Some pigments are easy to disperse, and some are difficult to disperse. If they are mixed together for grinding, it will inevitably cause the effect of difficult dispersibility and easy dispersibility. Therefore, the production of color paint should adopt the method of single-pigment grinding to ensure the quality and reduce consumption.
When carbon black and heavy calcium carbonate are used to prepare black paint, firstly, carbon black, heavy calcium carbonate and oil are pre-mixed and ground into a slurry with a fineness of 20-30 μm, and then mixed to obtain a black paint. If carbon black and heavy calcium carbonate are ground together with oil, the resulting paint will be dark gray and the hiding power will be significantly reduced. This is because the carbon black that is difficult to disperse is affected by the large particles of heavy calcium carbonate, and cannot be fully dispersed, and the coloring power is not fully exerted.
When the sand mill is used as the grinding and dispersing equipment, the following three different methods can be used to prepare the grinding slurry.
①Single pigment grinding method
For enamel containing multiple pigments, single-color grinding varnish can be prepared by single-pigment grinding, and enamel products of specified colors can be prepared by mixing single-color varnish when coloring the paint. Since each pigment is dispersed separately, suitable grinding equipment and operating conditions can be selected according to the characteristics of the pigment. This is conducive to the best performance of the pigment and the maximum production capacity of the equipment. However, if there are many kinds and patterns of enamel paint, a large number of single-pigment paint paste storage tanks with agitators are needed, and many equipments need to be used. The metering and conveying of single-color paint pulp is more intensive, so this method is suitable for production occasions with many designs and colors.
②Multiple pigment mixing grinding method
The method of mixing the pigments and fillers used in the paint product formula and grinding them with a sand mill to make a multi-pigment ground paint paste. After adding paint, solvents and additives to this paint paste, it can be directly made into a primer. Lacquer or single-color paint; multi-color enamel can also be produced after adjusting the color with a small amount of color paste, so it has the advantages of high equipment utilization and few auxiliary devices. However, the grinding and dispersing efficiency is reduced, the production capacity is reduced, and the product quality is easily affected. Due to the fluctuation of the color of each batch of paint paste, the difficulty of color matching is increased, and it is easy to cause the color difference of different batches of products to increase. Therefore, this method is suitable for paint workshops that produce primers, monochrome paints and enamel paints with limited varieties.
③Comprehensive pigment refining method
This method is a compromise between the above two methods. Mix certain kinds of pigments in the recolor paint formula to make a grinding paste of mixed pigments, and at the same time grind some difficult-to-disperse pigments (or pigments that interfere with other pigments) separately on another dispersion line to make a single Pigment paste, and then mix the two in the paint pot to make a paint. Make the main color paste (it can be pure coloring pigment, or a mixture of coloring pigment and filler) on a fixed grinding and dispersing line to make the main color paste, and make various coloring pigments on another small grinding and dispersing line A tinting paste is made, which is then mixed and tinted to create a finished paint in a range of colours. This method takes advantage of the above two methods to a certain extent and avoids their disadvantages. At present, this method has been widely used in the color paint workshop of preparing light-colored enamel paints of various color series with white pigment as the main color paste and transferring a small amount of other color toning paste.
