高固含量核壳型丙烯酸酯乳液的制备与性能研究

以甲基丙烯酸甲酯为硬单体,丙烯酸丁酯(BA)为软单体,采用半连续种子乳液聚合方法合成了具有核壳结构的高固含量(不挥发物质量分数≥50%)丙烯酸酯乳液。采用红外光谱(FT-IR)、激光粒度仪(LPA)、透射电镜(TEM)等检测手段对产物进行了表征,同时考察了乳化剂的用量及复配比、引发剂、交联剂以及核单体中软单体含量对乳液性能的影响。结果表明:软﹑硬单体发生了共聚反应;乳液粒径分布较窄,核层聚合时适当加入少量BA,乳液的稳定性能明显提高,复合乳化剂m(SDS)∶m(OP-10)为2∶1且质量分数为3%,引发剂KPS质量分数为0.5%,交联剂EGDMA质量分数为2%时可制得性能较好的乳液。     

A new concentrated emulsion polymerization pathway

To ensure the stability of the concentrated emulsions that are employed as precursors for polymerization, a two-step concentrated emulsion polymerization pathway is described. In the first step, the monomer is partially polymerized by heating at 50°C until a certain conversion is reached. Subsequently, the partially polymerized monomer is used as the dispersed phase to prepare a concentrated emulsion in which water constitutes the continuous phase. The concentrated emulsion has a large volume fraction of the dispersed phase (0.74–0.99) and the appearance of a gel. Several typical monomers are employed to correlate the stability of the concentrated emulsion and the extent of partial polymerization of the dispersed phase. It was found that monomers, which cannot lead to stable concentrated emulsions, can generate them after partial polymerization. Subsequent polymerization of the concentrated emulsion leads to latex particles. Copolymers and polymer composites were also prepared by the two-step procedure. In the latter case, water was replaced with a solution of a hydrophilic monomer in water as the continuous phase. © 1992 John Wiley & Sons, Inc.     

改性玻璃纤维短切毡粘结剂的研制

介绍了无碱玻璃纤维短切原丝毡的特性,短切毡的制法,粘结剂的种类及粘结剂对短切毡的影响。通过实验,分析了单体配比对乳液膜性能的影响。得出结论:在固定了BA和其他单体的质量分数后,随着单体A用量的增加,乳液膜的玻璃化温度下降,断裂伸长率也提高,同时拉伸强度有所下降;随着单体B用量的增加,乳液膜的玻璃化温度下降,断裂伸长率也提高,同时拉伸强度有所下降;单体A对玻璃化温度的效果稍微好一点。     

聚丙烯酸酯涂料印花黏合剂的合成与性能研究

以过硫酸铵(APS)为引发剂、甲基丙烯酸甲酯(MMA)为硬单体、丙烯酸丁酯(BA)和丙烯酸异辛酯(EHA)为软单体、丙烯酸(AA)为功能单体和N-羟甲基丙烯酰胺(NMA)为交联单体,采用预乳化法合成出一种聚丙烯酸酯涂料印花黏合剂。讨论了单体滴加方式、预乳化液滴加时间、阴/非离子型乳化剂配比及用量、交联剂和各单体用量等对该黏合剂乳液性能的影响。结果表明:当w(BA)=15%、w(EHA)=8%、w(MMA)=20%、w(NMA)=3.0%、滴加时间为2.5 h、复合乳化剂中m(SDS):m(OP-10)=1:2且w(复合乳化剂)=6%时,该黏合剂乳液具有优良的综合性能,能够满足织物印花的使用要求。     

Monomer-to-water ratios as a tool in controlling emulsion copolymer composition: The methyl acrylate–indene system

A drifting copolymer composition as a function of conversion is an aspect typical of copolymerization. Reducing this so-called composition drift in batch copolymerizations will lead to a decrease in chemical heterogeneity of the copolymers formed. For monomer systems in which the more water-soluble monomer is also the more reactive one, theory predicts that composition drift in emulsion copolymerization can be reduced or even minimized by optimizing the monomer-to-water ratio. The monomer combination methyl acrylate–indene (MA–Ind) meets the requirements needed to minimize composition drift in batch emulsion copolymerization. Therefore, this monomer combination is chosen as a model monomer system in order to verify this theoretical prediction. Reactivity ratios needed for model predictions have been determined by low conversion bulk polymerization, resulting in r_MA = 0.92 ± 0.16 and r_Ind = 0.086 ± 0.025. Furthermore, emulsion copolymerization reactions at the same monomer mole fraction are performed at different monomer to water ratios. From the good agreement between experiments and theoretical predictions for MA–Ind, it was concluded that control and even minimization of composition drift in batch emulsion copolymerization for monomer systems in which the more water-soluble monomer is also the more reactive one is indeed possible by changing the initial monomer-to-water ratio of the reaction mixture provided that the reactivity ratios of both monomers are not too far from unity. © 1994 John Wiley & Sons, Inc.     

Copolymer composition control in emulsion polymerization using technical grade monomers

A method to determine the minimum time monomer addition policy for composition control in emulsion polymerization systems when technical grade monomers are used is presented. The method involves a series of semicontinuous emulsion copolymerizations carried out under semistarved conditions. The values of the propagation rate constants, reactivity ratios and monomer partition coefficients are required to use the approach. The method is model-independent and does not require extremely accurate measurements of the particle size. The method was checked in the methyl methacrylate-ethyl acrylate seeded emulsion copolymerization. The monomers contained 4-methoxyphenol as inhibitor. It was found that the iterative approach converged rapidly.     

Removal of Residual Monomers from Polymer Emulsions by Steam Stripping

Abstract

Removal rates of residual monomers from polymer emulsions by batch steam stripping were modeled. Model parameters were emulsion batch charge, steam sparge rate, emulsion solids content, and phase—equilibrium relationships for systems containing monomer, polymer, and water. Experiments in which steam was sparged into a column partially filled with emulsion were performed to verify the model. The model and data showed good agreement. Theory and experiments demonstrated that monomer desorption was dependent upon steam sparge rate and solids content, whereas temperatures had little effect on monomer removal.     

Thiol-ene emulsion polymerization using a semi-continuous approach

The thermally initiated thiol-ene emulsion polymerization of diallyl phthalate (DAP) diene and ethylenedioxy diethanthiol (EDDT) dithiol monomers in batch and semibatch emulsion polymerization is investigated. The batch process leads to larger and broader particle sizes than when the polymerization is carried out in semibatch. The evolution of the particle size and the final particle size distribution indicate that the stability of the latexes is limited and, hence, aggregation phenomena occurred in both processes. In particular, the evolution of the particle size distribution (PSD) in the semibatch process indicates nucleation, growth, and aggregation occurring simultaneously that produced a bimodal particle size. When the diene monomer was changed to diallyl terephthalate (DATP), the semibatch polymerization yielded smaller particles and narrow distribution without any indication of aggregation. The partial substitution of the dithiol by a trithiol monomer that is substantially more water insoluble affected nucleation of the particles, yielding for both systems smaller particles. The polythioether polymers synthesized present low glass transition temperatures (~ −30/−40°C) and those containing the therephthalate yield crystalline films. The potential application of the polymers as pressure sensitive adhesives (PSAs) was preliminarily assessed.     

丙烯酸酯乳液的合成及改性研究

以丙烯酸丁酯(BA)和丙烯酸-2-乙基己酯(2-EHA)为软单体、甲基丙烯酸甲酯(MMA)为硬单体、丙烯酸(AA)为功能单体、甲基丙烯酸羟乙酯(HEMA)为交联单体和十二烷基硫酸钠(SDS)/乳化剂(OP-10)为阴/非离子型复合乳化剂,采用核/壳种子乳液聚合法制备了丙烯酸酯共聚乳液;然后在壳层聚合时寸加入HEMA,并用乙烯基有机硅进行改性,制得硅丙乳液。结果表明:当m(SDS):m(OP-10)=3:2、w(复合乳化剂)=3.4%、w(引发剂)=0.82%、w(HEMA)=3.5%、聚合温度为80℃以及聚合中期加入6.8%乙烯基硅油至壳单体中时,硅丙乳液及其胶膜的稳定性、耐水性和力学性能俱佳。     

影响苯丙乳液黏度与粒径的因素分析

采用种子乳液聚合法,以苯乙烯、丙烯酸丁酯、丙烯酸异辛酯、甲基丙烯酸甲酯等为主要原料合成了用于制备胶粘剂的苯丙乳液。重点研究了引发剂、乳化剂及种子单体的用量及硬软单体不同配比对苯丙乳波黏度和粒径的影响。实验结果表明,当引发剂用量为0.5％（占单体总质量,后同）、乳化剂用量为1％、种子单体用量为8％、硬软单体配比为30／46的条件下,合成的笨丙乳液黏度较高、粒径小、粒度分布宽,用该乳液制备的胶粘剂具有优良的施工性能.     

引发剂对醇酸-聚丙烯酸酯杂化乳液成膜性的影响

采用种子微乳液聚合法合成了醇酸-聚丙烯酸酯杂化乳液。通过不同的引发剂和用量导致所得乳液成膜性发生变化,探讨了引发剂对醇酸-聚丙烯酸酯杂化乳液成膜性的影响。结果表明:油性引发剂BPO比AIBN更适合接枝反应,以醇酸树脂与丙烯酸单体总量2%的BPO及丙烯酸单体量0.4%的APS组合体系引发聚合反应,所得杂化乳液涂膜透明、高光。     

The Effects of Monomer Size Distribution on the Radiative Properties of Black Carbon Aggregates

Black carbon (BC), normally existing as aggregates, significantly affects the Earth radiative forcing, energy balance, and climate by scattering and absorbing both solar radiation and terrestrial emission. The BC particles are usually treated as fractal aggregates with same-sized monomers. However, experimental studies show that monomer diameters of BC normally obey a lognormal distribution ranging from 10 nm to over 100 nm. This study investigates the effects of monomer size distribution on the radiative properties of BC particles. The fractal aggregates are generated by a cluster–cluster aggregation (CCA) algorithm, and the Multiple Sphere T-Matrix (MSTM) method is used to simulate the radiative properties of randomly oriented aggregates. The integral radiative properties of aggregates with different-sized monomers have normal distributions with large standard deviations, and it requires to average radiative properties of over 60 aggregate realizations to represent their ensemble-averaged properties. The aggregates with different-sized monomers exhibit much stronger scattering and absorption than the aggregates with same-sized monomers and the geometric mean diameter, whereas the absorption cross section becomes comparable to that given by aggregates with same-sized monomer and the equivalent volume diameter. Similar phase matrix elements are obtained for the aggregates with different-sized and same-sized monomers. Furthermore, the Rayleigh-Debye-Gans (RDG) approach is significantly challenged for approximating the absorption and scattering cross sections of the aggregates with different-sized monomers, whereas it performs quite accurately for the phase matrix elements.

Copyright 2015 American Association for Aerosol Research     

氟碳铝型材保护膜用压敏胶的制备与性能

以丙烯酸丁酯(BA)和丙烯酸异辛酯(2-EHA)为软单体、甲基丙烯酸甲酯(MMA)为硬单体、丙烯酸(AA)和丙烯酸羟丙酯(HPA)为功能单体,采用降低PSA(压敏胶)的Tg(玻璃化转变温度)和预乳化半连续乳液聚合法合成了丙烯酸酯PSA乳液。研究结果表明:当m(软单体)∶m(硬单体)∶m(功能单体)=90∶5∶5、m(BA)∶m(2-EHA)=1∶2、w(AA)=1.0%、w(HPA)=5%、w(缓冲剂)=0.25%、w(引发剂)=w(复合乳化剂)=0.6%且m(阴离子型乳化剂)∶m(非离子型乳化剂)=1∶1时,PSA乳液的综合性能相对最好,用该PSA制成的保护膜对氟碳铝型材具有良好的附着力,并且其耐湿热老化性能和耐热老化性能俱佳。     

丙烯酸酯核壳乳液合成及涂料耐沾污性的研究

讨论了丙烯酸酯乳液核壳单体中软硬单体的比例、壳层中掺交联单体、有机硅单体以及核壳乳液聚合中可聚合乳化剂的用量对丙烯酸酯外墙涂料沾污性的影响。结果表明,在壳层中HEMA的掺量以1．5％、可聚合乳化剂用量以1％～2％、有机硅单体掺量以4％时,有利于丙烯酸酯核壳乳胶涂料耐沾污性的提高。     

水溶性单体共聚法制备无皂苯丙乳液的研究

以苯乙烯(St)、丙烯酸(AA)、甲基丙烯酸甲酯(MMA)和丙烯酸丁酯(BA)为共聚单体,制备了无皂苯丙乳液;然后以AA含量、中和度、引发剂含量和软/硬单体配比等为试验因素,以乳液稳定性和粒径为考核指标,采用单因素试验法优选出制备无皂苯丙乳液的最佳工艺条件。结果表明:当w(引发剂)=1.2%和w(AA)=4.5%(均相对于单体总质量而言)、中和度为0.8、m(BA)∶m(St+MMA)=4∶6和反应温度为78℃时,可制得粒径为纳米级的高固含量稳定乳液。     

复合交联型JS防水乳液的研制

通过对一种JS乳液共聚配方的研究,在乳液反应过程中添加乳化剂和交联单体肛羟甲基丙烯酰胺、有机硅氧烷对JS乳液进行改性,提高了乳液的耐水性能、黏结强度和抗拉强度;调胶时,加入分散剂DA-02,保证水泥粉在乳液中更好地分散。并综合各方面因素对乳液性能的影响,得出了最优配方,即ⅥW_H-870=0．6％（乳液总量）、W_A-17=0．7％（单体总量）、W_NMAM=2．0％（单体总量）、W_DA-02=2．0％（乳液总量）时,得到JS乳液可以满足聚合物水泥防水涂料的要求。     

药物包衣用EA-MMA共聚物的聚合稳定性研究

以EA(丙烯酸乙酯)和MMA(甲基丙烯酸甲酯)为共聚单体、SDS(十二烷基硫酸钠)/OP-10(壬基酚聚氧乙烯醚)为阴/非离子型复合乳化剂,采用乳液聚合法制备出一种缓释型药物包衣用EA-MMA二元共聚物,并对其聚合稳定性进行了研究。结果表明:当m(SDS)∶m(OP-10)=1∶2.0、w(总乳化剂)=2.0%(相对于体系总质量而言)、w(引发剂)=0.60%(相对于单体总质量而言)、反应温度为80℃和反应时间为4 h时,制成的EA-MMA二元共聚物乳液稳定性较好、外观较佳、单体转化率(93.22%)和乳液固含量(29.85%)相对较高。     

改性苯丙乳液的单体筛选

对八甲基环四硅氧烷、乙烯基环四硅氧烷、三氟乙酸丙烯酯、含氢聚硅氧炕、乙烯基三乙氧基硅烷等改性苯丙乳液的反应体系稳定性及涂膜性能进行了比较。研究表明以上几种单体均可用于苯丙乳液改性,改性单体不同对反应速度影响不大,但以八甲基环四硅氧烷-乙烯基环四硅氧烷-三氟乙酸丙烯酯的混合物作改性单体所得乳液性能最优。     

单组分自乳化水性环氧树脂的合成及其涂膜性能研究

用有机硅、甲基丙烯酸及其酯类单体接枝改性环氧树脂,合成了具有自乳化性能的水性环氧树脂乳液。用激光粒度分析仪测定乳液的粒径及其分布,用傅里叶红外、热重分析仪对聚合产物作了结构表征和热分析。考察了温度、引发剂用量对接枝率及接枝率对乳液成膜性能的影响;甲基丙烯酸、有机硅及单体总量对乳液稳定性、成膜物耐水性和耐盐水性的影响。结果表明:当配方选用引发剂、有机硅用量分别为单体总质量的5.5%、2.5%,m(单体总量)∶m(环氧树脂)=1∶2,丙烯酸及其酯类单体的玻璃化温度Tg为30℃,体系酸值为35 mgKOH/g,接枝温度为110℃时,制得的水性环氧树脂乳液具有良好的稳定性、耐水性及耐盐水性。     

Measurements of monomer partitioning in emulsion copolymerization systems

A new apparatus to measure the equilibrium solvent activity in a multiphase system containing a particulated polymer is presented. An experimental procedure to determine the monomer partitioning in typical emulsion copolymerization systems is developed; the method is devised in a way that no phase separation between water and swollen polymer particles is required in order to determine the monomer content in each phase. The analytical technique used is quantitative gas chromatography, either of the vapor or of the liquid phases. Different monomers (styrene, methyl methacrylate, and vinyl acetate) and polymeric matrices (polystyrene and methyl methacrylate–vinyl acetate copolymer) are examined both above and below saturation conditions (corresponding to intervals II and III of an emulsion polymerization process). The experimental results are compared with predictions of a literature model. © 1996 John Wiley & Sons, Inc.