Study On The Technology Of Improving Reactivity Of Viscose-grade Dissolving Pulp

China is famous in the textile industry for both the production and the consumption of textiles ranking the first place in the world.With the rapid development of textile industry,the demand of all kinds of fiber raw materials increased dramatically.Then it promoted many countries finding renewable biomass materials for producing textiles.In the context,as the main raw material for textile,the viscose rayon obtained a rapid development,and this also led to the great development of dissolving pulp which is one of the main raw materials for producing the viscose rayon.Reactivity of dissolving pulp is one of the important parameters for judging the quality of dissolving pulp in producing viscose rayon.The problem which the reactivity was instable and lower perplexed many dissolving pulp industries.In this case,the cellulase treatment,ultrasonic treatment and mechanical treatment were used to improve the reactivity of dissolving pulp in this paper.The hardwood prehydrolysis kraft-based dissolving pulp was utilized to study the effect of cellullase treatment on the reactivity of dissolving pulp.The results showed that the cellulase treatment could result in the increase of reactivity dramatically,the decrease of viscosity and molecular weight,the decrease of average fiber length,the increase of microfiber content,and the increase of fiber specific surface area and pore size.But the yield decreased weakly.The optimized process of cellulase treatment was as follows:cellulase dosage of 0.076 IU/g dried pulp,treatment time of 30 min,pH 5.0,temperature 55℃.Under this condition,the properties of resulted dissolving pulp were as the following:Fock reactivity 78.82%,viscose filtering value 3142.12 s,viscosity 496.6 mL/g,specific surface area 2.930 m2·g-1,pore diameter 4.889 nm.The effect of mechanical treatment on the reactivity of dissolving pulp was discussed using the Valley beater to treat softwood prehydrolysis kraft-based dissolving pulp.The results showed that the fiber was cut by Valley beater and more end faces exposed to the carbon dioxide,so the accessibility and reactivity of dissolving pulp was improved.The Fock reactivity increased with the increase of beating degree,however,the viscose filtering value would decrease when the beating degree reached a certain value.The Valley beating could lead to the decrease of fiber length,the increase of microfiber content and specific surface area,and the increase of fiber pore size and water retention value.It is notable that the degradation of cellulose due to beating action was very little,which could be verified by the weak decrease of viscosity.At the beating degree of 16°SR,the Fock reactivity was increased from 54.43%to 68.37%,the viscose filtering value was decreased from 3743 s to 10.97 s,the fiber length was decreased from 1.557 mm to 1.084 mm,the specific surface area was increased from 2.199 g/m2to 2.739 g/m2,the water retention value of fiber increased by 73.18%.The effect of ultrasonic treatment on the reactivity of softwood prehydrolysis kraft-based dissolving pulp was also conducted.The results showed that the ultrasonic treatment similar to the mechanical beating action could cause the shift of cell walls,and the fiber structure loosed,as a result,the reactivity of dissolving pulp was increased.At the same time,the ultrasonic treatment could resulted in the increase of fiber water retention value,the increase of specific surface area and pore size,especially the obvious decrease of cellulose crystallinity,but the viscosity and molecular weight decreased very feeble.The effect on fiber morphology was also very weak.It should be pointed out that the ultrasonic time and power must be suitably controlled.The optimized process was as following:ultrasonic power 540 W,the ultrasonic time 5 min.Under this condition,the Fock reactivity was increased from 54.43%to 73.17%,the viscose filtering value was decreased from 3743 s to 15.44 s,and the specific surface area was increased from 2.199 g/m2 to 4.169 g/m2.Also,the water retention value of fiber increased by 16.6%,and the fiber pore diameter was increased from 3.825 nm to 4.298 run.