| 摘要 |
Crimped yarns are produced by subjecting a yarn of an un-acetalised polyvinyl alcohol to the successive action of aqueous alkali metal hydroxide solutions of increasing alkalinity until a crimp has developed in the yarn. The yarn is preferably treated with aqueous solutions of caustic soda, the first of concentration up to 20% by weight and the second of concentration between 35% by weight and saturation, at temperatures of 15 DEG -25 DEG C., at least the second treatment being continued until a crimp has developed in the yarn. The yarns may subsequently be acetalised by immersion in a bath containing formaldehyde, sulphuric acid and sodium sulphate and then treated with an organic, diisocyanate, preferably an aromatic diisocyanate, in solution in an organic solvent, e.g. methylene chloride, to produce soft high bulk yarns whose crimp is stable and which are insoluble in boiling water.
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