Injection molding method

JP7875004B2Active Publication Date: 2026-06-17SEKISUI CHEMICAL CO LTD
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Patent Information

Authority / Receiving Office
JP · JP
Patent Type
Patents
Current Assignee / Owner
SEKISUI CHEMICAL CO LTD
Filing Date
2022-03-31
Publication Date
2026-06-17

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Patent Text Reader

Abstract

To provide, in injection molding of a thick-wall molded article, an injection molding method capable of reducing contraction and warpage deformation of the molded article.SOLUTION: An injection molding method has the steps of: injecting a thermoplastic resin A from a first injection unit to mold a skin layer; and filling an inside of the skin layer with a thermoplastic resin B from a second injection unit to mold a core layer. In the step of molding the core layer, the thermoplastic resin B is filled inside the skin layer at a state where a temperature of the thermoplastic resin B is lower than a temperature of the thermoplastic resin A.SELECTED DRAWING: None
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Claims

1. A process of injecting thermoplastic resin A from a first injection unit to form a skin layer, The process includes a step of filling the inside of the skin layer with thermoplastic resin B from a second injection unit to form a core layer, An injection molding method comprising the step of molding the core layer, wherein the thermoplastic resin B is filled into the interior of the skin layer while the temperature of the thermoplastic resin B is lower than the temperature of the thermoplastic resin A, The thermoplastic resin A is a polyolefin-based resin, and the thermoplastic resin B is a polyolefin-based resin having the same main component as the thermoplastic resin A. The temperature of the thermoplastic resin A when it is injected into the mold is 180°C or higher and 240°C or lower. When the thermoplastic resin B is injected into the mold, its temperature is 40°C or more and 80°C or less lower than the temperature of the thermoplastic resin A. The proportion of the core layer to the total volume of the molded product is 20% by volume or more. The sum of the thickness of the skin layer and the core layer of the molded product is 8 mm or more. The aforementioned molded product is a pipe or fitting, and the method involves injection molding.

2. The injection molding method according to claim 1, wherein the melt flow rate (MFR) of the thermoplastic resin A is 0.01 g / 10 min or more and 25 g / 10 min or less.

3. The injection molding method according to claim 1 or 2, wherein the thermoplastic resin A and the thermoplastic resin B are the same resin.