Causes of coating precipitation and agglomeration and countermeasures

00coating in the storage process, its solid parts sink to the bottom of the container phenomenon, called precipitation, also known as sedimentation can be deposited. When the precipitation phenomenon is serious, particles such as pigments in the coating are precipitated into dense lumps that are not easily dispersed by stirring method, called lumps.01 phenomenon When the paint opens the barrel, with a mixing stick inserted into the paint bucket, lifted, if the adhered paint color consistency of one, there is no precipitation phenomenon

. If the upper and lower thick, the bottom has a difficult to stir feeling, that is, precipitation occurs. When the mixing stick can not be inserted into the bottom of the barrel, the bottom precipitated hard knot, can not be stirred evenly, the block appears. Common precipitation paint varieties are: red Dan paint, anti-fouling paint, anti-rust paint (such as mica iron oxide anti-rust paint), low-performance latex paint.02 cause (1) the pigment used in grinding is not fine, poor dispersion, in the formula, the pigment ratio is too large, pigment density and other factors easily cause precipitation.(2) due to the addition of too many thinners, paint viscosity is low, paint lost the normal surface suspension state, pigmentation produces precipitation.(3) a chemical polymerization reaction or mutual adsorption between the pigment and the resin, causing the gel to produce precipitation.(4) storage time is too long, beyond the retention period of the coating, especially long-term stationary placement. Color paint storage time is too long, pigment filler due to high density, at the bottom of the container to form precipitation, and eventually form a hard knot. Some resins also go bad.(5) storage temperature is too high, the storage temperature of general coatings in 15 to 25 degrees C is appropriate. At more than 30 degrees C, the suspension properties of certain pigments and resins in the paint are destroyed, reducing the viscosity of the coating and precipitated the cling.
03 Prevention and control measures . (1) In the design of paint formulation, consider the appropriate Yanji ratio, the general Yanji ratio should not exceed 2:1, except for special varieties. Paint fillers try to choose a smaller density, some pigments such as red dan powder, chromium yellow, mica iron oxide, iron red, precipitation of radon sulfate and other density are larger, less or as appropriate with low density pigment replacement.(2) paint viscosity can not be too low, the choice of pigments can not react with each other. Such as zinc powder, aluminum powder, zinc oxide and other more lively, in the storage of poor stability of the paint as far as possible not to use or sub-tank packaging. In the production of coatings, the use of suitable equipment, as far as possible grinding dispersion, to achieve the specified viscosity, fineness. For example, chlorinated rubber coatings, poor stability, easy to react with iron, the application of stainless steel or stone lining equipment production.(3) adds a sinking agent to the coating, using the special properties of a small number of additives, to make a denatured coating, change the paint suspension state. Commonly used anti-sinking agents are stingric acid series, gas-phase silica, modified benthic soil, hydrogenated castor oil and so on. There are many varieties of imported anti-sinking agents, generally add 0.1%-0.5%, can prevent precipitation, and add 2%-3%, the paint can be made into a denatured coating, forming a higher film thickness.(4) paint storage should be placed in a cool and ventilated place, regularly put the paint bucket across, upside down or shake several times. Pay attention to the storage period of the coating, the first use of the first storage. Be especially careful with some coatings with low storage life, such as chlorinated rubber, vinyl chloride, polyurethanes.(5) For precipitated coatings, they can be stirred evenly by hand or mechanically before being used. For the lump phenomenon, the flowable part should be poured out first, with a scraper from the bottom of the container to shovel the precipitation, shredded, and then the flow medium back into the original bucket, fully mixed. If the operation according to this method still can not be mixed, there is still dry precipitation, paint can only be scrapped or demoted for use.
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