JP2016166303A - Method for manufacturing branched polymer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a branched polymer having high melt viscosity.SOLUTION: A method for manufacturing a branched polymer includes: a polymerization step of causing an initiator having three or more hydroxyl groups at a terminal, a ring-opening polymerizable monomer and compressive fluid to have contact so as to ring-opening polymerize the ring-opening polymerizable monomer; a step of removing the compressive fluid while maintaining polymerization temperature so as to maintain in a state of normal pressure; and a step of taking out a product material from the state of normal pressure.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method for producing a branched polymer.

General-purpose resins made from petroleum, such as polyethylene, polypropylene, polyvinyl chloride, and polystyrene, are lightweight and have good processability, physical properties, and durability. Used in various fields such as building materials and food packaging.
However, these resin products have a disadvantage of good durability at the stage of finishing and discarding their functions, and are inferior in degradability in nature, and thus may affect the ecosystem.

  In order to solve such problems, biodegradable polyesters starting from renewable resources, represented by polylactic acid, which is a thermoplastic resin and biodegradable, are currently being widely developed.

  As a method for polymerizing a biodegradable polyester, for example, polylactic acid is produced by ring-opening polymerization of a ring-opening polymerizable monomer typified by lactide. As a method for producing a polymer by ring-opening polymerization of such a ring-opening polymerizable monomer, melt polymerization in which the ring-opening polymerizable monomer is reacted in a molten state, solution polymerization in which polymerization is performed in an organic solvent, and the like are known. .

  Most of these biodegradable polyesters that have been studied for practical use are linear polymers composed of hydroxy fatty acids or combinations of dicarboxylic acids and diols. Among them, polylactic acid is attracting attention as an alternative to existing petroleum-derived plastics because its mechanical strength is similar to that of existing plastics.

  However, biodegradable polyesters have a limited variety of monomer structures and are currently forced to be restricted in use due to lack of strength and heat resistance. In addition, polylactic acid has the disadvantages of high crystallinity and brittleness, is limited to the field of hard molded products, and has a problem that the melt viscosity of the polymer is insufficient. Because there are times, it is not used very much at present. For the above reasons, there are restrictions on the use of the biodegradable polyester alone.

In addition, in order to increase the melt viscosity, as an attempt to polymerize a ring-opening polymerizable monomer and obtain a high molecular weight polymer, a method of performing ring-opening polymerization by melting lactide in an organic solvent has been proposed (for example, Patent Document 1). According to this proposed method, linear poly-D-lactic acid having a molecular weight of 200,000 or more is obtained at a polymer conversion of 99.4% by polymerizing D-lactide in a dichloromethane solution.
However, since this polymer production method uses an organic solvent harmful to the human body and the environment, there is a problem in safety.

Accordingly, a ring-opening polymerization method of a ring-opening polymerizable monomer using a compressible fluid as a solvent in the presence of a metal catalyst has been proposed as an alternative to an organic solvent. According to this proposed method, linear poly-L-lactic acid having a weight average molecular weight of 200,000 or more at a pressure of 15 MPa and a temperature of 150 ° C. is obtained by polymerizing L-lactide in supercritical carbon dioxide ( For example, see Patent Document 2).
However, this proposed method can obtain a high molecular weight without using an organic solvent. On the other hand, since it is a linear polymer, its melt viscosity is insufficient, so that it can be used in soft and semi-rigid fields. There are still challenges.

  The subject of this invention is made | formed in view of the problem in the above prior art, and is providing the manufacturing method of the branched polymer which has high melt viscosity.

  The method for producing a branched polymer according to the present invention for solving the above-described problems is obtained by bringing an initiator having three or more hydroxyl groups at a terminal, a ring-opening polymerizable monomer, and a compressive fluid into contact with each other. A ring-opening polymerization of the polymerizable monomer, a step of removing the compressive fluid while maintaining the polymerization temperature and maintaining at a normal pressure, and a step of removing the product from the normal pressure. Features.

  According to the present invention, the conventional problems can be solved, and a branched polymer product having a high melt viscosity can be provided.

It is a phase diagram which shows the state of the substance with respect to temperature and pressure. It is a phase diagram for defining the range of compressible fluid. It is a systematic diagram showing an example of a continuous polymerization process. It is a systematic diagram showing an example of a continuous polymerization process. It is a systematic diagram showing an example of a batch type polymerization process. It is a systematic diagram showing an example of a batch type polymerization process.

  As a result of intensive research, the inventors of the present invention have made a polymerization reaction (ring-opening polymerization reaction) at each terminal hydroxyl group by reacting an initiator having three or more hydroxyl groups at the terminal with a ring-opening polymerizable monomer in a compressive fluid. ) Was found to proceed evenly. Finally, the polymerization reaction was advanced to normal pressure at the end of the polymerization, thereby succeeding in obtaining a branched polymer having a high melt viscosity.

  That is, the method for producing a branched polymer according to the present invention comprises contacting an initiator having three or more hydroxyl groups at the terminal, a ring-opening polymerizable monomer, and a compressive fluid to open the ring-opening polymerizable monomer. It comprises a polymerization step for polymerization, a step for removing the compressive fluid while maintaining the polymerization temperature and maintaining it at normal pressure, and a step for removing the product from the normal pressure state. .

  The production method of the polymer product of the present invention includes at least a polymerization step, a step of removing the compressive fluid while maintaining the polymerization temperature and maintaining at a normal pressure, and a removal step. These steps may be included.

  In the polymerization step, the ring-opening polymerizable monomer is opened by bringing at least an initiator (polyfunctional initiator) having three or more hydroxyl groups at the terminal, a ring-opening polymerizable monomer, and a compressive fluid into contact with each other. Polymerize.

  In the step of removing the compressive fluid while maintaining the polymerization temperature and maintaining it at normal pressure, the pressure of the compressive fluid in the reaction system is gradually released while maintaining the polymerization temperature, Put it in a state. In the step of removing the compressive fluid while maintaining the polymerization temperature and maintaining the pressure at normal pressure, the pressure gradually decreases, so that the ring-opening polymerization reaction proceeds. The release rate of the pressure can be appropriately selected according to the purpose, but in order to improve the melt viscosity of the polymer, 0.1 MPa / min or less is preferable, 0.05 MPa / min is more preferable, and 0 0.02 MPa / min or less is more preferable.

The above-mentioned holding of the polymerization temperature means holding within 2 ° C. from the polymerization temperature, preferably within 1 ° C., and more preferably within 0.5 ° C.
Moreover, the normal pressure mentioned above shows the state equal to atmospheric pressure. Although the polymerization reaction time after making it normal pressure can be suitably selected according to reaction conditions, 5 to 120 minutes are preferable, 5 to 60 minutes are more preferable, and 5 to 30 minutes are more preferable. If the polymerization reaction time after the normal pressure exceeds 120 minutes, the polymer may be thermally decomposed if the temperature is high.

  In the present invention, a branched polymer having a high melt viscosity is obtained by performing a polymerization reaction in the polymerization step and the subsequent step of removing the compressive fluid while maintaining the polymerization temperature and maintaining the pressure at normal pressure. However, no detailed clarification has been made as to why a branched polymer having a high melt viscosity can be obtained. In addition to obtaining a uniform branched structure probably due to the plasticizing effect of the polymer by the compressive fluid, the polymer concentration is reduced in the subsequent process of removing the compressive fluid while maintaining the polymerization temperature and maintaining it at normal pressure. This is considered to be due to the fact that the reaction proceeds further and the molecular weight is increased).

  The branched polymer (polymer product) in the present invention refers to a polymer having a branched structure, and specifically refers to a polymer having a multi-branched structure. The branched structure is, for example, radially from the central core. Examples include a star polymer having a plurality of linear segments as branched chains, and a graft polymer having a structure in which a branching polymer is introduced from the branched linear polymer chain. . Branched polyester is one type of branched polymer. These branched polymers may be used alone or in combination of two or more.

  The average degree of branching of the polymer product is not particularly limited and may be appropriately selected depending on the intended purpose, but is preferably 2.1 or more, more preferably 2.5 or more, and particularly preferably 3.0 or more. . When the average degree of branching is less than 2.1, the branch density of the polymer product is lowered, and the melt viscosity may be lowered.

The polymer product has a weight average molecular weight (Mw) measured by gel permeation chromatography of 200,000 or more, preferably 300,000 or more, and more preferably 400,000 or more. When the weight average molecular weight is less than 200,000, the mechanical strength becomes insufficient. The upper limit of the weight average molecular weight (Mw) is not particularly limited, but is preferably 1,000,000 or less, and more preferably 600,000 or less, from the viewpoint of moldability. As a measuring method of the weight average molecular weight in a polymer product, the method as described in the below-mentioned Example is mentioned.
In addition, according to the present invention, a branched polymer having a large weight average molecular weight (200,000 or more) can be obtained. This large weight average molecular weight is obtained by maintaining the polymerization temperature after the aforementioned polymerization step. This is probably due to the fact that the polymer concentration is increased by the process of removing the sex fluid and maintaining it at normal pressure, and the reaction proceeds further.

  The molecular weight distribution (Mw / Mn) obtained by dividing the weight average molecular weight (Mw) of the polymer product by the number average molecular weight (Mn) is not particularly limited and can be appropriately selected according to the purpose. 1.0 or more and 2.5 or less are preferable, and 1.2 or more and 2.0 or less are more preferable. When the molecular weight distribution (Mw / Mn) exceeds 2.5, the low molecular weight component increases and the mechanical strength may decrease. Examples of the method for measuring the molecular weight distribution in the polymer product include the methods described in Examples below.

  The content of the residual monomer in the polymer product is not particularly limited and may be appropriately selected depending on the intended purpose, but is preferably 5,000 ppm or less, more preferably 2,000 ppm or less, and 1,000 ppm or less. Is particularly preferred. The residual monomer contained in the polymer product includes an unreacted ring-opening polymerizable monomer as a raw material and a ring-opening polymerizable monomer generated by a depolymerization reaction. When the content of the residual monomer exceeds 5,000 ppm, the thermal characteristics and durability of the polymer product may be insufficient. Examples of the method for measuring the content of the residual monomer include the methods described in Examples below.

  The polymer product may or may not contain an organic solvent. The organic solvent is an organic solvent used as a reaction field that is liquid at normal temperature and does not chemically react with a solute. When the polymer product is polylactic acid obtained by a ring-opening polymerization reaction, examples of the organic solvent include chloroform, methylene chloride, toluene, tetrahydrofuran, and the like. “Substantially no organic solvent” means that the content of the organic solvent in the polymer product measured by the following measurement method is specifically less than the detection limit (5 ppm). It is preferable to use a compressive fluid (for example, supercritical carbon dioxide) alone as a solvent without using the organic solvent, from the viewpoint of safety and stability. However, the organic solvent as an entrainer and supercritical dioxide are preferable. Carbon can also be used in combination.

Next, the method for producing a branched polymer according to the present invention will be described in more detail.
Although the embodiments described below are preferred embodiments of the present invention, various technically preferable limitations are applied, but the scope of the present invention is limited to the following description. Unless otherwise described, the present invention is not limited to these embodiments.

  In the present invention, when the polymer product is a star polymer, an arm-first method and a core in which a linear segment to be a branched chain is synthesized and then grafted to the core are used. Any of the co-first methods for synthesizing a straight-chain segment to be a branched chain after synthesizing a polyfunctional initiator as a component to be used.

  Since the polymer product has a high molecular weight, when the polymer product is produced, the polymer product can be smoothly taken out by using an extrusion means in the production apparatus for producing the polymer product. it can.

〔raw materials〕
First, components such as a ring-opening polymerizable monomer, a raw material such as an initiator, and a catalyst used for the production of the above polymer product will be described. In this embodiment, the raw material is a material from which a polymer is produced, and includes a ring-opening polymerizable monomer and an initiator, and further includes optional components such as additives as necessary.
Here, the compressible fluid is also described.

There is no restriction | limiting in particular as a monomer used as the raw material of the said polymer product, Although it can select suitably according to the objective, It is preferable that it is a ring-opening polymerizable monomer.
The ring-opening polymerizable monomer can be appropriately selected according to the purpose, but is preferably a ring-opening polymerizable monomer having a carbonyl group in the ring. The carbonyl group is formed by π-bonding oxygen with high electronegativity to carbon. In the carbonyl group, π bond electrons are attracted, whereby oxygen is negatively polarized and carbon is positively polarized. Therefore, the carbonyl group is highly reactive. In addition, when the compressive fluid is carbon dioxide, the carbonyl group is similar to the structure of carbon dioxide, so it is presumed that the affinity between the carbon dioxide and the produced polymer product is increased. By these actions, the effect of plasticizing the produced polymer by the compressive fluid is enhanced. The ring-opening polymerizable monomer having a carbonyl group in the ring is more preferably a ring-opening polymerizable monomer having an ester bond (ring-opening polymerizable cyclic ester).

<Monomer>
Examples of the ring-opening polymerizable monomer include cyclic esters.
There is no restriction | limiting in particular as said cyclic ester (ring-opening polymerizable cyclic ester), Although it can select suitably according to the objective, L body and / or D of the compound represented by following General formula (1) A cyclic dimer obtained by dehydrating and condensing the product is preferred.
R-C * -H (-OH) (-COOH) ... General formula (1)
However, in said general formula (1), R represents a C1-C10 alkyl group and "C *" represents an asymmetric carbon.

  Examples of the compound represented by the general formula (1) include an enantiomer of lactic acid, an enantiomer of 2-hydroxybutanoic acid, an enantiomer of 2-hydroxypentanoic acid, and an enantiomer of 2-hydroxyhexanoic acid. , 2-hydroxyheptanoic acid enantiomer, 2-hydroxyoctanoic acid enantiomer, 2-hydroxynonanoic acid enantiomer, 2-hydroxydecanoic acid enantiomer, 2-hydroxyundecanoic acid enantiomer And enantiomers of 2-hydroxydodecanoic acid. Among these, enantiomers of lactic acid are particularly preferable from the viewpoint of reactivity or availability.

<Compressive fluid>
The compressive fluid will be described with reference to FIGS. 1 and 2. FIG. 1 is a phase diagram showing the state of a substance with respect to temperature and pressure. FIG. 2 is a phase diagram for defining the range of the compressible fluid.
The “compressible fluid” is a fluid in the phase diagram shown in FIG. 1 when it exists in any of the regions (1), (2), and (3) shown in FIG. Means.

  In such a region, it is known that the substance has a very high density and behaves differently from that at normal temperature and pressure. In addition, when a substance exists in the area | region of (1), it becomes a supercritical fluid. A supercritical fluid is a fluid that exists as a non-condensable high-density fluid in a temperature and pressure region that exceeds the limit (critical point) at which gas and liquid can coexist, and does not condense even when compressed. Further, when the substance is present in the region (2), it becomes a liquid, but in the present invention, it is obtained by compressing a substance that is in a gaseous state at normal temperature (25 ° C.) and normal pressure (1 atm). Represents liquefied gas. Further, when the substance is present in the region (3), it is in a gaseous state, but in the present invention, it represents a high-pressure gas whose pressure is 1/2 (1/2 Pc) or more of the critical pressure (Pc).

  Examples of the substance constituting the compressive fluid include carbon monoxide, carbon dioxide, dinitrogen monoxide, nitrogen, methane, ethane, propane, 2,3-dimethylbutane, and ethylene. Among these, carbon dioxide is preferable in that it has a critical pressure of about 7.4 MPa and a critical temperature of about 31 ° C., can easily create a supercritical state, and is nonflammable and easy to handle. These compressive fluids may be used alone or in combination of two or more.

<Initiator (multifunctional initiator)>
The polyfunctional initiator is not particularly limited as long as it is an initiator that gives a branched structure to the polymer product, and can be appropriately selected according to the purpose, but a polyhydric alcohol is preferable. What is necessary is just to adjust suitably the usage-amount of the said initiator according to the target molecular weight, and 0.1 mol%-5 mol% are preferable with respect to 100 mol% of the said ring-opening polymerizable monomers. In order to prevent the polymerization from starting inhomogeneously, it is preferable to mix the monomer and the initiator well before the monomer contacts the catalyst.

-Polyhydric alcohol-
Examples of the polyhydric alcohol include dihydric or higher alcohols, trihydric or higher alcohols, and among these, trihydric or higher alcohols are preferable. Examples of the trivalent or higher alcohol include trivalent or higher alcohol having 3 to 24 carbon atoms, and a castor oil-based polyol obtained by modifying a raw material derived from castor oil. Examples of the castor oil-based polyol include URIC H series manufactured by Ito Seiyaku Co., Ltd.
Further, a polymer having a plurality of hydroxyl groups may be used as the polyfunctional initiator. Examples of such a polymer include polymethacrylic acid derivatives having a hydroxyl group such as polyvinyl alcohol and poly (2-hydroxyethyl methacrylate).

The graft copolymer is a polymer that takes a form in which other polymers are arranged like branches in some places in the main copolymer, but the polymer having a plurality of hydroxyl groups as the polyfunctional initiator is used as the main polymer. In this case, the copolymer can be said to be a graft copolymer.
The polymer used as a trunk can also be expected to have a plasticizing effect depending on the compressible fluid selected. In the case of polyvinyl alcohol, a combination of dimethyl ether having an ether bond and in the case of polyhydroxymethacrylate 2-hydroxyethyl, a combination of carbon dioxide and the like is preferable. Moreover, you may copolymerize the copolymerization component in consideration of compatibility with a compressive fluid.

  Examples of the trivalent or higher alcohol having 3 to 24 carbon atoms include 1,2,4-butanetriol, 1,2,5-pentanetriol, 1,2,6-hexanetriol, 1,2,3. , 6-hexanetetrol, glycerin, diglycerin, triglycerin, tetraglycerin, pentaglycerin, hexaglycerin, triethanolamine, trimethylolethane, trimethylolpropane, ditrimethylolpropane, tritrimethylolpropane, 2-methylpropanetriol, 2-methyl-1,2,4-butanetriol, pentaerythritol, dipentaerythritol, tripentaerythritol, methylglucoside, sorbitol, mannitol, sucrose, 1,3,5-trihydroxybenzene, 1,2,4-trihydro Shibenzen and the like.

Among these, castor oil-based polyol, glycerin, diglycerin, trimethylolpropane, ditrimethylolpropane, pentaerythritol, and dipentaerythritol are preferable from the viewpoint of mechanical properties of the polymer product to be obtained, but not limited thereto.
Moreover, these polyfunctional initiators may be used individually by 1 type, and may use 2 or more types together.

  The polymer product is preferably formed by ring-opening polymerization of the ring-opening polymerizable cyclic ester using the polyhydric alcohol as an initiator.

<Other ingredients>
There is no restriction | limiting in particular as another component used when manufacturing the said polymer product, According to the objective, it can select suitably, For example, a catalyst, an additive, etc. are mentioned.

-Catalyst-
There is no restriction | limiting in particular as said catalyst, According to the objective, it can select suitably, A metal catalyst is used preferably.

--Metal catalyst--
The metal catalyst is not particularly limited and may be appropriately selected depending on the intended purpose. Examples thereof include tin compounds, aluminum compounds, titanium compounds, zirconium compounds, and antimony compounds.
Examples of the tin compound include tin octylate, tin dibutyrate, and di (2-ethylhexanoic acid) tin.
Examples of the aluminum compound include aluminum acetylacetonate and aluminum acetate.
Examples of the titanium compound include tetraisopropyl titanate and tetrabutyl titanate.
Examples of the zirconium-based compound include zirconium isoprooxide.
Examples of the antimony compound include antimony trioxide.

  The type and amount used of the catalyst vary depending on the combination of the compressive fluid and the ring-opening polymerizable monomer, and thus cannot be specified unconditionally. In the case of the metal catalyst, the amount used is the ring-opening polymerizable monomer. 0.001 mol% to 0.1 mol% is preferable with respect to 100 mol%, and 0.003 mol% to 0.01 mol% is more preferable. If the amount used is less than 0.001 mol%, the catalyst may be deactivated before the polymerization reaction is completed, and a polymer product having a target molecular weight may not be obtained. On the other hand, if the amount used exceeds 0.1 mol%, it may be difficult to control the polymerization reaction.

-Additives-
In the polymerization step, an additive may be added as necessary. Examples of the additive include a surfactant and an antioxidant.

--Surfactant--
As the surfactant, those that melt into the compressive fluid and have affinity for both the compressive fluid and the ring-opening polymerizable monomer are preferably used. By using such a surfactant, the polymerization reaction can be promoted uniformly, and a product having a narrow molecular weight distribution can be obtained, and effects such as easy to obtain a particulate polymer product can be expected. When the surfactant is used, it may be added to the compressive fluid or to the ring-opening polymerizable monomer. For example, when carbon dioxide is used as the compressive fluid, a surfactant having a parent carbon dioxide group and a parent monomer group in the molecule is used. Examples of such a surfactant include a fluorine-based surfactant and a silicone-based surfactant.

--Antioxidant--
As the antioxidant, 2,6-di-t-butyl-4-methylphenol, butylhydroxyanisole and the like are used.

  Although the compounding quantity of the said additive changes with purposes and the kind of additive to add, Preferably it is 0 to 5 mass parts with respect to 100 mass parts of polymer compositions.

[Continuous polymerization reactor]
Subsequently, an example of a polymerization reaction apparatus used for producing the polymer product will be described with reference to FIGS. 3 and 4. 3 and 4 are system diagrams showing an example of the polymerization process.
Here, the polymerization reaction apparatus 100 will be described with reference to FIG. 3, but the polymerization reaction apparatus in FIG. 4 is changed to the metering pump 14 shown in FIG. 3 to change the pressure in the reaction unit 13 and the delivery amount of the polymer product. The same applies except that the pressure adjusting valve 16 for adjusting is used.

  The polymerization reaction apparatus 100 includes a supply unit 100a that supplies raw materials such as a ring-opening polymerizable monomer and a compressive fluid, and a polymerization reaction as an example of a polymer manufacturing apparatus that polymerizes the ring-opening polymerizable monomer supplied by the supply unit 100a. And an apparatus main body 100b. The supply unit 100a has a tank (1, 3, 5, 7, 11), a measuring feeder (2, 4), and a measuring pump (6, 8, 12). The polymerization reaction apparatus main body 100b is connected to the contact portion 9 provided at one end of the polymerization reaction apparatus main body 100b, the liquid feed pump 10, the reaction section 13, the metering pump 14, and the other end of the polymerization reaction apparatus main body 100b. And an extrusion die 15 provided.

  The tank 1 of the supply unit 100a stores a ring-opening polymerizable monomer. The ring-opening polymerizable monomer to be stored may be a powder or a liquid state. The tank 3 stores a solid (powder or granular) material among the initiator, the catalyst, and the additive. The tank 5 stores a liquid one of the initiator, the catalyst, and the additive. Alternatively, a new tank can be installed in parallel with the tank 5 to store the initiator or the solid or liquid of the catalyst and additive. The tank 7 stores a compressible fluid. The tank 7 may store a gas (gas) or a solid that becomes a compressible fluid in the process of being supplied to the contact portion 9 or heated or pressurized in the contact portion 9. In this case, the gas or solid stored in the tank 7 is heated or pressurized to be in the state (1), (2), or (3) in the phase diagram of FIG. .

  The metering feeder 2 measures the ring-opening polymerizable monomer stored in the tank 1 and continuously supplies it to the contact unit 9. The weighing feeder 4 measures the solid stored in the tank 3 and continuously supplies it to the contact portion 9. The metering pump 6 measures the liquid stored in the tank 5 and continuously supplies it to the contact portion 9. The metering pump 8 continuously supplies the compressive fluid stored in the tank 7 to the contact portion 9 at a constant pressure and flow rate. In the present embodiment, continuous supply is a concept for a method of supplying batch by batch, and is supplied so that a polymer product obtained by ring-opening polymerization of a ring-opening polymerizable monomer is continuously obtained. It means to do. That is, each material may be supplied intermittently or intermittently as long as a polymer product obtained by ring-opening polymerization of the ring-opening polymerizable monomer is continuously obtained. In addition, when both the initiator and the additive are solid, the polymerization reaction apparatus 100 may not include the tank 5 and the metering pump 6. Similarly, when both the initiator and the additive are liquid, the polymerization reaction apparatus 100 may not include the tank 3 and the metering feeder 4.

  In the present embodiment, the polymerization reaction apparatus main body 100b has a monomer introduction port for introducing a ring-opening polymerizable monomer at one end and a polymer produced by polymerizing the ring-opening polymerizable monomer at the other end. It is a tubular device having a discharge port for discharging an object. Further, one end of the polymerization reaction apparatus main body 100b further has a compressive fluid inlet for introducing a compressive fluid, and a catalyst inlet for introducing a catalyst is provided between the one end and the other end. Have. Each apparatus of the polymerization reaction apparatus main body 100b is connected as shown in FIG. 3 by a pressure-resistant piping 30 for transporting raw materials, a compressive fluid, or a generated polymer product. Each device of the contact portion 9 of the polymerization reaction device, the liquid feed pump 10 and the reaction portion 13 has a tubular member through which the above raw materials and the like pass.

  The contact portion 9 of the polymerization reaction apparatus main body 100b includes raw materials such as ring-opening polymerizable monomers, initiators and additives supplied from the tanks (1, 3, 5), and a compressive fluid supplied from the tank 7. Are continuously contacted to form a pressure-resistant apparatus or tube for mixing raw materials (for example, melting or dissolving a ring-opening polymerizable monomer and an initiator). In this embodiment, “melting” means a state in which a raw material or a produced polymer product comes into contact with a compressive fluid and is plasticized or liquefied while swelling. Further, “dissolving” means that the raw material is dissolved in the compressive fluid.

  When the ring-opening polymerizable monomer is dissolved, a fluid phase is formed, and when it is melted, a molten phase is formed, but in order to proceed the reaction uniformly, either a molten phase or a fluid phase is formed. It is preferable. Moreover, it is preferable to melt the ring-opening polymerizable monomer in order to advance the reaction in a state where the ratio of the raw materials to the compressive fluid is high. In this embodiment, by continuously supplying the raw material and the compressive fluid, the raw material such as the ring-opening polymerizable monomer and the compressive fluid are continuously contacted at a constant concentration ratio in the contact portion 9. Can be made. Thereby, the raw materials can be efficiently mixed (for example, the ring-opening polymerizable monomer and the branched monomer are melted or dissolved).

  The contact portion 9 may be constituted by a tank-type device or a cylinder-type device, but a cylinder that supplies raw materials from one end and takes out a mixture such as a molten phase or a fluid phase from the other end. A mold is preferred. Furthermore, the contact part 9 may have a stirring device that stirs the raw material, the compressive fluid, and the like. A plurality of stirring devices may be provided. When the contact portion 9 has a stirring device, the stirring device includes a single-screw, a twin-screw that meshes with each other, a twin-screw mixer that has a large number of meshing elements that mesh or overlap each other, and a helical stirring element that meshes with each other. A kneader having a static mixer, a static mixer or the like is preferably used. In particular, a biaxial or multiaxial agitation device that meshes with each other is preferable because there is little adhesion of reactants to the agitation device or the container and there is a self-cleaning action. When the contact part 9 does not have a stirrer, the contact part 9 is preferably constituted by a part of the pressure-resistant piping 30. In addition, when the contact part 9 is comprised by the piping 30, in order to mix each material in the contact part 9 reliably, it is preferable that the ring-opening polymerizable monomer supplied to the contact part 9 is liquefied beforehand. .

  In the contact portion 9, an inlet 9 a as an example of a compressive fluid inlet for introducing the compressive fluid supplied from the tank 7 by the metering pump 8, and ring-opening polymerizability supplied from the tank 1 by the metering feeder 2. An introduction port 9b as an example of a monomer introduction port for introducing the monomer, an introduction port 9c for introducing the powder supplied from the tank 3 by the metering feeder 4, and an introduction for introducing the liquid supplied from the tank 5 by the metering pump 6 A mouth 9d is provided. In the present embodiment, each introduction port (9a, 9b, 9c, 9d) receives a tubular member such as a cylinder or a part of the pipe 30 for supplying raw materials and the like at the contact portion 9, and each raw material or compressive fluid. It consists of a joint that connects each pipe to be transported. This joint is not particularly limited, and known joints such as reducers, couplings, Y, T, and outlets are used. Moreover, the contact part 9 has the heater 9e for heating each supplied raw material and compressive fluid.

  The liquid feed pump 10 sends a mixture such as a molten phase or a fluid phase formed in the contact portion 9 to the reaction portion 13. The tank 11 stores a catalyst. The metering pump 12 measures the catalyst stored in the tank 11 and supplies it to the reaction unit 13.

  The reaction unit 13 mixes each raw material fed by the liquid feed pump 10 with the catalyst supplied by the metering pump 12, and a pressure-resistant apparatus or tube for ring-opening polymerization of the ring-opening polymerizable monomer. Etc. Although the reaction part 13 may be comprised by the tank type apparatus or the cylinder type apparatus, the cylinder type with few dead spaces is preferable. Furthermore, the reaction unit 13 may have a stirring device that stirs the raw materials, the compressive fluid, and the like. As a stirring device of the reaction unit 13, a twin shaft having screws that mesh with each other, a stirring element such as a 2-flight (oval) or a 3-flight (triangular shape), a disc or a multi-lobed (clover-shaped) stirring blade. Or the thing of a multi-axis is preferable from a viewpoint of self-cleaning.

In the case where the raw materials including the catalyst are sufficiently mixed in advance, a static mixer that performs multi-stage splitting and combining (merging) of the flow by the guide device can also be applied to the stirring device. Static mixers disclosed in Japanese Patent Publication No. 47-15526, Japanese Patent Publication No. 47-15527, Japanese Patent Publication No. 47-15528, Japanese Patent Publication No. 47-15533, etc. (multilayer mixer) And those disclosed in Japanese Patent Application Laid-Open No. 47-33166 (Kenix type) and similar mixing devices having no moving parts.

When the reaction unit 13 does not have a stirring device, the reaction unit 13 is configured by a part of the pressure-resistant piping 30. In this case, the shape of the piping is not particularly limited, but a spiral shape is preferably used in order to make the apparatus compact. Moreover, there is no limitation in particular about the diameter of piping, What is necessary is just to use properly by a use.

  The reaction unit 13 includes an introduction port 13 a for introducing the raw material mixed in the contact unit 9 and an introduction port 13 b as an example of a catalyst introduction port for introducing the catalyst supplied from the tank 11 by the metering pump 12. Is provided. In this embodiment, each inlet (13a, 13b) is a pipe member for supplying each raw material or compressive fluid, and a tubular member such as a cylinder or a part of the pipe 30 through which the raw material passes in the reaction section 13. It is comprised by the coupling which connects. This joint is not particularly limited, and known joints such as reducers, couplings, Y, T, and outlets are used. In addition, the reaction part 13 may be provided with a gas outlet for removing evaporated substances. Moreover, the reaction part 13 has the heater 13c for heating the sent raw material.

  Although FIG. 3 shows an example in which the reaction unit 13 is one, the polymerization reaction apparatus 100 may have two or more reaction units 13. In the case of having a plurality of reaction parts 13, the reaction (polymerization) conditions for each reaction part 13, that is, temperature, catalyst concentration, pressure, average residence time, stirring speed, etc. may be the same, It is preferable to select the optimum conditions. In order to increase the reaction time and complicate the apparatus, it is not a good idea to connect too many reaction units 13 in multiple stages, and the number of stages is preferably 1 or more and 4 or less, particularly preferably 1 or more and 3 or less.

  In general, when only one reaction portion is polymerized, the degree of polymerization of the polymer product obtained by polymerizing the ring-opening polymerizable monomer and the amount of residual monomer are unstable and easily fluctuate, which is not suitable for industrial production. It is said that. This seems to be due to instability due to the mixing of raw materials having a melt viscosity of several poise to several tens of poise and polymerized polymer products having a melt viscosity of about 1,000 poise. On the other hand, in this embodiment, since the raw material and the generated polymer product are melted (liquefied), it becomes possible to reduce the viscosity difference in the reaction section 13 (also referred to as a polymerization system). The polymer product can be produced stably even if the number of stages is reduced from that of the polymerization reactor.

  The metering pump 14 sends the polymer product P polymerized in the reaction unit 13 out of the reaction unit 13 from the extrusion die 15. In addition, the polymer product P can also be sent out from the reaction part 13 without using the metering pump 14 by utilizing the pressure difference inside and outside the reaction part 13. In this case, in order to adjust the pressure in the reaction part 13 and the delivery amount of the polymer product P, a pressure adjusting valve 16 can be used as shown in FIG.

  Moreover, the polymerization reaction apparatus main body 100b may have other means. The other means is not particularly limited and may be appropriately selected depending on the purpose. For example, the cooling means used for the cooling treatment (cooling step) of the polymer product, the drying used for the drying treatment (drying step). Means, extrusion means used in the extraction process (extraction process), and the like.

  Extrusion means is means for extruding the polymer product P obtained from the polymerization reaction apparatus main body 100b to the outside. Specific examples include, for example, a pump-type extruder such as a syringe pump and a gear pump, as well as a single-screw extrusion. And special type extruders such as a multi-screw type extruder and a screw type extruder. Among these extrusion apparatuses, a gear pump, a single-screw extruder, and a multi-screw extruder are particularly preferable because stable discharge is possible and there is little shear on the polymer after the polymerization reaction. A plurality of extrusion apparatuses may be provided.

Regarding the process of removing the compressive fluid while maintaining the polymerization temperature, which is a feature of the present invention, and maintaining the pressure at normal pressure, a pressure adjusting valve is provided between the liquid feed pump 10 and the extrusion die port 15 in FIGS. It is installed and gradually depressurized from it at a rate of 0.1 MPa / min or less. The number of valves installed between the liquid feed pump 10 and the extrusion port 15 can be appropriately selected according to the specifications of the apparatus, but 1 to 5 is preferable. In consideration of extruding the polymer product after depressurization, it is preferable to install a pressure adjusting valve in the extruder installed behind the reaction section 13. By having the process of depressurizing over time by the above method, the melt viscosity of the polymer product can be improved.

[First Embodiment]
Subsequently, a continuous production method of the polymer product (first embodiment) using the polymerization reaction apparatus 100 will be described. In this embodiment, the ring-opening polymerizable monomer, the initiator, the compressive fluid, and other components as necessary are continuously supplied and brought into contact with each other to continuously bring the ring-opening polymerizable monomer into contact. The polymer product is continuously obtained by ring-opening polymerization. In this case, first, each metering feeder (2, 4), the metering pump 6, and the metering pump 8 are operated, and the ring-opening polymerizable monomer, initiator, additive in each tank (1, 3, 5, 7), A compressive fluid is continuously supplied to the contact portion 9. When the catalyst is supplied to the contact portion 9, the catalyst may be supplied together with the ring-opening polymerizable monomer, the initiator, the additive, and the compressive fluid, or the catalyst may be supplied sequentially by adding a tank. The catalyst may be added at the reaction unit 13 (post-addition) without being added at the contact unit 9 (pre-addition). In this case, by adding the monomer to the homogeneous phase in a completely melted state, the contact area between the monomer and the catalyst can be increased, so that the effect of improving the polymer conversion rate can be obtained.

  A raw material and a compressive fluid are continuously introduced into the tube of the contact portion 9 from each introduction port (9a, 9b, 9c, 9d). In addition, solid (powder or granular) raw materials may have lower measurement accuracy than liquid raw materials. In this case, the solid raw material may be melted in advance and stored in the tank 5 in a liquid state and introduced into the tube of the contact portion 9 by the metering pump 6. The order in which each metering feeder (2, 4), metering pump 6 and metering pump 8 are operated is not particularly limited, but when the initial raw material is sent to the reaction unit 13 without contacting the compressed fluid, it solidifies due to a decrease in temperature. Therefore, it is preferable to operate the metering pump 8 first.

Each feed rate of each raw material by the metering feeder (2, 4) and metering pump 6 is adjusted to be a constant ratio based on a predetermined ratio of the ring-opening polymerizable monomer, initiator, catalyst and additive. Is done. Total mass of raw materials supplied per unit time by metering feeders (2, 4) and metering pump 6 (feed rate of raw materials (g / min)) is adjusted based on desired polymer properties, reaction time, etc. Is done. Similarly, the mass of the compressive fluid supplied per unit time by the metering pump 8 (supply rate of compressive fluid, (g / min)) is adjusted based on desired polymer properties, reaction time, and the like. The ratio between the supply speed of the compressive fluid and the supply speed of the raw material (the supply speed of the raw material / the supply speed of the compressive fluid, the feed ratio) is not particularly limited and can be appropriately selected according to the purpose. 1 or more is preferable, 3 or more is more preferable, 5 or more is further preferable, and 10 or more is particularly preferable. Moreover, there is no restriction | limiting in particular about the upper limit of feed ratio, Although it can select suitably according to the objective, 1,000 or less are preferable, 100 or less are more preferable, and 50 or less are especially preferable.
In addition, an organic solvent can also be used as an entrainer in the polymerization reaction, which may shorten the reaction time.

  By setting the feed ratio to 1 or more, when each raw material and the compressive fluid are sent to the reaction unit 13, the reaction is performed in a state where the concentration of the raw material and the generated polymer product (so-called solid content concentration) is high. proceed. The solid content concentration in the polymerization system at this time is the solid content concentration of the polymerization system when polymerizing by dissolving a small amount of ring-opening polymerizable monomer in an overwhelming amount of compressive fluid in the conventional production method. Are very different. The production method of this embodiment is characterized in that the polymerization reaction proceeds efficiently and stably even in a polymerization system having a high solid content concentration. In this embodiment, the feed ratio may be less than 1. Even in this case, there is no problem in the quality of the polymer product to be obtained, but the economical efficiency is inferior. On the other hand, if the feed ratio exceeds 1,000, the ability of the compressive fluid to melt the ring-opening polymerizable monomer may be insufficient, and the intended reaction may not proceed uniformly.

  Since each raw material and compressive fluid are continuously introduced into the tube of the contact portion 9, they are in continuous contact with each other. Thereby, in the contact part 9, raw materials, such as a ring-opening polymerizable monomer, an initiator, and an additive, mix. When the contact part 9 has a stirring device, each raw material and compressive fluid may be stirred. In order to prevent the introduced compressive fluid from turning into a gas, the temperature and pressure in the tube of the reaction unit 13 are controlled to a temperature and pressure at least above the triple point of the compressive fluid. In this case, the ring-opening polymerizable monomer and the compressive fluid are preferably contacted at a pressure of 3 MPa or more, and more preferably contacted at a pressure of 7.4 MPa or more. This pressure is controlled by, for example, the pump flow rate, pipe diameter, pipe length, pipe shape, and the like. This control is performed by adjusting the output of the heater 9e of the contact portion 9 or the supply speed of the compressive fluid.

  In the present embodiment, the temperature at which the ring-opening polymerizable monomer is melted may be a temperature equal to or lower than the melting point at normal pressure of the ring-opening polymerizable monomer. This is considered to be due to the high pressure in the contact portion 9 in the presence of the compressive fluid, and the melting point of the ring-opening polymerizable monomer being lower than the melting point at normal pressure. For this reason, even when the amount of the compressive fluid relative to the ring-opening polymerizable monomer is small, the ring-opening polymerizable monomer melts in the contact portion 9.

  You may adjust the timing which adds heat and stirring to each raw material and compressive fluid in the contact part 9 so that each raw material may mix efficiently. In this case, after bringing each raw material and the compressive fluid into contact, heat or stirring may be applied, or heat or stirring may be applied while bringing each raw material into contact with the compressive fluid. Moreover, in order to mix more reliably, for example, after applying heat more than melting | fusing point to a ring-opening polymerizable monomer beforehand, you may make a ring-opening polymerizable monomer and a compressive fluid contact. In the above embodiments, for example, when the contact portion 9 is a biaxial mixing device, the arrangement of the screws, the arrangement of the inlets (9a, 9b, 9c, 9d), and the temperature of the heater 9e are appropriately set. Is realized.

  In this embodiment, the additive is supplied to the contact portion 9 separately from the ring-opening polymerizable monomer, but the additive may be supplied together with the ring-opening polymerizable monomer. Moreover, you may supply an additive after a polymerization reaction. In this case, after taking out the obtained polymer product from the reaction part 13, it can also add, kneading | mixing an additive.

  Each raw material mixed in the contact part 9 is sent by the liquid feed pump 10 and supplied to the reaction part 13 from the inlet 13a. On the other hand, when the catalyst is added later, the catalyst in the tank 11 is measured by the metering pump 12 and supplied to the reaction unit 13 through the introduction port 13b.

  Each raw material and catalyst are heated to a predetermined temperature (polymerization reaction temperature) by the heater 13c while being sufficiently stirred or fed by the stirring device of the reaction unit 13 as necessary. Thereby, the ring-opening polymerizable monomer undergoes ring-opening polymerization in the reaction portion 13 in the presence of the catalyst (polymerization step). The polymerization reaction temperature is not particularly limited and may be appropriately selected depending on the intended purpose, but is preferably 200 ° C. or lower, more preferably 40 ° C. or higher and 180 ° C. or lower. When the polymerization reaction temperature exceeds 200 ° C., the depolymerization reaction, which is the reverse reaction of ring-opening polymerization, is likely to occur in equilibrium, and the polymerization reaction may be difficult to proceed quantitatively, and may be colored. . On the other hand, when the polymerization reaction temperature is lower than 40 ° C., depending on the ring-opening polymerizable monomer species, it takes a long time to melt by the compressive fluid, the melting is insufficient, or the activity of the catalyst is lowered. To do. As a result, the reaction rate tends to decrease during polymerization, and the polymerization reaction may not proceed quantitatively. The polymerization reaction temperature is controlled by, for example, a heater provided in the polymerization reaction apparatus or external heating.

  In the conventional polymer product manufacturing method using supercritical carbon dioxide, since supercritical carbon dioxide has low solubility of the polymer product, a large amount of supercritical carbon dioxide is used to polymerize the ring-opening polymerizable monomer. I was letting. According to the polymerization method of the present embodiment, in the method for producing a polymer product using a compressive fluid, the ring-opening polymerizable monomer can be subjected to ring-opening polymerization at an unprecedented high concentration. In this case, the inside of the reaction part 13 becomes a high pressure in the presence of the compressive fluid, and the glass transition temperature (Tg) of the produced polymer product is lowered. As a result, the viscosity of the produced polymer product is lowered, and thus the ring-opening polymerization reaction proceeds uniformly even when the concentration of the polymer product is increased.

  In the present embodiment, the polymerization reaction time (average residence time in the reaction part 13) is set according to the target molecular weight, but is usually preferably within 1 hour, more preferably within 45 minutes, and within 30 minutes. Is particularly preferred. According to the production method of the present embodiment, the polymerization reaction time can be set to 20 minutes or less. This is a short time that is unprecedented in the polymerization of ring-opening polymerizable monomers in a compressible fluid.

  The water content in the reaction unit 13 is preferably 4 mol% or less, more preferably 1 mol% or less, and particularly preferably 0.5 mol% or less with respect to 100 mol% of the ring-opening polymerizable monomer. When the amount of water exceeds 4 mol%, the water itself contributes as an initiator, so that it may be difficult to control the molecular weight. In order to control the amount of water in the polymerization system, an operation for removing water contained in the ring-opening polymerizable monomer and other raw materials may be added as a pretreatment as necessary.

  When discharging the polymer product P that has undergone the ring-opening polymerization reaction in the reaction section 13, first, gradually from the pressure adjustment valve between the liquid feed pump 10 and the extrusion die port 15 at a speed of 0.1 MPa / min or less. And the polymer product can be sent out of the reaction section 13 by an extruder or a pump 14. By having a step of maintaining a normal pressure state after the pressure is gradually released, the melt viscosity of the polymer product can be improved.

  The speed at which the metering pump 14 delivers the polymer product P is preferably constant in order to obtain a uniform polymer product by operating at a constant pressure in the polymerization reaction system filled with the compressive fluid. Therefore, the liquid feeding mechanism inside the reaction unit 13 and the liquid feeding amount of the liquid feeding pump 10 are controlled so that the back pressure of the metering pump 14 is constant. Similarly, the feeding speed of the liquid feeding mechanism, the measuring feeders (2, 4), and the measuring pumps (6, 8) in the contact portion 9 are controlled so that the back pressure of the liquid feeding pump 10 is constant. The control method may be an ON-OFF type, that is, an intermittent feed type, but a continuous or step method in which the rotational speed of a pump or the like is gradually increased or decreased is often more preferable. In any case, a uniform polymer product can be stably obtained by such control.

  The catalyst remaining in the polymer product obtained by this embodiment is removed as necessary. The removing method is not particularly limited, and examples thereof include distillation under reduced pressure and extraction using a compressible fluid. In the case of distilling off under reduced pressure, the reduced pressure condition is set based on the boiling point of the catalyst. For example, the temperature during decompression is 100 ° C. or higher and 120 ° C. or lower, and the catalyst can be removed at a temperature lower than the temperature at which the polymer product is depolymerized. For this reason, it is preferable to use a compressed fluid as a solvent also in extraction operation. As such an extraction operation, a known technique such as extraction of a fragrance can be diverted.

[Batch polymerization reactor]
Next, an example of a batch type polymerization reaction apparatus used for producing the polymer product will be described with reference to FIGS. 5 and 6. FIG.5 and FIG.6 is a systematic diagram which shows an example of a superposition | polymerization process.
Here, the polymerization reaction apparatus 400 will be described with reference to FIG. 5. The polymerization reaction apparatus 500 shown in FIG. 6 includes an addition pot 125, valves (123, 124, 126, 129), and joints (130a, 130b). 5 is the same configuration as the polymerization reaction apparatus 400 of FIG. 5 except that the pipe 130 is provided.

  The polymerization reaction apparatus 400 shown in FIG. 5 has a tank 121, a metering pump 122, an addition pot 125, a reaction vessel 127, and valves (123, 124, 126, 128, 129, 131). Each of the above devices is connected as shown in FIG. The pipe 130 is provided with joints (130a, 130b).

  The tank 121 stores a compressible fluid. The tank 121 may store a gas (gas) or a solid that becomes a compressible fluid by being heated and pressurized in a supply path supplied to the reaction vessel 127 or in the reaction vessel 127. In this case, the gas or solid stored in the tank 121 is heated or pressurized to be in the state (1), (2), or (3) in the phase diagram of FIG. .

  The metering pump 122 supplies the compressive fluid stored in the tank 121 to the reaction vessel 127 at a constant pressure and flow rate. The addition pot 125 stores the catalyst added to the raw material in the reaction vessel 127. The valves (123, 124, 126, 129) open and close each of them, thereby supplying the compressive fluid stored in the tank 121 to the reaction vessel 127 via the addition pot 125 and the addition pot 125. The route for supplying the reaction vessel 127 without going through is switched.

[Second Embodiment]
Subsequently, the second embodiment will be described while referring to differences from the first embodiment. In the second embodiment, the polymer product is produced by a batch process.

  The reaction vessel 127 contains a ring-opening polymerizable monomer, an initiator, and a catalyst in advance before starting the polymerization. The reaction vessel 127 is in contact with a ring-opening polymerizable monomer, an initiator, a catalyst, a compressive fluid supplied from the tank 121, and a catalyst supplied from the addition pot 125 by bringing them into contact with each other. It is a pressure-resistant container for polymerizing the polymerizable monomer. The catalyst can also be charged in the reaction vessel 127 in advance. In addition, the reaction vessel 127 may be provided with a gas outlet for removing evaporated substances. In addition, the reaction vessel 127 has a heater for heating the raw materials and the compressive fluid. Furthermore, the reaction vessel 127 has a stirring device for stirring the raw materials and the compressive fluid. When the density difference between the raw material and the produced polymer product occurs, the settling of the produced polymer product can be suppressed by adding the stirring of the stirring device, so that the polymerization reaction can proceed more uniformly and quantitatively. After completion of the reaction, the valve 131 installed at the upper part of the reaction vessel 127 was opened at a speed of 0.1 MPa / min or less at a speed of 0.1 MPa / min or less, and maintained at normal pressure. Open and discharge the polymer product P in the reaction vessel 127. In the case of this method, since the valve 131 is installed at the upper part of the reaction vessel 127, the polymer in the reaction vessel 127 foams violently and causes clogging unless it is slowly depressurized. Therefore, in addition to the valve 131, a plurality of valves may be further provided to secure the depressurization location.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples. However, the present invention is not limited to these examples.

[Example 1-1]
Ring-opening polymerization of L-lactide and a D-lactide mixture (L-lactide / D-lactide = 90/10 (mass ratio)) was performed using a batch polymerization reactor 400 shown in FIG. The structure of the polymerization reaction apparatus 400 is shown below.
Tank 121: Carbon dioxide gas cylinder Reaction vessel 127: 500 mL pressure vessel made of SUS316, Lactide in a liquid state as a ring-opening polymerizable monomer (L-lactide and D-lactide mixture (mass ratio 90/10) (Purac Co., Ltd.) Manufactured, melting point: 100 ° C.), 150 g of a mixture of 200 ppm of tin octylate as a catalyst and castor oil as an initiator (initiator is 0.1 mol with respect to 100 mol of monomer).
Here, the castor oil is a castor oil-based polyol (manufactured by Ito Oil Co., Ltd., URIC H-30) and refers to a polyhydric alcohol obtained by modifying castor oil. The same applies to the following.

In this study, the batch cell was reacted at a high pressure, and after the reaction, depressurization was performed at a rate of 0.1 MPa / min or less to obtain a polymer product having a high melt viscosity. Details of the method are shown below.
By operating the metering pump 122 and opening the valves (123, 126), the carbon dioxide stored in the tank 121 was supplied to the reaction vessel 127 without going through the addition pot 125. After replacing the space in the reaction vessel 127 with carbon dioxide, the polymerization density of supercritical carbon dioxide is increased to 130 kg / m ³ in the reaction vessel 127, and all valves are closed when the temperature reaches 180 ° C. and the pressure becomes 10 MPa. For 90 minutes. After completion of the reaction, the valve 131 was opened at a rate of 0.1 MPa / min (depressurization rate), and the pressure in the reaction vessel 127 was gradually returned to normal pressure. Then, after maintaining the normal pressure state for 30 minutes, the polymer product (polylactic acid) in the reaction vessel 127 was taken out.
The holding time in the normal pressure state was 30 minutes in all examples.

<Mixing ratio [raw material (g) / (compressible fluid + raw material) (g)]>
The mixing ratio [raw material / (compressible fluid + raw material)] was calculated by the following equation.
Space volume of supercritical carbon dioxide: 500 mL-150 g / 1.27 (specific gravity of raw materials) = 382 mL
Mass of supercritical carbon dioxide: 382 mL × 0.130 (specific gravity of carbon dioxide at 180 ° C. and 10 MPa) = 49.6
Mixing ratio: 150 g / (150 g + 49.6 g) = 0.75

<Polymerization density>
The polymerization density was determined from the polymerization temperature and pressure using the following calculation program.
EOS-SCx Ver. 0.2w
Calculation program for density and thermodynamic charge based on equations of state of water, ethanol and carbon dioxide Copyright (c) 2000-Tsutomu Ohmori

  Table 1 shows the measurement / calculation method and evaluation of the physical properties of the polymer product obtained (average branching degree, residual monomer content, weight average molecular weight, molecular weight distribution, melt viscosity).

[Examples 1-2 to 1-10]
Table 1 and Table 1 show the initiator species, catalyst species, catalyst amount, initiator amount, polymerization pressure, polymerization reaction temperature, polymerization density, reaction time, mixing ratio [raw material / (compressible fluid + raw material)], and depressurization rate. The polymer product (polylactic acid) of Examples 1-2 to 1-10 was produced in the same manner as in Example 1-1 except that the procedure was as described in 2. Furthermore, evaluation similar to Example 1-1 was performed. The results are shown in Tables 1 and 2.

[Example 2-1]
In Example 2-1, the continuous polymerization reaction apparatus 100 shown in FIG. 3 was used. The mixing device of the contact portion 9 has a cylinder inner diameter (d) of 30 mm having a biaxial agitation device fitted with screws that mesh with each other, the two rotating shafts rotate in the same direction, and the speed is 30 rpm. The reaction vessel of the reaction unit 13 is a twin-screw kneader (manufactured by Toshiba Corporation, TME-18).

  The gear pump (metering feeder 2) was operated, and the lactide in the molten state in the tank 1 was quantitatively supplied to the mixing device of the contact portion 9. The gear pump (metering feeder 4) was actuated, and pentaerythritol as an initiator in the tank 3 was quantitatively supplied to the mixing device of the contact portion 9 so as to be 0.1 mol% with respect to lactide. Further, the gear pump (metering feeder 6) was operated to supply tin octylate in the tank 5 to the inlet 9b so as to be 200 ppm with respect to lactide. The temperature of the cylinder of the mixing device of the contact portion 9 was 80 ° C. Carbon dioxide gas was supplied from the vent hole (introduction port 9a) so that the pressure in the system was 10 MPa.

  The cylinder temperature of the reaction vessel was set to 10 MPa by increasing the temperature in the vicinity of the raw material supply unit and the temperature at the tip part by 180 ° C. and increasing the pressure by the pump 10. The average residence time of the reactants in this container was 0.5 hours. After completion of the reaction, the valve attached to the extruder provided behind the reaction section 13 is gradually opened, the pressure is reduced at a rate of 0.1 MPa / min, and after reaching normal pressure, the extruder is operated. The polymer product (polylactic acid) was discharged. Evaluation similar to Example 1-1 was performed using the obtained polymer product (polylactic acid). The results are shown in Table 3.

[Example 2-2]
Example 2 except that the initiator type, initiator amount, polymerization pressure, polymerization reaction temperature, polymerization density, mixing ratio [raw material / (compressible fluid + raw material)], and depressurization rate were as described in Table 3. The polymer product (polylactic acid) of Example 2-2 was produced in the same manner as in Example-1. Furthermore, evaluation similar to Example 1-1 was performed. The results are shown in Table 3.

[Comparative Example 1-1]
Lactide, lauryl alcohol as an initiator, and tin octylate as a catalyst were placed in a batch reactor equipped with a mixer under the conditions shown in Table 4 and reacted for 90 minutes. Thereafter, the pressure was released at a rate of 1 MPa / min to obtain a polymer product (polylactic acid). Furthermore, evaluation similar to Example 1-1 was performed. The results are shown in Table 4.

[Comparative Examples 1-2 and 1-3]
Polymerization was carried out in the same manner as in Comparative Example 1-1 except that the initiator type, initiator amount, reaction temperature, reaction pressure, depressurization rate, polymerization density, mixing ratio and reaction time were changed to the conditions shown in Table 4. A polymer product (polylactic acid) was obtained. Comparative Example 1-3 represents an experiment under normal pressure without using a compressive fluid. Furthermore, evaluation similar to Example 1-1 was performed. The results are shown in Table 4.

[Comparative Examples 2-1 to 2-2]
Except having changed the initiator seed | species and the depressurization speed into the conditions shown in Table 5, it superposed | polymerized by the method similar to Example 2-1, and obtained the polymer product (polylactic acid). The obtained polymer product was evaluated in the same manner as in Example 1-1. The results are shown in Table 5.

  The physical properties and evaluation of the polymer product (polylactic acid) were performed as follows.

<Calculation method of branching degree of branched polylactic acid> The polymer product (polylactic acid) in the reaction vessel 127 is extruded into a strand form from an extrusion die (not shown) and submerged in water at 10 ° C, and then a cutter. The strands were cut and dried to obtain pellets. About this pellet (polymer product), the average branching degree was computed by the following formula | equation (1). Bu = NOH / N ′ = (OHV × 10 ⁻³ /56.1)/(1/Mn)=OHV×Mn×10 ⁻³ /56.1 (1) In the above formula (1), Bu is the average degree of branching, NOH is the number of hydroxyl groups per gram of branched polylactic acid, N ′ is the number of molecules per gram of branched polylactic acid, Mn is the number average molecular weight, OHV is the hydroxyl value of branched polylactic acid, 56.1 Represents the molecular weight of potassium hydroxide. The hydroxyl value of the polymer product can be determined by a method based on JIS K 0070.

<Weight average molecular weight of polymer product>
It measured on the following conditions by the gel permeation chromatography (GPC).
-Equipment: GPC-8020 (manufactured by Tosoh Corporation)
Column: TSK G2000HXL and G4000HXL (manufactured by Tosoh Corporation)
・ Temperature: 40 ℃
-Solvent: Chloroform-Flow rate: 1.0 mL / min 1 mL of a sample with a concentration of 0.5% by mass was injected, and a molecular weight calibration curve prepared from a molecular weight distribution of the polymer product measured under the above conditions using a monodisperse polystyrene standard sample Was used to calculate the number average molecular weight (Mn) and the weight average molecular weight (Mw) of the polymer product. The molecular weight distribution is a value obtained by dividing Mw by Mn.

<Measurement method of molecular weight>
The weight average molecular weight and the number average molecular weight can be measured by gel permeation chromatography (GPC), for example, under the following conditions.
-Equipment: GPC-8020 (manufactured by Tosoh Corporation)
Column: TSK G2000HXL and G4000HXL (manufactured by Tosoh Corporation)
・ Temperature: 40 ℃
・ Solvent: Chloroform ・ Flow rate: 0.5 mL / min 1 mL of a sample having a concentration of 0.5% by mass was injected, and a molecular weight calibration curve prepared by a monodisperse polystyrene standard sample from the molecular weight distribution of the polymer product measured under the above conditions. Is used to calculate the number average molecular weight (Mn) and the weight average molecular weight (Mw) of the polymer product. The molecular weight distribution is a value obtained by dividing Mw by Mn.

<Residual monomer content>
The content of the residual monomer in the obtained polymer product is “Voluntary standards for food containers and packaging made of synthetic resin such as polyolefin, third edition revised edition, June 2004 supplement, Part 3, Sanitation test method, P13”. It was determined according to the measurement method for the amount of residual monomer described. Specifically, a polymer product such as polylactic acid is uniformly dissolved in dichloromethane, and the supernatant obtained by reprecipitation of the polymer product by adding an acetone / cyclohexane mixed solution is gas chromatograph with a hydrogen flame detector (FID). The sample was subjected to (GC), and the residual monomer was separated and quantified by an internal standard method to measure the content of the residual monomer in the polymer product. The GC measurement was performed under the following conditions. “Ppm” in each table indicates a mass fraction.
<< GC measurement conditions >>
Column: capillary column (manufactured by J & W, DB-17MS, length 30 m × inner diameter 0.25 mm, film thickness 0.25 μm)
Internal standard: 2,6-dimethyl-γ-pyrone Column flow rate: 1.8 mL / min Column temperature: Hold at 50 ° C. for 1 minute. The temperature is raised at a constant rate of 25 ° C./min and held at 320 ° C. for 5 minutes.
・ Detector: Flame ionization method (FID)

<Measuring method of melt viscosity>
The test was conducted by the following method and evaluated according to the following evaluation criteria.
Apparatus: CAPILLARY RHEOMETER CFT-100D (manufactured by Shimadzu Corporation)
<< Temperature raising method >>
Temperature increase rate: 5.0 (° C / min)
Starting temperature: 40 ° C
Die hole diameter: 1.0mm
Preheating time: 240s
Value of melt viscosity at 190 ° C [Evaluation criteria]
◎: More than 2,000 Pa · s ○: More than 1,000 Pa · s and less than 2,000 Pa · s Δ: Less than 1,000 Pa · s

Each display in Tables 1 to 5 is as follows.
“Sn” represents tin octylate.
The starting amount (mol%) is the amount (mol%) relative to the monomer.
The catalyst amount (ppm) is an amount (ppm) based on the monomer.

  As can be seen from Tables 1 to 3, according to the method for producing a branched polymer of the present invention, the polymer product obtained has a high melt viscosity and does not cause problems during molding.

1 tank
DESCRIPTION OF SYMBOLS 9 Contact part 13 Reaction part 21 Tank 100 Polymerization reaction apparatus 125 Addition pot 127 Reaction container 100 Polymerization reaction apparatus 400 Polymerization reaction apparatus 500 Polymerization reaction apparatus
P polymer product

JP 2009-001614 A JP 2013-189616 A

Claims (5)

  A polymerization step of bringing the ring-opening polymerizable monomer into contact with an initiator having three or more hydroxyl groups at its end, a ring-opening polymerizable monomer, and a compressive fluid, and the compression while maintaining the polymerization temperature; A method for producing a branched polymer, which comprises a step of removing a natural fluid and maintaining it at a normal pressure, and a step of removing a product from the normal pressure.   The method for producing a branched polymer according to claim 1, wherein the initiator is a polyhydric alcohol, and the ring-opening polymerizable monomer is a cyclic ester.   The method for producing a branched polymer according to claim 1 or 2, wherein the compressive fluid contains carbon dioxide.   The branched product according to any one of claims 1 to 3, wherein the product has a branched chain composed of polylactic acid and has a weight average molecular weight of 200,000 or more as measured by gel permeation chromatography. Method for producing a mold polymer. The method for producing a branched polymer according to any one of claims 1 to 4, wherein the product has a residual monomer content of 5,000 ppm or less.

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