高固含量乳液聚合中的表面活性技术研究进展

如何提高乳胶产品固含量及其性能一直是乳液制备工作所追求的重要目标。乳液聚合中可以使用各种乳化剂,也可不用乳化剂,但都必须使乳胶粒子表面具有亲水性即表面活性,因此,乳液聚合中的原理与技术实际上可以归结为使乳胶粒子表面具有亲水性即表面活性技术。各种研究表明,采用不同乳化剂和表面活性技术所制备的乳胶性能差别很大,合适有效的表面活性技术不仅大幅度提高聚合物乳液的性能,还可以缩短反应时间,简化制备工艺。本文详细评述了近几年来高固含量乳液聚合中常规乳化剂、可聚合乳化剂、复合乳化剂和表面活性单体及其与之相应的表面活性技术的研究现状,并对高固含量乳液乳化剂的发展进行了展望。     

马来酸类可聚合乳化剂的合成及其在细乳液聚合中的应用

采用三步法合成了可聚合乳化剂马来酸单十六醇酯丙基磺酸钠.并用正交实验法优化了马来酸单十六醇酯合成工艺条件,结果表明反应的最佳条件为:催化剂质量分数1%,反应时间3.0h,反应温度90℃,马来酸酐与十六醇的摩尔比1.1:1.苯乙烯-丙烯酸丁酯细乳液聚合使用该乳化剂与传统乳化剂相比,在较低温度下(65℃)具有较高的转化率,且所得乳液具有较好的电解质稳定性,乳胶膜的耐水性也得到提高.     

可聚合非离子型乳化剂稳定的聚丙烯酰胺反相胶乳

近年来，新型可聚合乳化剂的研制及应用引起了人们的极大兴趣［１～４］．目前报道的可聚合乳化剂都是水溶性的，用于正相乳液聚合中改善聚合物膜的性能及聚合物的加工性能［１］，提高聚合物胶乳的稳定性以及制备功能化乳胶粒子等［５，６］．本文合成了油溶性可聚合非离...     

复合微乳液聚合制备P(MMA-UA)纳米乳胶粒子的研究

将聚氨酯预聚体可聚合乳化剂 (APUA)和甲基丙烯酸甲酯 (MMA)的复合微乳液体系 ,分别用水溶性过硫酸钾 (K2 S2 O8)和油溶性偶氮二异丁腈 (AIBN)作引发剂 ,进行微乳液聚合研究 ,制备了P(MMA UA)复合纳米乳胶粒子 .研究了APUA用量、聚合温度对聚合动力学的影响 ;用透射电子显微镜 (TEM)观察了不同乳化剂浓度及引发剂体系对胶粒形态、大小及分布的影响 .结果表明 ,用可聚合乳化剂APUA可制得稳定性很好的P(MMA UA)纳米级核 壳型乳胶粒子 ,乳胶粒径在 5 0nm左右 .随着乳化剂用量增加 ,粒子变小 ;不同类型的引发剂对胶乳的性质有较大影响 ,以APUA为乳化剂 ,K2 S2 O8为引发剂 ,在聚合反应过程中或在聚合反应后的放置中 ,会出现P(MMA UA)的纳米水凝胶 (Nanogel)现象 .     

活性/可控自由基无皂乳液聚合

活性自由基聚合与无皂乳液聚合都是近年来研究的热点课题,而活性自由基无皂乳液聚合兼具两种聚合方法的优点,有着重要的理论研究意义和广泛的工业应用前景.目前,实现活性自由基无皂乳液聚合主要通过两种途径:一是先利用活性自由基聚合方法制备含有活性引发基团的水溶性或两亲性聚合物,将这类聚合物溶解或分散在水中,无需加入其他乳化剂的条...     

含氨基、羟基丙烯酸乳液聚合的稳定性

采用间歇及半连续乳液聚合方式,以过硫酸铵/亚硫酸钠为引发体系,合成了甲基丙烯酸甲酯/丙烯酸丁酯/甲基丙烯酸羟乙酯/甲基丙烯酸二氨基乙酯四元共聚物胶乳.系统研究了乳化剂种类和浓度、聚合温度、乳化单体进料方式及进料速率对聚合过程稳定性的影响.聚合温度降低,乳化单体进料速度减慢有利于聚合过程的稳定,采用种子半连续聚合方式比间歇聚合过程更稳定,乳化剂浓度的增加有利于聚合稳定性的提高和乳胶粒子的均匀化.     

高固含量微乳液聚合的研究进展

微乳液聚合能够制备透明稳定的微胶乳,在涂料、催化及药物输送等领域具有许多潜在的应用.本文综述了高固含量微乳液聚合的研究现状,主要介绍了两类方法:高效乳化剂体系的应用和聚合工艺的改进,并对今后的发展方向进行了展望.     

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.     

多乙烯基硅油改性丙烯酸酯乳液的合成及性能

以自制阳离子型乳化剂H、多乙烯基硅油和丙烯酸类单体为主要原料,采用一步法和半连续种子乳液聚合法合成有机硅改性丙烯酸酯乳液。研究了不同聚合方法、不同有机硅含量对硅丙乳液乳胶膜的吸水率、疏水性能的影响,通过纳米粒度-Zeta电位分析仪、接触角仪、红外光谱、透射电镜对乳液及聚合物结构进行了表征。结果表明有机硅单体参与了聚合,乳液稳定性好、平均粒径小。采用半连续种子乳液聚合法合成乳液,有机硅最大添加量为40%(占壳层单体总量),乳胶膜的吸水率只有3.2%,对水的接触角达到105.2o。     

阳离子可聚合表面活性剂的研究进展

可聚合表面活性剂含有可聚合基团,以牢固的共价键键合到聚合物粒子上,成为聚合物的一部分,有效避免了表面活性剂的解吸及其在乳胶膜中的迁移,减少了乳胶膜表面的亲水基团,可以克服传统表面活性剂的许多弊端。阳离子可聚合表面活性剂主要为季铵盐,其容易吸附于一般固体表面,其水溶液一般有优异的杀菌性。本文综述阳离子可聚合表面活性剂,根据不同方式对其进行分类,分别介绍聚合基团不同的阳离子可聚合表面活性剂的合成和应用现状,并对其应用前景作了展望。     

A Facile One‐Step Method to Prepare Three‐Dimensional Ordered Latex Particles

Three‐dimensional ordered latex particles were prepared in presence of polymerizable anionic emulsifier—sodium undec‐10‐enoate (UDNa) in emulsion polymerization. Only under a certain monomer/emulsifier ratio can we get such a result. Three‐dimensional ordered latex particles cannot be acquired with the use of conventional emulsifiers such as sodium dodecyl sulfate (SDS), etc. The double bond of polymerizable emulsifier can copolymerize with the main monomer and become covalently bound to integrate with the main polymer chains which result in stable latexes. TEM and SEM images show that whether it is diluted or not the latexes can always keep in the three‐dimensional regularly order.     

St-BA copolymer emulsions prepared by using novel cationic maleic dialkyl polymerizable emulsifier

A novel polymerizable cationic dialkyl maleic emulsifier with 12 carbon atomic hydrophobic chain lengths (R = C₁₂H₂₅) as well as a similar conventional cationic emulsifier, cetyltrimethyl ammonium bromide (CTAB) as comparison, were investigated in batch emulsion copolymerization of styrene and butyl acrylate. A series of emulsion samples have been prepared with two kinds of emulsifiers, and their properties have been characterized and compared. Compared with the emulsions prepared by using cationic CTAB emulsifier, the emulsions prepared by using maleic emulsifier have larger particle size, higher surface tension, generally more stable on certain electrolytes and less water absorption ratio as 34.87% after 30 days vs. 50.65% for the emulsion containing CTAB emulsifier. Whereas, the maleic emulsifier itself has lower CMC and surface tension compared with cationic CTAB emulsifier.     

STUDY ON THE POLYMERIZATION KINETICS AND STABILITY OF P(UA)/MMA MICROEMULSION*

 Urethane acrylate anionomer (APUA) as a kind of new type polymerizable emulsifier was synthesized using 2,4-toluene diisocyanate (TDI), polypropylene glycol (PPG), 2-hydroxyethyl methacrylate (HEMA) and dimethylolpropionic acid (DMPA). The critical micelle concentration (CMC) of APUA was measured by the methods of conductance and surface tension. The comparative studies between polymerizable emulsifier AUPA and conventional emulsifier sodium dodecyl sulfate (SDS) were carried out in the emulsion polymerization of methyl methacrylate (MMA). Polymerization kinetics,stability, size and morphology of the latex particles were investigated. It was found that in APUA both water soluble initiator potassium persulfate (KPS) and oil soluble initiator 2,2'-azobisisobutyronitrile (AIBN) can start the reaction of MMA, and the polymerization rate and yield were very high. On using AIBN as an initiator, the conversion-time behavior of MMA with APUA as emulsifier was different to that of SDS as emulsifier, signifying a different nucleation mechanism of the polymer latex particle. The average size of the two kinds of particles is about 50 nm. The particle size decreases with increasing emulsifier concentration. On using KPS as the initiator, APUA as emulsifier, cross-linking hydrogel of PMMA would be formed, but SDS was used as emulsifier and the hydrogel of PMMA was not present.     

Properties and characterization of novel cationic polyacrylate latex containing fluorine and silicon prepared with soap-free emulsion polymerization

The novel cationic polyacrylate latex containing fluorine silicon was successfully prepared via soap-free emulsion polymerization of butyl acrylate, methyl methacrylate, vinyltriethoxysilane and hexafluorobutylmethacrylate in water phase, which were initiated with water soluble azo initiator and emulsified with the mixed surfactants polymerizable emulsifier and OP-10. The films of the resultant latex were characterized by Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and contact angle (CA) determinator, respectively. In comparison with the conventional polyacrylate latex, the thermal stability and water resistance of novel latex film are improved. The conditions of preparing the novel cationic acrylate latexes were optimized. The optimum conditions of preparing the novel latex are as follows: the amount of emulsifiers and the initiator are 6.0% and0.3%, respectively; both the amount of VETS and amount of HFMA are 6.0%. In this case, the conversion is high and the polymerization stability is good.     

Synthesis and characterization of covalently colored polymer latex based on new polymerizable anthraquinone dyes

Novel polymerizable red and yellow dyes, consisting of anthraquinone chromophore, alkyl spacer, and acryloyl group, were first synthesized and then used as comonomers in the semicontinuous emulsion copolymerization of styrene, butyl acrylate, and methacrylic acid to fabricate polymer latexes. The influences of the dye monomers on the emulsion polymerization process, the latex particle size and its distribution, the molecular weight of the latex polymer, as well as the light fastness of the polymer latex films, were investigated. Results indicated that, despite of the inhibition effect of the polymerizable dyes on polymerization, stable colored polymer latexes could be prepared with high conversion of total monomers, whereas the conversion of the polymerizable dye decreased as increasing the amount of dye. The light fastness of the covalently colored polymer latex films was proved to be much better than that of the noncovalently colored polymer latex films due to the covalent bond of dye and polymer chains.     

PREPARATION OF POLYSTYRENE/SiO2 COMPOSITE NANOPARTICLES BEARING SULFONIC GROUPS ON THE SURFACE VIA EMULSION COPOLYMERIZATION USING A POLYMERIZABLE EMULSIFIER

Functionalized PS/SiO_2 composite nanoparticles bearing sulfonic groups on the surface were successfully synthesized via emulsion copolymerization using a polymerizable emulsifierαolefin solfonate(AOS).As demonstrated by transmission electron microscopy and atomic force microscopy,well-defined core-shell PS/SiO_2 composite nanoparticles with a diameter of 50 nm were obtained.Sulfonic groups introduced onto the surface of the composite nanoparticles were quantified by FTIR,and can be controlled to some ex...     

Synthesis and Properties of Cationic Fluorinated Polyacrylate Soap-Free Latex

Cationic fluorinated polyacrylate soap-free latex (CFMBD) was synthesized by semi-continuous seeded emulsion polymerization of dodecafluoroheptyl methacrylate (DFMA), methyl methacrylate (MMA), butyl acrylate (BA), and dimethylaminoethyl methacrylate (DM) with a novel cationic polymerizable emulsifier, maleic acid double ester-octadecyl poly(ethyleneoxy)₂₀ ether-ethylene trimethyl ammonium chloride (R303), and 2,2′- azobis (2 - methylpropionamidine) dihydrochloride (VA-50) was utilized as the initiator. Effects of some factors, such as VA-50 amount, R303 amount and DFMA amount, on stability and average particle size of the CFMBD were discussed in detail, and the optimal polymerization condition was obtained. In addition, the emulsion and its film were characterized by Fourier transform infrared (FTIR) spectrometry, thermogravimetry analysis (TGA), contact angle goniometer, X-ray photoelectron spectroscopy (XPS), respectively. FTIR confirmed the structure of the CFMBD. With the increasing of DFMA amount, water absorption of the film decreased and water contact angle of the film increased. While the DFMA amount was more than 6 g in the recipe, the water contact angle (107.5°) and the water absorption (7.8 wt%) of the film showed no more changes. Meanwhile, thermal stability of the copolymer was greatly improved with the increasing of DFMA amount. XPS analysis indicated the fluoroalkyl groups had the tendency to enrich at the film-air interface.