Problems to be Noted in Producing Dyed Copying Paper

The copy paper is made from 100% bleached pulp, so direct dyes should be selected. The direct dye has a strong dyeing action on cellulose affinity and is simpler than basic dyes.
In order to ensure that the color paper has a higher brightness, it is best to use a dye. Although yellow and red can be formulated as orange, the resulting color is much less bright than with orange dyes.
The method of dissolving the dyes and the addition of direct dyes to the direct dyes are directly added to the pre-pulping pool with dry powder. This provides a sufficient time for the mixing of the pulp and the dyes and the adsorption of the dyes on the fibers, and is advantageous in enhancing the coloring effect when applied to the thickening pool. Easy to operate and easy to manage.
For basic dyes, due to poor solubility, we use a 2% acetic acid solution as a cosolvent to transfer the dye into a paste, add 50-60 degrees hot water to dissolve, the dissolved concentration is 1%, then filter plus People beat the pulp pool.
Application of mordant The direct dye is an azo compound containing a sulfonic acid group, which has a strong affinity for cellulose and can be directly dyed. Do not use a mordant D and the basic dye is an organic compound having an amino basic group. , It has strong affinity for lignin and weak affinity for cellulose. Due to the need of toning, basic dyes need to be added with mordant when they are used for bleaching pulp dyeing. Our factory chooses tannic acid as mordant, the dosage is 0.2% (for dry pulp). Tannic acid is dissolved in warm water prior to addition of the basic dye to the pulping cell.