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1.
Jaromír uprek 《应用聚合物科学杂志》1979,24(4):909-914
The factors affecting the amount of coagulum appearing during the semicontinuous emulsion polymerization of acrylic monomers were studied. Monomers were added into the polymerization reactor in the form of emulsion. The stability of the polymerization system was greatly affected by the distribution ratio of a constant amount of emulsifier between the initial charge in the polymerization reactor and the monomer emulsion. The amount of arising coagulum was dependent also on the alkyl length of the alkyl acrylate and increased from ethyl acrylate to 2-ethylhexyl acrylate. The amount of appearing coagulum was essentially decreased by copolymerization with acrylic acid and sulfoethyl methacrylate, respectively. In the case of insufficient covering of particle surface by emulsifier, the colloid stability of polymerizing system was greatly increased by the presence of strong as well as weak acid groups chemically bound on the particle surface. 相似文献
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G. W. Ceska 《应用聚合物科学杂志》1974,18(2):427-437
A study was made of the effect of carboxylic monomers on the surfactant-free emulsion polymerization of styrene and styrene–butadiene. Acid monomers, such as acrylic acid, methacrylic acid, and itaconic acid, were shown to play a critical role in particle formation and particle stabilization in such systems. In the emulsion polymerization of styrene, methacrylic acid forms particles more efficiently than acrylic acid. This difference is attributed to the more hydrophobic nature of the methacrylic monomer which allows it to diffuse more rapidly to the particle surface where it acts to prevent agglomeration. The ability of carboxyl groups to orient at the particle–water interface was studied by acid–base and soap titrations of carboxylated styrene–butadiene latices. The polymerization of itaconic acid onto the particle surface of a styrene–butadiene latex produces a surface carboxyl density much higher than is obtainable with classically adsorbed surfactants. This result is used to explain the greater stability of carboxylated versus noncarboxylated emulsion polymers. During the polymerization of styrene–butadiene latices, carboxyl groups dervied from methacrylic acid are shown to be buried more deeply into the particle as compared to carboxyls derived from the more hydrophilic acrylic acid which orient more at the particle–water interface. 相似文献
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It was studied how to localize carboxyl groups at the particle surface in a preparation of styrene (S)/butyl acrylate (BA)/methacrylic acid (MAA) polymer emulsion. The relative distribution of carboxyl groups in the emulsion was determined by conductometric titration method: in serum, at surface, and inside particle. By seeded (two-stage) emulsion polymerization that S–BA–MAA terpolymer emulsion was first prepared at low pH and then second stage polymerization of S–BA was continued at high pH, S/BA/MAA polymer emulsion particles in which carboxyl groups are localized predominantly at the surface could be prepared. 相似文献
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苯丙乳液碱增稠机理的研究 总被引:11,自引:0,他引:11
以苯乙烯、丙烯酸、丙烯酸丁酯和甲基丙烯酸甲酯为单体,采用乳液聚合合成了苯丙乳液。讨论了所用的乳化剂及其用量,并以特定的工艺所引起的苯丙乳液粒子表面羧基富集,着重讨论了其加碱增稠的机理,为苯丙乳液生产工艺的制定提供理论依据。 相似文献
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Soap-free carboxylated polystyrene latexes have been prepared by copolymerizing acrylic acid (AA) in a wide range of the degree of neutralization using a slight amount of soap; and the distribution of carboxyl groups was investigated from the determination of carboxyl groups localized on the surface of particles (surface carboxyl groups). It appears that the degree of neutralization of AA or the amount of AA has a considerable effect on the rate of polymerization as well as the stability of the polymerization system. At a degree of neutralization of approximately 0.80, stable latexes are obtained at a sufficient rate of polymerization. It is also clarified that the distribution of carboxyl groups is governed substantially by the degree of neutralization of AA. At a degree of neutralization of 0.80, approximately 30% of the total carboxyl groups are localized on the surface of particles. The amount of AA or the particle diameter seems to have little effect on the distribution of carboxyl groups. 相似文献
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Seeded batch emulsion polymerization of styrene and acrylic acid was studied. The influence of pH and acrylic acid content on the polymerization rate and the amount of carboxylic acid groups incorporated in the final latex products was investigated. The distribution of the functional groups over the aqueous phase, the latex particle surface, and the interior of the latex particle was determined using aqueous conductometric titration and nonaqueous potentiometric titration at intermediate and complete overall conversions. Combined with kinetic results, the carboxylic acid group distribution history provided valuable information about the process of incorporation of acrylic acid in latex products. Two‐step processes in which a shot of acrylic acid was performed in the last stage of the emulsion polymerization reaction were investigated as a strategy to increase the surface incorporation efficiency. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 875–885, 2000 相似文献
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M. Slawinski M. A. J. Schellekens J. Meuldijk A. M. Van Herk A. L. German 《应用聚合物科学杂志》2000,76(7):1186-1196
The seeded batch emulsion copolymerization of styrene and acrylic acid was studied. The polymerization rate was investigated with pH as the main parameter. Some attempts were made to evaluate the average number of growing chains per particle during Stage II of the emulsion polymerization process. The final latex products were characterized by means of conductometric aqueous titration and potentiometric titration in an organic solvent mixture. The distribution of the acid groups over the aqueous phase, the particle surface, and the interior of the particles together with the kinetic results provided insight into important features governing the incorporation of acrylic acid. The results indicate that pH is the dominating parameter for the incorporation process. An optimal incorporation on the surface of the particles is observed for a low value of pH. In that case, all the acid groups are protonated. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 1186–1196, 2000 相似文献
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Alkali-soluble random copolymer (ASR), poly(styrene/α-methylstyrene/acrylic acid) [Mn: 4,300; acid number: 190], was used as a polymeric emulsifier in the emulsion polymerization of styrene and methyl methacrylate, respectively. ASR containing a large number of carboxyl groups could form aggregates like micelles, and the solubilization ability of the aggregates was dependent on the neutralization degree of ASR. The polystyrene latexes prepared using ASR showed the small particle size (ca. 40 nm) and monodispersed particle size distribution. On the other hand, the particle size distribution of poly(methyl methacrylate) latexes became broader as the neutralization of ASR increased. This could be explained by the effects of water solubility of the monomer and the neutralization degree of ASR on particle formation. Thin layer chromatography/flame ionization detector analysis confirmed that the grafting reaction of polystyrene to ASR occurred during emulsion polymerization. The ζ potentials of final latexes showed high values due to ASR that was adsorbed and grafted on the surface of the latex particle. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 543–550, 1998 相似文献
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G. W. Ceska 《应用聚合物科学杂志》1974,18(8):2493-2499
An emulsion polymerization process is reported for the production of high-solids, surfactant-free styrene/butadiene latices. With this procedure latices require no surfactants, for stabilization is built into the emulsion particles by means of copolymerized acid monomers. This “pH variable” method is a two-step, batch-on-batch polymerization. In the first step, all the ingredients are present in the reaction mixture; however, only enough styrene and butadiene is added to reach a low solids content. This step, carried out at low pH, produces a carboxylated seed latex. On raising the pH of this low-solids emulsion, the copolymerized carboxyl groups ionize, and the now highly charged latex particles provide an expedient locus for the generation of stable, highsolids latices. Neutralizing the carboxyl groups of the seed latex before adding the remaining monomers induces the highly hydrophilic carboxyl anions to remain on the surface of the latex particle, nearer to the aqueous environment of the surrounding media. Hence, the maximum stabilization capacity of the acid monomers is utilized. The process was evaluated to ascertain the effects of the following variables: the particle size and solids content of the first step, the nature of the base used to raise the pH, the pH of the dispersion prior to the second step, and the effect of the acid monomer on the latex stability. 相似文献
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无皂乳液聚合制备增稠剂及其性能研究 总被引:3,自引:0,他引:3
以聚乙烯醇为胶体保护剂、N,N′-亚甲基双丙烯酰胺为交联剂,用过硫酸钾-亚硫酸钠引发丙烯酸、丙烯酰胺、丙烯酸丁酯进行无皂乳液聚合,以制备高性能的涂料印花增稠剂,所得产品稳定性好、增稠效果优良。并研究了交联剂、引发剂、胶体保护剂的用量等聚合条件对增稠剂性能的影响。引发剂用量增加,增稠剂黏度下降,黏度指数上升。交联剂用量增加可使增稠剂的黏度出现极大值,但黏度保留率下降。采用PVA作为胶体保护剂,产品增稠能力强,稳定性好,耐电解质等综合性能均较好。 相似文献
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主要研究了在以聚乙烯醇为保护胶体的醋酸乙烯乳液聚合中,乳液与环氧丙烯酸酯、聚氨酯、硅烷等官能团的接枝反应.在以过硫酸铵为引发剂、以聚乙烯醇为保护胶体的醋酸乙烯乳液聚合中,乳液与上述各类官能团间发生的接枝反应直接影响乳液的黏度、固体含量、剪切强度等宏观性质.研究发现官能单体脂肪醇聚氧乙烯醚、丙烯酸异辛酯(2-EHA)等单体和丙烯酸(AA)与乙烯基三乙氧基硅烷共同作用时对乳液的宏观性质影响显著. 相似文献
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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. 相似文献
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VAc-BA-AA三元乳液共聚合研究 总被引:2,自引:0,他引:2
用 (NH4) 2 S2 O8-Na2 SO3氧化还原体系引发醋酸乙烯 (VAc) -丙烯酸丁酯 (BA) -丙烯酸 (AA)三元乳液共聚合 ,研究了引发剂、乳化剂、聚合反应条件对聚合转化率 ,乳液粘度和乳液稳定性的影响。实验结果表明体系动力学与经典 Smith-Ewart的乳液合理论不一致。反应速率 (Rp)随着乳化剂浓度的增加而增大 ,乳液的稳定性受乳化剂浓度的影响。聚合温度、引发剂浓度、丙烯酸的浓度对三元共聚乳液的稳定性也有影响 相似文献
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An emulsion of polystyrene/poly (butylacrylate-methyl methacrylate acrylic acid) core/shell latex particles (PS/P (BA-MMA-AA)) has been prepared by use of three synthetic methods. The effects of synthetic methods on the distribution of carboxyl groups in latex particles were studied. The results show that the seed emulsion polymerization in which the pre-emulsified monomers were added by dropping method to the second stage is the best technique for obtaining the optimum distribution of carboxyl groups on the surface of the latex particles. Furthermore, by using PS/P (BA-MMA-AA), a type of novel composite emulsion of silica sol-PS/P (BA-MMA-AA) was synthesized with the above method. By observation through transmission EM, the morphology of the latex particles obtained shows that a composite structure has been formed between silica sol particles and organic polymer particles. 相似文献
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以甲基丙烯酸酯基烷氧基磷酸酯(PAM-100)、甲基丙烯酸甲酯、丙烯酸丁酯、丙烯酸等为单体,采用预乳化半连续乳液聚合法制备了含磷丙烯酸酯共聚乳液。研究了PAM-100用量对单体转化率、乳液稳定性和乳胶粒粒径及分布的影响,并通过红外光谱(FT-IR)和微型燃烧量热分析(MCC)对乳胶膜的结构及性能进行表征。结果表明:PAM-100的加入有利于提高乳液聚合的稳定性及乳胶膜阻燃性能。与纯丙乳液相比,当PAM-100用量为10wt%时,含磷丙烯酸酯共聚乳液的乳胶粒表面Zeta电位绝对值由34.6mV提高至41.3mV,粒径由169nm下降至132nm;同时,含磷丙烯酸酯乳胶膜热释放速率峰值(pHRR)由391.1W/g下降至333.3W/g,到达pHRR的时间由264s推迟至300s。 相似文献
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丙烯酸乳液胶粘剂的研究 总被引:3,自引:2,他引:3
采用半连续乳液聚合工艺,以MMA、BA、AA等为主要单体,加入乳化剂、引发剂、交联剂,经共聚反应,合成自交联型丙烯酸酯乳液胶粘剂。讨论了聚合机理,考查了固含量、离子稳定性、离心稳定性、剥离强度、拉伸强度、粒径、黏度等多项性能;根据综合的性能测试,分析了单体种类及配比、共聚物的玻璃化温度、丙烯酸用量、乳化剂用量及配比、引发剂用量、温度等因素对乳液型胶粘剂性能的影响,得出了最适宜的反应条件和胶粘剂最佳配方。通过性能对比,表明自交联型丙烯酸酯乳液胶黏剂性能更为优异。 相似文献