| 摘要 |
Polyfluoroethylene monomers such as C2F4 or C2ClF3 are polymerized at 0 DEG -200 DEG C. and at least 1 atm. with an aqueous solution of between 0,001 and 3 wt. per cent based on monomer, of a keto-acid (as defined below) or water-soluble derivative thereof, the solution being subjected to actinic, preferably ultra-violet radiation. In the keto-acid RCOR1 or RCOCH2 CH2COR11, R is alkyl, carboxyalkyl or carboxy, R1 is carboxyalkyl or sulphoalkyl and R11 is carboxyalkyl, the alkyl groups in R,R1 and R11 having each 1-4 carbon atoms; derivatives mentioned are metal ammonium or amine salts, C1-4 alkyl esters, amides and halides. Specified catalysts are 2-ketoglutaric acid; levulinic acid and its Na salt; 3:6-diketosebacic acid and its dimethyl ester; 3-ketopimelic acid, monoamide and Na salt; acetoacetic acid, amide and ester; 3-keto-n-caprylic, 4-ketoazelaic and acetone sulphonic acids; Na and K 3-ketobutanesulphonates. Paraffin wax (e.g. m.p. 52 DEG -56 DEG C.) and emulsifiers such as ammonium perfluorocaprylate or ammonium acetate/acetic acid may also be used in the process. The dried powder obtained by coagulation of the polymer suspension may be extruded or sintered, e.g. a C2F4 polymer may be mixed with 15 wt per cent of paraffin oil, extruded into shapes, extracted with trichloroethylene and sintered in a salt bath at 327 DEG C. or above. |
