A lubricating oil composition for heavy-load methanol fuel engine and preparation method thereof

Abstract

The present invention discloses a lubricating oil composition for a heavy-duty methanol fuel engine, comprising the following raw materials: a dispersed viscosity modifier, an antioxidant and anti-wear agent, a detergent, a dispersant, a pour point depressant, and a base oil. The lubricating oil composition for a heavy-duty methanol fuel engine of the present invention performs outstandingly in reliability bench tests, can cleverly achieve the isolation of engine oil, engine and combustion products such as formic acid, has excellent corrosion resistance, can provide strong protection for the engine, and effectively resists the erosion of acidic substances produced by methanol combustion. The composition can also form a stable boundary oil film, successfully resolve the problem of methanol scouring the cylinder wall oil film, has significant results in reducing friction and wear, and effectively ensures the smooth operation of the engine. This innovative lubricating oil composition has good application results, not only improves the engine's working efficiency, but also extends its service life, laying the foundation for ensuring the reliable operation of heavy-duty methanol fuel engines, and has great application prospects and practical value in related fields.

Description

Technical Field

[0001] The invention relates to the technical field of lubricating oils, and in particular to a lubricating oil composition for a heavy-load methanol fuel engine and a preparation method thereof. Background Art

[0002] The heavy-duty methanol fuel engine is oriented to the national "dual carbon" strategy, providing the industry with a new low-cost green hydrogen energy solution, opening up a new development direction for the transformation of traditional internal combustion engines to zero emissions and electrification, and promoting the upgrading and transformation of the internal combustion engine industry. Internal combustion engines will gradually realize the transformation from traditional fuel power to high-efficiency, zero-emission, and new energy power. Methanol is one of the best choices for energy diversification and reducing automobile exhaust emissions, and is an important way to solve the current energy crisis and environmental pollution problems.

[0003] Compared with traditional internal combustion engines, the combustion products of heavy-duty methanol fuel engines include formic acid, formaldehyde, and formic acid. These combustion products have the following effects on engines and lubricants: from the bench and road verification test disassembly, formic acid has very serious corrosion on engine parts, valve stem corrosion, and serious carbon deposits on the disc; exhaust side intake valve cylinder liner position corrosion, serious mesh wear; connecting rod small end bushing suspected corrosion; cylinder head airway corrosion; valve guide corrosion; methanol will react with antioxidants and anti-wear agents, resulting in serious decline in the high temperature and anti-deposition performance of engine lubricants, serious carbon deposits on the top of the piston, and high temperature discoloration and blackening of the bottom of the piston; bench and road test old oil detection found that the alkalinity value dropped rapidly, the acid value increased rapidly, and the water content increased a lot. Even if the alkalinity value is strengthened, the ash content has reached 1.2wt%, and the alkalinity value is reduced to 0 after the 200-hour bench test; there is currently no suitable methanol fuel engine special lubricant technology that can protect the corrosion resistance of engine parts. How to improve the anti-corrosion performance of engine oil is the key to the development of methanol engine technology.

[0004] Existing technology In the prior art, the invention patent with application number CN201911032689.5 and titled "Methanol Engine Lubricant Composition and Preparation Method" discloses a methanol engine lubricant composition composed of a viscosity index modifier, an antioxidant and an anti-corrosion agent, a friction modifier, a detergent, a demulsifier and a base oil composition, but no key added component that can reduce corrosion is seen.

[0005] The invention patent with application number 201310146696.4 and titled "Methanol fuel engine oil composition and its manufacturing method" discloses a methanol fuel engine oil composition and its manufacturing method, the composition contains Mannich base, antioxidant, metal detergent, ZDDP, organic molybdenum, metal corrosion inhibitor and lubricating oil base oil. The effect of the invention applied to methanol engines or simulated methanol fuel engine combustion products has not been seen. It is only a simple BRT simulation anti-wear test on a gasoline test bench, and the application effect is unknown. Summary of the invention

[0006] The purpose of the present invention is to solve the deficiencies of the above-mentioned background technology and to provide a lubricating oil composition for a heavy-load methanol fuel engine and a preparation method thereof.

[0007] Through the analysis of the results of the previous simulation tests and bench tests, as well as the strong polarity and volatility of formic acid and methanol, we have designed to "isolate" the combustion products such as formic acid and water from the oil and the metal surface of the engine, respectively, to achieve the anti-corrosion property of the oil. Through unremitting efforts, we thought of using a polymer dispersible viscosity agent containing an amphoteric structure of N-vinyl pyrrolidone as a lubricant composition. The copolymer of dodecyl methacrylate (CAM) and N-vinyl pyrrolidone (NVP) - poly (dodecyl methacrylate-co-N-vinyl pyrrolidone), namely P (CAM-co-NVP), combines the advantages of both: the molecular chain of this structure contains a five-membered ring of N atoms, which belongs to a lactam compound, and has both hydrophilic and lipophilic groups, making it very soluble in water and many solvents such as alcohols and carboxylic acids, including methanol, formic acid, acetic acid, etc. It contains a long chain of lipophilic groups and can be soluble in oil, so it can be used as a dispersible viscosity agent.

[0008] The dispersed viscosity modifier polymer has the following characteristics:

[0009] 1. Surface activity: From the structural point of view, the long polymer molecular chain contains both hydrophilic and affinity groups of lactam groups and lipophilic non-polar carbon chains; this molecular structure gives it a low surface activity, and the adsorption effect on the solid surface and the three-dimensional shielding ability formed by hydrophilicity make the solid particles have excellent dispersion stability. The hydrogen bond complexing ability with other organic and inorganic compounds gives it a cohesive and solubilizing effect, which can clarify and stabilize the liquid.

[0010] 2. Complexation: Polymers with "dissolving" ability. This "dissolving" ability is due to the fact that their molecular structure contains highly polar properties and amide groups that can accept hydrogen bonds, as well as non-polar groups that allow the polymer to form complexes with compounds containing hydroxyl groups, carboxyl groups and other active hydrogen atoms.

[0011] 3. Strong adsorption: It can be adsorbed on the metal surface to form a thick viscous oil film. These oil films enhance the formation of lubricating films under low speed and high temperature conditions, effectively reduce friction and wear, and can act as an isolation to prevent acid corrosion.

[0012] 4. Thickening property: The structure contains polydodecyl methacrylate, which is a viscosity modifier and a high molecular polymer that can increase the viscosity of engine oil.

[0013] In order to achieve the above object, the technical solution adopted by the present invention is:

[0014] A lubricating oil composition for a heavy-duty methanol fuel engine comprises the following raw materials in parts by mass:

[0015]

[0016]

[0017] The dispersed viscosity modifier is a P(CAM+NVP) polymer, which is a copolymer of dodecyl methacrylate (CAM) and N-vinyl pyrrolidone (NVP).

[0018] Preferably, the antioxidant and anti-wear agent is one or both of dialkyl zinc dithiophosphate and diaryl zinc dithiophosphate.

[0019] Preferably, the detergent is a mixture of alkyl salicylate and sulfonate.

[0020] Preferably, the dispersant is a boronated polyisobutylene succinimide dispersant.

[0021] Preferably, the pour point depressant is polymethacrylate.

[0022] Preferably, the base oil is a coal-to-hydrocarbon synthetic base oil.

[0023] Preferably, the structure of the alkyl salicylate is preferably as shown in Formula I:

[0024]

[0025] Wherein, R is an alkyl group containing 10 to 20 carbon atoms, M is Ca or Mg, and m and n are positive integers not equal to zero.

[0026] The structure of the sulfonate is preferably as shown in Formula II:

[0027]

[0028] Wherein, R1 is an alkyl group containing 14 to 28 carbon atoms, M is Ca or Mg, and m1 and n1 are positive integers not equal to zero.

[0029] The structure of the boronated polyisobutylene succinimide dispersant is shown in Formula VI:

[0030]

[0031] Wherein, PIB is polyisobutylene, the molecular weight is 900 to 1300, and r is a positive integer not equal to zero.

[0032] The structural formula of the zinc dialkyl dithiophosphate is preferably as shown in Formula VII:

[0033]

[0034] Where R3=C n H 2n+1 , n=3~10.

[0035] The structural formula of the zinc diaryl dithiophosphate is preferably as shown in Formula V:

[0036]

[0037] Where R4=C n H 2n+1 , n=1~8.

[0038] In the first aspect, in the above technical scheme, the present invention provides a method for synthesizing a dispersed viscosity modifier (P(CAM+NVP)) of dodecyl methacrylate (CAM) and N-vinyl pyrrolidone (NVP), comprising the following steps:

[0039] Mix dodecyl methacrylate, N-vinyl pyrrolidone, solvent and initiator; perform polymerization reaction at 40°C to 90°C for 4 to 10 hours, and perform vacuum distillation on the toluene solution of the obtained polymerization product. After vacuum filtration and alcohol washing, vacuum drying is performed to obtain a white or light yellow dispersed viscosity index agent P (CAM-co-NVP). The reaction formula is as follows:

[0040]

[0041] Preferably, the weight ratio of lauryl methacrylate to N-vinyl pyrrolidone may be 5:1 to 3:2, and 2:1 is preferred in the present invention.

[0042] Preferably, nitrogen is introduced into the device as a protective gas and pulse stirring is performed, and the polymerization reaction is heated in stages: 40°C to 50°C for 1 to 2 hours, 50°C to 70°C for 3 to 4 hours, and 70°C to 90°C for 2 to 3 hours to avoid "explosion" phenomenon.

[0043] The initiator can be: azobiscyanovaleric acid (ACVA), azobisisobutylnitrile (AI BN), dibenzoyl peroxide (BPO), azobisisoheptylcyanide (ABVN), etc., or any combination thereof. The present invention preferably uses dibenzoyl peroxide (BPO). The amount of the initiator can be 0.02% to 1.5% of the weight of dodecyl methacrylate and N-vinyl pyrrolidone. The present invention preferably uses 1.0% as the optimal requirement.

[0044] Preferably, the solvent toluene is used in an amount of 20 to 30 mL / mol, and 25 mL / mol is preferred in the present invention.

[0045] In the second aspect, the present invention also provides a method for preparing a lubricating oil composition for a heavy-duty methanol fuel engine, comprising the following steps:

[0046] Sol: First, cut the dispersed adhesive dry glue into pieces and mix it with part of the base oil according to the formula ratio, heat it to 125-135°C, stir and dissolve it, and let it stand for 8-10 hours to obtain product a;

[0047] Blending: Put product a and the remaining base oil into a blending kettle, add dispersant, pour point depressant, antioxidant and antiwear agent, and detergent in sequence according to the formula ratio, start stirring and heat to 55-65°C and keep warm, continue stirring for 4-8 hours to obtain a lubricating oil composition for a heavy-load methanol fuel engine.

[0048] Technical principle of the present invention:

[0049] 1. Synthesis Technology Principle of P(CAM+NVP) Dispersed Viscosity Index Agent

[0050] (I) Effect of raw materials

[0051] Dodecyl methacrylate (CAM) and N-vinyl pyrrolidone (NVP) monomers are the main reactants for synthesizing dispersed viscosity modifier P (CAM+NVP). They form the basic skeleton structure of the copolymer through polymerization reaction and determine the basic chemical composition and performance characteristics of the polymer.

[0052] Solvent (Toluene):

[0053] In solution polymerization, the solvent does not directly participate in the reaction, but it has a relevant influence on the reaction. The solvent also plays a certain reactive role in solution polymerization. It plays a role in chain transfer for chain free radicals and also has the effect of inducing decomposition of initiators. For copolymerization, the polarity of the solvent will have a significant effect on the reactivity of the reaction monomers and directly affect the copolymerization effect. When selecting a solvent, it is necessary to consider that the solvent has excellent solubility with the reaction monomers, initiators and polymerization products to facilitate the dissipation of the polymerization reaction heat and avoid the gel effect. The amount of solvent should be controlled. In solution polymerization, the amount of solvent has an effect on the concentration of the polymerization monomers, chain transfer, reaction rate and polymerization degree. At the same time, the fluidity of the solution will also be reduced, resulting in a large amount of heat that cannot be diffused out.

[0054] This synthesis uses toluene as a solvent, which provides a homogeneous reaction environment for the polymerization reaction, so that the monomer and the initiator can be evenly dispersed, which is conducive to the smooth progress of the reaction. The appropriate amount of solvent (20-30mL / mol, preferably 25mL / mol) can ensure that the concentration of the reaction system is appropriate, and the reaction will not be too violent and difficult to control due to too high a concentration, nor will the reaction rate be too slow due to too low a concentration.

[0055] Initiator (such as dibenzoyl peroxide BPO):

[0056] The polymerization rate and the square root of the concentration of the polymerization monomer and the concentration of the initiator are all positively correlated, while the kinetic chain length v is negatively correlated with the square root of the initiator concentration, indicating that the degree of polymerization of the polymerization product is directly related to the amount of initiator used, and the amount of initiator used directly affects the polymerization rate. In the initial stage of the reaction, too low or too high an initiator dosage will affect the number of free radicals, the probability of collision between particles, the conversion rate of the monomer, the average molecular weight of the polymerization product, etc. After reaching a certain level, the conversion rate of the monomer will not change much even if the amount of initiator is increased. The initiator can be: azobiscyanovaleric acid (ACVA), azobisisobutylnitrile (AIBN), dibenzoyl peroxide (BPO), azobisisoheptylcyanide (ABVN), etc., or any combination thereof. The present invention preferably uses dibenzoyl peroxide (BPO), and the amount used is 0.02%-1.5% (preferably 1.0% in the present invention) of the weight of dodecyl methacrylate and N-vinyl pyrrolidone. If the amount is too small, it is difficult to initiate the polymerization reaction or the reaction rate is too slow, resulting in incomplete polymerization; if the amount is too large, the reaction rate is too fast, and an "implosion" phenomenon occurs, which affects the structure and performance uniformity of the polymer.

[0057] (II) Necessity, importance and technical effect of optimizing raw material dosage and process parameters Optimization of raw material dosage:

[0058] The weight ratio of dodecyl methacrylate to N-vinyl pyrrolidone affects the performance of the copolymer. At different ratios, the molecular structure, solubility, thermal stability, etc. of the copolymer will be different. For example, the present invention prefers a ratio of 2:1. The dispersed viscosity index agent P (CAM-co-NVP) synthesized at this ratio shows better comprehensive performance in terms of viscosity-temperature performance, shear resistance, etc., and can better meet the requirements of a viscosity index agent for a heavy-load methanol fuel engine lubricating oil compared to other ratios.

[0059] Precise control of the initiator dosage is crucial. As mentioned above, the initiator dosage is directly related to the reaction rate and controllability of the reaction. The appropriate initiator dosage can ensure the smooth progress of the polymerization reaction and obtain a polymer with a uniform molecular structure and a narrow molecular weight distribution, so that it can better play the role of adjusting the viscosity index in the lubricating oil and improve the stability and fluidity of the lubricating oil at different temperatures.

[0060] Process parameter optimization:

[0061] The temperature in the free radical chain polymerization reaction not only affects the polymerization rate constant, but also affects the polymerization degree of the product. The conversion rate of the polymerization monomer and the polymerization rate will also increase with the increase of temperature. If the temperature is not properly controlled, implosion will occur; the polymerization degree of the polymerization product will decrease with the increase of temperature. The polymerization time also has a certain effect on the free radical polymerization reaction. The shorter the polymerization time of the polymerization monomer, the lower the conversion rate. The longer the polymerization time, the better the conversion rate of the polymerization monomer, and the higher the cost, but the molecular weight of the polymer does not change with the change of the polymerization time. Therefore, we must reasonably choose the reaction temperature and time, and ensure the quality of the polymerization product while ensuring that the reaction rate is not too low. By introducing nitrogen into the device as a protective gas and pulse stirring, the polymerization reaction is heated in stages: 40℃ to 50℃ for 1 to 2 hours, 50℃ to 70℃ for 3 to 4 hours, and 70℃ to 90℃ for 2 to 3 hours. The low temperature stage is conducive to the slow generation of free radicals by the initiator, so that the reaction starts initially and a small amount of polymer chains are formed; the medium temperature stage promotes the further progress of the polymerization reaction and makes the polymer chain grow; the high temperature stage is conducive to the completion of the reaction and the stability of the polymer structure. This staged heating method avoids the "explosion" phenomenon caused by excessive temperature or long reaction time, and at the same time can make the molecular structure of the polymer more regular and improve its performance as a viscosity modifier, such as better improving the viscosity change of lubricating oil at high and low temperatures, reducing the wear of the engine during startup and operation, and extending the service life of the engine.

[0062] 2. Preparation Technology Principle of Lubricating Oil Composition for Heavy-Duty Methanol Fuel Engine

[0063] (I) Effect of raw materials

[0064] Dispersed viscosity index improver (P(CAM+NVP)): Polydodecyl methacrylate polymer is a true viscosity index improver that can thicken lubricating oil. It has the characteristics of relatively low increase in lubricating oil viscosity at lower temperatures, but can greatly increase the viscosity of lubricating oil under high temperature conditions. This polymer has less impact on low-temperature cold start CCS viscosity than other types such as OCP. This superior low-temperature performance can solve the problem of low-temperature cold start difficulties for methanol fuel engines; the twelve carbons in the polymer molecular structure can make the polymer soluble in hydrocarbon solutions to maintain the stability of the lubricating oil system. By introducing highly polar N-vinylpyrrolidone (NVP) into dodecyl methacrylate, the high molecular polymer contains a five-membered ring of N atom, which is a lactam compound. It has both hydrophilic and lipophilic groups, making it very soluble in water and many alcohols, carboxylic acids and other solvents, including methanol, formic acid, acetic acid, etc. It contains lipophilic long-chain groups and is soluble in oil. It is a dispersed viscosity index improver that adjusts the viscosity index of the lubricating oil to keep a relatively stable viscosity of the lubricating oil at different temperatures. It can effectively inhibit the excessive reduction of the viscosity of the lubricating oil at high temperatures, ensure the thickness of the oil film, and reduce wear; it prevents a sharp increase in viscosity at low temperatures to ensure the smooth start of the engine.

[0065] Antioxidant and antiwear agent (such as zinc dialkyl dithiophosphate, zinc diaryl dithiophosphate):

[0066] Zinc dialkyl dithiophosphates and zinc diaryl dithiophosphates are multi-effect additives with anti-oxidation, anti-corrosion and anti-wear effects. They are adsorbed on the metal surface through electrostatic action to form coordination bonds and chemical adsorption films. This film has a certain anti-wear effect. As an antioxidant, it captures alkyl peroxyl radicals to inhibit chain reactions, inhibit the deterioration of lubricating oil due to oxidation during use, and generate harmful substances such as acidic substances and paint films, thereby extending the service life of the lubricating oil. The anti-wear performance is to form a protective film on the metal surface, reduce direct contact between friction pairs, reduce wear, and effectively protect the key components of the engine, especially under heavy load conditions.

[0067] Detergents (such as mixtures of alkyl salicylates and sulfonates)

[0068] Calcium salt detergents are insensitive to water and can better cope with the impact of water produced by the combustion of methanol fuel. The atomic weight of magnesium in magnesium salt detergents is 24, while the atomic weight of calcium is 40. At the same base value, the ash content of magnesium salt detergents is lower. Therefore, the use of magnesium salt detergents can minimize the ash content under the condition of high reserve base value. Ash is a harmful substance that is unfavorable to the engine. Magnesium salt detergents form less high-temperature deposits, but calcium salt detergents form soft high-temperature deposits. The impact of magnesium salt detergents on wear is much smaller than that of calcium salt detergents, while the impact on cylinder liner polishing is just the opposite. Magnesium salt detergents have an inhibitory effect on lead corrosion in engines. Therefore, this patent uses a compound of alkyl magnesium salicylate and calcium sulfonate to complement each other and meet the lubrication requirements of heavy-duty methanol fuel engines. Alkyl magnesium salicylate has certain antioxidant and corrosion resistance properties, which can neutralize the acidic substances produced by methanol combustion and prevent corrosion of metal parts inside the engine. At the same time, the combination of magnesium alkyl salicylate and calcium sulfonate can more effectively disperse and suspend dirt such as carbon deposits and paint films generated during engine operation in the oil, remove them from the engine through oil changes, keep the inside of the engine clean, and maintain good heat dissipation performance.

[0069] Dispersant (borated polyisobutylene succinimide dispersant): Contains a polar head end succinimide and an oil-soluble hydrocarbon tail end, which can clean the engine surface and prevent the formation of acidic by-products. Borated polyisobutylene succinimide dispersants evenly disperse insoluble substances such as oxidation products, colloids, soot, etc. in the lubricating oil in the oil to prevent them from aggregating and precipitating to form sludge, blocking the oil line and filter, and ensuring the normal circulation and lubrication effect of the lubricating oil. The boron in the borated polyisobutylene succinimide dispersant generates boric acid through reaction on the metal surface, thereby forming a layered structure of a weaker sandwich bond, which has a certain anti-wear and friction-reducing effect, protects the engine, and reduces the occurrence of piston ring adhesion, corrosion and wear.

[0070] Pour point depressant (polymethacrylate): The polymer in the structure of polymethacrylate pour point depressant contains some longer alkyl side chains, which are equivalent to the chain length of the base oil wax in the formula. It can influence each other through the growing wax crystals to reduce the pour point of the lubricant, so that the lubricant can still maintain good fluidity in low temperature environment, making it easier for the engine to start in cold conditions.

[0071] Base oil (synthetic base oil from coal): Synthetic base oil from coal has strong oxidation stability, low temperature fluidity, and a high viscosity index. It serves as the basic carrier of the lubricating oil composition, provides a dispersion medium for other additives, carries the functions of various additives, and has certain lubricating properties itself. The quality of its performance directly affects the performance foundation of the entire lubricating oil composition.

[0072] (II) Synergistic effects between raw materials and technical effects

[0073] Dispersible viscosity modifiers work in synergy with base oil: Dispersible viscosity modifiers are evenly dispersed in the base oil, and adjust the change of base oil viscosity with temperature through their own special structure and performance. The base oil provides a dispersing environment for the viscosity modifier, and the combination of the two makes the lubricating oil have a suitable viscosity in a wide temperature range, which can not only ensure sufficient oil film strength at high temperatures, but also flow quickly to various lubrication parts at low temperatures, reducing startup wear.

[0074] Antioxidant and antiwear agents work together with detergents and dispersants: Antioxidant and antiwear agents inhibit the oxidation process and reduce the generation of oxidation products. Detergents and dispersants deal with the oxidation products and carbon deposits that have already been produced. Detergents neutralize acidic substances and disperse dirt, and dispersants further disperse these impurities evenly to prevent them from depositing on the metal surface and destroying the protective film formed by the antioxidant and antiwear agents. Together, they maintain the cleanliness of the engine and the good condition of the lubricated surface, improving the operating reliability and durability of the engine.

[0075] Pour point depressant works in conjunction with other raw materials: Pour point depressant improves the fluidity of base oil at low temperatures, allowing lubricating oil to be pumped smoothly and reach lubrication points in low temperature environments. This works together with other additives such as dispersible viscosity modifiers, antioxidants and anti-wear agents to ensure that all components of the engine can be lubricated promptly and effectively when starting in cold conditions, avoiding dry friction and increased wear caused by low-temperature starting.

[0076] (III) Necessity, importance and technical effect of optimizing raw material dosage and process parameters Optimization of raw material dosage:

[0077] The amount of dispersible viscosity index agent (2-20 parts) needs to be precisely controlled. If the amount is too small, the viscosity index of the lubricant cannot be effectively adjusted, and the viscosity requirements of the engine under different working conditions cannot be met; if the amount is too large, the dispersibility and synergistic effect of other additives will be affected, resulting in a decrease in the overall performance of the lubricant.

[0078] The dosage of antioxidants and antiwear agents (1-4 parts), detergents (1-6 parts), dispersants (1-12 parts) and pour point depressants (0.001-0.01 parts) also has a specific range. Insufficient dosage of antioxidants and antiwear agents will not fully exert the antioxidant and antiwear effects, while excessive dosage will produce precipitation or affect other properties; improper dosage of detergents and dispersants will affect the internal cleaning effect of the engine and the degree of impurity dispersion; inappropriate dosage of pour point depressants will not effectively reduce the pour point or have a negative impact on other properties. Base oil (70-85 parts) is the main body, and its dosage cooperates with other additives to ensure the performance balance of the entire composition.

[0079] Process parameter optimization:

[0080] In the sol step, the dispersed viscosity modifier dry glue is cut into pieces and mixed with part of the base oil, heated to 125-135°C, stirred and dissolved, and left to stand for 8-10 hours. The appropriate temperature and time can ensure that the dispersed viscosity modifier is fully dissolved in the base oil to form a uniform and stable system, laying the foundation for the subsequent blending steps. Too low temperature or too short time will lead to incomplete dissolution of the dispersed viscosity modifier, affecting its dispersion and performance in the lubricating oil; too high temperature will cause slight deterioration of the base oil or the dispersed viscosity modifier.

[0081] In the blending step, the temperature is raised to 55-65°C and kept warm, and the stirring is continued for 4-8 hours. The process parameters can make various additives fully dispersed and mixed evenly in the mixture of base oil and dispersible viscosity modifier, and promote the synergistic effect between additives. Inappropriate temperature and time will lead to uneven dispersion of additives, and their respective functions cannot be fully exerted, so that the performance of the lubricating oil composition cannot achieve the expected effect, such as decreased lubrication performance, insufficient cleaning ability, and poor antioxidant performance. By optimizing these process parameters, the obtained lubricating oil composition for heavy-duty methanol fuel engines can show excellent comprehensive performance such as anti-wear, anti-oxidation, clean dispersion, low-temperature start-up and viscosity stability in heavy-duty methanol fuel engines, effectively extending the service life of the engine, improving the working efficiency of the engine, and reducing maintenance costs. This is an unexpected technical effect produced by the synergistic optimization of various raw materials and process parameters.

[0082] Compared with the prior art, the present invention has the following technical advantages:

[0083] 1. Excellent corrosion resistance and isolation performance

[0084] The dispersed viscosity index agent P (CAM-co-NVP) contained in the present invention has a very strong bipolar structural substance. The pyrrole ring on the side chain has a strong polarity and can dissolve polar substances such as formic acid, formaldehyde, water and incompletely burned methanol generated by the combustion of a methanol engine. The lipophilic long-chain molecules can dissolve in oil, and the combustion products such as formic acid and water are "isolated" from the engine oil and the metal surface of the engine, thereby greatly improving the corrosion resistance of the engine and the engine oil, preventing formic acid from corroding the surface of engine parts, and preventing water from rusting the engine parts.

[0085] 2. Ability to form stable emulsion

[0086] The dispersed viscosity index agent P (CAM-co-NVP) contained in the present invention contains a strong N polar group. Under the action of shear force, not only physical adsorption of the water phase and the oil phase occurs, but also the polar groups in the molecules undergo strong chemical adsorption with water molecules (the effect of hydrogen bonds), which greatly reduces the surface free energy of the oil and water, and also increases the strength of the emulsion interface film, and finally forms a stable emulsion. The combustion products of the heavy-load methanol engine include water. The present invention can make the water uniformly dispersed in the oil to form a stable oil-in-water emulsion, and solve the problems of rust, poor low-temperature fluidity, reduced anti-wear performance, etc. If the oil and water are separated, the water freezes at low temperatures, the oil flow becomes poor, and the ice blocks the oil pipeline, so that the engine cannot be started.

[0087] 3. Effective response to high temperature sediments

[0088] The present invention has a strong adsorption effect on the surface of high-temperature deposits due to the presence of a strong polar functional group of a five-membered ring of a N atom (belonging to a lactam compound). After adsorption, a firm adsorption film is formed on the surface of the high-temperature deposits, which not only disperses the high-temperature deposits but also prevents corrosion on the metal surface. At the same time, the dispersed viscosity index agent P (CAM-co-NVP) has high-temperature stability and can effectively play a dispersing role in engines running at high intensity, making up for the deficiency of polyisobutylene succinimide and solving the problem of deposits generated on the piston surface and piston ring of heavy-load methanol fuel engines.

[0089] 4. Stable protection of boundary oil film

[0090] Due to the presence of strong N-polar functional groups, the lubricating oil composition for heavy-load methanol fuel engines contains functional groups that can be strongly adsorbed on polar metal surfaces. At the same time, the polymer has a medium-to-high molecular weight, so it can form a thick boundary oil film on the metal surface of the engine, solving the problem of heavy-load methanol engines in which incomplete combustion of methanol scours the metal surface, destroys the oil film, and causes abnormal wear of parts.

[0091] 5. Excellent performance in reliability bench testing

[0092] The lubricating oil composition for heavy-duty methanol fuel engines of the present invention exhibits excellent performance in reliability bench tests. It can exquisitely achieve the isolation of engine oil, engine and combustion products such as formic acid, has excellent anti-corrosion properties, creates a strong protective barrier for the engine, and effectively resists the erosion of acidic substances produced by methanol combustion. The composition can also build a stable boundary oil film, smoothly resolve the dilemma of methanol scouring the cylinder wall oil film, and has remarkable results in reducing friction and wear, effectively ensuring the stable and smooth operation of the engine. This innovative lubricating oil composition has achieved remarkable results in practical applications. It can not only improve the working efficiency of the engine, but also extend its service life. It lays a solid foundation for ensuring the reliable operation of heavy-duty methanol fuel engines. It has broad application prospects in related fields and is highly competitive in the market.

[0093] 6. Extended oil change mileage and improved comprehensive benefits

[0094] From a technical perspective, the present invention effectively extends the oil change mileage of the lubricating oil composition for heavy-duty methanol fuel engines, and greatly improves the reliability of the engine. This not only saves users time and cost investment in maintenance, but also significantly enhances the competitiveness of the company's products in the market, injects strong momentum into the sustainable development of the company and provides solid technical support. BRIEF DESCRIPTION OF THE DRAWINGS

[0095] Figure 1 The test results of the oxidation value, nitration value and wear of the infrared test of the used oil on the two benches of Example 5 and Comparative Example 1 are shown;

[0096] Figure 2 This is a corrosion-free image of the piston skirt of the K15M engine bench after using Example 5;

[0097] Figure 3 The exhaust valve of the K15M engine bench after using Example 5 is clean and has less deposits;

[0098] Figure 4 This is a picture of the anti-corrosion layer falling off on the piston skirt of the K15M engine test bench after using comparative example 1.

[0099]

[0100]

[0101]

[0102] Effect Example 2

[0103] The embodiment 5 and comparative examples 1 and 2 with the best physical and chemical properties in effect example 1 were selected for the next step of simulation test verification.

[0104] (1) Emulsification test

[0105] Emulsion stability test: 400g of lubricating oil of Example 5, Comparative Examples 1 and 2 and 40g of water were added to a beaker and stirred at 6000r / min for 10min. The oils were stored at room temperature for 3 months and at high temperature of 150°C for 3 months, and the storage conditions of the oils were observed. The analysis results are shown in Table 3.

[0106] Table 3 Emulsion stability test

[0107]

[0108] It can be seen from Table 3 that Example 5 contains a dispersible viscosity modifier P (CAM+NVP), and the lubricating oil can maintain uniform emulsification without stratification when containing water. This is beneficial for the methanol fuel engine to prevent the water generated when working at low temperatures from freezing, and the engine can start normally. The non-separation of oil and water can play a rust-proof role. After the engine oil temperature rises, the water in the oil can evaporate and protect the engine.

[0109] (2) Anti-corrosion test

[0110] Anticorrosion test: Cut the cylinder sleeve into small pieces, take 400g of Example 5, Comparative Examples 1 and 2 lubricating oil, and 10g of formic acid into a conical flask, cover the bottle cap, place it on a heating plate, insert a temperature probe, and heat it at a speed of 1000r / min and an oil temperature of 100°C for 10 hours. The wear elements of the metal block and the lubricating oil were inspected and observed respectively, and the analysis results are shown in Table 4.

[0111] Table 4 Anticorrosion test

[0112]

[0113]

[0114] As can be seen from Table 4, in the case of formic acid, the metal block of Comparative Examples 1 and 2 was severely corroded, while in the case of formic acid, the surface of the metal block was not corroded. The iron content of the old oil comes from the corrosion of the metal block surface by formic acid. The more serious the corrosion, the higher the iron content of the old oil. It can be concluded from the wear element detection that this experiment has well verified that Example 5 can have good anti-corrosion performance in the case of formic acid. This anti-corrosion test fully proves that the lubricating oil containing the dispersed viscosity modifier P (CAM+NVP) has a very good anti-corrosion effect.

[0115] (3) High temperature sediment resistance test

[0116] The high temperature deposit resistance test uses a crankcase simulation test instrument to examine the high temperature resistance performance. The test conditions are: plate temperature reaction temperature 350°C, oil temperature 150°C, and duration 6 hours. The more coke weight, the worse the oil product's deposit resistance. Take 250g of Example 5, Comparative Examples 1 and 2 lubricating oil, and 6g of formic acid and put them into the crankcase simulation test instrument. Put 250g of Example 5, Comparative Examples 1 and 2 into the crankshaft simulation test instrument. After the test, weigh the coke weight of the aluminum plate, and the results are shown in Table 5.

[0117] Table 5 High temperature sediment resistance test

[0118] Test Project Rubber weight, mg Example 5+0g formic acid 8 Example 5+6g formic acid 7 Comparative Example 1+0g formic acid 14 Comparative Example 1+6g formic acid 29 Comparative Example 2+0g formic acid 13 Comparative Example 2+6g formic acid 26

[0119] From the test results in Table 5, it can be seen that Comparative Examples 1 and 2 have serious coking when containing formic acid, while Example 5 has the same coking weight as the oil without formic acid when containing formic acid. This test well verifies that Example 5 can play a good role in high temperature resistance under formic acid conditions. This fully proves that the lubricating oil containing the dispersible viscosity modifier P (CAM+NVP) has a very good effect in resisting high temperature deposits.

[0120] (4) Reliability bench test verification:

[0121] According to the oil monitoring data of the 300-hour reliability bench test of the K15M engine of Guangxi Yuchai Machinery Co., Ltd. under the power generation condition, the K15M engine reliability bench test was carried out on Example 5 and Comparative Example 1. From the test results, it can be seen that the wear amount of the product of the present invention is extremely low after the test, the overall level of oxidation value and nitration value growth is low, the TBN attenuation and TAN increase are small, and the test results are shown in FIG. Figure 1 to Figure 4 .from Figure 1 The test results show that after the 300-hour reliability bench test of the K15M engine power generation condition, the used oil of Example 5 and Comparative Example 1 was analyzed. The oxidation value and nitration value, wear elements iron and copper of Example 5 were still within the specified oil change index range (oxidation value, nitration value ≤ 30A / cm, iron ≤ 150ppm, copper ≤ 150ppm), while the oxidation value and nitration value, wear elements iron and copper of Comparative Example 1 exceeded the specified oil change index range. Figure 2 It can be seen that there is no corrosion on the piston skirt of the K15M engine bench after using Example 5. Figure 3 It can be seen that after using Example 5, the exhaust valve of the K15M engine bench is clean and has less deposits. Figure 4The anti-corrosion layer of the piston skirt of the K15M engine bench after using comparative example 1 fell off, and the corrosion resistance was poor compared with 1. The bench test advantageously proved that the present invention can reverse the problem of insufficient corrosion resistance, wear resistance and high temperature resistance of methanol lubricating oil on the market today, and can pass the 300-hour reliability bench test assessment of the K15M engine power generation condition of Guangxi Yuchai Machinery Co., Ltd., and through the disassembly scoring test, the product of the present invention has better performance in physical and chemical indicators, emulsification test and high temperature sediment resistance than existing market products.

[0122] In summary, the product of the present invention is a reliability test bench for realizing a lubricating oil composition for a heavy-load methanol fuel engine, which can realize the "isolation" of combustion products such as engine oil, engine, formic acid, etc., can play a strong role in anti-corrosion of the engine, can form a boundary oil film, and resist the unfavorable situation of methanol scouring the oil film on the cylinder wall. It is highly innovative and has a very good application effect.

[0123] The above are only specific embodiments of the present invention. It should be pointed out that the rest that are not described in detail are prior arts. Any changes or substitutions that can be easily thought of by any technician familiar with the field within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention.

Claims

1. A lubricating oil composition for a heavy-duty methanol fuel engine, characterized in that: The following raw materials are included by mass: The dispersed viscosity modifier is a P(CAM+NVP) polymer, which is a copolymer of dodecyl methacrylate and N-vinyl pyrrolidone.

2. The lubricating oil composition for a heavy-duty methanol fuel engine according to claim 1, characterized in that: The antioxidant and anti-wear agent is one or two of dialkyl zinc dithiophosphate and diaryl zinc dithiophosphate; The structural formula of the zinc dialkyl dithiophosphate is preferably as shown in Formula VII: Where R3=C n H 2n+1 , n = 3 to 10; The structural formula of the zinc diaryl dithiophosphate is preferably as shown in Formula V: Where R4=C n H 2n+1 , n=1~8.

3. The lubricating oil composition for a heavy-duty methanol fuel engine according to claim 1, characterized in that: The detergent is a mixture of alkyl salicylate and sulfonate; The structure of the alkyl salicylate is preferably as shown in Formula I: Wherein, R is an alkyl group containing 10 to 20 carbon atoms, M is Ca or Mg, and m and n are positive integers not equal to zero; The structure of the sulfonate is preferably as shown in Formula II: Wherein, R1 is an alkyl group containing 14 to 28 carbon atoms, M is Ca or Mg, and m1 and n1 are positive integers not equal to zero.

4. The lubricating oil composition for a heavy-duty methanol fuel engine according to claim 1, characterized in that: The dispersant is a boronated polyisobutylene succinimide dispersant; The structure of the boronated polyisobutylene succinimide dispersant is shown in Formula VI: Wherein, PIB is polyisobutylene, the molecular weight is 900 to 1300, and r is a positive integer not equal to zero.

5. The lubricating oil composition for a heavy-duty methanol fuel engine according to claim 1, characterized in that: The pour point depressant is polymethacrylate.

6. The lubricating oil composition for a heavy-duty methanol fuel engine according to claim 1, characterized in that: The base oil is a coal-to-hydrocarbon synthetic base oil.

7. The lubricating oil composition for a heavy-duty methanol fuel engine according to claim 1, characterized in that: The synthesis method of the dispersed viscosity modifier P (CAM+NVP) comprises the following steps: Mix dodecyl methacrylate, N-vinyl pyrrolidone, solvent and initiator; perform polymerization reaction at 40°C to 90°C for 4 to 10 hours, and perform vacuum distillation on the toluene solution of the obtained polymerization product. After vacuum filtration and alcohol washing, vacuum drying is performed to obtain a white or light yellow dispersed viscosity index agent P (CAM-co-NVP). The reaction formula is as follows:

8. The lubricating oil composition for a heavy-duty methanol fuel engine according to claim 7, characterized in that: The weight ratio of lauryl methacrylate to N-vinyl pyrrolidone is 5:1 to 3:2; The initiator includes one or more of azobiscyanovaleric acid, azobisisobutylnitrile, dibenzoyl peroxide, and azobisisoheptylcyanide, and the amount of the initiator is 0.02% to 1.5% by weight of lauryl acrylate and N-vinyl pyrrolidone; The solvent is toluene, and the amount used is 20-30 mL / mol.

9. The lubricating oil composition for a heavy-duty methanol fuel engine according to claim 7, characterized in that: Nitrogen was introduced into the device as a protective gas and pulse stirring was performed. The polymerization reaction was heated in stages: 40°C to 50°C for 1 to 2 hours, 50°C to 70°C for 3 to 4 hours, and 70°C to 90°C for 2 to 3 hours to avoid "explosion".

10. The method for preparing a lubricating oil composition for a heavy-load methanol fuel engine according to any one of claims 1 to 9, characterized in that: The steps include: Sol: First, cut the dispersed adhesive dry glue into pieces and mix it with part of the base oil according to the formula ratio, heat it to 125-135°C, stir and dissolve it, and let it stand for 8-10 hours to obtain product a; Blending: Put product a and the remaining base oil into a blending kettle, add dispersant, pour point depressant, antioxidant and antiwear agent, and detergent in sequence according to the formula ratio, start stirring and heat to 55-65°C and keep warm, continue stirring for 4-8 hours to obtain a lubricating oil composition for a heavy-load methanol fuel engine.

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