A silicone adhesive, a high-temperature-resistant adhesive release film and a preparation method thereof

Abstract

The present application relates to adhesive and composite forming auxiliary material technical field, especially to a kind of organic silicon adhesive, high-temperature-resistant gluing isolation film and preparation method thereof.A kind of organic silicon adhesive is disclosed, according to weight parts, including: polysiloxane, 80 weight parts-120 weight parts;Hydrosilicone oil, 0.5 weight parts-15 weight parts;Platinum catalyst, 0.01 weight parts-2 weight parts;Filler, 0 weight parts-50 weight parts.The organic silicon adhesive of the present application, high-temperature-resistant gluing isolation film and preparation method thereof, using organic silicon adhesive system, with platinum catalyst catalyzing polysiloxane and hydrosilicone oil occur silicon hydrogen addition reaction, no small molecule by-product release in curing process, the crosslinking network formed is dense and has very high thermal stability, so that adhesive layer does not decompose, does not soften, does not release migration in the process of composite material forming, ensure that the surface of composite material part is clean, meet subsequent coating, bonding and other secondary processing requirements.

Description

Technical Field

[0001] This invention relates to the field of adhesives and auxiliary materials for molding composite materials, and particularly to an organosilicon adhesive, a high-temperature resistant adhesive release film, and a method for preparing the same. Background Technology

[0002] In the molding process of composite materials (such as prepregs, glass fiber impregnation, resin transfer molding, etc.), the demolding process is crucial to prevent the parts from sticking to the mold or tooling surface. Traditional liquid release agents have problems such as transfer pollution, cumbersome application, and VOC emissions. To solve these problems, the industry has tried using fluoroplastic films as a physical release layer. However, fluoroplastic films are lightweight, prone to slippage, and difficult to stably position on the tooling surface. Therefore, it is necessary to laminate the fluoroplastic film with an adhesive layer to form an adhesive release film, which can then firmly adhere to the tooling surface.

[0003] The performance of the adhesive composition is crucial to the effectiveness of the coated release liner. Existing adhesives for fluoroplastic films mainly include acrylates and silicones. However, coated release liners used in high-temperature molding processes of composite materials place stringent requirements on the adhesive composition: First, the adhesive must possess excellent high-temperature resistance, remaining undecomposed, unsoftened, and gas-generating under prolonged high temperatures; otherwise, blistering, delamination, or contamination of the parts may occur. Second, the adhesive must have good adhesion to the fluoroplastic film. Third, after curing, the adhesive should maintain a certain pressure-sensitive or curable tack to allow for tooling application without becoming excessively sticky at high temperatures, ensuring complete removal of the release liner after demolding. Finally, the adhesive itself should not contain easily migrating low-molecular-weight substances to avoid contaminating the composite parts.

[0004] Some existing silicone adhesive compositions, such as condensation-type silicone adhesives, typically require prolonged curing at high temperatures. During curing, they may release small-molecule byproducts (such as alcohols and ketones), which can easily generate bubbles or cause transfer contamination in closed-loop molding systems. Furthermore, many existing adhesives add large amounts of solvents or low-molecular-weight tackifying resins to improve coating performance or reduce costs. These components can volatilize or migrate at high temperatures, leading to defects such as silicone oil spots and pinholes on the surface of the molded parts, affecting subsequent coating, bonding, and other secondary processing. Moreover, existing adhesives often have insufficient adhesion to fluoroplastic substrates such as polytetrafluoroethylene (PTFE), easily delaminating after curing or leaving adhesive residue upon peeling.

[0005] Therefore, developing an organosilicon adhesive composition specifically for fluoroplastic films that combines excellent high-temperature resistance, low transfer pollution, good adhesion stability, and convenient construction has become an urgent technical problem to be solved in this field. Summary of the Invention

[0006] This invention addresses the shortcomings of existing technologies by providing an organosilicon adhesive, a high-temperature resistant adhesive release film, and a method for preparing the same. The invention utilizes an organosilicon adhesive system, employing a platinum catalyst to catalyze a hydrosilylation reaction between polysiloxane and hydrogen-containing silicone oil. During curing, no small-molecule byproducts are released, resulting in a dense cross-linked network with extremely high thermal stability. This ensures that the adhesive layer does not decompose, soften, or release migration products during the composite material molding process, guaranteeing a clean surface for the composite parts and meeting the requirements of subsequent coating, bonding, and other secondary processing.

[0007] Therefore, the first objective of this invention is to provide an organosilicon adhesive.

[0008] The second objective of this invention is to provide a method for preparing a high-temperature resistant adhesive-coated release film.

[0009] The third objective of this invention is to provide a high-temperature resistant adhesive-coated release film.

[0010] To achieve the first objective of this invention, the technical solution of this invention provides an organosilicon adhesive, comprising, by weight: 80-120 parts by weight of polysiloxane; 0.5-15 parts by weight of hydrogen-containing silicone oil; 0.01-2 parts by weight of platinum catalyst; and 0-50 parts by weight of filler.

[0011] Compared with existing technologies, the technical advantages achieved by this solution are as follows: Polysiloxane, as the base polymer, provides the main structure and flexibility of the adhesive layer, and its range of 80 to 120 parts by weight ensures the basic film-forming properties and coatability of the adhesive; Hydrogen-containing silicone oil, as a crosslinking agent, undergoes a hydrosilylation reaction with polysiloxane under the action of a platinum catalyst to form a three-dimensional crosslinked network, and the ratio of 0.5 to 15 parts by weight ensures a moderate crosslinking density, giving the adhesive layer both sufficient cohesive strength and a certain degree of pressure-sensitive adhesion; The amount of platinum catalyst is 0.01 to 2 parts by weight, ensuring efficient curing while avoiding increased costs or side reactions caused by excessive catalyst; The amount of filler is 0 to 50 parts by weight, which can adjust the heat resistance, mechanical strength, and surface properties of the adhesive layer as needed, and allows for the extreme case of no filler added, reflecting the flexibility of the formulation. These characteristics collectively endow the composition with the advantages of being solvent-free, free of small molecule byproducts, high-temperature resistant, and low-migration, providing a core material basis for the subsequent preparation of high-temperature resistant coated release films.

[0012] In one embodiment of the present invention, the filler is selected from at least one of silica, mica powder, alumina, and carbon black.

[0013] Compared with existing technologies, the technical effects achieved by this solution are as follows: Silica significantly improves the thixotropy and reinforcing effect of adhesives, prevents the adhesive layer from flowing at high temperatures, and simultaneously increases cohesive strength; mica powder, as a flake filler, enhances the heat resistance and crack resistance of the adhesive layer and reduces the coefficient of thermal expansion; alumina has high thermal conductivity and excellent thermal stability, which helps to uniformly conduct heat during high-temperature molding and avoid local overheating; in addition to its reinforcing effect, carbon black also improves the antistatic properties and light-shielding properties of the adhesive layer. Adding at least one of these fillers to the composition can further improve the dimensional stability and long-term aging resistance of the adhesive at high temperatures without affecting the hydrosilylation reaction, ensuring that the release film does not decompose or carbonize during the composite material curing process above 200°C.

[0014] In one embodiment of the present invention, the polysiloxane is at least one of methyl vinyl polysiloxane and methyl phenyl vinyl polysiloxane.

[0015] Compared with existing technologies, the technical effects achieved by this solution are as follows: methyl vinyl polysiloxane, with its vinyl active groups, can efficiently undergo hydrosilylation reactions with hydrogen-containing silicone oils to form a uniform cross-linked network. Furthermore, the methyl side chains impart low surface energy and good anti-stick properties to the adhesive layer. Methyl phenyl vinyl polysiloxane, by introducing phenyl groups into its molecular chain, significantly increases the polymer's thermal decomposition temperature and radiation resistance, while also enhancing the compatibility of the adhesive layer with the fluoroplastic substrate. Using at least one of these polysiloxanes results in lower thermal weight loss rates in the silicone adhesive at high temperatures, leading to a denser cured adhesive layer. This further reduces the migration of low-molecular-weight substances at high temperatures, ensuring the cleanliness of the composite material surface and meeting the stringent requirements for secondary processing in aerospace, rail transportation, and other fields.

[0016] To achieve the second objective of this invention, the technical solution of this invention provides a method for preparing a high-temperature resistant coated release film, using an organosilicon adhesive as described in any of the above technical solutions, comprising the following steps: S100, substrate preparation: selecting a fluoroplastic film and performing surface treatment on it to obtain a substrate; S200, adhesive preparation: preparing an organosilicon adhesive according to the mass proportions; S300, coating: coating the organosilicon adhesive onto at least one surface of the substrate to obtain an intermediate; S400, curing: sequentially subjecting the intermediate to curing treatment and film coating treatment to obtain a high-temperature resistant coated release film.

[0017] Compared with existing technologies, the technical advantages achieved by this solution are as follows: First, by selecting fluoroplastic film as the substrate and performing surface treatment, the surface activity of this low-surface-energy material is significantly improved, creating conditions for strong adhesion of the adhesive layer and preventing delamination between the adhesive layer and the substrate during subsequent use. Second, the silicone adhesive used is high-temperature resistant, non-migrating, and produces no byproducts. Third, the coating step is limited to at least one surface of the substrate, allowing for either single-sided coating to reduce costs or double-sided coating to meet special tooling requirements, increasing product flexibility. Finally, after curing, a protective film, typically a PE release film, is applied to the adhesive layer surface, effectively preventing contamination or adhesion of the adhesive layer during storage and transportation. This also allows users to easily peel off the release film for application. The entire process is coherent and controllable, suitable for continuous industrial production, and the resulting release film product is stable in performance and easy to use.

[0018] In one technical solution of the present invention, in step S100, the fluoroplastic film is selected from at least one of polytetrafluoroethylene, perfluoroethylene-propylene copolymer, polyperfluoroalkoxy resin, and ethylene-tetrafluoroethylene copolymer film; the thickness of the fluoroplastic film is 12.5μm-250μm.

[0019] Compared with existing technologies, the technical advantages achieved by this solution are as follows: Polytetrafluoroethylene (PTFE) has the lowest surface energy and best heat resistance; perfluoroethylene-propylene copolymer and perfluoroalkoxy resin are melt-processable and bond more tightly to the adhesive layer; ethylene-tetrafluoroethylene copolymer combines high strength and good flexibility, allowing users to flexibly choose according to actual demolding requirements and tooling shapes. The film thickness is limited to between 12.5 μm and 250 μm: if too thin, the film strength is insufficient, making it prone to breakage during application or demolding; if too thick, material costs increase and flexibility decreases, making it difficult to fit complex curved surfaces. This thickness range achieves material economy while ensuring sufficient mechanical strength and ease of operation. Furthermore, the extremely low surface energy and chemical inertness of the fluoroplastic film itself ensure that the release liner does not chemically adhere to the composite material parts at high temperatures, resulting in thorough demolding.

[0020] In one technical solution of the present invention, in step S100, the surface treatment includes at least one of corona treatment, plasma treatment, and chemical etching treatment.

[0021] Compared with existing technologies, the technical advantages achieved by this solution are as follows: Corona treatment introduces polar groups on the film surface through high-voltage discharge, significantly increasing surface energy; it is fast, low-cost, and suitable for continuous online production; Plasma treatment uses high-energy particles to bombard the surface, generating micro-roughness and chemically active sites, causing minimal damage to the film and producing uniform results, making it particularly suitable for precision films; Chemical etching can form a deep modified layer on the surface of extremely difficult-to-bond materials such as polytetrafluoroethylene, achieving the strongest adhesion strength. By employing at least one of these treatment methods, the chemical inert barrier of the fluoroplastic surface can be broken, allowing the subsequently coated silicone adhesive to form a strong physical anchor or chemical bond with the substrate, thereby preventing the adhesive layer from detaching from the substrate during high temperatures or peeling processes, ensuring the integrity of the release film and reliable demolding.

[0022] In one technical solution of the present invention, in step S300, the coating method is at least one of gravure coating, comma blade coating, transfer coating, and spraying; the coating dry weight is 5g / m²-100g / m², so that the thickness of the cured adhesive layer is 5μm-100μm.

[0023] Compared with existing technologies, this technical solution achieves the following advantages: gravure coating is suitable for high-precision, low-coat-weight uniform coating; comma blade coating is suitable for thicker coatings and has wide adaptability to adhesive viscosity; transfer coating can achieve double-sided or ultra-thin coatings; and spraying is suitable for coating three-dimensional shapes or discontinuous surfaces. The availability of multiple options allows this method to adapt to different production scales and product requirements. The dry coating weight is controlled between 5g / m² and 100g / m², corresponding to a cured adhesive layer thickness of 5μm to 100μm. If the adhesive layer is too thin, the adhesion is insufficient, and the release liner is prone to lifting or shifting on the tooling; if the adhesive layer is too thick, it wastes material and increases curing time, and the adhesive layer may suffer cohesive failure and residue during peeling. This reasonable range ensures sufficient bonding strength while achieving cost control and process stability.

[0024] In one technical solution of the present invention, in step S400, the curing temperature is 80℃-200℃ and the curing time is 0.5min-30min.

[0025] Compared with existing technologies, the technical advantages achieved by this solution are as follows: the specific temperature and time window fully activates the platinum catalyst, ensuring complete hydrosilylation and the formation of a highly cross-linked, heat-resistant network. Simultaneously, no small molecules are released during curing, preventing bubble formation. The optimized curing conditions ensure the cohesive strength of the adhesive layer, its adhesion to the substrate, and its dimensional stability at high temperatures, resulting in a reliable final product in composite material molding processes.

[0026] To achieve the third objective of this invention, the technical solution of this invention provides a high-temperature resistant coated release film, which is prepared by the preparation method of the high-temperature resistant coated release film as described in any of the above technical solutions.

[0027] Compared with existing technologies, the technical advantages achieved by this solution are as follows: Specifically, the product has a three-layer structure: a fluoroplastic release layer, an silicone adhesive layer, and a peelable protective film. During use, the protective film is peeled off, and the adhesive side is attached to the tooling surface, achieving rapid positioning without slippage or wrinkling. During the high-temperature curing process of the composite material, the fluoroplastic layer provides a non-stick surface, while the silicone layer firmly fixes the release film without migration or decomposition, resulting in a clean and uncontaminated surface after demolding. This product exists in solid film form, is solvent-free, has no VOC emissions, exhibits good storage stability, and can be cut to any size, significantly simplifying the complex application process of traditional liquid release agents and improving the efficiency and yield of composite material molding production.

[0028] The technical solution provided by this invention can achieve at least one of the following effects: (1) Excellent high temperature resistance and extremely low transfer pollution. The silicone adhesive system is adopted, and the polysiloxane and hydrogen-containing silicone oil undergo hydrosilylation reaction catalyzed by platinum catalyst. No small molecule by-products are released during the curing process. The cross-linked network formed is dense and has extremely high thermal stability. At the same time, no low molecular weight plasticizers or easily migrating silicone oil components are added to the silicone adhesive. The fillers are selected from heat-resistant materials such as silica, mica powder, and alumina. The above technical features work together to ensure that the adhesive layer does not decompose, soften, or release migration products at high temperatures above 200°C when the composite material is molded. This completely avoids the problems of silicone oil pollution, cratering, and poor adhesion that are common in traditional liquid release agents or condensation adhesives, ensuring that the surface of the composite material parts is clean and meets the requirements of subsequent coating, bonding and other secondary processing. (2) It has strong adhesion to fluoroplastic substrates and is more convenient to construct. By performing surface treatments such as corona, plasma or chemical etching on the fluoroplastic film, its surface energy is significantly improved. Combined with preferred methyl vinyl or methyl phenyl vinyl polysiloxane, the silicone adhesive forms a strong physical anchor or chemical bond with the fluoroplastic substrate. The preparation method includes a film coating process, that is, covering the adhesive layer with a PE release film. When using it, the user only needs to peel off the release film to directly stick the release film to the tooling surface. No additional coating or waiting for curing steps are required to achieve reliable positioning. It effectively prevents the film from wrinkling, slipping or falling off during the layup process, greatly simplifies the cumbersome construction process of multiple spraying of traditional liquid release agents and waiting for drying, and significantly improves the molding efficiency of composite materials. (3) The process is highly adaptable and the product performance is controllable. The preparation method of the high temperature resistant adhesive release film can be flexibly adjusted according to different tooling requirements, so that the final product can be customized for different composite material molding processes, such as prepreg, glass fiber impregnation, resin transfer molding, etc., and achieve the best cost while ensuring performance. (4) Environmentally friendly and safe to operate. The silicone adhesive is a solvent-free system. There is no emission of volatile organic compounds during the entire coating, curing and subsequent use process. This fundamentally avoids the harm to the health of operators and the pollution to the environment caused by traditional liquid release agents containing organic solvents. The product is in the form of a solid film. There is no risk of leakage during storage and transportation. The waste after use is only a solid film, which is easy to collect and dispose of, meeting the urgent needs of modern manufacturing industry for green and environmentally friendly materials. Detailed Implementation

[0029] The technical solutions of various embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments described in the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0030]

Example 1

[0031]

Example 2

[0032]

Example 3

[0033] S200. Prepare the silicone adhesive according to the proportions in Example 1.

[0034] S300: Using gravure coating, the silicone adhesive is evenly coated on one surface of the substrate, with a dry coating amount of 30g / m².

[0035] S400. Place the coated intermediate in an oven and cure it at 150°C for 5 minutes. Then cover it with a PE release film and roll it up to obtain a high-temperature resistant adhesive release film.

[0036]

Example 4

[0037] S200. Prepare the silicone adhesive according to the proportions of Example 2.

[0038] S300 uses a comma-shaped doctor blade coating method, with a coating dry weight of 60 g / m².

[0039] S400 is cured at 180℃ for 10 minutes, covered with PE release film, and rolled up to obtain a high-temperature resistant adhesive release film.

[0040] Comparative Example 1 A commercially available condensation-type silicone adhesive (containing solvent) was applied to a corona-treated PTFE film using the same coating process and cured at 150°C for 10 minutes (the solvent needs to be removed) to obtain a comparative release film.

[0041] Performance testing The release films prepared in Examples 3, 4, and Comparative Example 1 (all of which were adhered to the surface of steel plates after the release film was removed) were used for the following tests: 1. High-temperature stability test: The steel plate with the release film was placed in a 200℃ oven and heated for 2 hours, and the appearance changes were observed. Test results: The release films of Examples 3 and 4 were intact, without blistering, delamination, or adhesive leakage; the release film of Comparative Example 1 showed local blistering and yellowing of the adhesive layer.

[0042] 2. Demolding performance test: Epoxy resin prepreg was laid on the surface of the release liner, and vacuum bag molding was used. The curing temperature was 180℃ and the time was 2 hours. Demolding was performed after curing. Test results: In Examples 3 and 4, the composite material parts and the release liner could be easily peeled off from the steel plate surface together. The surface of the parts was smooth and there was no adhesive residue. In Comparative Example 1, the release liner was stuck to the steel plate in some areas and was difficult to peel off. Oily stains appeared on the surface of the parts.

[0043] 3. Transfer Contamination Test: The surface of the demolded parts was sprayed with a primer of the same color, and after curing, the adhesion was tested by cross-cut method, and the appearance of the paint film was observed. Test Results: The paint film adhesion of the parts in Examples 3 and 4 reached level 0 (GB / T 9286-2021), with no pinholes or fisheyes; the paint film of the part in Comparative Example 1 showed multiple pinholes, and the adhesion was only level 2.

[0044] According to the above test results, the high-temperature resistant adhesive release films provided in Examples 3 and 4 have a complete appearance after being heated at 200°C for 2 hours, with no blistering, delamination, or glue flow. In contrast, Comparative Example 1 showed localized blistering and yellowing of the adhesive layer, indicating that the release film of the present invention has excellent high-temperature stability. In the composite material molding demolding test at 180°C for 2 hours, Examples 3 and 4 could easily peel the composite material parts and the release film from the steel plate surface together, with a smooth surface and no adhesive residue. In contrast, Comparative Example 1 had some areas that were stuck to the steel plate and difficult to peel off, and oily stains appeared on the surface of the parts, proving that the demolding performance of the release film of the present invention is significantly improved compared to the comparative example. In the transfer contamination test, the adhesion of the parts of Examples 3 and 4 after being coated with primer reached level 0, with no defects such as pinholes or fisheyes. In contrast, the paint film of the parts of Comparative Example 1 showed multiple pinholes, and the adhesion was only level 2. This indicates that the release film of the present invention does not migrate low molecular weight substances during the high-temperature curing process and has no adverse effect on the subsequent coating process of the composite material parts. A comparison of Examples 3 and 4 shows that the release films prepared using different types of fluoroplastic films (polytetrafluoroethylene and perfluoroethylene propylene copolymer) and different ratios of silicone adhesives can all achieve consistent and excellent high-temperature release performance and low transfer contamination effect, indicating that the technical solution of the present invention has wide applicability and stable process repeatability.

[0045] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered exemplary and not restrictive in all respects. The scope of the invention is defined by the appended claims, not by the foregoing description, and thus all variations falling within the meaning and scope of the equivalents of the claims are intended to be included within the present invention.

[0046] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. An organosilicon adhesive, characterized in that, By weight, it includes: Polysiloxane, 80-120 parts by weight; Hydrogen-containing silicone oil, 0.5 parts by weight to 15 parts by weight; Platinum catalyst, 0.01 parts by weight to 2 parts by weight; Filler, 0 parts by weight - 50 parts by weight.

2. The silicone adhesive according to claim 1, characterized in that, The filler is selected from at least one of silica, mica powder, alumina, and carbon black.

3. The silicone adhesive according to claim 1, characterized in that, The polysiloxane is at least one of methyl vinyl polysiloxane and methyl phenyl vinyl polysiloxane.

4. A method for preparing a high-temperature resistant adhesive-coated release film, using the silicone adhesive as described in any one of claims 1-3, characterized in that, Includes the following steps: S100, Substrate preparation: Select a fluoroplastic film and perform surface treatment on it to obtain the substrate; S200, Adhesive preparation: Prepare the silicone adhesive according to the specified parts by weight; S300, Coating: The silicone adhesive is coated onto at least one surface of the substrate to obtain an intermediate; S400, Curing: The intermediate is subjected to curing and coating treatments in sequence to obtain a high-temperature resistant adhesive release film.

5. The method for preparing the high-temperature resistant adhesive-coated release film according to claim 4, characterized in that, In step S100, the fluoroplastic film is selected from at least one of polytetrafluoroethylene, perfluoroethylene-propylene copolymer, perfluoroalkoxy resin, and ethylene-tetrafluoroethylene copolymer film; the thickness of the fluoroplastic film is 12.5 μm-250 μm.

6. The method for preparing the high-temperature resistant adhesive-coated release film according to claim 4, characterized in that, In step S100, the surface treatment includes at least one of corona treatment, plasma treatment, and chemical etching treatment.

7. The method for preparing the high-temperature resistant adhesive-coated release film according to claim 4, characterized in that, In step S300, the coating method is at least one of gravure coating, comma blade coating, transfer coating, and spraying; the coating dry weight is 5g / m²-100g / m², so that the thickness of the cured adhesive layer is 5μm-100μm.

8. The method for preparing the high-temperature resistant adhesive-coated release film according to claim 4, characterized in that, In step S400, the curing temperature is 80℃-200℃ and the curing time is 0.5min-30min.

9. A high-temperature resistant adhesive-coated release film, characterized in that, The high-temperature resistant adhesive-coated release film is prepared by the method described in any one of claims 4-8.