JPH08199080A - Shape memory complex - Google Patents

Abstract

(57) [Summary] (Modified) [Purpose] To provide a shape memory alloy and a composite of shape memory alloy having excellent corrosion resistance, insulation, and biocompatibility. [Structure] A shape memory alloy that remembers a certain shape recovery operation and a shape memory polymer that remembers a shape recovery operation in a direction different from that of the shape memory alloy, and the shape recovery temperature of the shape memory alloy (the martensite reverse transformation temperature). , Af is the shape recovery temperature (glass transition temperature, T
g) higher than that of shape memory alloy (recovery stress x cross-sectional area)
Alternatively, the temperature at which the generated force is the same as (recovery stress × cross-sectional area) of the shape memory polymer is set so as to be between Af and the martensite transformation temperature (Mf) of the shape memory alloy, and above the temperature, the shape memory is The shape-memory alloy retains the shape memorized by the recovery operation of the alloy to the memorized shape, and at a temperature below the temperature and above the Tg of the shape-memory polymer, the shape-memory polymer recovers the memorized shape by the recovery operation. A shape memory complex, wherein the polymer retains a memorized shape.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a shape memory composite comprising a shape memory alloy and a shape memory polymer.

[0002]

2. Description of the Related Art Many alloys and polymers having a shape memory effect are known.
Among them, shape memory alloys (hereinafter referred to as “SMA”) include Ti—Ni-based, copper-based, and stainless steel-based, and shape memory polymers (hereinafter referred to as “SMP”) include polynorbornene, polyisoprene, and styrene-butadiene. Polymers, polyurethanes, etc. are put to practical use. Further, as a complex composed of SMA and SMP, there is disclosed in Japanese Patent Laid-Open No. 3-4
In 9743, SMA and SMP having different shape recovery temperatures aiming at not being easily deformed by an external force even when the temperature becomes lower than the recovery temperature after changing to the memory shape on the high temperature side.
An actuator that combines and is disclosed. For the same purpose, a molded article composed of SMA and SMP is disclosed in JP-A-2-206539. In addition, the actual Kaihei 4-
19990, 3-7841, S. 63-21896
Etc., a combination of SMA and SMP has been proposed. In all of these, the problem that SMA softens at low temperature is solved by hard SMP at low temperature.
The shapes stored in SMP and SMP are in the same direction, and SMP is not intended to operate in a direction different from SMA.

Incidentally, in both SMA and SMP, shape recovery is unidirectional (irreversible) which occurs only in one direction.
Regarding SMA, by applying special heat treatment or processing conditions, it is possible to give bidirectionality (reversibility) that deforms (shape recovery) in one direction and deforms (shape recovery) in the opposite direction due to temperature change. However, it is difficult to restore the original shape once it has been deformed, because the shape recovery force greatly differs between heating and cooling. For example, FIG. 4 shows a swinging mechanism of an endoscope using a conventional SMA coil. Laser light is applied to the photothermal conversion parts (heaters) 7 and 7 ′ by the laser fiber, and SMA is applied.
A head swing operation is performed by heating the coils 8 and 8 '. In this case, both of the SMA coils are made to memorize the close-wound shape, and are slightly stretched from that state so that the endoscope is fixed so as to be balanced in a straight state. When this is operated in the direction A, the control wire 9 is pulled by heating the coil 8 with the heater 7 to recover the close-wound shape. Also, return it (it moves in the direction of B).
At this time, the heating of the heater 7 is stopped and the coil 8'is heated by the heater 7'to restore its shape to the close-wound shape, thereby pulling the control wire 9 '. Thus, the mechanism requires two SMA coils for simple unidirectional operation, yet each coil must be heated. That is, although reversible movement is possible, two SMA coils are required and there is a problem in miniaturization.

FIG. 5 shows a temperature sensor / actuator of a flap operating mechanism in which the orientation of the flap is changed by a conventional SMA coil and a bias spring. The SMA coil 10 stores the contracted shape. When it gets hot,
Coil 10 regains its shape and contracts, with flap 12 facing downward. When the temperature becomes low, the coil 10 softens, so that the force of the bias spring 11 overcomes and the bias spring 11 orients the flap 12 in the horizontal direction. With this mechanism, the flap can be repeatedly moved up and down,
Since the coil 10 itself does not have a force to return to the shape before the shape recovery, a component for returning the coil 10 to the shape before the recovery, that is, the bias spring 11 is necessary.

As described above, in order to allow the SMA, SMP or the composite thereof to have a shape recovering action in two directions, a component such as a bias spring which acts to restore the SMA or SMP to the shape before the recovery is required. was there. If the shape memory material itself can have a shape recovery operation in two directions, it is possible to dramatically reduce the size and weight of the device.

As a method for this, it has been considered to combine SMP and SMP, but since SMP is rubber-like at a temperature higher than the shape recovery temperature and resin-like at a lower temperature, one of them is heated to recover the shape recovery force. Even if occurs, there is a problem that the shape recovery operation is difficult because the other is hard.

An object of the present invention is to recover the shape of SMA,
It is an object of the present invention to provide a shape memory composite having a practical two-way shape recovery operation without requiring a part for returning the SMP to the shape before recovery.

[0008]

In view of the above situation, the present inventors have conducted diligent research and as a result, S which became soft at low temperature
The present invention has been completed by discovering that the above object can be achieved by applying a force to the SMP itself so as to change the shape of the MA. That is, the present invention comprises an SMA that stores a shape recovery operation and an SMP that stores a shape recovery operation in a direction different from the SMA recovery operation.
Shape recovery temperature of A (Martensite reverse transformation temperature, Af)
Is higher than the shape recovery temperature (glass transition temperature) of SMP,
SMA (recovery stress x cross-sectional area) or generated force is SMP
(Recovery stress x cross-sectional area) of Af and S
It is set so as to fall within the martensitic transformation temperature (Mf) of MA, and above that temperature, the shape remembered by the SMA is maintained by the recovery operation to the shape remembered by the SMA, and it is below this temperature and the Tg of the SMP. At a temperature above, the shape memory composite is characterized in that the shape remembered by the SMP is maintained by the recovery operation to the shape remembered by the SMP.

The SMP used in the present invention is currently SMP.
If it is used as, it can be used without any special limitation. For example, polyurethane, polynorbornene,
Examples include polyisoprene and styrene / butadiene copolymers. Among them, polyurethane is preferable in that the glass transition temperature (hereinafter referred to as “Tg”) can be arbitrarily set by changing the combination of constituent components.

Shape memory polyurethane is a block copolymer containing, as a main component, a polyol constituting a soft segment, a chain extender constituting a hard segment, and a diisocyanate. As the polyol, polyoxyalkylene polyol, polyester polyol, addition polymer of bisphenol A and propylene oxide, etc.,
Preferred polyols have a molecular weight of about 200 to 2000, short-chain glycols such as ethylene glycol and amines as chain extenders, tolylene diisocyanate, diphenylmethane diisocyanate as diisocyanates,
Hexamethylene diisocyanate and the like can be mentioned. The Tg, which is the shape recovery temperature, of the polyurethane can be freely changed from -30 ° C to 60 ° C by changing the molar ratio of the constituent components.

Shape memory polynorbornene has a molecular weight of 3
It is a polymer with a very high value of, 000,000 or more and the shape is recovered by the entanglement of polymers. The Tg (shape recovery temperature) of the polynorbornene is about 30 to 40 ° C.

Shape memory polyisoprene is a rubber consisting of 40% crystalline and surrounding amorphous parts. The shape recovery temperature of the polyisoprene is 60 to 70.
It is about ℃.

The shape memory styrene / butadiene copolymer is a block copolymer of polystyrene and crystallized polybutadiene, and has a total molecular weight of several hundred thousand.
The shape recovery temperature of the copolymer is about 60 to 90 ° C.

The SMA used in the present invention can be used without particular limitation as long as the shape recovery temperature of the SMA is equal to or lower than the molding temperature of SMP. For example, Ti-Ni-based SMA and copper-based SMA whose shape recovery temperature of SMA is considerably lower than the molding temperature of SMP are preferably used.

Examples of the Ti-Ni based SMA include a Ti-Ni binary alloy, a Ti-Ni-Cu alloy, a Ti-Ni-Nb alloy and a Ti-Ni-Fe alloy. Ti-Ni
The shape recovery temperature of the system alloy is -10 ° C to 100 ° C.

Ti-Ni type SMA has a martensite phase (hereinafter referred to as "M phase") structure at low temperature and is a material that undergoes phase transformation to a matrix phase (austenite phase) structure at a certain temperature or higher. The shape recovery effect utilizes this phase transformation. When the M-phase Ti-Ni-based SMA is heated, transformation to the parent phase (martensite reverse transformation) gradually occurs, and eventually the parent phase becomes a complete parent phase. Generally, the temperature at which this parent phase transformation starts is called the As point, and the temperature at which it ends is called the Af point. Normal A
Point f is the shape recovery temperature of the shape memory alloy. On the contrary, when cooling from the temperature range of the mother phase, martensitic transformation gradually occurs and eventually becomes a complete M phase. Like the parent phase transformation, the start temperature of martensitic transformation is Ms
The point and the end temperature are called the Mf point. The Ti—Ni binary alloy has a property that the Mf point is lower than the Af point by about 30 ° C. This is called temperature hysteresis, but this temperature hysteresis must be taken into consideration when operating Ti—Ni by changing the temperature. In addition, this Ti-
When Ni is subjected to thermomechanical treatment under specific conditions, a phase called R phase (rhombohedral structure) appears between the M phase and the mother phase. The R phase usually has a maximum shape memory recovery amount of about 6% between the M phase and the mother phase, but is small at 1% or less, but the temperature hysteresis is also small at about 2 ° C. When responsiveness is required, the parent phase-R phase transformation is often used. The Ti-Ni-Cu-based SMA has a temperature hysteresis of about 12 ° C, which is smaller than that of the Ti-Ni binary alloy, while the Ti-Ni-Nb-based SMA has a temperature of about 150 ° C, which is higher than that of the Ti-Ni binary alloy. . Therefore, each can be used properly according to the purpose.

Examples of the copper-based SMA include Cu-Zn-Al alloy and Cu-Al-Ni alloy. Copper-based SMA
Has a shape recovery temperature of −100 to 100 ° C. Copper SM
The shape memory mechanism of A is almost the same as that of the Ti-Ni-based SMA described above. Ti-in terms of strength, corrosion resistance and reliability
The Ni-based SMA is superior, but the copper-based SMA is superior in terms of workability and economy.

The composite of the present invention comprises the above-mentioned SMA and SM.
It can be arbitrarily selected from P and combined. However, since the SMP needs to be already softened when the shape of the SMA is recovered, the Af point of the SMA needs to be above the Tg of the SMP. Further, when the temperature is lowered from the Af point, it is necessary that the SMA undergo phase transformation until the SMP hardens, and the shape recovery force of the SMP becomes larger than the shape recovery force of the SMA. Tg
Must be below the SMA Ms point.

The difference between the shape recovery temperatures of SMA and SMP is not particularly limited, but considering practicality, Tg is 1 from the Ms point.
It is preferably 0 ° C. or more lower, preferably Tg is 10 ° C. or more lower than the Mf point, more preferably Tg is 20 to 40 ° C. lower than the Mf point.

The preferred combination of SMA and SMP is
Shape memory polyurethane having Tg of 20 to 40 ° C. and Ti—Ni based SMA having Af point of 50 to 80 ° C., particularly Ti—Ni binary alloy, Ti—Ni—Cu based SMA and the like can be mentioned.

As described above, the composite of the present invention retains the shape remembered by SMA at high temperature (above Af point of SMA), but at low temperature (below the Mf point of SMA and S
Above Tg of MP), SMP becomes softer than SM
It is necessary to overcome the shape retaining force of A and make the SMA conform to its own shape. Thus, the balance of the shape recovery forces of SMA and SMP is the shape recovery force of SMA, that is, (recovery stress x cross-sectional area) or generated force and (recovery stress x of SMP).
The temperature at which the cross-sectional areas are equal can be set by setting the temperature between the Af point and the Mf point of the SMA.

For example, the recovery stress of SMA is Ti--Ni
System SMA has a maximum of about 60 kgf / mm ² , and copper-based S
While the maximum is about 35 kgf / mm ^{2 for} MA,
SMP is, 1 kgf / mm ² or less in polyurethane SMP, 1~2kgf / mm ² at polyisoprene SMP,
Styrene-butadiene copolymer system SMP 1kgf /
It is extremely small, such as mm ² or less, and is 1 or less, which is several tens of SMA. Therefore, when coating SMA directly with SMP,
(Recovery stress x cross-sectional area) of SMA and (recovery stress x of SMP
The temperatures at which the cross-sectional areas) are equal are the SMA Af point and M
The types and cross-sectional areas of SMA and SMP are determined so that they are between points f.

When the SMA is used as the coil, the recovery stress is remarkably reduced by the amount of displacement, and thus the value is close to the recovery stress of the SMP. For example, Ti-Ni type SMA coil (strand diameter: 0.2 mm, coil outer diameter: 0.8 m
The generated force of m) is 50 to 70% of the amount of displacement of the coil and 0.2 to 0.3 kgf at the Af point. On the other hand, the recovery stress of the polyurethane SMP is about 0.2 to 0.3 kgf / mm ² at Tg for the same displacement amount as SMA. Therefore, when the SMA coil is covered with the SMP sheet, the cross-sectional area of the SMP may be about 1 mm ² . Thus, S
When coating an element such as an MA coil with SMP, the generated force of SMA is obtained by calculation or measurement, and the temperature at which (recovery stress x sectional area) of SMP becomes equal to the generated force is SMA.
The type of SMP and the thickness of the sheet may be determined so as to be between the Af point and the Ms point.

There is no particular limitation on the specific combination of SMA and SMP. For example, as shown in FIG.
1 may be directly coated with SMP2. The bent shape is stored in SMA1 and is stretched to form a linear shape, and SMP2 is coated thereon, and the linear shape is stored in the polymer. When heated above the shape recovery temperature of SMA1, SM
Since P2 is softened, the complex has a bent shape remembered by SMA. In the temperature range below the Ms point of SMA1 and above the Tg of SMP2, the recovering power of SMP2 increases as the temperature decreases, so that the composite has a linear shape.

The outside of the coil made of SMA is SMP
It may be surrounded by the film, sheet or cylinder of For example, as shown in FIG. 2, SMA1 is stored in the shape of a coil that is roughly wound, and SMA1 is compressed by SMP2 in the compressed state.
The outer circumference of 1 is surrounded and stored. This is SMA
When heated above the shape recovery temperature of No. 1, SMP2 is softened, and thus this complex exhibits the shape memorized by SMA1. In the temperature range below the Ms point of SMA1 and above the Tg of SMP2, the recovering power of SMP is predominant as the temperature decreases, resulting in a contracted shape.

FIG. 3 shows a swinging mechanism of an endoscope using the shape memory composite of the present invention. The state where the coil is extended is stored in SMA1 and the state where the coil is contracted is stored in SMP2. FIG. 3 shows a state in which the SMA-SMP composite 4 heated by the heat ray 3 such as laser light or infrared light is at the shape recovery temperature of SMA 1 or higher. The shape restoring force of the SMA 1 extends the coil, the control wire 5 is released, and the endoscope 6 returns to the direction B, that is, the straight shape due to the rigidity of the endoscope 6. On the other hand, the SMA-
When the SMP complex 4 falls below the Ms point of SMA, SM
A1 gradually softens, and eventually the shape recovery force of SMP2 becomes S.
In order to overcome the shape retaining force of MA1 and return to the shape of SMP2, that is, the contracted state, the endoscope 6 bends in the direction A in order to pull the control wire 5. In addition, in SMA-SMP composites such as these, low temperature (SMA
At a temperature below the Mf point), the shape remembered by the SMP is maintained. However, if it is desired to keep the shape remembered by the SMA even at low temperatures, for example, in FIG. When it is bent at a low temperature but it is desired to keep it straight even at a low temperature, it may be rapidly cooled from the shape-recovered state of the SMA (above the As point) to below the Tg of SMP by water cooling or the like. Since this SMA-SMP composite has a slow shape recovery speed of SMP, if it is cooled to Tg or less by quenching, it cures before the shape recovery operation of the SMP, so that the memory shape of the SMA can be stabilized. . It can be operated again by heating.

Specific examples of the composite of the present invention include a Ti-Ni SMA wire having a cross-sectional area of 0.1 to 1.0 mm ² and a polyurethane SMP having a Tg of 30 to 40 ° C. in a thickness of 1. Cover 3 to 4.5 mm. Diameter 0.2-0.3m
Outer diameter made from Ti-Ni-based SMA wire of 0.6-
The outer circumference of the 1.2 mm coil is made from polyurethane SMP having Tg of 30 to 40 ° C, and the thickness is 0.05 to 0.2 m.
Wrap with m sheet.

The composite of the present invention drives a shape memory alloy actuator which has conventionally required a bias spring, for example, a driving mechanism for a wind direction deflecting flap of an air conditioner, a bending mechanism of an endoscope such as a gastric camera or an industrial endscope. Actuators, temperature display actuators for electromagnetic cookers, valve switching actuators for automobile fuel evaporative emission control devices, pressure regulator actuators for siphon coffee makers, shutter opening / closing actuators for dry units of autodesicators, and damper switching for fireproof dampers. This is applied to actuators for automobiles, etc., and can reduce the size and space of elements.

The shape memory composite of the present invention can be manufactured by various methods. For example, a method of coating the surface of a plate-shaped, wire-shaped, or coil-shaped SMA with heat-melted SMP, the same plate-shaped,
SMP dissolved in solvent on the surface of wire or coiled SMA
How to apply and dry, SM in the form of plate, wire or coil
Examples of the method include a method of extrusion-coating SMP on A, a method of hot pressing, and the like. Further, there is also a method of covering the entire plate-shaped, wire-shaped, or coil-shaped SMA with an SMP sheet and hot-pressing. Specifically, for example, a coiled SM
When SMP is extrusion coated or hot pressed on A, the core wire is passed through the SMA coil that stores the rough winding state, the coil is compressed and fixed, and the SMP is extruded or hot pressed to cover it. Preferably. Whichever method is used, SM
Since it is necessary for P to store a shape different from that of SMA, it is necessary to transform the SMA into a shape that the SMP should remember, that is, before the SMP is covered, that is, the shape that the SMA remembers. Is. Also, when applying heat for SMP molding, applying heat of 400 ° C or higher causes SM
Re-memorization of A may occur, so 300 is preferable.
The heat is applied at a temperature of not higher than 0 ° C, more preferably not higher than 200 ° C.

[0030]

The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples. Example 1 An SMA wire rod of a Ti—Ni binary alloy (Af point: 80 ° C., Mf point: 50 ° C.) having a cross-sectional area of 1.0 mm ² was heat-treated, and FIG.
I remembered the bent shape. This SMA alloy is stretched into a straight line, and then polyurethane-based SM
P (Tg: 30 ° C.) was coated to a thickness of 4.5 mm. When heating this linear composite,
Deformation gradually began to occur at around 80 ° C, and the bent shape was almost remembered by SMA. If this is slowly cooled as it is, it begins to gradually grow from around 60 ° C.
At 0 ° C. or lower, the shape became almost linear, that is, the shape remembered by SMP. This operation was repeated 100 times, but there was almost no reduction in the amount of deformation.

Example 2 An SMA wire rod (Af point: 70 ° C., Mf point: 58 ° C.) of Ti—Ni—Cu alloy having a cross-sectional area of 0.3 mm ² and an outer diameter of 1.2 was used.
The shape memory heat treatment was performed in the state of the coarse coil of mm. This coil is compressed (closely wound), and in that state, a polyurethane SMP (Tg: 40 ° C.) sheet (thickness: 0.2 mm) is wound around it in a cylindrical shape as shown in FIG. It was heated and fixed in this shape. Using this composite, an endoscope having a structure as shown in FIG. 3 was produced. Since it is easier to manufacture the endoscope when the endoscope is in a straight shape, the composite is preliminarily heated to recover the shape of the SMA, that is, the composite that is rapidly cooled in the extended state is incorporated into the endoscope. The operation experiment was performed using. Initially, the composite is in the stretched state and the endoscope tip is straight. When this composite was irradiated with heat rays and heated, first, the composite gradually contracted from around 40 ° C. due to the shape recovery of SMP, and the tip of the endoscope bent (state A). When this was further heated to 70 ° C., the complex was elongated by the shape recovery of the SMA coil, and the endoscope became linear (state B). When the heat ray irradiation is stopped and the temperature of the composite body decreases, the composite body gradually begins to contract, and the endoscope enters a bent state (A state) at about 50 ° C. This shape was maintained. The swinging motion of the endoscope due to the expansion and contraction of this composite was repeated 100 times, but the deformation amount was hardly reduced.

[0032]

By applying the shape memory composite of the present invention to a place where a SMA and a bias spring are conventionally used in combination, the number of parts can be reduced, and the device can be downsized and the space can be saved. it can. Further, since the shape recovery force can be controlled by changing the coating film thickness of the SMP, it is possible to easily design a desired one according to the shape recovery force of the SMA. By coating with SMP, it has excellent corrosion resistance and insulating properties, and polyurethane SMP has excellent biocompatibility.
-Cu-Zn-Al-based SMA, which is cheaper than Ni-based SMA but inferior in biocompatibility, can be applied to medical applications, etc. By combining SMA and SMP, the range of applications can be expanded and the cost can be reduced. Also becomes.

[Brief description of drawings]

FIG. 1 is a view showing one embodiment of the shape memory complex of the present invention.

FIG. 2 is a view showing another embodiment of the shape memory complex of the present invention.

FIG. 3 is a diagram illustrating a swinging mechanism of an endoscope using the shape memory composite of the present invention.

FIG. 4 is a diagram illustrating a swinging mechanism of a conventional endoscope.

FIG. 5 is a configuration diagram of a sensor flap in which a conventional SMA coil and a bias spring are combined.

[Explanation of symbols]

 1 SMA 2 SMP 3 Heat ray (laser light, infrared ray, etc.) 4 Shape memory complex 5 Control wire 6 Endoscope 7, 7'Heater 8, 8 'SMA 9, 9' Control wire 10 SMA 11 Bias spring 12 Flap

Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display area C08G 61/08 NLG // C22K 1:00

Claims (7)

[Claims] 1. A shape memory alloy that stores a shape recovery operation and a shape memory polymer that stores a shape recovery operation in a direction different from the recovery operation of the shape memory alloy. Transformation temperature, A
f) is higher than the shape recovery temperature (glass transition temperature, Tg) of the shape memory polymer, the (recovery stress x cross-sectional area) of the shape memory alloy or the generated force is (recovery stress x of the shape memory polymer x
The temperature at which the cross-sectional area) becomes the same as that between Af and the martensitic transformation temperature (Mf) of the shape memory alloy, and above that temperature, the shape memory is restored by the recovery operation to the memorized shape. The alloy retains a memorized shape, and the shape memory polymer retains the memorized shape by the recovery operation of the shape memory polymer to the memorized shape at a temperature below the temperature and above the Tg of the shape memory polymer. Shape memory complex. 2. The shape memory composite according to claim 1, wherein the shape memory polymer is a polymer selected from polyurethane, polynorbornene, polyisoprene and styrene-butadiene copolymer. 3. The shape memory composite according to claim 1, wherein the shape memory alloy is a Ti—Ni-based shape memory alloy or a copper-based shape memory alloy. 4. The shape memory composite according to claim 1, wherein the shape memory alloy is coated with a shape memory polymer. 5. The shape memory composite according to claim 1, wherein a shape memory alloy coil is surrounded by a shape memory polymer. 6. A method for producing a shape memory composite, which comprises subjecting a shape memory alloy to extrusion coating or hot pressing with a shape memory polymer. 7. A method for producing a shape memory composite, which comprises covering the entire shape memory alloy with a sheet of shape memory polymer and hot pressing.