Inorganic-Organic Multiple Betterment Methods Of Urea-Formaldehyde Resin Adhesive

Urea-formaldehyde (UF) resin is the most widely used adhesive in artificialboards. Recently, with the improvement of people's consciousness onenvironment, more attention on UF resin is caught by most consumers andenvironment protection agency. Because its production release freeformaldehyde which do harm on human body in producing and using processes.So, how to produce a kind of UF resin with low content of free Formaldehyde,high adhesive strength and low cost of production, become a main point of studyon the production of artificial boards for wood.With the hole of synthesis technology, this paper gives modified bettermentto study and prepare low noxious UF resin. Firstly, synthesis route of organicbetterment was chosen, then, the influence of organic modifier on UF resinadhesive was studied by orthogonal experiments. The optimum condition oforganic betterment with adding melamine and polyvinyl alcohol is found basedon its traditional production process. From the results, the optimum conditions are obtained: the urea-formaldehyde ratio is 1:1.1, melamine is added at the finalstage of synthetic process with the content of 2%, and the free formaldehyde is0.29% in adhesive.Secondly, Inorganic betterment synthesis technology was studied bychoosing four inorganic modifiers. That is, white cement, silica fume, rice huskash and zeolite that all have properties of big surface-area and micro-holeabsorption. From the results, the optimum conditions are obtained: silica fume,zeolite and rice husk ash is added respectively in synthetic process with thecontent of 2%, white cement cannot be added. Under the same condition of U/Fmole ratio, compared with the pure product, the optimum scheme can make thefree formaldehyde content of resin drop by 41%.Thirdly, from considering both reducing production cost and improvingproducts performance, a compound betterment by adding organic and inorganicmodifiers was studied. By the compound betterment experiments, the optimumformula was obtained: the urea-formaldehyde ratio is 1:1.5 and urea was addedin three times; silica fume, zeolite and rice husk ash is added respectively insynthetic process with the content of 2% in middle stage; Melamine is added atthe final stage with the content of 2%. The Urea-formaldehyde resin product wemade has good integrated performance, and the free formaldehyde contentreduces to 0.44%, conform to the limitation of 0.5% in GB14732-93"Urea-formaldehyde, phenol-formaldehyde, melamine-formaldehyde resin forwood industry". Finally, the synthesis route in strong acid condition was studied. Therelation between reaction temperature and pH value was setting. By controllingtemperature, intense reaction was moderated. Furthermore, the stability andincessancy were strengthened in synthesis process. Compared to process ofalkali-acid-alkali, the reaction time was shortened greatly and heat energyconsumption was saved to a great extent. The synthesis technology of makingUF resin in low temperature was realized.