The Influence Of Emulsifier On Emulsification And Sizing Of Cellulose-Reactive Sizing Agent

With the increase of papermachine speed and wide application of retention aid, cationic sizing emulsions have been lost their superiority. At the same time, emulsifying sizing agents with anionic polymers not only reduce the charge amount of emulsifiers, but also can prepare emulsions with high solid content. In view of this, various polysaccharides with different functional groups or charge density were used as emulsifiers of ASA and AKD (reactive sizing agent). Their performance on emulsifying the reactive sizing agent, the sizing effects of the emulsions was investigated and compared with those of cationic starch and cationic starch stabilized emulsions. The optimum condition for emulsifying AKD, the properties of the emulsions and the factors influence the sizing performance of AKD emulsions were studied. The function of urea as an emulsifying and sizing promoter was investigated.The effect of short amines on emulsification and sizing were analyzed.The results show thtat a stable ASA emulsion with uniform droplet size could be prepared using oxidized starch as emulsifier under proper conditions. At the same conditions, the ASA emulsion stabilized by the oxidized starch had the smallest particle size, similar sizing efficiency compared with those stabilized by cationic starch. The optimized condition for oxidized starch to emulsify ASA is as follows: the dosage of emulsifier was 20%, ASA to water ratio was 1:3, the emulsification rate is 4000rpm and the time was 3 min.The carboxyl groups of CMC within certain amount may promote the emulsification and sizing performance of ASA. However, large amount of carboxyl groups may promote ASA hydrolysis and damage the emulsification. Methoxyl cellulose (MC) could not promote the sizing degree of ASA but the emulsion. Chitosan played a negative action on ASA emulsion. In addition, it was speculated that Al3+ enhanced the sizing degree of ASA sized handsheets not only by acting as a retention agent but also binding with ASA hydrolysis products.At the same condition, MC with a substituted degree of 0.9, MC with a viscosity of 800 mPa·s and chitosan with viscosity of 1000 mPa·s have excellent emulsification effect on melted AKD. The obtained emulsions are uniform and have small particles, and also show good sizing performance. They all get their best emulsification effects at the dosage of 6% and an AKD to water ratio of 1:5, where the AKD emulsions are uniform and have good sizing performance. It is also found that short amines have negative effects on AKD emulsification when CMC and MC are used as emulsifiers. CMC can promote the emulsification of AKD when used with chitosan, and the best dosage of CMC with the substituted degree of 0.9 is15% based on chitosan.Ethylamine and butylamine can't promote the emulsification and sizing development of ASA. Urea promotes both the stability and sizing performance of ASA emulsions. The sizing degree of ASA sized handsheets increased with the dosage of urea. Besides, the retention system also influences the sizing performance. CPAM/Laponite retention system performs better than CPAM/bentonite retention system.