Method for producing modified conjugated diene polymer latex

Abstract

Provided is a method for producing a modified conjugated diene polymer latex, the method comprising: a modification step for bringing a conjugated diene polymer into contact with a radical generating agent to obtain a modified conjugated diene polymer; and an emulsification step for emulsifying the modified conjugated diene polymer in water. In the modification step, the conjugated diene polymer is modified under the condition in which the total of 20 parts by weight or less of an organic solvent and water is used with respect to 100 parts by weight of the conjugated diene polymer.

Description

Technical Field

[0001] The present invention relates to a method for producing a modified conjugated diene polymer latex.

Background Art

[0002] Conventionally, it has been known that a latex composition containing a latex of natural rubber is dip-molded to obtain a dip-molded article used in contact with the human body, such as a nipple, a balloon, a glove, a balloon, a sack, etc. However, since the latex of natural rubber contains proteins that cause immediate-type allergy (Type I) symptoms in the human body, there may be a problem as a dip-molded article that directly contacts the living body mucosa or organs. Therefore, studies have been made to use a latex of synthetic rubber instead of the latex of natural rubber.

[0003] For example, Patent Document 1 discloses a latex containing an acid-modified conjugated diene polymer obtained by modifying a conjugated diene polymer with an acid group-containing compound, wherein the content of the structural unit derived from the acid group-containing compound in 100 parts by weight of the acid-modified conjugated diene polymer is 0.2 to 0.7 parts by weight, the content of the water-soluble polymer in the latex is 2 parts by weight or less with respect to 100 parts by weight of the acid-modified conjugated diene polymer, and the viscosities when the solid content concentration is 50% by weight and when the solid content concentration is 60% by weight are in a specific range.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, the technology described in Patent Document 1 involves dissolving a conjugated diene polymer in an organic solvent to obtain a solution of the conjugated diene polymer, and then modifying the conjugated diene polymer with an acid group-containing compound while it is in solution. Therefore, the process of dissolving in an organic solvent and removing the organic solvent are necessary, and improvements were desired from the viewpoint of increasing productivity. Furthermore, while the technology described in Patent Document 1 can reduce the viscosity at a solid content concentration of 50% by weight and the viscosity at a solid content concentration of 60% by weight to a specific range, further reduction in viscosity was desired from the viewpoint of improving the handling properties as a latex. This invention has been made in view of the above circumstances, and aims to provide a method for producing latex from a modified conjugated diene polymer that is excellent in productivity and handling, and can provide film-shaped articles such as dip-molded articles with high tensile strength and tear strength. [Means for solving the problem]

[0006] The inventors of the present invention conducted intensive research to solve the above problems and found that the above problems can be solved by adopting a method in which a modified conjugated diene polymer is obtained by contacting a conjugated diene polymer with a radical generator under conditions where the total amount of organic solvent and water used is below a specific amount, and then emulsifying the obtained modified conjugated diene polymer in water. Based on this finding, the present invention was completed.

[0007] In other words, according to the present invention, a modification step is made to obtain a modified conjugated diene polymer by contacting a conjugated diene polymer with a radical generator, A method for producing a latex of a modified conjugated diene polymer, comprising an emulsification step of emulsifying the modified conjugated diene polymer in water, A method for producing a latex of a modified conjugated diene polymer is provided, wherein the modification step is a step of modifying the conjugated diene polymer under the condition that the total amount of organic solvent and water used per 100 parts by weight of the conjugated diene polymer is 20 parts by weight or less.

[0008] In the method for producing a latex of a modified conjugated diene polymer of the present invention, the modification step preferably includes adding the radical generating agent to the conjugated diene polymer and kneading it, thereby bringing the conjugated diene copolymer into contact with the radical generating agent. A method for producing a latex of a modified conjugated diene polymer according to the present invention, wherein the modification step comprises contacting the solid conjugated diene copolymer with the radical generating agent, as described in claim 1 or 2. In the method for producing a latex of a modified conjugated diene polymer according to the present invention, it is preferable to use alkaline water when emulsifying the modified conjugated diene polymer in water during the emulsification step. In the method for producing a latex of a modified conjugated diene polymer according to the present invention, in the emulsification step, when emulsifying the modified conjugated diene polymer in water, it is preferable to use a surfactant in an amount of 0.01 to 5 parts by weight per 100 parts by weight of the modified conjugated diene polymer. In the method for producing a latex of a modified conjugated diene polymer of the present invention, it is preferable that the modification step is a step of obtaining the modified conjugated diene polymer by contacting the conjugated diene polymer with a radical generator in the presence of an acid group-containing compound and / or an acid anhydride. In the method for producing a latex of a modified conjugated diene polymer of the present invention, the modification step preferably includes using an amount of the acid group-containing compound and / or the acid anhydride that is 0.5 to 15 parts by weight per 100 parts by weight of the conjugated diene polymer. In the method for producing latex of a modified conjugated diene polymer of the present invention, it is preferable that the conjugated diene polymer is synthetic polyisoprene.

[0009] Furthermore, the present invention provides a method for producing a latex composition comprising the steps of: obtaining a latex of a modified conjugated diene polymer by the above method; and blending a sulfur-based vulcanizing agent with the latex of the modified conjugated diene polymer. Furthermore, according to the present invention, a method for manufacturing a dip-molded article is provided, comprising the steps of obtaining a latex composition by the above method and dip-molding the latex composition. [Effects of the Invention]

[0010] According to the present invention, it is possible to provide a method for producing latex from a modified conjugated diene polymer that is excellent in productivity and handling, and can yield film-shaped articles such as dip-molded articles with high tensile strength and tear strength. [Modes for carrying out the invention]

[0011] The present invention provides a method for producing latex from a modified conjugated diene polymer. A modification step to obtain a modified conjugated diene polymer by contacting a conjugated diene polymer with a radical generator, The process comprises an emulsification step of emulsifying the modified conjugated diene polymer in water, The modification step is a step of modifying the conjugated diene polymer under the condition that the total amount of organic solvent and water used per 100 parts by weight of the conjugated diene polymer is 20 parts by weight or less.

[0012] <Conjugated diene polymers> First, we will explain the conjugated diene polymer used in this invention. The conjugated diene polymer is not particularly limited and examples include synthetic polyisoprene, styrene-isoprene-styrene block copolymer (SIS), and natural rubber (including natural rubber from which proteins have been removed). Preferred conjugated diene polymers are synthetic polyisoprene, styrene-isoprene-styrene block copolymer (SIS), or natural rubber (including natural rubber from which proteins have been removed); more preferred are synthetic polyisoprene, styrene-isoprene-styrene block copolymer (SIS), or natural rubber from which proteins have been removed; even more preferred are synthetic polyisoprene or styrene-isoprene-styrene block copolymer (SIS); and synthetic polyisoprene is particularly preferred.

[0013] Synthetic polyisoprene can be obtained by solution polymerization of isoprene and other copolymerizable ethylenically unsaturated monomers, as needed, in an inert polymerization solvent using conventionally known methods, such as a Ziegler polymerization catalyst consisting of trialkylaluminum-titanium tetrachloride or an alkyllithium polymerization catalyst such as n-butyllithium or sec-butyllithium. Solid synthetic polyisoprene can then be obtained by coagulation of the polymer solution of synthetic polyisoprene obtained by solution polymerization. When a polymer solution of synthetic polyisoprene is obtained by the above method, impurities such as residues of the polymerization catalyst remaining in the polymer solution may be removed. Alternatively, commercially available solid synthetic polyisoprene can also be used.

[0014] In synthetic polyisoprene, there are four types of isoprene units depending on the bonding state of the isoprene: cis-bonded units, trans-bonded units, 1,2-vinyl-bonded units, and 3,4-vinyl-bonded units. From the viewpoint of improving the tensile strength of the resulting film-molded articles, such as dip-molded articles, the content of cis-bonded units in the isoprene units contained in synthetic polyisoprene is preferably 70% by weight or more, more preferably 90% by weight or more, and even more preferably 95% by weight or more, relative to the total isoprene units.

[0015] The weight-average molecular weight of synthetic polyisoprene is preferably 10,000 to 5,000,000, more preferably 500,000 to 5,000,000, and even more preferably 800,000 to 3,000,000, calculated on a standard polystyrene basis by gel permeation chromatography analysis. Having the weight-average molecular weight of synthetic polyisoprene within this range allows for a more controlled decrease in mechanical strength when the resulting film-molded body, such as a dip-molded body, is stored at high temperatures, and also tends to facilitate the production of synthetic polyisoprene latex.

[0016] The polymer Mooney viscosity (ML1+4, 100 °C) of the synthetic polyisoprene is preferably 50 to 85, more preferably 60 to 85, and even more preferably 70 to 85.

[0017] Also, as described above, a styrene-isoprene-styrene block copolymer (SIS) can be used as the conjugated diene polymer. In SIS, "S" represents a styrene block and "I" represents an isoprene block, respectively.

[0018] SIS can be obtained by block copolymerizing isoprene and styrene in an inert polymerization solvent using a known method, for example, an active organometal such as n-butyllithium as an initiator. Then, for the polymer solution of SIS obtained by solution polymerization, a solid can be obtained by performing a coagulation operation or the like. When a polymer solution of SIS is obtained by the above-described method, impurities such as residues of the polymerization catalyst remaining in the polymer solution may be removed. Also, a commercially available solid synthetic polyisoprene can be used.

[0019] The content of styrene units in the styrene block in SIS contained in the SIS latex is preferably 70 to 100% by weight, more preferably 90 to 100% by weight, and even more preferably 100% by weight, based on all monomer units. Also, the content of isoprene units in the isoprene block in SIS is preferably 70 to 100% by weight, more preferably 90 to 100% by weight, and even more preferably 100% by weight, based on all monomer units.

[0020] The content ratio of styrene units and isoprene units in SIS is in the weight ratio of "styrene units:isoprene units", usually 1:99 to 90:10, preferably 3:97 to 70:30, more preferably 5:95 to 50:50, and even more preferably 10:90 to 30:70.

[0021] The weight-average molecular weight of SIS, calculated as standard polystyrene by gel permeation chromatography, is preferably 10,000 to 1,000,000, more preferably 50,000 to 500,000, and even more preferably 100,000 to 300,000. Having a weight-average molecular weight within this range tends to facilitate the production of SIS latex.

[0022] The polymer Mooney viscosity (ML1+4, 100°C) of SIS is preferably 50-85, more preferably 60-85, and even more preferably 70-85.

[0023] Furthermore, as mentioned above, natural rubber can be used as the conjugated diene polymer, and even more specifically, natural rubber from which proteins have been removed can be used. In addition, nitrile group-containing conjugated diene copolymers, butadiene polymers, styrene-butadiene copolymers, etc., may be used as the conjugated diene polymer.

[0024] <Modification process> The modification step in the manufacturing method of the present invention is a step of obtaining a modified conjugated diene polymer by contacting the above-mentioned conjugated diene polymer with a radical generating agent. Furthermore, in the modification step of the manufacturing method of the present invention, the modification of the conjugated diene polymer is carried out under conditions in which the total amount of organic solvent and water used is 20 parts by weight or less per 100 parts by weight of the conjugated diene polymer. More specifically, the modification of the conjugated diene polymer is carried out by contacting the solid conjugated diene polymer with a radical generating agent.

[0025] In the modification process, a conjugated diene polymer is brought into contact with a radical generator. The radical generator acts on the carbon-carbon double bonds in the conjugated diene polymer, thereby introducing a modifying group into the conjugated diene polymer, and thus obtaining a modified conjugated diene polymer. Specifically, by acting the radical generator on the carbon-carbon double bonds in the conjugated diene polymer, hydrophilic groups such as carboxyl groups are introduced through the action of the radical generator, thereby obtaining a conjugated diene polymer modified by hydrophilic groups.

[0026] In the modification step, the total amount of organic solvent and water used is 20 parts by weight or less per 100 parts by weight of the conjugated diene polymer, and the conjugated diene polymer is brought into contact with the radical generator, preferably 5 parts by weight or less, more preferably 1 part by weight or less, and particularly preferably in a state where the organic solvent and water are substantially absent, or where the organic solvent and water are not actively added. In other words, the solid conjugated diene polymer is brought into contact with the radical generator in a state where volatile components are substantially absent.

[0027] According to the present invention, the total amount of organic solvent and water used is within the above range, and the solid conjugated diene polymer is brought into contact with a radical generator to modify the conjugated diene polymer with hydrophilic groups. Furthermore, such modifying groups can be introduced at a high rate. By introducing such modifying groups, the amount of surfactant used when dispersing the resulting modified conjugated diene polymer in water in the emulsification step described later to obtain the latex of the modified conjugated diene polymer can be reduced. As a result, the viscosity of the resulting modified conjugated diene polymer latex can be reduced, improving its handling properties. In addition, according to the present invention, the modified conjugated diene polymer obtained by the modification step can be dispersed in water in the emulsification step described later without going through a step of dissolving in an organic solvent. Therefore, the steps of dissolving in an organic solvent and removing the organic solvent are unnecessary, resulting in excellent productivity. Furthermore, even without going through such steps of dissolving in an organic solvent and removing it, film-molded articles such as dip-molded articles with high tensile strength and tear strength can be obtained.

[0028] The method for contacting the conjugated diene polymer with the radical generator is not particularly limited, but a preferred method is to add the radical generator to the conjugated diene polymer and knead it. This method is preferable because the heat generated by kneading promotes the generation of radicals by the radical generator. The contact temperature when contacting the conjugated diene polymer with the radical generator is preferably 50 to 260°C, more preferably 80 to 200°C, and the contact time is preferably 20 minutes to 2 hours, more preferably 30 minutes to 1 hour.

[0029] The radical generator is not particularly limited, but compounds that generate radicals upon heating are preferred, such as organic peroxides and azo compounds. For compounds that generate radicals upon heating, the half-life temperature at one minute is preferably 50 to 260°C, more preferably 100 to 230°C, and even more preferably 120 to 200°C. The radical generator can be used alone or in combination of two or more.

[0030] Examples of organic peroxides include methyl ethyl ketone peroxide, cyclohexanone peroxide, methylcyclohexanone peroxide, methyl acetate peroxide, acetyl acetate peroxide, 1,1-bis(t-hexyl peroxy)-3,3,5-trimethylcyclohexane, 1,1-bis(t-hexyl peroxy)cyclohexane, 1,1-bis(t-butyl peroxy)-3,3,5-trimethylcyclohexane, 1,1-bis(t-butyl peroxy)-2-methylcyclohexane, 1,1-bis( t-butylperoxy)cyclohexane, 1,1-bis(t-butylperoxy)cyclododecane, 1,1-bis(t-butylperoxy)butane, 2,2-bis(4,4-di-t-butylperoxycyclohexyl)propane, p-menthane hydroperoxide, diisopropylbenzene hydroperoxide, 1,1,3,3-tetramethylbutyl hydroperoxide, cumene hydroperoxide, t-hexyl hydroperoxide, t-butyl hydroperoxide, α,α'-bis(t-butylperoxy)diisopropyl Dibenzene, dicumyl peroxide, 2,5-dimethyl-2,5-bis(t-butylperoxy)hexane, t-butylcumyl peroxide, di-t-butyl peroxide, 2,5-dimethyl-2,5-bis(t-butylperoxy)hexyn-3, isobutyryl peroxide, 3,5,5-trimethylhexanoyl peroxide, octanoyl peroxide, lauroyl peroxide, stearoyl peroxide, succinate peroxide, m-toluylbenzoyl peroxide, benzoyl peroxide, di-n-pro Pill peroxydicarbonate, diisopropyl peroxydicarbonate, bis(4-t-butylcyclohexyl) peroxydicarbonate, di-2-ethoxyethyl peroxydicarbonate, di-2-ethoxyhexyl peroxydicarbonate, di-3-methoxybutyl peroxydicarbonate, di-s-butyl peroxydicarbonate, di(3-methyl-3-methoxybutyl) peroxydicarbonate, α,α'-bis(neodecanoylperoxy)diisopropylbenzene, cumyl peroxyneodecanoate, 1,1,3,3,-Tetramethylbutyl peroxyneodecanoate, 1-cyclohexyl-1-methylethyl peroxyneodecanoate, t-hexyl peroxyneodecanoate, t-butyl peroxyneodecanoate, t-hexyl peroxypivalate, t-butyl peroxypivalate, 1,1,3,3-tetramethylbutyl peroxy-2-ethylhexanoate, 2,5-dimethyl-2,5-bis(2-ethylhexanoyl peroxy)hexanoate, 1-cyclohexyl-1-methylethyl peroxy-2-ethylhexanoate, t-hexyl peroxy-2-ethylhexanoate, t-butyl peroxy-2-ethylhexanoate, t-hexyl peroxyisopropyl monocarbonate, t-butyl peroxyisobutyrate, t-butyl peroxymalate, t-butyl peroxy-3,5,5-tri Examples include methylhexanoate, t-butyl peroxylaurate, t-butyl peroxyisopropyl monocarbonate, t-butyl peroxy-2-ethylhexyl monocarbonate, t-butyl peroxyacetate, t-butyl perdiethylacetate, t-butyl peroxy-m-tolylbenzoate, t-butyl peroxybenzoate, bis(t-butyl peroxy)isophthalate, 2,5-dimethyl-2,5-bis(m-tolyl peroxy)hexane, t-hexyl peroxybenzoate, 2,5-dimethyl-2,5-bis(benzoyl peroxy)hexane, t-butyl peroxyallyl monocarbonate, t-butyl trimethylsilyl peroxide, 3,3',4,4'-tetra(t-butyl peroxycarbonyl)benzophenone, and 2,3-dimethyl-2,3-diphenylbutane. Among these, t-butyl perdiethyl acetate, dicumyl peroxide, and 1,1,3,3-tetramethylbutyl hydroperoxide are preferred, and dicumyl peroxide and 1,1,3,3-tetramethylbutyl hydroperoxide are more preferred.

[0031] Furthermore, azo compounds include 2-phenylazo-4-methoxy-2,4-dimethylvaleronitrile, 1-[(1-cyano-1-methylethyl)azo]formamide, 1,1'-azobis(cyclohexane-1-carbonitride), 2,2'-azobis(2-methylbutyronitrile), 2,2'-azobisisobutyronitrile, 2,2'-azobis(2,4-dimethylvaleronitrile), 2,2'-azobis(2,4-dimethyl-4-methoxyvaleronitrile), 2,2'-azobis(2-methylpropionamidine)dihydrochloride, 2,2 '-Azobis(2-methyl-N-phenylpropionamidine)dihydrochloride, 2,2'-Azobis[N-(4-chlorophenyl)-2-methylpropionamidine]dihydrochloride, 2,2'-Azobis[N-(4-hydrophenyl)-2-methylpropionamidine]dihydrochloride, 2,2'-Azobis[2-methyl-N-(phenylmethyl)propionamidine]dihydrochloride, 2,2'-Azobis[2-methyl-N-(2-propenyl)propionamidine]dihydrochloride, 2,2'-Azobis[N-(2-hydro [Xyethyl)-2-methylpropionamidine]dihydrochloride, 2,2'-azobis[2-(5-methyl-2-imidazolin-2-yl)propane]dihydrochloride, 2,2'-azobis[2-(2-imidazolin-2-yl)propane]dihydrochloride, 2,2'-azobis[2-(4,5,6,7-tetrahydro-1H-1,3-diazepine-2-yl)propane]dihydrochloride, 2,2'-azobis[2-(3,4,5,6-tetrahydropyrimidine-2-yl)propane]dihydrochloride, 2,2'-azobis[2-( 5-Hydroxy-3,4,5,6-tetrahydropyrimidine-2-yl)propane]dihydrochloride, 2,2'-azobis{2-[1-(2-hydroxyethyl)-2-imidazolin-2-yl]propane}dihydrochloride, 2,2'-azobis[2-(2-imidazolin-2-yl)propane], 2,2'-azobis{2-methyl-N-[1,1-bis(hydroxymethyl)-2-hydroxyethyl]propionamide}, 2,2'-azobis{2-methyl-N-[1,1-bis(hydroxymethyl)ethyl]propionamide}, 2,Examples include 2'-azobis[2-methyl-N-(2-hydroxyethyl)propionamide], 2,2'-azobis(2-methylpropionamide), 2,2'-azobis(2,4,4-trimethylpentane), 2,2'-azobis(2-methylpropane), dimethyl-2,2-azobis(2-methylpropionate), 4,4'-azobis(4-cyanopentanoic acid), and 2,2'-azobis[2-(hydroxymethyl)propionitrile]. Among these, 2,2'-azobisisobutyronitrile is preferred.

[0032] In the modification process, the amount of radical generator used is preferably 0.02 to 5 parts by weight, more preferably 0.5 to 3 parts by weight, and even more preferably 0.5 to 1 part by weight, per 100 parts by weight of the conjugated diene polymer. By using the radical generator within the above range, the modification reaction of the conjugated diene polymer can be sufficiently advanced, thereby reducing the amount of surfactant used when dispersing the resulting modified conjugated diene polymer in water to obtain the latex of the modified conjugated diene polymer. This allows for a lower viscosity of the resulting modified conjugated diene polymer latex, improving its handling properties.

[0033] Furthermore, in the modification process, it is preferable to contact the conjugated diene polymer with the radical generator in the presence of an acid group-containing compound and / or an acid anhydride. By doing so, the conjugated diene polymer can undergo a graft reaction or graft polymerization of the acid group-containing compound and / or acid anhydride. As a result, the amount of surfactant required when dispersing the resulting modified conjugated diene polymer in water to obtain the latex of the modified conjugated diene polymer can be further reduced. This allows for a lower viscosity of the resulting modified conjugated diene polymer latex, thereby improving its handling properties.

[0034] While not particularly limited, acid group-containing compounds include carboxyl group-containing compounds, sulfonic acid group-containing compounds, and phosphate group-containing compounds. However, carboxyl group-containing compounds are preferred because they can further increase the tensile strength and tear strength of the resulting film-molded articles, such as dip-molded articles. Specific examples of carboxyl group-containing compounds include ethylenically unsaturated monocarboxylic acids such as acrylic acid and methacrylic acid; ethylenically unsaturated polycarboxylic acids such as itaconic acid, maleic acid, and fumaric acid; ethylenically unsaturated polycarboxylic acid anhydrides such as maleic anhydride and citraconic anhydride; and ethylenically unsaturated polycarboxylic acid partial esters such as monobutyl fumarate, monobutyl maleate, and mono-2-hydroxypropyl maleate. Furthermore, as the acid anhydride, carboxylic acid anhydrides are preferred, including ethylenically unsaturated polycarboxylic acid anhydrides such as maleic anhydride and citraconic anhydride; and so on. Among these acid group-containing compounds and acid anhydrides, ethylenically unsaturated monocarboxylic acids and ethylenically unsaturated polycarboxylic acid anhydrides are preferred, acrylic acid, methacrylic acid, and maleic anhydride are preferred, and methacrylic acid and maleic anhydride are particularly preferred.

[0035] The amount of acid group-containing compound and / or acid anhydride used is preferably 0.5 to 15 parts by weight, and more preferably 5 to 10 parts by weight, per 100 parts by weight of the conjugated diene polymer. By setting the amount of acid group-containing compound and / or acid anhydride used within the above range, the amount of surfactant used when dispersing the resulting modified conjugated diene polymer in water to obtain the latex of the modified conjugated diene polymer can be further reduced. This makes it possible to keep the viscosity of the resulting modified conjugated diene polymer latex lower and improves its handling properties.

[0036] Furthermore, in the modification step, in addition to acid group-containing compounds and / or acid anhydrides, other ethylenically unsaturated compounds that can react with these may also be used. Examples of ethylenically unsaturated compounds include conjugated dienes such as 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, 2-methyl-3-ethyl-1,3-butadiene, 2-methyl-1,3-pentadiene, 1,3-hexadiene, and 1,3-cyclohexadiene; aromatic vinyl compounds such as styrene, α-methylstyrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, 2,4-dimethylstyrene, ethylstyrene, and p-tert-butylstyrene; α,β-unsaturated nitriles such as acrylonitrile and methacrylonitrile; unsaturated carboxylic acid esters such as methyl methacrylate, ethyl acrylate, and butyl acrylate; and non-conjugated dienes such as 1,5-hexadiene, 1,6-heptadiene, 1,7-octadiene, dicyclopentadiene, and 5-ethylidene-2-norbornene.

[0037] The amount of other ethylenically unsaturated compounds used is preferably 0.1 to 10 parts by weight, and more preferably 2 to 5 parts by weight, per 100 parts by weight of the conjugated diene polymer.

[0038] Furthermore, in the modification process, when the conjugated diene polymer is brought into contact with the radical generator, defoaming agents, preservatives, chelating agents, oxygen scavengers, dispersants, inorganic particles, etc., may be added.

[0039] <Emulsification process> The emulsification step in the manufacturing method of the present invention is a step of obtaining a latex of the modified conjugated diene polymer by emulsifying the modified conjugated diene polymer obtained in the modification step described above in water.

[0040] In the emulsification process, the modified conjugated diene polymer obtained in the modification process can be emulsified in water using an emulsifying device. However, from the viewpoint of further increasing production efficiency, it is preferable to first perform a grinding treatment in water on the modified conjugated diene polymer obtained in the modification process, and then supply the slurry containing the ground modified conjugated diene polymer to the emulsifying device to obtain the latex of the modified conjugated diene polymer.

[0041] The grinding device used for the grinding process is not particularly limited, and any device capable of grinding the modified conjugated diene polymer in the slurry containing the modified conjugated diene polymer obtained by grinding until the average particle size of the modified conjugated diene polymer after grinding is preferably about 0.1 to 1 mm is acceptable. Such a grinding device can be a mixer pump, a crusher pump, or a crushing pump, but a crusher pump or a crushing pump is preferred, and a crusher pump is more preferred. Examples of crushing devices include the trade name "High Shear Inline Mixer" (manufactured by Silverson), the trade name "Disintegrator" (manufactured by Husqvarna Zenoah), the trade name "Incrusher" (manufactured by Aikawa Iron Works), and the trade name "Milder" (manufactured by Taiheiyo Kiko Co., Ltd.). The conditions for the grinding process using the grinding device are not particularly limited, and the processing temperature, processing time, etc. should be appropriately selected to achieve the desired grinding state. Before the grinding process, the modified conjugated diene polymer may be cut into predetermined sizes suitable for grinding, and the cut modified conjugated diene polymer may be used.

[0042] Furthermore, when grinding the modified conjugated diene polymer obtained in the modification step in water, it is preferable to use alkaline water. Using alkaline water can increase the hydrophilicity of hydrophilic groups such as carboxyl groups contained in the modified conjugated diene polymer, thereby enabling more appropriate preparation of the latex of the modified conjugated diene polymer in the emulsification step. The pH of the aqueous phase before contact with the modified conjugated diene polymer is preferably in the range of 8 to 13, and more preferably in the range of 10 to 12. Examples of pH adjusting agents include alkali metal hydroxides such as sodium hydroxide and potassium hydroxide; alkali metal carbonates such as sodium carbonate and potassium carbonate; alkali metal bicarbonates such as sodium bicarbonate; ammonia; organic amine compounds such as trimethylamine and triethanolamine; and so on, but alkali metal hydroxides or ammonia are preferred.

[0043] Furthermore, when grinding the modified conjugated diene polymer obtained in the modification step in water, a surfactant may be used. The amount of surfactant used is preferably 0.01 to 5 parts by weight, more preferably 0.1 to 3 parts by weight, and even more preferably 0.5 to 1 part by weight, per 100 parts by weight of the modified conjugated diene polymer. According to the manufacturing method of the present invention, since the modified conjugated diene polymer is prepared by contacting the conjugated diene polymer with a radical generator in the modification step described above, even if the amount of surfactant used is relatively small as described above, emulsification following the grinding process can be carried out appropriately.

[0044] As the surfactant, it is preferable to use an ionic surfactant, and among these, it is more preferable to use an anionic surfactant. Examples of anionic surfactants include fatty acid salts such as sodium laurate, potassium myristate, sodium palmitate, potassium oleate, sodium linolenate, sodium rosinate, and potassium rosinate; alkylbenzene sulfonates such as sodium dodecylbenzenesulfonate, potassium dodecylbenzenesulfonate, sodium decylbenzenesulfonate, potassium decylbenzenesulfonate, sodium cetylbenzenesulfonate, and potassium cetylbenzenesulfonate; alkyl sulfosuccinates such as sodium di(2-ethylhexyl)sulfosuccinate, potassium di(2-ethylhexyl)sulfosuccinate, and sodium dioctylsulfosuccinate; alkyl sulfate esters 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; and monoalkyl phosphates such as sodium lauryl phosphate and potassium lauryl phosphate.

[0045] Among these anionic surfactants, fatty acid salts, alkylbenzene sulfonates, alkyl sulfosuccinates, alkyl sulfate esters, and polyoxyethylene alkyl ether sulfate esters are preferred, fatty acid salts and alkyl sulfate esters are more preferred, and the combined use of fatty acid salts and alkyl sulfate esters is particularly preferred. Sodium rosinate is preferred as the fatty acid salt, and sodium lauryl sulfate is preferred as the alkyl sulfate ester. When fatty acid salts and alkyl sulfate esters are used in combination, the weight ratio of "fatty acid salt" to "alkyl sulfate ester" is preferably in the range of 1:1 to 10:1, and more preferably in the range of 1.5:1 to 4:1.

[0046] Furthermore, when grinding the modified conjugated diene polymer obtained in the modification process in water, the amount of water used is preferably 60 to 2000 parts by weight, more preferably 70 to 800 parts by weight, and even more preferably 70 to 700 parts by weight, per 100 parts by weight of the modified conjugated diene polymer.

[0047] Then, in the emulsification process, the slurry containing the modified conjugated diene polymer obtained through such crushing treatment is supplied to the emulsifier to obtain the latex of the modified conjugated diene polymer. The slurry containing the modified conjugated diene polymer may be supplied directly to the emulsifier after the crushing treatment, in which case the pH of the water used for emulsification, the type and amount of surfactant, and the amount of water will be the same as in the crushing treatment. Furthermore, the slurry containing the modified conjugated diene polymer may be supplied to the emulsifier after further pH adjustment or the addition of surfactant and water, in which case these conditions should be the same as the preferred range in the crushing treatment described above. That is, in the emulsification process, the pH is preferably in the range of 8 to 13, more preferably in the range of 10 to 12, and the amount of surfactant used is preferably 0.01 to 5 parts by weight, more preferably 0.1 to 3 parts by weight, per 100 parts by weight of the modified conjugated diene polymer. Furthermore, the amount of water used is preferably 60 to 2000 parts by weight, more preferably 70 to 800 parts by weight, and even more preferably 70 to 700 parts by weight, per 100 parts by weight of the modified conjugated diene polymer.

[0048] Examples of emulsification equipment include batch-type emulsifiers such as the "Homogenizer" (manufactured by IKA), "Polytron" (manufactured by Kinetica), and "TK Autohomomicker" (manufactured by Tokushu Kika Kogyo Co., Ltd.); "TK Pipeline Homomixer" (manufactured by Tokushu Kika Kogyo Co., Ltd.), "Colloid Mill" (manufactured by Shinko Pantech Co., Ltd.), "Slusher" (manufactured by Nippon Coke Industries Co., Ltd.), "Trigonal Wet Grinding Machine" (manufactured by Mitsui Miike Chemical Machinery Co., Ltd.), and "Cavitron" (U Examples include continuous emulsifiers such as Rotec Corporation's "Fine Flow Mill" (Taiheiyo Kiko Co., Ltd.), high-pressure emulsifiers such as Mizuho Industries' "Microfluidizer," Nanomizer (Nanomizer Co., Ltd.), and Gaurin's "APV Gaurin" (Gaurin Co., Ltd.), membrane emulsifiers such as Reika Kogyo Co., Ltd.'s "Membrane Emulsifier," vibratory emulsifiers such as Reika Kogyo Co., Ltd.'s "Vibro Mixer," and ultrasonic emulsifiers such as Branson's "Ultrasonic Homogenizer." The conditions for emulsification using the emulsifier are not particularly limited, and the processing temperature, processing time, etc., should be appropriately selected to achieve the desired dispersion state.

[0049] Furthermore, in the manufacturing method of the present invention, the latex of the modified conjugated diene polymer obtained through the emulsification step may be concentrated as needed by methods such as vacuum distillation, atmospheric distillation, centrifugation, and membrane concentration in order to increase the solid content concentration of the modified conjugated diene polymer latex, and among these, concentration by centrifugation is preferred.

[0050] Centrifugation is preferably carried out using a continuous centrifuge, with a centrifugal force of preferably 100 to 10,000 G, a solid content concentration of the modified conjugated diene polymer latex before centrifugation of preferably 2 to 15% by weight, a flow rate of preferably 500 to 1700 kg / hr fed into the centrifuge, and a back pressure (gauge pressure) of preferably 0.03 to 1.6 MPa. The modified conjugated diene polymer latex can be obtained as a light liquid after centrifugation.

[0051] The solid content concentration of the modified conjugated diene polymer latex is preferably 45 to 70% by weight, more preferably 50 to 70% by weight. According to the manufacturing method of the present invention, the amount of surfactant contained in the modified conjugated diene polymer latex can be reduced, so even when the solid content concentration is relatively high as in the above range, the viscosity can be kept low, resulting in excellent handling properties when transported in pipes, etc.

[0052] The volume-average particle size of the modified conjugated diene polymer latex is preferably 0.1 to 10 μm, more preferably 0.5 to 3 μm, and even more preferably 0.5 to 2.0 μm. This volume-average particle size within the above range allows for appropriate latex viscosity while suppressing the formation of a film on the latex surface during storage. The volume-average particle size can be measured using a laser diffraction particle size distribution analyzer.

[0053] Furthermore, modified conjugated diene polymer latex may contain additives commonly used in the latex field, such as defoamers, preservatives, chelating agents, oxygen scavengers, and dispersants.

[0054] <Latex composition> The latex composition of the present invention contains a modified conjugated diene polymer latex obtained by the manufacturing method of the present invention described above, and a sulfur-based vulcanizing agent.

[0055] Sulfur-based vulcanizing agents are not particularly limited, but examples include sulfur such as powdered sulfur, sulfurous salt, precipitated sulfur, colloidal sulfur, surface-treated sulfur, and insoluble sulfur; and sulfur-containing compounds such as sulfur chloride, sulfur dichloride, morpholine disulfide, alkylphenol disulfide, caprolactam disulfide (N,N'-dithio-bis(hexahydro-2H-azepinone-2)), phosphorus-containing polysulfide, high molecular weight polysulfides, and 2-(4'-morpholinodithio)benzothiazole. Among these, sulfur is preferably used. Sulfur-based vulcanizing agents can be used alone or in combination of two or more.

[0056] The content of the sulfur-based vulcanizing agent in the latex composition is not particularly limited, but is usually 0.1 to 10 parts by weight, preferably 0.01 to 3 parts by weight, more preferably 0.2 to 2 parts by weight, and even more preferably 0.3 to 1 part by weight, per 100 parts by weight of the modified conjugated diene polymer contained in the latex composition. By having the sulfur-based vulcanizing agent content within the above range, it is possible to increase the tensile strength and tear strength of the resulting film-molded articles, such as dip-molded articles, while suppressing the occurrence of delayed-type allergy (Type IV) symptoms.

[0057] The latex composition of the present invention preferably further contains a vulcanization accelerator. As the vulcanization accelerator, it is preferable to use a xanthogenic compound, from the viewpoint of ensuring that the resulting film-formed articles, such as dip-molded articles, have the occurrence of delayed-type allergy (Type IV) symptoms suitably suppressed.

[0058] Xanthogene compounds are not particularly limited, but examples include xanthogenic acid, xanthogenic salt, xanthogene disulfide (a compound in which two xanthogenic acids are linked via a sulfur atom, etc.), and xanthogene polysulfide (a compound in which three or more xanthogenic acids are linked via a sulfur atom, etc.).

[0059] Xanthogenic salts can be any compound having a xanthogenic acid structure and are not particularly limited, but examples include compounds represented by the general formula (ROC(=S)S)xZ (where R is a linear or branched hydrocarbon, Z is a metal atom, and x is a number that matches the valence of Z, usually 1 to 4, preferably 2 to 4, and particularly preferably 2).

[0060] The xanthogenic salts represented by the general formula (ROC(=S)S)xZ above are not particularly limited, but include, for example, zinc dimethylxanthogenic acid, zinc diethylxanthogenic acid, zinc dipropylxanthogenic acid, zinc diisopropylxanthogenic acid, zinc dibutylxanthogenic acid, zinc dipentylxanthogenic acid, zinc dihexylxanthogenic acid, zinc diheptylxanthogenic acid, zinc dioctylxanthogenic acid, zinc di(2-ethylhexyl)xanthogenic acid, zinc didecylxanthogenic acid, zinc didodecylxanthogenic acid, potassium dimethylxanthogenic acid, potassium ethylxanthogenic acid, potassium propylxanthogenic acid, potassium isopropylxanthogenic acid, potassium butylxanthogenic acid, and pentylxanthogenic acid. Examples include potassium tonate, potassium hexylxanthogenicate, potassium heptylxanthogenicate, potassium octylxanthogenicate, potassium 2-ethylhexylxanthogenicate, potassium decylxanthogenicate, potassium dodecylxanthogenicate, sodium methylxanthogenicate, sodium ethylxanthogenicate, sodium propylxanthogenicate, sodium isopropylxanthogenicate, sodium butylxanthogenicate, sodium pentylxanthogenicate, sodium hexylxanthogenicate, sodium heptylxanthogenicate, sodium octylxanthogenicate, sodium 2-ethylhexylxanthogenicate, sodium decylxanthogenicate, sodium dodecylxanthogenicate, and the like. Among these, xanthogenic salts in the above general formula (ROC(=S)S)xZ where x is 2 or more are preferred, isopropyl xanthogenic salts and butyl xanthogenic salts are more preferred, and zinc diisopropyl xanthogenic acid and zinc dibutyl xanthogenic acid are particularly preferred. These xanthogenic salts may be used individually or in combination of multiple types.

[0061] Xanthogene disulfides are compounds in which two xanthogenic acids are bonded via a sulfur atom or the like, and are not particularly limited, but examples include dimethyl xanthogene disulfide, diethyl xanthogene disulfide, diisopropyl xanthogene disulfide, dibutyl xanthogene disulfide, dimethyl xanthogene polysulfide, diethyl xanthogene polysulfide, diisopropyl xanthogene polysulfide, and dibutyl xanthogene polysulfide. Among these, diisopropyl xanthogene disulfide and dibutyl xanthogene disulfide are preferred.

[0062] Xanthogene polysulfides are compounds in which three or more xanthogenic acids are linked via sulfur atoms or the like. Examples include xanthogene trisulfides, in which three xanthogenic acids are linked via sulfur; xanthogene tetrasulfides, in which four xanthogenic acids are linked via sulfur; and xanthogene pentasulfides, in which five xanthogenic acids are linked via sulfur.

[0063] These xanthogenic compounds may be included individually in the latex composition, but it is preferable that two or more are included. For example, when xanthogenic acid is blended into the latex composition, a portion of the blended xanthogenic acid may exist in the form of a xanthogenic salt, resulting in the latex composition containing two or more xanthogenic compounds. Alternatively, a portion of the xanthogenic acid blended into the latex composition may exist in the form of xanthogenic disulfide or xanthogenic polysulfide due to the action of a sulfur-based vulcanizing agent in the latex composition. Similarly, when xanthogenic salts, xanthogenic disulfide, or xanthogenic polysulfide are blended into the latex composition, these may exist in any of the following forms: xanthogenic acid, xanthogenic salt, xanthogenic disulfide, or xanthogenic polysulfide, respectively.

[0064] Furthermore, in the present invention, a vulcanization accelerator other than a xanthogene compound may be used as a vulcanization accelerator instead of a xanthogene compound, or in combination with a xanthogene compound.

[0065] Other vulcanization accelerators besides xanthogene compounds include those commonly used in film formation such as dip molding, such as dithiocarbamates including diethyldithiocarbamic acid, dibutyldithiocarbamic acid, di-2-ethylhexyldithiocarbamic acid, dicyclohexyldithiocarbamic acid, diphenyldithiocarbamic acid, dibenzyldithiocarbamic acid, and their zinc salts; 2-mercaptobenzothiazole, 2-mercaptobenzothiazole Examples include zinc ammonium compounds, 2-mercaptothiazoline, dibenzothiazyl disulfide, 2-(2,4-dinitrophenylthio)benzothiazole, 2-(N,N-diethylthio / carbailuthio)benzothiazole, 2-(2,6-dimethyl-4-morpholinothio)benzothiazole, 2-(4′-morpholino / dithio)benzothiazole, 4-morphonillyl-2-benzothiazole disulfide, and 1,3-bis(2-benzothiazole / mercaptomethyl)urea. The vulcanization accelerator can be used alone or in combination of two or more types.

[0066] The content of the vulcanization accelerator in the latex composition (or the total content if multiple vulcanization accelerators are included) is preferably 0.01 to 10 parts by weight, more preferably 0.1 to 7 parts by weight, and even more preferably 0.5 to 5 parts by weight, per 100 parts by weight of the modified conjugated diene polymer contained in the latex composition. By having the vulcanization accelerator content within the above range, the tensile strength and tear strength of film-molded articles such as dip-molded articles can be further improved.

[0067] Furthermore, if the latex composition of the present invention contains a xanthogenic compound as a vulcanization accelerator, the latex composition of the present invention may further contain an activator.

[0068] When crosslinking a film-molded body, such as a dip-molded body, obtained from a latex composition containing an activator, the activator acts as a vulcanization accelerator together with the xanthogene compound mentioned above, thereby further increasing the tear strength of the film-molded body, such as the dip-molded body.

[0069] While there are no particular limitations on the activator, it is preferable to use a metal compound from the viewpoint of further improving the tear strength of film-molded articles such as dip-molded articles. Examples of metal compounds are also not limited, but include metal oxides and metal compounds containing at least one carbon atom. While there are no particular limitations on the metal constituting the metal compound, typical metals (at least one element selected from the group consisting of Group 1, Group 2, Group 12, Group 13, Group 14, Group 15, Group 16, Group 17, and Group 18 elements) are preferred, Group 2, Group 12, Group 13, and Group 14 elements are more preferred, zinc, magnesium, calcium, aluminum, and lead are even more preferred, zinc, magnesium, and calcium are particularly preferred, and zinc is the most preferred. These metal compounds may be used individually or in combination of multiple types.

[0070] While there are no particular limitations on the metal oxide, zinc oxide, magnesium oxide, titanium oxide, calcium oxide, lead oxide, iron oxide, copper oxide, tin oxide, nickel oxide, chromium oxide, cobalt oxide, and aluminum oxide are preferred, with zinc oxide being more preferred, from the viewpoint of improving the tear strength of the resulting film-formed articles such as dip-molded articles.

[0071] As metal compounds containing at least one carbon atom, carbonates, bicarbonates, hydroxides, and organometallic compounds are preferred, and carbonates, bicarbonates, and organometallic compounds are more preferred, from the viewpoint of further improving the tear strength of the resulting film-formed articles such as dip-molded articles. Among these, inorganic salts such as carbonates and bicarbonates are particularly preferred from the viewpoint of having excellent stability of the compound itself and excellent availability.

[0072] The amount of activator in the latex composition is preferably 0.01 to 10 parts by weight, more preferably 0.1 to 5 parts by weight, and even more preferably 1 to 3 parts by weight, per 100 parts by weight of the modified conjugated diene polymer contained in the latex composition.

[0073] Furthermore, the latex composition may contain, as needed, other additives such as antioxidants, dispersants, activators, reinforcing agents such as carbon black, silica, and talc, fillers such as calcium carbonate and clay, UV absorbers, and plasticizers.

[0074] There are no particular limitations on the method of mixing various compounding agents into a latex composition. For example, one method involves obtaining a composition containing a modified conjugated diene polymer latex, a sulfur-based vulcanizing agent, and a vulcanization accelerator, and then mixing the obtained composition with various compounding agents as needed using a disperser such as a ball mill, kneader, or disperser. In addition, at least some of the compounding agents may be added after maturation, as described later.

[0075] Furthermore, as a latex composition of the present invention, it is preferable to have undergone aging (pre-vulcanization) before molding, in order to ensure sufficient mechanical properties of the resulting film-molded articles, such as dip-molded articles. The aging (pre-vulcanization) time is not particularly limited, but is preferably 8 to 120 hours, more preferably 24 to 72 hours. The aging (pre-vulcanization) temperature is not particularly limited, but is preferably 20 to 40°C. When using the above-described latex composition, after performing aging (pre-vulcanization) for a predetermined time, molding such as dip molding may be performed continuously while maintaining the aging (pre-vulcanization) conditions (continuing aging (pre-vulcanization)). In this case, the aging (pre-vulcanization) time and aging (pre-vulcanization) temperature may be within the above ranges.

[0076] <Dip molded product> The dip-molded article of the present invention is a film-like molded article obtained by dip-molding the latex composition of the present invention described above. Dip-molding is a method of immersing a mold in the latex composition, depositing the composition on the surface of the mold, then removing the mold from the composition, and then drying the composition deposited on the surface of the mold. The mold may be preheated before being immersed in the latex composition. Furthermore, a coagulant can be used as needed before immersing the mold in the latex composition or after removing the mold from the latex composition.

[0077] Specific examples of methods for using the coagulant include immersing the mold in a coagulant solution before immersion in the latex composition to allow the coagulant to adhere to the mold (anodic adhesion immersion method), and immersing the mold with the latex composition deposited in it in a coagulant solution (Teegue adhesion immersion method). However, the anodic adhesion immersion method is preferred because it yields a dip-molded body with less thickness variation.

[0078] Specific examples of coagulants include metal halides such as barium chloride, calcium chloride, magnesium chloride, zinc chloride, and aluminum chloride; nitrates such as barium nitrate, calcium nitrate, and zinc nitrate; acetates such as barium acetate, calcium acetate, and zinc acetate; and sulfates such as calcium sulfate, magnesium sulfate, and aluminum sulfate; among these, calcium salts are preferred, and calcium nitrate is more preferred. These water-soluble polyvalent metal salts can be used individually or in combination of two or more.

[0079] The coagulant can usually be used as a solution of water, alcohol, or a mixture thereof, and is preferably used in aqueous solution form. This aqueous solution may further contain water-soluble organic solvents such as methanol or ethanol, or nonionic surfactants. The concentration of the coagulant also 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.

[0080] After removing the mold from the latex composition, the deposits formed on the mold are usually heated to dry them. The drying conditions can be selected as appropriate.

[0081] Next, the dip-molded layer formed on the mold is crosslinked by heating. Crosslinking of the dip-molded layer can usually be achieved by heat treatment at a temperature of 80 to 150°C, preferably for 10 to 130 minutes. As for the heating method, external heating by infrared rays or heated air, or internal heating by high frequency can be used. Among these, external heating by heated air is preferred. Before heat treatment, the dip-molded layer may be immersed in water, preferably warm water at 30 to 70°C, for about 1 to 60 minutes to remove water-soluble impurities (for example, excess emulsifiers or coagulants). The removal of water-soluble impurities may be performed after heat treatment of the dip-molded layer, but it is preferable to perform it before heat treatment in order to remove water-soluble impurities more efficiently.

[0082] The dip-molded body is then obtained by detaching the dip-molded layer from the dip-molding mold. Detachment methods include peeling it off by hand or using water pressure or compressed air pressure. After detachment, a further heat treatment may be performed at a temperature of 60-120°C for 10-120 minutes.

[0083] The film thickness of the dip-molded body is preferably 0.03 to 0.50 mm, more preferably 0.05 to 0.40 mm, and particularly preferably 0.08 to 0.30 mm.

[0084] The dip-molded articles of the present invention are obtained using a latex composition containing a modified conjugated diene polymer latex obtained by the manufacturing method of the present invention described above, and therefore possess high tensile strength and tear strength, and can be particularly suitably used as gloves, for example. When the dip-molded articles are gloves, inorganic fine particles such as talc and calcium carbonate or organic fine particles such as starch particles may be scattered on the surface of the gloves, an elastomer layer containing fine particles may be formed on the surface of the gloves, or the surface layer of the gloves may be chlorinated in order to prevent adhesion at the contact surfaces of the dip-molded articles and to improve slipperiness when putting them on and taking them off.

[0085] Furthermore, the dip-molded body of the present invention can be used not only for gloves, but also for medical supplies such as baby bottle nipples, droppers, tubes, water pillows, balloon sacks, catheters, and condoms; toys such as balloons, dolls, and balls; industrial supplies such as pressure molding bags and gas storage bags; and finger cots. [Examples]

[0086] The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples. Unless otherwise specified, the "parts" below refer to weight. Various physical properties were measured as follows.

[0087] <Solid content concentration> Two g of the sample was accurately weighed onto an aluminum dish (weight: X1) (weight: X2), and dried in a hot air dryer at 105°C for two hours. After cooling in a 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 (wt%)=(X3-X1)×100 / X2

[0088] <Volume-average particle diameter> The volume-average particle size of the polymer particles constituting the latex was measured using a laser diffraction particle size distribution analyzer (product name "SALD2200", manufactured by Shimadzu Corporation).

[0089] <Viscosity at solid content concentrations of 55% and 57% by weight> The viscosity of modified conjugated diene polymer latex at a solid content concentration of 55% by weight and at a solid content of 50% by weight was measured using a B-type viscometer (Brookfield viscometer, model BL, manufactured by Tokyo Keiki Co., Ltd.) at 25°C. For the measurement of viscosity at 55% by weight, the modified conjugated diene polymer latex was diluted with water to a solid content of 55% by weight before measurement.

[0090] <Swell Index (SI)> Potassium hydroxide was added to the modified synthetic polyisoprene latex to adjust the pH to 8.2. A ceramic mold with a ground surface was prepared, washed, and preheated in a 70°C oven for 60 minutes. The preheated ceramic mold was then immersed for 5 seconds in an aqueous solution of a coagulant containing 18% by weight of calcium nitrate and 0.05% by weight of polyoxyethylene lauryl ether (product name "Emulgen 109P", manufactured by Kao Corporation). The ceramic mold was then removed from the aqueous solution of the coagulant, and the ceramic mold coated with the coagulant was dried in a 70°C oven for 20 minutes. Next, the ceramic mold coated with the coagulant was removed from the oven, and the removed ceramic mold was immersed in modified synthetic polyisoprene latex adjusted to pH=8.2 at 25°C for 10 seconds. After being removed, the ceramic mold coated with the modified synthetic polyisoprene latex was immersed in 60°C hot water for 2 minutes, and then dried at room temperature for 6 hours to obtain a ceramic mold coated with a measurement film. After sprinkling talc on this, the obtained film was peeled off the ceramic mold to obtain a dip film with a thickness of 0.2 mm. A test film with a diameter of 25 mm was cut from the obtained dip film, and the obtained test film was immersed in toluene at 25°C for 1 hour. The width of the test piece was measured before and after toluene immersion, and the swell index (SI) was calculated according to the following formula. Swell Index (SI) [%] = [{(Width of film after toluene immersion) - (Width of film before toluene immersion)} / (Width of film before toluene immersion)] × 100 A swell index in the range of 120-140% is preferable because it indicates that the gelation of the modified synthetic polyisoprene is adequately suppressed.

[0091] <Tensile strength of dip-molded body> Based on ASTM D412, dip-molded bodies were punched out using a dumbbell (product name "Super Dumbbell (model: SDMK-100C)", manufactured by Dumbbell Co., Ltd.) to prepare test specimens for tensile strength measurement. These test specimens were pulled at a tensile speed of 500 mm / min using a Tensilon universal testing machine (product name "RTG-1210", manufactured by Orientec Co., Ltd.), and the tensile strength (unit: MPa) just before fracture was measured.

[0092] <Tear strength of dip-molded body> Based on ASTM D624-00, dip-molded bodies were punched out using a dumbbell (product name "Die C," manufactured by Dumbbell Co., Ltd.) to prepare test specimens for tear strength measurement. These test specimens were pulled at a tensile speed of 500 mm / min using a Tensilon universal tester (product name "RTG-1210," manufactured by A&D Co., Ltd.) and the tear strength (unit: N / mm) was measured. A higher tear strength indicates that the dip-molded body has superior mechanical strength.

[0093] <Example 1> (Manufacturing of modified synthetic polyisoprene latex (A-1)) 100 parts of synthetic polyisoprene (product name "NIPOL IR2200L", manufactured by Nippon Zeon Co., Ltd.), 5 parts of styrene, 5 parts of maleic anhydride, and 0.5 parts of azobisisobutyronitrile (AIBN) were added to a sealed Banbury container set to 50°C, and the mixture was kneaded while purging with nitrogen for 5 minutes. Subsequently, the temperature was raised to 100°C while kneading and the mixture was kneaded for 30 minutes. The resulting mixture was then cooled and removed from the sealed Banbury container to obtain solid modified synthetic polyisoprene.

[0094] Next, the obtained solid modified synthetic polyisoprene was cut into approximately 1 cm cubes. 525 parts of the cut modified synthetic polyisoprene and 3500 parts of a 1 wt% sodium hydroxide aqueous solution were placed in a 10 L capacity stainless steel tank. The mixture was then transferred to a crusher pump (product name "Milder," manufactured by Taiheiyo Kiko Co., Ltd.) while stirring to perform a crushing process and obtain a slurry of modified synthetic polyisoprene. The pH of the aqueous phase of the obtained modified synthetic polyisoprene slurry was 12.

[0095] Next, the obtained modified synthetic polyisoprene (A-1) slurry was introduced into an emulsifier (product name "Cavitron," manufactured by Eurotech Co., Ltd.) and emulsified at a rotation speed of 4100 rpm to obtain an aqueous dispersion of modified synthetic polyisoprene. At this time, the feed flow rate of the modified synthetic polyisoprene slurry was 2,000 kg / hr, the temperature was 60°C, and the back pressure (gauge pressure) was 0.5 MPa.

[0096] The resulting aqueous dispersion of modified synthetic polyisoprene was concentrated by centrifugation at 8,000-9,000 G using a continuous centrifuge (product name "SRG510", manufactured by Alfa Laval) to obtain synthetic polyisoprene latex (A-1) with a solid content of 57% by weight as a light liquid. The centrifugation conditions were as follows: solid content of the aqueous dispersion before centrifugation was 13% by weight, flow rate during continuous centrifugation was 1300 kg / hr, and back pressure (gauge pressure) of the centrifuge was 0.1 MPa.

[0097] The viscosity and swell index (SI) of the obtained synthetic polyisoprene latex (A-1) were measured at solid content concentrations of 55% and 57% by weight, as shown in Table 1.

[0098] (Preparation of an aqueous sulfur dispersion) A sulfur aqueous dispersion was obtained by crushing 0.5 parts sulfur, 0.03 parts sodium salt of β-naphthalene sulfonic acid formalin condensate (product name "Demol T-45", manufactured by Kao Corporation) as an anionic surfactant (6.0 parts per 100 parts sulfur), 0.004 parts 5% potassium hydroxide aqueous solution, and 0.42 parts water using a ball mill (product name "Porcelain Ball Mill", manufactured by Nittokagaku Co., Ltd.). The mixing conditions using the ball mill were as follows: a mixture of ceramic porcelain balls with diameters from φ10 mm to φ35 mm (a mixture of ceramic porcelain balls of φ10 mm, φ15 mm, φ20 mm, φ25 mm, φ30 mm, and φ35 mm) was used, and the mixture was heated at 50 rpm for 72 hours.

[0099] (Preparation of aqueous dispersion of xanthogenic compounds) A xanthogene compound aqueous dispersion was obtained by crushing 2.5 parts of zinc diisopropylxanthogene (trade name "Noxellar ZIX", manufactured by Ouchi Shinko Chemical Industry Co., Ltd., volume average particle size: 14 μm, 95% volume cumulative diameter (D95): 55 μm) as a xanthogene compound, 0.45 parts of polyoxyethylene distyrenated phenyl ether (trade name "Emulgen A-60", manufactured by Kao Corporation) as a nonionic surfactant (18.0 parts per 100 parts of zinc diisopropylxanthogene), and 2.05 parts of water using a ball mill (trade name "Porcelain Ball Mill", manufactured by Nittokagaku Co., Ltd.). The mixing conditions using the ball mill were 50 rpm for 72 hours, using ceramic porcelain balls of φ10 mm to φ35 mm (a mixture of ceramic porcelain balls of φ10 mm, φ15 mm, φ20 mm, φ25 mm, φ30 mm, and φ35 mm).

[0100] (Preparation of latex composition) The modified synthetic polyisoprene latex (A-1) obtained above was stirred while deionized water was added to adjust the solid content to 40% by weight. Next, to 100 parts of the modified synthetic polyisoprene in the modified synthetic polyisoprene latex (A-1) with the adjusted solid content, the aqueous sulfur dispersion prepared above was added in an amount equivalent to 0.5 parts of sulfur, and the aqueous xanthogenic compound was added in an amount equivalent to 2.5 parts of zinc diisopropylxanthogenic acid.

[0101] Then, while stirring the resulting mixture, aqueous dispersions of each compounding agent were added in such a manner that, based on solid content, they amounted to 1.5 parts zinc oxide as an activator and 2 parts of an antioxidant (product name "Wingstay L", manufactured by Chukyo Oil & Fat Co., Ltd.) per 100 parts of modified synthetic polyisoprene in the mixture. Subsequently, the mixture was aged (pre-vulcanized) for 48 hours in a constant temperature water bath adjusted to 25°C to obtain the latex composition.

[0102] (Manufacturing of dip-molded products) A commercially available ceramic hand mold (manufactured by Shinko Co., Ltd.) was cleaned, preheated in a 70°C oven, and then immersed for 5 seconds in an aqueous solution of a coagulant containing 18% by weight of calcium nitrate and 0.05% by weight of polyoxyethylene lauryl ether (product name "Emulgen 109P," manufactured by Kao Corporation). The hand mold was then removed from the aqueous solution. Next, the hand mold was dried in a 70°C oven for 30 minutes or more to allow the coagulant to adhere to the hand mold, thereby coating it with the coagulant.

[0103] Subsequently, the hand mold coated with the coagulant was removed from the oven and immersed for 10 seconds in the 48-hour aged latex composition obtained above. Next, the hand mold was air-dried at room temperature for 10 minutes, and then immersed in 60°C hot water for 5 minutes to dissolve water-soluble impurities and form a dip-molded layer on the hand mold. Then, the dip-molded layer formed on the hand mold was vulcanized by heating in an oven at 130°C for 30 minutes, cooled to room temperature, sprinkled with talc, and peeled off the hand mold to obtain a glove-shaped dip-molded body. The tensile strength and tear strength of the obtained dip-molded body were then measured according to the method described above. The results are shown in Table 1.

[0104] <Example 2> (Manufacturing of modified synthetic polyisoprene latex (A-2)) Modified synthetic polyisoprene was obtained in the same manner as in Example 1, except that 10 parts of methacrylic acid were used instead of styrene and maleic anhydride, and 0.5 parts of 1,1,3,3-tetramethylbutyl hydroperoxide (trade name "Perocta H", manufactured by Nippon Oil & Fats Co., Ltd.) were used instead of azobisisobutyronitrile. Then, 3500 parts of an aqueous solution prepared by dissolving sodium rosinate and sodium lauryl sulfate were used instead of a 1 wt% aqueous sodium hydroxide solution, and the amounts of sodium rosinate and sodium lauryl sulfate in the slurry of the modified synthetic polyisoprene were adjusted to 0.6 parts and 0.3 parts, respectively, per 100 parts of modified synthetic polyisoprene. Grinding, emulsification, and centrifugation were performed in the same manner as in Example 1 to produce a modified synthetic polyisoprene latex (A-2) with a solid content of 57 wt%, and it was evaluated in the same manner. The results are shown in Table 1.

[0105] (Preparation of latex compositions, manufacture of dip molded products) Then, the latex composition was prepared and the dip-molded articles were manufactured in the same manner as in Example 1, except that the modified synthetic polyisoprene latex (A-2) obtained above was used, and the results were evaluated in the same manner. The results are shown in Table 1.

[0106] <Example 3> (Manufacturing of modified synthetic polyisoprene latex (A-3)) Modified synthetic polyisoprene was obtained in the same manner as in Example 1, except that styrene was not used, the amount of maleic anhydride used was changed to 7 parts, and 0.7 parts of dicumyl peroxide were used instead of azobisisobutyronitrile. Then, instead of a 1 wt% sodium hydroxide aqueous solution, 3500 parts of an aqueous solution prepared by dissolving sodium rosinate and sodium lauryl sulfate were used, and the amounts of sodium rosinate and sodium lauryl sulfate in the slurry of the modified synthetic polyisoprene were adjusted to 0.6 parts and 0.3 parts, respectively, per 100 parts of modified synthetic polyisoprene. Grinding, emulsification, and centrifugation were performed in the same manner as in Example 1 to produce a modified synthetic polyisoprene latex (A-3) with a solid content of 57 wt%, and it was evaluated in the same manner. The results are shown in Table 1.

[0107] (Preparation of latex compositions, manufacture of dip molded products) Then, the latex composition was prepared and the dip-molded articles were manufactured in the same manner as in Example 1, except that the modified synthetic polyisoprene latex (A-2) obtained above was used, and the results were evaluated in the same manner. The results are shown in Table 1.

[0108] <Comparative Example 1> (Manufacturing of modified synthetic polyisoprene latex (A-4)) Synthetic polyisoprene (trade name "NIPOL IR2200L", manufactured by Nippon Zeon Co., Ltd.) was mixed with n-hexane (boiling point: 69°C), and the temperature was raised to 60°C while stirring to dissolve it, preparing an n-hexane solution of synthetic polyisoprene with a concentration of 15% by weight. After transferring the n-hexane solution of synthetic polyisoprene to a reaction vessel, 5 parts of styrene, 5 parts of maleic anhydride, and 0.5 parts of azobisisobutyronitrile were added, and the temperature was raised to 75°C while stirring. The reaction was carried out at 75°C for 1 hour to obtain an n-hexane solution of modified synthetic polyisoprene.

[0109] On the other hand, sodium lauryl sulfate was added to water, and the temperature was raised to 60°C to dissolve it, preparing a 1.5% by weight aqueous solution of the surfactant.

[0110] Next, the n-hexane solution of the modified synthetic polyisoprene obtained above and the aqueous surfactant solution prepared above were mixed using a mixer (product name "Multi-line mixer MS26-MMR-5.5L", manufactured by Satake Chemical Machinery Industry Co., Ltd.) so that the amount of sodium lauryl sulfate in the aqueous surfactant solution was 10 parts for every 100 parts of modified synthetic polyisoprene in the n-hexane solution of modified synthetic polyisoprene. Subsequently, the mixture was mixed and emulsified using an emulsifier (product name "Milder MDN310", manufactured by Taiheiyo Kiko Co., Ltd.) at a rotation speed of 4100 rpm to obtain an emulsified dispersion. At this time, the total feed flow rate of the n-hexane solution of modified synthetic polyisoprene and the aqueous surfactant solution was 2,000 kg / hr, the temperature was 60°C, and the back pressure (gauge pressure) was 0.5 MPa. In Comparative Example 1, the amount of sodium lauryl sulfate used as a surfactant was 10 parts per 100 parts of modified synthetic polyisoprene. However, when the amount of sodium lauryl sulfate was reduced, emulsification did not proceed properly, so the amount used was set at 10 parts (the amount of surfactant used was determined for the same reason in Comparative Examples 2 and 3 described later).

[0111] Next, the resulting emulsified dispersion was heated to 80°C under reduced pressure of -0.01 to -0.09 MPa (gauge pressure) to remove n-hexane by distillation, yielding an aqueous dispersion of modified synthetic polyisoprene. During this process, at the time of maximum foaming, the liquid level rose to a height more than twice the liquid level at the start of reduced-pressure distillation, on a volume basis.

[0112] After the removal of n-hexane was complete, the resulting aqueous dispersion of modified synthetic polyisoprene was concentrated by centrifugation at 8,000-9,000 G using a continuous centrifuge (product name "SRG510", manufactured by Alfa Laval) to obtain modified synthetic polyisoprene latex (A-4) with a solid content of 57% by weight as a light liquid. The centrifugation conditions were as follows: solid content of the aqueous dispersion before centrifugation was 8% by weight, flow rate during continuous centrifugation was 1300 kg / hr, and back pressure (gauge pressure) of the centrifuge was 0.1 MPa.

[0113] The viscosity and swell index (SI) of the obtained modified synthetic polyisoprene latex (A-4) were measured at solid content concentrations of 55% and 57% by weight, as shown in Table 1.

[0114] (Preparation of latex compositions, manufacture of dip molded products) Then, the latex composition was prepared and the dip-molded articles were manufactured in the same manner as in Example 1, except that the modified synthetic polyisoprene latex (A-4) obtained above was used, and the results were evaluated in the same manner. The results are shown in Table 1.

[0115] <Comparative Example 2> (Manufacturing of modified synthetic polyisoprene latex (A-5)) Synthetic polyisoprene (trade name "NIPOL IR2200L", manufactured by Nippon Zeon Co., Ltd.) was mixed with n-hexane (boiling point: 69°C), and the temperature was raised to 60°C while stirring to dissolve it, thereby preparing an n-hexane solution of synthetic polyisoprene with a concentration of 15% by weight.

[0116] On the other hand, sodium rosinate and sodium lauryl sulfate were added to water, and the temperature was raised to 60°C to dissolve them, preparing an aqueous emulsifier solution containing 1.5% by weight of sodium rosinate and 0.75% by weight of sodium lauryl sulfate.

[0117] Next, the n-hexane solution of synthetic polyisoprene obtained above and the aqueous surfactant solution prepared above were mixed using a mixer (product name "Multi-line mixer MS26-MMR-5.5L", manufactured by Satake Chemical Machinery Industry Co., Ltd.) so that the amount of sodium rosinate in the aqueous surfactant solution was 10 parts and the amount of sodium lauryl sulfate in the aqueous surfactant solution was 5 parts, for every 100 parts of synthetic polyisoprene in the n-hexane solution of synthetic polyisoprene. Subsequently, the mixture was mixed and emulsified using an emulsifier (product name "Milder MDN310", manufactured by Taiheiyo Kiko Co., Ltd.) at a rotation speed of 4100 rpm to obtain an emulsified dispersion. At this time, the total feed flow rate of the n-hexane solution of synthetic polyisoprene and the aqueous surfactant solution was 2,000 kg / hr, the temperature was 60°C, and the back pressure (gauge pressure) was 0.5 MPa.

[0118] Next, the resulting emulsified dispersion was heated to 80°C under reduced pressure of -0.01 to -0.09 MPa (gauge pressure) to remove n-hexane by distillation, yielding an aqueous dispersion of synthetic polyisoprene. During this process, at the time of maximum foaming, the liquid level rose to a height that was 1.9 times the liquid level at the start of reduced-pressure distillation, on a volume basis.

[0119] After the removal of n-hexane was complete, the resulting aqueous dispersion of synthetic polyisoprene was concentrated by centrifugation at 8,000-9,000 G using a continuous centrifuge (product name "SRG510", manufactured by Alfa Laval) to obtain synthetic polyisoprene latex with a solid content of 57% by weight as a light liquid. The centrifugation conditions were as follows: solid content of the aqueous dispersion before centrifugation was 8% by weight, flow rate during continuous centrifugation was 1300 kg / hr, and back pressure (gauge pressure) of the centrifuge was 0.1 MPa.

[0120] Next, 130 parts of distilled water were added to 100 parts of synthetic polyisoprene in the obtained synthetic polyisoprene latex to dilute it. Then, to the synthetic polyisoprene latex, 0.8 parts of the sodium salt of β-naphthalene sulfonic acid formalin condensate (trade name "Demol T-45", manufactured by Kao Corporation) was added over 5 minutes to 100 parts of synthetic polyisoprene, diluted with 4 parts of distilled water per 100 parts of synthetic polyisoprene as a dispersant. Next, the synthetic polyisoprene latex with the added dispersant was charged into a reaction vessel with a stirrer that was purged with nitrogen, and the temperature was heated to 30°C while stirring. In addition, in a separate container, 3 parts of methacrylic acid as a carboxyl group-containing compound and 16 parts of distilled water were mixed to prepare a methacrylic acid dilution. This methacrylic acid dilution was added to the reaction vessel, which was kept at a temperature of 20°C, over 30 minutes.

[0121] Furthermore, using a separate container, a solution was prepared consisting of 7 parts distilled water, 0.30 parts sodium formaldehyde sulfoxylate (trade name "SFS", manufactured by Mitsubishi Gas Chemical Co., Ltd.), and 0.01 parts sodium ethylenediaminetetraacetate complex (trade name "Frost Fe", manufactured by Chubu Kirest Co., Ltd.). This solution was transferred to the reaction vessel, and 0.5 parts of 1,1,3,3-tetramethylbutyl hydroperoxide (trade name "Perocta H", manufactured by Nippon Oil & Fats Co., Ltd.) were added. The mixture was reacted at 30°C for 1 hour to obtain the latex after the modification reaction. The obtained latex after the modification reaction was then reacted at 40°C for 1 hour, and then concentrated using a centrifuge to obtain modified synthetic polyisoprene latex (A-5) with a solid content of 57% by weight.

[0122] The viscosity and swell index (SI) of the obtained modified synthetic polyisoprene latex (A-5) were measured at solid content concentrations of 55% and 57% by weight, as shown in Table 1.

[0123] (Preparation of latex compositions, manufacture of dip molded products) Then, the latex composition was prepared and the dip-molded articles were manufactured in the same manner as in Example 1, except that the modified synthetic polyisoprene latex (A-5) obtained above was used, and the results were evaluated in the same manner. The results are shown in Table 1.

[0124] <Comparative Example 3> (Manufacturing of modified synthetic polyisoprene latex (A-6)) Except for not using methacrylic acid (diluted methacrylic acid solution) and using 0.8 parts of t-butyl peroxydiethyl acetate (trade name "Trigonox 27", manufactured by Kayaku Nourion Co., Ltd.) instead of 1,1,3,3-tetramethylbutyl hydroperoxide as a radical generator, a modified synthetic polyisoprene latex (A-6) with a solid content of 57% by weight was prepared in the same manner as in Comparative Example 2 and evaluated in the same manner. The results are shown in Table 1.

[0125] (Preparation of latex compositions, manufacture of dip molded products) Then, the latex composition was prepared and the dip-molded articles were manufactured in the same manner as in Example 1, except that the modified synthetic polyisoprene latex (A-6) obtained above was used, and the results were evaluated in the same manner. The results are shown in Table 1.

[0126] [Table 1]

[0127] As shown in Table 1, when a radical generator is brought into contact with a solid conjugated diene polymer to obtain a modified conjugated diene polymer, the steps of dissolving in an organic solvent and removing the organic solvent are eliminated, resulting in excellent productivity. Furthermore, when dispersing in water to obtain the latex of the modified conjugated diene polymer, the amount of surfactant can be reduced, thereby reducing the viscosity of the resulting modified conjugated diene polymer latex, resulting in excellent handling properties, and the resulting dip molded articles possess high tensile and tear strength (Examples 1-3). On the other hand, when obtaining modified conjugated diene polymers, if the modification reaction is carried out while dissolved in an organic solvent or in the form of latex, steps to dissolve in an organic solvent and remove the organic solvent are required. Furthermore, a relatively large amount of surfactant must be used in the emulsification step, resulting in a higher viscosity of the latex of the resulting modified conjugated diene polymer (Comparative Examples 1-3).

Claims

1. A modification step to obtain a modified conjugated diene polymer modified by hydrophilic groups by contacting a conjugated diene polymer with a radical generator, A method for producing a latex of a modified conjugated diene polymer, comprising an emulsification step of emulsifying the modified conjugated diene polymer in water, The modification step is a step of modifying the conjugated diene polymer under the condition that the total amount of organic solvent and water used per 100 parts by weight of the conjugated diene polymer is 20 parts by weight or less. The emulsification step involves first performing a grinding treatment on the modified conjugated diene polymer in water, and then supplying the slurry containing the ground modified conjugated diene polymer to an emulsification device. A method for producing latex of a modified conjugated diene polymer using alkaline water with a pH of 10 to 12 in the pulverization process.

2. The method for producing a modified conjugated diene polymer latex according to claim 1, wherein the modification step includes adding the radical generator to the conjugated diene polymer and kneading it, thereby bringing the conjugated diene copolymer and the radical generator into contact.

3. A method for producing a latex of a modified conjugated diene polymer according to claim 1 or 2, wherein the modification step comprises contacting the solid conjugated diene copolymer with the radical generator.

4. A method for producing a latex of a modified conjugated diene polymer according to any one of claims 1 to 3, wherein, in the emulsification step, when emulsifying the modified conjugated diene polymer in water, alkaline water is used for emulsification.

5. A method for producing a latex of a modified conjugated diene polymer according to any one of claims 1 to 4, wherein, in the emulsification step, the modified conjugated diene polymer is emulsified in water using 0.01 to 5 parts by weight of a surfactant per 100 parts by weight of the modified conjugated diene polymer.

6. A method for producing a latex of a modified conjugated diene polymer according to any one of claims 1 to 5, wherein the modification step is a step of obtaining the modified conjugated diene polymer by contacting the conjugated diene polymer with the radical generator in the presence of an acid group-containing compound and / or an acid anhydride.

7. The method for producing a latex of a modified conjugated diene polymer according to claim 6, further comprising the modification step of using an amount of the acid group-containing compound and / or the acid anhydride of 0.5 to 15 parts by weight per 100 parts by weight of the conjugated diene polymer.

8. A method for producing a latex of a modified conjugated diene polymer according to any one of claims 1 to 7, wherein the conjugated diene polymer is synthetic polyisoprene.

9. A step of obtaining a latex of a modified conjugated diene polymer by the method of any one of claims 1 to 8, A method for producing a latex composition, comprising the step of blending a sulfur-based vulcanizing agent into the latex of the modified conjugated diene polymer.

10. The method according to claim 9 provides a step of obtaining a latex composition, A method for producing a dip-molded article, comprising the step of dipping the latex composition.

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