Calcium carbonate is an important and widely used inorganic salt. It is usually divided into heavy calcium carbonate and light calcium carbonate according to different processing methods. Calcium carbonate, whether it is heavy calcium carbonate or light calcium carbonate, is the most widely used powder filler in plastics, rubber, papermaking and other industries.
1. Production method
Heavy calcium is mainly a powder material obtained by mechanical grinding and processing of natural minerals such as calcite, marble, limestone, chalk, and white marble as raw materials;
Light calcium is mainly a powder material obtained from limestone as raw material through processes such as calcination, digestion, carbonization, dehydration, drying, and classification.
2. Packing density
The difference in product packing density is the most obvious difference between heavy calcium and light calcium.
The bulk density of heavy calcium products is relatively large, generally 0.8 to 1.3g/cm3;
The bulk density of light calcium products is small, generally 0.5-0.7g/cm3, and the bulk density of some nano-calcium carbonate products can even reach about 0.28g/cm3.
3. Oil absorption value
Due to its large particles, smooth surface and small specific surface area, heavy calcium has a low oil absorption value, generally 40-60mL/100g;
Light calcium particles are fine, the surface is rough, and the specific surface area is large, so the oil absorption value is high, generally 60 ~ 90mL/100g.
4. Whiteness
Due to the relatively large number of impurities in heavy calcium, the product whiteness is generally 89% to 93%, and very few products can reach 95%;
Light calcium products have high purity, so the whiteness is generally 92% to 95%, and some products can reach 96% to 97%.
5. Moisture content
The moisture content of heavy calcium products is generally 0.2% to 0.3%. The moisture content is relatively low and relatively stable. The moisture content of some high-end products can even reach about 0.1%;
Ordinary light calcium products have a moisture content of 0.3% to 0.8%, which sometimes fluctuates and is unstable.
6. Particle shape
The characteristics of heavy calcium powder are: irregular particle shape, and the particles have certain edges and corners, and the surface is rough; the particle size difference is large, the particle size distribution is wide, and the particle size is large. Crushing and refining will not change the crystal form of heavy calcium.
The characteristics of light calcium powder are: the particles have regular shape and can be regarded as monodisperse powder; the particle size distribution is narrow.
7. Taste
Due to the incomplete reaction of calcium oxide, light calcium has a residual lime taste, which will cause a choking taste when filling biscuits; heavy calcium does not.
8. Particle size
The particle size of heavy calcium products ranges from 0.5 to 45 μm. According to its original average particle size (d), it is divided into: coarsely ground calcium carbonate (d >3μm), finely ground calcium carbonate (d =1~3μm), ultrafine carbonate Calcium (d =0.5～1μm);
According to its original average particle size (d), light calcium can be divided into: micron calcium carbonate (d >5μm), micron powder calcium carbonate (d =1~5μm), fine calcium carbonate (d =0.1~1μm), ultrafine calcium carbonate (d =0.02～0.1μm), ultrafine calcium carbonate (d <0.02μm).
9. Settlement volume
The sedimentation volume is the volume of unit mass of calcium carbonate after shaking in 100 mL of water and letting it stand for 3 hours.
The larger the sedimentation volume, the smaller the product particle size, the lighter the density, and the higher the product grade.
The sedimentation volume of heavy calcium is 1.1~1.4mL/g;
The settling volume of light calcium is 2.4-2.8mL/g, and the settling volume of nano-light calcium is 3.0-4.0mL/g.
10. Specific surface area
The specific surface area of ordinary heavy calcium is generally about 1m2/g, and the specific surface area of heavy fine calcium carbonate is 1.45~2.1m2/g;
The specific surface area of ordinary light calcium is generally about 5m2/g, and the specific surface area of light and fine calcium carbonate is 27~87m2/g.
11. Liquidity
From the perspective of fluidity, the microstructure of light calcium is a spindle shape, and its own oil absorption value is relatively large, which can absorb components in the formula that promote flow such as lubricants, plasticizers, coupling agents, dispersants, etc. Therefore, its fluidity is not as good as heavy calcium. Generally, adding more than 25 parts will seriously affect the fluidity.
12. Price
The processing of heavy calcium is mainly achieved through mechanical crushing and grinding;
The production of light calcium is made through chemical reaction precipitation. The latter process is much more complicated than the former, and the requirements are correspondingly much stricter. Therefore, heavy calcium with the same particle size is about 30% cheaper than light calcium. If the performance allows It is more economical and cheaper to choose heavy calcium.
13. Modification function
Heavy calcium has better tensile strength, the processing fluidity of heavy calcium plastic is better, and the performance of heavy calcium filled plastic with smaller particle size is also better;
Light calcium has better impact strength and rigidity. Generally, plastics made with light calcium have a smoother surface and lower density.
14. Color and light controllability
Hue is the main hue of a color, while chromatic light is the afterglow of a color. Powders with different crystal forms have different hues. Calcium carbonate has three different crystal forms, so it also has different hues.
15. pH value
The pH value of heavy calcium is 8-9;
The pH value of light calcium is 9-10.
16. Comparison of mineral economics
Powder preparation cost: Conventional costs are equivalent and at the same competitive level, but if additional environmental control costs and resource waste rates are added, the expansion cost of light calcium is higher than that of heavy calcium.
17. Application performance
Heavy calcium: Mainly used in papermaking, rubber and plastics industries, the filling amount is generally large, mainly used as a volume filler to reduce the manufacturing cost of applied products;
Light calcium: It has a relatively wide range of application areas. The main application areas are plastics, rubber, coatings, adhesives, cigarette papers, inks, etc., mainly for volume filling, and nano calcium carbonate products are often used as modifications or reinforcements during the application process. When using other functional fillers, the filling amount is generally smaller.