| 摘要 |
An object of the present invention is to provide a purification method of separating impurities from a carboxyl group-containing polyoxyethylene derivative having a molecular weight of 2,000 to 100,000. The purification method according to the invention includes the following steps. The polyoxyethylene derivative is dissolved to form a solution using toluene, xylene, benzene, ethyl acetate, or butyl acetate in an amount 5 times by mass or more the amount of the polyoxyethylene derivative. A slurry is formed by adding to the solution an inorganic adsorbent containing at least one of an oxide and a hydroxide of one or more elements selected from the group consisting of magnesium, silicon, and aluminum in an amount 0.5 to 10 times by mass the amount of the polyoxyethylene derivative. The slurry is stirred at a temperature of 25° C. or higher. Toluene, xylene, benzene, ethyl acetate, or butyl acetate is added to a filtration cake obtained by filtration of the slurry, and further filtration is performed. Methanol, ethanol, or 2-propanol is added to the filtration cake in an amount 5 times by mass or more the amount of the polyoxyethylene derivative, filtration is performed, and the polyoxyethylene derivative is recovered from the resulting filtrate.
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