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Yuan Lei tells you about the preparation method and main application fields of calcium carbonate whiskers.

Release time:

2024-01-29 09:35

 

Yuan Lei tells you about the preparation method and main application fields of calcium carbonate whiskers.

 

Calcium carbonate whisker is generally a wide range of sources, low-cost limestone as raw material, through a simple process made at low temperature, low production cost, whisker performance is outstanding, non-toxic and harmless, is a new type of whisker material with better cost performance, has good prospects for development.

 

1. Preparation method of calcium carbonate whisker

The main preparation methods of calcium carbonate whiskers are as follows: double decomposition reaction method, urea hydrolysis method, carbonization method, calcium bicarbonate heating decomposition method, etc.

 

 

(1) metathesis reaction method

The double decomposition reaction method is through the slow mixing of soluble calcium salt and carbonate, under certain temperature conditions, so that the two slow decomposition reaction to generate calcium carbonate whiskers. The commonly used calcium salt is calcium chloride, and the carbonate is sodium carbonate or potassium carbonate.

Features: The advantages of preparing calcium carbonate whiskers by this double decomposition method are that the prepared whiskers have high purity, good whisker morphology and smooth crystal surface; the disadvantage is that the concentration of the added reactants is too low, so the yield of calcium carbonate whiskers per unit time is small. If the concentration of the soluble carbonate is increased, the purity of the aragonite-type calcium carbonate whiskers produced by the metathesis reaction is greatly reduced, and thus it is difficult to produce high-purity calcium carbonate whiskers in large yield. If the method is used to prepare calcium carbonate whiskers, it is necessary to use a specific crystal form control agent on the basis of increasing the concentration of reactants, but the prepared calcium carbonate whiskers have disadvantages such as poor aspect ratio or too long reaction time, which is difficult to achieve industrial production.

(2) Urea hydrolysis method

The principle of preparing calcium carbonate whiskers by urea hydrolysis is to use carbon dioxide gas generated by urea hydrolysis reaction as a reactant, and chemically react it with soluble calcium salts to generate calcium carbonate. In the reaction process, the reaction conditions such as temperature and pressure need to be controlled. Because the growth of aragonite calcium carbonate crystals needs to be carried out at a lower degree of supersaturation, it is necessary to control the rate of urea hydrolysis in the process of preparing whiskers by urea hydrolysis, and then control the CO2The rate of gas participation in the reaction reduces the supersaturation of calcium carbonate in the system to prepare aragonite whiskers with higher purity. Urea hydrolysis method needs to control the reaction conditions of the most important is the rate of urea hydrolysis.

Features: The urea hydrolysis method releases carbon dioxide slowly by controlling the urea hydrolysis rate, so the prepared whiskers have a relatively high purity, and also have the advantages of simple operation and easy preparation. However, this method also has disadvantages. On the one hand, it is necessary to control the reaction conditions, such as preparing high-purity whiskers under high temperature and high pressure conditions, which means high cost. On the other hand, the above review shows that the preparation of calcium carbonate whiskers requires a long reaction time, a long production cycle, and also increases the continuous cost of high temperature and high pressure. These aspects show that this method is not suitable for industrial production.

(3) calcium bicarbonate heating decomposition method

The heating decomposition method of sodium bicarbonate is a method of preparing calcium carbonate whiskers by decomposing calcium bicarbonate solution. Of course, it is necessary to prepare calcium bicarbonate solution first, and then it is heated and decomposed. In this process, the stability of calcium bicarbonate solution is the most important factor, otherwise it will easily lead to the failure of the experiment.

Features: The calcium carbonate whiskers prepared by this method have high purity and large aspect ratio, but the uniformity is relatively poor. At the same time, the concentration of reactants is too low, the reaction conditions are harsh, and the preparation cost is too high, so it is difficult to realize industrial production.

(4) Carbonization method

The carbonization method is to pass carbon dioxide gas into Ca(OH) at a certain rate.2A method of preparing calcium carbonate whiskers in suspension. But because the thermodynamics of calcite is more stable, CO2with Ca(OH)2The reaction has a tendency to form a calcite phase, and therefore, in general, the use of this method requires the addition of a crystal form control agent, typically a magnesium compound and a soluble phosphate, as crystal form control agents, to the system at the beginning of the carbonization reaction.

Features: The advantages of preparing calcium carbonate whiskers by carbonization method are simple preparation process and low production cost, but its disadvantages are also that the concentration of reactants needs to ensure the low supersaturation of the generated calcium carbonate, thus resulting in low production efficiency, and the addition of crystal type control agent may lead to the introduction of impurities, affecting the purity of the prepared whiskers, especially when the crystal type control agent cannot be recycled, it will lead to environmental pollution and waste of resources.

In the double decomposition reaction method, urea hydrolysis method, sodium bicarbonate heating decomposition method, carbonization method four methods,Carbonization method is the most simple production process, the lowest production cost, the most cost-effective preparation method, so industrial production is the use of carbonization method to prepare whiskers..

2. Main application fields of calcium carbonate whiskers

(1) Application of calcium carbonate whiskers in plastics

Calcium carbonate whisker has the characteristics of large aspect ratio and small crystal size, almost no dislocation, grain boundary and other defects in the general crystal, mechanical properties close to the complete crystal, so it is added to the plastic strong effect is very obvious, can effectively improve the strength, elastic modulus and other mechanical properties.

When calcium carbonate whiskers replace glass fibers filled into nylon materials, the resulting products have better surface smoothness, and this composite material can be used in the manufacture of precision plastic products.

In addition to being used as a filling material in the field of industrial manufacturing to change material properties to adapt to production, calcium carbonate whiskers also play an invaluable role in degradable plastics in the field of environmental protection. The use of calcium carbonate whiskers as a reinforcing material for degradable plastics will not cause secondary pollution to the natural environment, and can effectively reduce white pollution and protect the environment.

(2) Application of calcium carbonate whiskers in coatings

In the coating industry, calcium carbonate whiskers are widely used in water-based coatings. In water-based coatings, calcium carbonate whiskers can act as a skeleton in the coating due to their good morphology and good dispersion, giving full play to the excellent mechanical properties of calcium carbonate whiskers. The coating filled with calcium carbonate whiskers has improved gloss, better dispersion and reduced sedimentation. When calcium carbonate whiskers are used in the coating, the viscosity of the coating is significantly improved, and the thixotropy, bonding strength and storage stability are also significantly improved. In addition, due to the characteristics of calcium carbonate whiskers, it can be evenly distributed in the silica sol and emulsion solution, thereby reducing the discontinuity of the coating, and the effect is very obvious.

(3) Application of calcium carbonate whiskers in friction materials

Calcium carbonate whiskers as a filler for friction materials have been tested and applied for a long time. The high temperature resistance of calcium carbonate whiskers is good, the effect of enhancing the wear resistance of the friction material is significant, and the raw material cost is low, which meets the demand of acting as a friction material filler. Therefore, calcium carbonate whiskers are expected to replace asbestos in the field of friction materials.

(4) Application of calcium carbonate whisker in papermaking

In the paper industry, the use of granular calcium carbonate as a filling material has greatly improved the performance and printing speed of the paper, and the use of calcium carbonate whiskers as a filling material on the basis of the former, but also have a better printing adaptability, while calcium carbonate whiskers can be used as additives to produce high whiteness and better flatness of the paper. Calcium carbonate whiskers because of its special morphology and performance, the use of calcium carbonate whiskers made of paper than the use of calcite made of paper has better printability, higher strength and better retention. Therefore, due to this advantage, calcium carbonate whiskers have good development prospects in the paper industry, especially for some paper production with different uses and different needs, calcium carbonate whiskers are indispensable.

(5) Application of calcium carbonate whiskers in medical materials

Calcium carbonate whiskers are widely used in medical materials in addition to industrial manufacturing. Calcium is an indispensable element in the human body. It usually exists in the human body in the form of calcium phosphate and is the main component of bones. One can prepare artificial bone composites by filling calcium carbonate whiskers and improve the mechanical properties of the materials.

In addition, calcium carbonate whisker is also considered to be a green, non-toxic biomedical stimulant; calcium carbonate whisker in the medical field

It is also used as an active material to make a culture medium. Therefore, calcium carbonate whiskers can also shine in the medical field, and the application of calcium carbonate will also promote the development of the medical field.

Overall, the current domestic low-end calcium carbonate products market competition is very fierce, limited profit margins. With the continuous progress of calcium carbonate processing technology, calcium carbonate has changed from the original simple filler to new functional materials, and its application fields are becoming more and more extensive,Calcium carbonate whiskers, nano calcium carbonate and other high-end products will be the new trend of the future market.






























Method, calcium carbonate, preparation, material, urea, production, must be in, filling, solution

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