초록 ▼

Method for producing large size, low density, elongated thermoplastic cellular bodies comprising the steps of forming a mixture of a thermoplastic polymer and a blowing agent dissolved therein under pressure and at a temperature at which the viscosity of the mixture is sufficient to retain the blowi

Method for producing large size, low density, elongated thermoplastic cellular bodies comprising the steps of forming a mixture of a thermoplastic polymer and a blowing agent dissolved therein under pressure and at a temperature at which the viscosity of the mixture is sufficient to retain the blowing agent when the mixture is allowed to expand, extruding said mixture into a holding zone under conditions that prevent said mixture from foaming, the holding zone having an outlet die orifice opening into a zone of lower pressure and temperature at which said mixture foams and an openable gate closing the die orifice; periodically opening said gate and substantially concurrently applying mechanical pressure by a movable ram on the mixture, preferably while scraping the sides of the holding zone with said ram, to eject the mixture from the holding zone through the die orifice at a rate in excess of that at which substantial foaming in the die orifice occurs and less than that at which substantial irregularities in the cross-sectional area or shape of the cellular body occurs; and permitting the ejected mixture to expand unrestrained in at least one dimension to produce the elongated thermoplastic cellular body. Apparatus for producing elongated thermoplastic cellular bodies comprising an extruder for feeding a mixture of thermoplastic polymer and plasticizing blowing agent at a temperature suitable for producing a cellular body when the mixture is subjected to lower pressure; an expandable holding chamber receiving said mixture from the extruder and maintaining the mixture in a molten state at a pressure above the foaming pressure thereof, ram means for ejecting the mixture out of the chamber; a die having an orifice, preferably in line with the ram means, through which the mixture is ejected by operation of the ram means, and gate means contacting the exterior surface of the die for closing and sealing the die orifice while the holding chamber is being filled.

대표청구항 ▼

In a method for the production of an elongated, thermoplastic cellular body from a foamable mobile gel, that improvement providing low density, elongated cellular bodies of large lateral cross-sectional area comprising: forming a mixture of a thermoplastic polymer and, dissolved therein under pressu

In a method for the production of an elongated, thermoplastic cellular body from a foamable mobile gel, that improvement providing low density, elongated cellular bodies of large lateral cross-sectional area comprising: forming a mixture of a thermoplastic polymer and, dissolved therein under pressure, a blowing agent, said mixture having a temperature at which the viscosity of said mixture is sufficient to retain said blowing agent when said mixture is allowed to expand; extruding said mixture into a holding zone maintained at a temperature and pressure which does not allow the resulting mixture to foam, said holding zone having an outlet die defining an orifice opening into a zone of lower pressure at which said mixture foams, and an openable gate closing said die orifice; periodically opening said gate and substantially concurrently applying mechanical pressure by a movable ram on said mixture to eject said mixture from said holding zone through said die orifice into said zone of lower pressure, at a rate greater than that at which substantial foaming in said die orifice occurs and less than that at which substantial irregularities in cross-sectional area or shape occurs; and permitting said ejected mixture to expand unrestrained in at least one dimension to produce an elongated thermoplastic cellular body.