Fluorinated copolymer and ion exchange membrane

摘要

To provide a fluorinated copolymer which is capable of providing an ion exchange membrane having little adverse effect due to impurities in an alkali chloride aqueous solution on electrolysis of the alkali chloride aqueous solution. To use a fluorinated copolymer of a fluorinated monomer having a carboxylic acid type functional group with a fluorinated olefin, wherein the proportion of components having a common logarithm (log M) of a molecular weight M being from 2.0 to 3.5 is at most 10 mass % per 100 mass % of components having a common logarithm (log M) of a molecular weight M being at least 2.0, contained in a CClF2CF2CClFH soluble content.

主权项

1. A fluorinated copolymer comprising units of i) a fluorinated monomer having a carboxylic acid functional group or a functional group capable of being converted to a carboxylic acid group by hydrolysis or neutralization and ii) a fluorinated olefin,
wherein the proportion of components having a common logarithm (logM) of a molecular weight M of from 2.0 to 3.5 is at most 10 mass % per 100 mass % of components having a common logarithm (logM) of a molecular weight M of at least 2.0, and wherein the proportion of components is determined by measuring a soluble content of the fluorinated copolymer by the following extraction method: a powdery fluorinated copolymer comprising units of a fluorinated olefin and a fluorinated monomer having a carboxylic acid functional group or a functional group capable of being converted to a carboxylic acid group by hydrolysis or neutralization is mixed with CClF2CF2CClFH with a mass ten times the fluorinated copolymer; a resulting mixture is stirred at 65° C. for 5 or more hours; the mixture is cooled to room temperature, and then methanol with a mass twice the fluorinated copolymer is added to the mixture; the mixture is filtrated, and CClF2CF2CClFH and methanol are distilled off from a filtrate to obtain a soluble content.