High-elasticity oil-resistant expanded polytetrafluoroethylene sealing material and preparation method thereof

Abstract

The invention provides a high-elasticity oil-resistant expanded polytetrafluoroethylene sealing material and a manufacturing method thereof. The manufacturing method comprises the following steps: S10, providing an expanded polytetrafluoroethylene film; s20, the expanded polytetrafluoroethylene film is soaked in the fluorine-containing elastomer treating fluid, and pores of the expanded polytetrafluoroethylene film are filled with the fluorine-containing elastomer treating fluid; wherein the fluorine-containing elastomer treating fluid comprises the following components: a fluorine-containing elastomer, a solvent, a foaming agent and a vulcanizing agent; s30, the expanded polytetrafluoroethylene film is subjected to drying treatment; s40, the expanded polytetrafluoroethylene film is subjected to vulcanization treatment; s50, performing closed-cell foaming treatment on the expanded polytetrafluoroethylene film; and S60, after the expanded polytetrafluoroethylene film is cooled, the high-elasticity oil-resistant expanded polytetrafluoroethylene sealing material is obtained. According to the method, the expanded polytetrafluoroethylene sealing material with good oil resistance, rebound resilience and low density can be prepared.

Description

Technical Field

[0001] The invention relates to the technical field of polytetrafluoroethylene materials, and in particular to a highly elastic and oil-resistant expanded polytetrafluoroethylene sealing material and a manufacturing method thereof. Background Art

[0002] Expanded PTFE is a unique material with strong toughness and porosity that is made of 100% PTFE resin expanded by a special process. Expanded PTFE material not only maintains the unique properties of PTFE itself - excellent chemical stability (not affected by corrosion from general chemicals), extremely low friction coefficient, wide operating temperature and good aging resistance. Its multi-fiber structure makes it unimaginably tough as a sealing product. More importantly, it fundamentally solves the common problems of other types of PTFE sealing materials - creep and cold flow. Compared with pure PTFE sheets and filled PTFE sheets, its performance is greatly improved; therefore, it is widely used in aerospace, chemical engineering, pharmaceutical engineering and other fields.

[0003] However, compared with ordinary polytetrafluoroethylene (PTFE) materials, expanded polytetrafluoroethylene (ePTFE) materials are slightly worse in oil resistance. This is because during the preparation of the ePTFE material, it has undergone processes such as embryo making, extrusion, calendering and stretching, and a porous structure has been formed in the ePTFE material, which increases the surface area of ​​the ePTFE material. The ePTFE material exhibits high wettability and strong oil absorption, which enhances its ability to absorb liquids. Although the ePTFE material still has excellent performance in chemical resistance and has good tolerance to most organic matter and solvents, its oil resistance will decrease for certain types of oil substances, such as hydraulic oil, lubricating oil, fuel, etc. Therefore, in specific lubricating oil or oil contaminated environments, the ePTFE material needs to be modified to improve its oil resistance.

[0004] For example, the patent CN115819822B discloses a medium-resistant modified expanded polytetrafluoroethylene sealing material, which is prepared by stirring and mixing methyl acrylate, butyl methacrylate, and 120# solvent oil, and then adding initiator benzoyl peroxide to mix to obtain a treatment liquid; then the expanded polytetrafluoroethylene sheet is immersed in the treatment liquid, and finally the expanded polytetrafluoroethylene sheet is dried to obtain a medium-resistant modified expanded polytetrafluoroethylene sealing material. Although this modification method obtains certain medium resistance performance, the density of the ePTFE material is relatively large, the hardness is greatly improved, and the resilience is poor; in actual use, it cannot fit the material surface well, and a large sealing pressure needs to be applied to achieve the expected sealing effect. In addition, the resilience of the ePTFE material is poor, and the sealing performance life is lost quickly. At the same time, the material density is large, and the weight reduction effect cannot be achieved. Summary of the invention

[0005] The purpose of the present invention is to provide a method for producing a highly elastic and oil-resistant expanded polytetrafluoroethylene sealing material, which can produce an expanded polytetrafluoroethylene sealing material with good oil resistance and resilience and low density.

[0006] The present invention provides a method for preparing a highly elastic and oil-resistant expanded polytetrafluoroethylene sealing material, comprising the following steps:

[0007] S10: providing expanded polytetrafluoroethylene film;

[0008] S20: immersing the expanded polytetrafluoroethylene film in a fluorine-containing elastomer treatment liquid, so that the fluorine-containing elastomer treatment liquid fills the pores of the expanded polytetrafluoroethylene film; wherein the components of the fluorine-containing elastomer treatment liquid include a fluorine-containing elastomer, a solvent, a foaming agent and a vulcanizing agent;

[0009] S30: drying the expanded polytetrafluoroethylene film to remove the solvent in the fluorine-containing elastomer treatment liquid on the expanded polytetrafluoroethylene film;

[0010] S40: vulcanizing the expanded polytetrafluoroethylene film at a certain temperature and a certain pressure;

[0011] S50: performing closed-cell foaming treatment on the expanded polytetrafluoroethylene film at a certain temperature and a certain pressure;

[0012] S60: After the expanded polytetrafluoroethylene film is cooled, a highly elastic and oil-resistant expanded polytetrafluoroethylene sealing material is obtained.

[0013] In one achievable manner, the mass fractions of the components in the fluorine-containing elastomer treatment liquid are: 10% to 70% fluorine-containing elastomer, 50% to 90% solvent, 1% to 20% foaming agent, and 0.5% to 5% vulcanizing agent.

[0014] In one achievable manner, the fluorine-containing elastomer is one or more of tetrafluoroethylene-ethylene copolymer, tetrafluoroethylene-hexafluoropropylene copolymer and trifluorochloroethylene-ethylene copolymer, trifluoroethanol acrylate, trifluoroethyl methacrylate, tetrafluoroethylene, dimethylsiloxane, styrene-based thermoplastic elastomer, thermoplastic polyurethane elastomer, polyolefin-based thermoplastic elastomer and polyester elastomer.

[0015] In one achievable manner, the solvent is one or more of toluene, xylene, dimethyl sulfoxide, dimethylformamide, ethyl acetate, carbon tetrafluoride, trifluoroacetone, trifluoromethane, trifluoroethyl ether, dichloromethane and chloroform.

[0016] In one achievable manner, the blowing agent is one or more of 2,2'-azobisisobutyronitrile, barium azodicarboxylate, azoaminobenzene, p-toluenesulfonylhydrazide, trihydrazinotriazine, polysiloxane-polyalkoxy ether copolymer, cyclopentane, HCFC-14LB, CFC-11 and HFC-134A.

[0017] In one achievable manner, the vulcanizing agent is one or more of a platinum catalyst, an alkaline catalyst, a bis-24 vulcanizing agent, a bis-25 vulcanizing agent and phenol peroxide.

[0018] In one achievable manner, the drying treatment temperature of the expanded polytetrafluoroethylene film is 40°C to 120°C, the vulcanization treatment temperature of the expanded polytetrafluoroethylene film is 80°C to 180°C, and the closed-cell foaming treatment temperature of the expanded polytetrafluoroethylene film is 130°C to 280°C; the drying treatment temperature, vulcanization treatment temperature and closed-cell foaming treatment temperature of the expanded polytetrafluoroethylene film increase in sequence.

[0019] In one achievable manner, the vulcanization treatment pressure of the expanded polytetrafluoroethylene film is 0.2-5 MPa, and the vulcanization treatment time is 0.2-5 hours; the closed-cell foaming treatment pressure of the expanded polytetrafluoroethylene film is 0.2-5 MPa, and the closed-cell foaming treatment time is 0.5-2 hours.

[0020] In one achievable manner, in the above step S30, before or after the expanded polytetrafluoroethylene film is dried, the expanded polytetrafluoroethylene film is further cut and laminated to stack multiple layers of the expanded polytetrafluoroethylene film together.

[0021] The present invention also provides a high-elasticity and oil-resistant expanded polytetrafluoroethylene sealing material, which is manufactured by adopting the manufacturing method of the high-elasticity and oil-resistant expanded polytetrafluoroethylene sealing material.

[0022] The method for preparing the highly elastic and oil-resistant expanded polytetrafluoroethylene sealing material provided by the present invention comprises the following steps: immersing the expanded polytetrafluoroethylene film in a fluorine-containing elastomer treatment liquid composed of a fluorine-containing elastomer, a solvent, a foaming agent and a vulcanizing agent, and then subjecting the expanded polytetrafluoroethylene film to vulcanization treatment and closed-cell foaming treatment, thereby obtaining an expanded polytetrafluoroethylene sealing material having good oil resistance and resilience and low density. At the same time, this modification method does not destroy the softness of the expanded polytetrafluoroethylene material, so that the expanded polytetrafluoroethylene material can be adapted to various sealing interfaces with different flatnesses and achieve the expected sealing effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 The figure is a schematic diagram of the production process of the highly elastic and oil-resistant expanded polytetrafluoroethylene sealing material in the embodiment of the present invention.

[0024] Figure 2 Schematic diagram of the structure of the expanded polytetrafluoroethylene film during the impregnation treatment in an embodiment of the present invention.

[0025] Figure 3 This is an electron microscope image of the internal structure of the expanded polytetrafluoroethylene sealing material in the first embodiment of the present invention.

[0026] Figure 4 This is an electron microscope image of the internal structure of the expanded polytetrafluoroethylene sealing material in the second embodiment of the present invention.

[0027] Figure 5 This is an electron microscope image of the internal structure of the expanded polytetrafluoroethylene sealing material in the third embodiment of the present invention. DETAILED DESCRIPTION

[0028] The specific implementation of the present invention is further described in detail below in conjunction with the accompanying drawings and examples. The following examples are used to illustrate the present invention, but are not intended to limit the scope of the present invention.

[0029] The terms "first", "second", "third", "fourth" and the like (if any) in the description and claims of the present invention are used to distinguish similar objects and are not necessarily used to describe a particular sequence or order.

[0030] The directional words such as up, down, left, right, front, back, top, bottom, etc. (if any) involved in the specification and claims of the present invention are defined by the positions of the structures in the drawings and the positions of the structures relative to each other, and are only for the clarity and convenience of expressing the technical solution. It should be understood that the use of directional words should not limit the scope of protection claimed in the present invention.

[0031] like Figure 1 As shown, the embodiment of the present invention provides a method for manufacturing a highly elastic and oil-resistant expanded polytetrafluoroethylene sealing material, which is used to manufacture a highly elastic and oil-resistant expanded polytetrafluoroethylene sealing material. The method for manufacturing a highly elastic and oil-resistant expanded polytetrafluoroethylene sealing material comprises the following steps:

[0032] S10: providing an expanded polytetrafluoroethylene film, which has a porous structure (since the expanded polytetrafluoroethylene film is made of polytetrafluoroethylene resin by special processing methods such as stretching, the expanded polytetrafluoroethylene film has a large number of pores, and the pores are formed between fibers in the expanded polytetrafluoroethylene film).

[0033] S20: Immersing the expanded polytetrafluoroethylene film in a fluorine-containing elastomer treatment liquid so that the fluorine-containing elastomer treatment liquid fills the pores of the expanded polytetrafluoroethylene film (i.e., during the immersion process, the fluorine-containing elastomer treatment liquid will enter the pores of the expanded polytetrafluoroethylene film); wherein the components of the fluorine-containing elastomer treatment liquid include fluorine-containing elastomer, solvent, foaming agent and vulcanizing agent, and the fluorine-containing elastomer treatment liquid is obtained by mixing the fluorine-containing elastomer, solvent, foaming agent and vulcanizing agent.

[0034] S30: Drying the expanded polytetrafluoroethylene film to remove the solvent in the fluoroelastomer treatment liquid on the expanded polytetrafluoroethylene film; in this step, since the solvent in the fluoroelastomer treatment liquid is removed, on the one hand, the solute in the fluoroelastomer treatment liquid (including fluoroelastomer, foaming agent and vulcanizing agent) can remain in the pores of the expanded polytetrafluoroethylene film, preventing the solute from flowing out of the pores of the expanded polytetrafluoroethylene film with the solvent (if the solvent is not removed, the fluoroelastomer treatment liquid on the expanded polytetrafluoroethylene film is still in a flowing liquid state, and in the subsequent operation process, the solute may flow out of the pores with the solvent, that is, the amount of solute in the pores is reduced, thereby affecting the product effect), and on the other hand, it is convenient for the subsequent vulcanization treatment and closed-cell foaming treatment.

[0035] S40: vulcanization treatment is performed on the expanded polytetrafluoroethylene film at a certain temperature and pressure. Since there are fluorine-containing elastomers and vulcanizing agents in the pores of the expanded polytetrafluoroethylene film, during the vulcanization treatment, the fluorine-containing elastomer is promoted by the vulcanizing agent, and chemical bonds are cross-linked between the fluorine-containing elastomer and the expanded polytetrafluoroethylene film and compounded together to form a three-dimensional network structure.

[0036] S50: Under a certain temperature and a certain pressure, the expanded polytetrafluoroethylene film is subjected to a closed-cell foaming treatment. Since there is a foaming agent in the pores of the expanded polytetrafluoroethylene film, during the foaming process, the foaming agent decomposes and produces gas after reaching the decomposition temperature, thereby generating closed bubbles in the expanded polytetrafluoroethylene film. It should be noted that the closed-cell foaming treatment needs to be carried out under a certain pressure to prevent the gas generated by the foaming agent from flushing the fluorinated elastomer out of the pores of the expanded polytetrafluoroethylene film during the foaming process and affecting its oleophobic properties (during closed-cell foaming, the gas generated by the decomposition of the foaming agent has a relatively high pressure; if no external pressure is applied, the fluorinated elastomer in the pores may be carried out of the pores under the pressure shock of the decomposed gas).

[0037] S60: After the expanded polytetrafluoroethylene film is cooled (the cooling process may be room temperature cooling), the expanded polytetrafluoroethylene film is cut into a desired shape, so as to obtain a highly elastic and oil-resistant expanded polytetrafluoroethylene sealing material.

[0038] Through the above processing steps, the oil resistance and resilience of expanded polytetrafluoroethylene sealing materials can be greatly improved, and the density of the material can be reduced. The specific principles are:

[0039] (1) Principles for improving the oil resistance of materials: a. Since the fluorinated elastomer is filled in the pores of the expanded polytetrafluoroethylene film, that is, the fluorinated elastomer blocks the pores of the expanded polytetrafluoroethylene film, the expanded polytetrafluoroethylene film is transformed from a porous structure to a dense structure, thereby reducing its oil absorption capacity and improving its oleophobic performance; b. Since the fluorinated elastomer has an oleophobic fluorinated group, adding the fluorinated elastomer as a filler to the expanded polytetrafluoroethylene film can improve the oleophobic performance of the expanded polytetrafluoroethylene film, thereby improving its oil resistance (not only can improve its oil resistance, but also improve its resistance to other media).

[0040] (2) Principles for improving the resilience of materials: a. Fluorine-containing elastomers themselves have good elasticity, so adding fluorine-containing elastomers as fillers to expanded polytetrafluoroethylene films can improve the resilience of expanded polytetrafluoroethylene films; b. During the vulcanization process, under the promotion of the vulcanizing agent, chemical bonds are cross-linked between the fluorine-containing elastomer and the expanded polytetrafluoroethylene film to form a three-dimensional network structure, thereby reducing the plasticity of the material and further improving the resilience of the material; c. During the foaming process, the foaming agent decomposes to produce gas, which produces closed bubbles in the expanded polytetrafluoroethylene film, thereby further improving the resilience of the material.

[0041] (3) Principle of reducing material density: During the foaming process, closed bubbles are generated in the expanded polytetrafluoroethylene film, which increases the volume of the expanded polytetrafluoroethylene film and reduces its density (using closed-cell foaming to fill a small amount of filler, which can fill most of the pores in the expanded polytetrafluoroethylene film and reduce its density).

[0042] The method for preparing the highly elastic and oil-resistant expanded polytetrafluoroethylene sealing material provided in this embodiment is to immerse the expanded polytetrafluoroethylene film in a fluorine-containing elastomer treatment liquid composed of a fluorine-containing elastomer, a solvent, a foaming agent and a vulcanizing agent, and then perform vulcanization treatment and closed-cell foaming treatment to obtain an expanded polytetrafluoroethylene sealing material with good oil resistance and resilience and low density. At the same time, this modification method does not destroy the softness of the expanded polytetrafluoroethylene material, so that it can adapt to various sealing interfaces with different flatness and achieve the expected sealing effect.

[0043] As an implementation mode, the mass fractions of the components in the fluorine-containing elastomer treatment liquid are: 10% to 70% fluorine-containing elastomer, 50% to 90% solvent, 1% to 20% foaming agent, and 0.5% to 5% vulcanizing agent.

[0044] Preferably, the mass fractions of the components in the fluorine-containing elastomer treatment liquid are: 20% to 50% fluorine-containing elastomer, 60% to 80% solvent, 5% to 8% foaming agent, and 1% to 3% vulcanizing agent.

[0045] As an embodiment, the fluorine-containing elastomer is a combination of one or more of tetrafluoroethylene-ethylene copolymer, tetrafluoroethylene-hexafluoropropylene copolymer, trifluorochloroethylene-ethylene copolymer, trifluoroethanol acrylate, trifluoroethyl methacrylate, tetrafluoroethylene, dimethylsiloxane, styrene-based thermoplastic elastomer, thermoplastic polyurethane elastomer, polyolefin-based thermoplastic elastomer, and polyester elastomer. Of course, the types of fluorine-containing elastomers are not limited thereto.

[0046] As an embodiment, the solvent is a combination of one or more of toluene, xylene, dimethyl sulfoxide, dimethylformamide, ethyl acetate, carbon tetrafluoride, trifluoroacetone, trifluoromethane, trifluoroethyl ether, dichloromethane and chloroform. Of course, the type of solvent is not limited thereto.

[0047] As an embodiment, the blowing agent is a combination of one or more of 2,2'-azobisisobutyronitrile, barium azodicarboxylate, azoaminobenzene, p-toluenesulfonylhydrazide, trihydrazinotriazine, polysiloxane-polyalkoxy ether copolymer, cyclopentane, HCFC-14LB (i.e., monofluorodichloroethane), CFC-11 (i.e., monofluorotrichloromethane) and HFC-134A (i.e., tetrafluoroethane). Of course, the types of blowing agents are not limited thereto.

[0048] As an embodiment, the vulcanizing agent is one or more of a platinum catalyst, an alkaline catalyst, a bis-24 vulcanizing agent (i.e., 2,4-dichloroperoxybenzoyl), a bis-25 vulcanizing agent (i.e., 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane), and phenol peroxide. Of course, the type of the vulcanizing agent is not limited thereto.

[0049] As an embodiment, a certain amount of high modulus non-fluorine-containing elastomer, such as SEBS (i.e., a linear triblock copolymer with polystyrene as the terminal segment and ethylene-butene copolymer obtained by hydrogenating polybutadiene as the middle elastic block; referred to as hydrogenated styrene-butadiene block copolymer) can also be added to the fluorine-containing elastomer treatment liquid to further improve the rebound performance of the material.

[0050] As an embodiment, in the above step S20, the immersion time of the expanded polytetrafluoroethylene film in the fluorine-containing elastomer treatment liquid is 3 to 120 seconds, so that the fluorine-containing elastomer treatment liquid can fully fill the pores of the expanded polytetrafluoroethylene film. Preferably, the immersion time is 10 to 30 seconds.

[0051] like Figure 2As shown, as an embodiment, in the above step S20, the specific method of the impregnation treatment can be: unwinding the expanded polytetrafluoroethylene film 1 through the unwinding device 3, and applying appropriate tension to rewind the expanded polytetrafluoroethylene film 1 through the rewinding device 4. The impregnation container 2 stores a fluorine-containing elastomer treatment liquid. During the unwinding process, the expanded polytetrafluoroethylene film 1 passes through and is immersed in the fluorine-containing elastomer treatment liquid in the impregnation container 2; by adjusting the rewinding speed of the expanded polytetrafluoroethylene film 1, the immersion time of the expanded polytetrafluoroethylene film in the fluorine-containing elastomer treatment liquid is controlled (the slower the rewinding speed, the longer the immersion time). As an embodiment, the rewinding speed is 0.5 to 3 m / min, preferably 1 to 2 m / min.

[0052] As an implementation mode, the drying treatment temperature, vulcanization treatment temperature and closed-cell foaming treatment temperature of the expanded polytetrafluoroethylene film are increased in sequence, that is, the closed-cell foaming treatment temperature is greater than the vulcanization treatment temperature (closed-cell foaming can only be formed when the vulcanization treatment temperature is lower than the closed-cell foaming treatment temperature), and the vulcanization treatment temperature is greater than the drying treatment temperature; wherein, the vulcanization treatment temperature is the temperature of the elastomer vulcanization system, and the closed-cell foaming treatment temperature is the decomposition temperature of the foaming agent.

[0053] As an embodiment, in the above step S30, the drying temperature of the expanded polytetrafluoroethylene film is 40°C to 120°C, and the drying time is 5 to 24 hours. Preferably, the drying temperature is 50°C to 100°C, and the drying time is 8 to 12 hours. During drying, the expanded polytetrafluoroethylene film can be placed in an oven for low-temperature baking to remove the solvent.

[0054] As an embodiment, in the above step S40, the vulcanization temperature of the expanded polytetrafluoroethylene film is 80°C to 180°C, the vulcanization pressure is 0.2 to 5 MPa, and the vulcanization time is 0.2 to 5 hours. Preferably, the vulcanization temperature is 100°C to 150°C, the vulcanization pressure is 1 to 3 MPa, and the vulcanization time is 1 to 3 hours.

[0055] As an embodiment, in the above step S50, the closed-cell foaming treatment temperature of the expanded polytetrafluoroethylene film is 130°C to 280°C, the closed-cell foaming treatment pressure is 0.2 to 5 MPa, and the closed-cell foaming treatment time is 0.5 to 2 hours. Preferably, the closed-cell foaming treatment temperature is 160°C to 250°C, and the closed-cell foaming treatment pressure is 1 to 3 MPa.

[0056] As an embodiment, the vulcanization process and the closed-cell foaming process of the expanded polytetrafluoroethylene film are both carried out in a flat vulcanizer, that is, the expanded polytetrafluoroethylene film adopts flat vulcanization and flat foaming. Specifically, in the above step S40, the expanded polytetrafluoroethylene film after the solvent is removed is placed in a flat vulcanizer and a certain pressure and temperature are applied to perform vulcanization. In the above step S50, the vulcanized expanded polytetrafluoroethylene film is placed in a flat vulcanizer and a certain pressure and temperature are applied to perform closed-cell foaming.

[0057] As an embodiment, in the above-mentioned step S30, before or after the expanded polytetrafluoroethylene film is dried (preferably before the expanded polytetrafluoroethylene film is dried), the expanded polytetrafluoroethylene film is also cut and laminated to stack multiple layers of expanded polytetrafluoroethylene film together, so that the stacking thickness of the multiple layers of expanded polytetrafluoroethylene film reaches the required thickness requirement (that is, the thicker the required sealing material thickness, the greater the number of laminated films).

[0058] The embodiment of the present invention further provides a highly elastic and oil-resistant expanded polytetrafluoroethylene sealing material, which is manufactured by the above-mentioned manufacturing method of the highly elastic and oil-resistant expanded polytetrafluoroethylene sealing material.

[0059] The method for preparing the highly elastic and oil-resistant expanded polytetrafluoroethylene sealing material provided in the embodiment of the present invention is to immerse the expanded polytetrafluoroethylene film in a fluorine-containing elastomer treatment liquid composed of a fluorine-containing elastomer, a solvent, a foaming agent and a vulcanizing agent, and then perform a vulcanization treatment and a closed-cell foaming treatment to obtain an expanded polytetrafluoroethylene sealing material with good oil resistance and resilience and low density. At the same time, this modification method does not destroy the softness of the expanded polytetrafluoroethylene material, so that it can adapt to various sealing interfaces with different flatnesses and achieve the expected sealing effect.

[0060] Embodiment 1

[0061] (1) Preparation of fluorine-containing elastomer treatment liquid: 10 g of tetrafluoroethylene-ethylene copolymer, 10 g of styrene-based thermoplastic elastomer, 5 g of SEBS, 70 g of toluene, 1.8 g of 2,2'-azobisisobutyronitrile, and 7.5 g of a basic catalyst were mixed to prepare a fluorine-containing elastomer treatment liquid.

[0062] (2) Film impregnation: The expanded polytetrafluoroethylene film is unwound at a speed of 1 m / min, passed through a fluorine-containing elastomer treatment liquid, and rewound with appropriate tension.

[0063] (3) Cutting and laminating: Cut the rolled expanded polytetrafluoroethylene film and laminate it into an expanded polytetrafluoroethylene material with a thickness of 1.0 mm.

[0064] (4) Low-temperature solvent removal: The laminated expanded polytetrafluoroethylene material is placed in an oven and baked at 60°C for 3 hours to remove the solvent.

[0065] (5) Plate vulcanization: The expanded polytetrafluoroethylene material with the solvent removed is placed in a plate vulcanizer and a pressure of 0.2 MPa is applied, and the vulcanization treatment is carried out at 100°C for 0.5 h.

[0066] (6) Flat-plate foaming: Place the vulcanized expanded polytetrafluoroethylene material into a flat-plate vulcanizer and apply a pressure of 1 MPa, and perform closed-cell foaming at 140°C for 1 hour.

[0067] (7) Cooling and cutting: The expanded polytetrafluoroethylene material is cooled at room temperature and then cut to obtain the expanded polytetrafluoroethylene sealing material of the desired shape.

[0068] The expanded polytetrafluoroethylene sealing material was sampled and then subjected to electron microscope test, oil resistance test (specifically contact angle test) and rebound performance test (specifically dry stress relaxation rate test).

[0069] Embodiment 2

[0070] (1) Preparation of fluorine-containing elastomer treatment liquid: 8 g of trifluoroethyl methacrylate, 10 g of dimethylsiloxane, 15 g of trifluoroethanol acrylate, 65 g of a mixed solution of toluene and dimethylformamide, 3 g of barium azodicarboxylate, and 3 g of bis-24 vulcanizing agent were mixed to prepare a fluorine-containing elastomer treatment liquid.

[0071] (2) Film impregnation: The expanded polytetrafluoroethylene film is unwound at a speed of 2 m / min, passed through a fluorine-containing elastomer treatment liquid, and rewound with appropriate tension.

[0072] (3) Cutting and laminating: Cut the rolled expanded polytetrafluoroethylene film and laminate it into an expanded polytetrafluoroethylene material with a thickness of 1.5 mm.

[0073] (4) Low-temperature solvent removal: The laminated expanded polytetrafluoroethylene material is placed in an oven and baked at 70°C for 6 hours to remove the solvent.

[0074] (5) Plate vulcanization: The expanded polytetrafluoroethylene material with the solvent removed is placed in a plate vulcanizer and a pressure of 1.5 MPa is applied, and the vulcanization treatment is carried out at 130°C for 1 hour.

[0075] (6) Flat plate foaming: Place the vulcanized expanded polytetrafluoroethylene material into a flat plate vulcanizer and apply a pressure of 1 MPa to perform closed-cell foaming at 200°C for 2 hours.

[0076] (7) Cooling and cutting: The expanded polytetrafluoroethylene material is cooled at room temperature and then cut to obtain the expanded polytetrafluoroethylene sealing material of the desired shape.

[0077] The expanded polytetrafluoroethylene sealing material was sampled and then subjected to electron microscope test, oil resistance test (specifically contact angle test) and rebound performance test (specifically dry stress relaxation rate test).

[0078] Embodiment 3

[0079] (1) Preparation of fluorine-containing elastomer treatment liquid: 15 g of tetrafluoroethylene-ethylene copolymer, 10 g of tetrafluoroethylene-hexafluoropropylene copolymer, 5 g of thermoplastic polyurethane elastomer, 70 g of a mixture of xylene and dimethyl sulfoxide, 5 g of a polysiloxane-polyalkoxy ether copolymer, and 1 g of phenol peroxide are mixed to prepare a fluorine-containing elastomer treatment liquid.

[0080] (2) Film impregnation: The expanded polytetrafluoroethylene film is unwound at a speed of 1.5 m / min, passed through a fluorine-containing elastomer treatment liquid, and reeled up with appropriate tension.

[0081] (3) Cutting and laminating: Cut the rolled expanded polytetrafluoroethylene film and laminate it into an expanded polytetrafluoroethylene material with a thickness of 2.0 mm.

[0082] (4) Low-temperature solvent removal: The laminated expanded polytetrafluoroethylene material is placed in an oven and baked at 90°C for 6 hours to remove the solvent.

[0083] (5) Plate vulcanization: The expanded polytetrafluoroethylene material with the solvent removed is placed in a plate vulcanizer and a pressure of 2 MPa is applied, and the vulcanization treatment is carried out at 160°C for 1 hour.

[0084] (6) Flat-plate foaming: Place the vulcanized expanded polytetrafluoroethylene material into a flat-plate vulcanizer and apply a pressure of 2 MPa to perform closed-cell foaming at 220°C for 2 hours.

[0085] (7) Cooling and cutting: The expanded polytetrafluoroethylene material is cooled at room temperature and then cut to obtain the expanded polytetrafluoroethylene sealing material of the desired shape.

[0086] The expanded polytetrafluoroethylene sealing material was sampled and then subjected to electron microscope test, oil resistance test (specifically contact angle test) and rebound performance test (specifically dry stress relaxation rate test).

[0087] Comparative Example 1

[0088] (1) Preparation of fluorine-containing elastomer treatment liquid: 10 g of polyolefin thermoplastic elastomer, 10 g of polyester elastomer, 10 g of thermoplastic polyurethane elastomer, 70 g of a mixture of xylene and dimethyl sulfoxide, 5 g of a polysiloxane-polyalkoxy ether copolymer, and 1 g of phenol peroxide are mixed to prepare a fluorine-containing elastomer treatment liquid.

[0089] (2) Film impregnation: The expanded polytetrafluoroethylene film is unwound at a speed of 1.5 m / min, passed through a fluorine-containing elastomer treatment liquid, and reeled up with appropriate tension.

[0090] (3) Cutting and laminating: Cut the rolled expanded polytetrafluoroethylene film and laminate it into an expanded polytetrafluoroethylene material with a thickness of 1.5 mm.

[0091] (4) Low-temperature solvent removal: The laminated expanded polytetrafluoroethylene material is placed in an oven and baked at 90°C for 6 hours to remove the solvent.

[0092] (5) Plate vulcanization: The expanded polytetrafluoroethylene material with the solvent removed is placed in a plate vulcanizer and a pressure of 2 MPa is applied, and the vulcanization treatment is carried out at 120°C for 1 hour.

[0093] (6) Flat-plate foaming: Place the vulcanized expanded polytetrafluoroethylene material into a flat-plate vulcanizer, without applying pressure, and perform closed-cell foaming at 220°C for 2 hours.

[0094] (7) Cooling and cutting: The expanded polytetrafluoroethylene material is cooled at room temperature and then cut to obtain the expanded polytetrafluoroethylene sealing material of the desired shape.

[0095] The expanded polytetrafluoroethylene sealing material was sampled and subjected to an oil resistance test (specifically a contact angle test) and a rebound performance test (specifically a dry stress relaxation rate test).

[0096] Test results:

[0097] (1) Electron microscopic test results: The expanded polytetrafluoroethylene sealing materials prepared in Examples 1 to 3 were analyzed by electron microscopy. Figures 3 to 5 It can be seen from the electron microscope images shown that the expanded polytetrafluoroethylene sealing materials prepared in Examples 1 to 3 all have a good closed-cell foaming structure.

[0098] (2) Oil resistance test (specifically contact angle test): The expanded polytetrafluoroethylene sealing materials prepared in Examples 1 to 3 and Comparative Example 1 were respectively subjected to RP-3 aviation kerosene and lubricating oil contact angle tests (the larger the contact angle, the better the oleophobic performance). The test results are shown in the following table:

[0099] Serial number RP-3 contact angle (°) Lubricating oil contact angle (°) Embodiment 1 155 148 Embodiment 2 139 145 Embodiment 3 142 150 Comparative Example 1 70 68

[0100] As can be seen from the above table, the expanded polytetrafluoroethylene sealing materials of Examples 1 to 3 have a large contact angle for RP-3 aviation kerosene and lubricating oil, indicating that they have good oleophobic properties and oil resistance. The expanded polytetrafluoroethylene sealing material of Comparative Example 1 has a smaller contact angle for RP-3 aviation kerosene and lubricating oil, indicating that its oleophobic properties and oil resistance are relatively poor. This is because: in the flat foaming process of Comparative Example 1, the foaming process is not carried out under a certain pressure, so that the gas generated by the foaming agent flushes the fluorinated elastomer out of the pores of the expanded polytetrafluoroethylene film, and the expanded polytetrafluoroethylene sealing material does not form a closed-cell foaming structure, so that its oleophobic properties and oil resistance are poor.

[0101] (3) Rebound performance test (specifically dry stress relaxation rate test): The expanded polytetrafluoroethylene sealing materials prepared in Examples 1 to 3 and Comparative Example 1 were tested for dry stress relaxation rate (the smaller the dry stress relaxation rate, the better the rebound performance). The test steps are: Place the expanded polytetrafluoroethylene sealing material in a preheated compression device, pressurize the expanded polytetrafluoroethylene sealing material at the test temperature to a load of 5 MPa, and read the initial compression stress; read the compression stress of the material again after 24 hours, and the test is completed. Calculate the dry stress relaxation rate R(t):

[0102]

[0103] Where: σ0 is the initial compressive stress; σ t is the minimum compressive stress during the test.

[0104] The test results are shown in the following table:

[0105] Serial number Initial thickness Thickness after test Initial stress Minimum stress Dry stress relaxation rate Embodiment 1 1.02mm 0.97mm 5MPa 4.58MPa 8.4％ Embodiment 2 1.53mm 1.43mm 5MPa 4.65MPa 7％ Embodiment 3 2.02mm 1.86mm 5MPa 4.76MPa 4.8％ Comparative Example 1 1.55mm 0.89mm 5MPa 2.56MPa 48.8％

[0106] As can be seen from the above table, the dry stress relaxation rates of the expanded polytetrafluoroethylene sealing materials of Examples 1 to 3 are all less than 10% (the dry stress relaxation rate is less than 40% for qualified), and all three have good resilience performance. However, the dry stress relaxation rate of the expanded polytetrafluoroethylene sealing material of Comparative Example 1 is greater than 40%, and the resilience performance is relatively poor. This is because: in the flat foaming process of Comparative Example 1, the foaming process is not carried out under a certain pressure, so that the gas generated by the foaming agent flushes the fluorine-containing elastomer with good elasticity out of the pores of the expanded polytetrafluoroethylene film, and no closed-cell foaming structure is formed in the expanded polytetrafluoroethylene sealing material, so that its resilience performance is poor.

[0107] The above are only specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art who is familiar with the technical field can easily think of changes or substitutions within the technical scope disclosed by the present invention, which should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A method for producing a highly elastic and oil-resistant expanded polytetrafluoroethylene sealing material, characterized in that: The following steps are involved: S10: providing expanded polytetrafluoroethylene film; S20: immersing the expanded polytetrafluoroethylene film in a fluorine-containing elastomer treatment liquid, so that the fluorine-containing elastomer treatment liquid fills the pores of the expanded polytetrafluoroethylene film; wherein the components of the fluorine-containing elastomer treatment liquid include a fluorine-containing elastomer, a solvent, a foaming agent and a vulcanizing agent; S30: drying the expanded polytetrafluoroethylene film to remove the solvent in the fluorine-containing elastomer treatment liquid on the expanded polytetrafluoroethylene film; S40: vulcanizing the expanded polytetrafluoroethylene film at a certain temperature and a certain pressure; S50: performing closed-cell foaming treatment on the expanded polytetrafluoroethylene film at a certain temperature and a certain pressure; S60: After the expanded polytetrafluoroethylene film is cooled, a highly elastic and oil-resistant expanded polytetrafluoroethylene sealing material is obtained.

2. The method for producing a highly elastic and oil-resistant expanded polytetrafluoroethylene sealing material according to claim 1, characterized in that: The mass fractions of the components in the fluorine-containing elastomer treatment liquid are: 10% to 70% of fluorine-containing elastomer, 50% to 90% of solvent, 1% to 20% of foaming agent, and 0.5% to 5% of vulcanizing agent.

3. The method for producing a highly elastic and oil-resistant expanded polytetrafluoroethylene sealing material according to claim 1, characterized in that: The fluorine-containing elastomer is one or more of tetrafluoroethylene-ethylene copolymer, tetrafluoroethylene-hexafluoropropylene copolymer, trifluorochloroethylene-ethylene copolymer, trifluoroethanol acrylate, trifluoroethyl methacrylate, tetrafluoroethylene, dimethylsiloxane, styrene-based thermoplastic elastomer, thermoplastic polyurethane elastomer, polyolefin-based thermoplastic elastomer and polyester elastomer.

4. The method for producing a highly elastic and oil-resistant expanded polytetrafluoroethylene sealing material according to claim 1, characterized in that: The solvent is one or more of toluene, xylene, dimethyl sulfoxide, dimethylformamide, ethyl acetate, carbon tetrafluoride, trifluoroacetone, trifluoromethane, trifluoroethyl ether, dichloromethane and chloroform.

5. The method for producing a highly elastic and oil-resistant expanded polytetrafluoroethylene sealing material according to claim 1, characterized in that: The foaming agent is one or more of 2,2'-azobisisobutyronitrile, barium azodicarboxylate, azoaminobenzene, p-toluenesulfonylhydrazide, trihydrazinotriazine, polysiloxane-polyalkoxy ether copolymer, cyclopentane, HCFC-14LB, CFC-11 and HFC-134A.

6. The method for producing a highly elastic and oil-resistant expanded polytetrafluoroethylene sealing material according to claim 1, characterized in that: The vulcanizing agent is one or more of a platinum catalyst, an alkaline catalyst, a bis-24 vulcanizing agent, a bis-25 vulcanizing agent and phenol peroxide.

7. The method for producing a highly elastic and oil-resistant expanded polytetrafluoroethylene sealing material according to claim 1, characterized in that: The drying treatment temperature of the expanded polytetrafluoroethylene film is 40°C to 120°C, the vulcanization treatment temperature of the expanded polytetrafluoroethylene film is 80°C to 180°C, and the closed-cell foaming treatment temperature of the expanded polytetrafluoroethylene film is 130°C to 280°C; the drying treatment temperature, vulcanization treatment temperature and closed-cell foaming treatment temperature of the expanded polytetrafluoroethylene film increase in sequence.

8. The method for producing a highly elastic and oil-resistant expanded polytetrafluoroethylene sealing material according to claim 1, characterized in that: The vulcanization treatment pressure of the expanded polytetrafluoroethylene film is 0.2-5Mpa, and the vulcanization treatment time is 0.2-5 hours; the closed-cell foaming treatment pressure of the expanded polytetrafluoroethylene film is 0.2-5Mpa, and the closed-cell foaming treatment time is 0.5-2 hours.

9. The method for producing a highly elastic and oil-resistant expanded polytetrafluoroethylene sealing material according to any one of claims 1 to 8, characterized in that: In the above step S30, before or after the expanded polytetrafluoroethylene film is dried, the expanded polytetrafluoroethylene film is cut and laminated to stack multiple layers of the expanded polytetrafluoroethylene film together.

10. A highly elastic and oil-resistant expanded polytetrafluoroethylene sealing material, characterized in that: The sealing material is made by the method for making a highly elastic and oil-resistant expanded polytetrafluoroethylene sealing material as described in any one of claims 1 to 9.

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