自交联丙烯酸酯类反应性微凝胶乳液的聚合稳定性

采用半连续种子乳液聚合方法合成了自交联丙烯酸酯类反应性微凝胶乳液,研究了聚合工艺条件对聚合反应稳定性的影响。结果表明,当增大乳化剂SDS/OP-10的用量或加快预乳化单体的滴加速度时,聚合反应稳定性增加;随着引发剂过硫酸钾(KPS)、交联剂三羟甲基丙烷三丙烯酸酯(TMPTMA)和单体用量的增加,微凝胶颗粒分子间的交联反应增强,聚合反应稳定性下降。加入功能性单体甲基丙烯酸(MAA)和丙烯酸(AA)都能使聚合反应的稳定性增强,随着MAA用量的增加,聚合反应稳定性呈先增强后下降的趋势。当所加入的SDS/OP-10质量分数为3%~4%、KPS为0.4%~0.6%、TMPTMA为1%~3%、MAA不超过3%及单体为30%~40%,预乳化单体滴加速率为20~30 mL/h时,聚合过程的稳定性最好。由傅里叶变换红外光谱分析可知,通过优化聚合条件,得到了含有官能性环氧基和羧基的丙烯酸酯类反应性微凝胶乳液。     

Semibatch emulsion polymerization of butyl acrylate. II. Effects of emulsifier distribution

The effects of emulsifier distribution ratio between the initial charge and the feed on particle formation and kinetics of butyl acrylate emulsion polymerization, using sodium lauryl sulfate as emulsifier and potassium persulfate as initiator, were investigated. The number of particles increased with initial emulsifier concentration in the reactor charge. It was shown that traditional ranking, in terms of number of particles produced, of semibatch emulsion polymerization with monomer emulsion feed is not always justified and a semibatch emulsion polymerization can produce far more particles than a conventional batch emulsion polymerization. The number of polymer particles was found to be practically independent of the emulsifier distribution ratio between the charge and the feed for a high overall emulsifier concentration, while for a low overall emulsifier concentration, the number of particles increased with initial loading of the emulsifier. The polydispersity index (PDI) of the final latexes showed a minimum with emulsifier distribution. A bimodal particle size distribution, and a latex with a large PDI, was obtained when there was no emulsifier in the charge. As the initial emulsifier charge increased, a unimodal PSD with a smaller PDI was obtained. With higher proportions of emulsifier in the initial charge, the PDI rose again due to particle nucleation at monomer‐starved conditions, and a skewed unimodal PSD was obtained. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 79: 582–597, 2001     

Preparation and characterization of cationic copolymer latex. 1. Emulsion copolymerization of styrene with 4-vinylpyridine in the presence of non-ionic emulsifier

A study was made of the effect of 4-vinylpyridine (VP) on the kinetics of the emulsion polymerization of styrene (St) and on the distribution of polymeric VP in the cationic latex. Bimodal distribution of particle diameter was obtained in the polymerization under the conditions of low emulsifier concentration and high VP fraction in monomer feed. This would be caused by insufficient stabilization of resulting particles and by some changes in the character of growing radicals in aqueous phase with conversion. Polymerization under acidic conditions was affected by the amphiphilicity of VP-rich radicals which depended on VP fraction in monomer feed. On the surface of the latex particles prepared at pH 2 polymeric VP located preferentially whereas the latex particles prepared at pH 11 had a nearly statistical distribution of VP on their surface.     

桐油改性苯丙乳液的合成及在涂料中的应用

以桐油酸、苯乙烯、丙烯酸酯等为共聚单体,过硫酸钾和亚硫酸钠为引发剂,十二烷基硫酸钠和壬基酚聚氧乙烯醚为乳化剂,采用乳液聚合法合成桐油改性苯丙乳液.探讨了桐油酸、乳化剂与引发剂的用量以及反应温度和时间对单体转化率的影响.采用正交试验得到的最佳合成工艺为:m(桐油酸):m(苯乙烯):m(丙烯酸酯)=1.2:22.0:20....     

半连续乳液聚合法制备纳米苯丙乳液

探讨了苯乙烯和丙烯酸丁酯分别作为硬单体和软单体,用半连续乳液聚合工艺制备纳米苯丙乳液的条件;研究了乳化剂类型、配比、用量和乳液固体含量对乳液聚合及乳液涂膜性能的影响,特别是在不同条件下对制得的乳液粒径、黏度、凝聚率、贮存稳定性、钙离子稳定性、涂膜外观、吸水率、光泽度等的影响。结果表明,当乳化剂为SLS/OP复合乳化体系、其物质的量的比为2∶1、乳化剂用量为4%、乳液固体含量为40%时,可以得到纳米尺度的苯丙乳液,聚合反应稳定性和乳液性能良好。     

Polymer microgels prepared by emulsifier‐free emulsion polymerization of unsaturated polyesters and styrene

In the present work polymer microgels were prepared by emulsifier‐free emulsion copolymerization of unsaturated polyesters (UPs) with end carboxyl groups and styrene (St). The nucleation mechanism of UP‐St emulsifier‐free emulsion polymerization was proposed. The effects of the ratio of the monomers to water, pH, and the ratio of UP to St on the stability of polymerization and the yield of microgels were studied. It was found that the polymer microgels can be used to markedly improve the impact strength of UP. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 3049–3053, 2000     

Statistical experimental strategies approach to emulsion copolymerization of styrene and n-butyl acrylate

A batch emulsion copolymerization for the preparation of styrene-n-butylacrylate (St/BA) copolymer latexes is investigated. A series of n-butylacrylate-styrene copolymer latexes were obtained by emulsion copolymerization in the presence of K₂S₂O₈ (KPS) as initiator and with/without emulsifier (sodium lauryl sulfate). The effect of such preparation conditions as initiator concentration, the St/BA ratio, reaction temperature, agitation rate, and emulsifier concentration on the polymerization rate, particle size of copolymer latex, and molecular weight distribution of the resulting copolymer (∼ 80% conversion), respectively, is systematically studied using fractional factorial design methodology. Fractional factorial analysis indicates that the effects of the St/BA ratio, reaction temperature, emulsifier concentration, as well as the two-factor interaction of temperature and emulsifier concentration, are the key variables influencing the polymerization rate. At ∼ 80% monomer conversion, statistical analysis clearly isolates emulsifier concentration as the dominant factor affecting average particle size of copolymer latex; results also indicate that the effects of the St/BA ratio, reaction temperature, and emulsifier concentration are major effects influencing the polydispersity of polymer molecular-weight distribution. For 7.30 g KPS/100 g monomer and 500 rpm agitation rate, the conditions for minimizing molecular-weight distribution (∼ 80% conversion) occur for a reaction temperature, St/BA ratio, and surfactant concentration of 70°C, ∼ 3.59/1, and ∼ 2.08 g/100 g monomer, respectively, generating a minimum molecular-weight polydispersity of ∼ 3.0. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 551–563, 1998     

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.     

丙烯酰胺反相细乳液聚合

采用反相细乳液法,以白油为连续相,失水山梨醇单油酸酯/聚氧乙烯失水山梨醇单油酸酯为乳化剂,一种聚合物型乳化剂(聚异丁烯琥珀酸酯与山梨醇油酸酯的混合物)作为助稳定剂,通过正交实验确立了基本乳液体系,考察了微乳化工艺中转速变化、乳化剂体系组成、浓度及单体含量对聚合产物稳定性的影响,并研究了不同单体浓度和聚合时间等聚合工艺对微球粒径及分布的影响。结果表明,复合乳化剂含量为3.0%,转速为10 000 r/min下乳化20 min,在单体浓度55%,亲水疏水平衡值(HLB值)为5.5,采用氧化还原引发体系,聚合时间为6 h时,可以得到固含量35%以上、粒径数百纳米的长期稳定的亚微米级聚丙烯酰胺微球乳液。     

新型低温型聚丙烯酸酯乳液的合成

采用种子乳液聚合法合成新型低温反应型聚丙烯酸酯乳液粘合剂,即以丙烯酸丁酯（BA）、丙烯酸异辛酯（EHA）、苯乙烯（St）为软、硬单体,丙烯酸（AA）为功能单体,以过硫酸钾为引发剂,并选用一种适当的交联单体合成了性能优良的聚丙烯酸酯涂料印花粘合剂。讨论了引发剂用量、乳化剂用量、阴／非离子乳化剂的配比、乳液滴加时间、保温时间等对聚合物的影响。确定了乳液聚合最佳工艺条件：乳化剂用量为o8％,阴／非乳化剂质量比为4：3,引发剂用量为0．8％,乳液滴加时间60min,保温时间60min。     

反相乳液聚合合成聚丙烯酰胺

以甲苯为介质,Span80/Span20为乳化剂,叔丁基过氧化氢/亚硫酸氢钠氧化还原体系为引发剂,采用反相乳液聚合制备了分子量高达9.4×106的聚丙烯酰胺乳液。研究了乳化剂种类及用量、引发剂种类及用量、油水比、单体浓度,反应温度对共聚物相对分子量、聚合转化率以及聚合反应速率的影响。其最佳聚合配方及工艺条件为:油水体积比为1.4,单体浓度30%,引发剂用量0.003%,乳化剂用量12%,聚合温度30℃。     

Anionic ring-opening polymerization of octamethylcyclotetrasiloxane in emulsion above critical micelle concentration

Batch anionic ring-opening polymerization of octamethylcyclotetrasiloxane in emulsion using nonionic and cationic emulsifiers was studied. The concentration of emulsifiers was set above their critical micelle concentration. Effects of emulsifier concentration, nonionic/cationic emulsifier ratio and cationic emulsifier/initiator (KOH) ratio on the kinetics, average particle size and distribution and on the average molecular weight and distribution were investigated and discussed. At the beginning of the polymerization, empty micelles, active micelles (polymer particles) and monomer droplets co-exist in emulsion. The transport of monomer from monomer droplets toward empty micelles was confirmed by monomer droplets and empty micelles disappearance and by formation of smaller particles. The transport of monomer from monomer droplets toward polymer particles was not confirmed, since the average polymer particle size did not increase during polymerization. It was proposed, that at lower conversions, monomer diffuses from polymer particle interior to particle surface, while at higher conversions, the monomer diffuses from larger to smaller polymer particles. Emulsifier concentration, nonionic/cationic emulsifier ratio and cationic emulsifier/KOH ratio have an evident effect on the kinetics and on the average molecular weight, thus demonstrating that cationic emulsifier participates to the initiation reaction.     

Semibatch emulsion polymerization of butyl acrylate. I. Effect of monomer distribution

The effects of initial monomer charge on the particle formation and on the rate of polymerization were investigated for semibatch emulsion polymerization of butyl acrylate using sodium lauryl sulfate (SLS) as a surfactant and potassium persulfate (KPS) as an initiator. For the semibatch process with monomer (M) feed, it was found that by varying the monomer distribution ratio between the initial reactor charge and the feed it is possible to alter the contribution of monomer‐flooded and monomer‐starved nucleation mechanisms to the whole nucleation process. The number of particles increases as the initial monomer charge decreases, if the monomer concentration is below a critical value for any fixed system. The increase in number of particles is associated with a broad particle‐size distribution which might depict an emerging second peak on the particle‐size distribution curve. For low emulsifier concentration systems, a larger number of particles was obtained for a lower amount of monomer charge. Particle coagulation and emulsifier adsorption on the monomer droplets were counted as the main reasons for such behavior. For a semibatch process with monomer emulsion (ME) feed, the larger number of particles was formed at a lower initial monomer charge, similar to an M‐add semibatch process. However, the application of monomer charge to an ME‐add process was found to increase the possibility of secondary nucleation and led to the occurrence of a bimodal particle‐size distribution. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 3094–3110, 1999     

AM—DMC反相乳液的合成

采用反相乳液法合成了液体石蜡／span80-Tween80/水／烯酰胺-甲基丙烯酰氧乙基三甲基氯化铵共聚物阳离子反相乳液,通过主体实验分别考察了油水体积比、乳化剂浓度、引发剂浓度、单体配比、单体浓度对聚合反应的影响。最后通过正交实验确定了合成反应的最适宜条件。     

Emulsion polymerization of methyl methacrylate in concentration of emulsifiers below their CMCs—polymerization rate,particle size,and particle-size distribution

The emulsion polymerization of methyl methacrylate (MMA) in concentration of emulsifiers below their critical micelle concentrations (CMCs) initiated by K₂S₂O₈ (KPS) was studied. It was observed that the initiator concentration has little effect on both polymerization rate and particle size. However, the polymerization rate is faster and particle size is smaller obviously when decreasing the ratio of the water/monomer or increasing the temperature of polymerization or the amount of the emulsifier. In the range of a 200–400 rpm stirring speed, the polymerization rate is almost unchanged although the particle size become larger with increase in the stirring speed. The monodisperse particle (size about 100–200 nm) can be obtained using this process. The mechanism of emulsion polymerization of MMA in the emulsifier concentration below its CMC is discussed. © 1995 John Wiley & Sons, Inc.     

反相乳液聚合制备聚丙烯酰胺

采用反相乳液聚合法合成了聚丙烯酰胺（PAM）,测定了聚合反应转化率及产物特性粘度,并对其官能团进行了表征。考察了加料方式、单体质量分数、乳化剂用量、油水此对产物性能的影响。实验结果表明,最佳合成条件为：单体质量分数22．5％（对水相）,乳化剂质量分数2％（对油相）,油水比为1：2。     

用于防水涂料的自交联丙烯酸弹性乳液

：以N-羟甲基丙烯酰胺（NMA）为自交联单体,SDS/OP-10为复合乳化剂,过硫酸铵（APS）为引发剂,采用半连续种子乳液聚合工艺和正交试验方法研究了不同用量的引发剂、乳化剂、交联单体和反应温度对弹性丙烯酸酯乳液性能的影响.结果表明：当APS、复合乳化剂和NMA用量分别为单体总量的0.7％、3％和1％,聚合温度为75 ℃时,可以制备出凝聚率低、转化率高、黏度和交联度适中的自交联丙烯酸弹性乳液;以其为基料与水泥复合制备的防水涂料涂膜吸水率较低,拉伸强度和断裂伸长率达到了国家标准以上.     

核壳结构聚硅氧烷/丙烯酸酯复合乳液(Ⅰ)乳化剂对乳液聚合过程及粒径分布和粒子形态的影响

采用种子乳液半连续法合成了具有高有机硅含量的聚硅氧烷/丙烯酸酯核壳结构复合乳液,研究乳化剂的种类、复配比例及质量浓度对有机硅／丙烯酸酯壳核乳液性能与乳胶粒径、分布和结构的影响.结果表明：阴离子乳化剂十二烷基硫酸钠(SDS)、十二烷基磺酸钠(SDS-2)、十二烷基苯磺酸钠(SDBS)所合成的乳胶粒子粒径依次增大,SDS与非离子型乳化剂OP-10复配使用时,随OP-10质量分数的增加,聚合速率和转化率降低,化学稳定性增加,乳胶粒子粒径增大,分布变宽,确定了复合乳化剂的最佳配比.随复合乳化剂浓度的增加,聚合速率加快、转化率增加,乳胶粒子粒径减小而分布加宽.通过改变乳化剂加入方式可减小乳胶粒子的粒径分布.为减少壳层聚合物新粒子的产生,需严格控制乳化剂的浓度,使加入的壳层单体处于“饥饿”状态,在乳胶粒子表面富集、引发聚合,形成表层“过渡层”,最终形成核壳结构复合粒子.     

AM/AMPS/SSS三元反相乳液聚合体系稳定性研究

以丙烯酰胺(AM)为主单体、2-甲基-2-丙烯酰胺基丙磺酸(AMPS)、对苯乙烯磺酸钠(SSS)为抗温抗盐单体,以白油为连续相,Span 80/Tween 80为复合乳化剂,制得了AM/AMPS/SSS三元反相乳液聚合体系,考察了HLB值、乳化剂浓度、油水比、pH值、搅拌时间、搅拌速度对乳液稳定性的影响。结果表明,乳化剂含量为6%～7%(体系总量),HLB值为5.89,体系pH=8,油水体积比为1.8∶1,搅拌时间30～40 min,搅拌速度为500 r/min时得到稳定的反相乳液体系,适合进行三元反相乳液聚合。     

核壳型PVAc／PBA乳液的制备与表征

以醋酸乙烯酯（VAc）为核单体,丙烯酸丁酯（BA）为壳单体,二甲基丙烯酸乙二醇酯（EGDMA）为交联剂,采用分阶段饥饿态加料方式和半连续乳液聚合方法合成了具有硬核软壳结构的聚（醋酸乙烯酯／丙烯酸丁酯）。采用OP-10和十二烷基硫酸钠（SDS）质量比为2：1的复合乳化剂,用量为4％左右时乳液稳定;壳单体的滴加速度在5～6g／h时,聚合体系稳定,且转化率高。用FT—IR分析了聚合物的结构;并用透射电镜表征了乳胶粒结构。