JP3071556B2 - Polyester production method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing polyester, and more particularly to a method for producing polyethylene terephthalate from terephthalic acid and ethylene glycol.

[0002]

2. Description of the Related Art Polyethylene terephthalate is extremely useful industrially as a fiber, film or other molded product.

[0003] Various methods have been proposed for producing polyethylene terephthalate (hereinafter abbreviated as PET) from terephthalic acid (hereinafter abbreviated as TA) and ethylene glycol (hereinafter abbreviated as EG).

[0004] For example, Japanese Patent Publication No. 50-19313 discloses that the viscosity of an EG / TA slurry and the stability of the slurry viscosity are mainly specified and that there is a range suitable for the production of PET.

Japanese Patent Application Laid-Open No. 54-19928 discloses a rigid mixing apparatus in which a heating heat exchanger is provided outside and a reaction mixture is circulated by a thermosiphon effect as an apparatus for producing an intermediate suitable for the production of PET. The use of a tank has been proposed, which has been shown to be advantageous in terms of slurry handling, reaction efficiency and the like.

[0006] However, the slurry described above has too high a viscosity and is not practical, and it is considered that it is difficult to actually handle the slurry. In a circulation type reaction tank with a vessel, TA-E
There is a problem that TA is easily scattered to a distillation system (column) for extracting H ₂ O and excess EG generated by the G reaction.

It is generally known that increasing the average particle diameter of TA is effective in reducing the viscosity of the slurry. However, in this case, in particular, the above-mentioned scattering is large and the loss is large, and in addition, TA is mixed into H ₂ O and excess EG generated by the esterification reaction, and the H ₂ O and EG are filtered. Another problem is that the clogging of the filter increases, and the influence on the reaction process such as clogging of the transport pump becomes large.

[0008] It is also known that if the average particle size of TA is large, the reactivity with EG becomes poor, which is not preferable.

On the other hand, in spite of various proposals for a method for producing PET, various methods for producing PET have been proposed.
The range of TA properties suitable for the production of PET that can satisfy various points such as workability and reactivity has not been clarified.

[0010]

The object of the present invention is to produce a polyester comprising TA and EG with little influence on a reactor.
An object of the present invention is to clarify the range of TA properties excellent in workability and reactivity and to provide a method for efficiently producing polyester.

[0011]

DETAILED DESCRIPTION OF THE INVENTION TA used in the present invention is a slurry using 1.2 mol or more of EG per 1 mol of TA,
The slurry has a viscosity of 50 centipoise or less measured in a temperature range of 20 to 40 ° C. in a range of a shear rate (γ) of 0.1 to 3.0 represented by the following formula (1), and TA
Has an average particle size of 100 μm or less.

[0012]

(Equation 2)

In the present invention, the measurement range of the slurry viscosity is specified as “the temperature range of 20 ° C. to 40 ° C.” and “the range of the shear rate of 0.1 to 3.0”, and the molar ratio of EG to TA is further limited. doing. Slurry viscosity is temperature,
It is clear that it changes with the shear rate and the molar ratio,
This is to unify the standards when clarifying TA types suitable for polyester production.

The method of measuring the "slurry viscosity" will be described in more detail. In general, a rotary viscometer as shown in FIG. 1 [here, a single cylindrical rotary viscometer Bismetron (VS-A1) manufactured by Shibaura Co., Ltd.] The measurement is performed using the following procedure. (I) EG and TA are charged into a measurement container (outer cylinder: diameter is Dm). (Ii) Kneading for 20 minutes to form a slurry so as to be uniformly dispersed. (Iii) Immediately rotate the rotor (having a diameter of dm) in the measuring vessel containing the slurry and let the value after 40 seconds be the measured value of the slurry viscosity. However, it is necessary to control the measurement temperature to be constant, and the outer cylinder container diameter (D (m), the inner cylinder rotor diameter d (m), the rotation speed N (rpm), and the shear rate γ (1 / se
c) must be selected so that it is in the range of 0.1 to 3.0.

In the present invention, the "slurry viscosity" measured by this measuring method must be 50 centipoise or less. In the case of exceeding 50 centipoise, the power for stirring during slurrying and in the esterification reaction tank is large, and the power of the liquid sending pump is increased due to the increase in pipe resistance in the transportation pipe from the slurrying tank to the esterification tank, Further, the esterification reaction rate is reduced due to a decrease in the efficiency of absorption of the reaction heat in the esterification reaction tank, and it becomes necessary to extend the residence time in the reaction tank, so that side reactions such as diethylene glycol (DEG) generation are likely to occur. And the like.

The method of measuring the “average particle size” of TA is a particle size distribution measuring method generally called a wet method, and is measured by the following procedure. (I) Aperture 210 μm, 177 μm, 149 μm, 1
05μm, 74μm, 44μm sieve (diameter 200mm,
A set of 45 mm height stacked on a receiver in ascending order of opening, shaker (table-top standard sieve shaker VS manufactured by Tsutsui Rika)
(S-50 type). (Ii) Set a filter bottle (3 liters) at the outlet of the receiver line, insert a glass filter (165G-3), and connect to the aspirator. (Iii) Add about 150 g of TA and an appropriate amount of demineralized water and mix,
Pour into the top of the sieve. (Iv) Filtration is started using an aspirator. (V) While pouring demineralized water into the uppermost stage of the sieve at a flow rate of 0.8 liter / min, the shaker is permeated for 30 minutes and sieved. (Vi) The TA sieved in each stage is washed off on a glass filter, dried at 120 ° C. for 3 hours and allowed to cool, the weight is weighed, and the weight of TA captured by each sieve is determined. (Vii) Determine the percentage of the weight of TA captured on each stage relative to the sum of the weight of TA captured on each sieve. (Viii) For the average particle size, a cumulative curve of weight is drawn, and the particle size when the cumulative weight is 50% is read.

FIG. 2 shows a schematic diagram of the measuring apparatus.

Next, the “average particle size of TA” measured by this measuring method must be 100 μm or less.

When the average particle size exceeds 100 μm,
The production efficiency is lowered, such as the filter cleaning cycle of the distilling EG removal section in the distillation column of the esterification reaction tank is shortened, and the final PET polymer amount is reduced with respect to the TA usage amount. Further, in the case of an esterification reaction tank having an external heat exchanger, scattered TA adheres to the upper part of the heat exchanger, and unreacted T
Since it remains as A and is unsteadily mixed with the oligomer and then sent to the polymerization tank, there is a problem that the amount of foreign substances in the final polymer increases.

FIG. 3 shows a flow example of an esterification apparatus having an external heat exchanger, a distillation column, and a polymerization tank.

[0021]

EXAMPLES The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples. The reaction rate, DEG content, and average degree of polymerization are obtained by the methods described below.

(I) Reaction rate

[0023]

(Equation 3)

Acid value: A value obtained by dissolving a reaction product in benzyl alcohol under an N ₂ atmosphere and titrating with an alkali. Saponification value: A value obtained by subjecting a reaction product to alkali hydrolysis and back titrating with an acid.

(Ii) DEG content The reaction product is decomposed with hydrazine to convert all the DEG components to DE.
G was measured by gas chromatography.

(Iii) Average Degree of Polymerization The amount of carboxyl groups in the reaction product is determined by calculating the acid value, and the amount of hydroxyethyl groups is determined by dissolving a certain amount of the reaction product in nitrobenzene and reacting with benzoyl chloride. Then, it was decomposed with ethanol, quantified by gas chromatography, calculated from the field, and calculated from the sum of the two.

[0027]

Example 1 A polycondensation reaction was carried out from a continuous esterification reaction using the equipment shown in FIG. The mixing ratio of TA and EG is EG / TA = 1.2 in molar ratio, and the slurry has a slurry viscosity of 46 centipoise and an average particle size of 96 μm.
Was used to prepare a uniform slurry, and this slurry was continuously fed to an esterification reactor having an external heat exchanger by a pump. The feed rate was 2 tons / hr, the reaction conditions in the esterification reactor were temperature 270 ° C., normal pressure, and average residence time was 3 hours. The esterification rate of the oligomer after the esterification reaction in a steady state was 96%, and DEG
The content was 0.85 wt% and the average degree of polymerization was 9.

Further, the filter exchange cycle with the opening of the distilling EG filter at the bottom of the distillation column of the esterification tank being 100 μm was only required to be performed once every 168 hours, and the filter still hardly trapped the scattered matter. Further, the oligomer after the esterification reaction is placed in an initial polymerization tank (reaction temperature: 280 ° C., average residence time: 45 minutes, vacuum degree: 20 To
rr) and the subsequent polymerization tank (reaction temperature 27
5 ° C., average residence time 1 hour, degree of vacuum 2 Torr) to obtain a polymer having a degree of polymerization of 77 as a final polymer.

As a catalyst stabilizer, 30 mmol% of germanium oxide and 10 mmol% of orthophosphoric acid were added to an oligomer pipe between an esterification tank and an initial polymerization tank.

[0030]

Comparative Examples 1 to 4 The same procedure was performed as in Example 1 except that TA having different slurry viscosity and different average particle diameter was used. Table 1 shows the results obtained by summarizing the reaction rate, the DEG content, and the replacement cycle of the distilling EG filter.

[0031]

[Table 1]

[Brief description of the drawings]

FIG. 1 is an example of a rotary viscometer showing the measurement of slurry viscosity.

FIG. 2 is a schematic diagram of a measuring device.

FIG. 3 is a schematic diagram showing the flow of an esterification apparatus provided with an external heat exchanger, a distillation column, and a polymerization tank.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Kneader 2 Liquid transfer container 3 Rotational viscometer 4 Constant temperature bath 5 Flow meter 6 Sieve 8 Demineralized water inlet 9 Aspirator 10 Slurry preparation tank 11 Slurry supply pump 12 Esterification tank distillation column 13 Condenser 14 Distillation EG filter 15 Distillation Outlet EG extraction pump 16 Esterification reaction tank 17 External heat exchanger 18, 20 Vacuum line 19, 21 Initial and late polymerization tank 22, 23, 24 Oligomer and polymer pump 25, 26 Catalyst and stabilizer supply line

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) C08G 63/78-63/87

Claims (1)

(57) [Claims] In producing a polyester from terephthalic acid and ethylene glycol, a slurry containing 1.2 mol or more of ethylene glycol per 1 mol of terephthalic acid in a slurry at a temperature of 20 ° C. to 40 ° C. 1) When the slurry viscosity measured under the condition that the shear rate (γ) represented by the equation is in the range of 0.1 to 3.0 is 50,
A method for producing a polyester, characterized by using one having a centipoise or less and an average particle size of terephthalic acid of 100 μm or less. (Equation 1)