Release film for hot-press shaping and preparation method thereof

Abstract

The invention provides a release film for hot-press shaping and a preparation method thereof. The release film for hot-pressing shaping structurally comprises three layers, namely a base material layer, a matte high-surface-energy layer and a hot-pressing release layer from top to bottom in sequence, the matte high-surface-energy layer comprises the following raw materials: temperature-resistant resin, a filler, an auxiliary agent and a solvent; the hot-pressing release layer comprises the following raw materials: a silane precursor, an organic temperature-resistant elastic polymer, a catalyst and a solvent; physical matte vision is achieved by controlling the roughness of the matte high-surface-energy layer, meanwhile, exposed surface hydroxyl improves local surface energy, chemical binding sites are provided for silica condensation of the hot-pressing release layer, anchoring of the top layer is guaranteed, printability is not damaged, and release force stability, high surface energy and heat stability of the release film are facilitated.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of release film, in particular to a release film for hot-pressing and a preparation method thereof. BACKGROUND

[0002] Hot-pressing release film is a kind of functional film material commonly used in hot-pressing, compounding, laminating, molding and other processes. Its main function is to prevent the processed material from sticking to the mold or other contact surfaces during hot-pressing forming, thereby achieving smooth demolding and improving the smoothness and appearance quality of the product. The basic principle of the release film is that its surface has a low surface energy, making it difficult for the material in contact with it to form strong interfacial adhesion. For example, in the hot-pressing process of plastic film, composite sheet, carbon fiber prepreg or electronic packaging film, the release film acts as a barrier layer to effectively prevent the hot plastic resin from adhering to the mold surface under high temperature and pressure, ensuring the complete demolding of the product and maintaining good surface flatness and gloss.

[0003] The existing hot-pressing release film usually uses polyester (PET), polyimide (PI) or polytetrafluoroethylene (PTFE) as the base material, and achieves low surface energy characteristics by coating silicone, fluoride or acrylic release agent on its surface. However, in high-temperature hot-pressing processes, conventional release films still have many shortcomings. First, its heat resistance is limited. When the hot-pressing temperature reaches 200℃ or above, the coating of some conventional release films will undergo thermal decomposition or crosslinking, causing changes in surface structure, which will significantly increase the release force. Especially when hot-pressing with high-performance engineering plastics such as polyether ether ketone (PEEK) and polyimide (PI), it is difficult to peel off due to interfacial crosslinking or physical embedding, affecting production efficiency and causing mold contamination.

[0004] Secondly, to reduce the peeling force, conventional hot-pressing films usually use silicone-based release agents. However, silicone has very low surface energy, which will migrate to the surface of the pressed sheet during hot-pressing, causing the surface energy of the sheet to decrease after hot-pressing. This reduction in surface energy will directly affect the subsequent printing, plating or bonding secondary processing procedures, resulting in insufficient ink adhesion, plating layer falling off or reduced bonding strength, etc. Therefore, although the conventional silicone release system can improve the demolding performance, it is difficult to balance the adaptability of the subsequent processing.

[0005] In addition, some high-performance release films require high-temperature-resistant base materials and multi-layer coating structures, which have complex preparation processes and high costs, making them unsuitable for widespread application in medium and high-temperature hot-pressing fields.

[0006] Therefore, there is an urgent need for a release film that can still have good stability under high-temperature hot pressing conditions, controllable peeling performance, and can significantly improve the surface energy of the hot-pressed sheet. By designing a special coating structure, the surface energy of the substrate can be adjusted, the gloss and color can be controlled, and a high-temperature resistant release adhesive layer is used. The release film can maintain excellent release performance while providing better subsequent processing and product versatility to the hot-pressed sheet, thereby overcoming the problems of poor temperature resistance, low surface energy after peeling, and high cost in the prior art. SUMMARY

[0007] The purpose of the present application is to solve the problems mentioned in the background art. The present application provides a release film for hot pressing and a preparation method thereof.

[0008] Technical scheme of the present application: In a first aspect, the present application provides a release film for hot pressing, which comprises three layers in structure, from top to bottom, a substrate layer, a matte high surface energy layer, and a hot pressing release layer.

[0009] In some embodiments, the thickness of the substrate layer is 25-120pm, the thickness of the matte high surface energy layer is 15-30pm, and the thickness of the hot pressing release layer is 15-30pm.

[0010] In some embodiments, the material of the substrate layer is selected from one or more combinations of PET, PE, PI, and PEEK.

[0011] In some embodiments, the raw material of the matte high surface energy layer comprises temperature-resistant resin, filler, additive, and solvent; wherein the mass fraction ratio of temperature-resistant resin, filler, additive, and solvent is 50-80:10-20:1-2:100.

[0012] In some embodiments, the temperature-resistant resin is selected from one or more combinations of heat-resistant acrylic acid, epoxy-modified acrylic acid, temperature-resistant polyamide, and temperature-resistant polyester resin; for example, it can be selected from one of Duralco 4460, 4420, and 4400.

[0013] In some embodiments, the filler is hydroxyl-modified nanosilica with a D50 of 0.2-1.0pm.

[0014] The preparation method of the hydroxyl-modified nanosilica is as follows: Add an ethanol / deionized water mixed solution, ammonia water, and TEOS to the reactor, maintain stirring, and continue the reaction to obtain a sol; adjust the pH of the sol to 2, heat and reflux for reaction, centrifuge, wash, and dry after the reaction to obtain hydroxyl-modified nanosilica.

[0015] In some embodiments, the adjuvant is selected from one or more combinations of a compatibilizer, a coupling agent, a dispersant, an antifoaming agent.

[0016] In some embodiments, the raw material of the hot-pressing release layer comprises a silane precursor, an organic temperature-resistant elastic polymer, a catalyst, and a solvent; wherein the added mass fraction ratio of the silane precursor, the organic temperature-resistant elastic polymer, the catalyst, and the solvent is 70-90: 1-5: 0.1-0.2: 100.

[0017] In some embodiments, the silane precursor is selected from one or a combination of TEOS or MTMS.

[0018] In some embodiments, the organic temperature-resistant elastic polymer is selected from one or more combinations of tridecafluorooctyltriethoxysilane, tridecafluorooctyltrimethoxysilane, trifluoropropyltrimethoxysilane, 1H, 1H, 2H, 2H-heptadecafluorodecanyltrichlorosilane.

[0019] In some embodiments, the catalyst is acetic acid.

[0020] In a second aspect, the preparation method of the release film for hot-pressing shaping provided by the present application comprises the following steps: S1: preparing a substrate layer material, and making a film according to a known operation method, i.e. the substrate layer; S2: placing the substrate layer into a corona treatment machine, the frequency of the corona treatment machine is 25 kHz, the power is 8 kW, the processing speed is 25 m / min, the distance between electrodes is 1.7 mm, each side is treated twice, the substrate surface is washed with pure water, and hot air drying is performed at 52℃ for 35 min to obtain a pretreated substrate layer; S3: adding a temperature-resistant resin into a container, adding fillers, coupling agents, and dispersants while stirring, and grinding to obtain a matte high-surface-energy layer slurry; using a coating or spraying process, covering the corresponding matte high-surface-energy layer slurry on one side of the pretreated substrate layer, and completing the film with a matte high-surface-energy layer after drying treatment; S4: mixing a precursor and a solvent in a container, adding a catalyst and stirring; adding an organic temperature-resistant elastic polymer, and after aging, scraping and coating to the outside of the matte high-surface-energy layer, and obtaining a release film for hot-pressing shaping after drying and heat treatment.

[0021] Beneficial effects: 1. By controlling the roughness of the matte high-surface-energy layer, a physical matte visual effect is achieved, and the exposed surface hydroxyl group improves the local surface energy, provides a chemical binding site for the top layer of siloxane condensation, ensures the "anchoring" of the top layer without damaging the printability, and is beneficial to subsequent condensation and printing adhesion.

[0022] 2. The surface oriented fluorine group in the hot-pressing release layer forms a low contact area, low surface energy outer layer, thereby reducing the adhesion energy on the hot-pressing interface, providing easy demolding, low migration and temperature resistance, and the inorganic silicon-oxygen skeleton gives the film higher thermal stability and morphology retention ability, which is more stable at high temperature than a pure organic fluorine coating.

[0023] 3. The matte high surface energy layer provides rough / hydroxyl sites, and the hot-pressing release layer "anchors" on these sites and forms a very thin, outwardly directed fluorine group network, realizing a coupling synergistic effect, so that the release force is stable and the surface energy is high, improving the use experience. DETAILED DESCRIPTION

[0024] The application will be described in detail below with reference to specific embodiments. It should be noted that the following examples are examples of the application and are only used to illustrate the application, but not to limit the application. Other combinations and various modifications within the concept of the application can be made without departing from the spirit or scope of the application.

[0025] The chemical reagents used in the application are commercially available and are of analytical purity unless otherwise specified.

[0026] Preparation of hydroxyl-modified nanosilica In a three-necked flask, 600 mL of an ethanol / deionized water mixture (volume ratio 8:1) was added, 40 mL of ammonia water and 50 mL of TEOS were added at room temperature, and the mixture was stirred at 500 rpm in a fume hood and reacted for 2 h to obtain a sol. The sol was aged for 12 h, the pH was adjusted to 2 with 0.1 M HCl, and the sol was heated to reflux for 1 h. After the reaction was completed, the supernatant was discarded after centrifugation at 10,000 rpm for 20 min, and the sol was washed with ethanol and then deionized water. The sol was dried at 80°C under vacuum for 12 h to obtain a hydroxyl-modified nanosilica powder.

[0027] Characterization: SEM: D50≈0.4-1 μm; Surface hydroxyl groups / functionality: FTIR shows a characteristic peak of Si–OH at 3600 cm -1 Enhanced; Specific surface area: BET 200 m² / g.

[0028] Example 1 A release film, which is a three-layer structure from top to bottom, comprising a substrate layer, a matte high surface energy layer, and a hot-pressing release layer.

[0029] Substrate layer: PEEK (SABIC, product number LCL33), thickness 120 μm.

[0030] Matte high surface energy layer: 70 parts of temperature resistant resin (Duralco 4460), 10 parts of filler (hydroxyl modified nano-silica prepared above, D50 = 0.5 μm), 1 part of compatibilizer (ethylene glycol monoethyl ether), 1 part of dispersing agent (sodium dodecyl sulfate), and 100 parts of solvent (a mixture of ethanol / isopropanol in a volume ratio of 1:2); thickness 20 μm.

[0031] Hot-pressed release layer: 70 parts of silane precursor (TEOS), 10 parts of organic temperature-resistant elastomer polymer (PFOTES), 2 parts of catalyst (acetic acid), and 100 parts of solvent (a mixture of ethanol / deionized water in a volume ratio of 1:1); thickness 20 μm.

[0032] Preparation steps: S1: The substrate layer material was stirred uniformly in an extruder, and after co-extrusion, it was cooled and shaped in a casting station to obtain a substrate layer; S2: The substrate layer was placed in a corona treatment machine, the frequency of the corona treatment machine was 25 kHz, the power was 8 kW, the processing speed was 25 m / min, the electrode spacing was 1.7 mm, both sides were treated twice, the substrate surface was rinsed with pure water, and hot air drying was performed at 52°C for 35 min to obtain a pretreated substrate layer; S3: The temperature-resistant resin was added to the reactor, and the filler, coupling agent, and dispersing agent were added while stirring. After grinding to D50 = 0.5 µm, a matte high surface energy layer slurry was obtained. Using a coating process, the matte high surface energy layer slurry was applied to one side of the pretreated substrate layer, and after drying at 60°C for 1 h, the temperature was gradually increased to 120°C and dried for another 1 h to obtain a film with a matte high surface energy layer; S4: In the reactor, the precursor was mixed with the solvent, the catalyst was added and stirred; the organic temperature-resistant elastomer polymer was added, and after stirring and aging at room temperature for 2 h, it was scraped onto the outside of the matte high surface energy layer. First, the solvent was evaporated at 60°C, and then the release film was treated by baking at 120°C for 30 min.

[0033] Example 2 A release film, which is a three-layer structure from top to bottom, is a substrate layer, a matte high surface energy layer, and a hot-pressed release layer.

[0034] Substrate layer: PEEK (SABIC, product number LCL33), thickness 120 μm.

[0035] Matte high surface energy layer: 70 parts of temperature resistant resin (Duralco 4460), 10 parts of filler (hydroxyl modified nano-silica prepared above, D50 = 0.8 μm), 1 part of compatibilizer (ethylene glycol monoethyl ether), 1 part of dispersing agent (sodium dodecyl sulfate), and 100 parts of solvent (a mixture of ethanol / isopropanol in a volume ratio of 1:2); thickness 20 μm.

[0036] Hot-pressed release layer: 70 parts of silane precursor (TEOS), 10 parts of organic temperature-resistant elastomer (PFOTES), 2 parts of catalyst (acetic acid), and 100 parts of solvent (a mixture of ethanol / deionized water with a volume ratio of 1:1); thickness 20 μm.

[0037] The preparation steps are basically the same as those in Example 1.

[0038] Example 3 A release film, which is a three-layer structure from top to bottom, is a substrate layer, a matte high-surface-energy layer, and a hot-pressed release layer.

[0039] Substrate layer: PEEK (SABIC, product number LCL33), thickness 120 μm.

[0040] Matte high-surface-energy layer: 70 parts of temperature-resistant resin (Duralco 4460), 10 parts of filler (hydroxyl-modified nanosilica prepared above, D50 = 1 μm), 1 part of compatibilizer (ethylene glycol monoethyl ether), 1 part of dispersant (sodium dodecyl sulfate), and 100 parts of solvent (a mixture of ethanol / isopropyl alcohol with a volume ratio of 1:2); thickness 20 μm.

[0041] Hot-pressed release layer: 70 parts of silane precursor (TEOS), 10 parts of organic temperature-resistant elastomer (PFOTES), 2 parts of catalyst (acetic acid), and 100 parts of solvent (a mixture of ethanol / deionized water with a volume ratio of 1:1); thickness 20 μm.

[0042] The preparation steps are basically the same as those in Example 1.

[0043] Comparative Example 1 A release film, which is a three-layer structure from top to bottom, is a substrate layer, a matte high-surface-energy layer, and a hot-pressed release layer.

[0044] Substrate layer: PEEK (SABIC, product number LCL33), thickness 120 μm.

[0045] Matte high-surface-energy layer: 70 parts of temperature-resistant resin (Duralco 4460), 10 parts of filler (nanosilica, D50 = 0.5 μm), 1 part of compatibilizer (ethylene glycol monoethyl ether), 1 part of dispersant (sodium dodecyl sulfate), and 100 parts of solvent (a mixture of ethanol / isopropyl alcohol with a volume ratio of 1:2); thickness 20 μm.

[0046] Hot-pressed release layer: 70 parts of silane precursor (TEOS), 10 parts of organic temperature-resistant elastomer (PFOTES), 2 parts of catalyst (acetic acid), and 100 parts of solvent (a mixture of ethanol / deionized water with a volume ratio of 1:1); thickness 20 μm.

[0047] The preparation steps are substantially the same as in Example 1.

[0048] Comparative Example 2 A release film, which is a three-layer structure from top to bottom in turn is a substrate layer, a matte high surface energy layer and a hot-pressing release layer.

[0049] Substrate layer: PEEK (SABIC, product number LCL33), thickness 120 pm.

[0050] Matte high surface energy layer: 70 parts of temperature-resistant resin (Duralco 4460), 10 parts of filler (hydroxyl-modified nanosilica prepared above, D50=0.5 pm), 1 part of compatibilizer (ethylene glycol monoethyl ether), 1 part of dispersing agent (sodium dodecyl sulfate) and 100 parts of solvent (a mixture of ethanol / isopropanol in a volume ratio of 1:2); thickness 20 pm.

[0051] Release layer: 80 parts of PEEK (SABIC, product number LCL33); thickness 20 pm.

[0052] Preparation steps: S1: uniformly stir the substrate layer material in the extruder, co-extrude and then cool and shape in the casting station to obtain the substrate layer and release layer materials; S2: place the substrate layer into a corona treatment machine, the frequency of the corona treatment machine is 25 kHz, the power is 8 kW, the processing speed is 25 m / min, the electrode spacing is 1.7 mm, treat both sides twice, rinse the substrate surface with pure water, and hot air dry at 52°C for 35 min to obtain the pretreated substrate layer; S3: add the temperature-resistant resin into the reactor, while stirring, add the filler, coupling agent and dispersing agent, grind to D50=0.5 pm to obtain the matte high surface energy layer slurry; use a coating process to cover the matte high surface energy layer slurry on one side of the pretreated substrate layer, then place the release layer on the slurry, dry at 60°C for 1 h, then gradually heat to 120°C and dry for another 1 h to obtain the release film.

[0053] Comparative Example 3 A release film, which is a three-layer structure from top to bottom in turn is a substrate layer, a matte high surface energy layer and a hot-pressing release layer.

[0054] Substrate layer: PEEK (SABIC, product number LCL33), thickness 120 pm.

[0055] Matte high surface energy layer: 70 parts of temperature resistant resin (Duralco 4460), 1 part of compatibilizer (ethylene glycol monoethyl ether), 0 parts of filler, 1 part of dispersing agent (sodium dodecyl sulfate), and 100 parts of solvent (a mixture of ethanol / isopropyl alcohol at a volume ratio of 1:2); thickness 20 pm.

[0056] Hot-pressed release layer: 70 parts of silane precursor (TEOS), 10 parts of organic temperature-resistant elastic polymer (GPTMS), 2 parts of catalyst (acetic acid), and 100 parts of solvent (a mixture of ethanol / deionized water at a volume ratio of 1:1); thickness 20 pm.

[0057] The preparation steps are substantially the same as in Example 1.

[0058] The above obtained products were tested as follows: 1. 180° peeling force test: The release force test tape was respectively attached to the release films prepared above, and cut into 25 mm x 200 mm samples, and a standard rolling mill was used to roll back and forth three times, and after 20 min, the test was performed, using the GB-2792-1998 adhesive tape peeling strength test method, and an electronic universal testing machine was used for testing, with a peeling speed of 300 mm / min.

[0059] 2. Surface energy test: The release force test tape was respectively attached to the ordinary release film and the release film prepared in Example 2, and cut into 25 mm x 200 mm samples, and a standard rolling mill was used to roll back and forth three times, and then the release force test tape was peeled off, and then water drops were dropped onto the peeled release film, the water contact angle after peeling was measured, five different positions were taken, each position was measured once, the average value of five times was calculated, and then the above steps were repeated, and the two release films were peeled off multiple times, and the water contact angle was measured after each peeling.

[0060] 3. Glossiness test: According to the JIS Z 8741 international standard test specification, a gloss meter VGS-SENS0R manufactured by Nippon Denshoku Industries Co., Ltd. was used to test the glossiness (G60) of the above release film. The test conditions were that the incident angle and the light receiving angle were both 60° (N=5), and the average value was used.

[0061] 4. Thermal stability test: The release force test tape was respectively attached to the release films prepared above, and cut into 25 mm x 200 mm samples, and a standard rolling mill was used to roll back and forth three times, and after 200°C for 24 h, the test was performed, using the GB-2792-1998 adhesive tape peeling strength test method, and an electronic universal testing machine was used for testing, with a peeling speed of 300 mm / min.

[0062] The test results are shown in Table 1.

[0063] Table 1 Test results From the data of Examples 1-3, it can be seen that the matting degree and touch feeling are controlled by the particle size and loading of SiO2, and the matting transfer effect after hot pressing is increased.

[0064] At the same time, the roughness of the high surface energy layer exposes the surface hydroxyl of the filler, increases the local surface energy, provides chemical bonding sites for the silicon-oxygen condensation of the hot-pressed release layer, forms covalent / strong hydrogen bonds or van der Waals "hooking" through condensation, ensures the "anchoring" of the top layer without damaging the printability, and the release force of the release film is stable and the surface energy is high. After heating or pressure bonding, a part of the surface energy of the product surface can still "rise" or present a printable surface state, so that the three seemingly contradictory properties of "stable release force, high surface energy, and thermal stability" can be established at the same time. Therefore, as can be seen from the data of Comparative Examples 1-2, in the case where the filler in the matte high surface energy layer does not have hydroxyl groups or no silane precursor is added in the hot-pressed release layer, the release force is reduced and the thermal stability is poor.

[0065] The present application can also be embodied in other various embodiments without departing from the spirit and essential characteristics thereof, and the skilled in the art can make various corresponding changes and modifications to the present application according to the present application, but these corresponding changes and modifications should all belong to the protection scope of the claims appended to the present application.

Claims

1. A release film for hot pressing and setting, the release film comprising a three-layer structure, characterized in that, The three-layer structure consists of a substrate layer, a matte high surface energy layer, and a hot-pressed release layer, from top to bottom.

2. The release film for hot pressing and shaping according to claim 1, characterized in that, The thickness of the substrate layer is 25-120 μm, the thickness of the matte high surface energy layer is 15-30 μm, and the thickness of the hot-pressed release layer is 15-30 μm.

3. The release film for hot pressing and shaping according to claim 1, characterized in that, The material of the substrate layer is selected from one or more combinations of PET, PE, PI, and PEEK.

4. The release film for hot pressing and setting according to claim 1, characterized in that, The raw materials for the matte high surface energy layer include heat-resistant resin, filler, additives and solvent; wherein the mass ratio of the heat-resistant resin, filler, additives and solvent is 50-80:10-20:1-2:

100.

5. The release film for hot pressing and setting according to claim 4, characterized in that, The filler is hydroxyl-modified nano-silica with a D50 of 0.2-1.0 μm.

6. The release film for hot pressing and setting according to claim 5, characterized in that, The preparation method of the hydroxyl-modified nano-silica is as follows: An ethanol / deionized water mixture was added to a reactor, along with ammonia and TEOS. The mixture was stirred and the reaction continued to produce a sol. The pH of the sol was adjusted to 2, and the mixture was heated under reflux to continue the reaction. After the reaction was completed, the mixture was centrifuged, washed, and dried to obtain hydroxyl-modified nano-silica.

7. The release film for hot pressing and shaping according to claim 1, characterized in that, The raw materials for the hot-pressed release layer include silane precursors, organic heat-resistant elastic polymers, catalysts, and solvents. The mass ratio of the added silane precursor, organic heat-resistant elastic polymer, catalyst and solvent is 70-90:1-5:0.1-0.2:

100.

8. The release film for hot pressing and setting according to claim 7, characterized in that, The silane precursor is selected from one or a combination of two of TEOS or MTMS.

9. The release film for hot pressing and setting according to claim 7, characterized in that, The organic heat-resistant elastic polymer is selected from one or more combinations of tridecylfluorooctyltriethoxysilane, tridecylfluorooctyltrimethoxysilane, trifluoropropyltrimethoxysilane, 1H,1H,2H,2H-heptadecylfluorodecyltrichlorosilane.

10. The method for preparing a release film for hot pressing and setting according to any one of claims 1-9, characterized in that, Includes the following steps: S1: Prepare the substrate layer material and make a film according to known operating methods, which is the substrate layer; S2: The substrate layer is placed in a corona treatment machine with a frequency of 25kHz, a power of 8kW, a processing speed of 25m / min, and an electrode spacing of 1.7mm. Both sides are treated twice. The substrate surface is rinsed with pure water and dried with hot air at 52℃ for 35min to obtain the pretreated substrate layer. S3: Add the heat-resistant resin to a container, and add filler, coupling agent and dispersant while stirring. After grinding, a matte high surface energy layer slurry is obtained. Using a coating or spraying process, cover one side of the pretreated substrate layer with the corresponding matte high surface energy layer slurry. After drying, a film with a matte high surface energy layer is completed. S4: Mix the precursor and solvent in a container, add the catalyst and stir; add the organic heat-resistant elastic polymer, age it and then coat it onto the outside of the matte high surface energy layer with a doctor blade. After drying and heat treatment, a release film for hot pressing and shaping is obtained.

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