Preparation process of a grease containing carbon nanotubes

Abstract

The present invention relates to the technical field of greases, and discloses a preparation process of a grease containing carbon nanotubes. In the present invention, 70-80 parts by weight of fluorosilicone oil, 20-30 parts by weight of polytetrafluoroethylene, and 0.02-0.4 parts by weight of fluorosilicon-modified carbon nanotubes are added to a grease kettle, stirred and blended, and ground after cooling to obtain a grease containing carbon nanotubes. A polymer molecular chain containing trifluoromethyl and siloxane structures is grafted on the surface of the carbon nanotubes, so that the compatibility between the carbon nanotubes and the fluorosilicone oil is better, and they are evenly dispersed in the fluorosilicone grease matrix. As an anti-wear additive, it can better play the role of self-lubrication, play the role of a nano-scale micro-bearing during the lubrication process, reduce the wear scar diameter and friction coefficient of the grease, and improve the anti-wear performance of the grease.

Description

Technical Field

[0001] The present invention relates to the technical field of greases, and specifically to a preparation process of a grease containing carbon nanotubes. Background Art

[0002] Silicone oil-based greases have excellent properties such as low-temperature fluidity and thermal stability, and are widely used in fields such as aerospace, electronics and electrical, and automotive machinery. Introducing fluorine elements into the side chain of silicone oil, the obtained fluorosilicone oil has better lubricity, antioxidant properties, etc. To further improve the anti-wear performance of fluorosilicone oil greases, anti-wear additives need to be added, such as inorganic fillers like bentonite and molybdenum disulfide. The existing invention patent with the publication number CN105733754B discloses an insulating grease containing fluorosilicone oil and its preparation method, which uses fluorosilicone oil, polytetrafluoroethylene, coupling agent, fumed silica, molybdenum disulfide, powder surface treatment agent, mildew preventive, etc. as raw materials. The prepared insulating grease has good properties such as oil resistance, solvent resistance, and heat resistance, but the composition of this insulating grease is complex, which is not conducive to actual industrial production.

[0003] Carbon nanotubes have a unique two-dimensional tubular nanostructure and excellent self-lubricating properties, and are widely used in greases. Modifying the surface of carbon nanotubes can improve their dispersibility in greases. The literature "Study on the Preparation and Tribological Properties of Carbon Nanotube-based Bentonite Greases" elaborates that using oleic acid to modify multi-walled carbon nanotubes can be uniformly and stably dispersed in PAO6 base oil, and the obtained grease has good tribological properties, but the oleic acid-modified multi-walled carbon nanotubes do not show good dispersibility in fluorosilicone oil greases. Summary of the Invention

[0004] The present invention solves the problems of complex raw materials and poor anti-wear performance of existing fluorosilicone oil greases.

[0005] The technical solution of the present invention is as follows: A preparation process of a grease containing carbon nanotubes:

[0006] (1) Add triethylamine, 1,3-bis(3-hydroxypropyl)-1,1,3,3-tetramethyldisiloxane (CAS No. 18001-97-3), and 2,2-bis(4-acylchlorophenyl)hexafluoropropane to N,N-dimethylformamide, and carry out a polymerization reaction under a nitrogen atmosphere to generate a hydroxyl-terminated fluorosilicon polymer; then add acyl chloride-functionalized carbon nanotubes and carry out a grafting reaction. After filtration, wash successively with water, N,N-dimethylformamide, and dichloromethane, and dry to obtain fluorosilicon-modified carbon nanotubes. The preparation reaction route is:

[0007] .

[0008] (2) Add 70 - 80 parts by weight of fluorosilicone oil to the fat-making kettle, heat to the blending temperature, evacuate the air, add 20 - 30 parts by weight of polytetrafluoroethylene and 0.02 - 0.4 parts by weight of fluorosilicon-modified carbon nanotubes, stir and blend, cool after discharging, and grind three times in a three-roll grinder to obtain a grease containing carbon nanotubes.

[0009] Further, the ratio of triethylamine, 1,3 - bis(3 - hydroxypropyl)-1,1,3,3 - tetramethyldisiloxane, 2,2 - bis(4 - acylchlorophenyl)hexafluoropropane, and acyl-chlorinated carbon nanotubes in (1) is (100 - 240 mmol):(55 - 132 mmol):(50 - 120 mmol):100 g.

[0010] Further, the polymerization reaction in (1) is stirred at 20 - 35 °C for 8 - 12 h.

[0011] Further, the grafting reaction in (1) is stirred at 70 - 100 °C for 36 - 48 h.

[0012] Further, the blending temperature in (2) is 160 - 180 °C, and the blending time is 3 - 6 h.

[0013] Further, the preparation process of 2,2 - bis(4 - acylchlorophenyl)hexafluoropropane is as follows: Add 2,2 - bis(4 - carboxyphenyl)hexafluoropropane (CAS No. 1171 - 47 - 7) and the catalyst N,N - dimethylformamide to thionyl chloride, and the ratio of the three is (16 - 20 mL):1 g:(6 - 8 μL); heat to 70 - 75 °C, stir and carry out acyl-chlorination reaction under reflux for 3 - 5 h, carry out vacuum distillation, and recrystallize the product in dichloromethane to obtain 2,2 - bis(4 - acylchlorophenyl)hexafluoropropane. The preparation reaction formula is:

[0014] 。

[0015] Further, the preparation process of the acyl-chlorinated carbon nanotubes is as follows: Add carbon nanotubes to concentrated nitric acid, disperse them by ultrasonic wave, heat to 80 - 90 °C, carry out a reflux reaction for 8 - 12 h, filter and wash with water, dry to obtain carboxylated carbon nanotubes, add them to thionyl chloride, add N,N - dimethylformamide, heat to 70 - 75 °C, carry out a reflux reaction for 24 - 36 h, filter, wash with dichloromethane, and dry to obtain acyl-chlorinated carbon nanotubes. The preparation reaction route is:

[0016] 。

[0017] Advantages of the present invention: By using 1,3-bis(3-hydroxypropyl)-1,1,3,3-tetramethyldisiloxane and 2,2-bis(4-acylchlorophenyl)hexafluoropropane to carry out a polymerization reaction, a fluorosilicon copolymer with terminal hydroxyl groups is obtained. Then, the terminal hydroxyl groups react with the acyl chloride groups on the surface of carbon nanotubes to obtain fluorosilicon-modified carbon nanotubes. The present invention uses fluorosilicon-modified carbon nanotubes as an anti-wear additive, fluorosilicone oil as a base oil, and polytetrafluoroethylene as a thickener to blend and obtain a fluorosilicone grease. The fluorosilicone grease of the present invention has a simple composition and is convenient for industrial actual production. At the same time, a polymer molecular chain containing trifluoromethyl and siloxane structures is grafted on the surface of carbon nanotubes, making the compatibility between carbon nanotubes and fluorosilicone oil better and evenly dispersed in the fluorosilicone grease matrix, which can better play a self-lubricating role, acting as a nano-scale micro-bearing during the lubrication process, reducing the wear scar diameter and friction coefficient of the grease, and improving the anti-wear performance of the grease. Specific Embodiments

[0018] The technical solutions of the present invention will be clearly and completely described below through the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative efforts belong to the scope of protection of the present invention.

[0019] The following fluorosilicone oil, with the model of HOTOLUBE fluorosilicone grease, is purchased from Shanghai Hutou Chemical Co., Ltd. Polytetrafluoroethylene, with the model of nano-scale J24, is purchased from Shanghai Hongshunjiang New Materials Co., Ltd. The carbon nanotubes have a diameter between 8 - 15 nm and a length of 0.5 - 2 μm, and are purchased from Beijing Dekedaojin Technology Co., Ltd.

[0020] Example 1

[0021] (1) Add 0.5 g of 2,2-bis(4-carboxyphenyl)hexafluoropropane and 4 μL of N,N-dimethylformamide to 8 mL of thionyl chloride, heat to 75 °C, stir and reflux for 3 h, carry out vacuum distillation, and recrystallize the product in dichloromethane to obtain 2,2-bis(4-acylchlorophenyl)hexafluoropropane.

[0022] (2) Add 0.2 g of carbon nanotubes to 100 mL of concentrated nitric acid with a mass fraction of 70%, ultrasonically disperse, heat to 80 °C, stir and reflux for 8 h, filter and wash with water, dry, then add the carbon nanotubes to 50 mL of thionyl chloride, add 2.5 mL of N,N-dimethylformamide, heat to 70 °C, stir and reflux for 36 h, filter, wash with dichloromethane, and dry to obtain acyl chloride-functionalized carbon nanotubes.

[0023] (3) 0.18 mmol of triethylamine, 0.1 mmol of 1,3-bis(3-hydroxypropyl)-1,1,3,3-tetramethyldisiloxane, and 0.09 mmol of 2,2-bis(4-acyl chloride phenyl) hexafluoropropane were added to 60 mL of N,N-dimethylformamide. Under a nitrogen atmosphere, the mixture was stirred at 20 °C for 12 h, then 0.1 g of acyl chloride-functionalized carbon nanotubes was added, and the reaction was continued by stirring at 80 °C for 48 h. After filtration, the product was washed successively with water, N,N-dimethylformamide, and dichloromethane, and then dried to obtain fluorosilicon-modified carbon nanotubes.

[0024] (4) 75 g of fluorosilicone oil was added to a grease kettle and heated to the blending temperature. After evacuating the air, 25 g of polytetrafluoroethylene and 0.02 g of fluorosilicon-modified carbon nanotubes were added. The mixture was stirred and blended, cooled after discharging, and ground three times in a three-roll mill to obtain a grease containing carbon nanotubes.

[0025] Example 2

[0026] (1) 0.5 g of 2,2-bis(4-carboxyphenyl) hexafluoropropane and 3 μL of N,N-dimethylformamide were added to 10 mL of thionyl chloride. The mixture was heated to 70 °C, stirred, and refluxed with condensation for 5 h. After distillation under reduced pressure, the product was recrystallized from dichloromethane to obtain 2,2-bis(4-acyl chloride phenyl) hexafluoropropane.

[0027] (2) 0.2 g of carbon nanotubes was added to 70 mL of concentrated nitric acid with a mass fraction of 70%. The mixture was ultrasonically dispersed, heated to 90 °C, stirred, and refluxed with condensation for 12 h. After filtration, it was washed with water and dried. Then the carbon nanotubes were added to 40 mL of thionyl chloride, 2 mL of N,N-dimethylformamide was added, and the mixture was heated to 75 °C, stirred, and refluxed with condensation for 24 h. After filtration, it was washed with dichloromethane and dried to obtain acyl chloride-functionalized carbon nanotubes.

[0028] (3) 0.24 mmol of triethylamine, 0.132 mmol of 1,3-bis(3-hydroxypropyl)-1,1,3,3-tetramethyldisiloxane, and 0.12 mmol of 2,2-bis(4-acyl chloride phenyl) hexafluoropropane were added to 80 mL of N,N-dimethylformamide. Under a nitrogen atmosphere, the mixture was stirred at 35 °C for 8 h, then 0.1 g of acyl chloride-functionalized carbon nanotubes was added, and the reaction was continued by stirring at 70 °C for 48 h. After filtration, the product was washed successively with water, N,N-dimethylformamide, and dichloromethane, and then dried to obtain fluorosilicon-modified carbon nanotubes.

[0029] (4) 70 g of fluorosilicone oil was added to a grease kettle and heated to the blending temperature. After evacuating the air, 30 g of polytetrafluoroethylene and 0.1 g of fluorosilicon-modified carbon nanotubes were added. The mixture was stirred and blended, cooled after discharging, and ground three times in a three-roll mill to obtain a grease containing carbon nanotubes.

[0030] Example 3

[0031] (1) Add 0.1 mmol of triethylamine, 0.055 mmol of 1,3-bis(3-hydroxypropyl)-1,1,3,3-tetramethyldisiloxane, and 0.05 mmol of 2,2-bis(4-acylchlorophenyl)hexafluoropropane (prepared according to the method of Example 1) to 50 mL of N,N-dimethylformamide. Under a nitrogen atmosphere, stir and react at 25 °C for 12 h. Then add 0.1 g of acyl chloride-functionalized carbon nanotubes (prepared according to the method of Example 1), stir and react at 100 °C for 36 h. After filtration, wash successively with water, N,N-dimethylformamide, and dichloromethane, and dry to obtain fluorosilicon-modified carbon nanotubes.

[0032] (2) Add 80 g of fluorosilicone oil to a grease kettle, heat to the blending temperature, evacuate, add 20 g of polytetrafluoroethylene and 0.2 g of fluorosilicon-modified carbon nanotubes, stir and blend. After discharging, cool and grind three times in a three-roll mill to obtain a grease containing carbon nanotubes.

[0033] Example 4

[0034] (1) Add 75 g of fluorosilicone oil to a grease kettle, heat to the blending temperature, evacuate, add 25 g of polytetrafluoroethylene and 0.3 g of fluorosilicon-modified carbon nanotubes (prepared according to the method of Example 1), stir and blend. After discharging, cool and grind three times in a three-roll mill to obtain a grease containing carbon nanotubes.

[0035] Example 5

[0036] (1) Add 75 g of fluorosilicone oil to a grease kettle, heat to the blending temperature, evacuate, add 25 g of polytetrafluoroethylene and 0.4 g of fluorosilicon-modified carbon nanotubes (prepared according to the method of Example 1), stir and blend. After discharging, cool and grind three times in a three-roll mill to obtain a grease.

[0037] Comparative Example 1

[0038] (1) Add 75 g of fluorosilicone oil to a grease kettle, heat to the blending temperature, evacuate, add 25 g of polytetrafluoroethylene, stir and blend. After discharging, cool and grind three times in a three-roll mill to obtain a grease.

[0039] Comparative Example 2

[0040] (1) Add 75 g of fluorosilicone oil to a grease kettle, heat to the blending temperature, evacuate, add 25 g of polytetrafluoroethylene and 0.02 g of carbon nanotubes, stir and blend. After discharging, cool and grind three times in a three-roll mill to obtain a grease containing carbon nanotubes.

[0041] Comparative Example 3

[0042] (1) 0.18 mmol of triethylamine, 0.1 mmol of 1,6 - hexanediamine, and 0.09 mmol of 2,2 - bis(4 - acyl chloride phenyl) hexafluoropropane were added to 60 mL of N,N - dimethylformamide. Under a nitrogen atmosphere, the mixture was stirred at 20 °C for 12 h. Then, 0.1 g of acyl - chlorinated carbon nanotubes was added, and the mixture was stirred at 80 °C for 48 h. After filtration, it was washed successively with water, N,N - dimethylformamide, and dichloromethane, and then dried to obtain fluorine - modified carbon nanotubes.

[0043] (2) 75 g of fluorosilicone oil was added to a grease kettle, heated to the blending temperature, evacuated, 25 g of polytetrafluoroethylene and 0.02 g of fluorine - modified carbon nanotubes were added, and the mixture was stirred and blended. After discharging, it was cooled and ground three times in a three - roll mill to obtain a grease containing carbon nanotubes.

[0044] Comparative Example 4

[0045] (1) 0.18 mmol of triethylamine, 0.1 mmol of 1,3 - bis(3 - hydroxypropyl) - 1,1,3,3 - tetramethyldisiloxane, and 0.09 mmol of terephthaloyl chloride were added to 60 mL of N,N - dimethylformamide. Under a nitrogen atmosphere, the mixture was stirred at 20 °C for 12 h. Then, 0.1 g of acyl - chlorinated carbon nanotubes was added, and the mixture was stirred at 80 °C for 48 h. After filtration, it was washed successively with water, N,N - dimethylformamide, and dichloromethane, and then dried to obtain silicon - modified carbon nanotubes.

[0046] (2) 75 g of fluorosilicone oil was added to a grease kettle, heated to the blending temperature, evacuated, 25 g of polytetrafluoroethylene and 0.02 g of silicon - modified carbon nanotubes were added, and the mixture was stirred and blended. After discharging, it was cooled and ground three times in a three - roll mill to obtain a grease containing carbon nanotubes.

[0047] The four - ball tester was used to test the wear scar diameter and anti - wear performance of the grease according to the method of SH / T 0204 - 1992. During the test, the four - ball tester recorded the corresponding friction coefficient, as shown in Table 1 specifically.

[0048] Table 1 Anti - wear Performance Test of Grease

[0049]

[0050] As can be seen from Table 1, the wear scar diameter and friction coefficient of the fluorosilicone grease in Comparative Example 1 are relatively large, and its anti-wear performance is poor. The fluorosilicone greases of Examples 1-5 are added with fluorosilicon-modified carbon nanotubes, and polymer molecular chains containing trifluoromethyl and siloxane structures are grafted on the surface of the carbon nanotubes, so that the compatibility between the fluorosilicon-modified carbon nanotubes and the fluorosilicone oil is better and they are uniformly dispersed in the fluorosilicone grease matrix, and the self-lubricating effect can be better exerted. The fluorosilicon-modified carbon nanotubes act as anti-wear additives and play the role of nano-scale micro bearings during the lubrication process, reducing the wear scar diameter and friction coefficient of the grease and improving the anti-wear performance of the grease.

[0051] Compared with Example 1, the compatibility between the carbon nanotubes added in Comparative Example 2 and the fluorosilicone oil is poor, and the dispersibility in the grease is not good, so the self-lubricating effect is not well exerted, resulting in the wear scar diameter and friction coefficient of the grease being greater than those of Example 1, and the anti-wear performance of the grease is not good.

[0052] Compared with Example 1, in Comparative Example 3, 1,6-hexanediamine is used as a raw material to prepare fluorine-modified carbon nanotubes that do not contain siloxane structures, and the compatibility and dispersibility with the fluorosilicone grease are lower than those of Example 1; in Comparative Example 4, terephthaloyl chloride is used as a raw material to prepare silicon-modified carbon nanotubes that do not contain fluorine elements, and the compatibility and dispersibility with the fluorosilicone grease are lower than those of Example 1. The wear scar diameter and friction coefficient of the greases in Comparative Example 3 and Comparative Example 4 are both greater than those of Example 1, and the anti-wear performance of the greases is not good.

[0053] The above examples have described in detail the technical solutions and beneficial effects of the present invention. It should be understood that the above are only specific embodiments of the present invention and are not used to limit the present invention. Without departing from the spirit and scope of the present invention, the present invention will have various changes and improvements, and these changes and improvements all fall within the scope of the present invention claimed.

Claims

1. A process for preparing a grease containing carbon nanotubes, characterized in that: The preparation process comprises: (1) adding triethylamine, 1,3-bis(3-hydroxypropyl)-1,1,3,3-tetramethyldisiloxane and 2,2-bis(4-acylchlorophenyl)hexafluoropropane to N,N-dimethylformamide, and performing polymerization reaction in a nitrogen atmosphere, and then adding acyl chloride carbon nanotubes to perform grafting reaction, filtering, washing with water, N,N-dimethylformamide and dichloromethane in turn, and drying to obtain fluorine-silicon modified carbon nanotubes; (2) Add 70-80 parts by weight of fluorosilicone oil to a grease-making kettle, heat to the blending temperature, evacuate, add 20-30 parts by weight of polytetrafluoroethylene and 0.02-0.4 parts by weight of fluorosilicone-modified carbon nanotubes, stir and blend, cool and grind to obtain a grease containing carbon nanotubes.

2. The process for preparing a grease containing carbon nanotubes according to claim 1, characterized in that: The ratio of triethylamine, 1,3-bis(3-hydroxypropyl)-1,1,3,3-tetramethyldisiloxane, 2,2-bis(4-chlorophenyl)hexafluoropropane and chlorinated carbon nanotubes in (1) is (100-240 mmol): (55-132 mmol): (50-120 mmol): 100 g.

3. The process for preparing a grease containing carbon nanotubes according to claim 1, characterized in that: The polymerization reaction in (1) is stirred at 20-35°C for 8-12 hours.

4. The process for preparing a grease containing carbon nanotubes according to claim 1, characterized in that: The grafting reaction in (1) is stirred at 70-100° C. for 36-48 hours.

5. The process for preparing a grease containing carbon nanotubes according to claim 1, characterized in that: In the step (2), the blending temperature is 160-180° C. and the blending time is 3-6 h.

6. The process for preparing a grease containing carbon nanotubes according to claim 2, characterized in that: The preparation process of 2,2-bis(4-chlorophenyl)hexafluoropropane is as follows: 2,2-bis(4-carboxyphenyl)hexafluoropropane and N,N-dimethylformamide are added to thionyl chloride to carry out chlorination reaction, and the product is distilled under reduced pressure and recrystallized in dichloromethane to obtain 2,2-bis(4-chlorophenyl)hexafluoropropane.

7. The process for preparing a grease containing carbon nanotubes according to claim 6, characterized in that: The ratio of thionyl chloride, 2,2-bis(4-carboxyphenyl)hexafluoropropane and N,N-dimethylformamide is (16-20 mL): 1 g: (6-8 μL).

8. The process for preparing a grease containing carbon nanotubes according to claim 6, characterized in that: The acyl chloride reaction was stirred at 70-75°C and refluxed under condensation for 3-5h.

9. The process for preparing a grease containing carbon nanotubes according to claim 2, characterized in that: The preparation process of the acyl chloride carbon nanotubes is as follows: adding the carbon nanotubes to concentrated nitric acid, ultrasonically dispersing, heating to 80-90° C., condensing and refluxing for 8-12 hours, filtering, washing with water, and drying, then adding the carbon nanotubes to thionyl chloride, adding N,N-dimethylformamide, heating to 70-75° C., condensing and refluxing for 24-36 hours, filtering, washing with dichloromethane, and drying to obtain the acyl chloride carbon nanotubes.

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