| Gypsum whisker is an excellent new paper filler with fibrous single crystal, large aspect ratio, high brightness, wide range of sources, low price and set reinforced fiber and inorganic filler in one. However, Gypsum whisker is difficult to directly applied in papermaking industry due to its water solubility.This paper, combining with the characteristics of gypsum whisker, used phosphate and cationic starch composite coating modification method to reduce the gypsum whisker's water solubility, and papermaking with filling original and modified gypsum whisker to compare with their retention and investage its influence on paper properties. Then, we were investigated the influence of retention system on gypsum whisker's retention and paper properties by using different kinds of retention aid. Finally, the Ca2+ and SO42- dissolved in water were recycled. The application of gypsum whisker in the whole papermaking system was studied and the results are as follows:The solubility of gypsum whisker decreased obviously after modification. The solubility of modified whisker is 0.025g/100g water, which is significantly lower than original whisker's (0.224g/100g water) for 88.8%. The best conditions for modification:reaction temperature: 50?, modification time for phosphate: 5 min, the dosage of modifier (magnesium ammonium phosphate): 2%, Mg(OH)2 concentra- tion:0.07mol/L, NH4H2PO4 concentration: 0.08mol/L, starch dosage: 2%, starch reaction time:3min, drying time: 2h, drying temperature: 20-50?.The partical size of modified whisker is 109.0?m, which has a larger degree of reduce compared with original whisker's and it is relatively unstable because of the falling off of modifier on gyps?m whisker's surface with mixing process.Studied the retention system on two kinds of original whisker and found: without retention agent, The retention of whisker2 is significantly higher than whiskerl's, the two had a rate of 44.24% and 35.26% respectively. When retention agent was added, whisker 1 had the best retention rate of 52.73% by use of CPAM1, and whisker2 had the best retention rate of 55.01% by use of CPAM2. While the two kinds of microparticle retention system had poor retention effect. Under the optimal retention conditions, the strength of the paper with whisker added have a slight degree of decline.Studied the retention system on midified whisker and found: The retention rate of modified whisker was 59.67%, compared with original whisker(retention rate of 35.24%),the retention rate was increased by 69.3%. The retention rate of modified whisker was 66.56% after using CPAM2 and 65.06% after using CPAM1. The retention effect of the microparticle retention system on modified whisker was poor. The paper with modified whisker added have a slight degree of decline.The sediment treated from white water mixed with gypsum whisker was added to the papermaking. The results showed that the addition of 5% and 10% mixed sediment significantly not only improved the filler retention in the paper but also ensured the paper strength.On the premise of neglecting the cost of equipment corrosion and depreciation, paper filled gypsum whisker has a better paper strength and lower cost compared with the paper filled calcium carbonate.Above all, if we can improve the stability and the problem of easy to fall off of modified whisker and select a more appropriate retention system,gypsum whisker as a filler used in the paper industry will be just around the corner. |
PDF Full Text Request