Quality analysis of titanium dioxide and its effect on the physical anti-lightener powder

Abstract:
the traditional production process and formulation of titanium dioxide have changed under the pressure of increasing production cost of titanium dioxide. Therefore, in the actual production of powder coatings, the physical anti-lightener powder gloss has little impact on titanium dioxide, now the gloss interference is growing, by the vast number of engineering personnel attention. Through the analysis of the quality index of titanium white powder, the method of true and false identification of titanium white powder and the influence factors of titanium white powder on the luster of the physical anti-lightener powder
China
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1, foreword
titanium dioxide is manufactured in two production processes: sulphuric acid and chlorination. Goldstone-type titanium dioxide and sharp titanium-type titanium dioxide can be produced by any process.
method is the solution of titanium and the sulfate of titanium and other metals by dissolving the mineral sand containing titanium in sulfuric acid. Then go through a series of steps, including chemical reduction, purification, precipitation, washing, combustion. Then get the titanium dioxide intermediate. Most of the domestic titanium dioxide factory using this process of production, easy to pollute the environment.
chlorination method consists of two high temperature aluhydrated vapors opposite should be. Titanium ore and chlorine react under reduced conditions to produce titanium tetrachloride and metal chloride impurities, which are removed. High-purity titanium tetrachloride is oxidized at high temperatures to produce very bright titanium dioxide intermediates. This process produces high-quality products and is environmentally friendly, but relatively expensive.
intermediates are clusters of titanium dioxide crystals of pigment particles, which must be dispersed (grinded) and various wet processing methods to improve titanium dioxide. Hydrated oxides, including silicon, aluminum, or zinc, are wrapped on the surface of pigment particles. Individual hydration oxide treatments or combinations of different treatments can also be used to obtain optimal performance for special purposes.
The important issue in the manufacture of titanium dioxide is the supply of titanium ore, which, although listed in the top 10 elements, is widely distributed in nature at low concentrations and needs to be improved in mining and mineral processing operations to meet the economic requirements for the manufacture of titanium dioxide.
people's awareness of environmental protection, as well as the continuous improvement of natural resources protection, so that the titanium dioxide industry in the production process pollution control and titanium ore procurement pressure is increasing. Manufacturing costs are rising significantly higher than before.
However, in the domestic economic situation is not optimistic, titanium dioxide downstream main market (real estate, large-scale industrial projects, etc.) contracted, resulting in a continuous decline in demand for titanium dioxide, and led to a unilateral decline in prices;
, a price war has been started in the domestic market. From the 2013 price point of view, the price of goldstone titanium dioxide from the beginning of the year 17,000 to 18,000 yuan / ton, straight down to the end of the year 13,000 to 14,000 yuan / ton, a drop of 24 , even many enterprises trading price is less than 13,000 yuan / ton, sharp titanium-type titanium dioxide also from about 14,500 yuan / ton to 11,000 to 12,000 yuan / ton, the price reduction of 18%. Sales in the titanium-white industry are under great competitive pressure.
in the manufacturing costs and market competition factors, titanium dioxide manufacturers in order to survive, we must find a way to reduce the factory cost of products. However, workers' wages and benefits are gradually increasing rather than decreasing in principle, and the reduction of natural production costs depends mainly on technological innovation.
, the amount of titanium white powder coating process, coating raw materials and additives has changed due to the adjustment of technology and process. Unwittingly, the coating film reaction has catalytic material infiltration, so that the original physical anti-light agent powder coating gloss has little impact on titanium dioxide, now, also has a greater impact.
different manufacturers and models of titanium dioxide on the physical anti-light agent powder coating gloss has a great impact. For our powder engineers, choose the manufacturer and model of titanium dioxide until the batch. It has become one of the considerations in the formulation design of the powder coating of the physical anti-light agent. In addition, there are even some unspeed manufacturers or trade merchants fake, to titanium dioxide into the partial filling material, or into the goldstone-type titanium dioxide into part of the sharp titanium-type titanium dioxide re-sale, deceiving consumers.
the quality of titanium dioxide when we manufacture powder coatings? What indicators deserve our attention?
2, titanium dioxide white powder quality analysis
China GB /T1706-2006 "titanium dioxide pigment" is the use of international standard ISO591-1:2000 "color paint with titanium dioxide pigment part one: specifications and test methods" modified, is the technical requirements of titanium dioxide, test methods, test rules of the direction. The main indicators of its control are: TiO2 mass parts, 105 degrees C volatile mass parts, water solute mass parts, sieve residue (45 m) mass parts, color, scattering force, oil absorption, extract resistivity and so on.
the application characteristics of different industries, the requirements of titanium dioxide is not exactly the same, the test method will be different.
2.1 Requirements for titanium dioxide in the powder coating industry
Titanium white powder in the application of powder coatings, mainly used for coloring, white when the amount of white also plays a skeleton support role. According to its own process characteristics, the quality control index of titanium dioxide mainly includes: color, volatile, oil absorption, 300 mesh (48 m) sieve residue, particle size distribution, cover force, heat resistance, weather resistance, crystal structure, content, etc.
2.1.1 color
titanium dioxide as decorative color, according to the theory of color reduction, the color is of course the higher the whiteness of the better. When it contains black or other noise tones, it tends to turn gray and its whiteness decreases. The more mixed the noise pigment, the grayer it becomes and the whiter it becomes. In general, we use the first feed use confirmed qualified, the sample as a standard sample, as a later evaluation criteria. Can be visual contrast, can also be made in the same conditions dry plate, with the instrument measurement results contrast color difference.
2.1.2 Volatile
is one of the important indicators of titanium dioxide control in powder coating applications. Volatiles include the volatility of water and a variety of volatile gases produced by reactions at powder production and construction temperatures (95 to 200 degrees C). Too large a volatile part can cause pinholes in the coating surface and affect gloss. Volatiles are smaller the better. It can be measured by the weight change before and after baking.
2.1.3
the amount of refined flax kernel oil absorbed by the 100g sample under specified conditions. Available in ml/100g or g/100g. The amount of oil absorption is related to the wetting and dispersion of the coating, and too large will affect the smoothness and gloss of the coating film. Suitable surface treatment (organic coating) process, can improve the moisture and dispersion of titanium dioxide, and can properly control the amount of oil absorption of titanium dioxide.
method of measuring the amount of oil absorption: put the sample on the plate, with a titration tube drop and refined flaxen oil, each refueling amount does not exceed 10 drops, add and then use a tuning knife pressure research, so that the oil seeps into the sample under test, continue to add to the oil and sample table at this speed into a lump. From this point on, each add a drop after the need to fully grind with a tuning knife, when the formation of a uniform consistency of the paste, just not broken, but also adhere to the plate, that is, the end point. Record the amount of fuel consumed and all operations should be completed within 20 to 25min.
particle malady of 2.1.4 300 mesh (48 m) sieve residue
coating is one of the difficult problems in powder coating production. Therefore, it is best to prevent in advance. According to the thickness requirements of the powder coating, titanium white powder with 300 standard sample sieve water wet sieve, must be fully passed, and hands in the sieve brushing can not feel hard particles. If hard particles are felt, even if they can be screened completely, there will be particle defects in the coating.
2.1.5 particle size distribution
in theory, the narrower the particle size distribution of titanium dioxide is, of course, the better. If light is to be scattered effectively, the diameter of the titanium dioxide pigment particles should be slightly less than half the wavelength of the scattered light, because the naked eye is most sensitive to yellow and green light (wavelengths of about 0.55 m), so the particle size of titanium dioxide powder used in coatings is ideal between 0.2 and 0.3 m.
However, in a fully covered, non-absorbent white coating, changing the size of the pigment has no effect on color, but in a coating film that contains light-absorbing substances, reducing the amount of titanium dioxide increases the blueness. Titanium dioxide made by sulphuric acid method, large particle size, color red light.
color is not very white, gray or yellow. And a batch and a batch of particle size distribution is not consistent, resulting in different chroma, chlorination method of titanium dioxide, particle size fine, particle size distribution rules, pure white color, batch color stability, with blue phase. Therefore, titanium dioxide made by chlorination is the trend of choice in the coatings industry.
the dry powder of titanium dioxide is not dispersed well, it is recommended to use wet particle size spreader measurement.
2.1.6 masking force
titanium dioxide in powder coatings with different percentage pigment volume concentrations, will show different masking forces. At 10% of the pigment volume concentration (PVC) of titanium dioxide, the economical amount of good covering force is obtained.
When the PVC concentration of titanium dioxide increases to 10% (because the density of each coating variety is different, the concentration of 10% PVC is equivalent to about 22 to 32% of the weight), the refractive efficiency of the winding light is reduced due to the accumulation of titanium dioxide particles. The result of this effect is that the coating film loses part of the covering force, and when the PVC concentration of titanium dioxide is between 10% and 25%, the rate of refraction efficiency decreases more slowly than the increase in the concentration of titanium dioxide PVC can enhance the cover, and the increase of titanium dioxide will still increase. However, when the PVC concentration of titanium dioxide is more than 25%, the refractive efficiency is reduced faster than the increase of the concentration of titanium dioxide PVC can enhance the cover, with the addition of titanium dioxide, the masking force will be reduced.
In general, we use the first feed use confirmed qualified, with 10% weight (about 3% PVC concentration) did not fully cover the conditions, dry plate sample as a standard sample, as a standard for future evaluation. Because it is not completely covered, it is easier to tell the difference between the two titanium cover forces.
2.1.7 Heat resistance
heat resistance refers to the degree of color stability of titanium dioxide heat. Because the construction of powder coating baking equipment construction local temperature between 170 degrees C to 220 degrees C, when the titanium white heat resistance is not good, hanging in different locations in the oven will appear different colors. This is especially true when construction without light and white.
generally speaking, the titanium white powder of the redstone type is better than the sharp titanium titanium white powder heat resistance, and the titanium white powder through the coating is better than the non-encumbered titanium white powder heat resistance. During the inspection, titanium dioxide can be baked directly in the oven at different temperatures, after the specified time to remove, observe the baked and unbaked sample color changes in the temperature gradient, determine the heat resistance temperature of titanium dioxide.
2.1.8 Weather resistance and the effects of crystal structure and composition
Weather resistance refers to the chemical degradation of light, heat, humidity, and alternating environments of light, heat and humidity. The weather resistance of titanium dioxide has a great effect on the degree of color and gloss, as well as on the resistance to fading caused by mold and dust.
surface of pure TiO2 particles is photochemically active in the presence of water vapor and oxygen, and can even promote the degradation of the substation around its particles. Therefore, it is necessary to control TiO2 itself with light stabilization first. The degree of stability can be controlled by treating different types of inorganic oxides and their different components. That is, the TiO2 is treated with an inorder coating. The formation of a shielding film around TiO2 particles and between organic resins no longer promotes (or reduces) degradation of organic resins.
the denser the titanium white powder surface bread film will be more stable, the more weather resistance is guaranteed. And the denser the coating, the thicker the coating layer, and the amount of coating will increase. Therefore, for inorgis SiO2, ZrO₂, Al2O3 and other choices, and its amount in the titanium white coating, as well as titanium dioxide crystal structure, determines the weather resistance of titanium dioxide. Of course, sharp titanium crystal structure
titanium dioxide is not recommended for weather-resistant coatings. X-ray inspection is one of the important methods to identify the crystal structure and structure of titanium dioxide, but the equipment is more expensive. When we feed inspection, we usually make each batch of titanium dioxide on the same conditions as a dry plate, with fast aging instruments to verify weather resistance.
2.2 Adulteration and inspection of titanium white powder
the price difference between imported titanium dioxide and domestic titanium white powder, gold-redstone titanium white powder and sharp titanium white powder is more obvious. In the case of increasingly compressed profit margins, some bad trade (or agent) intermediaries in the operation of fraud, deceiving consumers. First of all, the domestic titanium white powder packaging for imported well-known brand titanium white powder; Adulteration methods are emerging, making it difficult to identify.
first of all, for the identification of packaging. Imported titanium dioxide powder usually has its characteristics (e.g. pattern, font, lot number, etc.) on its packaging, can first be identified on the appearance of its packaging, in addition, through the inspection report, MSDS and other accompanying information check. Of course, visuals are sometimes not very effective, and will not be discovered until the indicators have been compared.
, for the identification of some sharp titanium-type titanium dioxide impersonating redstone-type titanium white powder. It is difficult to test quickly by general chemical method and can only be identified by X-diffraction method. XRD:X-ray diffraction instrument consists of X-ray generation unit, diffraction angle determination unit, X-ray intensity recording unit, X-ray diffraction analysis is a known X-ray wavelength, by measuring the diffraction angle value to find out the crystal's crystal surface moment d value, by d value as a sign of the state of the material crystal.
The relative strength of the diffraction data d and diffraction ray of any crystalline substance I/I0 is the inevitable reflection of its crystal structure, so it is necessary to identify the phase of the crystalline substance according to the diffraction figure data, according to the diffraction intensity to determine the amount of the phase of the substance. This allows you to determine whether it is a redstone crystal or a sharp-shaped crystal, exactly how many servings.
again, for titanium dioxide powder mixed with calcium carbonate, Lid powder, vanadium sulfate, zinc oxide and other impurities. It can be identified by the characteristics of calcium carbonate and Lide powder after acid encountering acid. For example, for those with CaCO3 in titanium dioxide powder, if bubbles are creating when hydrochloric acid is added and the gas released causes the clarified lime water to become cloudy, this is indicated