A comparative study of the application of calcium carbonate in polyester powder coatings.

the application of different heavy calcium carbonate in polyester powder coatings
Xu Yonghua 1, Yu Yong 1, Fu Junxiang 1, 2, He Jiakang 2
(1. Jiangxi Guangyuan Chemical Co., Ltd., Jiangxi Ji'an 331500; 2. Jiangxi University of Technology School of Metallurgy and Chemical Engineering, Jiangxi Ganzhou 341000) 0 Introduction
Powder Coating is a new solvent-free 100% solid powder coating. It has the characteristics of solvent-free, pollution-free, recyclable, environmental protection, energy and resource saving, reducing labor intensity and coating mechanical strength. With people's growing awareness of environmental protection, powder coatings have attracted much attention. As an important part of powder coating, the nature of fillers has also begun to attract people's attention.In general, fillers should have the following properties: (1) insoluble in water and organic solvents, have good dispersion, colorless or white, do not contain a variety of impurities of ultra-fine powder particles; Calcium carbonate is the most widely used body pigment in coatings, with a series of advantages such as low price and easy access, stable chemical properties of products. With the EU's category of sulphate in heavy metal detection, the use of radon sulfate in export powder coatings will be greatly restricted. The heavy calcium carbonate has certain function after super-refinement, so it becomes the alternative to the powder coating of radon sulfate.
This paper selects the similar heavy calcium carbonate products produced by different primary ore by comparing the application in polyester powder coating, and studies in detail the effect of heavy calcium carbonate ore on the luster, whiteness, ratio, pencil hardness, adhesion and other properties of polyester powder coating.1 Experimental part
1.1 Experimental raw materials
Polyester resin (Anhui Shen jian), TGIC (Nintang Chemical), titanium white powder R-902 (DuPont), heavy calcium (Guangyuan Chemical), filler, leveling agent GLP-558 (Ningbo South China Sea), brightener GLP-701 (Ningbo South China Sea), Rest incense (Ningbo South China Sea).1.2 Main Instruments and Equipment
Scan Electroscope: IGMA Type, ZEISS Field Launch Scan Mirror; Particle Analyzer: 3 000E Type, Malvern Instruments Co., Ltd.; Reflectivity Meter: C84-III Type, Shanghai Hyundai; Glossy meter: CZ-II, Tianjin Expo; Coated pencil scratch hardness meter, Tianjin Central; White Scale: WSB-X, Hangzhou Dentons; Paint film slicing meter: QFH, Tianjin Central.1.3 Experimental Formula
experimental base formula, as in Table 1.1.4 Experimental process
high mix 10 min——— melt extrusion (1 zone temperature 100 degrees C, 2 region temperature 135 degrees C, melt temperature 125 degrees C) ——— planetary grinding crush 15min——— electrostetration spray———200 degrees C at 30 min baking.1.5 performance
the oil absorption value by GB/T 5211.15-1988; Gloss according to GB/T 9754-2007, whiteness by GB/T 1729-1979, ratio by GB/T 1726-1979, pencil hardness by GB/T6379-2006, adhesion by GB/T 9286-1998.2 Results and Analysis of the Physical Performance of
2.1 Fillers
The basic physical performance indicators of 7 types of heavy calcium carbonate from different primary mines were tested according to HG/T3249.2-2008, and the test results are in Table 2.can be seen from Table 2, the amount of oil absorbed by the filler increases gradually with the increase of the fineness of the powder. At the same time, the variety of raw ore has a certain impact on the amount of oil absorption: the same 800 products, dolomite products of oil absorption is significantly lower than the generous stone and small square solution stone. The whiteness of the powder has a certain relationship with the fineness of the filler and the type of raw ore, in general, under the same conditions, the whiteness of the filler increases with the fineness to a certain extent, the reason for the lower whiteness of the table 3,000 and 6,000 may be because it is a wet product, in drying using hot steam drying of coal, the whiteness of the powder will be reduced to a certain extent, The whiteness of the same specifications of large and small square stone products is significantly higher than that of dolomite products.
The above 7 fillers will be tested according to the formula in Table 1, by observing the processing performance of the product and measuring the luster, whiteness, ratio, pencil hardness, adhesion and other indicators of comparison, in order to determine the application of different heavy calcium carbonate in it, the specific results are as follows: from the production process, In other parameters unchanged, the same 800 purposes of dolomite feeding speed than the speed of generous stone and small square stone, mainly due to the square stone itself is relatively fluffy, small false proportion, is not conducive to the material. Therefore, from the processing point of view, dolomite series is better than large and small square stone series. The final polyester powder coating paint film performance indicators can be found in Table 3.can be seen from Table 3, the type and fineness of heavy calcium carbonate ore has no effect on the hardness and adhesion of the paint film, the hardness of the paint film is 2H, adhesion rating is 0 grade.2.2 Effect of fillers on paint film performance
2.2.1 Effect of dolomite fineness on paint film whiteness
The relationship between different fine heavy calcium carbonate produced by dolomite ore and paint film whiteness is shown in Figure 1.can be seen from Figure 1, under the same conditions as the original ore, the whiteness of the paint film is very positively related to the whiteness of the filler itself, and there is no direct relationship with the fineness of the filler.
2.2.2 Dolomite fineness on the ratio of the paint film
As can be seen from Figure 2, under the same conditions as the original ore, the ratio of the paint film with the increase of calcium carbonate fineness overall shows a trend of first rising and then decreasing, in the range of 1,250 to 1,500 to achieve the best masking effect.2.2.3 dolomite fineness on the luster of the paint film
Figure 3 shows that under the same conditions, the fineness of calcium carbonate has a positive effect on the gloss of the paint film, to a certain extent, the finer the filler, the higher the gloss of the paint film.effect of 2.2.4 ore species on the whiteness of the lacquer film
As can be seen from Table 2, the whiteness of the generous solution and the small square solution is significantly higher than that of dolomite, but Figure 4 shows that the whiteness of the paint film of dolomite is the highest of the three, and the same as the square stone products, the whiteness of the small square stone is 1.2 degrees higher than that of the generous solution stone, while the whiteness of the lacquer film is nearly 3 degrees lower than that. This shows that when the primary ore is different, the whiteness of the paint film is not directly related to the whiteness of the filler, or the whiteness of the paint film cannot be predicted directly from the whiteness of the filler.effect of 2.2.5 ore species on the ratio of paint film
As can be seen from Figure 5, in the case of the same fineness, in three different primary ore calcium carbonate varieties, dolomite ratio is the best, followed by generous calcite, small calcite ratio is the worst.effect of 2.2.6 ore species on the gloss of the lacquer film
can be seen from Figure 6, the fineness of the same situation, different primary ore heavy calcium carbonate on the gloss of the paint film has a greater impact. Among them, dolomite product gloss is the best, generous stone and small square stone gloss is equivalent, which may be due to the high oil absorption of the solution stone than dolomite caused.3 conclusion
synthesis of the above experimental results can be concluded that dolomite for the original production of heavy calcium carbonate, when applied to polyester powder coating, processing flow is better, paint film gloss, ratio, paint film whiteness and other properties are significantly better than the same specifications of small calcite and generous calcite products. And with the increase of its fineness, the gloss of the paint film appears to a certain extent, with the increase of whiteness, the whiteness of the final paint film also shows a certain degree of increase, in addition, different types of calcium carbonate for polyester powder coating pencil hardness and adhesion has no direct effect. Therefore, in polyester powder coating for calcium carbonate fillers, should be preferred to dolomite as the primary ore of heavy calcium carbonate..