High Absorbent Resin Synthesis

Super Absorbent Polymer(SAP) is a kind of functional polymer which has certain degree of cross-linking with hydrophilic group.SAP can rapidly imbibe several hundred times their own weight in water.SAPs are widely used in various areas, including personal care products,such as diapers,napkins,etc.SAP has become indispensable in human life.SAPs can be synthesized by modification of three kinds of raw materials:starch, cellulose and synthetic resin.The cross-linked polyacrylate sodium(PAA-Na) is considered as foreground among all synthetic-resin-type SAPs.PAA-Na can be prepared via free radical polymerization.Aqueous solution polymerization of acrylate sodium is used in this dissertation because of the advantage of acrylic acid product and manufacturing technology in Shanghai HuaYi Acrylic Acid Co.,Ltd.There are three stages in synthesis of PAA-Na type SAP:neutralization reaction, polymerization and surface-crosslinking reaction,respectively.After systemic researches on reaction mechanism and performance evaluation,we have screened and optimized excellent synthesis process and formulation through a lot of experiments results.The polymerization of PAA-Na can be carried out in an aqueous medium.This synthesis method has many excellent characteristics such as mildness and easy controllability in polymerization condition.The factors that influence the properties of SAP,such as cross-linker,initiator,and the degree of neutralization were investigated. Our experimental results indicated a significant direct correlation among properties of the SAP,such as the absorption capacity and centrifuge retention capacity,and the contents of cross-linker and initiator,and the degree of neutralization.With the addition of hydrophilic materials,the absorption capacity and salt-tolerant property was obviously increased.In addition to that,the amount of inhibitors and acrylic acid dimers in raw material,i.e.glacial acrylic acid was deeply studied through synthesis technology and the properties of final product.The experimental results indicated that the amount of inhibitors affected the polymerization induction period,and the amount of acrylic acid dimers affected the properties of final product,such as salt-tolerant property, absorption capacity and the amount of residual acrylic acid.If the amount of inhibitors and acrylic acid dimers was reduced,the properties of final product were improved greatly.Due to the high rate of radical polymerization,monomer is polymerized and high-molecular-weight polymer is formed instantly.This preparing technology is an irreversible process,and there is no intermediate product in the process.With the increasing of reaction time,the conversion of acrylic acid increases.If the polymerization time is too long,its production efficiency becomes low and it is unfavorable for industrial production.Through optimizing the formulation,we chose complex redox as initiating system and complex cross-linker as cross-linking system, respectively,and obtained a high performance SAP.The process of our synthesis technology is quite simple and low-cost,and it is suitable for industrial production. Through performance testing,we found that the molecular weight distribution of our SAP product was uniform and the physical properties were excellent.The comprehensive performance of our SAP product has approached advanced level in the world,such as the same product standards of BASF and Nippon Shokubai Co.Ltd.