Preparation of water-soluble syndiotacticity-rich high molecular weight poly(vinyl alcohol) microfibrillar fibers using copolymerization of vinyl pivalate and vinyl acetate and saponification

Water-soluble high molecular weight (HMW) syndiotactic poly(vinyl alcohol) (s-PVZA) microfibrillar fibers were prepared by the saponification with various conditions such as amount of alkali solution, saponification temperature, and saponification concentration from copoly-(vinyl pivalate (VPi)/vinyl acetate (VAc)) copolymerized using various VPi/VAc feed ratios. To produce s-PVA microbrillar fibers having various water-soluble temperatures for many industrial applications, the intrinsic viscosities, syndiotactic diad (S-diad) contents, and degrees of saponification (DS)s of PVAs were finely controlled to 1.2-3.6 dL/g, 56.3-58.3%, and 91.4-98.3%, respectively. Through a series of experiments, it was found that the amount of alkali may alter the structure of the saponified polymers, primarily the DS, and the structural variation changes viscosity. That is, intrinsic viscosity was sharply decreased as the amount of alkali solution was increased. DS was increased with an increase in the amount of alkali solution. S-diad content was increased with an increase in the VPi content. HMW s-PVA microfibrillar fibers having S-diad content of 56.3-58.3% prepared by the saponification of copoly(VPi/VAc) were completely soluble in water at 100°C.