JPH08325346A - Thermoplastic polyurethane and its molded product - Google Patents

Abstract

PURPOSE: To obtain a thermoplastic polyurethane excellent in moldability, heat resistance, abrasion resistance, and hydrolysis resistance, thus useful for molded products, etc., by reaction between a specific polyester diol, organic diisocyanate, and chain extender. CONSTITUTION: This polyurethane is obtained by reaction between (A) a polyester diol having a number-average molecular weight of 500 to 5000 obtained by polycondensation of a diol component unit containing 20mol% or more of 1,9-nonanediol unit of formula I, with a dicarboxylic acid component unit consisting mainly of an aliphatic dicarboxylic acid unit of formula II (n is 4 to 12) and an aromatic dicarboxylic acid unit of formula III (Ar is an aromatic hydrocarbon group), with the molar ratio of the aliphatic dicarboxylic acid unit to the aromatic dicarboxylic acid unit being (2:8) to (8:2) in the presence of a titanium-based esterfication catalyst, followed by deactivation of the titanium-based esterification catalyst, (B) an organic diisocyanate, and (C) a chain extender, in the presence of 0.3 to 15ppm, in terms of tin atoms, of a tin-based urethanization catalyst.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyurethane having excellent moldability, heat resistance, wear resistance, tensile rupture strength, hydrolysis resistance and low temperature properties, a polyurethane molded article and a method for producing the same.

[0002]

BACKGROUND OF THE INVENTION Polyester-based thermoplastic polyurethane has high strength and high elasticity, and has abrasion resistance, chemical resistance and flex resistance as compared with other thermoplastic elastomers. It is excellent and has been used in various fields. Particularly, a thermoplastic polyurethane obtained from a polymer diol obtained by copolymerizing an aromatic dicarboxylic acid has high strength and excellent durability such as water resistance and hydrolysis resistance. However, the thermoplastic polyurethane molded product formed into a product shape by injection molding, extrusion molding, or the like has a large decrease in molecular weight, and the molecular weight after polymerization cannot be retained, and it may be difficult to obtain the desired performance. .

The object of the present invention is to have excellent mechanical performance,
To provide a thermoplastic polyurethane from a polymer diol obtained by copolymerizing an aromatic dicarboxylic acid, which has good moldability and is excellent in heat resistance, abrasion resistance, hydrolysis resistance, and low temperature characteristics. It is in. Furthermore, another object of the present invention is to provide a molded article of thermoplastic polyurethane having the above-mentioned excellent properties and a method for producing the same.

[0004]

According to the present invention, the above object is a thermoplastic polyurethane obtained by reacting a polyester diol, an organic diisocyanate and a chain extender, wherein (i) the polyester diol comprises: The formula below

[0005]

Embedded image —O— (CH ₂ ) ₉ —O—

A diol component unit containing 20 mol% or more of 1,9-nonanediol unit represented by the following general formula (I)

[0007]

Embedded image —CO— (CH ₂ ) n—CO— (I)

(Wherein n represents an integer of 4 to 12) and an aliphatic dicarboxylic acid unit represented by the following general formula (I
I)

[0009]

Embedded image --CO--Ar--CO-- (II)

(In the formula, Ar represents an aromatic hydrocarbon group)
Is mainly composed of an aromatic dicarboxylic acid unit represented by
And a dicarboxylic acid component unit in which the molar ratio of the aliphatic dicarboxylic acid unit to the aromatic dicarboxylic acid unit is in the range of 2: 8 to 8: 2, (ii) the polyester diol is a titanium esterification catalyst After polycondensation in the presence,
A polyester diol having a number average molecular weight of 500 to 5000 obtained by deactivating the titanium esterification catalyst, and (iii) containing a tin urethane formation catalyst in an amount of 0.3 to 15 ppm in terms of tin atom. It is achieved by providing a thermoplastic polyurethane.

Further, the above object is to obtain a molded product obtained from the above thermoplastic polyurethane and a molded product obtained after molding using the above thermoplastic polyurethane.
The present invention is achieved by providing a method for producing a polyurethane molded article, which comprises performing a heat treatment at a temperature of ℃ or higher.

As described above, in the present invention, the polyester diol constituting the thermoplastic polyurethane is 1,9
A diol component unit containing 20 mol% or more of nonanediol units, an aliphatic dicarboxylic acid unit represented by the above general formula (I) [hereinafter, referred to as an aliphatic dicarboxylic acid unit (I)] and the above general An aromatic dicarboxylic acid unit represented by the formula (II) [hereinafter, referred to as an aromatic dicarboxylic acid unit (II)], which is mainly composed of an aliphatic dicarboxylic acid unit (I) and an aromatic dicarboxylic acid unit (II).
In the range of 2 to 8 to 8 to 2 [this means the molar ratio of the aliphatic dicarboxylic acid unit (I) to the aromatic dicarboxylic acid unit (II) and corresponds to the range of 0.25 to 4]. ] It is necessary to consist of the dicarboxylic acid component unit and the dicarboxylic acid component unit.

As for the diol component unit constituting the polyester diol, it is necessary that 20 mol% or more thereof is a 1,9-nonanediol unit. It is preferred that all of the diol component units are 1,9-nonanediol units. Other diol component units include ethylene glycol, diethylene glycol, 1,4-butanediol, 2-methyl-1,3-propanediol, 1,6-
Examples include divalent diol units derived from diols such as hexanediol, 3-methyl-1,5-pentanediol, neopentyl glycol and the like.

In the dicarboxylic acid component unit constituting the polyester diol, the aliphatic dicarboxylic acid unit (I) is used.
The molar ratio of the aromatic dicarboxylic acid unit (II) and the aromatic dicarboxylic acid unit (II) can be arbitrarily changed within the above range, but when the molar ratio is 4 or less, the resulting thermoplastic polyurethane has a moist heat resistance,
Excellent hot water resistance and hydrolysis resistance. However, when the molar ratio is larger than 4, the wet heat resistance, hot water resistance and hydrolysis resistance of the thermoplastic polyurethane are slightly inferior. On the other hand, when the above molar ratio is less than 0.25, the low temperature characteristics of the resulting thermoplastic polyurethane are poor.

The aliphatic dicarboxylic acid unit (I) has the following general formula (I ').

[0016]

Embedded image HOOC- (CH ₂ ) n-COOH (I ′)

It is derived from an aliphatic dicarboxylic acid represented by the formula: wherein n is as defined above. Examples of such an aliphatic dicarboxylic acid include adipic acid, azelaic acid, sebacic acid, dodecanedioic acid, etc., and the aliphatic dicarboxylic acid in which n is 4 to 8 in the above general formula (I ′) is particularly preferable. . Further, the aromatic dicarboxylic acid unit (II) has the following general formula (II ′)

[0018]

HOOC-Ar-COOH (II ')

(In the formula, Ar is as defined above)
Derived from an aromatic dicarboxylic acid represented by As the aromatic dicarboxylic acid, terephthalic acid, isophthalic acid, phthalic acid and the like are preferable. The aliphatic dicarboxylic acid unit (I) and the aromatic dicarboxylic acid unit (II) may each be composed of one type or two or more types.

In the present invention, the polyester diol constituting the thermoplastic polyurethane has a number average molecular weight of 50.
Within the range of 0 to 5000, it is necessary in terms of mechanical properties, low temperature characteristics, and moldability of the obtained polyurethane,
More preferably, it is in the range of 2000 to 3000. When the number average molecular weight of the polyester diol is less than 500, the molding strain and compression set of the obtained polyurethane are increased, and the performance such as heat resistance is deteriorated. On the other hand, when the number average molecular weight exceeds 5,000, the mechanical properties such as tensile rupture strength and elongation of the resulting polyurethane deteriorate, and the melt viscosity increases and the moldability deteriorates. Here, the number average molecular weight of the polyester diol referred to in this specification is the number average molecular weight calculated based on the hydroxyl value measured according to JIS K 1577.

The polyester diol in the present invention is
Using the above-mentioned diol component and dicarboxylic acid component,
Transesterification reaction in the presence of titanium-based esterification catalyst,
It is produced by polycondensation by direct esterification reaction, ester formation reaction such as ring-opening polymerization, or the like. As the titanium-based esterification catalyst, it is possible to use a titanium-based esterification catalyst which is generally known to be usable when producing ester-based polymers such as polyester and polycarbonate. Examples of preferable titanium-based esterification catalysts include titanic acid, tetraalkoxytitanium compounds, titanium acylate compounds, and titanium chelate compounds. More specifically, tetraisopropyl titanate, tetra-n-butyl titanate,
Tetraalkoxytitanium compounds such as tetra-2-ethylhexyl titanate and tetrastearyl titanate, titanium acylate compounds such as polyhydroxytitanium stearate and polyisopropoxytitanium stearate, titanium acetylacetonate, triethanolamine titanate, titanium ammonium lactate, titanium Examples thereof include titanium chelate compounds such as ethyl lactate and titanium octylene glycolate. In that case, the amount of the titanium-based esterification catalyst used is not particularly limited,
Generally, it is preferably in the range of about 0.1 to 50 ppm, based on the total weight of the diol component and the dicarboxylic acid component for forming the polyester diol, and about 1
More preferably, it is within the range of ˜30 ppm.

After the completion of the polycondensation reaction, the titanium esterification catalyst contained in the polyester diol is deactivated.
Examples of the deactivating method include a method in which a polyester diol obtained by a polycondensation reaction is brought into contact with water under heating conditions, and a polyester diol such as phosphoric acid, phosphoric acid ester, phosphorous acid, phosphorous acid ester Examples thereof include a method of treating with a compound, and among them, the former method of contacting with water under heating is preferable. When the titanium-based esterification catalyst is deactivated by contacting with water, water is added to the polyester diol obtained by the polycondensation reaction.
It is carried out by bringing them into contact with each other in an amount of not less than wt% and heating within a range of 70 to 150 ° C, preferably within a range of 90 to 130 ° C for 1 to 3 hours. The deactivation treatment of the titanium-based esterification catalyst may be performed under normal pressure or under pressure. It is desirable to depressurize the system after deactivating the titanium-based esterification catalyst because the water used for deactivation can be removed.

In the present invention, as the organic diisocyanate used in the production of thermoplastic polyurethane, any of the organic diisocyanates conventionally used in the production of polyurethane can be used, and the kind thereof is not particularly limited, and aromatic diisocyanate, oil One or more of cyclic diisocyanate and aliphatic diisocyanate can be used. Among these, aromatic diisocyanates such as p-phenylene diisocyanate, 4,4′-diphenylmethane diisocyanate, toluylene diisocyanate, and 1,5-naphthylene diisocyanate are preferable, and 4,4′-diphenylmethane diisocyanate is particularly preferable.

In the present invention, as the chain extender, any of the chain extenders conventionally used in the production of thermoplastic polyurethane can be used, and the kind thereof is not particularly limited, and aliphatic diols and alicyclic compounds can be used. One or more of diols and aromatic diols can be used. Among them, ethylene glycol, diethylene glycol,
1,4-butanediol, 1,5-pentanediol,
2-methyl-1,3-propanediol, 1,6-hexanediol, 3-methyl-1,5-pentanediol, neopentyl glycol, 1,9-nonanediol, 2-methyl-1,8-octane Diol, cyclohexanediol, cyclohexanedimethanol, 1,4
-Bis (β-hydroxyethoxy) benzene and the like are preferable.

The above-mentioned polyester diol,
The polyurethane of the present invention is produced by reacting an organic diisocyanate and a chain extender in the presence of a tin urethanization catalyst. The amount of the tin-based urethane-forming catalyst used is, in terms of tin atom, the thermoplastic polyurethane obtained (that is, the total weight of the reactive raw material compounds such as polyester diol, organic diisocyanate, and chain extender used for producing the thermoplastic polyurethane). 0.3 to 15
Within the range of ppm. When the tin-based urethane-forming catalyst is contained in the thermoplastic polyurethane in an amount of 0.3 ppm or more in terms of tin atom, the molecular weight of the thermoplastic polyurethane is maintained at a sufficiently high level even after molding, especially the tensile rupture strength and abrasion resistance. Is maintained at a high level, and further hydrolysis resistance, heat resistance, cold resistance, etc. are maintained well. However, if the content of the tin-based urethane-forming catalyst in the thermoplastic polyurethane exceeds 15 ppm in terms of tin atom, the performance such as hydrolysis resistance and thermal stability deteriorates, which is not preferable.

Examples of the tin-based urethane-forming catalyst include tin octylate, monomethyltin mercaptoacetate, monobutyltin triacetate, monobutyltin monooctylate, monobutyltin monoacetate, monobutyltin maleate, monobutyltin maleate. Benzyl ester salt, monooctyl tin maleate, monooctyl tin thiodipropionate, monooctyl tin tris (isooctyl thioglycolate ester),
Monophenyl tin triacetate, dimethyl tin maleate salt, dimethyl tin bis (ethylene glycol monothioglycolate), dimethyl tin bis (mercapto acetic acid) salt, dimethyl tin bis (3-mercapto propionic acid) salt, dimethyl tin bis (iso Octyl mercaptoacetate), dibutyltin diacetate, dibutyltin dioctoate, dibutyltin distearate,
Dibutyltin dilaurate, dibutyltin maleate, dibutyltin maleate polymer, dibutyltin maleate ester salt, dibutyltin bis (mercaptoacetic acid) salt, dibutyltin bis (mercaptoacetic acid alkyl ester) salt, dibutyltin bis (3-mercaptopropionic acid alkoxybutyl ester) salt , Dibutyltin bis (octylthioglycol ester) salt, dibutyltin bis (3-mercaptopropionic acid) salt, dioctyltin maleate, dioctyltin maleate ester salt, dioctyltin maleate polymer, dioctyltin dilaurate, dioctyltin bis ( Isooctyl mercaptoacetate), dioctyl tin bis (isooctyl thiogolic acid ester), dioctyl tin bis (3-mercapto) Propionate) acylate compound of tin, such as salts, such as mercapto carboxylic acid salt can be exemplified, and these may be used in combination of two or more kinds thereof may be used alone. Among the above tin-based urethane-forming catalysts, dibutyltin diacetate, dialkyltin diacylate such as dibutyltin dilaurate, dibutyltin bis (3
-Mercaptopropionic acid ethoxybutyl ester) salts and the like, and dialkyltin bismercaptocarboxylic acid ester salts and the like are preferable.

The tin-based urethane-forming catalyst may be added at the same time as the polyester diol, the organic diisocyanate and the chain extender during the production of the thermoplastic polyurethane, or one or two of these polyurethane raw materials.
It may be mixed in advance for more than one person. It is desirable to mix it in the polyester diol beforehand because the tin-based urethane-forming catalyst can be uniformly mixed and dispersed.

The reaction method for obtaining the thermoplastic polyurethane of the present invention is not particularly limited, and the above-mentioned polyester diol, organic diisocyanate and chain extender are used to utilize a known urethanization reaction technique to prepare a prepolymer. Method or one-shot method.
Among them, it is preferable to carry out melt polymerization in the substantial absence of a solvent, and particularly preferable is continuous melt polymerization using a multi-screw extruder.

Although it may vary depending on the content of the polyester diol used, the type of organic diisocyanate, the content of the chain extender, etc., when the thermoplastic polyurethane of the present invention is produced using a multi-screw type extruder, it is generally used. These raw material compounds are continuously or almost simultaneously supplied to the extruder continuously and at 190 to 280 ° C., preferably 210 to 280 ° C.
It is advisable to manufacture polyurethane by continuous melt polymerization at 260 ° C., and then extrude and cut to manufacture polyurethane in the shape of pellets, chips and the like.

If necessary, a coloring agent, a lubricant, a crystal nucleating agent, or
Additives such as flame retardants, UV absorbers, antioxidants, weather resistance improvers, hydrolysis inhibitors, tackifiers, antifungal agents, etc. 1
One kind or two or more kinds may be appropriately added.

The thermoplastic polyurethane of the present invention has good moldability, and various molded products can be smoothly produced by various molding methods such as extrusion molding, injection molding, blow molding and calender molding. Molded products obtained by these molding methods have excellent mechanical performance, excellent heat resistance, wear resistance, hydrolysis resistance, and low-temperature characteristics, and have a small compression set and are extremely excellent. Because of its unique properties, for example, films, sheets, tubes,
Belts, hoses, various rolls, screens, casters, gears, packing materials, automobile parts, squeegees, paper feed rolls, cleaning blades for copying, snow plows, chains, linings, solid tires, anti-vibration materials,
It can be effectively used for a wide range of applications such as vibration damping materials, shoe soles, sports shoes, marking materials, binders, adhesives, leather, elastic fibers, machine parts and the like.

The molded product made of the thermoplastic polyurethane of the present invention may be directly used after molding, but after molding, the molded product is heated to a temperature of 60 ° C. or higher, particularly 8 ° C.
Heat treatment (annealing) at a temperature in the range of 0 to 110 ° C. is desirable because it can further improve the heat resistance, heat resistance and heat resistance retention of the molded product, and further reduce the compression set. In that case, the heat treatment time depends on the content of the thermoplastic polyurethane, the size and thickness of the molded product,
It can be appropriately selected depending on the shape, etc., but is generally about 4 to 20.
It is preferable to carry out for about an hour.

[0033]

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited thereto. In the following examples, molding of test samples of thermoplastic polyurethane was carried out by the following methods, and tensile breaking strength, hydrolysis resistance, low temperature characteristics, hydrolysis resistance and Taber abrasion resistance were measured or evaluated by the following methods.

[Test sample molding] Thermoplastic polyurethane was molded using an injection molding machine "FS80S 12ASE" manufactured by Nissei Plastic Industry Co., Ltd.
A disk-shaped sheet-shaped molded product (test sample) of 120 mm is prepared, and after molding, it is subjected to 3 ° C. under a relative humidity of 65% RH at 23 ° C.
It was left for one day and subjected to the following various performance tests.

[Tensile Breaking Strength] The tensile strength of the test sample was measured at 23 ° C. and 100 ° C. according to JIS K-7311, and the stress at break was taken as the tensile breaking strength.

[Low temperature characteristics] 2 mm wide from the test sample,
A test piece having a thickness of 0.5 mm and a length of 40 mm was cut out, and the dynamic viscoelasticity of the test piece was measured by using a dynamic viscoelasticity measuring device “Rheospectra DVE-VI” manufactured by Rheology Co., Ltd. 11
Measured at a frequency of Hz, when Tα (temperature at which loss elastic modulus E ″ α dispersion has a maximum value) is −25 ° C. or lower, ○, −2
The case where the temperature exceeded 5 ° C was evaluated as x.

[Hydrolysis resistance] A test sample was tested at 100 ° C.
After soaking in distilled water for 5 days, the tensile strength at break was measured at 23 ° C., and the strength retention against the tensile strength at break before immersion was expressed in%.

[Taber wear resistance] JIS K-7331
The Taber abrasion resistance of the test sample was measured in accordance with. Wear a wear wheel (H-22) on the test sample and apply a load of 1
A wear test was performed by rotating the test sample 1000 times in kgf, and the weight after the wear test was subtracted from the weight of the test sample before the wear test to obtain the wear loss weight (mg).

The abbreviations for the compounds used in the following Reference Examples, Examples and Comparative Examples and the contents of the compounds are as shown in Table 1 below.

[0040]

[Table 1]

[Reference Examples 1 to 8] (Production of POH) A dicarboxylic acid component and a diol component were charged into a reactor so that the molar ratio was 1: 1.17, and the temperature was 210 ° C in the presence of 15 ppm of tetraisopropyl titanate. The esterification reaction was carried out by distilling water out of the system. When the distillation of water almost stopped, measure the acid value of the reaction product,
After confirming that it was 30 or less, 15 ppm of tetraisopropyl titanate was added. Then 22
It is heated to 0 ° C., dehydrated at a reduced pressure of 30 torr, and transesterified by a deglycolization reaction at a reduced pressure of 1 torr or less, and then the hydroxyl value is measured to confirm that the target molecular weight (number average molecular weight) is obtained. Confirm and desired POH
I got The resulting POH was subjected to treatment by Method A, Method B or Method C below. Table 2 shows the results.

Method A: POH was brought into contact with 3% by weight of water, heated at 100 ° C. for 2 hours, then dehydrated, and then 7 ppm of dibutyltin diacetate was added. Method B: POH was contacted with 3% by weight of water, heated at 100 ° C. for 2 hours and then dehydrated, but without addition of dibutyltin diacetate. Method C: No water treatment and no addition of dibutyltin diacetate.

[0043]

[Table 2]

[Example 1] POH (No.
1) and MDI and BD are twin-screw type extruders that rotate in the coaxial direction ("BP Engineering Laboratory" BP
-30-S]; φ30 mm, screw length 1080 m
m) and continuously melt-polymerized at 260 ° C. The resulting polyurethane melt was continuously extruded in strands into water, then cut with a pelletizer and formed into pellets. Test samples were prepared from the pellets by the method described above and subjected to various performance tests. The results are shown in Table 4. The resulting polyurethane has room temperature and 1
It was excellent in all properties such as tensile breaking strength at 00 ° C, low temperature characteristics, hydrolysis resistance, and Taber abrasion resistance.

[Example 2] POH (No.
2) and MDI and BD were melt-polymerized in the same manner as in Example 1, and various performances of the resulting polyurethane were evaluated in the same manner. Table 4 shows the evaluation results. The obtained polyurethane was excellent in all properties such as tensile breaking strength at room temperature and 100 ° C., low temperature characteristics, hydrolysis resistance, and Taber abrasion resistance.

[Example 3] POH (No.
3) was melt-polymerized with MDI and BD in the same manner as in Example 1, and various performances of the resulting polyurethane were evaluated in the same manner. Table 4 shows the evaluation results. The obtained polyurethane was excellent in all properties such as tensile breaking strength at room temperature and 100 ° C., low temperature characteristics, hydrolysis resistance, and Taber abrasion resistance.

[Example 4] POH (No.
4) and MDI and BD were melt-polymerized in the same manner as in Example 1, and various performances of the resulting polyurethane were evaluated in the same manner. Table 4 shows the evaluation results. The obtained polyurethane was excellent in all properties such as tensile breaking strength at room temperature and 100 ° C., low temperature characteristics, hydrolysis resistance, and Taber abrasion resistance.

[Comparative Example 1] POH (No.
5) and MDI and BD were melt-polymerized in the same manner as in Example 1, and various performances of the resulting polyurethane were evaluated in the same manner. Table 4 shows the evaluation results. The obtained polyurethane had insufficient tensile breaking strength at 100 ° C. and Taber abrasion resistance.

[Comparative Example 2] POH (No.
6) was melt-polymerized with MDI and BD in the same manner as in Example 1, and various performances of the produced polyurethane were evaluated in the same manner. Table 4 shows the evaluation results. The resulting polyurethane was significantly inferior in hydrolysis resistance.

[Comparative Example 3] POH (No.
7) and MDI and BD were melt-polymerized in the same manner as in Example 1 and various performances of the produced polyurethane were evaluated in the same manner. Table 4 shows the evaluation results. The resulting polyurethane was inferior in hydrolysis resistance and Taber abrasion resistance.

[Comparative Example 4] POH (No.
8) and MDI and BD were melt-polymerized in the same manner as in Example 1, and various performances of the resulting polyurethane were evaluated in the same manner. Table 4 shows the evaluation results. The resulting polyurethane was inferior in low temperature properties and hydrolysis resistance.

[0052]

[Table 3]

[0053]

[Table 4]

[0054]

According to the present invention, it has excellent mechanical performance,
Thermoplastic polyurethanes with excellent moldability, heat resistance, abrasion resistance, hydrolysis resistance, and low temperature characteristics are provided. From this polyurethane, various molded products can be molded with various molding methods by various molding methods. It can be manufactured. And
The polyurethane molded product of the present invention obtained by further subjecting to heat treatment under a specific temperature condition after molding is more excellent in properties such as heat resistance, heat resistance strength and heat resistance retention rate, and further has a smaller compression set and is further improved. It has characteristics.

Claims (3)

[Claims] 1. A thermoplastic polyurethane obtained by reacting a polyester diol, an organic diisocyanate and a chain extender, wherein (i) the polyester diol is represented by the following formula: -O- (CH ₂ ) ₉ A diol component unit containing 20 mol% or more of 1,9-nonanediol unit represented by —O—, and the following general formula (I): —CO— (CH ₂ ) n—CO— (I) (In the formula, n represents an integer of 4 to 12) and an aliphatic dicarboxylic acid unit represented by the following general formula (II): —CO—Ar—CO— (II) (wherein Ar is A dicarboxylic acid having a molar ratio of the aliphatic dicarboxylic acid unit to the aromatic dicarboxylic acid unit in the range of 2: 8 to 8: 2. From the acid component unit Ri, (ii) after the polyester diol is polycondensed in the presence of a titanium-based esterification catalyst, the number-average molecular weight obtained by deactivating the titanium-based esterification catalyst 500
~ 5000 polyester diols, and (ii
i) 0.3 to 1 tin-based urethane conversion catalyst in terms of tin atom
A thermoplastic polyurethane characterized by containing 5 ppm. 2. A molded product obtained from the thermoplastic polyurethane according to claim 1. 3. A method for producing a polyurethane molded article, which comprises molding the thermoplastic polyurethane of claim 1 and then heat-treating the obtained molded article at a temperature of 60 ° C. or higher.