Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
1998-02-17
2001-03-06
Merriam, Andrew E. C. (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C523S215000, C523S351000, C524S424000, C524S521000, C524S524000, C524S566000, C524S495000, C428S380000, C428S383000
Reexamination Certificate
active
06197848
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a composition comprising a treated filler material, preferably a treated carbonaceous filler material, a crosslinking agent and an ethylene containing polymer. A preferred treated filler material comprises carbon black and preferred ethylene containing polymers are ethylene-vinyl acetate (EVA), ethylene-propylene (EPR) and ethylene propylene diene monomer (EPDM).
BACKGROUND OF THE INVENTION
The treating of carbon black with polymeric binders is disclosed in the art. Previous patents disclose the art of incorporating additives to produce pelletized treated filler materials, in particular pelletized treated carbon blacks, with improved handling characteristics, for example, low dust.
The construction of insulated electrical conductors, i.e., wire and cables designed for medium and high voltage applications, is known in the art. Typical constructions include a core conductor which comprises one or more strands of a conducting metal or alloy such as copper or aluminum; a layer of a semiconductive shielding compound; a layer of insulation such as crosslinked polyethylene or ethylene-propylene rubber and a layer of a semiconductive insulation shield compound overlaying the insulation.
The conductor shield, the insulation shield and the overlaying semiconductive shield layer may be formed by either a two pass or by a single pass triple extrusion process. A two pass operation refers to a process whereby the conductor shield and the insulation layer are extruded in tandem and then crosslinked prior to extrusion of the semiconductor insulation layer. A single pass triple extrusion process refers to a process in which the conductor shield, the insulation layer and the semiconductive shield are all extruded in a common extrusion head and crosslinked simultaneously. The single pass triple extrusion process minimizes production steps and hence is a preferred method of manufacture. However, the single pass triple extrusion process generally makes the semiconductive shield layer more fully bonded to the insulation layer, than in a two pass operation.
Generally, in order to splice insulated electrical wires, or make terminal connections, the semiconductive shield layer should be stripped from the insulation layer. Stripping the semiconductive shield layer from the insulation shield layer is often very difficult. In a situation where the semiconductive shield layer contains carbon black, a carbon containing residue on the surface of the insulation shield often results. The carbon residue may disadvantageously promote treeing in the insulation layer which will ultimately lead to electrical breakdown of the cable. It is therefore advantageous and desirable for a semiconductive shield layer to have a low strip force (be easily separable) when being removed from the insulation layer and for the semiconductive shield layer to leave minimal amounts of carbon residue on the surface of the insulation shield.
Strippable conductive shield compositions are those which can be separated from a crosslinked insulation layer without leaving appreciable amounts of residue on the insulation layer. Usually, the force required to separate a strippable conductive shield composition is significantly lower than the separation force required for bonded shield compositions.
There is a significant cost difference between strippable and bonded semiconductive shield compositions based on existing technological approaches. It would be advantageous, to produce more cost effective strippable formulations than those developed from the technical approaches utilized to date.
SUMMARY OF THE INVENTION
The present invention provides a composition comprising:
25-75%, by weight, based on the total weight of the composition, of an ethylene containing polymer;
24-74%, by weight, based on the total weight of the composition, of a treated filler material; and
1-10%, by weight, based on the total weight of the composition, of a crosslinking agent;
wherein the treated filler material comprises 0.05-40%, by weight, based on the weight of the treated filler material, of a treating agent, and said treating agent is a polymer comprising acrylonitrile and at least one monomer selected from butadiene, isoprene, ethylene, propene, butene, hexene, octene, styrene, vinyl toluene, alpha methyl styrene, vinylidene chloride, vinyl chloride, acrylic acid, a C
1
-C
8
alkyl ester of acrylic acid, methacrylic acid, or a C
1
-C
8
alkyl ester of methacrylic acid; with acrylonitrile comprising 0.5-55%, by weight, based on the weight of the treating agent.
Preferably the ethylene containing polymer is: an ethylene vinyl acetate (EVA) polymer, ethylene propylene rubber (EPR) or ethylene propylene diene monomer (EPDM). More preferably, the ethylene containing polymer is an EVA polymer wherein the EVA polymer comprises 16-55%, by weight, based on the weight of the EVA polymer of a vinyl acetate monomer. A preferred treated filler material is a treated carbonaceous material, more preferably a treated carbon black. A preferred treating agent comprises: acrylonitrile and butadiene. More preferably, the treating agent comprises an acrylonitrile butadiene, or a carboxylated acrylonitrile butadiene polymer containing 20-55%, by weight, based on the weight of the treating agent, of an acrylonitrile monomer. Preferred crosslinking agents are an organic peroxide, such as dicumyl peroxide, sulfur, or a sulfur donor system. A preferred composition of the present invention is semiconductive.
The present invention also includes an article of manufacture produced utilizing the composition of the present invention. A preferred article of manufacture is cable insulation comprising a semiconductive composition of the present invention bonded to an insulation layer, wherein the insulation layer preferably includes an ethylene homopolymer or copolymer.
An advantage of the compositions of the present invention which are semiconductive is that the semiconductive compositions may be utilized as strippable semiconductive shield compositions in wire and cable insulation applications.
Further details and advantages of the present invention are set forth in the following more detailed description.
DETAILED DESCRIPTION OF THE INVENTION
According to the present invention, a composition comprises:
25-75%, by weight, based on the total weight of the composition, of an ethylene containing polymer;
24-74%, preferably 30-45%, by weight, based on the total weight of the composition, of a treated filler material; and
1-10%, preferably 1-6%, by weight, based on the total weight of the composition, of a crosslinking agent;
wherein the treated filler material comprises 0.05-40%, preferably 0.5-20%, more preferably 4-15%, by weight, based on the weight of the treated filler material, of a treating agent, and said treating agent is a polymer comprising acrylonitrile and at least one monomer selected from: butadiene, isoprene, ethylene, propene, butene, hexene, octene, styrene, vinyl toluene, alpha methyl styrene, vinylidene chloride, vinyl chloride, acrylic acid, a C
1
-C
8
alkyl ester of acrylic acid, methacrylic acid, or a C
1
-C
8
alkyl ester of methacrylic acid; with acrylonitrile comprising 0.5-55%, preferably 20-55%, more preferably 30-45%, by weight, based on the weight of the treating agent.
The ethylene containing polymer of the composition of the present invention is preferably: an ethylene vinyl acetate (EVA) polymer, ethylene propylene rubber (EPR) or ethylene propylene diene monomer (EPDM). More preferably, the ethylene containing polymer is an EVA polymer wherein the EVA polymer comprises 16-55%, preferably 18-45%, by weight, based on the weight of the EVA polymer of a vinyl acetate monomer.
A preferred treated filler material is a treated carbonaceous material, more preferably a treated carbon black. A preferred treating agent comprises: acrylonitrile and butadiene. More preferably, the treating agent comprises an acrylonitrile butadiene, or carboxylated acrylonitrile butadiene polymer containing 20-55%, by weight, based on t
Reed Thomas F.
Whitehouse Robert S.
Cabot Corporation
Merriam Andrew E. C.
LandOfFree
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