Synthesis Of Cellulosic Super Absorbent Resin With Eucalyptus Pulp

Eucalyptus trees are widely cultivated in southern China region because of strongadaptability to site conditions and a good growth rate. The eucalyptus pulp，which has goodquality and high cellulose content, is one of the best native celulose sources. Its cellulose canbe easily seperated from eucalyptus wood and is much cheaper than that from cotton fiber.Utilizing eucalyptus cellulose to making cellulosic super absorbent resin not only promotesaddional economic value to eucalyptus pulps, but also expand their application field.The impact factors of synthesizing bleached eucalyptus kraft pulp (BEKP) fiber graftedwithacrylicacid (AA) were studied with fractional factorial design. The results showed thatreaction temperature, the neutralization degree of acrylic acid, the dosage of initiator andcross-linking agent were the main effects. The optimal conditions of polymerization was foundas follows: reaction temperature the amount of initiator, crosslinker and the neutralizationdegree of acrylic acid were60℃,0.5%,0.05%and70%, respectively. The product’s waterabsorbent rate was up to524g/g at this condition. In addition, the FTIR showed that the acrylicmonomer has been grafted on the cellulose molecules.Four eucalyptus bleached kraft pulp (BKP) cellulose smples were treated by NaOH,cellulase, NaOH/urea solution system at low temperature and cellulase together withNaOH/urea solution at low temperature respectively. After enzyme treatment, the cellulosecrystal structure was not changed, but its degree of crystallinity increased slightly. However,the sample treated by17.5%NaOH changed its cystal structuer partly containing cellulose Iand cellulose II two kinds of crystal types, and its degree of crystallinity reduced to61.17%.During the process of8%NaOH/12%urea solution treatment, part of the sample’s crystal typewas disappeared, and the degree of crystallinity fell to51.04%.Togeter, cellulase tretment andNaOH/urea solution treatment on eucalyptus BKP cellulose led to crystalline region almostcompletely destroyed and crystallinity shaply reducing to2.73%. The better reaction activityofcellulose was with more hydroxyl exposed. So the sample treated by cellulase in coordination with NaOH/urea solution was the best one among all the samples to synthesizecellulose grafted with(AA) SAP, and its deionized water absorption rate wasup85%at968g/g.Effects of six factors such as the proportion of cellulose to AA, the dosage of initiator, thereaction temperature, the dogage of crosslinker, the neutralization degree of acrylic acid andthe reaction time on the absorbency propertyproducts were discussed in this work. The resultsindicated that the resin’s water absorbent rate decreased from988g/g to420g/g withincreasing of the proportion of cellulose to AA. The reaction time increased step by step andSAP’s water absorption ratio wass up and then after6h descended slightly with time extension.Thewater absorption curves of the other three factors kept the similar variation tendency thatwent up at first,and then went down. The highest absorbent rate was got when the dosage ofinitiator and crosslinking agent, the reaction temperature and the neutralization respectivelywere1.0%,0.06%,60℃and70%.In the research, polyvinyl alcohol sodium sulfate(SPS) was introduced into the netstructure of the polymer which was cellulose grafted with AA in order to prepare the SAP withan interpenetrating net-work(IPN) structure(CLS-AA-SPS).The absorbent rate of theCSL-AA-SPS resin droped after rising with the increasing of dosage of SPS, crosslinkingtemperature and the neutralization degree of acrylic acid. The optimum absorbent ratio was1126g/g with the SPS dosage of2%(relative to the dosage of acrylic acid), the crosslinkingtemperature of60.1℃and the neutralization degree of55.16%selected by response surfaceanalysis. The results showed that the salt resistanceof the SAP was increased19.8%due to theintroduction of SPS forming an interpenetrating network structure.In addition,theCLS-AA-SPS super absorbent polymer was proved to have an interpenetrating networkstructure by the FT-IR spectra and thermogravimetric analysis.