The effect of titanium white powder particle size distribution on the performance of powder coating was studied.

the effect of titanium white powder particle size distribution on the performance of powder coatings . Li Jianjun 1, Yang Zhen 1, Li Tianda 1, Li Haiyan 1, Feng Yuguang 1, Long Xiang 1, Cui Aly 2(1. Yunnan Metallurgical Xinli Titanium Co., Ltd., Kunming 650100; 2. Tsinghua University Department of Chemistry, Beijing 100084) 0 ForewordWith the increase of domestic environmental protection efforts, the coating industry gradually to high solid paint, water-based paint development. Powder coatings, which represent solvent-free, high solid sub-coatings, emit far less volatile organic compounds (VOLATILE compounds, or VOCs) than conventional solvent-based coatings, and some products have achieved zero VOC emissions. Coating utilization rate is high, the application process produces very little solid waste, can prevent air pollution and fire, is an environment-friendly coating. Powder coating is made of polyester, polyurethane, polyacrylic acid, epoxy resin and other polymers and pigments, additives and other uniform mix. Powder coating construction is simple, generally only need a coating to meet the requirements of use, in the coating process control is excellent, the coating film basically does not produce pores, acid and alkaline resistance, corrosion resistance performance; Comprehensive investment is smaller than traditional solvent-based coatings, powder coatings are not flammable products, more safe, convenient to use, storage and transportation, simple and economical, excessive spray coating powder can also be recycled, powder coatings because of the above advantages, since the invention has been widely concerned. The main industries of powder coating include: furniture manufacturing, home appliance kitchen manufacturing, steel pipe industry, automobile industry, agricultural machinery industry, fire equipment, electrical industry and construction industry.Titanium white powder is a stable materialized properties and excellent pigment performance of white pigments, it has the reputation of the king of white pigments, its main chemical composition is titanium dioxide, molecular style TiO2, molecular weight 79.9, is widely used in plastics, coatings, paper, ink, rubber, cosmetics and other industries. The main factors affecting the performance of powder coating are the content of titanium dioxide, the particle size distribution of titanium white powder, the dispersion performance of titanium white powder, the refractive index of resin and so on. In this paper, the effect of titanium white powder particle size distribution on the cover and gloss of powder coating is studied.1 Experimental Part 1.1 Experimental Raw Materials and Instruments 1.1.1 Experimental Reagents The raw materials and main reagents used in the experiment are shown in Table 1.1.1.2 Experimental equipment and instrumentsmain equipment and instruments used in laboratory experiments such as Table 2.1.2 Experimental MethodThe mixture of titanium dioxide, resin and additives is evenly added to the powder coating extruder, extruded and crushed in a high-speed multi-function shredder 1min, and the powder is sprayed into the powder coating spray gun on the cover force test plate and dried in a drying box. To determine the cover force and gloss, the formula is seen in Table 3, Table 4.. 1.3 Symptoms and testingtitanium white powder particle size: 0.2 g titanium white powder sample in 250 mL beech, add 50 mL water, then add 5 drops of dispersant, magnetic heating agitator stirring 10 min. After mixing with 2 mL, the sample is in the laser particle size meter Mastersizer 2000 Mu sample pool, put down the agitator, stir about 1min, repeat the determination, the results are stable. Pigment performance test: USCM-2600d spectrograph, direct characterize the coating film cover application performance measurement by PCQC color quality control system software, and use WGG-20 gloss meter to determine the gloss of the coating film.. 2 Results and discussion 2.1 Titanium particle size and particle size distributionFigure 1 is R-706 and R-960 titanium powder using laser particle size analyzer MS 2000 particle size distribution map. The measured condition is a color folding rate of 2.73 and an absorption rate of 0.1. The D10 of R-706 titanium dioxide is 0.225 m, D50 is 0.406 m, D90 is 0.744 m, and R-960 titanium powder has D10 of 0.290 m, D50 is 0.551 m, and D90 is 1.120 m. As can be known from Figure 1, R-706 has a narrow particle size distribution and a smaller average particle size, and R-960 has a wide particle size distribution and a large particle average diameter. The particle size distribution of R-960wider than R-706 and is larger.2.2 Different particle size distribution of titanium dioxide in the powder coating film cover force And the same kind of titanium dioxide dispersed in different thickness coating media, the resulting coating cover force is more different. In other words, the optimal granularity of the pigment is closely related to the thickness of the coating film used. Titanium dioxide powders distributed at different granularity do not have the same values in different formulations.figure 2 is a light cover attempt based on table 3 polyester powder coating base test formula determination, Figure 3 is based on epoxy powder coating base test formula determination light cover attempt. As can be seen from Figures 2 and 3, as the thickness of the coating film increases, the cover force of the small, narrowly distributed titanium dioxide R-706 and the widely distributed coarse particle size of the titanium dioxide R-960 increases at the same time; In the case of coating film thickness, the cover of small particle size, narrow distribution of titanium dioxide R-706 is higher, in the thin coating thickness, small particle size, narrow distribution of titanium dioxide R-706 is more likely to be hidden.. 2.3 Different particle size distribution of titanium dioxide in the epoxy resin formula gloss titanium white powder pigment is an important part of powder coating, titanium white pigment itself has no luster, evenly dispersed in the powder coating only gloss, but the actual production of titanium white powder pigment particle size distribution determines the gloss of the coating film. Because of the narrow particle size distribution of R-706 and the small average diameter of particles, it belongs to the product produced by fine-grained substit span, while the particle size distribution of R-960 is relatively wide and the average diameter of particles is relatively large, it belongs to the product produced by medium-grained substat. for the gold-redstone titanium dioxide powder distributed at different particle sizes, the gloss of the powder coating after coating is related to the thickness and particle size distribution of the coating film. Figure 4 is a gloss scattering chart based on the parallel determination of the base test formula of the epoxy resin powder coating in Table 4, and it can be seen from Figure 4 that two titanium dioxides with different particle size and particle size distribution levels show the same regularity when the thickness of the coating film changes, with smaller granularity and narrow distribution. The gloss of titanium white powder R-706 is higher than that of the larger particle size and wider distribution of titanium white powder R-960, because the small particle size and narrow particle size distribution of R-706 can maintain a good smooth coating surface. . 3 Conclusions this paper mainly studies the effect of titanium white powder particle size distribution on the cover and gloss of powder coatings. The conclusion is as follows: (1) Titanium white powder has a small particle size and a narrow particle size distribution, which can improve the masking power of the coating layer and increase the gloss of the coating. (2) in thin coating layer, small particle size, narrow particle size distribution of titanium dioxide is more likely to be hidden.
. .