JP3019419B2 - Shape memory polyolefin resin composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a shape memory resin composition, and more particularly to a low cost and excellent shape memory polyolefin resin composition.

[0002]

2. Description of the Related Art Recently, there has been proposed a shape memory resin, that is, a resin which retains a desired deformed shape near room temperature and has a performance of recovering the original shape memorized by heating. As such a shape memory resin, resin materials such as polynorbornene, styrene / butadiene copolymer, transisoprene, and polyurethane are known.

Further, there have been proposed techniques for improving the disadvantages of the above-mentioned shape memory resin, for example, molding workability, weather resistance, chemical resistance, and price. For example, Japanese Patent Application Laid-Open No. 2-91138 discloses a shape memory resin composition which is inexpensive and has excellent chemical resistance, weather resistance, and deformability by blending a polycaprolactone resin with a polyolefin resin. Are getting things. The composition is deformed to a certain shape at a temperature equal to or higher than the melting point of the polycaprolactone resin, and then retains the deformed shape when cooled to room temperature, and is stored again when heated to a temperature equal to or higher than the melting point. It recovers its shape.

[0004]

In the prior art described in the above-mentioned publication, although the characteristics of the polyolefin resin such as economy, weather resistance and chemical resistance are utilized, the structures of the two resin components to be blended are similar. Therefore, there was a problem that the compatibility was poor and the mechanical strength of the obtained resin composition, for example, tensile elongation, impact strength, etc., was extremely lower than that of the polyolefin resin.

[0005] Such a problem means that a molded article of the shape memory resin composition cannot be applied to an application exposed to a mechanical external force. An object of the present invention is to obtain a shape memory resin composition having the advantages of a polyolefin resin and having the same mechanical strength as that of the polyolefin resin.

[0006]

Generally, in a resin composition comprising two resin components, when their molecular structures are not similar, each component forms a domain structure having almost no mutual force. This leads to a significant decrease in the mechanical strength. As described above, the conventional multi-component shape memory resin composition is incompatible and has poor mechanical strength. Until now, a compatible material having excellent mechanical strength and exhibiting shape memory has not been found.

As a result of intensive studies, the present inventors have found that some compatible resin compositions having excellent mechanical strength have shape memory properties, and have completed the present invention.

Here, the gist of the present invention is to provide a shape-memory polyolefin resin comprising 25 to 99% by weight of a polyolefin resin and 1 to 75% by weight of a crystalline copolymer resin containing 65 to 85% of ethylene. A composition. Further, the present invention maintained the deformed shape by deforming a molded article made of the above composition at a temperature higher than the melting point of the crystalline ethylene copolymer resin and lower than the melting point of the polyolefin resin, followed by cooling. It is a shape memory polyolefin resin molded article.

The polyolefin resin used in the present invention is heat-resistant.
It is plastic and includes homopolymers and copolymers of olefins such as ethylene, propylene and butene. As the copolymer, those having an olefin content of 90% or more, desirably 95% or more, and having a melting point higher by 10 ° C. or more than the melting point of the crystalline ethylene copolymer resin to be blended can be used.

The ethylene copolymer resin used in the present invention is a crystalline resin containing 65 to 85% of ethylene. Specifically, ethylene / vinyl acetate copolymer resins and ethylene / methyl methacrylate resins having an ethylene content in this range are exemplified. In this ethylene copolymer resin,
When the ethylene content is less than 65%, the compatibility with the polyolefin resin becomes poor, and the strength of the obtained resin composition is greatly reduced. When the content exceeds 85%, the shape memory property of the obtained resin composition is poor. This does not satisfy the object of the present invention.

The composition of the present invention comprises 25 to 99% by weight of the polyolefin resin and 1 to 75% by weight of the ethylene copolymer resin. If the blending ratio of the polyolefin resin is less than 25%, the strength of the resin composition is reduced, and 99%.
%, The shape memory of the resin composition deteriorates.
It is suitably from 5 to 99% by weight, preferably from 50 to 90% by weight.

This composition may contain, if necessary, conventional resin additives such as a plasticizer, a release agent, a pigment, a lubricant, a filler, a flame retardant, an antioxidant, and an ultraviolet absorber. it can.

The composition of the present invention can be obtained by kneading a mixture of the above two components, if necessary, with additives, according to a conventional method. Specifically, a conventional polymer kneading apparatus such as a mill roll, a Banbury mixer, a single screw or twin screw extruder may be used.

The composition of the present invention obtained by kneading as described above is molded into a predetermined shape to be memorized by molding at a temperature higher than the melting point of the polyolefin resin used. Specifically, at 170 to 310 ° C., it can be formed into an arbitrary shape by a usual plastic molding method, for example, press working, extrusion molding, injection molding and the like.

Next, the molded article is deformed at a temperature not lower than the melting point of the ethylene copolymer resin to be used and lower than the melting point of the polyolefin resin, usually at 40 to 120 ° C., to give strain. The deformation can be performed by applying a strain such as compression, elongation, or bending using an appropriate mold, roll, drawing device, tension device, or the like. By cooling while maintaining the deformed shape, the deformed shape can be fixed, and the deformed shape can be maintained near room temperature.

When the molded product kept in the deformed shape is heated to a temperature higher than the melting point of the ethylene copolymer resin to be used and higher than the temperature used at the time of deformation, the molded product is restored to the stored original shape. This restoration can be performed by, for example, immersion in hot water, heating with hot air, or heating by another appropriate heating device.

In the present invention, the low shape memory property of the polyolefin resin is improved by blending a crystalline ethylene copolymer resin. Since it is a molten system, there is no decrease in mechanical strength. That is, the composition of the present invention can improve the shape memory property to a practically sufficient level while maintaining the excellent chemical and mechanical properties of the polyolefin resin, and since both components are inexpensive, the cost is low. Very advantageous.

As described above, the composition of the present invention is excellent in both shape memory properties and mechanical and chemical properties. By utilizing these properties, the joining material for pipes having different diameters and the inner lining material for pipes are used. A wide range of applications, including external laminates for pipes and rods, bumpers for automobiles, gap materials for housing partitions, stationery, teaching materials, toy materials, decorative materials, fastening pins, etc., architectural fixing materials, dental materials, etc. Having.

[0019]

The present invention will be described below with reference to examples.
The present invention is not limited by this.

In this embodiment, the shape memory property was evaluated using the following evaluation method. That is, a dumbbell-shaped test piece is cut out from a formed sheet having a thickness of 1 mm, and marked lines are drawn on parallel portions, and this is stretched at 80 ° C. by 90% to give a deformation. The deformed shape is fixed by cooling to room temperature while maintaining the deformed shape. The distance between the marked lines when this was heated to a constant temperature was measured, and its shape memory was evaluated by the recovery rate determined according to the following equation.

[0021]

[0022]

Example 1 As a crystalline ethylene copolymer resin, an ethylene / vinyl acetate copolymer resin having an ethylene content of 75% (Evatate K2010, manufactured by Sumitomo Chemical Co., Ltd.) was used. ) Were mixed in the proportions shown in Table 1 and the cylinder temperature was adjusted to 170 ° C. in the first zone, 180 ° C. in the second zone,
The temperature was adjusted to 180 ° C. in the fourth zone and 180 ° C. in the fourth zone, and kneading was performed under the conditions of a pellet die temperature of 180 ° C. and a screw rotation speed of 50 rpm to obtain pellets of the resin composition.

Using the above pellets, sheets having a thickness of 1 mm and 2 mm were formed at 180 ° C. by a hot press molding machine.
Using this 1 mm thick sheet, a shape memory recovery test was performed by the above method (heating method for recovery; dipping in warm water at 90 ° C. for 2 minutes). Also, using a 2mm thick sheet, JISK
A tensile test was performed under the conditions of 6760. Table 2 shows the test results.

[0024]

[Table 1]

[0025]

[Table 2]

From the results shown in Table 2, it is clear that the resin composition according to the present invention has improved shape memory recovery characteristics as compared to the polyethylene resin alone, and also maintains sufficient mechanical characteristics.

[0027]

Example 2 Ethylene methyl methacrylate having various ethylene contents (Aclift WD201, WH30 manufactured by Sumitomo Chemical Co., Ltd.) was used as a crystalline ethylene copolymer resin.
2, WH202, WH503, WM506) and medium density polyethylene resin (TR418, manufactured by Showa Denko KK)
X) were blended at the ratio shown in Table 3 and kneaded in the same manner as in Example 1 to obtain pellets of the resin composition. Furthermore, shape memory recovery and tensile strength characteristics were measured in the same manner as in Example 1, and the results are shown in Table 4.

[0028]

[Table 3]

[0029]

[Table 4]

From the results shown in Table 4, it can be seen that the resin composition according to the present invention has more excellent shape memory recovery characteristics than the polyethylene resin alone and also maintains the mechanical characteristics sufficiently. Furthermore, the ethylene content in the ethylene copolymer resin affects the shape memory properties and mechanical properties of the resin composition, that is, if the ethylene content is too high, the shape memory properties are reduced, and if the ethylene content is too low, the mechanical properties are reduced. It is clear that the properties are degraded.

[0031]

Example 3 As a crystalline ethylene copolymer resin, an ethylene / vinyl acetate copolymer resin having an ethylene content of 75% (Evatate K2010, manufactured by Sumitomo Chemical Co., Ltd.) was used and a block copolymer-polypropylene resin (manufactured by Mitsubishi Yuka). , BC8D) in the proportions shown in Table 5, and using a single screw extruder, set the cylinder temperature to 190 ° C. in the first zone,
Zone 200 ° C, third zone 210 ° C, fourth zone 210 ° C, pellet die temperature 210 ° C, screw rotation speed 50 rp
The mixture was kneaded under the conditions of m 2 to obtain resin composition pellets.

Using the above-mentioned pellets, sheets having a thickness of 1 mm and 2 mm were prepared at 210 ° C. by a hot press molding machine. Using this 1 mm thick sheet, a shape memory recovery test was performed by the above method (heating method for recovery;
Minutes). Also, using a 2 mm thick sheet, JISK
A tensile test was performed under the conditions of 6760. Table 6 shows the test results.

[0033]

[Table 5]

[0034]

[Table 6]

From the results in Table 6, it can be seen that the resin composition according to the present invention has improved shape memory recovery characteristics as compared to the polypropylene resin alone, and also maintains the mechanical properties of the polypropylene resin to a practically sufficient level. Is evident.

[0036]

According to the present invention, while the low shape memory property of the polyolefin resin can be improved and the shape memory property sufficient for practical purposes can be expressed, the excellent chemical and mechanical properties which are the advantages of the polyolefin resin can be obtained. A shape-memory resin composition having the same properties can be obtained. Since the shape memory resin composition is very advantageous in terms of cost compared to conventional ones, it can be applied to a wide range of applications such as inner lining of pipes.

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Claims (2)

(57) [Claims] 1. A thermoplastic polyolefin resin 25 to 99 wt%, crystalline ethylene copolymer containing ethylene 65-85% polymer resin 1-75 wt%, the shape memory polyolefin resin composition characterized by comprising the city . 2. A molded article comprising the composition according to claim 1, which is deformed at a temperature equal to or higher than the melting point of the crystalline ethylene copolymer resin and lower than the melting point of the polyolefin resin, and then cooled to obtain a deformed shape. Shape-retained polyolefin resin molded article which retains.