Polyvinylpyrrolidone Cross-Linked CAS 25249-54-1

As early as the 1930s, Walter Reppe and others just synthesized the water-soluble homopolymer of NVP, but until the 1950s, people began to prepare insoluble polymer PVPP. Since then, relevant literature has successively reported various methods for preparing Polyvinylpyrrolidone Cross-Linked, including radiation crosslinking, photocrosslinking and chemical crosslinking. Polyvinylpyrrolidone Cross-Linked is insoluble in water, strong acid, strong alkali and various organic solvents, and only has different degrees of swelling in the above solutions. Polyvinylpyrrolidone Cross-Linked prepared by different methods has different swelling ability and adsorption ability, and its appearance can be soft gel, white powder, or porous particles, so it is suitable for many application fields.
Crosslinked polymers of NVP can be prepared by crosslinking linear PvP. Utilize ultraviolet light or gamma ray to irradiate PVP aqueous solution, all can generate cross-linked PVP. Use various catalysts to synthesize the method of cross-linked polyvinylpyrrolidone mainly to contain following three kinds, now divide as follows:
1, Schildkneeht used NaZSZO in 1953:, KZSZO: Etc. persulfate treatment PVP aqueous solution generated cross-linked PVP gel. In order to obtain moderately strong gels, the required concentration of persulfate is large, generally twice the concentration of PVP. The exact mechanism of persulfate cross-linked PVP is not clear, and possible explanation is: persulfate is thermally cracked into sulfate ion free radicals and radical free radicals in aqueous solution, and they can take a hydrogen atom from polymer molecule, Macromolecular free radicals are generated, and these macromolecular free radicals can form stable covalent crosslinks through molecular or chain segment diffusion.
2. Hort and Grosse: use hydrogen peroxide and iodine to treat PVP aqueous solution for cross-linking reaction. In the PVP aqueous solution, hydrogen peroxide and navel were gradually added in a molar ratio of 2:1, and after reacting at 50°C for 3 hours, a cross-linked PVP gel was obtained. The product can be used as thickener, flocculant and protective colloid.
3. In the presence of peroxide, Merijan uses a. A diene crosslinked PVP solution. The cross-linking reaction is to mix 1molPVP and 0.02-0.3mol of a certain a. A diene such as 1,7-octadiene, and an organic solvent to form a reaction solution, wherein each mole of a, co-diene contains 0.5-1.omol peroxide, and the temperature is constant within the temperature range of 100-200 °C React for 1-30 hours, and then vacuum distill off the organic solvent to obtain the cross-linked product. The reaction solvent should use a. A general solvent for diene and PVP, various alcohols such as methanol, ethanol and 1,4-butanediol are applicable. Since the reaction temperature is high, if an organic solvent with a low boiling point is used, the reaction needs to be pressurized. Any alpha-diene with a molecular weight between 68 and 280 can be used as a crosslinking agent. By changing the relative concentration and reaction time of α-diene, various products with different degrees of solubility can be obtained, from cross-linked PVP with different solubility to completely water-insoluble PVP gel.
Cross-linked PVP can also be prepared by copolymerization of NVP monomers with a cross-linking agent. Field et al carried out precipitation polymerization of NVP and an appropriate amount of cross-linking agent and free radical initiator in an aqueous electrolyte solution, and the resulting product was a porous granular NVP cross-linked polymer after filtration, washing and drying. Commonly used crosslinking agents in polymerization systems include the following multifunctional compounds: alkylene bisacrylamide such as N, N’-methylenebisacrylamide, etc.; divinyl aromatic compounds such as divinylbenzene, divinyl Ethylbenzene, etc. Free radical initiators commonly used in vinyl polymerization are suitable for this reaction, including peroxide initiators such as dibenzophthalein peroxide, ditertbutyl peroxide, etc., and azo compounds such as azobisiso Ding Jing and so on. Because the NVP monomer can only be partially dissolved in the aqueous electrolyte solution, when the NVP dosage exceeds its saturation in the aqueous electrolyte solution, the heterogeneous polymerization system can be maintained by mechanical stirring. In the reaction system, a buffer solution such as disodium hydrogen phosphate is often added to make the reaction solution neutral or weakly alkaline.
Shih et al. used organic solvents to replace the aqueous electrolyte solution in the above-mentioned precipitation polymerization reaction system to prepare white powdery cross-linked PVP. The organic solvent adopted in the reaction system includes aliphatic hydrocarbons, such as cyclohexane, heptane, etc.; aromatic hydrocarbons such as toluene, etc. The solubility of PVP in these organic solvents does not exceed 1% at room temperature. The amount of solvent used in the reaction is such that the copolymerized precipitate can still be stirred near the end of the polymerization reaction. The cross-linked polymer prepared by this method has a higher degree of swelling in aqueous solution. To prepare highly cross-linked cross-linked PVP, popcorn flower polymerization or propagation polymerization can be used. In 1960, Grosser and Plainfield proposed to use alkali metal or alkaline earth metal compounds, such as their oxides, hydroxides or alkoxides, as catalysts to heat NVP monomers under anhydrous conditions to prepare white powdery insoluble NVP crosslinking polymerization. The reaction has a longer induction period, ranging from 4 to 24 hours. This is the first application of popcorn flower polymerization on NVP monomer. Subsequently, many researchers have done a lot of research work in this area.