Water-swellable semiconducting tape
A water-swellable semiconducting material with reduced thickness and improved conductivity is achieved by using a substrate with semiconducting layers and a crosslinked superabsorbent polymer matrix with dispersed conductive particles, enhancing cable protection and performance.
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- MATIV LUXEMBOURG
- Filing Date
- 2023-10-27
- Publication Date
- 2026-05-27
AI Technical Summary
Existing water-swellable semiconducting tapes have undesirable thicknesses greater than 0.25 mm and are not as conductive as semiconducting grade tapes.
A water-swellable semiconducting material comprising a substrate with first and second semiconducting layers and a crosslinked superabsorbent polymer matrix containing dispersed conductive particles, such as carbon black, forming conductive pathways within the matrix.
The material achieves reduced thickness by 50% and improved conductivity, providing high abrasion resistance, fire resistance, and effective water absorption to prevent water ingress and electrical stress in cables.
Smart Images
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Abstract
Description
Technical Field
[0001] Cross-reference of related applications This application claims the benefit of U.S. Provisional Application No. 63 / 420,517, filed Oct. 28, 2022, the entire disclosure of which is incorporated herein by reference. Field of Invention A semiconductive tape, particularly a semiconductive tape for use in electrical cables such as power cables, and more particularly a water-swellable semiconductive tape, is described herein.
Background Art
[0002] Water-swellable tapes, also called waterproof tapes, are commercially available, for example, as three-layer tapes in which the outer layer is a polyester non-woven fabric and the intermediate layer is a highly water-absorbent powder. FIG. 1 shows a representative three-layer waterproof tape. When water enters a cable protected by a waterproof (water-swellable) tape, the highly water-absorbent component in the tape rapidly absorbs the water and quickly expands to prevent further intrusion. This minimizes damage to the cable by water, localizes it, and aids in repair. Waterproof tapes are widely used in various cables and other applications.
[0003] [[ID=二十一]] [[ID=二十二]] Variations of water-swellable tapes, including water-swellable semiconducting tapes, are known in the art. Examples of such tapes include three-layer water-swellable tapes that adhere to a semiconducting tape to form a two-layer tape composite, and tapes in which a powdered superabsorbent polymer mixed with carbon black is sandwiched between nonwoven fabrics. However, known water-swellable semiconducting tapes may have undesirable thicknesses, e.g., greater than 0.25 mm, and / or are not as conductive as semiconducting grade tapes. Therefore, in this technical field, there is a need for water-swellable semiconducting tapes with reduced thickness and improved conductive properties. [Overview of the Initiative]
[0004] The following provides a simplified overview of the subject matter described in the claims to offer a basic understanding of some aspects of that subject matter. This overview is not a comprehensive overview of the subject matter described in the claims. It is not intended to identify the main or important elements of the subject matter described in the claims, nor to clarify the scope of the subject matter described in the claims. Its sole purpose is to present some concepts of the subject matter described in the claims in a simplified form, as an introduction to the more detailed description that will be presented later.
[0005] One aspect of the present disclosure provides a water-swellable semiconducting material with reduced thickness and superior performance. The water-swellable semiconducting material comprises a substrate and first and second semiconducting layers disposed on opposing surfaces of the substrate. The semiconducting water-swellable layer is disposed on one of the first or second semiconducting coatings, forming a multilayer structure. The semiconducting water-swellable polymer layer is a crosslinked superabsorbent polymer matrix in which conductive particles are dispersed within the polymer matrix. The conductive particles may be carbon black particles or other suitable conductive particles. The conductive particles are dispersed within the crosslinked acrylate polymer matrix and form conductive pathways within the crosslinked acrylate polymer matrix. Water-swellable semiconducting materials can take the form of multilayer tapes, where the base material is an elongated material of various sizes and materials, such as a nonwoven fabric or a woven fabric containing a polymer fabric such as nylon 6,6. In one embodiment, the water-swellable semiconducting material described herein is arranged in connection with a conductor to form a water-resistant cable such as an electrical cable. In another embodiment, the conductor is an electrical cable, and the water-swellable semiconducting material is in the form of a tape applied to the electrical cable.
[0006] Another aspect of the present disclosure provides a method for producing a water-swellable semiconducting material. The method includes the step of applying a semiconducting coating to a substrate to form a semiconducting substrate. Next, an aqueous composition comprising an acrylate polymer or acrylate prepolymer and conductive particles is applied to the semiconducting substrate, and the aqueous composition on the semiconducting substrate is then dried and cured so that the acrylate polymer or acrylate prepolymer is crosslinked and a semiconducting water-swellable polymer layer is formed on the semiconducting substrate. After drying and curing, the semiconducting water-swellable polymer layer consists of a crosslinked superabsorbent polymer matrix in which conductive particles are dispersed.
[0007] The aqueous composition can be applied to one side of the substrate. In some embodiments, the aqueous composition can be applied to both sides of the substrate. In other embodiments, the aqueous composition includes separate components that are mixed before application. The general statements above and the detailed statements below are illustrative and explanatory and should not be understood as limiting the disclosure. Additional features of this disclosure will be described in the following parts of this specification or will be understood through implementation of this disclosure. The accompanying drawings are incorporated herein and constitute part thereof, illustrating several embodiments and serving to illustrate certain principles in conjunction with the description. [Brief explanation of the drawing]
[0008] [Figure 1] This is an explanatory diagram of a prior art water-swellable tape. [Figure 2]This is a side view illustrating one embodiment of a water-swellable semiconducting (SC) tape according to the present disclosure. [Modes for carrying out the invention]
[0009] This specification and the accompanying drawings illustrate exemplary embodiments and should not be construed as limiting, with the claims defining the scope of the disclosure, including its equivalents. Various mechanical, compositional, structural, and operational modifications can be made without departing from the scope of this specification and the claims, including its equivalents. In some cases, well-known structures and techniques are not shown or described in detail, so as not to obscure this disclosure. Similar figures in two or more figures represent the same or similar elements. Furthermore, elements and related aspects described in detail with reference to one embodiment may, whenever possible, be included in other embodiments that are not specifically shown or described. For example, if an element is described in detail with reference to one embodiment but not with reference to a second embodiment, that element may nevertheless be claimed to be included in the second embodiment. Furthermore, the illustrations in this specification are for illustrative purposes only and do not necessarily reflect the actual shape, size, or dimensions of the system or illustrated components.
[0010] As used herein and in the appended claims, the use of the singular “a,” “an,” and “the,” and any singular word, includes multiple references unless expressly and clearly limited to one. As used herein, the term “include” and its grammatical variations are intended to be non-limiting, and the enumeration of items in a list does not exclude other similar items that may be substituted for or added to the listed items. Unless otherwise specified, quantitative values are approximations, regardless of whether or not words such as "approximately" or "roughly" are used. The materials, methods, and examples described herein are for illustrative purposes only and are not intended to limit the scope of this specification.
[0011] In one aspect of this disclosure, a water-swellable semiconducting (SC) material is provided. This material can be incorporated into tapes or cable wrapping for various conductors, including cables, and can also be used for other applications such as bonding and protection. The water-swellable semiconducting materials described herein effectively absorb water, swell rapidly to prevent water ingress, and promote good electrical contact. In some embodiments, water-swellable semiconducting tapes can be used to prevent galvanic corrosion of metal layers in medium-voltage to ultra-high-voltage cables. The water-swellable material can also be used to equalize field current around power conductors or cores and ensure electrical contact with the grounding system, thereby reducing electrical stress on the insulating material and improving performance.
[0012] In one embodiment, the water-swellable semiconducting material includes a tape. The water-swellable semiconducting tape includes a semiconducting substrate, for example, a woven fabric substrate (usually nylon). The semiconducting water-swellable layer is placed on the outer surface of the semiconducting substrate. In addition to the advantages described above, the water-swellable semiconducting tape described herein has many physical and electrical properties for a wide range of cable manufacturing applications. Some of the features and advantages of the water-swellable semiconducting tape include high abrasion resistance, excellent fire resistance, fast application, halogen-free, high electrical conductivity, reduced slip, high fit, and good long-term temperature stability. In addition, the water-swellable semiconducting tape according to this specification has a thickness reduced by 50% compared to conventional cable wrapping.
[0013] In one embodiment, a water-swellable semiconducting polymer material is provided. The water-swellable semiconducting polymer material comprises conductive particles dispersed within a crosslinked superabsorbent polymer matrix. Water-swellable superabsorbent polymers (SAPs) are a type of polymer capable of absorbing large amounts of water. Generally, SAPs consist of a network of cross-linked polymer chains, within which water diffuses and is stored. The type and degree of cross-linking determine the superabsorbent polymer's ability to absorb and retain large amounts of water. Suitable examples of superabsorbent polymers include aqueous solutions of acrylate polymers and prepolymers formed from water-soluble monomers such as acrylic acid, methacrylic acid, and 2-acrylamide (DAA) 2-methylpropanesulfonic acid. Other comonomers, such as acrylamide and N-isopropylacrylamide, can also be incorporated into SAPs. Examples of cross-linking agents include various polyfunctional monomers. These can be difunctional, trifunctional, or tetrafunctional and may have mixed polymerizable groups such as methacrylate.
[0014] In one embodiment, the crosslinked superabsorbent polymer matrix is a crosslinked acrylate polymer. The crosslinked acrylate polymer can be formed by applying an aqueous acrylate polymer or prepolymer (i.e., liquid SAP) to a substrate and curing it with heat. Upon curing, the acrylate polymer or prepolymer undergoes chemical crosslinking to form a crosslinked superabsorbent polymer matrix. Suitable aqueous solutions of acrylate polymers include Aquaswell 50, Aquaswell 75, and Aquaswell 100, commercially available from H&R ChemPharm (UK) Ltd. (Tipton, West Midlands, United Kingdom). A suitable crosslinked superabsorbent polymer formed on the substrate may also have a binding effect. In a particular embodiment, to significantly improve stability, the liquid SAP may be provided in two parts and mixed before use. Water-swellable semiconducting polymer materials have conductive particles dispersed within a crosslinked superabsorbent polymer matrix. In some embodiments, the conductive particles are pre-mixed with an aqueous acrylate polymer or prepolymer in solution and applied to the substrate. Upon curing, the semiconducting particles disperse within the crosslinked acrylate polymer matrix, forming conductive pathways within the matrix. In some embodiments, the conductive particles include carbon black particles. In one embodiment, the conductive particles are carbon black, present in an amount of 5 to 50 mass percent, optimally about 25 mass percent, in the aqueous composition. Examples of suitable carbon black particles include granular activated carbon with a mesh size of 0.06 to 0.25 mm, such as Filtracarb® FY5 30x60, commercially available from CPL Industries LTD (Killamarsh, Sheffield, United Kingdom). In another embodiment, a water-swellable semiconducting material is provided. This water-swellable semiconducting material includes a semiconducting substrate on which a semiconducting water-swellable polymer material is disposed.
[0015] In one embodiment, the substrate has first and second semiconducting layers disposed on the surface of the substrate. The substrate may be a cloth such as a nonwoven fabric or a woven fabric. A variety of materials can be used as the substrate, including polymer materials such as nylon and polyester, and other suitable materials such as woven glass, Hessian, and cotton. In one embodiment, the substrate is nylon 6,6. The semiconducting layers are disposed on either substrate surface by applying a semiconducting liquid mixture to the substrate surface once or multiple times to coat the substrate surface. The surface is coated on one side of the substrate. Of course, in some embodiments, the surface may be coated on both sides (opposing sides) of the substrate. Furthermore, the substrate can be coated multiple times depending on the desired mass and product specifications. When multiple coatings are applied, the coating is dried after each coating. Alternatively, the first and second semiconducting layers can also be applied by impregnating the substrate with a semiconducting liquid mixture and then drying it.
[0016] In one embodiment, the semiconducting layer comprises carbon black particles that are applied to a substrate in an aqueous mixture and then dried. The aqueous mixture of semiconducting particles may contain various additives that assist in the application of the particles, such as latex, dispersants, and stabilizers. In one embodiment, the aqueous mixture of semiconducting particles is a mixture of carbon black particles, water, latex, dispersant, and stabilizer in an aqueous solution. In another embodiment, the carbon black particles in the aqueous mixture have a particle size ranging from about 150 μm to about 400 μm. In some embodiments, the mass of the water-swellable semiconducting material conforms to the specifications shown in Table 1 below. [Table 1]
[0017] Referring next to Figure 2, a water-swellable semiconducting multilayer tape 100 is shown. The multilayer tape 100 has a substrate 104 and a first layer 102 including first and second semiconducting layers 106. A second layer 108 containing a semiconducting water-swellable polymer material is disposed on one of the first or second semiconducting layers 106. In one embodiment, the substrate 104 is an elongated material having first and second opposing surfaces, and the first and second semiconducting layers 106 are disposed on the first and second opposing surfaces of the woven substrate 102, as shown. The water-swellable semiconducting tapes according to this disclosure can be manufactured from a wide range of base material materials as described herein, and can have a wide range of widths, lengths, and thicknesses, and the tapes can be manufactured in the form of pads or long spools, in various widths.
[0018] In another embodiment, a water-resistant conductor is provided. The water-resistant conductor has an inner core, and a water-swellable semiconducting material is disposed in connection with the inner core. The water-swellable semiconducting material has a substrate 104, and first and second semiconducting coatings 106 are disposed on opposite side surfaces of the substrate and around the inner core. A semiconducting water-swellable polymer layer 108 is disposed on the outer surface of the first or second semiconducting coating 106. Other layers can include a protective coating or sheath. In some embodiments, the conductor is an electrical cable, and in other embodiments, the conductor is an electrical cable and the water-swellable semiconducting material is in the form of a tape applied to the electrical cable.
[0019] In another embodiment, a method of manufacturing a water-swellable semiconducting material is provided. The method includes the step of providing a substrate as described herein. A semiconducting coating is applied to the substrate to form a semiconducting layer on the substrate. The semiconducting coating may be applied as an aqueous mixture of semiconducting particles and dried to form a layer. The particles may be applied to the surface or embedded (impregnated) in the substrate. Next, an aqueous composition containing an acrylate polymer or acrylate prepolymer and conductive particles is applied to the semiconducting substrate. The aqueous composition on the semiconducting substrate is then dried and cured, whereby the acrylate polymer or acrylate prepolymer is crosslinked and a water-swellable semiconducting polymer layer disposed on the semiconducting substrate is formed. The water-swellable semiconducting polymer layer is composed of a crosslinked superabsorbent polymer matrix in which conductive particles are dispersed internally.
[0020] Examples As described herein, specimens and laboratory samples of the water-swellable semiconducting tape were prepared. The samples were analyzed according to the test protocol shown in Table 2. Since the laboratory samples were handmade (A4) laboratory samples, the data of the specimen samples are more reliable than the laboratory samples. The test data of the specimens and laboratory samples are shown in comparison with competing products from other companies.
Table 2
[0021] While the above specification may enable those skilled in the art to create and use what is currently considered the best, they will understand and acknowledge the existence of variations, combinations, and equivalents of the specific embodiments, methods, and examples described herein. Other embodiments will become apparent to those skilled in the art by considering this specification and the implementation of the embodiments disclosed herein. This specification and the examples should be considered illustrative only, and the true scope and spirit of the embodiments are indicated by the following claims.
[0022] For example, according to one embodiment, a first embodiment provides a water-swellable semiconducting material. This material comprises a substrate, first and second semiconducting layers disposed on opposing surfaces of the substrate, and a semiconducting water-swellable layer disposed on the outer surface of one of the first or second semiconducting coatings, wherein the semiconducting water-swellable polymer layer comprises conductive particles dispersed in a crosslinked superabsorbent polymer matrix. The second embodiment is the first embodiment of a water-swellable semiconducting material in which the conductive particles include conductive carbon black particles. The third embodiment is any combination of the first and second embodiments, wherein the conductive particles include carbon black particles having a particle mesh of about 0.06 to 0.25 mm. The fourth embodiment is any combination of the first to third embodiments, wherein the crosslinked superabsorbent polymer matrix includes a crosslinked acrylate polymer. The fifth embodiment is any combination of the first to fourth embodiments, wherein the superabsorbent polymer matrix comprises a crosslinked acrylate polymer matrix, and the conductive particles comprise carbon black particles, the carbon black particles being dispersed within the crosslinked acrylate polymer matrix to form conductive pathways within the crosslinked acrylate polymer matrix. The sixth embodiment is any combination of the first to fifth embodiments, wherein the superabsorbent polymer matrix is a coating placed on top of the first or second semiconducting coating. The seventh embodiment is any combination of the first to sixth embodiments, wherein the semiconducting water-swellable polymer layer is formed by applying an aqueous composition containing an acrylate polymer or acrylate prepolymer and conductive particles to the first or second semiconducting coating, and then drying the aqueous composition to form a superabsorbent polymer matrix in which the conductive particles are dispersed. The eighth embodiment is any combination of the first to seventh embodiments, wherein the conductive particles are carbon black and are present in the aqueous composition in an amount of 5 to 50 mass percent. The ninth embodiment is any combination of the first to eighth embodiments, wherein the conductive particles are carbon black and are present in the aqueous composition in an amount of about 25 mass percent. The tenth embodiment is any combination of the first to ninth embodiments, wherein the first and second semiconducting layers contain carbon black particles. The eleventh embodiment is any combination of the first to tenth embodiments, wherein the first and second semiconducting layers contain carbon black particles having a particle size of about 150 μm to about 400 μm. The twelfth embodiment is any combination of the first to eleventh embodiments, wherein the substrate is impregnated with highly conductive particles to form first and second semiconducting layers arranged on opposing surfaces of the woven fabric substrate. The thirteenth embodiment is any combination of the first to twelfth embodiments, wherein the water-swellable semiconducting material is a multilayer tape, and the multilayer tape includes a substrate and a first layer comprising first and second semiconducting layers. The substrate may be an elongated material. The elongated material may have first and second opposing surfaces. The first and second semiconducting layers may be arranged on the first and second opposing surfaces of the woven substrate. The tape may further include a second layer comprising a semiconducting water-swellable polymer layer. The second layer may be arranged on one of the first or second semiconducting layers. The 14th embodiment is any combination of the 1st to 13th embodiments, where the elongated material is a woven fabric. The 15th embodiment is any combination of the 1st to 14th embodiments, where the elongated material is a polymer material.
[0023] In a second embodiment, a first embodiment of a water-resistant cable is provided. The water-resistant cable comprises a conductor and a water-swellable semiconducting material disposed in connection with the conductor, the water-swellable semiconducting material comprising a substrate having first and second opposing surfaces, first and second semiconducting coatings disposed on the opposing surfaces of the woven substrate, and a semiconducting water-swellable polymer layer disposed on one of the outer surfaces of the first or second semiconducting coating, the semiconducting water-swellable polymer layer comprising conductive particles dispersed in a superabsorbent polymer matrix. The second embodiment is the first embodiment of a water-resistant cable in which the conductor is an electrical cable. The third embodiment is any combination of the first and second embodiments, wherein the conductor is an electrical cable, and the water-swellable semiconducting material is applied to the electrical cable in the form of a tape.
[0024] In a third aspect, a first embodiment of a method for producing a water-swellable semiconducting material is provided. This method includes the steps of preparing a substrate, applying a semiconducting coating to the substrate to form a semiconducting substrate, applying an aqueous composition containing an acrylate polymer or acrylate prepolymer and conductive particles to the semiconducting substrate, and drying the aqueous composition on the semiconducting substrate to crosslink the acrylate polymer or acrylate prepolymer to form a semiconducting water-swellable polymer layer disposed on the semiconducting substrate, wherein the semiconducting water-swellable polymer layer consists of a crosslinked superabsorbent polymer matrix in which conductive particles are dispersed. The second embodiment is the method of the first embodiment, in which the semiconductive coating is applied as a coating to opposing surfaces of the substrate. The third embodiment is any combination of the first and second embodiments, in which a semiconductive coating is impregnated into the substrate. The fourth embodiment is any combination of the first to third embodiments, in which the aqueous composition is applied to one side of the substrate. The fifth embodiment is any combination of the first to fourth embodiments, in which the aqueous composition is applied to both sides of the substrate. The sixth embodiment is any combination of the first to fifth embodiments, wherein the aqueous composition comprises separate components that are mixed before application.
Claims
1. A water-swellable semiconducting material, base material, First and second semiconducting layers disposed on opposing surfaces of the substrate, and A semiconductive water-swellable layer comprising a semiconductive water-swellable layer disposed on one outer surface of a first or second semiconductive coating, wherein the semiconductive water-swellable polymer layer comprises conductive particles dispersed within a crosslinked superabsorbent polymer matrix.
2. The water-swellable semiconducting material according to claim 1, wherein the conductive particles include conductive carbon black particles.
3. The water-swellable semiconducting material according to claim 1, wherein the conductive particles include carbon black particles having a particle mesh of about 0.06 to 0.25 mm.
4. The water-swellable semiconducting material according to claim 1, wherein the crosslinked superabsorbent polymer matrix comprises a crosslinked acrylate polymer.
5. The water-swellable semiconducting material according to claim 1, wherein the superabsorbent polymer matrix comprises a crosslinked acrylate polymer matrix, and the conductive particles comprises carbon black particles, wherein the carbon black particles are dispersed within the crosslinked acrylate polymer matrix to form conductive pathways within the crosslinked acrylate polymer matrix.
6. The water-swellable semiconducting material according to claim 1, wherein the superabsorbent polymer matrix is a coating disposed on a first or second semiconducting coating.
7. The water-swellable semiconducting material according to claim 1, wherein the semiconducting water-swellable polymer layer is formed by applying an aqueous composition containing an acrylate polymer or acrylate prepolymer and conductive particles to a first or second semiconducting coating, and then drying the aqueous composition to form the highly absorbent polymer matrix in which conductive particles are dispersed.
8. The water-swellable semiconducting material according to claim 7, wherein the conductive particles are carbon black and are present in the aqueous composition in an amount of 5% to 50% by mass.
9. The water-swellable semiconducting material according to claim 7, wherein the conductive particles are carbon black and are present in the aqueous composition in an amount of about 25% by mass.
10. The water-swellable semiconducting material according to claim 1, wherein the first and second semiconducting layers contain carbon black particles.
11. The water-swellable semiconducting material according to claim 1, wherein the first and second semiconducting layers contain carbon black particles having a particle size of about 150 μm to about 400 μm.
12. The water-swellable semiconducting material according to claim 1, wherein the substrate is impregnated with highly conductive particles to form the first and second semiconducting layers arranged on opposing surfaces of the woven fabric substrate.
13. The water-swellable semiconducting material is a multilayer tape, and the multilayer tape is Including the first and second layers, The first layer comprises the base material and the first and second semiconducting layers, the base material being an elongated material having first and second opposing surfaces, and the first and second semiconducting layers being arranged on the first and second opposing surfaces of the woven fabric base material. The water-swellable semiconducting material according to claim 1, wherein the second layer comprises the semiconducting water-swellable polymer layer, and the second layer is disposed on one of the first or second semiconducting layers.
14. The water-swellable semiconducting material according to claim 10, wherein the elongated material is a woven fabric.
15. The water-swellable semiconducting material according to claim 10, wherein the elongated material is a polymer material.
16. It is a water-resistant cable, A conductor and The conductor includes a water-swellable semiconducting material, wherein the water-swellable semiconducting material is, A substrate having first and second opposing surfaces, A first and second semiconductive coating disposed on opposing surfaces of a woven fabric substrate, A water-resistant cable comprising a semiconductive water-swellable polymer layer disposed on one outer surface of the first or second semiconductive coating, wherein the semiconductive water-swellable polymer layer contains conductive particles dispersed in a superabsorbent polymer matrix.
17. The water-resistant cable according to claim 16, wherein the conductor is an electrical conductor.
18. The water-resistant cable according to claim 16, wherein the conductor is an electrical cable, and the water-swellable semiconducting material is in the form of a tape applied to the electrical cable.
19. A method for producing a water-swellable semiconducting material, Steps to prepare the base material, A step of applying a semiconducting coating to the substrate to form a semiconducting substrate, The steps include applying an aqueous composition containing an acrylate polymer or acrylate prepolymer and conductive particles to the semiconducting substrate, and A method comprising the steps of drying the aqueous composition on the semiconductive substrate and crosslinking the acrylate polymer or acrylate prepolymer to form a semiconductive water-swellable polymer layer disposed on the semiconductive substrate, wherein the semiconductive water-swellable polymer layer is composed of a crosslinked superabsorbent polymer matrix in which conductive particles are dispersed inside.
20. The method according to claim 19, wherein the semiconducting coating is applied as a coating to opposing surfaces of the substrate.
21. The method according to claim 19, wherein the semiconducting coating is impregnated into the substrate.
22. The method according to claim 19, wherein the aqueous composition is applied to one side of the substrate.
23. The method according to claim 19, wherein the aqueous composition is applied to both sides of the substrate.
24. The method according to claim 19, wherein the aqueous composition comprises a separate component that is mixed together before application.