As a energy-saving, environmentally-friendly mineral material, heavy calcium carbonate is widely used in paper, plastics, rubber, paints, adhesives and adhesives due to its special physical and chemical properties, low price, wide raw materials and non-toxicity. Sealants and building materials industries. It is well known that heavy calcium carbonate is made of natural carbonate minerals such as calcite, marble, limestone, also known as ground calcium carbonate, which is a commonly used powdery inorganic filler. So, what is the difference between the heavy calcium powder processed by calcite, marble and limestone?
The chemical formula of calcite is CaCO 3 , and its theoretical chemical composition is: CaO 56.03%, CO 2 43.97%, belonging to trigonal system, colorless or white, sometimes dyed as light yellow, light red by elements such as iron, manganese and copper. Purple, brown, etc.
Natural marble, also known as marble, is recrystallized limestone, the main component of CaCO ₃. Limestone softens under high temperature and high pressure and recrystallizes to form marble when the mineral content changes. The main ingredients are calcium and dolomite, which have many colors and usually have obvious patterns and many mineral particles. The Mohs hardness is between 3 and 5 and is generally cubic.
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The main chemical components of limestone CaCO ₃, presentation to calcite particulate, crystalline form complex, often has scalenohedral and rhombohedral, gray or light gray, Mohs hardness of 3 to 4, the density of 2.5 ~ 2.8g / cm 3.
The three main components are CaCO ₃, contrast, slightly higher than the calcium calcite marble and limestone, calcite good calcium can reach 99%.
China's calcite, marble, limestone resources are very rich, especially calcite, the most common of the natural calcium carbonate is it. Moreover, China is one of the five major countries producing high-quality calcite in the world, and its distribution is relatively concentrated. It is mainly distributed in Guangxi, Jiangxi, and Hunan . Natural marble resources are spread all over the country, but the main component of artificial marble is not calcium carbonate . Confused.
Calcite, marble, and limestone ore are directly ground into heavy calcium carbonate fillers. Therefore, the purity and whiteness of the ore are extremely high, and the content of calcium oxide is almost close to the theoretical value. Therefore, not all limestone and marble can be used as raw materials for heavy calcium carbonate. It is especially important to note that limestone with high calcium content can make heavy calcium.
First, the industry generally does not perform mechanical beneficiation processing on the other side of the stone, only simple washing and hand selection; for limestone, it is only necessary to carry out simple washing, without the need for complex mineral processing to purify; in contrast, Marble is rich in color and variety, and the processing of mineral processing is more complicated than calcite and limestone.
Second, calcite has a Mohs hardness of 3, which is lower than that of marble and limestone. Therefore, the same power pulverizing equipment is more efficient in processing calcite than in processing marble and limestone.
Third, the ultrafine pulverization process of calcite mainly includes dry and wet methods. The dry process is generally used to produce products with d 97 ≥3~5μm, and the wet process generally uses products with d 97 ≤3~5μm (d 90 ≤2μm); limestone generally adopts dry pulverization process.
First of all, among the three, the heavy calcium carbonate processed by calcite is the most abundant inorganic filler in the organic polymer-based materials. The ore quality of calcite is very good, and the dispersibility, fluidity, particle size distribution and powder absorption and hiding rate of the powder are better than marble. Good calcite powder whiteness can be 95-97 or more (400 mesh powder), marble whiteness is lower, and the better is about 93-96 (400 mesh).
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Second, technical indicators vary from application to application, and calcite, limestone, and marble play different roles in different fields. Such as plastic products, plastic products technical requirements for processing of raw materials with calcite calcium carbonate is mainly the chemical composition (CaCO ₃ or CaO content, the insoluble hydrochloride, iron and heavy metal content), particle size and particle size distribution, degree of white and the like; coating inks generally require CaCO ₃ ≥97%, whiteness ≥90.
Due to the difference in trace metals contained in calcite and marble, the color of the powder is different. The product made from calcite powder filled in plastic will be milky yellow or milky red (also known as magnetic white, milky white). ), soft color, good hiding power.
In addition, due to the different crystal structure of calcite and marble, the tensile force and impact resistance will be different after filling in plastic products. Calcite belongs to the hexagonal crystal system. The crystals are generally jujube-nuclear, with long and short diameters. The marble crystals are generally cubic in shape and have small length and short diameter. The powder with relatively long and short diameters is filled in the plastic to have a certain reinforcing effect, and the tensile properties and impact resistance of the plastic products are better. If the calcite and calcium heavy calcium of the same particle size distribution are filled with PVC pipe profiles and the like under the same formulation conditions, the products made of marble powder are more brittle and less tough than the calcite powder.
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Moreover, the quality of heavy calcium carbonate products is largely due to the grade of raw materials . For example, in the papermaking industry, papermaking accounts for about 40% of the market share of heavy calcium. The raw materials for heavy calcium carbonate for papermaking are generally based on the physical properties and chemical composition of the ore, especially depending on the hardness of the ore. The lower the hardness of the ore, the softer the calcium carbonate raw material is, the more advantageous it is to the paper industry, because its lower wear value is more advantageous for protecting and extending the life of the filter screen, cutter head and other components of the paper machine.
At present, developed countries such as Europe generally use high-quality chalk with high purity and good whiteness as the preferred raw material for heavy calcium carbonate for papermaking. However, due to the different geological origins in China, there are few high-quality chalks with large reserves. Most of them use high-whiteness and high-purity marble and calcite as the main raw materials for heavy calcium carbonate in papermaking.
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In addition, limestone is more important for the preparation of light calcium carbonate than the preparation of heavy calcium carbonate. In addition to the preparation of ordinary light calcium carbonate, limestone can also prepare ultra-fine calcium carbonate and nano-calcium carbonate, and can also prepare ultra-fine active calcium carbonate by surface modification, and is used as a filler for rubber, plastic, paper, toothpaste, cosmetics and the like.
In recent years, with the extensive and deep application of heavy calcium carbonate in the fields of plastics, rubber, paper, medicine, food, building materials, chemicals, coatings, feed, etc., high-quality industrial heavy calcium carbonate raw materials have broad development and application prospects. The resources are limited, and the recycling of mine tailings is worthy of attention, such as Hezhou. Now in Hezhou has formed a perfect circulating stone industry chain: marble raw materials - marble plates and crafts - marble corner scrap recycling - heavy calcium calcium carbonate ultrafine powder - synthetic artificial marble - calcium carbonate new materials (paint, paper, etc.) - Comprehensive recovery and utilization of calcium carbonate solid waste. In addition, ultra-fine ultra-fine heavy calcium carbonate has become a development trend, in addition to the selection of raw materials, processing technology, equipment should also continue to innovate.
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