JP3374530B2 - Method for producing aliphatic polyester copolymer - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high molecular weight aliphatic polyester copolymer mainly composed of units derived from lactic acid and units derived from caprolactone, and a method for producing the same, and more particularly to biodegradable ones. , A high molecular weight aliphatic polyester copolymer excellent in mechanical strength, and a method for producing the same.

[0002]

2. Description of the Related Art Aliphatic polyesters produced from aliphatic oxyacids, represented by polylactic acid, polyglycolic acid, and copolymers thereof, have attracted attention as biodegradable polymers. Medical materials, medicines, pesticides,
It is used in various fields such as controlled release materials such as fertilizers. Furthermore, it is expected as a biodegradable general-purpose plastic as a packaging material for containers and films. For such applications, it is generally preferable to have high mechanical properties. In order to obtain a high molecular weight polymer, conventionally, lactide and glycolide are produced from lactic acid and glycolic acid, and these are subjected to ring-opening polymerization to obtain high A molecular weight polylactide, polyglycol was produced. Although a high molecular weight polymer can be obtained by this method, it is a two-step reaction, and a great deal of labor is required to obtain lactide and glycolide, which is not economical. On the other hand, the method of directly subjecting lactic acid and glycolic acid to a polycondensation reaction is economical, but on the other hand, it has a problem that it cannot have a high molecular weight and has not been industrialized. For example, a method of using a tin compound as a polycondensation catalyst and adding liquid paraffin at the time of polycondensation (Japanese Patent Laid-Open No. 62-64823) has been proposed in an attempt to increase the molecular weight, but it is not always sufficient. It could not be said that the molecular weight was high. Also, GeO
_Although it has been proposed to use an inorganic germanium compound such as ₂ as a catalyst (JP-A-5-43665), a polymer having a sufficiently satisfactory molecular weight has not been obtained. Polylactic acid has high strength, but its elongation is very small, so
It is a material that is harder and more brittle than ordinary engineering plastics, and has a problem of insufficient toughness.

For direct polycondensation of lactic acid and caprolactone
For the copolymers according to, for example, polymer,Three
1, 2006, 1990,
The polymer has a low molecular weight of 3700 or less.
Therefore, the mechanical properties were not sufficient.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide a high molecular weight aliphatic polyester copolymer having practical-level mechanical properties, and particularly high yield strength and elongation at break, and the aliphatic polyester copolymer. Another object of the present invention is to provide a production method capable of easily obtaining the compound by direct polycondensation reaction.

[0005]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and its gist is to provide 99 to 70 mol% of units derived from lactic acid and 1 to 1 units derived from caprolactone. The aliphatic polyester copolymer is mainly composed of 30 mol% and has a number average molecular weight of 10,000 to 100,000.

The present invention will be described in detail below. The aliphatic polyester copolymer of the present invention is mainly composed of 99 to 70 mol% of units derived from lactic acid and 1 to 30 mol% of units derived from caprolactone,
More specifically, 99-70 mol% of units derived from lactic acid, 1-30 mol% of units derived from caprolactone
And a unit derived from a copolymerization component capable of copolymerizing with lactic acid and caprolactone, 0 to 20 mol%, preferably 0 to
It is a random type aliphatic polyester copolymer consisting of 10 mol%.

The unit derived from a copolymerizable component capable of copolymerizing with lactic acid and caprolactone is derived from an oxy acid such as glycolic acid, mandelic acid, 3-hydroxybutyric acid, 4-hydroxybutyric acid, tartaric acid and citric acid. And a unit derived from an aromatic compound such as terephthalic acid, isophthalic acid and hydroxybenzoic acid, or a unit derived from a diol compound.

The number average molecular weight of the aliphatic polyester copolymer of the present invention is 10,000 to 100,000. The number average molecular weight is usually 10,000 or more and preferably 2 in order to obtain an aliphatic polyester copolymer having sufficient mechanical strength.
In addition, it is usually 100,000 or less, preferably 70,000 or less from the viewpoint of problems in the manufacturing method and deterioration of moldability.

The aliphatic polyester copolymer of the present invention is
It can be produced by polycondensing at least lactic acid and caprolactone in the presence of a catalyst. Further, a component which can be copolymerized with lactic acid and caprolactone can be further added as long as the effect of the present invention is not impaired. Lactic acid in the present invention is not particularly limited, and D
It may be a body, an L body, or a racemic body, and may have a solid, liquid, or aqueous solution shape.

Further, cyclized lactide can also be used. The polycondensation reaction is preferably performed in a solution state, and therefore an aqueous solution having a high lactic acid concentration is more preferable. As caprolactone in the present invention, caprolactone itself or a form of an oxy acid opened by hydrolysis can be used. It is preferably hydrolyzed before the reaction. In this case, since hydrolysis occurs when mixed with an aqueous lactic acid solution, it is particularly preferable to use it together with an 85-92% aqueous lactic acid solution.

Further, by adding caprolactone as a copolymerization component, the distillation of by-products tends to decrease. The composition ratio of lactic acid and caprolactone is 99-
It is in the range of about 70 mol% and about 1 to 30 mol% of caprolactone. Preferably, lactic acid is 95 to 75 mol% and caprolactone is 5 to 25 mol%, more preferably lactic acid is 91 to 79 mol% and caprolactone is 9 to 21 mol%.
Is. When the amount of lactic acid is larger than this, the physical properties are not extended and hard and brittle, and when the amount is small, it becomes rubbery, which is not preferable. It is preferable to mix and heat the raw materials when they are charged. Other copolymerizable components that can be copolymerized with lactic acid and caprolactone include glycolic acid, mandelic acid, 3-hydroxybutyric acid, 4-hydroxybutyric acid, tartaric acid, citric acid and other oxy acids, or terephthalic acid, isophthalic acid, hydroxybenzoic acid and the like. And aromatic compounds such as ethylene glycol, and diol compounds such as 1,4-butanediol.

As the catalyst used during the polymerization, polyester polymerization catalysts such as usual germanium-based, titanium-based, antimony-based and tin-based catalysts can be used, but germanium-based catalysts and titanium-based catalysts have high reactivity. ,preferable. Specific examples include germanium oxide, germanium alkoxides such as tetraethoxygermanium and tetrabutoxygermanium, tetraalkoxytitanium, and acetylacetonetitanium. From the viewpoint of polymerization rate and polymer coloration, a germanium-based catalyst is particularly preferable.

The addition of the catalyst to the reaction system is not particularly limited as long as it is before the polycondensation reaction, but it is preferably in the state of being dispersed in the raw material at the time of charging the raw material or in the state of being dispersed at the start of depressurization. It is a method of adding. The amount of the catalyst used is 0.01 to 3% by weight in terms of metal atom based on the amount of the monomer used, and more preferably 0.05 to 1.5.
% By weight.

The reaction conditions can be selected in accordance with ordinary polyester polycondensation conditions. Polycondensation temperature is 15
0 ° C or higher, preferably 160 ° C or higher, more preferably 18
It is 0 ° C or higher. The upper limit of the polycondensation temperature is lower than the decomposition temperature of the aliphatic polyester, specifically 250 ° C or lower, preferably 230 ° C or lower, and more preferably 210 ° C or lower.
When the temperature is lower than the above range, the amount of by-products is small, but the reaction rate is very slow, and a high molecular weight polymer cannot be obtained. On the contrary, when the temperature is above the above range, the decomposition of the polymer or the distillation of lactide as a by-product increases. The pressure during the reaction is 50 mmHg or less, preferably 40 mmHg
g or less, more preferably 30 mmHg or less. The lower limit of the pressure is preferably 1 mmHg or more.
If it is 50 mmHg or more, the water generated during polycondensation cannot be efficiently removed, and if it is 1 mmHg or less, the problem of distilling by-products or an increase in industrial cost is not preferable.

The above reaction is carried out, for example, under a reduced pressure atmosphere of an inert gas such as nitrogen gas. The reaction time is preferably 2 hours or longer, more preferably 4 hours or longer, and further longer, for example, 8 hours or longer in order to increase the degree of polymerization. However, if it is carried out for a too long time, a problem of coloring of the polymer occurs, so that 4 to 15 hours is preferable. Furthermore, it is also possible to carry out a solid phase polymerization reaction or the like in order to obtain a high molecular weight aliphatic polyester copolymer.

Specific uses of the aliphatic polyester copolymer of the present invention as a biodegradable material include fishing lines, fishing nets and non-woven fabrics for fibers, and disposable cups and trays for containers, toiletry products, cosmetics, etc. Bottles for beverages, agricultural flower pots and nurseries, and as films, packaging films, agricultural mulch films, shopping bags, fertilizer bags, tapes, etc. can be considered. In addition, as medical applications, DDS fields such as sutures, artificial bones, artificial skins, wound dressings, and microcapsules can be considered.
Further, in the electric field, the use of a toner or a binder of a thermal transfer ink is considered, but not limited to these.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to the following Examples unless it exceeds the gist. The characteristic values in the examples were measured by the following methods. Polymer composition: Determined by the ratio of the methine proton at the lactic acid site at 5.2 ppm and the methylene proton at the caprolactone site at 2.4 ppm by the NMR method.

Reduced viscosity (η _sp / C); polymer 0.12
5 g of phenol / tetrachloroethane (1/1 wt
%) Dissolved in 25 ml of mixed solvent and measured at 30 ° C. Number average molecular weight: A sample of 5 mg was dissolved in 5 g of THF and measured by polystyrene conversion using Tosoh GPCHLC-8020. PLgel 5μ on the column
MIX-C was used.

Mechanical Properties: Specimens were punched from a press film prepared by a hot press on a table. 100k for measurement
g Tensilon UTM-III L was used. Distance between fulcrums of sample is 25mm, pulling speed is 500mm / mi
It was measured by n.

[0020]

【Example】

<Example 1> 90 g of L-lactic acid (87% aqueous solution), 11 g of ε-caprolactone, and tetra-n-butoxygermanium 1 were placed in a reaction vessel equipped with a stirrer and a nitrogen introducing tube.
After charging 50 μl (0.15% by weight) and purging with nitrogen, the mixture was stirred under a nitrogen stream at 180 ° C. for 3 hours at normal pressure,
After that, the pressure was reduced to 20 mmHg over 1 hour, and the reaction was stirred for 2 hours. Subsequently, the temperature is raised and the pressure is reduced over 1 hour,
The polycondensation reaction was carried out for 8 hours at 200 ° C. and 2 mmHg. The obtained polymer was colored slightly yellow, the reduced viscosity was 0.63, and the number average molecular weight was 27,700.

<Comparative Examples 1 and 2> In Comparative Examples 1 and 2, the same operation as in Example 1 was performed except that the composition was polylactic acid alone. Further, in Comparative Example 1, the obtained polymer was crushed and heated to 135 to 155 ° C. (gradual heating),
Solid phase polymerization was carried out at 15 torr or less for 60 hours.

[0022]

[Table 1]

[0023]

The aliphatic polyester copolymer obtained by the present invention has an advantage that it has good mechanical properties and, in particular, is a flexible material having high yield strength and elongation at break. Further, according to the method of the present invention, a high molecular weight aliphatic polyester copolymer having excellent mechanical properties can be easily obtained by direct polycondensation reaction.

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yukiko Ishii 1000 Kamoshida-cho, Midori-ku, Yokohama-shi, Kanagawa Mitsubishi Kasei Co., Ltd. (56) Reference JP-A-5-255488 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) C08G 63/00-63/91

Claims (2)

(57) [Claims] 1. Touching at least lactic acid and caprolactone
Derived from lactic acid characterized by polycondensation in the presence of a medium
Derived from caprolactone with 99-70 mol% unit
Is mainly composed of 1 to 30 mol% of the unit
Aliphatic polyester copolymer having a molecular weight of 10,000 to 100,000
Manufacturing method. 2. The method for producing an aliphatic polyester copolymer according to claim 1 , wherein the catalyst is a germanium compound .