Dupont Canada Inc.

George White

David C King

Rupert M Lillis

Joining of metallic pipe lined with thermoplastic polymer

An improved method of inserting a liner into a metallic pipeline is disclosed. The liner is formed from a plurality of concentric tubes that are enveloped in a flexible, expansible, tear resistant material. When the concentric tubes are pulled into the pipeline, the tear resistant material provides protection against tearing of the tubes by burrs, snags or other imperfections on the inside of the metallic pipeline. The tear resistant material may be a fabric, woven material or mesh. Materials having a structure that permits escape of fluid entrapped during subsequent expansion of the concentric tubes on formation of the liner are preferred. The method permits the lining of pipeline sections that have bends, loops or the like, while protecting the liner from tearing during insertion into the pipeline.

Method of lining metallic pipe using concentric tubes of thermoplastic

This invention relates to an injection moulding process for the manufacture of multi-layered articles, especially articles having barrier properties. The process includes clamping a thermoplastic film over the cavity of a mould of an injection moulding process, the film being capable of being stretched. The film is then stretched within the mould by inserting the core of the mould, preferably using a core in which a central part enters the mould and partially stretches the film prior to the remainder of the core entering the mould. The mould is then closed, excess film is trimmed off and polymer is injected into the mould cavity. The resultant article is a multi-layered injection moulded article which, depending on the characteristics of the film and injected polymer, may have barrier properties to oxygen, liquids or the like that are superior to articles moulded from only the polymer. The process is particularly useful in the moulding of containers having a depth:width ratio of at least 0.5.

Process for the injection moulding of multi-layered articles

A method of lining of metallic pipe is disclosed. The method comprises forming a plurality of concentric flexible tubes of a thermoplastic polymer, such tubes being capable of being bonded together under the influence of heat and pressure. The plurality of concentric tubes is inserted into a section of metallic pipe that is to be lined. The tubes are then heated, especially under pressure e.g. using steam, to cause the tubes to bond together to form a single tube lining the pipe. Adhesives may be used to facilitate bonding. The method is particularly useful in the lining of metallic pipe that has bends, loops or the like.

Method of lining of metallic pipe using a plurality of concentric

A polyolefin blend comprising, in physical admixture, a major portion of particles of a first polyethylene and a minor portion of particles of a composition of a second polyethylene, is disclosed. The first polyethylene is selected from the group consisting of homopolymers of ethylene and copolymers of ethylene and at least one C.sub.4 -C.sub.10 higher alpha-olefin, and the second polyethylene is a copolymer of ethylene and at least one C.sub.4 -C.sub.10 higher alpha-olefin having a density of at least 0.890 g/cm.sup.3, especially at least 0.910 g/cm.sup.3, and a melt index of at least 40 dg/min. The density of the second polyethylene is at least about 0.005 g/cm.sup.3 lower than that of the first polyethylene and the melt index of the second polyethylene is at least 10 dg/min. higher than that of the first polyethylene. The composition of the second polyethylene contains an agent that is capable of reacting with polyolefins that are in a molten state. Such agents are selected from the group consisting of cross-linking agents and modifying agents, and mixtures thereof. In an alternative embodiment, the second polyethylene has a shear viscosity that is not more than 30% of that of the first polyethylene at 200.degree. C. and a shear rate of 400 sec.sup.-1 ; in this regard, the first and second polyethylene may be more broadly defined as being homopolymers and copolymers of hydrocarbon alpha-olefins having 2-10 carbon atoms. The blends may be used in a wide variety of processes, including blow-moulding processes, film and pipe extrusion processes, sheet thermoforming processes and rotational moulding processes.

Polyolefin blends containing reactive agents

A composition particularly adapted for use in a rotational moulding process is disclosed. The composition comprises polyethylene having a density of 0.920-0.970 g/cm.sup.3 and a melt index of 10-35 dg/min., 0.3-1.3% by weight of a bis(tert. alkyl peroxyalkyl) benzene, 0.2-1.5% by weight of a co-curing agent selected from triallyl cyanurate, triallyl isocyanurate and 1,2-polybutadiene, 0.01-0.05% by weight of a hindered phenolic antioxidant and 0.01-0.2% by weight of a secondary antioxidant. The preferred secondary antioxidant is tris di(tert.-butyl phenyl) phosphite. The composition may be used in for example, the moulding of tanks, barrels, containers and the like.

Cross-linkable polyethylene compositions

A process is provided for coating of substrate webs with polyethylene wherein the edge thickening and other processing difficulties caused by the necking-in phenomenon are minimized. The process comprises extruding a polyethylene having a melt index between 30 dg/min and 100 dg/min through a slot in a slotted die in the form of a sheet onto the moving substrate web to form the coated web, and passing the coated web through a nip roll assembly comprising a chill roll and a nip roll, the slotted die having at the extremities of the slot therein edge guides which are maintained at a temperature above the melting temperature of the polyethylene and are contoured to guide the adhered edges of the extruded sheet into the throat of the nip roll assembly.

Growing community of inventors

Glenburnie, Canada

George White