Formulation Design Of Water-borne Wood Coating Based On Polyurethane-acrylic Hybrid Emulsion

The research is about the study on the formulation design for water-borne wood coating based on polyurethane-acrylic hybride emulsion. In the experiments, the key factors of the manufacturing process, formulation and finishing technology have been discussed, and products of varnish and color paint have been prepared .Through the analysis of testing, the emulsion can be applied as a wood coating product of which main properties have reached or exceeded the national environmental standards. It suggested that various additives, including coalescent, defoamer, wetting agent, mildew fungicide and antifreeze, have great impact on the properties of varnish : as coalescent, ethylene glycol monobutyl ethers reagent can lead to the drop of minmimum film temperature from 13.8℃to 4℃with the equivalent weight amount of 2%-3%. Use of modified organic silicone defoamer Dehydran 1620 receive excellent defoaming effect, but the equivalent weight amount should not exceed 0.6%. Organic modified polysiloxane ether type of wetting agent Hydropalat 140 not only effectively reduce the surface tension of the emulsion and enhance wettability with the substrate, but also deal with the film’s shrinkage led by usage of defoamer; ammonia water is used to adjust the pH value of 8.5-9.0 which is conducive to the storage stability of the emulsion and water resistance of the film is not affected because of the volatilization of ammonia water. Isothiazolinone mildew fungicide Alex F-252 ,with the equivelant weight amount of 1%.,shows characteristics of high efficiency, broad range and low toxicity, also good compatibility with the system.On the study of color paint, wetting dispersing agent, thickener, defoamer, coalescent and their feed mode, grinding technology have a great impact on the product’s performance. wetting agents should be dispersed in water before joining the filler and pigment which effectively reduce the dispersion medium (water) surface tension and is in favor of the absorption of wetting dispersant to the pigment or filler particles, and the dispersion performance of polycarboxylic acid salts dispersant is better than that of polyphosphoric acid dispersant; thickener and filler particle size either have great impact on dispersion stability. The products are ground by three-roll grinding machine several times until the average particle size lower than 30μm. The appropriate viscosity under all levels of shearing rate has been obtained with combination of polyurethane thickener and alkali-swelling thickener; mineral oil defoamer Foamaster 8034 with equivalent weight amount of 0.6% gets relatively excellent result, which is respectively added twice during the process of grinding and modulation. The equivalent weight amount of coalescent should increase to 5%, as filler makes products difficult to film than varnish.After testing, the main performances of varnish and color paint have reached or exceeded the national standard of the environmental-friendly waterborne wood coatings. Varnish contains: adhesion of level 1, gloss (60°) of 90, hardness of 2H, flexibility of 1mm, impact strength of 50cm, abrasion resistance (750g/500r) <0.03g, good water and solvent resistance, as a high-gloss topcoat. Color paint contains: adhesion of level 1, hardness of 3H, flexibility of 1mm, impact strength of 50cm,abrasion resistance (750g/500r)<0.01g, good water and solvent resistance, good storage stability, as a colored primer.Finishing technology has been studied. Problems that should pay attention to have been summed up, and the common ills and the proposed solutions of the finishing process have been figured out.