A Study On Synthesis Of Modified Lignin Alkali Lignin Urea-formaldehyde Adhesive

Firstly, this article purified alkali lignin and analysed its component, came to the following conclusions: the percent of moisturemoisture content in purified alkali lignin is 2.31%, ash content is 7.93% and the total content of lignin is 82.90%;the alkali lignin used in experiment is straw lignin.Secondly, alkali lignin is modified hydroxymethylation, then by using and not using colloid mill for acid condensation separately to compare the two groups of the experimental results. We have found that: With the use of colloid mill for acid condensation, we can get a homogeneous solution with good flow property . Without using colloid mill for condensation reaction,the product is solid-liquid separation because of alkali lignin precipitation in acidic conditions.It is indicated that colloid mill can play an effective role in the solid-liquid heterogeneous reactions, so reaction can be carried out adequately.Finally, lignin urea-formaldehyde resin is modified by adding melamine and PVA . By this way, bonding strength and water resistance is strengthened.The result show that the bonding strength performance of resin reach the national standard. When the reaction temperature is 90℃, with reaction pH value of 5.5 , and about50% alkali lignin additives the adhesive possesses an upper bonding strength,Formaldehyde Emission achieves national E2 standards.