Common problems with water-based paint: the coating contains bubbles and degassing

Phenomenon:

During the production of waterborne coating, it is found that the coating contains bubbles after thickening.The bubble volume is big bubble, the volume is small bubble, This kind of phenomenon often happens in paint of equal thickness thick pulp of elastic drawing. Bubble may cause pinhole or prickly heat and affect the appearance of paint film.

Explain:

Formation of air bubbles in waterborne coatings:

In the paint manufacturing process, the dispersion of pigments and fillers, the stirring in the thickening and varnishing process, the vibration of the finished coating during the filtration and packaging process, the mixing of the paint in the toning process and the color paste, the introduction of air by the agitation, the air in the water The coating is stabilized by a surfactant and becomes a bubble in the coating.Specific to the water-based coating formulation and production process, the bubbles generated in the paint manufacturing process are mainly in the following processes.

1.The improper feeding sequence of pigments and fillers in the dispersing stage may easily lead to the generation of micro tip bubbles, especially in the coating system with high proportion of ultrafine fillers and high solids.The fillers with fine particle size have large specific surface area and absorb more air. They should be first put in at low viscosity to facilitate foam escape.If the fine particle size filler is put in the final stage, the slurry viscosity is high after the feeding of the fine filler, and a large amount of air brought by the fine filler enters the slurry to form microbubbles. It is difficult for the microbubbles to aggregate and rise until the surface of the coating is broken, so that it is difficult to escape the gas in the coating.

2.Excessive surfactant is used in the formulation of water - based coatings.The vibration in coating production, filtration and transportation, as well as the coating from the height of the dumping, mixing will produce bubbles again difficult to come out.

3.The design of the dispersing disc tooth of the dispersing machine is not reasonable, or the dispersing disc is placed in an improper position in the coating during the dispersing process. Under high-speed stirring, a large amount of air is brought into the high-speed dispersing coating by vortices.

Prevention and solutions:

1.Water-based coating production feeding should be in the order of first fine then coarse, which is conducive to the emergence of bubbles and prevents the generation of microbubbles;

2.Wetting agent should not be overused in the production of water-based paint formula. Wetting agent should not replace dispersant. If you have to use for a certain

requirement, it is appropriate to choose low foam wetting agent. Additional wetting agents are added during the paint conditioning phase.The antifoaming agent with high antifoaming ability was added into the slurry preparation.

3.Coating filtration, packaging and dumping should minimize vibration and dumping height;

4.Select a good dispersion plate, and determine the best position of the dispersion plate in the dispersed materials through practice, and do not form a large vortex in the dispersion to avoid bringing in a lot of air.

For more information on water-based coatings formulation and production, visit our Official website of Sinograce Chemical co., LTD .water-based coatings knowledge base.

You can also ask questions directly to us through our expert column on water-based paint.

For more information on water-based coatings, you can also visit SINOGRACE CHEMICAL water-based coatings knowledge base, and our water-based

paint recipes for water based metallic paints.

It is SINOGRACE CHEMICAL goal to promote the development of waterborne paint in China. I hope you found the above explanation helpful.

Sinograce Chemical co., LTD produces chemical additives for water based glue, such as defoaming agent, thickening agent, leveling agent, wetting agent

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