Method for producing low specific gravity molded foam by using propylene-based polymer

Abstract

Provided is a method for producing a low specific gravity molded foam by using a propylene-based polymer, comprising the steps of: providing a foamable composition comprising a mixture of a propylene-based polymer and thermally expansive microspheres; introducing the foamable composition into a mold for producing a molded foam; expanding the foamable composition in the mold by raising the temperature of the foamable composition to at least the expansion start temperature (Tstart) of the thermally expandable microspheres; forming a molded foam in a state that the foamable composition is expanded and filled with the mold; and demolding the molded foam from the mold.

Description

technical field [0001] The present invention relates to a method of manufacturing low specific gravity shaped foam, more particularly, relates to a method of manufacturing low specific gravity shaped foam using propylene polymer. Background technique [0002] Generally, propylene polymer shaped foams are produced by the following method. [0003] According to the first method, a propylene polymer containing a blowing agent as a raw material is fed into a hopper of a plastic molding machine, and is simply injection molded in a cold mold or while the volume of the mold cavity increases at a constant rate. [0004] According to the second method, a propylene polymer as a raw material is fed into a hopper of a plastic molding machine having an air injection hole formed in a predetermined portion of the barrel, and supercritical CO 2 Injection molding in the cold mold while the gas is introduced into the barrel through the gas injection holes. [0005] The third method is based...

AI Technical Summary

Problems solved by technology

[0007] The second method ensures a uniform cell structure and attractive appearance of the foamed product, but is inefficient in increasing the expansion ratio

Therefore, most large factories supply large quantities of beads, but small and medium-sized companies find it difficult to manufacture products made of various materials with different physical properties because they cannot directly process and use said materials

Due to the characteristics of steam box molding, the maximum attainable temperature of steam does not exceed 150°C, so ordinary polypropylene cannot be used, but only random copolymers with a melting point below 150°C, making it impossible to manufacture high-hardness products

In addition, using only random copolymers takes a long time to sufficiently melt the surface of the pre-foamed body at the time of steam box molding, resulting in an increase in manufacturing costs

Reduced melting time leads to insufficient melting, causing many problems such as low strength of formed foam

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