JPH0473698B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a method for producing a shape memory resin molded article having excellent heat-sensitive shape memory properties. Specifically, the present invention involves molding a memory resin material containing a polymer with a specific structure using the usual processing method used for plastics, deforming it in a specific temperature range, and freezing the distortion by cooling. The present invention relates to a method for producing a shape memory resin molded article exhibiting excellent heat-sensitive shape memory properties. [Prior Art] Shape memory alloys are already widely known as materials having shape memory properties. Examples of this type include Cu-Al-Ni alloy, Au-Cd alloy, In-Tl alloy, Ni-Ti alloy, etc. Although these shape memory alloys have excellent heat-sensitive shape memory properties, they are very expensive, or heat treatment or processing to exert their shape memory properties is not necessarily easy, so they are currently not used for anything other than special purposes. It has not yet been widely used. On the other hand, several types of polymer resins having heat-sensitive shape memory properties have already become known. Structurally, they can be classified as cross-linked polymers with moderate melting points or glass transition temperatures, or cold-worked polymers with moderate melting points or glass transition temperatures and significantly high molecular weights. In general, polymeric materials at temperatures below the glass transition temperature or melting point have their molecular chains restricted in motion and exhibit the properties of a hard solid. However, when this is heated above the glass transition temperature, it becomes a so-called rubber-like substance. This type of temperature dependence is a common property of all polymeric materials. From a practical standpoint, there are many points to consider, such as the temperature range of the glass transition temperature or melting point, ease of plastic deformation, etc., but most polymer materials that have some crosslinking points to the extent that strain is not relaxed are It can be said that it has a certain degree of shape memory. That is, a certain type of polymer resin molded product is produced by various molding methods, and a crosslinking reaction is performed to maintain the shape after molding. When this molded product is heated to a temperature higher than its glass transition temperature or melting point, deformed, and the temperature is lowered while being deformed, the deformation is maintained. This is because at temperatures below the glass transition temperature or melting point, the motion of molecular chains is restricted and strain is frozen. When this deformed molded product is heated again to a temperature higher than the glass transition temperature or melting point where molecular chains can move, the distortion is released and the molded product returns to its original shape. As this type of shape memory resin, cross-linked products of crystalline polyolefin (US Pat. No. 3,086,242) and cross-linked products of crystalline transpolyisoprene (JP-A-61-16956) are available.
), a crosslinked product of crystalline trans-polybutadiene (US Pat. No. 3,139,468), and the like are known. Among polyolefins, crosslinked products of crystalline polyethylene have been put to practical use, such as heat-shrinkable tubes. However, in order to prevent crosslinking from inhibiting crystallization in these crystalline polymers, it is necessary to perform crosslinking by low-temperature vulcanization or radiation irradiation while the polymer is crystallized, in order to exhibit shape memory properties. This type of shape memory resin has not yet been widely used except for specific applications. Furthermore, if the polymer has a significantly high molecular weight, even at temperatures above the glass transition temperature, the entanglement of molecular chains becomes crosslinking points, and strain is not alleviated, resulting in a shape memory function. Known examples of this shape memory resin include polynorbornene (Japanese Unexamined Patent Publication No. 59-53528), polyvinyl chloride, polymethyl methacrylate, polycarbonate, AB resin, and the like. However, in order for this type of polymer to fully exhibit its shape memory function, it is necessary to increase the molecular weight to a significantly high molecular weight (e.g., 2,000,000 or more), and in this case, the fluidity of the polymer decreases significantly, making it difficult to perform injection molding. Processing using plastic processing machines such as extrusion molding becomes difficult. There is also a technology that sets the molecular weight lower than this and performs cold processing (deformation at a temperature below the glass transition temperature), but this requires special operations.
It has difficult problems such as poor processing productivity, so it has not yet been widely used. In addition, there are methods for reversibly deforming the shape of polymeric materials using chemical energy such as pH, chelate formation, and redox reactions, and isothermal deformation of polymeric materials using photoreactions of photofunctional groups. Methods for reversible change are also known, but they have not yet been widely put into practical use. [Problems to be Solved by the Invention] The present invention solves the above-mentioned drawbacks of conventional shape memory materials, namely, difficulty in applying normal processing methods such as injection molding and extrusion, and problems such as crosslinking reactions. The purpose of the present invention is to provide a method for producing a shape memory resin molded product that solves the problems of complicated handling and poor performance due to the special operations required. [Means and effects for solving the problems] Therefore, the present inventors have made extensive studies on heat-sensitive shape memory resins, and have found that block or graft polymers having a specific structure can be used for the above-mentioned purposes, such as injection molding, extrusion molding, etc. It has been discovered that plastics can be easily processed using ordinary plastic processing machines, does not require any special operations such as cross-linking reactions to impart memory properties, and has excellent shape memory performance. Reached. That is, the present invention includes (a) at least two blocks A consisting of a homopolymer or copolymer having a glass transition temperature or crystal melting point Ta of 50° C. or higher and a weight average molecular weight of 1,000 to 100,000 in the polymer chain; and (b) The crystal melting point Tb is 25℃ or higher, and the relationship between Ta and Tb is
Ta>Tb, weight average molecular weight is 5000~
Contains at least one block B consisting of a homopolymer or copolymer of 1,000,000, and the overall weight average molecular weight is 10,000 to 1,200,000.
And the weight composition ratio of A and B blocks is A/
(A+B) At least 30% of the copolymer component consists of a polymer consisting essentially of a block copolymer or a graft copolymer in the range of 0.05 to 0.8.
After molding heat-sensitive shape memory resin containing % by weight at a temperature exceeding Ta, and after deforming at a temperature below Ta,
The present invention relates to a method for producing a heat-sensitive shape memory resin molded article, which is characterized by cooling to a temperature below Tb while maintaining deformation. Due to the above polymer structure, the polymer obtained in the present invention exhibits the following temperature-dependent properties in each temperature range. That is, at a temperature exceeding the glass transition temperature or crystal melting point Ta of block A, the polymer as a whole is completely melted and has good plastic fluidity. Therefore, the shape memory resin of the present invention can be easily processed using various plastic processing machines, as well as injection molding and extrusion molding. At temperatures below the melting point of block B, each block of the polymer crystallizes or becomes vitreous, and the polymer as a whole exhibits solidified resinous properties. Furthermore, in a temperature range below the glass transition temperature or crystal melting point Ta of block A and above the crystal melting point of block B, block B melts and becomes a rubber phase, and block A remains resinous and becomes a polymer of the rubber phase. It acts as a crosslinking point that meshes the chains. Therefore, in this temperature range, the polymer as a whole exhibits crosslinked rubber-like properties, and the strain caused by the applied deformation is substantially completely maintained. Therefore, in the present invention, the heat-sensitive shape memory resin can be molded at a temperature exceeding the glass transition temperature or crystal melting point Ta of the polymer block A. If this is deformed in a temperature range below Ta and above the melting point Tb of block B, and then cooled to a temperature below Tb while maintaining the deformation, the shape will be fixed with the distortion frozen and retained inside, and the temperature will exceed Tb again. When heated, the strain is released and the shape is restored. The glass transition temperature or crystal melting point Ta of block A constituting the block copolymer or graft copolymer contained in the heat-sensitive shape memory resin used in the present invention must be 50°C or higher. Preferably 60°C or higher and 300°C or lower, more preferably 80°C
℃ or more and less than 200℃. If Ta is less than 50°C, spontaneous relaxation of the memorized shape at room temperature will occur, resulting in a decrease in shape recovery, which is undesirable. Also
If Ta is too high, the processability of the resin may deteriorate, which is undesirable. The crystal melting point Tb of block B is 25℃ or higher, and
The relationship between Ta and Tb is Ta>Tb, that is, Ta>Tb
Must be ≧25℃. Preferably Ta−10
＞Tb≧35℃. If Tb is more than Ta, it will be difficult to freeze and preserve the distortion of the resin, and if Tb is less than 25°C, spontaneous recovery of the memorized shape will occur at room temperature, which is not preferable. The weight average molecular weight of block A is in the range of 1,000 to 100,000, preferably in the range of 2,000 to 50,000, and more preferably in the range of 5,000 to 30,000. If the weight average molecular weight is less than 1,000, the shape memory properties are unfavorably deteriorated, probably because the phase separation structure of the A and B blocks of the block copolymer contained in the resin is disrupted. On the other hand, if the weight average molecular weight exceeds 100,000, the processability of the resin, especially the moldability, will be markedly reduced, which is undesirable. The weight average molecular weight of block B is 5000-1000000
, preferably from 10,000 to 500,000, particularly preferably from 20,000 to 200,000. If the weight average molecular weight is less than 5,000, the shape memory properties are unfavorably deteriorated, probably because the phase separation structure of the A and B blocks of the block copolymer contained in the resin is disrupted. On the other hand, if the weight average molecular weight exceeds 1,000,000, the processability of the resin, especially the moldability, will be significantly reduced, which is not preferable. The overall weight average molecular weight of the block copolymer or graft copolymer is in the range of 10,000 to 1200,000, preferably in the range of 20,000 to 700,000, particularly preferably in the range of 40,000 to 300,000. If the weight average molecular weight is less than 10,000, the basic properties of the resin, such as rigidity and impact resistance, will deteriorate, which is undesirable. If the weight average molecular weight exceeds 1,200,000, the processability and moldability of the resin will significantly decrease, which is undesirable. The weight composition ratio of A and B blocks contained in the block copolymer or graft copolymer is A/
(A+B) is in the range of 0.05 to 0.8, preferably 0.1 to
It is in the range 0.6, particularly preferably in the range 0.2-0.4. If the weight composition ratio A/(A+B) is less than 0.05 or more than 0.8, the shape memory performance is unfavorably lowered. The shape memory resin used in the present invention contains at least 30% by weight, preferably 50% by weight or more, of a polymer essentially consisting of a block copolymer or a graft copolymer. If this content is less than 30% by weight, sufficient shape memory performance cannot be obtained. The preferred structural formula of the block copolymer contained in the shape memory resin used in the present invention is that at least A-B-A' or (A-B) _-oX structure (wherein A and A' are They may have the same structure or different structures. n is an integer of 2 or more and 10 or less, and X represents a reactive residue of the coupling agent). Further, a preferable graft polymer has at least B polymer main chain in the polymer chain,
It must contain a structure in which an average of two or more polymer A side chains are grafted. These copolymers contain the above-mentioned structure, and may also contain other polymer blocks or functional groups to improve other properties as long as the shape memory properties are not lost. In addition, the above block or graft copolymers may be used within the range that the objects of the present invention are achieved.
Homopolymer of block A or B or A
-B diblock polymer or the like may be included. The monomer components constituting blocks A and B are not an essential condition for achieving the object of the present invention, and are not particularly limited. Moreover, blocks A and B may be a homopolymer or a copolymer consisting of two or more types of monomers. As a specific example of blocks A and B,
The following polymers may be mentioned. However, these are just examples, and of course the invention is not limited to these. Examples of block A include polyvinyl chloride, polytetrafluoroethylene, polyacrylonitrile, polyvinyl formal, polyvinyl alcohol, polycarbonate, polyethylene terephthalate, polymethyl methacrylate, polystyrene,
Examples include poly-p-xylene, polyoxymethylene, polyterephthalate, polycaprolactam, polyhexamethylene adipamide, triacetyl cellulose, polyvinylidene chloride, polyvinyl fluoride, polychlorofluoroethylene, polytetrafluoroethylene, and the like. Examples of block B include polyethylene, polypropylene, polybutene-1, polyvinylidene chloride, polycaprolactone, polytrans-butadiene, polytrans-isoprene, and the like. The shape memory resin used in the present invention can be used alone as the above-mentioned block copolymer or graft copolymer, but depending on the application, the resin may have additional properties such as softening temperature, rigidity, strength, impact resistance, moldability, etc. In order to improve this, it may be preferable to use a mixture with other polymers. However, even in this case, the above block copolymer or graft copolymer accounts for at least 30% by weight as a polymer component.
If the above components are not included, the desired effects of the present invention cannot be sufficiently achieved. Furthermore, in addition to the above-mentioned polymer components, inorganic fillers and plasticity may be added as necessary to adjust hardness, plasticity, and the like. Further, stabilizers, pigments, etc., which are general additives added to polymer resin materials, can be appropriately added in the case of the present invention as well as in conventional resin materials. The amount of inorganic filler used is 100% of the polymer component
It is 1 to 100 parts by weight per part by weight. Examples of inorganic fillers include titanium oxide, calcium carbonate, clay, talc, mica, bentonite, and the like. Use of an inorganic filler in an amount exceeding 100 parts by weight is undesirable because it reduces the impact strength of the resulting polymer resin material. The amount of plasticizer used is usually 100% of the polymer component
It ranges from 1 to 20 parts by weight. Examples of plasticizers include dibutyl phthalate, di-(2-ethylhexyl) phthalate, di-(2-ethylhexyl) adipate, diethylene glycol dibenzoate, butyl stearate, butyl epoxy stearate, tri-(2-ethylhexyl)
Examples include phosphate. The shape memory resin molded product of the present invention is produced by molding the shape memory resin at a temperature exceeding the glass transition temperature or crystal melting point Ta of block A of the block copolymer or graft copolymer constituting the shape memory resin. It is obtained by deforming at a temperature below Ta and then cooling to a temperature below the crystal melting point Tb of block B while maintaining the deformation. Although processing and forming is possible at temperatures exceeding Ta,
To achieve sufficiently good workability, Ta should be set at 20
It is preferable to process at a temperature exceeding .degree. C. or higher. The temperature that causes deformation may be less than or equal to Ta, but
In order to exhibit high shape memory performance, the temperature is preferably from 10° C. or lower for Ta to higher than Tb. or,
In order to freeze and maintain the deformation strain, the temperature is below Tb, preferably 10°C below Tb, while maintaining the deformation after heating deformation.
Must be cooled to a temperature of: The heat-sensitive shape memory resin molding thus obtained is heated at the time of use, preferably exceeding Tb.
Good shape memory performance is exhibited by heating to a temperature below Ta. The shape of the molded product of the present invention may vary depending on its use, and is not particularly specified.
Further, it can be used in all applications where the shape memory performance, which is a feature of the present shape memory resin, can be sufficiently exhibited. Examples of specific uses include toys, joining materials for irregularly shaped pipes, internal laminate materials for pipes, lining materials, medical equipment such as tightening pins, casts, etc.
Stationery teaching materials, artificial flowers, dolls, interior laminated soundproofing material for computer dot printer rolls, parts that require deformation recovery after impact absorption such as car bumpers, gap prevention agent for residential partitions, folded when not in use. , portable containers that recover their shape during use, mechanical devices such as couplings, various shrink films, and various heat-shrinkable tubes. [Effects of the Invention] As detailed above, the shape memory resin used in the present invention is (a) easy to process using ordinary plastic processing machines such as injection molding and extrusion molding, and (b) crosslinking reaction, etc. (c) Since there is no need for any special operation to impart the memory properties of
The molded product that can be reworked and obtained is
(d) It has excellent characteristics as a heat-sensitive shape memory resin molded product, such as shape memory properties (high shape recovery rate, high shape recovery rate, and almost no natural recovery of shape). That is, the effect of the present invention is to provide a heat-sensitive shape memory resin molded product that effectively utilizes the characteristics of these extremely excellent heat-sensitive shape memory resins. [Example] The present invention will be specifically explained below with reference to Examples, but the scope of the present invention is not limited thereto. Example 1 Styrene and ε-caprolactone were sequentially block-polymerized by an anionic polymerization method, and then coupled with a dicarboxylic acid compound.
(A-B) _-2 Synthesize an X-type block copolymer.
The weight average molecular weight of the obtained copolymer is measured by gel permeation chromatography, and the glass transition temperature and crystal melting point are measured by a differential thermal analyzer. The obtained polymer was molded using an injection molding machine to a thickness of 3
Process and form into test pieces with a width of 10 mm. The test piece is heated to double its length, stretched and deformed, and then rapidly cooled to room temperature to freeze and maintain the deformation. This sample showed no natural recovery of its shape after a day and night at room temperature. In addition, if a sample that has been deformed for a day and night is heated again to the same temperature as the deformation temperature, it will change after 1 minute.
Achieves 90% shape recovery rate (15% residual strain).
The polymerization structure, conditions, and results are summarized in Table 1. Example 2 Polymer synthesis, analysis, molding, and shape memory property evaluation were carried out in exactly the same manner as in Example 1, except that a tetracarboxylic acid compound was used instead of a dicarboxylic acid compound, and similar good results were obtained. Shape recovery rate is 95%
It is. Example 3 An _o -type block copolymer (A-B) is synthesized by a condensation reaction between poly-ε-caprolactone and polyethylene terephthalate. The obtained polymer was analyzed, molded, and evaluated for shape memory properties in exactly the same manner as in Example 1, and the same good results were obtained. The shape recovery rate is 85%. Example 4 By reaction with poly-ε-caprolactone, polycarbonate and dicarboxylic acid compound, (A-
B) Synthesize an _o- type block copolymer. The obtained polymer was analyzed, molded, and evaluated for shape memory properties in exactly the same manner as in Example 1, and the same good results were obtained. The shape recovery rate is 90%.

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Claims (1)

[Scope of Claims] 1. In the polymer chain, there are at least two blocks A consisting of (a) a homopolymer or copolymer having a glass transition temperature or crystal melting point Ta of 50° C. or higher and a weight average molecular weight of 1,000 to 100,000. (b) The crystal melting point Tb is 25℃ or higher, and the relationship between Ta and Tb is
Ta>Tb, weight average molecular weight is 5000~
contains at least one block B consisting of a homopolymer or copolymer of 1,000,000, the overall weight average molecular weight is 10,000 to 1,200,000, and A,
The weight composition ratio of B block is A/(A+B)=
Molding a heat-sensitive shape memory resin containing at least 30% by weight of a polymer consisting essentially of a block copolymer or a graft copolymer in the range of 0.05 to 0.8 as a copolymer component at a temperature exceeding Ta. A method for producing a heat-sensitive shape memory resin molded article, which comprises deforming it at a temperature below Ta, and then cooling it to a temperature below Tb while maintaining the deformation. 2. The method for producing a shape memory resin molded article according to claim 1, wherein the block copolymer essentially consists of a chain polymer containing at least an A-B-A' structure in the polymer chain. [In the formula, A and A' blocks have a glass transition temperature Ta of 50
℃ or higher, a homopolymer or copolymer block with a weight average molecular weight of 1000 to 100000, and A and
A' may have the same structure or different structures. B has a crystal melting point Tb of 25℃ or higher, and Ta and
It is a homopolymer or copolymer block in which the relationship of Tb is Ta>Tb and the weight average molecular weight is 5,000 to 1,000,000. 3. Production of a shape memory resin molded product according to claim 1, wherein the block copolymer consists essentially of a star-shaped block copolymer containing at least (A-B) _o × structure in the polymer chain. Law. [In the formula, A and B blocks each have the same structure as the polymer block shown in claim 2, n is an integer of 2 or more and 10 or less, and X represents the reaction of the coupling agent. Residues are shown. 4. The graft copolymer consists essentially of a graft copolymer having a structure in which at least two or more side chains of the A polymer are grafted to the main chain of the B polymer in the polymer chain. A method for manufacturing the shape memory resin molded article described above. [The above A polymer chain and B polymer chain each have the same structure as the polymer block shown in claim 2. ]