Hollow fiber membrane and braided tubular support therefor
First Claim
1. An outside-in hollow fiber asymmetric membrane comprising a flexible macroporous tubular braid support having a tubular film of synthetic resinous material supported on the outer circumferential surface of the braid without the support being embedded in the film which has a wall thickness of less than 0.2 mm, the braid comprising, from about 16 to 60 separate yarns, each on its own carrier, each yarn using multifilament 150 to 500 denier (gm/9000 meters) yarn, each multifilament being made with from 25 to 750 filaments, each filament being from 0.5 to 7 denier, the braid being woven with from 1 to 3 multifilament ends at from 30 to 45 picks (crosses/inch), with a wall thickness in the range from about 0.2 mm but less than three times the diameter of the yarn from which said braid is woven, the braid having a stable heat-pre-shrunk length which is in the range from about 1% to 20% less than its unshrunk length, an air permeability in the range from about 1 to about 10 cc/sec/cm2 at 1.378 kPa, and extension at break of the pre-shrunk braid is at least 10%,such that the membrane is adapted for use as a microfiltration or ultrafiltration liquid separation membrane.
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Accused Products
Abstract
An asymmetric membrane comprising a tubular polymer film in combination with a tubular braid on which the film is supported, requires the braid be macroporous and flexible, yet sufficiently strong to withstand continuous flexing, stretching and abrasion during use for microfiltration (MF) or ultrafiltration (UF). The specifications for a braid of a long-lived membrane are provided. A membrane is formed by supporting a polymer film in which particles of calcined α-alumina are dispersed, on the defined tubular braid.
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Citations
11 Claims
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1. An outside-in hollow fiber asymmetric membrane comprising a flexible macroporous tubular braid support having a tubular film of synthetic resinous material supported on the outer circumferential surface of the braid without the support being embedded in the film which has a wall thickness of less than 0.2 mm, the braid comprising, from about 16 to 60 separate yarns, each on its own carrier, each yarn using multifilament 150 to 500 denier (gm/9000 meters) yarn, each multifilament being made with from 25 to 750 filaments, each filament being from 0.5 to 7 denier, the braid being woven with from 1 to 3 multifilament ends at from 30 to 45 picks (crosses/inch), with a wall thickness in the range from about 0.2 mm but less than three times the diameter of the yarn from which said braid is woven, the braid having a stable heat-pre-shrunk length which is in the range from about 1% to 20% less than its unshrunk length, an air permeability in the range from about 1 to about 10 cc/sec/cm2 at 1.378 kPa, and extension at break of the pre-shrunk braid is at least 10%,
such that the membrane is adapted for use as a microfiltration or ultrafiltration liquid separation membrane.
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6. In an outside-in hollow fiber asymmetric semipermeable membrane comprising,
(i) a macroporous foraminous tubular support means having an outer surface; - and,
(ii) a polymeric film of a reaction product of (a) a complex of polyvinylidene difluoride (PVDF) with calcined α
-alumina particles, and (b) a hydrophilic polymer adapted to impart hydrophilicity to said membrane;
said particles having a primary particle size in the range from about 0.1 μ
m to 5 μ
m being present in an amount at least 1 percent by weight, but less than 50 percent by weight, of said film;
said film being supported by said outer surface, and said film having a peripheral barrier layer or “
skin”
integral with successive microporous layers having pores having an average diameter in the range from about 0.01 μ
m to about 0.3 μ
m, in open communication with each other,the improvement comprising, a flexible macroporous tubular braid support comprising from about 16 to 60 separate yarns, each on its own carrier, each yarn using multifilament 150 to 500 denier (gm/9000 meters) yarn, each multifilament being made with from 25 to 750 filaments, each filament being from 0.5 to 7 denier, said braid being woven with from 1 to 3 multifilament ends at from 30 to 45 picks (crosses/inch), and said braid has a wall thickness in the range from about 0.2 mm but less than three times the diameter of the yarn from which said braid is woven, has a stable heat-pre-shrunk length which is in the range from about 1% to 20% less than its unshrunk length, and an air permeability in the range from about 2.67 to about 7.09 cc/sec/cm2 at 1.378 kPa, whereby said membrane is adapted for use as a microfiltration or ultrafiltration liquid separation membrane. - View Dependent Claims (7, 8, 9, 10, 11)
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Specification