Patent GB-827644-A (GB)
Title: Method of making fibrous strands and tobacco smoke filter therefrom
IPC: A24D3/08
Filed: 1956-03-26
Abstract: 827,644. Spinning yarns. AMERICAN VISCOSE CORPORATION. March 26, 1956 [April 18, 1955], No. 9292/56. Class 120(3) [Also in Groups VI and XXV] A strand e.g. thread, cord or rope, comprises non-uniform, non-elastomeric, thermoplastic fibres having a maximum diameter of 0.5-10 microns, the fibres being in progressive overlapping arrangement and bonded to each other at their points of contact: each fibre has at least a twofold variation in diameter along its length and tapers at its ends. Fibres may be of materials e.g. vinyl resins, enumerated, and formed from organic solvent solutions and/or hot melts as described in Specifications 794,725'and 827,641. Liquid which is sprayed to form the fibres may incorporate additives e.g. fillers, colouring dyes or pigments, plasticizer. Fibreforming streams may be projected into a stream of gas e.g. air, nitrogen, carbon dioxide, steam, by which they are attenuated and broken. Particulate material e.g. cork and emery dust or staple fibres of rayon, nylon or sisal, may be introduced into the gas stream so that it adheres to the thermoplastic fibres which are then in tacky condition: such added staple fibres have a diameter exceeding 10 microns and may constitute 20-60% of the fibre content of the strand. Similar or different forms of the strand may be intertwisted or twisted with cords of conventional fibres and filaments (prior or subsequent to activation of the fibres to render them adhesive) to form composite cords the components of which may be interbonded. Tobacco smoke filters may be formed from cut lengths of strand (see Group VI). As shown in Fig. 1, liquid sprayed from nozzles 5 on a rotating unit is converted into fibres 23 which are carried by a stream created by vanes 9 acting on air (and added particulate material) supplied through ducts 13 and an electrically charged ring 14 induces a charge thereon opposite to the charge maintained on a giude 19 toward which the fibres are thus attracted. A bundle of fibres 24 is continuously withdrawn by a roller 25 through guide 19 and an electrically heated die 21 and is then cooled to form the bonded strand: the die enables the bond between fibres in a superficial layer to be intensified while maintaining a core portion in open condition. A modified spray unit, Fig. 4 (not shown), dispenses with a conical shell 8. As shown in Fig. 3, liquid streams sprayed from nozzles 32 on a fixed unit 30 are converted into fibres 35 by high velocity gas streams emerging from nozzles 34. The velocity of the gas and/or liquid streams may be varied to regulate the diameter and/or length of the fibres. A secondary air stream supplied from a blower 36 (and containing the particulate material) through an intake 37 is directed into a vortex or swirling flow by a spiral fin 29 and thereby creates a reduced pressure along the axis of a tower 28 toward and along which fibres are thus carried and advanced. The fibres are deposited or collected as a strand 38 which is passed through a heating chamber 40 and is then cooled. The bonding of fibres in the strand e.g. in an open core portion, may be intensified by use of extended heating periods, or activating materials such as solvents or softening agents for the thermoplastic material or vapours thereof, or hot gases.