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EP-3978538-B1 - METHOD FOR PRODUCING CHLOROPRENE-BASED-POLYMER LATEX

EP3978538B1EP 3978538 B1EP3978538 B1EP 3978538B1EP-3978538-B1

Inventors

  • MIURA, YUKI
  • HASHIMOTO, YUJI
  • NAKAMURA, KEIICHI

Dates

Publication Date
20260506
Application Date
20200513

Claims (7)

  1. A method for removing residual volatile organic substances from a chloroprene-based polymer latex, wherein a mixed fluid of one or more gases selected from the group consisting of inert gases and air, and water is contacted with the latex at a gas pressure higher than a saturated water vapor pressure at a liquid temperature of the latex, and a temperature of the mixed fluid is a temperature lower than a boiling point of water at the gas pressure.
  2. The method according to claim 1, wherein the temperature of the latex contacted with the mixed fluid is 10 to 60°C.
  3. The method according to claim 1 or 2, wherein the temperature of the mixed fluid contacted with the latex is 10 to 60°C.
  4. The method according to any one of claims 1 to 3, wherein the mixed fluid is contacted with the latex by blowing the mixed fluid into the latex liquid.
  5. The method according to any one of claims 1 to 4, wherein a concentration of the residual volatile organic substance comprised in the latex before the latex is contacted with the mixed fluid is 150 to 10000 ppm by mass based on a total mass of the latex.
  6. The method according to any one of claims 1 to 5, wherein the concentration of the residual volatile organic substance comprised in the latex is reduced to less than 150 ppm by mass based on the total mass of the latex.
  7. The method according to any one of claims 1 to 6, wherein the residual volatile organic substance is a residual monomer in polymerization reaction in production of the latex.

Description

Technical Field The present invention relates to a method for efficiently removing residual volatile organic substances such as a residual monomer and a residual organic solvent from a chloroprene-based polymer latex. Background Art When chloroprene-based polymer latex is subjected to a stripping step or the like in its production process, chloroprene-based polymer latex is generally reduced in the concentration of residual volatile organic substances such as an unreacted monomer (residual monomer) in polymerization reaction to 1% by mass or less. However, awareness of influence which volatile organic substances have on the environment or the human body is growing in recent years, residual volatile organic substances in chloroprene-based polymer latex have been required to be further reduced therewith. As techniques for removing residual volatile organic substances from chloroprene-based polymer latex, heating evaporation and distillation at reduced pressure, stripping in which water vapor is introduced into latex, the promotion of volatilization by spraying latex, and the like are known. For example, Patent Literature 1 describes a method in which polymer latex is forcedly circulated in a circulation circuit and heated with an external heat exchanger, and a residual monomer is removed by evaporation. Patent Literature 2 describes a method for reducing a residual monomer by spraying a polymer dispersion liquid vertically (perpendicularly below) and radially in a container and discharging an evaporated monomer from the upper part of the container. Patent Literature 3 describes a method in which water vapor is fed to a polychloroprene dispersion material in a stripping tower, and chloroprene which is a residual monomer is discharged from the top of the tower. EP2241580 and US3930931 disclose methods for removing unreacted monomers and other volatile material from aqueous dispersions of polymeric substance, wherein steam stripping is carried out. Citation List Patent Literature PTL 1: JP 2003-147016 APTL 2: JP 51-37175 APTL 3: JP 2012-524132 A Summary of Invention Technical Problem In all the methods as described in the above-mentioned Patent Literatures 1 to 3, residual volatile organic substances are removed by treating chloroprene-based polymer latex at high temperatures of more than 60°C. However, the methods had a problem that when chloroprene-based polymer latex was treated at high temperature, agglomerates deposit easily by the evaporation of moisture, the solid concentration decreases, and the treatment had to be stopped due to the clogging of piping for the circulation of chloroprene-based polymer latex and gas, or the like. For this reason, operations for removing agglomerates in chloroprene-based polymer latex at high temperature and in the treatment system need to be conducted frequently to remove residual volatile organic substances safely while maintaining the properties of chloroprene-based polymer latex. The present invention has been completed to solve the problems as mentioned above, and an object of the present invention is to provide a method for efficiently removing residual volatile organic substances from a chloroprene-based polymer latex while suppressing the deposition of agglomerates. Solution to Problem The present invention is based on the finding that, according to stripping with a mixed fluid of inert gas and the like and water, residual volatile organic substances can be efficiently removed from chloroprene-based polymer latex, and the deposition of agglomerates can be suppressed, for example, even at comparatively low temperature such 60°C or less. The present invention is defined in the appended claims. Advantageous Effects of Invention According to the present invention, residual volatile organic substances can be efficiently removed from chloroprene-based polymer latex in the production of the latex while the deposition of agglomerates is suppressed. Brief Description of Drawings [Fig. 1] Fig. 1 shows a schematic diagram of a device used for implementing a test on removing residual volatile organic substances in chloroprene-based polymer latex in the Examples. Description of Embodiments Hereinafter, the method of the present invention will be described in detail. "Removal" mentioned in the present invention means removing at least a part. The method of the present invention is characterized in that when residual volatile organic substances contained in chloroprene-based polymer latex (hereinafter also called merely latex) are volatilized and removed, a mixed fluid of one or more gases selected from the group consisting of inert gases and air (hereinafter also called inert gas and/or the like), and water is contacted with the latex at a gas pressure higher than saturated water vapor pressure at a liquid temperature of the latex, and temperature of the mixed fluid is temperature lower than a boiling point of water at the gas pressure. According to the above-mentioned method, th