Filtration membrane with calcined .alpha.-alumina particles therein
First Claim
1. An outside-in hollow fiber asymmetric semipermeable membrane comprising,(i) a macroporous foraminous 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.
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Accused Products
Abstract
A filtration membrane for micro- or ultra-filtration is formed from a complex of PVDF and calcined α-alumina ("α-Al") particles, in which complex the particles are reacted and dispersed. The suspended complex is then mixed with a hydrophilic polymer such as polyvinyl alcohol (40%-90% hydrolyzed) referred to herein as HPVA, which reacts with the complex imparting hydrophilicity to the polymer. The novel membrane provides about 50% higher specific flux than a membrane made with the same polymer but without the α-Al particles. Unexpectedly, the net flux is improved by treating the membrane with a solution of sodium hypochlorite which fails to remove the HPVA from the novel membrane but does remove it from the prior art membrane which does not contain the α-Al. The preferred membrane comprises a macroporous support coated on its outer surface with a thin tubular asymmetric semipermeable film of polymer containing less than about 50% by is weight of α-A1 particles.
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Citations
12 Claims
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1. An outside-in hollow fiber asymmetric semipermeable membrane comprising,
(i) a macroporous foraminous 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. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
- and,
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10. A method for producing a membrane having a semipermeable asymmetric film supported on a flexible support having inner and outer surfaces, and inter-communicating macropores which place said inner and outer surfaces in fluid communication, said method comprising,
coating said support'"'"'s outer surface with a dope of a polymeric reaction product of (i) a complex of polyvinylidene difluoride (PVDF) with calcined α - -alumina particles having a primary particle size in the range from about 0.1 μ
m to about 5 μ
m, and(ii) a hydrophilic polymer having reactive nucleophilic groups adapted to impart hydrophilicity to said membrane; wherein said complex is formed by dispersing less than 50 parts by weight of said particles per 100 parts by weight of said particles and PVDF in a solvent for said PVDF; wherein said reaction product is formed by the addition of said hydrophilic polymer to said complex in said solvent; said dope having a viscosity sufficient to be supported on said outer surface, so as to provide said support with a dope-coated surface; passing said dope-coated surface through a sizing means to provide a wall thickness of dope on said support sufficient to form a film less than 0.2 mm thick; and
, coagulating said dope. - View Dependent Claims (11, 12)
- -alumina particles having a primary particle size in the range from about 0.1 μ
Specification