JPH0616790A - Aliphatic polyester and its production - Google Patents

Abstract

PURPOSE:To provide a new aliphatic polyester expected to have a high biodegradability, and to provide the method for producing the same. CONSTITUTION:The aliphatic polyester is characterized by comprising an aliphatic polyester in which the monomer units are randomly arranged in the polymer molecule and which has a reducing viscosity of >=0.1, the polyester substantially comprising the condensation reaction product of lactic acid or/and glycolic acid with 3-hydroxybutyric acid, and the method for producing the same. Since both the copolymerization units of the aliphatic polyester have biodegradability, respectively, the copolymer is expected to have a high biodegradability, and since the copolymer has a moldable mol.wt., a wide range of uses can be expected.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a novel aliphatic polyester and a method for producing the same, more specifically, a bio-absorbable or biodegradable copolymerizable aliphatic compound having a moldable molecular weight. The present invention relates to polyester and a method for producing the same.

[0002]

2. Description of the Related Art Conventionally, polylactic acid, polyglycolic acid and their copolymers have been used as sustained-release polymers as biodegradable medical materials such as surgical sutures and microcapsules for injections, and herbicides. It is used as an agrochemical composition.
In recent years, plastic pollution has become a serious problem, and attention has been paid to it as a biodegradable plastic that can be expected to be decomposed by enzymes and microorganisms, and research and development is proceeding. Among them, poly (3-hydroxybutyric acid) has long been known as a microorganism-produced plastic, and recently research and development as a biodegradable plastic has been advanced.

[0003]

The above-mentioned polylactic acid, polyglycolic acid or copolymers thereof have attracted attention as biodegradable polymers obtained by chemical synthesis, and research on copolymers with other aliphatic polyesters. Is being advanced. On the other hand, poly (3
-Hydroxybutyric acid) is also being actively researched. By the way, poly (3-hydroxybutyric acid) has high biodegradability, but has a low glass transition point, is hard and brittle,
Since molding is difficult, investigations have been made on copolymers that improve the moldability. However, almost all of these studies are based on fermentation synthesis by microorganisms, and few studies are conducted by chemical synthesis.

[0004]

SUMMARY OF THE INVENTION The inventors of the present invention have made earnest studies on the biodegradable aliphatic polyester obtained by chemical synthesis, and as a result, have finally completed the present invention. That is, the present invention is an aliphatic polyester in which monomer units are randomly arranged in a polymer molecule, and the polyester is substantially lactic acid or /
And an aliphatic polyester which is a condensation reaction product of glycolic acid and 3-hydroxybutyric acid, and a method for producing the same.

The aliphatic polyester in the present invention can be obtained, for example, by dehydration polycondensation of oxyacid or ring-opening polymerization of lactone and lactide. When performing the dehydration polycondensation, lactic acid and / or glycolic acid and 3
-Hydroxybutyric acid mixture is heated under reduced pressure or under a stream of an inert gas such as nitrogen. Lactic acid and 3-hydroxybutyric acid may be any of D, L and racemates, and it is also possible to use an ester such as methyl ester, in which case a dealcoholization reaction is carried out. Furthermore, the forms of these monomers may be used as solids, liquids, or aqueous solutions. However, when an aqueous solution is used, it is desirable to appropriately pre-concentrate before starting the reaction.

The dehydration polycondensation of the oxyacid is a sequential reaction, and the molecular weight increases with the reaction time. However, this reaction is an equilibrium reaction, and a catalyst may be used because its equilibrium constant is small. As a catalyst, a metal or a metal compound,
For example, compounds such as tin, titanium, antimony, germanium, zinc, tungsten, and niobium can be used, but the compounds are not limited to these. When these catalysts are used, they may be added at the same time as the monomers, or may be added when the reduced pressure is reached after the initial polymerization is completed. When using an aqueous solution for the monomer,
It is desirable to add after the concentration operation is completed. Further, the catalyst may be dissolved in a suitable solvent and added, or may be added as it is. The amount of catalyst used is 0.005
0.50 mol% is preferable, and 0.03 to 0.10.
mol% is preferred. If it is 0.005 mol% or less, almost no catalytic effect is recognized, and if it is 0.50 mol% or more, coloring and deterioration of the polymer are recognized during the reaction, which is not preferable.

Next, the polycondensation reaction in the present invention can be carried out by the following method, for example. The monomer and catalyst charged in the reaction vessel are replaced with an inert gas such as nitrogen, the temperature is gradually raised under an inert gas stream, and initial polymerization is performed at a predetermined temperature for a predetermined time. Continue to decompress,
The reaction is stopped for a predetermined time or when a predetermined torque is reached. The reaction temperature is determined by the composition of the polymer produced, but the degree of vacuum is 10 mmHg or less, especially 1 m.
It is desirable to set it to mHg or less.

On the other hand, when the polymer is synthesized by ring-opening polymerization,
Lactide and / or glycolide and β-butyrolactone are used as starting materials, and heated under an inert gas stream or under reduced pressure. Lactide and β-butyrolactone are
Any of D, L, racemate and meso form may be used. However, when lactones and lactides are used as starting materials, it is desirable to purify them by recrystallization or the like in advance. A catalyst is usually used for the ring-opening polymerization, and a metal compound such as tin, zinc, aluminum or antimony is used as the catalyst. It is also possible to add an end-capping agent such as alcohols and a molecular weight modifier to the reaction system.

Ring-opening polymerization can be carried out, for example, as follows. After the monomer and the catalyst are put into a reaction vessel and replaced with an inert gas, the reaction is carried out at a predetermined temperature under reduced pressure. After completion of the reaction, the produced polymer is taken out directly or after being dissolved in an appropriate solvent. When dissolved and taken out, it can be isolated by reprecipitation in water or the like.

In the present invention, direct polymerization and ring-opening polymerization may be used in combination, and for example, a mixture of oxyacid and lactide may be used as a starting material. The polymer obtained by the method described above is a sufficiently high molecular weight polymer, but post-treatment using solid-phase polymerization or the like may be sufficient to further increase the molecular weight.

[0011]

EXAMPLES The present invention will now be specifically described with reference to examples, but the present invention is not limited thereto. The characteristic values in the examples were measured by the following methods. Reduced viscosity (ηsp / c): 0.125 g of a polymer was dissolved in a mixed solvent of trichlorophenol / phenol (7/10 wt%) and measured at 30 ° C. Melting point: Using a DSC7 manufactured by Perkin Elmer Co., Ltd., it was measured under a nitrogen stream at a temperature rising / falling rate of 10 ° C./min. NMR: Measured with a mixed solvent of trifluoroacetic acid / deuterated chloroform using Gemini-200 manufactured by Varian.

Example 1 50 g of glycolic acid, 5 g of 3-hydroxybutyric acid (L-form) and 0.04 g of germanium oxide as a catalyst were placed in a reaction vessel equipped with a stirrer and a nitrogen introducing tube, and nitrogen substitution was carried out three times. It was Under a nitrogen stream, the temperature was raised to 180 ° C. at 10 ° C./minute, and the mixture was stirred for 1 hour. Subsequently, the pressure was reduced to 20 mmHg in 30 minutes, and the mixture was stirred for 1 hour. Further, the degree of vacuum was further raised to 1 mmHg, and at the same time, the temperature was raised to 220 ° C. and the stirring reaction was continued for 3 hours. After the reaction was completed, the polymer in a molten state was taken out. The obtained polymer was white and had a reduced viscosity of 0.41 and a melting point of 198 ° C.

Example 2 Instead of 3-hydroxybutyric acid in Example 1, 3-hydroxybutyric acid was used.
The same operation as in Example 1 was carried out except that hydroxybutyric acid methyl ester was used to obtain a white polymer. The reduced viscosity was 0.48 and the melting point was 201 ° C. N of this polymer
The MR spectrum is shown in FIG. As is clear from FIG. 1, glycolic acid unit, 1.3, 2.8
Absorption due to 3-hydroxybutyric acid units was observed at 5.3 ppm. Further, the obtained polymer is 180 ° C /
When solid phase polymerization was carried out in an ampoule at 0.5 mmHg for 24 hours, the reduced viscosity of this polymer was 0.68.

COMPARATIVE EXAMPLE 1 50 g of glycolic acid and D were placed in the same reaction vessel as in Example 1.
L-lactic acid 6g, germanium oxide 0.04g as a catalyst
Was charged, the atmosphere was replaced with nitrogen, the temperature was raised to 200 ° C., and the mixture was stirred for 1 hour. Subsequently, a stirring reaction was performed at 200 ° C./10 mmHg for 1 hour and at 230 ° C./0.5 mmHg for 2 hours to obtain a white polymer. The reduced viscosity was 0.57 and the melting point was 198 ° C. The NMR spectrum of this polymer is shown in FIG. As is clear from FIG. 2, absorption due to glycolic acid unit was observed at 4.9 ppm, and absorption due to lactic acid unit was observed at 1.6 ppm and 5.3 ppm.

Example 3 A reaction vessel similar to that used in Example 1 was charged with 40 g of glycolic acid and D.
5 g of L-lactic acid, 5 g of 3-hydroxybutyric acid, and 0.06 g of antimony oxide as a catalyst were added. After purging with nitrogen three times, the temperature was raised to 180 ° C. and the stirring reaction was carried out for 2 hours. 180 ° C / 20 mmHg for 2 hours, 200 ° C /
A light yellow polymer was obtained by continuing the reaction at 1 mmHg for 3 hours. This polymer was amorphous, had no melting point, and had a glass transition temperature of 41 ° C.

Example 4 In a reaction vessel similar to that of Example 1, D purified by recrystallization was used.
40 g of L-lactide, 7 g of β-butyrolactone and 0.06 g of tin octylate as a catalyst were added as a 1 cc toluene solution. The temperature was raised to 200 ° C. at 10 ° C./min in a nitrogen stream, the reaction was continued for 5 hours, and the polymer in a molten state was taken out. The polymer had a reduced viscosity of 0.66, no melting point, and a glass transition point of 48 ° C.

Example 5 10 g of glycolic acid and 2 g of 3-hydroxybutyric acid were placed in a glass ampoule and heated to 150 ° C. under a nitrogen stream. After reacting for 1 hour, the pressure was reduced to 10 mmHg, and when the reaction was continued for 1 hour, the system solidified. In the solidified state as it was, the degree of reduced pressure was increased to 0.5 mmHg and the reaction was carried out for 20 hours. The ampoule was cooled and crushed to remove the polymer inside. The obtained polymer was white and had a melting point of 188 ° C.

[0018]

The aliphatic polyester of the present invention having the above-mentioned constitution can be expected to have high biodegradability, and its physical properties such as crystallinity and amorphousness can be changed depending on its composition, so that it can be widely used. As a result, it will greatly contribute to industry and environmental protection.

[Brief description of drawings]

1 is an NMR spectrum of the polymer of the present invention obtained in Example 2. FIG.

FIG. 2 is an NM of the polymer obtained according to Comparative Example 1.
It is an R spectrum.

Claims (3)

[Claims] 1. An aliphatic polyester in which monomer units are randomly arranged in a polymer molecule and have a reduced viscosity of 0.1 or more, wherein the polyester is substantially lactic acid or / and glycolic acid and 3-hydroxybutyric acid. An aliphatic polyester which is a condensation reaction product of 2. Lactic acid or / and glycolic acid and 3-
A method for producing an aliphatic polyester, which comprises subjecting hydroxybutyric acid as a starting material to direct dehydration polycondensation. 3. Lactide and / or glycolide and β
-A method for producing an aliphatic polyester, which comprises using butyrolactone as a starting material and performing ring-opening polymerization.