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Poly(vinyl alcohol) Microfibrillar Short Fiber and Method for Its Use

This invention is a poly(vinyl alcohol) microfibrillar short fiber and its method of preparation, especially manufacturing a microfibrillar poly(vinyl alcohol) short fiber having high tensile strength, high tensile modulus, high fineness, and excellent alkali resistance using a special saponifying agent and through an advanced mechanical shearing operation in the course of saponification of poly(vinyl pivalate) to poly(vinyl alcohol) without requiring spinning, drawing, and heat treatment.This invention prepares high strength and high modulus PVA microfibrillar short fiber directly by dissolving syndiotacticity-rich high molecular weight poly(vinyl pivalate) in an organic solvent and adding a saponification agent while being stirred with an advanced mechanical stirrer. To prepare the PVA microfibrillar fiber having high tensile strength and modulus, excellent alkali resistance, high fineness, and good thermal resistance according to this invention, a high content of syndiotactic group, high molecular weight, degree of saponification of over 85%, good linearity of molecular chain, and absence of accompanying structure like 1,2-glycol, etc. should be kept. The most important factor which affects direct fiber formation during saponification and the physical properties of the PVA fiber is the syndiotacticity. The saponification agent has a main role in this invention. Poly(vinyl pivalate) is first converted into the syndiotactic PVA by saponification using a special saponification agent, and the definite amount of hydroxyl groups formed during saponification are bound with the saponifying agent to develop the molecular orientation of PVA in the fiber-axis direction. Then, after completing fibrillation, the saponification agent is separated from the microfibrillar fiber and the crystalline structure of PVA is formed.The saponification agent in this invention has a hydrogen bond forming ability with PVA and plays a role in providing high orientation to the PVA structure by mechanical shearing action, maintaining intramolecular hydrogen bonding, and forming a bridge between the intermolecular hydrogen bonding of PVA.