Abstract: Polypropylene resin pre-expanded particles having an expandability of 1.0 to 1.

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: 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: Polypropylene resin pre-expanded particles having a weight of 0.3 to 1.8 mg per particle and a mean cell diameter of at most 250 &mgr;m and exhibiting two fusion peaks on a DSC curve thereof one of which appearing on a higher temperature side has a specific heat of fusion QH, which can be molded in a mold in a shortened molding time to give cellular molded articles having a low density of 25 g/liter or less after being provided with an inorganic gas pressure of at least 1.5 atms when the heat of fusion QH is 2.8 to 6.0 cal/g, or after being provided with an inorganic gas pressure of 1.18 to 1.5 atms when the heat of fusion QH is from 0.3 to less than 2.8 cal/g.

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 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.

Abstract: A method for producing polyolefin resins granules are disclosed, which comprises extruding by using a homodirectional (co-rotating) twin-screw kneading extruder a polyolefin resin from a die nozzle having a diameter of less than 2 mm and a discharge amount per hole of 0.5-8 Kg/hr into warm water of 5-90.degree. C. which is lower than a temperature of the resin by 140-220.degree. C., and cutting the extrudate with a cutter blade in the warm water. According to this invention, uniformly dispersed compounds are obtained, and switching of a raw resin can be done speedily and economically, and further, resin granules of a desired shape can be produced.

Abstract: Heat temperature at the expansion molding of a finished expanded article is decreased by lowering the melting peak temperature of the pre-expanded particles of a polypropylene resin. Comprising the polypropylene resin and a .beta.-crystalline-nucleating agent, the percentage of the .beta.-form in the whole crystalline region is 5 to 100 parts by weight.

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: An improved process for preparing pre-expanded particles of a polyolefin resin, wherein polyolefin resin particles are dispersed in water in a pressure vessel, the particles are impregnated with a volatile blowing agent which is butane containing not less than 70 percent by weight of isobutane, the temperature of the mixture of particles in water is elevated to a temperature close to the melting point of the particles under a pressure equal to or higher than the vapor pressure of the blowing agent, and the mixture is released into a low pressure zone. The obtained pre-expanded particles are not fused together or adhered to each other, and are not shrunken. Environmental damage, such as destruction of the ozone layer, is avoided since fluorochlorocarbon is not used as a blowing agent.

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 preparing pre-expanded particles of a thermoplastic resin, which comprises heating an aqueous dispersion of thermoplastic resin particles containing a volatile blowing agent to a high temperature under pressure in a pressure vessel, and releasing the dispersion into an atmosphere maintained at a lower pressure than the pressure in the pressure vessel and at a temperature of not lower than 40.degree. C. According to the process of the present invention, there can be obtained pre-expanded thermoplastic resin particles with a large average diameter of cells. By molding the pre-expanded particles obtained by the present invention, molded articles which are small in dimensional shrinkage and excellent in surface appearance can be obtained without imparting expandability to the particles or aging the particles under pressure prior to molding.

Abstract: A method for aging an expansion-molded body of polyolefin prepared by heating pre-expanded polyolefin particles within a mold involves cooling the molded body within the mold so that the molded body is not substantially smaller than the volume of the mold cavity and is temporarily expandable after being removed from the mold to not more than 110% relative to the volume in the mold cavity, removing the molded body from the mold, placing the molded body in an atmosphere substantially under atmospheric pressure and having a temperature of 25.degree. to 55.degree. C. lower than the melting point of the polyolefin while the volume of the molded body is 70 to 110% relative to the volume of the mold cavity and holding the molded body in this atmosphere until the temperature of the molded body is at least equal to the temperature of the atmosphere.

Abstract: A pre-expanded particle suitable for foaming in a mold comprising non-crosslinked linear low density polyethylene which has a characteristic property that an inclination of slope line obtained on a graph when logarithmic values of melt tension of the polyolefin are plotted as ordinate and reciprocals of absolute temperature at which the melt tension is measured are plotted as abscissa is not more than 1,500 is provided. A foamed article produced from the pre-expanded particles has an excellent appearance, a flat surface and good mechanical strength, and is useful for wrapping material, insulating material, a container or a fender of cars.

Abstract: A pre-expanded particle suitable for foaming in a mold comprising polyolefin which has a characteristic property that an inclination of slope line obtained on a graph when logarithmic values of melt tension of the polyolefin are plotted as ordinate and reciprocals of absolute temperature at which the melt tension is measured are plotted as abscissa is less than 1,500 is provided. A foamed article produced from the pre-expanded particles has an excellent appearance, a flat surface and good mechanical strength, and is useful for wrapping material, insulating material, a container or a fender of cars.A process for preparing the above-mentioned pre-expanded particles is also disclosed.

Abstract: The mixture of water and the polyolefin resin particles impregnated with a volatile blowing agent are released from the interior of the pressure-resistant container under a constant temperature and constant pressure preferably keeping the partial pressure of the blowing agent constant, through at least one orifice having an area of 0.07 to 300 mm.sup.2, into a low-pressure zone.This invention gives various advantages when applied to the practical process resulting in expanded particles with superior properties which are free of blocking and remarkably uniform in the degree of expansion, and are useful for molding.

Abstract: Expandable thermoplastic polymer beads and method of producing same, wherein a core of a polymer of one or more vinyl monomers is substantially surrounded by a layer of a polyolefin comprising one or more vinyl monomers, with a foaming agent contained in at least the core.

Abstract: Disclosed are expandable thermoplastic polymer particles and process for preparing the same.Expandable thermoplastic polymer particles superior in processability as well as expansion are prepared by controlling an amount of inside moisture contained in said particles coated or impregnated with a blowing agent to not more than 1% by weight based on polymer, immediately after prepared.

Abstract: A substantially water-impermeable polyolefin foam made of expandable polyolefin beads. The polyolefin foam is prepared by a particular process in which after heating expandable polyolefin beads and before cooling the heated beads in a mold, the heated beads were allowed to stand in the state that the polyolefin resin maintains the flowability.

Abstract: Expandable thermoplastic polymer beads and method of producing same, wherein a core of a polymer of one or more vinyl monomers is substantially surrounded by a layer of a polyolefin comprising one or more vinyl monomers, with a foaming agent contained in at least the core.