JP2004137454A - Method for producing polybutylene terephthalate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing a polybutylene terephthalate resin, increasing the rate of esterification reaction, including less foreign materials and improving productivity. <P>SOLUTION: This method for producing the polybutylene terephthalate by performing the esterification reaction and polycondensation reaction of terephthalic acid component with 1, 4-butanediol component in the presence of a titanium and/or tin compound as a reaction catalyst is characterized by setting 16-100°C range temperature of 1, 4-butanediol returned to an esterification reaction vessel in recirculating by condensing 1, 4-butanediol distilled out from the esterification reaction vessel and returning it to the esterification reaction vessel independently of terephthalic acid. <P>COPYRIGHT: (C)2004,JPO

Description

【００３８】
【表２】

【００３９】
［実施例２］
２ｄを通して供給する再循環１，４−ブタンジオールの量を表に示す通りに変更した以外は、実施例１と同様に行った。
［実施例３］
２ｄを通して供給する再循環１，４−ブタンジオールの温度を表に示す通りに変更した以外は、実施例２と同様に行った。
［実施例４］
攪拌速度を変え、Ｐ／ｑを表に示す通りに変更した以外は、実施例１と同様に行った。
［実施例５］
原料の流量を変え平均滞留時間を１．１ｈｒとし、Ｐ／ｑを表に示す通りに変更した以外は、実施例１と同様に行った。
【００４０】
［実施例６］
エステル化反応温度を２４０℃にした以外は実施例１と同様に行った。
［実施例７］
添加する触媒量をチタン量として原料テレフタル酸（ＴＰＡ）に対する重量比で４７ｐｐｍ（得られるポリブチレンテレフタレートに対して３５ｐｐｍ）となるようにした以外は実施例１と同様に行った。
［実施例８］
添加する触媒量をチタン量として原料テレフタル酸（ＴＰＡ）に対する重量比で６７ｐｐｍ（得られるポリブチレンテレフタレートに対して５０ｐｐｍ）となるようにした以外は実施例１と同様に行った。
【００４１】
［比較例１］
原料から供給する再循環１，４−ブタンジオールを表に示す通りにし、２ｄを通して供給する再循環１，４−ブタンジオールを停止した以外は、実施例１と同様に行った。エステル化率が低く、異物量が多かった。
［比較例２］
２ｄを通して供給する再循環１，４−ブタンジオールの温度を２１９℃にした以外は実施例２と同様に行った。エステル化率が低かった。
［比較例３］
２ｄを通して供給する再循環１，４−ブタンジオールの量を表に示す通りにした以外は実施例１と同様に行った。エステル化率は高かったが留出液中のＴＨＦ量が増加した。
［比較例４］
触媒チタンの量をテレフタル酸に対して４００ｐｐｍ（得られるポリブチレンテレフタレートに対して３０２ｐｐｍ）とした以外は、実施例１と同様に行った。エステル化率は高く、留出液中のＴＨＦ量も少なかったが、オリゴマー中の異物量が増大した。
［比較例５］
２ｄを通して供給する再循環１，４−ブタンジオールの温度を２１９℃にし、Ｐ／ｑを表に示すとおりにした以外は実施例２と同様に行った。エステル化率が低下し、留出液中のＴＨＦ量が増加しただけでなく、異物量も増加した。
【００４２】
【発明の効果】
本発明により、エステル化反応時の反応率を上げ、異物が少なく、生産性が改良されたポリブチレンテレフタレート樹脂の製造方法を提供することができる。
【図面の簡単な説明】
【図１】本発明の好ましい一実施態様であるポリブチレンテレフタレートの製造装置の概略図である。
【図２】本発明の別の好ましい一実施態様であるポリブチレンテレフタレートの製造装置の概略図である。
【図３】本発明の別の好ましい一実施態様であるポリブチレンテレフタレートの製造装置の概略図である。
【図４】実施例１で使用したポリブチレンテレフタレートの製造装置の概略図である。
【符号の説明】
Ｐ１　原料供給ライン
Ｐ２　次工程（重縮合工程）への反応液抜出口
１　　スラリー調整槽
１ａ　ジカルボン酸成分供給口
１ｂ　ジオール成分供給口
２　　エステル化反応槽
２ａ　ベント用口
２ｂ　触媒供給口
２ｄ　再循環１，４−ブタンジオールの供給口（反応槽への直接供給）
３　　反応流出液の凝縮器
３ａ　減圧系配管
３ｂ　低沸点成分の回収ライン
３ｃ　余剰１，４−ブタンジオールの抜出口
４　　熱交換機
４ａ　再循環１，４−ブタンジオールの供給口（原料供給ラインへ供給）
５　　低沸点成分を分離するための蒸留塔
５ａ　低沸点成分の排出口
５ｂ　低沸点成分の分離された１，４−ブタンジオールの次工程へのライン
６　　高沸点成分を分離するための蒸留塔
６ａ　精製された１，４−ブタンジオールの次工程へのライン
６ｂ　高沸点成分の抜出口
７　　精製された１，４−ブタンジオールのタンク
Ｍ１，Ｍ２　攪拌装置
Ｇ１，Ｇ２　ギヤポンプ[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for producing polybutylene terephthalate. More specifically, the present invention relates to a method for producing polybutylene terephthalate, which has a higher conversion during an esterification reaction, has less foreign matter, and has improved productivity.
[0002]
[Prior art]
Polybutylene terephthalate, a representative engineering plastic among thermoplastic polyesters, has advantages in ease of molding, mechanical properties, heat resistance, chemical resistance, fragrance retention, and other physical and chemical properties. Because of its superiority, it is widely used in automobile parts, electric / electronic parts, precision equipment parts, and the like.
[0003]
Polybutylene terephthalate is manufactured through an esterification reaction when the raw material is terephthalic acid and a transesterification reaction when the raw material is dimethyl terephthalate. Recently, it has been continuously used to improve quality, improve production efficiency, and improve energy efficiency. A so-called continuous polymerization method, in which raw materials are supplied, esterification or transesterification is continuously performed, and post-processes are also continuously performed, has attracted attention. Above all, the so-called direct polymerization method using terephthalic acid as a raw material is becoming mainstream because of the high raw material unit consumption and no generation of toxic methanol. However, if the reaction rate of the esterification reaction (esterification rate) is low and sent to a high-temperature, high-vacuum post-process (polycondensation process), unreacted monomers may block valves and pumps in the transfer piping, There has been a problem that not only does it volatilize into the vent system of the polycondensation reaction tank and cause clogging of pipes, but also contamination of recovered 1,4-butanediol, tetrahydrofuran (THF) and the like. Therefore, it is preferable that the reaction rate at the outlet of the esterification reaction tank is high, and generally, the conditions under which the reaction is performed until the reaction rate becomes 90% or more are selected. As a method of increasing the reaction rate, in addition to a method of increasing the reaction time, a method of increasing the catalyst concentration or the reaction temperature is known. For example, Patent Literature 1 discloses a method in which a high catalyst concentration, a high temperature, and a low pressure are applied. Are proposed. However, in this method, there is a problem that a catalyst residue based on a high catalyst concentration causes an increase in foreign substances in a product, or a high temperature and a high catalyst concentration cause an increase in side reactions and consequently lower the quality of a product polymer. there were. Further, a low pressure setting causes an increase in 1,4-butanediol discharged as a distillate out of the system, and also has a problem that the equipment becomes excessive.
[0004]
On the other hand, Patent Document 2 defines the molar ratio of 1,4-butanediol and terephthalic acid, and suppresses the concentration of the organotitanium compound to a value or less calculated using the molar ratio, thereby suppressing the generation of foreign matter derived from the catalyst. Although a method of suppressing this has been proposed, the basis of this technique is to compensate for the decrease in catalytic activity caused by setting the concentration of the organotitanium compound low with an organotin compound, which was found in Patent Document 1. There was a problem that the problem based on the high catalyst concentration was not solved at all. In addition, setting the reaction temperature lower than that in Patent Document 1 results in an increase in the esterification reaction time, and a significant improvement has been demanded from the viewpoint of productivity.
[0005]
As described above, various attempts have been made to increase the reaction rate in the esterification reaction stage during the production of polybutylene terephthalate.However, when the reaction temperature is increased, the esterification reaction rate increases while the side reaction rate also decreases. There is a dilemma that the above increases, and when the amount of the catalyst is increased, the side reaction is suppressed, but there is a dilemma that the amount of foreign substances in the product increases and the thermal stability of the product decreases. Although a low reaction pressure setting is effective from the viewpoint of removing reaction products such as water to the outside of the system, it also promotes volatilization of unreacted 1,4-butanediol at the same time, and causes 1,4-butanediol present in the reaction system. Butanediol decreases and it is necessary to supply more 1,4-butanediol to maintain the reaction rate. As a result, side reactions such as THF conversion of 1,4-butanediol and energy loss occur. I was invited.
[0006]
[Patent Document 1]
JP-A-62-195017
[Patent Document 2]
JP-A-10-330469
[0007]
[Problems to be solved by the invention]
An object of the present invention is to provide a method for producing polybutylene terephthalate, which has a higher conversion during esterification or transesterification, has less foreign substances, and has improved productivity.
[0008]
[Means for Solving the Problems]
The present inventors have conducted intensive studies to solve the above problems, and as a result, have found that by performing an esterification reaction under specific conditions, it is possible to increase the reaction rate and improve productivity, and to complete the present invention. Reached.
That is, the gist of the present invention is to produce polybutylene terephthalate by subjecting a terephthalic acid component and a 1,4-butanediol component to an esterification reaction and a polycondensation reaction in the presence of a titanium or / and tin compound as a reaction catalyst. At
(1) a step of continuously performing an esterification reaction between terephthalic acid and 1,4-butanediol in an esterification reaction tank; and (2) a step of distilling out of the esterification reaction tank with a condenser. (3) a step of condensing 1,4-butanediol, and a step of returning the condensed 1,4-butanediol to the esterification reaction tank independently of terephthalic acid, and (4) a step of condensing 1,4-butanediol in the polybutylene terephthalate. The total amount of titanium atoms and tin atoms among the metals derived from the reaction catalyst present is 1 to 230 ppm based on the obtained polybutylene terephthalate, and (5) 1,4 returned to the esterification reaction in the recycle step The temperature of butanediol is in the range of 16 to 100 ° C., and (6) the molar ratio of terephthalic acid to 1,4-butanediol supplied to the esterification reactor per unit time (1,4 Butanediol / terephthalic acid) resides in the production method of polybutylene terephthalate, which is a 1.6 to 4.5.
The technical idea of the present invention is to increase the concentration of 1,4-butanediol participating in the reaction when the esterification reaction is carried out at or near the boiling point of 1,4-butanediol due to a request for an increase in the reaction rate, The purpose is to increase the main reaction rate and suppress side reactions. ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to raise the reaction rate at the time of an esterification reaction, suppressing a side reaction, without raising a reaction temperature, without raising a catalyst concentration, without losing energy, unnecessarily. .
[0009]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described in detail.
The polybutylene terephthalate in the present invention is a polymer having a structure in which terephthalic acid units and 1,4-butanediol units are ester-bonded, and 50 mol% or more of dicarboxylic acid units are composed of terephthalic acid units. 50% by mole or more of 1,4-butanediol units. Among them, terephthalic acid units preferably account for 70 mol% or more, more preferably 80 mol% or more, and particularly 95 mol% or more of all dicarboxylic acid units, and 70 mol% or more, and more preferably 80 mol% of the diol units. %, Especially 95 mol% or more is preferably occupied by 1,4-butanediol units. If the terephthalic acid unit or the 1,4-butanediol unit is less than 50 mol%, the crystallization rate of polybutylene terephthalate decreases, leading to deterioration in moldability.
[0010]
In the present invention, there is no particular limitation on dicarboxylic acid components other than terephthalic acid. For example, phthalic acid, isophthalic acid, 4,4′-diphenyldicarboxylic acid, 4,4′-diphenylether dicarboxylic acid, 4,4′-benzophenone dicarboxylic acid Acids, aromatic dicarboxylic acids 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, and 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.
[0011]
In the present invention, diol components other than 1,4-butanediol are not particularly limited. For example, ethylene glycol, diethylene glycol, polyethylene glycol, 1,2-propanediol, 1,3-propanediol, polypropylene glycol, polytetramethylene Glycol, dibutylene glycol, 1,5-pentanediol, neopentyl glycol, 1,6-hexanediol, aliphatic diols such as 1,8-octanediol, 1,2-cyclohexanediol, 1,4-cyclohexanediol, Alicyclic diols such as 1,1-cyclohexane dimethylol and 1,4-cyclohexane dimethylol, xylylene glycol, 4,4′-dihydroxybiphenyl, 2,2-bis (4-hydroxyphenyl) propane, bis ( - and aromatic diols such as hydroxyphenyl) sulfone and the like.
[0012]
In the present invention, hydroxycarboxylic acids such as lactic acid, glycolic acid, m-hydroxybenzoic acid, p-hydroxybenzoic acid, 6-hydroxy-2-naphthalenecarboxylic acid, p-β-hydroxyethoxybenzoic acid, and alkoxycarboxylic acids Monofunctional components such as acid, stearyl alcohol, benzyl alcohol, stearic acid, benzoic acid, t-butyl benzoic acid, benzoyl benzoic acid, tricarballylic acid, trimellitic acid, trimesic acid, pyromellitic acid, gallic acid, and trimethylolethane A trifunctional or higher polyfunctional component such as trimethylolpropane, glycerol, and pentaerythritol can be used as a copolymer component.
[0013]
The polybutylene terephthalate of the present invention preferably has an intrinsic viscosity of 0.5 to 1.5 dL / g measured at 30 ° C. using a mixed solvent of phenol / tetrachloroethane (weight ratio 1/1). It is more preferably from 1.6 to 1.4 dL / g, and still more preferably from 0.7 to 1.3 dL / g. If the intrinsic viscosity is less than 0.5 dL / g, the mechanical strength of the molded product may be insufficient. If the intrinsic viscosity exceeds 1.5 dL / g, the melt viscosity increases, the fluidity deteriorates, and the moldability may become poor.
[0014]
As an example of the method for producing polybutylene terephthalate of the present invention, the dicarboxylic acid component mainly containing terephthalic acid and the diol component mainly containing 1,4-butanediol are connected singly or in series. In a plurality of esterification reaction tanks, continuously in the presence of an esterification reaction catalyst, usually at a temperature of 180 to 260 ° C, preferably 200 to 240 ° C, particularly preferably 210 to 235 ° C, and usually 10 to 133 kPa, The esterification reaction is carried out at a pressure of preferably 13 to 101 kPa, particularly preferably 60 to 90 kPa, for 0.5 to 5 hours, preferably 1 to 3 hours, and the obtained oligomer as an esterification reaction product is polymerized. Transferred to the condensation reaction tank, in a single or a plurality of polycondensation reaction tanks connected in series, in the presence of a polycondensation reaction catalyst, preferably Continuously, at a temperature of usually 210 to 280 ° C., preferably 220 to 265 ° C., usually 27 kPa or less, preferably 20 kPa or less, particularly preferably 13 kPa or less under reduced pressure, for 2 to 10 hours with stirring, preferably 2 to 5 hours. For example, a method of performing a polycondensation reaction in a long time may be used.
[0015]
In addition, the resin obtained by the polycondensation reaction is usually transferred from the bottom of the polycondensation reaction tank to a polymer extraction die, extracted in a strand shape, and cooled with water or after water cooling, cut with a cutter, and pelletized. It is a granular material such as a chip.
As the esterification reaction catalyst in the present invention, a titanium compound and / or a tin compound are used, and among them, a titanium compound is preferably used. Specific examples of the titanium compound include, for example, tetramethyl titanate, tetraisopropyl titanate, titanium alcoholates such as tetrabutyl titanate, titanium phenolates such as tetraphenyl titanate, and the like, typical examples of which are tetrabutyl titanate. .
[0016]
Examples of the tin compound used as the reaction catalyst of the present invention include, for example, dibutyltin oxide, methylphenyltin oxide, tetraethyltin, hexaethylditin oxide, cyclohexahexylditin oxide, didodecyltin oxide, and triethyltin hydroxide. , Triphenyltin hydroxide, triisobutyltin acetate, dibutyltin diacetate, diphenyltin dilaurate, monobutyltin trichloride, tributyltin chloride, dibutyltin sulfide, butylhydroxytin oxide, methylstannoic acid, ethylstannoic acid, butylstannoic acid, And magnesium acetate, magnesium hydroxide, magnesium carbonate, magnesium oxide, magnesium oxide, etc. As a co-catalyst, a magnesium compound such as mualkoxide, magnesium hydrogen phosphate, etc., a calcium compound such as calcium acetate, calcium hydroxide, calcium carbonate, calcium oxide, calcium alkoxide, calcium hydrogen phosphate, etc., a manganese compound, a zinc compound, etc. Can be used.
[0017]
In the present invention, the total metal concentration of titanium atoms and tin atoms used in the esterification reaction and the polycondensation reaction is not only a cause of foreign substances if too large, but also causes a deterioration reaction during heat retention of the polymer and gas generation. If the amount is too small, the main reaction rate is reduced and a side reaction is apt to occur. Therefore, it is necessary that the content is 1 to 230 ppm with respect to the obtained polybutylene terephthalate, preferably 10 to 200 ppm, more preferably 15 ppm. To 150 ppm, particularly preferably 20 to 100 ppm.
[0018]
On the other hand, when emphasis is placed on foreign matter suppression, the total metal concentration of titanium atoms and tin atoms is preferably 1 to 65 ppm, more preferably 10 to 45 ppm, and particularly preferably 20 ppm, based on the obtained polybutylene terephthalate. ~ 35 ppm.
The amount of these metals can be measured using a method such as atomic luminescence, atomic absorption, Induced Coupled Plasma (ICP) after recovering the metals in the polymer by a method such as wet ashing.
As the polycondensation reaction catalyst, the catalyst added at the time of the esterification reaction may be subsequently used as the polycondensation reaction catalyst, so that a new catalyst may not be added, or the catalyst may be further added. Further, an antimony compound such as diantimony trioxide, a germanium compound such as germanium dioxide or germanium tetroxide, which is different from the reaction catalyst added during the esterification reaction, may be newly added. There is no particular limitation on the amount used at that time, but if it is too large, it not only causes foreign substances but also causes a deterioration reaction during heat retention of the polymer and gas generation, so that the metal is usually used for polybutylene terephthalate resin. As atoms, it is preferably at most 200 ppm, more preferably at most 150 ppm, particularly preferably at most 100 ppm, most preferably at most 50 ppm.
[0019]
In the esterification reaction and the polycondensation reaction, in addition to the catalyst, reaction aids such as orthophosphoric acid, phosphorous acid, hypophosphorous acid, polyphosphoric acid, and phosphorus compounds such as esters and metal salts thereof, Phenolic compounds such as 6-di-t-butyl-4-octylphenol, pentaerythrityl-tetrakis [3- (3 ′, 5′-t-butyl-4′-hydroxyphenyl) propionate], dilauryl-3,3 ′ Thioether compounds such as thiodipropionate, pentaerythrityl-tetrakis (3-laurylthiodipropionate), triphenylphosphite, tris (nonylphenyl) phosphite, tris (2,4-di-t-butylphenyl) ) Antioxidants such as phosphorus compounds such as phosphite, paraffin wax, microcrystalline wax, polyethylene wax Box, long chain fatty acids and their esters represented by montanic acid and montanic acid esters, may be present other additives release agent such as silicone oil.
[0020]
As the esterification reaction tank, known ones can be used, and any of a vertical stirring complete mixing tank, a vertical thermal convection type mixing tank, a tower type continuous reaction tank, and the like may be used. The tank may be a plurality of tanks in which the same or different tanks are arranged in series. Among them, a reaction vessel having a stirrer is preferable. As the stirrer, in addition to a normal type including a power unit, a bearing, a shaft, and a stirring blade, a turbine stator type high-speed rotary stirrer, a disk mill type stirrer, a rotor mill type stirrer and the like Can be used.
[0021]
There is no limitation on the form of stirring. In addition to the normal stirring method in which the reaction solution in the reaction tank is directly stirred from the upper, lower, and lateral portions of the reaction tank, a part of the reaction solution is connected to a pipe or the like outside the reactor. And agitating with a line mixer or the like to circulate the reaction solution.
Known types of stirring blades can be selected, and specific examples include propeller blades, screw blades, turbine blades, fan turbine blades, disk turbine blades, faudler blades, full zone blades, and max blend blades.
In the present invention, the total supply amount of raw materials per unit time is q (m³/ Sec), and when the stirring power to be applied is P (kw), it is preferable that the tank in which the esterification reaction is performed satisfies the following relationship.
[0022]
P / q ≧ 1500 kJ / m³
More preferably
P / q ≧ 2000 kJ / m³
Particularly preferred
P / q ≧ 3000 kJ / m³
Optimally
P / q ≧ 4000 kJ / m³
It is.
[0023]
In the above, the raw material represented by the total supply amount q per unit time refers to a slurry prepared by previously mixing terephthalic acid and 1,4-butanediol, and 1,4-butane supplied independently of terephthalic acid. Diols, for example, 1,4-butanediol collected in a distilling system and returned to the reaction tank, 1,4-butanediol refluxed by a reflux condenser, and the like are excluded.
P / q indicates the stirring energy given per unit volume, and the stirring power P can be detected by a method such as installing a torque meter on a stirring shaft or a power detector. P / q is 1500 kJ / m³If it is full, the esterification ratio tends to decrease.
[0024]
In producing the polybutylene terephthalate resin of the present invention, the molar ratio of terephthalic acid and 1,4-butanediol supplied from the outside to the reaction vessel per unit time during continuous esterification reaction is used. Needs to satisfy the following equation.
B / T = 1.6-4.5 (mol / mol)
(Where B is the number of moles of 1,4-butanediol externally supplied to the esterification reactor per unit time, and T is the number of moles of terephthalic acid externally supplied to the esterification reactor per unit time) Indicates)
Among them, B / T = 2.0 to 4.0, more preferably 2.5 to 3.5, and particularly preferably 2.7 to 3.3. When B / T is less than 1.6, the esterification rate decreases, and when B / T is more than 4.5, not only the thermal efficiency decreases, but also by-products such as tetrahydrofuran increase.
[0025]
In the present invention, the 1,4-butanediol supplied to the esterification reaction tank from the outside refers to 1,4-butanediol supplied together with terephthalic acid as a raw material slurry, and 1-butanediol supplied independently from these. , 4-butanediol, for example, 1,4-butanediol collected by a distilling system and returned to the reaction tank, 1,4-butanediol refluxed by a reflux condenser, or the like, enters the reaction tank from outside the reaction tank. It is the sum total of 1,4-butanediol.
[0026]
In the present invention, the excess 1,4-butanediol distilled in the esterification reaction tank is collected by using a condenser or the like, and the esterification reaction tank has a recirculation step independently of terephthalic acid. Generally, the distillate 1,4-butanediol is separated from components such as water and tetrahydrofuran after or while being collected by a condenser or the like, and is recycled to the reaction tank.
The temperature of the recirculated 1,4-butanediol when returning to the reactor needs to be in the range of 16 to 100 ° C, preferably 20 to 80 ° C, more preferably 30 to 75 ° C, and particularly preferably. Is 40 to 70 ° C. If the temperature of the recirculated 1,4-butanediol is lower than 16 ° C, troubles such as coagulation of 1,4-butanediol are caused. If the temperature is higher than 100 ° C, not only the effect of improving the esterification rate is not seen, but also The effect of suppressing the reaction such as the production of THF is no longer observed. In this case, the temperature of the recirculated 1,4-butanediol indicates a temperature near the reactor in a region where the influence of the heat medium jacket of the reactor is not exerted.
Since the temperature of the distilled 1,4-butanediol is usually near the boiling point of the reaction pressure of 1,4-butanediol, a cooling device may be used or low-temperature 1,4-butanediol may be newly added. And then recirculated to the reactor.
[0027]
Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.
In FIG. 1, P1 is a raw material supply port, 2 is an esterification reaction tank equipped with a stirrer, 2a is a vent pipe provided at the top of the reaction tank, 2d is a supply port of recirculated 1,4-butanediol, 3 is A condenser for the reaction distillate, 3a is a decompression system pipe, 3c is a discharge port for excess 1,4-butanediol, 4 is a heat exchanger, and P2 is a reaction liquid discharge port for the next step.
The raw material terephthalic acid is usually mixed with 1,4-butanediol and supplied to the reaction tank 2 in the form of a slurry from P1. Similarly, the catalyst is usually supplied to the reaction tank as a solution of 1,4-butanediol independently or mixed with the raw material slurry (omitted in the figure). Water, THF, excess 1,4-butanediol, and the like generated by the reaction are coagulated at 3 through 2a, and low-boiling components are discharged out of the system from 3a and are separately condensed and collected. On the other hand, the 1,4-butanediol is cooled in 4 and then recirculated to the reactor through 2d. Excess 1,4-butanediol is discharged out of the system from 3c, and a high boiling point component contained in a small amount in the distillate is discharged out of the system at a constant rate through 3c in a steady state, and is not concentrated in the system. It is driven as follows.
[0028]
FIG. 2 shows an embodiment in which part of the recirculated 1,4-butanediol returned to the reactor through 2d in FIG. 1 is returned to the feed line through 4a.
The embodiment in FIG. 3 shows a case where all the distilled 1,4-butanediol is purified by a distillation purification system, and a part or all of the distilled 1,4-butanediol is recycled to the esterification reaction. A distillation column for separating low-boiling components in butanediol, 5a is an outlet for low-boiling components, 5b is a line to the next step of 1,4-butanediol having low-boiling components separated, and 6 is a high-boiling line. A distillation column for separating components, 6a is an outlet for purified 1,4-butanediol, 6b is an outlet for high-boiling components, and 7 is a tank for purified 1,4-butanediol maintained at a constant temperature. The 1,4-butanediol distilled from the reaction tank 2 is stored in the tank 7 after being purified in 3, 5, and 6. Part or all of 1,4-butanediol in the tank is adjusted to 16 to 100 ° C. by a heat exchanger or the like, and is recycled to the reaction tank 2 through the line 2 d. (The temperature adjustment mechanism such as a heat exchanger is not shown.)
A single or a plurality of tanks for performing the esterification reaction can be installed in series, but the esterification reaction tank and the polycondensation reaction tank in the present invention are distinguished by the esterification rate represented by the following formula (1). Is 90% or less at the inlet of the reactor, it is regarded as an esterification reaction tank, and when it exceeds 90%, it is regarded as a polycondensation reaction tank.
[0029]
Esterification rate = (Saponification value−Acid value) × 100 / Saponification value (1)
(Here, the acid value is a value obtained by dissolving the oligomer in dimethylformamide and titrating with alkali, and the saponification value is a value obtained by subjecting the oligomer to alkaline hydrolysis and back titrating with an acid.)
The type of the polycondensation reaction tank used in the present invention is not particularly limited, and examples thereof include a vertical stirring polymerization tank, a horizontal stirring polymerization tank, and a thin-film evaporation polymerization tank. The polycondensation reaction tank may be a single tank or a plurality of tanks in which a plurality of tanks of the same type or different types are connected in series. It is preferable to select a horizontal stirring polymerization machine having a thin film evaporation function having excellent renewability, plug flowability and self-cleaning properties.
[0030]
INDUSTRIAL APPLICABILITY The method for producing a polybutylene terephthalate resin of the present invention has a large industrial value because it can increase the reaction rate during the esterification reaction, suppress foreign substances, and greatly improve productivity.
[0031]
【Example】
Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples.
In the examples and comparative examples, evaluation was performed as follows.
(A) Reaction time (average residence time of reaction tank)
The value obtained by dividing the substantial internal volume by the raw material supply amount q was adopted.
(B) THF concentration in distillate
It was quantified by gas chromatography. The smaller the number, the more the side reaction is suppressed.
[0032]
(C) Esterification rate of oligomer
It was calculated using the acid value and saponification value determined as follows.
[Acid value]
The oligomer was dissolved in dimethylformamide and titrated using a 0.1 N KOH / methanol solution.
[Saponification value]
The oligomer was hydrolyzed with a 0.5N KOH / ethanol solution and titrated with 0.5N hydrochloric acid.
[0033]
Esterification rate = (Saponification value−Acid value) × 100 / Saponification value
(D) Foreign matter amount
The oligomer is dissolved at a concentration of 20 wt% in hexafluoroisopropanol / chloroform = 2/3 (volume ratio), filtered through a pre-measured 5 μm pore diameter polytetrafluoroethylene membrane filter, and then sufficiently washed with the solvent. The filter was dried with a vacuum dryer at 80 ° C. for 12 hours, and the weight was measured. The value obtained by subtracting the weight of the filter previously measured from this weight was determined as the weight ratio to the oligomer.
This foreign matter remains almost as it is after the polycondensation.
[0034]
[Example 1]
FIG. 4 shows a flowchart of this embodiment. In the figure, 1 is a slurry preparation tank, 1a and 1b are raw material supply ports for a dicarboxylic acid component and a diol component, respectively, provided at the upper part of the slurry preparation tank 1, 2 is an esterification reaction tank, and 2a is an esterification reaction tank. A vent port provided at the upper part of 2, a catalyst supply port provided at the upper part of the esterification reaction tank 2, a sampling port of the esterification reaction tank 2 c, a supply of recirculated 1,4-butanediol Port 3 is a distillate condenser, 3a is a vent port connected to a decompressor (not shown), 3b is a low-boiling component recovery line, and 3c is a 1,4-butanediol discharge line to the outside. , 8 are tanks of 1,4-butanediol having a temperature control function. After being condensed by the condenser, the tank 8 is filled with 1,4-butanediol from which low-boiling components and high-boiling components have been removed. M1 and M2 are stirring devices, G1 and G2 are gear pumps, P1 is a pipe connecting the slurry preparation tank and the esterification reaction tank, and P2 is a pipe connecting the esterification tank and the post-process.
[0035]
A slurry prepared at a ratio of 1.80 mol of 1,4-butanediol to 1.00 mol of terephthalic acid was passed through a pipe P1 from a slurry preparation tank 1 by a gear pump G1 to obtain an esterification rate of 93% in advance. Is continuously supplied at 67 L / h to the esterification reaction tank 2 having a screw type stirrer filled with the polybutylene terephthalate oligomer of the above, and at the same time, the raw material terephthalic acid (TPA) is converted from the catalyst supply port 2b to titanium tetrabutyl titanate in the amount of titanium. ) Was continuously supplied at a weight ratio of 133 ppm (100 ppm based on the obtained polybutylene terephthalate). The slurry temperature at this time was 60 ° C. As the catalyst medium, 1,4-butanediol was used in a ratio of 0.03 mol to the supply amount of terephthalic acid of 1.00 mol, and the temperature was adjusted to 60 ° C.
The esterification reaction tank 2 is a vertical reaction tank provided with a stirring device M2 equipped with a screw-type stirring blade having a vertical rotation axis, and the stirring device M2 is provided with a device for detecting stirring power.
[0036]
The internal temperature of the esterification reaction tank 2 was 230 ° C., the pressure was 78 kPa, and the generated water, tetrahydrofuran, and excess 1,4-butanediol were passed through a vent port 2a connected to a pressure reducer (not shown). It was extracted and the whole amount was discharged out of the system. Simultaneously, the purified 1,4-butanediol is supplied as recirculated 1,4-butanediol to the esterification reaction tank 2 through 2d at a ratio of 1.20 mol to the supply amount of terephthalic acid of 1.00 mol. The esterification reaction was carried out. The temperature of this 1,4-butanediol was 52 ° C. when measured at the portion closest to the reactor without the influence of the heating medium jacket of the reaction vessel. At this time, the reaction liquid was withdrawn while controlling the liquid level so that the actual liquid in the esterification tank 2 became 100 L. After the system was stabilized, the esterification rate of the oligomer collected from the sampling port 2c was 98%, and the amount of foreign substances was small. Tables 1 and 2 show the results of Examples and Comparative Examples.
[0037]
[Table 1]

[0038]
[Table 2]

[0039]
[Example 2]
The procedure was as in Example 1, except that the amount of recirculated 1,4-butanediol fed through 2d was changed as indicated in the table.
[Example 3]
The procedure was as in Example 2, except that the temperature of the recirculated 1,4-butanediol fed through 2d was changed as indicated in the table.
[Example 4]
The procedure was performed in the same manner as in Example 1 except that the stirring speed was changed and P / q was changed as shown in the table.
[Example 5]
Example 1 was repeated except that the flow rate of the raw material was changed, the average residence time was set to 1.1 hr, and P / q was changed as shown in the table.
[0040]
[Example 6]
The procedure was performed in the same manner as in Example 1 except that the esterification reaction temperature was changed to 240 ° C.
[Example 7]
The procedure was carried out in the same manner as in Example 1 except that the amount of the catalyst to be added was 47 ppm (35 ppm based on the obtained polybutylene terephthalate) in terms of the weight ratio of titanium to the raw material terephthalic acid (TPA).
Example 8
The procedure was performed in the same manner as in Example 1 except that the amount of the catalyst to be added was made to be 67 ppm (50 ppm with respect to the obtained polybutylene terephthalate) in a weight ratio to the raw material terephthalic acid (TPA) as a titanium amount.
[0041]
[Comparative Example 1]
The procedure was as in Example 1, except that the recirculated 1,4-butanediol supplied from the raw materials was as shown in the table and the recirculated 1,4-butanediol supplied via 2d was stopped. The esterification rate was low and the amount of foreign substances was large.
[Comparative Example 2]
Example 2 was repeated except that the temperature of the recirculated 1,4-butanediol supplied through 2d was 219 ° C. The esterification rate was low.
[Comparative Example 3]
The procedure was as in Example 1, except that the amount of recirculated 1,4-butanediol fed through 2d was as shown in the table. Although the esterification rate was high, the amount of THF in the distillate increased.
[Comparative Example 4]
Example 1 was repeated except that the amount of the titanium catalyst was 400 ppm based on terephthalic acid (302 ppm based on the obtained polybutylene terephthalate). Although the esterification ratio was high and the amount of THF in the distillate was small, the amount of foreign substances in the oligomer increased.
[Comparative Example 5]
The procedure was as in Example 2, except that the temperature of the recirculated 1,4-butanediol fed through 2d was 219 ° C. and P / q was as indicated in the table. The esterification rate decreased, and not only the amount of THF in the distillate increased, but also the amount of foreign substances increased.
[0042]
【The invention's effect】
According to the present invention, it is possible to provide a method for producing a polybutylene terephthalate resin in which the reaction rate during the esterification reaction is increased, foreign substances are reduced, and the productivity is improved.
[Brief description of the drawings]
FIG. 1 is a schematic view of an apparatus for producing polybutylene terephthalate, which is a preferred embodiment of the present invention.
FIG. 2 is a schematic view of an apparatus for producing polybutylene terephthalate, which is another preferred embodiment of the present invention.
FIG. 3 is a schematic view of an apparatus for producing polybutylene terephthalate, which is another preferred embodiment of the present invention.
FIG. 4 is a schematic view of an apparatus for producing polybutylene terephthalate used in Example 1.
[Explanation of symbols]
P1 raw material supply line
P2 @ Reaction liquid outlet for next step (polycondensation step)
1 Slurry adjustment tank
1a dicarboxylic acid component supply port
1b diol component supply port
2 Esterification reaction tank
2a @ vent port
2b catalyst supply port
2d @ Recycle 1,4-butanediol supply port (direct supply to the reaction tank)
3) Condenser of reaction effluent
3a Decompression system piping
3b @ Recovery line for low boiling components
3c Extraction of excess 1,4-butanediol
4 heat exchanger
4a @ Supply port of recirculated 1,4-butanediol (supplied to raw material supply line)
5 Distillation column for separating low boiling components
5a @ low boiling point component outlet
5b: Line to the next step of 1,4-butanediol from which low-boiling components have been separated
6 Distillation column for separating high boiling components
6a Line of purified 1,4-butanediol to the next step
6b @ Extraction outlet for high boiling components
7 tank of purified 1,4-butanediol
M1, M2 stirrer
G1, G2 gear pump

Claims (7)

In the method for producing polybutylene terephthalate by subjecting a terephthalic acid component and a 1,4-butanediol component to an esterification reaction and a polycondensation reaction in the presence of a titanium or / and tin compound as a reaction catalyst, (1) esterification A step of continuously performing an esterification reaction between terephthalic acid and 1,4-butanediol in a reaction tank; (2) 1,4-butanediol distilled out of the esterification reaction tank in a condenser And (3) a recirculation step of returning the condensed 1,4-butanediol to the esterification reaction tank independently of terephthalic acid, and (4) a reaction catalyst originating in polybutylene terephthalate. The total amount of titanium atoms and tin atoms in the metal of (1) to (1) to 230 ppm with respect to the obtained polybutylene terephthalate; The temperature of 1,4-butanediol returned to the sterilization reactor is in the range of 16 to 100 ° C., and (6) terephthalic acid and 1,4-butanediol supplied to the esterification reactor per unit time Wherein the molar ratio of (1,4-butanediol / terephthalic acid) is from 1.6 to 4.5. The method for producing polybutylene terephthalate according to claim 1, wherein the reaction catalyst is an organic titanium compound or an organic titanium compound and an organic tin compound. 3. The method for producing polybutylene terephthalate according to claim 1, wherein the total metal concentration of titanium atoms and tin atoms is 1 to 65 ppm by weight based on the obtained polyethylene terephthalate. The method for producing polybutylene terephthalate according to any one of claims 1 to 3, wherein the temperature of the esterification reaction step is 200 to 240 ° C. The method for producing polybutylene terephthalate according to any one of claims 1 to 4, wherein the pressure in the esterification reaction step is 10 kPa to 130 kPa in absolute pressure. The method for producing polybutylene terephthalate according to any one of claims 1 to 5, wherein the average residence time in the esterification reaction step is 0.5 to 5 hours. In the esterification reaction step, when the total supply amount of the raw materials per unit time is q (m ³ / sec) and the stirring power to be given is P (kw), the following formula is satisfied. 7. The method for producing polybutylene terephthalate according to any one of 1 to 6.
P / q ≧ 1500 (kJ / m ³ )

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