Patent GB-1234358-A (GB)
IPC: D06N3/00
Filed: 1969-10-17
Abstract: 1,234,358. Making flat collagen films continuously. CENTRE TECHNIQUE DU CUIR. 17 Oct., 1969 [27 Nov., 1968], No. 51076/69. Heading B5B. [Also in Division B2] As shown in Fig. 1, an apparatus for making a flat collagen film in a continuous manner comprises a dispersion reactor 1 adapted for the production of solutions, dispersions or gels of collagen having a concentration of 1 to 5% in an aqueous medium or 1 to 15% in an organic solvent and for the aerating or deaerating of the dispersions or solutions formed. The dispersions or solutions may be matured for several hours alternately in vessels 2 from which they are metered by a gear pump 3 (driven by a constant speed motor provided with means for adjusting its speed to any desired constant value) through a wire gauze filter 4 to the extrusion die 5 having a straight slot extrusion orifice. The collagen dispersion or solution is extruded through the slot die 5 to form a thin layer on a travelling endless belt 7 of hydrophobic material such as polypropylene or polyvinyl chloride. The layer of collagen is carried by the band 7 through drying tunnels 11 and 11a when the solvent or the dispersion medium (whether water or a volatile organic solvent) is evaporated at a temperature within the range 30 to 40 C. The collagen of the film is coagulated in the form of fibrils or of fibres by neutralization with an alkali or by treatment with a saline solution, or a solution of an alkali in a solvent having a strong affinity for water. The coagulation of the collagen is preferably effected by directing a stream of gaseous ammonia on to the film by means of a nozzle 6 having a slot-shaped aperture. Alternatively, the collagen film may be neutralized and coagulated by passing the travelling band 7 through a low boiling point dehydration solvent such as acetone or methanol containing an organic or inorganic alkaline compound. The apparatus may advantageously comprise a device for the impregnation or coating of webs of woven and non-woven textile fabrics with a collagen film. The fabric web is supplied from a feed bobbin 9a or 9b and when the bobbin 9a is used, the collagen film may be drawn into the fabric web by means of a vacuum chamber 10. After leaving the drying tunnel 11a, the collagen film or the collagen-impregnated fabric web is stripped from the travelling band 7 and wound up at constant tension on the bobbin 27 by the device 13. In an example, a suspension of 300 grams of dry collagen fibres in 10 litres of water is deaerated in the reactor 1 by stirring under reduced pressure, a solution of 75 grams of lactic acid and 90 grams of glycerol in 4¢ litres of water is added and the mixture stirred under reduced pressure for 10 minutes. The air-free dispersion thus obtained is filtered and stored for 24 hours in one of the vessels 2. The dispersion is then metered by the gear pump 3 to the slot die 5 and delivered on to the travelling belt 7 to form a film web which is coagulated by gaseous ammonia delivered by the nozzle 6 and is thereafter passed through the drying tunnels 11 and 11a, stripped from the belt 7 and wound up on the bobbin 27. The film thereby formed is translucent and 0À03 mm. thick.