Low-alcoholysis-degree polyvinyl acetate (PVA) continuous alcoholysis process

Abstract

The invention discloses a novel polyvinyl acetate (PVA) continuous alcoholysis process. The process comprises the following steps of: adding polyvinyl acetate (PVAc) methanol solution and catalyst sodium hydroxide (NaOH) methanol solution into a prereactor according to a fixed amount and mixing quickly and uniformly; adding mixed solution into a reaction type double-screw extruder to perform an alcoholysis reaction; extruding from a machine head mould to obtain white granular products; and performing treatment of acid neutralization, drying and the like to obtain the final product. The process has the advantages of high reaction speed, high reaction capacity, controllable retention time of reactants, narrower retention time distribution, capability of continuous production and the like. Compared with the traditional process, the process also has the advantages of reducing the using amount of a solvent methanol and a catalyst NaOH, along with low recovery cost of the solvent and alkali and environmental friendliness. The low-alcoholysis-degree PVA product obtained by the process has narrow alcoholysis-degree distribution and stable properties.

Description

technical field [0001] The invention relates to a high molecular polymer production process, namely a continuous alcoholysis process for PVA with low alcoholysis degree. Background technique [0002] PVA is an important synthetic material, its performance is between rubber and plastic, and it is one of the few water-soluble polymers found so far. It is mainly used in the production of civilian clothing, industrial cord fabrics, filter cloths, Fishing nets, coatings, adhesives, emulsifiers, aviation and automotive safety glass, etc. According to the degree of alcoholysis, PVA can be divided into PVA with low degree of alcoholysis and PVA with high degree of alcoholysis. Low degree of alcoholysis PVA has high surface activity and low surface tension, and is widely used in PVC polymerization, rubber emulsion polymerization, emulsification technology, electronics industry and membrane material manufacturing. [0003] The traditional process generally adopts the "belt method" t...

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Problems solved by technology

However, the "belt method" has many disadvantages at the same time: firstly, the reaction temperature is generally lower than 50°C, and the reactants cannot be stirred during the reaction, so the reaction rate is very low; secondly, due to the limitation of the belt size and the low reaction rate The reason is that the production efficiency of the "belt method" is very low; the third, the "belt method" process reaction materials are mixed unevenly, and the degree of alcoholysis is widely distributed, which leads to unstable performance of the final product. Concentration method to solve this problem, generally the concentration of PVAc methanol solution is lower than 30%, the use of methanol solvent is large, and the recovery cost is high

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