Polyurea grease and preparation method thereof

Abstract

The present invention relates to the technical field of greases, specifically a polyurea grease and a preparation method thereof. The present invention prepares brominated 2-phenylbenzimidazole-5-sulfonic acid by nucleophilic substitution with liquid bromine, and then reacts with the amino group of 3,4,4'-triaminodiphenyl ether to generate an intermediate product, a modified amine, and further reacts with isocyanate to synthesize a polyurea thickener, whose side chain contains an imidazole structure and a sulfonic acid group, and then prepares a polyurea grease by mixing with a base oil and an additive through a prefabrication method. The obtained polyurea grease has a dropping point of 301°C, good high temperature resistance, a cone penetration of 231 / 0.1mm, a consistency grade of 3#, and a moderate hardness and softness of the grease. The obtained polyurea grease has good stability and good wear resistance. The obtained polyurea grease does not contain metal atoms and will not undergo a catalytic reaction with the base oil, so it has strong antioxidant properties.

Description

Technical Field

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

[0002] Grease is an important material for mechanical lubrication, and its performance is crucial to the normal operation and life of the equipment. Grease is composed of base oil, thickener, and additives. Depending on the thickener, there are metal-based grease, polyurea grease, bentonite grease, etc. Among them, polyurea grease is widely used in various fields such as electrical appliances, metallurgy, automobiles, and aviation due to its unique properties. Polyurea grease is mainly produced by the reaction of isocyanate and amine compounds to form urea, which is used as a thickener and mixed with base oil and other additives. Polyurea grease does not drip oil at high temperatures, has good oxidation stability, and is stable for a long time in high temperature environments, but the polyurea grease currently reported still has some problems.

[0003] Literature Wang, Y.; Zhang, P.; Lin, J.; Gao, X. Rheological and Tribological Properties of Lithium Grease and Polyurea Grease with Different Consistencies. Coatings 2022, 12, 527 prepared a polyurea grease, and measured the rheological properties of the polyurea grease at different temperatures and consistencies. The results show that the structural strength of the prepared PAO-polyurea grease is better than that of the base oil-lithium grease, and the rheological properties are strong. However, the prepared polyurea grease has a low dropping point and poor high temperature resistance. Another document, Jiabei Wang, Zhaoyang Guo, Wenjing Hu, Hengyi Lu, Jiusheng Li, Investigating the effects of base oil type on microstructure and tribological properties of polyurea grease, Tribology International, 2024, 194, 109573., synthesized three types of polyurea grease by adjusting the base oil type (poly (α-olefin) oil (PAO40), alkyl naphthalene oil (AN30) and polyether oil (OSP320)) and using the same thickener. The results show that the grease obtained from non-polar PAO40 has a three-dimensional network structure composed of long fibers and interconnected, has high structural strength, and has significant binding ability to the base oil. However, the prepared polyurea grease has a large cone penetration and the grease texture is too soft, which is not suitable for some special fields. Chinese invention patent CN201810504592.9, a method for preparing polyurea thickener powder, discloses a polyurea thickener powder for preparing polyurea grease. The method mentioned is a direct method, which is likely to cause side reactions of isocyanate and waste of raw materials, and the prepared polyurea grease has poor wear resistance and stability.

[0004] In addition, in the processing of polyurea grease, parameters such as temperature and raw material ratio need to be controlled to ensure the comprehensive performance of the grease. To this end, a polyurea grease and a preparation method thereof are proposed. Summary of the invention

[0005] The object of the present invention is to provide a polyurea grease and a preparation method thereof, wherein brominated 2-phenylbenzimidazole-5-sulfonic acid is prepared by nucleophilic substitution of 2-phenylbenzimidazole-5-sulfonic acid with liquid bromine, and then reacted with the amino group of 3,4,4'-triaminodiphenyl ether to generate an intermediate product, a modified amine, which reacts with isocyanate to synthesize a polyurea thickener, and then the polyurea grease is prepared by a prefabrication method.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] A method for preparing polyurea grease, characterized in that it comprises the following steps:

[0008] Weigh 1 portion of 2-phenylbenzimidazole-5-sulfonic acid, CAS number: 27503-81-7; dissolve the 2-phenylbenzimidazole-5-sulfonic acid in ethanol to obtain a 2-phenylbenzimidazole-5-sulfonic acid alcohol solution; dropwise add the 2-phenylbenzimidazole-5-sulfonic acid alcohol solution into liquid bromine, and add a first catalyst to obtain a first reaction solution; heat the first reaction solution at 40-65° C. for 6 hours to obtain brominated 2-phenylbenzimidazole-5-sulfonic acid;

[0009] Take 1 portion of the brominated 2-phenylbenzimidazole-5-sulfonic acid and dissolve it in acetonitrile to obtain a brominated 2-phenylbenzimidazole-5-sulfonic acid solution; weigh 3,4,4'-triaminodiphenyl ether, and dissolve the 3,4,4'-triaminodiphenyl ether in acetonitrile to obtain a 3,4,4'-triaminodiphenyl ether solution; dropwise add the brominated 2-phenylbenzimidazole-5-sulfonic acid solution to the 3,4,4'-triaminodiphenyl ether solution, and add an acid binding agent and a second catalyst to obtain a second reaction solution; place the second reaction solution at 50-80° C., stir and react for 6-12 hours, and obtain an intermediate product, a modified amine;

[0010] The intermediate product 1 is dissolved in anhydrous dimethyl sulfoxide to obtain an intermediate product solution; isocyanate is added to the intermediate product solution, and the mixture is stirred and refluxed at 75° C. for 6 hours to obtain a polyurea thickener; base oil, the polyurea thickener, and additives are mixed together to form a mixed liquid; the mixed liquid is uniformly heated to 90-150° C., and kept warm for 1 hour, and then cooled to obtain the polyurea grease.

[0011] Preferably, the chemical formula of 2-phenylbenzimidazole-5-sulfonic acid is C 13 H 10 N2O3S, its structural formula is

[0012]

[0013] Preferably, the molar ratio of the 2-phenylbenzimidazole-5-sulfonic acid to liquid bromine is 1:1-3; and the first catalyst is iron powder.

[0014] Preferably, the 3,4,4'-triaminodiphenyl ether CAS No. 6264-66-0 has a structural formula of

[0015]

[0016] Preferably, the molar ratio of the brominated 2-phenylbenzimidazole-5-sulfonic acid to the 3,4,4'-triaminodiphenyl ether is 1:1-2.

[0017] Preferably, the acid binding agent is triethylamine; and the second catalyst is sodium tert-butoxide or potassium carbonate.

[0018] Preferably, the molar ratio of the intermediate product 1 to the isocyanate is 1:1; the isocyanate is one or more of toluene diisocyanate, 4,4-diphenylmethane diisocyanate, and hexamethylene diisocyanate.

[0019] Preferably, the base oil accounts for 65%-90% of the total mass of the mixed liquid, the polyurea thickener accounts for 5%-30% of the total mass of the mixed liquid, and the additive accounts for 1-5% of the total mass of the mixed liquid.

[0020] Preferably, the base oil is cycloalkane oil KN4010; the additive is an antioxidant diisooctyl diphenylamine; and the uniform heating rate is 5°C / min.

[0021] A polyurea grease, characterized in that: the polyurea grease is prepared by nucleophilic substitution of 2-phenylbenzimidazole-5-sulfonic acid with liquid bromine to prepare brominated 2-phenylbenzimidazole-5-sulfonic acid, which is then reacted with the amino group of 3,4,4'-triaminodiphenyl ether to prepare an intermediate product, a modified amine, which reacts with isocyanate, and the synthesized polyurea thickener is mixed with base oil and additives; the polyurea grease is prepared by the preparation method as described above; the polyurea grease has a dropping point of 301°C; the polyurea grease has a cone penetration of 231 / 0.1mm, a consistency grade of 3#, and a grease texture with moderate hardness; the polyurea grease has good stability and a viscosity of 685Pa·s; the polyurea grease has a wear spot diameter of 0.416mm and good wear resistance; the polyurea grease has an oxidation resistance index pressure drop of 0.0085MPa and good oxidation resistance stability.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] 1. The present invention dissolves 2-phenylbenzimidazole-5-sulfonic acid in ethanol to obtain a solution, and then drops it into liquid bromine for bromination reaction, wherein the molar ratio of 2-phenylbenzimidazole-5-sulfonic acid to liquid bromine is 1:1.5, and iron powder is added as a catalyst to obtain a first reaction solution, and the first reaction solution is heated at 55°C for 6 hours to obtain brominated 2-phenylbenzimidazole-5-sulfonic acid. The present invention prepares brominated 2-phenylbenzimidazole-5-sulfonic acid by nucleophilic substitution of 2-phenylbenzimidazole-5-sulfonic acid and liquid bromine, which is convenient for reacting with the amino group of subsequent 3,4,4'-triaminodiphenyl ether, thereby preparing an intermediate product, a modified amine, which can react with isocyanate to synthesize a polyurea thickener. The electron cloud density of the C atom of the isocyanate is low and positive, and the N atom of the amine is highly electronegative and easily attacks the C atom, and then a rearrangement reaction occurs to generate a polyurea thickener, and then a polyurea grease is prepared by a prefabrication method, and the resulting polyurea grease has a dropping point of 301°C. When preparing the polyurea thickener, the present invention uses 2-phenylbenzimidazole-5-sulfonic acid, whose side chain contains an imidazole structure and a sulfonic acid group, so that the finally prepared polyurea thickener has a higher dropping point and thus has good high temperature resistance.

[0024] 2. The present invention adds a brominated 2-phenylbenzimidazole-5-sulfonic acid acetonitrile solution dropwise to a 3,4,4'-triaminodiphenyl ether acetonitrile solution, wherein the molar ratio of brominated 2-phenylbenzimidazole-5-sulfonic acid to 3,4,4'-triaminodiphenyl ether is 1:1.5, and adds triethylamine and sodium tert-butoxide to obtain a second reaction solution, and the second reaction solution is placed at 70° C. and stirred for reaction for 6 hours to obtain an intermediate product, a modified amine, and then the modified amine is reacted with isocyanate to prepare a polyurea grease. When preparing the modified amine, an intermediate product, the present invention utilizes the lone electron pair on the amino nitrogen of 3,4,4'-triaminodiphenyl ether to undergo an electrophilic reaction with the bromine of brominated 2-phenylbenzimidazole-5-sulfonic acid to prepare the modified amine. By controlling the material molar ratio for preparing the modified amine, the cone penetration of the finally prepared polyurea grease reaches 231 / 0.1mm, the consistency grade is 3# (the cone penetration range is 220-250), and the grease has a moderate hardness.

[0025] 3. The present invention dissolves the intermediate product, a modified amine, in anhydrous dimethyl sulfoxide, then adds a combination of toluene diisocyanate and 4,4-diphenylmethane diisocyanate in a mass ratio of 1:1, and the molar ratio of the intermediate product 1 to the isocyanate is 1:1, and stirs and refluxes at 75°C for 6 hours to obtain a polyurea thickener; the polyurea thickener obtained by the method is used to further prepare polyurea grease. The present invention selects the type of raw material isocyanate for preparing the polyurea thickener, and the obtained polyurea grease has good stability and a viscosity of 685Pa·s. This is because toluene diisocyanate and 4,4-diphenylmethane diisocyanate are both isocyanates containing a benzene ring structure, and the aromatic ring is directly connected to the -NCO group. There is a conjugation effect between the two functional groups, which makes the -NCO group highly reactive, so the prepared polyurea grease has a high viscosity and good stability. In addition, the two benzene ring molecules in the 4,4-diphenylmethane diisocyanate molecule are not located on the same plane, and this tetrahedral structure can enhance the stability of the grease. In addition, the lone electron pair of the nitrogen atom of the modified amine is polar, which can enhance the affinity of polyurea grease to the metal surface, thereby giving polyurea grease excellent anti-rust properties.

[0026] 4. The base oil of the present invention accounts for 85% of the total mass of the mixed liquid, the polyurea thickener accounts for 13% of the total mass of the mixed liquid, and the additives account for 2% of the total mass of the mixed liquid; the polyurea grease prepared by the said ratio has good wear resistance, which is manifested by the smallest wear spot diameter of 0.416 mm. When preparing polyurea grease, the present invention controls the proportion of polyurea thickener, base oil and additives, so that the wear resistance of polyurea grease can be improved. The prepared polyurea thickener molecule itself contains aromatic groups and has urea functional groups. The urea functional groups can form strong hydrogen bonds, further cross-link to form a stable network structure, and have good affinity with the base oil. The base oil is wrapped in the three-dimensional network structure formed by the thickener, thereby showing good wear resistance.

[0027] 5. In the present invention, the mixed liquid is heated to 140°C at a uniform speed and kept warm for 1 hour at a uniform heating rate of 5°C / min. After cooling, the polyurea grease is obtained. The present invention prepares polyurea grease by a prefabrication method, which can reduce the side reactions of active isocyanate groups during the reaction. After the polyurea thickener is prepared in the previous sequence, it is added to the base oil, and the polyurea grease is obtained by high-temperature insulation and cooling with the antioxidant diisooctyl diphenylamine. The prepared grease is tested for its antioxidant properties, and the oxygen pressure drop in the oxygen bomb is 0.0085MPa, and the antioxidant stability is the best. The polyurea grease prepared by the present invention does not contain metal atoms and will not undergo catalytic reaction with the base oil. Therefore, the antioxidant pressure drop (MPa) is not greater than 0.050, which meets industry standards. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1The present invention provides a reaction mechanism for preparing polyurea grease;

[0029] Figure 2 This is a test of the antioxidant stability of the polyurea grease prepared in Examples 40-45 of the present invention. DETAILED DESCRIPTION

[0030] The following will be combined with the drawings in 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.

[0031] See also Figure 1 to Figure 2 The present invention provides a polyurea grease and a preparation method thereof, and the technical scheme is as follows:

[0032] Example 1

[0033] A method for preparing polyurea grease comprises the following steps:

[0034] Weigh 1 portion of 2-phenylbenzimidazole-5-sulfonic acid, dissolve the 2-phenylbenzimidazole-5-sulfonic acid in ethanol to obtain a 2-phenylbenzimidazole-5-sulfonic acid alcohol solution, dropwise add the 2-phenylbenzimidazole-5-sulfonic acid alcohol solution into liquid bromine, wherein the molar ratio of 2-phenylbenzimidazole-5-sulfonic acid to liquid bromine is 1:1, and add iron powder to obtain a first reaction solution, heat the first reaction solution at 40° C. for 6 hours to obtain brominated 2-phenylbenzimidazole-5-sulfonic acid;

[0035] Dissolve 1 portion of bromo-2-phenylbenzimidazole-5-sulfonic acid in acetonitrile to obtain a bromo-2-phenylbenzimidazole-5-sulfonic acid solution, weigh 3,4,4'-triaminodiphenyl ether, and dissolve 3,4,4'-triaminodiphenyl ether in acetonitrile to obtain a 3,4,4'-triaminodiphenyl ether solution; dropwise add the bromo-2-phenylbenzimidazole-5-sulfonic acid solution to the 3,4,4'-triaminodiphenyl ether solution, wherein the molar ratio of bromo-2-phenylbenzimidazole-5-sulfonic acid to the 3,4,4'-triaminodiphenyl ether is 1:1, and add triethylamine and potassium carbonate to obtain a second reaction solution; place the second reaction solution at 50° C., stir and react for 6 hours to obtain an intermediate product 1;

[0036] The intermediate product 1 is dissolved in anhydrous dimethyl sulfoxide to obtain an intermediate product solution, toluene diisocyanate is added to the intermediate product solution, wherein the molar ratio of the intermediate product 1 to toluene diisocyanate is 1:1, and the mixture is stirred and refluxed at 75°C for 6 hours to obtain a polyurea thickener; the base oil, the polyurea thickener, and the additives are mixed together to form a mixed liquid; in the mixed liquid, the base oil accounts for 65% of the total mass of the mixed liquid, the polyurea thickener accounts for 30% of the total mass of the mixed liquid, and the additives account for 5% of the total mass of the mixed liquid; the mixed liquid is uniformly heated to 90°C and kept warm for 1 hour; the uniform heating rate is 5°C / min, and the polyurea grease is obtained after cooling.

[0037] The base oil cycloalkane oil KN4010 used in the examples of the present invention was from Shanghai Sinopharm Reagent Company; 3,4,4'-triaminodiphenyl ether was purchased from Beijing Bailingwei Technology Co., Ltd. The remaining chemical reagents can be purchased through conventional channels. The purity of the solvents used was analytical grade.

[0038] The molar ratio of 2-phenylbenzimidazole-5-sulfonic acid to liquid bromine and the reaction temperature of the first reaction solution in Example 2-10 are shown in Table 1. The remaining reagents and operations are the same as in Example 1.

[0039] Table 1 Molar ratio of 2-phenylbenzimidazole-5-sulfonic acid to liquid bromine and reaction temperature of the first reaction solution in Example 2-10

[0040]

[0041]

[0042] In Comparative Example 1, no iron powder was added, and the remaining reagents and operations were the same as in Example 5.

[0043] Embodiment 11

[0044] The dropping points of the polyurea greases prepared in the above Examples 1-10 and Comparative Example 1 were tested. The higher the dropping point, the better the high temperature resistance of the polyurea grease. The dropping point of the prepared polyurea grease was tested according to GB / T 3498-2008 "Determination of dropping point of lubricating grease over a wide temperature range", and the instrument used was a dropping point tester, model ST3498-2, from Wuhan Yanrun Technology Development Co., Ltd. The test results are shown in Table 2.

[0045] In Example 5, a solution obtained by dissolving 2-phenylbenzimidazole-5-sulfonic acid in ethanol is added dropwise to liquid bromine for bromination reaction, wherein the molar ratio of 2-phenylbenzimidazole-5-sulfonic acid to liquid bromine is 1:1.5, and iron powder is added as a catalyst to obtain a first reaction liquid, and the first reaction liquid is heated at 55°C for 6 hours to obtain brominated 2-phenylbenzimidazole-5-sulfonic acid. The present invention prepares brominated 2-phenylbenzimidazole-5-sulfonic acid by nucleophilic substitution of 2-phenylbenzimidazole-5-sulfonic acid with liquid bromine, which is convenient for subsequent reaction with the amino group of 3,4,4'-triaminodiphenyl ether, thereby preparing an intermediate product, a modified amine, which can react with isocyanate to synthesize a polyurea thickener, and its reaction mechanism is shown in Figure 1 , the electron cloud density of the C atom of isocyanate is low and positive, the N atom of amine is highly electronegative and easily attacks the C atom, and then a rearrangement reaction occurs to generate a polyurea thickener, and then a polyurea grease is prepared by a prefabrication method, and the resulting polyurea grease has a dropping point of 301°C. In the preparation of the polyurea thickener, the present invention uses 2-phenylbenzimidazole-5-sulfonic acid, whose side chain contains an imidazole structure and a sulfonic acid group, so that the final prepared polyurea thickener has a higher dropping point, and thus has good high temperature resistance. Comparative Example 1 does not add iron powder, which is not conducive to the bromination reaction of 2-phenylbenzimidazole-5-sulfonic acid, so the efficiency of the amino reaction with 3,4,4'-triaminodiphenyl ether will be reduced, and the prepared polyurea grease has a low dropping point of only 202°C, and poor high temperature resistance.

[0046] Table 2 Dropping points of polyurea greases prepared in Examples 1-10 and Comparative Example 1

[0047]

[0048]

[0049] Example 12

[0050] A method for preparing polyurea grease comprises the following steps:

[0051] Weigh 1 part of 2-phenylbenzimidazole-5-sulfonic acid, dissolve the 2-phenylbenzimidazole-5-sulfonic acid in ethanol to obtain a 2-phenylbenzimidazole-5-sulfonic acid alcohol solution, add the 2-phenylbenzimidazole-5-sulfonic acid alcohol solution dropwise into liquid bromine, wherein the molar ratio of 2-phenylbenzimidazole-5-sulfonic acid to liquid bromine is 1:1.5, and add iron powder to obtain a first reaction solution, heat the first reaction solution at 55° C. for 6 hours to obtain brominated 2-phenylbenzimidazole-5-sulfonic acid;

[0052] Dissolve 1 portion of bromo-2-phenylbenzimidazole-5-sulfonic acid in acetonitrile to obtain a bromo-2-phenylbenzimidazole-5-sulfonic acid solution, weigh 3,4,4'-triaminodiphenyl ether, and dissolve 3,4,4'-triaminodiphenyl ether in acetonitrile to obtain a 3,4,4'-triaminodiphenyl ether solution; dropwise add the bromo-2-phenylbenzimidazole-5-sulfonic acid solution to the 3,4,4'-triaminodiphenyl ether solution, wherein the molar ratio of bromo-2-phenylbenzimidazole-5-sulfonic acid to the 3,4,4'-triaminodiphenyl ether is 1:1.2, and add triethylamine and sodium tert-butoxide to obtain a second reaction solution; place the second reaction solution at 60° C., stir and react for 6 hours, and obtain an intermediate product 1;

[0053] The intermediate product 1 is dissolved in anhydrous dimethyl sulfoxide to obtain an intermediate product solution, toluene diisocyanate is added to the intermediate product solution, wherein the molar ratio of the intermediate product 1 to toluene diisocyanate is 1:1, and the mixture is stirred and refluxed at 75°C for 6 hours to obtain a polyurea thickener; the base oil, the polyurea thickener, and the additives are mixed together to form a mixed liquid; in the mixed liquid, the base oil accounts for 65% of the total mass of the mixed liquid, the polyurea thickener accounts for 30% of the total mass of the mixed liquid, and the additives account for 5% of the total mass of the mixed liquid; the mixed liquid is uniformly heated to 90°C and kept warm for 1 hour; the uniform heating rate is 5°C / min, and the polyurea grease is obtained after cooling.

[0054] The molar ratio of brominated 2-phenylbenzimidazole-5-sulfonic acid to 3,4,4'-triaminodiphenyl ether and the reaction temperature of the second reaction solution in Examples 13-20 are shown in Table 3. The remaining reagents and operations are the same as in Example 12.

[0055] Table 3 Molar ratio of brominated 2-phenylbenzimidazole-5-sulfonic acid to 3,4,4'-triaminodiphenyl ether, reaction temperature of the second reaction solution

[0056]

[0057]

[0058] Embodiment 21

[0059] The cone penetration of the polyurea grease prepared in Examples 12 to 20 above was tested. The cone penetration of the grease was tested according to GB / T 269-1991. The cone penetration reflects the hardness and thickness of the grease. The test results are shown in Table 4.

[0060] In Example 15, a brominated 2-phenylbenzimidazole-5-sulfonic acid acetonitrile solution was added dropwise to a 3,4,4'-triaminodiphenyl ether acetonitrile solution, wherein the molar ratio of brominated 2-phenylbenzimidazole-5-sulfonic acid to 3,4,4'-triaminodiphenyl ether was 1:1.5, and an acid binding agent triethylamine and a catalyst sodium tert-butoxide were added to obtain a second reaction solution, and the second reaction solution was placed at 70° C. and stirred for reaction for 6 hours to obtain an intermediate product, a modified amine, which was then reacted with isocyanate to prepare a polyurea grease. When preparing the intermediate product, a modified amine, the present invention utilizes the lone electron pair on the amino nitrogen of 3,4,4'-triaminodiphenyl ether to react electrophilically with the bromine of brominated 2-phenylbenzimidazole-5-sulfonic acid to prepare the modified amine. By controlling the material molar ratio of the modified amine, the cone penetration of the finally prepared polyurea grease reaches 231 / 0.1mm, the consistency grade is 3# (the cone penetration range is 220-250), and the lubricating grease has a moderate hardness. The cone penetration of the polyurea grease prepared in other embodiments is between 175-205, the consistency grade is 4#, and the lubricating grease is harder.

[0061] Table 4 Cone penetration of polyurea grease prepared in Examples 12-20

[0062]

[0063] Embodiment 22

[0064] A method for preparing polyurea grease comprises the following steps:

[0065] Weigh 1 part of 2-phenylbenzimidazole-5-sulfonic acid, dissolve the 2-phenylbenzimidazole-5-sulfonic acid in ethanol to obtain a 2-phenylbenzimidazole-5-sulfonic acid alcohol solution, add the 2-phenylbenzimidazole-5-sulfonic acid alcohol solution dropwise into liquid bromine, wherein the molar ratio of 2-phenylbenzimidazole-5-sulfonic acid to liquid bromine is 1:1.5, and add iron powder to obtain a first reaction solution, heat the first reaction solution at 55° C. for 6 hours to obtain brominated 2-phenylbenzimidazole-5-sulfonic acid;

[0066] Dissolve 1 portion of bromo-2-phenylbenzimidazole-5-sulfonic acid in acetonitrile to obtain a bromo-2-phenylbenzimidazole-5-sulfonic acid solution, weigh 3,4,4'-triaminodiphenyl ether, and dissolve 3,4,4'-triaminodiphenyl ether in acetonitrile to obtain a 3,4,4'-triaminodiphenyl ether solution; dropwise add the bromo-2-phenylbenzimidazole-5-sulfonic acid solution to the 3,4,4'-triaminodiphenyl ether solution, wherein the molar ratio of bromo-2-phenylbenzimidazole-5-sulfonic acid to the 3,4,4'-triaminodiphenyl ether is 1:1.5, and add triethylamine and sodium tert-butoxide to obtain a second reaction solution; place the second reaction solution at 70° C., stir and react for 6 hours to obtain an intermediate product 1;

[0067] The intermediate product 1 is dissolved in anhydrous dimethyl sulfoxide to obtain an intermediate product solution, toluene diisocyanate is added to the intermediate product solution, wherein the molar ratio of the intermediate product 1 to toluene diisocyanate is 1:1, and the mixture is stirred and refluxed at 75°C for 6 hours to obtain a polyurea thickener; the base oil, the polyurea thickener, and the additives are mixed together to form a mixed liquid; in the mixed liquid, the base oil accounts for 65% of the total mass of the mixed liquid, the polyurea thickener accounts for 30% of the total mass of the mixed liquid, and the additives account for 5% of the total mass of the mixed liquid; the mixed liquid is uniformly heated to 90°C and kept warm for 1 hour; the uniform heating rate is 5°C / min, and the polyurea grease is obtained after cooling.

[0068] The types of isocyanates in Examples 23 to 27 are shown in Table 5 below, and the remaining reagents and operations are the same as in Example 22.

[0069] Table 5 Isocyanate Types in Examples 23-27

[0070]

[0071] Embodiment 28

[0072] The viscosity of the polyurea grease prepared in Examples 22-27 above was tested. Low viscosity will weaken the "binding" ability of the thickener to the base oil, resulting in poor stability. The viscosity test results are shown in Table 6.

[0073] In Example 25, the intermediate product, a modified amine, is dissolved in anhydrous dimethyl sulfoxide, and then a combination of toluene diisocyanate and 4,4-diphenylmethane diisocyanate is added in a mass ratio of 1:1, wherein the molar ratio of the intermediate product 1 to the isocyanate is 1:1, and the mixture is stirred and refluxed at 75°C for 6 hours to obtain a polyurea thickener; the polyurea thickener obtained by the method is used to further prepare polyurea grease. The present invention selects the type of raw material isocyanate for preparing the polyurea thickener, and the obtained polyurea grease has good stability and a viscosity of 685Pa·s. This is because both toluene diisocyanate and 4,4-diphenylmethane diisocyanate are isocyanates containing a benzene ring structure, and the aromatic ring is directly connected to the -NCO group. There is a conjugation effect between the two functional groups, which makes the -NCO group highly reactive, so the prepared polyurea grease has high viscosity and good stability. In addition, the two benzene ring molecules in the 4,4-diphenylmethane diisocyanate molecule are not located on the same plane. This tetrahedral structure can enhance the stability of the grease. In addition, the lone electron pair of the nitrogen atom of the modified amine is polar, which can enhance the affinity of polyurea grease to the metal surface, thereby giving polyurea grease excellent anti-rust properties.

[0074] Table 6 Viscosity of polyurea grease prepared in Examples 22-27

[0075] Viscosity η(Pa·s) Embodiment 22 501 Embodiment 23 523 Embodiment 24 414 Embodiment 25 685 Embodiment 26 569 Embodiment 27 557

[0076] Embodiment 29

[0077] A method for preparing polyurea grease comprises the following steps:

[0078] Weigh 1 part of 2-phenylbenzimidazole-5-sulfonic acid, dissolve the 2-phenylbenzimidazole-5-sulfonic acid in ethanol to obtain a 2-phenylbenzimidazole-5-sulfonic acid alcohol solution, add the 2-phenylbenzimidazole-5-sulfonic acid alcohol solution dropwise into liquid bromine, wherein the molar ratio of 2-phenylbenzimidazole-5-sulfonic acid to liquid bromine is 1:1.5, and add iron powder to obtain a first reaction solution, heat the first reaction solution at 55° C. for 6 hours to obtain brominated 2-phenylbenzimidazole-5-sulfonic acid;

[0079] Dissolve 1 portion of bromo-2-phenylbenzimidazole-5-sulfonic acid in acetonitrile to obtain a bromo-2-phenylbenzimidazole-5-sulfonic acid solution, weigh 3,4,4'-triaminodiphenyl ether, and dissolve 3,4,4'-triaminodiphenyl ether in acetonitrile to obtain a 3,4,4'-triaminodiphenyl ether solution; dropwise add the bromo-2-phenylbenzimidazole-5-sulfonic acid solution to the 3,4,4'-triaminodiphenyl ether solution, wherein the molar ratio of bromo-2-phenylbenzimidazole-5-sulfonic acid to the 3,4,4'-triaminodiphenyl ether is 1:1.5, and add triethylamine and sodium tert-butoxide to obtain a second reaction solution; place the second reaction solution at 70° C., stir and react for 6 hours to obtain an intermediate product 1;

[0080] The intermediate product 1 is dissolved in anhydrous dimethyl sulfoxide to obtain an intermediate product solution, and a combination of toluene diisocyanate and 4,4-diphenylmethane diisocyanate in a mass ratio of 1:1 is added to the intermediate product solution, wherein the molar ratio of the intermediate product 1 to the isocyanate is 1:1, and the mixture is stirred and refluxed at 75°C for 6 hours to obtain a polyurea thickener; the base oil, the polyurea thickener, and the additives are mixed together to form a mixed liquid; in the mixed liquid, the base oil accounts for 65% of the total mass of the mixed liquid, the polyurea thickener accounts for 30% of the total mass of the mixed liquid, and the additives account for 5% of the total mass of the mixed liquid; the mixed liquid is uniformly heated to 90°C and kept warm for 1 hour; the uniform heating rate is 5°C / min, and the polyurea grease is obtained after cooling.

[0081] The mass proportions of the components in the mixed solutions of Examples 30-38 are shown in Table 7 below, and the remaining reagents and operations are the same as those of Example 29.

[0082] Table 7 Mass proportion of each component in the mixed solution of Examples 30-38

[0083] Base oil (%) Polyurea thickener (%) additive(%) Embodiment 30 65 30 5 Embodiment 31 75 20 5 Embodiment 32 75 23 2 Embodiment 33 85 10 5 Embodiment 34 85 13 2 Embodiment 35 85 14 1 Embodiment 36 90 5 5 Embodiment 37 90 8 2 Embodiment 38 90 9 1

[0084] Embodiment 39

[0085] The anti-wear performance of the polyurea grease prepared in the above Examples 29-38 was tested. According to the "Determination of Extreme Pressure Performance of Grease (Four-Ball Machine Method)" (SH / T 0202-1992), the anti-wear performance of the polyurea grease was characterized by measuring the wear spot diameter. The test results are shown in Table 8.

[0086] In the mixed liquid of Example 34 of the present invention, the base oil accounts for 85% of the total mass of the mixed liquid, the polyurea thickener accounts for 13% of the total mass of the mixed liquid, and the additives account for 2% of the total mass of the mixed liquid; the polyurea grease prepared by the said ratio has good wear resistance, which is manifested by the smallest wear spot diameter of 0.416 mm. When preparing polyurea grease, the present invention controls the proportion of polyurea thickener, base oil and additives, so that the wear resistance of polyurea grease can be improved. The prepared polyurea thickener molecule itself contains aromatic groups and has urea functional groups. The urea functional groups form hydrogen bonds with strong forces, and further cross-link to form a stable network structure, which has good affinity with the base oil. The base oil is wrapped in the three-dimensional network structure formed by the thickener, thereby showing good wear resistance. The wear spot diameter of the polyurea grease prepared in Example 34 of the present invention is smaller than that of the polyurea grease prepared in other embodiments, so it has the strongest anti-wear performance.

[0087] Table 8 Anti-wear properties of polyurea greases prepared in Examples 29-38

[0088]

[0089]

[0090] Embodiment 40

[0091] A method for preparing polyurea grease comprises the following steps:

[0092] Weigh 1 part of 2-phenylbenzimidazole-5-sulfonic acid, dissolve the 2-phenylbenzimidazole-5-sulfonic acid in ethanol to obtain a 2-phenylbenzimidazole-5-sulfonic acid alcohol solution, add the 2-phenylbenzimidazole-5-sulfonic acid alcohol solution dropwise into liquid bromine, wherein the molar ratio of 2-phenylbenzimidazole-5-sulfonic acid to liquid bromine is 1:1.5, and add iron powder to obtain a first reaction solution, heat the first reaction solution at 55° C. for 6 hours to obtain brominated 2-phenylbenzimidazole-5-sulfonic acid;

[0093] Dissolve 1 portion of bromo-2-phenylbenzimidazole-5-sulfonic acid in acetonitrile to obtain a bromo-2-phenylbenzimidazole-5-sulfonic acid solution, weigh 3,4,4'-triaminodiphenyl ether, and dissolve 3,4,4'-triaminodiphenyl ether in acetonitrile to obtain a 3,4,4'-triaminodiphenyl ether solution; dropwise add the bromo-2-phenylbenzimidazole-5-sulfonic acid solution to the 3,4,4'-triaminodiphenyl ether solution, wherein the molar ratio of bromo-2-phenylbenzimidazole-5-sulfonic acid to the 3,4,4'-triaminodiphenyl ether is 1:1.5, and add triethylamine and sodium tert-butoxide to obtain a second reaction solution; place the second reaction solution at 70° C., stir and react for 6 hours to obtain an intermediate product 1;

[0094] The intermediate product 1 is dissolved in anhydrous dimethyl sulfoxide to obtain an intermediate product solution, toluene diisocyanate and 4,4-diphenylmethane diisocyanate are added to the intermediate product solution in a mass ratio of 1:1, wherein the molar ratio of the intermediate product 1 to the isocyanate is 1:1, and the mixture is stirred and refluxed at 75°C for 6 hours to obtain a polyurea thickener; the base oil, the polyurea thickener, and the additives are mixed together to form a mixed liquid; the base oil in the mixed liquid accounts for 85% of the total mass of the mixed liquid, the polyurea thickener accounts for 13% of the total mass of the mixed liquid, and the additives account for 2% of the total mass of the mixed liquid; the mixed liquid is uniformly heated to 100°C and kept warm for 1 hour; the uniform heating rate is 5°C / min, and the polyurea grease is obtained after cooling.

[0095] Embodiment 41

[0096] The mixture was heated to 110°C at a uniform rate and kept warm for 1 hour. The remaining reagents were the same as in Example 40.

[0097] Embodiment 42

[0098] The mixed solution was heated to 120°C at a uniform rate and kept warm for 1 hour. The remaining reagents were the same as in Example 40.

[0099] Embodiment 43

[0100] The mixture was heated to 130°C at a uniform rate and kept warm for 1 hour. The remaining reagents were the same as in Example 40.

[0101] Embodiment 44

[0102] The mixed solution was heated to 140°C at a uniform rate and kept warm for 1 hour. The remaining reagents were the same as in Example 40.

[0103] Embodiment 45

[0104] The mixed solution was heated to 150°C at a uniform rate and kept warm for 1 hour. The remaining reagents were the same as in Example 40.

[0105] Comparative Example 2

[0106] The antioxidant diisooctyldiphenylamine was not added, and the rest was the same as in Example 44.

[0107] Embodiment 46

[0108] The polyurea greases prepared in Examples 40-45 above were tested for their antioxidant properties. Figure 2 The oxidation resistance of polyurea grease is determined according to the "Chemical Stability Test Method for Lubricating Greases" (SHT 0335-1992). The oxidation resistance of grease is evaluated by testing the decrease in oxygen pressure in the oxygen bomb before and after the experiment. The lower the oxygen pressure decrease in the oxygen bomb, the better the oxidation resistance. A pressure drop (MPa) of no more than 0.050 meets industry standards.

[0109] In Example 44, the mixed liquid is uniformly heated to 140°C and kept warm for 1 hour at a uniform heating rate of 5°C / min. After cooling, the polyurea grease is obtained. The present invention prepares polyurea grease by a prefabrication method, which can reduce the side reactions of active isocyanate groups during the reaction. After the polyurea thickener is prepared in the previous sequence, it is added to the base oil and the polyurea grease is obtained by high-temperature insulation and cooling with the antioxidant diisooctyl diphenylamine. The prepared grease was tested for its antioxidant properties, and the oxygen pressure drop in the oxygen bomb was 0.0085MPa, with good antioxidant stability. The polyurea grease prepared by the present invention does not contain metal atoms and will not undergo catalytic reaction with the base oil. Therefore, the antioxidant pressure drop (MPa) is no more than 0.050, which meets industry standards. The pressure drop of the polyurea grease prepared in Examples 40-43 and Example 45 is greater than that of the polyurea grease prepared in Example 44. Figure 2 The pressure drop of the polyurea grease prepared in Examples 40-45 is the lowest. The oxygen pressure drop of the grease in Example 44 is the lowest, so the anti-oxidation stability is the best. In Comparative Example 2, no antioxidant was added, and the pressure drop of the polyurea grease prepared in the anti-oxidation test was 0.058 MPa, indicating poor anti-oxidation performance.

[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 method for preparing a polyurea grease, characterized in that: The following steps are involved: Weigh 1 portion of 2-phenylbenzimidazole-5-sulfonic acid, CAS number: 27503-81-7; dissolve the 2-phenylbenzimidazole-5-sulfonic acid in ethanol to obtain a 2-phenylbenzimidazole-5-sulfonic acid alcohol solution; dropwise add the 2-phenylbenzimidazole-5-sulfonic acid alcohol solution into liquid bromine, and add a first catalyst to obtain a first reaction solution; heat the first reaction solution at 40-65° C. for 6 hours to obtain brominated 2-phenylbenzimidazole-5-sulfonic acid; Take 1 portion of the brominated 2-phenylbenzimidazole-5-sulfonic acid and dissolve it in acetonitrile to obtain a brominated 2-phenylbenzimidazole-5-sulfonic acid solution; weigh 3,4,4'-triaminodiphenyl ether, and dissolve the 3,4,4'-triaminodiphenyl ether in acetonitrile to obtain a 3,4,4'-triaminodiphenyl ether solution; dropwise add the brominated 2-phenylbenzimidazole-5-sulfonic acid solution to the 3,4,4'-triaminodiphenyl ether solution, and add an acid binding agent and a second catalyst to obtain a second reaction solution; place the second reaction solution at 50-80° C., stir and react for 6-12 hours, and obtain an intermediate product, a modified amine; the molar ratio of the brominated 2-phenylbenzimidazole-5-sulfonic acid to the 3,4,4'-triaminodiphenyl ether is 1:1-2; The intermediate product, a modified amine, is dissolved in anhydrous dimethyl sulfoxide to obtain an intermediate product solution; isocyanate is added to the intermediate product solution, stirred and refluxed at 75°C for 6 hours to obtain a polyurea thickener; the molar ratio of the intermediate product, a modified amine, to the isocyanate is 1:1; the isocyanate is toluene diisocyanate and 4,4-diphenylmethane diisocyanate; the base oil, the polyurea thickener and additives are mixed together to form a mixed liquid; the mixed liquid is heated uniformly to 90-150°C, kept warm for 1 hour, and cooled to obtain the polyurea grease.

2. The method for preparing a polyurea grease according to claim 1, characterized in that: The molar ratio of the 2-phenylbenzimidazole-5-sulfonic acid to the liquid bromine is 1:1-3; and the first catalyst is iron powder.

3. The method for preparing a polyurea grease according to claim 1, characterized in that: The acid binding agent is triethylamine; the second catalyst is sodium tert-butoxide or potassium carbonate.

4. The method for preparing a polyurea grease according to claim 1, characterized in that: The base oil accounts for 65%-90% of the total mass of the mixed liquid, the polyurea thickener accounts for 5%-30% of the total mass of the mixed liquid, and the additives account for 1-5% of the total mass of the mixed liquid.

5. The method for preparing a polyurea grease according to claim 1, characterized in that: The base oil is cycloalkyl oil KN4010; the additive is an antioxidant diisooctyl diphenylamine; and the uniform heating rate is 5°C / min.

6. A polyurea grease, characterized in that: The polyurea grease is prepared by nucleophilic substitution of 2-phenylbenzimidazole-5-sulfonic acid with liquid bromine to prepare brominated 2-phenylbenzimidazole-5-sulfonic acid, which is then reacted with the amino group of 3,4,4'-triaminodiphenyl ether to prepare an intermediate product, a modified amine, which reacts with isocyanate, and the synthesized polyurea thickener is mixed with base oil and additives; the polyurea grease is prepared by the preparation method according to any one of claims 1 to 5; the polyurea grease has a dropping point of 301°C; the polyurea grease has a cone penetration of 231 / 0.1 mm, a consistency grade of 3#, and a grease texture with moderate hardness; the polyurea grease has good stability and a viscosity of 685Pa·s; the polyurea grease has a wear spot diameter of 0.416 mm and good wear resistance; the polyurea grease has an oxidation resistance index pressure drop of 0.0085MPa and good oxidation resistance stability.

Images