中空聚合物微球的制备——种子及核乳胶粒的制备

为了制得具有中空结构的聚合物微球,首先以十二烷基苯磺酸钠(SDBS)为乳化剂,在其用量低于CMC的条件下,进行甲基丙烯酸甲酯(MMA)、甲基丙烯酸(MAA)和丙烯酸丁酯(BA)的乳液聚合,制备了带羧基的种子乳胶粒.然后采用MMA、MAA和二乙烯基苯为单体进行种子乳液聚合,制备了轻度交联的带羧基的核乳胶粒.该核乳胶粒经过核-壳乳液聚合和适当的碱处理工艺就可成为具有中空结构的聚合物微球.采用粒度仪测定了乳胶粒的直径及其分布,采用TEM对乳胶粒结构形态进行了表征.研究了种子及核乳胶粒制备过程中单体加料方式、乳化剂用量及羧基单体种类等因素对聚合稳定性、乳胶粒直径及其分布以及最终的中空聚合物微球结构形态的影响,确定了制备种子及核乳胶粒的最佳工艺条件.在制备种子阶段,SDBS用量为单体总量的0.5%,采用一次性加入单体的进料工艺;在核乳胶粒制备阶段,以MAA为羧基单体,所有单体采用"饥饿式"加料,半连续补加乳化剂并使乳化剂用量为核单体总量的0.15%时可保持聚合稳定性并保证无新乳胶粒生成.     

Stability of carboxylated poly(butyl acrylate) latices during semibatch emulsion polymerization

The stability of latex particles in the semibatch emulsion polymerization of butyl acrylate (BA) in the presence of 0–10% acrylic acid (AA) was investigated. The amount of coagulum (i.e., large flocs caused by intensive coagulation) can be greatly reduced by an increase in the concentration of sodium lauryl sulfate (SLS) in the monomer emulsion feed. On the other hand, increasing the concentration of SLS in the initial reactor charge can result in an increase in the percentage of the particle volume change (i.e., a measure of the degree of limited flocculation) later in the process. Both the scrap and percentage of the particle volume change increase with an increase in the electrolyte concentration. Both the coagulation and secondary nucleation process can result in a significant deviation from the Novak model. Experimental data also show that latex particles comprising pure BA can lose their stability rapidly at higher total solids content because of the crowding effect. Incorporation of only 5% AA into the emulsion polymers greatly improves the latex stability. © 1996 John Wiley & Sons, Inc.     

The role of auxiliary monomers and emulsifiers on wet scrub resistance of various latex paints at different pigment volume concentrations

This work is an attempt to study the effect of different latex types containing various auxiliary monomers and emulsifiers on their pigmentation and their corresponding behavior on scrub resistance. The auxiliary monomers investigated were acrylic acid (AA), methacrylic acid (MAA), and itaconic acid and the emulsifiers contained sodium lauryl sulfate (SLS) and sodium dodecylbenzene sulfonate (SDBS). It was shown that a semibatch polymerization technique which led to smaller particles and sharper size distributions is preferable. The best wet scrub results were obtained by using MAA and SLS. It was also shown that the proper selection of an auxiliary monomer generally depended on the range of incorporated pigment volume concentration (PVC). At high PVCs, AA gave better performances compared with MMA. The reverse effect was shown to occur at low PVCs. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

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.     

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.     

Influences of the polymerization ingredients on the porous morphology of soap‐free poly(methyl methacrylate/ethyl acrylate/methacrylic acid) seeded latex particles

Monodispersed soap‐free poly(methyl methacrylate/ethyl acrylate/methacrylic acid) latex particles were synthesized by the seeded emulsion polymerization of methyl methacrylate, ethyl acrylate, and methacrylic acid (MAA), and particles with a porous morphology were obtained after an alkali posttreatment. The effects of the unsaturated acid and crosslinking agent on the properties and morphology of the latex particles were investigated. The results showed that the particle size decreased and its distribution widened when the concentration of MAA was greater than 10.0 mol % or the concentration of ethylene glycol dimethacrylate (EGDMA) was greater than 1.5%. When more than 4.0 mol % MAA was used, a porous structure could be detected clearly under a transmission electron microscope, and the particle volume and pore size first gradually increased to a maximum and then decreased rapidly with an increase in the MAA concentration. The porous morphology disappeared completely as the MAA concentration reached 16.0 mol %. A multihollow morphology was generated when the EGDMA concentration exceeded 1.0%, and the particle volume decreased monotonously with the concentration of EGDMA increased. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 1934–1939, 2006     

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     

乳液聚合法制备PSA纳米微球与PS纳米微球的性能测定

以苯乙烯(St)和甲基丙烯酸(MAA)为原料,采用乳液聚合法共聚制备羧基化聚苯乙烯(PSA)纳米微球。通过改变乳化剂(SDS)的用量、St/MAA的质量配比控制微球性质和大小。利用透射电镜(TEM)、扫描电镜(SEM)、傅里叶红外光谱(FTIR)、差示扫描量热仪(DSC)、热重分析仪(TGA)和Zeta电位仪对PSA纳米微球进行表征。FTIR结果证实MAA成功引入到微球中,TEM和SEM表明当乳化剂用量为单体总质量的10%时,得到大小均匀,直径为45 nm的PSA微球。PSA的玻璃化转变温度和热分解温度随MAA的含量增加而提高。纯PS表面带负电荷,Zeta电位为-17 mV。共聚后的PSA纳米颗粒,其St与MAA物质的量比为10/1. 0,10/1. 5和10/2. 5时,Zeta电位分别为-31. 9、-39. 6和-44 mV。上述结果表明,采用共聚是调节PS微球热性质及表面性质的有效途径。     

自交联封闭性乳液的合成与性能

以双丙酮丙烯酰胺（DAAM）、甲基丙烯酸甲酯（MMA）、丙烯酸丁酯（BA）和甲基丙烯酸（MAA）为共聚单体,采用半连续种子乳液聚合工艺合成自交联封闭性聚丙烯酸酯乳液（PAE）,考察了DAAM和复合乳化剂对乳液聚合稳定性以及涂膜性能的影响。研究发现：随着DAAM含量的增加,乳液聚合稳定性下降,粒径增大,涂膜的耐介质性能和交联度提高,合适的DAAM加入量为总单体质量的3.0%,DAAM和己二酰肼(ADH)的最佳摩尔比为2∶1。采用SDBS+OP-10+OP-40为复合乳化剂体系,选用乳化剂的含量为2.35%,阴/非离子乳化剂质量比为1∶1.25;复合乳化剂在种子、核、壳比例为1.5∶1∶2,制备的乳液具有较好的聚合稳定性（乳液凝胶率低和单体转化率高）,乳液耐电解质（钙离子）稳定性好,涂膜具有优异的封闭性。傅里叶红外光谱（FTIR）表明在涂膜形成过程中DAAM的酮羰基与ADH的酰肼基反应生成腙（C=N）,TEM分析显示乳液的乳胶粒子呈核壳结构,TGA分析发现DAAM改性的PAE降低了涂膜的热稳定性。     

有机硅氧烷改性醋酸乙烯酯-丙烯酸酯乳液的合成与性能

采用种子乳液聚合,引入乙烯基三甲氧基硅烷(A-171),以十二烷基苯磺酸钠(DSB)和壬基酚聚氧乙烯(20)醚(OP-10)作复合乳化剂,以过硫酸钾(KPS)为引发剂,在反应温度为78±2℃条件下,合成了A-171改性醋酸乙烯酯(VAc)-丙烯酸酯共聚乳液。实验采用单体滴加工艺,考察了配方中丙烯酸丁酯(BA)、甲基丙烯酸(MAA)和A-171用量对共聚物性能和乳液聚合过程的影响,并用红外光谱仪(FTIR)、粒度仪和差示量热扫描仪(DSC)对共聚物的结构及性能进行了表征。结果表明,引入w(BA)=10%~15%(相对于配方中单体总质量,下同)、w(MAA)=4%、w(A-171)=1%到VAc-丙烯酸酯共聚物乳液中,共聚物乳液涂膜的吸水率<5.0%,耐寒性通过10个循环,60℃加速贮存稳定性>100 d。     

Preparation of multi-responsive amphiphilic particles by one-step soapless emulsion polymerization

A novel multi-responsive amphiphilic copolymer (mRAP) particles with tunable emulsifiability was successfully prepared via one-step soapless emulsion polymerization using common monomers, such as methyl methacrylate, methacrylic acid (MAA), butyl acrylate (BA) and N,N-diethylacrylamide (DEAA). The obtained monodisperse spherical mRAP particles were characterized by dynamic light scattering, Fourier transform infrared spectroscopy, scanning electron microscope and transmission electron microscope, which provided the information of particle size, components and anisotropic structure. Its multiple responsivities were investigated under the condition of diversified pH values, salinity and temperature. The results showed that the mRAP particles exhibited good dispersivity based on uniform particle size, as well as tunable emulsifiability and anticipated multiple responsiveness. Furthermore, the tunable emulsifiability of oil–water mixtures could be easily achieved by adjusting the mass ratios of MAA to DEAA. Meanwhile, the obtained multi-responsive polymers relying on simple and effective copolymerization can be used in fundamental research and industrial production.     

乳化法明胶亚微米粒子的制备

以A型明胶为原料,石蜡油为油相,采用乳化化学交联方法制备了明胶亚微米粒子. 用扫描电子显微镜(SEM)观察了明胶亚微米粒子的形貌和粒径. 研究了影响微球粒径的多种因素,包括明胶溶液浓度、乳化搅拌速度、乳化温度、乳化剂和固化剂. 结果表明,采用戊二醛为固化剂、增加明胶的浓度、提高乳化搅拌速度、使用混合性的乳化剂都有利于降低明胶粒子的粒径. 此外,对制备工艺进行了优化,并在7000 r/min左右高速搅拌的条件下,得到了成球性较好的粒径约为450 nm的明胶亚微米粒子.     

Synthesis and characterization of self-crosslinkable zinc polyacrylate latices at room temperature

The zinc ion self-crosslinkable polyacrylate latexes (PAs) cured at room temperature were synthesized by seeded semi-continuous emulsion polymerization with zinc oxide (ZnO) as crosslinker. The ZnO and methacrylic acid (MAA) mass contents, method of ZnO introduction in relation to the degree of crosslinking, and the properties of self-crosslinkable latices are examined and discussed. The characterization techniques such as Fourier transform infrared spectroscopy (FTIR), differential scanning calorimeter (DSC), transmission electron microscopy (TEM), and thermal gravimetric analysis (TGA) have been used to determine the structure and properties of PAs. The experimental results show that in a certain range, the average particle size decreases with an increase in the content of MAA, while the latex stability is undoubtedly improved. The optimum mass content of MAA is 12?% of the total monomers. The optimum amount of ZnO needed is 25?% (mole fraction) of MAA, and the optimum temperature of ZnO introduction is 60?°C. TEM analyses show that the latex particles are coarse spherical particles with surface enriched with comprising abundant carboxyl groups, and zinc ions are dissociated as zinc ammine complex in the aqueous phase. FTIR analyses confirm that the chelate crosslinking occurs between zinc ions and carboxylic acid during the film-forming process. The DSC results indicate that the glass transition temperature (T _g) of PAs increases as a function of the formation of a coordinate structure, and the obtained film exhibits excellent initial hardness and sandability. TGA analyses demonstrate that the introduction of ZnO evidently enhances the thermal stability of self-crosslinkable PAs.     

丙烯酸酯可再分散乳胶粉的性能与表征

丙烯酸丁酯(BA)、甲基丙烯酸甲酯(MMA)、甲基丙烯酸(MAA)和甲基丙烯酸羟乙酯(HEMA)为共聚单体合成了具有软核硬壳结构的丙烯酸酯乳液,经喷雾干燥法制得了丙烯酸酯可再分散乳胶粉.通过测试再分散液粒径及其分布、吸光度表征了乳胶粉再分散性及再分散液稳定性,并用扫描电镜(SEM)观察了再分散液的微观成膜效果,最后用傅立叶红外光谱(FT-IR)、透射电镜(TEM)、差示扫描量热(DSC)等测试对乳胶粉进行了表征.实验结果表明,制备的乳胶粉具有良好的再分散稳定性,再分散液和原乳液粒径大小及其分布基本相同,SEM显示再分散液具有良好的成膜性,FT-IR表明乳胶粉的分子结构与原乳液相比未发生明显改变,TEM显示再分散液粒子未发生变化仍保持核壳结构,DSC验证了制得的乳胶粉具有核(25℃和壳55℃两个玻璃化温度(T_g).所有分析表明乳胶粉再分散液与原乳液的性能和结构基本相同.     

Synthesis and characterization of porous poly(methacrylic acid‐co‐triethylene glycol dimethacrylate) by seed emulsion polymerization

Porous poly(methacrylic acid‐co‐triethylene glycol dimethacrylate) (poly MAA‐co‐3G) particles in the size range of 10–40 μm were prepared via seed emulsion polymerization. Mixtures of linear polymer, solvent, and/or nonsolvent were used as inert diluents. The prepared porous polymer was converted using hydroxylamine hydrochloride and sodium methoxide into the corresponding poly(hydroxamic acid). The surface area of the porous copolymer particles was determined colorimetrically. The effect of the diluent type and concentration on the surface area of the prepared porous polymer was examined. The metal ion absorption capacity of the resin toward the different metal ions was examined using an atomic absorption spectrophotometer. The thermal stability of the polymers was examined by thermal gravimetric analysis. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 1209–1215, 2000     

Synthesis and characterization of silicone-modified vinyl acetate–acrylic emulsion copolymers

The triethoxyvinylsilane (TEVS) containing vinyl acetate (VAc)/2-ethylhexylacrylate (2-EHA) copolymers were prepared by emulsion copolymerization. The polymerization was performed with methacrylic acid (MAA) and auxiliary agents at 80 °C in the presence of ammonium peroxodisulfate (APS) as the initiator. Alkyl phenol ether sulfate and Arkupal N-300 were used as anionic and nonionic emulsifiers, respectively. The resulting copolymers were characterized by using Fourier transform infrared spectroscopy (FTIR). Thermal properties of the copolymers were studied by using thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The morphology of copolymers was also investigated by scanning electron microscopy (SEM) and then the effects of temperature, agitation speed, initiator and silicone concentrations on the properties of the silicone-modified VAc–acrylic emulsion copolymers were discussed. The obtained copolymers have high solid content (53%) and can be used in emulsion paints as a binder. The calculations of monomer conversion versus time histories and monomer conversion indicate that by increasing the TEVS concentration, the polymerization rate and the number of polymer particles decrease, respectively.     

阳离子聚丙烯酰胺微球浓乳液制备及粒径演化

浓乳液聚合产品稳定性好,颗粒尺寸更接近地层孔隙尺寸,在油田开发中具有较大的应用价值。基于微乳液制备了一系列甲基丙烯酰氧乙基三甲基氯化铵和丙烯酰胺的浓乳液,通过电导率测试、流变性分析、显微镜观察,研究了聚合前后浓乳液结构、粒径分布及稳定性。结果表明浓乳液的黏度及屈服应力,随着水相单体浓度（C_M）增加而降低,随着油相中表面活性剂含量（m_S）增加先升高后降低,乳液稳定性有相同趋势;浓乳液在C_M>40%及m_S=2.5 g时的失稳,原因分别是渗滤作用和高黏度下乳化不充分;聚合前液滴粒径分布在1～30 mm,聚合后微球粒径在0.4～5 mm,且粒径分布由聚合前双峰变为聚合后单峰,这一现象可以由Kolmogoro-Hinze的乳化理论解释,并由微球乳液的黏度增加至原始浓乳液的10倍证实。     

The performance of the emulsion polymerization of styrene in a continuous loop tubular reactor

The emulsion polymerization of styrene in a continuous loop tubular reactor (CLTR) has been used to study the process kinetics under eigth levels of sodium lauryl sulfate (SLS) concentration, eight levels of potassium persulfate (KPS) concentration, and three levels of styrene monomer (St) concentration. A critical surfactant concentration for the overshoot phenomenon in the monomer conversion exists between 8.02 and 12.40 g-SLS/1-water. Overshoot was not eliminated by changing concentrations of the initiator and monomer. The overshoot in the number concentration of polymer particles was observed in all the polymerizations studied. The dependences of the rate of polymerization and the number concentration of particles in the steady state on the SLS and KPS concentrations are presented. The growth of the average cumulant diameter of particles shows a transient period followed by a steady state. The dependences of the volumetric growth rate of polymer particles on diameter are of the order of 1 for the lower SLS concentration and 0.5 for the higher SLS concentration, respectively. The steady state cumulant diameter depends on an order of ?0.24 for the SLS concentration.     

乙烯基三乙氧基硅烷/丙烯酸酯共聚乳液的研究

以聚丙烯酸丁酯为种子乳液，将乙烯基三乙氧基硅烷（VTES）与丙烯酸酯进行乳液共聚，制成了聚合稳定性良好，性能稳定的有机硅／丙烯酸酯共聚乳液，详细讨论了VTES用量对聚合过程稳定性和乳液粒径大小及分布的影响，采用动态光散射法跟踪了聚合过程的粒径大小及分布，采用TEM表征了粒子形态；同时研究了乳液的粘度及乳胶膜的耐水性能，结果表明：乳胶粒的平均粒径随聚合时间的延长逐渐增大，乳胶粒呈球形，具有核壳结构，随着VTES用量的增加，乳液聚合的稳定性变差，乳胶粒的平均粒均增大，乳液的粘度增加，乳胶膜的吸水率减小。     

Role of fluorocarbon surfactant in the preparation of polytetrafluoroethylene‐modified polyacrylate emulsion

Role of fluorocarbon surfactant in the preparation of polytetrafluoroethylene‐modified polyacrylate emulsion is investigated. The fluorocarbon surfactant has an efficient preemulsification to polytetrafluoroethylene (PTFE) powder. It enables PTFE powder to be introduced into the copolymer of n‐butyl acrylate, n‐methyl methacrylate, n‐styrene, and α‐methacrylic acid. Thereby, stable PTFE‐modified polyacrylate emulsion can be formed. The effects of fluorocarbon surfactant on the surface tension, particle size and particle size distribution of the emulsion, as well as the relation between fluorocarbon surfactant and the amount of PTFE powder are fully investigated. The particle size and the surface tension of emulsion strongly depend on the fluorocarbon surfactant concentration in the reaction system. The particle size distribution becomes narrower and the stability of the emulsion is improved with the increasing of the fluorocarbon surfactant concentration. According to the experiments, a possible mechanism of fluorocarbon surfactant in polymerization is proposed. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007