| 摘要 |
A vulcanizable rubber compound is prepared in two batches, each batch containing a vulcanizing agent which works in conjunction with a vulcanizing agent in the other batch to bring about vulcanization of the compound: for example, one batch may contain sulphur and the other may contain accelerator. Each batch is prepared in elongated form and both are fed simultaneously to an extruder where they are mixed and extruded in the required shape. Each batch may contain more than one agent. From the extruder the shaped compound may pass through a tube containing steam where it is vulcanized. The invention obviates premature vulcanization during preparation and handling of the compound before it is fed to the extruder, since, for example, each batch may be premixed and stored for extrusion when required. Each batch may contain half of the rubber and half of all the other ingredients except the vulcanizing agents, the batches being formed in strips and equal numbers thereof fed to the extruder. Or one strip may contain only a small part of the rubber and all of the sulphur or accelerator(s), in which case it is of smaller cross-section than the others and may be fed sandwiched between two others or in a groove or grooves in a single strip. Strips may be fed twisted together by means of rollers. The invention may be applied to the insulation and/or sheathing of electric cables. Specification 736,022 is referred to.
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