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US 5,015,275 AGranted
Isotropic microporous syndiotactic polystyrene membranes and processes for preparing the same
AssigneeThe Dow Chemical Company
InventorsHenry N. Beck, Robert D. Mahoney, Hawk S. Wan, Richard A. Lundgard
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Abstract
This invention relates to semi-permeable isotropic syndiotactic polystyrene microporous membranes and processes for preparing such membranes.
Claims21
A semi-permeable membrane comprising a thin isotropic syndiotactic polystyrene microporous membrane.
A process for preparing a semi-permeable isotropic syndiotactic polystyrene microporous membrane comprising the steps of;
- A. forming a mixture comprising;
- (i) syndiotactic polystyrene, and
- (ii) at least one solvent for the syndiotactic polystyrene;
- B. heating the mixture to a temperature under conditions such that a homogeneous fluid is formed which possesses sufficient viscosity to be formed into a membrane;
- C. extruding or casting the homogeneous fluid into a membrane;
- D. quenching or coagulating the membrane by passing the membrane through one or more zones under conditions such that the membrane solidifies;
- and
- E. simultaneously or consecutively leaching the membrane by passing the membrane through one or more zones under conditions such that at least a substantial portion of the solvent for the syndiotactic polystyrene is removed from the membrane;
- wherein the semi-permeable membrane so formed possesses isotropic microporous structure.
6 more elements
A process for preparing a semi-permeable isotropic syndiotactic polystyrene microporous membrane comprising the steps of;
- A. forming a mixture comprising;
- (i) syndiotactic polystyrene,
- (ii) at least one solvent for the syndiotactic polystyrene, and
- (iii) at least one non-solvent for the syndiotactic polystyrene;
- B. heating the mixture to a temperature under conditions such that a homogeneous fluid is formed which possesses sufficient viscosity to be formed into a membrane;
- C. extruding or casting the homogeneous fluid into a membrane;
- D. quenching or coagulating the membrane by passing the membrane through one or more zones under conditions such that the membrane solidifies;
- and
- E. simultaneously or consecutively leaching the membrane by passing the membrane through one or more zones under conditions such that at least a substantial portion of the solvent and non-solvent for the syndiotactic polystyrene is removed from the membrane;
- wherein the semi-permeable membrane so formed possesses isotropic microporous structure.
7 more elements
Dependencies are inferred from the claim text.