Photocurable color-changing composition and method for forming features on a film surface using the same

Abstract

Photocurable compositions that have a color change during cure, and methods for preparing and using such compositions. More particularly, the present invention relates to photocurable compositions that have a color change during cure and are useful for forming topographical features, such as spacer features, and / or crease protection coatings on portions of membrane surfaces, particularly membranes used in osmosis and reverse osmosis applications, such as membrane filters.

Description

[Technical Field]

[0001] background Technical Field The present disclosure generally relates to photocurable color-changing materials used to coat selected areas of membranes used in spiral wound filtration assemblies. More particularly, the present invention relates to photocurable compositions that undergo a reversible color change during cure and are useful for forming topographical features, such as spacer features and / or reinforcing coatings, on selected areas of a membrane surface, particularly on membranes used in spiral wound filtration assemblies for reverse osmosis applications.

[0002] Brief description of the related art Curable compositions are widely used in sealing, adhesive, coating and potting applications, in which the polymer backbone and polymer functionality are generally selected with reference to the particular end-use application and environment in which it is intended to be used.

[0003] In one embodiment, the curable composition is disposed on the membrane surface in a spaced pattern. Upon curing, the composition forms spacers that separate adjacent membranes, allowing liquids, such as water, to flow between them. The pattern of curable composition formed on the membrane offers advantages over more traditional mesh layer separators, particularly because the pattern reduces flow obstruction and reduces the buildup of filter debris (commonly referred to as fouling). Furthermore, spacers formed from the curable composition, when placed directly on the membrane surface, can have a height that is 50% lower than that of conventional mesh spacers. Such height reduction is not possible with conventional mesh spacers, as they would dramatically increase the feed pressure as well as the pressure drop across the element. Printed spacers are expected to achieve a reduced height without significantly reducing the feed pressure. For a given element diameter, the reduced height of printed spacers allows more membranes to be entrained in the element compared to conventional mesh spacers. For example, in some cases, a printed spacer can use an additional 7 lobes, for a total of 35 lobes, compared to the 28 lobes of a conventional mesh spacer design for the same 8-inch diameter element (i.e., a 25% increase). Also, in some cases, a 4-inch diameter element can use an additional 3 lobes, for a total of 10 lobes, instead of the typical 7 lobes (i.e., a 40% increase).

[0004] Commercially producing membranes with printed curable composition patterns, referred to herein as topographical features or spacers, presents many challenges. The topographical features must have a size and shape that provides sufficient spacing from adjacent layers, balanced with minimum coverage of the membrane's surface area to allow maximum fluid flow through the uncovered surface.

[0005] UV inks are capable of high aspect ratios and fast curing, but they are limited in the height they can print in a single pass. Building the height required for membrane spacer applications typically requires multiple passes of curable composition deposition over the same area, dramatically slowing printing speed and final product fabrication. Standard light-curing acrylics (LCA), or even gel LCAs, can only support low aspect ratios and therefore cannot meet the requirements for achieving print height. When using jet printing, the impact velocity of the curable composition as it strikes the membrane further reduces the aspect ratio. Jet printing can double printing speed, but at a significant cost to the aspect ratio.

[0006] Polyolefin (PO) hot melt compositions used in gravure printing allow for very fast production rates of printed films, but they also have the slowest curing rates, requiring over 30 seconds to cool. This requires a large space to hold the moving film and prevent damage to the pattern while it cools. When used with the high viscosities required for gravure printing, PO hot melts do not have sufficient aspect ratios. The print height is limited to the maximum possible print height per print pass, as multiple passes are not possible with this technology. This limited print height also limits the aspect ratio. Furthermore, the PO hot melt process is prone to stringing, long start-up times, and high film waste, making it very expensive for this market / application. Thus, the PO hot melt process is not an efficient process for this market.

[0007] Given the difficulty of printing and curing a large number of cured spacers on a membrane surface, it would be desirable to be able to quickly and easily verify the spacer printing. It would further be desirable to verify the degree of cure in the cured composition.

[0008] In another embodiment, the membrane leaves are typically "creased" or "folded" at the permeate tube location, which creates a weak point in the membrane leaves. Details of such assemblies are known and can be found, for example, in U.S. Patent Nos. 4,842,736 and 7,303,675, the contents of each of which are incorporated by reference in their entirety.

[0009] Adhesives have been used as coatings on the folded membrane leaf area in an attempt to improve membrane durability at the folds and prevent leakage during use. In some applications, membrane assemblies are subjected to daily cleaning with strong chlorine solutions or high-temperature (70-85°C) and high-pH (11.0-12.5) solutions. Adhesives used for fold protection must be resistant to these cleaning solutions and high-temperature and pH conditions and maintain their mechanical integrity without cracking or peeling from the membrane material.

[0010] Currently, two types of adhesives are used as crease protection materials: two-component polyurethane adhesives and adhesives based on acrylate chemistry. Polyurethanes have good flexibility and resistance to high pH and temperature environments, but require long curing times (8 hours to several days). Due to their long curing times, polyurethane-based adhesives are limited to offline processing in the manufacture of folded membrane packs. UV-curable acrylate adhesives have been proposed as crease protection materials. Some acrylate adhesives are too brittle for this application. Furthermore, flexible acrylate adhesives 1) cannot achieve a tack-free surface with short UV exposure, and 2) easily lose adhesive integrity, lose adhesion, and peel from the membrane under the required high temperature and pH conditions. Therefore, neither two-component polyurethane adhesives nor traditional acrylate adhesives are optimal as membrane crease protection materials.

[0011] Knowing the degree of polymerization is important because it relates to cured material properties, such as mechanical strength, adhesive strength, non-reactive residue, and chemical resistance, which can significantly affect the biocompatibility and migration of the material. However, it is difficult to quantitatively determine the degree of polymerization (cure) or hardening of a composition nondestructively. For both two-component polyurethane adhesives and traditional acrylate adhesives, there is no quick and easy way to check the degree of cure of the cured adhesive on a filter.

[0012] There is a need for photocurable compositions and processes for using such compositions that allow application to film surfaces. It is desirable for the composition to have a reversible color change during and after curing, thereby allowing a user to quickly and easily verify its presence on a surface. It is also desirable for a user to quickly and easily verify the degree of cure of the cured composition on a surface. In some embodiments, the photocurable composition preferably has rheological properties that, once applied, allow the volume of the curable composition to substantially maintain its dimensions even during removal of the template used to apply the curable composition to a film surface. In some embodiments, it is desirable to provide a high-performance crease protection adhesive that is rapidly curable and has good flexibility and resistance to high pH / temperature environments. Summary of the Invention [Means for solving the problem]

[0013] overview One aspect of the present disclosure provides photocurable compositions (i.e., compositions that cure upon exposure to sufficient actinic radiation), and methods for preparing and using such compositions. The compositions exhibit a reversible color change during and after curing. The color of the cured composition changes during and after curing, but can be renewed by subsequent exposure to actinic radiation. In one aspect, the color of the cured composition indicates the degree of cure of the composition.

[0014] Another aspect of the present disclosure provides a film having a color-changing light-curable adhesive applied over only a portion of the film surface, where the applied adhesive can form a spacer, a crease protector, or both.

[0015] Another aspect of the present disclosure provides a reverse osmosis filter including a fluid-permeable membrane having a pattern of spacers thereon, wherein the spacers are formed from a photocurable composition that changes color upon exposure to actinic radiation, and the spacers are formed by stencil printing or screen printing. Some fluids that may be used with these membranes include water, dairy products, alcoholic products, beverage products, etc.

[0016] Another aspect of the present disclosure provides a method for producing a filtration membrane having a curable composition disposed thereon, comprising the steps of: providing a membrane having a first surface and an opposing second surface; and depositing a photocurable composition in a predetermined shape and size on a portion of the first and / or second membrane surface. The cured composition exhibits a reversible color change during and after curing. The color of the cured composition changes but can be restored by subsequent exposure to actinic radiation. In one aspect, the color of the cured composition indicates the degree of cure of the composition.

[0017] Another aspect of the present disclosure provides a method for forming topographical features on a film surface, the method comprising the steps of: providing a film surface; providing a stencil or screen on the film surface, the stencil or screen having openings exposing the film surface for receiving a curable composition; depositing one or more layers of the curable composition into the stencil or screen openings and onto the film surface to form the topographical features, the openings defining the approximate shape and size of the topographical features; removing the stencil or screen to leave the topographical features in place on the film; and curing the curable composition, wherein each layer of the curable composition deposited in the depositing step produces topographical features having an aspect ratio (height / width) of about 0.2 to about 2. The cured composition exhibits a color change during curing. In one aspect, the color of the cured composition indicates the degree of cure of the composition. In another aspect, the color of the cured composition reverts to approximately the color before curing, but can be restored by subsequent exposure to actinic radiation.

[0018] Another aspect of the present disclosure provides a method for forming topographical features on a film surface, the method comprising the steps of: providing a film surface; providing a stencil or screen on the film surface, the stencil or screen having openings exposing the film surface for receiving a curable composition; depositing one or more layers of a photocurable composition onto the film surface through the stencil or screen openings to form the topographical features, the openings defining the approximate shape and size of the topographical features; and removing the stencil or screen to leave the topographical features in place on the film. The deposited photocurable composition is exposed to actinic radiation sufficient to cure the composition either before or after the stencil is removed. The cured composition exhibits a reversible color change during and after curing. The color of the cured composition changes but can be restored by subsequent exposure to actinic radiation. In one aspect, the color of the cured composition indicates the degree of cure of the composition.

[0019] Another aspect of the present disclosure provides a method for applying a color-changing light-curable adhesive to a fold area of ​​a film.

[0020] Another aspect of the present disclosure provides a method for producing a filtration membrane having a curable composition disposed thereon, comprising the steps of providing a membrane having a first surface and an opposing second surface; and depositing a photocurable composition in a defined shape and size on a portion of the first and / or second membrane surface. The cured composition exhibits a reversible color change during and after curing. The color of the cured composition changes but can be restored by subsequent exposure to actinic radiation. In one aspect, the color of the cured composition indicates the degree of cure of the composition. [Brief explanation of the drawings]

[0021] Reference is made to the drawings in which like elements are numbered likewise in the several views. [Figure 1] FIG. 1 is a schematic cross-sectional view of the membrane. [Figure 2] FIG. 2 is a schematic representation of a cut film having a color-shifting photocurable composition applied adjacent to a fold line. [Figure 3] FIG. 3 is a schematic diagram of a cut membrane folded around a feed spacer. [Figure 4] FIG. 4 shows a typical pattern of topographical features for water desalination or brackish water filtration. [Figure 5a] Figures 5a and 5b show the arrangement of a stencil and a membrane, with openings for depositing a curable composition on the membrane surface in the form of topographical features (showing three dimensions) of a desired size and shape, where the topographical features are sufficient to perform a spacing function when overlapped with another membrane surface. The aspect ratio of the features (providing the desired spacing ability) is shown. Figure 5a shows the stencil overlapped on the membrane surface, and Figure 5b shows the stencil and membrane separated from each other after the stencil has been removed from the membrane, leaving the topographical features. [Figure 5b]Figures 5a and 5b show the arrangement of a stencil and a membrane, with openings for depositing a curable composition on the membrane surface in the form of topographical features (showing three dimensions) of a desired size and shape, where the topographical features are sufficient to perform a spacing function when overlapped with another membrane surface. The aspect ratio of the features (providing the desired spacing ability) is shown. Figure 5a shows the stencil overlapped on the membrane surface, and Figure 5b shows the stencil and membrane separated from each other after the stencil has been removed from the membrane, leaving the topographical features. DETAILED DESCRIPTION OF THE INVENTION

[0022] Detailed Description The singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise.

[0023] As used herein, "about" or "approximately" when used in connection with a numerical value means the numerical value ±10%, preferably ±5%, more preferably ±1% or less.

[0024] As used herein, at least one means one or more, i.e., 1, 2, 3, 4, 5, 6, 7, 8, 9, or more. With respect to components, the designation refers to the type of component and not the absolute number of molecules. Thus, for example, "at least one polymer" means at least one type of polymer, i.e., one type of polymer or a mixture of multiple different polymers can be used.

[0025] As used herein, the terms "comprising," "comprises," and "comprised of" are synonymous with "including," "includes," "containing," or "contains," and are inclusive or open-ended and do not exclude additional, unrecited members, elements, or method steps.

[0026] When amounts, concentrations, dimensions, and other parameters are expressed in the form of ranges, preferred ranges, upper limits, lower limits, or preferred upper and lower limits, it is to be understood that ranges that can be obtained by combining any upper limit or preferred value with any lower limit or preferred value are also specifically disclosed, regardless of whether the resulting range is expressly stated in the context.

[0027] Preferred and preferred are frequently used herein to refer to embodiments of the present disclosure that may offer certain advantages, under certain circumstances. However, the recitation of one or more preferred or preferred embodiments does not imply that other embodiments are not useful, and is not intended to exclude such other embodiments from the scope of the present disclosure.

[0028] Unless otherwise indicated, all percentages quoted in connection with the compositions described herein refer to weight percent (wt%) with respect to the final composition with all components.

[0029] Molecular weights given in the text refer to number average molecular weights (Mn) unless otherwise specified. Molecular weight data can be obtained by gel permeation chromatography (GPC) calibrated against polystyrene standards according to DIN 55672-1:2007-08 at 35°C unless otherwise specified. Weight average molecular weight M w is M n As mentioned above, it can be measured by GPC. "Polydispersity index" refers to a measure of the distribution of molecular weights in a given polymer sample. The polydispersity index is calculated by dividing the weight average molecular weight (Mw) by the number average molecular weight (Mn).

[0030] Alkyl refers to a monovalent group containing carbon and hydrogen atoms, e.g., 1 to 8 carbon atoms, and is an alkane group, including linear and branched configurations. Examples of alkyl groups include, but are not limited to, methyl, ethyl, propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, n-hexyl, n-heptyl, and 2-ethylhexyl. In the present invention, such alkyl groups may be unsubstituted or optionally substituted. Preferred substituents include one or more groups selected from halo, nitro, cyano, amido, amino, sulfonyl, sulfinyl, sulfanyl, sulfoxy, urea, thiourea, sulfamoyl, sulfamido, and hydroxy. Halogenated derivatives of the exemplary hydrocarbon groups listed above may be particularly mentioned as examples of suitable substituted alkyl groups. Preferred alkyl groups include unsubstituted alkyl groups containing 1 to 6 carbon atoms (C1-C6 alkyl), e.g., unsubstituted alkyl groups containing 1 to 4 carbon atoms (C1-C4 alkyl).

[0031] Alkylene refers to a divalent group containing carbon atoms, e.g., 1 to 20 carbon atoms, and is an alkane group, including linear and branched organic groups, which may be unsubstituted or optionally substituted. Preferred alkylene groups include unsubstituted alkylene groups containing 1 to 12 carbon atoms (C1-C 12 alkylene)--for example, an unsubstituted alkylene group containing 1 to 6 carbon atoms (C1-C6 alkylene) or an alkylene group containing 1 to 4 carbon atoms (C1-C4 alkylene)-.

[0032] An alkenyl group refers to an aliphatic carbon group containing, for example, 2 to 8 carbon atoms and at least one double bond. Similar to the alkyl groups described above, alkenyl groups can be linear or branched, and can be unsubstituted or optionally substituted. Examples of C2-C8 alkenyl groups include, but are not limited to, allyl, isoprenyl, 2-butenyl, and 2-hexenyl.

[0033] Aryl or aromatic groups, used alone or as part of a larger moiety (as in "aralkyl group"), refer to unsubstituted or optionally substituted monocyclic, bicyclic, and tricyclic ring systems, where the monocyclic ring system is aromatic or at least one of the bicyclic and tricyclic ring systems is aromatic. Bicyclic and tricyclic ring systems include benzo-fused 2- to 3-membered carbocyclic rings. Exemplary aryl groups include phenyl; indenyl; naphthalenyl, tetrahydronaphthyl, tetrahydroindenyl; tetrahydroanthracenyl; and anthracenyl.

[0034] An arylene is a divalent aryl group, which may be unsubstituted or optionally substituted.

[0035] Aralkyl refers to an alkyl group substituted with an aryl group. An example of an aralkyl group is benzyl.

[0036] Acrylate refers to the monovalent -OC(O)-C=C moiety. Methacrylate refers to the monovalent -OC(O)-C(CH3)=C moiety. (Meth)acrylate refers to acrylate and methacrylate.

[0037] Acryloyl (ACR) refers to the -C(O)-C=C moiety. Methacryloyl (MCR) refers to the -C(O)-C(CH3)=C moiety. (Meth)acryloyl refers to acryloyl and methacryloyl.

[0038] Alkyne or alkynyl refers to a hydrocarbon chain or group containing one or more triple bonds between carbon atoms in the chain. 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, preferably 1 to 10 carbon atoms, and more preferably 1 to 6 carbon atoms. The alkyne can contain one or more conjugated triple bonds. In some embodiments, the alkyne can be substituted.

[0039] By anhydrous, it is meant that the mixture or components as applied contain less than 0.1 wt% water, based on the weight of the mixture or component.

[0040] By catalytic amount is meant a substoichiometric amount of catalyst relative to reactant.

[0041] Cycloalkyl means a saturated monocyclic, bicyclic, or tricyclic hydrocarbon group having 3 to 10 carbon atoms. Examples of cycloalkyl groups include cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, adamantane, and norbornane.

[0042] Ester refers to the structure RC(O)-O-R', where R and R' are independently selected hydrocarbyl groups with or without heteroatoms. The hydrocarbyl groups may be substituted or unsubstituted.

[0043] An ether refers to a compound that has an oxygen atom connected to two alkyl or aryl groups.

[0044] Halogen or halide refers to an atom selected from fluorine, chlorine, bromine and iodine.

[0045] A heteroatom is an atom other than carbon or hydrogen, such as nitrogen, oxygen, phosphorus, or sulfur. The phrase "interrupted by at least one heteroatom" means that the main chain of the residue contains at least one heteroatom as a chain member.

[0046] Hydrocarbyl refers to a group containing carbon and hydrogen atoms. Hydrocarbyl can be a linear, branched, or cyclic group. Hydrocarbyl can be alkyl, alkenyl, alkynyl, or aryl. In some embodiments, hydrocarbyl is substituted.

[0047] Oligomer refers to a small number of repeating monomer units, such as 2 to 5,000 units, preferably about 5 to about 2,000 units, polymerized to form a molecule. Oligomer is a subset of the term polymer. "Polymer" refers to a polymerized molecule with a chain length and molecular weight greater than that of an oligomer. As used herein, polymer can include both oligomers and polymers.

[0048] Polyether refers to a compound having two or more ether groups. Exemplary polyethers include polyoxymethylene, polyethylene oxide, and polypropylene oxide.

[0049] Polymerization conditions refer to reaction conditions suitable for combining monomers into a polymer.

[0050] Room temperature refers to a temperature of about 25°C.

[0051] "Substituted" refers to the replacement of an atom at any available position on the molecule with one or more substituents. Useful substituents are those that do not significantly impair the disclosed reaction. Exemplary substituents include, for example, alkyl, alkenyl, alkynyl, cycloalkyl, cycloalkenyl, cycloalkynyl, aryl, aralkyl, heteroaryl, heteroalicyclyl, heteroaralkyl, heteroalkenyl, heteroalkynyl, (heteroalicyclyl)alkyl, aryloxy, acyl, ester, mercapto, alkylthio, arylthio, carbonyl, thiocarbonyl, O-carbamyl, N-carbamyl, O-thiocarbamyl, N-thiocarbamyl, C-amide, N -Amido, S-sulfonamido, N-sulfonamido, C-carboxy, protected C-carboxy, O-carboxy, isocyanato, thiocyanato, isothiocyanato, silyl, sulfenyl, sulfinyl, sulfonyl, haloalkoxy, trihalomethanesulfonyl, trihalomethanesulfonamido, amino including mono- and di-substituted amino groups and their protected derivatives, carbamate, halogen, (meth)acrylate, epoxy, oxetane, urea, urethane, N3, NCS, CN, NO2, NX1 X 2 ,OX 1 , C(X 1 )3, COOX 1 ,SX 1 , Si(OX 1 ) i X 2 3-i , alkyl, alkoxy (wherein each X 1 and each X 2 independently include H, alkyl, alkenyl, alkynyl, aryl or halogen, and i is an integer of 0 to 3.

[0052] Unless otherwise indicated, all percentages quoted in connection with the compositions described herein refer to weight percent (wt%) of the final composition with all components.

[0053] In general, unless otherwise specified, the disclosed materials and processes may alternately be assembled to comprise, consist of, or consist essentially of any suitable components, moieties, or steps disclosed herein. The disclosed materials and processes may additionally or alternatively be assembled to lack or be substantially free of any components, ingredients, components, adjuvants, moieties, species, and steps used in prior art compositions or that are not otherwise necessary to achieve the function and / or purpose of the present disclosure.

[0054] The present invention relates to photocurable compositions and methods for their preparation, as well as the use of such compositions on filtration membranes. The cured compositions exhibit a reversible color change during and after curing. The color of the cured composition changes but can be restored by subsequent exposure to actinic radiation. In some embodiments, the color of the cured composition indicates the degree of cure of the composition.

[0055] One embodiment discloses a method of forming topographical features on a film surface according to the present invention, the method comprising the steps of: providing a film surface; providing a stencil or screen on the film surface, the stencil or screen having openings exposing the film surface for receiving a curable composition; depositing one or more layers of the curable composition into the stencil or screen openings and on the film surface to form the topographical features, the openings defining the approximate shape and size of the topographical features; removing the stencil or screen to leave the topographical features in place on the film; and curing the curable composition.

[0056] Another method for forming topographical features on a film surface according to the present invention includes the steps of: providing a film surface; providing a stencil or screen on the film surface, the stencil or screen having openings that expose the film surface for receiving a curable composition; depositing one or more layers of the curable composition into the stencil or screen openings and onto the film surface to form topographical features, the openings defining the approximate shape and size of the topographical features; and removing the stencil or screen, leaving the topographical features in place on the film. In some embodiments, the viscosity of the curable composition is 25°C, 10 seconds, or less. -1 and / or a thixotropic index (TI) (1 s -1 Viscosity at / 10 seconds -1 and / or the curable composition provides an aspect ratio (height / width) of the topographical features sufficient to substantially maintain the approximate size and shape of the features during removal of the stencil from the film surface prior to curing.

[0057] The topographical feature formation method of the present invention can be carried out using high speed production printing methods known in the art. Preferably, the method of the present invention uses direct printing through a stencil / screen or gravure printing methods.

[0058] As shown in Figure 5a, a membrane (10) is overlaid with a stencil (20) on one of the membrane's surfaces (not shown). Openings (30) in the stencil are filled with a curable composition to form topographical features, such as spacers (40). The composition is cured from the other side of the membrane. As shown in Figure 5b, once the stencil (20) is removed from the membrane (10), the partially cured composition is further cured by exposure to actinic radiation to form topographical features (40) on the membrane surface (50).

[0059] The topographical features formed on the membrane surface have physical properties suitable for providing spacing between stacked membrane layers. For example, the topographical features can provide appropriate spacing between layers of spiral reverse osmosis filtration membranes to optimize operation, cleaning, and life of reverse osmosis membrane elements using membranes with these topographical features. Furthermore, the topographical features are typically smooth or flat and do not have sharp edges that could damage the interdigitating membrane layers during operation.

[0060] The aspect ratio of the topographical features may be greater than 0.50 or greater than about 0.70. Combinations of aspect ratios may be used in patterns to provide predetermined spacing configurations between layers of membranes or other surfaces in the osmotic devices of the present invention. As used herein, the term "aspect ratio" refers to the ratio of the height of a topographical feature to the width of the topographical feature.

[0061] The height of the topographical feature once formed on the membrane can be from about 0.001 to about 0.05 inches, for example, from about 0.01 to about 0.04 inches. The height of the topographical feature is the distance from the base of the topographical feature (on the membrane surface or the interface between the topographical feature and the membrane) to the point on the topographical feature that is vertically furthest from the membrane surface.

[0062] The width of a topographical feature is defined as the smallest dimension of the footprint of the topographical feature on the film surface, where the footprint is the area or region of the coating on the substrate surface.

[0063] The pattern of topographical features can have a size and shape sufficient to maintain sufficient membrane spacing and expose sufficient membrane surface to ensure efficient membrane operation. In particular, the total surface area of ​​the membrane covered by topographical features (i.e., the area of ​​the footprint of each individual topographical feature multiplied by the number of topographical features per unit area of ​​membrane surface) does not exceed about 20% of the membrane surface (i.e., at least about 80% of the membrane surface remains exposed). The total surface area of ​​the membrane covered by topographical features is about 15% or less, for example, about 10% or less, or about 6% or less, or about 5% or less, or about 3% or less, or about 2% or less, or about 1% or less.

[0064] The pattern of topographic features is approximately 0.5 m 2 The topographical feature pattern may be formed on the membrane surface at a rate of about 1 m / min or more. 2 / min or faster, or approximately 2m 2 may form on the membrane surface at a rate of 1 / min or more.

[0065] The printing speed of topographical features can also be optimized, since the desired height can be achieved by depositing only a single layer of photocurable composition (as opposed to, for example, the need to coat and cure 10–20 layers of UV ink) without adversely affecting the aspect ratio and overall efficiency of the film. Furthermore, this single layer can be deposited simultaneously across the entire 40-inch width of the film. Therefore, the printing time for a single leaf is the linear speed of traveling the length of the leaf (also 40 inches). Therefore, multiple passes in both the X and Y directions are not required. Essentially, multiple layers of curable composition do not need to be deposited on the film before curing or pre-curing to achieve the desired height. This offers a significant speed advantage over other technologies. For example, UV ink can deposit heights of up to 0.001 inches per pass. Wet printing processes can deposit heights 10 times higher, or 0.010 inches per pass, and pre-curing processes can deposit heights 40 times higher, or 0.040 inches per pass. These processes also allow deposition to less than the maximum height in a single pass, allowing greater design freedom for topographical features.

[0066] The surface on which the topographical features are deposited can be any surface, but a membrane surface is most preferred. As used herein, "membrane" means a selective barrier that allows the passage of some substances while preventing the passage of other substances. The membrane can be a filter membrane, i.e., a membrane for filtering substances from a liquid carrier such as water. Filter membranes include reverse osmosis membranes, forward osmosis membranes, microfiltration membranes, ultrafiltration membranes, and nanofiltration membranes. The topographical features can be printed on the active surface of the membrane, on the non-active surface of the membrane, or both.

[0067] The photocurable composition may be deposited onto the membrane surface within and / or through the openings in a stencil or screen to form topographical features by depositing a single layer of the composition. The photocurable composition may be deposited onto the membrane surface within and / or through the openings in a stencil or screen to form topographical features by depositing multiple layers of the composition. The topographical features may be deposited on one surface of the membrane (either the feed or permeate side) or both surfaces.

[0068] The stencil or screen can be constructed of any useful material that prevents the curable composition from oozing onto the portion of the surface covered by the stencil and also allows for sufficient sealing of the stencil to the surface so that the stencil can be removed from the surface without damaging the surface or disturbing the deposited curable composition. The stencil or screen can be constructed from metals such as steel, aluminum, stainless steel, polymer-coated metals, ceramic-coated metals, metal cloths, composite materials, polymeric materials such as polyesters or fluoropolymers, or polymer cloths.

[0069] Stencil printing uses a stencil made from a single piece of material with a pattern cut into it. The stencil is attached to a frame, which may be attached to the frame with a mesh to provide tightness, flatness, and springiness. The mesh can be made of any suitable material, such as stainless steel, nylon, plastic, or carbon fiber. The thickness of the stencil is determined by the height of the printed feature, minus the effects of gravity and physical phenomena, which reduce the height by a certain factor during printing (typically about 20%). The pattern and opening size (aperture) also determine the amount of product that can be ejected from a stencil of maximum thickness. Stencils with excellent surfaces, with low surface energy, can provide higher ejection volumes. Wet printing is limited to a height about 20% lower than the stencil thickness. However, in pre-curing methods, which use a stencil as a mold, the product is pre-cured to the height of the stencil. Therefore, features can be pushed out of the stencil apertures because the curable composition is not fully cured and the stencil's low surface energy coating can cause the feature to miss the aperture. After the curable composition is fully cured, the height of the features will be the same as the height of the stencil.

[0070] Screen printing uses a stainless steel mesh or a polyester or nylon screen onto which an emulsion is applied, covering a portion of the screen or mesh and exposing the pattern where the curable composition will be deposited. The print thickness depends on the mesh thickness, the open area of ​​the mesh, and the thickness to which the emulsion is built up. Thickness is also affected by printer variables such as squeegee pressure and durometer, angle of attack, speed, and snap-off distance. The viscosity of the screen printing material can vary from low to high depending on the application requirements.

[0071] The openings or apertures in the stencil or screen pattern of the present invention can have any shape or combination of shapes necessary to generate the desired shape of the topographical feature. For example, the openings can be in the shape of a circle, ellipse, arc, square, rectangle, diamond, pentagon, hexagon, star, chevron, or any combination thereof. Such opening shapes generate three-dimensional topographical features having a cross-section corresponding to the opening shape and having the height and aspect ratios described herein. For example, a circular opening generates a cylindrical topographical feature. An exemplary topography of a feature pattern for water desalination or brackish water filtration is shown in Figure 4. The depth of the stencil determines the height of the topographical feature, and is selected to a desired height according to the desired aspect ratio. For example, the height can be about 0.005 to about 0.04 inches, preferably about 0.010 to about 0.025 inches, and more preferably about 0.012 to about 0.015 inches.

[0072] The topographical features can be substantially free of sharp edges after formation and stencil removal. For example, the edges of the stencil openings can be free of sharp edges, such that the deposited curable composition does not have sharp edges. Furthermore, upon removal of the stencil or screen, the curable composition is pulled up along with the stencil or screen, resulting in no sharp edges in the topographical features. Essentially, the curable composition slumps enough to maintain a rounded or flat surface, but does not slump so much that it loses its aspect ratio. Furthermore, the stencil coating is selected to have a sufficiently low surface energy so as not to pull on the curable composition when the stencil or screen is removed. Thus, the topographical features are typically smooth or flat, without sharp edges that could damage the mating layers of the film during operation.

[0073] In some embodiments, the curable composition can produce the thixotropic index values ​​and / or aspect ratios described herein and is actinically curable, making it suitable for use in production printing processes. The curable composition preferably has properties suitable for high-speed production printing processes described herein and known in the art. For example, it is desirable for the curable composition to provide fast cure speed, desirable rheological properties, excellent adhesion, chemical / temperature resistance, and flexibility / durability to meet various film application requirements. In preferred embodiments, the cured reaction product of the composition will have a color that allows for inspection of topographical features. This color may change over time but can be restored by subsequent exposure to actinic radiation. In some embodiments, the color of the cured composition indicates the degree of cure of the composition.

[0074] The curable composition in this embodiment should have an effectively balanced, optimized rheology that allows for shear thinning to flow through a screen or into a stencil printer, yet maintains its three-dimensional printing dimensions, e.g., height, width, and depth (and thus maintains its overall shape) after the screen or stencil is removed, allowing it to provide the aspect ratios described herein. Essentially, the curable composition of the present invention should exhibit sufficient thixotropy to maintain its physical structure before curing and not flow or sag. Furthermore, upon application of shear forces (e.g., during deposition onto a stencil or screen), the viscosity of the curable composition decreases, which helps the curable composition move through / fill the openings in the stencil or screen. As used herein, "thixotropy" refers to a material that becomes less viscous when stress (e.g., mixing or shaking) is applied, but becomes more viscous in the absence of such stress (e.g., under static conditions).

[0075] In general, the curable composition should be capable of being deposited into the stencil openings and onto the membrane surface, and once deposited and allowed to stand, maintain its shape during stencil removal and curing.

[0076] In some embodiments for the formation of topographical features, the curable composition should have a thixotropic index (TI) of 1 to about 15, preferably about 5 to about 10, and more preferably about 6 to about 8. The TI should be greater than about 2, greater than about 4, greater than about 6, greater than about 7, greater than about 8, greater than about 9, greater than about 10, or greater than about 11. As used herein, "thixotropic index" refers to the 1 s -1 Viscosity of the curable composition (in centipoise) at a rate of 10 seconds -1 The ratio (in centipoise units) of the viscosity of the curable composition at a speed of 1 / 2 s -1 Viscosity at / 10 seconds -1 viscosity at

[0077] In some embodiments for the formation of topographical features, the curable composition is applied at 25° and 10 seconds. -1 The viscosity (in centipoise units) at a speed of 1000 to 1500,000 should be about 5,000 to about 500,000, preferably 10,000 to 50,000. Viscosity can be measured by known methods, for example, using a cone and plate rheometer, a parallel plate rheometer, or a rotational viscometer such as a Brookfield viscometer.

[0078] The curable composition can be photocurable, i.e., it cures when exposed to actinic radiation, such as visible or ultraviolet (UV) light. Thus, the curable composition can be cured using a light source, such as a mercury arc lamp or an LED, that generates visible or UV light. The curable composition is at least partially cured by exposing the non-feature side of the film to a light source.

[0079] The curable composition can be fully cured before or after removal of the stencil or screen.

[0080] The curable composition can also be pre-cured, i.e., partially cured, prior to removal of the stencil, by exposing the side of the film that does not have the topographical features to a visible light source. After removal of the stencil or screen, the curable composition can then be fully cured using a UV or visible light source.

[0081] In this pre-cure method, the viscosity of the curable composition is increased prior to removal of the stencil or screen to help maintain the shape of the topographical features during removal of the stencil. In some embodiments, this pre-cure gels the curable composition or partially cures it to a semi-solid state. As mentioned above, the stencil or screen is made from a coated metal that provides a low surface energy that allows the curable composition to be released from the stencil via limited adhesion that occurs to the film during the pre-cure.

[0082] This pre-curing method allows for dramatically improved aspect ratios over wet printing, as any desired height (i.e., 0.005-0.040 inches) can be achieved in one step, instead of requiring the deposition of multiple layers to reach the required height.

[0083] In another embodiment, the curable composition is coated onto a portion of the membrane substrate surface and cured to form the crease protection material. Referring to the figures, one exemplary membrane 10 intended for filtration applications is a composite thin film sheet having a generally rectangular shape and a multilayer structure having the general structure shown in schematic cross section in FIG. 1. Membrane 10 typically includes two or three layers: an optional thin, dense, semipermeable barrier layer 12; a microporous substrate 14; and a porous support layer 16. The thin, dense, semipermeable barrier layer 12, if used, has a typical thickness of about 0.02 to 0.20 micrometers. The semipermeable barrier layer 12 is typically, but not necessarily, a polyamide film. The barrier layer 12 overlies a microporous substrate 14 having a typical thickness of about 40 to 50 micrometers. The microporous substrate 14 is typically, but not necessarily, composed of a polysulfone film. The microporous substrate 14 overlies a porous support layer 16 having a typical thickness of about 100 to 200 micrometers. The support layer 16 is generally constructed and arranged to allow the filtered fluid to pass easily through it while providing physical support to the other layers of the composite membrane 10. An example of a porous support layer is a polyester nonwoven material. The material of construction and its thickness can vary depending on the exact separation application for which the membrane 10 is intended. If present, the semipermeable layer 12, either by itself or in combination with the intermediate microporous substrate 14, can be the active surface of the membrane 10 to effect the separation, depending on the exact nature of the compounds to be separated. For example, if the membrane 10 is intended to be used to purify water, the membrane 10 will pass water but not contaminants such as salts. Referring to Figure 2, the membrane 10 is cut to the desired size. A fold line A is provided on the cut membrane. A curable composition 26 is mixed and applied to the membrane 10 adjacent to the fold line A. The curable composition 26 can be applied adjacent to the fold line A on the surface of the semipermeable layer 12, the surface of the support layer 16, or both. Application of the curable composition 26 can be accomplished by established methods. The applied curable composition 26 mixture is exposed to actinic radiation to initiate curing.After the curable composition 26 has cured, a feed spacer material 28 can be placed on the surface of the cut membrane 10, typically on the surface of the semi-permeable layer 12. In one variation, the feed spacer material 28 is not used and is replaced by spacers (not shown) printed onto the membrane surface with the curable composition 26.

[0084] 3, cut membrane 10 is folded along fold line A with feed spacer material 28 disposed between adjacent surfaces of the folded membrane. Cured composition 26 reinforces membrane 10 along fold line A. The combination of membrane 10, cured composition 26, and feed spacer 28 is used as a subassembly in a spiral wound filter such as used in a filtration assembly.

[0085] Photocurable compositions typically include an actinic radiation-curable (meth)acrylate oligomer or polymer; a diluent; a polymeric thioxanthone photoinitiator; an amine coinitiator; a filler, and optional additives.

[0086] (Meth)acrylate oligomer In one embodiment, the backbone of the (meth)acrylate oligomer may be a monofunctional (meth)acrylate monomer, such as a monofunctional C 1-10 Alkyl (meth)acrylate homopolymers and monofunctional C 1-10It is formed from a copolymer of alkyl (meth)acrylate. Particularly useful monomers used include ethyl acrylate, methoxyethyl acrylate, n-butyl acrylate, and homopolymers and copolymers thereof. Additional examples of useful monomers include (meth)acrylic monomers such as (meth)acrylic acid, methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, tert-butyl (meth)acrylate, n-pentyl (meth)acrylate, n-hexyl (meth)acrylate, and cyclohexyl (meth)acrylate. , n-heptyl (meth)acrylate, n-octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, nonyl (meth)acrylate, decyl (meth)acrylate, dodecyl (meth)acrylate, phenyl (meth)acrylate, tolyl (meth)acrylate, benzyl (meth)acrylate, 2-methoxyethyl (meth)acrylate, 3-methoxybutyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2- Hydroxypropyl (meth)acrylate, stearyl (meth)acrylate, glycidyl (meth)acrylate, 2-aminoethyl (meth)acrylate, gamma-(methacryloxypropyl)trimethoxysilane, (meth)acrylic acid-ethylene oxide adduct, trifluoromethylmethyl (meth)acrylate, 2-trifluoromethylethyl (meth)acrylate, 2-perfluoroethylethyl (meth)acrylate, 2-perfluoroethyl-2-perfluorobutylethyl (meth)acrylate, 2-perfluoroethyl (meth)acrylate, perfluoromethyl (meth)acrylate, diperfluoromethylmethyl (meth)acrylate, 2-perfluoromethyl-2-perfluoroethylmethyl (meth)acrylate, 2-perfluorohexylethyl (meth)acrylate, 2-perfluorodecylethyl (meth)acrylate, 2-perfluorohexadecylethyl (meth)acrylate, etc.;Styrenic monomers such as styrene, vinyltoluene, alpha-methylstyrene, chlorostyrene, styrenesulfonic acid and its salts; fluorine-containing vinyl monomers such as perfluoroethylene, perfluoropropylene, vinylidene fluoride, etc.; silicon-containing vinyl monomers such as vinyltrimethoxysilane, vinyltriethoxysilane, etc.; maleic anhydride, maleic acid, mono- and di-alkyl esters of maleic acid; fumaric acid, mono- and di-alkyl esters of fumaric acid; maleimide monomers such as maleimide, methylmaleimide, ethylmaleimide, propylmaleimide, butylmaleimide, hexylmaleimide, octylmaleimide, dodecylmaleimide, stearylmaleimide Examples of suitable monomers include phenylmaleimide, cyclohexylmaleimide, etc.; nitrile-containing vinyl monomers such as acrylonitrile and methacrylonitrile; amide-containing vinyl monomers such as acrylamide and methacrylamide; vinyl esters such as vinyl acetate, vinyl propionate, vinyl pivalate, vinyl benzoate, and vinyl cinnamate; alkenes such as ethylene and propylene; conjugated dienes such as butadiene and isoprene; vinyl chloride, vinylidene chloride, allyl chloride, and allyl alcohol. These monomers may be used alone or in combination.

[0087] Furthermore, the backbone of the (meth)acrylate oligomer may be formed from or include one or segments or units of polyurethane, styrene, polyolefin, acrylamide, nylon, (meth)acrylonitrile, and / or substituted (meth)acrylonitrile. Useful (meth)acrylate-functionalized urethanes include tetramethylene glycol urethane acrylate oligomers and propylene glycol urethane acrylate oligomers. Other (meth)acrylate-functionalized urethanes are urethane (meth)acrylate oligomers based on polyethers or polyesters reacted with aromatic, aliphatic, or cycloaliphatic diisocyanates and capped with hydroxyacrylates. Some useful examples include difunctional urethane acrylate oligomers, such as a polyester of hexanedioic acid and diethylene glycol terminated with isophorone diisocyanate and capped with 2-hydroxyethyl acrylate; a polyester of hexanedioic acid and diethylene glycol terminated with triene-2,6-diisocyanate and capped with 2-hydroxyethyl acrylate; a polyester of hexanedioic acid and diethylene glycol terminated with 4,4'-methylenebis(cyclohexyl isocyanate) and capped with 2-hydroxyethyl acrylate; a polyester of tolylene-2,4-diisocyanate terminated with 2-hydroxyethyl acrylate; Examples of (meth)acrylate-functionalized urethanes include a 4,4'-methylenebis(cyclohexyl isocyanate)-terminated, 2-hydroxyethyl acrylate-capped polyester of hexanedioic acid, 1,2-ethanediol, and 1,2-propanediol; a 4,4'-methylenebis(cyclohexyl isocyanate)-terminated, 2-hydroxyethyl acrylate-capped polyester of hexanedioic acid, 1,2-ethanediol, and 1,2-propanediol; and a 4,4'-methylenebis(cyclohexyl isocyanate)-terminated, 2-hydroxyethyl acrylate-capped polytetramethylene glycol ether. Still other (meth)acrylate-functionalized urethanes include monofunctional urethane acrylate oligomers, such as polypropylene terminated with 4,4'-methylenebis(cyclohexyl isocyanate) and capped with 2-hydroxyethyl acrylate and 1-docosanol.(Meth)acrylate-functionalized urethanes also include difunctional urethane methacrylate oligomers, such as polytetramethylene glycol ether terminated with toluene-2,4-diisocyanate and capped with 2-hydroxyethyl methacrylate; polytetramethylene glycol ether terminated with isophorone diisocyanate and capped with 2-hydroxyethyl methacrylate; polytetramethylene glycol ether terminated with 4,4'-methylenebis(cyclohexyl isocyanate) and capped with 2-hydroxyethyl methacrylate; and polypropylene glycol terminated with tolylene-2,4-diisocyanate and capped with 2-hydroxyethyl methacrylate. In some embodiments, polyether urethane acrylate oligomers are preferred over other oligomer types because they provide increased flexibility to the cured coating, as well as increased chemical, temperature, and pH resistance to the cured coating.

[0088] The number average molecular weight (Mn) of the (meth)acrylate oligomer may be 1000 to 100,000, more preferably 2000 to 50,000.

[0089] (Meth)acrylate oligomers can be prepared using standard techniques known in the art or obtained from suitable commercial sources. Preparation techniques include controlled radical polymerization processes, including single electron transfer living radical polymerization (SET-LRP), stable free radical polymerization (SFRP), such as reversible deactivation by coupling, or degenerative transfer (DT). Once polymerization is complete, the method may include further reacting the resulting polymer to form functional end groups on the polymer. Forming functional ends on the polymer can be achieved, for example, by either an end-capping reaction or a substitution reaction.

[0090] Diluent The curable composition can optionally contain at least one diluent or reactive diluent. Useful diluents can include monofunctional and polyfunctional (meth)acrylates. Illustrative examples of useful (meth)acrylates include alkyl (meth)acrylates, cycloalkyl (meth)acrylates, alkenyl (meth)acrylates, heterocycloalkyl (meth)acrylates, heteroalkyl methacrylates, and alkoxy polyether mono(meth)acrylates.

[0091] The alkyl group on the (meth)acrylate may be a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms, preferably 1 to 10 carbon atoms, and optionally having at least one substituent selected from an alkyl group having 1 to 10 carbon atoms, a substituted or unsubstituted cycloalkyl group having 1 to 20 carbon atoms, preferably 1 to 10 carbon atoms, a substituted or unsubstituted bicyclo or tricycloalkyl group having 1 to 20 carbon atoms, preferably 1 to 15 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, and an aryloxy group having 6 to 10 carbon atoms.

[0092] The alkenyl group on the (meth)acrylate may be a substituted or unsubstituted alkenyl group having 2 to 20 carbon atoms, preferably 2 to 10 carbon atoms, and optionally having at least one substituent selected from an alkyl group having 1 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, an aryloxy group having 6 to 10 carbon atoms, an epoxy group having 2 to 10 carbon atoms, hydroxyl, etc.

[0093] The heterocyclo group on the (meth)acrylate may be a substituted or unsubstituted heterocyclo group having 2 to 20 carbon atoms, preferably 2 to 10 carbon atoms, containing at least one heteroatom selected from N and O, and optionally having at least one substituent selected from an alkyl group having 1 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, an aryloxy group having 6 to 10 carbon atoms, or an epoxy group having 2 to 10 carbon atoms.

[0094] The alkoxy polyether mono(meth)acrylate may be substituted with an alkoxy group having 1 to 10 carbon atoms, and the polyether may have 1 to 10 repeating units.

[0095] Some exemplary (meth)acrylate monomers include, but are not limited to, (meth)acrylic acid, methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, tert-butyl (meth)acrylate, n-pentyl (meth)acrylate, n-hexyl (meth)acrylate, cyclohexyl (meth)acrylate ... (meth)acrylate, n-heptyl (meth)acrylate, n-octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, nonyl (meth)acrylate, decyl (meth)acrylate, dodecyl (meth)acrylate, phenyl (meth)acrylate, tolyl (meth)acrylate, benzyl (meth)acrylate, 2-methoxyethyl (meth)acrylate, 3-methoxybutyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2 hydroxypropyl (meth)acrylate, stearyl (meth)acrylate, glycidyl (meth)acrylate, 2-aminoethyl (meth)acrylate, γ-(methacryloyloxypropyl)trimethoxysilane, (meth)acrylic acid-ethylene oxide adduct, trifluoromethylmethyl (meth)acrylate, 2-trifluoromethylethyl (meth)acrylate, 2-perfluoroethylethyl (meth)acrylate, 2-perfluoroethyl-2-perfluorobutylethyl (meth)acrylate, 2-perfluoroethyl (meth)acrylate, perfluoromethyl (meth)acrylate, diperfluoromethylmethyl (meth)acrylate, 2-perfluoromethyl-2-perfluoroethylmethyl (meth)acrylate, 2-perfluorohexylethyl (meth)acrylate, 2-perfluorodecylethyl (meth)acrylate, and 2-perfluorohexadecylethyl (meth)acrylate. In one embodiment of the invention, the (meth)acrylate monomer is a polyethylene glycol diacrylate, for example, SR259 (polyethylene glycol (200) diacrylate from Sartomer).Some useful multifunctional (meth)acrylates include, for example, polyethylene glycol di(meth)acrylate, desirably triethylene glycol di(meth)acrylate, hydroxypropyl (meth)acrylate, bisphenol A di(meth)acrylates such as ethoxylated bisphenol A (meth)acrylate ("EBIPA" or "EBIPMA"), and tetrahydrofuran (meth)acrylate and di(meth)acrylate, citronellyl acrylate and citronellyl methacrylate, hexanediol di(meth)acrylate ("HDDA" or "HDDMA"), trimethylolpropane tri(meth)acrylate, tetrahydrodicyclopentadienyl (meth)acrylate, ethoxylated trimethylolpropane triacrylate ("ETTA"), triethylene glycol diacrylate, and triethylene glycol dimethacrylate ("TRIEGMA").

[0096] Photoinitiators and Co-initiators The curable composition comprises at least one polymeric thioxanthone derivative as a photoinitiator and at least one aromatic tertiary amine as a co-photoinitiator.

[0097] Polymeric thioxanthone photoinitiators initiate and induce cure of the curable composition upon exposure to a sufficient amount of actinic radiation. Useful polymeric thioxanthone derivative photoinitiators include GenopolTX (formula below), available from Rahn;

[0098] [ka] OMNIPOLTX (formula below) available from IGM;

[0099] [ka] and SPEEDCURE 7010-L, available from Lambson. Other photoinitiators are described in U.S. Patent Applications Nos. 9,278,949, 8,883,873, and 7,354,957, and International Patent Publication No. WO2009060235, the contents of each of which are incorporated herein by reference. Photoinitiators can be used in amounts of about 0.1% to about 5% by weight of the total composition. More desirably, the photoinitiator is present in an amount of 1.0% to about 4% by weight of the total composition.

[0100] Useful co-photoinitiators that initiate cure of the curable composition in response to UV radiation and cooperate with the photoinitiator to induce cure of the curable composition include, but are not limited to, aromatic tertiary amines such as ethyl-4-dimethylaminobenzoate (Genocure EPD), ethyl-4-dimethylaminobenzoate, polymeric aminobenzoate derivatives such as Genopol AB-2 and Omnipol ASA, and amine acrylates such as Genomer 5142, Genomer 5161, 5271, 6275, and 5695, and Photomer 4250, 4771, 4775, 4780, 4967, and 5006. One useful co-photoinitiator is Genopol AB-2, available from Rahn. The co-photoinitiator can be used in an amount of about 0.1% to about 5% by weight of the total composition. More desirably, the photoinitiator is present in an amount of 1.0% to about 4% by weight of the total composition.

[0101] Filler The curable composition may optionally contain at least one filler. Suitable fillers can be organic or inorganic. Some useful fillers include, for example, lithopone, zirconium silicate, diatomaceous earth, calcium clay, hydroxides such as hydroxides of calcium, aluminum, magnesium, and iron; carbonates such as sodium, potassium, calcium, and magnesium; and metal oxides such as metal oxides of calcium, zinc, magnesium, chromium, zirconium, aluminum, titanium, iron, and silicon. Another useful filler is silica. The silica may be fumed silica, which may be untreated, such as AEROSIL® 8200 available from Degussa, or treated with an adjuvant, such as HDK2000 available from Wacker-Chemie. Fillers may be used in an amount of about 5.0% to about 50% by weight of the total composition. More desirably, the filler is present in an amount of 15.0% to about 40% by weight of the total composition. Organic fillers such as polymer powders or fibers may also be used. Combinations of different fillers are also useful.

[0102] additives The curable composition can optionally contain one or more additives, such as stabilizers, inhibitors, oxygen scavengers, dyes, colorants, pigments, adhesion promoters, plasticizers, tougheners, reinforcing agents, fluorescent agents, wetting agents, antioxidants, rheology modifiers, thermoplastic polymers, tackifiers, diluents, reactive diluents, and combinations thereof. The curable composition can also be free of any or all of these additives.

[0103] In some embodiments, the photocurable color-changing composition has a formulation falling within one or more of the following ranges:

[0104] [Table 1]

[0105] In some embodiments, the photocurable color-changing composition has the following properties:

[0106] [Table 2]

[0107] The composition develops color when cured by exposure to actinic radiation. In some embodiments, the cured composition changes color and fades when stored in the absence of actinic radiation. Subsequent exposure of the faded cured composition to actinic radiation at about 405 nm causes the original cured color to reappear. This color change appears to be reproducible.

[0108] The color change during cure can be used to assess the degree of cure of the cured composition. When the composition is used to form topographical features such as spacers or fold protectors, the color change of the formed feature allows the manufacturer to quickly verify the degree of cure of the feature. Typically, membranes are stored after sheet production and shipped to a converter for formation into filtration assemblies. The converter can expose the received membrane sheets to actinic radiation to quickly verify the presence and degree of cure of the feature. This capability is an improvement over conventional curable compositions, which require sophisticated and expensive testing regimes to assess the state of cure.

[0109] In some embodiments, the curable composition, once cured, should not peel from the membrane surface or lose its integrity when immersed in an aqueous solution in the pH range of about 12.5 at a temperature of about 80° C. for 24 hours to 14 days.

[0110] In some embodiments, the curable composition should be capable of forming and maintaining topographical surface features having an aspect ratio (height / width) of greater than about 0.5 before curing.

[0111] In some embodiments, a reverse osmosis filter is provided that includes a fluid-permeable membrane having a pattern of curable composition spacers printed thereon, wherein the curable composition spacers are resistant to ionization for 10 seconds or more. -1and / or a thixotropic index (TI) (1 sec. -1 Viscosity at / 10 sec -1 and / or the one or more spacer layers have an aspect ratio (height / width) of about 0.2 to about 2.

[0112] In some embodiments, a method for making a filtration membrane having printed curable composition spacers is provided, the method comprising: providing a membrane having a first surface and an opposing second surface; and depositing a color-changing radiation-curable composition on the first and / or second membrane surface to form spacer features having a defined shape and size, wherein the radiation-curable composition is deposited on the membrane within 10 seconds. -1 and / or a thixotropic index (TI) of 5,000 to 500,000 centipoise (cP) at 1 s. -1 Viscosity at / 10 seconds -1 and / or the aspect ratio (height / width) of the curable composition is from about 0.2 to about 2. [Example]

[0113] List of materials used in the examples.

[0114] [Table 3]

[0115] [Table 4]

[0116] Sample Preparation: The sample was placed on a polyethylene film. The material was spread across the film using a drawdown bar at a height of 50 mils (2.27 mm) to create a sample with a thickness of 50 mils.

[0117] Sample Curing: Uncured 50 mil samples were cured using one of the following curing light units: Loctite LED 405 nm Flood, Loctite LED 375 nm Flood, and Loctite UV LOC 1000 Chamber with Mercury Arc Lamp. Sample cure time for each light was 30 seconds. After curing, the samples were removed from the polyethylene film for evaluation.

[0118] The curing light intensity for each curing unit is shown below: LOCTITE LED 405nm flood intensity was measured using a UV V radiometer. LOCTITE LED 375nm flood intensity was measured using a UV BA radiometer. LOCTITE UV LOC 1000 chamber intensity was measured using a UV Power Puck II.

[0119] [Table 5]

[0120] Test Method In the examples below, the following test methods were used.

[0121] Viscosity and thixotropy index Using a cone-plate rheometer (Anton Paar), the shear rate was 1 s -1 and 10 seconds -1 The viscosity was measured at 1 s. -1 and 10 seconds -1 The viscosity was calculated as the ratio of the viscosity at

[0122] Chemical Resistance - Adhesion Loss Film samples, each coated on one surface with the cured reaction product of one of the samples, were immersed in a high pH aqueous solution and placed in a temperature-controlled oven. The coated samples were observed. Any visible peeling of the adhesive from the film surface or leaching of the cured adhesive into the solution was considered a failure.

[0123] Bending test Flexural adhesion was tested using a flexural test. This test involves applying the adhesive composition to one or both sides of a membrane. The membranes used were commercially available and cut to a 3 inch x 3 inch sample size. The sample material was applied to the surface of the membrane to a thickness of approximately 0.2 to 0.3 mm and allowed to cure.

[0124] UV curing was performed by applying UV light with a wavelength of 405 nm to each side of the film at 0.844 W / cm 2 for 10 seconds, total energy per surface 7.85J / cm 2 The test was performed by irradiating the specimens with 1000 uV of UV radiation. After curing, the specimen surface was immediately tested for tack by touch. The coated film was folded once with the cured coating on the inside of the bend, returned to the flat starting position, and then folded a second time with the cured coating on the outside of the bend. The specimen was considered to have passed if no cracking or delamination of the cured coating from the film was observed.

[0125] Shore D hardness The Shore D hardness was measured according to ASTM D2240. The test material was sandwiched between two PE films and covered with two glass plates to form a 1 mm thick sheet, and then applied to both sides of the glass plates with an intensity of 1.5 W / cm. 2 The cured sheet was then cut into four pieces, laminated, and measured with a Shore durometer.

[0126] Color change evaluation The test material was sandwiched between two PE films and covered with two glass plates to form a 1 mm thick sheet. An intensity of 1.5 W / cm was applied from the top of the glass plates. 2 The cured samples were evaluated by 1) visual color observation and 2) color measurement using L, a, and b values. L, a, and b values ​​were measured according to ASTM D1003 using a Datacolor instrument available from Datacolor Corporation.

[0127] Degree of polymerization Degree of polymerization (or cure) testing is typically performed by FTIR using an ATR accessory. Once the IR spectrum is obtained, the relative degree of cure is calculated using the integrated peak area of ​​the C=C peak, with the C=O peak as the internal standard. The formula is as follows: Degree of polymerization (%) = (A0-A1) / A0 x 100 (where A0 is the ratio of the area of ​​the C=C peak to the area of ​​the C=O peak in the uncured sample, and A1 is the ratio of the areas of the same two peaks in the spectrum of the cured sample.)

[0128] Comparative Example 1 Photocurable composition using phosphine oxide as a photoinitiator In this example, the photocurable acrylate formulations without thioxanthone derivatives are shown in the table below: The visible light initiators used are Omnirad TPO-L and Omnirad 819, both based on phosphine oxides. Photocurable formulations using phosphine oxide photoinitiators

[0129] [Table 6]

[0130] Compositions A and B are cured for 30 seconds using all three curing light units. The color is evaluated visually and recorded in the table below. Color change after light curing

[0131] [Table 7]

[0132] Compositions using phosphine oxide visible light initiators turned pale yellow after cure exposure to either 405 nm LED, 375 nm LED, or mercury arc lamp light. After exposure, samples were stored at room temperature for 24 hours. The pale yellow color remained after 24 hours. No further color change was observed with further exposure to UV / visible light.

[0133] Example 2 Photocurable compositions containing the polymeric thioxanthone photoinitiator Genopol TX-2 and different acrylate oligomers and monomers were prepared as shown below. All amounts are in wt%. All compositions were cured using a 405 nm LED flood. Color was visually assessed and recorded.

[0134] [Table 8]

[0135] [Table 9] All of Samples 1 to 10 were pale yellow to pale brown before curing.

[0136] Compositions 1-10 were all cured using a 405 nm LED flood. Color was visually assessed and recorded.

[0137] Formulations 1, 4, 5, and 6, which contain urethane acrylate and polymeric photoinitiator Genopol TX-2, exhibit an orange color after curing (LED 405 nm light).

[0138] Formulations 2 and 3, which contain non-urethane acrylate oligomers and the polymeric photoinitiator Genopol TX-2, exhibit a pale orange or pale yellow color after curing (LED 405 nm light).

[0139] Formulations 8, 9, and 10, which contain non-urethane linked monomers and the polymeric photoinitiator Genopol TX-2, exhibit a pale orange or pale yellow color after curing (LED 405 nm light).

[0140] In all of the above formulations, the color faded remarkably after storing the cured material at room temperature for 24 hours. Even more remarkably, the color reappeared when the cured sample was again exposed to 405 nm light. In the table below, the polymeric amine synergist Genopol AB-2 was added to each of the above compositions.

[0141] [Table 10]

[0142] [Table 11] Compositions 1A-10A were all cured with a 405 nm LED flood. Color was assessed visually and recorded.

[0143] After curing, Samples 1A-10A all exhibited a pale yellow to pale orange to orange color. Surprisingly, this color faded after 24 hours of storage at room temperature. Even more surprising, the color reappeared when the cured samples were again exposed to 405 nm light.

[0144] Example 3 Photocurable formulations were prepared containing the polymeric thioxanthone photoinitiator Genopol TX-2, the polymeric amine synergist Genopol AB-2, and a urethane acrylate oligomer and a non-urethane linked monomer. All amounts are in wt%.

[0145] Examples 11-14 have no filler in the composition, while Examples 15-18 contain silane-treated fume silica filler. All compositions were cured and the color was visually evaluated and recorded at different time intervals.

[0146] [Table 12]

[0147] [Table 13]

[0148] [Table 14]

[0149] [Table 15]

[0150] The results showed that all formulations containing the polymeric photoinitiator Genopol TX-2 and the polymeric amine synergist Genopol AB-2 exhibited an orange color when cured under a mercury arc lamp or a 405 nm or 375 nm LED lamp. When the cured materials were stored at room temperature for 24 hours in the absence of UV light, the orange color faded to yellow in all samples. For samples cured with the 375 nm and 405 nm LED lamps, the orange color reappeared when the cured samples were exposed a second time to the 405 nm LED. For samples cured with the mercury arc lamp, the orange color did not reappear when the cured samples were exposed a second time to the 405 nm LED light.

[0151] Example 4 Photocurable acrylate formulations with different polymeric thioxanthone-based photoinitiators were prepared. All amounts are in wt%. All compositions were cured using a mercury arc lamp and a 405 nm LED flood. Color was assessed visually and recorded.

[0152] [Table 16]

[0153] Surprisingly, Sample 16, which used Genopol TX-2 polymeric thioxanthone photoinitiator, cured to a yellow color, while Comparative Samples C, D, and E cured to a yellow color. Additionally, the yellow color of Samples C, D, and E did not fade after curing, and remained unchanged when exposed to UV radiation after curing.

[0154] Example 5 The color of several cured sample formulations was evaluated using L, a, and b values. Each sample was cured for 20 seconds under a 405 nm LED lamp. L, a, and b values ​​were read immediately after curing, again 24 hours after placing the cured sample in the yellow light region, and again after storing the cured sample at 405 nm after re-exposing it to the LED light for an additional 10 seconds. The L, a, and b values ​​for the three samples are summarized below.

[0155] [Table 17]

[0156] Immediately after curing, Sample 16 exhibited an orange color, compared to Comparative Samples C and F, which were yellow and clear, respectively, after curing. The L, a, and b values ​​for each sample correspond to the visually apparent color. After 24 hours, the cured Sample 16 material exhibited a significant, visually apparent color change from orange to pale orange, which was also indicated by the L, a, and b values. After exposing Sample 16 to a 405 nm LED lamp, the color visually changed from pale orange to orange, which was also indicated by the L, a, and b values. Comparative Compositions C and F did not exhibit any orange color development, either visually or instrumentally, upon testing.

[0157] Example 6 In this example, the formulation of Sample 16 was exposed to 405 nm light from an LED lamp for different periods of time. Color was assessed visually and instrumentally immediately after exposure. The degree of polymerization was also measured after each exposure.

[0158] [Table 18]

[0159] These results show that both visual color observation and instrumental L, a, and b values ​​after curing indicate the cure time, double bond conversion, and degree of cure. As the exposure dose increases, the double bond conversion increases (indicating increased polymerization of the sample), and the cured sample shows a color change from a slight pale yellow to a pale orange and orange. This color change indicates the degree of polymerization.

[0160] Example 7 Photocurable acrylate formulations containing polymeric thioxanthone photoinitiators were prepared. All amounts are in wt%. All compositions were photocured using an LED lamp at 405 nm, 0.844 w / cm on each side of the film. 2 , 10 seconds, total energy per side: 7.85J / cm 2 It was hardened with.

[0161] [Table 19]

[0162] [Table 20] 1 Tested after immersion in a pH 10.5 solution at 70°C for 24 hours. 2 Tested after immersion in a pH 12.5 solution at 80°C for 24 hours.

[0163] Comparative samples G and H, which used phosphine oxide photoinitiators, failed the bend test and were unacceptable for membrane fold coating. Compositions 19, 20, and 21, which contained a polymeric thioxanthone photoinitiator and an amine co-initiator, all passed the bend test and were acceptable for membrane fold coating.

Claims

1. A filtration membrane, a surface on the membrane; and a photocurable color-changing composition disposed on at least a portion of a surface of the film, a. 20 to 60 wt. % of an acrylate oligomer; b. 10 to 60% by weight of a diluent c. A curing system comprising 0.1 to 5 wt % of a polymeric thioxanthone derivative photoinitiator and 0.1 to 5 wt % of an aromatic tertiary amine co-photoinitiator; d. optionally, 0 to 60 wt. % of a filler; and e. optionally, 0-20 wt. % of one or more additives Including, A photocurable color-changing composition, wherein the composition exhibits a color change during cure and fades upon storage in the absence of UV light for 24 hours, and the faded composition changes color during subsequent exposure to actinic radiation, such that the cured composition is yellow to orange. a filtration membrane comprising:

2. 10. The filtration membrane of claim 1, wherein the photocurable color-changing composition disposed on the surface is cured.

3. 3. The filtration membrane of claim 1 or 2, wherein the photocurable color-changing composition disposed on the surface comprises a plurality of spacers, a fold protective coating, or both a plurality of spacers and a fold protective coating.

4. The filtration membrane according to any one of claims 1 to 3, wherein the filtration membrane is a two-layer membrane comprising a filtration layer superimposed on a support layer.

5. The filtration membrane according to any one of claims 1 to 3, wherein the filtration membrane comprises a polyethersulfone layer.

6. A filtration membrane as described in claim 1, wherein the polymeric thioxanthone derivative photoinitiator is a compound represented by the following formula: 【Chemical 1】

7. core; a plurality of filtration membranes attached to a core, each filtration membrane having a surface; and a photocurable color changing composition disposed on at least a portion of a surface, a. 20 to 60 wt. % of an acrylate oligomer; b. 10 to 60% by weight of a diluent c. A curing system comprising 0.1 to 5 wt % of a polymeric thioxanthone derivative photoinitiator and 0.1 to 5 wt % of an aromatic tertiary amine co-photoinitiator; d. optionally, 0 to 60 wt. % of a filler; and e. optionally, 0-20 wt. % of one or more additives Including, 1. A membrane filter comprising a photocurable color-changing composition, wherein the composition exhibits a color change during curing, fades upon storage in the absence of UV light for 24 hours, and the faded composition undergoes a color change during subsequent exposure to actinic radiation, such that the cured composition is yellow to orange.

8. The membrane filter described in claim 7, wherein the polymeric thioxanthone derivative photoinitiator is a compound represented by the following formula: 【Chemistry 2】

9. core; a plurality of filtration membranes attached to the core, each filtration membrane having a surface defining a fold region; and a photocurable color changing composition disposed in at least a portion of the crease area, a. 20 to 60% by weight of an acrylate oligomer b. 10 to 60% by weight of a diluent c. a cure system comprising 0.1 to 5 wt % of a polymeric thioxanthone derivative photoinitiator and 0.1 to 5 wt % of an aromatic tertiary amine co-photoinitiator; and d. Optionally, 0-20 wt. % of one or more additives Including, A photocurable color-changing composition, wherein the composition exhibits a color change during cure and fades upon storage in the absence of UV light for 24 hours, and the faded composition changes color during subsequent exposure to actinic radiation, such that the cured composition is yellow to orange. a membrane filter.

10. The membrane filter described in claim 9, wherein the polymeric thioxanthone derivative photoinitiator is a compound represented by the following formula: 【Chemistry 3】

11. 1. A method for forming three-dimensional features on a film surface, comprising: providing a membrane surface; providing a stencil or screen over the membrane surface, the stencil or screen having openings exposing the membrane surface for receiving the curable composition; A photocurable color-changing composition is provided, the composition comprising: a. 20 to 60 wt. % of an acrylate oligomer; b. 10 to 60 wt. % of a diluent; c. A curing system comprising 0.1 to 5 wt % of a polymeric thioxanthone derivative photoinitiator and 0.1 to 5 wt % of an aromatic tertiary amine co-photoinitiator; d. optionally, 0 to 60 wt. % of a filler; and e. optionally, 0-20 wt. % of one or more additives Including, the composition exhibits a color change during cure and fades upon storage in the absence of UV light for 24 hours, and the faded composition undergoes a color change during subsequent exposure to actinic radiation, with the cured composition being yellow to orange; depositing one or more layers of a curable composition onto the membrane surface through the stencil or screen openings to form three-dimensional features, the openings defining the approximate shape and size of the three-dimensional features; removing the stencil or screen, leaving the three-dimensional features in place on the film; and exposing the curable composition to actinic radiation to cure the composition; wherein the monolayer of curable composition deposited in the depositing step produces three-dimensional features having an aspect ratio (height / width) of from about 0.2 to about 2.

12. storing the film and cured features in the absence of UV radiation, wherein the color of the cured features changes during storage; exposing the film and the cured feature to actinic radiation, whereby the cured feature changes color; and Assessing the degree of cure of the cured features by the color of the cured features after exposure to actinic radiation The method of claim 11 further comprising:

13. The method of claim 11, wherein the polymeric thioxanthone derivative photoinitiator is a compound represented by the following formula: 【Chemistry 4】

14. 1. A method for verifying the hardening of polymer-based features on a filtration membrane, comprising: providing a membrane having a surface; A photocurable color-changing composition is provided, the composition comprising: 20 to 60 wt. % of an acrylate oligomer; 10 to 60 wt. % of a diluent; a curing system comprising 0.1 to 5 wt % of a polymeric thioxanthone derivative photoinitiator and 0.1 to 5 wt % of an aromatic tertiary amine co-photoinitiator; optionally, 0 to 60 wt. % of a filler; and Optionally, 0 to 20 wt. % of one or more additives Including, the composition exhibits a color change during cure and fades upon storage in the absence of UV light for 24 hours, and the faded composition undergoes a color change during subsequent exposure to actinic radiation, with the cured composition being yellow to orange; coating a portion of the membrane surface with the composition; and exposing the coated composition to actinic radiation to cure the coated composition and form a cured feature, wherein the color of the composition changes during curing; and Evaluating the degree of cure of the cured composition by the color of the composition A method comprising:

15. The method of claim 14, wherein the polymeric thioxanthone derivative photoinitiator is represented by the following formula: 【Chemistry 5】

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