Patent ID: 11905403
Assignee: LG CHEM, LTD.
Field: Macromolecular chemistry, polymers (Chemistry)
Classification: CPC C | IPC C

Claim 0:
1. A method for preparing a vinyl alcohol-based copolymer, comprising the step of:
performing hydrolysis by a saponification reaction by adding a basic substance to a copolymer of an olefin-vinyl carboxylate-based compound,
wherein the copolymer of an olefin-vinyl carboxylate-based compound has a weight average molecular weight of 100,000 to 350,000 g/mol and a molecular weight distribution of 1.5 to 2.5,
wherein the vinyl alcohol-based copolymer comprises a first repeating unit derived from an olefin, a second repeating unit represented by Chemical Formula 1 containing a hydroxyl group, and a third repeating unit represented by Chemical Formula 2 containing a cyanoalkyloxy group,
wherein the first repeating unit is included in an amount of 10 to 70 mol % with respect to 100 mol % of a total amount of repeating units in the vinyl alcohol-based copolymer, and
wherein the third repeating unit is comprised in an amount of 2 mol % or more and less than 10 mol % with respect to 100 mol % of a total amount of the second repeating unit and the third repeating unit:, , in Chemical Formula 2, L is C1-10 alkylene,
wherein an unsaturated nitrile-based compound is added when the saponification reaction proceeds at least 95%, and reacted such that a cyanoalkyl substitution ratio according to Equation 1 is 2 mol % or more and less than 10 mol %:

Cyanoalkyl substitution ratio=[(mol % of third repeating unit)/(mol % of second repeating unit+mol % of third repeating unit)]×100  [Equation 1]

in Equation 1, the mol % of second repeating unit and the mol % of third repeating unit are values based on 100 mol % of the total amount of repeating units in the vinyl alcohol-based copolymer.