JP2018145220A - Method of producing aliphatic polyester - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively and continuously produce aliphatic polyester by suppressing by-production of THF (Tetrahydrofuran) when 1,4-BG (Butanediol) is effectively reused in a polycondensation reaction system, the 1,4-BG having been used as a drive steam source of a steam ejector for reducing a pressure in the polycondensation reaction system in the production of aliphatic polyester.SOLUTION: The aliphatic polyester is produced by performing an esterification reaction and/or a transesterification, a polycondensation reaction on a diol component mainly containing 1,4-BG and a dicarboxylic acid component mainly containing an aliphatic dicarboxylic acid component. The polycondensation reaction is performed under reduced pressure generated by a steam ejector using, as a drive steam, 1,4-BG steam obtained by gasifying 1,4-BG by a steam generator, the 1,4-BG steam used for the steam ejector is condensed to obtain a 1,4-BG-containing liquid, and acid value of the 1,4-BG-containing liquid sealed in the steam generator is set to be 30eq./ton or less when at least a part of the 1,4-BG-containing liquid is recycled and reused as the drive steam source of the steam ejector.SELECTED DRAWING: Figure 4

Description

  The present invention performs an esterification reaction and / or a transesterification reaction and a polycondensation reaction of a diol component mainly composed of 1,4-butanediol and a dicarboxylic acid component mainly composed of an aliphatic dicarboxylic acid component. In the process for producing an aliphatic polyester, 1,4-butanediol in the system is efficiently recycled and reused, and by-production of tetrahydrofuran (THF) is suppressed to produce an aliphatic polyester efficiently and continuously. Regarding the method.

  Polyesters obtained by performing esterification or transesterification and polycondensation reactions using a dicarboxylic acid component and a diol component as raw materials are used in various applications. In particular, polybutylene succinate (PBS) using 1,4-butanediol (hereinafter sometimes referred to as 1,4-BG) as a raw material diol and an aliphatic dicarboxylic acid such as succinic acid as a raw material dicarboxylic acid. Aliphatic polyesters such as) are useful as biodegradable polymers. An aromatic polyester such as polybutylene terephthalate (PBT) using an aromatic dicarboxylic acid such as terephthalic acid as a raw material dicarboxylic acid is highly versatile as an engineering plastic.

When industrially producing PBS or PBT, a continuous polymerization process is generally employed. For example, Patent Document 1 discloses a continuous manufacturing process of PBS.
The continuous production process described in Patent Document 1 includes an esterification process (FIG. 1 of Patent Document 1), a polycondensation process (FIG. 2 of Patent Document 1), a steam ejector, and a distillation purification process (FIG. 3 of Patent Document 1). Broadly divided.

  In the method described in Patent Document 1, the first, second, and third polycondensation reaction tanks (a), (d), and (k) of FIG. ) Vent lines (L2), (L4) and (L6), water generated by the reaction, THF produced as a by-product from 1,4-BG, and unreacted 1,4-BG gas were extracted, respectively. It is sent to a wet condenser (wet condenser) that is not shown in the figure, where 1,4-BG is condensed and collected, and the condensed and collected 1,4-BG is supplied again as raw material 1,4-BG to the swell process. To do. In this wet condenser, the gas extracted from each polycondensation reaction tank is usually condensed using 1,4-BG as a refrigerant.

Further, it is condensed in each of the wet condensers connected to the THF, water, and 1,4-BG gas, that is, the vent lines (L2), (L4), and (L6), which are not condensed and collected by the wet condenser. Those not present are supplied to the ejectors (A1), (B1), and (C1) through the vent lines (21), (31), and (41) of FIG.
The ejectors (A1), (B1), and (C1) use 1,4-BG as a driving steam source. In Patent Document 1, 1,4-BG as a driving steam source is supplied to a supply line (19). Then, the ejector (A1), (B1), (C1) is driven by supplying the steam generator (K) as new 1,4-BG from outside the system.

  In Patent Document 1, as described above, the vent lines (L2), (L4), and (L6) are decompressed by the ejectors (A1), (B1), and (C1), so that the polycondensation reaction tanks (a), ( d) The inside of (k) is depressurized.

  In Patent Document 1, 1,4-BG steam that is a drive source of the ejectors (A1), (B1), and (C1) is installed downstream of the ejectors (A1), (B1), and (C1). Prepared in a hot well tank (H1), (H2), (H3), and purified by removing THF, water, and high boiling components, which are light boiling components, in a distillation purification tank (J1) to prepare raw slurry There is a description that it is transferred to the tank and reused.

  Thus, when 1,4-BG is used as the drive steam source of the ejector, 1,4-BG used as the drive steam source contains THF generated by the heat history of steam generation. When THF-containing 1,4-BG is recycled and reused, problems such as inhibition of decompression by THF in 1,4-BG and, consequently, degradation of the quality of the produced polyester occur. In order to solve this problem, Patent Document 2 proposes that the THF concentration in the hot well tank be 4% by weight or less in the production of PBT.

JP 2010-132898 A Japanese Patent No. 3812557

In Patent Document 1, 1,4-BG used as a drive steam source for an ejector is purified in a distillation column (J1) via hot well tanks (H1), (H2), and (H3) and circulated as a raw material diol. Although there is a description that the liquid is reused, in order to reuse the liquid containing 1,4-BG more effectively, it may be circulated to the steam generator (K).
However, as a result of the study by the present inventors, when 1,4-BG purified in the distillation column (J1) is recycled to the steam generator (K) in this way, THF rapidly increases in the steam ejector system. As a result, it was found that the increase in the THF concentration in the system and that it was necessary to introduce a large amount of new 1,4-BG from outside the system in order to reduce the THF concentration.

  The present invention has been made in view of such problems, and in the production of aliphatic polyester, 1,4-BG used as a driving steam source of a steam ejector for reducing the pressure in the polycondensation reaction system, It is an object of the present invention to provide an industrially advantageous method for producing an aliphatic polyester capable of efficiently producing an aliphatic polyester by suppressing the by-product of THF when effectively reusing in the system.

  As a result of intensive studies to solve the above-mentioned problems, the present inventors have condensed the 1,4-BG steam used as the driving steam of the steam ejector and reused it as the driving steam source of the steam ejector. The inventors have found that the above problems can be solved by controlling the acid value of 1,4-BG, and have completed the present invention.

  That is, the gist of the present invention resides in the following [1] to [3].

[1] An esterification reaction and / or a transesterification reaction and a polycondensation reaction between a diol component having 1,4-butanediol as a main component and a dicarboxylic acid component having an aliphatic dicarboxylic acid component as a main component. In the method for producing a group polyester, the polycondensation reaction is performed under reduced pressure by a decompression device, and the decompression device drives 1,4-butanediol vapor obtained by vaporizing 1,4-butanediol with a steam generator. The 1,4-butanediol vapor used in the steam ejector is condensed to obtain a 1,4-butanediol-containing liquid, and at least a part of the 1,4-butanediol-containing liquid is obtained. A process for producing an aliphatic polyester that is recycled and reused as a driving steam source for the steam ejector, comprising 1,4-butanediol sealed in the steam generator. 30eq the acid value of the liquid. / Ton or less, The manufacturing method of the aliphatic polyester characterized by the above-mentioned.

[2] At least a part of the 1,4-butanediol-containing liquid is distilled in a distillation column, and at least a part of the purified 1,4-butanediol-containing liquid obtained from the bottom of the distillation tower is removed from the steam ejector. The method for producing an aliphatic polyester according to [1], wherein the recycle is used as a driving steam source.

[3] The polycondensation reaction apparatus for performing the polycondensation reaction has a reaction tank, and the reaction tank has a wet condenser for collecting unreacted gas distilled from the reaction tank, and the refrigerant of the wet condenser The method for producing an aliphatic polyester according to [1] or [2], wherein the 1,4-butanediol-containing liquid and / or the remainder of the purified 1,4-butanediol-containing liquid is used.

  According to the present invention, an esterification reaction and / or a transesterification reaction and a polycondensation reaction between a diol component mainly composed of 1,4-butanediol and a dicarboxylic acid component mainly composed of an aliphatic dicarboxylic acid component are carried out. 1,4-butanediol used as a driving vapor source of the vapor ejector for decompressing the inside of the polycondensation reaction system in the production of the aliphatic polyester by sufficiently suppressing the by-product of tetrahydrofuran, It can be effectively reused in the production process, and high quality aliphatic polyester can be efficiently and continuously produced.

It is the schematic which shows one Embodiment of the esterification process employ | adopted by this invention. It is the schematic which shows one Embodiment of the polycondensation process employ | adopted by this invention. It is the schematic which shows one Embodiment of the wet condensation process employ | adopted by this invention. It is the outline which shows one Embodiment of the steam ejector system and distillation purification system which are employ | adopted by this invention.

  Hereinafter, embodiments of the present invention will be described in detail. The description of the constituent requirements described below is an example (representative example) of an embodiment of the present invention, and the present invention is not limited to these contents unless it exceeds the gist.

  In the present specification, “mass%”, “mass ppm” and “part by mass” and “wt%”, “weight ppm” and “part by weight” have the same meaning, respectively.

  The method for producing an aliphatic polyester according to the present invention includes an esterification reaction and / or a transesterification reaction between a diol component mainly composed of 1,4-butanediol and a dicarboxylic acid component mainly composed of an aliphatic dicarboxylic acid component. In addition, in the method for producing an aliphatic polyester by performing a polycondensation reaction, the polycondensation reaction is performed under a reduced pressure by a decompression device, and the decompression device is a 1,4-butanediol vaporized by a steam generator. A vapor ejector using 4-butanediol vapor as driving vapor, and condensing the 1,4-butanediol vapor used in the vapor ejector to obtain a 1,4-butanediol-containing liquid; A method for producing an aliphatic polyester in which at least a part of a diol-containing liquid is circulated and reused as a driving steam source for the steam ejector, It has been 1,4 30 eq acid value of butanediol-containing solution. / Ton or less.

  Here, the “aliphatic dicarboxylic acid component” is a general term for aliphatic dicarboxylic acids that are raw materials for polyesters such as aliphatic dicarboxylic acid and aliphatic dicarboxylic acid derivatives such as aliphatic dicarboxylic acid alkyl esters. Hereinafter, the aliphatic polyester produced by the method for producing an aliphatic polyester of the present invention may be referred to as “the aliphatic polyester of the present invention”.

  In the present invention, “having 1,4-butanediol as a main component” means “the total molar ratio of 1,4-butanediol is the largest among the raw material diol components”. Among these, from the viewpoint of physical properties and biodegradability of the polyester, the total of 1,4-butanediol is preferably 50 mol% or more, more preferably 60 mol% or more, and more preferably with respect to the total of the raw material diol components. Preferably it is 70 mol% or more, Most preferably, it is 90-100 mol%.

  In the present invention, “having an aliphatic dicarboxylic acid component as a main component” means having at least one of aliphatic dicarboxylic acid derivatives such as an aliphatic dicarboxylic acid and an aliphatic dicarboxylic acid alkyl ester as a main component. This means that “the total molar ratio of aliphatic dicarboxylic acid derivatives such as aliphatic dicarboxylic acid and aliphatic dicarboxylic acid alkyl ester is the largest among the raw material dicarboxylic acid components”. Among these, from the viewpoint of physical properties and biodegradability of polyester, the total of aliphatic dicarboxylic acid derivatives such as aliphatic dicarboxylic acid and aliphatic dicarboxylic acid alkyl ester is 50 mol% or more based on the total of raw material dicarboxylic acid components. It is preferably 60 mol% or more, more preferably 70 mol% or more, and particularly preferably 90 to 100 mol%.

  In the present invention, each reaction step in producing the polyester can be carried out by a batch method or a continuous method. From the viewpoint of stabilization of quality and energy efficiency, the raw materials are continuously supplied and continuously. A so-called continuous method for obtaining polyester is preferred.

<Diol component>
The diol component used in the present invention is mainly composed of 1,4-butanediol. In the present invention, if the molar ratio of 1,4-butanediol is most frequently used in the raw material diol, other diol components that are usually used for the raw material of polyester can be used in combination without limitation.

  Examples of diol components other than 1,4-butanediol include ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7- Hexanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, alkylene diols such as neopentyl glycol, oxyalkylenes such as diethylene glycol, polyethylene glycol, polypropylene glycol, and polytetramethylene ether glycol Aliphatic diol components such as diol, 1,2-cyclohexanediol, 1,4-cyclohexanediol, 1,2-cyclohexanedimethanol, 1,4-cyclohexanedimethanol and other cycloalkylenediol Among these, from the viewpoint of physical properties of the obtained polyester, alkylene diols having 6 or less carbon atoms such as ethylene glycol and 1,3-propanediol, or cyclohexane having 6 or less carbon atoms such as 1,4-cyclohexanedimethanol. Alkylene diols are preferred. Two or more of these may be used in combination.

The proportion of 1,4-butanediol in the diol component is preferably 50 mol% or more based on the total diol component from the viewpoint of the melting point (heat resistance), biodegradability and mechanical properties of the polyester obtained. It is more preferably at least mol%, particularly preferably 90 to 100 mol%.
1,4-butanediol, ethylene glycol and 1,3-propanediol among the above aliphatic diol components can be derived from plant raw materials.

<Dicarboxylic acid component>
The dicarboxylic acid component used in the present invention is mainly composed of an aliphatic dicarboxylic acid component, and if the total molar ratio is most frequently used in the raw material carboxylic acid component, the one usually used as a polyester raw material is particularly used. Can be used without restriction.

Examples of the aliphatic carboxylic acid component include oxalic acid, malonic acid, succinic acid, succinic anhydride, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecadicarboxylic acid, dodecadicarboxylic acid, Examples include hydrogenated products of aliphatic dicarboxylic acids such as dimer acids, aromatic dicarboxylic acids such as hexahydrophthalic acid, hexahydroisophthalic acid, and hexahydroterephthalic acid. Among these, the physical properties of the resulting aliphatic polyester From the aspect, aliphatic dicarboxylic acid components such as succinic acid, succinic anhydride, adipic acid, and sebacic acid are preferable. In particular, aliphatic dicarboxylic acid components having 4 or less carbon atoms such as succinic acid and succinic anhydride are preferable. Two or more of these may be used in combination.
Among these aliphatic dicarboxylic acid components, succinic acid, succinic anhydride, adipic acid and the like can be derived from plant raw materials.

  When succinic acid is used as the dicarboxylic acid component, the proportion of succinic acid in the dicarboxylic acid component is 50 moles relative to the total dicarboxylic acid component from the viewpoint of the melting point (heat resistance), biodegradability and mechanical properties of the resulting polyester. % Or more, more preferably 70 mol% or more, and particularly preferably 90 to 100 mol%.

  Moreover, you may use together an aromatic dicarboxylic acid component as dicarboxylic acid components other than aliphatic dicarboxylic acid. Specific examples of the aromatic dicarboxylic acid component include terephthalic acid, isophthalic acid, naphthalenedicarboxylic acid, and diphenyldicarboxylic acid. These may be used alone or as a mixture of two or more thereof in addition to the aliphatic dicarboxylic acid component.

<Other copolymer components>
The polyester of the present invention may be copolymerized with other components other than the aliphatic diol component and the aliphatic dicarboxylic acid component. Copolymerization components that can be used in this case include lactic acid, glycolic acid, hydroxybutyric acid, hydroxycaproic acid, 2-hydroxy-3,3-dimethylbutyric acid, 2-hydroxy-3-methylbutyric acid, 2-hydroxyiso Oxycarboxylic acids such as caproic acid, malic acid, maleic acid, citric acid, and fumaric acid, and esters, lactones, and oxycarboxylic acid polymers of these oxycarboxylic acids, or trifunctional groups such as glycerin, trimethylolpropane, and pentaerythritol The above polyhydric alcohols, or trifunctional or higher polyvalent carboxylic acids such as propanetricarboxylic acid, pyromellitic acid, trimellitic acid benzophenone tetracarboxylic acid, and anhydrides thereof, or the anhydride thereof can be used.

  Of these, tri- or higher-functional oxycarboxylic acids, tri- or higher-functional alcohols, tri- or higher-functional carboxylic acids, and the like can be easily obtained by adding a small amount of polyester. Of these, oxycarboxylic acids such as malic acid, citric acid, and fumaric acid are preferable, and malic acid is particularly preferably used.

  In the case of using a trifunctional or higher polyfunctional compound, the amount used is preferably 0.001 to 5 mol%, more preferably 0.05 to 0.5 mol%, based on the total dicarboxylic acid component. . If the upper limit of this range is exceeded, gel (unmelted product) is likely to form in the resulting aliphatic polyester, and if it is less than the lower limit, the advantage of using a polyfunctional compound (usually the viscosity of the resulting polyester can be increased. Becomes difficult to obtain.

<Method for producing aliphatic polyester>
Hereinafter, the production method of the aliphatic polyester of the present invention will be described by taking a continuous production method as an example. In the following, a method for producing a polyester by an esterification reaction step and a polycondensation reaction step using an aliphatic diol and an aliphatic dicarboxylic acid will be exemplified, but the esterification step may be a transesterification step, It may be a step of performing both esterification reaction and transesterification reaction.

  In the continuous production method, for example, aliphatic dicarboxylic acid and aliphatic diol are produced by a method of continuously obtaining polyester pellets through an esterification reaction step and a melt polycondensation reaction step using a plurality of continuous reaction vessels. However, as long as the effects of the present invention are not hindered, the method is not limited to the continuous method, and conventionally known polyester production methods can be employed.

<Esterification reaction process>
In the esterification reaction step, at least a dicarboxylic acid component and a diol component are reacted to produce an esterification reaction product. The esterification reaction step and other subsequent steps can be carried out in a plurality of continuous reaction tanks or in a single reaction tank, but in order to reduce fluctuations in the physical properties of the resulting polyester, It is preferable to carry out in the reaction tank.

  The reaction temperature in the esterification reaction step is not particularly limited as long as it is a temperature at which the esterification reaction can be performed, but is preferably 200 ° C. or higher, more preferably 210 ° C. in that the reaction rate can be increased. In order to prevent the coloring of the polyester and the like, it is preferably 250 ° C. or lower, more preferably 245 ° C. or lower, and particularly preferably 240 ° C. or lower. If the reaction temperature is too low, the esterification reaction rate is slow, requiring a long reaction time, and undesirable reactions such as dehydration decomposition of aliphatic diols increase. If the reaction temperature is too high, the aliphatic diol and the aliphatic dicarboxylic acid are decomposed more, and the amount of scattered matter increases in the reaction tank, which may cause foreign matters and haze. Become. The esterification temperature is preferably a constant temperature. The esterification rate is stabilized due to the constant temperature. The constant temperature is a set temperature ± 5 ° C., preferably ± 2 ° C.

  The reaction atmosphere is preferably an inert gas atmosphere such as nitrogen or argon.

  The reaction pressure is preferably 50 kPa to 200 kPa, more preferably 60 kPa or more, further preferably 70 kPa or more, more preferably 130 kPa or less, and still more preferably 110 kPa or less. If the reaction pressure is less than the above lower limit, the amount of scattered matter in the reaction tank increases, the haze of the reaction product becomes high and foreign substances increase easily, and the distillation of aliphatic diol to the outside of the reaction system increases and the polycondensation reaction rate increases. It tends to cause a decline. If the reaction pressure exceeds the above upper limit, the aliphatic diol will be dehydrated and decomposed more easily and the polycondensation reaction will tend to decrease.

  The reaction time is preferably 1 hour or longer, and the upper limit is preferably 10 hours or shorter, more preferably 4 hours or shorter.

  The reaction molar ratio of the aliphatic diol to the aliphatic dicarboxylic acid in which the esterification reaction is performed is the ratio of the aliphatic dicarboxylic acid and the esterified aliphatic dicarboxylic acid present in the gas phase and reaction liquid phase of the esterification reaction vessel An aliphatic dicarboxylic acid that does not contribute to the esterification reaction and is decomposed in the reaction system, an aliphatic diol, and a decomposition product thereof are not included. Examples of those that are decomposed and do not contribute to the esterification reaction include those in which 1,4-butanediol, which is an aliphatic diol, is decomposed into tetrahydrofuran, and tetrahydrofuran is not included in this molar ratio. In the present invention, the lower limit of the reaction molar ratio is usually 1.10 or more, preferably 1.12 or more, more preferably 1.15 or more, and particularly preferably 1.20 or more. The upper limit is usually 2.00 or less, preferably 1.80 or less, more preferably 1.60 or less, and particularly preferably 1.55 or less. If the reaction molar ratio is less than the above lower limit, the esterification reaction tends to be insufficient, and the polycondensation reaction, which is a reaction in the subsequent step, hardly proceeds, and it is difficult to obtain a polyester having a high degree of polymerization. When the reaction molar ratio exceeds the above upper limit, the decomposition amount of the aliphatic diol and the aliphatic dicarboxylic acid tends to increase. In order to keep this reaction molar ratio within a preferable range, it is a preferable method to appropriately replenish the esterification reaction system with an aliphatic diol.

In the present invention, an esterification reaction product having an esterification rate of 80% or more obtained in the esterification reaction step is preferably subjected to a polycondensation reaction. In the present invention, the polycondensation reaction means a high molecular weight reaction of polyester performed at a reaction pressure of 50 kPa or less, the esterification reaction is 50 to 200 kPa, usually performed in an esterification reaction tank, and the polycondensation reaction is 50 kPa or less, preferably Is carried out in a polycondensation reaction tank at 10 kPa or less. In the present invention, the esterification rate indicates the ratio of the esterified acid component to the total acid component in the esterification reaction product sample, and is represented by the following formula.
Esterification rate (%) = (saponification value−acid value) / saponification value × 100

  The esterification rate of the esterification reaction product subjected to the polycondensation reaction step is preferably 85% or more, more preferably 88% or more, and particularly preferably 90% or more. When the esterification rate is less than the lower limit, the polycondensation reactivity in the polycondensation reaction step is deteriorated. Further, the amount of scattered matter during the polycondensation reaction increases, adheres to the wall surface and solidifies, and further, this scattered matter falls into the reaction product, which causes deterioration of haze (foreign matter generation) of the obtained polyester. The upper limit of the esterification rate is preferably higher for polycondensation reactivity in the polycondensation step, but is usually 99%.

  In the present invention, a continuous reaction is carried out with the reaction molar ratio of the dicarboxylic acid component and the diol component in the esterification reaction step, the reaction temperature, the reaction pressure, and the esterification reaction rate within the above ranges, and the esterification reaction product is continuously superposed. By using the condensation reaction step, a high-quality polyester having a low haze and a small amount of foreign matters can be efficiently obtained.

  As the esterification reaction tank, known ones can be used, and any of a vertical stirring complete mixing tank, a vertical heat convection mixing tank, a tower-type continuous reaction tank, etc. may be used. Alternatively, a plurality of tanks in which the same kind or different kinds of tanks are connected in series may be used. Among them, a reaction tank having a stirring device is preferable, and as a stirring device, a turbine stator type high-speed rotating stirrer, a disc mill type stirrer, a rotor mill type, in addition to a normal type including a power unit, a receiver, a shaft, and a stirring blade A type that rotates at high speed such as an agitator can also be used.

  There is no limitation on the form of stirring, and in addition to the normal stirring method in which the reaction liquid in the reaction tank is directly stirred from the top, bottom, side, etc. of the reaction tank, a part of the reaction liquid is piped outside the reaction tank, etc. It is possible to take a method of circulating the reaction liquid by taking it out with a line mixer and the like. Known types of stirring blades can also be selected, and specific examples include propeller blades, screw blades, turbine blades, fan turbine blades, disk turbine blades, fiddler blades, full zone blades, Max blend blades, and the like.

<Polycondensation reaction step>
In the production of the aliphatic polyester of the present invention, the polycondensation reaction is performed in the polycondensation reaction step following the esterification reaction step.

  The polycondensation reaction is performed under reduced pressure using a plurality of continuous reaction tanks and using a decompressor equipped with a steam ejector using 1,4-butanediol as a driving steam source. The lower limit of the reaction pressure in the final polycondensation reaction tank is usually 0.01 kPa or more, preferably 0.03 kPa or more, and the upper limit is usually 1.4 kPa or less, preferably 0.4 kPa or less. If the pressure during the polycondensation reaction is too high, the polycondensation time will be prolonged, and accordingly, the molecular weight will be lowered or colored due to thermal decomposition of the polyester, which tends to make it difficult to produce a polyester exhibiting practically sufficient characteristics. On the other hand, the method of producing using an ultra-high vacuum polycondensation equipment with a reaction pressure of less than 0.01 kPa is a preferred embodiment from the viewpoint of improving the polycondensation reaction rate, but requires extremely expensive equipment investment. Therefore, it is economically disadvantageous.

  The lower limit of the reaction temperature is usually 215 ° C, preferably 220 ° C, and the upper limit is usually 270 ° C, preferably 260 ° C. If the reaction temperature is less than the above lower limit, the polycondensation reaction rate is slow, and not only does it take a long time to produce a polyester with a high degree of polymerization, but also a high power stirrer is required, which is economically disadvantageous. On the other hand, if the reaction temperature exceeds the above upper limit, thermal decomposition of the polyester during production tends to be caused, and it tends to be difficult to produce polyester having a high degree of polymerization.

  The lower limit of the reaction time is usually 1 hour, and the upper limit is usually 15 hours, preferably 10 hours, more preferably 8 hours. If the reaction time is too short, the reaction is insufficient and it is difficult to obtain a polyester having a high degree of polymerization, and the mechanical properties of the molded product tend to be inferior. On the other hand, if the reaction time is too long, the molecular weight drop due to the thermal decomposition of the polyester becomes remarkable, the mechanical properties of the molded product tend to be inferior, and the terminal amount of the carboxyl group that adversely affects the durability of the polyester is thermally decomposed. May increase due to

  A polyester having a desired intrinsic viscosity can be obtained by controlling the polycondensation reaction temperature and time and the reaction pressure.

  There is no restriction | limiting in particular in the type of the polycondensation reaction tank used for this invention, For example, a vertical stirring polymerization tank, a horizontal stirring polymerization tank, a thin film evaporation type polymerization tank etc. can be mentioned. The number of polycondensation reaction tanks can be one, or a plurality of tanks of the same or different types can be connected in series. It is preferable to select a horizontal stirring polymerization machine having a thin film evaporation function excellent in renewability, plug flow property, and self-cleaning property.

  In addition, the polycondensation reaction tank extracts water generated by the reaction, tetrahydrofuran produced as a by-product from 1,4-butanediol, and vent gas containing unreacted 1,4-butanediol, and 1,4-butanediol. Wet condenser (wet condenser) that is cooled and condensed in

  As a wet capacitor, one or more shelves are provided, 1,4-butanediol is circulated and flowed down as a refrigerant from above to generate a liquid film, and exhaust is brought into contact with this liquid film to scatter the process. A shelf type that dissolves and collects substances, a shower nozzle is provided above, sprays 1,4-butanediol as a refrigerant, and exhausts are brought into contact with these droplets to dissolve and collect process scattered matters. There are a shower type, a combination of a shelf type and a shower type, and the shelf type is arranged at the top and the shower type is arranged at the bottom.

<Cyclic reuse of driving steam source>
In the present invention, the 1,4-butanediol vapor used in the vapor ejector of the decompression device is condensed to obtain a 1,4-butanediol-containing liquid, and at least a part of the 1,4-butanediol-containing liquid is generated by steam. The 1,4-butanediol vapor vaporized by the apparatus is circulated and reused as driving steam for the steam ejector. At that time, the acid value of the 1,4-butanediol-containing liquid sealed in the steam generator is set to 30 eq. / Ton or less.

  The acid value of the 1,4-butanediol-containing liquid sealed in the steam generator is 30 eq. When the amount exceeds / ton, tetrahydrofuran tends to be by-produced in the system of the decompression device, and in order to eliminate this by-product and accumulation of tetrahydrofuran, it is necessary to supply more 1,4-butanediol from outside the system. Which is undesirable. The lower the acid value of 1,4-butanediol sealed in the steam generator, the more preferable it is from the viewpoint of preventing the by-production of tetrahydrofuran in the system, and this acid value is 30 eq. / Ton or less, especially 15 eq. / Ton or less is preferable. However, in order to reduce the acid value of 1,4-butanediol sealed in the steam generator, it is necessary to reduce the recycling rate of 1,4-butanediol. In some cases, the object of the present invention, which increases the effective reuse rate of diol, cannot be achieved. From the viewpoint of effective recycling efficiency of 1,4-butanediol, the acid value of 1,4-butanediol recycled as a driving steam source is 2 eq. / Ton or more is preferable.

  Thus, the acid value of the 1,4-butanediol-containing liquid sealed in the steam generator is 30 eq. / Ton or less, at least a part of the 1,4-butanediol-containing liquid to be recycled is distilled in a distillation tower, and the purified 1,4-butanediol-containing liquid obtained from the bottom of the distillation tower At least a part is recycled and used as a driving steam source for the steam ejector, and the remainder consists of other processes, for example, a method of using as a refrigerant for a wet condenser of a polycondensation reaction tank, or consisting of succinic acid and 1,4-butanediol. The method used in the process of preparing a raw material slurry is mentioned.

  Thus, the 1,4-butanediol-containing liquid is purified by distillation, and only a part of it is recycled and used as a driving steam source for the steam ejector, and the rest is used as a refrigerant for a wet condenser or succinic acid. The acid value of the 1,4-butanediol-containing liquid sealed in the steam generator is kept low by using it in the step of preparing a raw material slurry consisting of 1,4-butanediol, By-product and accumulation of tetrahydrofuran can be prevented.

<Reaction catalyst>
The reaction can be promoted by using a reaction catalyst in the esterification reaction and the polycondensation reaction. However, in the esterification reaction, a sufficient reaction rate can be obtained even without the esterification reaction catalyst. In addition, if an esterification reaction catalyst is present during the esterification reaction, the catalyst may cause insoluble precipitates in the reaction product due to water generated by the esterification reaction, which may impair the transparency of the resulting polyester (ie, increase haze). Moreover, since it may become a foreign material, it is preferable not to use a reaction catalyst during esterification reaction. Moreover, when a catalyst is added to the gas phase part of the reaction vessel, the haze may be increased, and the catalyst may be converted into a foreign substance.

In the polycondensation reaction, it is difficult to proceed without a catalyst, and it is preferable to use a catalyst. As the polycondensation reaction catalyst, a compound containing at least one of the metal elements of Groups 1 to 14 of the periodic table is generally used. Specific examples of metal elements include scandium, yttrium, samarium, titanium, zirconium, vanadium, chromium, molybdenum, tungsten, tin, antimony, cerium, germanium, zinc, cobalt, manganese, iron, aluminum, magnesium, calcium, Examples include strontium, sodium and potassium. Among them, scandium, yttrium, titanium, zirconium, vanadium, molybdenum, tungsten, zinc, iron, and germanium are preferable, and titanium, zirconium, tungsten, iron, and germanium are particularly preferable. Furthermore, in order to reduce the polyester terminal density | concentration which affects the thermal stability of polyester, among the said metals, the periodic table 3-6 group metal element which shows Lewis acidity is preferable. Specifically, scandium, titanium, zirconium, vanadium, molybdenum, and tungsten are preferable, and titanium and zirconium are particularly preferable from the viewpoint of availability, and titanium is more preferable from the viewpoint of reaction activity.
Here, the periodic table refers to a long-period periodic table (Nomenclature of Inorganic Chemistry IUPAC Recommendations 2005).

  The catalyst is preferably a liquid at the time of polymerization or a compound that dissolves in a low ester ester polymer or a polyester because the polymerization rate increases when it is in a molten or dissolved state during the polymerization. The polycondensation is preferably carried out without a solvent. Alternatively, a small amount of solvent may be used to dissolve the catalyst. Examples of the solvent for dissolving the catalyst include alcohols such as methanol, ethanol, isopropanol, and butanol, diols such as ethylene glycol, butanediol, and pentanediol, ethers such as diethyl ether and tetrahydrofuran, and nitriles such as acetonitrile. , Hydrocarbon compounds such as heptane and toluene, water and mixtures thereof.

  As the catalyst for producing the aliphatic polyester of the present invention, a catalyst in which a titanium compound, an alkaline earth metal compound and a phosphorus compound, which will be described in detail below, are mixed in advance (hereinafter referred to as “catalyst for aliphatic polyester polycondensation of the present invention”). It is preferable to use.

The content of titanium atom, alkaline earth metal atom and phosphorus atom in the aliphatic polyester polycondensation catalyst of the present invention is such that the content of titanium atom is T (molar basis) and the content of alkaline earth metal is M ( When the phosphorus content is P (molar basis), the lower limit of T / P (molar ratio) is usually 0.1, preferably 0.3, more preferably 0.5, particularly preferably Is 0.7, and the upper limit is usually 5.5, preferably 4.0, more preferably 3.0, particularly preferably 1.5, and most preferably 1.0.
When the T / P (molar ratio) is less than or equal to the above upper limit, the produced aliphatic polyester is less colored, the stability of the catalyst is good, the catalyst is hardly deactivated, and the catalyst deactivation product is contained in the product. The risk of contamination and loss of product quality tends to be low. On the other hand, when the T / P (molar ratio) is not less than the above lower limit, the catalytic activity tends to be high.

On the other hand, the lower limit of M / P (molar ratio) is usually 0.1, preferably 0.5, more preferably 0.7, particularly preferably 0.9, and the upper limit is usually 5.5, preferably 3 0.0, more preferably 2.0, still more preferably 1.5, particularly preferably 1.2, and most preferably 1.1.
When the M / P (molar ratio) is not more than the above upper limit, the thermal stability of the aliphatic polyester obtained using this catalyst tends to be good. In addition, alkaline earth metal is unlikely to precipitate. On the other hand, when M / P (molar ratio) is not less than the above lower limit, the catalytic activity is high and the amount of terminal carboxy groups hardly increases.

  The catalyst for aliphatic polyester polycondensation of the present invention is produced by mixing a titanium compound, an alkaline earth metal compound, and an acidic phosphate compound. When mixing the catalyst components, a solvent is usually used. As the solvent, a titanium compound, an alkaline earth metal compound, and an acidic phosphate compound may be used as a uniform solution, but alcohol is usually used.

That is, the aliphatic polyester polycondensation catalyst of the present invention is preferably produced by mixing an alcohol, a titanium compound, an alkaline earth metal compound, and an acidic phosphate compound. The aliphatic polyester polycondensation catalyst of the present invention is particularly preferably produced by mixing an alcohol, a titanium compound, an alkaline earth metal compound, and an acidic phosphate compound and concentrating the mixture. To elaborate on this particularly preferred production method,
(i) Step of mixing, dissolving, and reacting alcohol, titanium compound, alkali metal compound and acidic phosphate compound
(ii) A step of concentrating by distilling off alcohol etc. from the reaction solution obtained in step (i) and further proceeding with the reaction to obtain a viscous liquid catalyst, solid catalyst, or a mixture thereof. Manufactured by. At this time, it is considered that the alcohol used does not participate in the reaction but only serves as a solvent.

  The difference between the viscous liquid catalyst, the solid catalyst, or a mixture thereof and the resulting catalyst is due to the degree of concentration. The catalyst obtained in step (ii) can be easily recovered after it is dissolved or dissolved in glycol such as 1,4-butanediol or ethylene glycol. In addition, what is distilled off at the time of concentration is an alcohol, an organic acid, or the like by-produced by a reaction between an alcohol used as a solvent, a titanium compound, an alkaline earth metal compound, and an acidic phosphate compound.

The weight of the catalyst thus obtained is always less than the total weight of the raw materials excluding the alcohol used as the solvent. The weight W ₁ of the resulting catalyst and the sum W ₀ of the weights of the titanium compound, alkaline earth metal compound, and acidic phosphate compound used for mixing, that is, mixed with alcohol in the step (i) above. The ratio W ₁ / W ₀ is usually 0.45 or more and 0.85 or less. This ratio varies depending on the type of raw material compound used and the composition ratio.

  In the present invention, the alcohol used for the production of the catalyst is not particularly limited as long as it is an alcohol in which a titanium compound, an alkaline earth metal compound, and an acidic phosphate compound are mixed to form a homogeneous solution. Examples thereof include monohydric alcohols such as ethanol, butanol, propanol, and 2-ethylhexanol, and dihydric alcohols such as glycol. Among these, monohydric alcohols are preferably used because of the solubility of the compound and ease of handling. These alcohols may be used alone or in combination of two or more. In particular, ethanol is preferred because the titanium compound, alkaline earth metal compound, and acidic phosphate compound have high solubility and have a low boiling point when the reaction solution is concentrated and are easy to remove.

  Examples of titanium compounds include tetraalkoxy titanates such as tetra-n-propyl titanate, tetra-i-propyl titanate, tetra-n-butyl titanate, tetra-n-butyl titanate tetramer, tetra-t-butyl titanate; acetyl- Examples include tri-i-propyl titanate; titanium acetate and the like, among which tetra-i-propyl titanate and tetra-n-butyl titanate, which are easily available and easy to handle, are preferable, and tetra-n-butyl titanate is particularly preferable. These titanium compounds may be used individually by 1 type, and may use 2 or more types together.

  As the alkaline earth metal compound, an organic acid salt of alkaline earth metal and / or a hydrate thereof is preferably used. Among them, preferred compounds include organic acid salts such as magnesium and calcium, and / or hydrates thereof. Magnesium compounds are preferred from the viewpoint of catalytic activity. Examples of the magnesium compound include organic acid salts such as magnesium acetate and magnesium butyrate. In particular, magnesium acetate and / or a hydrate thereof are preferable because of high solubility in alcohol and easy preparation of a catalyst. These alkaline earth metal compounds may be used alone or in combination of two or more. Also, different metal compounds such as magnesium compounds and calcium compounds can be used in combination.

  As the acidic phosphate compound, those having an ester structure of phosphoric acid having at least one hydroxyl group represented by the following general formula (I) and / or (II) are preferably used.

(Wherein R, R ′ and R ″ each represent an alkyl group having 1 to 6 carbon atoms, a cyclohexyl group, an aryl group or a 2-hydroxyethyl group. In formula (I), R and R ′ are the same. It may or may not be.)

  Specific examples of such acidic phosphate ester compounds include methyl acid phosphate, ethyl acid phosphate, isopropyl acid phosphate, butyl acid phosphate, octyl acid phosphate, and the like, and ethyl acid phosphate and butyl acid phosphate are preferred. These acidic phosphate ester compounds may be used alone or in combination of two or more.

  In addition, although there exist monoester body (II) and diester body (I) in an acidic phosphoric ester compound, since the catalyst which shows high catalyst activity is obtained, a monoester body or a monoester body and a diester body It is preferable to use a mixture. The mixing weight ratio of monoester and diester (monoester: diester) is preferably 80 or less: 20 or more, more preferably 70 or less: 30 or more, and particularly preferably 60 or less: 40 or more. Also, it is preferably 20 or more and 80 or less, more preferably 30 or more and 70 or less, and particularly preferably 40 or more and 60 or less.

  In the production of polyester, when a plurality of catalyst components are used as a catalyst, conventionally, a method of separately introducing each catalyst component into a reactor from a plurality of introduction locations has been taken. On the other hand, as described above, the titanium raw material, the alkaline earth metal compound, and the phosphorus compound which are catalyst raw materials are mixed and prepared before being introduced into the reactor. In the present invention, a plurality of independent catalyst addition apparatuses are not required, so that the introduction points of the catalyst into the reactor can be integrated, and complicated control of the catalyst component ratio at the time of catalyst introduction is not required, which is industrially necessary. This is an advantageous process.

  A conventionally known apparatus can be used for the process of mixing, dissolving, and reacting the titanium compound, alkaline earth metal and phosphorus compound, and may be performed in a single reaction tank or a plurality of reaction tanks. . The reaction vessel is preferably provided with a stirring and mixing device in order to cause a uniform reaction.

  The reaction temperature is usually 0 ° C. or higher, preferably 10 ° C. or higher, more preferably 20 ° C. or higher, and usually 100 ° C. or lower, preferably 80 ° C. or lower, more preferably 50 ° C. or lower. After the reaction, the prepared solvent and the like are distilled off at 150 ° C. or lower with a conventionally known concentrating device as necessary to obtain a liquid or solid homogeneous catalyst.

  The aliphatic polyester polycondensation catalyst of the present invention can be handled as a viscous liquid before being isolated as a solid catalyst, and can be used as it is. In order to reduce the viscosity of such a viscous liquid and make it easier to handle, the aliphatic polyester polycondensation catalyst of the present invention is obtained by dissolving and diluting with 1,4-butanediol used as a raw material diol. It is preferably used as a solution.

  The titanium atom concentration after diluting such a viscous liquid catalyst with 1,4-butanediol has a lower limit of usually 0.02% by weight, preferably 0.05% by weight, and an upper limit of usually 1% by weight, preferably Is 0.5% by weight.

  The time when the aliphatic polyester polycondensation catalyst of the present invention is brought into contact with the reaction raw material is not particularly limited as long as it is before the polycondensation reaction. If the catalyst coexists in the situation where it is generated, the catalyst may be deactivated, foreign matter may be deposited, and the quality of the product may be impaired. Therefore, it may be added after the esterification reaction and / or transesterification reaction is completed. Is preferred.

  The lower limit of the amount of titanium atoms in the catalyst with respect to the polyester to be produced is usually 1 ppm by weight, preferably 10 ppm by weight, more preferably 15 ppm by weight, particularly preferably 20 ppm by weight, and the upper limit is usually 30000 ppm by weight. , Preferably 150 ppm by weight, more preferably 100 ppm by weight, particularly preferably 70 ppm by weight. When the titanium atomic weight is not more than the above upper limit, it is economically advantageous and the thermal stability of the polymer becomes good. Moreover, it is preferable at the point of polymerization activity as it is more than the said minimum, and decomposition | disassembly of the polymer during polymer manufacture does not occur easily. Further, the smaller the amount of titanium atom, the smaller the amount of catalyst is preferable in that the carboxyl group terminal concentration of the produced polyester is reduced.

  The lower limit of the amount of magnesium atom in the catalyst relative to the polyester to be produced is usually 1 ppm by weight, preferably 5 ppm by weight, more preferably 10 ppm by weight, particularly preferably 20 ppm by weight, and the upper limit is usually 200 ppm by weight. , Preferably 100 ppm by weight, more preferably 70 ppm by weight, particularly preferably 50 ppm by weight. When the magnesium atomic weight is not more than the above upper limit, it is economically advantageous and the color tone of the polymer tends to be good. On the other hand, if it is at least the above lower limit, it is preferable from the viewpoint of polymerization activity, and the polymer is hardly decomposed during the production of the polymer.

  The lower limit of the amount of phosphorus atoms in the catalyst relative to the polyester to be produced is usually 1 ppm by weight, preferably 10 ppm by weight, more preferably 20 ppm by weight, particularly preferably 30 ppm by weight, and the upper limit is usually 200 ppm by weight. , Preferably 100 ppm by weight, more preferably 70 ppm by weight, particularly preferably 50 ppm by weight. When the phosphorus atom weight is not more than the above upper limit, it is economically advantageous and the polymerization activity is high, so that the polymer is hardly decomposed during the production of the polymer. Moreover, it is preferable at the point of the color tone of a polymer that phosphorus atom weight is more than the said minimum.

<Example of manufacturing process>
Hereinafter, a preferred embodiment of a method for producing an aliphatic polyester using succinic acid as an aliphatic dicarboxylic acid, 1,4-butanediol as an aliphatic diol, and malic acid as a polyfunctional compound will be described based on the drawings. However, the present invention is not limited to this.

  FIG. 1 is an explanatory diagram of an example of an esterification reaction step employed in the present invention, FIG. 2 is an explanatory diagram of an example of a polycondensation step employed in the present invention, and FIG. 3 is a wet condensation employed in the present invention. FIG. 4 is an explanatory diagram of an example of a process, and FIG. 4 is an explanatory diagram of an example of a steam ejector system and a distillation purification system employed in the present invention.

  In FIG. 1, succinic acid and malic acid as raw materials are usually mixed with 1,4-butanediol in a raw material mixing tank (not shown), and esterified in the form of slurry or liquid from the raw material supply line (1). It is supplied to the tank (A). Moreover, when adding a catalyst at the time of esterification, after making it the solution of 1, 4- butanediol in a catalyst adjustment tank (not shown), a catalyst solution is supplied from a catalyst supply line (3). In FIG. 1, the catalyst supply line (3) is connected to the recirculation line (2) of the recirculated 1,4-butanediol, and both are mixed and then supplied to the liquid phase part of the esterification reaction tank (A). showed that.

  The gas distilled from the esterification reaction tank (A) is separated into a high-boiling component and a low-boiling component in the rectifying column (C) through the distillation line (5). Usually, the main component of the high boiling component is 1,4-butanediol, and the main component of the low boiling component is water and tetrahydrofuran, which is a decomposition product of 1,4-butanediol.

  The high-boiling components separated in the rectification column (C) are extracted from the extraction line (6), passed through the pump (D), and partly from the recirculation line (2) to the esterification reaction tank (A). It is circulated and part is returned from the circulation line (7) to the rectification column (C). Further, the surplus is extracted outside from the extraction line (8). On the other hand, the light boiling components separated in the rectification column (C) are extracted from the gas extraction line (9), condensed in the condenser (G), and temporarily passed through the condensate line (10) to the tank (F). Can be stored. A part of the light boiling components collected in the tank (F) is returned to the rectification column (C) through the extraction line (11), the pump (E) and the circulation line (12), and the remainder is extracted. It is extracted outside through the line (13). The condenser (G) is connected to an exhaust device (not shown) via a vent line (14). The esterification reaction product generated in the esterification reaction tank (A) passes through the extraction pump (B) and the extraction line (4) of the esterification reaction product, and the first polycondensation reaction tank (a) shown in FIG. To be served.

  In the process shown in FIG. 1, the catalyst supply line (3) is connected to the recirculation line (2), but both may be independent. Moreover, the raw material supply line (1) may be connected to the liquid phase part of the esterification reaction tank (A).

  When adding a catalyst to the esterification reaction product before the polycondensation tank, a catalyst solution is prepared to a predetermined concentration in a catalyst preparation tank (not shown), and then passed through a catalyst supply line (L7) in FIG. , 4-butanediol) supply line (L8), further diluted with 1,4-butanediol, and then supplied to the esterification reaction product extraction line (4).

  The esterification reaction product supplied to the first polycondensation reaction tank (a) from the extraction line (4) of the esterification reaction product (a filter may be provided in this extraction line (4)) The polycondensation is carried out to form a low-polyester polymer, and then passed through the extraction gear pump (c) and the extraction line (L1) (a filter may be provided on this extraction line (L1)). It supplies to a polycondensation reaction tank (d). In the second polycondensation reaction tank (d), the polycondensation reaction usually proceeds further at a lower pressure than in the first polycondensation reaction tank (a). The obtained polycondensate passes through an extraction gear pump (e) and an extraction line (L3) which is an outlet channel (a filter may be provided in the extraction line (L3)), and then the third. It supplies to a polycondensation reaction tank (k). The third polycondensation reaction tank (k) is a horizontal reaction tank composed of a plurality of stirring blade blocks and equipped with a biaxial self-cleaning type stirring blade. The polycondensation reaction product introduced from the second polycondensation reaction tank (d) to the third polycondensation reaction tank (k) through the extraction line (L3) is further pelletized after the polycondensation reaction is further advanced here. It is transferred to the process.

  In the pelletizing step, the molten polyester is passed through the filter (n) through the extraction line (L5) by the extraction gear pump (m), and then cut with the underwater cutter (h) to obtain the polyester pellets. obtain. In addition, after extracting a melt strand in air | atmosphere and cooling with water, you may cut | disconnect and pelletize with a rotary cutter.

  Reference numerals (L2), (L4), and (L6) in FIG. 2 denote vents of the first polycondensation reaction tank (a), the second polycondensation reaction tank (d), and the third polycondensation reaction tank (k), respectively. The pressures of the respective polycondensation reaction tanks (a), (d), and (k) are from the vent lines (L2), (L4), (L6) to the wet condenser (Q1) shown in FIG. The pressure is reduced by the steam ejector system shown in FIG. 4 via (Q2) and (Q3). That is, the vent line (L2) is connected to the steam ejector system of FIG. 4 via the wet condenser (Q1) shown in FIG. 3 and the vent line (21). The vent line (L4) is connected to the steam ejector system of FIG. 4 via the wet condenser (Q2) shown in FIG. 3 and the vent line (31). The vent line (L6) is connected to the steam ejector system of FIG. 4 via the wet condenser (Q3) shown in FIG. 3 and the vent line (41).

  A hot well tank (H100) is connected to the wet condenser (Q1), and drain liquid discharged from the wet condenser (Q1) is introduced from the line (101). The drain liquid is composed of a liquid containing the collected and dissolved process scattered matter and 1,4-butanediol as a refrigerant. The drain liquid is returned to the wet condenser (Q1) via the line (103), the circulation pump (P100), and the line (104), and a part of the drain liquid is controlled by the liquid level control of the hot well tank (H100). Then, it is transferred to a raw material slurry preparation tank (not shown) and used as a part of the raw material diol.

  A hot well tank (H200) is connected to the wet capacitor (Q2), and drain liquid discharged from the wet capacitor (Q2) is introduced. The drain liquid is composed of a liquid containing the collected and dissolved process scattered matter and 1,4-butanediol as a refrigerant. The drain liquid is returned to the wet condenser (Q2) via the line (203), the circulation pump (P200), and the line (204), and a part of the drain liquid is controlled by the liquid level control of the hot well tank (H200). To the hot well tank (H100).

  A hot well tank (H300) is connected to the wet condenser (Q3), and a drain liquid discharged from the wet condenser (Q3) is introduced. The drain liquid is composed of a liquid containing the collected and dissolved process scattered matter and 1,4-butanediol as a refrigerant. The drain liquid is returned to the wet condenser (Q3) via the line (303), the circulation pump (P300), and the line (304). The bottom liquid of the distillation purification tower (J1) in FIG. 4 is supplied to the hot well tank (H300) via the lines (60) and (61), mixed with the drain liquid, and stored in the hot well tank (H300). It is mixed with the liquid and transferred to the hot well tank (H200) via the line (302) by the liquid level control of the hot well tank (H300).

  In the steam ejector system of FIG. 4, new 1,4-butanediol is supplied from outside the system to the 1,4-butanediol steam generator (K) for driving the ejector through the supply line (19). 1,4-butanediol vapor generated by heating in the generator (K) passes through the supply line (20) to each ejector (for the first polycondensation reaction tank: (A1), (A3), second heavy For condensation reaction tank: (B1), (B3), (B5), for third polycondensation reaction tank: (C1), (C3), (C5)). Further, by the liquid level control of the steam generator (K), the liquid consisting of 1,4-butanediol in the apparatus is withdrawn via the line (63) and transferred to a raw material slurry preparation tank (not shown). And used as part of the raw diol.

  A gas mainly composed of 1,4-butanediol, tetrahydrofuran and water distilled from the first polycondensation reaction tank (a) through the vent line (L2) is condensed in the wet condenser (Q1). The uncondensed gas (Q1) is introduced into the ejector (A1) via the line (21). The 1,4-butanediol vapor discharged from the ejector (A1) is condensed by the barometric condenser (A2), and the condensate is collected in the hot well tank (H2) through the atmospheric leg (25). On the other hand, the component that has not been condensed by the barometric condenser (A2) is sent to the second-stage ejector (A3), and the condensed liquid is collected in the hot well tank (H3) through the atmospheric leg (26). As in the first stage, components not condensed by the barometric condenser (A4) are discharged out of the system from the line (24) by the vacuum pump (A5). Lines (22) and (23) are 1,4-butanediol supply lines, and the entire amount is circulated and supplied from hot well tanks (H2) and (H3) (not shown).

  The gas mainly composed of 1,4-butanediol, tetrahydrofuran and water distilled from the second polycondensation reaction tank (d) via the vent line (L4) is condensed in the wet condenser (Q2). The uncondensed gas of (Q2) is introduced into the ejector (B1) via the line (31). The 1,4-butanediol vapor discharged from the ejector (B1) is condensed by the barometric condenser (B2), and the condensate is collected in the hot well tank (H1) through the atmospheric leg (36). On the other hand, the component that has not been condensed by the barometric condenser (B2) is sent to the second-stage ejector (B3), and the condensed liquid is collected in the hot well tank (H2) through the atmospheric leg (37). As in the first stage, the components that have not been condensed by the barometric condenser (B4) are sent to the third stage ejector (B5), and the condensate is collected in the hot well tank (H3) through the atmospheric leg (38). As in the second stage, components that have not been condensed by the barometric condenser (B6) are discharged out of the system from the line (35) by the vacuum pump (B7). Lines (32), (33) and (34) are supply lines for 1,4-butanediol, and the entire amount is circulated and supplied from hot well tanks (H1), (H2) and (H3) (not shown). .)

  A gas mainly composed of 1,4-butanediol, tetrahydrofuran and water distilled from the third polycondensation reaction tank (k) via the vent line (L6) is condensed in the wet condenser (Q3). The uncondensed gas (Q3) is introduced into the ejector (C1) via the line (41). The 1,4-butanediol vapor discharged from the ejector (C1) is condensed by the barometric condenser (C2), and the condensate is collected in the hot well tank (H1) through the atmospheric leg (46). On the other hand, the component that has not been condensed by the barometric condenser (C2) is sent to the second-stage ejector (C3), and the condensate is collected in the hot well tank (H2) through the atmospheric leg (47). As in the first stage, components that have not been condensed by the barometric condenser (C4) are sent to the third stage ejector (C5), and the condensate is collected in the hot well tank (H3) through the atmospheric leg (48). As in the second stage, components that have not been condensed by the barometric condenser (C6) are discharged out of the system from the line (45) by the vacuum pump (C7). Lines (42), (43) and (44) are 1,4-butanediol supply lines, and the entire amount is circulated and supplied from hot well tanks (H1), (H2) and (H3) (not shown). .)

  In the illustrated embodiment, after the 1,4-butanediol is supplied to the hot well tank (H1) from the outside via the line (51) and mixed with the condensate of the barometric condensers (B2) and (C2). Then, the liquid in the tank is supplied to the hot well tank (H2) through the line (52) by the liquid level control, and further the barometric capacitors (A2), (B4), (C4) in the hot well tank (H2). Then, the liquid in the tank is supplied to the hot well tank (H3) via the line (53) by liquid level control.

  The liquid containing 1,4-butanediol as the main component collected in the hot well tank (H3) passes through the pump (H6) and the line (56) and is a light-boiling component such as tetrahydrofuran and water in the distillation purification tower (J1). Is removed. The bottom liquid (purified 1,4-butanediol-containing liquid) of the distillation purification tower (J1) passes through the line (60) by the pump (J2) and partly passes through the line (62) to drive 1,4 for ejector driving. -It returns to the butanediol steam generator (K), and the remainder is supplied to the hot well tank (H300) of Fig. 3 through the line (61).

  In the present invention, for example, the amount of purified 1,4-butanediol-containing liquid, which is the bottom liquid of the distillation purification tower (J1), is supplied to each steam ejector by controlling the return amount to the steam generator (K). The acid value of the 1,4-butanediol-containing liquid, that is, the sealing liquid in the steam generator (K) is 30 eq. / Ton or less. In this case, the suitable return amount of the bottom liquid of the distillation purification tower (J1) to the steam generator (K) varies depending on the operating conditions of the entire aliphatic polyester production system, but generally the distillation purification tower. By returning 20 to 80% of the bottom liquid of (J1) to the steam generator (K) and supplying the remainder to the hot well tank (H300), the acid value of the sealing liquid in the steam generator (K) is set to 30 eq. . / Ton or less.

<Polyester composition>
You may mix | blend aromatic polyester, aliphatic oxycarboxylic acid, etc. with the aliphatic polyester of this invention. Furthermore, carbodiimide compounds, fillers, plasticizers, and other biodegradable resins that are used as necessary, such as polycaprolactone, polyamide, polyvinyl alcohol, cellulose ester, etc. Cellulose, paper, wood powder, chitin / chitosan, animal / plant substance fine powder such as coconut shell powder, walnut shell powder, or a mixture thereof can be blended. Furthermore, additives such as heat stabilizers, plasticizers, lubricants, anti-blocking agents, nucleating agents, inorganic fillers, colorants, pigments, ultraviolet absorbers, light stabilizers, etc. are used for the purpose of adjusting the physical properties and processability of the molded products. Further, a modifier, a crosslinking agent, etc. may be included.

  The method for producing the polyester composition from the aliphatic polyester of the present invention is not particularly limited, but is a method in which raw material chips of the blended polyester are melt-mixed in the same extruder, and are mixed after being melted in separate extruders. Examples thereof include mixing by kneading using a conventional kneader such as a method, a single screw extruder, a twin screw extruder, a Banbury mixer, a roll mixer, a Brabender plastograph, and a kneader blender. In addition, it is possible to obtain a molded body at the same time as preparing a composition by directly supplying each raw material chip to a molding machine.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited by a following example, unless the summary is exceeded.

[Preparation Example 1: Preparation of catalyst solution]
270 kg of ethanol (purity 99% by weight or more) and 60 kg of magnesium acetate tetrahydrate were added to a jacketed stirring tank (capacity: 600 L) equipped with a vacuum distillation column. Further, 270 kg of ethyl acid phosphate (mixing weight ratio of monoester and diester was 45:55) was added and stirred at room temperature. After confirming that magnesium acetate was completely dissolved, 74 kg of tetra-n-butyl titanate was added. Stirring was further continued to obtain a homogeneous mixed solution. Thereafter, warm water at 80 ° C. was passed through the jacket and concentrated under reduced pressure, and most of ethanol was distilled off to obtain a translucent viscous liquid. 1,4-Butanediol was added to this liquid to prepare a titanium atom content of 3.5% by weight.

[Example 1]
The esterification step shown in FIG. 1, the polycondensation step shown in FIG. 2, the wet condensation step shown in FIG. 3, the steam ejector system and the steam purification system shown in FIG. Manufactured.

  First, a slurry at 60 ° C. mixed at a ratio of 1.30 mol of 1,4-butanediol and 0.0028 mol of malic acid to 1.00 mol of succinic acid from a slurry preparation tank (not shown). Through the supply line (1), an aliphatic polyester oligomer having an esterification rate of 95% or more is prepared in a batch reaction in advance, and the esterification reaction tank (A) having a stirrer maintained at 230 ° C. has a capacity of 3500 kg / h. Was fed continuously. At the same time, the bottom component of the rectifying column (C) at 180 ° C. (98% by weight or more was 1,4-butanediol) was fed at 200 kg / h from the recirculation line (2).

  The internal temperature of the reaction vessel (A) is 230 ° C., the pressure is 101 kPa, and the produced water, tetrahydrofuran and excess 1,4-butanediol are distilled from the distillation line (5), and the rectification column (C) It separated into a high boiling component and a low boiling component. A part of the high boilers extracted from the bottom of the rectification column (C) through the line (6) was circulated through the line (7) to the rectification column (C). The high-boiling component at the bottom of the column after the system has been stabilized is 98% by weight or more of 1,4-butanediol, and the extraction line (8) so that the liquid level of the rectifying column (C) is constant. A part of it was extracted outside. On the other hand, a low boiling component mainly composed of water and tetrahydrofuran is withdrawn in the form of gas from the top of the column and condensed with a condenser (G), so that the liquid level in the tank (F) becomes constant. More extracted outside.

  A certain amount of the oligomer as the esterification reaction product generated in the reaction tank (A) is extracted from the oligomer extraction line (4) using the pump (B), and the succinic acid in the reaction tank (A) is liquid. The liquid level was controlled so that the residence time in terms of unit was 3 hours. The oligomer extracted from the extraction line (4) was continuously supplied to the first polycondensation reaction tank (a) in FIG. After the system was stabilized, the esterification rate of the reaction product collected at the outlet of the esterification reaction tank (A) was 90.6%.

  The catalyst solution prepared in Preparation Example 1 was further diluted with 1,4-butanediol from the supply line (L7) to the supply line (L8) in FIG. 2 so that the concentration as titanium atoms was 0.1% by weight. The liquid was supplied to the extraction line (4) for the esterification reaction product at 120 kg / h (the amount of new 1,4-butanediol (commercial product) used for preparing the catalyst solution was about 120 kg / h).

  The internal temperature of the first polycondensation reaction tank (a) is 240 ° C., the pressure is 2.66 kPa, and the liquid level is controlled so that the residence time is 2 hours. From the vent line (L2), water, tetrahydrofuran, An initial polycondensation reaction was performed while extracting 4-butanediol. The vent line (L2) was connected to the steam ejector system of FIG. 4 via the wet condenser (Q1) shown in FIG. 3 and the vent line (21).

  A hot well tank (H100) is connected to the wet condenser (Q1) of FIG. 3, and drain liquid discharged from the wet condenser (Q1) is introduced from the line (101). The drain liquid is composed of a liquid containing the collected and dissolved process scattered matter and 1,4-butanediol as a refrigerant. The drain liquid was returned to the wet condenser (Q1) via the line (103), the circulation pump (P100), and the line (104). A part of the drain liquid was transferred to a raw material slurry preparation tank (not shown) via the line (102) by the liquid level control of the hot well tank (H100) and used as a part of the raw material diol.

  On the other hand, the reaction liquid extracted from the first polycondensation reaction tank (a) in FIG. 2 is continuously connected to the second polycondensation reaction tank (d) via the extraction line (L1) by the extraction gear pump (c). Supplied.

  The internal temperature of the second polycondensation reaction tank (d) is 240 ° C., the pressure is 0.40 kPa, and the liquid level is controlled so that the residence time is 2.5 hours. From the vent line (L4), water, tetrahydrofuran, The polycondensation reaction was further advanced while extracting 1,4-butanediol. The vent line (L4) was connected to the steam ejector system of FIG. 4 through the wet condenser (Q2) shown in FIG. 3 and the vent line (31).

  A hot well tank (H200) is connected to the wet capacitor (Q2), and drain liquid discharged from the wet capacitor (Q2) is introduced. The drain liquid is composed of a liquid containing the collected and dissolved process scattered matter and 1,4-butanediol as a refrigerant. The drain liquid was returned to the wet condenser (Q2) via the line (203), the circulation pump (P200), and the line (204). A part of the drain liquid was transferred to the hot well tank (H100) via the line (202) by the liquid level control of the hot well tank (H200).

  On the other hand, the polyester obtained from the second polycondensation reaction tank (b) in FIG. 2 continues to the third polycondensation reaction tank (k) via the extraction line (L3) by the extraction gear pump (e). Supplied.

  The internal temperature of the third polycondensation reaction tank (k) is 240 ° C., the pressure is 0.13 kPa, and the liquid level is controlled so that the residence time is 3 hours. From the vent line (L6), water, tetrahydrofuran, The polycondensation reaction was further advanced while extracting 4-butanediol. The vent line (L6) was connected to the steam ejector system of FIG. 4 through the wet condenser (C3) shown in FIG. 3 and the vent line (31).

  A hot well tank (H300) is connected to the wet condenser (Q3), and a drain liquid discharged from the wet condenser (Q3) is introduced. The drain liquid is composed of a liquid containing the collected and dissolved process scattered matter and 1,4-butanediol as a refrigerant. The drain liquid was returned to the wet condenser (Q3) via the line (303), the circulation pump (P300), and the line (304).

  The bottom liquid of the distillation purification tower (J1) of FIG. 4 is supplied to the hot well tank (H300) at 1000 kg / h via lines (60) and (61), mixed with the drain liquid, The liquid in H300) was transferred to the hot well tank (H200) via the line (302) by the liquid level control of the hot well tank (H300).

  On the other hand, the polyester obtained in the third polycondensation reaction tank (k) passes through the extraction line (L5) by the extraction gear pump (m), and is a pleat using a laminated metal nonwoven fabric having an absolute filtration accuracy of 40 μm as a filter medium. An aliphatic polyester pellet was produced by passing through a mold polymer filter (n) and cutting with an underwater cutter (h).

  In addition, the pressure of each polycondensation reaction tank (a), (d), (k) was controlled using the steam ejector system shown in FIG.

  In the steam ejector system, new 1,4-butanediol (commercially available) is supplied from the outside to the 1,4-butanediol steam generator (K) for driving the ejector through the supply line (19) at 1350 kg / h. Continuously supplied, heated to 240 ° C. to generate 1,4-butanediol vapor of 2000 kg / h, and through each supply line (20), each ejector (for the first polycondensation reaction tank: (A1), (A3 ), For the second polycondensation reaction tank: (B1), (B3), (B5), for the third polycondensation reaction tank: (C1), (C3), (C5)). In addition, a liquid composed of 1,4-butanediol is extracted from the steam generator (K) via the line (63) by controlling the liquid level of the steam generator (K), and is supplied to a raw material slurry preparation tank (not shown). Transferred and used as part of the raw diol.

  The gas mainly composed of tetrahydrofuran and water distilled from the first polycondensation reaction tank (a) is introduced into the ejector (A1) through the wet condenser (Q1) and the line (21). The 1,4-butanediol vapor discharged from A1) is condensed in the barometric condenser (A2), and the condensate is collected in the hot well tank (H2) through the atmospheric leg (25). On the other hand, the components that were not condensed by the barometric condenser (A2) were sent to the second-stage ejector (A3), and the condensate was collected in the hot well tank (H3) through the atmospheric leg (26). As in the first stage, components not condensed by the barometric condenser (A4) were discharged out of the system from the line (24) using the vacuum pump (A5). Lines (22) and (23) were 1,4-butanediol supply lines, and the entire amount was circulated and supplied from hot well tanks (H2) and (H3) (not shown).

  A gas mainly composed of tetrahydrofuran and water distilled from the second polycondensation reaction tank (d) is introduced into the ejector (B1) through the line (31), and is discharged from the ejector (B1) at this time. 4-Butanediol vapor was condensed in a barometric condenser (B2) and the condensate was collected in a hot well tank (H1) through an atmospheric leg (36). On the other hand, the component that was not condensed by the barometric condenser (B2) was sent to the second-stage ejector (B3), and the condensate was collected in the hot well tank (H2) through the atmospheric leg (37). In the same manner as in the first stage, the components not condensed by the barometric condenser (B4) were sent to the third stage ejector (B5), and the condensate was collected in the hot well tank (H3) through the atmospheric leg (38). . As in the second stage, components not condensed by the barometric condenser (B6) were discharged out of the system from the line (35) using the vacuum pump (B7). Lines (32), (33), and (34) are 1,4-butanediol supply lines, and the entire amount was circulated and supplied from hot well tanks (H1), (H2), and (H3) (not shown). ).

  A gas mainly composed of tetrahydrofuran and water distilled from the third polycondensation reaction tank (k) is introduced into the ejector (C1) through the line (41), and is discharged from the ejector (C1) at this time. 4-Butanediol vapor was condensed in a barometric condenser (C2) and the condensate was collected in a hot well tank (H1) through an atmospheric leg (46). On the other hand, the component that was not condensed by the barometric condenser (C2) was sent to the second-stage ejector (C3), and the condensate was collected in the hot well tank (H2) through the atmospheric leg (47). As in the first stage, the components that were not condensed by the barometric condenser (C4) were sent to the third stage ejector (C5), and the condensate was collected in the hot well tank (H3) through the atmospheric leg (48). . As in the second stage, components not condensed by the barometric condenser (C6) were discharged out of the system from the line (45) using the vacuum pump (C7). Lines (42), (43) and (44) are 1,4-butanediol supply lines, and the entire amount was circulated and supplied from hot well tanks (H1), (H2) and (H3) (not shown). ).

  New 1,4-butanediol (commercially available) is supplied to the hot well tank (H1) from the outside at a line (51) at 50 kg / h and mixed with the condensate of the barometric condensers (B2) and (C2). After that, the liquid in the tank was supplied to the hot well tank (H2) via the line (52) by liquid level control. In the hot well tank (H2), after mixing with the condensate of the barometric condensers (A2), (B4), (C4), the liquid in the tank is supplied via the line (53) to control the hot well tank (H3 ).

  The liquid containing 1,4-butanediol as the main component collected in the hot well tank (H3) passes through the pump (H6) and the line (56) and is a light-boiling component such as tetrahydrofuran and water in the distillation purification tower (J1). , After returning from the pump (J2) and the line (60) through the line (62) to the 1,4-butanediol steam generator (K) for driving the ejector, and through the line (61) in FIG. It was supplied to a hot well tank (H300). Here, the amount of liquid returned to the steam generator (K) was 50% of the bottom liquid (liquid in line (60)) of the distillation rectification column (J1).

  Under the above operating conditions, the operation was stably continued for one month. The production amount of polyester (PBS) was 2500 kg / h.

[Comparative Example 1]
In Example 1, the supply (line (61)) of the bottom liquid of the distillation purification tower (J1) in FIG. 4 to the hot well tank (H300) was stopped, and the entire bottom liquid of the distillation purification tower (J1) was vaporized. As well as returning to the evaporator (K), new 1,4-butanediol (commercially available) was supplied from the line (64) to the hot well tank (H300) from the outside at 1000 kg / h, and the same as in Example 1 I started driving under conditions.

When the operation is continued, the pressure reduction of each polycondensation reaction tank (a), (d), (k) cannot be maintained gradually, and the supply rate of the raw slurry to the esterification reaction tank (A) must be reduced, Finally, operation was stable under the following conditions.
Circulation rate of the bottom component of the rectification column (C) from the recirculation line (2) (98% by weight or more is 1,4-butanediol): 140 kg / h
Feed rate of the catalyst solution (titanium atom equivalent concentration 0.1 wt%) to the extraction line (4) of the esterification reaction product: 85 kg / h
Supply amount of new 1,4-butanediol (commercial product) to the hot well tank (H300): 750 kg / h

  The polyester obtained in the third polycondensation reaction tank (k) passes through the extraction line (L5) by the extraction gear pump (m), and is a pleated polymer using a laminated metal nonwoven fabric having an absolute filtration accuracy of 40 μm as a filter medium. An aliphatic polyester pellet was produced by passing the filter (n) and cutting with an underwater cutter (h).

Except for the above, the operation for continuously producing the aliphatic polyester under the same conditions as in Example 1 was continued for 1 month.
Polyester (PBS) production was 1750 kg / h.

  The amount of novel 1,4-butanediol introduced from outside the system in Example 1 and Comparative Example 1 above and 1,4-butanediol in the line (63) were measured by the following method. Acid value of diol (this acid value corresponds to the acid value of 1,4-butanediol in the steam generator (K)), and tetrahydrofuran of 1,4-butanediol measured by the following method (THF) ) Concentration, production amount of produced polyester, introduction amount of new 1,4-butanediol per unit weight of the produced polyester (new 1,4-BG / production polyester) in comparison with Table 1 below Show.

<Method for Measuring Acid Value of 1,4-Butanediol>
While measuring the pH of an aqueous solution obtained by diluting 5 g of 1,4-butanediol to 100 mL with distilled water, titration was performed with a 0.01N aqueous sodium hydroxide solution. The acid value of butanediol was calculated.
Acid value (eq./ton)=0.01×0.1N aqueous sodium hydroxide titration (mL) / sample amount (g) × 1000

<Method for measuring THF concentration>
Tetrahydrofuran concentration in 1,4-butanediol by a gas chromatography method using a capillary column (J & W DB-wax (Agilent Technology Inc.) 60 m (L) × 0.32 mm (ID) × 0.5 μm (Thickness)) Was quantified.

  From Table 1, according to the present invention, by suppressing the by-product of THF in the system, the effective utilization efficiency of 1,4-butanediol used as the driving steam source of the steam ejector is increased, and the aliphatic polyester is stabilized. It can be seen that continuous production can be efficiently performed by operation.

DESCRIPTION OF SYMBOLS 1 Raw material supply line 2 Recirculation line 3 Esterification reaction tank catalyst supply line 4 Esterification reaction product (oligomer) extraction line 5 Distillation line 6 Extraction line 7 Circulation line 8 Extraction line 9 Gas extraction line 10 Condensation Liquid line 11 Extraction line 12 Circulation line 13 Extraction line 14 Vent line A Esterification reaction tank B Extraction pump C Rectification tower D, E Pump F Tank G Capacitors L1, L3, L5 Polycondensation reaction product extraction line L2 , L4, L6 Vent line L7 Catalyst supply line L8 Raw material supply line a First polycondensation reaction tank d Second polycondensation reaction tank k Third polycondensation reaction tank c, e, m Gear pump for extraction
h Submersible cutter n Filter Q1, Q2, Q3 Wet condenser H100, H200, H300 Hot well tank P100, P200, P300 Circulation pump 101, 201, 301 Drain liquid discharge line 102, 202, 302 Drain liquid transfer line 103, 104, 203 , 204, 303, 304 Drain liquid circulation lines A1, A3, B1, B3, B5, C1, C3, C5 Ejectors A2, A4, B2, B4, B6, C2, C4, C6 Barometric capacitors A5, B7, C7 Vacuum Pump H1, H2, H3 Hot well tank H6, J2 Pump J1 Distillation purification tower J3 Distillation purification tower reboiler K Ejector drive 1,4-butanediol steam generator 19, 51 External 1,4-butanediol Supply line 20 Ezek 1,4-Butanediol vapor supply line to the tank 21 Vent line from the first polycondensation reaction tank through the wet condenser 31 Vent line from the second polycondensation reaction tank through the wet condenser 41 Wet from the third polycondensation reaction tank Vent line through condenser 22, 23, 32, 33, 34, 42, 43, 44 1,4-butanediol supply line 24, 35, 45 Discharge gas line from vacuum pump 25, 26, 36, 37, 38 46, 47, 48 Atmospheric leg of barometric condenser 56 Supply line of 1,4-butanediol from hot well tank to distillation purification column 57 Extraction line of low boiling point component 60 Extraction line of bottom liquid of distillation purification column 61 Distillation Purification Tower Bottom Liquid Supply Line to Wet Capacitor Hot Well Tank 62 Distillation Purification Tower Bottom Liquid From return line 63 steam generator to the steam generator to the slurry preparation tank 1,4 extraction line

Claims (3)

An aliphatic polyester is obtained by performing esterification reaction and / or transesterification reaction and polycondensation reaction between a diol component mainly composed of 1,4-butanediol and a dicarboxylic acid component mainly composed of an aliphatic dicarboxylic acid component. In the manufacturing method,
The polycondensation reaction is performed under reduced pressure using a decompression device,
The decompression device has a steam ejector that uses 1,4-butanediol vapor obtained by vaporizing 1,4-butanediol as a driving steam,
The 1,4-butanediol vapor used in the steam ejector is condensed to obtain a 1,4-butanediol-containing liquid, and at least a part of the 1,4-butanediol-containing liquid is used as a driving steam source for the steam ejector. A method for producing an aliphatic polyester for recycling and recycling,
The acid value of the 1,4-butanediol-containing liquid sealed in the steam generator is 30 eq. / Ton or less, The manufacturing method of the aliphatic polyester characterized by the above-mentioned.   At least a part of the 1,4-butanediol-containing liquid is distilled in a distillation tower, and at least a part of the purified 1,4-butanediol-containing liquid obtained from the bottom of the distillation tower is used as a driving steam source for the steam ejector. The method for producing an aliphatic polyester according to claim 1, wherein the aliphatic polyester is recycled as   The polycondensation reaction apparatus for performing the polycondensation reaction has a reaction tank, and the reaction tank has a wet capacitor for collecting unreacted gas distilled from the reaction tank. The method for producing an aliphatic polyester according to claim 1, wherein the remainder of the 1,4-butanediol-containing liquid and / or the purified 1,4-butanediol-containing liquid is used.

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