| 摘要 |
PURPOSE:To obtain the titled article excellent in yellowing resistance, by coagulating a polymer solution based on a polyurethane elastomer in a specified nonsolvent by a wet process, washing the polymer, controlling the pH of the polymer to a desired value on the acid side and drying this polymer. CONSTITUTION:A polymer solution formed by dissolving a polymer based on a polyurethane elastomer in a solvent such as dimethylformamide is immersed in a mixture of nonsolvent and solvent such as DMF for said polymer to solidify the polymer by a wet process, and the polymer is washed to remove the solvent. This polymer is treated with an inorganic acid, an organic acid or its aqueous solution (e.g., aqueous citric acid solution) to control the pH to an acidity (in terms of a pH) of 6.9-3.5, and this polymer is dried.
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