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[Chemical Knowledge]：Production and manufacturing method and process flow of polyvinyl alcohol

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Polyvinyl alcohol (Polyvinyl Alcohol, referred to as PVA) is an important raw material for the production of chemical products, with a wide range of applications, such as adhesives, coatings, fibers, paper, medicine and so on. This article will introduce the manufacturing method of polyvinyl alcohol in detail.

1. Raw Material Preparation

The main raw material for manufacturing polyvinyl alcohol is vinyl acetate (Vinyl Acetate, referred to as VA). Vinyl acetate is a colorless, flammable liquid that is irritating and corrosive. In order to ensure production safety, high quality vinyl acetate should be selected, and its purity, water content and other indicators should be strictly controlled.

2. polymerization reaction

1. initiator addition: vinyl acetate monomer is added to the polymerization kettle, and initiator, such as persulfate, azo compound, etc. The function of the initiator is to decompose at an appropriate temperature to produce free radicals that initiate polymerization of the monomers.
2. Temperature control: The temperature in the polymerization vessel is controlled within a suitable range, usually between 50 and 80°C. Too high temperature may lead to too fast polymerization reaction and uneven molecular weight distribution; too low temperature may affect the polymerization rate.
3. Stirring speed control: maintain an appropriate stirring speed to ensure that the monomer is evenly dispersed in the kettle to avoid local overheating and gel phenomenon.

3. Alcoholysis Reaction

1. Alkali Catalyst Addition: Alkali catalysts, such as sodium hydroxide, potassium hydroxide, etc., are added to the polymerization product to promote the hydrolysis and alcoholysis reactions of vinyl acetate groups.
2. Temperature control: The reaction temperature is controlled within a suitable range, usually between 80 and 120°C. High temperature may lead to increased side reactions, affecting product quality; low temperature may affect the reaction rate.
3. pH value adjustment: adjust the pH value of the system according to the reaction process to maintain the smooth progress of the alcoholysis reaction.

4. Post-treatment

1. Neutralization: Neutralize the base catalyst in the system with acid, and adjust the pH to neutral or slightly acidic.
2. Washing: The product is washed with water to remove residual acetic acid, salt and other impurities.
3. Drying: The product is dried to the appropriate moisture content to obtain the final polyvinyl alcohol product.

The above is a basic method for producing polyvinyl alcohol. In the actual production process, it is also necessary to optimize the process parameters and equipment configuration according to the specific product specifications and quality requirements. At the same time, strengthen quality control and safety management in the production process to ensure product quality and production safety. In short, by mastering the manufacturing method of polyvinyl alcohol, it can provide important raw material support for chemical production and promote the development of related industries.

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