Do you know the 4 degrees of talcum powder?
As a plastic filler, talcum powder can not only save the use of resin, but also significantly improve the physical properties of the product and play a reinforcing role. Talc powder with sufficient fineness can significantly improve the stiffness, impact strength, creep resistance, hardness, surface scratch resistance, heat resistance and heat deformation temperature of the product.
When choosing talc, at least the "four degrees" of talc itself should be considered, namely: purity, whiteness, flakeness and fineness. Generally speaking, in order to evaluate the quality of talc products, at least the above four factors should be considered.
Purity
Purity refers to the talc content of the product. Talc contains impurities in nature and industrial production, and it is impossible for 100% pure talc products to exist in industry. Undoubtedly, the higher the purity of talc powder, the better the reinforcing effect. Some impurities in talc powder not only reduce the purity of talc powder, but also have a significant impact on the performance of the final product.
Whiteness
There are two types of whiteness in the talc industry: narrow whiteness and broad whiteness. Narrow whiteness is a general definition of whiteness, which can be expressed by blue light whiteness R457, Y, L*, Ganz whiteness and Hunter whiteness. Broad whiteness includes dry whiteness, wet whiteness and hue. The so-called wet whiteness is the whiteness measured after adding an appropriate amount of DMP (dimethyl phthalate) to talc powder.
For the same raw materials, the finer the particle size, the higher the whiteness. The higher the moisture content, the lower the whiteness. Although whiteness has no effect on the physical properties of the product, it is very important to maintain the purity of the color for light-colored products.
Flakes
The significant reinforcing effect of talcum powder on plastic products mainly comes from its unique micro-flaky structure. The more complete the flaky structure of talcum powder, the more obvious its reinforcing effect. The two main factors affecting the flake of the product are: the purity of talcum powder and the processing technology of powder.
Impurities in talcum powder do not have a flaky structure. The purer the talcum powder, the fewer impurities and the better the flaky structure. In the process of micronizing the product, the flaky structure of the product is maintained differently when different methods are used. Improper methods and operating conditions may even destroy its flaky structure.
Fineness
Micronization is the development trend of talcum products. The finer the product, the better the reinforcing effect. At the same time, the surface energy of the particles increases, it is easy to agglomerate, difficult to disperse, and expensive. Therefore, we need to choose products with appropriate fineness according to our own technical level and actual needs, not the finer the better.
The evaluation of the particle size of a talc product cannot be based on the average fineness alone. There are at least two indicators to evaluate the quality of a product: D50 and D100 (or D98).
As products become finer and finer, people have higher requirements for the microscopic shape and particle size distribution of fine talc after crushing. The main indicator for evaluating particle size distribution has shifted from D50 to D97, D98 and now D100. At the same time, the reproducibility of particle size distribution is more stringent. When evaluating a product, its average particle size must not only meet the requirements, but more importantly, the particle size distribution should be as narrow as possible, with as few large particles as possible.
The product should strive to achieve the same particle size distribution for each batch, which is very difficult in production practice. In high-end talc products, controlling particle size distribution, especially the number of coarse particles, is a very critical technology, which requires both high-efficiency, high-precision, and reliable grading equipment and rich operating experience and equipment maintenance capabilities. There are only 6-7 companies in China that have mastered relatively mature particle size control technology.
Particle size distribution can be measured by a particle size distribution instrument, including laser method and sedimentation method. However, in production practice, screening method is mostly used to detect the amount of coarse particles.
It is worth noting that talcum powder has a large specific surface area and a small volume density due to its own flaky structure. The volume density of 325 mesh talcum powder is 0.8-0.9g/cm3, while 1250 mesh talcum powder has dropped to 0.25-0.3g/cm3, and 4000 mesh is only about 0.12g/cm3. This causes serious dust pollution during use, difficulty in mixing, increased costs, and reduced yields. In addition, the freight cost of long-distance supply is quite high.
The Importance of Silicon Nitride (SiNx) in Chips
In chip manufacturing, there is a material that plays a vital role, that is silicon nitride (SiNx). Although it may not receive the same attention as other more well-known semiconductor materials such as silicon (Si), gallium arsenide (GaAs) or gallium nitride (GaN), its importance is unquestionable. It can be said that most chips will use this material.
In the semiconductor industry, silicon nitride used in various applications is often non-uniform, generally represented by SiNx. SiNx is an amorphous material whose properties depend on the ratio of nitrogen to silicon, that is, the value of x. When the value of x changes, the physical and chemical properties of silicon nitride will also change. Silicon nitride does come in many forms, including Si3N4, Si2N2, SiN, etc.
Si3N4 is a crystalline material, which means that the ratio of silicon to nitrogen is fixed. When the value of x is equal to 4/3, SiNx is equal to Si3N4. However, in practical applications, SiNx is often non-fixed, and its ratio of silicon to nitrogen can be adjusted by changing the parameters of the PVD or CVD process.
Silicon nitride has excellent insulation properties, with a resistivity of up to 10^14 Ω·cm, far exceeding some common insulating materials such as silicon oxide (SiO2). Its low dielectric constant makes it an ideal isolation layer in microwave and radio frequency applications. The silicon nitride layer also acts as a barrier to impurity diffusion in the chip. It can prevent dopants such as boron and phosphorus from changing device characteristics through diffusion. In addition, it can also prevent the diffusion of metal ions to prevent faults such as short circuits.
Silicon nitride has excellent thermal stability, which is determined by its special chemical properties and crystal structure. It can remain stable in high temperature environments without chemical decomposition or physical changes like other materials. That's because in the crystal structure of silicon nitride, each silicon atom is combined with four nitrogen atoms in the form of a tetrahedron, and each nitrogen atom is also combined with four silicon atoms in the form of a tetrahedron. This structure makes the crystal lattice of silicon nitride extremely stable and not easy to deform. Therefore, it is used as a gate insulating layer when manufacturing high electron mobility transistors (HEMTs).
What are the advantages of SiNx over SiO2?
Better thermal stability, harder hardness, and more difficult to etch.
The Difference and Application of Calcite and Dolomite
Calcite and dolomite are both carbonate rocks with similar crystal structures. They are common minerals in strata and are abundant in nature. Both can be ground and widely used in many fields, but their composition and uses are very different.
The main components of calcite and dolomite are calcium carbonate, but calcite, a sedimentary rock, is relatively solid, with poor porosity and low permeability, and underground fluids often cannot penetrate well into it. Although dolomite also contains a large amount of calcium carbonate, it also contains a considerable amount of magnesium carbonate. Dolomite has more cracks than calcium carbonate strata, so it has good permeability.
Both calcite and dolomite can be ground and used. Calcite can be ground into powder to obtain heavy calcium carbonate, which is a commonly used powdered inorganic filler. It has the characteristics of high chemical purity, high inertness, not easy to react chemically, and good thermal stability. Therefore, it can be used in rubber, plastic, papermaking, construction (dry mortar, concrete), artificial marble, feed, putty powder coating and other industries. Adding a large amount of calcite powder to rubber can make the rubber's tensile strength, tear strength and wear resistance better; adding calcite powder to plastic products can play a certain skeleton role, which can not only enhance the stability of the product, but also improve the hardness of the product, the smoothness of the surface, etc.
Dolomite has many uses after being ground into fine powder, among which the most widely used is in the field of coatings. 325 mesh dolomite powder is the main raw material of white powder, and can also produce putty powder and dry mortar. Grinding to more than 800 mesh, the whiteness reaches 95, and after surface treatment, it can be used as a filler for latex paint. Modified dolomite powder is also a filler in the rubber and paper industry, which can improve product performance and reduce costs. Ceramic blanks are also mixed with dolomite powder, which can reduce the firing temperature of the blank and increase the transparency of the blank. In addition, dolomite powder is also an ideal sewage purifier and adsorbent, and can also be used to make snow melting agents.
ALPA ball mill + extension production line integrates grinding and conveying, and can be used to prepare calcite and dolomite ultrafine powder
【Application fields】: building materials, chemicals, metallurgy, coatings, papermaking, rubber, medicine, food and other fields.
【Applicable materials】: bauxite, kaolin, barite, fluorite, talc, slag, lime powder, wollastonite, gypsum, limestone, phosphate rock, calcite, marble, dolomite, potassium feldspar, quartz sand, bentonite, manganese ore and other materials.
Application of Alumina Ceramics
Ceramics are used as biomaterials to fill defects in teeth and bones, fix bone transplants, fractures or prostheses to bones, and replace diseased tissues. They are called bioceramics. They are widely used in the medical field because of their excellent characteristics such as high strength, wear resistance, higher compression and bending strength, and high biocompatibility.
The concept of alumina ceramics covers a wide range. In addition to pure alumina ceramics, any ceramic material with an alumina content of more than 45% can be called alumina ceramics. Alumina ceramics have many isomorphous and heteromorphic crystals, but the most commonly used are only α-Al2O3 and γ-Al2O3. Due to their different crystal structures, they have different properties. Among them, α-Al2O3, also known as corundum, is the main crystal phase of alumina ceramics, with high mechanical strength, high temperature resistance, and corrosion resistance.
Application of Alumina Ceramics in Artificial Joints
High-purity alumina ceramics have a very low friction coefficient, high hardness, and good wettability, making them very suitable for use as joint friction surfaces. Only high-purity alumina can be used in the medical field, and impurities that can form glass grain boundary phases (such as silica, metal silicates, and alkali metal oxides) must be less than 0.1wt%, because the degradation of such impurities will lead to stress concentration sites where cracks will appear. Studies have found that by selecting appropriate sintering parameters (temperature, time, heating/cooling rates) and doping additives (such as magnesium oxide, zirconium oxide, and chromium oxide), the grain size and porosity of alumina can be controlled, and the toughness and fracture strength of alumina can be effectively improved.
Composite materials formed by zirconium oxide and alumina are called zirconium oxide toughened alumina (ZTA) or alumina toughened zirconia (ATZ), which also play an important role in artificial joint materials. These two composite materials depend on the content of the main components. These composite materials combine the toughening ability of zirconium oxide with the low sensitivity of alumina to degradation in low-temperature biological fluids. According to the design requirements of the material, ATZ can be used when high fracture toughness is required, while ZTA can be used when hardness is required. There is no sufficient clinical data to show that ZTA joint bearing surfaces have greater advantages in wear resistance. Studies have shown that the application of ZTA and zirconium oxide-based toughened alumina (ZPTA) in joint surgery is far greater than ATZ.
Application of Alumina Ceramics in Oral Restoration
Alumina ceramics have light transmittance and color that match those of real teeth, and are slightly toxic. Alumina ceramics have significantly low thermal conductivity, which reduces the stimulation of cold and hot foods on the pulp. Zirconia ceramics are resistant to wear, corrosion, and high temperatures, and their color is similar to that of real teeth. They are suitable for tooth restoration and have high strength. According to the physical composition of alumina ceramic materials and the different manufacturing processes, alumina ceramics used in the field of all-ceramic restoration can be divided into the following categories:
(1) Glass infiltration alumina ceramics
Glass infiltration, the full name is slurry coating glass infiltration method. Alumina, as a matrix material, presents a porous structure, and the lanthanum-borosilicate glass containing colorants penetrates into it. After forming, it has a microstructure in which alumina crystal phases and glass crystal phases interpenetrate each other.
(2) High-purity dense sintered all-alumina ceramics
It is composed of alumina with a purity of 99.9%. Alumina powder is pressed into a green body (dry pressing) under great pressure and then sintered. The pressure forming method gives alumina ceramics high density and low porosity.
(3) Glass-infiltrated zirconia toughened alumina ceramics
This type of ceramic is formed by adding 35% partially stabilized zirconia to glass-infiltrated alumina ceramic powder. Evenly distributed tetragonal zirconia can be observed inside the formed material.
With the continuous development of science and technology, alumina bioceramic materials are being used more and more widely in the medical field, and research on them will move towards emerging medical directions with higher added value and more prospects.
Application of calcium hydroxide in food industry
Calcium hydroxide, also known as slaked lime or quicklime, is made by calcining and digesting raw materials such as limestone or oyster shells containing limestone. It is generally in powder form and is widely used in food, medicine, chemical industry, drinking water treatment and other fields.
Since the solubility of calcium hydroxide is much smaller than that of sodium hydroxide and potassium hydroxide, the corrosiveness and alkalinity of its solution are relatively small. Therefore, it can be used as an acidity regulator in food to play a role in buffering, neutralization, and solidification. Food-grade calcium hydroxide has a relatively high activity, a relatively loose structure, high purity, good whiteness, low impurity content, and does not contain harmful elements such as Pb and As.
1. Calcium preparations
There are nearly 200 calcium preparations on the market, including calcium carbonate, calcium citrate, calcium lactate, and calcium gluconate. Calcium hydroxide is widely used as a raw material in the calcium preparation production industry. Among them, calcium gluconate is common. In my country, it is currently produced by fermentation.
2. Milk powder
Calcium hydroxide can be used as an acidity regulator in milk powder (including sweetened milk powder) and cream milk powder and its modulated products, and infant formula. The amount used is appropriate according to production needs.
Because milk powder, especially infant formula milk powder or food, contains a certain amount of different types of proteins, due to the presence of ionized side chains on the surface of proteins, proteins carry a net charge, and these side chains can be titrated.
3. Rice tofu and ice jelly
Use soaked rice, add water, grind into rice slurry, add slaked lime water and stir evenly, heat, and stir until the rice slurry is cooked and thick. Pour the boiled rice slurry into a mold, and after it is completely cooled, you can cut it into small pieces with a knife, and the rice tofu is ready. Among them, slaked lime acts as a coagulant and also provides calcium. Slaked lime also needs to be added during the production of ice jelly, which also acts as a coagulant.
4. Preserved eggs
Slaked lime, soda ash and wood ash are used as raw materials to make a slurry and wrap it on the surface of the egg. After a period of time, it becomes a preserved egg that can be eaten directly through chemical reactions. When protein encounters a strong alkali, it gradually turns into clear water. If the alkaline solution continues to enter the egg through the semipermeable membrane, the alkalinity continues to increase, and the alkaline protein molecules begin to polymerize and the viscosity gradually increases, turning into a gel to form a preserved egg. If the alkali is excessive, it will be detrimental to the quality of the preserved egg.
5. Konjac food
The production and use of konjac gel food by the Chinese people has a history of 2,000 years. The production method is to add 30-50 times the amount of water to konjac flour, stir it into a paste, add 5%-7% calcium hydroxide to konjac flour, mix and solidify it.
6. Sugar production
In the process of sugar production, calcium hydroxide is used to neutralize the acid in the syrup, and then carbon dioxide is introduced to make the remaining calcium hydroxide precipitate and filter out, so as to reduce the sour taste of sugar. It can also combine with sucrose to form sucrose salt, so it can be used for molasses desugaring or sugar refining.
7. Others
Calcium hydroxide can be used as a buffer, neutralizer, and curing agent for beer, cheese, and cocoa products. Due to its pH adjustment and coagulation effects, it can also be used in the synthesis of medicines and food additives, the synthesis of high-tech biomaterials HA, the synthesis of VC phosphates for feed additives, and the synthesis of calcium cyclohexaneate, calcium lactate, calcium citrate, additives for the sugar industry, water treatment, and other high-end organic chemicals. It is helpful for the preparation of acidity regulators and calcium sources such as edible meat semi-finished products, beverage products, and medical enemas.
The calcium hydroxide industry developed early, and its annual output can reach more than 10 million tons. It is mainly produced in the UK, the US, and Germany, and Japan and South Korea mainly produce high purity and high whiteness.
Limestone Powder Grinding Process
Limestone is the main raw material for producing cement, concrete coarse and fine aggregates, lime, calcium carbonate, etc. Its crushing and grinding generally adopt dry process, and the corresponding process is selected according to different application fields:
For limestone used in metallurgy and road construction, the ore is generally crushed and screened.
For fine powder products used as feed additives and ordinary fillers, the ore is generally crushed by granular crusher, hammer crusher, impact crusher, etc. and then directly ground by Raymond mill, vertical mill, roller mill, impact mill, etc.
For ultrafine limestone powder and high-grade fillers used for flue gas desulfurization, ultrafine crushing and fine classification are generally required, and the process equipment is basically the same as the ultrafine crushing of calcite.
At present, most of the limestone powder used in the building materials industry is limestone or stone chips generated in the production of aggregates, etc., which are ground to meet the specified fineness requirements.
1. Limestone grinding process
There are two main processes for limestone grinding:
Open-circuit process: the process in which the material passes through the mill once and is used as the finished product for the next stage of operation;
Closed-circuit process: the process in which the material is sorted at one or several levels after leaving the mill, and the fine particles are used as the finished product, and the coarse particles are returned to the mill for re-grinding.
The open-circuit process is relatively simple, with the advantages of less equipment, less investment, and easy operation. However, because all materials need to meet the fineness requirements before leaving the mill, over-grinding is prone to occur, and the finely ground materials are prone to form a buffer layer, which hinders the further grinding of coarse materials, greatly reduces the grinding efficiency, and increases power consumption.
Therefore, most limestone powder manufacturers currently choose the closed-circuit process, which can reduce over-grinding, improve mill efficiency, and reduce energy consumption. In addition, the limestone powder produced by the closed-circuit process has uniform particle size and is easy to adjust, which can meet different fineness requirements.
2. Example of closed-circuit production of limestone powder Raymond mill
Process description:
Limestone falls from the hopper at the bottom of the silo to the belt conveyor, and then is sent to the mill for grinding.
Because the grinding roller rolls tightly on the grinding ring under the action of centrifugal force, the material is scooped up by the shovel and sent to the middle of the grinding roller and the grinding ring, and the material is crushed into powder under the action of the grinding pressure.
The powdered material is blown out by the fan and classified by the classifier above the mill.
The classifier is composed of radial radial blade wheels and transmission devices. The blade wheels are driven by the transmission device to rotate at a certain speed, blocking the coarse particles in the air flow and returning them for re-grinding. The fine powder is sent to the cyclone separator with the air flow through the wind screen, so the classifier plays a screening role. The powder particle size can be freely adjusted by adjusting the air volume or changing the blade wheel speed.
The cyclone separator separates qualified products from the air, and the finished products are transported to the finished product warehouse through the bucket elevator through the pipeline, and the air flow returns to the blower through the return air duct for recycling.
The material contains a certain amount of moisture, and a certain amount of water vapor will be generated during grinding. In addition, the entire pipeline is not sealed absolutely tightly, so a certain amount of external gas is sucked into the system, which increases the system's circulating air volume. To ensure that the grinder works under negative pressure, the excess air enters the bag dust collector for purification and then is discharged into the atmosphere.
How to extend the life of vertical mill equipment
In cement production, vertical mill is a key equipment, and the operating status of its roller bearing is crucial to production safety and efficiency.
How to make the vertical mill roller last longer
1. Choose the right lubricant and replace it regularly
The choice of lubricant is crucial. You should choose high-quality lubricants suitable for high temperature and high pressure environments. At the same time, the lubricant needs to be replaced regularly to ensure its stability and cleanliness during use and avoid bearing damage caused by oil quality problems.
2. Strengthen daily maintenance, early detection and early treatment
Operators should regularly check the operating status of the lubrication system, especially in high temperature environments, and pay attention to changes in oil temperature. If the oil temperature is abnormal, the machine should be stopped immediately for inspection and continue to operate after troubleshooting. The wear of the bearings should also be checked regularly, and the problematic parts should be replaced in time to avoid further damage.
3. Regularly check and replace oil seals
Although the oil seal is small, it has a huge effect. The wear of the oil seal should be checked regularly, and the failed oil seal should be replaced in time to ensure that the lubricant does not leak and prevent external impurities from entering the bearing. This simple measure can greatly extend the service life of the bearing.
In addition to bearing problems, the wear resistance of the grinding roller and grinding disc liner is also an important factor affecting the life of the vertical mill. Different materials and manufacturing processes determine the wear resistance of the grinding roller and grinding disc.
1. Traditional casting: low cost, high risk
Traditional casting processes mainly use high manganese steel and high chromium cast iron as materials. The advantages of these materials are low cost, simple process, and suitable for large-scale production.
However, they also have obvious disadvantages. Although high manganese steel has good toughness, its wear resistance is relatively low. The wear resistance of high chromium cast iron has been improved, but its brittleness problem is still prominent, and it is easy to crack during use, which makes it impossible to repair and can only be used once.
2. Micro casting (surface cladding): cost-effective choice
Micro casting, also known as surface cladding technology, is currently the most widely used anti-wear solution. This process is to improve the wear resistance of grinding rollers and grinding discs by cladding a wear-resistant layer on an ordinary cast steel substrate.
3. Ceramic alloy composite casting: the future wear-resistant star
Ceramic alloy composite casting is an emerging wear-resistant technology that embeds ceramic particles into the surface of the cast iron matrix, significantly improving the wear resistance of the grinding roller and grinding disc. This material has extremely high wear resistance and toughness, and is particularly suitable for use under harsh working conditions.
However, the process of ceramic alloy composite casting is complex, the manufacturing cost is high, and there is also the problem of irreparability. It is more suitable for special working conditions with extremely high requirements for wear resistance, rather than ordinary cement production environments.
4. How to choose the most suitable solution?
When selecting the materials for grinding rollers and grinding disc liners, hardness, toughness, cost and repairability should be considered comprehensively according to specific working conditions.
Traditional casting is suitable for those occasions with high cost control requirements and relatively simple working conditions;
Micro casting is suitable for most cement plants. It can provide better wear resistance while reducing maintenance costs;
Ceramic alloy composite casting is suitable for some special working conditions. Although the cost is high, its extremely high wear resistance is worth paying attention to.
Application of Ultrafine Grinding Technology in Food Industry
Ultrafine grinding technology has emerged in recent years with the continuous development of modern chemical industry, electronics, biology, materials and mineral development and other high-tech technologies. It is a high-tech cutting-edge technology for food processing at home and abroad.
In the field of food processing, powders with a particle size below 25μm are usually called ultrafine powders, and the method of preparing ultrafine powders is called ultrafine grinding technology.
The ultrafine grinding technologies commonly used in food mainly include airflow type, high-frequency vibration type, rotating ball (rod) mill type, roller type, etc. Among them, airflow ultrafine grinding technology is more advanced, using the gas through the pressure nozzle to generate violent impact, collision and friction forces to achieve material grinding.
Classification of ultrafine grinding technology in the food industry
Although food ultrafine powder has been around for a short time, it has been used in condiments, beverages, canned foods, frozen foods, baked foods, health foods, etc., and the effect is better.
Application of ultrafine grinding technology in food processing
Soft drink processing
At present, soft drinks developed using airflow micro-grinding technology include powdered tea, bean solid beverages, and calcium-rich beverages prepared with ultrafine bone powder.
Tea culture has a long history in China. Traditional tea drinking is to brew tea with boiling water. The human body does not absorb a large amount of nutrients from tea. Most of the protein, carbohydrates and some minerals and vitamins are retained in the tea residue. If tea is made into tea powder (particle size <5μm) at room temperature and dry state, the absorption rate of its nutrients by the human body can be improved.
Adding tea powder to other foods can also develop new tea products. Plant protein beverages are milky products made from protein-rich plant seeds and fruit cores through soaking, grinding, homogenization and other operations.
Fruit and vegetable processing
Vegetables are ground into micro-paste powder at low temperature, which not only preserves the nutrients, but also makes the fiber taste better due to the micro-refining.
Grain and oil processing
Adding ultrafinely ground wheat bran powder, soybean powder, etc. to flour can make high-fiber or high-protein flour. Rice, wheat and other grains are processed into ultrafine powder. Due to the small particle size, the surface starch is activated, and the food filled or mixed with it has the excellent properties of easy maturation, good flavor and taste.
Soybeans are processed into soy milk powder after ultrafine grinding, which can remove the fishy smell. Beans such as mung beans and red beans can also be made into high-quality bean paste, soy milk and other products after ultrafine grinding.
Aquatic product processing
Spirulina, pearls, turtles, sharks and other cartilage ultrafine powders have unique advantages. For example, the traditional processing of pearl powder is to ball mill for more than ten hours to make the particle size reach several hundred meshes.
Functional food processing
Ultrafine powder can improve the bioavailability of functional substances and reduce the amount of base materials in food. The sustained release of microparticles in the human body can prolong the efficacy. In the process of developing solid honey, ultrafine grinding of ingredients with a colloid mill can increase the fineness of the product.
Processing of spices and condiments
Ultrafine grinding technology, as a new food processing method, can make spices and seasoning products (mainly fermented solid products of beans) processed by traditional processes more high-quality.
The huge porosity of spices and seasonings after micronization creates a collective cavity that can absorb and contain aroma, and the flavor lasts for a long time, and the aroma and taste are more intense.
At the same time, ultrafine grinding technology can make traditional seasonings finely broken into excellent ultrafine particles with uniform particle size and good dispersion performance, and the fluidity, dissolution rate and absorption rate are greatly increased, and the taste effect is also significantly improved.
For products with high sensory requirements, the particle size of spices after ultrafine grinding is extremely fine, up to 300-500 mesh, and the naked eye cannot observe the existence of particles at all, eliminating the generation of black spots in the product and improving the appearance quality of the product. At the same time, the corresponding equipment of ultrafine grinding technology has physical and chemical functions such as coating, emulsification, solid emulsification, and modification, creating a realistic prospect for the development of seasoning products.
What are the applications of titanium dioxide in different coatings?
In recent years, with the rapid development of the coatings industry, people have higher and higher requirements for the performance of titanium dioxide. Not only do they require titanium dioxide to have very good dispersibility, but they also require titanium dioxide to have very good hiding properties. At the same time, they also have very high requirements for the impurity content of titanium dioxide. Under such high requirements, the widely used titanium dioxide has continuously improved its production technology, improved its performance, and expanded its application direction.
Among them, pigment-grade titanium dioxide has a high refractive index and strong tinting power, and has very outstanding advantages in both hiding power and dispersibility. For this reason, pigment-grade titanium dioxide has been widely used in coatings and papermaking. The proportion of pigment-grade titanium dioxide in coatings is the largest, among which rutile titanium dioxide is widely used in industry.
As decorative coatings
The pigment performance of pigment-grade titanium dioxide is very good, and modern people mostly choose white or light colors to decorate houses in house decoration. Therefore, pigment-grade titanium dioxide has been widely welcomed by people in house decoration. Not only that, pigment-grade titanium dioxide is also widely used in external coatings for ships, cars, etc.
As architectural coatings
Pigment-grade titanium dioxide plays a very important role in the production process of coatings, and titanium dioxide is mainly used in architectural coatings.
Make pure white coatings
Most white coatings on the market use a large amount of pigment-grade titanium dioxide in the manufacturing process.
Make colorful pattern coatings
Many pattern coatings on the market now cannot do without pigment-grade titanium dioxide in terms of color ratio or pattern, so pigment-grade titanium dioxide plays a very important role in the production of colorful pattern coatings. Pigment-grade titanium dioxide has also been widely used in automotive exterior paint because pigment-grade titanium dioxide has very good color and high brightness.
Make special functional coatings
Many high-temperature resistant coatings use pigment-grade titanium dioxide in the production process, and high-temperature resistant coatings are a type of special functional coatings, so pigment-grade titanium dioxide is an indispensable raw material in the production of special functional coatings.
Making conductive materials
Titanium dioxide can also be used to make conductive materials. Since the surface of pigment-grade titanium dioxide particles can form a coating, titanium dioxide can also be used in the production of antistatic materials.
Making core-coated titanium dioxide
Pigment-grade titanium dioxide can also be used to make core-coated titanium dioxide, which is also often used in the production of coatings.
Making slurry titanium dioxide
There is also a slurry titanium dioxide in the classification of titanium dioxide. It does not require very complicated processes or very high production costs during the production process. Therefore, slurry titanium dioxide is very popular in people's production and life. Pigment-grade titanium dioxide is indispensable in the production process of slurry titanium dioxide, so pigment-grade titanium dioxide plays a very important role in the process of making slurry titanium dioxide.
UV shielding effect
Nano-grade titanium dioxide is widely used in the production of anti-UV coatings. In many places in people's lives, it is necessary to avoid ultraviolet radiation. Therefore, it is very necessary to use nano-grade titanium dioxide with the function of UV shielding to make anti-UV coatings.
UV absorption effect
Nano-grade titanium dioxide can not only shield ultraviolet rays, but also absorb ultraviolet rays to a certain extent. Therefore, many light-colored coatings use nano-grade titanium dioxide in the production process. In addition, this titanium dioxide can also improve the weather resistance of building exterior walls.
Effect pigments
Rutile nano-grade titanium dioxide is widely used in automotive exterior paint. It can not only effectively cover the poor gloss of the exterior surface of the car, but also present people with more exquisite light effects. In addition, the application of rutile nano-grade titanium dioxide on the automotive topcoat allows people to see different light effects from different angles, thereby meeting people's visual needs.
Whether calcite can produce high-end calcium carbonate depends on these indicators
Calcite is a natural calcium carbonate mineral and the main raw material for producing heavy calcium carbonate. The grade and impurity content of calcite ore are one of the important factors affecting the quality index of heavy calcium carbonate products, and are also the key to determining whether it is food and drug grade calcium carbonate or ordinary filler grade calcium carbonate.
1. CaO content
CaO is the only quality mark of the useful components of the ore. In the requirements of papermaking, coatings, plastics, rubber and food industries, it is expressed by the content of CaCO3 (which can be converted from CaO content).
2. Whiteness
Whiteness is the physical quality mark of the ore, which is related to the color and brightness of the finished product.
3. Hydrochloric acid insolubles
The components of hydrochloric acid insolubles (A.I.R) mainly include free silica (fSiO2), (aluminum) silicates and iron and manganese oxides, which are multi-mineral combination indicators.
4. Magnesium and alkali metal content
MgO is mainly used to evaluate the dolomite content in the ore. In the paper and plastic industries, when the dolomite content is less than 3% (equivalent to MgO≤0.65%), the impact is not significant. In the coating and rubber industries, this requirement can be relaxed to 6% (equivalent to MgO≤1.3%). MgO from talc and serpentine is generally considered to have little impact.
5. SiO2 content
SiO2, various ore tests show that it mainly comes from fSiO2, aluminosilicates and silicate minerals. Among them, silicate minerals are mainly wollastonite, which has a certain difference in hardness from calcite and affects the uniformity of product particle size. Water washing can remove some Si, Al and Fe in calcite and improve the whiteness of the ore.
6. Al2O3 content
Al2O3 mainly comes from aluminosilicate minerals and is one of the main components of hydrochloric acid insolubles. The allowable value should not be greater than the limit value of hydrochloric acid insolubles.
7. Fe2O3 content
Fe2O3 is a coloring component, and its content has an impact on the color of the product. According to the industry's experience, Fe2O3≤0.3% has no significant effect, and Fe2O3≤0.1% has almost no effect. Fe2+ exists in many minerals. If it changes in price during processing or use, its impact needs to be paid attention to.
8. MnO content
MnO in calcite ore mainly comes from manganese oxides, carbonate minerals and silicate minerals. MnO will affect whiteness. There are no requirements for manganese in the current industry standards. In previous indicators, the rubber industry application requires control of its content.
9. Harmful content
Heavy metals, barium, fluorine, arsenic, free alkali, (alkali metal + magnesium), sulfur and other indicators. These indicators need to be evaluated for use as food additives, toothpaste and food packaging paper production, or for rubber products and plastics and coating fillers that have an impact on health.
10. Content of dark foreign matter
The content of dark foreign matter and particle size have a certain impact on whiteness. Under the current conditions, it is recommended to conduct qualitative statistics on the content of dark foreign matter and particles to evaluate whether it is suitable for ultra-fine processing. When the content of dark foreign matter in heavy calcium carbonate for papermaking industry exceeds a certain content, it should be used as an evaluation indicator. Generally, it is required that no more than 5 dark foreign matter particles should be contained in each gram of sample.
11. Yellowness and transparency
The whiteness currently tested, also known as blue light whiteness, is actually the brightness of the material and cannot reflect the color difference of the material well. Therefore, heavy calcium carbonate for papermaking needs to evaluate yellowness and transparency. The papermaking industry hopes that the yellowness is low, the transparency is low, and the coverage is good. Calcite with high whiteness often has good transparency.