What is water-based color paste?

Brief introduction of water-based color paste 1, the coloring strength of color paste is an important index compared with water-based color paste, which reflects the color concentration, color rendering performance and flocculation of pigment dispersion. The data is measured by the number of copies of pigment paste required to reach the international standard depth (ISD) 1/25. The smaller the value, the higher the coloring ability. The numerical value indicates the grams of color paste to be added to the white base paint: the titanium dioxide content of the white base paint in latex paint is 25% (1/25ST). 2. Compatibility of color paste (color rendering performance-finger grinding method) The compatibility of color paste and application system is the key to affect the floating color, flocculation and some surface defects of color paint. Before using color paste, compatibility test must be carried out. Additives can often be used to solve the compatibility problem between color paste and coating. Add color paste to white paint, usually in medium or light color, and apply it on the surface of the coated object or imitate the surface of the coated object. When it is about to solidify, polish the surface of the coating with your fingers, and observe whether there is obvious color difference (visual inspection) after drying. If the fineness of color paste is not enough, the dispersion performance is not good, and the color development of color paste is not good, it will affect the reproducibility of color paint. 3. Dispersion performance of color paste (flocculation degree) The degree of deflocculation of pigment particles by additives determines the dispersion size and stability of color paste. Generally speaking, it is impossible to achieve complete deflocculation (that is, the pigment exists uniformly and stably in the form of primary particles in the system), but is uniformly distributed in the system in the form of pigment particle aggregates. A good color paste has a high degree of deflocculation, that is, the agglomerates are as small as possible, so it has good coloring power, excellent color rendering and storage stability. Because of the poor dispersibility of the color paste, the migration difference between the pigment flocs in the color paste and the white pigment and filler particles in the base material is easy to be reflected, which often makes the pigment flocs no longer evenly distributed. When the film is formed, the pigment floc and the paint base naturally participate in this movement due to the slight differences in temperature, density and surface tension in the film, and the pigment floc separates, resulting in floating color and blooming. If the dispersion of color paste is good, floating color and frosting can be avoided. In addition, the dispersity of the coating itself also directly affects the floating color and frosting of the coating. 4. One of the structural properties of the color paste (light resistance and weather resistance) The light resistance and weather resistance of the color paste are tested by outdoor exposure (for example, Florida in the United States and Toulefan in China have exposure fields, etc.). ), but the actual outdoor exposure time is too long, and now most of the general color paste performance tests are instrument and equipment simulation. Light resistance: outdoor acrylic latex paint is used to make 1/3ISD and 1/25ISD standard color samples for exposure. Xenon lamp light source (1000W) was exposed for 72 hours, 1-8 blue wool ruler and standard color sample were exposed at the same time, and the color difference was obtained for rating. 1 worst, 8 best. (Tested by color measuring software) Weather resistance: 1/3ISD, acrylic latex paint for outdoor use. After 500 hours of exposure with ATLAS artificial aging instrument, ISD grey card was used for color difference rating, with 1 as the worst and 5 as the best. (It has passed the evaluation of color measuring software) 5. The second structural property of color paste (chemical medium resistance) The chemical medium resistance of water-based color paste is mainly acid resistance and alkali resistance, that is, chemical migration resistance. The performance basically depends on the pigment itself, and outdoor color paste must consider this factor. General water-based coatings also require acid and alkali resistance, and do not require resistance to chemicals such as organic solvents. Acid resistance and alkali resistance: according to DIN 16524 standard, dry the color paste (105℃), put it in 1% sulfuric acid and 2.5% sodium hydroxide solution for 24 hours, take it out and wash it, and measure its acid resistance and alkali resistance. According to the color bleeding and color change, it is evaluated according to the 5-level standard. Grade 5 means excellent acid and alkali resistance, and grade 1 means extremely poor acid and alkali resistance. 6. Other physical and chemical parameters of the color paste (density, viscosity, PH value, pigment content, solid content, fineness and luster) Density: the unit is g/cm3, and the determination method is carried out according to GB/T 1756. Viscosity: an important index reflecting the storage stability of color paste. (STM-ⅲ Stormer viscometer) PH value: The PH value (PH value) of water-based high-quality color paste system measured by PHB-2 portable acidity meter is generally between 7- 10, so the color paste has excellent color retention, coloring power and color rendering in the coating system with PH value of 7- 10. Fineness and luster: an intuitive index reflecting the dispersion effect and storage stability of color paste. Generally speaking, for the same pigment paste, the smaller the fineness, the higher the gloss, and the better the dispersion effect and storage stability. 7. The quality stability (quality control) and storage stability of color paste are generally ensured by strictly controlling the production formula-raw materials-production process-finished products to ensure the consistency of solid content, fineness, viscosity, coloring power, color rendering, light resistance and weather resistance of color paste. (Evaluation by color matching software, Lab value and color difference control DE < 1.0) The storage stability of general water-based color paste is about 25℃ at room temperature for one year, and there are no obvious defects such as delamination, caking, coarsening and precipitation, and the physical and chemical properties such as coloring power and color rendering are not obviously reduced. Usually, aging judgment can be accelerated by hot storage and freezing experiments, and evaluated by can opening effect evaluation and color matching software. 8, how to choose color paste (color paste selection basis) According to the object of coloring and environmental requirements, color paste is mainly divided into two types: sun-resistant and non-sun-resistant. Generally, internal use is based on the principle of the lowest cost to achieve color requirements, and light fastness is not required when the systems are incompatible. The following factors must be considered for external use: a. light resistance and weather resistance; B. chemical medium resistance (mainly acid and alkali resistance); C. compatibility with the use of the system; D. coloring strength, hiding power and color rendering; E. matching between color pastes F. storage stability of color pastes; Generally, the color retention requirements of exterior wall coatings are very strict, so when selecting color paste, special attention should be paid to the light resistance, weather resistance, acid and alkali resistance of color paste. On the premise of good compatibility, coloring power, hiding power, color rendering and storage stability, the mutual matching of color pastes is also very important. Try to choose monochromatic color paste with excellent light resistance and weather resistance, but in fact it is often a composite color. Therefore, it is best to follow the principle that inorganic and inorganic, organic and organic or light resistance and weather resistance are close (diluted at 1/25ST, light resistance should be 7~8 or 8, and weather resistance should be 4~5 or 5), so as to ensure outdoor color retention and avoid outdoor problems.