Stability of acrylic latices in a semibatch reactor

The effects of various reaction variables on the stability of acrylic latices in a semibatch reactor were investigated by measuring the amount of coagulum formed and particle volume changes caused by limited flocculation. The amount of coagulum could be reduced signif-icantly with an increase in the level of sodium lauryl sulfate (SLS) in the monomer emulsion feed. An increase in the amount of SLS in the initial reactor charge resulted in an increase in the particle volume change due to limited flocculation later in the process. The larger the ratio of methyl methacrylate (MMA) to butyl acrylate (BA) in the copolymer, the greater the amount of coagulum produced. Both coagulum and particle volume change increased with an increase in the electrolyte concentration. Within the range studied (500–800 rpm), the agitation speed was not important to the coagulation process. Experimental data also indicated that the polymer particles could lose their stability rapidly above 40% total solids content because of the crowding effect. © 1996 John Wiley & Sons, Inc.     

Stability of nanoparticles during semibatch emulsion polymerization of butyl methacrylate,in the presence of methacrylic acid via RSM

The size and stability of latex particles in the semibatch emulsion polymerization of butyl methacrylate (BMA), in the presence of 0–10% methacrylic acid (MAA), were investigated. Response surface methodology (RSM), as a design of experiment, was used to obtain a more systematic understanding of the role of emulsifier and MAA in the stability of the particles. The amount of coagulum can be greatly reduced by increasing the concentration of sodium lauryl sulfate (SLS) in the monomer emulsion feed (MEF) and initial reactor charge (IRC). On the other hand, increasing the concentration of SLS in the IRC can result in a decrease of the particles size. According to the experimental data, the yield of reaction can be improved with incorporation of MAA into the emulsion polymers. The size and morphology of particles were obtained by scanning electron microscopy (SEM). FTIR and titration were used to determine the percentage of MAA in the copolymer. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Semibatch emulsion copolymerization of methyl methacrylate and butyl acrylate

The concentration of sodium lauryl sulfate (SLS) in the initial reactor charge is the most important parameter in determining the particle size of a semibatch emulsion copolymerization of methyl methacrylate (MMA) and butyl acrylate (BA). The number of particles formed is proportional to the concentration of SLS to the 0.5–1.2 power and it is proportional to the concentration of the nonyl phenol–40 mol ethylene oxide adduct to the 0.014–0.72 power. The number of particles is almost independent of the concentration of the initiator. The solubility of monomer in water has an important effect on the nucleation mechanism according to the literature. However, the ratio of MMA to BA does not show any significant effect on the latex particle size in our laboratory. The particle size also increases with increasing ionic strength or agitation speed. Experimental data of particle-size distribution and molecular weight distribution support the coagulative nucleation mechanism when the concentration of SLS is way below its critical micelle concentration (CMC). © 1995 John Wiley & Sons, Inc.     

有机硅/丙烯酸酯乳液的粒径与分散行为研究

采用半连续乳液聚合法合成了以丙烯酸丁酯和甲基丙烯酸甲酯为成核单体,丙烯酸丁酯(MAA)、甲基丙烯酸甲酯(BA)、丙烯酸(AA)和γ―甲基丙烯酰氧基丙基三甲氧基硅烷为成壳单体的核壳结构乳液。采用马尔文纳米粒度仪等研究了乳液的粒径及其分布与引发剂和乳化剂用量之间的关系,粒径对乳液稳定性的影响以及乳液粒径与温度的关系,通过透射电镜对乳液微粒形态进行了分析。结果表明,乳液的粒径随着引发剂和乳化剂用量的增加而减小,乳液粒径在30～60℃时较为稳定,当引发剂过硫酸铵质量分数为0.55%,乳化剂十二烷基苯磺酸钠质量分数为2%时,制得的乳液粒径在120 nm左右,具有明显的核壳结构和较好的稳定性。     

Preparation and characterization of stable and high solid content St/BA emulsifier-free latexes in the presence of AMPS

Stable and high solid content (about 50 wt%) St/BA emulsifier-free latexes were successfully synthesized using emulsifier-free emulsion polymerization with the addition of a small amount of reactive emulsifier AMPS. Properties of the latexes, such as the average particle diameter and its distribution, the morphology of latex particles, and stability were investigated. Physical properties of the latex films, i.e., glass transition temperature (T _g), water resistance, and solvent resistance were investigated as well. The size of latex particles is 400–600 nm in diameter, which is larger than that prepared by conventional emulsion polymerization. And the particle size distribution is narrow and uniform. It was found that the diameter of the latex particles decreases with the increasing content of the initiator KPS and the reactive emulsifier AMPS. Compared with the film prepared by conventional emulsion polymerization, water resistant and solvent resistant of the films prepared by emulsifier-free emulsion polymerization are improved greatly.     

Emulsifier‐minor emulsion copolymerization of BA‐MMA‐St‐MAA (or AA)‐N‐MA

A novel emulsion polymerization technique referred to as emulsifier‐minor emulsion polymerization was achieved by the copolymerization of methyl methacrylate, butyl acrylate, and styrene (MMA‐BA‐St) with a combination of water‐soluble ionic monomers [methacrylic acid (MAA) or acrylic acid (AA)] and nonionic monomers (N‐methylol acrylamide). In the technique, water‐soluble monomers play a crucial role in the stabilization of the latex particles as they can be bound to the particle surface and form a hydrate protective layer, which exhibits steric and/or electrostatic effects to prevent particle coagulation. The minor but over its critical micelle concentration emulsifier sodium alkylated diphenyl ether disulfonate (DSB) results in the nucleation of particles mainly by the micelle nucleation mechanism and thus determines the polymerization rate, the particle size, and the number. The film water resistance of the latices can be improved, and the foaming capacity of can be lowered by using technique instead of conventional emulsion polymerization. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 2923–2929, 2004     

醋酸乙烯-丙烯酸无皂乳液共聚的研究

研究了以醋酸乙烯(VAc)为主单体,丙烯酸(AA)为改性功能单体,以“半连续”加料方式进行无皂乳液共聚合过程,得到了稳定的乳液。并探讨了功能单体AA含量、反应温度等对共聚的影响。采用FTIR、粒度分析等方法对共聚物的组成、乳胶粒子的尺寸及分布进行了分析表征。结果表明:在(65±2)℃的温度下聚合,所得乳液稳定性好、转化率高,反应完全,且随着功能单体AA含量的增加,乳液粘度上升,单体转化率下降,乳胶粒粒径变小且粒径呈单分散性。     

St-BA-BVP无皂共聚物阳离子乳胶粒大小及形态研究

合成阳离子共单体 1-丁基 ,4 -乙烯吡啶溴化铵 ( BVP) ,并以偶氮二异丁基咪盐酸 ( A IBA)作引发剂 ,制备苯乙烯 /丙烯酸丁酯 ( St/ BA )共聚物乳液 ,通过 TEM研究改变 BVP的浓度、St/ BA主单体的配比及单体加料方式对 P( St/ BA / BV P)乳胶粒大小形态的影响 ,结果表明批量法和单体全滴加法制备的乳胶粒形状规则、分布均匀、半连续法制备的乳胶粒子呈多分散分布 ,粒径相差很大 ,且 P( St) / P( BA)得到的乳胶粒呈明显的核壳结构。     

An investigation of the emulsion terpolymerization of 2-ethylhexylacrylate–vinyl acetate–acrylic acid

An investigation of the emulsion polymerization of 2-ethylhexylacrylate (EHA)—vinyl acetate (VAc)—acrylic acid (AA) has been done. It was found that the polymerization rate depends on the AA level and that particle nucleation occurs throughout the entire conversion range. At the 5% AA level, there is significant coagulation. The number of particles depends on the balance between nucleation and coagulation. Addition of a small amount of water-soluble comonomer has no significant effect on the course of polymerization, but the viscosity of the latex can increase significantly. The dependence of latex viscosity on pH on neutralization has been studied. The maximum viscosity reached on neutralization depends on the acrylic acid level and the semibatch policy used in the latex synthesis. Addition of salt is a simple and effective way to control viscosity buildup during neutralization.     

Semi-continuous emulsion copolymerization of vinyl acetate and butyl acrylate in presence of AMPS

The emulsifier-free emulsion polymerization of vinyl acetate (VAc) and butyl acrylate (BA) in the presence of 2-acrylamido-2-methylpropane sulfonic acid (AMPS) was carried out by a semi-continuous process. AMPS was a reactive surfactant in the aqueous emulsion, due to its amphiphilic structure and the unsaturated double bonds. Potassium persulfate (KPS) was used as initiator. The following factors were mainly examined: quantity of AMPS, BA and KPS concentrations, which could significantly affect the particle size and its distribution, conversion, gel content, minimum film-forming temperature, etc. The particle size and its distribution were characterized by dynamic laser particle size analyzer, and morphology of the latex particles was characterized by transmission electron microscopy (TEM). Fourier transform infrared spectroscopy was used to characterize chemical structure of copolymers. The results indicated that AMPS was successfully reacted onto the resulted copolymer of vinyl acetate and butyl acrylate. A hydrophilic sulfonic acid group in the molecular structure of AMPS tended to be distributed in particles surface after polymerization. As a result, an electrostatic repulsion between the particles was produced in order to maintain stability of the system. Thermogravimetric analysis curves suggested that as BA content increased, thermal stability of the polymer increased accordingly. The conversion-time plots with varying AMPS and initiator contents were obtained, which illustrated that the initiator concentration could greatly influence the polymerization rate and the final conversion. The TEM micrographs of the final emulsifier-free latex particles for P(VAc/BA/AMPS) system revealed small particle size in monodisperse polymer latex. The particles of the latex were measured as about 150 nm.     

超高相对分子质量聚乙烯纤维粘合涂层用水乳型聚丙烯酸酯微乳液的合成

以甲基丙烯酸甲酯(MMA)、丙烯酸丁酯(BA)、丙烯酸(AA)及丙烯酸羟乙酯(HEA)为单体,以十二烷基硫酸钠(SLS)、OP-10和正辛醇的复合物为乳化剂,当m(BA)∶m(MMA)∶m(AA)∶m(HEA)=50∶50∶3∶10、w(乳化剂)=13%、反应温度为80℃及反应时间为3h时,合成了可用于超高相对分子质量聚乙烯纤维粘合涂层的水乳型聚丙烯酸酯微乳液,单体转化率为99 8%,乳胶粒径为30nm,乳液膜的玻璃化温度为-28℃,应用工艺简单,涂层粘附性好、柔软、耐磨。     

VAc/MA/AA三元无皂乳液共聚的研究

以过硫酸钾(KPS)为引发剂,对VAc/MA/AA三元无皂乳液共聚进行了研究。探讨了引发剂用量、功能单体用量(AA)对乳液稳定性、胶乳粒子粒径、粒径分布及胶乳粘度、粘接强度等性质的影响。结果表明: 引发剂用量小于单体总质量的0．7％时,随着KPS用量的增加,胶乳粒子粒径减小,粒径分布变窄;引发剂用量大于单体总质量的0．7％时,随着KPS用量的增加,胶乳粒径及分布都增大,KPS用量为单体总质量的6％时,单分散性好;共聚乳液的粒径随AA用量的增加而增加,粒径分布则随AA用量的增加而减小,乳液粘度随AA用量增大而降低,而粘接强度随AA用量增大而增加,耐水性下降。     

Using anionic polymerizable surfactants in ultrasonically irradiated emulsion polymerization to prepare polymer nanoparticles

An ionic polymerizable surfactant, sodium sulfopropyl‐laurylmaleate (M12), was synthesized and used as an emulsifier, an initiator, and a comonomer in ultrasonically irradiated emulsion polymerization. FTIR spectra and gravimetric method results indicated that copolymers P(Styrene‐M12) and P(Butylacrlate‐M12) were prepared successfully by ultrasonically irradiated emulsion polymerization and the composition of M12 elevated with the increasing concentration of M12 added. TEM photographs of P(St‐M12) showed that the nanoparticles with small diameters (20–45 nm) were prepared. With the increase of M12 concentration, the particle size became smaller and the size distribution became wider. The P(BA‐M12) particles size was also small (<100 nm) but the size distribution was wide due to the high reactivity of BA. Because surfmer M12 was chemically bonded with the latex particles, the stability of the copolymer latex prepared by ultrasonically irradiated emulsion polymerization was much better than that of the homopolymer latex (PSt or PBA) prepared by the same way. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Role of acrylic acid in the synthesis of core‐shell fluorine‐containing polyacrylate latex with spherical and plum blossom‐like morphology

The core‐shell fluorine‐containing polyacrylate latex was successfully synthesized by two‐stage semicontinuous emulsion copolymerization of methyl methacrylate (MMA), butylacrylate (BA), acrylic acid (AA), and dodecafluoroheptyl methacrylate (DFMA). The fluorine‐containing polyacrylate latex was characterized by Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), dynamic light scattering (DLS), zeta potential, thermal gravimetric analysis (TGA), differential scanning calorimetry (DSC). The effects of AA content on monomer conversion, polymerization stability, particle size, corsslinking degree, carboxyl groups distributions (latex surface, aqueous phase or buried in latex), as well as mechanical properties and water absorption rate of latex film were investigated. The obtained fluorine‐containing polyacrylate latex exhibited core‐shell structure with a particle size of 120–150 nm. The introduction of AA was beneficial for the increase of monomer conversion and the polymerization stability, and had little effects on the mechanical property of latex film. However, the hydrophilicity of AA made the water resistance of latex film get bad. With the increase of AA content, the carboxyl groups preferred to distribute on aqueous phase, and the possibility of homogeneous nucleation increased and more oligomers particles were formed. Moreover, the oligomers would distribute to the latex and continued to grow up, making the latex morphology changed from spherical to plum blossom‐like. The core‐shell latex had two T_g corresponding to the rubber polyacrylate core and hard fluorine‐containing polyacrylate shell, and the latex film possessed excellent thermal stability. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42527.     

Characterization of carboxylated poly(butyl acrylate) latices produced by a semibatch process

Several carboxylated poly(butyl acrylate) latices prepared by a semibatch emulsion poly-merization process were characterized in this study. A significant amount of polyelectrolyte was found in the latex product containing 10% AA, designated as AA10. On the other hand, latices containing 0.1% AA (AA0.1), 0.1% MAA (MAAC.1), and 10% MAA (MAA10) showed very low levels of polyelectrolyte in water. Based on the critical flocculation concentration data, it can be concluded that incorporation of 10% AA or 10% MAA into the emulsion polymers can greatly improve the chemical stability of the latex products, especially at higher pH. The data of the pH and conductometric titration experiments show that the MAA unit can be distributed more uniformly in the latex particles in comparision with the AA unit. This result is further confirmed by determination of the T_g's of the emulsion polymers by means of thermally stimulated current (TSC). © 1996 John Wiley & Sons, Inc.     

Acrylic latices stabilized by polymerizable non-ionic surfactant

The final latex particle size is controlled by the concentration of polymerizable non-ionic surfactant NE-40 in the emulsion copolymerization of methyl methacrylate (MMA) and butyl acrylate (BA). The particle size decreases with increasing NE-40 concentration and increases with increasing persulphate initiator concentration. The dependence of particle size on the initiator concentration does not follow conventional Smith–Ewart theory, which is attributed to the bridging flocculation process during the particle nucleation period. The differences in the particle nucleation and growth stages and colloidal stability observed in the NE-40 and nonyl phenol-40 mol ethylene oxide adduct (NP-40) stabilized systems can be attributed to the different distribution patterns of surfactant molecules in the particles. Experimental data also indicate that the particle size decreases with increasing electrolyte concentration, or agitation speed. The total scrap, presumably caused by the bridging flocculation process, increases rapidly with increase in the NaCl concentration The amount of large flocs formed during polymerization is generally greater for the run operated at higher agitation speed. As expected, the latex products stabilized by non-ionic surfactants show excellent stability toward added sodium salt.     

高固含量的苯乙烯/丙烯酸丁酯/丙烯酸共聚物乳液的制备

利用预乳化半连续乳液聚合方法,合成了固含量高达65%的苯乙烯/丙烯酸丁酯/丙烯酸(St/BA/AA)聚合物乳液,并系统研究了固含量、单体配比、乳化剂含量、引发剂浓度、聚合反应温度及功能单体浓度对聚合物乳液主要性能的影响,利用透射电子显微镜对乳胶粒子的微观形态进行了表征。     

含缩水甘油基／氨基丙烯酸酯共聚物乳液的聚合稳定性

研究了乳胶粒组成对含有缩水甘油基,羧基和胺基的丙烯酸酯多层核壳型乳液聚合稳定性的影响规律,探讨了聚合过程的凝聚机理。研究表明：官能团间的交联凝聚作用和水溶性聚合物的架桥凝聚作用是本体系凝聚物形成的主要原因。     

The influence of monomer types on the colloidal stability in the miniemulsion copolymerization involving alkoxysilane monomer

Unlike conventional emulsion polymerization, monomer droplet nucleation becomes dominant in miniemulsion polymerization, offering the miniemulsion polymerization a great advantage over conventional emulsion polymerization when incorporating alkoxysilane monomer, which can easily undergo premature hydrolysis and condensation reactions, into polymer latex. The extensive premature hydrolysis and condensation can lead to the issue of the colloidal instability. In this article, the influence of monomer types on the colloidal stability in the miniemulsion co-(or ter-)polymerization was investigated when incorporating alkoxysilane monomer into styrene or acrylate latex. In the cases of butyl acrylate (BA)/γ-methacryoxypropytrimethoxysilane (MPMS), BA/methyl methyacrlate (MMA)/MPMS, and BA/styrene (St)/MPMS miniemulsion polymerization, nearly no coagulum was observed. The obtained latex had a long shelf life. However, the coagulum was formed in the late stage of MMA/MPMS and St/MPMS miniemulsion copolymerization. The shelf life of the corresponding latex was short. The selection of the main monomer, which can fast consume alkoxysilane comonomer, was critical to obtain the stable latex. In this way, the alkoxysilane groups were completely buried in particles thus the coagulation caused by condensation reactions derived from the alkoxysilane hydrolysis among particles was suppressed.     

Synthesis of a latex with bimodal particle size distribution for coating applications using acrylic monomers

Multipart emulsion polymerization of methyl methacrylate (MMA) and butyl acrylate (BA) was carried out in this work. The target was to achieve stability during the polymerization and to determine the proper hydrophilic–lipophilic balance (HLB) value for the stable system, using different types of non-ionic emulsifiers, sodium lauryl sulphate and their combinations. After determination of proper value of HLB (36.2), the best emulsifier combination on the basis of minimization of coagulum level was determined. This combination was 20 wt.% of KENON30 to SLS. The effect of monomer feed composition on the dry latex film properties was investigated to approach a monomer feed composition dealt with a proper T_g. The prepared latex showed a bimodal particle size distribution, due to the proper feeding policy in semibatch emulsion copolymerization process. The monomer feed composition of 45 wt.% MMA and 55 wt.% BA with a proper T_g was selected for the final improvement of coating properties such as UV resistance and adhesion. Adding acrylic acid (AA) and N-methylol acrylamide (NMA) to the reaction mixture improved the UV resistance and adhesion property of dry latex film. The flow and leveling, gloss, adhesion, UV resistance and water resistance of the produced bimodal latex showed good quality in comparison with the similar commercial resins used in coating applications.