General knowledge of paint: introduction to manufacturing process of color paint (5)

Key tips: Section IV stabilization and formulation balance of paint paste After the slurry which has been grinded and dispersed to meet the specified requirements is transferred to the paint mixing process, the specified amount of paint, solvent and additives shall be added according to the operation procedure The work in the mixing stage includes adjusting the color, balancing the formula and stabilizing the grinding slurry by the correct feeding method 1、 Stabilization of lacquer paste In the production of color paint, there are always some disadvantages, such as resin precipitation turbidity and pigment re flocculation, which affect the quality slightly and make the paint deteriorated For example, in the production of black amino baking paint, after the dispersion reaches the fineness standard on the three roller mill, the remaining Paint knowledge how about Akzo Nobel Powder Coating Recommended introduction: powder coating is a kind of coating with different form from general coating, which is in powder form It is a new type of coating, because of its own advantages and more and more known by people Let's introduce Akzo Nobel Powder coating Akzo Nobel Powder coating is a cost-effective coating solution, which can be applied to different kinds of products After the treatment of static electricity and fire baking, a tough and durable coating surface will be formed, with the least impact on the environment Since the introduction of this technology, powder coating has been able to continue to maintain the Paint Home News: Section 4: after the slurry stabilization and formula balance are grinded and dispersed and the slurry meeting the established requirements is transferred to the paint mixing process, according to the operation procedures, the specified amount of paint materials, solvents and additives need to be added The work in the mixing stage includes adjusting the color, balancing the formula and stabilizing the grinding slurry by the correct feeding method 1、 In the production of color paint, the stabilization of paint slurry often encounters some disadvantages, such as resin precipitated turbidity and pigment re flocculation, which affect the quality slightly and make the paint deteriorated and unusable seriously For example, in the production of black amino baking paint, when the dispersion reaches the fineness standard on the three roller mill, but when the paint is mixed with the remaining paint materials and solvents, sometimes there will be local cementation of grains or paint slurry In the use process, sometimes the wrong way of feeding also causes quality accidents For example, in 1991, a unit in Shenzhen used the iron oxide epoxy primer of Tianjin paint factory, and pigment flocculation occurred after diluent was added Similarly, if water is used as diluent for electrophoretic paint, if the way of adding water is improper, the phenomenon of pigment flocculation will also appear The reason for these phenomena in the mixing process is mainly due to the incompatibility between the dispersed paint slurry and the added paint and solvent in terms of composition, viscosity, surface tension, etc It is an important part of paint mixing to study the instability of paint paste and take effective measures to avoid it The following are some forms of poor paint paste stability （1） Resin precipitation (resin precipitation) synthetic resin for coating has certain tolerance for dissolving organic solvent The solid content of resin solution (i.e paint material) is within the allowable range, and the resin can be dissolved Below this range, the resin will be separated from the solution e.g figure 12.10 is a processing diagram of grinding and dispersion of alkyd enamel by three roller machine Fig 12.10 schematic diagram of alkyd enamel processing (a) the preparation way of three roller machine for varnish; (b) the penetration effect of dilute solvent on the interface, so that the base material can be extracted from the pigment particles The paint in the product's abrasive paint slurry is an alkyd resin solution with a solid content of 67% The dilution limit of the resin in 200 paint solvent oil is that the solid content is not less than 27% To illustrate the problem, we assume that the slurry containing pigment is slowly added to the mixing tank containing solvent At the beginning of dilution, the resin content of solvent in the tank is zero With the addition of the slurry, the resin content in the diluent increased, and the resin content precipitated in the range of 0% ~ 27% Here, any strong agitation will only accelerate the generation of precipitation, the resin content is higher than 27%, the process goes in the opposite direction, the resin dissolves without precipitation, and finally the resin dissolves again, and the solid content of paint reaches 45% However, due to the temporary precipitation of resin in this process, the space potential resistance between the pigment particles that have been coated with resin film will be reduced, which is close to each other When they gather together, irreversible pigment flocculation will occur, and the stability of the dispersion system will be destroyed The above is only a hypothesis The normal operation will not add the abrasive slurry to the solvent, nor the abrasive slurry containing pigment to the paint with high solvent content On the contrary, the correct operation is to slowly add the paint with high solvent or solvent content into the abrasive paint slurry containing pigment when stirring （2） Resin peeling refers to the phenomenon that the resin wrapped on the surface of the pigment is dissolved rapidly by the solvent in the dispersed abrasive paint slurry, and the resin separated from the surface of the pigment enters the solution When a large amount of solvent is added to a small amount of paint slurry with high resin solid content, such as the paint slurry of three roller machine (see Fig 12.10b) the resin on the surface of the pigment particles dissolves and enters the solution, making the resin film coated with the pigment particles become thinner and thinner, resulting in the decrease of the space potential resistance, making the pigment particles approach again, and may gather into large particles （3） Solvent migration (solvent diffusion) when a kind of paint with high resin content is added into the abrasive paint slurry with high solvent content, such as the abrasive paint slurry of sand mill or ball mill, mutual migration and diffusion will occur immediately, but the main body of the transfer through the interface is almost completely the more mobile solvent component As a result, the pigment particles in the slurry are squeezed more and more intensively until they touch each other and agglomerate together, which will cause the coarsening phenomenon in the process of paint mixing Fig 12.11 preparation route of alkyd enamel dispersed by sanding machine (a) preparation route of alkyd enamel dispersed by sanding machine; (b) paint slurry solvent diffuses to the dilute paint rich in base material, leaving pigment particles solution: prepare abrasive paint slurry with high molecular weight solvent （4） When the resin used for coating is dissolved in the solution, it is generally dispersed in the form of micelles Under effective agitation, the micelles of the resin are usually subdivided into small particles When the agitation stops, they will gradually return to their original state 2、 The measures for stabilization are as follows 1 Under the effective mixing from beginning to end, slowly add the diluted paint to the grinding slurry 2 The feeding sequence of adding the paint for mixing first and then adding the solvent for diluting shall be followed 3 The composition difference between the diluent and the color paste should not be too large 4 High boiling point solvent shall be used for grinding paint slurry 5 Prevent the temperature or viscosity difference between the color paste and the diluent from being too large Home of coatings is specialized in coatings, diatom mud, paint coating, coating technology, fire retardant coating news and coating, diatom mud, paint coating, coating technology, fire retardant coating decoration knowledge and decoration renderings,