Epoxidized soybean oil-based lubricating grease and preparation method thereof

Abstract

The invention discloses epoxidized soybean oil-based lubricating grease and a preparation method thereof, and the epoxidized soybean oil-based lubricating grease comprises the following components in parts by weight: 80-85 parts of epoxidized soybean oil, 10-15 parts of cellulose, 1-5 parts of isocyanate and 0.1-1 part of an additive. The epoxidized soybean oil is used as base oil, the cellulose is used as a thickening agent, the isocyanate is used as a cross-linking agent, and the isocyanate can respectively react with epoxy groups in the epoxidized soybean oil and hydroxyl groups on the cellulose to form an epoxidized soybean oil-isocyanate-cellulose cross-linking system. And thickening the soybean oil to prepare the lubricating grease. The epoxidized soybean oil-based lubricating grease prepared by the invention is prepared from a renewable and degradable bio-based material, and has the advantages of high biodegradability, environmental friendliness, wide raw material source and the like.

Description

Technical Field

[0001] The invention relates to the technical field of lubricating materials, in particular to an epoxy soybean oil-based lubricating grease and a preparation method thereof. Background Art

[0002] Grease is a semi-solid lubricant product obtained by dispersing a thickener into a base oil for thickening. It can effectively reduce friction and wear of friction pairs, reduce energy waste, and extend the service life of machinery. Traditional greases usually use mineral oil or synthetic oil as base oil. Most of these base oils come from non-renewable petrochemical resources and will generate certain environmental loads during production and use. In addition, the current common metal soaps or polymer thickeners also have problems such as being difficult to degrade and harmful to the environment. With the increase of people's environmental awareness, greases prepared with environmentally friendly bio-based materials have attracted people's attention. Summary of the invention

[0003] Based on this, the present invention proposes an environmentally friendly bio-based grease, which uses epoxidized soybean oil as a base oil, cellulose as a thickener, and isocyanate as a cross-linking agent to construct an epoxidized soybean oil-isocyanate-cellulose cross-linking system, and then thickens the base oil to prepare a grease product. Compared with traditional greases, the epoxidized soybean oil-based grease has the advantages of being renewable, degradable, and having low carbon emissions, which meets the current social demand for green and environmentally friendly products.

[0004] To achieve the above object, the present invention provides an epoxy soybean oil-based grease, wherein the epoxy soybean oil-based grease comprises, by weight: 80 to 85 parts of epoxy soybean oil, 10 to 15 parts of cellulose, 1 to 5 parts of isocyanate, and 0.1 to 1 part of an additive; Among them, the epoxy soybean oil-based grease uses the epoxy soybean oil as the base oil, the cellulose as the thickener, and the isocyanate as the cross-linking agent. The isocyanate reacts with the epoxy group in the epoxy soybean oil and the hydroxyl group on the cellulose to form an epoxy soybean oil-isocyanate-cellulose cross-linking system, and then the soybean oil is thickened to obtain the grease.

[0005] Furthermore, the cellulose includes any one of microcrystalline cellulose, methyl cellulose, ethyl cellulose, hydroxymethyl propyl cellulose, nanocellulose or cellulose nanocrystals, or a combination of at least two thereof.

[0006] Further, the isocyanate includes any one or a combination of at least two of diphenylmethane diisocyanate, toluene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate and dicyclohexylmethane diisocyanate.

[0007] Furthermore, the additive includes any one of an antioxidant, an extreme pressure agent and a rust remover, or a combination of at least two of them.

[0008] The antioxidant includes any one or a combination of at least two of octylbutyl diphenylamine, diisooctyl diphenylamine, thiophenol antioxidants, p-methylphenol or tocopherol; The extreme pressure agent includes any one or a combination of at least two of calcium stearate, molybdenum di-n-butyl dithiocarbamate, zinc dialkylthiophosphate, borate or nano-grade zinc oxide; The rust remover comprises any one of medium-base calcium sulfonate, barium sulfonate or sodium sebacate, or a combination of at least two of them.

[0009] The present invention also provides a method for preparing the above-mentioned epoxy soybean oil-based grease, comprising the following steps: S1. Add epoxidized soybean oil and isocyanate into the reactor and stir thoroughly at 60-80 °C for 30-60 min. S2. Then, add cellulose and continue stirring for 60-120 min; S2. The mixture is heated to 140-160° C. and refined for 30-60 min, then cooled to room temperature and an additive is added, and the mixture is fully ground using a three-roll mill to obtain the epoxy soybean oil-based grease.

[0010] Furthermore, the mass ratio of the epoxy soybean oil, cellulose, isocyanate and additive is 80-85:10-15:1-5:0.1-1.

[0011] The present invention has the following beneficial effects: The invention provides an epoxy soybean oil-based lubricating grease. The epoxy soybean oil-based lubricating grease comprises, by weight, 80 to 85 parts of epoxy soybean oil, 10 to 15 parts of cellulose, 1 to 5 parts of isocyanate, and 0.1 to 1 part of an additive.

[0012] Epoxidized soybean oil is a natural environmentally friendly lubricant made from soybean oil through epoxidation reaction, with excellent physical and chemical properties. Epoxidized soybean oil has excellent antioxidant properties, can effectively protect the lubrication system, and has good adsorption to metals, can form a firm oil film on the metal surface, improve the strength of the oil film, and thus effectively reduce friction and wear.

[0013] Cellulose is the most abundant natural polymer on Earth, accounting for 40% to 50% of the Earth's total biomass reserves. It can produce 10 11 ~10 12Tons of cellulose, cellulose has a certain thickening ability and can be used as a thickener in water-based coatings, food additives and other fields. In summary, the preparation of grease with natural bio-based raw materials such as epoxidized soybean oil and cellulose has the advantages of low carbon and environmental protection, renewable and degradable, and energy saving and emission reduction. However, cellulose, as a polyhydroxy compound composed of glucose units connected by glycosidic bonds, has a large polarity, resulting in poor compatibility with epoxidized soybean oil. It is difficult to obtain a stable grease gel by directly using cellulose to thicken epoxidized soybean oil.

[0014] Based on this, the present invention uses isocyanate as a cross-linking agent, and utilizes the reactivity of the isocyanate group to react with the epoxy group in the epoxy soybean oil and the hydroxyl group on the cellulose, respectively, to form an epoxy soybean oil-isocyanate-cellulose cross-linking system, and then thickens the soybean oil to prepare grease. Because after the cross-linking system is formed, the fluidity of the soybean oil is constrained, so that the system becomes viscous and exhibits typical grease characteristics. Compared with traditional petroleum-based greases, epoxy soybean oil-based greases can be decomposed more quickly by microorganisms in the natural environment, reducing long-term pollution to the environment, and at the same time have the advantages of being renewable, low carbon emissions, and a wide range of raw material sources.

[0015] In addition, the main functions of additives in grease include the following aspects: 1. Lubrication: Grease additives can form a lubricating oil film on the friction surface, reduce direct contact between parts, thereby reducing wear and extending the service life of the machine. 2. Cleaning: Grease additives can remove pollutants from the lubrication parts of the bearing and disperse them into tiny particles for discharge to maintain the cleanliness of the bearing. 3. Cooling: Grease additives can effectively reduce the heat generated by friction, take away the heat through circulation, achieve the cooling effect of the bearing, and prevent bearing overheating and grease deterioration. 4. Anti-corrosion: Grease additives can protect bearing components from air and water erosion, prevent metal corrosion, and extend their service life. 5. Reduce friction coefficient: Grease additives can form a stable oil film on the metal surface, reduce the concentrated stress of the impact load on the bearing, and thus extend the fatigue life of the bearing. 6. Improve load-bearing capacity: The elemental organic compounds containing sulfur, phosphorus, and halogens in the grease additives can decompose active elements under friction conditions, react with the metal surface to form a surface film with low shear strength, and improve the load-bearing capacity of the friction pair. 7. Improve low-temperature fluidity: Grease additives can lower the freezing point, improve low-temperature fluidity, and enable the grease to maintain good lubrication effect even under low temperature conditions.

[0016] In addition to the above-described purposes, features and advantages, the present invention has other purposes, features and advantages. The present invention will be further described in detail with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The drawings constituting a part of this application are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings: Figure 1 Schematic diagram of the synthesis mechanism of epoxidized soybean oil-based grease; Figure 2 These are digital photos of the lubricating greases prepared in Example 1, Comparative Example 1 and Comparative Example 2 after being left to stand for a period of time; Figure 3 This is a comparison chart of high temperature DSC tests of Example 1 and commercial lithium-based grease. DETAILED DESCRIPTION

[0018] The embodiments of the present invention are described in detail below with reference to the accompanying drawings, but the present invention can be implemented in many different ways as defined and covered by the claims.

[0019] The experimental methods in the following examples are conventional methods unless otherwise specified. The raw materials involved in the following examples are common commercial products and can be purchased from the market unless otherwise specified; the detection methods are conventional detection methods unless otherwise specified.

[0020] Example 1 A method for preparing an epoxy soybean oil-based grease comprises the following steps: S1. Add 5 g of diphenylmethane diisocyanate to 80 g of epoxy soybean oil and stir thoroughly at 80 °C for 60 min.

[0021] S2. Then, add 15 g of microcrystalline cellulose and continue stirring for 60 min.

[0022] S3. Heat to 150 °C and refine for 60 min, then cool to room temperature and add 0.5 g of p-methylphenol. Grind thoroughly three times using a three-roll mill to obtain epoxy soybean oil-based grease.

[0023] Example 2 A method for preparing an epoxy soybean oil-based grease comprises the following steps: S1. Add 5 g of hexamethylene diisocyanate to 80 g of epoxy soybean oil and stir thoroughly at 60 °C for 30 min.

[0024] S2. Then, add 15 g of methyl cellulose and continue stirring for 60 min.

[0025] S3. Heat to 150 °C and refine for 60 min, then cool to room temperature and add 0.5 g of dialkyl zinc thiophosphate. Grind thoroughly three times using a three-roll mill to obtain epoxy soybean oil-based grease.

[0026] Example 3 S1. Add 5 g of diphenylmethane diisocyanate to 80 g of epoxy soybean oil and stir thoroughly at 80 °C for 30 min.

[0027] S2. Then, add 10 g microcrystalline cellulose and 5 g ethyl cellulose and continue stirring for 60 min.

[0028] S3. Heat to 150 °C and refine for 60 min, then cool to room temperature and add 1 g of medium-base calcium sulfonate. Grind thoroughly three times using a three-roll mill to obtain epoxy soybean oil-based grease.

[0029] Comparative Example 1 (without addition of isocyanate crosslinking agent) The difference between Comparative Example 1 and Example 1 is that in step S1, diphenylmethane diisocyanate is not added, and the other steps are the same as in Example 1.

[0030] Comparative Example 2 (no microcrystalline cellulose added) The difference between Comparative Example 2 and Example 1 is that in step S2, the amount of microcrystalline cellulose added is 0, and the other steps are the same as Example 1.

[0031] Comparative Example 3 (using soybean oil) The difference between Comparative Example 3 and Example 1 is that in step S1, soybean oil is used instead of epoxidized soybean oil, and the other steps are the same as Example 1.

[0032] Comparative Example 4 (too little amount of isocyanate added) The difference between Comparative Example 4 and Example 1 is that in step S1, the added amount of diphenylmethane diisocyanate is 0.5 g, and the other steps are the same as Example 1.

[0033] Comparative Example 5 (Too much isocyanate added) The difference between Comparative Example 5 and Example 1 is that in step S1, the added amount of diphenylmethane diisocyanate is 8 g, and the other steps are the same as Example 1.

[0034] Figure 1 This is a schematic diagram of the synthesis mechanism of epoxidized soybean oil-based grease. Isocyanate, as a cross-linking agent, can undergo a ring-opening addition reaction with the epoxy group in the epoxidized soybean oil and a nucleophilic addition reaction with the hydroxyl group in the cellulose, thereby forming a cross-linked network to achieve the purpose of thickening the base oil. Figure 2The digital photos of the greases prepared in Example 1, Comparative Example 1 and Comparative Example 2 after standing for a period of time. It can be found that the stratification phenomenon occurs in Comparative Example 1. This is because no isocyanate crosslinking agent is added in Comparative Example 1. When cellulose and epoxy soybean oil are directly mixed, the polarity of cellulose is large and the affinity with epoxy soybean oil is poor, so the two-phase separation phenomenon occurs after standing. In Comparative Example 2, only isocyanate is added. It can be found that it presents a thin liquid state and cannot form fat, indicating that pure isocyanate has no thickening ability for epoxy soybean oil. In contrast, Example 1 presents a semi-solid state of a typical grease with a certain structural strength, which indicates that epoxy soybean oil, isocyanate and cellulose interact with each other to form a crosslinking system, thereby improving the structural strength and enabling it to have functions such as sealing, lubrication and pressure resistance.

[0035] The tribological properties of Example 1, Comparative Examples 1-5, and commercial lithium-based grease were tested using a four-ball friction tester with a load of 40 kgf, a rotation speed of 1200 r / min, and a running time of 60 min. The wear spot diameter of the steel ball was observed using an optical microscope, and the relevant data are detailed in Table 1.

[0036] Table 1: It can be seen from the test results in Table 1 that compared with the grease in Comparative Example 1 to which no isocyanate crosslinking agent is added, the epoxy soybean oil-based grease in Example 1 has significantly reduced friction coefficient, friction force and wear spot diameter, showing excellent tribological properties. This is because compared with the grease made directly from cellulose, the present invention uses isocyanate as a crosslinking agent to crosslink the epoxy soybean oil, isocyanate and cellulose, thereby thickening the base oil into grease. During the working process of the grease, the base oil can be effectively prevented from being lost, and a firm oil film can be formed on the surface of the friction pair, thereby improving the tribological properties. However, since Comparative Example 2 only contains isocyanate, a crosslinking system is not formed, and the thickening ability is weak. The grease will cause the base oil to be lost during the working process, and the friction pair is in a fat-deficient state for a long time, thereby reducing the tribological properties. Similarly, Comparative Example 3 does not contain an epoxy group, and a crosslinking system between the three cannot be formed, so the tribological properties are also poor. In addition, isocyanate is used as a crosslinking agent, and too little or too much addition will affect the performance of the grease. When the amount of isocyanate added is too little (Comparative Example 4), it will not have the effect of crosslinking and thickening; when the amount of isocyanate added is too much (Comparative Example 5), the crosslinking density is too large, the oil separation performance is poor, and the tribological performance is reduced. Therefore, isocyanate should be added in an appropriate amount as a crosslinking agent. If the amount of isocyanate added is too little, the degree of crosslinking is low, the thickening ability is weak, and it cannot form fat; if the amount of isocyanate added is too high, the crosslinking density is too high, resulting in a large consistency of the grease and poor thixotropy. Compared with commercial lithium-based grease, Comparative Example 1 also shows excellent anti-friction and anti-wear properties. This is because epoxy soybean oil has good adsorption capacity with metals compared to mineral oil, and can form a firm oil film on the metal surface, thereby more effectively protecting the friction parts and improving the anti-friction and anti-wear performance. The all-bio-based greases prepared in Examples 2 and 3 have similar properties to those prepared in Example 1, and will not be repeated here.

[0037] The oxidation induction period of Example 1 was tested by differential scanning calorimetry (DSC) and compared with commercial lithium-based grease. Figure 3 As shown in the figure. The time corresponding to the peak oxidation temperature of commercial lithium-based grease at 180 °C is 18 minutes. In contrast, the time corresponding to the peak oxidation temperature of epoxy soybean oil-based grease at 210 °C is 35 minutes, and the anti-oxidation performance has been greatly improved. This is because the epoxy groups in the epoxy soybean oil can react with oxygen to form stable epoxy compounds, thereby consuming free radicals, preventing the further development of the oxidation process, and improving the anti-oxidation property of the epoxy soybean oil-based grease.

[0038] In summary, the present invention provides an epoxy soybean oil-based grease, which uses isocyanate as a crosslinking agent to form an epoxy soybean oil-isocyanate-cellulose crosslinking system, and then thickens the base oil to prepare an environmentally friendly bio-based grease. Thanks to the antioxidant properties of epoxy soybean oil and good adhesion to metal, the prepared epoxy soybean oil-based grease has excellent high temperature stability and tribological properties compared to commercial lithium-based grease.

[0039] The epoxidized soybean oil-based grease provided by the present invention not only reduces the dependence on limited petrochemical resources, but also can be decomposed more quickly by microorganisms in the natural environment, reducing long-term pollution to the environment. At the same time, it has the advantages of being renewable, degradable, low-carbon emission, environmentally friendly, and having a wide range of raw material sources, and is in line with the concepts of environmental protection and sustainable development.

[0040] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. An epoxy soybean oil-based grease, characterized in that: The epoxy soybean oil-based grease comprises, by weight: 80-85 parts of epoxy soybean oil, 10-15 parts of cellulose, 1-5 parts of isocyanate, and 0.1-1 parts of additives; Among them, the epoxy soybean oil-based grease uses the epoxy soybean oil as the base oil, the cellulose as the thickener, and the isocyanate as the cross-linking agent. The isocyanate reacts with the epoxy group in the epoxy soybean oil and the hydroxyl group on the cellulose to form an epoxy soybean oil-isocyanate-cellulose cross-linking system, and then the soybean oil is thickened to obtain the grease.

2. The epoxidized soybean oil-based grease according to claim 1, characterized in that: The cellulose includes any one of microcrystalline cellulose, methyl cellulose, ethyl cellulose, hydroxymethyl propyl cellulose, nanocellulose or cellulose nanocrystals, or a combination of at least two thereof.

3. The epoxidized soybean oil-based grease according to claim 1, characterized in that: The isocyanate includes any one of diphenylmethane diisocyanate, toluene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate and dicyclohexylmethane diisocyanate, or a combination of at least two thereof.

4. The epoxidized soybean oil-based grease according to claim 1, characterized in that: The additives include any one of an antioxidant, an extreme pressure agent and a rust remover, or a combination of at least two of them.

5. The epoxidized soybean oil-based grease according to claim 4, characterized in that: The antioxidant includes any one of octylbutyl diphenylamine, diisooctyl diphenylamine, thiophenol antioxidants, p-methylphenol or tocopherol, or a combination of at least two thereof.

6. The epoxidized soybean oil-based grease according to claim 4, characterized in that: The extreme pressure agent includes any one of calcium stearate, molybdenum di-n-butyl dithiocarbamate, zinc dialkylthiophosphate, borate or nano zinc oxide, or a combination of at least two thereof.

7. The epoxidized soybean oil-based grease according to claim 4, characterized in that: The rust remover comprises any one of medium-base calcium sulfonate, barium sulfonate or sodium sebacate, or a combination of at least two of them.

8. A method for preparing an epoxy soybean oil-based grease according to any one of claims 1 to 7, characterized in that: The steps include: S1. Add epoxidized soybean oil and isocyanate into the reactor and stir thoroughly at 60-80 °C for 30-60 min. S2. Add cellulose and continue stirring for 60-120 min; S3. The mixture is heated to 140-160° C. and refined for 30-60 min, then cooled to room temperature and an additive is added, and the mixture is fully ground using a three-roll mill to obtain the epoxy soybean oil-based grease.

9. The method for preparing an epoxy soybean oil-based grease according to claim 8, characterized in that: The mass ratio of epoxidized soybean oil, cellulose, isocyanate and additive is 80~85:10~15:1~5:0.1~1.

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