JP5075363B2 - Synthesis method and synthesis apparatus of polyhydroxycarboxylic acid - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a glycolide by condensing a glycolic acid and then depolymerizing the condensate in a synthesis method of a polyglycolic acid and a synthesis apparatus. <P>SOLUTION: The synthesis method of a polyhydroxycarboxylic acid comprises synthesizing the polyhydroxycarboxylic acid by ring-opening polymerizing a hydroxycarboxylic acid or a condensate thereof after depolymerized into a cyclic dimer, where melted matter containing the hydroxycarboxylic acid or the condensate thereof is formed into a thin layer by means of external force and is condensed and then the condensate is depolymerized to give the cyclic dimer. The synthesis apparatus is also provided. <P>COPYRIGHT: (C)2008,JPO&amp;INPIT

Description

  The present invention relates to a method and an apparatus for synthesizing polyhydroxycarboxylic acid, particularly polyglycolic acid, and in particular, after condensing and condensing hydroxycarboxylic acid such as glycolic acid, it is depolymerized and cyclic dimer such as glycolide. The present invention relates to a synthesis method and a synthesis apparatus for obtaining a body.

  Hereinafter, the case where glycolic acid is used as the hydroxycarboxylic acid will be mainly described. Polyglycolic acid is an aliphatic polyester made from glycolic acid. As one of the methods for synthesizing polyglycolic acid, glycolic acid oligomers are produced by condensing glycolic acid to reduce the water content and then condensing, and then adding a catalyst such as antimony oxide to depolymerize it once. There is a method in which a cyclic dimer (glycolide) is produced by the above-described method, and after purification by crystallization as necessary, a catalyst such as tin octylate is added to glycolide to perform ring-opening polymerization.

  In the concentration step, glycolic acid, which is a monomer, may contain about 10 to 15% of moisture (hereinafter referred to as free water) as an impurity. This free water is used to facilitate esterification between the monomers. Removal is performed. In this concentration step, moisture is removed by heating at 120 to 250 ° C. and, if necessary, reduced pressure using a vacuum pump or the like.

  In the condensation step, water produced by the esterification reaction between the monomers is vaporized and removed by heating at 120 to 250 ° C. and a reduced pressure environment such as a vacuum pump, preferably under a reduced pressure of 10 Torr or less. The reduced pressure here is different from that in the concentration step and is an essential condition for progressing the esterification reaction. By this condensation step, a glycolic acid condensate (hereinafter referred to as oligomer) is produced from the monomer.

  The oligomer produced in the condensation step is sent to the depolymerization step, and is heated with 120 to 250 ° C. and under a reduced pressure environment such as a vacuum pump, preferably under a reduced pressure environment of 100 Torr or less, and with a depolymerization catalyst such as antimony trioxide. Upon contact, glycolide (glycolic acid cyclic dimer ester) is produced. The produced glycolide is usually a gas in the environment in the depolymerization process and is often recovered by cooling and condensation. At that time, if the concentration reaction and the condensation reaction are insufficient, water may be mixed in glycolide. The mixed water reacts with a part of glycolide to return to linear monomers, etc., but these are factors that hinder the improvement of the polymerization degree due to the effect of the acid catalyst by the carboxyl group in the polyglycolic acid polymerization process by ring-opening polymerization. It becomes. Therefore, it is necessary to sufficiently concentrate and condense glycolic acid, which is a raw material, and to reduce the amount of water contained in glycolide after depolymerization as much as possible.

  Various techniques have been developed as a method for producing glycolide in polyglycolic acid synthesis. For example, there is one that obtains glycolide by depolymerizing an oligomer after obtaining a low polymer (oligomer) of glycolic acid by concentrating and condensing glycolic acid (Non-patent Document 1). Patent Document 1 discloses a method for obtaining polyglycolic acid from glycolic acid only by polycondensation reaction. This method uses a centrifugal thin film evaporator as a polycondensation reaction vessel, which increases the evaporation rate of water, accelerates the reaction, shortens the reaction time, prevents polymer thermal decomposition, and reduces impurities. It is possible.

JP 2004-51729 A Polymer Processing Vol 30, (1981) pp. 208-219

  In the non-patent document 1 described above, the glycolic acid polymer is thermally decomposed in the concentration step and the condensation step because it is exposed to heat as the time required for dehydration of water contained in the raw material and water generated in the condensation step becomes longer. This suggests a problem that the yield of glycolide decreases.

  In Patent Document 1, polyglycolic acid obtained by polycondensation reaction has a low degree of polymerization, a small molecular weight, a large molecular weight distribution, and a terminal group of the polymer is a carboxylic acid group. There is a problem that is likely to occur and is unstable.

  The present invention has been made in view of the above problems, and its object is to provide a method and apparatus for efficiently obtaining glycolide in the synthesis of polyglycolic acid having a high molecular weight and a small molecular weight distribution through depolymerization and ring-opening polymerization. Is to provide.

  In the present invention, after condensing and condensing hydroxycarboxylic acid and depolymerizing the condensate into a cyclic dimer, the ring-opening polymerization of the condensate is carried out by using an external force to form a melt containing hydroxycarboxylic acid or its condensate. The present invention provides a method for synthesizing a polyhydroxycarboxylic acid, characterized in that after thinning and condensation, this is depolymerized to obtain a cyclic dimer. The present invention also provides a hydroxycarboxylic acid supply device, a condensing device for condensing hydroxycarboxylic acid having an evaporator for thinning a melt containing hydroxycarboxylic acid or a condensate thereof using external force, and a condensate. An apparatus for synthesizing polyhydroxycarboxylic acid is provided in which depolymerization apparatuses for polymerization are sequentially arranged.

  ADVANTAGE OF THE INVENTION According to this invention, glycolide can be manufactured with high efficiency which can obtain a glycolic acid oligomer with few impurities in a short time by performing the condensation reaction of polyhydroxycarboxylic acid using a centrifugal thin film evaporator. Moreover, the suitable polyhydroxycarboxylic acid synthesis apparatus for enforcing this method can be provided.

In the present invention, hydroxycarboxylic acid is also referred to as hydroxy acid, and is a general term for organic compounds having a carboxyl group —COOH and an alcoholic hydroxyl group —OH in one molecule. For example, lactic acid. The present invention is particularly suitable for application to the polymerization of glycolic acid CH ₂ (OH) COOH. Further, there are α, β, γ, and δ-hydroxycarboxylic acids depending on the bonding position of the carboxyl group and the hydroxyl group, but the present invention is suitable for polymerization of α-hydroxyacids. α-Hydroxycarboxylic acid loses two molecules of water to form a cyclic ester lactide.

  In the case of glycolic acid, when heated to 100 ° C., one molecule of water is lost and condensed, and at 200 ° C., one more molecule of water is lost to become lactide glycolide.

  As a result of intensive studies on the above-mentioned problems in order to achieve the above object, the present inventors have found the following glycolide production method and apparatus. That is, the present invention provides a dehydration apparatus comprising a distillation tower between a raw material supply system and a condensation apparatus comprising a condensation tank using a device for thinning glycolic acid using external force, and water contained in the raw material and a condensation step The water generated in is removed with a dehydrator. Thus, the glycolic acid in the dehydrating apparatus is concentrated, and the concentrated glycolic acid is continuously supplied to the condensing apparatus.

  The evaporator is at least one of a falling film evaporator, a centrifugal thin film evaporator, and a stirring film evaporator, and a specific example is shown in FIG.

  In the present invention, as shown in FIG. 2 (a), the centrifugal thin film evaporator forms a liquid film by applying the liquid to be concentrated supplied into the apparatus to the inner surface of the apparatus casing by centrifugal force, Evaporation is promoted by heating from the outer surface of the device casing. Centrifugal force is applied to the liquid to be concentrated through a rotating blade and a rotor with blades installed in a fixed device casing. This method has the advantages that the equipment scale can be made compact, and the liquid film thickness can be controlled by controlling the gap width between the blade and the casing and the rotation of the blade. In addition, as a device for thinning and evaporating the concentrated liquid by flowing along the outer surface of the structure installed in a reduced pressure environment, the concentrated liquid is applied to the outer surface of the structure such as a tube group or a plate group from above. Pouring and promoting evaporation by forming a liquid film along the outer surface shape (horizontal tube descending film evaporator [FIG. 2 (b)] or vertical long tube descending film evaporator [FIG. 2 (c)] ]). About structures, such as a tube group and a board group, when it has a heat source in the inside, a liquid film can be heated. This method has an advantage that a thin film can be formed by natural flow of a liquid film due to gravity without using power.

  Furthermore, as a device with both the characteristics of a centrifugal thin film evaporator and a falling film evaporator, the liquid to be concentrated is poured from above along the inner surface of the structure, and the rotor with blades installed inside the structure is rotated. There is a stirring film type evaporator (FIG. 2D) that scrapes a liquid film having a predetermined thickness or more with a blade and promotes evaporation by heating from the outer surface of the structure. This method has an advantage that the liquid film thickness can be controlled by the gap width between the blade and the casing while the thin film is formed by the flow of the liquid film accompanying gravity without using power. Any of these apparatuses can be applied to the continuous depolymerization apparatus for molten oligomers in the present invention. Among these, in the case of an apparatus that forms a flow liquid film along the outer surface of the structure by gravity, it is necessary to add and disperse the catalyst in advance because the catalyst cannot be added and dispersed in the middle of the flow. Further, it is desirable to continuously discharge the flow reaching the lower end of the apparatus so as not to stay in the apparatus. The reason is that the flow reaching the lower end of the apparatus contains a high concentration of catalyst, and its remaining may increase optical isomerization.

  On the other hand, in the horizontal centrifugal thin film evaporator [FIG. 2 (a)], the catalyst can be retained in the apparatus, and the catalyst can be dispersed in the molten oligomer by the operation of the rotor and blades. Therefore, even if the molten oligomer is continuously supplied from one end of the apparatus, if the amount corresponds to the discharge amount of the cyclic dimer vapor, the retention amount can be kept constant, so it is not always necessary to continuously discharge from the other end. . When the retention amount increases due to the decrease in the efficiency of the depolymerization reaction due to the decrease in the catalyst activity or the accumulation of residues after depolymerization of the molten oligomer, the liquid in the apparatus is intermittently discharged and a new catalyst is added to the apparatus. Then you can resume driving.

  An embodiment of the present invention is shown schematically in FIG. In FIG. 1, glycolic acid supply device 1, glycolic acid concentrating device 2, reflux device 3, decompression device 4, glycolic acid condensation device 5, reflux device 6, cooler 7, decompression device 8, oligomer depolymerization device 9, reflux device. 10, a glycolide cooler 11, a purification device 12, an impurity cooler 13, and a decompression device 14. When the concentrated glycolic acid is continuously supplied to the glycolic acid condensing apparatus 5 which is a centrifugal thin film evaporator, a liquid film is formed on the inner surface of the casing by centrifugal force. Thereby, a glycolic acid oligomer is produced by a condensation reaction. Glycolide can be produced efficiently.

  Glycolic acid is supplied from the glycolic acid supply device 1 and water is removed in the glycolic acid concentrating device 2 to become concentrated glycolic acid. The concentrated glycolic acid is supplied to the glycolic acid condensing apparatus 5 and becomes an oligomer (glycolic acid condensate) by the condensation reaction. The oligomer is sent to a depolymerization apparatus and becomes glycolide by a depolymerization reaction.

  By thinning the concentrated glycolic acid, the contact area between the concentrated glycolic acid and the gas phase is increased, and the condensation reaction of glycolic acid can be accelerated by accelerating the evaporation of water produced by the condensation reaction. Examples of the external force for thinning the concentrated glycolic acid include gravity or centrifugal force. Examples of the apparatus for thinning the concentrated glycolic acid include a falling film evaporator, a centrifugal thin film evaporator, a stirring film evaporator, and the like.

  In the present invention, the falling film evaporator is a device that promotes thinning and evaporation by allowing concentrated glycolic acid to flow along the outer surface of a structure installed in a reduced pressure environment. About structures, such as a tube group and a board group, when it has a heat source in the inside, a liquid film can be heated. This method has an advantage that a liquid film can be formed by the flow of the liquid film due to gravity without using power.

  In the present invention, the centrifugal thin film evaporator is a device in which concentrated glycolic acid supplied in the apparatus is applied to the inside of the apparatus casing by centrifugal force to form a liquid film, and evaporation is promoted by heating from the outer surface of the apparatus casing. Centrifugal force is applied to the concentrated glycolic acid through the rotating blades by installing the rotor with the blades in a fixed device casing. This method has the advantages that the equipment scale can be reduced, and the liquid film thickness can be controlled by controlling the gap width between the blade and the casing and the rotation of the blade.

  In the present invention, the agitated membrane evaporator is a device having both the characteristics of a falling membrane evaporator and a centrifugal thin film evaporator. The concentrated glycolic acid is poured from above along the inner surface of the structure, and installed on the inner surface of the structure. By rotating the bladed rotor, a liquid film having a predetermined thickness or more is scraped off by the blade, and evaporation is promoted by heating from the outer surface of the structure. This method has the advantage that the liquid film thickness can be controlled by the gap width between the blade and the casing while forming a thin film by the flow of the liquid film accompanying gravity without using power.

  The centrifugal thin film evaporator has the following advantages. First, since it has a large evaporation capacity, it is suitable for processing high-viscosity substances. This is because the liquid is made into a uniform thin film by the rotating blades and is vigorously stirred, so that a high heat transfer coefficient can be obtained even with a high viscosity substance. Next, since the residence time is short, it is suitable for the treatment of thermally unstable substances. This is because the liquid is processed with a thin film and concentrated to a predetermined concentration in a very short time, which is suitable for the treatment of a thermally unstable substance. And since vacuum evaporation is suitable, it is suitable for the process of a thermally unstable substance and a high boiling point substance. This is because when the liquid is processed with a thin film, the boiling point is not increased by the liquid head, and the liquid can be evaporated at the boiling point in the degree of vacuum in the system. In addition, it is suitable for processing high-viscosity substances and slurry liquids because it can be continuously operated without being scaled. This is because the liquid is agitated by the rotor blades and the heat transfer surface is constantly updated with a new liquid.

  Since the centrifugal thin film evaporator is used as the concentrated glycolic acid condensation tank in the present invention, the temperature of the concentrated glycolic acid tends to rise in a short time, and the condensation reaction can be completed in a few seconds to a few minutes. Therefore, compared to the prior art described in Patent Document 1, the concentrated glycolic acid is thermally decomposed to produce less impurities and to obtain a highly pure oligomer, and further to obtain glycolide in a high yield. be able to. Since impurities that must be removed in the purification step are reduced, polyglycolic acid can be obtained efficiently. Unlike the prior art described in Patent Document 2, the condensation reaction, depolymerization reaction and ring-opening polymerization reaction are carried out in different reaction vessels, so that glycolide can be purified after the depolymerization reaction. Therefore, high purity glycolide can be used during the ring-opening polymerization reaction, and the production efficiency of polyglycolic acid can be improved. In addition, this invention is applicable also to hydroxycarboxylic acids other than glycolic acids, such as lactic acid, in the concentration process before condensation.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. The apparatus for synthesizing glycolide is arranged in the order of glycoglycolic acid supply apparatus 1, glycolic acid concentrating apparatus 2, glycolic acid condensing apparatus 5, depolymerization apparatus 6, glycolide cooler 11, and purification apparatus 12 from the upstream side of the reaction path. Made up.

  The glycolide production apparatus of the present invention is obtained by evaporating water contained in glycolic acid in a glycolic acid concentrating apparatus to form concentrated glycolic acid, and condensing the concentrated glycolic acid in a glycolic acid condensing apparatus to produce a glycolic acid oligomer. Glycolide is produced by depolymerizing the glycolic acid oligomer in a depolymerizer under reduced pressure. Free water contained in glycolic acid is preferably removed by heating and evaporating as much as possible.

  In the present invention, a glycolic acid oligomer is produced by heating glycolic acid under reduced pressure in a glycolic acid condensing apparatus. In the present invention, the glycolic acid oligomer includes a glycolic acid polymer having a molecular weight of about 50,000 to a dimer of glycolic acid. Although it is a concept, the molecular weight of the glycolic acid oligomer obtained by the glycolic acid condensation reaction is usually 1,000 to 10,000, preferably 3,000 to 5,000, in terms of average molecular weight.

  The glycolic acid condensation reaction is usually at a pressure of 100 Torr or less, desirably 10 Torr or less, more preferably 1 Torr or less, usually 160 to 220 ° C., preferably 170 to 200 ° C., usually 1 second to 5 minutes using a centrifugal thin film evaporator. It is preferably carried out in 1 second to 1 minute. By shortening the heating time as much as possible, thermal decomposition of glycolic acid and glycolic acid oligomer can be suppressed.

  Regarding the glycolic acid condensation reaction, a catalyst for the glycolic acid condensation reaction may be added as necessary. As the catalyst, a conventionally known catalyst can be used. For example, an organic tin-based catalyst (for example, tin lactate, tin tartrate, tin dicaprylate, tin dilaurate, tin dipalmitate, tin distearate, tin dioleate) , Α-tin naphthoate, β-naphthoate tin, tin octylate, etc.) and powdered tin.

  The glycolic acid condensation apparatus has at least a reactor, a concentrated glycolic acid supply port, and a glycolic acid oligomer discharge port. The reactor may be a vertical type or a horizontal type, but a centrifugal thin film evaporator is used.

  A centrifugal thin film evaporator is a device that applies centrifugal force by rotating blades in a fixed device casing, and the blades are usually plate-shaped parallel to the rotation axis and may be installed radially from the rotation axis. In many cases, the above blades are twisted to form a screw. Centrifugal thin film evaporators may have a rotation axis that is horizontal, vertical, or an intermediate angle.

  As a heating method in the reactor, a method generally used in this technical field can be used. For example, a heating medium jacket is installed on the outer periphery of the reactor, and the reaction liquid is heated by heat transfer through the reactor wall surface. There is a method, or a method of heating by heat transfer through a heating medium inside the rotating shaft of the stirring blade, and these may be used alone or in combination.

  The depolymerization apparatus is equipped with a depressurization apparatus, and the depolymerization reaction of glycolic acid oligomer is usually performed at 120 to 250 ° C., preferably 120 to 200 ° C. in a reduced pressure environment of 100 Torr or less, preferably 10 Torr or less. To implement. Glycolide is generated as a gas by the depolymerization reaction. In the present invention, glycolide refers to a cyclic ester produced by dehydrating two water molecules from two glycolic acid molecules.

  The depolymerization apparatus has at least a reactor, a glycolic acid oligomer supply port, and a glycolide discharge port. A normal thermometer is also installed. The reactor and system are not particularly limited, and a vertical reactor, a horizontal reactor, or a tank reactor can be used. As the stirring blade, a paddle blade, a turbine blade, an anchor blade, a double motion blade, a helical ribbon blade, or the like can be used.

  As a heating method in the reactor, a method generally used in this technical field can be used. For example, a heating medium jacket is installed on the outer periphery of the reactor, and the reaction liquid is heated by heat transfer through the reactor wall surface. There is a method, or a method of heating by heat transfer through a heating medium inside the rotating shaft of the stirring blade, and these may be used alone or in combination.

  In the depolymerization reaction, a catalyst for the depolymerization reaction may be added as necessary. A conventionally known catalyst can be used as the catalyst, for example, a catalyst made of a metal or a metal compound selected from the group consisting of Group IA, Group IIIA, Group IVA, Group IIB and Group VA of the periodic table is used. it can.

  Examples of those belonging to Group IA include alkali metal hydroxides (for example, sodium hydroxide, potassium hydroxide, lithium hydroxide), alkali metal and weak acid salts (for example, sodium lactate, sodium acetate, sodium carbonate). Sodium octylate, sodium stearate, potassium lactate, potassium acetate, potassium carbonate, potassium octylate, etc.), alkali metal alkoxides (eg sodium methoxide, potassium methoxide, sodium ethoxide, potassium ethoxide, etc.) Can be mentioned.

  Examples of those belonging to Group IIIA include aluminum ethoxide, aluminum isopropoxide, alumina, and aluminum chloride.

  Examples of those belonging to the group IVA include organotin-based catalysts (eg, tin lactate, tin tartrate, tin dicaprylate, tin distearate, tin dioleate, α-naphthoic acid tin, β-naphthoic acid tin, octylic acid). In addition to tin, etc., powder tin, tin oxide, tin halide and the like can be mentioned.

  Examples of those belonging to Group IIB include zinc powder, zinc halide, zinc oxide, and organic zinc compounds.

  Examples of those belonging to Group IVB include titanium compounds such as tetrapropyl titanate and zirconium compounds such as zirconium isopropoxide.

  Among these, it is preferable to use a tin compound such as tin octylate or an antimony compound such as antimony trioxide.

  The amount of the catalyst used is 0.01 to 20% by weight, preferably 0.05 to 15% by weight, more preferably about 0.1 to 10% by weight, based on the glycolic acid oligomer.

  Vapor containing glycolide generated in the depolymerization apparatus is discharged out of the depolymerization apparatus and supplied to the glycolide cooler. Here, glycolide is cooled, condensed and recovered, and then transferred to a purification apparatus.

  As for the glycolide cooler, a surface condenser in which the vapor and the refrigerant are in contact with each other through a metal tube is desirable. This is because glycolide decomposes to produce an acid when it comes into direct contact with a refrigerant containing water. This hinders the progress of the ring-opening polymerization reaction as an acid catalyst and may cause corrosion of a material such as a cooler. When the refrigerant is inert to glycolide, it is not limited to the above. In that case, it is necessary to sufficiently dry the refrigerant to reduce moisture.

  The present invention will be described in detail below with reference to examples, but the scope of the present invention is not limited thereto.

[Example 1]
The glycolic acid concentrator 2 evaporates and removes water contained in glycolic acid by heating. Heating is performed at 120 to 150 ° C. under a flow of an inert gas such as nitrogen gas.

  In the glycolic acid concentration reaction, water and glycolic acid are generated as gas. These gases enter the reflux device 3, glycolic acid is removed from the gas, and is refluxed to the lactic acid concentrator 2.

  The concentrated glycolic acid produced by the glycolic acid concentrating device 2 is sent to the glycolic acid condensing device 5.

  The glycolic acid condensing device 5 advances the condensation reaction of glycolic acid and evaporates the water generated therewith. The reaction is performed at a temperature of 120 to 250 ° C. under reduced pressure to 10 torr or less. In the glycolic acid condensation reaction, water, glycolic acid, a low molecular weight glycolic acid oligomer and glycolide generated by the decomposition thereof are generated as a gas. These move from the glycolic acid condensing device 5 toward the decompression device 8. These gases enter the reflux device 6, and glycolic acid, low-molecular glycolic acid oligomers, and glycolide are removed from the gas and are refluxed to the glycolic acid condensing apparatus 5. The glycolic acid oligomer produced by the glycolic acid condensation apparatus 5 is sent to the oligomer depolymerization apparatus 9.

  In the oligomer depolymerization apparatus 9, the depolymerization reaction of the glycolic acid oligomer proceeds. The reaction is carried out by reducing the pressure to 10 torr or less and bringing the glycolic acid oligomer into contact with a depolymerization catalyst such as antimony trioxide or tin octylate at a temperature of 120 to 250 ° C. The gaseous glycolide generated by this reaction is cooled and condensed in the glycolide cooler 11 and then sent to the purifier 12. The vapor that has not been condensed in the glycolide cooler 11 enters the impurity cooler 13 where it is condensed and liquefied. The liquefied impurities are usually discarded. The gas that has not been condensed in the impurity cooler 13 is discharged out of the system through the decompression device 14.

[Example 2]
When glycolic acid was condensed according to the above example, a glycolic acid oligomer having a weight average molecular weight of 10,000 was synthesized. When this glycolic acid oligomer was depolymerized and ring-opening polymerization was performed using the resulting glycolide, polyglycolic acid having a weight average molecular weight of 200,000 was obtained. In the ring-opening polymerization, since the hydroxylcarboxylic acid dimer is ring-opened and polymerized, the molecular weight of the polyhydroxycarboxylic acid can be easily controlled by factors of temperature, pressure, and time. On the other hand, since polycondensation directly polymerizes low molecular weight polyhydroxycarboxylic acids (oligomers) having various molecular weights to generate polyhydroxycarboxylic acids, the molecular weight is not easily controlled and the molecular weight distribution tends to be widened.

(Comparative example)
When glycolic acid was condensed in a condensation tank using a conventional tank type stirrer at a pressure of 100 Torr and a temperature of 200 ° C., a glycolic acid oligomer having a weight average molecular weight of 1800 was synthesized. When ring-opening polymerization was performed using glycolide obtained by depolymerizing the glycolic acid oligomer, polyglycolic acid having a weight average molecular weight of 100,000 was obtained.

It is the schematic which shows one Embodiment of the apparatus regarding the glycolide synthesis | combination of this invention. It is sectional drawing which shows the structure of the evaporator of the continuous open polymerization apparatus in embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Glycolic acid supply apparatus, 2 ... Glycolic acid concentration apparatus, 3 ... Refluxer, 4 ... Depressurization apparatus, 5 ... Glycolic acid condensation apparatus, 6 ... Refluxer, 7 ... Cooler, 8 ... Decompression apparatus, 9 ... Oligomer solution Polymerization apparatus, 10 ... refluxer, 11 ... glycolide cooler, 12 ... purification apparatus, 13 ... impurity cooler, 14 ... depressurization apparatus.

Claims (4)

After depolymerizing the condensate of hydroxycarboxylic acid into a cyclic dimer, this is subjected to ring-opening polymerization to synthesize polyhydroxycarboxylic acid. In the method for synthesizing polyhydroxycarboxylic acid, which is condensed and then depolymerized to obtain a cyclic dimer,
The condensation reaction is performed by controlling the liquid film thickness by controlling the gap width between the rotor blade and the stationary casing and the rotation of the rotor blade by a centrifugal thin film evaporator having a rotor blade in a horizontal fixed casing. A method for synthesizing a polyhydroxycarboxylic acid. Synthesizer of polyhydroxycarboxylic acids according to claim 1, wherein the depolymerization and performing by the centrifugal thin film evaporator. Hydroxycarboxylic acid supply apparatus, condensation apparatus having an evaporator for thinning a melt containing a condensate of hydroxycarboxylic acid using external force, a condensation apparatus for thinning and condensing hydroxycarboxylic acid, and depolymerizing the condensate In a polyhydroxycarboxylic acid synthesis apparatus in which a depolymerization apparatus and a ring-opening polymerization apparatus are sequentially arranged,
The evaporator is a centrifugal thin film evaporator having a rotary blade in a horizontal fixed casing, and the liquid film thickness is controlled by controlling the gap width between the rotary blade and the fixed casing and the rotation of the rotary blade. An apparatus for synthesizing polyhydroxycarboxylic acid. The depolymerization device synthesizer of polyhydroxycarboxylic acids according to claim 3, characterized in that it comprises the centrifugal thin film evaporator.

Images