Application of titanium dioxide in latex paint.

The application of titanium dioxide in latex paint Ma Yujie, Wang Jianwei, Zhang Liang, Wu Qiong (Jinzhou Titanium Co., Ltd., Liaoning Jinzhou 121005) 0 Introduction With the rapid development of China's economy, the construction industry has become a new growth point of China's economic development, the real estate market continues to heat up, the market demand for latex paint growth is strong, China has become the world's largest latex paint manufacturer. Latex paint rich in color, rich and elegant can be freely selected, good decorative effect, long use period, has become a beautiful "coat" to dress up the city buildings.pigments play an indispensable role as an important component in latex paint. The correct selection and use of pigments directly affect the color preservation of latex paint, and can guide the processing and production of high-quality latex paint. As one of the most important pigment fillers in latex paint, titanium white powder plays a decisive role in the cover and weather resistance of latex paint, and its output accounts for more than 70% of inorance pigments and consumption accounts for 95.5% of the total consumption of white pigments. At present, about 60% of the world's titanium dioxide is used in the preparation of a variety of coatings, especially redstone titanium white powder. Therefore, it is very important to choose titanium dioxide suitable for different types of latex paint.of 1 latex paintlatex paint mainly consists of pigment and base material.1.1 Pigmentspigments are substances that give color to colored materials. Pigments are colored, black, white or fluorescent particles, organic or inorganic solids, pigments in practical applications will not be affected by physical and chemical factors, generally insoluble in the use of the medium, but always in the original crystal state, its coloring effect is based on its selective absorption and scattering of light to achieve, such as white pigments mainly by scattering; Pigments are divided into organic and inorganic pigments. Inorganic pigments are made of natural minerals or inorganic compounds, most of which are low purity, darker color, low color, many varieties are toxic, but cheap, high cover, light resistance, good weather resistance; Pigments also have coloring pigments and body pigments: coloring pigments have cover and color, physical pigments do not cover, mainly used to adjust the system viscosity, moisture resistance, adjust the coating structure and as an incremental agent to reduce costs.1.2 substationthe base material consists of film-forming substances, additives and thinners. Latex paint film is basically emulsion, which is commonly used in: acetate emulsion, phenyl propylene emulsion, pure propylene emulsion, ethylene acetate polymer, polyethylene alcohol resin aqueous solution, silicone emulsion and so on. Additives commonly used in latex paint include moisturizers, dispersants, deblgants, film-forming agents, pH regulators, thickeners and rheumorants, mold preservatives, etc. Thinners are mainly water.. 2 Latex paint classificationby application area, latex paint can be divided into inner wall latex paint and outer wall latex paint.2.1 Inner wall latex paint inner wall latex paint film to vinyl acetate polymer, phenyl propylene emulsion-based, its main function is to decorate and protect the interior wall, so that it is beautiful, clean, the coating has a smooth texture, delicate, soft color and so on. The performance of latex paint with inner wall has four main index requirements: cover, wash resistance, anti-fouling and alkaline resistance.2.2 Exterior latex paintOuter wall latex paint film-forming material mainly phenylpropan emulsion, pure propylene emulsion and silicone propylene emulsion. The exterior wall latex paints the exterior wall of the decoration and protection of the building, so that the appearance of the building clean and beautiful, to achieve the purpose of beautifying the urban environment.
the outer wall latex paint with the sun, rain, wind, temperature and other long aging effect, the coating will appear cracking, shedding, powdering, color change and other phenomena, so that it loses the decorative and protective effect on the building. There are five main indicators of performance requirements for latex paint on the exterior walls:
weather resistance, stain resistance, water resistance, alkaline resistance and temperature resistance (freeze-thaw stability).. 3 Latex paint preparationlatex paint production generally includes grinding pulping process and modulation coating process, equipment is mostly high-speed dispersion machine or variable speed dispersion machine.3.1 Grinding pulping process Grinding pulping process is the main process of dispersion, generally added water, thickeners, pH regulators, freeze-thaw stabilizers, moisturizers, defrost agents, dispersants, titanium dioxide powder and fillers, etc., requires direct high-speed dispersion or dispersion after grinding with a sander, until the fineness is qualified.3.2 Modulation coating processmodulation coating process requires slow stirring, at this time mainly add film additives, desmoulators, emulsions, thickeners, pH regulators, preservatives, color paste and water. At this time the fineness has been qualified, mainly for the various properties of the coating, such as viscosity, dryness, gloss, etc. to adjust.. 4 Latex paint requirements for titanium dioxidepigments in latex paint mainly provide cover and decorative, fillers can improve the mechanical properties of the coating film and reduce coating costs. The proportion of pigments in latex paint is in most cases the largest. In half-light and light latex paint, the quality ratio of pigment and emulsion is more than 1.5:1 or even 6:1, there is the pigment and base material ratio in latex paint, mostly (0.4 to 0.7):1, so the role of pigment in latex paint should be paid attention to. Titanium white powder is the most important white pigment in latex paint, it provides excellent white effect by scattering light. Not only does white latex paint need it, but other color latex paints also need it as a base pigment to provide cover. For latex paint, titanium dioxide is an indispensable pigment, from its whiteness, color, brightness, cover, coloring force, particle size and its distribution, oil absorption value, density, light resistance, heat resistance, chemical reaction, impermeability, corrosion resistance, dispersion and other performance indicators to consider the impact of titanium white powder on latex paint performance. Here are a few of the more critical indicators.
4.1 whiteness . Latex paint is coated on the surface of a building as a decorative coating, so its aesthetics is particularly important. Aesthetics has two requirements: one is to provide a uniform color decorative coating, and the other is to cover the color of the building itself. The whiteness of titanium dioxide is the result of the effect of titanium white powder on light, which determines its ability to present white in the coating, which is a crucial indicator for latex paint.4.2 Cover ForceCover force refers to the ability of an object to cover the base color of the surface of the applied object when it is coated with a coating, so that the base color can no longer be revealed through the coating. The masking effect is mainly due to the scattering caused by titanium dioxide or the absorption caused by the presence of colored substances or the phenomenon of reducing the intensity of the incoming light due to the joint action of the above two reasons. The masking power of a pigment depends not only on its crystal structure, refractive index and ability to scatter light, but also on its ability to absorb light. However, titanium dioxide, like other white pigments, because of its small absorption capacity of light, although the absorption of light on the cover force, but no scattering capacity has a large impact, so its cover force is mainly affected by scattering force, but also with refractive index, particle size, particle size distribution and dispersion performance. The larger the relegation index, the greater the cover force, the smaller the granularity, the greater the cover force, but when its particle size is less than half the wavelength of visible light, the masking force decreases. The greater the cover force of titanium dioxide used on surfaces of the same area, the less paint required and the lower the production cost. Therefore, titanium white powder in latex paint cover is also an important indicator.
4.3 Coloring force . Coloring force is also one of the important characteristics of titanium dioxide, refers to titanium dioxide mixed with another pigment, the resulting mixture shows its own color ability. Sometimes in order to distinguish between white pigments and coloring pigments, the coloring ability of coloring pigments is called coloring force, the coloring ability of white pigments is called coloring force, that is, for white pigments, it is mixed with dark pigments, the lighter the color of the mixture, indicating that its coloration force is stronger. Coloring force is the result of pigment absorption and scattering of light. Titanium dioxide absorption of light is very small, the size of its coloring force mainly depends on its visible light scattering capacity, scattering force is large, coloring force is high. In real life, most use colored or light paint to coat buildings, less pure white paint. Generally first with titanium dioxide preparation of white color base paint, before coating the slurry added to the base paint, on-site color. When titanium dioxide is applied to the color-based coating, in addition to considering its covering power, it is more important to consider its coloring force. The greater the coloring force, the smaller its dosing, which can reduce production costs.4.4 Dispersionis an important application index of titanium dioxide. Dispersion will not only affect the coloring force, cover force, oil absorption and other indicators of titanium dioxide, but also directly affect the processing process of the product and the final product gloss and weather resistance. In recent years, in order to improve the production efficiency
rate, most of the coating plants cancelled the grinding process, which put forward higher requirements for the dispersion and dispersion stability of titanium dioxide.4.5 Weather resistance weather resistance of exterior coatings, i.e. outdoor durability, refers to exposure to outdoor environment conditions, external wall coating mechanical properties, such as mod, strength, bondability, color preservation, such as the degree of change, and whether there is brittleness, powdering, color change, loss of light, peeling and other phenomena. The main function of exterior coating is protection and decoration, coating film must be able to maintain until the next update, and can maintain good visual effects, therefore, weather resistance is very important. At present, my foreign wall paint generally requires weather resistance of 8 to 10 a or more.-causing oxidation degradation and hydrolysis are two major outdoor degradation processes that often take place simultaneously and sometimes promote each other, accelerating the destruction of the coating film. The surface lattice of titanium dioxide without inorgic surface treatment is defective, so that there are many photoactive points on its surface, under the effect of ultraviolet
light, the oxygen ions on its lattice lose two electrons into oxygen atoms, the electrons released are captured by Ti4 plus, reduced to Ti3 plus. The release of reactive oxygen atoms will cause the surrounding resin to break the chain, resulting in yellowing of the coating film, cracking and other aging problems. Therefore, in the outer wall latex paint, should be selected with good weather resistance of the gold-redstone type titanium white powder.. 5 Different latex paint applicable to the titanium white powder brandin the paint formulation design, titanium white powder dosage in the raw material cost accounted for a large proportion, and titanium white powder a wide variety of products are designed for certain performance, with different product characteristics. Different types of coating products to choose different characteristics of titanium dioxide as a pigment in order to make
products have excellent product performance. At present, titanium dioxide used in the field of latex paint mainly has the following types of performance characteristics of products: (1) general-purpose products: commonly used foreign brand products are DuPont R902 plus, Quist RCL595, Teno CR828, CR822, Ishihara R930, R980, Connors 2310, etc., commonly used domestic brand products are Jin titanium CR-501, CR-510, Longyu Lilian R996, BLR601, Dongjia R237, R2377, Zhong nuclear R215, Yuxing R818 and so on.(2) high weather-resistant products: commonly used foreign brand products are DuPont R706, R960, Quist RCL696, Teno CR826, etc. ; (3) High weather resistance, high dry cover products: commonly used foreign brand products are DuPont R931, TS6300, Ishihara R780, Kronos 2044, etc. ; In coating formulations, in addition to selecting the right titanium dioxide, another key issue is how to determine the optimal amount of titanium dioxide, depending on the color of the coating, cover requirements, but also by other factors, such as PVC (pigment volume concentration), wetting dispersion, coating thickness, coating solid content and other pigments.
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