JPS6146485B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an improvement in a direct esterification method for obtaining a substance mainly consisting of bis-β-hydroxyethyl terephthalate consisting of terephthalic acid and ethylene glycol and/or a low polymer thereof. Bis-β-hydroxyethyl terephthalate and/or its low polymer (hereinafter collectively 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. A direct polymerization method in which polyethylene terephthalate (hereinafter referred to as PET) is obtained by subjecting it to a polycondensation reaction is well known. Although the direct esterification method is theoretically superior to the transesterification method, it has the drawbacks of a low reaction rate and a large amount of diethylene glycol (hereinafter referred to as DEG) produced due to side reactions. In other words, in order to increase the reaction rate to an economical range, the reaction temperature must be increased or EG/TPA
It is necessary to have a high molar ratio of However, if only the reaction temperature is increased regardless of the conditions, a large amount of DEG, which is a dehydrated condensation product of EG, may be generated, or EG/
When the TPA molar ratio is increased, a large amount of DEG is produced as a by-product. For this reason, improvements have been made to shorten the reaction time and suppress the amount of DEG by-products. For example,
In a continuous esterification reaction method in which a slurry of TPA and EG is continuously supplied to the reaction system, the slurry supply rate is low in the first half and high in the second half (Japanese Patent Application Laid-Open No. 51-29459), or A method of continuously supplying slurry at a supply rate that maintains the number of reactive carboxyl groups within a specific range (Japanese Patent Publication No. 1973-
46218) has been proposed. However, although these methods appear to have shorter reaction times and less DEG production compared to conventional methods, they have not actually improved much;
Further improvements were desired. That is, the methods disclosed in the above-mentioned Japanese Patent Application Publications and Japanese Patent Application Publication No. 2003-100000 achieve a relatively low reaction rate of less than 97%, as is clear from the examples. Therefore, in order to give this a sufficiently high reactivity in a polycondensation reaction, if we try to further increase the reaction rate to a high reaction rate range (for example, a high reaction rate of 97% or higher, preferably 98% or higher). The amount of DEG produced is expected to be quite high. In addition, in the above-mentioned Japanese Patent Publication and Publication methods, BHT
Due to the low reaction rate of BHT, the polycondensation property is not satisfactory. Furthermore, when EG slurry of titanium oxide fine particles, which is a matting agent, is added to BHT with such a low reaction rate, the dispersibility of titanium oxide is poor. , there is a problem that coarse particles of titanium oxide are generated. If there are many coarse particles of titanium oxide, the internal pressure of the pack will increase during spinning.
This is undesirable because problems such as thread breakage occur. In view of the above problems, the present inventors
When a slurry of TPA and EG is supplied to a system containing BHT to perform an esterification reaction, the increase in the amount of DEG produced is improved, the polycondensation reactivity is satisfied, the color tone is good, and the esterification reaction time is The present invention was achieved through research aimed at obtaining BHT in a short and productive manner. That is, in the present invention, a slurry mainly consisting of TPA and EG is continuously supplied to a system where BHT is present, and the reaction temperature is 225 to 260°C and the pressure is 0 to 1.0 Kg/ ^cm2.
G, When carrying out the reaction under the conditions of a BHT storage rate of 30 to 65% and a total slurry supply time of 2.0 to 4.5 hours, the initial slurry supply rate Fa (Kg/hr) during the initial 15% of the total slurry supply time is This is a batch esterification method characterized by controlling so that the following formula is satisfied. 1.1Sv/Ft≦Fa≦5.0Sv/Ft However, Sv is the total slurry preparation amount per batch (Kg) Ft is the total slurry supply time (hr) In the present invention, in the batch type esterification method,
This is a method of supplying a slurry consisting of TPA and EG by changing the supply speed midway through the process, in which the slurry is supplied quickly in the beginning and slowly in the latter half. More specifically, the slurry supply average speed from the slurry supply start point to the initial 15% of the total slurry supply time (hereinafter referred to as initial slurry supply average speed) is,
The speed is 1.1 times or more and 5.0 times or less of the average total slurry supply speed. When such a slurry supply method is used, the previous amount of BHT stored before the reaction quickly becomes low in concentration, and the concentrations of TPA and EG increase.
Initial reaction rate increases. The initial water distillation rate also increases, resulting in a shorter reaction time.
The amount of DEG by-product can also be reduced. More preferably, when the slurry feeding rate is increased at the initial stage of the reaction according to the method of the present invention, the reaction mixture undergoes intense boiling from the early stage of the reaction, and the overall heat transfer on the surface of the heater using the heating medium is improved. Coefficient U (kcal/hr・^m2・
°C) increases, making it easier for the heat medium to conduct heat. As a result, the reaction time can be shortened because the slurry consisting of TPA and EG, which are reaction raw materials, can be charged quickly without lowering the reaction temperature too much. It is preferable to reduce the slurry supply speed at any point after the initial 15% of the total slurry supply time from the slurry supply start point. If the slurry is continuously fed at a high feed rate for a long time, the TPA in the reaction system will
and EG increase too much, an increase in TPA makes stirring difficult, and an increase in EG causes an increase in the reflux ratio of the rectification column or a decrease in the reaction temperature, both of which are unfavorable for the reaction. In the present invention, the initial slurry supply average speed Fa
may be arbitrarily changed during the initial 15% of the required slurry supply time, as long as the average speed within this time is 1.1Sv/Ft≦Fa≦5.0Sv/Ft. . Further, a preferable initial slurry supply rate Fa in the present invention is 1.3Sv/Ft≦Fa≦4.5Sv/Ft, and more preferably 1.5Sv/Ft≦Fa≦4.0Sv/Ft. If the average initial slurry supply rate Fa is less than 1.1 Sv/Ft, the intended purpose of the present invention will not be achieved in the early stage of the reaction, and the reaction time will have to be lengthened, leading to an increase in the amount of DEG byproducts. I don't like it. Also,
If the average initial slurry supply rate Fa exceeds 5.0 Sv/Ft, the reaction temperature will drop too much, the reaction time will become longer, and DEG will increase, which is not preferable. The reaction pressure of the present invention can be selected from the range of 0 to 1.0 Kg/cm ² G, for example, 0.1 to 1.0 during slurry supply.
A method of pressurizing to Kg/cm ² G and releasing or reducing the pressure to atmospheric pressure after finishing slurry supply, or setting the pressure to atmospheric pressure at the beginning of the reaction and increasing the pressure to 0.1 to 1.0 as the reaction time progresses.
A method can be adopted in which the pressure is increased to Kg/cm ² G, and after the slurry supply is finished, the pressure is released or reduced to atmospheric pressure. Note that the reaction rate here refers to the rate at which TPA is converted to ester. Further, the reaction temperature of the present invention can be selected from the range of 225 to 260°C, preferably 230 to 255°C, and more preferably 235 to 250°C. Of course, in the present invention, it is not necessary to carry out all reactions within this temperature range, and it is sufficient that the main reaction occurs within this temperature range. Therefore,
The temperature may be outside this range at the beginning of the reaction or near the end of the reaction. If the reaction temperature is below 225°C, the reaction will take a long time, whereas if it is above 260°C, it will be necessary to increase the size of the heater, which will increase the equipment cost, which is undesirable. As for the BHT to be pre-existing in the system prior to the reaction of the present invention, it is preferable to store a portion of the BHT after the previous reaction. And the storage rate is the total amount after the reaction.
30-65% of BHT is good. The preferred range of storage rate is 35 to 60%, more preferably 40 to 55%. If the retention rate is less than 30%, the esterification reaction time will become longer, which is undesirable, and in order to increase the retention rate to 65% or more, the reactor must be made enormous or the amount charged per batch must be reduced. I don't like it. The total slurry supply time (Ft) of the present invention is 2.0 ~
The time is preferably within the range of 4.5 hours, preferably 2.4 to 4.1 hours, and more preferably 2.8 to 3.8 hours. If the total slurry feed time (Ft) is less than 2.0 hours, the reaction rate will be too low and free EG will increase, requiring an increase in the fractionator reflux ratio, which will lower the reaction temperature and increase the time. I don't like how long it is.
Moreover, if the supply time exceeds 4.5 hours, the reaction time will increase accordingly, which is not preferable. Further, the total reaction time is not particularly limited, but is preferably 3.3 to 7.5 hours. The slurry of the present invention has an EG/TPA molar ratio of 0.9 to 1.50.
Good quality, EG unit component/TPA in the reaction system
The molar ratio of the unit components is preferably about 1.10 to 1.50. Another preferred embodiment is a method in which one part of EG is extracted from the reaction mixture during slurry supply, and all or part of the extracted EG is resupplied after slurry supply is complete. Known catalysts may be used in the esterification reaction of the present invention. The present invention also includes an esterification reaction to obtain a copolymerized polyester in which 80 mol% or more of the constituent units of the finally obtained polyester consist of ethylene terephthalate, and less than 20 mol% of TPA, Copolymerization components other than EG may be present during the esterification reaction. By carrying out the esterification reaction method of the present invention, it is possible to produce a product with low DEG content, high quality, excellent polycondensation reactivity, and good dispersibility of titanium oxide fine particles.
You can get BHT. The present invention will be specifically described below with reference to Examples. In addition, the reaction rate in the examples is -COO- with respect to the total amount of -COOH and -COO- in the reaction product.
The acid value (AV) and saponification value (SV) of the reaction product were measured and calculated using the following formula. Reaction rate = SV - AV / SV x 100 (%) SV: Saponification value (KOHmg/g) AV: Acid value (〃) In addition, the DEG content was determined by decomposing the reaction product with amines and analyzing it by gas chromatography. It was measured. In addition, the dispersibility of titanium oxide is similar to that of PET after polycondensation.
Collect 10 mg of particles, place them between two cover glasses, melt them at 280℃ while holding down the cover glasses to make a preparation, observe the entire field of view with an optical microscope at a magnification of 100, and estimate the diameter of a circle. Titanium lumps with a size of 10μ or more were counted and expressed in units/10mg. Further, the intrinsic viscosity was measured in orthochlorophenol at 25°C. Example 1 205 kg of BHT with an EG unit component/TPA unit component molar ratio of 1.21, a reaction rate of 98.2%, and a DEG of 0.71% by weight was placed in a 600 mm esterification reaction tank equipped with a stirring device (storage rate of 50%), and heated. It was kept at 249℃. Then, after pressurizing to 0.25Kg/cm ² G with N ₂ gas,
Slurry 241.0 consisting of TPA166.0Kg and EG75.6Kg
Kg (EG/TPA molar ratio 1.21) was fed in 3.5 hours using a metering pump, and the slurry feed rate was as described in Table 1. Note that the slurry supply speed was changed to a two-step supply speed, that is, up to 15% of the initial supply time, that is, up to 31.5 minutes after the start of slurry supply, and thereafter. The speed was constant at each stage. The reaction pressure during slurry supply is maintained at 0.25Kg/cm ² G using a control valve, and after slurry supply is completed, the reaction pressure is maintained at 0.25Kg/cm 2 G.
The pressure was gradually reduced over a period of minutes, and finally the pressure was reduced to 0 kg/cm ² G. The reaction temperature is as listed in Table 1.
The reaction was carried out under these conditions, and half of the BHT after the reaction, 205 kg, was transferred to the polycondensation tank, and the remaining 205 kg was stored in the esterification reaction tank and used for the next batch. The BHT transferred to the polycondensation tank contains 0.02% by weight of phosphoric acid, 0.04% by weight of antimony trioxide, and titanium oxide that has been classified in EG to remove particles larger than 5μ.
Add 15% by weight EG slurry to 0.5% by weight of titanium oxide based on the amount of polymer, then 10mm in 40 minutes.
The pressure was reduced to below Hg, and the temperature was raised to 285°C in 90 minutes. The temperature at the end of the polycondensation reaction was 290°C, and the degree of vacuum was 0.5 mmHg. The above operation was repeated 10 times for each level, and the average values of the results are shown in Table 1.

[Table] As is clear from Table 1, in Experiments Nos. 1 to 6, in which the slurry supply method was within the scope of the present invention, the esterification reaction time was short and the generation of DEG was small.
Moreover, the achieved reaction rate was also high. Furthermore, titanium dispersion during polycondensation was good, and the polycondensation time, DEG content in the polycondensation reaction product, and intrinsic viscosity also showed favorable values. On the other hand, in Comparative Example No. 7, the slurry supply rate was kept constant without changing, so the reaction was slow, and when the reaction was stopped at the same reaction time as Experiment No. 6, the reaction rate increased only to 96.1%. Moreover, the DEG content in the esterification reaction product was also high. In addition, the intrinsic viscosity did not increase during polycondensation, and there was a large amount of DEG in the polycondensation reaction product, and the dispersion of titanium was also poor. In Comparative Example No. 8, a large amount of slurry was initially charged at a rate outside the range of the present invention, which lowered the reaction temperature, prolonged the reaction time, and increased the DEG content in the esterification reaction product, which was undesirable. .

Claims (1)

[Claims] 1. A slurry mainly consisting of terephthalic acid and ethylene glycol is supplied to a system in which bis-β-hydroxyethyl terephthalate and/or its low polymer is present, and the reaction temperature is 225 to 260°C and the pressure is 0 to 0.
1.0Kg/cm ² G, bis-β-hydroxyethyl terephthalate and or its low polymer retention rate 30-65
%, the initial total slurry supply time when performing the reaction under conditions of 2.0 to 4.5 hours.
Initial slurry feeding average speed Fa (Kg/
A batch esterification method characterized in that hr) is controlled so that it satisfies the following formula. 1.1Sv/Ft≦Fa≦5.0Sv/Ft However, Sv is the total slurry preparation amount per batch (Kg) Ft is the total slurry supply time (hr)