JP2009132857A - Method and device for producing polymer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To inhibit coloring of a polymer caused by thermal decomposition in devolatilization of a monomer from a reactant. <P>SOLUTION: A device for producing a polymer includes a barrel-shaped horizontal container 41 having a supply port 42, which is positioned below the molten liquid level of a reactant, and a discharge port 43 for the reactant, a stirring means 45 for the reactant, a degassing means for extracting gas via a degassing port 44 of the horizontal container, a recovery container 37 connected to the degassing port for recovering a volatile substance in the gas, and a vacuum pump 36. The stirring means includes a plurality of stirring rods 46 oriented along the axis direction in the horizontal container and coupling members 47 for coupling the stirring rods mutually along the axis direction. The coupling members are placed spacing from the virtual rotation center of the stirring means. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a polymer production method and production apparatus, and more particularly to a technique for removing unreacted monomers from a ring-opening polymer such as polylactic acid.

  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.

  As a method for polymerizing polylactic acid, for example, a continuous system in which reaction vessels for ring-opening polymerization of lactide are connected in series, and raw material supply and polymer discharge are simultaneously performed is widely known. In this case, by appropriately adjusting the temperature, amount of catalyst, residence time, etc. in each reaction tank, it is possible to suppress coloring due to thermal decomposition of polylactic acid due to prolonged temperature history and accumulation of reaction heat accompanying polymerization. can do.

  By the way, since polylactic acid produced in this way contains a large amount of unreacted lactide and monomer, there is a problem that it is weak in strength or easily hydrolyzed. For this reason, an apparatus for removing unreacted lactide and monomers (demonomer) from polylactic acid as a final polymerized product in a reduced pressure environment is disclosed (see Patent Document 1). In the apparatus described in Patent Document 1, a stirrer in which a plurality of agitating blades are attached to a rotating shaft in parallel with each other at an interval is accommodated in a horizontal container, and the polymerized reactant is contained in this container. A (polymer) supply port and discharge port, and a deaeration port for degassing the gas are provided. The to-be-reacted substance supplied into the container moves inside the container as the stirring blades rotate, and is taken out in a state where unreacted monomers are devolatilized in a reduced-pressure atmosphere.

  In addition, in the invention described in Patent Document 2, for a polycondensation polyester, a plurality of blades and donut-shaped disks are alternately arranged in the length direction of the container to form a stirring body, A technique is disclosed in which the stirring body is rotated in the circumferential direction of the tank in the container to accelerate the polymerization reaction and to remove the by-product by devolatilization. In the present technology, stirring is performed on a surface (perpendicular surface) that is substantially orthogonal to the reaction liquid flowing in the longitudinal direction in the container, and the stirring axis is not provided at the virtual rotation center. Polymer adhesion can be suppressed.

  Similarly, in the invention described in Patent Document 3, a stirring device is described in which two rotor blades having no stirring shaft at the virtual rotation center are arranged in parallel in a container and are rotated in directions opposite to each other. ing. In this technique, stirring is performed with a glass-shaped stirring blade that becomes a surface substantially orthogonal to the reaction liquid flowing in the longitudinal direction in the container, and the rotating shaft is not provided with a stirring shaft at the virtual rotation center. It is possible to suppress polymer adhesion to the surface.

  Furthermore, in the invention described in Patent Document 4, for a polycondensation polyester, a stirring blade formed by connecting a rod-like rectangular frame in the longitudinal direction of the tank is arranged in parallel in the container and rotated. Techniques for making them disclosed are disclosed. In this technique, since stirring is performed by rotation of a rectangular frame that does not have a surface that is substantially orthogonal to the flow of the reaction liquid flowing in the longitudinal direction in the container, the surface of the stirring shaft or stirring blade at the center of virtual rotation is used. It is possible to suppress the adhesion of the polymer.

  On the other hand, in Patent Document 5, as a continuous ring-opening polymerization process centering on polylactic acid, two or more reactions connected in series with a horizontal polymerizer in the front stage and a vertical polymerizer in the rear stage are arranged. A technique for removing a residual monomer after the ring-opening polymerization reaction is disclosed. According to this technology, because the plug flow property of the reaction solution in the ring-opening polymerization process and the high heat removal performance allow the polymerization to proceed to a high degree of reactivity with little thermal degradation, a high-quality polymer Can be synthesized.

  Patent Document 6 describes a technique in which an additive is mixed into a reaction solution between a continuous ring-opening polymerization step centering on polylactic acid and a subsequent residual monomer removal step. Thereby, the high-quality polymer with little deterioration is compoundable by suppressing the depolymerization reaction in a residual monomer removal process.

Japanese Patent No. 3419609 JP-A-10-218998 JP 2004-10791 A Japanese Patent No. 2523770 JP 2005-220203 A JP 2007-126601 A

  However, since the reactant to be supplied to the apparatus of Patent Document 1 is in a polymer state in which the polymerization has already been completed, in addition to the originally high liquid viscosity, the liquid viscosity further increases as the demonomer proceeds. For this reason, when processing a to-be-reacted substance using the apparatus of patent document 1, there exists a possibility that a to-be-reacted substance with a high viscosity may adhere to the rotating shaft of a stirrer. As described above, there is a problem that the substance to be reacted attached to the rotating shaft is likely to be colored due to thermal decomposition due to an increase in residence time in the apparatus.

  Further, in the apparatus of Patent Document 1, the supply port for the reactant to be provided in the horizontal container is provided above the vessel, that is, above the surface of the molten liquid. The flow may be turbulent and may not be extruded. That is, the backflow in the container increases the residence time of the substance to be reacted, and coloring due to thermal decomposition tends to occur. Furthermore, when thermal decomposition occurs in the reactant, there is a problem that production efficiency is lowered.

  On the other hand, when using the devices of Patent Documents 2 and 3 instead of the device of Patent Document 1, the influence of polymer adhesion to the stirring shaft can be suppressed by having no stirring shaft at the center of virtual rotation, There is a possibility that the polymer adheres to the stirring blade having a surface orthogonal to the flow. In particular, this effect is expected to be significant since the melt viscosity of the polymer increases significantly as the residual monomer decreases.

  Moreover, when using the apparatus of patent document 4 instead of the apparatus of patent document 1, there is no stirring axis in the virtual rotation center, and the lattice-shaped stirring blade does not have a surface orthogonal to the flow of the reaction liquid. Therefore, it is expected that there is little possibility of polymer adhesion to the stirring shaft and the stirring blade. However, if the viscosity of the reaction liquid is not high to some extent, the lattice-shaped stirring blades will significantly reduce the performance of lifting and stirring and devolatilizing the reaction liquid. For this reason, it is expected that the devolatilization performance deteriorates for a reaction solution having a relatively low viscosity at the beginning of the demonomer step.

  Moreover, in patent documents 5 and 6, there is no description of the technique regarding the method and apparatus of the demonomer process after a ring-opening polymerization process, and the technique of an appropriate demonomer process is required in order to synthesize | combine a high quality polymer.

  The object of the present invention is to suppress thermal decomposition and coloration of the polymer due to the polymer adhering to the container in the step of devolatilizing and removing the unreacted monomer contained in the polymer of the reactant. It is in.

  In the present invention, in order to solve the above-mentioned problems, the polyhydroxycarboxylic acid obtained by subjecting a cyclic dimer of hydroxycarboxylic acid to a ring-opening polymerization reaction is stirred in a molten state, and under a lower pressure than during the ring-opening polymerization reaction. In the method for producing a polymer for devolatilizing and removing unreacted cyclic dimer residue, the ring-opening polymerization reaction includes a horizontal reaction tank containing a stirring body having a stirring shaft disposed horizontally with respect to the ground; A supply port that is formed at one end of the horizontal reaction tank and supplies a reactant, a discharge port that is formed at the other end of the horizontal reaction tank and discharges the reactant, and is installed in the horizontal reaction tank A horizontal polymerization vessel comprising one or more weirs is arranged in the first stage, and a vertical reaction vessel containing a stirring shaft arranged perpendicular to the ground, and an upper end of the vertical reaction vessel A supply port formed on the side for supplying a reactant; A vertical polymerization vessel formed on the lower end side of the mold reaction tank and having a discharge port for discharging the reactant to be reacted using a plurality of serial polymerization vessels arranged in the last stage The devolatilization is performed by supplying the material to be treated obtained by the ring-opening polymerization reaction from the supply port on one end of the horizontal tank, and connecting a plurality of rod-shaped rectangular frames in the longitudinal direction of the tank. A stirrer that does not have an agitation shaft at the center of rotation rotates in the tank circumferential direction in the tank, discharges the material to be processed from the discharge port on the other end side, and a devolatilization port above the melt surface of the material to be processed It is characterized by being continuously performed by discharging devolatilization gas from

  If a combination of the ring-opening polymerization step and the devolatilization step in the present invention is used, a polymer with high reactivity, that is, a high viscosity, can be supplied to the devolatilization step. The ability to lift and stir and devolatilize the reaction liquid can be ensured, and an apparatus having a rectangular frame-shaped stirring blade can be applied to the devolatilization step. Further, the present invention is characterized in that there is little thermal degradation in each of the ring-opening polymerization step and the devolatilization step, but the effect of reducing thermal degradation is more than a simple addition for the following reasons.

Thermal degradation or thermal decomposition is the destruction of the ester bond of the polymer molecule —CO—OCH (CH ₃ ) —, and the two polymer molecules formed by this decomposition have carboxyl groups —COOH and vinyl groups —CH Either one of = CH ₂ is generated. Since the carboxyl group is an acid and has a catalytic action that breaks other ester bonds in combination with heat, the thermal deterioration phenomenon is accelerated. Therefore, by synthesizing a polymer with little thermal degradation in the ring-opening polymerization step, the thermal degradation inhibiting effect in the devolatilization step is significantly improved.

  Specifically, the production apparatus for realizing the polymer production method of the present invention stirs polyhydroxycarboxylic acid obtained by ring-opening polymerization reaction of a cyclic dimer of hydroxycarboxylic acid in a molten state and also performs ring-opening polymerization. In a polymer production apparatus for devolatilizing and removing unreacted cyclic dimer residue under a pressure lower than that at the time of reaction, an apparatus for performing a ring-opening polymerization reaction has a stirring shaft disposed horizontally with respect to the ground. A horizontal reaction tank in which the stirring body is accommodated, a supply port that is formed at one end of the horizontal reaction tank to supply a reactant, and a discharge that is formed at the other end of the horizontal reaction tank to discharge the reactant. A vertical polymerization vessel that is equipped with an outlet and one or more weirs installed in a horizontal reaction vessel is arranged in the first stage and contains a stirring shaft arranged perpendicular to the ground. Formed on the reaction tank and the upper end of this vertical reaction tank. A vertical polymerization vessel having a supply port for supplying the reactants and a discharge port formed at the lower end side of the vertical reaction tank for discharging the reactants is arranged at the last stage. An apparatus comprising a plurality of serially connected polymerizers for performing devolatilization and removal includes a horizontal stirring tank, a stirring body housed in the stirring tank and supported to be rotatable in the tank circumferential direction, and one end side of the stirring tank. A supply port for supplying a material to be treated which is formed and subjected to a ring-opening polymerization reaction, a discharge port which is formed on the other end side of the stirring vessel and discharges the material to be treated, and melting of the material to be treated in the stirring vessel A devolatilization port that is formed above the liquid level and discharges the devolatilization gas, a recovery container that is connected to the devolatilization port and condenses or solidifies the devolatilization gas, and is connected to the recovery container. A vacuum pump that depressurizes the inside of the tank, and the stirrer connects a plurality of rod-shaped rectangular frames in the longitudinal direction of the tank It was formed, characterized in that no stirring shaft inserted through the virtual rotation center.

  In this case, the supply port for supplying the material to be processed and the discharge port for discharging the material to be processed to the other end side should be arranged below the melt surface of the material to be processed from the viewpoint of improving the plug flow property. Is desirable. Note that the apparatus for performing devolatilization removal does not necessarily have to be one stage, and other types than those described in the present invention as necessary, for example, including a devolatilizer such as an extruder, are arranged in multiple stages in series or in parallel. Can be used in combination.

  In addition, in the devolatilization process, from the viewpoint of suppressing thermal deterioration, by disposing the supply port of the stirring tank below the surface of the melt, the material to be treated supplied into the stirring tank through the supply port is melted. Since the flow of the processing substance is not disturbed and an extruded flow (plug flow property) of the melt is formed, a polymer having a narrow molecular weight distribution and difficult to decompose can be synthesized.

  Further, the stirring body in the stirring tank is provided with the stirring shaft away from the virtual rotation center, and the connecting member itself of the rectangular frame rotates at a predetermined peripheral speed with respect to the virtual rotation center. It can suppress that a substance adheres. In addition, since the stirring blade having a rectangular frame shape is hardly affected by the material to be treated that flows directly to the blade surface, adhesion of the polymer is reduced even in the latter half of the devolatilization step in which the residual monomer is reduced. . Therefore, an increase in the residence time of the substance to be treated in the container can be suppressed, coloring due to thermal decomposition can be suppressed, and a high-quality polymer having a high molecular weight can be produced.

  Further, means for adding at least one of an agent that deactivates the catalyst of the ring-opening polymerization reaction or an agent that reduces thermal degradation of the material to be treated to the material to be treated after the ring-opening polymerization reaction and before devolatilization and removal To be provided. Thereby, since the chemical | medical agent which deactivates a polymerization catalyst and the antioxidant of a polymer can be added and mixed with a to-be-processed substance, the thermal decomposition inhibitory effect in the technique of this invention can further be improved.

  Further, since the agitation tank is provided with a recovery container for recovering the volatile substances contained in the material to be treated, the volatile substances are recovered, and the recovered substances can be used for desired applications. In particular, a high-quality polymer can be synthesized in a high yield by returning the recovered substance to the previous step and reusing it as a raw material. When collecting the volatile substance in the collection container, for example, the volatile substance can be collected in a liquid or powder form by cooling the collection container with a predetermined cooling means.

  According to the present invention, when the unreacted monomer contained in the reaction material such as polylactic acid produced by the ring-opening polymerization reaction is devolatilized and removed, the reaction material due to the polymer adhering to the container is removed. Thermal decomposition and coloring can be suppressed.

  It also suppresses thermal decomposition and coloration of the reactants generated by devolatilization and removal of the reactants produced by other polymerization reactions, such as solvents contained in polystyrene produced by the solvent polymerization reaction. can do.

  Hereinafter, a polymer production method and production apparatus according to an embodiment to which the present invention is applied include a reaction apparatus and a reaction process for subjecting a reaction substance to a ring-opening polymerization reaction, and a target substance generated by the ring-opening polymerization reaction. It consists of a devolatilization apparatus and a devolatilization process for devolatilization, and is intended to obtain a final material by removing volatile substances contained in the material to be treated.

  Here, the material to be treated (hereinafter, appropriately referred to as a polymer or a polymer) introduced into the devolatilizer is mainly polylactic acid, but is not limited to this, and is generated by a ring-opening polymerization reaction. Polyesters synthesized by ring-opening polymerization reaction of cyclic dimers, for example, copolymers based on lactic acid, polyglycolic acid by ring-opening polymerization of glycolide, copolymers based on glycolic acid, etc. It can also be applied to.

  Furthermore, as a to-be-processed substance, it can apply also about the polymer produced | generated by solvent polymerization. The polymer produced by solvent polymerization refers to a polymer produced by addition polymerization of a polymer material with another polymer raw material, and examples thereof include a copolymer mainly composed of cellulose and acetic acid.

  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 Copolymerized polylactic acid obtained by copolymerizing and the like, and those in which additives are mixed as secondary components are included.

  Glycolide means a cyclic ester generated by dehydrating two molecules of water from two molecules of glycolic acid, polyglycolic acid means a polymer based on glycolic acid, and other ester bond-forming components, For example, it includes hydroxycarboxylic acids, lactones, copolymerized polyglycolic acid obtained by copolymerizing dicarboxylic acid and diol, and those in which additives are mixed as secondary components.

  Examples of hydroxycarboxylic acids other than lactic acid and glycolic acid include hydroxybutyl carboxylic 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. Polyalkylene ether oligomers and polymers 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.

  In the polymer production method and production apparatus of the present embodiment, the polymer devolatilization method and apparatus are monomers, oligomers, etc. contained in a polymer synthesized by polymerizing raw materials in a molten state, or a solvent used for melting. It is for removing. A raw material (reacted substance) means a monomer, a cyclic monomer, a cyclic condensate of a monomer, an oligomer, or the like, which is a component for synthesizing a polymer by a polymerization reaction.

  In the synthesis of polylactic acid, lactide is used as a raw material, a reaction liquid containing raw material lactide and a catalyst in a molten state is heated in a reaction apparatus, and lactide is polymerized in a molten state by performing a ring-opening polymerization reaction of lactide. To synthesize polylactic acid continuously or intermittently. In addition, in the synthesis of polyglycolic acid, glycolide is used as a raw material, a reaction liquid containing raw material glycolide and a catalyst in a molten state is heated in a reaction apparatus, and glycolide is melted by performing a ring-opening polymerization reaction of glycolide. Polymerization is carried out in the state to synthesize polyglycolic acid. Here, the reaction liquid refers to a melted polymer raw material, a mixture of a molten raw material and a catalyst, a mixture of a molten raw material, a catalyst, and a polymer of various polymerization degrees, or a melt or a product distributed in a polymer synthesis process. All are included.

  When the raw material is in a molten state, the catalyst can be added to the molten raw material as it is 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 The raw material is melted in advance by heating the raw material with The heating temperature in the raw material melting apparatus is not particularly limited as long as it is equal to or higher than the melting point of the raw material. Therefore, when the raw material is lactide, it is not particularly limited as long as it is 95 ° C. or higher, but it 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, well-known catalysts for polymerization of polylactic acid and polyglycolic acid can be used. For example, from groups IA, IVA, IVB and VA of the periodic table A catalyst containing at least one metal or metal compound selected from the group can be used.

  Examples of those belonging to the group IVA include organotin-based 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.) is there. 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 reaction vessel.

  In the present invention, the reaction apparatus for polymerizing the raw material includes three or more reaction vessels connected in series, and the polymerization reaction is performed by heating the reaction liquid containing the molten raw material and the catalyst in the reaction vessel. Is what you do. The number of reaction tanks contained in the reaction apparatus may be 2 or more, and is usually 2 to 5, preferably 2 to 4, more preferably 2. However, if there is no particular problem, using a reactor composed of one reaction vessel, additional addition of raw materials between the polymer raw material supply port and the final polymer discharge port, stirring and mixing with the intermediate polymer are performed. You can go.

  Below, embodiment is described about the reaction apparatus and reaction method for a polymerization reaction, and the devolatilization apparatus and devolatilization method for a devolatilization process.

  In the embodiment of the present invention, in the reactor, the raw material melt is additionally added to the intermediate state polymer between the raw material melt and the final polymer, and stirring and mixing are performed. About the shape of a reaction tank etc., it does not restrict | limit in particular, What is normally used in this technical field can be used. In addition, there is no particular problem even if a tank in which the polymerization reaction is not substantially performed is connected to a preceding stage of the tank in which the polymerization reaction is performed. Here, a case where two reaction vessels connected in series will be described as a reaction apparatus for carrying out the polymerization reaction.

  The reaction vessel in the first stage is not particularly limited, and those commonly used in this technical field can be used. However, the stirring device installed so that the rotation axis thereof is substantially horizontal with respect to the ground and its It is desirable to use a reaction vessel having at least one weir installed in the vessel. Hereinafter, a reaction tank having a stirring device installed so that its rotation axis is substantially horizontal with respect to the ground is referred to as a horizontal reaction tank.

  The term “substantially horizontal to the ground” does not mean that the rotation axis of the stirring device 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 °.

  The shape of the horizontal reaction tank is not particularly limited as long as it can be installed so that the rotating shaft of the stirring device is substantially horizontal with respect to the ground. It has a cylindrical shape with a horizontal central axis. Further, the horizontal reaction tank is provided with a supply port for supplying a reaction liquid containing a molten raw material at one end in the rotation axis direction of the stirring device, and a discharge port for taking out the reaction liquid at the other end. The reaction solution moves in a substantially horizontal direction from the supply port to the discharge port. The supply port is preferably positioned below the rotation axis of the stirring device, and the discharge port is preferably positioned below the rotation axis of the stirring device.

  The stirrer is, for example, a single-shaft mixer in which two or more stirrer blades such as a circle, an oval, a triangle, a quadrangle, or a multi-leaf are placed on the rotation axis at intervals, or two or more shafts that mesh with each other. Consists of A stirrer composed of a mixer having two or more shafts meshing with each other is preferable from the viewpoint of self-cleaning action because it can prevent the reaction liquid from adhering to the rotating shaft and the reaction tank. In the case of using a biaxial mixer having a plurality of stirring blades, 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 a rotation shaft member that actually exists at the virtual rotation center of the rotor blade, but also includes a rotation axis as a simple rotation center. Therefore, as long as the virtual rotation center of the rotational motion of the stirring device is arranged substantially horizontally with respect to the ground, the rotary shaft member does not necessarily have to exist at the virtual rotation center of the rotary blade.

  As a heating method in the horizontal reaction tank, a method generally used in this technical field can be used. In the present embodiment, a heat medium jacket is installed on the outer periphery of the reaction tank, and heat is transferred through the reaction tank wall. The method of heating the reaction solution is used, but is not limited to this, for example, a method of heating by heat transfer through the rotating shaft of the stirring device may be used, or these may be used alone or in combination. May be used. 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 accompanying the reaction heat, the heat medium from the reaction liquid is reversed. 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 becomes high due to the reaction heat and heat removal is necessary. Is 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 solidify and adhere to the inner surface of the reaction tank. In this case, the adhering substance can be peeled off by a stirring device installed in the reaction tank.

  The horizontal reaction tank has a weir in the tank. This weir acts to inhibit the reaction solution from flowing rapidly from the supply port to 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 reaction tank cross section perpendicular to the rotation axis of the stirring device. 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, there may be a case where a through hole is provided in the weir, and the through hole is present at the boundary with the portion near the bottom of the reaction vessel, preferably the inner wall of the reaction vessel bottom. 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 region between the two weirs acts in the same manner as a single mixing cell, and the reaction liquid is homogenized by being stirred by the stirring device. Thereby, the raw material melt with a low viscosity and the low-viscosity polymer with a low polymerization degree can flow faster than the high-viscosity polymer with a high polymerization degree, 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 effect of mixing the polymers with different viscosities 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 can move toward the discharge port by flowing to the subsequent region due to the head difference. 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 an 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 placed in the upper part of the horizontal reaction tank, and the measurement method is based on the amount of gamma rays that permeate through the reaction liquid. Then, by measuring the reflected wave, a cylindrical condenser is installed at the top of the horizontal reaction tank, and this is inserted into the reaction solution, and the change in the dielectric constant with the height of the reaction solution inside the tube There is a method to measure by measuring.

  The reaction conditions in the first horizontal reaction tank can be appropriately determined by those skilled in the art, but the average reaction temperature in the reaction tank is usually 140 to 180 ° C., preferably 160 to 170 ° C., residence time. The 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 usually 50,000 to 200,000, preferably 70,000 to 150,000 is obtained from the outlet of the first horizontal reaction tank.

  The first-stage reaction tank is a horizontal reaction tank, and a weir is provided in the reaction tank, so that a molten raw material having a low viscosity and a polymer having a low degree of polymerization and a viscosity are mixed with a polymer having undergone a polymerization reaction to some extent. Can be suppressed, and the piston flowability in the reaction vessel can be ensured. And it can prevent that a reaction liquid moves to the following process with unreacted, and sufficient reaction can be performed in the 1st step | paragraph reaction tank. Therefore, since it is possible to prevent the temperature history from being prolonged due to variations in residence time, deterioration of the polymer due to thermal decomposition is suppressed, and a high-quality polymer can be obtained.

  The second-stage reaction tank is a reaction apparatus for performing a polymerization reaction, and a reaction tank having a stirring device installed so that its rotation axis is substantially perpendicular to the ground is at least in its final stage. Use the reactor containing. Hereinafter, a reaction tank having a stirring device installed so that its rotation axis is substantially perpendicular to the ground is referred to as a vertical reaction tank. In the present embodiment, at least a vertical reaction tank is used for the final stage, but a vertical reaction tank may be further used for stages 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 the final stage vertical reaction tank, a tank in which the polymerization reaction is not substantially carried out may be connected to the subsequent stages.

  The term “substantially perpendicular to the ground” does not mean that the rotation axis of the stirring device is strictly perpendicular, and the angle between the ground, that is, the horizon and the rotation axis is usually 85 to 95 °, It means preferably 89 to 91 °, more preferably 90 °. As in the horizontal reaction vessel, the rotation axis does not necessarily mean a rotation shaft member that actually exists at the virtual rotation center of the rotary blade, but also includes a rotation axis as a simple rotation center. Therefore, as long as the virtual rotation center of the rotational motion of the stirring device is arranged substantially perpendicular to the ground, the rotary shaft member does not necessarily have to exist at the virtual rotation center of the rotary blade.

  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 shape. A cylindrical shape having a central axis substantially parallel to the rotation axis is preferable. The vertical reaction tank is provided with 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 solution moves in a direction substantially perpendicular to the direction from the supply port to the discharge port. 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 with the progress of the polymerization reaction, it is possible to prevent the polymer having a low polymerization degree from being mixed into the polymer having a high polymerization degree by providing a supply port in the upper part.

  The stirring device installed in the vertical reaction tank is not particularly limited as long as stirring is performed by rotation of a rotating shaft arranged substantially perpendicular to the ground. The stirrer is, for example, a single-shaft mixer in which two or more stirrer blades such as a circle, an oval, a triangle, a quadrangle, or a multi-leaf are placed on the rotation axis at intervals, or two or more shafts that mesh with each other. Consists of It is preferable that the stirrer composed of a mixer having two or more shafts meshing with each other is installed such that the stirring blades of the respective rotating shafts are staggered. In this case, it is preferable to rotate each rotating shaft in the reverse direction. A mixer having two or more shafts meshing with each other can prevent adhesion of a polymer or the like to a rotating shaft or a reaction tank. Therefore, from the viewpoint of self-cleaning action, the polymerization reaction proceeds and the viscosity of the polymer is increased. It is particularly advantageously used in the subsequent reaction tank.

  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. It is installed and the method of heating the reaction liquid by heat transfer through the reaction vessel wall is used, but for example, a method of heating by heat transfer through a rotating medium inside the rotating shaft of the stirring device may be used. They may be used or used in combination.

  The molten raw material supplied into the vertical reaction tank is initially heated by the jacket of the heat medium to advance the polymerization reaction. 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, the reaction is reversed. Heat escapes from the liquid 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 installing fins (irregularities on the side surface of the reaction tank) inside the vertical reaction tank. Moreover, the aspect which keeps a polymer warm by supplying the heat medium heated with the heat medium heating apparatus to the discharge port vicinity, and prevents overcooling is also considered.

  In the latter stage of the polymerization reaction, it is preferable to carry out the reaction at a high temperature. Therefore, degradation of the polymer accompanying the rise in temperature becomes a problem, but by using a vertical reaction tank in the final stage, the rise in temperature can be suppressed. Therefore, it is possible to reduce the influence of deterioration and coloring of the polymer.

  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 usually introduced only about half of the reaction tank capacity, 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 accompanying the polymerization of the raw material by heat transfer, the temperature rise of the reaction solution can be reduced, and in the latter stage of the polymerization reaction, the deterioration due to the thermal decomposition of the produced polymer is effectively suppressed, 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 have an uneven surface. In the configuration in which the unevenness is provided on the side surface, the high viscosity polymer stuck to the inner wall of the reaction tank can be scraped off by installing the stirring blade so as to mesh with the concave portion of the reaction tank.

  In the vertical reaction tank, as with 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 reaction tank discharge port. By feeding back to the above, 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 placed in the upper part of the horizontal reaction tank, and the measurement method is based on the amount of gamma rays that permeate through the reaction liquid. The ultrasonic wave or electromagnetic wave is emitted from the upper part of the horizontal reaction tank. Then, by measuring the reflected wave, a cylindrical condenser is installed at the top of the horizontal reaction tank, and this is inserted into the reaction liquid, and the change in the dielectric constant with the height of the reaction liquid inside the cylinder There is a method to measure by measuring.

  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 production apparatus of the present embodiment, a devolatilizer is installed after the reactor for polymerization, and unreacted raw materials are removed from the final polymer discharged from the reactor. In the devolatilization apparatus, lactide can be removed from unreacted raw materials or solvents such as polylactic acid by creating a negative pressure environment while maintaining a molten state.

  The devolatilizer is installed so that the virtual rotation center of the rotational motion of the stirring device is substantially horizontal with respect to the ground, and has a structure that does not have a rotating shaft member at the virtual rotation center. Hereinafter, the devolatilization apparatus of the present embodiment is referred to as a shaftless horizontal stirrer.

  Here, “substantially horizontal with respect to the ground” does not mean that the virtual rotation center of the stirring device is strictly horizontal, but the angle between the ground, that is, the horizon and the rotation center is usually − It means 5 ° to 5 °, preferably −1 ° to 1 °, more preferably 0 °.

  A shaftless horizontal stirrer is configured with a stirrer housed in a horizontal container, and this horizontal container can be installed so that the virtual rotation center of the rotational motion of the stirrer is substantially horizontal with respect to the ground. As long as it is a tank type or a cylindrical type, it is not particularly limited, but it is preferably formed in a cylindrical shape or a combination of cylinders having a rotation center substantially horizontal to the ground. In addition, the horizontal container has a supply port for supplying a reaction liquid (processed material) containing a molten raw material to be a final polymer at one end in the rotation axis direction of the stirring device, and a process target devolatilized at the other end. Each is provided with a discharge port for taking out. Accordingly, the supplied reaction solution moves substantially in the horizontal direction from the supply port to the discharge port.

  The supply port is installed so as to be always positioned below the reaction liquid level in the horizontal container. As a result, the flow of the reaction liquid is not disturbed when the reactant is supplied, and an extrusion flow can be realized. Therefore, thermal decomposition accompanying an increase in the residence time of the substance to be treated is suppressed, and coloring can be suppressed. it can. Note that, similarly to the supply port, the discharge port is preferably installed so as to be positioned below the rotation center of the stirring device.

  A stirrer installed in a shaftless horizontal stirrer is a stirrer having a stirring blade that rotates in the circumferential direction of a tank by connecting a plurality of rod-shaped rectangular frames in the length direction of the tank, and stirs around a virtual rotation center. It can be constituted by a mixer having one shaft or two or more shafts meshing with each other without a shaft.

  The stirrer can suppress the attachment of the reactant to the connecting member by rotating the rectangular frame around the virtual rotation center at a predetermined peripheral speed. As a result, it is possible to produce a high-quality polymer that suppresses thermal decomposition of the reactants, has little coloring, and has a high molecular weight. As examples of the stirring device, for example, a lattice blade polymerizer manufactured by Hitachi, Ltd., and a stirring device described in JP-A No. 2004-10791 can be used.

  Moreover, the shaftless horizontal stirrer is provided with a degassing port for degassing the gas in the horizontal container. The devolatilization port is connected to a suction port of a vacuum pump through a recovery device for the volatile material to be devolatilized, and the inside of the shaftless horizontal stirrer tank is kept at a negative pressure. For example, lactide devolatilized from polylactic acid is recovered in a recovery container. The recovery container can recover the volatile material in a liquid or solid state by cooling with a well-known cooling means. As the collection container, any kind of single stage or a combination of a plurality of stages in series or in parallel can be used. The lactide recovered in this way can be reused, for example, as a raw material for producing polylactic acid, so that the production efficiency of polylactic acid can be improved. There are various types of vacuum pumps such as an oil rotary type, an oil diffusion type, a roots type, and an ejector type, and any of them may be a combination of a plurality of stages in series or in parallel. Thereafter, the exhaust gas is discharged out of the system through a vacuum pump.

  Polylactic acid from which lactide has been devolatilized through a shaftless horizontal stirrer is subjected to pelletization by water cooling, a chip cutter, or the like, but these treatments can be omitted.

  In the present embodiment, a raw material melting apparatus, a catalyst supply apparatus, a reaction apparatus including various reaction tanks, a devolatilization apparatus, and the like used in a reaction apparatus for producing a polymer are respectively supplied with nitrogen gas. Although a nitrogen gas supply pipe and an exhaust pipe for purging are installed, it is preferable that the operation of the synthesis process is basically started after all apparatuses in the process are 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, and various reaction vessels are preferably operated at a pressure of about atmospheric pressure in order to reduce volatilization of the molten raw material.

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

  FIG. 1 is an overall view illustrating a process for producing polylactic acid to which the present invention is applied. FIG. 2 is a cross-sectional view of a polylactic acid devolatilizing apparatus to which the present invention is applied.

  The production process of the present embodiment is configured to include a reaction step of polymerizing and producing polylactic acid and a devolatilization step of devolatilizing the polylactic acid polymerized by this reaction step. In the reaction step, polylactic acid is polymerized by a configuration including a lactide supply device 1, a lactide melting device 2, a catalyst supply device 3, a polymerization initiator supply device 4, a lactide supply device 5, a horizontal reaction tank 6, and a vertical reaction tank 7. Do. In the reaction tank, two reaction tanks, a horizontal reaction tank 6 and a vertical reaction tank 7, are connected in series. In the devolatilization step, the unreacted lactide removed by the devolatilizer 8 is recovered in the recovery container 37 by the configuration including the devolatilizer 8 and the recovery container 37. About the liquid feeding pumps 9-15, the case where the viscosity of the liquid to transport is low and can send liquid using gravity, etc. can be partially omitted. Further, the valves 16 to 22 can be omitted if necessary.

  The lactide supply device 1 supplies solid or powdery lactide to the lactide melting device 2. As a transportation method of the lactide supply apparatus 1, there are methods such as transportation using a screw feeder, transportation using ultrasonic vibration, transportation using a gas flow, and the like. In the lactide melting device 2, the sent lactide is heated and melted. The temperature at that time is not less than the melting point of lactide, and preferably not more than 160 ° C. so as not to cause deterioration due to heat. When the raw material lactide is supplied as a liquid instead of solid or powder, the lactide supply device 1 serves as a liquid feed pump, and the lactide melting device 2 functions as a buffer tank.

  The melted lactide generated in the lactide melting device 2 is opened by the valve 16 and then discharged by the liquid feeding pump 9. The valves 17 and 18 are opened and the pumps 10 and 11 are used to perform catalyst and polymerization from the catalyst supply device 3. After the polymerization initiator is supplied to the molten lactide from the initiator supply device 4, the molten lactide is supplied to the lactide supply device 5. The flow rate of molten lactide discharged from the liquid feed pump 9, the ratio of the amount of catalyst supplied from the catalyst supply device 3 to the flow rate of molten lactide, and the molten lactide flow rate of the polymerization initiator supplied from the polymerization initiator supply device 4 The ratio to can be appropriately set as necessary.

  In the lactide supply device 5, the temperature of the molten lactide is maintained in the range of the melting point of lactide or higher and desirably 160 ° C. or lower. The lactide supply device 5 is essentially a buffer tank and may be omitted if not necessary. The molten lactide in the lactide supply device 5 opens the valve 19 and is continuously supplied to the horizontal reaction tank 6 by the liquid feed pump 12. When the lactide supply device 5 is omitted, the liquid feed pump 12 is also omitted. The liquid supply pipes before and after the liquid supply pumps 9, 12, 13 are all in the range above the melting point of lactide, preferably below 160 ° C., by heating, keeping warm, etc. in order to avoid coagulation and blockage of lactide due to temperature drop. Retained. Thermocouples are inserted in the pipes before and after the lactide melting device 2, the lactide supply device 5, and the liquid feed pumps 9, 12, and 13, and the temperature of the molten raw material at each position is measured.

  In the horizontal reaction tank 6, molten lactide flows due to the head difference between the supply port and the discharge port, and is heated by the jacket of the heat medium on the outer periphery of the reaction tank to proceed the polymerization reaction.

  The reaction liquid discharged from the discharge port of the horizontal reaction tank 6 is transported by a pump 13 to a supply port installed at the upper part of the vertical reaction tank 7, aiming at the lower discharge port of the vertical reaction tank 7 by gravity. The polymerization reaction proceeds. Thereby, it can prevent that the polymer with a low polymerization degree mixes in the polymer with a high polymerization degree. In the vertical reaction tank 7, the reaction solution is heated by a heat medium jacket on the outer periphery of the reaction tank, or is removed when the heat medium temperature is lower than that of the polymer.

  Since the vertical reaction tank 7 has a larger heat transfer area than the horizontal reaction tank 6, the efficiency of heating and heat removal is high. For this reason, by using the vertical reaction tank 7 in the final stage, it is possible to reduce the influence of deterioration of the polymer due to the temperature rise accompanying the reaction heat. In the vertical reaction tank 7, a stirrer having two rotating shafts provided with stirring blades suitable for stirring high viscosity polymer is used. The reaction liquid inside the vertical reaction tank 7 is continuously discharged by gravity and the liquid feed pump 14 with the valve 21 opened, and is transported to the devolatilizer 8. As the liquid feed pump 14, a screw for extraction or a gear pump can be selected according to the viscosity of the reaction liquid. The transport piping before and after the liquid feed pump 14 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.

  At the time of discharge by the liquid feed pump 14, the additive is supplied from the additive tank 50 by the supply pump 51 between the pump and the vertical reaction tank 7. Here, the additive is an appropriate amount such as a catalyst deactivator, an antioxidant, or a combination thereof. The added additive is mixed with the polymer by the shearing force of the liquid feeding pump 14. If there is a dedicated mixer, the supply point of the additive may be after the liquid feed pump 14.

  In this way, the polymerized polymer in the reaction process, that is, polylactic acid is supplied to the devolatilization apparatus 8 in the devolatilization process. The devolatilizer 8 creates a negative pressure environment while maintaining the molten state of polylactic acid, removes unreacted lactide, and discharges purified polylactic acid.

  As shown in FIG. 2, the devolatilization apparatus 8 of this embodiment includes a horizontal container 41, a mixer 45, a vacuum pump 36, and a recovery container 37. A supply port 42 for supplying unpurified polylactic acid is provided below one end side of the horizontal container 41 formed in a hollow cylindrical shape, and purified polylactic acid is discharged below the other end side. A discharge port 43 is provided. A deaeration port 44 for extracting gas from the container is provided above the other end of the horizontal container 41. A pipe is connected to the deaeration port 44, and a deaeration valve 35 is provided in the pipe. A recovery container 37 is connected to the downstream side piping of the deaeration valve 35, and a vacuum pump 36 is connected to the recovery container 37. The gas in the horizontal container 41 sucked by the vacuum pump 36 is recovered in a recovery container 37 provided on the suction side of the vacuum pump 36.

  Further, in order to heat the reaction liquid and maintain the predetermined temperature in the horizontal container 41, for example, a jacket of a heat medium is installed on the outer periphery of the container 41, and the reaction liquid is heated by heat transfer through the wall surface of the container. ing.

  A mixer 45 is accommodated in the horizontal container 41. The mixer 45 includes a plurality of stirring bars 46 arranged in parallel in the axial direction of the horizontal container 41 and a connecting bar 47 that connects the ends of adjacent stirring bars 46 to each other. It is formed by connecting rods 46 and connecting rods 47 alternately at right angles. A rotating shaft 48 is connected to the stirring rods 46 at both ends of the mixer 45 at a position coinciding with the virtual rotation center of the mixer 45. The rotating shaft 48 is supported by a bearing of the horizontal container 41 and driven. The drive shaft of the motor 49 is connected.

  As described above, in the mixer 45 of the present embodiment, the connecting rod 47 is disposed away from the virtual rotation center of the stirring rod 46. Therefore, when the mixer 45 rotates, the connecting rod 47 is around the virtual rotation center. Is revolved at a predetermined peripheral speed. Thereby, since it can suppress that polymer, such as polylactic acid, adheres to the connecting rod 47, thermal decomposition of the polymer is suppressed, and high-quality polylactic acid with little coloring and high molecular weight can be produced. .

  Further, since the supply port 42 is positioned below the liquid level 38 of the reaction solution, the supply port 42 is pushed out without causing any disturbance in the flow of the reaction solution in the horizontal container 41 when the reaction solution is supplied. Realizes flow and prevents backflow. Thereby, since the increase in the residence time of the polymer can be suppressed, the thermal decomposition of the polymer can be suppressed, and high-quality polylactic acid with little coloring and high molecular weight can be produced.

  On the other hand, during operation of the devolatilizer 8, the mixer 45 is operated by the drive motor 49 to stir polylactic acid in a molten state, the degassing valve 35 is opened, and the vacuum pump 36 is operated. The inside of the horizontal container 41 becomes a negative pressure environment, and unreacted lactide contained in polylactic acid is devolatilized. Unreacted lactide devolatilized from the polylactic acid is sent to the recovery container 37 through the deaeration port 44. The collection container 37 can collect the cooled and solidified lactide in powder form by cooling the container with a known cooling means. Further, in place of the cooling means, for example, by using the recovery container 37 as a solvent tank, the volatile substance can be precipitated and recovered. The lactide recovered in this way is sent to the production process by a predetermined transportation means (air conveyance or the like), for example, and reused as a raw material lactide. The exhaust gas after the lactide is removed is discharged out of the system through the vacuum pump 36.

  The polylactic acid purified by the devolatilizer 8 is continuously discharged by the liquid feed pump 15 with the valve 22 opened. As the liquid feed pump 15, an extraction screw, a gear pump, or the like can be selected according to the viscosity of the reaction liquid. The discharged polylactic acid is usually subjected to water cooling and pelletizing with a chip cutter.

  The lactide supply device 1, lactide melting device 2, catalyst supply device 3, polymerization initiator supply device 4, lactide supply device 5, horizontal reaction vessel 6, vertical reaction vessel 7, and devolatilizer 8 are each supplied with nitrogen gas. A nitrogen gas supply pipe and an exhaust pipe for purging the inside are installed. This is to prevent scorching of the reaction solution due to the presence of oxygen. The operation of the process should basically be started after a nitrogen purge of all equipment in the process. The lactide supply device 1, the lactide melting device 2, the catalyst supply device 3, the polymerization initiator supply device 4, the lactide supply device 5, the horizontal reaction tank 6, and the vertical reaction tank 7 are operated at a pressure of about atmospheric pressure. This is to reduce the volatilization of the molten lactide.

  As described above, according to the present example, the coloration of the polymer can be suppressed when removing unreacted monomers contained in the polymer such as polylactic acid produced by the ring-opening polymerization reaction. Moreover, as a polymer produced | generated by other polymerization reaction, when removing the solvent etc. which are contained in a polymer also produced | generated by the solvent polymerization reaction, for example, coloring of a polymer can be suppressed.

BRIEF DESCRIPTION OF THE DRAWINGS It is a general view explaining the manufacturing process of the polylactic acid formed by applying this invention. It is sectional drawing of the devolatilization apparatus of the polylactic acid formed by applying this invention.

Explanation of symbols

6 horizontal reaction tank 7 vertical reaction tank 8 devolatilizer 36 vacuum pump 37 recovery container 41 horizontal container 42 supply port 43 discharge port 44 deaeration port 45 mixer 46 stirring rod 47 connecting rod

Claims (7)

A polyhydroxycarboxylic acid obtained by ring-opening polymerization reaction of a cyclic dimer of hydroxycarboxylic acid is stirred in a molten state, and an unreacted cyclic dimer residue under a pressure lower than that during the ring-opening polymerization reaction In the method for producing a polymer for removing devolatilization
The ring-opening polymerization reaction includes a horizontal reaction tank that contains a stirring body having a stirring shaft that is disposed horizontally with respect to the ground, and a supply port that is formed on one end side of the horizontal reaction tank and supplies a reactant. A horizontal polymerization vessel comprising a discharge port formed on the other end side of the horizontal reaction tank and discharging the reactant, and one or more weirs installed in the horizontal reaction tank. A vertical reaction tank that houses a stirring shaft that is arranged perpendicular to the ground, a supply port that is formed on the upper end side of the vertical reaction tank and that supplies a reactant, and the vertical reaction tank. A vertical polymerization vessel formed on the lower end side of the mold reaction vessel and having a discharge port for discharging the reactant to be reacted using a plurality of serial polymerization vessels arranged in the last stage Done
The devolatilization is performed by supplying the material to be treated obtained by the ring-opening polymerization reaction from a supply port on one end of a horizontal tank, and connecting a plurality of rod-shaped rectangular frames in the longitudinal direction of the tank to perform virtual rotation. A stirring body that does not have a stirring shaft in the center is rotated in the tank circumferential direction in the tank, and the material to be processed is discharged from the discharge port on the other end side, and devolatilization above the melt surface of the material to be processed A method for producing a polymer, which is continuously performed by discharging a devolatilizing gas from a mouth.   At least one of an agent that deactivates the catalyst of the ring-opening polymerization reaction or an agent that reduces thermal degradation of the material to be treated is added to the material to be treated after the ring-opening polymerization reaction and before the devolatilization and removal. The method for producing a polymer according to claim 1.   The devolatilization gas discharged from the devolatilization port is condensed or solidified and recovered, and the recovered material is returned to the ring-opening polymerization reaction step or the step before it and reused. The method for producing a polymer according to claim 1 or 2. A polyhydroxycarboxylic acid obtained by ring-opening polymerization reaction of a cyclic dimer of hydroxycarboxylic acid is stirred in a molten state, and an unreacted cyclic dimer residue under a pressure lower than that during the ring-opening polymerization reaction In a polymer production apparatus for removing devolatilization,
The apparatus for performing the ring-opening polymerization reaction includes a horizontal reaction tank in which a stirring body having a stirring shaft disposed horizontally with respect to the ground is housed, and a reactant to be formed formed on one end side of the horizontal reaction tank. A horizontal type configured to include a supply port, a discharge port formed at the other end of the horizontal reaction tank to discharge the reactant, and one or more weirs installed in the horizontal reaction tank A vertical reaction vessel in which a polymerization vessel is arranged in the first stage and houses a stirring shaft arranged perpendicular to the ground, and a supply port that is formed on the upper end side of the vertical reaction vessel and supplies a substance to be reacted And a plurality of serial polymerizers arranged in the last stage, the vertical polymerizer formed on the lower end side of the vertical reaction tank and having a discharge port for discharging the reactants Consists of
The apparatus for performing devolatilization is a horizontal stirring tank, a stirring body housed in the stirring tank and rotatably supported in the circumferential direction of the tank, and formed on one end side of the stirring tank and the ring-opening polymerization A supply port for supplying the material to be treated obtained by the reaction, a discharge port for discharging the material to be treated formed on the other end side of the stirring tank, and a melt surface of the material to be treated in the stirring tank A devolatilization port for discharging devolatilized gas formed above, a recovery container connected to the devolatilization port to condense or solidify and recover the devolatilized gas, and a tank connected to the recovery container A vacuum pump for reducing the pressure inside,
The said stirring body is formed by connecting several rod-shaped rectangular frames to the longitudinal direction of a tank, and does not have a stirring axis in the virtual rotation center, The polymer manufacturing apparatus characterized by the above-mentioned.   The apparatus for producing a polymer according to claim 4, wherein the supply port and the discharge port formed in the agitation tank are disposed below the melt surface of the substance to be treated.   At least one of an agent that deactivates the catalyst of the ring-opening polymerization reaction or an agent that reduces thermal degradation of the material to be treated is added to the material to be treated after the ring-opening polymerization reaction and before the devolatilization and removal. The apparatus for producing a polymer according to claim 4 or 5, further comprising means.   The polymer production according to any one of claims 4 to 6, further comprising means for returning the substance collected in the collection container to a plurality of ring-opening polymerization steps by the polymerization vessel or a step prior thereto. apparatus.

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