Membrane filtration type hollow fibers and method for the preparation of same

Claim 2

A cellulose acetate membrane filtration type hollow fiber comprised of a single material phase, wherein the cylindrical wall defining said hollow fiber represents a three-dimensional net-like structure of fine filtering passages of 0.01 to 1 micron, said structure occupying the whole mass of said wall when seen in any cross-section of said wall, providing thus on effective and active filtering zone, the pore rate amounting to at least 55%, active points of the filtering passages for governing minimum passable sizes of said passages for solids included in a filtering liquor to be treated being distributed at random throughout at least said active zone, said passages being nearly uniform.

Claim 3

A process for the preparation of a membrane filtration type hollow fiber comprising the steps of: 1. dissolving the polymer in a first solvent in an amount of 10 to 35% by weight; 2. adding a core-forming substance to said solution in an amount of 40 to 150% by weight based on the weight of the polymr; 3.

Claim 4

A process for the preparation of a membrane filtration type hollow fiber comprising the steps of: 1. dissolving the polymer in a first solvent in an amount of 10 to 35% by weight; 2. adding a core-forming substance to said solution in an amount of 40 to 150% by weight based on the weight of the polymr; 3.

Claim 5

adding a second solvent having an affinity for said first solvent and capable of dissolving said core-forming substance but incapable of dissolving said polymer in an amount of 25 to 100% by weight based on the weight of the first solvent; 4. mixing thoroughly said constituents to an even spinning liquor; 5. discharging said spinning liquor under pressure through a ring orifice zone encircling an inner core orifice zone; 6. discharging concurrently under pressure a core stream of water or an aqueous solution containing a second and coagulation-controlling solvent, as an inside coagulating bath liquid through said core orifice zone; 7. leading the liquid discharged from the ring-shaped spinning liquid orifice to drop under gravity action into the space extending from the said spinning nozzle and covered with a hollow cylinder having at least one fine communication opening for substantially preventing communication between the covered limited space and surrounding ambient air atmosphere; 8. introducing the string product from the foregoing step (6) into a coagulation bath containing a third solvent incapable of dissolving said polymer and capable of dissolving evenly in said first solvent, for coagulating the tube of said polymer; and 9. introducing said coagulated tabular product into a further bath containing an extracting liquid, incapable of dissolving said polymer, yet capable of dissolving said core-forming substance and said second solvent liable to be accompanied by said substance, or at least having an affinity for said second solvent, thereby extracting said substance and said second solvent accompanied thereby, and forming thus a network of fine filtering passages throughout the wall of said tubular product or at least an active

Claim 6

adding a second solvent having an affinity for said first solvent and capable of dissolving said core-forming substance but incapable of dissolving said polymer in an amount of 25 to 100% by weight based on the weight of the first solvent; 4. mixing thoroughly said constituents to an even spinning liquor; 5. discharging said spinning liquor under pressure through a ring orifice zone encircling an inner core orifice zone; 6. discharging concurrently under pressure a core stream of water or an aqueous solution containing a second and coagulation-controlling solvent, as an inside coagulating bath liquid through said core orifice zone; 7. leading the liquid discharged from the ring-shaped spinning liquid orifice to drop under gravity action into the space extending from the said spinning nozzle and covered with a hollow cylinder having at least one fine communication opening for substantially preventing communication between the covered limited space and surrounding ambient air atmosphere; 8. introducing the string product from the foregoing step (6) into a coagulation bath containing a third solvent incapable of dissolving said polymer and capable of dissolving evenly in said first solvent, for coagulating the tube of said polymer; and 9. introducing said coagulated tabular product into a further bath containing an extracting liquid, incapable of dissolving said polymer, yet capable of dissolving said core-forming substance and said second solvent liable to be accompanied by said substance, or at least having an affinity for said second solvent, thereby extracting said substance and said second solvent accompanied thereby, and forming thus a network of fine filtering passages throughout the wall of said tubular product or at least an active

Claim 7

ring zone thereof. 3. A process according to claim 2, wherein the core-forming substance of step (2) is a metal salt.

Claim 8

A process according to claim 3, wherein the core-forming substance is CaCl 2 ·2H 2 O.

Claim 9

A process according to claim 2, wherein the second solvent is cyclohexanol.

Claim 10

A process according to claim 2, wherein the coagulation bath liquid in the step (8) and the inside coagulation bath liquid in the step (6) represent the same composition of methanol/water.