BEM含量对MAA-EA-MMA共聚物乳液的pH响应性研究

pH Response of Hydrophobic Modified Alkali Soluble Polymer Emulsion with Different Content of BEM

采用乳液聚合工艺合成了二十二烷基聚氧乙烯醚甲基丙烯酸酯(BEM)含量不同的疏水改性碱溶性甲基丙烯酸(MAA)-丙烯酸乙酯(EA)-甲基丙烯酸甲酯(MMA)聚合物乳液(HASE)。通过控制NaOH的加入量调节大分子链中MAA的中和度,即NaOH/MAA的物质的量比a,研究了pH值对HASE体系透光率和表观黏度的影响,分析了pH值在相态变化过程中的作用,以赫谢尔-巴尔克莱三参数流变方程模拟流变曲线,探讨pH值和BEM含量在pH值二次增加时对流变行为的影响。结果表明:pH值在NaOH/MAA的物质的量比a≈0. 3～0. 6时略降低; pH值最低时,亲水和静电斥力作用与疏水作用达到平衡,HASE分子由充分溶胀的乳胶粒子相态变为溶液; BEM含量增多,中和反应和相态转变的pH值越高;表观黏度、屈服应力、稠度系数和流变指数都存在pH (约为6. 7)敏感性,且BEM含量越多,敏感点的pH值越高。

The hydrophobic modified alkali soluble polymer emulsion(HASE)with different content of methylacrylic ester of ethoxylated(25 EO)C 22(BEM)were synthesized by emulsion polymerization method.Through controlling the mole ratio a of NaOH/MAA to adjust the neutralization degree of MAA in the macromolecular chain,the influence of pH on the transmittance and apparent viscosity of HASE system,and the function of pH in the process of phase transition were investigated.The rheological curves were simulated with three-parametric Herschel-Buckley model equation,and the effect of pH and BEM content on the rheological behavior at the secondary increase stage of pH was discussed.The results show that the pH value slightly decreases when the molar ratio of NaOH/MAA is 0.3 to 0.6,and the hydrophilic interaction and electrostatic repulsion are in balance with hydrophobic interaction at the lowest pH,meanwhile,the HASE molecule is turned into a solution from a fully swelled latex particle.The BEM content increases,the pH of the neutralization reaction and phase transition are higher;the apparent viscosity,yield stress,consistency coefficient and rheological index all have the sensitivity of pH(about 6.7),and the more BEM content,the higher the pH of the sensitive point.