JP3439304B2 - Method for producing biodegradable polyester - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for producing a biodegradable polyester, and more particularly to a method for efficiently producing a modified biodegradable polyester.

[0002]

2. Description of the Related Art In recent years, polyethylene, polypropylene,
A huge amount of plastic products such as polystyrene, polyethylene terephthalate, and vinyl chloride are used,
These waste treatments have been highlighted as one of the environmental problems. That is, the current waste treatment is incineration or burial treatment, but when polyethylene or the like is incinerated, the burning calories are high, and the incinerator is damaged and the life is shortened. Further, for example, when polyvinyl chloride or the like is incinerated, harmful gas is generated. On the other hand, land is limited for burying plastic products. Further, when discarded in the natural environment, their chemical stability is extremely high, and they are biologically hardly decomposed by microorganisms, etc., and remain almost semipermanently. Therefore, it causes problems such as spoiling the landscape and polluting the living environment of marine life.

In order to solve these problems, biodegradable polymers have been developed for conventional plastics.
For example, polyglycolic acid, polylactic acid, poly-β-hydroxybutyric acid (PHB), poly-ε-caprolactone (P
CL), polybutylene succinate (PBS), polyethylene succinate (PES) and other aliphatic polyesters.

Among the above biodegradable polyesters, for example, PHB is difficult to control its molecular weight and crystallinity in its production, and PCL has a low melting point. for that reason,
From these, it has been difficult to obtain molded products suitable for various uses.

Further, polylactic acid has excellent biodegradability and high biosafety, and in addition, lactic acid, which is a decomposition product, is absorbed in the body, is inexpensive, is transparent, and is colorable. Is excellent in that it is good. However, lactic acid homopolymer has too high crystallinity and is inferior in melt moldability, the obtained molded product is brittle and has low impact strength, and it is difficult to produce a practical fiber from polylactic acid. There were also points.

In view of such circumstances, it would be advantageous to obtain a biodegradable polyester modified so as to be suitable for a target molded article while maintaining the biodegradable characteristics of the biodegradable polyester. As a study from this point of view, for example, in Japanese Patent Laid-Open No. 7-53685, copolymerization of a second component (azelaic acid and a polyester of ethylene glycol) to lower the melting point of polylactic acid to improve the processability. It is disclosed. Further, JP-A-7-165896 discloses that by copolymerizing polylactic acid with polyethylene glycol, effects such as an increase in decomposition rate and an improvement in impact strength can be obtained.

[0007]

However, in all of these publications, modifying components such as polyester of azelaic acid and ethylene glycol and polyethylene glycol are allowed to exist in the polymerization system from the initial stage of copolymerization. Therefore, with a modifying component such as polyethylene glycol, which is easily decomposed, the modifying component is decomposed during the polymerization, so that there is a problem that a desired copolymer is difficult to obtain. Further, since the modifying component is allowed to be present in the polymerization system from the initial stage of copolymerization, it is necessary to carry out a completely different polymerization reaction when it is desired to produce another type of polymer suitable for another purpose.

[0008] Therefore, an object of the present invention is to solve the above-mentioned problems of the prior art and to provide a method capable of efficiently and stably producing a modified biodegradable polyester.

[0009]

Means for Solving the Problems As a result of intensive investigations by the present inventors, they found that the above object can be achieved by adding a desired modifying component to a polymerization system in the latter stage of polymerization.
The present invention has been completed.

That is, the method for producing a biodegradable polyester of the present invention is based on a lactic acid-based resin containing a lactic acid unit as a main constituent unit.
When polymerizing the polymer, in the latter stage of the polymerization reaction or the polymerization reaction
After completion, the reforming component while maintaining the molten state of the polymerization reaction system
Is added.

In the present invention, the "modification" of the biodegradable polyester means the properties of the biodegradable polyester obtained.
It is to change the physical properties, for example, deterioration of crystallinity,
Decrease in melting point, improvement in flexibility and elastic recovery, improvement in heat resistance, decrease or increase in glass transition temperature, improvement in dyeability, improvement in hydrophilicity and water repellency, improvement in moist heat resistance, adhesion with other components Properties, miscibility, control of degradability, control of molecular weight, etc. Further, the “modifying component” is a component capable of modifying the obtained biodegradable polyester.

The present invention will be described in detail below. Examples of the aliphatic polyester in the present invention include poly (α-hydroxy acid) such as polyglycolic acid and polylactic acid; poly (β-hydroxyalkanoate) such as poly-β-hydroxybutyric acid (PHB); poly-ε -Poly (ω-hydroxyalkanoates) such as caprolactone (PCL); polybutylene succinate (PBS),
Examples thereof include polyalkylene alkanoates such as polyethylene succinate (PES) .

In the present invention, the lactic acid-based polymer may be polymerized by either a direct dehydration condensation method of a lactic acid monomer or a ring-opening polymerization method of a cyclic dimer lactide. That is, the lactic acid monomer may be used as the main polymerization raw material for direct dehydration condensation, or the main polymerization raw material may be lactide for ring-opening polymerization. The direct dehydration condensation method is described in, for example, JP-A-7-33861, and the lactide ring-opening polymerization method is described in, for example, US Pat. No. 4,057,537.
, Published European patent application No. 261572,
Polymer Bulletin, 14, 491-495 (1985), and Makromo
Chem., 187, 1611-1628 (1986) and the like.

When direct dehydration condensation is carried out, L-lactic acid, D
-Lactic acid, or any lactic acid monomer of these mixtures may be used. Further, the reaction may be carried out in a suitable organic solvent, and water produced by dehydration condensation may be distilled out of the reaction system together with the organic solvent. Suitable organic solvents include toluene, xylene, chlorobenzene, acetophenone, benzophenone, dibutylbenzene, anisole and the like.

When ring-opening polymerization is carried out, L-lactide, D
Any lactide, lactide, meso-lactide or mixtures thereof may be used. When a lactide other than L-lactide is used, it is preferable to use a ratio such that the amount of D-lactic acid units in all the lactic acid units in the obtained polymer is at most 40 mol%. D-
It is more preferable that the ratio is such that the lactic acid unit is up to 20 mol%.

Examples of the modifying component in the present invention include aliphatic polyesters, alcohols, carboxylic acids, esters, lactic acid and water.

Aliphatic polyesters as modifying components include (1) hydroxycarboxylic acids such as glycolic acid, lactic acid and hydroxybutylcarboxylic acid, (2) glycolide, lactide, ε-caprolactone glycolide, ε-caprolactone. Aliphatic lactones such as β-propiolactone, δ-butyrolactone, β- or γ-butyrolactone, pivalolactone, δ-valerolactone, etc.
(3) Aliphatic diols such as ethylene glycol, propylene glycol, butanediol, hexanediol, etc., (4) Polyalkylene ether oligomers such as diethylene glycol, triethylene glycol, ethylene / propylene glycol, dihydroxydiethylbutane, polyethylene. Glycol, polypropylene glycol, polyalkylene glycol such as polybutylene ether, (5) polypropylene carbonate, polyalkylene carbonate glycol such as polybutylene carbonate, and oligomers thereof, (6) succinic acid,
Adipic acid, suberic acid, azelaic acid, sebacic acid,
It is an aliphatic polyester derived from an aliphatic dicarboxylic acid such as decanedicarboxylic acid, and may be a homopolymer or a copolymer of the aliphatic polyester.

The aliphatic polyesters include block copolymers of the above-mentioned aliphatic polyesters with other components such as aromatic polyesters, polyethers, polycarbonates, polyamides, polyureas, polyurethanes and polyorganosiloxanes. It may be a random copolymer. Alternatively, it may be a mixture of the above aliphatic polyester and the above other components.

Transesterification occurs by adding an aliphatic polyester as a modifying component to the polymerization reaction system at the latter stage of the polymerization reaction or after the completion of the polymerization reaction, and the modifying component is incorporated into the biodegradable polyester. it is conceivable that. The introduction of the aliphatic polyester generally improves the melt index, softening point, tensile strength, elastic modulus, spinnability, moldability, brittleness and biodegradability of the biodegradable polyester.

Of the above aliphatic polyesters, polyglycolic acid, PHB, PCL, PBS and PES are preferable from the viewpoint of biodegradability.

Examples of the reforming component alcohols include methyl alcohol, ethyl alcohol, propyl alcohol,
Butyl alcohol, pentyl alcohol, hexyl alcohol, heptyl alcohol, octyl alcohol, decyl alcohol, lauryl alcohol, myristyl alcohol, cetyl alcohol, octadecyl alcohol,
Isopropyl alcohol, isobutyl alcohol, sec-
Butyl alcohol, butyl alcohol, isopentyl alcohol, 2-methyl-1-butyl alcohol, pentyl alcohol, cyclopentanol, cyclohexanol, allyl alcohol, crotyl alcohol, methyl vinyl carbinol, benzyl alcohol, phenyl ethyl alcohol, phenyl ethyl Examples thereof include alcohol, diphenylcarbinol, triphenylcarbinol, cinnamyl alcohol, ethylene glycol, propylene glycol, 1,3-propanediol, glycerin, pentaerythritol and polyethylene glycol.

It is considered that the addition of the modifying component alcohol to the polymerization reaction system causes a part of the polyester formed by the polymerization reaction to be cleaved or the polymer terminal to be blocked. Therefore, by adding alcohols,
Generally, the molecular weight of the biodegradable polyester can be controlled (decreased).

Of the above alcohols, the number of carbon atoms is 6 to 10.
Of these, aliphatic alcohols, ethylene glycol, propylene glycol, and glycerin are preferable from the viewpoint of easy handling and transparency retention.

When polyethylene glycol among the above alcohols is added to the polymerization reaction system, a biodegradable polyester copolymerized with polyethylene glycol can be obtained, and the strength and heat resistance of the biodegradable polyester can be improved. it can.

The carboxylic acids as the modifying component include formic acid,
Acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, oleic acid, linoleic acid, linoleic acid, cyclohexanecarboxylic acid, phenylacetic acid, benzoic acid, o-toluic acid, m-toluic acid, p-
Toluic acid, o-chlorobenzoic acid, m-chlorobenzoic acid, p-chlorobenzoic acid, o-bromobenzoic acid, m-bromobenzoic acid, p-bromobenzoic acid, o-nitrobenzoic acid, m-nitrobenzoic acid , P-nitrobenzoic acid, phthalic acid, isophthalic acid, terephthalic acid, salicylic acid, p-hydroxybenzoic acid, anthranilic acid, m-aminobenzoic acid, p-aminobenzoic acid, o-methoxybenzoic acid, m-
Examples thereof include methoxybenzoic acid and p-methoxybenzoic acid.

It is considered that the addition of the modifying component carboxylic acid to the polymerization reaction system causes a part of the polyester formed by the polymerization reaction to be cleaved or the polymer terminal to be blocked. Therefore, as in the case of adding alcohols, the addition of carboxylic acids can generally control (decrease) the molecular weight of the biodegradable polyester.

Of the above-mentioned carboxylic acids, caproic acid, caprylic acid and oleic acid are preferable from the viewpoint of easy handling and biodegradability.

Examples of the modifying component ester include triethyl citrate, triacetin, ethyl benzoate, methyl benzoate and the like. Further, as an intramolecular ester, an aliphatic lactone such as glycolide, lactide, ε-caprolactone glycolide, ε-caprolactone, β-propiolactone, δ-butyrolactone, β- or γ-butyrolactone, pivalolactone, δ-valerolactone and the like. Can be mentioned.

It is considered that when the modifying component ester is added to the polymerization reaction system, transesterification with the polymerized polyester occurs, and the modifying component is incorporated into the biodegradable polyester. When the modifying component is, for example, a trifunctional ester, generally, the biodegradable polyester is partially crosslinked, and mechanical strength such as tensile strength and brittleness, thermophysical properties,
Biodegradability is improved.

Also, the addition of lactic acid lowers the molecular weight, broadens the molecular weight distribution, and improves biodegradability and plasticity. By adding water, a part of the polymerized polyester is hydrolyzed, and the molecular weight of the biodegradable polyester is reduced.

In the present invention, the aliphatic polyesters, alcohols, carboxylic acids, esters, lactic acid, and water as modifying components may be added alone or in admixture of two or more. It is also possible.

The amount of the modifying component to be added depends on the properties and physical properties of the biodegradable polyester to be modified and the type of the modifying component used, and is not particularly limited, but it is generally a polymerization. 0.001 to 50% by weight of raw material
Is. If it is less than 0.001% by weight, the modifying effect is small. Moreover, even if it is added in an amount of more than 50% by weight, the modification effect is not improved and it is not economically preferable.

For example, when a monoalcohol is added as a modifying component, 0.001 to 1% by weight based on the polymerization raw material is used.
The molecular weight of the biodegradable polyester can be controlled with a small addition amount. When polyethylene glycol is added for copolymerization, the amount added may be about 0.1 to 50% by weight, preferably about 1 to 10% by weight. When water is added as a modifying component, the addition amount is preferably about 0.001 to 1% by weight based on the polymerization raw material.

In the case of other aliphatic polyesters, carboxylic acids, esters, and lactic acid, the addition amount can be appropriately determined depending on the properties and physical properties of the biodegradable polyester to be modified.

In the method of the present invention, the modifying component is added at the latter stage of the polymerization reaction or after the completion of the polymerization reaction while maintaining the molten state of the polymerization reaction system. The latter stage of the polymerization reaction usually means a state in which 70% by weight or more of the polymerization raw material has reacted and converted into a polymer. The term “after completion of the polymerization reaction” refers to the point after the point where the polymer conversion rate of the polymerization raw material is saturated. In the present invention,
The modifying component is added preferably in a state where 80% by weight or more of the polymerization raw material has reacted, and more preferably in a state where 90% by weight or more of the polymerization raw material has reacted.

As described above, by adding the modifying component at the latter stage of the polymerization reaction or after the completion of the polymerization reaction, decomposition of the modifying component can be minimized even when the modifying component is easily decomposed such as polyethylene glycol. To be Further, even if the modifying component is added in the latter stage of the polymerization reaction or after the completion of the polymerization reaction, the modifying component does not simply blend with the already formed polymer, but the modifying component reacts with the polymer. For example, when a polymer such as an aliphatic polyester or polyethylene glycol is used as the modifying component, it is assumed that the total polymerization time is 20 hours, and the last 5
When the modifier polymer is added within 30 minutes, 60 to 90% by weight of the modifier polymer reacts to form a copolymer. Therefore, the property to be modified of biodegradable polyester
A modified biodegradable polyester can be obtained by selecting the type of modifying component according to the physical properties.

In the present invention, a polymerization catalyst can be used in the polymerization reaction. The polymerization catalyst is not particularly limited, but is usually group IA, group IIIA, group IVA of the periodic table,
A catalyst made of a metal or a metal compound selected from the group consisting of IIB group, IVB group and VA group can be used.

Examples of the compounds belonging to Group IA include alkali metal hydroxides (eg, sodium hydroxide, potassium hydroxide, lithium hydroxide, etc.), alkali metal and weak acid salts (eg, sodium lactate, sodium acetate). , Sodium carbonate, sodium octylate, sodium stearate, potassium lactate, potassium acetate, potassium carbonate, potassium octylate, etc.), alkali metal alkoxides (eg, sodium methoxide, potassium methoxide, sodium ethoxide, potassium ethoxide, etc.) )
Etc. can be mentioned.

Examples of members belonging to Group IIIA include
Aluminum ethoxide, aluminum isopropoxide, aluminum oxide, aluminum chloride, etc. can be mentioned.

Examples of members belonging to Group IVA include organotin catalysts (eg, tin lactate, tin tartrate, tin dicaprylate, tin dilaurate, tin dipalmitate, tin distearate, tin dioleate, α- (Tin naphthate, β-tin naphthate, tin octylate, etc.)
Besides, tin powder, tin oxide and the like can be mentioned.

Examples of members belonging to Group IIB include zinc dust, zinc halide, zinc oxide, and organic zinc compounds.

Examples of compounds belonging to Group IVB include titanium compounds such as tetrapropyl titanate and zirconium compounds such as zirconium isopropoxide.

Examples of members belonging to Group VA include antimony compounds such as antimony trioxide and bismuth oxide.
Examples thereof include bismuth compounds such as (III).

Of these, a catalyst made of tin or a tin compound is particularly preferable from the viewpoint of activity.

The amount of these catalysts used is, for example, about 0.0001 to 5% by weight based on the raw material lactic acid monomer or lactide in the case of lactic acid-based polymer polymerization.

The polymerization reaction can be carried out in the presence of the above-mentioned catalyst at a temperature of 100 to 200 ° C., though it varies depending on the catalyst species. Further, when the modifying component is added after the completion of the polymerization reaction, it is necessary to maintain the molten state of the polymerization reaction system, so that a rapid temperature decrease after the completion of the polymerization reaction is not preferable. The time required for the polymerization reaction depends on the type and amount of the polymerization catalyst, the polymerization reaction temperature and the like.

In the present invention, it is preferable to add a catalyst deactivator to deactivate the catalyst at the latter stage of the polymerization reaction or after the completion of the polymerization reaction. As the catalyst deactivator, an aluminum compound such as a phosphoric acid-based aluminum compound or aluminum oxide; monostearyl acid phosphate, distearyl acid phosphate, trimethyl phosphate, tri-n-butyl phosphate, triphenyl phosphate, phosphorous acid Phosphoric acid esters such as triphenyl, diethyl phosphite, dibutyl phosphite, trimethyl phosphite, tributyl phosphite; sodium dihydrogen phosphate, potassium pyrophosphate, bis (3,5-di-t-butyl) -4-Phosphoric acid-based metal salts such as ethyl cohydroxybenzylphosphonate) calcium;
An oxidizing agent such as dibenzoyl peroxide; a mixture thereof and the like can be mentioned. The amount of the catalyst deactivator added is about 0.5 to 20% by weight based on the amount of the catalyst used.

Further, the catalyst is deactivated in the latter stage of the polymerization reaction or after the completion of the polymerization reaction, and the unreacted lactide, lactic acid, and other low-molecular compounds are removed by depressurizing the catalyst in the molten state, and the resulting polymer contains them. It is preferable to reduce the amount. For example, the lactide content in the polymer is preferably 0.1% by weight or less from the viewpoint of product quality (decomposition stability, etc.).

Further, in the present invention, a stabilizer such as calcium stearate, a plasticizer such as phthalate ester, a coloring agent such as red lead yellow lead, titanium oxide and the like may be used in the latter stage of the polymerization reaction or after the completion of the polymerization reaction, if necessary. It is also possible to add various known additives.

The process according to the invention can be carried out either continuously or batchwise.

According to the method of the present invention, since the modifying component is added at the latter stage of the polymerization reaction or after the completion of the polymerization reaction while maintaining the molten state of the polymerization reaction system, the modifying component is easily decomposed such as polyethylene glycol. Even in this case, the decomposition of the modifying component can be suppressed to the minimum, and the desired biodegradable polyester can be obtained.

When it is desired to produce two or more kinds of polymers having different modifying components, the polymerization reaction can be carried out from the first stage of the polymerization reaction.
It is possible to obtain biodegradable polyesters of two or more kinds by standardizing the middle period and branching (or switching) the latter half of the polymerization reaction to two or more polymerization reaction systems and adding separate modifying components to each. It is possible to carry out rational and flexible polymer production. For example, by using a vertical reactor 2 unit and a horizontal reactor 1 unit which are arranged in series, the polymerization reaction in the first half to the middle period is performed in common, and then the latter polymerization reaction or demomerization is performed using an extruder. In this case, two extruders are arranged in parallel, and different reforming components are added at the inlets of the extruders, respectively, so that two kinds of polymers can be efficiently produced. In such a case, the residence time in the extruder is usually short (about 1 to 30 minutes), so switching the product type quickly,
Moreover, the waste of resin can be reduced.

[0053]

EXAMPLES The present invention will be described in more detail below with reference to examples and comparative examples.

The analysis was carried out as follows. <Weight Average Molecular Weight of Polymer> The weight average molecular weight of the polymer was measured by GPC (gel permeation chromatography) under the following conditions. Detector: RID-6A, Pump: LC-9A, Column oven: GT
O-6A, Column: Shim-pack GPC-801C, -804C, -806C, -8
025C in series (manufactured by Shimadzu Corporation) Mobile phase: chloroform, flow rate: 1 ml / min, sample amount: 200 μl (dissolved in chloroform so that the sample concentration becomes 0.5 w / w%), column temperature: 40
° C.

<Raw material conversion rate> A certain amount of sample was sampled from the reaction system and G
The conversion rate (%) was determined from the area ratio of the polymer and the monomer in the chromatogram obtained by the PC analysis.

[Example 1] One vertical reactor (Full Zone, manufactured by Shinko Pantec Co., Ltd.) and one vertical reactor (Log Horn, manufactured by Shinko Pantec Co., Ltd.)
A polymerization apparatus was used in which a reactor, a horizontal reactor (manufactured by Shinko Mex Co., Ltd.), and an extruder (HYPERKTX, manufactured by Kobe Steel Ltd.) were arranged in series in this order.

At the inlet of the first vertical reactor, L-lactide (manufactured by Shimadzu Corporation) and 0.001% by weight of tin octylate catalyst based on lactide were introduced, and the reaction temperature was 180.
The polymerization reaction was carried out at an average residence time of 18 hours at 3 ° C. in three reactors. The polylactic acid-lactide mixed melt at the outlet of the horizontal reactor had a raw material conversion rate of 95%. Polyethylene glycol (average molecular weight 6000, manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.) as a modifying component was added to this mixed melt in an amount of 5% by weight with respect to the raw material lactide and introduced into an extruder at a temperature of 180 ° C., a pressure of 5 mmHg, and an average residence While kneading for 10 minutes, unreacted lactide was removed, and polylactic acid-polyethylene glycol copolymer was obtained from the extruder outlet.

The weight average molecular weight of the obtained copolymer was G.
It was 170,000 as measured by PC. The glass transition temperature and melting point of the copolymer are measured by a differential scanning calorimeter (DS).
It was 50 degreeC and 170 degreeC, respectively, as measured by C). In addition, according to the proton nuclear magnetic resonance spectroscopy measurement ( ¹ H-NMR, CDCl ₃ ) of the reprecipitated copolymer, in addition to the signal due to the lactic acid unit around 1.5 and 5.1 ppm, around 3.6 ppm. It was confirmed that the copolymer has a signal due to the oxyethylene unit. The polyethylene glycol content (% by weight) in the copolymer is 1.5 ppm.
It was 4.5% by weight as determined from the integrated value of the methyl group of lactic acid unit and the integrated value of the methylene group of oxyethylene unit of 3.6 ppm as follows.

Since this copolymer has better stretchability than the polylactic acid of the Comparative Example described later, it is suitable for film and fiber applications.

[0060]

[Equation 1]

Example 2 1-octanol (Wako Pure Chemical Industries, Ltd.) was used as a molecular weight modifier instead of polyethylene glycol as a modifying component.
A polymer was obtained from the extruder outlet in the same manner as in Example 1 except that 0.01% by weight was added to the raw material lactide.

The weight average molecular weight of the obtained polymer was GP.
It was 90,000 as measured by C. The glass transition temperature and melting point of the polymer were 55 ° C. and 165 ° C., respectively, as measured by a differential scanning calorimeter (DSC).

This polymer has low viscosity and biodegradability in a short period of time as compared with the polylactic acid of Comparative Example described later,
Suitable for non-woven fabrics and molded products that require fast degradability.

Comparative Example A polymer was obtained from the extruder outlet in the same manner as in Example 1 except that the modifying component was not added.

The weight average molecular weight of the obtained polymer was GP.
It was 230000 as measured by C. The glass transition temperature and melting point of a polymer are measured by a differential scanning calorimeter (DSC).
The temperature was 60 ° C. and 175 ° C., respectively.

[0066]

As described above, according to the production method of the present invention, since the modifying component is added at the latter stage of the polymerization reaction or after the completion of the polymerization reaction while maintaining the molten state of the polymerization reaction system, the modifying component is decomposed. Even if it is easy to do, the decomposition of the modifying component can be suppressed to the minimum, and the target biodegradable polyester can be obtained.

According to the production method of the present invention, two or more types of biodegradable polyesters can be obtained by sharing the first half to the middle half of the polymerization reaction and branching or switching the latter half of the polymerization reaction to two or more polymerization reaction systems. Obtainable. Therefore, it has been modified so as to be suitable for a desired molded article use, that is, for example, a decrease in crystallinity, a decrease in melting point, an improvement in flexibility and elastic recovery, an improvement in heat resistance, a decrease or increase in glass transition temperature. Efficiently produce polymers with improved dyeability, improved hydrophilicity and water repellency, improved moist heat resistance, improved adhesion and miscibility with other components, controlled degradability, controlled molecular weight, etc. be able to. As a result, a cost reduction effect of polymer production can be obtained.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁷ Identification symbol FI // C08L 101/16 C08L 101/16 (72) Inventor Yasuhiro Fujii 1 Kuwaharacho, Nishinokyo, Nakagyo-ku, Kyoto-shi, Shimadzu Shimadzu Sanjo Co., Ltd. Inside the factory (72) Inventor Masahiro Ito 1 Nishinokyo Kuwabara-cho, Nakagyo-ku, Kyoto Prefecture Shimadzu Corporation Sanjo Factory (72) Inventor Hiroshi Maeda 4-3 Bingo-cho, Chuo-ku, Osaka Manufactured by Kobe Tsunasho Osaka Branch (72) Inventor Kunihiko Shimizu 4- 1-3 Bingocho, Chuo-ku, Osaka Co., Ltd. Kobe Steel Ltd. No. 3 Incorporated company Kobe Steel Co., Ltd. Osaka branch office (72) Inventor Koji Yamamoto 1-5-5 Takatsukadai, Nishi-ku, Kobe City Kobe Steel Co., Ltd. Kobe Research Institute In-house (56) Reference JP-A-6-145313 (JP, A) JP-A-6-16792 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) C08G 63/00- 63/91

Claims (6)

(57) [Claims] 1. A method for polymerizing a lactic acid-based polymer having a lactic acid unit as a main constituent unit, characterized in that a modifying component is added in the latter stage of the polymerization reaction or after the completion of the polymerization reaction while maintaining the molten state of the polymerization reaction system. , A method for producing a biodegradable polyester. 2. A using a polymerization main raw material as a cyclic dimer lactide of lactic acid the lactic acid-based polymer, performing ring-opening polymerization method for producing a biodegradable polyester according to claim 1. 3. The method for producing a biodegradable polyester according to claim 1 , wherein lactic acid is used as a main raw material for polymerizing the lactic acid-based polymer, and direct dehydration condensation is performed. After wherein more than 70% by weight of polymerized material was reacted, adding modifying components, a manufacturing method of a biodegradable polyester according to any one of claims 1-3. 5. The modifying component is at least one compound selected from aliphatic polyesters, alcohols, carboxylic acids, esters, lactic acid and water, wherein the modifying component is any one of claims 1 to 4 . The method for producing the biodegradable polyester according to item 1. 6. adding 0.001 to 50 wt% of the amount of modifying component to the polymerization raw material, manufacturing method of the biodegradable polyester according to any one of claims 1-5.