Abstract: Disclosed herein are propylene-base random copolymer particles suitable for use in the production of pre-foamed particles. The copolymer particles are obtained by heating starting copolymer particles to the crystallization temperature thereof and then quenching them in a medium of (the crystallization temperature-30.degree. C.) or lower. Processes for obtaining the copolymer particles are also disclosed. Pre-foamed particles produced using the copolymer particles contain large cells. They can thus provide foamed moldings which are substantially free of shrinkage and have good flexibility.

Abstract: For use in an automobile bumper, a core material composed of a molded article of prefoamed polyolefin resin particles. The core material has a density of 0.05 to 0.15 g/cm.sup.3 and the relation represented by the following expressionE.sub.20 /.rho..gtoreq.20 kg-cm/gwherein E.sub.20 is the amount of energy absorption (kg-cm/cm.sup.3) when the core material is compressed to 50% at 20.degree. C., and .rho. is the density (g/cm.sup.3) of the core material.

Abstract: A bumper core suitable for use in the fabrication of an energy-absorbing automobile bumper is formed by molding core-constituting members in accordance with the expansion molding process and then bonding them together at their confronting lengthwise end portions into a unitary body. The core-constituting members are formed into such configurations and dimensions that conform with configurations and dimensions obtained by longitudinally dividing the intended core into at least two parts. The bumper core enjoys extremely-high dimensional accuracy.

Abstract: Preliminarily foamed particles of a non-crosslinked polypropylene resin based on an alpha-olefin/propylene random copolymer having an amount of the heat of crystallization in the range of 5 to 15 cal/g, said preliminarily foamed particles having such a crystal structure that when a DSC curve is drawn by means of a differential scanning calorimeter, by heating 1 to 3 mg of the preliminarily foamed particles to 220.degree. C. at a rate of 10.degree. C./min., a high temperature peak is observed at a higher temperature than the temperature of the peak inherent to the base resin.

Abstract: In pre-foamed particles of a propylene-base resin obtained by foaming raw particles of the propylene-base resin, the relation, G.sub.1 -G.sub.2 .gtoreq.10%, exists between the content G.sub.1 (%) of matter, which is contained in the pre-foamed particles and is insoluble in boiling n-heptane, and the content G.sub.2 (%) of matter contained in the raw particles and insoluble in boiling n-heptane. The pre-foamed particles have excellent moldability and can hence provide with ease low-density (highly-expanded) molded articles, which enjoy superb dimensional accuracy, good surface conditions, low percent water absorption, excellent impact and chemical resistance.

Abstract: Preliminarily foamed particles of a non-crosslinked polypropylene-type resin based on a mixture of 10 to 95% by weight of an alpha-olefin/propylene random copolymer having an amount of the heat of crystallization of not more than 10 cal/g in differential scanning calorimetry and 90 to 5% by weight of an ethylene/propylene random copolymer as a base resin, said preliminarily foamed particles having such a crystal structure that when a DSC curve is drawn by heating 1 to 3 mg of the preliminarily foamed particles to 220.degree. C. at a rate of 10.degree. C./min. by means of a differential scanning calorimeter, a high temperature peak is observed at a higher temperature than the temperature of the peak inherent to the base resin. These preliminarily foamed articles can be molded under lower vapor pressures than in the prior art.

Abstract: A core material for automobile bumpers which is composed of a molded article of foamed particles of a polypropylene-type resin. The molded article has a density of 0.015 to 0.045 g/cm.sup.3 and a compression stress at 50% compression of at least 1 kg/cm.sup.2. The core material simultaneously has excellent energy absorbing property and dimensional recovery and a low density.

Abstract: A process for producing pre-foamed particles of a polypropylene resin which comprises expanding original pre-foamed particles of a polypropylene resin, said original pre-foamed particles having the following relation2<E.sup.1/3 .times.n.sup.1/2 <45wherein E is the expansion ratio of the original pre-foamed particles, and n is the number of cells per mm.sup.2 of the cross section of the original pre-foamed particles,by (1) imparting expanding ability to the original pre-foamed particles and then heating them with a heated gas to the heat distortion temperature of the base resin of the pre-foamed particles or a higher temperature or (2) heating the original pre-foamed particles with steam to the heat distortion temperature of the base resin of the particles or a higher temperature with or without imparting expanding ability thereto, whereby pre-foamed particles having an expansion ratio higher than the original expansion ratio E are obtained.

Abstract: A process for producing particles having an increased particle diameter from a powder of a polyolefin resin, which comprises heating the polyolefin resin powder at a temperature higher than the melting point of the resin in a dispersion medium in the presence of a dispersing agent and a surface-active agent.

Abstract: This invention provides an electrical conductive foam bead comprising a foamed bead core of a thermoplastic synthetic resin at least partially covered on the surface thereof with an electrical conductive layer, and a molded electrical conductive foamed article comprising a plurality of particulate bodies formed by mutually fusing such electrical conductive foam beads, the electrical conductive layers extending over all or a portion of the interface of the mutually fused particulate bodies. The conductive foam beads and molded conductive foamed articles both have improved antistatic effect and are used as packaging and cushioning materials, electromagnetic radiation shields, and the like.

Abstract: Prefoamed polymer particles having excellent moldability are produced by a process comprising a step (impregnating step) of impregnating carbon dioxide or carbon dioxide and a volatile blowing agent in polymer particles, a step (dispersing step) of dispersing the polymer particles into a dispersion medium in a sealed vessel, a step (heating step) of heating the polymer particles to a temperature higher than the softening point of said polymer particles, and a step (releasing step) of opening one end of said vessel and simultaneously releasing the polymer particles and dispersion medium from inside the vessel to an atmosphere held at a pressure lower than that of the vessel. In this process, the impregnating step, dispersing step and heating step need not be altogether effected separately. These steps can be performed simultaneously in one and the same vessel.

Abstract: In a method of producing a plate-like polystyrene resin foam which comprises extruding a molten mixture of a polystyrene resin and a volatile blowing agent from an extruder into a zone kept at a lower pressure than the inside of the extruder, the improvement wherein the volatile blowing agent is a mixture consisting of 50 to 80% by weight of dichlorodifluoromethane and 50 to 20% by weight of ethyl chloride and is present in said molten mixture in a proportion of 8 to 17 parts by weight per 100 parts by weight of the polystyrene resin.

Abstract: A method for pressurizing pre-foamed particles of a polyolefin resin by maintaining the pre-foamed particles in an atmosphere of a pressurized gas to impart a predetermined internal pressure thereto, which comprises first maintaining the particles under a pressure which does not cause shrinkage to the particles, and then increasing the applied pressure gradually under conditions which do not cause shrinkage to the particles.

Abstract: A process for producing a foamed and molded article of a polypropylene resin, which comprises pressurizing preliminarily-foamed particles of an ethylene/propylene copolymer having a melt index value of from 0.1 to 25, a latent heat of crystallization of not more than 28 cal/g and an ethylene content of from 1 to 30% by weight as a base resin with an inorganic gas or a gaseous mixture of the inorganic gas and a volatile blowing agent thereby to impart an elevated pressure to the inside of said particles, thereafter filling said particles in a mold capable of enclosing the particles but allowing escape of gases therefrom, and then heating said particles to expand them to the configuration of the mold.

Abstract: In a process for producing pre-foamed particles of a polyolefin resin which comprises impregnating a volatile blowing agent into particles of a polyolefin resin while dispersing the resin particles and the blowing agent in a dispersing medium under heat in a closed vessel, opening one end of the vessel and releasing the resin particles and the dispersing medium simultaneously into an atmosphere kept at a lower pressure than the inside pressure of the vessel; the improvement wherein the pressure of the inside of the vessel after opening its one end is maintained at a substantially constant pressure which is at least 0.7 times the vapor pressure of the blowing agent before opening the end of the vessel.

Abstract: A method for producing a foamed plastic sheet which comprises heating and kneading a thermoplastic synthetic resin composition containing a blowing agent in an extruder, extruding the resulting gel through a circular die provided at the end of the extruder, and pinching the tubular foamed extrudate with a pair of pinch rolls while it is still in the softened state to adhere the inside wall of the foamed tubing to itself, is characterized in that said pinching and adhesion are performed by using a pair of pinch rolls having a width at least 5% smaller than the width of the tubular foamed extrudate extruded in the flattened state so that non-adhered parts are formed at both side end portions of the pinched foamed sheet in the widthwise direction and the inside of the non-adhered parts communicates with the open air.

Abstract: In a process for producing a foamed article of a polyolefin resin which comprises filling in a mold pre-foamed particles of a polyolefin resin containing a gaseous mixture consisting of an inorganic gas and a volatile organic blowing agent in their cells and heating them to mold a foamed article; the improvement wherein the pre-foamed particles of the resin are those in which the total pressure of the gaseous mixture is 1.4 to 2.5 kg/cm.sup.2 (abs.), with the partial pressure of the inorganic gas being maintained at 0.4 to 1.1 kg/cm.sup.2 (abs.) and the partial pressure of the volatile blowing agent at 0.8 to 1.6 kg/cm.sup.2 (abs.).

Abstract: In a process for producing a plate-like polystyrene resin foam which comprises extruding a molten mixture consisting of a polystyrene resin and a volatile blowing agent by an extruder into a zone having a lower pressure than the inside of the extruder; the improvement wherein said volatile blowing agent is a mixture consisting of dichlorodifluoromethane, ethyl chloride and methyl chloride in which dichlorodifluoromethane accounts for 50 to 70% by weight of the mixture and the remainder consists of ethyl chloride and methyl chloride and the amount of ethyl chloride is at least 30% by weight based on the total amount of ethyl chloride and methyl chloride; and wherein said volatile blowing agent is present in said molten mixture in a proportion of 8 to 17 parts by weight per 100 parts by weight of the polystyrene resin component.

Abstract: Substantially non-crosslinked pre-foamed particles of a polypropylene resin, characterized by the fact that they are composed of an ethylene/propylene random copolymer or a mixture of an ethylene/propylene random copolymer with low density polyethylene and/or an ethylene/vinyl acetate copolymer as a base resin; and a process for producing pre-foamed particles of a polypropylene resin, which comprises dispersing substantially non-crosslinked particles of the polypropylene resin composed of an ethylene/propylene random copolymer or a mixture of an ethylene/propylene random copolymer with low-density polyethylene and/or an ethylene/vinyl acetate copolymer and a volatile blowing agent in water in the presence of a dispersing agent within a closed vessel; heating the dispersion to a temperature above a temperature at which the resin particles soften, thereby to impregnated the blowing agent in the resin particles; and while maintaining the pressure of the inside of the vessel higher than the vapor pressure of the

Abstract: In a method for producing a plastic foam of a desired expanded dimension which is constituted by extruding a melt of a thermoplastic synthetic resin containing a blowing agent through a die of an extruder and passing the extrudate through a shaping device located outwardly of the extruder and secured to the discharge end of the extruder while expanding and solidifying the molten mass so that it fills the shaping device; the improvement wherein at least a part of that area of the inside surface of the shaping device with which the expanded resin makes contact is formed of a plate of a fluorocarbon resin, said plate being secured to the inside surface of the shaping device by fitting portions, said fitting portions having a sufficient space for absorbing an increase in the volume of the fluorocarbon resin plate at the temperature of extrusion molding; and an apparatus for use in the above described process.