The Influence Of Calcium Carbonate Filler On Properties Of Paper Containing High-yield Pulp

High yield pulp(HYP)has been gaining increasing interest as a substitute for hardwood bleached kraft pulp in fine paper grades for the functionality(e.g.bulk,opacity)and cost advantage of the HYP,also calcium carbonate(CaC03)filler is at an increasing trend in many paper mills for the characteristic(e.g.brightness,printability)and cost-effective superiority.The objective of this study was to evaluate the impact of the addition of maple HYP which replaced a part of bleached hardwood kraft pulp and three kinds of CaCO3 filler(that is precipitated calcium carbonate,ground calcium carbonate and their mixture filler)on the bulk,optical properties and physical properties in fine paper grades.In addition,the effect of calendering operation on the properties of hand-sheets was also investigated.Finally,the SEM(scanning electron microscope)analysis were taken to observe the microstructure hand-sheets.The results showed there was a positive effect on boosting the bulk of fine paper grades in the presence of maple HYP in the pulp furnish.At the same ash level of 22%,the bulk of the hand-sheets,containing 20%maple HYP and filled by PCC,reached up to 1.96 g/cm3 which increased by 12.6%than that of no maple HYP addition.In addition,the addition of maple HYP reduced the whiteness and brightness slightly,but improved the opacity of paper.However,there was a negative effect on the tensile index of fine paper grades in the presence of maple HYP in the pulp furnish.In the other hand,the effect of CaCO3 filler on the properties of paper was explored by changing the ash levels of three filled paper.The ash levels were 22%,28%,35%,respectively.We can find out PCC had a superior advantage on the bulk and optical properties,while GCC provided a higher tensile index.The bulk of paper with 20%maple HYP reached up 2.0 g/cm3 at 35%ash level of PCC.Moreover,PCC filled paper had better optical properties than GCC.In the same ash level of 22%,the tensile index of GCC filled paper with 20%maple HYP was 31.8 N·m/g,which was 20.6%higher than PCC filled paper.Calendering changed the roughness,as well as the bulk and tensile index,but the neglible effect of optical properties.SEM analysis indicated the addition of maple HYP and PCC provided a bulky and porous structure,and GCC filled paper presented dense network structure.