Method and system for controlling pore size of microporous phase inversion membranes
View Patent ↗This invention provides for a method to control the pore size or bubble point of porous membranes made by phase inversion in a continuous manufacturing process by blending two or more solutions each capable of producing a porous membrane with different pore size or bubble point than the pore size or bubble point of the desired membrane, and blending these solutions by the method of this invention to produce the desired pore size or bubble point. This invention also provides for a method to monitor membrane pore size in a continuous process and adjust pore size during the continuous manufacturing process.
1. A method of controlling pore size in a continuous process for manufacturing porous membranes, comprising,
providing two or more polymer solutions wherein the two or more polymer solutions are formed of the same polymer solution, at least two of the two or more solutions have different pre-established Tmax profiles such that a first solution has a low TMax and at least a second solution has a Tmax greater than the first solution,
determining the pore size of the membrane that will result under said process for each polymer solution,
determining the ratio or proportions of each solution to be blended together to make a homogeneous manufacturing process polymer solution,
blending said two or more polymer solutions in the ratio or proportions calculated to obtain a blend of polymer solutions in a manner that affects the final solution properties only by the effect of the ratio or proportions of the two or more polymer solutions and
manufacturing membranes with said blend by said continuous process.
2. The method of claim 1 wherein the blending of the two or more solutions is done in an in-line blender.
3. The method of claim 1 further comprising,
determining the pore size of said manufactured membrane,
calculating an adjustment to the ratio or proportions of said polymer solutions to correct for variation from desired pore size,
adjusting the blend of said polymer solutions to reflect the adjusted ratio or proportions,
manufacturing membranes with said adjusted blend by said continuous process.
4. The method of claim 3 wherein the two or more solutions are blended in an in-line blender.
5. The method of claims 1 or 3 , wherein the two or more polymer solutions are made with one or more semi-crystalline polymers.
6. The method of claim 1 wherein the two or more polymer solutions are made with one or more semi-crystalline polymers and the semi-crystalline polymers are selected from the group consisting of polyamides, polyvinylidene fluoride and cellulose ester.
7. The method of claim 1 wherein the two or more polymer solutions have a lower critical solution temperature.
8. The method of claim 1 further comprising the step of adjusting pore size of the formed membrane by a feedback mechanism.
9. The method of claim 1 further comprising the step of adjusting pore size of the formed membrane by a feed-back mechanism and the feedback mechanism has the steps of
converting said measured property or properties into data form suitable to be used in a computer program designed to determine blend ratio or proportions, and
transmitting instructions to one or more valves to adjust the ratio or proportions of said polymer solutions during blending.
10. A method of adjusting pore size by a feedback mechanism in a continuous process for manufacturing porous membranes, comprising,
providing two or more polymer solutions formed of the same polymer solution, having different, pre-established, TMax profiles such that a first solution has a low TMax and at least a second solution has a Tmax greater than the first solution,
determining the pore size of the membrane that will result under said specified process for each polymer solution,
measuring one or more properties of the membrane as it is being manufactured,
converting said measured property or properties into data form suitable to be used in a computer program designed to determine blend ratio or proportions, and further designed to transmit control signals to means controlling the flow of the polymer solutions into said blend vessel,
transmitting instructions to one or more valves to adjust the ratio or proportions of said polymer solutions,
blending said two or more polymer solutions in the ratio or proportions so determined to obtain a blend of said polymer solutions in a manner that affects the final solution properties only by the effect of the ratio or proportions of the two or more polymer solutions and
manufacturing membranes with said adjusted blend by said continuous process.
11. The method of claim 10 wherein the blending occurs in an in-line blender.
12. The method of claim 10 wherein the polymer solution is made of one or more semi-crystalline polymers.
13. The method of claim 10 wherein the polymer solution is made of one or more semi-crystalline polymers selected from the group consisting of polyamides, polyvinylidene fluoride and cellulose ester.
14. The method of claim 10 wherein the two or more polymer solutions have a lower critical solution temperature.
15. The method of claim 1 wherein there are two solutions, a first solution having a low TMax and a second solution having a Tmax greater than the first solution.
16. The method of claim 10 wherein there are two solutions, a first solution having a low TMax and a second solution having a Tmax greater than the first solution.
17. The method of claim 1 wherein there are more than two solutions, a first solution having a low TMax and at least a second solution having a Tmax greater than the first solution.
18. The method of claim 10 wherein there are more than two solutions, a first solution having a low TMax and at least a second solution having a Tmax greater than the first solution.
19. The method of claim 1 wherein the two or more solutions have a first solution having a low TMax and at least a second solution having a Tmax greater than the first solution and the solution are used on at least one layer of co-cast multiple layered membrane.
20. The method of claim 10 wherein the two or more solutions have a first solution having a low TMax and at least a second solution having a Tmax greater than the first solution and the solution are used on at least one layer of co-cast multiple layered membrane.