Disperser and grinding mill for titanium dioxide(TiO2)and its comprehensive knowledge
Overview of Titanium Dioxide (TiO2)
Titanium dioxide stands out as the predominant white pigment utilized in waterborne architectural paints. Despite its status as one of the more costly constituents in the formulation, vulnerable to frequent price fluctuations and upheavals linked to alterations in hazard classification, titanium dioxide remains the most efficient pigment for imparting opacity to white and light tones.
Presently, it stands as the preeminent white pigment, finding application across a wide spectrum of fields. These encompass areas such as the life sciences, biotechnology, pharmaceuticals, and cosmetics, with specific uses in products like lipstick, cream, ointment, toothpaste, sunscreen, and powder.
Furthermore, titanium dioxide plays a pivotal role in the paint industry, the automotive sector, and wood preservation, and catalyzes the decomposition of nitrogen oxides in coal-fired power plants.
1.Need to disperse and grind titanium dioxide to minimize its particle size before it is used for paint? Coating? Ink? Pigment?
2. You need to know more about titanium dioxide?knowledge?
Please read this article, you can get answers inside. If you need to know more, just leave a message and let’s discuss more!
Z-mixer collected rich experience for providing machines for TiO2. Below are the guide for option: 1. High-speed disperser
Certain varieties of titanium dioxide pose challenges in high-gloss waterborne paints unless their particles undergo grinding in a bead mill. In instances where paint manufacturers lack bead mills in their equipment arsenal, they resort to producing high-gloss paints using a Cowles dissolver， which provides superior dispersion efficiency. The formulator of the paint recipe must judiciously choose the suitable type of titanium dioxide for milling in a Cowles dissolver to ensure proper dispersal and achieve the utmost glossiness. This decision should be grounded in data derived from research and case studies conducted across diverse apparatus, guaranteeing grinding at a level that optimizes gloss in paints with low pigment volume concentration (PVC).
To improve the quality of titanium dioxide, we must have titanium dioxide processing equipment: sand mill. The sand mill uses a material pump to mix the material that has been pre-dispersed and moistened by the mixer with the liquid material, so that the material and the grinding medium in the barrel are stirred by the high-speed rotating disperser, so that the solid particles in the material and the grinding medium They produce stronger collision, friction, and shearing effects with each other to achieve the purpose of accelerating the grinding of fine particles and dispersing aggregates; after the abrasives are dispersed, the abrasives are separated by a dynamic separator, and the abrasives flow out from the discharge pipe; horizontal sanding machines are particularly suitable for dispersing frosted products with high viscosity and fine particle size requirements. Nowadays, the fineness requirements of titanium dioxide have reached the nanometer level, so grinding and dispersion with a nanometer sand mill is necessary to obtain higher-quality titanium dioxide.
3. basket mill
The basket mill typically consists of a cylindrical vessel with a rotating shaft inside, equipped with multiple grinding baskets or grinding chambers. These baskets or chambers are filled with grinding beads or media, and the material to be processed, in this case, TiO2, is introduced into the mill. Dispersion: It breaks down agglomerates and clusters of TiO2 particles, ensuring a uniform distribution within the product. The rotating shaft and grinding media crush and grind the TiO2 particles, reducing their size and enhancing their surface area.
What is TiO2?
The chemical name of titanium dioxide: molecular formula TiO2, molecular weight 79.9, its mass composition is 59.95% Ti and O accounts for 40.05%.
We can also call it Titanic anhydride; Titanic oxide; Titanium dioxide; Titanium white; Titania; Titanium dioxide pigment .
Titanium dioxide is an inorganic white pigment. The chemical composition of titanium dioxide is titanium dioxide. It has stable chemical properties and does not react with most substances under normal circumstances . Titanium dioxide has three types of crystals: plate titanium type, anatase type and rutile type. The plate titanium type is an unstable crystal form and has no industrial value. The anatase type is referred to as type A, and the rutile type (rutile) is referred to as type R. Both have stable crystal lattice and are important white pigments and porcelain glazes. Compared with other white pigments, it has superior whiteness, tinting power, hiding power, weather resistance, heat resistance, and chemical stability, especially no toxicity. Therefore, titanium dioxide is also considered to be the best-performing white pigment in the world. Titanium dioxide is widely used in coatings, plastics, paper and ink industries, among which the largest amount is in the coating industry, accounting for about 60%.
Regardless of solvent-based or water-based coatings, if titanium dioxide is used, its role is not only to cover and decorate, but more importantly, to improve the physical and chemical properties of the coating, enhance chemical stability, and even improve hiding power, achromatic power, and anti-corrosion properties. , light resistance and weather resistance, enhance the mechanical strength and adhesion of the paint film, prevent cracks, prevent the penetration of ultraviolet rays and moisture, thereby delaying aging and extending life. At the same time, it can also save materials and increase varieties.
Properties: Titanium dioxide is a soft, odorless, tasteless white powder with strong covering and coloring power. The melting point is 1560°C ~ 1580°C. It is insoluble in water, dilute
inorganic acids, organic solvents and oils. It is slightly soluble in alkali and soluble in concentrated sulfuric acid. It turns yellow when heated and turns white again when cooled.
to titanium dioxide, which is mainly used as white pigment in industries such as coatings, inks, plastics, rubber, papermaking, chemical fiber, art pigments and daily cosmetics, as titanium dioxide, titanium dioxide pigment or titanium dioxide , and refers to it in enamel, Titanium dioxide whose purity is the main purpose used in welding rods, ceramics, electronics, metallurgy and other industrial sectors is called titanium dioxide or non-pigment grade titanium dioxide and non-coating titanium dioxide.
Viscosity of titanium dioxide slurry
The viscosity standard of titanium dioxide slurry refers to the viscosity value of the slurry under certain conditions. Generally speaking, the viscosity of titanium dioxide slurry should be between 50-150mPa.s. Its viscosity is affected by many factors, such as solid content, particle size, dispersant and solvent, etc.
Viscosity?Measurement
There are many methods for measuring viscosity, the commonly used ones are rotational viscometer method and stirring viscometer method. Among them, the rotational viscometer method is suitable for titanium dioxide slurries with good fluidity and low viscosity; while the stirring viscometer method is suitable for titanium dioxide slurries with higher viscosity.
Factors affecting viscosity
The viscosity of titanium dioxide slurry is affected by many factors, including the following:
Research on dispersion properties of titanium dioxide
The above different influencing factors have been studied on the dispersion properties of titanium dioxide, and the experiments show that :
1. The increase in the particle size of titanium dioxide has an impact on the dispersion performance . The smaller the particle size, the better the dispersion performance.
2. The higher the titanium dioxide content, the better the dispersion
3. The dispersion of titanium dioxide is better under weak acid conditions. Strong acid and strong alkali will affect the dispersion of titanium dioxide.
4. The more dispersant added, the better the dispersion performance will be.
Experimental materials and methods
1.1 Experimental materials
The material of this experiment is mainly titanium dioxide. Titanium dioxide raw materials with corresponding properties are selected according to different influencing factors. The water used is deionized water, and the pH adjuster uses 0.1 mol/L sulfuric acid and sodium hydroxide solution.
The dispersant involved is of analytical grade and prepared with deionized water to 0.1 mol/L. Other equipment includes pH meters, fluorescence spectrum analyzers, particle size distribution meters, viscometers, etc.
1.2 Experimental steps
(1) Take an appropriate amount of titanium dioxide and divide it into 5 parts. Crush it on a jet mill for different times to allow the particle size to differ. Then prepare these 5 parts of titanium dioxide into 700 g/L solutions. After fully dispersing, measure the viscosity and record it. .
(2) Take 8 portions of titanium dioxide with different titanium content and detect the components of the products respectively. Then prepare these 8 portions of titanium dioxide into 700 g/L solutions. After fully dispersed, measure the viscosity and record it.
(3) Take 10 parts of deionized water, use sulfuric acid solution and sodium hydroxide solution to prepare solutions with pH value = 2, 3, 4…11, keep the total volume the same, and then add the same mass of titanium dioxide to prepare the solution into a solution of 700g/L. After fully dispersed, measure the viscosity and record it.
(4) Take 9 parts of the same titanium dioxide to prepare a titanium dioxide solution with a concentration of 700 g/L, and add sodium silicate dispersant in the amounts of 0.05%, 0.10%, 0.15%, 0.20%, 0.25%, respectively. 0.30%, 0.35%, 0.40%, and make a blank control. After fully dispersed, measure the viscosity and record it.
2. Experimental results
2.1 Particle size experiment
After titanium dioxide is air-pulverized, its particle size decreases as the grinding time increases. The particle size distribution of the product is tested. The results are shown in Figure 1.
The measurement results after preparing the above 5 parts of titanium dioxide into solutions of the same concentration are shown in Figure 2.
It can be seen from Figure 1 that the particle size distribution of Sample 1 to Sample 5 gradually becomes wider, and the peak particle size also gradually becomes larger. Therefore, the average particle size of Sample 1 to Sample 5 gradually becomes larger.
As can be seen from Figure 2, the viscosity of titanium dioxide is positively correlated with the product particle size, that is, the larger the particle size of the product, the greater the viscosity, and the worse the dispersibility.
The difference in viscosity between sample 1 and sample 2 is small. From sample 3 onwards, the viscosity of the product increases rapidly. This shows that when the particle size is small, the difference in dispersion of the product is small. As the particle size of the product increases, the dispersion of the product decreases. The differences gradually emerged and increased exponentially.
2.2 Titanium content experiment
The most abundant substance in titanium dioxide is titanium dioxide, with the highest content reaching 99%. Usually, the titanium dioxide content of pigment-grade titanium dioxide is 85% to 95%.
Titanium dioxide content is one of the main indicators of titanium dioxide. The higher the titanium content, the better the whiteness performance of titanium dioxide, but the corresponding cost will be higher. Different application systems also have different requirements for titanium content.
Titanium dioxide with different titanium content was tested and prepared into solutions of the same concentration. After being fully dispersed, the viscosity was measured. The results are shown in Figure 3.
As can be seen from Figure 3, as the titanium content increases, the viscosity of the product shows a downward trend, that is, the higher the titanium dioxide content in titanium dioxide, the better the dispersibility of the product.
When the titanium content in the product is below 90%, the viscosity of the product changes greatly, while when the titanium content increases to more than 90%, the change is smaller.
Therefore, although high titanium dioxide content has the benefit of improving product dispersion to a certain extent, its improvement effect is not obvious when the titanium content increases to more than 90%.
2.3 Viscosity changes of titanium dioxide with different pH values
In the application of titanium dioxide, titanium dioxide is often dispersed in different pH values. For example, in the papermaking process, titanium dioxide is dispersed in an alkaline environment, and in latex paint systems, titanium dioxide is also dispersed in weakly acidic environments. environment of.
The same titanium dioxide was placed in different pH values and the viscosity was measured at the same concentration in the aqueous system. The results are shown in Figure 4.
As can be seen from Figure 4, at the same concentration, the pH value and the viscosity of titanium dioxide have a “U”-shaped relationship, that is, the dispersion of titanium dioxide is extremely poor in strong acid and alkali environments, and when the alkalinity is moderate, the dispersion of titanium dioxide is extremely poor. The dispersion is better.
The titanium dioxide shows excellent dispersion effect at pH value = 5.2. As the pH value increases, the viscosity increases rapidly. When the pH value increases to 12, the viscosity is close to 1900 mPa·s.
In a strongly acidic environment, the dispersion of titanium dioxide is better than that in a strongly alkaline environment. When the pH value = 4.2, the viscosity is only 508 mPa·s. Therefore, titanium dioxide is better dispersed in acidic conditions than in alkaline environments, especially in weakly acidic environments.
2.4 Dispersant experiment
Dispersants are an important means to improve dispersion performance, with the chosen dispersing agents playing a pivotal role in ensuring the pigment’s dispersion stability and quality control. The goal is to achieve high dispersion quality in paints, particularly those with low pigment volume concentration (PVC), ensuring high gloss and durability. dispersion quality of titanium dioxide is critical. Commonly used dispersants in the titanium dioxide industry include sodium hexametaphosphate, sodium silicate, etc., which can be selected and used according to different occasions. Figure 5 shows the effect of using sodium silicate as a dispersant to study the dispersion performance.
As can be seen from Figure 5, the addition of dispersant can effectively reduce the viscosity of titanium dioxide and improve the dispersion performance. Especially when the dispersant dosage is within 0.2%, the viscosity can be quickly reduced. When the dispersant dosage continues to increase, the viscosity decreases. The amplitude decreases and the effect is less obvious.
This is mainly because about 0.2% dispersant is enough to disperse 700 g/L titanium dioxide, and further increasing the dispersant will not further improve the dispersion effect.
3. Mechanism analysis
Through the study of the above experiments, the following dispersion mechanism can be summarized.
(1) The dispersion process of titanium dioxide is the process of turning large particles into small particles. When the particles of titanium dioxide are small enough, it is the moment when the dispersion performance is better.
The particles of titanium dioxide are relatively large, and their dispersion requires a certain amount of external force to turn large particles into small particles. These external forces include external power, dissolution force, molecular hydrogen bonds, etc.
These external forces are proportional to the size of the particles. The larger the particles, the greater the external force required. Under the same circumstances, the dispersion performance of large particles will be worse.
(2) The titanium content in titanium dioxide is one of the important indicators. Titanium element can show many properties, one of which is hydrophilicity.
There are many unsaturated bonds on the surface of titanium, which can form more hydrogen bonds with water molecules to form titanium hydrates. The presence of this substance can strengthen the affinity between titanium dioxide and water, thus increasing the dispersion of titanium dioxide.
(3) When the pH value in the titanium dioxide system changes, it actually changes the potential value of the system, and titanium dioxide itself has a certain Zeta potential. When the potential in the solution matches the Zeta potential of the titanium dioxide itself, the dispersion performance of titanium dioxide Just strengthen, which is the result of electrons repelling each other.
When the two potentials are the same, a large repulsive force is generated, causing water molecules and titanium dioxide molecules to repel each other, and the two tend to move away, thereby increasing the distance between them and achieving dispersion in the mixed system.
(4) The addition of dispersant can change the electrical properties of each aggregate in the solution. For example, anionic dispersant can make the surface of molecules in the solution negatively charged, thereby achieving dispersion under the action of repulsion; when too much dispersant is added, the negatively charged Instead, the substances will agglomerate, making the particles larger and the dispersion effect is not obvious.
4. Inspiration for production
Research on the dispersion properties of titanium dioxide aims to strengthen the production of titanium dioxide, and its guiding role in production is as follows.
(1) The particle size of titanium dioxide is an important parameter that affects the dispersion performance. During production, the particle size of titanium dioxide should be reduced as much as possible. The main methods are to control the hydrolysis particle size during titanium dioxide production, enhance the sanding strength of crude titanium dioxide, and increase titanium dioxide. Steam intensity during airflow crushing of white powder, etc.
Especially the intensity of airflow crushing, which is the last crushing process of titanium dioxide, the crushing effect is directly related to the quality of the product.
(2) Increasing the titanium content will increase the cost of titanium dioxide and also enhance the dispersion performance of the product. It is necessary to find a balance point between these two aspects. Generally, the titanium content of titanium dioxide in pigments can be controlled at 90% to 94%. Too much or too little will hurt product quality and cost.
(3) pH value is also an important control indicator in production, especially in the titanium dioxide coating process. The final coating pH value is the pH value of the product.
Through the study of factors affecting dispersion performance, it can be seen that better dispersion effects can be obtained in a weakly acidic environment. Therefore, it is best to use a weakly acidic coating end point as the end point of the product during the coating process.
(4) Dispersant is an important raw material for the production of titanium dioxide, especially during the sand grinding process. Controlling the dosage is an important means to improve the dispersion performance. As the product concentration increases, the dosage of dispersant can be appropriately increased to ensure The product is in a good dispersion environment.
Application of titanium dioxide
titanium dioxide in the coating industry accounts for 60%, of which the plastics industry accounts for 20%, the paper industry accounts for 14%, and other fields such as cosmetics, electronics, ceramics and other fields account for 6%. The fineness requirements of its application are relatively strict . When it is put into application, we need to grind the titanium dioxide to make its particle size very small. We need to use Z-MIXER disperser and grinder.
Application of titanium dioxide in coatings
Coatings are used on the surfaces of various products to provide outer layer protection and beautiful colors. Titanium dioxide is widely used in coatings to improve the chemical stability of the coating, improve its hiding power, weather resistance and anti-corrosion properties. In addition, the addition of titanium dioxide can also enhance the adhesion of the coating film on the device surface, improve the mechanical strength of the coating film, expand the scope of use, and extend the service life.
In the Paint manufacturing industry, paint is usually applied to a black background and a white background, and a spectrophotometer is used to measure the reflectance of the two. The ratio represents the hiding power. The higher the ratio, the stronger the hiding power. The hiding power is related to the scattering of light, and the scattering of light is closely related to the particle size of titanium dioxide. That is, when the particle size is 0.2~0.3μm (about half the wavelength of the incident light), titanium dioxide can produce the optimal light scattering rate. Coverage is optimal.
However, the agglomeration effect of the particles themselves often makes the particle size of titanium dioxide in the coating matrix larger than the optimal particle size. Therefore, surface modification is often used to ensure the particle size.
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1) As decorative coating. Pigment-grade titanium dioxide has very good pigment properties, and most modern people choose white or light colors to decorate their houses. Therefore, pigment-grade titanium dioxide is widely welcomed in house decoration. Not only that, pigment-grade titanium dioxide is also widely used in exterior coatings for ships, automobiles, etc.
(2) As architectural coatings. Pigment-grade titanium dioxide plays a very important role in the production process of coatings, and titanium dioxide is mainly used in architectural coatings.
(3) Make pure white paint. Most white paints on the market use large amounts of pigment-grade titanium dioxide in the manufacturing process.
(4) Make colorful pattern paint. Many pattern paints in the market today are inseparable from pigment-grade titanium dioxide in terms of color ratio and pattern. Therefore, pigment-grade titanium dioxide plays a very important role in the production of colorful pattern paints. Pigment-grade titanium dioxide is also widely used in automobile exterior paints because pigment-grade titanium dioxide has very good color and high brightness.
(5) Make special functional coatings. Pigment-grade titanium dioxide is used in the production process of many high-temperature-resistant coatings, and high-temperature-resistant coatings are a type of special functional coatings. Therefore, pigment-grade titanium dioxide is an essential raw material in the production of special functional coatings.
Effect of titanium dioxide particle size on coating hiding power
The different shapes and sizes of titanium dioxide particles have greatly different degrees of light scattering, which are key factors affecting the hiding power of titanium dioxide. Research shows that under the same conditions when the particle size of titanium dioxide is 160 to 350nm, that is, when the particle size is approximately 0.4 to 0.5 times the wavelength of visible light, it has a strong ability to scatter light, which will directly affect the application of coatings. of covering power. In the coating system, if the film-forming material is not enough to completely cover the titanium dioxide particles, the titanium dioxide particles will contact and agglomerate with each other, which to a certain extent is equivalent to an increase in the particle size of the titanium dioxide, thereby reducing the hiding power of the coating. decline.
Effect of titanium dioxide dispersion on coating hiding power
In the field of coatings, the degree of dispersion of powder particles determines product performance to a large extent. During the production of coatings, the dispersion of titanium dioxide requires wetting, sanding and dispersion processes. The stable suspension state of titanium dioxide in the coating will improve the hiding power of the coating. However, because titanium dioxide has a certain activity, the system environment used will have a certain impact on its dispersion, and it is prone to flocculation, precipitation, suspension and other poor dispersion states. Therefore, The degree of dispersion also affects the hiding power of the paint.
Effect of dispersant dosage on coating hiding power
When titanium dioxide is dispersed, its particles are smaller than fillers and tend to agglomerate. Therefore, the selection and dosage of dispersant will affect the dispersion of titanium dioxide and the hiding power of the paint film. Experiments have shown that the degree of dispersion of pigments and fillers increases with the increase in the amount of dispersant. The increase in dispersibility narrows the distribution range of pigment and filler particle sizes, and the particle size becomes smaller, thereby improving the hiding power of the paint film.
Sustainable development path of titanium dioxide for coatings
As an efficient light-scattering pigment, titanium dioxide provides excellent whiteness and hiding power for coating films. With the rapid rise of the automotive industry, construction industry and water-based coatings market, the overall demand for titanium dioxide is also increasing. The resulting constraints on resources, energy consumption and the environment have become increasingly prominent. It is urgent to improve the sustainable development capabilities of the titanium dioxide industry. In addition to the need to promote the development of new processes and technologies for titanium dioxide production, coating manufacturers also need to actively explore how to improve the efficiency of titanium dioxide use, or seek new alternatives to reduce the amount of titanium dioxide used.
As an efficient light-scattering pigment, titanium dioxide provides excellent whiteness and hiding power for coating films. With the rapid rise of the automotive industry, construction industry and water-based coatings market, the overall demand for titanium dioxide is also increasing. The resulting constraints on resources, energy consumption and the environment have become increasingly prominent. It is urgent to improve the sustainable development capabilities of the titanium dioxide industry. In addition to the need to promote the development of new processes and technologies for titanium dioxide production, coating manufacturers also need to actively explore how to improve the efficiency of titanium dioxide use, or seek new alternatives to reduce the amount of titanium dioxide used.
> Improve titanium dioxide usage efficiency
In practical applications, the agglomeration or flocculation of titanium dioxide results in the inability to obtain ideal covering even when the titanium dioxide content is high. Therefore, improving the light scattering efficiency of titanium dioxide has become a hot topic of research. Michael combined the Monte Carlo simulation method to explain that when equal volumes of fine fillers are used to replace coarse fillers in the coating formula, more spatial barriers will be obtained between titanium dioxide particles, thereby effectively improving the hiding power of the coating film. As the particle size of the filler decreases, the titanium dioxide pigment is better blocked, improving the light scattering efficiency of titanium dioxide. This means less titanium dioxide is used to achieve the same covering power. This spatial blocking of titanium dioxide is also known as the “pigment dilution” effect. However, there is also the possibility of re-aggregation of diluted titanium dioxide particles. In 2013, Dow won the U.S. President’s Green Chemistry Challenge Award for its successful development of EVOQUE precompounded polymer technology. If the distance between titanium dioxide particles in ordinary coatings is too close, the light scattering areas will overlap, reducing the efficiency. The pre-composite polymer is fixed on the surface of the titanium dioxide particles in the coating, forming an effective spatial barrier, thereby improving the distribution and light scattering efficiency of the titanium dioxide particles in the coating, improving the hiding power of the coating film, and enabling the coating formula to be modified. The dosage of medium titanium dioxide is reduced by 20%, achieving the same or even better covering effect at less cost. In addition, the addition of prepolymerized compounds can also help improve the stain resistance, corrosion resistance and other properties of the coating. The application of this technology can significantly reduce energy consumption. According to third-party verified life cycle assessment (LCA) results, EVOQUE pre-compounded polymers can reduce carbon emissions by more than 22% and water consumption by 30% in coating products. In 1997, Virtanen proposed a titanium dioxide particle pre-embedding technology, using titanium dioxide particles as the core and calcium carbonate as the shell, forming a functional pigment with a core-shell structure. The outer layer of calcium carbonate provides an effective spatial barrier between titanium dioxide particles and improves light scattering efficiency. The carbon footprint is about 70% lower than that of ordinary titanium dioxide, which can partially replace titanium dioxide. This pigment is commercially produced by FP Pigments. Similarly, Kemu Company has developed a surface-treated titanium dioxide TS-6300. Conventional surface treatment is often done to reduce the photocatalytic activity of titanium dioxide and improve dispersion. The highly processed technology in TS-6300 creates additional blocking space between titanium dioxide particles, reducing the agglomeration effect between titanium dioxide particles, thereby improving light scattering efficiency. Moreover, this surface treatment increases the oil absorption of titanium dioxide particles and reduces the level of CPVC, allowing the presence of air in the coating to be used to improve light scattering efficiency at lower PVC.
> Introduction of air
The presence of air in the coating film can reduce the refractive index of the resin/air mixture, thereby increasing the refractive index difference with the titanium dioxide pigment and improving the light scattering ability of the coating film. In coatings, there are generally three types of voids that help improve hiding: air within the resin, air within the filler particles, and air at the resin-pigment interface. A typical example of improving air covering in resin is the hollow polymer microsphere first developed by Kowalski et al. in 1984 and commercialized by Rohm and Haas under the name ROPAQUE. Latex particles containing carboxylic acid groups are selected for polymerization reaction with hard monomers such as styrene to obtain latex particles wrapped by a polymer hard shell with a high glass transition temperature (Tg). Then the system temperature is raised to above the Tg of the shell layer, and an alkali is used to neutralize and dissolve the carboxyl groups in the core to expand the core. The temperature is then lowered to finalize the shell, producing microspheres filled with water. As the coating dries, water evaporates through the polymer shell and is gradually replaced by air. In order to compare the effect of hollow polymers on wet covering and dry covering, the test showed that the coating containing only titanium dioxide had a higher initial wet covering, which gradually decreased with the increase of drying time until it reached a plateau of dry covering. Coatings containing both titanium dioxide and hollow polymers have similar initial wet coverage, then gradually decrease in covering power during the drying process, and after reaching the lowest point, the covering power gradually increases again due to the evaporation of water in the hollow polymer. to a stable state. When the content of titanium dioxide is reduced in the coating and combined with hollow polymers, the initial wet hiding ability is poor, but after drying, the coating film can achieve the same dry hiding ability as a coating film containing only titanium dioxide. Therefore, hollow polymers can be used to partially replace titanium dioxide, and can act as effective space barriers like ultrafine fillers to improve the efficiency of titanium dioxide. In addition, hollow polymers can also improve the stain resistance, stain resistance, and scrub resistance of the coating film, as well as provide excellent outdoor color retention. Similar to hollow polymers, the air inside the filler also contributes to coating film hiding. A focused particle beam image of a cross-section of microporous kaolin particles produced by Omya. The structure contains many micropores. This kaolin clay with closed micropores is prepared through a rapid calcination process. In the traditional kaolin calcination process, natural hydrated aluminum silicate is slowly heated to 1000°C over 30 minutes, causing the flaky clay particles to form irregularly shaped agglomerates. The heating process of this calcined kaolin with closed micropores only takes a few seconds. The hydroxyl groups in natural aluminum silicate dissociate when the temperature reaches 500°C and are released in the form of vapor. Because the heating speed is too fast, the steam has no time to release, causing the pressure inside the particles to increase and expand, eventually forming many micropores. The void volume within the particles accounts for about 20%, causing the density of kaolin to drop from the original 2.60 to 2.06. The enclosed air in microporous kaolin completely resists the penetration of resins, solvents or water in liquid paints, so these voids help improve both the wet and dry hiding of the paint. And it can provide high hiding power to the coating film when it is lower or higher than the CPVC of the coating, saving up to 20% of the use of titanium dioxide. Among them, in the formula lower than CPVC, the initial point is set to 20% titanium dioxide volume content without any other pigments and fillers, and then three contrast substances are added in a gradient of 5% PVC, that is, PVC starts from 20% Gradually increase to 45%, and the volume content of titanium dioxide remains unchanged by replacing resin with equal volumes during the entire process. It can be seen that traditional calcined kaolin has a minimal effect on the hiding power of the coating film because its refractive index is not much different from that of resin. The two substances containing closed pores, microporous kaolin and hollow polymer, greatly improve the hiding power of the coating film. Although the two have similar contributions to the hiding power of the coating, their effects on gloss are different. Microporous kaolin has a matte effect due to its micro-rough structure on the surface, while hollow polymers are beneficial to improving the gloss of the coating film. In formulations above CPVC, the starting point is 75% PVC containing 10% PVC titanium dioxide and 65% PVC calcium carbonate with an average particle size of 4μm. Then replace the calcium carbonate with the same gradient of 5% PVC, keeping the total PVC and volume solid content unchanged. On top of CPVC, microporous polymers outperform hollow polymers and traditional calcined kaolin clays. This is due to the simultaneous action of the voids inside and outside the microporous kaolin particles. And since the oil absorption of microporous kaolin is lower than that of traditional calcined kaolin, it will not harm scrub resistance. In addition, Nguyen et al. synthesized a composite nano-sandwich of polymer and titanium dioxide through free radical emulsion polymerization technology. In this structure, titanium dioxide particles are first embedded with a water-swellable hydrophilic inner polymer, and then coated with a hydrophobic outer layer. Finally, the inner hydrophilic polymer layer swells in an alkaline solution. , forming a sandwich structure containing air and titanium dioxide particles. This structure provides coverage in three ways: one is titanium dioxide particles; the other is air; and the third is the space barrier provided by the outer layer. To sum up, in the coating formula, according to different performance requirements, improving the light scattering efficiency by reducing the agglomeration of titanium dioxide, or adding additional light scattering by introducing air can make the coating obtain better hiding power. Achieve partial replacement of titanium dioxide, reduce carbon emissions, and enhance the sustainable development capabilities of titanium dioxide.
Application of titanium dioxide in ink
Physical ink is a viscous colloidal fluid formulated from colorants (pigments and fuels), fillers, auxiliaries and color developers . It is one of the important materials used for printing packaging materials. Through printing, patterns, text, etc. Appeared on the substrate . It is widely used in printing newspapers, books, pictures, printing text and patterns on metal, ceramics, rubber and plastic films, printing radio semiconductor circuit boards and other printing. Titanium dioxide has physical and chemical stability, uniform and fine particles, high tinting power, strong hiding power and high refractive index. It can be evenly dispersed in the developer and has excellent physical and chemical stability, making it an indispensable product in ink products. Mixing agent.
The proportion of titanium dioxide used in ink production is also relatively large, generally 25% to 50%, and a few use more than 50%. Different types of inks have different quality requirements for titanium dioxide. Generally speaking, rutile titanium dioxide has better application performance and is more commonly used in the preparation of various types of inks. Comparing the application performance indicators of rutile and anatase titanium dioxide inks, it can be found that rutile titanium dioxide is better than anatase titanium dioxide in terms of crystal shape, refractive index, tinting power, and fluorescence index.
Effect on ink hiding power
The refractive index of the titanium dioxide crystal itself will directly affect the hiding power of the ink. Generally, the refractive index of titanium dioxide is the best among white pigments. When preparing white ink, titanium dioxide with a high refractive index should be used to enhance the hiding power of the white ink.
Generally, in the range greater than 1/2 of the wavelength of visible light, the smaller the particle size, the smoother the particle surface, the better the dispersion of titanium dioxide in the resin connecting material, and the stronger its covering power. Because titanium dioxide itself has a significant crystal structure, its refractive index is larger than that of the developer. The greater the difference in the refractive index between the two, the stronger the hiding power of the titanium dioxide used. Practice has proven that rutile titanium dioxide has better hiding power than anatase titanium dioxide, so it is more widely used in ink production.
Effect on ink color strength
The coloring power of titanium dioxide depends on the ability of titanium dioxide to scatter visible light, and it has a direct impact on the coloring power of the ink. The greater the scattering coefficient, the stronger the coloring power; the higher the refractive index of titanium dioxide, the stronger the coloring power. powerful. Titanium dioxide has the highest refractive index among white pigments, and the refractive index of rutile titanium dioxide is higher than that of anatase titanium dioxide. Therefore, when choosing titanium dioxide, you must choose titanium dioxide with strong scattering ability and high refractive index.
Impact on decentralized function
Whether the shape of titanium dioxide particles and light reflection are uniform directly affect the dispersion function of titanium dioxide. It is believed that the surface of titanium dioxide particles is smooth and the reflection is uniform, the dispersion property is good, and the gloss and whiteness of the prepared white ink are also good; on the contrary, if the surface of the particles is rough and the diffuse reflection is increased, the gloss will be greatly reduced and the dispersion property will be poor. , directly affects the whiteness and transfer function of white ink. For this reason, titanium dioxide must be processed before it can be used. In addition, during the ink production process, titanium dioxide with different functions must be selected according to the specific characteristics and requirements of various types of inks.
Effect of particles on whiteness
Different titanium dioxide particles have a smooth shape and no sharp edges. If titanium dioxide with sharp edges on the particle surface is used, the light reflection effect will be greatly weakened and the whiteness of the ink will be reduced. The size of titanium dioxide particles should be controlled at 0.2~0.4μm, which is equivalent to about 1/2 of the wavelength of visible light, in order to obtain high scattering ability and make its color appear whiter. When the particle size is less than 0.1 μm, the crystal is transparent. If the particle size exceeds 0.5 μm, the light scattering ability of the pigment will be reduced and the whiteness of the ink will be affected. For this reason, titanium dioxide particles are required to be of appropriate size and evenly distributed to show good whiteness.
Effect of impurities on ink whiteness
Generally speaking, if trace amounts of iron, chromium, cobalt, copper and other impurities are mixed into titanium dioxide, the prepared ink will have a color shift and a decrease in whiteness. This is caused by impurity ions in titanium dioxide, especially metal ions, distorting the crystal structure of titanium dioxide and losing its symmetry. Rutile titanium dioxide is more sensitive to impurities. For example, iron oxide will show color when its content in rutile titanium dioxide is greater than 0.003%, while its color will appear only when its content in anatase titanium dioxide is greater than 0.009%. color reaction. Therefore, it is very important to choose precise and impurity-free titanium dioxide.
Application of titanium dioxide in plastics
As the second largest user of titanium dioxide, the plastics industry has been the fastest growing field in recent years, with an average annual growth rate of 6%. Among the more than 500 titanium dioxide brands in the world, more than 50 brands are dedicated to plastics. The application of titanium dioxide in plastic products not only utilizes its high hiding power, high achromatic power and other pigment properties, it can also improve the heat resistance, light resistance and weather resistance of plastic products, and protect the plastic products from UV light. Invasion, improve the mechanical properties and electrical properties of plastic products.
Since plastic products are much thicker than paint and ink coatings, they do not require a high pigment volume concentration. In addition, they have high hiding power and strong tinting power. The general dosage is only 3% to 5%. It is used in almost all thermosetting and thermoplastic plastics, such as polyolefins (mainly low-density polyethylene), polystyrene, ABS, polyvinyl chloride, etc. It can be mixed with resin dry powder or with additives. The liquid phase of plasticizer is mixed, and some processes titanium dioxide into masterbatch before use.
As the application range of plastic products continues to expand, many plastic products for external use, such as plastic doors, windows, building materials and other outdoor plastic products, also have high requirements for weather resistance. In addition to the use of rutile titanium dioxide, surface treatment is also required. This kind of surface treatment generally does not add zinc, but only silicon, aluminum, zirconium, etc. Silicon has a hydrophilic dehumidifying effect, which can prevent pores caused by water evaporation during high-temperature extrusion of plastics, but the amount of these surface treatment agents is generally not too large.
The quality requirements for titanium dioxide for plastic products are:
Hiding power: Titanium dioxide has good hiding power, and the plastic products produced are lighter and thinner;
Whiteness: Determines the appearance of light-colored or white plastic products;
Dispersion: Affects the production cost of plastic products. Poorly dispersed titanium dioxide in plastic products will affect the smoothness and brightness of the products;
Weather resistance: Plastic products and plastic doors and windows used outdoors must ensure the weather resistance of titanium dioxide.
Application of titanium dioxide in masterbatch
Plastic masterbatch is a highly concentrated, high-efficiency color preparation, that is, the pigment is evenly distributed in the carrier resin at an extraordinary concentration and forms particles of a certain particle size. It is mainly composed of core layer (pigment), coupling layer (coupling agent or surfactant), dispersion layer (lubricant or dispersant), mixing layer (carrier resin), etc. It is used as a dye in plastics. It is widely used in the production of plastic products such as film blowing, injection molding, hot pressing, and injection molding. Masterbatch has excellent coloring effect, is easy to use, saves energy, and is free of dust and sewage when used, so it is favored by users. The development speed of masterbatch is very fast. In addition, the production process of masterbatch is simple and the investment is low. There are currently hundreds of masterbatch factories in China, with varying production scale and technical level. The annual output of small ones is tens of tons, and the large ones are Thousands of tons, product competition is becoming increasingly fierce, profits of manufacturing companies are on a downward trend, and the quality of most masterbatch products is low. According to incomplete statistics, 20,000 to 30,000 tons of titanium dioxide are used for masterbatch production every year. The rutile used is divided into three grades: high, medium and low. The high-grade uses imported rutile, the mid-grade uses domestic rutile, and the low-grade uses domestic anatase. type titanium white. Huizhou Taiyangshen Chemical, China’s largest masterbatch production company, uses imported titanium dioxide to produce masterbatch mainly for export, and uses domestic titanium dioxide to produce masterbatch to meet the domestic market. Due to fierce competition, the use of anatase titanium dioxide masterbatch is increasing.
Masterbatch can be used to color PVC, polyethylene, polypropylene, polystyrene and ABS plastics. Its main ingredients include pigments, resins, dispersants, volume pigments, fluorescent whitening agents, antioxidants, anti-UV agents, antistatic agents, toughening agents, brighteners, etc. Titanium dioxide is used as a white pigment and has unlimited properties. It has the advantages of toxicity, stable chemical properties, high covering power and good dispersion.
There are several masterbatch production processes. Typical ones are: pigments, resins, dispersants, volume pigments, other additives, high-speed mixers, and twin-screw extruders.
Masterbatch is used as an industrial raw material, and its performance is usually reflected in subsequent product applications (such as film blowing or injection molding). Therefore, the performance of titanium dioxide in color masterbatch is also mainly reflected in the application process of color masterbatch. Mainly reflected in the following aspects:
1) The coloring ability of titanium dioxide: determines the amount of titanium dioxide used in the color of the same plastic product;
2) Whiteness of titanium dioxide: determines the appearance of light-colored (white) plastic products with the same titanium dioxide content;
3) The dispersion of titanium dioxide: affects the production cost of colored particles and the appearance, gloss and other indicators of plastic products;
4) The processing performance of titanium dioxide: affects the production cost of masterbatch.
Application of titanium dioxide in papermaking
Titanium dioxide can also be used in the papermaking field. About 11% of titanium dioxide consumption is used in the papermaking industry. Compared with the plastics industry, it uses similar application methods, and its role in this field is also similar to that of the plastics industry. The same, i.e. as its internal pigment. In the papermaking industry, titanium dioxide can also be used as a filler to improve the physical and mechanical properties of paper, improve its elasticity, whiteness and gloss, and reduce its hygroscopicity and penetration during printing.
Considering the production cost, low-grade paper generally does not use titanium dioxide, but uses materials such as talc powder, calcium carbonate, and calcined kaolin. It is mainly used in high-grade paper and thin paper. Paper filled with titanium dioxide is more uniform, smoother and has higher oil absorption value. In addition, adding titanium dioxide to chemical fibers can make light-resistant matte high-white paper, as well as brightly colored colored paper, and can achieve the effect of anti-ultraviolet paper.
To ensure the stability of the papermaking process and paper quality, the papermaking industry’s requirements for titanium dioxide are usually: good water dispersibility, fine and uniform particles, and low iron content. It is usually only used in high-grade paper and thin paper, or with other fillers. With the use of. Different grades of paper correspond to different crystal forms of titanium dioxide. For example, adding anatase titanium dioxide to ordinary paper can act as a fluorescent whitening agent. For advanced laminated paper, the paper requires high light resistance and high heat resistance. Titanium dioxide should be of rutile type.
Titanium dioxide has stable chemical properties and can be used for papermaking under various conditions. Adding TiO2 to functional paper can give it special effects. This functional paper can be used in home interior stickers to absorb harmful gases (formaldehyde, benzene, etc.). Adding titanium dioxide to paper products can also give the paper sterilization and disinfection functions.
Table 1: Performance comparison of titanium dioxide and other materials
As can be seen from Table 1, compared with other materials, titanium dioxide has high whiteness, high density, high refractive index, fine and uniform particles, which means that paper using titanium dioxide has good whiteness and strong hiding power. , high strength, thin and smooth, not easy to penetrate when printing.
Although the opacity of paper using titanium dioxide is 10 times higher than that of other materials, and the weight can be reduced by 15% to 30%. At the same time, the whiteness, gloss and UV penetration resistance are much greater than other materials, but the price of titanium dioxide is relatively high. , and when used, the particles are small and easy to agglomerate, resulting in large amounts of abrasion, which will have a certain impact on the equipment.
Photocatalyst industry
As a photocatalyst material, the primary material itself must have semiconductor characteristics. The energy difference between the charged band and the conductive band must be appropriate. Secondly, it should have a large inner empty orbit. Nanomaterials have such conditions. Almost all nanomaterials are semiconductors. Under light irradiation, electrons are excited and jump from the valence band to the conductive band. The potential energy generated is enough to electrolyze water to produce O2 and H2. Common semiconductor photocatalyst materials include TiO2, ZnO, SnO2 and CdS. Among them, TiO2 is recognized as the best photocatalyst material due to its strong redox ability, high chemical stability and non-toxic properties.
TiO2 in?Cosmetics?industry
First, titanium dioxide is used as a pigment in cosmetics. It can make the texture of cosmetics smoother and increase the covering power and ductility of the product. It also provides a luminous white effect, making skin look brighter and glowing. This is because titanium dioxide has excellent reflective properties and can reflect light, making the skin look brighter.
Secondly, first-line brand titanium dioxide also has a certain hiding power. It covers facial blemishes and dullness, making skin look more even. This is very helpful for people who want to achieve bright and fair skin. In addition, titanium dioxide can also absorb oil to keep the skin fresh, and it is also effective in controlling oiliness.
Chemical fiber industry
Titanium dioxide for chemical fibers is mainly used as a matting agent. Since the anatase type is softer than the gold-red type, the anatase type is generally used. Titanium dioxide for chemical fibers generally does not require surface treatment, but some special varieties require surface treatment in order to reduce the photochemical effect of titanium dioxide and avoid fiber degradation under the photocatalysis of titanium dioxide.
① Strong chemical stability: The selected titanium dioxide must not react negatively with the raw materials of synthetic fibers, otherwise impurities will be produced and affect the quality of the fibers.
② Good temperature and weather resistance: Most chemical fiber production and processing processes require a high-temperature environment, so the titanium dioxide used must have excellent temperature and weather resistance and cannot decompose, change color, or react to produce impurities at high temperatures (260-300°C). .
③Good dispersion: ensure that titanium dioxide can be evenly distributed in the polymer.
④ Fine and uniform particles: If the titanium dioxide used contains coarser particles, it will damage the fiber strength and even cause hazards such as broken filaments, clogged spinneret holes and frequent replacement of filters, affecting the production process, causing loss of raw materials and increasing costs.
Enamel industry
The enamel industry is an important application field of titanium dioxide. Enamel grade titanium dioxide has high purity, good whiteness, bright color, uniform particle size, strong refractive index and high achromatic power, and has strong opacification and Opacity makes the coating thin, smooth and acid-resistant after enamel application. In the enamel manufacturing process, it can be mixed evenly with other materials, does not agglomerate, and is easy to melt.
①Refractive index and strong achromatic power: Titanium dioxide is used as the strongest opacifying agent in the glaze. The opacifying intensity of the glaze is related to the refractive index of the opacifying agent. The refractive index of titanium dioxide is high, so the titanium dioxide enamel coating can be thin and white.
②High whiteness and purity: If it contains impurities such as Fe?O? and Cr?O?, the product will produce a yellowish shade.
③The particles are small and uniform: easy to mix with other materials during melting, making it easy to control the melting process.
Ceramic industry
The ceramic industry is also an important application field of titanium dioxide. Ceramic-grade titanium dioxide has the characteristics of high purity, uniform particle size, high refractive index, excellent high temperature resistance, and the ability to remain non-greying for 1 hour under high temperature conditions of 1200°C. It has high opacity, thin coating and light weight, and is widely used in ceramic materials.
Enamel is a kind of coating material used in the enamel industry. It is a product made by coating a layer of special enamel on the surface of a metal body and then melting it at high temperature. Enamel has many advantages, including good opacity, and certain acid, alkali, heat and abrasion resistance, which can protect metal and beautify products. In order to ensure the opacity of the enamel, an emulsifier must be added. Strong emulsion properties are especially required in white enamels. Titanium dioxide is one of the most effective emulsions in enamel. Products coated with titanium white enamel have a smooth surface, greater acid resistance, and very good color and gloss. Therefore, titanium dioxide is widely used in the enamel industry.
Rubber industry
Titanium dioxide is used as a colorant in the rubber industry and has reinforcing, anti-aging and filling functions. Mainly used in rubber shoes, rubber floors, gloves, sports equipment, etc., generally anatase type is the main type. However, during the production of automobile tires, a certain amount of rutile products is often added to enhance the resistance to ozone and ultraviolet rays.
① Good heat resistance: The rubber production and processing process requires a high-temperature environment. Titanium dioxide should have good heat resistance and should be vulcanized at 110°C to 170°C without yellowing.
②Good light and weather resistance: The anti-aging agents used in white and light-colored rubber products have weak protective effects and are easy to age under light. However, titanium dioxide has a strong ability to absorb the damaging ultraviolet rays in the sun and has good light and weather resistance. Titanium dioxide can make rubber products more resistant to aging and less likely to crack or discolor.
③Good stability: It has good stability against sulfur and other additives, and should not have any adverse effects on the performance of rubber products.
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