Abstract A polyethylene having a molecular weight in excess of 1,000,000 or a polypropylene having a molecular weight in excess of 400,000 can be easily extruded by this invention. A heterogeneous composite of either polyolefin and a carrier is established and supplied to an extruder comprising a transport screw having a surface providing frictional resistance to the movement of the composite no greater than that of polished steel and a die having a surface providing lower frictional resistance to the movement of the composite than polished steel. Within the die the heterogeneous composite is first shaped at a temperature below the melting point of the polyolefin and then is heated until the composite becomes homogeneous, after which the shape is cooled to solidify. The carrier can be a petroleum wax, certain liquid hydrocarbons, synthetic wax or mixtures thereof having certain attributes, defined herein, relative to the polyolefin.
A method according to claim 1 wherein the composite during passage through the die in steps (d) and (e) contacts die surfaces composed of a material selected from polyimide polymer, fluorocarbon polymer and chromium.
Claim 2
Dependent Claim
24 words
A method according to claim 2 wherein the composite in step (c) is transported through contact with chromium plated surfaces of the transport screw.
Claim 3
Dependent Claim
13 words
A method according to claim 1 wherein the carrier is a petroleum wax.
Claim 4
Dependent Claim
23 words
A method according to claim 1 wherein the polyolefin is polyethylene having a molecular weight in the range between from 1,000,000 to 6,000,000.
Claim 5
Dependent Claim
53 words
A method according to claim 5 wherein the composite in step (c) is transported through contact with chromium plated surfaces of the transport screw and wherein the composite during passage through the die in steps (d) and (e) contacts die surfaces composed of a material selected from polyimide polymer, fluorocarbon polymer and chromium.
Claim 6
Dependent Claim
23 words
A method according to claim 1 wherein the polyolefin is polypropylene having a molecular weight in the range between from 400,000 to 2,000,000.
Claim 7
Dependent Claim
53 words
A method according to claim 7 wherein the composite in step (c) is transported through contact with chromium plated surfaces of the transport screw and wherein the composite during passage through the die in steps (d) and (e) contacts die surfaces composed of a material selected from polyimide polymer, fluorocarbon polymer and chromium.