| 摘要 |
<p>Coagulated tetrafluoroethylene resin powders are claimed with an average particle size of 350-800 u consisting of agglomerated prim. particles with an av. particle size of 0.1-0.5 micron. The prim. particles are made up of >=2 parts, viz an external part and a bordering inner part. Each part consists of a copolymer of tetrafluoroethylene with units of a comonomer (a) of formula R1R3C=CFR2 in which R1 is F or H; R2 is F or Cl, and R3 is Cl, -R'FH, -OR'FH, -RFCl, -OCF2C(CF3)FO(CF2)2SO2F or -(OCF2C-(CF3)F)nOR"F, where R'F is a linear perfluoroalkylene gp. with 1-5C, the substits. being in the omega-position. -RFCl is 1-10C perfluorochloroalkyl, R"F is 1-9C perfluoroalkyl. and n = 1 or 2, or R"F may have the formula (I): and n is 0,1 or 2; and if R2 is F, R1 and R3 may together form a gp. (II): and/or (b) of formula R5R6C=CH2 in which R5 and R6 may be CH3, CF3 or CClF2 or one of the groups may be H and the other may be -OCOCH3, -OCORF, -OCOR'FH, -OCORFCl, -RF or R'FCl, in which R'F and RFCl have the above meaning and RF is a 1-10C perfluoroalkyl group. The internal part of the particles has a higher comonomer content than the external part. The fine powder prods. are esp. useful for paste extrusion processes in which a paste of the powder with a lubricant is extruded from a cylinder through a small nozzle and the extrudate is heated to remove the lubricant and to sinter the resin particles. The copolymer particles can be extruded at very high reduction ratios without the formation of faults and fissures in the sintered extrudate.</p> |
