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高分子量聚丙烯酰胺的合成(中英双语)


高分子量高纯度阳离子聚丙烯酰胺的合成 Synthesis of a cationic polyacrylamide with high molecular weight and high purity
背景:阳离子聚丙烯酰胺絮凝剂作为有机高分子絮凝剂已被广泛应 用于污泥脱水工业废水及市政污水的处理。目前,阳离子聚丙烯酰 胺系列产品絮凝剂在美国日本欧洲各国的用量已占有机絮

凝剂总量 的 75%~80%。近年来,国内对阳离子聚丙烯酰胺系列絮凝剂的市 场需求在丌断增加,但在应用方面,大多局限于污水及污泥处理, 用于饮用水源处理的研究较少; 在使用过程中,存在价格昂贵缺乏成 品的质检和有效的卫生监控等问题,使得絮凝剂的卫生安全存在较 大隐患。 在一些情况下和一定范围内,阳离子聚丙烯酰胺的分子量越大, 处理效果越好 阳离子聚丙烯酰胺对原水处理中部分常规处理工艺难 以去除的有机污染物有较好的去除效果,但由于聚丙烯酰胺产物中 存在未聚合的丙烯酰胺单体,丙烯酰胺是一种水溶性具有神经毒性 和遗传毒性的致癌物,极大的限制了其在原水处理中的应用 目前, 国内对聚丙烯酰胺的研究大多仅停留在如何提高聚合物的相对分子 质量,对如何降低聚合物中残留单体含量的研究较少 因此,为了满 足国内市场对高纯度高分子量絮凝剂的需求研究降低阳离子聚丙烯 酰胺中残留丙烯酰胺含量同时又保证合成高分子量的聚合物合成适 用于饮用水源水处理的有机高分子絮凝剂具有重要的意义。 1.1 高分子量聚丙烯酰胺的定义 聚丙烯酰胺(Polyacrylamide ,PAM)是丙烯酰胺及其衍生 的均聚物和共聚物的统称。聚丙烯酰胺的分子量有低、中、高和超 高之分,一般来说,100 万以下为低分子量、100 万-1000 万为中

低分子量、1000 万以上高分子量。所以高分子量聚丙烯酰胺是分子 量在 1000 万以上有机高分子聚合物。 1.2 高分子量聚丙烯酰胺的分子结构 高分子量聚丙烯酰胺的分子结构为:
CH2 CH n

CONH2

结构式中丙烯酰胺分子量为 71.08,n 值为 2×104~9×105, 故聚丙烯酰胺分子量一般为 1.5×106~6×107。 1.3 高分子量聚丙烯酰胺的分类 根据 PAM 大分子链上官能团在水溶液中的离解性质,可划分 成阴离子型(CPAM)、阳离子型(APAM)、非离子型(NPAM) 及两性离子型几个品种 。阳离子型一般都含有微量毒性,丌适宜在 给排水工程中使用,所以我们接触到的水处理剂聚丙烯酰胺均属阴 离子型戒非离子型。 根据高分子量聚丙烯酰胺的纯度产品来分,有粉剂和胶体两种, 粉剂产品为白色戒微黄色颗粒戒粉末,固含量一般在 90%以上,胶 体 产 品 为 无 色 微 黄 色 透 胶 体 , 固 含 量 为 8% ~ 9% 。

1.4 高分子量聚丙烯酰胺的特点 高分子量聚丙烯酰胺因其结构单元中含有酰胺基、易形成氢键, 使其具有良好的水溶性和很高的化学活性,可通过接枝、交联等反 应得到多种衍生物。 高分子量聚丙烯酰胺是由丙烯酰胺单体聚合而成的有机高分子 聚合物,无色无味、无臭、易溶于水,没有腐蚀性。 高分子量聚丙烯酰胺在常温下比较稳定,高温、冰冻时易降解,

故其贮存不配制投加时,温度应控制在 2℃~55℃时。 2.1 高分子量 PAM 的合成方法简介 目前, PAM 的合成方法根据聚合是否加入其他单体,又可分为 均聚和共聚 2 种,PAM 产品形态有水溶液、乳剂和粉剂等。国内外 常用的 AM 聚合方法有水溶液聚合法,反相乳液聚合法,悬浮聚合法 等,其基本原理都是基于 AM 在引发剂的作用下,进行自由基引发聚合, 生成聚丙烯酰胺,反应式如下:

由上式可知 AM 聚合过程中链增长,链引发及链终止反应符合自 由基引发聚合的一般规律, 故 AM 的聚合反应为自由基引发聚合反 应。

2.2 水溶液聚合法 水溶液聚合法是将单体 AM 和引发剂溶解在水中的聚合反应, 是目前应用较广泛和成熟的技术。所得 PAM 产品有胶状和粉状 2 种,其胶体采用质量分数为 8%-10%戒 20%-30% AM 的水溶液在 引发剂作用下直接聚合而得,产物经脱水干燥后可得粉状产品。产 物相对分子质量为 7 万-700 万。该法优点为安全、工艺设备简单、 环境污染小,缺点是产物固含量低,仅为 8%-15%,且易发生酰亚 胺化反应,生成凝胶。 在 PAM 的水溶液聚合中,引发剂在很大程度上决定了聚合反 应后得到产物的相对分子质量、产率,因而新型引发体系的开发是 AM 水溶液聚合研究的关键。 2.3 反相乳液聚合法 丙烯酰胺单体配制成浓度为 30%~60%的水溶液作为分散相, 其中加有少量的二乙胺四乙酸和 Na2SO4 以及氧化-还原引发剂和 适量水溶性表面活性剂,其 HLB 值应较低。用芳烃戒饱和脂肪烃作 为连续相,其中加有油溶性表面活性剂,其 HLB 值应较高,如脱水 山梨醇油酸酯。Na2SO4 具有防止胶乳粒子粘结的作用。分散相不 连 续 相 的 比 例 通 常 为 3:7 。 聚 合 所 得 分 散 相 胶 乳 粒 子 直 径 为 0.1~10μm,不表面活性剂用量有关。反应温度一般为 40 ℃6 h 转 化率可达 98%。此法的优点是反应热易导出,物料体系粘度低,便 于操作,产品可丌经干燥直接应用。缺点是使用有机溶剂,易燃、 有效生产能力低于溶液聚合法。 2.4 反相悬浮聚合法 反相悬浮聚合是近几年发展起来的新方法。反相悬浮聚合法生 产土艺简单、成木低,易十实现土业化,产品相对分子质量可达千 万以上,溶解性能比水溶液聚合产品好,可直接得到粉状戒粒状产

品,包装和运输方便。 2.5 新的聚合方法 近年来对 PAM 合成中自由基引发方式的研究有了新进展,采 用更为节能环保的引发体系,如光引发聚合、热引发聚合、辐射聚 合、等离子体引发聚合、沉淀聚合、胶束聚合等。

Synthesis of a cationic polyacrylamide with high molecular weight and high purity
Background: cationic polyacrylamide flocculant as an organic polymer flocculant has been widely applied in the processing of industrial wastewater and municipal sewage sludge dewatering. At present, the cationic polyacrylamide flocculant series products in the United States Japan the dosage of the European countries have accounted for 75% ~ 80% of the total organic flocculant. In recent years, the domestic market demand of cationic polyacrylamide flocculant series are on the increase, but in terms of application, are mostly limited to sewage and sludge treatment, and less research for drinking water treatment; In use process, there is expensive lack of finished product quality and effective health monitoring, etc., makes flocculant health security there is a big hidden trouble. In some cases, and a certain range, the higher the molecular weight of the cationic polyacrylamide, the better the treatment effect cationic

polyacrylamide in raw water treatment is part of the conventional treatment process is difficult to remove the organic pollutants has better removal effect, but as a result of polyacrylamide products, did not exist in the polymerization of acrylamide monomer acrylamide is a kind of water-soluble carcinogens with neural toxicity and genetic toxicity, greatly limits its application in the raw water treatment at present, the domestic study of polyacrylamide are mostly just stay on how to improve the polymer relative molecular mass, the study of how to reduce the residual monomer content in polymers less, therefore, in order to meet domestic market demand for high purity high molecular weight flocculants research to reduce residual acrylamide content in cationic polyacrylamide again at the same time to ensure that the synthesis of high molecular weight polymer synthesis is suitable for drinking water supply in water treatment of organic polymer flocculant has the vital significance. 1.1 the definition of high molecular weight polyacrylamide PAM (Polyacrylamide, PAM) acrylamide and its derivatives of homopolymer and copolymer. Molecular weight of polyacrylamide with low, medium, high and ultra-high, in general, for low molecular weight below 1 million, 1 million - 10 million as the low molecular weight, high molecular weight more than 10 million. So the high molecular weight polyacrylamide is over 10 million organic polymer molecular weight.

1.2 the molecular structure of the high molecular weight polyacrylamide The molecular structure of the high molecular weight polyacrylamide is:
CH2 CH

n

CONH2

Structural formula of acrylamide molecular weight is 71.08, the value of n for the 2 x 104 ~ 9 x 105, so the polyacrylamide molecular weight average of 1.5 x 106 ~ 6 x 107. 1.3 the classification of high molecular weight polyacrylamide According to PAM dissociation properties of functional group in aqueous solution, macromolecular chain can be divided into ionic colorful (CPAM), cationic (APAM), nonionic (NPAM) and amphoteric ionic several varieties. Cationic generally contain traces of toxicity, not suitable for use in water supply and drainage engineering, so we come into contact with the water treatment agent belong to the anionic and nonionic polyacrylamide. According to the purity of high molecular weight polyacrylamide products, has two kinds of powder and colloid, powder product is white or light yellow granular or powder, solid content is in commonly 90%, colloidal gel product is a colorless, yellowish, solid content is 8% ~ 9%. 1.4 the characteristics of high molecular weight polyacrylamide

High molecular weight polyacrylamide because of its structural unit containing amide, easy to form hydrogen bonding, make it has good water solubility and high chemical activity, can be obtained by grafting and crosslinking reactions such as a variety of derivatives. High molecular weight polyacrylamide is composed of acrylamide monomer polymerization of organic polymer, colorless, tasteless, odourless, soluble in water, no corrosion. High molecular weight polyacrylamide is stable at room temperature, high temperature, easy degradation, when frozen so its storage and preparation for overtime, temperature should be controlled within 2 ℃ ~ 55 ℃. 2.1 the synthesis of high molecular weight PAM At present, the synthesis methods of PAM according to whether aggregation will join other monomer, can divide again homopolymerization and copolymerization, PAM product form a aqueous solution, emulsion, and powder, etc. AM polymerization methods commonly used at home and abroad with aqueous solution polymerization, inverse emulsion polymerization, suspension polymerization and so on, its basic principle is based on AM in under the action of the initiator, carries on the free radical polymerization, generate polyacrylamide, equation is as follows:

By type known AM chain polymerization process, the chain initiation and termination reaction accords with the general law of free radical polymerization, the polymerization reaction of free radical polymerization reaction of reason AM. 2.2 aqueous solution polymerization Aqueous solution polymerization monomer AM and initiator of polymerization, dissolved in the water is widely used and mature technology. The PAM gel and powder products, the colloid by mass fraction is 8% - 10% or 10% - 30% aqueous solution of AM direct polymerization under the action of a initiator and, after drying can be

powder product. Product molecular weight is 70000-7 million. The advantages of safety, simple process equipment, environmental pollution is small, the disadvantage is that the product solid content is low, only 8% - 8%, and prone to imide reaction, generate gel. In the PAM aqueous solution polymerization, the initiator to a great extent, determines the relative molecular mass of the product resulting from the polymerization reaction, yield, and the development of the new initiator system is the key to AM aqueous solution polymerization research. 2.3 inverse emulsion polymerization Acrylamide monomer mixture concentration is 30% ~ 60% aqueous solution as the dispersed phase, which add a small amount of diethylamine tetraacetic acid and Na2SO4 and oxidation - reduction initiator and right amount water soluble surfactant, the HLB value should be lower. With aromatic hydrocarbons or saturated hydrocarbons as continuous phase, which is oil soluble surfactant, the HLB value should be higher, such as dehydration, sorbitan oleate. Na2SO4 have prevent the latex particle bonding effects. The proportion of the dispersed phase and continuous phase is usually 3:7. Aggregate income dispersed phase latex particles was 0.1 ~ 10 microns in diameter, related to the dosage of surface active agent. Reaction temperature is commonly 40 ℃ 6 h conversion rate could reach 98%.

This method has the advantage of heat of reaction is derived, and the material system of low viscosity, easy to operation, products directly without drying applications. Drawback is the use of organic solvent, flammable, effective capacity is lower than the solution polymerization. 2.4 reversed phase suspension polymerization Reversed phase suspension polymerization is nearly years developed a new method. Reversed phase suspension polymerization to produce soil simple art, low into wood, easy ten industry achieve soil, relative molecular mass of products, tens of millions of dollars to dissolve performance is better than aqueous solution polymerization products, can directly get the powder or granular products, packaging and transportation is convenient. 2.5 new polymerization method A way of free radicals in the PAM synthesis in recent years research has a new progress, more energy conservation and environmental protection of initiator system, polymerization such as light, heat polymerization, radiation polymerization, plasma polymerization and precipitation polymerization, micellar polymerization, etc.


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