[refractive index] when light shoots from one medium to another, it sometimes changes its direction due to the change of its velocity. This phenomenon is called refraction. When light is refracted from a vacuum into a medium, the ratio of the sine of the incident angle and the refraction angle is called the refractive index, and the refractive index is also called the optical index.
The relative whiteness is a function of wavelength and particle size. Whiteness combines the brightness and hue of white pigment.
[covering power] covering power refers to the ability of the pigment in the coating to cover the background color of the object to be coated when it is coated with a certain coating, so that the background color can no longer be exposed through the coating. Pigment mass (g) covering power = pigment mass (g) / surface area of coated object (cm2). The greater the hiding power of pigment is, the smaller the value is. The hiding power can also be expressed by the surface area per gram of pigment that can cover the object to be coated, which is the reciprocal of the previous method. The greater the covering power of the pigment expressed by this method, the greater the value, the thinner the film can be and the smaller the amount of coating required.
The achromatic power of a pigment is the ability of a pigment to show its own pigment when it is mixed with a pigment of another color. In the case of white pigment, when it is mixed with a dark pigment, the lighter the color of the mixture is, the stronger its achromatic power is.
[oil absorption] the oil absorption capacity of a pigment refers to the minimum quality of oil required for every 100g of pigment when it reaches complete wetting. Oil absorption is usually expressed as a percentage.
[effective ACID] in the titanium solution leached from acidolysis products, sulfuric acid mainly exists in three different forms: (1) sulfuric acid combined with titanium; (2) sulfuric acid combined with other metals (mainly iron); and (3) unbound and surplus free acid. Since it is impossible to determine the acid and free acid combined with titanium separately, only the sum of the two can be determined, so the sum of the two is called effective acid. Effective acid = acid bound to titanium + free acid
Acid ratio the ratio of available acid to total titanium content in titanium solution is called acid ratio. Acid ratio is also called acidity coefficient, usually expressed by F.
[stability of liquid titanium] stability, also known as stability, refers to the tendency of early hydrolysis of liquid titanium to precipitate white colloidal particles when conditions change in Titanium Dioxide production. The strength of this tendency is called the stability of liquid titanium. The characteristic indicating the strength of this tendency is called the stability of liquid titanium.
[early hydrolysis of titanium solution] Generally speaking, there should be no metatitanic acid and orthotitanic acid colloidal particles in the liquid titanium from acidolysis to post hydrolysis. However, sometimes in the process of leaching, reduction, transportation and storage of liquid titanium, the above two white colloidal substances appear in the liquid titanium due to improper operation or change of conditions. This phenomenon is called early hydrolysis of titanium liquid.
[acidolysis rate] the percentage of the total amount of soluble titanium salts (calculated by TiO2) in the solution to the total amount of titanium contained in the ilmenite (calculated by TiO2) is called acidolysis rate. Acid hydrolysis rate of total titanium content in solution (%) = (total titanium content in solution / total titanium content in ore powder) * 100
The solution obtained by leaching ilmenite after decomposition with sulfuric acid is a complex system with unclear turbidity. This solution has the properties of true solution and colloidal solution. It contains not only soluble sulfate mainly composed of titanium and iron, but also insoluble, large suspended mechanical impurities and colloidal impurities with small particles and high stability. The latter two insoluble solid impurities are called the residue of liquid titanium.
[Fe Ti ratio] the ratio of total Fe content to total TiO2 content in titanium solution is called Fe Ti ratio, and its formula is as follows: total Fe content (g / L) Fe Ti ratio = total Fe content (g / L) / total TiO2 content (g / L). The level of Fe Ti ratio has certain influence on the particle size and structure of metatitanic acid of hydrolysate. Therefore, in the production of titanium dioxide, especially in the production of coating titanium dioxide, it must be controlled in a certain range of iron titanium ratio.
[concentration of liquid titanium] water in liquid titanium is solvent and volatile, while titanium oxysulfate, titanium sulfate and ferrous sulfate in liquid titanium are solutes and are not volatile. With the help of heating, the solvent (water) in the liquid titanium is gradually vaporized and eliminated, and the concentration of solute is gradually increased. This process is called concentration.
[quality requirements for coating titanium dioxide] A. good whiteness; B. good grinding wettability; C. good weather resistance; D. good chemical stability; e. small particle size, large covering power, high achromatic power, good opacity and gloss.
[hydrolysis rate] hydrolysis rate is a value reflecting the degree of hydrolysis. That is, the percentage of liquid phase TiO2 transformed into solid phase TiO2. The high or low hydrolysis rate indicates the high and low conversion rate of TiO2 into solid-phase TiO2 in titanium solution.
[sedimentation rate] the settling rate of metatitanic acid particles in the slurry after hydrolysis is called sedimentation rate. It is a value reflecting the hydrolysis and the size of metatitanic acid particles. When the sedimentation rate is high, the metatitanic acid particles are fine; when the sedimentation rate is low, the metatitanic acid particles are coarse.
[salt treatment] the process of modifying metatitanic acid by adding a small amount of Chemical Additives before calcination is called salt treatment, also known as pretreatment.
[post treatment of titanium dioxide] the post-treatment of titanium dioxide is the process of surface modification of qualified particles after particle size classification.
[powdering, aging, weather resistance] the paint used for outdoor use is gradually damaged after exposure to the sun and rain, and the surface layer gradually loses luster, and the pigment particles separate out to form a layer of loose powder that can be wiped off. This phenomenon is called powdering. At the same time of chalking, white paint will turn yellow, color paint will fade, this phenomenon is called paint film aging. The degree to which the film can withstand this aging is called weatherability.
[dispersibility] in fact, the manufacture of coatings is to disperse pigments well in the adhesive liquid of various base materials by grinding or stirring. The dispersibility of pigment in the medium and the dispersion stability in the dispersion system are called dispersibility.
[sulfuric acid decomposition method of ilmenite] according to the concentration of sulfuric acid involved in the reaction and the state of the final reaction product, there are three acidolysis methods for ilmenite, namely liquid phase method, two-phase method and solid phase method.
[acid hydrolysis by solid phase method] the reaction was carried out in 5 ~ 30 min with more than 80% sulfuric acid, and the highest reaction temperature was 250 ℃.
[purpose of ripening] aging is required after acidolysis. The purpose is to allow the solid phase to cool gradually. During this cooling process, a part of the ore powder which has not been acidolysis will continue to interact with the existing free acid to improve the acidolysis rate.
[reduction of liquid titanium] there are both ferrous sulfate (FeSO4) and high iron sulfate Fe2 (SO4) 3 in the extracted titanium solution. Ferrous sulfate is stable in the acid solution, and hydrolysis starts only when the pH value is greater than 5. In the acidic solution with pH of 2.5, ferric sulfate begins to hydrolyze and forms ferric hydroxide precipitation. When washing with metatitanic acid, when the pH value reaches 2.5, hydrogen oxidation precipitate will be formed and mixed in metatitanic acid. When calcined, red brown ferric oxide will be mixed in the product, which will affect the whiteness of titanium dioxide. Therefore, the existence of trivalent iron is not allowed in liquid titanium, and it must be reduced to ferrous iron.
[purpose of freezing crystallization of liquid titanium] the liquid titanium obtained by acid hydrolysis of ilmenite and then leaching with water contains a large amount of ferrous sulfate. The main purpose of freezing crystallization is to make ferrous sulfate become crystal and precipitate, and then separate ferrous sulfate from titanium solution by filtration.
[purification of liquid titanium] after removing most of the residue by sedimentation and removing ferrous sulfate crystal by freezing crystallization, the liquid titanium still contains some small particles of solid particles caused by incomplete sedimentation. The solid phase is very fine and may have a certain charge on its surface. It is a kind of colloidal substance. Due to its small size, it can filter through and stay in the filtrate during the coarse filtration of ferrous sulfate crystal. In addition, there are soluble impurities in the liquid titanium, which must be removed. Filtration of liquid titanium is a means to remove solid phase and purify liquid titanium.
[purpose of concentration of titanium solution] the particles of metatitanic acid prepared by low concentration of titanium solution are coarse, and the pigment performance of titanium dioxide prepared is poor. In order to obtain homogeneous and fine metatitanic acid from titanium solution by hydrolysis, and then obtain titanium dioxide with superior pigment performance, it is necessary to concentrate the titanium solution with low concentration after crystallization filtration.
[function of adding seed before hydrolysis] because seed is the key to determine the shape and size of hydrolysate particles and the performance of the final product, and it is also the guide for the correct thermal hydrolysis. There are two functions of adding seed crystal: one is to ensure that the particle size is appropriate and uniform, and there is a certain structure of hydrated titanium dioxide; the other is to accelerate the hydrolysis rate, make the hydrolysis more complete, and obtain titanium dioxide with high hydrolysis rate and excellent pigment performance.
[purpose of liquid titanium hydrolysis] the hydrolysis of liquid titanium is to change the components of titanium dioxide from liquid titanium liquid to solid metatitanic acid, so as to separate it from soluble impurities in mother liquor, so as to extract pure titanium dioxide.
[purpose of washing with metatitanic acid] the purpose of water washing is to separate the liquid and solid by using the water solubility of metatitanic acid and impurity ions, so as to remove a large amount of iron, sulfuric acid and other soluble impurities in mother liquor absorbed by metatitanic acid, so as to obtain relatively pure metatitanic acid.
[vacuum filtration washing method] using the pressure difference caused by vacuum pumping, the filtrate is sucked through the filter medium, and the solid is adsorbed on the surface of the filter medium. When washing, the dissolved impurity ions will be removed by the filter layer.
[working principle of leaf filter] a material with many pores is used as the medium. Under the action of vacuum, the solution passes through the small hole and the solid is intercepted, so as to achieve the purpose of solid-liquid separation and solid water washing.
[purpose of bleaching] using trivalent titanium solution bleaching, iron hydroxide is removed, and Fe2O3 with the same crystal structure as rutile titanium dioxide will not be produced after calcination, so the whiteness and achromatic power of titanium dioxide will not decrease.
In addition, the titanium powder can be calcined at high temperature to achieve a certain quality.
[purpose of Grinding Titanium Dioxide] most of the calcined titanium dioxide is the coalescence of particles, and the particle size can meet the requirements of pigment standard by grinding, so as to obtain the highest opacity and other pigment properties.
[function of titanium dioxide coating] Coating is also called surface treatment, which is to coat a special film on the surface of titanium dioxide particles to separate the titanium dioxide particles from the external medium (air or oil). In this way, the photochemical activity of titanium dioxide can be prevented from affecting the stability of oil and the direct irradiation of ultraviolet light in the sunlight, so as to improve the weatherability of titanium dioxide and make it more suitable for outdoor use.
[inorganic coating] inorganic treatment agent is added to the titanium dioxide slurry, and its metal ions are deposited on the surface of titanium dioxide particles in the form of oxide or hydroxide to reduce photochemical activity and improve weather resistance.
[organic coating] organic treatment agent is added into titanium dioxide slurry solution, which is adsorbed on the surface of titanium dioxide particles in the form of physical adsorption and chemical adsorption, so as to change the surface properties of titanium dioxide and improve the dispersion of titanium dioxide in different media.
[opacity] refers to the degree to which light cannot pass through pigment particles. The opacity depends on the refractive index and particle size of the pigment, and also on the secondary characteristics of the pigment such as volume concentration and oil absorption.
Glossiness is the ability of a substance to reflect light from a source. The stronger the reflection, the greater the glossiness.
[hue] is the color and light feeling that pigments give people.
[coloring base phase] the color background is also known as gray paint tone, which is obviously affected by the average particle size and scattering force of the pigment.
[coloring power] the coloring power refers to the coloring ability of one pigment mixed with another pigment to give another pigment.
[type differentiation of titanium dioxide] titanium dioxide for coating can be divided into rutile type and anatase type. According to the international practice, rutile type is called R type by the first letter R of rutile, and anatase type is called a type. The rutile and anatase without post-treatment are called R1 and A1 respectively, and the rutile and anatase after post-treatment are called R2, R3 and A2 respectively. In China, anatase titanium dioxide for plastics is called AP type, and ah type titanium dioxide for chemical fiber is called ah type.
[quality requirements of titanium dioxide for enamel] 1. High purity; 2) less impurities (if Fe2O3 or Cr2O3 is contained, the product will produce yellow shade); ③ the particles are small and uniform (it makes it easy to mix with other materials during melting, so that the melting process is easy to control); ④ It has very strong refractive index and high achromatic power. It is used as opacifier in glaze, which has strong opacification and opacity, making the coating thin, smooth and acid resistant.
[quality requirements of titanium dioxide for welding electrodes] (1) the content of impurities is small, the content of sulfur and phosphorus should not exceed 0.05%, because the sulfur and phosphorus do not volatilize during welding and transfer to the weld metal, sulfur can cause bubbles and hot cracks (hot brittleness), phosphorus can produce cold cracks (cold brittleness); (2) the particles are small and uniform, and the residue in the 45 μ m sieve is less than 0.5%; (3) If the apparent specific volume is between 0.8 ~ 0.9g/ml, the viscosity will be poor if the apparent specific volume is too small. The amount of sodium silicate should be increased in the formula to affect the ignition of welding operation.
