Method for extruding profiled sections of expanded thermo plastic material having an integral skin

Claim 1

The method of claim 1 wherein the cavity inside the extruded material is produced by a mandrel coaxial with the die and disposed therein.

Claim 9

A method of producing a foamed extruded thermoplastic material product, the thermoplastic material being selected from the group consisting of polystyrene, polyvinyl chloride, polyethylene, acrylonitrile-butadiene-styrene copolymer, polyamides, polycarbonates, polyurethanes, styrene-acrylonitrile copolymers, polymethyl methacrylate, polyPropylene, cellulose propionate, and mixtures thereof, wherein the thermoplastic material with an expanding agent therein is extruded from a die outlet into and through a shaper, the shaper having an internal solid surface defining a channel, the channel having an inlet and an outlet, the inlet edge of the shaper channel substantially coinciding with outlet edges of the die, the channel area of the inlet circumscribing and being larger than the area of the die outlet thereby forming a void in the channel for expansion of the thermoplastic material, the channel outlet cross-section being substantially that of the product required, and the channel having substantially the same cross-sectional size and shape along its full length, cooling the internal solid surface of the shaper to a temperature below the softening point of the thermoplastic material, extruding the foamable thermoplastic material through the die outlet, the temperature of the thermoplastic material being in the range from 70* to 210*C, the extruded material having an external surface thereon, immediately contacting said external surface with the cooled internal solid surface of the shaper, thereby cooling rapidly said external surface below the softening point of the thermoplastic material to retard foaming of the extruded material along the entire length of the extruded product and to form a thick skin of higher density material thereon, thereby forming a continuous area of thick skin on the external surface of the extruded product and imparting sufficient mechanical strength thereto in the shaper to permit it to be extruded through the shaper, and expanding the extruded material from the external surface with the thick skin thereon toward the inside of the shaper channel to substantially fill the channel.

Claim 12

A method of producing a foamed extruded thermoplastic material product, the thermoplastic material being selected from the group consisting of polystyrene, polyvinyl chloride, polyethylene, acrylonitrile-butadiene-styrene copolymers, polyamides, polycarbonates, polyurethanes, styrene-acrylonitrile copolymers, polymethyl methacrylate, polypropylene, cellulose propionate, and mixtures thereof, wherein the thermoplastic material with an expanding agent therein is extruded from a die outlet into and through a shaper, the shaper having an internal solid surface defining a channel, the channel having an inlet and outlet, the inlet perimeter of the shaper substantially coinciding with outlet edges of the die for substantially the entire perimeter of the inlet of the shaper, the cross-sectional area of the shaper being substantially larger than the cross-sectional area of the die outlet, thereby providing a void in the channel for the expansion of the thermoplastic material, the channel outlet cross-section being substantially that of the product required, and the channel having substantially the same cross-sectional size and shape along its full length, cooling the internal solid surface of the shaper to a temperature below the softening point of the thermoplastic material, extruding the foamable thermoplastic material through the die outlet, the temperature of the thermoplastic material being in the range from 70* to 210*C, immediately contacting the external surface of the extruded thermoplastic material with the cooled internal solid surface of the shaper, thereby cooling rapidly the external surface of the thermoplastic material below the softening point of the thermoplastic material to retard foaming of the extruded material on the external surface and to form a thick skin of higHer density material thereon, thereby imparting sufficient mechanical strength to the extruded product in the shaper to permit it to be extruded through the shaper, and expanding the extruded material toward the inside of the channel to at least partially fill said void.