CN1438279A - Method for preparing high-white ness nano calcium carbide - Google Patents
Method for preparing high-white ness nano calcium carbide Download PDFInfo
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Abstract
The invention is a method of preparing high-whiteness degree nano CaCO3. It uses limestone, CaCO3 content>98%, whiteness degree>92% as raw material, washes to calcine into CaO, then adds in the cleaned hot water to get Ca(OH)2, prepares milk of lime by purifying, the concentration 2-10%, uses the cleaned flue gas of CaCO3, calcinations as CO2 source, makes the solution of milk of lime react with CO2 in special synthesis reactor, and adds in crystal-shaped controlling agent to control the time, temperature and stirring speed of the reaction, and after the reaction is finished, makes filtration, drying and depolymerization on the solution. The whole course adopts the technique of controlling whiteness degree.
Description
Technical Field
The invention belongs to the technical field of chemical industry.
Background
The calcium carbonate has rich raw material sources and low price, and is widely applied to industries such as rubber, plastics, papermaking, coating, printing ink, medicine, daily chemical industry and the like, and the nano calcium carbonate not only retains the performance of the raw material calcium carbonate, but also has the characteristics of nano particles, so that the nano calcium carbonate is emphasized by people. The nano calcium carbonate is a product of chemically synthesized calcium carbonate with the grain size of 0-100 nm. At present, most of domestic superfine active calcium carbonate products can only reach about 100nm in particle size and have wider particle size distribution; the whiteness of the product is below 95%; the preparation method has low efficiency and long preparation process, and is difficult to meet the market demand.
Because the nano calcium carbonate has excellent performance and wide application, the research and development of a preparation method and a new product thereof are widely regarded. According to different synthesis mechanisms, the preparation method of the current nano calcium carbonate can be summarized into three types: ca (HO)2-H2O-CO2 reaction system, Ca2+ -H2O-CO 32-reaction system and Ca2+ -R-CO 32-reaction system (Ris organic medium).
The Ca (OH)2-H2O-CO2 reaction system uses Ca (OH)2 water emulsion as a calcium source and uses CO2 to carbonize to prepare CaCO 3. Ca (oh)2 is typically obtained by calcining natural calcium carbonate to lime and then digesting the lime with flue gas from the calcination of the calcium carbonate as a source of CO2 for the carbonization reaction. By controlling different reaction conditions, a plurality of varieties such as spheres, cubes, needles, sheets, chains and the like which are suitable for different industry requirements can be prepared. As the Ca (OH)2-H2O-CO2 reaction system has rich raw materials and low cost, products with various crystal shapes can be produced, and the reaction system is adopted for preparing most of the nano calcium carbonate at present. In a specific operation, a Ca (OH)2-H2O-CO2 reaction system can be divided into a batch carbonization method and a spray carbonization method according to different specific processes. The control factors for preparing the nano calcium carbonate are different with different preparation processes.
The batch carbonization method is similar to the traditional preparation method of light calcium carbonate, except that the light calcium carbonate is reacted in a bubble column, while the preparation of the nano calcium carbonate is generally reacted in a stirring reactor, and the mass transfer and heat transfer effects of a reaction system are improved by stirring. It is important to strictly control the reaction conditions, and the main control factors are Ca (HO)2 concentration, CO2 flux, reaction temperature, additive amount, additive adding time and the like. By controlling different conditions, various nano calcium carbonate products with monomer particle size (or short diameter) larger than 10nm are prepared at present, and the crystal shapes include chain, needle, spherical, cubic, flaky and the like, including all the calcium carbonate crystal shapes prepared at present. Most of these products are calcite-type crystals and a part of the spherical crystals are nepheline-type crystals, which are obtained by adding a polymer additive during the reaction. In addition, a large amount of alcohol is added to the reaction system for carbonization to obtain amorphous calcium carbonate. Due to the popularization and application of alkaline sizing in papermaking, the development of special cubic and flaky nano calcium carbonate products suitable for papermaking is paid enough attention, and more patent documents are provided in this aspect recently. The intermittent carbonization method has the advantages of low investment and easy conversion, and the research and development are more at present, most of nano calcium carbonate products can be obtained by the method, and the method is the most applied method in the current industrial production.
However, the prior art has many unsatisfactory points, which are mainly shown in the following aspects:
(1) the whiteness of the product is not high and is usually below 95%.
(2) The product has coarse and uneven granularity and wide granularity range, and the granularity range is usually 10-100 nm.
(3) The production efficiency is low, the gas-liquid contact is poor, the preparation process time is long, usually, one-time reaction needs 2-4 hours, the yield is low, and the production capacity of an enterprise is limited.
(4) The additive (granularity and crystal form control agent) is expensive and has large dosage, which leads to high product cost.
(5) The variety is single, and the market demand can not be met.
Disclosure of Invention
Aiming at the defects of the existing nano calcium carbonate preparation technology, the invention aims to provide a preparation method of high-whiteness nano calcium carbonate, which is used for preparing a nano calcium carbonate product with high whiteness, narrow particle size distribution range and uniformity; the production efficiency is improved, the carbonization reaction time is shortened, and the production capacity is improved; a cheap and less-dosage crystal form control agent is selected, so that the production cost of the nano calcium carbonate is reduced; different crystal form control agents are selected to produce the nano calcium carbonate with different shapes. The invention is characterized in that:
a special whitening process is adopted, so that the whiteness of the nano calcium carbonate product reaches more than 98 percent;
a special synthesis reaction device is adopted, so that the production efficiency and the product quality (narrow and uniform particle size distribution range) are improved, and the synthesis reaction time is shortened;
and a proper crystal form control agent is selected to control the shape and the granularity of the nano calcium carbonate product and reduce the production cost.
The invention adopts an intermittent stirring carbonization method which is simple to operate and control and easy to convert. The process flow is as follows:
the natural calcium carbonate is cleaned and then calcined into CaO at the temperature of 900-1100 ℃, then purified hot water at the temperature of 40-80 ℃ is added to be digested into Ca (OH)2, lime milk with the concentration of 2-10% is prepared through purification, flue gas generated by calcining the calcium carbonate is used as a CO2 source for carbonization reaction, lime milk solution reacts with CO2 gas in a reactor, a crystal form control agent is added, the type and the using amount of the crystal form control agent are related to the shape and the granularity of a prepared product, the initial temperature of the solution in the reaction process is controlled between 15-30 ℃, the reaction is stopped when the pH value of the solution is neutral, and the reaction time is about 30-45 min. And after the reaction is finished, filtering the solution, wherein the solid content of a filter cake is 50-60%, drying after filtering, wherein the drying temperature is 100-200 ℃ to ensure that the water content of the product is below 0.1%, and finally depolymerizing to obtain the final product.
The chemical reaction equation for preparing nano calcium carbonate by using natural calcium carbonate is as follows:
wherein, the third chemical reaction is the reaction of lime milk and carbon dioxide gas, which is carried out in a synthesis reactor, and the reaction principle of the process is as follows:
① the raw material of limestone whose calcium carbonate content is greater than 98% and whiteness is greater than92%.
② the water for digestion is purified to remove the coloring ions such as Fe3+ and Mn2+ from the tap water at 40-80 deg.C.
③ flue gas containing CO2 generated by calcium carbonate calcination needs to be purified in two or three stages to remove impurities and dust in the flue gas, the purified CO2 is compressed by an air compressor and then enters a reactor, and the pressure of the CO2 entering the reactor is 1-2 atmospheric pressures.
④ Ca (OH)2 emulsion concentration is 2-10%.
⑤ the initial temperature of the reaction is 15-30 ℃.
⑥ reaction pressure-atmospheric pressure.
⑦ crystal form control agent and amount:
cube: the use of a special synthesis equipment makes it possible to dispense with the use of a crystal form-controlling agent.
Chain shape: AlCl3, the addition amount is 0.5-2% of the weight of calcium hydroxide;
sodium citrate: the adding amount is 0.6-1.8% of the weight of the calcium hydroxide.
⑧ the reaction time is 30-45 min (related to the introduction amount of CO2 gas).
⑨ stirring speed is 400-1000 rpm.
The key points of the whiteness control technology are that ① is preferably suitable for preparing raw materials of high-whiteness nano calcium carbonate, ② adopts an electromagnetic separation technology to remove magnetic substances such as iron mixed in the preparation process of the raw materials, ③ adopts a photoelectric separation technology and equipment to remove impurities such as coal coke in a calcined limestone product, namely calcium oxide, ④ adopts a water purification technology to remove dyeing impurities of process water in the preparation process of the nano calcium carbonate, the heat preservation of lime milk is carried out in the digestion process of ⑤ and is carried out for 20-50 hours at the temperature of 30-60 ℃, ⑥ is used for controlling the drying temperature of the modified nano calcium carbonate product within the range of 100-150 ℃ to avoid the carbonization of the particle surface and influence on the whiteness of the product.
Compared with other production methods of nano calcium carbonate, the method has the following outstanding characteristics:
average particle size of cubic nano calcium carbonate: 30 to 50 nm.
Average particle size of single particles of chain-like nano calcium carbonate: 10-30 nm, length-diameter ratio: 5 to 20.
The whiteness of the product is high and reaches more than 98 percent.
The product has narrow and uniform particle size distribution range and high quality.
The high-shear particle size homogenizer is used in the synthesis reaction process, and the functions of the homogenizer mainly comprise the following aspects: firstly, Ca (OH)2 solution is uniform and dispersed; secondly, carbon dioxide gas introduced into the synthesis reactor is uniformly dispersed to form fine bubbles; thirdly, the reaction process is accelerated, and the reaction time is shortened.
The synthesis process adopts patent equipment, namely a nano calcium carbonate synthesis reactor (patent number: ZL 01241020.9). The synthesis reactor has the following characteristics: the stirring intensity is proper, uniform and stable, and the shearing force is strong; the inflation is uniform, the bubbles are fine, and the dispersibility is good; the gas utilization rate is high. The above characteristics have important influence on the synthesis process of the nano calcium carbonate.
The synthesis reaction process adopts cheap crystal form control agent (see process parameters) and the dosage is less.
The carbonization time is shortened by 4-8 times compared with the traditional process.
The shape and particle size of the product can be controlled by adjusting the kind and addition amount of the control agent as required.
Simple process, low production cost and easy industrial production.
The nano calcium carbonate produced by the invention has small particles, belongs to the nano level, has large specific surface area and high surface activity, and is widely applied to the fields of rubber, plastics, papermaking, coatings, textiles, printing ink, daily chemical industry, food, pharmacy and the like. After the nano calcium carbonate is added into the rubber, the performance indexes such as tensile strength, tearing strength, wear resistance and the like are obviously improved, and the nano calcium carbonate can partially or even completely replace the rubber compounding agent white carbon black with high energy consumption and high cost through experimental verification; after the nano calcium carbonate is used in the plastic, various performance indexes are improved, the processing performance of the plastic is improved, the extrusion speed and the impact strength of plastic processing are improved, and the function of a reinforcing agent is achieved; in the paper making industry, a large amount of nano calcium carbonate is applied in the manufacturing process of high-grade heat-sensitive paper, art coated paper and the like, so that the indexes of the nano calcium carbonate, such as whiteness, opacity, gloss, ink absorption capacity and the like, are superior to those of common paper; in the ink industry, nano calcium carbonate is widely concerned due to good stability, high gloss, no influence on the drying performance of printing ink and strong adaptability.
Drawings
The attached drawing is a process flow chart of the invention.
Detailed Description
Example 1
The raw material is selected from the inner Mongolia red peak area, the limestone sample has fine and smooth appearance, the whiteness of a product with the granularity of-325 meshes is as high as 95 percent, the content of calcium carbonate in the limestone is 98.9 percent, and the main impurities are carbonate of magnesium, manganese and iron. Calcining limestone at about 900 ℃ to generate calcium oxide, taking 80 g of calcium oxide, digesting the calcium oxide by using deionized water at the temperature of 40-80 ℃, then removing impurities from a lime milk solution, refining the lime milk solution to prepare a 6% Ca (OH)2 solution, putting the solution into a synthesis reactor, opening a high-shear particle size homogenizer, starting stirring at the stirring speed of 400rpm, introducing CO2 gas at the gas flow rate of 9.6m3/hkgCa (OH)2, controlling the reaction process at 25 ℃ by using a conductivity meter and a pH meter, finishing the reaction when the pH value of the solution is less than or equal to 7, and controlling the whole reaction time to be 35 min. The solution was filtered, dried at 120 ℃ and depolymerized to yield 105 g of product. The detection result of the product by using a transmission electron microscope shows that the crystal form of the product is cubic, and the particle size is 20-40 nm; the whiteness detection of the product shows that the whiteness of the product is 98.3.
Example 2
The crystal form control agent was added in example 1 by the following specific method: when the reaction starts, adding a crystal form control agent sodium citrate, wherein the addition amount of the crystal form control agent sodium citrate is 0.6-1.8% of the weight of calcium hydroxide; then CO2 gas is introduced to start reaction, when the conductivity of the solution is reduced for the first time and is recovered, a crystal form control agent AlCl3 is added, the addition amount is 0.5-2% of the weight of calcium hydroxide, and the other conditions are the same as example 1, so that 107 g of the product is obtained. The detection result of the product shows that the crystal form is chain-shaped nano calcium carbonate, the average particle size of single particles is 10-30 nm, and the length-diameter ratio is 5-10; the whiteness of the product is 98.4.
Example 3
Calcining limestone at about 900 ℃ to generate calcium oxide, taking 20kg of calcium oxide, digesting the calcium oxide with deionized water at 80 ℃, then removing impurities from a lime milk solution, refining the lime milk solution to prepare 8% Ca (OH)2 solution, putting the solution into a synthesis reactor, opening a high-shear particle size homogenizer, starting stirring at the stirring speed of 400rpm, introducing CO2 gas at the gas flow rate of 9.6m3/hkgCa (OH)2, and carrying out the initial reaction at 20 ℃. When the reaction starts, adding a crystal form control agent sodium citrate, wherein the addition amount of the crystal form control agent sodium citrate is 0.6-1.8% of the weight of calcium hydroxide; and then introducing CO2 gas to start a reaction, adding a crystal form control agent AlCl3 when the conductivity of the solution is reduced for the first time and recovered, wherein the addition amount is 0.5-2% of the weight of the calcium hydroxide, monitoring the reaction process by using a conductivity meter and a pH meter, finishing the reaction when the pH of the solution is neutral, and keepingthe whole reaction time at 40 min. Filtering the solution, drying at 120 ℃, depolymerizing to obtain 35kg of product, and detecting the product by using a transmission electron microscope to show that the crystal form of the product is chain-shaped nano calcium carbonate, the average particle size of single particles is 10-30 nm, and the length-diameter ratio is 5-10; the whiteness of the product is 98.1.
Claims (5)
1. A preparation method of high-whiteness nano calcium carbonate is characterized in that limestone with calcium carbonate content of more than 98% and whiteness of more than 92% is used as a raw material, the limestone is cleaned and then calcined into CaO, the calcination temperature is 900-1100 ℃, and then purified hot water with the temperature of 40-80 ℃ is added to be digested into Ca (HO)2Purifying to prepare lime milk with the concentration of 2-10%, and taking flue gas generated by calcining calcium carbonate as CO generated in carbonization reaction2Source of lime milk solution and CO in a reactor2Gas reaction, adding a crystal form control agent according to the requirements on the shape and the granularity of the prepared nano calcium carbonate, controlling the initial temperature of a solution to be 15-30 ℃ in the reaction process, controlling the reaction pressure to be normal pressure, controlling the reaction time to be 30-45 min, controlling the stirring speed to be 400-1000 rpm, filtering, drying and depolymerizing the solution after the reaction is finished, and adopting a whiteness control technology in the whole process.
2. The method for preparing high-whiteness nano calcium carbonate according to claim 1, which is characterized in that the whiteness control technology comprises the following steps:
a. preferably selecting raw materials suitable for preparing high-whiteness nano calcium carbonate;
b. removing magnetic substances such as iron and the like mixed in the raw material preparation process by adopting an electromagnetic separation technology;
c. removing impurities such as coal coke and the like in a calcined limestone product, namely calcium oxide, by adopting a photoelectric separation technology and equipment;
d. in the process of preparing the nano calcium carbonate, a water purification process is adopted to remove dyeing impurities in process water;
e. carrying out heat preservation on the lime milk in the digestion process, and carrying out heat preservation for 20-50 hours at the temperature of 30-60 ℃;
f. the drying temperature of the modified nano calcium carbonate product is controlled within the range of 100-150 ℃ so as to avoid the carbonization of the particle surface and influence on the whiteness of the product.
3. The process for preparing high-whiteness nanocalcium carbonate according to claim 1 or 2, wherein the CO is used as the carbonization reaction2The flue gas from calcium carbonate calcination needs two-stage or three-stage purification to remove impurities and dust in the flue.
4. The method for preparing high-whiteness nano calcium carbonate according to claim 1, wherein the reactor used in the method is a nano calcium carbonate synthesis reactor.
5. The method for preparing high-whiteness nanocalcium carbonate according to claim 1, wherein the type and amount of the crystal form controlling agent added during the reaction are related to the shape and particle size of the product to be prepared,
a. cube: special synthesis equipment is adopted, and a crystal form control agent is not used.
b. Chain shape: the crystal form control agent is AlCl3The adding amount is 0.5-2% of the weight of the calcium hydroxide; sodium citrate: the adding amount is 0.6-1.8% of the weight of the calcium hydroxide.
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| CN100450932C (en) * | 2006-11-24 | 2009-01-14 | 清华大学 | Nm-class calcium carbonate carbonization process |
| CN102659160A (en) * | 2012-05-02 | 2012-09-12 | 浙江省建德市正发碳酸钙有限公司 | Method for preparing low alkalinity calcium carbonate |
| CN103061202A (en) * | 2012-07-18 | 2013-04-24 | 建德市宏兴钙业有限责任公司 | Activated calcium carbonate for papermaking filler and preparation method thereof |
| CN104263014A (en) * | 2014-06-17 | 2015-01-07 | 池州市大恒生化有限公司 | Preparing method of high-purity active calcium carbonate used for coating |
| CN104261418A (en) * | 2014-10-24 | 2015-01-07 | 山西玉竹活性石灰制造有限公司 | Method for preparing microporus, high-activity and low-density calcium silicate |
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| CN110817922A (en) * | 2019-12-11 | 2020-02-21 | 合肥工业大学 | Inorganic/organic composite inducer and application thereof in induced synthesis of nano calcium carbonate |
| CN112322286A (en) * | 2020-12-10 | 2021-02-05 | 湖北理工学院 | Rare earth ion doped nano calcium carbonate luminescent material with different morphologies as well as preparation method and application thereof |
| CN113583478A (en) * | 2021-08-20 | 2021-11-02 | 乌海市创美佳新材料科技有限公司 | Preparation method of nanoscale calcium carbonate special for automobile chassis paint |
| CN113956681A (en) * | 2021-11-15 | 2022-01-21 | 亚士创能科技(上海)股份有限公司 | Tourmaline coated with calcium carbonate and preparation method and application thereof |
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2002
- 2002-03-27 CN CN 02109349 patent/CN1200049C/en not_active Expired - Fee Related
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| CN100450932C (en) * | 2006-11-24 | 2009-01-14 | 清华大学 | Nm-class calcium carbonate carbonization process |
| CN102659160A (en) * | 2012-05-02 | 2012-09-12 | 浙江省建德市正发碳酸钙有限公司 | Method for preparing low alkalinity calcium carbonate |
| CN103061202A (en) * | 2012-07-18 | 2013-04-24 | 建德市宏兴钙业有限责任公司 | Activated calcium carbonate for papermaking filler and preparation method thereof |
| CN103061202B (en) * | 2012-07-18 | 2015-08-19 | 建德市宏兴钙业有限责任公司 | A kind of activated Calcium carbonate for papermaking filler and preparation method thereof |
| CN104263014A (en) * | 2014-06-17 | 2015-01-07 | 池州市大恒生化有限公司 | Preparing method of high-purity active calcium carbonate used for coating |
| CN104261418A (en) * | 2014-10-24 | 2015-01-07 | 山西玉竹活性石灰制造有限公司 | Method for preparing microporus, high-activity and low-density calcium silicate |
| CN109399683B (en) * | 2018-12-06 | 2020-12-01 | 东北大学 | Preparation method of nano calcium carbonate for yield enhancement of PVC (polyvinyl chloride) automobile primer |
| CN109370261A (en) * | 2018-12-06 | 2019-02-22 | 东北大学 | A kind of PVC weld joint sealant stick viscosity enhancing preparation method of nanometer calcium carbonate |
| CN109399683A (en) * | 2018-12-06 | 2019-03-01 | 东北大学 | A kind of preparation method of PVC automobile bottom gluing surrender enhancing nanometer calcium carbonate |
| WO2020113963A1 (en) * | 2018-12-06 | 2020-06-11 | 东北大学 | Preparation method for nano calcium carbonate used for enhancing viscosity of pvc welding seam sealing adhesive |
| CN109370261B (en) * | 2018-12-06 | 2020-07-31 | 东北大学 | Preparation method of nano calcium carbonate for enhancing viscosity of PVC welding seam sealing adhesive |
| CN110817922A (en) * | 2019-12-11 | 2020-02-21 | 合肥工业大学 | Inorganic/organic composite inducer and application thereof in induced synthesis of nano calcium carbonate |
| CN110817922B (en) * | 2019-12-11 | 2021-06-29 | 合肥工业大学 | Inorganic/organic composite inducer and application thereof in induced synthesis of nano calcium carbonate |
| CN112322286A (en) * | 2020-12-10 | 2021-02-05 | 湖北理工学院 | Rare earth ion doped nano calcium carbonate luminescent material with different morphologies as well as preparation method and application thereof |
| CN112322286B (en) * | 2020-12-10 | 2023-04-07 | 湖北理工学院 | Rare earth ion doped nano calcium carbonate luminescent material with different morphologies as well as preparation method and application thereof |
| CN113583478A (en) * | 2021-08-20 | 2021-11-02 | 乌海市创美佳新材料科技有限公司 | Preparation method of nanoscale calcium carbonate special for automobile chassis paint |
| CN113956681A (en) * | 2021-11-15 | 2022-01-21 | 亚士创能科技(上海)股份有限公司 | Tourmaline coated with calcium carbonate and preparation method and application thereof |
| CN115092950A (en) * | 2022-08-01 | 2022-09-23 | 中国铝业股份有限公司 | Method for recycling papermaking white mud |
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