W/W型PAM–MMT乳液的制备及性能研究

Study on Preparation and Characterization of the PAM–MMT W/W Emulsion

为了提高以明胶为稳定剂分散聚合制备的聚丙烯酰胺"水包水"(W/W型PAM)乳液的絮凝性能,首先,采用阳离子单体甲基丙烯酰氧乙基三甲基氯化铵(methacrylatoethyl trimethyl ammonium chloride, DMC)对钠基蒙脱土(sodium-montmorillonite, Na–MMT)进行插层改性制备有机蒙脱土(organic montmorillonite, OMMT),通过X射线衍射(X-ray diffraction, XRD)测试得到插层改性后蒙脱土的层间距由1.25 nm增加至1.43 nm,说明DMC单体已经成功插层进入蒙脱土片层。然后,将OMMT引入以明胶为稳定剂的W/W型PAM乳液的体系中,以制备W/W型PAM–MMT乳液。通过透射电镜(transmission electron microscope, TEM)乳液微观形貌进行观察,得到乳液结构是由以蒙脱土颗粒为"交联点"的聚丙烯酰胺高分子网络和W/W型PAM乳液的混合体。研究了OMMT用量、明胶浓度、体系pH值以及阳离子单体DMC添加比例对合成W/W型PAM–MMT乳液性能的影响规律。结果显示:在适宜条件下合成的乳液均具有较好的储存稳定性和在水中的再分散性。乳液的表观黏度和絮凝性能都与OMMT和明胶用量呈正相关性;当pH值在明胶等电点(isoelectric point,IEP)时,得到的乳液的表观黏度最低,絮凝效果最好;随着DMC单体用量比例增大,乳液表观黏度减小,高岭土悬浮液的絮凝效果先增大后减小。

In order to improve the flocculation ability of polyacrylamide(PAM),the organic montmorillonite(OMMT)was first prepared by the intercalation of methacrylatoethyl trimethyl ammonium chloride(DMC)into the interlayers of sodium montmorillonite(Na–MMT).X-ray diffraction(XRD)results showed that the interlayer space of Na–MMT is increased from 1.25 to 1.43 nm,which illustrated that DMC has intercalated into the interlayers of MMT.Then OMMT was introduced into the dispersion polymerization system of PAM W/W emulsion using gelatin as stabilizer to prepare PAM–MMT W/W emulsion.The microstructure of the emulsion was characterized through transmission electron microscope(TEM),and the result showed that the emulsion is a mixture of the polyacrylamide"crosslinked"by the MMT particles and PAM W/W emulsion.Effects of OMMT dosage,gelatin concentration,pH value and cationic monomer concentration on the properties of the PAM–MMT W/W emulsion were investigated,and the result showed that all the emulsion prepared under proper conditions have a good storage stability and re-dispersion ability in water.And the viscosity and flocculation ability both have a positive relationship with the OMMT dosage and gelatin concentration.When the pH value is at the isoelectric point(IEP)of gelatin,the emulsion has the lowest viscosity and best flocculation ability.With the increase of DMC concentration,the viscosity decreases,while the flocculation ability towards the kaolin suspension increases first and then decreases.