New breakthrough in surface lubricant of enameled wire

Enameled wire is the core material of electrical appliances, which plays a very important role in the development of the national economy, and its market demand is great. With the continuous deepening of reform and opening up, the production technology level of the electrical machinery industry has rapidly improved, and the requirements for the quality of enameled wire are getting higher and higher. As far as the surface quality is concerned, the enameled wire was basically not coated with lubricating oil before the 1990s, and only a very small number of users put forward the surface lubrication requirements (the requirements can also be met as long as they are coated with compressor oil). With the introduction of advanced European and American equipment and production technology, the production speed of domestic enameled wire and the winding speed of electrical coils have been greatly improved; if the surface of the enameled wire is not coated with lubricating oil, wire breakage and surface damage will occur, resulting in coil turns Bad time, seriously affecting the quality and service life of the finished products of motors and appliances. Therefore, relevant manufacturers began to pay attention to the study of surface lubrication of enameled wires.

In the past, many factories used paraffin wax to dissolve in gasoline for surface lubrication, and the slipperiness of the enameled wire has been greatly improved, but there are also many problems. If the solubility of paraffin wax is not good, it is easy to precipitate and cause problems: there is often a large amount of precipitation at the bottom of the barrel (especially at low temperatures in winter); when winding, a large amount of powder is often accumulated on the felt and guide wheel, and the ground is also caused by dripping. Dirty; the amount of dissolution varies with temperature, resulting in a corresponding change in the amount of coating per unit surface area of ​​the enameled wire, which makes the lubrication unstable; problems such as wax accumulation, bright spots on the paint surface, and frequent wire breakage are prone to occur when winding the coil. How to comprehensively consider various factors to meet the increasing lubrication requirements has become a thorny problem.

When winding, there is friction between the enameled wire and the tooling equipment (guide wheel, mold, winding machine parts, etc.), so the enameled wire itself must not only have sufficient mechanical strength, but its surface must be as smooth as possible without any lumps and fine particles. The lowest possible coefficient of friction. Only in this way can the enameled wire be smoothly wound into a tight and suitable coil; the wound coil can be quickly and completely embedded in the iron core slot of electronic components such as motors and transformers.

At present, the winding equipment of many factories is imported, which is several times faster than similar domestic equipment. Therefore, the requirements for the surface slippage of the enameled wire have been increased accordingly. Although the international and IEC standards for enameled wire have not yet clearly stipulated the slippage standard (or static friction coefficient) , But many customers put forward specific requirements when ordering (even rigidly stipulating the amount of lubricant per unit area), especially for export products.

The new technology of related industries involves the upgrading of this kind of products. New refrigerants such as R134a, R407, and R410 are in urgent need of supporting new materials and formulating technical standards (including enameled wire surface lubricants).

In addition, the environment, labor protection laws and regulations, as well as the increasing awareness of workers' health and safety, require improvement of working conditions, and enameled wire manufacturers and their users pay more attention to the surface lubrication of enameled wire.

In recent years, there have been some domestic or imported new enameled wire lubricants on the market.  of them are still wax solutions; some are resin solutions, but their slipperiness is poor. Therefore, some of the problems mentioned above still exist on these products. So far, no ideal enameled wire lubricant product has been seen.

After more than a year and hundreds of experiments, scientists and technicians finally found an ideal technical route to synthesize small molecule materials into macromolecular composite functional materials Q05-2, which not only solves the lubrication problem of enameled wire, but also solves the problem. In consideration of various issues such as process, safety, environmental protection, cost, etc., Q05-2 is a macromolecular functional material modified by a special method, which is resistant to high temperature, and has a lower static friction coefficient than silicone oil formulation, and has better slipperiness. Regarding the production and use of the product, whether it is a fully automatic winding and embedding equipment or manual embedding, users are quite satisfied. The only problem is that a few users report that the adhesive tape is not firmly attached after winding into a coil (solution: 1, Extend the adhesive tape slightly to bond the joints of the adhesive tape to fix the coil; 2. Use plastic clips to replace the adhesive tape to fix the coil. Because the clips can be recycled, it saves money, which is really two birds with one stone).

The first consideration in the trial production process is the solvent problem. At present,  of the enameled wire lubricants supplied on the market use mineral spirits or cyclohexane as solvents (or thinners). Foreign environmental protection requirements are strict, especially the EU RoHS directive, which clearly stipulates that some prohibited substances must be selected to meet the standards. The author believes that solvent oil has better comprehensive performance, low toxicity and low price, and it is worthy of popularization. Cyclohexane has certain physiological toxicity and high cost, so it should be controlled as much as possible. As for the use of water as a solvent, which is non-toxic and does not cause fires, the author has done some explorations. Its comprehensiveness is slightly worse than that of oil-based lubricants, and the solution is still far away.

Some people have also proposed to modify it with nano-materials to further improve the slipperiness. The author checked the information and found that under the current situation, some materials are not yet compatible, and some problems are still in the scientific research stage, although it is true in other types of lubricants. Some nano-materials are used, but the enameled wire lubricant is still very difficult due to its special circumstances.

If solvent-free lubrication can be realized, it is both environmentally friendly and safe. Some people do research and production applications abroad, but the technology is difficult and the one-time investment is high. At present, it may be difficult to realize industrialization and promote it on a large scale.

At present, the surface lubricating oil used in the domestic enameled wire industry is mainly produced by domestic factories, except for a small part of imported products from Germany, the United States and Taiwan, and some factories make their own preparations. From the types of lubricants,  are waxes, but also a few lipids, and a small amount of synthetic lubricants, such as 05-2 enameled wire oil. Because there are thousands of wax materials with different properties, how to choose waxes and formulate them to make them have excellent comprehensive performance? Experts from all walks of life have their own magical powers, and some also use synthetic materials to modify them to improve their performance. As far as the author knows, the slipperiness or dissolution performance is not ideal in  cases. It can be said that the dissolution of wax is very difficult. At present, the enameled wire lubricants (waxes including imported products) available on the market are not uniform solutions, at  are emulsions or dispersions. Therefore, there are different degrees of precipitation during the enameled wire production process, and the static friction coefficient is relatively high. Therefore, it can be said that how to choose wax materials, how to formulate and how to dissolve better are the three key links in the production of wax lubricants.

Compared with wax materials, synthetic lubricating oil has significantly different characteristics. First, it has good solubility and is a uniform and transparent solution regardless of room temperature (in winter). Therefore, there is no place in the enameled wire guide wheel, coated felt, etc. Precipitation and clean surface; secondly, good slippery. When the enameled wire is about Φ0.40mm, the static friction coefficient reaches about 0.05, which is obviously better than wax lubricants. However, synthetic lubricants also need special attention. At present, many people use silicone oil to improve the lubricity of waxes. Because silicone oil has a small molecular weight and is not resistant to high temperatures, when the working temperature of the motor is close to 150 degrees, a small amount of silicone oil will decompose to produce silicon oxide, which will reduce the insulation strength and cause safety accidents. Moreover, adding too much silicone oil will also affect the next process. Because of the dipping performance, it is not advisable to use silicone oil to improve the slipperiness of waxes. This is my personal opinion and I would like to discuss it with my colleagues.

In recent years, due to the destruction of the ozone layer, the earth has become warmer, and people’s living environment has been seriously threatened. "Low-carbon economy" has become the common goal of people all over the world. However, various refrigeration equipment (refrigerators, air conditioners, etc.) used a large amount of Freon in the past. As a refrigerant, it has become one of the main sources of pollution and its use is now strictly prohibited. The use of fluorine-free refrigerants is being promoted instead. Therefore, new requirements are put forward for the surface lubricant of the enameled wire. Because wax lubricants are incompatible with new fluorine-free refrigerants (such as R134a, R410 a, R407 a, etc.), if wax lubricants are applied to the refrigerant-resistant enameled wire by mistake, the capillary of the compressor will be blocked, thereby Cause a major accident. Although there are special refrigerant-resistant lubricants for L90 on the market, they have poor slip properties, poor solubility, and often have segregation phenomena, and the material prices are also very expensive. The launch of Q05-2 just made up for the defects of L90 and became an ideal lubricant for refrigerant-resistant enameled wires. A large domestic enameled wire factory began to use Q05-2 to produce refrigerant-resistant enameled wire in 2004, and the material cost was 1.5 million yuan a year (see http://www.zjyb.cn Zhuji website 2005-7-26). Considerable social and economic benefits.

As for the lubrication of enameled wires and the standard of lubricants, there is currently no unified standard at home and abroad. Some companies have formulated relevant internal control standards, mainly for the static friction coefficient control requirements of different wire gauges, and combined with actual hand feeling experience to determine whether Available. Some companies also conduct dynamic and friction coefficient tests. Practice has proved that some enameled coils with the same static friction coefficient are easy to be embedded in the slot, and some are difficult. The reason is that their dynamic friction coefficient is different. The lower dynamic friction coefficient has better embedding performance.