Calcium carbonate as an excellent filler, with the color of white matter pure, easy to color, stable chemical properties, low cost, particle size and particle shape can be controlled and other advantages, has been successfully applied in rubber, plastic, plastic steel doors and windows, PVC cable material, high-grade coatings, pipes, tires, soles, polyethylene blown film, sealing strips, FRP products, cable packaging cloth, papermaking, building materials, inks, daily chemicals, textile, feed, food additives, medicine and other industries. However, in these traditional applications, the profitability of calcium carbonate companies is often "winning by quantity", and there is room for further improvement in functional categories such as nano-calcium or high-purity calcium carbonate. Overall, the domestic calcium carbonate production process, equipment has not been much different from foreign countries, but in the downstream application of domestic products and technology to meet the high value of calcium carbonate applications need to be further strengthened.
Nano calcium carbonate
(Image source: Tianshi Nano)
First, the application of calcium carbonate with high value
The domestic calcium carbonate industry is relatively late, from 1931 there are 90 years of history, the entire industry has been relatively mature, but the production and application of technology there is still room for continuous progress, so "multi-legged" walking, while engaging in production technology, while exploring high-value product application technology, and finally to the combination of functionalization is very necessary. In terms of foreign countries, the United Kingdom, Japan, Italy, Germany, the United States and other developed countries have their own advantages in different areas of calcium carbonate production, such as the United Kingdom has advantages in high-grade coatings and automotive calcium plastics, and Japan has advantages in the application of calcium carbonate research. Below, Xiaobian and everyone take a look at some of the current high-value applications of calcium carbonate.
1. Conductive coatings
Due to its low cost and wide source of raw materials, lightweight calcium carbonate is widely used as a filler in rubber, plastics, coatings and other polymer materials, but calcium carbonate does not have conductivity and cannot solve the problem of static electricity. The CaCO3-polyaniline (PANI)/SiO2 conductive composite powder is prepared with calcium carbonate as the coating matrix, and it is applied to the field of conductive coatings, which not only reduces the cost of coatings, improves the mechanical strength of the coating film, but also gives the coating film a certain conductivity and antistatic properties, eliminating static hazards. Among them, SiO2 coating modification can significantly improve the acid resistance of calcium carbonate.
In addition, American researchers use calcium carbonate as a filler to prepare cooling coatings, which can isolate most of the heat. In principle, calcium carbonate has a large number of band gaps, which helps to reduce the amount of ultraviolet light absorbed by the paint.
2. Food and health care
Food grade calcium carbonate can be added in calcium nutrition and health food leavening agents or softgels and other products, and even in high-purity pharmaceutical grade calcium citrate, calcium lactate, calcium gluconate and other calcium agents have been added. In addition, chewing gum, chocolate and Wahaha will also add an appropriate amount of calcium carbonate.
(1) The development of nano calcium carbonate with a specific surface area of 30m2/g can improve the calcium content of milk drinks and inhibit precipitation.
(2) Research and development of nano calcium carbonate for hoisin sauce products, giving seawater sauce texture, increasing the strength of the sauce, obtaining a soft taste, and extending the shelf life.
(3) Calcium carbonate D3 chewable tablets (compound preparation, each tablet contains 1.25 grams of calcium carbonate), for children, pregnant and lactating women, menopausal women, the elderly, etc. calcium supplements, and to help prevent osteoporosis. Among them, the calcium carbonate content is about 50%-75%.
3. Ceramics
Developed cubic calcium carbonate with uniform particle distribution, which can be used for densifying ceramics manufactured at low temperatures of 600 °C. Nano calcium carbonate is applied to piezoelectric ceramics, and also has a relatively good effect.
4. Engineering plastics
The nano calcium carbonate prepared by the new double-layer modification technology is applied to engineering plastics, which can produce high-white and heat-resistant finished engineering plastics.
5. Lightweight filler
The development of spherical shell-shaped lightweight (lightweight) filler, the specific gravity is only 0.2-0.3cm/g, compared with other balloon fillers is not easy to break, can reduce the specific gravity, can be applied to rubber, plastics and other industries.
6. Carrying drugs
(1) Liu Nianxing et al. selected heavy calcium carbonate as raw material, prepared Dockering emulsion (a kind of interface-dominant material wrapped in intolerable substances in food), and used the characteristics of calcium ions and sodium alginate to cross-link to form a pH-responsive gel structure, added sodium alginate to the stable dockering emulsion of calcium carbonate particles, built a pH-responsive emulsion system, and used it as a nutrient or drug carrier to study its release in simulated gastrointestinal fluid. It provides new ideas for the design and construction of enteric-soluble preparations of bioactive factors.
(2) Zhu Lin et al. under physiological temperature, using anhydrous calcium chloride and sodium carbonate as raw materials, chondroitin sulfate as the targeting reagent, cancer cell secretions as morphological regulators, prepared petal-like calcium carbonate, and realized the high-efficiency loading of anti-tumor drugs doxorubicin hydrochloride (DOX). In addition, release experiments at different pH values showed that the DOX of the loading system was more likely to be released under weakly acidic conditions, and the release was slower and had better sustained release performance, while the cell activity (MTT) experiment showed that the loading system had a specific inhibitory effect on tumor cells.
7. Phosphorus removal in water
Many studies have suggested that the crystal phase and particle size of calcium carbonate have a significant effect on phosphorus removal. When calcium carbonate is mostly calcite phase and a few are bulbous lithofar phases, the morphology is dominated by spherical particles, accompanied by a small number of cubes. The particles are composed of small particles with an average particle size of 60 nm into 3 ~ 5um large particles, and the surface is rough, which has a good treatment effect on phosphorus-containing water quality, and the treatment efficiency is basically 73%.
8. "Life, Light, Electricity"
Japan uses calcium carbonate ≥ 99.5% pure for:
(1) Life science field: for example, calcium carbonate sintered body of artificial bone filling material, to study its applicability as a bone graft material and cell support carrier;
(2) Electronic field: for example, ceramic capacitors;
(3) Optical field: for example, luminescents.
Second, the distribution of domestic calcium carbonate mines
China is rich in calcium carbonate resources, such as: Sichuan (Ya'an Baoxing), Guangxi (Hezhou, Laibin, Hechi), Anhui (Chizhou), Guangdong (Lianzhou), Hunan (Linwu), Hubei, Hebei (Jingxing), Jiangxi, Zhejiang (Jiande, Quzhou), Henan (Nanzhao), Liaoning, Jilin, Heilongjiang, Gansu (Longnan Liangdang), Yunnan, Guizhou, Xinjiang, Shanxi, Shandong, Fujian, Shaanxi and Qinghai, Hainan and other basically each province in China. With the increasing attention of the state to natural resources, more requirements have been made in terms of development and utilization. Fine processing and high-value applications are the trends in mine development.