| 摘要 |
Polyvinyl alcohol fibres having a low degree of shrinkage are made by impregnating heattreated polyvinyl alcohol fibres in the form of endless filament, sliver or staple fibres at room temperature or below with an acid, salt-containing formaldehyde bath, squeezing or centrifuging off excess hardening liquor and then heating the fibres in a pressure vessel or in a tube in a loose state to a temperature of 50 DEG -100 DEG C. until, after washing out the hardening bath, their shrinkage in boiling water amounts to no more than 10%. When a sliver is treated it may be impregnated with the hardening bath, squeezed out and then cut into staple fibres prior to heating. Heating may be carried out in a closed vessel for 10-120 minutes. When the process is carried out in a continuous manner the impregnated sliver may be conducted in a loose state through a tube through which a current of hot air containing steam and having a temperature of 90 DEG -100 DEG C. is passed. In a modification of the process the fibres are impregnated with an acid, salt-containing bath which does not contain formaldehyde, excess of the bath is squeezed or centrifuged off and the fibres are then heated in a pressure vessel or tube in which the amount of formaldehyde necessary for the hardening process is volatilized in the presence of steam at a temperature of 50 DEG -100 DEG C. or into which the necessary amount of formaldehyde is introduced in the gaseous state at 50 DEG -100 DEG C. until, after washing out, the shrinkage of the fibres in boiling water amounts to no more than 10%. In the manufacture of crimped staple fibres the sliver may be cut and crimped prior to impregnation with the hardening bath or after hardening and washing. |
