Abstract: A process for producing expandable particles of a melt compounded blend of polyphenylene ether resin and polyolefin resin. A melt compounded blend of polyphenylene ether resin and polyolefin resin, a blowing agent and water are mixed in a pressure vessel to form a dispersion; the dispersion is heated in the sealed pressure vessel to impregnate the blowing agent in the melt compounded blend of resin particles; the dispersion is then cooled in the sealed pressure vessel; and a cooled blowing agent-impregnated, melt compounded blend of resin particles is removed from the reactor. A preferred blowing agent is Freon.RTM. 11. The particles are pre-expanded by heating, and the pre-expanded particles can be foamed in a conventional mold when heat is applied thereto. A resin molding composition comprising a melt compounded blend of heat-pre-expanded, low density, resilient polyphenylene ether resin and polyolefin resin particles having about 95.0 weight percent to about 5.

Abstract: The invention relates to expandable styrene polymers for elastic polystyrene foams, comprisinga) from 50 to 75% by weight of polystyrene and/or a styrene copolymer containing at least 50% by weight of copolymerized styrene,b) from 5 to 30% by weight of a styrene-soluble elastomer,c) from 5 to 20% by weight of at least one block copolymer containing styrene as one component,d) from 15 to 50% by weight of at least one polyolefin,e) from 1 to 15% by weight, based on the sum of a) and b), of a low-boiling blowing agent, and, if desired,f) conventional additives in effective amounts,and to foams produced therefrom.

Abstract: Disclosed are branched polyester compositions having an I.V. of at least about 0.7 dl/g and a melt viscosity sufficiently high to permit foaming during extrusion or molding operations. These branched polyesters are readily foamable with a wide range of foaming agents to provide low density shaped articles, films, and sheets.The branched polyesters comprise about 80 to about 99.9 wt % of a polyester and about 0.1 to about 20 wt % of an ethylene copolymer containing repeat units of ethylene and of a monomer selected from the group comprising acrylic acid, methacrylic acid, alkyl acrylate, alkyl methacrylate and vinyl alcohol.

Abstract: A continuous process for manufacturing foam beads using a simple apparatus, wherein the expansion agent can be easily recycled. Polymer particles and a dispersing medium are fed continuously to an unstirred mass transfer column having a high length to diameter ratio which is operated under pressure. The polymer particles and dispersing medium are subjected to thermal processing under pressure in the mass transfer column, and the resulting dispersion is sprayed into a low pressure space causing the polymer particles to expand. Accordingly, foam beads of constant quality and a uniform cell diameter and a uniform degree of expansion are manufactured without costly process means.

Abstract: There are provided polypropylene resin expanded particles which have a uniform bubble size, can be molded with an exceptionally low steam pressure, and can produce an expanded molded product having a good surface appearance and an excellent energy absorption property. The present particles are polypropylene resin expanded particles containing as a base resin an isotactic polypropylene resin polymerized in the presence of a metallocene polymerization catalyst.

Abstract: An expandable styrene polymer comprisinga) from 0 to 90% by weight of a styrene polymer or styrene copolymer other than b) contains at least 50% by weight of copolymerized styrene,b) from 10 to 100% by weight of a styrene/methacrylamide copolymer comprising from 0.5 to 50% by weight of at least one copolymerized N-substituted methacrylamide of the formula I ##STR1## where R.sup.1 and R.sup.2 are identical or different and are hydrogen, C.sub.1 - to C.sub.15 -alkyl, C.sub.6 - to C.sub.16 -cycloalkyl or C.sub.6 - to C.sub.20 -aryl, it being possible, if R.sup.1 and R.sup.2 contain at least 2 carbon atoms, for at least 2 carbon atoms to be linked via hetero atoms, andc) from 1 to 15% by weight, based on the sum of a) and b), of an aliphatic C.sub.3 - to C.sub.9 -hydrocarbon and/or carbon dioxide as blowing agent.

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: A pre-expanded particle of a polyethylene resin based on a non-crosslinked linear very low density polyethylene having a density of 0.88 to 0.915 g/cm.sup.3 and a melt index of 0.1 to 20 g/10 min. which can be used to produce a cellular molded article having superior flexibility, excellent bonding together of the particles, and both large tensile strength and large elongation at break.

Abstract: In manufacturing hollow particles, gas is supplied from a gas cylinder to a first tank under pressure for solution in a raw material liquid in the first tank for the particles. The resulting raw material liquid is supplied to a second tank where the liquid is stirred with a dispersing medium under pressure, thereby forming a compressed emulsion in the second tank. As the compressed emulsion is discharged to the outside, it is released from the compressed state so that the gas dissolved in corpuscles of the raw material liquid in the emulsion will come out as bubbles. Thus since the corpuscles in the emulsion become hollow particles, an emulsion containing fine hollow particles of the raw material liquid as nuclei is obtained. Therefore it is possible to obtain a large quantity of fine hollow particles with ease.

Abstract: Disclosed is a compatibilized carbon black useful in melt processing of plastic material. The carbon black is coated with a compatibilizing agent which enhances the dispersibility of the carbon black in a melt of the plastic material. Further disclosed are processes for making plastic foam structures with the compatibilized carbon black.

Abstract: Disclosed herein is a method of producing foamed particles of an ethylene-based resin, which have a high expansion ratio and are free from the formation of fine cells, by dispersing particles of the uncrosslinked ethylene-based resin, which are obtained using, as a base resin, an ethylene/.alpha.-olefin copolymer containing, as a comonomer component, 1.0-10 wt. % of an .alpha.-olefin having 4-10 carbon atoms, in a dispersion medium in the presence of a foaming agent in a closed vessel, heating the resultant dispersion to impregnate the resin particles with the foaming agent, and then releasing the resin particles into a region of a pressure lower than the internal pressure of the vessel at a foaming temperature not lower than the softening temperature of the resin particles, thereby expanding the resin particles.

Abstract: A process for producing expandable particles of a melt compounded blend of polyphenylene ether resin and polyolefin resin. A melt compounded blend of polyphenylene ether resin and polyolefin resin, a blowing agent and water are mixed in a pressure vessel to form a dispersion; the dispersion is heated in the sealed pressure vessel to impregnate the blowing agent in the melt compounded blend of resin particles; the dispersion is then cooled in the sealed pressure vessel; and a cooled blowing agent-impregnated, melt compounded blend of resin particles is removed from the reactor. A preferred blowing agent is Freon.RTM. 11. The particles are pre-expanded by heating, and the pre-expanded particles can be foamed in a conventional mold when heat is applied thereto. A resin molding composition comprising a melt compounded blend of heat-pre-expanded, low density, resilient polyphenylene ether resin and polyolefin resin particles having about 95.0 weight percent to about 5.

Abstract: Porous, distensible, gel-like membranes which in tubular form are suitable as implants, e.g., vascular prostheses and a process for the preparation thereof is described. The membranes are formed by a spraying, phase-inversion technique which employs thermodynamically unstable polymer solutions and is accomplished by separately spraying the unstable solution and a nonsolvent onto a rotating surface. Prostheses from the highly porous tubular membranes have shown a high degree of patency and completeness of the healing process and are useful for direct implantation in the body or for extracorporeal vascular accesses.

Abstract: Disclosed is a cross-linked ethylenic polymer foam structure of an ethylenic polymer material of a cross-linked, substantially linear ethylenic polymer. The substantially linear ethylenic polymer having in an uncross-linked state has: a) a melt flow ratio, I.sub.10 /I.sub.2, .gtoreq.5.63; b) a molecular weight distribution, M.sub.w /M.sub.n, defined by the equation: M.sub.w /M.sub.n <(I.sub.10 /I.sub.2)-4.63; and c) a critical shear rate at onset of surface melt fracture of at least 50 percent greater than the critical shear rate at the onset of surface melt fracture of a linear ethylenic polymer having about the same I.sub.2 and M.sub.w /M.sub.n. Further disclosed is a process for making the above foam structure.

Abstract: Foamed polyolefin particles are prepared by dispersion foaming of components consisting essentially of polyolefin particles, a liquid dispersing agent and optionally a volatile blowing agent in a reaction system consisting essentially of a reactor equipped with a stirrer containing said components and a discharge jet, comprising the step of:gassing the components of the reactor by injecting an inert gas into the dispersion below the surface of the liquid in the reactor;and simultaneouslydischarging a three phase mixture of liquid dispersing agent, polymer particles and gas through said jet.

Abstract: The invention relates to foamed polylactide articles obtainable by foaming a mixture of amorphous polylactide granules which contain a blowing agent and of a finely divided polylactide which does not contain a blowing agent, and to a process for producing same.

Abstract: Disclosed is an ethylenic polymer foam structure comprising an ethylenic polymer material. The ethylenic polymer material contains a substantially linear ethylenic polymer having: a) a melt flow ratio, I.sub.10 I.sub.2, .gtoreq.5.63; b) a molecular weight distribution, M.sub.w /M.sub.n, defined by the equation M.sub.w /M.sub.n .ltoreq.(I.sub.10 /I.sub.2)-4.63; and c) a critical shear rate at onset of surface melt fracture of at least 50 percent greater than the critical shear rate at the onset of surface melt fracture of a linear olefin polymer having about the same I.sub.2 and M.sub.w /M.sub.n. The foam structures have toughness and elasticity similar to those formed from conventional LLDPE without the poor dimensional stability and foam quality associated with those structures. The foam structures have foam quality similar to those made with conventional LDPE but with enhanced toughness and elasticity. Further disclosed is a process for making the above foam structure and making it in a foam bead form.

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: An artificial soil made from thermoplastic resin foamed particles is disclosed, in which a plurality of thermoplastic resin foamed particles and a plurality of fine substances are bonded to each other by heat fusion of the thermoplastic resin foamed particles to form a porous structure. The artificial soil is excellent in not only air permeability, hydrophobic properties, and draining properties but also water retention and fertilizer retention.

Abstract: Process for producing foamable particles of styrenic polymers, which consists in submitting said particles to a partial loss of foaming agent, performed in an oven at a lower temperature than the glass transition temperature (Tg) of said particles.

Abstract: Bead-form expandable styrene polymers are obtained by suspension polymerization of styrene with addition of from 1 to 10% by weight of C.sub.3 - to C.sub.7 -hydrocarbons and/or carbon dioxide as blowing agent and, if desired, conventional additives, using, as suspension stabilizer, a mixture of magnesium pyrophosphate, a sulfonate group-containing extender and an alkali metal carboxylate or alkaline earth metal carboxylate, the magnesium pyrophosphate being prepared immediately before the polymerization by combining an aqueous solution of alkali metal pyrophosphate with at least the stoichiometrically necessary amount of a magnesium salt.

Abstract: Porous, polymer particles comprising a functionalized cross-linked copolymer having microporous regions and macroporous regions in the polymer matrix thereof, wherein the functional groups are essentially present only within the macroporous regions, as well as processes for preparing these particles based on a template polymerization technique followed by removal of the template polymer from the particles are disclosed. The particles of the invention are useful in chromatography, and in various analytical, diagnostic techniques and solid state peptide, DNA synthesis.

Abstract: Disclosed is a process for making closed-cell, alkenyl aromatic polymer foam packing bodies. An alkenyl aromatic polymer material is heated to form a melt polymer material. The melt polymer material comprises greater than 50 percent by weight alkenyl aromatic monomeric units. A blowing agent is incorporated into the melt polymer material at an elevated pressure to form a foamable gel. The blowing agent has about 20 weight percent or more based upon the total weight of the first blowing agent selected from the group consisting of carbon dioxide and ethane. The foamable gel is extruded through a die to form a foam strand. The foam strand is pelletized to form a plurality of foam bodies. The bodies are further expanded by exposing them one or more times to heated air or steam. Preferably, the bodies are allowed to age for a preselected period of time after pelletizing and between subsequent expansions.

Abstract: The invention relates to an expandable styrene polymer, comprising(a) a styrene polymer,(b) from 1 to 10% by weight, based on (a), of a blowing agent or blowing agent mixture,(c) from 0.02 to 0.25% by weight, based on (a), of a first coating containing a coating composition comprising(c.sub.1) a bisamide made from a C.sub.2 -C.sub.8 -alkylenediamine and an aliphatic C.sub.6 -C.sub.20 -carboxylic acid and(c.sub.2) a conventional antistatic,in a (c.sub.1):(C.sub.2) weight ratio of from 1 to 50,and, if desired, further coating compositions or coating composition mixtures and conventional additives in effective amounts, and to a process for the preparation of screen fractions of bead-form, expandable styrene polymers prepared by suspension polymerization.

Abstract: Disclosed is composite hollow particles which are excellent in solvent resistance and mechanical stability and have strong walls and which can be easily synthesized. The composite hollow particles are prepared by uniformly dispersing the following ingredients in an aqueous medium;(a) an ethylenically unsaturated monomer having at least two radical polymerizable double bonds in one molecule,(b) another polymerizable monomer which is different from the monomer (a),(c) organic particles having an average particle size of 0.01 to 5 micrometer,(d) a initiator, and(e) a dispersant,and then dispersion-polymerizing.

Abstract: A syntactic foam product having a desired configuration is set forth. The product comprises a plurality of rigid gas filled bubbles arranged in the desired configuration. The bubbles are defined by respective individual and discrete substantially spherical shells preferably formed of a biodegradable shell material. The shells abut one another. They define open spaces where they are not abutting. Attaching material attaches the abutting shells to one another. The open spaces between the shells are not filled by the attaching material. The attaching material is environmentally degradable. It releases the bubbles under ambient conditions after a selected time interval. The shells are in contact with their surroundings and can relatively rapidly biodegrade.

Abstract: An expandable styrene polymer comprisinga) a styrene polymer,b) from 1 to 10% by weight, based on a), of a saturated C.sub.3 - to C.sub.6 -hydrocarbon as blowing agent, and, if desired,c) conventional assistants in effective amounts, has a benzene content of less than 1 ppm and a styrene content of less than 2000 ppm.

Abstract: A process for the production of particulate expandable styrene polymers which have a very low benzene concentration is described using perketal and/or monoperoxycarbonate polymerization initiators. The styrene polymers produced according to the invention can be foamed to give foamed particles and molded, if desired.

Abstract: Expandable styrene polymers containinga) from 80 to 99% by weight of polystyrene,b) from 1 to 20% by weight of a styrene-soluble polymer having a softening point above 140.degree. C.,c) from 3 to 10% by weight, based on the sum of a) and b), of a C.sub.3 - to C.sub.6 -hydrocarbon as blowing agent, and, if desired, d) conventional additives,the mixture of components a) and b) having a melt flow index MFI 200/5 of from 15 to 30, have high heat distortion resistance and a high capacity for expansion.

Abstract: Polyolefin foams having a density of from 0.01 to 0.1 g/cm.sup.3 and having 2 to 1000 cells/mm.sup.2 and containing a resin acid, a lower alkyl ester of a resin acid or (hydro) abietyl phthalate as organic foaming aid have a homogeneous cell structure.

Abstract: The invention relates to expandable polyurethane powder preparations containing blowing agents and to their use for the production of foamed polyurethane moldings.

Abstract: A method for improving the expandability of styrenic polymer particles is disclosed. The method comprises copolymerizing a styrenic monomer with an amount of an acrylate monomer effective to improve the expandability of the particles without adversely affecting their heat sensitivity. Polymer foams of low density can be prepared with reduced amounts of blowing agents.

Abstract: Crystalline polymers and copolymers of propylene in the form of spherical particles having a porosity (expressed in percentage of voids) greater than 15%. These polymers are useful in the preparation of masterbatch containing significant quantities of additives and/or pigments.

Abstract: Polyolefin foams having a density of from 0.01 to 0.1 g/cm.sup.3 and having 2 to 1000 cells/mm.sup.2 and containing a resin acid, a lower alkyl ester or a resin acid or (hydro) abietyl phthalate as organic foaming aid have a homogeneous cell structure.

Abstract: A method for manufacturing pre-expanded particles of polyolefin resin from strand pellets having Tm in melting temperature measured by DSC method, wherein the expansion ratio E of the pre-expanded particles of the resin, the length l and the average diameter d of the strand pellets after having been heated at a temperature (Tm-5.degree. C.) are in the following relational expression.0.04E+0.9.ltoreq.l/d<0.15E+1.3According to the method of the present invention, it is possible to manufacture uniform, spherical pre-expanded particles easily at a moderate cost and obtain a fine-looking expansion-molded articles.

Abstract: A process for the manufacture of core/shell polymer particles comprises forming a core particle containing acid functionality, a first shell around said core of a copolymer of a nonionic monoethylenically unsaturated aromatic monomer and a copolymerisable polar monomer in an amount of at least 15% by weight of the copolymer and having a solubility in water at 20.degree. C. of at least 1% by weight and a second shell around said first shell of a polymer or copolymer of a nonionic monomer having a solubility in water at 20.degree. C. of less than 1% by weight and swelling the particle with a non-volatile alkali to generate one or more vesicles.Preferably each shell contains a polymer or copolymer of styrene.

Abstract: High molecular weight polyethyleneterephthalate resin is currently being used in vast quantities in manufacturing tire cord and in manufacturing trays for frozen foods which can be heated in either microwave or convection ovens. In some applications polyester resins having ultra-high molecular weights are required. For example, some techniques for producing polyester yarn by solution spinning demand ultra-high molecular weight polyester. Unfortunately, it becomes progressively more difficult and expensive to produce polyester resins having higher and higher molecular weights utilizing standard commercial polymerization techniques. This invention discloses a technique for preparing porous polyester beads which can be solid state polymerized very rapidly to ultra-high molecular weights.

Abstract: Foamable photodegradable suspension polymers of vinyl aromatic monomers may be prepared by dissolving a copolymer of a vinyl aromatic monomer and a vinyl ketone in the vinyl aromatic monomer and suspension polymerizing the resulting mixture. The resulting polymer may be foamed and used in the manufacture of food containers.

Abstract: A porous, crystallized, aromatic polycarbonate prepolymer is disclosed, which comprises recurring aromatic carbonate units and terminal hydroxyl and aryl carbonate groups, wherein these terminal groups are in a specific molar ratio and has specific number average molecular weight, surface area and crystallinity. The prepolymer can readily be converted by solid-state condensation polymerization to a porous, crystallized, aromatic polycarbonate having excellent properties. The porous, crystallized, aromatic polycarbonate of the present invention can readily be molded to obtain a shaped, porous, crystallized polycarbonate. The porous, crystallized, aromatic polycarbonate and the shaped, porous, crystallized polycarbonate of the present invention have excellent heat resistance and solvent resistance and exhibit advantageously low water absorption so that these are suited for use as a filter material, an adsorbent or the like.

Abstract: Expandable styrene polymers which contain from 10 to 90% by weight of a crosslinked styrene-diene copolymer containing from 2 to 45% by weight of the diene, and from 1 to 10% by weight of a C.sub.3 -to C.sub.6 -hydrocarbon as blowing agent can be processed to give foams which have high resistance to aromatics.

Abstract: A porous, crystallized, aromatic polycarbonate prepolymer is disclosed, which comprises recurring aromatic carbonate units and terminal hydroxyl and aryl carbonate groups, wherein these terminal groups are in a specific molar ratio, and has specific number average molecular weight, surface area and crystallinity. The prepolymer can readily be converted by solid-state condensation polymerization to a porous, crystallized, aromatic polycarbonate having excellent properties. The porous, crystallized, aromatic polycarbonate of the present invention can readily be molded to obtain a shaped, porous, crystallized polycarbonate. The porous, crystallized, aromatic polycarbonate and the shaped, porous, crystallized polycarbonate of the present invention have excellent heat resistance and solvent resistance and exhibit advantageously low water absorption so that these are suited for use as a filter material, an adsorbent or the like.

Abstract: Foamable photodegradable suspension polymers of vinyl aromatic monomers may be prepared by dissolving a copolymer of a vinyl aromatic monomer and a vinyl ketone in the vinyl aromatic monomer and suspension polymerizing the resulting mixture. The resulting polymer may be foamed and used in the manufacture of food containers.

Abstract: Microsphere wet cake is mixed with a surface barrier coating effective to prevent agglomeration and surface bonding of the microspheres, and removing water by drying with continuous mixing at high shear. In a subsequent step, by the control of the application of heat and balancing temperature and low shear mixing, it is possible to also control expansion of the microspheres.The surface barrier coating in the present invention is any one of a wide diversity of materials which meet the requirements of the intended function, i.e., to prevent the agglomeration of the microspheres during the process. Suitable materials include, by way of example, dry inorganic pigments or filler materials, and the like, and related organic materials.

Abstract: An oil-resistant, expandable styrene polymer containsa) from 10 to 90% by weight of uncrosslinked polystyrene and/or an uncrosslinked styrene copolymer containing at least 50% by weight of copolymerized styrene,b) from 10 to 90% by weight of a crosslinked styrene polymer which contains at least 0.1% by weight, but less than 2% by weight, of a copolymerized monomer having at least two olefinic double bonds,c) from 1 to 10% by weight, based on the sum of a) and b), of a C.sub.3 - to C.sub.6 -hydrocarbon as blowing agent, and, if desired,d) conventional additives in effective amounts,the mixture of a) and b) having a melt flow index MFI (200.degree. C., 5.0 kp) in accordance with DIN 53 735 of from 1 to 20 [g/10 min].

Abstract: Expandable styrene polymers containinga) from 80 to 99% by weight of polystyrene,b) from 1 to 20% by weight of a styrene-soluble polymer having a softening point above 140.degree. C.,c) from 3 to 10% by weight, based on the sum of a) and b), of a C.sub.3 - to C.sub.6 -hyrocarbon as blowing agent, and, if desired, d) conventional additives,the mixture of components a) and b) having a melt flow index MFI 200/5 of from 15 to 30, have high heat distortion resistance and a high capacity for expansion.

Abstract: Flame retardant vinylaromatic thermoplastic resin compositions are provided comprising 100 parts vinylaromatic polymer, 0.1 to 2.0 parts of at least one brominated aliphatic compound, 0.5 to 3.0 parts of at least one other and different brominated organic compound having a higher volatilization temperature and greater heat stability than said brominated aliphatic compound and from 0.05 to 5 parts of at least one melt flow promoter.

Abstract: The cross-linkable, foamable polyolefin resin composition capable of forming foams with excellent mechanical properties and heat resistance is made of (a) .[.30-80.]. .Iadd.14-80 .Iaddend.weight % of a propylene-ethylene random copolymer having an ethylene content of 1.5-6 weight %; (b) 10-60 weight % of a propylene-ethylene random copolymer having an ethylene content of 0.2-1.0 weight %; (c) 10-60 weight % of a linear low-density polyethylene; and (d) 1-30 parts by weight, per 100 parts by weight of the above resin components, of a foaming agent.

Abstract: A stabilized powdered endothermic blowing agent .[.which.]. is a mixture or a polycarboxylic acid and an inorganic carbonate, .[.and.]. .Iadd.the .Iaddend.polycarboxylic acid and inorganic carbonate each having been surface treated with a component which prevents water from being absorbed thereby. The blowing agent is incorporated into a polymeric concentrate used for producing foamed products.