Multilayer composite membranes

Abstract

The present disclosure provides composite membranes including a porous substrate, a gutter layer, and a separation layer. The gutter layer is located between the porous substrate and the separation layer. The gutter layer includes a segmented polydiorganosiloxane copolymer that contains at least two repeat units of Formula (I): wherein: each R1 is independently an alkyl, haloalkyl, aralkyl, alkenyl, aryl, or aryl substituted with an alkyl, alkoxy, or halo; each Y is independently an alkylene, aralkylene, or a combination thereof; G is a divalent residue equal to a diamine of formula R3HN-G-NHR3 minus the two –NHR3 groups; R3 is hydrogen or alkyl or R3 taken together with G and to the nitrogen to which they are both attached form a heterocyclic group; n is independently an integer of 0 to 1500; p is an integer of 1 to 10; and q is an integer of 1 or greater.

Description

PA103183W002MULTILAYER COMPOSITE MEMBRANESBackground

[0001] Separation membranes are known; however, there is a continual need for effective composite membranes.Summary

[0002] In a first aspect, a composite membrane is provided. The composite membrane comprises a porous substrate, a gutter layer, and a separation layer. The gutter layer includes a segmented polydiorganosiloxane copolymer comprising at least two repeat units of Formula I:

[0003] wherein: each R1is independently an alkyl, haloalkyl, aralkyl, alkenyl, aryl, or aryl substituted with an alkyl, alkoxy, or halo; each Y is independently an alkylene, aralkylene, or a combination thereof; G is a divalent residue equal to a diamine of formula R3HN-G-NHR3minus the two -NHR3groups; R3is hydrogen or alkyl or R3taken together with G and to the nitrogen to which they are both attached form a heterocyclic group; n is independently an integer of 0 to 1500; p is an integer of 1 to 10; and q is an integer of 1 or greater. The gutter layer is disposed between the porous substrate and the separation layer.

[0004] The above summary of the present disclosure is not intended to describe each disclosed embodiment or every implementation of the present disclosure. The description that follows more particularly exemplifies illustrative embodiments. In several places throughout the application, guidance is provided through lists of examples, which examples may be used in various combinations. In each instance, the recited list serves only as a representative group and should not be interpreted as an exclusive list.Brief Description of Drawings

[0005] FIG. 1 is a schematic cross-sectional view of an exemplary composite membrane according to the present disclosure;

[0006] FIG. 2 is a schematic cross-sectional view of another exemplary composite membrane according to the present disclosure including various optional layers; and

[0007] FIG. 3 is a plot of carbon dioxide permeance versus gutter layer thickness for two different polyorganosiloxane materials.

[0008] While the above-identified figures set forth various embodiments of the disclosure, other embodiments are also contemplated, as noted in the description. In all cases, this disclosure presentsembodiments of the invention by way of representation and not limitation. The figures are not necessarily to scale. Like numbers used in the figures refer to like components. However, it will be understood that the use of a number to refer to a component in a given figure is not intended to limit the componelnt in another figure labeled with the same number.Detailed Description

[0009] Glossary:

[0010] The term “length” refers to the longest dimension of an object.

[0011] The term “layer” refers to a material that has a substantially larger length and width than height (e.g., substantially larger in the x-y plane than the z-plane).

[0012] The term “thickness” refers to the smallest dimension of a fdm or layer, e.g., in a z-axis while a major surface of the film or layer is in the x- and y-axes.

[0013] The term “porous substrate” refers to a support material that may include one or more layers and a plurality of pores.

[0014] The term “gutter layer” refers to a layer that is present on a major surface of a porous substrate and functions to channel gases towards pores of the porous substrate.

[0015] The term “separation layer” refers to a layer that functions to selectively separate at least two gases from each other.

[0016] The term “interfacial layer” refers to a layer that forms a common boundary between two other layers.

[0017] The term “protection layer” refers to a layer that functions to shield at least one other layer from damage.

[0018] The term “alkyl” refers to a monovalent group that is a radical of an alkane, which is a saturated hydrocarbon. The alkyl can be linear, branched, cyclic, or combinations thereof and typically has 1 to 20 carbon atoms. In some embodiments, the alkyl group contains 1 to 18, 1 to 12, 1 to 10, 1 to 8, 1 to 6, or 1 to 4 carbon atoms. Examples of alkyl groups include, but are not limited to, methyl, ethyl, n- propyl, isopropyl, n-butyl, isobutyl, tert-butyl, n-pentyl, n-hexyl, cyclohexyl, n-heptyl, n-octyl, ethylhexyl, n-dodecyl, 2-dodecyl, 3-dodecyl, 4-dodecyl, and 5-dodecyl.

[0019] The term “alkylene” is the multivalent (e.g., divalent or trivalent) form of the “alkyl” groups defined above.

[0020] The term “alkenyl” refers to a monovalent group that is a radical of an alkene, which is a hydrocarbon with at least one carbon-carbon double bond. The alkenyl can be linear, branched, cyclic, or combinations thereof and typically contains 2 to 20 carbon atoms. In some embodiments, the alkenyl contains 2 to 18, 2 to 12, 2 to 10, 4 to 10, 4 to 8, 2 to 8, 2 to 6, or 2 to 4 carbon atoms. Exemplary alkenyl groups include ethenyl, n-propenyl, and n-butenyl.

[0021] The term “alkoxy” refers to a monovalent group of formula -OR where R is an alkyl group.

[0022] The term “alkoxycarbonyl” refers to a monovalent group of formula -(CO)OR where R is an alkyl group and (CO) denotes a carbonyl group with the carbon attached to the oxygen with a double bond.

[0023] The term “aralkyl” refers to a monovalent group of formula -Ra-Ar where Rais an alkylene and Ar is an aryl group. That is, the aralkyl is an alkyl substituted with an aryl.

[0024] The term “aralkylene” refers to a divalent group of formula -Ra-Ara- where Rais an alkylene and Ara is an arylene (i.e., an alkylene is bonded to an arylene).

[0025] The term “aryl” refers to a monovalent group that is aromatic and carbocyclic. The aryl can have one to five rings that are connected to or fused to the aromatic ring. The other ring structures can be aromatic, non-aromatic, or combinations thereof. Examples of aryl groups include, but are not limited to, phenyl, biphenyl, terphenyl, anthryl, naphthyl, acenaphthyl, anthraquinonyl, phenanthryl, anthracenyl, pyrenyl, perylenyl, and fluorenyl.

[0026] The term “arylene” refers to a divalent group that is carbocyclic and aromatic. The group has one to five rings that are connected, fused, or combinations thereof. The other rings can be aromatic, non- aromatic, or combinations thereof. In some embodiments, the arylene group has up to 5 rings, up to 4 rings, up to 3 rings, up to 2 rings, or one aromatic ring. For example, the arylene group can be phenylene.

[0027] The term “aryloxy” refers to a monovalent group of formula -OAr where Ar is an aryl group.

[0028] The term “carbonyl” refers to a divalent group of formula -(CO)- where the carbon atom is attached to the oxygen atom with a double bond.

[0029] The term “ether” refers to a divalent group of formula -R-O-R-, where R is independently a hydrocarbon group.

[0030] The term “amide” refers to a monovalent group with a nitrogen atom bonded to a carbonyl carbon atom.

[0031] The term “halo” refers to fluoro, chloro, bromo, or iodo.

[0032] The term “haloalkyl” refers to an alkyl having at least one hydrogen atom replaced with a halo. Some haloalkyl groups are fluoroalkyl groups, chloroalkyl groups, or bromoalkyl groups.

[0033] The term “heteroalkylene” refers to a divalent group that includes at least two alkylene groups connected by a thio, oxy, or -NR- where R is alkyl. The heteroalkylene can be linear, branched, cyclic, or combinations thereof and can include up to 60 carbon atoms and up to 15 heteroatoms. In some embodiments, the heteroalkylene includes up to 50 carbon atoms, up to 40 carbon atoms, up to 30 carbon atoms, up to 20 carbon atoms, or up to 10 carbon atoms. Some heteroalkylenes are polyalkylene oxides where the heteroatom is oxygen.

[0034] The term “oxalyl” refers to a divalent group of formula -(CO)-(CO)- where each (CO) denotes a carbonyl group.

[0035] The terms “oxalylamino” and “aminoxalyl” are used interchangeably to refer to a divalent group of formula -(CO)-(CO)-NH- where each (CO) denotes a carbonyl.

[0036] The term “aminoxalylamino” refers to a divalent group of formula -NH-(CO)-(CO)-NRd- where each (CO) denotes a carbonyl group and Rdis hydrogen, alkyl, or part of a heterocyclic groupalong with the nitrogen to which they are both attached. In most embodiments, Rdis hydrogen or alkyl. In many embodiments, Rdis hydrogen.

[0037] The term “polydiorganosiloxane” refers to a divalent block or segment of formula:

[0038] where each R1is independently an alkyl, haloalkyl, aralkyl, alkenyl, aryl, or aryl substituted with an alkyl, alkoxy, or halo; each Y is independently an alkylene, aralkylene, or a combination thereof; and subscript n is independently an integer of 0 to 1500.

[0039] The terms “room temperature” and “ambient temperature” are used interchangeably to mean temperatures in the range of 20°C to 25°C.

[0040] The term “adjacent” as used herein when referring to two layers means that the two layers are in proximity with one another with no intervening open space between them. They may be in direct contact with one another (e.g., coated together) or there may be intervening layers.

[0041] The terms “polymer” and “polymeric material” include, but are not limited to, organic homopolymers, copolymers, such as for example, block, graft, random and alternating copolymers, terpolymers, etc., and blends and modifications thereof. Furthermore, unless otherwise specifically limited, the term “polymer” shall include all possible geometrical configurations of the material. These configurations include, but are not limited to, isotactic, syndiotactic, and atactic symmetries.

[0042] The terms “(co)polymer” or “(co)polymers” includes homopolymers and copolymers, as well as homopolymers or copolymers that may be formed in a miscible blend, e.g., by coextrusion or by reaction, including, e.g., transesterification. The term “copolymer” includes random, block and star (e.g. dendritic) copolymers.

[0043] The term “semi-crystalline” with respect to a (co)polymer means that the (co)polymer exhibits a crystalline melting temperature as determined using differential scanning calorimetry and is intended to refer to both partially crystalline and fully crystalline (co)polymers.

[0044] As used herein, the term “essentially free” in the context of a composition being essentially free of a component, refers to a composition containing less than 1% by weight (wt.%), 0.5 wt.% or less, 0.25 wt.% or less, 0.1 wt.% or less, 0.05 wt.% or less, 0.001 wt.% or less, or 0.0001 wt.% or less of the component, based on the total weight of the composition.

[0045] The words “preferred” and “preferably” refer to embodiments of the disclosure that may afford certain benefits, under certain circumstances. However, other embodiments may also be preferred, under the same or other circumstances. Furthermore, the recitation of one or more preferred embodiments does not imply that other embodiments are not useful, and is not intended to exclude other embodiments from the scope of the disclosure.

[0046] In this application, terms such as “a”, “an”, and “the” are not intended to refer to only a singular entity, but include the general class of which a specific example may be used for illustration. The terms “a”, “an”, and “the” are used interchangeably with the term “at least one.” The phrases “atleast one of’ and “comprises at least one of’ followed by a list refers to any one of the items in the list and any combination of two or more items in the list.

[0047] As used herein, the term “or” is generally employed in its usual sense including “and / or” unless the content clearly dictates otherwise.

[0048] The term “and / or” means one or all of the listed elements or a combination of any two or more of the listed elements.

[0049] Also herein, all numbers are assumed to be modified by the term “about” and preferably by the term “exactly.” As used herein in connection with a measured quantity, the term “about” refers to that variation in the measured quantity as would be expected by the skilled artisan making the measurement and exercising a level of care commensurate with the objective of the measurement and the precision of the measuring equipment used. Also herein, the recitations of numerical ranges by endpoints include all numbers subsumed within that range as well as the endpoints (e.g., 1 to 5 includes 1, 1.5, 2, 2.75, 3, 3.80, 4, 5, etc.).

[0050] As used herein as a modifier to a property or attribute, the term “generally”, unless otherwise specifically defined, means that the property or attribute would be readily recognizable by a person of ordinary skill but without requiring absolute precision or a perfect match (e.g., within + / - 20 % for quantifiable properties). The term “substantially”, unless otherwise specifically defined, means to a high degree of approximation (e.g., within + / - 10% for quantifiable properties) but again without requiring absolute precision or a perfect match. Terms such as same, equal, uniform, constant, strictly, and the like, are understood to be within the usual tolerances or measuring error applicable to the particular circumstance rather than requiring absolute precision or a perfect match.

[0051] In a first aspect, a composite membrane is provided. The composite membrane comprises:

[0052] a porous substrate;

[0053] a gutter layer comprising a segmented polydiorganosiloxane copolymer comprising at least two repeat units of Formula I:

[0054] wherein: each R1is independently an alkyl, haloalkyl, aralkyl, alkenyl, aryl, or aryl substituted with an alkyl, alkoxy, or halo; each Y is independently an alkylene, aralkylene, or a combination thereof; G is a divalent residue equal to a diamine of formula R3HN-G-NHR3minus the two -NHR3groups; R3is hydrogen or alkyl or R3taken together with G and to the nitrogen to which they are both attached form a heterocyclic group; n is independently an integer of 0 to 1500; p is an integer of 1 to 10; and q is an integer of 1 or greater; and

[0055] a separation layer.

[0056] Referring to FIG. 1, a schematic cross-sectional view is provided of an exemplary composite membrane 100. The composite membrane 100 includes a porous substrate 110, a gutter layer 120 on atleast a portion of a first major surface 111 of the porous substrate 110, and a separation layer 130 on at least a portion of a first major surface 121 of the gutter layer 120. The gutter layer 120 is disposed between the porous substrate 110 and the separation layer 130. In this embodiment, the gutter layer 120 is directly adjacent to the porous substrate 110 and directly adjacent to the separation layer 130.

[0057] Referring to FIG. 2, a schematic cross-sectional view is provided of another exemplary composite membrane 200 that includes several optional layers. The composite membrane 200 includes a porous substrate 110, a gutter layer 120 on at least a portion of a first major surface 111 of the porous substrate 110, and a separation layer 130. The gutter layer 120 is disposed between the porous substrate 110 and the separation layer 130.

[0058] In some cases, a composite membrane contains a surfactant present in at least one of: i) an interfacial layer disposed between the gutter layer and the separation layer; ii) within the separation layer; or iii) within the gutter layer. The composite membrane 200 depicted in FIG. 2 includes an optional interfacial layer 140 disposed between the gutter layer 120 and the separation layer 130. Such an optional interfacial layer may be designed to increase adhesion between the gutter layer and any layer that is directly adjacent to the gutter layer 120. In some cases, an interfacial layer comprises or consists of a surfactant.

[0059] In the composite membrane 200 depicted in FIG. 2, the separation layer 130 is a first separation layer and the composite membrane 200 further includes an optional second separation layer 132 disposed between the gutter layer 120 and the first separation layer 130. The composite membrane 200 depicted in FIG. 2 further comprises an optional protection layer 150. The optional protection layer 150 is disposed on the first separation layer 130. In this embodiment, the gutter layer 120 is directly adjacent to the porous substrate 110 and directly adjacent to the optional interfacial layer 140.

[0060] It is expressly contemplated that any combination of one or more of the optional layers 132, 140, or 150, may be included in select embodiments of composite membranes according to the present disclosure.

[0061] The exemplary porous substrate 110 that is shown in each of FIGS. 1 and 2 includes three layers that include a nanoporous layer 112, a microporous layer 114, and a macroporous layer 116 having a first major surface 111 and a second major surface 119. It should be understood that a porous substrate suitable for use in the composite membranes of the present disclosure does not require a macroporous layer 116. In select embodiments, a pore size of the nanoporous layer ranges from 10 nanometers (nm) to 100 nm. In a porous substrate 110, the pores are interconnected vertically (i.e., throughout the thickness “T” of the porous substrate 110). In certain preferred embodiments, the pores of the porous substrate 110 are interconnected horizontally (e.g., as in a microfiltration membrane) along dimension “H”.

[0062] It has been discovered that it is possible to form a successful gutter layer from segmented polydiorganosiloxane copolymer including two repeat units of Formula I. This was unexpected at least because polydiorganosiloxane copolymers tend to be soft, which could lead to significant intrusion into surface pores of a porous substrate on which the segmented polydiorganosiloxane copolymer is deposited. Blocking of pores decreases permeance of a gas through the composite membrane.Composite membranes according to the present disclosure, however, exhibit advantageously high permeance of carbon dioxide, as shown in the Examples below. In some embodiments, the separation layer of a composite membrane is selective for carbon dioxide. For instance, in certain cases, a composite membrane according to the present disclosure exhibits a carbon dioxide gas to nitrogen gas selectivity of at least 20 CO2 / N2, such as at least 25, 30, 35, 40, 45, 50, or even at least 55 CO2 / N2. The maximum selectivity is a material dependent property.

[0063] In certain cases, a composite membrane according to the present disclosure exhibits a carbon dioxide permeance of at least 100 gas permeation units (GPU), such as at least 200, 250, 500, 750, 1000, 1250, 1500, 1750, 2000, 2250. 2500, 2750, 3000, 3500, 4000, 4500, 5000, 5500, 6000, 6500, 7000, 7500, 8000, 8500, 9000, or even at least 9500 GPU. In some cases, the carbon dioxide permeance is as high as 10,000 GPU. Referring to FIG. 3, a graph is shown of carbon dioxide permeance in GPU versus gutter layer thickness for membranes coated with a two different polyorganosiloxane polymers. In particular, the triangles along the curved (and lower) line show the carbon dioxide permeance data from DOE report DE-FE0031596, 2023. The circles grouped near the straight (and higher) line show the carbon dioxide permeance data from Examples 1-5. The straight line indicates the intrinsic carbon dioxide permeance calculated from PDMS with a gas permeability of 3,400 Barrer. It can be seen that gutter layers according to at least certain embodiments of the present disclosure provide higher carbon dioxide permeance as a gutter layer on a membrane than other polyorganosiloxane materials

[0064] The composite membrane 100 may be suitable for gas separation. Gas separation is a process that involves a membrane in contact with a gas mixture on the feed or upstream side and a separated gas stream on the “permeate” or downstream side. Usually, a feed gas mixture is pressurized, for example, to 5 pounds per square inch (psi), 10 psi, 20 psi, 30 psi, 40 psi, 50 psi or above. Either a vacuum or sweep gas is applied on the downstream side of the membrane to provide a driving force for the process.

[0065] Preferably, each of the gutter layer 120 and the separation layer 130 is a continuous layer. As used herein, a “continuous layer” refers to a substantially continuous layer as well as a layer that is completely continuous. That is, as used herein, any reference to the gutter layer coating or covering the first major surface of the porous substrate includes the gutter layer coating all, substantially all, or only a portion of the first major surface of the porous substrate. The gutter layer is considered to coat substantially all of the first major surface of the porous substrate (i.e., be substantially continuous) and the separation layer is considered to coat substantially all of the first major surface of the gutter layer, when enough of the first major surface of the porous substrate is coated such that the composite membrane is able to selectively separate a desired amount of a first gas from a mixture of the first gas with a second gas. Gutter layer continuity may be evaluated by gas selectivity of CO2 / N2. A gutter layer coated membrane typically shows a gas selectivity of at least 3, at least 5, at least 7, or at least 9. In particular, the flux and the selectivity of the composite membrane is sufficient for the particular system in which the membrane is used.

[0066] Each of the materials used to form composite membranes are described in detail below.

[0067] Porous Substrates

[0068] Composite membranes according to the present disclosure include a porous substrate.

[0069] The porous substrate itself may be asymmetric or symmetric. The porous substrate may include one layer or multiple layers. For example, there may be two, three, four, or more layers. In some embodiments, the porous substrate is hydrophobic. In other embodiments, the porous substrate is hydrophilic. Preferably, the porous substrate exhibits a nitrogen gas permeance of between 10,000- 500,000 gas permeation units (GPU).

[0070] If the porous substrate is asymmetric, the first and second major surfaces have porous structures with different pore morphologies. For example, the porous substrate may have pores of differing sizes throughout its thickness. Analogously, if the porous substrate is symmetric, the major surfaces have porous structures wherein their pore morphologies are the same. For example, the porous substrate may have pores of the same size throughout its thickness.

[0071] Referring to FIG. 1, an asymmetric substrate is shown with different pore morphologies at the first major surface 111 and the second major surface 119. More specifically, there are three layers each of different pore size such that the overall substrate has pores of differing sizes throughout its thickness “T.” In certain embodiments, the nanoporous layer 112 alone could function as the porous substrate. In such embodiments, the porous substrate would be symmetric.

[0072] Suitable porous substrates include, for example, films, porous membranes, woven webs, nonwoven webs, hollow fibers, and the like. For example, the porous substrates may be made of one or more layers that include films, porous films, micro-filtration membranes, ultrafiltration membranes, nanofiltration membranes, woven materials, and nonwoven materials. The materials that may be used for each of the above-mentioned supports may be organic in nature (such as the organic polymers listed below), inorganic in nature (such as aluminum, steels, and sintered metals and / or ceramics and glasses), or a combination thereof. For example, the porous substrate may be formed from polymeric materials, ceramic and glass materials, metal, and the like, or combinations (i.e., mixtures and copolymers) thereof.

[0073] In composite membranes of the present disclosure, materials having good adhesion to each other are particularly desirable. In certain embodiments, the porous substrate is preferably a polymeric porous substrate.

[0074] Suitable polymeric materials include, for example, polystyrene, polyolefins, polyisoprenes, polybutadienes, fluorinated polymers (e.g., polyvinylidene fluoride (PVDF), ethylene-co- chlorotrifluoroethylene copolymer (ECTFE), polytetrafluoroethylene (PTFE)), polyvinyl chlorides, polyesters (PET), polyamides (e.g., various nylons), polyimides, polyethers, poly(ether sulfonejs, poly(sulfone)s, poly(phenylene sulfonejs, polyphenylene oxides, polyphenylene sulfides (PPS), poly(vinyl acetatejs, copolymers of vinyl acetate, poly(phosphazene)s, poly(vinyl esterjs, poly(vinyl etherjs, poly(vinyl alcoholjs, polycarbonates, polyacrylonitrile, polyethylene terephthalate, cellulose and its derivatives (such as cellulose acetate and cellulose nitrate), and the like, or combinations (i.e., mixtures or copolymers) thereof.

[0075] Suitable polyolefins include, for example, poly(ethylene), polypropylene), poly(l-butene), copolymers of ethylene and propylene, alpha olefin copolymers (such as copolymers of 1 -butene, 1-hexene, 1-octene, and 1-decene), poly(ethylene-co-l -butene), poly(ethylene-co-l-butene-co-l-hexene), and the like, or combinations (i.e., mixtures or copolymers) thereof.

[0076] Suitable fluorinated polymers include, for example, polyvinylidene fluoride (PVDF), polyvinyl fluoride, copolymers of vinylidene fluoride (such as poly(vinylidene fluoride-co- hexafluoropropylene)), copolymers of chlorotrifluoroethylene (such as ethylene-co- chlorotrifluoroethylene copolymer), polytetrafluoroethylene, and the like, or combinations (i.e., mixtures or copolymers) thereof.

[0077] Suitable polyamides include, for example, poly(imino(l-oxohexamethylene)), poly(iminoadipoylimino hexamethylene), poly(iminoadipoyliminodecamethylene), polycaprolactam, and the like, or combinations thereof.

[0078] Suitable polyimides include, for example, poly(pyromellitimide), polyetherimide, and the like.

[0079] Suitable poly(ether sulfone)s include, for example, poly(diphenylether sulfone), poly(diphenylsulfone-co-diphenylene oxide sulfone), and the like, or combinations thereof.

[0080] Suitable polyethers include, for example, polyetherether ketone (PEEK).

[0081] In some presently preferred embodiments, the porous substrate comprises a polymeric material selected from the group consisting of polyacrylonitrile (PAN), polydimethylsiloxane copolymer (e.g., a copolymer of polydimethylsiloxane / polyurea / polyurethane / polyamide / polyoxalyldiamine), polysulfone, cellulose acetate, polyether sulfone (PES), polyvinylidene fluoride (PVDF), polyetherimide (PEI), polyaminosiloxane, polydimethylphenylene oxide (PPO), polyvinylpyridine (PVP), ethylene chlorotrifluoroethylene (ECTFE), polytetrafluoroethylene (PTFE), polyamide, polyethylene, polypropylene, polymethylpentene, cellulose nitrate, polyester, polycarbonate, and polyimide.

[0082] Suitable porous substrates may have pores of a wide variety of sizes. For example, suitable porous substrates may include nanoporous membranes, microporous membranes, microporous nonwoven / woven webs, microporous woven webs, microporous fibers, nanofiber webs and the like. In some embodiments, the porous substrate may have a combination of different pore sizes (e.g., micropores, nanopores, and the like). In one embodiment, the porous substrate is microporous.

[0083] In some embodiments, the porous substrate includes pores that may have an average pore size less than 10 micrometers (pm). In other embodiments, the average pore size of the porous substrate may be less than 5 pm, or less than 2 pm, or less than 1 pm. In other embodiments, the average pore size of the porous substrate may be greater than 10 nm (nanometer). In some embodiments, the average pore size of the porous substrate is greater than 50 nm, or greater than 100 nm, or greater than 200 nm. In certain embodiments, the porous substrate includes pores having an average size in the range of from 0.5 nm up to and including 1000 pm. In some embodiments, the porous substrate may have an average pore size in a range of 10 nm to 10 pm, in a range of 50 nm to 5 pm, in a range of 100 nm to 2 pm, in a range of 200 nm to 1 pm, or in a range of 10 nm to 100 nm.

[0084] In certain embodiments, the porous substrate includes a nanoporous layer. In certain embodiments, the nanoporous layer is adjacent to or defines the first major surface of the poroussubstrate. In certain embodiments, the nanoporous layer includes pores having a size in the range of from 0.5 nanometers (nm) up to and including 100 nm. In accordance with the present disclosure, the size of the pores in the nanoporous layer may include, in increments of 1 nm, any range between 0.5 nm and 100 nm. For example, the size of the pores in the nanoporous layer may be in the range of from 0.5 nm to 50 nm, 1 nm to 25 nm, 2 nm to 10 nm, 10 nm to 100 nm, etc. Molecular Weight Cut-Off (MWCO) is typically used to correlate to the pore size. That is, for nanopores, the molecular weight of a polymer standard (retain over 90%) such as dextran, polyethylene glycol, polyvinyl alcohol, proteins, polystyrene, poly(methyl methacrylate) may be used to characterize the pore size. For example, one supplier of the porous substrates evaluates the pore sizes using a standard test, such as ASTM E1343-90-2001 using polyvinyl alcohol. In select cases, the porous substrate has a first major surface having a) an average pore size of less than 100 nm and b) a porosity of 0.1 to 20 percent.

[0085] In certain embodiments, the porous substrate includes a microporous layer. In certain embodiments, the microporous layer is adjacent to or defines the first major surface of the porous substrate. In certain embodiments, the microporous layer includes pores having a size in the range of from 0.01 pm up to and including 20 pm. In accordance with the present disclosure, the size of the pores in the microporous layer may include, in increments of 0.05 pm, any range between 0.01 pm up and 20 pm. For example, the size of the pores in the microporous layer may be in the range of from 0.05 pm to 10 pm, or 0.1 pm to 5 pm, or 0.2 pm to 1 pm, etc. Typically, the pores in the microporous layer may be measured by mercury porosimetry for average or largest pore size, bubble point pore size measurement for the largest pores, Scanning Electron Microscopy (SEM) and / or Atom Force Microscopy (AFM) for the average / largest pore size.

[0086] In certain embodiments, the porous substrate includes a macroporous layer. In certain embodiments, the macroporous layer is adjacent to or defines the first major surface of the porous substrate. In certain embodiments, the macroporous layer is embedded between two microporous layers, for example a BLA020 membrane obtained from 3M Purification Inc.

[0087] In certain embodiments, the macroporous layer comprises pores having a size in the range of from 1 pm and 1000 pm. In accordance with the present disclosure, the size of the pores in the macroporous layer may include, in increments of 1 pm, any range between 1 pm up to and including 1000 pm. For example, the size of the pores in the macroporous substrate may be in the range of from 1 pm to 500 pm, or 5 pm to 300 pm, or 10 pm to 100 pm, etc. Typically, the size of the pores in the macroporous layer may be measured by Scanning Electron Microscopy, or Optical Microscopy, or using a Pore Size Meter for Nonwovens. The macroporous layer is typically preferred at least because the macropores not only provide less vapor transport resistance, compared to microporous or nanoporous structures, but the macroporous layer can also provide additional rigidity and mechanical strength.

[0088] The thickness of the porous substrate selected may depend on the intended application of the membrane. Generally, the thickness of the porous substrate (“T” in FIG. 1) may be greater than 10 micrometers (pm). In some embodiments, the thickness of the porous substrate may be greater than1,000 gm, or greater than 5,000 gm. The maximum thickness depends on the intended use, but may often be less than or equal to 10,000 pm.

[0089] In certain embodiments, the porous substrate has first and second opposite major surfaces, and a thickness measured from one to the other of the opposite major surfaces in the range of from 5 pm up to and including 500 pm. In accordance with the present disclosure, the thickness of the porous substrate may include, in increments of 25 pm, any range between 5 pm and 500 pm. For example, the thickness of the porous substrate may be in the range of from 50 pm to 400 pm, or 100 pm to 300 pm, or 150 pm to 250 pm, etc.

[0090] In certain embodiments, the nanoporous layer has a thickness in the range of from 0.01 pm up to and including 10 pm. In accordance with the present disclosure, the thickness of the nanoporous layer may include, in increments of 50 nm, any range between 0.01 pm and 10 pm. For example, the thickness of the nanoporous layer may be in the range of from 50 nm to 5000 nm, or 100 nm to 3000 nm, or 500 nm to 2000 nm, etc.

[0091] In certain embodiments, the microporous layer has a thickness in the range of from 5 pm up to and including 300 pm. In accordance with the present disclosure, the thickness of the microporous layer may include, in increments of 5 pm, any range between 5 pm and 300 pm. For example, the thickness of the microporous layer may be in the range of from 5 pm to 200 pm, or 10 pm to 200 pm, or 20 pm to 100 pm, etc.

[0092] In certain embodiments, the macroporous layer has a thickness in the range of from 25 pm up to and including 500 pm. In accordance with the present disclosure, the thickness of the macroporous layer may include, in increments of 25 pm, any range between 25 pm up and 500 pm. For example, the thickness of the macroporous substrate may be in the range of from 25 pm to 300 pm, or 25 pm to 200 pm, or 50 pm to 150 pm, etc.

[0093] In certain embodiments, there may be anywhere from one to four layers in any combination within a porous substrate. The individual thickness of each layer may range from 5 nm to 1500 pm in thickness.

[0094] In certain embodiments, each layer may have a porosity that ranges from 0.5% up to and including 95%.

[0095] Gutter Layers

[0096] Composite membranes according to the present disclosure include a gutter layer comprised of a segmented polydiorganosiloxane polyoxamide block copolymer comprising at least two repeat units of the following Formula I:

[0097] In this formula, each R1is independently an alkyl, haloalky 1, aralkyl, alkenyl, aryl, or aryl substituted with an alkyl, alkoxy, or halo. Each Y is independently an alkylene, aralkylene, or acombination thereof. Subscript n is independently an integer of 0 to 1500, subscript p is an integer of 1 to 10, and subscript q is an integer of 1 or greater. Group G is a divalent group that is the residue unit that is equal to a diamine of formula R3HN-G-NHR3minus the two -NHR3groups. Group R3is hydrogen or alkyl (e.g., an alkyl having 1 to 10, 1 to 6, or 1 to 4 carbon atoms) or R3taken together with G and with the nitrogen to which they are both attached forms a heterocyclic group (e.g., R3HN-G-NHR3is piperazine or the like). Each asterisk (*) indicates a site of attachment of the repeat unit to another group in the copolymer such as, for example, another repeat unit of Formula I.

[0098] Preferably, n, p and q are selected so that the polydiorganosiloxane (e.g., block or segment) comprises at least 90 weight percent (wt.%), 91 wt.%, 92 wt.%, 93 wt.%, 94 wt.%, 95 wt.%, 96 wt.%, or even at least 97 wt.% of the polydiorganosiloxane polyoxamide copolymer; and 99.9 wt.% or less, 99.8 wt.%, 99.7 wt.%, 99.5 wt.%, 99 wt.%, 98.5 wt.%, or even 98 wt.% or less of the polydiorganosiloxane polyoxamide copolymer. In some presently preferred embodiments, the gutter layer is comprised of a segmented polydiorganosiloxane copolymer having greater than 90% polydiorganosiloxane (e.g., blocks or segments).

[0099] Suitable alkyl groups for R1in Formula I typically have 1 to 10, 1 to 6, or 1 to 4 carbon atoms. Exemplary alkyl groups include, but are not limited to, methyl, ethyl, isopropyl, n-propyl, n-butyl, and iso-butyl. Suitable haloalkyl groups for R1often have only a portion of the hydrogen atoms of the corresponding alkyl group replaced with a halogen.

[0100] Exemplary haloalkyl groups include chloroalkyl and fluoroalkyl groups with 1 to 3 halo atoms and 3 to 10 carbon atoms. Suitable alkenyl groups for R1often have 2 to 10 carbon atoms. Exemplary alkenyl groups often have 2 to 8, 2 to 6, or 2 to 4 carbon atoms such as ethenyl, n-propenyl, and n-butenyl. Suitable aryl groups for R1 often have 6 to 12 carbon atoms. Phenyl is an exemplary aryl group. The aryl group can be unsubstituted or substituted with an alkyl (e.g., an alkyl having 1 to 10 carbon atoms, 1 to 6 carbon atoms, or 1 to 4 carbon atoms), an alkoxy (e.g., an alkoxy having 1 to 10 carbon atoms, 1 to 6 carbon atoms, or 1 to 4 carbon atoms), or halo (e.g., chloro, bromo, or fluoro).Suitable aralkyl groups for R1usually have an alkylene group with 1 to 10 carbon atoms and an aryl group with 6 to 12 carbon atoms.

[0101] In some exemplary aralkyl groups, the aryl group is phenyl and the alkylene group has 1 to 10 carbon atoms, 1 to 6 carbon atoms, or 1 to 4 carbon atoms (i.e., the structure of the aralkyl is alkylenephenyl where an alkylene is bonded to a phenyl group).

[0102] In some repeat units of Formula I, at least 50 percent of the R1groups are methyl. For example, at least 60 percent, at least 70 percent, at least 80 percent, at least 90 percent, at least 95 percent, at least 98 percent, or at least 99 percent of the R1groups can be methyl. The remaining R1groups can be selected from an alkyl having at least two carbon atoms, haloalkyl, aralkyl, alkenyl, aryl, or aryl substituted with an alkyl, alkoxy, or halo.

[0103] Each Y in Formula I is independently an alkylene, aralkylene, or a combination thereof. Suitable alkylene groups typically have up to 10 carbon atoms, up to 8 carbon atoms, up to 6 carbon atoms, or up to 4 carbon atoms. Exemplary alkylene groups include methylene, ethylene, propylene,butylene, and the like. Suitable aralkylene groups usually have an arylene group with 6 to 12 carbon atoms bonded to an alkylene group with 1 to 10 carbon atoms. In some exemplary aralkylene groups, the arylene portion is phenylene. That is, the divalent aralkylene group is phenylene-alkylene where the phenylene is bonded to an alkylene having 1 to 10, 1 to 8, 1 to 6, or 1 to 4 carbon atoms. As used herein with reference to group Y, “a combination thereof’ refers to a combination of two or more groups selected from an alkylene and aralkylene group. A combination can be, for example, a single aralkylene bonded to a single alkylene (e.g., alkylene-arylene-alkylene). In one exemplary alkylene-arylene- alkylene combination, the arylene is phenylene and each alkylene has 1 to 10, 1 to 6, or 1 to 4 carbon atoms.

[0104] Each subscript n in Formula I is independently an integer of 0 to 1500. For example, subscript n can be an integer up to 1000, up to 500, up to 400, up to 300, up to 200, up to 100, up to 80, up to 60, up to 40, up to 20, or up to 10. The value of n is often at least 1, at least 2, at least 3, at least 5, at least 10, at least 20, or at least 40. For example, subscript n can be in the range of 40 to 1500, 0 to 1000, 40 to 1000, 0 to 500, 1 to 500, 40 to 500, 1 to 400, 1 to 300, 1 to 200, 1 to 100, 1 to 80, 1 to 40, or 1 to 20.

[0105] The subscript p is an integer of 1 to 10. For example, the value of p is often an integer up to 9, up to 8, up to 7, up to 6, up to 5, up to 4, up to 3, or up to 2. The value of p can be in the range of 1 to 8, 1 to 6, or 1 to 4.

[0106] Group G in Formula I is a residual unit that is equal to a diamine compound of formula R3HN-G-NHR3minus the two amino groups (i.e., -NHR3groups). The diamine can have primary or secondary amino groups. Group R3is hydrogen or alkyl (e.g., an alkyl having 1 to 10, 1 to 6, or 1 to 4 carbon atoms) or R3taken together with G and with the nitrogen to which they are both attached forms a heterocyclic group (e.g., R3HN-G-NHR3is piperazine). In most embodiments, R3is hydrogen or an alkyl. In many embodiments, both of the amino groups of the diamine are primary amino groups (i.e., both R3groups are hydrogen) and the diamine is of formula H2N-G-NH2.

[0107] In some embodiments, G is an alkylene, heteroalkylene, polydiorganosiloxane, arylene, aralkylene, or a combination thereof. Suitable alkylenes often have 2 to 10, 2 to 6, or 2 to 4 carbon atoms. Exemplary alkylene groups include ethylene, propylene, butylene, and the like. Suitable heteroalkylenes are often polyoxyalkylenes such as polyoxyethylene having at least 2 ethylene units, polyoxypropylene having at least 2 propylene units, or copolymers thereof. Suitable polydiorganosiloxanes include the polydiorganosiloxane diamines, which are described below, minus the two amino groups. Exemplary polydiorganosiloxanes include, but are not limited to, polydimethylsiloxanes with alkylene Y groups. Suitable aralkylene groups usually contain an arylene group having 6 to 12 carbon atoms bonded to an alkylene group having 1 to 10 carbon atoms. Some exemplary aralkylene groups are phenylene-alkylene where the phenylene is bonded to an alkylene having 1 to 10 carbon atoms, 1 to 8 carbon atoms, 1 to 6 carbon atoms, or 1 to 4 carbon atoms. As used herein with reference to group G, “a combination thereof’ refers to a combination of two or more groups selected from an alkylene, heteroalkylene, polydiorganosiloxane, arylene, and aralkylene. A combinationcanbe, for example, an aralkylene bonded to an alkylene (e.g., alkylene-arylene-alkylene). In one exemplary alkylene-arylene-alkylene combination, the arylene is phenylene and each alkylene has 1 to 10, 1 to 6, or 1 to 4 carbon atoms.

[0108] The polydiorganosiloxane polyoxamide tends to be free of groups having a formula -Ra- (CO)-NH- where Ra is an alkylene. All of the carbonylamino groups along the backbone of the copolymeric material are part of an oxalylamino group (i.e., the -(CO)-(CO)-NH- group). That is, any carbonyl group along the backbone of the copolymeric material is bonded to another carbonyl group and is part of an oxalyl group. More specifically, the polydiorganosiloxane polyoxamide has a plurality of aminoxalylamino groups.

[0109] The polydiorganosiloxane polyoxamide is a linear, block copolymer and can be an elastomeric material. Polydiorganosiloxane polyoxamides can be formulated to include greater than 50 weight percent polydiorganosiloxane segments based on the weight of the copolymer. The weight percent of the diorganosiloxane in the polydiorganosiloxane polyoxamides can be increased by using higher molecular weight polydiorganosiloxanes segments to provide greater than 60 weight percent, greater than 70 weight percent, greater than 80 weight percent, greater than 90 weight percent, greater than 95 weight percent, or greater than 98 weight percent of the polydiorganosiloxane segments in the polydiorganosiloxane polyoxamides. Higher amounts of the polydiorganosiloxane can be used to prepare elastomeric materials with lower modulus while maintaining reasonable strength.

[0110] Some of the polydiorganosiloxane copolymers can be heated to a temperature up to 200°C, up to 225°C, up to 25°C, up to 275°C, or up to 300°C without noticeable degradation of the material. For example, when heated in a thermogravimetric analyzer in the presence of air, the copolymers often have less than a 10 percent weight loss when scanned at a rate 50°C per minute in the range of 20°C to about 350°C. Additionally, the copolymers can often be heated at a temperature such as 250°C for 1 hour in air without apparent degradation as determined by no detectable loss of mechanical strength upon cooling.

[0111] Optionally, non-reactive additives such as fillers, pigments, stabilizers, antioxidants, flame retardants, compatibilizers, and the like can be added to the copolymeric materials.

[0112] The polydiorganosiloxane copolymers are soluble in many common organic solvents such as, for example, toluene, tetrahydrofuran, dichloromethane, aliphatic hydrocarbons (e.g., alkanes such as hexane), or mixtures thereof.

[0113] The polydiorganosiloxane polyoxamides can be cast from solvents as film, molded or embossed in various shapes, or extruded into films. The high temperature stability of the copolymeric material makes them well suited for extrusion methods of film formation.

[0114] In some exemplary embodiments, each Y is an alkylene having 1 to 10 carbon atoms, phenylene bonded to an alkylene having 1 to 10 carbon atoms, or phenylene bonded to a first alkylene having 1 to 10 carbon atoms and to a second alkylene having 1 to 10 carbon atoms.

[0115] In further exemplary embodiments, G is an alkylene, heteroalkylene, arylene, aralkylene, polydiorganosiloxane, or a combination thereof. In other exemplary embodiments, R3is advantageously selected to be H or methyl.

[0116] In some presently preferred embodiments, at least 50 percent, at least 60 percent, at least 70 percent, at least 80 percent, at least 90 percent, or even 100% of the R1groups are methyl.

[0117] In certain embodiments, n is at least 40, at least 50, at least 75, at least 100, at least 250, at least 500, at least 750, at least 1,000, or even up to 1500. In some such exemplary embodiments, n may be no more than 1400, no more than 1300, no more than 1200, no more than 1100, no more than 1000, no more than 750, no more than 500, no more than 250, or even no more than 100. In select cases, n is 50 or greater, 55, 60, or 65 or greater; and 80 or less, 75, 70, 65, or 60 or less; such as 50 to 80.

[0118] Suitable segmented polydiorganosiloxane copolymers and methods of making such copolymers are disclosed in U.S. Pat. No. 7,501,184, the entire disclosure of which is incorporated herein by reference in its entirety.

[0119] Optionally, the gutter layer is corona treated or plasma treated to increase the hydrophilicity of a hydrophobic material. In such cases, the treated surface (i.e., first major surface) of the gutter layer exhibits an advancing water contact angle of less than 80°.

[0120] Separation Layers

[0121] Composite membranes according to the present disclosure include at least one separation layer. As noted above, the term “separation layer” refers to a layer that functions to selectively separate at least two gases from each other, for example carbon dioxide from other gases in a mixture.

[0122] Optionally, the separation layer is comprised of a poly(ether-block-amide) (PEBA) copolymer. PEBA copolymers have been used for carbon dioxide separation, for instance as described in detail in “Poly (amide-6-b-ethylene oxide) multilayer composite membrane for carbon dioxide separation”, Ren et al., International Journal of Greenhouse Gas Control, 2012, volume 8, pp. 111-120.

[0123] Some suitable commercially available PEBA copolymers included for instance and without limitation, those available under the trade designation “PEB AX” from Arkema Inc. (King of Prussia, PA) (e.g., PEBAX grades 1657, 2533, 1074, 3533, 4033, 5533, 4011, or Rnew 30R51). Such PEBAX materials are thermoplastic block copolymers containing both rigid polyamide blocks and soft polyether blocks. In some presently preferred embodiments, the separation layer comprises a poly(ether-block- amide) copolymer in which the ether is polyethylene oxide or poly(tetramethylene oxide) and the amide is a saturated aliphatic polyamide segment (e.g., nylon 6 or nylon 12).

[0124] When there are two separation layers, the layers may be the same or different. In some cases, the second separation layer comprises a poly(ether-block-amide) copolymer.

[0125] The one or more separation layers may be formed by applying a coating of a solution containing a PEBA copolymer on a layer of the composite membrane (e.g., the gutter layer, another (optional) separation layer, or an (optional) interfacial layer), and allowing the coating to dry.

[0126] Interfacial Layers

[0127] Composite membranes according to the present disclosure optionally include an interfacial layer. As noted above, the term “interfacial layer” refers to a layer that forms a common boundary between two other layers. It is sometimes challenging to achieve good adhesion between a gutter layerand a directly adjacent layer, such as a separation layer. One approach to minimizing separation between the gutter layer and the adjacent layer is to incorporate an interfacial layer between the two.

[0128] In certain embodiments, an optional interfacial layer is comprised of a surfactant, such as one or more nonionic, anionic, cationic, or amphoteric surfactants. Suitable surfactants include for instance and without limitation, C8-C18 alkane sulfonates; C8-C18 secondary alkane sulfonates; alkylbenzene sulfonates; C8-C18 alkyl sulfates; alkylether sulfates; sodium laureth 4 sulfate; sodium laureth 8 sulfate; dioctylsulfosuccinate, sodium salt; lauroyl lacylate; stearoyl lactylate; silicone poly(ether) copolymers; amine functional organosilicone; siloxane compounds; or any combination thereof. One or more surfactants can be applied by conventional methods, such as by coating a solution containing the surfactant on the surface of a (e.g., gutter) layer and allowing the coating to dry.

[0129] Protection Layers

[0130] Composite membranes according to the present disclosure optionally include a protection layer. As noted above, the term “protection layer” refers to a layer that functions to shield at least one other layer from damage. Any highly gas permeable materials can be used for a protection layer; such as a crosslinked poly dimethylsiloxane (PDMS), poly(l -trimethylsilyl- 1 -propyne) (PTMSP), or a plasma generated coating or a glassy perfluoropolymer (e.g., both as described in detail in WO 2017 / 004495 (Zhou et al.)). In certain presently preferred embodiments, a protection layer is comprised of or consists of the same material as the gutter layer (i.e., a segmented polydiorganosiloxane block copolymer comprising at least two repeat units of Formula I), which is described in detail above. Such a protection layer may be applied to another layer of the composite membrane (e.g., a separation layer) in the same manner as the gutter layer may be applied. In some embodiments, an optional protection layer is disposed on the (e.g., first) separation layer opposite the gutter layer. Often, a protection layer is an exterior layer of the composite membrane.

[0131] Typically, the (optional) protection layer has an average thickness of 10 nanometers (nm) or more, such as 15 nm, 20 nm, 25 nm, 30 nm, 35 nm, 40 nm, 45 nm, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, 100 nm, 110 nm, 120 nm, 130 nm, 140 nm, 150 nm, 160 nm, 170 nm, 180 nm, 190 nm 200 nm, 210 nm,220 nm, 230 nm, 240 nm, 250 nm, 260 nm, 270 nm, 280 nm, 290 nm, or 300 nm or more; and 400 nm or less, 390 nm, 380 nm, 370 nm, 360 nm, 350 nm, 340 nm, 330 nm, 320 nm, 310 nm, 300 nm, 280 nm, 260 nm, 240 nm, 220 nm, 200 nm, 180 nm, 160 nm, 140 nm, 120 nm, 100 nm, 75 nm, or 50 nm or less.Stated another way, in certain cases the optional protection layer has an average thickness of 10 nm to 400 nm.

[0132] Exemplary Embodiments

[0133] In a first embodiment, the present disclosure provides a composite membrane comprising: a porous substrate; a gutter layer comprising a segmented polydiorganosiloxane copolymer; and a separation layer. The segmented polydiorganosiloxane copolymer comprises at least two repeat units of Formula I:

[0134] wherein: each R1is independently an alkyl, haloalkyl, aralkyl, alkenyl, aryl, or aryl substituted with an alkyl, alkoxy, or halo; each Y is independently an alkylene, aralkylene, or a combination thereof; G is a divalent residue equal to a diamine of formula R3HN-G-NHR3minus the two -NHR3groups; R3is hydrogen or alkyl or R3taken together with G and to the nitrogen to which they are both attached form a heterocyclic group; n is independently an integer of 0 to 1500; p is an integer of 1 to 10; and q is an integer of 1 or greater.

[0135] In a second embodiment, the present disclosure provides a composite membrane according to the first embodiment, further comprising a surfactant present in at least one of: i) an interfacial layer disposed between the gutter layer and the separation layer; ii) within the separation layer; or iii) within the gutter layer.

[0136] In a third embodiment, the present disclosure provides a composite membrane according to the first embodiment or the second embodiment, wherein the separation layer is selective for carbon dioxide.

[0137] In a fourth embodiment, the present disclosure provides a composite membrane according to any of the first through third embodiments, wherein the separation layer comprises a poly(ether-block- amide) copolymer.

[0138] In a fifth embodiment, the present disclosure provides a composite membrane according to any of the first through fourth embodiments, wherein the separation layer comprises a poly(ether-block- amide) copolymer in which the ether is polyethylene oxide or poly(tetramethylene oxide) and the amide is a saturated aliphatic polyamide segment.

[0139] In a sixth embodiment, the present disclosure provides a composite membrane according to any of the first through fifth embodiments, wherein the separation layer is a first separation layer and the composite membrane further comprises a second separation layer disposed between the gutter layer and the first separation layer.

[0140] In a seventh embodiment, the present disclosure provides a composite membrane according to the sixth embodiment, wherein the second separation layer comprises a poly(ether-block-amide) copolymer.

[0141] In an eighth embodiment, the present disclosure provides a composite membrane according to any of the first through seventh embodiments, further comprising a protection layer disposed on the first separation layer opposite the gutter layer.

[0142] In a ninth embodiment, the present disclosure provides a composite membrane according to the eighth embodiment, wherein the protection layer has an average thickness of 10 nanometers (nm) to 400 nm.

[0143] In a tenth embodiment, the present disclosure provides a composite membrane according to the eighth embodiment or the ninth embodiment, wherein the protection layer comprises a segmented polydiorganosiloxane block copolymer having greater than 90% polydiorganosiloxane blocks.

[0144] In an eleventh embodiment, the present disclosure provides a composite membrane according to any of the first through tenth embodiments, wherein the segmented polydiorganosiloxane block copolymer is a segmented polydiorganosiloxane polyoxamide block copolymer.

[0145] In a twelfth embodiment, the present disclosure provides a composite membrane according to any of the first through eleventh embodiments, wherein the segmented polydiorganosiloxane copolymer contains greater than 90% by mass polydiorganosiloxane.

[0146] In a thirteenth embodiment, the present disclosure provides a composite membrane according to any of the first through twelfth embodiments, wherein in Formula I at least 50 percent of the R1groups are methyl.

[0147] In a fourteenth embodiment, the present disclosure provides a composite membrane according to any of the first through thirteenth embodiments, wherein in Formula I each Y is an alkylene having 1 to 10 carbon atoms, phenylene bonded to an alkylene having 1 to 10 carbon atoms, or phenylene bonded to a first alkylene having 1 to 10 carbon atoms and to a second alkylene having 1 to 10 carbon atoms.

[0148] In a fifteenth embodiment, the present disclosure provides a composite membrane according to any of the first through fourteenth embodiments, wherein in Formula I n is 50 to 80.

[0149] In a sixteenth embodiment, the present disclosure provides a composite membrane according to any of the first through fifteenth embodiments, wherein in Formula I G is an alkylene, heteroalkylene, arylene, aralkylene, polydiorganosiloxane, or a combination thereof.

[0150] In a seventeenth embodiment, the present disclosure provides a composite membrane according to any of the first through sixteenth embodiments, wherein in Formula I R3is H or methyl.

[0151] In an eighteenth embodiment, the present disclosure provides a composite membrane according to any of the first through seventeenth embodiments, wherein the porous substrate has a first major surface having a) an average pore size of less than 100 nm and b) a porosity of 0.1 to 20 percent.

[0152] In a nineteenth embodiment, the present disclosure provides a composite membrane according to any of the first through seventeenth embodiments, wherein the porous substrate comprises a polymeric material selected from the group consisting of polyacrylonitrile (PAN), polydimethylsiloxane copolymer, polysulfone, cellulose acetate, polyether sulfone (PES), polyvinylidene fluoride (PVDF), polyetherimide (PEI), polyaminosiloxane, polydimethylphenylene oxide (PPO), polyvinylpyridine (PVP), ethylene chlorotrifluoroethylene (ECTFE), polytetrafluoroethylene (PTFE), polyamide, polyethylene, polypropylene, polymethylpentene, cellulose nitrate, polyester, polycarbonate, and polyimide.

[0153] In a twentieth embodiment, the present disclosure provides a composite membrane according to any of the first through eighteenth embodiments, wherein the gutter layer exhibits an advancing water contact angle of less than 80°.

[0154] In a twenty -first embodiment, the present disclosure provides a composite membrane according to any of the first through nineteenth embodiments, exhibiting a carbon dioxide gas to nitrogen gas selectivity of at least 20 CO2 / N2.

[0155] In a twenty-second embodiment, the present disclosure provides a composite membrane according to any of the first through twentieth embodiments, exhibiting a carbon dioxide gas permeance of at least 100 gas permeation units (GPU).Examples

[0156] The following Examples are merely for illustrative purposes and are not meant to be overly limiting on the scope of the appended claims.

[0157] Unless otherwise noted or otherwise apparent from the context, all parts, percentages, ratios, and the like in the Examples and the rest of the specification are provided on the basis of weight.

[0158] Materials Used in the Examples

[0159] Silicone poly(oxamide) used in this invention was prepared by the method of US 8,765,881, Example 11 from a PDMS diamine with an amine equivalent weight of 2580 g / mol in ethyl acetate at 70°C. Five batches prepared in this way from about 2600 g per batch of PDMS diamine afforded dried polymers with inherent viscosity values ranging from 1.0-1.08 dL / g in THF. The batches were blended prior to their use for composite membrane coating.

[0160] Toluene, EMD Millipore, Burlington MA

[0161] Isopropanol, VWR International LLC. Radnor, PA

[0162] Ethanol, EMD Millipore, Burlington, MA

[0163] Water, distilled water filtered with Millipore filtration system

[0164] PEBAX 1657, PEBAX MH 1657, Arkema Inc. King of Prussia, PA

[0165] PEBAX 2533, Arkema Inc. King of Prussia, PA

[0166] PAN350, polyacrylonitrile substrate, Nanostone Water, formerly known as Sepro MembranesInc., Oceanside, CA, used as received

[0167] EFKA SL3299, PDMS-EO copolymer, BASF Nederland B.V., Arnhem, Netherlands

[0168] EFKA SL3030, low MW PDMS-EO-PO copolymer BASF Nederland B.V., Arnhem, Netherlands

[0169] Vorasurf SZ 1952, PDMS-EO-PO copolymer, Dow Chemical Company, Midland MI

[0170] Vorasurf SZ1959, high MW PDMS-EO-PO copolymer, Dow Chemical Company, Midland MI

[0171] Vorasurf DC 3043, PDMS ether copolymer, Dow Chemical Company, Midland MI T-Maz 80K, ethoxylated sorbitan monooleate, BASF Corporation, Florham Park, New Jersey

[0172] APG325N, alkyl polyglycoside nonionic surfactant, Brenntag Company, Reading PA

[0173] Membrane permeation testing

[0174] Membrane permeation of pure gases (CO2 and N2) was tested using a constant volumevariable pressure approach with membrane disc samples of 47 mm diameter (effective diameter 42 mm).The test system includes a membrane cell installed between one feed gas reservoir (upstream) and one volume pre-determined permeate gas reservoir (downstream). Both upstream and downstream reservoirs were vacuumed after mounting a membrane sample for 2-10 min. One pure gas (CO2 or N2) of 10-50 psi was introduced to the upstream reservoir. Vacuum continued for another 0.5-2 min before closing downstream reservoir where pressure was monitored over time by a pressure transducer. Pressure increasing ratio (^p cmHg / sec) in the steady state was used to calculate the gas permeances (GPU; 1 GPU = 106cm3 (STP) cm2s1cmHg1) as follows,Gas permeance = 10° ■

[0175] where, po, pi, and p2(cmHg) represent pressure at standard-temperature-pressure (STP), upstream, and downstream, respectively. To, T, V2(cm3), and . 1 (cm2) are temperature at STP, system temperature, downstream volume, and membrane area, respectively.

[0176] CO2 / N2 gas selectivity was calculated from the permeance of pure gases

[0177] Coat solution preparation

[0178] PEBAX solutions

[0179] Polymer resins (PEBAX 1657, PEBAX 2533) as received were mixed with solvent mixtures in tightly sealed jars with a stirring bar. Jars were immersed in a heated water bath while stirring. Water bath temperature was set at 90-95°C. Dissolution process took up to 5 hours. Solutions were cooled to room temperature before using for coating.

[0180] Silicone poly(oxamide) solutions

[0181] Silicone poly(oxamide) solid was dissolved in a solvent mixture while stirring at room temperature until all solids disappeared to have clear solutions.

[0182] Examples 1-5

[0183] Silicone poly(oxamide) was dissolved in a solvent mixture (70 wt.% Toluene and 30 wt.% isopropanol) to formulate a 2.5 wt.% solution. PAN350 used as received was coated with the silicone poly(oxamide) solution in a pilot line equipped with a slot die coater, dry oven (10 feet long), web unwinder and winder. The oven temperature was set at 180°F and web speed at 5-10 feet per minutes. Various silicone poly (oxamide) dry thicknesses were coated as shown in Table 1.Table 1. Silicone poly (oxamide) coated membrane and pure gas data

[0184] PDMS membrane has CO2 / N2 selectivity 9.5 according to the report (Journal of Polymer Science: Part B: Polymer Physics, 2000, 38, 415-434). Samples from Examples 1-5 almost all show the selectivity over 10, implying a good film formation on top of the porous substrate of PAN350.

[0185] FIG. 3 shows the intrinsic line of gas permeance of PDMS material over its thickness; namely, the solid straight line in the graph. Examples with silicone poly(oxamide) coated membranes showed gas permeance clustered very close to the intrinsic line (i.e., the solid circles), which is in clear contrast to conventional PDMS coated membranes (DOE report DE-FE0031596, 2023) having dramatic drop in gas permeance (i.e., the triangles). It indicates silicone poly(oxamide) is an outstanding material to form a highly permeable gutter layer in a composite membrane.

[0186] Examples 6-10

[0187] PEBAX 1657 gave a translucent solution with 3 wt.% solid. Coating this PEBAX solution on top of a silicone poly(oxamide) coated membrane caused instant dewetting.

[0188] To change the surface property of a silicone poly(oxamide) coated membrane, corona treatment and plasma treatment were applied to the control membrane (Table 2), silicone poly(oxamide) coated PAN membrane. Compared to control samples in Table 2 and 3, air corona treatment can dramatically change water contact angle (measured by Surface Analyst, Brighton Science Company, OH) and make them coatable with PEBAX solutions. But gas selectivity tended to reduce with treatment where the corona treater has metal electrode and ceramic backing. A dual dielectric corona configuration where there are ceramic electrode and ceramic backing showed no impact on gas selectivity while changing contact angles (Example 8D in Table 2). A composite membrane by coating 3wt% PEBAX 1657 onto silicone poly(oxamide) coated membrane in Example 11 gave CO2 gas permeance 256GPU and CO2 / N2 selectivity of 42.9.

[0189] Plasma treatment is another approach to change the surface properties of a silicone poly(oxamide) coated membrane. As shown in Example 10, gas permeation performance of silicone poly(oxamide) coated membrane remained consistent while eliminating dewetting. A membrane after coating 3 wt.% PEBAX 1657 solution onto plasma surface treated silicone poly(oxamide) material in Example 10 and drying gave CO2 gas permeance 181 GPU and CO2 / N2 selectivity 41.6. The high gas selectivity indicates a good PEBAX film formation at the top of the surface treated silicone poly(oxamide) membrane.

[0190] Plasma treatment was performed in a custom-built parallel plate capacitively coupled plasma reactor. The chamber has a central cylindrical powered electrode with a surface area of about 1.70 m2. After loading the substrate into the chamber, the reactor chamber was pumped down to a base pressure of less than 1 mtorr. Process gas was introduced into the chamber at the flow rates detailed in Table 3 below. Plasma treatment was performed by coupling RF power into the reactor at a frequency of 13.56 MHz and an applied power of 1000 W (0.059 W / cm2). The treatment time was controlled by translating the film samples through the reaction zone, as detailed in Table 3 below. Following the treatment(s), the process gas flow, applied power, and film translation were stopped, and the chamber was returned to atmospheric pressure. Additional information regarding materials and processes for applying cylindrical plasma treatment and further details around the reactor used can be found in US8460568 B2.Table 2. Effect of air corona treatment on silicone poly(oxamide) coated membraneNote: Control is silicone poly (oxamide) coated PAN350 with target coating thickness 620 nm; Examples 8B, 8C, 8D were corona treated using a dual dielectric corona configurationTable 3. Effect of plasma surface treatment on silicone poly (oxamide) coated membraneNote: Control is silicone poly (oxamide) coated PAN350 with target coating thickness 620 nm

[0191] Examples 11-17

[0192] To demonstrate another approach to achieve highly selective membranes, an interfacial coat was applied on top of silicone poly(oxamide) coated membranes (Control in Table 2). Either PDMS based surfactants (Vorasurf SZ1952, Vorasurf SZ1959, Vorasurf DC 3043, or EFKA SL3030) or non- PDMS surfactants (APG325N alkyl polyglycoside surfactant or T-Maz 80k ethoxylated surfactants) were used as the interfacial layer. As shown in Tables 4 and 5, in the presence of the interfacial coat, PEBAX 1657 coatability was dramatically improved; and composite membranes showed good gas selectivity.Table 4. Interfacial coated membranes and solvent systemTable 5. Composite membranes with both an interfacial coat and PEBAX 1657 separation coat and their pure gas data

[0193] Examples 18-23

[0194] To demonstrate another approach to achieve highly selective composite membranes, an additional (e.g., second) separation coat from PEBAX with poly(tetramethylene oxide) segments; for example PEBAX 2533, was applied to silicone poly(oxamide) coated membranes before coating highly selective PEBAX 1657 (e.g., the first separation coat). PAN350 porous substrate was coated in a pilot line with three zone ovens at temperatures 120°F-160°F. Web speed was set 10-20 feet per minute. Four- pass coats were applied to the porous substrate including silicone poly(oxamide) coat, second separationcoat, first separation coat and protection coat. Each coat target thickness was shown in Table 6. It is noted that “second” and “first” designations of the separation coats are solely for distinguishing between two separation coats, and do not indicate the order of application of the separation coats.

[0195] Silicone poly(oxamide) coat was from 2.5 wt.% solution in a solvent mixture of 70 wt.% toluene and 30 wt.% isopropanol.

[0196] Second separation coat was from 2.0 wt.% PEBAX 2533 in in a solvent mixture of 70 wt.% toluene and 30 wt.% isopropanol.

[0197] First separation coat was from 2.5% wt. PEBAX 1657 solution in a solvent of 30 wt.% toluene, 55 wt.% isopropanol and 15 wt.% water.

[0198] Protection coat was from 2.0 wt.% silicone poly(oxamide) in a solvent mixture of 70 wt.% Toluene and 30 wt.% isopropanol.Table 6. Composite membranes with PEBAX 2533 as an interfacial coat and their pure gas data

[0199] It is reported that PEBAX 2533 has 3-4X higher gas permeability than PEBAX 1657 (P. Bernardo et al. Separation and Purification Technology 2012 (97) 73). However, PEBAX 2533 has much lower gas selectivity. It was surprising that PEBAX 2533 was well dissolved into the same solvent used for silicone poly(oxamide) coat solutions to form a very clear solution, which is in contrast to translucent solutions from PEBAX 1657. It made PEBAX 2533 much easier to coat into a thinner layer using a slot die coating process. Furthermore, the two PEBAX resins appear to have good adhesion. PEBAX 1657 solution showed no dewetting on top of the second separation layer. Composite membranes showed very high selectivity and consistent results.

[0200] Membranes from Examples 18-20 have a 200 nm-thick second separation coat, while ones from Examples 21-23 have a 100 nm-thick second separation coat. Gas fluxes of membranes increased with a thinner second separation coat.

[0201] Examples 24-31

[0202] To reduce the number of required coating passes, in Examples 24-31 , PDMS-based surfactants were added into PEBAX solutions. One solvent system was used in all Examples 24-31, and contained 30 wt.% toluene, 55 wt.% isopropanol and 15 wt.% water. In the presence of surfactants, no major visual dewetting was seen when coating on top of silicone poly(oxamide) coated membranes. However, the surfactant concentration in the coating solution did impact gas selectivity; and only less than 0.1 wt.% (1000 ppm) surfactant led to good gas selectivity. It could be explained a high percentage of surfactant in PEBAX film may tend to aggregate together to form low selective domains.Table 7. Composite membranes with surfactant in the PEBAX 1657 separation layer and their pure gas data

[0203] Although specific embodiments have been illustrated and described herein, it will be appreciated by those of ordinary skill in the art that a variety of alternate and / or equivalent implementations can be substituted for the specific embodiments shown and described without departing from the scope of the present disclosure. This application is intended to cover any adaptations or variations of the specific embodiments discussed herein. Therefore, it is intended that this disclosure be limited only by the claims and the equivalents thereof. Furthermore, all publications and patents referenced herein are incorporated by reference in their entirety to the same extent as if each individual publication or patent was specifically and individually indicated to be incorporated by reference. In the event of inconsistencies or contradictions between portions of the incorporated references and this application, the information in the preceding description prevails.

Claims

1. What is claimed is:

1. A composite membrane comprising: a porous substrate; a gutter layer comprising a segmented polydiorganosiloxane copolymer; and a separation layer, wherein the gutter layer is disposed between the porous substrate and the separation layer and wherein the segmented polydiorganosiloxane copolymer comprises at least two repeat units of Formula I:wherein: each R1is independently an alkyl, haloalkyl, aralkyl, alkenyl, aryl, or aryl substituted with an alkyl, alkoxy, or halo; each Y is independently an alkylene, aralkylene, or a combination thereof;G is a divalent residue equal to a diamine of formula R3HN-G-NHR3minus the two - NHR3groups;R3is hydrogen or alkyl or R3taken together with G and to the nitrogen to which they are both attached form a heterocyclic group; n is independently an integer of 0 to 1500; p is an integer of 1 to 10; and q is an integer of 1 or greater.

2. The composite membrane of claim 1, further comprising a surfactant present in at least one of: i) an interfacial layer disposed between the gutter layer and the separation layer; ii) within the separation layer; or iii) within the gutter layer.

3. The composite membrane of claim 1 or claim 2, wherein the separation layer is selective for carbon dioxide.

4. The composite membrane of any of claims 1 to 3, wherein the separation layer comprises a poly(ether-block-amide) copolymer.

5. The composite membrane of any of claims 1 to 4, wherein the separation layer comprises a poly(ether-block-amide) copolymer in which the ether is polyethylene oxide or poly(tetramethylene oxide) and the amide is a saturated aliphatic polyamide segment.

6. The composite membrane of any of claims 1 to 5, wherein the separation layer is a first separation layer and the composite membrane further comprises a second separation layer disposed between the gutter layer and the first separation layer.

7. The composite membrane of claim 6, wherein the second separation layer comprises a poly(ether- block-amide) copolymer.

8. The composite membrane of any of claims 1 to 7, further comprising a protection layer disposed on the first separation layer opposite the gutter layer.

9. The composite membrane of claim 8, wherein the protection layer has an average thickness of 10 nanometers (nm) to 400 nm.

10. The composite membrane of claim 8 or claim 9, wherein the protection layer comprises a segmented polydiorganosiloxane block copolymer having greater than 90% polydiorganosiloxane blocks.

11. The composite membrane of any of claims 1 to 10, wherein the segmented polydiorganosiloxane block copolymer is a segmented polydiorganosiloxane polyoxamide block copolymer.

12. The composite membrane of any of claims 1 to 11, wherein the segmented polydiorganosiloxane copolymer contains greater than 90% by mass polydiorganosiloxane.

13. The composite membrane of any of claims 1 to 12, wherein in Formula I at least 50 percent of the R1groups are methyl.

14. The composite membrane of any of claims 1 to 13, wherein in Formula I each Y is an alkylene having 1 to 10 carbon atoms, phenylene bonded to an alkylene having 1 to 10 carbon atoms, or phenylene bonded to a first alkylene having 1 to 10 carbon atoms and to a second alkylene having 1 to 10 carbon atoms.

15. The composite membrane of any of claims 1 to 14, wherein in Formula I n is 50 to 80.

16. The composite membrane of any of claims 1 to 15, wherein in Formula I G is an alkylene, heteroalkylene, arylene, aralkylene, polydiorganosiloxane, or a combination thereof.

17. The composite membrane of any of claims 1 to 16, wherein in Formula I R3is H or methyl.

18. The composite membrane of any of claims 1 to 17, wherein the porous substrate has a first major surface having a) an average pore size of less than 100 nm and b) a porosity of 0.1 to 20 percent.

19. The composite membrane of any of claims 1 to 17, wherein the porous substrate comprises a polymeric material selected from the group consisting of polyacrylonitrile (PAN), polydimethylsiloxane copolymer, polysulfone, cellulose acetate, polyether sulfone (PES), polyvinylidene fluoride (PVDF), polyetherimide (PEI), polyaminosiloxane, polydimethylphenylene oxide (PPO), polyvinylpyridine (PVP), ethylene chlorotrifluoroethylene(ECTFE), polytetrafluoroethylene (PTFE), polyamide, polyethylene, polypropylene, polymethylpentene, cellulose nitrate, polyester, polycarbonate, and polyimide.

20. The composite membrane of any of claims 1 to 18, wherein the gutter layer exhibits an advancing water contact angle of less than 80°.

21. The composite membrane of any of claims 1 to 19, exhibiting a carbon dioxide gas to nitrogen gas selectivity of at least 20 CO2 / N2.

22. The composite membrane of any of claims 1 to 20, exhibiting a carbon dioxide gas permeance of at least 100 gas permeation units (GPU).

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