Vacuum conductive lubricating grease and preparation method thereof

Abstract

The invention relates to vacuum conductive lubricating grease, which is prepared from the following raw materials in percentage by weight: 40 to 90 percent of base oil, 2 to 30 percent of thickening agent and 5 to 50 percent of conductive filler. Meanwhile, the invention also discloses a preparation method of the vacuum conductive lubricating grease. The vacuum conductive lubricating grease disclosed by the invention has the characteristics of extremely low vacuum volatilization loss, relatively high conductivity, excellent lubricating performance, good stability and the like, and is suitable for high and low temperatures, high vacuum, large and small currents and various application working conditions.

Description

Technical Field

[0001] The invention relates to the technical field of special lubricating grease, and in particular to a vacuum conductive lubricating grease and a preparation method thereof. Background Art

[0002] There is friction wear caused by mutual movement between electrical contact motion friction pairs, as well as electro-corrosion caused by current transmission. Under the coupling of multiple fields such as electric field, magnetic field, temperature field and stress field, as well as the coupling of multiple factors such as current, dynamic load and electrochemical corrosion, serious adhesive wear and abrasive wear occur. At the same time, brittle fracture, micro-motion wear and arc erosion may also occur, which seriously reduces the reliability, accuracy and service life of electrical equipment. Therefore, coating conductive grease with both lubricating and conductive properties between electrical contact motion friction pairs can effectively reduce interface friction wear, reduce interface contact resistance, improve the stability of current or electrical signal transmission, and ensure the service life of electrical equipment. Conductive grease is a semi-solid lubricating material prepared by combining base oil, thickener and conductive components through a specific process. Compared with traditional grease, conductive grease uses the conductive components (including metal powder, carbon-based materials, ionic liquids, conductive polymers and other conductive materials) therein to form a current path, thereby reducing the resistance at the joints of electrical equipment and preventing electrochemical corrosion caused by contact resistance and electro-corrosion caused by oil film breakdown.

[0003] With the development of aerospace and modern industrial technology, some special electrical moving parts need to operate in a vacuum environment and realize accurate and stable transmission of current or electrical signals. Due to the low saturated vapor pressure and difficulty in heat dissipation in a vacuum environment, ordinary conductive grease will volatilize, separate oil, creep, harden, etc. under vacuum conditions, and form a resistance film and high-temperature zone on the surface of the friction pair, resulting in insufficient lubrication and conductivity, causing the operating torque of the electrical contact moving parts to increase, severe wear, and increased contact resistance. In severe cases, even jamming and short circuits may occur. In addition, the large amount of volatilization and creep of grease will cause contamination of the vacuum chamber or other components, and the maintenance cost of equipment in a vacuum environment is high, and it may even be impossible to repair, which greatly limits the development of equipment technology in a vacuum environment. Therefore, the production of a conductive grease that has excellent conductivity and lubrication properties suitable for vacuum environments will greatly meet the technical development needs of the aerospace and vacuum industries. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a vacuum conductive grease with extremely low vacuum volatilization loss, high conductivity, excellent lubrication performance and good stability performance.

[0005] Another technical problem to be solved by the present invention is to provide a preparation method of the vacuum conductive grease.

[0006] In order to solve the above problems, the vacuum conductive grease described in the present invention is characterized in that the conductive grease is composed of the following raw materials by weight percentage: 40% to 90% base oil, 2% to 30% thickener, and 5% to 50% conductive filler.

[0007] The base oil is selected from a mixture of one or more of low vacuum volatilization synthetic hydrocarbon oil, synthetic silicon carbon oil, silicone oil, and perfluoropolyether oil.

[0008] The thickener is an inorganic thickener or an organic metal soap thickener.

[0009] The inorganic thickener is a mixture of one or more of nano-polytetrafluoroethylene, nano-boron nitride, nano-polyimide and nano-fluorinated graphene.

[0010] The organic metal soap thickener is produced by the reaction of dodecyl hydroxystearic acid, sebacic acid, boric acid and alkali.

[0011] The base is one or more of hydrated lithium hydroxide, hydrated barium hydroxide, and hydrated strontium hydroxide.

[0012] The conductive filler is selected from a mixture of one or more of graphite, conductive carbon black, graphene oxide, MXene nanosheets, nano silver powder, and nano copper powder.

[0013] The method for preparing the vacuum conductive grease as described above comprises the following steps: ⑴Weigh according to the ratio; (2) Pre-treating the base oil under vacuum heating conditions to obtain the pre-treated base oil; ⑶ Add the pretreated base oil to the thickener for thickening to obtain the base grease; (4) After the base grease is cooled to 80°C, the conductive filler is evenly mixed into it, the mixture is stirred evenly, and it is homogenized two to three times on a three-roll mill to make the conductive filler completely and evenly mixed, and then vacuum heating treatment is performed to obtain vacuum conductive grease.

[0014] The vacuum heating condition is that the heating temperature is 120-125°C and the vacuum pressure is less than 5×10 -3 Pa, and the heating time was 24 h.

[0015] Compared with the prior art, the present invention has the following advantages: 1. The base oil used in the present invention is a vacuum-specific lubricating oil with an extremely low saturated vapor pressure and a low volatility in a vacuum environment, which can significantly reduce the vacuum volatilization loss of the conductive grease. On the one hand, it avoids the change of the grease structure and performance caused by vacuum volatilization, and on the other hand, it avoids the contamination of the vacuum chamber or other equipment by vacuum volatiles.

[0016] 2. The base oil selected by the present invention has good high and low temperature resistance, which solves the problem of lubrication failure caused by low temperature environment that vacuum equipment may face, and the problem of high temperature lubrication failure caused by poor vacuum heat dissipation.

[0017] 3. The present invention completely removes vacuum volatiles such as moisture, air and light components in the raw materials and grease preparation process by initially vacuum heating the base oil and later vacuum heating the conductive grease, making the lubricating film more stable, enabling the conductive agent to form a complete current path, and improving the lubrication and conductivity of the conductive grease.

[0018] 4. The present invention selects a conductive agent with both lubricating and conductive properties, which significantly improves the lubricating properties of the conductive grease through the solid-liquid synergistic effect between the conductive agent and the lubricating oil, avoids the use of friction-reducing and anti-wear agents, and further improves the conductive properties of the conductive grease.

[0019] 5. The vacuum conductive grease of the present invention is suitable for high and low temperatures, high vacuum, large and small currents, and various application conditions. When used between electrical contact moving parts of vacuum equipment, it can significantly reduce the friction and wear of the friction pair, reduce contact resistance, improve current transmission stability, avoid the influence of vacuum volatiles on the chamber or other equipment, and effectively extend the service life of the mechanism. DETAILED DESCRIPTION

[0020] A vacuum conductive grease, which is composed of the following raw materials by weight percentage (g / g): 40% to 90% base oil, 2% to 30% thickener, and 5% to 50% conductive filler.

[0021] Wherein: the base oil is selected from a mixture of one or more of synthetic hydrocarbon oil, synthetic silicon hydrocarbon oil, silicone oil, and perfluoropolyether oil that volatilizes in low vacuum, preferably synthetic hydrocarbon oil.

[0022] The thickener is an inorganic thickener or an organic metal soap thickener.

[0023] The inorganic thickener is a mixture of one or more of nano polytetrafluoroethylene, nano boron nitride, nano polyimide and nano fluorinated graphene.

[0024] The organometallic soap thickener is produced by the reaction of dodecyl hydroxystearic acid, sebacic acid, boric acid and alkali.

[0025] The base is one or more of hydrated lithium hydroxide, hydrated barium hydroxide, and hydrated strontium hydroxide.

[0026] The conductive filler is selected from a mixture of one or more of graphite, conductive carbon black, graphene oxide, MXene nanosheets, nano silver powder, and nano copper powder, preferably a mixture of graphite and conductive carbon black.

[0027] A method for preparing vacuum conductive grease comprises the following steps: ⑴Weigh according to the ratio.

[0028] (2) Pre-treat the base oil under vacuum heating conditions, the heating temperature is 120~125℃, and the vacuum pressure is less than 5×10 -3 Pa, the heating treatment time is 24 h, the air, moisture, light components and other substances mixed in the base oil are removed, the quality of vacuum volatiles is reduced, and the pretreated base oil is obtained.

[0029] ⑶ Add the pretreated base oil to the thickener for thickening to obtain the base grease.

[0030] (4) After the base grease is cooled to 80°C, the conductive filler is evenly mixed into it, mixed and stirred evenly, and homogenized on a three-roll mill for two to three times to make the conductive filler completely and evenly mixed, and then vacuum heated at a temperature of 120-125°C and a vacuum pressure of less than 5×10 -3 Pa, the heating treatment time is 24 h, and the volatile substances in the conductive grease are completely removed to obtain vacuum conductive grease.

[0031] Example 1 A vacuum conductive grease is composed of the following raw materials: 160 g of base oil, 20 g of thickener, and 20 g of conductive filler.

[0032] Among them: the base oil is MACs hydrocarbon lubricant.

[0033] The thickener is a mixture of a saponify formed by dodecyl hydroxystearic acid and hydrated lithium hydroxide, and a saponify formed by sebacic acid and hydrated lithium hydroxide, and the mass ratio (g / g) of the two is 4:1; the molar ratio of dodecyl hydroxystearic acid to hydrated lithium hydroxide is 1:1; the molar ratio of sebacic acid to hydrated lithium hydroxide is 1:2; and the molar ratio of boric acid to hydrated lithium hydroxide is 1:1.

[0034] The conductive filler is a mixture of graphite and conductive carbon black, with a mass ratio (g / g) of 5:1.

[0035] The preparation method thereof comprises the following steps: ⑴Weigh according to the ratio; (2) At 125 °C, 3 × 10 -3 Pa conditions, 160 g of base oil was heated for 24 h to remove the air, moisture, light components and other substances mixed in the base oil, and the pretreated base oil was obtained.

[0036] ⑶ Add the pre-treated base oil to the thickener for thickening to obtain the base grease. The specific process is as follows: ① Take 53 g of the base oil and add it into a normal pressure reactor, add 15.7 g of dodecyl hydroxystearic acid and 3.77 g of sebacic acid, stir and heat to dissolve to obtain solution A; ② Dissolve 3.7 g of lithium hydroxide monohydrate in 10 g of water to prepare solution B. When the temperature of solution A in step ① is raised to 85°C, slowly add solution B into solution A to complete the reaction; ③ Gradually heat to 115 °C, dehydrate and saponify for 1 h, and add 53 g of base oil; ④ Gradually raise the temperature to 215 °C, add 0.02 g of boric acid, stir at constant temperature for 15 min, add the remaining 54 g of base oil, and gradually cool down to obtain the base grease.

[0037] (4) After the base grease is cooled to 80°C, 20 g of conductive filler is evenly mixed into it, mixed and stirred evenly, and homogenized on a three-roll mill for two to three times to make the conductive filler completely and evenly mixed, and then vacuum heated at a heating temperature of 120~125°C and a vacuum pressure of 10 -3 Pa, the heating treatment time is 24 h, and the volatile substances in the conductive grease are completely removed to obtain vacuum conductive grease.

[0038] Example 2 A vacuum conductive grease is composed of the following raw materials: 140 g of base oil, 10 g of thickener, and 50 g of conductive filler.

[0039] Among them: the base oil is MACs hydrocarbon lubricant.

[0040] The thickener is a mixture of a saponify of dodecyl hydroxystearic acid and hydrated barium hydroxide, and a saponify of sebacic acid and hydrated barium hydroxide, the mass ratio (g / g) of the two being 9:1; the molar ratio of dodecyl hydroxystearic acid to hydrated barium hydroxide is 2:1; the molar ratio of sebacic acid to hydrated barium hydroxide is 1:1; and the molar ratio of boric acid to hydrated barium hydroxide is 2:1.

[0041] The conductive filler is a mixture of graphite and conductive carbon black, with a mass ratio (g / g) of 3:2.

[0042] The preparation method thereof comprises the following steps: ⑴Weigh according to the ratio; (2) At 125 °C, 3 × 10 -3 140 g of base oil was pretreated by heating at 400 °C for 24 h under the conditions of Pa to remove the air, moisture, light components and other substances mixed in the base oil, thus obtaining the pretreated base oil.

[0043] ⑶ Add the pre-treated base oil to the thickener for thickening to obtain the base grease. The specific process is as follows: ① Take 46 g of the base oil and add it into a normal pressure reactor, add 7.34 g of dodecyl hydroxystearic acid and 0.60 g of sebacic acid, stir and heat to dissolve to obtain solution A; ② Grind 4.79 g of barium hydroxide octahydrate into powder in a crucible. When the temperature of solution A in step ① is raised to 85°C, slowly add the barium hydroxide octahydrate powder into solution A to complete the reaction; ③ Gradually heat to 115 °C, dehydrate and saponify for 1 h, and add 46 g of base oil; ④ Gradually raise the temperature to 215 °C, add 0.02 g of boric acid, stir at constant temperature for 15 min, add the remaining 48 g of base oil, and gradually cool down to obtain the base grease.

[0044] ⑷ After the base grease is cooled to 80℃, 50g of conductive filler is evenly mixed into it, mixed and stirred evenly, and homogenized on a three-roll mill for two to three times to make the conductive filler completely and evenly mixed, and then vacuum heated at a heating temperature of 120~125℃ and a vacuum pressure of 10 -3 Pa, the heating treatment time is 24 h, and the volatile substances in the conductive grease are completely removed to obtain vacuum conductive grease.

[0045] Example 3 A vacuum conductive grease is composed of the following raw materials: 100 g of base oil, 20 g of inorganic thickener, and 80 g of conductive filler.

[0046] Among them: the base oil is selected as perfluoropolyether lubricant.

[0047] The inorganic thickener is a mixture of nano-polytetrafluoroethylene, nano-polyimide and nano-fluorinated graphene, and the mass ratio (g / g) is 3:1:1.

[0048] The conductive filler is a mixture of graphite, conductive carbon black and MXene nanosheets with a mass ratio (g / g) of 5:2:2.

[0049] The preparation method thereof comprises the following steps: ⑴Weigh according to the ratio; (2) At 125 °C, 3 × 10 -3 The base oil was pretreated by heating at 4000 rpm for 24 h to remove the air, moisture, light components and other substances mixed in the base oil, thereby obtaining the pretreated base oil.

[0050] ⑶ Add inorganic thickener to the pre-treated base oil for thickening to obtain base grease. The specific process is as follows: ① Take 50 g of the base oil and add it into a normal pressure reactor, add 20 g of inorganic thickener, stir and heat to 150°C; ② Stir at 150 °C for 30 min, then add 50 g of base oil, stir and gradually cool down to obtain base grease.

[0051] ⑷ After the base grease is cooled to 80℃, 80g of conductive filler is evenly mixed into it, mixed and stirred evenly, and homogenized on a three-roll mill for two to three times to make the conductive filler completely and evenly mixed, and then vacuum heated at a heating temperature of 120~125℃ and a vacuum pressure of 10 -3 Pa, the heating treatment time is 24 h, and the volatile substances in the conductive grease are completely removed to obtain vacuum conductive grease.

[0052] Example 4 A vacuum conductive grease is composed of the following raw materials: 100 g of base oil, 10 g of thickener, and 90 g of conductive filler.

[0053] Among them: silicone oil lubricant is selected as the base oil.

[0054] The thickener is a mixture of a saponified product of dodecyl hydroxystearic acid and hydrated lithium hydroxide, and a saponified product of dodecyl hydroxystearic acid and hydrated strontium hydroxide, the mass ratio (g / g) of the two being 4:1; the molar ratio of dodecyl hydroxystearic acid to hydrated lithium hydroxide is 1:1; the molar ratio of dodecyl hydroxystearic acid to hydrated strontium hydroxide is 2:1; and the molar ratio of boric acid to hydrated lithium hydroxide is 1:1.

[0055] The conductive filler is a mixture of graphite, graphene oxide and MXene nanosheets with a mass ratio (g / g) of 5:1:1.

[0056] The preparation method thereof comprises the following steps: ⑴Weigh according to the ratio; (2) At 125 °C, 3 × 10 -3 100 g of base oil was heated and pretreated for 24 h under Pa conditions to remove the air, moisture, light components and other substances mixed in the base oil, thus obtaining the pretreated base oil.

[0057] ⑶ Add the pre-treated base oil to the thickener for thickening to obtain the base grease. The specific process is as follows: ① Take 33 g of the base oil and add it into a normal pressure reactor, add 9.47 g of dodecyl hydroxystearic acid, stir and heat to dissolve to obtain solution A; ② Dissolve 1.10 g of lithium hydroxide monohydrate and 0.74 g of strontium hydroxide octahydrate in 5 g of water to prepare solution B. When the temperature of solution A in step ① is raised to 85°C, slowly add solution B into solution A to complete the reaction; ③ Gradually heat to 115 °C, dehydrate and saponify for 1 h, and add 33 g of base oil; ④ Gradually raise the temperature to 215 °C, add 0.02 g of boric acid, stir at constant temperature for 15 min, add the remaining 34 g of base oil, and gradually cool down to obtain the base grease.

[0058] (4) After the base grease is cooled to 80°C, 90 g of conductive filler is evenly mixed into it, mixed and stirred evenly, and homogenized on a three-roll mill for two to three times to make the conductive filler completely and evenly mixed, and then vacuum heated at a heating temperature of 120~125°C and a vacuum pressure of 10 -3 Pa, the heating treatment time is 24 h, and the volatile substances in the conductive grease are completely removed to obtain vacuum conductive grease.

[0059] Example 5 A vacuum conductive grease is composed of the following raw materials: 120 g of base oil, 16 g of thickener, and 64 g of conductive filler.

[0060] Among them: the base oil is selected as silicon-carbon-hydrogen lubricating oil.

[0061] The thickener is a mixture of a saponify formed by dodecyl hydroxystearic acid and hydrated lithium hydroxide, a saponify formed by sebacic acid and hydrated barium hydroxide, and a saponify formed by dodecyl hydroxystearic acid and hydrated strontium hydroxide, and the mass ratio (g / g) of the three is 6:1:1; the molar ratio of dodecyl hydroxystearic acid to hydrated lithium hydroxide is 1:1; the molar ratio of sebacic acid to hydrated barium hydroxide is 1:1; the molar ratio of dodecyl hydroxystearic acid to hydrated strontium hydroxide is 2:1; and the molar ratio of boric acid to hydrated lithium hydroxide is 1:1.

[0062] The conductive filler is a mixture of graphite, conductive carbon black and MXene nanosheets with a mass ratio (g / g) of 10:1:1.

[0063] The preparation method thereof comprises the following steps: ⑴Weigh according to the ratio; (2) At 125 °C, 3 × 10 -3 Pa conditions, 120 g of base oil was heated for 24 h to remove the air, moisture, light components and other substances mixed in the base oil, and the pretreated base oil was obtained.

[0064] ⑶ Add the pre-treated base oil to the thickener for thickening to obtain the base grease. The specific process is as follows: ① Take 40 g of the base oil and add it into a normal pressure reactor, add 13.43 g of dodecyl hydroxystearic acid and 1.20 g of sebacic acid, stir and heat to dissolve to obtain solution A; ② Dissolve 1.65 g of lithium hydroxide monohydrate, 1.87 g of barium hydroxide octahydrate and 0.716 g of strontium hydroxide octahydrate in 5 g of water to prepare solution B. When the temperature of solution A in step ① is raised to 85°C, slowly add solution B into solution A for complete reaction; ③ Gradually heat to 115 °C, dehydrate and saponify for 1 h, and add 40 g of base oil; ④ Gradually raise the temperature to 215 °C, add 0.02 g of boric acid, stir at constant temperature for 15 min, add the remaining 40 g of base oil, and gradually cool down to obtain the base grease.

[0065] (4) After the base grease is cooled to 80°C, 64 g of conductive filler is evenly mixed into it, mixed and stirred evenly, and homogenized on a three-roll mill for two to three times to make the conductive filler completely and evenly mixed, and then vacuum heated at a heating temperature of 120-125°C and a vacuum pressure of 10 -3 Pa, the heating treatment time is 24 h, and the volatile substances in the conductive grease are completely removed to obtain vacuum conductive grease.

[0066] Example 6 A vacuum conductive grease is composed of the following raw materials: 120 g of base oil, 16 g of thickener, and 64 g of conductive filler.

[0067] Among them: the base oil is MACs hydrocarbon lubricant.

[0068] The thickener is the same as in Example 5.

[0069] The conductive filler is a mixture of graphite, conductive carbon black, nano silver powder and nano copper powder, and the mass ratio (g / g) is 8:1:1:1.

[0070] The preparation method is the same as Example 5.

[0071] The conductivity of the vacuum conductive grease obtained in Examples 1 to 6 was measured by a volume surface resistivity tester, and the lubrication performance was measured by a four-ball friction tester (40 kgf, 1200 r / min, 60 min). The conductivity and lubrication performance of the vacuum conductive grease were compared with those of PE01 vacuum grease. The results are shown in Table 1.

[0072] Table 1 Volume resistivity and four-ball wear spot diameter values ​​of PE01 vacuum grease and grease in the examples It can be seen from Table 1 that the volume resistivity of the conductive grease prepared by the present invention is 10 4 ~10 2 Ω•m order of magnitude, which is higher than the volume resistivity of PE01 vacuum grease (10 11The wear spot diameter is about 0.691 mm to 0.851 mm, which is about 19% to 34% lower than the wear spot diameter (1.050 mm) of PE01 vacuum grease. This proves that the conductive grease prepared by the present invention has excellent conductive properties and lubricating properties.

Claims

1. A vacuum conductive grease, characterized in that: The conductive grease is composed of the following raw materials by weight: 40% to 90% base oil, 2% to 30% thickener, and 5% to 50% conductive filler.

2. A vacuum conductive grease as claimed in claim 1, characterized in that: The base oil is selected from a mixture of one or more of low vacuum volatilization synthetic hydrocarbon oil, synthetic silicon carbon oil, silicone oil, and perfluoropolyether oil.

3. A vacuum conductive grease as claimed in claim 1, characterized in that: The thickener is an inorganic thickener or an organic metal soap thickener.

4. A vacuum conductive grease as claimed in claim 3, characterized in that: The inorganic thickener is a mixture of one or more of nano-polytetrafluoroethylene, nano-boron nitride, nano-polyimide and nano-fluorinated graphene.

5. A vacuum conductive grease as claimed in claim 3, characterized in that: The organic metal soap thickener is produced by the reaction of dodecyl hydroxystearic acid, sebacic acid, boric acid and alkali.

6. A vacuum conductive grease as claimed in claim 5, characterized in that: The base is one or more of hydrated lithium hydroxide, hydrated barium hydroxide, and hydrated strontium hydroxide.

7. A vacuum conductive grease as claimed in claim 1, characterized in that: The conductive filler is selected from a mixture of one or more of graphite, conductive carbon black, graphene oxide, MXene nanosheets, nano silver powder, and nano copper powder.

8. The method for preparing a vacuum conductive grease according to claim 1, comprising the following steps: ⑴Weigh according to the ratio; (2) Pre-treating the base oil under vacuum heating conditions to obtain the pre-treated base oil; ⑶ Add the pretreated base oil to the thickener for thickening to obtain the base grease; (4) After the base grease is cooled to 80°C, the conductive filler is evenly mixed into it, the mixture is stirred evenly, and it is homogenized two to three times on a three-roll mill to make the conductive filler completely and evenly mixed, and then vacuum heating treatment is performed to obtain vacuum conductive grease.

9. A method for preparing a vacuum conductive grease according to claim 8, characterized in that: The vacuum heating condition is that the heating temperature is 120-125°C and the vacuum pressure is less than 5×10 -3 Pa, and the heating time was 24 h.

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