Patent GB-767015-A (GB)
Title: Improvements in the production of filaments, films, and other articles of synthetic polymers
IPC: D01F1/10
Filed: 1953-11-23
Abstract: An aqueous mixture having a dispersion phase comprising a water-insoluble synthetic polymer in discrete particle form and having a solution phase comprising an aqueous medium and a matrix-forming material dissolved therein, is extruded through an orifice of appropriate shape into a setting medium so as to form a filament, film, foil, tape, ribbon, bristle, or like article; the extruded material is exposed to the action of the setting medium until the matrix-forming material is coagulated and the discrete particles are immobilized by the resultant matrix, and the resultant coagulum is then coalesced.  The water-insoluble synthetic polymer may be an acrylonitrile polymer or copolymer; polyacrylic or polymethacrylic ester, polyvinyl chloride, vinylidene chloride polymer, polyethylene, polytetrafluoroethylene, polychlorotrifluoroethylene, polyvinyl acetate, polymethylvinyl ketone, polyvinyl ether, chlorosulphonated polyethylene, polyvinyl carbazole, polyvinyl acetal, polyamide, polyurea, polyurethane, polyester, polyesteramide, polysulphonamide, polysulphone, polyether, or cellulose derivative.  In the aqueous dispersion, the polymer should have a particle size less than 15 microns, preferably 0.005-1.5 m .  Reduction of the particle size to the desired value may be effected while the polymer is in the dry state or in the form of a slurry, e.g. by means of ball mills.  The dispersion may be prepared from a solution of the polymer, or a suspension obtained by an emulsion polymerization process in aqueous medium may be employed directly.  The strength-providing matrix comprises a polymeric gel formed during the extrusion process by the physical or chemical action of the setting medium. Preferably the gellable polymer is one that is soluble in water or in an aqueous medium of a pH of 1-14. The matrix-forming material may be a polymeric cationic or anionic electrolyte, or a neutral polymeric material, or it may be a protein. Examples of matrix-forming materials include:-alginates, carboxyalkyl celluloses, cellulose sulphate, carbohydrate gum from Irish moss, locust bean gum, polymetaphosphates, silicates, lignin sulphates, pectinates, casein, zein, gelatine, egg albumin, starch glycolates, polyacrylates, b -carboxyethylacrylate polymer, water-soluble modified styrene polymers, partially hydrolysed polyacrylamide, vinyl acetate and allyl glycidyl ether copolymers, styrene-maleic anhydride copolymers, polyvinyl pyridine, deacetylated chitin, polyethyleneimine, diethylaminomethyl methacrylate polymer, N-vinyl phthalimide copolymer with hydrolysed vinyl acetate, poly-b -methacrylyl-oxymethyltriethyl ammonium bromide, propylene glycol alginic ester, methyl cellulose, hydroxyethyl cellulose, cellulose acetate, urea-formaldehyde and melamine - formaldehyde resins, amylopectin, allyl starch, polyvinyl alcohol, and polyacrylamide. The quantity of matrix-forming material present in the dispersion may be 0.10-10.0 per cent by weight of the dispersion which may contain 5-60 per cent of water-insoluble fibre-forming polymer.  The setting medium may be a liquid or vapour.  It may be a solution of an acid or of a salt containing polyvalent metal ions such as calcium, chromium, aluminium, beryllium, zinc, and manganese.  Solutions of sulphuric, hydrochloric, and sulphamic acid may be used.  Coalescence of the immobilized water-insoluble particles may be effected by various methods such as heating, or treatment with a hydrotropic salt, or solvent or plasticizer.  Organic vapours such as those of N,N-dimethyl formamide may be used as coalescing agents. Preferably the coalescing treatment is carried out separately from the setting of the extruded article, but, if desired, the dispersion may be extruded into a medium which will precipitate the matrix-forming material and will also exert a solvent action on the polymer particles in the precipitated matrix.  The coagulated polymer article may be passed through a solvent or the article which has occluded minor amounts of solvent may be subjected to air drying.  For coalescing gelled structures of polyacrylonitrile and many other polymers, solutions of the following salts may be used:-lithium thiocyanate, bromide, and iodide; sodium thiocyanate and iodide; potassium, magnesium, calcium and zinc thiocyanates; chlorides, bromides, and iodides of tin, iron, cobalt, zinc and cadmium. Guanidine thiocyanate, dimethyl formamide, m-cresol, cyclohexanone, acetophenone, petroleum oil, and other organic substances may be used for effecting the coalescence.  The temperature of this treatment is preferably 30-175 DEG  C.  When heating alone is used for coalescence there may be used as heating agent, molten Woods metal, an inert liquid hydrocarbon, air or other inert gas, radiant heat, or a heated surface.  The water-insoluble synthetic polymer may have a molecular weight of 10,000 up to a million or more.  In an example, acrylonitrile is polymerized at 40 DEG  C. in presence of water, sodium auryl sulphate and potassium persulphate, and to the aqueous dispersion of polymer obtained, an aqueous solution of sodium alginate is added.  The dispersion is extruded into a 70 per cent solution of zinc chloride containing hydrochloric acid. The filament obtained coalesces in a few seconds.  In another example, polyacrylonitrile of M.W. 270,000 is made by emulsion polymerization and sodium alginate is added to the dispersion which is then extruded into calcium thiocyanate solution.  The filaments are passed through a second bath containing a concentrated solution of calcium thiocyanate.  Sodium pectate may be used instead of the alginate.  An aqueous dispersion of a N-methoxymethyl nylon containing methanol, a dispersing agent, and sodium alginate is extruded into calcium chloride solution and the gel fibre obtained is passed through a heating zone.  A similar dispersion is extruded into dilute hydrochloric acid and the fibre obtained is heated in tetramethyl urea, or in a solution of sodium xylene sulphonate.  In another example, an aqueous polymer dispersion is made by heating under pressure a mixture of tetrafluoroethylene, water, sodium hexadecafluorononanoate, disuccinic acid peroxide, and paraffin. Sodium alginate solution is added and the dispersion is extruded into calcium chloride solution.  The gel filament obtained is lifted through a stream of hot air by a wheel, heated to 380 DEG  C.  In other examples, an aqueous dispersion of polystyrene, vinylidene chloride/acrylonitrile copolymer, polychlorotrifluoroethylene, or a mixture of polyethylacrylate and polyacrylonitrile, is extruded, after the addition of sodium alginate, into calcium chloride or thiocyanate solution, and coalescence of the gel fibre is obtained by heating in petroleum oil, by passage through hot air and over a heated surface, by simple drying in air at room temperature or by passage through hot calcium thiocyanate solution.  In another example, polyvinyl alcohol is mixed with a dispersion of polyacrylonitrile to act as matrix-forming material. In other examples, an aqueous dispersion of polyethylene glycol sebacate containing sodium alginate is extruded into calcium thiocyanate solution and the filament is coalesced in ethanol, benzene, or chloroform/methanol; an aqueous dispersion of a mixture of polyacrylonitrile and a copolymer of acrylonitrile with butadiene, or a dispersion of tetrafluoroethylene/perfluoropropylene copolymer, containing sodium alginate is extruded into dilute hydrochloric acid or calcium thiocyanate and the filament is coalesced by passage through concentrated calcium thiocyanate solution or over a heated roll.  An aqueous dispersion of polyacrylonitrile containing water-soluble cyanoethyl cellulose is extruded through a slot into hot and strong calcium thiocyanate solution to form a gel film which rapidly coalesces to a clear rubbery film. Polyacrylonitril in aqueous dispersion containing sodium alginate and the sodium salt of a styrene-maleic anhydride polymer is extruded into calcium thiocyanate solution and the filament is coalesced in a hot and strong calcium thiocyanate solution.  A similar dispersion is extruded into an aqueous solution containing sodium sulphate, aluminium sulphate, and sulphuric acid.  Coalescence is effected with a hot, strong solution of sodium thiocyanate.  Specifications 655,516 and 712,623 are referred to.