| Since the new century,with the rapid development of China's retail,packaging and express delivery industries,the demand for paper and paperboard has increased dramatically.With the continuous introduction of new capacity,the shortage of fiber in the paper industry has caused widespread concern.Therefore,the method to select suitable paper-making fillers and reduce the fiber utilization rate based on waste paper recycling has become a hot issue of concern and research in the paper industry.In this paper,a new type of biomass filler,sawdust,had been developed as a new filler in the paper industry.Sawdust refers to the foamy wood chips of the trees themselves that are scattered from the trees during the wood processing.It has the advantages of a wide range of sources,low prices,and environmental friendliness,and is a renewable resource.In this paper,firstly we classify the sawdust by grading and screening,through the yield and the physical properties of the paper after filling,comprehensively select the best suitable fraction range,and determine the research object;and through a series of orthogonal experiments,explore the best application process conditions for sawdust;subsequent modification of sawdust to increase its retention in the paper sheet and characterize it;finally,preliminary qualitative exploration of the change in sawdust retention rate and in paper and cardboard Application effect in the middle.The research results are as follows:Sifting to obtain six different grades of sawdust from+35-60 mesh,+60-80 mesh,+80-100 mesh,+100-120 mesh,+120-150 mesh,and+150-200 mesh.Through the cost comparison and the analysis and comparison of the performance of the paper after filling and the screening yield,the sawdust with+35-60 mesh fraction was selected as the research object;The optimum application conditions for sawdust were 30 SR° for beating degree(selected corrugated cardboard),and the filling amount was 10%(for dry pulp).To achieve the best dry strength,cationic starch should be used and the amount used was 2%(for dry pulp).In the medium alkaline system environment,the filling effect of the biomass filler is better.In this paper,the sawdust was mixed with cationic starch by kneading machine and then modified by semi-dry kneading at high solid content.After modification,the average particle size of the sawdust decreased from 561 ?m to 352 ?m;the zeta potential of the sawdust suspension decreased from-12.6 mV to-10.0 mV.The whiteness of sawdust was 34.35 and 32.43 before and after modification,and the change was not significant.After observation by SEM scanning electron microscopy,cationic starch was observed to coat the surface of the sawdust and form a tight bond with the fibers.The determination of the retention rate of sawdust before and after modification was qualitatively analyzed by measuring the suspension of wastewater and the average quantitative change of the paper.The results showed that the modified sawdust had a certain degree of improvement compared with the unmodified filler retention rate.When adding+35-60 mesh fraction sawdust,when the filling amount is 30%,the content of unmodified sawdust suspended solids in white water was determined to be 1539 mg/L,and the modified sawdust suspension content is 1220 mg/L.The post-suspension content was reduced by 20.73%;and the average quantification of the modified sawdust was increased by 1.50 g/m2 under the same conditions,which was increased by 2.62%.It can be proved that the sawdust is modified by cationic starch coating to improve the retention rate to some extent.The modified sawdust was initially applied to paper filling.The results were as follows:taking a paper with a basis weight of 60g/m2 as an example(adding 10%):the bursting index is reduced from 0.974 kPa·m2/g to 0.962 kPa·m2/g compared with the base paper;The index decreased from 18.40 N·m/g to 17.70 N·m/g;the tear index decreased from 7.16 mN·m2/g to 6.86 mN·m2/g;the ring pressure index decreased from 4.381 N·m/g to 3.200 N·m/g;only the paper sheet stiffness decreased by a large margin,from 142.5 mN to 103.75 mN,a decrease of 27.19%.Take the three-layer paperboard with three layers of 60 g/m2 as an example(the filling amount of each layer is 10%):compared with the base paper,the bulk thickness increased from 1.78 cm3/g to 2.54 cm3/g,which is 42.70%higher.And the physical properties had a certain decline.At the same time,the lamination strength of the paperboard gradually increased with the increase of the filling amount and decreased from 135 kPa to 103 kPa when the filling amount was 20%,which decreased by 23.7%.And after 10 times of white water circulation,the paper quality problem has dropped greatly.Compared with traditional fillers such as calcium carbonate,the addition of biomass fillers can reduce production costs and protect the environment.The large-scale use of biomass fillers in the paper industry is just around the corner if you choose the right amount of filling and ensure the quality of the paper. |
PDF Full Text Request