Abstract
It is found that polyvinyl alcohol is changed into colored high molecular compounds keeping fiber form by acetalizing heat-treated fiber with some hydroxy-aromatic aldehydes and subsequently by coupling with diazonium compounds. In order to obtain the colored fiber resistant to boiling water, formalizing or benzalizing is generally necessary in addition to the acetalizing with hydroxyaromatic aldehyde. Though in hydroxy-aromatic aldehyde having electro-negative group, e. g. nitro-, carboxyl-, or bromo-group, directly attatched to the aromatic ring, the acetalization proceeds more easily than in hydroxy-aromatic aldehyde having no electro-negative group, in the color-developing due to coupling with diazonium compounds the fiber acetalized with the latter is better, even if the degree of acetalization is considerably lower. Particularly even the fiber acetalized with hydroxvnaphthaldehyde or resolcylaldehyde to several tenth mole per cent is developed in heavier shades. By changing the hydroxy-aromatic aldehyde and particularly aromatic amine, red, orange. yellow, brown, purple, and black shades are obtained, but blue and green are not.
