Limestone is a carbonate rock with calcite as the main component. Limestone with calcium carbonate content above 98% is called calcite ore or calcium carbonate ore in industry.
The chemical formula of calcite is Ca[CO3], and its theoretical chemical composition is: CaO56.04%, CO243.96%, colorless or white, hardness 3, and density 2.6 ~ 2.8g/cm3.
Limestone often contains dolomite and clay minerals, which form a series of transition rocks with calcite. See table 3-7- 1 for the classification of limestone according to mineral composition and chemical composition, and see table 3-7-2 for ore types.
Table 3-7- 1 limestone classification
Table 3-7-2 Mineral Types and Characteristics of Limestone
There are abundant limestone resources in the world. Countries with an annual output of over 654.38 billion tons include the United States, China, the former Soviet Union and Japan, followed by Britain, Germany, Italy, Spain, Brazil, France, Poland, Venezuela and India.
China is rich in limestone mineral resources. There are nearly 1000 limestone deposits for cement, flux and chemical industry, and the producing areas are all over the country. All provinces, municipalities and autonomous regions can use local materials near industrial zones. It is especially gratifying that in recent years, some high-quality calcite minerals with high whiteness have been discovered in China, and fine and heavy calcium carbonate processing plants have been established one after another, which has promoted the development of inorganic filler industry in China.
Second, the main uses and quality standards of limestone
Limestone is an important industrial raw material in metallurgy, building materials, chemical industry, agriculture and other departments. The main uses of limestone are shown in Table 3-7-3.
Table 3-7-3 Main Uses of Limestone
The quality requirements of limestone vary according to different uses. At present, the national standard (ZBD600 1-85) has been formulated for limestone used in metallurgical industry in China, and the standards for other industries are formulated by the applicant department. See table 3-7-4 and table 3-7-5 for quality standards of limestone for metallurgy, table 3-7-6 for quality standards of limestone for cement, and table 3-7-7 ~ table 3-7-9 for quality standards of limestone for glass industry, calcium carbide and sugar filter aid for alkali production.
Table 3-7-4 Chemical Composition Requirements of Metallurgical Limestone (ZBD6000 1-85)
Note: 1. In ordinary limestone, when MgO is more than 3%, the standard of high magnesium limestone should be implemented.
2. The supplier shall regularly provide the analysis data of phosphorus and sulfur impurities in ordinary limestone or high-magnesium limestone, from Grade I to Grade IV, but it will not be used as the assessment basis for the time being.
Table 3-7-5 Grain Size Requirements of Metallurgical Limestone (ZBD6000 1-85)
Note: Other granularity limestone products can be supplied through negotiation. The particle size difference of limestone used for burning lime is not more than 40 mm
Table 3-7-6 Quality Requirements of Calcareous Raw Materials for Cement
Table 3-7-7 Quality Requirements of Limestone for Flat Glass
Table 3-7-8 Quality Requirements of Calcium Carbide and Limestone for Alkali Production
Table 3-7-9 Quality Requirements of Limestone Used as Filter Aid for Sugar Production
As a raw material for cement production, amorphous limestone is required to have a particle size of 30 ~ 80 mm See Table 3-7- 10 for the quality requirements of limestone by Japanese industrial departments.
Table 3-7- 10 Requirements of Japanese Ministry of Industry for Limestone Quality
Three. Mineral processing of limestone
Limestone resources are characterized by large reserves and good quality. Therefore, the main limestone producing countries in the world adopt the method of washing-crushing-classification to remove the pollution of topsoil, sand and clay. For low-grade limestone or limestone with different ore properties, some foreign countries adopt flotation or photoelectric beneficiation. Here are two examples of limestone mineral processing.
Example 1 Mineral Processing of Wulongquan Limestone Mine in WISCO
Wulongquan limestone deposit belongs to marine sedimentary limestone and dolomite deposit. The mud content of raw ore is 6. 1% ~ 13.5%, and some of them are as high as 18%. The topsoil and clods mixed with ore during mining are generally 6% ~ 12%, and the clods are sticky and difficult to remove. The mine mainly mines ordinary limestone, high-quality limestone and dolomite. In open-pit mining, ores are mined, transported, crushed and washed separately according to different mining areas and minerals. See figure 3-7- 1 for the principle process flow.
See table 3-7- 1 1 for product quality indicators.
Table 3-7- 1 1 quality index of limestone products in Wulongquan mine
Fig. 3-7- 1 process flow chart of new system principle of Wulongquan Phase III
Example 2 Limestone Flotation Plant of General Atlas Cement Company in Pennsylvania, USA
The main minerals in the ore are calcite and dolomite, accounting for 75%; Sericite is the second, accounting for15%; Timely accounting for 8.5%; And a small amount of pyrite and graphite. See fig. 3-7-2 for the process flow of mineral processing.
Fourthly, the deep processing of calcite ore.
Figure 3-7-2 Mineral Processing Flow Chart of Limestone Flotation Plant of Atlas Cement Company, USA
1. Preparation of quicklime and hydrated lime
Calcite is decomposed into CaO and CO2, the temperature of CaO is 1000 ~ 1300℃, and Cao is quicklime. The structure of quicklime formed by thermal decomposition of limestone mainly depends on calcination temperature, followed by the action time of temperature and impurity content. In China, quicklime is mainly made in vertical kilns.
Hydrated lime is prepared by hydration of quicklime, and the reaction formula is:
Cao +H2O→ Calcium hydroxide +65× 103J.
The methods of producing hydrated lime are wet digestion and dry digestion. Dry cooking is done in the digester.
2. Preparation and application of superfine heavy calcium carbonate powder
According to different processing technologies, calcium carbonate can be divided into heavy calcium carbonate (GL) and light precipitated calcium carbonate (PCC).
Heavy calcium carbonate is one of the widely used inorganic salt fillers and an important filler in today's high technology. It is mainly used as filler, reinforcing agent and whitening agent in papermaking, plastics, rubber, coatings, inks and adhesives. Heavy calcium carbonate (mainly marble) in China is rich in mineral resources, with high purity (CaCO3 > 99%) and whiteness > 94%. Moreover, calcite "rhombohedral" is well developed and easy to be made into flake powder, which provides raw material guarantee for preparing high-grade heavy calcium carbonate filler.
The main grinding equipment used to produce heavy calcium carbonate by physical method includes ball mill, raymond mill, vibration mill, stirring mill, jet mill, etc. According to its crushing degree, heavy calcium carbonate can be divided into: coarse heavy calcium carbonate (CGL) with an average particle size greater than 3 microns; Fine ground calcium carbonate (FGL) with an average particle size of 1 ~ 3 microns; Ultrafine ground calcium carbonate (UFGL) with an average particle size of 0.5 ~ 0.9 μ m.
In ISO 787- 1 ~ 25 (General test method for pigments and fillers), the International Organization for Standardization (ISO) clearly defined the physical and chemical properties of pigments and fillers and their test methods, but did not clearly specify their names. The products of major heavy calcium producers in the world generally have their own trade names.
The naming of calcium carbonate products in China consists of three parts. The first item is the Chinese phonetic alphabet Z or Q, which means category, Z means heavy calcium and Q means light calcium. The second term is Arabic numeral (1 ~ 5), which indicates the range of the average particle size d of the product, where 1 means > 5 microns, 2 means 1 ~ 5 microns, and 3 means 0. 1 ~ 1 micron; 4 stands for 0.02 ~ 0. 1 micron, 5 stands for < 0.02 micron ... The third item is the pinyin letter b or g, where b stands for unmodified and g stands for surface modification. For example, Z2G indicates that the product is surface-modified heavy calcium carbonate with an average particle size of1~ 5 μ m..
The main technological process for preparing heavy calcium carbonate is as follows:
Guide to the development and utilization of nonmetallic minerals in Henan Province
The product quality obtained by wet ultrafine grinding is generally better than that by dry ultrafine grinding, which is not only fine in particle size, but also flaky in powder. Whether it is wet or dry, measures must be taken to prevent the pollution of crushing and grinding equipment to materials and reduce the whiteness of materials.
With the world's paper-making process changing from acidic to alkaline and neutral, many paper mills use kaolin and talcum powder as fillers in acidic process and bicarbonate in alkaline process. As an alkaline mineral pigment, the usage of heavy calcium carbonate in paper industry is increasing rapidly. For example, the share of coating grade heavy calcium carbonate in Europe increased from 20% in 1980 to 42% in 1990. However, the share of kaolin decreased from 75% to 53%. By 2000, the occupation rate of heavy calcium carbonate reached 56%, about 3.2 million tons, and the consumption of 1995 coating grade heavy calcium carbonate in China was about 20,000 tons, so the demand for products was in short supply.
See table 3-7- 12 and table 3-7- 13 for the fineness data of four kinds of heavy calcium carbonate (GCC) commonly used in international papermaking at present. Paper mills generally require heavy calcium carbonate coating, and the maximum particle size should not exceed10μ m (100% <10μ m). Paper mill not only limits the maximum particle size of coated bicarbonate, but also limits its minimum particle size (dmin), and generally requires the particle content of 0.2μm to be less than 15% ~ 20%. This is because there are too many small particles, which not only leads to a large amount of glue and poor air permeability, but also leads to poor surface gloss of paper.
Table 3-7- 12 fineness of dicalcium in international papermaking (micron)
The main methods for determining the particle size and particle size distribution of bicarbonate are screening method, microscope method, laser method and sedimentation method.
Table 3-7- 13 Reference Index of Technical Performance of Products with Different Uses in Paper Industry
The particle size distribution of 400 mesh heavy calcium carbonate products can be determined by screening method; The particle size of 400 ~ 2500 mesh heavy calcium products can be determined by laser particle size analyzer and microscope with micro-R. For products with -2 micron accounting for more than 90%, it can be determined by centrifugal sedimentation particle size analyzer, and then verified by scanning electron microscope.
At present, there is no uniform regulation on particle size determination at home and abroad, and the results of the same sample are often very different due to the differences of instruments, determination principles and operators. Therefore, the determination personnel are required to be fixed, and the determination results must be verified by another method, and the results can only be reported if they are not out of tolerance.
The whiteness of heavy calcium carbonate for paper coatings and fillers should be greater than 90, and it is generally required to be above 94%.
China's coated paper, coated paper and other high-grade paper have low output and are imported from abroad every year. Neutral sizing and coated paper are the key development projects of China paper industry. UNESCO advocates the use of coated paper with low quantitative and low gloss in primary and secondary school textbooks. The printing industry will gradually transition from the current high-grade offset paper to high-filling paper and low-quantitative coated paper, which will certainly expand the demand for ultra-fine ground calcium carbonate. China has established some heavy calcium production plants, but due to equipment and technical problems, they mainly produce ordinary filler (-320 mesh) powder. The fully automatic grinding plant of calcium carbonate with an annual output of 6.5438+00,000 t filler grade and 50,000 t coating grade built in Tangshan has improved the production level of superfine heavy calcium carbonate in China.
3. Preparation and application of nanometer calcium carbonate
Nano-powder refers to the solid micro-particles in the transition area between atoms, molecules and macro-objects, and is a zero-dimensional material. The particle size of nano-powder is 1 ~ 100 nm. After the substance becomes nanoparticles, its surface area per unit mass is much larger than that of the original block solid, thus some new properties appear and become a new state of the substance.
Nanoparticles have two basic characteristics: one is surface effect, and the other is volume effect.
Surface effect With the decrease of particle size, the number of surface atoms increases. For particles with a particle size of 5nm, the proportion of surface atoms can reach 40%; When the particle size is 2nm, the proportion of surface atoms increases to 80%. At the same time, the specific surface area has increased to several hundred times. Because the spatial configuration and spin configuration of surface atoms are different from those in vivo, the interaction between atoms and the electronic energy state are also different from those in vivo, and the activity of surface atoms is higher than that of atoms in the structure. For example, nanocrystalline calcium carbonate, because of its large specific surface area and strong surface activity, can be firmly combined with rubber molecules to replace carbon black and silica as rubber reinforcing agent.
Volume effect Volume effect means that when the particle size is less than 1/2 of the wavelength of light, light can bypass the particle and appear transparent. For example, calcium carbonate particles below 80nm can be used for transparent and translucent rubber, plastic film, colorless pigment and so on.
At present, there are many methods for preparing nano-powders in the world, and there is no uniform standard for the classification of various methods. Generally, it is divided into gas phase method, liquid phase method and solid phase method according to the aggregation state of substances. Solid-phase method is to prepare nanoparticles directly from solid phase without phase transformation, including mechanical crushing method and thermal decomposition method. It is difficult to obtain ultrafine powder with particle size less than 0. 1μm by solid-state method, and the powder morphology is uneven. Gas phase method refers to the method that reactants synthesize the required products under high temperature gas phase conditions, and the products are quickly cooled to form nano-powders. The preparation of nano-powder by gas phase method is usually divided into evaporation-condensation method without chemical reaction in the system and chemical gas phase reaction method to synthesize the required compounds through chemical reactions (gas-solid reaction, gas-gas reaction and gas-liquid reaction). Gas phase method is mainly used to prepare metal, alloy and ceramic nano-materials, and some methods have been industrialized. The advantages of gas phase method are high purity, narrow particle size distribution and good dispersibility, but the disadvantages of this method are large equipment investment and high cost.
Nano-calcium carbonate is mainly synthesized by liquid phase method, which can be divided into three reaction systems according to different synthesis mechanisms, as shown in Figure 3-7-3.
Figure 3-7-3 Classification of Nano-calcium Carbonate by Liquid Phase Method
Firstly, calcium chloride reacts with alkali to make nascent state lime milk, and then reacts with sodium carbonate solution to make nano-calcium carbonate. The reaction process is as follows:
Calcium chloride +2 sodium hydroxide → calcium hydroxide +2 sodium chloride
Ca(OH)2+Na2CO3→CaCO3↓+2NaOH
Because the calcium carbonate produced by this process contains trace alkali, it is difficult to remove, which limits the use of the product. At present, batch carbonization and continuous spray carbonization are mainly used to produce nano-calcium carbonate in industry. Both processes are based on natural calcium carbonate, and the cost is low. The process flow is shown in Figure 3-7-4. The main reaction process is as follows:
Guide to the development and utilization of nonmetallic minerals in Henan Province
Figure 3-7-4 Preparation Process of Nano-CaCO3
In the preparation of nano-calcium carbonate, natural calcium carbonate is calcined and digested to obtain calcium hydroxide, and kiln gas from calcium carbonate calcination is purified and compressed to obtain carbon dioxide. Therefore, the preparation and pretreatment of raw materials include calcination, digestion, purification, gas compression and other links. The quality of raw material natural calcium carbonate has a great influence on the quality of nano-calcium carbonate products, which should be strictly controlled. The minimum requirements of its quality standard are: CaCO3 > 97%, MgO < 1%, SiO2 < 0.5%, Fe2O3 < 0.5% and Mn < 0.0045%. In addition, the technological conditions of calcination and digestion will also affect the activity of calcium hydroxide, and then affect the product quality.
1) batch carbonization method
The intermittent carbonization method is close to the traditional preparation method of light calcium carbonate, but the difference is that light calcium carbonate reacts in a bubble column, while the preparation of nano calcium carbonate is generally carried out in a stirred reactor, and the mass and heat transfer effects of the reaction system are improved by stirring. The key is to strictly control the reaction conditions, such as carbonization temperature, carbon dioxide flow and lime milk concentration. , and add appropriate additives. The main function of additives is to promote crystal nucleation and control crystal growth. There are two kinds of inorganic additives: inorganic acids and alkaline earth metal salts. The organic additive is a polycarboxylate coordination complex former. By controlling different conditions, a variety of nano-calcium carbonate products with different crystal forms (chain, needle, sphere, cube, flake, etc.) can be obtained. ) particle size is greater than 65438 00 nm. Intermittent carbonization method has the advantages of less investment, simple operation and easy transformation. At present, most nano-calcium carbonate is prepared by this method. The disadvantages of this method are low production efficiency, uneven particle size and wide distribution range, which need further improvement.
2) continuous spray carbonization method
The spray carbonization method is to atomize the refined lime milk into droplets with a diameter of about 0. 1mm under the action of a hollow prototype pressure nozzle, and then spray them evenly from the top of the carbonization tower, and then make counter-current contact with CO2 mixed gas entering from the bottom of the tower for carbonization reaction, so as to prepare nano-calcium carbonate. In the spray carbonization tower, the liquid phase is dispersed in the gas phase in the form of droplets. Because the atomized droplets are fine, the specific surface area is large, the gas-liquid contact is fully uniform, and there are many reaction centers, forming multiple crystal nuclei; Because the gas-liquid contact time is similar, the growth speed of each crystal nucleus is basically the same, thus ensuring the uniform particle size and narrow particle size distribution of the product; At the same time, due to the short gas-liquid contact time, CaCO3 particles precipitated on the reaction surface are not easy to deposit on the surface of reactants, and recrystallization, twinning and secondary coagulation are not easy to occur, which is beneficial to control the crystal form and particle size of products.
Spray carbonization generally adopts two-stage or three-stage continuous carbonization process, that is, lime milk is carbonized in the first-stage carbonization tower to form a reaction mixture, and then sprayed into the second-stage carbonization tower for carbonization to obtain the final product, or sprayed into the third-stage carbonization tower for three-stage carbonization to obtain the final product. Because the carbonization process is carried out in stages, the nucleation and growth process of crystals can be controlled in stages, and it is easier to control the shape and particle size of products compared with intermittent carbonization method.
This method is rarely used at present because of its large investment, high technology content and difficult management.
Nano-calcium carbonate is mainly used as filler and reinforcing agent in rubber industry at present. In Japan, where the production technology of nano-calcium carbonate is at an advanced level, 46.6% of nano-calcium carbonate is used in rubber industry. The elongation, tear strength, compression deformation and flex resistance of vulcanized rubber filled with nano-calcium carbonate are higher than those of vulcanized rubber filled with calcium carbonate. The addition of nano-calcium carbonate can reach more than 100% (by volume), while the addition of carbon black and silica in rubber compound can only reach 50% (by volume), so using nano-calcium carbonate as rubber filler not only plays a reinforcing role, but also can reduce the cost. The more complex the shape of nano-calcium carbonate is, the stronger its combination with rubber molecules is. The order of reinforcing properties of nano-calcium carbonate with different shapes in rubber from strong to weak is chain > needle > sphere and cube. After surface modification and activation, the compatibility between nano-calcium carbonate and rubber molecules is increased, and the mechanical strength of rubber products is enhanced.
As a filler of plastics, nano-calcium carbonate should be cubic or spherical in crystal form to reduce the absorption of plasticizer; The particle size is 40 ~100 nm; The surface is modified and activated. As a plastic filler, nano-calcium carbonate has a reinforcing effect, which improves the bending strength, bending elastic modulus, thermal deformation temperature and dimensional stability of plastics, and also endows plastics with hysteresis.
The fillers (bulk pigments) used in ink industry for a long time include aluminum hydroxide, barium sulfate, aluminum barium white and so on. With the popularization and application of synthetic resin binder in ink industry, these traditional ink fillers have been gradually replaced by nano-calcium carbonate. Nano-calcium carbonate as a filler in resin-based ink has the following advantages: cleaning alkaline nano-calcium carbonate as an ink filler can prevent the ink from gelatinizing or returning to coarseness, and has good stability; High gloss; Does not affect the drying performance of ink.
Nano-calcium carbonate as ink filler needs surface modification and activation, and its crystal form is spherical or cubic. The specifications of two kinds of nano-calcium carbonate commonly used in ink are as follows.
Transparent nano calcium carbonate Cao 52.6%; ZnO 2.3%； MgO 0.2%； Al2O3 and Fe2O3 0.2%; Moisture 2%; The combustion weight loss rate is 43.90%; Hydrochloric acid insoluble matter 0.10%; The PH value is 8.30; The density is 2.56g/cm3; ; Oil absorption is 36 ml/100g; Bulk density (JIS method) 3.60 ml/g; The average particle size is 30 nanometers; ; The specific surface area (BET method) is 87m2/g..
Semi-transparent nano calcium carbonate Cao 54%; MgO 0.2%； SiO 20. 1%； Other oxides 0.2%; Moisture 2%; The combustion weight loss is 45.65438 0%; The PH value is 8.6; The density is 2.57g/cm3; ; Oil absorption is 26 ml/100g; Bulk density (JIS method) 2.4 ml/g; The average particle size is 50 nanometers; ; The specific surface area (BET method) was 28 m2/g.
Nano-calcium carbonate has become an important inorganic chemical raw material. There are manufacturers of nano-calcium carbonate in Guangdong and Shanghai. For example, Guangdong Guangping Chemical Co., Ltd. introduced a frozen intermittent bubbling carbonization device, which belongs to an earlier domestic nano-calcium carbonate production enterprise with a scale of 5 kt/a; Nano-calcium carbonate produced by Shanghai Huaming Ultra-fine Calcium Carbonate Co., Ltd. by freezing intermittent stirring carbonization method has a scale of 3 kt/a; Beijing Chemical Building Materials Factory produced nano-calcium carbonate (2kt/a,-100 nm) for ink by freezing intermittent bubbling carbonization. See table 3-7- 14 and table 3-7- 15 for the quality standards of "Bai Yanhua" brand and "Huaming" brand nano-calcium carbonate produced in Guangdong and Shanghai respectively. Table 3-7- 16 lists the application of nano-calcium carbonate in Japanese rubber industry.
Table 3-7- 14 Physical and chemical properties of "Bai Yanhua" brand superfine activated calcium carbonate products
Note: Determination of specific surface area, BET method.
Table 3-7- 15 Physical and chemical properties of "Huaming" brand superfine activated calcium carbonate products
Table 3-7- 16 application examples of nano-calcium carbonate in Japanese rubber products
There are more than 10 kinds of nano-calcium carbonate produced in China, which are widely used in rubber, plastics, ink and other industries, but there are few specialized and functional varieties and products, which are far from meeting the domestic market demand. According to the demand forecast of automobile coatings, ink, rubber, plastics, coatings and other industries, the consumption will reach 50,000 tons by 2005. At present, domestic 10 ~ 50 nm calcium carbonate mainly depends on imports, and the import volume of 1999 alone reaches10000 t. In order to make the variety, output and quality of nano-calcium carbonate produced in China reach the international advanced level as soon as possible, some scientific research institutes, research institutes and universities have carried out a lot of experimental research, and some research results have reached the international leading level, and have entered the industrial implementation. For example, in beijing university of chemical technology, nano-calcium carbonate is produced by overweight carbonization, and the particle size of the product is ≤30nm. At present, a 3kt/a nano-calcium carbonate industrial plant has been established in Enping, Guangdong.
4. Light calcium carbonate (precipitated calcium carbonate, chalk powder)
Light calcium carbonate, abbreviated as light calcium, is a white light powder with a density of 2.7 1 ~ 2.9 1g/cm3, a refractive index of 1.65 and a particle size range of1.0 ~16 μ m; The specific surface area is 5 ~ 25m2/g, and it is hardly soluble in water and alcohol.
The preparation process of light calcium carbonate is similar to that of nano-calcium carbonate, and the continuous carbonization method is adopted. The process flow is shown in Figure 3-7-5. The raw material is limestone, which requires calcium carbonate > 98%, magnesium oxide ≤ 1% and iron and aluminum oxides < 0.5%. Firstly, limestone is crushed and screened into 50 ~ 150 mm feed, and white carbon black is crushed to a particle size of 38 ~ 50 mm, and the ratio of coal to limestone is 1: (8 ~ 1 1). The calcination temperature is 900 ~ 1 100℃, and the calcined quicklime is digested with 3 ~ 5 times of water at about 90℃. CO2 gas decomposed by calcination is purified by gas tank and sent to carbonization tower. The digested lime milk is filtered to remove impurities, and then carbonized in a carbonization tower. The carbonization temperature is 60 ~ 70℃ and the carbonization pressure is 7.84× 104Pa. Wet powder obtained after centrifugal dehydration of calcium carbonate slurry enters a rotary drying furnace for drying (or other types of drying equipment), and the water content is reduced to below 0.3%, and then the finished product is obtained after cooling, crushing and sieving. The reaction process is as follows:
CaCO3→CaO+CO2，
CaO+H2O→Ca(OH)2
Calcium hydroxide+carbon dioxide → calcium carbonate +H2O.
Figure 3-7-5 Production Process of Precipitated Calcium Carbonate
At present, there are about 300 manufacturers producing light calcium carbonate in China with an annual output of 2 million tons. Manufacturers are distributed in all provinces, municipalities and autonomous regions in China, among which Hebei, Sichuan and Shandong provinces are relatively concentrated, accounting for about 2/3 of the national total output.
Light calcium carbonate is mainly used in rubber, plastics, printing ink, paper making and other industries. See table 3-7- 17 for the industry standard of light calcium, and table 3-7- 18 for the standard of light calcium after surface modification. With the development of neutral sizing, paint, ink, rubber, daily chemical and other industries in engineering plastics and paper industry, the calcium carbonate industry is bound to develop rapidly, not only increasing its output, but also developing in a diversified, professional and functional direction. The main development direction of calcium carbonate industry is particle refinement, complex structure and surface activation. The finer the particles, the greater the surface activity, and the better the reinforcement performance when used in rubber products; When used in high-grade coatings, the dispersibility is better; Used in ink, the better the transparency.
See table 3-7- 19 ~ table 3-7-2 1 for application examples of light calcium in plastic industry.
Table 3-7- 17 Technical Requirements for Industrial Precipitated Calcium Carbonate (HG2226-9 1)
① It is the result of ex-factory inspection.
Table 3-7- 18 Quality Standard for Industrial Activated Precipitated Calcium Carbonate (Appearance: White Powder) (HG/T2567-94)
Table 3-7- 19 PVC profiles
Table 3-7-20 Flexible Polyurethane Foam
Table 3-7-2 1 polypropylene packing tape (APP material)
Main references
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Yuan et al. Characteristics, application and preparation of nano-powder materials. Geology of building materials, 1997. Supplement, P4 ~ 6.
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[1 1] Song Baoxiang, exploitation and development of calcium carbonate in paper mills, nonmetallic minerals, 1998.6, ~ 8.
[12] Cao tingchang, preparation of ultrafine calcium carbonate-high-grade ink filler 206#, inorganic salt industry, 2000.438+0,25.