Application Of Dolomite Used As Papermaking Filling

Filler is the largest accessory in addition to the pulp in the paper industry. Filling can notonly reduce paper costs、optical properties and printing adaptabities. The traditional fillers aretalc、calcium carbonate、titanium dioxide and kaolin. With the increase of waste paper recyclingand alkiline papermaking, calcium carbonate filler, especially ground calcium carbonate, theconsumption has dramatically increased with the replace of other filler in the paper industry,which rely on the fine runnability、good sizing and low effect on paper strength.Dolomite similar to calcium has a crystal structure、low price and high opacity, after wetgrinding,it can be used as paper filler with a partially substition of ground calcium carbonate,which can improve the performance of paper and the use of resources effectively. The purposeof the study is to explore the feasibility of dolomite used as filler in newspaper. In this work, weresearched the wet grinding process of dolomite and modification with carboxymethy cellulose.And the application of dolomite filler used in newspsper instead of ground carbonate calcium(GCC) was investigated.Firstly, the wet grinding technology of dolomite was investigated. The preparation processincluding grinding time, sluy concentration and dispersant dosage etc were all studied to choosethe optimum preparation conditions. It was found that when the60%of slurry concentration,0.5%of hexametahosphate additives, mass ratio of ball to power at6:1, and grinded at3000r/minfor45min, a papermaking filler with66.2%of particles less than2μm can be acquired. Theparticles size and morphology of the resulting dolomite were studied through SEM and toconfirm the sucessful grinding.The research investigated the possibility of using dolomite as filler and CPAM/MMT as dualretention system for papermaking. The result indicated that it is feasible to use dolomite as paperfiller after wet grinding and screening. Compared with the same dosage of GCC, the tensile index,opacity and the copper mesh wear while had a certain degree of improvement, while fillerretention rate, brightness and tear index did not change significantly.Then the use of carboxymethy cellulose on the modification of dolomite was studied, andthe effects of dosage of alum and carboxymethy cellulose on paper properties were explored.When the effects of dosage of alum and carboxymethy cellulose were10%and4%, the coppermesh wear of modified filler was11.1g/㎡,which had a30%lower in comparation to15.9g/㎡of dolomite filler. When the adding amount of filler was4%, the filler retention rate of modifiedfiller was improved39.5%than that of dolomite filler. And the tensile index and tear index alsohad a certain degree of improvement. Particle Size analysis and SEM images of filled paperindicated that filler aggregates were formed via surface modification and had a less effect onfiber bonding force.Finally the research investigated the applatication of using dolomite as filler in coated paperworkshop. Instead of GCC, the machine ran smoothly and chemicals consumpution had noobvious fluctuation. The opacity, roughness, tear strength, tensile strength and ash content had aslight increase, while filler retention smoothness, whiteness and visual whiteness decreased.