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What about the precipitation of paint?

Jan 07, 2019
What about the precipitation of paint?

The phenomenon that the solid component of the coating sinks to the bottom of the container during storage is called sedimentation, also called sinking or sedimentation. When the precipitation phenomenon is severe, particles such as pigments in the coating are precipitated into a dense mass which is not easily redispersed by stirring, and is called agglomeration.


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Phenomenon: When the paint is opened, it is inserted into the paint bucket with a stir bar. When the paint is lifted, if the color consistency of the adhered paint is consistent, there is no precipitation. If it is thick and thick, the bottom has a feeling of being difficult to stir, that is, precipitation occurs. When the stir bar cannot be inserted into the bottom of the bucket, the bottom precipitates tough and cannot be stirred evenly, and agglomeration occurs.


The reason

(1) The pigment used is not finely ground or poorly dispersed. In the formulation, the pigment base ratio is too large, and the density of the pigment filler is large, which is easy to cause precipitation;
(2) Due to too much diluent added, the viscosity of the coating is low, the coating loses its normal surface suspension state, and the pigment filler precipitates;
(3) some chemical polymerization reaction or mutual adsorption between the pigment and the resin causes gelation and precipitation;
(4) the powdery pigment particles are in an unstable state;

(5) The storage time is too long, exceeding the retention period of the paint, especially for a long time. The storage time of the color paint is too long, and the pigment filler has a large density, and a precipitate forms at the bottom of the sauce, eventually forming an induration. Some resins also deteriorate.

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Prevention and control measures

(1) in the design of paint formula, consider the suitable base ratio, generally do not exceed 2:1, except for special varieties.Yan packing as far as possible to choose a smaller density, some pigments such as red red powder, chrome yellow, mica iron oxide, iron red, precipitated barium sulfate and other density are larger, less use or as appropriate to use low density yan packing replacement.

(2) the viscosity of the coating should not be too low, the selected face filler can not react with each other.Be like zinc powder, aluminous powder, zinc oxide to wait to compare lively, need not use as far as possible in the coating with bad stability in storage or cent can package.When coating is produced, use appropriate equipment, grind as far as possible dispersive and even, achieve set viscosity, fineness.For example, chlorinated rubber coating, poor stability, easy to react with iron substances, stainless steel or stone lining equipment production.

(3) add anti-settling agent into the coating, and use a small amount of special properties of additives to make thixotropic coating and change the suspension state of the coating.Stearic acid series, gas phase silica, modified bentonite, hydrogenated castor oil are commonly used as anti - settling agents.Now import agent variety is very much, join 0.1% commonly -0.5%, can prevent precipitation, and join 2%-3%, can make coating thixotropic coating, form taller film thick.

(4) paint storage should be placed in a cool and ventilated place, regular paint bucket horizontal, inverted or shaking a few times.Pay attention to the paint storage period, the first into the first use.Be especially careful with paints with a low shelf life, such as chlorinated rubber, vinyl chloride, and polyurethane.

(5) for the precipitated coating, it can be mixed evenly by hand or machine before use.For the agglomeration phenomenon, should first pour out the flow part, with a scraper from the bottom of the container shovel precipitation, grinding, then pour the flow medium back to the original bucket, fully mixed.If this method is still unable to mix, there are still dry precipitation, paint can only be scrapped or degraded use.

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QuanZhou Neweco High Polymer Material Co.,Ltd.

Neweco is one of the leading unsaturated polyester resin manufacturers and  suppliers,widely used in automobiles, ships, rail transit, wind power  generation, pipe cans, heat and corrosion protection, building  materials, stone repair, sanitary ware, artificial stone and other  industries. Suitable for hand lay-up, spray, pultrusion, winding,  molding, vacuum introduction / RTM, casting and other molding processes. Neweco Resin is committed to excellence and focuses on the application  of composite materials to provide customers with comprehensive  solutions.

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