Calcium carbonate is one of the most common substances in nature. In industrial production, calcium carbonate is divided into heavy calcium carbonate and light calcium carbonate. Among them, light calcium carbonate is calcium carbonate prepared by chemical methods after calcination and purification of natural limestone; while heavy calcium carbonate is physical heavy calcium carbonate obtained from natural calcium carbonate ore through mechanical grinding and a grading system. The performance of the product is greatly related to the type of the original ore and the production process.

Calcium carbonate is one of the most common substances in nature. Industrially produced calcium carbonate is divided into heavy calcium carbonate and light calcium carbonate. Light calcium carbonate is calcium carbonate prepared by chemical methods after calcination and purification of natural limestone; while heavy calcium carbonate is physical heavy calcium carbonate obtained from natural calcium carbonate ore through mechanical grinding and a grading system. The performance of the product is greatly related to the type of original ore and the production process.

　　

　　Because of its wide sources and low price, heavy calcium carbonate is widely used as a filler in industries such as rubber, plastics, papermaking, coatings, inks, medicine, food, and daily chemicals. When heavy calcium carbonate is used as a filler in latex paint, it plays a filling role and has a certain dry hiding power, which reduces the cost of latex paint and also plays a skeleton role, improving the thickness, hardness, water resistance, and scrub resistance of the coating. Therefore, the application of heavy calcium carbonate in the building coatings industry is becoming increasingly widespread.

　　Different calcium carbonate ores, due to the differences in geological environment and ore-forming conditions in different regions, lead to different crystal forms and appearances of ores in different regions, and their physical properties will also be different. When applied to downstream fields, the performance indicators will also be different. Specifically, in interior wall latex paint, heavy calcium carbonate produced from different ores will have different properties, so it will have a certain impact on the whiteness, viscosity, hiding power, gloss, and scrub resistance of the latex paint.

　　The following uses three types of raw ores: large calcite, small calcite, and dolomite. They are processed into 800-mesh heavy calcium carbonate using a ring roller mill to test the differences in their physical properties, chemical composition, and particle morphology. Then, they are added to interior wall latex paint, and the whiteness, viscosity, contrast ratio, gloss, and scrub resistance of the latex paint film are measured to determine the performance impact of different ores on interior wall latex paint.

　　1

　　Experimental Section

　　1.1 Experimental Materials

　　Large calcite calcium carbonate

　　Dolomite calcium carbonate

　　Small calcite calcium carbonate

　　Other raw materials: dispersant, wetting agent, defoamer, ethylene glycol, dodecyl ester, hydroxyethyl cellulose, rutile titanium dioxide, kaolin, pH adjuster, styrene-acrylic emulsion 998A, bactericide.

　　1.2 Main Instruments and Equipment

　　Scanning electron microscope: ΣIGMA type

　　Particle size analyzer: 3000E type

　　Whiteness meter: WSB-X type

　　Atomic absorption spectrophotometer: A3F type

　　High-speed disperser: GFJ-0.4 type

　　Stormer viscometer, STM-IV type

　　Reflectance meter, C84-II type

　　Building coating scrub resistance tester, JTX-II type

　　Vacuum automatic coating machine, AFA-II type

　　Three-angle gloss meter, GZ-II

　　1.3 Experimental Formula

　　Experimental Formula Table

　

　　1.4 Preparation of Latex Paint

　　According to the experimental formula shown in the experimental formula table, components 1-7 are added in sequence. First, the speed is adjusted to 600 r/min, and dispersed for 5 min. Then, components 8-10 are added, the speed is adjusted to 1700 r/min, and high-speed dispersion is performed for 15 min. After that, components 12-15 are added, the speed is reduced to 600 r/min, and dispersed for 5 min to complete the preparation of the coating. It is then placed at room temperature (25℃) for later use.

　　1.5 Performance Testing

　　Viscosity test: according to GB/T9269-2009; Paint film whiteness test: according to GB/T1729-1979; Contrast ratio test: according to GB/T1726-1979; Gloss test: according to GB/T1743-1979; Scrub resistance test: according to GB/T9266-2009.

　　2

　　Results and Analysis

　　2.1 Physical Indicators of Heavy Calcium Carbonate Processed from Different Ores

　　Physical indicators of calcium carbonate processed from different ores

　　

　　From the table, it can be seen that the whiteness of the three calcium carbonates is above 93, among which HC-800 produced from Haicheng dolomite ore has the highest whiteness, reaching 98.1. From the analysis of powder fineness, using the same production equipment and the same process parameters to produce 800-mesh powder, the particle size distribution is basically the same. From the analysis of oil absorption, LZ-800 has the lowest oil absorption. The lower the oil absorption, the relatively smaller the demand for emulsion, but under the same conditions, the finished product may be thinner.

　　2.2 Chemical Composition of Calcium Carbonate Processed from Different Ores

　　Chemical composition of calcium carbonate processed from different ores

　　

　　From the table, it can be seen that YF-800 calcium carbonate processed from Lianzhou Xiangfa powder large calcite has the highest calcium carbonate content and the lowest content of impurity elements and heavy metals; LZ-800 processed from Lianzhou small calcite has the lowest SiO2, and the wear and tear on the processing equipment will be relatively low; HC-800 processed from Haicheng dolomite has a typical dolomite composition, with a high MgO content of 22.43%, and a lower calcium carbonate purity, so some properties of the powder may be affected.

　　2.3 Particle Morphology of Calcium Carbonate Processed from Different Ores

　　Scanning electron micrographs of calcium carbonate processed from different ores

　

　　The magnification of the above image is 2000 times. As can be seen from the figure, the three calcium carbonate particles are all irregular in shape. Among them, the YF-800 particles produced by large calcite have more pores and depressions on the surface, more complete crystallinity, and no too many small particles attached to the surface; while the powders processed from the other two ores have some small particles attached to their surfaces, some of which have become small aggregates. In terms of the uniformity of particle distribution, the particles of YF-800 are more uniformly distributed, and the particle sizes are basically consistent, while the particle sizes of the other two calcium carbonate particles vary greatly, and the particle distribution is relatively uneven.

　　2.4 Analysis of Latex Paint Viscosity

　　Influence of Different Original Calcium Carbonate on Latex Paint Viscosity

　

　　As can be seen from the table, HC-800 has the highest viscosity, and LZ-800 has the lowest viscosity. This is related to the oil absorption value of the three calcium carbonates. The higher the oil absorption value, the greater the adsorption of the emulsion, and the higher the overall viscosity, which is consistent with the oil absorption value test results.

　　2.5 Latex Paint Contrast Ratio Analysis

　　Influence of Different Original Calcium Carbonate on Latex Paint Contrast Ratio

　

　　As can be seen from the table, the contrast ratio of precipitated calcium carbonate produced from calcite ore used in latex paint is significantly higher than that of precipitated calcium carbonate produced from dolomite ore; among calcite products, the contrast ratio of precipitated calcium carbonate produced from large calcite is higher than that of precipitated calcium carbonate produced from small calcite.

　　2.6 Analysis of Latex Paint Film Scrub Resistance

　　Influence of Different Original Calcium Carbonate on the Scrub Resistance of Latex Paint Film

　　

　　As can be seen from the table, the latex paint film prepared with YF-800 processed from Yongfeng large calcite has the highest scrub resistance, reaching 771 times. Next is LZ-800 processed from Yongfeng large calcite, with a scrub resistance of 757 times, comparable to YF-800. The latex paint film prepared with HC-800 produced from Haicheng dolomite has the worst scrub resistance, with 696 times, but all are greater than 500 times, fully meeting the national standard.

　　Calcium carbonate products processed from large calcite have high whiteness, low content of impurity elements, and relatively uniform particle distribution; calcium carbonate processed from large calcite used in interior wall latex paint has significantly better contrast ratio and scrub resistance than heavy calcium carbonate produced from small calcite and dolomite.