JP2012180467A - Thermoplastic polyurethane - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide thermoplastic polyurethane whose whitening is reduced without damaging its various performances such moldability, dynamic strength and abrasion resistance.SOLUTION: The thermoplastic polyurethane is obtained by polymerizing: polymer polyol (A) having the number-average molecular weight of 500 to 5,000; organic diisocyanate (B); and a chain extender (C). The polycarboxylic acid unit composing the polymer polyol (A) is a mixture of a sebacic acid unit with a ≤9C polycarboxylic acid unit; regarding the ratio of the mixture, by molar ratio, (the sebacic acid unit)/(≤9C polycarboxylic acid unit)=(60/40) to (100/0), also, the diol unit composing the polymer polyol (A) is a mixture of a 1,3-propanediol unit and an alkyl branch-containing diol unit; and, regarding the ratio of the mixture, by a molar ratio, (the 1,3-propanediol unit)/(the alkyl branch-containing diol unit)=(50/50) to (97/3).

Description

  The present invention relates to a thermoplastic polyurethane having reduced whitening without significantly impairing various properties such as moldability, mechanical strength, and abrasion resistance.

  Thermoplastic polyurethane is highly elastic, has excellent wear resistance and oil resistance, and has many features such as the ability to apply ordinary plastic molding methods. As a substitute for rubber, it can be used in a wide range of applications. It has come to be used. However, especially in the field of low-temperature thermoplastic polyurethane, it is difficult to say that the properties such as moldability, mechanical strength, and wear resistance are sufficient to further replace rubber and the like, and performance improvement is required. ing.

For example, a thermoplastic polyurethane containing a specific amount of dimethyldecanedioic acid unit as a thermoplastic polyurethane with excellent properties such as injection moldability, mechanical strength, hydrolysis resistance, heat resistance, hot water resistance, and mold resistance. Polyurethanes have been proposed (Patent Documents 1 and 2). However, in these thermoplastic polyurethanes, the crystallinity of the polyester diol containing dimethyldecanedioic acid units is reduced, and there is still room for improvement in moldability, mechanical strength, wear resistance, and the like.
The inventors of the present invention have made extensive studies focusing on the crystallinity of polyester polyols. Polyurethanes comprising polyester diols composed of sebacic acid units and 1,3-propanediol units have excellent moldability, mechanical strength, It has been found that it has excellent properties such as wear resistance. However, the thermoplastic polyurethane has excellent moldability, mechanical strength, abrasion resistance, and the like derived from the high crystallinity of the polyester diol, while the surface of the molded product is whitened to deteriorate the appearance. It turned out to have.

JP-A-8-239442 JP-A-8-183831

  Accordingly, an object of the present invention is to provide a low-hardness thermoplastic polyurethane with reduced whitening without impairing various performances such as moldability, mechanical strength, and abrasion resistance.

As a result of intensive studies, the present inventors have determined that the thermoplastic polyurethane obtained by using a polymer polyol having a specific structure is low in hardness and can be whitened without impairing various properties such as moldability, mechanical strength, and wear resistance. It was found that it can be suppressed.
That is, the present invention
[1] A thermoplastic polyurethane obtained by polymerizing a polymer polyol (A) having a number average molecular weight of 500 to 5,000, an organic diisocyanate (B), and a chain extender (C),
The polycarboxylic acid unit constituting the polymer polyol (A) is a mixture of a sebacic acid unit and a polycarboxylic acid unit having 9 or less carbon atoms, and the mixture ratio is a sebacic acid unit / carbon number 9 or less as a molar ratio. Polycarboxylic acid unit = 60 / 40-100 / 0,
The diol unit constituting the polymer polyol (A) is a mixture of a 1,3-propanediol unit and a diol unit having an alkyl branch, and the mixture ratio is 1,3-propanediol unit / A thermoplastic polyurethane characterized in that the diol unit having an alkyl branch = 50/50 to 97/3;
[2] A diol unit having an alkyl branch, which is a diol unit constituting the polymer polyol (A), is 3-methyl-1,5-pentanediol, 2-methyl-1,3-propanediol, 2-methyl. The thermoplastic polyurethane according to the above [1], which is derived from at least one diol selected from the group consisting of -1,8-octanediol and 2-methyl-1,4-butanediol,
[3] The thermoplastic polyurethane according to the above [1] or [2], wherein the polycarboxylic acid unit having 9 or less carbon atoms, which is a polycarboxylic acid unit constituting the polymer polyol (A), is derived from adipic acid. ,
[4] The thermoplastic polyurethane according to any one of the above [1] to [3], wherein the crystallization enthalpy (ΔH) of the polymer polyol (A) is 30 to 79 J / g;
About.

  According to the present invention, a thermoplastic polyurethane with reduced whitening can be obtained without impairing various performances such as moldability, mechanical strength, and wear resistance.

  The present invention is most characterized by using a polymer polyol (A) having a specific structure. The polymer polyol (A) has sebacic acid as a polycarboxylic acid unit, and has 9 or less carbon atoms as another polycarboxylic acid unit from the viewpoints of injection moldability, extrusion moldability, mechanical strength, wear resistance, and the like. Of polycarboxylic acids. The mixing ratio of the sebacic acid unit and the polycarboxylic acid unit having 9 or less carbon atoms is, as a molar ratio, sebacic acid unit / polycarboxylic acid unit having 9 or less carbon atoms = 60/40 to 100/0, preferably 70 / It is in the range of 30 to 97/3, more preferably 80/20 to 95/5.

  Examples of the polycarboxylic acid having 9 or less carbon atoms include succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, methylsuccinic acid, 2-methylglutaric acid, 3-methylglutaric acid, trimethyladipic acid, 2- Aliphatic dicarboxylic acids such as methyloctanedioic acid, alicyclic dicarboxylic acids such as cyclohexanedicarboxylic acid; Aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, and orthophthalic acid; Trifunctional or higher polycarboxylic acids such as trimellitic acid, etc. Is mentioned. Of these, adipic acid is preferred. A polycarboxylic acid having 9 or less carbon atoms and a derivative thereof may be used alone or in combination of two or more.

  From the viewpoints of injection moldability, extrusion moldability, mechanical strength, abrasion resistance, and the like, the polymer polyol (A) contains 1,3-propanediol as an essential component as a polyol unit, and crystals of the polymer polyol (A) From the viewpoint of controlling properties, a diol having an alkyl branch is included as another polyol component. The ratio of 1,3-propanediol and diol having an alkyl branch is, as a molar ratio, 1,3-propanediol / diol having an alkyl branch = 50/50 to 97/3, preferably 50/50 to 95. / 5, more preferably in the range of 50/50 to 90/10.

  Examples of the diol having an alkyl branch include propylene glycol, 2-methyl-1,3-propanediol, 2,2-diethyl-1,3-propanediol, and 2-ethyl-2-butyl-1,3-propane. Diol, 1,3-butanediol, 2-methyl-1,4-butanediol, neopentyl glycol, 3-methyl-1,5-pentanediol, 3-methyl-2,4-pentanediol, 2,4- Diethyl-1,5-pentanediol, 2-ethyl-1,3-hexanediol, 2-methyl-1,8-octanediol, 2,7-dimethyl-1,8-octanediol, 2-methyl-1, C2-C15 aliphatic diols such as 9-nonanediol and 2,8-dimethyl-1,9-nonanediol; 2-methyl-1,1-cyclohexane And alicyclic diols such as dimethanol and dimethylcyclooctanedimethanol. Among these, propylene glycol, 2-methyl-1,3-propanediol, 2,2-diethyl-1,3-propanediol, 2-ethyl-2-butyl-1,3-propanediol, 2-methyl -1,4-butanediol, 3-methyl-1,5-pentanediol, 2,4-diethyl-1,5-pentanediol, 2-methyl-1,8-octanediol, 2,7-dimethyl-1 , 8-octanediol, 2-methyl-1,9-nonanediol and 2,8-dimethyl-1,9-nonanediol are preferred, and 3-methyl-1,5-pentanediol, 2-methyl-1,3 are preferred. -Propanediol, 2-methyl-1,8-octanediol, and 2-methyl-1,4-butanediol are more preferable.

  The polymer polyol (A) may be a mixture of several polymer polyols. However, when the polymer polyol (A) is a mixture, a diol having a sebacic acid unit, a polycarboxylic acid unit having 9 or less carbon atoms, a 1,3-propanediol unit, and an alkyl branch in the polymer polyol (A). The amount of units is determined based on the total polycarboxylic acid units and the total polyol units, respectively, in the mixture.

The number average molecular weight of the polymer polyol (A) is 500 or more (preferably 600 or more, more preferably 800 or more) and 5000 or less (preferably 4000 or less, more preferably 3000 or less). If the number average molecular weight is less than 500, a thermoplastic polyurethane excellent in moldability, mechanical strength, abrasion resistance and the like cannot be obtained.
On the other hand, when the number average molecular weight exceeds 5000, the moldability (particularly extrusion moldability) and tensile strength of the resulting thermoplastic polyurethane are poor. The number average molecular weight of the polymer polyol (A) can be calculated based on the hydroxyl value measured according to JIS K-1557.

  The crystallization enthalpy (ΔH) of the polymer polyol (A) is preferably 30 J / g or more, more preferably 50 J / g or more, preferably 79 J / g or less, more preferably 70 J / g or less. When ΔH is lower than 30 J / g, the moldability, mechanical strength, wear resistance and the like of the resulting thermoplastic polyurethane tend to be insufficient. On the other hand, if ΔH is greater than 79 J / g, highly crystalline bleed occurs on the surface of the molded product of the thermoplastic polyurethane, and there is a tendency that whitening occurs over time. ΔH of the polymer polyol (A) is a desired value by adjusting the content of sebacic acid units, polycarboxylic acid units having 9 or less carbon atoms, 1,3-propanediol units and diol units having an alkyl branch. Can be set. ΔH can be measured by differential scanning calorimetry (DSC) using the apparatus and conditions described in the examples described later.

  The manufacturing method of a high molecular polyol (A) is not specifically limited, A well-known manufacturing method is employable. For example, 1,3-propanediol and sebacic acid, diol having an alkyl branch and polycarboxylic acid having 9 or less carbon atoms are mixed and heated at a predetermined ratio, and the esterification reaction and subsequent polycondensation reaction proceed. By doing so, the polymer polyol (A) can be produced. In the production of the polymer polyol (A), a polycondensation catalyst such as a titanium catalyst or a tin catalyst may be used.

  Examples of the organic diisocyanate (B) include 4,4′-diphenylmethane diisocyanate (MDI), tolylene diisocyanate, phenylene diisocyanate, xylylene diisocyanate, 1,5-naphthylene diisocyanate, and 3,3′-dichloro-4,4. Examples include aromatic diisocyanates such as' -diphenylmethane diisocyanate; aliphatic or alicyclic diisocyanates such as hexamethylene diisocyanate, isophorone diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, and hydrogenated xylylene diisocyanate. An organic diisocyanate (B) may be used individually by 1 type, and may use 2 or more types together. When producing a thermoplastic polyurethane excellent in melt moldability and mechanical properties, it is preferable to use MDI. In this case, the content of MDI in the organic diisocyanate (B) is preferably 50 mol% or more, more preferably 80 mol% or more, still more preferably 95 mol% or more, and particularly preferably 100 mol%.

  The chain extender (C) is a low molecular compound having at least two active hydrogen atoms, and may be any compound that is usually used as a chain extender in the production of thermoplastic polyurethane. Examples of the chain extender (C) include ethylene glycol, propylene glycol, 1,3-propanediol, 1,4-butanediol, 3-methyl-1,5-pentanediol, 1,6-hexanediol, 2 -Diols such as methyl-1,8-octanediol, 1,9-nonanediol, 1,4-bis (β-hydroxyethoxy) benzene, cyclohexanedimethanol, bis (β-hydroxyethyl) terephthalate, xylylene glycol Diamines such as hydrazine, ethylenediamine, propylenediamine, xylylenediamine, isophoronediamine, piperazine or derivatives thereof, phenylenediamine, tolylenediamine, xylenediamine, adipic acid dihydrazide, isophthalic acid dihydrazide; aminoethyl alcohol And amino alcohols such as aminopropyl alcohol. A chain extender (C) may be used individually by 1 type, and may use 2 or more types together. Among these, since it is easily obtained industrially, an aliphatic diol having 2 to 10 carbon atoms (particularly 1,4-butanediol) or an aliphatic diamine having 2 to 10 carbon atoms (particularly ethylenediamine, hexanediamine or isophoronediamine). ) Is preferred. Furthermore, an aliphatic diol having 2 to 10 carbon atoms, particularly 1,4-butanediol is preferred because a thermoplastic polyurethane having excellent melt moldability and mechanical properties can be produced. In this case, the content of the aliphatic diol having 2 to 10 carbon atoms (particularly 1,4-butanediol) is preferably 50 mol% or more, more preferably 80 mol% or more, and more preferably 80 mol% or more in the chain extender (C). Preferably it is 95 mol% or more, Most preferably, it is 100 mol%.

  The thermoplastic polyurethane of the present invention can be produced by polymerizing the polymer polyol (A), the organic diisocyanate (B) and the chain extender (C) according to a known polyurethane production method. As a polymerization method, solution polymerization can be performed in a solvent inert to the reaction, or melt polymerization can be performed in the absence of a solvent. The solvent for the solution polymerization is not particularly limited as long as it is inactive in the polymerization reaction. Esters such as ethyl acetate and butyl acetate; Ketones such as acetone, methyl ethyl ketone and methyl isobutyl ketone; Hexane, octane and the like Aliphatic hydrocarbons; aromatic hydrocarbons such as toluene and xylene; amides such as dimethylformamide and dimethylacetamide. When producing a thermoplastic polyurethane excellent in melt moldability and mechanical properties, melt polymerization is preferred, and continuous melt polymerization using a multi-screw extruder is more preferred. The melt polymerization temperature is not particularly limited, but is preferably in the range of 150 ° C. or higher and 260 ° C. or lower. A thermoplastic polyurethane having excellent moldability can be obtained by maintaining the temperature at 150 ° C. or higher, and heat resistance and moldability of the resulting thermoplastic polyurethane can be improved by maintaining the temperature at 260 ° C. or lower.

  In the production of the thermoplastic polyurethane of the present invention, the amount of isocyanate group is preferably 0.90 mol or more with respect to 1 mol of the total amount of active hydrogen atoms contained in the polymer polyol (A) and the chain extender (C). (More preferably 0.95 mol or more), preferably 1.3 mol or less (more preferably 1.10 mol or less) in such a proportion that the organic diisocyanate (B) is used in the thermoplastic polyurethane It is preferable from the viewpoint of sufficiently obtaining various performances such as moldability, mechanical strength, and wear resistance.

  In the production of the thermoplastic polyurethane of the present invention, a urethanization reaction catalyst conventionally used in the production of thermoplastic polyurethane can be used. Examples of the urethanization reaction catalyst include organic tin compounds, organic zinc compounds, organic bismuth compounds, organic titanium compounds, organic zirconium compounds, and amine compounds. Of these, organotin compounds are preferred. Examples of the organic tin compound include tin octylate, monomethyltin mercaptoacetate, monobutyltin triacetate, monobutyltin monooctylate, monobutyltin monoacetate, monobutyltin maleate, monobutyltin maleate benzyl ester salt, monooctyltin Maleate, monooctyltin thiodipropionate, monooctyltin tris (isooctylthioglycolate), monophenyltin triacetate, dimethyltin maleate, dimethyltin bis (ethylene glycol monothioglycolate), Dimethyltin bis (mercaptoacetic acid) salt, dimethyltin bis (3-mercaptopropionic acid) salt, dimethyltin bis (isooctyl mercaptoacetate), dibutyltin diacetate , Dibutyltin dioctoate, dibutyltin distearate, dibutyltin dilaurate, dibutyltin maleate, dibutyltin maleate polymer, dibutyltin maleate ester salt, dibutyltin bis (mercaptoacetic acid), dibutyltin bis (mercaptoacetic acid alkyl ester) salt, dibutyltin bis (3-mercaptopropionic acid alkoxybutyl ester) salt, dibutyltin bisoctylthioglycol ester salt, dibutyltin (3-mercaptopropionic acid) salt, dioctyltin maleate, dioctyltin maleate, dioctyltin maleate polymer, Dioctyltin dilaurate, dioctyltin bis (isooctyl mercaptoacetate), dioctyltin bis (isooctylthioglyco) Le ester), dioctyltin bis (3-mercaptopropionate) acylate compounds such as salts, such as mercapto carboxylic acid salts can be exemplified. Among these, dialkyltin diacylate such as dibutyltin diacetate and dibutyltin dilaurate; dialkyltin bismercaptocarboxylic acid ester such as dibutyltin bis (3-mercaptopropionic acid ethoxybutyl ester) salt; and the like are preferable. A urethanization reaction catalyst may be used individually by 1 type, or may use 2 or more types together. When using a urethanization reaction catalyst, it is preferable to adjust so that it may become 0.1-100 ppm with respect to the mass of a thermoplastic polyurethane. If a urethanization reaction catalyst of 0.1 ppm or more is used, the original molecular weight is maintained at a sufficiently high level even after molding the thermoplastic polyurethane, and the original physical properties of the thermoplastic polyurethane are easily exhibited even in the molded product. . When a urethanization reaction catalyst is used in the production of thermoplastic polyurethane, the catalyst may be added to the reaction system during the polymerization of the polymer polyol (A), the organic diisocyanate (B) and the chain extender (C) (for example, The catalyst may be added in advance at the time of production of the polymer polyol (A) together with the polymer polyol (A).

As the nitrogen atom content constituting the hard segment in the thermoplastic polyurethane of the present invention, the nitrogen atom content derived from the organic diisocyanate (B) and the chain extender (C) is preferably 2% by mass or more, more preferably Is 2.5% by mass or more, preferably 6.5% by mass or less, more preferably 6.0% by mass or less. When the content of nitrogen atoms is less than 2% by mass, various properties such as moldability, mechanical strength, and wear resistance of the thermoplastic polyurethane may be insufficient. On the other hand, if the nitrogen atom content exceeds 6.5% by mass, the thermoplastic polyurethane has a high hardness, the flexibility and the like may be insufficient, and an unmelted product is likely to be generated during extrusion molding. The nitrogen atom content can be calculated by means such as elemental analysis measurement or ¹ H-NMR measurement.

  The thermoplastic polyurethane of the present invention may contain other additives (for example, colorants, lubricants, flame retardants, ultraviolet absorbers, light resistance improvers, antifungal agents, etc.). Other additives can be appropriately added during the polymerization of the thermoplastic polyurethane or after the polymerization. Further, other additives may be added in advance to the polymerization raw material {for example, the polymer polyol (A)} before the polymerization of the thermoplastic polyurethane.

  The thermoplastic polyurethane of the present invention is excellent in moldability even if it has a relatively low hardness (for example, Shore A hardness of about 80 or less). Therefore, the thermoplastic polyurethane of the present invention can be suitably used for various molding applications such as injection molding, extrusion molding, and calendar molding. The molded product obtained from the thermoplastic polyurethane of the present invention is excellent in various performances such as mechanical strength and abrasion resistance, like the thermoplastic polyurethane.

  EXAMPLES Hereinafter, although an Example and a comparative example are given and this invention is demonstrated more concretely, this invention is not limited to these Examples.

〔Measuring method〕
In the following Examples and Comparative Examples, the melting point, crystallization enthalpy (ΔH) and number average molecular weight of the polymer polyol (A), the melt viscosity of the thermoplastic polyurethane, and the solidification property, ultimate hardness, appearance (whitening) of the injection molded product ), Taber abrasion amount and hydrolyzability were measured by the following methods.

(1) Polymer polyol (A)
[Melting point and crystallization enthalpy]
The melting point and crystallization enthalpy (ΔH) of the polymer polyol (A) were measured with a differential scanning calorimeter [Seiko Instruments Inc., DSC2000]. The amount of sample was about 10 mg, and calorimetric measurement was performed under the condition of a temperature increase rate of 10 ° C./min from −50 ° C. to 200 ° C. under an air flow of 100 ml / min. The melting point was determined from the endothermic peak temperature, and the crystallization enthalpy (ΔH) was determined from the endothermic peak area.
(Measurement of number average molecular weight)
The number average molecular weight was calculated based on the hydroxyl value measured according to JIS K-1557.

(2) Thermoplastic polyurethane and its injection-molded product [melt viscosity]
Using a Koka type flow tester (manufactured by Shimadzu Corporation), the melt viscosity of the thermoplastic polyurethane which was dried under reduced pressure at 80 ° C. for 2 hours (1.3 × 10 ³ Pa [10 Torr] or less) with a load of 490.3 N (50 kgf), nozzle size = diameter 1 mm × length 10 mm, temperature 210 ° C.

[Solidification]
By injection molding (FS-80S12ASE manufactured by Nissei Plastic Industry Co., Ltd., cylinder temperature 200-210 ° C, mold temperature 30 ° C, injection time 5-8 seconds, cooling time 30 seconds) using a mold with a mirror-finished surface A disk-shaped molded product (diameter 120 mm, thickness 2 mm) was molded, and the Shore A hardness 30 seconds after the molded product was taken out at the same time as the mold was opened was measured as “solidification”. . The higher the solidification property (Shore A hardness after 30 seconds), the faster the solidification and the better the moldability.

[Achieved hardness]
The molded product was taken out from the mold and left to stand at 23 ° C. for 1 week, and the Shore A hardness was measured.

  In addition, Shore A hardness was measured with a Shore A hardness meter using three obtained disk-shaped molded products having a thickness of 2 mm in accordance with JIS K-6301.

[Appearance (whitening)]
The molded product was taken out from the mold and allowed to stand for 1 month at a temperature of 25 ° C., and the surface state of the molded product was visually observed to evaluate the presence or absence of whitening (fogging with a powdery material). After one month of injection molding (temperature condition of 25 ° C.), the surface of the molded product that does not whiten is indicated as “◯”, and the case that whitening occurs is indicated as “X”.

[Taber wear]
The same operation as in the above evaluation of solidification was performed to produce a disk-shaped molded product (diameter 120 mm, thickness 2 mm), and the resulting molded product was allowed to stand for 1 week at 23 ° C. Using a testing machine (load 1 kg, wear wheel H-22), the Taber wear amount was measured according to JIS K-7311.

[Compounds used in Examples]
The compounds used in Examples and Comparative Examples are as follows. In the following examples and comparative examples, the compounds used are indicated by abbreviations.

(1) Polymer polyol (A)
[Production Example 1]
In a glass three-necked flask with an internal volume of 2000 mL equipped with a magnetic stirrer, 447 g (5.88 mol) of 1,3-propanediol, 21 g (0.18 mol) of 3-methyl-1,5-pentanediol, 808 g of sebacic acid ( 4.00 mol) was added and gradually heated to 180 ° C. under normal pressure and nitrogen atmosphere, and the esterification reaction was carried out for 4 hours while distilling off the by-produced water. Next, 0.015 g (1 vol% toluene solution, 1.5 g) of tetraisopropoxytitanium was added and the esterification reaction was continued. Then, the excess diol component was distilled off under reduced pressure to obtain a number average molecular weight. 1068 g of 1005 polyester polyol was obtained (hereinafter abbreviated as POH-1). The obtained POH-1 had a melting point of 53 ° C. and ΔH of 78 J / g.

[Production Examples 2 to 15]
A reaction was carried out in the same manner as in Production Example 1 except that the amount of diol and the amount of polycarboxylic acid were changed to those shown in Table 1, and polyester polyols (POH-2 to POH-15) were obtained. The results are shown in Table 1.

ＰＤ：１，３−プロパンジオール
ＭＰＤ：３−メチル−１，５−ペンタンジオール
ＳｂＡ：セバシン酸
ＡＡ：アジピン酸
MPDiol：２−メチル−１，３−プロパンジオール

PD: 1,3-propanediol
MPD: 3-methyl-1,5-pentanediol SbA: sebacic acid
AA: Adipic acid
MPDiol: 2-methyl-1,3-propanediol

(2) Organic diisocyanate (B)
MDI: 4,4′-diphenylmethane diisocyanate
(3) Chain extender (C)
BD: 1,4-butanediol
(4) Urethane reaction catalyst SN: dibutyltin diacetate

[Example 1]
(1) Production of thermoplastic polyurethane POH-1, BD and MDI containing 10 ppm of SN were mixed at a molar ratio of POH-1: BD: MDI = 1.0: 0.4: 1.4 (nitrogen derived from MDI). A twin screw extruder (30 mmφ, L / D = 36; heating zone) that rotates in the same direction with an atomic content of 2.83 mass%) and a total feed amount of 200 g / min. It was continuously fed to the front part of the heating zone (divided into three zones, the front part, the central part and the rear part), and continuous melt polymerization was carried out at 260 ° C. The obtained melt was continuously extruded into water in the form of strands, then cut with a pelletizer, and the obtained pellets were dehumidified and dried at 50 ° C. for 8 hours to produce a thermoplastic polyurethane. The melt viscosity of the polyurethane was 310 Pa · s.

(2) Manufacture of injection-molded products Using the thermoplastic polyurethane obtained in (1) above, injection molding is performed by the method described in the evaluation of solidification properties, and the solidification properties, ultimate hardness, appearance, and Taber wear amount are evaluated. did. Table 2 shows the results.

[Examples 2-7, Comparative Examples 1-6]
(1) Production of thermoplastic polyurethane As in Example 1, except that POH-1 was changed to each polymer polyol (POH-2 to 7 and 9 to 14) containing 10 ppm of SN shown in Table 1. A thermoplastic polyurethane was produced by the following method.

(2) Manufacture of injection molded article Using the thermoplastic polyurethane obtained in the above (1), injection molding was performed by the method described in the evaluation of solidification property, and the solidification property, ultimate hardness and Taber abrasion amount were evaluated. Table 2 shows the results. Even when the molded products obtained in Examples 2 to 7 and Comparative Examples 2 to 4 and 6 were allowed to stand for 1 month at room temperature, no whitening of the molded product surface was confirmed, and a good appearance was maintained. On the other hand, in the molded products obtained in Comparative Examples 1 and 5, whitening was confirmed about 3 days after molding, and the molded products became opaque.

  The thermoplastic polyurethanes of Examples 1 to 7 have higher solidification properties and excellent moldability than Comparative Examples 2 to 4 and 6. Moreover, the injection molded products of Examples 1 to 7 have a small amount of Taber wear and are excellent in wear resistance.

Example 8
In a 200 mL glass separable flask equipped with a magnetic stirrer and a cooling tube, 50 g (0.05 mol) of POH-1 and 22.2 g (0.10 mol) of isophorone diisocyanate (IPDI) were placed under normal pressure. It heated at 80 degreeC under nitrogen atmosphere, and was made to react for 3 hours, and the urethane prepolymer was obtained. Into a glass separable flask having an internal volume of 500 mL equipped with a magnetic stirrer, a condenser and a dropping funnel, 8.14 g of isophoronediamine, 0.33 g of dibutylamine, 100 mL of ethyl acetate, and 100 mL of 2-propanol were added at normal pressure. The mixture was heated to 50 ° C. in a nitrogen atmosphere, and the prepolymer obtained above was added dropwise. After completion of the addition, the mixture was further reacted at 50 ° C. for 3 hours to obtain a polyurethane solution having a solid content concentration of 32%. The obtained polyurethane solution was applied on glass so as to have a film thickness of 100 μm using a bar coater, and dried at 80 ° C. to obtain a polyurethane coating film. The obtained coating film had a total light transmittance of 91.6, a diffuse transmittance of 3.0, and a haze of 3.3.

[Examples 9 to 15]
Except that POH-2 to POH-8 were used as the polymer polyol, the same operation as in Example 8 was performed to evaluate the polyurethane coating film. The results are shown in Table 3.

[Comparative Examples 7-9]
The same operation as in Example 8 was performed except that POH-9, 13 or POH-15 was used as the polymer polyol. The obtained polyurethane did not enter a solution state with ethyl acetate / 2-propanol (solid content 30%), but solidified at room temperature. The obtained solvent-containing polyurethane resin was melted at 60 ° C. and applied on glass to a film thickness of 100 μm. The obtained coating film was confirmed to be whitened and had a high haze value.

  The thermoplastic polyurethane of the present invention is a molded product such as a sheet, a film, an elastic fiber, a binder, an adhesive, a roll (paper feed roll, etc.), a belt, a squeegee, a copying machine cleaning blade, a snow plow, a chain, a lining, and a screen. , Gears, casters, tires, hoses, tubes, packing materials, anti-vibration materials, vibration-damping materials, shoe soles, sports shoes, caulking materials, synthetic leather, machine parts, automobile parts, etc.

Claims (4)

A thermoplastic polyurethane obtained by polymerizing a polymer polyol (A) having a number average molecular weight of 500 to 5,000, an organic diisocyanate (B), and a chain extender (C),
The polycarboxylic acid unit constituting the polymer polyol (A) is a mixture of a sebacic acid unit and a polycarboxylic acid unit having 9 or less carbon atoms, and the mixture ratio is a sebacic acid unit / carbon number 9 or less as a molar ratio. Polycarboxylic acid unit = 60 / 40-100 / 0,
The diol unit constituting the polymer polyol (A) is a mixture of a 1,3-propanediol unit and a diol unit having an alkyl branch, and the mixture ratio is 1,3-propanediol unit / A thermoplastic polyurethane, wherein the diol unit having an alkyl branch is 50/50 to 97/3.   The diol unit having an alkyl branch which is a diol unit constituting the polymer polyol (A) is 3-methyl-1,5-pentanediol, 2-methyl-1,3-propanediol, 2-methyl-1, The thermoplastic polyurethane according to claim 1, which is derived from at least one diol selected from the group consisting of 8-octanediol and 2-methyl-1,4-butanediol.   The thermoplastic polyurethane according to claim 1 or 2, wherein a polycarboxylic acid unit having 9 or less carbon atoms, which is a polycarboxylic acid unit constituting the polymer polyol (A), is derived from adipic acid.   The thermoplastic polyurethane according to any one of claims 1 to 3, wherein the crystallization enthalpy (ΔH) of the polymer polyol (A) is from 30 to 79 J / g.