1311818 Carbon fibres and fabrics BAYER AG 19 April 1971 [14 March 1970] 23907/71 Heading C1A Carbon fibres are produced by heating a carbonizable fibre material to a temp. of between 150‹ and 400‹ C. in the presence of free oxygen in a first zone and subsequently carbonizing the material in a second zone at a temperature of 1000‹ C. or higher in an atmosphere of inert gas, hydrogen or a mixture thereof, the fibre material being passed between the said zones through a liquid which is inert to the fibre material and substantially free of water, the liquid forming a substantially gas-tight seal through which the fibre enters into the second zone. The preferred carbonizable fibre is polyacrylonitrile. The free oxygen containing material utilized in the first zone may be air and fibre material may be under tension. The liquid seal may be at 0‹ to 50‹ C. The liquid used may be a material that is liquid below 100‹ C. and may be benzene, heavy gasoline of b.p. 123‹ C. or a eutectic mix of diphenyl and diphenyl ether. An apparatus suitable for performing the process comprises a stock roll 1 (see Fig.) from which a fibre strand is drawn, via rollers 4, by a first pair of tension rollers 3, and a second pair of tension rollers 5 through a furnace 6 into which air is passed. The strand then passes via roller 10 and funnel 18 into trough 15 where it passes via rollers 19 through liquid 17, exiting by dip tube 20 and rod 21 it passes into tubular furnace 12. Here the strand is carbonized in an oxygen free atmosphere and is finally wound up on roll 14.