What is green non-sulfur phosphorus organic molybdenum friction modifier?

Green non-sulfur phosphorus organic molybdenum friction modifiers refer to a class of organic molybdenum compounds that do not contain active elements such as sulfur and phosphorus in their molecular structure. Traditional sulfur-phosphorus organic molybdenum additives contain active elements such as sulfur and phosphorus, which will corrode metal parts after long-term use, and phosphorus will also cause poisoning of the exhaust gas three-way converter catalyst, causing environmental pollution. Low-sulfur phosphating of lubricating oil additives has become a major development trend. Obviously, green non-sulfur phosphorus organic molybdenum friction modifiers lack active elements such as sulfur and phosphorus, so their anti-wear and anti-oxidation properties are slightly inferior to those of sulfur-phosphorus organic molybdenum additives, but studies have shown that there is a good synergistic effect between inactive organic molybdenum additives and other sulfur-phosphorus additives.

Research progress of green non-sulfur phosphorus organic molybdenum friction modifiers

Wear refers to the surface damage or peeling phenomenon caused by sliding, rolling or impacting motion of friction surfaces in contact with each other. Studies have shown that energy consumption caused by various forms of friction and wear accounts for 33% to 50% of the world's total; if friction is reduced by 18%, at least 37% of fuel consumption will be saved and huge economic benefits will be brought. To this end, countries around the world are promoting the research of corresponding lubrication technology and friction-reducing materials.

Oil-soluble organic molybdenum compounds, as friction modifiers, show excellent anti-wear and friction-reducing properties. Many researchers have studied them, and they are now widely used in internal combustion engine oils and gradually extended to gear oils. Oil-soluble organic molybdenum compounds are usually divided into two categories in commercial applications: sulfur-phosphorus organic molybdenum and inactive organic molybdenum. Representative substances of sulfur-phosphorus organic molybdenum are alkyl-substituted molybdenum thiophosphates (MoDDP) and alkyl-substituted molybdenum thiocarbamates (MoDTC); representative substances of inactive organic molybdenum are molybdates and molybdenum amine complexes. The structural formulas of several representative substances are shown in Figure 1, where X is an O or S element and R is an alkyl group. Usually, the bridging X element is S and the double bond X element is O; but when the latter is S, the additive is more reactive.

Figure 1 Typical structure of oil-soluble organic molybdenum friction modifier

As the world's largest producer of organic molybdenum additives, R. T. Vanderbilt has been developing organic molybdenum additives since the 1960s. The company still ranks first in the world in the number of organic molybdenum additive technology patents it owns. Asahi Kasei Corporation of Japan has launched the Sakura-lube series of organic molybdenum products through technological innovation, obtained more than 20 Japanese patents, and has no less than 10 US patents. It is also one of the giants in the production of organic molybdenum additives. In addition, Infineum has launched a new type of tricyclic molybdenum multifunctional additive, which shows superior anti-wear and friction reduction performance and significant antioxidant performance compared with traditional dicyclic molybdenum additives.

Compared with developed industrial countries, my country's research on organic molybdenum additives started late, the production scale is relatively small, the product types are relatively single, and it has not yet been widely used. As the world's third oil-soluble organic molybdenum manufacturer, UNPChemicals has been engaged in the localization of imported additives since its establishment to solve the problem of localization of key additives that "choke" the domestic lubricant industry.

In recent years, the research on green non-sulfur and phosphorus organic molybdenum has made significant progress. This type of compound does not contain sulfur and phosphorus, which can avoid the problem of poisoning the exhaust catalyst, and has good friction reduction, antioxidant and corrosion resistance. Studies have found that non-sulfur phosphorus organic molybdenum can maintain a relatively stable chemical state under different temperatures, pressures and working conditions, and is not easy to decompose or fail. In addition, non-sulfur phosphorus organic molybdenum has good synergistic effects with other additives such as antioxidants and anti-wear agents, which can significantly improve the overall performance of lubricants.

The current commercial application of non-sulfur phosphorus organic molybdenum friction modifiers is mainly molybdenum amine complexes, which have poor tribological properties and are not widely used in the industry. However, the market for molybdate ester products with excellent tribological properties is still blank. As a leader in the consumption of organic molybdenum anti-friction materials, the molybdenum amine organic molybdenum anti-friction agent launched by R. T. Vanderbilt Company of the United States currently has a high market share.

UNPChemicals has invested a lot of R&D efforts to explore a green non-sulfur-phosphorus organic molybdenum friction modifier product, namely MSAIL^® 8550, whose main performance indicators are as follows:

1. The appearance of the product is a brown-red viscous oily substance, with good solubility in base oil 150SN (2 wt% concentration, no precipitation), and the color of the oil after oil adjustment should be less than 5.0 according to the ASTM 1500 standard;

2. Its structure is analyzed by Fourier transform infrared spectroscopy (FT-IR), and the molybdenum content (not less than 8 wt%) and nitrogen content (2.3%-3.3%) are determined by plasma emission spectroscopy (ICP);

3. In the fully formulated SAE 30 engine oil, 0.5% MSAIL® 8550 product is added, and the friction reduction performance is verified by SRV tribology experiments. The results show that the friction reduction performance is excellent;

4. The prepared non-sulfur-phosphorus organic molybdenum friction modifier is added to the finished oil for copper corrosion test. According to GB/T 5096 standard, a copper corrosion test was carried out at 100℃ for 3h, and the copper corrosion level was ≤1 at an addition of 0.5%.

Through independent research and development, the company has mastered the advanced production technology of new green non-sulfur phosphorus organic molybdenum anti-friction materials, so that the company's technical level in the structural design and synthesis process of liquid organic molybdenum anti-friction materials has reached international advanced level, filling the domestic gap, and can completely replace foreign imported products, breaking the technical monopoly of foreign organic molybdenum related products.

The mechanism of action of green non-sulfur phosphorus organic molybdenum in the friction process

The mechanism of action of green non-sulfur phosphorus organic molybdenum in the friction process mainly includes the following aspects:

Formation of physical adsorption film: Physical adsorption film is formed on the surface of friction pair. These adsorption films can reduce the friction coefficient and improve lubrication performance.

Generation of tribochemical reaction film: Under high temperature and high pressure environment, non-sulfur phosphorus organic molybdenum reacts with metal surface to generate compounds such as MoS₂, MoO₃, FePO₄, FeS, etc. The composite friction film formed by these compounds is the main reason for its friction reduction and anti-wear.

Self-repairing function: During the friction process, molybdenum elements are enriched on the friction surface, which has self-repairing function, can repair the worn surface and reduce wear.

Application research of green non-sulfur phosphorus organic molybdenum friction modifier

MSAIL^® 8550 product has the following characteristics:

Good thermal stability: It can still maintain a stable chemical state under high temperature environment.

Excellent anti-friction and anti-wear performance: Adding Molyvan 855 to lithium-based grease can significantly reduce the diameter of steel ball wear spots, make the wear spots more regular in shape, and make the furrows shallower.

Good compatibility: It has good synergistic effect with other additives such as dialkyl dithiophosphate molybdenum, sulfur phosphorus ammonia molybdenum and dialkyl dithiocarbamate molybdenum.

Environmental performance: It does not contain sulfur and phosphorus, meets environmental protection requirements, and is suitable for application scenarios with strict requirements on exhaust emissions.

Green non-sulfur phosphorus organic molybdenum has a wide range of applications in many fields, mainly including:

Lubricant additive: As a friction reducer and anti-wear agent for lubricating oil, it can significantly improve the tribological properties of lubricating oil. For example, adding 0.25% to 0.5% of non-sulfur phosphorus organic molybdenum (SPFMo) to 0W20 lubricant can significantly reduce the friction coefficient and wear diameter in the temperature range of 100℃ to 130℃.

Engine and automobile universal joint lubrication: Sulfur-free phosphorus organic molybdenum has excellent friction resistance, corrosion resistance and environmental protection performance, and is an ideal lubricating additive for key components such as engine and automobile universal joints.

Lubrication of various metal surfaces: Non-sulfur phosphorus organic molybdenum has a significant improvement on the tribological properties of different metal surfaces (such as bearing steel, aluminum alloy, titanium alloy, copper and gray iron), and can reduce the friction coefficient and wear rate.

In summary, green non-sulfur phosphorus organic molybdenum friction modifier has significant advantages in environmental protection and performance, and is expected to be widely used in more fields in the future.