Patent GB-1058472-A (GB)
Title: Method of treating absorbable collagen and product obtained thereby
IPC: A61L17/08
Filed: 1964-05-28
Abstract: Surgical sutures are made from collagen strands, obtained by treating an absorbable collagen 'tape' with one or more solutions containing, or containing between them, (a) an aldhehyde (b) an aluminium salt, and (c) 2,4-dihydroxybenzoic acid, or in a modification, with two solutions, one solution containing (a) and (b) and one solution containing (c).  Such a tape may be e.g. 4 mils thick and 60 mils wide and contains individual filaments. Sutures so made have adequate wet tensile strength, are resistant to enzymetic degradation in vivo and so retain sufficient tensile strength until the wound has healed. Modifications of the method enable sutures of light colour to be obtained, and absorbable sutures suitable for use with relatively fast healing wounds. Specified aldehydes are formaldehyde, acetaldehyde, glyoxal, succindialdehyde and malonic dialdehydes. Formaldehyde is preferred and, where colourless surgical sutures are to be made, monoaldehydes are to be used.  Specified aluminium salts include a luminium formoacetate, which is preferred, basic aluminium acetate, and potash alum.  Suitably the aluminium solution contains 0.5-2.5% aluminium formoacetate or 0.6-1.2% as Al2O3 and 0.05%-0.4% of formaldehyde, and the pH of the bath is 2-4.7.  The 2,4-dihydroxy benzoic acid solution suitably of 0.2-2.0% concentration may contain about 0.5% of a chelating agent e.g. the disodium salt of ethylene diamine tetra-acetic acid, and about 0.1% of a reducing agent e.g. sodium hydrosulphite or formaldehyde sodium sulphoxylate, and the pH of the bath is desirably adjusted to 7.5-10.5.  Citric acid in 0.5-5% concentration may be added to prevent discolouration due to iron. Methanol is used to dissolve the 2,4-dihydroxy benzoic acid. Several bath compositions for both the one-bath and the two-bath methods are exemplified.  The collagen tape is made by extrusion of a dispersion of substantially pure swollen tendon collagen fibres through a multi-orifice spinneret into an alkaline acetone dehydrating bath. On emerging from the bath, the multifilaments are very loosely united and approximately circular in cross-section, but bond together to form a ribbon-like tape on passing over the godet, owing to the tension on the still-wet filaments.  On drying, the tape form is retained, individual filaments being bonded together by cohesive forces.  In Fig. 1, collagen tape 11 from supply reel 12 is treated at 41 with an alkaline aqueous solution of 2,4-dihydroxybenzoic acid, stretched between godets 21 and 22, dried on passage through drying tube 16, maintained at about 150 DEG F. by circulation of hot air, treated at 42 with a solution containing the aldehyde and the aluminium salt, stretched between godets 22 and 23, wetted with water at jet 20 (to facilitate later false-twisting), dried on passage through drying tubes 17 and 18, maintained at 110-130 DEG F. and 155 DEG F. respectively by circulation of hot air, lubricated with water at jet 24, false-twisted at 19, treated with a solution of 0.08-0.3% formaldehyde maintained at pH 9 at jet 25, again dried, and the strand wound up at 13.  In Fig. 4, collagen tape 50 from supply reel 51 is treated in bath 65 with a solution containing an aldehyde, an aluminium salt, and 2,4 dihydroxybenzoic acid, while subjected to stretch between godets 53, 54, dried on passage through chamber 67 heated to about 110 DEG F.-130 DEG F., and further stretched between godets 55 and 56.  Water is applied at 69, and false-twist at 68. Excess moisture is removed in passage through the drying chamber 72, and the strand is wound up at 52.