含二十二烷基聚氧乙烯醚甲基丙烯酸酯功能单体的缔合型乳液增稠剂的制备及表征

以甲基丙烯酸、丙烯酸乙酯、邻苯二甲酸二烯丙酯和不同量的功能单体二十二烷基聚氧乙烯醚甲基丙烯酸酯(BEM)为原料,采用半连续乳液聚合方法合成了疏水改性碱溶性缔合型增稠剂乳液.测定了增稠剂乳液的粘度、透光率、乳胶粒粒径及其分布等性能,考察了不同固含量下乳液粘度和透光率随pH的变化情况.结果表明随着BEM用量的增加,乳胶粒粒径逐渐增大.随着pH值的增加,乳液的粘度首先迅速升高,然后缓慢下降.与不含BEM的增稠剂乳液相比,当乳液固含量大于0.5%,BEM含量占单体量低于5.0wt%时,该缔合型增稠剂的增稠效果和抗剪切性有显著提高,BEM含量较高(8.0wt%或更高)时反而使增稠效果和抗剪切性变差.在此基础上研究了增稠剂对苯丙乳液的增稠效应,结果显示BEM含量占单体量的2.5wt%时,对苯丙乳液的增稠作用最好.与使用功能单体三苯乙基苯酚聚氧乙烯醚甲基丙烯酸酯改性的增稠剂相比,含BEM的增稠剂在BEM用量较少的情况下就能起到明显的增稠效果.

Preparation and Characterization of Associative Latex Thickeners Using Behenyl Polyoxyethylene Ether Methacrylate as Functional Monomer

Hydrophobically modified alkali-soluble latex thickeners were prepared by semi-batch emulsion polymerization using methacrylic acid, ethyl acrylate, diallyl phthalate as the main monomers, with a varying amount of behenyl polyoxyethylene ether methacrylate (BEM) as functional monomer. Viscosity, light transmittance, particle size and its distribution of the thickener latexes were determined. Viscosity and light transmittance variations with pH were followed at different solids of the latexes. It was found that particle size increased with BEM content. Light transmittance of thickener latexes sharply increased when pH varied from 6.5 to 7.5, and remained relatively constant with continuing pH increase; while for the viscosity, a significant increase was also observed, this increase followed by a fast decline after a maximum. Compared with latex thickener without BEM, performance and shear resistance of the associative latex thickeners were enhanced when BEM content was below 5.0 wt% relative to total monomers mass and at 0.5 wt% solid or higher. However, performance and shear resistance of the thickeners bearing more BEM (8.0% or higher) were reduced. Thickening performance of thickeners for a latex of poly(styrene-acrylate) was investigated. Results showed that the samples done with 2.5 wt% BEM manifested highest thickening effect among all samples. Thickeners modified with BEM possessed higher thickening performance with less functional monomer than those prepared with triphenylethyl phenoxy polyoxyethylene ether methacrylate (SEM-25).