JP2010132898A - Polyester manufacturing method, and 1,4-butanediol heating device and steam generator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method and device whereby good quality polyester can be obtained by performing a polyester polycondensation reaction that is stable over a long period in the manufacture of polyester from starting materials that contain a diol component composed mostly of heated 1,4-butanediol. <P>SOLUTION: There is provided a method of manufacturing polyester by causing an esterification reaction and/or transesterification and a polycondensation reaction between a diol component composed mostly of 1,4-butanediol and a dicarboxylic acid component, wherein the diol component contains 1,4-butanediol that has been subjected to heating, and stainless steel that contains molybdenum is used in the parts of the heating device that implements the heating history and that contact the 1,4-butanediol. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a polyester production method, a 1,4-butanediol heating apparatus, and a steam generation apparatus, and more specifically, in the production of polyester using heated 1,4-butanediol as a raw material, it is stably continuous. In particular, it relates to a method capable of producing polyester.

Polyesters obtained by polycondensation reaction using dicarboxylic acid and diol as raw materials are used in various applications. 1,4-butanediol (hereinafter referred to as 1,4 butanediol) as the main component of the diol
It may be expressed as -BG. ) Using polybutylene terephthalate, polybutylene succinate and the like are usefully used as engineering plastics and biodegradable polymers.

The raw material 1,4-BG may contain a small amount of impurities, and in particular, 2- (4′-hydroxybutoxy) tetrahydrofuran (hereinafter sometimes referred to as BGTF) which is a monofunctional substance is heavy. 1,4-BG having a low BGTF content is desired, which is known to act as a condensation reaction terminator and to deteriorate the color tone of the resulting polyester. (Patent Document 1)
On the other hand, the polycondensation reaction, particularly the melt polycondensation reaction, is usually carried out at a high temperature and under reduced pressure, but this reduced pressure addition device has a vapor ejector, and it is known to use 1,4-BG vapor as the vapor. . (Patent Document 2)
However, in our study, if an ejector using 1,4-BG vapor is used as a decompression device, 1,4-BG vapor used in the ejector is condensed and used as a polycondensation reaction raw material for a long period of operation. In addition, there is a problem that the polycondensation reactivity is lowered and the quality of the obtained polyester tends to be deteriorated. Further, the 1,4-BG vapor used in the ejector is condensed and then purified by distillation. However, it has been found that there is a problem in that the polycondensation reactivity decreases and the quality of the resulting polyester tends to deteriorate when operated for a long period of time.

Japanese Patent Laid-Open No. 10-265418 International Publication No. 2004/026938 Pamphlet

  The present invention suppresses the production of BGTF in 1,4-BG by heating, and even when heated 1,4-BG is used as a raw material, the polycondensation reaction of polyester is performed stably for a long period of time. It is an object of the present invention to provide a method and an apparatus for obtaining polyester with good quality.

As a result of intensive studies on the above problems, the present inventors have found that when heating 1,4-BG for steam generation or 1,4-BG for heating 1,4-BG for distillation purification, The present inventors have found that the generation of BGTF at the time of heating can be suppressed by specifying the material of the portion (hereinafter, sometimes referred to as a BG wetted portion) in contact with 4-BG.
That is, the gist of the present invention is as follows.

(1) A polyester is produced by subjecting a diol component mainly composed of 1,4-butanediol and a dicarboxylic acid component to an esterification reaction, a transesterification reaction, or both reactions, and a polycondensation reaction. In the method, the diol component contains 1,4-butanediol subjected to a heating history of 160 ° C. or higher, and the stainless steel containing molybdenum in a portion of the heating device that gives the heating history is in contact with 1,4-butanediol A process for producing polyester, characterized in that
(2) Preferably, stainless steel having a molybdenum content of 0.1% by weight or more is used in the portion of the heating device that contacts 1,4-butanediol, The production of polyester according to (1) Method.

(3) In a method for producing a polyester by causing an esterification reaction, a transesterification reaction, or both of the diol component and the dicarboxylic acid component, and a polycondensation reaction, the polycondensation reaction is performed under reduced pressure. The decompressor comprises a 1,4-butanediol vapor ejector, condenses the 1,4-butanediol vapor used in the vapor ejector, and then uses it as a diol component and generates steam for driving the vapor ejector. A method for producing a polyester, characterized in that a stainless steel containing molybdenum is used in a portion of the apparatus that contacts 1,4-butanediol.
(4) The method for producing a polyester according to (3), wherein the molybdenum content in the stainless steel is preferably 0.1% by weight or more.
(5) Preferably, the 1,4-butanediol used in the steam executor is purified by using a distillation column using stainless steel containing molybdenum in the portion where 1,4-butanediol contacts. 1,4-butanediol is used as a diol component, The method for producing a polyester as described in (3) or (4).
(6) Preferably, the main component of the dicarboxylic acid component is terephthalic acid or an ester derivative thereof, The method for producing a polyester as described in any one of (1) to (5).

(7) The method for producing a polyester as described in any one of (1) to (5), wherein the main component of the dicarboxylic acid component is preferably succinic acid or an anhydride thereof.
(8) A device for heating 1,4-butanediol, wherein the material of the portion in contact with 1,4-butanediol is stainless steel having a molybdenum content of 0.1% by weight or more. An apparatus for heating 1,4-butanediol.
(9) A device for generating 1,4-butanediol vapor, wherein the material in contact with 1,4-butanediol is stainless steel having a molybdenum content of 0.1% by weight or more. A device for generating the characterized 1,4-butanediol vapor.

  According to the present invention, when a polyester having 1,4-BG as a main component of diol is produced, the polyester is stably and continuously produced even when heated 1,4-BG is used as a raw material. Can be produced.

Explanatory drawing of an example of the esterification process employ | adopted by this invention. Explanatory drawing of an example of the polycondensation process employ | adopted by this invention. Explanatory drawing of an example of the steam ejector system and distillation purification system which are employ | adopted by this invention.

DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail. However, the description of constituent elements described below is an example (representative example) of an embodiment of the present invention, and is not specified by these contents.
The polyester in the present invention is a polymer having a structure in which a dicarboxylic acid unit and a diol unit are ester-bonded. Specific examples of the dicarboxylic acid include terephthalic acid, isophthalic acid, 4,4′-diphenyldicarboxylic acid, 4, Aromatic dicarboxylic acids such as 4′-diphenyl ether dicarboxylic acid, 4,4′-benzophenone dicarboxylic acid, 4,4′-diphenoxyethane dicarboxylic acid, 4,4′-diphenylsulfone dicarboxylic acid, and 2,6-naphthalenedicarboxylic acid Cycloaliphatic dicarboxylic acids such as 1,2-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, Examples include aliphatic dicarboxylic acids such as azelaic acid and sebacic acid. Among the aromatic dicarboxylic acids, terephthalic acid, isophthalic acid, and aliphatic dicarboxylic acids are preferably succinic acid and adipic acid from the viewpoints of mechanical properties, wide application, and availability of raw materials. .

  These dicarboxylic acid components can be subjected to the reaction as a dicarboxylic acid, as a dicarboxylic acid anhydride, or as an alkyl ester of a dicarboxylic acid, preferably as a dialkyl ester, and may be a mixture of a dicarboxylic acid and a dicarboxylic acid alkyl ester. There are no particular restrictions on the alkyl group of the dicarboxylic acid alkyl ester, but if the alkyl group is long, the boiling point of the alkyl alcohol produced during the transesterification reaction will increase, and the reaction solution will not volatilize, resulting in polymerization as a terminator. In view of this, an alkyl group having 4 or less carbon atoms is preferable, and a methyl group is particularly preferable.

In particular, (1) the main component of the dicarboxylic acid component is preferably terephthalic acid or an ester derivative thereof, or (2) succinic acid or an anhydride thereof. In the present specification, the main component means the largest amount of components in terms of mole among components (dicarboxylic acid component or diol component) containing the main component.
In the present invention, the main component of the diol component is 1,4-BG. Components other than 1,4-BG include ethylene glycol, diethylene glycol, polyethylene glycol, 1,2-propanediol, 1,3-propanediol, polypropylene glycol, polytetramethylene glycol, dibutylene glycol, and 1,5-pentane. Diol, neopentyl glycol, aliphatic diol such as 1,6-hexanediol, 1,8-octanediol, 1,2-cyclohexanediol, 1,4-cyclohexanediol, 1,1-cyclohexanedimethylol, 1,4 -Arocyclic diols such as cyclohexane dimethylol, aromatic diols such as xylylene glycol, 4,4'-dihydroxybiphenyl, 2,2-bis (4-hydroxyphenyl) propane, bis (4-hydroxyphenyl) sulfone, Isosorbide, Examples include diols derived from plant materials such as somannide, isoidet, and erythritan. Ethylene glycol, 1,3-propanediol, 1,4-butanediol, and the like can also be derived from plant materials. .

  In the present invention, the diol component contains 1,4-BG that has undergone a heating history of 160 ° C. or higher. Here, receiving a heating history of 160 ° C. or higher means passing through a state of being heated to 160 ° C. or higher. Examples of 1,4-BG that has received a heating history include those heated by a heating device to be described later. Specifically, for example, 1,4-BG used in a 1,4-BG vapor ejector of a decompression device. -BG, 1,4-BG recovered by distillation purification, and the like. Although the ratio with respect to all the diol components of 1, 4-BG which received the heating history of 160 degreeC or more is not specifically limited, Usually, it is 20 mol% or more, Preferably it is 40 mol% or more. When the amount is too small, the amount of BGTF in 1,4-BG due to receiving the heating history is small in the first place, so that the problem of polymerization inhibition and color tone hardly occur, and the effect of the present invention becomes small. On the other hand, although an upper limit is not specifically limited from the point of the effect of this invention, Control of the amount of 1, 4- BG consumed by polyester manufacture and the amount of 1, 4- BG used by a 1, 4-BG steam ejector is carried out. From the viewpoint of balance, it is usually 95 mol% or less.

In addition, since the by-product of BGTF has a high heating temperature in many cases, the effect of this invention becomes more remarkable when the heating history temperature of 1, 4-BG is 200 degreeC or more, especially 225 degreeC or more. .
The upper limit of the temperature of the heating history is not particularly limited, but is about 260 ° C. from the viewpoint of equipment breakdown voltage.
In the present invention, a hydroxycarboxylic acid such as lactic acid, glycolic acid, m-hydroxybenzoic acid, p-hydroxybenzoic acid, 6-hydroxy-2-naphthalenecarboxylic acid, p-β-hydroxyethoxybenzoic acid, alkoxycarboxylic acid, etc. Monofunctional components (components having one hydroxy group or carboxyl group) such as acid, stearyl alcohol, benzyl alcohol, stearic acid, benzoic acid, t-butylbenzoic acid, benzoylbenzoic acid, tricarballylic acid, trimellitic acid, trimesin Trifunctional or more polyfunctional components (components having 3 or more hydroxy components and / or carboxylic acid components) such as acid, pyromellitic acid, gallic acid, malic acid, trimethylolethane, trimethylolpropane, glycerol, pentaerythritol, etc. As a copolymer component It can be used.

  Among them, (1) 50 mol% or more of dicarboxylic acid units, preferably 80 mol% or more, particularly preferably 95 mol% or more consists of terephthalic acid units, and 70 mol% or more of diol units, preferably 80 mol% or more, Particularly preferably, 95 mol% or more of polybutylene terephthalate composed of 1,4-butanediol units, or (2) 50 mol% or more, preferably 80 mol% or more, particularly preferably 95 mol% or more of dicarboxylic acid units. A polybutylene succinate composed of acid units and comprising 1,4-butanediol units in an amount of 70 mol% or more, preferably 80 mol% or more, particularly preferably 95 mol% or more of the diol units has a large production scale. The effect of the invention is great.

  The polyester of the present invention can be produced by the following method, but the production method of the present invention is not limited thereto. The conditions described below are suitable when a polyester is produced using an aliphatic dicarboxylic acid and an aliphatic diol, and are particularly suitable for the production of polybutylene succinate.

  The polyester production method is roughly divided into a so-called direct polymerization method using a dicarboxylic acid (for example, succinic acid) as a main raw material, a dicarboxylic acid dialkyl ester, preferably dimethyl dicarboxylate (for example, a dialkyl ester of succinic acid, preferably There is a transesterification method using dimethyl acid) as the main raw material. In the former, water is mainly generated in the initial esterification reaction, and in the latter, alcohol is mainly generated in the initial transesterification reaction. However, the reaction distillate is easily processed and the raw material intensity is high. From this viewpoint, a direct polymerization method is preferable. Moreover, from the viewpoint of stabilization of quality and energy efficiency, a so-called continuous method is preferred in which raw materials are continuously supplied to obtain a polyester (for example, polybutylene succinate) continuously.

  As an example of the direct polymerization method, the charged molar ratio of a diol (eg, 1,4-butanediol) containing 1,4-BG as a main component to a dicarboxylic acid (eg, succinic acid) is usually 0.95 to 2. 0, preferably 1.0 to 1.7, more preferably 1.05 to 1.40. Further, in the production of polybutylene succinate, it is preferable to use a polyfunctional component (for example, malic acid), and the charged mol% of the polyfunctional component relative to succinic acid is preferably 0.001 to 0.50 mol%.

  In the embodiment illustrated in FIG. 1, the esterification reaction is performed in one esterification reaction tank A, but may be performed in a plurality of continuous reaction tanks. The lower limit of the esterification reaction temperature is usually 150 ° C or higher, preferably 180 ° C or higher, and the upper limit is usually 260 ° C or lower, preferably 250 ° C or lower. The reaction atmosphere is usually an inert gas atmosphere such as nitrogen or argon. The reaction pressure is usually 10 kPa to 150 kPa, but normal pressure is preferred. The reaction time is usually 1 hour or longer, and the upper limit is usually 10 hours or shorter, preferably 6 hours or shorter, particularly preferably 4 hours or shorter.

  On the other hand, as an example of the transesterification method, a diol component mainly composed of a dicarboxylic acid dialkyl ester component and 1,4-BG (for example, the dicarboxylic acid ester component mainly composed of a dialkyl ester of succinic acid and 1,4 BG). -The diol component comprising butanediol as a main component) in a single-stage or multi-stage transesterification reactor, preferably in the presence of a transesterification catalyst, usually 110 to 260 ° C, preferably 140 to 245 ° C. More preferably, the temperature is 160 to 235 ° C., particularly preferably 180 to 220 ° C., and usually 10 to 133 kPa, preferably 13 to 120 kPa, particularly preferably 60 to 101 kPa, and usually 0.5 to 10 hours. , Preferably 0.5 to 5 hours, more preferably 1 to 3 hours. The esterification or transesterification reaction may be a batch method or a continuous method, but a continuous method is particularly preferable.

In both the direct polymerization method and the transesterification method, in the initial esterification reaction and transesterification reaction, a large amount of 1,4-butanediol, terahydrofuran, water, alcohol, etc. is distilled. It is preferable to provide a rectifying column for separating the product into a low-boiling substance and a high-boiling substance.
Next, the oligomer as the obtained esterification reaction product or transesterification reaction product is transferred to a polycondensation reaction tank. The polycondensation reaction is usually performed under reduced pressure. The lower limit of the reaction pressure of the final polycondensation reaction tank (k in the illustration of FIG. 2) 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. is there. 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 facility is a preferred embodiment from the viewpoint of improving the polycondensation reaction rate, but it is economically disadvantageous because it requires an extremely expensive equipment investment. The lower limit of the reaction temperature is usually 150 ° C or higher, preferably 180 ° C or higher, and the upper limit is usually 270 ° C or lower, preferably 260 ° C or lower. If this temperature is too low, 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, when the reaction temperature is too high, thermal decomposition of the polyester at the time of production is caused and it tends to be difficult to produce a polyester having a high degree of polymerization. The lower limit of the reaction time is usually 1 hour or longer, and the upper limit is usually 15 hours or shorter, preferably 8 hours or shorter, more preferably 6 hours or shorter. 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 thermal decomposition of the polyester becomes remarkable, and not only the mechanical properties of the molded product tend to be inferior, but also the carboxyl group terminal amount that adversely affects the durability of the polyester resin. May increase due to degradation.

The decompression to the polycondensation reaction tank is performed by a decompression device. For example, various forms such as a liquid ring pump, an oil rotary pump, a roots pump, and a steam ejector are known, and a number of methods for maximizing performance by combining a plurality of these have been implemented.
Among them, the decompression device includes a steam ejector, more specifically, a steam generator for driving the steam ejector (for example, K in FIG. 3), a steam ejector (for example, A1 in FIG. 3), and an ejector downstream portion. The combination of the connected capacitor (for example, A2 in FIG. 3) and the hot well tank (for example, H2 in FIG. 3) connected to the capacitor via the atmospheric leg (for example, 25 in FIG. 3) makes the device simple. Since there are few mechanical drive parts that are likely to cause trouble and a desired high vacuum can be obtained, they are widely used.

Water is often used as the steam source, but the diol of the polyester raw material is heated to obtain steam, which is connected to the ejector using the condenser, the condenser installed downstream of the ejector, and the condenser via an atmospheric leg. A method using a combination of hot well tanks is also known. If the latter method is used, it is possible to condense the organic component contained in the suction gas into the diol which is the sealing liquid of the condenser, and the diol obtained by condensing the organic component as it is or by distillation purification. Is advantageous in that it can be used as a polyester raw material. In the polyester production method of the present invention, since the raw material diol is a diol mainly composed of 1,4-BG, the vapor source of the vapor ejector is a diol mainly composed of 1,4-BG. 1,4-BG is particularly preferable because the effect of suppressing BGTH by-product is significant when the vapor source is 1,4-BG.

In a steam ejector that uses water vapor, organic components and the like contained in the suction gas are collected by the condenser and condensed in the sealed water of the hot well tank, leading to an increase in the COD of the wastewater and an increase in the load on the environment. The problem is likely to occur.
Further, the liquid containing 1,4-butanediol as a main component collected in a hot well tank (for example, H2 in FIG. 3) passes through a line (54 in FIG. 3) and a pump (H4 in FIG. 3). H5) in FIG. 3 and the whole amount is transferred to the raw slurry preparing tank through a pump (H6 in FIG. 3) and a line (55 in FIG. 3) as an unrefined raw material slurry. The total amount of the buffer tank (H5 in FIG. 3) is purified by the distillation purification tower (J1 in FIG. 3) through the pump (H6 in FIG. 3) and the line (56 in FIG. 3), and then the pump (J2 in FIG. 3). , It may be transferred to a raw material slurry preparation tank through a line (58 in FIG. 3) to be a part of the raw material diol.

  In addition, when performing the manufacturing method of polyester of this invention by a continuous method, as shown in FIG. 1, water, tetrahydrofuran, and the excess 1, 4- butanediol produced | generated by esterification reaction are taken from the distillation line (5). The distillate is separated into a high-boiling component and a low-boiling component in the rectification column (C), and a high-boiling component mainly composed of 1,4-butanediol is extracted from the column bottom through the line (6). A part may be supplied to the esterification reaction tank from line (2) as raw material 1,4-butanediol.

  In the present invention, 1,4-BG that has been subjected to a heating history of 160 ° C. or higher is included as a raw material diol component. In the present invention, as an apparatus for heating 1,4-BG, (1) 1,4-BG 1,4-BG rectification apparatus in BG production, (2) In any case of direct polymerization method and transesterification method, in the initial esterification reaction and transesterification reaction, 1,4-BG, terahydrofuran, water, Since there are many distillates of alcohol, etc., a rectifying column (C in FIG. 1 as an example) for separating distillate into low-boiling substances and high-boiling substances, (3) Esterification or transesterification reaction tank (as an example) 1) A), (4) 1,4-BG steam generator for driving a steam ejector (K in FIG. 3 as an example), (5) distillation purification apparatus for condensate collected in a hot well tank (as an example) Examples thereof include J1) in FIG.

  In the present invention, stainless steel containing molybdenum is used as a heating device when 1,4-BG is heated at 160 ° C. or higher. Stainless steel is an alloy steel containing at least 10.5% by weight or more of chromium in iron. By containing molybdenum, BGTF generation during heating can be suppressed. The content of molybdenum is usually 0.1% by weight or more, preferably 0.5% by weight or more, more preferably 1% by weight or more, and particularly preferably 1.5% by weight or more. On the other hand, it is usually 10% by weight or less, preferably 5% by weight or less, particularly preferably 4% by weight or less. If this value is too small, the effect of the present invention that can stably produce a good quality polyester (high viscosity, good color tone) in a long-term operation becomes insufficient, while if too large, the effect of the present invention is improved, It becomes a tendency not to be recognized any more, and becomes high-grade steel material and becomes expensive. Examples of the contained metal other than molybdenum include chromium and nickel.

The chromium content is preferably 10% by weight or more, more preferably 15% by weight or more. On the other hand, it is preferably 30% by weight or less, more preferably 25% by weight or less.
The content of nickel is preferably 3% by weight or more, more preferably 8% by weight or more. On the other hand, it is preferably 30% by weight or less, more preferably 20% by weight or less. Specific examples of the stainless steel include SUS316, SUS316L, SUS316N, SUS317, SUS329, and SUS436 among the stainless steels shown in JISG4304.

In addition, since the by-product of BGTF has many cases where heating temperature is high, the effect of this invention becomes remarkable when it heats to 200 degreeC or more, especially 225 degreeC or more.
In addition, when there are a plurality of heating devices that heat 1,4-BG to 160 ° C. or higher, stainless steel containing molybdenum is used as a member of the 1,4-BG wetted part of at least one heating device. Although the effects of the invention can be obtained, the members of the 1,4-BG wetted parts of the plurality of heating devices are preferably stainless steel containing molybdenum.

Among these, it is preferable that 1,4-BG is used as the driving steam for the ejector, and the member that contacts the 1,4-BG of the steam generator for driving the ejector is stainless steel containing molybdenum. In addition, the condenser condensed in the downstream part of the 1,4-BG steam ejector and the liquid condensed in the hot well tank are purified as it is or by distillation purification to obtain purified 1,4-BG, which is used as the raw material diol of polyester. However, it is preferable that the member in contact with 1,4-BG of the heating device in the distillation purification is stainless steel containing molybdenum.

In the present invention, in particular, when 1,4-butanediol vapor used in the steam ejector is condensed and then used as the diol component of the polyester production raw material, the steam generator driving steam generator 1 is used. More preferably, in addition to this, 1,4-butanediol is used as the 1,4-butanediol used in the steam executor. By purifying using a distillation tower using stainless steel containing molybdenum in the contact portion, and using the obtained 1,4-butanediol as the diol component of the polyester production raw material, even in long-term operation, Polyester of good quality (intrinsic viscosity, color tone, etc.) can be produced stably, which is industrially advantageous.

EXAMPLES Hereinafter, although an Example demonstrates this invention still in detail, this invention can be variously changed unless it exceeds the summary, and is not limited to a following example at all. In addition, the measurement method of the physical property and evaluation item which were employ | adopted in the following examples is as follows.
<Metal element analysis of stainless steel>
50 mg of a sample whose surface is polished is collected in a quartz beaker, and sulfuric acid and aqua regia are added to dissolve the acid while heating on a hot plate, and the sample is completely dissolved while supplementing the aqua regia that has been reduced until dissolution. After cooling the beaker, pure water is added and the whole volume is poured into a volumetric flask and made up to 100 mL. Thereafter, the sample was further diluted 10-fold and quantitatively analyzed using a plasma emission spectroscopic analyzer (ICP-AES ULTRACE JY-138U type manufactured by JOBIN YVON), and converted to the metal content (% by weight) of the steel material.

<BGTF analysis in 1,4-butanediol>
Using a capillary-type gas chromatograph, the content ratio (S wt%) of the BGTF component is obtained from the peak area corresponding to the BGTF component, and the water concentration (W wt%) obtained by moisture measurement is corrected by the following formula (1). Calculated.

X (weight%) = S × (100−W) / 100 Formula (1)
The apparatus is GC-14BPF manufactured by Shimadzu (split ratio: 1/90, RANGE: 10 ¹ ), and the column is DB-WAX manufactured by J & W (inner diameter: 0.32 mm, length: 60 m, membrane pressure: 0.5 μm). )It was used. The temperature of the injection section and detector was 240 ° C., the column temperature was held at 70 ° C. for 15 minutes, then the temperature was raised to 170 ° C. at 10 ° C./min, and held at 170 ° C. for 45 minutes. Nitrogen (1 mL / min) was used as the carrier gas.
In addition, the water concentration (% by weight) in the distillate was expressed as weight% with respect to the distillate by precisely weighing the distillate and measuring the water content (μg) with a Karl Fischer moisture meter.

<Analysis of metal elements in catalyst>
A sample of 0.1 g of a sample obtained by wet decomposition with hydrogen peroxide in the presence of sulfuric acid in a Kjeldahl flask and then with a constant volume of distilled water was used. ), And converted to the metal content (% by weight) in the catalyst.

<PH analysis of catalyst solution>
Using an automatic titrator (AUT-301 type) manufactured by Toa DKK, the pH electrode was immersed in a liquid catalyst and measured under the atmosphere.
<Esterification rate%>
It calculated from the acid value and the saponification value by the following calculation formula (2). The acid value was determined by heating 0.3 g of the esterification reaction product sample to 40 mL of benzyl alcohol at 180 ° C. for 20 minutes, cooling for 10 minutes, and titrating with a 0.1 mol·L ⁻¹ KOH / methanol solution.
The saponification value was determined by hydrolyzing the oligomer with a 0.5N KOH / ethanol solution and titrating with 0.5N hydrochloric acid.
Esterification rate (%) = ((saponification value−acid value) / saponification value) × 100 Formula (2)

<Intrinsic viscosity (IV) dL / g>
It calculated | required in the following way using the Ubbelohde type viscometer. That is, using a mixed solvent of phenol / tetrachloroethane (weight ratio 1/1) and measuring the number of seconds of dropping only the polyester sample solution having a concentration of 0.5 g / dL and the solvent at 30 ° C., the following formula (3 )

IV = ((1 + 4K _H η _sp ) ^0.5 −1) / (2K _H C) Formula (3)
(Where η _SP = η / η ₀ −1, η is the sample solution falling seconds, η ₀ is the solvent dropping seconds, C is the sample solution concentration (g / dL), and K _H is the Huggins constant. Yes, K _H is 0.33.)

<Color b value>
The pelletized polyester is filled in a cylindrical powder measurement cell having an inner diameter of 30 mm and a depth of 12 mm, and described in Reference Example 1 of JIS Z8730 using a colorimetric color difference meter Z300A (Nippon Denshoku Industries Co., Ltd.). The b value by the color coordinate of Hunter's color difference formula in the Lab display system was obtained as a simple average value of values measured at four locations by rotating the measurement cell by 90 degrees by the reflection method.

Example 1
[Preparation of aliphatic polyester polycondensation catalyst solution]
100 parts by weight of magnesium acetate tetrahydrate was placed in a glass eggplant-shaped flask equipped with a stirrer, and 1500 parts by weight of absolute ethanol (purity 99% by weight or more) was further added. Furthermore, 130.8 parts by weight of ethyl acid phosphate (mixing weight ratio of monoester and diester was 45:55) was added and stirred at 23 ° C. After confirming that magnesium acetate was completely dissolved after 15 minutes, 529.5 parts by weight of tetra-n-butyl titanate was added. Stirring was further continued for 10 minutes to obtain a uniform mixed solution. This mixed solution was transferred to an eggplant-shaped flask and concentrated under reduced pressure by an evaporator in an oil bath at 60 ° C. After 1 hour, most of ethanol was distilled off to obtain a translucent viscous liquid. The temperature of the oil bath was further raised to 80 ° C., and further concentrated under a reduced pressure of 655 Pa to obtain a viscous liquid. This liquid catalyst was dissolved in 1,4-butanediol to prepare a titanium atom content of 3.36% by weight. The storage stability in 1,4-butanediol was good, and the catalyst solution stored at 40 ° C. under a nitrogen atmosphere did not show the formation of precipitates for at least 40 days. The catalyst solution had a pH of 6.3.

[Continuous polycondensation of aliphatic polyester]
Through the esterification step shown in FIG. 1 and the polycondensation step shown in FIG. 2, an aliphatic polyester resin was produced in the following manner. First, a 60 ° C. slurry prepared by mixing 1.30 mol of 1,4-butanediol and 0.0033 mol of malic acid with respect to 1.00 mol of succinic acid from a slurry preparation tank (not shown). Through the supply line (1), continuously supplied to the esterification reaction tank (A) having a stirrer previously charged with an aliphatic polyester oligomer having an esterification rate of 99% and maintained at 230 ° C. so as to be 42 kg / h. did. At the same time, the bottom component of the rectifying column (C) at 100 ° C. (98% by weight or more was 1,4-butanediol) was supplied at 3.0 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 FIG. 2 (a). 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 advance by the above-described method was further diluted with 1,4-butanediol to adjust the concentration as titanium atom to 0.17% by weight. This liquid was supplied at 1.0 kg / h to the extraction line (4) of the esterification reaction product through the supply line FIG. 2 (L7).
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 in FIG. 3 (21) via a wet condenser (not shown, mainly condensing and collecting 1,4-butanediol). The extracted reaction liquid was continuously supplied to the second polycondensation reaction tank (d) via the extraction line (L1) by the extraction gear pump (c).

  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 1.5 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 in FIG. 3 (31) through a wet condenser (not shown, mainly collecting and collecting 1,4-butanediol). The obtained polyester was continuously supplied to the third polycondensation reaction tank (k) via the extraction line (L3) by the extraction gear pump (e).

  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 1 hour. From the vent line (L6), water, tetrahydrofuran, The polycondensation reaction was further advanced while extracting 4-butanediol. The vent line (L6) was connected to a steam ejector system in FIG. 3 (41) via a wet condenser (not shown, mainly condensing and collecting 1,4-butanediol). The obtained polyester is passed through a extraction line (L5) by an extraction gear pump (m), passed through a leaf disk type filter (n) using a laminated metal nonwoven fabric having an absolute filtration accuracy of 40 μm as a filter medium, and a die head ( An aliphatic polyester pellet was produced by extracting the strand from g) into a strand shape and cutting with a pelletizer (h).

In addition, the pressure of each polycondensation reaction tank (a, d, k) was controlled using the vapor ejector system shown in FIG.
The steam ejector system continuously supplies commercially available 1,4-butanediol to the steam generator (K) for driving the ejector through the supply line (19) to 240 ° C. Heated and generated 1,4-butanediol vapor is supplied to each ejector (for the first polycondensation reaction tank: A1, A3, for the second polycondensation reaction tank: B1, B3, B5, and third layer through the supply line (20). Condensation reaction tank use: C1, C3, C5). SUS316L stainless steel (Chromium content: 19.0 wt%, Nickel content: 13.5 wt%, Molybdenum content: 2) on the member contacting the 1,4-butanediol of the steam generator (K) for driving the steam ejector 0.5% by weight) was used.

A gas mainly composed of tetrahydrofuran and water distilled from the first polycondensation reaction tank (a) is introduced into the ejector (A1) via the line (21), and at this time, the gas discharged from the ejector (A1) 1, 4-Butanediol vapor was condensed in a barometric condenser (A2), and the condensate was collected in a hot well tank (H2) through an 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, 23) were 1,4-butanediol supply lines, and the entire amount was circulated and supplied from hot well tanks (H2, 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, 34) were 1,4-butanediol supply lines, and the entire amount was circulated and supplied from hot well tanks (H1, H2, 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 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, 44) were 1,4-butanediol supply lines, and the entire amount was circulated and supplied from hot well tanks (H1, H2, H3) (not shown).

The liquid mainly composed of 1,4-butanediol collected in the hot well tanks (H1, H2, H3) is sent to the buffer tank (H5) through the line (54) and the pump (H4). Through the pump (H6) and the line (55), it was transferred to the raw material slurry preparation tank as it was unrefined.
Lines (51, 52, 53) are supply lines from the outside of commercially available 1,4-butanediol to hot well tanks (H1, H2, H3). In addition, the supply of commercially available 1,4-butanediol from the outside during the stable operation of the continuous polycondensation process was only the line (19) and the lines (51, 52, 53), and each was set to a constant flow rate.
The operation was continued for one month under the above conditions.
Table 1 shows the BGTF content in the 1,4-butanediol collected after the first day of operation and the first month of operation and the quality evaluation results of the aliphatic polyester pellets.

(Comparative Example 1)
SUS304 stainless steel (chromium content: 19.0% by weight, nickel content: 9.5% by weight, molybdenum content: 0) on the member contacting the 1,4-butanediol of the steam generator (K) for driving the steam ejector 0.0 wt%) was used in the same manner as in Example 1 to produce an aliphatic polyester.
Table 1 shows the BGTF content in the 1,4-butanediol collected after the first day of operation and the first month of operation and the quality evaluation results of the aliphatic polyester pellets.

(Example 2)
The liquid mainly composed of 1,4-butanediol collected in the hot well tanks (H1, H2, H3) is sent to the buffer tank (H5) through the line (54) and the pump (H4). Implemented except that it was purified in the distillation purification tower (J1) through the pump (H6) and the line (56), and then transferred to the raw slurry preparation tank through the pump (J2) and the line (58) to form part of the raw diol. An aliphatic polyester was produced in the same manner as in Example 1.

SUS316L stainless steel (chromium content: 19.0% by weight, nickel content: 13.5% by weight, molybdenum content: 2.5% by weight) is used for the member that contacts 1,4-butanediol of the distillation purification tower (J1). Was distilled at a column top pressure of 26.6 kPa, a reflux ratio of 90, and a column bottom temperature of 215 ° C.
On the other hand, low-boiling components such as tetrahydrofuran separated in the distillation purification column (J1) were discharged out of the system through the line (57), and high-boiling components were discharged out of the system through the line (59).
The operation was continued for one month under the above conditions.
Table 1 shows the BGTF content in the 1,4-butanediol collected after the first day of operation and the first month of operation and the quality evaluation results of the aliphatic polyester pellets.

(Comparative Example 2)
SUS304 stainless steel (chromium content: 19.0% by weight, nickel content: 9.5% by weight, molybdenum content: 0) on the member contacting the 1,4-butanediol of the steam generator (K) for driving the steam ejector SUS304 stainless steel (chromium content: chromium content: 0 wt.%) And a member contacting the 1,4-butanediol of the distillation column (J1) for purifying the condensed 1,4-butanediol of the steam ejector. Aliphatic polyester pellets were produced in the same manner as in Example 2, except that 19.0% by weight, nickel content: 9.5% by weight, molybdenum content: 0.0% by weight) were used.
Table 1 shows the BGTF content in 1,4-butanediol collected after the third operation start and one month operation, and the quality evaluation results of the aliphatic polyester pellets.

(Example 3)
[Continuous polycondensation of aromatic polyester]
Through the esterification step shown in FIG. 1 and the polycondensation step shown in FIG. 2, an aromatic polyester resin was produced in the following manner. First, a 60 ° C. slurry mixed at a ratio of 1.80 moles of 1,4-butanediol with respect to 1.00 moles of terephthalic acid is passed through a raw material supply line (1) from a slurry preparation tank in advance with an esterification rate of 99. % Was continuously fed to a reactor (A) for esterification having a screw type stirrer filled with PBT oligomer at a rate of 40 kg / h. At the same time, the bottom component of the rectification column (C) at 185 ° C. (98% by weight or more is 1,4-butanediol) is supplied at 18.4 kg / h from the recirculation line (2), and the titanium catalyst supply line ( From 3), a 6.0 wt% 1,4-butanediol solution of tetra-n-butyl titanate at 65 ° C. was fed as a catalyst at 127 g / h. The moisture in the catalyst solution was 0.2% by weight.

  The internal temperature of the reactor (A) is 230 ° C., the pressure is 67 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. 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 generated in the reactor (A) is extracted from the oligomer extraction line (4) using the pump (B), and the average residence time in terms of the terephthalic acid unit in the liquid in the reactor (A). The liquid level was controlled so that was 3 hours. The oligomer extracted from the extraction line 4 was continuously supplied to the first polycondensation reactor (a). After the system was stabilized, the esterification rate of the oligomer collected at the outlet of the reactor (A) was 97.3%.

  The internal temperature of the first polycondensation reaction tank (a) is 245 ° 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 a steam ejector system at the vent line (21) via a wet condenser (not shown, mainly condensing and collecting 1,4-butanediol). The extracted reaction liquid was continuously supplied to the second polycondensation reaction tank (d) via the extraction line (L1) by the extraction gear pump (c).

  The internal temperature of the second polycondensation reaction tank (d) is 240 ° C., the pressure is 0.26 kPa, and the liquid level is controlled so that the residence time is 1.5 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 a steam ejector system at the vent line (31) via a wet condenser (not shown, mainly condensing and collecting 1,4-butanediol). The obtained polyester was continuously supplied to the third polycondensation reaction tank (k) via the extraction line (L3) by the extraction gear pump (e).

  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 1 hour. From the vent line (L6), water, tetrahydrofuran, The polycondensation reaction was further advanced while extracting 4-butanediol. The vent line (L6) was connected to a steam ejector system at the vent line (41) via a wet condenser (not shown, mainly condensing and collecting 1,4-butanediol). The obtained polyester is passed through a extraction line (L5) by an extraction gear pump (m), passed through a leaf disk type filter (n) using a laminated metal nonwoven fabric having an absolute filtration accuracy of 40 μm as a filter medium, and a die head ( An aromatic polyester pellet was produced by extracting the strand from g) into a strand shape and cutting with a pelletizer (h).

The pressure in each polycondensation reaction tank (a, d, k) was controlled in the same manner as in Example 1 using the vapor ejector system shown in FIG.
The operation was continued for one month under the above conditions.
Table 1 shows the BGTF content in 1,4-butanediol collected after the first day of operation and the first month of operation and the quality evaluation results of the aromatic polyester pellets.

(Comparative Example 3)
SUS304 stainless steel (chromium content: 19.0% by weight, nickel content: 9.5% by weight, molybdenum content: 0) on the member contacting the 1,4-butanediol of the steam generator (K) for driving the steam ejector 0.0% by weight) was used in the same manner as in Example 3 to produce aromatic polyester pellets.
Table 1 shows the BGTF content in 1,4-butanediol collected after the first day of operation and the first month of operation and the quality evaluation results of the aromatic polyester pellets.

  Comparative Examples 1, 2, and 3 are examples in which SUS304 containing no molybdenum is used in a portion where 1,4-butanediol contacts in any 1,4-BG heating apparatus. Long-term operation increased BGTF in 1,4-butanediol in the reaction system, decreased the intrinsic viscosity of the polyester, and increased coloration.

  In contrast, Examples 1 to 3 are examples in which SUS316L containing molybdenum is used in a part of the heating device that contacts 1,4-butanediol (Examples 1 and 3 are steam generation for driving a steam ejector). Example 2 is an example in which stainless steel containing molybdenum is used as a member in contact with 1,4-butanediol of the apparatus (K). In addition to this, Example 2 includes 1,4-butanediol of the distillation purification column (J1). In this case, there is no increase in BGTF in 1,4-butanediol in the reaction system even after long-term operation for one month, using a stainless steel containing molybdenum as a member in contact with butanediol. Further, neither a decrease in the intrinsic viscosity of the polyester nor a coloring of the resin was observed.

本発明を詳細にまた特定の実施態様を参照して説明したが、本発明の精神と範囲を逸脱することなく様々な変更や修正を加えることができることは当業者にとって明らかである。
本出願は、２００８年１１月５日出願の日本国特許出願（特願２００８−２８４３００）に基づくものであり、その内容はここに参照として取り込まれる。

Although the present invention has been described in detail and with reference to specific embodiments, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the invention.
This application is based on a Japanese patent application filed on November 5, 2008 (Japanese Patent Application No. 2008-284300), the contents of which are incorporated herein by reference.

  According to the present invention, a useful polyester having 1,4-butanediol as a main component of diol, such as polybutylene terephthalate and polybutylene succinate, can be stably produced with good quality. Therefore, the industrial value of the present invention is remarkable.

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 Condenser L1, L3, L5 Reactant extraction line L2, L4 , L6 Vent line L7 Catalyst supply line a First polycondensation reaction tank d Second polycondensation reaction tank k Third polycondensation reaction tank c, e, m Gear pump for extraction
n Filter g Die head h Pelletizer A1, A3, B1, B3, B5, C1, C3, C5 Ejector A2, A4, B2, B4, B6, C2, C4, C6 Barometric condenser A5, B7, C7 Vacuum pump H1, H2, H3 Hotwell tank H4, H6, J2, J4 Pump H5 Buffer tank J1 Distillation purification tower J3 Distillation purification tower reboiler K Ejector drive 1,4-butanediol steam generator 19, 51, 52, 53 From outside 1,4-butanediol supply line 20 Steam 1,4-butanediol supply line to ejector 21 Vent line from the first polycondensation reaction tank 31 Vent line from the second polycondensation reaction tank 41 Third layer Vent line from condensation reaction tank 22, 23, 32, 33, 34, 42, 4 3,44 1,4-butanediol supply line 24, 35, 45 Discharge gas line from vacuum pump 25, 26, 36, 37, 38, 46, 47, 48 Barometric condenser atmospheric leg 54 From hot well tank Extraction line to the buffer tank 55 1,4-butanediol supply line from the buffer tank to the raw slurry preparation tank 56 1,4-butanediol supply line from the buffer tank to the distillation purification column 57 Extraction of low-boiling components Line 58 Line for supplying 1,4-butanediol from the distillation purification tower to the raw slurry preparing tank 59 Line for extracting high-boiling components

Claims (9)

  In a method for producing a polyester by causing an esterification reaction, a transesterification reaction, or both reactions to a diol component and a dicarboxylic acid component mainly composed of 1,4-butanediol, and a polycondensation reaction, The diol component contains 1,4-butanediol that has undergone a heating history of 160 ° C. or higher, and a stainless steel containing molybdenum is used in a portion that contacts the 1,4-butanediol of the heating device that gives the heating history. A process for producing polyester, characterized in that   The method for producing a polyester according to claim 1, wherein stainless steel having a molybdenum content of 0.1 wt% or more is used in a portion of the heating device that contacts 1,4-butanediol. In a method for producing a polyester by causing an esterification reaction, a transesterification reaction or both of the diol component and the dicarboxylic acid component, and a polycondensation reaction,
(1) The polycondensation reaction is performed under reduced pressure,
(2) The decompressor comprises a 1,4-butanediol vapor ejector,
(3) 1,4-butanediol vapor used in the steam ejector is condensed and then used as a diol component, and (4) is in contact with 1,4-butanediol of the steam generator for driving the steam ejector. Use stainless steel containing molybdenum in the part,
A process for producing polyester, characterized in that   4. The method for producing a polyester according to claim 3, wherein the stainless steel has a molybdenum content of 0.1% by weight or more.   The 1,4-butanediol used in the steam executor was purified by using a distillation column using stainless steel containing molybdenum at the portion where the 1,4-butanediol comes into contact. The method for producing a polyester according to claim 3 or 4, wherein a diol is used as a diol component.   6. The method for producing a polyester according to claim 1, wherein the main component of the dicarboxylic acid component is terephthalic acid or an ester derivative thereof.   The method for producing a polyester according to any one of claims 1 to 5, wherein a main component of the dicarboxylic acid component is succinic acid or an anhydride thereof.   An apparatus for heating 1,4-butanediol, wherein the material of the part in contact with 1,4-butanediol is stainless steel having a molybdenum content of 0.1% by weight or more. An apparatus for heating 1,4-butanediol.   An apparatus for generating 1,4-butanediol vapor, wherein the material in contact with 1,4-butanediol is stainless steel having a molybdenum content of 0.1% by weight or more. An apparatus for generating 1,4-butanediol vapor.

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