Preparation Of Calcium Sulfate Whisker Coating And Its Effect On Printing Properties Of Coated Paper

With high brightness and high whiteness,calcium sulfate whisker as a new pigment can be applied in paper coating to produce pure color coated paper.Utilizing calcium sulfate whisker as coating pigments can not only improve paper properties and printing quality,but also expand the application amount of phosphate rock waste,increase its utilization rates,meanwhile,reduce waste accumulation and save land resource.The properties and grinding dispersion conditions of calcium sulfate whiskers were explored in the laboratory condition.The experimental results showed that the optimum grinding time of calcium sulfate whisker was 4h and the best ground speed was 2500rpm by wet grinding.The average particle size of calcium sulfate whiskers reached 1.9?m and proportion of less than 2?m particles was 75%.The results also indicated that organic dispersant has better dispersion effect than the inorganic dispersant,and the sodium poly acrylate was the best dispersing agent for the calcium sulfate whisker pigment,and the optimum amount was 0.5 part.The best adhesives and dosages for calcium sulfate whisker pigments were studied.The experimental results show that compared with cationic starch and polyvinyl alcohol,acrylic latex as adhesive had lower viscosity and better rheological properties,then optical properties and liquid penetration resistance of coated paper was higher but the ink absorption was lower;While the acrylic latex was used to an adhesive,the copy curve and tone reproduction of coated paper was better although the color gamut was in the middle.Consequently it could be used as the most suitable adhesive for calcium sulfate whisker pigment and the best dosage was 12 part.The paper also compared calcium sulfate whisker pigment with traditional pigment calcium carbonate.Adding calcium carbonate to partially replace calcium sulfate whisker to explore the effect of calcium carbonate on coating performance,coated paper properties and printing effect in the coating formulation.The study found that in coating viscosity,100%calcium sulfate whiskers>100%PCC>100%GCC,with increasing addition of calcium carbonate,the rheological properties of coating was improved;In terms of coated paper properties,the brightness,smoothness,gloss,surface strength 100%calcium sulfate whiskers>100%PCC>100%GCC;in ink absorption 100%GCC>100%PCC>100%calcium sulfate whisker.With the increasing of the amount of GCC the gloss of the coated paper trended to dropdown.On the contrary,the amount of PCC increased the gloss of the coated paper first and then decreased.In printed solid density,color gamut and tone reproduction,100%PCC>100%calcium sulfate whisker>100%GCC.When the amount of GCC reached 80 parts,the solid density of coated paper decreased,and with the rising amount of PCC the solid density of coated paper increased.The increased in the amount of GCC can lead to tone reproduction scale of coated paper shrink while added more PCC benefited for tone reproduction scale of coated paper.The best ratio of calcium sulfate whisker to GCC was 80:20,and the best ratio of calcium sulfate whisker to PCC was 40:60.