JP3103717B2 - Method for producing polyhydroxycarboxylic acid - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a process for producing a useful polyhydroxy carboxylic acid as a medical material or a biodegradable polymer of the general-purpose resin substitute.

[0002]

2. Description of the Related Art Polyhydroxycarboxylic acids have excellent mechanical, physical and chemical properties and are decomposed in a natural environment without causing any harm. It has a biodegradable function of becoming carbon dioxide gas, and in recent years has been attracting attention in various fields such as medical materials and alternatives to general-purpose resins from the viewpoint of environmental protection. Is expected.

[0003] In general, a method for producing a polyhydroxycarboxylic acid includes, in the case of a hydroxycarboxylic acid such as lactic acid or glycolic acid, dehydration and dimerization to obtain a cyclic dimer and then ring opening in the presence of various catalysts. A method for obtaining a polymer having a high molecular weight to be melt-polymerized is known. This method is not economical because it requires a great deal of labor and cost in the production of lactide or glycolide, which is a cyclic dimer. Some hydroxycarboxylic acids do not form a cyclic dimer, and in this case, this method cannot be used.

On the other hand, several methods for obtaining polyhydroxycarboxylic acids from hydroxycarboxylic acids and their oligomers by direct dehydration have been disclosed (JP-A-59-5959).
096123, JP-A-61-028521). However, the intrinsic viscosity of the polymer obtained by these methods is limited to about 0.3 dl / g, and does not have sufficient mechanical properties, and cannot be used depending on its use or purpose.

Further, the applicant of the present invention has previously azeotropically dehydrated a hydroxycarboxylic acid or an oligomer thereof in an organic solvent in the presence of a catalyst in an inert gas atmosphere. And a method of obtaining a polyhydroxycarboxylic acid having an average molecular weight of at least 30,000 or more by a method of returning the system to the system again (Japanese Patent Application No. Hei.
-337321). However, even in this method, it takes 17 to 50 hours under reflux to obtain a polyhydroxycarboxylic acid having an average molecular weight of 120,000 or more.

In the case of using a tank reactor equipped with a usual stirring blade, a low-boiling component (water in the case of polyhydroxycarboxylic acid formation) which causes a reaction delay is removed under reduced pressure or inert gas. It is performed under gas injection. However, in a tank reactor equipped with a usual stirring blade,
Even when the contact efficiency between the inert gas and the reactant is low or when the degree of pressure reduction is increased, it is difficult to efficiently remove low boiling components due to the liquid depth of the reactant.

[0007]

SUMMARY OF THE INVENTION The present inventors have conducted intensive studies on a direct dehydration polycondensation method capable of producing polyhydroxycarboxylic acid industrially efficiently, easily and inexpensively. It has been found that a higher molecular weight polyhydroxycarboxylic acid can be obtained in a short time by using the apparatus.

That is, the present invention provides a method for producing a high molecular weight polyhydroxycarboxylic acid by dehydrating polycondensation of a hydroxycarboxylic acid in the presence of a catalyst and an organic solvent .
Low molecular weight (about 10,000 to 30,000) polymerization in one step
A method for producing a high molecular weight polyhydroxycarboxylic acid, comprising subjecting a polymer to thermal polycondensation while separating and removing low-boiling components using a vertical high-viscosity reactor in the second step after the production.

The vertical high-viscosity reactor used in the present invention comprises:
The reactor is equipped with stirring blades of various shapes.These blades separate and cut the raw material components into thin films as the shaft rotates, renew the surface, and promote the scattering of low-boiling components. ,
Promotes polymerization reaction.

[0010] As a stirring blade, for example, a twisted lattice blade without a shaft to reduce material stagnation near the shaft, a combination of a max blend blade and a ribbon blade can cope with a sudden change in viscosity during operation, and a tank wall. Spiral wings to reduce the adhesion of the parts, to improve mixing performance, to have a wide gas-liquid contact surface, to have excellent surface renewal performance, to move the wings up and down while rotating And the like.

The vertical high-viscosity reactor is not particularly limited, but preferably has a strong stirring power, a wide heat transfer area and excellent surface renewal performance. For example,
A vertical type high-viscosity reactor, in which a ribbon-shaped stirring blade is provided inside, a ribbon-shaped stirring blade is provided inside, and the ribbon-shaped stirring blade is supported by a frame, a vertical conical shape, A ribbon-shaped agitating blade that provides a cone angle that is substantially the same as the cone angle of the reactor, a vertical cone, and a ribbon that has a cone angle that is substantially the same as the cone angle of the body inside. Provided with a blade-shaped stirring blade, and the ribbon-shaped stirring blade is supported by a frame.

Specific examples of the vertical high-viscosity reactor include “Advanced Ribbon Reactor (AR)” and “Vertical Cone Reactor (V)” manufactured by Mitsubishi Heavy Industries, Ltd.
CR) ”,“ Logborn (L
OGBORN) "," Torsion Lattice Blade "manufactured by Hitachi, Ltd.," Super Blend (concentric twin-shaft stirring tank) "manufactured by Sumitomo Heavy Industries, Ltd.," Victor (High Viscosity Stirring) "manufactured by Nissen Corporation. Machine) ”and the like.

In the method of the present invention, the vertical high-viscosity reactor may be used in all steps of the dehydration polycondensation, or may be used in a part of the dehydration polycondensation. In order to utilize the effect of improving the surface renewability in the reaction of a high viscosity solution from a medium viscosity in a vertical high viscosity reactor, it is preferable to use the polyhydroxycarboxylic acid after the molecular weight of the polyhydroxycarboxylic acid has increased to some extent.

The following are specific examples of the hydroxycarboxylic acid used in the present invention. Glycolic acid, lactic acid, 2-hydroxybutanoic acid, 2
-Hydroxypentanoic acid, 2-hydroxyhexanoic acid, 2-hydroxyheptanoic acid, 2-hydroxyoctanoic acid,
2-hydroxy-2-methylpropanoic acid,
2-hydroxy-2-methylbutanoic acid, 2
-Hydroxy-2-ethylbutanoic acid, 2-
Hydroxy-2-methylpentanoic acid, 2-
Hydroxy-2-ethylpentanoic acid, 2-
Hydroxy-2-propylpentanoic acid, 2
-Hydroxy-2-butylpentanoic acid, 2
-Hydroxy-2-methylhexanoic acid, 2
-Hydroxy-2-ethylhexanoic acid, 2
-Hydroxy-2-propylhexanoic acid,
2-hydroxy-2-butylhexanoic acid,
2-hydroxy-2-pentylhexanoic acid, 2-hydroxy-2-methylheptanoic acid, 2-hydroxy-2-methylheptanoic acid, 2-hydroxy-2-ethylheptanoic acid, 2-hydroxy-2-pentylhexanoic acid Hydroxy-2-propylheptanoic acid, 2-hydroxy-2-butylheptanoic acid, 2-hydroxy-2-pentylheptanoic acid, 2-hydroxy-2-hexylheptanoic acid, 2-hydroxy-2 -Methyloctanoic acid, 2-hydroxy-2-ethyloctanoic acid, 2-hydroxy-2-propyloctanoic acid, 2-hydroxy-2-butyloctanoic acid, 2-hydroxy-2-pentyl Octanoic acid, 2-hi Roxy-2-hexyl octanoic acid, 2-hydroxy-2-heptyl octanoic acid, 3-hydroxypropanoic acid, 3-hydroxybutanoic acid, 3-hydroxypentanoic acid, 3-hydroxyhexa Neuic acid, 3-hydroxyheptanoic acid, 3-hydroxyoctanoic acid, 3-hydroxy-3-methylbutanoic acid, 3-hydroxy-3-methylpentanoic acid, 3-hydroxy-3- Ethyl pentanoic acid, 3-hydroxy-3-methylhexanoic acid, 3-hydroxy-3-ethylhexanoic acid, 3-hydroxy-3-propylhexanoic acid, 3-hydroxy-3-methylhepta Neuqua , 3-hydroxy-3-ethylheptanoic acid, 3-hydroxy-3-propylheptanoic acid, 3-hydroxy-3-butylheptanoic acid, 3-hydroxy-3-methyloctanoic acid 3-hydroxy-3-ethyloctanoic acid, 3-hydroxy-3-propyloctanoic acid, 3-hydroxy-3-ethyloctanoic acid,
Hydroxy-3-butyloctanoic acid, 3-
Hydroxy-3-pentyloctanoic acid, 4
-Hydroxybutanoic acid, 4-hydroxypentanoic acid, 4-hydroxyhexanoic acid, 4-hydroxyheptanoic acid, 4
-Hydroxyoctanoic acid, 4-hydroxy-4-methylpentanoic acid, 4-hydroxy-4-methylhexanoic acid, 4-hydroxy-4-ethylhexanoic acid, 4-hydroxy-4-methyl Heptanoic acid, 4-hydroxy-4-ethylheptanoic acid, 4-hydroxy-4-propylheptanoic acid, 4-hydroxy-4-methyloctanoic acid, 4-hydroxy-4-ethyloctano Ic acid, 4-hydroxy-4-propyl octanoic acid, 4-hydroxy-4-butyl octanoic acid, 5-hydroxypentanoic acid, 5-hydroxyhexanoic acid, 5-hydroxyheptanoic acid , 5-hydroxy Octanoic acid, 5-hydroxy-5-methylhexanoic acid, 5-hydroxy-5-methylheptanoic acid, 5-hydroxy-5-ethylheptanoic acid, 5-hydroxy-5-methyloctano Ic acid, 5-hydroxy-5-ethyloctanoic acid, 5-hydroxy-5-propyloctanoic acid, 6-hydroxyhexanoic acid, 6-hydroxyheptanoic acid, 6-hydroxyoctanoic acid , 6-hydroxy-6-methylheptanoic acid, 6-hydroxy-6-methyloctanoic acid, 6-hydroxy-6-ethyloctanoic acid, 7-hydroxyheptanoic acid, 7-
Hydroxyoctanoic acid, 7-hydroxy-
Examples include aliphatic hydroxycarboxylic acids such as 7-methyloctanoic acid and 8-hydroxyoctanoic acid. These may be used alone or as a mixture of two or more. Particularly preferred hydroxycarboxylic acids are lactic acid, glycolic acid, 3-hydroxybutyric acid, 4-hydroxybutyric acid,
-Hydroxyvaleric acid, or a mixture thereof.

In the method of the present invention, an oligomer derived from the above-mentioned hydroxycarboxylic acid can be used as a raw material. And they may be used as one kind or a mixture of two or more kinds.

These hydroxycarboxylic acids and their oligomers have an optically active carbon and have D-form and L-form, respectively.
Although it may take the form of a body or a D / L body, the form is not limited in the present invention.

In the method of the present invention, the polymerization catalyst can be added or not arbitrarily selected depending on the degree of polymerization (intrinsic viscosity and molecular weight) of the target polymer. When producing a low molecular weight polymer (intrinsic viscosity less than about 0.3), the desired polymer can be easily obtained with or without the addition of a catalyst. On the other hand, when producing a polymer having a high molecular weight (intrinsic viscosity of about 0.3 or more), it is preferable to use a catalyst in view of the reaction time (reaction rate).

Examples of the catalyst used in the present invention include metals belonging to Groups I, II, III, IV and V of the Periodic Table of the Elements, or salts or hydroxides and oxides thereof. For example zinc,
Metals such as tin, aluminum, magnesium, antimony, titanium and zirconium. Tin oxide, antimony oxide,
Metal oxides such as lead oxide, aluminum oxide, magnesium oxide, and titanium oxide. Metal halides such as zinc chloride, stannous chloride, stannic chloride, stannous bromide, stannic bromide, antimony fluoride, zinc chloride, magnesium chloride, and aluminum chloride. Sodium hydroxide, potassium hydroxide, calcium hydroxide, magnesium hydroxide, aluminum hydroxide, zinc hydroxide, iron hydroxide, cobalt hydroxide, nickel hydroxide, copper hydroxide, cesium hydroxide, strontium hydroxide, hydroxide Metal hydroxides such as barium, lithium hydroxide and zirconium hydroxide. Sulfates such as tin sulfate, zinc sulfate, and aluminum sulfate. Carbonates such as magnesium carbonate, zinc carbonate and calcium carbonate. Organic carboxylate such as tin acetate, tin octoate, tin lactate, zinc acetate, aluminum acetate, iron lactate. Organic sulfonates such as tin trifluoromethanesulfonate and tin p-toluenesulfonate are exemplified.

In addition, an organic metal oxide of the above metal such as dibutyltin oxide or a metal alkoxide of the above metal such as titanium isopropoxide or an alkyl metal of the above metal such as diethylzinc. And ion exchange resins such as Dowex and Amberlite. The amount used is 0.0001 to 10% by weight of the above hydroxycarboxylic acid or oligomer thereof.

In the method of the present invention, either a method using an organic solvent or a method not using an organic solvent in the step of the dehydration polycondensation reaction can be adopted.

When an organic solvent is used, examples of the organic solvent used include aromatic hydrocarbons and ether-based aromatic hydrocarbons.

The aromatic hydrocarbons include toluene, xylene, naphthalene, biphenyl, chlorobenzene, o
-Chlorobenzene, m-chlorobenzene, p-chlorobenzene and the like.

Examples of the ether aromatic hydrocarbons include alkoxybenzenes and diphenyl ethers.

The alkoxybenzenes include anisole, ethoxybenzene, propoxybenzene, butoxybenzene, pentoxybenzene, 2,4-dimethoxybenzene, 2-chloromethoxybenzene, 2-bromomethoxybenzene, 4-chloromethoxybenzene, -Bromomethoxybenzene, 2,4-dichloromethoxybenzene and the like.

The diphenyl ethers include diphenyl ether, 4,4'-dimethyldiphenyl ether,
Alkyl-substituted diphenyl ethers such as 3,3'-dimethyldiphenyl ether and 3-methyldiphenyl ether; 4,4'-dibromodiphenyl ether, 4,4 '
Halogen-substituted diphenyl ethers such as dichlorodiphenyl ether, 4-bromodiphenyl ether, 4-methyl-4-bromodiphenyl ether; 4-methoxydiphenyl ether, 4,4′-dimethoxydiphenyl ether, 3,3′-dimethoxydiphenyl ether,
Alkoxy-substituted diphenyl ethers such as -methyl-4'-methoxydiphenyl ether. And cyclic diphenyl ethers such as dibenzofuran and xanthene. These may be used alone or in a mixture of two or more.

When using an organic solvent, the polymer concentration is as follows:
Depending on the molecular weight of the desired polyhydroxycarboxylic acid, the reaction temperature, the type of organic solvent used, etc.
Preferably from 10 to 95% by weight, more preferably from 25 to 7%.
0% by weight, more preferably 40 to 60% by weight.
If it is less than 10% by weight, there are difficulties in terms of economy and reaction rate.
If the concentration exceeds 95% by weight, the effect of using the organic solvent is not exhibited.

The vertical type high-viscosity reactor has various ribbon-shaped stirring blades in a vertical main body. With the rotation of the shaft, the raw material components rise on the wall surface of the container, and the surface is renewed in a flow manner descending at the center, thereby promoting the scattering of low boiling components and the polycondensation reaction.

FIGS. 1 to 4 show examples of shapes of stirring blades that can be taken in the present invention . FIG. 3 shows a double helical ribbon blade shown in FIGS. 1 and 2 supported by a rotating shaft. A double helical ribbon wing supported by a frame to improve the elimination and mixing of substances, and a conical double helical ribbon wing as shown in Fig. 4 supported by a frame to eliminate stagnation and improve mixing and product discharge characteristics. And the like.

The reaction may be carried out under normal pressure or under reduced pressure. When the reaction is performed under reduced pressure, a vacuum pump is connected. The stirring is carried out while blowing inert gas and / or under reduced pressure. Examples of the inert gas include nitrogen and argon.

The reaction is carried out by heating the inside of the high-viscosity reactor using a heat medium or by electric heating or the like. The reaction temperature differs depending on whether or not an organic solvent is used, and when an organic solvent is used, the boiling point of the solvent. Although it depends on the thermal stability of the produced polymer, it is preferably 50 to 250.
° C, more preferably 100-200 ° C. If the temperature is lower than 50 ° C., the reaction rate is low and it is not economical. If the temperature exceeds 250 ° C., the polymer tends to deteriorate.

In the method of the present invention, a polycondensation may be carried out by adding a coloring inhibitor in order to suppress coloring due to thermal deterioration during the polycondensation. As the coloring inhibitor to be used, phosphorus compounds such as phosphoric acid, triphenyl phosphate, pyrophosphoric acid, phosphorous acid and triphenyl phosphite are preferred. The amount added
It is 0.01 to 5% by weight, more preferably 0.5 to 2% by weight, based on the polymer. If it is less than 0.01% by weight, the effect of preventing coloring is small, and if it exceeds 5% by weight, the effect of preventing coloring is further reduced, and the degree of polymerization may not be increased.

[0032]

EXAMPLES Examples of the present invention will be described below, but the present invention is not limited to the methods and apparatuses described below. The average molecular weights of the polymers described in the examples were determined by gel permeation chromatography (column temperature: 40 ° C.) in comparison with polystyrene standard samples.

Synthesis Example 1 A 3-liter tank-type reactor equipped with a usual stirring blade (anchor type) and a reflux condenser was charged with 0.6 kg of 90% -L-lactic acid, and
The mixture was heated and stirred at 30 ° C./50 mmHg for 3 hours while removing water from the system. Diphenyl ether (DPE)
1.5 kg of tin powder and 0.5 g of tin powder were added, and a column packed with 100 g of molecular sieve 3A was prepared. The solvent distilled off by reflux was returned to the system through the molecular sieve column. The reaction conditions were set at 130 ° C./15 mmHg, and stirring was continued for 5 hours to obtain low molecular weight polylactic acid having a weight average molecular weight (Mw) of about 10,000.

Example 1 700 g of the low molecular weight polylactic acid solution obtained in Synthesis Example 1 was
The mixture was heated to 00 ° C. and supplied to a vertical high viscosity reactor having a capacity of 1 l shown in FIG. 1 by a supply pump. The high-viscosity reactor had a double helical ribbon blade and had excellent surface renewability. Thereafter, the pressure was gradually reduced to 130 ° C / 20-1.
300 g of diphenyl ether was distilled off at 5 mmHg and concentrated to a polylactic acid concentration of about 50% by weight. Next, a column filled with 100 g of molecular sieve 3A was prepared, and the solvent distilled off by reflux was returned to the system through the molecular sieve column. The reaction was continued at 130 ° C./15 mmHg, sampled at 10-hour intervals, and the weight average molecular weight was measured. Table 1 shows the results.

[0035]

[Table 1]

Comparative Example 1 400 g of the low molecular weight polylactic acid obtained in Synthesis Example 1 was transferred to a 1-liter reactor similar to the tank reactor used in Synthesis Example 1, and the reaction was continued. The reaction was continued under the conditions of 130 ° C./15 mmHg, and samples were taken at 10-hour intervals to measure the weight average molecular weight. Table 2 shows the results.

[0037]

[Table 2]

Synthesis Example 2 112.5 kg of 90% L-lactic acid (containing 10% water) was placed in a 500-liter glass-lined tank reactor equipped with an ordinary stirring blade (FIG. 5), a jacket, a thermometer, and a distilling tube.
(1125 mol), 0.405 kg (3.4 m) of tin powder
ol) and 236 kg of diphenyl ether, the jacket was heated to 140 ° C. and 130 ° C. /
Water was distilled off at 160 to 130 mmHg for 5 hours. Thereafter, the jacket temperature was raised to 150 ° C.
The operation of azeotropic dehydration at 110 ° C./110 to 100 mmHg and returning only DPE to the reactor excluding distilling water for 15 hours was continued, and a low molecular weight polylactic acid having a weight average molecular weight (Mw) of about 30,000 (concentration 25 wt. %)was gotten.

Example 2 This example was carried out using a reactor having a capacity of 20 l shown in FIG. Low molecular weight polylactic acid 15k obtained in Synthesis Example 1
g was heated to 100 ° C. and fed to the reactor by a feed pump. Thereafter, the pressure was gradually reduced to 130 ° C / 20 to 15m.
7.5 kg of DPE was distilled off over 2 hours at mHg, and the concentration of polylactic acid was concentrated to 50% by weight. Next, the distillate (DPE) of the reactor was cooled by a condenser, collected in a solvent storage tank, dried through a tower filled with 40 kg of 4A-molecular sieve, and then switched to a line returning to the reactor, at 150 ° C./20° C. The polycondensation reaction was performed at 15 mmHg. Samples were taken at 10 hour intervals and the weight average molecular weight was measured. Table 3 shows the results.

Example 3 This example was carried out using a reactor having a capacity of 90 l shown in FIG. Low molecular weight polylactic acid 65k obtained in Synthesis Example 2
g was heated to 100 ° C. and fed to the reactor by a feed pump. Thereafter, the pressure was gradually reduced to 130 ° C / 20 to 15m.
Distill 32.5 kg of DPE over 2 hours at mHg,
The concentration of polylactic acid was concentrated to 50% by weight. Next, the distillate (DPE) of the reactor was cooled by a condenser, collected in a solvent storage tank, dried through a tower filled with 40 kg of 4A-molecular sieve, and then switched to a line returning to the reactor, at 150 ° C./20° C. The polycondensation reaction was performed at 15 mmHg. Samples were taken at 10 hour intervals and the weight average molecular weight was measured. Table 3 shows the results.

Example 4 This example was carried out using a reactor having a capacity of 90 l as shown in FIG. Low molecular weight polylactic acid 65k obtained in Synthesis Example 2
g was heated to 100 ° C. and fed to the reactor by a feed pump. Thereafter, the pressure was gradually reduced to 130 ° C / 20 to 15m.
Distill 20.0 kg of DPE over 2 hours at mHg,
The concentration of polylactic acid was concentrated to 87% by weight. Thereafter, the same operation as in Example 3 was performed. Table 3 shows the results.

Example 5 This example was carried out using a reactor having a capacity of 90 l as shown in FIG. 78k of low molecular weight polylactic acid obtained in Synthesis Example 2
g was heated to 100 ° C. and fed to the reactor by a feed pump. Thereafter, the pressure was gradually reduced to 130 ° C / 20 to 15m.
Distill 48.0 kg of DPE over 2 hours at mHg,
The concentration of polylactic acid was concentrated to 60% by weight. Thereafter, the same operation as in Example 3 was performed. Table 3 shows the results.

Comparative Example 2 A part of the low molecular weight polylactic acid obtained in Synthesis Example 2 was continuously reacted in the tank reactor used in Synthesis Example 2. 130 ° C / 1
The reaction was continued under the condition of 5 mmHg, sampling was performed at intervals of 10 hours, and the weight average molecular weight was measured. Table 3 shows the results.

[0044]

[Table 3]

[0045]

The process of the present invention is a process which makes it possible to industrially and inexpensively obtain a high molecular weight polymer from hydroxycarboxylic acid or its oligomer by direct dehydration polycondensation.

[Brief description of the drawings]

FIG. 1 is a schematic view of a vertical high-viscosity reactor equipped with a ribbon-shaped stirring blade on a shaft, which is used for carrying out the present invention.

FIG. 2 is a schematic view of a vertical cone-shaped high-viscosity reactor equipped with a ribbon-shaped stirring blade on a shaft, which is used for carrying out the present invention.

FIG. 3 is a schematic view of a vertical high-viscosity reactor equipped with a ribbon-like stirring blade in a frame, which is used for carrying out the present invention.

FIG. 4 is a schematic view of a vertical cone-shaped high-viscosity reactor equipped with a ribbon-shaped stirring blade in a frame, which is used for carrying out the present invention.

FIG. 5 is a schematic view of a tank reactor used in a synthesis example and a comparative example of the present invention.

[Explanation of symbols]

 1. 1. Ribbon-shaped stirring blade Rotation axis 3. 3. Vertical high viscosity reactor Jacket 5. Frame 6. Glass-lined reactor 7. 3 swept wings

────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hiroyuki Ito 30 Asamuta-cho, Omuta-shi, Fukuoka Prefecture Examiner, Mitsui Toatsu Chemicals Co., Ltd. Satoshi Morikawa (56) References JP-A-4-249527 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) C08G 63/06 C08G 63/78-63/87

Claims (8)

(57) [Claims] Claims: 1. Hydroxycarboxylic acids are used as catalysts and organic solvents.
In the method of producing a high molecular weight polyhydroxycarboxylic acid by dehydration polycondensation in the presence of a medium , a low molecular weight
Amount (about 10,000-30000) of polymer was produced
Later, in the second step, using a vertical high-viscosity reactor,
A method for producing a high molecular weight polyhydroxycarboxylic acid, wherein thermal polycondensation is performed while separating and removing low boiling components. 2. The vertical high-viscosity reactor according to claim 1, wherein a ribbon-shaped stirring blade is provided inside.
A method for producing a high molecular weight polyhydroxycarboxylic acid. 3. The polymer according to claim 1, wherein the vertical high-viscosity reactor is provided with a ribbon-shaped stirring blade inside, and the ribbon-shaped stirring blade is supported by a frame.
A method for producing a polyhydroxycarboxylic acid. 4. A high molecular weight polymer according to claim 1, wherein a ribbon-shaped stirring blade for providing a cone angle substantially equal to the cone angle of the vertical high viscosity reactor is provided inside the vertical type high viscosity reactor. A method for producing a polyhydroxycarboxylic acid. 5. A vertical high-viscosity reactor, wherein a ribbon-shaped stirring blade for providing a cone angle substantially equal to the cone angle of the device is provided, and the ribbon-shaped stirring blade is supported by a frame. The method for producing a high molecular weight polyhydroxycarboxylic acid according to claim 1, wherein 6. The method according to claim 1, wherein the hydroxycarboxylic acid is lactic acid, glycolic acid, 3-hydroxybutyric acid, 4-hydroxybutyric acid, 3-hydroxyvaleric acid, or a mixture thereof. A process for producing the high-molecular-weight polyhydroxycarboxylic acid according to the above. 7. A method for producing a high molecular weight polyhydroxycarboxylic acid of claim 1, wherein the catalyst is characterized in that it is a tin-based catalyst. 8. The organic solvent is, claims, characterized in that an aromatic hydrocarbon or an ether-based aromatic hydrocarbons
Item 4. The method for producing a high molecular weight polyhydroxycarboxylic acid according to Item 1 .