JPS5827782B2 - Esther Kahouhou - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improved batch direct esterification method for obtaining a substance mainly consisting of bis-β-hydroxyethyl terephthalate and/or its low polymer from terephthalic acid and ethylene glycol. .

Bis-β-hydroxyethyl terephthalate and/or its low polymer (hereinafter referred to as BHT) is obtained from terephthalic acid (hereinafter referred to as TPA) and ethylene glycol (hereinafter referred to as EG) through an esterification reaction, and then subjected to a polycondensation reaction. by polyethylene terephthalate (
The direct polymerization method for producing PET (hereinafter referred to as PET) is well known.

Although the direct esterification method described above is theoretically superior to the transesterification method, the reaction rate is slow and the reaction rate is slow, and diethylene glycol (hereinafter referred to as DE) is
There is a problem in that the amount produced is large (referred to as C).

In other words, in order to accelerate the reaction rate to an economical range, it is necessary to increase the molar ratio of EG/TPA, but
When the TPA molar ratio is increased, DE, which is a dehydrated condensate of EG,
A large amount of G is produced and the quality of the final PET is degraded.

For this reason, improvements have been made to lower the EG/TPA molar ratio and increase the reaction rate. A method is known in which the boiling point is raised by esterification (~3.0 kg/cyiiG pressure).

However, although this method increases the reaction rate, it also increases the amount of DEG by-product as a result of the increased amount of EG released into the reaction system and the high reaction temperature.

In order to improve this drawback, a slurry of a mixture of TPA and EG of a specific quality is continuously supplied during BHT, the mixing ratio of the slurry is set to a relatively low EG/TPA molar ratio of 1.3 or less, and the reaction temperature is 240. Method of esterification at temperatures above ℃ (
Special Publick No. 50-19313, No. 5O-19314), BH
A slurry of TPA and EG was continuously fed into T, and the amount of unreacted carboxy groups in the reaction system was 0.5 to 1.5 meq/?
A method of esterification by holding in
2) etc. have been proposed.

Therefore, these methods are effective in suppressing the by-product of DEC, which is the inlet air of the method described above in which TPA and EG are simultaneously charged into a reaction tank and esterified under pressure.

However, the feature of these methods is that a slurry of a mixture of TPA and EG is continuously supplied to the system in which BHT is present, and the slurry is reacted in parallel with the supply, so that the slurry supply time and the esterification reaction time are approximated. It is in.

Therefore, it is necessary to take measures such as keeping the reaction temperature high, keeping the esterification reaction rate high, or making the amount of BHT relatively large, which is essential in terms of reaction speed and productivity. is also not a sufficient method.

The present inventors conducted studies with the aim of improving the slow reaction rate and low productivity of the method of esterification by supplying a mixed slurry of TPA and EG to a system where BHT exists. We have arrived at the present invention.

That is, in the present invention, the slurry consisting of TPA and EG is
An esterification method characterized by setting the supply time of TPA and EG slurry and the esterification reaction time so as to satisfy the following general formula when supplying to a system where HT is present and performing esterification in a batch manner. It is.

It≦0.87Rt It≧200 Rt≦510 [However, It: Supply time of the mixture of TPA and EG (minutes) Rt: Esterification reaction time (minutes)] The present invention is based on the supply time of TPA and EG slurry and the ester This specifies the relationship between the reaction time of TPA and E.
The supply time (It) of the G slurry needs to be 200 minutes or more, and more preferably 220 minutes or more.

If it is less than 200 minutes, the slurry of TPA and EG is supplied too quickly, and the reaction temperature becomes extremely low. As a result, the reaction time becomes longer, and as a result, the amount of DEC in the BHT after the reaction increases.

Furthermore, the ratio of solid unreacted TPA to solution components such as PET low polymer, EG, dissolved TPA, and water in the reaction system becomes high, resulting in decreased fluidity and thickening, which deteriorates the stirring effect.

Note that the slurry of TPA and EG may be supplied continuously or intermittently, but it is preferable to supply it continuously.

The esterification reaction time (Rt) was set at 51 to increase productivity.
It is necessary that the time is within 0 minutes, and more preferably within 420 minutes.

If the reaction time exceeds 510 minutes, not only will the productivity deteriorate, but also the DEC in the produced HT will increase due to the long thermal history, resulting in a decrease in quality.

The final esterification reaction rate needs to be 90% or more, but is more preferably 96% or more.

The relationship between the esterification reaction time (Rt) and the supply time (It) of the slurry of TPA and EG must satisfy It≦0.87Rt, and more preferably It≦0.82Rt.

If I t >0.87 Rt, the esterification reaction time will be prolonged and the productivity will be deteriorated.

This seems to be because the reaction system always maintains a high reaction rate, so the amount of unreacted TPA in the system decreases and the reaction becomes slow.

In addition, from the three equations regarding the esterification reaction time and the supply time of the slurry of TPA and EG, 0, 40 Rt
The following equations can be derived: ≦It, It≦44.4, and Rt≧230.

Specific means for bringing the slurry supply time, esterification reaction time, and their interrelationships within the formula range specified in the present invention include control of the esterification reaction temperature, selection of the type and amount of esterification catalyst, and precision. Control of the distillation column temperature, selection of the reflux-distillation distribution ratio of the distillate from the rectification bath, the EG/TPA molar ratio of the TPA and EG slurry, the amount and temperature of BHT stored in advance before the reaction In addition, the degree of polymerization, esterification reaction pressure, etc. may be combined.

That is, the esterification temperature during supply of the slurry of TPA and EG is preferably 215 to 280°C, more preferably 225 to 245°C.

As the esterification catalyst, known catalysts such as antimony, calcium, and tin compounds can be used, and the amount thereof may be any amount as long as the formula defined in the present invention is satisfied.

In addition, the temperature control of the rectification tower is performed at the upper, middle, and upper stages of the rectification tower.
The reaction can be carried out in any of the lower stages, but for example, in the case of the upper stage, the reaction may be carried out at an optimized temperature in the range of 98 to 120° C. when the atmospheric pressure is 760 mmJ1 g.

If the EG/TPA molar ratio of the supplied slurry is too high, the amount of free EGfif in the reaction system will increase, the rectification column reflux ratio will be low, the reaction temperature will drop, and the reaction time will be longer than DEG byproducts. This is not preferable because the amount increases.

On the other hand, if the EG/TPA molar ratio of the slurry is too low, the reaction rate will be slow, causing a problem.

The preferred range of the EG/TPA molar ratio of the feed slurry is 1.0.
2 to 1,80, more preferably 1.08 to 1.40.

Store BHT in advance before the reaction. If the amount of BHT is too large, the reaction temperature will be high and the reaction time will be shortened, but the T
The amount of PA and EG soot prepared decreases, resulting in a decrease in productivity.

Furthermore, when the amount of stored BHT is small, the esterification reaction temperature decreases, and the amount of DEG by-product increases due to the lengthening of the reaction time.

Therefore, the amount of stored BHT is preferably 20% to 60% of the total amount of BHT after the reaction, and it is desirable that the stored BHT is such that a part of the BHT after the esterification reaction remains.

The polymerization degree of stored BHT is preferably 1.5 to 30, and 2.5
-20 is more preferable.

The esterification reaction pressure can be selected within the range of -0.5 to 1.5 kg/iG pressure, but -0.2 to 1.0 kg/c
rit G is more preferred.

The present invention also includes an esterification reaction to obtain a polyester in which 80 mol% or more of the constituent units of the finally obtained poly(I) ester consist of ethylene terephthalate, and less than 20 mol% of polyester other than TPA and EG. may be present during the esterification reaction.

Note that high-quality PET with low DEC content can be obtained by polycondensing the product after the esterification reaction, but in this case, known anti-adhesive agents, additives,
Complementary color agents etc. can be used.

The effects of the method of the present invention are summarized as follows.

■ The amount of BHT stored before the reaction can be reduced, the reaction can be fast without excessive heating, and highly productive operation can be performed.
High-quality BHT with less EG byproducts can be obtained.

■ Since the slurry supply time between TPA and EG is quite short compared to the reaction time, blockages and
Even if there is a problem with quantitative supply due to a change in viscosity, it can be repaired without affecting the reaction time, and operations can be managed and stabilized.

■ A heating medium such as high-pressure steam can be used as a heating source, and the heat transfer area is approximately 1.5 x 10-3 to 1 per unit liquid volume.
．． It can be carried out using an apparatus of OX 10"m 7 kg.

Further, the heating method may be a simple heating method such as a jacket method or a coil method.

■ As the stirrer, a chi-type tool, an ikari-type tool, a helical-type tool, etc. can be used.

■ Ideal for batch production methods in which one esterification can and one polymerization can are connected in series.

Note that the polyester obtained by polycondensing the esterified product obtained by the method of the present invention is useful as fibers, films, and plastics.

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

In addition, the esterification reaction rate and DEC in the examples were measured according to the following method.

(Esterification reaction rate) (SV: saponification value unit KOHynq/?AV: acid value
] (DEC) After the sample is decomposed with NaOH in a conventional manner, it is quantified by gas chromatography and expressed in weight% relative to the sample.

Example 1 Under normal pressure, esterification reaction rate 98.8%, DEC061M
% BHT (average degree of polymerization 5.8) 1100 kg 25
After heating and stirring at 2°C, 42y of monobutylhydroxysulfur oxide and its low polymer were added, and then TPA
l A mixture slurry of 816 kg and EG 814 kg is
．． 74 kg was supplied to the esterification reactor at a rate of 1 minute.

The feeding was continuous for 4 hours.

The esterification reaction time was 5 hours and 20 minutes, and the reaction was carried out at (slurry supply time) = (0.75X reaction time).

The reaction temperature was set to 237°C 45 minutes after the start of slurry supply, maintained at 234 to 236°C during slurry supply, and gradually raised to 245°C after completion of slurry supply.

Distillation started 5 minutes after the start of slurry supply, and the amount of water distilled out from the reaction was almost linear, and it became a little faster after slurry supply, and was 382 kg at the end of the reaction.

The reaction rate of the produced BHT was 99.1%, and the DEC content was 0.56% by weight.

Example 2 ※※
Esterification was carried out using the same equipment and conditions as in Example 1, but varying the slurry supply rate.

Table 1 shows the results of the slurry supply time, reaction time, supply time/reaction time, reaction temperature, reaction rate and DEC content of the PET oligomer obtained after the reaction in this example.

In Comparative Examples 1 and 2, the value of slurry supply time/reaction time was 0.
．． Since the reaction time was higher than 87 and outside the scope of the present invention, the reaction time was long and DEC was also large, resulting in a method that was inferior in both productivity and quality.

In Comparative Example 3, the slurry supply time was shorter than the 200 minutes of the present invention range, so although the reaction time was short, the DEC increased, and this was not a preferable method.

In Comparative Example 4, the slurry supply time was even shorter than in Comparative Example 3, so the reaction temperature dropped too much and the reactants thickened, resulting in an excessive stirring PJ: r power and personnel force, and the stirring rotation speed was reduced to 80 r. , p, m, to 5 Or, p, m,.

As a result, the reaction time became longer and the DEC increased, which was not a preferable method.

Example 3 Continuous operation was continued using the same equipment and conditions as in Example 1. After the start of slurry supply (that is, after the start of the reaction), 2 hours 10
After 30 minutes had passed, it was discovered that the supply pipes for TPA and EG soot were clogged and the specified supply was not being made, so repairs were made after 30 minutes.

Due to this trouble, the supply of TPA and EG soot was interrupted for 30 minutes, but the reaction time was not affected and the reaction was completed in 6 hours and 7 minutes.

The reaction rate of the obtained BHT was 98.4%, and the DEC content was 0.
．． It was 67% by weight.

Example 4 Under normal pressure, esterification reaction rate 99.0%, DECo, 65
A predetermined amount of BHT (average degree of polymerization 6.7) by weight was heated and stirred, and then 8% of TPAI was added to the esterification catalyst.
A slurry of a mixture of 16 kg of EG and 780 kg of EG was continuously supplied to the esterification reactor, and the reaction was carried out until the esterification reaction rate of the produced reaction product reached 99.0%.

Amount of BHT stored in this example, slurry supply time, reaction time, supply time/reaction time, reaction temperature, PE obtained after reaction
Table 2 shows the results regarding the DEC content of T. o.

In Comparative Examples 5 and 6, the reaction time was longer than the range of the present invention, 510 minutes, and not only did productivity deteriorate, but D
EC has become quite high.

Claims (1)

[Scope of Claims] 1. When carrying out batchwise esterification by supplying a slurry of terephthalic acid and ethylene glycol to a system in which bis-β-hydroxyethyl terephthalate and/or its low polymer is present, terephthalic acid An esterification method characterized in that the supply time of the ethylene glycol slurry and the esterification reaction time are set so as to satisfy the following general formula. It≦0.87Rt It≧200 Rt≦510 (where, t: supply time of the mixture of terephthalic acid and ethylene glycol (minutes) Rt: esterification reaction time (minutes))