JPS5984918A - Method for continuous production of polyester low polymer - Google Patents

Abstract

PURPOSE:To obtain stably the titled polymer of uniform quality with a low ether linkage content, by feeding a slurry of terephthalic acid and ethylene glycol continuously to an esterification reactor under specific pressure conditions, and carrying out the esterification reaction. CONSTITUTION:A slurry containing (A) terephthalic acid and (B) ethylene glycol at a molar ratio between the ethylene glycol (B) and the terephthalic acid (A) adjusted to 1.7-2.5 is continuously fed to an esterification reactor kept under a reaction pressure satisfying formula I {P is the reaction pressure (kg/cm<2>.G); PL is expressed by formula II [X is the molar ratio of the component (B) to the component (A); T is the reaction temperature ( deg.C)]; PH is expressed by formula III}to carry out the esterification reaction. Thus, the aimed polyester low polymer consisting of ethylene terephthalate as main repeating units is continuously obtained by the direct polymerization method.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improved continuous production method for producing polyester low polymers (hereinafter referred to as oligomers) whose main repeating units are ethylene terephthalate by a direct polymerization method. The purpose of this method is to maintain the amount of KG in the esterification reaction system at the minimum amount without excess or deficiency, and to produce oligomers of uniform quality with few ether bond formations in a stable state.

The esterification reaction is usually carried out by mixing terephthalic acid (hereinafter referred to as TPA) and ethylene glycol (hereinafter referred to as IG) and heating the mixture to 240~270°C.
・It was carried out under G pressure. In this case, most of IflG is dissolved in the esterification reaction system, and the reaction can be carried out in a stable state by removing water produced in one reaction.

However, the concentration of hydroxyl groups in the esterification reaction system becomes high and the formation of ether bonds is inhibited (1), which lowers the softening point of the polymer), and the amines added as ether bond formation inhibitors cause coloring of the polymer. It had drawbacks. This drawback can be eliminated by lowering the reaction pressure. In other words, if the reaction pressure is lowered, 1! ! Since the amount of dissolved G is reduced and the concentration of hydroxyl groups is lowered, the formation of ether bonds can be suppressed, but the rate of esterification, which is the main reaction, decreases significantly as the reaction pressure decreases. Conventionally, oligomers with a carboxyl group concentration of 1000 to 2000 equivalents/xo'' were obtained by increasing the molar ratio of liG to TPA in the supplied slurry (hereinafter referred to as 110/T), but the reaction pressure There was a problem in that the carboxyl group concentration of the oligomer fluctuated greatly due to a slight change in .

As a result of intensive research by the present inventors to solve the above problems,
This has led to the completion of the present invention.

That is, in the present invention, an oligomer whose main repeating unit is ethylene terephthalate is continuously produced by a direct polymerization method. This is a continuous method for producing oligomers, characterized in that the esterification reaction is carried out by continuously supplying the oligomer to an esterification reactor maintained under a satisfactory reaction pressure.

PL≦PPH・・・・・・(1) [In the formula, P is the reaction pressure (~/c++t, G)P
L-28,44x -3,194T + 0.0054
87 T2+ 1,305θ@X+ 3.50807'
x -119619/T -8075X/T + 46
5.9, (H)PH-10,80x-2,049
T + 1,333 x2+ 0.003619 T2
% 49,73 (9/T -4498X/T+297
．． 3, ---,, ---0 (1) X is E/T, T is reaction temperature (C) θ represents average residence time (hours). ] Below, demonstration aspects of the present invention will be described.

First, in the raw material slurry mixing tank, TPA and final EGG are adjusted so that the mixing distortion E/T is 1.7 to 2.5.

In addition, 1riG in the raw material slurry mixing tank recovers and reuses EG from the steam generated in the esterification reactor, and also collects insufficient Va from outside the reaction system so that Ei/T is 1.7 to 2°5. It is desirable to adopt a method of replenishing.

The prepared slurry is continuously supplied at a constant flow rate to a single stage stellation reactor. Esterification reaction conditions are reaction temperature 2
45 to 265"c1 The reaction pressure is preferably in a range that satisfies the above formula (1) and the average residence time is 3 to 12 hours. Also, the reaction rate in the esterification reactor is preferably within the range of carboxyl group concentration 1000 equivalents/1o"1 It is preferable to keep it below. In this case, the hydroxyl group ratio (hydroxyl group concentration/hydroxyl group concentration/carboxyl group concentration) is 0.5 to 0°85, and the number average degree of polymerization is 3 to 7.
oligomers are obtained. Furthermore, this oligomer is processed into carboxyl groups in the next reactor under conditions of a reaction temperature of 250 to 270'C, a reaction pressure of normal pressure, and an average residence time of 0.5 to 2 hours, in some cases with the addition of a small amount of MIG. If the reaction continues at a concentration of 200 to 400 equivalent ft/106 ft,
An oligomer having a hydroxyl group ratio of 0.7 to 0.9 and an average degree of polymerization of 6 to 8 is obtained. It has been found that polyester of good quality can be obtained by polycondensation using this oligomer at high temperature and reduced pressure.

The steam generated from the esterification reactor contains 111C.
In addition to G, it contains a large amount of water produced by the esterification reaction, small amounts of aldehydes, oligomers, etc., and is dehydrated and purified by distillation.

In the distillation operation, water and a small amount of aldehydes come from the top of the distillation column, while E containing some water and oligomers comes from the bottom.
G is taken out. It is preferable to keep the moisture content in this extracted InG at 10% or less. If the water content is higher than this, the water in the recovered and reused EG will increase, and the heat load on the esterification reactor will increase. The extracted KG is supplied to the slurry mixing tank while being replenished with the EG consumed by the reaction.

Next, the present invention will be explained in more detail using the drawings.

FIG. 1 is an example of a process for continuously producing oligomers according to the present invention. In FIG. 1, 1 is a raw material slurry mixing tank, and TPA is supplied from a pipe 2. The recovered EG is supplied from pipe 3, and the amount of EG consumed by the reaction is supplied from pipe 4, and the E/T is adjusted to 1.7 to 2.5 in a raw material slurry mixing tank, and the mixture is stirred by stirring blades 5. Ru. The raw slurry is fed through a pipe 6 by a pump 7 to an esterification reactor 9 having a heating jacket 8 .

The obtained oligomer is sent to the next reaction step by a pump 11 through a pipe 10. On the other hand, esterification reactor 9
The steam generated in the distillation column 13 is supplied to the bottom of the distillation column 13 through a pipe 12. Here, components having a boiling point lower than that of EG such as water and aldehydes generated by side reactions are contained in the pipe 14.
After passing through the condenser 15 and condensing, a part of the pipe 16
The water is refluxed again to the distillation column 13, but the rest is refluxed to the distillation column 13.
The thread is pulled out from strand 7. On the other hand, EG is returned to the raw material slurry mixing tank 1 through the pipe 3 by the pump 18 and used again for the reaction.

In the present invention, the reason why the reaction pressure range is limited to a range that satisfies the above formula (I) will be explained below.

The present inventors have conducted intensive research on a method for continuously producing oligomers of uniform quality with a small amount of ether bonds in the oligomers, and have discovered the following fact. V
1. If the reaction pressure is kept constant and the reaction pressure is lowered, the carboxyl group concentration of the oligomer will gradually increase, and once the reaction pressure is below a certain level, the carboxyl group concentration will suddenly increase. exist. FIG. 2 shows the above phenomenon, and the pL point is the point at which the carboxyl group concentration of the oligomer becomes high. The present inventors investigated the reaction pressure (PL), E/T (x), reaction temperature (T), and average residence time (no. ~
It has been found that in the range of 2.5, there is a relationship as shown in equation (6) below.

P+-=28.44x3, 194・T+0.0
054871IT') 1.305・0・X+3, 5o
s-re [-1196・TVI'-8075-71'+
465, 9 ・(I)) As is clear from Figure 2, if the reaction pressure is 9 or higher, the amount of change in the carboxyl group concentration in the oligomer with respect to the change in reaction pressure is small;
It is possible to produce oligomers of uniform quality in a stable state. By the way, as mentioned above, when the reaction pressure is increased, the number of ether bonds in the oligomer increases. Generally, as the amount of ether linkages per ethylene terephthalate unit in the polyester chain increases, the melting point, mechanical properties, and thermal stability of the polyester decrease. Therefore, the present inventors conducted extensive research on reaction conditions with a small amount of ether bonds in the oricomer, and as a result, as shown in Figure 3, the reaction pressure when the amount of ether bonds per ethylene terephthalate unit in the oricomer is 2. (P,,) and g/T
(x), reaction temperature (T), and average residence time (a) were found to have the following relationship (Equation 110) when E/T is in the range of 1.7 to 2.5. .8011x-2,04911T+1.333
x"+0.003619・T't■ -49,73-&,'r -4498-y;/'l'+
297, 3-==・-・-α1 Wanao (11
) and formula (2) have P and PH as objective variables, respectively, and E/T (x), T and θ as explanatory variables.
It was obtained through multivariate analysis from five data sets. The contribution rate after adjusting the degree of freedom of the obtained multivariate analysis equation was 95 coefficients or more.

In the present invention, the range of reaction pressure (P) that can be produced in an oligomer with a small amount of ether bonds in which the amount of ether bonds per ethylene terephthalate unit in the oligomer is within 2% is the following formula (I) % formula % (1) On the other hand, when the reaction pressure is less than -Q, 6 Kg/ad, G, oligomers are entrained and the piping from the reactor to the distillation column and from the bottom of the distillation column to the raw material slurry mixing tank are said to be clogged. Since the problem occurs, the reaction pressure of the esterification reactor is -Q, 5 Kg/ad
” It is preferable to make it G or higher.

The xyl group concentration in the oligomer obtained in the present invention is preferably 1000 equivalents/10'f or less. If the temperature exceeds 10'S', undissolved solid TPA exists in the oligomer, which may accelerate the wear of the pump used to transfer the oil to the next process, or may cause problems when transferring to the next process due to the liquid level difference. This is not preferable because it may cause clogging of the liquid level control pulp.

The present invention will be specifically explained below with reference to Examples.

In addition, the diethylene glycol (hereinafter referred to as DEC) value in Example A is the amount of ether bonds per ethylene terephthalate unit in the oligomer (ch), and the AV value is the carboxyl group concentration in the oligomer (class/10'r). It is.

Example 1 In the apparatus shown in Fig. 1, TPA was supplied to one tank of raw material slurry at a rate of 43.2 Ry per hour, and EG to be recovered and reused from the distillation column was supplied so that E/T was 2.2. New E
Replenish G and make slurry (contains 550 mmol of antimony trioxide per 1 mol of TPA as a polymerization catalyst)
adjusted. The obtained slurry 78 and 7 hours was continuously supplied to the esterification reactor. The reaction pressure is normal pressure,
0. IKf/cnbG, 0.15 to 9/cT! I-
G, 0.2 K7/cd-G and 0.6 Ky/c
rl.G, the reaction temperature was 260° C., and the esterification reaction was carried out while continuously extracting the oligomer so that the average residence time was 3.5 hours. Table 1 shows the AV and DEG values of the oligomers obtained.

From Table 1, it can be seen that the AV value is greatly influenced by the reaction pressure when the reaction pressure is around 0 and 15 KVCffl·G.

If the reaction pressure is still 0, 6 to 9/cnh 0 or more, D
It can also be seen from Table 1 that the EG value exceeds 2.

When the P value is calculated using the above formula 00, the PL value is 0,
15 Kq/crl-G, and when the part is calculated using the above [phase] formula, P H1#i, 0, 59 K
y/crd ・G. That is, the reaction temperature is 260
℃, Vr is 2.2 and the average residence time is 3.5 hours, the reaction pressure is 0.15-0.59Kg/cn-Q
If the esterification reaction is carried out within this range, a good quality oligomer with a DEG value of 2 or less can be stably obtained almost unaffected by fluctuations in reaction pressure.

Example 2 In the apparatus shown in FIG. 1, TPA was supplied to a tank of raw material slurry at 43.2 Ky.7 hours, and the E/T was 2.7 hours.
4, the EG recovered and reused from the distillation column is newly replenished with EG, and the slurry V-(X with TPA as a gold catalyst
containing 550 mmol of antimony trioxide per mole). The obtained slurry -78,'7Ky1 hour was continuously supplied to the esterification reactor.

The reaction pressure was normal pressure, 0. IKy/cJ・G, 0.2K
p/c+J・G, 0.65Kp/cd-G and 0
．． The esterification reaction was carried out at 8 Kp/ci-G, at a reaction temperature of 250 C, and while the oligomer was continuously extracted so that the average residence time was 4.5 hours. Table 2 shows the AV and DEC values of the oligomers obtained.

Table 2 From Table 2, the reaction pressure is 0.2 and AV near 9/Cd-G.
It can be seen that the value is greatly affected by the reaction pressure.

In addition, when the reaction pressure is 0.65 K9/cA・0 or more,
It can also be seen from Table 2 that the DEG value exceeds 2%.

When the PL value is calculated using the above equation, the PL value is 0', 2
2Ky/crll-G, and using the above dynamic formula, P
Calculating the H value, PH1 direct is 0, 66 Ky/c shoulder.
It becomes G. In other words, if the esterification reaction is carried out within the range of Kg/crl-G, a good quality oligomer with a DEG value of 2% or less can be stably obtained almost unaffected by fluctuations in reaction pressure.

Example 3 In the apparatus shown in FIG. 1, TPA is supplied to one tank of raw material slurry at a rate of 43.2 Ky1 hours, and the E/T is 2.2 hours.
Fresh EG is added to the EG recovered and reused through the distillation column to create a slurry (with TPA 1 as a polymerization catalyst).
Contains 550 mmol antimony trioxide per mole)
adjusted. Obtained sura! J-78.7 Kp/h was continuously fed to the esterification reactor. The reaction pressure is -0
, 9/1dhG on 2, 9/cA-G on -0,1,
OKy/crrh G, 0.2Ky/1ri-G
and o, 4Kq/cd-G1 reaction temperature was 255°C,
Further, the esterification reaction was carried out while continuously extracting the oligomer so that the average residence time was 5.5 hours.

Table 3 shows the AV values and DEG values of the oligomers obtained.

Table 3 It can be seen that is greatly affected by the reaction pressure.

Also, the reaction pressure is 0,4 hlcr!・D for 0 or more
It can also be seen from Table 3 that the EG value exceeds the 2nd factor.

When calculating the error value using the above formula (6), P, - value is -0
, 11Ky/cM-G, and when the pH value is calculated using the above [phase] formula, the PI□ value is 0.36Ky/crt
It becomes hG. That is, the reaction temperature is 255°C and E/T is 2.
．． 2 and the average residence time is 5.5 hours, if the esterification reaction is carried out at a reaction pressure in the range of -0.11 to 0.36 Ky/crhG, it will not be affected by fluctuations in the reaction pressure ( Good quality oligomers with a DEG value of 2% or less can be stably obtained.

Example 4 In the apparatus shown in Fig. 1, TPA is supplied to one tank of raw material slurry at a rate of 43.2 PC9/hour, and a new EG is recovered and reused from the distillation column so that l is 1.8. Dani EG
was replenished to prepare a slurry (containing 550 mmol of antimony trioxide per 1 mol of TPA as a polymerization catalyst). 78.7 hours of the obtained slurry was continuously fed to the esterification reactor. The reaction pressure is normal pressure, 0,
IKp/i-G, 0, 2Kq/crl-G,
0.3 to 9/cdhG and 0,4Ky/cr! I
@G, the reaction temperature was 260 °C and the average residence time was still 4
．． The esterification reaction was carried out while continuously extracting the oligomer for 5 hours. Table 4 shows the AV values and DEG values of the oligomers obtained.

Table 4 It can be seen from Table 4 that the AV value is greatly influenced by the reaction pressure when the reaction pressure is around 0.3 Kg/crl.G.

Table 4 also shows that when the reaction pressure is 0.9 KV/CJIIG or higher, the D value exceeds 2.

When the PL value is calculated using the above formula (11), the PL value is 0.
．． 31 is 7/cd-G, and when the pH value is still calculated using the +l1l1 formula, the pH value is 0.86Ky/c.
It becomes rhG. That is, the reaction temperature is 260°C, and 1 is 1.
．． 8 and when the average residence time is 4.5 hours, if the esterification reaction is carried out at a reaction pressure in the range of 0.31 to 0.86 to 97 m.G., the reaction will be almost unaffected by fluctuations in reaction pressure. It is possible to stably obtain a good quality olicomer having a DEG value of 2 or less.

[Brief explanation of the drawing]

Fig. 1 is a schematic explanatory diagram of an example of a process for continuously producing oligomers, Fig. 2 is a schematic diagram showing the relationship between reaction pressure and carboxyl group concentration, and Fig. 3 is a schematic diagram showing the relationship between reaction pressure and ether bond 1:
FIG. 1: Raw material slurry mixing tank, 2: TPA supply pipe 3: Recovery EG supply pipe, 4: Replenishment EG supply pipe 9: Esterification reactor, 12: Generated steam supply pipe 13: Distillation column Patent applicant Toyo Boseki Co., Ltd. Procedures Amendment (Voluntary) February 28, 1981 Commissioner of the Patent Office 1 Indication of Case Patent Application No. 1988-1988 Title of Invention Process for Continuous Production of Polyester Low Polymer & Person Making Amendment Relationship to the case Patent applicant 2-2 Dojimahama, Kita-ku, Osaka j98-F3 East Subject of amendment = 148- (2) ``Insufficient'' in the second line of page 5 is corrected to ``1 shortage.'' Procedures Amendment (Spontaneous) L Indication of the case Japanese Patent Application No. 194880/1983 Title of the invention Continuous production method of polyester low polymer & Relationship to the person making the amendment Case Patent applicant 2-chome Dojimahama, Kita-ku, Osaka No. 2, No. 8 Sake: Target degree of correction) is rewritten as [Hydroxyl group concentration/(Hydroxyl group concentration, 10 Carboxyl group concentration)]. (2) "550 mmol" in line 17 of page 11R of the same document is corrected to "550 micromol." (3) "+y5o mmol" in line 10 of page 13 of the same document is corrected to "550 micromol." (4) Correct "550 mmol" in line 6 of page 15 to "550 micromol". (5) On page 16, line 19, "550 mmol" is corrected to "550 maf chromol."

Claims (1)

[Claims] When producing a polyester low polymer whose main repeating unit is ethylene terephthalate in a multi-continuous manner by direct polymerization, the molar ratio of ethylene glycol to terephthalic acid is adjusted to 1.7 to 2.5. 1. A method for continuously producing a polyester low polymer, which comprises continuously supplying the obtained slurry to an esterification reactor maintained under a reaction pressure satisfying the following formula (1) to carry out an esterification reaction. PL≦P≦PH,,,. (1) [wherein, PFi reaction pressure (9/eJ-G) PL-28,
44x -3,194T + 0.005487T
' + 1,305θ firefly X + 3.5080/x -11
96V-8075yr7'r + 465.9,,,
(1) PH-10,80x -2,049T + 1
．． 333 x2+ 0,003i9 T'-49,73
f) 7'r -4498x7'r + 297.3--
----------@(1) X is the molar ratio of ethylene glycol to terephthalic acid, T is the reaction temperature (°C), and b is the average residence time (hours). ]