A fluororubber cloth-stacked material for large oil cylinder V-group seals and its preparation method

Abstract

The present invention discloses a fluororubber-in-cloth material for large oil cylinder V-group seals and its preparation method. The fluororubber-in-cloth material comprises a polyester cloth as a skeleton material and a fluororubber compounded onto the polyester cloth surface via a treatment agent; the treatment agent is a dopamine-grafted silane coupling agent, KH-550; and the fluororubber is a vinylidene fluoride-hexafluoropropylene co-fluororubber. This invention solves the bonding problem between the fluororubber and the polyester cloth. The resulting fluororubber-in-cloth material exhibits excellent water and salt spray resistance in marine environments, meeting the high reliability requirements of large oil cylinder V-group seals over a 20-year service life.

Description

Technical Field

[0001] The present invention relates to the field of fluororubber cloth, and more particularly to a fluororubber cloth material for a large oil cylinder V-group seal and a preparation method thereof. Background Art

[0002] Ultra-long and ultra-large cylinders are widely used in large-scale engineering projects, large-scale equipment manufacturing, and the shipbuilding industry, playing a crucial role in the overall system. The luffing cylinder for pile-driving vessels is a prime example of this type of cylinder. Its large diameter (1m-1.6m), long stroke (14-22m), and high reliability requirements (leak-free operation for 20 years in marine environments) present significant design and manufacturing challenges. Traditional cylinder V-set seals rely on repeated compression adjustments to extend their service life, typically around five years, which falls short of the ship's lifespan requirements. Currently, commercially available V-set seals internationally utilize nitrile rubber / cotton fabric and fluororubber / cotton fabric. Cotton fabric offers excellent bonding with rubber, but its resistance to water and salt spray is poor, leading to long-term degradation in marine environments. Nitrile rubber also has a limited lifespan and cannot meet long-term operational requirements. Fluororubber used in foreign fabrics also exhibits poor water resistance, with a maximum operating temperature of only 80°C in water. Furthermore, its compression set at 200°C for 70 hours is very high (68%), making it difficult to achieve the high reliability and long-term service life required of a 20-year seal. Therefore, it is necessary to provide a cloth material for large oil cylinder V group seals to meet the performance requirements of water resistance, salt spray resistance and reliability. Summary of the Invention

[0003] An object of the present invention is to solve at least the above problems and to provide at least the advantages which will be described hereinafter.

[0004] To achieve these objects and other advantages according to the present invention, a fluororubber-cloth-reinforced rubber material for a large oil cylinder V-group seal is provided, comprising: a polyester cloth as a skeleton material; and fluororubber composited on the surface of the polyester cloth by a treating agent; the treating agent is a dopamine-grafted silane coupling agent KH-550; and the fluororubber is a vinylidene fluoride-hexafluoropropylene co-fluororubber.

[0005] Preferably, the vinylidene fluoride-hexafluoropropylene co-fluororubber is made of the following raw materials in parts by weight: 100 parts of vinylidene fluoride-hexafluoropropylene co-fluororubber, 3-6 parts of active magnesium oxide, 1-3 parts of DHT-4A, 0-30 parts of carbon black, 0-20 parts of mineral filler, and 2-3 parts of vulcanizing agent.

[0006] Preferably, the mineral filler is a combination of one or more of calcium silicate, talc, calcium carbonate, and diatomaceous earth.

[0007] Preferably, the mass per unit area of ​​the polyester cloth is 230-260 g / m2 The mass per unit area of ​​the fluororubber sandwich material is 550~620g / m 2 .

[0008] The present invention also provides a method for preparing a fluororubber cloth-stacked material for a large oil cylinder V-group seal, comprising the following steps:

[0009] S1. Immersing a polyester cloth in an aqueous solution of dopamine hydrochloride, stirring the cloth for reaction, removing the cloth, washing the cloth with water, and drying the cloth to form a polyester cloth having polydopamine deposited on the surface;

[0010] S2, immersing the polyester cloth with polydopamine deposited on the surface into an aqueous solution of silane coupling agent KH-550, stirring for reaction, and then taking out the polyester cloth, washing and drying it;

[0011] S3, preparing the fluororubber slurry, and applying it on the polyester cloth obtained in step S2, and obtaining the fluororubber-cloth-stitched material after drying.

[0012] Preferably, in step S1, the polyester cloth is immersed in a 1 g / L dopamine hydrochloride aqueous solution, reacted at 25-35° C. in the presence of oxygen and stirred for 4-12 hours, and the polyester cloth is taken out and washed and dried; the pH value of the dopamine hydrochloride aqueous solution is 7.5-8.5.

[0013] Preferably, in step S2, the polyester cloth with polydopamine deposited on the surface is immersed in a 10 g / L aqueous solution of silane coupling agent KH-550, reacted at 20-30° C. with stirring for 6-8 hours, and the polyester cloth is taken out, washed and dried; the pH value of the aqueous solution of silane coupling agent KH-550 is 7.5-11.

[0014] Preferably, in step S3, 100 parts of vinylidene fluoride-hexafluoropropylene co-fluororubber, 3-6 parts of activated magnesium oxide, 1-3 parts of DHT-4A, 0-30 parts of carbon black, 0-20 parts of mineral filler, and 2-3 parts of vulcanizing agent are mixed by weight to prepare a fluororubber compound, and the fluororubber compound is dissolved in an organic solvent to obtain the fluororubber slurry.

[0015] Preferably, the organic solvent is methyl isobutyl ketone, and a solution is prepared by mixing the fluororubber compound and methyl isobutyl ketone in a mass ratio of 1:3, and stirring the solution at room temperature for 4 hours to obtain the fluororubber slurry.

[0016] Preferably, the organic solvent is ethyl acetate, and the fluororubber compound and ethyl acetate are prepared into a solution in a mass ratio of 1:4, and stirred at room temperature for 6 hours to obtain the fluororubber slurry.

[0017] The present invention has at least the following beneficial effects:

[0018] (1) The bonding problem between fluororubber and polyester cloth was solved, and the bonding strength between the two was improved.

[0019] (2) The reaction product of dopamine-grafted silane coupling agent KH-550 was used as a crosslinking agent for fluororubber, which significantly increased the crosslinking density of fluororubber and enhanced the material's resistance to compression deformation.

[0020] (3) The prepared fluororubber cloth material has excellent water resistance and salt spray resistance in marine environments, and can meet the high reliability requirements of large cylinder V-group seals within a 20-year service life.

[0021] Other advantages, objectives and features of the present invention will be reflected in part from the following description and will be understood by those skilled in the art through study and practice of the present invention. DETAILED DESCRIPTION

[0022] The present invention is further described in detail below with reference to the embodiments so that those skilled in the art can implement the invention with reference to the description.

[0023] It should be noted that the experimental methods described in the following embodiments are conventional methods unless otherwise specified, and the reagents and materials can be obtained from commercial channels unless otherwise specified.

[0024] The present invention provides a fluororubber-cloth-sandwiched material for a V-group seal of a large oil cylinder, comprising: a polyester cloth as a skeleton material and a fluororubber compounded on the surface of the polyester cloth by a treating agent; the treating agent is a dopamine-grafted silane coupling agent KH-550; and the fluororubber is a vinylidene fluoride-hexafluoropropylene co-fluororubber.

[0025] In this technical solution, polyester cloth is used as the skeleton material. The polyester cloth is a polyester fiber material commonly used in the engineering field. Dopamine-grafted silane coupling agent KH-550 is used as a treating agent for the polyester cloth. Vinylidene fluoride-hexafluoropropylene copolymer is used as a fluororubber coating. This solves the adhesion problem between the fluororubber and the polyester cloth. The resulting fluororubber-cloth sandwich material has excellent water and salt spray resistance in marine environments, and can meet the high reliability requirements of large oil cylinder V-group seals within a 20-year service life.

[0026] Specifically, the vinylidene fluoride-hexafluoropropylene co-fluororubber is made of the following raw materials in parts by weight: 100 parts of vinylidene fluoride-hexafluoropropylene co-fluororubber, 3-6 parts of active magnesium oxide, 1-3 parts of DHT-4A, 0-30 parts of carbon black, 0-20 parts of mineral filler, and 2-3 parts of vulcanizing agent.

[0027] Furthermore, the mineral filler is a combination of one or more of calcium silicate, talc, calcium carbonate, and diatomaceous earth.

[0028] Specifically, the mass per unit area of ​​the polyester cloth is 230-260 g / m 2 The mass per unit area of ​​the fluororubber sandwich material is 550~620g / m 2 .

[0029] The present invention provides a fluororubber-in-cloth material for V-group seals of large oil cylinders. The silane coupling agent in the treatment agent is silane coupling agent KH-550. The hydrolysis product of aminosilane has amino groups on one side and silanol groups on the other side. This bifunctional structure has the ability to crosslink vinylidene fluoride-hexafluoropropylene copolymer under strong alkali and high temperature. Through thermal vulcanization crosslinking, on the one hand, it achieves adhesion between the coated fluororubber and polyester, and on the other hand, it can significantly increase the crosslink density of the fluororubber, reduce its elongation, and improve its compressive strength and compression modulus. This lays the material foundation for withstanding high pressure and low deformation in oil cylinders and extending the service life of seals. Specifically:

[0030] The original structure of KH-550 is , after hydrolysis, γ-aminopropylsilanol is generated, with the structural formula: ;

[0031] The reaction mechanism steps are:

[0032] 1. Remove HF to form a double bond:

[0033] Under alkaline conditions, the acidic hydrogen on the main chain of fluororubber (such as adjacent ) is attacked by base, removing HF to form a double bond (such as or )

[0034] 2. Nucleophile attacks double bond

[0035] Step 1: Nucleophilic attack

[0036] The amino group of KH-550 hydrolyzate ( ) deprotonates under alkaline conditions to generate amino anions ( ), as a nucleophile close to the β-carbon of the double bond:

[0037] Step 2: Nucleophilic Addition

[0038] The amino anion attacks the β-carbon, opening the double bond to form a CN bond and generating an intermediate:

[0039] Step 3: Proton transfer

[0040] The intermediate is stabilized by proton transfer, releasing (Needs acid acceptor magnesium oxide to neutralize):

[0041] 3. Cross-linking network formation

[0042] Repeated attack: The nucleophile at the other end (such as another amine or hydroxyl group) attacks the double bond of another fluororubber chain to form a three-dimensional cross-linked network;

[0043] Silanol condensation (cross-linking enhancement), silanol (-Si-OH) dehydrates and condenses to form Si-O-Si bonds, further increasing the cross-linking density;

[0044] Through the synergistic effect of CN bonds (amino linkage), CO bonds (hydroxyl linkage) and Si-O-Si bonds (siloxane condensation), a high-density cross-linked network is formed between fluororubber chains.

[0045] In the above reaction process, amino groups dominate cross-linking, and amino groups ( ) has higher reactivity than hydroxyl groups, preferentially forming C-N bonds and achieving rapid crosslinking. Three silanol groups provide additional crosslinking sites, while multiple hydroxyl groups synergistically form C-O bonds and Si-O-Si bonds to construct a high-density three-dimensional network, enhancing network density. Si-O-Si bonds are more resistant to hydrolysis under wet and hot conditions than purely organic crosslinks.

[0046] The aforementioned reaction occurs with the fluororubber in the polyester fabric interface layer, while the non-interface fluororubber undergoes conventional rubber crosslinking using the vulcanizing agent in the formulation. This results in a three-layer composite structure of polyester fabric, reinforced crosslinked fluororubber layer, and soft fluororubber layer.

[0047] The present invention also provides a method for preparing a fluororubber cloth-stacked material for a large oil cylinder V-group seal, comprising the following steps:

[0048] S1. Immersing a polyester cloth in an aqueous solution of dopamine hydrochloride, stirring the cloth for reaction, removing the cloth, washing the cloth with water, and drying the cloth to form a polyester cloth having polydopamine deposited on the surface;

[0049] S2, immersing the polyester cloth with polydopamine deposited on the surface into an aqueous solution of silane coupling agent KH-550, stirring for reaction, and then taking out the polyester cloth, washing and drying it;

[0050] S3, preparing the fluororubber slurry, and applying it on the polyester cloth obtained in step S2, and obtaining the fluororubber-cloth-stitched material after drying.

[0051] In step S1, a polyester cloth is immersed in a 1 g / L aqueous solution of dopamine hydrochloride, and the reaction is carried out at 25-35°C in the presence of oxygen and with stirring for 4-12 hours. The polyester cloth is then removed, washed, and dried. The pH value of the dopamine hydrochloride aqueous solution is 7.5-8.5. Specifically, a 1 g / L aqueous solution of dopamine hydrochloride is first prepared, and the pH value is then adjusted using tris-hydroxymethylaminomethane buffer.

[0052] In step S2, the polyester cloth with polydopamine deposited on its surface is immersed in a 10g / L aqueous solution of the silane coupling agent KH-550. The mixture is stirred at 20-30°C for 6-8 hours, and then the polyester cloth is removed, washed, and dried. The pH of the aqueous solution of the silane coupling agent KH-550 is 7.5-11. Specifically, the aqueous solution of the silane coupling agent KH-550 is prepared by adding 10g of the silane coupling agent KH-550 to 1 liter of deionized water, and then the pH is adjusted with sodium hydroxide.

[0053] In step S3, 100 parts of vinylidene fluoride-hexafluoropropylene co-fluororubber, 3-6 parts of activated magnesium oxide, 1-3 parts of DHT-4A, 0-30 parts of carbon black, 0-20 parts of a mineral filler, and 2-3 parts of a vulcanizing agent are mixed by weight to prepare a fluororubber compound. The fluororubber compound is then dissolved in an organic solvent to obtain a fluororubber slurry. The polyester cloth treated in step S2 is then coated with the slurry by blade or roller coating using industrial coating equipment. The distance between the blade and the cloth is adjusted to apply the slurry. After drying, the fluororubber-in-cloth material is obtained.

[0054] The organic solvent is methyl isobutyl ketone. A solution is prepared by mixing fluororubber compound and methyl isobutyl ketone in a mass ratio of 1:3, and the solution is stirred at room temperature for 4 hours to obtain the fluororubber slurry.

[0055] The organic solvent may also be ethyl acetate. A solution is prepared by mixing the fluororubber compound and ethyl acetate in a mass ratio of 1:4, and stirring the solution at room temperature for 6 hours to obtain the fluororubber slurry.

[0056] The present invention will be explained in detail below with reference to the embodiments.

[0057] Example 1

[0058] S1. Surface deposition of polydopamine

[0059] A 1 g / L aqueous solution of dopamine hydrochloride was prepared and the pH was adjusted to 8.5 using tris(hydroxymethyl)aminomethane buffer. A polyester cloth was placed in the aqueous solution of dopamine hydrochloride and reacted at 25°C in the presence of oxygen for 4 hours with stirring. The cloth was then removed, washed with water, and dried to obtain a polyester cloth with polydopamine deposited on its surface.

[0060] S2, Grafted silane coupling agent KH-550

[0061] A silane coupling agent aqueous solution was prepared by adding 10 g of silane coupling agent KH550 to 1 liter of deionized water, and the pH was adjusted to 11 with sodium hydroxide. The polyester cloth with polydopamine deposited on the surface was immersed in the silane coupling agent KH-550 aqueous solution. The reaction temperature was controlled to 20°C by heating in a water bath. The reaction was stirred for 8 hours, and the polyester cloth was taken out and washed and dried.

[0062] S3. Preparation of fluororubber cloth material

[0063] A fluororubber compound was prepared using a weight ratio of 100 parts fluororubber FKM2601 (China National Chemical Corporation, ML1+10, 121°C, 30MU), 3 parts activated magnesium oxide, 2 parts DHT-4A, 30 parts carbon black N990, and 2 parts Fluorine-Linked No. 5 curing agent. A solution of the fluororubber compound and methyl isobutyl ketone (MIBK) was prepared in a 1:3 mass ratio and stirred at room temperature for 4 hours to obtain a uniform fluororubber slurry. Using industrial coating equipment, the fluororubber slurry was applied to the polyester fabric treated in step S2 using a doctor blade coating process. After drying, the fluororubber-interposed fabric material A was obtained.

[0064] Example 2

[0065] Step S1 and step S2 are the same as those in Example 1.

[0066] S3. Preparation of fluororubber cloth material

[0067] A fluororubber compound was prepared by adding 100 parts by weight of fluororubber JHF2601 (Zhejiang Juhua, ML1+10, 121°C, 16-40MU), 3 parts of activated magnesium oxide, 1.5 parts of DHT-4A, 20 parts of diatomaceous earth, 5 parts of carbon black N990, and 3 parts of Fluorine-Linked No. 5 curing agent. A solution of the fluororubber compound and ethyl acetate was prepared in a 1:4 mass ratio and stirred at room temperature for 6 hours to obtain a uniform fluororubber mortar. Using industrial coating equipment, the fluororubber mortar was applied to the polyester cloth treated in step S2 using a doctor blade process. After drying, the fluororubber-interposed cloth material B was obtained.

[0068] Example 3

[0069] S1. Surface deposition of polydopamine

[0070] Prepare a 1 g / L aqueous solution of dopamine hydrochloride and adjust the pH to 7.5 with tris-hydroxymethylaminomethane buffer. Place a polyester cloth in the aqueous solution and allow it to react at 35°C in the presence of oxygen for 12 hours with stirring. Remove the cloth, rinse it with water, and dry it to obtain a polyester cloth with polydopamine deposited on its surface.

[0071] Step S2 and step S3 are the same as those in Example 2, and a fluororubber-insulated cloth material C is obtained.

[0072] Comparative Example 1

[0073] S1. Use industrialized double-dipping method to treat polyester cloth

[0074] S2. Preparation of fluororubber cloth material

[0075] A fluororubber compound was prepared using a weight ratio of 100 parts fluororubber FKM2601 (China National Chemical Corporation, ML1+10, 121°C, 30MU), 3 parts activated magnesium oxide, 2 parts DHT-4A, 30 parts carbon black N990, and 2 parts Fluorine-Linked No. 5 curing agent. A solution of the fluororubber compound and methyl isobutyl ketone (MIBK) was prepared in a 1:3 mass ratio and stirred at room temperature for 4 hours to obtain a uniform fluororubber slurry. Using industrial coating equipment, the polyester cloth treated in step S1 was coated with the fluororubber slurry using a doctor blade process. After drying, the fluororubber-inlaid material D was obtained.

[0076] Comparative Example 2

[0077] The silane coupling agent KH-550 in step S2 was replaced with the silane coupling agent KH-570 (γ-methacryloxypropyltrimethoxysilane), and the rest was the same as in Example 1 to obtain the fluororubber interlayer material E.

[0078] Fluororubber-reinforced fabric materials A-E were used to prepare standard 500 mm × 550 mm × 126 mm V-type seal specimens on a 1000-ton flatbed vulcanizer using a conventional process (170°C × 10 minutes). Their seawater resistance and adhesion properties were tested, and a 250 km mileage test was conducted at 25 MPa. The resulting performance data is shown in Table 1. Mileage test conditions: medium: L-HM46 hydraulic oil, pressure: 25 MPa, stroke: 400 mm, speed: 0.1 m / s, and room temperature.

[0079] Table 1 Fluororubber interlayer material performance data

[0080]

[0081] From Table 1 we can get:

[0082] (1) Compared with fluororubber interlayer materials D and E, fluororubber interlayer materials A to C have significantly less change in seawater resistance, which is beneficial to reduce volume expansion and reduce wear during movement;

[0083] (2) Compared with fluororubber interlayer materials A and D, the initial bonding strength is similar, but the bonding strength of fluororubber interlayer material D is lower after seawater aging, which is not conducive to long-term operation in a 20-year marine environment. From the increase in mass change, the water absorption capacity of fluororubber interlayer material D has greatly increased, which is also one of the reasons for the significant decrease in its bonding strength after seawater aging.

[0084] (3) Compared with fluororubber interlayer materials A~C and fluororubber interlayer material E, when other silane coupling agents are used to replace silane coupling agent KH-550, the amino cross-linking ability of fluororubber is lost, and the total height compression permanent deformation increases significantly after completing the 50km mileage test.

[0085] (4) Compared with fluororubber cloth materials A~C and fluororubber cloth materials D and E, after completing the 50km mileage test, the total height compression permanent deformation of fluororubber cloth materials D and E reached 67.6%-82.6%. In engineering applications, it is necessary to adjust the cylinder gasket and increase the compression amount to compensate for the permanent deformation. However, the total height compression permanent deformation of fluororubber cloth materials A~C is only 10.8%-14.2%, which has the ability to work stably and reliably for a long time.

[0086] Therefore, the fluororubber cloth-sandwiched material provided by the present invention significantly improves the performance and life of the seal through innovative processing technology and material formulation, providing a strong guarantee for the reliable operation of large oil cylinders in harsh environments.

[0087] Although the embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the description and implementation methods. They can be fully applied to various fields suitable for the present invention. For those familiar with the art, additional modifications can be easily implemented. Therefore, without departing from the general concept defined by the claims and the scope of equivalents, the present invention is not limited to specific details.

Claims

1. A fluororubber cloth-stacked material for large oil cylinder V-group seals, characterized in that: include: A polyester cloth as a skeleton material and a fluororubber compounded on the surface of the polyester cloth by a treatment agent; the treatment agent is a dopamine-grafted silane coupling agent KH-550; and the fluororubber is a vinylidene fluoride-hexafluoropropylene co-fluororubber; The vinylidene fluoride-hexafluoropropylene co-fluororubber is made of the following raw materials in parts by weight: 100 parts of vinylidene fluoride-hexafluoropropylene co-fluororubber, 3-6 parts of active magnesium oxide, 1-3 parts of DHT-4A, 0-30 parts of carbon black, 0-20 parts of mineral filler, and 2-3 parts of vulcanizing agent.

2. The fluororubber cloth-stacked material for large oil cylinder V-group seals according to claim 1, characterized in that: The mineral filler is a combination of one or more of calcium silicate, talc, calcium carbonate and diatomaceous earth.

3. The fluororubber cloth-stacked material for large oil cylinder V-group seals according to claim 1, characterized in that: The mass per unit area of ​​the polyester cloth is 230-260 g / m 2 The mass per unit area of ​​the fluororubber sandwich material is 550~620g / m 2 .

4. A method for preparing a fluororubber cloth-stacked material for a large oil cylinder V-group seal according to claim 1, characterized in that: The following steps are involved: S1. Immersing a polyester cloth in an aqueous solution of dopamine hydrochloride, stirring the cloth for reaction, removing the cloth, washing the cloth with water, and drying the cloth to form a polyester cloth having polydopamine deposited on the surface; S2, immersing the polyester cloth with polydopamine deposited on the surface into an aqueous solution of silane coupling agent KH-550, stirring for reaction, and then taking out the polyester cloth, washing and drying it; S3, preparing the fluororubber slurry, and applying it on the polyester cloth obtained in step S2, and obtaining the fluororubber-cloth-stitched material after drying.

5. The method for preparing a fluororubber cloth-stacked material for a large oil cylinder V-group seal according to claim 4, characterized in that: In step S1, the polyester cloth is immersed in a 1 g / L dopamine hydrochloride aqueous solution, reacted at 25-35° C. in the presence of oxygen and stirred for 4-12 hours, and the polyester cloth is taken out, washed and dried; the pH value of the dopamine hydrochloride aqueous solution is 7.5-8.

5.

6. The method for preparing a fluororubber cloth-stacked material for a large oil cylinder V-group seal according to claim 4, characterized in that: In step S2, the polyester cloth with polydopamine deposited on the surface is immersed in a 10 g / L aqueous solution of silane coupling agent KH-550, and the mixture is reacted at 20-30° C. with stirring for 6-8 hours. The polyester cloth is taken out, washed with water, and dried; the pH value of the aqueous solution of silane coupling agent KH-550 is 7.5-11.

7. The method for preparing a fluororubber cloth-stacked material for a large oil cylinder V-group seal according to claim 4, characterized in that: In step S3, 100 parts of vinylidene fluoride-hexafluoropropylene co-fluororubber, 3-6 parts of active magnesium oxide, 1-3 parts of DHT-4A, 0-30 parts of carbon black, 0-20 parts of mineral filler, and 2-3 parts of vulcanizing agent are mixed by weight to prepare a fluororubber compound, and the fluororubber compound is dissolved in an organic solvent to obtain the fluororubber slurry.

8. The method for preparing a fluororubber cloth-stacked material for a large oil cylinder V-group seal according to claim 7, characterized in that: The organic solvent is methyl isobutyl ketone. A solution is prepared by mixing fluororubber compound and methyl isobutyl ketone in a mass ratio of 1:3, and the solution is stirred at room temperature for 4 hours to obtain the fluororubber slurry.

9. The method for preparing a fluororubber cloth-stacked material for a large oil cylinder V-group seal according to claim 7, characterized in that: The organic solvent is ethyl acetate, and a solution is prepared by mixing the fluororubber compound and ethyl acetate in a mass ratio of 1:4, and stirring the solution at room temperature for 6 hours to obtain the fluororubber slurry.

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