DE69631412T2 - Process for the preparation of aliphatic copolyesters - Google Patents

Description

The present invention relates to the production of high molecular weight aliphatic copolyesters, which thanks to their high molecular weight through each of the all-purpose plastics molding processes used, such as injection molding, blow molding and extrusion molding, to desired Molded articles can be shaped. In particular, the present invention relates to manufacture aliphatic copolyesters that are biodegradable, the one Molecular weight, high enough for practical use and which is excellent thermal stability, tensile strength and the like.

So far there have been polyesters that like molded articles Foils and fibers should be molded, high molecular weight polyester with a number average molecular weight of 10,000 or more. These high molecular weight polyesters were on those Polyester limited, that from terephthalic acid and ethylene glycol or 1,4-butanediol (since the Polyesters of this type contain an aromatic component, i.e. H. their dicarboxylic acid component If aromatic, they are subsequently called aromatic polyesters referred to), and those polyesters that have no aromatic component included, d. H. aliphatic polyesters, were rarely used for molding used. The reasons, why aliphatic polyester is not so much put into practice were close the following: (1) the melting point of aliphatic polyester would be relative low; and (2) number average aliphatic polyesters the molecular weight of 15,000 or more would not be known by any Polycondensation reaction obtained because in the course of the reaction thermal decomposition tends to occur and aliphatic polyesters, whose number average molecular weight is approximately 10,000, none would sufficiently high strength for have practical use.

As in JP-OSen 189822/1992 and 287043/1993, an aliphatic polyester with high molecular weight and with a urethane bond through a Process obtained by using an isocyanate as a coupler Use that is added to a polyester diol, whose end group is essentially a hydroxyl group, the Number average molecular weight is 5,000 or more is preferred 10,000 or more, and which is in the molten state, by heating to its melting point or above. So far the As is known to inventors of the present invention, such Difficulties in dependence to appear from the molding conditions used such as the undesirable coloring of the Polyester and the unfavorable generation of microgels, though High molecular weight aliphatic polyester with a Urethane bond can be formed by one of the molding processes that for all-purpose plastics be used.

As suggested in JP-OS 310898/1993 a high molecular weight aliphatic polyester, whose end group is essentially a hydroxyl group and whose Number average molecular weight is 25,000 to 70,000, synthesized are by esterifying a glycol component and an aliphatic dicarboxylic acid, to obtain a polyester diol and by subjecting the polyester diol a glycol elimination reaction, which in the presence of a catalyst at a temperature in the range from 180 to 230 ° C is carried out under a highly reduced pressure of 0.005 to 0.1 mmHg. As far as we know, however, it is difficult industrially Achieve high vacuum condition.

In addition, JP-OS 43665/1993 discloses a process for producing an aliphatic polyester with a reduced viscosity from 0.67 to 0.89 in which an aliphatic oxycarboxylic acid such as Lactic acid or glycolic acid in the presence of a germanium compound in an inert gas stream or Thermally dehydrated and polycondensed under reduced pressure becomes. As far as we know, those own foils and others Molded articles, which are obtained from this aliphatic polyester, but none sufficiently high mechanical strength for practical use.

In addition, the JP-OSen beat 228675/1995 and 189822/1995 a process for the preparation of an aliphatic Relatively high molecular weight polyester. As far as we know, however, the method requires the use of an organic one Solvent, what the need for removal and recovery of the used solvent would entail and the so recovered solvent would one Require cleaning before its reuse, which makes the process would not be considered beneficial in commercial practice.

An object of the present invention is to provide aliphatic copolyesters that are sufficient high molecular weight for have practical use, excellent thermal stability, tensile strength and the like and which are also biodegradable are.

It has been found that when an aliphatic diol and an aliphatic dicarboxylic acid or a derivative thereof, main components are copolymerized with a specific amount of an aliphatic monohydroxymonocarboxylic acid such as lactic acid or glycolic acid in the presence of a catalyst comprising a germanium compound, the polymerization rate is drastically increased , so that an aliphatic polyester copolymer having a high molecular weight and having a number average molecular weight of 10,000 or more can be obtained extremely easily without using a chain extender can. The present invention has been accomplished on the basis of this finding.

The present invention is therefore intended provide a method of making an aliphatic copolyester. The process for producing an aliphatic copolyester, which is the reaction of an aliphatic dicarboxylic acid with an aliphatic Includes diol under condensation conditions for polyester production, is characterized in that the reaction in the presence of a Catalyst comprising a germanium compound and an aliphatic monohydroxymonocarboxylic is carried out in an amount of 2 to 20 mol per 100 mol of the aliphatic dicarboxylic acid, to obtain an aliphatic copolyester whose number average the molecular weight is at least 10,000.

The present invention is thus for an improvement in the process for producing an aliphatic Directed polyester in which an aliphatic carboxylic acid and an aliphatic diol with each other under the condensation conditions be implemented for polyester production. The improvement excludes use a germanium catalyst and a specific amount of an aliphatic monohydroxymonocarboxylic in the condensation reaction. Through this improvement, the present invention shown success in obtaining aliphatic polyester with high molecular weight, especially with a number average the molecular weight of 10,000 or more; it would have been impossible to have such a high molecular weight through conventional to achieve simple polycondensation reactions.

Since an aliphatic monohydroxymonocarboxylic acid in the Polycondensation reaction is present, it goes without saying that the aliphatic polyester produced is a copolyester. It is considered an interesting finding that an aliphatic Polyester with a raised Molecular weight can be obtained by using the aliphatic Polyester can assume such a copolymeric structure and by simultaneously reacting in the presence of a specific Catalyst, d. H. a germanium compound.

In addition to a high molecular weight the aliphatic copolyester of the present invention has one relatively high melting point and a sufficiently high strength for the practical use. Because the copolyester is an introduced hydroxycarboxylic acid component contains it also has reduced crystallinity and is therefore flexible. Also owns the aliphatic according to the invention High molecular weight polyester an excellent biological Degradability.

Preferred embodiments of the invention will now be described.

1. Basis the reaction for producing aliphatic polyester in the present invention

As previously mentioned, the method according to the invention comprises to produce an aliphatic copolyester basically the Step of implementing an aliphatic dicarboxylic acid with an aliphatic diol under the condensation conditions Polyester production.

The "condensation conditions for polyester production" close here not just the conditions under which a dehydration reaction between the essential bifunctional reactants, i.e. H. one dicarboxylic acid and a diol but also the conditions under which a condensation reaction carried out is when of a functional derivative / functional derivatives use is made of one or both of these reactants. To the Example is a functional derivative of an aliphatic dicarboxylic acid Di-lower alkyl esters thereof. In this case the condensation reaction takes place in an ester exchange reaction instead of elimination a lower alkanol is accompanied. If the aliphatic dicarboxylic acid Anhydride or acid halide on the other hand, the condensation reaction naturally goes beyond one Addition, followed by dehydration and / or ester exchange, or about dehydrohalogenation continues. Also included in the "condensation conditions for polyester production " here the use of a provisional provided oligomers that include such low Molecular weight such as bis-ester, the oligomer then the further condensation with elimination of the diol used is subjected to a polymer, as in the manufacture of Polyethylene terephthalate performed in which bis (β-hydroxyethyl) terephthalate is provided, which then undergoes deglycolation, or which is usually as "polycondensation" to a condensation product with higher Molecular weight is called.

Furthermore, the reduction in pressure and / or the application of heat and / or the use of an azeotropic agent in the case of dehydration or of alkali in the case of dehydrohalogenation to adapt are to easily those low molecular weight by-products to eliminate those formed in the course of the condensation reaction become, d. H. Water, lower alkanol, diol or hydrogen halide, for the exterior of the Reaction system also specific examples of the "condensation conditions for polyester production ".

The use is under the "condensation conditions for polyester production" a dicarboxylic acid or a di-lower alkyl ester thereof, especially the former, as aliphatic dicarboxylic acid and the reduction in pressure and / or the application of heat is preferred.

The degree of pressure reduction and / or the application of heat becomes common Lich increased as the condensation reaction progresses, ie as the degree of polycondensation of the polymer produced increases.

One of the characteristics of the present Invention resides in the reaction between those described above essential bifunctional monomer components that are used under the condensation conditions Polyester production is to be effected in the presence of a specific Amount of an aliphatic monohydroxymonocarboxylic acid (hereinafter referred to as aliphatic oxycarboxylic designated) performed which is also bifunctional. Of course, this is aliphatic Oxycarboxylic acid equivalent in relation to the essential monomer components described above on their hydroxyl and carboxyl groups. It is therefore considered that the aliphatic oxycarboxylic acid with the above essential monomer components to obtain a Copolyester reacts. For this reason, this is in the present Invention specified requirement that "the reaction under the condensation conditions carried out for polyester production will ", too applied to this aliphatic oxycarboxylic acid. Therefore, the in "Aliphatic oxycarboxylic acid" used in the present invention are also functional Derivatives thereof, e.g. B. Lower alkyl esters thereof (the details are given below).

As can be seen from the description above is close the terms "aliphatic Dicarboxylic acid "and" aliphatic oxycarboxylic acid "(which of course is a aliphatic monohydroxymonocarboxylic acid means) for the explanation of the present invention are used, each functional Derivatives that are in the sense described above.

2. Basis of the reaction for producing aliphatic polyester in the present invention (Secondly)

One of the reactants is that of the reaction be subjected to the condensation conditions described above carried out for polyester production is an aliphatic dicarboxylic acid. It is from the above Description apparent that this aliphatic dicarboxylic acid is functional Derivatives of which includes z. B. di-lower alkyl esters thereof.

The aliphatic dicarboxylic acids can thus be represented by the following formula: R ⁰ -CO-R ¹ -CO-R ⁰ (1) wherein R ^{1 is} a direct bond or a divalent aliphatic group and R ^{0 is} OH or a functional derivative of the carboxyl group, e.g. B. -OR ^a (R ^a : lower alkyl such as C ₁ -C ₄ -alkyl) or -X (X: halogen such as chlorine) or an anhydride group (-CO-O-CO-) which is defined by the two (CO-R ⁰ ) groups is formed. A preferred -OR ^a is OH or an anhydride group (-CO-O-CO-) which is formed by the two -OR ^a groups; the former, OH, is particularly preferred.

In the present invention, the "aliphatic group" includes an "alicyclic group". In addition can the aliphatic group may also be one that contains an ether oxygen contains as long as it does not adversely affect the advantages of the present invention.

Preferred specific examples of R ¹ are - (CH ₂ ) _m -, wherein m is 0 or an integer from 1 to 10, preferably 0 or an integer from 1 to 6. Particularly preferred specific examples of the aliphatic dicarboxylic acid are therefore those represented by the following formula: HOCO- (CH ₂ ) _m -COOH (1a).

Specific examples of such aliphatic dicarboxylic acids conclude oxalic acid, Succinic acid, glutaric acid, adipic acid, sebacic acid, dodecanedioic acid, cyclohexanedicarboxylic acid (in particular 4,4'-), lower Alcohol esters thereof, succinic anhydride and adipic anhydride on. Among them are succinic acid, adipic acid, sebacic, Anhydrides thereof and lower alcohol esters thereof in terms of preferred physical properties of the resulting copolymers, and succinic acid, Succinic anhydride and a mixture of these are particularly preferred. Also preferred is a mixture of (i) succinic acid and / or its anhydride and (ii) adipic acid. These aliphatic dicarboxylic acids can used either individually or in combination of two or more become.

An aliphatic diol represented by the following formula is suitable as the aliphatic diol, another reactant to be used in the production of an aliphatic polyester: HO-R ² -OH (2) wherein R ^{2 represents} a divalent aliphatic group. It is apparent from the above description that the "aliphatic group" indicated by R ² includes an "alicyclic group" and that it may contain an ether oxygen if necessary.

Preferred examples of the divalent aliphatic hydrocarbon group indicated by R ² include those represented by - (CH ₂ ) _n - (n is an integer from 2 to 10). Of these aliphatic hydrocarbon groups, those in which n is an integer from 2 to 6 are preferred.

Preferred aliphatic diols are therefore represented by the following formula: HO- (CH ₂ ) _n -OH (2a).

Preferred divalent alicyclic hydrocarbon groups are those represented by the formula (2), wherein R ^{2 has} a cyclic structure and has 3 to 10 carbon atoms. Particularly preferred alicyclic hydrocarbon groups are those of the formula (2) in which R ^{2 has} 4 to 6 carbon atoms. The alicyclic hydrocarbon groups can be of such a hybrid structure that it comprises a cyclic unit connected to a linear unit.

Specific examples of that through the aliphatic diol represented by the above formula include ethylene glycol, Trimethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,4-cyclohexanediol and 1,4-cyclohexanedimethanol on. Of these, 1,4-butanediol is physical Properties of the resulting copolymers are particularly preferred. These aliphatic diols can used either individually or in combination of two or more become.

3. Through the Improvements made by the present invention

Improvements in the above Basic process for producing an aliphatic polyester, the made by the present invention are such that a specific amount of an aliphatic oxycarboxylic acid in the condensation reaction system is included, and that a catalyst containing a germanium compound includes, for the condensation reaction is used. Through these improvements will it be possible to obtain a polyester whose molecular weight is 10,000 or is more preferred 20,000 or more, e.g. B. 10,000 to 200,000.

(1) Aliphatic oxycarboxylic acid

Those in the present invention defined "aliphatic Oxycarboxylic acid "is one such which is added in the reaction system when the reaction is below the condensation conditions for polyester production are carried out, and closes accordingly also functional derivatives thereof.

Therefore, the aliphatic oxycarboxylic acid can be represented by the following formula: HO-R ³ -CO-R ⁰ (3) wherein R ^{3 is} a divalent aliphatic group with preferably 1 to 11 carbon atoms, particularly preferably 1 to 6 carbon atoms. R ³ may also be either alicyclic or be a group containing an ether oxygen therein, such as R ¹ and R ² described above.

R ⁰ can be defined by the same definition as previously described with respect to aliphatic dicarboxylic acid (it should be noted that both R ⁰ groups need not be the same in a given reaction system). However, since this comonomer component is a monohydroxymonocarboxylic acid, it may be necessary to point out that there is a difference between R ⁰ in this component and that in the aliphatic dicarboxylic acid. Namely, in the case of oxycarboxylic acid, R ⁰ can not only represent a lower alkyl ester as in the case of dicarboxylic acid, but can also form an intramolecular ester. The anhydride of the ester in the latter case is an intermolecular anhydride. Preferred is -OR ⁰ in formula (3) -OH.

worin a 0 oder eine ganze Zahl von 1 bis 10 ist, bevorzugt 0 oder eine ganze Zahl von 1 bis 5.In the present invention, a particularly preferred aliphatic oxycarboxylic acid is one represented by the following formula, which provides remarkable polymerization reactivity according to the present invention:

wherein a is 0 or an integer from 1 to 10, preferably 0 or an integer from 1 to 5.

Specific examples of the aliphatic oxycarboxylic acid include lactic acid, glycolic acid, 2-hydroxy-n-butyric acid, 2-hydroxycaproic acid, 2-hydroxy-3,3-dimethylbutyric acid, 2-hydroxy-3-methylbutyric acid, 2-hydroxyisokaproic acid and a mixture thereof. In the event that this aliphatic oxy carboxylic acids have optical isomers, it is possible to use any of the D-isomer, L-isomer and a racemic mixture thereof. In addition, they can be either in the state of a solid or a liquid or in the form of an aqueous solution. Of these, lactic acid and glycolic acid are preferred, and particularly preferred are lactic acid which can remarkably speed up the polymerization rate and which is readily available. A 30-95% aqueous solution of the acid is preferred because such a solution is readily available. These aliphatic oxycarboxylic acids can be used either individually or in combination of two or more.

(2) Polycondensation reaction / use of catalyst

The polycondensation between one Diol and a dicarboxylic acid, including the reaction between functional derivatives of these reactants, in particular a reaction in which a functional derivative of a dicarboxylic acid is known. Moreover it is also known that oxycarboxylic acids with the functionalities of these essentially two reactants participate in the polycondensation.

The condensation reaction in the present invention may be similar Way with due consideration carried out be that of a catalyst that is a germanium compound includes, is used under the reaction conditions that appropriate according to the conventional condensation reactions selected become dependent of the reactants to be used and / or the desired one Polymerization.

In a preferred embodiment of the present invention is the carboxyl functionality of the reactant a carboxyl group, so that the condensation reaction via a Dehydration as mentioned before progresses. It is therefore preferred to use such a polycondensation reaction in the presence of essentially no water. Therefore is a preferred embodiment the present invention to carry out the condensation reaction in the presence of essentially no water. However, water is generally a suitable solvent for the three reactants used in this reaction, and in the event that the catalyst used is soluble in an aqueous medium, it is acceptable to use only a small amount of water to provide some of the reactants and / or the catalyst, or to have it in the reaction system as a solution. This is why the requirement "in the presence of essentially none Water " becomes. In addition to using no water, it is also preferred to use essentially no organic solvent unless it is because it will be for the purpose of azeotropic removal of water and by-products the condensation reaction used. For this reason, it is preferred embodiment the present invention to carry out the condensation reaction in the presence of essentially no solvent.

The amount is stoichiometric of the aliphatic diol used is essentially equimolar to that of the aliphatic dicarboxylic acid used. Generally however, the aliphatic diol is used in an excess of 1 to 50 mol%, preferably 5 to 30 mol% over the amount of aliphatic dicarboxylic acid used, 101 up to 150 mol, preferably 105 to 130 mol per 100 mol of the aliphatic dicarboxylic acid, because it can escape in the course of the polycondensation reaction.

If the added amount of aliphatic oxycarboxylic acid is too small you don't get the benefits of adding. If, on the other hand, the Amount of aliphatic oxycarboxylic acid is too high, the resulting may Copolyester insufficient in heat resistance and mechanical Properties. For this reason, the amount to be added the aliphatic oxycarboxylic acid 2 to 20 mol to 100 mol of the aliphatic dicarboxylic acid used.

There is no particular time limit and the manner of adding the aliphatic oxycarboxylic acid as long as it is present in the polycondensation reaction, and the following Species can as Examples are: (1) a way in which a solution, e.g. B. an aqueous Solution, aliphatic oxycarboxylic acid, in which a catalyst is dissolved was added to the reaction system; and (2) a way in which the aliphatic oxycarboxylic acid is added simultaneously with the addition of a catalyst if filled the starting materials become.

The aliphatic copolyester of the present invention can be produced by performing the condensation reaction in the presence of a polymerization catalyst. A germanium compound is suitable as a catalyst. There is no particular limitation on the germanium compound as long as it has catalytic activity for polycondensation, and each of the inorganic germanium compounds such as. B. germanium oxide and germanium halides (z. B. germanium chloride), and the organic germanium compounds, such as. B. tetraalkoxy germanium compounds (alkoxy: C ₁ -C ₁₂ , preferably about C ₁ -C ₆ ) can be used. Of these, germanium oxide, tetraethoxy germanium and tetrabutoxy germanium are preferred because they are readily available at reasonable prices; and germanium oxide is particularly preferred.

In the present invention can the catalyst comprising such a germanium compound, either soluble or insoluble be in the polycondensation reaction system. However, it is preferred that the catalyst is at least partially soluble in the reaction system.

Other catalysts known in the art for the Polycondensation can can also be used together with the germanium catalyst, as long as they fail to achieve the objects of the present invention affect. examples for the catalysts used together with the germanium catalyst can be conclude organic or inorganic compounds of Ti, Zn, Mg, Ca or Sn a.

The amount of catalyst to use is 0.001 to 3% by weight, preferably 0.005 to 1.5% by weight, of the total amount of the reactants used. It is sufficient that the catalyst is present in the reaction system during the polycondensation reaction carried out becomes. There is no particular limitation on when to add of the catalyst as long as this is before the start of the polycondensation reaction lies. The catalyst can either be added at the time when the starting materials are filled in, or at the time when the reaction system pressure reduction is started. It is preferred to adopt one of the following types: a type in which the catalyst simultaneously with the addition of the aliphatic oxycarboxylic acid, such as z. B. lactic acid or glycolic acid, is added when the starting materials are filled; and a way in which a solution which by dissolving the Catalyst prepared in water or in an aqueous solution of the aliphatic oxycarboxylic acid is added to the reaction system. Of these, the type in which a solution by dissolving of the catalyst in an aqueous solution the aliphatic oxycarboxylic acid is added to the reaction system, particularly preferably because the catalyst is very durable in such a solution.

The conditions such as B. temperature, Pressure and duration under which the aliphatic polyester copolymer are generated as follows: the reaction temperature can be from the Range from 150 to 260 ° C selected be, preferably from the range of 180 to 230 ° C; the reaction pressure in the polycondensation reaction can range from 10 mmHg or less, preferably in the range of 2 mmHg or less selected become. The temperature and / or the degree of pressure reduction can in the later Step of the reaction according to the usual Way in conventional Polycondensation reactions are increased, that progress sequentially.

The duration of the polymerization can be over the range from 2 h or more, preferably from the range from 4 to 15 h selected become. The polymerization time generally depends on the desired one Degree of polymerization of a polyester to be produced. Inherent in of the present invention the aliphatic oxycarboxylic acid used to the effects of increasing the Polymerization. It can therefore be said that the polymerization time in the present invention is the time required to the number average molecular weight of a polyester at least 10,000 for a given temperature and / or pressure condition and / or for given catalytic conditions reached.

The by the inventive method available Aliphatic copolyesters generally have the following compositional aspects. The diol unit and the aliphatic dicarboxylic acid unit are essentially equimolar. Moreover it is preferred that the amount of the aliphatic diol unit and that of the aliphatic dicarboxylic acid unit in each case from the Range from 35 to 49.99 mol%, preferably from the range of 40 to 49.75 mol%, particularly preferably in the range from 45 to 49.5 mol% selected become. It is preferred the amount of the aliphatic oxycarboxylic acid unit select from the range of 0.02 to 30 mol%. If the amount of aliphatic oxycarboxylic is more than 30 mol%, the resulting polyester is not satisfactory in heat resistance and in mechanical properties. On the other hand, if the amount the aliphatic oxycarboxylic acid is less than 0.02 mol%, would they be Benefits accompanying their addition are not available. The preferred area for the The amount of the aliphatic oxycarboxylic acid is 0.5 to 20 mol%, and the particularly preferred range is 1.0 to 10 mol%.

The number average molecular weight of the aliphatic according to the invention Copolyesters is generally 10,000 or more, and preferably 20,000 or more, especially preferably 30,000 or more. The upper limit of the number average the molecular weight of the copolymer is not limited to a certain level, however can e.g. B. 300,000. The "number average" used in this description of molecular weight " the one that is measured by the GPC method, which will be described in detail later is described.

Other comonomer components can be incorporated into the aliphatic polyester copolymer of the present invention as long as they do not interfere with the advantages of the present invention. Examples of such other comonomeric components include aromatic oxycarboxylic acids such as hydroxybenzoic acid, aromatic diols such as bisphenol A, aromatic dicarboxylic acids such as terephthalic acid and isophthalic acid, polyhydric alcohols such as trimethylolpropane, glycerol and pentaerythritol, polycarboxylic acids such as trimellitic acid and anhydrides thereof and hydroxypolycarboxylic acid such as hydroxypolycarboxylic acid. Of these, malic acid, trimethylolpropane, glycerin and pentaerythritol are preferred. If these "optional components" are bifunctional in terms of producing a polyester and at the same time aromatic, their use would deviate from the object of the present invention which is to increase the molecular weight of an aliphatic polyester. On the other hand, if the optional components are trifunctional or higher functional, a polyester can be obtained as an undesirable cross-linked product become. Therefore, it is preferred to use these optional components in such a small amount of 10 mol or less, preferably 5 mol or less, e.g. B. about 0.01 to 5 mol, to use 100 mol of the aliphatic dicarboxylic acid, which is an essential component in the present invention.

As mentioned above, the present is based Invention on the fact that an aliphatic copolyester with high molecular weight, that of aliphatic diol unit, aliphatic Carboxylic acid unit and aliphatic oxycarboxylic acid unit in a specific ratio exists and a number average molecular weight of 10,000 or more, preferably 20,000 or more, particularly preferably 30,000 or more, as a polymer with high strength and a melting point can be obtained that is high enough for practical use are. Typically, a high molecular weight can be extremely light by using an aliphatic oxycarboxylic acid such as lactic acid and in the presence of a catalyst which is a germanium compound includes.

(3) Use the generated one polyester

The aliphatic copolyesters according to the invention with high molecular weight can to shaped objects such as foils, laminated foils, sheets, plates, stretched sheets, monofilaments, Multifilaments, nonwovens, flat yarns, staple fibers, crimped Fibers, grooved ribbons, split yarns, composite fibers, blown bottles and foams each of the molding processes are processed for general purpose plastics such as injection molding, blow molding and extrusion molding. When the molding is done will, can a nucleating agent, an antioxidant, a lubricant, a dye, a release agent, a filler or other polymers can be added as needed.

In addition, the aliphatic according to the invention High molecular weight copolyesters are biodegradable and possess the property completely within two to twelve Months to be broken down by earthbound bacteria so that they are very advantageous from an environmental and hygiene point of view. It is therefore expected that the polymers according to the invention are used for production of shopping bags, garbage bags, foils for use in agriculture, cosmetic containers, soap containers, bleach containers, fishing lines, Fishnets, ropes, knotting fabrics, seams, Packaging materials for Sanitary ware, insulating containers, damping materials and the like can be used.

Examples

The following examples are provided for a more specific explanation of the present invention. The present invention is not limited by these examples, and any modification can be made as long as it does not go beyond the scope of the invention.

• (1) Polymere Zusammensetzung: erhalten durch Berechnung aus dem Verhältnis der Flächen der durch das ¹H-NMR-Verfahren erhaltenen Spektren.
• (2) Zahlenmittelwert des Molekulargewichts (Mn): gemessen durch das GPC-Verfahren. Eine in Chloroform gelöste Probe und ein von Tosoh Corporation, Japan, hergestelltes "GPC HLC-8020" wurden für die Messung verwendet. Der Messwert wurde in Bezug auf Polystyrol berechnet. Die verwendete Säule war eine von Tosoh Corporation, Japan, hergestellte "PLgel-10 micron-MIX".
• (3) Thermische Eigenschaften: der Schmelzpunkt wurde durch das DSC-Verfahren bestimmt (gemessen mit einer Heizgeschwindigkeit von 16°C/min unter Stickstoff).
• (4) Zugeigenschaften: Eine Folie mit einer Dicke von 0,30 bis 0,37 mm wurde aus jedem der in den Beispielen und Vergleichsbeispielen erhaltenen Polyester durch das Labor-Heißpressverfahren erhalten. Aus dieser Folie wurden Hantelprüfkörper vom Typ Nr. 2 gemäß JIS K7127 hergestellt. Die Bruchdehnung und Bruchfestigkeit jedes Hantelprüfkörpers wurden gemäß JIS K7127 gemessen.
• (5) Test der biologischen Abbaubarkeit: Eine Folie mit einer Dicke mit 0,30 bis 0,37 mm wurde durch das Labor-Heißpressverfahren aus dem erhaltenen Polyester hergestellt und dann in Stücke mit Abmessungen von 2 cm × 2 cm geschnitten. Die so erhaltenen Probekörper wurden im Boden für drei Monate aufbewahrt. Die biologische Abbaubarkeit des Polymers wurde durch visuelle Beobachtung dieser Probekörper bestätigt.

It is noted that the property values shown in the following examples are those obtained by the following methods.

• (1) Polymer composition: obtained by calculation from the ratio of the areas of the spectra obtained by the ¹ H-NMR method.
• (2) Number average molecular weight (Mn): measured by the GPC method. A sample dissolved in chloroform and a "GPC HLC-8020" manufactured by Tosoh Corporation, Japan were used for the measurement. The measured value was calculated in relation to polystyrene. The column used was a "PLgel-10 micron-MIX" manufactured by Tosoh Corporation, Japan.
• (3) Thermal properties: the melting point was determined by the DSC method (measured at a heating rate of 16 ° C / min under nitrogen).
• (4) Tensile properties: A film having a thickness of 0.30 to 0.37 mm was obtained from each of the polyesters obtained in the examples and comparative examples by the laboratory hot press method. Type 2 dumbbell test specimens were produced from this film in accordance with JIS K7127. The elongation at break and breaking strength of each dumbbell specimen were measured in accordance with JIS K7127.
• (5) Biodegradability test: A sheet having a thickness of 0.30 to 0.37 mm was produced from the obtained polyester by the laboratory hot press method and then cut into pieces measuring 2 cm × 2 cm. The test specimens thus obtained were kept in the soil for three months. The biodegradability of the polymer was confirmed by visual observation of these test specimens.

[Example 1]

35.4 g of succinic acid, 28.4 g of 1,4-butanediol and 2.9 g of a 90% were placed in a 100 ml reaction vessel equipped with a stirrer, a nitrogen inlet tube, a heater, a thermometer and an inlet for additives. aqueous solution of DL-lactic acid, in which 1% by weight of germanium oxide had previously been dissolved. While stirring the contents of the reaction vessel, nitrogen gas was introduced into the vessel passes. Under a nitrogen atmosphere, the temperature of the mixture was raised to 180 ° C, and the reaction was carried out at the temperature for 45 minutes and then under a reduced pressure of 20 mmHg for 1.75 hours. Thereafter, the temperature of the reaction mixture was raised to 220 ° C, and the polymerization was effected under a reduced pressure of 0.5 mmHg for 4 hours to obtain a polyester.

The polymeric composition of the polyester, as determined by ¹ H-NMR, was as follows: the lactic acid unit was 4.6 mol%, the 1,4-butanediol unit was 48.1 mol%, and the succinic acid unit was 47.3 mol%. The Mn and melting point of the polyester were 58,900 and 108 ° C, respectively. This polyester was made into a film using a laboratory hot press. The film obtained was found to be tough. This film was subjected to the biodegradability test. After 3 months, a large number of holes such as worm holes were found on the film; it has thus been confirmed that the polyester is biodegradable.

Example 2

In one with a stirrer, one Nitrogen inlet pipe, a heater, a thermometer and an inlet for additives equipped 150 ml reaction vessel were 59.1 g succinic acid, 49.6 g of 1,4-butanediol, 5.0 g of a 90% aqueous solution of L-lactic acid and 180 ul tetrabutoxy germanium filled. With stirring of the contents of the reactor, nitrogen gas was introduced into the vessel. Under a nitrogen atmosphere the temperature of the mixture was raised to 185 ° C and the reaction was started at the temperature for 50 min and then under a reduced pressure of 20 mmHg for 1.8 h carried out. Subsequently the temperature of the reaction mixture was raised to 220 ° C, and the polymerization was carried out under a reduced pressure of 0.5 mmHg for 2 h caused to obtain a polyester.

The polymeric composition of the polyester, determined by ¹ H-NMR, was as follows: the lactic acid unit was 4.4 mol%, the 1,4-butanediol unit was 47.8 mol%, and the succinic acid unit was 47.8 mol%. The Mn of the polyester was 69,000 and the tensile properties of the polyester were as shown in Table 1. It was also confirmed that this polyester had biodegradability comparable to that of the polyester obtained in Example 1.

Example 3

In one with a stirrer, one Nitrogen inlet pipe, a heater, a thermometer and an inlet for additives equipped 300 ml reaction vessel were 118.1 g succinic acid, 99.1 g of 1,4-butanediol and 6.3 g of a 90% aqueous solution of DL-lactic acid, in which had previously been dissolved by 1% by weight of germanium oxide. Under stir the contents of the reaction vessel Nitrogen gas introduced into the vessel. Under a nitrogen atmosphere the temperature of the mixture was raised to 185 ° C and the reaction was started at the temperature for 0.5 h. The temperature of the inside of the reactor was then raised to 220 ° C, and the reaction was continued at the temperature for 0.5 h. Then was causes the polymerization under a reduced pressure of 0.5 mmHg for 4 h, to get a polyester.

The polymeric composition of the polyester, as determined by ¹ H-NMR, was as follows: the lactic acid unit was 3.0 mol%, the 1,4-butanediol unit was 48.8 mol%, and the succinic acid unit was 48.2 mol%. The Mn of the polyester was 62,500 and the tensile properties of the polyester were as shown in Table 1. It was also confirmed that this polyester had biodegradability comparable to that of the polyester obtained in Example 1.

Example 4

In the same reaction tube as it is used in Example 3, 118.1 g of succinic acid, 99.1 g 1,4-butanediol and 6.3 g of a 70% aqueous solution of glycolic acid, in which had previously been dissolved by 1% by weight of germanium oxide. Under stir the contents of the reaction vessel Nitrogen gas introduced into the vessel. Under a nitrogen atmosphere the temperature of the mixture was raised to 185 ° C and the reaction was started at the temperature for 0.5 h. The temperature of the inside of the reactor was then raised to 220 ° C, and the reaction was continued at the temperature for 0.5 h. Then was causes the polymerization under a reduced pressure of 0.5 mmHg for 6 h, to get a polyester.

The polymeric composition of the polyester, as determined by ¹ H-NMR, was as follows: the glycolic acid unit was 2.4 mol%, the 1,4-butanediol unit was 49.5 mol%, and the succinic acid unit was 48.1 mol%. The Mn value of the polyester was 42,500. It was also confirmed that this polyester had a biodegradability comparable to that of the polyester obtained in Example 1.

Example 5

In one with a stirrer, one Nitrogen inlet pipe, a heater, a thermometer and an inlet for additives equipped 300 ml reaction vessel were 100.3 g succinic acid, 21.9 g adipic acid, 103.1 g 1,4-butanediol and 6.3 g of a 90% aqueous solution of L-lactic acid, in which had previously been dissolved by 1% by weight of germanium oxide. Under stir the contents of the reaction vessel Nitrogen gas introduced into the vessel. Under a nitrogen atmosphere the temperature of the mixture was raised to 185 ° C and the reaction was started at the temperature for 0.5 h. The temperature of the reaction mixture was then raised to 220 ° C, and the reaction was continued at the temperature for 0.5 h. Then was polymerization under a reduced pressure of 0.5 mmHg for 4 h.

The Mn value and the melting point of the polyester obtained were 71,000 and 95 ° C, respectively. The tensile properties of the polyester were as shown in Table 1. In addition, the polymer composition of the polyester, as determined by ¹ H-NMR, was as follows: the lactic acid unit was 2.8 mol%, the 1,4-butanediol unit was 48.9 mol%, the succinic acid unit was 40.8 mol%, and the adipic acid unit was 7.5 mol%. A film made of the polyester was subjected to the biodegradability test. After three months it was found that the film was torn; it was thus confirmed that the polyester was biodegradable.

Comparative Example 1

In the same reaction tube as it is used in Example 2, 59.1 g of succinic acid, 47.3 g 1,4-butanediol and 0.05 g germanium oxide filled. While stirring the The contents of the reaction vessel became nitrogen gas introduced into the vessel. Under a nitrogen atmosphere the temperature of the mixture was raised to 185 ° C and the reaction was started at the temperature for 50 min and then carried out under a reduced pressure of 20 mmHg for 2 h. Then was the temperature of the reaction mixture increased to 220 ° C, and the polymerization was effected under a reduced pressure of 0.5 mmHg for 4 h.

The Mn value of the polyester obtained was 1,500 and the tensile properties of the polyester were as in Table 1 shown.

Comparative Example 2

In one with a stirrer, one Nitrogen inlet pipe, a heater, a thermometer and an inlet for additives equipped 300 ml reaction vessel were 118.0 g succinic acid, 99.1 g of 1,4-butanediol and 6.3 g of a 90% aqueous solution of DL-lactic acid, in which had previously dissolved 1% by weight of antimony oxide. Under stir the contents of the reaction vessel Nitrogen gas introduced into the vessel. Under a nitrogen atmosphere the temperature of the reaction mixture was raised to 185 ° C and the reaction was at the temperature for 0.5 h. The temperature of the reaction mixture was then raised to 220 ° C, and the reaction was continued at the temperature for 0.5 h. Then the Polymerization effected under a reduced pressure of 0.5 mmHg for 4 h.

The Mn value of the polyester obtained was 8,800. In addition, the polymer composition of the polyester, determined using ¹ H-NMR, was as follows: the lactic acid unit was 2.9 mol%, the 1,4-butanediol unit was 48.7 mol %, and the succinic acid unit was 48.4 mol%.

Table 1

• (1) Die erfindungsgemäßen Polyestercopolymere mit aliphatischer Oxycarbonsäureeinheit besitzen ein hohes Molekulargewicht (Beispiele 1 bis 5) und zeigen ausgezeichnete Zugeigenschaften (Beispiele 2 und 3); und
• (2) im Gegensatz dazu besitzen die in den Vergleichsbeispielen erhaltenen Polyestercopolymere ein niedriges Molekulargewicht und sind in den Zugeigenschaften unzureichend (Vergleichsbeispiele 1 und 2).

The results obtained in the above examples and comparative examples clearly show the following:

• (1) The polyester copolymers according to the invention with an aliphatic oxycarboxylic acid unit have a high molecular weight (Examples 1 to 5) and show excellent tensile properties (Examples 2 and 3); and
• (2) In contrast, the polyester copolymers obtained in the comparative examples have a low molecular weight and are insufficient in tensile properties (comparative examples 1 and 2).

Example 6

In one with a stirrer, one Nitrogen inlet pipe, a heater, a thermometer and an inlet for additives equipped 300 ml reaction vessel were 100.1 g succinic anhydride, 99.1 g of 1,4-butanediol and 6.3 g of a 90% aqueous solution of DL-lactic acid (6.3 mol% of the molar amount of succinic anhydride), in which 1% by weight of germanium oxide had previously been dissolved. The Reaction was carried out under a nitrogen atmosphere at 185 ° C for 0.5 h. The The temperature of the reaction mixture was then raised to 220 ° C, and the reaction was continued at the temperature for 0.5 h. Then was polymerization under a reduced pressure of 0.5 mmHg for 6 h.

The polyester obtained had a white color. The Mn value and melting point of the polyester were 67,600 and 108 ° C, respectively. In addition, the polymer composition of the polyester, as determined by ¹ H-NMR, was as follows: the lactic acid unit was 3.2 mol%, the succinic acid unit was 48.4 mol%, and the 1,4-butanediol unit was 48.4 mol%. This polymer was processed into a film with a thickness of 0.35 mm using a laboratory hot press at 200 ° C. and by applying a pressure of 100 kg / cm ² . The film obtained was found to be tough. The tensile strength of this film was measured. As a result, the breaking strength was 320 kg / cm ² and the breaking elongation was 330. The film was also subjected to the biodegradability test. After three months, a large number of holes such as worm holes were found on the film. It was thus confirmed that the polyester was biodegradable.

Example 7

In one with a stirrer, one Nitrogen inlet pipe, a heater, a thermometer and an inlet for additives equipped 300 ml reaction vessel were 100.1 g succinic anhydride, 99.1 g of 1,4-butanediol, 10.6 g of a 90% aqueous solution of L-lactic acid (10.6 mol% of the molar amount of succinic anhydride) and filled with 0.2 g of tetrabutoxy germanium. The reaction was under a nitrogen atmosphere at 185 ° C for 0.5 h performed. The temperature of the reaction mixture was then raised to 220 ° C, and the reaction was continued at the temperature for 0.5 h. Then was polymerization under a reduced pressure of 0.5 mmHg for 5 h.

The polyester obtained had a white color. The Mn and melting point of the polyester were 70,000 and 103 ° C, respectively. In addition, the polymer composition of the polyester, as determined by ¹ H-NMR, was as follows: the lactic acid unit was 4.9 mol%, the succinic acid unit was 47.5 mol%, and the 1,4-butanediol unit was 47.6 mol%. This polymer became a sheet with a thickness of 0.35 mm processed using a laboratory hot press. The film obtained was found to be tough. The tensile strength of this film was measured. As a result, the breaking strength was 470 kg / cm ² and the breaking elongation was 630. The polyester was found to have a biodegradability comparable to that of the polyester obtained in Example 6.

Example 8

In one with a stirrer, one Nitrogen inlet pipe, a heater, a thermometer and an inlet for additives equipped 300 ml reaction vessel were 50.1 g succinic anhydride, 59.1 g succinic acid, 99.1 g 1,4-butanediol and 6.3 g of a 70% aqueous solution of glycolic acid (11 mol% of the total molar amount of succinic anhydride and succinic acid), in which had previously dissolved 1.% by weight of germanium oxide. The Reaction was carried out under a nitrogen atmosphere at 185 ° C for 0.5 h. The The temperature of the reaction mixture was then raised to 220 ° C, and the reaction was continued at the temperature for 0.5 h. Then was polymerization under a reduced pressure of 0.5 mmHg for 5 h.

The polyester obtained was white in color and its Mn was 60,000. In addition, the polymer composition of the polyester, as determined by ¹ H-NMR, was as follows: the glycolic acid unit was 5.0 mol%, the succinic acid unit was 47.3 mol%, and the 1,4-butanediol unit was 47.7 mol%. This polymer was made into a sheet 0.35 mm thick using a laboratory hot press. The film obtained was found to be tough. The tensile strength of this film was measured. As a result, the breaking strength was 300 kg / cm ² and the breaking elongation was 310. The polyester was found to have a biodegradability comparable to that of the polyester obtained in Example 6.

Comparative Example 3

In one with a stirrer, one Nitrogen inlet pipe, a heater, a thermometer and an inlet for additives equipped 300 ml reaction vessel were 100.1 g succinic anhydride and filled with 99.1 g of 1,4-butanediol. The reaction was carried out under a nitrogen atmosphere at 185 ° C for 0.5 h. The The temperature of the reaction mixture was then raised to 220 ° C, and the reaction was continued at the temperature for 0.5 h. Then were 0.06 g of tetrabutyl titanate was added to the reaction mixture, and the Polymerization effected under a reduced pressure of 0.5 mmHg for 4 h.

The polyester obtained was an ash colored Wax, and its Mn was 7,500. An attempt was made to create a slide made of this polyester using a laboratory hot press to obtain. However, the polyester was so brittle that it did not become one Foil could be processed.

Comparative Example 4

An aliphatic polyester ("Bionolle # 1010" manufactured by Showa Highpolymer Co., Ltd., Japan) composed of a 1,4-butanediol unit and a succinic acid unit with a small amount of urethane bond, with a number average molecular weight of 65,100 , was made into a film with a thickness of 0.35 mm using a laboratory hot press. This film was subjected to a tensile test. As a result, the breaking strength was 330 kg / cm ² and the elongation at break was 280%.

Comparative Example 5

In one with a stirrer, one Nitrogen inlet pipe, a heater, a thermometer and an inlet for additives equipped 200 ml reaction vessel were 103.5 g of a 90% aqueous Solution of L-lactic acid and 0.05 g germanium oxide filled. Under a nitrogen atmosphere the mixture was at 180 ° C under normal pressure for Stirred for 2 hours. The pressure was then reduced to 20 mmHg over 1 h and the reaction was for 2 hours. Subsequently the temperature of the reaction mixture was raised for one hour, and the polycondensation reaction was carried out at 200 ° C under a reduced pressure of 2 mmHg for 8 hours.

The polylactic acid obtained was transparent but slightly yellowish and its Mn was 28,000. It an attempt was made to make a film of this polylactic acid by using a Laboratory hot press to obtain. However, the polymer was so brittle that it did not become one Foil could be processed.

Example 9

In one with a stirrer, one Nitrogen inlet pipe, a heater, a thermometer and an inlet for additives equipped 200 ml reaction vessel were 38.4 g succinic acid, 32.2 g of 1,4-butanediol, 2.03 g of a 90% aqueous solution of DL-lactic acid, in of which 1% by weight of germanium oxide had previously been dissolved, and 6.07 g of one 90% aqueous solution of DL-lactic acid (25 mol lactic acid to 100 mol succinic acid) filled, The reaction was carried out under a nitrogen atmosphere at 185 ° C for 0.5 h. The The temperature of the reaction mixture was then raised to 220 ° C, and the reaction was continued at the temperature for 0.5 h. Then was polymerization under a reduced pressure of 0.5 mmHg for 4 h. A white crystalline formed in the course of the polycondensation reaction Product in the reaction system. The polyester obtained had a brownish-white color. The Mn value and the melting point of the polyester were 65,700 or 94 ° C. It was found that 22 moles of lactic acid were introduced per 100 moles of succinic acid were.

Comparative Example 6

In one with a stirrer, one Nitrogen inlet pipe, a heater, a thermometer and an inlet for additives equipped 200 ml reaction vessel were 38.4 g succinic acid, 32.2 g of 1,4-butanediol, 8.12 g of a 90% aqueous solution of DL-lactic acid (25th moles of lactic acid to 100 mol succinic acid) and filled with 0.66 g of tin powder. The reaction was carried out under a nitrogen atmosphere at 185 ° C for 0.5 h. The The temperature of this reaction mixture was then raised to 220 ° C., and the reaction was continued at the temperature for 0.5 h. Then was polymerization under a reduced pressure of 0.5 mmHg for 4 h. The polyester obtained had an orange color, and its Mn was only 9,600. It was found that 15 mol lactic acid to 100 mol succinic acid introduced had been.

An attempt was made to slide out a slide this polyester using a laboratory hot press to obtain. However, the polyester was so brittle that it did not become one Foil could be processed.

Example 10

The procedure outlined in Example 2 was followed except that 4.9 g DL-2-hydroxy-n-butyric acid instead of 5.08 g one 90% aqueous solution of DL-lactic acid were used to make an aliphatic polyester copolymer.

The polyester obtained had a polymeric composition, determined by ¹ H-NMR, of: 2.9 mol% of the DL-2-hydroxy-n-butyric acid unit, 48.9 mol% of the 1,4-butanediol unit and 48.2 mol% the succinic acid unit. The Mn value and the melting point of the polymer were 65,000 and 110 ° C, respectively. This polymer was made into a film using a laboratory hot press. The film obtained was found to be tough. The film was subjected to the biodegradability test. After three months, a large number of holes, such as worm holes, were found on the film, confirming that the film was biodegradable.

Example 11

The procedure outlined in Example 3 was followed except that in addition 5.71 g ε-caprolactone have been used to produce an aliphatic polyester copolymer.

The polyester obtained had a polymeric composition, determined by ¹ H-NMR, of: 3.9 mol% of the lactic acid unit, 2.7 mol% of the hydroxycaproic acid, 47.6 mol% of the 1,4-butanediol unit and 45.7 mol% the succinic acid unit. The Mn and melting point of the polyester were 71,000 and 107 ° C, respectively. This polymer was made into a film using a laboratory hot press. The film obtained was found to be tough. The film was subjected to the biodegradability test. After three months, the film was torn, confirming that the film was biodegradable.

Example 12

The procedure outlined in Example 3 was followed except that in addition 0.2 g of DL-malic acid was used to produce an aliphatic polyester copolymer.

The polyester obtained was white in color and its Mn and melting point were 75,000 and 111 ° C, respectively. This polymer was made into a film using a laboratory hot press. The film obtained was found to be tough. The film became the biodegradability test subjected. After three months, a large number of holes were found on the film, thus confirming that the film was biodegradable.

• (1) Die erfindungsgemäßen aliphatischen Copolyester haben ein ausreichend hohes Molekulargewicht für die praktische Verwendung und können zu gewünschten Formgegenständen durch jedes der Formverfahren geformt werden, die für Allzweckkunststoffe verwendet werden; die Formgegenstände, wie z. B. Folien und Fasern, sind ausgezeichnet hinsichtlich thermischer Stabilität und physikalischer Eigenschaften, wie z. B. Zugfestigkeit; und
• (2) die erfindungsgemäßen aliphatischen Copolyester sind höchst biologisch abbaubar.

The aliphatic copolyesters according to the invention have the following advantages, so that their usefulness in industrial fields is considerable:

• (1) The aliphatic copolyesters of the present invention have a sufficiently high molecular weight for practical use and can be molded into desired molded articles by any of the molding methods used for general-purpose plastics; the shaped objects, such as. B. films and fibers are excellent in terms of thermal stability and physical properties such. B. tensile strength; and
• (2) The aliphatic copolyesters according to the invention are highly biodegradable.

Claims (12)

A process for producing an aliphatic copolyester comprising reacting an aliphatic dicarboxylic acid with an aliphatic diol under condensation conditions for polyester production, characterized in that the reaction in the presence of a catalyst comprising a germanium compound and an aliphatic monohydroxymonocarboxylic acid in an amount of 2 to 20 mol to 100 mol of the aliphatic dicarboxylic acid is carried out in order to obtain an aliphatic copolyester whose number average molecular weight is at least 10,000. Process for the preparation of an aliphatic copolyester according to claim 1, wherein the amount of the aliphatic diol is 101 to 150 mol per 100 mole of aliphatic dicarboxylic acid is. A process for producing an aliphatic copolyester according to claim 1 or 2, wherein the aliphatic dicarboxylic acid is represented by the following formula: R ⁰ -CO-R ¹ -CO-R ⁰ (1) wherein R ^{1 represents} a direct bond or an aliphatic group and R ^{0 represents} OH or a functional derivative of the carboxyl group. A process for producing an aliphatic copolyester according to claim 3, wherein the aliphatic dicarboxylic acid is represented by the following formula: HOCO- (CH ₂ ) _m -COOH (1a) wherein m is 0 or an integer from 1 to 10. A process for producing an aliphatic copolyester according to any one of claims 1 to 4, wherein the aliphatic diol is represented by the following formula: HO-R ² -OH (2) wherein R ^{2 represents} a divalent aliphatic group. A process for producing an aliphatic copolyester according to claim 5, wherein the aliphatic diol is represented by the following formula: HO- (CH ₂ ) _n -OH (2a) where n is an integer from 2 to 10. A process for producing an aliphatic copolyester according to any one of claims 1 to 6, wherein the aliphatic monohydroxymonocarboxylic acid is represented by the following formula: HO-R ³ -CO-R ⁰ (3) wherein R ^{3 represents} a divalent aliphatic group. A process for producing an aliphatic copolyester according to claim 7, wherein the aliphatic Monohydroxymonocarboxylic acid is represented by the following formula:

wherein a is 0 or an integer from 1 to 10. Process for the preparation of an aliphatic copolyester according to one of claims 1 to 8, wherein the aliphatic dicarboxylic acid is succinic acid and / or the anhydride is thereof, optionally in admixture with adipic acid; the aliphatic diol is 1,4-butanediol; and the aliphatic monohydroxymonocarboxylic acid lactic acid or glycolic acid is. Process for the preparation of an aliphatic copolyester according to one of claims 1 to 9, wherein the germanium compound to be used as a catalyst from germanium oxide, germanium halides and tetraalkoxy germanium compounds selected becomes. Process for the preparation of an aliphatic copolyester according to claim 10, wherein the germanium compound is germanium oxide. Process for the preparation of an aliphatic copolyester according to one of claims 1 to 11, wherein the catalyst is in the form of a solution in an aqueous solution the aliphatic monohydroxymonocarboxylic acid is used.