Powder resin fluidized bed dip coating method

Zhang Junyu, Lian Jiying, Pan Xinru, Liu Feifei, Zhao Liao

Tianjin Pinggao Intelligent Electric Co.
, Ltd.
 

Abstract: This article first gives a basic overview of the powder resin fluidized bed dipping process, and then combines the relationship between the powder resin structure and performance to analyze the overall powder resin fluidized bed dipping method, aiming to promote the flow of powder resin in my country The level of chemical bed dip coating technology has been improved to provide a reference.

Keywords: powder resin; powder coating; fluidized bed; method analysis

1 Basic overview of powder resin fluidized bed dip coating

The powder resin method has a variety of applications in the processing process, such as electrostatic spraying, fluidized bed dip coating and so on.

The process of powder resin dip coating is similar to that of PVC gel dip com" href="http://">coating .
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2 The relationship between powder resin structure and performance

2.

1 Powder resin structure

For multi-component copolymer resins, it is more difficult to increase the glass transition temperature of the copolymer, especially in the development process of powder resin, this problem is more prominent.

In order to increase the vitrification temperature of the copolymer, it needs to be carried out from the following two aspects: ①resin structure; ②method and technology of polymerization process.

In addition, when the resin composition conditions and process options are relatively simple, in order to increase the glass transition temperature of the copolymer resin, the polymerization method can be changed by the polymerization method, so as to form different solvent types, solvent ratios and solvents.
Dosage, etc.
, comprehensively change the reactivity ratio of various monomers, thereby adjusting the distribution of comonomers in the resin structure.
In this way, the relative molecular weight of the copolymer resin can be significantly improved, and the fluidity effect of the resin can be improved, thereby achieving the purpose of increasing the glass transition temperature of the copolymer resin.

2.
2 The relationship between powder resin structure and performance

The structure of the powder resin is similar to the solvent-based value, but there are some differences.
Combining different manufacturing processes, various manufacturers make powder resin and solvent-based resin have different composition characteristics in the production process of powder resin.
In the actual application process, powder resins have high performance requirements.
In addition to basic resin general performance, they also need to have excellent storage stability and fluidity, and have yellowing resistance under high temperature environments, and Easy to process.
Therefore, compared with solvent-based resin, powder resin is more difficult in the process of manufacturing and formula selection.

3 Powder resin fluidized bed dip coating method

3.

1 Material selection

At present, many manufacturers in my country use epoxy powder.

Because the powder is relatively fragile, has a low service life, and has a long processing process cycle, it has high requirements for powder raw materials and overall production economic investment, so the application range is small.

In the process of selecting fluidized materials for the circuit breaker contact arm, a comprehensive evaluation is required from the aspects of the comprehensive performance of the material, the manufacturing process, and the economic cost.
If PVC powder is used, although its requirement for economic investment is low, the adhesion between PVC and basic materials is poor, and quality problems are prone to occur at low temperatures.
In actual construction, the plasticization temperature is close to the decomposition temperature, which increases The difficulty of controlling the overall process flow is improved.
Compared with other powders, HDPE powder has better low-temperature performance, stronger adhesion to the base material, low-cost overall raw materials, simpler use process, and can be widely used in the use of circuit breaker contact arms.

3.
2 Powder preparation

In order to make products with excellent performance and appearance, it is necessary to add some anti-aging and pigment agents during the resin powder dipping process.
These additives are mixed with the resin, and after grinding, they are screened, sealed and reserved, so as to make the resin Its strength, uniformity and shape fully meet the requirements of use.
However, in the process of production, care should be taken to avoid using too fine powder.
The too fine powder will produce stronger electrostatic reaction during the fluidization process, thereby forming powder agglomerates.
When the resin particle size is selected, it is necessary to be as uniform as possible and increase the particle size range.
In this way, the grooves of the fine particle resin can be actively promoted during the dipping of the fine particle resin, so that the large particle resin can continuously improve the surface of the workpiece.
Optimized to reduce the probability of agglomeration.
Generally, in the selection process of particle shape, it is best to choose particles with a neat appearance and no tails, which can increase the quality of product production and improve the product qualification rate.

3.
3 Fluidized bed

The powder tank of the fluidized bed can be divided into round and square, and the sidewalls have different tapers, which can effectively improve the powder in the fluidized state.

According to different application requirements, ventilated ceramic separators can be used to increase the ventilating effect.

3.
4 Specific process flow

In the specific fluidized bed dip coating process, the workpiece is first cleaned to remove rust spots, and then fluidized for standby.
Generally, the workpiece is preheated in a high-temperature oven, and the preheating temperature needs to be higher than the fluidization temperature of the powder.
The temperature of the HDPE powder is generally set at about 200°C.
After preheating, the workpiece enters the fluidized bed for dipping.
In order to increase the uniform effect of the coating, avoid the workpiece from moving up and down during the dipping process, and adjust the overall soaking time reasonably according to the requirements of different coating thicknesses.
Generally, the thickness of shelf products is required to be 0.
6 mm, and the dip coating time can be controlled within 4 seconds.
After the dip coating is completed, the surface of the product appears loose, the coating surface is rough, and the strength is low, so you need to put it in immediately The oven performs heating, heat preservation and plasticization.
The temperature of the plasticizing oven can be set at 230°C, and the plasticizing time can be controlled within one minute according to the coating thickness requirement of 0.
1 mm.
It should be noted that in the plasticizing process, the plasticizing time needs to be strictly controlled to avoid longer plasticization and reduce the probability of oxidative yellowing.
In order to improve the flatness and smoothness of the surface of the product, the product needs to be cooled after the plasticization is completed, and it can be directly immersed in water, or spraying and soaking methods can be used.

3.
5 Overlay process analysis

Since the heat of resin melting mainly depends on the dipping of the workpiece in the fluidized bed, the selection process of the resin thickness needs to be carried out simultaneously with the workpiece.
Combined with the quality of the powder resin in the fluidized bed dipping process, the workpiece can be melted by heat.
Due to the limited heat capacity of the fine powder, it needs to be covered with a corresponding thickness of resin and connected to the surface of the workpiece to form an effective protective function .
Then, more free particles are used to cover the surface of the vulcanized dip-coated workpiece until a loose and uniform resin coating is formed on the surface of the workpiece, thereby increasing its tensile strength and improving the roughness of the surface.
On this basis, the resin layer is continuously melted until it forms a uniform and dense protective layer, and finally it is heated and plasticized, and the plasticization time is controlled according to the requirements of different products.
After the plasticization is completed, the corresponding performance test is carried out in combination with the corresponding appearance inspection standards and the increase of insulation performance, and the parts that do not meet the requirements of the product are corrected and optimized.
Qualified parts have a smooth overall surface, dim color, and high-quality low-temperature impact strength and crack resistance.
Therefore, the staff needs to make the surface of the part smooth and have the highest impact strength during the production process, so that the two can be effectively coordinated.

3.
6 Product testing

Generally, after the fluidized bed dipping product is finished, the corresponding appearance inspection test and thickness measurement test are required to test the adhesion of the coating.
At the same time, the density of the insulating layer is measured in accordance with the requirements of different product protective layers.
The spark pinhole breakdown test makes it meet the inspection standards of different products.
Take the low-temperature impact test and stress cracking resistance test as examples.
During the test, it is necessary to clean the rust on the thin steel plate, and then apply uniform methyl silicone oil on the surface of the steel plate, and pre-process it according to different dipping conditions.
The heat, dipping and plasticizing processes are peeled off after the cooling, so as to carry out the corresponding impact test.
In addition, the sheet samples of the contact arm products of the circuit breaker can be soaked in 5% hydrochloric acid, 15% sulfuric acid, 4% acetic acid and edible oil for 12 hours, and then the resin products can be observed to check whether they are There are problems such as swelling, discoloration and delamination.

3.
7 Analysis of insulation function of fluidized bed dip coating

Some live equipment needs to be protected against electric shock during the application process, and the fluidized bed dip coating process can achieve a good insulation effect.
Some problems are prone to occur in the actual insulation function.
In order to make the insulation effect fully play, technicians need to take different measures to improve the insulation performance of the equipment.

4 Conclusion

In summary, the fluidized bed dip coating process is widely used for powder resin products.

In addition to making circuit breaker contact arms, it can also be used to make various daily shelf racks.
The fluidized bed dip coating can significantly improve the powder resin fluidized bed dip coating effect.