Patent GB-1053758-A (GB)
IPC: A61L17/08
Abstract: 1,053,758. Surgical sutures. ETHICON Inc. Oct. 25, 1963, No. 42208/63. Heading A5R. [Also in Divisions B5 and D1] Surgical sutures are made from a round collagen strand of uniform cross-section throughout its length, made by stretching and simultaneously twisting a multiplicity of extruded wet collagen monofilaments under controlled conditions of humidity to wring out a controlled amount of moisture and to bond the monofilaments into a unitary structure, drying the monofilaments while in the twisted condition, and removing the twist. Monofilaments are defined as single threads of collagen fibrils as extruded through single spinneret orifices. The wet collagen monofilaments may be obtained in the form of a ribbon, i.e. a thin film of collagen fibrils as extruded through a slit, the wet collagen ribbon twisted to wring out excess moisture, dried while in the twisted condition to form a bonded unitary structure of circular cross-section, and the twist removed. In a preferred method, a collagen dispersion is de-aerated, aged for 31 hours at 25‹C. and 16 hours at 5‹C., and spun from the reservoir 114 under a pressure of 15 1bs. The dispersion is pumped through the homogenizing jets 116 and 117 and the filter to the spinneret and is extruded upwardly into the spinning column which contains a continuously circulating acetone dehydrating bath 145, the filaments passing over idler pulley 137 and around guide 138 to the godet 101. The collagen filaments are wrapped three times around godet 101 before passing to the first stretching stage. Three wraps suffice to prevent slippage because the collagen is wet at this point. In the first stretching stage, between godets 101 and 102, the filaments are twisted. by false twister 112 to improve their tensile strength and thus prevent breaks during processing, and also to wring out the moisture. which is further removed by the heater-blower 133, adjusted to give an indicated tension of 45 to 50 gms. on the tensometer 142. The extent of bonding occurring during this stage may be increased by wetting out the filaments at godet 101 with water and by operating in a moist atmosphere. Twelve wraps around godet 102 are required to prevent slippage owing to the relative dryness of the filaments. In the second stretching stage, the moving filaments are continuously washed and/or tanned by contact with a downward flow of tanning solution 144 in a direction opposite to that of the travel of the filaments. The wetted-out filaments from a freely rotating idler' pulley 132 are returned to an idler pulley 105 and contact the tanning bath a second time. The tanning bath is an aqueous solution containing 4 mls. of 40 % w/v aqueous formaldehayde and 1 gm. anhydrous aluminium ammonium sulphate per litre. The filaments are then given, a reverse twist by passage through false-twister 113, which serves to bond the collagen filaments together to form a unitary strand, and to wring out moisture therefrom. Heater-blower 134 is adjusted so that the indicated tension at the tensometer 143 is about 190 gms. Under these conditions, the wet tanned strand dies out before the reverse twist is applied by false twister 113. Since the strand is substantially dry at the point of contact with the false twister, the roundness imparted to the strand when wet is not removed. The strand is finally taken up on the spool 147. For details of the falsetwisting devices used, see Division D1 abridgment.