Dry goods | distinguish between heavy calcium carbonate and light calcium carbonate from 12 angles!

The 2018 Calcium Carbonate Fine Processing Application Technology Improvement and Practical Training Course will be held in Hezhou, Guangxi on November 6-8, 2018

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 have partial overlap in their application fields, such as 5-0.1 μm ultra-fine heavy calcium carbonate and light calcium carbonate can be replaced by each other in about 90% of the case.

Therefore, the distinction between light calcium carbonate and heavy calcium carbonate has been plaguing most users, and today the powder technology network introduces its differences from 12 aspects such as production mode, oil absorption value, particle shape, application performance, etc.

1. Production mode

Heavy calcium carbonate is mainly based on calcite, marble, limestone, chalk, white jade and other natural minerals as raw materials, through mechanical grinding processing of powder materials;

Lightweight calcium carbonate is mainly a powder material obtained by calcination, digestion, carbonization, dehydration, drying, grading and other processes using limestone as raw material.

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 large, generally 0.8~1.3g/cm3;

The bulk density of light calcium carbonate 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. Sedimentation volume

The sedimentation volume is the volume of calcium carbonate per unit mass after oscillation in 100mL of water and standing for 3h. The larger the sedimentation volume, the smaller the 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.

4. Specific surface area

The average particle size of calcium carbonate is intrinsically related to its specific surface area, and the average particle size can be more accurately judged by the size of 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;

The specific surface area of ordinary light calcium carbonate is generally about 5m2/g, and the specific surface area of light and 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 in the filler, that is, the oil absorption value has important guiding significance for the selection of fillers.

Due to the large particles, smooth surface and small specific surface area, the heavy calcium carbonate has a low oil absorption value, generally about 40-60mL/100g;

Lightweight calcium carbonate particles are fine, the surface is rough, the specific surface area is large, so the oil absorption value is high, generally about 60-90mL/100g.

6. Whiteness

Due to the relative number of impurities in heavy calcium carbonate, the whiteness of products is generally 89% to 93%, and very few products can reach 95%;

Lightweight calcium carbonate products have a high purity, so the whiteness is generally 92% to 95%, and some products can reach 96% to 97%.

7. Moisture content

Heavy calcium carbonate product moisture is generally 0.2% to 0.3%, the moisture content is relatively low, but also relatively stable, some high-grade product moisture can even reach about 0.1%;

Ordinary lightweight calcium carbonate products have a moisture content of 0.3% to 0.8%, sometimes with certain fluctuations and are not very stable.

8. Particle size

The particle size of heavy calcium carbonate products ranges from 0.5 to 45 μm, and is divided into crudely ground calcium carbonate (> 3 μm), finely ground calcium carbonate (1-3 μm), and ultrafine calcium carbonate (0.5-1 μm) according to its original average particle size (d). The smaller the particle size of the product, the higher the price, there is no industrial production of nano-scale heavy calcium carbonate, but in some fine calcium products contain a very small amount of particles with a particle size of about 100 nm.

The particle size of ordinary lightweight calcium carbonate products is generally 0.5 to 15 μm, and the particle size of nano calcium carbonate is generally 20 to 200 nm. According to its original average particle size (d), light calcium carbonate can be divided into: micro-particle calcium carbonate (>5 μm), micro-powdered calcium carbonate (1-5 μm), fine calcium carbonate (0.1-1 μm), ultra-fine calcium carbonate (0.02-0.1 μm), ultra-fine calcium carbonate (<0.02 μm).

9. Particle shape

The powder characteristics of heavy calcium carbonate are: the particle shape is irregular, and the particles have certain edges and angles, and the surface is rough; the particle size difference is large, the particle size distribution is wider, and the particle size is larger. Crushing and refinement will not change the crystal form of heavy calcium carbonate, generally calcite heavy calcium carbonate is hexagonal crystalline, marble heavy calcium carbonate is cubic crystal form, mainly related to the place of origin.

The powder of light calcium carbonate is characterized by a regular particle shape and can be regarded as a monodisperse powder, and a narrow particle size distribution. According to the shape of the grain, lightweight calcium carbonate can be divided into spindle shape, cubic, needle, chain, spherical, flake and diamond shape.

Spindle-shaped calcium carbonate is the most common crystal shape in light calcium carbonate, with an average major shaft particle size of 5-12 μm and an average short shaft particle size of 1-3 μm;

The average particle size of needle-shaped calcium carbonate is 0.01-0.1 μm, and the average length-to-diameter ratio is 5-100;

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

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

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

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

10. Taste

For food grade calcium carbonate, product taste is also one of the important indicators. Light calcium carbonate due to the incomplete calcium oxide reaction, residual lime flavor, such as filled biscuits will have a choking taste, while heavy calcium carbonate does not.

11. Comparison of mineral economics

Powder preparation cost: the conventional cost is comparable, at the same level of competition, but if the additional environmental control cost and resource waste rate, the light calcium carbonate expansion cost is higher than that of heavy calcium carbonate;

Environmental balance: in addition to noise, there is no "three wastes" emissions in the production of heavy calcium carbonate, and the environment is easy to coordinate and control; the production and emission of light calcium carbonate emissions "three wastes", especially combustion waste gas, the total environmental balance is low.

Resource utilization rate: Heavy calcium carbonate is easy to comprehensive utilization of mineral resources, and light calcium carbonate is not easy to control the reasonable utilization rate of mineral resources by virtue of chemical processing capacity.

12. Application performance

In the application process, heavy calcium carbonate products are mainly used in papermaking, rubber and plastics and other industries, and the filling volume is generally large, mainly as a volumetric filler, reducing the manufacturing cost of the application product.

Lightweight calcium carbonate products are relatively widely used, the main application areas are plastics, rubber, coatings, adhesives, cigarette paper, inks, etc., mainly for volume filling, while nano calcium carbonate products are often used as functional fillers such as modification or reinforcement in the application process, and the filling amount is generally less. Lightweight calcium carbonate products

(1) Papermaking: After the promotion of neutral sizing in papermaking, the demand for calcium carbonate has increased sharply, but the lightweight calcium carbonate has a damage to the sizing effect due to its high oil absorption value and large rubber consumption; in addition, the lightweight calcium carbonate has strong water retention, and the paper strength is poor compared to the heavy calcium carbonate.

However, in the production of cigarette paper, light calcium carbonate is superior to heavy calcium carbonate. Calcium carbonate for cigarette paper at home and abroad is mainly based on light calcium carbonate, especially spindle-shaped light calcium carbonate, because its crystal shape determines the accumulation of particles, crossed together, will produce a bridging effect, more loose, the breathability, opacity, whiteness of the paper are more favorable, is the best choice for high-grade cigarette paper with calcium carbonate.

(2) Plastic: ordinary lightweight calcium carbonate due to the high oil absorption value, in some plastics to add appear too light, mixing has certain difficulties, increase the amount of addition is more difficult, can only be used as a general incremental agent. Therefore, in plastic products, pipes, injection molding or hollow products, heavy calcium carbonate is commonly used.

(3) Rubber: Lightweight calcium carbonate due to small particle size, large sedimentation volume, can increase the volume of rubber, improve rubber vulcanization performance, play a semi-reinforcing or reinforcing role.

(4) Others: In architectural coatings, putty, felt layer packaging, feed, etc., due to the coarser particle size to meet the needs, therefore, the main use of heavy calcium carbonate.

2018 Calcium carbonate fine processing application technology improvement and practical training course

November 6-8, 2018 Hezhou, Guangxi

Training Outline:

1. Clean production technology of calcium carbonate powder

2. Fine processing and preparation technology of calcium carbonate powder

3. Development and application of surface modification technology of calcium carbonate powder

4. Application technology of calcium carbonate powder in organic polymer materials

5. Practice of calcium carbonate fine processing technology

Source: Powder Technology Network