FI102284B - Elastic, biodegradable material - Google Patents

Description

1 102284

ELASTIC BIODEGRADABLE MATERIAL

The present invention relates to a process according to the preamble of claim 1 for producing a thermoplastic, biodegradable copolyester.

According to such a method, the hydroxy acid monomers are first formed into a low molecular weight polyester prepolymer, which is then copolymerized with its end-reactive monomer to form a high molecular weight polymer.

There are areas of application for biodegradable polymers, such as disposable packaging, paper coating, or compostable waste packaging materials, where compostability is a significant competitive advantage. Conventional biodegradable polymers 15. however, use in packaging and other pulp applications is limited by the very expensive price of the polymer. One important application of biodegradable polymers is in medical applications such as surgical sutures and screws and nails for the treatment of fractures.

20 One group of biodegradable plastics consists of aliphatic polyesters, the biodegradability of which is largely based on hydrolysable ester bonds. Polyesters are generally prepared from hydroxy acids or diacid and diol. In order for an apathetic polyester to have sufficient mechanical properties, its molecular weight must be quite high, and the most common way to achieve a high molecular weight is to prepare the polyester with a ring-opening mechanism of 25 lactones.

Lactic acid is one of the potential raw materials for biodegradable bulk polymers. The preparation of polylactide (PLA) by a ring-opening mechanism from lactic acid via the lactide step produces a high molecular weight polymer, but requires? 0 many intermediate steps and very pure starting materials, and the overall yield of the polymer from lactic acid remains quite low.

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The product polymer in its homopolymer form is quite strong but brittle, with elongation at break typically less than 5%.

PLA is a straight chain polyester in structure, and there are no long chain branches. The theological properties of straight-chain polyester melt make their use difficult in most manufacturing methods using extrusion technology, such as blow molding, film blowing, and paper coating. However, these processing methods, which require sufficient melt strength and elasticity from the polymer, are key manufacturing techniques in the packaging industry.

10

Methods of copolymerizing lactide with ε-caprolactone by ring-opening polymerization have also been reported. In this way, rubbery copolymers have been prepared. However, their application to large-scale production is impossible because the polymerization is based on the use of lactides, and the production of lactides 15 is in turn difficult and expensive.

Typically, direct condensation polymerization of aliphatic diols and diacids or hydroxy acids results in a number average molecular weight of up to about 10,000 g / mol, and often a technically and economically reasonable molecular weight is? 0 about 2,000 to 5,000 g / mol.

A method is known for producing high molecular weight polyurethane suitable for melt processing from lactic acid monomers. According to the solution disclosed in F1 patent application 924699, the polymer is prepared in two steps by first polymerizing lactic acid to a low molecular weight oligomer and then copolymerizing the oligomer with an isocyanate to a higher molecular weight polyester urethane.

It is an object of the present invention to provide an alternative way of preparing high molecular weight polymers based on hydroxy acid monomers which can be melt processed and thus easily modified into the desired shape. It is a further object of the invention to provide a biodegradable polymer, 3 102284 in which all or almost all of the hydrolyzable bonds are ester bonds and which is substantially free of nitrogen-containing free functional groups. The object of the invention is specifically to provide a strong but tough polymer in connection with the above-mentioned production method. In this case, elastic biodegradable materials can be obtained by the preferred polymerization technique. This elasticity goal was achieved when it was found that in the case of lactic acid oligomeration, ε-caprolactone was surprisingly copolymerized into the polylactic acid oligomer structure.

The invention is based on the idea that in a two-step process based on the oligomerization of 10 lactic acids and the coupling of oligomers by some chemical reactions, e.g. using diisocyanate or epoxides, The oligomer thus obtained having a caprolactone comonomer is then coupled by known methods. 15 The purpose of the caprolactone units is to bring flexibility to the material, and to lower the glass transition temperature, and to act as an internal plasticizer. Caprolactone is a preferred comonomer in that it is biodegradable, so that the biodegradability of the final product is maintained.

The process according to the invention is essentially a two-step process, the first step comprising the polymerization of a prepolymer which can produce hydroxy acid and caprolactone in a reasonable time into a linear polyester of the desired molecular weight, either hydroxyl- or carboxylic acid-terminated, with low lactide formation. Key parameters in the process include monomer-25 amounts, polymerization temperatures, temperature-raising profile, condensation removal methods, comonomers, and catalysts. In the second step of the process, a higher molecular weight polyester is produced, whereby the molecular weight of the hydroxyl- or carboxylic acid-terminated prepolymer is increased by means of a functional coupling agent such as a diisocyanate or a diepoxy compound. At this stage, the key polymerization temperatures, the temperature profile, the coupling agents used and their amount (e.g. isocyanate / OH molar ratio), the catalysts and the technical solutions for the polymerization (melt polymerization) are important. Typically, the molar ratio of the chain-end difunctional groups of the coupling agent to the prepolymer is about 1: 1.

The object of the present invention is to eliminate the disadvantages typical of lactic acid polymers, in particular the brittleness of the material.

5

The melt-processable, tough copolyester according to the invention contains polyester-derived structural units, typically derived from lactic acid and partly from caprolactone, and partly also other structural units, such as urethane or epoxy bonds, depending on the material used to couple the oligomers. The resulting polymer typically has a molecular weight Mn greater than 10,000 g / mol and a weight average molecular weight Mw greater than 20,000 g / mol, and a molecular weight distribution (ratio M *, / Mn) greater than 2. Preferably, the number average molecular weight is 10,000 to 200,000 g / mol, especially preferably about 15,000 to 100,000 g / mol, the weight average molecular weight is 20,000 to 1,000,000 g / mol, preferably about 30,000 to 15,600,000 g / mol and the molecular weight distribution is 2 to 20, preferably 3 to 12.

By controlling the polymerization conditions, either a linear or branched polymer can be obtained, and the width of the molecular weight distribution can be separately controlled. The ratios of the different stereo forms of lactic acid can also affect the final product.

The prepolymer used in the manufacture of the high molecular weight elastic material includes units derived from hydroxy acid, typically lactic acid, as well as longer chain flexible structural units, typically structural units derived from caprolactone. In addition, the prepolymer is terminally functionalized with either -OH or -COOH

-functional by adding either a diol or an acid anhydride at the end of the prepolymerization. This means that all or at least almost all of the terminal functional groups of the prepolymer have been rendered reactive for the coupling agent. If the coupling agent is e.g. diisocyanate, -OH functionality is required, and if the coupling agent is epoxide, -COOH functionality is required. The prepolymer has a number average molecular weight of between 500 and 20,000 g / mol, preferably about 1,000 to 8,000 g / mol, a lactone content of less than 10% by weight and a free hydroxy acid content of less than 10% by weight.

Copolymerization of caprolactone in the preparation of the prepolymer and reacting the polyester prepolymer described above with a difunctional coupling agent provides a new copolyester with quite advantageous properties: - The polymer is a mechanically tough strong plastic or rubbery material / type is shown in Figure 1.

10 m x / en / / £ / / 15 / /

Percent Strain (%) 20

Figure 1.

- The degree of rubberiness can be adjusted by changing the composition.

- The polymer is biodegradable (i.e. it degrades in a biological aqueous environment with the hydrolysis of ester bonds, typically by the microorganism) and is compostable.

- The polymer is melt processable and has sufficient mechanical properties for many practical applications. Examples of uses for the polymer are: 30 - injection molded articles - thermoformed and blow molded packaging and bottles, - use of the polymer in the extrusion coating of paper or board, and 6 102284 polymer coated paper or board bags, sachets and foils, - sacks, - foams and foam products, 5 - fibers and non-woven products, and - use of the polymer as coatings or matrices, eg in controlled release fertilizers or medicines.

- The raw material cost of the final test polyester is very close to the price of the hydroxy acid (eg 10 lactic acid) used to make the prepolymer, as the conversion of the monomers used to the polymer is more than 95%.

Another advantage of the invention is that by means of the disclosed method, the molecular weight distribution, long chain branching and crosslinking of the copolyester can be adjusted to the desired level, resulting in controlled Theological properties of the polymer melt as well as desired elastic and rubber properties. The polymerization process is relatively simple and existing polyester processes can be easily utilized. The process makes it possible to prepare not only aliphatic copolyesters but also aromatic copolyesters.

20

The invention will now be examined in more detail by means of a detailed description and a few application examples.

Preparation of Prepolymer Depending on the amount of starting materials, the polyester prepolymer typically consists of 80 to 99.9% hydroxy acid monomers and 20 to 0.1% diacid monomer or cyclic acid anhydride. If desired, the carboxyl-terminated polyester-30 prepolymer can be prepared from a hydroxy-terminated polyester prepolymer.

This situation may be encountered if the same batch of prepolymer is to be used for the production of both copolyesters and polyurethanes. Diols, typically present in an amount of 10 to 0% in the present prepolymer, are typically used to prepare the hydroxy-terminated polyester. The porosity percentages shown above are calculated from the total amount of polymer.

The hydroxy acid monomers used in the invention to prepare the prepolymer typically consist of α-hydroxy acids, β-hydroxy acids or lactone. It is particularly preferred to use aliphatic or aromatic α-hydroxy acid monomers, such as L-lactic acid, D-lactic acid or mixtures thereof (e.g. so-called racemic D, L-lactic acid), glycolic acid, L- or D-mandelic acid, hydroxy-10 isobutanoic acid , lactide or mixtures thereof, the content of free hydroxy acid monomers and lactones not exceeding 10% by weight of the polymer. Hydroxy acid monomers can also be multifunctional. An example of these monomers is malic acid.

15 Hydroxy acid monomers are commercial products and readily available. Thus, for example, monomeric lactic acid can be prepared by fermentation of glucose. The lactic acid does not have to be pure, but may contain, for example, reactive sugar waste.

The rubbery toughness is achieved according to the invention by adding to the mixture of hydroxy acid monomers the desired amount of typically 1-60% by weight of a cyclic aliphatic lactone, e.g. ε-caprolactone, which according to the invention is surprisingly copolymerized into the resulting oligomer.

The preparation of the prepolymer, i.e. the condensation polymerization of lactic acid, can be carried out in any apparatus suitable for esterification reactions. One. according to a preferred alternative, the polyesterification is carried out as a bulk polymerization in a melt, whereby the water formed as a condensation product can be removed by introducing a dry inert gas into the polymer melt while stirring. The removal of water can also be improved by using a vacuum, whereby the pressure of the reaction is calculated stepwise.

102284 8

In the examples below, the polyester was prepared on a laboratory scale with "Rotavapor" type equipment for continuous water removal.

Preferably, the polyesterification is carried out in the presence of a catalyst, in which case, according to a preferred embodiment, typical polyesterification catalysts are used as catalyst. Such catalysts are, for example, alkyl or alkoxy compounds of tin or titanium, such as Sndboctoate.

The growth rate of the molecular weight of the polyesterification product depends on the polymerization temperature. As the polymerization temperature rises above 210 ° C, the degradation of the polymer chains begins to limit the polymerization rate. The formation of a harmful by-product, lactide, also increases significantly at temperatures above 220 ° C. For the reasons mentioned above, the temperature of the polyesterization is preferably raised stepwise at a temperature of 140 to 200 ° C at a rate of 50 ° C per hour and from 200 to 300 ° C at a rate of 0 to 30 ° C per hour.

According to a preferred alternative, the polyesterification starts from a temperature of about 160 ° C, which is gradually raised to 210 ° C. The pressure is reduced in steps of 230 to 30 mbar, respectively, and the condensation product is removed continuously with nitrogen. The standard process described above typically provides a polyester prepolymer having a number average molecular weight of about 2,000 to 8,000 g / mol (e.g., about 6,000 g / mol) and a polydispersity of about 1.7.

In the final stage of polyesterification, the low molecular weight fraction can be removed from the reaction mixture, if desired, by lowering the pressure, whereby the said fraction is distilled off.

Functionalization and coupling of prepolymer chain ends

In the process according to the invention, the terminal functionalization of the oligomer can be made to meet the requirements of the coupling reactions, either mainly as hydroxyl groups or mainly as carboxylic acid groups. The terminal functionalization technique has been described, for example, by Härkönen et al. The purpose of terminal functionalization is to provide the best possible reactivity for increasing molecular weight using coupling agents.

5

By appropriately changing the conditions of polyesterification and functionalization, the number average molecular weight of the prepolymer can be obtained between 500 and 20,000; preferably it is about 1,000 to 8,000 g / mol. Typically, the polyester prepolymer produced by condensation polymerization has a molecular weight of about 2,000 to 5,000 g / mol.

10

The coupling technique is described e.g. ed. in said reference [1], wherein the terminal functionality is a hydroxyl group and the coupling agent is a diisocyanate. When using carboxylic acids for terminal functionalization as a coupling agent, e.g. diepoxides are suitable.

15

According to the invention, a biodegradable copolyester having a relatively high molecular weight can be prepared from the terminated prepolymer and the coupling agent in relatively short polymerization times. Most preferably, the coupling reaction, hereinafter also referred to as copolymerization, is performed as a bulk polymerization in the molten state.

20

In copolymerization, the molar ratio between the reactive groups of the coupling agent and the end groups of the polyester is typically 0.5 to 1.5, e.g. 0.7 to 1.2, preferably about 1. The molar ratio between the functional groups of the coupling agent and the end groups of the polyester may also be greater than 1, preferably about 1. 2-1.5 if it is desired to obtain at least a partially crosslinked product. The crosslinked product is also obtained by continuing the polymerization for a sufficient time and carrying out the polymerization at a sufficiently high temperature and using a catalyst.

Härkönen, M., Hiltunen, K., Malin, M. and Seppälä, J., Properties and Polymerization of biodegradable thermoplastic poly (Ester-urethane), J. M. S.-Pure Appl. Chem., A32 (5) (1995) 857-862.

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The copolymerization is carried out at a temperature of about 110 to 220 eC, preferably 130 to 200 eC, and the copolymerization is continued until the resulting copolyester is at least substantially free of free coupling agent functional groups. Preferably, the copolymerization is continued until the molecular weight distribution of the resulting copolyester, expressed as Mw / Mn, is at least 2.

On a laboratory scale, the copolymerizations have been performed in a 300 ml glass reactor under an argon atmosphere as bulk polymerization. A blender suitable for viscous masses has been used as the mixer and the switching temperatures have been 150 ° C and 180 ° C. The progress of the coupling reaction has been monitored by sampling the polymerization mixture every 10 minutes. Reaction times are about 1 min to 100 h, preferably about 0.5 to 50 h.

Properties of the polymer 15

The number average molecular weight of the coupled polymer is 10,000 to 200,000 g / mol, typically about 20,000 to 90,000 g / mol. The molecular weight distributions of polymers made from lactic acid and glycolic acid are generally wide, but if these monomers are copolymerized with other hydroxy acids, e.g., mandelic, α-hydroxy-20 isobutanoic, or malic acid, even narrow molecular weight distributions can be obtained.

The long chain branching and wide molecular weight distribution of the polymer, especially the increase in the proportion of long polymer chains, generally has an effect on the melt processing properties of the polymer in particular, typically increasing the melt elasticity and melt strength. These properties are particularly advantageous in processing methods utilizing extrusion technology, such as paper coating and film production.

The content of free hydroxy acid monomers and lactides is at most 3% by weight of the polymer, typically less than 1%.

The polymer must be melt-processed, the viscosity of the polymer melt being between 10 and 102284 5,000 Pas, preferably 50 to 2,000 Pas, measured with a capillary rheometer at a temperature of 200 ° C at a shear rate of 200 l / s.

One condition for biodegradability is that the polymer is hydrolytically degradable. 5 The notion that the primary mechanism of degradation, especially for polymers formed from lactic acid, is hydrolysis, in which the aqueous environment is a prerequisite for degradation, is widely accepted. Hydrolysis is a precursor to biodegradability, after which microbes can more easily degrade low molecular weight hydrolysis products.

10

As can be seen from the experiments below (see Example 7), the polyester urethane of the invention is hydrolytically degradable.

Mechanical properties have also been determined for the coupling polymerization products. 15. Example 6 describes these results in more detail. In this context, it should be noted that the tensile strength and stiffness of the polymer are quite good. Stiffness or flexibility, hardness or softness and the degree of rubberiness can be adjusted by changing the polymer composition, in particular by changing the number of flexible structural units.

20

Blending, filling and consolidation of copolyesters

The novel rubbery copolymer can be used as a toughness and impact enhancing component in other polymers, especially other biodegradable polymers such as polylactide or the brittle polyester urethane described in the reference.

The new copolyester can also be filled or reinforced with fillers or reinforcements, in which case, for example, the heat resistance of the copolyester can be increased, the mechanical properties can be improved or the price can be reduced. Suitable fillers are, for example, chalk, talc, starch, cellulose or derivatives thereof. 12 102284 e.g. cellulose fibers or hemp can be used as reinforcements.

Applications of the copolyester 5 Due to the long chain branching of the polymer, the new polyesters are particularly well suited for coating paper or board, where LD polyethylene with long chain branches is now widely used for coating technical reasons.

The new polymers have a wide range of applications. Thus, they can be made into 10 injection molded pieces and thermoformed and blow molded packages, sacks, bags and bottles. The polymer can be used as a coating for sacks, bags and films made of paper and board. They can be used to produce blown or flat films, which in turn can be used to make packages, bags and sacks. Polymers can also be used to make fibers and nonwovens (non-woven products) and can be used to produce expanded plastic products, foams and foam, which are suitable, for example, for filling packaging. Finally, they are also suitable as a coating or matrix for controlled release fertilizers, plant protection products, insecticides and pharmaceuticals.

20 In all of the above applications, the unique properties of the new copolyesters, which combine biodegradability with good mechanical properties, can be exploited.

The following examples further illustrate the invention:

Example 1

Preparation of hydroxyl-terminated prepolymer A 2-liter rotary evaporator was used as a reactor, to which were added 450 g of L-lactic acid, 15.0 g of ε-caprolactone (corresponding to 2 mol% ε-caprolactone), 9.4 g of 1,4-butanediol and 0.24 g of tin (II) octoate. Dry nitrogen was introduced into the reactor and an absolute pressure of 13 102284 230 mbar was sucked in. The reaction vessel was partially immersed in an oil bath at 160 ° C. The temperature of the oil bath was raised at 20 ° C / h to 200 ° C and the reaction mixture was stirred by rotating at 100 rpm. The temperature of the oil bath was raised steadily at a rate of 20 ° C / h to a temperature of 200 ° C, and further at a rate of 5 ° C / h to a temperature of 210 ° C where it was kept until the end of the polymerization. The pressure was reduced every hour in the following steps: 230 (start) - 180 - 130 - 100-80-60-50-40-30 mbar, where it was kept until the end of the polymerization. Nitrogen bubbling was continued throughout the polymerization and the water formed in the reaction was recovered as it formed. 10 The total polymerization time was 16 hours.

The molecular weight of the obtained polymer was analyzed by GPC (Gel Permeation Chromatography) to give a number average molecular weight of 7900 g / mol compared to polystyrene standards, and the polydispersity was 1.5. DSC analysis (Differential Scanning Calorimetry) showed that the glass transition temperature of the polymer was 33 ° C and no melting peak of the crystals was observed, so the polymer was completely amorphous.

Example 2 20

Preparation of hydroxyl-terminated prepolymer

The polymerization was carried out as in Example 1, but the amounts of the substances were 450 g of L-lactic acid, 184.6 g of ε-caprolactone (corresponding to 20 mol% of ε-caprolactone), 11.5 g of 1,4-butanediol and 0.32 g tin (II) octoate, and the polymerization time was 22 hours.

*

The number average molecular weight of the obtained polymer, determined by GPC equipment, was 7900 g / mol compared to polystyrene standards, and the polydispersity was 1.5. DSC analysis showed that the glass transition temperature of the polymer was -3 ° C and no melting peak was observed.

14 102284

Example 3

Preparation of hydroxyl-terminated prepolymer The polymerization was carried out as in Example 1, but the amounts of substances were 180 g of L-lactic acid, 672 g of ε-caprolactone (corresponding to 70 mol% of ε-caprolactone), 12.0 g of 1,4-butanediol and 0.43 g of g of tin (II) octoate. The polymerization temperature was raised to 200 eC, respectively, and the polymerization time was 16 hours.

The number average molecular weight of the obtained polymer as determined by GPC equipment was 5900 g / mol compared to polystyrene standards and the polydispersity was 2.1. DSC analysis showed that the glass had a glass transition temperature of -55 ° C and a melting point of 27 ° C.

15 Table 1 summarizes the preparation of prepolymers where LACL

5 corresponds to the polymer of Example 1, LACL 6 of Example 2 and LACL 4 of Example 3.

20 Example 4

Preparation of polyester urethane from a copolymer of L-lactic acid and ε-caprolactone containing 2 mol% of ε-caprolactone (LACL51 in Table 2).

A 300 ml glass reactor with a paddle stirrer was used as the reactor. 40 g of the prepolymer prepared according to Example 1 were weighed into the reactor. After purging with argon (15 min), it was lowered into an oil bath set at 150 ° C.

After the prepolymer melted (20 min), the mixer was started and after 15 min, 2.5 ml of 1,6-hexamethylene diisocyanate (nNCO: nHH = 1: 1) was added. After the addition, the temperature of the oil bath was raised to 180 ° C. The polymerization was continued as the stirrer torque increased, however, as long as the polymer did not contain isocyanate groups (detected by FTIR spectrometry), in this polymerization 65 min.

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The final product was a urethane polymer having a number average molecular weight of 69,000 g / mol as determined by GPC and a weight average molecular weight of 307,000 5 g / mol. The polydispersity was 4.5. Glass transition temperature of amorphous polymer

The Tg as measured by DSC was 45 eC.

Example 5 10

Preparation of polyester urethane from a copolymer of L-lactic acid and ε-caprolactone containing 20 mol% of ε-caprolactone (LACL 63 in Table 2).

The polymerization was carried out as in Example 4, but the prepolymer of Example 15 2 was used as the prepolymer, and 2.3 ml of 1,6-hexamethylene diisocyanate was used. The polymerization time was 70 min.

The final product was a rubbery urethane polymer having a number average molecular weight as determined by GPC of 73,800 g / mol and a weight average molecular weight * 20 mass of 387,000 g / mol. The polydispersity was 5.24. The glass transition temperature of the amorphous polymer as measured by Tg DSC was 9 ° C.

Table 2 shows the results of the preparation of polyester urethane from different prepolymers.

25

Example 6

Table 3 shows the mechanical properties of the polyester urethanes prepared in the above examples.

16 102284

Example 7

The polymer of Example 5 was hydrolyzed in a test tube at 37 ° C in pH 7.4 buffered water. Already after a week, a clear hydrolytic 5 decomposition had occurred.

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Table 3. Tensile properties of poly (Ester-urethane) copolymers. 102284

Sample Conditions and Tensile Maximum Yield stress Maximum Elongation method modulus stress strain at yield (MPa) (MPa) (MPa) (%) (%)

Poly (ester-urethane) copolymers (98/2) LACL51 air-conditioned, 1 2095 ± 4 42.7 ± 0.8 - 4.7 ± 1.7 LACL52 air-conditioned, 1 2000 ± 23 40.7 ± 0 , 8 - 3.6 ± 0.5 (96.5 / 3.5) LACL81 air-conditioned, 1,1724 ± 127 36.1 ± 0.9 - 6.9 ± 4.6 LACL82 air-conditioned, 1,1115 ± 111 18.3 ± 1.2 9.6 ± 0.2 437 ± 20 31.5 ± 5.4 (95/5) LACL71 air-conditioned, 1,1297 ± 125 22.5 ± 2.7 12.3 ± 0.9 414 ± 16 49 ± 22 (90/10) LACL32 air-conditioned, 2 79 ± 23 8.6 ± 0.4 1.9 ± 0.1 441 ± 38 35 ± 10 (80/20) LACL61 air-conditioned, 2 1.6 ± 0.1 1.0 ± 0.1 0.50 ± 0.04 774 ± 84 69 ± 11 LACL63 air-conditioned, 2 1.7 ± 0.6 0.36 ± 0 .01 0.33 ± 0.01> 1100 55 ± 16 (70/30) LACL21 air-conditioned, 2 1.5 ± 0.4 0.15 ± 0.01 0.12 ± 0.02> 1100 35 ± 15 LACL24 air-conditioned, 2 1.5 ± 0.2 1.60 ± 0.04 0.52 ± 0.03 898 ± 45 84 ± 12 (50/50) LACL16 air-conditioned, 2 1.6 ± 0 .3 0.14 ± 0.01 0.12 ± 0.01 733 ± 67 33 ± 2 (30/70) LACL41 air-conditioned, 2 5.3 ± 1.4 0.09 ± 0.01 0.06 ± 0.01> 1200 16 ± 6

Homopolymers PEU air-conditioned 1927 ± 60 46.8 ± 1.8 - 3.7 ± 0.3 PLLA dry 1720 ± 50 46.5 ± 1.3 - 2.9 ± 0.2 air-conditioned 1620 ± 70 44.5 ± 3 , 6 - 3.0 ± 0.4 PDLLA dry 1930 ± 80 34.5 ± 1.4 - 2.0 ± 0.0 air-conditioned 1540 ± 70 33.0 ± 1.8 - 2.5 ± 0.1 PCL dry 250 ± 10 15.0 ± 0, 3 15.0 ± 0.3> 100 20 ± 1 air-conditioned 260 ± 3 15.5 ± 140 16.0 ± 0.2> 100 20 ± 2

Methods: I) 5 mm / min. 2) 50 mm / min - no yield point

Claims (12)

20 102284 A biodegradable elastic copolymer, consisting mainly of structural units derived from hydroxy acids, characterized in that said composition of the copolymer precursor oligomer, which is formed mainly by polycondensation, is based on lactic acid and a long elastic hydrocarbon chain hydroxy acid or diactone. Biodegradable elastic copolymer according to Claim 1, characterized in that the composition of the precursor oligomer is based on lactic acid and ε-caprolactone. Biodegradable elastic copolymer according to Claim 1, characterized in that the ε-caprolactone content is from 1 to 50% by weight and is copolymerized into a polymer composition in the oligomer formation step. Biodegradable elastic copolymer according to Claim 1, characterized in that the molecular structure of the polymerization product is straight-chain, partially branched or partially crosslinked. Biodegradable elastic copolymer according to Claim 1, characterized in that the polymerization product is a tough plastic or a strong rubbery material. Biodegradable elastic copolymer according to Claim 1, characterized in that the possible crosslinking of the polymer product can take place partially or completely in the processing step. Biodegradable elastic copolymer according to claim 1, characterized in that the elongation at break of the product is typically 3 to 500% and the tensile strengths are typically 5 to 50 MPa. Biodegradable elastic copolymer according to Claim 1, characterized in that the copolymer is biodegradable and hydrolysable. 21 102284 Process for the stepwise preparation of a biodegradable elastic copolymer, characterized in that the preparation is carried out first by oligomerizing most of the monomers into oligomers by a direct polyesterification reaction, terminally functionalizing the oligomers known per se and then coupling the oligomers thus obtained to other oligomers. Process according to Claim 9, characterized in that the end groups of the oligomers are hydroxyl or carboxyl groups. Process according to Claim 9, characterized in that diisocyanates or epoxides are used as coupling agent. Use of a biodegradable elastic copolymer according to claim 1 in applications requiring tough and / or elastic biodegradable materials such as surgery, controlled drug delivery and other medical applications, paper coating, packaging film manufacturing and other applications in the packaging industry, injection molded and extruded doors, injection molded products, in the manufacture of bottles, in the manufacture of fibers and nonwovens, and as an ingredient in various coatings, binders and 20 hot-melt adhesives, and as an impact-resistant composite component in biodegradable plastics. • «22 102284