JP2003165833A - Method for producing polyhydroxycarboxylic acid - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress a side reaction generated at the time of polycondensation by a simple method when producing a high molecular weight and high quality polyhydroxycarboxylic acid by polycondensation, and to increase a polycondensation rate. SOLUTION: In producing polyhydroxycarboxylic acid by polycondensation, after absorbing an inert gas into a molten polymer having a weight-average molecular weight of 20,000 or more. And polycondensation under reduced pressure.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for producing a high molecular weight polyhydroxycarboxylic acid useful as a biodegradable polymer for medical materials or as an alternative to general-purpose resins by polycondensation.

[0002]

2. Description of the Related Art In recent years, the problem of plastic waste has come to be addressed from the viewpoint of protection of the natural environment, and there has been a demand for polymers and their molded products that decompose in the natural environment. Polyhydroxycarboxylic acid has heat resistance,
Since it has an excellent balance in terms of mechanical strength and hydrolyzability, it has attracted attention as a biodegradable polymer material, and several production methods have already been proposed.

As a method for obtaining polyhydroxycarboxylic acid, for example, hydroxycarboxylic acid is once dehydrated and condensed, and then thermally decomposed to form a cyclic dimer ester, which is subjected to ring-opening polycondensation in the presence of a catalyst to obtain a high-concentration compound. A method for obtaining a molecular weight polycondensate is known (for example, JP-A-63-1792).
No. 9, etc.). However, this method has a merit that a polymer having a high molecular weight can be obtained, but it requires a great deal of labor and cost in the step of producing a cyclic dimer ester and the step of purifying the produced ester, and therefore, it is very difficult. It was not an economical manufacturing method.

On the other hand, as a method for economically producing polyhydroxycarboxylic acid, a method of directly polycondensing a hydroxycarboxylic acid or an oligomer thereof is known, but this method has various problems. Was there. For example, in the method of directly polycondensing hydroxycarboxylic acid under melting conditions, the viscosity of the polycondensation system increases as the degree of polycondensation increases, and the reaction by-product water and other low molecular weight components are removed from the system. However, there is an essential problem that it is difficult to increase the degree of polycondensation because it is difficult to distill off. That is, in the large-scale vertical stirring tank polycondensor, the ratio of the evaporation area to the liquid volume is usually smaller than in the case of the small scale, and the liquid depth is large. In this case, even if the degree of vacuum is increased in order to increase the degree of polycondensation, the lower part of the stirring tank has a liquid depth, so that it is polycondensed at a substantially high pressure, and by-product water is efficiently generated. It is difficult to remove it.

In order to solve this problem, various measures have been taken to efficiently extract condensed water and the like. For example,
In JP-A-6-65360, a hydroxycarboxylic acid or an oligomer thereof is dehydrated and condensed in a reaction mixture containing an organic solvent in the substantial absence of water to give a weight average molecular weight of about 15,000 or more. A method of making a polyhydroxycarboxylic acid is disclosed. According to this method, it is possible to produce a polyhydroxycarboxylic acid having a weight average molecular weight of about 100,000 to 200,000, but since an organic solvent is used, dehydration drying of the organic solvent, separation or recovery, purification, etc. are performed. Equipment is required.

On the other hand, in a method of directly polycondensing under a solvent-free and melting condition, the evaporation surface area or surface renewal property is increased by forcibly stirring or kneading a high-viscosity molten polymer. Attempts have been made to accelerate the distillation of by-product water and the like to polycondense the high molecular weight polyhydroxycarboxylic acid. For example, JP-A-7-304859 and JP-A-8-143649 disclose a method for producing polylactic acid using a screw extruder with a vent, but the molecular weight of the obtained polymer is still sufficient. I couldn't say. When the polycondensation reaction time is increased to produce a high molecular weight product, the resin is thermally decomposed,
There was a tendency to color.

A method of polycondensing using an inert gas when producing a polyhydroxycarboxylic acid by the melt polycondensation method is known. For example, JP-A-10-2189
Japanese Unexamined Patent Publication No. 80 proposes a method for producing polylactic acid by polycondensation, in which the polycondensation is allowed to proceed while the molten polymer is dropped along the support. This publication describes that the polycondensation reaction can be carried out under an inert gas stream.

However, the use of the inert gas in this publication efficiently supplies the inert gas into the polycondensation reactor which is carried out under a reduced pressure condition so that the partial pressure of the condensed water or the like produced by the polycondensation reaction can be efficiently increased. The polycondensation is promoted, whereby the polycondensation is promoted. When producing polyhydroxycarboxylic acid directly by polycondensation, another problem is that the hydroxycarboxylic acid is dehydrated between the hydroxyl groups of the hydroxycarboxylic acid under the polycondensation condition as represented by the chemical formula (1). An etherification reaction that causes a reaction may occur as a side reaction to form a dihydroxycarboxylic acid skeleton.

[0009]

[Chemical 1]

Generally, when a high molecular weight polycondensate is produced by polycondensation, it is necessary to maintain equimolarity of functional groups during polycondensation. However, in the case of producing polyhydroxycarboxylic acid, a side reaction greatly disrupts the functional group balance during polycondensation, which makes it difficult to produce a high molecular weight polymer. However, little has been known so far about the method of suppressing this side reaction.

[0011]

SUMMARY OF THE INVENTION An object of the present invention is to suppress side reactions that occur during polycondensation by a simple method when producing polyhydroxycarboxylic acid of high molecular weight and high quality by polycondensation. Another object of the present invention is to provide a method for industrially efficient production at a high polycondensation rate.

[0012]

Means for Solving the Problems As a result of intensive studies for solving the above-mentioned problems, the present inventors have made polyhydroxycarboxylic acid in a molten state having a specific molecular weight or more absorb an inert gas, and then, under reduced pressure. In the case of polycondensation in, surprisingly, compared with the case of polycondensing without absorbing the inert gas without directly supplying the inert gas into the polycondensator during the polycondensation, It was found that polyhydroxycarboxylic acid can be obtained at a high polycondensation rate.

Further, in this case, since the polycondensation reaction proceeds rapidly, the content of the dihydroxycarboxylic acid skeleton formed by the side reaction is reduced, and it was found that a high molecular weight product was obtained, and the present invention was completed. It was That is, the present invention is as follows. (1) When producing a polyhydroxycarboxylic acid by polycondensation, polyhydroxy is characterized in that a molten polymer having a weight average molecular weight of 20,000 or more is allowed to absorb an inert gas and then polycondensed under reduced pressure. Method for producing carboxylic acid. (2) Pressure P (Pa) when absorbing an inert gas,
Weight average molecular weight of the molten polymer before absorption of inert gas (M
w) is the mathematical formula (1)

[0014]

[Equation 2]

The method for producing a polyhydroxycarboxylic acid according to (1), which satisfies the relationship of (3) After absorbing an inert gas, the polymer obtained by polycondensation under reduced pressure is crystallized and solid-phase polymerized at a temperature that maintains a solid state (1) or ( The method for producing a polyhydroxycarboxylic acid according to 2). (4) The method for producing a polyhydroxycarboxylic acid according to any one of (1) to (3), wherein the inert gas is absorbed by using an inert gas absorption facility. (5) Any one of (1) to (4), characterized in that in all or a part of the polycondensation process, the polymer in the course of polycondensation is dropped along the support to promote polycondensation. 1. The method for producing a polyhydroxycarboxylic acid according to one. (6) In all or some of the steps of polycondensation, the polycondensation is carried out while the polymer being polycondensed is dropped along the support, and a part or all of the dropped polycondensate is circulated. Then, the polycondensation is carried out again while dropping along the support, and the method for producing a polyhydroxycarboxylic acid according to (5). (7) The inert gas is nitrogen (1)
~ The method for producing a polyhydroxycarboxylic acid according to any one of (6).

The present invention will be described in detail below. In the present invention, a hydroxycarboxylic acid and / or a derivative thereof is mainly used as a raw material of the polyhydroxycarboxylic acid, and a copolycondensation component can be used in combination, if necessary. For example, as the raw material of the polyhydroxycarboxylic acid used in the present invention, glycolic acid, lactic acid, 2-hydroxy-2,2-dimethylacetic acid, 2-hydroxy-2-butyric acid, 3-hydroxypropionic acid, 3-hydroxybutyric acid. , Hydroxycarboxylic acids such as 3-hydroxyvaleric acid and 4-hydroxybutyric acid, polyhydric hydroxycarboxylic acids such as glyceric acid and diglyceric acid, hydroxycarboxylic acid derivatives shown below, and β-propiolactone and γ-
Lactones such as butyrolactone, δ-valerolactone and ε-caprolactone can be mentioned. These may be monomers or oligomers thereof. Of these, as the hydroxycarboxylic acid, glycolic acid, lactic acid and glyceric acid are preferable.

As the hydroxycarboxylic acid derivative, an ester of the above-mentioned hydroxycarboxylic acid and an alcohol having 1 to 10 carbon atoms, for example, methanol, ethanol, propanol, isopropanol, butanol, pentanol, hexanol, octanol, etc., Cyclic diesters such as glycolide and lactide of hydroxycarboxylic acid can be mentioned. You may use these individually or in mixture of 2 or more types.

In the present invention, a copolycondensation component can be used in addition to the hydroxycarboxylic acid. When the copolycondensation component is used, the hydroxycarboxylic acid monomer unit content in the polyhydroxycarboxylic acid is 50 mo.
It is preferably 1% or more, and more preferably 75 mol% or more. When the hydroxycarboxylic acid monomer unit content is less than 50 mol%, the side reaction reduces the effect of reducing the amount of dihydroxycarboxylic acid skeleton introduced into the polymer.

Examples of the copolycondensation component include polyvalent carboxylic acids, polyvalent carboxylic acid esters, polyvalent carboxylic acid anhydrides, polyvalent hydroxycarboxylic acids, polyvalent hydroxycarboxylic acid esters, polyhydric alcohols, amino acids, Examples thereof include polyvalent amine and lactam. Such copolycondensation components may be used alone or in combination of two or more. As the polycarboxylic acid, those having 2 to 20 carbon atoms are preferable. As such carboxylic acid, for example, oxalic acid, malonic acid, glutaric acid, succinic acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecanedioic acid, dodecanedioic acid, fumaric acid, maleic acid, Diglycolic acid, aliphatic dicarboxylic acids such as 1,4-cyclohexanedicarboxylic acid, aromatic dicarboxylic acids such as phthalic acid, isophthalic acid and terephthalic acid, tricarboxylic acids such as propanetricarboxylic acid, trimellitic acid and pyromellitic acid Can be mentioned. These polyvalent carboxylic acids include alcohols having 1 to 10 carbon atoms, such as methanol, ethanol, propanol,
It can also be used in the form of an ester with isopropanol, butanol, pentanol, hexanol, octanol or the like, or a corresponding polyvalent carboxylic acid anhydride.

The polyhydric alcohol has 2 to 20 carbon atoms.
Are preferred. Examples of such alcohols include ethylene glycol, 1,3-propanediol,
1,2-propanediol, 1,4-butanediol,
2,3-butanediol, 1,5-pentanediol,
1,8-octanediol, 1,10-decanediol, 1,12-dodecanediol, 1,4-cyclohexanediol, 1,2-cyclohexanediol, 1,
3-cyclohexanediol, diethylene glycol,
Diols such as triethylene glycol and neopentyl glycol, triols such as glycerin and butane-1,2,3-triol, starch, glucose, cellulose, hemicellulose, xylan, xylose, xylitol, pentaerythritol, chitin, chitosan, dextrin. , Dextran, carboxymethyl cellulose, amylopectin, glycogen and other polysaccharides.

The amino acid preferably has 2 to 20 carbon atoms. Examples of such amino acids include glycine, (+)-alanine, β-alanine, (-)-asparagine, (+)-aspartic acid, (-)-cysteine, (+)-glutaminesan, (+)- glutamine,
(-)-Hydroxylysine, (-)-leucine, (+)
-Isoleucine, (+)-lysine, (-)-methionine, (-)-serine, (-)-threonine, (+)-valine, aminobutyric acid, azaserine, arginine, ethionine and the like can be mentioned.

As the polyvalent amine, those having 0 to 20 carbon atoms are preferable. Examples of such amines include hydrazine, methylhydrazine, monomethylenediamine, dimethylenediamine, trimethylenediamine, tetramethylenediamine, pentamethylenediamine, hexamethylenediamine, heptamethylenediamine, octamethylenediamine, nonamethylenediamine, deca. Examples thereof include methylenediamine, undecamethylenediamine, dodecamethylenediamine and the like.

The lactam preferably has 2 to 20 carbon atoms. Examples of such a lactam include glycine anhydride, propanelactam, α-pyrrolidone, α-
Piperidone, ε-caprolactam, α-methyl-caprolactam, β-methyl-caprolactam, γ-methyl-
Caprolactam, δ-methyl-caprolactam, ε-methyl-caprolactam, N-methyl-caprolactam,
β, γ-dimethyl-caprolactam, γ-ethyl-caprolactam, γ-isopropyl-caprolactam, ε-
Isopropyl-caprolactam, γ-butyl-caprolactam, γ-hexacyclobenzyl-caprolactam,
Examples include ω-enanthlactam, ω-capryllactam, caprylolatam, laurolactam, and a dimer of caprolactone.

In addition to the above, a combination of a polyvalent carboxylic acid and a polyvalent alcohol, a polyvalent carboxylic acid and a polyamine, and a polyvalent carboxylic acid, a polyhydric alcohol and a polyamine may be used in combination. In the case where some of the above compounds have an asymmetric carbon atom and D-form, L-form, and D / L mixture can exist, any of them can be used in the present invention. .

According to the present invention, when a polyhydroxycarboxylic acid is produced by polycondensation using the above-mentioned raw materials, after a molten polymer having a weight average molecular weight of 20,000 or more is allowed to absorb an inert gas, It is characterized in that it is polycondensed under reduced pressure. When the weight average molecular weight of the molten polymer when absorbing the inert gas is less than 20,000, the viscosity of the molten polymer is low, and when the polycondensation is carried out under reduced pressure after absorbing the inert gas, Almost no effect of increasing the condensation rate is observed. The upper limit of the weight average molecular weight of the molten polymer absorbing the inert gas is not limited, but is preferably 400,000 or less, more preferably 3
10,000 or more and 200,000 or less, most preferably 4
It is 50,000 or more and 150,000 or less.

The amount of the inert gas absorbed into the molten polymer is not limited, but 0.001 mass ppm or more and 10,000
The range of 0 mass ppm or less is preferable. In the present invention,
In the steps before and after the absorption of the inert gas, the polycondensation may be carried out while supplying the inert gas, or the polycondensation may be carried out without being supplied. However, the effect of the present invention is not achieved by simply supplying an inert gas into the polycondensator and conducting polycondensation throughout the entire process without absorbing the inert gas in the molten polymer. Not only does the rate decrease, but the amount of ether units formed in the resulting polyhydroxycarboxylic acid significantly increases over time, making it impossible to obtain a high molecular weight product.

Generally, in polycondensation, the reason why the polymerization rate is increased by continuously supplying and reacting an inert gas into the polymerization vessel is to lower the partial pressure of the condensation product in the polymerization vessel and It is understood to favor the progress of the polymerization. On the other hand, in the present invention, the weight average molecular weight is 20,000.
By adopting a configuration in which 0 or more molten polymer absorbs an inert gas and then polycondensates under reduced pressure, an inert gas that hardly lowers the partial pressure of by-products during the polycondensation reaction. Is only absorbed by the polymer,
The vigorous foaming phenomenon that occurs in the molten polymer improves the agitation state inside and on the surface of the molten polymer. As a result of improving the stirring state, not only can the polycondensation reaction be allowed to proceed rapidly, but further, the content of the dihydroxycarboxylic acid skeleton produced by the side reaction is also reduced, resulting in a high molecular weight polyhydroxycarboxylic acid. Can be manufactured.

Specific examples of the inert gas include nitrogen, helium, neon, argon, krypton, xenon, carbon dioxide and lower hydrocarbons. These gases can be used as one kind or a mixed gas of two or more kinds. Of these, the preferred gas is nitrogen. As a means for absorbing the inert gas in the molten polymer, a method of directly supplying the gas to the reactor used for polycondensation and absorbing the inert gas, an inert gas absorption facility is provided, and the inert gas is absorbed by this facility. Examples include a method of absorption.

The inert gas absorption equipment is not limited as long as it is an equipment capable of absorbing these inert gases in the molten polymer. For example, chemical equipment design / operation series No. 2, (published on March 15, 1981, published by Kagaku Kogyo Co., Ltd., revised gas absorption p.45-54), packed tower type absorption device, tray type absorption device, spray tower type absorption device,
Fluidized packed tower type absorption device, liquid film cross-flow contact type absorption device, high speed swirl flow type absorption device, mechanical force type absorption device, absorb the molten polymer while dropping it along the support in an inert gas atmosphere Equipment and the like. Among these, the means for absorbing the inert gas in the inert gas absorbing equipment is preferably used from the viewpoint of industrial productivity.

The temperature at which the inert gas is absorbed is not limited as long as the polymer is in a molten state and varies depending on the type, composition, molecular weight, etc. of the molten polymer, but preferably 1
It is in the range of 30 ° C or higher and 350 ° C or lower, more preferably 150 ° C or higher and 300 ° C or lower, and most preferably 170 ° C or higher and 250 ° C or lower. Pressure P when absorbing inert gas
It is preferable that (Pa) and the weight average molecular weight (Mw) of the molten polymer before absorbing the inert gas satisfy the relationship of the following mathematical expression (1).

[0031]

[Equation 3]

The upper limit of the pressure when absorbing the inert gas
There is no limitation, but preferably 5 × 10 ⁷Less than Pa, better
1x10 is better⁷Pa or less, most preferably 5 × 10⁶
Pa or less. The pressure when absorbing the inert gas is
If pressure or pressure is applied, increase the gas absorption rate.
In addition to being able to reduce the size of the equipment to be absorbed,
More preferable. The pressure P (P
When a) does not satisfy the relationship of the formula (1), polycondensation
It is introduced into the polymer by the effect of increasing the speed and side reactions.
The effect of reducing the amount of skeleton of dihydroxycarboxylic acid
Get smaller. Pressure is 5 × 10⁷If it exceeds Pa,
Equipment is enlarged to provide pressure resistance.

In the present invention, the time required for the molten polymer to absorb the inert gas varies depending on the type of the molten polymer, the inert gas used, the type of equipment for absorption, temperature conditions, pressure conditions, etc. Preferably 0.
01 seconds to 10 hours, more preferably 10 seconds to 3
Less than an hour. The weight average molecular weight of the polyhydroxycarboxylic acid obtained by the present invention is preferably 30,000 or more, more preferably 50,000 or more and 500,000 or less, most preferably 80, from the viewpoint of clearly expressing the characteristics of the present invention. It is 000 or more and 400,000 or less.

The reactor used for the polycondensation of the present invention is not limited, and examples thereof include a stirred tank reactor, a surface renewal stirred tank reactor, a thin film reactor, a centrifugal thin film evaporation reactor, and a surface renewal reactor. Axial kneading reactor, biaxial horizontal stirring reactor, wet wall reactor, perforated plate reactor for polycondensation while free fall
It is possible to use a polycondenser that causes the molten polymer to drop along the support to proceed with polycondensation, for example, a wire-type perforated plate reactor. These reactors can be used alone or in combination of two or more.

When an inert gas absorption facility is provided to absorb the inert gas, at least one inert gas absorption facility is used. When using two or more polycondensers, an inert gas absorption facility may be provided in front of all polycondensers, or an inert gas absorption facility may be provided only in front of some polycondensers. Good. When carrying out polycondensation using two or more polycondensers and installing an inert gas absorption equipment in front of all or some of the polycondensers, the temperature and pressure conditions of the inert gas absorption equipment May be the same or different.

In the present invention, a molten polymer is produced, for example, by polycondensing a hydroxycarboxylic acid or an oligomer thereof at the initial stage of polycondensation using a vertical stirring tank and / or a surface renewal stirring tank reactor. , Surface renewal type biaxial kneading reactor, biaxial horizontal stirring reactor, wet wall type reactor, perforated plate type reactor for polycondensation while free-falling, dropping molten polymer along the support A method of polycondensing using at least one polycondenser selected from the group consisting of polycondensers for promoting polycondensation is preferably used.

Among these, the polycondensation device for advancing the polycondensation by dropping the molten polymer in the course of the polycondensation along the support has excellent sealing properties, and therefore it is possible to produce a polymer with little coloring. Further, when the molten polymer absorbing the inert gas is dropped along the support, the foaming phenomenon of the molten polymer occurs violently, and the phenomenon of improving the stirring state of the molten resin is remarkable, which is more preferable. . The confirmation of the foaming state can be observed, for example, by providing a side glass in the polycondenser. When using a polycondensation machine which advances a polycondensation by making a molten polymer fall along a support body, it is preferred to install an inert gas absorption equipment before all polycondensation machines.

The molten polymer in the course of polycondensation means a melt having a lower degree of polymerization than a polyhydroxycarboxylic acid having a target weight average molecular weight. The reaction temperature at the time of producing a polyhydroxycarboxylic acid by polycondensing a hydroxycarboxylic acid, an oligomer thereof or the like is not limited because it varies depending on the kind of polyhydroxycarboxylic acid and the molecular weight, but is preferably 50 ° C. or higher and 350 ° C. The range is more preferably 80 ° C. or higher and 280 ° C. or lower. 5
If the temperature is below 0 ° C, the reaction rate tends to decrease,
If it exceeds the range, coloration tends to occur due to thermal decomposition of the polymer.

When a molten polymer is produced by polycondensing a hydroxycarboxylic acid, an oligomer thereof or the like, it is preferably carried out under an inert gas atmosphere and / or under reduced pressure. When the reaction is carried out under reduced pressure, it usually depends on the type of hydroxycarboxylic acid and the operating temperature, but is usually 1.333P.
An example is a range of a or more and 1.014 × 10 ⁵ Pa or less. At this time, a method of circulating an inert gas under reduced pressure or normal pressure, and a method of carrying out while adjusting the operating temperature and / or the operating pressure in multiple stages are preferable modes.

The polycondensation reaction after absorbing the inert gas in the molten polymer is carried out under reduced pressure. The preferred pressure varies depending on the type of polyhydroxycarboxylic acid, the molecular weight and the reaction temperature, but is 1.3 Pa or more and 5.4 × 10 ⁵ Pa.
It is less than or equal to 1.3 × 10 Pa and 6.7 × 10 ³ Pa
The following is more preferable. The time required for this reaction varies depending on the type and molecular weight of the molten polymer, the molecular weight of the target polyhydroxycarboxylic acid, the type of polycondensator used, the reaction conditions and the like, and is not limited, but is preferably 0. 0.01 second or more and 100 hours or less, more preferably 1
It is 0 minutes or more and 30 hours or less. The above polycondensation is preferably carried out while adjusting the operating temperature and / or the operating pressure in multiple stages.

When the above-mentioned polycondensation reaction is carried out by using a polycondensator which causes the molten polymer to drop along the support to promote polycondensation, the polycondensation drops from the holes of the perforated plate along the support. Polycondensation is carried out while producing a polyhydroxycarboxylic acid. The perforated plate is usually selected from a flat plate, a corrugated plate, a plate having a thick central portion, and the like. The shape of the perforated plate is not limited, but it is usually selected from a circular shape, an oval shape, a triangular shape, a polygonal shape, and the like. The shape of the holes of the perforated plate is not limited and is usually selected from a circular shape, an oval shape, a triangular shape, a quadrangular shape, a polygonal shape, a slit shape, a star shape, and the like. The cross-sectional area of the hole is
Preferably in the range of 0.01 cm ² or more 100 cm ² or less. The distance between the holes of the perforated plate is not limited, and the distance between the centers of the holes is preferably 1 mm or more and 500 mm or less. The holes of the perforated plate may be holes penetrating the perforated plate, tapered holes, those in which a tube is attached to the perforated plate, or the like.
There are no restrictions on the manner in which the holes are provided in the perforated plate, but it is more preferable to install the holes at each vertex of the regular hexagon and the center of gravity of the regular hexagon because the holes are densely packed in the perforated plate. The number of holes in the perforated plate is not limited and varies depending on the reaction temperature, the reaction pressure, the amount of catalyst, the range of the molecular weight for polycondensation, etc., but is preferably 5 to 10 ⁶ .

The support means a material having a large ratio of the length in the cross section and the vertical direction to the average length of the outer periphery of the cross section in the horizontal direction, and this ratio is preferably 10 or more and 1,000,000 or less. The support may be directly connected to the holes of the perforated plate or may be separated from the holes. Preferred specific examples include those in which a support is penetratingly connected to the central portion of each hole of the perforated plate, those in which a support is connected to the outer peripheral portion of each hole of the perforated plate, and the like. The lower end of the support may be in contact with the bottom liquid surface of the polycondenser,
You may be separated. The shape of the cross section of the support is not limited, and is usually selected from a circular shape, an oval shape, a triangular shape, a quadrangular shape, a polygonal shape, a star shape, and the like. The shape of the cross section may be constant in the length direction or may be different.

The support may be hollow.
If the support is hollow, polycondensation while dropping the polymer on the outside of the support, a method of putting a heating medium in the hollow part,
On the contrary, it is also possible to carry out polycondensation while dropping the polymer into the hollow portion of the support, and to bring the heating medium into contact with the outside of the support. The support may be a single wire-shaped support or a combination of a plurality of supports. The surface of the support may be smooth or may have irregularities. Further, it may have a projection partially.

Examples of the method of dropping the molten polymer in the course of polycondensation along the support through this porous plate include a method of dropping it by its own weight, a method of pushing it out from the holes of the porous plate by a pump or the like. The polycondensate after dropping along the support may be dropped as it is to the liquid reservoir, or may be forcibly taken into the liquid reservoir by a winder or the like. Further, the polycondensate after being dropped along the support may be extracted as it is, but it is preferable that the polycondensate is circulated and again dropped along the support to cause polycondensation.
In this case, depending on the reaction time required for the polycondensation reaction in the liquid distillation section or the circulation line after being dropped along the support,
The residence time can be extended.

The dropping distance when the molten polymer is dropped along the support is not limited because it varies depending on the type of the molten polymer and the reaction conditions, but is preferably 0.3.
m or more and 50 m or less, more preferably 0.5 m or more and 30 m
It is the following. The flow rate of the molten polymer passing through the holes is not limited because it varies depending on the type of the molten polymer and the reaction conditions, but is preferably 10 ⁻⁴ Kg / hr per hole.
Or more and 10 ⁴ Kg / hr or less, more preferably 10 ^-2 Kg
/ Hr or more and 10 ² Kg / hr or less. There is no limit to the time required to drop along the support, but
The range of 01 seconds or more and 100 hours is preferable.

The series of polycondensation operations of the present invention may be carried out continuously, or each unit operation may be carried out batchwise. In the present invention, the production of the polyhydroxycarboxylic acid can be carried out without adding a catalyst, but a catalyst can be used if necessary in order to increase the polycondensation rate. Examples of the catalyst that can be used in the present invention include periodic tables IA, IIA, IIIA, IV and V of the periodic table of elements.
Examples thereof include metals of A, VIII, IVB, and VB, metal salts, metal oxides, metal hydroxides, metal alkoxides, and metal sulfonates. For example, titanium, zirconium, niobium, tungsten, zinc, germanium, tin,
Metals such as antimony, magnesium oxide, titanium oxide,
Metal oxides such as zinc oxide, silica, alumina, tin oxide, antimony oxide, tin fluoride, antimony fluoride, magnesium chloride, aluminum chloride, zinc chloride, stannous chloride, stannic chloride, stannous bromide , Metal salts such as stannic bromide, aluminum sulfate, zinc sulfate, tin sulfate, magnesium carbonate, calcium carbonate, zinc carbonate, lithium hydroxide, sodium hydroxide, potassium hydroxide, magnesium hydroxide, calcium hydroxide, Metal hydroxides such as strontium hydroxide, barium hydroxide, aluminum hydroxide, zirconium hydroxide, iron hydroxide, cobalt hydroxide, nickel hydroxide, copper hydroxide and zinc hydroxide, magnesium acetate, aluminum acetate, acetic acid Metal carboxylates such as zinc, tin acetate, tin octoate, tin stearate, iron lactate, tin lactate, magnesium, lanthanum , Alkoxides of metals such as titanium, hafnium, iron, germanium, tin, antimony, organic metals such as dibutyltin oxide, tin methanesulfonate, tin trifluoromethanesulfonate, tin p-toluenesulfonate, and other organic sulfonates, Examples thereof include ion exchange resins such as Amberlite and Dowex, but are not limited thereto. When a catalyst is used, these catalysts may be used alone or in combination of two or more.

These catalyst species are used, for example, by directly adding them to a monomer solution containing a raw material monomer or an aqueous solution, or by adding them after polycondensation of an oligomer or a prepolymer to be used. If necessary, after hydrolyzing in the presence of water and / or hydroxycarboxylic acid, it may be added to the polycondensate of the raw material monomer, oligomer, prepolymer or the like. When these catalysts are used, the amount thereof is preferably in the range of 1 × 10 ⁻¹⁰ mol or more and 1 × 10 ⁻² mol or less as a metal atom per 1 g of the raw material monomer. When the amount of the catalyst used per 1 g of the raw material monomer is less than 1 × 10 ⁻¹⁰ mol of metal atoms, the effect of increasing the polycondensation rate is not sufficiently exerted and 1 ×
If it exceeds 10 ^-2 mol, side reactions such as coloring of the resin tend to increase.

In order to suppress coloration due to heat deterioration during polycondensation, a polycondensation reaction may be carried out by adding a coloring inhibitor.
The anti-coloring agent can be added to the reaction system as it is or after being dissolved or mixed in an appropriate liquid. There is no limitation on the timing of addition of the anti-coloring agent, and it may be added to the reaction system at any time from the process of concentrating or condensing the raw material monomers to the completion of the polycondensation reaction.
The addition may be done all at once or in portions.

As the heat stabilizer used, phosphoric acid,
Trimethyl phosphate, triethyl phosphate, triphenyl phosphate, polyphosphoric acid monoethyl ester, polyphosphoric acid diethyl ester, pyrophosphoric acid, triethyl pyrophosphate, pyrophosphoric acid hexamethylamide, phosphorous acid, triethyl phosphite, triphosphorous acid Phosphoric acid compounds such as phenyl are preferably used. These heat stabilizers can be used alone or in combination of two or more. The addition rate of the heat stabilizer is preferably in the range of 0.0005% by mass to 10% by mass, more preferably 0.01% by mass to 6% by mass, based on the raw material monomer. Even if the heat stabilizer is added in an amount of more than 10% by mass, the effect of preventing coloration does not increase, and if the amount of addition is less than 0.0005% by mass, the effect of preventing coloration does not sufficiently appear.

When the polyhydroxycarboxylic acid obtained in the present invention is a crystalline polymer, the polymer is shaped and crystallized, and then subjected to solid phase polymerization.
It is preferable because a high molecular weight polyhydroxycarboxylic acid excellent in color tone can be produced. There is no limitation on the method of shaping the polyhydroxycarboxylic acid, but for example, polyhydroxycarboxylic acid in a molten state may be treated with nitrogen, helium, neon, argon, krypton, xenon, carbon dioxide or a lower saturated hydrocarbon. Agglomerates or strands by solidifying in active gas, a method of pulverizing or cutting the agglomerates or strands into particles or pellets, or by contacting with a liquid such as water, particles or pellets Or a method of making a lump by contacting with a liquid such as water, a method of crushing the lump to a particle, further,
Examples thereof include a method in which molten polyhydroxycarboxylic acid is transferred to an extruder and pelletized.

The method of contacting the molten polyhydroxycarboxylic acid with a liquid such as water is not limited,
For example, spherical pellets can be obtained by adding polyhydroxycarboxylic acid in a molten state dropwise to water and solidifying it. When shaping is performed by contacting with a liquid such as water, it is possible to subsequently perform drying by a known method. There is no limitation on the shape of the shaped polyhydroxycarboxylic acid, but the general shape is powder, crushed, chips, spheres, cylinders, tablets, marbles, or a mixture thereof. It is a thing. Of these, spherical, columnar, marbled and tablet shapes are preferable. At this time, the particle size of the solid polyhydroxycarboxylic acid is not limited. Generally, the smaller the particle size of the solid prepolymer, the larger the surface area, which is advantageous in terms of the polymerization reaction, but the handling property deteriorates. Therefore, it is usually 10 μm or more and 20 mm or less, preferably 0 μm or more. .1m
It is m or more and 10 mm or less.

There is no limitation on the method of crystallizing the shaped polyhydroxycarboxylic acid, and a known method can be used. For example, by cooling and solidifying the prepolymer under nitrogen, helium, neon, argon, krypton, xenon, carbon dioxide, or an inert gas atmosphere such as a lower saturated hydrocarbon or under a flow or under reduced pressure, or a combination thereof, Can be performed by heating under pressure of the inert gas. In addition, it is also possible to carry out in a liquid such as water, alcohols, aliphatic hydrocarbons, aromatic hydrocarbons, ketones, ethers, esters or the like, which does not dissolve polyhydroxycarboxylic acid.

The temperature for crystallizing the shaped polyhydroxycarboxylic acid varies depending on the type of polymer, but is generally in the range of not less than the glass transition temperature of the polyhydroxycarboxylic acid and not more than 220 ° C. This crystallization process is
It can also be carried out in multiple steps within the above temperature range. The time required for the crystallization treatment of the polyhydroxycarboxylic acid may be such that the crystallization is performed under the crystallization treatment temperature condition,
It is set arbitrarily in consideration of the crystallization temperature and the like. Generally, it is 0.5 minutes or more and 360 minutes or less, preferably 1 minute or more and 240 minutes or less, more preferably 5 minutes or more and 120 minutes or less.

The polyhydroxycarboxylic acid obtained by crystallization by this method is referred to as a crystallized polyhydroxycarboxylic acid in the present invention. The weight average molecular weight of the crystallized polyhydroxycarboxylic acid used in the solid phase polymerization is preferably 30,000 or more in order to clearly express the characteristics of the present invention. In the present invention, the solid phase polymerization reaction can be carried out under an inert gas flow, under reduced pressure, under pressure, or a combination thereof. At this time, since it is necessary to remove water generated by the polymerization, it is preferable to carry out the solid phase polymerization reaction under an inert gas flow and / or under reduced pressure.

When solid phase polymerization is carried out under an inert gas flow,
Examples of the inert gas include nitrogen, helium, neon, argon, krypton, xenon, carbon dioxide, and lower saturated hydrocarbon. As the circulating inert gas, a gas having a water content as low as possible and being substantially anhydrous is preferable. In this case, the gas may be passed through a layer filled with a molecular sieve or the like or an ion exchange resin or the like, or may be dehydrated and used by cooling the gas to an extremely low temperature. When showing the water content of the circulating gas in terms of dew point, it is preferably -10 ° C or lower, and more preferably -40 ° C or lower.

The flow rate of the circulating gas depends on the shape of the prepolymer,
Considering the particle size, crystallinity, reaction temperature, etc., it suffices to be able to distill off the produced water to the extent that a glycolic acid copolymer having a sufficiently high weight average molecular weight can be obtained. Generally, the higher the flow rate of the flowing gas is, the higher the efficiency of removing the generated water is, but usually, 0.02 ml / min or more and 2000 ml / min or less in terms of atmospheric pressure per 1 g of the crystallization prepolymer, preferably It is 0.5 ml / min or more and 1600 ml / min or less, more preferably 1 ml / min or more and 1000 ml / min or less.

When the solid-phase polymerization reaction is carried out under reduced pressure, the degree of pressure reduction in the reaction system substantially maintains the progress of the solid-state polymerization reaction to obtain polyhydroxycarboxylic acids having a sufficiently high weight average molecular weight. It may be within the range. From the viewpoint of the polymerization rate and the achieved weight average molecular weight, the preferable degree of reduced pressure is 13.
The range is ³ Pa or more and 1.33 × 10 ³ Pa. on the other hand,
When the solid phase polymerization reaction is carried out under pressure, the pressure in the reaction system is substantially within the range in which the progress of the solid phase polymerization reaction is maintained and a glycolic acid copolymer having a sufficiently high weight average molecular weight is obtained. If

The reaction temperature for carrying out the solid phase polymerization is not limited as long as the crystallized polyhydroxycarboxylic acid present in the reaction system maintains a substantially solid state, but in view of the polymerization rate, it is 100. The melting point of the crystallized polyhydroxycarboxylic acid is preferably not lower than the melting point of the crystallized polyhydroxycarboxylic acid, and more preferably not lower than 120 ° C and not higher than the melting point of the crystallized polyhydroxycarboxylic acid. At this time, the solid phase polymerization reaction temperature does not have to be constant during the reaction as long as it is within the above-mentioned temperature range.

During the solid phase polymerization reaction, when the melting point of the crystallized polyhydroxycarboxylic acid rises due to the increase of the molecular weight or the annealing effect, the reaction temperature is raised to the range of the melting point of the crystallized polyhydroxycarboxylic acid at that time to solidify. It is also possible to carry out a phase polymerization reaction. The weight average molecular weight of the polyhydroxycarboxylic acid obtained by the solid phase polymerization obtained according to the present invention is 30, from the viewpoint of clearly expressing the characteristics of the present invention.
It is preferably 000 or more, more preferably 50,000 or more and 500,000 or less, and most preferably 80,000 or more and 400,000 or less.

The polyhydroxycarboxylic acid obtained in the present invention can be esterified by reacting it with an acid anhydride such as acetic anhydride after the polycondensation reaction, if necessary. There is no limitation on the material of the polycondensor used in the present invention, and usually,
Glass, stainless steel, carbon steel, nickel, hastelloy, titanium, chromium, zirconium, other alloys, and polymer materials having high heat resistance are used.
Further, the surface of the polycondenser may be subjected to various treatments such as plating, lining, passivation treatment, acid cleaning, and alkali cleaning, if necessary.

The polyhydroxycarboxylic acid obtained by the present invention can be melted and processed into a molded body or a molded container, a film or sheet, a foam, a fiber or the like.
If necessary, heat treatment or the like can be performed after the molding. Examples of molded bodies or molded containers include beverages, cosmetics, detergent bottles, disposable cups, containers such as trays, cold storage boxes and casings for various cartridges, agricultural flower pots and growing beds, pipes that do not need to be dug out, and temporary fixings. material,
Building materials such as blocks, civil engineering materials, stationery such as ballpoint pens, mechanical pens, pencils, etc., and members such as golf tees can be mentioned. Examples of the film or sheet include agricultural mulch films, shopping bags, packaging films, wrap films, various tapes, fertilizer bags, and the like.
Examples of the foam include food trays, buffers, and heat insulating materials. Examples of the fibers include fishing lines, fishing nets, non-woven fabrics, sutures and the like. As a special example, it can be mixed with fertilizer and used as various compounding agents such as slow-acting fertilizer.

[0062]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be specifically described with reference to Examples, but these Examples do not limit the scope of the present invention. The characteristics of the polyhydroxycarboxylic acid used in the present invention are measured by the methods described below. (1) Content of Specific Monomer Unit Constituting Polyhydroxycarboxylic Acid The content of the specific monomer unit forming polyhydroxycarboxylic acid is measured by ¹ H-NMR measurement at 400 MHz using deuterated hexafluoroisopropanol as a solvent. The obtained results are analyzed to calculate the abundance of the specific monomer units with respect to the total number of monomer units in mol%.

(2) Weight average molecular weight of polyhydroxycarboxylic acid: Determined by the following method using a gel permeation chromatography (GPC) analyzer. Hexafluoroisopropanol in which 80 mM sodium trifluoroacetate was dissolved was used as an eluent, and the column temperature was 40 ° C. and the eluent flow rate was 1 ml / min.
Tosoh Corporation Tskkel (registered trademark) G5000H
HR and Tskgel (registered trademark) G manufactured by Tosoh Corporation
3000 HHR each consisting of one in series),
Molecular weight 1,577,000, 685,000, 333
000, 100, 250, 62, 600, 24, 30
A calibration curve obtained from the elution time by RI detection of a monodisperse polymethylmethacrylate standard substance with a known molecular weight of 0, 12,700, 4,700, 1,680 was prepared in advance, and the weight average molecular weight was calculated from the elution time. To do.

(3) Dihydroxycarboxylic acid content The content is determined by the following method using a high performance liquid chromatography (HPLC) analyzer. 5 g of sufficiently dried and finely pulverized polyhydroxycarboxylic acid was weighed, hydrolyzed at room temperature with 10 ml of 20 ml 8N-NaOH aqueous solution for 48 hours, and an aqueous solution acidified with 12.5 ml of concentrated hydrochloric acid aqueous solution was used as a sample solution. And The sample aqueous solution was adjusted to 0.
A column temperature of 40% was used with a 75% by mass phosphoric acid aqueous solution as an eluent.
A column under the conditions of ℃ and an eluent flow rate of 1 ml / min (column composition is RSpak (registered trademark) KC
811 are connected in series) and U
The absorbance of the peak corresponding to the corresponding dihydroxycarboxylic acid detected by the V detector (wavelength 210 nm) is measured. The content rate of dihydroxycarboxylic acid present in the polymer is calculated as the mass% of dihydroxycarboxylic acid present with respect to the weight of the resin which is dried and weighed, using a calibration curve of the corresponding dihydroxycarboxylic acid body prepared separately.

(4) Melting point of polyhydroxycarboxylic acid Determined according to JIS K7121. It is determined from a DSC curve obtained by increasing the temperature of polyhydroxycarboxylic acid from -20 ° C to 250 ° C at a temperature increase rate of 10 ° C / min using DSC-7 manufactured by Perkin Elmer Co., Ltd. At this time, when there are a plurality of melting peaks, among the melting peaks represented by one baseline, the peak top temperature of the peak on the highest temperature side is taken as the melting point.

[0066]

Reference Example 1 A 90% L-lactic acid aqueous solution was added to a glass-lined vertical stirring tank equipped with a distilling tube and a stirring blade, and 0.007% by mass of tin powder (as metal atoms per 1 g of monomer was added to the lactic acid aqueous solution). (6.6 × 10 ⁻⁷ mol) was charged, and after nitrogen substitution, the temperature was raised from 130 ° C. to 150 ° C. over 2 hours under a nitrogen stream, and the temperature was maintained at 150 ° C. for 1 hour for dehydration. . After this, the temperature is 150 ° C. and 1.013 × 1
The pressure was reduced from 0 ⁵ Pa to 6.7 × 10 ² Pa over 1 hour, and subsequently the reaction was performed at a reduced pressure degree of 6.7 × 10 ² Pa for 6 hours, and the condensation water was continuously removed. Then, the temperature is raised to 200 ° C., and the reaction is performed at a reduced pressure of 6.7 × 10 ² Pa for 6 hours,
A polylactic acid having a weight average molecular weight of 30,000 (hereinafter, abbreviated as molten polymer A) was produced. The dilactic acid content determined by extracting a part of the resulting product, hydrolyzing it, was 0.01% by mass.

[0067]

Reference Example 2 Polycondensation was performed in the same manner as in Reference Example 1 except that the final polycondensation conditions were set to a temperature of 200 ° C. and a reduced pressure of 6.7 × 10 ² Pa for 1 hour.
000 polylactic acid (hereinafter, abbreviated as molten polymer B) was produced. The dilactic acid content determined by extracting a part of the resulting product, hydrolyzing it, was 0.01% by mass.

[0068]

[Reference Example 3] A 70% glycolic acid aqueous solution and 90% L were added to a glass-lined vertical stirring tank equipped with a distillation pipe and a stirring blade.
An aqueous lactic acid solution was charged in a mass ratio of 100 to 11.5, and further, 0.05% by mass of tetraisopropoxygermanium (2.2 × 10 ⁻⁶ mol of metal atom per 1 g of monomer was added to the raw material aqueous solution). ) Is charged,
Nitrogen substitution was performed. Then, the temperature was raised from 130 ° C. to 150 ° C. over 2 hours under a nitrogen stream, and the temperature was maintained at 150 ° C. for 1 hour for dehydration. After this, the temperature is 150 ° C,
The pressure was reduced from 1.013 × 10 ⁵ Pa to 6.7 × 10 ² Pa over 1 hour, and subsequently the degree of pressure reduction was 6.7 × 10 ² P.
The reaction was carried out for 3 hours in a and the removal of condensation water was continued.

Thereafter, the temperature was raised to 200 ° C., and after the temperature was raised, the reaction was carried out at a reduced pressure of 2.0 × 10 ² Pa for 12 hours to give a glycolic acid unit content of 89 mol% and a weight average molecular weight of 4
3,000 glycolic acid-lactic acid copolycondensates (hereinafter abbreviated as molten polymer C) were produced. Only diglycolic acid was detected as the dihydroxycarboxylic acid, and its content was 0.01% by mass.

[0070]

Reference Example 4 As a raw material, 70% glycolic acid aqueous solution and 90% L-lactic acid aqueous solution were charged at a mass ratio of 100: 11.5, and 0.02% by mass of magnesium oxide was further added to the raw material aqueous solution. Reference Example 3 except that (6.9 × 10 ⁻⁶ mol of metal atom per 1 g of monomer) was charged.
In the same manner as above, a glycolic acid-lactic acid copolycondensate having a glycolic acid unit content of 89 mol% and a weight average molecular weight of 45,000 (hereinafter, abbreviated as melt polymer D) was produced. As the dihydroxycarboxylic acid, only diglycolic acid was detected, and its content was 0.02% by mass.

[0071]

[Reference Example 5] 70% glycolic acid aqueous solution, 90% L in a glass lined vertical stirring tank equipped with a distillation tube and a stirring blade
An aqueous solution of lactic acid, ethylene glycol, and adipic acid were charged at a mass ratio of 10,000: 1157: 0.53: 1.86, and further magnesium oxide was charged at 0.02% by mass relative to the raw material aqueous solution (per 1 g of monomer). Except for the metal atom (6.9 × 10 ⁻⁶ mol), the contents of glycolic acid unit, lactic acid unit, ethylene glycol unit, and adipic acid unit are 88.82 mol% and 11 respectively in the same manner as in Reference Example 3. 0.16 mol%, 0.1.
Weight average molecular weight of 4 at 008 mol% and 0.012 mol%
4,000 glycolic acid-lactic acid-ethylene glycol-adipic acid copolycondensates (hereinafter abbreviated as melt polymer E) were produced. As the dihydroxycarboxylic acid, only diglycolic acid was detected, and the content rate was 0.
It was 02 mass%.

[0072]

[Reference Example 6] A 70% glycolic acid aqueous solution and 90% L were added to a glass lined vertical stirring tank equipped with a distillation tube and a stirring blade.
An aqueous lactic acid solution was charged at a mass ratio of 100: 4.5, and further 0.05% by mass of tetraisopropoxygermanium was charged to the raw material aqueous solution (2.3 × 10 3 metal atoms per 1 g of the monomer). ^-6 mol) later,
Nitrogen substitution was performed. Then, the temperature was raised from 130 ° C. to 150 ° C. over 2 hours under a nitrogen stream, and the temperature was maintained at 150 ° C. for 1 hour for dehydration. After this, the temperature is 150 ° C,
The pressure was reduced from 1.013 × 10 ⁵ Pa to 6.7 × 10 ² Pa over 1 hour, and subsequently the degree of pressure reduction was 6.7 × 10 ² Pa.
The reaction was continued for 3 hours and the condensation water was continuously removed.

Thereafter, the temperature was raised to 225 ° C., and the degree of vacuum was 6.7.
After reacting at × 10 ² Pa for 10 hours, the content of glycolic acid unit was 95 mol% and the weight average molecular weight was 44,
000 glycolic acid-lactic acid copolycondensates (hereinafter abbreviated as molten polymer F) were produced. As the dihydroxycarboxylic acid, only diglycolic acid was detected, and its content was 0.04% by mass.

[0074]

Reference Example 7 A zirconium vertical surface renewal reactor (VCR manufactured by Mitsubishi Heavy Industries, Ltd.) with an internal volume of 90 L equipped with a distilling tube and an inverted conical ribbon blade type stirring blade was mixed with 70% glycolic acid aqueous solution and 90%. Mass ratio of L-lactic acid aqueous solution to 100: 11.5
Of the raw material aqueous solution, and further 0.0
After charging 5% by mass of tetraisopropoxy germanium (2.2 × 10 ⁻⁶ mol of metal atom per 1 g of monomer), nitrogen substitution was carried out. Then, under a nitrogen stream, the temperature was raised from 130 ° C to 150 ° C over 2 hours.
It was dehydrated by holding it at 0 ° C. for 1 hour.

Thereafter, the temperature is 150 ° C. and 1.013 ×
The pressure was reduced from 10 ⁵ Pa to 6.7 × 10 ² Pa over 1 hour, and subsequently the reaction was performed at a reduced pressure degree of 6.7 × 10 ² Pa for 3 hours to continue the removal of condensed water. Then, the temperature was raised to 200 ° C., and after the temperature was raised, the reaction was carried out at a reduced pressure of 2.0 × 10 ² Pa for 6 hours to obtain a glycolic acid having a content of glycolic acid unit of 89 mol% and a weight average molecular weight of 45,000. -A lactic acid copolycondensate (hereinafter abbreviated as molten polymer G) was produced. Only diglycolic acid was detected as the dihydroxycarboxylic acid, and its content was 0.01% by mass.

[0076]

Example 1 An inert gas absorption facility 1 as shown in FIG.
Polylactic acid was produced by using a polycondensation reaction device including a polycondensation device 10 having a plurality of columnar supports 13 and a device in which a reflux pipe was attached to the vacuum vent port 15.
This polycondensation reactor has the following structure. The inert gas absorption facility 1 is SUS3 with a thickness of 2 mm and a length of 4 m.
Seven 16 columnar supports 4 are provided, and the molten polymer supplied from the supply port 2 is uniformly distributed to each columnar support 4 by the dispersion plate 3. An inert gas supply port 5 is provided in the lower part of the inert gas absorption equipment, and a vent port 6 for controlling the pressure of the inert gas supply equipment is provided in the upper part. The outside of the inert gas absorption equipment 1 is a jacket, which is heated by a heat medium. The polycondensator 10 is provided with 62 SUS316-made holes having a diameter of 4 mm and a diameter of 8 mm, and 62 columnar support bodies 13 arranged in a hexagonal close-packed arrangement of 8 mm at the distance between the holes. The molten polymer supplied from the supply port 11 is uniformly distributed to each support 13 by the dispersion plate 12. An inert gas supply port 14 is provided in the lower part of the polycondenser, and a vacuum vent port 15 is provided in the upper part. The outside of the polycondenser 10 is a jacket and is heated by a heat medium. Further, the discharge port 19 and the supply port 2 are connected by a circulation line, and by switching the valve of the supply port 2, the polymer dropped to the bottom of the polycondenser 10 can be supplied to the supply port 2 again through the circulation line.

The molten polymer A produced in Reference Example 1 was continuously supplied from the supply port 2 of this polycondensation apparatus to the water absorption equipment 1 at a flow rate of 10 kg / hr for 3 hours. The inert gas absorption facility 1 was set to 200 ° C., and nitrogen was supplied from the inert gas supply port 5 so that the pressure was maintained at 200,000 Pa while the vent was closed. The supply amount of nitrogen was 0.5 NL / hr. The polycondenser 10 is supplied from the discharge port 8 of the inert gas absorption equipment 1 by the discharge pump 9 from the supply port 11 so that the amount of the molten polymer 7 at the bottom of the inert gas absorption equipment 1 becomes constant.
Is continuously supplied to the bottom of the polycondenser 10
Accumulated 6. After that, the valve of the raw material supply port 2 was switched, and the polymer polycondensed in the polycondensator 10 was discharged from the discharge port 17 by the discharge pump 18 from the polycondensator 10 via the discharge port 19. After that, until 1 hour later,
At a circulation flow rate of 60 kg / hr through the circulation line, thereafter, the polylactic acid 16 at the bottom of the polycondenser 10 is continuously circulated from the discharge port by the discharge pump 18 so as to maintain the liquid level, and Condensation was performed. From the sight glass 20, the foamed molten polymer is a cylindrical support 1
It was observed that the surface of 3 was dropped while the surface was renewed well.

The polycondensator 10 has a temperature of 200 ° C. and a pressure of 93.
Pa and the reflux pipe were set to a temperature of 95 ° C. and a pressure of 93 Pa. 2NL / hr of nitrogen is supplied from the inert gas supply port 14.
Supplied. Four hours, six hours, and nine hours after starting the supply of the molten polymer A, the supply ports 2 and 11 were respectively supplied.
When the molecular weight of the molten polymer in was measured, the weight average molecular weight of the supplied molten polymer was 30,
It was more than 000. The weight average molecular weights of the two were the same, and the polycondensation reaction in the inert gas absorption equipment did not proceed. The polylactic acid obtained from the outlet after 13 hours of reaction time was white, its weight average molecular weight was 190,000, and the dilactic acid content determined by hydrolysis and quantification was as low as 0.02% by mass. The value on the right side of Expression (1) was always 283 or less, while the value on the left side was 200,000, which satisfied the relationship of Expression (1).

[0079]

Comparative Example 1 In FIG. 1, instead of connecting the exhaust port 19 and the supply port 2 with a circulation line without passing through an inert gas absorption facility, the discharge port 19 and the supply port 11 are connected with a circulation line. Except that the polymer dropped at the bottom of the polycondenser 10 can be supplied to the supply port 11 again through the circulation line by switching the valve of the supply port 11.
Polylactic acid was produced in the same manner as in Example 1.

In this example, the polymer falling along the cylindrical support 13 was not foamed. Molten polymer A
The polylactic acid sampled from the outlet 13 hours, 17 hours, and 25 hours after the start of the supply of the above was white, and its weight average molecular weight was 135,000,
The content of 140,000, 140,000 and dilactic acid are 0.16% by mass, 0.17% by mass and 0.17% by mass, respectively.
Was increasing.

[0081]

[Embodiment 2] An inert gas absorption facility 1 similar to that of Embodiment 1.
And a plurality of columnar supports 13
The molten polymer A produced in Reference Example 1 was continuously supplied from the supply port 2 at a flow rate of 10 Kg / hr by using an apparatus including one. The inert gas absorption facility 1 has a temperature of 20.
0 ° C., pressure 200 with the vent port closed,
Nitrogen was supplied from the inert gas supply port 5 so as to maintain 000 Pa. At this time, the amount of nitrogen supplied to the inert gas absorption equipment was 0.5 NL / hr.

The molten polymer is continuously supplied from the supply port 11 to the polycondenser 10 by the discharge pump 9 so that the amount of the molten polymer 7 at the bottom of the inert gas absorption equipment 1 becomes constant. Polycondensation was carried out while continuously discharging polylactic acid from the discharge port by the discharge pump 18 so that the amount of polylactic acid 16 was constant at the bottom. From the sight glass 20, the foamed molten polymer is a cylindrical support 1
It was observed that the surface of 3 was dropped while the surface was renewed well.

The conditions in the polycondensator 10 are that the temperature is 200.
The temperature was 93 ° C., the pressure was 93 Pa, and no inert gas was supplied from the inert gas supply port. When the molecular weight of the molten polymer at the supply port 2 of the inert gas absorption facility and the supply port 11 of the polycondensator 10 was measured, the weight average molecular weight of the supplied molten polymer was 30,000, and the inert gas absorption The polycondensation reaction in the equipment did not proceed. The polylactic acid discharged from the discharge port 19 50 hours after the start of continuous operation is almost white, and its weight average molecular weight is 5
The content of 5,000 and dilactic acid was as low as 0.01% by mass. The right side of Expression (1) is 283 or less, while the value on the left side is 200,000, which satisfies the relationship of Expression (1).

[0084]

Comparative Example 2 Using the molten polymer B produced in Reference Example 2, polylactic acid was produced under the same conditions as in Example 2.
It was observed from the sight glass 20 that the foamed molten polymer fell on the cylindrical support 13, but the foamed state was poor. The polylactic acid discharged from the discharge port 19 50 hours after the start of continuous operation was almost white, but its weight average molecular weight was low at 12,000. As a result of hydrolysis of the polymer, the dilactic acid content was found to increase to 0.03% by mass. The right side of Expression (1) was 283 or less, while the value on the left side was 200,000, which satisfied the relationship of Expression (1).

[0085]

[Embodiment 3] An inert gas absorption facility 1 similar to that of Embodiment 1.
And the same device 5 consisting of the polycondensor 10 having a plurality of columnar supports 13 are connected in series, and the supply port 2 and the discharge port 1 are respectively provided.
A glycolic acid-lactic acid copolycondensate was produced using a process in which a reflux pipe was attached to each vacuum vent port 15 in a process in which 9 were continuously connected. The combinations of the inert gas absorption device and the polycondenser are represented as (a), (b), (c), (d), and (e) from the preceding process side, respectively.

The molten polymer C produced in Reference Example 3 was continuously fed from the feed port 2 at a flow rate of 10 kg / hr to produce a glycolic acid-lactic acid copolycondensate. The inert gas absorption facility 1 is under the conditions of a temperature of 200 ° C. and a pressure of 100,000 Pa in (a) to (d) and a temperature of 210 ° C. and a pressure of 200,000 Pa in (e), and the vent ports are closed. Pressure (100) in (a)-(d)
In the case of 00 Pa and (e), nitrogen was supplied from the inert gas supply port 5 so as to maintain the pressure of 200,000 Pa. (A)
The supply amount of nitrogen in (e) is about 0.3 NL / hr.
Met. The molten polymer is polycondensed from the supply port 11 by the respective discharge pumps 9 of (a) to (e) so that the amount of the molten polymer 7 at the bottom of the inert gas absorption equipment 1 in (a) to (e) becomes constant. Continuously supplied to the vessel 10,
Glycolic acid at the bottom of the polycondenser 10 of (a) to (e)
-To keep the amount of lactic acid copolycondensate 16 constant (a) ~
Polycondensation was carried out while continuously extracting the glycolic acid-lactic acid copolycondensate from the discharge port by the discharge pump 18 of (e). From the sight glass 20, it was observed that the foamed molten polymer dropped on each of the columnar supports 13 while the surface was being renewed well.

The conditions in the polycondensator 10 are from (a) to
(D) 200 ° C., 93 Pa, (e) temperature 210
The temperature was 95 ° C. and the pressure was 93 Pa, and all the reflux tubes had a temperature of 95 ° C. and a pressure of 93 Pa. Further, nitrogen was supplied at 1 NL / hr from the inert gas supply port 14 of (a) to (e).
In each of (a) to (e), the molecular weight of the molten polymer at the supply port 2 of the inert gas absorption equipment and the supply port 11 of the polycondensator 10 was measured, and the weight average molecular weight between them was (a) to (e). It was the same in (e), and the polycondensation reaction in the inert gas absorption equipment did not proceed. The glycolic acid-lactic acid copolycondensate discharged from the outlet 19 of (e) 50 hours after the start of continuous operation is almost white, and its weight average molecular weight is 170,000, and only diglycolic acid is a dihydroxycarboxylic acid body. It was detected, and the content rate was as low as 0.03 mass%.

(A) 50 hours after the start of continuous operation
The weight average molecular weight of the molten polymer supplied to the supply port 2 of (e) is 43,000, 60,000,
82,000, 113,000, 143,000, and the values on the right side of the equation (1) corresponding to each are 2
It was 13 or less and small with respect to the value on the left side of 100,000 or 200,000, which satisfied the relationship of Expression (1).

[0089]

[Embodiment 4] The pressure condition in the polycondenser 10 is (a)
Is 600 Pa, (b) is 400 Pa, and (c) is 1
40 Pa, 93 d in (d), 40 Pa in (e), and glycol under the same conditions as in Example 3 except that a reflux pipe was not attached to each of the polycondensers 10 in (a) to (e). An acid-lactic acid copolycondensate was produced.
The supply amount of nitrogen to (a) to (e) is approximately 0.3 NL / h.
It was r, and it was observed from the sight glass 20 of each polycondenser that the foamed molten polymer dropped on each columnar support 13 while the surface was renewed very well.

In each of (a) to (e), the supply port 2 of the inert gas absorption equipment and the supply port 1 of the polycondensator 10
The molecular weight of the molten polymer in Example 1 was measured, but the weight average molecular weight between them was the same in (a) to (e), and the polycondensation reaction in the inert gas absorption equipment did not proceed. 50 hours after the start of continuous operation, the glycolic acid-lactic acid copolycondensate discharged from the discharge port 19 of (e) is almost white, and its weight average molecular weight is 163,00.
0, only diglycolic acid was detected as a dihydroxycarboxylic acid body, and the content rate was as low as 0.03 mass%.

(A) after 50 hours from the start of continuous operation
The molecular weight of the molten polymer supplied to the supply port 2 of (e) is 43,000, 57,000, 76.0, respectively.
The values on the right side of the equation (1) corresponding to 00, 108,000, and 135,000 are all 213 or less,
The value was small with respect to the value on the left side of 100,000 or 200,000, and the relationship of Expression (1) was satisfied.

[0092]

Example 5 Example 1 was repeated except that the molten polymer C produced in Reference Example 3 was used and the following (1) to (3) were changed.
A glycolic acid-lactic acid copolycondensate was prepared in the same manner as in. (1) Inert gas absorption facility With the vent port of the inert gas absorption facility 1 closed, nitrogen is supplied from the inert gas supply port 5 so as to maintain a pressure of 100,000 Pa. (2) The pressure of the polycondenser 10 is set to 40 Pa. (3) Molten polymer 7 at the bottom of the inert gas absorption facility 1
The molten polymer is continuously supplied from the supply port 11 to the polycondensor 10 so that the amount of
After accumulating the glycolic acid-lactic acid copolycondensate 16 at the bottom of the polycondensor 10, the valve of the raw material supply port 2 is switched, and the circulation flow rate is 50 kg / hr until 1 hour later, and thereafter the polycondenser 10 is used. The glycolic acid-lactic acid copolycondensate is continuously circulated through the discharge port by the discharge pump 18 so as to maintain the liquid level of the bottom glycolic acid-lactic acid copolycondensate 16.

The amount of nitrogen supplied to the inert gas absorption equipment is
It was approximately 0.3 NL / hr. When the molecular weight of the molten polymer at the supply ports 2 and 11 was measured 4 hours, 6 hours, and 9 hours after starting the supply of the molten polymer C, the weight average molecular weight of the supplied molten polymer was It was more than 43,000. Further, the weight average molecular weights of the two were the same, and the polycondensation reaction in the inert gas absorption equipment did not proceed.

In the polycondensation process, it was observed from the sight glass 20 that the foamed polymer dropped onto the cylindrical support 13 while renewing the surface very well. 15 hours after starting the supply of the molten polymer C, the discharge port 1
The glycolic acid-lactic acid copolycondensate obtained from Example 9 was almost white, its weight average molecular weight was 172,000, and only diglycolic acid was detected as a dihydroxycarboxylic acid compound, and its content was 0.03% by mass. Was low.

The right side of the equation (1) is always 213 or less, while the value on the left side is 100,000, which satisfies the relation of the equation (1).

[0096]

Example 6 A reaction was carried out in the same manner as in Example 5 except that polycondensation was carried out in the polycondensator 10 without supplying nitrogen.
Nitrogen supply to the inert gas absorption facility is approximately 0.3 NL
It was / hr. When the molecular weight of the molten polymer at the supply ports 2 and 11 was measured 4 hours, 6 hours, and 9 hours after starting the supply of the molten polymer C, the weight average molecular weight of the supplied molten polymer was It was more than 43,000. Further, the weight average molecular weights of the two were the same, and the polycondensation reaction in the inert gas absorption equipment did not proceed.

In the polycondensation process, it was observed from the sight glass 20 that the foamed polymer dropped on the cylindrical support 13 while renewing the surface very well. 15 hours after starting the supply of the molten polymer C, the discharge port 1
The glycolic acid-lactic acid copolycondensate obtained from Example 9 was almost white, its weight average molecular weight was 166,000, only diglycolic acid was detected as a dihydroxycarboxylic acid compound, and its content was 0.04% by mass. Was low. The right side of Expression (1) is always 213 or less, while the value on the left side is 10 or less.
The value was 10,000, which satisfied the relationship of Expression (1).

[0098]

[Embodiment 7] The pressure of the inert gas absorption equipment 1 is set to 1,000.
The reaction was carried out in the same manner as in Example 5 except that Pa and a reflux pipe were not attached to the vacuum vent port. The supply amount of nitrogen to the inert gas absorption facility was about 0.004 NL / hr. 4 hours after starting the supply of the molten polymer C, 6
After 9 hours and 9 hours, the molecular weight of the molten polymer at the supply ports 2 and 11 was measured.
That was all. Further, the changes in the weight average molecular weight between the two are 2,000, 1,000, and 1.00, respectively.
It was 0.

In the polycondensation process, it was observed from the sight glass 20 that the foamed polymer dropped on the cylindrical support 13 while the surface was renewed very well. 15 hours after starting the supply of the molten polymer C, the discharge port 1
The glycolic acid-lactic acid copolycondensate obtained from Example 9 was almost white, its weight average molecular weight was 164,000, only diglycolic acid was detected as a dihydroxycarboxylic acid compound, and its content was 0.03% by mass. Was low. The right side of the equation (1) is always 213 or less, while the value on the left side is 1,
000, which satisfied the relationship of the mathematical expression (1).

[0100]

[Embodiment 8] Glycolic acid-lactic acid copolycondensation is carried out in the same manner as in Embodiment 5 except that the inert gas supplied in the inert gas absorption facility 1 is argon and the gas supplied to the polycondenser 10 is argon. A condensate was produced. The amount of argon supplied to the inert gas absorption facility was approximately 0.3 NL / hr.

Four hours, six hours, and nine hours after starting the supply of the molten polymer C, the supply ports 2 and 1 were respectively supplied.
When the molecular weight of the molten polymer in 1 was measured, the weight average molecular weight of the molten polymer supplied was 4
It was 3,000 or more. Further, the weight average molecular weights of the two were the same, and the polycondensation reaction in the inert gas absorption equipment did not proceed. In the polycondensation process,
It was observed from the sight glass 20 that the foamed polymer dropped on the cylindrical support 13 while renewing the surface very well.

15 after starting the supply of the molten polymer C
After a lapse of time, the glycolic acid-lactic acid copolycondensate obtained from the outlet 19 was almost white and had a weight average molecular weight of 15
Only 2,000 and diglycolic acid were detected as the dihydroxycarboxylic acid body, and the content was low at 0.03 mass%. The right side of the formula (1) is always 213 or less, while the value on the left side is 100,000, which satisfies the relation of the formula (1).

[0103]

Example 9 The temperature and pressure of the inert gas absorption equipment 1 were 210 ° C. and 10,000 Pa, and the reaction temperature and pressure of the polycondenser 10 were 210 ° C. and 40 Pa, respectively, and the molten polymer D produced in Reference Example 4 was used. From the supply port 2 to 10 kg /
The reaction was carried out in the same manner as in Example 5 except that the mixture was continuously supplied at a flow rate of hr for 3 hours to produce a glycolic acid-lactic acid copolycondensate.

The amount of nitrogen supplied to the inert gas absorption equipment is
It was approximately 0.2 NL / hr. After the reaction time of 4 hours, 6 hours, and 9 hours after the start of the supply of the molten polymer D, the molecular weight of the molten polymer at the supply ports 2 and 11 was measured. All were 45,000 or more. Further, the changes in the weight average molecular weight between the two were 2,000, 1,000 and 1,000, respectively.

During the polycondensation process, it was observed from the sight glass 20 that the foamed polymer dropped on the cylindrical support 13 while renewing the surface very well. Fifteen hours after starting the supply of the molten polymer D, the glycolic acid-lactic acid copolycondensate obtained from the outlet 19 is almost white, its weight average molecular weight is 178,000, and only diglycolic acid is dihydroxyl. It was detected as a carboxylic acid body, and its content rate was as low as 0.04 mass%. The right side of equation (1) is always 205 or less, while the value on the left side is 1
The value was 10,000, which satisfied the relationship of Expression (1).

[0106]

Example 10 The molten polymer E produced in Reference Example 5 was
Glycolic acid-
A lactic acid-ethylene glycol-adipic acid copolycondensate was produced. The amount of nitrogen supplied to the inert gas absorption equipment is
It was approximately 0.2 NL / hr. When the molecular weight of the molten polymer at the supply ports 2 and 11 was measured 4 hours, 6 hours, and 9 hours after the start of the supply of the molten polymer E, the weight average molecular weight of the supplied molten polymer was It was 44,000 or more. The amount of change in the weight average molecular weight between the two is 2,000,
It was 1,000 and 1,000.

During the polycondensation process, it was observed from the sight glass 20 that the foamed polymer dropped onto the cylindrical support 13 while renewing the surface very well. 15 hours after starting the supply of the molten polymer E, the discharge port 1
The glycolic acid-lactic acid-ethylene glycol-adipic acid copolycondensate obtained from Example 9 was almost white, its weight average molecular weight was 189,000, and only diglycolic acid was detected as a dihydroxycarboxylic acid compound, and its content was Was as low as 0.05% by mass.

The right side of the equation (1) is always 209 or less, while the value on the left side is 10,000, which satisfies the relation of the equation (1).

[0109]

[Embodiment 11] The pressure of the inert gas absorption equipment 1 is set to 500P.
A glycolic acid-lactic acid-ethylene glycol-adipic acid copolycondensate was produced in the same manner as in Example 10 except that a was used. At this time, the amount of nitrogen supplied to the inert gas absorption facility was about 0.002 NL / hr.

Four hours, six hours, and nine hours after starting the supply of the molten polymer E, the supply ports 2 and 1 were respectively supplied.
When the molecular weight of the molten polymer in 1 was measured, the weight average molecular weight of the molten polymer supplied was 4
It was 4,000 or more. The change in weight average molecular weight between the two was 1,000 in each case. In the polycondensation process, it was confirmed from the sight glass 20 that the polymer slightly foamed on the cylindrical support 13 and dropped while the surface was being renewed.

15 after starting the supply of the molten polymer E
Glycolic acid-lactic acid-obtained from outlet 19 after time
The ethylene glycol-adipic acid copolycondensate is almost white, the weight average molecular weight is 154,000, and only diglycolic acid is detected as a dihydroxycarboxylic acid body,
The content rate was as low as 0.06 mass%. The right side of the formula (1) is always 209 or less, while the value on the left side is 500, which satisfies the relation of the formula (1).

[0112]

[Embodiment 12] Instead of the polycondenser 10 shown in FIG.
1.5m inner volume with two stirring shafts with a rotating diameter of 0.4m
3, the reaction was carried out using a biaxial horizontal stirring reactor made of SUS316 with a vacuum vent having a length of 4 m. The inert gas absorption equipment is the same as that of the first embodiment. The molten polymer F produced in Reference Example 6 was continuously supplied to the inert gas supply equipment 1 from the supply port 2 at a flow rate of 60 Kg / hr.

The inert gas supply facility 1 has a temperature of 225 ° C.
The pressure was 200,000 Pa, the nitrogen was supplied from the inert gas supply port 5 so that the pressure was kept at 200,000 Pa while the vent port 6 was closed. The amount of nitrogen supplied to the inert gas supply facility was 1.8 NL / hr. The molten polymer was supplied to the biaxial horizontal stirring reactor with a vacuum vent by the discharge pump 9 so that the amount of the molten polymer 7 at the bottom of the inert gas absorption equipment 1 was constant.
The polycondensation temperature, the pressure, the supply amount of nitrogen, and the rotation speed of the stirring shaft are 225 ° C., 93 Pa, 10 NL / hr, and 15 r, respectively.
It was pm.

After 4 hours and 6 hours from the start of continuous operation,
After 9 hours, when the molecular weights of the molten polymers at the supply ports 2 and 11 were measured, the weight average molecular weights of the molten polymers supplied were all 44,000 or more. Further, the weight average molecular weights of the two were the same, and the polycondensation reaction in the inert gas absorption equipment did not proceed. After 30 hours from the start of continuous operation, the glycolic acid-lactic acid copolycondensate discharged from the discharge port of the biaxial horizontal stirring reactor was almost white, and its weight average molecular weight was 18
30,000, only diglycolic acid was detected as a dihydroxycarboxylic acid body, and its content was as low as 0.06 mass%. The right side of equation (1) is always 209 or less, while
The value on the left side was 200,000, which satisfied the relationship of Expression (1).

[0115]

Comparative Example 3 Two biaxial horizontal stirring reactors of Example 12 were connected in series without passing through an inert gas absorption facility, and the molten polymer F produced in Reference Example 6 was directly fed to the biaxial horizontal stirring reactor. A glycolic acid-lactic acid copolycondensate was produced in the same manner as in Example 12 except for supplying 60 after starting continuous operation
The glycolic acid-lactic acid copolycondensate sampled from the discharge port of the biaxial horizontal stirring reactor in the previous stage after time was almost white, but the weight average molecular weight was as low as 80,000. Moreover, only diglycolic acid was detected as a dihydroxycarboxylic acid body, but the content rate was 0.48% by mass.
Was increasing.

80 hours after the start of continuous operation, the glycolic acid-lactic acid copolycondensate discharged from the discharge port of the subsequent biaxial horizontal stirring reactor was colored light brown and had a weight average molecular weight of 81,000. Only diglycolic acid was detected as a dihydroxycarboxylic acid body, but the content rate increased to 0.50 mass%.

[0117]

EXAMPLE 13 Instead of the polycondensator 10 shown in FIG.
The reaction was carried out using a horizontal glasses blade polymerizer with a vacuum vent made of SUS316 (Hitachi Glasses Blade Polymerizer (registered trademark), manufactured by Hitachi, Ltd.) having a total volume of 25 L and a protrusion amount of 6 L. The inert gas absorption equipment is the same as in Example 1 except that the number of SUS316 columnar supports 4 is three.

The molten polymer G produced in Reference Example 7 was continuously supplied to the inert gas supply equipment 1 from the supply port 2 at a flow rate of 0.8 Kg / hr. The inert gas supply equipment 1 is under the conditions of a temperature of 200 ° C. and a pressure of 200,000 Pa, a pressure of 200,000 Pa with the vent port 6 closed.
Nitrogen was supplied from the inert gas supply port 5 so that The supply amount of nitrogen was 0.03 NL / hr. The molten polymer was continuously supplied to the biaxial horizontal stirring reactor with a vacuum vent by the discharge pump 9 so that the amount of the molten polymer 7 at the bottom of the inert gas absorption equipment 1 was constant.
The polycondensation temperature, pressure, and rotation speed of the stirring shaft were each 200
C., 93 Pa, 6 rpm, and nitrogen was not supplied to the polycondenser.

The molecular weight of each molten polymer at the inlet 2 and the outlet 8 of the inert gas absorption equipment was measured 10 hours, 20 hours, and 30 hours after the continuous operation was started. 45,000
The polycondensation reaction in the inert gas absorption equipment did not proceed. Forty hours after the start of continuous operation, the glycolic acid-lactic acid copolycondensate discharged from the discharge port of the horizontal glasses-type blade polymerization device with a vacuum vent was almost white, and its weight average molecular weight was 178,000. In the copolycondensate, only diglycolic acid was detected as a dihydroxycarboxylic acid body, and its content rate was as low as 0.07% by mass. The right side of the formula (1) is always 205 or less, while the value on the left side is 200,000, which satisfies the relation of the formula (1).

[0120]

[Embodiment 14] A polycondenser 1 having one inert gas absorption facility 1 and a plurality of columnar supports 13 as in the first embodiment
0 (No reflux tube is attached to the vacuum vent port.)
The molten polymer G produced in Reference Example 7 was continuously supplied from the supply port 2 at a flow rate of 10 Kg / hr by using the apparatus composed of 1 unit of No. The inert gas absorption facility 1 has a temperature of 200.
℃, the pressure is 200, with the vent closed.
Nitrogen was supplied from the inert gas supply port 5 so as to maintain 000 Pa. At this time, the supply amount of nitrogen to the inert gas absorption equipment was 0.4 NL / hr.

Molten polymer was continuously supplied from the supply port 11 to the polycondenser 10 by the discharge pump 9 so that the amount of the molten polymer 7 at the bottom of the inert gas absorption equipment 1 was constant. Polycondensation was performed while continuously extracting the glycolic acid-lactic acid copolycondensate from the discharge port by the discharge pump 18 so that the amount of the glycolic acid-lactic acid copolycondensate 16 was constant at the bottom. The polycondensator 10 was set to a temperature of 200 ° C. and a pressure of 600 Pa. No inert gas was supplied from the inert gas supply port.

The foamed molten polymer is a cylindrical support 13.
From the sight glass 20, a state in which the surface was dropped while the surface was renewed very well was observed. After 30 hours from the start of continuous operation, the molecular weights of the molten polymers at the inlets 2 and 11 were measured. The weight average molecular weights between the two were the same as 45,000, and the polycondensation reaction in the inert gas absorption equipment was It wasn't in progress. The glycolic acid-lactic acid copolycondensate discharged from the discharge port 19 after 30 hours from the start of continuous operation was white, the weight average molecular weight was 56,000, and the diglycolic acid content was as low as 0.01% by mass.

The right side of Expression (1) is 205 or less, while the value on the left side is 200,000, which satisfies the relationship of Expression (1). Using the obtained glycolic acid-lactic acid copolycondensate, a solid phase polymerization operation was subsequently performed. The resulting glycolic acid-lactic acid copolycondensate having a weight average molecular weight of 56,000 was extruded with a twin-screw extruder, water-cooled, and then strand-cut to give a circle having a diameter of about 1.5 mm and a length of about 2 mm. Columnar pellets were produced.

Then, the pellets were dried in a dry nitrogen circulation dryer at 80 ° C. for 1 hour. The resulting dry pellets are placed under a nitrogen atmosphere at 130 ° C. for 30 minutes, followed by 150
Crystallization was performed at ℃ for 1 hour to obtain a crystallized glycolic acid-lactic acid copolycondensate. The melting point of the crystallized glycolic acid-lactic acid copolycondensate is 189 ° C., and the weight average molecular weight is 54.0.
It was 0. Subsequently, a solid-state polymerization reaction was carried out in an SUS vertical reactor. The reaction conditions are a temperature of 170 ° C. and a reaction pressure of 7
Nitrogen gas having a dew point of −85 ° C. was charged at 60 Torr, and the flow rate was 10 as a flow rate per 1 kg of glycolic acid-lactic acid copolycondensate.
The reaction time was set to 0 NL / min and the reaction time was set to 20 hours. The glycolic acid-lactic acid copolycondensate obtained after the solid phase polymerization was almost white, the weight average molecular weight was 183,000, and the diglycolic acid content was as low as 0.01% by mass.

[0125]

Fifteenth Embodiment Similar to the fourteenth embodiment, three identical devices, each consisting of an inert gas absorption facility 1 and a polycondenser 10 having a plurality of columnar supports 13, are connected in series, and a supply port 2 and a discharge port 19 are respectively provided. A glycolic acid-lactic acid copolycondensate was produced using a process in which The combination of the inert gas absorption equipment and the polycondensator is (A),
Represented as (B) and (C).

The molten polymer G produced in Reference Example 7 was continuously supplied from the supply port 2 at a flow rate of 10 kg / hr to produce a glycolic acid-lactic acid copolycondensate. (A) ~
In the inert gas absorption equipment 1 of (C), the temperature is set to 200 ° C., and the pressure is 200,000 P with the vent port closed.
Nitrogen was supplied from the inert gas supply port 5 so as to keep a. The supply amount of nitrogen to each of the inert gas absorption facilities (A) to (C) was approximately 0.4 NL / hr.

In order to keep the amount of the molten polymer 7 at the bottom of the inert gas absorption facility 1 in (A) to (C) constant, the molten polymer is supplied through the discharge ports 9 of (A) to (C). More continuously supplied to the polycondensator 10,
Glycolic acid at the bottom of the polycondenser 10 of (A) to (C)
-To keep the amount of lactic acid copolycondensate 16 constant (A) ~
Polycondensation was carried out while continuously extracting the glycolic acid-lactic acid copolycondensate from the discharge port by the discharge pump 18 of (C).

At this time, it was observed from the sight glass 20 that the foamed molten polymer dropped on each of the columnar supports 13 while renewing the surface very well. Polycondenser 1
The conditions at 0 are 200 ° C. at reaction temperatures (A) to (C), 600 Pa at (A), and 4 at (B).
00Pa, 140C in (C), (A) ~
From the inert gas supply port 14 of (C), 1 NL /
supplied for hr.

In (A) to (C), the molecular weight of the molten polymer was measured at each of the supply port 2 of the inert gas absorption equipment and the supply port 11 of the polycondensator 10. The weight average molecular weight between the two was (A). ) To (C) are equivalent, and the polycondensation reaction in the inert gas absorption equipment did not proceed. The glycolic acid-lactic acid copolycondensate discharged from the discharge port 19 of (C) 50 hours after the start of continuous operation is white, its weight average molecular weight is 110,000, and only diglycolic acid is detected as a dihydroxycarboxylic acid compound. The content rate was as low as 0.02% by mass.

(A) after 50 hours from the start of continuous operation
The molecular weight of the molten polymer supplied to the supply port 2 of the inert gas absorption equipment of (C) is 45,000 and 5 respectively.
6,000 and 75,000, and the value on the right side of Equation (1) corresponding to each is always 205 or less, which is small with respect to the value on the left side of 200,000, and satisfies the relationship of Equation (1). Was there. The obtained weight average molecular weight 111,
000 glycolic acid-lactic acid copolycondensates were then subjected to the same pelletizing, drying, crystallization and solid phase polymerization steps as in Example 14.

At this time, the melting point of the crystallized glycolic acid-lactic acid copolycondensate was 190 ° C., and the weight average molecular weight was 10
It was 8,000. The glycolic acid-lactic acid copolycondensate obtained after the solid phase polymerization is almost white, its weight average molecular weight is 252,000, and its diglycolic acid content is 0.0
It was as low as 2% by mass.

[0132]

Comparative Example 4 A glycolic acid-lactic acid copolycondensate was produced in the same manner as in Example 15, except that the inert gas absorption equipment was not passed. Continuous operation start 50
The glycolic acid-lactic acid copolycondensate discharged from the discharge port 19 of the polycondensator of (C) after a lapse of time was light brown in color, its weight average molecular weight was 68,000, and only diglycolic acid was a dihydroxycarboxylic acid body. Detected, the content rate is 0.
It increased to 43% by mass.

The resulting glycolic acid-lactic acid copolycondensate having a weight average molecular weight of 68,000 was subjected to the same pelletizing, drying, crystallization and solid phase polymerization steps as in Example 14. At this time, the melting point of the crystallized glycolic acid-lactic acid copolycondensate was 189 ° C. The glycolic acid-lactic acid copolycondensate obtained after the solid phase polymerization was brown, its weight average molecular weight was 98,000, and its diglycolic acid content was 0.45% by mass. Further, solid phase polymerization was carried out for 20 hours under the same conditions, and the weight average molecular weight was 98,000.
It was 0, and no increase in molecular weight was observed.

[0134]

According to the present invention, when a polyhydroxycarboxylic acid is produced by a direct polycondensation method from a hydroxycarboxylic acid or the like as a raw material, the polycondensation rate is high, and
It is possible to suppress a side reaction and produce a high-molecular-weight and high-quality polyhydroxycarboxylic acid.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing an example of a polycondensation reaction device used in the present invention.

[Explanation of symbols]

1 Inert gas absorption equipment 2, 11 Supply port 3,12 Dispersion plate 4,13 Cylindrical support 5,14 Inert gas supply port 6 vent 7 Molten polymer 8, 17, 19 outlet 9,18 discharge pump 10 Polycondenser 15 Vacuum vent port 16 Polyhydroxycarboxylic acid 20 side glasses

Claims (7)

[Claims] 1. When producing a polyhydroxycarboxylic acid by polycondensation, a molten polymer having a weight average molecular weight of 20,000 or more is allowed to absorb an inert gas, and then polycondensed under reduced pressure. Method for producing polyhydroxycarboxylic acid. 2. The pressure P (P
a) and the weight average molecular weight (Mw) of the molten polymer before absorption of the inert gas are represented by the mathematical formula (1) The method for producing a polyhydroxycarboxylic acid according to claim 1, wherein the relationship of is satisfied. 3. The polymer obtained by polycondensing under reduced pressure after absorbing an inert gas, is crystallized, and is solid-phase polymerized at a temperature maintaining a solid state. Or the method for producing a polyhydroxycarboxylic acid according to item 2. 4. The method for producing a polyhydroxycarboxylic acid according to claim 1, wherein an inert gas absorption facility is used to absorb the inert gas. 5. The polycondensation process according to claim 1, wherein in all or some of the polycondensation processes, the polymer being polycondensed is dropped along the support to allow the polycondensation to proceed. The method for producing a polyhydroxycarboxylic acid according to item 1. 6. In all or some of the polycondensation steps, the polycondensation is allowed to proceed while dropping the polymer in the course of polycondensation along the support, and a part or all of the dropped polycondensate is removed. The method for producing a polyhydroxycarboxylic acid according to claim 5, wherein the polycondensation is carried out by circulating and dropping along the support again. 7. The method for producing a polyhydroxycarboxylic acid according to claim 1, wherein the inert gas is nitrogen.