JPH0665359A - Biodegradable, optically active polyester and its production - Google Patents

Abstract

PURPOSE:To obtain a new optically active polyester compound useful as a functional material having biodegradability and hydrolyzability by selecting a specified biodegradable, optically active polyester. CONSTITUTION:A biodegradable, optically active polyester of formula I (wherein R<1> is 1-4C alkyl; k is 0 or 1; and (m) and (n) are each 10-2000). This polyester can be obtained desirably by copolymerizing (+ or -)-beta-butyrolactone of formula II or L-lactide of formula III with an optically active gamma-alkyl-gamma-lactone of formula IV through ring opening in the presence of at least one catalyst selected from among diethylzinc, a diethylzinc/water complex and a borontrifluoride/ether complex.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a biodegradable optically active polyester and a method for producing the same. More specifically,
The present invention relates to a biodegradable optically active polyester obtained by ring-opening copolymerization of an optically active γ-lactone derivative and (±) -β-butyrolactone or L-lactide, and a method for producing the same. The polyester according to the present invention is a thermoplastic resin having optical activity, biodegradability (enzymatic degradability), and hydrolyzability, and is widely used as a clean plastic that does not pollute the environment because it is decomposed by microorganisms existing in soil or water. It is a functional polymer that can be used.

[0002]

2. Description of the Related Art The 5-membered ring .gamma.-lactone corresponding to the basic skeleton of the polymer of the present invention is extremely unlikely to undergo ring-opening polymerization, and .gamma.-butyrolactone having no side chain has a condition of 20,000 atm and 160.degree. Polymerize with (F. Kor
te, W. Gelt, Polymer Letters., 4, 685 (1966)), and by adding a small amount of water to the reaction system at 200 ° C. without using a catalyst, γ-butyrolactone is copolymerized with glycolic acid or lactic acid. Things (H. Fukuzaki etal. Macromol. C
hem., 190, 1553-1559 (1989); Eur. Polym. J., Vol.
26, No. 4, 457-461 (1990)) has been reported.

On the other hand, recently, polyesters having optically active 3-hydroxybutyric acid and optically active lactic acid units have biodegradability, that is, enzymatic degradability, hydrolyzability, biocompatibility, etc. Is attracting attention as a biodegradable material (biodegradable polymer material, edited by Yoshiharu Dohi, published by Industrial Research Group 1990) However, γ-lactone having a substituent at the γ-position has low ring-opening polymerizability,
There is a problem in synthesizing a novel polyester by ring-opening copolymerization of -alkyl-γ-lactone.

Therefore, the object of the present invention is to combine optically active γ-substituted-γ-butyrolactone, which is less likely to undergo ring-opening polymerization, with another ring-opening copolymerizable monomer to contain a 4-hydroxybutyric acid unit, It is intended to provide a novel optically active polyester excellent in degradability (enzymatic degradability) and hydrolyzability, and to provide a method for producing the polyester.

[0005]

Means for Solving the Problems As a result of intensive studies to solve the above problems, the present inventors have found that optically active γ-alkyl-γ-butyrolactone and (±) -β-butyrolactone or L-lactide The present invention has been completed by discovering that the ring-opening copolymerization of the above-mentioned compound was carried out in the presence of a specific catalyst to give a corresponding optically active polyester. That is, the present invention

1) General formula (I)

[Chemical 6] (In the formula, R ¹ represents an alkyl group having 1 to 4 carbon atoms, k
Represents 0 or 1, and m and n represent numbers from 10 to 2000. ) A biodegradable optically active polyester represented by
and

Formula 2)

[Chemical 7] (±) -β-butyrolactone represented by

[Chemical 8] L-lactide represented by the general formula (II)

[Chemical 9] (Wherein R ¹ has the same meaning as described in ¹ above), and the optically active γ-alkyl-γ-lactone is represented by (i)
Diethyl zinc, (ii) diethyl zinc-water complex and (iii)
General formula characterized by ring-opening copolymerization in the presence of at least one catalyst selected from boron trifluoride ether complex
(I)

[Chemical 10] (Wherein R ¹ , k, m and n have the same meanings as described in 1 above), and a method for producing a biodegradable optically active polyester.

The present invention will be described in detail below. Optically active γ-alkyl-γ-, which is one of the raw materials for the polymer of the present invention
Butyrolactone is a method described in JP-A-4-108782, that is, the general formula (III)

[0009]

[Chemical 11]

(In the formula, R ² represents an alkyl group having 1 to 4 carbon atoms, and R ³ represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms.) Γ-keto acid or γ-keto ester Can be easily obtained by asymmetric hydrogenation using a ruthenium-optically active phosphine complex as a catalyst to perform intramolecular ring closure.

Specific examples of the optically active γ-alkyl-γ-butyrolactone include γ-methyl-γ-butyrolactone, γ-ethyl-γ-butyrolactone, γ-n-butyl-γ-butyrolactone and γ-isopropyl-γ-. Butyrolactone and the like can be mentioned.

Further, (±) -β-butyrolactone and L-lactide, which are the other raw materials of the polymer of the present invention, are commercially available and are purified before use. Purification can be carried out, for example, by repeating the operation of adding calcium hydride and distilling twice, and the purified product stored in an inert gas can also be used.

In the present invention, the optically active γ-alkyl-γ-butyrolactone and (±) -which are used in the ring-opening copolymerization reaction are used.
The ratio with β-butyrolactone is 3 to 95: 97: 5, preferably 7 to 90:93 to 1 in terms of the molar ratio of the former to the latter.
0, and the ratio of the optically active γ-alkyl-γ-butyrolactone and L-lactide is 10 to 90:90 to 10, preferably 15 to 85: 8 in terms of the mole ratio of the former to the latter.
5 to 15. In the ratio of γ-alkyl-γ-butyrolactone and (±) -β-butyrolactone or L-lactide, if the former exceeds the above range, copolymerization hardly occurs, and if it is less than the above range, γ-alkyl −
The content of γ-butyrolactone unit decreases, and biodegradability decreases.

Ring-opening copolymerization is an optically active γ-alkyl-
γ-butyrolactone and (±) -β-butyrolactone or L-lactide are charged into a reaction vessel under an inert gas such as nitrogen or argon at an appropriate ratio within the above range, and a catalyst is added thereto at normal pressure. 20-40 ° C (preferably 25
C.-35.degree. C.) with stirring in the usual way at a temperature of 30.
The reaction is carried out for minutes to 2 weeks, preferably 3 to 5 hours.

As the catalyst, diethyl zinc, diethyl zinc-water complex, boron trifluoride ether complex (BF ₃ .Et.
₂ O) and the like are used. These catalysts can use at least 1 type or 2 types. The catalyst is 1/10 to 1/2000 times the mol of the total number of mols of the raw material monomers,
It is preferably used in an amount of 1/100 to 1/500 times the molar amount.

The proportion of the monomer units in the ring-opening copolymer obtained by the method of the present invention depends on the charged amount of the monomers, but the proportion of the optically active γ-alkyl-γ-butyrolactone and (±) -β-butyrolactone is The former: latter molar ratio is 15-40: 85-60, and the ratio of the optically active γ-alkyl-γ-butyrolactone and L-lactide is 1-5: latter: 99-95
Is.

[0017]

INDUSTRIAL APPLICABILITY According to the present invention, an optically active γ-alkyl-γ-butyrolactone and (±) -β-butyrolactone or L-lactide are subjected to ring-opening copolymerization to give an optical composition containing a 4-hydroxybutyric acid unit. A useful polymer, which is a new functional material having characteristics of active, biodegradable (enzymatic) and hydrolyzable, can be easily produced by an industrially advantageous method. Such an optically active polyester of the present invention can be used for medical materials such as surgical thread and materials for agricultural sheets.

[0018]

The present invention will be described in more detail with reference to examples and test examples, but the present invention is not limited to these examples. The analytical instruments used in the examples and the facilities used in the biodegradability test are as follows. Nuclear magnetic resonance spectrum (NMR): Varian XL-200 type device (200 MHz) (manufactured by Varian) Molecular weight: HLC-802A (manufactured by Tosoh Corporation) Differential scanning calorimeter (DSC): DSC-3100 (Mac Science Co., Ltd.) Optical rotation: PM-101 type high-sensitivity automatic polarimeter (manufactured by Union Giken Co., Ltd.) Biodegradability test: "Test method for new chemical substances" using activated sludge from Takasago International Corporation ( Environmental protection business No. 5, Yakuhin 615, 49 base station 392, Showa 49
(July 13, 2013) (degradation test of chemical substances by microorganisms) and Y. Doi, A. Segawa, and M. Kuniok
a, Int. J. Biol. Macromol., 1990, Vol.12, April, 1
06. Performed according to the description.

Examples 1-5 : (R) -γ-methyl-γ-
Synthesis of polyester by ring-opening copolymerization of butyrolactone and L-lactide

Example 1 (R) -γ-methyl-γ-butyrolactone (hereinafter abbreviated as γVL) 0.3 g (3.0 mmol) and L-lactide (hereinafter abbreviated as LLA) were placed in a 20 ml reaction vessel.
1.7 g (11.8 mmol) and 0.02 g (0.16 mmol) of diethyl zinc were stirred at 25 ° C. for 30 minutes under a nitrogen stream. To the reaction solution was added 0.1 ml of methanol to stop the reaction, and the product was dissolved in 2 ml of chloroform to obtain 20 m of methanol.
The resulting polyester was reprecipitated to obtain the title polyester (yield 51.9%). ¹ H-NMR (CDCl ₃ ) δppm: γVL part 1.4-
1.7 (3H, m), 1.8 ~ 2.1 (2H, m), 2.6 ~ 2.7 (2H, m), 4.3 ~ 4.
5 (1H, m) LLA part 1.5-1.7 (3H, m), 5.1-5.3 (1H, m).

Example 2 The title polyester was obtained in the same manner as in Example 1 except that 0.5 g (5.0 mmol) of γVL and 1.5 g (10.4 mmol) of LLA were used.

Example 3 The title polyester was obtained in the same manner as in Example 1 except that 1.0 g (10.0 mmol) of γVL and 1.0 g (6.9 mmol) of LLA were used.

Example 4 The title polyester was obtained in the same manner as in Example 1 except that 1.2 g (12.0 mmol) of γVL and 0.8 g (5.6 mmol) of LLA were used.

Example 5 The title polyester was obtained in the same manner as in Example 1 except that 1.3 g (13.0 mmol) of γVL and 0.7 g (4.9 mmol) of LLA were used.

Examples 6 to 12 : Synthesis of polyester by ring-opening copolymerization from γVL and (±) -β-butyrolactone

Example 6 0.2 g (2.0 mmol) of γVL in a 20 ml reaction vessel,
(±) -β-butyrolactone (hereinafter abbreviated as βBL) 1.8 g (20.9 mmol), BF ₃ · Et ₂ O 0.5
Mol% (0.11 mmol) was stirred under a nitrogen stream at 25 ° C for 13 days. 0.1 ml of methanol was added to the reaction solution to stop the reaction, the product was put into 10 ml of a mixed solvent of ether / hexane = 1, and reprecipitated to obtain the title polyester (yield 51.2%). 1 H-NMR (CDCl ₃ ) δppm: γVL part 1.1-
1.3 (3H, m), 1.7 ~ 2.0 (2H, m), 2.2 ~ 2.4 (2H, m), 4.8 ~ 5.
1 (1H, m) βBL 1.3-1.4 (3H, m), 2.4-2.8 (2H, m), 5.1-5.3
(2H, m).

Example 7 The title polyester was obtained in the same manner as in Example 6 except that 0.4 g (4.0 mmol) of γVL and 1.6 g (18.6 mmol) of βBL were used.

Example 8 The title polyester was obtained in the same manner as in Example 6, except that 0.7 g (7.0 mmol) of γVL and 1.3 g (15.1 mmol) of βBL were used.

Example 9 The title polyester was obtained in the same manner as in Example 6, except that 1.0 g (10.0 mmol) of γVL and 1.0 g (11.6 mmol) of βBL were used.

Example 10 The title polyester was obtained in the same manner as in Example 6, except that 1.3 g (13.0 mmol) of γVL and 0.7 g (8.1 mmol) of βBL were used.

Example 11 The title polyester was obtained in the same manner as in Example 6, except that 1.6 g (16.0 mmol) of γVL and 0.4 g (4.6 mmol) of βBL were used.

Example 12 The title polyester was obtained in the same manner as in Example 6 except that 1.8 g (18.0 mmol) of γVL and 0.2 g (2.3 mmol) of βBL were used.

Copolymers obtained by ring-opening copolymerization from γVL and LLA of Examples 1 to 5 and Examples 6 to
Regarding the copolymer obtained by ring-opening copolymerization of 12 from βBL and LLA, the content ratio of monomer units in the copolymer (measured by ¹ H-NMR), the number average molecular weight of the copolymer (Mn ), Molecular weight distribution (Mw / Mn), yield,
Data of glass transition point (Tg), melting point (Tm), and optical rotation (in acetone, c0.9 g / dl) are summarized in Table 1 and Table 2, respectively.

[0034]

[Table 1]

Test Example 1: Biodegradability test of the polymer of Example 3 The acclimatized species (aerobic sludge) of the returned sludge of Takasago International Corporation's Hiratsuka Plant was 500 ppm (600 ml), pH 6.0-.
Used under conditions of 7.0 and 25 ° C., a thin film of the polymer obtained in Example 3 having a size of 1 cm × 2 cm and a thickness of 0.05 to 0.1 mm (the polymer is dissolved in methylene chloride or chloroform and poured into a petri dish or the like to evaporate the solvent). 20 to 30 mg of the product (those formed into films) were put in a 50 ml flask and tested using a shaking constant temperature water bath manufactured by Titec Co., Ltd. After one week, the weight of the polymer was measured to determine the residual weight ratio. As a result, it was found that the polymer film obtained in Example 3 was decomposed by 5% after 1 week.

Test Example 2: Biodegradability test of the polymer of Example 8 As in Test Example 1, the polymer obtained in Example 8 was subjected to a biodegradation test in the same manner as in Test Example 1.
It was found that the decomposition was 10% after 1 week.

Front page continued (72) Inventor Yoshiharu Kimura 11261-1 Takakaicho, Omihachiman City, Shiga Prefecture

Claims (2)

[Claims] 1. A compound represented by the general formula (I): (In the formula, R ¹ represents an alkyl group having 1 to 4 carbon atoms, k
Represents 0 or 1, and m and n represent numbers from 10 to 2000. ) A biodegradable optically active polyester represented by. 2. The formula: (±) -β-butyrolactone or a compound represented by the formula: And L-lactide represented by the general formula (II) (In the formula, R ¹ has the same meaning as described in claim 1.)
The optically active γ-alkyl-γ-lactone represented by
(i) diethyl zinc, (ii) diethyl zinc-water complex and (i
ii) General formula (I), characterized in that the ring-opening copolymerization is carried out in the presence of at least one catalyst selected from boron trifluoride ether complex. (In the formula, R ¹ , k, m and n have the same meanings as described in claim 1.) The method for producing a biodegradable optically active polyester represented by the formula ( ¹ ).