Coating technology: introduction to production technology and production method of emulsion paint

Key tips: 1 Color and filler feeding In the operation of premixed pigment paste, the feeding sequence of pigments and fillers has a certain influence on the whole latex paint production process No matter what kind of dispersion process, we all hope to be able to pre mix slurry very evenly, that is to say, pigment particles have been well wetted, which provides a good basis for pigment dispersion For the premixing stage of pigment, the following points are summarized roughly: 1) Before adding pigments and fillers, first add water to the agitator (water should be added in part) Application scope and advantages of roller ceramic coating Recommended introduction: the surface of ceramic rubber plate used for roller ceramic coating is cast into durable rubber plate by hundreds of independent small ceramic pieces Each ceramic piece has raised characteristics Under general conveyor belt pressure, thousands of unique cast bumps can produce positive traction, prevent slipping and extend the service life of conveyor belt roller At the same time, the bottom layer adopts high-quality rubber, which has strong elasticity and can play a good impact resistance role The scope of application of roller ceramic coating is one three six 83857180 (the same as V) 1 Roller coating in extremely harsh working environment 2 The belt joint is not suitable for fixing with iron buckle; 3 It is suitable for leather Paint Home News: 1 In the aspect of color and filler feeding, in the operation process of premixed pigment slurry, the feeding sequence of color and filler has a certain impact on the whole latex paint production process No matter what kind of dispersion process, we all hope to be able to pre mix slurry very evenly, that is to say, pigment particles have been well wetted, which provides a good basis for pigment dispersion For the premixing stage of pigments, the following points are summarized: 1) before adding pigments and fillers, first add water (water should be added to a part), pigment dispersant and other auxiliaries to the agitator, and then put pigments and fillers after stirring evenly; 2) if you want to add a variety of pigments to your system, you should first add pigments that are difficult to disperse, and then put pigments that are easy to disperse; 3) If you want to add a variety of fillers to your system, first put the fillers with small density, large water absorption and fine particle size in the order, so when purchasing fillers, you must make clear the relevant indicators of each product; 4) the feeding process must be carried out under the condition of mixing, and the powder is added to the vortex The feeding speed shall be consistent with the mixing speed as much as possible In the process of feeding, we will find that agglomeration and wall attachment are usually caused Therefore, the residual material on the wall of the kettle should be scraped into the kettle and stirred after each addition of raw material At the end of feeding, clean the inner wall of the kettle thoroughly with some water Continue mixing for a period of time, and mix well When the pigment and filler are fully wetted, grind and disperse them However, for many small and medium-sized latex paint manufacturers, due to their own conditions, they seldom grind and disperse Therefore, we suggest that low-speed mixing should be used when the pigment is put in After feeding, the mixing speed should be increased to make the pigment disperse evenly 2 In terms of defoamer feeding, we all know that the defoamer is added to the emulsion paint in two times First, the pigment is added in the premixing stage, then in the mixing stage The antifoaming agents added for the two times can be the same, but two kinds of antifoaming agents should be selected and used for the compound effect The best one has good antifoaming effect and the other has good antifoaming effect The inhibition effect is good in the premixed stage of the pigment slurry, because there is hardly any bubbles in the system at this time The main function of the system is to restrain the bubbles generated in the premixing stage The defoamer added in the paint stage is mainly aimed at defoaming property, so as to effectively remove the foam that has been produced in the system, and restrain the bubbles generated during the process of the paint The formation and collapse of foam in latex paint system follows such a rule: the viscosity of the system is small, the foam is easy to generate, and the foam is also broken easily On the contrary, the greater the viscosity of the system, the more difficult the foam will disappear To give this rule our attention should be paid to two points: 1) as the viscosity of the pigment slurry is large, the antifoaming defoamer should be added in the premixed stage to make the system as few bubbles as possible 2) during the paint stage, the viscosity of the system will be reduced to the minimum when the emulsion is added to the pigment slurry, so adding defoamer at this time is the easiest way to remove the foam 3) for the thickening of the paint stage, the foam must be removed after the paint is basically eliminated, otherwise the thickening foam will be more difficult to eliminate 3 In the production process of latex paint, film-forming additives can be used in the mixing stage or in the premixing stage of pigment slurry If the polymer emulsion has good stability to the film forming AIDS, it can be added in the paint stage after the emulsion is added, and can also be put into the pre mixing stage before adding the pigment If the emulsion is not good for the stability of the film forming agent, it is easy to produce flocculation and expansion It should be added in the premixed stage, so that the film builder is diluted, and then mixing with the emulsion will not cause what serious problems However, in this case, some film-forming AIDS will be absorbed by pigments, resulting in "loss" of film-forming AIDS At this time, the amount of film-forming AIDS will increase Therefore, the compatibility of film forming AIDS and emulsions greatly affects the performance and cost of coatings Therefore, when using film forming AIDS, we must pay attention to the problem of mixing stability between them 4 Thickener plays an important role in many emulsion paint systems In the production process, most thickeners should be put into use in the premixing stage, because the dispersion of pigment requires that the premixed slurry has enough viscosity At this time, adding thickener, especially the thickener in the form of powder and the thickener in the form of water, is also conducive to the uniformity and stability of emulsion paint Adding thickener in the mixing stage is to adjust the viscosity of emulsion paint It is recommended to add thickener after adding all other raw materials Some kinds of thickeners still need to be diluted with water or propylene glycol additives, so as to improve the stability of the system The following mainly discusses the powder thickener such as cellulose derivative, natural polysaccharide thickener For this kind of thickener, it can be directly sieved into the kettle or made into about 2% aqueous solution In general, the problems of agglomerate and viscosity fluctuation of emulsion paint caused by directly adding powder can be reduced by adding solution into the system Therefore, we suggest that the powder thickener should be added to the emulsion paint in the form of aqueous solution The method of preparing aqueous solution of powder thickener is as follows: in the dissolving tank, first add the water of the formula, start the low-speed agitation, stir it into the powder, stir it into the powder, adjust the pH value of the system in a few minutes, then increase the viscosity of the system, then increase the speed (the proper rotation speed should make the liquid surface rotate smoothly), stir until the powder is completely dissolved, and the viscosity of the solution No more rise (about 10min) During the preparation of the solution, the following points should be paid attention to: 1) cold water must be used to dissolve the thickener powder, because hot water will cause the thermal degradation of cellulose, and the viscosity of the system will be reduced during the storage process; 2) the cellulose powder must be slowly added into the non alkaline solvent (water) to prevent caking, and after it is fully dispersed, add the alkaline substance, and adjust its pH value; 3) During the dissolution process, the mixing cannot be stopped If the powder is not fully dissolved and the mixing is interrupted, the thickener may agglomerate; 4) the solution prepared by the thickener is easy to deteriorate during storage, so a certain amount of bactericide should be added if it is stored 5 In the field of emulsion paint mixing, we who are engaged in emulsion paint production all know that the mixing stage of emulsion paint is a very important link in the whole emulsion paint production project, which greatly affects the quality of emulsion paint The paint for latex paint is added to the already dispersed pigment paste and latex paint is made from the related auxiliaries In the production process of latex paint, the whole system is divided into two stages: pulping and painting This is because the stability of polymer emulsion in grinding with high shear force exists Because of this, it should be carried out at low speed in the paint mixing stage The success of the painting process also depends on the close integration of the emulsion and the pigment dispersions, so that all particles produce a stable and uniform suspension Therefore, it is necessary to pay attention to the pH value, the existence of electrolyte, the charge of surfactant, the size, shape and distribution of suspended particles in the two dispersing systems of emulsion and pigment slurry If the compatibility of these two dispersions is good, the whole system will be stable In the production process, we found that even if the paint operation is very careful, the emulsion and pigment slurry will inevitably appear slightly coagulation For both of them, it is probably the most important to protect the polymer particles and make them disperse as high as possible Therefore, in the process of painting, a strict requirement is to add polymer emulsion to pigment dispersions Usually, when the emulsion is added to the pigment slurry, the viscosity of the system will decrease, so thickeners are often added to improve the viscosity We find that thickeners with this function will cause flocculation of emulsion polymer particles more or less If this action is excessive, it will cause instability of latex paint, resulting in cracking and adhesion loss of paint film Therefore, in the selection of thickener, it is necessary to select a thickener system that causes as little polymer agglomeration as possible Of course, the production process of latex paint is a complex process, so there will be some problems in the production engineering Therefore, as a coating manufacturer or developer, in addition to fully understanding the characteristics of the system, it is more important to clarify the role of each raw material in the system and the characteristics of the raw material itself For this series of problems, only in the long-term production process is good at summary and analysis can fundamentally solve the problem 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,