JP2005097602A - Manufacturing apparatus and method for polybutylene terephthalate oligomer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method for a polybutylene terephthalate oligomer which reduces a foreign substance and an unreacted material while raising an esterification reaction rate and controlling a side reaction. <P>SOLUTION: This apparatus is a continuously manufacturing apparatus for the polybutylene terephthalate oligomer by reacting a dicarboxylic acid comprising terephthalic acid as a principal component and a diol comprising 1,4-butanediol as a principal component which comprises (1) having a heat exchanger inside a reactor, (2) in at least one of horizontal sections in the reactor, installing the heat exchanger in the vicinity of a peripheral area, and having a space without the heat exchanger in the vicinity of a central part, and (3) installing a funnel shape wall becoming smaller in diameter from an upper part toward a lower part in an upper part of the space of the above (2). <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an apparatus and a method for producing a polybutylene terephthalate oligomer.

  Polybutylene terephthalate resin, a typical engineering plastic among thermoplastic polyester resins, is easy to mold, mechanical properties, heat resistance, chemical resistance, aroma retention, other physical and chemical properties Because of its excellent characteristics, it is widely used in automobile parts, electrical / electronic parts, precision equipment parts, and the like.

  Polybutylene terephthalate is produced by first producing a polybutylene terephthalate oligomer by an esterification reaction when the raw material is terephthalic acid, or by a transesterification reaction when the raw material is dialkyl terephthalate, followed by a polycondensation reaction. Recently, however, a direct esterification process using terephthalic acid as a raw material has attracted attention because of the superiority of the raw material basic unit, the ease of recovery of by-product THF, the availability of raw materials, and the like. Above all, terephthalic acid and 1,4-butanediol are continuously supplied from the aspect of quality stabilization, production efficiency improvement, and energy efficiency improvement, and a polybutylene terephthalate oligomer is produced by continuous esterification reaction. In addition, so-called direct continuous polymerization, in which the subsequent polycondensation reaction is continuously performed, has been attracting attention. However, if the conversion rate of the esterification reaction (the esterification rate of the oligomer) is low and it is sent to the post-process (polycondensation process) at high temperature and high vacuum, unreacted monomers are blocked by the valves and pumps in the transfer piping. Or volatilizes in the vent system of the polycondensation reactor and induces blockage of the piping, etc., but also causes contamination of recovered 1,4-butanediol, tetrahydrofuran (THF), etc., and easily deactivates the catalyst. There was a problem.

Therefore, in the direct continuous polymerization method, it is important to sufficiently advance the esterification reaction of terephthalic acid and 1,4-butanediol and then send it to the polycondensation step. As described above, an excess of 1,4-butanediol is used with respect to terephthalic acid, and the reaction is performed under reduced pressure. However, in the esterification reactor that performs this reaction, in addition to the evaporation of water generated by the esterification reaction, evaporation of 1,4-butanediol and by-product THF occurs in parallel, resulting in a large heat load. Therefore, Patent Document 2 proposes that a multi-tube heat exchanger is installed inside the reactor, and the inside of the reactor is made uniform by natural circulation by heat convection. However, as the scale of the reactor increases, the amount of water, THF, and 1,4-butanediol generated increases, increasing the gas linear velocity at the top of the heat exchanger and increasing the bubble rate of the reaction solution. Resulting in a decrease in the esterification reaction rate due to drift and stagnation of the flow, and other inconveniences such as entrainment and localization of raw terephthalic acid, leading to a decrease or fluctuation in the esterification rate of the polybutylene terephthalate oligomer. There was a problem. Further, in order to compensate for the decrease in the esterification reaction rate, increasing the supply ratio of 1,4-butanediol to terephthalic acid or extending the residence time results in an increase in the amount of THF produced as a by-product, There was also a problem that the basic unit deteriorated.
Japanese Patent Laid-Open No. 62-195017 Japanese Patent Laid-Open No. 2001-232101

  The present invention uniformly and sufficiently mixes in a reactor for producing a polybutylene terephthalate oligomer, thereby increasing the esterification reaction rate, reducing foreign substances and unreacted substances, and suppressing side reactions. The object of the present invention is to provide a method for producing a terephthalate oligomer and a production apparatus therefor.

As a result of intensive studies to solve the above problems, the present inventor has increased the esterification reaction rate by using a reactor having a specific structure, and has few unreacted substances and foreign matters in a short time. It has been found that a polybutylene terephthalate oligomer having a reduced amount can be produced, and the present invention has been completed.

That is, the first gist of the present invention is an apparatus for continuously producing a polybutylene terephthalate oligomer by reacting a dicarboxylic acid containing terephthalic acid as a main component with a diol containing 1,4-butanediol as a main component. ,
(1) having a heat exchanger inside the reactor,
(2) In at least one horizontal cross section in the reactor, a heat exchanger is installed near the periphery, and a space where no heat exchanger is installed near the center,
(3) A funnel-shaped wall whose diameter decreases from the upper part to the lower part is installed in the upper part of the space in (2) above.
(4) When the major axis of the funnel-shaped wall in (3) is D and the minor axis is d, the following formula (I) is satisfied:
D / d ≧ 1.5 (I)
(5) The horizontal cross-sectional area of the part closest to the funnel-shaped wall in the space where the heat exchanger is not installed in (2) is S, and the horizontal part of the part surrounded by the funnel-shaped wall is closest to the space. It exists in the continuous manufacturing apparatus of the polybutylene terephthalate oligomer characterized by satisfy | filling the following Formula (II), when a cross-sectional area is set to s.
s / S = 0.6 to 2.0 (II)

 In addition, the second gist of the present invention is that when the polybutylene terephthalate oligomer is produced using the continuous reaction apparatus, at least a part of the dicarboxylic acid is continuously supplied to the reaction apparatus as a slurry with diol, Lies in a method for producing a polybutylene terephthalate oligomer in which the above is supplied to a space surrounded by a funnel-shaped wall.

   The third gist of the present invention resides in a method for producing a polybutylene terephthalate oligomer at an internal temperature of 200 to 245 ° C. and an absolute pressure of 40 to 100 kPa using the continuous reaction apparatus.

  The technical idea of the present invention is to separate a large amount of gas components generated by reaction and boiling when producing polybutylene terephthalate oligomers from liquid components at the top of the reactor to ensure fluidity in the reactor, and to increase the reaction rate. And to increase the uniformity of the reaction solution. According to the present invention, it is possible to promote the esterification reaction while suppressing side reactions such as THF formation from 1,4-butanediol, and drift and local residence that cause foreign substances. .

  According to the present invention, since the inside of the reactor can be uniformly and sufficiently mixed, a polybutylene terephthalate oligomer in which foreign substances and unreacted substances are reduced while increasing the esterification reaction rate and suppressing side reactions. It can be manufactured.

Hereinafter, the present invention will be described in detail, but the description of the constituent elements described below is a representative example of the present invention, and is not limited to these contents.
The polybutylene terephthalate oligomer in the present invention is a mixture of a low-order polymer having an average degree of polymerization of 10-mer or less when a structure in which terephthalic acid units and 1,4-butanediol units are ester-bonded is a monomer. From the viewpoint of fluidity in the reactor, the average degree of polymerization is preferably 1 to 7 mer, more preferably 2 to 5 mer. Moreover, 50 mol% or more of dicarboxylic acid units say what consists of a terephthalic acid unit, and 50 mol% or more of a diol component consists of a 1, 4- butanediol unit. Among them, terephthalic acid units preferably occupy 70 mol% or more, more preferably 80 mol% or more, particularly 95 mol% or more of all dicarboxylic acid units, and 70 mol% or more, more preferably 80 mol of diol units. It is preferable that 1,4-butanediol units occupy% or more, particularly 95 mol% or more. When the amount of terephthalic acid units or 1,4-butanediol units is less than 50 mol%, the final crystallization rate of polybutylene terephthalate is lowered, and the moldability is deteriorated.

In the present invention, the dicarboxylic acid component other than terephthalic acid is not particularly limited, and examples thereof include phthalic acid, isophthalic acid, 4,4′-diphenyldicarboxylic acid, 4,4′-diphenylether dicarboxylic acid, and 4,4′-benzophenone dicarboxylic acid. Acid, aromatic dicarboxylic acid such as 4,4′-diphenoxyethanedicarboxylic acid, 4,4′-diphenylsulfonedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 1,2-cyclohexanedicarboxylic acid, 1,3-cyclohexane Alicyclic dicarboxylic acids such as dicarboxylic acid and 1,4-cyclohexanedicarboxylic acid, aliphatic dicarboxylic acids such as malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid and sebacic acid be able to.

  In the present invention, the diol component other than 1,4-butanediol is not particularly limited, and examples thereof include ethylene glycol, diethylene glycol, polyethylene glycol, 1,2-propanediol, 1,3-propanediol, polypropylene glycol, and polytetramethylene. Glycol, dibutylene glycol, 1,5-pentanediol, neopentyl glycol, 1,6-hexanediol, aliphatic diol such as 1,8-octanediol, 1,2-cyclohexanediol, 1,4-cyclohexanediol, Alicyclic diols such as 1,1-cyclohexanedimethylol and 1,4-cyclohexanedimethylol, xylylene glycol, 4,4′-dihydroxybiphenyl, 2,2-bis (4-hydroxyphenyl) propane, bis ( - and aromatic diols such as hydroxyphenyl) sulfone and the like.

  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 such as acid, stearyl alcohol, benzyl alcohol, stearic acid, benzoic acid, t-butylbenzoic acid, benzoylbenzoic acid, tricarbaric acid, trimellitic acid, trimesic acid, pyromellitic acid, gallic acid, trimethylolethane Trifunctional or polyfunctional components such as trimethylolpropane, glycerol and pentaerythritol can be used as the copolymerization component.

The reactor for producing the polybutylene terephthalate oligomer of the present invention needs to have a heat exchanger for heat exchange, a so-called internal heat exchanger, inside the reactor. Although there is no restriction | limiting in the form of this heat exchanger, The form which can take a wide heat exchange area, such as a coil type | mold and a multi-tube type, is preferable, and a multi-tube type heat exchanger is especially preferable. The heat exchanger may allow the process liquid to flow on either the core side or the shell side, but the present invention is improved when the process liquid flows on the inner side of the tube and the heat medium flows on the shell side. Great effect.
In particular, when a multi-tubular heat exchanger is installed in the vertical direction, its openings are above and below, and the length of the exchanger is 1 m or more, and further 2 m or more, the bubble ratio at the top of the pipe is large. Since the gas linear velocity is also increased, the improvement effect of the present invention is remarkable.

Further, in the reactor of the present invention, in order to promote heat convection, in at least one horizontal section of the reactor, a heat exchanger is installed near the periphery, and no heat exchanger is installed near the center. It is necessary to have a space (hereinafter, simply referred to as a space), and it is preferable that a stirring blade is installed in the space. Furthermore, in order to promote convection in the reactor, it is preferable to use a blade shape and a rotation direction that cause a downward flow by stirring.
Furthermore, the reactor of the present invention is characterized in that a funnel-shaped wall whose diameter decreases from the upper part toward the lower part is installed in the upper part of the space. This wall may be in contact with the heat exchanger inside the reactor, or may be installed at a location away from the heat exchanger by taking support from the periphery, etc. It is preferable that a part of the liquid on the inner side and the outer side can circulate with each other by a slit or the like without completely separating the outer side.

Examples of the structure of the funnel-shaped wall in the present invention are shown in FIGS. FIG. 1 shows a reactor having a multi-tubular heat exchanger and a stirring blade inside, and shows a mode in which a funnel-like wall is installed in the upper part of the space so that the lower part is in contact with the heat exchanger. FIG. 2 shows a mode in which the wall in FIG. 1 does not come into contact with the upper part of the heat exchanger. In the vicinity of the upper part of the heat exchanger, the internal liquid can be circulated. FIG. 3 further shows a mode in which a slit is formed in a part of the wall in FIG. 2, and FIG. 4 shows a mode in which a cylindrical wall is attached to the lower part of the funnel-shaped wall in FIG. 5 shows an embodiment in which the lower part of the cylindrical wall in FIG. 4 is in contact with the upper part of the heat exchanger and the cylindrical wall part has a slit, and FIG. 6 is installed with two walls in FIG. A mode in which a slit is provided between two walls is shown. FIG. 7 shows a mode in which the conical wall in FIG. 2 is replaced with a hemispherical wall, and FIG. 8 shows a mode in which a coil type heat exchanger is installed in FIG. 4 instead of the multi-tubular heat exchanger. Further, FIG. 9 shows an embodiment without the stirring device in FIG.

FIGS. 10 to 12 show an example of a raw material supply method and an oligomer extraction method based on the reactor of the embodiment of FIG. In these drawings, reference numeral 1 denotes a raw slurry supply line, 2 denotes an oligomer extraction line, and 3 denotes a vent line. In FIG. 10, the raw slurry is continuously supplied from the line 1 to the inside of the funnel wall, the oligomer is continuously extracted through the line 2, and the inside of the reactor is maintained at a predetermined pressure through the vent line 3. FIG. 11 shows an embodiment in which the oligomer extraction line 2 is installed at the top of the heat exchanger in FIG. 10, and FIG. 12 shows an embodiment in which the raw slurry supply line 2 is installed at the bottom of the reactor in FIG. As shown, the embodiment shown in FIG. 11 is preferred, in which the raw slurry is supplied to a space surrounded by a funnel-shaped wall.
In the present invention, as shown in FIG. 13, when the major axis of the funnel-shaped wall is D and the minor axis is d, it is necessary to satisfy the following formula (I).
D / d ≧ 1.5 (I)
Furthermore, it is preferable to satisfy the following formula (III), in particular, (IV), particularly (V).
3.5 ≧ D / d ≧ 1.6 (III)
2.5 ≧ D / d ≧ 1.65 (IV)
2.2 ≧ D / d ≧ 1.7 (V)

When D / d is less than 1.5, the gas generated in the reaction and the reaction liquid are not well separated at the top of the heat exchanger, and the flow of the reaction liquid at the top of the heat exchanger is disturbed, resulting in a uniform flow. If a stirrer not only disappears but also has an effect of pushing down the reaction liquid in the space, it becomes easy to entrain the gas near the stirring blade, and the buoyancy of the gas and the push-down of the stirrer will antagonize. Cause cavitation, and fluidity deteriorates or wasteful power is consumed.
In particular, as shown in FIG. 13, when the wall is exposed from the liquid level to the gas phase, the following formula (VI), particularly (VII), especially between the diameter D ′ and the minor axis d on the liquid level: It is preferable that (VIII) holds.
3.5 ≧ D ′ / d ≧ 1.6 (VI)
2.5 ≧ D ′ / d ≧ 1.65 (VII)
2.2 ≧ D ′ / d ≧ 1.7 (VIII)

Further, when the length between the openings at both ends of the wall is L, preferably the following formula (IX), particularly (X)
It is preferable to satisfy.
10d ≧ L ≧ 0.3d (IX)
5d ≧ L ≧ d (X)

When L is larger than 10d or smaller than 0.3d, the fluidity improving effect of the present invention tends to be small.
In the present invention, when the horizontal sectional area of the portion closest to the funnel-shaped wall in the space is S and the horizontal sectional area of the portion closest to the space of the funnel-shaped wall is s, the following equation (II) is satisfied. It is necessary to satisfy the following formula (XI), particularly the following formula (XII).
s / S = 0.6 to 2.0 (II)
s / S = 0.6 to 1.7 (XI)
s / S = 0.8 to 1.3 (XII)

  The horizontal sectional area s closest to the space of the funnel-shaped wall is indicated by the area of a circle whose diameter is d shown in FIG. 13 when the funnel-shaped wall is conical. Further, the horizontal cross-sectional area S at the upper part of the space is represented by the area of a circle having a diameter C as shown in FIG. 13 when the space is cylindrical. Even if s / S is smaller than 0.6 or larger than 2.0, the reaction liquid does not smoothly flow from the funnel-like wall to the space, and the gas-liquid separation is deteriorated, the fluid state is deteriorated, and thus esterification is achieved. Since the reduction of the rate and the increase of byproduct THF are caused, the improvement effect of the present invention tends to be small.

In the production of the polybutylene terephthalate oligomer using the reactor of the present invention, the dicarboxylic acid component mainly composed of terephthalic acid and the diol component mainly composed of 1,4-butanediol are mixed in a raw material adjusting tank. It is made into a slurry and is usually carried out at a temperature of 180 to 260 ° C., preferably 200 to 245 ° C., particularly preferably 210 to 235 ° C. in the presence of an esterification reaction catalyst. Among these, the improvement effect of the present invention is great when the reaction is carried out at a temperature higher than the boiling point of 1,4-butanediol. The boiling point of 1,4-butanediol depends on the reaction pressure, but is 230 ° C. at 101.1 kPa (atmospheric pressure) in absolute pressure and 205 ° C. at 50 kPa. When the reaction temperature is lower than 180 ° C., the reaction is not completed in a practical time. When the reaction temperature is higher than 260 ° C., side reactions such as dimerization of 1,4-butanediol and conversion to THF tend to occur.

The reaction pressure is usually 10 to 133 kPa in absolute pressure, preferably 40 to 100 kPa, particularly preferably 60 to 90 kPa. If the pressure is too high, the water concentration in the system increases, resulting in a slow reaction. Side reactions such as the conversion of 1,4-butanediol to THF are likely to occur, and if the pressure is too low, the concentration of 1,4-butanediol in the liquid will decrease, and more 1,4-butanediol will not be supplied. Because the reaction is slow, extra energy is required.
The average residence time when producing a polybutylene terephthalate oligomer using the reactor of the present invention is usually 0.5 to 6 hours, preferably 1 to 3 hours. If it is too long, side reactions will emerge and it will be too short. And the reaction does not proceed sufficiently.
The esterification reaction to obtain the polybutylene terephthalate oligomer can be performed using a multi-stage reactor, but in the present invention, the esterification reaction rate has been greatly improved, from the viewpoint of energy efficiency and production efficiency. Is preferably performed in one stage.
In the production of the polybutylene terephthalate oligomer in the present invention, a metal compound catalyst is used, and among these, a titanium compound is preferably used. Specific examples of titanium compounds include inorganic titanium compounds such as titanium oxide, titanium alcoholates such as tetramethyl titanate, tetraisopropyl titanate, and tetrabutyl titanate, titanium phenolates such as tetraphenyl titanate, and the like. Of these, organic titanium compounds are preferred, and tetrabutyl titanate is particularly preferred.

  Further, as the catalyst, in addition to the titanium compound, for example, dibutyltin oxide, methylphenyltin oxide, tetraethyltin, hexaethylditin oxide, cyclohexahexylditin oxide, didodecyltin oxide, triethyltin hydroxide, triphenyl Tin such as tin hydroxide, triisobutyltin acetate, dibutyltin diacetate, diphenyltin dilaurate, monobutyltin trichloride, tributyltin chloride, dibutyltin sulfide, butylhydroxytin oxide, methylstannic acid, ethylstannic acid, butylstannic acid A compound or the like can be used.

In the present invention, the amount of the metal compound catalyst is not limited, but the weight ratio of the metal atom to the terephthalic acid component is usually 150 ppm or less, more preferably 100 ppm or less, especially 80 ppm or less, and particularly preferably 60 ppm or less. Is 50 ppm or less. If the amount of the metal catalyst is too large, it causes foreign matter generation and side reactions, and if it is too small, the reaction rate decreases.
The obtained polybutylene terephthalate oligomer is continuously withdrawn from the reactor and sent to the subsequent polycondensation step, preferably continuously, usually 210 to 280 ° C, preferably 220 to 265 ° C, particularly preferably. The molecular weight is further increased in a range of 2 to 12 hours, preferably 3 to 10 hours under stirring under a reduced pressure of 235 to 245 ° C., usually 27 kPa or less, preferably 10 kPa or less, particularly preferably 3 kPa or less. The obtained polybutylene terephthalate is usually extracted in the form of a strand and cut into a pellet by a rotary cutter or the like.

In the manufacturing method of the polybutylene terephthalate oligomer in this invention, it is preferable that the molar ratio of the terephthalic acid supplied to a reactor and 1, 4- butanediol satisfy | fills the following Formula.
B / T = 1.6 to 4.5 (mol / mol)
(B represents the number of moles of 1,4-butanediol supplied from the outside to the reactor per unit time, and T represents the number of moles of terephthalic acid supplied from the outside to the reactor per unit time)
Among these, B / T = 2.0 to 4.0, more preferably 2.5 to 3.8, and particularly preferably 2.7 to 3.5. If B / T is less than 1.6, the conversion rate decreases, and foreign matters and haze resulting from the deactivation of the catalyst emerge. On the other hand, as B / T increases, the conversion rate increases and the deactivation of the catalyst is suppressed, but the amount of gas generated simultaneously increases. In the present invention, even if B / T increases and the amount of gas generated increases, it is possible to prevent adverse effects on gas-liquid separation and fluidity. However, when B / T is larger than 4.5, not only the thermal efficiency decreases, but also by-products such as THF tend to increase.

In the present invention, 1,4-butanediol supplied to the reactor from the outside is 1,4-butanediol supplied together with terephthalic acid as a raw slurry or solution, The total of 1,4-butanediol entering the reactor from outside the reactor, such as 4-butanediol and 1,4-butanediol used as a solvent for the metal compound catalyst.

It is the schematic which showed one embodiment of the manufacturing apparatus provided with the funnel-shaped wall of this invention. It is the schematic which showed another one embodiment of the manufacturing apparatus provided with the funnel-shaped wall of this invention. It is the schematic which showed another one embodiment of the manufacturing apparatus provided with the funnel-shaped wall of this invention. It is the schematic which showed another one embodiment of the manufacturing apparatus provided with the funnel-shaped wall of this invention. It is the schematic which showed another one embodiment of the manufacturing apparatus provided with the funnel-shaped wall of this invention. It is the schematic which showed another one embodiment of the manufacturing apparatus provided with the funnel-shaped wall of this invention. It is the schematic which showed another one embodiment of the manufacturing apparatus provided with the funnel-shaped wall of this invention. It is the schematic which showed another one embodiment of the manufacturing apparatus provided with the funnel-shaped wall of this invention. It is the schematic which showed another one embodiment of the manufacturing apparatus provided with the funnel-shaped wall of this invention. It is the schematic which showed supply of the raw material and extraction of the oligomer in the manufacturing apparatus of this invention. It is the schematic which showed supply of the raw material and extraction of the oligomer in the manufacturing apparatus of this invention. It is the schematic which showed supply of the raw material and extraction of the oligomer in the manufacturing apparatus of this invention. It is one embodiment of the manufacturing apparatus provided with the funnel-shaped wall of this invention, Comprising: It is the schematic which showed the dimension of each site | parts, such as a funnel-shaped wall.

Explanation of symbols

1 Raw material slurry supply line 2 Oligomer extraction line 3 Vent line

M Motor D Long diameter of funnel-shaped wall d Short diameter of funnel-shaped wall D 'Diameter of liquid surface of funnel-shaped wall L Length between openings at both ends of funnel-shaped wall C Diameter of cylindrical space

Claims (9)

An apparatus for continuously producing a polybutylene terephthalate oligomer by reacting a dicarboxylic acid containing terephthalic acid as a main component with a diol containing 1,4-butanediol as a main component,
(1) having a heat exchanger inside the reactor,
(2) In at least one horizontal cross section in the reactor, a heat exchanger is installed near the periphery, and a space where no heat exchanger is installed near the center,
(3) A funnel-shaped wall whose diameter decreases from the upper part to the lower part is installed in the upper part of the space in (2) above.
(4) When the major axis of the funnel-shaped wall in (3) is D and the minor axis is d, the following formula (I) is satisfied:
D / d ≧ 1.5 (I)
(5) The horizontal cross-sectional area of the part closest to the funnel-shaped wall in the space where the heat exchanger is not installed in (2) is S, and the horizontal part of the part surrounded by the funnel-shaped wall is closest to the space. An apparatus for continuously producing a polybutylene terephthalate oligomer, which satisfies the following formula (II) when the cross-sectional area is s.
s / S = 0.6 to 2.0 (II) The apparatus for continuously producing a polybutylene terephthalate oligomer according to claim 1, wherein the heat exchanger is a multitubular heat exchanger. The apparatus for continuously producing a polybutylene terephthalate oligomer according to claim 2, wherein the multi-tubular heat exchanger is installed in the vertical direction, the openings thereof are vertically arranged, and the length of the exchanger is 1 m or more. In at least one horizontal section of the reactor, there is a space where a heat exchanger is installed near the periphery and no heat exchanger is installed near the center, and a stirring blade is installed in the space The continuous production apparatus for polybutylene terephthalate oligomer according to any one of claims 1 to 3. When the polybutylene terephthalate oligomer is produced using the reactor according to any one of claims 1 to 4, at least a part of the dicarboxylic acid is continuously supplied to the reactor as a slurry with diol, and the slurry is supplied. A continuous process for producing a polybutylene terephthalate oligomer, wherein the process is carried out in a space surrounded by a funnel-shaped wall. A method for continuously producing a polybutylene terephthalate oligomer at an internal temperature of 200 to 245 ° C. and an absolute pressure of 40 to 100 kPa using the reaction apparatus according to claim 1. The process for producing a polybutylene terephthalate oligomer according to claim 5 or 6, wherein the production process of the polybutylene terephthalate oligomer is one stage. The method for producing a polybutylene terephthalate oligomer according to any one of claims 5 to 7, wherein a titanium compound is used as a catalyst, and the amount used is 100 ppm or less in terms of a weight ratio of titanium atoms to terephthalic acid. The method for producing a polybutylene terephthalate oligomer according to any one of claims 5 to 8, wherein a molar ratio of terephthalic acid to 1,4-butanediol satisfies the following formula.
B / T = 1.6 to 4.5 (mol / mol)
(B represents the number of moles of 1,4-butanediol supplied from the outside to the reactor per unit time, and T represents the number of moles of terephthalic acid supplied from the outside to the reactor per unit time)

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