WO1996007687A1 - Biodegradable polyester and a material made therefrom - Google Patents

Abstract

The invention concerns a biodegradable polyester (in particular, a material) which is broken down in the natural environment by micro-organisms such as those classified according to DIN 53739D or ASTM D5338-92. The polyester in question is characterized by the fact that it is produced from an aliphatic polyol and an aromatic polycarboxylic acid and simultaneously from an aliphatic polycarboxylic acid as the monomer components, and has constitutional repeated or recurring units consisting of (i) polyol and aromatic polycarboxylic acid on the one hand and (ii) polyol and aliphatic polycarboxylic acid on the other, over 90 % of the units (i) being directly coupled with no other such unit or with at most one other such unit.

Description

BIODEGRADABLE POLYESTER AND MATERIAL THEREOF

The invention relates to biodegradable polyesters (in particular in the form of a material or material) and materials made from the polyester.

Polyesters are part of the state of the art. For example, EP-A-0 007 445 describes a mixed polyester based on 1,4-butanediol and terephthalic acid, 10 to 30 mol% of the terephthalic acid being a mixture of 20 to 80 mol% of adipic acid, 10 up to 60 mol% glutaric acid and 10 to 40 mol% succinic acid are replaced and the percentages add up to 100. These known mixed polyesters are intended for the production of molded parts by injection molding or extrusion. However, such mixed polyesters are not biodegradable, which (as will be seen from the later explanations) can be attributed to the high minimum proportion of 70 mol% terephthalic acid as an aromatic polycarboxylic acid. EP-A-0 028 687 also describes copolyesters composed of 40 to 85 mol% terephthalic acid (which can be replaced up to 50% by other dicarboxylic acids, for example sebacic acid), 60 to 15 mol% adipic acid and C ₂ _g- Alkane diols such as butylene glycol. These known copolyesters are in the form of hot-melt adhesives or powder coating agents provided so that the question of their biodegradability does not arise. For the production and use of these known copolyesters, EP-A-0 028 687 refers to much older prior art.

It is known that certain polymeric materials can undergo biodegradation. Mainly materials that are obtained directly or after modification from naturally occurring polymers are to be mentioned here, for example polyhydroxyalkanoates, such as polyhydroxybutyrate, plastic celluloses, cellulose esters, plastic starches, chitosan and pullulan. A targeted variation of the polymer composition or the structure, as is desirable on the part of the polymer application, is difficult and often only possible to a very limited extent due to the natural synthesis process.

In contrast, many synthetic polymers are not attacked by microorganisms or only very slowly. Mainly synthetic polymers which contain heteroatoms in the main chain are considered to be potentially biodegradable. The polyesters represent an important class within these materials. Synthetic polyesters which contain only aliphatic monomers have a relatively good biodegradability, and because of their material properties, they can be used only to an extremely limited extent; see Witt et al. in Macrom. Chem. Phys., 195 (1994) 793-802. Aromatic polyesters, on the other hand, show no biodegradation with good material properties.

An object of the present invention is to synthesize copolymers (in particular in the form of a material or material) which at the same time have biodegradability and good thermal and mechanical properties. This goal is achieved by producing synthetic copolymers with a defined composition. The object on which the invention is based is thus achieved by a biodegradable Dissolvable polyester, which is degraded in the natural environment under the influence of microorganisms, for example according to DIN 53739D or ASTM D5338-92, the polyester being characterized in that the polyester consists of an aliphatic polyol and an aromatic polycarboxylic acid as well ¬ at the time an aliphatic polycarboxylic acid was produced as a monomer component and has constitutional repeating units or recurring units which

(i) on the one hand consist of polyol and aromatic polycarboxylic acid and (ii) on the other hand consist of polyol and aliphatic polycarboxylic acid, more than 90% of the units according to (i) being directly linked to none or at most one further unit according to (i).

According to the invention, it has surprisingly been found that it is possible to synthesize copolyesters from diols and aromatic and aliphatic dicarboxylic acids which are subject to biodegradation with material properties which are relevant to the application.

The polyester according to the invention can have a molecular weight of 1,000 to 70,000 g / mol.

Furthermore, the polyester according to the invention can have a melting point of 40 to 150 ° C. and in particular 90 to 150 ° C.

Furthermore, the polyester according to the invention can be made from

an aliphatic C2_g diol, preferably 1,2-ethanediol,

1,2-propanediol, 1,3-propanediol, 1,4-butanediol, 2,3-butanediol or 1,6-hexanediol,

vorzugsweise Adipin- säure oder Sebacinsäure, kondensiert worden sein.- An aromatic dicarboxylic acid, preferably terephthalic acid, and - an aliphatic

preferably adipic acid or sebacic acid, have been condensed.

While little or no improvement in the material properties of the polymer can be observed for small proportions of aromatic constituents, a drastic increase, for example of the melting point, can be observed for medium proportions of 3 to 65 and in particular 35 to 55 mol% of aromatic component of the dicarboxylic acid . Such copolyesters can show significant weight losses in environments such as compost or soil within two to three months.

Accordingly, the invention further relates to a polyester with a proportion based on an aromatic dicarboxylic acid as a monomer component of 3 to 65 and in particular 35 to 55 mol% (based on total acid content).

Another object of the present invention is to provide a work material or a material which at the same time has biodegradability and good thermal and mechanical properties. This object is achieved according to the invention by a material made from a biodegradable polyester according to the invention, the material being in the form of flat material, in particular foils, single filaments, filamentous material or molded parts, in particular injection molded, extruded or foamed molded parts. Filamentous material can be in the form of fibers, felt or fabric. The material according to the invention can be a composite material.

Exemplary applications of the material according to the invention are compiled below, namely: Foils, in particular packaging foils, for example for packaging fresh goods in retail, or for pre-packaged goods in retail, such as outer packaging (bundling of individual packaging), "skin packaging" (for small parts, such as nails), blister packaging ( Films on cardboard carriers, for example for coated tablets), protective packaging or transparent films, for example as a florist's requirement; Composting bags, in particular for household waste (for example 10 1) or garden waste (for example 100 1); Films in the medical field, for example for or as disposable clothing or gloves; Foils as or in the form of baby diapers; "Big Bag", in particular large-volume bags, for example for bulk goods, such as fertilizers or animal feed; Cover foils, for example in agriculture; Labels; or weather balloons; furthermore transport packaging, clothes bags, building foils or bed pads;

- Fibers, felts or fabrics, in particular binding material for landscaping or as a florist's requirement; Tree nets, for example to protect crops from birds; Covering nets for floors, for example against soil erosion; Nets for food packaging, for example for vegetables or fruit; Nets for selling trees or shrubs, such as Christmas trees; Fishing nets; Household wipes, such as wipes; Diaper pads; Fleece in the hygiene and cosmetics sector; Medical fleece; Extractor filters; Car interior filter; Filters for the food sector, for example for breweries; Filters for aquariums and ponds;

- extruded molded parts, in particular disposable tableware; Food packaging, for example yoghurt cups, bottles or tubes; Cosmetic packaging, for example bottles or tubes; Bag closures; Disposable items in the medical field, for example syringes or spatulas; Plastic parts for fireworks; Plastic ammunition, for example for military purposes; Cemetery and burial requirements, for example grave containers, grave lights or coffin applications; Golf tees; Pellets for controlled release, for example for fertilizer or crop protection; Carrier body for drinking water treatment; Plant pots; Support rods, for example for garden centers; Support parts for earthworks, for example when planting slopes;

- composite materials, especially beverage packaging; Composite paper cans, for example for snacks, milk powder or raisins; coated papers, for example with improved moisture resistance; Cloths, for example made of fibers according to the invention in combination with natural fibers; Press fiber mats, for example as "adhesives", also in the form of plant pots or for car interior trims; Fiber composite, for example furniture parts or load-bearing car interior linings;

- foamed materials, especially packaging chips; Packaging foam body; Plant pots; Floor aerators; Disposable tableware; Packaging trays, for example for meat, fruit, eggs or ampoules; or upholstery material.

The invention is explained in more detail below by examples, wherein the degradability of the polyesters according to the invention is also dealt with.

The question of the cause of the biodegradation of the specially composed copolyesters synthesized from aromatic and aliphatic dicarboxylic acids could be answered by examining the biological metabolizability of model oligomers. Oligomers from, for example, terephthalic acid and 1,3-propanediol are only partially biodegraded, it being possible to show a sharp section with regard to the length of the oligomers. From the degradation behavior of the model oligomers and the calculated or measured monomer distribution in the copolymer, the degree of metabolism of such copolymers in natural environments, such as compost or soil, can be concluded. 1. Synthesis of the polycondensates

For the production of statistical polyester copolymers by condensation of aliphatic diols with aliphatic and aromatic dicarboxylic acids, the monomer components specified in Table 1 are suitable, which are either available in large quantities and inexpensively by known petrochemical processes or at least partly by biotechnological ones Processes from renewable raw materials are accessible (1,3-propanediol, 2,3-butanediol, adipic and sebacic acid).

The synthesis of the polyester copolymers was carried out as described in Examples 1-9 and leads to polycondensates of structural formula 1.

Polyester copolymers

Table 1: Components for polyester copolymers diols dicarboxylic acid

1,2-ethanediol adipic acid 1,3-propanediol sebacic acid 1,4-butanediol. Terephthalic acid 2,3-butanediol 1,6-hexanediol

Examples of the polycondensates relevant to the invention, their average molecular weights, their melting points and their film properties are summarized in Table 2. Table 2: Properties of typical synthesized polyester copolymers of the general composition according to relationship (1)

ETA (x 2, y 4) poly (dimethylene-hexanedioate-co-dimethylene-terephthalate)]

PTA (x 3, y 4) poly [(trimethylene hexanedioate-co-trimethylene terephthalate)]

PTS (x 3, y 8) poly [(trimethylene-decanedioate-co-trimethylene-terephthalate)]

BTA (x 4, y 4) poly [(tetramethylene hexanedioate co-tetramethylene terephthalate)]

Polymer * consistency T film properties ° C g / mol

ETA (33/62) fiber 30,000 87 flexible, opaque ETA (44/56) fiber 39,000 135 flexible, opaque

PTA (5/95) powder 47,000 50 brittle, opaque PTA (17/83) powder 24,000 44 brittle, opaque PTA (23/77) powder 40,000 40 brittle, opaque PTA (39/61) fiber 51,000 96 flexible, opaque PTA ( 43/57) fiber 40,000 119 flexible, opaque

PTS (3/97) powder 17,500 56 brittle, opaque PTS (7/93) powder 22,000 55 brittle, opaque PTS (9/91) powder 23,000 48 brittle, opaque PTS (29/71) powder 25,000 40 brittle, opaque PTS ( 41/59) fiber 53,500 95 flexible, opaque PTS (56/44) fiber 49,000 139 f iiexiihoreli, traarnesnrt

^BTA (34/66) fiber 47,000 88 flexible, opaque BTA (42/53) fiber 46,000 117 flexible, opaque

BTA (51/49) fiber 50,000 142 flexible, opaque

in brackets: molar ratio of aromatic to aliphatic dicarboxylic acid

** determined by GPC measurement based on polystyrene standard E: dimethylene T: terephthalic acid A: adipic acid

P: trimethylene S: sebacic acid

B: tetramethylene

2. Thermal properties

The thermal properties are characterized by the melting points (see Table 2). In the case of copolyesters with 1,3-propanediol as diol components such as PTA and PTS, which have a middle position due to their C number, the melting behavior became dependent the proportion of terephthalic acid examined in more detail. Up to a terephthalic acid content of approx. 30 mol% (based on the acid content in the copolyester) there are melting points and material properties that correspond to those of the pure aliphatic polyester (e.g. SP36: Saturated polyester made of 1,3-propanediol and adipic acid. SP3iθ: Saturated polyester from 1,3-propanediol and sebacic acid). The purely aliphatic polyesters have proven to be biodegradable, but have a strong deficit in material properties (Witt, Müller, Augusta, Widdecke and Deckwer, Macrom. Chem. Phys. 195 (1994), 793-802). As Fig. 1 shows, melting points and material properties for the investigated PTA and PTS copolyesters rise suddenly at a terephthalic acid content (T content) of approx. 35 mol%. As will be shown in the following, there is a narrow, optimal range between degradability on the one hand and material properties on the other hand for such copolyester systems, which lies at T fractions of approx. 35-50 mol%. The lower part results from the minimum requirements for the usage properties (such as melting points of at least 90 ° C, sufficient film and fiber properties), the upper part from the requirement for biodegradability (see Sections 4 and 5).

3. Stability against hydrolysis

In order to be able to clearly assess the biological degradation studies, it was examined to what extent the synthesized polyester copolymers are subject to hydrolytic degradation. As described in Example 10, these tests were carried out with the exclusion of microorganisms at room temperature and 60 ° C.

After exposure to room temperature for three months, there were no weight losses or other measurable degradation phenomena in films made from PTA and PTS copolyesters.

In the tests at 60 ° C, there were slight or slight weight losses after 10 weeks of exposure. For copolyesters these were PTS (41/59) and PTS (56/44) _C a. o, o% and for the copolyesters PTA (39/61) and PTA (43/57) approx. 3.5 and 6 ^% . Thus, stronger chemical hydrolysis was observed in the PTA esters with adipic acid as the aliphatic dicarboxylic acid component than in the PTS copolyesters with sebacic acid as the dicarboxylic acid component. As shown in the following section, the weight however, pleasure from hydrolysis is only a fraction of what is achieved during biodegradation at 60 ° C (composting).

4. Biodegradation

Investigations in the aquatic system

Polyester foams (25 mm 0, 100 microns thickness) were treated in 100 ml liquid volume at 25 ° C with stirring and air supply. A corresponding mineral salt medium and an earth or compost eluate were added. As shown in Fig. 2, PTA and PTS copolyesters are well degraded up to a terephthalic acid content of 30% in the specified aquatic system. A breakdown of the statistical copolyesters with terephthalic acid components> 30 mol% (based on the acid component) could not be observed in the aquatic system. Obviously, the presence of the microbial mixed culture and the mineral salts is not sufficient for microbial degradation in the observed period.

Degradation studies in the case of burial

As described in Example 11, degradation studies were carried out by digging into soil in accordance with DIN 53739D at a relative humidity of 60% and at room temperature. The results of these investigations are shown in Fig. 3. It can be seen from this that the polyester copolymers with low proportions of terephthalic acid (PTS (41/59) and PTA (39/61)) can no longer be isolated after 7 and 8 weeks, respectively.

PTA (43/57) showed a weight loss of 14% after 8 weeks.

In contrast, no weight loss and no visual evidence of a microbial attack could be found for PTS (56/44).

Composting at 60 ° C

In addition to the digging tests, the degradability in compost was checked at 60 ° C with 60% relative humidity. A compost of green waste from the post-rotting phase of the Watenbüttel composting plant (Braunschweig) was used. The results in Fig. 4 shows the dependence on the treatment time. The statistical copolyesters with adipic acid (PTA) can no longer be isolated from the compost after 6-7 weeks. The PTS copolyesters are also attacked biologically and show significant weight losses, which are significantly greater than can be expected after purely chemical hydrolysis. For PTS

(41/59) the weight loss is approx. 40% and for PTS (56/44) approx. 20% after a total of 10 weeks of treatment.

5. Use of model oligomers with terephthalic acid as the acid component

Most known

Polyesters with purely aliphatic acids can be completely biodegraded. The degradation results shown under 4. show that this is also possible if the proportion is aromatic

Dicarboxylic acid does not exceed a certain value. In order to obtain information about which structural units can still be broken down with aromatic dicarboxylic acids, investigations were carried out with model oligomers, 1, 3- as the diol.

Propanediol was used because of its middle position and terephthalic acid. The synthesis of these oligo-trimethylene terephthalates or poly-trimethylene terephthalates (PTMT) is in example

12 described. Table 3 shows the average molecular weights (determined by GPC with

Polystyrene as standard) and their melting points.

Tab. 3: Aromatic PTMT oligomers through 1,3-propanediol excess

Oligomer M _w [g / mol] T _m [° C] 1,3-propanediol excess [mol%]

PTMT 1 2630 194 20 PTMT 2 2010 184 50 PTMT 3 1680 176 100

These model oligomers were examined in a modified storm test with 1% compost eluate as inoculum, the biopolymer polyhydroxybutyrate / valerate (PHB / V) being used for comparison. The results are shown in Fig. 5 in the form of CO ₂ development as a function of the observation time. It can be seen from this that the degradable fraction increases significantly with decreasing average molecular weight of the aromatic oligomers. Partial degradation was achieved after less than 20 days. After this time, the CO ₂ development only increases slightly. It is remarkable that the adaptation time was in all cases even shorter than when PHB / V was broken down. Table 4 shows the C balance sheets, which are in principle well fulfilled. To prepare the C balances, protein was also determined in the Lowry biomass and residual polymer after the biomass was destroyed by hypochlorite. The dissolved components were determined by determining the chemical oxygen demand.

Tab. 4: C balance of the aromatic PTMT oligomers after microbial degradation in the Sturm test (4 weeks, 25 ° C, 1% by volume compost eluate, * PHB / V served as "degradation standard")

Carbon [% of theory] determined via

Oligomer a) b) c) Residual Σ a, b, c + CO ₂ development Biomass Soluble polymer Residual polymer components (COD)

PTMT 1 10.2 <0.1 0.0 87.1 97.3 PTMT 2 16.3 <0.1 2.5 78.8 97.4 PTMT 3 23.2 <0.1 4.0 74, 9 102.2

PHB / V * 54.5 46.6 3.8 0.0 104.9

The distribution of the oligomers in PTMT 1 - 3 was examined by gel permeation chromatography before and after degradation. The molecular weights Mps obtained from the GPC refer to polystyrene as the calibration standard. The average difference between these values (= 377, excluding the peak "CD") based on the mass of the constitutional repeating unit of the PTMT oligomers (= 206) gives a factor of 0.55. Multiplying M s ¹ by this factor gives M _GPC . With the help of mass spectroscopy, after GPC fractionation, a complete assignment of all polymerization products (MH ⁺ _MS ) was obtained. The peak assignment obtained in this way is given in Table 5 and Fig. 6 shows the chromatogram for the synthesized oligomer mixture PTMT3 before it is used in degradation studies. The peak CD occurring at an elution time of 8.84 min is cyclic

'D PS - = polystyrene standard Dimer that occurs as a by-product of PTMT synthesis.

Tab. 5: Allocation of the mass peaks in the GP chromatogram

Peak M _{ps based} on GPC M _GPC [g / mol] M _jj , [g / mol] MH ^{+ MS} from mass to PS standard [g / mol] (= Mps / 0.55) spectrometry [g / mol]

1 420 231 282 283

CD (540) (297) 412 413

2,780,429,488,489

3 1160 638 694 695

4 1550 853 900 901

Fig. 7 now shows the GP chromatograms of PTMT 1 - 3 before and after the breakdown in the storm test. It can be seen from this that the partially degraded constituents are always the same peaks (n = 1 and 2). The degradable constitutional repeating unit is thus

Constitution"!!" R »p» tl «r« lnl> »lt (M _(h - 206)

with n <2. Since the proportion of these degradable repeat units (n <2) in the oligomer increases with decreasing molecular weight, the proportion of the degraded oligomer mass also increases (see Fig. 5 and CO ₂ development in Table 4). Repetition of the degradation tests with 1 and 10 vol inoculum over a period of 8 weeks at 30 ° C. gave completely identical chromatograms in the GPC examinations before and after the degradation. Even with composting at 60 ° C., no degradation of aromatic sequences with n> 3 of the PTMT oligomers was observed. This means that the investigated period (8 weeks) and the specified conditions exclude the degradability of aromatic sequences with n> 3. The specified optimal range of 35-50 mol% T-part in the acid part cannot be shifted to larger T-parts without increasing the proportion of non-degradable aromatic sequences in the copolyester. Since PTA and PTS copolycondensates are not statistical alternating, but statistical polyesters, the statistical distribution depending on the monomer composition was calculated to estimate the degree of biodegradability. Fig. 8 shows the theoretical dependence of the sequence length distribution n> 2 on the monomer concentration (T content). For the statistical copolyesters used in the degradation studies, the proportions of aromatic block lengths given in Tab. From this it can be seen that the proportion of degradable aromatic constitutional repeat units in the copolymer is over 90% if the proportion of terephthalic acid in the acid portion does not exceed 50%.

Tab. 6: Percentage of aromatic sequences with n 3 in polyester copolymers

Polyester% by weight of aromatic 1% by weight of aromatic and 2 sequences in the polymer Sequences> 3 in the polymer

PTA (39/61) 94.3 5.7 PTA (43/57) 92.3 7.7 PTS (41/59) 94.1 5.9 PTS (56/44) 84, 7 15, 3

Examples

example 1

Synthesis of poly [(trimethylene hexanedioate) -co-trimethylene terephthalate)] PTA (39/61)

0.207 mol of 1, 3 propanediol, 0.074 mol of dimethyl terephthalate (DMT), 0.112 mol of adipic acid and 0.04 g of zinc acetate dihydrate as a catalyst are polycondensed by condensation in the melt. A 100 ml three-necked flask with vacuum stirring system, nitrogen feed and condenser is used as the polymerization reactor. The reaction flask is flushed with nitrogen and gradually heated to 170 ° C. in the course of 10 h with stirring (50 rpm). The majority of the condensate that forms condenses off. The pressure is then gradually reduced to 0.01 mbar and condensed under GPC control to the desired molecular weight of M ^ = 30,000-70,000 g / mol. In this case, excess diol also condenses. The copolyester is cooled under vacuum, repeatedly dissolved in chloroform and precipitated in ice-cold methanol (technical grade), and then dried in vacuo for 24 hours.

Example 2

Synthesis of poly [(trimethylene hexanedioate) -co-trimethylene terephthalate)] PTA (43/57)

0.207 mol of 1,3-propanediol, 0.093 mol of dimethyl terephthalate (DMT), 0.093 mol of adipic acid and 0.04 g of zinc acetate dihydrate are condensed as in Example 1.

Example 3

Synthesis of Poly [(trimethylene decanedioate) -c £ -trimethylene terephthalate)] PTS (41/59)

0.207 mol of 1,3-propanediol, 0.074 mol of dimethyl terephthalate (DMT), 0.112 mol of sebacic acid and

0.05 g of zinc acetate dihydrate are condensed as in Example 1. Example 4

Synthesis of Poly [(trimethylene decanedioate) -co-trimethylene terephthalate)] PTS (56/44)

0.207 mol of 1,3-propanediol, 0.093 mol of dimethyl terephthalate (DMT), 0.093 mol of sebacic acid and 0.05 g of zinc acetate dihydrate are condensed as in Example 1.

Example 5

Synthesis of Poly [(ethylene hexanedioate) - o-ethylene terephthalate)] ETA (38/62)

, 220 mol of 1,2-ethanediol, 0.080 mol of dimethyl terephthalate (DMT), 0.112 mol of adipic acid and 0.04 g of zinc acetate dihydrate are condensed as in Example 1.

Example 6

Synthesis of Poly [(ethylene hexanedioate) -cj -ethylene terephthalate)] ETA (44/56)

, 022 mol 1, 2 - ethanediol, 0.100 mol dimethyl terephthalate (DMT), 0.100 mol adipic acid and 0.04 g zinc acetate dihydrate are condensed as in Example 1.

Example 7

Synthesis of poly [(tetramethylene hexanedioate) -co-tetramethylene terephthalate)] BTA (34/66)

0.165 mol of 1,4-butanediol, 0.045 mol of dimethyl terephthalate (DMT), 0.105 mol of adipic acid and 0.04 g of zinc acetate dihydrate are condensed as in Example 1. Example 8

Synthesis of poly [(tetramethylene hexanedioate) - σ-tetramethylene terephthalate)] BTA (42/58)

0.165 mol of 1,4-butanedioi, 0.060 mol of dimethyl terephthalate (DMT), 0.090 mol of adipic acid and 0.04 g of zinc acetate dihydrate are condensed as in Example 1.

Example 9

Synthesis of poly [(tetramethylene hexanedioate) -co-tetramethylene terephthalate)] BTA (51/49)

0.165 mol of 1,4 butanedioi, 0.075 mol of dimethyl terephthalate (DMT), 0.075 mol of adipic acid and 0.04 g of zinc acetate dihydrate are condensed as in Example 1.

Example 10

The resistance to hydrolysis at room temperature is determined on the statistical copolyesters prepared in Examples 1-4. Polyester films are sterilized with ethanol and shaken in sterile water at room temperature (150 rpm). No changes in weight loss and chain splitting (determined by GPC measurements) can be observed in the examined period of 3 months. In addition, the resistance to hydrolysis at 60 ° C. is determined on the statistical copolyesters prepared in Examples 1-4. Polyester films are sterilized with ethanol and shaken in sterile water at 60 ° C (150 rpm). The statistical copolyesters PTS (41/59) and PTS (56/44) showed no weight loss after 10 weeks, the PTA (39/61) and PTA (43/57) 3.5% and 6% weight loss, respectively.

Example 11

The degradability of the statistical copolyesters is checked in an earth digging test (DIN 53739D). For this purpose, test specimens with a wall thickness of 100 mm and a diameter of 25 mm are welded into polyethylene nets and buried in soil with 60% relative humidity. The The test is carried out at approx. 20 ° C. The mass loss of the samples is determined at time intervals, ie the percentage loss in weight of the polyester film. For this, a test specimen is taken at every time interval, with dist. Washed water and dried in vacuo for 24 h. This removed specimen is then not used again in the burial test, but is available for analytical investigations. The test was carried out with the following polymeric materials: PTA (39/61), PTA (43/57), PTS (41/57) and PTS (56/44). The results are Fig. 3 can be seen.

In addition, the degradability of the statistical copolyesters is checked in a composting at 60 ° C and 60% relative humidity. The specimen dimensions, burials and withdrawals correspond to the earth digging. The compost based on green waste comes from the post-rotting phase and was taken from the Watenbüttel composting plant (Braunschweig). The results are shown in Fig. 4.

The mass loss is plotted against the time (in weeks) in the diagrams. When digging into the ground, the copolyesters PTA (39/61) and PTS (41/59), with lower terephthalic acid content, can no longer be isolated after 7 - 8 weeks. After this time, the PTS (43/57) showed a weight loss of 14%. No weight loss in the excavation

Room temperature showed PTS (56/44). Example 10 shows that there is no hydrolytic influence at room temperature in the observed period for the polyesters examined. One can speak of a microbial degradation.

At 60 ° C. composting, all polyesters produced in Examples 1-4 show degradation. Here, the PTA copolyesters with adipic acid as the aliphatic dicarboxylic acid component can no longer be isolated after only 6-7 weeks. The copolyesters with sebacic acid as the aliphatic dicarboxylic acid component show significant weight losses (PTS (41/59) approx. 0%, PTS (56/44) approx. 20% after 10 weeks). Example 10 illustrates that the hydrolytic influence at 60 ° C. fulfills a function that supports microbial degradation. This influence is more pronounced with adipic acid as an aliphatic dicarboxylic acid component than with sebacic acid as an aliphatic dicarboxylic acid component. By a suitable choice of the monomer components and the stochiometry of the statistical copolyesters, tailored polyesters can thus be produced with regard to the rate of degradation and material properties. Example 12

Synthesis and degradation of model oligomers of poly (trimethylene terephthalate) (PTMT)

0.131 mol of 1,3-propanediol, 0.131 mol of DMT and 0.04 g of zinc acetate dihydrate are each condensed with 20, 50 and 100 mol% excess of 1,3-propanediol in the melt at 210 ° C. under a nitrogen atmosphere and normal pressure . The oligomers are ground, washed successively with water and diethyl ether and dried in vacuo for 24 h. The aromatic oligomers listed in Table 3 result.

The degradation of the obgomer is examined in a modified storm test. The only carbon source are the PTMT oligomers. 1% by volume of a compost eluate serves as the degradation culture and a mineral salt medium according to DIN 53739C serves as the nutrient source. The test is carried out at 25 ° C., an air supply of approx. 2 l / h and in 100 ml of liquid volume.

While the oligomer fractions with n <3 are subject to extensive microbial degradation, fractions with n> 3 show no degradation by the microorganisms. The results are shown in Figure 7.

Example 13

Synthesis and degradation of model oligomers of poly (ethylene terephthalate) (PET)

0.161 mol of 1,2-ethanediol, 0, 161 mol of DMT and 0.04 g of zinc acetate dihydrate are condensed with 100 mol% excess of I, 2-Ethandioiin the melt at 210 ^* C, under a nitrogen atmosphere and at normal pressure. The oligomer is ground, washed successively with water and diethyl ether and dried in vacuo for 24 h.

The biodegradation was examined as in Example 12 and gives analogous results. Example 14

Synthesis and degradation of model oligomers of poly (tetraethylene terephthalate) (PBT)

0.111 mol of 1, 4-butanediol, 0.111 mol DMT and 0.04 g of zinc acetate dihydrate are condensed with 100 mol% excess of i.4-Butandioiin the melt at 210 ^* C, under a nitrogen atmosphere and at normal pressure. The oligomer is ground, washed successively with water and diethyl ether and dried in vacuo for 24 h.

The biodegradation takes place as described in Example 12 and gives analogous results.

Claims

claims 1. Biodegradable polyester (in particular in the form of a material or material), which is degraded in the natural environment under the action of microorganisms, for example according to DIN 53739D or ASTM D5338-92, characterized in that the polyester consists of an aliphatic polyol and a aromatic polycarboxylic acid and at the same time an aliphatic polycarboxylic acid has been produced as monomer components and has constitutional repeating units or recurring units which (i) on the one hand consist of polyol and aromatic polycarboxylic acid and (ii) on the other hand consist of polyol and aliphatic polycarboxylic acid, more than 90% of the units according to (i) being directly linked to none or at most one further unit according to (i). 2. Polyester according to claim 1, characterized in that the polyester has a molecular weight of 1000 to 70000 g / mol. 3. Polyester according to claim 1, characterized in that the polyester has a melting point of 40 to 150 ° C and in particular 90 to 150 ° C. 4. Polyester according to one of claims 1 to 3, characterized gekenn¬ characterized in that the polyester an aliphatic C ₂ -g diol, preferably 1, 2-ethanediol, 1, 2-propanediol, 1, 3-propanediol, 1,4-butanediol, 2, 3-butanediol or 1, 6-hexanediol, - An aromatic dicarboxylic acid, preferably terephthalic acid, and - an aliphatic C2_ _] _ _Q dicarboxylic acid, preferably Adipic acid or sebacic acid, has been condensed. 5. Polyester according to any one of claims 1 to 4, characterized in that the polyester has a proportion which is based on an aromatic dicarboxylic acid as a monomer component, from 3 to 65 and in particular 35 to 55 mol% (based on total acid content ). 6. Material made of a biodegradable polyester according to one of the preceding claims in the form of flat material, in particular films, single filaments, fila entösem material or molded parts, in particular injection molded, extruded or foamed molded parts. 7. Material according to claim 6 in the form of fibers, felt or fabric as a filamentous material. 8. Material according to claim 6 or 7 as a composite material.