Controlling melt-viscosity for extrusion foam coating of HF cables - by metering crosslinking agent to plastics foam matrix to give less than thirty per:cent degree of crosslinking

摘要

Parent patent describes the mfr. of an envelope of plastics foam for elongated articles by plasticising a plastics in an extruder; introducing a gas into the plasticised melt to thoroughly distribute it in the me applying the gas-enriched melt onto the elongated article; and initiating a chemical cross-linking of the plastics immediately before it issues from the extruder. In the addn. the amt. of cross-linking agent added to the plastics is metered so that it suffices for a max. degree of crosslinking of 30%. Used e.g. for plastics-insulating coaxial H.F. cables. It has been found that less than 30% crosslinking is sufficient to achieve an adequate rise of melt viscosity for further processing.