Active zinc oxide is a kind of zinc oxide which is activated on the surface of particles. Active zinc oxide is a kind of white or yellowish spherical fine powder with a density of 5.47g/cm3, melting point of 2073K. Insoluble water and alcohol, soluble in acid, alkali, ammonium chloride solution and ammonia, and can slowly absorb carbon dioxide and water to form zinc carbonate in air.
Active zinc oxide has the characteristics of small particle size, large specific surface area and high vulcanization activity, as well as non-toxicity, non-migration, fluorescence, piezoelectric and strong ability to absorb and scatter ultraviolet rays. It not only has the properties and uses of ordinary zinc oxide, but also has the properties of ultra-fine particles.
Active zinc oxide has many unique properties and wide application prospects. It is mainly used as raw materials in rubber, paint, printing and dyeing, feed, pharmaceutical, chemical and ceramic industries. Active zinc oxide is used as reinforcing agent, colorant, vulcanizing agent and compounding agent to increase thermal conductivity in rubber industry; its coloring power, hiding power, anticorrosion and luminescence are mainly used in coating industry; in printing and dyeing industry, it is used as anti-dyeing agent; in feed industry, it is used as feed additive. In addition, active zinc oxide is also used as raw material for the production of milky glass, zinc white oil and watercolor pigments, cosmetics and various zinc salts.
Active zinc oxide vs. Zinc oxide
The particle size of active zinc oxide is small, the particle size of ordinary zinc oxide is about 0.5 μ m, while that of active zinc oxide is about 0.05 μ m; their particle shapes are also different, ordinary zinc oxide particles are columnar or rod-shaped, while active zinc oxide particles are spherical; the specific surface area of active zinc oxide is large, the specific surface area of ordinary zinc oxide is 1~5m2/g, while the specific surface area of active zinc oxide is 35~55m2/g.
Preparation method of active Zinc oxide.
1. Alkaline reduction of organic compounds: alkaline reduction of waste zinc from organic compounds, washing with water, heating to high temperature, alone or mixed with a small amount of sulfur to produce active zinc oxide suitable for rubber fillers.
2. The method of entering carbon dioxide: add high-purity large particles of zinc oxide to an airtight container full of carbon dioxide containing water vapor. For example, zinc oxide prepared by wet method is kept above room temperature to convert zinc oxide into basic zinc carbonate. Then the active zinc oxide of about 0.05 μ m can be obtained by heating and decomposing.
3. Zinc oxalate decomposition method: the two solutions of oxalate and zinc chloride were heated to 70 ℃ respectively, and then zinc chloride was added to the oxalate solution to get very fine zinc oxalate precipitation, then washed and dried. Active zinc oxide was obtained by calcining 10min at 40 ℃.
4. Alkaline method:
(1) using the by-product of the production of insurance powder or other zinc and zinc ash as raw materials, using the "Beyer process" similar to the production of aluminum hydroxide to convert into active zinc oxide, the crude zinc raw material is pulped in sodium hydroxide to form sodium zincate (Na2ZnO2) solution. The solution is hydrolyzed to form zinc hydroxide precipitation, filtration, washing and calcination to obtain active zinc oxide.
(2) leaching zinc ash or zinc residue with dilute sulfuric acid or hydrochloric acid, purifying the leaching solution, then reacting with sodium hydroxide aqueous solution to pH7~11, and then preparing active zinc oxide from zinc hydroxide. Its specific surface area is 21m2/g and the price of the product is cheaper than that of dry process.
(3) 6.5m342% sodium hydroxide was added to the mixture containing 2000kg zinc, sodium 720kg nitrate (as oxidant) and 10m3, water within 2 hours. Zinc is completely dissolved at 90 ℃ for 8 h. Then the temperature is lowered to 30 ℃, carbon dioxide is added, precipitated zinc oxide and zinc hydroxide are filtered, dried and calcined to obtain active zinc oxide.
5. Add methanol and water glass method: dissolve zinc salt in water, mix with sodium hydroxide, add methanol, and then add industrial water glass (Na2SiO3). The resulting sediment is filtered, washed and dried. The active zinc oxide particles obtained are much finer than ordinary zinc oxide particles, and the vulcanization rate can be increased by 2 times when used in rubber.
6. The manufacturing method of active grade zinc with large specific decay area is as follows: zinc chloride or zinc sulfate is dissolved in methanol or acetone and fed with ammonia at about 0 ℃ to form zinc hydroxide precipitation, which is washed with methanol. The specific surface area of the obtained active zinc oxide reached 600m2/g by X-ray diffraction analysis.
7. Sodium carbonate method: a certain concentration of sodium carbonate solution is added to a certain concentration of zinc sulfate (or zinc chloride) solution to form basic zinc carbonate precipitation. Then active zinc oxide was obtained by filtering, washing, drying and burning satin at 450-650 ℃. The product active zinc oxide contains little carbon dioxide and about 1% moisture.
8. Nitrogen carbonate method: various zinc-containing raw materials are leached with dilute sulfuric acid. The prepared zinc sulfate solution is purified to remove iron, manganese and other impurities. The purified zinc sulfate solution reacts with cheap hydrogen carbonate and ammonia (a small amount) to form basic zinc carbonate precipitation. Then the active zinc oxide product is obtained by washing precipitation, drying and calcination. The bicarbonate used in the production method has the advantages of low price and low cost.
What is Active Zinc oxide used for?
1. Rubber industry.
Compared with ordinary zinc oxide, active zinc oxide can be used in some products when it is used as rubber accelerator. Because active zinc oxide is very fine, it is suitable for soft rubber products and latex products, especially transparent and translucent rubber. Active zinc oxide is also widely used as anti-softening agent in vulcanized products. It is also widely used in mechanical and transmission products and high elastic products with good aging properties. Active zinc oxide powder combined with thiamide accelerator can promote vulcanization. Active zinc oxide powder can be used as hardener and is not easy to deform during vulcanization.
In addition, active zinc oxide has the characteristics of fine grain, large specific surface area, easy to disperse in rubber and high activity, and can improve the setting property of vulcanized products. Therefore, in NR and most SR compounds, because active zinc oxide has strong activation effect, when the amount of active zinc oxide is reduced to 60% of that of ordinary zinc oxide, the curing rate, tensile strength and breaking permanent deformation of the compound remain unchanged. The elasticity, tear strength and aging resistance were improved. In addition, as an important roof surfactant in the curing system of tire compound, active zinc oxide can significantly increase the formation rate of cross-linking bonds and the degree of vulcanization, thus improving the physical properties. At the same time, it has the advantages of anti-aging, anti-friction and ignition, long service life, small dosage and so on.
2. Self-cleaning ceramics and antibacterial glass.
The glass with active zinc oxide can resist ultraviolet light, wear resistance, antibacterial and deodorization, and can be used as automobile glass and building glass. The UV protective layer of the glass is composed of active zinc oxide.
3. Ultraviolet absorbing material.
Adding active zinc oxide to cosmetics can not only shield ultraviolet rays from sunscreen, but also resist bacteria and deodorize.
4. Rheostat material.
The rheostat is obtained by using active zinc oxide as the main body, sintered with powder materials such as Bi2O3, and the rest of the materials are covered with zinc oxide particles.
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