Bentonite lubricating grease and preparation method thereof

Abstract

The invention provides bentonite lubricating grease and a preparation method thereof. The bentonite lubricating grease disclosed by the invention is prepared from the following components in percentage by weight on the basis of the total mass of the lubricating grease: 0.1 to 10 percent of antioxidant, 0.1 to 10 percent of antirust agent, 0.1 to 10 percent of extreme pressure agent, 3 to 35 percent of organic bentonite and 60 to 95 percent of pentaerythritol ester, the pentaerythritol ester comprises the following components in percentage by mass: 5 to 50 percent of pentaerythritol ester as shown in a formula (I) and 50 to 95 percent of pentaerythritol ester as shown in a formula (II), wherein an R group is C1-C14 straight chain or branched chain alkylene; and each R'group is independently selected from C3-C9 straight chain or branched chain alkyl. The bentonite lubricating grease provided by the invention has excellent oxidation resistance, low-temperature performance, colloid stability, heat resistance and anti-corrosion and anti-rust performance, and can meet the lubrication requirement in a wider temperature range.

Description

Technical Field

[0001] The present invention relates to lubricating grease, in particular to bentonite lubricating grease and a preparation method thereof. Background Art

[0002] Bentonite greases made with modified bentonite thickened base oils exhibit excellent heat resistance, oxidation stability, and colloidal stability. They are widely used for lubrication of metallurgical equipment, casting and rolling equipment, heavy mining machinery, large trucks, papermaking machinery, cement production equipment, high-temperature tunnel pit cars, aircraft wheel bearings, railway diesel locomotives, and pipe thread seal assemblies. With the rapid development of the machinery industry, increasingly stringent requirements are being placed on lubricating materials, which need to meet the requirements of both high- and low-temperature operating conditions.

[0003] In recent years, there have been many studies on wide-temperature greases. CN 102250671B prepared a wide-temperature extreme-pressure composite lithium-based grease by using polyalphaolefins, ester oils, composite lithium-based thickeners, antioxidants, anti-corrosion and anti-rust agents, and extreme-pressure and anti-wear agents. CN104194875A used a mixed oil of polyalphaolefins and castor-based polyethylene glycol sebacate to prepare a degradable castor-based wide-temperature bearing grease. CN 108102773A used polyalphaolefins and alkyl naphthalene as base oils and polyurea as a thickener to prepare a wide-temperature extreme-pressure, water-resistant and anti-wear grease. CN 103602494A proposed a heat-resistant grease. However, none of the above documents simultaneously addressed the antioxidant properties and -60°C low-temperature performance of the grease.

[0004] Developing bentonite grease with a wider operating temperature range and better oxidation stability is still one of the research and development directions of those skilled in the art. Summary of the Invention

[0005] The invention provides a bentonite grease and a preparation method thereof.

[0006] The bentonite grease of the present invention comprises, based on the total mass of the grease, 0.1% to 10% of an antioxidant, 0.1% to 10% of a rust inhibitor, 0.1% to 10% of an extreme pressure agent, 3% to 35% of an organic bentonite, and 60% to 95% of a pentaerythritol ester; the pentaerythritol ester comprises, by mass, 5% to 50% of a pentaerythritol ester represented by formula (I) and 50% to 95% of a pentaerythritol ester represented by formula (II):

[0007]

[0008] The R group is C1~C 14 Each R' group is independently selected from a C3 to C9 straight chain or branched chain alkyl group.

[0009] According to the present invention, the R group is preferably a C2 to C8 straight chain or branched alkylene group; each R' group is preferably selected from two or more (for example, three or four) of a C3 straight chain or branched alkyl group, a C4 straight chain or branched alkyl group, a C5 straight chain or branched alkyl group, a C6 straight chain or branched alkyl group, a C7 straight chain or branched alkyl group, a C8 straight chain or branched alkyl group, and a C9 straight chain or branched alkyl group, more preferably selected from a C3 straight chain alkyl group, a C4 straight chain alkyl group, a C5 straight chain alkyl group, a C6 straight chain alkyl group, a C7 straight chain alkyl group, a C8 straight chain alkyl group. % of C5 linear alkyl, 5.0 mol% to 45.0 mol% of C6 linear alkyl, 0 to 30.0 mol% of C7 linear alkyl, 0 to 15.0 mol% of C8 linear alkyl, and 0 to 10.0 mol% of C9 linear alkyl.

[0010] According to the present invention, the pentaerythritol ester preferably comprises, by mass, 5% to 25% of the pentaerythritol ester represented by formula (I) and 75% to 95% of the pentaerythritol ester represented by formula (II).

[0011] The preparation method of pentaerythritol ester of the present invention comprises the following steps:

[0012] (1) Excessive monopentaerythritol and C 3～16 The dibasic fatty acid undergoes esterification reaction to obtain esterification product A1;

[0013] (2) Esterification product A1 and excess C 4～10 The monobasic fatty acids undergo esterification reaction and the products are collected.

[0014] According to the present invention, in step (1), the monopentaerythritol and C 3～16 The molar ratio of the dibasic fatty acid can be (2.05-100):1, preferably (3-60):1, and more preferably (3-30):1; in step (2), the hydroxyl group and C in the esterification product A1 4～10 The molar ratio of the carboxyl groups in the monobasic fatty acid may be 1:(1.05-1.30), preferably 1:(1.10-1.20).

[0015] According to the present invention, the reaction temperature of step (1) is 50-180°C, preferably 80-150°C, and the reaction time is 1-20h, preferably 2-10h; the reaction temperature of step (2) is 50-250°C, preferably 100-220°C, and the reaction time is until water is no longer produced, which can generally be 1-20h, or 5-10h.

[0016] According to the present invention, the dibasic fatty acid can be one or more of malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, dodecanedioic acid, tetradecanedioic acid, and hexadecanedioic acid.

[0017] According to the present invention, the monobasic fatty acid is preferably selected from two or more (for example, three or four) of n-butyric acid, isobutyric acid, n-pentanoic acid, isovaleric acid, n-hexanoic acid, isohexanoic acid, n-heptanoic acid, isoheptanoic acid, n-octanoic acid, isooctanoic acid, n-nonanoic acid, isononanoic acid, n-decanoic acid, and isodecanoic acid, and is more preferably selected from two or more (for example, three or four) of n-butyric acid, n-pentanoic acid, n-hexanoic acid, n-heptanoic acid, n-octanoic acid, n-nonanoic acid, and n-decanoic acid. Further preferably, the monobasic fatty acid may include 0-10.0 mol% of n-butyric acid, 0-35.0 mol% of n-pentanoic acid, 30.0 mol%-75.0 mol% of n-hexanoic acid, 5.0 mol%-45.0 mol% of n-heptanoic acid, 0-30.0 mol% of n-octanoic acid, 0-15.0 mol% of n-nonanoic acid, and 0-10.0 mol% of n-decanoic acid.

[0018] According to the present invention, a catalyst may be added to the esterification reaction in step (1) and / or step (2), and the catalyst includes one or more of concentrated sulfuric acid, sodium bisulfate, p-toluenesulfonic acid, zinc oxide, a cation exchange resin, an ionic liquid, stannous oxide, a titanate, and activated carbon. The amount of the catalyst added may be in accordance with the amount used in the esterification reaction in the prior art and is not particularly limited. The catalyst may be removed after the esterification reaction by methods well known in the art, such as alkali washing, water washing, and filtration, and is not particularly limited.

[0019] According to the present invention, a solvent may be added during the esterification reaction in step (1) and / or step (2). The solvent may be one or more of xylene, toluene, and cyclohexane. The amount of the solvent added may be in accordance with the amount used in the esterification reaction in the prior art and is not particularly limited. The solvent may be removed after the esterification reaction by methods well known in the art, such as distillation, and is not particularly limited.

[0020] According to the present invention, the esterification reaction in step (1) and / or step (2) can be carried out under nitrogen protection.

[0021] According to the present invention, preferably, in step (2), the esterification product A1 is reacted with an excess of C 4～10 The product of the esterification reaction of the monobasic fatty acid is purified by one or more of the following methods: reduced pressure distillation, alkaline washing, dehydration, decolorization, and filtration. After the purification, a mixture of the pentaerythritol ester represented by formula (I) and the pentaerythritol ester represented by formula (II) with higher purity can be obtained.

[0022] The pentaerythritol ester of the present invention has a high viscosity index (>130), a low pour point (<-60°C), a relatively low kinematic viscosity at -40°C (<10000mm 2 / s) and good high temperature oxidation stability.

[0023] According to the present invention, the antioxidant is an organic sulfide or an organic selenide, for example, phenothiazine, dodecyl selenium, or diaryl selenium; the rust inhibitor is a nitrogen-containing heterocyclic rust inhibitor or an inorganic salt rust inhibitor, for example, benzotriazole, sodium nitrite, or trisodium phosphate; the extreme pressure agent can be one or more of molybdenum disulfide, boron nitride, graphite, and graphene; the organic bentonite can be commercial organic bentonite or can be prepared independently. A typical method for preparing organic bentonite is to first convert the bentonite into sodium bentonite, then add a covering agent so that it is completely attached to the end faces of the bentonite grain structure, and then filter, wash, dry, and pulverize to obtain a finished product. The product can also be prepared according to existing methods in public literature, for example, according to the method disclosed in CN 1052094A.

[0024] The preparation method of the bentonite grease of the present invention comprises:

[0025] Mix pentaerythritol ester and organic bentonite and stir evenly; add dispersant and stir rapidly until a grease structure is formed; heat to 80-90°C and maintain for 5-30 minutes, add antioxidant, rust inhibitor and extreme pressure agent, and grind into grease after cooling.

[0026] According to the present invention, the dispersant is one or more of C1-C5 alcohols (monohydric alcohols or polyhydric alcohols), C1-C5 ketones and C1-C5 esters, for example, it can be one or more of methanol, ethanol, ethylene glycol, glycerol, pentaerythritol, acetone and propylene carbonate.

[0027] According to the present invention, the amount of the dispersant added may be 0.5% to 10% of the sum of the mass of the pentaerythritol ester and the organobentonite.

[0028] The bentonite grease of the present invention has excellent antioxidant performance, low-temperature performance, colloid stability, heat resistance, and corrosion and rust prevention performance, and can meet lubrication requirements in a wider temperature range. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is the infrared spectrum of monopentaerythritol raw material.

[0030] Figure 2 The infrared spectrum of the pentaerythritol ester product prepared in Example 1 is shown in FIG.

[0031] Figure 3 This is the Fourier transform ion cyclotron resonance spectrum of the pentaerythritol ester product prepared in Example 1. DETAILED DESCRIPTION

[0032] The present invention is further described in detail below by way of examples, but the present invention is not limited thereto.

[0033] The present invention is concerned with the monopentaerythritol, C 4～10 Monobasic fatty acids, C 3～16 The source of the dibasic fatty acid is not particularly limited, and any commercially available product or homemade product of the above raw materials well known to those skilled in the art can be used.

[0034] Example 1

[0035] In a 1 L four-necked flask equipped with a stirring rod, a thermometer, a condenser, and a water separator, 50.0 g of monopentaerythritol (0.367 mol), 4.3 g of adipic acid (0.027 mol), 80 ml of xylene, and 1.5 g of tetrabutyl titanate catalyst were added, and the mixture was reacted at 150° C. for 4 h under nitrogen protection to obtain an esterification product A1, which was then cooled to room temperature. Then, 36.0 g of n-pentanoic acid, 110.0 g of n-hexanoic acid, 58.0 g of n-heptanoic acid, and 2.0 g of tetrabutyl titanate catalyst were added, and under nitrogen protection, the reaction temperature was heated to 150° C., then raised to 220° C. using a temperature program of 10° C. / h, and reacted until no water was produced to obtain a crude esterification product B1. The mixture was cooled to room temperature, subjected to reduced pressure distillation, alkali washing, water washing, dehydration, decolorization, and filtration to obtain the pentaerythritol ester of the present invention, which was labeled J1.

[0036] Infrared spectra of the monopentaerythritol raw material and the pentaerythritol ester product prepared in Example 1 were respectively tested. The infrared spectra of the monopentaerythritol raw material were shown in FIG. Figure 1 The infrared spectrum of the pentaerythritol ester product obtained in Example 1 is shown in FIG. Figure 2 By comparison, in the infrared spectrum of monopentaerythritol, 3200~3400cm -1 is the absorption peak of the alcoholic hydroxyl group in monopentaerythritol; the 3200-3400 cm-1 peak does not exist in the infrared spectrum of the pentaerythritol ester product prepared in Example 1. -1 Absorption peak, including 1744cm -1It is the stretching vibration peak of the C=O bond in the pentaerythritol ester product prepared in Example 1, indicating that the excess monobasic fatty acid in step (2) causes the excess monopentaerythritol in step (1) to react completely, and there is no alcoholic hydroxyl group in the product.

[0037] Example 2

[0038] In a 1 L four-necked flask equipped with a stirring rod, a thermometer, a condenser, and a water separator, 50.0 g of monopentaerythritol (0.367 mol), 8.6 g of adipic acid (0.06 mol), 100 ml of xylene, and 2.0 g of p-toluenesulfonic acid catalyst were added, and the mixture was reacted at 150° C. for 7 h under nitrogen protection to obtain an esterification product A1, which was then cooled to room temperature. Then, 56.0 g of n-pentanoic acid, 92.0 g of n-hexanoic acid, 23.0 g of n-heptanoic acid, 25.5 g of n-octanoic acid, and 2.0 g of p-toluenesulfonic acid catalyst were added, and under nitrogen protection, the reaction temperature was heated to 150° C., then raised to 220° C. using a temperature program of 10° C. / h, and reacted until no water was produced to obtain a crude esterification product B1. The mixture was cooled to room temperature, subjected to reduced pressure distillation, alkali washing, water washing, dehydration, decolorization, and filtration to obtain the pentaerythritol ester of the present invention, which is labeled J2.

[0039] Example 3

[0040] In a 1 L four-necked flask equipped with a stirring rod, a thermometer, a condenser, and a water separator, 50.0 g of monopentaerythritol (0.367 mol), 7.6 g of malonic acid (0.073 mol), 4.0 g of suberic acid (0.023 mol), 100 ml of xylene, and 1.5 g of tetrabutyl titanate catalyst were added, and the mixture was reacted at 150° C. for 7 h under nitrogen protection to obtain an esterification product A1, which was then cooled to room temperature. Then, 36.0 g of n-pentanoic acid, 98.5 g of n-hexanoic acid, 46.0 g of n-heptanoic acid, 12.7 g of n-octanoic acid, and 2.0 g of tetrabutyl titanate catalyst were added. Under nitrogen protection, the reaction temperature was heated to 150° C., then increased to 220° C. using a temperature program of 10° C. / h, and reacted until no water was produced to obtain a crude esterification product B1. The mixture was cooled to room temperature, subjected to reduced pressure distillation, alkali washing, water washing, dehydration, decolorization, and filtration to obtain the pentaerythritol ester of the present invention, which was labeled J3.

[0041] The pentaerythritol ester prepared in Example 1 was subjected to Fourier transform ion cyclotron resonance (FTIR) analysis using an electrospray ionization source (ESI+) in positive ion mode. The test conditions were: ion transport capillary temperature of 350°C, spray voltage of 2.8 kV, m / z scanning range of 100-1500, and mass resolution of 70,000. The measured spectrum is shown in FIG. Figure 3 .from Figure 3 It can be seen that C 26 H 46 O8~C 36 H 36O8 represents the ester formed by monopentaerythritol and monobasic fatty acid (hereinafter referred to as monobasic acid ester), C 51 H 88 O 16 ~C 59 H 104 O 16 with C 73 H 124 O 24 ~C 79 H 136 O 24 It represents the ester formed by the esterification product of adipic acid and monopentaerythritol and then reacting with a monobasic fatty acid (hereinafter abbreviated as dibasic acid ester).

[0042] The physical and chemical properties of the pentaerythritol ester of the present invention are illustrated by taking commercial pentaerythritol ester as comparative example 1. The commercial pentaerythritol ester is mixed pentaerythritol ester MIXPE1 produced by Zhejiang Quzhou Chemical Co., Ltd., and its kinematic viscosity at 100°C is 5.02 mm 2 / s.

[0043] The physical and chemical properties of the pentaerythritol esters of Examples 1-3 and the pentaerythritol ester of Comparative Example 1 were evaluated. The results are shown in Table 1.

[0044] The content distribution of the pentaerythritol esters prepared in Examples 1-3 and the pentaerythritol ester of Comparative Example 1 was determined according to the method for determining the boiling range distribution of petroleum fractions (NB / SH / T 0829), i.e., the content of the monobasic and dibasic esters in Examples 1-3 or the content of the monopentaerythritol ester and dipentaerythritol ester in Comparative Example 1 was determined. The results of the determinations are shown in Table 1. For example, the results of the determination of the product of Example 1 showed that the content of the ester formed by monopentaerythritol and a monobasic fatty acid (i.e., the monobasic ester) was 88.2% (with a boiling range of 350-500°C), and the content of the ester formed by the esterification product of adipic acid and monopentaerythritol and then reacting with a monobasic fatty acid (i.e., the dibasic ester) was 11.8% (with a boiling range of >500°C).

[0045] As can be seen from Table 1, compared with the comparative pentaerythritol ester MIXPE1, the pentaerythritol ester of the present invention has a lower pour point (≤-66°C) and a higher viscosity index (≥135), indicating that the pentaerythritol ester base oil of the present invention has better low-temperature fluidity and viscosity-temperature properties.

[0046] Table 1 Physical and chemical indicators of pentaerythritol esters

[0047]

[0048]

[0049] The sources of the raw materials used in the greases prepared below are as follows:

[0050] Organic bentonite HFGEL310, Zhejiang Fenghong New Materials Co., Ltd.

[0051] Acetone, propylene carbonate, sodium nitrite, Aladdin Reagent Co., Ltd.

[0052] Dodecyl selenium, Shanghai Yuyu New Material Technology Co., Ltd.

[0053] Benzotriazole, phenothiazine, molybdenum disulfide, Inokite Technology Co., Ltd.

[0054] Boron nitride, Tianyuan Aerospace Materials Technology Co., Ltd.

[0055] Example I-1 of preparing grease

[0056] Raw material components: 85 g of the pentaerythritol ester product J1 of Example 1; 15 g of organic bentonite; 3 g of acetone; 0.5 g of dodecyl selenium; 2 g of benzotriazole; and 5 g of molybdenum disulfide.

[0057] Preparation method: Mix 85g of pentaerythritol ester J1 and 15g of organic bentonite and stir evenly; add 3g of acetone and stir rapidly until a grease structure is formed; heat to 80°C and hold for 20min, add 0.5g of dodecyl selenium, 2g of benzotriazole, and 5g of molybdenum disulfide, cool to room temperature, and grind into grease on a three-roll mill.

[0058] Example I-2 of preparing grease

[0059] Raw material components: 80 g of the pentaerythritol ester product J2 of Example 2; 20 g of organic bentonite; 1.5 g of propylene carbonate; 1 g of phenothiazine; 1 g of sodium nitrite; and 3 g of boron nitride.

[0060] Preparation method: Mix 80g of pentaerythritol ester J2 and 20g of organic bentonite and stir evenly; add 1.5g of propylene carbonate and stir rapidly until a grease structure is formed; heat to 90°C and hold for 10 minutes, add 1g of phenothiazine, 1g of sodium nitrite, and 3g of boron nitride, cool to room temperature, and grind on a three-roll mill 2-3 times to form a grease.

[0061] Example I-3 of preparing grease

[0062] Raw material components: 90 g of the pentaerythritol ester product J3 of Example 3; 10 g of organic bentonite; 3 g of propylene carbonate; 0.5 g of phenothiazine; 0.5 g of sodium nitrite; and 5 g of boron nitride.

[0063] Preparation method: Mix 90g of pentaerythritol ester J3 and 10g of organic bentonite and stir evenly; add 3g of propylene carbonate and stir rapidly until a grease structure is formed; heat to 90℃ and hold for 15min, add 0.5g of phenothiazine, 0.5g of sodium nitrite and 5g of boron nitride, cool to room temperature and grind into grease on a three-roll mill.

[0064] Comparative Example D-1 for preparing grease

[0065] A lubricating grease was prepared according to the method of Example I-1, except that the pentaerythritol ester J1 was replaced with the mixed pentaerythritol ester MIXPE1.

[0066] The performance of the above-mentioned grease examples and comparative examples was evaluated using the following method:

[0067] The dropping point was determined using the GB / T 3498 method;

[0068] The cone penetration was determined using the GB / T 269 method;

[0069] The oxidation stability was determined using the SH / T 0325 method;

[0070] The oil separation of steel mesh is determined using the NB / SH / T 0324 method;

[0071] The anti-corrosion performance was determined using the GB / T 5018 method;

[0072] GB / T 7326 method was used to determine copper corrosion;

[0073] The low temperature performance is determined using the SH / T 0338 method;

[0074] The evaluation results are shown in Table 2.

[0075] Table 2 Grease performance evaluation

[0076]

Claims

1. Bentonite grease comprising, based on the total mass of the grease, 0.1% to 10% of an antioxidant, 0.1% to 10% of a rust inhibitor, 0.1% to 10% of an extreme pressure agent, 3% to 35% of an organic bentonite, and 60% to 95% of a pentaerythritol ester; the pentaerythritol ester comprising, by mass, 5% to 50% of a pentaerythritol ester of formula (I) and 50% to 95% of a pentaerythritol ester of formula (II): The R group is C1~C 14 Each R' group is independently selected from a C3 to C9 straight chain or branched chain alkyl group.

2. The bentonite grease according to claim 1, characterized in that The R group is a straight chain or branched chain alkylene group of C2 to C8; each R' group is selected from two or more of a straight chain or branched chain alkyl group of C3, a straight chain or branched chain alkyl group of C4, a straight chain or branched chain alkyl group of C5, a straight chain or branched chain alkyl group of C6, a straight chain or branched chain alkyl group of C7, a straight chain or branched chain alkyl group of C8, and a straight chain or branched chain alkyl group of C9.

3. The bentonite grease according to claim 1, characterized in that: The pentaerythritol ester comprises, by mass, 5.0% to 25% of the pentaerythritol ester represented by formula (I) and 75% to 95% of the pentaerythritol ester represented by formula (II).

4. The bentonite grease according to claim 1, characterized in that The preparation method of the pentaerythritol ester comprises the following steps: (1) Excessive monopentaerythritol and C 3～16 The dibasic fatty acid undergoes esterification reaction to obtain esterification product A1; (2) Esterification product A1 and excess C 4～10 The monobasic fatty acids undergo esterification reaction and the products are collected.

5. The bentonite grease according to claim 4, characterized in that: In step (1), the monopentaerythritol and C 3～16 The molar ratio of the dibasic fatty acid is (2.05-100):1; in step (2), the hydroxyl group and C 4～10 The molar ratio of the carboxyl group in the monobasic fatty acid is 1:(1.05~1.30).

6. The bentonite grease according to claim 4, characterized in that: The reaction temperature of step (1) is 50-180° C., and the reaction time is 1-20 h; the reaction temperature of step (2) is 50-250° C., and the reaction time is until water is no longer produced.

7. The bentonite grease according to claim 4, characterized in that: The dibasic fatty acid is one or more of malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, dodecanedioic acid, tetradecanedioic acid, and hexadecanedioic acid; the monobasic fatty acid is selected from two or more of n-butyric acid, isobutyric acid, n-valeric acid, isovaleric acid, n-hexanoic acid, isohexanoic acid, n-heptanoic acid, isoheptanoic acid, n-octanoic acid, isooctanoic acid, n-nonanoic acid, isononanoic acid, n-decanoic acid, and isodecanoic acid.

8. The bentonite grease according to claim 4, characterized in that: Adding a catalyst to the esterification reaction of step (1) and / or step (2), wherein the catalyst is selected from one or more of concentrated sulfuric acid, sodium bisulfate, p-toluenesulfonic acid, zinc oxide, cation exchange resin, ionic liquid, stannous oxide, titanate and activated carbon; and / or, The esterification reaction in step (1) and / or step (2) is carried out under nitrogen protection.

9. The bentonite grease according to any one of claims 1 to 8, characterized in that: The antioxidant is an organic sulfide or an organic selenide; the rust inhibitor is a nitrogen-containing heterocyclic rust inhibitor or an inorganic salt rust inhibitor; and the extreme pressure agent is one or more of molybdenum disulfide, boron nitride, graphite and graphene.

10. The bentonite grease according to claim 9, characterized in that The antioxidant is one or more of phenothiazine, dodecyl selenium and diaryl selenium; the rust inhibitor is one or more of benzotriazole, sodium nitrite and trisodium phosphate.

11. The method for preparing the bentonite grease according to any one of claims 1 to 10, comprising: Mix pentaerythritol ester and organic bentonite and stir evenly; add dispersant and stir rapidly until a grease structure is formed; heat to 80-90°C and maintain for 5-30 minutes, add antioxidant, rust inhibitor and extreme pressure agent, and grind into grease after cooling.

12. The method according to claim 11, characterized in that The dispersant is one or more of C1-C5 alcohols, C1-C5 ketones and C1-C5 esters.

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