Preparation Of Polyvinylpyrrolidone

PVP is made from monomer vinylpyrrolidone (NVP) as raw material and is obtained through bulk polymerization, solution polymerization and other methods. In the process of bulk polymerization preparation, due to the high viscosity of the reaction system, the polymer is not easy to diffuse, and the heat of polymerization reaction is not easy to remove, resulting in local overheating. Therefore, the molecular weight of the obtained product is low, the content of residual monomer is high, and it is mostly Yellow, not of much practical value. In industry, solution polymerization is generally used to synthesize PVP. There are two main routes for PVP production and polymerization. The first is solution polymerization of NVP in organic solvents and then steam stripping. The second route is aqueous solution polymerization of NVP monomers and water-soluble cationic, anionic or nonionic monomers. Directly heat the NVP monomer to above 140°C, or add an initiator to the NVP solution for heating, or add an initiator to the NVP solution (the solvent can be water, ethanol, benzene, etc.) to polymerize through free radical solution, or directly use PVP homopolymer can be obtained by irradiating NVP monomer or its solution with light. Different polymerization methods result in different polymer structures and properties. Among them, the polymer obtained by free radical solution polymerization has a more uniform composition and structure. The performance is also relatively stable, and it is the most commonly used method for NVP homopolymerization. By adjusting the monomer concentration, polymerization temperature, initiator dosage and other reaction conditions, PVP homopolymers with different molecular weights and different water solubilities can be obtained.
Process 1: Configure NVP into a solution with a mass fraction of 50%, use a small amount of hydrogen peroxide as a catalyst, and initiate polymerization at 50°C under the action of azobisisobutyronitrile, so that almost all NVP is converted into PVP. Then add ammonia water to the polymer to decompose the remaining azobisisobutyronitrile. The monomer polymerization conversion rate is nearly 100% and the solid content is 50%.
Process 2: Add 0.4g of dispersant P (NVP-co-VAc) and 80g of dispersion medium ethyl acetate into a 250 mL four-necked flask. After stirring and dissolving in a 70°C constant temperature water bath, add 20g of monomer NVP and 0.15g of initiator AIBN. , react under a nitrogen atmosphere for 6 hours, cool and filter, and place the insoluble matter in a vacuum drying box for vacuum drying for 24 hours to obtain white PVP solid powder.
Most of the polymerization of PVP uses AIBN as the initiator. There is no literature on using water-soluble azo initiators to initiate the synthesis of PVP, but some people are doing work in this area. Since both NVP monomer and PVP are soluble in water, water-soluble azo initiators can be used to initiate polymerization to generate linear PVP polymers. Moreover, AIBN contains cyano groups that are harmful to the human body, and water-soluble azo initiators Most initiators do not contain cyano groups, and PVP is mostly used in products that come into direct contact with the human body, so water-soluble azo initiators have more advantages than AIBN.