| 摘要 |
The present invention provides a surfactant making it possible to obtain particles comprising a fluoropolymer at a size smaller in diameter in an aqueous dispersion obtained by polymerization in the presence of the same. The present invention is a surfactant comprising a fluorine-containing-sulfobutanedioic-acid-ester derivative represented by the general formula (i): <?in-line-formulae description="In-line Formulae" end="lead"?>Y-Rf<SUP>1</SUP>-(CH<SUB>2</SUB>)<SUB>m</SUB>-OCOCH(SO<SUB>3</SUB>M)-CH<SUB>2</SUB>COO-(CH<SUB>2</SUB>)<SUB>n</SUB>-Rf<SUP>2</SUP>-Y (i) <?in-line-formulae description="In-line Formulae" end="tail"?> wherein Y represents hydrogen atom or fluorine atom; when Y is hydrogen atom, one of Rf<SUP>1 </SUP>and Rf<SUP>2 </SUP>is -(CF<SUB>2</SUB>CF<SUB>2</SUB>)<SUB>3</SUB>- and the other is -(CF<SUB>2</SUB>CF<SUB>2</SUB>)<SUB>2</SUB>- or -(CF<SUB>2</SUB>CF<SUB>2</SUB>)<SUB>3</SUB>- and, when Y is fluorine atom, Rf<SUP>1 </SUP>and Rf<SUP>2 </SUP>are the same or different and each is a divalent hydrocarbon group containing 1 to 4 carbon atoms and containing at least one fluorine atom; m and n are the same or different and each represents an integer of 1 to 3; and M represents NH<SUB>4</SUB>, Li, Na, K or H.
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