Patent GB-1080790-A (GB)
Title: Improvements relating to collagen products
IPC: B29C48/08
Filed: 1964-12-10
Abstract: 1,080,790. Surgical sutures. ETHICON Inc. Dec. 10, 1964 [Dec. 12, 1963], No. 50310/ 64. Heading A5R. [Also in Division B5] A collagen film consisting essentially of collagen fibrils having throughout their entire length the typical banding at intervals of approximately 640 Angstrom units, consists of a multiplicity of extruded elongated collagen sheets disposed in parallel contiguity with respect to each other and bonded to each other along their contiguous surfaces to form a unitary laminated structure, substantially all of said fibrils having an alignment parallel to the longitudinal access of the laminated sheets which contain them and the longitudinal axis of the said sheets being parallel to the longitudinal axis of the total structure. Such films are made by causing a homogenous dispersion of swollen collagen fibrils to flow under pressure through a constricted zone, thereby imparting rectilinarity and orientation in the direction of flow to the fibrils, and extruding the dispersion of oriented collagen fibrils through a slit onto a moving belt to form a collagen film, followed by extrusion in the same manner of one or more additional collagen films onto the first formed collagen film while on said belt, the subsequently applied sheet or sheets adhering to the previously deposited sheet or sheets. Preferably, the moving belt has a polyethylene terephthalate resin surface or a polypropylene surface. After removal from the surface, the sheet may be slit to form a tape, washed, tanned and twisted to form a rounded strand of uniform circular cross-section. In apparatus as shown, a homogeneous mass of swollen collagen fibrils is moved under pressure from pumps 10, 11, 12, 13 through pipe 55 and chamber 54 (Fig. 8) of extruder heads 14, 15, 16, 17 to contricted zones 52 thereof and thence to slits 14', 15'. Constricted zones 52 are formed by the interposition of thin shims 51 between plates 49 and 50. (see also plan view of extruder head, Fig. 7, not shown). Thus a collagen film 19 is formed the thickness of which increases with each additional application of collagen. The film 19 adheres to the surface of the belt 18 and is contained by the belt through the enclosure 20 in which it is dried by moving currents of air from blowers 21, 22, heated by heaters 23. The apparatus of Fig. 1 enables successive layers of collagen to be deposited on the belt by repeated passes through the enclosure 20. The film is finally removed by the take-up roll 37. Fig. 11, (not shown) illustrates a modified extrusion head adapted to extrude a collagen film of about 18 inches in width. Construction is similar to that of Fig. 8 except for the provision of additional entry ports. Fig. 12 (not shown) is a modified form of the apparatus of Fig. 1, adapted to utilise the wide extruder head 57, the principle of operation being similar. In the Example, a laminated collagen film of about two mils thickness is made. After removal from the take-up spool the film is washed with methanol to remove cyanoacetic acid, and air-dried. The film is then cut longitudinally and the resulting tapes are then tanned, stretched, false-twisted and dried to form a uniform strand. The collagen strands so made are cut into five-foot lengths, packaged in a tubing fluid and electron beam sterilsed and are then suitable for use as surgical sutures.