Spandex of a particular composition and process for making same

Abstract

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 - 4 . (canceled)  
     
     
         5 . A process for making spandex comprising the steps of: 
 a) providing poly(tetramethylene ether) glycol;    b) providing 1-isocyanato-4-[(4-isocyanatophenyl)methyl]benzene;    c) contacting the poly(tetramethylene ether) glycol and the 1-isocyanato-4-[(4-isocyanatophenyl)methyl]benzene to form a capped glycol wherein the weight percent of isocyanate moiety is from about 2.2 to about 2.9 based upon the weight of the capped glycol;    d) providing a solvent;    e) mixing the solvent and the capped glycol to form a capped glycol solution;    f) contacting the capped glycol solution and a mixture of chain extenders comprising: 
 from about 35 mole percent ethylene diamine;  
 to about 55 mole percent ethylene diamine; and  
 from about 45 mole percent 1,2-propanediamine;  
 to about 65 mole percent 1,2-propanediamine  
 to form a polyurethaneurea solution; and  
   g) spinning the polyurethaneurea solution to form the spandex.    
     
     
         6 . The process of  claim 5  wherein steps c) and f) are carried out as batch steps and the falling ball viscosity of the polyurethaneurea solution is about 1000 to 4000 poise.  
     
     
         7 . The process of  claim 5  wherein the solvent is dimethylformamide and the poly(tetramethylene ether) glycol is substantially free of diols having molecular weight of less than 250 daltons.  
     
     
         8 . The process of  claim 5  wherein the mixture of chain extenders comprises at least about 40 mole percent ethylene diamine, at most about 50 mole percent ethylene diamine, at least about 50 mole percent 1,2-propanediamine, and at most about 60 mole percent 1,2-propanediamine.  
     
     
         9 . The process of  claim 5  wherein the mixture of chain extenders of step (f) further comprises at least one primary amine chain terminator.  
     
     
         10 . (canceled)