| 摘要 |
Paper is made from flat, tubular viscose fibres having a tubular flattened part extending over at least 60% of their length the cross-section of the long axis of the fibre being at least 5 times, preferably at least 10 times, that of the short axis. Such fibres are made by spinning an unripe viscose having a Hottenroth value of more than 16 and containing 2 to 50% (based on the cellulose in the viscose) of an organic water-swelling high molecular weight substance and 2-4% (based on the viscose) of anhydrous alkali cabonate into a coagulating bath containing sulphuric acid and at least one metallic sulphate. The unripe viscose may be mixed with a conventional viscose. Specified organic water-swelling high molecular weight substances include polyvinyl alcohol and its derivatives, hemicellulose, methyl cellulose, ethyl cellulose, cyanoethyl cellulose, carboxymethyl cellulose, hydroxy ethyl cellulose and other water-swellable, so-called alkalisoluble cellulose derivatives, which are preferably present in the fibre in a proportion of 5-30%. Preferably the Hottenroth value of the viscose is about 20. A coagulating bath consisting of sulphuric acid, sodium sulphate and zinc sulphate may be used, but zinc sulphate is not essential and sodium sulphate may be replaced by a mixture of magnesium and aluminium sulphates. In Examples, the coagulating bath used is at a temperature of 60 DEG C and consists of 12% by weight sulphuric acid, 2.5% anhydrous zinc sulphate and 25% anhydrous sodium sulphate. The filaments are then stretched to a draw ratio of 1.4 or 1.5 in a hot water bath or 1% sulphuric acid bath at 50 DEG C, wound up and may be cut to short fibres, which are useful in paper-making. In Examples the fibres, of 0.7-8 denier, are cut to a length of 4mm., dispersed in water and paper made according to the TAPPI process, without adding any other binder, by manual working, the wet paper being pressed and dried by a hot press at a pressure of 0.5 kg/cm2 and at 100/C. In an example, such a paper had a weight of 52.45 g/sq. m. thickness 0.08 mm., breaking length 38 km. and tear factor 190. If desired, the hollow fibres may be mixed with 20-30% of solid fibres.
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