Preliminary Study On Phosphogypsum Whisker In Papermaking Coating

The continuous accumulation of phosphogypsum not only takes up a large amount of land,but also has a serious impact on the local climate and environment.Due to the high cost of processing and low added value,phosphogypsum application only accounts for the annual comprehensive development rate about 30%.Let phosphogypsum become phosphogypsum whisker and be applicable to coating pigment in papermaking.Not only can it make from low-grade gypsum materials into high-grade functional materials,but also it provides a new type of phosphogypsum research direction.Furthermore,this new type of technology also increases the comprehensive utilization of phosphate rock waste and saves natural mineral resources.In this paper,the feasibility of preparing 60%solid phosphogypsum whisker coating for paper coating was studied.Exploring and finding the most suitable dosage of the additives and pigments in coating compositions.The optimal compounding condition for coating by changing pH、temperature、dispersion strength and so on were researched.When the viscosity of the coating is still relatively high,adding dispersant and viscosity reducing agent can further improve the quality of the coating.In order to reduce the coating preparation workload,designing experiments to explore the effect of modified phosphogypsum whiskers on the quality of coatings was investigated,and observing and analyzing the modification of phosphogypsum whiskers with the detection value of infrared,contact angle and SEM were also studied.The experimental results show that the whiteness of phosphogypsum whisker is equivalent to the kaolin and slightly higher than GCC,the density is lower than kaolin.The Zeta potential of phosphogypsum whisker is different from GCC 0.12mV.The grinding efficiency of the basket style grinder is higher than the ball grinder.Grinding will reduce the particle size from 13.61μm to 3.24μm about four hours.According to the addition order of the dispersant solution phosphogypsum Whisker adhesive,the coating viscosity is the lowest.Adding 12 copies of acrylic latex as the adhesive will formulate a relatively low viscosity coating.Adding 2 copies of the cationic starch as the coating adhesive will increase the surface strength of the coating paper 16.49%.With 40 copies of GCC instead of phosphogypsum whisker,the viscosity of the coating decreased by 10.18%,the glossiness increased by 17.1,but the surface strength decreased by 12.69%.The optimum pH value for preparing low viscosity coatings is 8,and inorganic electrolytes are not suggested to be added to the coatings.The optimum preparation temperature of the coating is 40 C,the dispersion strength is increased from 1000rPm to 2000rPm,and the viscosity value can be reduced by 4.6%.The addition of 0.7%polycarboxylate sodium salt can increase the Zeta potential of the coating by 23.22%.Urea and sodium polyacrylate have obvious effect on the viscosity of coating,but urea can reduce the viscosity of the coating by 37.86%,and the effect of viscosity reduction is more obvious.Using titanate coupling agent,surface PE6800 emulsifier connected with phosphogypsum whisker modified the phosphogypsum whisker paint viscosity can be reduced by 40.83%.The chemical reaction of the modifier on the surface of the phosphogypsum whisker has been found in the infrared.The hydrophilicity of the modified phosphogypsum whisker is lower,but it still belongs to the hydrophilic substance.SEM detection showed that the surface of adsorbed phosphogypsum whisker decreased after the modified phosphogypsum whisker,which reduced the possibility of floc between phosphogypsum whiskers in the later stage of coating.In the four kinds of coating formulations,optimizing the coating formula and modifying the phosphogypsum whisker are two effective approaches to reduce the viscosity of the coating,which reduce viscosity of the coating by 47.58%and 42.94%respectively.The compound GCC helps to improve the whiteness of the coating paper,but the modified phosphogypsum whisker coating reduces the whiteness of the coating paper by 1.49.Adding additives to coating can increase the surface strength of the coated paper by 14.72%.The surface strength of the modified phosphogypsum whisker coating paper reduces by 35.05%compared to the original coating formula.According to the effects of coating results,optimizing the coating formula is the best way to cut coating viscosity.