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[Chemical Knowledge]：Production method and process of polyamide

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Polyamide (PA) is a widely used engineering plastic with high mechanical strength, heat resistance, abrasion resistance and chemical resistance. In the field of raw materials for chemical production, there are two main methods for manufacturing polyamides: polycondensation and ring-opening polymerization. This article will detail these two manufacturing methods.

1. polycondensation method
The
polycondensation method is a method of preparing a polyamide by polycondensation reaction of a dibasic acid and a diamine. In this process, diacids and diamines react to form polymers and water molecules. Commonly used dibasic acids include adipic acid, terephthalic acid and the like, and diamines include hexamethylenediamine, ethylenediamine and the like.

1. continuous polycondensation method

continuous polycondensation method is to continuously add dibasic acid and diamine monomer into the reactor in a certain proportion, control the reaction temperature and pressure, and carry out polycondensation reaction. The water molecules generated by the reaction need to be removed in time to keep the reaction in the direction of polyamide formation. After completion of the reaction, the polymer was extruded, cooled, and pelletized to obtain a polyamide product.

2. Batch Polycondensation Process

The batch polycondensation process is a process in which a polycondensation reaction is carried out in a batch reactor. The dibasic acid and diamine monomers are added into the reactor according to a certain proportion, and heated to a certain temperature to carry out polycondensation reaction. The water molecules generated by the reaction need to be removed in time to maintain the reaction equilibrium. After completion of the reaction, the polymer was taken out and post-treated to obtain a polyamide product.

2. Ring-Opening Polymerization
The
ring-opening polymerization method is a method of preparing a polyamide by ring-opening polymerization of a cyclic monomer. Commonly used cyclic monomers are ε-caprolactone, δ-valerolactone, etc.

1. Anionic Ring-Opening Polymerization Method

The anionic ring-opening polymerization method is a method of initiating ring-opening polymerization of a cyclic monomer using an alkali metal compound as an initiator. In this process, the initiator reacts with the cyclic monomer to form an active anion, which continuously reacts with the cyclic monomer to open the ring and attach the monomer to the polymer chain. After completion of the reaction, the polymer was taken out and post-treated to obtain a polyamide product.

2. Cationic Ring-Opening Polymerization Method

The cationic ring-opening polymerization method is a method of initiating ring-opening polymerization of a cyclic monomer using a protonic acid or a Lewis acid as an initiator. In this process, the initiator reacts with the cyclic monomer to form an active cation, which continuously reacts with the cyclic monomer to ring-open the monomer and attach it to the polymer chain. After completion of the reaction, the polymer was taken out and post-treated to obtain a polyamide product.

In general, both polycondensation and ring-opening polymerization can be used to prepare polyamides, but the two methods are different in terms of raw materials, processes, and equipment. In actual production, a suitable manufacturing method can be selected according to factors such as product performance requirements and production costs. At the same time, in order to ensure the quality and performance stability of polyamide products, it is also necessary to strictly control the temperature, pressure, material ratio and other parameters in the production process to ensure the smooth progress of the reaction and the purity of the product.

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