JP-2026075105-A - Method for producing an aqueous dispersion

Abstract

[Problem] To provide a method for efficiently producing an aqueous dispersion containing fluoropolymer particles that has excellent dispersibility in liquid without requiring a fluorine-based emulsifier. [Solution] A method for producing an aqueous dispersion, comprising forming a reaction system containing fluoroolefin polymer particles and water, but not containing a fluorine-based emulsifier, and polymerizing at least gaseous perfluoroolefin in the reaction system to obtain an aqueous dispersion containing fluoropolymer particles, wherein the viscosity of the reaction system is less than 2 mPa·s, the ratio of the average particle diameter of the fluoropolymer particles contained in the aqueous dispersion to the average particle diameter of the fluoroolefin polymer particles is greater than 1, and the ratio of the content of fluoropolymer particles in the aqueous dispersion to the content of fluoroolefin polymer particles in the reaction system is 2 or more. [Selection Diagram] None

Inventors

• 柴崎 浩輔
• ▲柳▼谷 碧
• 佐橋 祐亮
• 松本 真理子
• 巨勢 丈裕
• 田口 大輔
• 大継 聡
• 阿部 香織
• 豊田 瑞菜

Assignees

• ＡＧＣ株式会社

Dates

Publication Date

20260507

Application Date

20260219

Priority Date

20240619

Claims (15)

1. A method for producing an aqueous dispersion, comprising forming a reaction system containing particles of a fluoroolefin polymer and water, but without a fluorine-based emulsifier, and polymerizing at least gaseous perfluoroolefin in the reaction system to obtain an aqueous dispersion containing fluoropolymer particles, The viscosity of the reaction system is less than 2 mPa·s. The ratio of the average particle diameter of fluoropolymer particles in the aqueous dispersion to the average particle diameter of fluoroolefin polymer particles in the reaction system is greater than 1. The ratio of the content of fluoropolymer particles in the aqueous dispersion to the content of fluoroolefin polymer particles in the reaction system is 2 or more. A method for producing an aqueous dispersion.
2. A method for producing an aqueous dispersion according to claim 1, wherein the ratio of the viscosity of the aqueous dispersion to the viscosity of the reaction system is greater than 1.
3. The method for producing the aqueous dispersion according to claim 1, wherein the viscosity of the aqueous dispersion is less than 10 mPa·s.
4. The method for producing an aqueous dispersion according to claim 1, wherein the thixotropy ratio of the reaction system liquid is 0.95 or more and 1.05 or less.
5. The method for producing an aqueous dispersion according to claim 1, wherein the gaseous perfluoroolefin is tetrafluoroethylene or hexafluoropropylene.
6. The method for producing an aqueous dispersion according to claim 1, wherein the polymerization is carried out by copolymerizing a gaseous perfluoroolefin with a monomer other than the gaseous perfluoroolefin.
7. The method for producing an aqueous dispersion according to claim 6, wherein the monomer other than the gaseous perfluoroolefin is ethylene, chlorotrifluoroethylene, vinylidene fluoride, propylene, fluoroalkylethylene, perfluoroalkyl vinyl ether, perfluoroalkyl allyl ether, or a fluoromonomer having a fluorosulfonyl group, a carboxyl group, or an alkoxycarbonyl group.
8. The method for producing an aqueous dispersion according to claim 1, wherein the ratio of the average particle sizes is 10 or less.
9. A method for producing an aqueous dispersion according to claim 1, wherein the average particle size of the fluoroolefin polymer particles is 10 nm or more and less than 150 nm.
10. A method for producing an aqueous dispersion according to claim 1, wherein the average particle size of the fluoropolymer particles is greater than 50 nm and less than or equal to 1000 nm.
11. A method for producing an aqueous dispersion according to claim 1, wherein the particle size distribution of the fluoropolymer particles is unimodal, and the polydispersity index of the particle size of the fluoropolymer particles is 0.5 or less.
12. The method for producing an aqueous dispersion according to claim 1, wherein the content of the fluoroolefin polymer in the reaction system is 0.01% by mass or more and 4.0% by mass or less.
13. The method for producing an aqueous dispersion according to claim 1, wherein the formation of the reaction system is carried out by polymerizing at least a gaseous fluoroolefin in the presence of water and a polymerization initiator, without using a fluorine-based emulsifier.
14. The method for producing an aqueous dispersion according to claim 13, wherein the gaseous fluoroolefin is vinyl fluoride, vinylidene fluoride, tetrafluoroethylene, or hexafluoropropylene.
15. A method for producing an aqueous dispersion according to claim 14, wherein the polymerization is carried out by copolymerizing a gaseous fluoroolefin with ethylene, chlorotrifluoroethylene, propylene, perfluoroalkyl vinyl ether, or perfluoroalkyl allyl ether.

Description

This disclosure relates to a method for producing an aqueous dispersion. Fluoropolymers containing units based on fluoroolefins are used in various industrial fields due to their excellent heat resistance, chemical resistance, flame retardancy, and weather resistance. One method for producing fluoropolymers involves emulsion polymerization of fluoroolefins in water using a fluorine-based emulsifier (see Patent Document 1, etc.). International Publication No. 2007/046377 The meanings of the terms used in this disclosure are as follows: Numerical ranges expressed using "~" signify a range that includes the values before and after "~" as the lower and upper limits. In numerical ranges described stepwise in this specification, the upper or lower limit stated in one range may be replaced with the upper or lower limit of another stepwise numerical range. Furthermore, in numerical ranges described in this specification, the upper or lower limit stated in one range may be replaced with the values shown in the examples. In this specification, each component may be represented by a single substance or by a combination of two or more substances. When two or more substances are used in combination for each component, the content of that component refers to the total content of all substances used, unless otherwise specified. In this specification, a combination of two or more preferred embodiments is a more preferred embodiment. A "unit" is a general term for atomic groups derived from a single monomer molecule directly formed by the polymerization of monomers, and atomic groups obtained by chemically transforming a portion of the above-mentioned atomic group. A "monomer-based unit" will hereafter also be simply referred to as a "unit," and a "monomer A-based unit" will hereafter also be simply referred to as a "monomer A unit." In this specification, the content (mass %) or molar %) of each unit relative to the total units contained in the polymer is determined by analyzing the polymer using solid-state nuclear magnetic resonance spectroscopy (NMR). However, the content of each unit calculated from the amount of each monomer used typically closely matches the actual content of each unit. In this specification, "gaseous compound" refers to a compound with a boiling point of less than 25°C at atmospheric pressure (10¹³ hPa), and "liquid compound" refers to a compound with a boiling point of 25°C or higher at atmospheric pressure (10¹³ hPa). The present disclosure describes a method for producing an aqueous dispersion (hereinafter also referred to as "the Method") which involves forming a reaction system containing particles of a fluoroolefin polymer (hereinafter also referred to as "FO polymer") (hereinafter also referred to as "FO particles") and water, and not containing a fluorine-based emulsifier, and polymerizing at least gaseous perfluoroolefin in the reaction system to obtain an aqueous dispersion containing particles of a fluoropolymer (hereinafter also referred to as "F polymer") (hereinafter also referred to as "F particles"). The method is characterized in that the viscosity of the reaction system is less than 2 mPa·s, the ratio of the average particle diameter of the F particles to the average particle diameter of the FO particles (hereinafter also referred to as "particle size ratio") is greater than 1, and the ratio of the content of F particles to the content of FO particles (hereinafter also referred to as "content ratio") is 2 or more. The content ratio is a value calculated from the respective content (mass%). The reason why this method allows for the efficient and direct production of aqueous dispersions containing dense fluoropolymer particles with excellent dispersibility in liquid, without the presence of fluorine-based emulsifiers, is not entirely clear, but the following reasons can be cited. In this method, the reaction system contains water, but its viscosity is within a predetermined low range. Therefore, the degree of freedom of the FO polymer particles (FO particles), which contain fluorine atoms and are generally highly hydrophobic, is increased, and the interactions between FO particles are relatively weakened. As a result, aggregation and modification of FO particles are suppressed in the reaction system; in other words, the FO particles can be considered to be in a highly dispersed state in the liquid. The gaseous perfluoroolefin introduced into such a reaction system is easily adsorbed by the FO polymer, which contains fluorine atoms and has a high affinity for them. In other words, the FO particles are considered to function highly as a polymerization site for the perfluoroolefin. Furthermore, in a highly fluid reaction system with a viscosity within a certain range—in other words, a reaction system that easily forms a highly turbulent state—the heat transfer associated with the adsorption and polymerization of gaseous perfluoroolefin is easily promoted, and it is considered that polym