Description
Introduction
| Heavy calcium carbonate, relative molecular weight :100.09. |
| Calcium Carbonate is an important and widely used inorganic salt. Heavy Calcium Carbonate (also known as Ground Calcium Carbonate (GCC for short, Kotamite in the USA) is produced by the direct mechanical grinding of natural calcite, limestone, chalk, shells, etc. Because it has a smaller settling volume (1.1-1.4mL/g) than light calcium carbonate produced by chemical methods (2.4-2.8mL/g), it is called heavy calcium carbonate. |
Property
| Physical Property | | | |
| According to different particle size, it can be divided into ordinary heavy calcium powder, super fine heavy calcium carbonate, wet grinding super fine calcium carbonate, super fine surface modified heavy calcium carbonate. |
Chemical Property
| The chemical formula of calcium carbonate is CaCO3, and its crystals are mainly composed of polytripartite trihedral calcite and rhombic aragonite. Under normal temperature and pressure, calcite is stable and aragonite is quasi-stable. At present, calcite is mainly used. The proportion of heavy calcium is 2.711. |
| At atmospheric pressure, calcite heated to 898℃ and aragonite heated to 825℃ will decompose into calcium oxide and carbon dioxide. Calcium carbonate reacts with all strong acids to form water and corresponding calcium salts (such as calcium chloride CaCl2), and carbon dioxide is released at the same time. At room temperature (25 ℃), the concentration of calcium carbonate in water is 8.7 ×1029, the solubility is 0.0014, the pH value of calcium carbonate aqueous solution is 9.5~10.2, and the pH value of air saturated calcium carbonate aqueous solution is 8.0~8.6. Calcium carbonate is non-toxic, odorless and non-irritating. It is usually white and has a relative density of 2.7~2.9. Mohs hardness is 3 for calcite and 3.5~4 for aragonite. Calcite has three sets of rhombohedral cleavage, and aragonite also has cleavage. Sedimentation volume of heavy calcium carbonate :1.2~1.9ml/g, specific surface area is about 1m/g; Heavy calcium carbonate due to large particles, smooth surface, small specific surface area, so the oil absorption value is low, about 48ml/100g. |
State
| White powder, colorless, tasteless. Stable in air. Almost insoluble in water, insoluble in alcohol. In case of dilute acetic acid, dilute hydrochloric acid, dilute nitric acid occur bubble boiling, and dissolve. Heating to 898℃ begins to decompose into calcium oxide and carbon dioxide. |
| The shape of heavy calcium carbonate is irregular, its particle size difference is large, and the particles have a certain edge, rough surface, the particle size distribution is wide, the particle size is large, the average particle size is generally 1~10μm. According to the original mean particle size (d), heavy calcium carbonate can be divided into coarse ground calcium carbonate (> 3μm), fine ground calcium carbonate (1~3μm), ultrafine calcium carbonate (0.5~1μm heavy calcium carbonate powder characteristics :a. Particle shape is irregular; b. Wide particle size distribution; c. Large particle size. |
Difference from light calcium
| Both calcium carbonate light and calcium carbonate heavy consist of calcium carbonate, which are commonly used as fillers in coatings, plastics and other industries. Grade 1 contains 99.1% and Grade 2 contains 97.9%. The difference between heavy and light calcium carbonate is as follows: |
| 1. The main difference is the use of different light calcium used in filler, electrode, organic synthesis, heavy calcium used in the production of anhydrous calcium chloride, sodium dichromate, cement, etc. |
| 2. ground calcium carbonate (ground calcium carbonate or heavy calcium carbonate) refers to natural calcium carbonate, which is produced by grinding calcite and is cheap. Compared with light calcium carbonate, it is easy to settle when used in latex paint. precipitated calcium carbonate (precipitated calcium carbonate) is also called precipitated calcium carbonate, with smaller particle size, larger oil absorption and higher price. They are commonly used fillers in latex paint, the best collocation. |
| 3. Heavy calcium is naturally crushed ore, light calcium is made by artificial synthesis. There are large applications in coatings. |
| 4. Heavy calcium is stable, but easy to sink compared to light calcium. |
| 5. Light calcium is better in settlement, but the oil absorption is greater than heavy calcium, and the price is generally more expensive than heavy calcium. Although the stability is not as good as heavy calcium, it still has stability, even if it is exterior wall paint, its application is also very large. |
Production method
| There are two production processes for heavy calcium carbonate: | |
| 1. Dry production process: Firstly, hand-selected calcite, limestone, chalk, seashells, etc. transported from the quarry to remove gangue; Then the limestone is coarse crushed by crusher, and then the limestone powder is pulverized by Ramune (pendulum) grinding. Finally, the grinding powder is graded by classifier. The powder meeting the particle size requirements is packaged as the product and stored in storage, otherwise it is returned to the grinding machine for grinding again. |
| 2. Wet production process: suspension made from dry fine powder is placed in the mill for further grinding, and superfine heavy calcium carbonate is prepared after dehydration and drying. |
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| Light calcium is light calcium carbonate, also known as precipitated calcium carbonate, referred to as light calcium, is limestone and other raw materials burned to produce lime and carbon dioxide, then add water to digest lime to produce lime milk (the main component of calcium hydroxide), through carbon dioxide carbonized lime milk to produce calcium carbonate precipitation, through dehydration, drying and grinding. Or from sodium carbonate and calcium chloride double decomposition reaction to produce calcium carbonate precipitation, dehydration, drying and grinding. |
| Chinese Name | 轻钙 | Alias | Light calcium carbonate; Also known as precipitated calcium carbonate, sedimentation calcium carbonate light ultrafine calcium carbonate, commonly known as light calcium | | English Name | Calcium carbonate light | | | | Molecular Formula | CaCO3 | Molecular weight | 100.09 |
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Morphological characteristics
| The sedimentation volume of light calcium carbonate is 2.4-2.8mL/g. Ordinary light calcium particles in the case of fully dispersed in the shape of date kernel, about 5~ |
| The short diameter is 1~3μm, and the average powder diameter is 2~3μm. But due to the end of the surface treatment, in the light calcium generation and dehydration, drying, often many particles condensed together to form like grape dew, so in the national standard for light calcium quality requirements only from 125μm and 45μm sieve residue to judge, and does not directly reflect the true particle size and distribution. |
Main component
| Main Component (CaCO3)% 98.0-100.0 97.0-100.0 97.0-100.0 |
| PH (10% suspension) 8.0-10.0 8.0-10.5 8.0-11.0 |
| Content of volatile matter at 105℃ %≤ 0.35 0.64 1.00 |
| Hydrochloric acid insoluble content %≤ 0.10 0.20 0.30 |
| Settling volume m1/g≥ 2.8 2.6 2.4 |
| Iron (Fe) content %≤ 0.08 0.10 0.10 |
| Manganese (Mn) content %≤ 0.006 0.008 0.010 |
| Sieve residue :125um test sieve %≤ 0.005 0.010 0.015 |
| Screen residue :45um test screen %≤ 0.30 0.40 0.50 |
| Whiteness ≥ 90.0 90.0 85 |
Properties of light calcium
White powder. Tasteless and odorless. The specific gravity is about 2.71. Decomposition at 825~896.6℃. Melting point 1339℃. There are two forms of amorphous and crystalline, crystalline form can be divided into rhombic system and hexagonal system, columnar or rhombic. Insoluble in water and alcohol. Dissolved in acid, at the same time release carbon dioxide, an exothermic reaction. Also dissolved in ammonium chloride solution. Stable in air with slight moisture absorption.
Preparation of light calcium
Carbonization method: limestone and white coal mixed in a certain proportion, after high temperature calcination, water digestion, carbon dioxide carbonization, and then centrifugal dehydration, drying, cooling, grinding, screening ready to get the finished product. CaCO3= high temperature =CaO+CO2↑ CaO+H2O=Ca(OH)2 Ca(OH)2+ CO2=== =CaCO3↓+H2O 1. Light calcium is calcination of limestone and other raw materials to produce lime (mainly calcium oxide) and carbon dioxide, and then add water to digest lime to produce lime milk (mainly calcium hydroxide). Then through carbon dioxide carbonized lime milk to produce calcium carbonate precipitation, and finally through dehydration, drying and grinding to prepare. 2. Calcium carbonate is precipitated by the double decomposition reaction of sodium carbonate and calcium chloride, and then obtained by dehydration, drying and grinding. Because the sedimentation volume of light calcium carbonate (2.4-2.8mL/g) is larger than that of heavy calcium carbonate (1.1-1.4mL/g), it is called light calcium carbonate.
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