| 摘要 |
1355912 Plexifilaments SOLVAY & CIE 4 Aug 1972 [6 Aug 1971] 36573/72 Heading B5B In a process for the production of discontinuous fibrils, a two-phase liquid mixture comprising a molten polymer and a solvent are held at an elevated temperature and pressure until the pressure is suddenly released thus causing evaporation of the solvent and solidification of the polymer into fibrils. The solvent and the concentration of the polymer are chosen to give a two-phase system at elevated temperatures and pressures, the pressure is chosen as that above which the system comprises just one phase and the temperature is sufficiently high to cause the solvent to evaporate upon the release of the pressure but not too high to prevent the solidification of the polymer. In the process, a fluid is introduced into the two-phase system before the pressure reduction is complete. This introduction may be either before the reduction is started, or whilst it is proceeding. One embodiment of apparatus suitable for carrying out the process is illustrated in Fig. 1. It consisits of a pre-release chamber 1, into which a solution of polymer is injected and where the loss of pressure is sufficient to cause the formation of two phases, and channel 4 leading to the orifice at which the pressure is suddenly reduced to ambient. The liquid is introduced into the two-phase system by means of channels 3. Examples illustrate the formation of filaments of polyvinyl chloride, polyvinylidene fluoride and polyethylene. The fluids used in the examples are nitrogen, water and dichloroethane. |
