WO2020069475A1

WO2020069475A1 - Polypropylene glycol-based pre-polymers for the isocyanate component of a two-component polyurethane adhesive for bonding membranes

Info

Publication number: WO2020069475A1
Application number: PCT/US2019/053702
Authority: WO
Inventors: Zachary BRYAN; Chih-Min Cheng; James M. Murray; Shuhua Jin; Li KANG
Original assignee: Henkel IP and Holding GmbH
Current assignee: Henkel IP and Holding GmbH
Priority date: 2018-09-28
Filing date: 2019-09-28
Publication date: 2020-04-02
Anticipated expiration: 2021-03-28

Abstract

Disclosed is a high-penetration two-component polyurethane adhesive for separation apparatus, such as thin film composite reverse osmosis filtration membranes. The polyurethane side of the two-component adhesive is a pre-polymer made with certain polypropylene glycols. Surprisingly, high-viscosity pre-polymers having a low weight percent of isocyanate functionality exhibited excellent penetration of these membranes. Also disclosed is a method of using these two component polyurethane adhesives to bond these membranes.

Description

POLYPROPYLENE GLYCOL-BASED PRE-POLYMERS FOR THE ISOCYANATE COMPONENT OF A TWO-COMPONENT POLYURETHANE ADHESIVE FOR

BONDING MEMBRANES

FIELD OF THE INVENTION

[0001] This invention relates to two-component curable polyurethane systems that are used as the adhesive to bond together membrane leaves used for reverse osmosis. The inventive compositions, when the two components are combined, result in polyurethane adhesives that are able to effectively penetrate the separation membrane. The invention is also directed to the membrane leaf that is bonded using this two- component curable polyurethane system. One component of such curable systems comprises an isocyanate functional pre-polymer that is the reaction product of a mixture comprising a polyisocyanate and polypropylene glycol. The pre-polymer comprises an average of at least two isocyanate functionalities per molecule. The other component of the two-component system is a composition comprising an isocyanate reactive component. The two components must be stored separately. These two components are mixed just before use and react together (“cure") to form a polymer, generally in 1 to 8 hours after mixing. Typically, but not always, the isocyanate reactive component is a polyol or polyamine that is capable of reacting with the polyisocyanate pre-polymer, thereby forming a polyurethane (if a polyol is reacted) or polyurea (if a polyamine is reacted). In one preferred embodiment this invention relates to synthesizing these pre- polymers to control the viscosity and the weight percent of the isocyanate (-N=C=0) or “% NCO” of the polyisocyanate pre-polymer component of these two-component curable polyurethane systems, thereby also controlling the viscosity of the mixed two- component curable polyurethane system.

BACKGROUND OF THE INVENTION

[0002] Mixed two-component curable polyurethane adhesive systems can be applied using a number of methods. Viscosity of the newly mixed adhesive will be a composite of the viscosity of each component. Each application method will require the newly mixed adhesive to be within a defined viscosity range for successful use; below this range the applied mixture will spread and run and above this range the mixed adhesive may not apply evenly or at all. Two-component curable polyurethane systems have traditionally relied on modification of the polyol component to effectively increase the viscosity or“thicken” mixtures of the two components. There currently are very few options available to effectively thicken the polyisocyanate component. The most common method of increasing viscosity of the polyisocyanate component is to make an isocyanate functional pre-polymer, but pre-polymers, by their nature have a lower weight percent of NCO functionality, which historically results in poorer properties of the cured adhesive, reduced penetration of filtration in membranes and membrane problems such as blistering.

SUMMARY OF THE INVENTION

[0003] In membrane filtration, there is a growing need for adhesives that can penetrate deeply into the materials of the membrane layers to help solve common problems such as blistering.“Blistering” is generally understood to mean a failure of the membrane near the bonded portion of the membrane, usually due to the incursion of water between the layers of a thin-film composite membrane Polyurethane adhesives that have high penetration into membrane layers have been previously limited to those having a high weight percent of NCO functionality. However, materials having a too high weight percent of NCO functionality are not as stable as lower percent NCO materials and cannot be stored as long as desired in some commercial applications. Using the polyisocyanate pre-polymers synthesized with polypropylene glycol as described herein as the isocyanate component of a two-component adhesive for these membranes, we have been able to reduce the weight percent NCO, while

simultaneously controlling the viscosity of the resulting adhesive and improving stability. The disclosed two-component adhesive materials maintain the ability to penetrate the membrane layer materials, even at lower weight percent of the reactive isocyanate functionality in the pre-polymer. Generally, improved penetration of the membrane (greater than 40%) by the adhesive is correlated with lower incidence of blistering. For consumers, less blistering means fewer failures of the membrane, which gives them greater reliability and value. [0004] Polypropylene glycol (PPG) reacted with 2,4- and/or 4,4'-diphenylmethane diisocyanate (MDI) is a widely used and known isocyanate pre-polymer for numerous polyurethane applications. However, it is most common in one-component as opposed to two-component systems. Generally, in the art it is considered to be counter-intuitive and counter-productive to use PPG in the isocyanate pre-polymer for adhesives intended to be used to bond together membrane leaves of spiral-wound membrane filtration cartridges. This is because PPG-based pre-polymers are considered to produce a final adhesive that is too soft and too flexible for this demanding membrane application. In addition, polypropylene glycol is hygroscopic, which is also considered to be a non-desirable attribute for adhesives used to bond together leaves of reverse- osmosis membranes used to purify water.

[0005] Surprisingly, an embodiment of the two-component polyurethane adhesive disclosed herein, made with the particular polypropylene glycol-based isocyanate pre- polymers disclosed herein, exhibits good adhesion to, and unexpected good penetration of, these semi-permeable filtration membrane materials.

[0006] Demonstrated herein is the ability of PPG when used as the polyol component of an isocyanate pre-polymer, together with MDI, to allow control of the weight percent of isocyanate (reactive -N=C=0 functionality) in the pre-polymer or“% NCO” and increase the viscosity of the pre-polymer and the resulting adhesive, while not sacrificing penetration on commercial thin film composite reverse osmosis filtration membranes.

[0007] This invention is specifically applicable to 2-component polyurethanes, used on filtration membranes. One embodiment comprises an isocyanate pre-polymer made from reactants comprising an MDI (4,4-MDI, 2,4-MDI, modified MDI, polymeric MDI), and a long-chain PPG (average molecular weight from 700 to 2000 Daltons) which together produce an isocyanate pre-polymer providing control of viscosity of the two-component adhesive comprising the pre-polymer. The two-component adhesive comprising this PPG-based pre-polymer maintains good penetration on commercial filtration media. Unlike many other common polyol-based polyisocyanate pre-polymers, PPG-based polyisocyanate pre-polymers can enable the two-component polyurethane adhesive to achieve penetration of semi-permeable barrier membranes intended for reverse osmosis or nano-filtration applications even at NCO weight percent as low as 8% or even lower. The PPG-based pre-polymer disclosed herein can optionally comprise other components. Non-limiting examples of these optional components include: PPG having weight average molecular weight below 700 Dalton, dipropylene glycol which is usually a mixture of the three isomers (DPG), ethohexadiol (EH Diol), polytetrahydrofuran (PTMEG), castor oil, and other optional ingredients such as are known in the art, and mixtures thereof.

[0008] Within this specification, embodiments have been described in a way which enables a clear and concise specification to be written, but it is intended and will be appreciated that embodiments may be variously combined or separated without departing from the invention. For example, it will be appreciated that all preferred features described herein are applicable to all aspects of the invention described herein.

BRIEF DESCRIPTION OF THE FIGURES

[0009] Figure 1 shows a schematic cross section of a typical reverse-osmosis membrane;

[0010] Figure 2 shows a schematic representation of a spiral-wound membrane element in use;

[0011] Figure 3 shows a step in the construction of a membrane leaf element; and

[0012] Figure 4 shows another step in the construction of a membrane leaf element as part of a spiral-wound membrane element.

[0013] Figure 5 is a graph showing consistent penetration with increasing viscosity.

[0014] Figure 6 is a graph showing PPG molecular weight, viscosity and penetration.

[0015] Figure 7 is a schematic representation of a portion of a membrane leaf element. DETAILED DESCRIPTION OF THE INVENTION

[0016] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as is commonly understood by one of ordinary skill in the art. As used herein for each of the various embodiments, the following definitions apply.

[0017] “Alkyl” or“alkane" refers to a hydrocarbon chain or group containing only single bonds between the chain carbon atoms. The alkane can be a straight

hydrocarbon chain or a branched hydrocarbon group. The alkane can be cyclic. The alkane can contain 1 to 20 carbon atoms, advantageously 1 to 10 carbon atoms and more advantageously 1 to 6 carbon atoms. In some embodiments the alkane can be substituted. Exemplary alkanes include methyl, ethyl, n-propyl, isopropyl, isobutyl, n- butyl, sec-butyl, tert-butyl, isopentyl, neopentyl, tert-pentyl, isohexyl and decyl.

[0018] “Alkenyl" or“alkene” refers to a hydrocarbon chain or group containing one or more double bonds between the chain carbon atoms. The alkenyl can be a straight hydrocarbon chain or a branched hydrocarbon group. The alkene can be cyclic. The alkene can contain 1 to 20 carbon atoms, advantageously 1 to 10 carbon atoms and more advantageously 1 to 6 carbon atoms. The alkene can be an allyl group. The alkene can contain one or more double bonds that are conjugated. In some

embodiments the alkene can be substituted.

[0019] “Alkoxy" refers to the structure -OR, wherein R is hydrocarbyl.

[0020] “Alkyne" or“alkynyl” refers to a hydrocarbon chain or group containing one or more triple bonds between the chain carbon atoms. The alkyne can be a straight hydrocarbon chain or a branched hydrocarbon group. The alkyne can be cyclic. The alkyne can contain 1 to 20 carbon atoms, advantageously 1 to 10 carbon atoms and more advantageously 1 to 6 carbon atoms. The alkyne can contain one or more triple bonds that are conjugated. In some embodiments the alkyne can be substituted.

[0021] “Amine” refers to a molecule comprising at least one -NHR group wherein R can be a covalent bond, H, hydrocarbyl or polyether. In some embodiments an amine can comprise a plurality of -NHR groups (which may be referred to as a polyamine).

[0022] “Aryl" or“Ar” refers to a monocyclic or multicyclic aromatic group. The cyclic rings can be linked by a bond or fused. The aryl can contain from 6 to about 30 carbon atoms; advantageously 6 to 12 carbon atoms and in some embodiments 6 carbon atoms. Exemplary aryls include phenyl, biphenyl and naphthyl. In some embodiments the aryl is substituted.

[0023] “Ester” refers to the structure R-C(0)-0-R’ where R and R’ are

independently selected hydrocarbyl groups with or without heteroatoms. The

hydrocarbyl groups can be substituted or unsubstituted.

[0024] “Halogen" or“halide” refers to an atom selected from fluorine, chlorine, bromine and iodine.

[0025] Hetero" refers to one or more heteroatoms in a structure. Exemplary heteroatoms are independently selected from N, O and S.

[0026] “Heteroaryl" refers to a monocyclic or multicyclic aromatic ring system wherein one or more ring atoms in the structure are heteroatoms. Exemplary

heteroatoms are independently selected from N, O and S. The cyclic rings can be linked by a bond or fused. The heteroaryl can contain from 5 to about 30 carbon atoms;

advantageously 5 to 12 carbon atoms and in some embodiments 5 to 6 carbon atoms. Exemplary heteroaryls include furyl, imidazolyl, pyrimidinyl, tetrazolyl, thienyl, pyridyl, pyrrolyl, thiazolyl, isothiazolyl, oxazolyl, isoxazolyl, thiazolyl, quinolinyl and isoquinolinyl. In some embodiments the heteroaryl is substituted.

[0027] “Hydrocarbyl" refers to a group containing carbon and hydrogen atoms. The hydrocarbyl can be linear, branched, or cyclic group. The hydrocarbyl can be alkyl, alkenyl, alkynyl or aryl. In some embodiments, the hydrocarbyl is substituted.

[0028] “(Meth)acrylate” refers to acrylate and methacrylate.

[0029] “Molecular weight” refers to weight average molecular weight unless otherwise specified. The number average molecular weight M_n, as well as the weight average molecular weight M_w, is determined according to the present invention by gel permeation chromatography (GPC, also known as SEC) at 23°C using a styrene standard. This method is known to one skilled in the art. The polydispersity is derived from the average molecular weights Mw and M_n. It is calculated as PD = Mw/Mn.

Polydispersity indicates the width of the molecular weight distribution and thus of the different degrees of polymerization of the individual chains in polydisperse polymers.

For many polymers and polycondensates, a polydispersity value of about 2 applies. Strict monodispersity would exist at a value of 1. A low polydispersity of, for example, less than 1.5 indicates a comparatively narrow molecular weight distribution.

[0030] “Oligomer’ refers to a defined, small number of repeating monomer units such as 2-5,000 units, and advantageously 10-1 ,000 units which have been

polymerized to form a molecule. Oligomers are a subset of the term polymer.

[0031] “Polyether” refers to polymers which contain multiple ether groups (each ether group comprising an oxygen atom connected top two hydrocarbyl groups) in the main polymer chain. The repeating unit in the polyether chain can be the same or different. Exemplary polyethers include homopolymers such as polyoxymethylene, polyethylene oxide, polypropylene oxide, polybutylene oxide, polytetrahydrofuran, and copolymers such as poly(ethylene oxide co propylene oxide), and EO tipped

polypropylene oxide.

[0032] “Polyester" refers to polymers which contain multiple ester linkages. A polyester can be either linear or branched.

[0033] “Polymer” refers to any polymerized product greater in chain length and molecular weight than the oligomer. Polymers can have a degree of polymerization of about 20 to about 25000. As used herein polymer includes oligomers and polymers.

[0034] “Polyol” refers to a molecule comprising two or more -OH groups.

[0035] “Substituted” refers to the presence of one or more substituents on a molecule in any possible position. Useful substituents are those groups that do not significantly diminish the disclosed reaction schemes. Exemplary substituents include, for example, H, halogen, (meth)acrylate, epoxy, oxetane, urea, urethane, N3, NCS, CN, NCO, NO2, NX¹X², OX¹, C(X¹)₃, C(halogen)₃, COOX¹ , SX¹, Si(OX¹)iX² _3-i, alkyl, alcohol, alkoxy; wherein X¹ and X² each independently comprise H, alkyl, alkenyl, alkynyl or aryl and i is an integer from 0 to 3.

[0036] “Thiol” refers to a molecule comprising at least one -SH group. In some embodiments a thiol can comprise a plurality of -SH groups (which may be referred to as a polythiol).

[0037] This invention relates to two-component or two-part curable polymeric systems. [0038] The first component of such systems comprises a PPG-based

polyisocyanate pre-polymer component that is made from a polyisocyanate and polypropylene glycol (PPG).

[0039] The second component of the two-part curable polymeric system is a material that is capable of reacting with the PPG-based polyisocyanate pre-polymer material to form a polymeric material. This component is referred to herein as“the isocyanate reactive component”.

Isocyanate reactive component

[0040] The isocyanate reactive component of the present invention comprises one or more isocyanate reactive compounds. As used herein an isocyanate reactive compound is a compound containing one or more, preferably two or more, functional moieties that will react with an isocyanate moiety. The isocyanate reactive component can be a single compound comprising an alcohol moiety, an amine moiety, a thiol moiety, or a compound with a combination of these moieties. The isocyanate reactive component can be a mixture of compounds with each compound comprising one or more moieties independently selected from alcohol, amine, thiol and aminoalcohol.

One or more of the polyols, amines, thiols and aminoalcohols described below can individually be used or excluded from the isocyanate reactive component as desired.

[0041] In one embodiment the isocyanate reactive component can comprise or be an alcohol. In an advantageous embodiment the alcohol is a polyol. A polyol is understood to be a compound containing more than one OH group in the molecule. A polyol can further have other functionalities on the molecule. The term "polyol" encompasses a single polyol or a mixture of two or more polyols.

[0042] Some suitable polyol components include aliphatic alcohols containing 2 to 8 OH groups per molecule. The OH groups may be both primary and secondary. Some suitable aliphatic alcohols include, for example, ethylene glycol, propylene glycol, butane-1 ,4-diol, pentane-1 ,5-diol, hexane-1 , 6-diol, heptane-1 ,7-diol, octane-1 ,8-diol and higher homologs or isomers thereof which the expert can obtain by extending the hydrocarbon chain by one CH2 group at a time or by introducing branches into the carbon chain. Also suitable are higher alcohols such as, for example, glycerol, trimethylol propane, pentaerythritol and oligomeric ethers of the substances mentioned either individually or in the form of mixtures of two or more of the ethers mentioned with one another.

[0043] Some suitable polyols include the reaction products of low molecular weight polyhydric alcohols with alkylene oxides, so-called polyether polyols. The alkylene oxides preferably contain 2 to 4 carbon atoms. Some reaction products of this type include, for example, the reaction products of ethylene glycol, propylene glycol, the isomeric butane diols, hexane diols or 4,4'-dihydroxydiphenyl propane with ethylene oxide, propylene oxide or butylene oxide or mixtures of two or more thereof. The reaction products of polyhydric alcohols, such as glycerol, trimethylol ethane or trimethylol propane, pentaerythritol or sugar alcohols or mixtures of two or more thereof, with the alkylene oxides mentioned to form polyether polyols are also suitable. Thus, depending on the desired molecular weight, products of the addition of only a few mol ethylene oxide and/or propylene oxide per mol or of more than one hundred mol ethylene oxide and/or propylene oxide onto low molecular weight polyhydric alcohols may be used. Other polyether polyols are obtainable by condensation of, for example, glycerol or pentaerythritol with elimination of water. Some suitable polyols include those polyols obtainable by polymerization of tetrahydrofuran.

[0044] The polyethers are reacted in known manner by reacting the starting compound containing a reactive hydrogen atom with alkylene oxides, for example ethylene oxide, propylene oxide, butylene oxide, styrene oxide, tetrahydrofuran or epichlorohydrin or mixtures of two or more thereof.

[0045] Suitable starting compounds are, for example, water, ethylene glycol, 1 ,2- or 1 ,3-propylene glycol, 1 ,4- or 1 ,3-butylene glycol, hexane-1 , 6-diol, octane-1 , 8-diol, neopentyl glycol, 1 ,4-hydroxymethyl cyclohexane, 2-methyl propane-1 ,3-diol, glycerol, trimethylol propane, hexane-1 , 2, 6-triol, butane-1 , 2, 4-triol, trimethylol ethane,

pentaerythritol, mannitol, sorbitol, methyl glycosides, sugars, phenol, isononylphenol, resorcinol, hydroquinone, 1 ,2,2- or 1 ,1 ,2-tris-(hydroxyphenyl)-ethane, ammonia, methyl amine, ethylenediamine, tetra- or hexamethylenediamine, triethanolamine, aniline, phenylenediamine, 2,4- and 2,6-diaminotoluene and polyphenylpolymethylene polyamines, which may be obtained by aniline/formaldehyde condensation, or mixtures of two or more thereof.

[0046] Some suitable polyols include diol EO/PO (ethylene oxide/propylene oxide) block copolymers, EO-tipped polypropylene glycols, or alkoxylated bisphenol A.

[0047] Some suitable polyols include polyether polyols modified by vinyl polymers. These polyols can be obtained, for example, by polymerizing styrene or acrylonitrile or mixtures thereof in the presence of polyetherpolyol.

[0048] Some suitable polyols include polyester polyols. For example, it is possible to use polyester polyols obtained by reacting low molecular weight alcohols, more particularly ethylene glycol, diethylene glycol, neopentyl glycol, hexanediol, butanediol, propylene glycol, glycerol or trimethylol propane, with caprolactone. Other suitable polyhydric alcohols for the production of polyester polyols are 1 ,4- hydroxymethyl cyclohexane, 2-methyl propane-1 , 3-diol, butane-1 , 2, 4-triol, triethylene glycol, tetraethylene glycol, polyethylene glycol, dipropylene glycol, polypropylene glycol, dibutylene glycol and polybutylene glycol.

[0049] Some suitable polyols include polyester polyols obtained by

polycondensation. Thus, dihydric and/or trihydric alcohols may be condensed with less than the equivalent quantity of dicarboxylic acids and/or tricarboxylic acids or reactive derivatives thereof to form polyester polyols. Suitable dicarboxylic acids are, for example, adipic acid or succinic acid and higher homologs thereof containing up to 16 carbon atoms, unsaturated dicarboxylic acids, such as maleic acid or fumaric acid, cyclohexane dicarboxylic acid (CHDA), and aromatic dicarboxylic acids, more particularly the isomeric phthalic acids, such as phthalic acid, isophthalic acid or terephthalic acid. Citric acid and trimellitic acid, for example, are also suitable tricarboxylic acids. The acids mentioned may be used individually or as mixtures of two or more thereof. Polyester polyols of at least one of the dicarboxylic acids mentioned and glycerol which have a residual content of OH groups are suitable. Suitable alcohols include but are not limited to propylene glycol, butane diol, pentane diol, hexanediol, ethylene glycol, diethylene glycol, triethylene glycol, dipropylene glycol, tripropylene glycol, cyclohexanedimethanol (CHDM), 2-methyl-1 , 3-propanediol (MPDiol), or neopentyl glycol or isomers or derivatives or mixtures of two or more thereof. High molecular weight polyester polyols may be used in the second synthesis stage and include, for example, the reaction products of polyhydric, preferably dihydric, alcohols (optionally together with small quantities of trihydric alcohols) and polybasic, preferably dibasic, carboxylic acids. Instead of free polycarboxylic acids, the corresponding polycarboxylic anhydrides or corresponding polycarboxylic acid esters with alcohols preferably containing 1 to 3 carbon atoms may also be used (where possible). The polycarboxylic acids may be aliphatic, cycloaliphatic, aromatic or heterocyclic or both. They may optionally be substituted, for example by alkyl groups, alkenyl groups, ether groups or halogens. Suitable polycarboxylic acids are, for example, succinic acid, adipic acid, suberic acid, azelaic acid, sebacic acid, phthalic acid, isophthalic acid, terephthalic acid, trimellitic acid, phthalic anhydride, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, tetrachlorophthalic anhydride, endomethylene tetrahydrophthalic anhydride, glutaric anhydride, maleic acid, maleic anhydride, fumaric acid, dimer fatty acid or trimer fatty acid or mixtures of two or more thereof. Small quantities of monofunctional fatty acids may optionally be present in the reaction mixture.

[0050] The polyester polyol may optionally contain a small number of terminal carboxyl groups. Polyesters obtainable from lactones, for example based on e- caprolactone (also known as "polycaprolactones"), or hydroxycarboxylic acids, for example w-hydroxycaproic acid, may also be used.

[0051] Polyester polyols of oleochemical origin may also be used. Oleochemical polyester polyols may be obtained, for example, by complete ring opening of epoxidized triglycerides of a fatty mixture containing at least partly olefinically unsaturated fatty acids with one or more alcohols containing 1 to 12 carbon atoms and subsequent partial transesterification of the triglyceride derivatives to form alkyl ester polyols with 1 to 12 carbon atoms in the alkyl group.

[0052] Some suitable polyols include C36 dimer diols and derivatives thereof. Some suitable polyols include castor oil and derivatives thereof. Some suitable polyols include fatty polyols, for example the products of hydroxylation of unsaturated or polyunsaturated natural oils, the products of hydrogenations of unsaturated and polyunsaturated polyhydroxy natural oils, polyhydroxyl esters of alkyl hydroxyl fatty acids, polymerized natural oils, soybean polyols, and alkylhydroxylated amides of fatty acids. Some suitable polyols include the hydroxy functional polybutadienes known, for example, by the commercial name of“Poly-bd^®" available from Cray Valley USA, LLC Exton, PA. Some suitable polyols include polyisobutylene polyols. Some suitable polyols include polyacetal polyols. Polyacetal polyols are understood to be compounds obtainable by reacting glycols, for example diethylene glycol or hexanediol or mixtures thereof, with formaldehyde. Polyacetal polyols may also be obtained by polymerizing cyclic acetals. Some suitable polyols include polycarbonate polyols. Polycarbonate polyols may be obtained, for example, by reacting diols, such as propylene glycol, butane-1 , 4-diol or hexane-1 ,6-diol, diethylene glycol, triethylene glycol or tetraethylene glycol or mixtures of two or more thereof, with diaryl carbonates, for example diphenyl carbonate, or phosgene. Some suitable polyols include polyamide polyols.

[0053] Some suitable polyols include polyacrylates containing OH groups. These polyacrylates may be obtained, for example, by polymerizing ethylenically unsaturated monomers bearing an OH group. Such monomers are obtainable, for example, by esterification of ethylenically unsaturated carboxylic acids and dihydric alcohols, the alcohol generally being present in a slight excess. Ethylenically unsaturated carboxylic acids suitable for this purpose are, for example, acrylic acid, methacrylic acid, crotonic acid or maleic acid. Corresponding OH-functional esters are, for example, 2- hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, 2- hydroxypropyl methacrylate, 3-hydroxypropyl acrylate or 3-hydroxypropyl methacrylate or mixtures of two or more thereof.

[0054] The isocyanate reactive component can comprise or be a compound comprising an amine moiety. The amine moieties can be primary amine moieties, secondary amine moieties, or combinations of both. In some embodiments the compound comprises two or more amine moieties independently selected from primary amine moieties and secondary amine moieties (polyamine). In some embodiments the compound can be represented by a structure selected from HRN-Z and HRN-Z-NRH where Z is a hydrocarbyl group having 1 to 20 carbon atoms and R can be a covalent bond, H, hydrocarbyl, heterohydrocarbyl or polyether. In some embodiments Z is a straight or branched alkane or a straight or branched polyether. In some embodiments Z can be a heterohydrocarbyl group. In some embodiments Z can be a polymeric and/or oligomeric backbone. Such polymeric/oligomeric backbone can contain ether, ester, urethane, acrylate linkages. In some embodiments R is H. The term polyamine refers to a compound contains more than one -NHR group where R can be a covalent bond, H, hydrocarbyl, heterohydrocarbyl.

[0055] Some suitable amine compounds include but are not limited to aliphatic polyamines, arylaliphatic polyamines, cycloaliphatic polyamines, aromatic polyamines, heterocyclic polyamines, polyalkoxypolyamines, and combinations thereof. The alkoxy group of the polyalkoxypolyamines is an oxyethylene, oxypropylene, oxy-l, 2-butylene, oxy-l, 4-butylene or a co-polymer thereof.

[0056] Examples of aliphatic polyamines include, but are not limited to

ethylenediamine (EDA), diethylenetriamine (DETA), triethylenetetramine (TETA), trimethyl hexane diamine (TMDA), hexamethylenediamine (HMDA), N-(2- aminoethyl)- l,3-propanediamine (N3-Amine), N,N'-l,2-ethanediylbis-l,3- propanediamine (N4-amine), and dipropylenetriamine. Examples of arylaliphatic polyamines include, but are not limited to m-xylylenediamine (mXDA), and p- xylylenediamine. Examples of

cycloaliphatic polyamines include, but are not limited to, 1 ,3-bisaminocyclohexylamine (1 ,3-BAC), isophorone diamine (IPDA), and 4,4'- methylenebiscyclohexanamine.

Examples of aromatic polyamines include, but are not limited to diethyltoluenediamine (DETDA), m-phenylenediamine, diaminodiphenylmethane (DDM), and

diaminodiphenylsulfone (DDS). Examples of heterocyclic polyamines include, but are not limited to N-aminoethylpiperazine (NAEP), and 3,9-bis(3-aminopropyl) 2,4,8,10- tetraoxaspiro(5,5)undecane. Examples of polyalkoxypolyamines where the alkoxy group is an oxyethylene, oxypropylene, oxy- 1 ,2-butylene, oxy-l, 4-butylene or a co-polymer thereof include, but are not limited to 4, 7-dioxadecane-l, 10-diamine, 1- propanamine, 2, l-ethanediyloxy))bis(diaminopropylated diethylene glycol). Suitable commercially available polyetheramines include those sold by Huntsman under the Jeffamine^® trade name. Suitable polyether diamines include Jeffamines^® in the D, SD, ED, XTJ, and DR series. Suitable polyether triamines include Jeffamines^® in the T and ST series.

[0057] Suitable commercially available polyamines also include aspartic ester- based amine-functional resins (Bayer); dimer diamines e.g. Priamine^® (Croda); or diamines such as Versalink^® (Evonik). [0058] The amine compound may include other functionalities in the molecule. The amine compound encompasses a single compound or a mixture of two or more amine compounds.

[0059] The isocyanate reactive component can comprise or be a thiol. In some embodiments the thiol comprises two or more -SH moieties (polythiol). In some embodiments the thiol comprises at least one -SH moiety and at least another functional moiety selected from -OH, -NH, -NH2, -COOH, or epoxide. In some embodiments the thiol can be represented by the structure HS-Z-SH where Z is a hydrocarbyl group, a heterohydrocarbyl group having 1 to 50 carbon atoms. In some embodiments Z is a straight or branched alkane or a straight or branched polyether. Some suitable thiols include but are not limited to pentaerythritol tetra-(3- mercaptopropionate) (PETMP), pentaerythritol tetrakis(3- mercaptobutylate) (PETMB), trimethylolpropane tri-(3-mercaptopropionate) (TMPMP), glycol di-(3- mercaptopropionate) (GDMP), pentaerythritol tetramercaptoacetate (PETMA), trimethylolpropane trimercaptoacetate (TMPMA), glycol dimercaptoacetate (GDMA), ethoxylated trimethylpropane tri(3-mercapto-propionate) 700 (ETTMP 700), ethoxylated trimethylpropane tri(3-mercapto-propionate) 1300 (ETTMP 1300), propylene glycol 3- mercaptopropionate 800 (PPGMP 800), propylene glycol 3-mercaptopropionate 2200 (PPGMP 2200), pentaerythritol tetrakis(3-mercaptobutanoate) (KarenzMT PE-1 from Showa Denko), and soy polythiols (Mercaptanized Soybean Oil). The term“thiol” encompasses a single thiol or a mixture of two or more thiols.

[0060] The isocyanate reactive component can comprise or be a compound comprising an aminoalcohol moiety. As used herein an aminoalcohol moiety comprises at least one amino moiety and at least one hydroxyl moiety. In some embodiments the amine group is terminal to the aminoalcohol compound molecule. In some embodiments the amine group is a secondary amino group on the chain of the aminoalcohol compound molecule. In some embodiments the aminoalcohol compound includes a terminal primary amine and a secondary amine. In some embodiments the

aminoalcohol compound can be represented by one of the following structures: HO-Z- NH-Z-OH or H2N-Z-NH-Z-OH or H2N-Z-(OH)2 where Z is a hydrocarbyl group and/or an heterohydrocarbyl having 1 to 50 carbon atoms. In some embodiments Z is a straight or branched alkane or a straight or branched polyether. In some embodiments Z contains cycloaliphatic moiety or aryl moiety. Some suitable aminoalcohols include but are not limited to diethanolamine, dipropanolamine, 3-amino-1 , 2-propanediol, 2-amino-1 ,3- propane diol, 2-amiono-2-methyl-1 , 3-propanediol, diisopropanolamine. The

aminoalcohol compound encompasses a single compound or a mixture of two or more aminoalcohol compounds.

Additives:

[0061] The two-component polyurethane adhesives can optionally contain one or more additives. The additives can be contained in either or both of the PPG-based polyisocyanate pre-polymer component or the polyisocyanate-reactive component.

[0062] The curable compositions (two component polyurethane adhesives) disclosed herein can include a catalyst or cure-inducing component to modify speed of the initiated reaction. Some suitable catalysts are those conventionally used in polyurethane reactions and polyurethane curing, including organometallic catalysts, organotin catalysts and amine catalysts. Exemplary catalysts include (1 ,4- diazabicyclo[2.2.2]octane) DABCO^® T-12 or DABCO^® crystalline, available from Evonik; DMDEE (2,2'-dimorpholinildiethylether); DBU (1 ,8-diazabicyclo[5.4.0]undec-7-ene). The curable composition can optionally include from about 0.01% to about 10% by weight of composition of one or more catalysts or cure-inducing components. Preferably, the curable composition can optionally include from about 0.05 % to about 3% by weight of composition of one or more catalysts or cure-inducing components.

[0063] The curable composition can optionally include filler. Some useful fillers include, for example, lithopone, zirconium silicate, hydroxides, such as hydroxides of calcium, aluminum, magnesium, iron and the like, diatomaceous earth, carbonates, such as sodium, potassium, calcium, and magnesium carbonates, oxides, such as zinc, magnesium, chromic, cerium, zirconium and aluminum oxides, calcium clay, nanosilica, fumed silicas, silicas that have been surface treated with a silane or silazane such as the AEROSIL^® products available from Evonik Industries, silicas that have been surface treated with an acrylate or methacrylate such as AEROSIL^® R7200 or R711 available from Evonik Industries, precipitated silicas, untreated silicas, graphite, synthetic fibers and mixtures thereof. When used, filler can be employed in concentrations effective to provide desired properties in the uncured composition and cured reaction products and typically in concentrations of about 0% to about 90% by weight of composition, more typically 1 % to 30% by weight of composition of filler. Suitable fillers include

organoclays such as, for example, Cloisite^® nanoclay sold by Southern Clay Products and exfoliated graphite such as, for example, xGnP^® graphene nanoplatelets sold by XG Sciences. In some embodiments, enhanced barrier properties are achieved with suitable fillers.

[0064] The curable composition can optionally include a thixotrope or rheology modifier. The thixotropic agent can modify rheological properties of the uncured composition. Some useful thixotropic agents include, for example, castor oil derivatives such as RHEOCIN and THIXIN and silicas, such as fused or fumed silicas, that may be untreated or treated so as to alter the chemical nature of their surface. Virtually any reinforcing fused, precipitated silica, fumed silica or surface treated silica may be used. Examples of treated fumed silicas include polydimethylsiloxane-treated silicas, hexamethyldisilazane-treated silicas and other silazane or silane treated silicas. Such treated silicas are commercially available, such as from Cabot Corporation under the tradename CAB-O-SIL^® ND-TS and Evonik Industries under the tradename AEROSIL^®, such as AEROSIL^® R805. Also useful are the silicas that have been surface treated with an acrylate or methacrylate such as AEROSIL^® R7200 or R711 available from Evonik Industries. Examples of untreated silicas include commercially available amorphous silicas such as AEROSIL^® 300, AEROSIL^® 200 and AEROSIL^® 130. Commercially available hydrous silicas include NIPSIL^® E150 and NIPSIL^® E200A manufactured by Japan Silica Kogya Inc. The rheology modifier can be employed in concentrations effective to provide desired physical properties in the uncured composition and cured reaction products and typically in concentrations of about 0% to about 70% by weight of the composition and advantageously in concentrations of about 0% to about 20% by weight of the composition. In certain embodiments the filler and the rheology modifier can be the same. [0065] The curable composition can optionally include an antioxidant. Some useful antioxidants include those available commercially from BASF under the tradename IRGANOX^®. When used, the antioxidant should be present in the range of about 0 to about 15 weight percent of curable composition, such as about 0.3 to about 1 weight percent of curable composition.

[0066] The curable composition can optionally include a reaction modifier. A reaction modifier is a material that will increase or decrease reaction rate of the curable composition. For example, 8-hydroxyquinoline (8-HQ) and derivatives thereof such as 5-hydroxymethyl-8-hydroxyquinoline can be used to adjust the cure speed. When used, the reaction modifier can be used in the range of about 0.001 to about 15 weight percent of curable composition.

[0067] The curable composition can optionally contain a thermoplastic polymer. The thermoplastic polymer may be either a functional or a non-functional thermoplastic. Non-limiting examples of suitable thermoplastic polymers include acrylic polymer, functional (e.g. containing reactive moieties such as -OH and/or -COOH) acrylic polymer, non-functional acrylic polymer, acrylic block copolymer, acrylic polymer having tertiary-alkyl amide functionality, polysiloxane polymer, polystyrene copolymer, divinylbenzene copolymer, polyetheramide, polyvinyl acetal, polyvinyl butyral, polyvinyl chloride, methylene polyvinyl ether, cellulose acetate, styrene acrylonitrile, amorphous polyolefin, olefin block copolymer [OBC], polyolefin plastomer, thermoplastic urethane, polyacrylonitrile, ethylene acrylate copolymer, ethylene acrylate terpolymer, ethylene butadiene copolymer and/or block copolymer, styrene butadiene block copolymer, and mixtures of any of the above.

[0068] The curable composition can optionally include one or more adhesion promoters that are compatible and known in the art. Examples of useful commercially available adhesion promoters include amino silane, glycidyl silane, mercapto silane, isocyanato silane, vinyl silane, (meth)acrylate silane, and alkyl silane. Common adhesion promoters are available from Momentive under the trade name Silquest or from Wacker Chemie under the trade name Geniosil. Silane terminated oligomers and polymers can also be used. The adhesion promoter can be used in the range of about 0% to about 20% percent by weight of curable composition and advantageously in the range of about 0.1 % to about 15% percent by weight of curable composition.

[0069] The curable composition can optionally include one or more coloring agents. For some applications a colored composition can be beneficial to allow for inspection of the applied composition. A coloring agent, for example a pigment or dye, can be used to provide a desired color beneficial to the intended application. Exemplary coloring agents include titanium dioxide, C.l. Pigment Blue 28, C.l. Pigment Yellow 53 and phthalocyanine blue BN. In some applications a fluorescent dye can be added to allow inspection of the applied composition under UV radiation. The coloring agent will be present in amounts sufficient to allow observation or detection, for example about 0.002% or more by weight of total composition. The maximum amount is governed by considerations of cost, absorption of radiation and interference with cure of the composition. More desirably, the coloring agent may be present in amounts of up to about 20% by weight of total composition.

[0070] The curable composition can optionally include from about 0% to about 20% by weight, for example about 1% to about 20% by weight of composition of other additives known in the arts, such as tackifier, plasticizer, flame retardant, diluent, reactive diluent, moisture scavenger, and combinations of any of the above, to produce desired functional characteristics, providing they do not significantly interfere with the desired properties of the curable composition or cured reaction products of the curable composition.

[0071] When used as an adhesive, the curable compositions can optionally include up to 80% by weight of the total weight of the curable composition of a suitable solvent. This type of adhesives is known as solvent-based adhesives. Upon application of the curable composition on a first substrate, the solvent is quickly evaporated away, for example by heated ovens, then a second substrate is laminated onto the curable composition coated side of the first substrate to form a laminated structure. PPG-based polvisocvanate pre-polvmers

[0072] The polyisocyanate pre-polymers described herein are synthesized by reacting a stoichiometric excess of a polyisocyanate with at least one polyol comprising polypropylene glycol (PPG) wherein the reaction product pre-polymers have an NCO weight % between 8% and 25%. In some embodiments the polyol used to form the PPG-based polyisocyanate pre-polymer comprises at least 20% or more by weight of polyol of polypropylene glycol (PPG). Preferably, most or all of the polyol used to form the prepolymer is polypropylene glycol (PPG). The polyol used to form the prepolymer can be a mixture of polypropylene glycols of different molecular weights. A

polyisocyanate is defined as a compound comprising at least two reactive isocyanate groups. Likewise, a polyol is understood to mean a compound comprising at least two hydroxyl groups per molecule that can react with the isocyanate groups on the polyisocyanate.“Excess” is understood to mean that there are more equivalents of isocyanate functionality from the polyisocyanate compound than equivalents of hydroxyl functionality from the polyol present during reaction to form the pre-polymer. All of the PPG is reacted and the resulting PPG-based polyisocyanate pre-polymers comprise reactive isocyanate groups. In this disclosure, it is to be understood that the term“PPG- based polyisocyanate pre-polymer" is applied to any compound made according to the foregoing description, i.e., as long as the compound is made with a stoichiometric excess of isocyanate groups to hydroxyl groups. Note that the weight percent of reactive NCO in the pre-polymer is a function of the weight average molecular weight of the PPG used to make the pre-polymer. If the weight average molecular weight of the PPG is higher, there will be a lower weight percent of reactive NCO in the resulting prepolymer.

Polvisocvanates used for synthesis of the PPG-based pre-polvmers:

[0073] Aromatic polyisocyanates are characterized by the fact that the isocyanate groups are positioned directly on the benzene ring. Suitable aromatic polyisocyanates include diphenyl methane diisocyanate (MDI) including the 2,2’- 2,4’- and 4,4'- isomers, polymeric MDI (pMDI), the isomers of toluene diisocyanate (TDI) and naphthalene-1 , 5- diisocyanate (NDI). Other suitable polyisocyanates include but are not limited to hydrogenated MDI (HMDI), xylylene diisocyanate (XDI), tetramethyl xylylene diisocyanate (TMXDI), 4,4'-diphenyl dimethyl-methane diisocyanate, di- and

tetraalkylene diphenylmethane diisocyanate, 4,4'-dibenzyl diisocyanate, 1 ,3-phenylene diisocyanate, 1 ,4-phenylene diisocyanate, the isomers of toluene diisocyanate (TDI), 1- methyl-2,4-diisocyanatocyclohexane, 1 ,6-diiso-cyanato-2, 2, 4-trimethyl hexane, 1 ,6- diisocyanato-2, 4, 4-trimethyl hexane, 1-isocyanatomethyl-3-isocyanato-1 ,5,5-trimethyl cyclohexane (IPDI), chlorinated and brominated diisocyanates, phosphorus-containing diisocyanates, 4,4'-diisocyanatophenyl perfluoroethane, tetramethoxybutane-1 ,4- diisocyanate, butane-1 ,4-diisocyanate, hexane-1 ,6-diisocyanate (HDI),

dicyclohexylmethane diisocyanate, cyclo-hexane-1 ,4-diisocyanate, ethylene

diisocyanate, phthalic acid-bis-isocyanatoethyl ester; diisocyanates containing reactive halogen atoms, such as 1-chloromethylphenyl-2, 4-diisocyanate, 1-bromomethylphenyl- 2, 6-diisocyanate or 3,3-bis-chloromethylether4,4'-diphenyl diisocyanate. Aromatic polyisocyanates are preferred and diphenyl methane diisocyanate (MDI) and polymeric MDI (pMDI) are more preferred as part or all of the polyisocyanates used for synthesis of the PPG-based pre-polymers. One or more of the polyisocyanates described above can individually be used or excluded from the isocyanate reactive component as desired.

Polypropylene glycol used for synthesis of the PPG-based pre-polymer:

[0074] The polypropylene glycols (PPG) used in the preparation of the PPG- based pre-polymers disclosed herein advantageously have a weight average molecular weight between 200 and 2500 Daltons and more typically between 400 and 2000 Daltons. The polypropylene glycols (PPG) used in the preparation of the PPG-based pre-polymers disclosed herein advantageously have a functionality of 2 or more and typically about 2. Linear and branched polypropylene glycols are both suitable. The PPG-based pre-polymers disclosed herein can be prepared using a mixture of different polypropylene glycols. Polypropylene glycol is understood to mean, for example, a polyether polymer comprising the general structure:

wherein n can have an average range from 8- 40. The PPG can optionally contain minor amounts (e.g., up to 10 weight) of other epoxides such as ethylene oxide (EO) or butene oxide. EO-tipped PPG or EO/propylene oxide random copolymers can also be used in the practice of this invention or excluded. Dipropylene glycol and butane diol may also be incorporated or excluded.

Membranes and use of the two component adhesive made with PPG-based polvisocvanate pre-polvmer:

[0075] The following description refers to FIGS. 1-4.

[0076] A typical thin-film composite membrane 10 intended for reverse osmosis and/or nanofiltration is generally rectangular in shape and is comprised of overlying layers having the general structure shown as a schematic cross-section in FIG. 1. The membrane 10 comprises generally three layers: a thin, dense semi-permeable barrier layer 12 overlying a microporous substrate 14, the microporous substrate 14 overlying a porous support layer 16. The porous support layer 16 is for example, a non-woven polyester, but is not necessarily limited to a non-woven polyester. The porous support layer 16 is generally constructed and arranged to allow fluid to pass through it easily, while providing physical support for the other layers of the composite membrane 10. Likewise, the semi-permeable barrier layer 12 is commonly, but not necessarily a polyamide film, and the microporous substrate 14 is usually but not always comprised of a polysulfone film. The materials of construction and their thickness, etc. may be varied depending on the exact separation application for which the membrane 10 is intended to be used.

[0077] The semi-permeable layer 12 is the active surface of the membrane 10 and is usually considered to be effecting the separation, either on its own or in combination with the intermediate microporous substrate 14, depending on the exact nature of the compounds being separated. For instance, if the membrane 10 is intended to be used to purify water, the membrane 10 will allow water to pass through, but not contaminants such as salt ions. [0078] A plurality of these membranes 10 are bonded together into a spiral- wound membrane element, using the two-component polyurethane adhesive that comprises, as the isocyanate component, the PPG-based pre-polymer disclosed herein.

[0079] FIGS. 2 - 4 show together, a typical spiral-wound membrane element 20 (FIG. 2) and the various components and the construction of the spiral-wound membrane element 20.

[0080] FIG. 2 shows schematically one embodiment of a spiral-wound membrane element 20 comprised of a center perforated permeate tube 26, around which is wound one or more membrane leaf elements 30 (one shown in FIG.7). During use one end of the permeate tube 26 is open to allow permeate 22 to flow out and the opposing end is sealed to prevent ingress of a feed stream 18 into the permeate tube 26. The membrane leaf elements 30 are described in more detail below. Each membrane leaf element 30 may be separated by a feed spacer 28, typically a polymeric net structure.

A feed stream 18 enters the spiral-wound membrane element 20 flowing through the space between the membrane leaf element provided by the feed spacer 28. The feed stream 18 is comprised of at least two constituents. A typical illustrative example of the feed stream 18 would be salt water having an initial concentration of salt. Water with none or a lower concentration of salt goes through the membranes 10 to form a permeate stream 22 of clean water. The remainder of the feed stream 18, now having a higher concentration of salt than it started with, forms a concentrate stream 24. The permeate stream 22 is directed through a porous permeate carrier layer 32 into the permeate tube 26 and discharged therefrom. The concentrate stream 24 flows through a feed spacer 28 between the membrane leaf elements 30 and is discharged separately from the permeate stream 22.

[0081] In one embodiment shown in FIG. 7 each membrane leaf element 30 is comprised of two membranes, each 10, separated by a porous permeate carrier layer 32. The membranes 10 are arranged so that each barrier layer 12 faces outwardly and each support layer 16 is adjacent to the carrier layer 32. The two-component polyurethane adhesive 36 having the PPG-based polyisocyanate pre-polymer described herein is applied to a portion of the porous permeate carrier layer 32 and/or one or both of the adjacent porous support layers 16. Adhesive 36 is applied only adjacent one or more edges of the membrane material and is not applied over the entire surface. The method of applying the two-component polyurethane adhesive 36 is not particularly limited and suitable methods are known to the skilled person. For instance, the components of two-component polyurethane adhesive 36 can be mixed just before use and applied as a continuous bead along the open edges of the porous permeate carrier 32, as seen in FIG. 4. The bead size is not particularly limited but it should bond only the edges of folded sheet 10 to the permeate carrier 32, leaving the interior portion of each unbonded. Suitable bead widths can be for instance about 0.3 cm to about 2 cm or about .3 cm to about 0.6 cm. The layers 10, 32, 10 are superimposed. It is desirable for the adhesive 36 to penetrate through the permeate carrier layer 32 and into or through each of the membranes 10. The adhesive seals the membrane edges 10 to prevent the feed stream from entering into the membrane 10 and carrier layer 32 and also prevent permeate 22 from exiting the membranes except through the permeate tube 26. Importantly, the adhesive 36 must penetrate 40% or more into all three layers (porous support layer 16, microporous layer 14 and the barrier layer 12 shown in FIG. 1) of the membrane 10 and permeate carrier 32 to be acceptable. Penetration of 50%, 60%, 70%, 80% or more is preferable. This bonding process, i.e. bonding the porous permeate carrier layer 32 to the center perforated permeate tube 26, and/or bonding the folded membrane sheet 10 (that has the feed carrier 28 between the folded sheet 10) to the porous permeate carrier layer 32 on three sides, to form a membrane leaf element 30 is repeated as many times as necessary until the desired number of membrane leaf elements are formed and attached to the permeate tube 26. The membrane leaf elements 30 are then wound tightly around the permeate tube 26 to form the spiral- wound element 20.

[0082] In one variation the membrane leaf element 30 layers, whether of a single wound membrane leaf element or of a plurality of membrane leaf elements, are separated by a layer of feed spacer or feed carrier 28. As shown in FIG. 3, a layer of membrane 10 is laid out such that the semi-permeable layer 12 is facing toward the inside of the sheet 10 and the support layer 16 (not visible in FIG. 3) is on the outside. A layer of feed spacer or feed carrier 28 is placed over a portion of the surface of permeable layer 12. The combined layers are folded along line A-A to form a composite structure with the feed spacer 28 disposed between two membrane layers 10. The feed spacer or feed carrier layer 28 is intended to provide space so that the feed 18 can flow freely inside the folded membrane sheet 10. The particular details of the materials and thickness of the feed carrier 28 depend on the intended application of the spiral-wound membrane element 20, but usually it is a non-woven material that allows free flow of the feed stream 18 between the adjacent folded portions of membrane sheet 10. Note that the feed carrier 28 may be slightly smaller than the folded membrane sheet 10, as shown schematically in FIG. 3.

[0083] In some applications only one membrane leaf element is wound around the permeate tube. In larger applications a plurality of membrane leaf elements can be wound around a single permeate tube. FIG. 4 shows one embodiment in which a single leaf element 30 is wound around the permeate tube 26. In this embodiment the permeate tube 26 has a plurality of perforations 34. The porous permeate carrier layer 32 of the membrane leaf element 30 is wrapped around and bonded to the center perforated permeate tube 26 with adjacent layers of the leaf element separated by a feed carrier 28. The two-component polyurethane adhesive 36 having the PPG-based polyisocyanate pre-polymer described herein can optionally be used to bond the carrier layer 32 to the permeate tube 26. The porous permeate carrier 32 provides a flow channel to allow permeate 22 to flow through membrane 10, through the permeate carrier 32 and into the permeate tube 26.

Materials and abbreviations used in the following Examples:

[0084] PPG: Polypropylene glycol

NCO: -N=C=0 isocyanate functionality, reported as weight percent of the polyisocyanate or polyisocyanate pre-polymer

MDI: methylene diphenylene diisocyanate; can be 1 ,4- or 2,4-MDI

DPG: Dipropylene glycol; molecular weight: 134.2; mixture of the three isomers; chain extender, functionality 2.0 (Univar)

Castor Oil: usually used as the polyol component of the two-component adhesive]; molecular weight 923.7 Daltons, average functionality 2.7 (Vertellus) 2-EH diol: Ethohexadiol; molecular weight: 146 Daltons, functionality 2.0 chain extender (Dixie Chemical)

PolyTHF/ PTMEG: Polytetrahydrofuran; molecular weight 997.4 Daltons;

alternative type of polyol (BASF)

RHEOCIN^®: A micronized hydrogenated castor oil; rheology modifier (BYK) Reverse Osmosis Membrane: Dow membrane BW30: (Dow)

ARCOL^® PPG 425: polypropylene glycol; molecular weight 426.6 Daltons, functionality 2.0 (Covestro)

ARCOL^® PPG 725: polypropylene glycol; molecular weight 763.2 Daltons, functionality 2.0 (Covestro)

ARCOL^® PPG 1000: polypropylene glycol; molecular weight 1010.8 Daltons, functionality 2.0 (Covestro)

ARCOL^® PPG 2000: polypropylene glycol; molecular weight 2003.6 Daltons, functionality 2.0 (Covestro)

ARCOL^® Poly-G 30-168: Polyether Triol; molecular weight 1002.0 comprises all secondary OH groups; glycerol propoxylated, functionality 3.0 (Covestro)

1 ,4-BDO: 1 ,4-Butanediol; chain extender; molecular weight 180 Daltons, functionality 2.0 (Lyondel)

TMP: Trimethylolpropane; crosslinker; molecular weight 135.3, functionality 3.0 (Nexeo)

MONDUR^® MB: high-purity grade difunctional isocyanate; diphenylmethane 4,4'- diisocyanate; 33.6% NCO; molecular weight 250.0, functionality 2.0 (Covestro)

MONDUR^® CD: modified 4,4’-MDI; modified with carbodiimide; 29.5% NCO; molecular weight 314.6, functionality 2.2 (Covestro)

MONDUR^® MLQ: mixture of 4,4-methylene diphenylene diisocyanate (MDI) and 2,4-MDI; 33.6% NCO; molecular weight 250.0, functionality 2.0 (Covestro)

MONDUR^® MR Light: poly MDI (mixture of polymerized 4,4- and 2,4 pMDI ); 33.5% NCO; molecular weight 372.4, functionality 2.8 (Covestro)

FILMTEC™ BW30: reverse osmosis membrane (Dow) EXAMPLES:

Representative Procedures:

Preparation of polypropylene glycol (PPG)-based pre-polymers:

[0085] The polyisocyanate was first melted at 50°C prior to use, if it is not liquid.

In practice, usually only the 4,4-MDI usually needed to be melted.

[0086] Next the polyisocyanate was charged into a reactor heated to about 70°C. The PPG was charged into the reactor next. Selection of the weight average molecular weight (typically, 700 - 2000 Dalton) of the PPG is based on the target weight percent NCO of pre-polymer. One or more optional components were also charged to the reactor if they were being used. These can include, but are not limited to, EH-Diol, DPG, PPG, PTMEG, and mixtures thereof. Catalysts can optionally also be used.

[0087] When all of the reactants were charged to the reactor, they were mixed at about 70°C for about 1 hour until the reaction was complete. The resulting propylene glycol (PPG)-based pre-polymers were removed from the reactor and packaged under nitrogen. As noted above, when using other polyisocyanates (such as 2,4-MDI, pMDI, modified MDI) it was not necessary to melt materials because they are liquid at room temperature.

Preparation of the isocyanate reactive component:

[0088] A polyol formulation used as the isocyanate reactive component to mix with the PPG-based polyisocyanate pre-polymers was prepared as follows. A mixture of 96.5 weight % Castor Oil and 3.5 % RHEOCIN^® was prepared by mixing these materials together at about 50°C for one hour at high shear in a temperature-controlled double planetary reactor under vacuum. The mixture was then cooled to room

temperature by turning off the heat and mixing at a low shear for 30 minutes.

Preparation of the two-component polyurethane adhesive composition

comprising PPG-based polyisocyanate pre-polymers as the isocyanate component:

[0089] The various PPG-based polyisocyanate pre-polymers described below were evaluated by mixing them with the isocyanate reactive component described above. The PPG-based polyisocyanate pre-polymer and the isocyanate reactive component were weighed out to provide a mixed adhesive with a 1.1-1.2 index (i.e., with a slight stoichiometric excess of isocyanate moieties from the PPG-based polyisocyanate pre-polymer) and mixed in a speed mixer at 2000 RPM for 30 seconds.

Measuring percent penetration of the membrane by the adhesive.

[0090] Squares of membrane (approximately 7.5 cm X 7.5 cm) were placed on a surface of the porous support layer 16. Approximately 5 grams of the mixed adhesive was placed on that membrane. The porous support layer 16 of a second membrane was placed on top of the mixed adhesive. A non-stick plastic square (polyethylene, dimensions approximately 12 cm X 12 cm) was placed on top of the assembled membranes. An approximately 450 gram weight was then placed over the top of the entire non-stick plastic square. The weight was left for 20 minutes and then removed. The assembly was allowed to cure for at least 8 hours and the percent penetration was evaluated visually and reported as membrane penetration. Unless otherwise noted FILMTEC™ BW30 membranes were used for penetration testing.

[0091] Penetration was qualitatively estimated by visual analysis of the ratio of dark area to light area on the back side (i.e. on the barrier layer side 12 opposite the support layer 16). No visual change would be 100% light area and would correspond to 0% penetration. Complete penetration would be 100% dark area and would correspond to 100% penetration. The samples were evaluated side-by-side by more than one person to ensure consistency.

Measuring viscosity of the PPG-based polvisocyanate pre-polvmers:

[0092] Samples were conditioned at 25°C in an oven for at least 18 hours before testing. They were quickly removed and tested using Brookfield RV Spindle 6 at 20 RPM. If the viscosity was over 50,000 mPa-sec, it was tested at 2 RPM using spindle 6. In one case it was over 1 M mPa-sec, so this was tested with Spindle 7 at 2 RPM.

Results are reported as mPa-sec. Measuring weight percent NCO:

[0093] The reported weight percent of NCO in most of the samples herein were calculated. However, a few of the samples were tested by titration and the calculated weight percent was determined to be within ± 0.5% of the measured amount.

[0094] The viscosities in the results for all of the following examples are reported only for the isocyanate functional pre-polymers, not the mixed adhesives. The %NCO is reported for the isocyanate functional pre-polymers.

[0095] All of the membrane penetration results below are reported for a mixed two-component adhesive, using the specified pre-polymer and the isocyanate reactive component prepared above. The two components were used in an amount to provide an index of 1.15 in the final mixed two-component adhesive. “Index” is understood to mean: (number of isocyanate groups/number of groups reacting with the isocyanate) X 100.

[0096] There are no comparative examples using monomeric isocyanates in place of a polypropylene glycol (PPG)-based pre-polymer in this adhesive system. The inventors found that the viscosity of a mixed adhesive using monomeric polyisocyanates in place of the polypropylene glycol (PPG)-based pre-polymer was so low that the material would not stay on the membrane to be tested for penetration. Such materials would not be suitable for use in bonding membranes.

Example 1 : Effect of type of isocyanate and molecular weight of PPG in the pre- polvmer on membrane penetration

[0097] The pre-polymer formulations shown in Table 1 were made and evaluated. The pre-polymer formulations are shown as weight percent. The viscosities are reported for the pre-polymer and the percent of membrane penetration is for the final adhesive.

[0098] These results demonstrate that if the pre-polymer percent NCO is above 12 and the viscosity of the pre-polymer is below 55,000 mPa-sec, adequate penetration of the membrane (greater than 40%) is achievable. The comparative A sample using a higher functionality (2.8) isocyanate exhibited much higher viscosity and significantly poorer penetration.

Example 2: Effect of weight percent NCO in the pre-polvmer

[0099] The pre-polymers shown in Table 3 were made and evaluated. In the example, the molecular weight of the PPG used to make the pre-polymers was kept constant at 1000 Daltons and the likewise only one type of polyisocyanate was used to prepare the pre-polymers. Therefore, the effect of weight percent NCO on membrane penetration is demonstrated. The pre-polymer formulations are shown as weight percent. The viscosities are reported for the pre-polymer and the percent of membrane penetration is for the final adhesive.

[0100] These results demonstrate that if the pre-polymer is prepared such that the viscosity of the pre-polymer is below 20,000 mPa sec, the NCO of the pre-polymer can be as low as 8 weight percent but the membrane penetration remains 85% or more, well above the minimum level of 40% needed to prevent blister formation.

Example 3: Effect of PPO molecular weight on membrane penetration

[0101] The pre-polymers shown in Table 2 were made and evaluated. The pre- polymer formulations are shown as weight percent. The viscosities are reported for the pre-polymer and the percent of membrane penetration is for the final adhesive.

[0102] These results demonstrate that pre-polymers made with PPG having molecular weights of approximately 2000, 1000 and 750 Daltons provided membrane penetration well above the minimum of 40% when used in the two-component adhesive

Example 4: The effect on membrane penetration of blends of various molecular weight of PPG in the pre-polymer

[0103] The pre-polymers shown in Table 4 were made and evaluated. The prepolymer formulations are shown as weight percent.

[0104] These results demonstrate that in general, while neither PPG having a molecular weight as low as 425 Daltons nor glycerol propoxylate (Poly-G 30-168) used alone in the pre-polymer provide adequate membrane penetration, they can be used in a blend with a longer chain PPG. Notably, and surprisingly, this example demonstrates that the relationship between viscosity and penetration is not linear.

[0105] The non-linear effect can be seen by comparing sample 12 (45% penetration; 21 ,750 mPa-sec viscosity) to sample 11 (90% penetration; 30,850 mPa-sec viscosity). These two samples have the same weight percent NCO.

[0106] The viscosities are reported for the pre-polymer and the percent of membrane penetration is for the final adhesive. Example 5: The effect of chain extenders in the pre-polvmer on membrane penetration

[0107] The pre-polymer formulations shown in Table 5 were made and evaluated.

The pre-polymer formulations are shown as weight percent.

[0108] These results demonstrate generally that chain extenders tend to increase the viscosity of the pre-polymer and as seen in previous Examples, if the viscosity is more than approximately 50,000 to 60,000 mPa-sec, the membrane penetration will be unacceptably low. However, as noted in Example 4, the effect of viscosity on the membrane penetration is not linear.

Example 6: The effect of using castor oil to make the pre-polymers compared to using PPO

[0109] The pre-polymer formulation shown in Table 6 were made and evaluated. The pre-polymer formulations are shown as weight percent. [0110] The viscosities are reported for the pre-polymer and the percent of membrane penetration is for the final adhesive.

[0111] These results demonstrate the unexpected improvement in membrane penetration when PPG is used to make the pre-polymers, compared to using castor oil as part of the pre-polymer. The use of castor oil in the pre-polymer is clearly detrimental to the membrane penetration Although comparative sample X670-B1 had adequate membrane penetration of 70%, the viscosity was still quite low compared to some of the inventive samples. In addition, it is notable that adding just 6% more castor oil in the pre-polymer as seen in sample G resulted in no membrane penetration at all. Sample 21 with 34.3 % PPG-1000 had good membrane penetration of 85%, but the 10% PPG- 1000 in sample 22 was not enough to mitigate the detrimental effect of the castor oil in the pre-polymer, as shown by the membrane penetration of only 25%. These results demonstrate that including PPG in the pre-polymer can result in pre-polymers having a much lower NCO% than castor oil. Pre-polymers made with PPG effectively penetrated the membrane even with % NCO lower than 8%, but castor oil used alone had 0% penetration at 10 % NCO. However, a blend of an adequate amount of PPG with castor oil in pre-polymer improved the membrane penetration by 15% compared to castor oil alone. Notably and surprisingly, the results show that this blending effect is not linear. Sample G, made with all castor oil (46.5%) had 70% penetration, while sample 22 made with 36.5% castor oil and 10% PPG having molecular weight of approximately 1000 only had membrane penetration of 25%.

[0112] In some embodiments, the invention herein can be construed as excluding any element or process step that does not materially affect the basic and novel characteristics of the composition or process. Additionally, in some embodiments, the invention can be construed as excluding any element or process step not specified herein.

[0113] Although the invention is illustrated and described herein with reference to specific embodiments, the invention is not intended to be limited to the details shown. Rather, various modifications may be made in the details within the scope and range of equivalents of the claims and without departing from the invention.

[0114] Within this specification, embodiments have been described in a way which enables a clear and concise specification to be written, but it is intended and will be appreciated that embodiments may be variously combined or separated without departing from the invention. For example, it will be appreciated that all preferred features described herein are applicable to all aspects of the invention described herein.

Claims

What is claimed is:

1. A separation apparatus comprising:

a membrane layer capable of separating a first constituent from a feed fluid mixture comprising the first constituent and a second constituent;

a porous layer; and

a mixed, two component polyurethane adhesive disposed in one or more discrete areas between the membrane layer and the porous layer to form a bonded area, wherein the two component polyurethane adhesive comprises:

A) a component A comprising a polypropylene glycol-based isocyanate

functional pre-polymer having an average isocyanate functionality (NCO) of at least 2 and between 8 and 20 weight percent NCO functionality, wherein the polypropylene glycol-based isocyanate functional pre-polymer comprises the reaction product of:

i) between 25 and 75 weight percent of a polyisocyanate, ii) between 25 and 75 weight percent of at least one polyol

comprising polypropylene glycol having a weight average molecular weight between 200 and 2500 Daltons; and

B) a component B comprising an isocyanate reactive component which has

isocyanate reactive functional groups, wherein the component B is capable of reacting with the polypropylene glycol-based polyisocyanate pre-polymer of the component A;

wherein the mixed, two component polyurethane adhesive has a percent penetration into the membrane layer prior to curing.

2. The separation apparatus according to claim 1 , wherein the percent penetration of the membrane layer by the polyurethane adhesive is at least 40%.

3. The separation apparatus according to claim 1 or claim 2, wherein the percent penetration of the membrane layer by the polyurethane adhesive is at least 60%.

4. The separation apparatus according to any of claims 1 to 3, wherein the percent penetration of the membrane layer by the polyurethane adhesive is at least 80%.

5. The separation apparatus according to any of claims 1 to 4, wherein the separation apparatus further comprises a feed carrier material.

6. The separation apparatus according to any of claims 1 to 5, wherein the separation apparatus further comprises a porous permeate carrier layer which is bonded to the porous layer with the two component polyurethane adhesive.

7. The separation apparatus according to any of claims 1 to 6, wherein the component A has a viscosity of less than 55,000 mPa sec at 25°C.

8. The separation apparatus according to any of claims 1 to 7, wherein the polypropylene glycol-based polyisocyanate pre-polymer comprises the reaction product of:

i) between 25 and 75 weight percent of a polyisocyanate;

ii) between 25 and 75 weight percent of a polypropylene glycol having a weight average molecular weight between 500 and 2500 Daltons; and

iii) 0.1 to 10 weight percent a polypropylene glycol having a weight average molecular weight between 200 and 500 Daltons.

9. The separation apparatus according to any of claims 1 to 8, wherein the viscosity of the component A at 25°C is less than 25,000 mPa sec, measured on a Brookfield viscometer at 20 RPM and spindle 6.

10. The separation apparatus according to any of claims 1 to 9, wherein the weight percent of NCO functionality in component A is between 8 and 14 weight percent.

11. The separation apparatus according to any of claims 1 to 10, wherein the component A and the component B are present in a stoichiometric ratio of 0.95:1 to 1.40: 1 based on the number of moles of isocyanate groups in component A and the number of moles of isocyanate-reactive groups in component B.

12. The separation apparatus according to any of claims 1 to 1 1 , wherein component B is selected from the group consisting of, polyols, polyamines, polythiols,

aminoalcohols, and mixtures thereof.

13. The separation apparatus according to any of claims 1 to 12, wherein component B comprises polyol.

14. The separation apparatus according to any of claims 1 to 13, wherein component B comprises castor oil.

15. The separation apparatus according to any of claims 1 to 14, wherein the polyisocyanate comprises methylene diphenyl diisocyanate.

16. The separation apparatus according to any of claims 1 to 15, wherein the polyisocyanate comprises polymeric methylene diphenyl diisocyanate.

17. The separation apparatus according to any of claims 1 to 16, wherein the membrane layer comprises a barrier layer disposed adjacent one surface of a microporous substrate and a support layer disposed adjacent an opposing surface of the microporous substrate.

18. The separation apparatus according to any of claims 1 to 17, including a membrane leaf element having two opposing edges, the membrane leaf element comprising the membrane layer disposed adjacent a surface of the porous carrier layer and a second membrane layer disposed adjacent an opposing surface of the porous carrier layer, the mixed two component polyurethane adhesive penetrating into the membrane leaf element inward from each edge, wherein cured reaction products of the mixed two component polyurethane adhesive form a barrier along the membrane leaf edges to the fluid feed mixture, the first constituent and the second constituent and the porous carrier layer provides a flow channel within the membrane leaf element for the first constituent permeating either membrane layer.

19. A process for bonding a separation membrane to a porous backing using a polyurethane adhesive comprising the steps of:

mixing a component A with a component B to form the polyurethane adhesive, wherein component A comprises:

a polypropylene glycol-based isocyanate functional pre-polymer wherein having an average isocyanate functionality (NCO) of at least 2 and between 8 and 20 weight percent NCO functionality, wherein the polypropylene glycol- based isocyanate functional pre-polymer comprises the reaction product of:

i) between 25 and 75 weight percent of a polyisocyanate, ii) between 25 and 75 weight percent of a polyol comprising

polypropylene glycol having a weight average molecular weight between 200 and 2500 Daltons; and

and component B comprises:

an isocyanate reactive component comprising isocyanate reactive functional groups, wherein the component B is capable of reacting with the polypropylene glycol-based polyisocyanate pre-polymer of the component A;

applying the polyurethane adhesive to at least one of the separation membrane and the porous backing to form a bonded area; and

allowing the polyurethane adhesive to cure;

whereby a percent penetration of the membrane is at least 40%.

20. The process according to claim 19, wherein the weight percent of NCO in the component A is between 8 and 14 weight percent.

21. The process according to claim 19 or claim 20, wherein the component A has a viscosity of less than 55,000 mPa sec at 25°C measured on a Brookfield viscometer at 20 RPM and spindle 6.

22. The process according to any of claims 19 to 21, wherein the component A further comprises iii) less than 10 weight percent of a different polypropylene glycol having a molecular weight in the range of 200 to 500.

23. Use of the two component polyurethane adhesive of any of claims 1 to 22 to bond a membrane leaf element.