DE1642111A1 - Surgical sutures and process for their manufacture - Google Patents

Description

V ^ M YWO \ ^ \\ ίθ θθΓ) are absorbable by the body surgical articles, particularly sutures in the form of * filaments consisting of a lactic acid polymer of intrinsic viscosity of v / enigstens 1.0 at a concentration of 0.1 wt -.% in benzene at 25 ° C. and further characterized by a shrinkage of less than 15% when immersed in 77 ° C water for a period of 5 minutes. The main patent also relates to the production of absorbable surgical suture material by a process which is characterized in that polylactic acid with the properties described above is pressed by the melt spinning process through a nozzle with a hole size of approximately 0.5-1.8 mm, the threads obtained stretched to at least 4 times their original length and thereby oriented, and the oriented threads in the tightened state are annealed by heating to 60 - IpO ⁰ C until they shrink less than $ 15 when they are subsequently immersed in the untensioned state in water of 77 Show ° C.

The present invention is directed to highly oriented, very strong filaments made from copolymers of

109853/1398 originally inspected

Lactic acid exist, / ebe also exhibit excellent dimensional stability in Körpergev and preferably, also zusammenziehen- of courier search, in which they are immersed in water at 77 ⁰ C for 5 minutes to less than 15 $.

This Fädenj viewed as a surgical suture _r are be prepared from lactic acid copolymers which have a limiting viscosity of at least 1, preferably greater than 1.2, determined at a concentration of 0.1 $ in benzene at 25 ⁰ O prior to orientation. These polylactides contain up to about 15 $, preferably up to about 10-12 Gew _o - $ recurring units of the following mold

R- 0 j ti ο * - C.

_k ο (ι)

R "

Herein, H is a lower alkylene radical, preferably methylene (-0H ₂ -) or ethylene (-0HpOH ₂ -) - m is the number 0- or 1, R 'is hydrogen or a lower alkyl radical, and H "" stands for hydrogen or an alkyl radical with up to about 22 carbon atoms, if m =? 0. and for hydrogen or a lower alkyl radical, if m = 1, where R "and R 'can be the same or different <, If the remaining proportion of more than 85 $ of the polylactide to 100 $ is optically active. The above! units (1) can not be derived from the same optically active lactic acid _5, and when the remaining portion of more than 85 $ of the Polylactida is optically inactive to 1QO $, the above units (1) can preferably not originate from DL-IIilchsäure. because of the availability of the starting materials are recurring units derived from a-hydroxycarboxylic acids, _o h _o d units of the above formula in which m is zero "is by far preferred because of the characteristics of the produced therefrom

^H optically active carbon
109853/1398

Sutures have recurring units or corona units derived from glycoid or BL-lactide, ie, recurring units of the formula (Ί). in the m for zero. R ^; for hydrogen or methyl and R ^r for hydrogen, but with the abovementioned limitations .; which "are already covered by the main patent" In other words, the number of σ atoms in the repeating units is 2 Ms about 24 _:. preferably 2 to about 8 _P, especially 2-3 c-

When m is zero, R- is methyl and R "is hydrogen, the repeating unit in formula (Ό could refer to BL-lactide. Which is a copolymer ₅ or to the main unit, which would mean that the polylactide is a homopolymer which is covered by the main patent

As examples of the Comononians. which can be used with the lactide to form the copolymers suitable for the production of the filaments according to the invention may be mentioned as glycolic acid, tropiolaetone, tetramethyl glycolide; . _{ß-butyrolactone:} Y-butyrolactone, Pi ^"r aloiacton and intermolecular cyclic esters of a-Hydrozybutter- · acid a-hydroxycaproic acid Hydroxyisobuttersäurer a _f c - hydroxy-a ~ äthy butyric acid, α-Hydroxyiso cap ronsäur e _r.! α-Kydroxy-ß-methylvaleriansäure5 α-hydroxyheptanoic. a-Hyaroxyoctansaure .; α-hydroxydecanoic acid. a ~ ^r Hydroxj myristic acid ;: α-hydroxystearic acid and α _c -Hydroxyliguocerinsäure

The threads are zv / eclanäßig by melt spinning the Polylactic acid through a spinneret and then single-stage or multi-stage drawing of the threads to at least 4 times their original length, with an orientation and improvement of the tensile strength takes place, produced, for example, in the main application described

1098 5 3/1398 bad original

The polymer can monofilament or multifilament spun and stretched ,, For the production of multifilament braided suture monofilaments or groups can be used of filaments for braiding _o The diameter of the filaments obtained can be used for Einzelfädenivon more "fädigem suture 2. 5 / rev or less and for very heavy monofilament suture up to 1.15 mm be "generally, however, the diameter of the threads erf.indungsgemässen is not larger than 5 ^ o - o, 64 mm _and preferably are monofilaments of about o, o25 -.. ο. , 5 mm diameter and multi-thread suture material with single threads of less than 2.5 to 5o / U diameter «

109853/1398

BATH ORIGINAL

To further improve the dimensional accuracy and especially those of maintaining the tensile strength they can subject to a partial treatment, as described in the Main notification is described "

Since a seam has the task of holding severed tissue together until healing proceeds, and of preventing separation as a result of body movements or exercises; the seam must have sufficient strength. It is particularly important that the material remains firm when the thread is tied - and during the actual tightening of the knot =, The tensile strength γόη Katgut in this regard is known to be limited loads made of lactic acid copolymers in a high molecular weight, oriented form are, in contrast, exceptionally tear-resistant and preserve, which is extremely important _5, to a large extent, their tear strength at the junction, as can be seen from the following table

catgut

Copolymer
from L ~ (-) - Iiac
tid and
Ύ-eutyrolactone (95/5)

Table ^

Elongation at break and breaking strength ,, keit fo (straight pull)

Tear strength - decrease in the ability (surgical strength at the knot knot) (3) compared to · kg / cm ² the straight addition fo

3500 (1) 3100 (2)

20 20

2040
1900

42 39

17th

2950

29

4150 (4)

1) Ohromgut, size 3-0 (0.2-0.25 mm diameter)

2) Ohromgut, size 2-0 (0.25-0.33 mm diameter)

3) According to [IcS .. Pharmacopeia

4) Intrinsic viscosity (starting polymer) = 3 (spun threads «1., 6 _S IC times drawn, 0 - 23 mm diameter)

109853/1398

As can be seen from Table 1, the intrinsic viscosity. of the spun. CLH * oriented yarn be somewhat lower than that of the starting polymer, because during stretching some degradation of the polymer may occur depending on the applied stretching conditions * · \ "hen! the suture is sterilized by high-energy radiation, a v / urther lowering the molecular weight is the polymer take place, Venn, however, lactic acid polymers UNAE -oopolymeren with Grenzviskos.itäten of at least i assumed the suture produced therefrom is completely satisfactory, even if some decrease in the intrinsic viscosity eingetreten.:ist by spinning and the orientation and possibly sterilization .

The thread material according to the invention is also characterized by its hydrolysis behavior and its resorbability. When treated with boiling water for a period of 100 hours, it loses at least $ 20, preferably at least about 5% of its weight. When treated with boiling water for a period of 50 hours, the polymers and copolymers lose at least about 8? S. preferably at least about 35 $ their weight _o

The rate of hydrolysis (resorption) of the suture material can be adjusted by changing the type and amount of the monomer used. In contrast to the extremely different rates of resorption of catgut, the resorption of polylactide is relatively more independent of the location in the body where it is needed and the condition of the patient., Ea the rate of hydrolysis of a given lactic acid copolymer at a fixed temperature of, for example for example, _P v / ar-poly Irlactid be 3J ⁰ O is constant, can accelerate the absorption for example by using different Copolyliierer in the back muscle of a rat after 270 days

109853/1398 I.

15s3 $ reabsorbed _o Under comparable conditions a copolymer of L (~) -lactide and PL-lactide (97: 3) was "to" 18.5 $ 5. a copolymer of L (-) - lactide and OL-lactia (95s5) £ u 29. C ^. an Oopolymer of L (~) -Lactide and Glykoliü (95: 5) to 27.3 $ and chromium-coated catgut to 67 $ resorbed <·

Y / ie mentioned earlier; For example, high tear strength is a highly desirable property of surgical sutures. The threads according to the invention are characterized in that they have a tensile strength of at least 1760, preferably more than 2800 kg / cm * Certain thread material according to the invention has tensile strengths of up to ICOO kg / cm ² and more _c their knot strength, expressed in kg tensile . exceeds the minimum limits set for absorbable sutures in the U _C S, Pharmacopeia _f namely from 0.057 kg for a thread of 25-50 ? x to 11.34 kg for a thread of 0 «9 ~ 0.0 mm.

The corresponding intermolecular cyclic ester or the intramolecular cyclic ester (Laeton) of the hydroxy acid is used to produce the oleopolymer ₅ according to the invention from which the threads according to the invention are produced. * These esters can be derived from pure!; (-) - or L (+) - Lactic acids mixed with the optically inactive DL-lactic acid mixture. any desired mixtures of pure DO) ~ and L (-t -) - lactic acids and other a ~ ₅ SS or Y ~ Hydrcxysäuren, wirdc said about the later Da general, for the introduction of recurring BIR Iiactidein ~ units in Copolymers preferably used as starting material lactides, which are derived either from the pure L (O- »acid or from the pure D (-) - acid, because the polymers obtained with them have a higher melting point, much less water-sensitive and stronger and have a higher degree of crystallinity

109853/1398

BATH ORIGINAL

as polymers derived from the DL acid mixtures. For example, the polylactides the DL-acid melting at 150 - 14O ⁰ C, while the polylactides the Lfi -) - acid at 3Λ5 - melt I75 ° C. The polylactides of L (-ί -) - acid or D (-) - acid are less sensitive to alcohol, a sterilization medium generally used in surgery, than the polylactides of DL-acid. The L (-: -) - form is more readily available than the D (-) - acid and is therefore particularly preferred. Of course, the various lactides can be prepared from the corresponding lactic acids by various published methods including the method of United States Patent 2,703 3ίβ.

In the following Table 2 the properties of Polymers, which are made from L (-) - lactide and from DL-lactide, compared to each other.

Table 2

Limiting viscosity
Melting point
Optical activity
Thermally stable
solubility

density

Tear strength (Monofilair.ent)

Elongation at break (monofilament) Tear strength (dry film) Limiting viscosity (film) elongation at break (film)

DL-lactide 0.7 - 2.0 130-140 ⁰ C no
Yes

CHCl,

Benzene acetone

1.26

1400-2800 kg / cir. ² I'D - 30% 1δ25 kg / cm ² 1.29-

from_ 0.7 - 3.5

yes (-186 °) yes

Eenz'ol Aceücn

1.26

49CO-7CO0 kg / cm ²

15 -

204ο kg / cm ²

"• 'Taken from U.S. Patent 2,758,987.

109853/1398

BATH ORIGINAL

Ira general take the. Tensile modulus ₃ the melting point and the specific rotation of lactic acid homopolymers with increasing amounts of the antipode in the mixture. In some cases this is desirable in order to obtain mostly ^{1 of the} threads of improved suppleness without any appreciable loss of strength.

When producing other copolymers, the repeating units derived from the comonomers discussed above are grounded; introduced by using the corresponding cyclic esters. For repeating units that are derived from α-hydroxy acids, these are usually the intermolecular cyclic esters that contain six rings, z - .. Έο G-lykolid: For repeating units that are derived from ß ~ or Are derived from T-hydroxy acids? are usually the monomeric lactones, ζ-B- ß-propiolactone and Y-butyrolac-. used-.

In the manufacture of the thread material according to the invention, it is essential; To use polymers and copolymers made from very pure I & ctienes as described in the parent application. For example, the L (-) - lactide must have a melting point of at least 96 ⁰ O and a specific rotation of more than -295 ° to achieve excellent results - the polymerization is carried out by contacting the lactide in the presence of a polyvalent metal oxide or a compound thereof _s is heated under anhydrous conditions in an inert atmosphere to a temperature which is above its melting point below about 215 .However ⁰ O.

Particularly suitable catalysts are just like the "/ experience of the main patent zinc oxide, zinc carbonate, basic zinc carbonate, zinc diethyl, titanium, magnesium or barium compounds ^ lead monoxide u, dglo amount and The type of catalyst used are the same as in the 'procedure of the main patent'

; -ν- 109853/1398

BATH

ic

The general procedure for making the copolymers * !; which are suitable for processing into the threads according to the invention is the same as described in the main application » Furthermore, the production of the thread material is the same as already described in detail in the Hauptamr.ei-. application described.

Small amounts of inert additives, e.g. coloring substances and plasticizers, by adding to the pre-formed polymer known processes are incorporated, Eany plasticizers = Z-B- glyceryl triacetate, ethyl benzoate and Diallyl phthalate, in particular, can be advantageous Polj'-L-lactide can be used. The Weichmaoher crowd can be '. -40 $ of the polymer weight "The plasticizer not only makes the threads smoother and easier to process, it also makes spinning easier. "Inert" means substances that are chemically with respect to the polymer or copolymer as well as with respect to living tissue are indifferent, great, no unfavorable Cause effect; such as granulation, excessive edema

A mixture of 9d parts of L (-) ~ lactide and 5 parts of DL-lactide was melted under nitrogen and treated with Ο.125 parts of zinc diethyl as a 25% solution in heptane. The mixture was kept for 1 hour at normal pressure in a nitrogen atmosphere at 1C5 °. "? öige solution in benzene at 34.5 ⁰ C). ~ the copolymer was ground into a fine powder ^ which was pressed into a stopper, was suitable for processing in a Schmelzspir.nvorrichtung. threads of Gopolymeren were at about 20O ⁰ C spun through a spinneret with a 0.9 mm hole size and in glycerine

BAD ORlOiHAL

109853/1398

at about 12O ⁰ C to 6.4 times its original length stretched ,. The drawn threads had the following properties:

Intrinsic viscosity 1 _f 7

Diameter 3I8 tx

Tear strength 4113 kg / cn

Elongation at break

Module 0.076 χ 1O ⁶

Knot strength 2600 kg / cm ²

Shrinkage after 5 minutes
• in water at 7? Oc $ 235

-Weight loss after 50 hours in cold water

Intrinsic viscosity 0.55

Tear strength 1335 kg / cn ²

Loss of weight 2

J.J3L

Intrinsic viscosity 0.38

Tear strength 352 kg / en ²

Weight loss $ 7.0

A number of other lactide copolymers were prepared in the manner described in Example 1 and spun into threads.If the comonomer was liquid at ordinary temperature (ß-propiolactone _r Ύ-butyroiactone or pivalolactone) it was only added to the lactide after it had melted, . The properties of the starting polymer, the spinning conditions and the properties of the co-polymers in thread form are compiled in Table 3 below

109853/1398 ^ _1n .,

ORIGINAL

Table 3

Attempt. 1 2 3 4 5 '6 7 8

$ Comonomeres 7.55 »TXr- 10 $ DL- 15 $ El- 5 $ GIy- 10 $ GIy- 5 $ ß-pro- 55 $ γ-Buty- 5 $ Pivalo-

Lactid lactid lactid colid colid piolacton. rolactone lactone.

Limit viscosity

(Starting poly-

meres) 2.87 2.50 2 ₅ 39 2.53 2.52 1.31 2 _? 99 2 ₃ 68

Southern temperature, 190 205 200 210 195 Stretching ratio * 8.6 8, I ₁ 7 ₅ 5 8.8 8,, ü Stretched butt. ⁰ C 128 125 100 125 100 D985 ■ Green viscosity
(stretched
load) 1 _S 75 1.75 1.4Y 1.84 1.70 VAS Diameter, mm 0.29 0 _r 28 0.32 0.26 0.22 1391 Tear resistance,
kg / cn2 3747 4850 3725 5400 1933 OO Fractional idea, $ 20th 20.7 18.5 14th 32 Module, kg / cm 98,400 77> 33O 77o330 77,330 32.3 Knot strengthening
speed, kg / cr.2 2636 2610 2110 3023 1900 BATH ( shrinkage
(H ₂ O / 77 ° G / 5 min. 135t $ 27.5-44 $ 72 $ 12 $ 73

39 Gevrichtsver-

O lust (HpO / 100 C /

ξ 50 hours) $ 44 $ 48 $ 65 $ 45

170 170 10 10 115 100 1 j 73 1.64 0.24 0.22 4H5 5480 17th 22nd - 84u360 2950 3375 about $ 15 approx "$ 15

α> οι u>

Table 3 (cont.)

1 2 __2 Ο:

After 30 days in water at 37 ° C

0.54 '- 0.58 ² - 1673 - 1828 3.5% - 1A%

Nac h 9, 0 days in water at 37 ⁰ C

Tear Strength, kg / cm ² - - Weight Loss - - - $ 12.1

Try

Intrinsic viscosity (drawn thread)

Tensile strength, kg / cm 'weight loss

Intrinsic viscosity, (drawn thread)

6. 7

0.81 0.72

.6% 0.5%

0.58 0.35

At υie1_ 2

Copolymers of L-lactide with the intermolecular cyclic esters of a-Kydroxybuttersäure and a "Hyäroxyheptansäure were prepared essentially by the procedure described in Example 1 produced a mixture of 44 ₅ 2 g of L-lactide and 5.8 g of the cyclic ester of a- hydroxybutyric acid was melted under nitrogen and treated with 0.08 g of 25 ^c / s ° ± & solution of diethylzinc in heptane Ό The mixture was for 3 hours at normal pressure in a nitrogen atmosphere at 105-106 ⁰ C held The polymer obtained from L-lactide and the intermolecular cyclic ester of a-hydroxybutyric acid (88.4: 11 * 6) had an intrinsic viscosity of 2 _f 15 solution in benzene),

Bas copolymers of L-lactide and the intermolecular cyclic Ester of α-hydroxyheptanoic acid (90:10) was made in a similar manner from 45 g of L-lactide and 5 g of the cyclic ester and 0.08 g of a 2% solution of zinc diethyl in heptane made "After the mixture has been heated for 3 hours the polymer formed had an intrinsic viscosity of 2.28,

lie spinning conditions and the properties of the threads of these Copolymers are listed in Table 4.,

lie intermolecular cyclic esters of .a-hydroxybutyric acid and a-hydroxyheptanoic acid were essentially by the method of Bischoff and Walden., knn »27.9, prepared 100 (1895 ;, ,, The sodium salts of the corresponding a ~ bromoacids were prepared from the acids and sodium methoxide made in a mixture of ethyl ether and ethyl _β the cyclic esters were prepared by reacting the sodium salts were heated under reduced pressure at 300-315 ⁰ C. the Buttersäuredetfivat was removed by distillation at 78-85 ⁰ C / 0.07 mm Hg, and by crystallization purified from ethyl alcohol-petroleum ether and cooling in solid carbon dioxide. ”The heptanoic acid derivative was obtained by crystallization from pentane

1098S3 / 1398

Cooling in solid colil dioxide and from ethyl alcohol purified, the two cyclic esters were characterized by the elemental analysis and the infrared spectra.

attempt

ϊό CoEionomeres

Limit viscosity (unspoken polymer)

Spinning temperature, stretching ratio, stretching temperature Limit viscosity tear strength, kg / cm * elongation at break

ρ Koöul, kg / cm

Shrinkage 5 minutes *!

77 ⁰ C

Table 4 2 . ..- 1 10 * internole
kular eycli
shear ester "
of a-hydroxy
he τ> ± anic acid 11y6 $ intermolecular
cyclic ester of
oc-hydroxybutyric acid 2.28 2.15 190 ⁰ O- 185 ⁰ O 8th 10 * 98 ⁰ O 94 ⁰ Oj 122 ⁰ C * 1.63 ** 1.42 ** 4155 4660 18.3 * 22.3 * 66ο785 73c'OO 55.0 * 20.6 * 63, 6 * 5 60.5'S

Weight sνe r1ust (Η _ο 0 / 'ί00 ° 0/48 hours)

* This thread was drawn in two stages. In the first stage it was drawn 7 times (draw ratio 7) at 94 ° 0 and in the second stage at 122 ° C _? that the total draw ratio was 10 *

** Measured on the undrawn thread _c The limiting viscosities of the threads were measured on the drawn material ';

Example_3.

A mixture of 206 g powdery copolymer of L-lactide. and DL-lactide (90:10) and 0 _s 6182 g of the conosodium salt of 4 -_ / T- (Ji-Athy 1-p-sulfobenzylamino) diphenylmethylene7 -_ / i '- (ii_ethyl-Np-sulfoniumbenzyl) - Δ

¹ U / 'Z ^F £ & 0 (Food, Drug and Cosmetic) Green No. ₀ f7

^2j '-cyclohexadiene-

109853/1398

was in a Fisher-Kendall-Ilischer 48 hours at room temperature The homogeneous mixture obtained was pressed into a stopper and onto that described in Example 1 Wise monofilament spun into green threads »

In the experiments described above, the polymerization was used in bulk for the production of polylactides, however, the polymerization can also take place in solution or suspension. When using solution polymerization, this can Ratio of ionomer to solvent ': 1 to 5:' are Aromatic hydrocarbons such as xylenes and ethers such as tetrahydrofuran are suitable solvents. Eioxane and 1.2-limethoxyathan,

Although the invention has been specifically described in connection with monofilament spun threads ₅ , the polyhydric acid can also be used in the form of multi-thread yarn _; Z ₁₅ B, braided structures as well as rods, foils and tubes are used. "Braided" is suture material that contains more than a single strand of a polylactide. The threads can be braided into valuable suture material in the most varied of ways. z-, B. according to the Kethode _; which is usually used for the production of Manila sell, SchnürenUrdglc _c in the final braid-shaped suture material at least 50S of the individual strands must be oriented _r Preferably the individual threads that form the (braid "should be oriented 90 ;? or more

The products made according to the invention are suitable for surgical purposes where an absorbable auxiliary or support material is required. for example in the formation of "cn surgical slings; absorbable staples, artificial tendons or cartilage material, as well as for other purposes where temporary support during the wedging process is necessary. They can also be beneficial for healing vc-i fractures ·;. πα - zvv anchoring of lo ^ kei · gev / oenen organs

1 ! If ■: ',' i 1. · ■ HB

BAD ORiQlNAL

Claims (1)

Claims Surgical articles which can be absorbed by the body, in particular suture material in the form of threads, consisting of a lactic acid polymer with an intrinsic viscosity of at least 1.0 at a concentration of ο ,, Ι $ in benzene at 25 ⁰ C and further characterized by a shrinkage of less than 15 % _3aot when immersed in water of 77 ⁰ C for a period of 5 minutes after the main patent, _{a, os> 'aooooaBO \;} > _oaaoo (patent application P 32 769 IVa / 30 i)., consisting of oriented threads of lactic acid copolymers, which contain up to 15 % recurring units of the formula; _R t 0 'tt R " contain - in which R is a lower alkylene radical., m is the number 0 or 1. R 'is hydrogen or a lower alkyl radical., and R''.,the' same or different from R ^! can be hydrogen or an alkyl radical with up to 22 carbon atoms is ^ if m = 0, and is hydrogen or a "lower alkyl radical. If m = I ^ where the polylactide before orientation through an intrinsic viscosity of at least 1 ^ o at a concentration of o, l wt .. -.% in benzene at 25 ° C and by a Gev / maybe loss of "'is at least 2O% when treated with boiling water for a period of loo hours in and the threads through a tear strength of 1760 to 7000 kg / cm with a diameter of 2.5 / u to Ι..1Λ3 mm are marked, 109853/1398 A fully absorbable surgical suture according to claim 1 consisting essentially of one oriented monofilament from 25 μ to 0.5 ram E diameter of a lactic acid copolymer., the monofilament being drawn by drawing at a temperature of 7o to 14o ° C oriented to a stretch ratio of up to 11 times, ο suture material according to claims 1 and 2 _S characterized in that the polylactide is a homopolymer of L. (-) lactic acid is ~ » 4, suture material according to claims 1 to 3. » wherein the lactic acid copolymer contains up to 12% recurring units of glycolide " 5c sutures according to claims 1 to 3, wherein the lactic acid copolymer consists of poly-L (-) - lactic acid and up to ± 5 % of four repeating units of DL-lactic acid β ο suture material according to claims 1 to 5 ^ containing lower ones Quantities of an inert dye and plasticizer, Jc suture material according to claims 1 to 6 ^ containing glyceryl triacetate as plasticizer ^ ■ _ c sutures according to claims 1 to 1 _s wherein the lactic acid copolymer is a 95: 5 propolyiEer ^ of ^ "- L (-) - lactic acid and DL-lactic acid, 9ο absorbable surgical suture material according to claim in the form of a braided structure, where at least 5o # of the filaments making up the braided structure, the diameter of the filaments of 2.5 / U to 1.1 ^ 3 mm and the braided structure through a tear strength of 1760 to 7000 kg / cm is marked " ν 109853/1398 164211t Io _t A process for preparing vcn absorbable surgical suture material according to claim 1 by melt-spinning a lactic acid copolymers having an intrinsic viscosity of at least l, o, at a concentration of o ^ l GEWC ™ # in benzene at 25 ° C through a nozzle having a hole size vcn o, 5 to 1.8 mm stretching the resulting threads to at least ¹ \ times their original length for orienting and tempering the resulting oriented threads by heating to 6o to 15o ° C while they are held essentially taut until they shrink less than 15 $ Subsequent immersion in the relaxed. Show state in water / water of 77 ° C, characterized in that such lactic acid copolymers are used, which are up to about 155 '. preferably up to about Io to 12 repeating units of the formula: R ^T O C t ι ι where R is a lower alkyl radical .. preferably methylene (-CH ₂ -) or ethylene (-CH ₂ -)., m O or I.- R 'are hydrogen or a lower alkyl radical and R ^! 'J which can be the same or different from R ¹ . Is hydrogen or an alkyl radical having up to about 22 carbon atoms when m = O and hydrogen or a lower alkyl radical. If = 1 where xienn the remaining portion vcn more than 85 fo the polylactide to lco% is optically active m ., the mentioned units of the formula cannot be derived from the same optically active lactic acid, and if the remaining proportion of more than 85 % of the polylactide is too inactive; - the gensr.ter. Units 0 3/139 »BADORfGfNAL 1842111 of the general formula are not derived from DL-lactic acid can, 11. The method according to claim 10, characterized in that the stretching takes place in the temperature range from 8o to 10o ⁰ C and the stretching ratio of 5; 1 to lo; 1 is., BATH ORIGINAL 109853/1398