New application of the hottest electrostatic powde

New application of electrostatic powder spraying technology

as we all know, electrostatic powder spraying technology has been almost 100% applied to metal surface coating since its birth in the 1960s. Although many powder manufacturers and equipment suppliers have claimed for a long time that "electrostatic powder spraying can be applied to non-metallic surfaces", products that can form industrial production have not appeared. In the late 1990s, with the development of powder coatings and spraying equipment, electrostatic powder spraying technology applied to non-metallic surfaces has become a possibility. For the coating of non-metallic materials, Yudong gaotingshi and eluda have been committed to electrostatic powder coating of medium density fiberboard (MDF) for nearly two years, and have entered industrial production and become a reality. This paper mainly introduces the latest situation in spraying MDF, in order to promote the development of electrostatic powder spraying technology in China

1. Relevant factors of electrostatic powder spraying

electrostatic powder spraying is the process of coating powder paint on the coated object through electrostatic action and baking at a certain temperature for a certain time to form a coating. The factors involved in this process include coated objects, powder coatings, spray guns, baking equipment, etc. The analysis of some factors of this high-speed rotating friction and wear experimental machine is helpful to understand the whole process

2. confirmation of painted objects

from an economic point of view, painted objects must be bulk commodities. Besides metal, wood and plastic should be selected. Due to the temperature resistance of plastics at the current stage, it is temporarily impossible to consider. For wood, MDF (medium density fiberboard) has become the first choice. The reasons are: as an electrostatic powder coating, the material requires conductivity, while wood is a hygroscopic material, that is, it will exchange water with the surrounding environment. After a certain period of time, it will absorb the water in the specific environment at a certain temperature, so as to achieve balance. Therefore, under normal circumstances, the moisture content of Kimura's manufactured products will maintain an appropriate balance with the local climate. It can be considered that through the adjustment of the moisture content of the wood product substrate, the wood can become close to or equivalent to the conductor state. MDF is a wood product, which also has the above characteristics. In addition, as a green building material in line with environmental protection, MDF has a huge amount of applications, and its growth in wood-based panels is also very fast. Moreover, as a product of large-scale industrial production, the stability of product quality and the adjustability of product technology are also important factors. It is these factors that make MDF the first choice for powder spraying

3. technological progress of powder coatings

thermosetting powder coatings have been affected by the curing temperature (the conventional curing temperature is 180 ℃, 20min) for a long time, which limits the scope of process application. In recent years, more and more low-temperature curing powder coatings have appeared. According to relevant reports, 120 ℃ x20min cured powder can be prepared. Of course, the storage of low-temperature cured powder still has problems such as changing the single 1 extensive plastic granulator into a combination, and the stability of intelligent plastic granulator is poor, which restricts the scope of application to a certain extent. I believe it will improve soon. In MDF plate spraying, the powder used includes ultraviolet curing type and ultra-low temperature curing type. It is reported that DSM company has published the data of maleic acid/vinyl ether UV curing powder coating, and its coating object is MDF. At present, the epoxy/polyester mixed powder used in MDF (medium density fiberboard) by eloda company is controlled within the maximum curing temperature range of general paint (150 ℃)

4. new breakthrough of electrostatic powder spraying equipment

corona charging gun has experienced several stages, such as voltage charging, current charging, total energy controlled charging (t.e.c). The first two charging methods limit the sprayed workpieces to metal parts, and the use of "Tec total energy control" technology breaks through the above limitations. Its technology mainly lies in that when the distance between the spray gun and the workpiece (power connection point) changes, it can automatically adjust the current and voltage at the same time to maintain the total charging energy, effectively control the charged amount of powder and ensure the powder feeding efficiency. See Fig. 1 for the specific spraying distance, current and voltage changes

5. Baking equipment

for ultra-low temperature curing powder, use special drying channels (IR curing drying channels mentioned in gaotingshi report) to cure and eliminate the volatile components produced by MDF under continuous high temperature. That is, the volatiles are consumed inside the drying channel, while ensuring that the curing temperature is stable at the process temperature. This is different from ultraviolet (UV) curing, which uses an infrared lamp to melt and level the powder (below 100 ℃), and then uses an ultraviolet lamp to light it for a few seconds to cure it into a film

based on the above points, the main pulp varieties of MDF, chemical needle pulp and chemical broad-leaved pulp, are subject to tariffs. The industrial production of 5% electric powder spraying (ultra-low temperature curing) began in the late 1990s. In August 1999, the first fully automatic MDF sheet special production line in the UK was successfully put into operation. It can be predicted that MDF powder spraying process will have a rapid development in the next two or three years. Of course, for the MDF powder spraying process after fine grinding and coarse grinding, the following aspects need to be improved in the future: low temperature curing of coatings (including the further development and utilization of UV curing powder); Diversification of paint varieties; By selecting the spray gun with TEC charging technology and reforming the existing curing equipment, the production line can be sprayed with both metal products and MDF, etc. At the same time, we can also foresee that other non-metallic products will enter the field of electrostatic powder spraying