JPH04224843A - Shape-memory polyolefin resin composition - Google Patents

Abstract

PURPOSE:To prepare the title compsn. having high mechanical strengths and advantageous properties inherent in a polyolefin resin by blending a polyolefin resin with a specific crystalline ethylene copolymer resin in a specified ratio. CONSTITUTION:The title compsn. is prepd. by blending 25-99wt.% polyolefin resin with 1-75wt.% crystalline ethylene copolymer resin contg. 65-85% ethylene. A shape-memory polyolefin resin molding retaining the deformed shape is obtd. by deforming a molding made from the compsn. at a temp. higher than the m.p. of the crystalline resin and lower than the m.p. of the polyolefin resin and then cooling the molding.

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 shape-memory polyolefin resin composition that is inexpensive and has excellent physical properties.

0002

2. Description of the Related Art Recently, shape memory resins have been proposed, that is, resins that exhibit the ability to maintain a desired deformed shape near room temperature and recover to the original memorized shape by heating. As such shape memory resins, resin materials such as polynorbornene, styrene/butadiene copolymer, transisoprene, and polyurethane are known.

[0003] Furthermore, techniques have been proposed to improve the disadvantages of the above-mentioned shape memory resins, such as moldability, weather resistance, chemical resistance, and cost. For example, a representative example is JP-A-2-91138.
In the publication, by blending polyolefin resin with polycaprolactone resin, it is inexpensive, has chemical resistance,
A shape memory resin composition with excellent weather resistance and deformability has been obtained. This composition deforms into a certain shape at a temperature above the melting point of the polycaprolactone resin, retains that deformed shape when cooled to room temperature, and when heated again to a temperature above the melting point. It will recover to its shape.

0004

[Problem to be Solved by the Invention] Although the conventional technology described in the above-mentioned publication takes advantage of the characteristics of polyolefin resins such as economic efficiency, weather resistance, and chemical resistance, the structure of the two resin components to be blended is similar. As a result, compatibility is poor, and the resulting resin composition has a problem in that its mechanical strength, such as tensile elongation and impact strength, is extremely lower than that of polyolefin resins.

[0005] Such problems mean that molded articles of this shape memory resin composition cannot be applied to applications where they are exposed to external mechanical forces. The present invention aims to provide a shape memory resin composition that has the advantages of polyolefin resins and has mechanical strength equivalent to that of polyolefin resins.

[0006]

[Means for Solving the Problem] Generally, in a resin composition consisting of two resin components, if the molecular structures of the two resin components are not similar, each component forms a domain structure with almost no mutual force. This results in a significant decrease in the strength of the target. As mentioned above, conventional multi-component shape memory resin compositions are incompatible and have poor mechanical strength. Until now, no compatible material with excellent mechanical strength that exhibits shape memory has been found.

As a result of extensive studies, the present inventors have discovered that there are compatible resin compositions with excellent mechanical strength that have shape memory properties, and have completed the present invention.

The gist of the present invention is to provide a shape-memory polyolefin resin comprising 25-99% by weight of a polyolefin resin and 1-75% by weight of a crystalline copolymer resin containing 65-85% ethylene. It is a composition. Further, the present invention provides a method of 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, and then cooling it.
This is a shape-memory polyolefin resin molded article that retains its deformed shape.

[0009] The polyolefin resin used in the present invention includes:
Included are homopolymers or copolymers of olefins such as ethylene, propylene, and butene. The copolymer that can be used has an olefin content of 90% or more, preferably 95% or more, and a melting point that is 10° C. or more higher than the melting point of the crystalline ethylene copolymer resin to which it is blended.

The ethylene copolymer resin used in the present invention is a crystalline resin containing 65 to 85% ethylene. Specifically, ethylene/vinyl acetate copolymer resins, ethylene/methyl methacrylate resins, etc. having an ethylene content within this range are exemplified. In this ethylene copolymer resin,
If the ethylene content is less than 65%, the compatibility with the polyolefin resin will be poor, resulting in a large decrease in the strength of the resulting resin composition, and if it exceeds 85%, the shape memory of the resulting resin composition will be poor. Therefore, the object of the present invention is not satisfied.

The composition of the present invention comprises 25 to 99% by weight of the above polyolefin resin and 1 to 75% by weight of the above ethylene copolymer resin. Regarding the blending ratio of polyolefin resin, if it is less than 25%, the strength of the resin composition will decrease, and 99%
If it exceeds 2%, the shape memory properties of the resin composition will decrease.
5 to 99% by weight is suitable, preferably 50 to 90% by weight.

[0012] This composition may contain conventional resin additives such as plasticizers, mold release agents, pigments, lubricants, fillers, flame retardants, antioxidants, and ultraviolet absorbers, as necessary. can.

The composition of the present invention can be obtained by kneading a mixture of the above-mentioned two components and optionally additives by a conventional method. Specifically, conventional polymer kneading equipment such as mill rolls, Banbury mixers, single-screw or twin-screw extruders may be used.

The composition of the present invention obtained by kneading in this manner is molded into a predetermined shape to be memorized by molding at a temperature equal to or higher than the melting point of the polyolefin resin used. Specifically, it can be molded into any shape at 170 to 310° C. by ordinary plastic molding methods such as press working, extrusion molding, injection molding, etc.

Next, this molded article is deformed and strained at a temperature that is higher than the melting point of the ethylene copolymer resin used and lower than the melting point of the polyolefin resin, usually from 40 to 120°C. Deformation can be carried out by applying distortion such as compression, elongation, bending, etc. using an appropriate mold, roll, drawing device, tension device, etc. By cooling while maintaining this deformed shape, the deformed shape can be fixed and the deformed shape can be maintained near room temperature.

[0016] The molded article kept in its deformed shape will restore its original shape when it is heated to a temperature higher than the melting point of the ethylene copolymer resin used and higher than the temperature used at the time of deformation. This restoration can be performed, for example, by immersion in hot water, heating with hot air, or heating with other suitable heating devices.

[0017] In the present invention, the low shape memory properties of polyolefin resins are improved by blending crystalline ethylene copolymer resins. Since it is a soluble type, there is no decrease in mechanical strength. That is, the composition of the present invention can improve the shape memory properties to a practically sufficient degree while maintaining the excellent chemical and mechanical properties of polyolefin resins, and since both components are inexpensive, the composition is cost effective. Very advantageous.

As described above, the composition of the present invention has excellent shape memory properties as well as mechanical and chemical properties, so these properties can be used as a joining material for pipes of different diameters and as an inner lining material for pipes. , external laminate materials for pipes and rod-shaped objects, automobile bumpers, gap materials for residential partitions, stationery, educational materials, toy parts, decorative parts, clamping pins, construction fixing materials, dental materials, etc. has.

[0019]

[Examples] The present invention will be explained below with reference to Examples.
The present invention is not limited thereby.

In this example, shape memory properties were evaluated using the following evaluation method. That is, a dumbbell-shaped test piece was cut out from a molded sheet with a thickness of 1 mm,
A marked line is attached to the parallel portion, and this is stretched by 90% at 80° C. to give deformation. The deformed shape is fixed by cooling to room temperature while maintaining the deformed shape. When this was heated to a constant temperature, the distance between the marked lines was measured, and its shape memory property was evaluated by the recovery rate determined according to the following formula.

[0021]

[0022]

[Example 1] As a crystalline ethylene copolymer resin, an ethylene/vinyl acetate copolymer resin with an ethylene content of 75% (
Evatate K2010 (manufactured by Sumitomo Chemical) was mixed with medium density polyethylene resin (TR418X, manufactured by Showa Denko) in the proportions shown in Table 1, and the cylinder temperature was adjusted to 170°C in the first zone using a single-screw extruder. , second zone 180
℃, the third zone was 180℃, the fourth zone was 180℃, the pellet die temperature was 180℃, and the screw rotation speed was 5.
The mixture was kneaded at 0 rpm to obtain pellets of the resin composition.

Using the above pellets, sheets with thicknesses of 1 mm and 2 mm were formed at 180° C. using a hot press molding machine. Using this 1 mm thick sheet, a shape memory recovery test was conducted using the method described above (heating method for recovery; immersion in 90° C. hot water for 2 minutes). Further, a tensile test was conducted using a 2 mm thick sheet under the conditions of JIS K6760. The results of these tests are shown in Table 2.

[0024]

[Table 1]

[0025]

[Table 2]

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

[0027]

[Example 2] Ethylene methyl methacrylate (manufactured by Sumitomo Chemical, Acrift WD201, WH30) having various ethylene contents was used as a crystalline ethylene copolymer resin.
2, WH202, WH503, WM506) and medium density polyethylene resin (manufactured by Showa Denko, TR418).
X) in the proportions 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 properties and tensile strength characteristics were measured using the same method as in Example 1, and the results are shown in Table 4.

[0028]

[Table 3]

[0029]

[Table 4]

From the results in Table 4, it can be seen that the resin composition according to the present invention has better shape memory recovery characteristics than polyethylene resin alone, and also maintains sufficient mechanical properties. In addition, the ethylene content in the ethylene copolymer resin affects the shape memory and mechanical properties of the resin composition. It is clear that the properties deteriorate.

[0031]

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

Using the above pellets, sheets with thicknesses of 1 mm and 2 mm were formed at 210° C. using a hot press molding machine. Using this 1 mm thick sheet, a shape memory recovery test was conducted according to the method described above (heating method for recovery;
℃ warm water for 2 minutes). Further, a tensile test was conducted using a 2 mm thick sheet under the conditions of JIS K6760. The results of these tests are shown in Table 6.

[0033]

[Table 5]

[0034]

[Table 6]

From the results in Table 6, the resin composition according to the present invention has improved shape memory recovery characteristics compared to polypropylene resin alone, and also maintains the mechanical properties of polypropylene resin to a practically sufficient level. is clear.

[0036]

[Effects of the Invention] According to the present invention, it is possible to improve the low shape memory properties of polyolefin resins and develop sufficient shape memory properties for practical purposes, while also achieving excellent chemical and mechanical properties, which are the advantages of polyolefin resins. A shape memory resin composition having the same properties can be obtained. This shape-memory resin composition is very advantageous in terms of price compared to conventional compositions, so it can be applied to a wide range of applications including the inner lining of pipes.

Claims (2)

[Claims] [Claim 1] Polyolefin resin 25-99% by weight
and 1 to 75% by weight of a crystalline ethylene copolymer resin containing 65 to 85% of ethylene. 2. A molded article made of the composition according to claim 1 is deformed at a temperature 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 the deformed shape. A shape-memory polyolefin resin molded body that retains.