Study On The Crossliking Reaction Of Lignin Sand Stabilizer

The basic theoretical problem about using lignin from the paper-making waste liquor to synthetize sand stabilizer was solved so that the synthetical theory could be proposed in the research.Firstly, Six lignin model compounds were reacted with formaldehyde to investigate the effects of the functional group on a-C and the substitution of methoxyl on C-3 and C-5 on the hydroxymethylization of lignin. The results showed that the hydroxylmethyl could be introduced after modification. The reaction could occur on free C-3 and C-5. The functional group on a-C also played an important role on hydroxylmethylation. Compared with the model compounds with a-hydroxyl, the compounds with a-aldehyde introduced less hydroxylmethyl.. Cannizzuro reaction also happened in the process.Secondly, hydroxymethylated lignin model compounds were reacted with formaldehyde and urea to study the reaction mechanism. The results showed that the amide could be introduced after modification. The urea resin including a hydroxyl was mainly produced in the addition reaction. Then, amino hydrogen atoms of urea resin could be reacted with the hydroxyl of hydroxymethylated lignin model compounds through dehydrated crosslinking reaction under the acidic condition to form more products of lignin-urea resin-lignin structure.Finally, crude alkaline lignin, purified alkaline lignin and lignosulphonate were chosen as raw materials. According to the diversity of reaction abilities of different aromatic lignin, synthetical theory of lignin sand stabilizer was proposed to choose pulping effluent appropriately. The results showed that the optimal pH of hydroxylmethylation was 11. The degrees of hydroxylmethylation were related with structures and groups connected with lignin. Also, the degrees of hydroxylmethylation of lignin which contained same structures and groups were proportional to the content of lignin. Viscosity was improved after condensation reaction. Compared with lignosulphonate, the solubility of crude alkaline lignin in the acid condition was poor so that part of the lignin might dissolve out which made the viscosity become low.Lignosulphonate was an appropriate raw material for the preparation of lignin sand stabilizer. However, the applicability of crude alkaline lignin could be improved through appropriate improvement to the modification.