Abstract: Polypropylene-based resin extruded expanded particles have a low open cell ratio and are inexpensively obtainable. The polypropylene-based resin extruded expanded particles are obtained by extrusion expansion of a resin composition that contains a polypropylene-based resin (A) which has a branched structure and a polypropylene-based resin (B) in which a branched structure is not introduced. Furthermore, the polypropylene-based resin (B) has a weight average molecular weight of not less than 500,000 and a flexural modulus of not less than 950 MPa.

Abstract: A novel modified polypropylene resin is provided which makes it possible to provide, by an extrusion expansion method, expanded polypropylene-based resin particles having an expansion ratio which falls within a wide range and having a low open cell ratio. The novel modified polypropylene resin is obtained by a method of producing the modified polypropylene resin where the method includes a melting and kneading step of melting and kneading a particular random polypropylene resin, a conjugated diene compound, and a particular radical polymerization initiator to obtain the modified polypropylene resin.

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 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 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.