JSP

[Problems] To provide polypropylene-based resin foamed particles which include a recycled polypropylene and can suppress the deterioration rate of the physical properties of a polypropylene-based resin foamed molded article over time, thereby maintaining the favorable physical properties of the molded article over a long period.[Resolution means] The polypropylene-based resin foamed particles contain 50 mass% or more of a recycled polypropylene-based resin (R). The oxidation induction time t of the polypropylene-based resin foamed particles at 200°C, as measured in accordance with ISO 11357-6:2018, is 5 minutes or more and 360 minutes or less.

[Problems] To provide a method for producing polypropylene-based resin foamed particles, a method for determining a polypropylene-based resin, and a method for producing a polypropylene-based resin, which include a recycled polypropylene-based resin and can suppress the deterioration rate of the physical properties of a molded article thereby maintaining the favorable physical properties of the molded article over a long period.[Resolution means] The method for producing polypropylene-based resin foamed particles includes a foaming step involving foaming a polypropylene-based resin composition containing a polypropylene-based resin and a foaming agent. The base resin is created using a recycled polypropylene-based resin (R). The blend amount of the polypropylene-based resin (R) in the base resin is 15 mass% or more. The melting point of the polypropylene-based resin (R) is lower than 160°C. The oxidation induction temperature T3 of the polypropylene-based resin (R), measured in accordance with ISO 11357-6:2018, is 220°C or higher.

A method for producing a polypropylene-based resin expanded bead, including expanding polypropylene-based resin particles, wherein the resin particles are composed of a mixed resin of a virgin material and a polypropylene-based resin recycled material; the recycled material contains a propylene copolymer as a base material resin; the virgin material has a melting point MP1 of 130°C or more and less than 150°C; a melting point MP2 (°C) of the recycled material and the melting point MP1 (°C) of the virgin material satisfy a specific relationship; a melt flow rate MFR2 (g/10 minutes) of the recycled material and a melt flow rate MFR1 (g/10 minutes) of the virgin material satisfy a specific relationship; and a crystallization temperature CP2 (°C) of the recycled material and a crystallization temperature CP1 (°C) of the virgin material satisfy a specific relationship.

An expanded bead has a foamed layer made of a polypropylene-based resin and a specific shape including one or more defective portions. The polypropylene-based resin constituting the foamed layer contains a polypropylene-based resin (A) having a melting point of 135°C to 150°C and a flexural modulus of less than 1000 MPa, and a polypropylene-based resin (B) having a melting point of 145°C to 160°C and a flexural modulus of 1000 MPa or more. The mass ratio between the resin (A) and the resin (B) in the polypropylene-based resin is represented by resin (A):resin (B)= 65:35 to 35:65.

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