Preparation Of PPVA And Its Application And Mechanism On Surface Sizing

The surface strength and printing quality of paper sheet can be improved though surface sizing. With the rapid development of paper manufacturing Industry and printing technique, surface sizing has became more and more important, and expoitation of surface sizing agent became a hotspot. The optimal synthesis process and application of PPVA were studied in this dissertation; the mechanism of surface sizing was also primarily studied.Results are as following:1. The synthesis process of PPVA (phosphorylated polyvinyl alcohol) was discussed; through the orthogonal experiment, the optimal technology is: PVA 12g, phosphoric50.4g, urea 35g, dicyandiamide 25g, and reaction temperature 135℃, reaction time 2h. The topmost phosphorylation degree is 28.04 %(mass percent of P₂O₅).2. Infrared spectrum and potentiometer titration curve were applied to analyze the structure of PPVA, and the results showed that the method of synthesize is effective.3. The results of contact angle showed that: PPVA was better than PVA on water-resistance, and the contact angle increased with increasing degree of phosphorylation.4. The process of surface sizing and the sizability were studied. The preferable sizing conditions are as follows: the quality ratio of PPVA and oxide starch is 1:5, the dosage range of sizing agent is 1.2-1.7 g/m², total concentration is 4%, sizing temperature is 65℃, drying temperature is 85℃, pH7.0. Under the same sizing condition, compared with the PVA and SAE, PPVA4 has better sizability. Surface strength was improved by 10.31% compared with SAE, 98.15% compared with PVA; The degree of surface sizing increased by 68.90% compared with PVA, and 45.32% compared with SAE; The tensile strength increased by 21.75% compared with SAE, but compared with PVA the tensile strength increased not clearly; PPVA has no obvious effect on smoothness.5. Analyzed by SEM photos and XPS spectrum, combined with the normal surface sizing mechanism, the surface sizing mechanism of PPVA was primarily considered that:â‘ PPVA can form a continuous film on the surface of paper, which interrupted the permeation of water or delay the penetration time. Phosphate can react with free hydroxyls of fibers, which can improve the surface strength.â‘¡It is also possible that in the process of drying, cross linking reaction of phosphates has happened; The film on the surface has better water-resistance after thermofixation.â‘¢The gaps of fibers were filled up with PPVA and the mechanical binding power of themselves enforced the surface strength of paper.