| 摘要 |
<p><PICT:0633187/IV (a)/1> High tenacity threads of thermoplastic cellulose derivatives suitable for weaving are produced by heating the pre-formed threads to a temperature sufficient to render them plastic, stretching the threads at least 50 per cent while they are in the heated plastic state, and then permitting the threads to shrink at least 8 per cent while they are in a heated plastic state, the plasticity of the thread during both the stretching and shrinking steps being effected solely by the action of heat. The thermoplastic cellulose derivative may be cellulose acetate, in which case a temperature of 210 DEG to 360 DEG C. may be used. The stretching and shrinking steps may be effected in two stages; the range for the first stretching operation may be 40 to 150 per cent and that for the second stretching may be 20 to 150 per cent. The threads are preferably shrunk 10 to 20 per cent. The Figure shows an apparatus which may be used in the process of the invention, in which four rotating rollers are provided of such diameters and speeds that the thread is stretched as it passes through heating tubes 1 and 2 and shrunk as it passes through heating tube 3. Cellulose acetate thread 8, drawn from a bobbin 9 is passed twice round roller 4, down heating tube 1, round roller 5, down heating tube 2 and round roller 6; thence it passes down heating tube 3, round roller 7 and after an extended travel through the air is collected on bobbin 27. Instead of using a continuous process, the thread from wheel 5 may be collected and subsequently reheated and shrunk, or restretched and then shrunk. Specifications 323,846, [Class 2 (ii)], and 475,650 are referred to.</p> |
