Light calcium carbonate with different morphologies

Release date:2017-05-11 Author:亿欣公司 Click:

China Powder Network News Commonly known as: calcium carbonate, limestone, stone powder, marble, etc. White solid, tasteless, odorless. There are two forms of amorphous and crystalline. Calcium carbonate is classified into heavy calcium carbonate and light calcium carbonate depending on the method of producing calcium carbonate.

One. Heavy calcium carbonate vs. light calcium carbonate

Heavy calcium carbonate	Light calcium carbonate
It can be obtained by mechanically pulverizing natural calcite, limestone, chalk, shells, etc. by mechanical means (using Raymond mill or other high pressure mill).	Limestone and other raw materials are calcined to form lime and carbon dioxide, and then water is digested to form lime milk, which is then passed into carbon dioxide carbonized lime milk to form calcium carbonate precipitate, and finally dehydrated, dried and pulverized.
Low whiteness	High whiteness (national standard 90 or above)
Bulk density is 0.8~1.3g/cm3	Bulk density 0.5~0.7g/cm3
Irregular form, amorphous	Crystalline, orthorhombic and hexagonal
Large particle size, minimum micron	Small particle size, can be nanoscale
Heavy calcium products have low moisture and are also relatively stable, generally 0.2 to 0.3%. Some high-grade heavy calcium products can even reach 0.1%.	Light calcium products generally have a moisture content of 0.3 to 0.8%, and the water stability is poor, and sometimes there is a certain fluctuation.

Crystalline type of light calcium carbonate

晶型	方解石	文石型	球霰石
晶系	六方晶系	六方晶系	斜方晶系

Second, the preparation of light calcium carbonate

1. Preparation of light calcium carbonate by carbonization

Traditional light CaCO3 production process The traditional production process of light calcium carbonate is based on limestone, which is calcined at over 900 °C to produce quicklime and release CO2. The carbonized calcium carbonate can be further divided into an intermittent bubbling carbonization method, a multi-stage bubble carbonization method, a continuous spray carbonization method, and a supergravity carbonization method. Its general production process is:

The main chemical reactions are:

Limestone calcination: CaCO3→CaO+CO2

Lime reacts with water to form hydrated lime: CaO+H2O→Ca(OH) 2

CO2 reacts with slaked lime to form light calcium carbonate: Ca(OH)2+CO2→CaCO3+H2O

2. Steel slag produces light calcium carbonate

The process of producing light calcium carbonate by steel slag acetic acid method is as follows: acetic acid medium extracts calcium ions from steel slag, silicon removal, CO2 dissolution and carbonation reaction, pure calcium carbonate precipitation formation and filtration separation. The main chemical reactions are as follows:

Extraction of steel slag from acetic acid medium: CaSiO3+2CH3COOH → Ca2++2CH3COO-+SiO2+H2O

Alkalinization with sodium hydroxide: Ca(CH3COO)2+2NaOH → 2CH3COONa+Ca(OH)2

Carbonization reaction : Ca(OH)2+CO2 → CaCO3+H2O

three. Reaction conditions determine the morphology and use of light calcium carbonate

The morphology of light calcium carbonate has a spindle shape, a cuboid shape, a needle shape, a chain shape, a spherical shape and a sheet shape. These different shapes of calcium carbonate can be prepared by controlling the reaction conditions.

(1) PH and reaction temperature have a decisive influence on the morphology of light calcium carbonate particles.

(2) Molar ratio and crystal form controlling agent affect the morphology of spherical light calcium carbonate

At <40 ° C, spherical calcite calcium carbonate particles can be obtained by adding 0.8 mole of hydrogen peroxide per mole of calcium hydroxide to the calcium hydroxide suspension and then carbonizing with a carbon dioxide-containing gas. When carbon dioxide is used to carbonize the lime emulsion, NH2CH2CH2OH is added to obtain spherical light calcium carbonate having a uniform particle size distribution.

Light calcium carbonate use with different morphologies

Calcium carbonate is one of the most widely used inorganic fillers. Light calcium carbonate is widely used in rubber, paint, plastics, paper, toothpaste, cosmetics, ink and so on because of its higher stability and small and uniform particle size distribution. In the field of adhesives and the like.

(1) Spindle-shaped light calcium carbonate

Improve the yield, improve the anti-wear performance and wet end yield of the papermaking; similar to microfibers give paper excellent properties such as bulkiness, writing, opacity, retention, smoothness, printability and so on. It can also be used in rubber, plastics, paint sealants, pressure sensitive adhesives, etc.

(2) cubic light calcium carbonate

High whiteness and opacity in paper; plastic filler improves the electrical properties, flame retardancy, impact resistance and processing characteristics of plastic products; rubber filler replaces white carbon black, making the surface of the product bright, long-term, strong tensile It is resistant to bending and cracking and is an excellent white reinforcing filler.

(3) Needle-like light calcium carbonate

Thermally sensitive paper with low noise, no need for ink developer, and improved whiteness, opacity, and smoothness. Acicular calcium carbonate has high whiteness, low production cost, high strength and good filling performance. It is expected to replace fiber materials such as glass and asbestos and expensive whisker materials such as potassium titanate and titanium carbide in paper, plastic, rubber and paint. The industrial sector is used in large quantities.

(4) Spherical light calcium carbonate

Papermaking: good opacity and absorption of ink. Spherical calcium carbonate can be added to the lubricating oil to greatly improve its lubricating properties. It can also be used in the production of toothpaste, cosmetics and electronic ceramics.

(5) Chain light calcium carbonate

The nano-sized chain-shaped light calcium carbonate has high activity, good dispersibility and obvious reinforcing effect. Often used as a white rubber reinforcing agent. Or mix with other fillers to achieve reinforcement, filling and other functions.

(6) flaky light calcium carbonate

It has good optical properties and printing properties, and the paper thus produced has high whiteness, brightness and shading performance. When used for coated paper coating pigments, it has good fluidity and dispersibility and exhibits better gloss and smoothness than ordinary spindle calcium carbonate, so it can replace or partially replace the increasingly scarce flaky kaolin.

four. Production Status and Prospects of Light Calcium Carbonate in China

Although there are many manufacturers of light calcium carbonate in China, the production process is backward, the variety is single, and the products are mostly spindle-shaped light calcium carbonate with low added value. The other forms of light calcium carbonate with higher added value are less, and there is still a big gap with countries such as Japan. Although the country is strongly promoting green environmental protection, the study of heavy calcium has received more attention. However, due to the backwardness of technology and equipment, it takes a certain time to produce more refined heavy calcium instead of light calcium.

In recent years, China's high-quality light calcium carbonate mainly relies on imports. With the development of major industries such as rubber, paint, plastics and inks in China, the demand for light calcium carbonate is also increasing, and the market prospect is optimistic. At the same time, different industries have different requirements for light calcium carbonate. The development of China's light calcium carbonate should move toward more refined, specialized and high-grade.