US-12617132-B2 - Foam-molded product, method for manufacturing foam-molded product, and method for suppressing appearance defect of foam-molded product

US12617132B2US 12617132 B2US12617132 B2US 12617132B2US-12617132-B2

Abstract

A foam-molded product including a foam layer, and a skin layer covering the foam layer, in which the maximum diameter of bubbles in the foam layer is 0.90 mm or less; and a method for manufacturing a foam-molded product and a method for suppressing an appearance defect of a foam-molded product, including an injection process and a foaming process, wherein the foam-molded product after molding includes a foam layer and a skin layer covering the foam layer, the skin layer having an average thickness of from 0.3 mm to 0.7 mm, and wherein expanding of the volume of the cavity includes performing a core-back process of the mold such that a thickness of the foam-molded product after molding is within ±0.2 mm of a predetermined target thickness.

Inventors

Naoko MITSUISHI
Shingo Nakano
Kouji Yamada
Hiroaki Fujino
Hirofumi SHIOKAWA
Yoji Hirai

Assignees

SHOWA DENKO MATERIALS CO., LTD.

Dates

Publication Date: 20260505
Application Date: 20201006
Priority Date: 20191010

Claims (10)

1 . An automobile interior or exterior part comprising a foam-molded product, the foam-molded product comprising a foam layer, which comprises bubbles, and a skin layer covering the foam layer, wherein: the foam-molded product is a molded product of a resin material comprising at least one selected from the group consisting of a polypropylene resin having a branched chain and a melt flow rate of 35 g/10 minutes or more at 230° C., and an acrylonitrile-butadiene-styrene copolymer resin (ABS), the foam layer and the skin layer are made of the same material, a maximum diameter of the bubbles in the foam layer is from 0.05 to 0.20 mm, an average diameter of the bubbles in the foam layer is from 0.02 mm to 0.15 mm, and the skin layer has an average thickness of from 0.3 mm to 0.7 mm.
2 . The automobile interior or exterior part according to claim 1 , wherein the automobile interior or exterior part is an automobile exterior part.
3 . The automobile interior or exterior part according to claim 1 , wherein the automobile interior or exterior part is not painted on a surface thereof.
4 . The automobile interior or exterior part according to claim 1 , wherein the automobile interior or exterior part is at least one selected from the group consisting of a console box, a door trim, a deck side trim, a back door trim, an instrument panel, an arch molding, a rocker molding, and a side panel.
5 . The automobile interior or exterior part according to claim 1 , wherein a content of the polypropylene resin having a branched chain is 4% by mass or more with respect to the total amount of the resin material.
6 . The automobile interior or exterior part according to claim 1 , wherein the resin material further comprises an organic foaming agent.
7 . The automobile interior or exterior part according to claim 6 , wherein the organic foaming agent is azodicarbonamide.
8 . The automobile interior or exterior part according to claim 1 , wherein: the average diameter of the bubbles in the foam layer is from 0.02 mm to 0.10 mm; the maximum diameter of the bubbles in the foam layer is from 0.10 mm to 0.20 mm; and the foam layer has an average thickness of from 1.0 mm to 4.0 mm.
9 . A method for manufacturing an automobile interior or exterior part comprising a foam-molded product, the method comprising: injecting a resin material into a cavity of a mold to fill the cavity with the resin material; and expanding a volume of the cavity to foam the resin material in the cavity to form the foam-molded product of the automobile interior or exterior part, wherein: the foam-molded product is a molded product of the resin material comprising at least one selected from the group consisting of a polypropylene resin having a branched chain and a melt flow rate of 35 g/10 minutes or more at 230° C., and an acrylonitrile-butadiene-styrene copolymer resin (ABS), the foam-molded product after molding comprises a foam layer, which comprises bubbles, and a skin layer covering the foam layer, the skin layer has an average thickness of from 0.3 mm to 0.7 mm, and an average diameter of bubbles in the foam layer is from 0.02 mm to 0.15 mm, the foam layer and the skin layer are made of the same material, and the expanding of the volume of the cavity comprises performing a core-back process of the mold such that a thickness of the foam-molded product after molding is within +0.2 mm of a predetermined target thickness, as a result of which a maximum diameter of the bubbles in the foam-molded product is from 0.05 to 0.20 mm.
10 . A method for suppressing an appearance defect of an automobile interior or exterior part comprising a foam-molded product, the method comprising: injecting a resin material into a cavity of a mold to fill the cavity with the resin material; and expanding a volume of the cavity to foam the resin material in the cavity to form the foam-molded product of the automobile interior or exterior part, wherein: the foam-molded product is a molded product of the resin material comprising at least one selected from the group consisting of a polypropylene resin having a branched chain and a melt flow rate of 35 g/10 minutes or more at 230° C., and an acrylonitrile-butadiene-styrene copolymer resin (ABS), the foam-molded product after molding comprises a foam layer, which comprises bubbles, and a skin layer covering the foam layer, the skin layer has an average thickness of from 0.3 mm to 0.7 mm, and an average diameter of bubbles in the foam layer is from 0.02 mm to 0.15 mm, the foam layer and the skin layer are made of the same material, and the expanding of the volume of the cavity comprises performing a core-back process of the mold such that a thickness of the foam-molded product after molding is within ±0.2 mm of a predetermined target thickness, as a result of which a maximum diameter of the bubbles in the foam-molded product is from 0.05 to 0.20 mm.

Description

TECHNICAL FIELD The present disclosure relates to a foam-molded product, a method for manufacturing a foam-molded product, and a method for suppressing an appearance defect of a foam-molded product. BACKGROUND ART Foam injection-molded products of thermoplastic resins such as polypropylene-based resins and acrylonitrile-butadiene-styrene copolymer-based resins are used for members of automobiles, from the viewpoint of their light weight and excellent rigidity. Examples of the foam injection molding method include a core-back method. The core-back method is a method in which injection molding is performed with a thermoplastic resin composition containing a foaming agent, filling the mold with the thermoplastic resin composition, followed by sliding a movable mold to expand the volume of the cavity, and obtaining a molded product. This molding method forms a non-foaming layer (a skin layer) at the outer part of the molded product and a foam layer in the inner part of the molded product (e.g., see Patent Document 1). RELATED ART DOCUMENT Patent Document [Patent Document 1] Japanese Patent Application Laid-Open (JP-A) No. 2014-121793 SUMMARY OF INVENTION Technical Problem When foam injection-molded products are used as automobile interior parts such as console boxes, door trims, deck side trims, back door trims and instrument panels, or automobile exterior parts such as arch moldings, rocker moldings and side panels, the foam injection-molded products are desired to be lightweight and thin, and to have a good appearance. However, foam injection-molded products are susceptible to appearance defects on the surface thereof, including small circular or elliptical dents (sometimes referred to as “pock marks”) and linear marks formed on the surface of the molded products along the flow of the resin during the molding (sometimes referred to as “swirl marks”), which may cause problems in appearance. Pock marks are generated during foam injection molding when bubbles remain in the surface of the resin and rupture, and swirl marks are generated when the portions at which the bubbles have ruptured are dragged by the flow of the resin. In view of the foregoing circumstances, the present disclosure is directed to providing a foam-molded product in which appearance defects such as pock marks or a swirl marks are suppressed, a method for manufacturing a foam-molded product that enables suppressing an appearance defect of the molded product, and a method for suppressing an appearance defect of a foam-molded product. Solution to Problem Means for solving the above-described problems include the following aspects. (1) A foam-molded product, including a foam layer, and a skin layer covering the foam layer, wherein a maximum diameter of bubbles in the foam layer is 0.90 mm or less.(2) The foam-molded product according to (1), wherein the skin layer has an average thickness of from 0.3 mm to 0.7 mm.(3) The foam-molded product according to (1) or (2), wherein an average diameter of the hubbies in the foam layer is from 0.02 mm to 0.15 mm.(4) A method for manufacturing a foam-molded product, the method including: injecting a resin material into a cavity of a mold to fill the cavity with the resin material; andexpanding a volume of the cavity to foam the resin material in the cavity, wherein:the foam-molded product after molding includes a foam layer, and a skin layer covering the foam layer, the skin layer having an average thickness of from 0.3 mm to 0.7 mm, andthe expanding of the volume of the cavity includes performing a core-back process of the mold such that a thickness of the foam-molded product after molding is within +0.2 mm of a predetermined target thickness. (5) The method for manufacturing a foam-molded product according to (4), wherein the core-back process of the mold is performed such that the thickness of the foam-molded product after molding is within +0.2 mm of a predetermined target thickness, as a result of which a maximum diameter of the bubbles in the foam-molded product is 0.9 mm or less.(6) The method for manufacturing a foam-molded product according to (4) or (5), wherein an average diameter of the bubbles in the foam layer is from 0.02 mm to 0.15 mm.(7) A method for suppressing an appearance defect of a foam-molded product, the method including: injecting a resin material into a cavity of a mold to fill the cavity with the resin material; andexpanding a volume of the cavity to foam the resin material in the cavity, wherein:the foam-molded product after molding includes a foam layer, and a skin layer covering the foam layer, the skin layer having an average thickness of from 0.3 mm to 0.7 mm, andthe expanding of the volume of the cavity includes performing a core-back process of the mold such that a thickness of the foam-molded product after molding is within ±0.2 mm of a predetermined target thickness. (8) The method for suppressing an appearance defect of a foam-molded produ