The Preparation And Properties Of Calcium Carbonate-fines Composite Filler

Today, the direction of development of paper products is to an increasing degree determined by customers.the buyers of paper want to reduce the postage expenses. Further, paper buyers want products which have a lower grammage while still meeting high quality standards.The prupose of this study is to balance the contradiction between paper strength,filler amount and retention.Calcium carbonate-fines composite filler is a new type filler. The new composite filler is produced by precipitating calcium carbonate on pulp fines. The calcium carbonate is on the surface of fibrils, adhering to them, the fibrils with calium carbonate particles precipitated on them form fibres resmbling pearl necklaces. This new precipitated, calcium carbonate based filler of the study bestows paper better optic properties and a clearly greater strength, furthermore, the filler allows the filler content of paper to be increased without impairing its other properties, saves the plant fibers, decreases the deforestation. Further, the new filler has a clearly better retention in paper manufacture, and has a very important role for reducing environmental pollution.The production of composite filler in this study is using chloride method. The precipitation can be advantageously effected in a reactor, the carbonation reaction is implemented by supplying calcium chloride and sodium carbonate into the reactor, then the calcium carbonate is precipitated and performed on the surface of fibrils. This study discusses the factors that affect the preparation of composite filler, and through analysising and testing the properties of paper filled by this new filler, and determine the optimum conditions of the production of new filler; the effects of composite fillers on paper properties was investigated by comparing with fillers pre-mixed and added normally to the stock; the effects of PLA and PVA fibers on paper strength was also discussed.The major findings of this study are as follows:1,The optimum conditions of the production of new filler are:the reaction temperature is 30～40℃;pH is 7;stirring speed is 500rpm; the ration of calcium chloride and fines is 3:1; the method of reagent supplying is mixing the fines and calcium chloride first, then adding the sodium carbonate; the sodium carbonate adding rate is 15ml/min.2,For the filled sheet, the tensile strength, tear strength, burst strength, surface bonding strength, Internal bond strength, ISO whiteness and light-scattering were determined. Composite filler provides paper with a significantly improved combination of light-scattering coefficient and strength compared with fillers pre-mixed and added normally to the stock, and the ISO whiteness of composite filler filled paper is a little lower than commercial Pcc filler. The composite filler also has higher retention rate than normal pcc filler, when the paper ash was as high as 50%, the retention rate was also obtained 87%.Composite filler has poor drainability, and prolongs the drainage time.3,PLA and PVA fibers can affect the strength properties of paper. The optimum application condition of PVA fibers are:the adding amount of PVA fibers is probably 5%, dry temperature is about 75～80℃;The optimum application condition of PLA fibers are:the hot pressing temperature is 170～180℃, the hot pressing time is 120s, the adding amount of PLA fibers is probably 4%.