JP3438027B2 - Method for producing biodegradable high molecular weight aliphatic polyester - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to 3-alkoxy-1,2
The present invention relates to a method for producing a high elongation biodegradable high molecular weight aliphatic polyester containing a propanediol moiety. [0002] Synthetic polymers such as polyolefins and aromatic polyesters are used in large quantities as raw materials indispensable for daily life, but these synthetic polymers are not decomposed in the natural environment. With the increase in consumption, environmental problems have become apparent. For this reason, biodegradable plastics are being developed, and aliphatic polyesters are receiving attention as biodegradable polymers. Above all, polybutylene succinate produced from succinic acid or a derivative thereof and butanediol has been noted for its excellent melting point and mechanical strength (JP-A-5-70566,
JP-A-9-26991, JP-A-9-13259, etc.). However, since polybutylene succinate alone cannot always provide sufficient mechanical strength and workability for practical use, improvement of physical properties by copolymerization with various polyhydric alcohols, hydroxy acids, and the like has been studied (see, for example, Japanese Patent Application Laid-Open No. H11-157556). Kaihei 9-31176
And Japanese Patent Application Laid-Open No. 9-40762 ) and the present inventors have previously made it possible to homopolymerize 3-alkoxy-1,2-propanediol by copolymerizing it with an aliphatic dicarboxylic acid diester and an aliphatic glycol. A high molecular weight aliphatic polyester having a novel structure exhibiting a higher elongation than a polymer was proposed (Japanese Patent No. 3066500). [0004] The present invention relates to the above-mentioned patent.
A method for industrially producing a biodegradable high molecular weight aliphatic polyester having a higher elongation at break and excellent processability by improving the method for producing a high molecular weight aliphatic polyester presented in No. 3066500. The task is to provide [0005] The inventors of the present invention have conducted intensive studies to solve the above-mentioned problems, and as a result, have completed the present invention. That is, according to the present invention, the following general formula (1)
A compound containing a 3-alkoxy-1,2-propanediol moiety represented by the following formula: (Wherein, ^{R 1} represents an aliphatic group having 1 to 22 carbon atoms, ^{R 2}
Represents a divalent aliphatic group having 1 to 12 carbon atoms) and an aliphatic diol represented by the following general formula (2): HO-R ³ —OH (2) (wherein R ³ is A divalent aliphatic group having 1 to 12 carbon atoms) aliphatic dicarboxylic anhydride represented by the following general formula (3):
Alternatively, an ester of an aliphatic carboxylic acid represented by the following general formula (4) is copolymerized: (Wherein, R ² represents a divalent aliphatic group having 1 to 12 carbon atoms). (Wherein, R ² represents a divalent aliphatic group having 1 to 12 carbon atoms,
R ⁴ represents an alkyl group having 1 to ⁴ carbon atoms) having an ester portion A represented by the following general formula (5) and an ester portion B represented by the following general formula (6). (In the formula, R ² and R ³ are the same as described above. P represents the mole fraction of the ester moiety (A) represented by the general formula (5).) (In the formula, R ¹ and R ² are the same as above. R represents the mole fraction of the ester moiety (B) represented by the general formula (6).) Provided. [0006] The process for producing a polymer weight fat side polyesters of the present invention, a compound represented by the general formula (1), the general
Condensation reaction between the aliphatic diol represented by the formula (2) and the aliphatic dicarboxylic anhydride represented by the general formula (3) or the aliphatic dicarboxylic diester represented by the general formula (4) It is characterized by. The compound containing a 3-alkoxy-1,2-propanediol moiety represented by the general formula (1) is preferably a compound represented by the following general formula (7).
It is synthesized by reacting an alkoxy-1,2-propanediol with an aliphatic dicarboxylic anhydride represented by the general formula (3). Embedded image (In the formula, R ¹ represents an aliphatic group having 1 to 22 carbon atoms.) In this case, the aliphatic carboxylic acid anhydride represented by the general formula (3) is excessively present or the general formula (3) By selecting an embodiment performed in the presence of the aliphatic carboxylic acid ester represented by 4), the operation of adding these carboxylic acid components in the subsequent condensation reaction with the compound represented by the general formula (1) can be omitted. Therefore, it is desirable to adopt such a reaction mode in the present invention. The proportion of 3-alkoxy-1,2-propanediol used may be within a range such that the molecular weight of the target polymer is 10,000 or more, and is usually from 0.0005 to 1 per mol of the aliphatic dicarboxylic acid unit. 0.20 mol, preferably 0.0
It is a ratio of 01 to 0.10 mol. If the use ratio of 3-alkoxy-1,2-propanediol is more than the above range, the resulting polymer (polycondensate) does not increase in the degree of polymerization and a fragile polymer is produced, which is not preferable. The 3-alkoxy-1,2-propanediol represented by the general formula (7) can be obtained, for example, by reacting glycerin with an alcohol. Examples of the alcohol in this case include saturated and unsaturated alcohols having an aliphatic group having 1 to 22 carbon atoms. Examples of such alcohols include methyl alcohol, ethyl alcohol, butyl alcohol, octyl alcohol, lauryl alcohol, pentadecyl alcohol, stearyl alcohol, docosyl alcohol, allyl alcohol, crotyl alcohol, cyclopentanol, cyclohexanol and the like. No. The aliphatic diol represented by the general formula (2) to be condensed with the compound represented by the general formula (1) includes ethylene glycol, propylene glycol,
Examples thereof include 1,4-butanediol, 1,6-hexanediol, and 1,4-cyclohexanedimethanol. An aliphatic dicarboxylic anhydride represented by the general formula (3) and an aliphatic dicarboxylic acid anhydride represented by the general formula (4) are condensed with the compound represented by the general formula (1) together with the aliphatic diol. Examples of the dicarboxylic acid diester include anhydrides and diesters of aliphatic dicarboxylic acids such as succinic acid, adipic acid, suberic acid, sebacic acid, and dodecane diacid. The proportion of the aliphatic diol represented by the general formula (2) is equal to or slightly greater than the total number of moles of the aliphatic dicarboxylic acid derivatives represented by the general formulas (1), (3) and (4). Is preferably used. These dicarboxylic acid components may be added after the formation of the compound represented by the general formula (1), but the reaction system for forming the compound represented by the general formula (1) as described above is used. Can be added in advance. According to the latter reaction method, the addition step is omitted, which is extremely advantageous for industrial production. The condensation reaction according to the present invention is preferably carried out in the presence of a conventionally known catalyst for transesterification.
In the above reaction, the reaction temperature is 100 to 300 ° C, preferably 120 to 250 ° C. The reaction pressure can be reduced pressure, normal pressure or slightly increased pressure (0.5 kg / cm ² G or less),
Preferably, the pressure is from normal pressure to reduced pressure. When carrying out the condensation reaction, the reaction is preferably carried out with 3-alkoxy-1,2 by an aliphatic dicarboxylic anhydride.
Esterification of both alcohol parts of 1-propanediol (Part 1
Step: a step of forming a compound represented by the general formula (1)), a precondensation step (second step) in which an aliphatic diol and a dicarboxylic acid component are added, and a high-molecular-weight step (third step). In the precondensation step, a low molecular weight condensate having an aliphatic diol bonded to the terminal is formed. The number average molecular weight of this condensate is preferably from 5000 to 10,000,
The molecular weight can be appropriately adjusted depending on the reaction conditions and reaction time. In the high molecular weight step, a high molecular weight condensate is formed by condensing the aliphatic diol bonded to the terminal of the low molecular weight condensate while removing the aliphatic diol. Can produce more than 10,000 condensates. The reaction conditions in this case may be any conditions under which the by-produced aliphatic diol can exist as a gas. This molecular weight conversion step can be performed in the same apparatus as the reaction apparatus for performing the precondensation step or in a polymerization apparatus having high stirring efficiency. When the same apparatus is used, after the completion of the precondensation reaction, the reaction conditions may be changed, for example, the reaction temperature may be increased and the reaction pressure may be decreased to carry out the condensation reaction of the precondensate. The biodegradable high molecular weight aliphatic polyester obtained by the method of the present invention comprises an ester moiety A represented by the above general formula (5).
And the ester moiety B of the general formula (6). In this case, in the general formula (5) showing the ester moiety A, R ² represents a chain or cyclic divalent aliphatic group, and has 1 to 12, preferably 2 to 6 carbon atoms. Examples of such a divalent aliphatic group include an alkylene group such as methylene, ethylene, propylene, butylene, hexylene, octylene, dodecylene, cyclohexylene, and cyclohexane dimethylene. R ³ represents a linear or cyclic divalent aliphatic group, and has 1 to 12, preferably 2 to 6 carbon atoms. As such a divalent aliphatic group, an alkylene group, for example, methylene, ethylene, propylene,
Butylene, hexylene, octylene, dodecylene, cyclohexylene, cyclohexane dimethylene, and the like. In the general formula (6) representing the ester moiety B, R ² has the same meaning as described above, and R ¹ has 1 to ¹ carbon atoms.
And 22 aliphatic groups. Such aliphatic groups include
Alkyl or alkenyl groups such as methyl, ethyl, propyl, butyl, hexyl, octyl, nonyl,
Decyl, dodecyl, lauryl, stearyl, icosyl,
Docosyl, allyl, oleyl, behenyl, dodecenyl,
Cyclohexylene, cyclohexane dimethylene and the like can be mentioned. The high molecular weight polyester of the present invention has a number average molecular weight of 10,000 or more, preferably 30,000 or more. In this case, the upper limit of the number average molecular weight is about 1,000,000. The high-molecular-weight aliphatic polyester produced according to the present invention has a copolymerized structure with 3-alkoxy-1,2-propanediol, and has an elongation at break when a small amount of 3-alkoxy-1,2-propanediol is added. Mechanical strength such as degree can be greatly improved. Further, in this manufacturing method, the patent No. 3066 is used.
Compared with the method described in No. 500, a larger amount of 3-alkoxy-1,2-propanediol can be copolymerized without lowering the elongation at break. Moreover, this high molecular weight aliphatic polyester is
It has biodegradability based on its aliphatic ester bond. Next, the present invention will be described in detail with reference to examples. Various physical property values of the aliphatic polyester were measured by the following methods. (Molecular Weight and Molecular Weight Distribution) A calibration curve was prepared from standard polystyrene using gel permeation chromatography (GPC), and the number average molecular weight (Mn),
Weight average molecular weight (Mw) and molecular weight distribution (Mw / Mn)
I asked. The eluent used was chloroform. (Thermal Properties) Differential Scanning Calorimeter (DS)
The melting temperature and glass transition point were determined by C). The thermal decomposition temperature was determined by a thermogravimetric analyzer (TG). (Mechanical strength) Measured using a tensile tester. EXAMPLE 1 5.01 g (0.050 mol) of succinic anhydride and dimethyl succinate in a 100 ml glass reactor equipped with stirring blades were added.
0 g (0.130 mol), 0.187 g (0.544 mmol) of batyl alcohol (3-octadecyloxy-1,2-propanediol),
20 ml (0.1 mmol) of titanium tetraisopropoxide was charged, and two alcohols of batyl alcohol were esterified at 160 ° C. under a nitrogen atmosphere. After 2 hours, 17.0 g (0.189 mol) of 1,4-butanediol was added and reacted at 160 ° C. for 1 hour. After raising the temperature and reacting at 180 ° C for 1 hour, 30 minutes later, 200 ° C
The temperature rose. After another 30 minutes, the reaction temperature was raised to 215 ° C., the pressure was gradually reduced, and the vacuum reached 0.1 mmHg in 30 minutes. Thereafter, the reaction was continued for another 4 hours. The resulting polymer was white and had Mn of 97,100, Mw of 201,000, and its Mw / Mn was 2.07. Its melting temperature was 114.9 ° C and its 2% weight loss temperature was 307 ° C. 3 contained in this polymer
The ratio of -methoxy-1,2-propanediol is 0.30 per 100 mol of the aliphatic dicarboxylic acid component contained in the polymer.
It is a mole ratio. When the mechanical strength was measured, the elastic modulus was 216 MPa, the upper yield point stress was 23.1 MPa, and the breaking stress was 56.
It was 3 MPa and the elongation at break was 721%. COMPARATIVE EXAMPLE 1 26.34 g (0.180 mol) of dimethyl succinate, 16.90 g (0.188 mol) of 1,4-butanediol, and 18 ml (0.09 mol) of titanium tetraisopropoxide were placed in a glass reactor having a capacity of 100 ml with stirring blades. Mmol), and the reaction was started at 160 ° C. under a nitrogen atmosphere to elute methanol.
One hour later, the reaction temperature was raised to 180 ° C and the temperature was raised. After another 30 minutes 200 ° C
The temperature rose. After another 30 minutes, the reaction temperature was raised to 215 ° C., the pressure was gradually reduced, and the vacuum reached 1 mmHg in 30 minutes. Thereafter, the reaction was continued for another 7 hours. The resulting polymer was milky white and had Mn of 32,400, Mw of 52,800, and its Mw / Mn was 1.63. Its melting temperature was 114.1 ° C and its 2% weight loss temperature was 322 ° C. Further, when the mechanical strength was measured, the elastic modulus was 459 MPa, the upper yield point stress was 26.0 MPa, the breaking stress was 23.1 MPa, and the breaking elongation was 119%. COMPARATIVE EXAMPLE 2 26.32 g (0.180 mol) of dimethyl succinate, 16.83 g (0.187 mol) of 1,4-butanediol,
Octadecyl-1,2-propanediol) 0.187 g (0.541
Mmol), titanium tetraisopropoxide 20 ml (0.1
Mmol), and the reaction was started at 160 ° C. under a nitrogen atmosphere to elute methanol. 1 hour after reaction temperature 180
℃ and heated. After another 30 minutes, the temperature was raised to 200 ° C. 3 more
After 0 minute, the reaction temperature was raised to 215 ° C., the pressure was gradually reduced, and the vacuum reached 0.1 mmHg in 30 minutes. Thereafter, the reaction was continued for another 3 hours. The obtained polymer is light brown, Mn 68,900, Mw 113,
It had a Mw / Mn of 1.65. The ratio of batyl alcohol contained in the polymer is 0.3 mol per 100 mol of the aliphatic dicarboxylic acid component contained in the polymer. When the mechanical strength was measured, the elastic modulus was 277 MPa, the upper yield point stress was 24.7 MPa, the breaking point stress was 40.3 MPa,
The elongation at break was 470%. Example 2 5.02 g (0.050 mol) of succinic anhydride and 19.0 g of dimethyl succinate were placed in a glass reactor having an inner volume of 100 ml with stirring blades.
g (0.130 mol), 0.31 g (0.902 mmol) of batyl alcohol (3-octadecyloxy-1,2-propanediol), and 20 ml (0.1 mmol) of titanium tetraisopropoxide at 160 ° C. under a nitrogen atmosphere. Were esterified. After 1 hour, 16.90 g (0.188 mol) of 1,4-butanediol was added, and the mixture was reacted at 160 ° C. for 1 hour. After raising the temperature and reacting at 180 ° C for 1 hour, 30 minutes later, 200 ° C
The temperature rose. After another 30 minutes, the reaction temperature was raised to 215 ° C., the pressure was gradually reduced, and the vacuum reached 0.1 mmHg in 30 minutes. Thereafter, the reaction was continued for another 5 hours. The resulting polymer was milky white and had Mn 78,200, Mw 149,400 and its Mw / Mn was 1.91. Its melting temperature was 113.7 ° C, and its 2% weight loss temperature was 301 ° C. The ratio of batyl alcohol contained in the polymer is 0.50 mol per 100 mol of the aliphatic dicarboxylic acid component contained in the polymer. When the mechanical strength was measured, the elastic modulus was 225MP.
a, the upper yield point stress was 24.8 MPa, the breaking stress was 51.5 MPa, and the breaking elongation was 710%. EXAMPLE 3 5.06 g (0.050 mol) of succinic anhydride and 19.0 g of dimethyl succinate were placed in a glass reactor having an internal volume of 100 ml with stirring blades.
g (0.130 mol), 0.621 g (1.83 mmol) of batyl alcohol (3-octadecyloxy-1,2-propanediol), and 20 ml (0.1 mmol) of titanium tetraisopropoxide at 160 ° C. under a nitrogen atmosphere. Were esterified. After 1 hour, 16.90 g (0.188 mol) of 1,4-butanediol was added, and the mixture was reacted at 160 ° C. for 1 hour. After raising the temperature and reacting at 180 ° C for 1 hour, 30 minutes later, 200 ° C
The temperature rose. After another 30 minutes, the reaction temperature was raised to 215 ° C., the pressure was gradually reduced, and the vacuum reached 0.1 mmHg in 30 minutes. Thereafter, the reaction was continued for another 5 hours. The resulting polymer was milky white and had Mn of 64,300, Mw of 119,600, and its Mw / Mn was 1.86. Its melting temperature was 115.0 ° C and its 2% weight loss temperature was 311 ° C. The ratio of batyl alcohol contained in the polymer is 1.01 mol per 100 mol of the aliphatic dicarboxylic acid component contained in the polymer. When the mechanical strength was measured, the elastic modulus was 259MP.
a, the upper yield point stress was 22.3 MPa, the break point stress was 50.0 MPa, and the break elongation was 731%. Example 4 5.00 g (0.050 mol) of succinic anhydride and 19.0 g of dimethyl succinate were placed in a glass reactor having an internal volume of 100 ml with stirring blades.
g (0.130 mol), 1.24 g (3.60 mmol) of batyl alcohol (3-octadecyloxy-1,2-propanediol), and 20 ml (0.1 mmol) of titanium tetraisopropoxide at 160 ° C. under a nitrogen atmosphere. Were esterified. After 2 hours, 16.96 g (0.188 mol) of 1,4-butanediol was added, and the mixture was reacted at 160 ° C. for 1 hour. After raising the temperature and reacting at 180 ° C for 1 hour, 30 minutes later, 200 ° C
The temperature rose. After another 30 minutes, the reaction temperature was raised to 215 ° C., the pressure was gradually reduced, and the vacuum reached 0.1 mmHg in 30 minutes. Thereafter, the reaction was continued for another 5 hours. The resulting polymer was milky white and had Mn of 98,300, Mw of 171,000, and its Mw / Mn was 1.74. Its melting temperature is 113.7 ℃, 2% of which
The weight loss temperature was 311 ° C. The ratio of batyl alcohol contained in the polymer is 2.00 mol per 100 mol of the aliphatic dicarboxylic acid component contained in the polymer. When the mechanical strength was measured, the elastic modulus was 180M.
Pa, upper yield point stress was 20.5 MPa, rupture stress was 50.9 MPa, and rupture elongation was 777%. Example 5 5.01 g (0.050 mol) of succinic anhydride and 19.1 g of dimethyl succinate were placed in a glass reactor having an internal volume of 100 ml with stirring blades.
g (0.131 mol), 3.11 g (9.04 mmol) of batyl alcohol (3-octadecyloxy-1,2-propanediol), and 20 ml (0.1 mmol) of titanium tetraisopropoxide at 160 ° C. under a nitrogen atmosphere. Were esterified. After 1 hour, 17.0 g (0.189 mol) of 1,4-butanediol was added and reacted at 160 ° C. for 1 hour. After raising the temperature and reacting at 180 ° C for 1 hour, 30 minutes later, 200 ° C
The temperature rose. After another 30 minutes, the reaction temperature was raised to 215 ° C., the pressure was gradually reduced, and the vacuum reached 0.1 mmHg in 30 minutes. Thereafter, the reaction was further continued for 6.5 hours. The resulting polymer was white and had Mn 71,800, Mw 127,100, and its Mw / Mn was 1.77. Its melting temperature is 108.8 ℃, 2% of which
The weight loss temperature was 308 ° C. The ratio of batyl alcohol contained in the polymer is 5.01 mol per 100 mol of the aliphatic dicarboxylic acid component contained in the polymer. When the mechanical strength was measured, the elastic modulus was 147M.
Pa, the upper yield point stress was 17.2 MPa, the break point stress was 40.5 MPa, and the break elongation was 833%. EXAMPLE 6 5.01 g (0.050 mol) of succinic anhydride and 19.1 g of dimethyl succinate were placed in a glass reactor having an internal volume of 100 ml with stirring blades.
g (0.131 mol), 3-methoxy-1,2-propanediol 0.972
g (9.16 mmol), titanium tetraisopropoxide 20 ml
(0.1 mmol), and two alcohols of batyl alcohol were esterified at 160 ° C. under a nitrogen atmosphere. 1
After an hour, 16.9 g (0.188 mol) of 1,4-butanediol was added and reacted at 160 ° C. for 1 hour. After the temperature was raised and reacted at 180 ° C. for 1 hour, the temperature was raised to 200 ° C. after 30 minutes. After another 30 minutes, the reaction temperature was raised to 215 ° C., and the pressure was gradually reduced.
Hg reached. Thereafter, the reaction was continued for another 5 hours. The resulting polymer was white and had Mn 65,400, Mw 115,800, and its Mw / Mn was 1.77. Its melting temperature is 11
4.9 ° C. and its 2% weight loss temperature was 304 ° C. The ratio of 3-methoxy-1,2-propanediol contained in the polymer is 5.10 mol per 100 mol of the aliphatic dicarboxylic acid component contained in the polymer. When the mechanical strength was measured, the elastic modulus was 288 MPa, the upper yield stress was 20.6 MPa, the stress at break was 62.8 MPa, and the elongation at break was 817%. Example 7 19.2 g (0.192 mol) of succinic anhydride and a mixture of batyl alcohol (3-
0.622 g of octadecyloxy-1,2-propanediol (1.
81 mmol), titanium tetraisopropoxide 20 ml (0.1
Mmol) and esterified two alcohols of batyl alcohol at 160 ° C. under a nitrogen atmosphere. One hour later, 17.0 g (0.189 mol) of 1,4-butanediol was added, and 160
Reaction was performed at ℃ for 1 hour. After the temperature was raised and reacted at 180 ° C. for 1 hour, the temperature was raised to 200 ° C. after 30 minutes. After an additional 30 minutes, the reaction temperature
The temperature was reduced to 15 ° C., the pressure was gradually reduced, and the pressure reached 0.1 mmHg in 30 minutes. Thereafter, the reaction was further continued for 6.5 hours. The resulting polymer was white and had Mn 86,600, Mw 149,000, and its Mw / Mn was 1.72. Its melting temperature was 114.2 ° C and its 2% weight loss temperature was 318 ° C. The ratio of batyl alcohol contained in this polymer was 0.9 per 100 moles of the aliphatic dicarboxylic acid component contained in the polymer.
42 moles. When the mechanical strength was measured, the elastic modulus was 232 MPa, the upper yield point stress was 25.6 MPa, and the breaking stress was 58.
It was 0 MPa and the elongation at break was 787%. The high molecular weight aliphatic polyester produced according to the present invention has a copolymerized structure with 3-alkoxy-1,2-propanediol, and a small amount of 3-alkoxy-1,2-propanediol. The mechanical strength such as elongation at break can be greatly improved by the addition of. In the conventional production method, 3-alkoxy-1,2-
Since the reactivity of the secondary alcohol of propanediol is lower than the reactivity of other primary alcohols, the addition of 3-alkoxy-1,2-propanediol to a certain degree or more decreases the degree of polymerization of the formed polyester, The elongation at break tended to decrease significantly. In this production method, 3-alkoxy-
Since the two alcohols of 1,2-propanediol are esterified from the beginning, a large amount of 3-alkoxy-1,2-propanediol can be copolymerized without decreasing the degree of polymerization, and the elongation at break is high. Can be produced. Moreover, the high molecular weight aliphatic polyester has biodegradability based on the aliphatic ester bond.

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Takashi Masuda 1-1-1 Higashi, Tsukuba, Ibaraki Pref., National Institute of Advanced Industrial Science and Technology (56) References JP 9-31176 (JP, A) US Patent 5,487,966 (US, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C08G 63/00-63/91 CA (STN) REGISTRY (STN)

Claims (1)

(57) [Claim 1] A compound containing a 3-alkoxy-1,2-propanediol moiety represented by the following general formula (1): (Wherein, ^{R 1} represents an aliphatic group having 1 to 22 carbon atoms, ^{R 2}
Represents a divalent aliphatic group having 1 to 12 carbon atoms) and an aliphatic diol represented by the following general formula (2): HO-R ³ —OH (2) (wherein R ³ is A divalent aliphatic group having 1 to 12 carbon atoms) aliphatic dicarboxylic anhydride represented by the following general formula (3):
Or copolymerizing a diester of an aliphatic carboxylic acid represented by the following general formula (4): (Wherein, R ² represents a divalent aliphatic group having 1 to 12 carbon atoms). (Wherein, R ² represents a divalent aliphatic group having 1 to 12 carbon atoms,
R ⁴ represents an alkyl group having 1 to ⁴ carbon atoms) of a biodegradable high molecular weight aliphatic polyester having an ester portion A represented by the following general formula (5) and an ester portion B represented by the following general formula (6) Production method. Embedded image (In the formula, R ¹ and R ² are the same as described above. P represents the mole fraction of the ester portion (A) represented by the general formula (5).) (In the formula, R ¹ and R ² are the same as described above. R represents the mole fraction of the ester moiety (B) represented by the general formula (6).)