POVAL (PVOH)

Overview

The chemical name of POVAL is polyvinyl alcohol, which is a water-soluble synthetic resin that was first industrially produced in Japan and is used as an ingredient in vinylon synthetic fibers.
The unique qualities of POVAL are today not only utilized as an ingredient in vinylon synthetic fibers, but also in a wide variety of applications both in Japan and overseas.Such applications include on ingredient in film and acetal resin, fiber processing agents, adhesives, vinyl chloride polymer stabilizers, and inorganic binders.

J-POVAL (POVAL trademark of Japan VAM & Poval Co., Ltd.) is largely classified into two types of products; granules and powders.

Type	Granule (J Type)	Powder (V Type)
Photograph of shape
Characteristics	Easy to handle	High purity (Few volatile components and little sodium acetate) Little acetate smell or thermal color change Good compatibility with cellulose resins, such as starches Has high bulk and the fine powder products have many fiber protrusions
Main applications	A wide range of general industrial applications	Films Cosmetic ingredients and pharmaceutical additives Paper processing agents (clear coat, reinforcement)

Basic Formula of POVAL

POVAL Production Outline

J POVAL is made by hydrolyzing polyvinyl acetate, which is obtained through polymerization of vinyl acetate monomer. Diversifying the specific degrees of polymerization and hydrolysis, J POVAL is produced in various types of grades.

Polymerization Process

During the polymerization process the vinyl acetate (VAc) is formed into several chains in the methanol solvent, and then a reaction is performed to convert these into polyvinyl acetate (PVAc). This process controls the length (called degree of polymerization) of the vinyl acetate molecular chains. The POVAL membrane strength, aqueous solution viscosity, and other properties vary greatly depending on the degree of polymerization. It is also possible to produce POVAL with different characteristics by copolymerizing other monomers during this process.

Hydrolysis Process

During the hydrolysis process an alkaline catalyst is used in the methanol solvent to convert the acetate groups of the polyvinyl acetate to hydroxyl groups to generate a reaction to form POVAL. This process controls the amount of hydroxyl groups (called the degree of hydrolysis). The solubility and membrane water resistance of POVAL vary greatly depending on the degree of hydrolysis.
*Degree of hydrolysis (mol%) = (hydroxyl groups) ÷ (Number of hydroxyl groups + acetate groups) x 100

Recovery Process

During the recovery process the solvent used and that produced as a byproduct in the polymerization and hydrolysis processes is recovered, refined, and reused.