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 described 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: 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 method of producing a polypropylene resin molded product from foamed polypropylene particles is disclosed, which comprises introducing a pressurizing gas into foamed polypropylene particles having closed cells so that the particles have an internal gas pressure of from 0.3 to 2.5 Kg/cm.sup.2 G, charging the particles in a mold cavity while compressing the particles with a pressurizing inorganic gas until the initial apparent volume of the particles is reduced to 50 to 99%, removing the gas from the mold cavity while keeping the foamed particles in a compressed state, and introducing steam in the cavity to cause adhesion of the compressed foamed particles. The method produces a molded product having satisfactory appearance and excellent adhesion among particles in a shortened molding cycle.