JPH1036495A - Continuous production of polyester having excellent transparency - Google Patents

Abstract

PROBLEM TO BE SOLVED: To continuously produce a polyester having an excellent transparency in the presence of an antimony trioxide catalyst. SOLUTION: A polyester having a limiting viscosity of at least 0.50dl/g is continuously produced by continuously feeding a slurry comprising terephthalic acid and ethylene glycol in a molar ratio of 1/1.0 to 1/2.5 and phosphoric acid in an amt. of 3 to 10mol per mole of antimony trioxide to be added in the polycondensation reaction into an esterification tank 2 containing an oligoester and then conducting esterification while removing the water formed from the reaction system until an esterification rate of at least 90% is obtained. Then the esterification product is continuously sent into a polycondensation reactor 3, and 0.5 to 1.5×10<-4> mol, per mole of the acid component constituting the polyester, of antimony trioxide and 0.5 to 1.5mol, per mole of antimony trioxide, of a sulfuric acid compound are added to conduct polycondensation.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for continuously producing polyester having excellent transparency suitable for hollow containers such as bottles.

[0002]

2. Description of the Related Art Polyethylene terephthalate (abbreviated as PET) has excellent mechanical properties, chemical stability, etc., and is lightweight and inexpensive, so that it is widely used for various sheets, films, containers, and the like. In particular, growth for hollow containers such as carbonated drinks, fruit drinks, liquid seasonings, edible oils, sake, and wine is remarkable.

[0003] PE for hollow containers such as bottles
In the production of T, it is customary in Japan to use expensive germanium dioxide without using antimony trioxide, which is generally widely used as a polycondensation catalyst.
However, germanium compounds are very expensive and have a problem in cost.

On the other hand, in recent years, PET for hollow containers has been used overseas.
Inexpensive antimony trioxide has come to be used as a polycondensation catalyst also in the production of. Antimony trioxide has excellent catalytic performance and safety has been confirmed. However,
PET manufactured using antimony trioxide has lower transparency than PET manufactured using germanium dioxide, and antimony trioxide and its reduced product insoluble in PET serve as a nucleating agent, thereby reducing the crystallization rate of PET. There was a problem that the hollow container was apt to whiten during molding due to the speeding.

As a solution to such a problem, antimony trioxide and a sulfonic acid compound are used in combination as a catalyst.
There has been a method of suppressing the deterioration of transparency due to the use of antimony trioxide and appropriately suppressing the formation of a diethylene glycol component in PET due to the use of a sulfonic acid compound. Further, a method of improving the disadvantage that the color tone of PET becomes yellowish by using a sulfonic acid compound is improved by adding a phosphorus compound.

[0006] Phosphorus compounds, especially phosphoric acid, are inexpensive and PE
It is excellent in handleability because the amount of contribution to the reaction is controlled without distilling into the distillation and decompression system in the production process of T, and fractionation by recycling is unnecessary. However, addition in combination with antimony trioxide requires 30
Until the phosphoric acid is esterified after reacting for about 60 minutes, antimony and phosphoric acid react with each other, resulting in a problem that not only the catalytic effect is reduced but also the transparency of PET is impaired. Therefore, in the batch method, a method of adding phosphoric acid and reacting it before the esterification reaction is generally used.

[0007] With the recent increase in consumption, transparent PET for hollow containers has been increasingly produced in a continuous system. In this case, in the continuous production of PET in which antimony trioxide, a sulfonic acid compound and phosphoric acid are added as described above, even if phosphoric acid is added before the esterification reaction, the ethylene glycol and phosphoric acid are added. Possibly due to insufficient reaction of phosphoric acid causing a short path, PE
There was a problem that T became cloudy.

[0008]

SUMMARY OF THE INVENTION An object of the present invention is to solve such a problem and to provide a method for continuously producing a polyester having excellent transparency using an antimony trioxide catalyst system.

[0009]

Means for Solving the Problems The present invention solves the above-mentioned problems, and the gist of the invention is to continuously produce a polyester having an intrinsic viscosity of 0.50 dl / g or more. A slurry of 1.0 to 2.5 moles of ethylene glycol to 1 mole of terephthalic acid and phosphoric acid in an amount of 3 to 10 times the amount of antimony trioxide added in the polycondensation reaction are continuously supplied to the existing esterification reaction tank. The esterification reaction rate is 90% while removing generated water out of the system.
The esterification reaction was continued until the above was reached, and then the esterified product was continuously fed to the polycondensation reaction tank, and antimony trioxide was added in an amount of 0.5 to 1 mol of the acid component constituting the polyester.
The present invention relates to a continuous process for producing a polyester having excellent transparency, characterized by adding a sulfonic acid compound in an amount of from 1.5 to ^10-4 mol and 0.5 to 1.5 mol times the amount of antimony trioxide for polycondensation.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.

The polyester to be produced in the present invention has an intrinsic viscosity of 0.50 dl / g or more. When the intrinsic viscosity is less than 0.50 dl / g, the moldability is poor and the strength of the obtained hollow container is low, so that it cannot be practically used as a container.

[0012] The composition of the slurry supplied to the esterification reaction tank is as follows:
It is necessary to have a ratio of 1.0 to 2.5 mol. If this ratio is less than 1.0, the esterification reaction takes a long time,
In some cases, the reaction does not proceed. On the other hand, if this ratio is larger than 2.5, the content of diethylene glycol bonds in the polyester becomes too large, and the melting point decreases.

In the present invention, it is necessary to add phosphoric acid in the esterification step and use antimony trioxide and a sulfonic acid compound in combination as a catalyst for the polycondensation reaction. Antimony trioxide alone is inferior in transparency compared to polyester produced using germanium dioxide,
Since antimony trioxide and its reduced product insoluble in polyester serve as a nucleating agent to increase the crystallization speed of polyester, the hollow container tends to whiten during molding. On the other hand, although the degree of polymerization is increased by using only the sulfonic acid compound, continuous polymerization is not preferable because it requires a long time and the generation of diethylene glycol bonds in the polyester becomes too large. Further, it is necessary to suppress the drawback that the color tone of the polyester becomes yellowish by using a sulfonic acid compound by adding phosphoric acid.

The amount of antimony trioxide to be added is 0.5 × 10 ^-4 to 1.5 × 1 to 1 mol of the acid component constituting the polyester.
It needs to be ^0-4 mol. If the amount of antimony trioxide is larger than this, the transparency of the polyester is deteriorated, and if it is smaller than this, it is difficult to increase the degree of polymerization.

The amount of the sulfonic acid compound added must be such that the sulfonic acid groups are 0.5 to 1.5 times the molar amount of antimony trioxide. If the addition amount of the sulfonic acid compound is more than this, not only does the color tone of the polyester deteriorate, but also the content of diethylene glycol bonds in the polyester increases, and the glass transition point of the polyester decreases,
If the amount is less than this, the catalytic effect is insufficient, and it is difficult to increase the degree of polymerization.

The amount of phosphoric acid added is 3
It is necessary that the amount be 10 to 10 times the molar amount. If the amount of phosphoric acid is larger than this, the excess phosphoric acid reacts with antimony trioxide, which not only reduces the catalytic effect but also deteriorates the transparency of the polyester. Insufficient and the color tone of polyester deteriorates.

By combining the above three compounds in appropriate amounts, an antimony trioxide catalyst system having a problem in the transparency of the polyester and having the same level of transparency as the polyester obtained in the germanium dioxide catalyst system can be obtained. It is done.

Specific examples of the sulfonic acid compound include acetyl sulfate, dimethyl sulfate, ethanesulfonic acid, benzenesulfonic acid, p-toluenesulfonic acid, p-benzenedisulfonic acid, o-sulfobenzoic anhydride, and 5-sulfosalicylic acid. And the like.

It is desirable to select the reaction conditions so that the content of diethylene glycol bonds in the polyester is 2 to 5 mol%. When the content of the diethylene glycol bond is larger than this, the glass transition point of the polyester is lowered. When the content is smaller than this, the crystallization speed of the polyester is increased.

Next, the method of the present invention will be described with reference to the drawings. In FIG. 1, 1 is a slurrying tank, 2 is an esterification reaction tank, 3 is a first polycondensation reaction tank, 4 is a second polycondensation reaction tank, 5 is a catalyst addition pump, 6 is a glycol distillation column, and 7 is a reduced pressure. The device is shown.

First, terephthalic acid (abbreviated as TPA), ethylene glycol (abbreviated as EG) and phosphoric acid are slurried in a slurrying tank 1 and continuously supplied to an esterification reaction tank 2 in which a polyester low polymer is present. .

In the esterification reaction tank 2, a temperature of 200 to 270
The esterification reaction is carried out at normal pressure or under pressure at a temperature of 0 ° C. while removing generated water out of the system. It is necessary to carry out the esterification reaction so that the esterification reaction rate becomes 90% or more. If the esterification reaction rate is less than 90%, the subsequent polycondensation reaction may take an extremely long time, which is not preferable.

As the esterification reaction tank, conventionally, PET is used.
What has been widely adopted in the continuous esterification step can be used.

Next, the esterified product (polyester low polymer) is continuously extracted from the esterification reaction tank 2 and sent to the first polycondensation reaction tank 3.

A polycondensation catalyst solution supply pipe is connected to the esterification product supply pipe, and the catalyst solution is supplied to a pump 5.
Is supplied via the Internet. Here, what is supplied as the polycondensation catalyst is antimony trioxide and a sulfonic acid compound, which are usually supplied as an EG solution.

In the first polycondensation reaction tank 3, a polycondensation reaction is carried out under a reduced pressure of 1 to 30 hPa at a temperature of 220 to 300 ° C., preferably 230 to 290 ° C., and a polyester having an intrinsic viscosity of 0.1 to 0.3 dl / g is produced. I do.

Subsequently, the polyester is continuously withdrawn from the first polycondensation reaction tank 3 and
Continuously in the second polycondensation reaction tank 4 for 1 hP
a Polycondensation reaction is carried out at a temperature of 250 to 290 ° C under the following reduced pressure to obtain a polyester having a high degree of polymerization.

[0028]

It is not clear why polyesters having excellent transparency can be obtained by the method of the present invention, but some sort of EG ester of phosphoric acid, unreacted phosphoric acid, antimony trioxide and sulfonic acid compound is required. It is considered that the interaction causes the solubility of antimony trioxide in the polyester to be improved.

[0029]

Next, the present invention will be described specifically with reference to examples and comparative examples. The characteristic values were measured by the following method. (a) Intrinsic viscosity [η] Measured at a temperature of 20 ° C. using an equal weight mixture of phenol and ethane tetrachloride as a solvent. (b) Esterification reaction rate f The acid value (AV) and saponification value (SN) were determined by the following method, and the esterification reaction rate f was calculated by the following formula. f (%) = (1−AV / SN) × 100 AV: The sample was dissolved in dioxane, and the content was determined by a suitable amount of a potassium hydroxide methanol solution. SN: The sample was saponified with an ethanol solution of potassium hydroxide under reflux for 2 hours, and the excess potassium hydroxide was determined by reverse titration with hydrochloric acid. (c) Diethylene glycol bond content (D%) After alkaline hydrolysis of polyester, GC-1 manufactured by Shimadzu Corporation was used.
EG and diethylene glycol (DEG) were quantified by 4B-type gas chromatography and determined as the ratio of DEG to the total number of moles of EG and DEG. (d) Color tone (b value) It was measured using a # 80 color difference meter manufactured by Nippon Denshoku. [The b-value represents a yellow-blue hue (yellow on the + side and bluish on the-side), and the smaller the better, unless it is extremely small. (E) Plate haze For a plate 5 mm thick x 10 cm long x 6 cm wide obtained by injection-molding dried polyester at a molding temperature of 285 ° C,
The transparency was evaluated using a turbidity meter MODEL1001DP manufactured by Nippon Denshoku Industries Co., Ltd. (Air: haze 0) (The smaller the plate haze value, the better the transparency. If this value is less than 10, it is acceptable.)

Examples 1 to 12 and Comparative Examples 1 to 9 In the slurrying tank 1, TPA having the proportions shown in Tables 1 and 2 was used.
A slurry composed of EG and phosphoric acid was prepared, and this slurry was continuously supplied to the esterification reaction tank 2 in which the polyester low polymer was present at a rate such that the amount of TPA became 100 mol / h. The reaction conditions in the esterification reactor 2 are as follows.
The temperature and the average residence time were maintained at the values shown in Tables 1 and 2 at 400 hPa. Table 1 and Table 2 from the esterification reactor 2
The esterified product having the esterification reaction rate shown in Table 1 was continuously withdrawn, and antimony trioxide and a sulfonic acid compound were added as catalysts in the amounts shown in Tables 1 and 2 in the form of an EG solution to the esterification product feed line. To the first polycondensation reaction tank 3. The reaction conditions in the first polycondensation reaction tank 3 are as follows:
The pressure was 20 hPa, the temperature was 275 ° C, and the average residence time was as shown in Table 1.
And the values shown in Table 2 were maintained. The polyester was continuously extracted from the first polycondensation reaction tank 3 and continuously supplied to the second polycondensation reaction tank 4. The reaction conditions in the second polycondensation reaction tank 4 were such that the pressure was 0.5 hPa and the temperature was 280 ° C., and the average residence time was maintained at the values shown in Tables 1 and 2. The polyester was continuously extracted from the second polycondensation reaction tank 4 and was subjected to Tables 1 and 2
A polyester having the characteristic values shown in Table 1 was obtained. Table 1 shows the results
And Table 2.

[0031]

[Table 1]

[0032]

[Table 2]

In each of the examples, a polyester having good transparency was obtained. However, the comparative example had the following problems.

In Comparative Example 1, the color of the polyester was poor because the amount of phosphoric acid was small, and in Comparative Example 2, the polyester was cloudy because of the large amount of phosphoric acid. In Comparative Example 3, the amount of antimony trioxide added was small, so that the degree of polymerization of the polyester was not sufficiently increased. In Comparative Example 4, the amount of antimony trioxide was too large, and the polyester was cloudy. In Comparative Example 5, since the amount of the sulfonic acid compound added was small, the degree of polymerization of the polyester was not sufficiently increased.
In this case, since the addition amount of the sulfonic acid compound was too large, the color tone of the polyester was poor and D% was large. In Comparative Example 7, the EPA with respect to TPA used in the esterification reaction was
Since the ratio of G is large, D% is large.
Due to the small ratio of EG to PA, the TPA particles did not dissolve in the reaction system even when they were retained in the esterification reaction tank for 20 hours, and could not be supplied to the polycondensation step. In Comparative Example 9, since the esterification reaction rate of the esterified product of less than 90% was supplied to the polycondensation reaction tank, the polymerization degree did not increase even after allowing the mixture to stand for 8.2 hours.

[0035]

According to the present invention, it is possible to continuously produce a polyester having excellent transparency using an antimony trioxide catalyst system.

[Brief description of the drawings]

FIG. 1 is a diagram schematically showing the flow of the method of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Slurry tank 2 Esterification reaction tank 3 1st polycondensation reaction tank 4 2nd polycondensation reaction tank 5 Catalyst addition pump 6 Glycol distillation column 7 Decompression device

Claims (1)

[Claims] When a polyester having an intrinsic viscosity of 0.50 dl / g or more is continuously produced, 1.0 to 2.5 mol of ethylene glycol is added to 1 mol of terephthalic acid in an esterification reaction tank in which a polyester low polymer is present. Of the slurry and 3 to 10 parts of antimony trioxide added in the polycondensation reaction.
A molar amount of phosphoric acid is continuously supplied, the esterification reaction is performed until the esterification reaction rate becomes 90% or more while removing generated water outside the system, and then the esterified product is continuously supplied to the polycondensation reaction tank. And a polycondensation of 0.5 to 1.5 × 10 ^-4 moles of antimony trioxide and 0.5 to 1.5 mole times the amount of antimony trioxide with respect to 1 mole of the acid component constituting the polyester. A continuous process for producing polyester having excellent transparency.