JP4752339B2 - Shape memory resin having excellent shape recovery ability in two stages and molded article comprising cross-linked product of the resin - Google Patents

Description

  The present invention relates to a resin composition having excellent shape recovery ability in two stages. The present invention also relates to a molded product composed of a crosslinked product of the molded resin composition, a deformed molded product, and methods for using them.

  Conventionally, there are alloy materials and resin materials that show shape memory properties. Shape memory alloys are used for pipe joints and orthodontics, and shape memory resins are used for medical purposes such as heat-shrinkable tubes, clamping pins, laminates, and casts. Used for equipment. Compared to shape memory alloys, shape memory resins can be processed into complex shapes, have a large shape recovery rate, are lightweight, can be freely colored, and are low in cost. Attention has been paid.

  In general, shape memory resin is deformed by applying a predetermined temperature to the resin, then it can be fixed to a desired shape by cooling to room temperature, and it can be restored to its original shape by heating again. Have. The shape memory resin is a non-phase fluid which is fluidized at a certain temperature (glass transition temperature (Tg) or melting point (Tm) inside the reversible phase) above a stationary phase consisting of physical or chemical bonding sites (crosslinking points). It is comprised from the reversible phase which consists of a bridge | crosslinking part, It is characterized by the above-mentioned.

  The mechanism of the shape memory resin will be described in more detail, but the following steps 1 to 3 realize the provision of the shape memory, the deformation of the molded product, and the recovery of the memory shape. FIG. 1 is a conceptual diagram.

1. Molding process When the shape memory resin is molded by a predetermined method (heating, melting, solidifying), the initial state (original) consisting of a stationary phase and a reversible phase (hard) (Fig. (A) and partially enlarged view (b) ) Is stored.

2. Deformation of molded product In order to transform a molded product into an arbitrary shape, the stationary phase is not melted, but only the reversible phase is melted, that is, heated to Tg or Tm above the reversible phase and shifted to the reversible phase (soft). It can be deformed by applying an external force in this state ((d)). When the deformed molded article is cooled to less than Tg or less than Tm (or less than Tc (crystallization temperature)), the reversible phase is also completely solidified and fixed in a deformed state ((e) in the figure).

3. Recovery of Memory Shape The shape of the molded product deformed into an arbitrary shape is maintained in its deformed state by a reversible phase that is temporarily forcedly fixed. Accordingly, when the temperature reaches a temperature at which only the reversible phase is softened by heating, the resin exhibits a rubber-like characteristic and becomes a stable state and recovers its original shape ((c) in the figure). Further, by cooling to less than Tg or less than Tm (or less than Tc), the molded body in the initial state shown in FIG.

  Here, it is known that the stationary phase is classified into a thermosetting type and a thermoplastic type depending on the type of cross-linking, and each has advantages and disadvantages. Moreover, it can be classified into a glass transition type (Tg utilization type), a crystal transition type (Tc utilization type) and a three-dimensional cross-linking formation type (Ta utilization type) according to the method of immobilizing the reversible phase. .

  First, a method for crosslinking the stationary phase will be described. The stationary phase of the thermoplastic shape memory resin is composed of a crystal part, a glassy region of a polymer, entanglement between polymers, metal cross-linking, and the like. Since this stationary phase melts by heating, it has the advantage that it can be reshaped, ie recycled. However, since the bonding force of the thermoplastic stationary phase is weaker than that of the thermosetting type which is covalent bond crosslinking, it has a disadvantage that it is inferior in shape recovery power to the thermosetting type.

  Examples of the thermoplastic shape memory resin include polynorbornene (Patent Document 1: Japanese Patent Laid-Open No. 59-53528). It is described that the entanglement between the polymers is a stationary phase, and the site without the entanglement is a reversible phase and has shape memory. However, this shape memory resin has a problem that the shape recovery time is long and the molecular weight is very high, so that the processability is poor.

  An example of polyurethane (Patent Document 2: JP-A-2-92914) is also known, in which the stationary phase is a crystalline part and the reversible phase is an amorphous part. However, this shape memory resin also has a long shape recovery time. Moreover, since tensile strength is very weak, it is difficult to use for the member for electronic devices.

  A styrene-butadiene copolymer (Patent Document 3: JP-A 63-179955) is also known. The stationary phase is a glassy region of polystyrene, and the reversible phase is a crystal part of transpolybutadiene. However, this shape memory resin also has a problem that the shape recovery time is long and the shape recovery rate is low.

  A method for improving the shape memory characteristics of the thermoplastic shape memory resin has also been proposed. For example, in Patent Document 4 (Patent Publication No. 2692195), the shape recovery rate and recovery are achieved by hydrogenating 80% or more of the olefinic unsaturated bonds in the ternary block copolymer similar to Patent Document 3. It is said that a shape memory resin excellent in time can be provided. However, in Non-Patent Document 1 (Masao Karushi, “Material Development of Shape Memory Polymer”, CMC, pp. 30-43, published in 1989), styrene-butadiene-based thermoplastic shape memory resin is shaped by repeated deformation. It has been pointed out that the memory recovery rate decreases.

  On the other hand, the stationary phase of the thermosetting shape memory resin has a crosslinked structure by a covalent bond. As an advantage of the thermosetting type, it has a high effect of preventing the resin from flowing, has an excellent shape recovery force and dimensional stability, and has a high recovery speed.

  For example, trans-1,4-polyisoprene (Patent Document 5: Japanese Patent Laid-Open No. 62-192440) is given as a specific example of a conventional thermosetting shape memory resin. This is a resin obtained by cross-linking trans-1,4-polyisoprene with sulfur or peroxide, and the stationary phase is a cross-linked site, and the reversible phase is a crystal portion of trans-1,4-polyisoprene. The crystallization temperature of this resin is 12 ° C., and Tg is −70 ° C. or lower. If this glass transition is used for fixing the third shape, shape memory over two stages is possible. That is, the memory of the second shape is performed by crystallization, and the third shape is fixed at the glass transition temperature, but the memory of the second shape uses weak intermolecular force like the thermoplastic type, The recovery time and recovery rate to the second shape are also lowered.

  Next, a method for fixing the reversible phase will be described. Resins can be classified into crystalline resins and amorphous resins. Tc (crystallization temperature) is specific to crystalline resins, whereas Tg (glass transition temperature) is the amorphous phase of resin (amorphous). This phenomenon is caused not only by the amorphous resin but also by the amorphous part of the crystalline resin, and is therefore present in any resin. Ta (bond formation temperature) is a bonding temperature of a thermoreversible bonding reaction and is a phenomenon peculiar to a resin having a functional group capable of this reaction.

  The characteristics of the Tc utilization type will be described. Tc (or Tm (crystalline phase melting temperature)) is a phenomenon caused by freezing (or melting) of molecular motion due to crystallization of the resin, and the elastic modulus of the resin increases in a temperature range below Tc (or Tm). It becomes possible to fix the deformed shape. Since the degree of increase in the elastic modulus varies depending on the ratio of crystallized portions (crystallinity) of the crystalline resin, the hardness of the entire resin depends on the type of resin and the crystallization conditions. That is, it is possible to design a soft material in the operating temperature range. In many cases, the shape memory alloy is used for soft characteristics such as a frame of glasses or an antenna of a mobile phone. If a shape memory resin that is soft at room temperature is obtained, it can be used as an inexpensive and lightweight material instead of these shape memory alloys. In addition, when the shape is fixed by Tc (or Tm), since the transition is generally faster than that of Tg (because of transition at a narrow temperature range), it is excellent in practicality as a shape memory resin. (Non-Patent Document 2 A. Lenden et al., Angew. Chem. Int. Ed., 2002, 41, 2034-2057)

  Next, the characteristics of the Tg utilization type will be described. Tg is a phenomenon caused by freezing and melting of the molecular motion of the amorphous phase, and the elastic modulus of the resin increases in a temperature region below Tg, so that the deformed shape can be fixed. When Tg type fixation is performed, the increase in elastic modulus depends on the ratio of the amorphous phase and the phase separation structure, but since it is in the glass state in the operating temperature range, it is possible to easily obtain a hard resin. Therefore, it is preferable for applications that require high rigidity in the operating temperature range.

  Examples of fixing the reversible phase by glass transition include the above-mentioned polynorbornene (Patent Document 1: Japanese Patent Laid-Open No. 59-53528) and polyurethane (Patent Document 2: Japanese Patent Laid-Open No. 2-92914). However, since shape memory is performed by entanglement and crystallization between molecules, it has already been described that there are problems with the recovery time and recovery power of the shape.

  As an example in which a thermoreversible cross-linked structure is introduced into the resin and the reversible phase of the shape memory resin is fixed by thermoreversible cross-linking, there is Patent Document 6 (Japanese Patent Laid-Open No. 2-258818). As thermoreversible covalently crosslinked structures, covalently crosslinked structures using ionic crosslinking groups such as carboxyl groups, Diels-Alder reactions, and dimerization reactions of nitroso groups are disclosed. The claims include a cross-linked product obtained by using a block copolymer of an aromatic vinyl monomer and a conjugated diene monomer as a base polymer, and cross-linking the base polymer thermoreversibly, The glass transition temperature (Tg) of the dissociated polymer of the crosslinked product (the base polymer) is higher than the dissociation (cleavage) temperature (Td) of the thermoreversible crosslinking contained in the crosslinked product, and the glass transition temperature is It is characterized by being in the range of 70 ° C to 140 ° C.

  In the lower right column of page 3, the dissociation temperature of thermoreversible crosslinking should be lower than the glass transition temperature of the dissociated polymer, but practically the dissociation temperature is 10 ° C. or higher than the glass transition temperature of the dissociated polymer. It is preferably low. " In this block copolymer, similarly to the styrene-butadiene copolymer (Patent Document 3), an aromatic resin having a Tg of about 100 ° C. functions as a stationary phase. On the other hand, a crystalline diene polymer having a melting point lower than the Tg of the aromatic resin works as a reversible phase. The thermoreversible covalently crosslinked structure is introduced into the double bond part in the diene polymer. When heated to Td or higher, the bond (crosslinked) is cleaved, deformed in this state, and then cooled to Td or lower. By doing so, re-bonding (re-crosslinking) and shape memory property are obtained, and by heating to Tg or more of the aromatic resin, moldability is improved and re-molding is possible. That is, in this shape memory resin, as shown in FIG. 2, the resin part becomes a stationary phase and the cross-linked part functions as a reversible phase ((a) in FIG. 2), and the cross-linking is cleaved by heating to Td or higher. (Drawing (b)), further maintaining the heating state and applying external force to deform (Drawing (c)), cooling to below Td and re-crosslinking to show in (d) The shape is stored as follows. In order to recover the shape, it is carried out by heating again to Td or higher to cleave the bridge, and then cooled to return to the original shape. By heating to Tg or more of the aromatic resin at the time of re-molding, the resin portion of the stationary phase has fluidity and can be re-molded as shown in FIG.

  However, since the crosslinking is cleaved at the time of shape recovery, this resin is a thermoplastic type, and an excellent shape recovery power cannot be obtained, and usable resins and thermoreversible binding cross-linked structures are limited. In addition, since the dissociation temperature of the crosslinked structure due to the covalent bond is high (Diels-Alder type: 120 to 160 ° C., nitroso group type: 70 to 160 ° C.), there are actually restrictions on resins and crosslinking sites that satisfy the conditions of this patent. In particular, since the temperature margin during shape memory is in a very narrow range, it is not practical.

  By the way, as an example using thermoreversible reaction for crosslinking, Non-Patent Document 3 (Engle et al., J. Macromol. Sci. Re. Macromol. Chem. Phys., Vol. C33, No. 3, pages 239-257, 1993). (Annual) describes Diels-Alder reaction, nitroso dimerization reaction, esterification reaction, ionene reaction, urethanization reaction, and azlactone-phenol addition reaction.

  Non-Patent Document 4 (Yoshinori Nakane and Masahiro Ishidoya et al., Coloring Materials, Vol. 67, No. 12, pp. 766-774, published in 1994); Non-Patent Document 5 (Yoshinori Nakane and Masahiro Ishidoya et al., Coloring materials, 69, No. 11, pp. 735-742, published in 1996); Patent Document 7 (Japanese Patent Laid-Open No. 11-35675) describes a thermoreversible cross-linking structure utilizing a vinyl ether group.

  In addition, an example in which a reversible reaction by an esterification reaction of an acid anhydride is used to improve heat resistance and recyclability is described in Patent Document 8 (Japanese Patent Application Laid-Open No. 11-106578), and a carboxylic acid is added to a vinyl polymerization compound. A technique for introducing an anhydride and crosslinking with a linker having a hydroxy group is shown.

  However, there is no description about shape memory property, and there is no example used as shape memory resin.

  In order to cope with environmental problems, shape memory resins using various biodegradable polymers have also been proposed. For example, Patent Document 9 (Japanese Patent Application Laid-Open No. 9-221539) discloses a biodegradable shape memory resin composed of an aliphatic polyester resin such as a polylactic acid resin. However, since these are also thermoplastic resins, their shape recovery force and recovery speed are insufficient.

  A shape memory resin using a biodegradable heat or photocurable resin is described in Patent Document 10 (Japanese Patent Publication No. 2002-503524). FIG. 5 of this patent document shows shape memory by photocrosslinking and shape recovery by crosslink cleavage by heat or light. Also, although multiple shape memories have been described, this is simply a polymer blend obtained by blending thermoplastic shape memory resins, and in this method, two excellent shape memories by covalent cross-linking. And reversibility cannot be obtained.

JP 59-53528 A JP-A-2-92914 JP-A 63-179955 Patent Publication No. 2692195 JP 62-192440 A JP-A-2-258818 JP 11-35675 A JP-A-11-106578 JP-A-9-221539 Special table 2002-503524 gazette Masao Karabushi, “Material Development of Shape Memory Polymer”, CMC, 30-43, published in 1989 A. Lenden et al., Angew. Chem. Int. Ed., 2002, 41, 2034-2057 Engle et al. Macromol. Sci. Re. Macromol. Chem. Phys. , C33, No.3, pp.239-257, published in 1993 Yoshinori Nakane and Masahiro Ishidoya et al., Coloring Materials, Vol. 67, No. 12, pp. 766-774, published in 1994 Yoshinori Nakane and Masahiro Ishidoya et al., Coloring Material, Vol. 69, No. 11, pp. 735-742, 1996

  In addition to the conventional shape memory characteristics, if another shape memory is possible, the application can be further expanded. For example, a conventional heat-shrinkable tube is used to join two pipes by using the restoration of the contracted shape memorized by heating, and it was necessary to cut the tube when removing the pipe . On the other hand, it is possible to make a tube that uses a resin capable of shape memory in two stages and restores to a contracted shape by heating in a low temperature region, and conversely restores to an expanded shape by heating in a high temperature region. is there. By using this, the tube once used for bonding can be expanded and removed by further heating. Further, in the case of a tightening pin, conventionally, it was used for pin tightening by heating and bending, and it was simply removed by restoring it to its original straight shape by heating again. If the two-stage shape memory resin is used, the pin is automatically bent and tightened by heating in a low temperature region, and then the pin is again straightened and removed by heating in a higher temperature region. In this way, a wide range of applications not found in conventional shape memory alloys and shape memory resins can be expected.

  An object of the present invention is to provide a shape memory resin having a two-stage and excellent restoring force, which was not obtained by a conventional method, and a molded body made of the resin.

  According to the present invention for achieving the above object, it is possible to provide a molded body using a shape memory resin having a two-stage memory shape and having an excellent shape recovery ability.

  The present inventor believes that the Tg (or Tm) of the resin is normal temperature or higher, a covalent bond at a temperature lower than Td (reversible cross-linking dissociation temperature) and a temperature higher than Td at a temperature lower than Td (reversible cross-linking dissociation temperature). The shape memory resin having a cross-linked site due to thermoreversible bonding that resumes cracking at 1 can memorize the first shape due to irreversible cross-linking and the second shape due to thermo-reversible cross-linking, and the first shape at a temperature of Td or higher. Since shape recovery to a shape is possible, it has been found that it can be used for molded products that require excellent shape recovery force, such as electronic device members. Further, since the third shape can be imparted at Tg (or Tm), shape memory can be performed in two stages. Furthermore, by using a non-petroleum raw material such as a plant-derived resin for a part or all of the resin, it is possible to obtain a material having further excellent environmental compatibility.

That is, this invention consists of the following structures.
(1) A resin having a site to be crosslinked by a covalent thermoreversible reaction that is covalently bonded by cooling and cleaved by heating, and a site to be crosslinked by a covalent irreversible reaction, and having a glass transition temperature (Tg ) Or crystal melting temperature (Tm) is in the range of 40 ° C. or higher and 200 ° C. or lower, the cleavage temperature (Td) of the thermoreversible reaction is 50 ° C. or higher and 300 ° C. or lower, and Tg (or Tm) + 10 ° C. ≦ Td. A shape memory resin characterized by the above.

(2) The ratio of the cross-linked site by the covalent thermoreversible reaction in the cross-linked site of the resin is 10% or more and 50% or less.

(3) The thermoreversible reaction is at least one selected from the group consisting of Diels-Alder type, nitroso dimer type, acid anhydride ester type, urethane type, azlactone-hydroxyaryl type and carboxyl-alkenyloxy type. It is characterized by the form.

(4) The resin is biodegradable.

(5) The resin is a resin derived from a plant-derived resin.

(6) The resin is a resin using polybutylene succinate or polyhydroxyalkanoate as a raw material.

(7) The resin is made from polybutylene succinate or polyhydroxyalkanoate, and the thermoreversible reaction is Diels-Alder type.

(8) A shape memory resin molded article comprising a cross-linked product of the shape memory resin.

(9) The shape memory resin precursor is molded into a predetermined first shape to be memorized by crosslinking and curing so as to form a crosslinked site by a covalent irreversible reaction, and then the obtained molded product Further, the shape-memory-resin-molded article, wherein the second shape is memorized by applying deformation at a temperature equal to or higher than Td and cooling to a temperature equal to or lower than the reversible crosslinking temperature (Ta) to fix the deformed shape. .

(10) The molded body of the above (9) is deformed at a temperature of Tg (or Tm) or more and less than Td and fixed at a temperature of less than Tg (or crystallization temperature (Tc) or less) to form a third shape. A shape memory resin molded product to which is added.

(11) The molded body provided with the third shape of (10) is heated to a temperature of Tg (or Tm) or higher and lower than Td to recover the original second shape stored, and Td or higher, A method of using a shape memory resin molded article, wherein the first shape is recovered by heating to a temperature lower than the thermal decomposition temperature of the resin.

  The shape memory resin of the present invention uses a network structure formed by covalent bonds for the first shape memory and the second shape memory, and thus has an excellent shape recovery ability. Since crystallization is used, it can be fixed quickly and easily. In addition, by making the glass transition (or crystallization) used for fixing the third shape 40 ° C. or higher, which is a temperature range higher than room temperature, it was used as a molded body such as a member of an electronic device used near room temperature. In this case, it is useful because a third shape that can be fixed quickly and easily can be used.

  Specifically, there is provided a shape memory resin in which a covalent irreversible reaction and a thermoreversible reaction are introduced into a crosslinking site. A thermoreversible reaction refers to a reaction in which a bond is cleaved at a predetermined temperature and recombined upon cooling. By cross-linking the resin by an irreversible reaction, a shape memory resin in which the cross-linked site is the first stationary phase and the other resin portions are the reversible phase is obtained. By crosslinking the other resin parts by a thermoreversible reaction, the thermoreversible cross-linking site becomes the second stationary phase and the remaining resin parts become the reversible phase, and the second shape memory characteristic is obtained. Furthermore, since it is covalently crosslinked in the practical temperature range, it functions as a thermosetting type, and when deformed to the second shape or recovered to the first shape, the thermoreversible bond is cleaved by heating (semi-) thermosetting type And the elastic modulus also decreases. For this reason, at the time of recovery to the first shape, a shape memory resin having an advantage of having an excellent shape recovery force is obtained. Moreover, since it recombines at the time of cooling, a shape memory resin equivalent to that before molding is obtained, and the shape recovery rate does not decrease due to repeated deformation.

  The third shape deformation or the recovery to the second shape is performed at a temperature of Tg (or Tm) or more and Td or less, and Tg (or Tc) that firmly restrains the entire resin can be used for fixing the third shape. In addition, if a non-petroleum raw material such as a plant-derived resin is used for the main chain, the environmental load can be further reduced.

Next, embodiments of the present invention will be described in detail.
The mechanism of the shape memory resin of the present invention will be described in detail, but by the following steps 1 to 6, molding processing (giving a first shape (memory)), deformation processing (giving a second shape (memory)) , Deformation processing (giving a third shape), recovery of the second shape memory, recovery of the first shape memory and re-molding. FIG. 3 shows a conceptual diagram.

1. Molding process The shape memory resin of the present invention is stored in the first shape by heating the precursor at a predetermined temperature and causing a crosslinking reaction by irreversible covalent bonding. By cooling this to room temperature, further thermoreversible crosslinking and glass transition occur and the first shape molded body (a) is obtained.

2. Deformation processing (second shape)
In order to deform the molded body storing the first shape into an arbitrary shape, it may be heated to Td or higher at which the thermoreversible cross-linked portion of the stationary phase is cleaved. When Tg (or Tm) or more is reached, the resin softens as shown in state (b), but the thermoreversible cross-linked portion is not cleaved until Tg or more. Furthermore, when heated to Td or higher, the thermoreversible cross-linked portion is cleaved as shown in state (c). In this state (c), the elastic modulus is low and it can be freely deformed. In this state, it can be deformed by applying an external force ((d) in the figure). When the deformed molded product is cooled to Ta (reversible cross-linking formation temperature) or lower, the reversible cross-linking is re-formed in the deformed state (FIG. 5E), so the second shape is stored. By cooling to room temperature, a glass transition occurs and a second shaped molded body is obtained ((f) in the figure).

3. Deformation processing (third shape)
By heating the second shape molded body at Tg (or Tm) or more and less than Td, the elastic modulus decreases, and the state (g) is easily deformed by an external force. This deformation is fixed as a third shape by cooling to a temperature range (low temperature range) below Tg (or below Tc) ((h) in the figure).

4). Recovery of second shape memory The third shape is kept in a deformed state by a reversible phase (crystalline phase or vitrified amorphous phase) temporarily forcedly fixed. Therefore, when the temperature reaches the temperature at which only the amorphous phase vitrified by heating softens or the temperature at which the reversible crystalline phase melts (intermediate temperature range of Tg (or Tm) or more and less than Td), a part of the resin has rubber-like properties. The original second shape is restored (e) and cooled to room temperature to become the second shape (f).

5. Recovery of first shape memory The deformed state of the second shape is maintained by a reversible phase (thermo-reversible crosslinking) that is temporarily forcedly fixed. Accordingly, when the molded body is heated to the dissociation temperature (Td) of the reversible phase in the reversible phase by heating, the elastic modulus further decreases and becomes a stable state, and the original first shape is recovered ((c) in the figure). At this time, since there is irreversible covalent cross-linking, it is possible to achieve excellent resilience. Further, by cooling to less than Tg (or below Tc), it is fixed to the molded body in the initial state of FIG.

  As for the resin, a resin having Tg (or Tm) in a range not higher than Td of the thermoreversible reaction to be introduced and not lower than a temperature that can be withstood when a molded body such as an electronic device member is used is selected. Although the heat resistant temperature varies depending on the member to be used, the Tg (or Tm) of the resin is preferably 40 ° C. or higher and 200 ° C. or lower. If Tg (or Tm) is less than 40 ° C., the rigidity at room temperature is low and the shape stability is poor, and if Tg (or Tm) is higher than 200 ° C., the moldability and workability are both poor and a large amount of energy is required. This is disadvantageous in terms of productivity and economy. The Tg (or Tm) of the resin is preferably 40 ° C. or higher and 120 ° C. or lower. When a user memorizes the shape of a product, a dryer, hot water, or the like can be considered as a practical heating means. Especially when heating with hot water, the temperature can be controlled relatively accurately in a temperature range of 100 ° C. or lower, which is preferable. . On the other hand, when used for an outdoor use, Tg (or Tm) is preferably 60 ° C. or higher. Moreover, when using for the use for which higher heat resistance is required, such as the interior for motor vehicles, Tg (or Tm) has preferable 80 degreeC or more. Further, if the Tg (or Tm) of the resin is equal to or higher than Td, the cross-link is cleaved before the resin softens, so that shape memory excellent in shape memory property cannot be achieved. A resin having a Tg (or Tm) lower by 10 ° C. or more than the Td of the thermoreversible reaction to be introduced is preferable.

  FIG. 4 shows an application example to a split pin as an application example of the shape memory resin of the present invention. In the shape memory resin of the present invention, the first shape (b: stretched state) of the cotter pin provided by the manufacturer is heated to a temperature not lower than Td and lower than the decomposition temperature (Tdec) of the resin. It is possible to give the second shape (c or d; open state) bent at an arbitrary length according to the application. Accordingly, the split pin returns to the original first state (b) only by heating to Td or more, and can be easily removed. Furthermore, in the present invention, two-stage shape memory is possible, and the assembling worker can temporarily fix an arbitrary third shape (e). For example, it is possible to fix the third shape by extending it in the same manner as the first shape and cooling it to less than Tg (or less than Tc). By heating to Tg (or Tm) or more and less than Td, the memorized second shape (f: open state) is obtained. Even if the pin cannot be opened from the opposite side such as a closed container or wall as shown in the figure, it is convenient because the pin automatically opens only by heating the pin. Furthermore, if it is heated to Td or more and less than Tdec, it returns to the first state (b: stretched state), so it can be easily disassembled, and the memory of the second shape is lost by this operation. As recyclable. Moreover, if this resin is produced from a biodegradable resin such as a plant-derived resin, the environmental compatibility is further improved.

  The cleavage temperature (Td) of the thermoreversible reaction bond used for the cross-linked site is in the range of 50 ° C to 300 ° C. In the practical temperature range, the stationary phase and the reversible phase are not in a cured state, so that the mechanical properties usable for the electronic device member cannot be obtained. Therefore, when Td is less than 50 ° C., it is difficult to apply to electronic device members due to the problem of heat resistance. On the other hand, if Td exceeds 300 ° C., there is a problem in thermal decomposition of the resin and work, which is not appropriate.

  Next, Td is Tg (or Tm) of the resin + 10 ° C. or more. At the time of shape memory, the resin is deformed by heating at a temperature equal to or higher than Tg (or Tm) to soften the reversible phase, but if the stationary phase is not crosslinked at this temperature, the fluidity of the resin cannot be prevented. I can't remember the shape. In order to widen the deformable temperature range, Td is desirably Tg (or Tm) + 20 ° C. or more. More preferably, Td is desirably Tg (or Tm) + 30 ° C. or higher.

  The temperature during storage of the second shape and recovery of the first shape is Td or higher. If it is less than Td, dissociation of the thermoreversible crosslinking of the resin does not occur, so that the second shape memory and the first shape cannot be recovered.

In summary, the following formula is obtained.
40 ° C. ≦ Tg (or Tm) ≦ 200 ° C. (1)
50 ° C. ≦ Td ≦ 300 ° C. (2)
Tg (or Tm) + 10 ° C. ≦ Td (3)
40 ° C. ≦ Tg (or Tm) ≦ Tt3 <Td ≦ Tt2 <Tdec (4)
(In the above equation (4), Tt2 and Tt3 are the deformation temperatures to the second shape and the third shape, respectively, and Tdec is the decomposition temperature of the resin.)

The thermoreversible reaction can realize excellent shape memory property and recyclability as long as it includes one reaction type, but may include two or more reaction types. When two or more reaction types are included and each Td is different, assuming that the highest temperature Td is Td1 and the lowest temperature Td is Td2, the above equations (3) and (4) are as follows: .
Tg (or Tm) + 10 ° C. ≦ Td 2 (3 ′)
Tg (or Tm) ≦ Tt3 <Td2 <Td1 ≦ Tt2 <Tdec (4 ′)
Also, when there is a temperature difference of 10 ° C. or more between two adjacent Td (Tda, Tdb), that is,
Tda + 10 ° C. ≦ Tdb (5)
If so, in addition to the shape memory at Tt2 and Tt3, it is possible to store another shape. When the deformation temperature when performing another shape memory is Tt2 ′, the following relationship is established.
Tt3 <Tda ≦ Tt2 ′ <Tdb (6)

  Further, when a crystalline resin material clearly showing Tm (and Tc) is used, another shape memory is performed even when a temperature difference of 10 ° C. or more exists between Tm (and Tc) and Tg. be able to. In this case, if Tm (and Tc) is 40 ° C. or higher, Tg may be less than 40 ° C. For example, when a resin having a Tg of 10 ° C. or lower is used, a soft molded body can be obtained at room temperature, and can be suitably used for medical purposes. On the other hand, if Tg is 40 ° C. or higher, a molded article that is hard at room temperature can be obtained, which is suitable for applications where the hardness of the material is required at room temperature.

  In addition, when a polymer blend forms different cross-linked structures to form a so-called interpenetrating polymer network or the like, a plurality of shapes may be stored.

  In the present invention, as a method for introducing an irreversible covalent bond and a thermoreversible covalent bond, a resin precursor having a functional group necessary for the irreversible covalent bond and a functional group necessary for the thermoreversible covalent bond (type A) ), A resin precursor having a functional group necessary for irreversible covalent bond (B type) and a resin precursor having a functional group necessary for thermoreversible covalent bond (C type) are mixed. There is a technique to use. Further, a method of combining A type with B type or C type may be used.

  The thermoreversible crosslinking reaction is one or more types selected from the group consisting of Diels-Alder type, nitroso dimer type, acid anhydride ester type, urethane type, azlactone-hydroxyaryl type and carboxyl-alkenyloxy type. .

  The irreversible cross-linking reaction includes those of the above reaction types where the temperature of the dissociation reaction is practically irreversible at 300 ° C. or higher, vinyl polymerization of an olefin, anionic polymerization, cationic polymerization, photopolymerization, radiation polymerization, etc. One or more types selected from the group consisting of addition types, condensation types that generate ethers, sulfides, amines, silanes, amides, esters, carbonates, and polyaddition types such as isocyanates, isothiocyanates, maleimides, and epoxies ( Reference: Synthesis and reaction of polymer (3) p.13- Kyoritsu Shuppan Co., Ltd.).

  It is preferable that the ratio of the cross-linked site by the covalent thermoreversible reaction in the cross-linked site of the resin is 10% or more and 50% or less. If it is less than 10%, the memory recovery power of the second shape may be insufficient, and if it exceeds 50%, the memory recovery power of the first shape may be insufficient.

(Introduction of resin functional groups)
Functional groups necessary for the covalent thermoreversible reaction and the covalent irreversible reaction may be introduced at the molecular chain terminal of the resin material (precursor) or may be introduced into the molecular chain. However, when the number of functional groups in the molecule is small, the presence of a functional group at the end of the molecular chain is preferred because more molecular chains can be incorporated into the crosslinked structure. Moreover, as an introduction method, an addition reaction, a condensation reaction, a copolymerization reaction, or the like can be used.

  For example, as a method for introducing a functional group into a molecular chain, various methods for introducing a functional group such as carboxylation or nitration of polystyrene are known. In addition, halogenation of polystyrene is also known, and necessary functional groups can be introduced by utilizing various chemical reactions of halogen groups such as conversion to amine groups.

  Resins having a functional group in the main chain can also be used. For example, a polymer having a hydroxyl group, such as polyvinyl alcohol, has been known to introduce a functional group such as esterification or etherification. In addition, a resin having a carboxylic acid group such as polymethacrylic acid can undergo various chemical reactions of carboxyl groups such as esterification. It is also possible to copolymerize these resins and resins having no functional group.

  As a method for introducing a functional group into the molecular chain terminal, for example, a functional group can be introduced using a terminal blocking agent during polymerization. For example, because the end of a living polymer such as styrene is a highly reactive carbanion, it reacts almost quantitatively with carbon dioxide, ethylene oxide, halogenated alkyl derivatives with functional groups protected by protecting groups, etc. It is possible to introduce a carboxylic acid group, a hydroxyl group, an amino group, a vinyl ether group, or the like. It is also possible to introduce a functional group at the end of the resin chain using a polymerization initiator having a functional group.

  In addition, functional groups can be introduced into polyester resins such as polyalkanoates by esterification reaction. In addition to acid and alkali, esterification can be carried out using a reagent such as carbodiimide. It is also possible to esterify by reacting with a hydroxyl group after derivatizing the carboxyl group into an acid chloride using thionyl chloride or allyl chloride. In addition, for polyesters synthesized using dicarboxylic acid and diol as raw materials, all the terminal groups of the molecular chain can be converted to hydroxyl groups by increasing the molar ratio of diol / dicarboxylic acid of the raw material used to more than 1. Is possible.

  Moreover, it is possible to make a terminal into a hydroxyl group by transesterification. That is, the polyester resin having a terminal hydroxyl group is obtained by transesterifying the polyester resin with a compound having two or more hydroxyl groups.

  If a compound having three or more hydroxyl groups is used as the compound having a hydroxyl group, it is particularly desirable because a crosslinking point having a three-dimensional crosslinked structure can be formed. For example, by transesterifying the ester bond of hydroxyalkanoates such as polyhydroxybutyrolactone and polyhydroxyvalylate with pentaerythritol, a polyester having a total of four hydroxyl groups at the molecular chain ends can be obtained.

  Examples of the compound having two or more hydroxyl groups include dihydric alcohols such as ethylene glycol, propylene glycol, dipropylene glycol, 1,3- and 1,4-butanediol, 1,6-hexanediol, glycerin, triglyceride, and the like. Trivalent alcohols such as methylolpropane, trimethylolethane and hexanetriol, tetrahydric alcohols such as pentaerythritol, methylglycoside and diglycerin, polyglycerin such as triglycerin and tetraglycerin, and polypenta such as dipentaerythritol and tripentaerythritol Examples include erythritol, cycloalkane polyols such as tetrakis (hydroxymethyl) cyclohexanol, and polyvinyl alcohol. Examples thereof include sugar alcohols such as adonitol, arabitol, xylitol, sorbitol, mannitol, iditol, tallitol, dulcitol, and sugars such as glucose, mannose glucose, mannose, fructose, sorbose, sucrose, lactose, raffinose, and cellulose. Examples of the polyhydric phenol include monocyclic polyhydric phenols such as pyrogallol, hydroquinone and phloroglucin, bisphenols such as bisphenol A and bisphenol sulfone, and phenol / formaldehyde condensates (novolaks).

  Incidentally, a resin having a carboxylic acid at a terminal part or a compound having an unreacted hydroxyl group can be easily purified and removed.

  By performing an ester reaction with a hydroxybenzoic acid on the precursor and a precursor modified with a hydroxyl group, the hydroxyl group can be modified to a phenolic hydroxyl group.

  When a carboxyl group is required, it can be modified to a carboxyl group by bonding a compound having a bifunctional or higher carboxylic acid to the hydroxyl group by the above esterification reaction. In particular, when an acid anhydride is used, a precursor having a carboxyl group can be easily prepared. As the acid anhydride, pyromellitic anhydride, trimellitic anhydride, phthalic anhydride, hexahydrophthalic anhydride, maleic anhydride, and derivatives thereof can be used.

(Chemical structure of thermoreversible crosslinking site)
The thermoreversible crosslinking site is composed of two first functional groups and second functional groups that are cleaved by heating and covalently bonded by cooling. When solidifying at a temperature lower than the melt processing temperature, the first functional group and the second functional group form a crosslink by a covalent bond. Above a predetermined temperature such as the melt processing temperature, the thermoreversible cross-linking site is Cleavage into a first functional group and a second functional group. The binding reaction and cleavage reaction at the cross-linked site proceed reversibly with temperature changes. The first functional group and the second functional group may be different functional groups or the same functional group. When the same two functional groups are bonded symmetrically to form a crosslink, the same functional group can be used as the first functional group and the second functional group.

(1) Diels-Alder type reaction Diels-Alder [4 + 2] cyclization reaction is utilized. By introducing conjugated diene and dienophile as functional groups, a shape memory resin crosslinked by a thermoreversible reaction is obtained. Examples of the conjugated diene include a furan ring, a thiophene ring, a pyrrole ring, a cyclopentadiene ring, 1,3-butadiene, a thiophene-1-oxide ring, a thiophene-1,1-dioxide ring, and a cyclopenta-2,4-dienone. Ring, 2H pyran ring, cyclohexa-1,3-diene ring, 2H pyran 1-oxide ring, 1,2-dihydropyridine ring, 2H thiopyran-1,1-dioxide ring, cyclohexa-2,4-dienone ring, pyran A 2-one ring and a substituted product thereof are used as a functional group. As the dienophile, an unsaturated compound that additionally reacts with a conjugated diene to give a cyclic compound is used. For example, a vinyl group, an acetylene group, an allyl group, a diazo group, a nitro group, or a substituted product thereof is used as a functional group. The conjugated diene may also act as a dienophile.

  Among these, for example, cyclopentadiene can be used for the crosslinking reaction, and Td is 150 ° C. or higher and 250 ° C. or lower. Dicyclopentadiene has both conjugated diene and dienophile effects. Dicyclopentadiene dicarboxylic acid, which is a dimer of cyclopentadiene carboxylic acid, can be easily obtained from commercially available sodium cyclopentadienyl (reference: E. Ruksenstein et al., J. Polym. Sci. Part A: Polym. Chem., 38, 818-825, 2000). This dicyclopentadiene dicarboxylic acid is introduced into a site having a hydroxyl group by a esterification reaction into a precursor having a hydroxyl group, a precursor modified with a hydroxyl group, or the like.

  For example, when 3-maleimidopropionic acid and 3-furylpropionic acid are used, a thermoreversible reaction with Td of 80 ° C. is obtained. A crosslinking site can be easily introduced into a site where a hydroxyl group exists in a precursor having a hydroxyl group, a precursor modified with a hydroxyl group, or the like by an esterification reaction.

  For the esterification reaction used for the introduction of the crosslinking site, a catalyst such as carbodiimide can be used in addition to the acid and alkali. It is also possible to esterify by reacting with a hydroxyl group after derivatizing a carboxyl group into an acid chloride using thionyl chloride or allyl chloride. If an acid chloride is used, it easily reacts with an amino group, so that it can be introduced into the amino group side of amino acids and derivatives thereof.

  A maleimide derivative which is a dienophile can be synthesized from a polyamine having at least two amino groups in one molecule. For example, trimethylenediamine, tetramethylenediamine, hexamethylenediamine, xylylenediamine, 3,9-bis (3-aminopropyl) -2,4,8,10-tetraoxaspiro [5.5] undecane, bis ( Aliphatic amines such as 4-aminocyclohexyl) methane and tris (2-aminoethyl) amine, m-phenylenediamine, p-phenylenediamine, 4,4′-diaminodiphenylmethane, 4,4′-diaminodiphenylsulfone, 4, 4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl sulfide, 3,3'-diaminodiphenyl sulfone, 2,2-bis- (4-aminophenyl) propane, bis- (4-aminophenyl) diphenylsilane Bis- (4-aminophenyl) methylphosphine oxide Bis- (3-aminophenyl) methylphosphine oxide, bis- (4-aminophenyl) -phenylphosphine oxide, bis- (4-aminophenyl) pheniramine, 1,5-diaminonaphthalene, 2,4-diaminotoluene, 2,6-diaminotoluene, 3,3′-dimethyl-4,4′-diaminophenylmethane, 2,2′-dimethyl-4,4′-diaminophenylmethane, 3,3 ′ · 5,5′-tetra Methyl-4,4′-diaminodiphenylmethane, 3,3′-diethyl-4,4′-diaminodiphenylmethane, 3,3 ′ · 5,5′-tetraethyl-4,4′-diaminophenylmethane, 3,3 ′ -Di-n-butyl-4,4'-diaminodiphenylmethane, 3,3'-di-tert-butyl-4,4'-diaminodiphenyl Tan, 2,2-bis [4- (4-aminophenoxy) phenyl] propane, bis [4- (4-aminophenoxy) phenyl] sulfone, bis (3-chloro-4-aminophenyl) methane, triaminobenzene , Triaminotoluene, triaminonaphthalene, triaminodiphenyl, triaminopyridine, triaminophenyl ether, triaminodiphenylmethane, triaminodiphenyl sulfone, triaminobenzophenone, triaminophenyl orthophosphate, tri (aminophenyl) phosphine oxide, tetra Aminobenzophenone, tetraaminobenzene, tetraaminonaphthalene, diaminobenzidine, tetraaminophenyl ether, tetraaminophenylmethane, tetraaminophenylsulfone, bis (diaminophen Nil) aromatic amines such as pyridine and melamine, aromatic polyamines obtained by condensation reaction of aniline and formaldehyde, tetrafunctional aromatic polyamines which are reaction products of aromatic dialdehydes and aromatic amines, aromatic Aromatic polyamines obtained from mixtures of dialdehyde and formaldehyde and aromatic amines, polymers of vinylanilines, aliphatic polyamines such as polyallylamine, polylysine, polyortinin, polyethyleneimine, polyvinylamine, chitin, chitosan, etc. Aminopolysaccharides are mentioned. Naturally derived amino compounds are preferred as resin materials from the viewpoint of environmental problems.

  The Diels-Alder type reaction between these functional groups, for example, cyclopentadienyl groups, forms a thermoreversible crosslinked structure as shown in the following general reaction formula (I).

(2) Nitroso dimer type reaction In the general reaction formula (II), two nitroso groups form a nitroso dimer upon cooling to form a bridge. The Td of this cross-linking is 110 ° C. to 150 ° C.

  For example, a dimer of 4-nitroso-3,5-benzylic acid (Reference: US Pat. No. 3,872,057 discloses a method for synthesizing a dimer of 4-nitroso-3,5-dichlorobenzoyl chloride. Can be easily thermoreversible at the site where the hydroxyl group is present by reacting with the hydroxyl group of the precursor having a hydroxyl group, the hydroxyl group of a precursor modified with a hydroxyl group, etc. Cross-linking sites can be introduced. In addition, when acid chlorides are used, they can be easily introduced into the amino group side of amino acids and derivatives thereof because they easily react with amino groups.

  The dimerization reaction of the nitroso group forms a thermoreversible crosslinked structure as shown in the following general reaction formula (II).

(3) Acid anhydride ester type reaction (reaction of acid anhydride group and hydroxyl group)
Acid anhydrides and hydroxyl groups can be used for the crosslinking reaction. As the acid anhydride, aliphatic carboxylic anhydride and aromatic carboxylic anhydride are used. Moreover, although both a cyclic acid anhydride group and a non-cyclic anhydride group can be used, a cyclic acid anhydride group is used suitably. Examples of the cyclic acid anhydride group include a maleic anhydride group, a phthalic anhydride group, a succinic anhydride group, and a glutaric anhydride group. Examples of the acyclic acid anhydride group include an acetic anhydride group and a propionic anhydride group. And benzoic anhydride groups. Among them, maleic anhydride group, phthalic anhydride group, succinic anhydride group, glutaric anhydride group, pyromellitic anhydride group, trimellitic anhydride group, hexahydrophthalic anhydride group, acetic anhydride group, propionic anhydride group, anhydrous A benzoic acid group and a substituted product thereof are preferable as an acid anhydride that reacts with a hydroxyl group to form a crosslinked structure.

  As the hydroxyl group, a hydroxyl group such as a hydroxyl group of a precursor having a hydroxyl group or a precursor into which a hydroxyl group has been introduced by various reactions is used. Moreover, you may use hydroxy compounds, such as diol and a polyol, as a crosslinking agent. Furthermore, diamines and polyamines can also be used as crosslinking agents. For example, if an acid anhydride having two or more acid anhydrides such as pyromellitic anhydride is used, it can be used as a crosslinking agent for a precursor having a hydroxyl group, a precursor modified with a hydroxyl group, etc. .

  Further, a compound having two or more maleic anhydrides can be easily obtained by copolymerizing maleic anhydride with an unsaturated compound by vinyl polymerization (reference: JP-A-11-106578 (Patent Document 8), No. 2000-34376). This can also be used as a crosslinking agent for precursors having hydroxyl groups, precursors modified with hydroxyl groups, and the like.

  The acid anhydride and hydroxyl group as described above form a thermoreversible cross-linked structure as shown in the following general reaction formula (III). In the general reaction formula (III), an acid anhydride group and a hydroxyl group form an ester upon cooling to form a crosslink. The Td of this crosslinking is 260 ° C.

(4) Urethane type reaction (reaction of isocyanate group and active hydrogen)
A thermoreversible crosslinking site can be formed from isocyanate and active hydrogen. For example, polyisocyanate is used as a crosslinking agent and reacts with the hydroxyl group, amino group, and phenolic hydroxyl group of the precursor and its derivatives. In addition, a molecule having two or more functional groups selected from a hydroxyl group, an amino group and a phenolic hydroxyl group can be added as a crosslinking agent. Further, a catalyst can be added to bring the cleavage temperature into a desired range. Moreover, dihydroxybenzene, dihydroxybiphenyl, a phenol resin, etc. can also be added as a crosslinking agent.

  In addition, polyisocyanate is used as a crosslinking agent and reacted with the hydroxyl group, amino group, and phenolic hydroxyl group of the precursor and its derivative. Dihydroxybenzene, dihydroxybiphenyl, phenol resin and the like can be added as a crosslinking agent. Examples of the polyvalent isocyanate include tolylene diisocyanate (TDI) and a polymer thereof, 4,4′-diphenylmethane isocyanate (MDI), hexamethylene diisocyanate (HMDI), 1,4-phenylene diisocyanate (DPDI), 1,3- Phenylene diisocyanate, xylylene diisocyanate, lysine diisocyanate, 1-methylbenzene-2,4,6-triisocyanate, naphthalene-1,3,7-triisocyanate, biphenyl-2,4,4'-triisocyanate, triphenylmethane -4,4 ', 4 "-triisocyanate, tolylene diisocyanate, lysine triisocyanate and the like can be used.

  In order to adjust the cleavage temperature, organic compounds such as 1,3-diacetoxytetrabutyl distanoxane, amines, metal soaps and the like may be used as the cleavage catalyst.

  The urethanization reaction with the above functional group forms a thermoreversible crosslinked structure as shown in the following general reaction formula (IV). In the general reaction formula (IV), the phenolic hydroxyl group and the isocyanate group form urethane by cooling to be crosslinked. Td of this crosslinking is 120 ° C. or more and 250 ° C. or less, and can be adjusted by a catalyst.

  (5) Azlactone-hydroxyaryl type reaction (reaction of azlactone group and phenolic hydroxyl group)

  Examples of the aryl group include a phenyl group, a tolyl group, a xylyl group, a biphenyl group, a naphthyl group, an anthryl group, a phenanthryl group, and a group derived from these groups, and a phenolic hydroxyl group bonded to these groups. Reacts with the azlactone structure contained in the group forming the crosslinked structure. As the compound having a phenolic hydroxyl group, a precursor having a phenolic hydroxyl group, a precursor modified with hydroxylphenols, or the like is used.

  As the azlactone structure, 1,4- (4,4′-dimethylazulactyl) butane, poly (2-vinyl-4,4′-dimethylazalactone), bisazulactone benzene, bisazlactone hexane and the like Azlactone is preferred.

  Moreover, bisazulactyl butane etc. of azlactone-phenol reaction bridge | crosslinking can also be used, These are described in the said nonpatent literature 1, for example.

  These functional groups form a thermoreversible crosslinked structure as shown in the following general reaction formula (V). In the general reaction formula (V), the azlactone group and the phenolic hydroxyl group form a covalent bond by cooling to form a crosslink. Td of this crosslinking is 100 ° C. or more and 200 ° C. or less.

(6) Carboxyl-alkenyloxy reaction As those having a carboxyl group, a precursor having a carboxyl group, a precursor modified with a carboxyl group, and the like are used. Examples of the alkenyloxy structure include vinyl ethers, allyl ethers, and structures derived from these structures, and those having two or more alkenyloxy structures can also be used.

  Alkenyl ether derivatives such as bis [4- (vinyloxy) butyl] adipate and bis [4- (vinyloxy) butyl] succinate can also be used as a crosslinking agent.

  These functional groups form a thermoreversible crosslinked structure as shown in the following general reaction formula (VI). In the general reaction formula (VI), a carboxyl group and a vinyl ether group form a hemiacetal ester by cooling to form a crosslink (reference: JP-A-11-35675 (Patent Document 7), JP-A-60-179479). Issue gazette). The Td of this crosslinking is 100 ° C. or more and 250 ° C. or less, and can be adjusted by the crosslinked structure.

(Crosslinking agent)
As explained above, a compound having in the molecule two or more functional groups capable of forming a thermoreversible crosslinking site can serve as a crosslinking agent.

  Examples of the crosslinking agent having an acid anhydride group include a bisphthalic anhydride compound, a bissuccinic anhydride compound, a bisglutaric anhydride compound, a bismaleic anhydride compound, and substituted products thereof.

  Examples of the crosslinking agent having a hydroxyl group include dihydric alcohols such as ethylene glycol, propylene glycol, dipropylene glycol, 1,3- and 1,4-butanediol, and 1,6-hexanediol, glycerin, trimethylolpropane, Trivalent alcohols such as trimethylolethane and hexanetriol, tetrahydric alcohols such as pentaerythritol, methylglycoside and diglycerin, polyglycerins such as triglycerin and tetraglycerin, polypentaerythritol such as dipentaerythritol and tripentaerythritol, tetrakis Examples include cycloalkane polyols such as (hydroxymethyl) cyclohexanol, and polyvinyl alcohol. Examples thereof include sugar alcohols such as adonitol, arabitol, xylitol, sorbitol, mannitol, iditol, tallitol, dulcitol, and sugars such as glucose, mannose glucose, mannose, fructose, sorbose, sucrose, lactose, raffinose, and cellulose.

  Examples of the crosslinking agent having a carboxyl group include oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, phthalic acid, maleic acid, and fumaric acid.

  Examples of the crosslinking agent having a vinyl ether group include bis [4- (vinyloxy) butyl] adipate, bis [4- (vinyloxy) butyl] succinate, ethylene glycol divinyl ether, butanediol divinyl ether, 2,2-bis [p -(2-vinyloxyethoxy) phenyl] propane, tris [4- (vinyloxy) butyl] trimellitate.

  Examples of the crosslinking agent having a phenolic hydroxyl group include monocyclic polyphenols such as dihydroxybenzene, pyrogallol, and phloroglucin, bisphenols such as dihydroxybiphenyl, bisphenol A, and bisphenol sulfone, resol type phenol resins, and novolac type phenol resins. It is done.

  Examples of the cross-linking agent having an isocyanate group include 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 4,4′-diphenylmethane diisocyanate, 2,4′-diphenylmethane diisocyanate, p. -Aromatic diisocyanates such as phenylene diisocyanate, aliphatic diisocyanates such as hexamethylene diisocyanate and lysine diisocyanate, alicyclic diisocyanates such as isophorone diisocyanate, and aryl aliphatic diisocyanates such as xylylene diisocyanate. Examples of trifunctional isocyanates include 1-methylbenzene-2,4,6-triisocyanate, naphthalene-1,3,7-triisocyanate, biphenyl-2,4,4′-triisocyanate, triphenylmethane. -4,4 ', 4 "-triisocyanate, trimer of tolylene diisocyanate, lysine triisocyanate and the like.

  Examples of the crosslinking agent having an azlactone group include bisazulactone butane, bisazulactone benzene, and bisazulactone hexane.

  Examples of the crosslinking agent having a nitroso group include dinitrosopropane, dinitrosohexane, dinitrosobenzene, and dinitrosotoluene.

(Selection of cross-linked structure)
As described above, the reversible reaction forms by bonding by cooling to form a crosslinking site and cleavage by heating, as described above, Diels-Alder type, nitroso dimer type, acid anhydride ester type, urethane type, azlactone-hydroxy Aryl and carboxyl-alkenyloxy types can be used.

  However, there are cases where it is better to avoid deterioration of the main chain due to thermal decomposition or hydrolysis resin, or chemical reaction in which the crosslinking site is deactivated by side reaction. For example, polyester resins such as polylactic acid and polycarbonate are not suitable for acid anhydride ester type crosslinking because hydrolysis occurs by carboxylic acid. A resin having a large number of hydroxyl groups such as polyvinyl alcohol is not suitable because it causes a curing reaction with urethane type, azlactone-hydroxyaryl type and carboxyl-alkenyloxy type. On the other hand, since the Diels-Alder type is hydrophobic, it can be applied to a resin that is easily hydrolyzed, and the reactive group is not deactivated by moisture or the like, so that it can be applied to various resins. It can also be suitably used for plant-derived resins having many ester bonds.

(resin)
(Plant-derived resin material)
If a resin material that is a plant-derived material is used as the resin of the cross-linked product, the resin has high environmental harmony.

  Such plant-derived resin materials include monomers, oligomers and polymers that can be artificially synthesized from biomass raw materials; monomer derivatives that can be synthesized from biomass raw materials, modified oligomers and modified polymers; Monomers, oligomers and polymers that are available and available; derivatives of monomers that are synthesized and available mainly in nature, modified oligomers, modified polymers, etc. are mainly used.

  Examples of the artificially synthesized oligomer and polymer include polyhydroxy such as polylactic acid (manufactured by Shimadzu Corporation, trade name: “Lacty”, etc.), polyglycolic acid, polyepsilon caprolactone (manufactured by Daicel Corporation, trade name: “Placcel”, etc.) Polyaminoalkanoates, polyalkylene alkanoates which are polymers of butylene succinate, polyesters such as polybutylene succinate, polyamino acids such as poly-γ-glutamate (manufactured by Ajinomoto Co., Inc., trade name: “polyglutamic acid”, etc.), etc. Can be mentioned.

  In addition, modified products of these artificially synthesized oligomers and polymers can be suitably used.

  Naturally synthesized oligomers and polymers include starch, amylose, cellulose, cellulose ester, chitin, chitosan, gellan gum, carboxyl group-containing cellulose, carboxyl group-containing starch, pectic acid, alginic acid and other polysaccharides; hydroxy synthesized by microorganisms Examples include polybetahydroxyalkanoate which is a polymer of butyrate and / or hydroxyvalerate (manufactured by Zeneca, trade name: “Biopol”, etc.), among which starch, amylose, cellulose, cellulose ester, Preferred are chitin, chitosan, polybetahydroxyalkanoate which is a polymer of hydroxybutyrate and / or hydroxyvalerate synthesized by microorganisms.

  Naturally modified oligomers and modified polymers can also be suitably used.

  Furthermore, lignin etc. can be used as a modified body of natural synthetic oligomer and polymer. Lignin is a biodegradable dehydrogenated polymer of coniferyl alcohol and sinapyr alcohol contained in wood by 20-30%.

  Among the biodegradable resin materials as described above, artificial synthetic biodegradable oligomers and polymers, modified artificial biodegradable oligomers and polymers, natural synthetic biodegradable oligomers and modified polymers are intermolecular bonds. Since the force is moderate, it is excellent in thermoplasticity, the viscosity at the time of melting does not increase remarkably, and it is preferable because it has good moldability.

  Of these, polyesters and modified products of polyesters are preferable, and aliphatic polyesters and modified products of aliphatic polyesters are more preferable. Polyamino acids and modified products of polyamino acids are preferable, and aliphatic polyamino acids and modified products of aliphatic polyamino acids are more preferable. Also, polyols and modified products of polyols are preferable, and aliphatic polyols and modified products of aliphatic polyols are more preferable.

  Among the above plant-derived resin materials, those having a Tg (or Tm) of a resin composition using this in the range of 40 ° C. ≦ Tg (or Tm) ≦ 200 ° C. can be used. For example, polylactic acid has a Tg of around 50 to 60 ° C., and therefore can be suitably used. Moreover, since Tg (or Tm) of the final resin composition should just be in the above-mentioned temperature range, an alloy and a copolymer are based on two or more kinds of resins selected from the above-mentioned plant-derived resins. It is also possible to form and use this. For example, it is possible to blend polylactic acid with other polyhydroxyalkanoates or polybutylene succinates.

  Even if the Tg alone is less than 40 ° C., the Tg can be adjusted by copolymerization or blending with a resin having a high Tg. Even if the resin has a high Tg, the Tg can be adjusted by adding a plasticizer.

  Moreover, Tg can be adjusted by the crosslinked structure of the resin. For example, by decreasing the molecular weight of the precursor or increasing the number of functional groups of the precursor, the crosslink density can be increased and the Tg of the resin can be increased. By increasing the molecular weight of the precursor or reducing the number of functional groups of the precursor, the crosslinking density can be lowered and the Tg of the resin can be lowered. The Tg of the crosslinked product can be adjusted to 40 ° C. or higher and 200 ° C. or lower by the above method.

  The precursor has a number average molecular weight (hereinafter abbreviated as molecular weight) in the range of 100 to 1,000,000. Preferably, it is 1,000-100,000, More preferably, it is 2,000-50,000. If the molecular weight of the precursor is less than 100, the mechanical properties and processability of the resin may be inferior. On the other hand, if it exceeds 1,000,000, the cross-linking density is lowered, so that the shape memory property may be inferior.

  From the viewpoint of shape memory properties and heat resistance, a three-dimensional crosslinked structure is preferable as the crosslinked structure. The crosslinking density of the three-dimensional crosslinked structure is set to a desired value by setting the number of functional groups of the resin material, the mixing ratio of each member, and the like to predetermined values. The crosslinking density of the three-dimensional crosslinked structure is represented by the number of moles of crosslinking points of the three-dimensional structure contained per 100 g of the resin material. That is, (number of functional groups−2) in one molecule of the raw material was defined as the number of moles of crosslinking points of the molecule.

  In order to achieve sufficient shape memory properties, the crosslink density is preferably 0.0001 or more, and more preferably 0.001 or more. On the other hand, the crosslinking density is preferably 1 or less, particularly preferably 0.3 or less. This is because if the crosslink density is less than 0.0001, a network structure is not formed, and it may be difficult to recover the shape. On the other hand, if it is greater than 1, it will not exhibit sufficient rubber-like properties at Tg or higher and cannot be deformed, so that it may not function as a shape memory resin.

Further, the ratio of storage rigidity G ′ (Pa) at temperatures above and below Td (G ′ {Td} / G ′ {Td + 20 ° C.} and the ratio of storage rigidity G ′ (Pa) at temperatures above and below Tg (or Tm). (G ′ {Tg (or Tm)} / G ′ {Tg (or Tm) + 20 ° C.}) is 1.0 × 10 ¹ or more, preferably 2.0 × 10 ¹ or more, and (G ′ {Tg (Or Tm)} / G ′ {Td + 20 ° C.}) is used in the range of 1.0 × 10 ⁷ or less, preferably 1.0 × 10 ⁵ or less, where G ′ is a temperature of Tg or more. Is lower due to the entropy elasticity based on the micro Brownian motion, and further lowers at Td and above because the molecular restraint due to crosslinking is reduced, and the ratio of Tg and Td (or the ratio of G ′ at the upper and lower temperatures is easily deformed). This (G ′ {Tg} / G ′ {Tg + 2 ° C.}) is also less likely to be deformed not exhibit sufficient rubber in a temperature range of Tg or more is less than 1.0 × 10 ^1, the (G '{Tg (or Tm)} / G' {Td + 20 ℃}) 1 If it is larger than 0.0 × 10 ⁷ , the network structure is not formed and the shape memory property is lost.

  In obtaining the shape memory resin of the present invention, an inorganic filler, an organic filler, a reinforcing material, a colorant, a stabilizer (such as a radical scavenger and an antioxidant), an antibacterial agent, and the like, as long as desired properties are not impaired. An antifungal material, a flame retardant, etc. can be used together as needed. As the inorganic filler, silica, alumina, talc, sand, clay, slag and the like can be used. As the organic filler, organic fibers such as polyamide fibers and plant fibers can be used. As the reinforcing material, glass fiber, carbon fiber, polyamide fiber, polyarylate fiber, acicular inorganic material, fibrous fluororesin, or the like can be used. As the antibacterial agent, silver ions, copper ions, zeolites containing these, and the like can be used. As the flame retardant, silicone flame retardant, bromine flame retardant, phosphorus flame retardant, inorganic flame retardant and the like can be used.

  The resin and resin composition as described above can be used in various electrical and electronic equipment applications such as housings for electrical appliances, depending on general thermosetting resin molding methods such as compression molding, transfer molding, mold casting, and RIM molding. Can be processed into a compact.

  The present invention will be described in more detail with reference to the following examples, but these examples do not limit the present invention. Unless otherwise specified, commercially available high-purity products were used as reagents. The number average molecular weight was measured by gel permeation chromatography and converted using standard polystyrene. The performance was evaluated by the following method.

    Glass transition temperature (Tg), cleavage temperature (Td): measured using a DSC measuring device (trade name: DSC6000) manufactured by Seiko Instruments Inc., at a heating rate of 10 ° C./min, and glass transition temperature (Tg) It was determined. The endothermic peak was taken as the cleavage temperature (Td).

    Storage rigidity: measured with a viscoelasticity measuring device (trade name: “Rheograph Solid S-1”, 10 Hz, heating rate 2 ° C./min) manufactured by Toyo Seiki Co., Ltd., using a test piece having a thickness of 1.8 mm. .

    Shape memory property: A molded body (first shape) of 2 cm × 5 cm × 1.0 mm is prepared, heated at Td + 20 ° C. (for example, 170 ° C. in Example 1), the center of the molded body is bent at 30 ° for 5 seconds. After the deformation, the shape was kept at 100 ° C. for 1 hour to obtain a second shape. Evaluation was made based on the angle (A1) of the molded body at this temperature. 20 ° ≦ A1 ≦ 30 ° was evaluated as “◯”, 10 ° ≦ A1 <20 ° as “Δ”, and 0 ° ≦ A1 <10 ° as “×”. Next, the molded body was bent in the reverse direction at Tg + 20 ° C. (for example, 65 ° C. in Example 1) (−30 °), deformed for 5 seconds, and then cooled to a temperature equal to or lower than Tg to obtain a third shape. The deformability of the molded body at this time was evaluated by the angle (A2). −20 ° ≦ A2 ≦ −30 ° was evaluated as “◯”, −10 ° ≦ A2 <−20 ° as Δ, and 0 ° ≦ A2 <−10 ° as “×”. It was again heated to Tg + 20 ° C. (for example, 65 ° C. in Example 1), and the recoverability was evaluated by the angle (A3). 0 ° <A3 ≦ 10 ° was taken as x, 10 ° <A3 ≦ 20 ° was taken as Δ, and 20 ° ≦ A3 ≦ 30 ° was taken as ○. Further, the molded body was heated at Td + 20 ° C. for 60 seconds, and the recoverability was evaluated by the angle (A4). 20 ° <A4 ≦ 30 ° was evaluated as x, 10 ° <A4 ≦ 20 ° as Δ, and 0 ° ≦ A4 ≦ 10 ° as ○.

  Examples using polylactic acid as a precursor are shown below. Since polylactic acid is biodegradable and is a plant-derived material, it is a preferable material from the viewpoint of environmental problems. In order to impart two-stage shape memory to polylactic acid, the following material design was performed. First, since polylactic acid was thermally decomposed at 200 ° C. or higher, a reversible crosslinking site having a dissociation temperature (Td) of 50 ° C. or higher and 200 ° C. or lower was selected. As this reversible reaction, Diels-Alder type, carboxyl-alkenyloxy type, urethane type and the like can be used. First, polyfunctional furan and polyfunctional maleimide capable of covalent thermoreversible reaction are mixed with polylactic acid into which a hydroxyl group capable of covalent irreversible reaction is introduced, and then polyfunctional isocyanate is added. As a result, a resin having irreversible and reversible three-dimensional crosslinking was obtained. The two-stage shape memory property and biodegradability of this crosslinked resin were verified.

  Examples in which a Diels-Alder type furan-maleimide bond is introduced into polylactic acid are shown below. The dissociation temperature of the furan-maleimide bond is described as 80 ° C. or 140 ° C. in the literature (Non-patent Document 2). As shown in the following examples, the dissociation temperature is 150 ° C. It becomes a suitable cross-linking site.

[Example 1]
2500 g (0.0243 mol) of commercially available polylactic acid (“Lacty” (trade name), manufactured by Shimadzu Corporation) and 191 g (1.41 mol) of pentaerythritol were transesterified by melt mixing at 200 ° C. for 4.5 hours. This was dissolved in chloroform, poured into excess methanol, and reprecipitated to obtain terminal hydroxypolylactic acid [R1]. (The molecular weight by H-NMR is about 3,200)

  Next, 44.1 g (0.45 mol) of 2-furfuryl alcohol and 40.1 g (0.15 mol) of lysine triisocyanate were mixed and stirred at 80 ° C. for 7 hours to obtain a trifunctional furan compound [R2]. .

  Exo-3,6-epoxy-1,2,3,6-tetrahydrophthalic anhydride dissolved in 250 ml of DMF after heating 25 ml of tris (2-aminoethyl) amine dissolved in 100 ml of dimethylformamide (DMF) to 75 ° C. 100 g was added dropwise over 1 hour and stirred for 2 hours. Further, 200 ml of acetic anhydride, 10 ml of triethylamine and 1 g of nickel acetate were added and stirred for 3 hours. After stirring, 1000 ml of water was added, the solvent was heated under reduced pressure at 60 ° C., dissolved in chloroform, and washed with water. Chloroform was distilled off under reduced pressure and purified by silica gel chromatography. Further, the mixture was refluxed with toluene under nitrogen for 24 hours and then recrystallized to obtain trifunctional maleimide [R3] (yield 52%).

  [R1] (0.0027 mol) and lysine triisocyanate (Kyowa Hakko Chemical Co., Ltd.) (0.0036 mol) (total 9.5 g) and a covalent thermoreversible crosslinking as raw materials for the covalently irreversible crosslinking moiety [R2] (0.0005 mol) and [R3] (mol 0.0005) (0.5 g in total) were weighed as part raw materials. These were heated at 160 ° C. for 2 hours in a mold and then cooled to room temperature to obtain a crosslinked product.

[Example 2]
[R1] (0.0025 mol) and lysine triisocyanate (Kyowa Hakko Chemical Co., Ltd.) (0.0034 mol) (9 g in total) as a raw material for the covalent irreversible crosslinking moiety and the covalent thermoreversible crosslinking moiety [R2] (0.0011 mol) and [R3] (mol 0.0011) (1 g in total) were weighed as raw materials. These were heated at 160 ° C. for 2 hours in a mold and then cooled to room temperature to obtain a crosslinked product.

[Example 3]
[R1] (0.0022 mol) and lysine triisocyanate (Kyowa Hakko Chemical Co., Ltd.) (0.0030 mol) (total 8 g) as a raw material for the covalent irreversible crosslinking moiety and the covalent thermoreversible crosslinking moiety [R2] (0.0021 mol) and [R3] (0.0021 mol) (total 2 g) were weighed as raw materials. These were heated at 160 ° C. for 2 hours in a mold and then cooled to room temperature to obtain a crosslinked product.

[Example 4]
[R1] (0.0017 mol) and lysine triisocyanate (Kyowa Hakko Chemical Co., Ltd.) (0.0022 mol) (total 6 g) and a covalent thermoreversible crosslinking moiety as raw materials for the covalent irreversible crosslinking moiety [R2] (0.0042 mol) and [R3] (0.0042 mol) (4 g in total) were weighed as raw materials. These were heated at 160 ° C. for 2 hours in a mold and then cooled to room temperature to obtain a crosslinked product.

[Example 5]
[R1] (0.0014 mol) and lysine triisocyanate (Kyowa Hakko Chemical Co., Ltd.) (0.0019 mol) (total 5 g) as a raw material for the covalent irreversible crosslinking moiety and the covalent thermoreversible crosslinking moiety [R2] (0.0053 mol) and [R3] (0.0053 mol) (total 5 g) were weighed as raw materials. These were heated at 160 ° C. for 2 hours in a mold and then cooled to room temperature to obtain a crosslinked product.

[Example 6]
[R1] (0.0011 mol) and lysine triisocyanate (Kyowa Hakko Chemical Co., Ltd.) (0.0015 mol) (4 g in total) as a raw material for the covalent irreversible crosslinking moiety and the covalent thermoreversible crosslinking moiety [R2] (0.0063 mol) and [R3] (0.0063 mol) (6 g in total) were weighed as raw materials. These were heated at 160 ° C. for 2 hours in a mold and then cooled to room temperature to obtain a crosslinked product.

[Comparative Example 1]
[R1] (0.0028 mol) and lysine triisocyanate (Kyowa Hakko Chemical Co., Ltd.) (mol) (total 10 g) were weighed as raw materials for the covalently irreversible cross-linking moiety. These were heated at 160 ° C. for 2 hours in a mold and then cooled to room temperature to obtain a crosslinked product.

[Comparative Example 2]
[R2] (0.011 mol) and [R3] (0.011 mol) (total 10 g) were weighed as raw materials for the covalently bondable thermoreversible cross-linking moiety. These were heated at 160 ° C. for 2 hours in a mold and then cooled to room temperature to obtain a crosslinked product.

[Comparative Example 3]
A commercially available thermoplastic shape memory resin ("Diaplex" (trade name), manufactured by Mitsubishi Heavy Industries, Ltd.) was heated and melted and solidified at 250 ° C in a mold to produce a molded product for evaluation. .

[Comparative Example 4]
4,4′-Diphenylmethane diisocyanate (0.1 mol) and poly (oxytetramethylene) glycol (average molecular weight 650) (0.05 mol) were heated and mixed at 65 ° C. for 3 hours. 1,4-butanediol (0.05 mol) was added thereto, and these were melt-mixed at 160 ° C. and heated for 2 hours to obtain a polymer (R4). R4 (10 g) was compression-molded using a 230 ° C. mold and cooled to room temperature to obtain a crosslinked product.

[Comparative Example 5]
4,4′-Diphenylmethane diisocyanate (0.6 mol) and poly (oxytetramethylene) glycol (average molecular weight 650) (0.05 mol) were heated and mixed at 65 ° C. for 3 hours. 1,4-butanediol (0.55 mol) was added thereto, and these were melt-mixed at 160 ° C. and heated for 2 hours to obtain a polymer (R5). R5 (10 g) was compression molded using a 230 ° C. mold and cooled to room temperature to obtain a crosslinked product.

[Comparative Example 6]
R4 (5 g) and R5 (5 g) were weighed, compression molded using a 230 ° C. mold, and cooled to room temperature to obtain a crosslinked product.

[Shape memory]
The above 11 examples were evaluated for shape memory property, shape recovery property, and remoldability. (Table 1)

  As apparent from Table 1, Td does not exist in Comparative Examples 1 and 3, and Comparative Example 2 has a small difference in elastic modulus before and after Tg.

  Looking at the evaluation results of the shape memory properties in Table 2, all of the materials shown in Examples 1 to 6 exhibited two-stage shape memory properties. In Examples 2 to 4, the difference between the elastic moduli before and after Tg and Td was sufficiently large, so that the third shape was fixed and the first shape was excellently recovered. Since Comparative Examples 1, 3, 4 and 5 were not reversibly crosslinked, it was impossible to maintain the second shape. Further, since Comparative Example 2 did not have irreversible crosslinking, it was dissolved by heating at Td or higher (for this reason, A2 to A4 could not be evaluated). Comparative Example 6 was a mixture of urethane-based shape memory resins having different Tg, but the third shape could be retained at the low temperature side Tg1, but the second shape could not be retained at the high temperature side Tg2. Therefore, in the case of a shape memory resin based only on non-covalent cross-linking, a two-stage shape memory cannot be performed even by simply mixing resins having shape memory temperatures with different shapes fixing ability.

  In the above embodiment, Tg is used for fixing the third shape, but Tm can also be used. For example, polybutylene succinate is a resin with a Tm of about 110 ° C and a Tg of around -30 ° C. If polybutylene succinate is used instead of polylactic acid, the third shape can be fixed at Tm. It becomes.

  The product of the present invention having such excellent shape memory property can be used for various molded products such as electronic device members. For example, exterior materials for electronic devices (such as personal computers and mobile phones), screws, fastening pins, switches, sensors, information recording devices, rollers for OA equipment, parts such as belts, packing materials for sockets, pallets, etc. It can be used for on-off valves, heat-shrinkable tubes, etc. In addition, it can be applied in various fields as automobile members such as bumpers, handles, rearview mirrors, household members such as casts, toys, glasses frames, orthodontic wires, bed slip prevention bedding, and the like.

It is a conceptual diagram explaining the principle of the shape memory in the conventional shape memory resin. It is a conceptual diagram explaining the principle of shape memory and remolding in a shape memory resin into which a conventional thermoreversible crosslinking structure is introduced. It is a conceptual diagram explaining the principle of shape memory and remolding in the shape memory resin of this invention. It is a conceptual diagram explaining the application example of the shape memory resin of this invention.

Claims (10)

A resin having a site crosslinked by a covalent thermoreversible reaction that is covalently bonded by cooling and cleaved by heating, and a site crosslinked by a covalent irreversible reaction, and having a glass transition temperature (Tg) or crystal melting temperature (Tm) is in the range of 200 ° C. 40 ° C. or higher, the heat cleavage temperature reversible reaction (Td) is 50 ° C. or higher 300 ° C. or less, Tg (or Tm) + 10 Ri range near the ° C. ≦ Td of the crosslinking sites of the resin, the proportion of the cross-linked sites by covalent thermal reversible reaction, the shape memory resin to the der Rukoto wherein 10% or more 50% or less.   The thermoreversible reaction is one or more types selected from the group consisting of Diels-Alder type, nitroso dimer type, acid anhydride ester type, urethane type, azlactone-hydroxyaryl type and carboxyl-alkenyloxy type. The shape memory resin according to claim 1. The resin, a shape memory resin of claim 1 or 2 characterized by having a biodegradability. The shape memory resin according to claim 3 , wherein the resin is a resin derived from a plant-derived resin. The shape memory resin according to claim 4 , wherein the resin is a resin using polybutylene succinate or polyhydroxyalkanoate as a raw material. 6. The shape memory resin according to claim 5 , wherein the resin is made of polybutylene succinate or polyhydroxyalkanoate as a raw material, and the thermoreversible reaction is a Diels-Alder type. A shape memory resin molded article comprising a cross-linked product of the shape memory resin according to any one of claims 1 to 6 . The shape memory resin precursor according to any one of claims 1 to 6 is molded into a predetermined first shape to be memorized by crosslinking and curing so as to form a crosslinked site by a covalent irreversible reaction. Then, the obtained molded body was deformed at a temperature equal to or higher than Td, and the second shape was memorized by fixing the deformed shape by cooling to a temperature equal to or lower than the reversible crosslinking temperature (Ta). A shape memory resin molded product characterized by The molded body according to claim 8 is deformed at a temperature of Tg (or Tm) or more and less than Td and fixed at a temperature of less than Tg (or crystallization temperature (Tc) or less) to give a third shape. Shaped memory resin molded body. The molded body imparted with the third shape according to claim 9 is heated to a temperature of Tg (or Tm) or higher and lower than Td to recover the original second shape stored therein, and Td or higher of the resin is recovered. A method for using a shape memory resin molded article, wherein the first shape is recovered by heating to a temperature lower than the thermal decomposition temperature.

Images