高吸水树脂的4种合成方法
4 synthetic methods of super absorbent resin
高吸水树脂（Super Absorbent Polymer，SAP）的合成常采用自由基聚合，聚合反应是化学中最难的一种反应，即在一定条件下（如高温高压及引发剂或催化剂存在），烯烃分子中的π键断裂，发生同类分子间的加成反应生产高分子化合物。自由基聚合有本体聚合、溶液聚合、悬浮聚合及乳液聚合等四种实施方法。
Super Absorbent Polymer (SAP) is often synthesized by free radical polymerization. Polymerization is the most difficult reaction in chemistry, that is, under certain conditions (such as high temperature and pressure and the presence of initiator or catalyst), the pi bond in olefin molecules is broken, and the addition reaction between the same molecules occurs to produce polymers. Chemical compound. Free radical polymerization includes four methods: bulk polymerization, solution polymerization, suspension polymerization and emulsion polymerization.
本体聚合
bulk polymerization
本体聚合是指单体之外只有少量引发剂或没有引发剂的聚合。聚合过程可以是均相的，也可以是非均相的，主要决定于聚合体在单体中的溶解能力。本体聚合法的优点在于实施工艺流程短，工艺简单，设备少，生产速度块，成本低。易根据成型要求制成各种形状的产品，所以本体聚合法是最理想的聚合生产工艺。
Bulk polymerization refers to polymerization with only a small amount of initiator or initiator outside the monomer. The polymerization process can be homogeneous or heterogeneous, depending on the solubility of the polymer in the monomer. The advantages of bulk polymerization are short process flow, simple process, less equipment, high production speed and low cost. It is easy to make various shapes of products according to molding requirements, so bulk polymerization is the most ideal polymerization process.
溶液聚合
solution polymerization
溶液聚合是指单体和引发剂溶于适当的溶剂中进行的聚合，其特点是能转化反应中的聚合热。同样，溶液聚合可是均相的，也可是非均相的，主要决定于聚合体在单体溶液中的溶解能力。由于有溶剂的存在，使得体系的黏度较低，混合和传热较容易，温度较易控制，因而溶液聚合反应的热控制要比本体聚合反应容易得多。
Solution polymerization refers to the polymerization of monomers and initiators in appropriate solvents, which is characterized by the conversion of polymerization heat in the reaction. Similarly, solution polymerization can be homogeneous or heterogeneous, depending on the solubility of the polymer in the monomer solution. Because of the existence of solvents, the viscosity of the system is lower, mixing and heat transfer are easier, and the temperature is easier to control, so the thermal control of solution polymerization is much easier than bulk polymerization.
悬浮聚合
suspension polymerization
悬浮聚合是指单体以液滴状悬浮于水中的聚合。体系由单体、水、引发剂、分散剂组成，在反应机制上类似本体聚合。每个液体小珠相当于一个本体聚合单元。一般聚合物都不溶于水，因而悬浮聚合都属于非均相聚合。借助机械搅拌或剧烈振荡和悬浮剂的作用，使单体呈分散液状分散于悬浮介质中进行聚合反应，因此又称为珠状聚合。其主要优点是反应热通过介质容易传出，温度较易控制，所得聚合物的分子量较大，质量均匀、纯净。
Suspension polymerization refers to polymerization of monomer suspended in water by droplet. The system is composed of monomer, water, initiator and dispersant, and is similar to bulk polymerization in reaction mechanism. Each liquid bead is equivalent to a bulk polymerization unit. General polymers are insoluble in water, so suspension polymerization is heterogeneous polymerization. With the help of mechanical stirring or violent oscillation and suspension agent, monomers are dispersed in suspension medium for polymerization, so it is also called bead polymerization. Its main advantages are that the reaction heat is easily transmitted through the medium, the temperature is easy to control, the molecular weight of the polymer is large, the quality is uniform and pure.
乳液聚合
emulsion polymerization
乳液聚合是单体和水由乳化剂配成乳液状态所进行的聚合。体系基本是由单体、水、引发剂、乳化剂组成。乳液聚合是在微小的胶束和乳胶中进行的。乳液聚合法不仅反映速度快，分子量高，而且各种不同性能的单体均可聚合，单体于大分子也可进行共聚。其缺点在于必须经过凝聚、洗涤、脱水、干燥等一些列后处理工作，才能将聚合物从乳液中分离出来，这就增加了生产成本。
Emulsion polymerization is the polymerization of monomers and water by emulsions in the form of emulsion. The system is made up of monomer, water, initiator and emulsifier. Emulsion polymerization is carried out in tiny micelles and latex. Emulsion polymerization not only reflects fast speed and high molecular weight, but also can polymerized monomers with various properties, and monomers can also copolymerized with macromolecules. The drawback is that it is necessary to separate the polymer from the emulsion after some post treatment such as coagulation, washing, dehydration, drying and so on, which increases the production cost.
