Highly permeable composite membranes with nanoselective surfaces for organic solvent nanofiltration

Abstract

To provide an organic solvent nano filtration membrane.SOLUTION: The organic solvent nano filtration membrane includes an expanded polyparaxylylene (ePPX) membrane coated with at least one polymer. A base material / support layer can be disposed on one side of the ePPX membrane. In some embodiments, the base material / support layer is held between the ePPX membranes. A method for producing and using such an organic solvent nano filtration membrane is also provided. The organic solvent nano filtration membrane can separate and / or condense a solute from a solution containing a low-molecular-weight organic solvent of higher permeability. The ePPX membrane coated with the polymer can have resistance to chemical attacks, resistance to gamma rays, thermal stability, biocompatibility, and strength.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates generally to organic solvent nanofiltration, and more particularly to an organic solvent nanofiltration membrane comprising an expanded polyparaxylylene membrane having at least one polymer coating thereon. Methods for making and using the expanded polyparaxylylene organic solvent nanofiltration membrane are also provided. [Background technology]

[0002] Organic synthesis in the chemical and pharmaceutical industries is often carried out in organic solvents. Separation of soluble products from organic solvents is often energy intensive and a significant part of the total production cost (Marchetti et al. Chem. Rev. 114:10735-10806 (2014)). Organic solvent nanofiltration (OSN) is a versatile technique that is becoming an attractive alternative to traditional separation and purification techniques such as distillation.

[0003] Nanofiltration is a membrane process that utilizes membranes with pores typically in the 0.1-5 nm range, preferably 0.5-5 nm, and molecular weight cutoffs (MWCOs) in the 200-2000 Da range. The MWCO of a membrane is generally defined as the molecular weight of molecules that exhibit at least 90% rejection when subjected to nanofiltration through the membrane. While nanofiltration has been widely applied to the filtration of aqueous fluids, the lack of suitable solvent-stable membranes has limited its application to the separation of solutes in organic solvents (i.e., organic solvent nanofiltration). OSNs have many potential applications in manufacturing, including solvent exchange, catalyst recovery and recycling, purification, and concentration. OSN membranes have been known since the 1980s. Nevertheless, the number of commercially available membranes is still very limited, and the majority are based on crosslinked or non-crosslinked polyimide materials (PI). Crosslinking PI OSN membranes can improve solvent resistance and confer long-term stability in several polar aprotic solvents, including acetone, tetrahydrofuran, and dimethylformamide. However, such membranes are often unsuitable for use in chlorinated solvents, strong amines, strong acids, or strong bases. Furthermore, the recommended maximum operating temperature for such membranes is only 50°C, which poses serious limitations when implementing OSNs in, for example, catalytic processes. Typically, such catalytic reactions are performed in aggressive solvents (e.g., dimethylformamide (DMF)) at high temperatures (e.g., above 100°C) and with high concentrations of strong acids or bases, meaning that only the most stable OSN membranes are suitable. While ceramic membranes have been shown to have greater resistance to organic solvents and high temperatures, their suitability is hindered by their brittle structure and processing difficulties, making it difficult to achieve the desired nanofiltration properties. Furthermore, some large-scale industrial process OSN separations use modules containing hollow fibers or spiral-wound membrane cartridges to provide high surface areas. These modules are typically pressurized to high differential pressures of 5 to 100 bar. These high pressures further exacerbate the problems faced by conventional membranes due to their poor chemical, solvent, mechanical, and temperature stability.

[0004] Porous polytetrafluoroethylene (PTFE) has been used as a filter medium for separating relatively large nanoparticles (e.g., about 20 nanometers (nm) to about 100 nm) from liquid media, for example, to prepare ultrapure water for use in the semiconductor and pharmaceutical industries. Porous PTFE can be in an expanded form, often referred to as expanded polytetrafluoroethylene (ePTFE), which has a node and fibril microstructure that provides a highly porous network that can be fabricated with small average pore sizes for relatively large nanoparticle filtration. However, ePTFE membranes have not been identified for effective use in the nanofiltration of organic solvents.

[0005] There is a need in the art for organic solvent nanofiltration membranes and methods for making such membranes. Summary of the Invention

[0006] According to one embodiment ("Embodiment 1"), an organic solvent nanofiltration (OSN) membrane comprises at least one expanded polyparaxylylene (ePPX) membrane having at least one polymer coating thereon, the ePPX membrane having a microstructure comprising nodes, fibrils, and pores, the nodes being interconnected by the fibrils, the pores being void spaces between the nodes and the fibrils, and the ePPX membrane having an average pore size of about 0.1 nm to about 5 nm.

[0007] According to another embodiment ("Embodiment 2"), in addition to embodiment 1, the polymer coating is on one or both sides of the ePPX membrane.

[0008] According to another embodiment ("embodiment 3"), in addition to embodiments 1 and 2, the nodes and fibrils are at least partially coated with the polymer coating.

[0009] According to another embodiment ("embodiment 4"), in addition to any of the above embodiments, the polymer coating is crosslinked.

[0010] According to another aspect (“Aspect 5”), in addition to any of the above aspects, the at least one polymer coating comprises polyethyleneimine (PEI), branched polyethyleneimine (BPEI), polyvinyl alcohol (PVA), polyvinylidene difluoride (PVDF), amorphous perfluoropolymer, fluorinated ethylene propylene (FEP), and combinations thereof.

[0011] According to another embodiment ("embodiment 6"), in addition to any of the embodiments above, the at least one polymer coating is a crosslinked polymer coating.

[0012] According to another embodiment ("Embodiment 7"), in addition to any of the above embodiments, the at least one stretched ePPX membrane is a composite ePPX membrane, and the composite ePPX membrane comprising the ePPX membrane is bonded on at least one side to at least one additional porous substrate.

[0013] According to another embodiment ("embodiment 8"), in addition to any of the above embodiments, the additional porous substrate is a porous polyolefin.

[0014] According to another embodiment (“Embodiment 9”), in addition to any of the embodiments above, the additional porous substrate comprises polytetrafluoroethylene (PTFE), modified PTFE, or a non-melt-processible copolymer or terpolymer comprising tetrafluoroethylene (TFE).

[0015] According to another embodiment ("embodiment 10"), in addition to any of the above embodiments, the additional porous substrate is an expanded PTFE (ePTFE) membrane.

[0016] According to another embodiment ("embodiment 11"), in addition to any of the above embodiments, the organic solvent nanofiltration membrane is a polymer-coated ePPX-ePTFE composite membrane.

[0017] According to another embodiment ("embodiment 12"), in addition to any of the embodiments above, the at least one polymer coating is not polyparaxylylene.

[0018] According to another embodiment (“Embodiment 13”), in addition to any of the embodiments described above, the ePPX membrane comprises a polyparaxylylene polymer selected from PPX-N, PPX-AF4, PPX-VT4, or any combination thereof.

[0019] According to another embodiment ("embodiment 14"), in addition to any of the above embodiments, the present invention further comprises at least one porous support.

[0020] According to another embodiment (“Aspect 15”), in addition to any of the above embodiments, the porous support is a stainless steel mesh, membrane, woven fabric, or nonwoven fabric made from any combination of crosslinked polyimide, polyamide, polybenzimidazole (PBI), PTFE, crosslinked polyvinyl chloride (PVC), polybutylene terephthalate (PBT), polyethylene terephthalate (PET), polyether ether ketone (PEEK), polyaramid, inorganic silica, or copolymers thereof.

[0021] According to another embodiment ("Embodiment 16"), a system includes: (1) the organic solvent nanofiltration membrane of any of the above embodiments; and (2) (a) a solution passed therethrough, the solution including at least one solute having a first molecular weight and at least one organic solvent having a second molecular weight, the second molecular weight being less than the first molecular weight.

[0022] According to another embodiment (“Embodiment 17”), in addition to embodiment 16, the solute is a pharmaceutical molecule, a petrochemical molecule, a plant extract, a plant oil, an animal extract, a cell extract, a protein, an enzyme, a lipid, an organic catalyst, or an inorganic catalyst.

[0023] According to another embodiment ("embodiment 18"), an article includes the organic solvent nanofiltration membrane of any of the preceding embodiments.

[0024] According to another embodiment (“Embodiment 19”), a filtration device includes: (1) a filtration housing including at least one fluid inlet configured to direct a feed fluid into the filtration housing and at least one fluid outlet configured to direct a filtrate from the filtration housing; and (2) at least one organic solvent nanofiltration membrane of any of the preceding embodiments.

[0025] According to another embodiment (“Embodiment 20”), a method for organic solvent nanofiltration includes (1) providing a filtration housing as disclosed in embodiment 19 and a solution comprising at least one solute having a first molecular weight and at least one organic solvent having a second molecular weight; and (2) passing the solution through the filtration device, wherein percent rejection of the solute is at least 40%, 50%, 60%, 70%, 80%, 90%, 95%, 98%, or 99%.

[0026] According to another embodiment (“Embodiment 21”), in addition to embodiment 20, the solute is a pharmaceutical molecule, a petrochemical molecule, a plant extract, a plant oil, an animal extract, a cell extract, a protein, an enzyme, a lipid, an organic catalyst, or an inorganic catalyst.

[0027] According to another embodiment (“embodiment 22”), further to embodiment 20 or 21, the first molecular weight is at least 150 g / mol, preferably from 150 g / mol to 2500 g / mol.

[0028] According to another embodiment (“embodiment 23”), further to embodiment 20 or 21, the second molecular weight is less than or equal to 450 g / mol, preferably less than 250 g / mol, and most preferably less than 100 g / mol.

[0029] According to another embodiment (“Embodiment 24”), further to embodiments 20 or 21, the first molecular weight is at least 100 g / mol greater than the second molecular weight, preferably at least 250 g / mol greater, and most preferably at least 500 g / mol greater. [Brief explanation of the drawings]

[0030] The accompanying drawings are included to provide a further understanding of the disclosure, and are incorporated in and constitute a part of this specification, illustrate embodiments, and together with the description, serve to explain the principles of the disclosure.

[0031] [Figure 1] FIG. 1 is an elevational view of a filtration device having an organic solvent nanofiltration membrane, according to some embodiments.

[0032] [Figure 2] FIG. 2 is a schematic diagram of a system used to apply a polymer coating to an expanded polyparaxylylene (ePPX) membrane, according to some embodiments.

[0033] [Figure 3] FIG. 3 is a schematic diagram of a nanofilter stirred cell testing apparatus, according to some embodiments.

[0034] [Figure 4] FIG. 4 is a flow chart illustrating an organic solvent nanofiltration process, according to some embodiments.

[0035] [Figure 5] FIG. 5 is a scanning electron micrograph (SEM) of an organic solvent nanofiltration membrane prepared as described in Example 6, according to some embodiments.

[0036] [Figure 6] FIG. 6 is an SEM of an organic solvent nanofiltration membrane prepared as described in Example 7, according to some embodiments. DETAILED DESCRIPTION OF THE INVENTION

[0037] Glossary The term "PPX" refers to polyparaxylylene or parylene.

[0038] The term "PPX polymer" is intended to include all forms of PPX, including but not limited to those shown in Table 1 and combinations thereof. [Table 1]

[0039] As used herein, the term "PPX polymer film" is intended to refer to unstretched PPX polymer in either a free-standing configuration without an underlying substrate, or in a composite configuration on one or more sides of a substrate (e.g., PPX polymer film / substrate, PPX polymer film / substrate / PPX polymer film).

[0040] As used herein, the terms "PPX polymer membrane" or "stretched PPX membrane" or "ePPX membrane" are intended to refer to a PPX polymer film that has been stretched in one or more directions and comprises a node and fibril microstructure with pores.

[0041] As used herein, the terms "polymer-coated ePPX membrane," "ePPX membrane having at least one polymer coating," and "coated ePPX membrane" refer to an ePPX membrane to which a polymer coating has been applied that partially occludes and reduces the average pore size to a range suitable for organic solvent nanofiltration, or alternatively, increases the solute rejection rate for solutes having molecular solution dimensions less than 5 nm, such as 0.5 nm to 2 nm. The ePPX membrane can be in a composite configuration with another porous expanded polymer membrane, such as an ePTFE membrane (referred to herein as a "composite ePPX membrane"), prior to application of the polymer coating that partially occludes and reduces the average pore size to a range suitable for organic solvent nanofiltration.

[0042] The terms "composite polymer-coated ePPX membrane" and "organic solvent nanofiltration membrane" refer to a composite ePPX membrane (i.e., an ePPX membrane having at least one additional expanded polymer membrane substrate / support layer (such as an ePTFE membrane) that may have a node and fibril microstructure), where the composite ePPX membrane is coated with at least one polymer that partially occludes and thus reduces the average pore size of the composite ePPX membrane.

[0043] As used herein, the terms "biaxial" or "biaxially oriented" are intended to describe a polymer, film, preform, or article that has been stretched in at least two directions, either simultaneously or sequentially. The ratio of the matrix tensile strengths (MTS) in two orthogonal directions (i.e., longitudinal / machine direction vs. transverse direction, x / y plane) can be used to describe the relative "balance" of a biaxially oriented film. Balanced films typically exhibit an MTS ratio of about 2:1 or less.

[0044] As used herein, the phrase "partially plugging the pores" refers to the application of a polymer coating to a porous ePPX membrane (or ePPX composite membrane) that effectively reduces the average pore size to a range suitable for organic solvent nanofiltration applications. The amount of polymer coating applied is controlled so as not to completely plug (completely clog / block) the pores of the ePPX membrane, rendering the resulting composite unsuitable for organic solvent nanofiltration applications. The type of polymer coating and the relative thickness of the coating can be adjusted to tune / adjust organic solvent nanofiltration performance (e.g., permeance / flux, solute rejection, concentration factor, or any combination thereof).

[0045] The term "organic solvent nanofiltration" or "OSN" refers to a filtration process using at least one nanoporous membrane to separate and / or concentrate one or more bulky solutes (i.e., solutes having a molecular weight greater than about 150 g / mol, greater than about 300 g / mol, greater than about 500 g / mol, between about 150 g / mol and about 2500 g / mol, between about 300 g / mol and about 2500 g / mol) from lower molecular weight organic solvents (i.e., organic solvents typically less than or equal to 450 g / mol, less than or equal to 250 g / mol, less than 150 g / mol, or less than or equal to 100 g / mol). The organic solvent and solute should have a relative difference in molecular weight such that the ePPX membrane can selectively separate them by size. In one embodiment, the solute has a molecular weight at least 100 g / mol, at least 250 g / mol, or at least 500 g / mol higher than the molecular weight of the organic solvent. Filtration of organic solutions through OSN membranes allows the organic solvent to preferentially pass through the membrane (i.e., filtrate / permeate), while larger solute molecules are concentrated on the retentate side of the membrane. Due to the often harsh filtration conditions (solvent, temperature, pressure, UV light, etc.), it is desirable to use membranes that are thin, strong, chemically inert, and / or thermally stable.

[0046] As used herein, the term "thin" is intended to describe a thickness of less than about 50 microns.

[0047] Detailed Description Those skilled in the art will readily appreciate that various aspects of the present disclosure can be implemented by any number of methods and apparatuses configured to perform the intended functions. It should also be noted that the accompanying drawings referenced herein are not necessarily drawn to scale and may be exaggerated to illustrate various aspects of the present disclosure, and in that regard, the drawings should not be construed as limiting. It should be understood that the terms "OSN" and "organic solvent nanofiltration" can be used interchangeably herein. It should also be understood that the terms "substrate / support layer" and "support layer" can be used interchangeably herein. It should be further understood that in the present disclosure, occlusive coatings may not be strictly separated based on pore size. For example, occlusive layers can be "non-porous" (e.g., completely blocked) within the pores and separate via solution diffusion.

[0048] Referring initially to FIG. 1 , an embodiment of an organic solvent nanofiltration (OSN) device 100 is shown with an OSN membrane 102 disposed within the interior volume of a filtration housing 104. The OSN membrane 102 comprises a porous expanded polyparaxylylene (ePPX) polymer membrane having at least one polymer coating thereon. The exemplary OSN membrane 102 includes a first polymer-coated ePPX membrane 110, a second polymer-coated ePPX membrane 112, and an intermediate substrate / support layer 114. In some embodiments, the intermediate layer is a polymer membrane having a node and fibril microstructure, such as, but not limited to, an ePTFE membrane. It should be understood that in some embodiments, the substrate / support layer may be porous but not have a node and fibril microstructure. Alternatively, the OSN membrane 102 can have a composite configuration including a composite polymer-coated ePPX membrane layer 110, a composite polymer-coated ePPX membrane layer 112 (which may be the same as or different from the composite polymer-coated ePPX membrane layer 110), and an intermediate substrate / support layer 114. As one example, the organic solvent nanofiltration membrane 102 can be disc-shaped. However, the size and shape of the organic solvent nanofiltration membrane 102 can be modified to fit within a desired filtration housing 104 and / or to accommodate the intended organic solvent nanofiltration application. For example, the organic solvent nanofiltration membrane 102 can have a cylindrical shape, a pleated cartridge shape, a spiral wound shape, or another suitable shape.

[0049] Filtration housing 104 has at least one fluid inlet port 120 in fluid communication with polymer-coated ePPX membrane layer 110 and at least one fluid outlet port 122 in fluid communication with polymer-coated ePPX membrane layer 112. It also includes one or more support structures, such as annular shelf 106, configured to support OSN membrane 102 within filtration housing 104 between fluid inlet port 120 and fluid outlet port 122.

[0050] During operation of the fluid filtration device 100, a feed fluid 124 containing a solution having at least one solute in an organic solvent is fed into the filtration housing 104 through the fluid inlet port 120 in the direction indicated by arrow A1. The feed fluid 124 can include at least one organic solvent or a blend or more than one organic solvent. The feed fluid 124 can be used in the pharmaceutical, microelectronics, chemical, and / or food industries. In certain embodiments, the feed fluid 124 can be concentrated. The solutes in the feed fluid 124 are bulkier and have a higher molecular weight than the organic solvent. During use, the feed fluid 124 moves through the housing 104 toward the OSN membrane 102 in the direction indicated by arrow A2. The OSN membrane 102 separates (at least partially) the solutes from the feed fluid 124, and a filtrate / permeate containing the organic solvent 126 moves through the housing 104 in the direction indicated by arrow A3 and is removed from the filtration housing 104 through the fluid outlet port 122 in the direction indicated by arrow A4. In certain embodiments, filtration device 100 includes a second fluid outlet port 128 that removes retentate 129 in the direction indicated by arrow A5, as shown in Figure 1. In other embodiments, filtration device 100 lacks second fluid outlet port 128, and the retained solutes remain on or within organic solvent nanofiltration membrane 102.

[0051] Each of the polymer-coated ePPX membranes 110, 112 of the OSN membrane 102 has a node and fibril microstructure. In at least one embodiment, the fibrils of one or both of the polymer-coated ePPX membranes 110, 112 comprise PPX polymer chains oriented along the fibril axis.

[0052] 1, the organic solvent nanofiltration membrane 102 has two polymer-coated ePPX membranes 110, 112 on either side of the substrate / support layer 114. However, it is within the scope of this disclosure for the OSN membrane 102 to include a single polymer-coated ePPX membrane on only one side of the substrate / support layer 114. It is also within the scope of this disclosure for the OSN membrane 102 to include more than two polymer-coated ePPX membrane layers.

[0053] The substrate / support layer 114 of the organic solvent filtration membrane 102 is not particularly limited, so long as the substrate / support layer 114 is dimensionally stable. If desired, the substrate / support layer 114 may be removable from the polymer-coated ePPX membrane layers 110, 112. If the substrate / support layer 114 is not removed from the polymer-coated ePPX membrane layers 110, 112 and remains part of the composite filtration membrane 102, the substrate / support layer 114 should be porous to allow the feed fluid 124 to pass through the pores of the substrate 114. Non-limiting examples of porous materials suitable for the substrate / support layer 114 include stainless steel mesh, membranes, ultrafilters, nanofilters, woven or nonwoven materials made from any combination of cross-linked polyimide, polyamideimide, polyamide, glass, zinc, polybenzimidazole (PBI), PTFE, cross-linked polyvinyl chloride (PVC), polybutylene terephthalate (PBT), polyethylene terephthalate (PET), polyether ether ketone (PEEK), polyaramid, inorganic silica, or copolymers thereof. In some embodiments, the substrate / support layer 114 can be formed from a partially expanded ePTFE tape or membrane that can be substantially deformed in one or more directions. While the organic solvent nanofiltration membrane 102 of FIG. 1 has a single substrate / support layer 114, it is within the scope of this disclosure for the filtration membrane 102 to include multiple substrate / support layers.

[0054] Various properties of each of the polymer-coated ePPX membranes 110, 112 of the filtration membrane 102 and / or the substrate / support layer 114 can be optimized to achieve the desired filtration performance with the desired permeability to the particular solutes to be separated from the feed fluid 124. As discussed in the following paragraphs, properties that can be optimized include, for example, thickness, average pore size, % porosity, polymer coating type, and polymer coating thickness. Other properties that can be optimized include, for example, node and / or fibril geometry, or ePPX membrane size and density.

[0055] As discussed above, the thickness of the polymer-coated ePPX membranes 110, 112 and the substrate / support layer 114 can be optimized for a desired application. Each of the polymer-coated ePPX membranes 110, 112 of the organic solvent nanofiltration membrane 102 can have a nominal thickness of less than about 50 microns, less than about 40 microns, less than about 30 microns, less than about 20 microns, less than about 10 microns, less than about 5 microns, less than about 3 microns, less than about 2 microns, or less than about 1 micron. In some embodiments, each of the polymer-coated ePPX membranes 110, 112 has a thickness of about 0.1 microns to about 50 microns, about 0.1 microns to about 40 microns, about 0.1 microns to about 30 microns, about 0.1 microns to about 20 microns, about 0.1 microns to about 10 microns, about 0.1 microns to about 5 microns, about 0.1 microns to about 3 microns, about 0.1 microns to about 2 microns, or about 0.1 microns to about 1 micron. In comparison, the substrate / support layer 114 of the organic solvent nanofiltration membrane 102 can be relatively thick (eg, greater than about 50 microns).

[0056] Additionally, the porosity of the polymer-coated ePPX membranes 110, 112 and the substrate / support layer 114 can be optimized. Each of the polymer-coated ePPX membranes 110, 112 of the organic solvent nanofiltration membrane 102 can have relatively small pore sizes of less than about 3 nanometers (nm), less than about 2 nm, less than about 1 nm, or less than about 0.5 nm. In some embodiments, each of the polymer-coated ePPX membranes 110, 112 can have pores of about 0.01 nm to about 5 nm, about 0.5 nm to about 5 nm, about 0.5 nm to about 3 nm, about 0.5 nm to about 2 nm, or about 0.5 nm to about 1 nm. Additionally, each of the polymer-coated ePPX membranes 110, 112 can have a porosity of at least about 5%, at least about 10%, at least about 15%, at least about 20%, at least about 25%, at least about 30%, at least about 35%, at least about 40%, at least about 45%, at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90% or up to about 95% (and inclusive).

[0057] The organic solvent nanofiltration membrane 102 can have one or more different microstructures. In at least one embodiment, the polymer-coated ePPX membranes 110, 112 share the same or substantially the same microstructure, such that the microstructures are indistinguishable from one another. In another embodiment, the polymer-coated ePPX membrane 110 has a first microstructure, and the polymer-coated ePPX membrane 112 has a second microstructure that is different from the first microstructure. Differences between the various microstructures of the polymer-coated ePPX membranes 110, 112 can be measured, for example, by differences in porosity, differences in node and / or fibril geometry or size, and / or differences in density.

[0058] 1 , the small pores of the polymer-coated ePPX polymer membranes 110, 112 can enable the organic solvent nanofiltration membrane 102 to separate and retain various types and sizes of solutes, as long as the solutes are bulkier / larger than the organic solvent. In certain embodiments, such as when separating relatively large solutes from a feed fluid 124, the organic solvent nanofiltration membrane 102 can achieve solute retention rates of about 40% or more, about 60% or more, about 80% or more, or about 90% or more with each pass. The organic solvent filtration membrane 102 can achieve different degrees of filtration depending on the size of the pores in the PPX polymer membranes 110, 112.

[0059] Additionally, the thin structure of the polymer-coated ePPX membranes 110, 112 and / or the relatively large pores of the substrate / support layer 114 create a highly permeable (i.e., low resistance to flow) organic solvent nanofiltration membrane 102 that can accommodate a high flow rate of feed fluid 124 at a given pressure. For example, the organic solvent nanofiltration membrane 102 can have a permeability of at least about 100 LMH / bar, at least about 20 LMH / bar, at least about 10 LMH / bar, at least about 1 LMH / bar, or at least about 0.5 LMH / bar. The organic solvent nanofiltration membrane 102 can also be resistant to chemical attack, resistant to gamma radiation, thermally stable, biocompatible, robust, or any combination thereof.

[0060] The organic solvent nanofiltration membrane 102 can also include one or more support layers / backers depending on the application. Examples of suitable supports / backers include membranes made from materials such as cross-linked polyimide, polytetrafluoroethylene (PTFE), expanded PTFE (ePTFE), cross-linked polyvinyl chloride (PVC), polybutylene terephthalate (PBT), polyethylene terephthalate (PET), polyether ether ketone (PEEK), aramid (e.g., KEVLAR®), ultrafilters, nanofilters, woven or non-woven fabrics, stainless steel mesh, inorganic silica membranes, or any combination thereof.

[0061] Referring now to Figure 2, a method (200) for applying a polymer coating to an ePPX membrane is shown. A solution (210) containing dissolved polymer is placed (270) in contact with a (hoop and supported) ePPX membrane (230) positioned on a support / substrate (240) within a glass funnel (220). A vacuum (295) applied to a Buchner flask (250) draws the coating solution (210) through the supported ePPX membrane (230), collecting excess coating solution (290) at the bottom (280) of the flask. A rubber stopper (260) can be used to hold the glass funnel (220) above the flask (250). Scanning electron micrographs (SEM) of exemplary organic solvent nanofiltration membranes are provided as Figures 5 and 6.

[0062] Figure 3 is a diagram of a system (300) used to measure membrane performance, including a pressurized nanofiltration (NF) stirred cell (Millipore / Amicon 8050) apparatus (310) equipped with a magnetic stirrer (315) and magnetic stir plate (317). In Figure 3, an organic solvent nanofiltration membrane (325) is attached adjacent to an O-ring (322) and sealed to the bottom of the stirred cell according to the manufacturer's instructions using a gasket with a nonwoven support disk (320) to enhance flow distribution. The cell is filled with the charge solvent / solute, and gas pressure is supplied by a nitrogen source (330) and adjusted via a pressure regulator (340) to the desired set-point pressure, as read by a pressure gauge (345), to achieve the set pressure for the test. Liquid is forced from a liquid reservoir within the stirred cell through the filter media downstream of the filter and into tubing (350) through an outlet port. The liquid exits the tube and is collected in a reservoir (360) on an electronic balance (370) connected to a computer data acquisition system (380) that records the mass as a function of time.

[0063] Referring now to Figure 4, a general organic solvent nanofiltration process (400) is shown in which a solution (410) containing solutes in at least one organic solvent is filtered (430) through an organic solvent nanofiltration membrane (420). A fluid filtrate / permeate containing organic solvent (450) is collected. At least a portion of the solutes are preferentially retained and concentrated on the retentate (440) side of the OSN membrane (420).

[0064] Polymer coating applied to ePPX membrane

[0065] Various polymers can be used to coat and partially block the pores of ePPX membranes. Such polymers include, but are not limited to, polyvinylidene difluoride (PVDF), polyvinyl alcohol (PVA), polyethyleneimine (PEI), branched polyethyleneimine (BPEI), amorphous perfluoropolymer, fluorinated ethylene propylene (FEP), and combinations thereof. In one embodiment, the amount and thickness of the applied polymer coating are adjusted to optimize organic solvent nanofiltration performance (selectivity, permeability, etc.). In another embodiment, the polymer coating can be crosslinked with a suitable crosslinking agent.

[0066] The polymer coating can be applied using a variety of techniques, such as chemical vapor deposition, atomic layer deposition, sputter coating, solvent coating / absorption, nanoparticle dispersion coating, and any combination thereof. The polymer coating can be applied to one side (e.g., using a slot die) or both sides (e.g., dip coating) of the ePPX film. In one embodiment, solvent coating follows the process described in the examples and shown in FIG. 2.

[0067] The thickness of the polymer coating can vary as long as it does not completely block the pores (i.e., does not completely block the flow of organic solvent) but still promotes selective separation of the solute from the organic solvent. In one embodiment, the thickness of the polymer coating ranges from 100 nm to 5 μm.

[0068] The final average pore size range (after coating) is about 0.1 nm to about 5 nm, about 0.5 nm to about 3 nm, about 0.5 nm to about 2 nm, about 0.5 to about 1.5 nm, or about 0.5 nm to about 1 nm.

[0069] solute

[0070] The compositions and methods described herein can be used to selectively separate and / or concentrate a solute or solutes from a solution containing at least one organic solvent. In one embodiment, the organic solvent nanofiltration membranes of the present invention separate solutes that are relatively larger / bulkier than the corresponding organic solvent in the fluid matrix. In one embodiment, the solute can have a molecular weight greater than about 150 g / mol, greater than about 300 g / mol, greater than about 500 g / mol, from about 150 g / mol to about 2500 g / mol, from about 300 g / mol to about 2000 g / mol, or from about 500 g / mol to about 1000 g / mol. The corresponding organic solvent can have a molecular weight of about 450 g / mol or less, about 250 g / mol or less, about 150 g / mol or less, or about 100 g / mol or less, as long as the solute has a larger molecular weight than the organic solvent in the fluid matrix.

[0071] In one embodiment, the solute is a pharmaceutical ingredient / intermediate, a high molecular weight / high boiling point petrochemical molecule, a food industry molecule, such as a plant extract / oil (e.g., vegetable oil), an animal extract (e.g., oil, etc.), a cell extract (biomolecule, protein, enzyme, lipid, etc.), a monomer, or a catalyst, to name a few.

[0072] In another embodiment, polymer-coated ePPX membranes can be used to selectively separate multiple solutes from complex feedstreams such as those found in petrochemical refineries. For example, the solutes can be crude oil or fractions such as bottle oil, white oil, or wide-cut diesel fuel. Additional solutes can include wide- or heavy-cut hydrocarbons of various aliphatic, olefinic, paraffinic, and naphthalene species, and the solvent can include complex mixtures of low-boiling linear or cyclic hydrocarbons, such as, but not limited to, the BTEX series (e.g., benzene, toluene, ethylbenzene, and xylene). Polymer-coated ePPX membranes can separate these from higher molecular weight compounds or within individual families (e.g., xylene to paraxylene). Furthermore, polymer-coated ePPX membranes can achieve separation of components with different degrees of oxidation state, chirality, or other molecular fractionation. Such examples include the dewaxing of lubricating fluids.

[0073] Typically, the pressure used for the membrane OSN may include 4 to 200 bar, or 4 to 60 bar.

[0074] organic solvents

[0075] Table 2 provides a non-limiting list of common organic solvents, along with their respective molecular weights and chemical formulas. [Table 2]

[0076] Organic solvent nanofiltration process conditions

[0077] Typical organic solvent nanofiltration (OSN) separations vary widely depending on the application and are performed on flat disks measuring tens of cm 2 filter areas (e.g., in the purification of pharmaceuticals or the filtration of catalysts from pilot stirred-tank reactors) to several thousand m 2(for separations in the petrochemical industry) The membranes utilized preferably exhibit stable rejection of solutes, the ability to concentrate these solutes, and the ability to permeate them at an appropriate rate.

[0078] In one embodiment, the percent (%) rejection of solutes by the polymer-coated ePPX membrane is at least about 40%, about 50%, about 60%, about 70%, about 80%, about 90%, about 95%, about 98%, or about 99%. In a further embodiment, the % solute rejection is greater than or equal to 13.4 cm after at least 75% by volume of the starting solution volume has been collected in the permeate. 2 In addition to high percent (%) rejection, the polymer-coated ePPX membranes have a high percent (%) rejection of at least about 1, about 5, about 10, about 15, about 20, about 50, or about 100 (liters / m²) as measured using a differential pressure of 60 psi (about 413.7 kPa) over an effective filter area of ​​100 liters / m². 2 It also has a transmittance of 1 / hr) / bar.

[0079] In another embodiment, the concentration factor (CF; fold increase of solute in the retentate) is at least about 1.1, about 1.25, about 1.5, about 1.75, about 2, about 3, about 4, about 5, about 10, about 25, about 50, or about 100.

[0080] Membrane performance can also be characterized by the membrane nominal molecular weight cutoff (MWCO), which is defined as the smallest solute molecular weight for which the membrane has at least 90% rejection. In one embodiment, the MWCO of the polymer-coated ePPX is about 300, about 400, about 500, about 600, about 700, about 800, about 900, about 1000, about 1500, or about 2000 Da.

[0081] Test Method Although particular methods and apparatus are described below, it should be understood that other methods or apparatus may be substituted as deemed suitable by those skilled in the art.

[0082] Thickness

[0083] The thickness of the samples was measured using a Keyence LS-7010M digital micrometer (Keyence Corporation, Mechelen, Belgium).

[0084] Mass per area (mass / area) The mass / area of ​​the membrane was calculated by measuring the mass of a well-defined area of ​​the membrane sample using a scale. The sample was cut into a defined area using a die or any precise cutting device.

[0085] density

[0086] Density was calculated by dividing the mass per area by the thickness.

[0087] Determining organic solvent nanofiltration performance using rose bengal dye.

[0088] The nanofiltration performance of various polymer-coated expanded polyparaxylylene (ePPX) membranes was measured using an organic solution containing Rose Bengal dye (4,5,6,7-tetrachloro-2',4',5',7'-tetraiodofluorescein disodium salt; CAS 632-69-9; MW 1017.64 g / mol). The preparation of polymer-coated ePPX membranes is described in U.S. Patent Publication No. US2016 / 0032069 to Sbriglia. Coated ePPX-PTFE membrane samples were punched to size and mounted on the nonwoven fabric of an AMICON® stirred cell concentrator / separator (Merck KGaA, Darmstadt, Germany). Solvent nanofiltration performance was tested using Rose Bengal dye solution. Rose Bengal dye rejection was recorded, and the average ethanol-Rose Bengal dye permeability was measured. The tests were conducted at a constant nitrogen pressure of 60 psi (approximately 413.7 kPa), the cells were filled with 20 mL of Rose Bengal dye solution at a concentration of 5 mg / L, and 15 mL of fluid was collected as permeate at the end of the test unless otherwise noted.

[0089] LMH / bar (liters per meter 2 The permeation rate (at saturation pressure / hour / bar) was recorded. As used herein, the term "permeation rate" is defined as a measure of the degree to which a material allows fluid to pass through it and is calculated as the filtration flux divided by the test pressure. As used herein, "filtration flux" is defined as the volumetric flow rate in liters / hour divided by the effective filtration area. The volumetric flow rate (L / hr) was determined by measuring the mass of liquid filtered by collection on a calibrated scale and dividing this by the density of ethanol (approximately 0.8 g / cm at 20°C). 3 ) to convert to volume and then divided by the filtration time. Filtration time was determined by electronic logging using a data logger (PendoTECH, Princeton, NJ) with a computer or by recording the filtration time with a stopwatch. The effective filter area was 13.4 cm as specified by the stirred cell manufacturer for the Millipore / Amicon 8050 stirred cell (Merck KGaA, supra). 2 The pressure was determined using a pressure gauge.

[0090] Organic solvent nanofiltration membranes can efficiently separate solute molecular species, such as Rose Bengal dye, from organic solvent feed streams, such as ethanol. One measure of separation efficiency is the concentration of the solute downstream of the filter (Csolute down ) is the concentration of solute upstream of the filter (Csolute upstream ) minus 1 and multiply by 100 (Equation 1). [Number 1] Formula 1: % Elimination Rate=((Csolute down / Csolute upstream )-1)x100

[0091] Indeed, effective industrial processes require efficient separation membranes that allow for a % rejection of solutes from the solvent of at least 60%, more preferably at least 80%, and most preferably at least 90%. Furthermore, in many industrial settings, it is desirable to separate and concentrate solutes. Solute concentration can be achieved by varying the stage cut in a recirculating cross-flow system or dead-end stirred cell as used herein. In the case of concentration, the concentration factor CF is the ratio of Csolute in the retentate to Csolute in the retentate. initial (upstream) / Csolute final It is often convenient to calculate the enrichment factor, given as the ratio of (upstream) to (Equation 2). [Number 2] Formula 2: CF=Csolute initial (upstream) / Csolute final (upstream)

[0092] For the dead-end stirred cell used in the examples herein, CF = CSolute final (upstream) / Csolute initial (upstream), where "initial" refers to the input value at time = 0 and "final" refers to the concentration at the end of the test after permeation of a finite volume. For example, it may be desirable to increase the concentration of a diluent molecule to a concentration useful for applying a concentration factor of at least 1.5X, preferably at least 2X, and more preferably greater than 3X.

[0093] Rose Bengal dye concentrations were analytically determined using spectrophotometry as described in the literature (Linden, S.M., and D.C. Neckers, "Type I and type II sensitizers based on Rose Bengal ionium salts," Photochem. Photobiol. 47, 543-550 (1988)). An Agilent Cary UV-vis spectrophotometer (Agilent Technologies Inc., Santa Clara, CA) was used with a quartz cuvette. A Beer's Law calibration curve was constructed by serially diluting the dye in ethanol using the peak absorbance at 560 nm. Transmission samples were then collected and diluted as necessary, and the measured absorbance was compared to the Beer's Law curve to calculate the solution concentration. [Example]

[0094] example

[0095] The invention of this application has been described both generically and with reference to specific embodiments. It will be apparent to those skilled in the art that various modifications and variations can be made to the embodiments without departing from the scope of the present disclosure. Thus, it is intended that the embodiments cover the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.

[0096] Example 1 (comparison)

[0097] Expanded polyparaxylylene (ePPX) membrane - no additional polymer coating

[0098] Using the method described in U.S. Patent Application Publication No. 2016 / 0032069 to Sbriglia, a film of polyparaxylylene (PPX-AF4) with a nominal thickness of 1 μm was deposited on both sides of a blended, extruded, and dried PTFE tape. This tape is typically manufactured by a commercially available vapor deposition process (Specialty Coating Systems, 7645 Woodland Drive, Indianapolis, IN 46278) following the teachings of U.S. Patent No. 3,953,566 to Gore. The coated article was then cut to 200 mm x 200 mm and placed in the grips of a pantograph-type twin-screw batch expander equipped with a convection oven. The coated article (tape) was subjected to a constant temperature of 350°C for 300 seconds. The coated tape was then simultaneously stretched at an engineering strain rate (ESR) of 100 percent (%) / sec to a stretch ratio of 4:1 in the tape machine direction (MD) and 4:1 in the tape cross direction (TD). The stretched article (stretched film) was cooled to room temperature (about 22°C) under the restraint of the pantograph biaxial expander grips. After cooling, the stretched polyparaxylylene film was removed from the expander grips.

[0099] The expanded polyparaxylylene membrane had a gas-liquid bubble point of >250 pounds per square inch (psi) (>1.72 MPa). The expanded polyparaxylylene membrane was die-cut and mounted on a Typar® 3151 polypropylene spunbond nonwoven (Typar Geosynthetics, Roseville, MN) in an AMICON® / Millipore Model 8050 stirred cell concentrator / separator (Merck KGaA, Darmstadt, Germany). Solvent nanofiltration performance was tested using a solution of Rose Bengal lactone dye (Santa Cruz Biotechnology, Dallas, Texas) (4,5,6,7-tetrachloro-2',4',5',7'-tetraiodofluorescein disodium salt; CAS11121-48-5; MW 1017.62 g / mol) in ethanol. No rejection of Rose Bengal dye was observed (0% rejection) and an average ethanol-Rose Bengal flux of 235 LMH / bar was recorded (Table 3).

[0100] Example 2 (comparison)

[0101] Commercially available nanofiltration membranes

[0102] A DURAMEM® 500 modified polyimide membrane (molecular weight cut-off (MWCO) 500 Da; Evonik Degussa Corp., Parsipany, NJ) was die-cut and mounted on a Typar® 3151 polypropylene spunbond nonwoven (Typar Geosynthetics, supra) in an AMICON® stirred cell (Merck KGaA, supra) and tested for solvent nanofiltration performance using the rose bengal and ethanol solution prepared as described above. Seventy-five percent (75%) of the feed load was filtered to obtain the filtrate / permeate. Rejection of rose bengal dye was observed (60% rejection), and an average ethanol-rose bengal flux of 0.5 LMH / bar was recorded (Table 3).

[0103] Example 3

[0104] Polyvinyl alcohol (PVA) coating on composite stretched polyparaxylylene film

[0105] Using the method described in U.S. Patent Publication No. 2016 / 0032069 to Sbriglia, a nominally 1 μm thick film of PPX-AF4 was deposited on both sides of a blended, extruded, and dried PTFE tape. The tape was manufactured by a commercially available vapor deposition process (Specialty Coating Systems, cited above) following the teachings of U.S. Patent No. 3,953,566 to Gore. The composite ePPX film was then cut to 200 mm x 200 mm dimensions and placed in the grips of a pantograph-type biaxial batch expander equipped with a convection oven. The composite ePPX film was subjected to a constant temperature of 350°C for 300 seconds. The composite ePPX film was then simultaneously stretched at an engineering strain rate (ESR) of 100% / sec to a 4:1 draw ratio in the tape machine direction and a 4:1 draw ratio in the cross-tape direction. The stretched composite ePPX membrane was cooled to room temperature (about 22° C.) under the restraint of the pantograph biaxial expander grips. After cooling, the stretched composite ePPX membrane was removed from the expander grips.

[0106] The stretched composite ePPX membrane had a gas-liquid bubble point of >250 psi (>1.72 MPa). The stretched composite ePPX membrane was pre-wetted with 10 mL of isopropanol. The pre-wetted stretched composite ePPX membrane was mounted on a filter paper support in a 90 mm or 150 mm diameter glass vacuum funnel and was then loaded with 0.69 mg / cm. 2A coating solution of polyvinyl alcohol polymer USP (MW approximately 100,000) (Spectrum Chemical, New Brunswick, NJ) in water (the polymer was slowly dissolved in reverse osmosis-purified water by gentle heating and stirring on a hot plate at 0.04 molar, then cooled and diluted to 0.004 molar) was dosed in water by methods known in the art. The PVA solution was drawn into a stretched composite ePPX membrane via vacuum at 15 mmHg (approximately 20 mbar) until no liquid was visible on the membrane surface. The composite polymer-coated ePPX membrane (organic solvent nanofiltration membrane) was removed from the vacuum funnel, restrained in a hoop, and then air-dried. The dried composite polymer-coated ePPX membrane was placed coated-side up in an AMICON® stirred cell concentrator / separator (Merck KGaA, as described above), and its organic solvent nanofiltration performance was tested as described above. Seventy-five percent (75%) of the feed charge was filtered to obtain filtrate. The concentration factor CF = 2.7X, the average rejection rate was 57, and the average permeation rate was 15.4 LMH / bar (Table 3).

[0107] Example 4

[0108] Branched polyethyleneimine (BPEI)-crosslinked coatings on composite stretched polyparaxylylene films

[0109] Using the method described in U.S. Patent Publication No. 2016 / 0032069 to Sbriglia, a film of polyparaxylylene (PPX-AF4) with a nominal thickness of 1 μm was deposited on both sides of a blended, extruded, and dried PTFE tape. This tape is generally manufactured by a commercially available vapor deposition process (Specialty Coating Systems, cited above) following the teachings of U.S. Patent No. 3,953,566 to Gore. The composite ePPX film was then cut to 200 mm x 200 mm and placed in the grips of a pantograph-type biaxial batch expander equipped with a convection oven. The composite ePPX film was subjected to a constant temperature of 350°C for 300 seconds. The composite ePPX film was then simultaneously stretched at an engineering strain rate (ESR) of 100% / sec to a 4:1 draw ratio in the tape machine direction and a 4:1 draw ratio in the cross-tape direction. The stretched composite ePPX membrane was allowed to cool to room temperature (approximately 22°C) under the restraint of the pantograph biaxial expander grips. After cooling, the stretched composite ePPX membrane was removed from the expander grips. The stretched composite ePPX membrane had a gas-liquid bubble point of >250 psi (>1.72 MPa). The stretched composite ePPX membrane was then pre-wetted with 10 mL of isopropanol. The pre-wetted stretched composite ePPX membrane was mounted on a filter paper support in a 90 mm or 150 mm diameter glass vacuum funnel and diluted to 0.05 mg / cm. 2 of branched poly(ethyleneimine) (BPEI) coating solution (catalog no. 181978, Sigma-Aldrich, St Louis, MO) was administered.

[0110] Branched poly(ethyleneimine) solution was dissolved in isopropanol (Sigma Aldrich, St. Louis, MO) at a concentration of 0.64 mg BPEI / L isopropanol by stirring. The BPEI coating solution was drawn through the stretched composite ePPX membrane via vacuum at 15 mmHg (approximately 20 mbar) until no liquid was visible on the surface of the stretched composite ePPX membrane. The stretched composite ePPX membrane was then contacted with 0.1 g multifunctional glycidyl glycerol-ether crosslinking solution (catalog number 9221-50, Polysciences Inc., Warrington, PA) in 20 mL of IPA by vacuum filtering the solution through the stretched composite ePPX membrane for 1 minute, as with the initial coating solution. It was then successively rinsed with 40 mL of IPA and 40 mL of water by continuous vacuum filtering, as was done throughout the coating process. The BPEI-crosslinked stretched PPX-PTFE membrane (the composite polymer-coated ePPX membrane) was removed from the vacuum funnel, restrained in a hoop, and allowed to air dry. The dried PPX-PTFE membrane was placed on an AMICON® stirred cell concentrator / separator (Mark KGaA, supra) with the upper side facing the vacuum coating solution and tested for organic solvent nanofiltration performance as described above. Seventy-five percent (75%) of the feed charge was filtered to filtrate / permeate. The feed concentration was increased to CF=3.94X, with an average rejection of 98% and an average flux of 23.2 LMH / bar (Table 3).

[0111] Example 5

[0112] Polyvinylidene difluoride (PVDF) coating on stretched PPX film

[0113] Using the method described in U.S. Patent Publication No. 2016 / 0032069 to Sbriglia, a film of polyparaxylylene (PPX-AF4) with a nominal thickness of 1 μm was deposited on both sides of a blended, extruded, and dried PTFE tape. This tape is typically made by a commercially available vapor deposition process (Specialty Coating Systems, cited above) following the teachings of U.S. Patent No. 3,953,566 to Gore. The composite ePPX film (tape) was then cut to a dimension of 200 mm x 200 mm and placed in the grips of a pantograph-type biaxial batch expander equipped with a convection oven. The composite ePPX film was subjected to a constant temperature of 350°C for 300 seconds. The composite ePPX film was then simultaneously stretched at an engineering strain rate (ESR) of 100% / sec to a 4:1 draw ratio in the tape machine direction and a 4:1 draw ratio in the cross-tape direction. The stretched composite ePPX membrane was allowed to cool to room temperature (approximately 22°C) under the restraint of the pantograph biaxial expander grips. After cooling, the stretched composite ePPX membrane was removed from the expander grips. The stretched composite ePPX membrane had a gas-liquid bubble point of >250 psi (>1.72 MPa). The stretched composite ePPX membrane was pre-wetted with 10 mL of isopropanol. The pre-wetted stretched composite ePPX membrane was mounted on a filter paper support in a 90 mm or 150 mm diameter glass vacuum funnel and dissolved in 0.34 mg / cm2 of dimethylacetamide (DMAc) at 70°C. 2A polyvinylidene difluoride (PVDF) coating solution (Grade 955 from Arkema (Arkema Inc., King of Prussia, PA)) was dosed at 2.2 g / L and stirred overnight using methods known in the art. The room-temperature PVDF solution was drawn through a stretched composite ePPX membrane pre-wetted with 20 mL of acetone via vacuum at 15 mmHg (approximately 20 mbar) until no liquid was visible on the surface. This was followed by rinsing with 20 mL of water and 20 mL of isopropyl alcohol via vacuum filtration at the same pressure differential as the initial coating. The PVDF-coated ePPX-PTFE membrane (composite polymer-coated ePPX membrane) was removed from the vacuum funnel, restrained in a hoop, and then air-dried. The dried PVDF-coated ePPX-PVDF membrane was placed face-up in an AMICON® stirred-cell concentrator / separator (Merck KGaA, supra) and tested for organic solvent nanofiltration performance as described above. Seventy-five percent (75%) of the feed charge was filtered to filtrate / permeate. The feed concentration was increased to CF=3.7X with an average rejection of 90% and an average permeation rate of 24.7 LMH / bar (Table 3).

[0114] Example 6

[0115] CYTOP® Type A amorphous perfluoropolymer coating on composite stretched PPX film

[0116] Using the method described in U.S. Patent Application Publication No. 2016 / 0032069 to Sbriglia, a film of polyparaxylylene (PPX-AF4) with a nominal thickness of 1 μm was deposited on both sides of the blended, extruded, and dried PTFE. This tape is generally manufactured by a commercially available vapor deposition process (Specialty Coating Systems, cited above) following the teachings of U.S. Patent No. 3,953,566 to Gore. The composite ePPX membrane (tape) was then cut to a dimension of 200 mm x 200 mm and placed in the grips of a pantograph-type biaxial batch expander equipped with a convection oven. The composite ePPX membrane was subjected to a constant temperature of 350°C for 300 seconds. The composite ePPX membrane was then simultaneously stretched at an engineering strain rate (ESR) of 100% / sec to a 4:1 draw ratio in the tape machine direction and a 4:1 draw ratio in the cross-tape direction. The stretched composite ePPX membrane was cooled to room temperature (approximately 22°C) under the restraint of the pantograph biaxial expander grips. After cooling, the stretched composite ePPX membrane was removed from the expander grips. The stretched composite ePPX membrane had a gas-liquid bubble point of >250 psi (>1.72 MPa). The stretched composite ePPX membrane was then pre-wetted with 10 mL of isopropanol. The pre-wetted stretched composite ePPX membrane was mounted on a filter paper support in a 90 mm or 150 mm diameter glass vacuum funnel and filled with 0.05 mg / cm of isopropanol dissolved in HFE-7500 (3-ethoxyl-1,1,1,2,3,4,4,5,5,6,6,6-dodecafluoro-2-trifluoromethylhexane (also known as Novec 7500™; MW = 414.1; 3M Corporation, St. Paul, MN). 2A CYTOP® amorphous perfluoropolymer coating solution (CYTOP® Polymer Type A; typical molecular weight 250K-300K; AGC Chemicals Americas, Inc., Exton PA) was dosed at 0.2 weight percent by methods known in the art. The CYTOP® coating solution was drawn into the stretched composite ePPX membrane via vacuum at 15 mmHg (approximately 20 mbar) until no liquid was visible on the surface. The composite polymer-coated ePPX membrane was removed from the vacuum funnel, restrained in a hoop, air-dried, and oven-dried at 360°C for 10 minutes. The dried CYTOP®-coated composite ePPX membrane was placed face-up in an AMICON® stirred cell concentrator / separator (Merck KGaA, as described above) and tested for organic solvent nanofiltration performance as described above. Seventy-five percent (75%) of the feed charge was filtered to obtain the filtrate / permeate. The feed concentration was increased to CF = 3.61X, with an average rejection of 88% and an average permeation rate of 100 LMH / bar. Figure 5 shows a scanning electron micrograph (SEM) of a CYTOP®-coated stretched composite ePPX membrane.

[0117] Example 7

[0118] Fluorinated ethylene propylene (FEP) coating on composite stretched PPX film

[0119] Using the method described in U.S. Patent Publication No. 2016 / 0032069 to Sbriglia, a nominally 1 μm thick film of polyparaxylylene (PPX-AF4) was deposited on both sides of a blended, extruded, and dried PTFE tape. This tape is typically made by a commercially available vapor deposition process (Specialty Coating Systems, cited above) following the teachings of U.S. Patent No. 3,953,566 to Gore. The composite ePPX film (tape) was then cut to 200 mm x 200 mm dimensions and placed in the grips of a pantograph-type biaxial batch expander equipped with a convection oven. The composite ePPX film was subjected to a constant temperature of 350°C for 300 seconds. The composite ePPX film was then simultaneously stretched at an engineering strain rate (ESR) of 100% / sec to a 4:1 draw ratio in the tape machine direction and a 4:1 draw ratio in the cross-tape direction. The stretched composite ePPX membrane was allowed to cool to room temperature (approximately 22°C) under the restraint of the pantograph biaxial expander grips. After cooling, the stretched composite ePPX membrane was removed from the expander grips. The stretched composite ePPX membrane had a gas-liquid bubble point of >250 psi (>1.72 MPa). The stretched composite ePPX membrane was then pre-wetted with 10 mL of isopropanol. The pre-wetted stretched composite ePPX membrane was then mounted on a filter paper support in a 90 mm or 150 mm diameter glass vacuum funnel and immersed in 0.06 mg / cm2 of isopropanol. 2of FEP coating solution (fluorinated ethylene propylene 121 D dispersion (The Chemours Company, Wilmington, Del.) diluted to a 0.25 weight percent solids concentration in isopropanol by methods known in the art) was applied to the expanded composite ePPX membrane via a vacuum of 15 mmHg (approximately 20 mbar) until no liquid was visible on the surface. The FEP-coated ePPX-PTFE membrane was removed from the vacuum funnel, restrained in a hoop, air-dried, and then oven-dried at 360°C for 10 minutes. After oven-drying, the ePPX-PTFE membrane was placed face-up in an AMICON® stirred-cell concentrator / separator (Merck KGaA, supra) and tested for nanofiltration performance as described above. Seventy-five percent (75%) of the feed charge was filtered to filtrate / permeate, and the feed concentration increased to CF = 3.76X, with an average rejection of 92% and an average flux of 1 LMH / bar (Table 3). Figure 6 shows the SEM image of the FEP-coated membrane. [Table 3]

Claims

1. 1. An organic solvent nanofiltration (OSN) membrane comprising at least one expanded polyparaxylylene (ePPX) membrane having at least one polymer coating thereon, wherein the ePPX membrane has a microstructure comprising nodes, fibrils, and pores, the nodes being interconnected by the fibrils, the pores being void spaces between the nodes and the fibrils, the at least one polymer coating partially blocking the pores, and the organic solvent nanofiltration membrane having an average pore size of 0.1 nm to 5 nm.

2. 10. The organic solvent nanofiltration membrane of claim 1, wherein the polymer coating is on one or both sides of the ePPX membrane.

3. 3. The organic solvent nanofiltration membrane of claim 1, wherein the nodes and fibrils are at least partially coated with the polymer coating.

4. The organic solvent nanofiltration membrane of any one of claims 1 to 3, wherein the polymer coating is crosslinked.

5. 5. The organic solvent nanofiltration membrane of claim 1, wherein the at least one polymer coating comprises polyethyleneimine (PEI), branched polyethyleneimine (BPEI), polyvinyl alcohol (PVA), polyvinylidene difluoride (PVDF), amorphous perfluoropolymer, fluorinated ethylene propylene (FEP), and combinations thereof.

6. The organic solvent nanofiltration membrane of any one of claims 1 to 5, wherein the at least one polymer coating is a cross-linked polymer coating.

7. 7. The organic solvent nanofiltration membrane of claim 1, wherein the at least one expanded ePPX membrane is a composite ePPX membrane, the composite ePPX membrane comprising the ePPX membrane bonded on one side to at least one additional porous substrate.

8. The organic solvent nanofiltration membrane of claim 7 , wherein the additional porous substrate is a porous polyolefin.

9. 8. The organic solvent nanofiltration membrane of claim 7, wherein the additional porous substrate comprises polytetrafluoroethylene (PTFE), modified PTFE, or a non-melt-processible copolymer or terpolymer comprising tetrafluoroethylene (TFE).

10. The organic solvent nanofiltration membrane of claim 7, wherein the additional porous substrate is expanded PTFE (ePTFE).

11. The organic solvent nanofiltration membrane according to any one of claims 1 to 10, wherein the organic solvent nanofiltration membrane is a polymer-coated ePPX-ePTFE composite membrane.

12. The organic solvent nanofiltration membrane of any one of claims 1 to 11, wherein said at least one polymer coating is not polyparaxylylene.

13. The organic solvent nanofiltration membrane of any one of claims 1 to 12, wherein the ePPX membrane comprises a polyparaxylylene polymer selected from PPX-N, PPX-AF4, PPX-VT4, or any combination thereof.

14. The organic solvent nanofiltration membrane of any one of claims 1 to 13, further comprising at least one porous support.

15. 15. The organic solvent nanofiltration membrane of claim 14, wherein the porous support is a stainless steel mesh, membrane, ultrafilter, nanofilter, woven fabric, or nonwoven fabric made from any combination of cross-linked polyimide, polyamide, polybenzimidazole (PBI), PTFE, cross-linked polyvinyl chloride (PVC), polybutylene terephthalate (PBT), polyethylene terephthalate (PET), polyether ether ketone (PEEK), polyaramid, inorganic silica, or copolymers thereof.

16. 10. The organic solvent nanofiltration membrane of claim 1, wherein the membrane is configured to filter a solute from a solution and has a percent rejection of the solute of at least 40%.

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