JP3308369B2 - Polyurethane and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyurethane and a method for producing the same, and a method for producing molded articles or fibers using the polyurethane. In detail, even if the melt molding or melt spinning is performed continuously for a long time, the appearance of the product is excellent with very few fish eyes and bumps in the obtained molded product or fiber, and the yarn breakage during spinning, Polyurethane capable of continuously producing high-quality molded products and fibers with good processability for a long time without causing operation defects of a melt molding device or a melt spinning device, and a method for producing the same, and using such a polyurethane This is a method for producing molded articles or fibers, and the polyurethane of the present invention can be produced by using a specific polymer diol and a chain extender.

[0002]

2. Description of the Related Art Thermoplastic polyurethanes are used in a wide range of fields because of their excellent elastic properties and abrasion resistance.
2. Description of the Related Art Molded articles such as tubes and pipes, various molded articles obtained by injection molding and the like, and elastic fibers obtained by melt-spinning are effectively used in various applications due to their excellent properties. Thermoplastic polyurethane is generally obtained by simultaneously or sequentially reacting an organic diisocyanate with a polymer diol, a chain extender, and the like.
Taking advantage of the property of thermoplasticity, molding or spinning is often performed using a single-screw or multi-screw type melt extrusion molding machine, melt injection molding machine, melt spinning device, or the like.

[0003] However, when polyurethane is subjected to melt molding or melt spinning for a long period of time, a large number of transparent, translucent, white, etc. fish eyes and spots are generated on molded articles and fibers obtained over time. However, there has been a problem that the appearance of molded articles and fibers becomes rough and becomes extremely poor. In addition, when performing melt molding or melt spinning for a long time, such fish eyes and buttocks occur frequently,
Occasionally, the operation of the melt-forming apparatus or the melt-spinning apparatus itself may be poor, and there is a problem that the fibers frequently break during melt-spinning and the spinning processability is reduced.

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method for performing melt molding and melt spinning continuously for a long time.
The object is to provide a polyurethane which does not generate fish eyes or bumps which impair the appearance of molded articles and fibers, and which does not cause breakage during melt spinning, operation failure of a melt molding device or melt spinning device, and the like. It is an object of the present invention to provide a method for producing such a polyurethane. Further, an object of the present invention is to perform melt molding or melt spinning using the above-mentioned polyurethane which does not increase fish eyes or lumps, to smoothly produce molded articles and fibers having excellent properties such as appearance and mechanical strength. Is to provide a way to

[0005]

As a result of various studies by the present inventors, a polymer diol mainly composed of polytetramethylene ether glycol, 1,4-butanediol and a specific alkylene When a chain extender containing diol and a specific ratio is reacted, the number of fish eyes and spots hardly increases even when melt molding and melt spinning are performed continuously for a long time, and the mechanical properties are excellent. The present invention was completed by finding that a thermoplastic polyurethane was obtained.

That is, the present invention relates to a polyurethane obtained by reacting an organic diisocyanate, a polymer diol mainly composed of polytetramethylene ether glycol having a number average molecular weight of 500 to 3,000 and a chain extender, Is 1,4-butanediol and the following formula (I):

[0007]

Embedded image HO— (CH ₂ ) m—C (R) (H) — (CH ₂ ) n—OH (I) (wherein R is a hydrogen atom or a methyl group, and m and n are each one or more An integer, wherein the sum of m and n is 4 to 10
And the molar ratio of {1,4-butanediol} in the chain extender: {diol represented by the above formula (I)} is 97: 3 to 7
0: 30 and a nitrogen atom content of 4.0% by weight or more.

The present invention relates to a method for producing a polyurethane by reacting an organic diisocyanate, a polymer diol mainly composed of polytetramethylene ether glycol having a number average molecular weight of 500 to 3,000, and a chain extender, comprising the steps of: As an agent, 1,4-butanediol and the following formula (I);

[0009]

Embedded image HO— (CH ₂ ) m—C (R) (H) — (CH ₂ ) n—OH (I) (wherein R is a hydrogen atom or a methyl group, and m and n are each one or more An integer, wherein the sum of m and n is 4 to 10
And the molar ratio of {1,4-butanediol} in the chain extender: {diol represented by the above formula (I)} is 97: 3 to 7
A process for producing a polyurethane, characterized by using a chain extender having a ratio of 0:30.

Further, the present invention is a method for producing a molded article or fiber by performing melt molding or melt spinning using the above polyurethane.

According to the present invention, one of the active hydrogen-containing raw material compounds for polyurethane has a number average molecular weight of 500-3.
Use is made of a high molecular weight diol consisting mainly of 000, preferably 800-2000, polytetramethylene ether glycol. The polymer diol used in the present invention preferably contains polytetramethylene ether glycol having a number-average molecular weight of 500 to 3,000 in an amount of 40 mol% or more based on the total amount of the polymer diol, and 60 mol% or more,
More preferably, it is more preferably 70 to 100 mol%. If the number average molecular weight of the polytetramethylene ether glycol, which is the main component of the high molecular diol, is less than 500, the polyurethane obtained therefrom will have reduced cold resistance and impact resistance and become brittle, while if it has a number average molecular weight greater than 3,000, it will be less brittle. The moldability of the resulting polyurethane decreases.

Examples of other high molecular weight diols which can be used together with polytetramethylene ether glycol having a number average molecular weight of 500 to 3,000, if necessary, usually in a proportion of not more than 60 mol%, are those having a number average molecular weight of from 500 to 3,000. Other polyether glycols such as polytetramethylene ether glycol, polyethylene glycol and polypropylene glycol, polyester diols obtained from aliphatic dicarboxylic acids and aliphatic glycols, obtained from aliphatic dicarboxylic acids, aromatic dicarboxylic acids and aliphatic glycols Polyester diols, polycarbonate diols, and polycaprolactone diols.

In the present invention, 1,4-butanediol and the diol represented by the above formula (I) [hereinafter referred to as “diol (I)”] are mainly used as a chain extender together with the above polymer diol. Is used. In the chain extender used in the present invention, the molar ratio of {1,4-butanediol}: {diol (I)} is 97: 3 to
70:30, 95: 5 to 80:
More preferably, it is 20. Based on the total amount of 1,4-butanediol and diol (I), diol (I)
If the ratio is less than 3 mol%, the resulting molded articles and fibers will have more fish eyes and bumps, while if it exceeds 30 mol%, the resulting molded articles and fibers will have reduced rupture strength and practicality. Disappears or decreases.

Specific examples of the diol (I) used in the present invention include 1,5-pentanediol, 2-methyl-1,
5-pentanediol, 3-methyl-1,5-pentanediol, 1,6-hexanediol, 2-methyl-
1,6-hexanediol, 3-methyl-1,6-hexanediol, 1,7-heptanediol, 2-methyl-1,7-heptanediol, 3-methyl-1,7-heptanediol, 4-methyl -1,7-heptanediol, 1,8-octanediol, 2-methyl-1,8-
Octanediol, 3-methyl-1,8-octanediol, 4-methyl-1,8-octanediol, 1,9
-Nonanediol, 2-methyl-1,9-nonanediol, 3-methyl-1,9-nonanediol, 4-methyl-1,9-nonanediol, 1,10-decanediol, 2-methyl-1,10 -Decanediol, 3-methyl-1,10-decanediol, 4-methyl-1,10
-Decanediol or 5-methyl-1,10-decanediol. The diol (I) may be used alone or in combination of two or more. Among the above-mentioned diols (I), 1,9-nonanediol is preferable in view of the mechanical properties, moldability and low-temperature properties of the polyurethane obtained.

In the present invention, two or more active groups such as a hydroxyl group and an amino group capable of reacting with an isocyanate group may be used as a chain extender together with the above-mentioned 1,4-butanediol and diol (I). If the amount of the bifunctional low molecular weight compound is small (generally 1 to the total amount of the chain extender)
0 mol% or less). Examples of such other bifunctional low molecular weight compounds include ethylene glycol, propylene glycol, hydrazine, ethylenediamine, propylenediamine, xylylenediamine, isophoronediamine, piperazine, phenylenediamine. , Tolylenediamine, adipic dihydrazide, isophthalic dihydrazide and the like. In some cases, a small amount of a low-molecular polyol having three or more functionalities such as glycerin and pentaerythritol may be used.

In the present invention, it is necessary that the polyurethane obtained by reacting the above components has a nitrogen atom content of 4.0% by weight or more, and the nitrogen atom content is 4.3 to 5. It is preferably 0% by weight. In order to obtain a polyurethane having a nitrogen atom content of 4.0% by weight or more, the proportion of the polymer diol mainly composed of polytetramethylene ether glycol having a number average molecular weight of 500 to 3,000 and the above-described chain extender is adjusted. In general, a high molecular weight diol mainly composed of polytetramethylene ether glycol having a number average molecular weight of 500 to 3,000 and the above-mentioned chain extender in a ratio of 1: 1.1 to 1: 8.
When used in a molar ratio of 5, the nitrogen atom content is 4.0% by weight.
The above polyurethane can be obtained. If the nitrogen atom content in the polyurethane is less than 4.0% by weight, the mechanical properties and durability are poor, which is not preferable.

In the present invention, as the organic diisocyanate, any of the organic diisocyanates conventionally used in the production of thermoplastic polyurethanes can be used. Examples of such organic diisocyanates include 4,4'-diphenylmethane diisocyanate, Tolylene diisocyanate, 1,5-naphthylene diisocyanate, xylylene diisocyanate, phenylene diisocyanate,
Aromatic diisocyanates such as 3,3'-dichloro-4,4'-diphenylmethane diisocyanate and toluylene diisocyanate; fats such as hexamethylene diisocyanate, isophorone diisocyanate, 4,4'-dicyclohexylmethane diisocyanate and hydrogenated xylylene diisocyanate Examples thereof include group or alicyclic diisocyanates, and these organic diisocyanates may be used alone or in combination of two or more.

In the production of polyurethane, based on the total amount of active hydrogen atoms (hydrogen atoms capable of reacting with isocyanate) contained in the polymer diol, chain extender and other components, per equivalent of active hydrogen atoms, It is preferable to use the organic diisocyanate so that the isocyanate group equivalent is about 0.9 to 1.5, and it is particularly preferable to use the organic diisocyanate so that the isocyanate group equivalent is about 1.

Depending on the type of the organic diisocyanate to be used, the molecular weight of the polymer diol (particularly polytetramethylene ether glycol), the content (type) and molecular weight of the chain extender, and the proportion used thereof, they are obtained by reacting them. Although the molecular weight and the viscosity of the polyurethane obtained differ, the polyurethane of the present invention has a logarithmic viscosity of 0.5 to 2.0 dl / g when measured at 30 ° C. as a 0.5 g / dl dimethylformamide solution. However, it is preferable in terms of mechanical performance, moldability, durability and the like, and the type and combination of the raw material components, polymerization conditions, and the like may be selected so as to obtain a polyurethane having such a viscosity.

Further, in the present invention, optional components such as a catalyst, a reaction accelerator, an internal mold release agent, a filler, a reinforcing agent, a dye and a pigment, and a stabilizer which are usually used in producing polyurethane are required. Can be used accordingly.

The method for producing the polyurethane of the present invention includes:
Any known urethanation reaction technique can be used, and both the prepolymer method and the one-shot method can be used. To give an example of a method for producing the polyurethane of the present invention,
Polymer diol in single or multi screw extruder,
The chain extender and the organic diisocyanate may be continuously or substantially simultaneously supplied with other components, if necessary, so that 6
A method of producing a polyurethane by continuous melt polymerization at 0 to 280 ° C, preferably 200 to 260 ° C, mixing an active hydrogen-containing compound such as a polymer diol and a chain extender and heating the mixture to 60 to 90 ° C. In which the molar ratio of active hydrogen atoms to isocyanate groups is from 1: 1 to 1
A method of adding an organic diisocyanate in a ratio of 1: 1.5, stirring the mixture for a short time, and then heating the mixture to, for example, 200 to 260 ° C. to produce a polyurethane, extruding an organic diisocyanate and a polymer diol into an extruder or other reaction apparatus A method of producing a polyurethane by reacting a chain extender after preliminarily reacting to form an isocyanate group-terminated prepolymer, a polymer diol, a chain extender, and an organic diisocyanate, if necessary, together with other components in an organic solvent. And a method of producing a polyurethane in an organic solvent by adding to the above, but of course, the method is not limited to these methods. In particular, the above-mentioned method is preferable because the desired polyurethane can be continuously produced very simply by simultaneously or almost simultaneously supplying all of the reaction components to the extruder.

When melt-forming or melt-spinning is carried out using the polyurethane of the present invention, even if the molding or spinning is carried out continuously for a long time, almost no fish eyes or bumps are generated in the molded product or fiber. In addition, there are no breaks during spinning, no operation failure when extruding equipment, injection molding equipment, melt spinning equipment, etc. are operated continuously for a long time, and sheets, films, rolls, and gears with excellent mechanical performance such as breaking strength. Can smoothly manufacture various products such as solid tires, belts, hoses, tubes, packing materials, anti-vibration materials, shoe soles, sports shoes, machine parts, automobile parts, sporting goods, elastic fibers, etc. The inventive polyurethanes are suitable for use in melt extrusion. Hereinafter, the present invention will be described specifically with reference to Examples and the like, but the present invention is not limited thereto.

[0023]

EXAMPLES In the following Examples and Comparative Examples, the nitrogen atom content of polyurethane was measured by the following method.

[0024]Nitrogen atom content of polyurethane (weight
%): Element analyzer (“2400- manufactured by PerkinElmer”)
Type 2 ").

Table 1 below summarizes the abbreviations and contents of the components used in the following Examples and Comparative Examples.

[0026]

[Table 1]

Example 1 (1) Polytetramethylene ether glycol (PT
G1000) 47.4% by weight, 4,4'-diphenylmethane diisocyanate (MDI) 41.2% by weight, 1,9-
At a ratio of 1.9% by weight of nonanediol (ND) and 9.5% by weight of 1,4-butanediol (BD), a twin-screw extruder (L
/ D = 34; φ = 30 mm) continuously at 260 ° C.
To produce a polyurethane. When the nitrogen atom content of the obtained polyurethane was measured by the above method, it was as shown in Table 2 below.

(2) The polyurethane obtained in the above (1) is melt-extruded at a temperature of 210 ° C. using a single screw extruder (L / D = 25, φ = 25 mm) to obtain an outer diameter of 8 mm and an inner diameter of 6 mm.
The tube was continuously extruded for 5 hours, and immediately after the start of steady extrusion (0 hour), 1 hour and 5 hours later, the number of fish eyes per meter on the entire surface of the extruded tube was visually observed. Counted in. Table 2 shows the results.
Shown in (3) Using the polyurethane obtained in the above (1), a 100 μm-thick film is produced by melt extrusion molding at a temperature of 210 ° C., and its breaking strength is measured according to JIS-K7311.
It measured according to. Table 2 shows the results.

Example 2 The same ratio of PTG1000 used in Example 1 as 46.4% by weight, MDI as 41.2% by weight, ND as 4.6% by weight and BD as 7.8% by weight. Then, in the same manner as in (1) of Example 1, the mixture was continuously supplied to a twin-screw extruder and polymerized at 260 ° C. to produce a polyurethane. The nitrogen atom content of the obtained polyurethane was measured by the above method. Table 2 shows the results. The obtained polyurethane was continuously extruded for 5 hours in the same manner as in Example 1 (2) to produce a tube, and the number of fish eyes was counted in the same manner as in Example 1 (2). The results were as shown in Table 2. Using the polyurethane obtained here, a film having a thickness of 100 μm was manufactured by extrusion in the same manner as in (3) of Example 1, and the breaking strength was measured in the same manner. It was as follows.

Example 3 The same proportions of PTG1000 used in Example 1 as 45.7% by weight, MDI as 41.2% by weight, ND as 5.7% by weight and BD as 7.4% by weight. Then, in the same manner as in (1) of Example 1, the mixture was continuously supplied to a twin-screw extruder and polymerized at 260 ° C. to produce a polyurethane. Table 2 shows the nitrogen atom content of the obtained polyurethane measured by the above method. Further, the polyurethane obtained here was continuously extruded for 5 hours in the same manner as in (2) of Example 1 to produce a tube, and the number of fish eyes was determined in the same manner as in (2) of Example 1. The results are shown in Table 2. Further, using the obtained polyurethane, a film having a thickness of 100 μm was produced by extrusion in the same manner as in (3) of Example 1, and the breaking strength was measured in the same manner. It was as follows.

Example 4 46% by weight of polytetramethylene ether glycol (PTG2000) and 4 parts of MDI
Biaxial as in (1) of Example 1 at a ratio of 0.2% by weight, 4.2% by weight of 3-methyl-1,5-pentanediol (MPD) and 9.6% by weight of BD. The mixture was continuously supplied to an extruder and polymerized at 260 ° C. to produce a polyurethane. Table 2 shows the nitrogen atom content of the obtained polyurethane measured by the above method. Also,
The polyurethane obtained here was extruded continuously for 5 hours in the same manner as in (2) of Example 1 to produce a tube.
The number of the fish eyes was counted in the same manner as in (2) of Example 1, and the results were as shown in Table 2. Furthermore,
Using the polyurethane obtained here, a film having a thickness of 100 μm was produced by extrusion in the same manner as in (3) of Example 1, and the breaking strength was measured in the same manner. there were.

Example 5 PTG2000 was 51.5% by weight, MDI was 36.7% by weight, MPD was 4.2% by weight, and BD was 7.6% by weight. In the same manner as described above, the mixture was continuously supplied to a twin-screw extruder and polymerized at 250 ° C. to produce a polyurethane. Table 2 shows the nitrogen atom content of the obtained polyurethane measured by the above method. Further, the polyurethane obtained here was continuously extruded for 5 hours in the same manner as in (2) of Example 1 to produce a tube, and the number of fish eyes was determined in the same manner as in (2) of Example 1. The results are shown in Table 2. Using the polyurethane obtained above, a film having a thickness of 100 μm was produced by extrusion in the same manner as in (3) of Example 1, and the breaking strength was measured in the same manner. there were.

Comparative Example 1 A twin-screw extruder was used in the same manner as in Example 1 (1), except that PTG1000 was 48.6% by weight, MDI was 41.2% by weight, and BD was 10.2% by weight. And polymerized at 250 ° C. to produce a polyurethane. Table 2 shows the nitrogen atom content of the obtained polyurethane measured by the above method. Further, the polyurethane obtained here was continuously extruded for 5 hours in the same manner as in (2) of Example 1 to produce a tube, and the number of fish eyes was determined in the same manner as in (2) of Example 1. The results are shown in Table 2. Further, using the obtained polyurethane, a film having a thickness of 100 μm was produced by extrusion in the same manner as in (3) of Example 1, and the breaking strength was measured in the same manner. As shown in Table 2, Met.

Comparative Example 2 (1) of Example 1 with 39.1% by weight of PTG1000, 41.2% by weight of MDI, 9.4% by weight of ND, and 5.3% by weight of BD In the same manner as described above, the mixture was continuously supplied to a twin-screw extruder and polymerized at 260 ° C. to produce a polyurethane. Table 2 shows the nitrogen atom content of the obtained polyurethane measured by the above method. Further, the polyurethane obtained here was continuously extruded for 5 hours in the same manner as in (2) of Example 1 to produce a tube, and the number of fish eyes was determined in the same manner as in (2) of Example 1. The results are shown in Table 2. Further, using the polyurethane obtained above, a film having a thickness of 100 μm was produced by extrusion in the same manner as in (3) of Example 1, and the breaking strength was measured in the same manner. there were.

Comparative Example 3 54.6% by weight of PTG1000, 37.0% by weight of MDI and 8.4% by weight of BD
, And continuously supplied to a twin-screw extruder in the same manner as in Example 1, (1), and polymerized at 260 ° C to produce a polyurethane. Table 2 shows the nitrogen atom content of the obtained polyurethane measured by the above method. Further, the polyurethane obtained here was continuously extruded for 5 hours in the same manner as in (2) of Example 1 to produce a tube, and the number of fish eyes was determined in the same manner as in (2) of Example 1. I counted Using the polyurethane obtained above, a film having a thickness of 100 μm was produced by extrusion in the same manner as in (3) of Example 1, and the breaking strength was measured in the same manner. there were.

Comparative Example 4 A twin-screw extruder was used in the same manner as (1) of Example 1 except that PTG2000 was 46.0% by weight, MDI was 41.2% by weight, and BD was 12.8% by weight. , And polymerized at 260 ° C. to produce a polyurethane. Table 2 shows the nitrogen atom content of the obtained polyurethane measured by the above method. Further, the polyurethane obtained here was continuously extruded for 5 hours in the same manner as in (2) of Example 1 to produce a tube, and the number of fish eyes was determined in the same manner as in (2) of Example 1. The results are shown in Table 2. Further, using the obtained polyurethane, a film having a thickness of 100 μm was produced by extrusion in the same manner as in (3) of Example 1, and the breaking strength was measured in the same manner. As shown in Table 2, Met.

Comparative Example 5 PTG2000 was 50.8% by weight, MDI was 36.7% by weight, MPD was 7.1% by weight, and BD was 5.4% by weight. In the same manner as described above, the mixture was continuously supplied to a twin-screw extruder and polymerized at 250 ° C. to produce a polyurethane. Table 2 shows the nitrogen atom content of the obtained polyurethane measured by the above method. Further, the polyurethane obtained here was continuously extruded for 5 hours in the same manner as in (2) of Example 1 to produce a tube, and the number of fish eyes was determined in the same manner as in (2) of Example 1. The results are shown in Table 2. Further, using the polyurethane obtained above, a film having a thickness of 100 μm was produced by extrusion in the same manner as in (3) of Example 1, and the breaking strength was measured in the same manner. Met.

[0038]

[Table 2]

From the results shown in Table 2 above, in the case of the polyurethanes obtained in Examples 1 to 5, the number of fish eyes in the molded product (tube) increased with time even after continuous extrusion molding for a long time. Even if it is the same as that at the time of extrusion, it is the same or very little increase, and it is possible to continuously produce a molded article excellent in appearance with very few fish eyes for a long time, and the molded article obtained from the polyurethane has a breaking strength. It is clear that the mechanical properties are excellent.

On the other hand, in the case of the polyurethanes of Comparative Examples 1, 3 and 4 obtained by using only 1,4-butanediol without using diol (I) as a chain extender, The number of fish eyes increases with the lapse of molding time, resulting in a molded article having a rough surface and poor appearance, and both 1,4-butanediol and diol (I) are used as chain extenders. However, Comparative Example 2 and Comparative Example 5 in which the ratio of both was out of the range of the present invention.
In the case of polyurethane, although the number of fish eyes does not increase so much, the breaking strength of the obtained molded product is low,
It turns out that it is not suitable for practical use.

[0041]

When the polyurethane of the present invention is used, even if melt-formed or melt-spun continuously for a long time, the appearance of the product is extremely small since fish eyes and buttocks are extremely low in the obtained molded product or fiber. Is good. Moreover,
High-quality molded products and fibers can be continuously produced with good processability for a long time without causing breakage during spinning or operation failure of the melt-forming apparatus or the melt-spinning apparatus. Further, the polyurethane of the present invention has excellent mechanical properties, and is highly practical.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-4-351619 (JP, A) JP-A-3-17114 (JP, A) JP-A-58-79007 (JP, A) JP-A-6-1994 10211 (JP, A) JP-A-4-255712 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C08G 18/00-18/87 D01F 6/70

Claims (4)

(57) [Claims] 1. A polyurethane obtained by reacting an organic diisocyanate, a polymer diol mainly composed of polytetramethylene ether glycol having a number average molecular weight of 500 to 3,000, and a chain extender, wherein the chain extender is 1,4. - butanediol and the following formula (I); [formula 1] _{HO- (CH 2) m-C} (R) (H) - (CH 2) n-OH (I) ( wherein, R represents a hydrogen atom or The methyl group, m and n are each an integer of 1 or more, and the sum of m and n is 4 to 10
And the molar ratio of {1,4-butanediol} in the chain extender: {diol represented by the above formula (I)} is 97: 3 to 7
0: 30 and a nitrogen atom content of 4.0% by weight or more. 2. An organic diisocyanate is reacted with an active hydrogen atom-containing compound mainly composed of a polymer diol and a chain extender such that the isocyanate group equivalent per equivalent of active hydrogen atom is 0.5 to 1.5. Wherein the molar ratio of {the high molecular diol structural unit mainly composed of polytetramethylene ether glycol}: {the structural unit composed of a chain extender} in the polyurethane is 1: 1.1 to 1 in molar ratio. : 8.5. 3. A method for producing a polyurethane by reacting an organic diisocyanate, a polymer diol mainly composed of polytetramethylene ether glycol having a number average molecular weight of 500 to 3,000 and a chain extender, wherein 1 , 4-butanediol and the following formula:
(I); HO— (CH ₂ ) m—C (R) (H) — (CH ₂ ) n—OH (I) (wherein R is a hydrogen atom or a methyl group, and m and n are Each is an integer of 1 or more, and the sum of m and n is 4 to 10
And the molar ratio of {1,4-butanediol} in the chain extender: {diol represented by the above formula (I)} is 97: 3 to 7
A method for producing a polyurethane, comprising using a chain extender having a ratio of 0:30. 4. A method for producing a molded article or fiber by performing melt molding or melt spinning using the polyurethane according to claim 1 or 2.