Patent GB-615519-A (GB)
Title: Improvements in or relating to methods of conditioning vegetable bast fibres for spinning
IPC: D01C1/02
Filed: 1945-03-29
Abstract: The natural gums are partially removed from bast fibres of flax, hemp or ramie by treating them with an aqueous solution of chlorous acid, its salts or anhydride, at a pH of 3.5-11 and a temperature of 50-100 DEG  C., and thereafter treating them with a weak alkaline solution at 50-100 DEG  C.  About one part by weight of oxidizing agent is used to treat from 10 to 50 parts of fibres, and the alkaline solution may consist of a solution of caustic alkali or a carbonate in concentration of 0.1 to 5 per cent.  The fibres may be given a preliminary treatment with water or spent alkali solution from a previous batch.  An incidental bleaching of the fibres occurs during the treatment.  In an example, mature dry flax straw is decorticated and wound on bobbins and then treated firstly with water at 100 DEG C. and then with a solution containing sodium chlorite and acetic acid at 95 DEG  C.  After washing with cold water, the fibres are treated with 1 per cent sodium hydroxide solution at 95 DEG  C. to give a roving which can be spun to a linen yarn of 20 to 30 lea.  In a second example, the process is repeated except that the sodium hydroxide solution is replaced by a solution containing sodium carbonate and sodium hexametaphosphate.  A third example is given in which the preliminary washing is carried out with the spent alkali of the second example, and the process is then completed as in the first example.  Specification 567,774 is referred to.  The Specification as open to inspection under Sect. 91 refers also to the use of hydrogen peroxide, per-acids, salts of per-acids such as sodium percarbonate and sodium perborate, organic peroxides such as benzoyl peroxide, and other oxygen-containing acids of the halogen series, their salts or anhydrides, e.g. chlorine dioxide.  This subject-matter does not appear in the Specification as accepted.ALSO:The natural gums are partially removed from bast fibres of flax, hemp or ramie by treating them with an aqueous solution of chlorous acid, its salts or anhydride, at a pH of 3.5-11 and a temperature of 50-100 DEG  C. and thereafter treating them with a weak alkaline solution at 50-100 DEG C.  About one part by weight of oxidizing agent is used to treat from 10 to 50 parts of fibres, and the alkaline solution may consist of a solution of caustic alkali or a carbonate in concentration of 0.1 to 5 per cent.  The fibres may be given a preliminary treatment with water or spent p  alkali solution from a previous batch.  An incidental bleaching of the fibres occurs during the treatment.  In an example, mature dry flax straw is decorticated and wound on bobbins and then treated firstly with water at 100 DEG  C. and then with a solution containing sodium chlorite and acetic acid at 95 DEG C.  After washing with cold water, the fibres are treated with 1 per cent sodium hydroxide solution at 95 DEG  C. to give a roving which can be spun to a linen yarn of 20 to 30 lea.  In a second example, the process is repeated except that the sodium hydroxide solution is replaced by a solution containing sodium carbonate and sodium hexametaphosphate.  A third example is given in which the preliminary washing is carried out with the spent alkali of the second example, and the process is then completed as in the first example. Specification 567,774 is referred to.  The Specification as open to inspection under Sect. 91 refers also to the use of hydrogen peroxide, per-acids, salts of per-acids such as sodium percarbonate and sodium perborate, organic peroxides such as benzoyl peroxide and other oxygen-containing acids of the halogen series, their salts or anhydrides, e.g. chlorine dioxide.  This subject-matter does not appear in the Specification as accepted.