Kabel-und Metallwerke Gutehoffnungshutte Aktiengesellschaft

Hermann U Voigt

Fritz Glander

Hans-Martin Schmidtchen

Eckard Schleese

Martin Volker

Frank Patzke

Lothar Werwitzke

Hans-Dieter Stenzel

Hans Peter Stehmann

The base material for silance grafting is to be a mixture of at least 50% of a polyolefin (compound A) and of not more than 50% of a different polymer or elastomer serving as property modifier (compound B). The compound A is silane grafted separately or together with compound B. The grafted material is extruded around a conductor or a tube followed by crosslinking in the presence of moisture.

Base material for silane grafted, crosslinked thermoplastic or

A shrink-fit article is made by extruding a silane-grafted polymer which foams, at least at its surface, and cross-links. Upon completion of foaming and cross-linking, the article is expanded while (still) warm and cooled in the expanded state.

Foamed polymeric shrink-fit objects and their process of manufacture

Silane is grafted upon polymer molecules and the material is shaped (e.g., extruded or injection-molded) and caused to cross-link. Both steps must be completed before expanding (following reheating, if necessary) and cooling the object at the expanded state. Cap- and sleeve-making is disclosed, including internal as well as external exposure to water for cross-linking, possibly combined with the requisite preheating for the expansion.

Making shrink-fit objects

Granulated polyethylene is agitated and mixed with a solution of silane with peroxide, activators and anti-oxidants and at a temperature between 80.degree. to 100.degree. C. to obtain diffusion of these additives into the polyethylene particles which is followed by grafting through extrusion or radiation which in turn is followed by exposure to and/or development of water to obtain cross-linking. A catalyst is added preferably by mixing polyethylene powder with the catalyst and adding that powder to the powder with diffused silane, after that diffusion has been completed.

Grafting of silane on thermoplastics or elastomers for purposes of cross

A blend of high and low density polyethylene and azodicarbonamid added as blowing agent is heated in an extruder to a temperature above the melting point of the high density component and fed to a shear head having a hollow rotating mandrel through which tubing is fed for depositing thereon a hose at the nozzle exit of the head. A peroxide is fed to the shear head for mixing with the polymer blend and immediately initiating crosslinking; blowing begins just prior to the depositing, the material being already crosslinked to a considerable extent.

Thermally insulating tubes

A cross-linking polyolefine, preferably a polyethylene powder is mixed with a silane solution (containing additives, such as a graft initiator, activator and anti-oxidant) and heated while worked, so that the wetted powder melts. The silane solution can also be blended into the melting powder. Grafting occurs in the melt and the stream of molten material is then degassed, while still warm in the final work shaping device, e.g. an extruder jacketing a conductor. The resulting product (to the extent it consists of the said material) will then cross-link.

Processing a graft polymer or elastomer

Granulated polyethylene is agitated and mixed with a solution of silane with peroxide, activators and anti-oxidants and at a temperature between 80.degree. to 100.degree. C to obtain diffusion of these additives into the polyethylene particles which is followed by grafting through extrusion or radiation which in turn is followed by exposure to and/or development of water to obtain cross-linking. A catalyst is added preferably by mixing polyethylene powder with the catalyst and adding that powder to the powder with diffused silane, after that diffusion has been completed.

Grafting of silane on thermoplastics or elastomers for purposes of

Siloxane cross-linking of polyethylene is carried out under in situ development of water by chemical reaction between an organic acid and a non-hygroscopic metal oxide producing a neutral salt and water. Specifically, an ester peroxide is used as additive to be mixed with silane and polyethylene. The ester peroxide decomposes during grafting in free acid, alcohol and graft initiators for obtaining the grafting of silane on polyethylene, and the acid reacts with zinc oxide or tin oxide, also used as additive, to obtain salt and water. Alternatively, stearic acid or adipic acid and zinc oxide or tin oxide are added to a polyethylene silane mixture to develop water and salt of the acid.

Preparing thermo-plastic or elastomeric materials for cross-linking of

A stranded filament bundle is coated with a cross-linking plastic that contains carbon black followed by enveloping in a plastic that cross-links in the presence of moisture. The inner coating will cross-link either when the outer layer cross-links by water treatment; or by conduction of heat in the extruder for the outer layer; or by microwave heating.

High voltage cable

Insulation is extruded onto a conductor and immediately quench-cooled to obtain solidification for retaining concentricity of conductor and envelope. The envelope is reheated under pressure to melt a surface zone, followed by gradual cooling whereby the melted zone migrates into the interior. Reheating under pressure and gradual cooling, possibly also under pressure, improves texture, and provides for a more ordered crystal structure and/or fuller crosslinking. Following extrusion, and on reheating, the cable is freely suspended and assumes catenoidal contour while advancing to avoid sliding contact of the outer surface until adequately stable solidification has taken place.

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Langenhagen, Germany

Hermann U Voigt