Oil-resistant undersea valve rubber and method of making same

Abstract

The application discloses an oil-resistant submarine valve rubber and a preparation method thereof, and belongs to the technical field of rubber sealing materials. The rubber is prepared from the following raw materials: base rubber, molybdenum disulfide nanoflower, vulcanizing agent and additive. The molybdenum disulfide nanoflower is a flower-like aggregate formed by self-assembly of molybdenum disulfide nanosheets, and has interlayer mesopores. The preparation method comprises the following steps: dissolving the molybdenum disulfide nanoflower and the base rubber in organic solvents respectively, mixing the two, co-precipitating with water to obtain rubber masterbatch, and then mixing and vulcanizing the rubber masterbatch, the vulcanizing agent and the additive to form the rubber. The molybdenum disulfide nanoflower single filler can simultaneously realize the triple functions of labyrinth barrier, interlayer mesopore oil storage and solid lubrication, can effectively inhibit the swelling of the rubber in oil-based mud, and can maintain the size stability of the conical surface seal.

Description

Technical Field

[0001] This invention relates to the field of rubber sealing materials technology, and in particular to an oil-resistant rubber sheet for a subsea valve in an oil drilling mud tank and its preparation method. Background Technology

[0002] The bottom valve (also known as the bottom flow valve or tank bottom valve) of the oil drilling mud tank is a key valve in the mud circulation system that controls the flow and isolation of mud between different compartments.

[0003] Subsea valves in oil drilling mud tanks rely on the conical contact between a rubber sheet and a metal valve seat for sealing. When using oil-based drilling mud, the base oil in the mud causes the nitrile rubber sheet to swell, leading to dimensional mismatch of the conical sealing surface and seal failure. Existing technologies typically improve oil swelling resistance by increasing the rubber crosslinking density, but increasing the crosslinking density sacrifices rubber elasticity, thus reducing sealing force. Therefore, how to effectively suppress the swelling of the subsea valve sheet in oil-based mud while maintaining rubber elasticity and ensuring the dimensional stability of the conical seal remains a persistent technical challenge in this field. Summary of the Invention

[0004] This invention aims to solve the technical problem of conical seal failure caused by rubber swelling in oil-based mud in existing subsea valve rubber sheets, and provides an oil-resistant subsea valve rubber sheet and its preparation method that can effectively suppress swelling and maintain the dimensional stability of the conical seal while maintaining the elasticity of the rubber.

[0005] An oil-resistant subsea valve rubber sheet, the raw materials of which, by weight, include: 80-90 parts of base rubber, 10-15 parts of molybdenum disulfide nanoflowers, 0.5-3 parts of vulcanizing agent, and 2-8 parts of additives; wherein the molybdenum disulfide nanoflowers are flower-shaped aggregates formed by the self-assembly of molybdenum disulfide nanosheets, and the flower-shaped aggregates have interlayer mesopores between the molybdenum disulfide nanosheets inside.

[0006] Specifically, the base rubber is nitrile rubber or hydrogenated nitrile rubber.

[0007] Specifically, the additive contains 1-2 parts of phenolic reinforcing resin.

[0008] This invention also provides a method for preparing an oil-resistant subsea valve rubber sheet, comprising the following steps: (1) Molybdenum disulfide nanoflowers were dispersed in a first organic solvent and ultrasonically assisted to obtain a molybdenum disulfide suspension; (2) Dissolve the base rubber in a second organic solvent to obtain a rubber solution; (3) The molybdenum disulfide suspension is mixed with the rubber solution to obtain a mixed dispersion; (4) Add water to the mixed dispersion under stirring conditions to allow the base rubber and molybdenum disulfide nanoflowers to precipitate together. Collect the precipitate and dry it to constant weight to obtain rubber masterbatch coated with molybdenum disulfide nanoflowers. (5) The rubber masterbatch is mixed with vulcanizing agent and additives until uniformly dispersed, and then vulcanized to obtain the oil-resistant sea valve rubber sheet.

[0009] Specifically, in steps (1) and (2), the first organic solvent and the second organic solvent are each independently selected from one or more of acetone, toluene, butanone, and cyclohexanone.

[0010] Specifically, the drying temperature in step (4) is 40-80°C. Specifically, the mixing temperature in step (5) is 40-60°C, the vulcanization molding is carried out at 140-170°C and 10-20MPa, and the vulcanization time is 10-30min.

[0011] Specifically, the molybdenum disulfide nanoflowers are prepared by the following steps: dissolving sodium molybdate and thiourea in water, with a molar ratio of sodium molybdate to thiourea of ​​1:2 to 1:4, and hydrothermally reacting at 180-220°C for 12-24 hours. After cooling, the nanoflowers are washed and dried to obtain molybdenum disulfide nanoflowers.

[0012] Specifically, in step (3), the molybdenum disulfide suspension and the rubber solution are mixed by stirring and / or ultrasonic mixing.

[0013] Specifically, the stirring speed in step (4) is 200-800 rpm.

[0014] By adopting the above technical solution, the present invention has the following beneficial effects compared with the prior art: Molybdenum disulfide nanoflowers are used as a single-functional filler. Their flower-like aggregate structure combines the dual functions of layered barrier and interlayer mesoporous oil storage. On one hand, the molybdenum disulfide nanosheets create a labyrinth effect, extending the diffusion path of oil molecules in the rubber matrix. On the other hand, the interlayer mesopores between the nanosheets provide non-swellable storage space for infiltrated oil molecules, diverting some oil molecules from the rubber phase to the rigid molybdenum disulfide framework, thus reducing the actual swelling of the rubber matrix. Simultaneously, the inherent solid lubrication properties of molybdenum disulfide can reduce frictional wear between the rubber sheet and the metal valve seat.

[0015] During vulcanization, phenolic reinforcing resin forms an interpenetrating network with the base rubber, improving the rubber's hardness and resistance to compression deformation. The rigid flower-like skeleton of molybdenum disulfide nanoflowers forms dispersed load-bearing units within the rubber matrix, sharing local compressive stress. Together, they enhance the rubber's load-bearing capacity under high-pressure conditions, reduce permanent compression deformation during repeated high-pressure opening and closing processes, and extend the seal's service life.

[0016] This invention uses a solution co-precipitation method to prepare molybdenum disulfide nanoflowers, avoiding the shearing damage to the flower-like structure caused by traditional mechanical mixing. This allows the molybdenum disulfide nanoflowers to retain their complete aggregate morphology and interlayer mesoporous structure in the final product, ensuring the effective performance of their dual functions. Detailed Implementation

[0017] The technical solution of the present invention will be further described below through specific embodiments. Unless otherwise defined, all technical terms used herein have the meanings commonly understood by those skilled in the art.

[0018] Sodium molybdate and thiourea were dissolved in deionized water at a molar ratio of 1:2 to 1:4. After complete dissolution, the solution was transferred to a hydrothermal reactor lined with polytetrafluoroethylene (PTFE) and reacted at 180-220°C for 12-24 hours. After the reaction, the mixture was allowed to cool naturally to room temperature. The resulting black precipitate was washed three times with deionized water and anhydrous ethanol, and then vacuum dried at 60-80°C for 8-12 hours to obtain molybdenum disulfide nanoflowers.

[0019] The resulting product is a spherical flower-like aggregate formed by the self-assembly of molybdenum disulfide nanosheets, with a diameter of 200-500 nm, an interlayer mesopore diameter of 2-50 nm, a specific surface area of ​​20-80 m² / g, and a pore volume of 0.05-0.25 cm³ / g.

[0020] It should be noted that in the above preparation method, the molar ratio of sodium molybdate to thiourea can be adjusted within the range of 1:2 to 1:4. Increasing the molar ratio increases the petal density and specific surface area of ​​the resulting nanoflowers. The reaction temperature can be adjusted within the range of 180-220°C. As the temperature increases, the diameter of the nanoflowers tends to decrease. The reaction time can be adjusted within the range of 12-24 hours. Those skilled in the art can select appropriate process conditions within the above range according to the target product parameters.

[0021] In one specific embodiment, 1.21 g of sodium molybdate and 1.52 g of thiourea were dissolved in 60 mL of deionized water and stirred for 30 min until completely dissolved, yielding a clear solution. The solution was transferred to a 100 mL hydrothermal reactor lined with polytetrafluoroethylene (PTFE), sealed, and placed in an oven at 200°C for 18 h. After the reaction, the mixture was allowed to cool naturally to room temperature. The resulting black precipitate was washed three times each with deionized water and anhydrous ethanol, and then vacuum-dried at 70°C for 10 h to obtain molybdenum disulfide nanoflowers. The following examples and comparative examples all use the molybdenum disulfide nanoflowers obtained in this embodiment.

[0022] The obtained molybdenum disulfide nanoflowers are spherical flower-like aggregates formed by the self-assembly of molybdenum disulfide nanosheets, with a diameter of 200-500 nm, a nanosheet thickness of 5-10 nm, an interlayer mesopore diameter of 2-50 nm, a specific surface area of ​​35 m² / g, and a pore volume of 0.12 cm³ / g.

[0023] Example 1 An oil-resistant subsea valve rubber sheet comprises, by weight, the following raw materials: 85 parts nitrile rubber, 12 parts molybdenum disulfide nanoflowers, 2 parts dicumyl peroxide vulcanizing agent, and 8 parts additives. The additives include 3 parts zinc oxide, 1 part stearic acid, 1 part antioxidant TMQ, 1 part carbon black N330, and 2 parts phenolic reinforcing resin.

[0024] The preparation method of the oil-resistant sea valve rubber is as follows: (1) Add 12 parts of molybdenum disulfide nanoflowers to 500 parts of acetone and disperse them under ultrasonic power of 300W for 30 minutes to obtain molybdenum disulfide suspension. (2) Dissolve 85 parts of nitrile rubber in 850 parts of acetone and stir until completely dissolved to obtain a rubber solution; (3) Mix the molybdenum disulfide suspension with the rubber solution and stir at 400 rpm for 30 min to obtain a uniform mixed dispersion. (4) Under stirring at 400 rpm, deionized water was added to the mixed dispersion at a rate of 1 L / min. Nitrile rubber gradually precipitated and molybdenum disulfide nanoflowers were co-precipitated. The precipitate was collected and dried at 60°C for 24 h to constant weight to obtain rubber masterbatch coated with molybdenum disulfide nanoflowers. (5) Plasticize the rubber masterbatch at 50°C on a two-roll mill, add 2 parts of vulcanizing agent DCP, 3 parts of zinc oxide, 1 part of stearic acid, 1 part of antioxidant TMQ, 1 part of carbon black N330, and 2 parts of phenolic reinforcing resin, mix until uniformly dispersed, and then vulcanize at 160°C and 15MPa for 20 minutes to obtain oil-resistant sea valve rubber.

[0025] Example 2 The only difference from Example 1 is that the amount of molybdenum disulfide nanoflowers used is 10 parts.

[0026] Example 3 The only difference from Example 1 is that the amount of molybdenum disulfide nanoflowers used is 15 parts.

[0027] Example 4 The only difference from Example 1 is that the base rubber is replaced with hydrogenated nitrile rubber.

[0028] Comparative Example 1 The only difference from Example 1 is that 12 parts of molybdenum disulfide nanoflowers are replaced with an equal amount of carbon black N330, that is, the total amount of carbon black N330 used is 13 parts.

[0029] Comparative Example 2 The only difference from Example 1 is that 12 parts of molybdenum disulfide nanoflowers were replaced with an equal amount of conventional molybdenum disulfide powder. Conventional molybdenum disulfide powder is a commercially available product with an average particle size of 5 μm, a specific surface area of ​​8 m² / g, and no flower-like aggregate structure.

[0030] Comparative Example 3 The only difference from Example 1 is that 12 parts of molybdenum disulfide nanoflowers were replaced with an equal amount of flake graphite. The average particle size of the flake graphite was 200 μm.

[0031] Comparative Example 4 An oil-resistant subsea valve rubber sheet comprises, by weight, the following raw materials: 85 parts nitrile rubber, 12 parts molybdenum disulfide nanoflowers, 2 parts dicumyl peroxide vulcanizing agent, and 6 parts additives. The additives include 3 parts zinc oxide, 1 part stearic acid, 1 part antioxidant TMQ, 1 part carbon black N330, and 2 parts phenolic reinforcing resin.

[0032] The preparation method of the oil-resistant sea valve rubber is as follows: 85 parts of nitrile rubber were plasticized on a two-roll mill at 50°C for 5 minutes. After the rubber wrapped around the rolls, 12 parts of molybdenum disulfide nanoflowers were added in three batches, mixing for 3 minutes after each addition, for a total of 9 minutes. Then, 3 parts of zinc oxide, 1 part of stearic acid, 1 part of antioxidant TMQ, 1 part of carbon black N330, and 2 parts of phenolic reinforcing resin were added sequentially and mixed for 5 minutes. Finally, 2 parts of vulcanizing agent DCP were added and mixed for 3 minutes. The mixture was then rolled into triangular shapes 6 times, thin-passed 5 times, and sheeted to obtain the compound. The compound was vulcanized at 160°C and 15MPa for 20 minutes to obtain the oil-resistant subsea valve rubber sheet.

[0033] Comparative Example 5 The only difference from Example 1 is that phenolic reinforcing resin is not added. The additives are 3 parts zinc oxide, 1 part stearic acid, 1 part antioxidant TMQ, and 1 part carbon black N330, totaling 6 parts.

[0034] The following performance tests were performed on the rubber sheets prepared in the above embodiments and comparative examples: (1) Resistance to oil swelling under normal pressure Test conditions: atmospheric pressure (0.1MPa), medium is No. 3 white oil, immersion temperature is 60°C, immersion time is 72h.

[0035] Test method: Weigh the rubber sample and measure its volume; completely immerse the sample in a sealed container containing No. 3 white oil and place it in a 60°C constant temperature oven under normal pressure; after 72 hours, remove the sample, quickly wipe off the residual oil on the surface with filter paper, and complete the weighing and volume measurement within 1 minute; calculate the mass change rate = (mass after immersion - mass before immersion) / mass before immersion × 100%, and the volume change rate = (volume after immersion - volume before immersion) / volume before immersion × 100%.

[0036] (2) High pressure resistance to oil swelling Test conditions: pressure 5MPa, medium is No. 3 white oil, immersion temperature 60°C, immersion time 72h.

[0037] Test method: Weigh and measure the volume of the rubber sample, place it in an autoclave, inject No. 3 white oil until the sample is completely submerged, seal it, pressurize it to 5 MPa, heat it to 60°C and maintain the pressure and temperature for 72 hours; after depressurization, take out the sample, quickly wipe the residual oil on the surface with filter paper, and complete the weighing and volume measurement within 1 minute; calculate the mass change rate and volume change rate using the same formula as above.

[0038] (3) Dimensional retention rate of the atmospheric pressure conical surface Test conditions: atmospheric pressure (0.1MPa), medium is No. 3 white oil, immersion temperature is 60°C, immersion time is 72h.

[0039] Test method: Mark three measurement points evenly on the sealing surface of the rubber cone. Measure the thickness of the rubber at each marked point with a micrometer and take the average value as the thickness before immersion. After immersion in No. 3 white oil at 60°C for 72 hours under normal pressure, remove the rubber and measure the thickness at each marked point again. Take the average value as the thickness after immersion. Calculate the cone surface dimensional retention rate = average thickness after immersion / average thickness before immersion × 100%.

[0040] (4) High-pressure cone surface dimensional retention rate Test conditions: pressure 5MPa, medium is No. 3 white oil, immersion temperature 60°C, immersion time 72h.

[0041] Test method: The measurement method is the same as (3), except that the immersion condition is carried out under a pressure of 5MPa in an autoclave. After depressurization, the sample is taken out and the thickness is measured within 1 minute.

[0042] (5) Tensile properties The test was conducted according to GB / T 528-2009, with a tensile speed of 500 mm / min and a test temperature of 23±2°C, using dumbbell-shaped specimens.

[0043] (6) Compression permanent deformation The test was conducted according to GB / T 7759, using type B specimens, a compression ratio of 25%, a test temperature of 60°C, and a test duration of 24 hours. After removing the specimens, they were left at room temperature for 30 minutes, and the recovered thickness was measured. The permanent compression deformation was calculated as follows: (initial thickness - recovered thickness) / (initial thickness - compressed thickness) × 100%.

[0044] (7) Wear resistance Akron abrasion test was conducted according to GB / T 1689. The sample was strip-shaped, with a length of 215 mm, a width of 12.7 mm, and a thickness of 3.2 mm. The grinding wheel speed was 34±1 r / min, the load was 26.7±0.2 N, and the test stroke was 1.61 km.

[0045] Table 1 Performance comparison of each embodiment and comparative example As can be seen from the data in Table 1: Under normal pressure, the volume change rates of Examples 1-4 were significantly lower than those of Comparative Examples 1, 2 and 3, indicating that the flower-like aggregate structure and interlayer mesopores of molybdenum disulfide nanoflowers have a significant effect on inhibiting oil swelling.

[0046] Under a high pressure of 5 MPa, the volume change rate of all examples and comparative examples increased compared to that under normal pressure, but the increase varied significantly: the increase in examples 1-4 was only 1.3-1.9 percentage points, while the highest increase in comparative examples 1-3 reached 4.8 percentage points. This indicates that the interlayer mesopores of molybdenum disulfide nanoflowers can still effectively store and divert oil under high pressure, suppressing the accelerating effect of high pressure on oil permeation; while pure carbon black, conventional MoS2 powder, and flake graphite, lacking interlayer mesopore structure, cannot provide oil storage buffer under high pressure, resulting in increased swelling.

[0047] Under high pressure, the dimensional retention rates of Examples 1-4 were significantly better than those of Comparative Example 1, and the gap between the Examples and the Comparative Example was further widened compared to the conditions under normal pressure. This indicates that the oil storage and shape preservation effect of molybdenum disulfide nanoflowers increased the driving force for oil penetration under high pressure conditions, while the oil storage and diversion mechanism of the interlayer mesopores effectively offset this adverse factor and maintained the dimensional accuracy of the conical sealing surface.

[0048] The compression set of Examples 1-4 was significantly lower than that of Comparative Examples 1 and 5. Comparative Example 5 had a similar formulation to Example 1 but did not contain phenolic reinforcing resin. Its compression set was 5.6 percentage points higher than that of Example 1, confirming the synergistic effect of phenolic reinforcing resin and molybdenum disulfide nanoflowers in enhancing the rubber's resistance to compression set: the phenolic resin and rubber form an interpenetrating network to improve the resilience of the matrix, while the rigid skeleton of the molybdenum disulfide nanoflowers shares the compressive stress. Together, they reduce permanent deformation under repeated high-pressure compression.

[0049] The high-pressure volume change rate of Comparative Example 4 was 4.6 percentage points higher than that of Example 1, the compression set was 2.8 percentage points higher than that of Example 1, and the tensile strength and elongation at break were both lower than those of Example 1. This is because the shear force of mechanical mixing destroyed the flower-like aggregate structure of the molybdenum disulfide nanoflowers, resulting in the loss of a large number of interlayer mesopores, thereby weakening the oil storage and load-bearing functions.

[0050] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. An oil-resistant sea valve rubber sheet, characterized in that, The raw materials, by weight, include: 80-90 parts of base rubber, 10-15 parts of molybdenum disulfide nanoflowers, 0.5-3 parts of vulcanizing agent, and 2-8 parts of additives; the molybdenum disulfide nanoflowers are flower-shaped aggregates formed by the self-assembly of molybdenum disulfide nanosheets, and the flower-shaped aggregates have interlayer mesopores between the molybdenum disulfide nanosheets inside.

2. The oil-resistant sea valve rubber sheet according to claim 1, characterized in that, The base rubber is nitrile rubber or hydrogenated nitrile rubber.

3. The oil-resistant sea valve rubber sheet according to claim 1, characterized in that, The additive contains 1-2 parts of phenolic reinforcing resin.

4. A method for preparing an oil-resistant subsea valve rubber sheet as described in any one of claims 1-3, characterized in that, Includes the following steps: (1) Molybdenum disulfide nanoflowers were dispersed in a first organic solvent and ultrasonically assisted to obtain a molybdenum disulfide suspension; (2) Dissolve the base rubber in a second organic solvent to obtain a rubber solution; (3) The molybdenum disulfide suspension is mixed with the rubber solution to obtain a mixed dispersion; (4) Add water to the mixed dispersion under stirring conditions to allow the base rubber and molybdenum disulfide nanoflowers to precipitate together. Collect the precipitate and dry it to constant weight to obtain rubber masterbatch coated with molybdenum disulfide nanoflowers. (5) The rubber masterbatch is mixed with vulcanizing agent and additives until uniformly dispersed, and then vulcanized to obtain the oil-resistant sea valve rubber sheet.

5. The preparation method according to claim 4, characterized in that, In steps (1) and (2), the first organic solvent and the second organic solvent are each independently selected from one or more of acetone, toluene, butanone, and cyclohexanone.

6. The preparation method according to claim 4, characterized in that, The drying temperature in step (4) is 40-80°C.

7. The preparation method according to claim 4, characterized in that, The mixing temperature in step (5) is 40-60°C, and the vulcanization molding is carried out at 140-170°C and 10-20MPa for 10-30 minutes.

8. The preparation method according to claim 4, characterized in that, The molybdenum disulfide nanoflowers are prepared by the following steps: dissolving sodium molybdate and thiourea in water, with a molar ratio of sodium molybdate to thiourea of ​​1:4, and hydrothermally reacting at 180-220°C for 12-24 hours. After cooling, the nanoflowers are washed and dried to obtain molybdenum disulfide nanoflowers.

9. The preparation method according to claim 4, characterized in that, In step (3), the molybdenum disulfide suspension and the rubber solution are mixed by stirring and / or ultrasonic mixing.

10. The preparation method according to claim 4, characterized in that, The stirring speed in step (4) is 200-800 rpm.

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