JPH0417980B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a shape-recoverable foam that has a shape-recovery effect at low temperatures of 100 degrees or lower.

It is well known that cross-linked plastic products have a large shape memory effect, but the traditional cross-linked polyethylene foam of cross-linked foam products has a small shape memory effect, and it is difficult to recover the shape.
The drawback was that it required heating to a high temperature of over 120 degrees, making it impractical.

The present invention was made to eliminate the above-mentioned conventional drawbacks, and provides a shape-recoverable foam that has a large shape memory effect and can easily recover its shape (dimensions) at a low temperature of 100 degrees or less. The purpose is to foam polycaprolactam by extruding it into a predetermined shape, then crosslinking it, softening it by heating, expanding it, etc. to change its shape and dimensions, and then cooling and solidifying it. It is characterized by what it did.

The polycaprolactam used has a molecular weight of 40,000 or more. Although conventional foaming means and processes may be used, extrusion foaming is suitable for obtaining an uncrosslinked foam.

In the present invention, for example, fluorocarbon gas (F114) is added as a foaming agent to polycaprolactam having a molecular weight of 70,000, and the mixture is extruded and foamed using an extruder with a screw diameter of 40φ and a length/diameter ratio of 32 to achieve a foaming ratio of approximately 20.
A string-like non-crosslinked foamed molded product with a high expansion ratio was obtained, and then the string-like non-crosslinked foamed molded product with a high expansion ratio was crosslinked by irradiating about 6.5 Mrad of ionizing radiation. Approximately above its melting point (60 degrees)
It is heated to 80 degrees to soften it, expand to about 6 times its length, and then cooled and solidified in this shape. When this stretched string-like crosslinked foam molded product was immersed in warm water of about 80 degrees, it recovered about 80%, exhibiting a large shape (dimension) recovery effect.

In addition, when the foamed molded product is in the shape of a string or sheet, the crosslinking treatment by irradiation with ionizing radiation described above is suitable, but in the case of a thick rod shape or a complicated shape, chemical crosslinking treatment is suitable. There is.

As described above, the foam of the present invention, which is deformed by crosslinking the foam and subjecting it to secondary processing, has a large shape memory effect and can easily recover almost its memory shape by heating at a low temperature. Stretched thin sheet materials can be used as insulation and cushioning materials, for example, because the insertion opening is small compared to the filling space, it is not possible to fill in sufficient insulation with conventional methods, and electric appliances that do not like high-temperature heating. It has a wide range of uses, such as being able to easily fill the heat insulating filling space in the heat insulating parts of appliances.

Claims (1)

[Claims] 1. A non-crosslinked foamed molded product whose main component is polycaprolactam with a molecular weight of 40,000 or more is made, which is crosslinked, heated and softened to change its shape and dimensions, and then cooled and solidified to recover the shape. foam.