The difference between light calcium carbonate and heavy calcium carbonate_Industrial additives

At present, the main industrial calcium carbonate products on the market are light calcium carbonate (PCC) and heavy calcium carbonate (GCC). The two not only have certain similarities in mineralogy characteristics, but also have some application fields. Overlap, for example, 5-0.1μm ultra-fine heavy calcium carbonate and light calcium carbonate can replace each other in about 90% of cases. Therefore, the distinction 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 method, oil absorption value, particle shape, and application performance.

The difference between light calcium carbonate and heavy calcium carbonate 1. Production method

Heavy calcium carbonate is mainly a powder material obtained by mechanical grinding and processing of natural minerals such as calcite, marble, limestone, chalk, white marble, etc.; light calcium carbonate is mainly made of limestone as raw material, which is calcined, Powder materials obtained through digestion, carbonization, dehydration, drying, classification and other processes.

The difference between light calcium carbonate and heavy calcium carbonate 2. Bulk density

The difference in product bulk density is the most obvious difference between heavy calcium carbonate and light calcium carbonate. The bulk density of heavy calcium carbonate products is relatively large, generally 0.8-1.3g/cm³; the bulk density of light calcium carbonate products is relatively small, generally 0.5-0.7g/cm ³, the bulk density of some nano-calcium carbonate products can even reach about 0.28g/cm³.

The difference between light calcium carbonate and heavy calcium carbonate 3. 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 carbonate is 1.1-1.4mL/g; the sedimentation volume of light calcium carbonate is 2.4-2.8mL/g, and the sedimentation volume of nano-light calcium carbonate is 3.0-4.0mL/g.

The difference between light calcium carbonate and heavy calcium carbonate 4. Specific surface area

The average particle size of calcium carbonate is intrinsically related to its specific surface area. The average particle size can be judged more accurately by its specific surface area. The specific surface area of ​​ordinary heavy calcium carbonate is generally about 1m²/g, and the specific surface area of ​​heavy fine calcium carbonate is 1.45~2.1m²/g; ordinary light carbonate The specific surface area of ​​calcium is generally about 5m²/g, and the specific surface area of ​​light and fine calcium carbonate is 27 to 87m²/g.

The difference between light calcium carbonate and heavy calcium carbonate 5. Oil absorption value

In practical applications, most fillers use the oil absorption value to roughly predict the filler’s demand for resin picolinate chromium, that is, the oil absorption value has important guiding significance for the selection of fillers. Heavy calcium carbonate has large particles, smooth surface, and small specific surface area, so its oil absorption value is low, generally around 40-60mL/100g; light calcium carbonate has fine particles, rough surface, and large specific surface area, so its oil absorption value is high. , generally around 60-90mL/100g.

The difference between light calcium carbonate and heavy calcium carbonate 6. Whiteness

Due to relatively large amounts of impurities, heavy calcium carbonate products generally have a whiteness of 89% to 93%, and very few products can reach 95%; light calcium carbonate products have higher purity, so the whiteness is generally 92 %～95%, some products can reach 96%～97%.

The difference between light calcium carbonate and heavy calcium carbonate 7. Moisture content

The moisture content of heavy calcium carbonate 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%; the moisture content of ordinary light calcium carbonate products is 0.3% to 0.8 %, sometimes there will be certain fluctuations and it is not very stable.

The difference between light calcium carbonate and heavy calcium carbonate 8. Particle size

The particle size of heavy calcium carbonate products ranges from 0.5 to 45 μm. According to its original average particle size (d), it is divided into: coarsely ground calcium carbonate (>3μm), finely ground calcium carbonate (1-3μm), ultra-thin calcium carbonate Fine calcium carbonate (0.5-1μm). The smaller the particle size of the product, the higher the price. Currently, there is no industrially produced nano-sized heavy calcium carbonate, but some fine calcium products contain a very small amount of particles with a particle size of about 100nm.

The particle size of ordinary light calcium carbonate products is generally 0.5~15μm, and the particle size of nano calcium carbonate is generally 20~200nm. Light calcium carbonate can be divided into: micron calcium carbonate (>5μm), micronized calcium carbonate (1-5μm), fine calcium carbonate (0.1-1μm), ultrafine calcium carbonate (0.02-1μm) according to its original average particle size (d). 0.1μm), ultrafine calcium carbonate (<0.02μm).

The difference between light calcium carbonate and heavy calcium carbonate 9. Particle shape

The characteristics of heavy calcium carbonate 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 carbonate. Generally, calcite heavy calcium carbonate is in the hexagonal crystal form, and marble heavy calcium carbonate is in the cubic crystal form, which is mainly related to the place of origin. The characteristics of light calcium carbonate powder are: the particles have regular shape and can be regarded as monodisperse powder; the particle size distribution is narrow. According to the shape of the crystal grains, light calcium carbonate can be divided into spindle-shaped, cubic, needle-shaped, chain-shaped, spherical, flaky and rhombus-shaped.

Spindle-shaped calcium carbonate is the most common type of light calcium carbonate.The seed crystal form has an average long-axis particle size of 5-12 μm and an average short-axis particle size of 1-3 μm;

The average particle size of acicular calcium carbonate is 0.01-0.1μm, and the average aspect ratio is 5-100;

The average particle size of chain calcium carbonate is 0.01-0.1μm, and the average aspect ratio is 10-50;

The average particle size of spherical calcium carbonate is 0.03-0.05μm;

The average particle size of cubic calcium carbonate is 0.02-0.1μm;

The average particle size of flake calcium carbonate is 1-3μm.

The difference between light calcium carbonate and heavy calcium carbonate 10. Taste

For food-grade calcium carbonate, product taste is also one of the important indicators. Due to the incomplete reaction of calcium oxide, light calcium carbonate has a residual lime taste. It will have a choking taste when filling biscuits, while heavy calcium carbonate does not.

The difference between light calcium carbonate and heavy calcium carbonate 11. 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 carbonate is higher than that of heavy calcium carbonate; environmental balance: heavy calcium carbonate In addition to noise, production has no “three wastes” emissions, and the environment is easy to coordinate and control; the production of light calcium carbonate emits “three wastes”, especially combustion exhaust gas, and the overall environmental balance is low. Resource utilization rate: Heavy calcium carbonate is easy to comprehensively utilize mineral resources, while light calcium carbonate is difficult to control the reasonable utilization rate of mineral resources due to its chemical processing capabilities.

The difference between light calcium carbonate and heavy calcium carbonate 12. Application performance

During the application process, heavy calcium carbonate products are mainly used in industries such as papermaking, rubber and plastics. The filling amount is generally larger and is mainly used as a volume filler to reduce the manufacturing cost of applied products. Light calcium carbonate products have a relatively wide range of applications. The main application areas are plastics, rubber, coatings, adhesives, cigarette papers, inks, etc., mainly for volume filling, while nano calcium carbonate products are often used as modifications during the application process. Functional fillers such as sex or reinforcement are used, and the filling amount is generally small.

(1) Papermaking: After the promotion of neutral sizing in papermaking, the demand for calcium carbonate has increased sharply. However, light calcium carbonate has high oil absorption value and large glue consumption, which damages the sizing effect; in addition, light carbonate Calcium has strong water retention and is added to machine paper. The strength of the paper is poor compared to heavy calcium carbonate.

But for the production of cigarette paper, light calcium carbonate is better than heavy calcium carbonate. Calcium carbonate used in cigarette paper at home and abroad is mainly light calcium carbonate, especially spindle-shaped light calcium carbonate. Because its crystal shape determines the accumulation and intersection of particles, it will produce a bridging effect and is relatively loose, which is detrimental to the quality of the paper. The air permeability, opacity and whiteness are all favorable, making it the best choice for calcium carbonate for high-end cigarette paper.

(2) Plastics: Due to its high oil absorption value, ordinary light calcium carbonate is too light to be added to some pyridine dicarboxylic acid plastics, making it difficult to mix. It is difficult to increase the amount of addition, so it can only be added generally. Dosage. Therefore, heavy calcium carbonate is commonly used in plastic products, pipes, injection molding or hollow products.

(3) Rubber: Due to its small particle size and large settlement volume, light calcium carbonate can increase the volume of rubber, improve the vulcanization performance of rubber, and play a semi-reinforcing or reinforcing role.

(4) Others: In terms of architectural coatings, putty, felt packaging, feed, etc., since coarser particle size meets the needs, heavy calcium carbonate is mainly used.