JPH06298920A - Production of high-molecular weight aliphatic polyester - Google Patents

Abstract

PURPOSE:To provide a biodegradable high-molecular weight aliphatic polyester free from generation of a microgel and useful for various kinds of uses such as a molding, a film and fiber. CONSTITUTION:Production of a high-molecular weight aliphatic polyester having >=30000 weight-average molecular weight is carried out by admixing and reacting [II] 0.1 to 5 pts.wt. organic peroxide with [I] 100 pts.wt. unsaturated aliphatic polyester synthesized by reacting (1) an aliphatic or cyclic aliphatic glycol component with (2) an acid component composed of 98 to 99.99mol% aliphatic dicarboxylic acid or its anhydride and 0.01 to 2mol% unsaturated dicarboxylic acid or its anhydride and having >=20000 weight-average molecular weight.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a process for producing a biodegradable high molecular weight aliphatic polyester which is useful in various fields in which polymers have been conventionally used such as molded articles, films and fibers.

[0002]

2. Description of the Related Art A biodegradable polymer, that is, a polymer which disintegrates in soil or water under the action of microorganisms, has been attracting attention as one of means for solving recent plastic waste problems as a biodegradable polymer. , Its appearance is strongly desired. At this stage, it is no exaggeration to say that the completely biodegradable polymer, apart from the natural product, is the only synthetic polyester that is still synthetic. However, it has been generally accepted that aliphatic polyesters do not have sufficient thermal stability and cannot be called useful polymers with high molecular weight.

The inventors of the present invention have made various studies on the increase in the molecular weight of aliphatic polyesters and have obtained some findings, one of which has already been proposed as JP-A-4-189822. Japanese Unexamined Patent Publication No. 4-189822 is a method in which a high-molecular-weight aliphatic polyester is reacted with a specific amount of diisocyanate to further increase the molecular weight to a high-molecular region that is practically usable. This method is extremely useful for increasing the molecular weight, and the molecular weight (number average) of the aliphatic polyester is 2
It was confirmed that it was increased to more than 10,000 and showed practical physical properties and was biodegradable. However, with the progress of research thereafter, the process of practical application, in which the workability was a problem, came into question because of the generation of microgel and the control of the molecular weight distribution.

Microgel means 0.1 in the polymer produced.
It means that a few mm of gel-like resin is mixed, but the presence of this microgel has a great influence on the film-forming property, the appearance and physical properties of the film, or the filament moldability, and also has a commercial value on the product. Remarkably reduce. The presence of this microgel is also found in polyolefins, but in the case of polyolefins, it is said that it occurs due to the nature of the catalyst, while in contrast to the above-mentioned JP-A-4-189822, polyesters that react a small amount of diisocyanate In the case of, microgels result from the reaction of polyesters with diisocyanates at elevated temperatures. The urethane bond formed by the reaction between the isocyanate group and the hydroxyl group has a thermal dissociation property, and decreases at high temperature stirring of 200 ° C. or higher, but does not completely disappear.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for producing a high molecular weight aliphatic polyester in which the control of the molecular weight distribution and the generation of microgels, particularly microgels, have been solved.

[0006]

Means for Solving the Problems The inventors of the present invention have conducted extensive research to obtain an aliphatic polyester having a molecular weight that does not cause microgel formation and has practically sufficient physical properties, without using isocyanates. As a result, by introducing a small amount of unsaturated groups into the polyester, the resulting unsaturated aliphatic polyester, by further adding an organic peroxide in the molten state of the polyester, by adding the unsaturated groups in the polyester The inventors have found that the above-mentioned objects are effectively achieved, the physical properties are practically sufficient, and a high molecular weight aliphatic polyester free of microgel can be obtained, and the present invention was completed.

That is, the first aspect of the present invention is [I] (1) an aliphatic or cycloaliphatic glycol component, and (2) an aliphatic dicarboxylic acid or its acid anhydride 98 to 99.99 mol%.
And unsaturated dicarboxylic acid or its acid anhydride 0.01
0.1 to 5 parts by weight of organic peroxide with respect to 100 parts by weight of unsaturated aliphatic polyester having a weight average molecular weight of 20,000 or more obtained by reacting with an acid component consisting of ˜2 mol%. The present invention relates to a method for producing a high-molecular-weight aliphatic polyester, which comprises adding and reacting a substance to obtain a weight average molecular weight of 30,000 or more.

A second aspect of the present invention is (1) the aliphatic or cycloaliphatic glycol component of [I] of the first aspect,
(2) In the reaction of the aliphatic dicarboxylic acid or its acid anhydride and the unsaturated dicarboxylic acid or its acid anhydride, 3
In the first invention, at least one polyfunctional compound selected from the group consisting of a polyfunctional alcohol having a functionality or higher, a polycarboxylic acid having a functionality of 3 or higher or an acid anhydride thereof and an oxydicarboxylic acid having a functionality of 3 or higher is used in combination. It relates to a method for producing the described high molecular weight aliphatic polyester.

It has long been known that saturated polyesters, especially rubbers, are crosslinked by a hydrogen abstraction reaction with an organic peroxide. In this case, it is well known that a tertiary carbon, that is, a structure in which one hydrogen is bonded to a carbon atom is necessary. A polyester having a structure as described above is, for example, a polyester using a glycol such as propylene glycol or 2-methylpropanediol-1,3 as at least one component of a raw material. Polyesters synthesized using glycols having only a methylene bond such as ethylene glycol and 1,4-butanediol do not have a cross-linking reaction due to hydrogen abstraction even when an organic peroxide is used in combination unless the dicarboxylic acid component has tertiary carbon. It was confirmed that it would not happen. However, when an unsaturated dicarboxylic acid or its acid anhydride is used in an appropriate amount, an addition reaction occurs with the combined use of an organic peroxide, and it is possible to increase the molecular weight without gelation. There is significance of invention.

The aliphatic polyester used in the method of the present invention comprises (1) an aliphatic or cycloaliphatic glycol component as raw materials, and (2) an aliphatic dicarboxylic acid or its acid anhydride and an unsaturated dicarboxylic acid or its acid. An acid component composed of an anhydride, or (1) an aliphatic or cycloaliphatic glycol component, and (2) an acid component composed of an aliphatic dicarboxylic acid or an acid anhydride thereof and an unsaturated dicarboxylic acid or an acid anhydride thereof, (3 ) At least one polyfunctional compound selected from the group consisting of trifunctional or higher polyhydric alcohols, trifunctional or higher polyvalent carboxylic acids or acid anhydrides thereof, and trifunctional or higher oxydicarboxylic acids, each of these components being used. Is esterified (dehydrated condensation), followed by a deglycol reaction in the presence of a metal compound catalyst.

As the aliphatic or cycloaliphatic glycol component, a type which forms an amorphous polyester such as propylene glycol is used in view of the fact that a melting point of 70 ° C. or more which is the lower limit of molding of the produced polyester and crystallinity are required. Difficult, eg ethylene glycol, 1,4-
It is preferable to use butanediol, 1,4-cyclohexanedimethanol and the like. When these glycols are used in combination with other glycols, 1,6-hexanediol, decamethylene glycol, etc. may be used in combination as long as the melting point of the produced polyester can be kept at 70 ° C. or higher.

As the dicarboxylic acid or its acid anhydride for forming a polyester in combination with the above glycol component, an aliphatic dicarboxylic acid or its acid anhydride is used in view of biodegradation. When the melting point of the aliphatic polyester is 70 ° C. or lower, the molding processability is significantly impaired. Therefore, as the aliphatic dicarboxylic acid or its acid anhydride, succinic acid, adipic acid, suberic acid, sebacic acid and dodecanedioic acid And the like, and these may be used in combination. Aliphatic dicarboxylic acids having an odd number of carbon atoms or acid anhydrides thereof are not suitable because they lower the melting point.

As the unsaturated dicarboxylic acid or its acid anhydride used in the present invention, for example, maleic anhydride, maleic acid, fumaric acid and itaconic acid are common and commercially available. A dicarboxylic acid having a cyclic unsaturated bond such as endomethylenetetrahydrophthalic anhydride can be used from the viewpoint of crosslinking, but when crystallinity is required for the polyester, the structure may be disturbed depending on the amount used. So it is not always appropriate.

The proportion of the aliphatic dicarboxylic acid or its acid anhydride and the unsaturated dicarboxylic acid or its acid anhydride used is
When the total number of moles of the polybasic acid component used is 100 mol%, an aliphatic dicarboxylic acid or its acid anhydride 98 to 9
It is composed of 9.99 mol%, preferably 99 to 99.9 mol%, and 0.01 to 2 mol%, preferably 0.1 to 1 mol% of an unsaturated dicarboxylic acid or its acid anhydride. When the proportion of the unsaturated dicarboxylic acid or its acid anhydride used is less than 0.01 mol%, it cannot be substantially distinguished from the case of using no unsaturated dicarboxylic acid or its acid anhydride, and the proportion used is 2 mol%.
If the amount is larger, there is a higher risk of gelation due to the addition of organic peroxide. When the ratio of the unsaturated dicarboxylic acid or its acid anhydride used is in the range of 0.1 to 1 mol%, it is possible to increase the molecular weight and control the molecular weight distribution without gelation.

The ratio of the glycol component and the acid component used is preferably about 1.05 to 1.2 mol% of the glycol component with respect to 1 mol of the acid component.

In the present invention, when the aliphatic or cycloaliphatic glycol component is reacted with an acid component consisting of an aliphatic dicarboxylic acid or its acid anhydride and an unsaturated dicarboxylic acid or its acid anhydride, trifunctionality is obtained. By using at least one polyfunctional compound selected from the group consisting of the above polyhydric alcohols, trifunctional or higher polyvalent carboxylic acids or their anhydrides and trifunctional or higher oxydicarboxylic acids, for example, branching can be achieved. When introduced, the molecular weight distribution of polyester can be expanded and the melt viscosity required when molding a molded article can be adjusted.

Examples of trifunctional or higher polyhydric alcohols include glycerin, trimethylolpropane, pentaerythritol, triallyl isocyanurate ethylene oxide adduct and the like. It is also possible to use the dehydrated form of the monoepoxy compound glycidol.

As the trifunctional or higher polyvalent oxycarboxylic acid or its anhydride, commercially available products can be used, but malic acid, tartaric acid and citric acid are preferable from the viewpoint of low cost. is there.

Examples of trifunctional or higher polyvalent carboxylic acids or anhydrides thereof include trimesic acid, propanetricarboxylic acid, trimellitic anhydride, pyromellitic dianhydride, benzophenonetetracarboxylic anhydride, cyclopentatetracarboxylic anhydride. The thing etc. are mentioned. Particularly, trimellitic anhydride and pyromellitic dianhydride are preferable.

The respective components of the above polyfunctional compound can be mixed and used as needed. The amount of the polyfunctional compound used is 1 part of the aliphatic dicarboxylic acid or its anhydride component.
It is 0.1 to 5 mol% in total with respect to 00 mol%, and can be added from the beginning of esterification.

In the present invention, a glycol removal reaction is carried out to adjust the weight average molecular weight of the unsaturated aliphatic polyester to 2
It is necessary to adjust the amount to more than 10,000, but for that purpose it is necessary to use a catalyst for the deglycolization reaction in combination. Examples thereof are organic or inorganic metal compounds of at least one metal selected from the group consisting of titanium, tin, antimony, cerium, germanium, zinc, cobalt, manganese, iron, aluminum, magnesium, calcium and strontium. The amount used is 0.0 per 100 parts by weight of the unsaturated aliphatic polyester produced.
It is from 01 to 0.5 parts by weight. If the amount of the metal compound catalyst used is less than 0.001 part by weight, the deglycolization reaction is delayed and becomes unpractical, and if it is used in excess of 0.5 part by weight, the decomposition reaction is intensified, which is not preferable. The preferred amount used is 0.0 depending on the type of metal,
05 to 0.2 parts by weight. As the metal compound catalyst,
For example, metal alkoxides, organic acid salts, chelates, oxides, etc. are used, and organic compounds of titanium such as alkyl titanate, titanium oxyacetylacetonate, and titanium oxalate are particularly useful.
So-called biodegradable polyesters are subject to microbial degradation in soil, but metal catalysts or metals are expected to remain in soil and must therefore be of a safe type. From such a point of view, preferable metals include titanium, germanium, zinc, magnesium, calcium and the like.

The esterification reaction is carried out at 160 to 230 ° C. for 5
It can be carried out for up to 16 hours, preferably under an inert gas atmosphere. When the temperature is lower than this temperature, the reaction rate is slow and the practicality is poor. If the temperature is higher than this temperature, the risk of decomposition becomes high and it is better to avoid it. Therefore, it is preferred to carry out the first stage esterification reaction at a temperature between 180 and 220 ° C. The esterification reaction is carried out until the acid value of the unsaturated aliphatic polyester reaches 30 or less, preferably 15 or less, more preferably 10 or less. In this case, the higher the molecular weight, the smoother the increase in the molecular weight due to the deglycolization reaction. The deglycolization reaction is carried out at 170 to 230 ° C. under a reduced pressure of 5 Torr or less.
It is carried out for 16 hours. More preferably, it is carried out at 180 to 210 ° C. under a high vacuum of 1 Torr or less from the viewpoint of reaction rate and prevention of decomposition. The resulting polyester has a hydroxyl group as the terminal group and has an acid value of zero.

The unsaturated aliphatic polyester thus obtained must have a weight average molecular weight of 20,000 or more. If the weight average molecular weight is not 20,000 or more, the effect of using the unsaturated dicarboxylic acid or its acid anhydride becomes poor. When the weight average molecular weight is less than 20,000, the effect of increasing the molecular weight cannot be expected unless the proportion of the unsaturated dicarboxylic acid or its acid anhydride used is more than 2 mol%, but at the same time, the unsaturated dicarboxylic acid or The increased use of the acid anhydride adversely affects moldability. That is, when the use ratio of the unsaturated dicarboxylic acid or its acid anhydride increases, it becomes difficult to control the melt flow rate, and the physical properties of the molded product are impaired, and brittleness appears. In short, the properties of the thermoplastic polymer are impaired, and the properties of the thermosetting resin are added. Therefore, the film forming ability becomes very difficult. The reason why the weight average molecular weight is used in the present invention is that it is dominant in moldability and melt viscosity.

In the present invention, subsequently, an organic peroxide is added to the unsaturated aliphatic polyester having a weight average molecular weight of 20,000 or more and reacted to give a weight average molecular weight of 30,
000 or more. The organic peroxide used for this purpose is not particularly limited, but for the present invention, a high temperature decomposition type, for example, dialkyl peroxides such as dicumyl peroxide, peroxy esters such as t-butyl perbenzoate, and the like are preferable. Used for.

The amount of the organic peroxide used is 0.1 to 5 parts by weight based on 100 parts by weight of the unsaturated aliphatic polyester,
It is preferably 0.5 to 3 parts by weight. When the amount of the organic peroxide used is less than 0.1 parts by weight, the effect of addition is poor as a practical problem, and even when it is used in excess of 5 parts by weight, the improvement of the effect cannot be expected.

The addition of the organic peroxide to the unsaturated aliphatic polyester is preferably carried out in the molten state of the unsaturated aliphatic polyester. As a result, unsaturated groups in the unsaturated polyester are added to each other, and the weight average molecular weight is 30,0.
It can be 00 or more.

When the weight average molecular weight of the high molecular weight aliphatic polyester obtained by adding an organic peroxide to an unsaturated aliphatic polyester and reacting it is less than 30,000, the melt viscosity for molding a desired molded article is obtained. Will not be enough.

The high molecular weight aliphatic polyester of the present invention is
It is biodegradable and can be used for various purposes. Further, it is needless to say that the high molecular weight aliphatic polyester of the present invention can be used in combination with an organic or inorganic filler, a reinforcing material, a polymer, a lubricant, a coloring agent, a plasticizer, etc. in practical use.

[0029]

EXAMPLES Examples will be shown below to facilitate understanding of the present invention.

The melting point was measured by the DSC (differential scanning calorimeter) method. The molecular weight was measured by the following GPC measurement. Shodex GPC SYSTEM-11 Eluent CF ₃ COONa 5 mmol / HFIP (hexafluoroisopropanol, 1 liter) column Sample column HFIP-800P HFIP-80M × 2 reference columns HFIP-800R × 2 column temperature 40 ° C Flow rate 1.0 ml / min Detector Shodex RI STD: PMMA (Shodex STANDARD
M-75)

Example 1 200 g of 1,4-butanediol, 222 g of succinic acid and 2.4 g of fumaric acid were charged in a 1 liter separable flask equipped with a stirrer, a fractionating condenser, a thermometer and a gas introduction tube. After esterification at 195 to 200 ° C. in a nitrogen stream to give an acid value of 7.9, 0.05 g of tetraisopropyl titanate was added and the condenser was replaced.
Finally, the glycol removal reaction was carried out at 220 ° C. under a reduced pressure of 0.6 Torr for 6 hours. Obtained polyester (a)
Is a white waxy crystal having a number average molecular weight of 14,
000, weight average molecular weight 36,000, melting point about 11
It was 3 ° C.

300 g of polyester (a) was placed in another flask, heated and melted at 200 ° C. under a nitrogen stream, 1.5 g of dicumyl peroxide was added, and the mixture was further stirred for 5 minutes.
It was poured into a metal vat and solidified. The number average molecular weight of the obtained crosslinked polyester (A) was 26,100, the weight average molecular weight was 119,000, and the melting point was about 115 ° C.

Polyester (A) was press-molded to form a sheet having a thickness of about 70μ, but no generation of microgel was observed. A 2.5 cm × 15 cm test piece was buried in the soil of a tennis court about 20 cm below the surface and allowed to stand. After 6 months, the test piece became tattered and the original shape was not stopped, and it was confirmed to be biodegradable.

Example 2 A 1-liter separable flask equipped with a stirrer, a fractionating condenser, a thermometer, and a gas inlet tube was charged with 204 g of ethylene glycol, 298 g of succinic anhydride, and 6 g of itaconic acid.
Was added, and after esterification in a nitrogen stream at 195 to 200 ° C to an acid value of 9.4, 0.05 g of tetraisopropyl titanate was added, and finally at 215 to 220 ° C under a reduced pressure of 0.5 Torr for 10 hours. A deglycol reaction was performed. The obtained polyester (b) was white crystalline and had a number average molecular weight of 22,900 and a weight average molecular weight of 6
The melting point was 2,000 and the melting point was about 105 ° C.

300 g of polyester (b) was weighed into another flask, heated and melted at 200 ° C. in a nitrogen stream,
4.5 g of t-butyl perbenzoate was added. The polyester (B) obtained by stirring until foaming was completed had a melting point of 105 ° C., a number average molecular weight of 31,000 and a weight average molecular weight of 133,000.

In a sheet having a thickness of about 100 μ obtained by molding in the same manner as in Example 1, generation of microgel was not recognized. This was placed in a warm air tank and subjected to an activated sludge immersion test.
After 60 days, it decomposed almost completely and became tattered, and the original shape was not stopped.

Example 3 In a 1-liter separable flask equipped with a stirrer, a fractionating condenser, a thermometer, and a gas introduction tube, 310 g of 1,4-cyclohexanedimethanol, 290 g of adipic acid,
After charging 2 g of maleic anhydride and 2 g of trimethylolpropane and esterifying at 190 to 195 ° C. in a nitrogen stream at an acid value of 8.8, tetraisopropyl titanate of 0.2 was added.
05 g was added, and the reaction was continued at 215 to 220 ° C. for 6 hours under a reduced pressure of 0.6 Torr. The obtained polyester (C-1) was an ivory white crystal,
The melting point was about 105 ° C., the number average molecular weight was 13,900, and the weight average molecular weight was 42,800.

300 g of polyester (C-1) was weighed in another flask, melted at 200 ° C. in a nitrogen gas stream, and 6 g of cumene hydroperoxide was added. After stirring at 200 ° C. for 30 minutes, the number average molecular weight of the obtained polyester (C-2) was 20,200, and the weight average molecular weight was 14
The melting point was 5,000 and the melting point was about 108 ° C.

Polyester (C-2) was molded in the same manner as in Example 1 to obtain a sheet having a thickness of about 100 μm. No generation of microgel was observed on the sheet. This is Example 1
Similarly, when it was buried in soil and examined for biodegradability, numerous insect-eating-like holes were observed on the surface after 6 months, confirming that it was biodegradable.

[0040]

According to the method of the present invention, it is possible to provide a biodegradable high molecular weight aliphatic polyester which can be molded into molded articles, films, fibers and the like without generation of microgel.

[Procedure amendment]

[Submission date] November 18, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] Claim 2

[Correction method] Change

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[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0008

[Correction method] Change

[Correction content]

A second aspect of the present invention is [1] of the first aspect.
(1) an aliphatic or cycloaliphatic glycol component,
(2) In the reaction of the aliphatic dicarboxylic acid or its acid anhydride and the unsaturated dicarboxylic acid or its acid anhydride, 3
In the first invention, at least one polyfunctional compound selected from the group consisting of a polyfunctional alcohol having a functionality of 3 or more, a polycarboxylic acid having a functionality of 3 or more, or an acid anhydride thereof and an oxycarboxylic acid having a functionality of 3 or more is used in combination. It relates to a method for producing the described high molecular weight aliphatic polyester.

[Procedure 3]

[Document name to be amended] Statement

[Correction target item name] 0010

[Correction method] Change

[Correction content]

The aliphatic polyester used in the method of the present invention comprises (1) an aliphatic or cycloaliphatic glycol component as raw materials, and (2) an aliphatic dicarboxylic acid or its acid anhydride and an unsaturated dicarboxylic acid or its acid. An acid component comprising an anhydride, or (1) an aliphatic or cyclic aliphatic glycol component, and (2) an aliphatic dicarboxylic acid or an acid anhydride thereof and an unsaturated dicarboxylic acid or an acid component comprising an acid anhydride thereof, ( 3) Using at least one polyfunctional compound selected from the group consisting of trifunctional or higher polyhydric alcohols, trifunctional or higher polycarboxylic acids or acid anhydrides thereof, and trifunctional or higher oxycarboxylic acids, It is synthesized by esterifying (dehydrating and condensing) the components and then deglycolizing them in the presence of a metal compound catalyst.

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0016

[Correction method] Change

[Correction content]

In the present invention, when the aliphatic or cycloaliphatic glycol component is reacted with an acid component consisting of an aliphatic dicarboxylic acid or its acid anhydride and an unsaturated dicarboxylic acid or its acid anhydride, trifunctional By combining at least one polyfunctional compound selected from the group consisting of the above polyhydric alcohols, trifunctional or higher polycarboxylic acids or their anhydrides and trifunctional or higher oxycarboxylic acids, for example, branching When introduced, the molecular weight distribution of polyester can be expanded and the melt viscosity required when molding a molded article can be adjusted.

[Procedure Amendment 5]

[Document name to be amended] Statement

[Correction target item name] 0018

[Correction method] Change

[Correction content]

As the tri- or higher functional oxycarboxylic acid, commercially available products can be used, but malic acid, tartaric acid and citric acid are preferable from the viewpoint of being available at low cost.

[Procedure correction 6]

[Document name to be amended] Statement

[Correction target item name] 0036

[Correction method] Change

[Correction content]

Generation of microgel was not observed in the sheet having a thickness of about 100 μ obtained by molding in the same manner as in Example 1. When this was subjected to an activated sludge immersion test in an aeration tank, it was decomposed almost completely after 60 days, and it was broken into pieces and the original shape was not stopped.

Claims (2)

[Claims] 1. [I] (1) an aliphatic or cycloaliphatic glycol component, and (2) an aliphatic dicarboxylic acid or its acid anhydride 98 to 99.99 mol% and an unsaturated dicarboxylic acid or its acid anhydride. The weight average molecular weight obtained by reacting with an acid component consisting of 0.01 to 2 mol% is 20,000.
[II] 0.1 to 5 parts by weight of an organic peroxide is added to 100 parts by weight of an unsaturated aliphatic polyester of 0 or more and reacted to give a weight average molecular weight of 30,000 or more. A method for producing a high molecular weight aliphatic polyester, which is characterized. 2. In the reaction of (1) the aliphatic or cycloaliphatic glycol component of [I] with (2) the aliphatic dicarboxylic acid or its acid anhydride and the unsaturated dicarboxylic acid or its acid anhydride, 3. At least one polyfunctional compound selected from the group consisting of trifunctional or higher polyhydric alcohols, trifunctional or higher polyvalent carboxylic acids or acid anhydrides thereof, and trifunctional or higher oxydicarboxylic acids is used in combination. The method for producing a high molecular weight aliphatic polyester according to 1.