Analysis on Application of defoaming agent in wood coatings in PU-Iota

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Service > Analysis on Application of defoaming agent in wood coatings in PU

Analysis on Application of defoaming agent in wood coatings in PU

Polyurethane wood paint market in China occupies very important position, with improvement of user requirements, competition intensifies, PU wood coatings also put forward more high, update requirements, which appeared in the some issues worthy of discussion, such as: dry winter, Pu matt finish anti scratching, PU paint fire bubble, Pu decoration paint brush in hand leveling, yellowing resistance, Pu primer collapse, PU paint thick painted with prickly heat, PU paint dark bubble, to bite the end and other series of problems, this paper focuses on the PU paint for fire bubble problem were discussed.
PU wood coatings in the production process of stir, stir in the filling and construction process are very easy to introduce air bubbles, combined with wood is a kind of porous material, in the hole for full air and water vapor, in the coating process is also very easy to have a bubble, the existence of these bubbles, if not promptly removed will eventually causing Qimo dry appeared pinholes, bubbles, shrinkage hole and unacceptable surface defects, affecting the decorative effect. Thus, the elimination of the foam agent has its significance.
The bubble is caused by the foam surface tension and the bubble surface tension caused by the foam surface.. Defoaming agent must is certain incompatibility and product formulation system, generally speaking, compatible worse, fire foam ability is strong, but may cause turbidity of the products, or other surface defects (such as shrinkage hole phenomenon). Conversely, if the foaming agent and the formulation system compatibility is good, the foam agent can not well penetrate into the thin layer of foam, resulting in the effect of the bubble elimination is not ideal.. As we all know, coatings formulation system will add a lot of other surfactants, such as leveling agent, silicone feeling agent, liquid wax, metal soap and so on, the use of these surfactants, tend to reduce the surface tension of the thin layer of foam, so this to the Engineer in the choice of good fire foam agent to increase the difficulty. For example, leveling agent, generally better leveling agent more prone to bubbles, more strong defoaming agent is more prone to shrinkage, both of which originally is contradictory, so to think in defoaming agent and system of other foam stabilizing surfactant in find equilibrium point, need engineers through a lot of experiments to find a proper proportion, this is the best prescription system. The author in practice trials found that formula system of different types of PU coatings, formula system of different construction methods used defoaming agent types and dosage will be different, many will match two kinds of defoaming agent in order to achieve good defoaming effect (such as hand painting), another example of Pu primer, in order to improve the grinding effect often use this kind of raw material of zinc stearate, zinc stearate is due to the unsaponifiable matter, its activity is very high, it is easy to produce and stabilize the foam. Therefore, the type and amount of the used bubble can be different. At present, the use of more PU wood coatings in the defoaming agent types are: silicone, acrylic, solvent etc.. Their characteristics are as follows:
Table 2 is several companies defoaming products in PU wood light clear topcoat system application, fire foam agent a is an acrylic acid type fire foam products, foam breaking capacity is insufficient, defoaming agent B is organic siloxane type, good defoaming performance, but prone to shrinkage, and the paint liquid turbid phenomenon is serious, a and B match use and can provide excellent fire bubble effect and does not produce shrinkage phenomena, effects of liquid paint gloss appearance are also reduced to a minimum.
To sum up, in the PU wood coatings in selection of defoaming agent and need to fully consider and resin compatibility, defoaming ability and persistence, to substantially eliminate foam as the principle, not excessive pursuit of defoaming effect, in order to avoid other side effects. The author thinks, do PU wood paint formulations and our daily cooking knowledge is communicated, system used in a variety of additives like cooking oil, salt, sauce, vinegar and ingredients, they have the meaning of existence, indispensable, cannot add more nor less, but can not mess with, or even the most expensive food is not as delicious food.

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