| 摘要 |
1,081,935. Making plastics pipes. WAVIN N.V. Sept. 18. 1964 [Sept. 19, 1963], No. 38149/64. Heading B5A. In a process for making a pipe of thermoplastics material, e.g. of polyvinyl chloride, a pipe is extruded and then annealed at temperatures between 70‹ and 160‹ C. for at least 15 minutes, and the annealed pipe cooled to a temperature in the region of ambient temperature, the composition of the thermoplastics material being so selected that the pipe so produced has a benzene absorption below 20%. A pipe is extruded from an extruder 1 at a temperature of 160‹ to 180‹ C. and, after passing through a calibration box 3, is sprayed with cooling water from a tank 5 and then immersed in a tank 6 of water at 100‹ C. for 15 minutes to 1 hour. The pipe is then transferred to a tank 9 containing a cooling spiral 10 connected to a refrigerator 11, and is removed therefrom after a predetermined period when it is at approximately ambient temperature. The tanks 5, 6 may be omitted, the extruded pipe being passed directly from the extruder 1 to the tank 9. |
