一.Introduction of application principle

During the painting process, the coating rate of the paint is only 40 to 60%, and more than half of the paint splashes into the air to form a spray spray fog, seriously polluting the surrounding air and environment. In order to effectively protect the environment and clean the construction site, the circulating water system of the wet spray booth is usually used in the painting industry to capture the oversprayed paint mist. In order to maintain the performance of the spray booth, improve the painting working environment, and make the purification system operate normally, a small amount of chemical substances must be added to and maintained in the circulating water, commonly known as paint mist coagulants. It can contact with the paint particles caught by water, and then react with it and make it destabilized and disstick, gather into a flocculant with a certain particle size, called paint slag, and separate from water, so that the water cycle can be used for a long period. Paint mist coagulants mainly include strong alkali dispersing type, condensation adsorption type, water-based paint mist condensation type, etc. The above types of products can make the paint disstick and flocculate in the following ways: make the paint mist saponification, eliminate its viscosity, generate a water-insoluble alkali soap substance, dispersed in water; At the same time, the paint mist is condensed by neutralizing the charge of the outer layer of the paint mist. The condensed particles are bonded into flocculant by colliding with each other, and then the polymer flocculant is adsorbed and bridged to form larger flocculant.

二.How to correctly judge the effect of paint mist flocculant

The effect of paint mist coagulant is generally judged from slag, water, foam, odor and so on.
(1) Paint slag: The viscosity should be as small as possible, and the comprehensive appearance rating should be at least 3 to 4 (paint slag is granular or fine sand).
(2) Water: in the Eisenmann side flow slagging device, before slagging and before adding agent B, the paint should be highly dispersed turbidity water, and the water after adding agent B should be as clear as possible, and the water quality rating should be at least grade 3 (slightly turbid).
(3) Foam: the height of the foam in the pool should be appropriate, and should not be significantly higher than the height of the foam generated by water containing only pharmaceuticals under the same conditions. The foam is too high, indicating that the separation effect of paint and water is not good.
(4) Odor: During the specified operating time, no obvious unpleasant odor should be produced, which indicates that the water system has microbial hazards such as mildew and bacteria, and may also be caused by poor separation of paint and water, but the use of paint mist coagulants will not produce irritating odor, and most paint mist coagulants are added to antibacterial agents.

三.Factors influencing the effect of paint mist flocculant

(1) Types of paint. Although no correlation has been found between the type of resin and the effect of use, it is known that paint mist coagulants are sensitive to the polarity of the resin. Paint mist coagulants of different polarity and hydrophilicity should be used respectively for paints of different polarity.

(2) PH value or alkalinity. It has been known that proper alkalinity or pH contributes to the dissticking of paint. The pH value is too high, the paint is destroyed for stable particles dispersed in water difficult to flocculate, too low can not be completely destroyed. The general control is 9.0, and the control is very important in the operation of circulating water.

(3) paint booth process and paint slag post-treatment process. The commonly used spray painting room process mainly includes washing type, water curtain type, water curtain – washing type, water swirl type, Venturi type and other types, and the commonly used slag removal methods mainly include scraper plate, centrifugal type, etc. The spray painting room process, circulating water flow rate, velocity, and slag removal method will affect the use effect.

(4) hydrochemical factors. Impurities in the water, such as hardness, will affect the size of the paint dispersion particles, thus affecting the loss of viscosity, so the hardness should be as small as possible. The impurities introduced in the spray painting process, such as solvents, especially non-polar solvents, can significantly reduce the absorption capacity of water to paint fog.

(5) Dosage and dosing method of paint mist coagulant. If the dosage is too small, the condensation effect is not ideal, and if it is too large, it has a dispersion effect and does not produce condensation. Different spray booth paint absorption processes require different optimal dosing methods, which need to be explored and determined in actual use.

(6) Microbial factors. The concentration of organic matter in the circulating water is very high, and the operating conditions of the circulating water are suitable for the reproduction and growth of microorganisms. If not carefully controlled, the breeding of microorganisms will have a negative impact on the use of paint mist coagulants. Bactericidal or bacteriostatic agents should be added regularly when the temperature is high.