US3630205A

US3630205A - Polypropylene monofilament sutures

Info

Publication number: US3630205A
Authority: US
Inventors: Gregory J Listner
Original assignee: Ethicon Inc
Current assignee: Ethicon Inc
Priority date: 1969-07-31
Filing date: 1969-07-31
Publication date: 1971-12-28
Anticipated expiration: 1988-12-28
Also published as: DK155869B; DE2037813A1; GB1305420A; NL7011148A; DK155869C; NL167596B; NO133310B; SE382387B; FI53923B; DE2037813B2; FR2055680A5; JPS5314649B1; DE2037813C3; NL167596C; NO133310C; CA968244A; FI53923C; ZA705280B

Abstract

A flexible, uniform monofilament of isotatic polypropylene having an improved hand and an ultimate elongation greater than 35 percent is prepared by extruding isotatic polypropylene having a weight average molecular weight between 299,000 and 316,000 to form a monofilament, stretching said monofilament at 300* F. to about 6.6 times its original length, and subsequently permitting the stretched monofilament to contract to between 91 percent and 76 percent of its stretched length.

Description

United States Patent [72] inventor Gregory J. Listner 3,106,442 10/1963 Compostella et a1. 264/290 Kendall Park, NJ. 3,152,380 10/1964 Martin 264/290X [21] AppLNo. 846,412 3,359,983 12/1967 Northey 128/3355 [22] Filed July 31,1969 3,413,397 11/1968 Bierbaum et a1 264/342 :ZZESZ: g g ii Primary Examiner-Dalton L. Truluck Somerviue, J A!!0rneys Robert W. Kell and Robert L. Mmler ABSTRACT: A flexible, uniform monofilament of isotatic [54] :PNOFILAMENT SUTURES polypropylene having an improved hand and an ultimate elonrawmg gation greater than 35 percent is prepared by extruding [52] U.S.Cl 128/3355, isolatic polypropylene having a weight average molecular 161/150, 161/161 weight between 299,000 and 316,000 to form a monofila- [51] 1nt.Cl A611 17/00 ment. Stretching said mo fi a 300 to about [50] Field ofSearch 128/3355; times its original length. n u q n ly p rmi ing h 161/150, 175;264/210 F, 290, 342R stretched monofilament to contract to between 91 percent and 76 percent of its stretched length. [56] References Cited UNITED STATES PATENTS 3,105,493 10/1963 Usher 128/3355 Jf /'e s5J.' /'a/ CZ/rre '0 i o k .f/oayaf/bn PATENTED DEC28 I97! SHEET 2 [1F 5 INVENTOR. .CPiqa/vy J l/sr/vm flllllllnllllllllllllll'llll A TTU/f. Iii

PATENTED UEB28 Ian SHEET 0F 5 Z/li PATENTEU M62819?! 3.630.205

SHEET 5 or 5 ATTORNEY 1 POLYPROPYLENE MONOFILAMENT SUTURES BACKGROUND OF THE INVENTION are of the second type; i.e. they are nonabsorbable in the human body.

The strongest polypropylene monofilaments can generally be made from resins of high molecular weight and high crystallinity. The processing conditions along with the resin physical properties determine the final filament properties, and it is known that to obtain the tenacity that is required of a surgical suture, the extruded polypropylene monofilament must be stretched to alignthe polymer molecules.

Some of the advantages of oriented isotatic polypropylene as a suture material are described in US. Pat. No. 3,359,983. Isotatic polypropylene monofilarnentis so highly inert that minimal tissue reaction occurs in the suture area.

It has long been recognized that the drawing or stretching of polypropylene monofilament that is required to impart the necessary tenacity for suture use reduces the flexibility of the resulting product and results in poor handling qualities. While the handling characteristics of the suture are difficult to define, a suture should not be wiry or stiff and should remain in the position in which it is placed until moved by the surgeon. I

Generally speaking, a stiff suture that has poor handling characteristics is inelastic and will break upon stretching. The polypropylene sutures of the prior art were characterized by an ultimate elongation (the percent increase in the length of the monofilament when stretched at room temperature to the breaking point) of less than 25 percent. By contrast, the flexible polypropylene monofilaments of the present invention are characterized by an ultimate elongation of 35 to about 63 percent.

It is another disadvantage of the polypropylene monofilaments previously known that they exhibit memory and will tend to retain the shape of the package. Stated in another way, a monofilament that is packaged as a coil will to a large extent retain the coil form after removal from the package. This makes it difficult for the surgeon to handle and tie down the monofilament particularly in the large sizes, i.e., size 2/0 and above.

These problems have been resolved by the present invention which enables one to manufacture a polypropylene monofilament suture of satisfactory tenacity and knot strength while retaining the percent elongation and flexibility that is demanded by the surgeon.

SUMMARY 'OF THE INVENTION It has now been discovered that the flexibility of an extruded, isotatic polypropylene suture can be greatly improved with little sacrifice in tensile strength by stretching under controlled conditions to about 6.6 times the original extruded length and then relaxing or shrinking the monofilament to between 91 and 76 percent of the stretched length.

The extruded polypropylene monofilament may be drawn at conventional temperatures, i.e., between about 260 and 325 F. At about 330 F., the monofilament is approaching the molten stage, and breakage can be a problem. The tenacity of the monofilament is somewhat higher if the drawing is effected at the low temperature (in the-neighborhood of 260 F.). Thus a product, the tensile strength of which is suitable for suture use (tenacity 3.3 to 8.5 grams per denier), may be obtained with a draw ratio of about 6.6:] at 260-325 F. The preferred drawing temperature for practicing the present invention is 300 F.

The relaxing of shrinking of the monofilament is also carried out at an elevated temperature, which may be within the range of the drawing temperature, i.e., 260 to 325 F. Again, it is preferred to shrink the monofilament at a temperature of 300 F.

Monofilaments that have not contracted to 91 percent of the stretched length have an ultimate elongation of about 25 percent, a Young's Modulus greater than about 6X10" and are lacking in flexibility as determined on the Gurley'tester. F ilaments that have contracted more than 76 percent of the stretchedlength have an excellent hand but may be deficient in tensile strength. The preferred amount of shrinkage that results in a polypropylene suture of good hand and tensile strength is about 82-85 percent.

As indicated above, a stiff or wiry suture is difficult for the surgeon to handle and tie down. A flexible suture by contrast has a "dead quality and may be characterized by the surgeon as throwable." Fortunately, the hand of the monofilament suture can be related to certain physical characteristics that will enable one to predict its acceptability to the surgeon independent of such subjective parameters as throwability, deadness, flexibility, or hand. One instrument that has been specifically designed to measure the stifi'ness or flexibility of textile materials is the Gurley tester. The Gurley stiffness of a monofilament suture as measured by this instrument is a measure of the desirability of a suture from the standpoint of its handling characteristics.

Other physical characteristics of polypropylene monofilaments that may be directly related to the ease of handling by the surgeon are Youngs Modulus, which is a measurement of flexibility, plastic flow, which is a measure of extendability, yield stress data and the percent elongation at the breaking point. These properties are an indication of the acceptability of a polypropylene monofilament to the surgeon. The method of determining these characteristics and their correlation with pliability are described below.

BRIEF DESCRIPTION OF THE DRAWING The invention will appear more clearly from the following detailed description when taken in connection with the following drawings which show by way of example a preferred embodiment of the inventive idea.

FIGS. la and lb illustrate apparatus for extruding and drawing polypropylene monofilament in accordance with the invention.

FIG. 2 is a perspective view of two godets that draw and orient the polypropylene monofilament.

FIG. 3 is a perspective view of the godets shown in FIG. 2 and illustrates the simultaneous drawing of four polypropylene monofilaments.

FIG. 4 is a perspective view of a creel.

FIG. 5 is an enlarged view partially in section of the lower left leg of the creel as viewed from the right in FIG. 4, showing the creel in an extended position.

FIG. 6 is a sectional view of the leg of the creel illustrated in FIG. 5, showing the creel in a modified position.

FIG. 7 is a sectional view of the leg of the creel illustrated in FIG. 5, showing the creel in a retracted position.

FIG. 8 is a sectional view of the leg of the creel on the line 8-8 of FIG. 5.

FIG. 9 is a perspective view of a Gurley stifiness tester.

FIG. 10 is a perspective view of a jig designed to be used with the Gurley tester, and

FIG. 11 is a sectional view on the Line ll 11 of FIG. 10.

FIG. 12 is a reproduction of a stress-strain curve, obtained by applying stress at a constant rate to a polypropylene strand that has been produced in accordance with the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT The preferred method for preparing the flexible polypropylene sutures of the present invention utilizes as the raw material pellets of isotatic polypropylene having a weight average molecular weight of from about 299,000 to about 316,000 and a number average molecular weight of from about 78,400 to about 82,100. The computed ratio of MN,,JMW, is 3.84. Polypropylene of this grade is available in both powder and pellet form. Pellets, the maximum diameter of which do not exceed one-fourth inch, may be used in the process to be described.

Referring now to the apparatus illustrated in FIGS. la and lb and to the physical steps involved in extruding, orienting, and relaxing the polypropylene monofilament, the extruder that is used to form the polypropylene monofilament has a cylindrical barrel 11 supported in a horizontal plane and terminating at one end at an adapter section 12 which leads to an extrusion die 14. A longitudinal screw 16 is mounted for rotation within the barrel 11 and is driven by the sprocket gear 18 positioned at the end of the extruder that is remote from the die through the chain 19 and a variable speed motor not shown. Polypropylene pellets flow by gravity from the hopper 21 into the cylindrical barrel of the extruder and are moved by the screw 16 in the direction of the die. The temperature of the extruder is controlled by three

electrical heating units

22, 23, and 24, which surround the barrel 11 and the die 14. A cooling jacket 25 surround that end of the extruder barrel that is most remote from the die and removes heat from that end of the screw 16 that lies beneath the hopper.

The die 14 is constructed with a long land length and may have one or more orifices. Preferably, the die orifice has an entrance angle of 20. With this entrance angle, streamlined flow is obtained insuring uniform extrudate.

Polypropylene pellets, the maximum dimension of which is less than one-fourth inch, are placed in the hopper 21 and flow by gravity into the barrel 12 of the extruder which is at that point maintained at room temperature or below by water flowing through the cooling jacket 25. The screw 16 conveys the polypropylene pellets through the feeding zone 22 into the metering zone 23 of the extruder wherein the polypropylene pellets are compressed and metered. The melted polypropylene then passes through the die 14, the temperature of which is controlled by a heating jacket 24, and into a quenching bath 27, which may be a water bath. In normal operation, the feeding zone 22 is maintained at about 430F., the metering zone 23 between 400 and 450 F., the die 14 between 400 and 450 F., and the quenching bath at about 75 to 85 F.

The extruded monofilament 28 is solidified as it moves downwardly into the quench bath. The monofilament passes around the idler 30, over the roller 32, and is wrapped around the

godets

33 and 34 to prevent the slipping that might otherwise occur as a result of stretching the monofilament to orient the same and increase its tensile strength.

The monofilament from the godet 33 is stretched and oriented by passing it through the heating chamber 36 and around the

godets

38 and 39 which rotate at a higher peripheral velocity than the

godets

33 and 34, thereby stretching the monofilament from six or seven times its original length and orienting the monofilament. The manner of wrapping the polypropylene monofilament around the

godets

38 and 39 is shown in FIGS. 2 and 3. FIG. 3 illustrates the arrangement of four monofilaments extruded simultaneously through a die having four orifices. The temperature of the monofilament as it passes through the chamber 36 is maintained at about 260 to 325 F.

The stretched and oriented monofilament from the godet 38 passes over the guides 40 and the reciprocating guide 41 and is collected on spool 42. The spools of polypropylene monofilament may be stored for further processing.

In the second stage processing of polypropylene, the monofilament is permitted to shrink. This step may be carried out by a discontinuous process whereby a fixed length of polypropylene monofilament is heated to about 300 F. and permitted to shrink to between 92 and 75 percent of its original length.

The discontinuous finishing process is illustrated in FIGS. 4 through 8. The polypropylene monofilament is transferred from spool 42 to a creel 43 by rotating the creel on its axle 44, power being supplied by the motor 46 through the pulleys 47 and 48 and the belt 49. The creel 43 may be conveniently constructed of channel iron with two-

leg sections

50 and 52 that are welded at one end to a crossbar 53. The opposite ends of these leg sections slidably receive channel sections 54 and 55, which are welded to a crossbar 57. The position of the crossbar 57 is fixed with respect to the opposite crossbar 53 by the stay bolts 58 and 59 which pass through the channel section 54 and the leg section 50. Similar bolts 58 and 59' pass through the channel section 55 and the leg section 52. The long dimension of the creel measures 50% inches when extended as shown in FIG. 4.

After layer of polypropylene monofilament has been wound onto the creel 43, a retention strip 56 is fastened to the crossbar 53 of the creel by bolts 51, thereby compressing the polypropylene monofilaments between the retention strip and the end of the creel. A second retention strip 56' is bolted to the opposite crossbar 57 of the creel thereby preventing the polypropylene from shifting during the heat-shrinking step. When the retention strips are in position, the creel is supported on its axle 44 with the movable crossbar 57 of the creel in its lowermost position, and the

stay bolts

58, 59, 58 and 59 are removed from each leg of the creel. The channel sections 54 and 55 are then telescoped into the legs 50 and 52 a distance corresponding to the desired amount of shrinkage and the stay bolts replaced. The creel is then placed in an oven maintained at 300 F. and rotated at 5-20 r.p.m. to insure uniform heating. At this temperature, the polypropylene that is wrapped on the creel shrinks causing the channel sections 54 and 55 of the creel to telescope into the

leg sections

50 and 52 as indicated by FIG. 6. The creel is removed from the oven after 10 minutes and is permitted to cool to room temperature. The position of the end 57 of the creel after the heatshrinking step is shown in FIG. 7. As indicated above, the creel in its extended position (FIG. 5) has a length of 50% inches, which may be reduced to 42 inches (FIG. 7) after shrinkage of each 505a-inch length of polypropylene amounts to 8% inches (from 50% inches to 42 inches in increments that permit shrinking of the monofilament from 91 to 75.6 percent.

Straight polypropylene monofilaments 42 inches in length are removed from the creel by cutting the filaments at the opposite ends 53 and 57 of the creel. Needles may be swaged to one end of the monofilaments so obtained. The heat-relaxed monofilaments with or without needles attached thereto are cooled, packaged, and sterilized for use as surgical sutures.

The present invention will be further illustrated by the following examples which describe the manufacture of polypropylene sutures (size 2 through 7/0) and the physical properties thereof. In all of the following examplesisotatic polypropylene is used having a weight average molecular weight of between about 294,000 and about 316,000 and a number average molecular weight of between about 78,400 and about 82,100. To this resin is added 0.5 percent by weight of copper phthalocyanine dye, which imparts a dark blue color to the resin and the monofilaments extruded therefrom.

Heat stabilizers and other processing compounds known in the art may be added to improve the resistance to oxidation during the extrusion and processing steps. Compounds commonly used for this purpose are tertiary butyl-o-cresol (IONOL) together with dilauryl thio-propionate in amounts of about 0.25 percent each.

The tensile strength and percent elongation at break reported in examples I through XIII are determined by A.S.T.M. method D225666T using a constant rate of extension tester, namely a table model INSTRON universal testing instrument manufactured by the Instron Corporation of Canton, Massachusetts. This test method is described in the 1966 Book of A.S.T.M. Standards, part 24 (published in Aug. of 1966 by the American Society for Testing Material, I916 Race Street, Philadelphia, Pennsylvania). The 20 seconds to break is approximated by using a 1-inch sample (or gauge length) with the INSTRON Tester crosshead speed set at 1 inch per minute.

The knot strength is determined by the test method described in the US. Pharmacopeia, Vol. XVII, page 921.

Young's Modulus is detennined on a Table Model lN- STRON instrument using line contact jaw faces to minimize slippage. A 10.0-inch sample is elongated at the rate of 5.0

inches per minute (crosshead speed), the chart speed is 20.0

inches per minute. lt has been noted that the pliability of a polypropylene suture may be correlated with its behavior under stress. Physical tests that may be used to reliably evaluate the subjective characteristics of "hand," flexibility, and extensibility are described in example I.

The Gurley stiffness is measured with a motor-operated Gurley Stiffness Tester (Model 4171) manufactured by W. and L.. E. Gurley of Troy, New York. This instrument, illustrated in FIG. 9, consists of a balanced pendulum or pointer 60, which is center pivoted and which can be variously weighted below itscenter with a removable weight 61. The pointer moves parallel to a sine scale 62 graduated in both directions. In the test, 10, 2-inch polypropylene monofilament strands, a total of at least 20 inches, are required per sample. The strands used should be relatively straight.

The 10, 2-inch strands 63 are inserted in the jig illustrated in FIGS. and 11. The jig is constructed with 10 parallel holes drilled on )-inch centers. The polypropylene strands are inserted so that at least I inch of each strand protrudes beyond the bending bar 64, and a locking pin 65 is inserted to clamp the monofilaments in the jig.

A razor blade is used to shave closely the strand tips which extend from the back of the jig, and all 10 strands are cut 1 inch from the edge of the bending bar 64 on the opposite side of the clamp.

The jig is placed on the motor-driven arm 68 of the Gurley instrument so that the clamp-bending bar lies one-half inch above the edge 70 of the swinging pendulum. When the motor-driven arm 68 presses the monofilaments 63 against the edge 70 of the pendulum, the pointer is deflected until the sample scrapes past the pendulum and may be read on the scale 62. The resistance of the pendulum and thus the sensitivity of the machine to materials of different stiffness can be adjusted in two ways: by changing the distance from the fulcrum 67 of the weight 61 and by changing the weight itself.

The machine is operated for one or two cycles to adjust the weight-distance combination if necessary. This adjustment should be made so that the average reading will fall between 2.0 and 7.0 Gurley units. (A cycle is defined as a left plus a right swing of the pointer 60. A Gurley unit is the unit reading marked on the sine scale). After the necessary adjustments are made, the machine is operated for 10 cycles without recording the results. After each half cycle, the oscillation of the pendulum is stopped before continuing. The readings of cycles 11 through 15 are recorded and averaged. The stiffness of the polypropylene monofilament sample may then be calculated by use of the following formula:

Gurley stiffness (mg) 0.0002 RWD, where R test reading in Gurley units W counterweight (g.) D distance of counterweight from fulcrum (inches) The present invention will be further illustrated by the following examples which describe the manufacture of polypropylene sutures of different sizes, all of which have a Youngs Modulus below 6 l0 p.s.i. and an elongation at break.of at least 35 percent.

EXAMPLE I All Viscoelastic measurements reported in the tables are made on a Table Model lNSTRON Tensile Tester using a Type C Tension Cell; full-scale range 1 to 50 pounds. The measurements are made in an air-conditioned laboratory at 72 F. and 50 percent relative humidity. To hold the specimen suture strand, two line contact jaws are used. The diameter of the strand is measured to 0.0001 inches and the area of the strand is calculated. A 10-inch sample is placed between the jaws and both jaws closed, under 20 p.s.i. air pressure. The area compensator on the lNSTRON Tester is set for the correct diameter of the suture (to give readout in p.s.i.) and the strand is elongated at a constant rate to 122.5 percent of the original length (preset on the lNSTRON). The lNSTRON machine is operated at a crosshead speed of 5 inches per minute and a chart speed of 20 inches per minute.

Stress-strain curves produced under these conditions have the general shape illustrated in FIG. 12. Youngs Modulus (p.s.i. X 10 is the initial modulus as determined from the slope of the curve A of FIG. 12. Young's Modulus is the ratio of applied stress to strain in the elastic region and measures the elastic component of a suture's resistance to stress. This value is related to the flexibility of a suture.

Plastic flow (p.s.i. X 10) is the viscoelastic modulus as determined from the slope of the curve B of FIG. 12. It measures the plastic component of a sutures resistance to stress and is related to the "give a suture exhibits under a force in excess of the yield stress.

The yield stress (p.s.i. X 10) is the first point of inflection in the stress-strain curve or the point of intersection C of the slopes A and B of FIG. 12. Yield Stress measures the force required to initiate viscoelastic flow and is related to the straightenability of a suture.

Typical pliability data as determined from the stress-strain curves of the polypropylene sutures of the present invention is summarized in table I. The date is obtained after aging the sample for 1 month.

A size 7/0 polypropylene suture, diameter 2.6 mils, is prepared by the general procedure described above. The die orifice measures 20 mils in diameter, and the flow rate of the polypropylene through the die orifice is 0.06 pounds per hour. The temperature of the feed zone is maintained at 430 F., and the temperature of the die and extruder barrel is maintained at 450 F. The ratio of the rate of takeup of the godet 33 to the linear rate of extrusion (draw ratio) is 5.9. The water bath is maintained at 75-84 F.

The heating chamber is 7 feet in length and is maintained at 285 F., as measured with a pyrometer. The polypropylene monofilament enters the chamber at the linear rate of 50 feet per minute andjis taken up on the godet 38 at the linear rate of 330 feet per minute (stretched 6.6 times its original length). The propylene monofilament after hot stretching is collected on the takeup spool 42 and transferred to the creel 43 illustrated in FIGS. 4-8. The tension strips are applied to either end of the creel and the distance between the

crossbars

53 and 57 is adjusted by the

stay bolts

58, 59, 58' and 59 to permit the desired amount of shrinkage. The creel is then heated in an oven at 285 F. and rotated at 10 r.p.m. for 10 minutes; during which time the monofilament shrinks to 5% times its original length (from 50% to 42 inches or 83.5 percent).

in a control experiment, polypropylene from the same extrusion batch (stretched 6.6 times its original length) is removed from the takeup spool 42, placed on the creel, and heated in an oven at 300 F. for 10 minutes with no relaxation. The length of the monofilament is 52% inches prior to and after the 10 minutes heat treatment at 300 F. The following table shows the differences in the physical properties of polypropylene monofilament that has been (1) hot stretched 6.6 X while maintaining the temperature at 285 F.; (2) hot stretched 6.6 X its original length while maintaining the temperature at 285 F. and then annealing for l minutes at 300 F. without relaxation; and (3) hot stretched 6.6 X its original length while maintaining the temperature at 285 F. and the annealing for 10 minutes at 300 F. while relaxing to 5.5 X its original length (83.5 percent of its hot stretched length). The data is obtained after aging the samples for 1 month.

TABLE ll (2) Polypropyl- (3) lolypro yiene stretched one stretc red (1) Poly- 6.6:1nnd 6.621 and propylene nnneuled at relnxcd to 83.5% stretched 300 F. for of stretched 6.5:1 10 min. length Lot number 115325 115325 115325 Diameter, mils 2. 4 2.3 2. 6 Denler....... 24 22 .38 Tensile strength:

Grams/denier n. X 8. 8. ll P.s.l.X 11.26 12.15 10.16 Knot strcn th:

Grams denier 7. 7 8.8 7. J P.s.i.X10' 8.83 0.28 0.03 Break elongation,

percent 27 37 ii (Inrlcy stiflness, rng... 1 l l Young's modulus, p.s.isoxim 8.03X10 -l.-li)Xl0 EXAMPLE [ii A size 5/0 polypropylene suture, diameter 4.9 mils. is prepared by the general procedure described above. The die orifice measures mils in diameter, and the flow rate of the polypropylene through the die orifice is 0.09 pounds per hour. The temperature of the feed zone is maintained at 430 F.. and the temperature of the die and extruder barrel is maintained at 450 F. The ratio of the rate of takeup of the godet 33 to the linear rate of extrusion (draw ratio) is 2.32. The water bath is maintained at 75-84 F.

The heating chamber is 7 feet in length and is maintained at 285 F. as measured with a pyrometer. The polypropylene monofilament enters the chamber at the linear rate of 30 feet per minute and is taken up on the godet 38 at the linear rate of 198 feet per minute (stretched 6.6 times its original length). The polypropylene monofilament after hot stretching is collected on the takeup spool 42 and transferred to the creel 43 illustrated in FIGS. 4-8. The tension strips are applied to either end of the creel and the distance between the crossbars $3 and 57 is adjusted by the stay bolts 58, 59, 58' and 59' to permit the desired amount of shrinkage. The creel is then heated in an oven at 285 F. and rotated at 10 r.p.m. for ID minutes; during which time the monofilament shrinks to 5 V2 its original length (from 50% to 42 inches or 83.5 percent).

In a control experiment, propylene from the same extrusion batch (stretched 6.6 times its original length) is removed from the takeup spool 42, placed on the creel, and heated in an oven at 300 F. for l0 minutes with no relaxation. The length of the monofilament is 52% inches prior to and after the 10- minute heat treatment at 300 F. The physical properties of the product so obtained are summarized in the following table. The data is obtained after aging the samples for l month.

EXAMPLE IV A size 4/0 polypropylene suture, diameter 6.9 mils, is prepared by the general procedure described above. The die orifice measures 34 mils in diameter, and the flow rate of the polypropylene through the die orifice is 0.24 pounds per hour.

TABLE III (1) Polypropyl- (3) lolyprn xylene strutc red enrsire! v ltil (l) Poly 6.621 and 6.6:1 nmi propylene nnnenled ut i't'lnserl to $3.5"; stretched 300 F. for of stretched 6.6:]. 10min. length Lot llllillbtL. 107M251 107925 1071 125 llinmet er, mils. -i. ll 5. n 5. '3 Denier"... .IS 10'. ill Tensile strength:

(il'tliliS/tltllltl'. (i. 5 ii. 7 5. 7 1.s.i.Xl0-- T. 4;! 7. 63 (L511 Knot strength:

(lrnins/denier. 5. S 5. l 4 l.s.l.Xl0 ti. 0'. ti. '..'i ii. 2i llrenk elongation.

percent. '27 30 3S Hurley stiilness. lllll. 4. l 3. -l 3. l Youngs modulus. p.s.l. 7. 15x10 6. 411x10 142x10 the temperature of the die and extruder barrel is maintained at 430 F. The ratio of the rate of takeup of the godet 33 to the linear rate of extrusion (draw ratio) is 3.62. The water bath is maintained at -84 F. The data is obtained afler aging the samples for l month.

The heating chamber is 7 feet in length and is maintained at 295 F. as measured with a pyrometer. The polypropylene monofilament enters the chamber at the linear rate of 40 feet per minute and is taken up on the godet 38 at the linear rate of 264 feet per minute (stretched 6.6 times its original length). The polypropylene monofilament after hot stretching is collected on the takeup spool 42 and transferred to the creel 43 illustrated in FIGS. 4-8. The tension strips are applied to either end of the creel and the distance between the crossbnrs 53 and 57 is adjusted by the stay bolts 58. 59. 58 and 59' to permit the desired amount of shrinkage. The creel is then heated in an oven at 300 and rotated at l0 r.p.m. for 10 minutes; during which time the monofilament shrinks to 5% times its original length (from 50% to 42 inches or 83.5 percent).

ln a control experiment, polypropylene from the same extrusion batch (stretched 6.6 times its original length) is removed from the takeup spool 42, placed on the creel, and heated in an oven at 300 F. and rotated at l0 r.p.m. for l0 minutes with no relaxation. The length of the monofilament is 52% inches prior to and after the lO-minutc heat treatment at 300 F. The difl'erence in the physical properties of polypropylene monofilament that has been drawn, annealed without relaxation and heat relaxed to 83.5 percent of its original length is summarized in the following table. The data is obtained after aging the sample for 1 month.

TABLE i\' (2) lolypropyl- (Ii) lolypro )ylone strctc red one strete red (1) loly- 6.011 nnd tl.ti:l and propylene annealed at r'elnxed to 83.6? stretched for oistretchcd 6.6:l l0 rnln. length Lot uumher.. 107930 107M110 1071 30 Dinmeter, inlls.... 6. 1| 13.5 7.1 l enier........ 194 1241i 223 Tensile strength:

Grunts/denier... 5. 7 n T 5 I l.s.l.Xl0- 7 7.- T 70' ill Knot strength:

Grains/denier... 4.4 4.7 1.5 i'.s.l.Xl0' 5.08 5.37 b. llrenk elongntlon,

percent. L'] 28 30 Hurley stillness, mg. 15.5 11.4 IL. 4 Young's modulus, p.s.i. ti. x10 10x10 1 l8 10 EXAMPLE V A size 3/0 polypropylene suture, diameter 8.6 mils, is prepared by the general procedure described above. The die orifice measures 34 mils in diameter, and the flow rate of the polypropylene through the die orifice is 0.24 pounds per hour. The temperature of the feed zone is maintained at 430F.. and

The temperature f the f d long is maintain; at 430 [and the temperature of the die and extruder barrel is maintained at 430 F. The ratio of the rate of takeup of the godet 33 to the linear rate of extrusion (draw ratio) is 2.26. The water bath is maintained at 75-84 F.

The heating chamber is 7 feet in length and is maintained at 260 F. as measured with a pyrometer. The polypropylene monofilaments enters the chamber at the linear rate of 25 feet per minute and is taken up on the godet 38 at the linear rate of 165 feet per minute (stretched 6.6 times its original length). The polypropylene monofilament after hot stretching is collected on the takeup spool 42 and transferred to the creel 43 illustrated in FIGS. 4-8. The tension strips are applied to either end of the creel and the distance between the

crossbars

53 and 57 is adjusted by the stay bolts 58, 59, 58' and 59' to permit the desired amount of shrinkage. The creel is then heated in an oven at 300 F. and rotated at 10 r.p.m. for 10 minutes; during which time the monofilament shrinks to 5% times its original length (from 50% to 42 inches or 83.5 percent).

In a control experiment, polypropylene from the same extrusion batch (stretched 6.6 times its original length) is removed from the takeup spool 42, placed on the creel, and heated in an oven at 300 F. and rotated at 10 r.p.m. for 10 minutes with no relaxation. The length of the monofilament is 52% inches prior to and after the l-minute heat treatment at 300 F. The difference in the physical properties of polypropylene monofilament that has been drawn, annealed without relaxation and heat relaxed to 83.5 percent of its original length is summarized in the following table. The data is obtained after aging the samples for 1 month.

TABLE V 'Gurley stiffness, mg.-.

(3) Polypropylp p py ed ene stretche ene stretch 6.6:1 and annealed at 300 F. for 10 min.

(1) Polypropylene stretched 6.6:1

25 20. 0 Young's modulus, psi. 8. 21X10 6.6:1 and relaxed to 83.5% of stretched length EXAMPLE VI A size 2/0 polypropylene suture, diameter 1 1.1 mils, is prepared by the general procedure described above. The die orifice measures 54 mils in diameter, and the flow rate of the polypropylene through the die orifice is 0.60 pounds per hour. The temperature of the feed zone is maintained at 430 F., and the temperatures of the die and extruder barrel is maintained at 430 F. The ratio of the rate of takeup of the godet 33 to the linear rate of extrusion (draw ratio) is 3:33. The water bath is maintained at 75-84 F.

The heating chamber is to 7 feet in length and is maintained at 230 F. as measured with a pyrometer. The polypropylene monofilament enters the chamber at the linear rate of 38 feet per minute and is taken up on the godet 38 at the linear rate of 250 feet per minute (stretched 6.6 times its original length). The polypropylene monofilament after hot stretching is collected on the takeup spool 42 and transferred to the creel 43 illustrated in FIGS. 4-8. The tension strips are applied to either end of the creel and the distance between the

crossbars

53 and 57 is adjusted by the stay bolts 58, 59, 58' and 59' to permit the desired amount of shrinkage. The creel is then heated in an oven at 300 F. and rotated at 10 r.p.m. for 10 minutes; during which time the monofilament shrinks to 5 A its original length (from 50% to 42 inches or 83.5 percent).

In a control experiment, polypropylene from the same extrusion batch (stretched 6.6 times its original length) is removed from the takeup spool 42, placed on the creel, and heated in an oven at 300 F. and rotated at 10 r.p.m. for 10 minutes with no relaxation. The length of the monofilament is 52% inches prior to and after the IO-minute heat treatment at 300 F. The difference in the physical properties of polypropylene monofilament that has been drawnannealed withoutrelaxation and heat relaxed to 83.5 percent of its original length is summarized in the following table. The data is obtained after aging the samples for 1 month.

TABLE VI (2) polypropyl- (3) Polypropylene stretched one stretched (1) loly- 6.6:1 and 6.6:1 and propylene annealed at relaxed to 83.6% stretched 300 F. for of stretched 6.6:1 10 min. length Lot number 115358 115358 115358 11. 1 11.3 12. 4 Denier 603 521 627 Tensile strength:

Grams/denier. 5. 4 5.7 4. X 'l.s.l. 10- (l. 1'.) ll. 48 5. 4t) Knot strength:

Grams/denier. 3. ll 3. .l 3. 5 l.s.l.) 10* 4. 44 4.48 4. 05 Break elongation,

percent 25 34 38 Gurley stiffness, mg 68.0 55. 0 61.0 Youngs modulus, p.s.i 6. 48X10 6. lJfiXlO 4. 015x10 EXAMPLE VII A size of 0 polypropylene suture, diameter 13.8 mil, is prepared by the general procedure described above. The die orifice measures 54 mils in diameter, and the flow rate of the polypropylene through the die orifice is 0.59 pounds per hour. The temperature of the feed zone is maintained at 430 F., and the temperature of the die and extruder barrel is maintained at 430 F. The ratio of the rate of takeup of the godet 33 to the linear rate of extrusion (draw ratio) is 2.22. The water bath is maintained at -84 F.

The heating chamber is 7 feet in length and is maintained at 240 F. as measured with a pyrometer. The polypropylene monofilament enters the chamber at the linear rate of 25 feet per minute and is taken up on the godet 38 at the linear rate of feet per minute (stretched 6.6 times its original length). The polypropylene monofilament after hot stretching is collected on the takeup spool 42 and transferred to the creed 43 illustrated in FIGS. 4-8. The tension strips are applied to either end of the creel and the distance between the

crossbars

53 and 57 is adjusted by the stay bolts 58, 59, 58' and 59' to permit the desired amount of shrinkage. The creel is then heated in an oven at 300 F. and rotated at 10 r.p.m. for 10 minutes; during which time the monofilament shrinks to 5% times its original length (from 50% to 42 inches or 83.5 percent.). 1

In a control experiment, polypropylene from the same extrusion batch (stretched 6.6 times its original length) is removed from the takeup spool 42, placed on the creel, and heated in an oven at 300 F. and rotated at 10 r.p.m. for 10 minutes with no relaxation. The length of the monofilament is 52% inches prior to and after the 10-minute heat treatment at 300 F. The difference in the physical properties of polypropylene monofilament that has been drawn annealed without relaxation and heat relaxed to 83.5 percent of its original length is summarized in the following table. The data is obtained after aging the samples for 1 month.

EXAMPLE VIII A size 1 polypropylene suture, diameter 16.1 mil, is prepared by the general procedure described above. The die orifice measures 54 mils in diameter, and the flow rate of the polypropylene through the die orifice is 0.80 pounds per hour. The temperature of the feed zone is maintained at 430 F., and the temperature of the die and extruder barrel is maintained at TABLE VII p yp pylene stretched (3) Polypropylene stretched (1) Poly- 6.621 and 6.611 and propylene annealed at relaxed to 83. 5% stretched 300 F. for of stretched 6.6:1 10 min. length Lot number 107947 107947 107947 Diameter, mils 13. 8 14.0 14.8 i.D en

773 798 8 4 Tensile strength:

Gra ns/denier 5. 1 5. 3 4. 7 P.s.r.X10 5.88 6.04 5.40 Knot strength:

Grams/denier 3. 8 3. 9 3. 4 P.s.i. 10- 4.41 4.41 3. 95 Break elongation,

percent 27 36 53 Gurley stiffness, mg. 159.0 134. 124. 0 Young's modulus, psi- 6. 33x10 5. 73x10 3. 54X10 430 F. The ratio of the rate of takeup of the godet 33 to the linear rate of extrusion (draw ratio) is 1.61. The water bath is maintained at 75-84 F.

The heating chamber is 7 feet in length and is maintained at 255 F. as measured with a pyrometer. The polypropylene monofilament enters the chamber at the linear rate of 23 feet per minute and is taken up on the godet 38 at the linear rate of 152 feet per minute (stretched 6.6 times its original length). The polypropylene monofilament after hot stretching is collected on the takeup spool 42 and transferred to the creel 43 illustrated in FIGS. 4-8. The tension strips are applied to either end of the creel and the distance between the

crossbars

53 and 57 is adjusted by the

stay bolts

58, 59, 58' and 59 to permit the desired amount of shrinkage. The creel is then heated in an oven at 300 F. and rotated at r.p.m. for 10 minutes; during which time the monofilament shrinks to 5% times its original length (from 50% to 42 inches or 83.5 percent).

ln a control experiment, polypropylene from the same extrusion batch (stretched 6.6 times its original length) is removed from the takeup spool 42, placed on the creel, and heated in an oven at 300 F. and rotated at 10 r.p.m. for 10 minutes with no relaxation. The length of the monofilament is 52% inches prior to and after the lO-minute heat treatment at 300 F. The difference in the physical properties of polypropylene monofrlament that has been drawn annealed without relaxation and heat relaxed to 83.5 percent of its original length is summarized in the following table. The data is obtained after aging the samples for 1 month.

TABLE VIII (2) polypropyl- (3) Polypropylone stretched ene stretched (1) Poly- 6.6:1 and 6.6:1 and propylene annealed at relaxed to 83.57 stretched 300 F. for of stretched 6.6:1 10 min. length Lot number 107942 107042 107942 Diameter, mils- 16. l 16. 4 18. 1 Denier. 1,058 1,097 1,339 Tensile strength:

Grams/denier 5. 2 5. 2 4. 4 I.S.i.X10- 5. 00 5.86 5.01 Knot strength:

Grams/denier. 3. 8 3. 7 3. 4 P.s.i.Xl0- 4.37 4.21 3.88 Break elongation,

percent 31 40 51 Gurley stillness, mg. 262. 0 240. 0 232. 0 Young's modulus, p.s.i 6. 25X10 5. 72X10 3. 13x10 EXAMPLE 1x A size 2 polypropylene suture, diameter 19.4 mils is prepared by the general procedure described above. The die orifice measures 64 mils in diameter, and the flow rate of the polypropylene through the die orifice is 1.1 pounds per hour. The temperature of the feed zone is maintained at 430 F and the temperature of the die and extruder barrel is maintained at 430 F. The ratio of the rate of takeup of the godet 33 to the linear rate of extrusion (draw ratio) is 1.70. The water bath is maintained at 75-84 F.

The heating chamber is 7 feet in length and is maintained at 230 F. as measured with a pyrometer. The polypropylene monofilament enters the chamber at the linear rate of 26 feet per minute and is taken up on the godet 38 at the linear rate of 168 feet per minute (stretched 6.6 times its original length). The polypropylene monofilament after hot stretching is collected on the takeup spool 42 and transferred to the creel 43 illustrated in FIGS. 4-8. The tension strips are applied to either end of the creel and the distance between the crossbars 53 and S7 is adjusted by the stay bolts 58, 59, 58' and 59' to permit the desired amount of shrinkage. The creel is heated in an oven at 300 F. and rotated at l0 r.p.m. for 10 minutes; during which time the monofilament shrinks to 5% times its original length (from 50% to 42 inches or 8.35 percent).

in a control experiment, polypropylene from the same extrusion batch (stretched 6.6 times its original length) is removed from the takeup spool 42, placed on the creel, and heated in an oven at 300 F. and rotated at 10 r.p.m. for 10 minutes with no relaxation. The length of the monofilament is 52% inches prior to and after the 10-minute heat treatment at 300 F. The difference in the physical properties of polypropylene monofilament that has been drawn, annealed without relaxation and heat relaxed to 83.5 percent of its original length is summarized in the following table. The data is obtained after aging the samples for 1 month.

TABLE 1X (2) polypropyl- (3) Polypropylcne stretched enusin-tolled (1) loly- 60:1 and (5.0:1 and propylene annealed at I'l'lflXLLl to 83.5% stretched tor of stretched 6.6:1 10 min. length Lot number 115351 115351 115351 Diameter, mils. ll). 4 111.4 20. 5 l)onlcr 1,536 1,536 1.714 Tensile strength:

Grams/denier... 4. 2 4.11 .1. u 1.s.l. 10 4. 5. 24 4. 44 Knot strength:

Grams/denier... 3. 0 3. it 1!. 3 1.s.l.X10- 3.45 3. 7'. 3. 51 Break elongation.

percent 34 37 0'3 (lurley stillness, mg. 370. 7 3112.0 3128.0 Young's modulus, psi. 5. 4TX10 4. 07x10 3. 313x10 EXAMPLE X A size 3/0 polypropylene suture, diameter 9.14 mils, is prepared by the general procedure described in example V. Instead of stretching the polypropylene monofilament 6.6 times, however, it is stretched 6.0 times its original length in a heating chamber maintained at 260 F.

The polypropylene monofilament after hot stretching is collected on the takeup spool 42 and transferred to the creel 43 illustrated in FIGS. 4-8. The tension strips are applied to either end of the creel and the distance between the

crossbars

53 and 57 is adjusted by the stay bolts 58, 59, 58 and S9 to permit the desired amount of shrinkage. The creel is then heated in an oven at 300 F. and rotated at 10 r.p.m. for 10 minutes; during which time the monofilament shrinks to 5% times its original length (91.6 percent).

In a control experiment, polypropylene from the same extrusion batch (stretched 6.0 times its original length) is removed from the takeup spool 42, placed on the creel and heated in an oven at 300 F. and rotated at 10 r.p.m. for l0 minutes with no relaxation. The length of the monoiilament is 52% inches prior to and after the lO-minute heat treatment at 300 F.

The difference in the physical properties of polypropylene monofilament that has been drawn, annealed without relaxation and heat relaxed to 91.6 percent of its stretched length is summarized in the following table. The data is obtained after aging the samples for 1 month.

TABLE X Polypropylene Polypropylene stretched 6.0: 1 Polystretched 6.0: 1 and relaxed propylene and annealed to 91.6% of stretched at 300F. for stretched 6.0: 1 10 min. length Lot number 127642-141 127642-A2 127642-A3 Diameter, mils. 9. 14 9. 15 0. 61 Denier 341 342 376 Tensile strength:

Grams/denier. 4. 7 5. 3 4. 8 P.s.1.X10 5.44 6.06 5.47 Knot strength:

Grams/denier 3. 5 4. 1 4. P.s.i.X10- 4. 04 4. 66 4. 53 Break elongation, percent 26 36 37 Gurley stillness, mg. 31. 3 26. 28.0 Youngs modulus, p.s.i 8. 95X10 7. 76x10 6. 27x10 EXAMPLE Xl A size 3/0 7 suture, diameter 8.84 mils, is prepared by the general procedure described above in example V. Instead of stretching the polypropylene monofilament 6.6:] however, it is stretched 7 times its original length in a heating chamber maintained at 260 F. The polypropylene monofilament after hot stretching is transferred to the creel 43 illustrated in FIGS. 4-8 and permitted to shrink to 5.5 times its stretched length by heating for minutes at 300 F.

In a control experiment, polypropylene from the same extrusion batch (stretched 7.0 times its original length) is removed from the takeup spool 42, placed on the creel and heated in an oven at 300 F. and rotated at 10 r.p.m. for 10 minutes with no relaxation. The length of the monofilament is 52% inches prior to and after the 10-minute heat treatment at 300 F.

The difi'erence in the physical properties of polypropylene monofilament that has been drawn, annealed without relaxation, and heat relaxed to 78.5 percent of its stretched length is summarized in the following table. The data is obtained after aging the samples for l month.

TABLE XI Polypropylene Polypropylene stretched 7 .0:1 Polystretched 7 .0:1 and relaxed propylene and annealed to 78.6% of stretched at 300 F. for stretched 7.0: 1 10 min. length Lot number 127642-01 127642-C2 127642-03 Diameter, mils. 8. 54 8. 45 0. 60 Denier 298 291 376 Tensile strength:

Grams/denier. 6.0 5. 3 4. 7 P.s.i. 10- 6. 82 6.08 5. 41 Knot strength:

Grams/denier. 3. 9 4. 1 3. 8 P.s.i.X10' 4.41 4. 70 4.33 Break elongation, p

cent 25 H 41 Gurley stillness, mg. 22. 7 22. 5 21. 2 Young's modulus, p.s.i. 11. 23X10 9. 35x10 6. 16x10 EXAMPLE Xll A size 0 polypropylene suture, diameter 13.9 mils, is prepared by the general procedure described above in example VII. The die orifice measures 54 mils in diameter, and the flow rate of the polypropylene through the die orifice is 0.59 pounds per hour. The temperature of the feed zone is maintained at 430 F., and the temperature of the die and extruder barrel is maintained at 430 F. The ratio of the rate of takeup of the godet 33 to the linear rate of extrusion (draw ratio) is 2.22. The water bath is maintained at 7S-84 F.

The heating chamber is 7 feet in length and is maintained at 240 F. as measured with a pyrometer. The polypropylene monofilament enters the chamber at the linear rate of 25 feet per minute and is taken up on the godet 38 at the linear rate of 165 feet per minute (stretched 6.6 times its original length). The polypropylene monofilament after hot stretching is collected on the takeup spool 42 and transferred to the creel 43 illustrated in FIGS. 4-8. The tension strips are applied to either end of the creel and the distance between the

crossbars

53 and 57 is adjusted by the stay bolts 58, 59., 58' and 59' to pennit the desired amount of shrinkage. The creel is then heated in an oven at 300 F. and rotated at 10 r.p.m. for l0 minutes; during which time the monofilament shrinks to 6.0 times its stretched length.

In a control experiment, polypropylene from the same extrusion batch (stretched 6.6 times its original length) is removed from the takeup spool 42, placed on the creel, and heated in an oven at 300 F. and rotated at l0 r.p.m. for 10 minutes with no relaxation. The length of the monofilament is 52% inches prior to and after the 10-minute heat treatment at 300 F. The difference in the physical properties of polypropylene monofilament that has been drawn, annealed without relaxation and heat relaxed to 9l percent of its stretched length is summarized in the following table. The data obtained after aging the sample for 1 week is as follows.

TABLE XII Polypropylene stretched 6.6:1 and annealed at 300 F. for 10 min.

Polypropylene stretched 6.6:] and relaxed to 91% of stretched length Poly ropy cne stretched 6.6:1

Lot number Diameter, mils. Denier Tensile strength:

Gra ns/denier Break elongation, percent Gurley stiffness, mg...

Young's modulus, p.s.i.

23 25. 0 1'38. 0 .L 78X10 5. 23X 10 EXAMPLE Xlll TABLE XIII Polypropylene Polypropylene Poly rostretched 6.6:1 stretched 6.6:1 py ene and annealed at and relaxed to stretched 300 F. for 10 111% of 6.6:1 min. stretched length Lot number 1108051) 127042-0 2 1108421) Diameter, mils. 13.0 8. 45 15.11 Denier 788 201 'JEI. Tensile strength:

Grams/denier... 5.1 5.3 4.2 P.s.i.X1O- 5. 86 ii. 08 -l. 81 Knot strength:

Grams/denier... 3.8 1. 1 3. 3 P.S.i.Xl0 4. 35 4. 70 3. 70 Break elongation, perctl'lt 27 Z3 50 (.lurley stillness, n1g. 148. 0 25. 0 132. 0 Young's modulus. psi. 6. 72x10 0. 78X1U 3 31x10 While both monofilament and braided multifilament sutures are commonly used in the operating room, the monofilament structure is preferred by many surgeons. Polypropylene monofilament sutures prepared as described above are easy to use and tie because of their flexibility. The polypropylene sutures may be attached to surgical needles, sterilized with ethylene oxide and packaged in sterile containers for use in the operating room.

What is claimed is:

1. An isotactic polypropylene monofilament suture the diameter of which is in the range of from about 0.002 to about 0.020 inches, said isotactic polypropylene having the following characteristics:

Weight Average Molecular Weight Number Average Molecular Weight Tensile Strength Knot Strength Break Elongation 2. A needled surgical suture comprising an isotactic about 294.000 to about 3l6,000

about 78.400 to about 82.]

3.9 to 8.9 gratin/denier 3 3 to 7.9 grams/denier 36% to 62% polypropylene suture attached to a surgical needle, said needle and said suture being sterile, said isotactic polypropylene having approximately the following characteristics:

Weight Average Molecular Weight Number Average Molecular Weight Tensile Strength 7 Knot Strength about 294,000 to about 3l6,000

about 78,400 to about 82,l00

3.9 to 8.9 grams/denier denier 3.3 to 7.9 grams/denier Break Elongation 36% to 62% Young! Modulus about 3.l3Xl0' p.|.i. to

Weight Average Molecular Weight about 294,000 to about 6,000 Number Average Molecular Weight about 78,400 to about 82.l00 Tensile Strength 3.9 to 8.9 grams/denier Knot Strength 3.3 to 7.9 grarmldenier Break Elongation 36% to 62% Young's Modulus about 3.l3 l0' p.:.i. to

mg UNITED STATES PATENT oEElcE CERTIFICATE OF CORRECTION Patent No. 3,630,205 Dated December 28,1971

Inventor(s) Gr gory J. Listner It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

T- Column 3, line 23, "surround" should read surrounds 1 Column 6, line 6, "122.5" should read 112.5

Column 7, line 59, 5 1/2 should read ---5 1/2 times Column 8, line 35, "300" should read 300%.

Column 9, line 61, "is to 7 feet" should read 1 1-- is 7 feet Column 9, line 7 "5 1/2" should read 5 1/2 times Column 10, line +8, creed" should read ---creel Column 12, line 1 8.35: should read 83.5

Column 1.3,line 19, "3/0 7" should read 3/0 polypropylene ture Signed and sealed this 1 8th day of July 1 972.

(SEAL) Attest:

EDWARD M.FLETCHER,JR. ROBERT GOTTSCHALK Attesting Officer Commissioner of Patents

Claims

2. A needled surgical suture comprising an isotactic polypropylene suture attached to a surgical needle, said needle and said suture being sterile, said isotactic polypropylene having approximately the following characteristics: Weight Average Molecular Weight about 294,000 to about 316,000 Number Average Molecular Weight about 78,400 to about 82,100 Tensile Strength 3.9 to 8.9 grams/denier denier Knot Strength 3.3 to 7.9 grams/denier Break Elongation 36% to 62% Young''s Modulus about 3.13 X 105 p.s.i. to about 5.23 X 105 p.s.i.
3. A surgical suture package comprising a sterile enclosure and therein a sterile needled surgical suture comprising an isotactic polypropylene suture attached to the surgical needle, said isotactic polypropylene having approximately the following characteristics: Weight Average Molecular Weightabout 294,000 toabout 316, 000Number Average Molecular Weightabout 78,400 toabout 82, 100Tensile Strength3.9 to 8.9 grams/denierKnot Strength3.3 to 7.9 grams/denierBreak Elongation36% to 62%Young''s Modulusabout 3.13 X 105 p.s.i. toabout 5.23 X 105 p.s.i.