Application analysis of defoamers in water-based coatings

With the development of volatile organic compounds (VOC) limit standards and regulations, water-based coatings with its green environmental protection, energy-saving and safe, easy to use and so on, has been rapid development in various countries.
Water-based coatings, especially water-based industrial coatings with various types of emulsions as the base, due to the characteristics of the substation itself and the high requirements of the coating surface state and the high requirements for construction, it is necessary to add a variety of additives in the formulation design process, of which the choice of desiccant is very important.
if there are more bubbles in the coating will limit production capacity, affect product quality, result in waste, pollution of the environment, and may bring safety

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The main causes of foam in
water-based coatings are
bubbles generated by stirring during the production of coatings, bubbles generated during the canning of
coatings,
bubbles produced during construction, such as roller coating or airless spraying,
coatings produce gases during the curing process, and
bubbles produced by construction on porous substrates, such as stone, wood or cement sheets.
stability factors of air bubbles are generally the role of surfactants, in the application of coatings, surfactants may be resin substrate itself, emulsifiers, substrate moisturizers, wetting dispersants and so on.
addition of defrosting agents to water-based coatings is the main way to reduce foaming in the whole production and application process, and the main functions of defrosting agents include de-foaming and anti-foaming.
there are many kinds of desticants currently used in the united States, while there are three main categories of desosters used in water-based coatings: mineral oils, with a market share of 80%, silicones, with a market share of 17%, and polyethers, with a market share of 3%. Among them, mineral oil deblisters are the most cost-effective, more commonly used, can be used in the vast majority of flat and semi-light latex paint, but the foaming and deblistering effect is less than silicone and polyether deblisters. Silicone-type deblister surface pressure is very low, deblistering and anti-foaming ability is excellent, the film gloss on the impact is very small, but the use of not at that time, will produce poor re-coating, coating shrink holes and other ills. Polyether deboulants are mainly used in systems with high compatible requirements, with weak debug capacity and less market share. Through the compounding, modified and other technical means can improve the compatibility of the above-mentioned de-foaming agent and de-foaming performance.
desculation agent can be evaluated from the aspects of anti-foaming, de-foaming, compatibility, degassing and brushing.
methods used to evaluate the performance of anti-foaming are: high-speed dispersion method, bottle shaking method, blowing method, concussion method and circulating bubble method, these methods are used to evaluate the performance of deboulants by changing the volume of foam.
The evaluation of desobbists has no fixed criteria, are through mutual comparison to judge the performance of deblistering, test methods, test conditions, desobbists concentration, stirring time and strength have an impact on the test results, which method to choose to evaluate, depending on the actual application.
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