Non-metallic mineral beneficiation and purification method and main process equipment
Naturally produced non-metallic ores contain other mineral impurities or co-associated minerals to varying degrees. For specific non-metallic mineral products, some of these mineral impurities are allowed to exist, such as a small amount of dolomite and wollastonite contained in calcite, and part of pyrophyllite and chlorite contained in talc; Various iron minerals and other metal impurities contained in minerals such as kaolin, quartz, diatomaceous earth, talc, stone mother, wollastonite, and calcite that may be removed. There are also some minerals, such as graphite, diatom, sandy kaolin, coal-based kaolin, etc., the raw material minerals have low grades, and must be purified or calcined to meet the application requirements.
For non-metallic minerals, purity in many cases refers to their mineral composition rather than their chemical composition. There are many non-metallic minerals whose chemical composition is basically similar, but the mineral composition and structure are far from each other, so their functions or application properties are also different. This is the biggest difference between non-metallic ores and metallic minerals, such as quartz and diatoms. Although the chemical components of soil are all silica, the former is a crystalline structure (silicon-oxygen tetrahedron), while the latter is a non-quality porous structure with a complex structure. Therefore, their application properties or functions are also different. In addition, in the process of beneficiation of non-metallic minerals, the crystal structure of useful minerals should be maintained as much as possible, so as not to affect its industrial use and use value.
At present, the commonly used beneficiation methods for non-metallic minerals include: sorting, washing, gravity separation, flotation, magnetic separation, electrical separation, chemical beneficiation, selective flocculation, calcination and shape sorting.
Is a good quartz mine equal to a good quartz sand?
Quartz sand is mainly used in two segments in the photovoltaic industry: photovoltaic glass and crucible. Among them, photovoltaic glass has low requirements on the purity of quartz sand, SiO2 ≥ 98.55%, and high light transmittance of glass is mainly required.
But the quartz sand used in the crucible is much stricter. The quartz crucible is basically translucent and is divided into three layers: the outer layer (opaque layer) and the middle inner layer (vacuum transparent layer). The inner layer affects the success rate of single crystal growth and the quality of the crystal rod, so the quality of the inner layer sand is relatively high, and imported ones are generally used, such as Unimin from the United States and TQC from Norway. The outer layer contains a large number of air bubbles, which is heated evenly and has a good thermal insulation effect. Domestic enterprises mainly make sand for the inner and outer layers of the crucible.
Quartz mines are widely distributed around the world, and industrial quartz mines include natural crystal, quartz sandstone, vein quartz, powder quartz, natural quartz sand and granite. However, the application fields of different types of sand are different. For example, some are suitable for the production of quartz tubes and quartz rods, so not all these minerals can be used to produce quartz crucibles.
In fact, there are very few deposits that are really suitable for producing quartz crucibles, mainly concentrated in the United States, Norway and India. At present, there are only three companies in the world that can mass-produce high-purity quartz sand, namely Unimin in the United States, TQC in Norway and domestic quartz shares.
Quartz sand is a natural resource, and the scarcity of ore is the key to restricting the supply of high-purity quartz sand. Unimin and TOC use mines in the United States, but since quartz mines are associated mines, it is difficult to accurately measure the output. In addition, companies such as Unimin are highly integrated, and quartz is only a part of it, and because it is an associated mine, to increase the output of quartz, it is necessary to increase other products accordingly. Therefore, the relative expansion is limited. In addition, in addition to producing photovoltaic sand, Unimin also produces semiconducting sand, and semiconducting sand is more expensive, so there is insufficient power to transfer production capacity.
Except for the mines in the United States, which are Indian mines, because very few domestic quartz sand mines can be used as crucibles, domestic companies mainly buy mines from India, and most of the quartz shares use Indian mines. The sand from the Indian mine has few bubbles after being made into a product, is easy to purify, and has a moderate cost, which is suitable for crucible sand.
Therefore, it is not the purification technology that really restricts the production capacity of high-purity quartz sand, because the domestic purification technology is not weaker than that of foreign countries, and the core is the resource of the ore. It can be said that "whoever has good ore will have good sand".
Barite beneficiation and purification technology and research progress
Barite is often associated with minerals such as quartz, calcite, dolomite, fluorite, siderite, rhodochrosite, pyrite, galena and sphalerite. In deposits such as , silver and rare earth, barite is often a common gangue mineral. Therefore, the sorting process of barite is restricted by factors such as deposit type, mineral composition, and characteristics of barite and gangue phases.
At present, barite beneficiation and purification technologies mainly include hand separation, gravity separation, magnetic separation, flotation and combined processes.
1. Hand selection
The manual selection process is to manually select high-grade lump ore based on intuitive physical indicators such as the color and shape of the ore. It is suitable for selecting ores with high grade, simple composition and stable quality. Many small private mines in my country often use this method for sorting. For example, Pancun Mine, Xiangzhou, Guangxi, selects high-grade barite ore by hand selection process. The concentrate particle size is 30-150mm, and the barite grade can be as high as 95%. The process is simple and easy to implement, requires low mechanization of equipment, but has high labor intensity, low production efficiency, and serious waste of resources.
2. Re-election
Different minerals with large differences in density can be separated by gravity separation. The density of barite is 4.5g/cm3, which is much higher than other common gangue minerals (such as quartz 2.65g/cm3, calcite 2.6g/cm3). Therefore, the gravity separation process can be used to separate barite and gangue minerals. Select different gravity separation equipment according to the size of the ore grade. The coarse grade (-5+0.45mm) ore can use the jigging method, and the fine grade (-0.45mm) ore can use the shaking table or the spiral chute method.
This process has the advantages of simple equipment, good stability, no beneficiation agent, low cost, and less environmental pollution. Therefore, it is difficult to efficiently recover barite resources by a single gravity separation process, and it is necessary to further recover barite by combining magnetic separation or flotation processes.
3. Magnetic separation
When there is a significant difference in the magnetic properties of the minerals, the magnetic separation process can be used for separation. Barite is a non-magnetic mineral. When magnetic minerals (such as iron oxides) are the main gangue minerals, a magnetic separation process can be used to separate barite and gangue minerals. The resulting concentrate has a high BaSO4 content, which can be used as a requirement. Barite raw material for barium-based pharmaceuticals with very low iron content. Magnetic separation is often used to select pyrrhotite, magnetite, limonite and hematite.
4. Flotation
Flotation is an important way to deal with refractory barite resources such as low-grade ores, associated ores and tailings, and this process has good adaptability to various types of barite ores with complex inlays, and is also capable of recovering fine-grained weight. Effective way of spar. The flotation process generally includes positive flotation and reverse flotation.
5. Combined process
For associated ores, flotation tailings, and refractory ores with fine-grained mineral inlays, the recovery of barite by a single gravity or magnetic separation process is not satisfactory, and a combined process is required to efficiently recover barite. Common combined processes are: flotation-reelection, gravity-magnetic separation, magnetic separation-flotation and magnetic separation-re-election-flotation.
What kind of ore can produce high-purity quartz?
High-purity quartz is a high-quality quartz produced in nature (such as crystal) or processed from relatively pure quartz raw materials. It is necessary for the production of high-tech industries such as semiconductors, high-temperature lamps, communications, precision optics, microelectronics, and solar energy. raw materials.
Naturally formed high-purity quartz is scarce or extremely limited (such as crystal). In order to obtain high-purity quartz, the natural high-purity quartz raw material is often purified into high-purity quartz. Therefore, the evaluation of high-purity quartz raw materials, as well as the research on the occurrence and formation mechanism of high-purity quartz raw materials, will be beneficial to the sustainable supply of high-purity quartz raw materials and the processing and purification of high-purity quartz.
1. Comprehensive evaluation of high-purity quartz raw materials
Judging the quality of quartz by chemical composition alone is one-sided, and various factors should be considered comprehensively in evaluating quartz. As far as the quartz mineral itself is concerned, five factors should be considered: the chemical composition of quartz, the embedded particle size, the symbiotic gangue minerals, inclusions and lattice impurities.
2. Ideal source rock for high-purity quartz raw materials
Quartz may be contained in magmatic rocks, sedimentary rocks, metamorphic rocks and hydrothermal veins. The quantity and quality of quartz in rocks of different geological origins vary widely, the purification techniques and difficulties vary widely, and the industrial uses are also quite different.
(1) Magmatic rock
(2) Metamorphic rocks
(3) Sedimentary rocks
3. Geological origin of high-purity quartz raw materials
Generally, the composition of trace elements in quartz is related to the properties of the melt/fluid during quartz crystallization and the later transformations (such as tectonic deformation, metamorphism, hydrothermal metasomatism, etc.) after crystallization. Therefore, relatively pure quartz can be directly crystallized in a melt/fluid with few impurities in a suitable external environment; if the purity and particle size of the quartz formed by the melt/fluid are not good at the beginning, it can also be transformed later (such as structural deformation). , metamorphism, hydrothermal metasomatism, etc.), the impurities can be "purified" by removing impurities through lattice recovery, particle boundary migration, etc.; of course, it can also be formed in the superposition of the above two methods.
4. The influence of impurities on the purification of high-purity quartz
The theoretical chemical composition of quartz is SiO2, but pure SiO2 quartz does not exist in nature. Quartz more or less contains some impurity elements (such as Al, Ti, K, Na, Ge, etc.), the type and content of which are related to the melting/fluid and external environment when the quartz is crystallized and the transformation received after crystallization.
The impurity content and occurrence state in the quartz crystal are important constraints to determine whether the quartz crystal can become high-purity quartz. When comprehensively evaluating the metallogenic potential of high-purity quartz in combination with technological indicators and commercial value, it is necessary to comprehensively examine the inlaid characteristics of quartz minerals, coexisting gangue minerals and types. The detailed identification of the occurrence state, quantity and distribution characteristics of impurity elements in the quartz crystal is very important for the subsequent mineral purification processing and discussion of its industrial use.
Surface modification method and functional design of fly ash
Surface modification and refunctionalization of fly ash particles is one of the main means to improve their high value-added utilization. Surface modification of fly ash particles and loading some functional additives can obtain a new type of functional material . The method can greatly increase the added value of the fly ash, can greatly mobilize the enthusiasm of the enterprise for the deep utilization of the fly ash, and promote the deep resource utilization of the fly ash.
Present Status of Surface Modification Technology of Fly Ash
By modifying pulverized coal, a product with a larger specific surface area can be obtained, which can better exert its adsorption performance. Using physical modification methods, such as mechanical grinding, microwave treatment, ultrasonic wave and high temperature treatment, etc., can destroy the network structure of fly ash glass body, increase the specific surface area, and can also change the electromagnetic properties of fly ash particles by coating. Modification methods, such as fire modification, hydrothermal modification, acid modification, alkali modification, mineral salt modification, calcium oxide treatment, etc., can also destroy the silicate network structure, promote the dissolution of the surface of the glass body, and improve the ratio surface area and ion exchange capacity.
Methods of chemical modification also include modification using surfactants, such as cationic surfactant treatment, coupling agent treatment, and stearic acid treatment.
Cationic surfactants can change the surface electrical properties of fly ash particles and improve their surface adsorption capacity, and are mainly used in various wastewater treatment processes; stearic acid can achieve the purpose of hydrophobic modification, making fly ash in the polymer ( Such as PVC, PP) as a filler; the coupling agent modification treatment method can improve the dispersibility of inorganic pigments and the adhesion of glass and metal surfaces, etc. These methods have good effects in the treatment of fly ash, and have been It shows good results in various applications.
Surface functional design of fly ash particles
There are many methods for functional design and modification of the surface of fly ash particles, generally through the design of groups on the interface, and then loading the corresponding functional groups to obtain fly ash-based functional materials.
(1) Fly ash-based hydrophobic film material
Hydrophobic films have many applications, such as building exterior walls, packaging materials, and mildew-proof places. For example, the surface of coal fly ash is hydrophobically modified with cationically dispersed rosin gum to prepare a hydrophobic fiber material.
The fly ash was modified with stearic acid, and then the relationship between the pigment volume concentration and the critical pigment volume concentration in the organic/inorganic composite material was used to adjust the hydrophobic properties of the film.
In a word, the hydrophobic film material prepared by using fly ash has low cost, can be used in occasions with high requirements for packaging materials and mildew resistance, and has good practicability.
(2) Fly ash-based composite humidity control material
The fly ash-based humidity-conditioning material is a composite humidity-conditioning material that can be obtained by compounding hydrophilic polymers and salts after hydrophilic modification of fly ash, which can be recycled to prepare powder or paint. Applied to different occasions, it has the advantages of passive, intelligent humidity control, low cost, energy saving and environmental protection.
(3) Formaldehyde capture material
The use of modified fly ash to load formaldehyde scavenger is equivalent to combining the two effects of physical adsorption and chemical neutralization. On the one hand, the physically adsorbed formaldehyde reacts with the scavenger, and there is no problem of desorption, which completely eliminates formaldehyde; It is easy to use and can eliminate formaldehyde more completely.
Utilizing the loading of formaldehyde scavenger on the surface of fly ash, an environmental purification material with excellent performance can be obtained, which has a very high added value. While having good economic benefits, it also has very good social benefits.
The surface functional modification of fly ash has very strong pertinence, which can turn solid waste fly ash into a functional material. In short, only reasonable, full and deep utilization of fly ash can truly make fly ash no longer a solid waste, but an industrial raw material with low price and excellent performance.
Nano-zinc oxide - a new functional fine inorganic chemical material
Nano-zinc oxide is a new type of functional fine inorganic chemical material, which has the characteristics of cheap and easy to obtain raw materials, high melting point, good thermal stability, good electromechanical coupling, good luminescence performance, antibacterial performance, catalytic performance and excellent ultraviolet shielding performance. , widely used in antibacterial additives, catalysts, rubber, dyes, inks, coatings, glass, piezoelectric ceramics, optoelectronics and household chemicals and other fields.
Nano-zinc oxide has good dispersibility, loose and porous, good fluidity, easy to disperse during smelting, and small heat generation of the rubber compound. As a vulcanization activator, the compound added to the target product has stronger activity, improving the microstructure of vulcanized rubber and improving the quality of rubber products. Finish, mechanical strength, tear strength, thermal oxidation resistance, and has the advantages of anti-aging, anti-friction and fire, prolonging service life, etc. When the dosage is 30-50% of ordinary zinc oxide, it can make the rubber tire side rubber anti-folding The performance is increased from 100,000 times to 500,000 times, which can effectively reduce the production cost of enterprises.
2. Ceramic crystallizer
Nano-zinc oxide has nano-effect, small particle size, large specific surface area, and has higher chemical activity than ordinary zinc oxide, which can significantly reduce the sintering and densification degree of the material, save energy, and make the composition of ceramic materials dense and uniform. , to improve the performance of ceramic materials. Due to its volume effect and high dispersing ability, it can be used directly without processing and grinding. Compared with ordinary zinc oxide, its dosage can be reduced by 30%-50%. The sintering temperature of ceramic products is 40-60℃ lower than that of ordinary zinc oxide. It can also make ceramic products have antibacterial and self-cleaning functions.
3. Antioxidant of lubricating oil or grease
Nano-zinc oxide has strong chemical activity and can capture free radicals, thereby destroying the free radical chain reaction. At the same time, nano-zinc oxide is an amphoteric oxide, which can neutralize the acid accumulated on the hydrocarbon chain of the lubricating oil over time, which can prolong the service life of the lubricating oil.
4. UV absorber
Nano-zinc oxide can absorb ultraviolet rays and generate electronic transitions, thereby absorbing and blocking medium-wave ultraviolet (UVB) and long-wave ultraviolet (UVA). Due to the small particle size of nano-zinc oxide, the ultraviolet absorption rate per unit addition amount is greatly improved. Nano-zinc oxide is an inorganic metal oxide, which can maintain long-term stability without degradation, thus ensuring long-term stability and effectiveness of its ultraviolet shielding effect. This product is suitable for environments with strong ultraviolet radiation, and can be used in wooden furniture protective coatings, resins, plastics and rubbers, as well as cosmetics and other products.
5. Anti-mold and bacteriostatic agent
Nano-zinc oxide is a self-activating semiconductor material. Under the irradiation of ultraviolet light and visible light, it will decompose freely moving electrons and leave positive electron holes at the same time. Holes can react with oxygen and water on the surface of zinc oxide to generate hydroxyl radicals, reactive oxygen species, etc., thus causing a series of biological reactions. It can effectively oxidize and degrade biomass, so as to play the role of anti-mildew and antibacterial. Due to the nano-effect of nano-zinc oxide, its specific surface area is significantly increased, its photocatalytic oxidation activity is higher, and it has more efficient antibacterial, antibacterial, and antifungal properties. . It can be applied to antibacterial and anti-mildew of coatings, sealants, plastics, rubber, and textile products.
Fast charging is becoming an industry trend, introducing five types of fast charging anode materials
With the advancement of power battery technology, the cruising range of new energy vehicles has been greatly improved, and the problem of battery life anxiety has gradually eased. In addition to battery life, charging anxiety is another problem that new energy vehicles need to face. The level of charging efficiency directly affects the car experience.
Shortening the charging time is one of the keys to enhancing the brand power and user experience of new energy vehicles. Some analysts believe that with the rapid increase in the penetration rate of new energy vehicles, the competition of car companies will become deeper and more diversified, and the advancement of fast charging technology and the improvement of energy replenishment efficiency have also become the next outlet of the new energy vehicle industry chain.
1. What is fast charging?
The charging of new energy vehicles is divided into AC slow charging and DC fast charging. In order to achieve "fast charging", it is necessary to rely on DC fast charging. The indicator that determines the charging rate is the charging power. There is no clear regulation on high-power charging in the industry, which is a broad industry term. Generally speaking, charging power above 125kW is high-power.
Power battery fast charging is the use of high-power charging. The market-leading power battery packs can already support 2C charging rate (charging rate is a measure of charging speed, charging rate = charging current/battery rated capacity). Generally speaking, 1C charging can fully charge the battery system in 60 minutes, and 4C means that the battery can be fully charged in 15 minutes. The charge-discharge rate determines the rate of the lithium-deintercalation reaction of the battery cell, and it is also accompanied by different degrees of heat generation or lithium evolution. The higher the rate, the more serious the lithium evolution and heat generation.
2. The negative electrode is the decisive factor for fast charging batteries
Fast-charging batteries need to be changed and upgraded in battery materials to improve the fast-charging performance of the battery, which is similar to the barrel effect. The short board is the negative electrode, which is the determining factor for the battery charging rate.
The negative electrode has a stronger impact on fast charging than the positive electrode. Several studies have shown that the degradation of the cathode and the growth of the cathode CEI film have no effect on the fast charging of conventional Li-ion batteries. Factors affecting lithium deposition and deposition structure (lithium precipitation) include: ① the diffusion rate of lithium ions within the anode; ② the concentration gradient of the electrolyte at the anode interface; and ③ side reactions at the electrode/electrolyte interface.
3. What are the negative electrode materials for fast charging?
Graphite Material
Silicon Based Material
Hard Carbon Material
Lithium Titanate Material
Aluminum Base Material
The Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences recently reported the latest achievements in aluminum-based composite anode materials. Aluminum foil is both a negative electrode and a current collector. Lithium ions move to the surface of the negative electrode of the aluminum foil, which can quickly form an aluminum-lithium alloy; during discharge, lithium ions can be easily extracted from the aluminum-lithium alloy, which has the inherent advantage of fast charging. According to reports, the battery product of this achievement can be fully charged in 20 minutes. If the composite aluminum foil is used as a fast charging negative electrode, it has great advantages in cost control, large-scale and stable preparation, etc.
With the rapid development of lithium battery technology, the energy density of batteries has been greatly improved, and the demand for shortening the charging time in the power battery market is also increasing. Fast charging technology has become an important trend in the development of lithium battery technology in recent years. With the continuous improvement of battery materials, fast charging may become a new competition in the field of new energy vehicles, and the application of fast charging technology will be more extensive in the future.
Organic modification of titanium dioxide and its effect on ABS engineering plastics
Due to the defects of titanium dioxide itself and the strong polarity on the surface, titanium dioxide without surface treatment is easy to absorb water and agglomerate during production, storage and transportation, which limits its application in organic polymers due to its easy agglomeration. Therefore, effective surface modification of titanium dioxide to improve its dispersibility in organic polymers and compatibility with the application system has become the key to the wide application of titanium dioxide. In order to improve the wetting, dispersion and rheological properties of titanium dioxide in various dispersion media, it is usually necessary to carry out organic modification.
The organic surface modification of titanium dioxide was carried out with different organic modifiers, and the effects of different organic modifiers on the surface hydrophilicity and hydrophobicity, Lab and oil absorption of titanium dioxide powder were studied, as well as the effects of different organic surface treatments on melt index, tensile strength, etc. The influence of material properties such as tensile strength and impact strength. The results showed that:
(1) The use of polysiloxane A, polysiloxane B, and polyol organic modifier to treat titanium dioxide has no significant effect on the Lab value of the powder, and the oil absorption index of the product is reduced;
(2) The titanium dioxide treated with polysiloxane exhibits hydrophobic properties, which enhances its compatibility with plastic resins;
(3) The titanium dioxide modified by polyols is hydrophilic, and it is easy to absorb water, which affects the application performance of plastics;
(4) In the ABS resin system, titanium dioxide treated with polysiloxane A is added, which has the least influence on the mechanical properties of plastic products, and the tensile properties and impact strength of the material are the best.
(5) It is recommended that the titanium dioxide used in the engineering plastics field be modified with polysiloxane modifiers, and organic modifiers containing different groups should be selected according to different application systems to improve the overall performance of the material.
Heavy calcium, light calcium, nano calcium, who is the favorite of PVC?
Calcium carbonate is widely used to fill polyvinyl chloride (PVC), polyethylene (PE) and other resins. Appropriate addition of calcium carbonate helps to improve the performance and processing performance of PVC products, such as improving the dimensional stability of products and improving product quality. Stiffness and hardness, improve the heat resistance of products, improve the printability of products, etc. Because the price of calcium carbonate itself is relatively low, only a comprehensive understanding of the properties of different types of calcium carbonate and the processing technology during use can better improve the cost performance of products.
1. Selection of calcium carbonate types
Heavy calcium is widely used in the foam layer of PVC calendered synthetic leather.
Light calcium is widely used in calendered leather surface layer, calendered hard sheet and calendered film. The light calcium used in calendering molding has a fine particle size and is easy to agglomerate, which is easy to cause white spots on the product, so the surface needs to be activated. The surface organic coating of calcium carbonate can make it hydrophobic, reduce agglomeration, increase the compatibility with PVC polymer, and improve its mechanical properties.
The particle size of nano-calcium carbonate is 1~100nm, which shows better performance than active calcium, and has a certain reinforcing effect.
2. The effect of calcium carbonate addition on the properties of calendered products
Calcium carbonate mainly plays a role in increasing capacity and reducing cost in PVC calendered products. With the increase of calcium carbonate filling ratio, the mechanical properties of calendered products gradually decrease. Among them, nano-calcium carbonate has little effect on the strength of PVC products. In the case of requirements on the mechanical properties of products, nano-calcium carbonate can be preferred.
3. The effect of calcium carbonate surface treatment on product performance
Calcium carbonate, especially light calcium carbonate and nano-calcium carbonate, have small particle size, large surface area, strong hydrophilicity, and easy secondary agglomeration, so their surface needs to be treated to obtain hydrophobic calcium carbonate.
Heavy calcium carbonate mainly has a filling and compatibilizing effect on PVC. It has poor compatibility with PVC and has a great impact on mechanical properties. It is recommended to be used in the foam layer of PVC calendered synthetic leather or in application scenarios where mechanical properties are not required. middle. For application scenarios that require high mechanical properties, it is better to use light calcium carbonate and nano-calcium carbonate. Light calcium carbonate or nano calcium carbonate.
4. The influence of the feeding sequence on the product
The feeding sequence of calcium carbonate is very important in the PVC processing process. Add PVC powder, calcium carbonate and stabilizer in sequence to the high-speed mixer, stir evenly at low speed, then turn to high-speed stirring until the temperature rises to 40~60°C, and add plasticizer and other liquids while stirring at high speed. Continue to stir to 100~120°C, the mixture is preferably in the form of flowable sand, and then put into an internal mixer for kneading and calendering to form a film.
5. Abnormal problems and improvement of calcium carbonate in the application of PVC calendering
The abnormal problems of calcium carbonate in the application of PVC calendering are mainly miscellaneous spots, white spots, drag lines, white folds, and decreased mechanical properties. Miscellaneous spots appear in calendered products, the reason is that calcium carbonate is mixed with impurities during production or transportation. You can observe the sieve residue during incoming inspection to see if there are variegated particles, and replace the qualified batch of calcium carbonate. The main cause of white spots and drag lines is the secondary agglomeration of calcium carbonate. The solution is to replace it with surface-treated calcium carbonate. The outer packaging of calcium carbonate should be protected from moisture to reduce the secondary agglomeration of calcium carbonate caused by moisture. For ultra-thin products with white spots, it is recommended to replace nano-scale calcium carbonate for production.
For the whitening or the decline of mechanical properties caused by the addition of excessive calcium carbonate, it is necessary to reduce the amount of calcium carbonate added, or replace it with light calcium carbonate or nano-scale calcium carbonate to improve the mechanical properties of the product.
Common 3 Types Of Flame Retardant Mineral Materials
Flame retardant mineral materials are flame retardants processed on the basis of natural minerals. According to their flame retardant mechanisms, they can be divided into ordinary minerals (hydroxides, carbonates, sulfates, etc.), clay minerals, and expandable minerals. Graphite etc.
1. Common mineral flame retardants
Metal hydroxides, carbonates, sulfates, etc. as flame retardants generally meet the following conditions: they can endothermic decomposition at a certain temperature (100-300 °C), and can release more than 25% of H2O or CO2 by mass fraction. and good filling performance; rich raw materials, low cost, low solubility and less harmful impurities. Such minerals can absorb the heat released by the combustion of the polymer and the radiant energy in the flame during the decomposition process, and the water vapor or (and) CO2 generated by the decomposition can dilute the concentration of the combustible gas and oxygen generated by the combustion of the polymer, reduce the surface of the material. The temperature can slow down the combustion speed and prevent the combustion from continuing; the metal oxide produced by the decomposition can be used as a covering layer to isolate the air and block the flame to prevent the flame from spreading. Compared with halogen-based and phosphorus-based flame retardants, it does not produce toxic and corrosive gases during the flame retardant process, and has obvious advantages in environmental protection, showing a vigorous development trend.
2. Nanoclay mineral flame retardant
Clay minerals are usually uniformly dispersed in polymers at the nanoscale, and the nanosheets of clay minerals act as a barrier to small molecules, combustible vapors and heat released from polymer combustion in two-dimensional directions, and degrade the polymer condensed phase. Combustion has a significant impact, and the clay platelets in the two-dimensional direction can also hinder the feedback of heat generated by gas-phase combustion to the condensed phase, thereby improving the flame retardant properties of the polymer. The nano-sized dispersed clay platelets have an obvious limiting effect on the mobility of polymer macromolecular chains, so that the macromolecular chains have a higher decomposition temperature than the completely free molecular chains when thermally decomposed.
3. Expandable graphite flame retardant
Expandable graphite (EG) is a special graphite intercalation compound formed by chemical treatment of natural flake graphite. Graphite has a layered structure, and alkali metals, strong oxidizing oxoacids, etc. can be embedded between the layers to form interlayer compounds, which begin to expand through the decomposition, gasification and expansion of the interlayer compounds at about 200 °C, and reach about 900 °C. The maximum value, the expansion range can reach 280 times, the expanded graphite changes from flake-like to low-density "worm" shape, which enhances the stability of the carbonized layer in the form of a cross-linked network, prevents the carbonized layer from falling off, and can be used on the surface of the material. The formation of a high-efficiency thermal insulation and oxygen barrier layer can block the transfer of heat to the surface of the material and the diffusion of small-molecule combustible gases generated by the decomposition of the material to the combustion area on the surface of the material, preventing further degradation of the polymer, thereby blocking the combustion chain. To the effect of efficient fire and flame retardant.
EG exists in a stable crystal form and has excellent weather resistance, corrosion resistance and durability. The carbon layer formed by expansion has good stability and can play a good skeleton role. As a new type of halogen-free physical intumescent flame retardant, EG has a very low heat release rate in fire, very little mass loss, and generates little smoke. It meets the requirements of environmental protection and can be used as a synergist for expansion systems. Synergists and flame retardants are used to prepare new intumescent flame retardant products with halogen-free, low smoke, low toxicity, better physical and chemical properties and fire resistance. EG will be widely used as a flame retardant.