JP2002234926A - Thermoplastic polyurethane elastomer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thermoplastic polyurethane elastomer which have good scratch resistance, chemical resistance, moldability and meltable at a lower temperature by subjecting the crystalline polyurethane elastomer to a specified heat treatment, and is suitable for a powder slush molding and the like. SOLUTION: A crystalline polyurethane elastomer having a calorific value to be represented by the area of an exothermic peak to be obtained from the graph of differential scanning calorimetry(DSC) measured in the process of cooling after melting of >=6 mJ/mg and a temperature T of the above exothermic peak of >=100 deg.C is subjected to heat treatment to lower the temperature T1 of an endothermic peak corresponding to the temperature T of the above exothermic peak, measured by differential scanning calorimetry(DSC) in the process of heating, by 10 deg.C or more.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermoplastic polyurethane elastomer, and more particularly to a thermoplastic polyurethane elastomer which is suitably used for powder molding such as powder slush molding and has high crystallinity and low melting temperature. The present invention relates to a thermoplastic polyurethane elastomer capable of achieving a high level of scratch resistance, chemical resistance, moldability, meltability, and the like.

[0002]

2. Description of the Related Art For example, vehicle interior materials such as instrument panels are formed by bonding a skin material to the surface of a base material such as a resin obtained by injection molding. This skin material,
It is desirable to have a beautiful appearance, not to be easily damaged, and to be excellent in light resistance, heat resistance, durability and the like. As a material from which such a skin material can be produced, polyvinyl chloride (hereinafter referred to as PVC) or the like has been suitably used.

However, from the viewpoint of preventing environmental pollution in recent years, acrylonitrile-styrene-acrylate copolymer resins or polyolefin-based elastomers have been replaced with PVC containing a large amount of chlorine, which is one of the sources of dioxin and acid rain. As a material, a skin material obtained by removing a raw material resin from PVC has come to be used.

As a molding method for processing each of these materials into a skin material, powder slush molding, which is more excellent in embossing transferability than vacuum forming and can form a highly luxurious skin material with a high design quality, is suitably employed. ing. However, when a skin material is produced by powder slush molding using the acrylonitrile-styrene-acrylate copolymer resin, it is pointed out that the skin material is inferior in moldability and cannot be formed with an excellent appearance and the like. The formability referred to here indicates the effect of pinholes associated with air contained on the surface of the skin material when a skin material of a corresponding shape is obtained using a mold having a required shape. If a large number of the pinholes are present on the surface, the appearance is poor and the commercial value is lost. Hereinafter, “formability” described in the present specification is used in the above-mentioned meaning.

[0005] In view of these points, various production methods have been considered which can suitably produce the skin material and the like using a polyolefin-based elastomer having little problem of environmental pollution as a raw material. However, the skin material made of the elastomer is PVC.
As compared with a skin material made of lacquer as a raw material, that is, the scratch resistance is poor. In this regard, a composition that can be dealt with by optimizing the blending composition has been studied, but the cost is high and it is not practical.

[0006] As a method for solving these problems, the invention "thermoplastic polyurethane elastomer for slush molding, thermoplastic polyurethane elastomer powder for slash molding, and skin material using the same" was devised by the present inventor. No. 2000-313729) has been proposed. An object of the present invention is to provide a thermoplastic polyurethane elastomer having specific viscoelastic properties or thermal properties and suitable for slush molding.
As shown in the figure, the calorific value represented by the area of the exothermic peak when the differential scanning calorific value (hereinafter, referred to as DSC) in the process of cooling after melting is 6 mJ / mg or more,
The object is also achieved by using a thermoplastic polyurethane elastomer having an exothermic peak temperature of 100 ° C. or higher.

[0007] The reason why the DSC data was measured during the temperature-falling process is that the generation of hydrogen bonds and crystallinity are clearly shown as compared with the case of the temperature-rise process. The “temperature of the exothermic peak” represents the peak value of the exothermic temperature when the melted TPU recrystallizes as the temperature decreases, and a TPU having a peak value of less than 100 ° C. has a large molecular weight. Sufficient crystallization has not been achieved due to factors that inhibit crystallization, such as having a cross-linked structure or bulky substituents, resulting in poor moldability. This peak temperature is 100
When the temperature is at least 105 ° C., more preferably at least 105 ° C. (usually at most 125 ° C.), it is possible to improve the moldability and to obtain a molded article having an excellent appearance and the like.

[0008]

However, in the case of a thermoplastic polyurethane elastomer having high crystallinity which is achieved by "the calorific value represented by the area of the exothermic peak is 6 mJ / mg or more", the above-mentioned high scratch resistance is obtained. However, while sufficient chemical resistance and moldability can be ensured, the melting point also increases with the improvement of the crystallinity, and as a result, the temperature required during molding, the so-called molding temperature, increases. Was inherent. That is, when an excessive temperature load is applied to a mold used at the time of molding, deterioration and the like are hastened, which has been a factor of increasing manufacturing costs and the like.

[0009]

SUMMARY OF THE INVENTION The present invention has been made in view of the problems inherent in the thermoplastic polyurethane elastomer according to the technique described in Japanese Patent Application Laid-Open No. 2000-313729 devised by the inventor of the present invention, and is preferably solved. By applying a predetermined heat treatment to the thermoplastic polyurethane elastomer obtained by the above-mentioned technology, good scratch resistance, chemical resistance and moldability, and at a lower temperature It is an object of the present invention to provide a thermoplastic polyurethane elastomer which has both meltability and powder slush molding.

[0010]

In order to overcome the above-mentioned problems and achieve the intended object, the polyurethane elastomer of the present invention has a differential scanning calorimetry measured in a cooling process after being melted.
(DSC) A crystalline polyurethane elastomer having a calorific value represented by an exothermic peak area obtained from the graph of 6 mJ / mg or more and a temperature of the exothermic peak of 100 ° C. or more. After the heat treatment, the differential scanning calorie (DS
The temperature of the endothermic peak corresponding to the temperature of the exothermic peak when C) is measured is lower by at least 10 ° C.

In order to overcome the above-mentioned problems and achieve the intended purpose, the polyurethane elastomer of the present invention according to the present invention uses a differential scanning calorimeter (DSC) measured in a cooling process after melting.
When the calorific value represented by the area of the exothermic peak obtained from the graph of 6) is 6 mJ / mg or more, and the temperature of the exothermic peak is 100
A crystalline polyurethane elastomer having a temperature of at least ℃,
After subjecting the crystalline polyurethane elastomer to heat treatment, the temperature of the endothermic peak corresponding to the temperature of the exothermic peak when measuring the differential scanning calorimetry (DSC) in the heating process is lower than the second temperature. Characterized by having an endothermic peak temperature of

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Next, a thermoplastic polyurethane elastomer according to the present invention will be described with reference to preferred embodiments. The inventor of the present application avoids environmental problems by performing a heat treatment on a thermoplastic polyurethane elastomer (hereinafter, referred to as TPU) having a certain crystallinity, and achieves good moldability, scratch resistance, chemical resistance, and the like. It has been found that while securing such properties, characteristics that can be easily formed by melting at a lower temperature can be obtained.

The TPU is basically produced by a one-shot method and comprises a polyol component forming a soft segment phase and an isocyanate forming a hard segment phase. For example, adipic acid and 1,4-butanediol are condensed, and a polyaddition reaction (urethane-forming reaction) between adipate-type polyester polyol having hydroxyl groups at both terminals and hexamethylene diisocyanate (HDI), which is a short-chain diisocyanate, is performed. The TPU to be generated is exemplified. In addition to the above-described one-shot method, it can also be manufactured by a conventionally known prepolymer method.

The one-shot method is a general method for producing a TPU, and is a production method in which four components, which are basic raw materials, a polymer polyol, an isocyanate, a chain extender and a catalyst, are mixed together.

Among these TPUs, those having the following conditions have high crystallinity, and as a result, the present inventors have proposed that they exhibit good moldability due to rapid melting, high scratch resistance and chemical resistance. JP 2000-31372 issued
No. 9 is described. Its molecular structure is easy to arrange linearly. The number of urethane bonds per molecule is large, and the bonding force due to hydrogen bonding is greatly expressed. Does not have an excessive crosslinked structure in the structure.

TPU satisfying each of the above conditions
Is produced by reacting an isocyanate, which is a main raw material, with a polyol. In this case, 100 to 100 mol of a chain extender such as a short-chain diol and about 1 to 5 moles of the polyol are used. About 500 ppm of a urethane polymerization catalyst is added. The polyol and isocyanate used may have not only two functional groups but also three or more functional groups.

The equivalent ratio (NCO / OH ratio) of the isocyanate group (NCO group) in the structure of the isocyanate to the hydroxyl group (OH group) of the polyol contained in the polyol component is 0.95 to 1 .05 is preferable. When the NCO / OH ratio is less than 0.95, the moldability during powder slush molding is improved,
The resulting molded article has reduced chemical resistance and the like. On the other hand, when this ratio exceeds 1.05, the degree of crosslinking of the TPU due to allophanate bonds or burette bonds becomes too high, and the moldability decreases. Even if the NCO / OH ratio is large, when the blending amount of the polymerization catalyst is large, the NCO group is consumed by a side reaction, and the NC which does not contribute to urethane formation is used.
In some cases, the number of O groups increases, the molecular weight does not increase, and a decrease in moldability is suppressed.

As the isocyanate, the aforementioned HD
I, diphenylmethane diisocyanate (MDI),
Hydrogenated MDI or isophorone diisocyanate can also be used, and the type is not limited. HDI, MDI and / or hydrogenated MD, especially those having a symmetric molecular structure
I and the like are preferred. When an isocyanate-terminated prepolymer having isocyanates at both ends is used, it is possible to increase the hydrogen bonding force of the hard segment phase and to enhance the crystallinity.

Examples of the polyol include condensation-polymerized polyester polyols, polyester polyols obtained by ring-opening polymerization of cyclic esters such as ε-caprolactone, polyether polyols obtained by ring-opening polymerization of cyclic ethers, and copolymers thereof. A polyetherester polyol or the like obtained by polymerization can be used. Further, a polymer polyol such as a polycarbonate polyol having a carbonate group can also be used. Further, a monomer polyol such as 1,4-butanediol may be used in combination with each of these polyols.

The number average molecular weight of the polyol is as follows:
Those having a size of about 500 to 10,000 are used.
The range of from 00 to 3,000 is preferred. If the number average molecular weight is too large, the soft segment phase relatively increases and the crystallinity decreases, so that excellent moldability cannot be maintained. On the other hand, if the number average molecular weight is too small, the number of hard segment phases increases, and the finished elastomer becomes hard, which may cause a problem in terms of tactile sensation when used for a skin material.

When the above-mentioned monomer polyol is used in combination,
A partial hard segment phase grows in the molecular chain, and the crystallinity further increases. At this time, if the amount of the monomer polyol used is large, it is necessary to pay attention to the fact that the elastomer becomes harder as the crystallization proceeds. On the other hand, in particular, the polyester polyol is hydrogen-bonded to a urethane bond, and the soft segment phase becomes longer and the hard segment phase becomes relatively shorter, so that the crystallinity may be lowered. As described above, many factors influence the quantitative ratio between the hard segment phase and the soft segment phase of the elastomer.

Further, isocyanates having three or more functional groups and / or
And the use of a polyol, it is possible to reduce the crystallinity or suppress the decrease in viscosity during molding.However, in order to set the crystallinity in a range that achieves the intended object of the present invention, It is necessary to keep the blending amount to 5 mol% or less. In addition, for other additives and the like, in order to obtain a TPU having desired characteristics, it is necessary to study the action and effect of the raw material composition and the like.

When a predetermined heat treatment is applied to the above-mentioned TPU, the melting temperature decreases and the crystallinity increases. When the differential scanning calorie (hereinafter referred to as DSC) in the process of cooling after melting obtained by the conventional technique is measured, the data shown in FIG. 7 is obtained.
FIG. 1 shows the result of measuring DSC in the process of heating U as it is in the untreated (initial state) state. FIG. 1 shows the DSC measured in the process of heating the TPU obtained by performing the heat treatment at a temperature of 110 ° C. for 24 hours. FIG. 2 shows the results, and FIG. 3 shows the results of measuring DSC in the process of heating the TPU obtained by performing the heat treatment at a temperature of 110 ° C. for 72 hours.

Referring to FIG. 1, basically, the temperature—the temperature at which the heating value graph shown in FIG.
In the endothermic graph, an endothermic peak corresponding to the exothermic peak is observed, and the calorific value indicating the respective peak temperatures (the exothermic peak temperature T and the endothermic peak temperature T1) and the crystallinity correspond to the endothermic amount. Basically, there is almost no difference between the temperature lowering process and the temperature raising process, and the temperature lowering process is different from the temperature raising process in that hydrogen bond generation and crystallinity are clarified, that is, there is a difference in precision. There is only. As for FIG. 2, in addition to the differences shown in FIG.
An endothermic peak having a valley at temperature T1 is different in that it is separated into two endothermic peaks having valleys at two temperatures T1 and T2, and an endothermic amount indicating crystallinity is greatly increased. I understand. As for FIG.
Both of the two endothermic peaks appearing in the heat treatment for 24 hours increase quantitatively, that is, the crystallinity increases, and according to the DSC data, the temperature T1 (in terms of temperature, between the two temperatures T1 and T2) is defined as a valley. A large 1 where two endothermic peaks overlap
It has two endothermic peaks. The heat absorption is about twice that of the initial state and about 1.5 times that of the heat treatment for 24 hours. That is, a decrease in the melting temperature and an increase in the crystallinity were recognized by the heat treatment, and the decrease in the melting temperature and the increase in the crystallinity are inferred as follows.

In the case of the one-shot method in which the four basic components of the polymer polyol, isocyanate, chain extender and catalyst are mixed together, both the polymer polyol having an OH group at its terminal and the chain extender are Reacts with. The reaction rate at this time largely depends on the respective molecular weights, that is, the diffusion rate, and the chain extender having a smaller molecular weight reacts with the isocyanate with a higher probability.
(Polymerization) to form the hard segment phase. And the polymer polyol and the isocyanate react with a lower probability than that of the chain extender, that is, with a delay (polymerization).
To form the soft segment phase.

In general, the hard segment phase and the soft segment phase are not completely compatible with each other, and the hard segment phase and the soft segment phase are separated by cooling and solidification after the reaction, and the hard segment phase has crystallinity. It is expressed. This model is an ester-based polymer polyol having an ester group formed by condensation polymerization of dicarponic acid and a diol component, or an ether-based polymer polyol having an ether group formed by ring-opening polymerization of a cyclic ether such as ethylene oxide. This is apparent from the fact that the soft segment phase has the ester group or the ether group, respectively, whereas the hard segment phase does not have the same functional group, and therefore has poor chemical affinity and is hardly compatible. From these facts, it can be said that the portion exhibiting crystallinity in the TPU manufactured by the ordinary one-shot method is a portion of the hard segment phase.

However, considering that the one-shot method performs batch mixing of raw materials, the isocyanate and
It is unlikely that the chain extender or the polymer polyol alone completes the polymerization alone. That is, when a part of the polymer polyol is simultaneously involved during the polymerization of the hard segment phase in which the reaction proceeds predominantly, it is considered that the polymerization reaction of the polymer polyol is performed together with the polymerization reaction of the chain extender to form a copolymer. Can be Despite having a hard segment phase, the copolymer synthesized in this way does not show as high a crystallinity as a single hard segment phase.

Therefore, it is inferred that the TPU manufactured and cooled and solidified by the one-shot method takes a structural model as shown in FIG. 4 as a concept. This structural model shows a state in which mutually incompatible ones are dispersed without receiving an external pressure. In this case, any one of the hard segment phase and the soft segment phase constituting the TPU (FIG. 4) In this case, it is considered that the hard segment phase has a sea-island structure in which the hard segment phase exists as an island having a minimum interface area. That is, it has a structure composed of a hard segment phase 12 exhibiting crystallinity, a non-crystalline soft segment phase 14 and a copolymer 16 having relatively low crystallinity (see FIG. 4A). Here, the copolymer 16 includes a copolymer 16a mixed in the soft segment phase 14,
Copolymer 16b mixed around the periphery of the island
And two types. The copolymer 16a is obtained by incorporating a small amount of a polymer polyol into the hard segment phase 12, while the copolymer 16b cannot participate in crystal growth upon cooling and solidification, and the soft segment phase 1
4 is left behind.

When heat is applied to the TPU having such a structure, the copolymer 16b behaves to separate from the soft segment phase 14 due to the cohesive energy of the hard segment phase 12 and move toward crystal growth. That is, the copolymer 16b grows so as to further surround the copolymer 16a to form the second hard segment phase 18 and the second hard segment phase 18 which is newly independent in the soft segment phase 14.
Is formed, and apparently, the hard segment phase 12 (island portion) exhibiting crystallinity seems to behave like an increase (see FIG. 4B). The peak appearing at the low temperature T2 (see FIG. 2) is considered to appear when the second hard segment phase 18 melts at a low temperature due to its low crystallinity.

When the second hard segment phase 18 exhibiting new crystallinity is thus formed, when DSC data is measured in the process of heating the TPU having the second hard segment phase 18, An endothermic peak on the low temperature side due to the second hard segment phase 18 appears. Then, as can be seen from the endothermic amount obtained from the DSC data, the region having crystallinity, that is, the crystallinity is quantitatively increased, and as a result, the scratch resistance, chemical resistance and moldability expressed by the crystallinity are increased. improves. The reason that the moldability is good is that a sharp change in viscosity occurs at the temperature point indicated by the endothermic peak, and bubbles trapped in the raw material are expelled out of the raw material. Also, good moldability is achieved even at the low temperature side. That is, although the crystallinity is increased, the molding temperature required for molding is lowered.

The degree of the decrease in the molding temperature achieved at this time is desirably 20 ° C. or higher, which is empirically found to reduce the load on the molding die and the like.
It is desired that the temperature T1 of the endothermic peak be lowered by at least 10 ° C. or more in order to allow this reduction in molding temperature. If a decrease of 10 ° C. or more is not observed, the molding temperature cannot be expected to have such an effect that the load on the molding die is greatly reduced.

The temperature at which the heat treatment is performed is lower than the temperature T2 of the second endothermic peak generated by the heat treatment in a temperature range lower than the melting temperature of the TPU to be subjected to the heat treatment, and is as high as possible. Good temperature. If the temperature of the heat treatment is low, it takes time to form the second hard segment phase exhibiting the second endothermic peak temperature T2. The time for performing the heat treatment depends on the temperature at which the heat treatment is performed, but good results can be obtained by performing the heat treatment continuously for 12 hours or more.

As other heat treatment conditions, DS when heat treatment was performed for 72 hours at a treatment temperature of 80 ° C.
The C data is shown in FIG. As compared with the DSC data of the TPU obtained by the heat treatment at 110 ° C. for 72 hours shown in FIG. 3, it is confirmed that the heat absorption amount is reduced and the crystallinity is low. In other words, when the temperature for the heat treatment is not sufficient, the crystallinity is increased as compared with the initial state, but it is expected that it will take a long time to obtain a sufficient result. Further, as compared with the DSC data of the TPU obtained by the heat treatment at 110 ° C. for 24 hours shown in FIG. 2, the difference in the temperature T2 of the endothermic peak on the lower temperature side newly appearing depends on the temperature of the heat treatment. The newly formed second
This is probably because the hard segment phases have different crystal structures.

Further, in order to examine the deterioration of the heat-treated TPU, the TPU shown in FIG. 5 was heated at 250 ° C. to be completely melted / cooled and solidified, and thereafter the same DSC data was obtained. The result is shown in FIG. DSC shown in FIG.
The data is almost the same as FIG. 1 showing the DSC data of the unprocessed (initial state) TPU. From this, only the crystal structure is changed by the heat treatment, and the deterioration is not progressing. Not confirmed.

The temperature of each endothermic peak shown by the DSC data shown in FIGS. 1 to 3, FIG. 5 and FIG. 6 simply indicates the temperature range where the viscosity decreases sharply as a result of the measurement. It should be noted that the measured melting point of TPU did not decrease. The endothermic amount and the temperature of the endothermic peak shown in FIGS. 1 to 3, 5, and 6 are started from room temperature and increased at a rate of 10 ° C./min (accuracy ± 0.5 ° C./min). JIS K 7121, 7122 and 712 were obtained from the respective DSC data obtained under the conditions of heating.
3 (Japanese Standards Association 1997 Edition "JIS Handbook 11
446-455 ").

[0036]

EXPERIMENTAL EXAMPLES Preferred experimental examples of the thermoplastic polyurethane elastomer according to the present invention are shown below, but the thermoplastic polyurethane elastomer according to the present invention is not limited to these experimental examples.

(Experimental Conditions) Using TPU subjected to heat treatment under various conditions as a raw material, a state similar to powder slush molding was reproduced on a 230 ° C. heating mold. Then, the moldability of each TPU at that time was evaluated by visually confirming the state of the pinhole. Those subjected to the heat treatment described in the present application are described as Experiments 1 and 2, and the others are described as Comparative 1 to Comparative 5. Table 1 below shows the heat treatment conditions, the state of the pin poles, and the moldability applied to each of the TPUs. -Materials used: General-purpose TPU (trade name: E785QSDH; manufactured by Nippon Milactran)-Thermal characteristics device: Model SSC5200; manufactured by Seiko Electronics Co., Ltd.

[0038]

[Table 1]

(Results) The formability confirmed from the state of the pinholes was evaluated as ×: many pinholes were unsuitable, Δ: pinholes were present and the commercial value was low, ○: no problem. As a result, it was confirmed that a heat treatment at 110 ° C. for 24 hours was required, and good results could be obtained within the range described in the present invention.

[0040]

As described above, according to the thermoplastic polyurethane elastomer according to the present invention, by applying a predetermined heat treatment to a crystalline polyurethane elastomer having a predetermined crystallinity, high scratch resistance can be obtained. It is possible to obtain a thermoplastic polyurethane elastomer having a combination of chemical resistance, moldability and lower melting temperature. This has the effect of significantly reducing the energy required to obtain a molded article of a required shape from the thermoplastic polyurethane elastomer and the load on the molding die and the like.

[Brief description of the drawings]

FIG. 1 is a graph showing DSC data before heat treatment of a thermoplastic polyurethane according to a preferred embodiment of the present invention.

FIG. 2 is a graph showing DSC data when the temperature of a thermoplastic polyurethane according to an example subjected to a heat treatment at a temperature of 110 ° C. for 24 hours is increased.

FIG. 3 is a graph showing DSC data when the temperature of a thermoplastic polyurethane according to an example subjected to a heat treatment at a temperature of 110 ° C. for 72 hours is increased.

FIG. 4 is a schematic diagram showing a structural model before and after heat treatment of a thermoplastic polyurethane according to an example.

FIG. 5 is a graph showing DSC data when the temperature of a thermoplastic polyurethane subjected to a heat treatment at a temperature of 80 ° C. for 72 hours is raised.

FIG. 6 is a graph showing DSC data when the temperature of a thermoplastic polyurethane that has been completely melted after being subjected to a heat treatment at a temperature of 80 ° C. for 72 hours and then cooled and solidified is raised.

FIG. 7 shows a conventional thermoplastic polyurethane elastomer heated to 250 ° C. and completely melted.
FIG. 4 is a graph showing DSC data when the temperature is lowered at a rate of 0 ° C./min.

[Explanation of symbols]

 T Temperature of exothermic peak T1 Temperature of endothermic peak T2 Temperature of second endothermic peak

Continued on front page F-term (reference) 4J034 BA08 DA01 DF01 DF03 DF12 DF16 DF20 HA01 HA07 HC03 HC12 HC17 HC22 HC52 HC64 HC67 HC71 HC73 JA42 LA22 QB03 QB15 RA00

Claims (9)

[Claims] An exothermic peak represented by an area of an exothermic peak obtained from a graph of differential scanning calorimetry (DSC) measured in a cooling process after melting, is 6 mJ / mg or more, and the temperature of the exothermic peak (T ) Is a crystalline polyurethane elastomer having a temperature of 100 ° C. or higher, and the crystalline polyurethane elastomer after subjected to the heat treatment has a temperature of the exothermic peak (differential scanning calorimetry (DSC) in a heating process) when measured. A thermoplastic polyurethane elastomer, wherein the temperature (T1) of the endothermic peak corresponding to T) is lower by at least 10 ° C. or more. 2. The heat treatment according to claim 1, wherein the melting temperature of the crystalline polyurethane elastomer is from −50 ° C. to −20 ° C.
The thermoplastic polyurethane elastomer according to claim 1, which is carried out in a temperature range of ° C. 3. The thermoplastic polyurethane elastomer according to claim 1, wherein the heat treatment is performed continuously for at least 12 hours. 4. The thermoplastic polyurethane elastomer according to claim 1, wherein the thermoplastic polyurethane elastomer is subjected to powder molding such as powder slush molding. 5. A calorific value represented by an area of an exothermic peak obtained from a graph of differential scanning calorimetry (DSC) measured in a cooling process after melting, is 6 mJ / mg or more, and a temperature (T ) Is a crystalline polyurethane elastomer having a temperature of 100 ° C. or higher, and the crystalline polyurethane elastomer after subjected to the heat treatment has a temperature of the exothermic peak when a differential scanning calorimetry (DSC) in a heating process is measured ( A thermoplastic polyurethane elastomer having a second endothermic peak temperature (T2) lower than the endothermic peak temperature (T1) corresponding to (T). 6. The thermoplastic polyurethane elastomer according to claim 5, wherein the temperature (T2) of the second exothermic peak is lower by at least 10 ° C. than the temperature (T1) of the endothermic peak. 7. The heat treatment according to claim 1, wherein the melting temperature of the crystalline polyurethane elastomer is from −50 ° C. to −20 ° C.
The thermoplastic polyurethane elastomer according to claim 5 or 6, which is carried out in a temperature range of ° C. 8. The thermoplastic polyurethane elastomer according to claim 5, wherein the heat treatment is performed continuously for at least 12 hours. 9. The thermoplastic polyurethane elastomer according to claim 5, wherein the thermoplastic polyurethane elastomer is subjected to powder molding such as powder slush molding.