At present, the main industrial calcium carbonate products on the market are light calcium carbonate (PCC) and heavy calcium carbonate (GCC), which not only have certain similarities in mineralogical characteristics, but also partially overlap in their application fields. For example, in about 90% of cases, 5-0.1 μ m ultrafine heavy calcium carbonate and light calcium carbonate can be replaced by each other. Therefore, the problem of distinguishing between light calcium carbonate and heavy calcium carbonate has always troubled most users. Today, Powder Technology Network will introduce their differences from 12 aspects such as production mode, oil absorption value, particle shape, and application performance.
1. Production mode
(1) Heavy calcium carbonate is mainly made of natural minerals such as calcite, marble, limestone, chalk, White Marble, etc. as raw materials, which are mechanically grinded and processed into powder materials;
(2) Light calcium carbonate is mainly a powder material obtained from limestone through processes such as calcination, digestion, carbonization, dehydration, drying, and grading.
2. Bulk density
The most obvious difference between heavy calcium carbonate and light calcium carbonate is the difference in product bulk density.
The bulk density of heavy calcium carbonate products is relatively high, generally ranging from 0.8 to 1.3 g/cm3
The bulk density of lightweight calcium carbonate products is relatively small, usually 0.5-0.7g/cm3, and some nano calcium carbonate products can even reach a bulk density of about 0.28g/cm3.
3. Settlement volume
The settling volume is the volume of a unit mass of calcium carbonate shaken in 100mL (milliliters) of water and allowed to settle for 3 hours (hours). The larger the settlement volume, the smaller the particle size, lighter the density, and higher the product grade.
The settling volume of heavy calcium carbonate is 1.1-1.4mL/g;
The settling volume of light calcium carbonate is 2.4-2.8mL/g, and the settling volume of nano light calcium carbonate is 3.0-4.0mL/g.
4. Specific surface area
The average particle size of calcium carbonate is inherently related to its specific surface area, and the size of the average particle size can be accurately determined by its specific surface area.
The specific surface area of ordinary heavy calcium carbonate is generally around 1m2/g, while the specific surface area of heavy fine calcium carbonate is 1.45-2.1m2/g
The specific surface area of ordinary light calcium carbonate is generally around 5m2/g, while the specific surface area of light fine calcium carbonate is 27-87m2/g
5. Oil absorption value
In practical applications, most fillers use the oil absorption value as an indicator to roughly predict the demand for resin, which has important guiding significance for selecting fillers
(1) Due to its large particles, smooth surface, and small specific surface area, heavy calcium carbonate has a lower oil absorption value, generally around 40-60mL/100g
(2) Light calcium carbonate particles are fine and have a rough surface, with a large specific surface area, resulting in a high oil absorption value, generally around 60-90mL/100g
6. Whiteness
Due to the relatively high amount of impurities, the whiteness of heavy calcium carbonate products is generally 89% to 93%, and a very small number of products can reach 95%
Light calcium carbonate products have high purity, so the whiteness is generally 92% to 95%, and some products can reach 96% to 97%
7. Moisture content
The moisture content of heavy calcium carbonate products is generally 0.2% to 0.3%, which is relatively low and stable. Some high-end products even have a moisture content of about 0.1%
Ordinary lightweight calcium carbonate products have a moisture content of 0.3% to 0.8%, sometimes with some fluctuations and instability
8. Particle size
The particle size of heavy calcium carbonate products ranges from 0.5 to 45 μ m. According to their original average particle size (d), they are divided into coarse ground calcium carbonate (>3 μ m), fine ground calcium carbonate (1-3 μ m), and ultrafine calcium carbonate (0.5-1 μ m). The smaller the particle size of the product, the higher the price. Currently, there is no industrialized production of nanoscale heavy calcium carbonate, and only a very small amount of particles with a particle size of about 100nm are contained in some micro calcium products.
The particle size of ordinary light calcium carbonate products is generally 0.5-15 μ m, and the particle size of nano calcium carbonate is generally 20-200nm. Light calcium carbonate can be divided into: micro particle calcium carbonate (>5 μ m), micro particle calcium carbonate (1-5 μ m), micro particle calcium carbonate (0.1-1 μ m), ultrafine calcium carbonate (0.02-0.1 μ m), and ultrafine calcium carbonate (<0.02 μ m) according to its original average particle size (d).
9. Particle shape
The characteristics of heavy calcium carbonate powder are: irregular particle shape, with certain edges and rough surface; There is a significant difference in particle size, a wide distribution of particle size, and a larger particle size. Crushing and refining will not change the crystal structure of heavy calcium carbonate. Generally, heavy calcium carbonate in calcite is hexagonal, and heavy calcium carbonate in marble is cubic, which is mainly related to the place of origin
The powder characteristics of lightweight calcium carbonate are: regular particle shape, which can be regarded as monodisperse powder; The particle size distribution is relatively narrow. According to the different grain shapes, lightweight calcium carbonate can be divided into spindle shaped, cubic shaped, needle shaped, chain shaped, spherical, flake shaped, and diamond shaped.
(1) Spindle shaped calcium carbonate is the most common crystal form in light calcium carbonate, with an average long axis particle size of 5-12 μ m and an average short axis particle size of 1-3 μ m
(2) The average particle size of needle shaped calcium carbonate is 0.01-0.1 μ m, and the average aspect ratio is 5-100
(3) The average particle size of chain calcium carbonate is 0.01-0.1 μ m, and the average aspect ratio is 10-50 μ m
(4) The average particle size of spherical calcium carbonate is 0.03-0.05 μ m
(5) The average particle size of cubic calcium carbonate is 0.02-0.1 μ m
(6) The average particle size of flaky calcium carbonate is 1-3 μ m
10. Taste
For food grade calcium carbonate, product taste is also one of the important indicators. Light calcium carbonate has a residual lime flavor due to incomplete calcium oxide reaction, which can cause a choking taste when filling cookies, while heavy calcium carbonate does not
11. Comparison of Mineral Economics
Preparation cost of powder: The conventional cost is comparable and at the same competitive level, but if additional environmental control costs and resource waste rates are added, the expansion cost of light calcium carbonate is higher than that of heavy calcium carbonate
Environmental balance: The production of heavy calcium carbonate produces no 'three wastes' emissions except for noise, making it easy to coordinate and regulate the environment; The production of lightweight calcium carbonate emits 'three wastes', especially combustion exhaust gas, resulting in low overall environmental balance
Resource utilization rate: Heavy calcium carbonate is easy to comprehensively utilize mineral resources, while light calcium carbonate is difficult to control the rational utilization rate of mineral resources based on its chemical processing ability.
12. Application performance
In the application process, heavy calcium carbonate products are mainly used in industries such as papermaking, rubber, and plastics, with generally large filling amounts. They are mainly used as volumetric fillers to reduce the manufacturing cost of application products
Lightweight calcium carbonate products have a relatively wide range of applications, mainly in plastics, rubber, coatings, adhesives, cigarette paper, inks, etc., with volume filling as the main method. However, nano calcium carbonate products are often used as functional fillers for modification or reinforcement in the application process, and the filling amount is generally small. Light calcium carbonate products
(1) Papermaking: After promoting neutral sizing in papermaking, the demand for calcium carbonate has increased dramatically. However, lightweight calcium carbonate has a high oil absorption value and consumes a large amount of sizing, which can damage the sizing effect; In addition, light calcium carbonate has strong water retention, and when added to machine paper, the paper strength is relatively poor compared to heavy calcium carbonate.
But for the production of cigarette paper, light calcium carbonate is superior to heavy calcium carbonate. Both domestically and internationally, lightweight calcium carbonate is the main type of calcium carbonate used in cigarette paper, especially spindle shaped lightweight calcium carbonate. Due to its crystal shape, the particles are stacked and crossed together, creating a bridging effect. It is relatively loose and beneficial for the air permeability, opacity, and whiteness of the finished paper, making it the best choice for high-end cigarette paper calcium carbonate.
(2) Plastic: Ordinary lightweight calcium carbonate, due to its high oil absorption value, appears too light to be added to some plastics, making mixing difficult and increasing the amount of addition difficult. It can only be used as a general additive. Therefore, heavy calcium carbonate is commonly used in plastic woven products, pipes, injection molded or hollow products.
(3) Rubber: Lightweight calcium carbonate, due to its small particle size and large settling volume, can increase the volume of rubber, improve its vulcanization performance, and play a semi reinforcing or reinforcing role.
(4) Others: In areas such as architectural coatings, putty, felt packaging, and feed, heavy calcium carbonate is mainly used due to its coarser particle size meeting the requirements.
