Preparation And Properties Investigation Of Formaldehyde-eliminative Wood Coatings

Formaldehyde is a common indoor air pollutant. Due to the harmfulness to human being’s health, formaldehyde attracts more and more attention, especially for its carcinogenicity. There are many kinds of technologies to eliminate formaldehyde, including physical adsorption, catalitical oxidation, and chemical transfering. Various functional materials applied in wood coatings were selected for the formaldehyde-elimination ability investigation and the coating preparation. The formaldehyde-eliminative functional wood coating can decorate and protect the wood-base panels, eliminate the formaldehyde inside panels, and purify the environment at the same time. An optimized recipe was confirmed after the investigations on the the formaldehyde-elimination ability and the workability affected by the addition of functional materials and the curing agents.Firstly, the changes of coatings’ appearances were investigated, and the changes might be caused by the added functional materials, including the appearances of resins, the storage stabilities, and the appearances of films. The results showed that the catalysts and adsorption materials did affect the appearances of coatings; β-dicarbonyl materials hardly affected the appearances of coatings; materials with priamary amine reacted immediately with isocyanate curing agents, and therefore no film could be prepared; acyl-terminated polyamide CYD-135 E and ethyleneurea hardly affected the appearances of coatings.Secondly, the formaldehyde-elimination abilities of coatings were tested by meas of AHMT-coloration and RGB-pick(AHMT-RGB) method qualitatively and atmosphere cabin method quantitively. Test results showed that the coating containing 4 wt% ethyleneurea had the best formaldehyde-elimination ability of 91%, and the eliminative persistence was 90%; the formaldehyde-elimination abilities of the coatings containing 2 wt% Pt-TiO2 and Pt-SiO2 respectively were 68% and 65%; the rest coatings respectively containing 2 wt% nano-HAP, active carbon, 3 wt% molecular sieve, or 4 wt% CYD-135 E, diacetone and ethyle acetoacetate showed the formaldehyde-elimination abilities below 50%, but still higher than the ability of blank comparative coating.Thirdly, by controlling the addition of ethyleneuera in coatings, the formaldehyde-elimination abilities of coaitings were analyzed. It was shown that the formaldehyde-elimination ability rose with the increasing addition of ethyleneurea. When the ethyleneurea addition was more than 0.5 wt% in coating, the formaldehye-elimination ability could reach the requirement of standard II in JC/T 1074-2008. By chaging the compunds of curing agents, the pot-life, drying rate and water-resisting property were analyzed with the ethyleneurea addition of 0.5 wt% in coating. The results showed that when the curing angent contains 40% TMP-TDI adduct and 20% TDI trimer, and the solid content reached 40%, the formaldehyde-eliminative coating could meet the requirements of application. The resultant formed by ethyleneurea and formaldehyde was analyzed. The result showed that the formaldehyde could be eliminated by ethyleneurea because the secondary amine on the urea structure reacted with formaldehyde as nucleophilic addition and produced chain-liked resultants.