What Is Polyvinylpyrrolidone?
Polyvinylpyrrolidone (PVP), also known as povidone or poly(N-vinylpyrrolidone), is a nonionic, water-soluble polymer synthesized from N-vinyl-2-pyrrolidone. It finds extensive use across a spectrum of industrial products, everyday items, and food products due to its versatility and safety.
Uses of Polyvinylpyrrolidone
Thanks to its excellent solubility in water, high moisture absorption, film-forming capabilities, adhesion, and dispersibility, PVP is beneficial in various sectors. Its safety for human health and environmental compatibility further extend its use in pharmaceuticals and food additives.
1. Pharmaceuticals
PVP serves multiple roles in the pharmaceutical industry. It’s a base for the antiseptic povidone-iodine, stabilizes suspensions and emulsions, acts as a binder in tablets and capsules, and is a component of ointment and cream bases. Additionally, it enhances the hemocompatibility of hollow fibers in artificial kidneys.
2. Food Additives
As a stabilizer, binder, and dispersant, PVP is integral to vitamin and mineral supplements. Polyvinylpolypyrrolidone (PVPP), a cross-linked variant, is utilized as a clarifying agent in beer and wine and reduces astringency in tea-based beverages. Unlike PVP, PVPP is insoluble in water.
Properties of Polyvinylpyrrolidone
PVP is a linear, hygroscopic, non-crystalline polymer with a slight specific odor or odorless characteristic, a density of 1.2 g/cm3, a glass transition temperature range of 150~180℃, and a decomposition temperature of around 400℃. It dissolves in water, alcohols, and most polar solvents but not in acetone, esters, ethers, and hydrocarbons. Its nonionic nature provides low electrical conductivity and excellent insulating properties.
Other Information on Polyvinylpyrrolidone
Production Process of Polyvinylpyrrolidone
Polyvinylpyrrolidone is produced from acetylene and formaldehyde through the following processes:
1. Synthesis of Gamma-Butyrolactone
After reacting acetylene and formaldehyde under pressure, 1,4-butanediol is obtained by catalytic reduction. When this is heated to 200°C under a copper catalyst, an intramolecular dehydration reaction occurs, yielding γ-butyrolactone.
C2H2 + HCHO → HOCH2CH2CH2CH2OH (1,4-butanediol) → C4H6O2 (γ-butyrolactone)
2. Synthesis of N-Vinyl-2-Pyrrolidone
N-vinyl-2-pyrrolidone is obtained by treating γ-butyrolactone with ammonia to form 2-pyrrolidone, which is then subjected to pressurized acetylene.
C4H6O2 + NH3 → C4H7NO (2-pyrrolidone)
C4H7NO + C2H2→ C6H9NO
Another way to synthesize N-vinyl-2-pyrrolidone from γ-butyrolactone is by reacting it with monoethanolamine. Here, N-hydroxyethylpyrrolidone is produced from γ-butyrolactone and monoethanolamine. This is then vapor-phase dehydrated to yield N-vinyl-2-pyrrolidone.
C4H6O2 + HOCH2CH2NH2 → C6H11O3 (N-hydroxyethylpyrrolidone)
C6H11O3 → C6H9NO + H2O
3. Polymerization of N-Vinyl-2-Pyrrolidone
Vinylpyrrolidone is obtained by polymerization of N-vinyl-2-pyrrolidone by heating in the presence of hydrogen peroxide.