Thermally expandable microcapsule and foam-molded article

Abstract

The present invention has its object to provide a thermally expandable microcapsule, which shows excellent heat resistance and a high expansion ratio and thereby can be suitably used for molding processes involving high shearing force, such as kneading molding, calender molding, extrusion molding, and injection molding. The present invention also has its object to provide a foamed product using the thermally expandable microcapsule. The present invention relates to a thermally expandable microcapsule, which comprises: a shell made of a polymer; and a volatile expansion agent as a core agent encapsulated in the shell, the storage elastic modulus (E′) of the shell at a temperature of 200° C. and a frequency of 10 Hz being 1×105 N / m2 or more, the storage elastic modulus (E′) of the shell at a temperature of 250° C. and a frequency of 10 Hz being 1×105 N / m2 or more, and a maximum displacement amount measured by thermomechanical analysis being 300 μm or more.

Description

TECHNICAL FIELD[0001]The present invention relates to a thermally expandable microcapsule, which shows excellent heat resistance and a high expansion ratio and thereby can be suitably used for molding processes involving high shearing force, such as kneading molding, calender molding, extrusion molding, and injection molding. The present invention also relates to a foamed product using the thermally expandable microcapsule.BACKGROUND ART[0002]Thermally expandable microcapsules have been used for various applications as a design-imparting agent or a weight-reducing agent. They have been also used for paint, such as foaming ink and wallpaper, to achieve weight reduction.[0003]As such a thermally expandable microcapsule, widely known is one in which a thermoplastic shell polymer includes a volatile expansion agent that can change to a gas state at a softening temperature or lower of the shell polymer. Patent Document 1, for example, discloses a method for producing a thermally expandab...

AI Technical Summary

Benefits of technology

[0097]According to the present invention, it is possible to provide a thermally expandable microcapsule, which shows excellent heat resistance and a high expansion ratio and thereby can be suitably used for molding processes involving high shearing force, such as kneading molding, calender molding, extrusion molding, and injection molding.

Problems solved by technology

Accordingly, this method has a drawback in that a thermally expandable microcapsule having excellent heat resistance is difficult to produce.

Thus, it is difficult to produce thermally expandable microcapsules with excellent heat resistance , such as ones having a maximum foaming temperature of 180° C. or higher.

Although such a thermally expandable microcapsule shows a very high maximum foaming temperature, it is difficult to keep the expanded state.

Thus, it is not suitable for prolonged use at a high temperature.

However, upon use in molding processes involving strong shearing force, such as kneading molding, calender molding, extrusion molding, and injection molding, especially for injection molding, deformation may arise because of some problems in heat resistance and strength of the thermally expandable microcapsule in melt kneading.

Otherwise, the thermally expandable microcapsule may be crushed.

However, such a method still leaves problems of heat resistance and strength.

Thus, there is a limitation in the expansion ratios after molding such as injection molding.