Talk about the development of special pearl powder coating for aluminum profiles.

Abstract:
analysis of experimental data, the paper discusses the key technology of a powder coating with high weather-resistant pearlescent effect in aluminum profiles.
research includes: saturated polyester resins, pigments, additives, detergents, pearlescent pigments, which make up aluminum-specific weather-resistant powder coatings, and find out various raw materials that meet the requirements of gb5237.4-2008 powder spray profile standards.
introduction
2000, with the rapid development of the real estate market, aluminum profile market has seen a blowout-type development

. Powder coating technology is also innovating, using environmentally friendly and efficient powder spraying process, has basically replaced paint spray.
market is growing steadily at a rate of 7% per year, and powder consumption is increasing rapidly year by year, with a good outlook.
powder coating profiles on water and air pollution is small, low energy consumption, coating mechanical properties such as hardness, wear resistance, impact resistance, and rich colors, more reflect the diversity and personalization of buildings, marking China's aluminum market powder coating industry has entered a mature and stable period.
1 Experimental part
1.1 coating formulations and raw materials
the basic formulation of aluminum powder coatings can be found in Table 1.
1.2 Test equipment
test equipment: electronic balance, extruder, grinder, electrostectonic spray gun, oven, thickness meter, manual processing aging test box, impact instrument and so on.
1.3 test method
according to the formula weighing raw materials, mixed evenly, extruded with a twin screw extruder, crushed with a high-speed shredder, over 180 mesh standard sieve, the resulting powder coating using electrostectrical spraying, curing conditions of 200 degrees C / 10min, and then carry out various tests.1.4 test method
the performance of aluminum according to the GB5237.4-2008 powder spray profile standard.
2 Research Content
2.1 Research on resins for coating formulations
High weather-resistant resins and curing agents for aluminum coating are available from major manufacturers at home and abroad. Using different resins and TGIC curing agents, with water-resistant cooking, scratch-resistant, mortar-resistant, anti-aging and other performance as an evaluation means, to determine aluminum with pearl powder coating with polyester resin brand and curing agent type.because the aluminum market generally requires bright powder (20 to 30GU), according to the formulation needs, choose a two-part de-lighting system of saturated polyester resin, not only can save costs, but also can effectively control the gloss.
generally choose high acid polyester resin (A), acid value of 50 to 55 mg KOH/g, viscosity 7500 to 8000mPa.s (200 degrees C), glacification temperature (Tg) 60 to 70 degrees C, and TGIC curing agent ratio of 90/10;
low acid polyester resin (B), acid value of 20 to 25 mg KOH/g, viscosity of 7500 to 8000mPa.s (200 degrees C), Tg for 60 to 70 degrees C, with TGIC ratio of 95/5. The two dry mix and match, and then configure 20% to 30% of the powder composition of the powder coating (see Table 1), with good storage stability.2.2 pigment selection
is mainly based on its sun exposure preservation rate and in the coating of powder resistance, scratch resistance to screening. The available fillers are calcium silicate, talcum powder, silicon powder, vanadium sulfate, alumina and so on.
are mainly iron red, iron yellow, organic yellow, organic green, organic blue and so on. Poor weather resistance of sharp titanium-type titanium dioxide powder and easily powdered calcium carbonate fillers should not be used.
in the sample process, according to the special requirements of the formula to be added, in the selection of fillers usually choose good weather resistance, stable water-resistant cooking performance, suitable for outdoor work for formulation commissioning.
white powder is selected in the gold-redstone type. Pigment selection requires light resistance of 7 to 8 levels, 8 levels of the best, weather resistance of 4 to 5 levels, 5 levels of the best.2.3 anti-light
in aluminum powder are generally divided into two types, respectively, plus and intro extrusion. Aluminum powder is generally used in the external mixed lighting system, external mixed light is applied to A, B dry mixed outdoor weather-resistant polyester / TGIC system, can provide 10% to 40% of the low gloss, generally do gloss 20% to 30% aluminum base powder.
Advantages: Price has obvious advantages, meet the requirements of low-volume and low
-cost powder coating preparation, and has good mechanical properties, color and gloss stability; The appearance is worse than that of the ind) product. The amount of internal extrusion anti-light agent is 2% to 6% of the total weight of the formula, and also provides 10% to 40% gloss.
advantages: the coating is dense and delicate, more gloss options, 20% to 90% can be selected, according to the desired gloss to choose the dosing;According to the experiment, the selection of suitable for aluminum production of external mixed anti-light agent, because the main component of the anti-light agent is modified wax, after boiling 2h in high-pressure water, the powder coating of the anti-lighting agent wax powder will be different degrees of analysis, resulting in the powder coating whitening condition, as shown in Figure 1.
According to the "GB5237.4-2008 powder spray profile standard" in the requirements of boiling water resistance, the anti-light agent A1 and A3 effect can not meet the national standard requirements, the final selection of water after cooking color has not changed A2 anti-light agent as the main anti-light agent in the powder coating formulation design.2.4 Pearl pigment selection
Now the aluminum market competition is fierce, the powder market launched relatively high value-added products, outdoor metal effect of powder coatings occupy a larger market share.
Such a metal effect of silver powder and pearlescent pigments put forward specific weather-resistant requirements, only good weather-resistant aluminum pigments and pearlescent pigments can be selected, after testing that special coating treatment of aluminum powder and pearlescent powder can improve the powder coating water-resistant, mortar and acid-resistant, alkaline resistance.
-pearl pigment is a transparent metal oxide with high refractive index on the surface of a transparent mica slice, exposed to the natural environment, refracted and reflected by sunlight, resulting in a beautiful and elegant look and gloss.
Pearl mainly has silver, rainbow and metal three series, which the market MERCK (Merck) weather-resistant pearlescite pigment performance and color are to meet the aluminum market performance requirements, and meet gb/T5237.4-2008 standards, to meet weather resistance requirements, recommended choice. The experimental results of
Table 3 show that according to the GB5237.4-2008 powder spray profile standard, the German Merck company's pearlescent pigment A is resistant to xylene wipe, mortar, water-resistant cooking, significantly better than the domestic pearlescent pigment company.
pigments will not be affected by daylight, chemicals and heat. They are also better compatible with aluminum formulation systems and are better distributed and glossy in resin coatings than other companies. Therefore, in the aluminum formulation system, the preferred performance of Merck's pearlescing pigments.
3 The study of the Bonding . Aluminum special metal and pearl powder coating to achieve the construction requirements of aluminum vertical spray line, must go through the hot bonding Bonding mixing process, Merck pearl powder A and base powder added to the special Bonding cylinder, heated to close to the powder coating near Tg, so that the metal effect powder coating and base powder bonded together, in order to improve the stability of aluminum powder coating site construction.
and Bonding process to improve product recycling powder color instability and metal pigment accumulation gun head and other construction problems, is now a popular process on the market.3.1 Settings of Bonding Process Parameters
The process settings for Bonding machine include heating speed, Bonding speed, cooling speed and temperature parameters and Bonding time setting. By setting specific process parameters, the effect of aluminum-specific pearl powder coating can be achieved.(1) Bonding temperature research: Bonding powder coating resin Tg, when the Bonding machine heats up, is the most sensitive ingredient in the formula: the temperature is too high, powder in the Bonding process, the production of gelding particles, serious time even card machine failure
; The test was carried out using NH3307 from Dynasky Resin, as shown in Figure 2.
shown in Figure 2, the Tg of the individual resin is 66.28 degrees C, and the Tg of the powder is 63.4 degrees C, it can be known that the Tg of the powder coating is 4 to 5 degrees C lower than the Tg of the resin.
However, in the test powder coating and metal effect pigment Bonding temperature instrument shows the temperature is often some lag, so set the state temperature slightly higher than the Tg temperature of 1 degree C, Bonding effect will be better, in this temperature to maintain the bonding time of 3 to 4min.
(2) speed study: Bonding machine bonding number includes heating speed, Bonding speed and cooling speed three parts. Heating speed requires the base powder and metal pigments in high-speed rotation heating, Bonding base powder and silver powder by the pre-State is relatively independent state, after the Bonding machine high-speed rotation, base powder and metal pigments in each other's media evenly dispersed.
show that when bonding speed is set to 300 to 800r/min, the powder and metal pigments can be evenly glued to produce a good bonding effect of the powder, and do not damage the coating, resulting in coating defects.
4 Conclusion . In order to produce qualified aluminum profiles with pearl powder coating, we must fully understand the technical performance requirements under the premise of ensuring the screening of raw materials, scientific and reasonable formulation design, strict grasp of the production process and Bonding process.
the process characteristics of aluminum profile powder, establish a strict product quality management system, to ensure the preparation of qualified aluminum pearl powder coating.
products should meet the "GB5237.4-2008 powder spray profile standards" requirements, to provide customers with long-term use of protection. With the rapid development of China's aluminum profile industry, aluminum profile spraying market contains huge business opportunities and development space, will give customers a huge profit margin.
source: Guangzhou Dynasky Materials Technology Co., Ltd
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