Method for the selective absorption of a volatile liquid foaming agent by heating in forming plastic articles

Abstract

Abstract IMPROVEMENTS IN FORMING AN INTEGRAL FOAM LAYER ON THE OUTER SURFACE OF THE SIDEWALL OF A THIN WALLED THERMOPLASTIC CONTAINER WHICH INVOLVES CONTACTING THE INNER SURFACE OF THE CONTAINER OPPOSITE THE OUTER SURFACE PORTION TO BE FOAMED, PRIOR TO EXPOSURE TO THE FOAMING AGENT, WITH AN ELEVATED TEMPERATURE SURFACE TO PREHEAT THE WALL PORTION OF THE CUP WHICH IS TO BE FOAMED, THEREBY INCREASING THE RATE OF PENETRATION OF THE FOAMING AGENT INTO THE THERMOPLASTIC DURING ITS SUBSEQUENT EXPOSURE AND PREFERABLY AVOIDING THE NECESSITY OF A PEROID OF AGING THE CONTAINER AFTER ITS REMOVAL FROM EXPOSURE TO THE FOAMING AGENT AND PRIOR TO FOAMING. THE ELEVATED TEMPERATURE SURFACE IS PREFERABLY THAT OF A MANDREL CONFORMING IN SHAPE TO THE INNER SURFACE OF THE CONTAINER AND WHICH MAY HAVE RELIEVED AREAS THEREON WHICH DO NOT CONTACT AND THEREFORE, DO NOT HEAT THE WALL OF THE CONTAINER, THEREBY LEAVING UNFOAMED, INDICIA BEARING OR PATTERNED PORTIONS WITHIN THE FOAM BOUNDARY AFTER VAPORIZATION OF THE FOAMING AGENT. AN ADDITIVE MAY BE INCORPORATED INTO THE FOAMING AGENT TO DECREASE THE RATE OF GNERATION OF THE FOAM CELLS DURING FOAMING AND TO IMPROVE THE UNIFORMITY OF CELL SIZE OR, WHEN THE RELIEVED SURFACE MANDREL IS USED, A DYE WHICH VAPORIZES AT SUBSTANTIALLY THE TEMPERATURE OF THE FOAMING AGENT MAY BE EMPLOYED TO GENERATE A FOAM LAYER OF ONE COLOR HAVING AN INDICIA BEARING OR PATTERNED AREA OF ANOTHER COLOR. THE THERMOPLASTIC OF THE CONTAINER PREFERABLY HAS A COLORING PIGMENT INCORPORATED THEREIN WHICH HAS BEEN FOUND TO ACT AS AN EFFECTIVE NUCLEATING AGENT.

Inventors

• 👤 J Studer

Bibliographic Details