核/壳乳液聚合工艺中乳化剂的定量研究

以十二烷基硫酸钠(SDS)为乳化剂,采用多步种子乳液聚合方法制备了核/壳结构乳液,研究了乳化剂加入量以及加料速率对核壳乳液聚合的影响,并推导了核及壳乳液聚合阶段所需乳化剂量的计算公式.研究表明,当种子、核、壳乳液聚合阶段单体量分别为12g、50g和50g,种子乳液聚合阶段加入的乳化剂量为0.44g时,控制核、壳乳液聚合阶段乳化剂的加入量分别在0.64～2.07g及0.04～2.12g之间,且预乳化单体的滴加速度低于2.3g/min时,可以防止二次成核及新乳胶粒子的形成,制得粒径分布窄、核/壳结构明显的乳胶粒子.利用透射电镜(TEM)对所制备的核壳结构乳胶粒子的结构形态进行了验证,试验结果与理论预测结果一致.

STUDY OF THE AMOUNT OF SURFACTANT IN THE CORE-SHELL EMULSION POLYMERIZATION

In order to prepare a core-shell structure latex with a narrow size distribution and without the secondary nucleation to form new latex particles,a method was given for calculating the amount of surfactant,sodium dodecyl sulfate(SDS),in the process of multi-step seeded semi-continuous emulsion polymerization.From the total area of soap adsorbed particles and the effective molecular surface area of the soap,the above quantities can be calculated.In this method,the number of particles was the weight of monomer divided by the average particle weight,the seed particle density and average particle size could be measured by weighing strips of particles of measured volume and TEM,and the effective molecular surface area of the soap could be determined by soap titration.The influence of the amount and dropping speed of surfactant in every polymerization stage on the particles structure was studied.The amount of surfactant needed in the second and third polymerization stage was decided by both the amount surfactant added in the seeded polymerization and the particle size of seeds.A core-shell latex was synthesized with a narrow size distribution and without secondary nucleation when the amount of monomer for the seed,core and shell was 12 g,50 g and 50 g,the amount of surfactant was 0.4 g,0.64～2.07 g and 0.04～2.12 g,respectively,and the dropping speed of pre-emulsified monomer was below 0.021 mol/min.The core-shell morphology,size distribution of the final latex were confirmed by TEM analysis.