Preparation Of Carboxymethyl Cellulose From Waste Paper Fiber And Its Application In The Paper Coating

Carboxymethyl cellulose(CMC)is an anionic surfactant.Because of its high viscosity,water retention,good emulsification and non-toxic,CMC is widely used in architecture,daily chemical industry,food,papermaking,oil drilling,medicine and other fields.It has been described as ‘industrial monosodium glutamate'.In recent years,the raw materials for the preparation of CMC are lack and the price is high,which inevitably leads to the increased production cost.Thus,broadening the source of raw materials for CMC production has attracted great attention.The main component of waste paper fiber is cellulose,which is rich in resources,low in price and wide range of sources.Based on this,this work is aim to use waste paper as raw material for the efficient extraction of cellulose,which may convert waste materials into treasure.In this sense,high value can be added to the waste paper materials.This work may be helpful in broadening the source of CMC's raw materials and providing new ways and new methods for the efficient preparation of CMC.In general,this research has important economic and social benefits.First of all,in the present work,the bleached deinking pulp of 37# office waste paper was selected and used as the raw material for the extraction of cellulose.The optimum extraction process of cellulose based on the alkali boiling method at high temperature normal pressure was investigated.The content of ?-cellulose and the average degree of polymerization in the final extracted paper fibers were 91% and 603,respectively.The results of FT-IR and XRD proved that the impurities such as hemicellulose,lignin and pectin were effectively removed from the waste paper fibers after alkali cooking.The results of TG showed that the thermal stability of the fiber was improved after alkali cooking.SEM analysis showed that the surface of the waste paper fiber became rough after alkali cooking,which was beneficial to the subsequent carboxylation reaction.Afterwards,CMC was prepared from cellulose by alkalization and etherification.Based on the degree of substitution(DS)of CMC,the optimum preparation process of CMC was obtained by adjusting the water content and the reaction conditions of alkalization and etherification.The degree of substitution(DS)of CMC prepared by this experiment could reach 0.82,the viscosity of 2% CMC aqueous solution>300 mPa · s,the effective component>90%.FT-IR results proved that cellulose had the chemical reaction with chloroacetic acid,and the partial hydroxyl hydrogen on the cellulose molecules was successfully replaced by carboxymethyl.XRD results showed that the crystal structure of cellulose was changed due to the substitution reaction.TG results showed that the initial thermal decomposition temperature of CMC from waste paper was lower than that of cellulose,but it still had high thermal stability.Eventually,the prepared CMC was applied to the paper coatings.The ground calcium carbonate(GCC)and kaolin were used as the main pigment,styrene-butadiene latex as the main adhesive and CMC with different contents(0.4%,0.7%,1.0%,relative to the pigment)as auxiliary agent.The results showed that the prepared CMC effectively improved the stability,dispersibility and water retention of the paper coatings,and made the coatings exhibit obvious shear thinning tendency.Furthermore,the viscosity of the coatings were greatly increased by the addition of CMC,and the viscosity of the coating with 0.7% CMC was increased from the 0.121 Pa·s of the pure coatings to over 100 Pa·s.Meanwhile,the prepared CMC addition can lead to the increase of tensile strength and elongation of coated paper.But the excessive CMC content would affect the coating uniformity and lead to the decreased folding resistance.