Patent GB-1019711-A (GB)
Title: Method of making spun collagen product
Inventor: GRISET ERNEST JACK
IPC: D01F4/00
Filed: 1962-03-16
Abstract: A homogeneous aqueous dispersion of swollen collagen fibrils, for extrusion into filaments (Division B5) is obtained by the sequence of operations shown in Fig. 1.  Sliced mallamian tendon, e.g. bovine deep flexor tendon, is treated with enzyme e.g. Pancreatin ficin or malt diastase, to free the tendon from elastin. Soluble protein and liquids are then removed by treatment with a chelating agent e.g. ethylene diamine tetrasodium tetraacetate.  The collagen slices are then swollen in an aqueous or <PICT:1019711/C3/1> <PICT:1019711/C3/2> aqueous methanol acidic solution, containing e.g. perfluorobutyric acid or cyano-acetic acid, to form a dispersion of collagen fibrils. This dispersion may be homogenized in a kettle (Fig. 3) which is provided with an eccentric paddle 106 and homogenizing jets 108, 109 through which the dispersion is circulated.  The temperature of the collagen, subsequent to addition of the acid is preferably maintained below 25 DEG  C.  The dispersion is then separated from unswollen non-collagenous material e.g. connective tissue by passage through a leaf filter, and is then aged at room temperature for 24 hours. Before spinning into filaments the dispersion is dearated.  The collagen dispersion is two-phase (i.e free fluid plus swollen fibrils) and may contain e.g. 0.67-0.88% solids.ALSO:A two-phase liquid dispersion of substantially uniformly dispersed swollen collagen fibrils is extruded through a stationary spinneret into a dehydrating and coagulating bath to form a multifilament, the natural structure typical of the fibrils being preserved, and the individual fibrils being oriented parallel to the principal axis of the multifilament, and the multifilament is formed into a strand or a tape, which is then dried.  The solids content of the dispersion e.g. an aqueous methanol dispersion, is such that a two-phase system (i.e. free fluid plus swollen fibrils) is maintained and may be 0.67-0.88%. The dehydrating bath may be made up of acetone containing 120-140 milligrams per litre of ammonia.  The concentration of acetone in the dehydrated multifilament may be reduced by volatilising the acetone, methanol and water in the ratio determined by their respective vapour pressures, whereby the collagen content of the multifilament is increased, and the ratio of water to other liquids present in the multifilament is also increased.  The multifilament may be formed into a tape by squeezing the wet multifilament through rollers.  A rounded strand may be formed by stretching and twisting the tape or the multifilament itself.  The relative humidity may be maintained at 60-65% throughout the steps of twisting, stretching, squeezing and drying.  The spun filaments pass over a godet and are there washed or tanned by passing them over a subsidiary godet immersed in treating liquid. On contact with these godets the filaments cohere to form a tape or ribbon-like structure, which is converted to a round strand by a false-twister.  The strand then passes, via a hot air dryer to further godets where it is tanned by contact with streams of tanning bath as it passes thereover.  The strand is further twisted, by which time it is substantially dry, and is completely dried by a heated air source.  The tape or strand is twice stretched between pairs of godets.  Preferably, the apparatus is encased in closed cover to maintain constant humidity.  In further embodiments the collagen dispersion is spun horizontally or vertically downwards.  In another embodiment the multifilament is converted to a tape, which is wound up as such, to be subsequently converted into a rounded strand.  The multifilament is squeezed between a driven godet and roll to form a tape or ribbon of cohered filaments.  The tape passes through an air-drying tube and thence to a godet and roll to complete the drying and is then wound.  The dried tape may be further processed i.e. repeatedly stretched, tanned and dried and then false-twisted to form a rounded strand which is treated with aqueous formaldehyde from a jet, stretched and dried.  The collagen strands are used as absorbable sutures (Division A5)ALSO:A suture is made by extruding a two-phase liquid dispersion of substantially uniformly dispersed collagen fibrils through a stationary spinneret, into a dehydrating and coagulating bath to form a multifilament, the natural structure typical of the fibrils being preserved, and the individual fibrils being oriented parallel to the principal axis of the multifilament, and twisting the multifilament, or a tape formed by compressing the multifilament, into a rounded strand, which is then dried. Extrusion, washing, tanning and stretching processes are described and illustrated (DIVISION B5).  The sutures are composed of a plurality of collagen monofilaments arranged in parallel (see Specification 1, 019, 712.  The sutures are absorbable and have greater strength than sutures made from gut.