Fujian Wan'an Industrial Group Co., Ltd.
Abstract: solvent-based coatings under environmental pressure has been difficult to sustain, "paint powder" has become one of the inevitable direction, the development of solvent-based coating surface decoration effect of low-temperature powder coatings, has become an increasingly urgent need.
With the improvement of people's living standards and scientific and technological progress, people are becoming more and more aware of environmental protection, for the traditional solvent-based coatings containing solvents raised objections, the government is also taking strong measures to gradually limit the use of solvent-based coatings, which has long-term use of traditional solvent-based coatings in the electric vehicle industry and other industries presented a serious challenge. As one of the varieties of environmentally friendly coatings, powder coatings need to step up the pace of research and development, timely introduction from the appearance of decorative, glossy, leveling, low-temperature curing, storage and other aspects to achieve the replacement of traditional oil-based
. At present, similar low-temperature cured powder coating and system performance is as follows:
2 electric vehicle powder coating requirements
decorative: good appearance leveling, high gloss, bright colors, strong cover;
curing conditions: can use the existing paint curing furnace, curing conditions 20-30min@140 degrees C, curing complete, adhesion ≤1 level (except for atom ash), good mechanical performance;
process adaptability: can be applied to different surface treatment processes, such as: acid wash phosphorus, cathode electrophoresis primer, atom ash, etc., no obvious defects in the surface of the curing film;
3 Test Part
3.1 Experimental equipment and instruments
SL-30D twin screw extruder, laboratory shredder, electric blow drying box, electrostature spray gun, impact tester, gloss instrument, HTECHMT adhesion tester, gel tester, QNIX film thickness meter, 180 mesh screen, etc.
3.2 Experimental process parameters set
Due to the high curing activity of the low-temperature curing type powder, the temperature of each area of the extruder is set to 70 to 80 degrees C in zone 1 and 90 to 90 in zone 2. 95 degrees C, 3 zones 100 to 105 degrees C, and with an infrared gun to monitor the extruder feed temperature below 130 degrees C, extruder host speed is set to 40 to 45HZ.
3.3 Polyester selection
According to the needs of the experiment, we select different manufacturers, different reaction activity of low acid polyester resin as the experimental material, and the number is as follows: polyester resin A, polyester resin B, low viscosity polyester resin C, polyester resin D, polyester resin E.
3.4 Additive Selection
According to the characteristics of the industry, we need to consider the final material degassing, atomic ash degassing, silicone sealant use, part of the need to cover the light with transparent powder, added a variety of functional additives, surface improvement aids, etc., respectively, 1 , 2 , 3 , 3.
3.5 Promoter Selection
This experimental product is a low temperature curing product, relying on some polyester activity may be defective, so in the formulation design experimented with different promoter, divided into promoter A, promoter B, promoter C.
3.6 Test formula design
from the above performance comparison table can be seen that polyester resin C activity and viscosity is more suitable, the powder sample gloss is high, smooth, performance pass, moderate activity. Polyester A and B activity is too strong, poor level, polyester D and E made of powder coating gloss is low, weak activity, so in the later test, we will choose polyester resin C as a special polyester resin paint powder.
From the table above, it can be seen that the promoter B selected in formula 2 has a small effect on powder coating leveling due to a slightly higher melting point, and is basically not yellowing, while the promoter C reaction activity is high, and yellowing occurs.
3.7 Test Results
Formula 1 powder sprayed on polished atomic ash substrate, cured film covered with pores, severe loss of light; Formula 2 sample powder because of the addition of 2 additives, surface pores less, higher gloss; Formula 3 on the front basis of the addition of modified additives, coating film Less pores, good light leveling, but formula 3 in the cover transparent powder led to a transparent coating serious orange peel phenomenon, can be applied to a single coating system; Therefore, in summary, formula 4 is the final confirmation formula.
4 New electric vehicle special powder coating and liquid coating comparison
a large number of experiments have proved that if you want to be comparable to the paint effect of weather-resistant polyester powder coating, the selection of raw materials and formulation design is particularly important, the need to develop a special low viscosity, medium high activity, high Tg polyester resin, select suitable additives and modified filler varieties, complete use of the existing equipment and processes of the coating plant, in order to meet customer and market requirements of the powder.
electric vehicle-specific powder coating project, because of its excellent appearance and decoration performance, has been successfully recognized by customers and the market, for improving the environmental protection of the electric vehicle industry, completely solvent-based paint emissions and environmental pollution problems, while greatly reducing the powder coating curing temperature, saving energy waste and so on are of great significance. At the same time, in order to promote powder coatings to oil-based coatings market expansion has made a positive exploration and paving, with huge market opportunities and economic benefits.