JPS63130653A - Shape-restoring elastomer composition - Google Patents

Abstract

PURPOSE:To provide the title compsn. which gives a molded product which has an ability of temporarily retaining its shape and a moderate ability of restoring its original shape, containing polynorbornene and a styrene/diene elastomer having a specified styrene content. CONSTITUTION:Norbornene is subjected to ring opening polymn. to obtain a polynorbornene (A) having an MW of not lower than 2,000,000. 100pts.wt. component A is blended with 20-75pts.wt. styrene/diene elastomer (B) having a styrene content of 15-55wt% (e.g., styrene/butadiene rubber) to obtain the title compsn. The compsn. is crushed to obtain a powdered mixture. The mixture is press-molded or injection-molded to obtain a molded product which is deflected merely by applying a force thereto at room temp., can be bent into a desired shape, retains the shape for many hours and can restore its original shape after a given period of time.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a shape-recoverable elastomer that can change the shape of a molded product by applying force at room temperature and has a gradual ability to recover its original shape. The present invention relates to a composition.

BACKGROUND OF THE INVENTION For example, doll toys that are enjoyed by bending the joints of the limbs and the like by applying appropriate force and adopting various postures are popular. In this product, a metal wire is attached to the center of an elastic plastic molded product, and the plastic deformation of the wire is used to maintain the deformation of the doll's limbs. For this reason, as the wire is bent repeatedly, the wire breaks, and the broken tip pierces the plastic and protrudes, making it extremely dangerous as a toy.

Problems to be Solved by the Invention The inventors believe that in such cases, if there is a polymeric material that can temporarily retain its shape without using plastic deformation of the metal, an extremely highly safe product can be obtained. We focused on the fact that polynorbornene obtained by ring-opening polymerization of norbornene (C7H11) has a glass transition point of +35°C, which is higher than room temperature, and that polynorbornene molded products can be plastically deformed into any shape at room temperature. After much research into methods for restoring this plastically deformed material to its original shape, they discovered that a composition containing a specific styrene-diene elastomer would return to its original shape over time, and thus completed the present invention. I ended up doing it.

Means for Solving the Problems The shape-recoverable elastomer composition according to the present invention contains 20 parts to 100 parts by weight of polynorbornene and 20 parts to 100 parts by weight of a styrene-diene elastomer containing 15 to 55 parts by weight of styrene. It is characterized by containing 75 parts by weight.

That is, a shape-recoverable molded article is obtained by balancing the plastic deformability of polynorbornene at room temperature and the recovery due to the rubber elasticity of a diene elastomer that is compatible with polynorbornene.

The polynorbornene used in the composition of the present invention is obtained by ring-opening polymerization of norbornene, and has a glass transition point of +35°C.
It is a white powder-like non-grade polymer with 9 molecules ff of 12 million or more and a specific gravity of 0.96. Because it has a double bond in its main chain, it can be vulcanized using a vulcanization system normally used in the rubber industry. S
A mixture can be obtained by kneading with a diene elastomer such as BR.

As the styrene φ diene elastomer added to polynorbornene, styrene-butadiene rubber (SBR
), styrene-isoprene block copolymer (SIS
) are used, and the styrene content in these elastomers is suitably in the range of 15% to 55% by weight. 15
(wt%) i4 is inferior in temporary retention of shape when mechanically deformed to the molded product, and at 55 wt% or more, cracks tend to occur when mechanically deformed, for example when bent, and are not suitable. .

In addition, even when using not only one elastomer but also multiple elastomers with different styrene contents, the average styrene content of the mixed elastomers is the same 15 to 5.
It is sufficient if it is 5% by weight.

Further, the amount of 1 of the styrene-diene elastomer added to polynorbornene is in the range of 20 parts by weight to 75 parts by weight based on 100 parts by weight of polynorbornene. With 20 parts by weight, the elasticity of the product is weak and it takes too long to restore the original shape after being mechanically deformed, and with 75 parts by weight or more, the elasticity is strong and it takes too long to restore to the original shape. This is because the length is too short, making it unsuitable for ordinary applications such as toys.

This composition can be manufactured using kneading and molding methods that are normally used in the production of rubber products, and as long as it does not impair temporary shape retention and restorability, it can be made using the same methods normally used in the rubber industry during processing. Auxiliary raw materials.

It goes without saying that colorants such as pigments may be added.

Next, as a method for forming the composition, first, the styrene-diene elastomer is kneaded with a roll, wound around a roll, and kneaded while gradually adding polynorbornene powder, and then cut to form a granular mixture. get.

This mixture is molded into a desired shape by press molding or injection molding.

The rod-shaped, plate-shaped, or bone-shaped products made in this way can be bent and bent into free shapes by the force of children's fingertips, as can be seen in toys. Moreover, it can retain its shape for a long time, and after a predetermined period of time, it will be restored to its original shape.

EXAMPLES Hereinafter, the present invention will be specifically explained with reference to Examples. As a styrene-diene elastomer, styrene-butadiene rubber (SBR) #1502 (bonded styrene fit
23.5%), special styrene-butadiene rubber (styrene bond content 50%), high styrene rubber J (styrene content 65%), and styrene-isoprene block copolymer (SIS).

Styrene-containing ff115%) was used, and as polynorbornene, CDF Simi rCdf Ch
Manufactured by ia+ieJ, trade name Nosolex, molecular weight 20
00,000 or higher, glass transition point: +35°C (white powder).

First, elastomers are kneaded alone or as a blend,
The desired styrene content was adjusted.

A predetermined weight part of the styrene-diene rubber was kneaded and wrapped around a kneading roll in advance, and a total of 100 parts by weight of polynorbornene powder was added little by little and kneaded to form a sheet. From this cross section 8m1Ix81III11
．． A square bar with a length of 125 mm+ was produced and used as a test sample.

The test method for shape retention is that an included angle of 60 mm is measured at the center of the bar plane.
After bending it so that the angle was 30 seconds and holding it in that state for 30 seconds, it was left to stand at room temperature, and the relationship between the return angle from the folded angle after 2 hours and time was investigated.

Evaluation of shape retention is as follows.

Return angle within 5 degrees after 2 hours Excellent ◎Same
Good within lOo
10' or more Impossible Δ Also, when bending by 120°, the presence or absence of cracks at the bent part was examined. The composition of the test piece and the evaluation results are shown in Table 1 below.

Below is the margin: Table 1 As shown in the comparative examples in Table 1 above, those whose ST content or elastomer content is outside the range of the present invention, return too quickly as in Comparative Example 1.4, or 2,3.
5, which is unsuitable because it cracks when bent, but it can be seen that the material according to the present invention gradually returns to its original shape.

Effects of the Invention The polynorbornene-styrene diene elastomer composition according to the present invention has temporary shape retention properties and gradually returns to its initial shape before deformation, so it can be applied to toys such as dolls, for example, It is possible to bend the wire as appropriate and return it to its original shape, and unlike placing a wire inside and bending and stretching it, there is no danger of the wire breaking, making it extremely interesting.

In addition, by taking advantage of its ability to retain its shape for a specified period of time,
It can be used as a packing material or a filler, and after recovering its original shape, it can be sealed or filled without any gaps. Further, for example, after being used as a single temporary mold, it can be reused as a mold of another shape, and can be used for various purposes by taking advantage of its temporary shape retention properties.

Claims (1)

[Claims] (1) A shape-recoverable elastomer composition containing 20 to 75 parts by weight of a styrene-diene elastomer with a styrene content of 15 to 55 weight% based on 100 parts by weight of polynorbornene.