SE444891B - PROCEDURE FOR THE PREPARATION OF ABSORBABLE SURGICAL PRODUCT THROUGH COPOLYMERIZATION IN CONSEQUENCE OF GLYCOLIDE AND TRIMETHYL CARBONATE - Google Patents

Description

Following the polymerizations in the same reaction vessel by sequentially adding the comonomers thereto; however, if desired, one or more of the polymer segments may be prepared and used as such for further chemical reaction to form the polyesters in a different reaction vessel of choice while still retaining the benefits of and falling within the scope of the present invention. The present invention encompasses a process for the preparation of a sterile absorbable surgical product, which process is characterized by: 1) the preparation of a synthetic absorbable copolymer of copolymerizable monomers comprising glycolide as the predominant monomer and trimethylene carbonate monomer, the polymerization being carried out at between about 180 and 220 ° C in two or more steps using additive due to the comonomers, each step forming a polymer chain having a different composition from the polymer chain formed in that or each other step by different monomer amount ratios; and (2) preparing a sterile surgical product from the copolymer obtained in step (1).

The two lactides conventionally preferred for use in the manufacture of surgical articles are L (-) - lactide and glycolide. They are also preferred for use in the present invention.

In addition, it is generally preferred here to use them together in a sequential polymerization process. Other cyclic comonomers conventionally used therewith, such as trimethylene carbonate, 2-keto-1,4-dioxane and one or more of the following compounds may also be used as one of the comonomers for copolymerization with a lactide in the practice of the present invention: -propio- lactone tetrametylglykolid, B-butyrolactone, gamma-butyrolactone, delta-valerolactone, epsilon-caprolactone, pivalolactone, and intermolecular cyclic esters of afhydroxismörsyra, aßhydroxiisosmör- acid, aßhydroxivaleriansyra, aßhydroxiisovaleriansyra, aßhydroxi- caproic, q & hydrcxi al xfetylsmörsyra, a: hydroxyisocaproic, dfhydroxi -B-methylvaleric acid, achydroxyheptanoic acid, dehydroxyoctanoic acid, α-hydroxydecanoic acid, αL-hydroxymyristic acid, α-hydroxystearic acid, 1% -hydroxylignoceric acid, β-diethyltropropiolactone, ethylene carbonate, 2,5-dichetomoxylicin, 2,5-dichetomoxylicin, 2,11-octan-7-one, disalicylide, trioxane, 3-methyl-1,4-dioxane-2,5-dione, 3,5-dimethyl-1,4-dioxan-2-one.

One of the preferred areas of use of the present invention relates to the preparation of sterile, synthetic, absorbable surgical articles (particularly sutures) in which glycolide is used as the predominant lactide comonomer in the preparation of the polyesters. The state of the art is such that detailed absorption mechanisms and details concerning the polymer structures at the molecular levels are not known with certainty.

One of the preferred embodiments of the present invention relates to copolymerization due to lactide [preferably L (-) - lactide] with glycolide. Three-segment structures prepared by copolymerizing in sequences and sequentially (L (-) - lactide, glycolide and L (-) - lactide, respectively, are also of interest.In the latter case, the polyester produced It is assumed that the three common morphological units, namely spheres, rods (or cylinders) and lamellae which are well known in AB and ABA type poly (styrene-b-butadiene) (PSB), would be present in the polyesters of the glycolide polymer chains. present units to butadiene units in 80/20, spherical regions have been observed by electron micrograph.When the molar ratio decreases with relatively larger amounts of butadiene units, the morphology of the microphase separation changes from spheres of butadiene units in a matrix of control units to rods of butadiene units in a matrix When the molar ratio is further reduced until the butadiene predominates, the control units f first as cylindrical or rod-like microphase separations in a matrix of butadiene units, after which, when the molar ratio is further reduced, the styrene units appear as spheres in a matrix of butadiene units. For a description of this, reference is made to M. Matsuo, S. Sagai and H. Asai, Polymer, Ig, p. 79, 1969.

In preparing the absorbable sutures in accordance with the practice of the present invention, polyesters may be used in which minor amounts of a monomeric homopolymer, such as an L (-) - 1-block active moiety or one or more The stable segment or segments can be used in relatively small amounts whereby it is assumed that the morphology for microphase separation would exist, for example, as rods of L (-) - lactide units in a matrix of glycolide units or more suitable spherical regions of L (-) - lactide units in a matrix of glycolide units./ The surgical articles are prepared from the polyesters using the procedures conventionally used with the polyesters described in the above reference. articles in a conventional way.

The present examples illustrate procedures which are appropriate in the context of the practice of the present invention but are not to be construed as limiting it.

Unless otherwise indicated, all parts and percentages are Examples 1-2 An ethereal solution of SnCl 2 '2H 2 O expressed by weight. was prepared together with an ethereal solution of lauryl alcohol containing 10 mg / ml lauryl alcohol. A sufficient volume of the above solutions was added to two polymerization tubes so that when the solvent was removed, the final amounts of catalyst and lauryl alcohol per 20.0 g of L (-) ~ lactide monomer: Table I tube no mg Sn C12-2H 2 O mg lauryl alcohol 2.0 125 4.0 250 After the solvent was removed, 20.0 g of L (-) lactide was added to each tube. The tubes were evacuated and sealed under vacuum. They were then placed in an oil bath at 180 ° C for 24 hours. They were removed from the oil bath and allowed to cool to room temperature. The tubes were opened, the polymer was ground in a large Wiley mill through a 20 mesh screen and dried for 24 hours at SOOC at 0.1 mm Hg. The resulting polymers from tubes 1 and 2 had been formed in 86 h and 89% conversion and had I.V. values of 0.33 and 0.27, respectively. The percentage conversion to polymer was obtained by dividing the amount by weight of polymer after drying by the weight of polymer before drying. I.V. means an intrinsic viscosity of a solution of 0.5 g of dried polymer / 100 ml of hexafluoroacetone sesquihydrate, determined at 30 ° C.

To a three-necked, 100 ml round bottom flask equipped with a R glass shaft and Teflon (DuPont Company, Ulmington, Delaware, USA) paddle stirrer, connected to an agitator and a gas inlet tube connected to an argon cylinder was added 7.0 g of the poly L (-) - lactide with IV value of 0.33 as described above. the flask was purged with argon gas for 15 minutes. SPo1ningen was maintained throughout; : i, ..._._ .. '__':.:,. ~ .... t ...._ <'..._ ¿... iii,. 5 7805831-o polymerization. The flask was placed in an oil bath at 190 ° C.

The vessel content reached 180 ° 1 2 ° C within 15 minutes. Then 3.5 g of glycolide were added with stirring and the oil bath temperature was set so that the temperature of the vessel contents was maintained at 180 ° at 2 ° C for 30 minutes with continuous stirring. The temperature of the oil bath was then raised so that for 30 minutes the temperature of the vessel contents reached 2200 at 2 ° C. Then the residue of the glycolide, 31.5 g, was added, and the temperature of the vessel holder was maintained at 2 ° C for 2 ° C for 1.5 hours with continuous stirring. At this time, the oil bath was removed, stirring was stopped and the vessel contents were allowed to cool to approximately room temperature during the argon purge. This flushing was then stopped. The glass flask was then broken and the polymer was removed and ground in a Wiley mill through a 20 mesh screen. 3.0 g of the ground polymer was prepared into a fibrous sheet for implantation by first dissolving the polymer in 60 ml of hexafluoroacetone sesquihydrate (HFAS) at a temperature of 60 ° C. The polymer was precipitated by adding this solution dropwise to 600 ml of methanol with stirring. The polymer was collected by filtration and extracted with acetone in a Soxhlet apparatus for 2 days to remove the residual fluorinated solvent. The polymer was then dried in a vacuum oven overnight at 50 ° C at 0.1 mm Hg. The yield of polymer was 95%. The intrinsic viscosity of HFAS was 0.77.

The mole percentage of lactic acid units in the polymer chain according to NMR was 8.8. The melting point determined by the peak endotherm observed in a differential thermal analysis (DTA) device was 21a ° C.

A second two-step copolymer was prepared as follows. To a three-necked, 100 ml round-bottomed flask equipped with a glass shaft and a Teflon R paddle stirrer barrel with a stirring motor and a gas inlet tube connected to an argon cylinder was added while stirring 4.0 g of the poly L (-) alkide whose intrinsic viscosity was 0 , 27. This was purged with argon gas for 15 min.

This argon gas purge was maintained throughout the following polymerization. The flask was placed in an oil bath at a temperature of 190 ° C. The vessel content reached 1800 1 2 ° C within 15 minutes. Then 3.6 g of glycolide were added with stirring and the oil bath temperature was set so that the temperature of the vessel contents was kept at 1800 at 2 ° C for 30 minutes with continuous stirring. 7805851-0 6 The temperature of the oil bath was then raised so that at the end of 30 minutes the temperature of the vessel contents reached 2200 in 2oC.

Then 31.4 g of glycolide were added and the temperature of the vessel contents was maintained at 2200 É 200 for 1.5 hours of continuous stirring. At this time, the oil bath was removed, stirring was stopped and the vessel contents were allowed to cool to approximately room temperature during the argon purge. This flushing was then stopped.

The glass flask was broken and the polymer was removed and ground in a Wiley mill through a 20 mesh screen. 3.0 g of this polymer was dissolved in 60 ml of hexafluoroacetone sesquihydrate (HFAS) having a temperature of 60 ° C and the polymer precipitated by adding this solution dropwise to 600 ml of methanol with stirring.

The polymer was collected by filtration and extracted with acetone in a Soxlet extractor for 2 days. The polymer was then dried in a vacuum oven overnight at 50 ° C \ dd 0.1 mm Hg. The yield of polymer was 95%. The intrinsic viscosity of HFAS was 0.82. The mole percentage of lactic acid units in the polymer determined by NMR was 5.9. Melting point determined by the peak endotherm observed in a D19 device of 29 ° C. Example 3 A sample of poly L (-) - lactide was prepared by the procedure of Examples 1-2 except that it was prepared in 98% conversion with an intrinsic viscosity of 0.5 using 0.2 mg of Sn C12-2H2O and 7.5 mg lauryl alcohol.

In a three-necked, 100 ml round-bottomed flask equipped with a glass shaft and a Teflon R paddle stirrer connected to a stirring engine and a gas inlet tube connected to an argon cylinder was added 10.0 g of the poly L (-) lactate. This was purged with argon for 15 min. This argon flush was maintained during the following polymerization. The flask was placed in an oil bath at a temperature of 19 ° C. xäriinnehåiiet reached 1800 in 2 ° c within 15 min. Then 2 g of glycolide were added with stirring and the oil bath temperature was set so that the temperature of the vessel contents was kept at 1800 at 2 ° C for 30 minutes with continuous stirring.

The temperature of the oil bath was then raised so that at the end of 30 minutes the temperature of the vessel contents reached 2200 É 2oC.

Then 18.0 g of glycolide were added and the temperature of the vessel contents was maintained at 2200 ° C for 1.5 hours with continuous stirring. At this time, the oil bath was removed, stirring was stopped and the vessel contents were allowed to cool to approximately room temperature during argon purge. This flushing was then stopped.

The glass flask was broken and the polymer was ground in a Wiley mill through a 20 mesh screen. 20.0 g of this polymer were dissolved in 400 ml of hexafluoroacetone cisohydrate (HFAS) at a temperature of 60 DEG C. and the polymer precipitated by adding this solution dropwise to 4000 ml of methanol with stirring. The polymer was collected by filtration and extracted with acetone in a Soxhlet extractor for 2 days. The polymer was then dried in a vacuum oven overnight at 500 at 0.1 mm Hg. The yield of polymer was 72%. The intrinsic viscosity of HFAS was 0.60. The mole percent of lactic acid units in the polymer determined by NMR was 33. The melting point determined by the peak endotherm observed in a differential thermal analysis (DTA) apparatus was 219 ° C. To a three-necked, 100 ml round bottom flask equipped with a glass shaft and a Teflon R paddle stirrer connected to a stirring motor and a gas inlet tube connected to an argon cylinder was added 6.0 g of a poly L (-) lactide with an intrinsic viscosity of 0.29 which is prepared in the same manner as in Example 3 except that a heating time of 1.5 hours at 200 ° C is used. This flask was played with argon for 15 minutes. This argon flush was maintained throughout the polymerization. The flask was placed in an oil bath at 200 ° C and the bath temperature was raised until the temperature of the vessel contents reached 2000 in 2 ° C. This happened within 15 minutes.

Then 48.0 g of glycolide were added with stirring and the temperature of the oil bath was raised to the temperature of the vessel contents was 2250 É 2 ° C. This happened within 30 minutes. Stirring was continued for 1.5 hours at this temperature. Then 6.0 g of L (-) - lactide were added (while stirring the vessel contents) and stirring was continued for 1.5 hours at this temperature. At this time, the oil bath was removed, stirring was stopped and the vessel contents were allowed to cool to approximately room temperature during the argon purge.

This flushing was then stopped. The glass flask was broken and the polymer was removed and ground in a Wiley mill through a 20 mesh screen. 5.0 g of this polymer was dissolved in 100 ml of hexafluoroacetone sesquihydrate (HFAS) and the polymer precipitated by adding this solution dropwise to 1000 ml of methanol with stirring. The polymer was collected by filtration and extracted with acetone in a Soxhlet extractor for 2 days.

The polymer was dried in a vacuum oven overnight at 50 ° C at 1.0 mm Hg. The yield of polymer was 82%. The intrinsic viscosity 7805831-0 8 in HFAS was 0.81. The mole percent of lactic acid units in the polymer chain determined by NMR was 11.2. The melting point determined by the peak endotherm in a differential thermal analysis (DTA) apparatus was 216 ° C.

Example 5 To a three-necked, 100 ml round-bottomed flask equipped with a glass shaft and a Teflon R paddle stirrer connected to a stirring engine and a gas intake tube connected to an argon cylinder was added 4.5 g of poly (epsilon-caprolactone) whose internal viscosity was 42.

The poly (epsilon-caprolactone) polymer was prepared in the same manner as Example 1 except that 8.0 mg of Sn C12-2H2O and 500 mg of lauryl alcohol were used and epsilon-caprolactone was used instead of the L (-) lactide. The flask was played with argon for 15 min. The argon purge was maintained throughout the subsequent polymerization. The flask was placed in an oil bath at 190 ° C. The vessel content reached 1800 É ZOC within 15 min. Then 0.35 g of glycolide was added with stirring and the oil bath temperature was set so that the temperature of the vessel contents was maintained at 1800 DEG C. 2 ° C for 30 minutes with continuous stirring. The temperature of the oil bath was then raised so that after 30 minutes the temperature of the vessel contents was 2200 É ZOC. Then, 12.15 g of glycolide was added with stirring and the temperature of the vessel contents was maintained at 2200 in ZOC for 1.5 hours with continuous stirring.

At this time, the oil bath was removed, stirring was stopped and the vessel contents were allowed to cool to approximately room temperature during the argon purge. This flushing was then stopped. The glass flask broke and the polymer was removed and ground in a Wiley mill through a 20 mesh screen. 4.0 g of this polymer was dissolved in 80 ml of HFAS at a temperature of 60 DEG C. and the polymer precipitated by adding this solution dropwise to 1000 ml of methanol with stirring. The polymer was collected by filtration and extracted with acetone in a Soxhlet extractor for 2 days. The polymer was then dried overnight in a vacuum oven at SOOC at 0.1 mm Hg. The yield of polymer was 73%. The intrinsic viscosity of HFAS was 0.77. The mole percentage of epsilon-hydroxy-caproic acid units in the polymer chain determined by NMR was 12.3.

This corresponds to 12.1% by weight of caprolactone units. The melting point determined by the peak endotherm in a differential thermal analysis (DTA) apparatus was 288 ° C.

Example 6 To a three-necked, 100 ml round-bottomed flask equipped with a 9 ~ 7805831-0 glass shaft and a TeflonR paddle stirrer connected to a stirring engine and a gas intake tube connected to an argon cylinder was added 7.0 g of poly (trimethylene carbonate) whose internal viscosity was 0.34.

The poly (trimethylene carbonate) was prepared by the procedure of Example 1 except that the trimethylene carbonate was used in place of the L (-) lactide and that 4.0 mg of SnCl 2 -H 2 O was used with 250 mg of lauryl alcohol. The conversion was 48%. The flask was purged with argon for 15 minutes. The argon purge was maintained throughout the subsequent polymerization. The flask was placed in an oil bath at 190 ° C. The vessel content reached 1800 É 2oC within 15 min. Then 3.5 g of glycolide was added with stirring and the oil bath temperature was set so that the temperature of the vessel contents was kept at 1800 ° C for 30 minutes with continuous stirring. The temperature of the oil bath thereafter so that at the end of 30 minutes the temperature of the vessel contents was 2200 É 2 ° C. Then, 31.5 g of glycolide was added with stirring, and the temperature of the vessel contents was maintained at 2200 DEG-2 DEG C. for 1.5 hours with continuous stirring. at this time, the oil bath was removed, the stirring was stopped and the vessel contents were allowed to cool to approximately room temperature under argon purge. This flushing was then stopped.

The glass flask was broken and the polymer was removed and ground in a Wiley mill through a 20 mesh screen. 5.0 g of this polymer was dissolved in 100 ml of HFAS at a temperature of 60 ° C and the polymer was precipitated by adding this solution dropwise to 1000 ml of methanol with stirring. The polymer was collected by filtration and extracted with acetone in a 2-day Soxhlet extractor. The polymer is dried overnight in a vacuum oven at 50 ° C at 0.1 mm Hg. The yield of polymer was 86%. The intrinsic viscosity of HFAS was 0.64. The mole percentage of units derived from trimethylene carbonate in the polymer chain determined by NMR was 16, 4. This value corresponds to 14, 7% by weight of trimethylene carbonate units. The melting point determined by the peak endotherm in a differential thermal analysis (DTA) apparatus was 288 ° C.

Example 1 L (-) - lactide (1612 g), SnCl 2 .2H 2 O (.204 g) and lauryl alcohol (4.77 g) were added to a stirred reactor which had been preheated to 140 ° C. The reactants were heated with stirring under a nitrogen atmosphere for 30 minutes to 200 ° C and then kept at said temperature for 2 hours.

The reactor was evacuated to a pressure of 50 mm Hg and the mixture was stirred for 30 minutes during which time the temperature of the mixture was allowed to drop to 180 ° C.

Atmospheric pressure was established by introducing nitrogen into the reaction vessel and the temperature was raised to 20 ° C for 5 minutes.

The molten glycolide (5198 g) previously preheated to 100 ° C was added and the temperature was raised for 15 minutes to 22 ° C and maintained via said value for a further 10 minutes.

The contents of the reactor were drained and the polymer mass was broken up after it had been cooled to room temperature. The polymer was then ground and vacuum dried at 8-10 mm Hg for 11 hours at 140 ° C to remove all volatiles before spinning and determining the viscosity of the polymer.

The intrinsic viscosity of the polymer is 1.14 measured at 30 ° C in a 0.5% solution in hexafluoroacetone sesquihydrate. The mole percent of lactic acid units in the finished polymer was determined to be 20.3% by NMR. The melting range of the product was determined to be 2150-223.5 ° C using a popping microscope with a hot table.

A portion of the dried polymer was added to the hopper of a small continuous extruder operating at about 230 ° C. The extruder was equipped with a nozzle having a 1.5 mm cylindrical opening and a length to diameter ratio of 4 to 1.

The extrudate was water cooled and collected at a rate of 13.4 mm / min. It was then pulled out to approximately 4.5 times its original length at SSOC in a hot air draw device. A sample of the glycolide homopolymer having an intrinsic viscosity hub of 1.05 was extruded and drawn in the same manner and then post-treated with the above copolymer fiber at 3 hours at 135 ° C at a pressure of 1 mm Hg.

The copolymer fiber having a diameter of 0.06l2 mm was found to have exceptional tensile strength (2432 kp / cm 2) properties in an accelerated tensile strength test and very good initial tensile strength (6784 kp / cm 2) despite its high comonomer content ( 20.3 mole percent).

In contrast, the initial strength of the homopolymer fiber having a diameter of 0.052 mm was 9840 kp / cm 2 and the corresponding strength maintained in an accelerated test was 1778 kp / cm 2.

As mentioned above, it is believed that such copolymer polyesters are characterized by microphase separations having spherical regions in the molten state, prior to orientation in which the chain segments composed of lactic acid units overlap with themselves in a matrix of glycolic acid units.

It is assumed that polyesters having such microphase separation will exist when the mole percent L (-) - lactide incorporated into the polymer chains amounts to about 25%. At from about 25% to about 40% lactic acid units, it is assumed that cylindrical ranges of lactic acid units will prevail. This would also be the case when lactic acid units predominate at both ends of the polyester chains as a result of sequential polymerization followed by L (-) - lactide, glycolide and then L (-) - lactide. Although the geometry of the regions in the molten state is speculative, evidence for the existence of phase separation or precipitation of the polymers can be seen by comparing their melting points with that of the homopolymer of the main component.

Accordingly, preferred surgical products made in accordance with the present invention constitute sterile synthetic absorbable surgical sutures made from a lactide polyester, the polyester being composed of a copolymer having cylindrical or more preferably spherical regions of L (-) - basic lactide units. of glycolide units. The polyesters used may have the relative amounts of glycolide units and L (-) lactide units given above. The sutures may be in the form of a sterile surgical needle and suture combination. Conventional suture designs and sterilization methods can be used. Preferably, a single-fiber or multi-fiber braided polyester yarn is shrunk into the end of a surgical needle and the needled suture is then sterilized using a oxidant such as ethylene oxide. Polyesters prepared by sequential polymerization followed by L (-) - lactide and glycolide are most preferred for use therein.

While the surgical products of the present invention are generally suitable in conventional ways for preserving living tissue in a desired position and relationship during a healing procedure by adjusting and placing living tissue therewith, such as when ligating blood vessels, they are needled the sutures are particularly suitable for sealing wounds of living tissue by suturing the edges thereof using conventional suturing procedures. Example 8. 30 g of trimethylene carbonate (TMC), 3.3 mg of SnCl 2 .2H 2 O and 0.133 g of lauryl alcohol are added to a stirred reactor preheated to 15,300 under a stream of nitrogen. The temperature is raised for 30 minutes. to 18000 and after stirring another 30 min. at said temperature a 2.5 gram sample is subtracted and 17Vg of glycolide is added. The temperature is then raised for 30 minutes. to 22300 and after stirring for 45 min. at said temperature 153 g of glycolide are added. Stirring is continued for 1 hour at said temperature, the polymer is then discharged, cooled, finally ground so that the mixture passes through a 10 mesh screen and dried for 48 hours at 140 ° C and 0.25 mm Hg.

The sample of 2.5 g of poly (TMC) removed at 180 ° C is dissolved in methylene chloride. The solution is added dropwise to methanol and the precipitated polymer is collected and dried for 24 hours at 4000 and 0.25 mm Hg. The resulting homopolymer has an intrinsic viscosity of 0.32 (3000, 0.5% solution in HFAS).

The intrinsic viscosity of the final copolymer is 0.81, the concentration of TMC units according to NMR analysis is 17 mol% or 15% by weight. Using a differential scanning caloric value at 10 ° C / min. the glass transition temperature is 3200 and the peak for the melting end thermometer is 216fC. Example 2 The copolymer of Example 8 was spun at a temperature of 23,000 at a rate of 0.23 kg / hour through a 30 ml capillary having a length to diameter ratio of 4 to 1.

The extrudate was passed through a surrounding water cooling head at room temperature and collected on a bib at a speed of 61 m / min.

The resulting extrudate was then drawn through a hot air chamber set at 40 ° C at a speed of 3.05 m / min. and a draw ratio of 5.2 times to produce a monofilament yarn falling within USP range 6/0. vsosasl-o 13 The physical properties of the drawn fiber were: nregnå1lfeetnet = 6932An »æn3 Tensile elongation at break; 35% Knot rain gauge = 5526 kp / emz Module: 90,700 kp / cmz Ilameterz 0.096 mm Example 10

Samples of the monofilament from Example 9 were implanted subcutaneously in rats. After 2 days, the samples were removed and their tensile strength was determined on an Instron Universal Testing Machine Model III25 (Instron Corp., Canton, USA). The samples retained an average of 45% of their original tensile strength.

Example ll. 20 g of trimethylcarbonate, 4 mg of SnCl 2 .2H 2 O and 0.199 g of lauryl alcohol were added to a stirred reactor which had been previously heated to 14,000. The reaction mixture was stirred for 2 hours at this temperature under a nitrogen atmosphere at which time a vacuum of 50 mm Hg was purged and maintained. for 30 minutes. The vacuum was released with nitrogen and glycol § lid (180 g), preheated to 14000, was added to "under nitrogen flow. The reactor was then heated for a period of 30 minutes to a temperature of 220 ° C. The temperature was maintained at 22o-222 ° c for an additional 45 minutes at which time the polymer was discharged, the polymer was cooled, cut into small pieces and dried for 24 hours at 130 ° C (1 mm Hg).

The intrinsic viscosity of the polymer was found to be 0.86 determined at 30 DEG C. 10 DEG C. in solution of nexeflnereneeneeneequilhydrate (HFAS). The concentration of trimethylene carbonate units in the copolymer was found to be 9 mole percent by NMR. This value corresponds to eight weight percent trimethylene carbonate units.

Using differential scanning calorimetry, the glass transition temperature was found to be 37 ° C; the melting range was 196-225 ° C, the peak of the melting endotherm occurred at 22100 H 7805831-0 14 and 1 & Hf (melting heat) was 17.6 calories / gram. A portion of the polymer (130 g) was further treated by heating for 3 days at 180 ° C (0.2 mm Hg) under a nitrogen flow of 56.6 dm 3 / hour. The final product weighed 120 g, had an intrinsic viscosity of 0.96 and contained 8.3 mol% (7.4% by weight) of trimethylene carbonate units.

Example 12.

The copolymer of Example 11 was extruded at a temperature of 230 DEG C. through a 60 ml capillary having a length to diameter ratio of 4 to 1. The extrudate was passed through a water cooling bath at room temperature and collected on a bobbin at a speed of 15.2 m / min. . The resulting extrudate was then drawn in a draw ratio of 8 times through a hot air chamber set at 50 ° C. The physical properties of the drawn fiber were: 50¿o kp / cm2 Tensile strength: Tensile elongation at break: 31% xnuc tensile strength = 3824 kp / cmz Module: 90,000 kp / cm2 Diameter: 0.164 mm

Claims (4)

w 7805831-0 PATENTKRAV A process for the preparation of a sterile absorbable surgical product, characterized by: (1) the preparation of a synthetic absorbable copolymer of copolymerizable monomers comprising glycolide as the predominant monomer and trimethylene carbonate monomer, the polymerization being carried out at between about 180 and 220 ° C in two or more steps using additive due to the comonomers wherein in each step a polymer chain with different composition is formed from the polymer chain formed in the one or every other step by different monomer amount ratios; and g (2) preparing a sterile surgical product of the copolymer obtained in step (1). A process according to claim 1, characterized in that a copolymer is prepared in which units of formula (II) O-O- (CH 2) 3 -O-C- constitute up to about 50% by weight. 3. A process according to claim 2, characterized in that a copolymer is prepared in which units of formula (II) constitute up to about 35% by weight. A process according to claim 3, characterized in that a copolymer is prepared in which units of formula (II) constitute between about 10% and 20% by weight.