GB1362476A - Polyethylenes - Google Patents

Abstract

1362476 Treating high density polyethylene MONTECATINI EDISON SpA 2 Feb 1972 [4 Feb 1971] 4969/72 Heading C3P The processability of linear high density polyethylene is improved by treating polyethylene having an intrinsic viscosity [#] and a melt index m lying on or above the line [#]= 1À5 m.<SP>-0À164</SP> with an organic peroxide at elevated temperature under homogenizing conditions such that its density, melting point, intrinsic viscosity and solubility in tetrahydronaphthalene at 135‹ C. are practically unaltered, but such as to provoke a decrease in the melt index to values below said line. The proportion of peroxide may be such as to decrease the melt index by at least 20% but insufficient to render the polyethylene insoluble in tetrahydronaphthalene at 135‹ C. The treatment may be effected at 140‹ to 250‹ C. in an extruder, the peroxide being fed laterally as a master batch in polyethylene. In examples polyethylenes and mixtures of polyethylenes are homogenized in extruders at elevated temperatures in the presence of 2,5-dimethyl-2,5-di-t-butylperoxyhexane, 2,5-dimethyl-2,5-di-t-butylperoxyhexyne or mixtures of para- and meta-α,α<SP>1</SP>-bis(t-butylperoxy) diisopropylbenzene to give products which may be extruded at greater rates than the starting materials without the occurrence of "sharkskin" effects or melt fracture.