CN1131172C - Process for preparing nm-class calcium carbonate - Google Patents

Abstract

The present invention relates to a preparation method of nanoscale superfine calcium carbonate. Firstly, raw materials are added into water to prepare a suspension, and complexing agents and water-soluble inorganic salts are added to the suspension to control the appearance and appearance of the calcium carbonate product. Structure, and then pass in the mixed gas of carbon dioxide and air to carry out carbonization reaction, add surfactant at the same time, finally filter and dry to get the nano-calcium carbonate product of the present invention. The method of the invention has the advantages of simple process, convenient operation, low cost and stable quality, and is suitable for application by small and medium-sized enterprises. The product of the invention can be used in industries such as rubber, plastics, paint and printing ink, and can be used as a filler and a reinforcing agent for materials.

Description

A kind of preparation method of nanoscale superfine calcium carbonate

The invention relates to a preparation method of nanoscale ultrafine calcium carbonate, which belongs to the technical field of inorganic chemical industry.

As an important inorganic chemical product, calcium carbonate has the characteristics of simple production process and stable performance. It is widely used in industrial sectors such as rubber, plastics, paint, paper, ink, food, medicine, and feed. In the past, calcium carbonate was mainly used as a filler, which only played the role of increasing and reducing costs. In recent years, due to the development of ultrafine calcium carbonate preparation technology and surface treatment technology, its application range has been further expanded. For example, precipitated calcium carbonate with a particle size of 1-3 μm only acts as a compatibilizer when added to plastics or rubber, while ultrafine calcium carbonate with a particle size of 0.01-0.1 μm acts as a reinforcing agent. At present, although there are more than 100 light calcium carbonate manufacturers in my country with an annual output of nearly 2 million tons, the technology is backward and the variety is single. Basically, a simple intermittent bubbling carbonization process is adopted, and most of the products are large grains with low prices. diameter (> 2-3μm) spindle-shaped products, while the output of ultrafine calcium carbonate with a particle size of less than 0.1μm with higher added value and faster market demand growth is very small, accounting for about 2-5% of the total output. my country has started research and production of ultrafine calcium carbonate since the 1980s. In addition to spending a lot of foreign exchange to introduce several production lines, there have also been reports of domestic technology being put into production (thousands of tons per year) in recent years. The current problem is that these technologies require a huge investment of more than tens of millions, and it is difficult for small and medium-sized enterprises to adapt. At the same time, most of the existing technologies only control the morphology of calcium carbonate by adding inorganic reagents, resulting in the need for harsh synthesis conditions such as low temperature cooling, and it is difficult to guarantee product quality.

With the development of modern industrial technology, all walks of life have higher and higher requirements for light calcium carbonate, and the demand is also increasing. For example, industries such as rubber, plastics, coatings, and inks often require nano-calcium carbonate particles with a particle size of less than 0.1 μm as functional fillers. The composite materials thus prepared have good mechanical strength and wear resistance. However, due to factors such as high cost, harsh conditions, unstable performance, and the need for huge investment, the existing methods for preparing nano-calcium carbonate are difficult to promote on a large scale. Reasons were rejected. Therefore, small and medium-sized enterprises urgently need to improve product grades through technological innovation and produce high-tech products with higher added value, so that my country's rich calcium carbonate resources can be fully and rationally utilized.

At present, the large-scale industrial method of producing calcium carbonate in various countries in the world is mainly carbonization method. Usually, the _CO2- containing kiln gas generated during lime calcination is refined and purified, and then passed into milk of lime for carbonization. The disadvantage of the conventional carbonization method is that the solubility of calcium hydroxide is very small, and the size of the bubbles containing carbon dioxide is often large. Since the carbonization reaction involves a gas-liquid-solid three-phase system, the calcium ions in the solution react with carbon dioxide on the surface of the bubbles. Calcium carbonate solids are generated, so the carbonization rate is usually relatively slow, the generated calcium carbonate particles have large particle sizes and uneven distribution, and the crystal form is difficult to control. In order to prepare ultra-fine products, people often obtain calcium carbonate particles of the required shape and size by adding so-called crystal form control agents. Since the appearance of the carbonization process product is very sensitive to the external environment such as temperature, it is usually necessary to use forced cooling. To control the carbonization temperature by means, the cost is very high, and the morphology and particle size of the product fluctuate greatly.

The purpose of this invention is to propose a preparation method of nano-scale ultrafine calcium carbonate, which uses the method of adding specific additives to control each link of the carbonization reaction, so that the process is simple, the operation is convenient, the cost is low, the quality is stable, and it is suitable for small and medium-sized enterprises. .

The preparation method of the nanoscale superfine calcium carbonate that the present invention proposes, comprises the following steps:

(1) Add raw lime (calcium oxide) or calcium hydroxide to water to prepare a 5-15% suspension, add complexing agent EDTA (ethylenediaminetetraacetic acid) or its salts (such as sodium salt) to the suspension , magnesium salt, calcium salt) as the control agent of liquid phase components, its addition is 1-10% of raw material (calcium oxide or calcium hydroxide) weight.

(2) Add water-soluble inorganic salts such as sodium hexametaphosphate, magnesium chloride, zinc chloride, aluminum chloride, calcium chloride to control the morphology and structure of the calcium carbonate product, and the addition is 1-10% of the raw material weight .

(3) Under agitation, in the above-mentioned mixed phase, feed a mixed gas of carbon dioxide/air containing 15-40% carbon dioxide (its composition is similar to that of the kiln gas of an actual lime kiln) for carbonization reaction, and the ventilation rate is 3-10 liters per minute, add surfactants such as sodium dodecylbenzenesulfonate, polyvinyl alcohol, etc. that have the function of retarding the coalescence of bubbles to inhibit the formation of large bubbles, and the amount added is 1-8% of the weight of the raw material , thus controlling the absorption rate constant of carbon dioxide to be 0.7-2.5/sec. The temperature of the whole carbonization process is controlled at 15-45°C.

(4) Stop the reaction when the pH of the suspension drops to 6.5-7.5, filter and dry at 100-110° C. to obtain the nano-calcium carbonate product of the present invention.

The method of the present invention increases the concentration of soluble calcium ions in the solution by adding a complexing agent, strengthens the dissolution of calcium hydroxide and the generation process of ultrafine calcium carbonate; realizes the flexibility of calcium carbonate particles in morphology and structure by adding specific inorganic salts. Control preparation; by adding specific surfactants to prevent bubbles from coalescing, thereby increasing the gas-liquid contact surface, accelerating the carbonization rate, and promoting the formation of ultra-fine calcium carbonate particles. After adopting the above measures, the process can produce nano-products under the mild condition of 15-45°C, without the need of traditional forced cooling system, and the cost of equipment and operation is greatly reduced. The additives used in this process are cheap and easy to obtain, and most of the required equipment is conventional chemical equipment, which is easy to be used by small and medium-sized enterprises. At present, the production cost of general nano-calcium carbonate is 1500-2000 yuan/ton, and it takes about 20-30 million yuan to build a production plant with an annual output of 10,000 tons; while the production cost using this process is only 700-800 yuan/ton, It only needs 7-8 million yuan to build a production plant with an annual output of 10,000 tons, and the economic benefits are very obvious. The superfine calcium carbonate product prepared by the invention can be used in industries such as rubber, plastics, paint and printing ink, and can be used as a filler and a reinforcing agent for materials.

Description of drawings:

Fig. 1 and Fig. 2 are respectively the morphology diagram of the product prepared by the method of the present invention.

The content of the present invention will be described in detail below in conjunction with examples of implementation.

Embodiment one

Preparation concentration is 500 milliliters of the calcium hydroxide solution of 10 gram calcium oxide/100 milliliters of waters, stirring and digesting 30 minutes and leaving standstill aging, after solution temperature drops to room temperature (25 ℃), add 2 grams of EDTA sodium salt, 4 grams of magnesium chloride, Sodium dodecylbenzene sulfonate 3 grams, under stirring state, pass into the mixed gas of carbon dioxide/air containing carbon dioxide 30% and carry out carbonization reaction, and ventilation rate is 5 liters/min. During the carbonization process, the temperature of the reaction system was controlled by circulating cooling water to be 25° C. After 1 hour of reaction, the pH of the solution was reduced to 7.0, the carbonization reaction was stopped, the slurry was filtered, and 89 grams of calcium carbonate product was obtained after drying at 105° C. The morphology of the product was observed with a field emission scanning electron microscope, and it was found that the obtained calcium carbonate particles were spherical, and the average particle size was 120 nanometers. Fig. 1 represents the morphology of embodiment 1 gained product.

Embodiment two

Preparation concentration is 500 milliliters of the calcium hydroxide solution of 10 grams of calcium oxide/100 milliliters of water, stirring and digesting for 30 minutes and leaving it to stand for aging, adding 4 grams of EDTA sodium salt after the solution temperature drops to room temperature (25 DEG C), 4 grams of magnesium chloride, Sodium dodecylbenzene sulfonate 3 grams, under stirring state, pass into the mixed gas of carbon dioxide/air containing carbon dioxide 30% and carry out carbonization reaction, and ventilation rate is 5 liters/min. During the carbonization process, the temperature of the reaction system was controlled by circulating cooling water to be 25° C. After 1 hour of reaction, the pH of the solution was reduced to 7.0, the carbonization reaction was stopped, the slurry was filtered, and 89 grams of calcium carbonate product was obtained after drying at 105° C. The morphology of the product was observed with a field emission scanning electron microscope, and it was found that the obtained calcium carbonate particles were spherical, and the average particle size was 100 nanometers.

Embodiment three

Prepare 500 milliliters of milk of lime solution with a concentration of 10 grams of calcium oxide/100 milliliters of water, stir and digest for 30 minutes, then let it stand for aging, add 2 grams of EDTA, 4 grams of zinc chloride, and ten 3 grams of sodium dialkylbenzene sulfonate, under stirring state, pass into the mixed gas of carbon dioxide/air containing carbon dioxide 30% and carry out carbonization reaction, and ventilation rate is 5 liters/min. During the carbonization process, the temperature of the reaction system was controlled by circulating cooling water to be 25° C. After 1 hour of reaction, the pH of the solution was reduced to 7.0, the carbonization reaction was stopped, the slurry was filtered, and 89 grams of calcium carbonate product was obtained after drying at 105° C. The morphology of the product was observed with a field emission scanning electron microscope, and it was found that the obtained calcium carbonate particles were spherical and had an average particle size of 100 nanometers.

Embodiment four

Prepare 500 milliliters of milk of lime solution with a concentration of 5 grams of calcium oxide/100 milliliters of water, stir and digest for 30 minutes and leave to stand for aging. After the solution temperature drops to room temperature (25° C.), add 2 grams of EDTA, 4 grams of zinc chloride, ten 3 grams of sodium dialkylbenzene sulfonate, under stirring state, pass into the mixed gas of carbon dioxide/air containing carbon dioxide 30% and carry out carbonization reaction, and ventilation rate is 5 liters/min. During the carbonization process, the temperature of the reaction system was controlled by circulating cooling water to be 25° C. After 1 hour of reaction, the pH of the solution was reduced to 7.0, the carbonization reaction was stopped, the slurry was filtered, and 89 grams of calcium carbonate product was obtained after drying at 105° C. The morphology of the product was observed with a field emission scanning electron microscope, and it was found that the obtained calcium carbonate particles were spherical and had an average particle size of 80 nanometers.

Embodiment five

Prepare 500 ml of milk of lime solution with a concentration of 5 grams of calcium oxide/100 ml of water, stir and digest for 30 minutes, then let it stand for aging, add 4 grams of EDTA, 4 grams of magnesium chloride, and dodecane after the solution temperature drops to room temperature (25°C). Sodium phenyl sulfonate 3 grams, under stirring state, pass into the mixed gas of carbon dioxide/air that contains carbon dioxide 30% and carry out carbonization reaction, and ventilation rate is 5 liters/min. During the carbonization process, the temperature of the reaction system was controlled by circulating cooling water to be 25° C. After 1 hour of reaction, the pH of the solution was reduced to 7.0, the carbonization reaction was stopped, the slurry was filtered, and 89 grams of calcium carbonate product was obtained after drying at 105° C. The morphology of the product was observed with a field emission scanning electron microscope, and it was found that the obtained calcium carbonate particles were spherical and had an average particle size of 100 nanometers.

Embodiment six

Prepare 500 milliliters of milk of lime solution with a concentration of 10 grams of calcium oxide/100 milliliters of water, stir and digest for 30 minutes, then let it stand for aging, add 2 grams of EDTA, 4 grams of zinc chloride, and ten 4 grams of sodium dialkylbenzene sulfonate, under stirring state, pass into the mixed gas of the carbon dioxide/air that contains carbon dioxide 30% and carry out carbonization reaction, and ventilation rate is 10 liters/min. During the carbonization process, the temperature of the reaction system was controlled by circulating cooling water to be 25° C. After 1 hour of reaction, the pH of the solution was reduced to 7.0, the carbonization reaction was stopped, the slurry was filtered, and 88 grams of calcium carbonate product was obtained after drying at 105° C. The morphology of the product was observed with a field emission scanning electron microscope, and it was found that the obtained calcium carbonate particles were spherical and had an average particle size of 80 nanometers.

Embodiment seven

Prepare 500 milliliters of milk of lime solution with a concentration of 10 grams of calcium oxide/100 milliliters of water, stir and digest for 30 minutes, then let it stand for aging, add 2 grams of EDTA, 4 grams of zinc chloride, and ten 3 grams of sodium dialkylbenzene sulfonate, under stirring state, pass into the mixed gas of carbon dioxide/air containing carbon dioxide 30% and carry out carbonization reaction, and ventilation rate is 10 liters/min. During the carbonization process, the temperature of the reaction system was controlled by circulating cooling water to be 35° C. After 1 hour of reaction, the pH of the solution was reduced to 7.0, the carbonization reaction was stopped, the slurry was filtered, and 88 grams of calcium carbonate product was obtained after drying at 105° C. The morphology of the product was observed with a field emission scanning electron microscope, and it was found that the obtained calcium carbonate particles were spherical and had an average particle size of 80 nanometers.

Embodiment eight

Preparation concentration is 500 milliliters of the milk of lime solution of 10 grams of calcium oxide/100 milliliters of water, stirs and digests for 30 minutes and then leaves it to stand for aging, adds 2 grams of EDTA, 4 grams of zinc chloride after the temperature of the solution drops to room temperature (25°C), Vinyl alcohol 3 grams, under stirring state, pass into the mixed gas of carbon dioxide/air containing carbon dioxide 30% and carry out carbonization reaction, and ventilation rate is 10 liters/min. During the carbonization process, the temperature of the reaction system was controlled by circulating cooling water to be 35° C. After 1 hour of reaction, the pH of the solution was reduced to 7.0, the carbonization reaction was stopped, the slurry was filtered, and 88 grams of calcium carbonate product was obtained after drying at 105° C. The morphology of the product was observed with a field emission scanning electron microscope, and it was found that the obtained calcium carbonate particles were spherical and had an average particle size of 40 nanometers. Fig. 2 represents the morphology of the product obtained in embodiment eight.

Claims (1)

1, a kind of preparation method of nanoscale superfine calcium carbonate, comprises the following steps: (1) Add raw material calcium oxide or calcium hydroxide in water to prepare a suspension with a concentration of 5-15%, and add complexing agent ethylenediaminetetraacetic acid or its salts to the suspension as the control of liquid phase components agent, its addition is 1-10% of the raw material; (2) adding water-soluble inorganic salt, the addition is 1-10% of raw material weight, and described water-soluble inorganic salt is magnesium chloride or zinc chloride; (3) Under stirring state, pass into the mixed gas containing carbon dioxide 15-40% carbon dioxide and air in the above-mentioned mixed phase, the ventilation rate is 3-10 liters/minute, add the surface that has the function of retarding the coalescence of bubbles at the same time The active agent is added in an amount of 1-8% of the weight of the raw material, thereby controlling the absorption rate constant of carbon dioxide to be 0.7-2.5/second, the temperature of the entire carbonization process is controlled to be 25-45°C, and the surfactant is twelve Sodium alkylbenzene sulfonate or polyvinyl alcohol; (4) Stop the reaction when the pH of the suspension drops to 6.5-7.5, filter and dry at 100-110° C. to obtain a nano-calcium carbonate product with a size range of 80-120 nanometers.

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