Low haze thermoplastic polyurethane using mixture of chain extenders including 1,3- and 1,4-cyclohexanedimethanol
View Patent ↗The present invention is a low haze thermoplastic polyurethane (TPU) prepared from a chain extender mixture that includes an acyclic diol and a mixture of 1,3- and 1,4-cyclohexanedimethanol. The TPU elastomers exhibit good optical clarity, particularly when formed into relatively thick injection molded parts.
1. A thermoplastic polyurethane elastomer which is a polymer of (1) at least one high equivalent weight difunctional compound selected from a polyester diol, a polyether diol, a polycarbonate diol or a mixture thereof, (2) a chain extender mixture and (3) diisocyanatodiphenylmethane (MDI), wherein the chain extender mixture includes at least 60 mole-% of an acyclic diol having a molecular weight of up to about 400 and at least 8 mole-% of a mixture of cyclohexanedimethanol isomers, the mixture of cyclohexanedimethanol isomers including at least 20 weight percent each of 1,3-cyclohexanedimethanol and 1,4-cyclohexanedimethanol, based on the weight of the cyclohexanedimethanol isomers.
2. The thermoplastic polyurethane elastomer of claim 1 , wherein the mixture of cyclohexanedimethanol isomers includes cis-1,3-cyclohexanedimethanol, trans-1,3-cyclohexanedimethanol, cis-1,4-cyclohexanedimethanol and trans-1,4-cyclohexanedimethanol.
3. The thermoplastic polyurethane elastomer of claim 1 , wherein the chain extender mixture includes 1,4-butanediol and the mixture of cyclohexanedimethanol isomers.
4. The thermoplastic polyurethane elastomer of claim 1 , wherein the high equivalent weight difunctional compound includes an A-B type polyester diol corresponding to a reaction product of a glycol and adipic acid.
5. The thermoplastic polyurethane elastomer of claim 1 , which has a Shore A durometer hardness of at least 60 and a Shore D durometer hardness of up to 75.
6. The thermoplastic polyurethane elastomer of claim 5 , which has a hard segment content of from 35 to 55% by weight.
7. The thermoplastic polyurethane elastomer of claim 1 , which is in the form of an injection molded article.
8. The thermoplastic polyurethane elastomer of claim 1 , which is in the form of an extruded article.
9. The thermoplastic polyurethane elastomer of claim 1 , which exhibits a haze value of no greater than 30%, as measured using an Hunterlab Colorquest Instrument on 6.25×87.5×162 mm specimens, which specimens are injection molded, using an 80° F. (27° C.) tool, an injection molder barrel temperature of 220° C. at the nozzle and 190° C. in the feed throat with an incremental temperature profile from feed throat to nozzle, at an injection speed of 25.4 mm/sec, and with an in-mold residence time of 110 seconds.
10. The thermoplastic polyurethane elastomer of claim 9 , which exhibits a haze value of no greater than 10%.
11. A thermoplastic polyurethane elastomer which is a polymer of (1) at least one high equivalent weight poly(caprolactone) diol or mixture thereof with one or more other high equivalent weight diols, (2) a chain extender mixture that includes at least 60 mole-% of 1,4-butanediol and at least 8 mole-% of a mixture of cyclohexanedimethanol isomers, and (3) at least one diisocyanate, wherein the mixture of cyclohexanedimethanol isomers include at least 40 weight percent each of 1,3-cyclohexanedimethanol and 1,4-cyclohexanedimethanol.
12. The thermoplastic polyurethane elastomer of claim 11 , wherein the mixture of cyclohexanedimethanol isomers includes cis-1,3-cyclohexanedimethanol, trans-1,3-cyclohexanedimethanol, cis-1,4-cyclohexanedimethanol and trans-1,4-cyclohexanedimethanol.
13. The thermoplastic polyurethane elastomer of claim 12 , which has a Shore A durometer hardness of at least 60 and a Shore D durometer hardness of up to 75.
14. The thermoplastic polyurethane elastomer of claim 13 , which has a hard segment content of from 35 to 55% by weight.
15. The thermoplastic polyurethane elastomer of claim 14 , which is in the form of an injection molded article.
16. The thermoplastic polyurethane elastomer of claim 15 , which exhibits a haze value of no greater than 30%, as measured using an Hunterlab Colorquest Instrument on 6.25×87.5×162 mm specimens, which specimens are injection molded, using an 80° F. (27° C.) tool, an injection molder barrel temperature of 220° C. at the nozzle and 190° C. in the feed throat with an incremental temperature profile from feed throat to nozzle, at an injection speed of 25.4 mm/sec, and with an in-mold residence time of 110 seconds.
17. The thermoplastic polyurethane elastomer of claim 16 , which exhibits a haze value of no greater than 10%.
18. The thermoplastic polyurethane elastomer of claim 13 , which is in the form of an extruded article.