Application of Dolomite Powder

Dolomite is a carbonate mineral, including iron dolomite and manganese dolomite. Its crystal structure is like calcite, often in the form of rhombohedrons; bubbles will slowly appear when exposed to cold dilute hydrochloric acid; some dolomites emit orange-red light under cathode ray irradiation. Dolomite is the main mineral component of dolomite and dolomitic limestone.

Dolomite can be used in building materials, ceramics, glass and refractory materials, chemical industry, agriculture, environmental protection, energy saving and other fields. It is mainly used as a flux for alkaline refractories and blast furnace ironmaking; production of calcium magnesium phosphate fertilizer and preparation of magnesium sulfate; and ingredients for the production of glass and ceramics. It is also used as a flux in the glaze. Some ancient kilns in the north, such as Ding Kiln, often add dolomite to the glaze, and dolomite is also added to some glazes in Jingdezhen, which requires a dolomite mill. support.

Dolomite powder is pure white, insoluble in water, with a relative density of 2.5, stable chemical properties, and a slippery feel. As a plastic filler, dolomite powder can improve the hardness, fire resistance, acid and alkali resistance, electrical insulation and dimensional stability of the product. It is widely used in plastics, rubber, cables, paints, coatings, ceramics, EVA, and other industries.

1.   Used in rubber, it can increase the volume of the rubber, improve the processability of the rubber, play a role of semi-reinforcement or reinforcement, and can adjust the hardness of the rubber.

2.  In plastics, it can increase the volume of the plastic, reduce the cost of the product, improve the dimensional stability of the plastic and the hardness and rigidity of the plastic, improve the heat resistance of the plastic, and improve the astigmatism of the plastic.

3.  Used for exterior wall insulation mortar, putty powder, ball factory lawn self-leveling mortar, epoxy floor, exterior wall latex paint, real stone paint, FRP sand pipe, plastic, rubber, paint, coating, etc.

It can be seen that the application market of dolomite has broad prospects.

Dolomite powder processing is generally divided into dolomite coarse powder processing (0-3mm), fine powder processing (20 mesh-400 mesh), and dolomite ultrafine powder deep processing (400 mesh-1250 mesh) and micro powder processing (1250 mesh) -3250 mesh) four types, select the appropriate equipment according to different processing techniques.

by ALPA Powder

Selection of Ultrafine Grinding Equipment for Traditional Chinese Medicine

Ultra-micro grinding generally refers to the process of pulverizing material particles above 3mm to below 10~25μm. After ultra-fine grinding, traditional Chinese medicine has the following advantages: improve the bioavailability of the medicine, improve the dissolution of the medicine, improve the performance of the medicine, reduce the dosage of the medicine, save resources, improve the preparation technology, not easy to produce pollution during processing, high grinding precision, powder Good body shape.

Classification of Chinese medicine

• Plant Chinese Medicine

Starch-based drugs, such as myrtle, mung bean, etc.; fibrous drugs, such as angelica, licorice, etc.; oleaginous volatile drugs, such as frankincense, schisandra, nootropics, etc.

• Animal Chinese Medicine

Such as shark cartilage, silkworm pupae, pearls, etc.;

• Mineral Chinese Medicine

Such as talc and so on.

Application of Chinese Medicine Ultrafine Grinding

Ultrafine grinding of traditional Chinese medicine is widely used, such as wolfberry, Shouwu, American ginseng, licorice, pollen, Ganoderma lucidum, hawthorn nucleus, animal bones, minerals and hundreds of traditional Chinese medicine products can be ultrafine grinding.

Principles of equipment selection

Ultra-fine grinding is not as fine as possible, but to control the powder according to customer or process requirements.

The selection of crushing equipment should be based on factors such as the characteristics of the material to be ground, the output of the material to be ground, the fineness requirements of the material to be ground, the value of the Chinese medicine product of the material to be ground, and the cost of grinding.

Chinese medicine ultrafine grinding equipment

• Mechanical impact mill

An impeller driven by a motor to rotate at a high speed is equipped with a movable blade (or hammer) to grind traditional Chinese medicine. It is suitable for grinding medium-soft and hard Chinese medicines, brittle Chinese medicines such as mineral medicines, and Chinese medicines with a lot of starch, such as rice and mung beans.

Mechanical impact grinding has high efficiency, large crushing ratio, simple structure and stable operation. However, the high-speed operation causes the temperature to rise, and the efficacy of the medicine may be lost, and the passage of the sticky wall may be blocked, and the resulting abrasion may cause the pollution of the medicine.

• Jet mill

The high-pressure airflow is used to make the particles of the ground material violently collide, impact, and friction with each other, and the direct shearing effect of the airflow on the material is used to achieve the grinding effect. Chinese medicine suitable for grinding: brittle Chinese medicine, heat sensitive materials.

The products of the jet mill can be pulverized very fine (particle size up to 1-10μm), narrow particle size distribution range, easy to clean, and low temperature. However, this method is not applicable to medicinal materials containing volatile components, and a certain degree of fineness is required before the powder is ground.

• Vibration mill

Using the medium rotation and medium impact generated by the vibration, the material to be ground is impacted in a positive direction and at the same time subjected to tangential shear, thereby realizing high-energy, high-speed grinding.

The vibration mill has high grinding efficiency, low loss, strong adaptability to the processing object, fully enclosed operation, no dust pollution, and low grinding temperature. However, it is prone to sticking to the wall, and the water content of the material is relatively high.

• Cryogenic Grinder

It is suitable for crushing high value-added Chinese medicinal materials and foods that are difficult to grind at room temperature, easily deteriorated and decomposed by heat, as well as ultra-low melting point, super heat sensitive and super viscous materials (especially animal Chinese medicinal materials with high fat and high protein) )

The low-temperature grinder is non-polluting and has a wide range of applications. However, the crushing cost is very high and is rarely used.

• Knife Grinder

Chinese medicine suitable for grinding fibers.

The knife mill increases the shearing effect, and the grinding efficiency is higher.

• Grinding unit

It is suitable for grinding medicines containing more fiber, lignin, colloidal fat, resin, sugar and other ingredients.

The crushing unit has fine particle size and large output.

Among the above-mentioned various ultra-fine grinding equipments, jet mills and vibration mills are widely used. Among the jet mills, the fluidized bed type jet ultrafine pulverizer is the most widely used. Vibration mill is a kind of ultrafine grinding equipment for traditional Chinese medicine with the most research and application. Vibration mills are mostly used for ultra-fine grinding of animal and plant drugs in Germany and Japan.

Unsolved issues

Pharmaceutical production has its own strict quality inspection standards. General grinding equipment is not directly applicable to the production of medicines. At present, most of the equipment developed and produced is improved from mineral grinding equipment. As for how to prevent cross-contamination during the crushing process, how to achieve cleaning , Disinfection and automation control, etc., are all under study.

Since traditional Chinese medicine has certain medicinal properties and at the same time, it has certain toxicity. When the medicinal properties are fully displayed after ultra-fine grinding, further research is needed for its toxicity.

by ALPA Powder

The particle size of the heavy calcium carbonate powder is more uniform by using the air classifier

It is well known in the industry that there are different processes for the processing of heavy calcium carbonate powder in dry and wet methods. Dry processing is more conducive to achieving industrial scale and a certain degree of product refinement. Therefore, many companies have chosen to use air classifiers to obtain more refined heavy calcium carbonate powder.

The heavy calcium carbonate powder with uneven thickness moves to the classification area at high speed from the inlet of the lower end of the air flow classifier with the updraft under the suction force of the fan. Under the action of the strong centrifugal force generated by the high-speed rotating classification turbine, the coarse and fine materials are separated. The fine particles that meet the particle size requirements enter the cyclone separator or dust collector through the gap of the grading wheel blades, and the coarse particles entrain the part of the fine particles after hitting the wall. The speed disappears. The washing action separates the coarse and fine particles, the fine particles rise to the classification zone for secondary classification, and the coarse particles fall to the discharge port.

The particle size of the heavy calcium carbonate powder processed by the air classifier is more concentrated, and the heavy calcium carbonate powder processed by the air classifier is more widely used:

1.   Heavy calcium powder for artificial marble industry: 325 mesh, whiteness requirement: 95%, calcium carbonate content: 98.5%, pure and no impurities. Calcium carbonate has been widely used in the production of artificial marble.

2.   Heavy calcium powder for floor tile industry: 400 mesh, whiteness requirement: 95%, calcium carbonate content: 98.5%, pure and no impurities. Calcium carbonate can be used in the floor tile industry to increase the whiteness and tensile strength of the product, improve the toughness of the product, and reduce the production cost.

3.   Heavy calcium powder for paper industry: 325 mesh, whiteness requirement: 95%, calcium carbonate content: 98%. The important role of calcium carbonate in the paper industry: it can ensure the strength and whiteness of the paper, and the cost is low.

4.   Heavy calcium powder for construction industry (dry mortar, concrete): 325 mesh, whiteness requirement: 95%, calcium carbonate content: 98%. Calcium carbonate plays an important role in concrete in the construction industry, not only can reduce production costs, but also increase the toughness and strength of the product.

5.   Heavy calcium powder for fire-proof ceiling industry: 600 mesh, whiteness requirement: 95%, calcium carbonate content: 98.5%. Calcium carbonate is used in the production process of fireproof ceilings, which can improve the whiteness and brightness of the product, and the fireproof performance will also increase.

by ALPA Powder

The processing and application of talc

The color change of talc is mainly caused by impurities. The more impurities, the darker the color. The pure ones are white, and the impurities are slightly yellow, pink, light green, light brown and other colors. The dense block has a shell-like fracture, the relative density is 2.58-2.83, and it is rich in slippery, with a glassy luster, the cleavage surface is pearly luster, and the cleavage sheet is flexible (flexibility refers to the flaky cleavage Minerals, its thin slices can be significantly bent without breaking under the action of boundary forces, but cannot be restored to their original properties after the external force is removed).

There are few natural pure talc mines, and the common associated minerals are chlorite, serpentine, magnesite, tremolite, and dolomite.

The theoretical chemical composition of talc is 4.75% H₂O, 31.68% MgO and 63.47% SiO₂.

Molecular structure of talc                                        The microstructure of talc

Physical and chemical properties of talc

• Physical properties

Adsorption: oil absorption is 49%~51%;

Thermal performance: Refractoriness is as high as 1490-1510 ℃;

Electrical insulation performance: When iron-containing minerals appear, the insulation performance is reduced;

Coverage: Ultra-fine talcum powder can form a fire-resistant and weather-resistant film;

Chemical stability: Generally speaking, it does not react with strong acids and bases;

Other properties: low hardness and strong slippery feeling; when the impurity minerals increase, the lubricating performance will decrease obviously; the talc is dense and low in hardness, and has good mechanical processing and carving performance.

• Chemical nature

The chemical composition is relatively stable. Si is sometimes replaced by Al or Ti (Al can reach 5%, Ti can reach 0.1%), Mg is often replaced by Fe and a small amount of Mn, Ni, Al (FeO reaches 5%, Fe₂O₃ reaches 4.2% , NiO up to 1%), sometimes containing a small amount of K, Na, Ca, these elements may be located between the talc layers or mechanically mixed, the variant of iron-rich end members-iron talc, containing FeO up to 33.7%.

Classification of talc

Talc can be divided into block talc (talc content>70%), talc rock (talc content 30-70%), talc rock can be divided into talc-chlorite rock, talc-carbonate rock.

• Talc

• Talc rock

According to its mineral type, it can be divided into chlorite rock and carbonate rock.

Chlorite rock contains chlorite, sometimes serpentine and pyroxene, with darker color and greater hardness than talc. The carbonate symbiotic minerals include magnesite, dolomite, calcite, etc., which are generally lighter in color and much harder than talc.

Talc processing technology

• Beneficiation and purification

Beneficiation and purification include flotation (talc has good natural floatability), manual sorting (talc and gangue minerals have different slippery properties), electrostatic beneficiation (talc is negatively charged and has different electrical properties from impurity minerals), magnetic separation (using magnetic Selecting and removing iron-containing minerals), photoelectric sorting (the surface optical properties of talc and impurity minerals are different), crushing and screening (the crushing methods of talc and gangue minerals are different).

• Fine grinding and superfine grinding

Talc is finally applied in powder form, therefore, fine grinding and ultra-fine grinding are one of the necessary processing techniques for talc. Talc has a Mohs hardness of 1, which is naturally crushable and has good grindability. At present, the processing of ultrafine talc powder mainly adopts a dry process. Although wet pulverization has been studied, it is rarely used in industry.

Dry grinding equipment includes impact mill, jet mill, vortex mill, vibration mill, stirring mill, and tower mill.

The principle of jet pulverization process of talc is: talc block→coarse crushing→drying→medium crushing→fine grinding (Raymond mill)→superfine grinding (jet mill)→cyclone aggregate→package, the product fineness can reach 500~5000 Item.

The mechanical impact superfine crushing process of talc is: talc block→crushing (hammer crusher)→mechanical impact superfine crusher→turbine type fine classifier→cyclone aggregate→packaging.

• Surface modification

The modification of talc mainly adopts dry modification process, and the surface modifiers used mainly include paraffin, titanate, zirconium aluminate coupling agent, silane coupling agent, phosphate ester, and various surface modifiers.

• Calcined

The calcining is mainly for black talc, and the calcining temperature is generally 600~1200℃. In this temperature range, the higher the temperature, the higher the whiteness of talc after calcination, and the maximum whiteness of calcination can reach more than 90.

Resource distribution of talc

The prospective reserves of talc in the world are more than 2 billion tons, and the proven reserves are about 800 million tons, covering more than 40 countries. Countries with large proven reserves are: Finland, China, the United States, Russia, and France.

There are 250 known talc deposits in the world, of which 80 are currently being mined. Among these 80, 40 have an annual output of more than 5,000 tons, and the current world's annual output is about 6 million tons.

Application of talc

• Papermaking

Ultrafine talc can be used together with kaolin, calcium carbonate, and titanium dioxide pigments to control the matt, ink, gloss, brightness and opacity of paper.

• Plastic, rubber, cable

• Ceramics and refractory materials

It can be used as ingredients to effectively control the thermal expansion of the ceramic body, and as a glaze can provide a cheap source of magnesium oxide. It can be directly processed into plates and can be used as furnace lining and kiln lining.

• Coating

Talc can be well dispersed in both polar and non-polar matrix, and at the same time has chemical inertness and high oil absorption.

• Textile

Used as filling and brightening agent and lubricant in textiles.

• Cosmetic

Various emollient powder, beauty powder, talcum powder, etc.

• Medicine, food

Medicine tablets, sugar coatings, prickly heat powder, Chinese medicine prescriptions, food additives, release agents, etc.

• Other

Carriers for pesticides and fertilizers, arts and crafts, release agents, waterproof ointments, etc.

by ALPA Powder

The processing technology and application of diatomite

Diatomite is deposited 10,000 to 20,000 years after death to form diatomaceous earth. Diatomaceous earth is a kind of biogenic siliceous sedimentary rock, which is mainly composed of the remains of ancient diatoms. It is soft, loose, delicate, porous and light, and has adsorption properties. Sex, permeability.

Diatomaceous earth has an amorphous structure with a large number of micropores, and the number of micropores per unit area is thousands of times higher than that of charcoal. Common microstructures include straight chain type, round screen type, feather pattern and crown plate type.

According to the different mineral content in the ore, diatomaceous earth is divided into diatomaceous earth, clay-containing diatomaceous earth, clay diatomaceous earth, and diatomaceous clay.

Diatomite deposits are divided into marine deposits and continental lacustrine deposits according to their formation conditions. Diatomite mineral products are divided into A type fine ore with a particle size less than 0.25mm and B type lump ore with a particle size greater than 0.25mm according to the particle size. Diatomite is divided into first grade, second grade, and third grade according to product quality.

Diatomite processing technology

Natural high-purity diatomaceous earth ore is rare, and most of them require ore dressing and purification before they can be used. The beneficiation method is determined by the type and nature of impurity minerals and the purity requirements of the product. The method of beneficiation includes physical method (wet method, dry method) and chemical method (acid leaching method, calcination method).

• Physical method

The wet beneficiation process is often used for low-quality ore. The process is raw earth ore → scrubbing pulp → dilution → sedimentation separation → negative pressure dehydration → hot air drying → fine classification → diatomaceous earth.

The dry beneficiation process is often used for high-quality ore. The process is raw earth ore→crushing→mixing→grinding→drying→grinding→drying→air separation and classification→diatomite.

• Chemical method

Physical beneficiation and purification can only improve the purity of diatomite, and it has little effect on increasing the specific surface area. Chemical methods can remove organic impurities and structured water, and improve the purity of diatomaceous earth.

The process flow of the acid leaching method is raw earth ore → roughing → stripping → acid leaching treatment (acid) → sedimentation and separation → filter press → washing → drying → diatomaceous earth.

The calcining process can purify diatomaceous earth alone, or it can be used in conjunction with other processes. The calcining method is divided into room temperature calcining and flux calcining. The calcining temperature is between 600°C and 800°C, and flux is added for flux calcining. The process flow of the calcination method is raw earth ore → roughing → calcination to remove impurities → jet pulverization → classification → diatomaceous earth.

Application of diatomite

• Water treatment industry

Porosity and adsorption are used as adsorbents to treat sewage in water treatment.

• Building Materials Industry

Production of thermal insulation materials and lightweight building materials.

• Rubber industry

Used as a reinforcing agent and filler. Improve the physical properties of rubber products and enhance durability.

• Coating industry

Used as a matting agent and filler. It can improve the dispersibility of the coating, and it is not easy to aggregate and precipitate. At the same time, diatom mud is also a new type of environmentally friendly green coating material.

• Paper industry

Used as a functional filler, based on the good physical and chemical properties of diatomaceous earth, it can be used to produce functional paper.

• Agriculture field

Diatomaceous earth itself is an insecticidal pesticide. It can also be used as a carrier and anti-caking agent for pesticides or fertilizers. The use of fertilizers can also improve fertilizer efficiency.

• Petrochemical industry

Used as the carrier of various catalysts, such as the carrier of nickel catalyst in hydrogenation process.

• Other industry

Diatomaceous earth is used as filter aid or porous ceramic filter element is widely used in the production and filtration of daily necessities such as medicine, wine and sugar.

by ALPA Powder

The relationship between powder and medicine

What should you do if you have a cold, fever, or diarrhea?

Of course you have to take medicine!

People's healthy life is inseparable from medicine. Common types of medicine include pills, granules, etc. They are all made from raw materials after making powder!

Let’s take a look at the inseparable relationship between medicine and powder...

Raw material-powder-medicine

In pharmaceutical products, solid pharmaceutical preparations account for about 70% to 80%. The dosage forms containing solid drugs include powders, granules, capsules, tablets, powder injections, and suspensions.

The preparation process of pharmaceutical solid dosage forms is as follows:

What are the pharmaceutical powder equipment

Solid dosage form preparation

Crushing: ball mill, impact mill, vibration mill, jet mill, etc.

Screening: rotary vibrating screen, sample sieve, cyclone separator, etc.

Mixing: trough mixer, cone mixer, three-dimensional motion mixer, V-type mixer, etc.

Granulation: fluidized granulator, stirring granulator, centrifugal granulator, extrusion granulator, etc.

Tableting: single-punch tablet machine, rotary multi-punch tablet machine, high-speed tablet press, etc.

Drying: spray desiccant, granulating desiccant, hollow paddle dryer, fluidized bed dryer, etc.

Detection: laser particle size analyzer, density meter, surface area and pore size distribution meter, powder rheometer, etc.

Most solid dosage forms need to be processed according to different requirements to improve the properties of the powder and meet the requirements of product quality and powder operation.

The powder processing process is different, the powder properties of the particles are also very different!

• Fluidized granulation

It is suitable for tableting, with low particle density, high porosity and low strength.

• Stirring granulation

It is suitable for encapsulating, with compact particles and high strength.

• Centrifugal granulation

It is suitable for encapsulating and coating, the particles are round, dense and uniform.

What are the effects of powder properties on the process and quality of pharmaceutical preparations

The nature of the powder

The first property is the property of a single particle, such as shape, size, surface area, porosity, etc. The second property is the properties of the powder aggregate, such as fluidity, filling property, compression molding property, etc.

Solid pharmaceutical products are often mixed with multiple ingredients. In order to ensure the uniformity of the drug content in the formulation, each ingredient needs to be crushed and sieved to form a powder with a certain particle size before mixing.

• Influence of powder properties on mixing uniformity

From the perspective of powder, the factors that affect the uniformity of mixing include particle size, particle size difference and density difference between components, particle morphology and surface state, static electricity and surface energy.

• Influence of powder properties on divided doses of solid preparations

The fluidity of powder is related to particle size, particle size distribution, particle morphology, surface state, and bulk density. When the angle of repose α<30°, the fluidity is good, and when α>45°, the fluidity is poor. In actual production, α<40° can meet the production requirements of divided doses.

The size, shape, particle size distribution, bulk density and porosity of the powder particles can intuitively reflect its filling properties.

• Influence of powder properties on compression formability

The radial crushing force of the powder—hardness, and the crushing force per unit area—tensile strength are measured, and the ability of the powder to reduce volume under pressure and form a certain shape tightly combined is obtained.

• The effect of powder properties on the quality of preparations

The process of solid pharmaceutical preparations is to disintegrate, release the drug and be absorbed by the human body; increase the porosity to promote disintegration, reduce the particle size to increase the dissolution, and reduce the particle size to enhance the efficacy.

• Influence of powder properties on bioavailability and curative effect

The smaller the particle size, the greater the bioavailability; the larger the specific surface area, the greater the bioavailability; the smaller the particle size, the greater the bioavailability.

What are the applications of powder technology in pharmaceutical preparations?

• Application in prescription design

Ensure the quality of pharmaceutical preparations: dissolution, disintegration, stability, appearance, uniformity of active substances, strength, etc.

To ensure the smooth progress of the production process: fluidity, filling, compression molding, sticking, pushing, etc.

• Application in solid preparation production process

Control parameters: particle size, particle size distribution, fluidity, filling, moisture content, upper and lower punching pressure, residual pressure on the mold wall, etc., and finally a qualified product.

• Convenient to control the quality of solid preparations, which is conducive to the implementation of GMP

Promote automated, continuous, and modern production to prevent drug contamination, cross-contamination and confusion.

• Promote the development of modern technology and new dosage forms

The advantages of ultra-fine pulverization technology in the production and application of Chinese medicine include: cell wall breakage, improving the dissolution rate of active ingredients; improving the utilization of medicinal materials, effectively protecting Chinese medicinal resources; promoting drug absorption and enhancing efficacy; safe and hygienic, and convenient for clinical application.

The advantages of nanotechnology in pharmaceutical applications include: enabling drugs to act on the central nervous system through the blood-brain barrier, penetrating the epidermis to enhance the absorption of the preparation, and enhancing the targeting effect of the drug.

The powder + medicine complement each other, and the prospects are promising!

Powder and medicine are closely related. With the promotion and implementation of GMP standardization in the pharmaceutical industry, powder technology has received more and more attention from people in the pharmaceutical industry, providing new development paths for the research of higher-efficiency drugs; at the same time, the pharmaceutical industry continues to Development also puts forward higher requirements on powder technology and equipment. The two industries complement each other for mutual benefit and win-win!

[Knowledge Popularization] Do you know what mineral drugs are available?

by ALPA Powder

Carbon black modification & its application in rubber

Carbon black is a loose, light, extremely fine, black powdery amorphous carbon. It is the most important reinforcing filler in the rubber industry and is widely used in printing and dyeing, rubber, plastic processing, and transportation industries. Studies have shown that chemical modification of carbon black can greatly improve various properties of carbon black, which is also a hot topic in the current research on carbon black.

In order to meet the special requirements for the performance of carbon black in some applications, the purpose of modification can be achieved by post-processing the carbon black. Starting from the element composition and surface functional groups of carbon black, there are three ways to enhance the hydrophilic modification of carbon black: oxidation modification, graft modification, and coating modification.

Graft modification

Graft modification is one of the most widely studied methods of rubber modification. Graft modification is to graft polymer chains or low-molecular compounds on the surface of carbon black and bond them firmly to the surface of carbon black to prevent aggregation between particles to achieve the purpose of dispersion.

1.  Grafting of carbon black and low molecular weight

AO-80 (an organic antioxidant) decomposes under high temperature conditions to generate small molecular free radicals. In supercritical CO₂ fluid, small organic molecules (AO-80) are used to graft carbon black on the surface to prepare small organic molecules Grafted nano carbon black particles. The analysis of the particle size map after grafting AO-80 molecules onto the surface of carbon black draws the conclusion that the particle size of the modified carbon black aggregates is smaller and narrower.

2.  Grafting of activated carbon black and polymer

Utilizing the characteristics of a large number of end groups of hyperbranched polymers, and modifying carbon black with light end hyperbranched polymers can weaken the aggregation of modified carbon black particles. Hyperbranched polymer graft modified carbon black: the carbon black is first methylated, and then AB₃ type hyperbranched poly(amide ethyl) is grafted onto the surface of the carbon black.

3. Grafting to capture free radicals on the surface of carbon black

Sodium polystyrene sulfonate (PSS) is a water-soluble polymer with good interfacial activity. In an ultrasonic environment, the monomer sodium styrene sulfonate undergoes free radical polymerization, and the generated polymer long-chain free radicals are captured by the surface of the carbon black to prepare polymer grafted carbon black.

Oxidation modification

Carbon black particles are oxidized by an oxidant to undergo modification. The oxidation treatment of carbon black can change the specific surface area, porosity and conductivity of carbon black.

Surface oxidation treatment (gas phase oxidation and liquid phase oxidation) increases the type and number of oxygen-containing functional groups on the surface of carbon black, which can increase the volatile content of carbon black, reduce pH, and improve surface activity and polarity.

1. Gas phase method

Gas-phase modification of carbon black is a traditional modification method. Oxygen, ozone, dry air, and atomic oxygen or humid air are the main oxidants. The inert gas is introduced under closed conditions, and then the temperature is raised to the reaction temperature, and then the oxidant is introduced to carry out the modification reaction. After the reaction, inert gas is introduced. The experimental results show that as the test time increases and the reaction temperature increases, the more oxygen-containing groups on the carbon black surface, the better the dispersibility in the rubber matrix.

2. Liquid phase method

Liquid phase method, also known as chemical oxidation method, is a modification method in which an oxidant reacts with carbon black to generate a few radicals, carboxyl radicals and light radicals on the surface of the carbon black. The Cabot Elastomer Composite (CEC) researched by Wang Mengjiao and others is the first NR filler masterbatch produced by a continuous liquid phase mixing process. This technology makes it possible for environmental protection, low energy consumption, simple process, and low labor consumption. Compared with dry rubber compounding, this material can significantly improve the properties of vulcanized rubber, including reducing hysteresis loss, improving cutting resistance and flexing resistance, and increasing the wear resistance of vulcanized rubber when the amount of filler is increased.

Coating modification

Mix carbon black with water-dispersed white carbon black to make a slurry, add a proper amount of methanol, methyl triethoxy silane, sodium silicate and other dispersants to make the white carbon black coat the surface of the carbon black, and the resulting modified carbon black is filled In tires, conveyor belts and rubber rollers, it can give vulcanized rubber excellent physical properties such as high wear resistance, high grip and low rolling resistance.

Application of modified carbon black in rubber

In the rubber industry, carbon black is widely used as a reinforcing agent, and 90% of global carbon black production is used in the rubber industry.

• Application in NR (Natural Rubber)

The carbon black modified by the pyrolysis gas is used as a reinforcing agent and added to the rubber with HAF. As the amount of modified carbon black increases, the 300% tensile stress of the vulcanized compound increases, the elongation decreases, and the compression set decreases. The tear strength has been reduced.

The effect of pyrolysis gas modification-I and HAF on the performance of NR

• Application in EPDM (ethylene propylene diene monomer rubber)

EPDM rubber (EPDM) has excellent ozone resistance and aging resistance. It is often filled with carbon black modified by glycidyl methacrylate (GMA) monomer grafting to improve its processing and mechanical properties.

Carbon black was modified with unsaturated light fatty acid to enhance the vulcanization and physical and mechanical properties of EPDM rubber. It was found that the addition of unsaturated fatty acid significantly improved the tearing performance and flexing performance of the vulcanized rubber while maintaining relatively high performance. Good thermal oxygen aging performance can be well applied to shock-absorbing rubber products.

• Application in SBRL (vulcanized styrene butadiene rubber)

Styrene butadiene rubber is a commonly used industrial latex, which has the advantages of low cost and wide sources. Sodium styrene sulfonate is used to modify carbon black to prepare nano-dispersed carbon black suspension, and then the carbon black suspension is mixed with SBRL to prepare modified carbon black reinforced SBRL, which is applied to tire repair fluid.

• Application in polyurethane sealant

In the presence of the initiator benzoyl peroxide, the surface of ordinary carbon black is organically modified with styrene.

Performance comparison of carbon black added to sealant before and after modification

The sealant made of modified carbon black compound has good tensile strength, hardness, elongation and shear strength, and reduces the cost, and is widely used in sealing fields such as construction and automobiles.

by ALPA Powder

Five key points for quality control of silicon powder products

Silica powder is a silica powder material made from natural quartz ore, fused quartz, etc., processed by multiple processes such as grinding, precision classification, and impurity removal. Grinding is one of the core processes in the production of silicon powder products. It directly affects its purity, particle size distribution and production cost.

In order to produce silicon powder products with stable quality and high performance, it is necessary to strengthen management and control from the following points:

1.  Ball mill control

It is possible to effectively control the impurity content and increase the service life of the equipment by reasonably selecting the grinding media material, controlling the media ratio and filling rate; according to the length to diameter ratio of the ball mill, the structure and distribution of the liner, and the particle size of the grinding, the speed of the ball mill can be reasonably adjusted to promote the grinding The material in the cavity maintains a good state of motion, thereby improving the grinding effect.

2.  Particle shaping

By optimizing the process conditions such as equipment operating speed, internal pressure and temperature, material residence time, etc., the regularity of the surface of the silicon powder can be improved, and the fluidity of the product can be improved. dispersion.

3.  Mixed compound

Unimodal silica powder cannot achieve the tightest packing, difficult to meet high filling requirements, and cannot maximize the excellent performance of silica powder. One of the ways to increase the filling rate is to mix the silicon micropowder products with different particle size distributions, and form a multimodal distribution through the mixing ratio, which achieves high filling and reduces the oil absorption value of the silicon micropowder.

4.  Surface modification

As an inorganic filler, silicon micropowder has problems of poor compatibility and difficulty in dispersion when mixed with organic resins, resulting in poor heat resistance and moisture resistance of materials such as integrated circuit packaging and substrates, which affects the reliability and stability of the product. In order to improve the problem of interface bonding between silicon micropowder and organic polymer materials and improve its application performance, it is generally necessary to modify the surface of silicon micropowder.

5.  Production condition control

The key to the production of electronic grade silicon powder is to remove the conductive impurities in the quartz. Therefore, in addition to the selection of purer raw materials, every link of production should minimize the pollution of the product by containers, the environment, and chemicals, and operate strictly.

To avoid contamination of materials during grinding, the grinding media used should be non-metallic materials, such as alumina ceramic balls or silica; the barrel of the mill must also be lined with high-strength wear-resistant materials, such as alumina ceramics, silica or Polyurethane rubber.

by ALPA Powder

Powder in life

No powder is not a material. Powder is the foundation of modern industry, the most important technical support force for high-tech industry, the most important cornerstone of modern defense industry, and the most basic raw material for all walks of life. Powder is everywhere and is closely related to our lives.

The term powder first appeared in the early 1950s. It is characterized by many discontinuous surfaces, a relatively large specific surface area, and is composed of many small granular materials. In a further generalization, powder is an aggregate composed of countless relatively small granular substances.

Powder refers to a collection of solid fine particles, <100μm is powder (dust), >100μm is (particle).

Powder exists in liquid, gas, and solid forms. The powder usually refers to a small-sized solid. The solid substance is divided into a dispersed state and an aggregate state. Most powders are in a dispersed state.

Basic properties of powder

• The geometric properties of the powder: the size, particle size distribution, particle shape, and accumulation state of the powder particles.
• Mechanical properties of powder: friction angle of powder, powder pressure, fluidity and movement properties in fluid.
• Other physical and chemical properties of the powder: the electrical, magnetic, optical, acoustic, and thermal properties of the powder, as well as its adhesion, adsorption, cohesion, wettability, and explosive properties.

Classification of powder

According to the cause, it can be divided into natural powder and artificial powder. According to the preparation method, it can be divided into mechanical crushing method and chemical method powder. According to the particle size, it can be divided into primary particles, aggregate particles, aggregate particles, and floc particles. According to the dispersion state, it can be divided into coarse powder (>0.5mm), medium and fine powder (0.074~0.5mm), fine powder (10~74μm), fine powder (0.1~10μm), nano powder (<100nm).

Common powder materials

Metal powders include reduced iron powder, zinc powder, copper powder, nickel powder, and aluminum powder. Non-metal powders include perlite, diatomaceous earth, tourmaline, icelandite, brucite, organic materials, natural rubber, and synthetic fibers. , Starch, cellulose, synthetic resin, inorganic materials include calcium carbonate, silicate, aluminate, phosphate, silicon powder.

In addition, there are carbon-based materials such as carbon black, graphene, carbon fiber, nanomaterials, composite materials, and powdered Chinese medicine.

Powder technology

• Preparation: various physical, chemical and mechanical methods.
• Processing: crushing, classification, dispersion, mixing, granulation, surface treatment, fluidization, drying, forming, sintering, dust removal, dust explosion, transportation, storage, packaging, etc.
• Test: Characterization of various geometric mechanical, physical and chemical properties of powder.

Powder in life

• Clothes

The different colors of clothes are due to the addition of oxides, chromates, sulfates, silicates, hydroxides, sulfides, metals, etc. Different powder materials can be used to make various buttons, such as resin buttons, ceramic (zirconia) buttons, plastic buttons, metal buttons (copper), etc. Adding calcium carbonate, kaolin, talc, barite and other powders to rubber shoes can enhance the tensile strength and wear resistance of the shoes. Adding nano titanium dioxide, nano zinc oxide, nano silicon oxide, etc. can inhibit bacteria and deodorize the worn socks. Adding carbon black, tin dioxide, zinc oxide, titanium dioxide, etc. can make clothes antistatic; adding some far-infrared nano ceramic powder can make clothes warmer.

• Food

Common food flour, soy milk, milk powder, coffee, salt, etc. are all powders; baking soda is needed to make bread and steamed bread; medical stone mineral water is called a treasure in mineral water; zeolite has also been developed as a health product. For anti-aging, remove heavy metals accumulated in the body. Commonly used bezoar detoxification pills and heat-clearing detoxification granules may be added with talc, lumps, pumice, alunite, arsenic, gypsum, etc.; aseptic tableware and aseptic food packaging made of nano-materials are already available.

• Residence

cement. Diatom mud with diatomaceous earth as the main raw material has good air purification and formaldehyde adsorption functions. Perlite insulation board is not only light in bulk density, but also high in strength, suitable for all kinds of buildings. Commonly used architectural coatings are added with kaolin, sepiolite, bentonite, gypsum powder, quartz powder, etc. Refractory materials such as silicon, magnesia, and carbon are used in various constructions.

• Travel

Carbon fiber, aluminum, and magnesium help reduce the weight of vehicles and airplanes; car tires, seats, steering wheels, etc. are filled with calcium carbonate, wollastonite powder, mica powder, aluminum hydroxide, etc.; carbon nanotubes can be used in integrated circuits; metals Lithium is used in the manufacture of lithium batteries; aluminum powder, mica powder, etc. are added to the paint.

Powder materials, powder technology, equipment and operations are used in various industries such as chemicals, plastics, paints, coatings, textiles, building materials, food, electronics, national defense, and environmental protection.

Intensify research efforts in mineral homogenization, purification, ultra-fine grinding, classification and grading, surface modification, etc.; develop in the direction of miniaturization, functionalization, high purification, and refinement; modernization and intelligentization of powder equipment.

Strengthen the application of mineral functional materials in energy saving and fire protection, filling and coating, environmental protection management, energy storage and moisturizing, etc.; extend to the fields of life science and information science.

by ALPA Powder

Preparation method of spherical alumina

Spherical alumina is also called sand alumina, alpha alumina. In the crystal lattice of α-type alumina, oxygen ions are densely packed in hexagons, and AI³⁺ is symmetrically distributed in the octahedral coordination center surrounded by oxygen ions. The lattice energy is large, so the melting point and boiling point are high. It has the characteristics of corrosion resistance, wear resistance, high temperature resistance, high strength, good insulation, large surface area, high hardness, and oxidation resistance.

Spherical alumina preparation process

• Ball milling method (high energy ball milling)

Ball milling is the most common method for preparing ultrafine alumina powder. The ball mill itself is a horizontal cylinder with built-in steel ball grinding media, so that after the material enters the cylinder, the impact force generated by the collision with the steel ball achieves the effect of crushing. Adding a grinding aid during the ball milling process can improve the uniformity of powder particle size.

The factors affecting the preparation of ultra-fine alumina powder by high-energy ball milling are ball milling time and ball milling speed. The advantages are simple operation, low cost and high output. The disadvantage is that the particle size distribution of the product is not uniform, the minimum particle size is mechanically restricted, and it is difficult to obtain spherical particles.

• Polymer network sol-gel method

The advantage is that the prepared alumina powder has a small particle size. The disadvantage is that the sphericity is very poor.

• Alkoxide hydrolysis

The advantage is that the particle size of the prepared powder is small. The disadvantage is that the cost is too high and the sphericity is poor.

• Template method

The template method uses a spherical raw material as a reagent for controlling the morphology in the process. The product is usually hollow or has a core-shell structure.

The main process is to use polystyrene microspheres as a template, coating with carbonic acid functionalized alumina nanoparticles, and then washing with toluene to prepare hollow alumina spheres.

The advantage is a good way to prepare hollow spheres. The disadvantages are high requirements for the template agent, many steps in the preparation process, and difficult operation.

• Aerosol decomposition method

Aerosol decomposition usually takes aluminum alkoxides as raw materials, uses the properties of aluminum alkoxides to be easily hydrolyzed and high-temperature pyrolysis, and adopts the physical means of phase change to vaporize the aluminum alkoxides, and then contact with water vapor to hydrolyze and atomize. After high-temperature drying or direct high-temperature pyrolysis, the gas-liquid-solid or gas-solid phase transformation is realized, and finally spherical alumina powder is formed.

The advantages are that water decomposition can be carried out without adding alkali, the reaction conditions are mild, and the operation is simple. The disadvantage is the high cost.

• Drop ball

The drop ball method is to drop alumina sol into the oil layer (usually paraffin, mineral oil, etc.), and form spherical sol particles by the action of surface tension, and then the sol particles are gelled in the ammonia solution, and finally the gel particles A method of drying and sintering to form spherical alumina.

The advantage is that the emulsion technology is applied to the aging stage of the sol, and the oil phase is kept intact, eliminating the need for separation of powder and oily reagents. The disadvantage is that it is usually used to prepare spherical alumina with a larger particle size, which is mainly used for adsorbents or catalyst supports.

• Radio frequency induction plasma method

Irregularly shaped alumina particles are sprayed into the plasma torch by a carrier gas through a feeding gun, and are quickly heated and melted. The molten particles form highly spherical droplets under the action of surface tension, and in a very short time The inside solidifies quickly, forming spherical particles.

• Flame melting

The flame melting method is to directly spray irregularly shaped alumina powder into the flame, so that the alumina powder is melted into a ball in the flame.

The advantage is that the process is simple, the cost control is more advantageous than the plasma flame spray method, the spheroidized product has high thermal conductivity, good sphericity, and controllable particle size.

• Homogeneous precipitation

The precipitation process in the homogeneous precipitation method is the formation of crystal nuclei, then agglomeration and growth, and finally the process of precipitation from the solution, usually in a non-equilibrium state, but if the concentration of the precipitation agent in the homogeneous solution can be reduced, even slowly The formation of nuclei will uniformly generate a large number of tiny crystal nuclei, and the resulting fine precipitation particles will be uniformly dispersed in the entire solution, and will maintain a state of equilibrium for a long time. This method of obtaining precipitation It is called homogeneous precipitation method.

The advantages are simple process, low cost, high purity, mass production of equipment, simple manufacturing, and short process flow. The disadvantage is that the existing colloids are difficult to precipitate, wash and filter, the powder is easy to mix with precipitating agent, the powder components are not easy to separate during precipitation, the precipitate can be re-dissolved during the washing process, and the precipitating agent will also cause a large amount of complex ions .

• Emulsion method

In order to obtain spherical powder particles, people use the interfacial tension between the oil phase and the water phase to produce tiny spherical droplets, so that the formation and gelation of the sol particles are limited to the tiny droplets, and finally spherical precipitates are obtained. Particles.

The advantage is simple operation. The disadvantage is that the cost is too high and the sphericity is poor.

• Sol-emulsion-sol method

Takashi Ogihara et al. used aluminum alkoxide hydrolysis to prepare spherical alumina powder through a sol-gel process. The entire hydrolysis system is relatively complicated. Among them, the octanol dissolving aluminum alkoxide accounts for 50%, the ethanol solvent accounts for 40%, and the octanol butanol disperses water. Alcohol accounted for 9% and 1% respectively, and propyl cellulose was used as a dispersant to obtain spherical γ-alumina powder with very good sphericity.

The advantage is that no impurity ions are introduced during the process. The disadvantage is that the price of raw materials is high, the particle size of the obtained powder is small, and the distribution is narrow.

• Spray method

The essence of the spray method for preparing spherical alumina is to realize the phase transition in a relatively short time. The product is made spherical by the effect of surface tension. According to the characteristics of the phase transition, it can be divided into spray pyrolysis, spray drying and spray melting. Law.

The advantages are stable chemical composition, high purity, excellent performance, and mass production. The disadvantage is that it is only effective for soluble salts and has certain limitations.

Application of spherical alumina

• Ceramic material

Under the same process conditions, spherical alumina powder has advantages in shape, which can change the microstructure of the material, increase the strength and density of the ceramic, reduce the sintering temperature, and significantly improve the performance of the ceramic.

• Surface protection layer material

Spraying ultra-fine alumina powder on the surface of plastic, paint, glass, alloy and metal materials can improve the wear resistance, corrosion resistance, stability and surface strength of the material.

• Catalyst and catalyst carrier

Ultra-fine alumina has strong adsorption characteristics, has many surface active points, has high reaction activity and selectivity, and provides necessary conditions for catalytic reactions. The spherical alumina used directly as a catalyst can reduce abrasion and increase the service life of the catalyst, thereby reducing production costs.

• Chemical mechanical polishing abrasive

Chemical mechanical polishing has been widely used in integrated circuit chips, microelectronic mechanical systems, and computer hard drives. As a polishing material, spherical alumina can avoid slip marks. Spherical alumina powder has a high packing density, which can reduce the scattering of the luminous body, effectively reduce the loss of transmitted light, and thus can improve the brightness of the screen.

• Luminescent material

Spherical alumina powder has a high packing density, which can reduce the scattering of the luminous body, effectively reduce the loss of transmitted light, and thus can improve the brightness of the screen.

• Petrochemical industry

In the petrochemical industry, alumina is the most widely used carrier.

Article source: China Powder Network

by ALPA Powder