| The traditional chlorine bleaching in the paper industry and the organic chlorides caused by elemental chlorine-free bleaching have a significant impact on the environment and are not conducive to the sustainable development of the paper industry.To promote the green development of the paper industry,environmentally friendly hydrogen peroxide bleaching has been used as the main method of bleaching pulp fibers in the paper industry.Hydrogen peroxide bleaching often requires the use of sodium silicate as a stabilizer to achieve stable decomposition of hydrogen peroxide.However,sodium silicate is prone to calcium,and magnesium ions generate insoluble silicate,which deposits hard silica scale on the equipment,causing blockage of the pipeline,which is not conducive to the smooth progress of the bleaching process.Therefore,the development of non-silicon stabilizers suitable for hydrogen peroxide bleaching is of positive significance to promoting the development of hydrogen peroxide bleaching.To replace the sodium silicate used in the hydrogen peroxide bleaching process,this topic uses amide and carboxyl groups as important groups for chelating metal ions to prepare organic compounds rich in heavy metal ion chelating functional groups to promote the hydrogen peroxide bleaching process.Silicon-free development.The effects of factors such as the ratio of acrylamide and maleic anhydride,the temperature and reaction time of the reaction system,and the amount of initiator on the chelating properties of acrylamide-maleic anhydride non-silicon stabilizer were studied.It is found that the reaction temperature and reaction time have a more obvious influence on the copolymerization reaction of the two.Increase the reaction temperature and prolong the reaction time,the number of carboxyl groups and amide groups within the polymer molecule will change and steric hindrance will occur;at the same time,increase the monomer ratio of acrylamide and maleic anhydride to increase the initiation.The dosage of the agent will increase the self-polymerization effect of the monomer,thereby reducing its chelating performance for iron and calcium ions.Combining the relationship between the reaction conditions on the internal composition of the polymer and the polymer yield,it is determined that the best synthesis process of acrylamide and maleic anhydride non-silicon stabilizer is the ratio of acrylamide and maleic anhydride is 1:2.5,the reaction temperature is 85℃,the reaction time is 2h,and the amount of initiator is 7%.Under these conditions,the chelation values of the prepared non-silicon stabilizer to Mg2+,Ca2+,Fe3+are 55,96,and 270,respectively,and the polymer yield is 86%.The application of sodium silicate and self-made non-silicon stabilizers to the alkaline hydrogen peroxide bleaching of chemical thermomechanical pulp(CTMP)was studied.The research results show that it is determined that the homemade stabilizer can effectively improve the bleaching efficiency of hydrogen peroxide,and its dosage has a significant effect on the content of residual hydrogen peroxide.When other processes are the same,compared with sodium silicate as a stabilizer,when the amount of self-made non-silicon stabilizer is 0.5%,the hydrogen peroxide bleaching efficiency is equivalent to that of 2.5%Na2SiO3.The whiteness of the bleached pulp is 62.62%ISO,and the residual amount of hydrogen peroxide after bleaching is 0.21 g/L.Further increasing the amount of self-made non-silicon stabilizer will increase the content of residual hydrogen peroxide,but it is not conducive to the whiteness of the bleached pulp.To make up for the shortcomings of self-made non-silicon stabilizers in pH buffering,the stabilizers can maintain high efficiency and stability in a strongly alkaline environment.In this study,the self-made non-silicon stabilizer and disodium hydroxyethylidene diphosphonate(HEDP·Na2)were compounded to obtain the compound stabilizer.The basic properties and application performance of the compound stabilizer were studied.The effect of Mg2+,Ca2+,the chelation values of Fe3+ three metal ions are 91,198,and 336,respectively.The bleaching results of the compound stabilizer show that the compound stabilizer can stabilize the decomposition of hydrogen peroxide more effectively and can obtain higher bleaching whiteness under the condition of higher hydrogen peroxide residue.When the compound stabilizer is used when the dosage is 0.4%,the whiteness of the bleached pulp is 65.78%ISO,and the residual hydrogen peroxide content is 0.36g/L. |
