As (B), a vinyl chloride resin having a vinyl chloride unit as a main component is more preferable.

The vinyl chloride resin as the polymer (B) may be any of a vinyl chloride homopolymer and a copolymer of vinyl chloride and a monomer copolymerizable with vinyl chloride. As the vinyl chloride resin as the polymer (B), a vinyl chloride homopolymer is preferable. When the vinyl chloride resin is a copolymer, the content of the vinyl chloride monomer unit in the vinyl chloride resin is preferably 50% by weight or more, more preferably 75% by weight or more, and further preferably 75% by weight or more. 90% by weight or more.

Examples of the monomer copolymerizable with vinyl chloride include α-olefin monomers such as ethylene, propylene, 1-butene, 4-methyl-1-pentene, 1-hexene and 1-octene; styrene and α-methyl. Aromatic monomers such as styrene and vinylpyridine; α, β-ethylenically unsaturated monocarboxylic acids such as acrylic acid, methacrylic acid, crotonic acid and silicic acid; ethyl (meth) acrylate, (meth) acrylic Esters of α, β-ethylenically unsaturated monocarboxylic acids such as butyl acid and 2-ethylhexyl (meth) acrylate; α, β-ethylenically unsaturated polyvalent carboxylic acids such as maleic acid, fumaric acid and itaconic acid; Α, β-Ethylene unsaturated polyvalent carboxylic acid monoesters such as monomethyl maleate, monoethyl maleate, monoethyl itaconate; dimethyl maleate, di-n-butyl fumarate, dimethyl itaconate, di-2-itaconate Α, β-Ethylene unsaturated polyvalent carboxylic acid polyvalent ester such as ethylhexyl; vinyl ester monomer such as vinyl acetate and vinyl propionate; α, β-ethylenically unsaturated monocarboxylic acid such as acrylamide and methacrylamide Amid; N-substituted maleimides; vinyl ether monomers such as vinyl methyl ether, vinyl ethyl ether, vinyl cetyl ether; vinylidene compounds such as vinylidene chloride; and the like; among these, vinyl ester monomers, α, The ester of β-ethylenically unsaturated monocarboxylic acid is preferable, and vinyl acetate and (meth) acrylic acid ester are more preferable. That is, the vinyl chloride resin as the polymer (B) is preferably a copolymer of vinyl chloride and vinyl acetate, or a copolymer of vinyl chloride and (meth) acrylic acid ester.

The method for producing the latex of the vinyl chloride resin as the polymer (B) is not particularly limited as long as it is a method capable of polymerizing the above-mentioned monomer, but is not particularly limited, but is known emulsion polymerization by radical polymerization, seed emulsion polymerization, and fine particles. Examples thereof include a method using suspension polymerization.

The K value of the vinyl chloride resin as the polymer (B) measured according to JIS K 7376-2 is preferably 50 to 95, more preferably 60 to 80.

Further, as the vinyl chloride resin as the polymer (B), it is preferable that the plasticizer is contained in an amount of 20 parts by weight or less with respect to 100 parts by weight of the polymer (B), and it is more preferable to use a resin that does not contain the plasticizer. Preferably, this makes it possible to improve the oil grip of the obtained dip molded product. In this case, "does not contain a plasticizer" may be any aspect as long as the vinyl chloride resin particles constituting the latex of the vinyl chloride resin do not substantially contain the plasticizer. The content of the plasticizer may be suppressed to 10% by weight or less.

As the polymer (B), in addition to the vinyl chloride resin, for example, polystyrene resin, polymethyl methacrylate resin, PTFE resin, acrylic resin and the like may be used. As the polymer (B), a vinyl chloride resin or a polystyrene resin is preferable, and a vinyl chloride resin is more preferable from the viewpoint of oil grip property, chemical permeability, and oil resistance during continuous use of the obtained dip molded product. In addition, these polymers may be used individually by 1 type, and may be used in combination of 2 or more type.

The glass transition temperature of the polymer (B) constituting the latex of the polymer (B) is more than 10 ° C., preferably 30 ° C. or higher, more preferably 50 ° C. or higher, still more preferably 70 ° C. That is all. The upper limit of the glass transition temperature of the polymer (B) is not particularly limited, but is preferably 200 ° C. or lower, and more preferably 150 ° C. or lower.

The latex composition for dip molding of the present invention comprises a latex of a conjugated diene polymer (A) having a glass transition temperature of 10 ° C. or lower and a latex of a polymer (B) having a glass transition temperature of more than 10 ° C. , A latex composition for dip molding obtained by mixing in a latex state is preferable. When the latex of the conjugated diene polymer (A) and the latex of the polymer (B) are mixed in a latex state to obtain a dip molded product using such a latex composition, a liquid at the time of molding. It is possible to further suppress who and make the obtained dip molded product even more excellent in oil grip.

In particular, by mixing the latex of the conjugated diene polymer (A) and the latex of the polymer (B) in a latex state, the particles of the conjugated diene polymer (A) can be mixed in the latex composition. The particles of the polymer (B) can be finely dispersed uniformly. Then, when the dip-molded product is formed by dip molding, the polymer (B) is finely dispersed in the matrix of the conjugated diene-based polymer (A) in the obtained dip-molded product. It can be precipitated. Therefore, due to the action of the finely dispersed polymer (B), the obtained dip molded product can be made even more excellent in oil grip. Further, since it is easy to make the matrix of the conjugated diene polymer (A) continuous and uniform in the obtained dip molded product, the obtained dip molded product is also excellent in chemical permeability. It is something that can be made. In the present invention, it is preferable that the latex of the conjugated diene polymer (A) and the latex of the polymer (B) are mixed in a latex state to obtain a latex composition. The latex composition for dip molding may be a latex composition in which the particles of the conjugated diene polymer (A) and the particles of the polymer (B) are dispersed in an aqueous medium, and can be obtained by mixing these latexes. It is not particularly limited to what can be done.

If the glass transition temperature of the polymer (B) constituting the latex of the polymer (B) is too low, the obtained dip molded product will be inferior in oil grip. The method for setting the glass transition temperature of the polymer (B) in the above range is not particularly limited. For example, when a vinyl chloride resin latex is used as the latex of the polymer (B), vinyl chloride is used. Examples thereof include a method in which the content of the vinyl chloride monomer unit in the resin is preferably 50% by weight or more, more preferably 75% by weight or more.

The volume average particle diameter of the particles of the polymer (B) constituting the latex of the polymer (B) is preferably 0.05 to 500 μm, more preferably 0.05 to 60 μm, still more preferably 0.05 to 50 μm. Even more preferably, it is 0.05 μm or more and less than 3 μm, and particularly preferably 0.05 μm or more and less than 0.5 μm. By setting the volume average particle diameter of the particles of the polymer (B) in the above range, the polymer (B) is better finely dispersed in the conjugated diene-based polymer (A) in the obtained dip molded product. This allows the wear resistance to be enhanced.

Further, from the viewpoint that the surface tension of the latex composition for dip molding is within a suitable range described later, the surface tension of the latex of the polymer (B) at 25 ° C. is preferably 34 to 72 mN / m, more preferably. It is 35 to 65 mN / m, more preferably 36 to 60 mN / m. The surface tension of the latex of the polymer (B) is a method for adjusting the amount of the emulsifier used for emulsion polymerization, and the volume average particle diameter of the particles of the polymer (B) constituting the latex of the polymer (B) is adjusted. It can be adjusted by the method.

The content of the conjugated diene-based polymer (A) and the content of the polymer (B) in the latex composition for dip molding of the present invention are not particularly limited, but the weight contained in the latex composition for dip molding is not particularly limited. 100 parts by weight of the combined component (when the polymer component contains only the conjugated diene polymer (A) and the polymer (B), the conjugated diene polymer (A) and the polymer (B) The content of the conjugated diene polymer (A) in (100 parts by weight in total) is preferably 40 parts by weight or more, more preferably 40 to 95 parts by weight, and 40 to 80 parts by weight. Is more preferable. The content of the polymer (B) is preferably 5 to 80 parts by weight, preferably 10 to 70 parts by weight, based on 100 parts by weight of the polymer component contained in the latex composition for dip molding. More preferably, it is 20 to 60 parts by weight. Further, the content ratio of the conjugated diene polymer (A) and the polymer (B) in the latex composition for dip molding of the present invention is "conjugated diene polymer (A): polymer (B). The weight ratio is preferably 99: 1 to 10:90, more preferably 95: 5 to 20:80, still more preferably 90: 10 to 30:70, and particularly preferably 75: 25 to 45:55. Is. By setting the contents of the conjugated diene polymer (A) and the polymer (B) in the above range, the oil grip property of the obtained dip molded product can be further enhanced.

The latex composition for dip molding of the present invention contains a thickener in addition to the latex of the conjugated diene polymer (A) and the latex of the polymer (B).

Examples of the thickener used in the present invention include vinyl compounds such as polyvinyl alcohol and polyvinylpyrrolidone; cellulose derivatives such as hydroxyethyl cellulose, hydroxypropyl cellulose and carboxymethyl cellulose and salts thereof; polycarboxylic acid compounds such as polyacrylic acid. And its sodium salt; a polyoxyethylene derivative such as polyethylene glycol ether; and the like. Among these, a vinyl compound and its carboxylic acid-modified compound or a polyoxyethylene derivative are preferable, and a vinyl-based compound and its carboxylic acid-modified compound are more preferable, from the viewpoint of chemical permeability. Further, as the thickener, it is preferable to use a nonionic thickener from the viewpoint of chemical permeability, and among them, polyvinyl alcohol is preferably used. These thickeners may be used alone or in combination of two or more.

When polyvinyl alcohol is used as the thickener, the saponification degree of polyvinyl alcohol is preferably 75 mol% or more, more preferably 80 mol% or more. The upper limit of the saponification degree of the thickener is not particularly limited, but is usually 99.9 mol% or less. When the saponification degree of polyvinyl alcohol is within the above range, the obtained dip molded product has excellent oil grip and chemical permeability.

The amount of acid in the thickener is not particularly limited, but is preferably 10 mmol / g or less, more preferably 5 mmol / g or less, still more preferably 2.5 mmol / g or less, and particularly preferably 1 mmol / g. It is as follows. The lower limit of the acid amount of the thickener is not particularly limited, but is usually 0.001 mmol / g or more. When the amount of acid in the thickener is in the above range, the obtained dip molded product has excellent oil grip and chemical permeability.

The acid amount of the thickener used in the present invention can be measured by, for example, the following method.
First, 50 g of a thickener aqueous solution (a solid thickener in 50 g of a thickener aqueous solution) prepared by adding distilled water to a 200 ml glass container washed with distilled water to adjust the solid content concentration to 0.2 to 1%. The amount is W (g)), set in a solution conductivity meter (Kyoto Denshi Kogyo Co., Ltd .: CM-117, cell type used: K-121), and stirring is started. Next, while stirring was continued, 0.1N sodium hydroxide was added so that the pH of the aqueous solution was 12 or more, and the electrical conductivity after 6 minutes had passed was measured, and the obtained measurement was performed. The value is taken as the electrical conductivity at the start of measurement. Then, 0.5 ml of 0.1N hydrochloric acid was added to this thickener aqueous solution to measure the electrical conductivity 30 seconds later, and 0.5 ml of 0.1N hydrochloric acid was added again and electricity was added 30 seconds later. The operation of measuring the conductivity is repeated at intervals of 30 seconds until the electrical conductivity becomes twice or more the electrical conductivity at the start of the measurement. Then, the obtained electrical conductivity data is plotted on a graph with vertical axis: electrical conductivity (mS) and horizontal axis: cumulative amount of added hydrochloric acid (mmol), and two variations as shown in FIG. 1 are plotted. Obtaining the amount of hydrochloric acid-electrical conductivity curve with curved points, the X coordinates of the two inflection points obtained and the X coordinates at the end of the addition of hydrochloric acid are P ₁ , P ₂ and P, respectively, in ascending order of value. _{Let it be 3,} and for the data in the three categories of X coordinates from zero to P ₁ , P ₁ to P ₂ , and P ₂ to P _{3 , the approximate straight lines L 1} , L ₂ and L, respectively, by the minimum square method. Find _3. Further, the X coordinate of the intersection of _{L 1} and L _{2 is A 1} (mmol), and the X coordinate of the intersection of _{L 2} and L _{3 is A 2} (mmol). Then, the amount of acid per 1 g of the thickener is calculated from the following formula.
Amount of acid per gram of thickener = (A _2- A ₁ ) / W (mmol / g)

When two or more kinds of thickeners are used in combination, a thickener obtained by mixing each thickener at the same ratio as the abundance ratio of each thickener in the latex composition for dip molding. The amount of acid in the thickener mixture obtained by measuring the mixture in the same manner as described above can be used as the amount of acid in the thickener.

When the thickener used in the present invention is a 4 wt% aqueous solution, the viscosity is not particularly limited, but is preferably 1 mPa · s or more, more preferably 10 mPa · s or more, and preferably 20,000 mPa · s or less. More preferably, it is 000 mPa · s or less. The viscosity of the thickener used in the present invention as a 1 wt% aqueous solution is not particularly limited, but is preferably 1 mPa · s or more, more preferably 10 mPa · s or more, and preferably 20,000 mPa · s or less. More preferably 10,000 mPa · s or less. The viscosity of the thickener aqueous solution can be measured using, for example, a B-type viscometer under the conditions of 25 ° C. and 6 rpm.

The blending amount of the thickener used in the present invention is preferably 0.01 to 10 parts by weight, more preferably 0.1 to 5 parts by weight, based on 100 parts by weight of the polymer component contained in the latex composition for dip molding. Parts, more preferably 0.15 to 4.5 parts by weight. When the blending amount of the thickener is within the above range, the obtained dip molded product has excellent chemical permeability.

Further, the latex composition for dip molding of the present invention may further contain a sulfur-based cross-linking agent in addition to the latex of the conjugated diene-based polymer (A), the latex of the polymer (B), and the thickener. preferable.

The sulfur-based cross-linking agent is not particularly limited, but 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, and dibenzothia. Sulfur-containing compounds such as zirdisulfide, caprolactam disulfide, phosphorus-containing polysulfides, and high molecular weight polysulfides; sulfur-donating compounds such as tetramethylthiuram disulfide, selenium dimethyldithiocarbamate, 2- (4'-morpholinodithio) benzothiazole; etc. Can be mentioned. These sulfur-based cross-linking agents may be used alone or in combination of two or more.

The content of the sulfur-based cross-linking agent is preferably 0.01 to 5 parts by weight, more preferably 0.05 to 3 parts by weight, and further, with respect to 100 parts by weight of the polymer component contained in the latex composition for dip molding. It is preferably 0.1 to 2 parts by weight.

Further, the latex composition for dip molding of the present invention preferably further contains a cross-linking accelerator (vulcanization accelerator) and zinc oxide in addition to the sulfur-based cross-linking agent.
The cross-linking accelerator (vulcanization accelerator) is not particularly limited, and for example, dithiocarbamines such as diethyldithiocarbamic acid, dibutyldithiocarbamic acid, di-2-ethylhexyldithiocarbamic acid, dicyclohexyldithiocarbamic acid, diphenyldithiocarbamic acid, and dibenzyldithiocarbamic acid. Acids and their zinc salts; 2-mercaptobenzothiazole, 2-mercaptobenzothiazole zinc, 2-mercaptothiazolin, dibenzothiazil disulfide, 2- (2,4-dinitrophenylthio) benzothiazole, 2- (N, N-diethylthiocarbamoylthio) benzothiazole, 2- (2,6-dimethyl-4-morpholinothio) benzothiazole, 2- (4'-morpholinodithio) benzothiazole, 4-morpholinyl-2-benzothiazil disulfide, Examples thereof include 1,3-bis (2-benzothiazil-mercaptomethyl) urea, and among these, zinc diethyldithiocarbamate, zinc dibutyldithiocarbamate, 2-mercaptobenzothiazole, and 2-mercaptobenzothiazole zinc are preferable. These cross-linking accelerators may be used alone or in combination of two or more.

The content of the cross-linking accelerator is preferably 0.1 to 10 parts by weight, more preferably 0.5 to 5 parts by weight, based on 100 parts by weight of the polymer component contained in the latex composition for dip molding. The zinc oxide content is preferably 0.1 to 10 parts by weight, more preferably 0.5 to 5 parts by weight, based on 100 parts by weight of the polymer component contained in the latex composition for dip molding. ..

The solid content concentration of the latex composition for dip molding of the present invention is 42% by weight or more and 55% by weight or less, and is not particularly limited, but the lower limit of the solid content concentration is preferably 43.5% by weight or more. It is preferably 43.8% by weight or more, and more preferably 44.1% by weight or more. The upper limit of the solid content concentration is not particularly limited, but is preferably 53.0% by weight or less. If the solid content concentration of the latex composition for dip molding is too low, it is not possible to achieve both suppression of dripping during molding and development of oil grip properties of the obtained molded product. On the other hand, if the solid content concentration of the latex composition for dip molding is too high, it becomes difficult to satisfactorily disperse the polymer (B) in the latex composition for dip molding, and the conjugated diene in the obtained dip molded body. Since it is difficult to satisfactorily finely disperse the polymer (B) in the matrix of the system polymer (A), the obtained molded product is inferior in oil grip property.

As a method of setting the solid content concentration of the latex composition for dip molding within the above-mentioned range, for example, the solid content concentration of each component such as the latex of the conjugated diene polymer (A) or the latex of the polymer (B) can be set. Examples thereof include a method of adjusting and a method of adjusting by a concentration treatment or a dilution treatment described later. Among these, the method of adjusting by concentration treatment is preferable from the viewpoint of productivity.

The pH of the latex composition for dip molding of the present invention is preferably 5 to 13, more preferably 7 to 10, and even more preferably 7.5 to 9. By setting the pH of the latex composition for dip molding within the above range, mechanical stability can be improved, the generation of coarse agglomerates during transfer of the latex composition for dip molding can be suppressed, and dip molding can be performed. The viscosity of the latex composition for dip molding becomes appropriate, and the handleability of the latex composition for dip molding is improved.

The viscosity of the latex composition for dip molding of the present invention at 25 ° C. is preferably 1,000 to 100,000 mPa · s, more preferably 1,500 to 50,000 mPa · s, and even more preferably 2,500 to 2,500 mPa · s. It is 20,000 mPa · s. The viscosity of the latex composition for dip molding at 25 ° C. can be measured using, for example, a B-type viscometer under the conditions of 25 ° C. and a rotation speed of 6 rpm. The viscosity of the latex composition for dip molding at 25 ° C. is, for example, a method for adjusting the concentration of the polymer component in the latex composition for dip molding, or a compound having a thickening effect on the latex composition for dip molding. It can be adjusted by the method of addition.

The surface tension of the latex composition for dip molding of the present invention at 25 ° C. is preferably 34 to 72 mN / m, more preferably 35 to 65 mN / m, and even more preferably 36 to 60 mN / m. By setting the surface tension of the latex composition for dip molding within the above range, the oil grip property of the obtained dip molded product can be further enhanced. Further, the surface tension of the latex composition for dip molding is, for example, a method of adjusting the surface tension of the latex of the conjugated diene polymer (A) or the latex of the polymer (B) within the above range, or the polymer (B). ), The surface tension of the latex of the polymer (B) can be adjusted within the above range.

Further, the latex composition for dip molding of the present invention includes carbon black, silica, calcium carbonate, aluminum silicate, magnesium silicate, calcium silicate, magnesium oxide, zinc (meth) acrylate, magnesium (meth) acrylate, and titanium oxide. A filler such as may be added. Further, in the latex composition for dip molding of the present invention, if necessary, additives other than the above-mentioned water-soluble salts and fillers, for example, antioxidants, antioxidants, preservatives, antibacterial agents, wetting agents, etc. Various additives such as dispersants, pigments, dyes, reinforcing agents, and pH adjusters can also be added in a predetermined amount.

The latex composition for dip molding of the present invention can be prepared, for example, by mixing the above-mentioned components and further concentrating or diluting them as necessary. The mixing order of each component is not particularly limited, but from the viewpoint of further enhancing the dispersibility of each component, the latex of the conjugated diene polymer (A) and the latex of the polymer (B) are mixed in advance and then increased. A method of adding a thickener and each component to be blended as needed and mixing them is preferable. The method for mixing the latex of the conjugated diene polymer (A) and the latex of the polymer (B) is not particularly limited, but from the viewpoint of further enhancing dispersibility, the conjugated diene polymer (A) A method of mixing the latex and the latex of the polymer (B) in a latex state (latex blend) is preferable.

The latex composition for dip molding of the present invention is preferably obtained through a concentration treatment. The concentration treatment method is not particularly limited, and examples thereof include methods such as vacuum distillation, atmospheric distillation, centrifugation, and membrane concentration. Among these, a concentration method involving heating is preferable, and vacuum distillation with heating is more preferable. By adopting a concentration method that involves heating, it is possible to reduce the bacteria that cause odors or suppress the growth of bacteria that cause odors, and the latex composition for dip molding has excellent low odor properties. Can be considered.

In the concentration method involving heating, the heating temperature is preferably 50 ° C. to 100 ° C. Further, in vacuum distillation, the pressure is preferably 20 kPa to 90 kPa.

The concentration treatment may be applied to a mixture containing a part of the components to be blended in the latex composition for dip molding, or may be applied to a mixture containing all the components to be blended in the latex composition for dip molding. May be good. From the viewpoint of dispersibility and production efficiency of the latex composition for dip molding, it is preferable to concentrate the mixture of the latex of the conjugated diene polymer (A) and the latex of the polymer (B).

That is, as a method for producing the latex composition for dip molding of the present invention, the latex of the conjugated diene polymer (A) and the latex of the polymer (B) are mixed in advance, and then the obtained mixture is concentrated. After increasing the solid content concentration by applying the above, a method of adding a thickener and each component to be blended as necessary and mixing them to bring the solid content concentration into the above range is preferable.

<Dip molded body>
The dip molded product of the present invention is a molded product obtained by using the above-mentioned latex composition for dip molding of the present invention, and is usually dip-molded using the above-mentioned latex composition for dip molding of the present invention. Obtained by

Since the dip molded product of the present invention is a molded product obtained by using the above-mentioned latex composition for dip molding of the present invention, the above-mentioned conjugated diene polymer (A) having a glass transition temperature of 10 ° C. or lower (A) ( Hereinafter, it is appropriately referred to as “conjugated diene polymer (A)”) and the above-mentioned polymer (B) having a glass transition temperature of more than 10 ° C. (hereinafter, appropriately referred to as “polymer (B)”. It has at least a polymer layer containing () and. The preferred range of the content ratio of the conjugated diene polymer (A) and the polymer (B) in the dip molded product of the present invention is the conjugated diene weight in the latex composition for dip molding of the present invention. The preferred range of the content ratio of the coalescence (A) and the polymer (B) is the same as the above-mentioned range.

The dip molded product of the present invention is a film made of a dip molding latex composition obtained by immersing a dip molding mold in a dip molding latex composition such as the above-mentioned dip molding latex composition of the present invention. It may be a molded product, or it may be a laminate of a base material and a polymer layer composed of a latex composition for dip molding, which is obtained by immersing the base material in a latex composition for dip molding. May be good. In the following, a case where the dip molded product of the present invention is a laminate of a base material and a polymer layer composed of a latex composition for dip molding will be described by way of example. It is not limited.

The base material is not particularly limited, but when the dip molded product of the present invention is used as a protective glove, a fiber base material can be preferably used. The fiber base material is not particularly limited, but for example, a single-fiber twisted yarn is used as the fiber, and a glove-shaped twisted yarn can be used by weaving the twisted yarn. The average thickness of the fiber substrate is preferably 50 to 3,000 μm, more preferably 100 to 2,000 μm.

The dip molded product of the present invention is produced, for example, by immersing a base material in a latex composition for dip molding to form a polymer layer composed of the latex composition for dip molding on the base material. Can be done. In this case, it is preferable to immerse the base material in the latex composition for dip molding with the base material covered with a molding mold having a desired shape in advance.

The molding mold for covering the base material is not particularly limited, but various materials such as porcelain, glass, metal, and plastic can be used. The shape of the molding mold may be a desired shape according to the shape of the final product. For example, when the dip molded product of the present invention is used as a protective glove, a molding mold for various gloves such as a molding mold having a shape from a wrist to a fingertip is used as a molding mold for covering a base material. Is preferable.

Further, before immersing the base material in the latex composition for dip molding, it is preferable to immerse the base material in the coagulant solution in advance and attach the coagulant solution to the base material. In this case, it is preferable to immerse the base material in the coagulant solution in a state where the base material is previously covered with a molding mold having a desired shape. Examples of the molding mold having a desired shape include those described above. Further, it is preferable to remove the solvent contained in the coagulant solution by adhering the coagulant solution to the base material, adhering the coagulant solution to the base material, and then drying. The drying temperature at this time is not particularly limited and may be selected depending on the solvent used, but is preferably 10 to 80 ° C, more preferably 15 to 70 ° C. The drying time is not particularly limited, but is preferably 600 to 1 second, more preferably 300 to 5 seconds.

Next, the base material to which the coagulant solution is attached is dipped in the latex composition for dip molding while being covered with the molding mold having a desired shape to coagulate the latex composition for dip molding. A polymer layer made of a latex composition for dip molding is attached onto the base material.

Then, after immersing the base material in the latex composition for dip molding, it is preferable to perform drying. The drying temperature at this time is not particularly limited, but is preferably 10 to 80 ° C, more preferably 15 to 80 ° C. The drying time is not particularly limited, but is preferably 120 minutes to 5 seconds, more preferably 60 minutes to 10 seconds.

When a latex composition for dip molding containing a sulfur-based cross-linking agent is used, a latex composition for dip molding that has been aged in advance (also referred to as pre-vulcanization) may be used. ..

The temperature conditions for aging are not particularly limited, but are preferably 20 to 50 ° C. In addition, the time required for aging improves the wear resistance when the obtained dip molded product is used as protective gloves from the viewpoint of preventing peeling between the base material and the polymer layer made of the latex composition for dip molding. From the viewpoint of making the mixture, it is preferably 4 hours or more and 120 hours or less, and more preferably 24 hours or more and 72 hours or less.

Next, it is preferable to crosslink the polymer component contained in the latex composition for dip molding by heating the latex composition for dip molding attached to the substrate.

The heating temperature for crosslinking is preferably 60 to 160 ° C, more preferably 80 to 150 ° C. By setting the heating temperature within the above range, the time required for the crosslinking reaction can be shortened to improve the productivity of the dip molded product, and the oxidative deterioration of the polymer component due to excessive heating can be suppressed. The physical properties of the dip molded product can be improved. The heating time for crosslinking may be appropriately selected according to the heating temperature, but is usually 5 to 120 minutes.

The polymer layer formed on the substrate is dipped in warm water at 20 to 80 ° C. for about 0.5 to 60 minutes to add weight to the dip molded product thus obtained. It is preferable to remove water-soluble impurities (emulsifier, water-soluble polymer, coagulant, etc.) from the coalesced layer. Such a treatment of immersing the polymer layer in warm water may be performed after the polymer components in the polymer layer are crosslinked, but the polymer layer can be used to remove water-soluble impurities more efficiently. It is preferable to carry out before cross-linking the polymer component of.

After being immersed in warm water, it may be further dried. The drying temperature and drying time at this time are not particularly limited, but can be the same as the drying temperature and drying time in the drying step after being immersed in the latex composition for dip molding described above.

Then, after forming a polymer layer on the base material with the base material covered with the molding mold as described above, the dip molded product is obtained by desorbing (or removing) from the molding mold. Can be done. As a desorption method, a method of manually peeling from the molding mold or a method of peeling by water pressure or compressed air pressure can be adopted.

Before or after the dip molded body is detached from the molding die, heat treatment (post-crosslinking step) may be further performed at a temperature of 60 to 120 ° C. for 10 to 120 minutes. Further, after the dip molded product is detached from the molding mold, a surface treatment layer may be formed on the inner and / or outer surfaces of the dip molded product by chlorination treatment, coating treatment, or the like.

The dip molded product of the present invention thus obtained forms a polymer layer composed of the above-mentioned latex composition for dip molding of the present invention on a substrate by coagulation using a coagulant. Therefore, the film thickness is preferably 0.05 to 1.0 mm, more preferably 0.06 to 0.8 mm, further preferably 0.07 to 0.7 mm, particularly preferably more than 0.3 mm and 0.7 mm. The film can be made relatively thick as follows, and thereby, the abrasion resistance of the obtained dip molded product can be enhanced. Further, normally, when a relatively thick film is used, the oil grip property tends to decrease. However, according to the dip molded product of the present invention, even when a relatively thick film is used ( For example, even when the thickness exceeds 0.3 mm, excellent oil grip can be realized.

The dip molded product of the present invention has excellent oil grip, and can be suitably used for, for example, glove applications, particularly protective glove applications. In the above description, the case where the dip molded product of the present invention is a laminate of a base material and a polymer layer composed of a latex composition for dip molding has been described as an example. The invention is not limited to such an embodiment, and a film molded product made of a latex composition for dip molding, which is obtained by immersing a dip molding mold in a latex composition for dip molding, can also be used. Of course it is possible.

Hereinafter, the present invention will be described in detail by way of examples, but the present invention is not limited to these examples. Unless otherwise specified, the following "parts" are based on weight. Various physical properties were measured as follows.

<Amount of acid in thickener>
The acid amount of the thickener was measured by the following method.
First, 50 g of a thickener aqueous solution (a solid thickener in 50 g of a thickener aqueous solution) prepared by adding distilled water to a 200 ml glass container washed with distilled water to adjust the solid content concentration to 0.2 to 1%. The amount was W (g)) and set in a solution conductivity meter (Kyoto Denshi Kogyo Co., Ltd .: CM-117, cell type used: K-121), and stirring was started. Next, while stirring was continued, 0.1N sodium hydroxide was added so that the pH of the aqueous solution was 12 or more, and the electrical conductivity after 6 minutes had passed was measured, and the obtained measurement was performed. The value was taken as the electrical conductivity at the start of measurement. Then, 0.5 ml of 0.1N hydrochloric acid was added to this thickener aqueous solution to measure the electrical conductivity 30 seconds later, and 0.5 ml of 0.1N hydrochloric acid was added again and electricity was added 30 seconds later. The operation of measuring the conductivity was repeated at intervals of 30 seconds until the electrical conductivity was twice as high as that at the start of the measurement.

Then, the obtained electrical conductivity data is plotted on a graph with vertical axis: electrical conductivity (mS) and horizontal axis: cumulative amount of added hydrochloric acid (mmol), and two variations as shown in FIG. 1 are plotted. Obtaining the amount of hydrochloric acid-electrical conductivity curve with curved points, the X coordinates of the two inflection points obtained and the X coordinates at the end of the addition of hydrochloric acid are P ₁ , P ₂ and P, respectively, in ascending order of value. _{Let it be 3,} and for the data in the three categories of X coordinates from zero to P ₁ , P ₁ to P ₂ , and P ₂ to P _{3 , the approximate straight lines L 1} , L ₂ and L, respectively, by the minimum square method. I asked for _3. Further, the X coordinate of the intersection of _{L 1} and L _{2 was set to A 1} (mmol), and the X coordinate of the intersection of _{L 2} and L _{3 was set to A 2} (mmol). Then, the amount of acid per 1 g of the thickener was calculated from the following formula.
Amount of acid per gram of thickener = (A _2- A ₁ ) / W (mmol / g)

<Thickener viscosity>
The thickener was precisely weighed, placed in a beaker, water was added, and the thickener was uniformly dissolved while stirring with a stirrer to obtain an aqueous thickener solution prepared in an amount of 1% by weight or 4% by weight. The viscosity of the thickener aqueous solution is determined by the B-type viscometer and the rotor NO. The measurement was carried out using M3 under the conditions of 25 ° C. and a rotation speed of 6 rpm.

<Solid concentration of latex composition for dip molding>
2 g of the sample was precisely weighed on an aluminum plate (weight: X1) (weight: X2), and this was dried in a hot air dryer at 105 ° C. for 2 hours. Then, after cooling in the desiccator, the weight of the 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

<Viscosity of latex composition for dip molding>
The viscosity of the latex composition for dip molding is determined by the B-type viscometer and rotor NO. The measurement was carried out using M3 under the conditions of 25 ° C. and a rotation speed of 6 rpm.

<Volume average particle size>
The volume average particle size of the particles of the nitrile group-containing conjugated diene polymer (A-1) constituting the latex of the nitrile group-containing conjugated diene polymer (A-1), and the vinyl chloride resin (B-1). The volume average particle diameter of the particles of the vinyl chloride resin (B-1) constituting the latex was measured using a light scattering diffraction particle measuring device (manufactured by Coulter, trade name “LS-230”).

<Oil grip>
Cylindrical metal molds weighing 1.0 kg, 2.0 kg, 3.0 kg, 4.0 kg, 5.0 kg, 7.0 kg, and 10 kg were prepared, and the test oil IRM903 was attached to these metal molds. Then, the operator was asked to put on protective gloves (dip molded body), and the metal mold to which the test oil IRM903 was attached was lifted in order from the lightest weight to the maximum weight that could be lifted. I asked. The above measurement was performed by 10 workers, the average value of the maximum weight that could be lifted was calculated, and the evaluation was performed by dividing into levels from LEVEL0 to LEVEL3. It can be judged that the larger the maximum weight that can be lifted, the better the oil grip property.
LEVEL 3: 2.9 kg or more LEVEL 2: 1.7 kg or more and less than 2.9 kg LEVEL 1: 1.7 kg or more

<Chemical resistance>
The oil permeation amount was measured by the following procedure.
(1) Protective gloves (dip molded body) were cut into an appropriate circular size and used as a sample.
(2) 2 mL of the test oil IRM903 was placed in a reagent bottle.
(3) The rubber layer of the sample (dip molded product) was placed on the reagent bottle containing the test oil IRM903 so as to be in contact with the liquid.
(4) The reagent bottle and the sample were firmly adhered to each other using a fixture.
(5) In order for the test oil IRM903 to come into contact with the sample, the reagent bottle was turned upside down, placed on a filter paper whose weight (W1) was measured in advance, and left at room temperature.
(6) After leaving for 24 hours, the weight (W2) of the filter paper was measured.
(7) The amount of the test oil IRM903 that permeated the sample (oil permeation amount) was calculated by the following formula.
Oil permeation amount (g) = W2-W1
It can be judged that the smaller the value of the oil permeation amount, the better the chemical permeation resistance to chemicals such as oil.

<Dripping during molding>
The polymer layer of the protective glove (dip molded product) was visually observed, and the presence or absence of defects due to dripping during molding, such as an abnormal shape at the end of the protective glove and uneven thickness of the protective glove, was evaluated.

<Example 1>
(Preparation of aqueous dispersion of colloidal sulfur)
Colloidal sulfur (manufactured by Hosoi Chemical Industry Co., Ltd.) 1.0 part, dispersant (manufactured by Kao Co., Ltd., trade name "Demor N") 0.5 part, 5 wt% potassium hydroxide aqueous solution (manufactured by Wako Pure Chemical Industries, Ltd.) 0. An aqueous dispersion of colloidal sulfur having a solid content concentration of 50% by weight was prepared by pulverizing and stirring 0015 parts and 1.0 part of water in a ball mill for 48 hours.

(Preparation of aqueous dispersion of zinc dibutyldithiocarbamate, aqueous dispersion of zinc oxide, and aqueous dispersion of titanium oxide)
Dibutyldithiocarbamic acid in the same manner as above, except that zinc dibutyldithiocarbamate (manufactured by Ouchi Shinko Kagaku Kogyo Co., Ltd.), zinc oxide (manufactured by Shodo Kagaku Kogyo Co., Ltd.), and titanium oxide were used instead of colloidal sulfur. An aqueous dispersion of zinc, an aqueous dispersion of zinc oxide, and an aqueous dispersion of titanium oxide were prepared.

(Preparation of Latex of Nitrile Group-Containing Conjugated Diene Polymer (A-1))
In the polymerization reactor, 65 parts of 1,3-butadiene as a conjugated diene monomer, 30 parts of acrylonitrile as an α, β-ethylenic unsaturated nitrile monomer, and 5 methacrylic acid as an ethylenically unsaturated monocarboxylic acid monomer. , T-dodecyl mercaptan 0.4 parts, ion-exchanged water 132 parts, sodium dodecylbenzene sulfonate 3 parts, β-naphthalin sulfonate formalin condensate sodium salt 0.5 parts, potassium persulfate 0.3 parts and ethylenediamine tetra 0.05 part of sodium acetate was charged, the polymerization temperature was maintained at 30 to 40 ° C., polymerization was carried out, and the reaction was carried out until the polymerization conversion rate reached 94% to obtain a latex of a copolymer.

Then, after removing the unreacted monomer from the obtained latex of the copolymer, the pH and solid content of the latex of the copolymer are adjusted to have a solid content concentration of 40% by weight and pH = 8, 25. A latex of a nitrile group-containing conjugated diene polymer (A-1) having a surface tension of 31 mN / m at ° C. was obtained. The glass transition temperature (Tg) of the nitrile group-containing conjugated diene polymer (A-1) contained in the latex of the obtained nitrile group-containing conjugated diene polymer (A-1) was measured and found to be-. It was 27 ° C. Further, the volume average particle diameter of the particles of the nitrile group-containing conjugated diene-based polymer (A-1) constituting the latex of the nitrile group-containing conjugated diene-based polymer (A-1) is 110 nm, and the nitrile group-containing conjugated diene-based polymer (A-1) has a nitrile group-containing conjugate. The monomer composition of the diene polymer (A-1) was almost the same as the charging ratio.

(Preparation of latex composition for dip molding)
Latex of nitrile group-containing conjugated diene polymer (A-1) obtained above and latex of vinyl chloride resin (B-1) (manufactured by Nissin Chemical Industry Co., Ltd., trade name "Viniblanc 985") And were mixed so that the weight ratio of "nitrile group-containing conjugated diene polymer (A-1): vinyl chloride resin (B-1)" was 70:30, and 5% by weight of potassium hydroxide was added. By adding, a latex composition having a solid content concentration of 42.5% by weight and a pH of 9.0 was prepared. As the latex of the vinyl chloride resin (B-1), the glass transition temperature (Tg) of the vinyl chloride resin (B-1) is 80 ° C., and the volume average particle diameter of the particles of the vinyl chloride resin (B-1) is The thickness was 0.08 μm, and the vinyl chloride resin (B-1) contained substantially no plasticizer.

Next, the latex composition obtained above was concentrated by vacuum distillation at 80 ° C. for 5 hours under a reduced pressure condition of 70 kPa to obtain a concentrated latex composition having a solid content concentration of 46.4% by weight. rice field.

Then, 5% by weight of potassium hydroxide was added again to adjust the pH to 9.0, and then 100 parts of the polymer component of the concentrated latex composition obtained above was converted into solid content. The aqueous dispersion of each compounding agent prepared above was added so as to have 1.0 part of colloidal sulfur, 1.0 part of zinc dibutyldithiocarbamate, 1.5 part of zinc oxide, and 3.0 part of titanium oxide. , Stirred for 24 hours. When the aqueous dispersion of each compounding agent was added, a predetermined amount was slowly added while the latex composition was agitated. Then, after each compounding agent is uniformly mixed, PVA22-88 (polyvinyl alcohol, manufactured by Kuraray Co., Ltd., trade name "Kuraray Poval 22-88", acid amount 0.1 mmol / g, 4% by weight" is used as a thickener. 0.5 parts of the aqueous solution having a viscosity of 15 mPa · s, an average degree of polymerization of 1750, and a saponification degree of 88 mol%) was added to obtain a latex composition for dip molding. The solid content concentration and viscosity of the obtained latex composition for dip molding were measured according to the above method. The results are shown in Table 1.

(Preparation of coagulant solution)
A coagulant solution was prepared by dissolving calcium nitrate as a coagulant in methanol at a ratio of 3.0% by weight.

(Manufacturing of protective gloves (dip molded body))
First, the latex composition for dip molding obtained above was aged (also referred to as pre-vulcanization) at a temperature of 30 ° C. for 48 hours. Next, a ceramic glove mold covered with a glove-shaped fiber base material (material: nylon, linear density: 300 denier, gauge number: 13 gauge, thickness: 0.8 mm) was added to the coagulant solution prepared above in 5 After immersing for seconds and withdrawing from the coagulant solution, the mixture was dried at a temperature of 30 ° C. for 1 minute. Then, the ceramic glove mold is immersed in the above-mentioned latex composition for dip molding for 5 seconds, pulled up from the latex composition for dip molding, dried at a temperature of 30 ° C. for 30 minutes, and then dried at a temperature of 70 ° C., By heating under the condition of 10 minutes and cross-linking, a polymer layer having a thickness of 0.6 mm was formed on the fiber substrate. Then, the ceramic glove mold on which the polymer layer was formed was immersed in warm water at 60 ° C. for 90 seconds to elute water-soluble impurities from the polymer layer, and then dried at a temperature of 30 ° C. for 10 minutes. Further, the polymer in the polymer layer was crosslinked by performing a heat treatment at a temperature of 125 ° C. for 30 minutes. Next, the fiber base material on which the polymer layer was formed was peeled off from the ceramic glove mold to obtain a protective glove (dip molded product). Then, using the obtained protective gloves (dip molded product), the chemical permeability and the oil grip property were measured according to the above method, and the dripping during molding was evaluated. The results are shown in Table 1.

<Example 2>
The latex composition obtained in the same manner as in Example 1 was concentrated by vacuum distillation at 80 ° C. for 6 hours under a reduced pressure condition of 70 kPa to obtain a concentrated latex composition having a solid content concentration of 49.2% by weight. Got Using the obtained concentrated latex composition, a latex composition for dip molding was obtained and evaluated in the same manner as in Example 1 except that the amount of PVA22-88 used was changed to 0.4 part. rice field. The results are shown in Table 1.

Then, using the obtained latex composition for dip molding, protective gloves (dip molded body) having a polymer layer having a film thickness of 0.6 mm were obtained in the same manner as in Example 1, and evaluation was carried out in the same manner. rice field. The results are shown in Table 1.

<Example 3>
The latex composition obtained in the same manner as in Example 1 was concentrated by vacuum distillation at 80 ° C. for 6.2 hours under a reduced pressure condition of 70 kPa to concentrate a latex having a solid content concentration of 49.8% by weight. The composition was obtained. Using the obtained concentrated latex composition, a latex composition for dip molding was obtained in the same manner as in Example 1 except that the amount of PVA22-88 used was changed to 0.3 parts, and evaluation was performed in the same manner. rice field. The results are shown in Table 1.

Then, using the obtained latex composition for dip molding, protective gloves (dip molded body) having a polymer layer having a film thickness of 0.6 mm were obtained in the same manner as in Example 1, and evaluation was carried out in the same manner. .. The results are shown in Table 1.

<Example 4>
PVA22-88 Instead of 0.3 parts, PVA95-88 (polyvinyl alcohol, manufactured by Kuraray, trade name "Kuraray Poval 95-88", acid content 0.6 mmol / g, viscosity of 4 wt% aqueous solution 90 mPa · s, A latex composition for dip molding was obtained in the same manner as in Example 3 except that 0.4 parts (average degree of polymerization: 3500, saponification degree 88 mol%) was used, and the evaluation was carried out in the same manner. The results are shown in Table 1.

Then, using the obtained latex composition for dip molding, protective gloves (dip molded body) having a polymer layer having a film thickness of 0.6 mm were obtained in the same manner as in Example 1, and evaluation was carried out in the same manner. rice field. The results are shown in Table 1.

<Example 5>
The mixing ratio of the latex of the nitrile group-containing conjugated diene polymer (A-1) and the latex of the vinyl chloride resin (B-1) is described as "nitrile group-containing conjugated diene polymer (A-1): vinyl chloride. A latex composition having a solid content concentration of 40.9% by weight was obtained in the same manner as in Example 1 except that the weight ratio of "resin (B-1)" was changed to 60:40.

The obtained latex composition was concentrated under reduced pressure conditions of 70 kPa at 80 ° C. for 6 hours by vacuum distillation to obtain a concentrated latex composition having a solid content concentration of 47.0% by weight. Using the obtained concentrated latex composition, a latex composition for dip molding was obtained in the same manner as in Example 1 except that the amount of PVA22-88 used was changed to 0.3 parts, and evaluation was performed in the same manner. rice field. The results are shown in Table 1.

Then, using the obtained latex composition for dip molding, protective gloves (dip molded body) having a polymer layer having a film thickness of 0.6 mm were obtained in the same manner as in Example 1, and evaluation was carried out in the same manner. rice field. The results are shown in Table 1.

<Comparative example 1>
A latex composition was obtained in the same manner as in Example 1. With respect to 100 parts of the polymer component of the obtained latex composition, 1.0 part of colloidal sulfur, 1.0 part of zinc dibutyldithiocarbamate, 1.5 parts of zinc oxide, and titanium oxide in terms of solid content, respectively. The aqueous dispersion of each compounding agent prepared above was added so as to have 0 parts, and the mixture was stirred for 24 hours. When the aqueous dispersion of each compounding agent was added, a predetermined amount was slowly added while the latex composition was agitated. Then, after each compounding agent was uniformly mixed, 1.1 parts of PVA22-88 was added as a thickener to obtain a latex composition for dip molding. The obtained latex composition for dip molding was evaluated in the same manner. The results are shown in Table 1.

Then, using the obtained latex composition for dip molding, protective gloves (dip molded body) having a polymer layer having a film thickness of 0.6 mm were obtained in the same manner as in Example 1, and evaluation was carried out in the same manner. rice field. The results are shown in Table 1.

<Comparative example 2>
A latex composition for dip molding was obtained in the same manner as in Comparative Example 1 except that the amount of PVA22-88 used was changed to 0.7 parts, and the evaluation was carried out in the same manner. The results are shown in Table 1.

Then, using the obtained latex composition for dip molding, protective gloves (dip molded body) having a polymer layer having a film thickness of 0.6 mm were obtained in the same manner as in Example 1, and evaluation was carried out in the same manner. rice field. The results are shown in Table 1.

<Comparative example 3>
Except that the latex of the vinyl chloride resin (B-1) was not blended and the latex of the nitrile group-containing conjugated diene polymer (A-1) was blended in terms of solid content with respect to 100 parts of the latex. A latex composition having a solid content concentration of 45% by weight was obtained in the same manner as in Example 1. Next, instead of 1.1 parts of PVA22-88, carboxymethyl cellulose (manufactured by Daicel Co., Ltd., trade name "Daicel2200", acid content: 3.7 mmol / g, viscosity of 1 wt% aqueous solution: 850 mPa · s, weight average molecular weight: 550. 000) A latex composition for dip molding was obtained in the same manner as in Comparative Example 1 except that 0.3 part was used, and the evaluation was carried out in the same manner. The results are shown in Table 1.

Then, using the obtained latex composition for dip molding, protective gloves (dip molded body) having a polymer layer having a film thickness of 0.6 mm were obtained in the same manner as in Example 1, and evaluation was carried out in the same manner. rice field. The results are shown in Table 1.

As shown in Table 1, the latex of the conjugated diene polymer (A) having a glass transition temperature of 10 ° C. or lower, the latex of the polymer (B) having a glass transition temperature of more than 10 ° C., and the thickener. According to the latex composition for dip molding, which contains 42% by weight or more and 55% by weight or less of solid content, it is possible to suppress dripping during molding and obtain a dip molded product having excellent oil grip. The result was possible (Examples 1 to 5).

On the other hand, when the solid content concentration of the latex composition for dip molding was less than 42% by weight, dripping during molding could not be suppressed (Comparative Examples 1 and 2).
Further, when the latex of vinyl chloride resin as the latex of the polymer (B) having a glass transition temperature of more than 10 ° C. was not blended, the obtained dip molded product was inferior in oil grip property (comparison). Example 3).

Claims (14)

It contains a latex of a conjugated diene polymer (A) having a glass transition temperature of 10 ° C. or lower, a latex of a polymer (B) having a glass transition temperature of more than 10 ° C., and a thickener.
A latex composition for dip molding having a solid content concentration of 42% by weight or more and 55% by weight or less. The latex composition for dip molding according to claim 1, wherein the amount of acid of the thickener is 2.5 mmol / g or less. The latex composition for dip molding according to claim 1 or 2, wherein the solid content concentration is 43.5% by weight or more and 55% by weight or less. The latex composition for dip molding according to any one of claims 1 to 3, wherein the conjugated diene polymer (A) is a nitrile group-containing conjugated diene polymer. The latex composition for dip molding according to any one of claims 1 to 4, wherein the content of the conjugated diene polymer (A) in 100 parts by weight of the polymer component is 40 parts by weight or more. The latex composition for dip molding according to any one of claims 1 to 5, wherein the glass transition temperature of the polymer (B) is 30 ° C. or higher. The latex composition for dip molding according to claim 6, wherein the glass transition temperature of the polymer (B) is 50 ° C. or higher. The latex composition for dip molding according to any one of claims 1 to 7, wherein the polymer (B) contains a monomer unit having a halogen atom. The latex composition for dip molding according to claim 8, wherein the polymer (B) is a vinyl chloride resin. The latex composition for dip molding according to claim 9, wherein the vinyl chloride resin does not contain a plasticizer. The latex composition for dip molding according to any one of claims 1 to 10, further containing a sulfur-based cross-linking agent. A dip molded product using the latex composition for dip molding according to any one of claims 1 to 11. A dip-molded body obtained by immersing the latex composition for dip molding according to any one of claims 1 to 12 in a substrate. The dip molded product according to claim 12 or 13, wherein the polymer layer made of the latex composition for dip molding has a film thickness of 0.05 to 1.0 mm.

Images