Research On Stability And Impaction On Printing Of Fluorescent Whitening Agents

Fiber, as the raw materials for paper making, lignin in it cannot be removed absolutely, which results in yellowed paper. In order to get high whiteness paper, one of the most effective ways is to add Fluorescent Whitening Agents (FWA). FWAs for paper mostly are bis(triazinylamino-stilbene), the whitening mechanism is that its function radicals absorb UV light and emits visible blue and violet light, FWA adsorbed on the fiber by intermolecular forces, and the yellow tone of lignin has been counteracted, so the whiteness of paper improved. However,FWA have certain biological toxicity, cannot be used widely, therefore, the purpose of this study is increasing the adsorption of FWA on fiber and whitening effect to reduce the cost and harm by decreasing dosage of FWA.Started with the structure and whitening mechanism of FWA, studied several factors which influence its stability of whitening effect, and had found that more dosage of FWA didn't mean higher whiteness, it will be decreased when the dosage reach a certain level; Concentration of the pulp, contact time with the fiber and water hardness all can change the adsorption rate of FWA, and then alter the whiteness effect; The more the Precipitated Calcium Carbonate (PCC) used, the lower the whiteness effect is and higher cationic charge density leads to lower whiteness.The results of experiment showed that using both FWA and dye than any one alone can lead to higher whiteness and better effection, a kind of synergies had been found between them. By controlling the proportion of FWA & dye, the whiteness will reach the highest cost performance.This thesis comparatively analyzed the carrier of FWA, the dosage of the carrier and another two factors with orthogonal experimental design and general full-factor experimental design, obtained a highest whiteness with full chemical pulp, Polyvinyl Alcohol (PVA) as carrier and its dosage is 0.1%, PCC as filler and its dosage is 10%, it is the best formula.PVA can improve the adsorption of FWA on fiber, reduce FWA from washing away.The hue and local reflectivity of paper have been changed by adding FWA, an experiment that imitate printing with several paper which have different dosage of FWA had been established. By determining density and chroma of the proof, drawing a hexagon color gamut we found that FWA affects the highlight more than middle tone and the dark tone is almost unaffected when color restoring.