| 摘要 |
522,648. Compound sheet materials. BAKELITE, Ltd. Dec. 16, 1938, No. 36748. Convention date, June 17. [Class 140] [Also in Groups V and XVI] In moulding articles, such as printing plates, thermo-setting plastic material, such as natural or synthetic rubber, vinyl derivatives or phenol or urea aldehyde resins, is forced through the whole or portions of a foraminous sheet which is composed of textile fabric impregnated with a fixative serving to lock the threads where they ,cross but not filling the spaces between the threads, such sheet being placed over the face of a matrix so that plastic material is extruded into the depression or depressions of the matrix and sufficient material remains as a bed for the sheet which thereafter' constitutes a part of the moulded article. A composite sheet for use in the moulding operation comprises a layer of uncured rubber composition superimposed on and attached to a foraminous sheet of textile fabric which has been previously impregnated with a heat-hardenable resin and cured so that the threads of the fabric are locked where they cross but the spaces between them are not filled up. The textile fabric may have been pre-shrunk and the threads locked together with a varnish fixative such as one containing a heat-hardenable phenol' resin. The fixative may however be starch, silicate of soda or glue. The sheet may be a cotton fabric having a mesh of 80 threads per inch or less. A composite sheet is formed by calendering a layer of rubber composition on to the foraminous sheet. |
