Fiber Loading Of Calcium Silicate By In-situ Deposition And Its Application In Highly Filled Paper

With the yield of paper and paperboard increasing yearly,the fiber resources are increasingly precious,and the paper industry has to constantly study the substitute for partly replacing fiber.Mineral fillers,which can endow paper with new properties and reduce the cost of papermaking and energy consumption,are widely used in the papermaking.China,as a coal-fire country,produces a large amount of fly ash and the rate of utilization to the solid waste is low which results in a big pollution to environment.The novelty calcium silicate,synthesized by desilication liquor and lime cream,can reduce the cost and achieve the highly effective utilization of fly ash.The paper applied the desilication liquor and lime cream to synthesize calcium silicate by in-situ deposition.In this way the calcium silicate can deposit in the fiber and the fibrillation in order to achieve the purpose of fiber loading.The article also studied the treatment of fiber,processing parameters and dispersant to fiber loading.The results showed that when the fiber was beat by PFI beater,the effect of beating degree to the strength and optical properties of the handsheet made by softwood was bigger than the handsheet made by hardwood.With the increasing of beating degree,the fiber loading volume of calcium silicate declined,the ash content of handsheet increased,the strength properties of handsheet lost.When the ratio of softwood and hardwood fiber was 1:1,the lower the degree of softwood was,the greater the fiber loading volume of calcium silicate was,the higher burst and tensile strength was,but the tear strength changed little.The pre-dip of desilication liquor could increase the retention of calcium silicate,but would also reduce the fiber loading volume of calcium silicate,and reduced the paper strength properties.Through the single factor test,the article studied the effect of the processing conditions to synthesize calcium silicate to fiber loading,respectively on the filler amount of 30%?40%?50%.When the filler amount was 30%,the ratio of consumption of softwood and hardwood pulp was 1:1,the temperature was 60?,the rotate speed was 500r/min and the pulp consistency was 5%,the result showed that the fiber loading volume of calcium silicate was 20.1%,the ash content of paper was 30.1%,the opacity was 89.0%,the whiteness was 85.6%ISO,the tensile index was 23.5N·m·g-1,the burst index was 1.32kPa m2·g-1,the tear index was 6.88mN·m2·g-1.While the filler amount was 40%,the pulp consistency was 4%and the rotate speed was 800r/min,the result showed that the fiber loading volume of calcium silicate was 23.7%,the ash content of paper was 40.1%,the opacity was 92.1%,the whiteness was 88.2%ISO,the tensile index was 11.4N·m·g-1,the burst index was0.54kPa·m2·g-1,the tear index was 3.86mN·m ·g-1.While the filler amount was 50%,when the reactive time was 30min,the desilication liquor and lime cream reacted completely on the whole.When the reactive time was 60min,the deposition of calcium silicate remained stable.And When the rotate speed was 600r/min,with the augment of lime cream,the ash content increased but the fiber loading volume of calcium silicate and strength properties decreased.The dry strength additive was applied to improve paper strength effectively.The use of dispersant could increase the fiber loading volume of calcium silicate.