High-temperature-resistant anti-shearing lubricating grease composition and preparation method thereof

Abstract

The invention discloses a high-temperature-resistant anti-shearing lubricating grease composition and a preparation method thereof, and belongs to the technical field of lubricating grease, the lubricating grease composition comprises base oil, a polyurea thickening agent and an additive, the additive is prepared from 40 to 60 weight percent of a carbon nano tube and / or an epoxy-hydroxyl terminated hyperbranched polyester modified carbon nano tube. Compared with a bipolyurea compound, the tetrapolyurea compound contains a large number of ureido groups and a formed compact fiber structure, so that the phenomenon of high-temperature hardening can be effectively improved. The introduction of the carbon nanotubes can improve the ability of the lubricating grease to disperse and transfer heat and avoid the breakage of molecular chains of the polyurea thickening agent caused by heat piling in the lubricating grease and further hardening, meanwhile, the carbon nanotubes are embedded in the lubricating grease structure, the high-rigidity structure can improve the ability of the material to resist deformation, and the shear resistance of the lubricating grease is obviously improved.

Description

Technical Field

[0001] The invention belongs to the technical field of lubricating greases, and in particular relates to a high temperature resistant and shear resistant lubricating grease composition and a preparation method thereof. Background Art

[0002] Polyurea grease is obtained by thickening base oil with organic compounds containing urea groups. Unlike general soap-based grease, polyurea grease does not contain metal ions and has excellent oxidation resistance. Under high temperature conditions, there will be no phenomenon of metal ions catalyzing the oxidation of grease. Therefore, polyurea grease has a high dropping point, excellent oxidation stability and a long lubrication service life, and is widely used in the lubrication of various high-grade precision bearings.

[0003] However, polyurea grease still has some defects and shortcomings. The most prominent of which is that polyurea grease will harden after running for a period of time under high temperature conditions. In actual application, the hardening of polyurea grease at high temperature will affect the lubrication effect. In severe cases, it will block the grease supply pipeline, causing the grease to fail to reach the required parts in time, bringing safety hazards to the use of mechanical equipment, thereby limiting the application scope of polyurea grease. Summary of the invention

[0004] The object of the present invention is to provide a high temperature resistant and shear resistant grease composition and a preparation method thereof, so as to solve the problem of high temperature hardening and poor high temperature resistance of polyurea grease.

[0005] The purpose of the present invention can be achieved through the following technical solutions:

[0006] In the first aspect, the present invention provides a high temperature resistant and shear resistant grease composition, comprising a base oil, a polyurea thickener and an additive, wherein the polyurea thickener is a tetraurea compound; the additive comprises 40 to 60 wt % of carbon nanotubes and / or epoxy-hydroxyl terminated hyperbranched polyester modified carbon nanotubes.

[0007] By adopting the above technical solution, the tetraurea compound contains more urea-based molecules than the traditional diurea compound, so that the fiber structure formed by the polyurea thickener in the base oil is compact, the wrapping effect on the base oil is enhanced, and the base oil is not easily lost in a high temperature environment; in a high temperature environment, since the NH bonds and C=O bonds contained in the polyurea thickener are easily broken, it will cause the polyurea grease to harden, while the tetraurea compound has a high content of effective groups and will not be completely destroyed at high temperatures, and the high-temperature hardening phenomenon is significantly improved.

[0008] At the same time, carbon nanotubes and / or epoxy-hydroxyl terminated hyperbranched polyester modified carbon nanotubes are added to the grease of the present application. In addition to reducing friction and wear and improving the lubricating properties of the grease, the carbon nanotubes themselves have good thermal stability, and their high thermal conductivity can improve the high temperature resistance of the polyurea grease composition, help to quickly disperse and transfer heat, reduce heat accumulation inside, and further reduce the thermal decomposition problem of the polyurea grease composition, and improve the high temperature hardening problem of the polyurea grease. Compared with carbon nanotubes, epoxy-hydroxyl terminated hyperbranched polyester modified carbon nanotubes have better dispersibility and more significant improvement in material performance.

[0009] In addition, carbon nanotubes have a high aspect ratio and rigidity. After being embedded in the structure of the polyurea grease composition, they can significantly improve the stability and load-bearing capacity of the structure, improve the grease's ability to resist shear deformation, and also show good stability and recovery ability under high-temperature shear.

[0010] Preferably, the grease composition comprises the following raw materials in parts by weight:

[0011] 70-80 parts of base oil;

[0012] 15-20 parts of polyurea thickener;

[0013] 6 to 12 parts of additives.

[0014] Preferably, the base oil comprises a combination of one or more of mineral oil, polyalphaolefin synthetic oil, ester synthetic oil, ether synthetic oil and silicone oil; the kinematic viscosity of the base oil at 40°C is 100 to 600 mm 2 / s.

[0015] More preferably, the base oil has a kinematic viscosity at 40°C of 200 to 500 mm 2 / s.

[0016] Preferably, the additive further comprises 8-12 wt% antioxidant, 20-30 wt% extrusion anti-wear agent and 10-20 wt% rust inhibitor.

[0017] Preferably, the antioxidant is a phenolic antioxidant and / or an amine antioxidant.

[0018] More preferably, the phenolic antioxidant includes a combination of one or more of 2,6-di-tert-butyl-p-cresol, 4,4'-methylenebis(2,6-di-tert-butylphenol), and 2,6-di-tert-butyl-4-methylphenol; the amine antioxidant includes a combination of one or more of N-phenyl-a-naphthylamine, alkylated naphthylamine, didodecyldiphenylamine, octylbutyldiphenylamine, and diisooctyldiphenylamine.

[0019] Preferably, the extrusion anti-wear agent includes one or a combination of dialkyl dithiocarbamate, zinc dialkyl dithiophosphate, molybdenum dibutyl dithiocarbamate and sulfurized isobutylene.

[0020] Preferably, the rust inhibitor comprises one or a combination of barium dinonylnaphthalenesulfonate, imidazoline derivatives and zinc naphthenate.

[0021] By adopting the above technical solution, the present application adopts a base oil with a higher viscosity, which can improve the high temperature resistance of the grease, and at the same time cooperate with other additives to improve the overall performance of the grease composition.

[0022] Preferably, the raw materials for epoxy-hydroxyl terminated hyperbranched polyester modified carbon nanotubes include multi-walled carbon nanotubes and epoxy-hydroxyl terminated hyperbranched polyester in a mass ratio of 1:(5-7).

[0023] By adopting the above technical solution, carbon nanotubes generally have poor oil solubility in grease and tend to agglomerate after a long time, resulting in uneven dispersion of the carbon nanotubes, which in turn affects the improvement effect of the carbon nanotubes on the grease. Epoxy-hydroxyl terminated hyperbranched polyester modified carbon nanotubes can improve the compatibility and dispersibility with the grease and enhance the performance of the grease.

[0024] At the same time, the epoxy and hydroxyl groups in the epoxy-hydroxyl terminated hyperbranched polyester molecular chain segments can interact with the polyurea thickener through hydrogen bonds and covalent bonds, so that the modified carbon nanotubes and the polyurea thickener form a more compact three-dimensional structure and are evenly embedded in the grease structure. The macromolecular hyperbranched polyester can also reduce the free rotation between molecules, improve the ability of the grease to resist deformation, and improve the shear resistance of the grease while improving the stability of the grease structure. The hardening phenomenon of polyurea grease caused by the breakage of molecular bonds at high temperatures can be compensated and restored by the introduction of epoxy and hydroxyl groups to restore the molecular chain breakage after the functional groups are destroyed, stabilize the cross-linked structure of the grease, and prevent hardening, thereby improving the high-temperature stability of the polyurea grease.

[0025] Preferably, the epoxy-hydroxyl terminated hyperbranched polyester is prepared according to the following method:

[0026] The pentaerythritol and dihydroxy acid are mixed and heated to 130-140° C., stirred and dissolved, and then an acid catalyst is added. Under a nitrogen atmosphere, the mixture is stirred and reacted at 100-120° C. for 5-6 hours, and then washed, vacuum distilled and dried to obtain a hydroxyl-terminated hyperbranched polyester;

[0027] Epichlorohydrin is added to a solvent, and the mixture is stirred and dissolved to obtain a pre-reaction liquid; the temperature of the obtained hydroxyl-terminated hyperbranched polyester is raised to 60-70° C., a Lewis acid catalyst is added, and the mixture is stirred and mixed; the pre-reaction liquid is added under a nitrogen atmosphere, and the mixture is stirred and reacted for 6-8 hours; and then the epoxy-hydroxyl-terminated hyperbranched polyester is obtained through washing, reduced pressure distillation, and drying, wherein the mass ratio of the hydroxyl-terminated hyperbranched polyester to epichlorohydrin is 100:(3.5-4).

[0028] Preferably, the dihydroxy acid is one or a combination of 2,2-dimethylolbutanoic acid and 2,2-dimethylolpropionic acid.

[0029] Preferably, the mass ratio of pentaerythritol to dihydroxy acid is 1:(12-15).

[0030] Preferably, the acidic catalyst comprises a combination of one or more of p-toluenesulfonic acid, phosphoric acid and sulfuric acid.

[0031] Preferably, the solvent is aqueous sodium hydroxide solution.

[0032] By adopting the above technical scheme, the hydroxyl-terminated hyperbranched polyester is subjected to epoxidation modification treatment, and by setting the raw materials and parameters in the preparation process, part of the epoxy groups can be grafted onto the terminal molecular chains of the hyperbranched polyester, while retaining the hydroxyl groups on the original hyperbranched polyester. The simultaneous introduction of epoxy groups and hydroxyl groups can enhance the interaction with the polyurea thickener, can timely fill the molecular chain breaks at high temperatures, re-form a new structure, and avoid the occurrence of high-temperature hardening.

[0033] Preferably, the epoxy-hydroxyl terminated hyperbranched polyester modified carbon nanotubes are prepared according to the following method:

[0034] Pretreatment of carbon nanotubes: adding multi-walled carbon nanotubes to a strong acid solution, raising the temperature to 40-50°C, stirring and dispersing for 10-12 hours, standing for stratification, washing, drying, and grinding to obtain pretreated carbon nanotubes;

[0035] Preparation of epoxy-hydroxyl terminated hyperbranched polyester modified carbon nanotubes: pretreated carbon nanotubes and epoxy-hydroxyl terminated hyperbranched polyester are added to N,N-dimethylformamide, the temperature is raised to 50-60°C, dispersed for 2-3 hours, and then the temperature is further raised to 110-130°C. The reaction is stirred at a constant temperature for 24-36 hours, and finally the epoxy-hydroxyl terminated hyperbranched polyester modified carbon nanotubes are obtained by washing, filtering, drying and grinding.

[0036] By adopting the above technical solution, the multi-walled carbon nanotubes are firstly treated with acid to expose more oxygen-containing functional groups which can further react and link with the functional groups in the epoxy-hydroxyl terminated hyperbranched polyester, thereby improving the grafting rate of the carbon nanotubes.

[0037] Preferably, the raw materials of the polyurea thickener include diisocyanate, monoamine and diamine in a molar ratio of 1: (0.5-0.6): (0.8-1); the monoamine is a C12-C18 long-chain fatty monoamine; and the diamine is an aromatic diamine.

[0038] Preferably, the diisocyanate includes one or a combination of 4,4-diphenylmethane diisocyanate, diphenyl diisocyanate, toluene diisocyanate, cyclohexane diisocyanate, and 4,4-dicyclohexylmethane diisocyanate.

[0039] More preferably, the aromatic diamine includes one or a combination of diaminodiphenylmethane, p-diaminobenzidine, and m-phenylenediamine.

[0040] By adopting the above technical scheme, the polyurea thickener of the present application is obtained by the reaction between diisocyanate and a mixture of monoamine and diamine. Specifically, the monoamine adopts a long-chain fatty monoamine, which can adjust the thickening degree and extensibility of the thickener. The diamine adopts an aromatic diamine, which can increase the benzene ring content in the polyurea thickener, thereby improving the thermal stability of the material. The structure of the polyurea thickener is not easy to change under high temperature conditions, which is conducive to the improvement of the high-temperature hardening problem.

[0041] Preferably, the raw material of the polyurea thickener further includes an aminosilane coupling agent; the molar ratio of the aminosilane coupling agent to the diisocyanate is (0.1-0.2):1.

[0042] Preferably, the aminosilane coupling agent includes a combination of one or more of γ-aminopropyltriethoxysilane, γ-aminopropyltrimethoxysilane, N-β (aminoethyl)-γ-aminopropylmethyldimethoxysilane, N-β (aminoethyl)-γ-aminopropyltrimethoxysilane, and N-β (aminoethyl)-γ-aminopropyltriethoxysilane.

[0043] By adopting the above technical solution, an aminosilane coupling agent is also added to the polyurea thickener, which can improve the interfacial force between the polyurea thickener and the carbon nanotubes, making the intercalation between the carbon nanotubes and the polyurea grease tighter, and at the same time coordinating the internal cross-linking structure of the polyurea grease, improving the shear resistance of the grease, improving the stability of the grease in a high temperature environment, and improving the hardening phenomenon of the polyurea thickener.

[0044] In a second aspect, the present application also provides a method for preparing a high temperature resistant and shear resistant grease composition, comprising the following process steps:

[0045] S1. Add diisocyanate and carbon nanotubes and / or epoxy-hydroxyl-terminated hyperbranched polyester modified carbon nanotubes to 70 to 80 wt % of base oil, and raise the temperature to 70 to 90 ° C to obtain a mixed solution;

[0046] S2. adding monoamine and diamine to the remaining base oil, raising the temperature to 70-90°C after mixing, and then adding to the mixed solution obtained in step S1, stirring and reacting at 80-100°C for 30-60min, and then continuing to raise the temperature to 160-200°C, refining at a constant temperature to obtain a premix;

[0047] S3. Cool the premix to 60-80° C., add other additive components, and mix well to obtain a high temperature resistant and shear resistant grease composition.

[0048] More preferably, in step S2, an aminosilane coupling agent is also added to the remaining base oil.

[0049] Beneficial effects of the present invention:

[0050] 1. The grease composition of the present application uses a tetraurea compound as a polyurea thickener. The large amount of urea groups contained and the compact fiber structure formed can effectively improve the high-temperature hardening phenomenon; the introduction of benzene ring groups during the preparation process can further improve the thermal stability and shear resistance of the grease.

[0051] 2. The grease composition of the present application contains carbon nanotubes, which can improve the lubrication effect while improving the ability of the grease to disperse and transfer heat, avoiding the problem of heat accumulation inside the grease, which causes the molecular chain to break and the polyurea thickener to harden. The carbon nanotubes modified with epoxy-hydroxyl terminated hyperbranched polyester can improve the dispersibility in the grease, and the introduction of epoxy and hydroxyl groups can help the carbon nanotubes to better interact with the polyurea thickener, so that the carbon nanotubes are evenly embedded in the grease structure, and the material's ability to resist shear deformation is improved. DETAILED DESCRIPTION

[0052] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0053] Preparation Example

[0054] Preparation Example 1: An epoxy-hydroxyl terminated hyperbranched polyester modified carbon nanotube is prepared according to the following method:

[0055] Preparation of epoxy-hydroxyl terminated hyperbranched polyester:

[0056] Take 10g of pentaerythritol and 130g of 2,2-dihydroxymethylbutyric acid, mix them, raise the temperature to 140°C, stir and dissolve, then add 3g of p-toluenesulfonic acid, stir and react at 110°C for 6h under nitrogen atmosphere, then wash, distill under reduced pressure and dry to obtain hydroxyl-terminated hyperbranched polyester; add 3.8g of epichlorohydrin to 50mL of 20% sodium hydroxide aqueous solution by mass, stir and dissolve to obtain a pre-reaction liquid; take 100g of the obtained hydroxyl-terminated hyperbranched polyester, raise the temperature to 65°C, add 1.5g of boron trifluoride ether and stir and mix, add the pre-reaction liquid under nitrogen atmosphere, stir and react for 8h, then wash, distill under reduced pressure and dry to obtain epoxy-hydroxyl-terminated hyperbranched polyester.

[0057] Preparation of Epoxy-Hydroxyl-Terminated Hyperbranched Polyester Modified Carbon Nanotubes:

[0058] 10 g of multi-walled carbon nanotubes (average diameter of 8.7-10 nm) were added to 250 mL of strong acid solution (concentrated sulfuric acid and concentrated nitric acid in a mass ratio of 2:1), the temperature was raised to 45°C, the mixture was stirred and dispersed for 12 hours, and after standing for stratification, the pretreated carbon nanotubes were obtained by washing, drying and grinding; 10 g of the pretreated carbon nanotubes and 60 g of the epoxy-hydroxyl-terminated hyperbranched polyester obtained above were added to 500 mL of N,N-dimethylformamide, the temperature was raised to 60°C, and after dispersion for 3 hours, the temperature was further raised to 120°C, and the reaction was stirred at a constant temperature for 32 hours. Finally, the epoxy-hydroxyl-terminated hyperbranched polyester-modified carbon nanotubes were obtained by washing, filtering, drying and grinding.

[0059] Preparation Example 2, an epoxy-hydroxyl terminated hyperbranched polyester modified carbon nanotube, is different from Preparation Example 1 only in that the added amount of 2,2-dihydroxymethylbutyric acid is 120 g, the added amount of epichlorohydrin is 3.5 g, and the added amount of epoxy-hydroxyl terminated hyperbranched polyester is 50 g.

[0060] Preparation Example 3, an epoxy-hydroxyl terminated hyperbranched polyester modified carbon nanotube, is different from Preparation Example 1 only in that the added amount of 2,2-dihydroxymethylbutyric acid is 150 g, the added amount of epichlorohydrin is 4 g, and the added amount of epoxy-hydroxyl terminated hyperbranched polyester is 70 g.

[0061] Preparation Example 4, an epoxy-hydroxyl terminated hyperbranched polyester modified carbon nanotube, is different from Preparation Example 1 only in that the amount of epichlorohydrin added is 3 g.

[0062] Preparation Example 5, an epoxy-hydroxyl terminated hyperbranched polyester modified carbon nanotube, is different from Preparation Example 1 only in that the amount of epichlorohydrin added is 4.5 g.

[0063] Preparation Example 6, an epoxy-hydroxyl terminated hyperbranched polyester modified carbon nanotube, prepared according to the following method:

[0064] Preparation of hydroxyl terminated hyperbranched polyester:

[0065] Take 10g of pentaerythritol and 130g of 2,2-dihydroxymethylbutyric acid, mix them and raise the temperature to 140°C. After stirring and dissolving, add 3g of p-toluenesulfonic acid. Stir and react at 110°C for 6h under nitrogen atmosphere. Then, wash, distill under reduced pressure and dry to obtain hydroxyl-terminated hyperbranched polyester.

[0066] Preparation of Epoxy-Hydroxyl Terminated Hyperbranched Polyester Modified Carbon Nanotubes:

[0067] 10 g of multi-walled carbon nanotubes (average diameter of 8.7-10 nm) were added to 250 mL of strong acid solution (concentrated sulfuric acid and concentrated nitric acid in a mass ratio of 2:1), the temperature was raised to 45°C, the mixture was stirred and dispersed for 12 hours, and after standing for stratification, the pretreated carbon nanotubes were obtained by washing, drying and grinding; 10 g of the pretreated carbon nanotubes and 60 g of the hydroxyl-terminated hyperbranched polyester obtained above were added to 500 mL of N,N-dimethylformamide, the temperature was raised to 60°C, and after dispersion for 3 hours, the temperature was further raised to 120°C, and the reaction was stirred at a constant temperature for 32 hours. Finally, the epoxy-hydroxyl-terminated hyperbranched polyester-modified carbon nanotubes were obtained by washing, filtering, drying and grinding.

[0068] Preparation Example 7, an epoxy-hydroxyl terminated hyperbranched polyester modified carbon nanotube, is different from Preparation Example 1 only in that the added amount of epoxy-hydroxyl terminated hyperbranched polyester is 40 g.

[0069] Preparation Example 8, an epoxy-hydroxyl terminated hyperbranched polyester modified carbon nanotube, is different from Preparation Example 1 only in that the added amount of epoxy-hydroxyl terminated hyperbranched polyester is 80 g.

[0070] Example

[0071] Example 1, a high temperature resistant and shear resistant grease composition is prepared according to the following process steps:

[0072] S1. Add 70 g of 4,4-diphenylmethane diisocyanate and 50 g of multi-walled carbon nanotubes (average diameter of 8.7 to 10 nm) to 600 g of poly-alpha-olefin synthetic oil (model PA040), and raise the temperature to 80 ° C to obtain a mixed solution;

[0073] S2. 38 g of octadecylamine and 55 g of diaminodiphenylmethane were added to 150 g of polyalphaolefin synthetic oil (model PA040), the temperature was raised to 80 ° C after mixing, and then added to the mixed solution obtained in step S1, stirred at 100 ° C for 40 min, and then the temperature was further raised to 190 ° C, and the mixture was refined at a constant temperature to obtain a premix;

[0074] S3. The premix is ​​cooled to 70° C., 10 g of 2,6-di-tert-butyl-p-cresol, 25 g of dialkyl dithiocarbamate and 15 g of barium dinonylnaphthalenesulfonate are added, and the mixture is mixed evenly to obtain a high temperature resistant and shear resistant grease composition.

[0075] Examples 2 to 5 are high temperature resistant and shear resistant grease compositions, which differ from Example 1 only in that the raw material ratios are adjusted, as shown in Table 1:

[0076] Table 1 Formula table of Example 1 to Example 5

[0077]

[0078]

[0079] Wherein, single-walled carbon nanotubes (average diameter of 1.6 nm) are used in Examples 2 and 3, and multi-walled carbon nanotubes (average diameter of 8.7-10 nm) are used in Examples 4 and 5.

[0080] Example 6, a high temperature resistant and shear resistant grease composition, is different from Example 1 only in that an equal amount of epoxy-hydroxyl terminated hyperbranched polyester modified carbon nanotubes prepared in Preparation Example 1 is used to replace the multi-walled carbon nanotubes.

[0081] Example 7, a high temperature resistant and shear resistant grease composition, is different from Example 1 only in that an equal amount of epoxy-hydroxyl terminated hyperbranched polyester modified carbon nanotubes prepared in Preparation Example 2 is used to replace the multi-walled carbon nanotubes.

[0082] Example 8, a high temperature resistant and shear resistant grease composition, is different from Example 1 only in that an equal amount of epoxy-hydroxyl terminated hyperbranched polyester modified carbon nanotubes prepared in Preparation Example 3 is used to replace the multi-walled carbon nanotubes.

[0083] Example 9, a high temperature resistant and shear resistant grease composition, is different from Example 1 only in that an equal amount of epoxy-hydroxyl terminated hyperbranched polyester modified carbon nanotubes prepared in Preparation Example 4 is used to replace the multi-walled carbon nanotubes.

[0084] Example 10, a high temperature resistant and shear resistant grease composition, is different from Example 1 only in that an equal amount of epoxy-hydroxyl terminated hyperbranched polyester modified carbon nanotubes prepared in Preparation Example 5 are used to replace the multi-walled carbon nanotubes.

[0085] Example 11, a high temperature resistant and shear resistant grease composition, is different from Example 1 only in that the multi-walled carbon nanotubes are replaced with an equal amount of epoxy-hydroxyl terminated hyperbranched polyester modified carbon nanotubes prepared in Preparation Example 6.

[0086] Example 12, a high temperature resistant and shear resistant grease composition, differs from Example 1 only in that an equal amount of epoxy-hydroxyl terminated hyperbranched polyester modified carbon nanotubes prepared in Preparation Example 7 are used to replace the multi-walled carbon nanotubes.

[0087] Example 13, a high temperature resistant and shear resistant grease composition, is different from Example 1 only in that an equal amount of epoxy-hydroxyl terminated hyperbranched polyester modified carbon nanotubes prepared in Preparation Example 8 are used to replace the multi-walled carbon nanotubes.

[0088] Example 14, a high temperature resistant and shear resistant grease composition, is different from Example 6 only in that in step S2, 10 g of γ-aminopropyltrimethoxysilane is further added to the base oil.

[0089] Comparative Example

[0090] Comparative Example 1, a high temperature resistant and shear resistant grease composition, is prepared according to the following process steps:

[0091] S1. 80 g of 4,4-diphenylmethane diisocyanate and 50 g of multi-walled carbon nanotubes (average diameter of 8.7 to 10 nm) were added to 600 g of poly-alpha-olefin synthetic oil (model PA040), and the temperature was raised to 80 ° C to obtain a mixed solution;

[0092] S2. 80 g of octadecylamine was added to 150 g of polyalphaolefin synthetic oil (model PA040), the temperature was raised to 80 ° C after mixing, and then added to the mixed solution obtained in step S1, stirred at 100 ° C for 40 min, and then the temperature was further raised to 190 ° C, and the mixture was refined at a constant temperature to obtain a premix;

[0093] S3. The premix is ​​cooled to 70° C., 10 g of 2,6-di-tert-butyl-p-cresol, 25 g of dialkyl dithiocarbamate and 15 g of barium dinonylnaphthalenesulfonate are added, and the mixture is mixed evenly to obtain a high temperature resistant and shear resistant grease composition.

[0094] Comparative Example 2 is a high temperature resistant and shear resistant grease composition, which is different from Example 1 only in that the added amount of multi-walled carbon nanotubes is 30 g.

[0095] Comparative Example 3 is a high temperature resistant and shear resistant grease composition, which is different from Example 1 only in that the added amount of multi-walled carbon nanotubes is 7 g.

[0096] Comparative Example 4 is a high temperature resistant and shear resistant grease composition, which is different from Example 1 only in that multi-walled carbon nanotubes are not added.

[0097] Performance testing

[0098] 1. Shear resistance test: Test the shear resistance of grease according to GB / T 269-2023 "Cone penetration test of grease and petroleum grease". Specifically, the shear resistance of grease is tested by extending the working time of grease by 10 5 The difference between the cone penetration after the second shearing and the working cone penetration (60 times) reflects the ability of the grease composition to maintain appropriate consistency and prevent leakage after repeated shearing.

[0099] 2. High temperature resistance test:

[0100] (1) The high temperature and oxidation resistance of grease is measured according to the industry standard SH / T 0428-2008 "Method for determining the life of grease in ball bearings at high temperatures". The test conditions are: speed 10,000 rpm, temperature 177°C. The high temperature and oxidation resistance of grease is determined by the results of the Gaowen high-speed life bench test.

[0101] (2) The grease was kept at a constant temperature for 3 h at different temperatures, and the cone penetration (0.1 mm) of the grease after high temperature treatment was tested to compare the hardening of the grease composition. The temperature was selected to be 120°C and 180°C.

[0102] The above test results are shown in Table 2:

[0103] Table 2 Performance test results

[0104]

[0105] According to Table 1, in combination with Example 1 and Example 2 to Example 5, it can be seen that the performance test results of Example 2 to Example 5 are not much different from those of Example 1, indicating that the shear resistance and high temperature resistance of Example 2 to Example 5 are not significantly different from those of Example 1. The difference between Example 2 to Example 5 and Example 1 is only that the ratio of the raw materials is adjusted within the required range, which has little effect on the final performance.

[0106] In combination with Example 1 and Example 6 to Example 13, it can be seen that the performance parameters of Example 6 are improved compared with those of Example 1, the difference in cone penetration is reduced, the shear resistance is enhanced, the cone penetration changes little at high temperatures, and the hardening phenomenon is better improved. The reason is that the carbon nanotubes in Example 6 are modified with epoxy-hydroxyl terminated hyperbranched polyester, and have better dispersibility in the grease, enhanced interaction with the thickener, improved high temperature resistance, and the introduction of epoxy and hydroxyl groups also enables the grease molecular chain to be restored in time after breaking, which can effectively improve the high temperature hardening phenomenon of the material. Compared with Example 6, Examples 7 and 8 only adjust the raw materials within the required range, so the performance is not greatly affected. Compared with Example 6, Examples 9 to 11 adjust the content of epoxy groups in the epoxy-hydroxyl terminated hyperbranched polyester. In Example 9, the content of epoxy groups is reduced, and the interaction force between the system decreases, resulting in a decrease in shear resistance and high temperature resistance. In Example 11, no epoxy groups are added, and the performance decreases more significantly. In Example 11, the content of epoxy groups is increased, resulting in a decrease in the hydroxyl content in the system, a decrease in the hydrogen bonding effect between the thickener, and a decrease in shear resistance. Compared with Example 6, Examples 12 and 13 change the modification amount of the hyperbranched polyester. A decrease in the grafting rate will lead to a decrease in the interaction force between the carbon nanotubes and the polyurea thickener. An excessive grafting rate will affect the lubricating performance of the grease itself, and the cone penetration will decrease.

[0107] Combining Example 6 and Example 14, it can be seen that the performance of Example 14 is improved compared with that of Example 6. The reason is that Example 14 also adds an aminosilane coupling agent, which can improve the interfacial force between the polyurea thickener and the carbon nanotubes, so that the carbon nanotubes can be better embedded in the grease system, thereby improving the material's ability to resist deformation.

[0108] Combining Example 1 and Comparative Examples 1 to 4, it can be seen that the performance of Comparative Examples 1 to 4 is significantly reduced compared to that of Example 1. Specifically, the thickener used in Comparative Example 1 is a diurea compound, which has a significantly reduced stability compared to the tetraurea compound, and lacks the introduction of rigid groups such as benzene rings, resulting in a decrease in the high temperature resistance of the obtained grease, and a more obvious hardening phenomenon. Comparative Examples 2 to 4 mainly adjust the amount of carbon nanotubes added in the system. A small amount of carbon nanotubes is not conducive to the improvement of the material, and a large amount of carbon nanotubes will easily cause carbon nanotubes to agglomerate, affecting performance improvement. Without adding carbon nanotubes, the heat of the material cannot be dispersed and transferred in time, and the internal accumulation is very likely to cause the hardening of the polyurea thickener, and the material's ability to resist deformation will also be significantly reduced.

[0109] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device.

[0110] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A high temperature resistant and shear resistant grease composition comprising a base oil, a polyurea thickener and an additive, It is characterized in that The polyurea thickener is a tetraurea compound; the additive comprises 40-60 wt % of carbon nanotubes and / or epoxy-hydroxyl terminated hyperbranched polyester modified carbon nanotubes.

2. The high temperature resistant and shear resistant grease composition according to claim 1, It is characterized in that The grease composition comprises the following raw materials in parts by weight: 70-80 parts of base oil; 15-20 parts of polyurea thickener; 6 to 12 parts of additives.

3. The high temperature resistant and shear resistant grease composition according to claim 1, It is characterized in that The raw materials of the epoxy-hydroxyl-terminated hyperbranched polyester modified carbon nanotubes include multi-walled carbon nanotubes and epoxy-hydroxyl-terminated hyperbranched polyester in a mass ratio of 1:(5-7).

4. The high temperature resistant and shear resistant grease composition according to claim 3, It is characterized in that The epoxy-hydroxyl terminated hyperbranched polyester is prepared according to the following method: The pentaerythritol and dihydroxy acid are mixed and heated to 130-140° C., stirred and dissolved, and then an acid catalyst is added. Under a nitrogen atmosphere, the mixture is stirred and reacted at 100-120° C. for 5-6 hours, and then washed, vacuum distilled and dried to obtain a hydroxyl-terminated hyperbranched polyester; Epichlorohydrin is added to a solvent, and the mixture is stirred and dissolved to obtain a pre-reaction liquid; the temperature of the obtained hydroxyl-terminated hyperbranched polyester is raised to 60-70° C., a Lewis acid catalyst is added, and the mixture is stirred and mixed; the pre-reaction liquid is added under a nitrogen atmosphere, and the mixture is stirred and reacted for 6-8 hours; and then the epoxy-hydroxyl-terminated hyperbranched polyester is obtained through washing, reduced pressure distillation, and drying, wherein the mass ratio of the hydroxyl-terminated hyperbranched polyester to epichlorohydrin is 100:(3.5-4).

5. The high temperature resistant and shear resistant grease composition according to claim 3, It is characterized in that The epoxy-hydroxyl terminated hyperbranched polyester modified carbon nanotubes are prepared according to the following method: Pretreatment of carbon nanotubes: adding multi-walled carbon nanotubes to a strong acid solution, raising the temperature to 40-50°C, stirring and dispersing for 10-12 hours, standing for stratification, washing, drying, and grinding to obtain pretreated carbon nanotubes; Preparation of epoxy-hydroxyl terminated hyperbranched polyester modified carbon nanotubes: pretreated carbon nanotubes and epoxy-hydroxyl terminated hyperbranched polyester are added to N,N-dimethylformamide, the temperature is raised to 50-60°C, dispersed for 2-3 hours, and then the temperature is further raised to 110-130°C. The reaction is stirred at a constant temperature for 24-36 hours, and finally the epoxy-hydroxyl terminated hyperbranched polyester modified carbon nanotubes are obtained by washing, filtering, drying and grinding.

6. The high temperature resistant and shear resistant grease composition according to claim 1, It is characterized in that The raw materials of the polyurea thickener include diisocyanate, monoamine and diamine in a molar ratio of 1: (0.5-0.6): (0.8-1); the monoamine is a C12-C18 long-chain fatty monoamine; and the diamine is an aromatic diamine.

7. The high temperature resistant and shear resistant grease composition according to claim 6, It is characterized in that The raw materials of the polyurea thickener also include an aminosilane coupling agent; the molar ratio of the aminosilane coupling agent to diisocyanate is (0.1-0.2):

1.

8. The high temperature resistant and shear resistant grease composition according to claim 1, It is characterized in that The base oil comprises a combination of one or more of mineral oil, polyalphaolefin synthetic oil, ester synthetic oil, ether synthetic oil and silicone oil; the kinematic viscosity of the base oil at 40°C is 100-600 mm 2 / s.

9. The high temperature resistant and shear resistant grease composition according to claim 1, It is characterized in that The additives also include 8-12 wt% antioxidant, 20-30 wt% extrusion anti-wear agent and 10-20 wt% rust preventive.

10. A method for preparing a high temperature resistant and shear resistant grease composition according to any one of claims 1 to 9, It is characterized in that The method comprises the following steps: S1. Add diisocyanate and carbon nanotubes and / or epoxy-hydroxyl-terminated hyperbranched polyester modified carbon nanotubes to 70 to 80 wt % of base oil, and raise the temperature to 70 to 90 ° C to obtain a mixed solution; S2. adding monoamine and diamine to the remaining base oil, raising the temperature to 70-90°C after mixing, and then adding to the mixed solution obtained in step S1, stirring and reacting at 80-100°C for 30-60min, and then continuing to raise the temperature to 160-200°C, refining at a constant temperature to obtain a premix; S3. Cool the premix to 60-80° C., add other additive components, and mix well to obtain a high temperature resistant and shear resistant grease composition.

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