Structure, Performance And Application In Wastepaper Deinking Of Ethylene Oxide And Propylene Oxide Block Copolymer

Block copolyether of ethylene oxide(EO)and propylene oxide(PO)is an important class of high-performance surfactants.It has potential applications in deinking of waste paper.Hydrophile-lipophile balance(HLB)value is a key parameter in determining the solution properties of surfactants.The HLB value is often used as an index of how much a surfactant molecule like water in contrast to oil. This thesis consists of three parts.First,we compared three different methods for HLB measurement,namely, partition coefficient,critical micellar concentration(CMC),and cloud point methods. Each method has its limitations.The partition coefficient method becomes complicated and inaccurate in measuring high HLB surfactants;The CMC method becomes difficult in measuring low HLB surfactants with big experimental errors; The cloud point method has a limited range of temperature due to the boiling point of water so that it fails in some aqueous systems.Second,we developed a new theory to estimate the HLB values from the molecular structure of surfactants.In this theory,we introduced a decay function for the contribution of the sequential units for the block copolyether of ethylene oxide (EO)and propylene oxide(PO).It was found that this new equation has much better correlation with the experimental data than the previous models reported in the literature.In addition,we evaluated the performnace of the single component surfactants and their blends(non-ionic PEO-PPO-PEO and anionic SDS)in deinking four different types of waste paper,namely,Chinese newsprint,American newsprint, Chinese used office paper and American used office paper.It was found that the non-ionic and anionic blend systems are significantly better than the single component surfactants.The blends are also more cost effective in applications.This thsis work provides good insight to the mechanisms involved in the use of surfactants in deinking applications and practical guidance for the development of effective surfactant systems.