3 Major Degradable Plastic Modification Technologies
At present, the price of degradable plastic resin is relatively high, and most of the degradable plastic products are ordinary daily necessities, which will seriously hinder the large-scale promotion and application of degradable plastic products. The development of cheap degradable plastic products is one of the core contents of the application of degradable plastics. Therefore, starch, calcium carbonate, talc, etc., which do not affect the degradation performance of products and can be absorbed by the environment, are used in the modification system of degradable plastics. In particular, the high proportion of filling technology has become one of the important technologies in the development of degradable plastic products.
Common modification techniques in the application process of degradable plastics include filling modification, alloying modification and copolymerization modification.
1. Filling modification
Filling modification is to add non-melting powder additives to the degradable plastic resin, mainly including starch and inorganic powder. Its main purpose is to prepare cheap special materials, and sometimes it can also improve the mechanical properties such as the strength of special materials.
A commonly used filler aid is starch. It is a common natural degradable polymer with a wide range of sources and low price. The degradation products are carbon dioxide and water, which do not pollute the environment, and it is a renewable biomass resource. The most important thing to pay attention to in this filling technology is the treatment of starch, because the compatibility of starch and degraded plastics is poor, and it is necessary to plasticize the starch so that the starch can be better combined with the plastic matrix.
Another filling aid is inorganic powders such as calcium carbonate and talc. They are all natural mineral powders, which can be absorbed by nature after returning to nature, so they will not affect the degradation performance of the entire degradable plastic system, but can effectively reduce the cost of modified materials and improve the strength of materials to a certain extent. Therefore, it is very common to use calcium carbonate and other fillers in products that do not require high mechanical properties. The filling technology should pay attention to the coupling treatment of the powder surface, which will directly affect the product performance and the amount of inorganic powder that can be added.
2. Alloying modification
Alloying modification is one of the most important technologies in the application of degradable plastic modification. Alloying material refers to a special material composed of two or more different varieties of degradable plastics by melt blending and compounding, generally containing one continuous component and other dispersed components. Some properties of the material show continuous phase properties and some properties show dispersed phase properties. Therefore, new special materials can be obtained that concentrate the advantages of several degradable plastics, which can meet the needs of more products.
3. Copolymerization modification
Copolymerization modification refers to the introduction of other structural units on the molecular chain of the polymer to change the chemical structure of the polymer and realize the modification of the material. For example, PLA is a hydrophobic polymer, which limits its application in some fields (such as drug carriers). An effective method is to use lactide to copolymerize with hydrophilic polymers (such as polyethylene glycol, polyglycolic acid, polyethylene oxide) to introduce hydrophilic groups or blocks into the PLA molecule. For example, the PLA-PEG-PLA sustained-release material is prepared by ring-opening polymerization of polyethylene glycol and lactide, which improves the hydrophilicity and degradation rate of the PLA material, and the prepared PLA-PEG-PLA can become a sustained-release material. Material of drug-loaded microspheres.
PHBV has many excellent properties such as biocompatibility and optical activity, and is widely used, but its products are hard and brittle and difficult to process. The graft modification method can be used to introduce the polar functional group polyvinylpyrrolidone (PVP) on the main chain of PHBV to synthesize the graft copolymer PHBV-g-PVP of PHBV and PVP. The crystallization rate and crystallinity of the copolymer decreased, the hydrophilicity of the membrane increased, and the sustained drug release rate increased.
7 Types And Uses Of Quartz Mines
Natural quartz deposits have various origins. At present, the common industrial types of quartz deposits available for development and utilization include natural crystal, quartz sandstone, quartzite, vein quartz, powder quartz, natural quartz sand and granite quartz.
1. Natural crystal
Natural crystal is a transparent large quartz crystal mineral, the main component is silicon dioxide. Crystals are mostly formed by natural growth in caves, rock cracks or joints, and faults. Their growth conditions are relatively harsh, and four conditions must be met at the same time: ample growth space, capable of providing silica-rich hydrothermal fluid, and a certain temperature. and stress, enough time to grow.
Natural crystal deposits have small reserves, poor mining conditions, scarce resources, and high prices, making it difficult to meet the needs of large-scale industrial production. However, due to the rich colors of natural crystal, crystal clear, beautiful and pure, it is mainly used for carving various handicrafts at present.
2. Quartz sandstone
Quartz sandstone is a sandy sedimentary rock consolidated by sedimentation. The content of quartz and siliceous clasts is generally >95%. The accessory minerals are mostly feldspar, mica and clay minerals, and the cement is generally siliceous.
Quartz sandstone deposits are generally large in scale, with stable geological occurrence and good mining conditions. At the same time, the ore hardness is generally relatively low, the natural particle size is moderate, and it is easy to be broken, classified and produced in large-scale industrial production. However, due to the complex composition of quartz sandstone cement, it is usually used in the production of daily glass sand, glass fiber, metal silicon, refractory materials, white carbon black, organic silicon and other fields.
3. Quartzite
Quartzite is usually a metamorphic rock formed by quartz sandstone or other siliceous rocks through regional metamorphism or thermal contact metamorphism. In addition to feldspar, mica and clay minerals, the associated minerals often contain trace amounts of tourmaline and hematite. and zircon etc. Compared with quartz sandstone, the ore of quartzite is more dense and hard.
4. Pulse Quartz
It is mainly formed under the action of magmatic hydrothermal fluid, usually in the form of a dense block structure. Its mineral composition is single, almost all of which are quartz, and the SiO2 content is generally above 99%. Vein quartz deposits are generally small in scale, steep in appearance, generally several meters to tens of meters in thickness, and generally ten to several hundred meters in length. A mining area can be composed of one vein or multiple veins.
The resource reserves of vein quartz deposits are generally relatively small, and the mining difficulty is relatively high. However, due to its low impurity content and stable resource quality, it is mostly used for the preparation of SiO2 99% to 99.9% silicon micropowder and low-iron quartz. Sand, optical glass, semiconductor and other high-quality quartz products.
5. Pink Quartz
Sedimentary weathered deposits are usually formed by weathering and disintegration of siliceous parent rocks under special geological structural conditions (temperature and humidity paleoclimate, gentle topography, paleogeography, hydraulic action, etc.). The quartz content is usually 95%~98%. can be as high as 99% or more.
6. Natural quartz sand
Natural quartz sand is a kind of sandy quartz mineral raw material with quartz as the main mineral component, which is formed by the long-term weathering of parent rocks such as granite, quartzite, quartz sandstone and vein quartz. Its associated minerals include feldspar, cuttings, Mica, clay minerals and heavy minerals such as zircon, tourmaline, ilmenite and amphibole are mainly marine sedimentary placer deposits and river-lake sedimentary placer deposits.
7. Granite
Refers to the quartz in large-grained granite or granite pegmatite (white granite) formed by the consolidation of magma. The quartz grade in this type of deposit is mostly about 25%, and the mineral impurities mainly come from the fluid inclusion-level lattice impurity elements in the quartz particles. This type of deposit is the main raw material for the production of high-purity quartz, which is currently mainly produced in Spruce Pine, North Carolina, USA.
The surface modifier has been selected, how should it be used?
The use of surface modifiers mainly includes: dosage, preparation, dispersion, addition method and the dosing sequence when two or more surface modifiers are used.
1. Amount of surface modifier
Theoretically, the optimal dosage is required to achieve monomolecular layer adsorption on the particle surface. This dosage is related to the specific surface area of the powder raw material and the cross-sectional area of the surface modifier molecules, but this dosage is not necessarily 100% coverage. The actual optimum amount of surface modifier should be determined by modification test and application performance test, because the amount of surface modifier is not only related to the uniformity of dispersion and coating of surface modifier during surface modification It is also related to the specific requirements of the application system for the surface properties and technical indicators of the powder raw materials.
When chemical coating modification is carried out, there is a certain corresponding relationship between the amount of surface modifier and the coating rate. Generally speaking, at the beginning, with the increase of the amount, the surface coating amount of the powder increases rapidly, but then The increase trend slowed down, and after a certain dosage, the surface coating amount no longer increased. Therefore, an excessive amount is unnecessary, which increases the production cost from an economical point of view.
2. Preparation method of surface modifier
Different surface modifiers require different formulation methods, such as:
For some silane coupling agents, it is silanol that acts as a bond with the surface of the powder. Therefore, in order to achieve a good modification effect (chemical adsorption), it is best to hydrolyze it before adding it.
For other organic surface modifiers that need to be diluted and dissolved before use, such as titanate, aluminate, stearic acid, etc., corresponding organic solvents should be used, such as absolute ethanol, isopropanol, glycerol, toluene, ether, Acetone etc. for dilution and dissolution.
3. How to Add Surface Modifiers
The best way to add the surface modifier is to make the surface modifier contact the powder uniformly and fully to achieve high dispersion of the surface modifier and uniform coating of the surface modifier on the particle surface.
Therefore, it is best to use the continuous spray or drop (addition) method that is linked with the powder feeding speed. Of course, only the continuous powder surface modifier can be used to continuously add surface modifiers.
4. Dosing sequence of surface modifiers
Due to the inhomogeneity of the powder surface, especially the surface properties of inorganic fillers or pigments, sometimes mixing surface modifiers is better than using a single surface modifier. For example, the combined use of titanate coupling agent and stearic acid to modify the surface of calcium carbonate can not only improve the surface treatment effect, but also reduce the amount of titanate coupling agent and production cost.
However, when two or more surface modifiers are used to treat the powder, the order of dosing has a certain influence on the final surface modification effect.
When determining the order of addition of surface modifiers, first of all, it is necessary to analyze the respective roles of the two surface modifiers and the way they interact with the powder surface (either physical adsorption or chemical adsorption). Generally speaking, the surface modifier that plays the main role and mainly based on chemical adsorption is added first, and then the surface modifier that plays a secondary role and mainly based on physical adsorption is added, but it is finally determined by application tests.
Plate sand: the main raw material for the production of quartz stone plates
Quartz sheet is a benchmark product in the history of the development of artificial building materials. It has the properties of wear resistance, scratch resistance, heat resistance, corrosion resistance and durability. It has gradually become a new favorite in the home improvement market and is very popular among consumers. With the continuous development of the artificial quartz stone plate market, quartz sand, the raw material for the production of quartz stone plates, has also attracted much attention.
Compared with natural stone and other artificial stone plates, artificial quartz stone has dense structure, hard texture, no radiation, zero formaldehyde, moderate hardness and easy processing. It is widely used in interior decoration such as kitchens, bathrooms, public restaurants and other countertops. decoration area.
Artificial quartz stone plate is usually made of 95%~99% quartz sand or quartz powder, which is bonded and cured by resin, pigment and other additives. The quality of quartz sand or quartz powder determines the performance of artificial quartz stone plate to a certain extent.
Quartz sand and quartz powder are made from the mined quartz ore through crushing, screening, washing and other processes. Generally speaking, products with a fineness of less than 120MESH are called quartz sand, and products with a fineness of more than 120MESH are called quartz powder.
Quartz sand has high temperature resistance, small thermal expansion coefficient, high insulation, corrosion resistance, piezoelectric effect, resonance effect and its unique optical properties.
Quartz sand is made of quartz ore mined in mines through crushing, screening, washing and other processes.
For the sand washing process, different methods are adopted according to the quality of the quartz ore. If the ore quality is clean and the pollution is very low, ordinary water washing can be used. subsequent process.
Acid leaching is a kind of chemical purification of quartz sand, which uses quartz insoluble in acid (except HF acid), and other impurity minerals can react with acid to form soluble salts to purify quartz.
Quartz sand is an important industrial mineral raw material and plays an important role in glass, casting, ceramics and refractory materials, smelting ferrosilicon, metallurgical flux, metallurgy, construction, chemical industry, plastics, rubber, abrasives and other industries. Plate sand is ubiquitous in people's lives today, which brings a lot of convenience to people's lives. However, with the hot quartz sand market, high-quality quartz sand resources are becoming less and less, and quartz stone plate enterprises are faced with the problem of shortage of raw materials. Possessing high-quality raw material resources has become one of the core competitiveness of sheet metal enterprises.
Surface modification of mica powder and its application in industrial anti-corrosion coatings
Mica has excellent chemical inertness, so it can improve the corrosion resistance of coatings such as neutral salt spray resistance, acid resistance, alkali resistance, etc. At the same time, with its unique lamellar structure, it can adjust the internal stress of the coating and improve the continuity and density of the coating film. It can effectively slow down the penetration of corrosive substances in the coating film and alleviate the corrosion of steel substrates. Adding mica to anti-corrosion coatings can significantly improve the corrosion resistance of coatings.
However, like many natural minerals, mica has a hydrophilic and oleophobic surface, and is difficult to wet and disperse in the organic phase. Due to its large specific surface area and high oil absorption, it is difficult to achieve high filling in the coating system and is compatible with the resin in the coating. Poor performance, unsatisfactory interfacial bonding, and easy flocculation. In order to change this phenomenon, at present, various coating companies mainly add different additives directly in the coating production process, but this method will cause waste of additives, and the dispersion effect is not good, causing the anti-corrosion performance of the coating to fail to meet expectations.
Therefore, in order to give full play to the function of mica, so that the mica can be uniformly dispersed in the coating system, and can form a stable interface with the coating resin after curing, so as to improve the performance of the anti-corrosion coating, it is possible to consider pre-treatment and surface modification of the mica, and then Add it to the coating system.
The surface of mica powder was modified by silane modifier, and the actual functional performance of mica powder before and after modification in the field of industrial anti-corrosion coatings was explored. The results show that:
(1) The use of silane modifier to modify mica powder can significantly improve the application performance of mica in the coating system. The optimum amount of modifier is 1.5%.
(2) The modified mica powder is better than the unmodified mica powder in improving the production efficiency and application performance of the coating system. With the increase of the amount of mica powder added, the viscosity of the system tends to increase due to the increase of oil absorption, and the time for the decrease of fineness will be prolonged, which has a negative impact on the production and efficiency. Compared with the unmodified product, the influence of modified mica powder on the viscosity of the system is significantly reduced, which can improve the production efficiency and system viscosity.
(3) The addition of mica powder has no obvious adverse effect on the physical properties of the coating film.
(4) When the addition amount of mica powder is less than 5%, the anti-corrosion performance of the coating film is slightly poor. Within a suitable range, the larger the addition amount, the better the anti-corrosion performance.
(5) Comprehensive production efficiency and anti-corrosion performance, in industrial anti-corrosion coatings, the reasonable addition amount of unmodified mica powder is 8% to 12%, and the reasonable addition amount of modified mica powder is 10% to 15%. the best overall performance.
How much fineness is suitable for talc powder for plastic reinforcement and modification?
Plastic reinforcement modification is an important application field of talc, especially for polypropylene modification in the automotive and home appliance industries. Micronization is the development trend of talc products. The change trend of talc powder fineness (d50) used for enhancement and modification is as follows: in the 1980s, it was mainly 10-15µm, in the 1990s, it was mainly 8-10µm, and in 2000, it was mainly 5-10µm. , currently in the range of 3.5 to 7 µm.
Generally speaking, the finer the product, the better the enhancement effect, but the cost increases, and at the same time, it is easy to agglomerate, and it is difficult to process and use. It is necessary to choose a product with an appropriate fineness according to its own level of dispersion technology and the expected performance of the product, and it is not necessarily the finer the better.
The evaluation of the particle size of a talc product cannot be based only on the average particle size d50. The average particle size does not characterize the particle size distribution of the product, nor does it characterize the maximum particle size. The evaluation requires at least two indicators, the average particle size d50 and the maximum particle size d98 (or d100). The size and amount of coarse particles have a significant adverse effect on the mechanical properties of the product and need to be strictly controlled.
In recent years, with the application of electric vehicles, the thin-walled and low-density automotive plastic parts have higher requirements for the rigidity of modified plastics and the filling amount of talc. 3000-5000 mesh ultra-fine talcum powder is increasingly used in thin-walled and high-rigidity modified plastic products, especially automotive bumpers with a thickness of 2mm. The mainstream products in this field include Imerys' Jetfine, Liaoning Aihai's HTPultra5L and other products. Relying on high-purity raw materials and swirl grinding process, the ultra-fine powder retains the talc flake structure better, which can increase the flexural modulus by 10% to 15% and reduce the talc filling amount by 5% to 6%.
One disadvantage of fine-mesh talc is its small bulk density, difficulty in direct mixing, low yield, and dust pollution. In recent years, the new technology of exhaust compression has been adopted to improve the bulk density. The density of 1250-5000 mesh powder before compression is 0.25-0.15, and it can reach 0.70-0.45 after compression, and the dispersion is basically unaffected. The exhaust compression can also significantly reduce the amount of air brought into the extruder by the talc powder, reduce the residence time of the material in the extruder, and help improve the anti-aging performance, and the yield can be increased by 15% to 25%.
PLA: The Most Promising Biodegradable Plastic
PLA (polylactic acid) is a new type of degradable material, which can be obtained by extracting starch from renewable plants, then biologically fermented to obtain lactic acid, and finally prepared by chemical synthesis. PLA has good degradability and can be completely degraded by microorganisms. Products made of PLA can be completely degraded into CO2 and water after use, and are non-toxic and non-irritating.
PLA has mechanical properties similar to polypropylene, while its gloss, clarity and processability are similar to polystyrene, and its processing temperature is lower than that of polyolefin. The processing method of plastic is processed into various packaging materials, fibers and nonwovens, etc., which are widely used in industrial, agricultural, medical and civil fields.
The preparation method of PLA can be generally divided into direct polycondensation method and ring-opening polymerization method (lactide method). The direct polycondensation method, also known as the PC method or the one-step method, uses the activity of lactic acid to remove carboxyl and hydroxyl groups in the presence of dehydration groups, so that the lactic acid molecules are polycondensed to form low-molecular polymers, and then the molecules are directly dehydrated by high temperature. One of the processes to condense PLA into PLA is usually melt polymerization, solution polymerization and melt-solid phase polymerization, among which melt polymerization is the most widely used.
The ring-opening polymerization method is also called the ROP method, that is, the lactic acid monomer is first dehydrated and cyclized to synthesize lactide, and then the recrystallized lactide is polymerized to obtain PLA. This method can obtain PLA with extremely high molecular weight. It is about 700,000 to 1 million (low molecular weight PLA can be rapidly degraded, which is conducive to drug release and is suitable for the medical field; high molecular weight PLA has important commercial value in the fiber, textile, plastic and packaging industries), so it is the current industrial The polylactic acid synthesis process mainly used in the above.
Polylactic acid has high strength, high modulus, and good transparency and air permeability, but its crystallization rate is too slow during processing, which leads to prolonged processing cycle and poor heat resistance, which greatly limits the application field of polylactic acid products. . At present, the most common way to improve the performance of polylactic acid is to add a nucleating agent, and in actual enterprise processing applications, talc is the most commonly used inorganic nucleating agent for polylactic acid, which can improve the stretching and bending of polylactic acid, etc. Mechanical properties, improve its heat resistance.
At present, the global PLA production capacity is about 653,500 tons, and the main PLA manufacturers are mainly concentrated in the United States, China, Thailand, Japan and other countries. American Nature Works is the world's largest PLA manufacturer, with an annual production capacity of 180,000 tons, accounting for about 30% of the global PLA production capacity. The production of PLA in my country started relatively late, and the main raw materials of lactide mainly rely on imports. Due to technical reasons or lack of raw material lactide, some PLA plants cannot operate stably or are in a shutdown state. The actual effective production capacity is about 48,000 tons/year, and the output is about 18,000 tons/year.
PLA has a wide range of applications and has been successfully used in plastic packaging, biomedicine, and textile fibers. The harmless properties of PLA make it have broad application prospects in the field of packaging, mainly used as food packaging, product packaging and agricultural mulching films. PLA has a smooth surface, good transparency and excellent barrier properties, and can completely replace PS (polystyrene) and PET (polyethylene terephthalate) in many places, thereby reducing the problem of plastic pollution. PLA degradable fiber integrates degradability, moisture conductivity and flame retardancy, as well as molding, application and degradability, and is widely used in the field of textile fibers. At the same time, PLA has excellent biocompatibility and good physical properties. After its degradation, it generates carbon dioxide and water, which is harmless to the human body and can be degraded naturally. Therefore, PLA is increasingly used in the field of biomedicine, such as tissue consolidation (such as Bone screws, fixation plates and plugs), wound dressing (eg artificial skin), drug delivery (eg diffusion control), and wound closure (eg application of sutures).
Modified bentonite is an important direction for industry upgrading
Bentonite is an important non-metallic mineral whose main component is montmorillonite, which has adsorption, expansion and pulping properties. With the continuous advancement of science and technology, the application field of bentonite has been continuously expanded, the market's requirements for its performance and quality have continued to increase, the technical research of bentonite has continued to deepen, and new processes have continued to emerge. Modified bentonite can improve the performance of traditional bentonite and enhance one aspect of its characteristics, which is an important direction for the diversified and high-end development of the bentonite industry.
Modified bentonite uses bentonite as raw material for performance improvement. Globally, bentonite resources are mainly distributed in China, the United States, Canada, Mexico, Brazil, India, Japan and other countries. China is rich in bentonite reserves, and its proven reserves are ranked first in the world. There are mineral deposits in most parts of the country, mainly in Xinjiang, Guangxi, Inner Mongolia and other places. In the past five years, our annual output of bentonite has been maintained at about 5.6 million tons, which is the largest bentonite producer in the world, providing sufficient raw materials for the development of my country's modified bentonite industry.
The common preparation methods of modified bentonite mainly include activation modification method and modifier modification method. The activation modification method also includes thermal activation method, acid activation method, hydrogen activation method, salt activation method, etc. The first two methods are widely used; the modifier modification method can use inorganic modifiers, organic modifiers, composite Modifier to modify. Modified bentonite can improve some of its properties, such as improving its adsorption, thereby improving its efficiency and application value, thereby expanding its application range and expanding its demand scale.
Modified bentonite can be widely used in papermaking, textile printing and dyeing, plastics, environmental protection and other fields. In the field of papermaking, modified bentonite with large specific surface area, excellent dispersibility, high whiteness and high purity can be used as a multifunctional white mineral filler for paper, and can reduce the water permeability of paper; in the field of textile printing and dyeing, modified bentonite It can be used to produce sizing and dyestuffs, and it can disperse, stabilize and bond during sizing and coloring, so as to improve the quality and production efficiency of sizing and dyeing. In the field of plastics, modified bentonite can be used as filler to modify resins. In the field of environmental protection, modified bentonite can be used for wastewater and waste gas treatment, adsorbing heavy metal ions, oil, tar and other pollutants.
There are a large number of bentonite production enterprises in my country, but most of them focus on the production of low-end products, the technical content and added value of the products are low, the competitiveness of enterprises is weak, and the profitability is limited. my country's bentonite industry is undergoing transformation and upgrading, and the market demand for high-performance bentonite continues to increase, and modified bentonite has a good development prospect.
Choose surface modifier, mainly look at these 3 aspects!
Modifiers are the key to achieve the intended purpose of powder surface modification, but there are many types and strong pertinence. From the point of view of the interaction between the surface modifier molecules and the surface of the inorganic powder, the surface modifier that can chemically react or chemically adsorb with the surface of the powder particles should be selected as much as possible, because the physical adsorption is strong in the subsequent application process. Easy to desorb under stirring or squeezing.
However, other factors must also be considered in the actual selection, such as product use, product quality standards or requirements, modification process, cost, environmental protection, etc.
Selection factor 1: The purpose of the product
This is the most important consideration in selecting the variety of surface modifiers, because different application fields have different technical requirements for powder application properties, such as surface wettability, dispersion, pH value, electrical properties, weather resistance, gloss, antibacterial properties This is one of the reasons for selecting the variety of surface modifiers according to the application.
Selection factor 2: Modification process
The modification process is also one of the important considerations in selecting the variety of surface modifiers. The current surface modification process mainly adopts dry method and wet method.
For the dry process, it is not necessary to consider its water solubility; but for the wet process, the water solubility of the surface modifier should be considered, because only water-soluble can fully contact and react with powder particles in a wet environment.
Selection factor 3: price and environmental factors
Finally, the selection of surface modifiers should also consider price and environmental factors. On the premise of meeting application performance requirements or application performance optimization, try to use cheaper surface modifiers to reduce the cost of surface modification. At the same time, attention should be paid to the selection of surface modifiers that do not pollute the environment.
Types And Processes Of Inorganic Coating Of Titanium Dioxide
In order to meet the requirements for the application performance of titanium dioxide in the actual industry, domestic and foreign scholars have carried out a large number of experimental studies on the inorganic coating of titanium dioxide. Among them, the titanium dioxide coating layer is mostly Al3+, Si4+, Zr4+, Be2+, Ti4+, Mg2+, Mn2+, Cr3+, Ce4+ and other hydrated oxides or hydroxides. In the current industrial production, Al3+, Si4+, Zr4+ are the most widely used.
Studies have shown that the application performance of titanium dioxide depends on the type of inorganic coating on its surface. The surface-coated alumina can be used to improve the dispersion stability in the aqueous system of the product, and the coated silica can be used to increase the weather resistance of titanium dioxide products. performance, the coated zirconium dioxide layer can be used to improve the light resistance of titanium dioxide. Coating a single type or multiple types of inorganic film layers on the surface of titanium dioxide can meet the application performance requirements of titanium dioxide in different application fields. According to the difference of coating composition, inorganic coating can be divided into unit inorganic coating and multi-component inorganic coating.
1. Alumina coating
Coating principle: When the surface of titanium dioxide is coated with alumina, hydrated alumina (Al2O3·nH2O) slowly forms a film on the surface of titanium dioxide particles to form a coating layer.
2. Silica coating
Coating principle: When amorphous hydrated silica is formed, sodium silicate acidifies and precipitates orthosilicic acid in the form of Si(OH)4. The solution only contains orthosilicic acid hydrolysis products H3SiO4- and H3SiO42-, and there is no metasilicon. acid ions. However, H3SiO4- and H3SiO42-monomers are extremely unstable, and the condensation and polymerization reactions proceed rapidly to generate condensed silicic acid with silicon-oxygen bonds.
3. Zirconium dioxide coating
When the titanium dioxide unit is coated with zirconium dioxide, the coating agents are mainly zirconium sulfate, zirconium tetrachloride, zirconium oxychloride and zirconium nitrate. Among them, zirconium sulfate and zirconium oxychloride have the advantages of low cost and less environmental pollution during use. , has been widely used in industry.
4. Silica-alumina composite coating
5. Zirconia-alumina composite coating
6. Ternary inorganic coating