What is paper dyes and its application?
In the dyeing process of papermaking, the object of the dye is the paper fiber. The mechanism of action between dyes and different pulps is different. For example, basic dyes have a great affinity for lignin and are suitable for dyeing pulp with high lignin content; if the surface of the pulp has strong negative charge, it hardly absorbs the negative ions of direct dyes. , With the decrease of the actual surface charge, the dye is fixed close to the fiber surface. This adsorption is caused by non-static forces. Aluminum vanadium is a commonly used dye retention agent in papermaking. Because most papermaking dyes are anionic, cationic aluminum compounds can form cationic precipitation with anionic dyes and adsorb on the surface of the fiber to be retained. This mechanism occurs when the pH value is 4.0-5.2. At this time, the charge density of aluminum ions is high, and the charge effect is strong.
Each dye has its advantages and disadvantages. Water-soluble direct dyes have been widely used in the paper industry. Pigments are often used in colored coated paper. The dyes and paper fibers have covalent bonds, ionic bonds, complex bonds, and hydrogen bonds. And intermolecular force binding, the color fastness mainly depends on the strength of the binding force, and which combination is the main one depends on the structure of the dye molecule.
Papermaking dyes mainly include basic bright yellow O (special bright yellow for papermaking, fire paper dyeing, kraft paper dyeing), direct red 4BE (firecracker paper coloring), alkaline rose essence (cultural paper dyeing, brushing paper coloring), acid scarlet GR (brushing Paper couplet red), direct yellow-brown MD (yellow board paper coloring), direct dark brown MM (tea board paper dyeing), alkaline fuchsia blue (newsprint dyeing, brush paper dyeing), basic fuchsia green (cultural paper dyeing) ,Paper coloring), Basic fuchsin, direct sun tanning, direct lake blue 5B (cardboard dyeing), basic violet 5BN (cultural paper, special for brushing paper), fluorescent brightener VBL (toilet paper whitening), direct Frozen Yellow G (toilet paper coloring, white paper coloring), alkaline orange block (kraft paper coloring).