Abstract: A repositionable pressure-sensitive adhesive comprising from about 70% to about 99% hollow, polymeric, acrylate, inherently tacky, infusible, solvent-insoluble, solvent-dispersible, elastomeric microspheres comprising at least one alkyl acrylate or alkyl methacrylate ester, a majority of the microspheres having one or more interior voids having a diameter of at least about 10% of the diameter of the microsphere, and correspondingly, from about 30% to about 1% of a binder copolymer comprising an elastomeric polymeric backbone having pendant therefrom high Tg polymeric moieties.

Abstract: Certain organobromines are added to blends of polyphenylene ether and alkenyl aromatic polymer to reduce mold cool time of the composition. These organobromines also reduce residual blowing agent in the composition after expansion and especially following molding of the composition.

Abstract: Styrene polymer foam particles of from 10 to 30 kg/m.sup.3 in density are obtained by foaming styrene polymers which, per kg, contain from 0.7 to 3 moles of blowing agent mixture composed of from 60 to 90 mol % of water and from 10 to 40 mol % of the C.sub.4 - or C.sub.5 -hydrocarbon with the aid of microwaves.

Abstract: Expandable styrene polymers formed from 50 to 83% by weight of polystyrene and from 17 to 50% by weight of styrene-soluble styreneacrylonitrile copolymer having a total acrylonitrile content of not less than 5% by weight, containing from 3 to 10% by weight of a C.sub.3 -C.sub.6 -hydrocarbon with or without customary additives, are notable for high oil resistance and can be prepared by suspension polymerization of a solution of the styrene-acrylonitrile copolymer in styrene.

Abstract: Hollow, polymeric, acrylate, infusible, inherently tacky, solvent-insoluble, solvent-dispersible, elastomeric, nitrogen-containing, acid-free pressure-sensitive adhesive microspheres having an average diameter of at least about 1 micrometer wherein a majority of the microspheres contain multiple interior voids, a majority of the voids having a diameter of less than about 10% of the diameter of the microsphere, the total of the diameters of the voids being at least about 10% of the diameter of the microsphere.These hollow microspheres are useful as repositionable pressure-sensitive adhesives. The invention also provides pressure-sensitive adhesives consisting essentially of such acid-free hollow microspheres. Aqueous suspensions of these microspheres, processes for their preparation, spray repositionable pressure-sensitive adhesive compositions, and pressure-sensitive adhesive coated sheet materials are also provided.

Abstract: Expandable styrene polymers of from 95 to 99.5% by weight of polystyrene and from 0.15 to 5% by weight of a styrene-soluble styrene/acrylonitrile copolymer having a total content of not less than 0.15% by weight of acrylonitrile, which contain from 3 to 10% by weight of a C.sub.3 -C.sub.6 -hydrocarbon and may contain conventional additives, give foams which do not shrink. The said styrene polymers can be prepared by suspension polymerization of a solution of the styrene/acrylonitrile copolymer in styrene.

Abstract: Expandable and expanded plastic materials having a majority of alkyl acrylate monomeric repeat units are disclosed. These materials when expanded have a volume expansion of at least 60 and maintain that volume expansion for a period of at least 30 minutes under expansion conditions after reaching the volume expansion of 60. Expandable and expanded plastic materials having a majority of alkyl acrylate monomeric repeat units and an inhibitor for the monomer(s) and a crosslinker incorporated into the plastic material upon monomer polymerization are also disclosed. Also disclosed are expandable and expanded plastic materials having majority of alkyl acrylate monomeric repeat units with blowing agents of 2,2-dimethylbutane, 2,3-dimethylbutane or mixtures of one or both with 1-chloro-1,1-difluoroethane or mixtures of at least 30 percent of one or both with other volatile blowing agents.

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.6 -hydrocarbons as blowing agents and, if desired, customary additives, where(a) the polymerization is initiated by rapidly heating the polymerization batch to form 80.degree. to 90.degree. C. within a maximum of 2 hours,(b) subsequently allowing the reaction temperature to increase to from 120.degree. C. to 130.degree. C. by from 8.degree. to 17.degree. C. per hour, and(c) the conversion is formed 30 to 60% when 100.degree. C. is reached, and(d) the conversion is 80% or more when the maximum temperature is reached, and(e) the batch is subsequently kept at from 100.degree. to 130.degree. C. until the residual monomer content in the polymer has dropped to less than 0.1%.

Abstract: Fire-retardant expandable vinyl aromatic polymer beads are prepared by an aqueous suspension method whereby micronized hexabromocyclododecane and a volatile aliphatic hydrocarbon foaming agent are incorporated into particles of a thermoplastic such as polystyrene. The beads are useful in the preparation of molded foam articles having excellent resistance to flame.

Abstract: High molecular weight polyester resins such as polyethylene terephthalate, are sometimes produced from low molecular weight polyester prepolymers having the same composition by solid state polymerization. The low molecular weight polyester prepolymers which are used in such solid state polymerizations are normally prepared by conventional melt polymerizations and are generally in the form of pellets or chips. Solid state polymerization rates can be greatly improved by utilizing polyester prepolymers which are in the form of porous pills. By utilizing polyester prepolymers that are in the form of porous pills, higher molecular weights can be achieved after shorter solid state polymerization times.This invention relates to an improved process for solid state polymerizing porous pills which are made by compacting fine fibers of the polyester prepolymer.

Abstract: Expandable styrene polymers which contain a C.sub.3 -C.sub.6 -hydrocarbon as a blowing agent, an organic bromine compound as a flameproofing agent and small amounts of ammonium salt and of an organic amine give, on expansion, foams which have a particularly homogenous foam structure and a good heat insulation effect.

Abstract: Multi-stage polymer particles containing one or more void space(s) therein are produced by sequential emulsion polymerization of an essentially low-acid earlier polymer stage, encapsulation of said low-acid polymer stage with at least a final polymer stage, contacting said polymer particles with a non-polymeric carboxylic acid or anhydride to permit the acid or anhydride to be absorbed into said low-acid polymer stage and swelling the polymer particles by contacting the particles with an aqueous base. The low-acid polymer stage is formed by emulsion polymerizing a monomer system comprising ethylenically unsaturated monomer(s) and containing less than 5% by weight of monomer(s) containing acid functionality. The low-acid polymer stage is swubsequently encapsulated by one or more polymer stages by emulsion polymerizing ethylenically unsaturated monomer(s) in the presence of the low-acid polymer stage. The final stage has a glass transition temperature (Tg) of about 50.degree. C.

Abstract: Hollow, polymeric, acrylate, infusible, inherently tacky, solvent-insoluble, solvent-dispersible, elastomeric, nitrogen-containing, acid-free pressure-sensitive adhesive microspheres having an average diameter of at least about 1 micrometer wherein a majority of the microspheres contain multiple interior voids, a majority of the voids having a diameter of less than about 10% of the diameter of the microspheres, the total of the diameters of the voids being at least about 10% of the diameter of the microsphere.These hollow microspheres are useful as repositionable pressure-sensitive adhesives. The invention also provides pressure-sensitive adhesives consisting essentially of such acid-free hollow microspheres. Aqueous suspensions of these microspheres, processes for their preparation, spray repositionable pressure-sensitive adhesive compositions, and pressure-sensitive adhesive coated sheet materials are also provided.

Abstract: A pre-expanded particle of a non-crosslinked linear low density polyethylene having an average cell diameter as large as 120 to 1,200 .mu.m which can be molded, without further imparting an expandability prior to molding or without aging under pressure, by heating in a closed mold permeable to a fluid heating medium such as steam to form a well bonded unitary cellular molded article having a good appearance, a high expansion ratio and improved heat resistance and mechanical property with a slight volumetric shrinkage.

Abstract: A process for producing expandable thermoplastic resin beads which comprises suspending in an aqueous medium interpolymer beads comprising a polyphenylene ether resin and a polymerized vinyl aromatic monomer such as styrene, polymerizing the vinyl aromatic monomer in the presence of a polymerization catalyst to interpolymerize the vinyl aromatic monomer with the polyphenylene ether and, optionally, adding a cross-linking agent, to form interpolymerized thermoplastic resin beads, and introducing a blowing agent under pressure into the thermoplastic resin beads. The resulting resin beads have excellent foamability and molding fusability, and a foamed shaped article having superior thermal stability can be prepared from these beads.

Abstract: A process for producing porous, low molecular weight vinyl polymers and copolymers via suspension polymerization in the presence of a dual function porosifier/low molecular weight modifier is disclosed. The process is especially advantageous in that it can be run at a wide variety of temperatures to obtain super porous, low molecular weight resins. Novel super porous, low molecular weight resins are also disclosed.

Abstract: There is a growing demand for high molecular weight polyester resin. For instance, the market for high molecular weight polyethylene terephthalate resin is rapidly expanding. High molecular polyethylene terephthalate resin is currently being used in vast quantities in manufacturing bottles for carbonated beverages, trays for frozen foods which can be heated in either microwave ovens or convection ovens, and in tire cord. There is a growing trend toward higher molecular weights in many applications for such polyester resins. 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 by which polyester resin having extremely high molecular weight can be prepared utilizing a very rapid solid state polymerization process.

Abstract: The present invention relates to a foamable vinyl chloride resin composition for powder molding containing a foaming agent and method for the production thereof.

Abstract: Vinyl halide copolymer resins having relatively high porosity levels are produced by polymerizing a vinyl halide with a comonomer of an acrylated caprolactone. The product produced exhibits high absorbtivity of plasticizer, easy processability and films made therefrom have low fish-eye content.

Abstract: Pre-formed particles of an uncrosslinked, linear low-density polyethylene have a crystalline structure characterized in that two endothermic peaks appear on a DSC curve obtained by differential scanning calorimetry of the pre-foamed particles (said DSC curve having been obtained by heating 1-5 mg of the pre-foamed particles to 220.degree. C. at a rate of 10.degree. C./min by a differential scanning calorimeter) and the energy at the endothermic peak on the higher-temperature side is 5 J/g or more. A process for the production of the pre-foamed particles of the uncrosslinked, linear low-density polyethylene is also disclosed.

Abstract: The present invention provides novel spherical grains of polyamino acid wh can be used as a filler in chromatography, cosmetic powder and the like. The spherical grains can be produced by a method which comprises the steps of preparing a solution of hydrophobic polyamino acid such as poly n-leucine dissolved in an organic solvent; adding the solution to an aqueous medium and agitating said medium so as to obtain a dispersion of the spherical grains of the polyamino acid dispersed in the aqueous medium while evaporating the organic solvent; and taking out the spherical grains of polyamino acid from the dispersion.

Abstract: A process for post-treating pre-expanded polyolefin resin particles which comprises charging in a vessel pre-expanded polyolefin resin particles which are pre-expanded by using an inflammable blowing agent, supplying an inert gas into the vessel, and then discharging the inert gas with the inflammable blowing agent gas extracted from the pre-expanded polyolefin resin particles, from the vessel. According to the process of the invention, the inflammable blowing agent can be extracted efficiently, safely and in a short time from the pre-expanded polyolefin resin particles which are pre-expanded by using the inflammable blowing agent. Consequently, the spontaneous cambustion of the particles can be completely avoided even if sparks are generated on the surface of the pre-expanded particles, therefore, it becomes easy to handle the pre-expanded polyolefin resin particles because the particles can be dried and transported by a pneumatic conveyer.

Abstract: Expanded thermoplastic resinous materials are obtained by mixing styrene-based polymers having mainly a syndiotactic configuration or a thermoplastic resin composition containing said styrene-based polymer and a foaming agent, and then heating the resulting mixture. These expanded materials are excellent in heat resistance and are usefully employed in applications where high heat resistance is needed, e.g., as construction materials, buffer materials and so forth.

Abstract: The present invention provides polypropylene resin pre-expanded beads formed by shrinking polypropylene resin pre-expanded beads originally having a bulk density of not higher than 0.0930 g/cc to give then a bulk volume ratio of 10-75% at the normal temperature and the normal pressure, a manufacturing method thereof and an expansion-molding method with the aforementioned pre-expanded beads. According to this invention, it is possible to greatly reduce storing and transporting costs per unit weight of pre-expanded beads.

Abstract: Expandable and expanded plastic materials having a majority of alkyl acrylate monomeric repeat units are disclosed. These materials when expanded have a volume expansion of at least 60 and maintain that volume expansion for a period of at least 30 minutes under expansion conditions after reaching the volume expansion of 60. Expandable and expanded plastic materials having a majority of alkyl acrylate monomeric repeat units and an inhibitor for the monomer(s) and a crosslinker incorporated into the plastic material upon monomer polymerization are also disclosed. Also disclosed are expandable and expanded plastic materials having a majority of alkyl acrylate monomeric repeat units with blowing agents of 2,2-dimethylbutane, 2,3-dimethylbutane or mixtures of one or both with 1-chloro-1,1-difluoroethane or mixtures of at least 30 percent of one or both with other volatile blowing agents.

Abstract: Expandable polymers in particle form for the preparation of foams having high heat distortion resistance contain from 20 to 94.9% by weight of a styrene polymer, from 0.1 to 75% by weight of a polyphenylene ether and from 5 to 20% by weight of a blowing agent mixture of aliphatic or cycloaliphatic hydrocarbons on the one hand and aromatic hydrocarbons, alcohols, ketones, ethers, esters and/or chlorohydrocarbons on the other hand.

Abstract: A polyamide powder consisting essentially of elementary porous particles having a "gypsum rose" structure and a process for preparing a polyamide powder comprising polymerizing by anionic polymerization lactam in a solvent medium in the presence of a catalyst, an activator, and at least one amide; one of which is N,N'-alkylene bisamide; said polymerization being initiated with said lactam and said amide used in an amount such that the solvent is in the supersaturated state at the polymerization initiation temperature.

Abstract: Certain organobromines are added to blends of polyphenylene ether and alkenyl aromatic polymer to reduce mold cool time of the composition. These organobromines also reduce residual blowing agent in the composition after expansion and especially following molding of the composition.

Abstract: A volatile foaming agent for thermoplastic foam is a blend of about 65 to 75 weight percent chlorodifluoro-methane and from about 25 to 35 weight percent pentane.

Abstract: A process for producing expandable thermoplastic resin beads which comprises suspending in an aqueous medium interpolymer beads comprising a polyphenylene ether resin and a polymerized vinyl aromatic monomer such as styrene, polymerizing the vinyl aromatic monomer in the presence of a polymerization catalyst to interpolymerize the vinyl aromatic monomer with the polyphenylene ether and, optionally, adding a cross-linking agent, to form interpolymerized thermoplastic resin beads, and introducing a blowing agent under pressure into the thermoplastic resin beads. The resulting resin beads have excellent foamability and molding fusability, and a foamed shaped article having superior thermal stability can be prepared from these beads.

Abstract: Expandable and expanded particles are prepared from an alkenyl aromatic polymer and a volatile fluid blowing agent mixture of a first blowing agent of 1,1-difluoro-1-chloroethane; and a second blowing agent selected from normal pentane, isopentane, neopentane or mixtures of the various pentanes.

Abstract: A process for producing hollow polymer latex particles, which comprises(1) adding a base to a carboxyl-containing polymer latex obtained by emulsion polymerization of a monomeric mixture composed of at least 0.1% by weight of an ethylenically unsaturated carboxylic acid and another ethylenically unsaturated monomer copolymerization with the carboxylic acid to adjust the pH of the polymer latex to at least 7 and swell the polymer latex particles, and(2) adding an acid to the polymer latex formed in (1) to adjust the pH of the latex to not more than 7.

Abstract: Foamed particles of a propylene resin are described which comprises, as a base resin, a random copolymer of propylene and 1-butene, said random copolymer having a 1-butene content of from 3 to 12% by weight.A foamed mold article is also described which is composed of a random copolymer of propylene and 1-butene, and having a density of from 0.015 to 0.09 g/cm.sup.3.A bumper core material for use in automobile bumpers is also discribed which is composed of a foamed mold article of a random copolymer of propylene and 1-butene, said random copolymer having a 1-butene content of from 3 to 12% by weight, said foamed mold article having a density of from 0.02 to 0.08 g/cm.sup.3, a compression stress at 50% compression as measured at 20.degree. C. of 2.5 to 10 kg/cm.sup.2, and an energy absorption efficiency as measured at 20.degree. C. of 60 to 90% the ratio (E.sub.80 /E.sub.20) of the amount of the energy absorption of said foamed mold article as measured at 80.degree. C. (E.sub.

Abstract: A process for producing crosslinked polymer particles which comprises a first step of polymerizing a polymerizable monomer containing from 0.1 to 2.0% by weight, based on the entire polymerizable monomer, of a crosslinkable monomer in a medium in which the polymerizable monomer is soluble but the resulting polymer is insoluble, to obtain crosslinked polymer particles having a particle size of from 0.8 to 10 .mu.m, and a second step of letting the crosslinked polymer particles absorb from 1 to 50 times by weight of a polymerizable monomer containing from 2 to 100% by weight, based on the entire polymerizable monomer, of a crosslinkable monomer in an aqueous medium, followed by polymerization to obtain crosslinked polymer particles having a particle size of from 1 to 30 .mu.m and a crosslinking degree of from 1.0 to 98%.

Abstract: A process for producing crosslinked polymer particles which comprises a first step of polymerizing a polymerizable monomer containing from 0.1 to 2.0% by weight, based on the entire polymerizable monomer, of a crosslinkable monomer in a medium in which the polymerizable monomer is soluble but the resulting polymer is insoluble, to obtain crosslinked polymer particles having a particle size of from 0.8 to 10 .mu.m, and a second step of letting the crosslinked polymer particles absorb from 1 to 50 times by weight of a polymerizable monomer containing from 2 to 100% by weight, based on the entire polymerizable monomer, of a crosslinkable monomer in an aqueous medium, followed by polymerization to obtain crosslinked polymer particles having a particle size of from 1 to 30 .mu.m and a crosslinking degree of from 1.

Abstract: Foamed products are prepared by subjecting a crosslinked polymer such as an ethylene-carbon monoxide copolymer susceptible to heating by high frequency electromagnetic radiation such as microwave or radio frequency which has been imbibed or impregnated with a suitable mechanical or physical blowing agent such as a halogenated hydrocarbon to sufficient high frequency electromagnetic radiation to cause foaming of the polymer.

Abstract: Prefoamed particles of a polyolefin resin are produced by dispersing starting particles of the polyolefin resin, which contains a volatile foaming agent, in a dispersant in a pressure vessel, heating the resultant dispersion to a temperature of at least the softening point of the starting particles in said pressure vessel and then opening the vessel at one end thereof so as to release the starting particles and dispersant into an atmosphere of a pressure lower than the internal pressure of the vessel. The release of the starting particles and dispersant is performed while feeding a heating liquid.

Abstract: Foamed products are prepared by subjecting a crosslinked polymer such as an ethylene-carbon monoxide copolymer susceptible to heating by high frequency electromagnetic radiation such as microwave or radio frequency which has been imbibed or impregnated with a suitable mechanical or physical blowing agent such as a halogenated hydrocarbon to sufficient high frequency electromagnetic radiation to cause foaming of the polymer.

Abstract: A process for producing expandable thermoplastic resin beads which comprises suspending in an aqueous medium interpolymer beads comprising a polyphenylene ether resin and a polymerized vinyl aromatic monomer such as styrene, polymerizing the vinyl aromatic monomer in the presence of a polymerization catalyst to interpolymerize the vinyl aromatic monomer with the polyphenylene ether and, optionally, adding a cross-linking agent, to form interpolymerized thermoplastic resin beads, and introducing a blowing agent under pressure into the thermoplastic resin beads. The resulting resin beads have excellent foamability and molding fusability, and a foamed shaped article having superior thermal stability can be prepared from these beads.

Abstract: Vinyl halide copolymer resins having relatively high porosity levels are produced by polymerizing a vinyl halide with a comonomer of an acrylated caprolactone. The product produced exhibits high absorbtivity of plasticizer, easy processability and films made therefrom have low fish-eye content.

Abstract: Moldable foam beads comprising a silane-crosslinked polyolefin foam are produced by mixing a composition comprising a silane-modified polyolefin (such as a silane-grafted polyethylene) and a silanol condensation catalyst in an extruder to produce a melt, then injecting a blowing agent into the melt at a rate effective to produce a desired foam density in the extrudate; extruding and cutting the melt to form foam beads; and exposing the foam beads to moisture to produce silane crosslinking of the polyolefin foam.

Abstract: The present invention discloses a vinylidene chloride resin type in-mold foam molding having a broad cross-sectional area and a free shape, which is useful as thermal insulating plate materials or as anti-shock molded vessels, and also to foam particles, which are or expandable particles convenient for the preparation thereof. The present invention is also related to a series of advantageous foaming techniques for completion of such a molding.

Abstract: The present invention relates to expandable and expanded alkenyl aromatic polymer particles having the ability to use a decreased amount of blowing agent to produce an expanded alkenyl aromatic polymer particle of an equivalent bulk density or the same amount of blowing agent to produce an expanded alkenyl aromatic polymer particle having a decreased bulk density by including a density modifier in the expandable alkenyl aromatic polymer particle in an amount of about 0.005 to 0.5 weight percent by weight of the total mixture. Also included as part of the invention are methods of making the expandable and expanded alkenyl aromatic polymer particles wherein the expandable and expanded alkenyl aromatic polymer particles have a density modifier included in an amount of about 0.005 percent to about 0.5 weight percent by weight of the total mixture.

Abstract: The present invention provides a process for production of expansion-molded articles in a mold of a linear low density polyethylene resin which comprises compressing pre-expanded linear low density polyethylene resin beads having two melting points when measured by differential scanning calorimetry and, when the melting point at a low temperature side and the melting point at a high temperature side are designated T.sub.ML and T.sub.MH respectively, between said two melting points and the peak fusion area at said T.sub.ML is designated A.sub.L and the peak fusion area at said T.sub.MH is designated A.sub.H satisfying:5%.ltoreq.A.sub.H /A.sub.L .ltoreq.

Abstract: The polymerization of compositions containing styrene by an aqueous suspension process in which is used a suspending agents system constituted by a mineral agent and, an extending agent which is at least a rosin acid derivative (abietic acid, neoabietic acid, dextropimaric acid) or their salts of a metal belonging to Group IIa of the Periodic Classification of elements. The use of this extending agent has the advantage of ameliorate the surface aspect of moulded articles obtained from expanded polymer pearls prepared with the above polymerization process.

Abstract: A process of forming hollow microspheres containing carbon or a polymer which is a carbon precursor. The process comprises forming a solution in a liquid solvent of a polymer having the following properties (a) a molecular weight of at least 10,000 and a long chain structure; (b) an ability to be coagulated by or precipitated from the solution by a non-solvent for the polymer; (c) an ability to form a continuous stretchable film when coagulated or precipitated from solution; (d) a chemical structure which is infusible or capable of being rendered infusible, and (e) a high carbon yield of at least 30% by weight upon being carbonized in a non-reactive atmosphere. An insoluble particulate blowing agent is incorporated into the solution and the solution is then divided into droplets and the droplets are introduced into a liquid bath containing a suitable non-solvent for the polymer.

Abstract: A process for producing pre-expanded particles of a thermoplastic resin, wherein said particles are polyolefin resin particles which are obtained by polymerizing an olefin in the presence of a Ziegler-Natta catalyst, said polyolefin resin particles containing no more than 1% by weight of particles having a particle diameter of 105 .mu.m or smaller and having a particle size distribution represented by equation:R(Dp)=100exp[-(Dp/De).sup.n ]wherein Dp represents a particle diameter (.mu.m) of polymer particles; R(Dp) represents a cummulative weight percentage; De represents an absolute size constant that is a particle diameter (.mu.m) corresponding to R(Dp)=36.8% by weight; and n represents a distribution constant, in which De is 300 or more, and n is 2.5 or more. Pre-expanded polyolefin resin particles free from scatters of cell diameter or particle diameter and having a high expansion ratio can be obtained without using pelletized polymer particles or pulverized pellets of polymer particles.

Abstract: Cups have been molded from expandable styrene polymer particles having a portion or all of the blowing agent replaced by isopentane. Cups molded from these beads were coffee leak tested and generally exhibited enhanced retention of coffee.

Abstract: Prefoamed particles consisting essentially of an ethylene/propylene random copolymer, wherein said prefoamed particles are obtained by foaming particles of an ethylene/propylene random copolymer containing 1 to 4% by weight of random-copolymerized ethylene at a temperature in the range of from Tm - 15.degree. C. to Tm - 5.degree. C. (in which Tm is a temperature at which to terminate melting of the copolymer) and within the range of 141.degree. to 151.degree. C., and wherein said prefoamed particles have a crystal structure characterized in that in a DSC curve obtained by heating 1 to 3 mg of the copolymer prefoamed particles to 220.degree. C. at a heating rate of 10.degree. C./min. with a differential scanning calorimeter, there appear a peak (characteristic peak) characteristic of the copolymer and another peak (high temperature peak) at a higher temperature than a temperature at which the characteristic peak appears.

Abstract: The present invention provides novel spherical grains of polyamino acid wh can be used as a filler in chromatography, cosmetic powder and the like. The spherical grains can be produced by a method which comprises the steps of preparing a solution of hydrophobic polyamino acid such as poly n-leucine dissolved in an organic solvent; adding the solution to an aqueous medium and agitating said medium so as to obtain a dispersion of the spherical grains of the polyamino acid dispersed in the aqueous medium while evaporating the organic solvent; and taking out the spherical grains of polyamino acid from the dispersion.