Continuous process for the liquid ammonia treatment of fabrics

Abstract

The disclosure relates to a continuous process for the treatment, with liquid ammonia, of moving webs of fabric, the fabric having at least a partial content of natural or regenerated cellulose fiber. Fabric in substantially continuous web form is guided into a treatment chamber and there impregnated with liquid ammonia, desirably by immersion in a bath thereof. The advantageous effects of the liquid ammonia reaction are substantially realized, while undesirable excessive shrinkage of the fabric is avoided, by strictly limiting the time within which liquid ammonia reactions may occur and controllably terminating the reaction at the end of the controlled period. In the process of the invention, the liquid ammonia reaction period commences when the fabric is first introduced into the bath of liquid ammonia and is controllably terminated by bringing the ammonia-saturated web of fabric into contact with a heated drum. As a significant feature of this invention, the reaction period for a fully saturated fabric web is controlled to have a duration of between 0.6 and 9 seconds. Pursuant to one aspect of the invention, a fabric web is conveyed through a processing zone under controlled lengthwise or warp-direction tension, while substantially free of tension in the width or filling direction. The precise duration of the liquid ammonia reaction period, within the specified overall range of 0.6 to 9 seconds, is controlled to achieve a desired level of residual shrinkage of the fabric in the filling direction. Residual shrinkage of the fabric in the warp-direction is controlled to desired levels by desired control of the lengthwise tension of the fabric. After termination of the reacting period, the fabric web is exposed to further processing, including continued heating and, in most cases, steaming, to rid the fabric of interstitial ammonia and to effect release of the ammonia-cellulose bonds. The process of the invention enables a fabric to be processed rapidly and economically, to achieve many desirable effects of mercerization, while at the same time maintaining ammonia-induced shrinkage of the fabric.

Dependencies are inferred from the claim text.