【作者】 徐小琳；

【导师】 邵谦；

【作者基本信息】 山东科技大学 ， 矿物加工工程， 2007， 硕士

【摘要】 采用反应性乳化剂代替传统乳化剂制备无皂苯丙乳液，由于乳化剂参与聚合反应，成膜后成为膜的组成部分，因此可以解决传统乳液聚合产品中游离乳化剂的存在使涂膜耐水性、表面性质下降的缺点。将无皂苯丙乳液与无机纳米粒子复合制备无机纳米粒子／无皂苯丙复合乳液，可综合无皂乳液涂膜耐水性好和无机物高刚性、高强度的优点，使乳液具有更优异的性能。本文首先研究了反应性乳化剂存在下的无皂苯丙乳液聚合。根据各单体的作用及对乳液性能的影响，确定了苯乙烯、甲基丙烯酸甲酯、丙烯酸丁酯、丙烯酸、丙烯腈五元单体共聚体系，以赋予乳液涂膜较高的硬度。在反应性乳化剂SE-10N的存在下，通过正交实验和单因素实验，研究了丙烯酸、丙烯腈、反应性乳化剂、引发剂的用量及甲基丙烯酸甲酯与苯乙烯的质量比、聚合温度等因素对乳液性能的影响，确定了合成无皂苯丙乳液的组成及条件为：相对于体系总投料量，St为15.2％，MMA为9.9％，AN为3.7％，n-BA为15.6％，AA为2.3％，反应性乳化剂为0.9％，引发剂为0.3％，链转移剂为0.9％，缓冲剂为0.2％，聚合温度为85℃。在此基础上，采用预乳化半连续种子乳液聚合工艺，将改性无机纳米粒子与无皂苯丙乳液复合，原位合成了无机纳米粒子／无皂苯丙复合乳液。通过无机纳米粒子种类的选择及正交实验，对聚合条件进行了优化，最终确定了合成纳米TiO₂／无皂苯丙复合乳液的工艺条件为：纳米TiO₂用量为单体总质量的1.5％，预乳化的混合单体占其总量的25.0％，种子乳液聚合阶段所加引发剂的量为引发剂总量的30.0％，聚合反应温度85℃。热分析实验表明所制得的复合乳液的热稳定性比未加纳米TiO₂粒子的无皂苯丙乳液高，且其性能总体上优于纳米TiO₂／有皂苯丙复合乳液，其中涂膜铅笔硬度可高达2H级，吸水率降低了29.0％，耐水性提高。透射电镜分析结果表明该复合乳液乳胶粒具有核壳结构，激光粒度分析仪的测定结果显示其乳胶粒的平均粒径为79.8nm。对该聚合体系进行了表观动力学及成核机理的研究。结果表明，种子乳液聚合阶段以吸附了乳化剂分子的改性纳米TiO₂粒子成核为主，在壳层聚合阶段则为胶束成核机理。体系的表观动力学方程为R_p=k[I]^0.15[E]^0.83[M]^0.69，表观活化能为104.3KJ·mol^-1。通过研究滴加速率对聚合反应表观速率的影响，引入动力学系数K，对乳液聚合过程的反应状态进行描述。结果表明，随着滴加速率的增加，反应逐渐由饥饿态向半充溢态转变直至间歇法代表的全充溢态。要使体系聚合状态保持在饥饿态，混合单体的滴加时间应控制在多于140min。此外，本文分别对以无皂苯丙复合乳液、无皂苯丙乳液及有皂苯丙复合乳液、有皂苯丙乳液为基料制备的水性乳胶涂料进行了性能测试。结果表明，反应性乳化剂与纳米TiO₂的复合可使涂层耐水性、耐洗刷性得到明显改善，其中用无皂苯丙复合乳液制备的涂料涂层耐水性达126小时不脱落、不起泡，且耐洗刷次数在10000次以上，涂料的性能明显提高。本文的研究为无机纳米粒子／无皂苯丙复合乳液的聚合及其应用提供了一定的理论及实验基础。更多还原

【Abstract】 The technique of styrene-acrylate emulsion polymerization using reactive emulsifier which can participate in polymerization and can become parts of the formed film after reaction in place of traditional emulsifier can solve the disadvantages of traditional emulsion products such as the film water resistance and surface properties declining because of the dissociative emulsifier existing. It is possible that emulsions with more excellent function can be prepared on condition that inorganic nano-particles are compounded with emulsifier-free emulsions. This kind of composite can combine the perfect film water resistance of emulsifier-free emulsions and high rigid and strength of nano-particles.The styrene-acrylate emulsion polymerization using reactive emulsifier was studied first, in order to obtain harder film, the five-unit system of styrene, butyl acrylate, acrylic acid, acrylonitrile and methyl methacrylate was chosen according to the monomers characteristics and roles played in emulsion system. Furthermore, influences of the concentration of acrylic acid, acrylonitrile, reactive emulsifier, initiator, monomer proportion between styrene and methyl methacrylate, polymerization temperature on properties of emulsion were studied through orthogonal test and single factor test using reactive emulsifier. The better experimental components and conditions that were gotten finally were : St was 15.2%, MMA was 9.9%, AN was 3.7%, n-BA was 15.6%, AA was 2.3%, reactive emulsifier was 0.9%, initiator was 0.3%, chain transfer agent（DDMC） was 0.9%, NaHCO₃ was 0.2%, polymerization temperature was 85℃.On the basis, using the technique of pre-emulsification semi-continuous seeded polymeriz -ation system, modified inorganic nano-particles/styrene-acrylate composite emulsions obtained by in-situ emulsion polymerization had been prepared. The polymerization conditions were opt -imized through the inorganic nanoparticles choosing and orthogonal test. The results showed that the pre-emulsification mixture was 25.0% of its total weight, the nano-TiO₂ was 1.5% of the total monomers weight, the initiator using in seeded polymerization was 30% of its total weight, the seeded polymerization temperature was 85℃were the best experimental conditions. The thermal analysis results showed that the composite latex film presented higher thermal stability than the latex film unmodified by the nano-particles, and its physical properties were superior to nano-TiO₂ / emulsifier-included styrene-acrylate composite emulsion on the whole. The film of the nano-TiO₂/ emulsifier-free styrene-acrylate composite emulsion had a hardness up to 2H grade, and the water absorption was reduced by 29% which indicated that the film water resistance was improved. The structure and the morphology of the composite emulsion particles had been characterized. The TEM images showed that the emulsifier-free composite emulsion particles had core-shell structure. The light scattering experiments showed that the average particle size of nano-TiO₂/ emulsifier-free styrene-acryla -te composite emulsion was 79.8nm.Furthermore, the apparent kinetics and particles nucleation mechanism of nano-particles / emulsifier-free styrene-acrylate composite emulsion were studied. The results showed that in the stage of seeded polymerization, the modified nano-TiO₂ particles adsorbed emulsifier were the predominant particle nucleation, in the stage of shell-polymerization, the nucleation mechanism was "micellar nucleation". The apparent kinetics equation was R_p= k[I]^0.15[E]^0.83[M]^0.69, and the apparent active energy of the polymerization system was 104.3kJmol"1. Through the study of the effect of different dropping speed on the rate of polymerization, the coefficient of apparent kinetics K was used to discuss the polymerization condition. The results showed that with the increasing of mixture dropping speed, the condition of polymerization changed from starved to semi-starved semi-flowed state, and untill over-flowed state of the batch process finally. If the polymerization wanted to keep starved condition steadily, the time of feeding should be longer than 140min.In addition, the physical properties of coatings which were prepared by using nano-TiO₂ / emulsifier-free styrene-acrylate composite emulsions, emulsifier-free styrene- acrylate emulsio -ns and nano-TiO₂/ emulsifier-included styrene-acrylate composite emulsions, emulsifier-inclu -ded styrene-acrylate emulsions respectively were tested. The results showed that compoundin -g of nano-TiO₂ and reactive emulsifier could improve the coating film water resistance and the scrub resistance. The film water resistance of coating that was prepared by using nano-TiO₂ / emulsifier-free styrene-acrylate composite emulsions was over 126h, and its scrub number was over10000, which indicated that the coating property was improved obviously.This study results provide some theoretical and experimental basises for the polymerizati on and application of inorganic nano-particles / emulsifier-free styrene-acrylate composite emulsion.更多还原