Patent GB-886814-A (GB)
Title: Process of preparing surgical suture
IPC: A61L17/08
Filed: 1959-02-13
Abstract: Surgical sutures are prepared by extruding an acid collagen gel containing 0,5 to 1,5% of solids and having a pH of 2,5 to 4,5 into an alkaline coagulating bath to form a continuous filament, said bath comprising a lower monohydric alcohol miscible with water in all proportions and containing not more than 50% by volume of water and containing in solution at least 0,1% by weight of ammonia or of a lower aliphatic amine which is volatile at ordinary temperatures, compressing the filament into a flat ribbon, drying the ribbon below 150 DEG F., curing the filament either by allowing it to remain in contact with the coagulating bath for at least 30 minutes or by treating it with ammonia or a lower aliphatic amine volatile at ordinary temperatures, passing the ribbon into a dilute aqueous or alcoholic solution of a bichromate under tension to effect partial stretching and to initiate tanning, twisting the chromed stretched ribbon into a twisted cord, completing the stretching by placing the twisted cord under tension in an atmosphere of at least 25% relative humidity until a total minimum elongation of at least 20% is obtained, drying the twisted cord, and passing the dry stretched cord through a reducing bath to complete the tanning, the twisting and stretching being carried out in any order but with at least some of the stretching following the twisting.  In an example, an aqueous collagen gel containing 0,85% of solids and acidified with hydrochloric acid is extruded through an orifice one-eighth inch in diameter into a liquid consisting of 3 parts of 28% ammonia per 97 parts of 95% ethanol.  The extruded filament is allowed to remain in the precipitating bath for more than 2 hours and is then passed through the nips of compression rolls to form a ribbon which is passed over drying rolls at 110 to 120 DEG  F.  The dry ribbon is successively immersed in a 1,5% aqueous solution of ammonium dichromate and a 1,5% aqueous solution of potassium carbonate, stretched about 20% white wet, and then rolled in a tight spiral to produce a smooth cylindrical strand.  The strand is stretched in a humid atmosphere at room temperature to an overall elongation of 30-40% and then allowed to dry for 2 hours. The dry strands are immersed for 3 hours in a 5% aqueous solution of sodium bisulphite at 20 DEG  C., transferred to a 2% aqueous solution of sodium bicarbonate, washed for an hour in water, wound p  on pegs under tension to produce straight lengths and sterilized by dry heat. Specification 606,427 is referred to.ALSO:Surgical sutures in the form of cords of circular cross-section are prepared by extruding an acid collagen gel (see Group IV (a)) into an alkaline aqueous alcohol coagulating bath to form a continuous filament, compressing the filament into a flat ribbon, first drying and then curing the ribbon, treating the cured ribbon under tension with a dilute solution of a bichromate, twisting the chromed stretched ribbon into a twisted cord, stretching and drying the cord and passing the dry stretched cord through a reducing bath to complete the tanning of the cord. Specification 606,427 is referred to.