Process for continuous production of a multilayer electric cable

Claim 2

A process for continuously manufacturing a multilayer electric cable comprising the steps of: (a) providing an elongated conductive core; (b) extruding at least one extrudable unvulcanized polymeric material around said elongated conductive core to form at least one layer of inner polymeric material coaxial with and contiguous to said conductive core; (c) extruding an extrudable unvulcanized polymeric material capable of being strippably bonded to said inner polymeric material and comprising: (i) a copolymer of ethylene, alkylacrylate, and monoalkyl ester of 1-4 butenedioic acid; (ii) conductive carbon black; (iii) a curing agent for said copolymer; and (iv) polyethylene or a polyethylene copolymer in an amount not to exceed 50 parts by weight of total polymer; around said inner polymeric material to form a semiconducting outer layer of polymeric material coaxial with and contiguous to said inner polymeric material; (d) simultaneously vulcanizing the combination of said inner and outer unvulcanized polymeric materials in a pressurized, high temperature, dry gas atmosphere; and (e) during said simultaneous vulcanizing step, strippably bonding said outer polymeric material and said inner polymeric material whereby the surfaces of the contiguous layers of said multilayer cable are minimally contaminated, and both the uniformity of adhesion between the layers and the continuity of the electric shield are enhanced.

Claim 3

A process for continuously manufacturing a multilayer electric cable comprising the steps of: (a) providing an elongated conductive core as a center strand; (b) extruding a first extrudable unvulcanized polymeric material around said elongated conductive core to form a strand shield layer of said first polymeric material coaxial with and contiguous to said conductive core; (c) extruding a second extrudable unvulcanized polymeric material around said strand shield layer to form an insulation layer of said second polymeric material coaxial with and contiguous to said strand shield layer; (d) extruding a third extrudable unvulcanized polymeric material capable of being strippably bonded to said insulation layer and comprising: (i) a copolymer of ethylene, alkylacrylate and monoalkyl ester of 1-4 butenedioic acid; (ii) conductive carbon black; (iii) a curing agent for said copolymer; and (iv) polyethylene or a polyethylene copolymer in an amount not to exceed 50 parts by weight of total polymer; around said insulation layer to form a semiconductive outer insulation shield layer of said third polymeric material coaxial with and contiguous to said insulation layer; (e) simultaneously vulcanizing the combination of said first, second and third unvulvanized polymeric materials in a pressurized, high temperature, dry gas atmosphere; and (f) during said simultaneous vulcanizing step, strippably bonding said insulation layer and said insulation shield layer whereby the surfaces of the contiguous layers of said multilayer cable are minimally contaminated and both the uniformity of adhesion between the layers and the continuity of the electric shield are enhanced.

Claim 4

A process for continuously manufacturing a multilayer electric cable comprising the steps of: (a) providing an elongated conductive core as a center strand; (b) extruding a first extrudable unvulcanized polymeric material around said elongated conductive core to form a strand shield layer of said first polymeric material coaxial with and contiguous to said conductive core; (c) extruding a second extrudable unvulcanized polymeric material around said strand shield layer to form an insulation layer of said second polymeric material coaxial with and contiguous to said strand shield layer; (d) extruding a third extrudable unvulcanized polymeric material capable of being strippably bonded to said insulation layer and comprising: (i) a copolymer of ethylene, alkylacrylate and monoalkyl ester of 1-4 butenedioic acid; (ii) conductive carbon black; (iii) a curing agent for said copolymer; and (iv) polyethylene or a polyethylene copolymer in an amount not to exceed 50 parts by weight of total polymer; around said insulation layer to form a semiconductive outer insulation shield layer of said third polymeric material coaxial with and contiguous to said insulation layer; (e) simultaneously vulcanizing the combination of said first, second and third unvulvanized polymeric materials in a pressurized, high temperature, dry gas atmosphere; and (f) during said simultaneous vulcanizing step, strippably bonding said insulation layer and said insulation shield layer whereby the surfaces of the contiguous layers of said multilayer cable are minimally contaminated and both the uniformity of adhesion between the layers and the continuity of the electric shield are enhanced.

Claim 5

A process for continuously manufacturing a multilayer electric cable as in claim 2 wherein the second extrudable unvulcanized polymeric material is the same as the first extrudable unvulcanized polymeric material.

Claim 6

A process for continuously manufacturing a multilayer electric cable as in claim 1 or 2 wherein the high temperature of the dry gas atmosphere is at least about 500° F.

Claim 7

A process for continuously manufacturing a multilayer electric cable as in claim 1 or 2 wherein the dry gas atmosphere is pressurized to at least 75 psig.

Claim 8

A process for continuously manufacturing a multilayer electric cable as in claim 1 or 2 further comprising the step of incorporating a plurality of axially extending drain wires disposed within the semiconducting unvulcanized outer layer after the semiconducting outer layer of polymeric material has been extruded.

Claim 9

A process for continuously manufacturing a multilayer electric cable as in claim 1 or 2 wherein the semiconducting outer layer of extrudable unvulcanized polymeric material comprises, in parts by weight per 100 parts by weight of total polymer: ______________________________________ (a) conductive carbon black 10-150 parts (b) curing agent 1-20 parts (c) polyethylene or polyethylene copolymer 17-50 parts. ______________________________________

Claim 10

A process for continuously manufacturing a multilayer electric cable as in claim 7 wherein the semiconducting outer layer of extrudable unvulcanized polymeric material comprises in parts by weight: ______________________________________ ethylene/acrylate/ester copolymer 50-83 parts polyethylene or polyethylene copolymer 17-50 parts conductive carbon black 10-150 parts curing agent 1-20 parts. ______________________________________

Claim 11

A process for continuously manufacturing a multilayer electric cable as in claim 8 wherein the semiconducting outer layer of extrudable unvulcanized polymeric material further comprises 31-99 parts by weight of additives selected from the group consisting of oxidation resistance improvers, lubricants, and flame retarders.

Claim 12

A process for continuously manufacturing a multilayer electric cable as in claim 8 wherein the semiconducting outer layer of extrudable unvulcanized polymeric material comprises, in parts by weight: ______________________________________ ethylene/acrylate/ester copolymer 75 parts polyethylene or polyethylene copolymer 25 parts conductive carbon black 25 parts curing agent 10 parts. ______________________________________

Claim 13

A process for continuously manufacturing a multilayer electric cable as in claim 8 wherein the semiconducting outer layer of extrudable unvulcanized polymeric material comprises, in parts by weight: ______________________________________ ethylene/acrylate/ester copolymer 75 parts polyethylene or polyethylene copolymer 25 parts conductive carbon black 57 parts curing agent 10 parts. ______________________________________

Claim 14

A process for continuously manufacturing a multilayer electric cable as in claim 10 wherein the semiconducting outer layer of extrudable unvulcanized polymeric material further comprises: ______________________________________ antioxidant 2.0 parts lubricant 4.5 parts flame retarder 49.5 parts. ______________________________________

Claim 15

A process for continuously manufacturing a multilayer electric cable as in claim 11 wherein the semiconducting outer layer of extrudable unvulcanized polymeric material further comprises: ______________________________________ antioxidant 2.0 parts lubricant 4.5 parts flame retarder 49.5 parts. ______________________________________