| 摘要 |
<p>1465132 Blending polyolefins and polysiloxanes DOW CORNING CORP 26 July 1974 [3 Aug 1973] 33066/74 Headings C3T and C3P A blend of a polyolefin and a polydiorganosiloxane gum is obtained by mixing (1) a low or high density polyethylene, polypropylene, polymethylpentene or a copolymer of tetrafluoroethylene and ethylene with (2) a toluene-soluble polysiloxane gum of Williams plasticity over 0À020 inch and a ratio of organic groups to silicon atoms of 2 : 1, the organic groups being Me, Ph, Vi or allyl, 1À5-17 mol. per cent of the siloxane units having vinyl or allyl groups and no more than 50 mol per cent of the organic groups being Ph, in a weight ratio of (1) : (2) of 25 : 75 to 93 : 7; at a shear rate, using a torque rheometer, of over 10 sec.<SP>-1</SP> for a time sufficient to give a viscosity at least 60% of the maximum obtainable under the conditions at a temperature of 175-300‹ C. for LDPE, 200- 320‹ C. for HDPE, 215-300‹ C. for PP, 225- 300‹ C. for PMP and 275-350‹ C. for PTFE/PE copolymers. The mixing when the siloxane (2) exceeds 55 wt. per cent of the mixture preferably takes place in the presence of oxygen. In examples blends are prepared of each of the materials (1) listed with various proportions of polydimethylsiloxane diol gums containing 2- 15 mol per cent MeViSiO units and in one case 34-62 mol per cent MePhSiO units, in most cases for 20 mins at 180‹ or 185‹ C. for LDPE, 220‹ C. for HDPE, 240‹ C. for PP and PMP, and 305‹ C. for PTFE/PE. The blends are cured with 2 : 5 - dimethyl - 2 : 5 - bis - (t - butylperoxy)hexane to give rubbers.</p> |
