JP-7856090-B2 - Method for producing modified conjugated diene polymer latex

Inventors

• 佐藤 吉隆

Assignees

• 日本ゼオン株式会社

Dates

Publication Date

20260511

Application Date

20220215

Priority Date

20210225

Claims (10)

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, comprising the modification step of adding the radical generating agent to the conjugated diene polymer and kneading it, thereby bringing the conjugated diene copolymer and the radical generating agent into contact.
3. The method for producing a modified conjugated diene polymer latex according to claim 1 or 2, comprising the modification step of contacting the solid conjugated diene copolymer with the radical generating agent.
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, alkaline water is used to emulsify the modified conjugated diene polymer in water.
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 generating agent in the presence of an acid group-containing compound and/or an acid anhydride.
7. The method for producing a modified conjugated diene polymer latex according to claim 6, further comprising the modification step, wherein the amount of the acid group-containing compound and/or the acid anhydride used is 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.

Description

This invention relates to a method for producing modified conjugated diene polymer latex. Conventionally, it is known that dip-molded latex compositions containing natural rubber latex can be used to produce dip-molded articles that come into contact with the human body, such as nipples, balloons, gloves, and sacks. However, natural rubber latex contains proteins that can cause immediate-type allergic reactions (Type I) in the human body, which has posed problems for dip-molded articles that come into direct contact with biological mucous membranes or organs. Therefore, studies have been conducted to explore the use of synthetic rubber latex instead of natural rubber latex. 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 structural units 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 water-soluble polymer in the latex is 2 parts by weight or less per 100 parts by weight of the acid-modified conjugated diene polymer, and the viscosity when the solid content concentration is 50% by weight and the viscosity when the solid content concentration is 60% by weight are within a specific range. International Publication No. 2019/171981 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. <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. 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. 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. 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 suppression of the 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. The polymer Mooney viscosity (ML1+4, 100°C) of synthetic polyisoprene is preferably 50 to 85, more preferably 60 to 85, and even more preferably 70 to