Abstract:
Highly purified polyvinyl alcohol (PVA) which meets the standard of pharmaceutical grade is provided. The PVA has of less than 0.1 wt% of residual methanol, less than 0.1 wt% of residual methyl acetate, and less than 0.3 wt% of residual sodium acetate. A method for obtaining highly purified PVA is further provided.
Abstract:
The invention relates to an efficient polymerization process and its use to produce novel copolymers with a specific microstructure. In particular, the invention relates to butyl rubbers with novel microstructure, preferably those obtainable by copolymerization of monomer mixtures comprising isobutylene and isoprene. In a further aspect the invention relates to halogenated copolymers obtainable from such novel copolymers by halogenation.
Abstract:
A method for producing a polymer has: a polymerization step of polymerizing at least a conjugated diene monomer in a hydrocarbon solvent using an organolithium compound as a polymerization initiator, and obtaining a polymer; and, following steps (1) to (4), successively performing after the polymerization step: (1) a step of mixing an acid and water of 20 to 300 parts by mass into the solution containing the polymer of 100 parts by mass, (2) a step of adjusting an amount of the water to 10 parts by mass or less based on 100 parts by mass of the solution containing the polymer, (3) a step of adding a carbon oxide gas and/or a compound to be decarboxylated to the solution containing the polymer, and (4) a step of removing a solvent from the solution containing the polymer until a concentration of the polymer reaches 95 mass% or more.