Coating knowledge: coating morbid condition and Countermeasures - precipitation and caking

Core tips: 1 Define the phenomenon that the solid component of the paint sinks to the bottom of the container during the storage process, which is called sedimentation, also known as sedimentation at the bottom When the precipitation is serious, the pigment and other particles in the coating precipitate into a dense block which is not easy to be redistributed by stirring method, which is called caking 2 Phenomenon when the paint is opened, a mixing rod is inserted into the paint bucket When lifting, if the color consistency of the adhered paint is uniform, there is no precipitation If the upper part is thin and the lower part is thick, there is a feeling that it is difficult to stir at the bottom, namely, precipitation occurs When the mixing rod can not be inserted into the bottom of the barrel, the bottom sediment is hard and cannot be stirred evenly, caking occurs The common types of precipitate coating are: 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: 1 Define the phenomenon that the solid component of the paint sinks to the bottom of the container during the storage process, which is called sedimentation, also known as sedimentation at the bottom When the precipitation is serious, the pigment and other particles in the coating precipitate into a dense block which is not easy to be redistributed by stirring method, which is called caking 2 Phenomenon when the paint is opened, a mixing rod is inserted into the paint bucket When lifting, if the color consistency of the adhered paint is uniform, there is no precipitation If the upper part is thin and the lower part is thick, there is a feeling that it is difficult to stir at the bottom, namely, precipitation occurs When the mixing rod can not be inserted into the bottom of the barrel, the bottom sediment is hard and cannot be stirred evenly, caking occurs The common types of precipitate coating are: red lead paint, antifouling paint, antirust paint (such as mica iron oxide antirust paint), low-performance emulsion paint, etc 3 The reasons are as follows: (1) the pigment used is not well ground and dispersed; in the formula, the factors such as the ratio of pigment to base is too large and the density of pigment and filler is large are easy to cause precipitation (2) Due to the addition of too many diluents and the low viscosity of the coating, the coating lost its normal surface suspension state, resulting in the precipitation of pigments and fillers (3) there is chemical polymerization or adsorption between the pigment and the resin, resulting in gelation and precipitation (4) The storage time is too long, which exceeds the retention period of the coating, especially for a long time The storage time of color paint is too long Because of the high density of pigments and fillers, the precipitate is formed at the bottom of container, and finally the harden is formed Some resins also deteriorate (5) If the storage temperature is too high, the storage temperature of general coating should be 15-25 ℃ When the temperature is over 30 ℃, the suspension property of some pigments and resins in the paint is destroyed, which makes the viscosity of the paint reduce and precipitate and agglomerate 4 Prevention and control measures (1) in the design of paint formulation, consider the appropriate ratio of pigment to base, generally the ratio should not exceed 2:1, except for special varieties Some pigments such as red lead powder, chrome yellow, micaceous iron oxide, iron red, precipitated barium sulfate and so on have higher density, so low density pigments and fillers should be used less or replaced as appropriate (2) The viscosity of the coating shall not be too low, and the selected pigments and fillers shall not react with each other For example, zinc powder, aluminum powder, zinc oxide, etc are relatively active, which should not be used or packaged separately in the coatings with poor storage stability In coating production, suitable equipment shall be used to grind and disperse evenly as far as possible to reach the specified viscosity and fineness For example, chlorinated rubber coating, with poor stability, is easy to react with iron, and is produced with stainless steel or stone lined equipment (3) A thixotropic coating is prepared by adding anti settling agent into the coating and using the special properties of a small amount of additives to change the suspension state of the coating Commonly used anti sedimentation agents include stearic acid series, fumed silica, modified bentonite, hydrogenated castor oil, etc At present, there are many kinds of imported anti sedimentation agents, generally 0.1% - 0.5% can prevent sedimentation, and 2% - 3% can make the coating into thixotropic coating, forming a higher film thickness (4) The paint shall be stored in a cool and ventilated place, and the paint barrel shall be placed horizontally, upside down or shaken several times regularly We should pay attention to the storage period of the coating, and use the coating before warehousing Special attention should be paid to some coatings with low storage life, such as chlorinated rubber, vinyl chloride and polyurethane (5) For the precipitated coating, it can be used after manual or mechanical mixing For caking, pour out the movable part first, shovel the sediment from the bottom of the container with a scraper, grind it, and then pour the flowing medium back into the original barrel for full mixing If the mixture is still unable to be mixed and there is still dry deposition, the coating can only be scrapped or degraded for use 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,