Dupont Canada Inc.

Du Pont of Canada Limited

David A Harbourne

John R Boocock

Evelyn M Lundhild

Stephen Peter Beaton

Mark G Dokurno

A concentrate comprising a carrier polymer and at least 30%, by weight of the carrier polymer, of at least one modifying agent for a thermoplastic polymer is disclosed. The carrier polymer is a polymer of alpha-olefins having a heat of crystallization of less than 70 J/g and, if the copolymer is an ethylene/vinyl acetate copolymer, containing at least 18% by weight of vinyl acetate comonomer. The modifying agent is absorbed into the carrier polymer. In embodiments, the modifying agent is a polymerizable monomer. The concentrates provide a versatile method of addition of modifying agents into thermoplastic polymers.

Concentrates of modifying agents in polymers

A concentrate comprising a copolymer and 65 to 300%, by weight of the copolymer, of a vinyl silane is disclosed. The vinyl silane is vinyl trimethoxysilane and/or vinyl triethoxysilane. The copolymer is a copolymer of ethylene with at least one comonomer selected from the group consisting of carbon monoxide, vinyl acetate, alkyl acrylates and alkyl methacrylates, in which the alkyl groups have 1-4 carbon atoms. The copolymer is in a particulate form and has a heat of crystallization of less than 70 J/g, and if said copolymer is ethylene/vinyl acetate copolymer, then the copolymer has a vinyl acetate content of at least 18% by weight. The concentrate is maintained in a moisture-free environment and is in solid form. The concentrates are used in the moisture cross-linking of alpha-olefin polymers and offer versatility in processes for such cross-linking.

Moisture cross-linking of polymers

Filled thermoplastic compositions are disclosed. The compositions comprise (a) 30 to 90 parts of homopolymers of ethylene and/or copolymers of ethylene and C3-C10 alpha-olefins, (b) 10 to 70 parts of homopolymers of ethylene and/or copolymers of ethylene and C4-C10 alpha-olefins modified by grafting with ethylenically unsaturated carboxylic acids or anhydrides thereof, the blend of (a) and (b) having a melt index of less than 15 dg/min. and (c) 20 to 70 percent, based on the amount of (a) and (b) of a filler. The filler is selected from magnesium hydroxide, calcium hydroxide, aluminum trihydrate and hydroxyl-containing carbonates of at least one of magnesium and calcium, and mixtures thereof. The compositions exhibit a useful combination of stiffness and toughness, especially as measured by impact strength and tensile strength.

Filled thermoplastic polymer compositions

A fire-retardant sheet material, the manufacture thereof and a fire-retardant polymer composition are disclosed. The sheet is manufactured from a composition of polyethylene, 55 to 75% by weight of the composition of alumina trihydrate and/or magnesium hydroxide, and optionally zinc borate and/or calcium carbonate, at least 2% by weight of the composition being in the form of a graft copolymer with an ethylenically unsaturated carboxylic acid or anhydride. The composition has a melt index of 0.05 to 4.0 dg/min. In an embodiment, the graft copolymer has a shear viscosity at 200.degree. C. and a shear rate of 400 sec.sup.-1 that is not more than 50% of that of the polyethylene. The sheet material may be used for, in particular, ceiling tile. In embodiments of the composition, 60 to 90% by weight may be alumina trihydrate and/or magnesium hydroxide, and optionally zinc borate and/or calcium carbonate.

Fire-retardant sheet material

The present invention provides a process for the manufacture of a polyethylene film having improved tear strength in the transverse direction. The process involves extruding a partially crosslinked polyethylene into film having a thickness between 10 and 100 .mu.m, by a blown film process. The blow-up ratio is in the range of 1.2:1 to 4:1 and the MD draw-down ratio is in the range of 2 to 60. Polyethylenes used in the present invention had prior to being partially crosslinked a density in the range of 0.940 to 0.970 g/cm.sup.3 and a melt index in the range of 0.2 to 15.0 g/10 min. The polyethylene is crosslinked to an extent sufficient to provide a film having an Elmendorf tear strength in the transverse direction substantially less than the tear strength of film made from the uncrosslinked polyethylene. Crosslinking may be accomplished using any known method e.g. by irradiation, through use of crosslinking agents. The film so produced is useful in packaging operations where transverse cutting or tearing performance of the film is important.

Manufacture of film from partially crosslinked polyethylene

A process for the extraction of nickel values from a nickel oxide/silicate ore having a high magnesia/low iron oxide content, e.g. 15-50% magnesia and 0-20% iron oxide by contacting the ore with an aqueous polyalkylenehexamine solution in the presence of oxygen. The general formula for the polyalkylenehexamine is NH.sub.2 (CH.sub.2).sub.n NH(CH.sub.2).sub.m NH(CH.sub.2).sub.n NH(CH.sub.2).sub.m NH(CH.sub.2).sub.n NH.sub.2 where n and m are 2 or 3, n and m being the same or different. Preferably n is 2 and m is 3.

Extraction of nickel from nickel-bearing ores

A process for the treatment of lead sulphide with an aqueous solution of sulphur dioxide at a temperature of at least 20.degree. C and in the absence of oxygen is disclosed. In a preferred embodiment the lead sulphate and/or lead sulphite so formed is heated with lead sulphide at a temperature of 700.degree. to 1200.degree. C in the absence of oxygen. Metallic lead is obtained. In the preferred embodiment the lead sulphide may contain zinc sulphide whereby both metallic lead and metallic zinc may be obtained.

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Kingston, Canada

David A Harbourne