DK155869B - ISOTACTIC POLYPROPYLENE MONOFILAMENTS AND PROCEDURES FOR PREPARING THEREOF - Google Patents

Description

. DK 155869 B

in

The present invention relates to an isotactic polypropylene monofilament suture of the kind set forth in the preamble of claim 1 which is characterized by the characterizing portion of claim 1. The invention further relates to a method of producing sutures which is characterized by the characterizing part of claim 2.

Sutures can be divided into two general groups: absorbable sutures that are absorbed into the human body and non-absorbable sutures that remain in the body without change or are removed from the skin when the underlying tissue is healed. The polypropylene sutures of the present invention are of the second type, i.e. that they are non-absorbable in the human body.

The strongest polypropylene monofilaments can generally be made from high molecular weight and high crystal 1 resin resins. The conditions of manufacture, together with the physical properties of the resin, determine the final filament properties and it is known that in order to obtain the tenacity required by a surgical suture, the extruded polypropylene monofilament must be stretched so that the polymeric molecules lie line.

Some of the advantages of oriented isotactic polypropylene as a suture material are described in U.S.A. U.S. Patent No. 3,359,983. Isotactic polypropylene monofilament is inert to such a degree that minimal tissue reaction occurs in the suture area.

It has long been known that the pulling or stretching of polypropylene monofilament required to provide the tenacity needed for suture use reduces the flexibility of the resulting product and leads to poor grip properties. Although the properties of the suture with respect to the grip are difficult to define, one must require that a suture is not wire-like or rigid and that it remains in the position in which it is placed until it is moved by the surgeon.

In general, it can be said that a rigid suture which has poor properties with respect to the grip is inelastic and will break when stretched. The known polypropylene sutures have a fracture elongation (the percentage length increase of the filament when stretched at room temperature to the rupture point) of less than 25%. In contrast, the polypropylene monofilaments of the present invention are distinguished by a fracture elongation of 36 to 62%.

By the U.S.A. Patent No. 3,106,442 states that isotactic

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2 polypropylene fibers or yarns, which are made to have a high elastic recovery, shrink considerably in hot water, and this shrinkage can result in difficulties during subsequent drying and processing of the fiber. To stabilize the fiber against such shrinkage 5 in hot water, the filaments of this patent are stretched at a temperature of 80-140 ° C and the filaments are kept at 80-160 ° C (preferably 135-145 ° C) for a short time while 0 to 15%. shrinkage is allowed. As a result of this treatment, the shrinkage of the filaments in hot water is reduced to 3 to 4%. According to the examples, the treated filaments are further characterized by having a rupture extension in the range of 19 to 26%.

The present invention differs from that of this patent in both the method used and the product obtained. First of all, the present invention relates to sootactic polypropylene having a specific molecular weight, which is not shown in the counterpart. Films of the present invention are then stretched and heat treated under carefully controlled conditions, i.e. and approx. 6.6 x stretch at 125-163 ° C and heat treatment at 141-149 ° C, allowing a shrinkage of 9 to 24%. These carefully regulated conditions result in a filament which, among the other mentioned properties, has a break-20 elongation in the range of 36-62%, which is considerably higher than the 19-26% elongation obtained by U.S.A. patent specification no.

3106442. This high fracture elongation is accompanied by a low Young's 2 module in the range of approx. 22,000 to approx. 36,800 kg / cm, indicating a high degree of filament softness and flexibility, which is desirable for surgical sutures. Although the filaments of U.S.A. Patent No. 3,106,442 is not identified by softness or Young's modulus, they are expected to have considerably greater stiffness than the filaments of the present invention.

In general, it can be said that a rigid suture having poor grip properties is inelastic and will break when stretched. The prior art polypropylene sutures are characterized by a rupture extension (the percentage length increase of the filament when stretched at room temperature to the rupture point) of less than 25%. In contrast, the polypropylene monofilaments of the present invention are distinguished by a fracture elongation of 36 to 62%.

Another disadvantage of the previously known polypropylene monofilaments is that they have memory and will try to preserve the shape of the packaging. Put another way, a monofilament packaged 3

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as a coil, to a considerable extent preserve the coil shape after removing the packaging. This makes it difficult for the surgeon to handle and bind the monofilament in the large sizes, i.e. size 2/0 and above.

These problems have been resolved by the present invention, which enables a polypropylene monofilament suture to be produced with satisfactory tenacity and knot strength while maintaining the percent elongation and flexibility required by the surgeon.

It has now been found that the flexibility of an extruded isotactic polypropylene suture can be significantly increased at little expense to the tensile strength of stretching under controlled conditions to approx. 6.6 times the original extruded length with subsequent tensioning or shrinkage of the monofilament to between 91 and 76% of the stretched length.

The extruded polypropylene monofilament can be drawn at usual temperatures, i.e. between 125 and 163 ° C. At about 166 ° C, the monofilament is approaching the molten stage and fracture may be a problem. The tenacity of the monofilament is somewhat higher if the drawing occurs at the lower temperature (near 125 ° C). Thus, a product having a tensile strength suitable for use (tenacity 3.3 to 8.5 g per denier) can be obtained at a tensile ratio of approx. 6.6: 1 at 125 to 163 ° C. The preferred drawing temperature for practicing the present invention is 149 ° C.

The tensioning or shrinking of the monofilament is also carried out at an elevated temperature which may be in the range of the tensile temperature, i.e. 125 to 163 ° C. Again, it is preferred to shrink the monofilament at a temperature of 149 ° C.

Monofilaments that have not contracted to 91% of the stretched length have a rupture extension of approx. 25%, a Young's 6x10 ^ module and has insufficient flexibility determined on the so-called Gurley-30 tester. Filaments that have contracted more than 76% of the stretched length have excellent grip, but may have deficiencies in tensile strength. The preferred amount of shrinkage leading to a good grip and tensile strength polypropylene suture is to approx. 82 to 85%.

As stated above, a rigid or wire-like suture is difficult to handle and bind to the surgeon. A flexible suture, in contrast, is "dead" and can be characterized by the surgeon as "throwable". Fortunately, the grip of the monofilament suture can be related to certain physical properties which allow its acceptability to predict

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4 the surgeon independent of subjective parameters such as casting, mortality, flexibility or grip. The so-called Gurley tester is an instrument specially designed to measure the stiffness or flexibility of textile materials. The gurley stiffness of a monofilament suture measured by this instrument is a measure of how attractive a suture is, given its handling characteristics.

Other physical properties of polypropylene monofilament that can be directly related to the surgeon's handling ease are Young's modulus of flexibility, plastic flow, a measure of elasticity, yield stress and percentage elongation at the breaking point. These characteristics are indicative of the acceptability of a polypropylene monofilament for the surgeon. The method for determining these properties and their correlation with flexibility is described below.

BRIEF DESCRIPTION OF THE DRAWINGS The invention is further illustrated in the following with reference to the drawing which shows an example of a preferred embodiment of the invention, in which fig. 1a and 1b show an apparatus for extruding and drawing a polypropylene monofilament in accordance with the invention; 2 is a perspective view of two coils pulling and oiling the polypropylene monofilament; FIG. 3 is a perspective view of those of FIG. 2 to illustrate the simultaneous drawing of four polypropylene monofilaments; FIG. 4 is a perspective view of a frame member; FIG. 5 is an enlarged cross-sectional view of the lower left leg of FIG. 4 is a right side view showing the frame member in an extended position; FIG. 6 is a cross-sectional view of the one shown in FIG. 5 shows the legs of the frame member showing the frame member in a changed position; FIG. 7 is a cross-sectional view of the embodiment of FIG. 5 shows the legs of the frame member showing the frame member in a contracted position; FIG. 8 is a cross-section through the legs of the frame member along line VIII-VIII of FIG. 5, FIG. 9 is a perspective view of a Gurley tester for measuring rigidity; FIG. Figure 10 is a perspective view of a guide member designed for use with the Gurley tester; 11 is a cross-section along the line XI-XI of FIG. 10, and FIG. 12 shows 5

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a depiction of a force-elongation curve obtained by applying voltage at a constant rate to a polypropylene strand made in accordance with the present invention.

In the preferred method of preparing the flexible polypropylene sutures of the present invention, isotactic polypropylene pellets having a weight average molecular weight of about 5 are used as raw material. 294,000 to approx. 316,000 and a number average molecular weight of about 78,400 to approx. 82,100. The calculated ratio MNw / MWfl is 3.84. Polypropylene of this quality is available in both powder and pellet form.

10 Pellets whose maximum diameter does not exceed approx. 6 mm can be used in the method to be described.

Referring now to FIG. 1a and 1b and the physical steps involved in extruding, orienting and relaxing the polypropylene monofilament, there is shown an apparatus with an extruder 10 which is used to form the polypropylene monofilament and which has a cylinder 11 supported in a horizontal plane 11 terminating at one end in a connecting section 12 which extends into an extrusion nozzle 14. An elongated screw 16 is designed to rotate inside the cylinder 11 and is driven by a sprocket 18 disposed in the farthest from the nozzle head. end of the ex-20 jumper, via a chain 19 and a variable speed motor not shown. The polypropylene pellet flows by gravity from a feed hopper 21 into the extruder cylinder and is moved by the screw 16 in the direction of the nozzle head. The extruder temperature is controlled by 3 electric heaters 22, 23 and 24 which surround the cylinder 11 and 25 die 14. A cooling jacket 25 surrounds the end of the extruder cylinder which is farthest from the die and removes heat from the end of the screw 16 which is located. during the feeding.

The die 14 is constructed elongated and may have one or more nozzles. The die nozzle preferably has an input angle of 20 °. At this angle of entry, streamlined movement is achieved to ensure uniform extrudate.

Polypropylene pellets with a maximum dimension of less than approx. 6 mm is placed in the feed hopper 21 and flows by gravity into the cylinder 12 of the extruder, which at this point is kept at room temperature or below by water flowing through the cooling jacket 25.

The screw 16 transports polypropylene pellets through the feed zone 22, to the extruder processing zone 23, in which these polypropylene pellets are compressed and measured. The molten polypropylene then passes 6

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through the die 14, the temperature of which is controlled by the heat jacket 24, and into a cooling bath 27 which may be a water bath. During normal operation, the feed zone 22 is maintained at approx. 221 ° C, the treatment zone 23 between 204 and 232 ° C, the matrix 14 between 204 and 232 ° C and the cooling bath of approx. 24 to 298C.

5 The extruded monofilament 28 solidifies as it moves downward to the cooling bath. The monofilament passes around an intermediate wheel 30, over the roller 32, and is wound around coils 33 and 34 to prevent the slippage which may otherwise occur as a result of the stretching of the monofilament for orientation thereof and increasing its tensile strength.

The monofilament from coil 33 is stretched and oriented by passing through a heating chamber 36 and around coils 38 and 39 rotating at a greater peripheral speed than coils 33 and 34, so that the monofilament is extended to 6 to 7 times its original length and informed. The manner in which the polypropylene monofilament is wound around the coils 38 and 39 is shown in FIG. 2 and 3. FIG. 3 illustrates the design with four monofilaments that are simultaneously extruded through a die with four nozzles. The temperature of the monofilament as it passes through the chamber 36 is maintained at approx. 127 to 163 ° C.

The stretched and oriented monofilament from coil 38 passes over 20 conductors 40 and reciprocating conductors 41 and is collected on coil 42. The polypropylene monofilament coils can be stored for further processing.

In the second treatment step, the monofilament is allowed to shrink. This step can be done by a discontinuous process whereby a fixed length polypropylene monofilament is heated to approx. 149 ° C and allowed to shrink to 25 between 92 and 75% of its original length.

The discontinuous completion process is illustrated in FIG. 4-8. The polypropylene monofilament is transferred from coil 42 to a frame member 43 by rotation of the frame member about its shaft 44, energy being supplied by a motor 46, over pulleys 47 and 48 and belt 49. The frame member 43 30 may be conventionally constructed of hollow iron with two leg sections 50 and 52 welded at one end to a transverse bar 53. The opposite ends of these leg sections slide in sliding fashion to channel sections 54 and 55 welded to a transverse bar 57. The position of the transverse bar 57 relative to the opposite bar 53 is determined by means of bolts 58 and 59 which pass through passage section 54 and leg section 50. Similarly, bolts 58 'and 59' pass through passage section 55 and leg section 52. The frame member has a length of 128.3 cm when it is extended as shown in FIG. 4th

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7 When a layer of polypropylene monofilament has been wound on the frame 43, a retaining strip 56 is secured to the cross bar 53 of the frame by bolts 51 such that the polypropylene monofilaments are compressed between the retaining strip and the end of the frame. Another retaining strip 56 'is bolted to the opposite crossbar 57 of the frame, thereby preventing the polypropylene from moving during the heat shrinkage step. When the retaining strips are in position, the frame member on its shaft 44 is supported by the movable crossbar 57 of the frame in its lower position, and the bolts 58, 59, 58 'and 59' are removed from each of the frame legs. The channel sections 54 and 10 55 are then spaced a distance into the legs 50 and 52, corresponding to the desired amount of shrinkage, and the said bolts are reattached. The frame member is then placed in an oven maintained at 149 ° C and rotated at 5 to 20 rpm. to ensure uniform heating. At this temperature, the polypropylene wound on the frame member creeps causing channels -15 sections 54 and 55 of the frame to be displaced into the leg sections 50 and 52, as shown in FIG. 6. After 10 minutes, the frame member is removed from the oven and allowed to cool to room temperature. The position of the end 57 of the frame member after the heat shrinkage step is shown in FIG. 7. As indicated above, in the extended position (Fig. 5), the frame member has a length of 128.3 cm, which can be reduced to 106.7 cm (Fig. 7) after shrinking each 128.3 cm length of polypropylene or 21.6 cm (from 128.3 cm to 106.7 cm in steps allowing shrinkage of the monofilament from 91 to 75.6%).

Straight polypropylene monofilaments having a length of 106.7 cm are removed from the frame by cutting the filaments at opposite ends 53 and 57 of the frame. Needles can be attached to one end of the monofilaments thus obtained. The heat-stressed monofilaments with or without attached needles are cooled, packaged and sterilized for use as surgical sutures.

The invention is further illustrated in the following examples which describe the preparation of polypropylene sutures (size 2 - 7/0) and the physical properties thereof. In all of the following examples, in sootactic polypropylene having a weight average molecular weight of approx. 294,000 to approx.

316,000 and a number average molecular weight of about 78,400 to approx. 82,100. To this resin is added 0.5 wt% copper phthalocyanine dye which gives the resin and the extruded monofilaments a dark blue color.

Heat stabilizers and other treatment compounds known in the art may be added to improve oxidation resistance

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8 during the extrusion and treatment steps. Compounds commonly used for this purpose are tertiary butyl-o-cresol (IONOL) together with dilaurylthiopropionate in amounts of about 0.25% of each.

The tensile strength and the percentage elongation given in Examples 1 to 13 are determined by A.S.T.M. method D-2256-66T using a constant speed extender, namely a table model of an INSTRON universal apparatus from Instron Corporation of Canton, Massachusetts. This study method is described in the 1966 issue of A.S.T.M. Standards, Part 24 (published in August 1966 by the American 10 Society for Testing Material, 1916 Race Street, Philadelphia,

Pennsylvania). The 20 seconds for breaking are approximated using a 2.54 cm sample (or gauge length) and the INSTRON device's crosshead set at a rate of 2.54 cm per minute. minute.

The knot strength is determined by the study method described in U.S. Pat. Pharmacopeia, Vol. XVII, page 921.

Young's module is determined on a table model of an INSTRON instrument using line contact jaw surfaces to obtain the least possible slip. A 25.4 cm sample is extended at a rate of 12.7 cm per and the chart speed is 50.8 cm per minute. minute.

It has been noted that the flexibility of a polypropylene suture can be correlated with its behavior under tension. Physical studies that can be used to reliably assess the subjective characteristics of "grip", flexibility, and elasticity are described in Example 1.

Gurley stiffness is measured with a motor-driven Gurley Stiffness Tester 25 (model 4171) manufactured by W. and L.E. Gurley, Troy, New York. This instrument shown in FIG. 9 consists of a balanced pendulum or tip 60 which is pivotally mounted at its center point and can be loaded variably below its center point by a removable solder 61. The tip moves parallel to a "sine" scale 62 divided into both 30 directions. During the test, ten 5.08 cm of propypropylene monofilament threads, for a total of at least 50.8 cm, are required for each sample. The threads used should be relatively straight.

The ten 5.08 cm strands 63 are inserted into the one shown in FIG. 10 and 11. The guide member is constructed with ten parallel holes drilled 35 of approx. 3 mm center. The polypropylene strands are inserted such that at least 2.54 cm of each strand protrudes behind a folded rod 64 and a locking rod 65 is inserted such that it clamps the monofilaments in the guide member.

9

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A razor blade is used to precisely cut the string tips protruding from the back of the guide member, and all 10 strands are cut 2.54 cm from the edge of the folded rod 64 on the opposite side of the clamp.

5 The guide means is placed on the motor-driven arm 68 of the Gurley instrument so that the clamping bar is 1.27 cm above the edge 70 of the pivoting pendulum. As the motor-driven arm 68 presses the monofilaments 63 against the edge 70 of the pendulum, the tip swings out until the sample slides past the pendulum and can be read on the scale 62. The pendulum resistance 10 and thus the sensitivity of the machine to materials of different stiffness can be adjusted in two ways, namely changing the distance of the solder 61 to the pivot point 67 and by changing the solder itself.

If necessary, the machine is run one or two cycles to adjust the weight-distance combination. This adjustment should be made so that the 15 average reading falls between 2.0 and 7.0 Gurley units. (A cycle is defined as a left turn plus a right turn of the tip 60.

A Gurley unit is the unit reading marked on the sine scale). After making the necessary adjustments, the machine will run for ten cycles without recording the results. After every half cycle, the 20 pendulum swing stops before continuing. Cycles Nos. 11 to 15 are read and the average calculated. The stiffness of the polypropylene monofilament sample can then be calculated using the following formula:

Gurley stiffness (mg) = 0.0002 RWD, where R = experimental reading in Gurley units 25 W = counterweight (g) D = counterweight distance from the pivot point (inches).

The invention is further illustrated by the following examples which describe the preparation of polypropylene sutures of various sizes, all having a Young's modulus of less than 42,000 kg / cm and a fracture elongation of at least 35%.

EXAMPLE 1

All the viscoelastic measurements reported in the tables are made on a table model INSTRON Tensile Tester using a Type C Tension Cell; full scale range 1-50 pounds (0.454 to 22.68 kg).

The measurements are made in an air-conditioned laboratory at 21 ° C and 50% relative humidity. Two line contact jaws are used to hold

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10 the suture test. The diameter of the thread is measured to an accuracy of 2.5 inches and the area of the wire is calculated. A 25.4 cm sample is placed between the jaws and both jaws are closed under an air pressure of 1.4 kg / cm. The area compensator on the INSTRON instrument is set to the correct suture diameter (which gives 5 readings in psi) and the wire is extended at a constant rate up to 112.5% of its original length (ratio set to INSTRON). The INSTRON machine is operated at a cross head speed of 127 mm per second. per minute and a chart speed of 508 mm per minute. minute.

Force-elongation curves produced under these conditions have the same as in FIG. 12 in general form. Young's modulus (kg / cm) is the initial modulus determined from the slope of curve A of FIG. 12. Young's modulus is the ratio of applied tension to extension in the elastic region and measures the elastic component of a suture's resistance to tension. This value is related to the flexibility of a suture.

2 15 Plastic flow (kg / cm) is the viscoelastic modulus determined from the slope of curve B in FIG. 12. It measures the plastic component of a suture's resistance to tension and is related to the "given by" that a suture exhibits under a force greater than the yield stress. The flow stress (kg / cm) is the first bending point on the force-extension curve or the intersection point C between lines A and B in FIG.

12. The buoyancy stress is the measure of the force required to start viscoelastic flow and is related to the elasticity of a suture.

Typical flexibility data determined from the force-elongation curves of polypropylene sutures of the present invention are summarized in Table I. These data were obtained after aging the sample for 1 month.

TABLE I

Flexibility values 2

Size Young's module (kg / cm) 30 _ 2 22,700 1 22,000 0 24,900 2/0 28,500 35 3/0 31,400 4/0 29,000 5/0 24,000 7/0 31,600 11

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EXAMPLE 2

A size 7/0 polypropylene suture, diameter 66 µm, is prepared by the general method described above. The die has a nozzle aperture of 0.508 mm in diameter and the flow rate of polypropylene through the die nozzle is 27.22 g per meter. hour. The temperature in the feed zone is maintained at 221 ° C and the temperature of the die and extruder cylinder is maintained at 232 ° C. The ratio of the collection rate of coil 33 to the linear extrusion rate (draw ratio) is 5.9. The water bath is kept at 24-29 ° C.

The heating chamber is 2.13 m long and is maintained at 141 ° C measured with a pyrometer. The polypropylene monofilament enters the chamber at a linear velocity of 15.24 m / s. and recorded on coil 38 at a linear speed of 100.6 m per minute. minute (stretched to 6.6 times its original length). After hot stretching, the polypropylene monofilament is collected on the collecting coil 42 and transferred to the frame member 43 shown in FIG. 4 to 8. The retaining strips are placed at both ends of the frame and the distance between the transverse bars 63 and 57 is adjusted by the bolts 58, 59, 58'and 59 'to allow the desired amount of shrinkage. The frame member is then heated in an oven at 141 ° C and rotated at 10 rpm. for 10 minutes, during which time the monofilaments shrink to 5-1 / 2 times the original length (from 128.3 to 106.7 cm or 83.5%).

During a control experiment, polypropylene from the same extrusion portion is stretched to 6.6 times the original length removed from the collection coil 42, placed on the frame member and heated in an oven at 149 ° C for 25 minutes without any stress. The length of the monofilament is 133.4 cm before and after the 10 minute heat treatment at 149 # C. The following table shows the differences in physical properties between polypropylene monofilament which have been (1) heat-stretched 6.6 times while maintaining a temperature of 141 ° C, (2) heat-stretched to 6.6 times the original length while maintaining a temperature of 141 ° C and subsequently heat treated for 10 minutes at 149 ° C with no relaxation, and (3) heat stretched to 6.6 times the original length while maintaining a temperature of 14PC and subsequently heat treated 10 minutes at 149 ° C under relaxation to 5 , 5 times the original length (83.5% of the heat-stretched length). The data obtained are after aging the samples for 1 month.

12

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TABLE II

(1) Polypropylene (2) Polypropylene (3) Polypropylene stretched 6.6: 1 stretched 6.6: 1 and stretched 6.6: 1 and 5 heat treated by relaxing to 83.5% _149 ° C for 10 minutes. of stretched length

Item number 115325 115325 115325

Diameter, µπ \ 61 58.4 66

Denier 24 22 22 10 Tensile Strength

Gram / denier 9.8 8.5 8.9 kg / cm2 x 10 "3 0.78 0.85 0.71

Knud Strength

Gram / denier 7.7 8.8 7.9 15 kg / cm2 x 10 "3 0.621 0.652 0.635

Elongation at break 27% 37% 41%

Gurley stiffness 1 mg 1 mg 1 mg

Young's modulus kg / cm2 x 105 0.67 0.56 0.316 Example 3

Size 5/0 polypropylene suture, diameter 124 mm, is prepared by the general method described above. The die nozzle has a diameter of 0.508 mm and the flow rate of the polypropylene through the die nozzle is 40.8 g / ml. hour. The temperature in the feed zone is maintained at 22TC and the temperature of the die and extruder cylinder is maintained at 232 ° C. The ratio of the collection rate of the coil 33 to the linear extrusion rate (draw ratio) is 2.32. The water bath is kept at 24-29 ° C.

The heating chamber has a length of 2.13 m and is maintained at 141 ° C measured with a pyrometer. The polypropylene monofilament enters the chamber at a linear velocity of 9.14 m / s. and collected on the coil 38 at a linear speed of 60.35 m per minute. minute (stretched to 6.6 times the original length). After heat stretching, the polypropylene monofilament 35 is collected on collection coil 42 and transferred to the one shown in FIG. 4-8 frame members 43. The retaining strips are placed at both ends of the frame member and the distance between the transverse bars 53 and 57 is adjusted by the bolts 58, 59, 58 'and 59' to allow the desired amount of shrinkage. The frame member 13

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then heated in an oven at 14Γ0 and rotated at 10 rpm. for 10 minutes, during which time the monofilament shrinks to 5-1 / 2 times its original length (from 128.3 to 106.7 cm or 83.5%).

During a control experiment, polypropylene from the same extrusion portion (stretched to 6.6 times the original length) is removed from the collection coil 42, placed on the frame member and heated in an oven at 149 ° C for 10 minutes without stress. The length of the monofilament is 133.4 cm before and after the 10 minute heat treatment at 149 ° C. The physical properties of the product thus obtained are given in the following table. The data were obtained after aging the samples for 1 month.

TABLE III

(1) Polypropylene (2) Polypropylene (3) Polypropylene 15 stretched 6.6: 1 stretched 6.6: 1 and stretched 6.6: 1 and heat treated at relaxed to 83.5% _149 ° C for 10 minutes. of stretched length

Part Number 107925 107925 107925

Diameter, / zm 124 127 132 20 Denier 98 102 110

tensile strength

Gram / denier 6.5 6.7 5.7 kg / cm2 x 10 "3 0.522 0.536 0.463

Node strength 25 Grams / denier 5.8 5.4 5.4 kg / cm2 x 10'3 0.465 0.437 0.437

Elongation at break 27% 30% 38%

Gurley stiffness 4.1 mg 3.4 mg 3.4 mg

Young's module 30 kg / cm2 x 105 0.503 0.456 0.240 Example 4

A size 4/0 polypropylene suture, diameter 0.175 mm, is prepared by the general method described above. The die nozzle has a diameter of 0.864 mm and the flow rate of the polypropylene sole through the die nozzle is 108.9 g / ml. hour. The temperature in the feed zone is maintained at 221 ° C and the temperature of the die and extruder cylinder is maintained at 221 ° C. The ratio of the pickup speed of the coil 33 to the line speed

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The 14 honor extrusion rate (draw ratio) is 3.62. The water bath is kept at 24-29 ° C. The indicated data are obtained after aging the samples for 1 month.

The heating chamber has a length of 2.13 m and is maintained at 146 ° C as measured by a pyrometer. The polypropylene monofilament arrives at the chamber at a linear velocity of 12.19 m / s. and recorded on coil 38 at a linear speed of 62.91 m per minute. minute (stretched to 6.6 times the original length). After heat stretching, the polypropylene monofilament is collected on the collection coil 42 and transferred to the frame member 43, as shown in FIG.

4-8. The retaining strips are placed at both ends of the frame member and the distance between the transverse bars 53 and 57 is adjusted by the bolts 58, 59, 58 'and 59' to allow the desired amount of shrinkage. The frame member is then heated in an oven at 149 ° C and rotated at 10 rpm. for 10 minutes, during which time the polypropylene monofilament lamina shrinks to 5-15 1/2 times the original length (from 128.3 to 106.7 cm or 83.5%).

During a control experiment, polypropylene from the same extrusion portion (stretched to 6.6 times the original length) is removed from the collection coil 42, placed on the frame member and heated in an oven at 149 ° C and rotated at 10 rpm. without relaxation. The length of the monofilament is 20 133.4 cm before and after the 10 minute heat treatment at 149 ° C. The difference in the physical properties of polypropylene monofilament that has been drawn, heat treated without tension and heat-relaxed to 83.5% of the original length is summarized in the following table. The indicated data are obtained after aging the samples for 1 month.

25 30 35 15

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TABLE IV

(1) Polypropylene (2) Polypropylene (3) Polypropylene stretched 6.6: 1 stretched 6.6: 1 and stretched 6.6: 1 and heat treated at relaxed to 83.5% 5 _149 ° C for 10 minutes. of stretched length

Item number 107930 107930 107930

Diameter, sore 175 173 188

Denier 194 189 223

Tensile strength 10 Grams / denier 5.7 6.7 5.9 kg / cm2 x 10'3 0.545 0.541 0.474

Knud Strength

Gram / denier 4.4 4.7 4.5 kg / cm2 x 10 ~ 3 0.357 0.378 0.359 15 Fracture elongation 21% 28% 36%

Gurley stiffness 15.5 mg 11.4 mg 12.4 mg

Young's modulus kg / cm2 x 105 0.626 0.510 0.290

EXAMPLE V

A size 3/0 polypropylene suture, diameter 0.218 mm, is prepared by the general procedure described above. The die nozzle has a diameter of 0.864 mm and the flow rate of the polypropylene sole through the die nozzle is 108.9 gm. hour. The temperature in the feed zone is maintained at 221 ° C and the temperature of the die and extruder cylinder is maintained at 22Γ0. The ratio of the collection rate of coil 33 to the linear extrusion rate (draw ratio) is 2.26. The water bath is kept at 24-29 ° C.

The heating chamber has a length of 2.13 m and is maintained at 127 ° C as measured by a pyrometer. The polypropylene monofilament arrives at the chamber at a linear velocity of 7.62 m / s. and collected on coil 38 at a linear speed of 49.29 m per minute. minute (stretched to 6.6 times the original length). The polypropylene monofilament is collected after heat stretching on the collection coil 42 and transferred to the frame member 43 as shown in FIG.

4-8. The retaining strips are placed at both ends of the frame member and the distance between the transverse bars 53 and 57 is adjusted by the bolts 58, 59, 58 'and 59' to allow the desired amount of shrinkage. The frame member is then heated in an oven at 149 ° C and rotated at 10 rpm. for 10 minutes, 16

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during which time the monofilament shrinks to 5 1/2 times its original length (from 128.3 to 106.7 cm or 83.5%).

During a control experiment, polypropylene from the same extrusion portion (stretched to 6.6 times the original length) is removed from the collection coil 42, placed on the frame member and heated in an oven at 149 ° C and rotated at 10 rpm. for 10 minutes without relaxation. The length of the monofilament is 133.4 cm before and after the 10 minute heat treatment at 149 ° C. The difference in the physical properties of polypropylene monofilament that has been drawn, heat treated without tension and heat-relaxed 10 to 83.5% of the original length is given in the following table. The indicated data are obtained after aging the samples for 1 month.

TABLE V

(1) Polypropylene (2) Polypropylene (3) Polypropylene stretched 6.6: 1 stretched 6.6: 1 and stretched 6.6: 1 and heat-treated at relaxed to 83.5% _149 ° C for 10 minutes. of stretched length

Part Number 107946 107946 107946 20 Diameter, pi 218 213 231

Denier 302 288 338

tensile strength

Gram / denier 5.9 6.3 5.4 kg / cm2 x 10 "3 0.472 0.507 0.432 Knot strength

Gram / denier 4.1 4.4 4.3 kg / cm2 x 10 "3 0.326 0.357 0.350

Elongation at break 25% 34% 41%

Gurley stiffness 29.0 mg 25.0 mg 22.0 mg 30 Young's modulus kg / cm2 x 105 0.577 0.481 0.314

EXAMPLE VI

A size 2/0 polypropylene suture, diameter 0.282 mm, is prepared by the general procedure described above. The die nozzle has a diameter of 1.372 mm and the flow rate of the polypropylene sole through the die nozzle is 272 g / ml. hour. The temperature in the feed zone is maintained at 221 ° C and the temperature of the die and the extruder cylinder is maintained at

DK 155869 B

17 22TC. The ratio of the collection rate of the coil 33 to the linear extrusion rate (draw ratio) is 3.33. The water bath is kept at 24-29 ° C.

The heating chamber has a length of 2.13 m and is maintained at 110 ° C as measured by a pyrometer. The polypropylene monofilament arrives at the chamber at a linear velocity of 11.58 m / s. and collected on coil 38 at a linear velocity of 76.2 m per minute. minute (stretched to 6.6 times the original length). The polypropylene monofilament is collected after heat stretching on the collection coil 42 and transferred to the frame member 43 as shown in FIG.

4-8. The retaining strips are placed at both ends of the frame member and the distance between the transverse bars 53 and 57 is adjusted by the bolts 58, 59, 58 'and 59' to allow the desired amount of shrinkage. The frame member is then heated in an oven at 149 ° C and rotated at 10 rpm. for 10 minutes, during which time the monofilament shrinks to 5 1/2 times its original length (from 128.3 to 106.7 cm or 83.5%).

During a control experiment, polypropylene from the same extrusion portion (stretched to 6.6 times the original length) is removed from the collection coil 42, placed on the frame member and heated in an oven at 149 ° C and rotated at 10 rpm. for 10 minutes without relaxation. The length of the mono-20 filament is 133.4 cm before and after the 10 minute heat treatment at 149 ° C. The difference in the physical properties of polypropylene monofilament that has been drawn, heat treated without tension and heat-relaxed to 83.5% of the original length is given in the following table. The indicated data are obtained after aging the samples for 1 month.

25 30 35

TABLE VI

DK 155869B

18 (1) Polypropylene (2) Polypropylene (3) Polypropylene stretched 6.6: 1 stretched 6.6: 1 and stretched 6.6: 1 and heat treated by relaxing to 83.5% 5 _149 ° C for 10 minutes. of stretched length

Item number 115358 115358 115358

Diameter, / tm 282 287 315

Denier 503 521 627

Tensile strength.ke ...........

10 Grams / denier 5.4 5.7 4.8 kg / cm2 x 10'3 0.435 0.456 0.384

Knud Strength

Gram / denier 3.9 3.9 3.5 kg / cm2 x 10 "3 0.312 0.315 0.285 15 Elongation at break 25% 34% 38%

Gurley stiffness 68.0 mg 55.0 mg 61.0 mg

Young's modulus kg / cm2 x 105 0.456 0.489 0.285

EXAMPLE VII

A size 2/0 polypropylene suture, diameter 0.351 µm, is prepared by the general procedure described above. The die nozzle has a diameter of 1.372 mm and the flow rate of the polypropylene sole through the die nozzle is 268 g / ml. hour. The temperature in the feed zone is maintained at 221 ° C and the temperature of the die and extruder cylinder is maintained at 221 ° C. The ratio of the collection rate of coil 33 to the linear extrusion rate (draw ratio) is 2.22. The water bath is kept at 24-29 ° C.

The heating chamber has a length of 2.13 m and is maintained at 116 ° C as measured by a pyrometer. The polypropylene monofilament arrives at the chamber at a linear velocity of 7.62 m / s. and collected on coil 38 at a linear velocity of 50.3 m per minute. minute (stretched to 6.6 times the original length). The polypropylene monofilament is collected after heat stretching on the collection coil 42 and transferred to the frame member 43 as shown in FIG.

4-8. The retaining strips are placed at both ends of the frame member and the distance between the transverse bars 53 and 57 is adjusted by the bolts 58, 59, 58 'and 59' to allow the desired amount of shrinkage. The frame member is then heated in an oven at 149 ° C and rotated at 10 rpm. for 10 minutes, 19

DK 155869 B

during which time the monofilament shrinks to 5 1/2 times its original length (from 128.3 to 106.7 cm or 83.5%).

During a control experiment, polypropylene from the same extrusion portion (stretched to 6.6 times the original length) is removed from the collection coil 42, placed on the frame member and heated in an oven at 149 ° C and rotated at 10 rpm. for 10 minutes without relaxation. The length of the monofilament is 133.4 cm before and after the 10 minute heat treatment at 149 ° C. The difference in the physical properties of polypropylene monofilament that has been drawn, heat treated without tension and heat-relaxed 10 to 83.5% of the original length is given in the following table. The indicated data are obtained after aging the samples for 1 month.

TABLE VII

(1) Polypropylene (2) Polypropylene (3) Polypropylene 15 stretched 6.6: 1 stretched 6.6: 1 and stretched 6.6: 1 and heat treated at relaxed to 83.5% _149 ° C for 10 minutes. of stretched length

Part Number 107947 107947 107947

Diameter, / zm 350.5 355.6 376 20 Denier 773 798 894

tensile strength

Gram / denier 5.1 5.3 4.7 kg / cm2 x 10'3 0.413 0.425 0.38

Knot Strength 25 Grams / Denier 3.8 3.9 3.4 kg / cm2 x 10 "3 0.310 0.310 0.278

Elongation at break 27% 36% 53%

Gurley stiffness 159.0 mg 134.0 mg 124.0 mg

Young's module 30 kg / cm2 x 105 0.445 0.403 0.249

EXAMPLE VIII

A size 1 polypropylene suture, diameter 0.409 mm, is prepared by the general procedure described above. The die 35 has a diameter of 1.4 mm and the flow rate of the polypropylene through the die is 363 g per meter. hour. The temperature in the feed zone is maintained at 221 ° C and the temperature of the die and extruder cylinder is maintained at 221 ° C. The ratio of the pickup speed of the coil 33 to it

DK 155869 B

The 20 linear extrusion rate (tensile ratio) is 1.61. The water bath is kept at 24-29 ° C.

The heating chamber has a length of 2.13 m and is maintained at 124 ° C measured with a pyrometer. The polypropylene monofilament arrives at the chamber at a 5 linear velocity of 7.01 m / s. and collected on coil 38 at a linear velocity of 46.33 m per minute. minute (stretched to 6.6 times the original length). The polypropylene monofilament is collected after heat stretching on the collection coil 42 and transferred to the frame member 43 as shown in FIG.

4-8. The retaining strips are placed at both ends of the frame member and the distance 10 between the rods 53 and 57 is adjusted by the bolts 58, 59, 58 'and 59' to allow the desired amount of shrinkage. The frame member is then heated in an oven at 149 ° C and rotated at 10 rpm. for 10 minutes, during which time the monofilament shrinks to 5 1/2 times its original length (from 128.3 to 106.7 cm or 83.5%).

During a control experiment, polypropylene from the same extrusion portion (stretched to 6.6 times the original length) is removed from the collection coil 42, placed on the frame member and heated in an oven at 149 ° C and rotated at 10 rpm. for 10 minutes without relaxation. The length of the monofilament is 133.4 cm before and after the 10 minute heat treatment at 20 149 ° C. The difference in the physical properties of polypropylene monofilament that has been drawn, heat treated without tension and heat-relaxed to 83.5% of the original length is given in the following table. The indicated data are obtained after aging the samples for 1 month.

25 30 35 21

DK 155869B

TABLE VIII

(1) Polypropylene (2) Polypropylene (3) Polypropylene stretched 6.6: 1 stretched 6.6: 1 and stretched 6.6: 1 and heat treated at relaxed to 83.5% 5 _149 ° C for 10 minutes. of stretched length

Part Number 107942 107942 107942

Diameter, sore 409 416.6 460

Denier 1,058 1,097 1,339

Tensile strength 10 Grams / denier 5.2 5.2 4.4 kg / cm2 x 10 "3 0.421 0.412 0.352

Knud Strength

Gram / denier 3.8 3.7 3.4 kg / cm2 x 10'3 0.307 0.296 0.273 15 Elongation at break 31% 40% 51%

Gurley stiffness 262.0 mg 240.0 mg 232.0 mg

Young's modulus kg / cm2 x 105 0.439 0.402 0.220

EXAMPLE IX

A size 2 polypropylene suture, diameter 0.493 mm, is prepared by the general procedure described above. The die nozzle has a diameter of 1.63 mm and the flow rate of the polypropylene sole through the die nozzle is 499 g / ml. hour. The temperature in the feed zone is maintained at 221 ° C and the temperature of the die and extruder cylinder is maintained at 221 ° C. The ratio of the collection rate of coil 33 to the linear extrusion rate {tensile ratio) is 1.70. The water bath is kept at 24-29 ° C.

The heating chamber has a length of 2.13 m and is maintained at 110 ° C as measured by a pyrometer. The polypropylene monofilament arrives at the chamber at a linear velocity of 7.92 m / s. and collected on coil 38 at a linear velocity of 66.45 m per minute. minute (stretched to 6.6 times the original length). The polypropylene monofilament is collected after heat stretching on the collection coil 42 and transferred to the frame member 43 as shown in FIG.

4-8. The retaining strips are placed at both ends of the frame member and the distance between the transverse bars 53 and 57 is adjusted by the bolts 58, 59, 58 'and 59' to allow the desired amount of shrinkage. The frame member is then heated in an oven at 149 ° C and rotated at 10 rpm. for 10 minutes, 22

DK 155869 B

during which time the monofilament shrinks to 5 1/2 times its original length (from 128.3 to 106.4 cm or 83.5%).

In a further experiment, polypropylene from the same extrusion portion (stretched to 6.6 times the original length) is removed from the collection coil 42, placed on the frame member and heated in an oven at 149 ° C and rotated at 10 rpm. for 10 minutes without relaxation. The length of the monofilament is 133.4 cm before and after the 10 minute heat treatment at 149 ° C. The difference in the physical properties of polypropylene monofilament that has been drawn, heat treated without tension and heat-relaxed to 83.5% of the original length is given in the following table. The indicated data are obtained after aging the samples for 1 month.

TABLE IX

15 (1) Polypropylene (2) Polypropylene (3) Polypropylene stretched 6.6: 1 stretched 6.6: 1 and stretched 6.6: 1 and heat treated at relaxed to 83.5% _ 1498C for 10 min. of stretched length

Part Number 115351 115351 115351 20 Diameter, µπι 493 493 520.7

Denier 1,536 1,536 1,714

tensile strength

Gram / denier 4.2 4.6 3.9 kg / cm2 x 10 "3 0.345 0.368 0.312 Node strength

Gram / denier 3.0 3.3 3.3 kg / cm2 x 10 "3 0.243 0.266 0.268

Elongation at break 34% 37% 62%

Gurley stiffness 370.7 mg 392.0 mg 328.0 mg Young's modulus kg / cm2 x 105 0.385 0.349 0.226 Example X (CONTROL TEST)

A size 3/0 polypropylene suture, diameter 0.232 mm, is prepared by the general procedure described above (Example V).

However, instead of stretching the polypropylene monofilament 6.6 times, it is stretched to 6.0 times its original length in a heating chamber at 127 ° C.

23

DK 155869 B

The polypropylene monofilament is collected after hot stretching on the collection coil 42 and transferred to the frame member 43 as shown in FIG. 4-8. The retaining strips are placed at both ends of the frame member and the distance between the transverse bars 53 and 57 is adjusted by the bolts 58, 59, 58 '5 and 59' to allow the desired amount of shrinkage. The frame member is then heated in an oven at 149 ° C and rotated at 10 rpm. for 10 minutes, during which time the monofilament shrinks to 5 1/2 times its original length (91.6%).

In a further experiment, polypropylene from the same extrusion portion (stretched to 6.0 times the original length) is removed from the collection coil 42, placed on the frame member and heated in an oven at 149 ° C and rotated at 10 rpm. for 10 minutes without relaxation. The length of the monofilament is 133.4 cm before and after the 10 minute heat treatment at 149 ° C.

15 The difference in the physical properties of polypropylene monofilament that has been drawn, heat treated without tension and heat relaxed to 91.6% of its stretched length is given in the following table. The indicated data are obtained after aging the samples for 1 month.

TABLE X

(1) Polypropylene (2) Polypropylene (3) Polypropylene stretched 6.0: 1 stretched 6.0: 1 and stretched 6.0: 1 and heat treated at relaxed to 91.6% _149 ° C for 10 minutes. of stretched length 25 Item number 127642-A1 127642-A2 127642-Ά3

Diameter, sore 232.2 232.4 244.1

Denier 341 342 376

tensile strength

Gram / denier 4.7 5.3 4.8 30 kg / cm2 x 10 ~ 3 0.382 0.426 0.385

Knud Strength

Gram / denier 3.5 4.1 4.0 kg / cm2 x 10'3 0.284 0.328 0.318

Fracture elongation 26% 36% 37% 35 Gurley stiffness 31.3 mg 26.5 mg 28.0 mg

Young's module kg / cm2 x 105 0.629 0.546 0.440 24

DK 155869 B

EXAMPLE XI (CONTROL TEST)

A size 3/0 polypropylene suture, diameter 0.225 mm, is prepared by the general procedure described in Example V above. However, instead of stretching the 6.6: 1 polypropylene monofilament, it extends 5 to 7 times its original length in a heating chamber maintained at 127 ° C. After hot-stretching, the polypropylene monofilament is transferred to the frame member 43 as shown in FIG. 4-8 and allowed to shrink to 5.5 times its stretched length by heating for 10 minutes at 149 ° C.

In a further experiment, polypropylene from the same extrusion portion (stretched to 7.0 times the original length) is removed from the collection coil 42, placed on the frame member and heated in an oven at 149 ° C and rotated at 10 rpm. for 10 minutes without relaxation. The length of the monofilament is 133.4 cm before and after the 10 minute heat treatment 15 at 149 ° C.

The difference in the physical properties of polypropylene monofilament that has been drawn, heat treated without tension and heat-relaxed to 78.5% of its stretched length is given in the following table. The indicated data are obtained after aging the samples for 1 month.

20

TABLE XI

(1) Polypropylene (2) Polypropylene (3) Polypropylene stretched 7.0: 1 stretched 7.0: 1 and stretched 7.0: 1 and heat treated at 78.6% 25 _149 ° C for 10 min. of stretched length

Part Number 127642-C1 127642-C2 127642-C3

Diameter, sore 216.9 214.6 243.8

Denier 298 291 376

Tensile Strength 30 Grams / Denier 6.0 5.3 4.7 kg / cm2 x 10'3 0.479 0.427 0.380

Knud Strength

Gram / denier 3.9 4.1 3.8 kg / cm2 x 10 "3 0.310 0.330 0.304 35 Elongation at break 25% 23% 41%

Gurley stiffness 22.7 mg 22.5 mg 21.2 mg

Young's module kg / cm2 x 105 0.790 0.657 0.433

DK 155869 B

25

EXAMPLE XII

A size 0 polypropylene suture, diameter 0.353 mm, is prepared by the general procedure described in Example VII above. The die nozzle has a diameter of 1.37 mm and the flow rate of the 5 polypropylene sole through the die is 267.6 g / ml. hour. The temperature in the feed zone is maintained at 22TC and the temperature of the die and extruder cylinder is maintained at 221 ° C. The ratio of the collection rate of coil 33 to the linear extrusion rate (draw ratio) is 2.22. The water bath is kept at 24-29 ° C.

10 The heating chamber has a length of 2.13 m and is kept at U6eC measured with a pyrometer. The polypropylene monofilament arrives at the chamber at a linear velocity of 7.62 m / s. and collected on coil 38 at a linear velocity of 50.3 m per minute. minute (stretched to 6.6 times the initial straight length). The polypropylene monofilament is collected after hot stretching on the collection coil 42 and transferred to the frame member 43 as shown in FIG. 4- 8. The retaining strips are placed at both ends of the frame member and the distance between the transverse bars 53 and 57 is adjusted by the bolts 58, 59, 58 'and 59' to allow the desired amount of shrinkage. The frame member is then heated in an oven at 149 ° C and rotated at 10 rpm. for 10 minutes, 20 during which time the monofilament shrinks to 6.0 times its stretched length.

During a control experiment, polypropylene from the same extrusion portion (stretched to 6.6 times the original length) is removed from the collection coil 42, placed on the frame member and heated in an oven at 149 ° C and rotated at 10 rpm. for 10 minutes without relaxation. The length of the monofilament is 133.4 cm before and after the 10 minute heat treatment at 149 ° C.

The difference between the physical properties of polypropylene monofilament that has been drawn, heat treated without tension, and heat-stressed to 91% of its stretched length is given in the following table. The indicated data are obtained after aging the sample for 1 week.

35

TABLE XII

DK 155869 B

26 (1) Polypropylene (2) Polypropylene (3) Polypropylene stretched 6.6: 1 stretched 6.6: 1 and stretched 6.6: 1 and heat-treated at 91% 5 _149 ° C for 10 min. of stretched length

Part Number 110805D 127642-C2 110842B

Diameter, sore 353 214.6 365.8

Denier 788 291 822

Tensile strength 10 Grams / denier - 5.1. . 5.3. 5.1 kg / cm2 x 10 "3 0.412 0.427 0.410

Knot strength g / denier 3.8 4.1 3.8 kg / cm2 x 10'3 0.306 0.330 0.307 15 Elongation at break 27% 23% 42%

Gurley stiffness 148.0 mg 25.0 mg 128.0 mg

Young's module kg / cm2 x 103 0.472 0.688 0.368

EXAMPLE XIII

A size 0 polypropylene suture, diameter 0.353 mm, is prepared by the general procedure described in Example XII above, except that the polypropylene monofilament, after heat stretching to 6.6 times its original length, is relaxed to 5.0 times its original length. . The difference between the physical properties of polypropylene monofilament in the lament, which has been drawn, heat treated without tension and heat-relaxed to 76% of the stretched length, is given in the following table. The indicated data are obtained after aging the sample for 1 week.

30 35

Claims (2)

10 Grams / denier 5.1 5.3 4.2 kg / cm2 x 10 "3 0.412 0.427 0.338 Knot strength Gram / denier 3.8 4.1 3.3 kg / cm2 x 10" 3 0.306 0.330 0.264 15 Fracture elongation 27% 23% 59% Gurley stiffness 148.0 mg 25.0 mg 132.0 mg Young's modulus kg / cm2 x 105 0.472 0.688 0.233 20 Although both monofilament and twisted multifilament sutures are commonly used in the operating room, the monofilament structure is preferred by many surgeons. Polypropylene monofilament sutures made as described above are easy to use and bond because of their flexibility. The polypropylene sutures can be attached to surgical needles, sterilized with ethylene oxide and packaged in sterile containers for use in the operating room. 1. Isotactic polypropylene monofilament suture having a diameter in the range of from approx. 0.05 mm to approx. 0.5 mm, a tensile strength of 3.9 to 8.9 g per denier and a knot strength from 3.3 to 7.9 per. denier, FEATURED that the monofilament has a fracture elongation from 36 to 62% and a 2 Young's modulus from ca. 22,000 to approx. 36,800 kg / cm, and the AT polypropylene has a weight average molecular weight of approx. 294,000 to approx. 316,000 and a number average molecular weight of about 78,400 to approx. 82,100. DK 155869 B 2. A process for making a sootactic polypropylene monofilament suture according to claim 1, characterized in that an extruded in sootactic polypropylene monofilament is stretched at a temperature in the range of 125 ° C to 163 ° C to approx. 6.6 times the original length, after which the monofilament is heated at a temperature in the range of 141 ° C to 149 ° C and the stretched monofilament is allowed to contract to between 91% and 76% of its original length. 10