JPS62192440A - Shape memory molding and use thereof - Google Patents

Abstract

PURPOSE:To obtain the titled molding which can be deformed into any desired shape and whose deformation can be fixed at a temperature higher than the m.p. of the polymer, by using a crosslinkable composition based on a crystalline diene polymer of a specified melting range and containing a crosslinking agent. CONSTITUTION:A crosslinkable composition is obtained by mixing 100pts.wt. crystalline diene polymer of m.p. of 40-100 deg.C (e.g. trans-1,4-polysoprene having a degree of crystallinity of at least 90%) comprising a conjugated diene such as butadiene, isoprene or chloroprene with, optionally, 40pts.wt. natural rubber and/or synthetic rubber such as a synthetic cis-1,4-polyisoprene rubber, and mixing the resulting mixture with a crosslinking agent (e.g., S or an S-donating compound) in an amount to give a crosslinking density <=2.5X10<-4>mol/g. A crosslinked molding A formed by molding the above crosslinkable composition into any desired shape by extrusion, injection or the like and crosslinking the obtained molding is further deformed by heating and compression. This deformation is fixed by cooling to a temperature lower than the m.p. of the polymer (e.g., room temperature) to obtain a molding B. When this molding is heated again, it is restored to a molding C in the same state as before.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to a crosslinked molded article having shape memory properties using a crystalline diene polymer having a melting point of 40 to 100° C., and a method for using the same.

(b) Conventional technology When it is difficult to attach, assemble, or transport a molded article of a polymer compound in its original shape, it is possible to deform it so that it can be easily handled during work. The main point is to restore the predetermined shape by heating operation etc. after the modification, installation, assembly, etc., and to make it work as intended, or to restore the deformed molded product to its original state. In the past, various studies have been conducted on materials suitable for applications such as shape-memory molded bodies.

Conventionally, shape-memory molded products have been produced, for example, norbornene-based polymer molded products (see Japanese Patent Publication No. 59-53528), conjugated diene or epoxy group-containing materials, and aromatic vinyl, unsaturated nitrile or acrylic esters. Polycaprolactone is known as a cross-linked molded product (see JP-A-60-28433) or a cross-linked molded product using polycaprolactone (see JP-A-59-11315). All of them had their pros and cons, such as not being good or requiring high temperatures to recover the shape.

(c) Problems to be Solved by the Invention The present invention has excellent moldability, and in its original form it is difficult to bag, assemble, and
A shape suitable for use in cases where work such as transportation is difficult, by temporarily deforming into a shape that is easy to work with, and then restoring it to the original predetermined shape by heating operation after performing the work to complete the work. The present invention was completed as a result of extensive research aimed at providing a shape-memory molded article and a method for using the same, the purpose of which is to restore a memorized molded article or a deformed molded article to its original state. 9.

B.) Means for Solving the Problems According to the present invention, the above object is to produce a crosslinked molded product from a composition containing a crystalline diene polymer having a melting point of 40 to 100°C as a main component, and to obtain a desired shape. A shape-memory molded article having a melting point of 40 to 100° C. can be deformed to a temperature of 40 to 100° C., and the deformation can be fixed at a temperature below the melting point of the polymer.
A shape-memory crosslinked molded product obtained by deforming a crosslinked molded product made from a composition containing a crystalline diene polymer as a main component into a desired shape, and then cooling the deformation to a temperature below the melting point of the polymer to fix the deformation. This is achieved by a method of use comprising heating the molded article to a temperature above the melting point of the polymer to restore the original shape of the molded article.

Even if the molded body is deformed at a certain temperature after being cross-linked into the shape required for actual use, the deformation is automatically removed by heating it again to the specified temperature, and the molded body returns to its original state. Since it can be restored to the shape or a shape close to it, it can be used in various fields where such functions are required.

In the present invention, a composition mainly composed of a crystalline diene polymer with a melting point of 40 to 100°C is used. It is made by taking advantage of the property that it can be molded at a relatively low temperature. 5 In the present invention, the melting point refers to the endothermic peak on the highest temperature side of the endothermic peaks due to melting of crystals of the polymer measured by differential thermal analysis.

Polymers that meet these conditions include butadiene,
Any crystalline polymer consisting of a conjugated diene such as isogrene or chloroprene may be used, and the most preferred example is:
Trans-1,4-polyimprene or syndiotactic-1,2-polybutadiene may be mentioned. In particular, trans-1°4-polyinprene is most suitable.

If the crystallinity of these crystalline polymers is low, the strength of the crosslinked molded product obtained from the composition containing the polymer as a main component will be insufficient, so the polymer has a structure that exhibits high stereoregularity. For example, in the case of trans-1゜4-polyimprene, it is desirable to contain trans-1,4M of 90% or more, preferably 95% or more. In the case of 2-polybutadiene, it is desirable to have 90% or more, preferably 95% or more of 1,2-bonds.In addition, if the molecular weight of the crystalline diene polymer is too small, its strength will decrease. On the other hand, if the molecular weight is too large, the melt viscosity will increase and the molding processability will decrease. Therefore, the crystalline diene polymer used in the present invention has an intrinsic viscosity of 1.2 to 4.5 in toluene at 30°C, preferably is 1.5 ~
It is desirable to keep it within the range of 3.5.

Such crystalline polymers include natural trans-1,4-polyisoprene, such as balata or gutta-percha, or synthetic trans-1,4-polyisoprene. Synthetic trans-1 preferably used in the present invention
In the case of ,4-polyimprene, isoprene monomer is polymerized using a Ziegler catalyst, and in the case of syndiotactic-1,2-polybutadiene, butadiene monomer is polymerized using an anionic catalyst. It can be obtained by polymerization using

In the present invention, in order to create the sound of a crosslinked molded product, the composition is mainly composed of a crystalline diene polymer having a melting point of 40 to 100°C and contains a crosslinking agent.
-110°C, preferably 50-100°C, within a range that does not impair workability or strength, and does not cause cracking noise when deformed when made into a crosslinked molded product. Crystalline diene polymer 1003! Natural rubber, synthetic cis-1,4 within a range of 40 parts by weight or less
-Polyisoprene rubber (IR), polybutadiene rubber (
BR), styrene-butadiene combination='mu(SB
R), styrene-imprene copolymer rubber (SIR),
Acrylonitrile-butadiene copolymer rubber (NBR)
, acrylonitrile-isoprene copolymer rubber (NIR
), ethylene-propylene copolymer rubber (EPRl or E
Rubbers such as PDM) or butyl rubber (IIR) or mixtures thereof may also be incorporated. Alternatively, if necessary, fillers, rubber reinforcing agents, rubber softeners, abposable agents, etc.
Rubber and plastic compounding agents such as crystal nucleating agents, anti-aging agents, antioxidants, anti-ozonants, ultraviolet absorbers, pigments, dyes, or tackifying resins may be added.

In the present invention, a crosslinking agent is blended into a composition for a crosslinked molded article which is mainly composed of a crystalline diene polymer having a melting point of 40 to 100°C. As the crosslinking agent, for example, a vulcanizing agent commonly used in the rubber and plastic industries is used. Examples of preferred vulcanizing agents include sulfur and sulfur-donating organic compounds, and organic peroxides such as dicumyl peroxide. When blending the crosslinking agent, vulcanization chemicals such as vulcanization accelerators, vulcanization aids, or activators may be used.

The amount of crosslinking agent used is generally within the range used in the normal rubber industry, but it depends on the crystalline diene polymer, the type of crosslinking agent,
It varies depending on the amount of other compounding agents, etc., and cannot be determined unconditionally from the relationship with shape memory.The amount of crosslinking agent used is determined from the relationship with shape memory and the crosslink density of the crosslinked molded product. is preferable. The crosslinked molded product exhibits shape memory properties so that inconveniences such as cracking in the molded product do not occur when the molded product is deformed into a desired shape or when the deformed molded product is returned to its original shape. In order to
lX10 to 2.5X10 mol/'s, particularly preferably 0.3 X 10-' to 2.2 X 10-'mol/'
It is desirable to use an amount within the range of f. If the crosslinking density is too low, the applied crosslinked molded product will not recover to its original shape even if it is heated after being deformed. When the crosslinking density falls within a suitable range, it is preferable that 60% of the original state after deformation is removed.
% or more, particularly preferably 95% or more. On the other hand, if the crosslinking density is too high, cracks will occur when the crosslinked molded product is shaped or returned to its original shape.

Here, the crosslink density (ν) of the crosslinked molded body is determined by the degree of swelling q,
The volume fraction (v2) of the crystalline diene polymer in the swollen sample is determined from the degree of swelling, and the Flory-Boucher equation (P, J, Flory, A, M, Bu
s che). Degree of swelling (Q
The crosslinked molded body is immersed in an immersion liquid (using benzene), the amount before and after swelling is measured, and the amount is calculated from the following formula based on the measurement.

In the formula, Wb: weight of the crosslinked molded product after swelling Wa: amount of Ja of the crosslinked molded product before swelling ρl: density of the crystalline diene polymer (r//?II) ρ
2: Density of the immersion liquid (na-) γ: Correction factor due to formulation The volume fraction (v2) of the polymer in the swollen sample is calculated by the following formula.

Further, the Floriebouche equation is expressed by the following equation.

/Mc Number of crosslinks per unit weight of crab (mol/f) MC: Average molecular weight of chains between crosslinks μ: Mutual solubility coefficient of polymer ■1:1: Volume of immersion liquid (cc/mol) M: Average molecular weight of polymer before crosslinking Production of a crosslinked molded product involves adding a crystalline diene polymer, a crosslinking agent, and rubber and plastic compounding agents to them as necessary, for example, using an open roll, a Banbury mixer, or a kneader. - etc. to prepare a crosslinkable composition,
The composition is then molded into a desired shape by, for example, extrusion molding, injection molding, compression molding, etc., and then crosslinked.

The composition can be molded at a temperature exceeding the melting point of the crystalline diene polymer before crosslinking treatment such as heating. The molding conditions and crosslinking conditions are not particularly limited as long as the desired shape and crosslinking density are within the above-mentioned range.

The crosslinked molded product thus formed into the desired shape is shaped into the desired second shape using bare hands, a tool, or a device such as a compression molding machine, depending on the shape or wall thickness of the molded product. Used in modified form. The temperature at which the molded body is deformed may be a temperature that allows the molded body to be easily deformed and does not cause cracks during deformation. Generally, the temperature is preferably higher than the melting point of the crystalline diene polymer. When the deformation temperature is above the melting point, it is preferable to rapidly cool the material after deformation to below the melting point to fix the deformation.

In order to return the shape memory molded body obtained in this way to its original shape or a shape close to it, it is sufficient to heat it above the melting point of the crystalline diene polymer, and the deformation is thereby automatically removed. , the shape is restored. In the above heating, hot water at 60 to 100°C and hot air at around 100°C are preferably used.

In addition, even if the molded product is heated to a temperature of 60 to 100°C, the molded product has low thermal conductivity, so there is no risk of burns even if it comes into contact with human skin, and this is also an advantage of the shape memory molded product of the present invention. There are benefits.

The shape-memory molded article of the present invention can recover a once-deformed molded article to a predetermined shape, so when using the molded article,
When mounting, assembling, transporting, etc. is difficult in that shape, the ladder shape is changed to make it easier to handle, and after the mounting, assembly, etc. are completed, it is restored to the specified shape by heating operation, and the original purpose is achieved. It can be used for purposes that focus on restoring a deformed molded body to its original state. Specifically, the former includes bonding materials and sealing materials for joints of pipes and electric wires, external laminate materials for pipes and rod-shaped objects, splint materials, various fixing materials, impact absorbing materials, etc., and the latter includes materials for toys. These include parts, stationery materials, teaching materials, decorative materials, etc.

(E) Examples and Effects The present invention will be specifically explained below with reference to Examples, but the present invention is not limited to these Examples. In addition,
In the examples, "part" means "heavy section" unless otherwise specified.

Example 1 Intrinsic viscosity measured in toluene at 30°C, 3,2, 199% trans-1°4- with trans-1,4 alloy
100 parts of polyisoprene [Kurarein Prene Chemical ■, Kuraray Transbolyisoprene TP-301], 30 parts of light calcium carbonate, 0.5 parts of sulfur, dicumyl peroxide [manufactured by Nippon Oil & Fats Corporation, ) Ku-cumyl D) 3 Part 8
Using an inch open roll, mix 75 parts at 5℃,
I created a sheet.

This sheet was preheated at 100°C for 5 minutes using a compression set mold, compression molded at 100°C for 5 minutes at a pressure of 60 KQ/crA, and then vulcanized at 145°C for 30 minutes, resulting in a crosslinked molded product. Obtain a sample. Next, this molded body (5) was heated at 80°C for 10 molecules, and then compressed using a 4-magnet frame at 100°C for 5 minutes at a pressure of 60Kf/- to give it deformation, and then cooled to room temperature to fix the deformation. did. This deformed molded body (B)
After immersion in 0°C hot water for 10 minutes, the molded body recovered to its original state, indicating that a shape-memory molded body had been obtained.

FIG. 1 shows the state in which the compact was compressively deformed and then recovered by heating. When the deformation recovery rate (%) determined by the following formula was determined as an index of shape memory property, the deformation recovery rate at the diameter opening and height were each 100%.

Deformation recovery rate (%) DO = Diameter of the sample before compression deformation D1: Diameter of the sample after compression deformation D2: Diameter of the sample after heating recovery TO: Height of the sample before compression deformation T1: Height of the sample after compression deformation T2 :The height of the compressed sample was 1. In order to check the crosslinking density of the crosslinked molded body (5), the benzene solubility and benzene swelling degree were investigated under the following conditions, and the former was 247% and the latter was 5.0%. Rarely.

・Sample immersion conditions in benzene at 80°C for 60 minutes ・Benzene solubility Wa - Wc Solubility = wa × 100 ・Benzene swelling degree Wb - We Swelling degree (1%) = wo × 100 Example 2 The amount of light calcium carbonate used was 150 A cross-linked molded body was produced in the same manner as in Example 1 except that When the deformation recovery rate was investigated using the same method as in Example 1, the results shown in Table 1 were obtained.

Example 3 A crosslinked molded body was produced in the same manner as in Example 1, except that the amount of light calcium carbonate used was 150 parts, the naphthenic process oil was added 30 parts, and the vulcanization time was 40 minutes. The deformation recovery rate is shown in Table 1.

Example 4 Use of trans-1,4-polyisoprene tit't7
A crosslinked molded body was produced in the same manner as in Example 1 except that 30 parts of cis-1,4-polyinprene was added. The deformation recovery rate is shown in Table 1.

Example 5 A crosslinked molded article was entirely prepared in the same manner as in Example 1, except that dicumyl peroxide was not used at all, 3 parts of a vulcanization accelerator was added, and the vulcanization time was 25 minutes. The deformation recovery rate is shown in Table 1.

Comparative Examples 1 and 2 Molded bodies were produced in the same manner as in Example 1 except that sulfur and dicumyl peroxide were not used at all. In addition, in this method, a molded body was produced in the same manner as above except that the amount of trans-1,4 polyimprene used was 70 parts and cis-1,4-polyisoprene was added 30 parts. The deformation recovery rate of the molded bodies thus prepared was investigated. The results are shown in Table 1.

[Brief explanation of drawings]

FIG. 1 is an example showing the change in shape when the shape memory molded article of the present invention is subjected to compression deformation and heating recovery. In the figure, A
is a shape memory molded body, B is a compressed and deformed molded body,
C is a deformed material that has been heated and recovered.

Claims (4)

[Claims] (1) A crosslinked molded article made from a composition mainly composed of a crystalline diene polymer with a melting point of 40 to 100°C, which can be deformed into a desired shape and can be deformed at a temperature below the melting point of the polymer. A shape-memory molded body characterized by being able to be fixed. (2) The molded article according to claim 1, wherein the crystalline diene polymer is trans-1,4-polyisoprene. (3) A crosslinked molded product made from a composition mainly composed of a crystalline diene polymer with a melting point of 40 to 100°C is deformed into a desired shape, and then cooled to a temperature below the melting point of the polymer to remove the deformation. A method for using a shape-memory molded article, which comprises heating the fixed shape-memory crosslinked molded article to a temperature equal to or higher than the melting point of the polymer to recover the original shape of the molded article. (4) The method of use according to claim 3, wherein the crystalline diene polymer is trans-1,4-polyisoprene.