Shawcor Ltd.

Shaw Industries, Inc.

Marcus P Heydrich

Peter Jackson

Robert Edward Steele

Dilip K Tailor

Amarjit Tathgur

Karen Schnuelle

Robert E Steele

An article suitable for use as an insulating or coating material comprises a radiation-crosslinked composition comprising a polyethylene, a polypropylene and optionally an ethylene-propylene elastomer. The polyethylene component is selected from high density polyethylene (HDPE), medium density polyethylene (MDPE) and linear medium density polyethylene (LMDPE) and the polypropylene component is either a homopolymer or copolymer. The composition is predominantly based on the polyethylene component and contains the polyethylene component in an amount of at least 50 percent by weight. The article is radiation-crosslinked to a sufficient degree that it possesses thermoset properties, such that when the article is heated to a temperature above the crystalline melting point of the polypropylene homopolymer or copolymer, it is softened but does not become liquid. The article is formed by first blending the polyethylene, polypropylene and optionally the ethylene-propylene elastomer, melt processing the blend to produce an article, crosslinking the article by exposing it to radiation, and optionally heating, stretching and cooling the article to impart heat shrinkability to the article.

Radiation-crosslinked polyolefin compositions

A crosslinked, predominantly polypropylene-based article comprises a silane-modified ethylene-based polyolefin, at least 50 percent by weight of a non silane-modified polypropylene, and a silane condensation catalyst. The article is moisture crosslinked to a sufficient degree that it possesses thermoset properties such that, when the article is heated to a temperature above the crystalline melting point of the non silane-modified polypropylene, it is softened but does not become liquid. The article preferably comprises a heat-shrinkable sleeve for a high-temperature transmission pipeline.

Crosslinked, predominantly polypropylene-based compositions

A heat-shrinkable article suitable for use as an insulating or coating material comprises a crosslinked composition of a polypropylene homopolymer or copolymer and an ethylene-propylene elastomer. The article is formed by a process comprising: i) creating a blend of the polypropylene homopolymer or copolymer and the ethylene-propylene elastomer by melt mixing; ii) melt processing the blend produced in i) to produce a melt processed material; iii) crosslinking the melt processed material produced in ii) by exposing it to radiation to produce a crosslinked material; iv) stretching the crosslinked material at a first temperature close to or above its softening or melting point and subsequently cooling it to a second temperature below its softening or melting point, to thereby freeze the crosslinked material in its stretched form. Subsequent heating of the article close to or above its softening point or crystalline melting point results in recovery of the pre-stretched dimensions of the article. Due to its relatively high content of polypropylene, the heat-shrinkable article thus produced has greater toughness and rigidity than polyethylene-based systems, making it suitable for use as insulation for wires and cables a heat-shrinkable corrosion resistant sleeves for high-temperature transmission pipeline joints, and for heat-shrinkable tubing or shapes for electrical insulation and mechanical protection.

Crosslinked, heat shrinkable polypropylene compositions

A tracking resistant electrical insulating material or article suitable for medium to high voltage applications comprising a silane-modified polyolefin, and a heat-shrinkable article prepared therefrom. Said material or article is preferably prepared by a process comprising: (a) reacting polyolefin with a silane in the presence of a free-radical initiator to form a silane-grafted polyolefin, or copolymerising a polyolefin with silane; (b) preparing a mixture of one or more silane-modified polyolefins prepared in (a) with optionally one or more non silane-modified polyolefins, antitrack ingredients, and a silanol condensation catalyst; (c) forming the insulating material or article by melt extruding or moulding said mixture; and (d) crosslinking the insulating material or article by exposing it to moisture, preferably at elevated temperature. The silane-modified, moisture-crosslinkable polyolefin provides the insulating material with high resistance to tracking even in the absence of conventional anti-tracking fillers.

Tracking-resistant, electrical-insulating material containing silane-modified polyolefins

A moisture-crosslinkable polyolefin material, comprising a silane-grafted polyolefin blend, and coatings or insulations, including heat-shrinkable coatings and insulations, prepared therefrom. The coating material is formed by a process comprising: (a) reacting a pre-blended mixture of polyolefin and polypropylene, or higher polyolefin, resins and optional compatibilizing agent, with an appropriate silane and silane-grafting initiator to produce a silane-modified polyolefin blend composition; (b) forming the coating or insulating material by melt processing the composition produced in step (a) with a silanol condensation catalyst; and (c) crosslinking the formed coating or insulating material by exposing it to moisture, preferably at an elevated temperature.

Crosslinked compositions containing silane-modified polypropylene blends

A moisture-crosslinkable polypropylene material, comprising silane-grafted polyolefin or olefin-silane copolymer and non silane-modified polypropylene homopolymer or copolymer; and coatings or insulations, including heat-shrinkable coatings and insulations, prepared therefrom. The coating material is formed by a process comprising: (a) reacting polyolefin with a silane in the presence of a free-radical initiator to form a silane-grafted polyolefin, or copolymerizing a polyolefin with silane; (b) preparing a mixture of the silane-modified polyolefin prepared in (a) with polypropylene homopolymer or copolymer, and a silanol condensation catalyst; (c) forming the coating or insulating material by melt processing the mixture formed in step (b); and (d) crosslinking the coating or insulating material by exposing it to moisture, preferably at an elevated temperature.

Crosslinked compositions containing silane-modified polyolefins and polypropylenes

Heat-shrinkable cap comprising a heat-shrinkable tube sealed at one end by heat recovering that end of tube over a dimensionally stable, solid plug. The tube and plug are mutually weldable under heat, or are bonded together, thereby providing an air and water-tight seal at the sealed end. The open end of the cap may be internally coated with adhesive to provide an air and water-tight seal over an object such as a cable-end when the cap is heat recovered over said object.

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Mississauga, Canada

Marcus P Heydrich