(6ac) Preparing of a Composite Nano Disperse Dye Using a Hydroxypropyl Sulfonated Lignin Dispersant and the Interaction of Dispersant and Dye Surface

Teaching Interests: Communication lignin and cellulose, Conversion process of biomass to biofuel.

Lignin is the second or third most abundant organic polymer in terrestrial plants. It consists of chains of partly crosslinked phenylpropanoid units, mainly of guaiacyl and syringylpropans, but grasses also contain up to 20% of 4-alkoxy-phenylpropanes. Traditional technical lignins, mainly lignosulfonates, alkali lignins and organosolv lignin, are byproducts of pulp and paper industry. Enzymatic hydrolysis lignin (EHL) is a new kind of lignin, which derived from biofuel production possesses many differences compared to kraft lignin, lignosulfonates obtained by pulping processes. It is closer to the native lignin with weak chemical activity. In addition, an abundant source will be obtained with the fast development of the biofuel industry. So, developing a way to utilize EHL is a potential strategy to prosper biofuel industry.

Here we prepared a light-colored hydroxypropyl sulfonated lignin (HS-EHL) based on enzymatic hydrolysis lignin (EHL) by grafted-sulfonation and crosslinking reaction processes. The sulfonic group content and Mw of the product is elevated by this reaction. The color of HS-EHL turned to light yellow compared to the dark brown color of EAL. HS-EHL has also a low staining effect on fiber. Moreover, it has the best dispersion ability and temperature stability and dye uptake.

HS-EHL was further used as dye dispersant to prepare composite nano disperse dye (CL-NDD) by self-assembly in ethanol or acetone solution. Particles sizes of disperse dye in dye bath great affect its dyeing quality. CL-NDD with average particles size of 94.25 nm exhibited good dispersion, stability at high temperature compared with two milling dye (one commercial disperse dye and one is milling dye with HS-EHL analyzed by particle analyzer, SEM, TEM and AFM. The reducing effect of CL-NDD as low as 5.39% due to HS-EHL had low phenolic hydroxyl group content can prevent to reduce azo disperse dye. The uptake of CL-NDD reached to amazing of 94.27%. The adsorption characters of dispersants onto dye surface were tested by employing QCM-D and AFM to reveal the interaction of dispersant and dye surface. A higher adsorption amount of HS-EHL exhibited a more viscoelastic adsorption layer than sodium lignosulphonate (NaLS) due to HS-EHL had the long alkyl chain with higher sulfonic group content can touch with water phase to form strong electrostatic repulsion. What’s more, higher molecular weight of HS-EHL can provided stronger hydrophobic effect and higher adsorption amount to keep dye particles stable in dye bath.