Dry process membrane for filtration
The development of dry process microporous membranes with controlled pore sizes and thicknesses addresses stability issues, enabling efficient and stable filtration processes for gases and liquids.
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- CELGARD LLC
- Filing Date
- 2026-03-18
- Publication Date
- 2026-07-29
AI Technical Summary
Existing filtration membranes for nanofiltration and ultrafiltration lack mechanical stability, dimensional stability, and have pore sizes that are too large for effective commercial applications, leading to unpredictable performance during filtration processes.
Development of dry process microporous membranes with average pore sizes less than 0.035 microns and thicknesses less than 14 microns, composed of polypropylene-containing layers, with low shrinkage rates and suitable for use in single, two, three, or multilayer configurations, enhancing mechanical and dimensional stability.
The membranes exhibit high dimensional stability and appropriate pore sizes, ensuring reliable performance and efficient filtration of gases and liquids, with flow times ranging from 400 to 40,000 seconds, making them suitable for nanofiltration and ultrafiltration processes.
Smart Images
Figure 2026122948000001_ABST
Abstract
Description
Technical Field
[0001] This application is directed to dry process membranes suitable for use in filtration processes. Such processes may include ultrafiltration or nanofiltration.
Background Art
[0002] The main use of filtration membranes is to remove unwanted materials from the flow of useful fluids. Many gaseous and liquid fluids in industry, including ambient air, drinking water, fuels, liquid industrial solvents and process fluids, industrial gases used in manufacturing or processing, and liquids for medical or pharmaceutical applications, are processed using filters. Unwanted materials removed from the fluid include impurities and contaminants such as particles, microorganisms, and dissolved chemical species. Specific examples of impurity removal applications for filtration membranes include use in the pharmaceutical industry to remove particles or bacteria from therapeutic solutions, use to process ultra-pure aqueous and organic solvent solutions for use in microelectronics processing, and use for air and water purification processes. Nanofiltration and / or ultrafiltration are often used in these processes. Membranes for nanofiltration and ultrafiltration desirably exhibit one or more of the following characteristics: mechanical stability, dimensional stability, flow rates suitable for commercial applications, and low levels of contaminants. Improvements in any or all of these areas are desirable.
Summary of the Invention
[0003] Dry process microporous membranes for use in filtration are described herein. In some embodiments, at least one layer of the membrane has an average pore size of less than 0.035 microns and a thickness of less than 14 microns. In some embodiments, the average pore size of a single layer may be less than 0.03 microns, less than 0.025 microns, or less than 0.020 microns. In some preferred embodiments, the average pore size may be about 0.010 to about 0.020 microns. In some preferred embodiments, the average pore size may be about 0.010 to about 0.020 microns. In some embodiments, at least one layer may have an average pore size of less than 0.035 microns, and the thickness of the layer may be less than 12 microns. In some embodiments, the average pore size of a single layer may be less than 0.03 microns, less than 0.025 microns, or less than 0.020 microns. In some preferred embodiments, the average pore size may be about 0.010 to about 0.020 microns. In some embodiments, the average pore size of at least one layer may be less than 0.035 microns, and the thickness of the layer may be less than 10 microns. In some embodiments, the average pore size of a single layer may be less than 0.03 microns, less than 0.025 microns, or less than 0.020 microns. In some preferred embodiments, the average pore size may be about 0.010 to about 0.020 microns.
[0004] In some of the embodiments described herein, at least one layer may be a polypropylene-containing layer.
[0005] In some of the embodiments described above, the film may be a single-layer film, a two-layer film, a three-layer film, or a multilayer film. A two-layer film, a three-layer film, or a multilayer film may be formed by laminating two or more layers, co-extruding two or more layers, or by a combination of lamination and extrusion steps.
[0006] In some of the embodiments described above, the film may be a three-layer film comprising a polypropylene-containing layer, a polyethylene-containing layer, and a polypropylene-containing layer in that order.
[0007] In some of the embodiments described herein, the film thickness is less than 14 microns, less than 12 microns, or less than 10 microns.
[0008] In some embodiments, the film is translucent or transparent. In some embodiments, the film may have a bluish tint and may be translucent or transparent.
[0009] In some of the embodiments described herein, the shrinkage rate of the film at 90°C for 1 hour is less than 25%, less than 20%, less than 15%, less than 10%, or less than 5%.
[0010] In some of the embodiments described herein, the membrane has a flow time of 400 to 40,000 seconds. The flow time may be measured using isopropyl alcohol (IPA), and the flow time is 12.5 cm 2 This is the time it takes to flow 500 ml of isopropyl alcohol through a 47 mm disc of a membrane having a surface area at a temperature of 21°C and a pressure of 0.1 MPa.
[0011] In some embodiments, the film may have a hydrophilic treatment or coating on at least one side. This may be useful for filtration where water or alcohol is used as the solvent.
[0012] In another embodiment, an ultrafiltration or nanofiltration process is described. One step of the process is to filter a solvent through the aforementioned membranes described herein.
[0013] In another element, a filtration element comprising the aforementioned membrane and a housing is described herein. [Brief explanation of the drawing]
[0014] [Figure 1] Figure 1 is a SEM image of the dry-process microporous membrane described herein. [Modes for carrying out the invention]
[0015] The subject matter of the aspects of this disclosure is described herein in a manner that satisfies legal requirements. However, the description itself does not limit the scope of the patent. Rather, the inventors intended that the subject matter described in the claims could also be embodied in other ways to include, together with other current or future technologies, different steps or combinations of steps similar to those described in this document. Furthermore, the terms “step” and / or “block” may be used herein to imply different elements of the method used, but these terms should not be construed as implying any particular order among or between the various steps disclosed herein, except where the order of the individual steps is expressly stated, and with the exception of that case.
[0016] Accordingly, the embodiments described herein can be more readily understood by referring to the following detailed description, examples, and figures. However, the elements, apparatus, and methods described herein are not limited to the specific embodiments presented in the detailed description, examples, and figures. It should be recognized that the exemplary embodiments herein are merely principles of the present invention. Numerous modifications and adaptations will be immediately obvious to those skilled in the art without departing from the spirit and scope of the invention.
[0017] Furthermore, it should be understood that all scopes disclosed herein encompass any sub-scopes incorporated herein. For example, the stated range "1.0 to 10.0" should be considered to encompass any sub-scopes beginning with a minimum value of 1.0 or greater and ending with a maximum value of 10.0 or less, such as 1.0 to 5.3, or 4.7 to 10.0, or 3.6 to 7.9.
[0018] All scopes disclosed herein should also be considered to include the endpoints of the scope unless otherwise expressly stated. For example, the scopes “between 5 and 10,” or “5 to 10,” or “5 to 10” should generally be considered to include endpoints 5 and 10.
[0019] Furthermore, when the phrase "up to" is used in relation to quantity or amount, it must be understood that the quantity is at least one detectable quantity or amount. For example, material present in an amount "up to" a specified amount may exist from a detectable amount up to that amount containing the specified amount.
[0020] In addition, in any disclosed embodiment, the terms “substantially,” “approximately,” and “about” may be replaced within the specified [percentage], such percentages encompassing 0.1, 1, 5, and 10 percent.
[0021] Dry process microporous membranes for use in filtration are described herein. In some embodiments, at least one layer of the membrane has an average pore diameter of less than 0.035 microns and a thickness of less than 14 microns, less than 13 microns, less than 12 microns, less than 11 microns, less than 10 microns, less than 9 microns, less than 8 microns, less than 7 microns, less than 6 microns, less than 5 microns, less than 4 microns, less than 3 microns, less than 2 microns, or less than 1 micron. In some embodiments, at least one layer of the membrane has an average pore diameter of less than 0.030 microns and a thickness of less than 14 microns, less than 13 microns, less than 12 microns, less than 11 microns, less than 10 microns, less than 9 microns, less than 8 microns, less than 7 microns, less than 6 microns, less than 5 microns, less than 4 microns, less than 3 microns, less than 2 microns, or less than 1 micron. In some embodiments, at least one layer of the film has an average pore diameter of less than 0.025 microns and a thickness of less than 14 microns, less than 13 microns, less than 12 microns, less than 11 microns, less than 10 microns, less than 9 microns, less than 8 microns, less than 7 microns, less than 6 microns, less than 5 microns, less than 4 microns, less than 3 microns, less than 2 microns, or less than 1 micron. In some embodiments, at least one layer of the film has an average pore diameter of less than 0.020 microns and a thickness of less than 14 microns, less than 13 microns, less than 12 microns, less than 11 microns, less than 10 microns, less than 9 microns, less than 8 microns, less than 7 microns, less than 6 microns, less than 5 microns, less than 4 microns, less than 3 microns, less than 2 microns, or less than 1 micron. In some embodiments, at least one layer of the film has an average pore diameter of less than 0.015 microns and a thickness of less than 14 microns, less than 13 microns, less than 12 microns, less than 11 microns, less than 10 microns, less than 9 microns, less than 8 microns, less than 7 microns, less than 6 microns, less than 5 microns, less than 4 microns, less than 3 microns, less than 2 microns, or less than 1 micron.In some embodiments, at least one layer of the film has an average pore diameter of less than 0.010 microns and a thickness of less than 14 microns, less than 13 microns, less than 12 microns, less than 11 microns, less than 10 microns, less than 9 microns, less than 8 microns, less than 7 microns, less than 6 microns, less than 5 microns, less than 4 microns, less than 3 microns, less than 2 microns, or less than 1 micron. In some embodiments, at least one layer of the film has an average pore diameter of less than 0.005 microns and a thickness of less than 14 microns, less than 13 microns, less than 12 microns, less than 11 microns, less than 10 microns, less than 9 microns, less than 8 microns, less than 7 microns, less than 6 microns, less than 5 microns, less than 4 microns, less than 3 microns, less than 2 microns, or less than 1 micron. In some preferred embodiments, at least one layer of the film has an average pore size of about 0.010 to about 0.020 microns and a thickness of less than 14 microns, less than 13 microns, less than 12 microns, less than 11 microns, less than 10 microns, less than 9 microns, less than 8 microns, less than 7 microns, less than 6 microns, less than 5 microns, less than 4 microns, less than 3 microns, less than 2 microns, or less than 1 micron. , has.
[0022] In some of the embodiments described herein, at least one layer may be a polypropylene-containing layer. The polypropylene-containing layer may be a layer containing, consisting of, or essentially comprising a polypropylene homopolymer, copolymer, or combination thereof. The polypropylene-containing layer may contain, consist of, or essentially consist of 50% or more of a polypropylene homopolymer, copolymer, or combination thereof.
[0023] In some of the embodiments described above, the film may be a single-layer film, a two-layer film, a three-layer film, or a multilayer film. A multilayer film may have four or more layers. A two-layer, three-layer, or multilayer film may be formed by laminating two or more layers, co-extruding two or more layers, or by a combination of lamination and extrusion steps.
[0024] In some embodiments, the membrane may have a total thickness of less than 20 microns, less than 19 microns, less than 18 microns, less than 17 microns, less than 16 microns, less than 15 microns, less than 14 microns, less than 13 microns, less than 12 microns, less than 11 microns, less than 10 microns, less than 9 microns, less than 8 microns, less than 7 microns, less than 6 microns, less than 5 microns, less than 4 microns, less than 3 microns, less than 2 microns, or less than 1 micron.
[0025] For example, in one embodiment, the membrane may be a single-layer membrane, at least one layer of the membrane has an average pore size of less than 0.035 (preferably between 0.010 and 0.020 microns), has a thickness of 7 microns, and the total membrane thickness is 7 microns. The membrane may be two layers, at least one layer of the membrane has an average pore size of less than 0.035 (preferably between about 0.010 and 0.020 microns), has a thickness of 4 microns, and the total membrane thickness is 8 microns.
[0026] In some of the foregoing embodiments, the membrane may be a three-layer membrane including a polypropylene-containing layer, a polyethylene-containing layer, and a polypropylene-containing layer in this order. In some of the foregoing embodiments, the membrane may be a three-layer membrane including a polyethylene-containing layer, a polypropylene-containing layer, and a polyethylene-containing layer. The polyethylene-containing layer may be a layer, a layer consisting of, or a layer consisting essentially of a polyethylene homopolymer, copolymer, or a combination thereof. The polyethylene-containing layer may contain, consist of, or consist essentially of 50% or more of a polyethylene homopolymer, copolymer, or a combination thereof.
[0027] A dry process membrane, as understood by those skilled in the art, is a membrane formed without using a solvent or oil to form pores. In some embodiments, membranes formed by using particulate pore formers may also be excluded from the dry process membranes. Such membranes can include beta-nucleated biaxially oriented polypropylene (BNBOPP) membranes. The dry process membrane has a distinct and uniform pore structure recognizable by those skilled in the art. For example, refer to FIG. 1 showing a uniaxially stretched dry process membrane. As can be seen from FIG. 1, the dry process film has elongated pores or slit-shaped pores. The pores of the biaxially stretched dry process membrane may be too large for use in ultrafiltration or nanofiltration applications.
[0028] In some of the foregoing embodiments of the present specification, the shrinkage rate of the membrane at 90 °C for 1 hour is less than 25%, less than 20%, less than 15%, less than 10%, or less than 5%, less than 4%, less than 3%, less than 2%, or less than 1%. A low shrinkage rate is an indicator of high dimensional stability and is significant. During filtration applications or during filter assembly, the shrinkage of the membrane can cause the membrane to break, tear, or modify other properties, thereby rendering the performance no longer sufficient and / or unpredictable. The shrinkage rate is measured by measuring the membrane (L1), placing the membrane in an oven at 90 °C for 1 hour without fixing it, measuring the membrane after placing it in the oven (L2), and calculating the shrinkage rate using the following formula 1. [[ID=[7]] (L1 - L2 / L1) × 100 (1)
[0029] The flow times using IPA are 400 seconds or more, approximately 400 seconds to approximately 40,000 seconds, 500 seconds to approximately 40,000 seconds, 600 seconds to approximately 40,000 seconds, 700 seconds to approximately 40,000 seconds, 800 seconds to approximately 40,000 seconds, 900 seconds to approximately 40,000 seconds, 1,000 seconds to approximately 40,000 seconds, 2,000 seconds to approximately 40,000 seconds, 3,000 seconds to approximately 40,000 seconds, 4,000 seconds to approximately 40,000 seconds, 5,000 seconds to approximately 40,000 seconds, and 6,000 seconds. The flow time may be within the range of approximately 40,000 seconds, 7,000 seconds to approximately 40,000 seconds, 8,000 seconds to approximately 40,000 seconds, 9,000 seconds to approximately 40,000 seconds, 10,000 seconds to approximately 40,000 seconds, approximately 11,000 seconds to approximately 40,000 seconds, 17,000 seconds to approximately 40,000 seconds, 20,000 seconds to approximately 40,000 seconds, 25,000 seconds to approximately 40,000 seconds, 30,000 seconds to approximately 40,000 seconds, or within the range of 35,000 seconds to approximately 40,000 seconds. The flow time may also be the flow time using IPA (isopropyl alcohol), and the flow time is 12.5 cm. 2 This is the time for flowing 500 ml of isopropyl alcohol (IPA) through a 47 mm disc of a membrane having a surface area at a temperature of 21°C and a pressure of 0.1 MPa. [Examples]
[0030] Example 1 is a dry-process single-layer polypropylene-containing film having a total thickness of 7 microns.
[0031] Example 2 is a dry-process three-layer film containing three polypropylene-containing layers with a total thickness of 6 microns. The polypropylene-containing layer with the smallest pore size has a thickness of approximately 2 microns and a pore size of 22 nm.
[0032] Example 3 is a dry-process film having a pore size of 20 nm.
[0033] Comparative Example 1 is a dry-process single-layer polypropylene-containing film having a total thickness of 7 microns.
[0034] Comparative Example 2 is a dry-process three-layer film containing a polypropylene-containing layer, a polyethylene-containing layer, and another polypropylene-containing layer in that order. The total thickness of the film is 20 microns, with an additional PP-containing layer thickness of 14 microns. The average pore size of the PP is 35 nm.
[0035] [Table 1]
[0036] Comparative Example 2 has the problem of having pores that are too large for nanofiltration or ultrafiltration processes. Comparative Example 1 has a high shrinkage rate, which makes it unsuitable for use due to its low dimensional stability. Shrinkage of the film during application or assembly may result in rupture, tearing, or modification of other properties of the film, thereby making the performance insufficient and / or unpredictable. Examples 1 and 2 have high dimensional stability (e.g., low shrinkage rate) and sufficiently small pore size for use in nanofiltration or ultrafiltration processes (including filtration of gases or liquids).
Claims
1. A dry process microporous membrane for filtration, wherein at least one layer of the membrane has an average pore diameter of less than 0.035 microns and a thickness of less than 14 microns.
2. The dry process microporous film according to claim 1, wherein the average pore diameter is less than 0.030 microns.
3. The dry process microporous film according to claim 1, wherein the average pore diameter is less than 0.025 microns.
4. The dry process microporous film according to claim 1, wherein the average pore diameter is less than 0.020 microns.
5. The dry process microporous film according to claim 1, wherein the average pore size is 10 nm to 20 nm.
6. A dry process microporous film according to claim 1, having a thickness of less than 12 microns.
7. The dry process microporous film according to claim 6, wherein the average pore diameter is less than 0.030 microns.
8. The dry process microporous film according to claim 6, wherein the average pore diameter is less than 0.025 microns.
9. The dry process microporous film according to claim 6, wherein the average pore diameter is less than 0.020 microns.
10. The dry process microporous film according to claim 6, wherein the average pore size is between 10 nm and 20 nm.
11. A dry process microporous film according to claim 1, having a thickness of less than 10 microns.
12. The dry process microporous membrane according to claim 11, wherein the average pore diameter is less than 0.030 microns.
13. The dry process microporous film according to claim 11, wherein the average pore diameter is less than 0.025 microns.
14. The dry process microporous film according to claim 11, wherein the average pore diameter is less than 0.020 microns.
15. The dry process microporous film according to claim 11, wherein the average pore size is 10 nm to 20 nm.
16. The dry process microporous membrane according to claim 1, wherein at least one of the layers is a polypropylene-containing layer.
17. The dry process according to claim 6, wherein at least one of the layers is a polypropylene-containing layer. Microporous membrane.
18. The dry process microporous membrane according to claim 11, wherein at least one of the layers is a polypropylene-containing layer.
19. The dry process microporous membrane according to claim 1, wherein the membrane is a single-layer membrane.
20. The dry process microporous membrane according to claim 6, wherein the membrane is a single-layer membrane.
21. The dry process microporous membrane according to claim 11, wherein the membrane is a single-layer membrane.
22. The dry process microporous membrane according to claim 1, wherein the membrane is a two-layer membrane.
23. The dry process microporous membrane according to claim 6, wherein the membrane is a two-layer membrane.
24. The dry process microporous membrane according to claim 11, wherein the membrane is a two-layer membrane.
25. The dry process microporous membrane according to claim 1, wherein the membrane is a three-layer or multilayer membrane.
26. The dry process microporous membrane according to claim 6, wherein the membrane is a three-layer or multilayer membrane.
27. The dry process microporous membrane according to claim 11, wherein the membrane is a three-layer or multilayer membrane.
28. The dry process microporous membrane according to claim 25, wherein the membrane is a three-layer structure comprising a polypropylene-containing layer, a polyethylene-containing layer, and a polypropylene-containing layer in that order.
29. The dry process microporous membrane according to claim 26, wherein the membrane is a three-layer structure comprising a polypropylene-containing layer, a polyethylene-containing layer, and a polypropylene-containing layer in that order.
30. The dry process microporous membrane according to claim 27, wherein the membrane is a three-layer structure comprising a polypropylene-containing layer, a polyethylene-containing layer, and a polypropylene-containing layer in that order.
31. The dry process microporous membrane according to claim 25, wherein the membrane is a three-layer structure comprising a polyethylene-containing layer, a polypropylene-containing layer, and a polyethylene-containing layer in that order.
32. The dry process microporous membrane according to claim 26, wherein the membrane is a three-layer structure comprising a polyethylene-containing layer, a polypropylene-containing layer, and a polyethylene-containing layer in that order.
33. The dry process microporous membrane according to claim 27, wherein the membrane is a three-layer structure comprising a polyethylene-containing layer, a polypropylene-containing layer, and a polyethylene-containing layer in that order.
34. The dry process microporous film according to claim 25, wherein the film has a total thickness of less than 14 microns, less than 12 microns, or less than 10 microns.
35. The dry process microporous film according to claim 28, wherein the film has a total thickness of less than 14 microns, less than 12 microns, or less than 10 microns.
36. The dry process microporous membrane according to claim 1, wherein the shrinkage rate at 90°C for 1 hour is less than 25%, less than 20%, less than 15%, less than 10%, or less than 5%.
37. The dry process microporous membrane according to claim 6, wherein the shrinkage rate at 90°C for 1 hour is less than 25%, less than 20%, less than 15%, less than 10%, or less than 5%.
38. The dry process microporous membrane according to claim 11, wherein the shrinkage rate at 90°C for 1 hour is less than 25%, less than 20%, less than 15%, less than 10%, or less than 5%.
39. A dry process microporous membrane according to claim 1, having a flow time using IPA of 400 to 40,000 seconds.
40. A dry process microporous membrane according to claim 6, having a flow time using IPA of 400 to 40,000 seconds.
41. A dry process microporous membrane according to claim 11, having a flow time using IPA of 400 to 40,000 seconds.
42. A dry process microporous membrane according to claim 1, having a flow time using IPA of 11,000 to 40,000 seconds.
43. A dry process microporous membrane according to claim 6, having a flow time using IPA of 11,000 to 40,000 seconds.
44. A dry process microporous membrane according to claim 11, having a flow time using IPA of 11,000 to 40,000 seconds.
45. The dry process microporous membrane according to claim 1, wherein the membrane is transparent or translucent.
46. The dry process microporous membrane according to claim 6, wherein the membrane is transparent or translucent.
47. The dry process microporous membrane according to claim 11, wherein the membrane is transparent or translucent.
48. A dry process microporous membrane according to claim 1, comprising hydrophilic treatment or coating on at least one side.
49. The dry process microporous membrane according to claim 6, comprising hydrophilic treatment or coating on at least one side.
50. The dry process microporous membrane according to claim 11, comprising hydrophilic treatment or coating on at least one side.
51. An ultrafiltration or nanofiltration process comprising filtering a solvent through the membrane described in claim 1.
52. The process according to claim 51, wherein the solvent is an aqueous solvent, an alcohol, or an organic solvent.
53. A filtration element comprising a dry process membrane according to claim 1 and a housing.