Application of Bonding Mixers

The Bonding process was first introduced by Benda-Lutz when mixing metal effect powders, and later, many powder coating plants have applied this technology. There are two types of Bonding mixers: single-cylinder and double-cylinder. Single-cylinder type is the first generation of products, bonding and cooling are in the same cylinder, the appearance and flip mixer is similar, but the shape of the mixing paddle and the speed of the mixing paddle is different. Nowadays, it is mostly a double-cylinder type, where the bonding cylinder and cooling cylinder are not the same cylinder. In this way, the bonded powder coating can be cooled quickly, with a small probability of caking and less loss, and the powder utilization rate is close to 100%.

Bonding mixing unit is composed of main and vice mixing paddle, material cylinder, frame and electric control, temperature control system, nitrogen gas ventilation system. The powder can contact the place (main and secondary stirring paddles, material cylinder) with a sandwich layer can be cooled down quickly by circulating cooling water to prevent the agglomeration of powder, and the bonding on the paddle and pot wall. Below we discuss the application and the precautions to be taken in the application.

l Bonding mixer application practice

l Softening point of powder coatings

l Cooling water temperature and flow rate

l Bonding stirring paddle speed

l Constant temperature bonding time

Bonding mixer application practice

Bonding mixer in the production of mixed metal powder, due to the different formulations of the main material of metal powder (powder coating) lead to its different tree ester ratio, specific gravity, softening point; metal pigments also have different types and properties. The above factors directly affect the dispersion and bonding effect of the material. Bonding mixers must have a wide range of operating parameters to adapt and meet the requirements of the above-mentioned different factors on the machine. In its production application practice, the solution is focused on the following aspects.

Softening point of powder coatings

The softening point of the powder coating is the main basis for the bonding temperature setting of the bonding machine, the higher the softening point, the higher the bonding temperature should be. The higher the bonding temperature, the better the bonding effect will be, but too high will produce caking phenomenon. Usually, the actual bonding temperature is generally about one-half of the softening point. In order to accurately set the bonding temperature, first of all, a formula should be softening point measurement before test mixing; then set the bonding temperature according to this test mixing, and after several tests to find the best bonding temperature as the operating parameters of the batch. Each batch of material softening point will be different, therefore, each batch of material in the formal mixing should be measured before the point, test mixing, to determine the three work to ensure that nothing is wrong.

Cooling water temperature and flow rate

Reduce the cooling water temperature, increase the flow of water, can improve the efficiency of heat absorption, improve the cooling efforts. It is conducive to maintaining the constant temperature bonding under high-speed dispersion conditions. When the expected effect cannot be achieved with normal temperature and pressure cooling water, low temperature water and measures to increase the pressure or flux of water should be considered.

Bonding stirring paddle speed

As the speed of the stirring paddle increases, the frictional heat between the paddle and the material increases, which will make the material warm up faster. At the same time, the intensity of the material being dispersed will also increase. The former increases the tendency of the paddle surface to agglomerate; the latter is of great benefit to the bonding effect. Therefore, it is necessary to find a balanced and moderate main paddle speed for a particular recipe. Under the premise of ensuring the effect of bonding, try to reduce the speed to ensure that the material is warmed up smoothly and evenly, so that the tendency of impurities is reduced.

Constant temperature bonding time

In general, the appropriate extension of the constant temperature bonding time, can make the bonding effect improved. Too long time material caking tendency to increase.

Conclusion

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