Patent GB-807192-A (GB)
Title: Improvements in cellulose triacetate textile materials
Inventor: FINLAYSON DONALD
IPC: D06M11/05
Filed: 1956-02-24
Abstract: Filamentary materials of substantially flat cross-section consisting essentially of cellulose triacetate are treated to impart to them an increased degree of crystallinity and a sticking temperature of at least 220 DEG  C.  The sticking temperature is defined as the lowest temperature at which a heated iron sticks to the surface after standing for 10 seconds on a fabric of the material.  The materials treated may be straws, ribbons and like materials which are considerably wider than they are thick and may have a straight or curved cross-section, or may be fabrics made at least in part of these materials.  Cellulose triacetate materials of substantially flat cross-section, obtained by melt spinning, wet spinning or dry spinning and having a normal degree of crystallinity and a sticking temperature of about 200 DEG  C. may be subjected to a dry or wet heat treatment at such a temperature and for such time as is sufficient to effect the required increase in crystallinity and sticking temperature.  The heat treatment may be carried out using dry heat (e.g. hot air or other gas) at 180-240 DEG  C., and especially at 185-220 DEG  C. for a period between 10 minutes at 185 DEG  C. and 15 seconds at 220 DEG  C.  Lower temperatures may be used with wet heat, such as wet steam or hot water at 120-160 DEG  C. and especially 125-150 DEG  C., treatment times varying from 5 seconds at 160 DEG  C. to 1-2 minutes at 120 DEG  C. Heat may also be applied by the use of a molten alloy such as Wood's metal or a low-melting mixture of salts at 185-205 DEG  C.  An alternative method comprises acting on the straws with an organic liquid which is a swelling agent for cellulose triacetate, e.g. aqueous acetic acid of about 8-15 per cent by weight concentration at or near its boiling point, or other agents mentioned in Specification 776,346.  The heat treatment may be applied to individual batches of material, or may be applied continuously, either to the straws themselves or to structures containing them.  The treatment may also be applied to cellulose triacetate materials obtained by further acetylation either of straws of acetone-soluble cellulose acetate which have not been orientated, as by stretching, or of structures comprising such straws.  The treatment raises the safe ironing temperature of the material and improves its dimensional stability at high temperatures.  The Provisional Specification refers also to the application of the treatment to straws of another cellulose ester having a high degree of substitution and capable of existing in a form having a relatively high degree of crystallinity, as for example cellulose propionate of propionyl value 63 per cent or higher (expressed as propionic acid), or a cellulose acetate-butyrate of butyryl value (expressed as butyric acid) 25-35 per cent and a total degree of substitution at least 2.65 and preferably 2.7 or more, as described in Specification 753,461.  Specifications 443,707, 443,773, [both in Group IV], 758,442, 778,395 and 797,661 also are referred to.