Tetra Pak Developpement Sa

Peter P Hoj

A method for the molecular orientation of plastic material by expanding a tube of plastic material, includes introducing the tube into a container filled with heated liquid, preferably water of a temperature of 70.degree.-100.degree. C. The tube is expanded by introducing a pressurized liquid into the tube. An apparatus for carrying out the method and a plastic material are also disclosed.

Method for the molecular orientation of plastic material

A web of thermoplastic material and a method and apparatus for manufacture of the web are disclosed with the web having a repeating pattern of alternately thick and thin portions. A molten thermoplastic material is extruded through a duct between a first rotatable driven roll and a circular-cylindrical seat. The first driven roll includes a surface having a pattern of recessed portions. The web is transferred from the first driven roll to a second driven roll having a smooth surface. The temperatures of the first and second rolls may be selectively maintained. The thermoplastic material may be extruded through a plurality of ducts leading to the surface of the first driven roll. Transfer of the web from the first roll to the second may be encouraged by means of a vacuum. Furthermore, complete filling of the recesses of the first driven roll by the thermoplastic material may be encouraged by the use of a vacuum.

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Espergarde, Denmark

Peter P Hoj