Abstract: Expandable thermoplastic polyurethane comprising blowing agent, wherein the Shore hardness of the thermoplastic polyurethane is from A 44 to A 84.

Abstract: The invention relates to a process for preparing a foamed polymer composition using expandable hollow microbeads, wherein, in a first process strand, first starting materials, which include at least the predominant portion of the polymer or polymers to be used, are mixed and degassed to give a premix, whereafter this premix is subjected to a pressure such that the pairing of this pressure with the temperature of the premix is below the pressure and temperature pairing that is critical for triggering the expansion of the hollow microbeads to be used, wherein, in a second process strand, second starting materials, including the hollow microbeads to be used, are degassed, whereafter the second starting materials treated in the second process strand are added to the premix prepared in the first process strand, whereafter the second starting materials are mixed with the premix.

Abstract: A process for producing pre-expanded particles, comprising the steps of: impregnating 100 parts by weight of polystyrene type resin particles with a volatile blowing agent in the presence of 0.1 to 2.0 parts by weight of a first antistatic agent to obtain expandable resin particles; and bringing 100 parts by weight of the expandable resin particles into contact with 0.1 to 2.0 parts by weight of a second antistatic agent in the presence of an antifoaming agent, and then pre-expanding the particles, thereby obtaining pre-expanded particles, wherein the second antistatic agent and the antifoaming agent are used in a ratio by weight of 1:0.04 to 1.50.

Abstract: The present invention provides pre-expanded polypropylene resin beads comprising (A) a glycerin monoester of a C6 to C24 fatty acid and/or a polyglycerin monoester of a C6 to C24 fatty acid and (B) a glycerin diester of a C6 to C24 fatty acid(s) and/or a polyglycerin diester of a C6 to C24 fatty acid(s), in such a manner that a weight ratio [=(A)/(B)] between (A) and (B) in the polypropylene resin particles is 1.3 or more but 10 or less, and a total content [=(A)+(B)] is 0.3 parts by weight or more but 5 parts by weight or less with respect to 100 parts by weight of the polypropylene resin. The resin particles can be excellently used in in-mold foaming, without requiring washing with a chemical like nitric acid or metaphosphate soda, and can provide a polypropylene resin in-mold foamed product with good antistatic properties.

Abstract: A process for producing expanded polyolefin resin particles with use as a foaming agent of water contained in an aqueous dispersion medium. The process includes dispersing polyolefin resin particles together with the aqueous dispersion medium into a closed vessel; heating the polyolefin resin particles up to or above a softening temperature of the polyolefin resin particles and pressurizing the polyolefin resin particles; and releasing the polyolefin resin particles into a zone whose pressure is lower than an internal pressure of the closed vessel. The polyolefin resin particles are composed of a polyolefin resin composition including polyolefin resin, polyvalent alcohol and a foam nucleating agent.

Abstract: A process for producing expanded polyolefin resin particles with use as a foaming agent of water contained in an aqueous dispersion medium. The process includes dispersing polyolefin resin particles together with the aqueous dispersion medium into a closed vessel; heating the polyolefin resin particles up to or above a softening temperature of the polyolefin resin particles and pressurizing the polyolefin resin particles; and releasing the polyolefin resin particles into a zone whose pressure is lower than an internal pressure of the closed vessel. The polyolefin resin particles are composed of a polyolefin resin composition including polyolefin resin, a water-absorbing substance, and a foam nucleating agent.

Abstract: Process for producing expanded polyolefin resin particles with use as a foaming agent in water contained in an aqueous dispersion medium. The process includes dispersing polyolefin resin particles with use as a foaming agent of water contained in an aqueous dispersion medium. The process includes dispersing polyolefin resin particles together with the aqueous dispersion medium into a closed vessel, heating the polyolefin resin particles up to or above a softening temperature of the polyolefin resin particles and pressurizing the polyolefin resin particles, and releasing the polyolefin resin particles into a zone whose pressure is lower than an internal pressure of the closed vessel. The polyolefin resin particles are composed of a polyolefin resin composition including a polyolefin resin, polyethylene glycol homopolymer and a foam nucleating agent.

Abstract: The invention relates to a cellular elastomer which is anisotropic, with anisotropy being defined by the compressive modulus in one of three orthogonal directions being greater than that in the other two directions by a factor of at least 1.5. The invention also relates to a cellular elastomer containing magnetizable particles which have a chain-like alignment along one spatial direction. The invention also relates to a process for producing a cellular elastomer containing magnetiable particles and the use of such elastomers in articles of manufacture.

Abstract: The present invention relates to a particulate expandable polylactic acid which functions as a starting material for producing foamed moulded products. The present particulate expandable polylactic acid is provided with a coating so as to improve the fusion properties. The present invention also relates to a method for producing a particulate expandable polylactic acid as well as to a method for producing a foamed moulded product and to the moulded product obtained thereby.

Abstract: A roof mounting system can include a roof substrate and flashing supportable on the substrate and including an outwardly extending projection having a concave interior side and an aperture extending through the projection between top and bottom surfaces of the flashing. A seal can extend through the aperture and contact at least a portion of the top surface and at least a portion of the bottom surface. The seal can be conformable with the concave interior side and can define a seal aperture substantially aligned with the flashing aperture. A mounting bracket can be supportable on the flashing and can define an aperture sized to receive at least a portion of each of the seal and the projection. A fastener can extend through the mounting bracket aperture, seal aperture, and flashing aperture to inhibit fluid flow through the flashing aperture.

Abstract: Foamed polyolefin resin beads having antistatic properties obtained by a process, which includes dispersing polyolefin resin beads into an aqueous medium, injecting a blowing agent, stirring and allowing the polyolefin resin beads to foam and expand. The polyolefin resin beads are composite resin beads comprising a core layer of a core layer polyolefin resin and a covering layer of a covering layer polyolefin resin.

Abstract: A method of reducing an odor of composite resin particles comprising the step of: fluidizing the composite resin particles, which contain a polyolefin-based resin and a polystyrene-based resin and which are used for producing an expanded molded article, in a container with a gas that is blown thereinto from its bottom and that has a temperature of (T?40)° C. to (T?10)° C. (T is a softening temperature of the composite resin particles), to reduce the odor generated from a raw material of the composite resin particles and generated according to a method of the composite resin particles, wherein the composite resin particles whose odor is reduced are impregnated with a blowing agent; and the resultant is pre-expanded and then subject to an in-mold forming to make the expanded molded article have an odor strength of 3 or less in average value in odor test in which odor of an isovaleric acid diluted 100000 times is defined as 3, which means a reference odor, within 0 to 5 levels of the odor strength.

Abstract: The invention provides a composition and process for producing expandable beads from a compostable or biobased thermoplastic polymer. A key aspect of this invention is the ability to incorporate sufficient amounts of hydrocarbon blowing agent into the matrix of the compostable or biobased polymer. The following process may be used. First, the raw materials of compostable or biobased polymers, hydrophobic additive, and other additives are mixed by melt processing techniques. Next, a hydrocarbon blowing agent is added to the admixture, either by addition into the melt or by impregnation into the solid, to produce an expandable bead. Small, lightweight, foamed beads are produced by heating the expandable bead. Then, the expanded beads are subsequently used in conventional operations for molding into foamed articles.

Abstract: Process for the preparation of foamed thermoplastic polyurethanes characterised in that the foaming of the thermoplastic polyurethane is carried out in the presence of thermally expandable microspheres.

Abstract: A pre-expanded polypropylene resin particle can be produced in the following manner: a polypropylene resin particle produced by an under water cut method, water, a dispersing agent, and a foaming agent are charged in a pressure-resistant container, the resulting mixture is heated to a temperature equal to or higher than the softening temperature of the polypropylene resin particle to allow the polypropylene resin particle to be impregnated with the foaming agent under pressure, and the resulting product is released into the atmosphere having a pressure lower than the pressure of the inside of the pressure-resistant container. As the polypropylene resin composition, a composition is used which comprises 100 parts by weight of a polypropylene resin and 1 to 20 parts by weight of a polyethylene resin having a melt viscosity of 10 to 2000 mPa·s at 140° C.

Abstract: A thermally foamable microsphere having a structure that a foaming agent is encapsulated in an outer shell formed from a polymer, wherein the foaming agent contains isododecane, and a production process of the thermally foamable microsphere by a suspension polymerization process using a polymerizable monomer and a foaming agent containing dodecane.

Abstract: A method for forming a fire resistant material is disclosed. The method comprises providing a plurality of expandable beads of a polymeric material. The beads are coated with an exfoliable graphite. The exfoliable graphite is adhered to the beads with a resin having a solubility parameter of the polymeric material. The beads are thereafter caused or allowed expand and fuse.

Abstract: A method for forming a fire resistant material is disclosed. The method comprises providing a plurality of expandable beads of a polymeric material. The beads are coated with an exfoliable graphite. The exfoliable graphite is adhered to the beads with a resin having a solubility parameter of the polymeric material. The beads are thereafter caused or allowed to expand and fuse.

Abstract: Process for preparing polymer, e.g. polystyrene, particles that may not or may contain a water-retaining agent and that require only a one-step process for incorporating the water-retaining agent. The polymer particles may be prepared via an extrusion process, or a bulk polymerization process wherein a water-retaining agent is blended into the polymer melt. Water is incorporated into the particles by soaking them in hot or cold water or treating the particles with steam for a predetermined time depending on the desired water content in the particles. The water-retaining agent may be starch, zeolite, silica dioxide or poly (N-isopropyl acrylamide) ranging from 0.1% to 10.0% by weight. The particles can be expanded via appropriate means to form pre-expanded or expanded particles in a conventional manner.

Abstract: Olefin polymer-based, durable, open-cell foam compositions, structures and articles derived from same; methods for preparation of such foams; and use of the dry durable foams in various applications are disclosed. Further described is use of the foams and structures and articles made of same in absorption, filtration, insulation, cushioning and backing applications, and in particular for odor removal, hygiene and medical applications due to, among other properties, good absorption capabilities, softness and/or flexibility of the foams and their recyclable nature.

Abstract: Closed cell polyamide foams are prepared by subjecting a polyamide resin to inert gases at an elevated pressure and at a temperature above the softening point of the resin and reducing the pressure while the temperature is maintained above the softening point of the resin, resulting in expansion of the resin.

Abstract: Expanded and extruded biodegradable polymer foams are obtained using biodegradable polymers and environmentally benign non-VOC methyl formate as a blowing agent. The blowing agent can be a blend further including at least one co-blowing agent, preferably an environmentally friendly species (e.g., non-VOC), which is either a physical co-blowing agent (e.g. an inorganic agent, a hydrocarbon, a halogenated hydrocarbon, a hydrocarbon with polar, functional group(s), water or any combination thereof), or a chemical co-blowing agent, or combinations thereof. The blowing agent blend can include any combination of methyl formate and one or more co-blowing agents. The polymer foam can include a biodegradable polymer or its blends with other biodegradable polymers or conventional (non-biodegradable) polymers. The methyl formate-based blowing agent blends produce stable foams for various applications, including containers, packaging systems, as well as for insulation and protective cushioning.

Abstract: Process for processing expandable polymer particles e.g. polystyrene (EPS) that eliminates the maturing step between the pre-expander and molding steps. The expandable particles are first over pressurized with gas, e.g. air, carbon dioxide, nitrogen, and mixtures thereof, at a pressure between 500 and 8000 kPa and a temperature between ?20° C. and 130° C. for 15 to 7200 minutes to create a gas pressure in the particles. Using the gas pressure in the particles, pre-expanding the particles with a heating medium, e.g. steam at a temperature between 100° C. and 120° C. and at a pressure ranging above atmospheric pressure and below the gas pressure in said particles, i.e. 50 to 200 kPa for 5 to 120 seconds. The pre-expanded particles are air dried in the pre-expander while holding a positive pressure in the particles; are optionally transferred to a pressure silo; and then are transferred to a molding machine where the gas pressure in the particles is used to form a foam article.

Abstract: Process for the preparation of foamed thermoplastic polyurethanes characterized in that the foaming of the thermoplastic polyurethane is carried out in the presence of thermally expandable microspheres.

Abstract: A heat-peelable adhesive sheet which comprises a substrate and, formed on at least one side thereof, a heat-expandable layer containing heat-expandable microspheres and an adhesive layer comprising an adhesive substance and in which the substrate has heat resistance and stretchability can be used to cut an adherend so as to form and secure a sufficient space between the resultant cut pieces and can withstand a heat treatment for expanding the heat-expandable layer. Consequently, the adhesive sheet can heighten the operating efficiency and working efficiency in the step of separating and recovering the cut pieces.

Abstract: A heat-peelable adhesive sheet which comprises a substrate and, formed on at least one side thereof, a heat-expandable layer containing heat-expandable microspheres and an adhesive layer comprising an adhesive substance and in which the substrate has heat resistance and stretchability can be used to cut an adherend so as to form and secure a sufficient space between the resultant cut pieces and can withstand a heat treatment for expanding the heat-expandable layer. Consequently, the adhesive sheet can heighten the operating efficiency and working efficiency in the step of separating and recovering the cut pieces.

Abstract: The present invention relates to an imaging element comprising at least one image receiving layer and a support, wherein said image receiving layer comprises an open celled microcellular foam. The present invention also relates to an imaging element comprising at least one image receiving layer, an absorbing layer and a support, wherein the absorbing layer comprises an open celled microcellular foam.

Abstract: The present invention provides polypropylene resin pre-expanded particles having small fluctuation in cell diameter and expansion ratio compared to in the past. The pre-expanded particles are obtained by having as a base resin, a polypropylene resin composition comprising polypropylene resin (A), a compound having a triazine skeleton and molecular weight of at most 300 per triazine skeleton unit (B) and as a random component, hydrophilic polymer (C) and inorganic filler (D) and water as the foaming agent. By using the pre-expanded particles, a polypropylene resin in-mold expanded article having decreased unevenness in color and fluctuation in weight can be obtained.

Abstract: The invention relates to a process for the production of expanded or expandable polyolefin beads by impregnating polyolefin granules with a volatile blowing agent in suspension under pressure. As suspension aid, use is made of a mixture of a water-insoluble inorganic compound and a surfactant, and the impregnation is carried out in the presence of a surface-active polymer carrying carboxyl or carboxylate groups.

Abstract: Pre-expanded particles of polyolefin resin having less fluctuation in expansion ratio, uniform particle size and low expansion ratio are provided without using any volatile foaming agent. The low expansion ratio means 2 to 10 times, preferably 3 to 8 times. Resin particles to be released are uniformly contacted with saturated vapor at the time of pre-expanding polyolefin resin particles by dispersing the resin particles into an aqueous dispersion medium in a closed vessel, heating the resin particles to temperature of at least the softening point of the polyolefin resin and releasing the particles from the closed vessel into an atmosphere of lower pressure than the inner pressure of the closed vessel.

Abstract: A water-containing polyolefin resin composition containing a polyolefin resin and a hydrophilic polymer and having a water content of 1 to 50% by weight which is suitable for use in preparation of polyolefin resin pre-expanded particles, and pre-expanded particles of a polyolefin resin prepared by pre-expanding the water-containing polyolefin resin composition the particles having a an apparent expansion ratio of 5 to 60, a closed cell ratio of 80 to 100% and an average cell diameter of 50 to 500 &mgr;m.

Abstract: Polyolefin resin pre-expanded particles having two fusion peaks on DSC curve wherein the proportion of the heat of fusion Qh of the peak appearing on the high temperature side based on the total heat of fusion of the two peaks represented by the equation: [Qh/(Ql+Qh)]×100 falls within the range of 10 to 60% in which Ql is the heat of fusion of the peak appearing on the low temperature side, and the standard deviation of said proportion is not more than 1.2. The pre-expanded particles are prepared by releasing an aqueous dispersion of resin particles impregnated with a blowing agent from a vessel into an atmosphere of lower pressure than the inner pressure of the vessel to expand the particles, while stepwise or continuously raising the inner temperature or the inner pressure of the vessel at a specific rate, and can be molded with stable molding cycle to give cellular molded articles having stable dimensions.

Abstract: To provide a process for preparing polyolefin resin pre-expanded particles which enables to prepare pre-expanded particles having lower fluctuation in expansion ratios. Polyolefin resin pre-expanded particles are prepared by a process comprising steps of dispersing polyolefin resin particles into an aqueous dispersion medium in an autoclave; heating the resin particles to temperature of at least the softening point of the polyolefin resin and pressuring the same; releasing said resin particles from the autoclave through a release port into an atmosphere of lower pressure than the inner pressure of the autoclave; thereby pre-expanding the resin particles, wherein at the releasing step, the resulting pre-expanded particles are contacted with gas of at least 60° C. and collided with a collision board or a container wall disposed at a distance of 5 mm<D, D representing the distance from the release port to the collision board or the container wall.

Abstract: Process for the preparation of expandable polyvinylarene particles in which compact polyvinylarene particles are impregnated by an inorganic N2- and/or O2-containing gas at a temperature below 95° C. and at a pressure of 100 to 2,000 kPa gauge.

Abstract: Porous polyvinylarene particles having a apparent density do of 600 to 200 kg/m3, which particles contain a nucleating agent and 2.0% by weight or less, based on the amount of polyvinylarene, of a volatile organic blowing agent. The invention also relates to a process for the preparation of these particles as well as to the use of these particles in the preparation of expanded particles and foamed articles.

Abstract: A process for preparing pre-expanded particles of a thermoplastic resin without washing the prepared pre-expanded particles to remove a dispersing agent remaining thereon and without discharging waste water, which comprises charging particles of a thermoplastic resin and an aqueous dispersion medium containing a dispersing agent into a closed pressure vessel, heating the resulting aqueous dispersion to a temperature of not less than the softening point of the thermoplastic resin, thereby impregnating the particles with water to have a water content of 1 to 50% by weight, releasing the dispersion into a lower pressure atmosphere, thereby expanding the particles, recovering the dispersion medium containing the dispersing agent, and recycling it as a dispersion medium to the pressure vessel.

Abstract: The invention relates to expandable olefin bead polymers which comprise a blowing agent with a boiling point of from −5 to 150° C., selected from the group consisting of alkanes, alkanols, ketones, ethers and esters. The particles are unfoamed and have a bulk density above 500 g/l, and can be foamed to a bulk density below 200 g/l after storage for one hour at room temperature in free contact with the atmosphere. They are prepared by impregnating polyolefin pellets in suspension in a pressure vessel with the blowing agent, cooling the batch below 100° C., reducing the pressure and isolating the particles.

Abstract: Polyolefin resin pre-expanded particles having two fusion peaks on DSC curve wherein the proportion of the heat of fusion Qh of the peak appearing on the high temperature side based on the total heat of fusion of the two peaks represented by the equation: [Qh/(Ql+Qh)]×100 falls within the range of 10 to 60% in which Ql is the heat of fusion of the peak appearing on the low temperature side, and the standard deviation of said proportion is not more than 1.2. The pre-expanded particles are prepared by releasing an aqueous dispersion of resin particles impregnated with a blowing agent from a vessel into an atmosphere of lower pressure than the inner pressure of the vessel to expand the particles, while stepwise or continuously raising the inner temperature or the inner pressure of the vessel at a specific rate, and can be molded with stable molding cycle to give cellular molded articles having stable dimensions.

Abstract: Process for the preparation of expanded polyvinylarene particles in which polyvinylarene particles pre-expanded to an apparent density do ranging between 600 and 200 kg/m3 are impregnated by an inorganic gas, and the impregnated particles thus obtained are expanded to an apparent density of at least three times lower than do.

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

Abstract: In a process for multifoaming expandable plastics, such as, for instance, EPS, EPE, EPP or polymer mixtures, with prefoaming being effected in a first step and afterfoaming of already prefoamed material being effected in at least one further step, it is provided that discontinuous or batchwise foaming is carried out as final afterfoaming. A device for multifoaming expandable plastics, such as, for instance, EPS, EPE, EPP or polymer mixtures, includes at least one storage or supply means and a foaming vessel for the discontinuous or batchwise afterfoaming of the prefoamed expandable plastics, whereby precisely adjustable bulk densities are attainable in an afterfoaming procedure while observing tight environmental conditions.

Abstract: A process for multifoaming expendable plastics, such as, for instance, EPS, EPE, EPP or polymer mixtures, wherein prefoaming is effected in a first step and after foaming of already prefoamed material is effected in at least one further step. The process also provides that discontinuous or batchwise foaming is carried out as final afterfoaming.

Abstract: The object of the present invention is to provide an in-mold foaming article of a propylene resin composition having improved productivity and stable quality in internal molding, and simultaneously a compressive strength and a tensile strength thereof at high density range are improved at the same time. The in-mold foaming article is obtained by using a pre-foamed particle having a density of 90 to 300 g/L and an open cell ratio of at most 12%, wherein the pre-foamed particle comprises a resin composition having (A) 100 parts by weight of a polypropylene resin and (B) 0.01 to 20 parts by weight of a hydrophilic polymer as a base material resin, and water as a foaming agent, the pre-foamed particle having at least two endothermic peaks in a DSC curve obtained in differential scanning calorimetry.

Abstract: The invention relates to a process for the preparation of expanded polystyrene particles in which polystyrene beads containing water as the sole expanding agent are expanded. The process involves the following stages: A) the polystyrene beads are pre-expanded at temperatures above 100° C., B) the pre-expanded particles are dried in dry air at temperatures between 20° and 95° C. over a period of from 1 to 10 hours, C) the dried expanded particles are further expanded with steam at temperatures ranging from 100° to 140° C., and D) the stages b and c are repeated as often as is necessary to achieve the desired bulk density.

Abstract: The present invention relates to a homogeneous composition of an expandable styrene polymer in the form of beads comprising (a) 100 parts b.w. of a styrene polymer having a weight-average molecular mass of 150,000 to 300,000 and a residual monomer content of less than 2,000 ppm, (b) from 2 to 9 parts by weight of at least one blowing agent comprising n-pentane, (c) from 0.1 to less than 1.0 part by weight of a petroleum wax comprising a mixture of C18 to C80 alkanes, and (d) from 0 to 1.0 part by weight of a nucleating agent chosen from synthetic Fisher-Tropsch or polyolefin waxes. The composition allows the step of pre-expanding the beads to be improved by increasing the rate of expansion of the beads and by improving the productivity of the pre-expansion step, without substantially affecting the final molding step.

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

Abstract: A process comprises producing expanded polyolefin particles by impregnating polyolefin granules with a volatile blowing agent in suspension under pressure, and then releasing the pressure. The suspension medium has a lower density than the polyolefin granules and the suspension is practically free from suspension agents.

Abstract: There is provided a pre-expanded particle having a high expansion ratio and excellent flexibility and cushioning property. The in-mold articles made thereof do not lose mechanical strength, heat resistance, and water resistance, without conventional volatile organic foaming agents or carbon dioxide gas. A pre-expanded particle of a polypropylene resin is prepared by pre-expanding a water-containing propylene resin composition comprising (A) 100 parts by weight of a polypropylene resin having melt flow rate (230° C., 2.16 kg load) of 10 to 70 g/10 min and tensile elongation at break of at least 300%, (B) 0.05 to 10 parts by weight of a hydrophilic polymer and (C) 0 to 3 parts by weight of a filler and having a water content of 1 to 20% by weight under a water vapor pressure at the melting point of the polypropylene resin, said particle having an apparent expansion ratio of 25 to 70 times, a closed cell content of at least 85% and an average cell diameter of 50 to 500 &mgr;m.

Abstract: A method of washing pre-expanded particles having a substantially water insoluble inorganic compound attached thereto by contacting the pre-expanded particles with an aqueous washing solution of a water soluble compound. The water soluble compound has a solubility with water of at least 1 g/100 g of water and has 1-500 surface bonding functional groups and 1-500 hydrophilic functional groups. At least one of the surface bonding functional groups of the water soluble compound attaches to the water insoluble inorganic compound.

Abstract: A pre-expanded particle made of a blend of 10 to 90% by weight of a polypropylene resin having a melt index of 6 to 10 g/10 minutes and 90 to 10% by weight of a polypropylene resin having a melt index of 0.5 to 3 g/10 minutes. The melt index of the blend being within the range of 2 to 5 g/10 minutes. The pre-expanded particles can be molded by an in-mold foaming method in a short time without causing sink to give polypropylene resin cellular molded articles having good surface property and good melt adhesion of the particles.