Preparation and application background and application of polycarbonate
Polycarbonate is a type of high molecular weight compound that is commonly used as a thermoplastic material and is therefore widely used in various fields of economic development and construction. According to different molecular compositions and structures, polycarbonate compounds can be divided into aliphatic, alicyclic, and aromatic categories. However, the current application of polycarbonate compounds is restricted by factors such as processing performance and production costs. Therefore, the only type of polycarbonate compounds currently used for industrial production and application is bisphenol A aromatic polycarbonate. This type of polycarbonate compound is also the compound with the largest production volume and the widest range of applications. The polycarbonates mentioned in this article all refer to bisphenol A polycarbonate compounds.
As a thermoplastic engineering plastic, polycarbonate has strong impact resistance, good stability, good heat resistance, low water absorption, non-toxicity, and excellent dielectric properties. , it is widely used in various industries, such as electrical appliances, transportation, machinery, instrumentation, optical materials, data equipment, aerospace, and even national defense and military industries. And the application of polycarbonate has grown rapidly in recent years.
Preparation and Application Preparation of Polycarbonate
As for the synthesis process of polycarbonate, the synthesis process can be divided into two categories according to whether phosgene is used as raw material in the synthesis process. One is the phosgene method, which uses phosgene as the production raw material; the other is the non-phosgene method. Phosgene method, in this type of production process, phosgene will not be used as raw material.
Preparation and Application of Polycarbonate 1 Phosgene Method
1.1 Solution phosgene method
The production process uses phosgene and bisphenol A as raw materials, and the reaction process is carried out in an alkaline aqueous solution and dichloromethane (or dichloroethane) solution. The raw materials complete the polycondensation reaction in the solution to obtain polycarbonate glue, which is washed, precipitated, dried, and then made into polycarbonate products through a granulation process. However, the significant shortcomings of this process are its high cost and greater harm to the environment. Therefore, it is not in line with the sustainable development strategy and has been eliminated.
1.2 Interfacial polycondensation method
According to different synthesis processes, the interfacial polycondensation method is divided into two-step interfacial polycondensation and one-step interfacial polycondensation.
1.2.1 Two-step interfacial polycondensation method. The raw materials used to synthesize polycarbonate using this method include bisphenol A sodium salt and phosgene. The chemical reaction formula during the synthesis process is shown in (1). The reaction process of this method is divided into two steps, one is not the phosgenation stage, and the other is the polycondensation stage, and the two-step processes are carried out one after another.
1.2.2 One-step interfacial polycondensation method. The one-step interfacial polycondensation method is evolved on the basis of the two-step interfacial polycondensation method. During the reaction process, due to the addition of catalyst, the reaction speed of the chloroformate group and bisphenol A sodium salt is significantly accelerated, and As a result, while the phosgenation reaction of bisphenol A sodium salt is proceeding, the subsequent polycondensation reaction is also proceeding, and the two reactions proceed almost simultaneously. Polycarbonate produced through one-step interfacial polycondensation method has a fast reaction speed and effectively reduces the loss of raw materials. The production process is mature and easy to control, and it is currently a relatively mature polycarbonate synthesis method.
1.3 Transesterification method
The production process of transesterification can be divided into two parts: one is transesterification reaction and the other is polycondensation reaction. First, phenol is used as raw material, and then diphenyl carbonate is obtained through interfacial phosgenation reaction. Then, under the action of a catalyst, diphenyl carbonate and bisphenol A undergo transesterification reaction, and the oligomer obtained is in the second step – Polycarbonate is produced in the polycondensation reaction. In the transesterification production process, the transesterification stage and the polycondensation stage are both reversible equilibrium reactions, because in order to increase the yield of the product, the generated diphenyl carbonate or low relative molecular products must be removed from the reaction system in a timely manner reaction system. In the early stages of the production of polycarbonate using the transesterification method, the products produced by this process have poor optical properties and the catalyst is prone to pollution problems, and large-scale industrialChemical production is not easy to achieve, so the process was not widely used in the early days. Since the 1980s, countries such as Europe, the United States, and Japan have begun to apply for a large number of patents related to the research of this process. Improvements in the transesterification method mainly focus on the selection and configuration of catalysts during the reaction process. In recent years, the process has been greatly improved and production efficiency has been continuously improved.
Preparation and Application of Polycarbonate 2 Non-phosgene Method
The production of polycarbonate through the non-phosgene transesterification method is the same as the traditional transesterification method in the resin polymerization stage. Both bisphenol A and diphenyl carbonate are produced through transesterification and polycondensation reaction to produce polycarbonate. Carbonate, the difference lies in the production process of diphenyl carbonate. The traditional transesterification method uses phosgene as a raw material to produce diphenyl carbonate, while the non-phosgene method uses dimethyl carbonate through a transesterification reaction. Diphenyl carbonate. In the production process using the non-phosgene transesterification method, no matter from the raw material monomer sodium bicarbonate to the finished product, no phosgene is used in the entire process, so this process can ensure green, safe and pollution-free. This process does not use phosgene as a raw material, which not only protects the environment, but also protects the health of operators. However, this process also has certain problems, that is, in the reaction of transesterification of dimethyl carbonate and phenol to obtain diphenyl carbonate, the reaction yield is low, and further research is needed in this regard.
