Must-have tips for colorants
1. What are the performance and application requirements of water-based color paste?
1.1 Performance requirements: The color paste should have as high a pigment content as possible, coloring power, hiding power, resistance (light resistance, weather resistance, acid resistance, alkali resistance, temperature resistance, resistance to other media, etc.), good dispersion, fluidity, exhibition Color, batch stability (reproducibility) and compatibility with a variety of systems, high cost performance.
1.2 Requirements for storage stability: During storage, the water-based color paste does not have granulation, flocculation, no obvious stratification, no sinking and hard bottom, and is easy to stir evenly.
1.3 Environmental requirements: no or low content of volatile organic compounds (VOC), APEO, and heavy metals.
2. What is relative tinting strength?
Relative tinting strength refers to the tinting strength of the color paste to be tested relative to the standard color paste. For the comparison of water-based colorants, tinting strength is an important indicator, which reflects the color concentration, color development performance and flocculation of pigment dispersions of colorants. Tinting strength is generally tested for dark color (1/1ST dilution) and light color (1/25ST dilution). The tinting strength of the color paste to be tested can generally be measured by a spectrophotometer or calculated according to a formula.
3. Compatibility of color paste and latex paint
The compatibility between the color paste and latex paint mainly depends on the dispersibility, anti-flocculation, pigment concentration, viscosity, dispersion stability, viscosity, particle size, and selected dispersing agent of the color paste itself. Wet system, emulsion, thickening system, etc. The compatibility of color paste and latex paint is the key to the disadvantages of paint film such as color development, flocculation, floating color and blooming of color paint.
Compatibility test method of color paste and latex paint: finger research. Add an appropriate amount of color paste to the latex paint, stir evenly, and scrape it on the white cardboard. Before the surface of the paint film is completely dry (do not do it when the surface of the paint film is wet), rub it with your index finger along the same direction for 5-6 times , compare the color difference between the finger-grinding area and the non-finger-grinding area to judge whether the compatibility is good or not.
4. How to choose the color paste?
4.1 According to the different use environments outdoors and indoors, the selection of colorants can be divided into external colorants and internal colorants. The lightfastness and weather resistance of the external colorants are very high (the lightfastness of 1/25 diluted color should be At grades 7-8, the weather resistance should be at grades 4-5), while there are no high requirements for internal colorants. Therefore, the color paste for external use can be used internally, but the color paste for internal use must not be used externally.
4.2 According to the acid and alkali resistance of the color paste, choose the color paste with good acid and alkali resistance according to the specific environment of the object of use.
4.3 According to the compatibility of the color paste with the paint system used, use a color paste with good compatibility.
4.4 According to the coloring strength of the colorant in the paint system, select the colorant with high coloring strength and good cost performance.
4.5 Consider the matching between color paste and color paste to select color paste, and do a matching test before mixing color paste from different manufacturers.
Considering the above factors comprehensively, the color paste used outdoors should follow the principles of light fastness, good weather resistance, and good chemical medium resistance to select the color paste. When selecting colors, the color system or similar color system of iron oxide pigments is preferred, and light fastness should be selected for organic bright colors. It is a color paste with 7-8 grades, 4-5 grades of weather resistance, and 4-5 grades of acid and alkali resistance. Indoor use of color paste follows the principle of good compatibility, good color development, low cost and high cost performance.
5. How to test the light resistance and weather resistance of color paste?
The light fastness and weather resistance of the color paste can be tested in two ways: natural outdoor exposure and artificial accelerated aging. Outdoor exposure generally requires selection of places with typical climatic conditions, and the detection cycle is long. At present, the artificial accelerated aging test is generally selected to obtain the results of light resistance and weather resistance similar to natural conditions.
Lightfastness: 1/1 and 1/25 ISO standard depth color samples made with exterior acrylic latex paint for exposure. Or use the Q-UV light fastness tester to test for 500 hours, use the 1-8 grade blue wool ruler to expose to the sun at the same time as the standard color sample, and get the color difference for rating, grade 1 is the worst, grade 8 is the best.
Weatherability: 1/1 and 1/25 ISO standard depth color samples for exposure using exterior acrylic latex paint. Or use the ATLAS artificial aging instrument to expose to the sun for 500 hours, and use the ISO gray card to evaluate the color difference. Level 1 is the worst and level 5 is the best. It can also be graded by measuring the color difference of the sample before and after aging with a spectrophotometer.
6. What is the chemical resistance of color paste?
The chemical medium resistance of water-based color paste mainly refers to the acid and alkali resistance of the selected pigments. For different applications, when selecting water-based color paste, the acid and alkali resistance indicators should be considered when using the building exterior wall Color paste with good acid and alkali resistance.
Acid and alkali resistance test method: Make a board made of colored paint, cover the surface of the paint film with filter paper soaked in 2% hydrochloric acid or saturated calcium hydroxide solution, cover it with a glass plate, add a weight, and let it stand for 24 hours. Check the template for discoloration. Acid resistance and alkali resistance are divided into 5 grades, grade 1 is the worst and grade 5 is the best.
7. How to evaluate the quality of water-based color paste?
In general, we can use the following indicators as the parameters for judging the color paste:
After strict control of the color paste, it is necessary to ensure that the coloring power, fineness, color development, viscosity, specific gravity, light resistance, weather resistance, and chemical medium resistance of the color paste are consistent between different batches of color paste. , especially the control of chromatic aberration.
