Research Of Modified Lignin For Dye Dispersant

According to historical records, it is five thousand years since human began to use the natural dyes, but the application of synthetic dyes only began in the19th century. There are all kinds of dyes and most of the them are soluble in water. Once the disperse dye which can’t be insoluble is added to water, it will start to congregate, and the particle crystals grew up by degrees. Especially when at high temperature, it can promote the agglomeration to a higher degree, which is called "cohesion". In order to strengthen the application of the disperse dye, we add the additives called "dispersant" to enhance the dye’s dispersion.Dye dispersant is the key to the preparation of the disperse dye which has high temperature stability. At present, the dye dispersants including naphthalene sulfonate formaldehyde condensate, polyolefin sulfonic salt, polycarboxylic acid, alkali lignin and lignosulfonate are commonly used in industry. The paper-making waste liquor which has distinctive feature in rich materials and renewable is the main source of dyes. However the lignin dispersants also have disadvantages such as poor dispersion, poor stability and so on. Nowadays, the modification of lignin has become the foucs of the study in dye dispersants in order to improve the dispersant force and temperature stability.Firstly, the modification of lignin sulfonate including sulfonated condensation sulfomethylated condensation was investigated. Experiment conditions such as the amount of sulfonating agent, the sulfonation temperature, the amount of condensing agent, the condensation temperature of the dispersion properties were studied respectively. The structure of the modified lignin dispersant has been analysed by mean of FTIR and it proves the experiment successful. Sulfonation and sulfomethylation reaction can improve the product’s water-solubility, which enhanced the dispersion force; condensation reaction increased product’s molecular weight with an improvement of thermodynamic stability. In the optimal conditions, the dispersion forces of62%and55%were reached respectively.An experiment was conducted to synthesize new dye dispersant by means of modified reaction of phenol liquefaction of rice straw with with formaldehyde and sodium sulfite in alkaline conditions. The structure of new dye dispersant was analyzed by FTIR and its performances were tested by dispersing power, high temperature stability and abrasive. Influences of reaction conditions such as reaction temperature, reaction time, the amount of formaldehyde and sodium sulfite were studied. The optimum modified reaction conditions were obtained as reaction temperature110℃, for5hours, the amount of formaldehyde7mol/kg, the amount of sodium sulfite3mol/kg by single factor and orthogonal test. Scattered force84.7%and high temperature stability130℃were obtained under these conditions.