Multilayer film and method for preparing the same

Abstract

The present application discloses a multilayer film and a method for preparing the same. The multilayer film comprises: a substrate and one or more barrier layers disposed on the substrate, wherein at least one of the one or more barrier layers has protective layers disposed on both surfaces. Since at least one barrier layer has protective layers disposed on both surfaces, the barrier layer is protected by the protective layers disposed on the two surfaces, and thus the barrier layer is not easily corroded or oxidized and damaged even in a special environment such as acidic, alkaline or high temperature, thereby solving the problems in the prior art.

Description

Technical Field

[0001] The present application relates to the field of material processing technology, and in particular to a multilayer film and a preparation method thereof. Background Art

[0002] With the continuous development of society, multilayer films are often used in the sealing process of food, beverage bottles, medicines, optics and electronics industries. Existing multilayer films usually include a substrate and a barrier layer arranged on the surface of the substrate, and the barrier layer can mainly provide sealing protection. However, due to the wide application of multilayer films, in certain environments, such as acidic or alkaline environments, high temperature environments, etc., the barrier layer in the multilayer film is easily corroded or oxidized and destroyed, thereby affecting the performance of the multilayer film. Summary of the invention

[0003] The embodiments of the present application provide a multilayer film and a method for preparing the same, which are used to solve the problem in the prior art that the barrier layer in the multilayer film is easily destroyed by corrosion or oxidation.

[0004] An embodiment of the present application provides a multilayer film, comprising: a substrate and one or more barrier layers disposed on the substrate, wherein, among the one or more barrier layers, both surfaces of at least one barrier layer are provided with protective layers.

[0005] Preferably, the protective layer specifically includes: an anti-oxidation layer, an acid-resistant layer, an alkali-resistant layer, a chemical solvent-resistant layer and / or a high temperature-resistant layer.

[0006] Preferably, the thickness of the protective layer is greater than or equal to 1 nanometer and less than or equal to 20 micrometers.

[0007] Preferably, the thickness of the substrate is greater than or equal to 5 microns and less than or equal to 250 microns.

[0008] Preferably, the thickness of the barrier layer is greater than or equal to 20 nanometers and less than or equal to 100 micrometers.

[0009] The embodiment of the present application also provides a method for preparing a multilayer film, comprising:

[0010] forming a first protective layer on a provided substrate;

[0010] Generating a barrier layer on the surface of the first protective layer;

[0012] Generating a second protective layer on the surface of the barrier layer.

[0011] Preferably, generating a first protective layer on the provided substrate specifically comprises:

[0012] Adding glyoxal to a polyvinyl alcohol aqueous solution of a preset concentration;

[0013] Adjusting the pH value of the mixed solution after adding glyoxal to 1-3;

[0014] The mixed solution after adjusting the pH value is evenly coated on the surface of the provided substrate to form the first protective layer.

[0015] Preferably, the polyvinyl alcohol aqueous solution of the preset concentration specifically includes: a polyvinyl alcohol aqueous solution with a mass fraction greater than or equal to 10% and less than or equal to 20%.

[0016] Preferably, after uniformly coating the mixed solution after adjusting the pH value on the provided substrate surface, the preparation method further comprises:

[0017] The uniformly coated substrate is heat-treated at 70° C. to 90° C. for 2 to 5 minutes to initiate a cross-linking reaction between the polyvinyl alcohol and glyoxal to form the first protective layer.

[0018] Preferably, forming a barrier layer on the surface of the first protective layer specifically includes:

[0019] Soaking the substrate after forming the first protective layer in an aqueous solution of m-phenylenediamine;

[0020] The substrate including the first protective layer is immersed in a cyclohexane solution of trimesoyl chloride to perform an interfacial polymerization reaction, so as to form the barrier layer on the surface of the first protective layer.

[0021] At least one of the above technical solutions adopted in the embodiments of the present application can achieve the following beneficial effects:

[0022] The multilayer film provided in the embodiment of the present application has a structure in which protective layers are provided on both surfaces of at least one barrier layer. Thus, the barrier layer is protected by the protective layers provided on the two surfaces. Therefore, even if encountering special environments such as acidity, alkalinity or high temperature, the barrier layer is not easily corroded or oxidized and destroyed, thereby solving the problems in the prior art. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The drawings described herein are used to provide a further understanding of the present application and constitute a part of the present application. The illustrative embodiments of the present application and their descriptions are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

[0024] Figure 1 A specific cross-sectional schematic diagram of a multilayer film provided in an embodiment of the present application;

[0025] Figure 2 A schematic diagram of a specific process of a multilayer film preparation method provided in an embodiment of the present application;

[0026] Figure 3 A schematic diagram of a specific process for preparing a protective layer in the method for preparing a multilayer film provided in an embodiment of the present application;

[0027] Figure 4 Provided for the embodiments of the present application, a comparison chart of the performance tests of the multilayer film provided in the present application and two multilayer films in the comparative examples. DETAILED DESCRIPTION

[0028] In order to make the purpose, technical solution and advantages of the present application clearer, the technical solution of the present application will be clearly and completely described below in combination with the specific embodiments of the present application and the corresponding drawings. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present application.

[0029] The technical solutions provided by various embodiments of the present application are described in detail below in conjunction with the accompanying drawings.

[0030] As mentioned above, in an environment such as an acidic or alkaline environment or a high temperature environment, the barrier layer in the existing multilayer film is easily corroded or oxidized and damaged, thereby affecting the performance of the multilayer film. Based on this, the embodiment of the present application provides a multilayer film that can be used to solve the problems in the prior art.

[0031] like Figure 1 The figure shows a schematic diagram of the structure of the multilayer film 10. The multilayer film 10 comprises: a substrate 11, and one or more barrier layers 12 disposed on the substrate, and at least one of the one or more barrier layers has protective layers 13 disposed on both surfaces of the barrier layer.

[0032] In the structure of the multilayer film 10, protective layers 13 are provided on both surfaces of at least one barrier layer 12. Since the barrier layer 12 is protected by the protective layers 13 provided on the two surfaces, the barrier layer 12 is not easily corroded or oxidized and damaged even in special environments such as acidity, alkalinity or high temperature, thereby solving the problems in the prior art.

[0033] According to different specific application scenarios, the substrate 11 is used to provide mechanical support and / or fluid flow channels. For example, for the film of a beverage bottle, it is mainly used to provide a fluid flow channel; for the sealing film of the electronics industry, it is mainly used to provide mechanical support.

[0034] Furthermore, the material of the substrate 11 may be an organic material and / or an inorganic material and a mixture thereof, such as the substrate 11 may be a single block or a structure comprising a plurality of adjacent blocks of different materials. The material of the substrate 11 may be a thermoplastic. The material of the substrate 11 may also be an organic polymer resin, such as but not limited to polyethylene terephthalate (PET), polyacrylate, polynorbornene, polycarbonate (PC), silicone, epoxy resin, silicone functionalized epoxy resin, or polyethylene terephthalate (PEN). The material of the other substrate 11 may be an ultra-thin glass layer or a metal foil or a molten ceramic, which has pores, pinholes or cracks. In addition, the materials of the substrate 11 with different industrial names may include Aclar, Vectran, Tefzel, Surlyn, PET ST504, PET mylar D, Armstrong A661, Tedlar, BRP-C, PVC Black, P0100, P0 130, Kapton, PVC clear, Korad, EVA, PVB, TPU, DC Sy1guards, GE RTV 615. It should be noted that a combination of materials formed by a plurality of materials is also within the protection scope of the present application.

[0035] For example, the material of the substrate 11 can be a flexible organic material such as PET, thereby preparing a flexible organic substrate with flexibility; the material of the substrate 11 can also be a metal material such as gold, silver, copper, etc., thereby using these metal materials to process and prepare a metal foil substrate 11.

[0036] In addition, for the thickness of the substrate 11, its thickness can be greater than or equal to 5 microns and less than or equal to 250 microns. For example, the thickness of the substrate 11 is 5 microns, 10 microns, 15 microns, 20 microns, 30 microns, 50 microns, 80 microns, 100 microns, 110 microns, 135 microns, 150 microns, 170 microns, 195 microns, 200 microns, 220 microns, 230 microns, 250 microns or other thickness values ​​between 5 microns and 250 microns. In practical applications, the specific thickness of the substrate 11 can be determined according to specific conditions such as specific application scenarios and the material of the substrate 11.

[0037] One or more barrier layers 12 are disposed on the substrate, wherein the specific number of barrier layers 12 is usually 1. Of course, when higher sealing performance is required, there may be multiple barrier layers 12, such as 2, 3, 4 or other numbers, and these barrier layers 12 may be stacked and disposed on one surface of the substrate 11. In addition, one or more barrier layers 12 may be disposed on both surfaces of the substrate 11, respectively.

[0038] For example, one surface of the substrate 11 includes a barrier layer 12, and the other surface has no barrier layer 12; or, one surface of the substrate 11 includes a barrier layer 12, and the other surface includes one or more barrier layers 12; or, one surface of the substrate 11 includes multiple barrier layers 12, and the other surface includes multiple barrier layers 12, etc.

[0039] The thickness of any barrier layer 12 may be greater than or equal to 20 nanometers and less than or equal to 150 micrometers. For example, the thickness of the barrier layer 12 is 20 nanometers, 70 nanometers, 100 nanometers, 15 nanometers, 300 nanometers, 500 nanometers, 700 nanometers, 1000 nanometers, 1 micrometer, 3 micrometers, 8 micrometers, 15 micrometers, 19 micrometers, 25 micrometers, 30 micrometers, 35 micrometers, 45 micrometers, 60 micrometers, 80 micrometers, 90 micrometers, 100 micrometers, 110 micrometers, 135 micrometers, 150 micrometers, or other thickness values ​​between 20 nanometers and 150 micrometers.

[0040] The barrier layer 12 can be made of metal material or ceramic material and produced by dipping, spraying, physical vapor deposition, chemical vapor deposition (CVD), plasma enhanced chemical vapor deposition (PECVD), magnetron sputtering and / or reactive sputtering or other methods.

[0041] The material of the barrier layer 12 may be nitride, such as silicon nitride. The material of the barrier layer 12 may also be organic material, inorganic material, ceramic material, or any combination thereof.

[0042] For example, in one example, the material of the barrier layer 12 is a recombination product from reactive plasma species and deposited onto the substrate 11. In another example, the material of the barrier layer 12 is an organic barrier coating material, which generally may include carbon and hydrogen, and optionally other elements such as oxygen, nitrogen, silicon, sulfur, and the like.

[0043] The material of the barrier layer 12 may also be an inorganic material, a ceramic material, generally including oxides, nitrides, borides or any combination thereof of elements of Groups IIA, IIIA, IVA, VA, VIA, VIIA, IB or IIB; metals of Groups IIIB, IVB or VB or rare earth elements. For example, the barrier layer 12 comprising a silicon carbide material may be deposited onto the substrate 11 by recombination of a plasma generated from silane and an organic material such as methane or xylene. The barrier layer 12 comprising a carbon-containing silicon oxide material may be deposited from a plasma generated from silane, methane and oxygen, or silane and propylene oxide, or from a plasma generated from an organic silicone precursor such as tetraethoxyorthosilane (TEOS), hexamethyldisiloxane (HMDS), hexamethyldisilazane (HMDZ) or octamethylcyclotetrasiloxane (D4). The barrier layer 12 comprising a silicon nitride material may be deposited from a plasma generated from silane and ammonia. The barrier layer 12 comprising an aluminum oxycarbonitride material may be deposited from a plasma generated, for example, from a mixture of aluminum tartrate and ammonia.

[0044] In some embodiments, the barrier layer 12 containing organic materials can be deposited by known methods, such as but not limited to spin coating, flow coating, doctor blading, extrusion, gravure printing or micro-gravure printing, dip coating, spraying, vacuum deposition, chemical vapor deposition (CVD), plasma enhanced chemical vapor deposition (PECVD), or similar methods such as radio frequency plasma enhanced chemical vapor deposition (RF-PECVD), expansion thermal-plasma chemical vapor deposition, reactive sputtering, electron-cyclotron-resonance plasma enhanced chemical vapor deposition (ECRPECVD), inductively coupled plasma enhanced chemical vapor deposition (ICPECVD), sputtering deposition, evaporation, layer deposition or a combination thereof.

[0045] Since metal materials have high density, metal materials such as gold, silver, and aluminum can also be used as the material of the barrier layer 12. In particular, these metal materials can be used to generate the barrier layer 12 by magnetron sputtering. Since the magnetron sputtering method has low cost and simple operation, it can usually reduce the production cost of the barrier layer 12.

[0046] The protective layer 13 included in the multilayer film 10 can be an anti-oxidation layer, an acid-resistant layer, an alkali-resistant layer, a chemical solvent-resistant layer and / or a high-temperature-resistant layer according to specific needs in practice. Among them, the anti-oxidation layer can be used to prevent the barrier layer 12 from being oxidized; the acid-resistant layer can be used to prevent the barrier layer 12 from being corroded by acid; the alkali-resistant layer can be used to prevent the barrier layer 12 from being corroded by alkali; and the high-temperature-resistant layer can be used to prevent the barrier layer 12 from being damaged by high temperature.

[0047] For example, there are three barrier layers 12 in the multilayer film 10, namely barrier layer A, barrier layer B and barrier layer C, and both surfaces of barrier layer A are provided with an anti-oxidation layer, both surfaces of barrier layer B are provided with an acid-resistant layer, and both surfaces of barrier layer C are provided with a chemical solvent-resistant layer, etc. At this time, the same barrier layer 12 has the same protective layer on both surfaces.

[0048] In addition, the two surfaces of the same barrier layer 12 can also be set as different protective layers. For example, there are two barrier layers 12 in the multilayer film 10, namely barrier layer D and barrier layer E, wherein one surface of barrier layer D is provided with an anti-oxidation layer, and the other surface is provided with an acid-resistant layer, and one surface of barrier layer E is provided with an alkali-resistant layer, and the other surface is provided with a high-temperature resistant layer.

[0049] In addition, as for the thickness of the protective layer 13, the greater the thickness of the protective layer 13, the better the protection effect on the protected barrier layer 12, but the corresponding preparation cost is also higher. The specific thickness of the protective layer 13 can be determined in combination with actual needs, such as acid-base environment, ambient temperature, cost requirements, etc. For example, the thickness of the protective layer 13 can usually be greater than or equal to 1 nanometer and less than or equal to 20 micrometers. For example, it can be 1 nanometer, 5 nanometers, 47 nanometers, 80 nanometers, 120 nanometers, 150 nanometers, 180 nanometers, 200 nanometers, 260 nanometers, 310 nanometers, 380 nanometers, 400 nanometers, 450 nanometers, 500 nanometers, 537 nanometers, 600 nanometers, 680 nanometers, 730 nanometers, 810 nanometers, 870 nanometers, 930 nanometers, 1 micrometer, 3 micrometers, 5 micrometers, 8 micrometers, 10 micrometers, 12 micrometers, 15 micrometers, 17 micrometers, 19 micrometers, 20 micrometers, or other thicknesses between 1 nanometer and 20 micrometers.

[0050] Based on the same concept as the multilayer film 10 provided in the embodiment of the present application, the embodiment of the present application also provides a method for preparing the multilayer film. For any unclear points in the preparation method, please refer to the embodiment of the structure of the multilayer film 10. Figure 2 The specific process diagram of the preparation method is shown, which includes the following steps:

[0051] Step S31: providing a substrate.

[0052] The substrate may be any substrate of the multilayer film 10 described above, for example, a substrate made of PET material.

[0053] In addition, an additional barrier layer can be generated on the surface of the substrate prepared from the PET material in the following manner: polysulfone particles (polysulfone content is about 20%) are dispersed in dimethylformamide (DMF), and then continuously stirred and dissolved at about 60°C for 6 hours, filtered through a steel wire mesh with a mesh size of 0.38 mm, and then allowed to stand and degas for 24 hours under a vacuum degree of 80 kPa to obtain a clear polysulfone solution.

[0054] The clarified polysulfone solution is evenly coated on a substrate made of PET material by a coating machine, and solidified and cleaned in pure water at 25°C to obtain a polysulfone ultrafiltration membrane substrate, which includes a substrate made of PET material and an additional barrier layer made of polysulfone and arranged on the surface thereof.

[0055] Step S32: generating a first protective layer on the provided substrate.

[0056] The first protective layer may be an anti-oxidation layer, an acid-resistant layer, an alkali-resistant layer, a chemical solvent-resistant layer or a high temperature-resistant layer.

[0057] For example, when the first protective layer is an anti-oxidation layer, the Figure 3 The first protective layer is formed on the substrate in the manner shown, which specifically includes the following steps:

[0058] Step S321: preparing a polyvinyl alcohol aqueous solution of a preset concentration.

[0059] The preset concentration may be a mass fraction greater than or equal to 10% and less than or equal to 20%. For example, the preset concentration is a mass fraction of 10%, a mass fraction of 12%, a mass fraction of 15%, a mass fraction of 17%, a mass fraction of 19%, a mass fraction of 20%, or other mass fractions between 10% and 20%.

[0060] For example, 15 grams of polyvinyl alcohol (PVA) with a degree of alcoholysis of 98% and a degree of polymerization of 1700 can be weighed and dispersed in 1000 grams of deionized water, and stirred and heated until the PVA is dissolved, thereby preparing a polyvinyl alcohol aqueous solution with a concentration of about 15%.

[0061] Step S322: adding glyoxal to the polyvinyl alcohol aqueous solution of a preset concentration.

[0062] After the prepared PVA solution is cooled to room temperature, 10 grams of glyoxal may be added under stirring.

[0063] Step S323: adjusting the pH value of the mixed solution after adding glyoxal to 1-3.

[0064] The pH value of the mixed solution can be adjusted to 1 to 3 (for example, 2 or other values) using dilute hydrochloric acid or the like.

[0065] Step S324: evenly apply the mixed solution after adjusting the pH value to the surface of the provided substrate to form the first protective layer.

[0066] The mixed solution after adjusting the pH value can be evenly coated on the surface of the provided substrate, and the coating thickness can be about 0.1 micrometer to 10 micrometers.

[0067] Step S325: heat-treating the uniformly coated substrate at 70° C. to 90° C. for 2 to 5 minutes to initiate a cross-linking reaction between the polyvinyl alcohol and glyoxal to form the first protective layer.

[0068] The evenly coated substrate is heat-treated at 70° C. to 90° C. for 2 to 5 minutes, such as being placed in an oven at 80° C. for 3 minutes, to initiate a cross-linking reaction between the polyvinyl alcohol and glyoxal to form a first protective layer.

[0069] Step S33: generating a barrier layer on the surface of the first protective layer.

[0070] The barrier layer may be generated by using any of the methods in the above embodiments.

[0071] For example, an interfacial polymerization technique can be used to generate a barrier layer on the surface of the first protective layer. First, a 5.0% by mass fraction of an aqueous solution of m-phenylenediamine (MPD) and a 0.3% by mass fraction of a cyclohexane solution of trimesoyl chloride (TMC) are prepared. Then, the substrate is immersed in the MPD aqueous solution for about 60 seconds, and after being taken out, the excess solution on the surface of the first protective layer is removed, and then it is immersed in a TMC cyclohexane solution for an interfacial polymerization reaction for about 40 seconds. After the reaction, it is left to stand in an indoor environment until the cyclohexane solution on the surface of the first protective layer is completely volatilized to generate a barrier layer.

[0072] The thickness of the barrier layer may be greater than or equal to 50 nm and less than or equal to 1000 nm.

[0073] Step S34: generating a second protective layer on the surface of the barrier layer.

[0074] The second protective layer and the first protective layer can be the same or different protective layers, and the first protective layer and the second protective layer can be independently selected from any one of the following: an anti-oxidation layer, an acid-resistant layer, an alkali-resistant layer, a chemical solvent-resistant layer or a high-temperature-resistant layer.

[0075] For example, when the second protective layer is also an antioxidant layer, a polyvinyl alcohol aqueous solution of a preset concentration can be prepared first, and then glyoxal is added to the polyvinyl alcohol aqueous solution of the preset concentration, and then the pH value of the mixed solution after adding glyoxal is adjusted to 1-3, and then the mixed solution after adjusting the pH value is evenly coated on the provided substrate surface, and the coating thickness can be about 10 microns, and then the evenly coated substrate is heat treated at 70°C to 90°C for about 15 minutes to induce a cross-linking reaction between polyvinyl alcohol and glyoxal to generate the second protective layer.

[0076] For example, when the second protective layer is also an acid-resistant layer or an alkali-resistant layer, the second protective layer can be prepared using graphene material, thereby utilizing the acid-resistant and alkali-resistant properties of the graphene material to prevent acid or alkali from corroding the barrier layer.

[0077] The above are the specific contents of the multilayer film and the multilayer film preparation method provided in the embodiments of the present application. The effects thereof can be further explained below in conjunction with specific examples.

[0078] Comparative Example 1: The provided multilayer membrane includes a polysulfone ultrafiltration membrane substrate and a barrier layer disposed on the surface of the polysulfone ultrafiltration membrane substrate, wherein the barrier layer is the barrier layer generated by the interfacial polymerization reaction of MPD and TMC in step S33.

[0079] Comparative Example 2: The multilayer membrane provided includes a polysulfone ultrafiltration membrane substrate and a barrier layer arranged on the surface of the polysulfone ultrafiltration membrane substrate, and the barrier layer is the same as that in Comparative Example 1; in addition, in the multilayer membrane of Comparative Example 2, the outer surface of the barrier layer is provided with a second protective layer (anti-oxidation layer) generated in step S34, wherein the surface of the barrier layer close to the substrate is called the inner surface, and the other surface is called the outer surface.

[0080] Example 1: The provided multilayer membrane includes a polysulfone ultrafiltration membrane substrate and a barrier layer arranged on the surface of the polysulfone ultrafiltration membrane substrate, and the barrier layer is the same as that in Comparative Example 1; in addition, a first protective layer (anti-oxidation layer) generated by the method of steps S321 to S325 is provided on the inner surface of the barrier layer, and a second protective layer (anti-oxidation layer) generated by step S34 is provided on the inner surface of the barrier layer.

[0081] The multilayer films provided in Example 1, Comparative Example 1 and Comparative Example 2 were oxidized with an aqueous sodium hypochlorite solution containing 1000 ppm of available chlorine, and the performance of each multilayer film was tested. The comparative data are shown in FIG. Figure 4 As shown:

[0082] In this Figure 4 In the figure, the ordinate is the relative desalination rate R, and the abscissa is ppm hour, where:

[0083] R relative desalination rate = desalination rate after sodium hypochlorite immersion treatment / initial desalination rate * 100%

[0084] ppm hour = effective concentration of sodium hypochlorite solution (1000ppm) * immersion time (hours)

[0085] from Figure 4 It can be seen that the relative salt rejection rate of R of the multilayer membrane provided by Example 1 does not show a significant downward trend as the horizontal axis ppm hours increases. However, the relative salt rejection rate of R of the multilayer membranes provided by Comparative Examples 1 and 2 decreases sharply as the horizontal axis ppm hours increases. Therefore, Example 1 can effectively protect the barrier layer from oxidation relative to Comparative Examples 1 and 2.

[0086] Example 2: The provided multilayer membrane includes a polysulfone ultrafiltration membrane substrate, a first acid-resistant layer disposed on the surface of the polysulfone ultrafiltration membrane substrate, a barrier layer disposed on the surface of the first acid-resistant layer, and a second acid-resistant layer disposed on the surface of the barrier layer.

[0087] The first acid-resistant layer can be formed on the surface of the polysulfone ultrafiltration membrane substrate in the following manner: weigh 15 grams of PVA with a degree of alcoholysis of 98% and a degree of polymerization of 1700, disperse it in 1000 grams of pure water, stir and heat until completely dissolved, cool the resulting PVA solution to room temperature, add 10 grams of glyoxal under stirring conditions, and adjust the solution pH to 2 with dilute hydrochloric acid to obtain a PVA aqueous solution; weigh 0.5 grams of graphene oxide powder, place it in 1000 grams of pure water, and ultrasonically disperse it until the solution does not settle to obtain a graphene aqueous dispersion; mix the prepared PVA aqueous solution with the graphene aqueous dispersion and stir evenly to obtain a graphene and PVA mixed solution. The mixed solution is evenly coated on the surface of the polysulfone ultrafiltration membrane substrate, and the coating thickness is 0.2 μm. After coating, the membrane is placed in an 80°C oven for heat-induced cross-linking treatment, and the heat treatment time is 3 minutes.

[0088] The barrier layer in Example 2 is the same as that in Comparative Example 1, and will not be described in detail here.

[0089] The second acid-resistant layer can be formed on the surface of the barrier layer in the following manner: the graphene and PVA mixed solution is coated on the barrier layer surface again, with a coating thickness of 0.2 μm. The coated film is placed in an oven at 80° C. for heat-induced crosslinking treatment for 3 minutes to obtain the second acid-resistant layer.

[0090] Comparative Example 3: Compared with the multilayer film of Example 2, the multilayer film provided in Comparative Example 3 does not have the first acid-resistant layer and the second acid-resistant layer.

[0091] Comparative Example 4: Compared with the multilayer film of Example 2, the multilayer film provided in Comparative Example 4 does not have the first acid-resistant layer.

[0092] After Example 2, Comparative Example 3 and Comparative Example 4 were immersed in a 200000 ppm sulfuric acid aqueous solution, the performance of the membranes was tested. The comparative data are shown in Table 1 below.

[0093] Table 1

[0094]

[0095] Where: R relative desalination rate = desalination rate after immersion in 20% sulfuric acid solution / initial desalination rate * 100%

[0096] It can be seen from Table 1 that, as time goes by, the R relative desalination rate of the multilayer membrane provided in Example 2 does not decrease significantly. In contrast, the R relative desalination rate of the multilayer membrane provided in Comparative Example 3 is also significantly lower in the first week, and decreases significantly as time goes by. The R relative desalination rate of the multilayer membrane provided in Comparative Example 4 also decreases faster than the multilayer membrane provided in Example 2 as time goes by. Therefore, it can be seen that the multilayer membrane provided in Example 2 benefits from the protection of the barrier layer by the acid-resistant layers on both surfaces of the barrier layer, making the acid-resistant performance of the multilayer membrane significantly stronger.

[0097] It should be noted that the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, commodity or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, commodity or device. In the absence of further restrictions, the elements defined by the sentence "comprises a ..." do not exclude the existence of other identical elements in the process, method, commodity or device including the elements.

[0098] The above are only embodiments of the present application and are not intended to limit the present application. For those skilled in the art, the present application may have various changes and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application should be included within the scope of the claims of the present application.

Claims

1. A multilayer film, characterized in that include: A substrate and one or more barrier layers disposed on the substrate, wherein at least one of the one or more barrier layers has protective layers disposed on both surfaces of the barrier layer; The substrate is a polysulfone ultrafiltration membrane substrate, which includes a substrate made of PET material and an additional barrier layer made of polysulfone and arranged on the surface of the substrate; The surface of the barrier layer close to the substrate is provided with a first protective layer, and the other surface away from the substrate is provided with a second protective layer; The method for preparing the multilayer film comprises: forming a first protective layer on a provided substrate; forming a barrier layer on the surface of the first protective layer; forming a second protective layer on the surface of the barrier layer; Generating a first protective layer on the provided substrate specifically includes: adding glyoxal to a polyvinyl alcohol aqueous solution of a preset concentration; adjusting the pH value of the mixed solution after adding glyoxal to 1 to 3; and uniformly coating the mixed solution after adjusting the pH value on the surface of the provided substrate to form the first protective layer; Generating a barrier layer on the surface of the first protective layer specifically comprises: immersing the substrate after the first protective layer is formed in an aqueous solution of m-phenylenediamine; immersing the substrate including the first protective layer after the immersion in a cyclohexane solution of trimesoyl chloride to perform an interfacial polymerization reaction, so as to generate the barrier layer on the surface of the first protective layer; The second protective layer is prepared by adding glyoxal to a polyvinyl alcohol aqueous solution of a preset concentration, adjusting the pH value of the mixed solution after adding glyoxal to 1-3, and uniformly coating the mixed solution after adjusting the pH value on the surface of the provided barrier layer; or, The second protective layer is prepared using graphene material.

2. The multilayer film according to claim 1, characterized in that The thickness of the protective layer is greater than or equal to 1 nanometer and less than or equal to 20 micrometers.

3. The multilayer film according to claim 1, wherein The thickness of the substrate is greater than or equal to 5 micrometers and less than or equal to 250 micrometers.

4. The multilayer film according to claim 1, wherein The thickness of the barrier layer between the first protective layer and the second protective layer is greater than or equal to 20 nanometers and less than or equal to 100 micrometers.

5. The multilayer film according to claim 1, wherein The polyvinyl alcohol aqueous solution of the preset concentration specifically includes: a polyvinyl alcohol aqueous solution with a mass fraction greater than or equal to 10% and less than or equal to 20%.

6. The multilayer film according to claim 1, wherein After uniformly coating the pH-adjusted mixed solution on the provided substrate surface, the preparation method further comprises: heat-treating the uniformly coated substrate at 70°C to 90°C for 2 to 5 minutes to initiate a cross-linking reaction between polyvinyl alcohol and glyoxal to generate the first protective layer.

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