Patent GB-787999-A (GB)
Title: Improvements relating to the extraction of soluble material from artificial particularly synthetic filaments, films and the like
IPC: D01D10/04
Filed: 1954-11-30
Abstract: Soluble material is continuously extracted from gelatinous artificial fibres, consisting of a polymeric solid material contaminated with a liquid, by causing the fibres to travel in continuous length through a bath of a liquid extracting medium which is a solvent for the liquid contaminant, and simultaneously directing against the surface of the fibres one or more streams of bubbles of a gas which is inert to the fibres, to the soluble material and to the extraction medium and which is substantially insoluble in the extraction medium.  The air bubbles may be supplied from orifices located in pipes submerged in the bath of the liquid extracting medium or in the bottom of the wash trough, or from porous structures, e.g. refractories or sintered powdered metal structures.  Thus the entire wash trough may have a porous false bottom, or porous discs or strips may be inserted in pipes or channels submerged in the bath.  Suitably, a multifilament strand of acrylonitrile copolymer fibre in the coagulated swollen gelatinous state and containing dilute aqueous sodium thiocyanate solution passes downward into a wash trough 12.5 feet long and 15 inches wide, under a positively driven roll, then through the length of the trough about 1.5 to 2 inches beneath and parallel with the surface of the liquid in the trough, then under a second positively driven roll, and finally emerges from the trough.  A stream of solvent is passed through the trough in countercurrent to the strand to provide a bath about 9 inches deep.  Air under slight superatmospheric pressure is supplied to a horizontal pipe disposed across the width of the trough with its upper surface located about 4-6 inches below the surface of the liquid, the pipe having a number of small holes from which the air issues in streams of small bubbles. More than one perforated air pipe may be provided in the trough.  The fibres may pass through a series of troughs in succession, the wash liquid flowing in countercurrent from trough to trough. Specifications 672,775, 689,743, 689,744, 689,770 and 695,448, [all in Group IV (a)], are referred to.ALSO:Soluble material is continuously extracted from gelatinous artificial fibres or films, consisting of a polymeric solid material contaminated with a liquid, by causing the fibres or films to travel in continuous length through a bath of a liquid extracting medium which is a solvent for the liquid contaminant, and simultaneously directing against the surface of the fibres or films one or more streams of bubbles of a gas which is inert to the fibres or films, to the soluble material and to the extraction medium and which is substantially insoluble in the extraction medium.  The air bubbles may be supplied from orifices located in pipes submerged in the bath of the liquid extracting medium or in the bottom of the wash trough, or from porous structures, e.g. refractories or sintered powdered metal structures. Thus the entire wash trough may have a porous false bottom, or porous discs or strips may be inserted in pipes or channels submerged in the bath.  Suitably, a multifilament strand of acrylonitrile copolymer fibre in the coagulated swollen gelatinous state and containing dilute aqueous sodium thiocyanate solution passes downward into a wash trough 12.5 feet long and 15 inches wide, under a positively driven roll, then through the length of the trough about 1.2 to 2 inches beneath and parallel with the surface of the liquid in the trough, then under a second positively driven roll, and finally emerges from the trough.  A stream of solvent is passed through the trough in countercurrent to the strand to provide a bath about 9 inches deep.  Air under slight superatmospheric pressure is supplied to a horizontal pipe disposed across the width of the trough with its upper surface located about 4-6 inches below the surface of the liquid, the pipe having a number of small holes from which the air issues in streams of small bubbles.  More than one perforated air pipe may be provided in the trough.  The fibres or films may pass through a series of troughs in succession, the wash liquid flowing in countercurrent from trough to trough.  The process is especially adapted for the treatment of multifilament tows of homopolymers of acrylonitrile or copolymers of acrylonitrile with ethylenic monomers such as vinyl pyridines (e.g. 2-methyl 4-vinyl pyridine), methyl acrylate, vinyl acetate, and vinyl chloride, produced as described in Specifications 672,775, 689,743, 689,744, 689,770 and 695,448.  In these processes solutions of polymeric acrylonitrile in concentrated aqueous sodium thiocyanate are spun into 10 per cent aqueous sodium thiocyanate solution maintained at about 0 DEG  C. The process may also be applied to filaments spun from viscose and cuprammonium rayon, and in the manufacture of regenerated cellulose film.