WO1999010400A1

WO1999010400A1 - Polyurethane polymers having excellent hydrolytic stability and solvent resistance

Info

Publication number: WO1999010400A1
Application number: PCT/US1998/016881
Authority: WO
Inventors: Wally L. Chang
Original assignee: Witco Corporation
Priority date: 1997-08-26
Filing date: 1998-08-13
Publication date: 1999-03-04

Abstract

Polyurethanes produced by reacting a linear polyester polyol of the formula (I): H-[O-(CH2)x-O-C(=O)-(CH2)m-C(=O)-]nO-(CH2)x-OH, wherein x in each occurrence is 2 - 12, n is 1 - 20, and m is either 10 in each occurrence or is 10 in some occurrences and 4 in all other occurrences, provided that the ratio by weight of -O-C(=O)-(CH2)10-C(=O)O- segments to -O-C(=O)-(CH2)4-C(=O)O- segments is greater than 1, with (a) diphenylmethane diisocyanate to form a prepolymer, and then chain extending the prepolymer with a diol at a mole ratio of NCO:OH groups of 0.8:1 to 1.20:1; or (b) toluene diisocyanate to form a prepolymer, and then chain extending the prepolymer with a diamine at a mole ratio of NCO:NH groups of 0.8:1 to 1.20:1, exhibit high hydrolytic stability and high solvent resistance.

Description

POLYURETHANE POLYMERS HAVING EXCELLENT

HYDROLYTTC STABILITY AND SOLVENT RESISTANCE

Field of the Invention The present invention relates to polyurethane elastomers and thermoplastic polyurethanes (referred to herein as TPUs) having high hydrolytic stability and solvent resistance.

Background of the Invention Polyurethanes are an established type of polymers whose properties and manner of formulation lend themselves well to a variety of applications, such as in the formation of coatings and films, in molding and casting, and other uses. In general, polyurethanes are formed by first reacting a diol or polyol component and a diisocyanate or polyisocyanate component, to form a prepolymer, and thereafter chain extending the prepolymer by reaction with a suitable chain extending reagent such as a diol or diamine. A variety of reactants have been recognized as useful in carrying out these reactions. However, to date little significance has been ascribed to the effect that a particular structure may have on the properties of the polyurethane product. Polyurethanes, like other products, are required to exhibit certain useful properties in order to be useful in the applications to which they may be exposed. One particular property that is essential for many potential uses of polyurethanes is hydrolytic stability, that is, stability against (and resistance to) swelling, distortion, dissolution and/or decomposition upon exposure to water. This property relates directly to the usefulness of the polyurethane as a coating or film which will be exposed to water or dampness, especially in the presence of temperatures above ambient. Another property that is essential for many such potential uses of polyurethanes is solvent resistance, that is, resistance to swelling, distortion, dissolution and/or decomposition upon exposure to solvents. This property, too, relates directly to the usefulness of the polyurethane as a coating or film, and to its usefulness as a cast object which will be exposed to solvents. While polyurethanes are known which are the to exhibit hydrolytic stability and/or solvent resistance, there remains a need for elastomeric polyurethane polymers, and for thermoplastic polyurethanes, which exhibit those properties to a higher extent, while retaining the other useful properties of polyurethanes. The prior art discloses polyurethanes which exhibit certain characteristics as to their structure, but these polyurethanes are not considered elastomeric or thermoplastic and they have other features which distinguish them from those of the present invention. For instance, U.S. Patent No. 5,019,638 (1991) discloses that a reactive hot melt adhesive with a very high setting rate is obtained from the reaction product of polyisocyanate and poly(hexamethylene dodecanedioate) glycol. However, the products disclosed in this patent are adhesives, not polyurethane elastomers or TPU (thermoplastic polyurethanes). Also, this patent does not disclose or suggest the excellent hydrolytic stability or the excellent solvent resistance which is obtained with the polyurethanes of the present invention. U.S. Patent No. 4,871,818 (1989) discloses polyester-based Spandex filament made from a specific polyester polyol, i.e. , poly(neopentyl dodecanedioate) glycol. However, this patent discloses Spandex fibers, not polyurethane elastomer or TPU. Also, this patent discloses the reaction of branched polyester polyol based on neopentyl glycol which is 2,2-dimethyl-l,3-propylene glycol. Japan Kokai 49-121895 (1974) discloses polyurethane products with better hydrolytic resistance using dodecanedioic acid- based polyester but reacted with a specific diisocyanate, i.e. , 1 ,5 -naphthalene diisocyanate.

Brief Summary of the Invention One aspect of the present invention is polyurethanes produced by reacting a polyester polyol of the formula (1):

H-[O-(CH₂)_x-O-C( = O)-(CH₂)_m-C( = O)-]_nO-(CH₂)_x-OH (1)

wherein x in each occurrence is an integer from 2 to 12, n is an integer from 1 to 20, and m is either 10 in each occurrence or is 10 in some occurrences and 4 in all other occurrences, provided that the ratio by weight of -O-C( = O)-(CH₂)₁₀-C(=O)O- segments to -O-C(=O)-(CH₂)₄-C(=O)O- segments is greater than 1, with

(a) diphenylmethane diisocyanate to form a prepolymer, and then chain extending the prepolymer with a polyol at a mole ratio of NCO:OH groups of 0.8: 1 to 1.20:1; or

(b) toluene diisocyanate to form a prepolymer, and then chain extending the prepolymer with a diamine at a mole ratio of NCO:NH groups of 0.8: 1 to 1.20: 1.

Another aspect of the present invention is the process of producing a polyurethane having high hydrolytic stability and high solvent resistance, comprising reacting a polyester polyol of the formula (1):

H-[O-(CH₂)_x-O-C(=O)-C_mH_(2m+2rC( = O)-]_nO-(CH₂)_x-OH (1)

wherein x in each occurrence is an integer from 2 to 12, n is an integer from 1 to 20, and m is either 10 in each occurrence or is 10 in some occurrences and 4 in all other occurrences, provided that the ratio by weight of -O-C( = O)-(CH₂)₁₀-C( = O)O- segments to -O-C( = O)-(CH₂)₄-C( = O)O- segments is greater than 1, with

(a) diphenylmethane to form a prepolymer, and then chain extending the prepolymer with a diol at a mole ratio of NCO:OH groups of 0.8: 1 to 1.20: 1 ; or (b) toluene diisocyanate to form a prepolymer, and then chain extending the prepolymer with a diamine at a mole ratio of NCO:NH groups of 0.8: 1 to 1.20: 1.

In each aspect of the invention, the polyester diol is linear, such that the polyester diol is derived from diacid and diol precursors which are linear.

Detailed Description of the Invention and Preferred Embodiments

The polyester of formula (1) is linear. To achieve this, it is prepared from diacid and diol precursors which are linear.

Referring to formula (1), it should be noted that the polyester diol can be derived entirely from one diacid, namely linear dodecanedioic acid, and one diol, which must be linear; from dodecanedioic acid and a blend of two or more diols of varying chain lengths, provided all of the diols are linear; from a blend of two diacids, namely dodecanedioic and adipic, in which case more than 50 weight % of the mixture must be dodecanedioic, and one linear diol; or from the blend of two diacids and a blend of two or more linear diols. In addition, the polyester diol can be prepared by preparing a subpoly ester from one linear diol and the one, or the blend of two, diacids, and a second subpolyester from a different linear diol and the one, or the blend of two, diacids, and then attaching the subpolyesters to each other to form a (AB)_x(AB')_y type of structure. It should also be recognized that polyester diols useful in this invention include mixtures of polyesters of formula (1).

Also, the polyester diol is capped at both ends with hydroxyl groups. Achieving this capping requires simply using an appropriate excess of diol in the synthesis of the polyester.

In accordance with this invention, one can prepare thermoplastic polyurethanes and elastomeric polyurethanes, each of which exhibit improved hydrolytic stability and improved solvent resistance compared to polyurethanes made from other components. The procedure for preparing thermoplastic polyurethanes involves first reacting a polyester diol of formula (1) with one or a blend of diphenylmethane diisocyanates, such as MDI (4,4'-diphenylmethane diisocyanate) or a MDI isomer, for example, 2,4'-diphenylmethane diisocyanate), under conventionally known conditions whereby the terminal hydroxyl groups of the polyester diol react with the isocyanate groups. Since the resulting prepolymer which is formed should contain isocyanate groups, the polyester diol and the diphenylmethane diisocyanate reactants should be present in amounts providing a ratio of NCO groups to OH groups of greater than 1 :1. The product of this reaction is termed a prepolymer.

Then, the prepolymer is chain-extended by reaction with a suitable polyol, such as a C₂-C₆ alkyl diol or glycol. The prepolymer and polyol reactants should be present at a mole ratio of NCO: OH groups of 0.8: 1 to 1.20: 1, and preferably 0.95: 1 to 1.10: 1. The preferred polyols are diols, such as 1 ,4-butanediol. Other preferred polyol chain extenders include: diethylene glycol, ethylene glycol, propylene glycol, 1,3-dihydroxypropane, 2-butene-l,4-diol, neopentyl glycol, 1,6- hexanediol, 1,3-butylene glycol, 2,2,4-trimethyl-l,4-pentanediol, 1,9-nonanediol, decamethylene glycol, cyclohexanedimethanol, ethoxylated Bisphenol A, propoxylated Bisphenol A, dipropylene glycol, di-(2-hydroxyethyl)-5,5'- dimethylhydantoin, hydroquinone di(beta-hydroxyethyl) ether, N,N'-bis(2- hydroxypropyl) aniline, 2-(sodiosulfo)-l,4-butanediol, tetraethylene glycol, triethylene glycol, 2,2'-iminodiethanol, 2,2'-methyliminodiethanol, glycerine, tris(2- hydroxyethyl) isocyanurate, tris(2-hydroxypropyl) isocyanurate, tri- isopropanolamine, trimethylolpropane, trimethylolethane, pentaerythritol, glucose, D-sorbitol, sucrose, dipentaerythritol, and tripentaerythritol.

The procedure for preparing elastomeric polyurethanes involves first reacting a polyester diol of formula (1) with one or a blend of toluene diisocyanates ("TDI") such as 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, or a blend thereof, under conventionally known conditions whereby the terminal hydroxyl groups of the polyester diol react with the isocyanate groups. Since the resulting prepolymer which is formed should have isocyanate groups, the polyester diol and the diphenylmethane diisocyanate reactants should be present in amounts providing a ratio of NCO groups to OH groups of greater than 1 : 1. The product of this reaction is termed a prepolymer.

Then, the prepolymer is chain-extended by reaction with a suitable diamine. The ratio of NCO groups to NH groups of 0.8: 1 to 1.20: 1, and preferably 0.95: 1 to 1.10: 1. Suitable diamines include C₂-C₆ alkyl diamines and aryl diamines. A preferred diamine is methylenebis(o-chloroaniline). Other preferred diamine chain extenders include 1,2-diaminocyclohexane, 2-methylpentamethylenediamine, ethylene diamine, hexamethylene diamine, 3-aminomethyl-3,5,5-trimethylcyclohexylamine, 3- amino- 1 -cyclohexylaminopropane , diethy lenetriamine , m-pheny lenediamine , diethyltoluenediamine, 4,4'-methylenebis(2-chloroaniline) and 4,4-methylenebis(3- chloro-2 , 2-diethy laniline) . The following are illustrative examples of the present invention which are provided for purposes of description and are by no means limiting.

The test procedures employed are as follows: HYDROLYTIC STABILITY AT 80°C TEST

1. Cut four pieces of tensile dumbbells using a die with a quarter of an inch width following ASTM D-412. Measure thickness along the narrow strip.

Take the smallest reading.

2. Make a small hole in each piece, near the top center of the dumbbell. 3. Thread pieces onto a stainless steel wire and place the wire into a wide mouth glass quart jar. The wire must be shaped so as to permit the pieces to hang inside the jar. The pieces should not touch each other or the bottom or side of the jar. Maximum eight (8) pieces to a wire. 4. Fill jar (containing the wire and pieces) with tap water. Seal with cap and place into an oven at 80°C, for seven (7) days.

5. Repeat the above procedure for 14, 21, and 28 days study, as well.

6. After the desired time period has elapsed, remove the pieces from the wire and dry them in an oven at 100°C, for four (4) hours. 7. Remove the pieces from the oven and allow them to cool down to room temperature, at least overnight.

8. Determine tensile strength of the pieces using ASTM procedure D-412.

9. The % retention of tensile strength is calculated as follows:

% retention = (Tensile strength after test/tensile strength before test ) x 100%

SOLVENT UPTAKE % TEST

1. Cut one piece of elastomer using a rectangular die (four inches x one half inch).

2. Using scissors, cut the piece into halves of equal size. 3. Make a small hole in each piece, near the top center. Record the weight of each piece using an analytical balance.

4. Thread the pieces through a stainless steel wire and place into a wide mouth glass quart jar. The wire must be shaped so as to permit the pieces to hang inside the jar. The pieces should not touch each other or the bottom or side of the jar. Maximum eight (8) pieces to a wire.

5. Fill the jar (containing the wire and the pieces) with methyl ethyl ketone (MEK). Seal with cap and leave at room temperature, for seven (7) days. The pieces must be completely covered by the methyl ethyl ketone (MEK).

6. Repeat the above procedure using isopropyl alcohol (IP A). Solvents must not be reused. After the desired time period has elapsed (7 days), remove the pieces from the wire, quickly wipe them with a paper towel, and immediately record their weight.

8. Report results as % weight gain. uptake % = (W_f - W₀)/ W₀ x 100%

Example 1: Preparation of MDI-based polyurethane elastomer

The polyol was vacuum-dehydrated to a moisture content of less than

0.03% prior to elastomer preparation. The MDI was decanted and filtered at 50°C to eliminate any insolubles.

Polyurethane elastomer and TPU (thermoplastic polyurethane) were made by the prepolymer method. The isocyanate-terminated polyurethane prepolymer s were prepared by reacting diisocyanate with polyester polyol, whereby a calculated amount of the dry polyester polyol at approximately 70°C was added to MDI at 50°C in a four neck glass flask with stirring under a nitrogen blanket. Upon completion of the polyester polyol addition, the mixture was then heated for 3 hours at 80°C. NCO % analysis confirmed the completion of the reaction to finished prepolymer based on theoretical NCO % . The finished prepolymer was then degassed, kept at 100°C, and extended with 1 ,4-butanediol at room temperature. The mixture after one minute stirring was cast into ASTM plaque and button molds, preheated to 110°C, cured at 120°C for 1 hour in the mold, followed by post curing at 100°C for 24 hours in an oven. The cured elastomers were conditioned for a minimum of one week at room temperature prior to testing.

The results are as follows: % retention of tensile strength after 28 days: 98%

% uptake in MEK after 7 days: 24%

% uptake in IPA after 7 days: 5 %

Comparison Example 1: Preparation of MDI-based polyurethane elastomer The procedure was the same as Example 1 except PHAG-2000 [poly(hexamethylene adipate) glycol, M.W. 2,000], a polyester available from Witco Corporation under the tradename FOMREZ® 66-56, was used.

The results are as follows:

% retention of tensile strength after 28 days: 60% % uptake in MEK after 7 days: 82%

% uptake in IPA after 7 days: 13%

Example 2: Preparation of MDI-based polyurethane elastomer

The procedure was the same as Example 1 except PBDG-2000 [poly(butylene dodecanedioate) glycol, M.W. 2,000] was used. The results are as follows: % retention of tensile strength after 28 days: 62% % uptake in MEK after 7 days: 24% % uptake in IPA after 7 days: 6%

Comparison Example 2: Preparation of MDI-based polyurethane elastomer The procedure was the same as Example 1 except PBAG-2000 [poly(butylene adipate) glycol, M.W. 2,000] ], a polyester available from Witco Corporation under the tradename FOMREZ® 44-56, was used.

The results are as follows: % retention of tensile strength after 28 days: 18%

% uptake in MEK after 7 days: 72%

% uptake in IPA after 7 days: 11 %

Example 3: Preparation of MDI-based polyurethane elastomer The procedure was the same as Example 1 except PEDG-2000 [poly (ethylene dodecanedioate) glycol, M.W. 2,000] was used.

The results are as follows:

% retention of tensile strength after 28 days: 25%

% uptake in MEK after 7 days: 20% % uptake in IPA after 7 days: 3%

Comparison Example 3: Preparation of MDI-based polyurethane elastomer

The procedure was the same as Example 1 except PEAG-2000 [poly(ethylene adipate) glycol, M.W. 2,000], a polyester available from Witco Corporation under the tradename FOMREZ® 22-56, was used. The results are as follows: % retention of tensile strength after 28 days: 0% % uptake in MEK after 7 days: 63% % uptake in IPA after 7 days: 6%

Example 4: Preparation of MDI-based polyurethane elastomer The procedure was the same as Example 1 except PHDAG-2000 [poly(hexamethylene dodecanedioate/adipate) glycol, M.W. 2,000] was used. The molar ratio of dodecanedioic acid to adipic acid was 87: 13 (weight ratio was 91 :9). The results are as follows:

% retention of tensile strength after 28 days: 77% % uptake in MEK after 7 days: 36% % uptake in IPA after 7 days: 5%

Example 5: Preparation of MDI-based elastomer

The procedure was the same as Example 1 except PHDAG-2000 [poly(hexamethylene dodecanedioate/adipate) glycol, M.W. 2,000] was used. The molar ratio of dodecanedioic acid to adipic acid was 63:37 (weight ratio was 73:27). The results are as follows: % retention of tensile strength after 28 days: 65 % % uptake in MEK after 7 days: 80% % uptake in IPA after 7 days: 8%

Example 6: Preparation of MDI-based elastomer

The procedure was the same as Example 1 except PHDAG-2000 [poly(hexamethylene dodecanedioate/adipate) glycol, M.W. 2,000] was used. The molar ratio of dodecanedioic acid to adipic acid was 42:58 (weight ratio 53:47).

The results are as follows:

% retention of tensile strength after 28 days: 70%

% uptake in MEK after 7 days: 82%

% uptake in IPA after 7 days: 11 %

Comparison Example 4: Preparation of MDI-based polyurethane elastomer

The procedure was the same as Example 1 except PCLG-2000 [polycaprolactone glycol, M.W. 2,000], a polyester available Union Carbide Corporation under the tradename TONE 0240 HP, was used. The results are as follows:

% retention of tensile strength after 28 days: 20%

% uptake in MEK after 7 days: 82%

% uptake in IPA after 7 days: 14% Example 7: Preparation of TDI-based polyurethane elastomer

The polyol was vacuum-dehydrated to a moisture content of less than 0.03 % prior to elastomer preparation.

Polyurethane elastomers were made by the prepolymer method. The isocyanate- terminated polyurethane prepolymers were prepared by reacting diisocyanate with polyester polyol, whereby a calculated amount of the dry polyester polyol at approximately 70°C was added to TDI 80/20 at 25 °C in a four-neck glass flask with stirring under a nitrogen blanket. Upon completion of the polyester polyol addition, the mixture was then heated for 3 hours at 80°C. NCO % analysis confirmed the completion of the reaction to finished prepolymer based on theoretical NCO % . The finished prepolymer was then degassed, kept at 100°C, and extended with molten MOCA at 116°C. The mixture after one minute stirring was cast into ASTM plaque and button molds, preheated to 110°C, cured at 120°C for 30 minutes in the mold, followed by post curing at 100°C for 16 hours in an oven. The cured elastomers were conditioned for a minimum of one week at room temperature prior to testing.

The results are as follows: % retention of tensile strength after 28 days: 50%

% uptake in MEK after 7 days: 32%

% uptake in IPA after 7 days: 6%

Comparison Example 5: Preparation of TDI-based polyurethane elastomer The procedure was the same as Example 6 except PHAG-2000 [poly(hexamethylene adipate) glycol, M.W. 2,000], a polyester available from Witco Corporation under the tradename FOMREZ® 66-56, was used.

The results are as follows:

% retention of tensile strength after 28 days: 40% % uptake in MEK after 7 days: 95 %

% uptake in IPA after 7 days: 15%

Example 8: Preparation of TDI-based polyurethane elastomer

The procedure was the same as Example 7 except PBDG-2000 [poly(butylene dodecanedioate) glycol, M.W. 2,000] was used.

The results are as follows:

% retention of tensile strength after 28 days: 42%

% uptake in MEK after 7 days: 32%

% uptake in IPA after 7 days: 7%

Comparison Example 6: Preparation of TDI-based polyurethane elastomer

The procedure was the same as Example 1 except PBAG-2000 [poly(butylene adipate) glycol, M.W. 2,000], a polyester available from Witco Corporation under the tradename FOMREZ® 44-56, was used. The results are as follows:

% retention of tensile strength after 28 days: 0%

% uptake in MEK after 7 days: 80% % uptake in IPA after 7 days: 12%

Example 9: Preparation of TDI-based polyurethane elastomer

The procedure was the same as Example 1 except PEDG-2000 [poly(ethylene dodecanedioate) glycol, M.W. 2,000] was used.

The results are as follows:

% retention of tensile strength after 28 days: 20%

% uptake in MEK after 7 days: 20%

% uptake in IPA after 7 days: 6%

Comparison Example 7: Preparation of TDI-based polyurethane elastomer

The procedure was the same as Example 6 except PEAG-2000 [poly(ethylene adipate) glycol, M.W. 2,000], a polyester available from Witco Corporation under the tradename FOMREZ® 22-56, was used. The results are as follows:

% retention of tensile strength after 28 days: 0%

% uptake in MEK after 7 days: 78%

% uptake in IPA after 7 days: 7%

Comparison Example 8: Preparation of TDI-based polyurethane elastomer

The procedure was the same as Example 1 except PCLG-2000 [polycaprolactone glycol, M.W. 2,000], a polyester available Union Carbide Corporation under the tradename TONE 0240 HP, was used. The results are as follows: % retention of tensile strength after 28 days: 18% % uptake in MEK after 7 days: 100% % uptake in IPA after 7 days: 18%

Claims

What is claimed is:

1. A polyurethane produced by reacting a linear polyester polyol of the formula (1):

H-[O-(CH₂)_x-O-C(=O)-(CH₂)_m-C( = O)-]_nO-(CH₂)_x-OH (1)

wherein x in each occurrence is an integer from 2 to 12, n is an integer from 1 to 20, and m is either 10 in each occurrence or is 10 in some occurrences and 4 in all other occurrences, provided that the ratio by weight of -O-C( = O)-(CH₂)₁₀-C(=O)O- segments to -O-C( = O)-(CH₂)₄-C(=O)O- segments is greater than 1 , with

(a) diphenylmethane diisocyanate to form a prepolymer, and then chain extending the prepolymer with a polyol at a mole ratio of NCO.OH groups of 0.8: 1 to 1.20: 1; or

(b) toluene diisocyanate to form a prepolymer, and then chain extending the prepolymer with a diamine at a mole ratio of NCO:NH groups of 0.8:1 to 1.20:1.

2. The polyurethane according to claim 1, produced by reacting a linear polyester polyol of formula (1) with diphenylmethane diisocyanate to form a prepolymer substituted with isocyanate groups, and then chain extending the prepolymer with polyol at a mole ratio of NCO:OH groups of 0.8: 1 to 1.20: 1.

3. The polyurethane according to claim 1 , wherein m is 10 in each occurrence.

4. The polyurethane according to claim 3, wherein x in each occurrence is the same.

5. The polyurethane according to claim 4, wherein x is 2 to 6.

6. The polyurethane according to claim 2, wherein m is 10 in some occurrences and 4 in all other occurrences, provided that the ratio by weight of -O-C( = O)-(CH₂)₁₀-C(=O)O- segments to -O-C(=O)-(CH₂)₄-C(=O)O- segments is greater than 1.

7. The polyurethane according to claim 6, wherein x in each occurrence is the same.

. The polyurethane according to claim 7, wherein x is 2 to 6.

9. The polyurethane according to claim 2, wherein the prepolymer is chain extended with 1,4-butanediol.

10. The polyurethane according to claim 1, produced by reacting a linear polyester polyol of formula (1) with (b) toluene diisocyanate to form a prepolymer, and then chain extending the prepolymer with a diamine at a mole ratio of NCO:NH groups of 0.8:1 to 1.20:1.

11. The polyurethane according to claim 10, wherein m is 10 in each occurrence.

12. The polyurethane according to claim 11, wherein x in each occurrence is the same.

13. The polyurethane according to claim 12, wherein x is 2 to 6.

14. The polyurethane according to claim 10, wherein m is 10 in some occurrences and 4 in all other occurrences, provided that the ratio by weight of -O-C( = O)-(CH₂)₁₀- C( = O)O- segments to -O-C(=O)-(CH₂)₄-C(=O)O- segments is greater than 1.

15. The polyurethane according to claim 14, wherein x in each occurrence is the same.

16. The polyurethane according to claim 15, wherein x is 2 to 6.

17. The polyurethane according to claim 10, wherein the prepolymer is chain extended with methylenebis(o-chloroaniline) .

18. A process of producing polyurethane comprising reacting a linear polyester polyol of the formula (1):

H-[O-(CH₂)_x-O-C(=O)-(CH₂)_m-C(=O)-]_nO-(CH₂)_x-OH (1) wherein x in each occurrence is an integer from 2 to 12, n is an integer from 1 to 20, and m is either 10 in each occurrence or is 10 in some occurrences and 4 in all other occurrences, provided that the ratio by weight of -O-C(=O)-(CH₂)₁₀-C(=O)O- segments to -O-C(=O)-(CH₂)₄-C(=O)O- segments is greater than 1, with

(a) diphenylmethane diisocyanate to form a prepolymer, and then chain extending the prepolymer with a diol at a mole ratio of NCO: OH groups of 0.8: 1 to 1.20: 1 ; or

19. The process according to claim 18, comprising reacting a linear polyester polyol of formula (1) with diphenylmethane diisocyanate to form a prepolymer, and then chain extending the prepolymer with a diol at a mole ratio of NCO: OH groups of 0.8:1 to 1.20:1.

20. The process according to claim 19, wherein m is 10 in each occurrence.

21. The process according to claim 20, wherein x in each occurrence is the same.

22. The process according to claim 21, wherein x is 2 to 6.

23. The process according to claim 19, wherein m is 10 in some occurrences and 4 in all other occurrences, provided that the ratio by weight of -O-C(=O)-(CH₂)₁₀-C(=O)O- segments to -O-C(=O)-(CH₂)₄-C(=O)O- segments is greater than 1.

24. The process according to claim 23, wherein x in each occurrence is the same.

25. The process according to claim 24, wherein x is 2 to 6.

26. The process according to claim 19, wherein the prepolymer is chain extended with 1,4-butanediol.

27. The process according to claim 18, comprising reacting a linear polyester polyol of formula (1) with toluene diisocyanate to form a prepolymer, and then chain extending the prepolymer with a diamine at a mole ratio of NCO:NH groups of 0.8:1 to 1.20:1.

28. The process according to claim 27, wherein m is 10 in each occurrence.

29. The process according to claim 28, wherein x in each occurrence is the same.

30. The process according to claim 29, wherein x is 2 to 6.

31. The process according to claim 27, wherein m is 10 in some occurrences and 4 in all other occurrences, provided that the ratio by weight of -O-C(=O)-(CH₂)ι₀-C( = O)O- segments to -O-C( = O)-(CH₂)₄-C( = O)O- segments is greater than 1.

32. The process according to claim 31, wherein x in each occurrence is the same.

33. The process according to claim 32, wherein x is 2 to 6.

34. The process according to claim 27, wherein the prepolymer is chain extended with methylenebis(o-chloroaniline) .