JPH10265561A - Production of polyester - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a polyester by reusing a distilled and recovered glycol component as a part of the raw material in a process for producing the polyester, enabling to safely produce the polymer having constant physical values without changing the reactivity and physical properties of the polymer, even when the recovered and unurified glycol is used. SOLUTION: In this method for producing a polyester by continuously polymerizing a dicarboxylic acid component consisting mainly of terephthalic acid or its lower alkyl ester with a glycol component consisting mainly of ethylene glycol in the presence of a catalyst, the glycol component distilled out and recovered in the process for producing the polyester is again supplied to the reaction system as a part of the raw material. Therein, the amount of the catalyst contained in the recovered glycol component is detected by the use of a detector (preferably a fluorescent X-ray analyzer during the transport of the recovered glycol component, and the amounts of the catalyst and/or the glycol component newly supplied to the reaction system are controlled in response to the detection results.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a method for producing a polyester. More specifically, the present invention relates to an improvement in a method of reusing a glycol component distilled and recovered in a polyester production process as a part of a raw material. Polyester is excellent in mechanical strength, chemical stability, transparency, hygiene, gas barrier properties, etc., and is lightweight and inexpensive, so it is widely used as a sheet and container for various packaging materials. I have.

[0002]

2. Description of the Related Art Generally, a polyester is produced by subjecting a dicarboxylic acid component and a glycol component to an esterification reaction, and then reacting the esterification reaction product in the presence of a polycondensation catalyst. In this polycondensation step, the polycondensation reaction is performed while distilling off the distillate generated in the polycondensation reaction outside the system. The distillate is mainly a glycol component (eg, ethylene glycol), and the stabilizer and the polycondensation catalyst added in the polycondensation step are also distilled out of the reaction system together with the glycol component. Among the polycondensation catalysts, 15 to 20% for the antimony catalyst and 50 to 50% for the germanium catalyst.
60% is contained in the distillate.

[0003] Various attempts have heretofore been made to attempt to recycle the glycol component or the catalyst component distilled and recovered from the polycondensation step for the production of polyester. For example, in Japanese Patent Publication No. 48-6398,
A method has been proposed in which a distillate is concentrated, water is added to hydrolyze it, and a germanium compound is recovered as germanium dioxide and then reused. Also, Japanese Patent Application Laid-Open No. 54-8 / 1979
JP-A-3995 and JP-A-55-110120 propose a method of reusing a distillate, that is, a glycol component containing a catalyst distilled and recovered in a production process, without separating and purifying the same. I have.

[0004]

However, the method of using the distillate as it is is extremely advantageous in terms of cost, but especially in the case of continuous polymerization, the distillate to be added again as a raw material is used. The amount of catalyst in the reaction system is not stable for a long time until the amount of catalyst contained in the solvent and the amount of catalyst in the distillate distilled off from the polycondensation step reach equilibrium. If the amount of the catalyst in the system is not stable, not only the reaction state of the melt polymerization or the solid-phase polymerization performed as needed after the melt polymerization, but also the physical properties of the polymer fluctuate accordingly. Furthermore,
Even if the amount of the polymerization catalyst is slightly changed, fine adjustment in a short time is very difficult for the above-mentioned reason. To address this problem, once the distillate is once stored in the tank, sampling and manual analysis of the catalyst can be performed, and the amount of newly added catalyst can be adjusted according to the results.
Since such a method is complicated and requires a plurality of distillate storage tanks, there is a problem that the advantage of reuse is not sufficiently exhibited.

It is an object of the present invention to provide a process for producing a polyester by reusing a distillate-collected glycol component (hereinafter referred to as “recovered glycol”) as a part of a raw material in a polyester production process. It is an object of the present invention to provide a method for producing a polyester capable of stably producing a polymer having a constant physical property value without changing the reactivity and the polymer physical properties even when the recovered glycol is reused.

[0006]

Means for Solving the Problems The present inventors have conducted intensive studies in order to solve the above-mentioned problems, and as a result, have found that recovered glycol is
When adding to the reaction system, the amount of the catalyst and the amount of the stabilizer contained in the recovered glycol in the transfer line were measured, and the purified glycol (the catalyst addition pipe and the stabilizer addition pipe and / or the freshly supplied glycol free of the catalyst) was measured. The amount of the catalyst and the stabilizer in the system can be adjusted arbitrarily by feeding back to the addition pipe of the "purified glycol"), so that the reactivity and the polymer properties were not changed, and were distilled out of the system. The inventors have found that the catalyst and the glycol component can be effectively reused, and have completed the present invention.

That is, the gist of the present invention is to continuously produce polyester in the presence of a catalyst using a dicarboxylic acid component mainly composed of terephthalic acid or a lower alkyl ester thereof and a glycol component mainly composed of ethylene glycol as main raw materials. In doing so, when the glycol component distilled and recovered in the polyester production process is supplied to the reaction system again as a part of the raw material, the amount of the catalyst contained in the recovered glycol component being transferred is measured using a detector. Detecting the amount of the catalyst and / or glycol component to be newly supplied to the reaction system in accordance with the detection result, and adjusting the supply amount of the glycol component. Hereinafter, the present invention will be described in detail.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION

(Production of Polyester) The polyester to be used in the present invention is obtained by esterifying a dicarboxylic acid component mainly composed of terephthalic acid or lower alkyl ester and a glycol component mainly composed of ethylene glycol, followed by polycondensation. Manufactured. In addition, the lower alkyl ester of terephthalic acid refers to dimethyl ester or diethyl ester of terephthalic acid.

The dicarboxylic acid components other than terephthalic acid include phthalic acid, isophthalic acid, naphthalenedicarboxylic acid, 4,4'-diphenylsulfonedicarboxylic acid,
4′-biphenyldicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, 1,3-phenylenedioxydiacetic acid and structural isomers thereof, dicarboxylic acids such as malonic acid, succinic acid, adipic acid and derivatives thereof, p- Oxy acids such as hydroxybenzoic acid and glycolic acid or derivatives thereof are mentioned.

The glycol components other than ethylene glycol include diethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, pentamethylene glycol, hexamethylene glycol, neopentyl glycol and the like. Examples thereof include aliphatic glycols, alicyclic glycols such as cyclohexane dimethanol, and aromatic dihydroxy compound derivatives such as bisphenol A and bisphenol S.

In the present invention, recovered glycol is used as at least a part of the glycol component. The recovered glycol may, of course, be used as it is, or may be used after a treatment such as filtration. The amount of recovered glycol used is usually 0.0
It is 4-0.66, preferably 0.125-0.66. The raw material containing the dicarboxylic acid component, the purified glycol component, and the recovered glycol as described above is allowed to form bis (β-hydroxyethyl) terephthalate and / or an oligomer thereof by an esterification reaction. The melt polycondensation is performed under high temperature and reduced pressure in the presence of the agent to form a polymer.

The esterification catalyst does not need to be particularly used because terephthalic acid serves as an autocatalyst in the esterification reaction, but it can be carried out in the presence of an esterification catalyst. It can be carried out in the presence of. As the polycondensation catalyst, germanium compounds,
Compounds soluble in the reaction system such as an antimony compound, a titanium compound, a cobalt compound, and a tin compound are used alone or in combination.

Examples of the stabilizer include phosphoric esters such as trimethyl phosphate, triethyl phosphate and triphenyl phosphate, triphenyl phosphite,
Phosphites such as trisdodecyl phosphite,
Methyl acid phosphate, dibutyl phosphate,
Monobutyl phosphate acidic phosphate, phosphoric acid,
Phosphorus compounds such as phosphorous acid, hypophosphorous acid and polyphosphoric acid are preferred.

The use ratio of the above-mentioned catalyst is as follows:
Usually 5 to 2000 ppm by weight of metal in the catalyst,
It is preferably in the range of 10 to 500 ppm, and the proportion of the stabilizer used is generally 10 to 1000 ppm, preferably 20 to 100 ppm, as the weight of phosphorus atoms in the stabilizer in all the polymerization raw materials.
It is in the range of 200 ppm. The supply of the catalyst and the stabilizer can be performed at any stage of the esterification reaction in addition to the preparation of the raw material slurry, and further, can be performed at an early stage of the polycondensation reaction step.

The reaction temperature of the esterification reaction is usually 240
To 280 ° C., and the reaction pressure is usually 1 to 3 kg / cm ²
G. The reaction temperature during the polycondensation reaction is usually 25
0 to 300 ° C., and the reaction pressure is usually 500 to 0.1 m
mHg. Such an esterification reaction and a polycondensation reaction may be performed in one step or may be performed in a plurality of steps. The polyester thus obtained has an intrinsic viscosity of usually 0.45 to 0.70 dl / g, and is formed into chips by a conventional method. The average particle size of the polyester chips is
Usually 2.0 to 5.5 mm, preferably 2.2 to 4.0 m
m.

Next, the polymer obtained by the melt polycondensation as described above is subjected to solid-phase polymerization, if necessary. The polymer chip to be subjected to solid-state polymerization is preliminarily crystallized by heating to a temperature lower than the temperature at which solid-state polymerization is performed,
It may be subjected to solid phase polymerization. The solid-state polymerization step comprises at least one stage, usually at 190 to 230 ° C, preferably at 19 ° C.
Polymerization temperature of 5 to 225 ° C, usually 1 kg / cm ² G to 10
mmHg, preferably 0.5 kg / cm ² G to 100 m
The reaction is carried out under a polymerization pressure of mHg under a flow of an inert gas such as nitrogen, argon or carbon dioxide. The solid-state polymerization time may be shorter as the temperature is higher, but is usually within 1 to 50 hours, preferably 5 to 30 hours, more preferably 10 to 30 hours.
25 hours. The intrinsic viscosity of the polymer obtained by solid-state polymerization is usually in the range of 0.68 to 0.90 dl / g.

(Detection of amount of catalyst and the like in recovered glycol)
The present invention, in the above polyester production process, when the distillate and recovered glycol component is supplied to the reaction system again as a part of the raw material, using a detector installed in the transfer line of the recovered glycol component, Detects the amount of catalyst and stabilizer contained in the recovered glycol component during transfer, and adjusts the amount of newly supplied catalyst and stabilizer and / or purified glycol and / or recovered glycol according to the results. The feature is that it does. Among them, a method of adjusting the supply amounts of the catalyst and the stabilizer is preferable because the most stable control can be performed. As a specific preferable control method, in the step of preparing the slurry comprising the dicarboxylic acid component and the glycol component, the supply rate of the recovered glycol is maximized as much as possible, and the desired amount of the main glycol component is determined by the amount of the purified glycol. Adjust to. Further, in this method, the amount of the catalyst and the amount of the stabilizer supplied from the recovered glycol component, which is insufficient, is supplied from each supply pipe. In the case of a multi-stage reaction, all of the glycol components may be supplied to the first-stage esterification reaction tank as a mixed slurry with the dicarboxylic acid component. The supply amount may be adjusted.

The detector used in the present invention is preferably an online type analyzer which does not hinder the flow of the recovered glycol, and the type is not particularly limited. As generally known analyzers, there are an atomic absorption analyzer, a plasma emission analyzer, a fluorescent X-ray analyzer, and the like, and as an online analyzer installed in a plant, a fluorescent X-ray analyzer is particularly preferable. . Further, in the case of a phosphorus compound as a stabilizer, a colorimetric analyzer may be additionally provided.

Such a detector is preferably installed in a transfer line of the recovered glycol. However, a side pipe branched from the transfer line is provided, and a detector is installed in this side pipe, and the recovered glycol flowing through the side pipe is provided. You may analyze the content of a component. It is preferable to be in the transfer line because the measurement error is small. In addition, the objective can be achieved even if the sample collected from the transfer line is analyzed by a detection tube in another place.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described with reference to an embodiment based on a schematic diagram showing an example of a polyester production apparatus shown in FIG. 1, but the present invention is limited to the embodiment unless it exceeds the gist thereof. Not something.

Example 1 Using terephthalic acid (hereinafter referred to as "TPA") and ethylene glycol (hereinafter referred to as "EG") as raw materials, germanium dioxide as a catalyst, and phosphoric acid as a stabilizer,
A polyester was produced in a reaction system as shown in FIG. Bis (β-hydroxyethyl) terephthalate (hereinafter referred to as “B
HET ") in the first-stage esterification reactor 5
The mixture of purified EG and full recovered EG is continuously supplied with a slurry in which the molar ratio of EG to TPA is 1.5 at 3.4 Ton / Hr, and esterification is performed in the first and second esterification reaction tanks 5 and 6. After that, supply to the polycondensation reaction step,
A continuous operation was performed for 10 days. During this operation, a fluorescent X-ray analyzer (manufactured by Metorex, CO
(URIER 10), the amount of germanium and the amount of phosphorus in the collected EG were continuously measured. For phosphorus analysis, a colorimetric analyzer (manufactured by Mitsubishi Chemical Corporation, TP-30) was also installed and measured. From the measurement results, the amount added to the polymer after melt polymerization was 77 pp as the amount of germanium metal.
The supply amount of germanium dioxide and the supply amount of phosphoric acid in the slurry preparation tank 2 were controlled so that m and the phosphorus amount became 38 ppm. During such a continuous operation,
The polymer after the melt polymerization was sampled at intervals of 4 hours, and the amount of germanium metal of germanium dioxide as a catalyst, the amount of phosphoric acid as a stabilizer and the intrinsic viscosity were measured. The metal content of germanium in the polymer is 40.0 ± 0.8 p
pm, the amount of phosphorus was 34.0 ± 0.4 ppm, and the intrinsic viscosity was 0.550 ± 0.005 dl / g.

Comparative Example 1 The recovered EG was extracted at two-hour intervals without performing on-line control, and the amounts of germanium and phosphorus caused by the catalyst were measured, and the amounts of catalyst and stabilizer added were controlled manually.
Performed under the same conditions as in Example 1. The metal content of germanium in the polymer is 40.0 ± 3.2 ppm, and the phosphorus content is
34.0 ± 1.6 ppm, intrinsic viscosity 0.550 ± 0.
It was 012 dl / g.

Comparative Example 2 Without performing on-line control of the recovered EG, the polymer after completion of melt polymerization was withdrawn at 2 hour intervals, and the amount of catalyst, phosphorus, and intrinsic viscosity were measured. The operation was performed under the same conditions as in Example 1 except that the amount of phosphorus was controlled. The catalyst amount of the polymer is 40.0 ± 7.4 p
pm, the amount of phosphorus was 34.0 ± 3.1 ppm, and the intrinsic viscosity was 0.550 ± 0.018 dl / g.

From the examples and comparative examples, according to the production method of the present invention, even if the recovered ethylene glycol is used,
It can be seen that the polyester amount after the melt polymerization, the amount of the stabilizer and the limiting viscosity can all be produced in a uniform polyester with no variation in the values. It can be seen that polyester was not obtained in which both the amount of the stabilizer and the intrinsic viscosity were greatly varied and the values were constant.

[0025]

According to the present invention, even when the recovered glycol component generated in the polyester production process is recovered and reused without purification, the reactivity and the polymer properties are not changed, and the catalyst and the catalyst can be used. The glycol component can be effectively reused.

[Brief description of the drawings]

FIG. 1 is a schematic view showing an example of a polyester production apparatus used for carrying out the present invention.

[Explanation of symbols]

 Reference Signs List 1 TPA hopper 2 Slurry preparation tank 3 Catalyst preparation tank 4 Stabilizer preparation tank 5 First esterification reaction tank 6 Second esterification reaction tank 7 Metal analyzer 8 Purified glycol supply line 9 Recovered glycol supply line

Claims (4)

[Claims] 1. A method for producing a polyester continuously using a dicarboxylic acid component mainly composed of terephthalic acid or a lower alkyl ester thereof and a glycol component mainly composed of ethylene glycol in the presence of a catalyst in the presence of a catalyst. When the glycol component distilled and recovered in the manufacturing process is supplied to the reaction system again as a part of the raw material, the amount of catalyst contained in the recovered glycol component being transferred is detected using a detector, and the result is determined. A method for producing a polyester, characterized in that a supply amount of a catalyst and / or a glycol component newly supplied to a reaction system is adjusted accordingly. 2. A method for producing a polyester continuously using a dicarboxylic acid component mainly composed of terephthalic acid or a lower alkyl ester thereof and a glycol component mainly composed of ethylene glycol in the presence of a catalyst and a stabilizer. When the glycol component distilled and recovered in the polyester production process is supplied to the reaction system again as a part of the raw material, the amount of the catalyst and the stabilizer contained in the recovered glycol component being transferred is determined by using a detector. A method for producing a polyester, comprising detecting the amount of a catalyst and a stabilizer and / or a glycol component to be newly supplied to a reaction system in accordance with the detection result. 3. The method according to claim 1, wherein the amount of the catalyst contained in the recovered glycol component is detected using a fluorescent X-ray analyzer. 4. The method according to claim 2, wherein the amounts of the catalyst and the stabilizer contained in the recovered glycol component are simultaneously detected using a fluorescent X-ray analyzer.