Preparation method of flexible graphite gasket and application of flexible graphite gasket in balance sealing ring

Abstract

The invention relates to the field of sealing materials, and provides a preparation method of a flexible graphite gasket and application of the flexible graphite gasket in a balance sealing ring. The preparation method comprises the following steps: 1) preparing a polyacrylate solution by taking methyl methacrylate, ethyl acrylate and cinnamyl alcohol as monomers; (2) mixing a polyacrylate solution with a silanol hydroxyl-terminated organic silicon resin solution, immersing a graphite gasket prepared from expanded graphite into the mixture, adding an amine curing agent, and pressurizing and impregnating; and 3) taking out the impregnated graphite gasket, and curing to obtain the flexible graphite gasket. The invention further provides application of the flexible graphite gasket in a balance sealing ring. The graphite gasket is impregnated with polyacrylate and organic silicon resin, the outer surface of the graphite gasket is coated with a layer of cross-linking curing film, and the graphite gasket is used in the balance sealing ring to improve the sealing performance and prolong the service life of the balance sealing ring.

Description

Technical Field

[0001] The invention relates to the field of sealing materials, in particular to a preparation method of a flexible graphite gasket and application of the same in a balanced sealing ring. Background Art

[0002] The sealing ring is an annular seal with a gap, which acts as a seal by pressing against the inner hole wall of the stationary part due to its elasticity after being pressed together. Expanded graphite has low density, is loose and porous, has good softness, anisotropy, excellent compression resilience, self-lubrication, and impermeability, and can be post-processed into flexible graphite for use as a sealing material. For example, patent CN103881655A discloses a method for producing a corrosion-resistant flexible graphite sealing material, which uses high-carbon, low-sulfur expandable graphite particles as raw materials to prepare a graphite gasket, evenly applies a layer of molybdenum disulfide on its surface, and finally dries it to obtain a corrosion-resistant flexible graphite sealing material with high strength, good flexibility and elasticity, and good sealing effect. However, current graphite seals generally still cannot meet high sealing requirements, and an ideal solution is needed. Summary of the invention

[0003] The present invention provides a method for preparing a flexible graphite gasket and its application in a balanced sealing ring. The graphite gasket is impregnated with polyacrylate and silicone resin, and a cross-linked cured film is coated on the surface of the graphite gasket, which is used in the balanced sealing ring to improve the sealing performance and service life of the balanced sealing ring.

[0004] In order to achieve the above object, the present invention adopts the following technical solutions: A method for preparing a flexible graphite gasket comprises the following steps: 1) preparing a polyacrylate solution using methyl methacrylate, ethyl acrylate and cinnamyl alcohol as monomers; 2) mixing the polyacrylate solution with the silanol hydroxyl-terminated silicone resin solution, immersing the graphite gasket made of expanded graphite therein, adding an amine curing agent, and impregnating under pressure; 3) The impregnated graphite gasket is taken out and a flexible graphite gasket is obtained by curing.

[0005] Preferably, the mass ratio of methyl methacrylate, ethyl acrylate and cinnamyl alcohol is 30-50:8-12:10-15.

[0006] Preferably, the polyacrylate solution is prepared by dispersing the monomer in a solvent, heating to 100-110° C., adding an initiator and reacting for 5-8 hours. More preferably, the solvent is butyl acetate and the initiator is BPO.

[0007] Preferably, the silanol hydroxyl terminated silicone resin has a functionality of 5-10 and a molecular weight of 2000-4000.

[0008] Preferably, the mass ratio of polyacrylate to silanol hydroxyl-terminated silicone resin is 1:5-7; the mass concentration of the polyacrylate solution is 50-65%, and the mass concentration of the silanol hydroxyl-terminated silicone resin solution is 30-40%.

[0009] Preferably, the carbon content of the expanded graphite is ≥99wt%. The method for preparing the expanded graphite is prior art. Before impregnation, the surface of the graphite gasket is cleaned to remove surface debris and oil stains, placed in a drying oven (105°C) to dry to constant weight, and then cooled to room temperature for use; the impregnation liquid is allowed to stand to remove bubbles generated by pouring.

[0010] Preferably, the immersion pressure is 0.5-1 MPa, the temperature is 30-50° C., and the time is 20-40 min.

[0011] After the impregnation is completed, open the exhaust valve to release the pressure in the kettle, take out the impregnated graphite sample, clean and wipe the surface and dry it to complete one impregnation.

[0012] Preferably, the dipping is repeated 1 to 3 times.

[0013] Preferably, the curing is carried out by gradually increasing the temperature from room temperature to 60°C at 8-10°C / h, then to 90°C at 5-6°C / h, and then to 160°C at 8-10°C / h, and keeping the temperature for 3-6h.

[0014] The present invention also provides the application of the flexible graphite gasket in a balanced sealing ring, which comprises an upper end ring, a middle laminated graphite ring and a lower end ring from top to bottom, and the middle laminated graphite ring is formed by stacking a number of the flexible graphite gaskets.

[0015] Preferably, the layers of the balancing sealing ring are bonded together by adhesive and are molded in a mold.

[0016] Therefore, the beneficial effects of the present invention are: impregnating a graphite gasket with polyacrylate and silicone resin, coating a layer of cross-linked cured film on the surface of the graphite gasket, and using it in a balancing sealing ring to improve the sealing performance and service life of the balancing sealing ring. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a structural schematic diagram of a balanced sealing ring.

[0018] In the figure: 1. End ring, 2. Laminated graphite ring. DETAILED DESCRIPTION

[0019] The technical solution of the present invention is further described below through specific embodiments.

[0020] In the present invention, unless otherwise specified, the raw materials and equipment used can be purchased from the market or are commonly used in the art. The methods in the embodiments, unless otherwise specified, are all conventional methods in the art. Unless otherwise specified, parts are all weight parts, temperatures are expressed in ° C or at ambient temperature, and pressures are atmospheric pressure or near atmospheric pressure. There are many variations and combinations of reaction conditions (such as component concentrations, desired solvents, solvent mixtures, temperatures, pressures, and other reaction ranges) and conditions that can be used to optimize the purity and yield of the product obtained by the method, and only reasonable routine experiments will be required to optimize such method conditions.

[0021] Example 1. A method for preparing a flexible graphite gasket The following steps are involved: (1) Using methyl methacrylate, ethyl acrylate and cinnamyl alcohol as monomers, methyl methacrylate, ethyl acrylate and cinnamyl alcohol are dispersed in a solvent of butyl acetate in a mass ratio of 30-50:8-12:10-15, heated to 100-110° C., and added with initiator BPO to react for 5-8 hours to obtain a polyacrylate solution; the mass concentration of the polyacrylate solution is adjusted to 50-65% for standby use.

[0022] (2) Selecting a silanol hydroxyl-terminated silicone resin with a functionality of 5-10 and a molecular weight of 2000-4000, preparing a solution with a mass concentration of 30-40%, and mixing it with the polyacrylate solution obtained in step (1), wherein the mass ratio of polyacrylate to silanol hydroxyl-terminated silicone resin is 1:5-7.

[0023] (3) Clean the surface of the graphite gasket made of expanded graphite with a carbon content of ≥99wt%, remove surface debris and oil stains, place it in a drying oven (105°C) and dry it to constant weight, then cool it to room temperature for use; let the impregnation liquid stand to remove the bubbles generated by pouring. Then immerse the graphite gasket in the mixed solution obtained in step (2), place it in an autoclave, add an amine curing agent, pressurize it to a pressure of 0.5-1MPa, heat it to a temperature of 30-50°C, and immerse it for 20-40 minutes. After the impregnation is completed, open the exhaust valve to release the pressure in the autoclave, take out the impregnated graphite sample, clean and wipe the surface and dry it, and the impregnation is completed. Repeat the above impregnation steps 1-3 times.

[0024] (4) The impregnated graphite gasket is gradually heated and cured, first from room temperature to 60°C at 8-10°C / h, then to 90°C at 5-6°C / h, and then to 160°C at 8-10°C / h, kept warm for 3-6h, and cooled to obtain a flexible graphite gasket.

[0025] Methyl methacrylate and ethyl acrylate can adjust the hardness of polyacrylate, and cinnamyl alcohol brings phenyl and hydroxyl groups to polyacrylate. Polyacrylate, silicone resin terminated with silanol hydroxyl group and amine curing agent are cross-linked and cured to form a network structure. Although it cannot reach the complete molecular level penetration, the network structure is between physical mixing and interpenetrating network structure. As the surface film of graphite gasket, it can improve the compression resilience and sealing of graphite gasket.

[0026] 2. A balanced sealing ring The above-prepared flexible graphite gasket is used for balancing the sealing ring. Figure 1 As shown, the graphite ring is composed of an end ring 1 and a laminated graphite ring 2. The balanced sealing ring is composed of an upper end ring, a middle laminated graphite ring 2 and a lower end ring from top to bottom. The middle laminated graphite ring 2 is formed by stacking several flexible graphite gaskets (the required number of layers is related to the product height). The layers of the balanced sealing ring are bonded with adhesive and molded in a mold. The upper end ring and the lower end ring are preferably inner and outer Inconel600 metal wire reinforced graphite packing.

[0027] Example 1 A method for preparing a flexible graphite gasket, the steps are as follows: (1) Using methyl methacrylate, ethyl acrylate and cinnamyl alcohol as monomers, methyl methacrylate, ethyl acrylate and cinnamyl alcohol are dispersed in a solvent of butyl acetate in a mass ratio of 40:10:12, heated to 100° C., and added with initiator BPO to react for 6 hours to prepare a polyacrylate solution; the mass concentration of the polyacrylate solution is adjusted to 60% for standby use; (2) selecting a silanol hydroxyl-terminated silicone resin with a functionality of 8 and a molecular weight of 3000, preparing a solution with a mass concentration of 35%, and mixing it with the polyacrylate solution obtained in step (1), wherein the mass ratio of the polyacrylate to the silanol hydroxyl-terminated silicone resin is 1:6; (3) Clean the surface of the graphite gasket made of expanded graphite with a carbon content of ≥99wt%, remove surface debris and oil stains, place it in a drying oven (105°C) and dry it to constant weight, then cool it to room temperature for use; let the impregnation liquid stand to remove the bubbles generated by pouring. Then immerse the graphite gasket in the mixed solution obtained in step (2), place it in an autoclave, add an amine curing agent, pressurize it to a pressure of 0.8MPa, raise the temperature to 40°C, and immerse it for 30 minutes. After the impregnation is completed, open the exhaust valve to release the pressure in the autoclave, take out the impregnated graphite sample, clean and wipe the surface and dry it, and one impregnation is completed. Repeat the above impregnation steps twice, that is, a total of three impregnations; (4) The impregnated graphite gasket is gradually heated and cured, first from room temperature to 60°C at 9°C / h, then to 90°C at 5°C / h, and then to 160°C at 9°C / h, kept at this temperature for 5 hours, and then cooled to obtain a flexible graphite gasket.

[0028] The above-prepared flexible graphite gasket is used for the balanced sealing ring. The balanced sealing ring is composed of an upper end ring, a middle laminated graphite ring and a lower end ring from top to bottom, and the middle laminated graphite ring is formed by stacking several of the flexible graphite gaskets. The layers of the balanced sealing ring are bonded with adhesive and molded in a mold. The upper end ring and the lower end ring are inner and outer Inconel600 metal wire reinforced graphite packing. The size of the balanced sealing ring is 4 inches.

[0029] Example 2 A method for preparing a flexible graphite gasket, the steps are as follows: (1) Using methyl methacrylate, ethyl acrylate and cinnamyl alcohol as monomers, methyl methacrylate, ethyl acrylate and cinnamyl alcohol are dispersed in a solvent butyl acetate in a mass ratio of 30:8:10, heated to 110° C., and added with initiator BPO to react for 5 hours to prepare a polyacrylate solution; the mass concentration of the polyacrylate solution is adjusted to 50% for standby use; (2) selecting a silanol hydroxyl-terminated silicone resin with a functionality of 5 and a molecular weight of 2000, preparing a solution with a mass concentration of 30%, and mixing it with the polyacrylate solution obtained in step (1), wherein the mass ratio of the polyacrylate to the silanol hydroxyl-terminated silicone resin is 1:5; (3) Clean the surface of the graphite gasket made of expanded graphite with a carbon content of ≥99wt%, remove surface debris and oil stains, place it in a drying oven (105°C) and dry it to constant weight, then cool it to room temperature for use; let the impregnation liquid stand to remove the bubbles generated by pouring. Then immerse the graphite gasket in the mixed solution obtained in step (2), place it in an autoclave, add an amine curing agent, pressurize it to a pressure of 0.5MPa, raise the temperature to 30°C, and immerse it for 40 minutes. After the impregnation is completed, open the exhaust valve to release the pressure in the autoclave, take out the impregnated graphite sample, clean and wipe the surface and dry it, and the impregnation is completed. Repeat the above impregnation steps once, that is, a total of two impregnations; (4) The impregnated graphite gasket is gradually heated and cured, first from room temperature to 60°C at 8°C / h, then to 90°C at 6°C / h, and then to 160°C at 8°C / h, kept at this temperature for 3h, and then cooled to obtain a flexible graphite gasket.

[0030] Example 3 A method for preparing a flexible graphite gasket, the steps are as follows: (1) Using methyl methacrylate, ethyl acrylate and cinnamyl alcohol as monomers, methyl methacrylate, ethyl acrylate and cinnamyl alcohol are dispersed in a solvent of butyl acetate in a mass ratio of 50:12:15, heated to 100° C., and added with initiator BPO to react for 8 hours to prepare a polyacrylate solution; the mass concentration of the polyacrylate solution is adjusted to 65% for standby use; (2) selecting a silanol hydroxyl-terminated silicone resin with a functionality of 10 and a molecular weight of 4000, preparing a solution with a mass concentration of 40%, and mixing it with the polyacrylate solution obtained in step (1), wherein the mass ratio of the polyacrylate to the silanol hydroxyl-terminated silicone resin is 1:7; (3) Clean the surface of the graphite gasket made of expanded graphite with a carbon content of ≥99wt%, remove surface debris and oil stains, place it in a drying oven (105°C) and dry it to constant weight, then cool it to room temperature for use; let the impregnation liquid stand to remove the bubbles generated by pouring. Then immerse the graphite gasket in the mixed solution obtained in step (2), place it in an autoclave, add an amine curing agent, pressurize it to a pressure of 1MPa, raise the temperature to 50°C, and immerse it for 20 minutes. After the impregnation is completed, open the exhaust valve to release the pressure in the autoclave, take out the impregnated graphite sample, clean and wipe the surface and dry it to complete one impregnation. Repeat the above impregnation steps three times, that is, a total of four impregnations; (4) The impregnated graphite gasket is gradually heated and cured, first from room temperature to 60°C at 10°C / h, then to 90°C at 6°C / h, and then to 160°C at 10°C / h, kept at this temperature for 6 hours, and then cooled to obtain a flexible graphite gasket.

[0031] Example 4 The difference from Example 1 is that methyl methacrylate, ethyl acrylate and cinnamyl alcohol are dispersed in the solvent butyl acetate in a mass ratio of 40:10:20, that is, the amount of cinnamyl alcohol exceeds the preferred range. The details are as follows: A method for preparing a flexible graphite gasket, comprising the following steps: (1) Using methyl methacrylate, ethyl acrylate and cinnamyl alcohol as monomers, methyl methacrylate, ethyl acrylate and cinnamyl alcohol are dispersed in a solvent butyl acetate in a mass ratio of 40:10:20, heated to 100° C., and an initiator BPO is added to react for 6 hours to prepare a polyacrylate solution; the mass concentration of the polyacrylate solution is adjusted to 60% for standby use; (2) selecting a silanol hydroxyl-terminated silicone resin with a functionality of 8 and a molecular weight of 3000, preparing a solution with a mass concentration of 35%, and mixing it with the polyacrylate solution obtained in step (1), wherein the mass ratio of the polyacrylate to the silanol hydroxyl-terminated silicone resin is 1:6; (3) Clean the surface of the graphite gasket made of expanded graphite with a carbon content of ≥99wt%, remove surface debris and oil stains, place it in a drying oven (105°C) and dry it to constant weight, then cool it to room temperature for use; let the impregnation liquid stand to remove the bubbles generated by pouring. Then immerse the graphite gasket in the mixed solution obtained in step (2), place it in an autoclave, add an amine curing agent, pressurize it to a pressure of 0.8MPa, raise the temperature to 40°C, and immerse it for 30 minutes. After the impregnation is completed, open the exhaust valve to release the pressure in the autoclave, take out the impregnated graphite sample, clean and wipe the surface and dry it, and one impregnation is completed. Repeat the above impregnation steps twice, that is, a total of three impregnations; (4) The impregnated graphite gasket is gradually heated and cured, first from room temperature to 60°C at 9°C / h, then to 90°C at 5°C / h, and then to 160°C at 9°C / h, kept at this temperature for 5h, and then cooled to obtain a flexible graphite gasket.

[0032] Example 5 The difference from Example 1 is that the molecular weight of the silanol hydroxyl terminated silicone resin is 5000, which is beyond the preferred range. A method for preparing a flexible graphite gasket, comprising the following steps: (1) Using methyl methacrylate, ethyl acrylate and cinnamyl alcohol as monomers, methyl methacrylate, ethyl acrylate and cinnamyl alcohol are dispersed in a solvent of butyl acetate in a mass ratio of 40:10:12, heated to 100° C., and added with initiator BPO to react for 6 hours to prepare a polyacrylate solution; the mass concentration of the polyacrylate solution is adjusted to 60% for standby use; (2) selecting a silanol hydroxyl-terminated silicone resin with a functionality of 8 and a molecular weight of 5000, preparing a solution with a mass concentration of 35%, and mixing it with the polyacrylate solution obtained in step (1), wherein the mass ratio of the polyacrylate to the silanol hydroxyl-terminated silicone resin is 1:6; (3) Clean the surface of the graphite gasket made of expanded graphite with a carbon content of ≥99wt%, remove surface debris and oil stains, place it in a drying oven (105°C) and dry it to constant weight, then cool it to room temperature for use; let the impregnation liquid stand to remove the bubbles generated by pouring. Then immerse the graphite gasket in the mixed solution obtained in step (2), place it in an autoclave, add an amine curing agent, pressurize it to a pressure of 0.8MPa, raise the temperature to 40°C, and immerse it for 30 minutes. After the impregnation is completed, open the exhaust valve to release the pressure in the autoclave, take out the impregnated graphite sample, clean and wipe the surface and dry it, and one impregnation is completed. Repeat the above impregnation steps twice, that is, a total of three impregnations; (4) The impregnated graphite gasket is gradually heated and cured, first from room temperature to 60°C at 9°C / h, then to 90°C at 5°C / h, and then to 160°C at 9°C / h, kept at this temperature for 5h, and then cooled to obtain a flexible graphite gasket.

[0033] Example 6 The difference from Example 1 is that the mass ratio of polyacrylate to silanol hydroxyl terminated silicone resin is 1:3. Specifically: A method for preparing a flexible graphite gasket, comprising the following steps: (1) Using methyl methacrylate, ethyl acrylate and cinnamyl alcohol as monomers, methyl methacrylate, ethyl acrylate and cinnamyl alcohol are dispersed in a solvent of butyl acetate in a mass ratio of 40:10:12, heated to 100° C., and added with initiator BPO to react for 6 hours to prepare a polyacrylate solution; the mass concentration of the polyacrylate solution is adjusted to 60% for standby use; (2) selecting a silanol hydroxyl-terminated silicone resin with a functionality of 8 and a molecular weight of 3000, preparing a solution with a mass concentration of 35%, and mixing it with the polyacrylate solution obtained in step (1), wherein the mass ratio of the polyacrylate to the silanol hydroxyl-terminated silicone resin is 1:3; (3) Clean the surface of the graphite gasket made of expanded graphite with a carbon content of ≥99wt%, remove surface debris and oil stains, place it in a drying oven (105°C) and dry it to constant weight, then cool it to room temperature for use; let the impregnation liquid stand to remove the bubbles generated by pouring. Then immerse the graphite gasket in the mixed solution obtained in step (2), place it in an autoclave, add an amine curing agent, pressurize it to a pressure of 0.8MPa, raise the temperature to 40°C, and immerse it for 30 minutes. After the impregnation is completed, open the exhaust valve to release the pressure in the autoclave, take out the impregnated graphite sample, clean and wipe the surface and dry it, and one impregnation is completed. Repeat the above impregnation steps twice, that is, a total of three impregnations; (4) The impregnated graphite gasket is gradually heated and cured, first from room temperature to 60°C at 9°C / h, then to 90°C at 5°C / h, and then to 160°C at 9°C / h, kept at this temperature for 5h, and then cooled to obtain a flexible graphite gasket.

[0034] Example 7 The difference from Example 1 is that the mass ratio of polyacrylate to silanol hydroxyl terminated silicone resin is 1:8. Specifically: A method for preparing a flexible graphite gasket, comprising the following steps: (1) Using methyl methacrylate, ethyl acrylate and cinnamyl alcohol as monomers, methyl methacrylate, ethyl acrylate and cinnamyl alcohol are dispersed in a solvent of butyl acetate in a mass ratio of 40:10:12, heated to 100° C., and added with initiator BPO to react for 6 hours to prepare a polyacrylate solution; the mass concentration of the polyacrylate solution is adjusted to 60% for standby use; (2) selecting a silanol hydroxyl-terminated silicone resin with a functionality of 8 and a molecular weight of 3000, preparing a solution with a mass concentration of 35%, and mixing it with the polyacrylate solution obtained in step (1), wherein the mass ratio of the polyacrylate to the silanol hydroxyl-terminated silicone resin is 1:8; (3) Clean the surface of the graphite gasket made of expanded graphite with a carbon content of ≥99wt%, remove surface debris and oil stains, place it in a drying oven (105°C) and dry it to constant weight, then cool it to room temperature for use; let the impregnation liquid stand to remove the bubbles generated by pouring. Then immerse the graphite gasket in the mixed solution obtained in step (2), place it in an autoclave, add an amine curing agent, pressurize it to a pressure of 0.8MPa, raise the temperature to 40°C, and immerse it for 30 minutes. After the impregnation is completed, open the exhaust valve to release the pressure in the autoclave, take out the impregnated graphite sample, clean and wipe the surface and dry it, and one impregnation is completed. Repeat the above impregnation steps twice, that is, a total of three impregnations; (4) The impregnated graphite gasket is gradually heated and cured, first from room temperature to 60°C at 9°C / h, then to 90°C at 5°C / h, and then to 160°C at 9°C / h, kept at this temperature for 5h, and then cooled to obtain a flexible graphite gasket.

[0035] Example 8 The difference from Example 1 is that the curing adopts one-step temperature increase. The details are as follows: A method for preparing a flexible graphite gasket, comprising the following steps: (1) Using methyl methacrylate, ethyl acrylate and cinnamyl alcohol as monomers, methyl methacrylate, ethyl acrylate and cinnamyl alcohol are dispersed in a solvent of butyl acetate in a mass ratio of 40:10:12, heated to 100° C., and added with initiator BPO to react for 6 hours to prepare a polyacrylate solution; the mass concentration of the polyacrylate solution is adjusted to 60% for standby use; (2) selecting a silanol hydroxyl-terminated silicone resin with a functionality of 8 and a molecular weight of 3000, preparing a solution with a mass concentration of 35%, and mixing it with the polyacrylate solution obtained in step (1), wherein the mass ratio of the polyacrylate to the silanol hydroxyl-terminated silicone resin is 1:6; (3) Clean the surface of the graphite gasket made of expanded graphite with a carbon content of ≥99wt%, remove surface debris and oil stains, place it in a drying oven (105°C) and dry it to constant weight, then cool it to room temperature for use; let the impregnation liquid stand to remove the bubbles generated by pouring. Then immerse the graphite gasket in the mixed solution obtained in step (2), place it in an autoclave, add an amine curing agent, pressurize it to a pressure of 0.8MPa, raise the temperature to 40°C, and immerse it for 30 minutes. After the impregnation is completed, open the exhaust valve to release the pressure in the autoclave, take out the impregnated graphite sample, clean and wipe the surface and dry it, and one impregnation is completed. Repeat the above impregnation steps twice, that is, a total of three impregnations; (4) The impregnated graphite gasket is cured by heating the temperature in one step, from room temperature to 160° C. at a rate of 9° C. / h, kept at this temperature for 5 h, and then cooled to obtain a flexible graphite gasket.

[0036] Comparative Example Comparative Example 1 The difference from Example 1 is that the graphite gasket is not impregnated.

[0037] Comparative Example 2 The difference from Example 1 is that only the organic silicone resin solution terminated with silanol hydroxyl groups is used to impregnate the graphite gasket.

[0038] Comparative Example 3 The difference from Example 1 is that the monomer of the polyacrylate does not contain ethyl acrylate.

[0039] Comparative Example 4 The difference from Example 1 is that the monomer of the polyacrylate does not contain cinnamyl alcohol.

[0040] Performance Testing The compressibility, resilience and sealing properties of the flexible graphite gaskets prepared in each embodiment and comparative example were tested. (1) The compression rate and resilience rate were measured according to test method A of GB / T 12622-2008 "Test method for compression rate and resilience rate of pipe flange gaskets". (2) The sealing property test method is: a 4-inch balanced sealing ring similar to that in embodiment 1 was prepared using a flexible graphite gasket, and the gas leakage was calculated after 10,000 tests according to GBT4213-2008 pneumatic control valve. The maximum gas leakage standard of a 4-inch valve under 0.4MPa nitrogen medium is 21773mL / min. The results are shown in the following table.

[0041] It can be seen from the above table that compared with the unimpregnated bare graphite gasket in comparative example 1, the compression resilience of the flexible graphite gaskets prepared in each embodiment of the present invention is significantly improved, which can partially eliminate the influence of pressure, temperature changes and mechanical vibrations, and can be used in sleeve regulating valves with high sealing requirements to meet internal leakage requirements.

[0042] Compared with Example 1: (1) The impregnation liquid of Comparative Example 2 contains only silicone resin terminated with silanol hydroxyl groups, but no polyacrylate, so it is impossible to form a mesh structure on the surface of the graphite gasket, and the compression resilience is reduced. The monomers of polyacrylate in Comparative Examples 3 and 4 are missing ethyl acrylate and cinnamyl alcohol, respectively, and the compression resilience of the flexible graphite gasket is also reduced, because the three monomers of polyacrylate can only achieve good results when they cooperate with each other. In Example 4, cinnamyl alcohol is excessive, and the rigidity of the formed polymer film is increased, which affects the compression resilience, so the dosage of the three monomers must be within the preferred range to achieve the best effect.

[0043] (2) The molecular weight of the silicone resin terminated with silanol hydroxyl groups in Example 5 is too high, which is not conducive to entering the pores of graphite and forming meshing with graphite, so the leakage of the balanced sealing ring is reduced. The ratio of the silicone resin terminated with silanol hydroxyl groups and the polyacrylate in Examples 6 and 7 is not within the preferred range, and the network structure of the polymer film formed on the surface of the graphite gasket is changed, which also affects the compression resilience.

[0044] (3) Example 8 adopts one-step temperature curing, and the uniformity and adsorption force of the microstructure of the polymer film on the surface of the graphite gasket are not as good as those of Example 1 by step temperature curing, so the performance of the balanced sealing ring is reduced.

[0045] The above is only a preferred comparative example of the present invention, and does not constitute any form of limitation to the present invention. Although the present invention has been disclosed as a preferred comparative example as above, it is not used to limit the present invention. Any technician familiar with the profession can make some changes or modifications to equivalent comparative examples using the technical contents disclosed above without departing from the scope of the technical solution of the present invention. However, any simple modification, equivalent change and modification made to the above comparative examples based on the technical essence of the present invention without departing from the content of the technical solution of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A method for preparing a flexible graphite gasket, characterized in that: The following steps are involved: 1) Prepare polyacrylate solution using methyl methacrylate, ethyl acrylate and cinnamyl alcohol as monomers; 2) Mix the polyacrylate solution with the silanol hydroxyl terminated silicone resin solution, immerse the graphite gasket made of expanded graphite therein, add an amine curing agent, and impregnate under pressure; 3) Take out the impregnated graphite gasket and obtain a flexible graphite gasket after curing.

2. The method for preparing a flexible graphite gasket according to claim 1, characterized in that: The mass ratio of methyl methacrylate, ethyl acrylate and cinnamyl alcohol is 30-50:8-12:10-15.

3. The method for preparing a flexible graphite gasket according to claim 1 or 2, characterized in that: The preparation method of the polyacrylate solution is as follows: dispersing the monomer in a solvent, heating to 100-110°C, adding an initiator and reacting for 5-8 hours.

4. The method for preparing a flexible graphite gasket according to claim 1, characterized in that: The functionality of the silanol hydroxyl terminated silicone resin is 5-10 and the molecular weight is 2000-4000.

5. The method for preparing a flexible graphite gasket according to claim 1 or 4, characterized in that: The mass ratio of the polyacrylate to the silanol hydroxyl terminated silicone resin is 1:5-7.

6. The method for preparing a flexible graphite gasket according to claim 1, characterized in that: The immersion pressure is 0.5-1 MPa, the temperature is 30-50 °C, and the time is 20-40 min.

7. The method for preparing a flexible graphite gasket according to claim 1 or 6, characterized in that: Repeat the dipping 1-3 times.

8. The method for preparing a flexible graphite gasket according to claim 1, characterized in that: The curing adopts gradual temperature increase, from room temperature to 60 ℃ at 8-10 ℃ / h, then to 90 ℃ at 5-6 ℃ / h, and then to 160 ℃ at 8-10 ℃ / h, and keep warm for 3-6 hours.

9. Application of the flexible graphite gasket prepared by the preparation method according to any one of claims 1 to 8 in a balanced sealing ring, characterized in that: The balancing sealing ring comprises an upper end ring, a middle laminated graphite ring and a lower end ring from top to bottom, wherein the middle laminated graphite ring is formed by stacking a plurality of the flexible graphite gaskets.

10. The use according to claim 9, characterized in that: The layers of the balance sealing ring are bonded by adhesive and are molded in a mold.

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