COPOLYMER FIBER AND ASSOCIATED METHOD AND ARTICLE
A copolymer fiber is prepared from a composition that includes specific amounts of a block polyestercarbonate-polysiloxane and a flame retardant. The fiber has an equivalent circular diameter of 10 to 60 micrometers. Also described are a method of forming the fiber, and various articles incorporating the fiber, including woven fabrics, knit fabrics, and nonwoven fabrics.
1 . A copolymer fiber:
wherein the copolymer fiber comprises a composition comprising, based on the total weight of the composition,
90 to 98 weight percent of a block polyestercarbonate-polysiloxane comprising a polyester block comprising resorcinol ester units having the structure
a polycarbonate block comprising carbonate units having the structure
wherein at least 60 percent of the total number of R 1 groups are aromatic divalent groups, and a polysiloxane block comprising dimethylsiloxane units; wherein the block polyestercarbonate-polysiloxane comprises, based on total moles of carbonate and ester units, 30 to 90 mole percent of the resorcinol ester units, 5 to 35 mole percent of carbonate units wherein R 1 is 1,3-phenylene, and 5 to 35 mole percent of carbonate units wherein R 1 is
and further comprises, based on the weight of the block polyestercarbonate-polysiloxane, 0.2 to 4 weight percent dimethylsiloxane units; and
2 to 10 weight percent of a flame retardant comprising an organophosphate ester;
wherein the fiber has an equivalent circular diameter of 10 to 60 micrometers.
2 . The fiber of claim 1 , wherein the block polyestercarbonate-polysiloxane comprises 0.5 to 2 weight percent dimethylsiloxane units.
3 . The fiber of claim 1 , wherein the organophosphate ester comprises an oligomeric phosphate ester.
4 . (canceled)
5 . The fiber of claim 1 , wherein the composition comprises, based on the total weight of the composition, 91 to 96 weight percent of the block polyestercarbonate-polysiloxane, and 4 to 9 weight percent of the flame retardant.
6 . The fiber of claim 1 , wherein the total amount of the block polyestercarbonate-polysiloxane and the flame retardant is 98 to 100 weight percent.
7 . The fiber of claim 1 , wherein the block polyestercarbonate-polysiloxane comprises, based on total moles of carbonate and ester units, 70 to 90 mole percent of the resorcinol ester units, 5 to 15 mole percent of carbonate units wherein R 1 is 1,3-phenylene, and 5 to 15 mole percent of carbonate units wherein R 1 is
and further comprises, based on the weight of the block polyestercarbonate-polysiloxane, 0.5 to 2 weight percent dimethylsiloxane units.
8 . The fiber of claim 1 , wherein the composition comprises 0 to 1 part per million by weight of colorants.
9 . A method of forming a fiber, the method comprising:
melt spinning a composition to form a fiber;
wherein the composition comprises, based on the total weight of the composition,
90 to 98 weight percent of a block polyestercarbonate-polysiloxane comprising a polyester block comprising resorcinol ester units having the structure
a polycarbonate block comprising carbonate units having the structure
wherein at least 60 percent of the total number of R 1 groups are aromatic divalent groups, and a polysiloxane block comprising dimethylsiloxane units; wherein the block polyestercarbonate-polysiloxane comprises, based on total moles of carbonate and ester units, 30 to 90 mole percent of the resorcinol ester units, 5 to 35 mole percent of carbonate units wherein R 1 is 1,3-phenylene, and 5 to 35 mole percent of carbonate units wherein R 1 is
and further comprises, based on the weight of the block polyestercarbonate-polysiloxane, 0.2 to 4 weight percent dimethylsiloxane units; and
2 to 10 weight percent of a flame retardant comprising an organophosphate ester; and
wherein the fiber has an equivalent circular diameter of 10 to 60 micrometers.
10 . The method of claim 9 , wherein the melt spinning is characterized by a draw down ratio of 280 to 550, an apparent shear rate of 170 to 1700 second −1 , and a mechanical draw ratio of 0.95 to 1.2.
11 . An article comprising the fiber of claim 1 .
12 . The article of claim 11 , wherein the article comprises a woven fabric comprising the fiber.
13 . The article of claim 11 , wherein the article comprises a knit fabric comprising the fiber.
14 . The article of claim 11 , wherein the article comprises a nonwoven fabric comprising the fiber.