公开(公告)号：US20230407035A1

公开(公告)日：2023-12-21

申请号：US18030561

申请日：2021-10-13

Applicant: JSP CORPORATION

Inventor： Tetsu OTSUKA

IPC: C08J9/18 ,  C08J9/12 ,  C08J9/228

CPC classification number: C08J9/18 ,  C08J9/228 ,  C08J9/12

Abstract: A method for producing polyamide-based resin multi-stage expanded beads includes an internal pressure applying step of placing polyamide-based resin expanded beads in a pressure-resistant container, impregnating the polyamide-based resin expanded beads with a physical blowing agent in the pressure-resistant container to apply internal pressure higher than atmospheric pressure; and a heating and foaming step of heating and expanding the polyamide-based resin expanded beads to which internal pressure is applied obtained in the internal pressure applying step to obtain polyamide-based resin multi-stage expanded beads having apparent density lower than that of polyamide-based resin expanded beads used in the internal pressure applying step, in the internal pressure applying step, polyamide-based resin expanded beads in a wet state having a water content of 1% or more being impregnated with the physical blowing agent at a temperature higher than change-point temperature of storage modulus of the polyamide-based resin expanded beads in a wet state.