The Research Of Pre-flocculation Of Synthetic Calcium Silicate And Its Application In Papermaking

Synthetic calcium silicate is a new type of paper filler.At present,the application of synthetic calcium silicate and the relevant technolo-ies are not yet mature in the paper industry.In order to give full play to the excellent performance of synthetic calcium silicate in application of papermaking,and reduce the negative effect of filling on paperproperities,the pre-flocculated method was adopted to improve the properties of paper with synthetic calcium silicate filler.Firstly,in this study,the properties of synthetic calcium silicate filler were analyzed,and the properities of synthetic calcium silicate in paper fillings were compared with the conventional filler GCC.The results show that the synthetic calcium silicate is a porous papermaking filler with a large specific surface area and porosity,a specific surface area of 134.7 m2.g-1,a porosity of 0.267 mL.g-1;the particle size of synthetic calcium silicate is larger,the average particle size of synthetic calcium silicate is 37.8μm;It has a strong negative charge,the Zeta potential is-33.9mV.Compared with GCC,synthetic calcium silicate’s one-way retention rate is higher.When the ash content is close,the thickness,opacity of paper with syntheticcalcium silicate filler is higher than that of GCC;the whiteness,tensile strength,folding resistance and Cobb absorption are poor.The bulk of paper with synthetic calcium silicate filler is 26.3% higher and the opacity is four point higher than that paper with GCC,while the tensile index was lower with 19.1%.The synthetic calcium silicate filler can improve the bulk properties of paper significantly,but it has an adverse effect on tensile strength、cobb absorption,so effective measures need to be taken to reduce these adverse effects.Next,the process of pre-flocculating the synthetic calcium silicate with cationic starch was studied.The results showed that the four factors,such as the amount of cationic starch,the concentration of pre-flocculation system,the reaction temperature and the stirring speed,had a great influence on the performance of pre-flocculation ofsynthetic calcium silicate.The single-factor experiment and orthogonal experiment were used to optimize the technological conditions: the dosage of CS was 2%,the solid content of the pre-flocculation system was 5%,the reaction temperature was 40 ℃and the stirring speed was 200 r / min.It was found that the average particle size increased from 37.8μm to 67.9μm after pre-flocculation of cationic starch,and the span of particle size distribution decreased from 2.17 to 1.61.The distribution uniformity is improved greatly.Then,the filling performance of pre-flocculation synthetic calcium silicate was studied in this study.The results showed that the one-way retention rate of the synthetic calcium silicate filler increased by 13.3% after pre-flocculation with cationic starch compared with the un-treated filler.When the ash content is about 20%,the opacity and bulk of the pre-flocculated synthetic calcium silicate paper remain unchanged,the tensile index is 37.6N.m.g-1 with an improvement of 17.1%,the burst index is 2.61 Kpa.m2.g-1 with an increase of 12.9%.