polyvinylpyrrolidone properties

Nature of PVP

poly vingt pyrrollidone (PVP) is a kind of non-ionic polymer compound. It is the most distinctive, best-studied and widely used fine chemical variety of N-vinyl- acyl-serving polymers. At present, it has developed into abundant ions and cations. Anion category, work weight grade. Pharmaceutical grade, food suture 3 specifications, the relative molecular shield amount from thousands to more than one million polymer, copolymer and polymer series products, and with its excellent and unique performance in widely used, PVP is divided into confining energy according to its average molecular weight size, usually expressed by the K value, different K values represent the corresponding

The average molecular weight range of PVP. The K value is actually an eigenvalue related to the relative viscosity of PVP aqueous solution, and the viscosity is a physical quantity related to the molecular weight of polymers, so the average molecular weight of PVP can not be characterized by K value. Usually, the K value is very large, and the greater the privacy, the stronger the viscosity linearity.

PVP production polymerization

PVP was obtained from NVP by means of polybox and solution acid synthesis. In the process of bulk polymerization, the mechanical degree of the system is large due to the existence and application. The polymer is not easy to diffuse, the polymerization reaction heat is not easy to remove resulting in overheating of the local phase and other problems, the product obtained from this country has low molecular weight, the residue to the monomer content is high, and more yellow, there is not much practical value. At present, the synthesis of PVP by sea polymerization is generally adopted in industry.

There are two main routes for PVP production polymerization, the first is the solution polymerization of N-2-pyrrolidone (NVP) in organic solvents and then steam stripping, and the second route is the aqueous polymerization of NVP monomer with water-soluble cation, negative and non-high monomer.PVP homopolymer can be obtained by directly heating NVP monomer to more than 140℃, or adding initiator to NVP solution for heating, or adding in NVP solution (solvent can be water, ethanol, etc.) to initiate polymerization by free radical solution, or directly irradiating NVP monopolymer or its solution with light.

The polymerization methods are different. The structure and properties of the obtained polymers are different, and the composition of the polymers obtained by free collector polymerization is different. PVP homopolymers with different molecular weight and water solubility can be obtained by adjusting monomer concentration, polymerization temperature, initiator dosage and other reaction conditions.

Process 1: The NVP is configured into a solution with a mass fraction of 50%, and a small amount of peroxide is used as an egg-laying example. Under the action of diisobutoxide, polymerization is initiated at 50℃, so that almost all NVP is converted into PVP. The remaining diisobutylxenon was decomposed by adding ammonia to the polymer. The conversion rate of monomer polymerization was nearly 100% and the solid content was 50%.

Process 2:0.4g dispersant P (NVP-CO-VAC) and 80g dispersing medium ethyl acetate were added into 250mL four-way flask. After stirring and spraying with constant temperature water at 70℃, 20g monomer NVP and 0.15g initiator AIBN were added under nitrogen atmosphere

Reaction for 6h, cooling and filtration, insoluble substance in vacuum drying oven for 24h vacuum drying, white PVP solid powder.

In PVP polymerization, AIBN is used as initiator in most cases, and there is no literature on the synthesis of PVP by water-pants azo initiators. However, some people are working on the value of this aspect, because the NVP monomer and PVP are homogeneous in water, it is completely possible to use water-soluble azo to trigger the trigger fruit to produce linear PVP polymers. HAIBN contains group cyanogen which is harmful to human body, while most water-soluble azo initiators do not contain iguana group, and PVP is mostly used in direct contact with human body products. Therefore, water-soluble azo initiators have more advantages than AIBN.