JPH05320328A - Production of polyester - Google Patents

Abstract

PURPOSE:To produce a polyester having excellent workability and reactivity, not causing clogging of a reactor, by using a slurry comprising terephthalic acid and ethylene glycol having physical properties in a specific range. CONSTITUTION:A slurry comprising 1mol terephthalic acid and >=1.2mol ethylene glycol, having <=50 centipoise slurry viscosity measured under a condition to give 0.1-3.0 shear rate of the formula gamma is shear rate 1/sec; d is diameter m of measuring rotor of rotational viscometer; D is outer diameter m of measuring container in measurement by rotational viscometer; N is number of revolutions rpm; pi is the ratio of the circumference of a circle to its diameter) in 20-40 deg.C temperature range, having <=100mum average particle diameter of terephthalic acid is used to produce a polyester.

Description

Detailed Description of the Invention

[0001]

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 This polyethylene terephthalate is industrially extremely useful as a fiber, film or other molded product.

Various proposals have hitherto been made for a method for producing polyethylene terephthalate (hereinafter abbreviated as PET) from terephthalic acid (hereinafter abbreviated as TA) and ethylene glycol (hereinafter abbreviated as EG).

For example, Japanese Examined Patent Publication (Kokoku) No. 50-19313 discloses that the viscosity of an EG / TA slurry and the stability of the slurry viscosity are mainly regulated, and that the range is suitable for the production of PET.

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

However, the above-mentioned slurry is too viscous and impractical, and it is considered that it is difficult to handle the slurry in addition to the above-mentioned external heat exchange depending on the reactor. In a circulation type reaction tank with a reactor, TA-E is affected by the effect of slurry circulation.
There is a problem that TA is likely to be scattered to a distillation system (column) for extracting H ₂ O generated by the G reaction and excess EG.

It is generally known that the effect of increasing the average particle diameter of TA is large in order to reduce the viscosity of the slurry. However, in this case, in particular, the above-mentioned scattering is large and the loss is large, and TA is mixed in H ₂ O and surplus EG produced by the esterification reaction, and these H ₂ O and EG are filtered. There is also a problem in that the clogging of the filter to be used is increased, and the influence on the reaction process such as clogging of the transportation pump is increased.

Further, it is known that if the average particle diameter of TA is large, the reactivity with EG is deteriorated, which is not preferable.

On the other hand, in spite of various proposals as a method for producing PET from the past, the influence on the reaction device,
The range of TA physical properties suitable for the production of PET that can satisfy various points such as workability and reactivity is not clear.

[0010]

The object of the present invention is to produce a polyester composed of TA and EG, which has less influence on the reactor,
It is an object of the present invention to provide a method for efficiently producing a polyester by clarifying a TA physical property range having excellent workability and reactivity.

[0011]

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

[0012]

[Equation 2]

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

The method of measuring the "slurry viscosity" will be described in more detail. Generally, a rotary viscometer as shown in FIG. 1 [here, a single cylinder rotary viscometer (VS-A1) manufactured by Shibaura Co., Ltd.] is used. And use the following procedure. (I) Charge EG and TA into a measurement container (outer cylinder container: diameter is Dm). (Ii) Knead for 20 minutes, and make a slurry so as to uniformly disperse. (Iii) Immediately, the rotor (diameter dm) is rotated in the measuring container containing the slurry, and the value after 40 seconds is used as the slurry viscosity measured value. However, the measurement temperature must be controlled to be constant, and the outer cylinder container diameter (D (m), inner cylinder rotor diameter d (m), rotation speed N (rpm), and shear rate γ (1 / se
It is necessary to select c) so that it falls within 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. When it exceeds 50 centipoise, the stirring power during slurrying and in the esterification reaction tank is large, and the power of the liquid feed pump increases with the increase in pipe resistance in the transportation pipe from the slurry tank to the esterification tank. Furthermore, the rate of esterification reaction decreases with the decrease of the reaction heat absorption efficiency in the esterification reaction tank, and side reaction such as diethylene glycol (DEG) generation is likely to occur because it is necessary to extend the residence time in the reaction tank. 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 it is measured by the following procedure. (I) Opening 210 μm, 177 μm, 149 μm, 1
05μm, 74μm, 44μm sieve (diameter 200mm,
A set of 45 mm in height) is stacked on the receiver in order of increasing aperture (shaking machine for tabletop standard sieve VS manufactured by Ritsutsui Rika)
S-50 type) vibration plate. (Ii) Set a filter bottle (3 liters) at the outlet of the receiver line, insert a glass filter (165G-3) and connect it 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) Start filtration using the 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 allowed to infiltrate for 30 minutes and sieved. (Vi) The TA sieved in each stage is washed on a glass filter, dried at 120 ° C. for 3 hours, allowed to cool, and then weighed to obtain the weight of TA captured in each sieve. (Vii) Obtain the percentage of the weight of the TA component captured in each stage to the sum of the weight of the TA components captured on each sieve. (Viii) For the average particle diameter, write a cumulative curve of weight, and read the particle diameter when the cumulative weight is 50%.

FIG. 2 shows a schematic view of the measuring device.

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

If the average particle size exceeds 100 μm,
The production efficiency decreases such that the filter cleaning cycle of the distilling EG take-out part in the distillation column of the esterification reaction tank becomes shorter and the final PET polymer amount decreases with respect to the TA usage amount. Further, in the case of an esterification reaction tank having an external heat exchanger, the scattered TA adheres to the upper part of the heat exchanger, and unreacted T which has deteriorated with the passage of time.
Since it remains as A and is mixed non-steadily with the oligomer and then sent to the polymerization tank, there is an adverse effect that the amount of foreign matter in the final polymer increases.

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

[0021]

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 the reaction product in benzyl alcohol under an N ₂ atmosphere and titrating with alkali. Saponification value: A value obtained by alkali hydrolysis of the reaction product and back titration with an acid.

(Ii) DEG content The reaction product is decomposed with hydrazine to remove all DEG components from DE.
Measured by gas chromatography as G.

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

[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 terms of molar ratio, and the TA having a slurry viscosity of 46 centipoise and an average particle size of 96 μm is used.
Was used to prepare a uniform slurry, and this slurry was continuously fed by a pump to an esterification reaction tank having an external heat exchanger. The feed rate was 2 tons / hr, the reaction conditions in the esterification reaction tank were a temperature of 370 ° C., normal pressure, and an average residence time of 3 hours. Also, the esterification rate of the oligomer after the esterification reaction in the steady state is 96%,
The content was 0.85 wt% and the average degree of polymerization was 9.

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

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

[0030]

Comparative Examples 1 to 4 The same conditions as in Example 1 were used except that TAs having different slurry viscosities and average particle sizes were used. Table 1 shows the results in which the reaction rate, the DEG content, and the replacement cycle of the distillate EG filter were summarized.

[0031]

[Table 1]

[Brief description of drawings]

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

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

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

[Explanation of symbols]

 1 Kneader 2 Container for liquid transfer 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 tower 13 Condenser 14 Distillation EG filter 15 Distillation Egg extraction pump 16 Esterification reaction tank 17 External heat exchanger 18, 20 Vacuum line 19, 21 Early and late polymerization tanks 22, 23, 24 Oligomer and polymer pump 25, 26 Catalyst and stabilizer supply line

[Procedure amendment]

[Submission date] May 10, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] 0027

[Correction method] Change

[Correction content]

[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 terms of molar ratio, and the TA having a slurry viscosity of 46 centipoise and an average particle size of 96 μm is used.
Was used to prepare a uniform slurry, and this slurry was continuously fed by a pump to an esterification reaction tank having an external heat exchanger. The supply rate was 2 tons / hr, the reaction conditions in the esterification reaction tank were a temperature of 270 ° C., normal pressure, and an average residence time of 3 hours. Also, the esterification rate of the oligomer after the esterification reaction in the steady state is 96%,
The content was 0.85 wt% and the average degree of polymerization was 9.

Claims (1)

[Claims] 1. When producing a polyester from terephthalic acid and ethylene glycol, in a slurry using 1.2 mol or more of ethylene glycol with respect to 1 mol of terephthalic acid, the following (in the temperature range of 20 ° C. to 40 ° C.) The slurry viscosity measured under the condition that the shear rate (γ) represented by the formula 1) is in the range of 0.1 to 3.0 is 50.
A method for producing a polyester, characterized in that a polyester having a mean particle size of terephthalic acid of 100 μm or less is used. [Equation 1]