Abstract: Ethylene vinyl acetate (EVA)/ethylene-styrene interpolymer (ESI) blends are described that are useful in preparing foams which exhibit improved compression set resistance, dimensional stability and rebound resilience at similar foam densities than known foam systems, e.g. EVA. The cross-linked foams of this invention are particularly useful in fabricating footwear and gasket products.

Abstract: New cross-linked polymeric foam compositions, and methods for making the same, are provided. The new compositions utilize novel cross-linked polyolefin copolymers and show improvements in strength, toughness, flexibility, heat resistance and heat-sealing temperature ranges as compared to conventional low density polyethylene compositions. The new compositions also show processing improvements over linear low density polyethylene. The novel polyolefins, which are essentially linear, comprise ethylene polymerized with at least one alpha-unsaturated C3 to C20 olefinic comonomer, and optionally at least one C3 to C20 polyene, and exhibit, in an uncross-linked sense, a resin density in the range of about 0.86 g/cm.sup.3 to about 0.96 g/cm.sup.3, a melt index in the range of about 0.5 dg/min to about 100 dg/min, a molecular weight distribution in the range of from about 1.5 to about 3.5, and a composition distribution breadth index greater than about 45 percent.

Abstract: A process is developed for recycling a polyolefin cross-linked substance having a cross-linkage, a polyolefin foamed substance free from a cross-linkage or a polyolefin foamed substance having a cross-linkage. The process includes the step of heating the polyolefin cross-linked substance together with a cross-linkage breaking agent, whereby breaking the cross-linkage to recycle the polyolefin cross-linked substance into a moldable thermoplastic resin. Further, the process includes the step of adding a foaming-agent-decomposition facilitating agent to the polyolefin foamed substance in the course of thermally melting the polyolefin foamed substance, whereby decomposing a residual foaming agent remaining in the polyolefin foamed substance.

Abstract: The present invention pertains to improved alkenyl aromatic polymer foams (and processes for their preparation) having increased heat distortion temperature and improved dimensional stability while maintaining good tensile/tear, creep and environmental dimensional change properties.The closed cell low density alkenyl aromatic polymer foams exhibit increased heat distortion temperature, when substantially random interpolymers of about 21 to about 65 mol % styrene are blended in. When these same alkenyl aromatic polymer foams are made without these interpolymers, the heat distortion temperature is not improved.

Abstract: The present invention relates to a foamable composition comprising a low viscosity thermoplastic composition comprising at least one ethylene/.alpha.-olefin. The foamable composition may comprise a single ethylene/.alpha.-olefin or a blend of such. Optionally, the foamable composition may further comprise at least one diluent including waxes, plasticizers such as oil, tackifying resin, and mixtures thereof. The present invention also relates to a method of foaming such compositions and articles constructed therefrom. More specifically, the present invention relates to foamable thermoplastic compositions having particular utility as cabinet sealant and as foam layers in disposable articles such as disposable diapers, incontinent devices, medical devices such as bandages and dressings, as well as a variety of other uses.

Abstract: A process additive for polyolefin films and foams produces products having reduced greasiness and reduced grease-like transfer as compared to glycerol monostearate (GMS). The process additive comprises a fatty acid N-aliphatic alcohol amide of the general formula R--CON(R')R". R is a fatty hydrocarbon radical having from about 8 to 30 carbons. R' typically is hydrogen. R' can also be an alkyl radical of from about 1 to 6 carbons or an alkyl alcohol radical of from about 1 to 6 carbons. R" is an alkyl alcohol fragment of from about 1 to 6 carbons. The alkyl alcohol fragments can be monohydric or polyhydric. Secondary fatty monoalkanolamides in which R' is hydrogen are particularly useful, especially stearamide monoethanolamine (MEA). The benefits of the invention can be achieved and enhanced in some examples by mixing the fatty acid N-aliphatic alcohol amide with an ester of a long chain fatty acid with a polyhydric alcohol, including GMS.

Abstract: New cross-linked polymeric foam compositions, and methods for making the same, are provided. The new compositions utilize novel cross-linked polyolefin copolymers and show improvements in strength, toughness, flexibility, heat resistance and heat-sealing temperature ranges as compared to conventional low density polyethylene compositions. The new compositions also show processing improvements over linear low density polyethylene. The novel polyolefins, which are essentially linear, comprise ethylene polymerized with at least one alpha-unsaturated C3 to C20 olefinic comonomer, and optionally at least one C3 to C20 polyene, and exhibit, in an uncross-linked sense, a resin density in the range of about 0.86 g/cm3 to about 0.96 g/cm3, a melt index in the range of about 0.5 dg/min to about 100 dg/min, a molecular weight distribution in the range of from about 1.5 to about 3.5, and a composition distribution breadth index greater than about 45 percent.

Abstract: New cross-linked polymeric foam compositions, and methods for making the same, are provided. The new compositions utilize novel cross-linked polyolefin copolymers and show improvements in strength, toughness, flexibility, heat resistance and heat-sealing temperature ranges as compared to conventional low density polyethylene compositions. The new compositions also show processing improvements over linear low density polyethylene. The novel polyolefins, which are essentially linear, comprise ethylene polymerized with at least one alpha-unsaturated C3 to C20 olefinic comonomer, and optionally at least one C3 to C20 polyene, and exhibit, in an uncross-linked sense, a resin density in the range of about 0.86 g/cm.sup.3 to about 0.96 g/cm.sup.3, a melt index in the range of about 0.5 dg/min to about 100 dg/min, a molecular weight distribution in the range of from about 1.5 to about 3.5, and a composition distribution breadth index greater than about 45 percent.

Abstract: Disclosed herein are processes for polymerizing ethylene, acyclic olefins, and/or selected cyclic olefins, and optionally selected olefinic esters or carboxylic acids, and other monomers. The polymerizations are catalyzed by selected transition metal compounds, and sometimes other co-catalysts. Since some of the polymerizations exhibit some characteristics of living polymerizations, block copolymers can be readily made. Many of the polymers produced are often novel, particularly in regard to their microstructure, which gives some of them unusual properties. Numerous novel catalysts are disclosed, as well as some novel processes for making them. The polymers made are useful as elastomers, molding resins, in adhesives, etc. Also described herein is the synthesis of linear .alpha.-olefins by the oligomerization of ethylene using as a catalyst system a combination a nickel compound having a selected .alpha.-diimine ligand and a selected Lewis or Bronsted acid, or by contacting selected .alpha.

Abstract: Polypropylene films which have cavities distributed in the film and on the surfaces are suitable for writing or printing and have a low density. The films have surface qualities of each side of surface within .+-.2.times.10.sup.-6 inch of the average depth of the cavities, .+-.2% of the average of the gloss at 45.degree. angle and .+-.0.02 of the average of coefficient of friction. Such a film is obtained by passing the molded film from the calender through a set of heating rolls at temperatures revealed in this invention before entering the stretching system. The obtained polypropylene film has superior printability, low density and high stiffness, and thus is suitable for use as a paper substitute.

Abstract: An expandable thermoplastic composition is disclosed for extrusion foaming wherein the composition comprises a polyethylene resin and a blowing agent comprising ethane present in an amount of at least about 40 percent or more by weight based upon the total weight of the blowing agent and a different alkane selected from the group consisting of C.sub.1, C.sub.2, C.sub.3, C.sub.4, C.sub.5, and C.sub.6 alkanes and mixtures thereof, wherein the minimum percentage of ethane increases above 40 percent as the arithmetic mean carbon number of the different alkane increases from 3 to 5. A process for extrusion foaming of the composition is also disclosed.

Abstract: A process which combines a calender with a stretching system and a set of heating rolls is provided in this invention to produce films of polypropylene resin of wide thickness range. The polypropylene films which have cavities distributed in the film and on the surfaces are suitable for writing or printing and have a low density. The films have surface qualities of each side of surface within .+-.2.times.10.sup.-6 inch of the average depth of the cavities, .+-.2% of the average of the gloss at 45.degree. angle and .+-.0.02 of the average of coefficient of friction. Such a film is obtained by passing the molded film from the calender through a set of heating rolls at temperatures revealed in this invention before entering the stretching system. The obtained polypropylene film has superior printability, low density and high stiffness, and thus is suitable for use as a paper substitute.

Abstract: A stability control agent composition for foamable polyolefin compositions comprising at least one compound that is a partial ester of fatty acid with polyol, and at least one compound selected from the group consisting of higher alkyl amines, fatty acid amides and/or complete esters of higher fatty acids.

Abstract: Disclosed is a normally solid, high molecular weight, gel-free, amorphous to predominantly crystalline, propylene polymer characterized by high melt strength due to strain hardening which is believed to be caused by free-end long chain branches of the molecular chains forming the polymer.Also disclosed is a process for making the polymer by high energy radiation of a normally solid, high molecular weight, linear, propylene polymer in a reduced active oxygen environment, maintaining the irradiated material in such environment for a specific period of time, and then deactivating free radicals in the material.Further disclosed is the use of the strain hardening polymer in extensional flow operations such as, for example, extrusion coating, film production, and thermoforming.

Abstract: This invention relates to a polymer foam prepared by dispersing an organophilic multi-layered material into a melt comprising an olefinic or styrenic polymer having polar functionality so that at least a portion of the polymer intercalates between layers of the particles; and expanding the polymer with a blowing agent under such condition to form the polymer foam. The organophilic multi-layered material can also be dispersed into an olefinic or styrenic monomer, which can then be polymerized to form a polymer melt prior to, or along with the foaming step.

Abstract: The present invention provides a process for producing thermoplastic foam, including:(a) melting a thermoplastic polymer to produce a polymer melt;(b) introducing a carbon dioxide blowing agent into the polymer melt;(c) adding to the polymer melt one or more additives selected from the group consisting of(1) polysiloxane, and(2) mineral oil; and(d) extruding and foaming the melted polymer melt, blowing agent, and one or more additives to produce thermoplastic foam.The resultant thermoplastic foam can be thermoformed into various foamed articles, such as foam packaging trays. The quality of foams made from a carbon dioxide blowing agent, and particularly 100% carbon dioxide, has been found to be substantially improved by adding one or more of the foregoing additives, i.e., polysiloxane, mineral oil and, optionally, polyolefin to the polymer melt during the extrusion and foaming process.

Abstract: An expandable thermoplastic composition is disclosed for extrusion foaming wherein the composition comprises a polyethylene resin and a blowing agent comprising ethane present in an amount of at least about 40 percent or more by weight based upon the total weight of the blowing agent and a different alkane selected from the group consisting of C.sub.1, C.sub.2, C.sub.3, C.sub.4, C.sub.5, and C.sub.6 alkanes and mixtures thereof, wherein the minimum percentage of ethane increases above 40 percent as the arithmetic mean carbon number of the different alkane increases from 3 to 5. A process for extrusion foaming of the composition is also disclosed.

Abstract: A process for producing an automotive molded roof material is provided which comprises sheeting a foamable sheet forming composition comprising a specified propylene resin, a glass fiber, a radical initiator, a crosslinking auxiliary and a foaming agent in specific proportions into a foamable sheet, lining one side of the foamable sheet with a backing sheet so as to integrate these and irradiating the foamable sheet with ionizing radiation to thereby crosslink the propylene resin, followed by heating the foamable sheet so as to cause the foamable sheet to foam, placing a cover sheet on the other side of the foamed sheet before the sheet cools to solidify and press molding the cover sheet on the foamed sheet to cover. There is also provided an automotive molded roof material produced by the above process. An automotive molded roof material is obtained which can be recycled, is lightweight and has high rigidity.

Abstract: A foaming resin composition consisting essentially of (A) an organic compound having a carbon-carbon double bond, (B) a compound having an SiH group, and (C) a compound having an OH group is foamed and cured at room temperature or under heat at relatively low temperatures, to obtain hard, semi-hard or soft plastic foam having good weather resistance and good compatibility with coating compositions and adhesives.

Abstract: Biaxially oriented films from high molecular weight polyethylene are characterized by a gas permeable structure formed from random-arranged microfibrils. The films have coefficients of static friction and kinetic friction of not more than 1.0. The biaxially oriented films are further characterized by service smoothness as well as tensile (tangent) modulus and tensile strength. The films may be used for lamination, filter, or for packaging for moisture absorbers. The biaxially oriented films may be obtained by extracting a hydrocarbon plasticizer from a sheet formed from the high molecular weight polyethylene and a hydrocarbon plasticizer, stretching the resulting sheet to obtain an oriented film having a specific surface area of at least 70 m.sup.2 /g and a fibril structure, and heating the oriented film under a standard length constraint to reduce the oriented film in specific area by at least 20 m.sup.2 /g.

Abstract: A method of manufacturing a rigid foamed product includes the steps of mixing a metal adhesive resin, a foaming agent, a foaming accelerator, a crosslinking agent, a monomer, and a fibrous material to formulate a foamable composition, arranging the foamable composition thus formulated in a cavity of a formed metal component, and heating the metal component with the foamable composition.

Abstract: Catalyst support containing an .alpha.-olefin polymer which is in the form of particles of mean size from 5 to 350 .mu.m in which the pore volume generated by the pores of radius from 1,000 to 75,000 .ANG. is at least 0.2 cm.sup.3 /g.Catalyst usable for the polymerization of .alpha.-olefins, including a compound containing at least one transition metal belonging to groups IIIb, IVb, IVb and VIb of the Periodic Table, bound in or on this support.

Abstract: The production of approximately spherical polyolefin foam particles having a coarse cell structure and a narrow cell size distribution by dispersion foaming is achieved by a process in which the reactor contents, which essentially comprise polyolefin particles, a liquid dispersion medium and, if desired, a volatile blowing agent, are first treated at a first temperature above the crystallite melting point T.sub.m of the polyolefin, and subsequently passed through a cooling device, in which the dispersion is brought to a second, lower temperature, and the polymer particles are then foamed at this temperature. The foamed particles can be converted into moldings by known methods.

Abstract: The present invention relates to uncrosslinked polyethylene particles for the production of expanded particles that can easily and securely produce expanded particles which can be molded without applying a special internal pressure, are excellent in moldability, such as secondary expansion, fusion and dimensional accuracy, and have a high expansion rate and to uncrosslinked polyethylene expanded particles made of said uncrosslinked polyethylene particles. The present uncrosslinked polyethylene particles for the production of expanded particles are resin particles whose base resin is an uncrosslinked polyethylene having a density of over 0.920 g/cm.sup.3 and up to and including 0.940 g/cm.sup.3 and wherein, in the DSC curve that is obtained by using a differential scanning calorimeter in such a manner that after 1 to 10 mg of the resin particles is heated to 200.degree. C. at 10.degree. C./min and then is cooled to room temperature at 10.degree. C./min, heating is again carried out to 200.degree. C. at 10.

Abstract: Disclosed herein is a method of producing foamed particles of a polyolefin resin, which are prevented from fusion-bonding among the particles upon their production, and exhibit excellent moldability without impeding fusion bonding property among the foamed particles upon their molding. The method includes dispersing the particles of the polyolefin resin along with a finely particulate silicate mineral as a dispersing agent and at least carbon dioxide as a foaming agent in a dispersion medium in a closed vessel, heating the dispersion to impregnate the resin particles with the foaming agent, and then releasing the resin particles and dispersion medium into an atmosphere of a pressure lower than the internal pressure of the vessel, thereby expanding the resin particles.

Abstract: Foamed propylene polymer articles are prepared by subjecting pre-foamed beads, that consist essentially of propylene polymers having a melt strength from 5 to 40 cN, to thermoforming by sintering.

Abstract: Isotropic porous polymer beads having a high surface porosity and large pore diameters from about 0.002 to about 5 microns are produced from solutions of a polymer or a copolymer by a thermally-induced phase separation process. The use of mixed solvent-non-solvent combinations as solvents for the polymers, produces high pore content, substantially spherical beads having a morphology ideally suited to the chromatography of large molecules, such as proteins, and for enzyme-binding.

Abstract: Crystalline olefin polymers and copolymers in the form of spherical particles having porosity (expressed in percentage of voids) higher than 15%, with more than 90% of the pores having a pore diameter greater than one micron. These polymeric particulate materials find many applications, including, e.g., the preparation of masterbatches containing significant quantities of additives and/or pigments.

Abstract: A method of making a foamed polymer article by injection molding, using a foaming agent that evolves minimal water and does not form byproducts which could pit or chalk the polymer surface. The foaming agent contains sodium borohydride in an amount from 0.01 weight percent of the polymer to be foamed, and a polyhydric alcohol such as six-carbon mannitor as an activator to react with the sodium borohydride and produce hydrogen gas. Boric acid can be included with the alcohol. the sodium borohydride is kept separated from the other reactive components such as by encapsulation until gas production is desired when the polymer is heated and molded.

Abstract: A thermoformable, rigid or semi-rigid polypropylene foam sheet having a smooth surface and a uniform cell structure and a density of at least 2.5 lbs/ft.sup.3 is prepared by extruding a mixture of a nucleating agent, a physical blowing agent and a polypropylene resin having a high melt strength and high melt elasticity.

Abstract: A thermoformable, rigid or semi-rigid polypropylene foam sheet having a smooth surface and a uniform cell structure and a density of at least 2.5 lbs/ft.sup.3 is prepared by extruding a mixture of a nucleating agent, a physical blowing agent and a polypropylene resin having a high melt strength and high melt elasticity.

Abstract: A method of making a foamed polymer article by injection molding, using a foaming agent that evolves minimal water and does not form byproducts which could pit or chalk the polymer surface. The foaming agent contains sodium borohydride in an amount from 0.01 weight percent of the polymer to be foamed, and a polyhydric alcohol such as six-carbon mannitol as an activator to react with the sodium borohydride and produce hydrogen gas. Boric acid can be included with the alcohol. The sodium borohydride is kept separated from the other reactive components such as by encapsulation until gas production is desired when the polymer is heated and molded.

Abstract: A method of making a foamed polymer article by injection molding, using a foaming agent that does not form byproducts which could pit or chalk the polymer surface. The foaming agent contains sodium borohydride in an amount from 0.01 to 5.0 weight percent of the polymer, and sodium dihydrogen phosphate as an activator to react with the sodium borohydride and produce hydrogen gas. The sodium borohydride and the sodium dihydrogen phosphate are kept separated from direct contact with each other, such as by encapsulating the components, until gas production is desired when the polymer is heated.

Abstract: A thermoformable, rigid or semi-rigid polypropylene foam sheet having a smooth surface and a uniform cell structure and a density of at least 2.5 lbs/ft.sup.3 is prepared by extruding a mixture of a nucleating agent, a physical blowing agent and a polypropylene resin having a high melt strength and high melt elasticity.

Abstract: A sponge is disclosed, comprising a copolymer of ethylene, an .alpha.-olefin, and a diolefin, said copolymer (a) containing the ethylene units and the .alpha.-olefin units at a weight ratio of from 73:27 to 40:60, (b) having a Mooney viscosity (ML.sub.1+4 121.degree. C.) of from 135 to 200, and (c) containing the diolefin units giving an iodine value of from 10 to 36.A sponge composition is also disclosed, comprising 100 parts by weight of the aforesaid copolymer and from 30 to 130 parts by weight of a plasticizer.

Abstract: Novel foams having a density of from 0.01 to 0.1 g/cm.sup.3, based on a copolymer comprising ethylene, propylene and a C.sub.4 - to C.sub.8 -.alpha.-olefin, and having a torsion modulus of from 100 to 800 N/mm.sup.2 have high tensile, compressive and flexural strengths and at the same time high elongation at break.

Abstract: Disclosed is a semiconductive rubber foam having a volume resistivity that can be controlled to a practical level and retaining an initial softness (hardness) even after the lapse of time. This semiconductor rubber foam is composed of a molded article obtained by curing and foaming a rubber composition comprising (A) 100 parts by weight of a chlorinated ethylene/.alpha.-olefin copolymer rubber and (B) 10 to 50 parts by weight of carbon black. The volume resistivity of this semiconductive rubber foam has is in the range of from 10.sup.5 to 10.sup.11 .OMEGA.-cm.

Abstract: The invention relates to polyethylene compositions comprising 20-98 wt % branched polyethylene a) with a density of between 915 and 940 kg/m.sup.3 and a melt flow index of between 0.05 and 40 dg/minute, prepared by a high pressure radical process, and 2-80 wt % substantially linear polyethylene b) with a density of between 850 and 915 kg/m.sup.3, a melt flow index of between 0.05 and 25 dg/minute and a DSC crystallinity at 23.degree. C. of at least 10%, prepared with the aid of a transition metal catalyst, the difference between the highest crystallization temperature of branched polyethylene a) and the highest DSC crystallization temperature of linear polyethylene b) being at most 10.degree. C. and the mixture having modulus of elasticity of at most 280 N/mm.sup.2 and objects made therefrom. These polyethylene compositions, when processed to foamed objects, have a high resistance to high temperatures ss well as a high flexibility.

Abstract: An adhesive foam comprises a foamed mixture of a foamable homo- or co-polymer and a foamable olefin-unsaturated carboxylic acid copolymer, the mixture containing at least 3 weight percent of polymer units derived from the acid.

Abstract: A heat-foamable crosslinked propylene resin composition in the form of a melt-shaped sheet structure comprising[1] 100 parts by weight of a crosslinked propylene resin composition obtained by mixing at least four components composed of (A) a propylene resin, (B) an olefin resin other than the resin (A), (C) a radical initiator and (D) a crosslinking agent, and[2] 0.5 to 5 parts by weight of a blowing agent; wherein(a) the propylene resin (A) is in an amount of 60 to 95 parts by weight per 100 parts by weight of the resins (A) and (B) combined, and has a melt flow rate (MFR) of 0.1 to 50 g/10 min.

Abstract: A heat-foamable crosslinked propylene resin composition in the form of a melt-shaped sheet structure comprising[1] 100 parts by weight of a crosslinked propylene resin composition obtained by mixing at least four components composed of (A) a propylene resin, (B) an olefin resin other than the resin (A), (C) a radical initiator and (D) a crosslinking agent, and[2] 0.5 to 5 parts by weight of a blowing agent; wherein(a) the propylene resin (A) is in an amount of 60 to 95 parts by weight per 100 parts by weight of the resins (A) and (B) combined, and has a melt flow rate (MFR) of 0.1 to 50 g/10 min.

Abstract: The invention relates to the process of the invention provides a radiation-crosslinked polypropylene foam by extrusion at a low temperature (about 170.degree. C.) below the decomposition point of the blowing agent. The resulting foamed item has by far better heat resistance than conventional ones.The raw resin can be prepared by mixing a resin in the pellet form and a blowing agent in the powder form on account of the low-temperature flowability. Heretofore, such mixing was impossible because the blowing agent does not disperse completely.This outstanding effect of the invention was not expected at all from the known prior arts.

Abstract: A heat resistant shrinkable film comprising a composition of (i) 50% to 90% by weight of an ethylene-propylene block copolymer with an ethylene content of 3% to 20% by weight and (ii) 50% to 10% by weight of an ethylene-propylene random copolymer with an ethylene content of 2 to 15% by weight and having a foam ratio of 3.0 or less.

Abstract: Foams are prepared from a linear low density polyethylene and, optionally, other olefinic polymers, such as a low density polyethylene using a chemical cross-linking agent. The resulting cross-linked polyethylene foams exhibit an excellent balance of properties at generally lower densities than foams prepared from low density polyethylene only.

Abstract: A process for producing porous films which comprises blending 100 parts by weight of a polyolefin resin with 50 to 500 parts by weight of barium sulfate preferably having an average particle diameter of 0.1 to 7 .mu.m, melting the resulting resin composition and forming it into a film, and then stretching the film at least uniaxially by a factor of 1.5 to 7.

Abstract: Prefoamed polypropylene-base particles have a crystalline structure featuring a high-temperature peak appeared on the higher temperature side than the peak inherent to polypropylene-base resins on a DSC curve obtained by differential scanning calorimetry upon heating 1-3 mg of the prefoamed polypropylene-base particles at a constant heating rate of 10.degree. C./min. to 220.degree. C. by means of a differential scanning calorimeter and the internal pressure decreasing velocity coefficient k of the particles is either equal to or smaller than 0.70 (k.ltoreq.0.70) at 25.degree. C. and 1 atm. The prefoamed polypropylene-base particles can be formed into an expansion-molded polypropylene-base article by imparting foamability to the particles, filling the resultant particles in a mold and then heating the particles so as to cause their expansion.

Abstract: A process for dimensionally stabilizing low density foamed polyolefins utilizing a dimensionally stabilizing control additive comprising a nitrogen-containing compound (having an unsaturated leg) said compound represented by formulas (I) and (II): ##STR1##

Abstract: A blowing agent composition, comprising: (i) azodicarbonamide; (ii) zinc oxide and/or zinc carbonate; and (iii) at least one member selected from the group consisting of zinc salts of C.sub.1 -C.sub.6 organic acids, and C.sub.1 -C.sub.6 organic carboxamides characterized by a high gas evolution rate. The blowing agent composition may be used in effective amounts in formulations containing a foamable polymer to yield an efficiently gas expanded polymeric composition upon exposure to heat. Suitable C.sub.1 -C.sub.6 organic acids for said zinc salts include straight-chain carboxylic acids, and useful organic carboxamides include formamide.

Abstract: Propylene-base random copolymer particles suitable for use in the production of pre-foamed particles are obtained by heating starting copolymer particles of ethylene-propylene random copolymer to the crystallization temperature thereof and then quenching them in a medium at a temperature of (the crystallization temperature-30.degree. C.) or lower. Pre-foamed particles produced using the copolymer particles contain large cells are columnar in shape with an average diameter D of 1.7 mm or less and an L/D.gtoreq.1. 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.