Study On Mg-Al Hydrotalcite Used As Papermaking Functional Filler And The Related Wet Chemical Behavior

Mg-Al hydrotalcite(HT)possesses ion-exchange and adsorption properties,and so has a wide range of industrial applications,such as flame retardant and stabilizer of polymer materials,waste water treatment agent,modifier and intermediate of various materials.This paper focused on the study of HT used as a papermaking functional filler and its influence on the behavior in wet end chemistry.The possibility of HT used as a papermaking flame-retardant filler and its influence on the properties of paper were investigated.The experimental results showed that HT can increase the opacity and brightness of paper,at the same time,it can decease the strength properties of paper in a certain degree.The oxygen index of paper is above 25%and reaches the grade which is difficult to burn when without adding CPAM and with filling 40%HT.The oxygen index reaches 26.2%when adding 0.025%CPAM and filling 30%HT.The oxygen index is close to 25%when the basis weight of paper is 240 g/m² and HT dosage is 20%,and basically reaches the grade which is difficult to burn.The possibility of HT as a papermaking functional filler catching anionic trash was investigated.The results showed that CC₃^2--HT with Mg-Al molar ratio of 5:1 was the best for dissolved,and colloidal substances(DCS)catching.The optimum time of waste paper pulp treatment with CO₃^2--HT was 10¹5 min,and the effect of temperature was not significant. The turbidity of white water was as low as 18.6 NTU and the conductivity was almost zero when adding 20%of CO₃^2--HT.Cl^--HT with the Mg-Al molar ratio of 5:1 was the best for colloidal substances(CS)catching.The CS in white water was undetectable,and the turbidity was zero when adding 15%of C1^--HT.NO₃^--HT and CO₃^2--HT had better results for dissolved substances(DS)catching,and the conductivity of white water could reach almost zero when adding 10%of the HT.For DCS catching,HT is far superior to some common porous fillers, such as zeolite and opal.Hereby,HT can effectively catch anionic trash through selecting and optimizing the treatment conditions,the Mg-Al molar ratio and interlayer anion of HT while it is used as a papermaking functional filler.HT as a papermaking filler and its impact on AKD sizing were investigated.The results showed that the industrial-grade HT would affect AKD sizing greatly.Along with the amount of HT increasing,the Cobb value of HT filled paper would continue to increase until the filled paper had no hydrophobic properties.The Cobb value of HT filled paper would reduce with the amount of AKD increasing.It could reduce to 30 g/m² when filling 0.4%of AKD and 10% of HT.This study also investigated the impact of the self-made HTs which had different Mg-Al ratios or different layers of anions with Mg-Al ratio of 5:1 on AKD sizing.The results showed that the Cobb values of paper filled with self-made HT were between 14 g/m² to 17 g/m² when filling 20%of HT,0.3%of AKD and 0.03%of CPAM.The AKD sizing effect of SO₄^2--HT filled paper was similar to that of PCC filled paper.HT filled flame-retardant paper prepared in this study has good flame-retardant properties and good processability.It is easy to realize large-scale production by using the current papermaking technology.At the same time,HT could effectively catch anionic trash.HT has a lot of advantages such as simple preparation technology,good environmental stability and cheap raw materials.The flame-retardant paper successfully manufactured in this research will expand the use range of HT,and it is significant for the industrialized application of HT.