In addition, PVP is also widely used as a disintegrant, adhesive, desalination membrane and artificial kidney dialysis membrane; in the food and beverage industry, adding insoluble cross-linked PVP to beer and tea beverages can remove polyphenols and excess tannins in beer and tea beverages, and it does not remain in them, which stabilizes the color, ensures that the flavor of beer and tea beverages remains unchanged for a long time, and removes the astringency. It is an excellent beverage clarifier and stabilizer; it is even more widely used in daily chemical industry, especially in cosmetics, such as PVP used in hair spray, which has excellent hair fixation, gloss increase, moisturizing functions, and does not absorb dust; In the coating industry, using PVP's excellent film-forming properties, paints produced with PVP as a coating agent have transparent film formation without affecting the original color, and low molecular weight PVP can make ink. The ink has good dispersion stability and gives it the property of not fading easily; in polymer polymerization reactions, PVP can be used as a thickener, used in polymer emulsion polymerization, suspension polymerization and other reaction processes, to improve the performance of resins, etc. With the development of science and technology, the application field of PVP is becoming more and more extensive. It has been applied in high-tech fields such as photocurable resin, optical fiber, laser video disc, drag reduction materials, etc. In other fields, such as building materials, metallurgy, steelmaking, electroplating, etc., application research has also been carried out. It can be said that PVP has penetrated into all areas of the national economy and people's lives.
PVP and its monomer NVP were first synthesized by J. Walter Reppe of BASF using acetylene as the main raw material. This method is called the Reppe method, also known as the acetylene method. In the 1950s, ISP of the United States, GAF of the time and BASF of Germany successively established NVP production lines based on the acetylene method, and then produced various brands of PVP products. To date, these two companies are still the main manufacturers of PVP products.
The acetylene method uses acetylene, formaldehyde, hydrogen and other starting materials, and undergoes five steps of catalytic aldehyde addition, catalytic hydrogenation, catalytic dehydrogenation cyclization, amination, and alkyne addition to synthesize the monomer NVP. Then, under certain conditions, polymerization can obtain PVP with different molecular weights. NVP is copolymerized with other monomers, such as vinyl acetate and acrylamide, to obtain copolymerized PVP, or a specific cross-linking agent with bifunctional groups, such as N, N-methylenebisacrylamide, is added to carry out cross-linking polymerization to obtain cross-linked PVP. The acetylene method has strict requirements on operating conditions because the main raw material acetylene used has strict requirements on operating conditions. The process needs to be carried out under high pressure and high temperature conditions. It has high requirements on equipment, long process flow, and huge equipment. It is only suitable for large-scale production and not suitable for the construction of medium and small manufacturers. Therefore, so far only BASF in Germany and ISP in the United States use this process to produce NVP and PVP products.
