EP-3636682-B1 - FLUORINE-CONTAINING ELASTIC COPOLYMER AND PRODUCTION METHOD THEREFOR

Inventors

• HATTORI, Yukiko
• KOSE, TAKEHIRO

Dates

Publication Date

20260506

Application Date

20180529

Claims (5)

1. A method for producing a fluorinated elastic copolymer, which comprises coagulating a fluorinated elastic copolymer in a latex containing the fluorinated elastic copolymer by using an acid having no metal elements and no chloride ions, wherein a coagulation treatment is carried out by mixing the latex and an acid aqueous solution, a concentration of the acid in the acid aqueous solution is from 0.1 to 50 mass%, and the content of metal elements in water to be employed in the preparation of the aqueous acid solution is from 0 ppb to 2.0 ppm by mass and the content of chloride ion is from 0 to 1 ppm by mass, recovering a coagulated fluorinated elastic copolymer by filtration; and washing the coagulated fluorinated elastic copolymer with a liquid medium having a content of metal elements from 0 ppb to 2.0 ppm by mass, and a content of chloride ions from 0 to 2 ppm by mass, wherein the total amount of the liquid medium to be used for washing is at least 10 parts by mass, to 100 parts by mass of the fluorinated elastic copolymer, wherein the liquid medium used for washing is water, and in the fluorinated elastic copolymer after washing and drying, the content of metal elements is from 0.3 to 20.0 ppm by mass, and the content of chloride ions is at most 1 ppm by mass, wherein the content of metal elements and the content of chloride ions are measured according to the description.
2. The method for producing a fluorinated elastic copolymer according to Claim 1, wherein said acid is nitric acid.
3. The method for producing a fluorinated elastic copolymer according to Claims 1 or 2, wherein the fluorinated elastic copolymer after washing is dried under reduced pressure at a temperature of lower than 100°C.
4. The method for producing a fluorinated elastic copolymer according to any one of Claims 1 to 3, wherein in the fluorinated elastic copolymer after washing and drying, the content of anions derived from the acid is at most 20.0 ppm by mass wherein the content of anions is measured according to the description.
5. The method for producing a fluorinated elastic copolymer according to any one of Claims 1 to 4, wherein the fluorinated elastic copolymer is a fluorinated elastic copolymer having units based on tetrafluoroethylene, and units based on a compound represented by the following formula (1), CF 2 =CFOR f1 (1) wherein R f1 is a C 1-10 perfluoroalkyl group.

Description

TECHNICAL FIELD The present invention relates to a method for producing a fluorinated elastic copolymer. BACKGROUND ART A crosslinked rubber article obtained by crosslinking a fluorinated elastic copolymer is excellent in chemical resistance, solvent resistance, heat resistance, etc., and thus, is suitable as a sealing material for a semiconductor manufacturing apparatus to be used in harsh environments. The sealing material for a semiconductor manufacturing apparatus, is required not to release metal components which adversely affect semiconductor products, as far as possible. Thus, as the sealing material for a semiconductor manufacturing apparatus, it is necessary to use one having a small content of metal elements. As the fluorinated elastic copolymer having a small content of metal elements, the following one has been proposed. A fluorinated elastic copolymer obtained by obtaining a latex containing a fluorinated elastic copolymer by an emulsion polymerization method using no metal compound, coagulating the fluorinated elastic copolymer in the latex by using an acid containing no metal elements, and washing the coagulated fluorinated elastic copolymer with a water-insoluble solvent (Patent Document 1). Patent Document 2 describes high purity perfluoroelastomer composites and a process to produce the same. PRIOR ART DOCUMENT PATENT DOCUMENT Patent Document 1: WO 99/50319Patent Document 2: JP 2013 177631 A DISCLOSURE OF INVENTION TECHNICAL PROBLEM However, in Examples of Patent Document 1, hydrochloric acid is used as the acid containing no metal elements, and the coagulated fluorinated elastic copolymer is washed with a water-insoluble fluorinated solvent, whereby in the finally obtainable fluorinated elastic copolymer, chloride ions remain substantially. Chloride ions may corrode metal parts of a semiconductor manufacturing apparatus. Therefore, the content of chloride ions in the fluorinated elastic copolymer is desired to be as small as possible. The present invention is to provide a method for producing a fluorinated elastic copolymer, whereby it is possible to obtain a fluorinated elastic copolymer in which the contents of metal elements and chloride ions are low. SOLUTION TO PROBLEM The present invention is set out in the appended set of claims. ADVANTAGEOUS EFFECTS OF INVENTION The fluorinated elastic copolymer obtained by the method of the present invention has low contents of metal elements and chloride ions. Since it has low contents of metal elements and chloride ions, even when it is used in a semiconductor manufacturing apparatus, it is not only less likely to release metal components which affect semiconductor products, but also less likely to corrode metal parts of the apparatus. Further, since it contains a trace amount of metal elements, when it is made into a fluorinated elastic copolymer composition, dispersibility of the filler will be improved, and at the same time, the cross-linkability will also be improved. DESCRIPTION OF EMBODIMENTS Hereinafter, a compound represented by the formula (1) will be referred to as a compound (1). Compounds represented by other formulae will be referred to in the same manner. The meanings of the following terms in this specification are as follows. A "unit based on a monomer" is a generic term for an atomic group to be directly formed by polymerization of one molecule of the monomer, and an atomic group obtainable by chemically converting a part of said atomic group. In this specification, a unit based on a monomer, may simply be referred to also as a monomer unit. An "acid having no metal elements and no chloride ions" is meant for a compound wherein no metal elements and no chloride ions are present as elements constituting the compound having the property as an acid. The content of metal elements in a liquid medium is the total value of contents of 29 types of metal elements (Fe, Na, K, Li, Be, Mg, Al, Ca, Ti, V, Cr, Mn, Co, Ni, Cu, Zn, Ga, Rb, Sr, Zr, Mo, Ag, Cd, In, Sn, Cs, Ba, Pb, Bi) measured by the absolute calibration curve method using an inductively coupled plasma mass spectrometer. The content of chloride ions in a liquid medium is a value measured using an ion chromatography apparatus. The content of metal elements in a fluorinated elastic copolymer is the total value of contents of 29 types of metal elements (Fe, Na, K, Li, Be, Mg, Al, Ca, Ti, V, Cr, Mn, Co, Ni, Cu, Zn, Ga, Rb, Sr, Zr, Mo, Ag, Cd, In, Sn, Cs, Ba, Pb, Bi) measured by the absolute calibration curve method using an inductively coupled plasma mass spectrometer, with respect to a liquid obtained by putting the fluorinated elastic copolymer in a platinum crucible and ashing it in a high temperature electrically heated furnace, followed by sulfuric acid white fume treatment, and then by dissolution in dilute nitric acid. The content of anions in a fluorinated elastic copolymer is a value measured using an ion chromatography apparatus, with respect to a solution obtained by addi