Yanlin Qin

Structure and Properties of Sodium Lignosulfonate with Different Molecular Weight Used as Dye Dispersant

Three purified sodium lignosulfonates (SLs) with different molecular weights were prepared by ultrafiltration. The structural characteristics of SL and their effects on the properties of dye were investigated. When the molecular weight is increased, the chroma, purity, and the content of guaiacyl of SL increases, whereas the phenolic hydroxyl, carboxyl, and sulfonic groups in SL decrease, the dispersibility, heat stability properties, and dyeing rate of SL on dye improve, and the fiber staining of SL weakens at high concentration. The fraction of SL with the cutoff molecular weight above 2.5 kDa has the weakest reduction effect on dyestuffs. GRAPHICAL ABSTRACT

A light-colored hydroxypropyl sulfonated alkali lignin for utilization as a dye dispersant

Abstract A light-colored hydroxypropyl sulfonated alkali lignin (HSAL) was synthesized based on pine alkali lignin (AL) by grafted-sulfonation and crosslinking reaction processes. The reactions were evaluated by gel-permeation chromatography (GPC), infrared (IR) and proton nuclear magnetic resonance (1H-NMR) spectroscopy. The sulfonic group content and the molecular weight (Mw) of HSAL significantly increased, while the phenolic hydroxyl groups diminished by around 80% compared to AL. The color of HSAL turned to light yellow compared to the dark brown color of AL, that is, it stained less the fiber. The dispersity, heat stability, and dye uptake of dye bath with HSAL was significantly improved compared to sodium lignosulfonate, sulfomethylated AL, and dispersants of the naphthalene series.

Adsorption Characteristics of Naphthalene Sulfonate Formaldehyde Condensate with Different Molecular Weights

Naphthalene sulfonate formaldehyde condensate (FDN) consists of the hydrophobic naphthalene groups and hydrophilic sulfonate groups. Four FDN fractions with different molecular weights were prepared by using ultrafiltration. The adsorption characteristics of different fractions were investigated by ultraviolet spectrophotometer, Zeta potential meter and x-ray photoelectron spectroscopy. The adsorption of FDN with high molecular weight follows Langmuir model and belongs to monolayer adsorption on cement surface. The adsorption characteristic of unfractionated FDN displays the multilayer adsorption. The greater adsorption amount and the higher adsorption layer thickness of FDN with higher molecular weight can provide sufficient steric hindrances and electrostatic repulsion between the particles.

Etherification to improve the performance of lignosulfonate as dye dispersant

Lignosulfonates (SLs) are widely used as dye dispersants. However, they have some disadvantages, including poor high temperature dispersibility and severe fiber staining resulting from the abundant phenolic hydroxyl content in the SL molecules. In this work, etherified lignosulfonates (ESLs) were obtained by using epichlorohydrin to reduce the content of phenolic hydroxyl while increasing the molecular weight. ESLs with lighter color can reduce fiber staining rate by 52% due to whitening by the epichlorohydrin process. The lower adsorption capacity of ESLs onto the surface of fibers can reduce the fiber staining effect, owing to the lower phenolic hydroxyl content. The ESLs also exhibit superior high temperature stability to SL because of their higher adsorption capacity and more rigid adsorption films.

Preparation of a Low Reducing Effect Sulfonated Alkali Lignin and Application as Dye Dispersant

A novel grafting hydroxypropyl sulfonated and blocking condensed lignin (GSBAL) dye dispersant was prepared based on alkali lignin (AL) by sulfonation and etherification reactions. The significant increase in the sulfonic group content and the molecular weight endow GSBAL with excellent dispersity and stability at high temperatures. More importantly, the unfavorable property of the reducing effect of AL was largely reduced since over 80% of the phenolic hydroxyl groups were blocked. The functional azo groups in the dye could be mostly retained. The reducing rate of dye with GSBAL was decreased to 6.54% (25 °C), much lower than 18.62% for sulfomethylated alkali lignin (SAL) and 15.73% for sodium lignosulfonate (NaLS). The dispersity and exhaustion of the dye bath with GSBAL dispersant was significantly improved compared with that of a dye bath with SAL and NaLS.