Prepolymer catalysts suitable for preparing spandex fibers
View Patent ↗Segmented polyurethane/ureas useful for the production of spandex, particularly spandex fibers, are made from isocyanate-terminated prepolymers formed by reacting excess isocyanate with an isocyanate-reactive component satisfying specified compositional requirements in the presence of a catalyst which promotes linear polymerization but does not cause degradation of the polymer. Suitable catalysts include metal salts of organic fatty acids and/or of naphthenic acid. The isocyanate-reactive component includes at least 10 equivalent percent of a polyoxypropylene diol having a number average molecular weight of at least about 1500 Da and an average unsaturation level less than or equal to 0.03 meq/g and up to 90 equivalent percent of a polytetramethylene glycol having a number average molecular weight of at least 200 Da.
1. A process for the production of a polyurethane/urea in solution comprising
a) reacting
1) a diisocyanate
with
2) an isocyanate-reactive component comprising
(i) a diol component comprising
(a) from about 10 to about 100 equivalent percent of at least one polyoxypropylene diol having a number average molecular weight of at least about 1500 Da and an average unsaturation level less than or equal to 0.03 meq/g,
(b) up to 90 equivalent percent of at least one polytetramethylene glycol having a number average molecular weight of at least 200 Da, and optionally,
(ii) an isocyanate-reactive material which is different from 2)(i)(a) and 2)(i)(b),
in the presence of
3) a catalyst which promotes linear polymerization but does not cause degradation of a polymer produced therewith under processing conditions,
in amounts such that an NCO prepolymer having an NCO group content of from about 1.0 to about 3.75% will be formed, and
b) chain extending the NCO prepolymer with
4) at least one aliphatic diamine chain extender
in
5) a solvent
to form the polyurethane/urea in solution.
2. The process of claim 1 in which the catalyst is used in an amount of from about 0.002 to 0.020% by weight, based on the diol component.
3. The process of claim 1 in which the catalyst used is a metal salt or soap of a C 6 -C 20 monocarboxylic acid or of naphthenic acid.
4. The process of claim 1 in which the catalyst used is a naphthenic acid or a C 6 -C 20 monocarboxylic acid salt of a metal selected from the group consisting of zinc, barium, lead, calcium, cerium, cobalt, copper, tin, lithium, manganese, bismuth, and zirconium.
5. The process of claim 1 in which the catalyst used is zinc octoate.
6. The process of claim 1 in which a chain terminator is employed.
7. The process of claim 1 further comprising a step of spinning the polyurethane/urea solution to form fiber.
8. The process of claim 1 in which from about 60 to about 90 equivalent percent of the diol component is polyoxypropylene diol (a).
9. The process of claim 1 in which the polyoxypropylene diol (a) has a number average molecular weight of from about 2000 to about 8000 Da.
10. The process of claim 1 in which the polyoxypropylene diol (a) has an unsaturation level of less than 0.02 meq/g.
11. The process of claim 1 in which the diisocyanate is 4,4′-diphenylmethane diisocyanate.
12. The process of claim 1 in which the solvent is a highly polar solvent.
13. The process of claim 1 in which the solvent is dimethyl acetamide.
14. The process of claim 1 in which the chain extender comprises ethylene diamine.
15. The polyurethane/urea produced by the process of claim 8 .