Patent ID: 6053214
Filing Date: 2000-04-25
Classification: B29C,B29K,B29L,B32B,F16L

Abstract:
A method of forming and continuously orienting an article comprising a crystalline or semi-crystalline thermoplastic polymeric material(s) at a temperature greater than the crystalline melting temperature of raid material(s), which comprises the steps of:adding a chemically reactive substance(s) to the polymeric material before or during forming of either the entire article, or to one or more layers of a multilayer article, or to axial or helical stripes of the article, or to certain segments of the article in the axial direction;plasticizing and forming a parison of the polymeric material(s) thus prepared at a temperature not high enough to activate the reaction of the said reactive substance(s);optionally, inducing shear at least to the layer(s) where the chemically reactive substance(s) have been added to and/or stretching the still soft parison in one or both of two directions, simultaneously or stepwise, said stretching including axial draw to effect thermoplastic orientation of the material in the longitudinal direction of the parison and/or radial expansion to effect thermoplastic orientation of the material in the hoop direction of the parison;decreasing the mobility of the molecules in the layer(s) to be oriented by activating a chemical reaction between the chemically reactive substance(s) and the polymeric material(s) having the chemically reactive substance(s) added thereto when the polymeric material(s) still is/are in a molten state;inducing shear at least to the product, layer(s), stripes, or segments to which the chemically reactive substance(s) have been added and/or stretching the still soft, at least partly reacted parison in two directions, simultaneously or stepwise, said stretching comprising axial draw to effect orientation of the material in the longitudinal direction of the parison and radial draw to effect orientation of the material in the transverse direction of the parison;calibrating and cooling the parison in the oriented condition to make the orientation permanent at least in the layer(s) where the chemical reaction(s) has taken place.