Abstract: High quality articles which are large or of complex shapes are difficult to mold from low density expandable thermoplastic polymers, such as LDPP (Low Density PolyPropylene) because their low heat capacity density causes premature cooling and setting as they try to reach extremities and narrow regions of an injection mold cavity. To overcome these problems the invention provides cycling, during article production, of heating and cooling in the regions of the mold that are near these extremities and narrow regions. The resulting system offers production of low material cost polymer articles in lower cost, lower pressure injection molds and machine systems.

Abstract: Pre-expansion of expandable polystyrene (EPS) and other expandable polymer beads has long been carried out with heat of condensation from steam, which permeates the beads and deposits water droplets within expanding cells of each bead. Because long conditioning periods (to dry the pre-expanded beads) allow much of the blowing agent (e.g. pentane) to escape, the resultant pre-expanded beads often lack sufficient pentane to permit adequate final expansion when the pre-expanded beads are used to mold coffee cups and other articles. When conditioning periods are too short, excess water droplets often cause variations in bead fusing and even leaks in the molded product. The present invention avoids these long-standing problems by using a heated gas, such as air, to pre-expand the raw EPS beads through conduction only.

Abstract: From an environmental viewpoint, it is desireable to cause degradation of expanded EPS beads and foam cups and other products formed from expanded EPS beads, which are composed of polystyrene and a blowing agent such as pentane. For this purpose, the present invention utlizes the pre-expansion step as an opportunity to initiate foam product degradation by treating the expandable polymer beads during their pre-expansion. The objective of this degradation treatment is to initiate degradation of at least the surfaces of individual beads during their pre-expansion and before they are molded into the final foam articles. For this purpose, a number of degradation treatment options are disclosed for application during bead pre-expansion, including heating the beads by circulation with heated air, admixture of the beads with ozone, aromatic ketones such as acetophenone and benzophenone, and metallic salts, as well as irradiation of the expanding beads with uv radiation (e.g of a wavelength of about 260 nanometers).

Abstract: From an environmental viewpoint, it is desireable to cause degradation of expanded EPS beads and foam cups and other products formed from expanded EPS beads, which are composed of polystyrene and a blowing agent such as pentane. For this purpose, the present invention utlizes the pre-expansion step as an opportunity to initiate foam product degradation by treating the expandable polymer beads during their pre-expansion. The objective of this degradation treatment is to initiate degradation of at least the surfaces of individual beads during their pre-expansion and before they are molded into the final foam articles. For this purpose, a number of degradation treatment options are disclosed for application during bead pre-expansion, including heating the beads by circulation with heated air, admixture of the beads with ozone, aromatic ketones such as acetophenone and benzophenone, and metallic salts, as well as irradiation of the expanding beads with uv radiation (e.g of a wavelength of about 260 nanometers).