Spandex of a particular composition and process for making same
View Patent ↗The invention provides spandex having improved hysteresis and a method for making such spandex. The spandex of the invention comprises the polyurethaneurea reaction product of: (a) poly(tetramethylene ether) glycol (b) 1-isocyanato-4-[(4-isocyanatophenyl)methyl]benzene wherein the mole ratio of diisocyanate to glycol is from about 1.52 to about 2.04; and (c) a mixture of chain extenders comprising: from about 35 to about 55 mole percent ethylene diamine; and from about 45 to about 65 mole percent 1,2-propanediamine.
1. Spandex comprising the polyurethaneurea reaction product of:
(a) poly(tetramethylene ether) glycol
(b) 1-isocyanato-4-[(4-isocyanatophenyl)methyl]benzene wherein the mole ratio of diisocyanate to glycol is from about 1.52 to about 2.04; and
(c) a mixture of chain extenders comprising:
from about 35 to about 55 mole percent ethylene diamine; and
from about 45 to about 65 mole percent 1,2-propanediamine;
wherein the poly(tetramethylene ether) glycol is substantially free of diols having molecular weights of less than about 250 daltons.
2. The spandex of claim 1 wherein the poly(tetramethylene ether) glycol has a number average molecular weight of from about 1600 daltons to about 2500 daltons.
3. The spandex of claim 1 wherein the mixture of chain extenders comprises from about 40 to about 50 mole percent ethylene diamine, and from about 50 to about 60 mole percent 1,2-propanediamine.
4. The spandex of claim 1 wherein the mixture of chain extenders further comprises at least one primary amine chain terminator.
5. Fabrics comprising the spandex of claim 4 .