Release film as well as preparation method and application thereof

Abstract

The invention discloses a preparation method of a release film, which comprises the following steps: a, mixing cycloolefin resin, chlorine-containing resin, a cross-linking agent and an organic solvent to obtain a release agent; b, coating a substrate film with the release agent obtained in the step a, and carrying out heating treatment to obtain a release film prefabricated product; and c, carrying out electron beam radiation crosslinking on the release film prefabricated product prepared in the step b to prepare the release film. The release film prepared by the method disclosed by the invention has good temperature resistance and tensile strength, lower stripping force and lower surface roughness, the adhesion of a release layer and a base material is excellent, the release agent can be effectively prevented from being transferred to the proton exchange membrane, and the preparation process requirements of the proton exchange membrane can be met.

Description

Technical Field

[0001] The present invention belongs to the technical field of thermal transfer release materials, and in particular relates to a release film and a preparation method thereof, and further relates to the application of the release film. Background Art

[0002] Release films, also known as isolating films, peeling films, and separating films, are commonly found on plastic films such as PET, PI, and PP. These films are coated with silicone oil, fluorine, or non-silicone release agents, resulting in extremely light and stable release forces. Due to their non-stick properties, isolation, and protective properties, release films are now widely used in industries such as packaging, printing, screen printing, and electronics.

[0003] The proton exchange membrane (PEM) is a core component of PEM fuel cells, conducting protons, serving as an electrode reaction medium and catalyst carrier, and isolating cathode and anode reactants. Its fabrication process is currently a hot topic in the fuel cell field. PEM fabrication processes include cast film coating and melt extrusion. In the cast film coating process, the performance of the release film, such as peel strength, contact angle, temperature resistance, and release agent transfer, significantly influences the film-forming process of the perfluorosulfonic acid resin solution.

[0004] Currently, common silicone oil-based or fluorine-based release films prevent perfluorosulfonic acid resin solutions from forming films or transferring silicon. Non-silicone release films generally use acrylic coatings, but perfluorosulfonic acid resin solutions exhibit significant peel strength after forming. Therefore, further research and improvement of release films is necessary to meet the requirements of proton exchange membrane preparation. Summary of the Invention

[0005] The present invention is based on the inventors' discovery and understanding of the following facts and problems: COC resin is an amorphous copolymer resin with a cyclic olefin structure. It has advantages such as temperature resistance, low water absorption, friction resistance, and chemical stability, making it an excellent release agent material. However, COC resin, when used as a coating, exhibits weak adhesion to substrate films, necessitating further research to develop release films suitable for proton exchange membranes.

[0006] The present invention aims to at least partially address one of the technical problems in the related art. To this end, embodiments of the present invention provide a release film and a method for preparing the same. The resulting release film exhibits good temperature resistance and tensile strength, low peel force and surface roughness, excellent adhesion between the release layer and the substrate, and can effectively prevent transfer of the release agent to the proton exchange membrane, thus meeting the requirements of the proton exchange membrane preparation process.

[0007] A method for preparing a release film according to an embodiment of the present invention comprises the following steps:

[0008] a. mixing a cycloolefin resin, a chlorine-containing resin, a cross-linking agent and an organic solvent to obtain a release agent;

[0009] b. coating the release agent obtained in step a on a substrate film, and heating the substrate film to obtain a release film preform;

[0010] C. Subjecting the release film preform obtained in step b to electron beam radiation cross-linking to obtain a release film.

[0011] The advantages and technical effects brought by the preparation method of the release film of the embodiment of the present invention are as follows: 1. In the method of the embodiment of the present invention, cycloolefin resin is used as the release agent material, and chlorine-containing resin is introduced into the release agent as an adhesion promoter, so that the release film has excellent release effect, low surface roughness and high temperature resistance; 2. In the method of the embodiment of the present invention, a cross-linking agent is introduced into the release agent, and radiation cross-linking is performed after coating. The chlorine-containing resin in the release agent is cross-linked with the cycloolefin resin, which improves the cohesive force of the release layer polymer and effectively avoids the transfer of the release agent to the proton exchange membrane. At the same time, the cross-linking of the chlorine-containing resin and the cycloolefin resin generates intermolecular force between the release layer and the substrate film, effectively improving the bonding force between the release layer and the substrate film, and making the release effect stable. The release membrane prepared by the embodiment of the present invention has excellent performance and can meet the preparation process requirements of the proton exchange membrane.

[0012] In some embodiments, in step a, the chlorine-containing resin includes at least one of vinyl chloride, polyvinylidene chloride, or chlorinated polypropylene; the cross-linking agent includes at least one of triallyl isocyanurate, diallyl phthalate, and pentaerythritol tetraacrylate; the organic solvent includes xylene and tetrahydrofuran, and the mass ratio of xylene to tetrahydrofuran is (4:6)-(7:3); the glass transition temperature of the cycloolefin resin is 120°C-180°C.

[0013] In some embodiments, in step a, the mass ratio of the chlorine-containing resin to the cycloolefin resin is (1-10):100; the mass of the cross-linking agent is 0.5%-5% of the total mass of the chlorine-containing resin and the cycloolefin resin; and the mass of the cycloolefin resin is 3%-20% of the mass of the organic solvent.

[0014] In some embodiments, in step b, the substrate film includes a polyimide film, a polyester film, or a polyphenylene sulfide film.

[0015] In some embodiments, in step b, the substrate film is a film with a single-side corona treatment, and the release agent is coated on the corona-treated surface; the thickness of the substrate film is 75-125 μm.

[0016] In some embodiments, in step b, the thickness of the wet film after the release agent is applied is 5-50 μm.

[0017] In some embodiments, in step b, the temperature of the heating treatment is 120-150° C., and the time of the heating treatment is 3-5 minutes.

[0018] In some embodiments, in step c, the electron beam energy of the electron beam radiation cross-linking is 5-10 MeV, and the radiation dose is 20-60 KGy.

[0019] In some embodiments, in step c, after the release film preform is cross-linked by electron beam radiation, it is kept at 120° C.-150° C. for 0.5-2 hours to obtain a release film.

[0020] The present invention also provides a release film produced using the release film production method of the present invention. The release film of the present invention has good temperature resistance, tensile strength, low peel force, and low surface roughness. Furthermore, the release layer and the substrate film have strong adhesion, resulting in a stable release effect. Furthermore, there is no transfer of the release agent to the proton exchange membrane, thus meeting the requirements of the proton exchange membrane production process.

[0021] An embodiment of the present invention also provides an application of a release membrane in preparing a proton exchange membrane. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 Schematic diagram of the structure of the release film prepared in accordance with an embodiment of the present invention. DETAILED DESCRIPTION

[0023] The embodiments of the present invention are described in detail below, and examples of the embodiments are shown in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and intended to be used to explain the present invention, but should not be understood as limiting the present invention.

[0024] A method for preparing a release film according to an embodiment of the present invention comprises the following steps:

[0025] a. mixing a cycloolefin resin, a chlorine-containing resin, a cross-linking agent and an organic solvent to obtain a release agent;

[0026] b. coating the release agent obtained in step a on a substrate film, and baking to obtain a release film preform;

[0027] C. Subjecting the release film preform obtained in step b to electron beam radiation cross-linking to obtain a release film.

[0028] In the preparation method of the release film of the embodiment of the present invention, a cycloolefin resin and a chlorine-containing resin are used to prepare a release agent, so that the release film has excellent release effect, low surface roughness and high temperature resistance. In the method of the embodiment of the present invention, a cross-linking agent is introduced into the release agent, and radiation cross-linking is performed after coating. The chlorine-containing resin in the release agent and the cycloolefin resin are cross-linked, thereby improving the cohesive force of the release layer polymer and effectively avoiding the transfer of the release agent to the proton exchange membrane. At the same time, the cross-linking of the chlorine-containing resin and the cycloolefin resin generates intermolecular forces between the release layer and the substrate film, effectively improving the adhesion between the release layer and the substrate film, and the release effect is stable. The release membrane prepared in the embodiment of the present invention has excellent performance and can meet the preparation process requirements of the proton exchange membrane.

[0029] In some embodiments, in step a, the chlorine-containing resin includes at least one of vinyl chloride (PVC), polyvinylidene chloride (PVDC) or chlorinated polypropylene (CPP); the organic solvent includes xylene and tetrahydrofuran, and the mass ratio of xylene to tetrahydrofuran is (4:6)-(7:3); the glass transition temperature of the cycloolefin resin is 120°C-180°C; the mass ratio of the chlorine-containing resin to the cycloolefin resin is (1-10):100; the mass of the cycloolefin resin is 3%-20% of the mass of the organic solvent.

[0030] In some embodiments, in step a, the crosslinking agent includes at least one of triallyl isocyanurate (TAIC), diallyl phthalate (DAP), and pentaerythritol tetraacrylate (TMMTA). In embodiments of the present invention, the use of a preferred crosslinking agent further enhances the adhesion between the release layer and the substrate layer, improving the release effect.

[0031] In some embodiments, in step a, the mass of the crosslinking agent is 0.5%-5% of the total mass of the chlorine-containing resin and the cycloolefin resin. In the embodiments of the present invention, the amount of the crosslinking agent is further optimized. If the amount of the crosslinking agent is too small, it is not conducive to improving the adhesion between the release layer and the substrate layer. If the amount of the crosslinking agent is too large, it is not conducive to improving the thermal stability of the release layer.

[0032] In some embodiments, in step b, the substrate film preferably comprises a polyimide film, a polyester film (such as PET, PEN), or a polyphenylene sulfide film, more preferably a polyimide film. In the embodiments of the present invention, the use of the preferred polyimide film as the substrate not only further improves the temperature resistance of the release film, but also increases the tensile strength of the release film.

[0033] In some embodiments, in step b, the substrate film is a film that has been corona-treated on one side, and the release agent is applied to the corona-treated side. The thickness of the substrate film is 75-125 μm. In embodiments of the present invention, corona treatment of the substrate film increases the surface roughness of the film, thereby enhancing the adhesion between the substrate film and the release layer.

[0034] In some embodiments, in step b, the thickness of the wet film after the release agent coating is 5-50 μm; the temperature of the heat treatment is 120-150°C, and the heating treatment time is 3-5 minutes. In embodiments of the present invention, heating the coated wet film helps ensure uniformity of the coating and subsequent cross-linking.

[0035] In some embodiments, in step c, the electron beam energy for the electron beam crosslinking is 5-10 MeV, and the radiation dose is 20-60 KGy. Furthermore, preferably, after the release film preform is crosslinked by electron beam radiation, it is then incubated at 120°C-150°C for 0.5-2 hours to produce the release film. In the embodiments of the present invention, the electron beam energy and radiation dose for the radiation crosslinking are preferably selected. If the electron beam energy and radiation dose are too low, the degree of crosslinking is insufficient, which is not conducive to improving the adhesion between the release layer and the substrate. If the electron beam energy and radiation dose are too high, it may cause material degradation, which is not conducive to improving the performance of the release film.

[0036] The embodiment of the present invention further provides a release film, which is prepared by the method for preparing the release film of the embodiment of the present invention. Figure 1 As shown, crosslinking occurs between the chlorine-containing resin and the cycloolefin resin in the release layer of the release film of the embodiment of the present invention, which increases the cohesive force of the release layer polymer and effectively prevents the transfer of the release agent to the proton exchange membrane. At the same time, the crosslinking of the chlorine-containing resin and the cycloolefin resin generates intermolecular forces between the release layer and the substrate film, effectively increasing the adhesion between the release layer and the substrate film, and stabilizing the release effect. The release film of the embodiment of the present invention has good temperature resistance, tensile strength, low peel force, and low surface roughness. At the same time, the release layer has excellent adhesion to the substrate, and there is no transfer of the release agent to the proton exchange membrane, which can meet the requirements of the preparation process of the proton exchange membrane.

[0037] An embodiment of the present invention also provides an application of a release membrane in preparing a proton exchange membrane.

[0038] The present invention is described in detail below with reference to the embodiments.

[0039] Example 1

[0040] 1. Prepare the substrate: Use a polyimide film (PI film) with a thickness of 100 μm as the substrate and perform single-sided corona treatment on the PI film.

[0041] 2. Preparation of release agent: 100 g of a mixed solvent was prepared by mixing xylene and tetrahydrofuran in a mass ratio of 7:3, 20 g of cycloolefin resin (COC resin) and 2 g of vinyl chloride (PVC resin) were added to the mixed solvent, heated to 80 ° C in an oil bath, stirred for 1 hour, cooled to room temperature, and insoluble particles were filtered out. 1.1 g of triallyl isocyanurate (TAIC) was added to the above solution and stirred for 30 minutes to prepare a release agent, wherein triallyl isocyanurate was 5% of the total mass of cycloolefin resin and vinyl chloride, cycloolefin resin was 20% of the mass of the mixed solvent, and the mass ratio of vinyl chloride to cycloolefin resin was 10:100.

[0042] 3. Preparation of release film preform: The release agent prepared in step 2 is coated on the corona surface of the PI film in step 1 with a wet film thickness of 5 μm, and heated at 150° C. for 5 minutes to prepare a release film preform.

[0043] 4. Preparation of release film: The release film preform of step 3 was subjected to electron beam radiation crosslinking with an electron beam energy of 10 MeV and a radiation dose of 60 KGy, and then kept at 150° C. for 1 hour to obtain a release film.

[0044] Example 2

[0045] 1. Prepare the substrate: Use a polyimide film (PI film) with a thickness of 100 μm as the substrate and perform single-sided corona treatment on the PI film.

[0046] 2. Preparation of release agent: 100 g of a mixed solvent was prepared by mixing xylene and tetrahydrofuran in a mass ratio of 7:3, 3 g of cycloolefin resin (COC resin) and 30 mg of vinyl chloride (PVC resin) were added to the mixed solvent, heated to 80 ° C in an oil bath, stirred for 1 hour, cooled to room temperature, and insoluble particles were filtered out. 15 mg of triallyl isocyanurate (TAIC) was added to the above solution and stirred for 30 minutes to prepare a release agent, wherein triallyl isocyanurate was 0.5% of the total mass of cycloolefin resin and vinyl chloride, cycloolefin resin was 3% of the mass of the mixed solvent, and the mass ratio of vinyl chloride to cycloolefin resin was 1:100.

[0047] 3. Preparation of release film preform: The release agent prepared in step 2 is coated on the corona surface of the PI film in step 1 with a wet film thickness of 50 μm, and heated at 150° C. for 5 minutes to prepare a release film preform.

[0048] 4. Preparation of release film: The release film preform of step 3 was subjected to electron beam radiation crosslinking with an electron beam energy of 10 MeV and a radiation dose of 60 KGy, and then kept at 150° C. for 1 hour to obtain a release film.

[0049] Example 3

[0050] 1. Prepare the substrate: Use a polyimide film (PI film) with a thickness of 100 μm as the substrate and perform single-sided corona treatment on the PI film.

[0051] 2. Preparation of release agent: 100 g of a mixed solvent was prepared by mixing xylene and tetrahydrofuran in a mass ratio of 4:6, 3 g of cycloolefin resin (COC resin) and 30 mg of vinyl chloride (PVC resin) were added to the mixed solvent, heated to 80 ° C in an oil bath, stirred for 1 hour, cooled to room temperature, and insoluble particles were filtered out. 15 mg of triallyl isocyanurate (TAIC) was added to the above solution and stirred for 30 minutes to prepare a release agent, wherein triallyl isocyanurate was 0.5% of the total mass of cycloolefin resin and vinyl chloride, cycloolefin resin was 3% of the mass of the mixed solvent, and the mass ratio of vinyl chloride to cycloolefin resin was 1:100.

[0052] 3. Preparation of release film preform: The release agent prepared in step 2 is coated on the corona surface of the PI film in step 1 with a wet film thickness of 50 μm, and heated at 150° C. for 5 minutes to prepare a release film preform.

[0053] 4. Preparation of release film: The release film preform of step 3 was subjected to electron beam radiation crosslinking with an electron beam energy of 10 MeV and a radiation dose of 60 KGy, and then kept at 150° C. for 1 hour to obtain a release film.

[0054] Example 4

[0055] 1. Prepare the substrate: Use a polyimide film (PI film) with a thickness of 100 μm as the substrate and perform single-sided corona treatment on the PI film.

[0056] 2. Preparation of release agent: 100 g of a mixed solvent was prepared by mixing xylene and tetrahydrofuran in a mass ratio of 4:6, 3 g of cycloolefin resin (COC resin) and 30 mg of vinyl chloride (PVC resin) were added to the mixed solvent, heated to 80 ° C in an oil bath, stirred for 1 hour, cooled to room temperature, and insoluble particles were filtered out. 15 mg of triallyl isocyanurate (TAIC) was added to the above solution and stirred for 30 minutes to prepare a release agent, wherein triallyl isocyanurate was 0.5% of the total mass of cycloolefin resin and vinyl chloride, cycloolefin resin was 3% of the mass of the mixed solvent, and the mass ratio of vinyl chloride to cycloolefin resin was 1:100.

[0057] 3. Preparation of release film preform: The release agent prepared in step 2 is coated on the corona surface of the PI film in step 1 with a wet film thickness of 50 μm, and heated at 150° C. for 5 minutes to prepare a release film preform.

[0058] 4. Preparation of release film: The release film preform in step 3 was subjected to electron beam radiation crosslinking with an electron beam energy of 5 MeV and a radiation dose of 20 KGy, and then kept at 150° C. for 1 hour to obtain a release film.

[0059] Example 5

[0060] The method is the same as that of Example 1, except that the substrate in step 1 is a PET film with a thickness of 100 μm, and the PET film is subjected to single-sided corona treatment.

[0061] Comparative Example 1

[0062] The method is the same as that of Example 4, except that no PVC resin is added in the preparation of the release agent in step 2.

[0063] Comparative Example 2

[0064] The method is the same as that of Example 4, except that the crosslinking agent triallyl isocyanurate is not added in the preparation of the release agent in step 2, and the electron beam radiation crosslinking in step 4 is omitted.

[0065] Performance test: The release films prepared in each embodiment and comparative example were tested for film thickness, release layer adhesion, surface roughness, tensile strength, elongation at break, water contact angle, Nafion solution contact angle, and thermal shrinkage. The test results are shown in Table 1.

[0066] Preparation of proton exchange membrane samples: A perfluorosulfonic acid resin dispersion was coated on the release membrane prepared in each example and comparative example, and then a layer of reinforcement membrane was laid flatly. The perfluorosulfonic acid resin dispersion was then coated again. After drying to form a film, a proton exchange membrane was prepared. The peel force and release agent transfer performance tests were performed. The test results are shown in Table 1.

[0067] Table 1

[0068]

[0069] Note: 1. The release layer adhesion test refers to GB / T 33049-2016 Determination of Adhesion of Optical Thin Film Coatings on Polarizers;

[0070] 2. Peel force test: GB / T 25256-2010 Test method for 180° peel force and residual adhesion of release films for optical functional films.

[0071] 3. Release agent transfer test: The prepared proton exchange membrane was tested by EDS elemental analysis.

[0072] The release film produced in the embodiments of the present invention has low surface roughness and peel force. The release layer adhesion test showed excellent performance, with a detachment area of ​​0%. In the release agent transfer test, no release agent was detected on the surface of the proton exchange membrane, indicating that no release agent transfer occurred. Furthermore, the release film of the embodiments of the present invention has excellent mechanical properties and high temperature resistance, with a tensile strength of over 135 MPa, an elongation at break of over 40%, and a thermal shrinkage of no more than 0.95% at 160°C for 15 minutes. The film has excellent overall performance and can meet the requirements of the proton exchange membrane preparation process.

[0073] In Comparative Example 1, since no chlorine-containing resin was introduced, the polarity of the cycloolefin resin and the substrate film was different, resulting in poor adhesion. As a result, the release layer adhesion test showed a 100% peeling area, and the release agent was transferred to the proton exchange membrane.

[0074] In Comparative Example 2, since no cross-linking agent was introduced and no electron beam radiation cross-linking treatment was performed, the cyclic olefin and the chlorine-containing resin were only physically blended without chemical cross-linking. The interaction force between the release layer polymers was insufficient, which easily led to the transfer of the release agent to the proton exchange membrane. In addition, the adhesion between the release layer and the substrate film was reduced, resulting in a 63% peeling area.

[0075] In the present invention, the terms "one embodiment", "some embodiments", "examples", "specific examples", or "some examples" mean that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine different embodiments or examples described in this specification and the features of different embodiments or examples without contradiction.

[0076] Although the embodiments of the present invention have been shown and described above, it will be understood that the above embodiments are illustrative and are not to be construed as limitations on the present invention. A person skilled in the art may change, modify, replace and modify the above embodiments within the scope of the present invention.

Claims

1. A method for preparing a release film, characterized in that: The steps include: a. mixing a cycloolefin resin, a chlorine-containing resin, a crosslinking agent and an organic solvent to obtain a release agent; b. coating the release agent obtained in step a on the substrate film, and heating the substrate film to obtain a release film preform; c. Subjecting the release film preform obtained in step b to electron beam radiation cross-linking to obtain a release film.

2. The method for preparing a release film according to claim 1, characterized in that: In the step a, the chlorine-containing resin includes at least one of vinyl chloride, polyvinylidene chloride or chlorinated polypropylene; And / or, the cross-linking agent includes at least one of triallyl isocyanurate, diallyl phthalate, and pentaerythritol tetraacrylate; And / or, the organic solvent comprises xylene and tetrahydrofuran, and the mass ratio of xylene to tetrahydrofuran is (4:6)-(7:3); And / or, the glass transition temperature of the cycloolefin resin is 120°C-180°C.

3. The method for preparing a release film according to claim 1, characterized in that: In the step a, the mass ratio of the chlorine-containing resin to the cycloolefin resin is (1-10): 100; And / or, the mass of the cross-linking agent is 0.5%-5% of the total mass of the chlorine-containing resin and the cycloolefin resin; And / or, the mass of the cycloolefin resin is 3%-20% of the mass of the organic solvent.

4. The method for preparing a release film according to claim 1, characterized in that: In the step b, the substrate film includes a polyimide film, a polyester film or a polyphenylene sulfide film; The substrate film is a film with a single-side corona treatment, and the release agent is coated on the corona-treated surface; And / or, the thickness of the substrate film is 75-125 μm.

5. The method for preparing a release film according to claim 1, characterized in that: In the step b, the thickness of the wet film after the release agent is applied is 5-50 μm.

6. The method for preparing a release film according to claim 1, characterized in that: In the step b, the temperature of the heating treatment is 120-150° C., and the time of the heating treatment is 3-5 minutes.

7. The method for preparing a release film according to claim 1, characterized in that: In the step c, the electron beam energy of the electron beam radiation cross-linking is 5-10 MeV, and the radiation dose is 20-60 KGy.

8. The method for preparing a release film according to claim 1, characterized in that: In the step c, after the release film preform is cross-linked by electron beam radiation, it is kept at 120° C.-150° C. for 0.5-2 h to obtain a release film.

9. A release film, characterized in that: The method according to any one of claims 1 to 8 is adopted to prepare the present invention.

10. Use of a release membrane prepared by the method according to any one of claims 1 to 8 or the release membrane according to claim 9 in preparing a proton exchange membrane.

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