JP-7856924-B2 - Method for producing an aqueous fluoropolymer dispersion, aqueous fluoropolymer dispersion, and paint composition

Inventors

• 山部 拓也
• 吉田 裕俊
• 山崎 蘭奈
• 山本 絵美
• 加藤 丈人
• 中谷 安利
• 山中 拓

Assignees

• ダイキン工業株式会社

Dates

Publication Date

20260512

Application Date

20230727

Priority Date

20220727

Claims (18)

1. A method for producing an aqueous fluoropolymer dispersion containing a fluoropolymer, In a reactor, a fluoropolymer-containing aqueous dispersion is prepared by polymerizing a fluoromonomer in the presence of a fluorine-containing surfactant, a polymerization initiator, and an aqueous medium. The aqueous dispersion is subjected to heat treatment. A nonionic surfactant is added to a heat-treated aqueous dispersion. An aqueous dispersion containing a nonionic surfactant is brought into contact with an ion exchange resin. A manufacturing method for concentrating an aqueous dispersion obtained after contact with an ion exchange resin.
2. The manufacturing method according to claim 1, wherein, after preparing an aqueous dispersion by polymerization, before heat-treating the aqueous dispersion, at least one of the following operations is performed: (a) removing fluoromonomers remaining in the reactor, and (b) recovering the aqueous dispersion in the reactor and storing it in a container different from the reactor.
3. The manufacturing method according to claim 2, wherein a radical generator is added to the aqueous dispersion after performing at least one of operations (a) and (b), and before heat treatment of the aqueous dispersion.
4. The manufacturing method according to claim 1 or 2, wherein after preparing an aqueous dispersion by polymerization, a radical generator is added to the aqueous dispersion before heat treatment, thereby preparing an aqueous dispersion containing a radical generator.
5. The manufacturing method according to claim 1 or 2, wherein the heat treatment temperature is 50°C or higher.
6. The manufacturing method according to claim 5, wherein the heat treatment temperature is 95°C or lower.
7. The manufacturing method according to claim 5, wherein, after heat treatment, the aqueous dispersion is cooled to below 50°C before contacting the ion exchange resin.
8. The manufacturing method according to claim 1 or 2, wherein an aqueous dispersion is prepared by adding a nonionic surfactant to a heat-treated aqueous dispersion, so that the content of the nonionic surfactant in the aqueous dispersion is 5% by mass or more relative to the fluoropolymer.
9. The manufacturing method according to claim 1 or 2, wherein the nonionic surfactant is represented by general formula (i). R 6 -O-A 1 -H (i) (In the formula, R 6 is a linear or branched primary or secondary alkyl group having 8 to 18 carbon atoms, and A 1 is a polyoxyalkylene chain.)
10. The manufacturing method according to claim 1 or 2, wherein contact between the aqueous dispersion and the ion exchange resin is repeated two or more times.
11. A manufacturing method according to claim 1 or 2, comprising separating the aqueous dispersion into two or more phases and concentrating the aqueous dispersion by recovering the concentrated phase.
12. A method for producing the present invention according to claim 1 or 2, comprising adding a nonionic surfactant to a concentrated aqueous dispersion.
13. A fluoropolymer aqueous dispersion, It contains a fluoropolymer, a nonionic surfactant, and a fluorine-containing compound having a hydrophilic group with 7 or fewer carbon atoms. The fluoropolymer content is 50 to 70% by mass relative to the aqueous dispersion of fluoropolymer. The content of the nonionic surfactant is 4.0 to 12% by mass relative to the fluoropolymer. A fluoropolymer aqueous dispersion in which the content of a fluorine-containing compound having a hydrophilic group with 7 or fewer carbon atoms is greater than 0 ppb by mass and less than 300 ppb by mass relative to the fluoropolymer aqueous dispersion.
14. The fluoropolymer aqueous dispersion according to claim 13 , wherein the nonionic surfactant is represented by general formula (i). R 6 -O-A 1 -H (i) (In the formula, R 6 is a linear or branched primary or secondary alkyl group having 8 to 18 carbon atoms, and A 1 is a polyoxyalkylene chain.)
15. The aqueous dispersion of a fluoropolymer according to claim 13 or 14 , wherein the fluoropolymer contains perfluoro(alkyl vinyl ether) units.
16. The aqueous fluoropolymer dispersion according to claim 15 , wherein the content of a fluorine-containing compound having a hydrophilic group represented by general formula (2) is 50 ppb by mass or less . General formula (2): [C n-1 F 2n-1 COO − ]M + (In the formula, n is an integer between 9 and 14, and M + represents a cation.)
17. The aqueous dispersion of a fluoropolymer according to claim 13 or 14 , wherein the fluoropolymer is polytetrafluoroethylene.
18. A paint composition containing the aqueous dispersion of fluoropolymer according to claim 13 or 14 .

Description

This disclosure relates to a method for producing an aqueous fluoropolymer dispersion, the aqueous fluoropolymer dispersion, and a paint composition. Patent Document 1 describes a method for decomposing fluorinated carboxylic acids, characterized by treating at least one fluorinated carboxylic acid selected from fluorinated carboxylic acids, their salts, and their precursors with hot water in a sealed container containing peroxodisulfate ions. Japanese Patent Publication No. 2008-285449 Before specifically describing this disclosure, we define or explain some terms used in this disclosure. In this disclosure, fluororesin is a partially crystalline fluoropolymer, or fluoroplastic. Fluororesin has a melting point and is thermoplastic, but may be melt-processable or non-melt-processable. In this disclosure, melt processability means that the polymer can be melted and processed using conventional processing equipment such as extruders and injection molding machines. Therefore, melt processable fluororesins typically have a melt flow rate of 0.01 to 500 g/10 min, as measured by the measurement method described later. In this disclosure, fluororubber refers to an amorphous fluoropolymer. "Amorphous" means that the magnitude of the melting peak (ΔH) observed in differential scanning calorimetry (DSC) (heating rate 10°C/min) or differential thermal analysis (DTA) (heating rate 10°C/min) of the fluoropolymer is 4.5 J/g or less. Fluororubber exhibits elastomeric properties upon crosslinking. Elastomer properties refer to the ability of a polymer to be stretched and to retain its original length when the force required to stretch the polymer is no longer applied. A monomer that provides crosslinking sites is a monomer (curation site monomer) that has crosslinkable groups that provide crosslinking sites to a fluoropolymer for crosslinking by a curing agent. In this disclosure, polytetrafluoroethylene [PTFE] is preferably a fluoropolymer in which the content of tetrafluoroethylene units relative to the total polymerization units is 99 mol% or more. In this disclosure, it is preferable that both the fluororesin (excluding polytetrafluoroethylene) and the fluororubber are fluoropolymers in which the content of tetrafluoroethylene units relative to the total polymerization units is less than 99 mol%. In this disclosure, the content of each monomer constituting the fluoropolymer can be calculated by appropriately combining NMR, FT-IR, elemental analysis, and X-ray fluorescence analysis depending on the type of monomer. In this disclosure, "organic group" means a group containing one or more carbon atoms, or a group formed by removing one hydrogen atom from an organic compound. Examples of such "organic groups" are: Alkyl molecules which may have one or more substituents, An alkenyl group which may have one or more substituents, An alkynyl group which may have one or more substituents, A cycloalkyl group which may have one or more substituents, A cycloalkenyl group which may have one or more substituents, A cycloalkadienyl group which may have one or more substituents, An aryl group which may have one or more substituents, An aralkyl group which may have one or more substituents, A non-aromatic heterocyclic group which may have one or more substituents, A heteroaryl group which may have one or more substituents, Cyano group, formyl group, RaO-, RaCO-, RaSO 2 - RaCOO-, RaNRaCO-, RaCONRa-, RaOCO-, RaOSO 2 , and RaNRbSO 2 - (In these formulas, Ra is independent, Alkyl molecules which may have one or more substituents, An alkenyl group which may have one or more substituents, An alkynyl group which may have one or more substituents, A cycloalkyl group which may have one or more substituents, A cycloalkenyl group which may have one or more substituents, A cycloalkadienyl group which may have one or more substituents, An aryl group which may have one or more substituents, An aralkyl group which may have one or more substituents, A non-aromatic heterocyclic group which may have one or more substituents, A heteroaryl group which may have one or more substituents, Rb is independently an alkyl group which may have H or one or more substituents. It includes. The above organic group is preferably an alkyl group which may have one or more substituents. Furthermore, in this disclosure, “substituent” means a substituteable group. Examples of such “substituent” include aliphatic groups, aromatic groups, heterocyclic groups, acyl groups, acyloxy groups, acylamino groups, aliphatic oxy groups, aromatic oxy groups, heterocyclic oxy groups, aliphatic oxycarbonyl groups, aromatic oxycarbonyl groups, heterocyclic oxycarbonyl groups, carbamoyl groups, aliphatic sulfonyl groups, aromatic sulfonyl groups, heterocyclic sulfonyl groups, aliphatic sulfonyloxy groups, aromatic sulfonyloxy groups, heterocyclic sulfonyloxy groups, sulfamoyl groups, aliphatic sulfonamide groups, aromatic sulfonamide groups, heterocyclic sulfonamide groups, amino groups, al