Method of forming a round collagen strand



Dec. 17, 1963 E. J. GRlsET, JR METHODMOF4 FORMING A ROUND COLLAGEN STRAND Original Filed April 13,-'1'959 4 Sheets-Sheet 1 Y @M Mgg Dec. 17, 1963 E. J. GRISE-T, JR 3,114,235 METHOD oF FDRMING A ROUND coLLAGEN STRAND original Filed April 13, 1959 4 sheets-sheet 2 INVENToR. CP/V537- Z' 3P/:57k ,4 7' TUR/VE Y Dec. 17, 1963 E. J. GRlsET, JR METHOD OF FORMING A ROUND COLLAGEN STRAND Original Filed April 13, 1959 4 she'ets-sheet s QM u) ,4 T TOR/VN Dec. 17, 1963 E.; GRlsET, JR METHOD 0F' FORMING A ROUND COLLAGEN STRAND OriginalFiled April 13, 1959 4 Sheets-Sheet 4 INVENTOR. United States Patent yO 3,114,235 METHD F FGRMI-NG A ROUND COLLAGEN STRAND Ernest J. Griset, Jr., Bound Brook, NJ assigner to Ethicon, lne., a corporatonof New Jersey @riginal application Apr. 13, 1959, Ser. No. 806,067. Divided and this application Dec. 1, 1960, Ser. No. 4 Claims. (Cl. 57-157) swollen in acid solution to a diameter of about 200 to I 2G00 Angstrom'units. The term monoilament, as used herein, means a single thread of oriented collagen fibrils as extruded through a single orifice in a spinnerette. The term multilament, as used herein, means a group of individual separate filaments or incompletely bonded filaments that have been extruded through a spinnerette. rEhe term Vopen multilament as used herein means a fluffy multilainent, the bull; of which is large due to the separation of adjacent monoiilaments. The term ribbon, as used herein, means a thin film of oriented collagen fibrils, for example, as extruded through a slit. The term multiribbom as used herein, means a group of individual ribbons extruded through a plurality of slits. s The term strand, as used herein, means a group of filaments or ribbons that have been united to form a bonded structure. The termv cord, as used herein, means a group of filaments or ribbons that have been twisted together and re bonded or partially bonded. Practically the entire production of absorbable sutures and ligatures is currently made from sheep or beef gut by a process that isV time consuming and expensive, and yet is not adapted to produce a uniformi product. The percent of ,production that is rejected, therefore, for some defect such as lack of tensile strength or lack of uniformity, is large. The starting material, e.g., sheep intestines, is available only in limited quantities and one i can notpredetermine the exact size of the finished product. In view of the obvious deficiencies of such surgical catgut and the disadvantages of the ,present method of manufacture, many attempts have been made to obtain a better product by treating collagen to form a swollen fibrous mass that is extruded into a dehydrating bath. It has been found necessary to stretch the extruded collagen to orient it as unoriented collagen lacks the strength that is required of a suture. xtruded collagen is quite fragile asit leaves the dehydrating bath and often breaks upon stretching. In addition, the tensiony causes the extruded collagen to flatten and become deformed through Contact with the godets of the spinning machine unless eps are taken to prevent this. It is an object of the present invention, therefore, to stretch an extruded collagen multililament or multiribbon without breaking it. It is also an object of this invention to prepare a round Mice collagen strand or cord that is of uniform cross-section throughout its length. lt is another object of the present invention to vcontrol the amount of moisture in an extruded collagen multifilament, multiribbon, strand or cord. till another object of the present invention is to produce a cord of collagen multilament or multiribbon. I have now discovered a method of subjecting a continuously moving wet collagen multiilament, ribbon, multiribbon or strand to a wringing action, whereby the amount of moisture in the collagen is controlled. I do this by the use of a device called a false twister that automatically imparts a false twist to the strand. A false twist may be defined as a twist whose direction on one side of a point of contact is reversed on the opposite side, lthus cancelling the twist. By varying the speed of the false twister, I can adjust the moisture in the collagen multilament, ribbon, multiribbon or strand and thereby the tension during the spinning process. The mount of moisture that is present in the extruded collagen is quite important, as moisture decreases the tensile strength so that a wet collagen product can not 'oe stretched Sullicientiy without breaking. ln addition, twisting a collagen multiiilament, ribbon, multiribbon or strand as it leaves the dehydrating bath increases the strength of the moving collagen at the place where it is weakest. The method of operating the false twister may be varied in accordance with the present invention to achieve dierent results. Thus, the speed of the false twister is one of the spinning conditions that determines the extent to which the multiiilament is united to form a strand. If the false twister rotates slowly in a humid atmosphere, a strand is obtained, but the dryer the atmosphere, the less the tendency to bond. It it rotates rapidly in a moist atmosphere, the tendency not to bond, which results from the rapid rotation, is compensated for by the moisture and bonding is achieved. The invention #will Iapps-ar `more cleanly from the follorvving detailed description when t-alten in connection with fthe `accompanying drawings, which show, by way of example, a preferred embodiment of the invent-ive idea. Referring now to the drawings, FIGURE ll is 'a schematic View of the one form of spinning machine that maybe used in the manufacture of Icontinuous collagen mlultiflarnents or stnands. FIGURE 2 isa perspective view of a false twisterwhich is used to wiring moisture out of the inultila-ment and to round the strand during the spinning proces-s. FlGURE `3 is another perspective view of the false twister of FlGURE 2i. FIGURE 4 is la sectional view of the false twister illustnated in FlGURE 3. FlGURE 5 is .a perspective view of an improved false twister. FIGURE 6 is `a sectional view of the false twister illustrated in FIGURE 5 showing a gear driving means. Throughout the present specification, collagen multifilament that is traveling from the spinnere-tte, through the spinning column, over the idler pulley 137, around guide 138, and prior to contact with godet ltlsl, will be referred to as in the extrusion 1st-age. Collagen multililarnent, or strand, that is traveling betwt-:env godet lill land idler pulley 139, and prior to contact with godet 1h21, will tbe referred to as in .the first stretching stage. Collagen multililarnent, strand or cord that is traveling between godet 102, `around the idler pulleys and 136, and prior to contact with godet ltl, will Ibe referred -to as in the second stretching st-age. Referring now to FGURE l of the dra-Wings, which villustrates a vertically upward spinning machine, there are three godets $101, 102 and 103, of equal circumference (about 3 inches), and they may lbe made of nylon. It will Ibe noted that the collagen dispersion in a reservoir 114 is maintained under a pressure that is continuously indicated by a gauge 141. This dispersion is forced by a pump 115 througgh homogenizing jets 116 and 117' and a filter and is extnuded vertically upward through a recirculating dehydrating bath 145, over an idler pulley 137, around a guide 13S Vand onto godet 101. The extruded collagen is pulled vertically upward out of the bath by godet 101. The extruded collagen 146, as it leaves the dehydrating bath 14S and passes through the extrusion stage, is quite moist, so that there is very little tension between the idler pulley 137 and the guide 138. The collagen multifilament is wrapped three times around godet 101 before passing to the first stretching stage. Three wraps are sufficient to prevent slippage because the collagen is wet as it reaches this point. At the end of the first stretching stage, however, the collagen is comparatively dry, so that about twelve wraps around the godet 102 are required to prevent slippage. In the first stretching stage, a false twister 112 twists the collagen multifilament as it leaves godet 101, and thus improves the tensile strength throughout the portion of the multilament extending from the top of the false twister 112 to the godet 101. It is this section of the extruded collagen that is most weak because of occluded moisture, and the twist imparted by the false twister 112 prevents breaks that would otherwise occur as the collagen multifilament leaves the godet 101. The false twister 112 also wrings the moisture out of the multifilament and, together with a heater 133, controls the moisture content of the collagen multifilament. In the first stretching stage, the collagen multifilament may be partially rounded and partially bonded by the false twister to form a strand. The amount of bonding that occurs in the first stretching stage may be increased by wetting out the multifilament at godet 101 with water and operating in a moist atmosphere (between 30 and 60 grains of moisture per pound of dry air). It is customary, however, to spin in a dry atmosphere (less than 20 grains of moisture per pound of dry air), and, under these conditions, there is little or no bonding of the collagen multifilament in the first stretching stage. As pointed out above, the speed of the false twister 112 controls the amount of moisture in the collagen multifilament, and thereby effects the tension as registered by a tensiometer 142 and the amount of stretch that may be applied without breaking the strand. The speed at which the false twister is operated depends upon the relative humidity of the spinning atmosphere, the size (cross-sectional area) of the collagen multifilament or strand, and the character of the collagen dispersion. I have noted that increasing the speed of the false twister tends to reduce the amount of bonding and a dry open multitilament is collected on godet 102 if the moisture content of the atmosphere is kept low. On the other hand, operating the false twister at a slower speed will result in partial or complete bonding if the multifilament or atmosphere is moist. The stretch imparted between godets 101 and 102 provides orientation of the drying multifilament or strand and improves the tensile strength. When the false twisters 112 and 113 are operated properly, spinning conditions may be controlled so that godet 101 is operated at l0 rpm., godet 102 is operated at 14 rpm., and godet 103 at 15 r.p.m. Under these conditions, one would obtain, in addition to the 40% stretch between godets 101 and 102, another 10% stretch between godets 102 and 103. The over-all stretch is preferably varied from about 20% to 50%. Since the optimum amount of stretch will result in maximum strength, the machine is preferably operated to give a CII stretch somewhat less than that required to break the filaments of the strand. ln the second stretching stage, the moving multifilament or strand is continuously washed and/ or tanned by contact with a downward flow of tanning solution 144 in a direction opposite to the direction of strand travel. The wetted out strand from a freely rotating idler pulley 132 is returned to an idler pulley and contacts the tanning bath a second time. In its wet condition, the tanned strand is stretched an additional 10% by the more rapidly rotating godet 103. The problem in the second stretching stage is to completely bond the multifilament to form a strand that is round. Multiple passages over the circular godet surfaces, especially when the filaments are under tension, forms a attened strand. The deformation takes place most readily when the strand is wettest, as it leaves the spin bath and tanning bath. Moisture, however, is required to bond together the collagen filaments to form a unitary strand. 1n the practice of the present invention, this problem has been solved by using a false twister 113 to place a twist in the strand. The twist backs up to the idler pulley and as the wet strand emerges from it, a gradual tapering takes place which rounds the strand and wrings out the moisture. By locating the idler pulley 135 a sutiicient distance above the false twister 113 (preferably about 4 feet) so that the strand is quite dry when it contacts the false twister, I have found that the roundness may be permanently bonded into the strand and is not removed as the resulting cord passes below the false twister. If necessary, a heater 134 may be directed to dry the strand below the false twister and permanently set the uniform circular cross-section that is characteristic of the strand above the false twister 113. The wringing action during the formation of the twist assists in drying the strand. A preferred type of false twister characterized by three idler pulleys rotating in a common plane, is illustrated in FIGURES 5 and 6 of the drawings. In these figures, 1 represents the twister head, 2 the hollow vertical drive shaft, 3 the horizontal drive shaft, 4 ball bearings for the shaft 3, 5 ball bearings for the shaft 2, 6 the bevel gear fixed to the horizontal shaft 3, 7 the hollow bevel gear fixed to the shaft 2, 8 and 9 the small rollers, 13 the axis of roller 10, 11 and 12 the axes of rollers 8 and 9, 10 the large roller, 14 the multifilament, ribbon, multiribbon or strand, and 15 is one of several set screws that fix the twister head 1 to the hollow vertical drive shaft 2. The arrows in FIGURE 5 indicate the relative motion of the multifilament and the twister head. It has been found advantageous to allow the multifilament to traverse the false twist mechanism in the direction indicated, since in such use, it passes in a highly twisted condition through the hollow bore of the vertical shaft 2. The central guidance of the multifilament is obtained by placing the rollers 3 and 9 on their axes 11 and 12 at right angles with the axis of rotation of the vertical shaft 2 in such a manner that the perimeter of each roller is approximately tangential to the axis of rotation of the vertical shaft. The large roller 10 is disposed between the rollers 8 and 9 on the axis 13, which is parallel with the axes 11 and 12 but offset therefrom. Thus the rollers 8, 9 and 10 rotate in a common plane, but the position and diameter of the roller 10 is so chosen that the path of travel of the multilament 14 deviates at roll 10 from straight line travel along the axis of rotation of shaft 2 by a distance of the order of 1/2 inch. The dimensions of the rollers 8, 9 and 10 and the eccentricity of the axis 13 are not critical as it is only necessary to provide suflicient frictional engagement of the multitilament 14 to twist the same when the twister head 1 is rotated. FIGURES 2 through 4 illustrate an alternate type of false twister that may be used in the practice of the present invention. The false twister of FIGURE 2 is air driven by a jet of air from the nozzle 16, which is intercepted by the vanes 17, thereby causing rotation of the gear 18. This gear 18 meshes with the upper flange 19 of the false twister 20 and causes rotation thereof in the direction shown. As indicated in FIGURE 3, the false twister may be constructed with a slot 21 extending from the centralfopening and vertical axis of the twister 22 to the circumference of the twister head 23. This slot facilitates threading the false twister in the event that the collagen strand breaks during processing. The preferred shape of the roller 24 is best shown in FIGURE 4. The conical taper from the inner flange 25 of the roller 24 to the outer iiange 26 minimizes abrasion of the collagen strand as it passes through the false twister. The operation of the false twisting device perse and in conjunction with the procedures applied to collagen multiilarnents is believed to be apparent from the `foregoing description and no further eiucidation is deemed necessary as those skilled in the art will now understand how the false twister operates. It will also be understood by those skilled in the art that the false twister will operate to round and dry not only collagen multilamentbut also collagen ribbon and collagen multiribbon. The false twister illustrated in FIGURE 5 is particularly well adapted to the manufacture of round collagen strands from collagen multiilament according to the spinning scheme illustrated in FIGURE 1. For this particular use, when the rate of spinning is aboutV 30-50 inches per minute, the false twisters may be rotated aboutlOO r.p.n1. to 1G00 rpm. When spinning a size 5/0 strand, both false twisters may be operated at about 600-900 r.p.m. During the manufacture of a larger strand (size 2/0), the speed of both false twisters is preferably reduced to about 400 rpm. As mentioned above, the speed of the false twisters may be varied to compensate for spinning conditions. If bonding is obtained, when an open multifilament is desired, the speed of the'false twisters may be increased. Slower rotation of the false twisters provides the best conditions for bonding and rounding the strand. The tensiorneters 142 and 143 shown in FIGURE 1 measure tension placed on the dry multilament strand by godets 102 and 163. The tension effected by godet 102 varies from to 300 grams with the humidity, temperature, speed of the false twister and other operating conditions. These operating variables are preferably adjusted to spin with a tension of between 75 and 150 grams. The tension on the dry strand effected by godet 1% is between 200 and 500 grams. The dried strand is removed from godet 103 by the takeup spool at approximate.y 45 inches per minute. It has been observed that atmospheric humidity, a variable during the spinning of a strand, plays an irnportant part in the stretch, the iinal tensilestrength and the bonding of the col-lagen multifilament to form a strand. if the atmospheric humidity is sufficiently low, an open multilament may be collected. The humidity is preferably controlled by encasing the spinning operation within the smallest practical enclosure. Air lof controlled humidity is introduced into this enclosure to replace the humidity of the building atmosphere wlith the humidity of a compressed air system. Superior bonded strands are spun when the humidity -is controlled between 3() and 60 lgrains of moisture per pound of ydry air. Multiiilaments may be spun when the humidity is less than 20 grains per pound. When the humidity is above 60 grains of moisture per pound, the laments are soft and it is dii'cult to maintain spinning tension. The spinning of the dispersion of swollen collagen fibrils to produce a round bonded strand having outstanding properties wil-l be illustrated by Example `I. In Exarnpie i1, the false twister is operated in a dry atmosphere to produce an open unbonded collagen multilament. In the examples, all quantities are expressed in parts by weight unless otherwise indicated. Example I A collagen dispersion, prepared as described in U.S. Patent No. 2,919,998 is deaerated under 4vacuum for 4 hours, aged for 3l hours at 25 C. and 16 hours at 5 C., and then spun iny the vertically upward spinning machine illustrated in FIGURE The pressurek in the dispersion reservoir as indicated by the pressure gauge li141 is l5 pounds. The pump 115 is operated to extrude 2.82 milliiliters of the dispersion each minute. The pressure at lthe iilter, as `measured by the gauge 119 is approximately 10 pounds. The spinnerette employed -may lbe a brass pla-te drilled with 40 openings arranged in three concentric circles.v The acetone dehydrating bath is continuously circulated to the spinning column at the rate of about 900 milliliters per minute. The speed of the godets 1&1, 192 and 103 is maintained at l0, 13.5 and 14 r.p.rn., respectively. The false twisters 1112 and 113` are both rotated at 600 The strand vis continuously tanned at godet 102 by contacting an aqueous solution containing 4 milliliters of 40% aqueous formaldehyde and 1 gram of aluminum amrnonium sulfate per liter, which solution is circulated at therate of 50V cubic centimeters per minute (25 cubic centimeter per minute through each jet). The blower `113 is `adjusted to maintain a tension of 45 to` 50* grams as indicated by the tensiometer 142i. The blower 134 is directed above the false twister 1113 in a manner such that the tension indicated by the tensiometer 143 is about 190 grams. The humidity is maintained at about 30 grains* of moisture per pound of dry air lthroughout the spinning. Under these conditions, the wet tanned strand dries ou-t before the reverse twist is applied by false twister '113. Since lthe 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 spinning machine operates continuously and without any difficulties, such as broken strands, under these conditions. rPhe rate of talteup at the spool 147 is about 42 inches per minute. At the end of 6 hours continuous spinning, about 1300 linear feet of a round and uniform collagen bonded strand (size 5/0, -244 denier) is collected. l The tensile strength characteristics of this product exceed the requirements set out in the Pharmacopeia of the United States, Vol. XV, page 708. Example II A collagen dispersion (0.86% solids) is spun in the vertically upward spinning machine illustrated in FIG- URE 1. The pump 115 is operated to extrude 19.1 milliliters of the dispersion each minute. The spinning column used has an inside diameter of 11/16 inches, and the acetone dehydrating bath -is circulated through this spinning column at the rate of about 238() millilters per minute. The multilament that emenges from the dehydrating bath is wrapped 11/2 times around the godet :101 and passes to the false twister 112. To avoid bonding of the multilarnent, a dry atmosphere is maintained (less than 20 grains of moisture per pound of dry air), and the false twister 1112 is rotated at 200 r.p.m. The speed of godets 1G11 land 1012 is maintained at 10 and 13 r.p.m., respectively, thus producing a stretch between godets 101 and 102 of 30%. Heat is applied by the heater 133` below false twister 1-1-2, and the dried multiiilament is wrapped 12 times around the godet 102. From godet 102, the multilament passes directly to .the takeup spool. This multiiilarnent may be wet out, tanned, stretched, and bonded as described in Example I 4above to form a strand (size 2/0), Vthat is equivalent in all respects to cat gut manufactured from intestines. While the description abo-ve refers specifically to the extrusion and treatment of multiiilament, it will be recognized that a ribbon or multiribbon may be extruded in a similar manner and process with only minor modications in the machine illustrated fin FGURE 1, such as using a spinnerette with one or more slots instead of the orifices. The addition of a bonding agent to the collagen {ilaments or ribbons is not required because 4the individual collagen laments will adhere to each other in the Wet stage. Bonding agents may, however, be used in the practice of the present invention when it is desired -to manufacture with the false twisters `a round strand of fibrils, iilaments or ribbons that would not adhere to each other in the absence of a bonding agent, or because of the employment of operating conditions which would otherwise produce only an 'incompletely bonded multifilament. The necessity of completing the bonding step before the reverse twist is applied will, of course, be appreciated. While the invention has been described in detail according to the preferred manner of carrying out the process and yielding the products, it will be obvious to those skilled in the art, Iafter understanding the invention, that changes and modifications may be made therein without departing from the spirit or scope of the invention, and it is intended in the appended claims to cover such changes and modilications. The present application is a division of application Serial No. 806,067, led April 13, 1959, now abandoned. What is claimed is: 1. In the method of manufacturing a round collagen strand of uniform cross-section throughout its length, 'the steps which include twisting a multiplicity of wet collagen monolaments to wring out excess moisture and to bond the monolaments into a unitary structure, drying the monotilaments while in the twisted condition, and removing the twist. 2. A method of bonding and rounding wet collagen ribbon to form a suture which comprises the steps of twisting the wet collagen ribbon to wring out excess moisture, drying the collagen ribbon while in the twisted condition to form a bonded unitary structure of circular crosssection and removing the twist. 3. A method of bonding `and rounding a wet collagen multilament to form a strand which comprises the steps of: (a) twisting the collagen ymultilament in its wet state to wring out excess moisture; (b) `drying the collagen multililament While in the twisted condition to form a strand of circular crosssection, the filaments of which are firmly bonded together; and, (c) untwisting the dried collagen strand. 4. A method of manufacturing a collagen strand which comprises the steps of: (a) twisting wet collagen multiilament to wring out excess moisture; (b) drying the laments while in the twisted condition; and, (c) removing the twist. (Corresponding to Great Britain No. 814,637, June 10, 1959)



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Cited By (10)

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    US-3270492-ASeptember 06, 1966Hosiery And Allied Trade Res AProduction of yarns
    US-3287888-ANovember 29, 1966Monsanto CoApparatus for the treatment of synthetic filaments
    US-3363409-AJanuary 16, 1968Kugelfischer G Schaefer & CoRotary tube for crimping filamentary synthetic fibers by imparting thereto a false twist
    US-3365874-AJanuary 30, 1968Monsanto CoTreatment of synthetic filaments
    US-3407585-AOctober 29, 1968Leesona CorpYarn handling apparatus
    US-3451206-AJune 24, 1969Alexander W P MackintoshMachines for imparting twist to yarns
    US-3501908-AMarch 24, 1970Klinger Mfg Co LtdFalse twisting method
    US-3518994-AJuly 07, 1970Ethicon IncLaminated collagen suture
    US-6361551-B1March 26, 2002C. R. Bard, Inc.Collagen hemostatic fibers
    US-6454787-B1September 24, 2002C. R. Bard, Inc.Collagen hemostatic foam