Research On Pulping And Papermaking And Aging Resistant Properties Of Wikstroemia

In light of its toughness（high strength）,insect resistance and durability,handmade paper has been indispensable in the fields of ancient book restoration,calligraphy and painting,art,national cultural inheritance and so on.Based on the limitations of traditional ancient papermaking technology,this paper used Wikstroemia bast as raw material to study the influence of traditional pulping technology on pulp fiber properties and paper properties,and investigated the influence of cooking conditions and bleaching methods on the aging resistance of paper using dry-heat aging experiment.Furthermore,the effect of enzyme pretreatment on the atmospheric pressure pulping properties of Wikstroemia bast was discussed.This provides a theoretical basis for the inheritance and development of the production techniques of traditional hand-made paper and the preparation of Wikstroemia paper with excellent performance.The chemical composition and fiber morphology of Wikstroemia bast were studied,and it was found that the content of holocellulose（69.6%）and pectin（11.2%）were high,but the content of lignin（17.4%）was lower than that of wood materials.The fiber was slender and had a length width ratio of 192,which indicates that it is an excellent raw material for papermaking.With reference to the traditional cooking techniques,the properties of pulping and papermaking of Wikstroemia bast were studied.The study found that with the increase of K₂CO₃ dosage and cooking time,the fiber length changed slightly,the pulp yield,kappa number and fiber width decreased during normal pressure cooking,while the degree of polymerization increased with the dissolution of low molecular weight substances.The degree of polymerization could reach1742,tensile strength 12.27 N·m/g,,tear strength 17.13 m N·m2/g,bursting strength 8.7k Pa·m2/g and folding strength 1669 times at normal pressure cooking with Na OH,but the yield of good pulp was low and the aging resistance was poor.The aging resistance of Wikstroemia paper with 6 groups of different cooking conditions and 3 different bleaching methods（calcium hypochlorite bleaching,hydrogen peroxide bleaching and formamidine sulfinic acid bleaching）were evaluated.The results showed that the yellowing,degree of polymerization and strength decreased after the dry heat accelerated aging treatment.The fiber surface shrinked and"peels"when heated,and the crystallinity of cellulose decreased.Compared with Na OH cooking,weak alkali atmospheric pressure cooking could give the paper excellent aging resistance.After aging for 80 days,the retention rates of tensile strength,folding strength,tear strength and polymerization degree were 94.2%,19.6%,47.9%and 66.9%respectively.Bleaching could improve paper properties of the pulp,but it would lead to the deterioration of the aging resistance of the paper.The degree of effect of calcium hypochlorite,hydrogen peroxide and formamidine sulphonic acid on the paper durability is as follows:calcium hypochlorite>formamidine sulphonic acid>hydrogen peroxide.The Wikstroemia bast before cooking was pretreated with pectinase,hemicellulase and pectinesterase,and the effects of different enzyme pretreatment methods on the pulping and papermaking properties were investigated.The results showed that the enzymatic pretreatment could improve the cooking performance of the raw material of Wikstroemia bast,and the pulp yield,kappa number and dust degree decreased by about 4.7～14.5%,0.8～6.7%and 20.7～84.2%,respectively,and the pulp whiteness increased by 2.3～18%.On the basis of reducing the amount of cooking chemicals,the yield of fine pulp increased by 4.5%,the residue screening rate decreased by 2.3%,and the length width ratio and curl degree of fiber increased.Among the paper obtained from the experiment,folding strength,tensile index,tear index,bursting index and zero distance tensile index increased by 23.3%,12.9%,10.4%,18.1%and 4.0%respectively.