Novel polyurethanes and molded article comprising the same

Abstract: The present invention provides a polyurethane comprising a polyester diol component, an organic diisocyanate component and a chain extender component, 30 mole % or more of dicarboxylic acid units constituting said polyester diol being units from 3,8-dimethyldecanedioic acid unit and/or units from 3,7-dimethyldecanedioic acid unit, said polyester diol having a number-average molecular weight of 500 to 6000; a molded article comprising the same; a polyurethane fiber comprising the same; and said polyester diol. The present invention provides a process for producing a dimethyldecanedioic acid represented by the general formula (II) HOOC-CH 2 -CH(CH 3 )-CH 2 -CH 2 -CH 2 -CH(A)-CH(B)-CH 2 -COOH wherein either of A and B represents a methyl group and the rest represents a hydrogen atom, which comprises oxidizing a dimethyldecanedial represented by the general formula (I) OHC-CH 2 -CH(CH 3 )-CH 2 -CH 2 -CH 2 -CH(A)-CH(B)-CH 2 -CHO wherein either of A and B represents a methyl group and the rest represents a hydrogen atom. The present invention provides a dimethyldecanedial represented by the general formula (I). Furthermore, the present invention provides a process for producing a dimethyldecanedial represented by the general formula (I), comprising hydroformylating a diolefin represented by the general formula (III) CH 2 =C(CH 3 )-CH 2 -CH 2 -CH 2 -CH(A)-CH(B)=CH 2 wherein either of A and B represents a methyl group and the rest represents a hydrogen atom. The polyurethane of the present invention is superior in various properties such as resistance to hydrolysis, heat resistance, resistance to hot water, cold resistance, fungal resistance and mechanical performances e.g., strength at break and elongation at break, as well as injection moldability. The polyurethane fiber of the present invention is superior in heat resistance, resistance to hot water, cold resistance and resistance to hydrolysis, and is dyeable under high-temperature and high-pressure conditions. Furthermore, it is superior, after dyeing, in tensile strength and elongation, elastic recovery, fungal resistance, resistance to chlorine and color fastness. The dimethyldecanedial of the present invention is useful as a raw material of production of the dimethyldecanedioic acid represented by the general formula (II). Furthermore, the polyester diol containing the dimethyldecanedioic acid as a dicarboxylic acid component, shows excellent resistance to hydrolysis and is useful as a raw material for producing high-performance polyurethanes.

Description: The present invention relates to a polyurethane and a molded article comprising the same. The polyurethane of the present invention is superior in various properties such as resistance to hydrolysis, heat resistance, resistance to hot water, cold resistance, fungal resistance and mechanical performances, as well as in injection moldability, and hence useful as a material for various molded articles. The present invention also relates to a polyurethane fiber which is superior in heat resistance, resistance to hot water, cold resistance and resistance to hydrolysis and, dyeable at a high temperature and pressure. The polyurethane fiber of the present invention is usable in combination with other fibers such as polyester fiber which require high-temperature and high-pressure conditions for dyeing. Furthermore, the present invention relates to a polyester diol, containing a dimethyldecanedioic acid as a dicarboxylic acid component, which shows excellent resistance to hydrolysis and is useful as raw material for producing high-performance polyurethanes. Polyurethanes have high elasticity besides many advantageous characteristics such as excellent wear and abrasion resistance, and oil resistance, and have hence been watched as replacement of rubber and plastics and hitherto used for a wide variety of end uses. As polyurethanes, polyether-based polyurethanes, polyester-based polyurethanes and polycarbonate-based polyurethanes are hitherto known. These polyurethanes are widely used as a material of fibers, sheets, films, adhesives, coating agents and the like. Among these conventional polyurethanes, the polyether-based ones are superior in resistance to hydrolysis, but inferior in resistance to light, resistance to heat aging and resistance to chlorine. The polyester-based polyurethanes are superior in mechanical characteristics and wear and abrasion resistance in comparison with the polyether-based ones, but are inferior in resistance to hydrolysis and fungal resistance. Use of the polyester-based polyurethanes is limited because the surface thereof becomes adhesive or cracks within a relatively short period of time. The polycarbonate-based polyurethanes are superior, besides the above advantages of the polyester-based ones, in durability, but inferior in cold resistance, and are extremely expensive. In order to improve the resistance to hydrolysis of the polyester-based polyurethanes, it is considered to be effective to decrease the concentration of ester group of the polyester diol used for producing the polyurethanes and the following polyurethanes hitherto are proposed for this purpose: (1) a polyurethane using a polyester diol, as raw material, obtained by using hexamethylene glycol and 1,10-decanediol (see JP-A-60-173117/1985); (2) a polyurethane using, as raw material, a polyester diol comprising 2,2,4- or 2,4,4-trimethylhexanediol and adipic acid (see JP-A-47-713/1972); (3) a polyurethane using, as raw material, a polyester diol obtained by using 2,5-hexanediol or 2,2-dimethyl-1,3-propanediol (see US-A-3,097,192); and (4) a polyurethane using (2,2-dimethyl-1,3-propanedodecanedioate) glycol (see JP-A-63-97617/1988). In order to improve the resistance to hydrolysis of polyester-based polyurethanes, it is attempted to use a polyester diol as raw material of polyurethane, which contains branched dicarboxylic acid units having one methyl side-chain. For example, the following polyurethanes are proposed: (5) a polyurethane using a polyester diol, as raw material, obtained by reacting a dicarboxylic acid containing 3-methylpentanedioic acid and a glycol (see JP-A-60-26018/1985); and (6) a polyurethane using a polyester diol as raw material containing 10 mole % or more of 2-methyloctanedioic acid of total dicarboxylic acid units (see JP-A-5-320302/1993). However, as to the polyurethanes described in (1) through (4), the resistance to hydrolysis is improved, but the cold resistance and low temperature characteristics such as flex resistance and flexibility extremely decrease upon standing in low-temperature atmosphere because these polyurethanes strongly tend to crystallize. Among these, the polyurethane described in (1) obtained by using a diol with linear long chain further has the disadvantage of low elastic recovery. Further, the polyurethanes described in (2) through (4) using a diol with two or three methyl groups as side-chain are disadvantageous in heat resistance, elastic recovery and cold resistance. Compared with conventional polyurethanes, the polyurethanes described in (5) and (6) are improved in resistance to hydrolysis but only to an insufficient level, and the cold resistance, heat resistance and injection moldability thereof are also considered to be at insufficient level for practical purposes. Furthermore, compared with conventional polyurethane fibers, polyurethane fibers described in (5) and (6) are improved in heat resistance, resistance to hot water, elastic recovery, and cold resistance, which is not yet sufficient in practice. Therefore, it is difficult that these polyurethane fibers are used in combination with polyester fiber and the like, and are dyed stably and industrially with disperse dye under high-temperature and high-pressure conditions. Furthermore, it is hard to say that the tensile strength and elongation, elastic recovery resistance to chlorine, color fastness and the like of these polyurethanes after dyeing are sufficient for practical purposes. In addition to the compositions discussed above, EP-A-271 789 discloses polyurethanes comprising polyols on the basis of 2-methyl-1,5-pentanediol, 2-ethyl-1,4 butanediol, 2-methyldicarboxylic derivatives. It is an object of the present invention to provide a polyurethane which is superior in various properties such as resistance to hydrolysis, heat resistance, resistance to hot water, cold resistance, fungal resistance and mechanical performance, as well as in injection moldability, and hence useful as a material for various molded articles; and a molded article comprising said polyurethane. Another object of the present invention is to provide a polyurethane fiber which has excellent heat resistance, resistance to hot water, resistance to hydrolysis and like properties, is dyeable under high- temperature and high-pressure conditions and, after dyeing, superior in tensile strength and elongation, elastic recovery, fungal resistance, resistance to chlorine and color fastness. Still another object of the present invention is to provide a polyester diol which is useful as raw material of polyurethanes. A still further object of the present invention is to provide novel dimethyldecanedials which can economically give 3,8- or 3,7-dimethyldecanedioic acid and a process for producing the same. The present invention provides a polyurethane comprising a polyester diol component, an organic diisocyanate component and a chain extender component, said polyurethane comprising 30 mole % or more of dicarboxylic acid units constituting said polyester diol being units from 3,8- and/or 3,7-dimethyldecanedioic acid units, and said polyester diol having a number-average molecular weight of 500 to 6000. The present invention also provides a molded article and polyurethane fiber, each comprising said polyurethane. The present invention further provides a polyester diol, 30 mole % or more of dicarboxylic acid units constituting said polyester diol being units from 3,8- and/or 3,7-dimethyldecanedioic acid units, and said polyester diol having a number-average molecular weight of 500 to 6000. The dimethyldecanedioic acids represented by the general formula (II) used in the present invention may be produced via a process comprising oxidizing dimethyldecanedials represented by the general formula (I); OHC-CH 2 -CH(CH 3 )-CH 2 -CH 2 -CH 2 -CH(A)-CH(B)-CH 2 -CHO wherein either of A and B represents a methyl group and the rest represents a hydrogen atom, HOOC-CH 2 -CH(CH 3 )-CH 2 -CH 2 -CH 2 -CH(A)-CH(B)-CH 2 -COOH wherein either of A and B represents a methyl group and the rest represents a hydrogen atom. The dimethyldecanedial represented by the general formula (I) may be produced by a process comprising hydroformylation of a diolefin represented by the general formula (III). CH 2 =C(CH 3 )-CH 2 -CH 2 -CH 2 -CH(A)-C(B)=CH 2 wherein either of A and B represents a methyl group and the rest represents a hydrogen atom. The polyurethane of the present invention is markedly superior in various properties e.g., resistance to hydrolysis, heat resistance, resistance to hot water, cold resistance, fungal resistance, and mechanical performance such as tensile strength, elongation at break, and is excellent in injection moldability as well. The polyurethane fiber of the present invention is superior in heat resistance, resistance to hot water, cold resistance and resistance to hydrolysis, and is dyeable under high-temperature and high-pressure conditions. This fiber is also excellent in tensile strength and elongation after dyeing, elastic recovery, fungal resistance and resistance to chlorine. The dimethyldecanedials of general formula (I) are useful as raw material for producing the dimethyldecanedioic acids represented by the general formula (II). The polyester diol containing the dimethyldecanedioic acids as dicarboxylic acid component shows excellent resistance to hydrolysis and is useful as the raw material for producing the high- performance polyurethanes. The dimethyldecanedials represented by the general formula (I) can be produced by hydroformylation of a diolefin represented by the general formula (III). Namely, 3,8-dimethyldecanedial represented by the general formula (I) with A=H and B=Me can be produced by hydroformylation of 2,7-dimethyl-1,7-octadiene represented by the general formula (III) with A=H and B=Me using a mixed gas of carbon monoxide and hydrogen in the presence of a catalyst, and 3,7-dimethyldecanedial represented by the general formula (I) with A=Me and B=H can be produced, in the same way as the above, from 2,6-dimethyl-1,7-octadiene represented by the general formula (III) with A=Me and B=H. 2,7-Dimethyl-1,7-octadiene and 2,6-dimethyl-1,7-octadiene are produced from isoprene, a formic acid salt and water by action of a palladium catalyst (see JP-B-41576/1987 and JP-A-157521/1980, respectively). As the catalyst for the reaction to produce the dimethyldecanedials represented by the general formula (I), any one having catalytic action for the reaction of olefin, carbon monoxide and hydrogen, that is, hydroformylation of olefin is usable, but these containing an element belonging to the groups 8, 9 or 10 (VIII) of the periodic table or a combination thereof with a phosphorus compound or nitrogen compound are suitable. Among these, those comprising a rhodium compound and phosphorus compound are particularly suitable. As the above rhodium compound, any one having catalytic activity for hydroformylation or being capable of gaining the catalytic activity through an activation treatment within the reactor of hydroformylation can be used. Examples thereof include inorganic salts such as rhodium oxide, rhodium chloride and rhodium bromide; carboxylic acid salts such as rhodium acetate and rhodium propionate; chelate compounds such as rhodium acetylacetonate; carbonyl compounds such as Rh 4 (CO) 12 , [Rh(CO) 2 Cl] 2 and Rh(CO) 2 (CH 3 COCHCOCH 3 ); and metals such as Rh/C, Rh/silica, Rh/alumina and Rh black. The amounts used of these compounds, which vary depending on the kind and amount of the phosphorus compound used, or on the reaction conditions, are in a range of from 0.005 to 5 mg-atom /liter, preferably in a range of from 0.1 to 0.5 mg-atom/liter in terms of a concentration of rhodium atom in a reaction mixture. As the phosphorus compound used in combination with the above rhodium compound, any one capable of increasing the catalytic activity and/or improving a catalyst life in comparison with the case of the single use of the rhodium compound is usable, and examples thereof includes phosphines such as tributylphosphine, tricyclohexylphosphine, triphenylphosphine, tri(o-tolyl)phosphine, sodium m-diphenylphosphinobenzenesulfonate, diphenylphosphinoethane, diphenylphosphinopropane, and diphenylphosphinobutane; and phosphites such as triethyl phosphite, trimethylolpropane phosphite, triphenyl phosphite, tri(o-tolyl) phosphite, tri(2-t-butylphenyl) phosphite, and tris(2,6-di-t-butylphenyl) phosphite. The amounts used of these organic phosphorus compounds are in a range of from 1 to 1000 mole per 1 g-atom of rhodium, preferably in a range of from 10 to 500 mole per 1 g-atom of rhodium and particularly preferably in a range of from 50 to 300 mole per 1 g-atom of rhodium. The reaction to produce the dimethyldecanedials represented by the general formula (I) is preferably conducted at a temperature ranging from 60 to 150°C, especially from 90 to 130°C. When the reaction temperature is lower than 60°C, the rate of the reaction becomes low; and when it exceeds 150°C, maintenance of the catalytic stability tends to become difficult. The reaction pressure, which depends on a reaction temperature, is preferably in a range of from 10 to 150 bar, especially in a range of from 60 to 120 bar. When the reaction pressure is lower than 10 bar, the reaction rate and the selectivity may be lowered. Although there is no specific upper limit on the reaction pressure, pressures below 150 bar are industrially preferable to conduct the reaction in view of reaction apparatus and operatability. The ratio between the carbon monoxide and hydrogen used in the reaction is preferably in a range of carbon monoxide/hydrogen = 1/3 to 3/1 as the molar ratio of the gases fed to the reaction vessel. Gases inert to the hydroformylation may coexist. A solvent is not always necessary to use for the reaction but may be used unless it does not affect the hydroformylation. Examples of usable solvents include hydrocarbons such as hexane, cyclohexane, benzene, toluene, and xylene; ethers such as dibutyl ether, tetrahydrofuran, dioxane, ethylene glycol dimethyl ether and polyethylene glycol dimethyl ether; esters such as methyl acetate, ethyl acetate, and butyl acetate; alcohols such as ethanol, isopropyl alcohol, n-butanol, t-butanol, ethylene glycol, diethylene glycol and polyethylene glycol; amides such as N,N-dimethylformamide and N-methylpyrrolidone; and sulfur-containing compounds such as dimethyl sulfoxide and sulfolane. The amount of the solvent used is arbitrary but, in view of capacity efficiency, amounts less than 50 parts by weight based on that of the raw material olefin represented by the general formula (III) are suitable. The reaction can be conducted either batchwise or continuously. When conducted batchwise, either of the following procedures is adoptable; a procedure comprising charging catalyst components, the diolefin represented by the general formula (III) and a solvent if necessary, followed by pressurizing with a mixed gas of carbon monoxide and hydrogen, and then reacting at a prescribed temperature; or a procedure comprising feeding catalytic components and a solvent to the reaction vessel followed by pressurizing with carbon monoxide and hydrogen and raising a temperature, and then feeding the diolefin represented by the general formula (III) or if necessary a mixture thereof with a solvent. The reaction can be conducted to a conversion of either 100 % or less. After the reaction, carbon monoxide and hydrogen are purged, if necessary the solvent is recovered by distillation and then the dimethyldecanedials represented by the general formula (I) are obtainable through purification means such as distillation, film evaporation, steam distillation or extraction. The catalyst components separated through a purification process are reusable. From the dimethyldecanedials thus obtained, represented by the general formula (I), the dimethyldecanedioic acids represented by the general formula (II) can be produced by oxidation. This can be conducted by any usual method known for conversion of aldehyde to carboxylic acid, e.g., oxidation with oxygen in the presence of a metal salt as a catalyst. The dimethyldecanedials represented by the general formula (I) can be subjected to the above oxidation either after or without purification by means mentioned above. As the catalyst of the reaction to produce the dimethyldecanedioic acids represented by the general formula (II) from the dimethyldecanedials represented by the general formula (I), there can be used transition metals such as copper, cobalt, manganese and iron; their halides such as chlorides, bromides and iodides; carboxylic acid salts such as acetic acid salts, propionic acid salts and 2-ethylhexanoic acid salts; and diketone complexes such as acetylacetonate. These metals or metal salts are usable singly or in combination of two or more, and the metal salts may be in either hydrous or anhydrous form. The amount used of these catalysts, which varies depending on the reaction conditions, is in a range of from 0.1 to 1000 ppm, preferably in a range of from 1 to 100 ppm in terms of the concentration of the metal atom in the reaction mixture. The reaction need not always use a solvent, but the solvent can be used so long as it is inert to the oxidation. The usable solvents are, for example, carboxylic acids such as acetic acid and propionic acid; and water. They are usable singly or in combination of two or more. The amount used of solvent is arbitrary but, in view of capacity efficiency, amounts not more than 50 parts by weight based on that of the dimethyldecanedials represented by the general formula (I) as raw material are suitable. It is preferable to conduct the oxidation of the dimethyldecanedials represented by the general formula (I) at a temperature ranging from 10 to 100°C, especially from 30 to 80°C, which also depends on the melting point of the reaction mixture. When the reaction temperature is lower than 30°C, the reaction rate becomes low; and when it exceeds 80°C, control of the reaction tends to become difficult. The oxidation reaction can be conducted in oxygen or a mixture thereof with an inert gas, such as air. It is industrially advantageous to use air. There is no particular upper limit on the reaction pressure, but it is preferable to conduct the reaction at a pressure lower than 50 bar especially 10 bar in view of the reaction apparatus and safety. The reaction can be conducted either batchwise or continuously. When conducted batchwise, the following procedures are adoptable: a procedure comprising charging the catalyst, the dimethyldecanedials represented by the general formula (I) and a solvent if necessary, and then conducting the reaction at a prescribed temperature and pressure in the presence of oxygen or the mixture of oxygen and the inert gas, such as air; or a procedure comprising, while maintaining the reaction vessel charged with the catalyst and a solvent, at a prescribed temperature and pressure in the presence of oxygen or a mixture of oxygen and an inert gas, such as air, feeding thereto the dimethyldecanedials represented by the general formula (I) singly or if necessary as a mixture thereof with the solvent. In either of the procedures, oxygen or a mixture of oxygen and an inert gas may be used either as a whole batch or in a continuous flow. The oxidation reaction is conductable to a conversion of either 100 % or less. After the reaction, the dimethyldecanedioic acids represented by the general formula (II) are obtainable through a procedure comprising purging the gas in the system, if necessary followed by distilling the solvent to recover, and then purification by means of crystallization, distillation, film evaporation, steam distillation, extraction or the like. The polyester diol of the present invention substantially comprises diol units and dicarboxylic acid units. The content of 3,8-dimethyldecanedioic acid units and/or 3,7-dimethyldecanedioic acid units in the dicarboxylic acid units constituting the polyester diol of the present invention is necessarily at least 30 mole %, preferably at least 50 mole % and more preferably at least 80 mole %. When the content of 3,8-dimethyldecanedioic acid units and/or 3,7-dimethyldecanedioic acid units is less than 30 mole % of the dicarboxylic acid units constituting the polyester diol, the obtained polyurethane is inferior in resistance to hydrolysis, fungal resistance, resistance to hot water and cold resistance, which is not preferable. The ratio of 3,8-dimethyldecanedioic acid units and 3,7-dimethyldecanedioic acid units (molar ratio) is not specifically limited, but in view of resistance to hydrolysis, fungal resistance and resistance to hot water of the obtained polyurethane, the ratio is preferably in a range of from 50:50 to 100:0, more preferably in a range of from 70:30 to 100:0. As the dicarboxylic acid units constituting the polyester diol, there may be contained units other than 3,8-dimethyldecanedioic acid units or 3,7-dimethyldecanedioic acid units and derived from e.g., saturated aliphatic dicarboxylic acids such as glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid and sebacic acid; saturated alicyclic dicarboxylic acids such as cyclohexane dicarboxylic acid; aromatic dicarboxylic acids such as phthalic acid, terephthalic acid and isophthalic acid; unsaturated aliphatic dicarboxylic acids such as maleic acid, fumaric acid and itaconic acid; halogen-containing dicarboxylic acids such as tetrabromophthalic acid; or units derived from ester forming derivatives of the foregoing, such as esters and anhydrides thereof. These components may be contained singly or in combination of two or more, provided that the content thereof is less than 70 mole % based on that of the total carboxylic acid units constituting the polyester diol. Furthermore, if necessary, units derived from a polybasic acid having three or more functionalities, such as trimellitic acid and pyromellitic acid may be contained in a small amount. Examples of diol units constituting the polyester diol are aliphatic diols such as ethylene glycol, propylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, neopentyl glycol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 3-methyl-1,5-pentanediol and 2-methyl-1,8-octanediol; and alicyclic diols such as cyclohexanedimethanol and cyclohexanediol. These units may be contained singly or in combination of two or more. It is preferable that units from 1,4-butanediol be contained in an amount of at least 30 mole %, more preferably at least 50 mole % and further more preferably at least 80 mole % of total diol units constituting the polyester diol, since the solidification rate of the resulting polyurethane when molded becomes fast, and the heat resistance and resistance to hot water are excellent. If necessary, units derived from a polyalcohol such as trimethylolethane, trimethylolpropane, glycerine, 1,2,6-hexatriol and pentaerythritol may also be contained in a small amount. The number average molecular weight of the polyester diol is in a range of from 500 to 6000, preferably in a range of from 1000 to 4000 and more preferably in a range of from 1000 to 3500. When the number average molecular weight is less than 500, the heat resistance, resistance to hot water and moldability of obtained polyurethane may be lowered; while the number average molecular weight exceeds 6000, the tensile elongation, elastic recovery, injection moldability and like properties of the obtained polyurethane may become inferior, which is not preferable. The number average molecular weight herein is calculated based on the hydroxyl group value determined in accordance with JIS K 1577. The polyester diol is produced by polycondensation of the carboxylic acid component and diol component described above through hitherto known ester exchange reaction, direct esterification or the like. The polycondensation can be conducted in the presence of a titanium-based or tin-based polycondensation catalyst. When the titanium-based polycondensation catalyst is used, it is preferable to deactivate the catalyst contained in the polyester diol after the reaction. When the titanium-based polycondensation catalyst is used to produce the polyester diol, any of the titanium-based polycondensation catalysts hitherto used for production of polyester diols can be used with no specific limitation, and examples of preferred titanium-based polycondensation catalyst include titanium acid, tetraalkoxy titanium compounds, titanium acylate compounds, and titanium chelate compounds. More specifically, tetraalkoxy compounds such as tetraisopropyl titanate, tetra-n-butyl titanate, tetra-2-ethylhexyl titanate; and tetrastearyl titanate, titanium acylate compounds such as polyhydroxy titanium stearate and polyisopropoxy titanium stearate; and titanium chelate compounds such as titanium acetylacetonate, triethanolamine titanate, titanium ammonium lactate, titanium ethyllactate and titanium octylene glycolate can be used. The amount used of the titanium-based polycondensation catalyst, which can be suitably controlled according to intended polyester diol, the quality of the polyurethane produced therefrom etc., and is not specifically limited, is generally preferably in a range of from about 0.1 to about 50 ppm based on total weight of reacting components to form the polyester diol, more preferably in a range of from about 1 to about 30 ppm on the same basis. Deactivation of the titanium-based polycondensation catalyst contained in the polyester diol is achieved through, for example, a process which comprises contacting the polyester diol, after completion of esterification, with hot water with heating and a process which comprises treating the polyester diol, with a phosphorus compound such as phosphoric acid, a phosphoric acid ester, phosphorous acid or a phosphorous acid ester. In the case of contacting the catalyst with hot water, it is recommended to add 1 weight % or more of water to the polyester diol obtained through the esterification reaction, and then heating the mixture at a temperature ranging from 70 to 150°C, preferably ranging from 90 to 130°C, for 1 to 3 hours. The deactivation treatment of the titanium-based polycondensation catalyst may be conducted under either an atmospheric pressure or a pressurized condition. It is preferable to reduce the pressure of the system after deactivation of the catalyst, because the water used for deactivation can be removed. When the polyurethane of the present invention is produced, if necessary a polymer diol other than the polyester diol, such as polycarbonate diol may be used in a small amount. There is no specific limitation to the type of the organic diisocyanate used for producing the polyurethane of the present invention, and any organic diisocyanate hitherto used for producing the usual polyurethanes is usable. The organic diisocyanate used preferably has a molecular weight of not higher than 500. Examples of the organic diisocyanates include aromatic diisocyanates such as 4,4'-diphenylmethane diisocyanate, p-phenylene diisocyanate, tolylene diisocyanate, 1,5-naphthalene diisocyanate, 3,3'-dichloro-4,4'-diphenylmethane diisocyanate and xylylene diisocyanate, and aliphatic and alicyclic diisocyanates such as hexamethylene diisocyanate, isophorone diisocyanate, 4,4'-dicyclohexylmethane diisocyanate and hydrogenated xylylene diisocyanate. These diisocyanates may be used singly or in combination. Use of 4,4'-diphenylmethane diisocyanate or p-phenylene diisocyanate is particularly preferred. Furthermore, if necessary, polyisocyanates having 3 or more functionalities, such as triphenylmethane triisocyanate are usable in a small amount. As the chain extender used for producing the polyurethane of the present invention, any chain extender hitherto used for producing the usual polyurethanes is usable, with no specific limitation, but use of a low-molecular-weight-compound having a molecular weight of not more than 300 and having at least two hydrogen atoms reactive with isocyanate group is preferable. Examples of preferred chain extenders are diols such as ethylene glycol, 1,4-butanediol, 1,6-hexanediol, 1,4-bis(β-hydroxyethoxy)benzene, 1,4-cyclohexanediol, bis(β-hydroxyethyl)terephthalate and xylylene glycol; diamines such as hydrazine, ethylenediamine, propylenediamine, xylylenediamine, isophorone diamine, piperazine, a piperazine derivative, phenylenediamine, tolylenediamine, adipic dihydrazide and isophthalic dihydrazide; and amino alcohols such as aminoethyl alcohol and aminopropyl alcohol. These compounds may be used singly or in combination of 2 or more. Among these, 1,4-butanediol, 1,4-bis(β-hydroxyethoxy)benzene, ethylenediamine or propylenediamine is preferable. The amount used of the chain extender is not specifically limited and is suitably selected depending on a hardness and like properties to be given to the polyurethane, but usually, it is preferable to use the chain extender in a ratio ranging from 0.1 to 10 mole per mole of the polyester diol, especially preferable in a ratio ranging from 0.3 to 7 mole per mole of the polyester diol. In the production of the polyurethane, it is recommended to use an organic diisocyanate in such an amount as to permit the ratio between the equivalents of isocyanate groups present in the organic diisocyanate and the equivalent of active hydrogen atoms present in the polyester diol, chain extender and other polymer diol used if necessary, to fall preferably within a range of from 0.90 to 1.20, more preferably within a range from 0.95 to 1.15. By use of the organic diisocyanate in such a ratio, the resulting polyurethane becomes especially superior in heat resistance and elastic recovery. When the polyurethane is produced by using the above polyester diol, organic diisocyanate, chain extender and if necessary other components, a tin-based urethanization catalyst having catalytic activity for urethanization can be used. When the tin-based urethanization catalyst is used, therefore, the molecular weight of the resulting polyurethane increases rapidly, and the polyurethane becomes excellent in various physical properties, because the molecular weight of the polyurethane is maintained in a sufficiently high level even after molding. Examples of the tin-based urethanization catalyst include dialkyltin dialkylates such as dibutyltin diacetate and dibutyltin dilaurate; and dialkyltin bismercaptocarboxylic acid ester salts such as dibutyltin bis(3-mercaptopropionic acid ethoxybutyl ester)salt. The amount of these tin-based urethanization catalysts used is preferably in a range of from 0.5 to 15 ppm in terms of tin atom, based on the obtained polyurethane (that is, total weight of all reactive raw compounds such as the polyester diol, organic diisocyanate and chain extender used for producing the polyurethane). If necessary, there may be added suitably during or after polymerization of the polyurethane, 1 or more of additives such as coloring agent, lubricant, crystallization nucleus agent, flame retardant, ultra-violet absorber, antioxidant, weatherability improver, hydrolysis preventing agent, tackifier and mildew-proofing agent. There are no specific restrictions with respect to the process for producing the polyurethane and known urethanization processes using the above polyester diol, organic diisocyanate, chain extender and, as necessary, other components are usable with either one of the prepolymer process and one-shot process. Examples of the process for producing the polyurethane include 1 ○ one which comprises mixing a polyester diol and low-molecular-weight compound (chain extender) having active hydrogen atoms, heating the mixture, adding an organic diisocyanate to the mixture, stirring the resulting mixture for a short period of time and then heating the mixture to obtain the polyurethane; 2 ○ one which comprises mixing the polyester diol, chain extender and organic diisocyanate, and kneading the mixture at a high temperature (e.g., from 180 to 260°C) to obtain the polyurethane; 3 ○ one which comprises continuously feeding the polyester diol, chain extender and organic diisocyanate to an extruder such as multi-screw extruder and subjecting the resulting mixture to a continuous melt-polymerization at a high temperature (e.g., from 180 to 260°C) to obtain the polyurethane; and 4 ○ one which comprising reacting the polyester diol, chain extender and organic diisocyanate to form the polyurethane, in an organic solvent (e.g., dimethylformamide, dimethylacetamide, dimethyl sulfoxide, tetrahydrofuran, toluene, methyl ethyl ketone, ethyl acetate, isopropanol, ethyl cellosolve and N-methylpyrrolidone). Naturally, it is not required to use these processes limitedly. Among the above processes for producing the polyurethane, the processes of 1 ○ through 3 ○ above, which comprise melt-polymerizing the polyester diol, chain extender and organic diisocyanate with substantially no solvent are preferable, especially continuous meltpolymerization of 3 ○ above using a multi-screw extruder is preferable. The inherent viscosity of the polyurethane of the present invention, as determined at 30°C by measurement on 0.5 g/dl polyurethane solution in N,N-dimethylformamide solution containing 0.05 mole/l of n-butylamine is preferably in a range of from 0.3 to 2.0 dl/g, more preferably in a range of from 0.5 to 2.0 dl/g, still more preferably in a range of from 0.8 to 2.0 dl/g, and most preferably in a range of from 1.0 to 2.0 dl/g. The polyurethane having an inherent viscosity of 0.3 to 2.0 dl/g is superior in mechanical performances, resistance to hydrolysis, heat resistance, elastic recovery, cold resistance and like properties. The polyurethane of the present invention, which is superior in various properties such as resistance to hydrolysis, heat resistance, resistance to hot water, cold resistance, fungal resistance and mechanical performances, as well as in injection moldability, is useful as a material for a wide variety of end uses such as sheets, films, squeeze, chains, belts, screens, cleaning blade for copier, various rolls, gears, casters, solid tires, hoses, tubes, packings, vibration insulators, vibration dampers, shoe soles, sports shoes, machine parts, automobile parts, sporting goods, fibers, artificial leathers, fiber treatments, adhesives, coating agents, binders and paints. As a process for producing the polyurethane fiber of the present invention by using the above polyurethane, any of hitherto known processes for producing polyurethane fibers such as dry spinning, wet spinning or melt spinning is adoptable. Preferable spinning process is, for example, (A) a process which comprises producing a polyurethane by melt-polymerizing polyester diol, chain extender and organic diisocyanate containing substantially no solvent through a multi-screw extruder or the like and directly extruding the resultant polyurethane through a spinning nozzle directly connected to the multi-screw, into filaments; and (B) a process which comprises producing a polyurethane through melt polymerization, pelletizing the polyurethane and then melt-spinning the pellet into filaments. In view of spinning stability, etc., the process of (A) is especially preferred. When the polyurethane fiber is produced through melt spinning, it is preferable to set the spinning temperature not higher than 250°C, in particular between 200 and 235°C. The polyurethane fiber of the present invention is usable as either neat fiber as it is or as covered yarn covered with a hitherto known fiber such as polyamide fiber, wool, cotton or polyester fiber. In general, in order to dye polyester fiber and like fibers, the use of a disperse dye, and a high temperature of 110°C or more and a high pressure are required. Therefore, it is difficult to dye under high-temperature and high-pressure conditions, conventional polyurethane fibers having only poor heat resistance and resistance to hot water together with polyester fiber and the like used in combination therewith. On the other hand, the polyurethane fiber of the present invention is dyeable under high-temperature and high-pressure conditions due to superior heat resistance and resistance to hot water and hence dyeable even after being processed by mixing with other fibers such as polyester fiber, by the use of disperse dye workable only at a high temperature as e.g. 110 to 130°C and a high pressure. Furthermore, the polyurethane fiber of the present invention maintains superior tensile strength and elongation, elastic recovery and like properties even after dyeing. Through dyeing with a conventional disperse dye under high-temperature and high-pressure, the polyurethane fiber of the present invention becomes colored to the same degree as that of other fibers like polyester fiber used mixedly therewith and is improved in the visual indistinguishability, color reproducibility and color fastness. Example of disperse dye used in this case are quinone-type and azo-type disperse dyes. After being dyed with a disperse dye, it is preferable to conduct reduction cleaning to accelerate fixing of the dye. Examples of end uses of the polyurethane fiber of the present invention include clothing such as swimsuits, skiwears, cycling wears, leotards, lingeries, foundation garments, underwears, panty hoses, stockings; clothing miscellaneous such as supporters, caps, gloves, power nets and bandages; and non-clothing such as gut for tennis racket, ground thread for integrally molded car seat, metal-covered yarn for robot arm, bands for packaging and conveyor belts. EXAMPLES Other features of the invention will become more apparent in the course of the following descriptions of exemplary embodiments which are given for illustration of the invention and are not intended to be limiting thereof. In the Examples and Comparative Examples that follow, the following methods were used to determine the number average molecular weight and resistance to hydrolysis of the polyester diol; inherent viscosity, resistance to hydrolysis, heat resistance, cold resistance, mechanical performance and injection moldability of the polyurethane; and the inherent viscosity, tensile strength and elongation, elastic recovery, resistance to hydrolysis, resistance to hot water, cold resistance, color fastness, tensile strength and elongation after dyeing, elastic recovery and resistance to chlorine of the polyurethane fiber. [Number average molecular weight of polyester diol] JIS K 1577 is applied to determine the hydroxyl group value, from which the molecular weight is calculated. [Resistance to hydrolysis of polyester diol] A polyester diol sample is immersed in hot water of 100 °C for 10 days, and then the acid value is determined to evaluate resistance to hydrolysis. [Inherent viscosity of polyurethane or the fiber thereof] A polyurethane or its fiber sample is dissolved in a concentration of 0.5 g/dl in N,N-dimethylformamide solution containing n-butylamine in a concentration of 0.05 mole/l, and then the resultant solution is subjected to observation for a time of fall with Ubbelohde viscometer, from which the viscosity is calculated as follows: Inherent viscosity = {ln(t/t 0 )}/c wherein t (sec) is the time of fall of the polyurethane solution, t 0 (sec) is the time of fall of the solvent and c (g/dl) is the concentration of the polyurethane. [Resistance to hydrolysis of polyurethane] Specimens prepared from a 2-mm thick polyurethane sample sheet are immersed in hot water of 100°C for 10 days, and the strengths at break of the films before and after the immersion are compared with each other to obtain retention ratio, by which resistance to hydrolysis is evaluated. [Heat resistance of polyurethane] Specimens prepared from a 2-mm thick polyurethane sheet are tested for dynamic viscoelasticity at a frequency of 11 Hz with DVE Rheospectra (produced by Rheology Co., Ltd.). The terminal temperature on the high-temperature side of rubber-like plateau of the dynamic storage elastic modulus is taken as an index of heat resistance. [Cold resistance of polyurethane] Specimens prepared from a 2-mm thick polyurethane sheet are tested for dynamic viscoelasticity at a frequency of 11 Hz with DVE Rheospectra (produced by Rheology Co., Ltd.) to determine a temperature (Tα ) at which the dynamic elasticity loss (E'') reaches the maximum. The cold resistance is evaluated by Tα . [Mechanical performances of polyurethane] The procedure defined in JIS K 7311 is applied. That is, a 2-mm thick polyurethane sample sheet is obtained by injection molding and dumbbell-shaped test specimens are prepared therefrom. The specimens are tested for tensile strength and elongation at break at an extension rate of 30 cm/min, to evaluate dynamic performance. [Injection moldability of polyurethane] Injection molding is conducted with varying molding cycle time (injection time + cooling time), and the obtained molded articles are tested for determining the molding cycle time at which no sinkmark and deformation are caused, to evaluate injection moldability. [Tensile strength and elongation of polyurethane fiber] JIS L 1013 is applied. [Resistance to hydrolysis of polyurethane fiber] A polyurethane fiber sample of 40 dr is allowed to stand under the condition of a natural length at 70°C, 95% RH for 35 days. The fiber is tested for tensile strength at break before and after this exposure. Resistance to hydrolysis is evaluated by the retention ratio of the strengths before and after the exposure. [Cold resistance of polyurethane fiber] 33 to 37 mg of a polyurethane fiber sample of 60 mm long is evenly arranged so as to be 1-mm thick and 5-mm wide and bonded at both ends with an adhesive to prepare sample specimen. The specimens are tested for dynamic viscoelasticity at a frequency of 11 Hz with DVE Rheospectra (produced by Rheology Co., Ltd.) to determine a temperature (Tα ) at which the dynamic elasticity loss (E'') reaches the maximum. The cold resistance is evaluated in terms of Tα. [Color fastness] Color fastness to washing: JIS L 0844A2 is applied. Color fastness to water : JIS L 0846B is applied. Color fastness to perspiration: JIS L 0848A is applied. Color fastness to light: JIS L 0842 the third method for exposure to light is applied. Color fastness to chlorine: JIS L 0856 is applied. The higher the grades of these tests, the more superior the color fastness of the fiber. The abbreviations of the compounds used in the following Examples and Comparative examples are shown below. (Abbreviation) (Name of compound) 3,8-DMSA 3,8-dimethyldecanedioic acid 3,7-DMSA 3,7-dimethyldecanedioic acid AD adipic acid SB sebacic acid AZ azelaic acid DDA dodecanedioic acid MPA 3-methylpentanedioic acid MOA 2-methyloctanedioic acid BD 1,4-butanediol PD 1,3-propanediol HD 1,6-hexanediol MPD 3-methyl-1,5-pentanediol ND 1,9-nonanediol MOD 2-methyl-1,8-octanediol NPG neopentyl glycol DD 1,10-decanediol HPD 1,7-heptanediol MDI 4,4'-diphenylmethane diisocyanate Example 1 A 5-l pressure reaction vessel was charged with a solution comprising 83.3 mg of Rh(CO) 2 (CH 3 COCHCOCH 3 ), 20.87 g of tris(2,6-di-t-butylphenyl) phosphite and 500 ml of benzene, and the vessel was pressurized to 80 bar with a mixed gas of carbon monoxide/hydrogen (1/1). After the temperature had been elevated to 100°C, 2.05 kg of 2,7-dimethyl-1,7-octadiene was fed thereto over a period of 5 hours, during which the pressure was maintained at 80 bar. After completion of the feed, the reaction was continued for further 5 hours at the same temperature and pressure. The reaction vessel was cooled and then the gas therein was purged. The reaction mixture was taken out and distilled to remove benzene under a reduced pressure. The resultant residue was purified by distillation to give 3,8-dimethyldecanedial as a colorless clear liquid having a boiling point of 77 to 78°C at 0.27 hPa. The yield was 56% (1.64 kg). Analytical data used for structural determination are shown below. NMR (CDCl 3 solvent): δ 0.96 (d, 6H); 1.29 (brs, 8H); 2.05 (m, 2H); 2.18∼ 2.45 (m, 4H); 9.85 (t, 2H) IR: ν 2,970∼ 2,850; 2,730; 1,725; 1,460; 1,380; 1,015 cm -1 GC-MS: m/z (relative intensity) 71 (100), 41 (74), 55 (74), 81 (62), 69 (60), 43 (40),95 (37). Example 2 A 5-l pressure reaction vessel was charged with 0.19 g of Cu(OCOCH 3 ) 2 (H 2 O) and 1.5 l of acetic acid, and the vessel was pressurized to 7 bar with air and then warmed to 50°C. While air was flown into at a rate of 240 l/hr, the mixture of 750 g of 3,8-dimethyldecanedial and 750 ml of acetic acid was fed thereto over a period of 3 hours. After completion of the feed, the reaction was conducted for an additional 4 hours at the same temperature and pressure. The reaction vessel was cooled, the gas therein was purged and then the reaction mixture was taken out. This mixture was heated at 110 °C for 1 hour under nitrogen atmosphere. The acetic acid was distilled off under a reduced pressure and the residue was recrystallized twice repeatedly from a mixed solvent of acetic acid/water (1/1), to yield 449 g of 3,8-dimethyldecanedioic acid as a white solid having a melting point of 76.5 to 77.5°C. Additionally, the mother liquid was distilled to remove acetic acid and water, and then recrystallized in the same manner as above to obtain 99 g of 3,8-dimethyldecanedioic acid. The total yield of these acid portions was 63%. Data of instrumental analysis are shown below. NMR (CDCl 3 solvent): δ 0.97 (d, 6H), 1.28 (brs, 8H); 1.96 (m,2H); 2.09 ∼ 2.38 (m, 4H); 10.4 (br) IR (Nujol): ν 1,700 cm -1 FAB-MS: m/z (relative intensity) 231 (100), 213 (100). Example 3 A 5-l pressure reaction vessel was charged with a solution comprising 83.3 mg of Rh(CO) 2 (CH 3 COCHCOCH 3 ), 20.87 g of tris(2,6-di-t-butylphenyl) phosphite and 500 ml of benzene, and the vessel was pressurized to 90 bar with a mixed gas of carbon monoxide/hydrogen (1/1). After the temperature had been elevated to 100°C, 2.05 kg of 2,6-dimethyl-1,7-octadiene was added over a period of 5 hours, during which the pressure was maintained at 90 bar. After completion of the feed, the reaction was continued for further 5 hours at the same temperature and pressure. The reaction vessel was cooled and then the gas therein was purged. The reaction mixture was taken out and then benzene was distilled off under vacuum. The residue was subjected to simple distillation to remove the catalytic components. The resulting distillate was rectified to give 3,7-dimethyldecanedial as an almost colorless liquid having a boiling point of 99 to 100°C at 1.13 hPa. The yield was 41% (1.20 kg). Analytical data used for structural determination are shown below. NMR (CDCl 3 solvent): δ 0.89 (d, 3H); 0.95 (d, 3H); 1.10∼ 1.50 (m, 8H); 1.65 (m, 1H); 2.04 (m, 1H); 2.19∼ 2.47 (m, 4H); 9.85 (m, 2H) IR: ν 2,960∼ 2,850; 2,720; 1,720; 1,455; 1,375 cm -1 GC-MS: m/z (relative intensity) 41 (100), 55 (100), 71 (75), 81 (73), 95 (63), 154 (3), 165 (2). Example 4 A 5-l pressure reaction vessel was charged with 0.19 g of Cu(OCOCH 3 ) 2 (H 2 O) and 1.5 l of acetic acid, and the vessel was pressurized to 7 atm with air and then warmed to 50°C. While air was flown into at a rate of 240 l/hr, a mixture of 750 g of 3,7-dimethyldecanedial and 750 ml of acetic acid was fed thereto over a period of 3 hours. After completion of the feed, the reaction was conducted for an additional 6 hours at the same temperature and pressure. The reaction vessel was cooled, the gas therein was purged and then the reaction mixture was taken out. This mixture was heated at 110°C for 1 hour under nitrogen atmosphere. The acetic acid was distilled off under a reduced pressure and the residual liquid was distilled to give 3,7-dimethyldecanedioic acid as an almost colorless clear liquid having a boiling point of 175 to 180°C at 1.06 hPa. The yield was 61% (435 g). Instrumental-analysis data are shown below. NMR (CDCl 3 solvent): δ 0.89 (d, 3H); 0.97 (d, 3H); 1.08∼ 1.50 (m, 8H); 1.68 (m, 1H); 1.95 (m, 1H); 2.10∼ 2.42 (m, 4H); 11.4 (br, 2H) IR: ν 3,000∼ 2,850; 2,730; 1,720∼ 1,700; 1,280; 1,220; 930 cm -1 Examples 5 through 7 A 100-ml pressure reaction vessel was charged with 1.3 mg of Rh(CO) 2 (CH 3 COCHCOCH 3 ), 324 mg of tris(2,6-di-t-butylphenyl) phosphite, 20 ml of each of solvents described in Table 1 and 20.0 g of each of dimethyloctadienes represented by the general formula (III) with A and B shown in Table 1, and the vessel was pressurized to 80 atm with a mixed gas of carbon monoxide/hydrogen (1/1). Each of the reaction mixtures was heated to a temperature shown in Table 1, respectively and then heated at the same temperature for 6 hours with stirring while the pressure thereof was maintained at 80 bar. The reaction vessel was cooled and then the gas therein was purged. The reaction mixture taken out was subjected to gas chromatographic analysis. The results show that each dimethyldecanedial represented by the general formula (I) with A and B shown in Table 1 is formed in a yield described in Table 1. Example Dimethyloctadiene Solvent Temperature (°C) Dimethyldecanedial yield (%) A B 5 H CH 3 isopropyl alcohol 120 51 6 H CH 3 toluene 100 70 7 CH 3 H benzene 120 45 Examples 8 through 11 A 100-ml pressure reaction vessel was charged with 3.5 mg of each one of the metal salts described in Table 2 and 20 ml of acetic acid, and the vessel was pressurized with air to 7 bar, and then heated to a temperature of 50°C. A mixture of 10 g of each of dimethyldecanedials represented by the general formula (I) with A and B shown in Table 2 and 20 g of acetic acid was fed thereto over a period of 20 minutes, while air was flown into at a rate of 5 l/hr. After completion of the feed, the reaction was allowed to continue for additional 6 hours at the same temperature and pressure. After the reaction vessel had been cooled, the gas therein was purged and then the reaction mixture was taken out. An aliquot of the reaction mixture was esterified and then the resulting mixture was analyzed by gas chromatography, affording a result showing the formation of the dimethyldecanedioic acids represented by the general formula (II) in a yield as shown in Table 2. Example Dimethyldecanedial Metal salt Dimethyldecanedioic acid yield (%) A B 8 H CH 3 copper acetate 85 9 H CH 3 cobalt acetate 80 10 H CH 3 iron acetate 63 11 CH 3 H manganese acetate 55 Example 12 6900g of 3,8-dimethyldecanedioic acid and 3240 g of 1,4-butanediol were fed to a reaction vessel and then esterified at 200 °C and atmospheric pressure, while the water that formed was removed out of the system. When the acid value of the reaction mixture became not higher than 30, 134 mg of tetraisopropyl titanate was added thereto and the reaction was allowed to continue while a reduced pressure of 266 to 133 hPa was maintained. When the acid value reached 1.0, the pressure of the system is further reduced gradually with a vacuum pump, the reaction was completed. After that, the reaction mixture was cooled to 100°C, 180 g of water was added thereto, the mixture was heated with stirring at this temperature for 2 hours to deactivate the titanium-based polycondensation catalyst. Then the water therein was distilled off under a reduced pressure. In this way, a polyester diol having a number average molecular weight of 1980, hydroxyl group number of 56.7 and acid value of 0.01 was obtained (hereinafter, referred as to polyester diol A). As shown in Table 3, the test results for resistance to hydrolysis of the polyester diol A are very superior. Examples 13 through 22 Polyester diols B through K were obtained by esterification followed by deactivation of the titanium-based polycondensation catalyst, in the same manner as in Example 12 except that the corresponding dicarboxylic acid component and diol component described in Table 3 were used. As shown in Table 3, the test results for the polyester diols obtained from Examples 13 through 22 are very good. Comparative examples 1 through 8 Polyester diols L through S were obtained by esterification followed by deactivation of the titanium-based catalyst in the same way as in Example 12 except that the corresponding dicarboxylic acid component and diol component described in Table 3 were used. Each of the test results with respect to the resistance to hydrolysis of the polyester diols L through S is inferior in comparison with those for the polyester diols A through K obtained in Examples 12 through 22. When the polyester diols A through D (Examples 12 through 15) and those Q through S (Comparative examples 6 through 8) are compared, it is understood that the reason why the polyester diol of the present invention is superior in resistance to hydrolysis is not the low concentration of the ester group alone, because ratios of acid-value-increment of the polyester diols A through D are not more than a half of those of the polyester diols Q through S. Examples 23 through 33 Continuous melt polymerization was conducted by feeding continuously through metering pumps to a same-direction twin-screw extruder (30 mm⊘ , L/D = 36 , set temperature: 200 ∼ 250°C) each of the polyester diols A through K obtained in Examples 12 through 22, 1,4-butanediol, and 4,4'-diphenylmethane diisocyanate heat melted at 50°C, in such amounts as to make the molar ratio (polyester diol:1,4-butanediol:4,4'-diphenylmethane diisocyanate) 1:2:3 and at a total rate of 300 g/min. The obtained melts of a thermoplastic polyurethane were extruded into water to form a strand, which was then cut with a pelletizer into pellets. The pellets thus obtained were dried at 80°C for 20 hours. With these dry pellets, injection moldability at 200°C was evaluated. Further, with 2-mm thick polyurethane sheets prepared by the injection molding at 200°C, the inherent viscosity, resistance to hydrolysis, heat resistance, cold resistance and mechanical performance (strength at break and elongation at break) were tested. The results are shown in Table 4. Comparative examples 9 through 16 Continuous melt polymerization was conducted by feeding continuously through metering pumps to a same-direction twin-screw extruder (30 mm⊘ , L/D = 36 , set temperature: 200 ∼ 250°C) each of the polyester diols L through S obtained in Comparative examples 1 through 8, 1,4-butanediol, and 4,4'-diphenylmethane diisocyanate heat melted at 50°C, in such amounts as to make the molar ratio (polyester diol:1,4-butanediol:4,4'-diphenylmethane diisocyanate) 1:2:3 and at a total rate of 300 g/min. The obtained melts of a thermoplastic polyurethane were extruded into water to form a strand, which was then cut with a pelletizer into pellets. The pellets thus obtained were dried at 80°C for 20 hours. With these dry pellets, injection moldability at 200°C was evaluated. Further, with 2-mm thick polyurethane sheets prepared by the injection molding at 200°C, the inherent viscosity, resistance to hydrolysis, heat resistance, cold resistance and mechanical performance (strength at break and elongation at break) were tested. The results are shown in Table 4. As clearly shown from the results given in Table 4, compared with the polyurethanes of Comparative examples 9 through 16, the polyurethanes of Examples 23 through 33 using the polyester diols A through K, which contain 30 mole % or more of 3,8-dimethyldecanedioic acid unit and/or 3,7-dimethyldecanedioic acid unit in the dicarboxylic acid units, are not only very excellent in resistance to hydrolysis but also excellent in heat resistance, cold resistance and injection moldability without spoiling dynamic performance such as strength at break and elongation at break. It is understood that the polyurethanes using, particularly, a polyester diol containing 1,4-butanediol as a diol component are more superior in heat resistance and injection moldability. In the case of the polyurethane of Comparative Example 9, which uses the polyester diol containing only 20 mole % of 3,8-dimethyldecanedioic acid units in the dicarboxylic acid units, the mechanical performances such as strength at break and elongation at break are almost in the same level as those of the polyurethanes of Example 23 through 33. However, the resistance to hydrolysis, heat resistance, cold resistance and injection moldability are inferior when compared with these of Examples 23 through 33. Compared with the polyurethanes of Examples 23 through 33, the polyurethanes (Comparative examples 15 and 16) obtained by using the polyester diols which contain a branched dicarboxylic acid component (3-methylpentanedioic acid unit or 2-methyloctanedioic acid unit) in the same concentration of ester groups as those of the polyester diols A through D are inferior in resistance to hydrolysis, heat resistance, cold resistance and injection moldability. Examples 34 through 38 Continuous melt polymerization was conducted by feeding continuously, through metering pumps to a same-direction twin-screw extruder (30 mm⊘ , L/D = 36 , set temperature: 200 ∼ 250°C), each of the polyester diols A, C, D, J and K obtained in Examples 12, 14, 15, 21 and 22, 1,4-butanediol, and 4,4'-diphenylmethane diisocyanate heat melted at 50°C, in such amounts as to make the molar ratio (polyester diol:1,4-butanediol:4,4'-diphenylmethane diisocyanate) 1:2:3.09 and at a total rate of 300 g/min. The formed polyurethane is fed as it is to a spinning machine and spun at a spinning temperature of 220°C, a dew point of cooling wind of 10°C and a spinning speed of 500 m/min, to give a polyurethane yarn of 40 denier/1 filament. The yarn thus obtained was aged at 90°C for 12 hours under a humidity of dew point of -30°C, further continuously aged at 25°C for 3 days under a humidity of 50%, and then tested for physical properties. The results are shown in Table 6. Furthermore, the polyurethane fiber obtained above was knitted into knit fabric with a circular knitting machine (gauge 20). The knit fabric was dyed under conditions as described in Table 5. The dyed knit fabric was washed thoroughly with water, dried and then tested for color fastness and physical properties. The results are shown in Table 7. dyeing conditions [scouring under relaxation] at 80°C for 1 minute. [dyeing] Dyeing machine: Drum type dyeing machine 2.0% owf Composition of dyeing agent: Dye: Sumikaron Red-E-RPD (quinone-type, made by Sumitomo Chemical Co., Ltd.) Dispersion assistant: Disper TL (manufactured by Meisei Chemical Co., Ltd.) 1 g/liter pH regulator: ammonium sulfate 1 g/liter acetic acid 1 g/liter Bath ratio: 1:30 Dyeing temperature: Temperature elevated from 40°C to 130°C over 30 minutes and kept at this temperature for another 30 minutes [Reduction cleaning] Reduction liquor composition: soda hydrosulfite 3 g/liter soda ash 2 g/liter Amiladin (made by Dai-Ichi Kogyo Seiyaku Co., Ltd.) 1 g/liter Bath ratio: 1:30 Cleaning Temperature: 80°C for 20 minutes Example Raw material of polyurethane Physical properties of polyurethane fiber Polyester diol (molar ratio) Organic diisocyanate (molar ratio) Chain extender visco(molar ratio) Inherent sity (dl/g) Tensile strength (g/d) Elongation (%) Resistance to hydrolysis (%) Cold resistance Tα (°C) Example 34 A (1) MDI (3.09) BD (2) 1.23 1.7 490 92 -46 35 C (1) MDI (3.09) BD (2) 1.20 1.5 500 90 -46 36 D (1) MDI (3.09) BD (2) 1.18 1.4 480 89 -46 37 J (1) MDI (3.09) BD (2) 1.19 1.6 490 85 -42 38 K (1) MDI (3.09) BD (2) 1.15 1.3 470 84 -42 Comparative example 17 L (1) MDI (3.09) BD (2) 1.22 1.5 460 54 -35 18 M (1) MDI (3.09) BD (2) 1.16 1.4 490 32 -34 19 Q (1) MDI (3.09) BD (2) 1.10 1.3 380 70 10 20 R (1) MDI (3.09) BD (2) 1.11 1.4 410 76 -23 21 S (1) MDI (3.09) BD (2) 1.17 1.5 420 68 -26 Example Color fastness of polyurethane fiber to Physical properties of polyurethane fiber after dyeing Washing (class) Water (class) Perspiration (class) Light (class) Chlorine (class) Resistance to chlorine (%) Example 34 4∼5 4∼5 4∼5 4∼5 4∼5 99 35 4∼5 4∼5 4∼5 4∼5 4∼5 98 36 4∼5 4∼5 4∼5 4∼5 4∼5 98 37 4∼5 4∼5 4∼5 4∼5 4∼5 97 38 4∼5 4∼5 4∼5 4∼5 4∼5 96 Comparative example 17 2∼3 2∼3 2∼3 3 3 40 18 2 2 2 2 2 - 19 3∼4 3∼4 3∼4 3∼4 3∼4 75 20 3∼4 3∼4 3∼4 3∼4 3∼4 82 21 3∼4 3∼4 3∼4 3∼4 3∼4 76 Comparative Examples 17 through 21 Polyurethane fibers were produced in the same manner as in Examples 34 through 38 except for using each of the polyester diols L, M, Q, R and S obtained in Comparative examples 1, 2, 6, 7 and 8 as the polyester diol, and the fibers thus obtained were tested for physical properties. The results are shown in Table 6. Furthermore, after dyeing, washing with water and drying in the same manner as in Examples 34 through 38, the physical properties of the polyester fiber after dyeing were tested. The results are shown in Table 7. As clearly seen in Tables 6 and Table 7, compared with the polyurethane fibers of Comparative examples 17 through 21, the polyurethane fibers of Examples 34 through 38 using the polyester diols A, C, D, J and K, which contain 30 mole % or more of 3,8-dimethyldecanedioic acid units and/or 3,7-dimethyldecanedioic acid units in the dicarboxylic acid units, are excellent not only in resistance to hydrolysis but also in cold resistance without spoiling the mechanical performances such as strength and elongation. Further, the color fastnesses of the polyurethane fibers of the present invention are all Class 4 to 5, clearing Class 3 which is generally required for clothing, and therefore excellent. In addition, the physical properties of the polyurethane fiber after dyeing are also superior. In the case of the polyurethane fiber of Comparative Example 17 which uses the polyester diol L containing only 20 mole % of 3,8-dimethyldecanedioic acid units in the dicarboxylic acid units, the strength and elongation is almost at the same level as those of the polyurethane fibers of Examples 34 through 38, but the resistance to hydrolysis is inferior when compared with those of Examples 34 through 38. Furthermore, the color fastness and physical properties of the polyurethane fibers after dyeing are also inferior. Compared with the polyester fibers of Examples 34 through 38, the polyurethane fiber of Comparative example 18 which uses the polyester diol M having a high ester-group-concentration is not only extremely inferior in resistance to hydrolysis, but also inferior in cold resistance. Furthermore, the physical properties of the polyurethane after dyeing are very inferior. Compared with the polyurethane fibers of Examples 33 through 38, the polyurethane fiber of Comparative Example 19, which uses the polyester diol Q having the same ester group concentration as those of the polyesters A, C, D, J and K, is somewhat inferior in resistance to hydrolysis, and also inferior in cold resistance and elongation. Furthermore, the physical properties of the polyester after dyeing are also inferior. Compared with the polyurethane fibers of Example 34 through 38, the polyurethane fiber of Comparative Examples 20 or 21 which uses the polyester diol R or S containing the dicarboxylic acid unit having single methyl-branch (3-methylpentanedioic acid unit or 2-methyloctanedioic acid unit) is inferior in cold resistance, elongation and resistance to hydrolysis. Furthermore, the physical properties of the polyurethane fiber after dyeing are also inferior.

Claims: A polyurethane comprising a polyester diol component, an organic diisocyanate component and a chain extender component, at least 30 mole % of dicarboxylic acid units that constitute said polyester diol being units from 3,8-dimethyldecanedioic acid and/or units from 3,7-dimethyldecanedioic acid, and the number-average molecular weight of said polyester diol being in a range from 500 to 6000. The polyurethane according to Claim 1, wherein 30 mole % or more of diol units constituting the polyester diol are units from 1,4-butanediol. The polyurethane according to either Claim 1 or Claim 2, having an inherent viscosity of 0.3 to 2.0 dl/g. A molded article comprising the polyurethane according to any one of Claim 1 through Claim 3. A polyurethane fiber, comprising the polyurethane according to any one of Claim 1 through Claim 3. A polyester diol, 30 mole % or more of a dicarboxylic acid units that constitute said polyester diol being 3,8-dimethyldecanedioic acid units and/or 3,7-dimethyldecanedioic acid units, said polyester diol having a number average molecular weight of 500 to 6000. The polyester diol according to Claim 6, wherein 30 mole % or more of diol units constituting the polyester diol are units from 1,4-butanediol.

Inventors: HIRAI KOJI, ISHIGURO MICHIHIRO, NAKAYAMA KIMIO, OSHITA TATUYA, SUZUKI SHIGEAKI, YOSHIMURA NORIAKI, HIRAI, KOJI, ISHIGURO, MICHIHIRO, NAKAYAMA, KIMIO, OSHITA, TATUYA, SUZUKI, SHIGEAKI, YOSHIMURA, NORIAKI, Hirai, Koji, c/o Kuraray Co, Ltd., Ishiguro, Michihiro, c/o Kuraray Co, Ltd., Nakayama, Kimio, c/o Kuraray Co, Ltd., Oshita, Tatuya, c/o Kuraray Co, Ltd., Suzuki, Shigeaki, c/o Kuraray Co, Ltd., Yoshimura, Noriaki, c/o Kuraray Co, Ltd.
Applicants: KURARAY CO, KURARAY CO., LTD.
Application year: 1995
Main classification: C07C47
IPC codes: C07C51, C08G63, C08G18, C07C47, C07C45