JPH0548258B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a novel polylactide resin composition.

[Conventional technology]

Lactic acid exists in L-form, D-form, and D,L-form, and their polymer, poly-L-lactide, is crystalline, and poly-D, L-lactide is an amorphous polymer. be.

Poly-L-lactide is particularly interesting because it is non-enzymatically hydrolyzed in vivo, and its decomposition product, lactic acid, enters the normal metabolic pathway and is ultimately released from the body as carbon dioxide and water. It is a biodegradable and absorbable polymer.

Poly-L-lactide was developed as a drug carrier utilizing its ability to be biodegraded and absorbed, i.e., a new drug delivery system.
DDS) is being considered for use as a sustained release agent.

Moreover, it is usefully used as a surgical suture material as a monofilament.

[Problem that the invention seeks to solve]

As described above, lactic acid polymers are useful as functional polymers that can be used in a variety of ways, but in any case, in order to be used as polymeric compounds, they must be easy to mold. It is also important to improve the physical properties of the obtained molding material, such as heat resistance.

[Means for solving problems]

The present inventors have arrived at the present invention as a result of intensive studies aimed at improving the physical properties of polylactide based on the above background.

That is, the present invention uses 10 to 90 parts by weight of poly-L-lactide with a molecular weight of 2,000 to 600,000 and a molecular weight of 2,000 to 600,000.
The present invention relates to a resin composition prepared by blending 90 to 10 parts by weight of 600,000 poly-D-lactide in a solution state.

In the present invention, both poly-L-lactide and poly-D-lactide have molecular weights of 2000 to 2000.
600,000. The measurement used the viscosity method. The synthesis was carried out in the following manner.

As the starting material L-lactic acid, a commercially available 90% aqueous solution was used, and D-lactic acid produced by a fermentation method was used.

D or L- which is a cyclic dimer of D or L-lactic acid
Lactide from Lowe (CELowe, USP 2668162)
It was synthesized by thermal decomposition of D- or L-lactic acid oligomers according to the method of .

Note that the D or L-oligomer was synthesized from the corresponding D or L-lactic acid by a conventionally known esterification method. Specific optical rotation of the obtained lactide [α]
(dioxane 25℃, 578nm) is D-isomer +260,
It was L-260. Ring-opening polymerization of lactide was carried out by bulk polymerization. As catalysts, a series of synthetic or commercially available ring-opening polymerization catalysts were used. Specifically, tin octylate (0.03% for lactide) was used as a catalyst.
%) and lauryl alcohol (relative to lactide)
0.01%) was used. The reaction temperature was in the range of 130°C to 220°C. Characterization of the obtained polymer was performed by high-resolution NMR, optical rotation measurement, etc.

Figure 1 shows poly-D and L obtained by bulk polymerization.
-lactide, poly-L-lactide and poly-D
- Shows the NMR spectrum of lactide. poly
In D and L-lactide, splitting is observed in the signal of the methyl group at about 1.6 ppm, but this is not observed in the L- and D-forms.

Further, the specific optical rotation of the obtained poly-D-lactide is +147, and that of poly-L-lactide is -
It was 147.

On the other hand, in a blend resin composition of poly-D-lactide and poly-L-lactide, a completely new crystal structure appears by simply blending both polymers in a solution state, and along with this, the thermal properties are amazing. It was found that there was an improvement.

The blend ratio of poly-D-lactide and poly-L-lactide is preferably in the range of 10 to 90 to 90 to 10 (weight ratio); outside this range, the properties shown in the examples described later will not be found. .

〔Effect of the invention〕

The blend resin composition of poly-D-lactic acid and poly-L-lactic acid according to the present invention can be used in the same way as poly-L-lactic acid, in split absorbable materials, such as absorbable sutures used in vivo, bone Applications include plates, artificial tendons, artificial ligaments, artificial blood vessels, sustained release carriers for pharmaceuticals, agricultural cultivation films, fibers, ropes, sustained release carriers for agricultural chemicals, and industrial separation films. In all of the above, it is possible to provide a material with improved physical properties.

〔Example〕

Examples will be described in detail below.

Example 1 D-lactic acid was synthesized by a fermentation method and purified by a methyl esterification method. D-
D-lactide, a cyclic dimer of lactic acid, was developed by Lowe (C.
D- according to the method of E. Lowe, US Pat. 2668162)
It was synthesized by thermal decomposition of lactic acid oligomer. Specific rotation of the obtained D-lactide (dioxane 25℃,
578nm) was +260.

The ring-opening polymerization of D-lactide was carried out using tin octylate (0.03% relative to lactide) and lauryl alcohol (0.01% relative to lactide) as catalysts.
The temperature range was 130°C to 220°C. The molecular weight of the obtained poly-D-lactide was determined by a viscosity method and was approximately 70,000. In addition, the obtained poly-D
-The specific rotation of lactide was +147.

Example 2 Poly-L-lactide and poly-D with a molecular weight of approximately 70,000
- Lactide was dissolved in chloroform in various proportions, and films were produced by a casting method.

The DSC curve of the sample is shown in Figure 2. Poly-L-
The DSC curves of lactic acid and poly-D-lactic acid each have a single peak and show a melting point of 180°C, but a new peak appears around 230°C in their blend, and when the blend ratio is 1. In the case of Pair 1, the peak at 180°C disappeared and the peak at 230°C became clear.

There have been no reports on blends of L-form and D-form optically active polymers, and therefore, the fact that thermal properties can be greatly improved by a simple blend has not been known at all.

The molecular form of poly-L-lactide is left-handed helical, and poly-D-lactide is right-handed. The increase in melting point due to these blends is due to the fact that when left-handed helical and right-handed helical are mixed in a solution state, they take on a structure that cannot be obtained with the same type of helical form.
This is thought to be due to the creation of a completely new crystal structure. The appearance of this new crystal structure was confirmed by X-turn diffraction. The results of X-ray diffraction measurements are shown in FIG. In the samples of poly-L-lactide and poly-D-lactide alone, 2θ is mainly 15°, 16.6° and 19°.
Only three peaks appear nearby, but in a one-to-one blend, in addition to those peaks, 2θ
Three new peaks at 12°, 21°, and 24° are observed. These results indicate that a completely new crystal structure, which does not exist in homopolymers of poly-L-lactide and poly-D-lactide, appears as a result of blending them.

[Brief explanation of drawings]

Figure 1 shows NMR spectra of poly-D, L-lactide, poly-L-lactide and poly-D-lactide; Figure 2 shows mixtures of poly-L-lactide and poly-D-lactide in various proportions. Figure 3 shows the DSC curve of a film made of poly-L-
FIG. 3 is an X-ray diffraction diagram of lactide, a blend of poly-D-lactide and poly-L-lactide, and poly-D-lactide.

Claims (1)

[Claims] 1 Poly-L-lactide with a molecular weight of 2000 to 600000
Poly-D with 10 to 90 parts by weight and a molecular weight of 2000 to 600000
- A resin composition prepared by blending 90 to 10 parts by weight of lactide in a solution state.