JP2008169282A - System and method for synthesizing polymer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a system and a method for synthesizing a polymer, intended for preventing the polymer from discoloration stemming from its thermal decomposition to improve the quality of the polymer. <P>SOLUTION: The system for synthesizing a polymer by polymerizing a to-be-polymerized material in a molten state is provided, comprising a horizontal-type reaction vessel 17 working in such a way that the to-be-polymerized material charged via a feed port on one side is agitated and conveyed in a molten state and discharged via the other discharge port, a mechanism working in such a way that the reaction vessel 17 is charged with the to-be-polymerized material in a molten state via an opening provided in between the feed port and the discharge port, a mechanism for detecting the temperature of the molten to-be-polymerized material in between the feed port and the discharge port in the reaction vessel 17, and a mechanism for controlling the amount of the to-be-polymerized material to be charged by the relevant mechanism based on the temperature detected by the relevant mechanism. As such, temperature rise of the molten to-be-polymerized material can be suppressed by adding the to-be-polymerized material lower in temperature than the molten to-be-polymerized material in the reaction vessel 17, thereby discoloration accompanying thermal decomposition of the molten to-be-polymerized material can be prevented. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a polymer synthesizing apparatus and a polymer synthesizing method for synthesizing a polymer by polymerizing a polymer in a molten state.

  Polylactic acid, which is one of the polymers synthesized by ring-opening polymerization reaction, is a colorless and transparent polyester made from lactic acid, which is one of hydroxycarboxylic acids. One method of synthesizing polylactic acid from lactic acid is to condense lactic acid to form an oligomer, and then add a catalyst such as antimony oxide to depolymerize it to form lactide, which is a cyclic condensate (a dimer of lactic acid). And a ring-opening polymerization method by adding a catalyst such as tin octylate to the lactide.

  By the way, in the ring-opening polymerization, a part of polylactic acid may be thermally decomposed and colored due to a temperature rise accompanying reaction heat. When coloring occurs in this way, colorless transparency, which is one of the characteristics of polylactic acid, is impaired and the quality is deteriorated. Therefore, it is desired to suppress this. The same applies to polyglycolic acid synthesized by ring-opening polymerization of glycolide, which is a cyclic dimer of glycolic acid.

  In contrast, a plurality of reaction vessels for ring-opening polymerization of lactide are prepared, and these are connected in series to adopt a continuous method in which the raw material is supplied and the polymer is discharged at the same time. In addition, a method for reducing thermal decomposition due to a prolonged temperature history by operating while changing the catalyst amount and residence time has been disclosed (see Patent Document 1).

JP-A-8-259676

  However, according to Patent Document 1, for example, a polymer having a low polymerization degree and a viscosity and a polymer having a high polymerization degree and a high viscosity are mixed in the same reaction tank. Sufficient studies have not been made on factors that increase coloration, such as longer time and acceleration of thermal decomposition accompanying accumulation of reaction heat due to ring-opening polymerization.

  This invention makes it a subject to suppress the coloring by the thermal decomposition of a polymer and to improve quality.

  The inventors of the present invention have added a polymer having a temperature lower than the temperature of the melt, for example, a raw material in a molten state, and mixed with the melt in which the heat of reaction is stored and the temperature is increased by polymerization. The inventors have found that the temperature rise of the melt is suppressed and the quality of the polymer is stabilized, and the present invention has been completed.

  Specifically, the polymer synthesizer of the present invention synthesizes a polymer by polymerizing a polymer in a molten state, and the polymer introduced from one supply port is stirred and transferred in a molten state. Then, a horizontal reaction vessel discharged from the other discharge port, an opening formed between the supply port and the discharge port of the reaction vessel, and a polymer to be melted from the opening are added into the reaction vessel. An addition means, a temperature detection means for detecting the temperature of the melt between the supply port and the discharge port in the reaction vessel, and based on the detected temperature of the temperature detection means, the polymer to be added by the addition means The said subject can be solved by providing the control means which controls addition amount.

  According to this configuration, when the temperature of the melt moving in the reaction vessel rises, the molten polymer is added into the reaction vessel through the opening. The polymer to be added here is a polymer to be supplied from the supply port of the reaction vessel, that is, a raw material, and thus is maintained at a temperature lower than that of the melt. For this reason, the polymer added to the reaction vessel absorbs the heat of the melt by being mixed with the melt and lowers the temperature, so that coloring of the polymer accompanying thermal decomposition can be suppressed. . On the other hand, since the polymer to be polymerized supplied into the reaction vessel can obtain heat necessary for the polymerization reaction from the melt, it can have high reactivity as a raw material for the polymerization reaction.

  Further, in place of the above, the present invention comprises a plurality of horizontal reaction vessels connected in series by stirring and transferring a polymer introduced from one supply port in a molten state and discharging it from the other discharge port. The reaction apparatus is formed, and at least one of the reaction containers includes an opening formed between the supply port and the discharge port of the reaction container, and the molten polymer is introduced into the reaction container from the opening. Addition means to be added, temperature detection means for detecting the temperature of the melt between the supply port and the discharge port, and the addition amount of the polymer added by the addition means based on the detected temperature of this temperature detection means The above-mentioned problem can be solved by providing control means for controlling the above.

  When a plurality of reaction vessels are connected in series in this way, the temperature of the melt tends to increase as the reaction vessel on the rear stage side increases. For this reason, for example, the polymer may be added to a predetermined reaction vessel excluding the first stage. The polymer to be added here may be, for example, a raw material such as a monomer to be supplied to the first-stage reaction vessel as long as it is lower than the temperature of the melt to be added. It may be a polymer having a predetermined degree of polymerization discharged from the container.

  In this case, for example, the control unit may control the addition amount so that the detected temperature does not exceed the set temperature. Here, the set temperature can be predetermined for each polymer in consideration of, for example, the temperature at which the melt is thermally decomposed.

  Further, the reaction vessel is formed in a horizontal cylindrical shape, and includes a stirrer having a plurality of stirring blades attached to a rotation shaft provided extending in the vessel at intervals, and the opening is formed on the rotation shaft. It is located between the stirring blades in the axial direction and is formed above the liquid level of the melt. By forming the opening at such a position, the polymer can be prevented from coming into contact with the melt in the reaction vessel at and near the opening, and solidification by rapid cooling of the melt by the polymer. Can be suppressed, and blockage of the opening can be prevented.

  Further, the liquid level detection means for detecting the liquid level of the melt is provided, and the liquid level control means for controlling the liquid level of the reaction vessel is provided so as to keep the distance between the liquid level and the opening within a set range. preferable. Here, as the liquid level control means, for example, there is a method of controlling the supply amount from the supply port of the reaction vessel, the discharge amount from the discharge port, and the like.

  In the polymer synthesis method of the present invention, the polymer to be supplied supplied from one side of the horizontal reaction vessel is stirred and transferred in a molten state, and the polymer is taken out from the other side, and polymerized in the reaction vessel. The above-mentioned problem can be solved by detecting the temperature of the melt and adding a polymer to be melted to the melt so that the temperature does not exceed the set temperature.

  According to the present invention, it is possible to improve the quality by suppressing coloring due to thermal decomposition of the polymer.

  The polymer synthesizing method and the synthesizing apparatus to which the present invention is applied are suitably used for a polymerization reaction of a polymer that generates reaction heat along with the polymerization reaction.

  Such polymers include polymers produced by ring-opening polymerization reactions or addition polymerization reactions, and examples of polymers produced by ring-opening polymerization reactions include polyesters synthesized by dimer ring-opening polymerization reactions. . Moreover, it is suitably used for the synthesis of polylactic acid, a copolymer containing lactic acid as a main component, polyglycolic acid, a copolymer containing glycolic acid as a main component, and the like.

  Here, lactide used as a raw material for polylactic acid means a cyclic ester produced by dehydrating two molecules of water from two molecules of lactic acid, and polylactic acid means a polymer mainly composed of lactic acid, Poly L-lactic acid homopolymer, poly D-lactic acid homopolymer, poly L / D-lactic acid copolymer, and other ester bond-forming components such as hydroxy carboxylic acid, lactones, dicarboxylic acid and diol, etc. Copolymerized polylactic acid obtained by copolymerizing the above and those mixed with additives as secondary components.

  In addition, glycolide used as a raw material for polyglycolic acid means a cyclic ester formed by dehydrating two molecules of water from two molecules of glycolic acid, and polyglycolic acid is a polymer mainly composed of glycolic acid. Meaning other ester bond-forming components such as hydroxycarboxylic acids, lactones, copolymerized polyglycolic acid obtained by copolymerizing dicarboxylic acid and diol, and those mixed with additives as secondary components .

  Examples of hydroxycarboxylic acids other than lactic acid and glycolic acid include hydroxybutylcarboxylic acid and hydroxybenzoic acid, examples of lactones include butyrolactone and caprolactone, and examples of dicarboxylic acids include aliphatic dicarboxylic acids having 4 to 20 carbon atoms. Examples of aromatic dicarboxylic acids and diols such as acid, phthalic acid, isophthalic acid, terephthalic acid and naphthalenedicarboxylic acid include aliphatic diols having 2 to 20 carbon atoms.

  In addition, oligomers and polymers of polyalkylene ethers such as polyethylene glycol, polypropylene glycol, and polybutylene ether are also used as copolymerization components. Similarly, oligomers and polymers of polyalkylene carbonate are also used as copolymerization components.

  Examples of additives include antioxidants, stabilizers, ultraviolet absorbers, pigments, colorants, inorganic particles, various fillers, mold release agents, plasticizers, and the like. The addition ratio of these copolymerization components and additives is arbitrary, but the main component is lactic acid or derived from lactic acid, and the copolymerization components and additives are preferably 50% by weight or less, particularly preferably 30% or less.

  The polymer synthesizing method and apparatus of the present embodiment polymerize a polymer by heating and stirring in a molten state, and synthesize the polymer continuously or intermittently. The reaction apparatus for polymerizing the material to be polymerized is formed, for example, by connecting two or more reaction tanks in series, and the molten raw material supplied to the first-stage reaction vessel is polymerized in the vessel and subjected to predetermined polymerization. In addition, this polymer is supplied as a polymer to be polymerized to the second stage reaction vessel to increase the degree of polymerization. Then, a polymer having a desired degree of polymerization is synthesized before being discharged from the final reaction vessel. Here, the raw material means a monomer, a cyclic monomer, a cyclic condensate of the monomer, an oligomer, and the like, which are constituent elements for synthesizing a polymer by a polymerization reaction, and the raw material in a molten state is referred to as a molten raw material.

  In the synthesis of polylactic acid, lactide is used as a raw material, a reaction liquid containing raw material lactide in a molten state and a catalyst is supplied to a reactor, heated and stirred, and lactide is subjected to a ring-opening polymerization reaction. Is polymerized in a molten state to synthesize polylactic acid continuously or intermittently. In addition, in the synthesis of polyglycolic acid, glycolide is used as a raw material, a reaction solution containing raw material glycolide and a catalyst in a molten state is supplied to a reactor, heated and stirred, and a ring-opening polymerization reaction of glycolide is performed. Thus, glycolide is polymerized in a molten state to synthesize polyglycolic acid continuously or intermittently. Here, the reaction liquid includes a polymer in a molten state. For example, a polymer such as a molten raw material, a mixture of a molten raw material and a catalyst, a mixture of a molten raw material, a catalyst, and a polymer having a predetermined polymerization degree is used. All melts and products distributed in the synthesis process should be wrapped.

  In the present embodiment, continuously or intermittently synthesized has the meaning normally used in the art, and when the time zone for supplying the raw material and discharging the polymer as a product overlaps at least partially, This includes the case where the raw material is supplied continuously or intermittently and the polymer is discharged continuously or intermittently.

  When the raw material is in a molten state, a catalyst can be added to the molten raw material and supplied to the reaction apparatus to be subjected to a polymerization reaction. However, if the raw material is in a solid form such as powder, the raw material melting apparatus, etc. The raw material is heated and melted in advance. The heating temperature at this time will not be restrict | limited especially if it is more than melting | fusing point of a raw material. For example, when the raw material is lactide, it is not particularly limited as long as it is 95 ° C. or higher, but is usually 95 to 160 ° C., preferably 110 to 130 ° C. By setting the temperature to 160 ° C. or less, deterioration of lactide due to heat can be prevented. Moreover, when a raw material is glycolide, if it is 83 degreeC or more, it will not specifically limit, Usually, 83-160 degreeC, Preferably it is 90-130 degreeC. By setting the temperature to 160 ° C. or less, deterioration of glycolide due to heat can be prevented.

  As a catalyst for the polymerization reaction, those skilled in the art can appropriately select a suitable catalyst depending on the polymer to be synthesized. For example, as a catalyst used for ring-opening polymerization of lactide and glycolide, conventionally known polylactic acid and polyglycolic acid polymerization catalysts can be used. For example, periodic groups IA, IVA, IVB and VA A catalyst containing at least one metal or metal compound selected from the group consisting of can be used.

  Examples of those belonging to the group IVA include organotin catalysts (for example, tin lactate, tin tartrate, tin dicaprylate, tin dilaurate, tin dipalmitate, tin distearate, tin dioleate, tin α-naphthoate). , Β-naphthoic acid tin, octylic acid tin, etc.) and powdered tin. 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 give. Examples of those belonging to Group IVB include titanium compounds such as tetrapropyl titanate and zirconium compounds such as zirconium isopropoxide. Examples of those belonging to Group VA include antimony compounds such as antimony trioxide. Among these, an organotin catalyst or a tin compound is particularly preferable from the viewpoint of activity.

  The catalyst can be added to the molten raw material by a catalyst addition apparatus usually used in the art. The catalyst may be added to the molten raw material and then supplied to the reactor, or the catalyst may be added directly to the reactor.

  In this embodiment, the polymer reaction apparatus is composed of three reaction vessels connected in series, and performs a polymerization reaction by heating a reaction solution containing a molten raw material and a catalyst in the reaction vessel. is there. Here, the present invention can be applied even if the number of reaction vessels is less than 3, but preferably 3 to 5, more preferably 3 to 4.

  Hereinafter, it demonstrates concretely using the polymer synthesizer of this embodiment.

  In the present embodiment, the reactor for carrying out the polymerization reaction is configured by connecting three reaction vessels in series. Note that a tank in which a polymerization reaction is not substantially performed may be connected to the reaction apparatus, for example, before the first stage.

  In each reaction tank, a supply port is formed on one side and a discharge port is formed on the other side. The stirrer is formed by attaching a plurality of stirring blades at intervals to a rotation shaft provided to extend in the tank. Is provided. The discharge port of the first-stage reaction tank, the supply port of the second-stage reaction tank, the discharge port of the second-stage reaction tank, and the supply port of the third-stage reaction tank are connected by piping via pumps, respectively. ing.

  The first stage reaction tank is provided with an agitator installed so that the rotation axis is substantially horizontal with respect to the ground, and at least one weir in the tank. The term “substantially horizontal to the ground” does not mean that the rotation axis of the stirrer is strictly horizontal, and the angle between the ground, that is, the horizon and the rotation axis, is usually −5 ° to 5 °. °, preferably -1 ° to 1 °, more preferably 0 °. Hereinafter, a reaction tank having a stirrer installed so that the rotation shaft is substantially horizontal with respect to the ground is referred to as a horizontal reaction tank.

  The shape of the horizontal reaction vessel is not particularly limited as long as the stirrer can be installed so that the rotation axis thereof is substantially horizontal with respect to the ground. And a cylindrical shape having a substantially horizontal central axis. This horizontal reaction tank has a supply port for supplying a molten raw material at one end in the rotation axis direction of the stirrer and a discharge port at the other end. Accordingly, the supplied reaction solution moves substantially horizontally from the supply port to the discharge port. The supply port is preferably positioned below the axis of the stirring device, and the discharge port is preferably positioned below the rotation axis of the stirring device.

  The stirrer installed in the horizontal reaction tank is not particularly limited as long as the stirring is performed by rotation around a rotating shaft arranged substantially in the horizontal direction with respect to the ground. For example, a mixer having two or more shafts in which two or more agitating blades such as a circle, an oval, a triangle, a quadrangle, and a multi-leaf are installed on a rotating shaft with a space therebetween, or two or more shafts that mesh with each other. . Two or more agitators that mesh with each other are preferable from the viewpoint of a self-cleaning action because they can prevent the reaction liquid from adhering to the rotating shaft and the reaction tank. When a biaxial stirrer having a plurality of stirring blades is used, it is preferable that the stirring blades of the respective rotating shafts are installed alternately, and it is preferable to rotate the respective rotating shafts in the opposite directions. The rotation axis does not necessarily mean an actual rotation shaft member, but includes a rotation axis as a simple rotation center. Therefore, if the rotational center of the rotational motion of the stirrer is arranged substantially horizontally with respect to the ground, the actual rotating shaft member does not necessarily have to exist.

  As a heating method in the horizontal reaction tank, a method generally used in this technical field can be used. In this embodiment, a heat medium jacket is installed on the outer periphery of the reaction tank, and the reaction is performed by heat transfer through the reaction tank wall. Although the method of heating a liquid is used, for example, there is a method of heating by heat transfer through a rotating medium inside a rotating shaft of a stirrer, and these may be used alone or in combination. The reaction vessel is preferably heated at a substantially constant temperature.

  The molten raw material supplied into the horizontal reaction tank is initially heated and polymerized by the heat medium jacket. However, when the temperature of the reaction liquid becomes higher than that of the heat medium due to the temperature rise caused by the reaction heat, conversely, from the reaction liquid to the heat medium. Therefore, this method can also act as a cooling method. Therefore, in the case of a polymer in which reaction heat is generated by the polymerization reaction, heat can be effectively released, which is advantageous.

  Further, if necessary, a heating method in which the inside of the reaction vessel is divided into a plurality of regions and the heat medium temperature can be changed for each of the divided regions may be used. Therefore, it is conceivable to use a plurality of heat medium jackets. The inside of the reaction vessel can be divided based on the area between the weirs, for example. Thereby, for example, the heat medium temperature is set high in the region where the low temperature reaction liquid is heated, and the heat medium temperature is set low in the region where the reaction liquid temperature is high due to the reaction heat and heat removal is necessary. It becomes possible. A temperature gradient can also be set inside the reaction tank by supplying the heating medium heated by the heating medium heating device to the vicinity of the supply port. When the temperature of the heating medium is lowered, a part of the melt may be solidified and adhere to the inner surface of the reaction tank. In this case, the adhering substance can be peeled off by a stirrer installed in the reaction tank.

  The horizontal reaction tank has a weir in the tank. This weir acts to inhibit the reaction liquid from flowing rapidly from the supply port toward the discharge port. The shape of the weir may be a shape that can inhibit the flow of the reaction solution, and can be determined based on the shape of the reaction tank, and preferably has a plate shape. The method for installing the weir is not particularly limited. For example, when the weir is plate-shaped, the weir is installed at an angle close to the vertical. Further, the weir is installed on the bottom inner wall of the reaction tank so as to block the lower side, for example, the lower half or 1/3 of the cross section of the reaction tank perpendicular to the rotation axis of the stirrer. Here, the angle close to perpendicular to the ground means that the angle formed by the ground and the plate-like weir is 85 to 95 °, preferably 89 to 91 °, more preferably 90 °. As the material of the weir, it is preferable to use a material having heat insulating properties.

  From the viewpoint of improving the flowability of the polymer, the weir may be provided with a through-hole, and the through-hole is present at the boundary with the portion near the bottom of the reaction tank, preferably the bottom inner wall of the reaction tank. The number of through holes is usually 1 to 10, preferably 1 to 5. By providing such a through hole, the reaction solution can be circulated at an appropriate speed. A person skilled in the art can appropriately determine the installation position and interval of the weir based on reaction conditions and the like. For example, the installation position of the weir can be determined so as to divide the region where the viscosity distribution of the polymer is about the same. In addition, after deciding the position of the weir in the reaction tank, the resistance when the reaction liquid passes through the through hole at a predetermined flow rate penetrates so as to be smaller than the driving force due to the reaction liquid head difference before and after the weir. The hole diameter of the hole can be determined. The area between the two weirs acts in the same way as a single mixing cell, and the reaction liquid is homogenized by being stirred by a stirrer. Thereby, the low viscosity melt and the low viscosity melt having a low degree of polymerization can flow faster than the high viscosity polymer having a high degree of polymerization, and the influence of mixing of both can be suppressed. The weir may be omitted when the viscosity of the polymer can be expected to some extent and the mixing effect is small.

  By providing a head difference between the supply port and the discharge port in the horizontal reaction tank, a driving force for moving the reaction solution from the supply port to the discharge port can be applied. The reaction liquid flows through the through hole of the weir, or the reaction liquid at a position higher than the weir flows to the subsequent region due to the head difference, so that the horizontal reaction tank can flow toward the discharge port. In the horizontal reaction tank, the supply amount of the reaction liquid is not particularly limited, but is normally supplied in an amount of 10 to 70%, preferably 40 to 50% with respect to the capacity of the horizontal reaction tank. Moreover, it is preferable to supply with the quantity which does not exceed the height of a weir. It is because it can suppress effectively that unreacted lactide flows rapidly. In the horizontal reaction tank, if necessary, a device for measuring the liquid level of the reaction liquid is installed, and the measurement signal is fed back to the liquid feed pump at the reaction tank supply port or the liquid feed pump at the reaction tank discharge port, etc. The transport amount of the reaction liquid can be adjusted so that the height of the liquid level becomes a predetermined value.

  As a method for measuring the liquid level, for example, a radioactive substance is installed in the upper part of the horizontal reaction tank, and a method of measuring the amount of gamma rays generated from the reaction liquid through the reaction liquid, ultrasonic waves or electromagnetic waves are emitted from the upper part of the horizontal reaction tank. A method of measuring the reflected wave by measuring it, installing a cylindrical condenser at the top of the horizontal reaction tank, inserting it into the reaction liquid, and measuring the change in dielectric constant with the height of the reaction liquid inside the cylinder The measuring method etc. are mention | raise | lifted.

  The reaction conditions in the first horizontal reaction tank can be appropriately determined by those skilled in the art. The average reaction temperature in the reaction tank is usually 140 to 180 ° C, preferably 160 to 170 ° C, and the residence time. Is usually 5 to 15 hours, preferably 7 to 10 hours. It is preferable to set the reaction conditions so that a polymer having a weight average molecular weight of 50,000 to 200,000, preferably 70,000 to 150,000 is obtained from the outlet of the first horizontal reaction tank.

  By making the first-stage reaction tank a horizontal reaction tank, and by providing a weir in the first-stage reaction tank, a molten raw material having a low viscosity and a polymer having a low degree of polymerization and a viscosity are polymerized to some extent. Can be prevented from mixing with the polymer having advanced, and the piston flow property in the reaction vessel can be ensured. And it can prevent that a reaction liquid moves to the following process with unreacted, and can fully react in the 1st stage | paragraph reaction tank. Therefore, since the temperature history resulting from the variation in residence time is prevented from being prolonged, deterioration of the polymer due to thermal decomposition is suppressed, and a high-quality polymer can be obtained.

  The polymer polymerized in the first stage reaction tank constructed in this way is withdrawn from the discharge port as a reaction solution together with the unreacted raw material in the molten state, and supplied from the supply port to the second stage reaction tank. Is done. In the second-stage reaction tank, the polymer supplied into the tank is heated and stirred as a polymer (hereinafter referred to as a raw material polymer), and a molten polymer (hereinafter referred to as a polymerized polymer) having a predetermined degree of polymerization. , Called final polymerized product).

  The second-stage reaction tank is a horizontal reaction tank as in the first-stage reaction tank, but a two-axis stirrer is preferably used as the stirrer rather than one axis. It is preferable that two or more stirring blades are installed at a predetermined interval on the rotating shaft of the stirrer. This is because the polymer can be prevented from adhering to the rotating shaft of the stirrer and the reaction tank. From the viewpoint of the self-cleaning action, the subsequent reaction tank in which the polymerization reaction proceeds and the viscosity of the polymer is increased. Is particularly effective. As for the rotation direction of each rotating shaft, as long as a plurality of stirring blades are engaged with each other, either a rotating member rotating in the opposite direction or a rotating member rotating in the same direction may be used. From the viewpoint of performance, those that rotate in the same direction are desirable. This is because the effect of mixing the reactant and the raw material by stretching and folding increases due to the large shearing force applied to the melt between the blades. About the shape of a stirring blade, common things, such as circular, an oval, a triangle, a quadrangle, and a multileaf shape, can be used, for example, and it is not specifically limited. Further, the supply port of the reaction tank is preferably located below the axis of the stirring device, and the discharge port is preferably located below the rotation axis of the stirring device.

  In the second stage reaction tank, the molten material moving in the tank, that is, the polymer in the intermediate state between the raw material polymer and the final polymer (hereinafter referred to as prepolymer) is melted as the polymer in the molten state. The polymerization reaction is advanced while adding the raw materials and stirring and mixing. That is, by mixing the molten raw material and the prepolymer and absorbing the reaction heat accumulated in the prepolymer as the enthalpy of the molten raw material, the temperature of the prepolymer is lowered, so that thermal decomposition can be suppressed. On the other hand, the molten raw material receives heat from the prepolymer, so that the temperature required for the progress of the polymerization reaction can be obtained even if there is little external heating.

  Here, when the difference in viscosity between the molten raw material and the prepolymer is large, the mixing property by stirring may be lowered. In such a case, for example, as disclosed in JP-A-6-218260, the stirring blade installed on one rotating shaft is slightly spaced apart from the stirring blade of the other rotating shaft in the axial direction. A stirrer arranged in mesh is effective. This is because the gap between the adjacent blades is narrow, so that a large shearing force is applied to the molten raw material and the prepolymer between the blades by stirring, and the mixing property is improved. By increasing the mixing property between the molten raw material and the prepolymer, the heat mobility from the prepolymer to the molten raw material is improved, and the effect of suppressing thermal decomposition of the prepolymer can be increased.

  The addition port of the reaction vessel to which the molten raw material is added is one or more in the axial direction so as to be above the liquid level of the prepolymer and positioned between the stirring blades. By providing the addition port at such a position, it is possible to prevent the molten raw material and the prepolymer from coming into direct contact, avoid solidification of the prepolymer caused by the rapid cooling of the molten raw material, and prevent the addition port from being blocked. Can do.

  The heating method in the second-stage reaction tank, the heating method by dividing the inside of the reaction tank into a plurality of regions, and the liquid level measurement method are all handled in the same manner as in the first-stage reaction tank. In addition, a weir may be installed in the tank to prevent the reaction liquid from rapidly flowing from the supply port to the discharge port of the reaction tank as necessary. The reaction conditions in the reaction vessel can be appropriately determined by those skilled in the art, but the average reaction temperature in the reaction vessel is usually 140 to 200 ° C, preferably 160 to 180 ° C, and the residence time is usually 0.8. 5 to 15 hours, preferably 1 to 5 hours. It is preferable to set the reaction conditions so that a polymer having a weight average molecular weight of 70,000 to 300,000, preferably 100,000 to 200,000 is obtained from the outlet of the second stage reaction tank.

  By adding the molten raw material to the prepolymer in the second-stage reaction tank and advancing the polymerization reaction while stirring and mixing, deterioration of the polymer due to thermal decomposition is suppressed, and a high-quality polymer can be obtained.

  The final polymer polymerized in the second-stage reaction tank configured as described above is extracted from the discharge port as a reaction solution together with unreacted raw materials in a molten state, and supplied to the third-stage reaction tank. . In the third-stage reaction tank, the polymer supplied in the tank is heated and stirred as a raw material polymer, and the final polymer in a molten state that has been increased to a desired degree of polymerization is discharged from the discharge port. .

  As a reaction vessel for performing the polymerization reaction, a reaction vessel having a stirrer whose rotation axis is substantially perpendicular to the ground is used as the third-stage reaction vessel. The reactor included in is used. Hereinafter, a reaction tank having a stirrer installed so that its rotation axis is substantially perpendicular to the ground is referred to as a vertical reaction tank.

  In the present embodiment, the reaction apparatus has a vertical reaction tank at least in the final stage, but may further have a vertical reaction tank in a stage other than the final stage. The shape of the reaction vessel other than the final stage is not particularly limited, and those usually used in the art can be used. In this embodiment, a reaction apparatus including a vertical reaction tank is used in the final stage, but a reaction apparatus including a tank in which the polymerization reaction is not substantially performed in subsequent stages is used. Such cases are also included in the scope of the present invention.

  Substantially perpendicular to the ground does not mean that the rotation axis of the stirrer is strictly perpendicular, but the angle between the ground, i.e. the horizon and the rotation axis, is usually 85-95 °, It means preferably 89 to 91 °, more preferably 90 °. Similar to the horizontal reaction vessel, the rotating shaft does not necessarily mean an actual rotating shaft member, but also includes a rotating axis as a simple center of rotation. Therefore, if the rotational center of the rotational motion of the stirrer is disposed substantially perpendicular to the ground, the actual rotating shaft member does not necessarily have to exist.

  The shape of the vertical reaction tank is not particularly limited as long as the stirring device can be installed so that the rotation axis thereof is substantially perpendicular to the ground, and may be a tank type or a cylindrical type, but is preferably not limited. A cylindrical shape having a central axis substantially parallel to the rotation axis of the stirrer. This vertical reaction tank has a supply port for supplying the reaction liquid from the previous reaction tank at one end in the rotation axis direction of the stirrer, and a discharge port for taking out the reaction liquid at the other end. Therefore, the supplied reaction liquid moves from the supply port to the discharge port in a substantially vertical direction. The supply port is preferably present in the upper part of the reaction tank, and the discharge port is preferably present in the lower part of the reaction tank. Since the specific gravity of the polymer increases as the polymerization reaction proceeds, by providing a supply port in the upper part, it is possible to prevent a polymer having a low polymerization degree from being mixed into a polymer having a high polymerization degree.

  The stirrer installed in the vertical reaction tank is not particularly limited as long as the stirring is performed by rotation around a rotation axis that is arranged substantially perpendicular to the ground. For example, a mixer having two or more shafts in which two or more agitating blades such as a circle, an oval, a triangle, a quadrangle, and a multi-leaf are installed on a rotating shaft with a space therebetween, or two or more shafts that mesh with each other. . A two-shaft mixer having a plurality of stirring blades is preferably installed such that the stirring blades of the respective rotating shafts are staggered. Moreover, in this case, it is preferable to rotate each rotating shaft in the reverse direction. Two or more shaft stirrers that mesh with each other can prevent the polymer from adhering to the rotating shaft of the stirrer and the reaction vessel, and the viscosity of the polymer increases as the polymerization reaction proceeds from the viewpoint of self-cleaning action. The latter reaction tank is particularly advantageously used.

  As a heating method in the vertical reaction tank, a method usually used in this technical field can be used as in the case of the horizontal reaction tank. In the present embodiment, a heating medium jacket is provided on the outer periphery of the reaction tank. Install and use the method of heating the reaction liquid by heat transfer through the reaction tank wall, for example, the method of heating the reaction liquid by heat transfer through the reaction tank wall or the heat transfer through the rotating shaft of the stirrer There are various methods such as a method of heating by heating, and these may be used alone or in combination.

  The raw material polymer supplied into the vertical reaction tank is initially heated by the above heating method and the polymerization reaction proceeds. However, when the temperature of the reaction liquid becomes higher than that of the heating medium due to the temperature rise accompanying the reaction heat, The heat escapes from the reaction solution to the heat medium. Therefore, as in the case of the horizontal reaction tank, a heating method may be used in which the inside of the reaction tank is divided into a plurality of regions and the heating medium temperature can be changed for each of the divided regions as necessary. Thereby, for example, the heat medium temperature is set high in the region where the low temperature reaction liquid is heated, and the heat medium temperature is set low in the region where the reaction liquid temperature becomes high due to the reaction heat and heat removal is necessary. Is possible. If further heat removal is required, the heat removal efficiency can be further improved, for example, by providing fins (irregularities on the inner surface of the reaction tank) inside the vertical reaction tank. Moreover, the aspect which keeps a polymer warm by supplying the heat medium heated by the heating means to the discharge port vicinity, and prevents overcooling is also considered.

  Since it is preferable to perform the reaction at a high temperature in the latter stage of the polymerization reaction, degradation of the polymer accompanying the temperature rise becomes a problem, but by using a vertical reaction tank in the final stage, the temperature rise can be suppressed, It is possible to reduce the influence that the polymer is deteriorated and colored.

  In the vertical reaction tank, the supply amount of the reaction liquid is not particularly limited, but is normally supplied in an amount of 20 to 100%, preferably 60 to 100% with respect to the capacity of the vertical reaction tank. Therefore, compared with the conventional horizontal reaction tank in which the reaction liquid is introduced only about half the normal volume of the reaction tank, the area where the reaction liquid is in contact with the inner wall of the reaction tank is large and the heat transfer area can be increased.

  By removing the heat of reaction associated with the polymerization of the raw material polymer by heat transfer, the temperature rise of the reaction solution can be reduced, and the degradation caused by thermal decomposition of the produced polymer is effectively suppressed at the later stage of the polymerization reaction. And coloring can be prevented. In particular, in the ring-opening polymerization of lactide, coloring of polylactic acid can be effectively prevented. Moreover, the heat transfer area can be further increased and the heat removal efficiency can be improved by making the shape of the vertical reaction tank into a shape having irregularities on the side surfaces. In the embodiment in which the side surface is provided with irregularities, the high viscosity polymer stuck to the inner wall of the reaction vessel can be scraped off by installing the stirring blade so as to mesh with the concave portion on the side surface of the reaction vessel.

  The reaction conditions in the final vertical reaction tank can also be appropriately determined by those skilled in the art, but the average reaction temperature in the reaction tank is usually 180 to 220 ° C., preferably 190 to 210 ° C., residence time. Is usually 1 to 7 hours, preferably 3 to 5 hours. It is preferable to set the reaction conditions so that a polymer having a weight average molecular weight of usually 100,000 to 500,000, preferably 150 to 300,000 can be obtained from the outlet of the vertical reaction tank in the final stage.

  In the polymer synthesizing apparatus of the present embodiment, a remaining raw material removing device is installed at the subsequent stage of the polymerization reaction device, whereby unreacted raw material can be removed from the reaction liquid discharged from the reaction device. In this residual raw material removal apparatus, an unreacted raw material, for example, lactide is evaporated and removed by creating a negative pressure environment while maintaining the molten state of the reaction liquid. Furthermore, although the polymer obtained through the synthesis method of the present embodiment is usually subjected to water cooling and pelletizing treatment with a chip cutter, these treatments can be omitted.

  In addition, the inside of the apparatus for synthesizing the polymer according to the present embodiment, such as a raw material melting apparatus, a catalyst supply apparatus, a reaction apparatus including various reaction tanks, and a residual raw material removal apparatus, is purged with nitrogen gas. For this purpose, a nitrogen gas supply pipe and an exhaust pipe are preferably installed. And the operation of the synthesis process is basically preferably started after all the equipment in the process has been purged with nitrogen. Thereby, scorching of the reaction liquid due to the presence of oxygen can be prevented. In addition, the raw material melting apparatus, the catalyst supply apparatus, the raw material supply apparatus, various reaction vessels, and the like are preferably operated at a pressure of about atmospheric pressure. By doing so, volatilization of the molten raw material can be reduced.

  In the second-stage reaction tank, a device for measuring the liquid level of the prepolymer is installed, and the measurement signal is fed back to the liquid feed pump at the reaction tank supply port or the liquid feed pump at the reaction tank discharge port. In addition, a liquid level control device for adjusting the transport amount of the reaction liquid may be provided so that the height of the liquid level is lower than the supply port for additionally adding the raw material melt. This always prevents direct contact between the raw material melt and the prepolymer at the raw material melt supply port, avoids solidification of the raw material melt due to rapid cooling of the prepolymer, and prevents the supply port from being blocked. Can do.

  In the vertical reaction tank, as in the horizontal reaction tank, a device for measuring the liquid level of the reaction liquid is installed as necessary, and the measurement signal is sent to the liquid feed pump at the reaction tank supply port or the liquid feed pump at the discharge port. By feeding back, the transport amount of the reaction liquid can be adjusted so that the height of the liquid surface becomes a predetermined value.

  As a method for measuring the liquid level, for example, a radioactive substance is installed in the upper part of a horizontal reaction tank, and the measurement is performed by the amount of gamma rays transmitted from the reaction liquid to the reaction liquid. Ultrasonic or electromagnetic waves are emitted from the upper part of the reaction tank. A method of measuring the reflected wave, installing a cylindrical condenser at the top of the reaction tank, inserting it into the reaction solution, and measuring the change in dielectric constant with the height of the reaction solution inside the tube The measuring method etc. are mention | raise | lifted.

  Hereinafter, an embodiment of a polylactic acid synthesis apparatus to which the present invention is applied will be described in more detail. Note that a part of the description overlapping with the above description is partially omitted.

  FIG. 1 is an overall configuration diagram of a polylactic acid synthesis apparatus to which the present invention is applied.

  The synthesizing apparatus of the present example is to synthesize polylactic acid by supplying raw material lactide to a reaction apparatus in a molten state, polymerizing by heating and stirring, and first lactide supply apparatuses 1 to 3, lactide melting Devices 4-6, catalyst supply devices 7-9, polymerization initiator supply devices 10-12, second lactide supply devices 13-15, first reaction tank 16, second reaction tank 17, third reaction tank 18, remaining A lactide removing device 19, liquid feeding pumps 20 to 35, and valves 36 to 51 are provided.

  In the present synthesis apparatus, the reaction apparatus is configured by connecting a first reaction tank 16, a second reaction tank 17, and a third reaction tank 18 in series. The first reaction tank 16 and the second reaction tank 17 are horizontal reaction tanks, and the third reaction tank 18 is a vertical reaction tank. The molten raw material is supplied from the first supply system to the first reaction tank 16 through the supply port, while being supplied from the second and third supply systems to the second reaction tank 17 through the addition port. .

  The first supply system includes a first lactide supply device 1, a lactide melting device 4, a catalyst supply device 7, a polymerization initiator supply device 10, and a second lactide supply device 13. The second supply system includes a first lactide supply device 2, a lactide melting device 5, a catalyst supply device 8, a polymerization initiator supply device 11, and a second lactide supply device 14. The third supply system includes a first lactide supply device 3, a lactide melting device 6, a catalyst supply device 9, a polymerization initiator supply device 12, and a second lactide supply device 15.

  About the supply system of the molten raw material to the 2nd reaction tank 17, it is not limited to 2 systems, The number of systems can be increased / decreased as needed. About the liquid feeding pumps 20-35, the viscosity of the liquid to be transported is low, and the case where the liquid can be fed using gravity can be partially omitted. Further, the valves 36 to 51 can be omitted as necessary.

  The lactide supply devices 1 to 3 quantitatively supply solid or powdery raw material lactide to the first lactide melting devices 4 to 6. As a transportation method of the lactide supply devices 1 to 3, there are methods such as transportation by a screw feeder, transportation by ultrasonic vibration, transportation by a gas flow, and the like. In the 1st lactide melting apparatus 4-6, the raw material lactide sent is heated and fuse | melted in a container. The temperature at that time is not lower than the melting point of lactide, and is preferably in the range of 160 ° C. or lower, for example, so that deterioration due to heat does not occur. When the raw material lactide is supplied as a liquid instead of solid or powder, the lactide supply devices 1 to 3 serve as liquid feed pumps, and the lactide melting devices 4 to 6 function as buffer tanks.

  In the first supply system, the melted lactide generated by the lactide melting device 4 is discharged by the liquid feed pump 20 with the valve 36 opened, and then the valves 39 and 42 are opened, and the catalyst supply device 7, polymerization is performed. The catalyst and the polymerization initiator are supplied from the initiator supply device 10 to the molten lactide by the pumps 23 and 26 and then supplied to the lactide supply device 13. The flow rate of molten lactide discharged from the liquid feed pump 20, the ratio of the catalyst amount supplied from the catalyst supply device 7 to the flow rate of molten lactide, and the molten lactide flow rate of the polymerization initiator supplied from the polymerization initiator supply device 10. The ratio to the need not be the same, and can be changed as needed.

  Also in the second and third supply systems, similarly to the first supply system, molten lactide is generated via the lactide melting devices 5 and 6 and the lactide supply devices 14 and 15, and the second reaction tank 17. To be supplied. In the second and third supply systems, when there is no need to add a catalyst or a polymerization initiator to the molten lactide, valves 40 to 41, 43 to 44, pumps 24 to 25, 27 to 28, catalyst supply The apparatuses 8 to 9 and the polymerization initiator supply apparatuses 11 to 12 can be omitted.

  In the second lactide supply devices 13 to 15, the temperature of the molten lactide is maintained in the range of not less than the melting point of lactide and desirably not more than 160 ° C. The second lactide supply devices 13 to 15 are essentially buffer tanks and may be omitted if not necessary. The molten lactide in the second lactide supply device 13 is continuously supplied to the horizontal reaction tank 16 by the liquid feed pump 29 with the valve 45 opened. In addition, when the 2nd lactide supply apparatus 13 is abbreviate | omitted, the liquid feeding pump 29 is also abbreviate | omitted.

  Moreover, in order to avoid coagulation | solidification and obstruction | occlusion of lactide accompanying the temperature fall, all the liquid supply piping before and behind the liquid supply pumps 20-29, 31-32 is more than melting | fusing point of lactide by heating, heat retention, etc., Preferably it is 160 It is kept in the range of ℃ or less. Thermocouples are inserted in the pipes before and after the lactide melting devices 4 to 6, the lactide supply devices 13 to 15, and the liquid feed pumps 20 to 22, 29, and 31 to 32, and the temperature of the molten raw material at each position is It is to be measured.

  FIG. 2 shows an enlarged cross section of the first reaction tank 16. In the first reaction tank 16 which is a cylindrical horizontal reaction tank, a plurality of weirs 101 are provided so as to be orthogonal to the axial direction from the bottom of the inner wall, and through holes 52 are formed in these weirs 53 in the axial direction. ing. The first reaction tank 16 has a supply port at one end and a discharge port at the other end. The first reaction tank 16 extends from the supply port to the discharge port. Is equipped with a stirrer. In the region 54 between the weirs, the reaction liquid is homogenized by stirring (this region can be regarded as a single mixing cell). And only the reaction liquid in a position higher than the weir 53 can flow into the subsequent mixing cell due to the head difference. The reaction liquid in the tank is heated by a heat medium jacket 94 on the outer periphery of the reaction tank.

  A liquid level gauge 55 for measuring the liquid level of the reaction liquid is installed in the first reaction tank 16 as necessary, and the measurement signal is sent to the liquid feed pump 29, so that the liquid level becomes a predetermined value. Alternatively, by feeding back to the liquid feed pump 30, the transport amount of the reaction liquid is appropriately adjusted.

  The reaction liquid in the first reaction tank 16 opens the valve 48 and is transported to the second reaction tank 17 by gravity and a liquid feed pump 30. As for the liquid feed pump 30, a screw for extraction, a gear pump, or the like can be selected according to the viscosity of the reaction liquid. Further, when the reaction liquid can be extracted from the first reaction tank 16 only by gravity, the liquid feeding pump 30 can be omitted. The transport pipes before and after the liquid feed pump 30 are heated in order to avoid clogging associated with the solidification of the internal reaction liquid. The temperature at that time is preferably kept at 200 ° C. or lower so that the reaction solution does not thermally decompose.

  FIG. 3 shows an enlarged cross-sectional view of the second reaction tank 17. The second reaction tank 17, which is a cylindrical horizontal reaction tank, is provided with a supply port at one end and a discharge port at the other end, and is provided extending from the supply port to the discharge port. A stirrer in which a stirring blade 56 is attached to each of the rotating shafts 57 at intervals is provided. In this stirrer, a stirring blade 56 installed on one rotating shaft is arranged to mesh with the stirring blade 56 of the other rotating shaft in the axial direction at a minute interval. The rotating shafts 57 of these stirring blades are configured to rotate in the same direction, for example.

  In the second reaction tank 17, the prepolymer is transferred by the stirring action of the stirrer and the head difference between the supply port and the discharge port, and the polymerization reaction proceeds. Here, the reaction liquid in the tank is heated by the jacket 96 of the heat medium on the outer periphery of the reaction tank.

  A second supply system and a third supply system are connected to the second reaction tank 17 through two addition ports 90 so that molten lactide is supplied into the tank. The molten lactide of the second lactide supply device 14 opens the valve 46 and is supplied to the one addition port 90 by the liquid feeding pump 31, and the molten lactide of the third lactide supply device 15 opens the valve 47 to supply the liquid It is supplied to the other addition port 90 by the pump 32. In addition, when the 2nd, 3rd lactide supply apparatuses 14 and 15 are abbreviate | omitted, the liquid feeding pumps 31 and 32 are also abbreviate | omitted.

  Two addition ports 90 are formed in the axial direction at a position higher than the reaction liquid level 91 and at a gap 92 between the stirring blades. As a result, the molten lactide and the prepolymer are not in direct contact with each other at the addition port 90, and the prepolymer is solidified by cooling with the molten lactide, and the addition port 90 can be prevented from being blocked.

  If a mixture of a prepolymer with a relatively high viscosity and a melted lactide with a low viscosity is placed in a minute space between the stirring blades, the viscosity of the mixture decreases due to a large shear force due to the rotation of the blades at the front and rear positions. For this reason, the homogenization of the mixture proceeds. In the second reaction tank 17, a substantially complete mixing tank having a predetermined number of stirring blades (a local area of the mixture in the region behind it) according to the viscosity of the mixture of prepolymer and added molten lactide at each position. A plurality of regions that can be regarded as a single mixed cell in which no typical backflow phenomenon exists are generated. The number of complete mixing tanks is preferably equal to or greater than the number of raw material supply systems in the second reaction tank 17.

  In the present embodiment, the temperature of the mixture of the prepolymer and the molten lactide is measured in correspondence with the position of the addition port 90 of the second reaction tank 17. This measurement is performed by a thermocouple 97 provided by being inserted into a tank corresponding to the position of the addition port 90.

  The amount of molten lactide supplied by the second and third lactide supply devices 14 and 15 is controlled such that the mixture temperature of the prepolymer and molten lactide in the second reaction tank 17 has a predetermined value. That is, in the prepolymer flow direction, the result measured by the thermocouple 94 is input to, for example, a control device (not shown) and compared with a set temperature, and the liquid feed pumps 31 and 32 are operated based on the result. Thus, the supply amount of molten lactide is controlled. In this way, depending on the measured temperature of the prepolymer, for example, by controlling the temperature of the prepolymer to be always lower than the set temperature by adding molten lactide that is controlled at a temperature lower than that temperature. And discoloration associated with thermal decomposition can be suppressed. In this case, the supply amount may be variably controlled based on the measured temperature, or a predetermined supply amount may be determined in advance. In this example, two addition ports 90 are provided in the prepolymer flow direction of the second reaction tank 17, but the present invention is not limited to this, and the number may be single according to the size of the reaction tank. Three or more places may be installed. In this case, a thermocouple is also provided corresponding to the position of the addition port.

  Further, in the second reaction tank 17, a liquid level gauge 58 is installed, and for example, a measurement signal is sent to the liquid feed pumps 30 and 33 so as to keep the height of the reaction liquid level 91 lower than the height of the addition port 90. And the transport amount of the reaction solution may be adjusted. As a result, the molten lactide and the prepolymer are not in direct contact with each other at the addition port 90, and it is possible to prevent the addition port 90 from being blocked due to the solidification of the prepolymer by cooling with the molten raw material. Alternatively, when the second reaction tank 17 is operated in a full liquid state, the liquid level gauge 58 can be removed unless particularly required. For example, the liquid feed pump 33 is adjusted to the flow rate of the liquid feed pumps 30 to 32. Adjusted.

  In this example, as a melting raw material to be added to the addition port, molten lactide is used from the viewpoint of ease of temperature adjustment and supply stability, but if it is lower than the temperature of the prepolymer at the addition position, For example, a lactide polymer having a predetermined degree of polymerization may be used.

  Further, the supply system of the raw material lactide is connected only to the second reaction tank 17, but is not limited to this example. For example, in a reaction apparatus configured by connecting more reaction tanks, the first reaction tank And a plurality of reaction tanks (horizontal reaction tanks) excluding the final reaction tank.

  Next, the reaction liquid in the second reaction tank 17 is transported to the third reaction tank 18 by gravity and the liquid feed pump 33 with the valve 49 opened. As for the liquid feed pump 33, a screw for extraction and a gear pump can be selected according to the viscosity of the reaction liquid. Further, when the reaction liquid can be extracted from the third reaction tank 17 by gravity, the liquid feed pump 33 can be omitted. The transport piping before and after the liquid feed pump 33 needs to be heated and kept warm in order to avoid clogging due to the solidification of the internal reaction liquid. The temperature at that time is preferably 200 ° C. or lower so that the reaction solution does not thermally decompose.

  FIG. 4 shows an enlarged cross-sectional view of the third reaction tank 18. The third reaction tank 18, which is a cylindrical vertical reaction tank, is spaced from each other by two rotating shafts 98 extending from the upper supply port to the lower discharge port. A stirrer to which a stirring blade 99 is attached is provided. The rotating shaft 98 of the stirring blade 99 rotates in the same direction, for example.

  In the third reaction tank 18, for example, a liquid level gauge 59 for measuring the liquid level of the reaction liquid is installed as necessary, similarly to the first reaction tank 16, in order to set the liquid level to a predetermined value. The measurement signal is fed back to the liquid feed pump 33 or the liquid feed pump 34 so that the transport amount of the reaction liquid is adjusted.

  When the reaction liquid transported from the second reaction tank 17 is supplied from the supply port to the third reaction tank 18, it flows toward the discharge port by gravity, and the polymerization reaction proceeds during that time. For this reason, it can prevent that the polymer with a low polymerization degree mixes in the polymer with a high polymerization degree. In the third reaction tank 18, the reaction liquid is heated by the heat medium jacket 100 on the outer periphery of the reaction tank, or is removed when the heat medium temperature is lower than the polymer.

  In the present reaction tank, the inner peripheral surface is formed to have an uneven cross section, and for example, the area of the heat transfer surface 60 can be increased as compared with the first reaction tank 16, and therefore the amount of heat removed when the temperature of the polymer is higher than the heat medium And the influence of thermal degradation of the polymer in the final stage can be further reduced. Moreover, a high-viscosity polymer can be efficiently stirred by using a biaxial stirrer. In addition, when it is not necessary to take large heat removal amount, it is not necessary to have such an uneven side surface.

  The reaction liquid in the third reaction tank 18 is continuously discharged by gravity and the liquid feed pump 34 with the valve 50 opened, and is transported to the residual lactide removing device 19. As the liquid feed pump 34, an extraction screw, a gear pump, or the like can be selected according to the viscosity of the reaction liquid. The transport piping before and after the liquid feed pump 34 needs to be heated and kept warm in order to avoid clogging due to the solidification of the internal reaction liquid. The temperature at that time is preferably 200 ° C. or lower so that the polymer is not thermally decomposed.

  The residual lactide removing device 19 creates a negative pressure environment while maintaining a molten state, and removes unreacted lactide. The treated reaction liquid is continuously discharged by the liquid feed pump 35 with the valve 51 opened. As the liquid feed pump 35, an extraction screw, a gear pump, or the like can be selected according to the viscosity of the reaction liquid. The discharged polymer is usually subjected to water cooling and pelletizing with a chip cutter.

  1st lactide supply apparatus 1-3, lactide melting apparatus 4-6, catalyst supply apparatus 7-9, polymerization initiator supply apparatus 10-12, 2nd lactide supply apparatus 13-15, 1st reaction tank 16, 1st Each of the second reaction tank 17, the third reaction tank 18, and the residual lactide removal device 19 is provided with a nitrogen gas supply pipe and an exhaust pipe for purging the inside with nitrogen gas. This is to prevent scorching of the reaction solution due to the presence of oxygen. It is desirable that the operation of the process is basically started after nitrogen purge of all equipment in the process. Also, lactide supply devices 1 to 3, first lactide melting devices 4 to 6, catalyst supply devices 7 to 9, polymerization initiator supply devices 10 to 12, second lactide supply devices 13 to 15, and first reaction tank 16 The second reaction tank 17 and the third reaction tank 18 are operated at a pressure of about atmospheric pressure. This is to reduce the volatilization of the molten lactide.

1 is an overall configuration diagram of a polylactic acid synthesis apparatus to which the present invention is applied. FIG. It is a cross-sectional enlarged view of the 1st reaction tank of the synthesis apparatus of the polylactic acid formed by applying this invention. It is a cross-sectional enlarged view of the 2nd reaction tank of the synthesis apparatus of the polylactic acid formed by applying this invention. It is a cross-sectional enlarged view of the 3rd reaction tank of the synthesis apparatus of the polylactic acid formed by applying this invention.

Explanation of symbols

1-3 1st lactide supply apparatus 4-6 lactide melting apparatus 7-9 catalyst supply apparatus 10-12 polymerization initiator supply apparatus 13-15 2nd lactide supply apparatus 16 1st reaction tank 17 2nd reaction tank 18 1st 3 Reactor 19 Residual lactide removal device 20 to 35 Liquid feed pump 52 Through hole 53 Weir 55, 58, 59 Level gauge 57, 98 Rotating shaft 56, 95, 99 Stirring blade

Claims (6)

In a polymer synthesizer for synthesizing a polymer by polymerizing a polymer to be polymerized,
A polymer introduced from one supply port is stirred and transferred in a molten state, and formed between the supply port and the discharge port of the horizontal reaction vessel that discharges from the other discharge port. The temperature of the melt between the supply port and the discharge port in the reaction vessel, and an addition means for adding the polymer to be melted from the opening into the reaction vessel A polymer synthesizing apparatus comprising: a temperature detection unit; and a control unit configured to control an addition amount of the polymer added by the addition unit based on a temperature detected by the temperature detection unit. In a polymer synthesizer for synthesizing a polymer by polymerizing a polymer to be polymerized,
Including a reaction device formed by connecting a plurality of horizontal reaction vessels connected in series, stirring and transferring a polymer introduced from one supply port in a molten state, and discharging from the other discharge port; At least one of the opening formed between the supply port and the discharge port of the reaction vessel, addition means for adding the polymer to be melted from the opening into the reaction vessel, Temperature detection means for detecting the temperature of the melt between the supply port and the discharge port, and the addition amount of the polymer added by the addition means is controlled based on the temperature detected by the temperature detection means A polymer synthesizing apparatus. The polymer synthesizing apparatus according to claim 1 or 2, wherein the control unit controls an addition amount so that the detected temperature does not exceed a set temperature. The reaction vessel includes a stirrer that is formed in a horizontal cylindrical shape and has a plurality of stirring blades attached to a rotating shaft that extends in the vessel at intervals, and the opening is the rotation 4. The polymer synthesizing apparatus according to claim 1, wherein the polymer synthesizing apparatus is located between the stirring blades in an axial direction of the shaft and above the liquid surface of the melt. Liquid level detection means for detecting the liquid level of the melt is provided, and liquid level control means for controlling the liquid level of the reaction vessel so as to keep the distance between the liquid level and the opening within a set range. The polymer synthesizer according to claim 4. In the polymer synthesis method in which the polymer supplied from one of the horizontal reaction vessels is stirred and transferred in a molten state, and the polymer is taken out from the other.
A polymer synthesis method comprising detecting a temperature of a melt polymerized in the reaction vessel, and adding the polymer to be melted to the melt so that the temperature does not exceed a set temperature.

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