JP2022073216A - Compact having reversible thermal elasticity, and actuator - Google Patents

Abstract

To provide a compact excellent in reversible thermal elasticity; and to provide an actuator.SOLUTION: A compact has reversible thermal elasticity at optional temperature and load region, in which a shrinkage ratio per unit time by heating is 0.07%/°C or more. An actuator containing the compact is also provided.SELECTED DRAWING: Figure 1

Description

The present invention relates to a molded body and an actuator having reversible thermal elasticity.

With the advent of an aging society in developed countries, the development of robotics, and the shift to human intellectual activities, the motorization of various articles is required, and various actuators have been proposed. Actuator is a general term for devices that create movement and force, such as motors, pneumatic / pneumatic cylinders, piezoelectric elements, and artificial muscles. An actuator is a driving body whose material itself is deformed by energy such as electricity, heat, light, and fuel, and its basic deformation pattern is expansion / contraction, bending / stretching, twisting, expansion / contraction.

Currently, the most widely used motors have problems such as being hard, heavy, and making a loud noise. On the other hand, in recent years, the development of soft actuators such as artificial muscles having various characteristics such as small size and light weight, various drive sources, silence, and movement in water or air under extreme conditions has been promoted.

For example, Patent Document 1 discloses that nylon fibers are twisted and a coil-shaped actuator exhibits reversible thermal expansion and contraction.
Patent Document 2 and Non-Patent Document 1 disclose an actuator in which a linear low-density polyethylene fiber is formed into a coil shape to have a high heat shrinkage rate per unit temperature and achieve a high displacement with a small temperature change. ing.
Patent Document 3 discloses a fiber for an actuator that expands and contracts reversibly by heating and cooling and has abundant flexibility, and describes that a nylon fiber has a coil shape and a spring index is increased to a specific value or more. ..

International Publication No. 2014/022667 International Publication No. 2017/022146 International Publication No. 2020/054633

Power-effective low-temperature wave coiled fiber actuator for wearable applications; SCIENTTIFIC REPOTS 2016, 6: 36358.

However, in Patent Document 1, the heat shrinkage rate per unit temperature of the nylon fiber itself is about 0.002% / ° C., which is low. In Patent Document 2 and Non-Patent Document 1, although the heat shrinkage of the linear low-density polyethylene fiber itself is higher than that of nylon, it is not sufficient as an actuator. In Patent Document 3, since nylon is used, the heat shrinkage rate per unit temperature of the fiber itself is low, and there is a limitation that the shrinkage rate cannot be increased unless the spring index of the coil is increased.

An object of the present invention is to provide a molded body and an actuator having excellent reversible thermal elasticity.

1. 1. A molded product having reversible thermal elasticity in an arbitrary temperature and load region, and having a shrinkage rate of 0.07% / ° C. or more per unit temperature due to heating.
2. The molded product according to 1, wherein the shrinkage rate per unit temperature due to heating is 0.07% / ° C. or higher under a tensile load of 2.1 to 20 MPa.
3. 3. The molded product according to 1 or 2, wherein the shrinkage rate per unit temperature is 0.07% / ° C. or higher in the temperature range of −30 ° C. to 200 ° C.
4. The molded product according to any one of 1 to 3, wherein the shrinkage rate when a temperature change of 50 ° C. is applied by heating in a temperature range of −30 ° C. to 200 ° C. is 3.5% or more.
5. The fiber according to 4 having a restoration rate of 90% or more when the temperature is lowered by 50 ° C. after shrinkage due to a temperature change of 50 ° C. by heating.
6. The molded product according to any one of 1 to 5, which has a crosslinked structure inside the molded product.
7. 6. The molded product according to 6, wherein the crosslinked structure includes a silane crosslink.
8. The molded product according to any one of 1 to 7, which is made of an olefin polymer.
9. 8. The molded product according to 8, wherein the olefin polymer is polyethylene.
10. The molded product according to any one of 1 to 9, wherein the gel content is 50% or more.
11. The molded product according to any one of 1 to 10, wherein the degree of crystallinity is 60% or less and the degree of crystal orientation is 80% or more.
12. The molded product according to any one of claims 1 to 11, wherein the molded product is in the form of a fiber, a plate, a sheet, or a film, or has a multilayer structure of one or more of these.
13. 12. The molded product according to 12, wherein the molded product is fibrous and the fineness of the single fiber of the fibrous molded product is 50 to 10000 dtex.
14. 12. The molded product according to 12 or 13, wherein the molded product is fibrous and the diameter of a single fiber of the fibrous molded product is 80 to 1200 μm.
15. The molded product according to any one of 1 to 14, which partially has a portion that does not shrink due to heat.
16. The molded product according to any one of 1 to 15 formed in a coil shape.
An actuator comprising the molded product according to any one of 17.1 to 16.
An actuator composed of a plurality of the molded bodies according to any one of 18.1 to 16 and formed by arranging the molded bodies in parallel and / or in series.

According to the present invention, it is possible to provide a molded body and an actuator having excellent reversible thermal elasticity.

It is a figure which shows an example of the fiber which partially has a fibrous molded body which has a reversible thermal elasticity of this invention. It is a figure which shows an example of the molded body which formed the fibrous molded body of this invention into a coil shape. It is a figure which shows an example of the fibrous molded body formed in the coil shape which increased the coil diameter D. It is a figure which shows an example of the molded body formed into the coil shape which covered the fibrous molded body of this invention by winding the fibrous molded body of this invention around the molded body which formed the fibrous molded body of this invention as a core into a coil shape. It is a figure which shows an example of the molded body which twisted two molded bodies formed in the coil shape of this invention.

The molded product of the embodiment of the present invention has reversible thermal elasticity in an arbitrary temperature and load region, and has a shrinkage rate of 0.07% / ° C. or more per unit temperature due to heating.
Reversible thermal elasticity means that shrinkage due to heating and expansion due to cooling are repeated with approximately constant displacement, but the scope of the present invention is particularly the temperature range for heating and the characteristic change due to deterioration phenomenon due to repeated operation. Is not restricted in.
In a preferred embodiment having reversible thermal elasticity, expansion and contraction with a restoration rate of 90% can be performed once or more, more preferably 10 times or more, further preferably 100 times or more, and most preferably 1000 times or more. A more preferable embodiment having reversible thermal elasticity is that the expansion and contraction with a restoration rate of 95% can be performed once or more, more preferably 10 times or more, further preferably 100 times or more, and most preferably 1000 times or more. A more preferable embodiment having reversible thermal elasticity is that the expansion and contraction with a restoration rate of 97% can be performed once or more, more preferably 10 times or more, further preferably 100 times or more, and further preferably 1000 times or more.

The molded product according to the embodiment of the present invention can be sufficiently displaced as an actuator as long as the heat shrinkage rate per unit temperature when heated under an arbitrary load is 0.07% / ° C. or higher. be. From the above viewpoint, the heat shrinkage rate per unit temperature is more preferably 0.08% / ° C. or higher, further preferably 0.10% / ° C. or higher.
The higher the heat shrinkage rate per unit temperature, the higher the industrial applicability as an actuator, and the upper limit is not particularly limited, but if it is 0.20% / ° C, the performance as an actuator is very high, 0.18. % / ° C is sufficiently effective. Therefore, the heat shrinkage rate per unit temperature can be set in the range of 0.07% / ° C. or higher and 0.20% / ° C. or lower, or 0.07% / ° C. or higher and 0.18% / ° C. or lower. ..
The actuator in the present invention is sometimes called a soft actuator, and the material itself has elasticity.

The restoration rate in the reversible thermal elasticity is preferably maintained at 90% or more, more preferably 95% or more, still more preferably 97% or more in order to function as an actuator with respect to the initial measurement length.
The number of times to maintain the restoration rate is preferably 10 times or more, more preferably 100 times or more, still more preferably 1000 times or more.

There may be a portion of the molded body that does not have reversible thermal elasticity as long as the function as an actuator is not deteriorated. In this case, the portion of the molded product having reversible thermal expansion and contraction is preferably 50% or more, more preferably 80% or more, and most preferably 100% in the direction of thermal expansion and contraction of the molded product. On the other hand, by making the molded body into a coil shape, it is possible to increase the elasticity due to heat, but by making the molded body into a molded body with a high thermal expansion / contraction rate, it is lightweight and space-saving. Can be achieved.

The molded product according to the embodiment of the present invention preferably has a shrinkage rate of 0.07% / ° C. or more per unit temperature due to heating under a tensile load of 1 to 20 MPa.
When the shrinkage rate per unit temperature due to heating is 0.07% / ° C or higher under a tensile load of 1 MPa or more in the thermal expansion and contraction direction of the molded body, shrinkage stress is applied even with a small number of molded bodies or a thinner molded body. It can be expressed and is effective as an actuator. From the above viewpoint, the tensile load state when the shrinkage rate per unit temperature due to heating satisfies 0.07% / ° C. or higher is more preferably a tensile load state of 3 MPa or more, and a tensile load state of 4 MPa or more. Is even more preferable.
From the above viewpoint, the upper limit of the tensile load state is not particularly limited, but if the shrinkage rate per unit temperature when heated under the tensile load state of 10 MPa satisfies 0.07% / ° C. or higher, the application can be used as an actuator. It is highly applicable and can be said to be an excellent actuator. Therefore, the tensile load state when the shrinkage rate satisfies 0.07% / ° C. or higher can be set in the range of 1 to 20 MPa or 1 to 10 MPa.

The molded product according to the embodiment of the present invention preferably has a shrinkage rate of 0.07% / ° C. or more per unit temperature in a temperature range of −30 ° C. to 200 ° C.
If the shrinkage rate per unit temperature is 0.07% / ° C. or higher in the temperature range of -30 ° C to 200 ° C, the application is highly applicable as an actuator, and it can be said that the actuator is excellent.
The lower limit of the operating temperature range in which the shrinkage rate is 0.07% / ° C or higher is not particularly limited as it can be operated even in a low temperature environment and can be used as an actuator, but it may be 20 ° C or higher. For example, it is preferable as an actuator that can be realized near room temperature. When the lower limit of the operating temperature region is 0 ° C. or higher, it is preferable as an actuator that can be realized even in a cold region, and when it is −30 ° C. or higher, it is preferable as an actuator that is practical even in an extremely cold region.
The upper limit of the operating temperature range is not particularly limited, but if it is 90 ° C. or lower, it is preferable as an actuator that can be relatively easily heated and can be realized in a general environment, and if it is 150 ° C. or lower, it is preferable as an actuator that can be realized in a high temperature atmosphere. , 200 ° C. or lower is preferable as an actuator that can be realized in a high temperature atmosphere such as near an engine. However, the operable temperature range can be arbitrarily adjusted by the glass transition temperature of the polymer, and the present invention is not limited by the usage environment, and the material can be designed according to the desired usage environment.

The molded product according to the embodiment of the present invention preferably has a shrinkage rate of 3.5% or more when a temperature change of 50 ° C. is applied in a temperature range of −30 ° C. to 200 ° C.
If the shrinkage rate is 3.5% or more when a temperature change of 50 ° C is applied in the temperature range of -30 ° C to 200 ° C, it is possible to take a high displacement as an actuator with a feasible change, so this is an application. It is effective as an excellent actuator with a wide range of applications. From the above viewpoint, the shrinkage rate is preferably 4.0% or more, more preferably 5.0% / ° C. or higher. The upper limit of this shrinkage rate is not particularly limited, but if it is 10.0%, it is sufficiently effective as an actuator. Therefore, this shrinkage rate can be set in the range of 3.5 to 10.0%.

The molded product according to the embodiment of the present invention preferably has a restoration rate of 90% or more when the temperature is lowered by 50 ° C. after shrinking by heating at a temperature change of 50 ° C.
When the molded product of the present invention is used as an actuator, it is important that it can repeatedly contract and contract. If the restoration rate of the length in the heat shrinkage direction of the molded product of the present invention when the temperature is lowered to the temperature before shrinkage after being heated and shrunk is 90% or more, it can be sufficiently used as an actuator. From this point of view, the restoration rate is more preferably 95% or more, further preferably 97% or more.

The molded body of the embodiment of the present invention preferably has a crosslinked structure inside the molded body. The crosslinked structure means a structure in which the polymers constituting the molded product are crosslinked.
By having a crosslinked structure, it is easy to obtain a high heat shrinkage rate per unit temperature due to the entropy elasticity.
The type of cross-linking is not particularly limited, but is cross-linked by the reaction of phenol with a base catalyst and excess formamide, the reaction with amine, carboxylic acid anhydride, dicyandiamide, ketimine or acid catalyst using the ring-opening reaction of the epoxy group. Cross-linking by the reaction in, cross-linking by the reaction of condensing urea, melamine, benzoguanamine and formaldehyde in the presence of a weak alkaline catalyst, reaction of a compound having two or more isosianate groups with a bifunctional or higher hydroxyl group or amine compound. Cross-linking by urethane bond or urea bond, cross-linking by condensation reaction of silanol, cross-linking by reaction under peroxide of compound having double bond in side chain or main chain, alkoxide or chelate compound of Al, Ti, Zr Examples thereof include cross-linking by a coordination bond used as a cross-linking agent and cross-linking by a reaction using a photoradical polymerization initiator.

The molded product of the embodiment of the present invention preferably has a silane crosslink.
Since the molded product of the embodiment of the present invention has a silane crosslink, it is easy to obtain a high heat shrinkage rate per unit temperature.
Silane cross-linking can be formed by exposing a pre-silane-modified polymer to a water-containing atmosphere and allowing the reaction between silanol groups (so-called silane bond) to proceed.
More specifically, in a silane-modified polymer, a hydrolyzable alkoxy group derived from a graft-introduced alkoxysilane (for example, an unsaturated silane compound) reacts with water and hydrolyzes in the presence of a silanol condensation catalyst. As a result, silanol groups are generated, and the silanol groups are dehydrated and condensed to promote a cross-linking reaction between the silane-modified polymers. As a result, the silane-modified polymers are bonded to each other to form a silane bridge.

The silane-modified polymer can be produced by graft-introducing alkoxysilane into a polymer such as polyolefin and silane-modifying. The method of silane modification can be carried out according to a known method and is not particularly limited. For example, solution denaturation, melt denaturation, solid phase denaturation by irradiation with electron beam or ionizing radiation, denaturation in a supercritical fluid, and the like are preferably used. Among these, melt modification with excellent equipment and cost competitiveness is preferable, and melt kneading modification using an extruder with excellent continuous productivity is more preferable. Examples of the apparatus used for melt-kneading modification include a single-screw screw extruder, a twin-screw screw extruder, a Banbury mixer, a roll mixer, and the like. Among these, a single-screw extruder and a twin-screw screw extruder having excellent continuous productivity are preferable.

The conditions for forming the silane bridge are determined by the conditions of exposure to the water-containing atmosphere, and are not particularly limited, but are usually preferably in a temperature range of 20 to 130 ° C. and a time range of 1 minute to 1 week, more preferably 20 to 130 ° C. It is in a temperature range and a time range of 1 hour to 160 hours. When air containing moisture is used, the relative humidity may be appropriately adjusted within the range of 1 to 100%.

The molded product of the embodiment of the present invention is preferably made of an olefin polymer.
Since it is easy to increase the number of entanglements and the number of crosslinks of the olefin polymer such as polyolefin which is a flexible polymer, it is possible to obtain a molded product having a high heat shrinkage rate per unit temperature.
The olefin-based polymer includes polyolefins such as polyethylene, polypropylene, and ethylene-propylene copolymer, as well as ethylene-based polymers such as ethylene-vinyl acetate copolymer, ethylene-vinyl alcohol copolymer, and ethylene-ethyl acrylate copolymer. Examples thereof include olefin polymers such as polymers, fluoropolymers such as polyvinylidene fluoride, and chlorine-based polymers such as polyvinylidene chloride.
Polymers and additives other than olefin-based polymers can be contained as long as the required reversible thermal stretchability can be obtained.

The molded product of the embodiment of the present invention is preferably made of polyethylene.
Since the molded product of the embodiment of the present invention is made of polyethylene, the polyethylene material is relatively inexpensive, has excellent spinnability, and is easy to introduce crosslinks, so that a molded product having a high heat shrinkage rate can be obtained at low cost. be able to.

The molded product of the embodiment of the present invention preferably has a gel fraction of 50% or more.
The gel fraction indicates the degree of cross-linking, and the higher the value, the higher the degree of cross-linking. The gel fraction can be measured by the method for measuring the gel fraction described later.
In the molded product of the embodiment of the present invention, the effect of heat shrinkage is more likely to be obtained as the degree of cross-linking increases. Therefore, when the gel fraction is 50% or more, the heat shrinkage rate per unit temperature due to heating can be sufficiently increased. .. From this point of view, the gel fraction is more preferably 60% or more, still more preferably 70% or more. The gel fraction can be increased by increasing the degree of cross-linking of the polymer and increasing the molecular weight. The upper limit of the gel fraction is not particularly limited, but can be set to 100% or less, or can be set to 95% or less or 90% or less.

The type of cross-linking is not particularly limited, and examples thereof include the following cross-linking exemplified in the description of the cross-linking structure. Cross-linking by reaction of phenol with base catalyst and excess formamide, cross-linking by reaction with amine, carboxylic acid anhydride, dicyandiamide, ketimine or reaction with acid catalyst using ring opening reaction of epoxy group, urea, melamine and benzoguanamine Cross-linking by a reaction that condenses formyl and formaldehyde in the presence of a weak alkaline catalyst, cross-linking by a urethane or urea bond between a compound having two or more isocyanato groups and a bifunctional or higher hydroxyl group or amine compound, and a condensation reaction of silanol. Cross-linking by, cross-linking by reaction under peroxide of compound having double bond in side chain or main chain, cross-linking by coordination bond using alkoxide of Al, Ti, Zr or chelate compound as cross-linking agent, photoradical Examples thereof include cross-linking by a reaction using a polymerization initiator.

Among the above-mentioned crosslinks, a silane crosslink formed by a bond (silane bond) by a condensation reaction between silanol groups is preferable.
As an example, by increasing the graft ratio (modification amount) of alkoxysilane (unsaturated silane compound) in the silane-modified polyolefin, the type and blending amount of the silanol condensation catalyst, the conditions (temperature, time) for crosslinking, etc. are changed. The gel fraction of the silane crosslinked polyolefin molded product can be adjusted.

In order to carry out the cross-linking treatment, first, the unstretched product is stretch-oriented to obtain a crystal-oriented stretched molded product, and then the cross-linking treatment is performed, so that the mechanical properties and crystal orientation of the molded product are not impaired. The crosslinked structure can be formed while maintaining the above.

The molded product of the embodiment of the present invention preferably has a crystallinity of 60% or less and a crystal orientation of 80% or more.
The lower the crystallinity, the more amorphous that can contribute to heat shrinkage during heating, and a better heat shrinkage effect can be exhibited. Therefore, the crystallinity is preferably 60% or less, more preferably 50% or less, and more preferably 40% or less. Is even more preferable. The lower limit of the crystallinity is not particularly limited, but can be set to 0% or more, or can be set to 5% or more or 10% or more.

The higher the crystal orientation, the more the polymer chains are arranged along the stretching direction of the molded body, and the anisotropic heat shrinkage effect can be sufficiently exhibited with respect to the stretching direction of the molded body. Therefore, the crystal orientation is 80%. The above is preferable, 84% or more is more preferable, and 90% or more is further preferable. The upper limit of the degree of crystal orientation is not particularly limited, but can be set to 100% or less, or 98% or less or 95% or less.

The degree of crystal orientation can be increased by performing a stretching operation. The stretching operation can be performed in one stage or in multiple stages of two or more stages. From the viewpoint of increasing the degree of crystal orientation, the draw ratio can be sufficiently increased if the draw ratio is 2 times or more, preferably 3 times or more. When the stretching operation is performed in multiple stages of two or more stages, the stretching ratio of the first stage is set to 2 times or more, preferably 3 times or more, and the stretching ratio of the second stage is smaller than that of the first stage. For example, it can be set in the range of 1.05 to less than 2.0 times, or 1.05 to 1.5 times. The upper limit of the draw ratio is not particularly limited, but 20 times or less is preferable, 10 times or less is more preferable, and 6 times or less is further preferable, from the viewpoint of preventing the occurrence of defects due to excessive stretching.

The molded product of the embodiment of the present invention is preferably in the form of fibers, plates, sheets or films, or preferably has one or more multilayer structures selected from these.
The shape of the molded body may be any shape as long as it is thermally expanded and contracted in one direction.
If it is fibrous, it can be easily formed into a coil shape, the shrinkage stress can be increased, and the flexibility can be imparted. If it is a plate shape, it can be used in a place where stress is applied, and a product having a high shrinkage stress can be obtained. If it is a sheet shape or a film shape, the shrinkage stress can be easily increased by rounding the shape.
Further, depending on the intended use as an actuator, a plurality of molded bodies having the same shape may be used to form a multi-layer structure, or molded bodies having different shapes may be combined to form a multi-layer structure.

When the molded product of the embodiment of the present invention is fibrous, it is preferable that the single fiber fineness of the fibrous molded product is 50 to 10000 dtex.
The single fiber fineness (dtex) means the weight (g) per 10,000 m of one fiber.
The lower limit of the single fiber fineness is not particularly limited because it depends on the strength and elastic modulus of the material, but the single fiber fineness is preferably 50 dtex or more from the viewpoint of the strength of post-processing and the increase of the spring index when coiled. 100 dtex or more is more preferable, and 200 dtex or more is further preferable.
The upper limit of the single fiber fineness is not particularly limited because it depends on the flexibility of the material, but the single fiber fineness is preferably 10,000 dtex or less, more preferably 5000 dtex or less, and 1000 dtex or less from the viewpoint of flexibility and ease of post-processing. More preferred.

When the molded product of the embodiment of the present invention is fibrous, it is preferable that the diameter of the single fiber of the fibrous molded product is 80 to 1200 μm.
The lower limit of the diameter of the single fiber is not particularly limited because it depends on the strength of the material, the elastic modulus, etc. From the viewpoint of increasing the index, the diameter of the single fiber is preferably 80 μm or more, more preferably 120 μm or more, still more preferably 170 μm or more.
The upper limit of the diameter of the single fiber is not particularly limited because it depends on the flexibility of the material, but if the diameter of the single fiber is small, it is flexible and easy to post-process, so the diameter of the single fiber is preferably 1200 μm or less. , 840 μm or less is more preferable, and 380 μm or less is further preferable.

The molded product of the embodiment of the present invention can partially have the molded product of the above-described embodiment, that is, can partially have a portion that does not shrink heat. For example, as shown in FIG. 1, it can take a form having a main fiber portion a including the central portion of the fiber (the portion of the fiber of the above embodiment) and end portions b including the fiber ends on both sides thereof. a is a portion having a high heat shrinkage rate per unit temperature due to heating, for example, 0.07% / ° C. or higher, La is the length of the main fiber portion a, and b is a heat shrinkage rate per unit temperature. For example, a portion having low heat shrinkage (or no elasticity) of less than 0.07% / ° C., Lb indicates the length of the end portion b.
When used for an actuator, since both ends are fixed, it is preferable that the fixed portion has low elasticity or does not expand or contract.
The total length along the fiber axis direction (fiber length direction) (in FIG. 1, the sum of the length La of the main fiber portion a, the length Lb of one end b, and the length Lb of the other end b). ), The ratio of the length of the portion having high heat shrinkage (La in FIG. 1) is preferably 50% or more, more preferably 80% or more in order to obtain good heat shrinkage, and fixing of both ends is performed. It is preferably 98% or less from the point of fixing without loosening.

As a method for forming the portion having low elasticity or non-expansion, for example, a state in which both ends of the fiber are unlikely or do not undergo a crosslinking reaction during crosslinking (in the case of silane crosslinking, for example, they are not exposed to a water-containing atmosphere). By setting it to the state), it is possible to form a portion having low elasticity or non-expansion.

The molded body of the embodiment of the present invention can be formed into a coil shape.
The coil-shaped molded body can significantly amplify the heat shrinkage of the formed molded body.
FIG. 2 shows an example of a coil-shaped molded body. In the figure, d indicates the fiber diameter of the fibers constituting the coil, and D indicates the coil diameter (coil average diameter).
The method for producing the coil-shaped molded body is not particularly limited, but for example, a stable coil is formed by continuously twisting one to a plurality of fibers under a constant load to form a coil shape and then annealing. The shape can be obtained. Further, by inserting the core rod immediately before coiling and coiling, the coil diameter D can be increased as shown in FIG. 3 according to the diameter of the core rod, and the obtained coil shape can be formed. The body can obtain good contraction displacement.

Further, the coil-shaped molded body may be composed of a plurality of fibrous molded bodies or coil-shaped molded bodies. The coil shape formed from a plurality of fibrous molded bodies is not particularly limited, but is a covered coil shape in which a fibrous molded body or a coil-shaped molded body is wound around a fibrous molded body or a coil-shaped molded body as a core. A stable contraction displacement can be obtained by forming the coil shape (for example, the form shown in FIG. 4) or the coil shape twisted together (for example, the form shown in FIG. 5). FIG. 4 shows an example of a coil-shaped molded body in which the fibrous molded body of the present invention is wound and covered around a coil-shaped molded body of the present invention as a core. FIG. 5 shows an example of a coil-shaped molded body obtained by twisting and twisting the coil-shaped molded body of the present invention.

(Applications for molded bodies with reversible elasticity and coil-shaped molded bodies)
The actuator of the embodiment of the present invention is an actuator including the molded body of the embodiment, or an actuator formed by arranging the molded bodies of the embodiment in parallel and / or in series.
The actuator of the present embodiment can have at least a configuration including the molded body and a heater. In addition, it can also have a cooler.
By arranging the molded bodies in parallel, the contraction force can be increased. Further, by arranging them in series, the contraction displacement can be increased.
The method for heating the actuator according to the embodiment of the present invention is not particularly limited, but for example, in addition to direct heating with warm air, heating by an electric field can also be performed by combining a metal coating or a heating wire. Further, although cooling is not always essential, efficient cooling can be achieved by combining air cooling with a fan or a Pelche element.
The actuator of the present embodiment is preferably used for a power assist suit that requires a high contractile force and a high telescopic displacement, a sensor drive that requires light weight and quietness, and an air conditioning outlet control. It can be used as an in-vehicle device or a thermostat driven by temperature changes.

(Measurement method of heat shrinkage rate and restoration rate)
For the fibers of Examples and Comparative Examples, a thermomechanical analyzer (manufactured by Hitachi High-Tech Science Corporation, model: TMA6100) was used, and the heat shrinkage rate and the restoration rate were measured as follows.
First, a tensile load of 5 MPa is applied to the fiber sample, and two marks are made at intervals of about 5 mm.
Next, with the tensile load applied, the temperature is raised from 35 ° C to 85 ° C and then lowered to 35 ° C. With the temperature lowered to 35 ° C., the distance (L1) between the two marks previously attached to the fiber is measured. Then, the temperature is raised again from 35 ° C. to 85 ° C., and the distance (L2) between the two marks on the fiber is measured.
From the distances L1 and L2, the heat shrinkage rate is obtained by the following formula.
Heat shrinkage rate (%) = (L1-L2) x 100 / L1
Heat shrinkage rate per unit temperature (% / ° C) = (L1-L2) x 100 / L1 / 50
Subsequently, the temperature was lowered to 35 ° C., the distance (L3) between the two marks attached to the fiber was measured, and in the same manner, the temperature was raised and lowered 9 times, and then the fiber was attached to the fiber. Measure the distance (L3) between the marks of the place.
From the distances L1 and L3, the restoration rate is calculated by the following formula.
Restoration rate (%) = 100- ｜ Initial test length change rate ｜
Initial trial length change rate = (L3-L1) x 100 / L1
In Table 1, the one in which the temperature rise and fall are repeated once is referred to as “restoration rate 1”, and the one in which the temperature is repeatedly raised and lowered 10 times is referred to as “restoration rate 10”.

(Measuring method of single fiber fineness)
The mass W (g) of the fiber per 1 m was measured and multiplied by 10,000 to calculate the single fiber fineness (dtex).
Single fiber fineness (dtex) = W × 10000

(Measuring method of single fiber diameter)
The diameter of the single fiber was measured with an ultra-high speed and high precision dimensional measuring instrument (manufactured by KEYENCE, model: LS-9006).

(Measuring method of gel fraction)
The gel fraction was measured by the following method. This gel fraction represents the degree of cross-linking, and the higher the value, the higher the degree of cross-linking.
First, the mass (M1) of the fiber sample to be measured is measured. Next, the fiber sample is subjected to Soxhlet extraction at the boiling point of xylene for 10 hours using xylene, and then the remaining fiber sample is dried and the mass (M2) of the fiber sample is measured. From M1 and M2, the gel fraction is calculated by the following formula.
Gel fraction (%) = M2 / M1 × 100
In the above measurement method, when the fiber sample is melted with a solvent (xylene), the part that remains undissolved is made into a gel (the crosslinked part remains as a gel), and the mass of this gel part and the fiber sample before being melted with the solvent. The degree of progress of cross-linking is evaluated by using the ratio (percentage) with the mass as the "gel fraction".

(Measuring method of crystallinity)
The crystallinity of the fiber was measured using an X-ray generator (Rigaku, ultraX 18, wavelength λ = 1.54 Å).
The drawn yarn was cut to a length of about 5 cm, aligned in the uniaxial direction so that the fibers did not overlap, and attached to the sample holder.
The tube voltage was 40 kV, the tube current was 200 mA, the irradiation time was 120 minutes, and the imaging plate was exposed.
The obtained two-dimensional diffraction image was integrated from β = 0 ° to 360 °, and then the background was subtracted to obtain the final one-dimensional profile.
In separating the one-dimensional profile into a crystal peak and an amorphous peak, the crystal peak is set at a diffraction angle known in the literature, and the amorphous peak is set so as to complement the difference from the profile. Fitting was performed using the waveform separation analysis software Fitik (open source software). The crystallinity was calculated by dividing the sum of the crystal peak integrated intensities by all the peak integrated intensities. As the fitted peak function, a pseudo Voigt function, which is a superposition of the Gaussian function and the Lorentz function, was used, and the ratio of the Gaussian function and the Lorentz function was fixed at 1: 1.

(Measuring method of orientation)
The fiber orientation was measured using a sample horizontal strong X-ray diffractometer (Rigaku, RINT-TTRIII, wavelength λ = 1.54 Å).
The fibers were cut to about 5 cm, aligned in the uniaxial direction so that the fibers did not overlap, and attached to the sample holder.
The tube voltage is 50 kV, the tube current is 300 mA, the scanning range is 5 to 40 °, and the scan speed is 10 ° / min. After finding the crystal peak, the detector is fixed at the angle of the maximum intensity crystal peak. Then, the diffraction intensity was measured while rotating the sample holder on the surface that divides the angle formed by the incident X-ray and the reflected X-ray into two equal parts.
Let β be the rotation angle of the sample holder at that time. Set the baseline by setting the rotation angle of the sample holder when the crystal peak is found to β = 180 ° and setting the intensity of β = 90 ° and 270 ° of the diffraction intensity profile obtained by rotating the sample holder to 0. .. From the profile obtained by subtracting the baseline, the half width α of the peak at β = 180 ° was read, and the degree of crystal orientation was calculated by the following formula.
Crystal orientation = (180-α) × 100/180

(Example 1)
Silan crosslinkable polyethylene (manufactured by Mitsubishi Chemical Co., Ltd., product name "Linkron" MF900N, density ρ = 0.90 g / cm ³ , MFR = 1 g / 10 minutes (190 ° C, load 2.16 kg, 10 minutes)) and silanol. A condensation catalyst master batch (LZ082 manufactured by Mitsubishi Chemical Co., Ltd.) was charged into an extruder of a melt spinning apparatus at a ratio of 5 parts by mass of the catalyst master batch to 100 parts by mass of silane crosslinkable polyethylene, and melt-kneaded at 220 ° C. Then, the resin at 220 ° C. is discharged from a spinning nozzle having a discharge hole diameter of 1.25 mmφ and a discharge hole of 1 hole at a discharge rate of 0.67 g / min, and is not wound up on a bobbin at a take-up speed of 6 m / min. A drawn yarn was obtained.

The obtained undrawn yarn was drawn on a hot plate at a yarn temperature of 50 ° C. and a draw ratio of 3.5 times for the first-stage drawing. The second-stage drawing was continuously performed by hot plate drawing at a yarn temperature of 55 ° C. and a drawing ratio of 1.2 times. Subsequently, the heat annealing treatment was performed at a yarn temperature of 70 ° C. and a draw ratio of 1.0 times.

Then, the annealed fiber was immersed in warm water at 90 ° C. for 24 hours under constant length tension to carry out a crosslinking treatment.

Measurements were performed to determine the diameter, fineness, crystallinity, crystal orientation, gel fraction, heat shrinkage, and restoration rate of the obtained crosslinked fibers. These results are shown in Table 1.

(Example 2)
Silane crosslinkable polyethylene with different densities of silane crosslinkable polyethylene (manufactured by Mitsubishi Chemical Co., Ltd., SL800N, density ρ = 0.88 g / cm ³ , MFR = 1 g / 10 minutes (190 ° C, load 2.16 kg, 10 minutes)) Crosslinked fibers were obtained in the same manner as in Example 1 except that the fibers were replaced with.
Measurements were performed to determine the diameter, fineness, crystallinity, crystal orientation, gel fraction, heat shrinkage, and restoration rate of the obtained crosslinked fibers. These results are shown in Table 1.

(Comparative Example 1)
Linear low-density polyethylene (manufactured by SIGMA-ALDRICH, product number: 428878, MFR = 1.0 g / 10 minutes (190 ° C., load 2.16 kg, 10 minutes)) was put into an extruder of a melt spinning apparatus, and 220. Melted and kneaded at ℃, and the resin at 220 ℃ is discharged from a spinning nozzle with a discharge hole diameter of 1.0 mmφ and a number of discharge holes of 1 hole at a discharge rate of 0.63 g / min and a take-up speed of 2.0 m / min. It was wound on a bobbin to obtain an undrawn yarn.

The obtained undrawn yarn was drawn on a hot plate at a yarn temperature of 80 ° C. and a draw ratio of 9.4 times in the first step. The second-stage drawing was continuously performed by hot plate drawing at a yarn temperature of 100 ° C. and a drawing ratio of 1.1 times. Subsequently, the heat annealing treatment was performed at a yarn temperature of 110 ° C. and a draw ratio of 1.0 times.

Measurements were performed to determine the diameter, fineness, crystallization degree, crystal orientation, gel fraction, heat shrinkage rate, and restoration rate of the obtained fibers. These results are shown in Table 1.

(Comparative Example 2)
Low-density polyethylene (manufactured by Nippon Polyethylene Co., Ltd., product name: Novatec LC522, MFR = 4.0 g / 10 minutes (190 ° C, load 2.16 kg, 10 minutes)) was put into the extruder of the melt spinning machine and at 190 ° C. After melt-kneading, the resin at 190 ° C. is discharged from a spinning nozzle with a discharge hole diameter of 1.0 mmφ and a discharge hole number of 1 hole at a discharge rate of 0.63 g / min, and into a bobbin at a take-up speed of 1.6 m / min. The undrawn yarn was obtained by winding.

The obtained undrawn yarn was drawn on a hot plate at a yarn temperature of 90 ° C. and a draw ratio of 3.5 times in the first step. The second-stage drawing was continuously performed by hot plate drawing at a yarn temperature of 85 ° C. and a drawing ratio of 1.1 times. Subsequently, the heat annealing treatment was performed at a yarn temperature of 100 ° C. and a draw ratio of 1.0 times.

Measurements were performed to determine the diameter, fineness, crystallization degree, crystal orientation, gel fraction, heat shrinkage rate, and restoration rate of the obtained fibers. These results are shown in Table 1.

Claims (18)

A molded product having reversible thermal elasticity in an arbitrary temperature and load region, and having a shrinkage rate of 0.07% / ° C. or more per unit temperature due to heating. The molded product according to claim 1, wherein the shrinkage rate per unit temperature due to heating is 0.07% / ° C. or higher under a tensile load of 1 to 20 MPa. The molded product according to claim 1 or 2, wherein the shrinkage rate per unit temperature is 0.07% / ° C. or higher in the temperature range of -30 ° C to 200 ° C. The molded product according to any one of claims 1 to 3, wherein the shrinkage rate when a temperature change of 50 ° C. is applied by heating in a temperature range of -30 ° C to 200 ° C is 3.5% or more. The molded product according to claim 4, wherein the restoration rate when the temperature is lowered by 50 ° C. after shrinking by heating at a temperature change of 50 ° C. is 90% or more. The molded product according to any one of claims 1 to 5, which has a crosslinked structure inside the molded product. The molded product according to claim 6, wherein the crosslinked structure includes a silane crosslink. The molded product according to any one of claims 1 to 7, which is made of an olefin polymer. The molded product according to claim 8, wherein the olefin polymer is polyethylene. The molded product according to any one of claims 1 to 9, wherein the gel fraction is 50% or more. The molded product according to any one of claims 1 to 10, wherein the degree of crystallinity is 60% or less and the degree of crystal orientation is 80% or more. The molded product according to any one of claims 1 to 11, wherein the molded product is in the form of a fiber, a plate, a sheet, or a film, or has a multilayer structure of one or more of these. The molded product according to claim 12, wherein the molded product is fibrous and the fineness of the single fiber of the fibrous molded product is 50 to 10000 dtex. The molded product according to claim 12 or 13, wherein the molded product is fibrous and the diameter of a single fiber of the fibrous molded product is 80 to 1200 μm. The molded product according to any one of claims 1 to 14, which partially has a portion that does not shrink due to heat. The molded product according to any one of claims 1 to 15, which is formed in a coil shape. An actuator comprising the molded product according to any one of claims 1 to 16. An actuator composed of a plurality of the molded bodies according to any one of claims 1 to 16 and formed by arranging the molded bodies in parallel and / or in series.

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