高固含量聚丙烯酰胺反相微乳液的制备

研究了高单体质量分数(25%～40%)下丙烯酰胺的反相微乳液聚合反应,使用工业白油作为分散介质,使用复合非离子乳化剂稳定反应体系,使用焦亚硫酸钠引发聚合。研究了引发剂组成及浓度、交联剂浓度、温度及单体浓度对反应转化率和聚合物分子质量的影响。结果表明,转化率和分子质量主要受引发剂浓度及单体浓度的影响。根据筛选出来的优化条件,制备了固含量接近40%、分子质量约850万的聚丙烯酰胺微乳液。     

Inverse microemulsion copolymerization of butyl acrylate and acrylamide: kinetics,colloidal parameters and some model applications

The inverse microemulsion copolymerization of acrylamide and butyl acrylate initiated by ammonium peroxodisulphate, a water‐soluble initiator, and stabilized by anionic emulsifiers sodium bis‐2‐ethylhexylsulfosuccinate and sodium dodecylsulphate (SDS) has been studied. An increase of SDS concentration was observed to increase both the rate of polymerization and the particle size. The average number of radicals per particle (n?) is much below 0.5, which indicates desorption of monomeric radicals from polymer particles. The exit (desorption) rate constants k′_des (cm² s^?1) and k_des (s^?1) were evaluated as a function of SDS concentration (or the particle size) according to the Ugelstad/O'Toole (I), Nomura (II) and Gilbert (III) models. The value of k_des (s^?1) decreases with increasing particle size (or SDS concentration) for all three (I, II and III) models. A complex trend appears for k′_des (cm² s^?1): the Ugelstad/O'Toole model estimates a decrease, the Nomura model finds no variation and the Gilbert model estimates even a slight increase in k′_des with increasing SDS concentration. Copyright © 2006 Society of Chemical Industry     

反相微乳液聚合引发剂对聚丙烯酰胺分子质量影响的研究

分别以三种引发剂体系为引发剂,从引发机理出发,通过正交实验研究了丙烯酰胺反相微乳液聚合中引发剂种类、引发剂浓度、反应温度、单体浓度等对聚丙烯酰胺(PAM)相对分子质量的影响。结果表明,引发剂种类对水溶性PAM相对分子质量有显著的影响;过硫酸铵-亚硫酸氢钠和偶氮二异丁腈复合引发体系是合成高相对分子质量PAM的有效引发体系。该引发体系在反应温度为40℃,氧化还原引发剂与偶氮的质量比为1∶4,单体浓度为20%,引发剂浓度为0.3%,pH为9的最佳条件下合成的PAM相对分子量为1.44×107。     

反相微乳液聚合制备丙烯酰胺类聚合物微球的研究进展

反相微乳液聚合技术具有稳定性好、固含量高、聚合速率快等优点而成为研究热点。本文系统地综述了近年来国内外应用反相微乳液聚合制备丙烯酰胺类聚合物微球的研究进展,概述了微乳液的基本理论及其特征,对稳定微乳液的制备进行了讨论;着重归纳了丙烯酰胺类的反相微乳液聚合,详述了聚合体系各组分的选择,同时探讨了影响聚合反应的因素,认为应研究新型表面活性剂以实现高单体浓度的聚合;介绍了聚合物微球在油田应用中提高采收率方面的应用现状。最后指出了其在深部调剖堵水领域存在的问题,以离子液体代替传统聚合体系组分制备集智能性、复合性、多功能性等综合性能于一体的聚合物微球是其未来发展方向之一。     

Polymerization of acrylamide in styrene containing inverse microemulsions: polymerization kinetics and polymer product composition studies

The kinetics of free‐radical homopolymerization and copolymerization of acrylamide (AAm) and styrene (S) initiated by water‐soluble ammonium peroxodisulfate, (APS) or by toluene‐soluble dibenzoyl peroxide (DBP) in inverse microemulsion toluene/S/AOT (sodium bis(2‐ethylhexyl)sulfosuccinate)/water/AAm characterized by a low volume fraction of the aqueous phase (Φ_aw ≈ 0.08) as a function of the concentration of S in the oil phase of the inverse microemulsion system have been studied. S strongly decreases the rate of AAm/S (co)polymerization. This is valid for both APS and DBP initiators. Kinetic measurements indicate the important role for cross‐initiation of water soluble AAm growing chains and of oil soluble S analogues activated by the primary free‐radicals generated from APS (or from DBP) in the dispersed water droplets (or in the continuous oil‐phase) of the inverse microemulsion, respectively. With inverse microemulsions containing toluene (70.73 %)/S (2.44 %)/AOT(17.56 %)/water (7.32 %)/AAm (1.95 %), after polymerization (initiator APS, 3.04 × 10⁻² mol dm⁻³ of water) and separation of the polymeric components, the following yields were obtained: AAm/S (co)polymer (89.20 mass%; ie 62.24 mass% of AAm structural units and 26.96 mass% of S structural units), polyacrylamide (9.4 mass%) and polystyrene (1.4 mass%). © 2000 Society of Chemical Industry     

辛烷/Span80-Tween60/丙烯酰胺/水反相微乳液聚合动力学

对辛烷／Ｓｐａｎ８０－Ｔｗｅｅｎ６０／丙烯酰胺／水反相微乳液聚合的研究表明,其反应速度快,不到３０ｍｉｎ单体转化率即可达９０％以上。聚合过程中基本不存在恒速期,聚合速率在转化率接近２０％时达到峰值后随即迅速下降。通过进一步考察单体浓度（［Ｍ］）、引发剂浓度（［Ｉ］）、乳化剂浓度（［Ｅ］）、乙酸钠浓度以及反应温度对转化率为５％时的聚合速率（Ｒｐ,５％）和最大聚合速率（Ｒｐ,ｍａｘ）以及聚合物平均相对分子质量（Ｍｖ）的影响,得到如下动力学关系式：Ｒｐ,５％∝［Ｍ］１．０２［Ｉ］０．４５［Ｅ］－０．３…     

Photoinitiated copolymerization of acrylamide and styrene in oil-in-water microemulsion

This article describes the copolymerization of acrylamide with styrene in oil-in-water microemulsion, using dodecyl betaine as emulsifier and α-hydroxy-α,α-dimethyl acetophenone or α,α-dimethoxy-phenyl acetophenone as photoinitiator. Results indicated that the photoinitiation of polymerization occurs at the interface between the oil phase and the water phase and that the polymerization occurs in the microemulsion droplet. Particle size increased with increasing polymerization time. The copolymer chain consisted of isolated acrylamide units randomly distributed among styrene groups. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 66: 2543–2549, 1997     

Preparation of partly hydrophobized,crosslinked polyacrylamide particles by terpolymerization of acrylamide/ N,N‐methylenebisacrylamide/styrene in inverse microemulsion

Free‐radical polymerization of a termonomer system comprising acrylamide (AAm) N,N ′‐methylenebisacrylamide (MBAAm) and styrene (S) initiated by water‐soluble ammonium peroxodisulphate (APS) or by toluene‐soluble dibenzoyl peroxide (DBP) in inverse microemulsion (toluene/S/AOT//water//AAm/MBAAm), leads to the formation of partly hydrophobized crosslinked polymer particles of tailored chemical composition, degree of crosslinking and polymer particle size. Styrene strongly decreases the rate of terpolymerization, while the presence of MBAAm has almost no effect on the polymerization rates observed. This conclusion is valid for both APS and DBP initiators. Increase of the S/T mass ratio (T is toluene) in inverse microemulsion leads to an increase of polymer particle diameter from about 20 nm to about 50 nm attributed to toluene swelling of the styrene‐rich structural moieties of AAm‐co‐S copolymer located on the surface of polymer particles. Polymerization kinetics measurements pointed to the important role of exiting water soluble AAm and MBAAm monomer radicals generated by thermal decomposition of APS in water pools of inverse micelles for initiation of polymerization reactions of sparingly water‐soluble S monomer in the oil‐phase of the inverse microemulsion. It was shown that the polymerization and copolymerization reactions of S in the presence of AAm and/or MBAAm are effectively initiated by water‐soluble APS and also by oil‐soluble DBP initiators. During dialysis the polymerized single‐phase water/oil Winsor IV inverse microemulsion gradually converts itself into a two‐phase oil/water Winsor I dispersion system with volume fraction of aqueous phase Φ_aw ≈ 0.950. The water phase contains water swelled, crosslinked polymer particles of diameters 80–300 nm. During dialysis, toluene and the sodium salt of bis(2‐ethyl hexyl)sulphosuccinic acid (AOT) partition between the oil phase of the dialysed dispersion system and the water dialysate. After evaporation of water from the dialysed inverse microemulsion, solid, dried, crosslinked polymer particles in the form of a transparent film, almost uncontaminated by AOT surfactant, were obtained. © 2000 Society of Chemical Industry     

The inverse emulsion polymerization of acrylamide with pentaerythritolmyristate as emulsifier. 1. Experimental studies

The inverse emulsion polymerization of aqueous acrylamide solutions in isooctane as dispersing media with the emulsifier pentaerythritolmyristate and an oil-soluble azo initiator was studied, particularly with respect to the influence of the chemically pure emulsifier. In this free radical polymerization, a water-in-oil emulsion with droplet sizes around 10μm is converted into a latex with average particle diameters between 80 and 200nm containing a polymer with molar masses up to 16×10⁶gmol^-1 Kinetic data were measured by adiabatic as well as by isothermal calorimetry. The influences of various parameters on polymerization kinetics, particle numbers and molar mass averages were studied. Experimental results show a positive influence of the emulsifier concentration on the reaction rate and indicate the dominance of a bimolecular termination re-action with respect to the polymer radicals above a certain initiator concentration. © 1998 SCI.     

The inverse emulsion polymerization of acrylamide with pentaerythritolmyristate as emulsifier. 2. Mathematical modelling

A mathematical model of the inverse emulsion polymerization of aqueous acrylamide solutions in isooctane as dispersing media with the chemically pure emulsifier pentaerythritolmonomyristate and an oil-soluble azo initiator has been developed. A Monte Carlo method was used successfully to calculate the kinetics, molar mass averages and average particle sizes. The computation time of the method was reduced by calculating the chain length of the polymer molecules via the life-time of the radicals. It is shown that a few assumptions based on the mirror image of an ideal conventional emulsion polymerization with Smith–Ewart case 2 kinetics are sufficient to comprehensively describe the experimental findings. © 1998 SCI.     

Inverse micro-emulsion polymerization of acrylamide in the presence of a mixture of oleophilic/hydrophilic surfactants

The effect of sodium dodecyl sulphate (SDS) on the formation of inverse micro-emulsion toluene/sodium bis(2-ethylhexyl)sulphosuccinate (AOT)/water/acrylamide (AAm)/SDS and on polymerization of acrylamide initiated by oil soluble dibenzoyl peroxide was studied. The presence of SDS shifts the value of the volume fraction of aqueous phase (Φ_aw) at which a two-phase Winsor II system forms, to higher values. It was shown that an increase of the mass ratio of SDS/water led to a decrease of acrylamide polymerization rate, of polyacrylamide particle size and of polyacrylamide molecular mass distribution. It was also found that in the presence of SDS, a nearly constant value for acrylamide polymerization rate in inverse micro-emulsion in the range of Φ_aw values between 5% and 50% can be obtained. The polymerization kinetics and polymer particle formation were explained as consequences of the initiation of acrylamide polymerization in two reaction loci—in inverse micelles and in the oil macrophase of the inverse micro-emulsion. © 1998 SCI.     

The inverse emulsion polymerization of acrylamide using poly(methyl methacrylate)‐graft‐polyoxyethylene as the stabilizer

Inverse emulsion polymerization of an aqueous solution of acrylamide (AM) in toluene is carried out using poly(methyl methacrylate)‐graft‐polyoxyethylene (PMMA‐g‐PEO) as an emulsifier. The kinetics of polymerization, morphology of the particle, and particle size of the inverse emulsion have been investigated. The rates of polymerization are found to be proportional to the initiator concentration, the monomer concentration, and the emulsifier concentration. The morphology of particles shows a spherical structure. The mechanism of inverse emulsion polymerization using amphipathic graft copolymer as the emulsifier is proposed. The resulting molecular weights of polyacrylamide are extremely high, and relate to the amphipathic graft copolymer structure. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 79: 528–534, 2001     

Synthesis of cationic flocculants by the inverse microemulsion copolymerization of acrylamide with 60% 2‐acryloxyethyltrimethyl ammonium chloride in the monomer feed. I. Initiation by ammonium persulfate/sodium disulfite redox system

Acrylamide/2‐acryloxyethyltrimethyl ammon‐ium chloride copolymers in inverse microemulsion, with a cationic charge density of 60% and a concentration of active matter of 30 wt %, of interest as flocculants have been obtained by inverse microemulsion copolymerization. Interesting inverse microemulsion formulations from both industrial and economical standpoints were selected from pseudoternary phase diagrams. These formulations were polymerized by semicontinuous free radical copolymerization in inverse microemulsion using sodium disulfite and ammonium persulfate as initiators. Influence of initiators and initiator addition conditions (specific flow rate and concentration) on semicontinuous polymerization and final product properties as flocculants have been studied. A strong difference in copolymer solution viscosity has been found when an aqueous solution of sodium disulfite is used as initiator instead of sodium disulfite/ammonium persulfate couple redox, specially for low sodium disulfite solution feeding flow. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 2826–2836, 2007     

Synthesis of cationic flocculants by the inverse microemulsion copolymerization of acrylamide with 60% 2‐acryloxyethyltrimethyl ammonium chloride in the monomer feed. II. Influence of the formulation composition,hydrophilic‐lipophilic balance,starting polymerization temperature,and reaction time

Acrylamide/2‐acryloxyethyltrimethylammonium chloride copolymers in inverse microemulsions, with 60% 2‐acryloxyethyltrimethyl ammonium chloride in the monomer feed and a concentration of active matter of 30% (w/w) as flocculants, were obtained by inverse microemulsion copolymerization. Inverse microemulsion formulations of comonomers, interesting from both technical and economical viewpoints, were polymerized by semicontinuous free‐radical copolymerization with sodium disulfite as the initiator. The influence of the formulation composition, hydrophilic‐lipophilic balance (HLB), starting polymerization temperature, and reaction time on the polymerization and final properties of the products as flocculants was studied. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103:186–197, 2007