JPH10147636A - Production of polyester - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a process for the production of a polyester while efficiently reusing an unreacted dihydroxy compound and a polycondensation catalyst recovered in the production process. SOLUTION: A polyester is produced from a dicarboxylic acid and a dihydroxy compound by a process including an esterification step and a polycondensation step. A polycondensation catalyst is dissolved in a distillate distilled out and recovered in the polycondensation step and containing the dihydroxy compound and the polycondensation catalyst. The obtained catalyst solution is supplied to the esterification step and/or the polycondensation step.

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 a polyester, and more particularly, to a polyester capable of efficiently recycling an unreacted dihydroxy compound and a polycondensation catalyst which are distilled and recovered in a production step. It relates to a manufacturing method.

[0002]

BACKGROUND OF THE INVENTION Conventionally, polyesters such as polyethylene terephthalate have been widely used in bottles, fibers, films, sheets and the like. A polyester is usually produced by subjecting a dicarboxylic acid and a dihydroxy compound to an esterification reaction, and then subjecting the resulting esterification reaction product (lower polycondensate) to polycondensation in the presence of a polycondensation catalyst. After the polyester obtained by this polycondensation reaction is formed into chips, it is usually further solid-phase polycondensed to increase the intrinsic viscosity.

In such a polyester production process, the polycondensation process is carried out while distilling unreacted dihydroxy compound (eg, ethylene glycol) out of the system. Part of the polycondensation catalyst supplied to the polycondensation step (for example, 60 to 70% for a germanium catalyst)
Is distilled out of the system together with the dihydroxy compound. For this reason, the polyester is usually produced while continuously supplying a polycondensation catalyst to the esterification step and / or the polycondensation step.

When the dihydroxy compound containing the polycondensation catalyst, which has been distilled off and recovered from the polycondensation step, is recycled to the esterification step and / or the polycondensation step, the dihydroxy compound and the polycondensation catalyst can be effectively used. Can be. However, the amount of polycondensation catalyst contained in the distillate distilled from the polycondensation step is usually smaller than the desired amount of catalyst. For this reason, a dihydroxy compound solution containing a polycondensation catalyst is separately added so that a desired amount of catalyst is obtained in the polycondensation step.However, since an excess dihydroxy compound is added, the polycondensation reaction time is reduced. There was a problem of becoming long.

[0005]

DISCLOSURE OF THE INVENTION The present invention has been made in view of the above-mentioned prior art, and comprises an esterification step comprising dissolving a polycondensation catalyst in a distillate recovered from the polycondensation step and recovering the distillate. And / or to supply to a polycondensation step, a raw material for producing a polyester and a polycondensation catalyst can be effectively used, and an object of the present invention is to provide a method for producing a polyester which does not deteriorate the quality of the polyester. And

[0006]

SUMMARY OF THE INVENTION According to the present invention, there is provided a method for producing a polyester, wherein a polyester is produced from a dicarboxylic acid and a dihydroxy compound by a process including an esterification step and a polycondensation step, and the polyester is distilled and recovered from the polycondensation step. It is characterized in that the polycondensation catalyst is dissolved in the distillate containing the dihydroxy compound and the polycondensation catalyst, and the obtained catalyst solution is supplied to the esterification reaction and / or the polycondensation step.

As a method of dissolving the polycondensation catalyst in the distillate, there are a method of dissolving by heating, a method of dissolving in the presence of an organic acid, and a method of dissolving in the presence of a basic compound.

The polycondensation catalyst includes germanium dioxide, antimony trioxide, antimony acetate and the like.
In the present invention, the distillate is subjected to a purification step including (a) a distillation step, (b) a depolymerization step, (c) a decolorization step, and, if necessary, (d) an iron removal step. May be dissolved in the distillate.

[0009]

DETAILED DESCRIPTION OF THE INVENTION Hereinafter, the method for producing the polyester of the present invention will be specifically described. In the present invention, when a polyester is produced from a dicarboxylic acid and a dihydroxy compound by a step including an esterification step and a polycondensation step, the polyester is distilled and recovered from the polycondensation step.
The polycondensation catalyst is dissolved in the distillate containing the dihydroxy compound and the polycondensation catalyst, and the resulting catalyst solution is supplied to the esterification reaction and / or the polycondensation step.

[0010] In the esterification step, a slurry containing a dicarboxylic acid and a dihydroxy compound is supplied. In the present invention, a catalyst solution obtained by dissolving a polycondensation catalyst in a distillate recovered from the polycondensation step and recovered as described later is supplied to the esterification step and / or the polycondensation step described later.
The catalyst solution is preferably supplied to the esterification step. The slurry and the catalyst solution may be mixed in advance and supplied to the esterification step, or may be separately supplied to the esterification step.

When the slurry and the catalyst solution are preliminarily mixed and supplied to the esterification step, the mixture usually contains 1.02 to 2.0 mol, preferably 1.03 to 2.0 mol, per mol of dicarboxylic acid. Desirably, 1.5 moles of the dihydroxy compound is included. When the slurry and the catalyst solution are separately supplied to the esterification step, the dicarboxylic acid contained in the slurry and the dihydroxy compound contained in the slurry and the catalyst solution are used so as to have the above ratio.

The dicarboxylic acids include aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, phthalic acid, naphthalenedicarboxylic acid, diphenyldicarboxylic acid and diphenoxyethanedicarboxylic acid; succinic acid, adipic acid, azelaic acid, sebacic acid, decane acid Aliphatic dicarboxylic acids such as dicarboxylic acids; alicyclic dicarboxylic acids such as cyclohexanedicarboxylic acids; Further, these ester derivatives can also be used.

The dihydroxy compounds include ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, trimethylene glycol, butanediol, cyclohexanediol, polytetramethylene glycol, cyclohexanedimethanol, 1,3-bis (2-hydroxyethoxy) Benzene, 1,4-
Bis (2-hydroxyethoxy) benzene, bis (4-β-
(Hydroxyethoxyphenyl) sulfone and the like. Further, these ester derivatives can also be used.

The slurry may contain other compounds, for example, monofunctional compounds such as benzoylbenzoic acid, diphenylsulfonemonocarboxylic acid, stearic acid, methoxypolyethylene glycol and phenoxypolyethylene glycol, and trimesic acid. , Trimethylolethane, trimethylolpropane, trimethylolmethane, and pentaerythritol. These other compounds are used in an amount of 0.1% based on the total amount of the dicarboxylic acid and the dihydroxy compound.
It is optionally used in an amount of from 01 to 20 mol%, preferably from 0.05 to 10 mol%.

The esterification reaction is carried out by using a reactor in which at least two esterification reactors are connected in series, and under conditions where the dihydroxy compound is refluxed, water produced by the reaction is removed outside the system by a rectification column. It is implemented while. When the esterification reaction is carried out, for example, in two stages, the first-stage esterification reaction is usually carried out at a temperature of 240 to 270 ° C., preferably 245 to 265 ° C., and usually 0.2 to 270 ° C.
3kg / cm ² -G, preferably 0.5~2kg / cm ² -
It is performed under G pressure. The second stage esterification reaction is
Usually at a temperature of 250 to 280 ° C, preferably 255 to 275 ° C, usually 0 to 1.5 kg / cm ² -G, preferably 0
It is performed under a pressure of ~ 1.3 kg / cm ² -G.

[0016] The esterification reaction may be carried out in the presence of a small amount of a basic compound. Examples of the basic compound include tertiary amines such as triethylamine, tri-n-butylamine and benzyldimethylamine, tetraethylammonium hydroxide, tetra-n-butylammonium hydroxide,
Examples include quaternary ammonium hydroxides such as trimethylbenzyl ammonium hydroxide and lithium carbonate, sodium carbonate, potassium carbonate, sodium acetate and the like.
If, for example, terephthalic acid and ethylene glycol are subjected to an esterification reaction in the presence of such a basic compound, polyethylene terephthalate having a small content of dioxyethylene terephthalate component units can be obtained.

In this esterification step, a low-order condensate is obtained as an esterification reaction product of the dicarboxylic acid and the dihydroxy compound.
A low order condensate of about 5000 is obtained. This low-order condensate is then supplied to a polycondensation (liquid-phase polycondensation) step.

In the polycondensation step, in the presence of a polycondensation catalyst,
The low-order condensate obtained in the esterification step is heated under reduced pressure to a temperature equal to or higher than the melting point of the obtained polyester (usually 270-3
(00 ° C.) for polycondensation. This polycondensation reaction is carried out while distilling unreacted dihydroxy compounds and the like out of the reaction system. The distillate collected by distillation contains a dihydroxy compound, a polycondensation catalyst and the like. In the present invention, a catalyst solution in which a polycondensation catalyst is dissolved in a distillate distilled and recovered from the polycondensation step may be supplied to the polycondensation step.

The polycondensation reaction may be performed in one stage or may be performed in a plurality of stages. For example, if the polycondensation reaction is 2
When carried out in stages, the first stage polycondensation reaction is usually performed at 250 to 290 ° C, preferably 260 to 280 ° C.
At a temperature of 500 ° C., usually 500 to 20 Torr, preferably 2 to 20 Torr.
It is performed under a pressure of 00 to 30 Torr. The second stage polycondensation reaction is usually performed at 265 to 300 ° C., preferably at 27 to 300 ° C.
The reaction is carried out at a temperature of 0 to 295 ° C., usually at a pressure of 10 to 0.1 Torr, preferably 5 to 0.5 Torr.

As the polycondensation catalyst, germanium compounds such as germanium dioxide, germanium tetraethoxide and germanium tetra-n-butoxide; antimony catalysts such as antimony trioxide and antimony acetate; and titanium catalysts such as titanium tetrabutoxide are used. Can be. Among these catalysts, it is preferable to use germanium dioxide, antimony trioxide, and antimony acetate.

In the polycondensation step, a stabilizer may be added. Examples of the stabilizer include phosphates such as trimethyl phosphate, triethyl phosphate, tri-n-butyl phosphate, trioctyl phosphate, and triphenyl phosphate; Phosphate esters such as phosphates, methyl acid phosphate, isopropyl acid phosphate, butyl acid phosphate, dibutyl phosphate, monobutyl phosphate and dioctyl phosphate, and phosphorus compounds such as phosphoric acid and polyphosphoric acid are used.

In the polycondensation reaction, the polycondensation catalyst reacts with the dicarboxylic acid in an amount of 0.00 in terms of metal atoms in the polycondensation catalyst.
005-0.2% by weight, preferably 0.001-0.1%
Desirably it is present in a proportion by weight. Therefore, when a catalyst solution in which a polycondensation catalyst is dissolved in a distillate is supplied to the esterification step and / or the polycondensation step, the catalyst concentration of the catalyst solution is such that the catalyst concentration in the polycondensation step is low. It is adjusted so as to be within the above range.

The intrinsic viscosity [η] of the polyester obtained in the above polycondensation step is usually 0.40 to 1.0 dl.
/ G, preferably in the range of 0.50 to 0.90 dl / g. The polyester obtained in the polycondensation step is usually melt-extruded and formed into particles (chips).

In the present invention, the polyester obtained in the polycondensation step may be further subjected to solid phase polycondensation. For example, the chip-like polyester obtained above is heated at 160 ° C.
Solid phase polycondensation may be carried out at a temperature lower than the melting point, preferably at a temperature of 170 to 220 ° C., for 8 to 40 hours, preferably 15 to 30 hours. The intrinsic viscosity of the polyester after the solid-phase polycondensation is desirably 0.60 to 1.00 dl / g, preferably 0.75 to 0.95 dl / g.

The polyester production step including the esterification step and the polycondensation step as described above can be carried out by either a batch system or a semi-continuous system. In the present invention, the catalyst solution obtained by dissolving the polycondensation catalyst in the distillate distilled and recovered in the above polycondensation step is supplied again to the esterification step and / or the polycondensation step. . The distillate distilled and recovered in the polycondensation step contains an unreacted dihydroxy compound at a ratio of about 80 to 95% by weight, and an insoluble oligomer at a rate of about 5% by weight or less. Further, the distillate contains a polycondensation catalyst. Since the content of the polycondensation catalyst in this distillate is small, when the distillate is supplied again to the esterification step and / or the polycondensation step, the concentration of the polycondensation catalyst in the polycondensation step becomes low. For this reason, it is necessary to add a polycondensation catalyst to the distillate in order to make the polycondensation catalyst concentration in the polycondensation step a desired concentration.

As a method of preparing a catalyst solution by dissolving the polycondensation catalyst in the distillate, there is a method of dissolving the polycondensation catalyst in the distillate by heating. The heating temperature at this time is 60-
The temperature is 250 ° C, preferably 70 to 190 ° C, more preferably 80 to 180 ° C. When the heating temperature is lower than 60 ° C., the amount of the polycondensation catalyst dissolved is small. When the heating temperature is higher than 250 ° C., the polymerization activity of the polycondensation catalyst may decrease or the polyester may be colored. At the time of the heating, low-temperature distillates such as water and aldehyde can be removed.

Another method for preparing a catalyst solution by dissolving the polycondensation catalyst in the distillate includes dissolving the polycondensation catalyst in the distillate in the presence of an organic acid. Examples of the organic acid include oxalic acid, citric acid, tartaric acid, malic acid, glycolic acid, lactic acid, and glutaric acid. Among these, if oxalic acid, citric acid or tartaric acid is used, the solubility of the polycondensation catalyst is high. The organic acid is used in an amount of 5 to 30 parts by weight, preferably 20 to 25 parts by weight, based on 100 parts by weight of the dihydroxy compound in the distillate.

As another method for preparing a catalyst solution by dissolving the polycondensation catalyst in the distillate, there is a method in which the catalyst is dissolved in the distillate in the presence of a basic compound. Examples of the basic compound include tertiary amines such as triethylamine, tri-n-butylamine and benzyldimethylamine; and quaternary ammonium hydroxides such as tetraethylammonium hydroxide, tetra-n-butylammonium hydroxide and trimethylbenzylammonium hydroxide. And lithium carbonate, sodium carbonate, potassium carbonate, sodium acetate and the like. The basic compound is used in an amount of 5 to 30 parts by weight, preferably 20 to 25 parts by weight, based on 100 parts by weight of the dihydroxy compound in the distillate.

The distillate contains oligomers such as cyclic trimers and low polymers of dihydroxy compounds and dicarboxylic acids, and most of the insoluble oligomers are cyclic trimers. For example, when the dihydroxy compound is ethylene glycol and the dicarboxylic acid is terephthalic acid, the distillate is a cyclic trimer of ethylene glycol and terephthalic acid, bis-β-hydroxyethyl terephthalate or a low polymer thereof. Oligomers are contained.

In the present invention, the distillate may be purified before dissolving the polycondensation catalyst in the distillate distilled off from the polycondensation step to prepare a catalyst solution. Purification of the distillate includes the following (a) distillation step, (b) depolymerization step and (c) decolorization step, and if necessary (d) iron removal step, (e)
It is performed by a purification step including a filtration step. Each step is
(A), (b), and (c) are preferably performed in this order. When the purification step includes (d) an iron removal step, (a)
(B), (c), and (d) are preferably performed in this order. Further, when the method includes the (e) filtration step, it is preferable to perform the (e) filtration step after the (b) depolymerization step.

(A) In the distillation step, the distillate is distilled to remove water, low-temperature distillate and the like in the distillate. Distillation of the distillate is preferably performed under reduced pressure and at a temperature not higher than the boiling point of the dihydroxy compound. For example, when the dihydroxy compound is ethylene glycol, specifically, 20 to 600 Torr, preferably 50 to 1 Torr
The reaction is performed at a pressure of 50 Torr and a temperature of 100 to 200 ° C, preferably 120 to 170 ° C. In this (a) distillation step, the water content of the distillate is desirably 1.0% or less, preferably 0.5% or less. (A) The distillate that has passed through the distillation step has been removed from the distillate that has not passed through the distillation step because of removal of water, low-temperature distillate, etc., in the (c) decolorization step and (d) the iron removal step. This has the effect of reducing the load and prolonging the breakthrough time.

(B) In the depolymerization step, oligomers and the like in the distillate are depolymerized. For example, when the dihydroxy compound is ethylene glycol and the dicarboxylic acid is terephthalic acid, an insoluble matter such as a cyclic trimer present in the distillate is heated in a state in which ethylene glycol is excessively coexisted. The insoluble matter dissolved in the distillate is depolymerized to, for example, bishydroxyethyl terephthalate.

(B) In the depolymerization step, the distillate is subjected to reduced pressure, atmospheric pressure or increased pressure at a temperature of usually 100 to 180 ° C., preferably 130 to 170 ° C., for 10 minutes to 5 hours, preferably It is carried out by holding for 30 minutes to 4 hours, more preferably for 1 hour to 4 hours. (B) The depolymerization step comprises:
Usually, at a temperature of 100 to 180 ° C, preferably 130 to 170 ° C, the residence time is usually 10 minutes to 5 hours, preferably 3 minutes.
It can also be carried out using a distillation column having a bottom part volume so as to be 0 minutes to 4 hours, more preferably 1 hour to 4 hours. (B) In the depolymerization step, the insoluble oligomer content of the distillate is desirably 0.2% by weight or less, preferably 0.1% by weight or less, more preferably 0.05% by weight or less. The distillate (depolymerized solution) that has passed through the depolymerization step (b) has a low content of oligomers, particularly insoluble oligomers.
These steps can be performed without blocking even if the iron removing step is performed.

(C) In the decolorizing step, the colored matter in the distillate is removed by contacting the distillate with activated carbon. The contact between the distillate and the activated carbon is usually performed at a temperature of 50 to 100 ° C., preferably 70 to 90 ° C., and the superficial velocity is usually 0.1 to 100 ° C.
6.0 hr ^-1 , preferably 0.167 to 4.0 hr ^-1 ,
More preferably, the reaction is performed at 0.20 to 2.0 hr ^-1 . In this (c) decolorization step, the distillate T ₃₈₀ (wavelength 3
The transmittance of light having a wavelength of 80 nm is usually 97% or more, preferably 98% or more. When a distillate having a T ₃₈₀ of 98% or more is supplied to the esterification step, the quality of the obtained polyester, particularly, the hue is not reduced. T ₃₈₀ is a spectrophotometer (U-110 manufactured by Hitachi, Ltd.)
Using 0), a sample (distillate) is placed in a 10 mm quartz cell, and measurement is performed using distilled water as a control solution. (C) In the decolorizing step, the colored matter in the distillate can be removed without substantially reducing the amount of the polycondensation catalyst in the distillate.

The distillate may contain iron, and when removing the iron, (d) a step of removing iron is performed as necessary. (D) In the iron removing step, iron in the distillate is removed by contacting the distillate with the ion exchange resin. Examples of the ion exchange resin include a cation exchange resin, an anion exchange resin, and an amphoteric ion exchange resin. Among them, a cation exchange resin, particularly a strongly acidic cation exchange resin is preferable. The contact between the distillate and the ion exchange resin is usually 50 to 100 ° C, preferably 70 to 100 ° C.
At a temperature of 90 ° C., the superficial velocity is usually 0.1 to 6.0 h.
The reaction is carried out at r ^-1 , preferably 0.167 to 4.0 hr ^-1 , more preferably 0.20 to 2.0 hr ^-1 . In this (d) iron removing step, the iron content of the distillate is reduced to 2 pp.
m, preferably 0.5 ppm or less. When a distillate having an iron content of 2 ppm or less is supplied to the esterification step and / or the polycondensation step, the hue of the obtained polyester is hardly reduced.

In the present invention, (e) a filtration step may be further performed in addition to the above steps. (E) In the filtration step, insoluble oligomers in the distillate are removed by filtering the distillate. (E) The filtration step is preferably performed after (b) the depolymerization step, and (e) after the (b) depolymerization step.
When the filtration step is performed, a large-sized filtration device such as a pressure filtration device or a vacuum filtration device is not particularly required, and the insoluble oligomer is filtered and removed by a simple filtration device such as a commonly used cartridge filter and a strainer. Is possible. Further, if the filtration step is performed after the depolymerization step, the filtration time can be reduced and the filtration equipment can be simplified. Further, the life of the filter can be extended.

The distillate purified as described above preferably contains a dihydroxy compound in a proportion of 96.0 to 99.0% by weight, preferably 96.5 to 98.5% by weight. . The water content of the purified distillate is preferably 1.0% by weight or less, more preferably 0.5% by weight or less.

As described above, the polyester obtained by supplying the catalyst solution obtained by dissolving the polycondensation catalyst in the distillate to the esterification step and / or the polycondensation step is different from the polyester produced from unused raw materials. It has almost the same quality.

[0039]

According to the polyester production method of the present invention, the dihydroxy compound and the polycondensation catalyst distilled off from the polycondensation step can be effectively reused, so that the production efficiency is improved and the production cost is reduced. Can be
Moreover, the quality of the obtained polyester is not reduced.

[0040]

EXAMPLES Hereinafter, the present invention will be described more specifically based on examples, but the present invention is not limited to these examples.

[0041]

Example 1 Esterification step (1) 100 parts by weight of terephthalic acid and ethylene glycol
Esterification was carried out by a conventional method using 8 parts by weight. The esterification reaction was carried out at a reaction temperature of 260 ° C. and a pressure of 1.7 kg /
cm ² -G.

Polycondensation step (1) The esterification reaction product obtained in the esterification step (2) was added to germanium dioxide 0.019 parts by weight, oxalic acid 0.038 parts by weight, water 0.037 parts by weight, ethylene A catalyst-containing solution consisting of 2 parts by weight of glycol and 0.029 parts by weight of trimethyl phosphate were added, and a reaction temperature of 2% was added.
A liquid-phase polycondensation reaction was carried out at 75 ° C. under a pressure of 3 Torr for 3 hours to obtain a polyester chip having an intrinsic viscosity of 0.55 dl / g. Distillate (1) was obtained by this liquid phase polycondensation reaction. This distillate (1) contained 87.1% by weight of ethylene glycol and 0.1% of diethylene glycol.
It contained 6% by weight, 12.0% by weight of water and 0.3% by weight of insoluble oligomer.

Distillation Step Distillate (1) is distilled at 150 ° C. and 80 Torr to remove water and low boiling components and distillate (2) (distillate residue)
I got

The depolymerization step Next, to obtain a depolymerized distillate by stirring for 2 hours distillate (2) at 0.99 ° C. (3) (depolymerization solution).

Filtration Step Next, the distillate (3) was passed through a membrane filter (pore size 3.
(0 μm) at 80 ° C. to remove insoluble oligomers to obtain a distillate (4) (filtrate). The filtered insoluble oligomer was 0.002% by weight. The T ₃₈₀ of the obtained filtrate was 93.7%, the filtrate was clear, and no suspended matter could be confirmed visually.

At this time, when 300 ml of the distillate (3) was filtered at 80 ° C. using a filter having a filtration area of 9.6 m ² (pore size: 3.0 μm), the filtration time was 3.5 minutes. The filtration time when ethylene glycol was filtered under the same conditions was 3.5 minutes, and it was found that the distillate (3) after depolymerization was filtered with the same filtration time as ethylene glycol. .

Decolorization Step Next, the distillate (4) and activated carbon (Calgon APA; manufactured by Toyo Calgon Co., Ltd.) while maintaining the distillate (4) at 80 ° C.
Is contacted with a superficial tower speed of 0.5 hr ^-1 to perform a decolorization treatment,
A distillate (5) was obtained.

The iron removal step Subsequently, the distillate remains held at 80 ° C. (5), a strongly acidic cation-exchange resin (Amberlyst 15WET, manufactured by Organo Co., Ltd.) and, superficial velocity 0.5 hr ^-1 To remove iron and to obtain a distillate (6).

The distillate (6) obtained through the above-mentioned purification step was composed of 98.1% by weight of ethylene glycol, 0.9% by weight of diethylene glycol, 0.8% by weight of water and 0% by weight of iron. 0.0000000% by weight and 0.23% by weight of Ge. Further, T ₃₈₀ was 98.9%.

Catalyst Solution Preparation Step To 100 parts by weight of the distillate (6), 0.038 parts by weight of germanium dioxide was newly added, and heated and stirred at 120 ° C. for 4 hours to dissolve germanium dioxide. The resulting catalyst solution was clear.

Esterification step (2) 100 parts by weight of terephthalic acid and ethylene glycol 3
4. 9.6 parts by weight of the catalyst solution obtained above.
2 parts by weight (including 5.1 parts by weight of ethylene glycol and 0.01 parts of germanium in terms of germanium dioxide)
9 parts by weight) to carry out an esterification reaction in the same manner as in the esterification step (1).

Polycondensation step (2) The esterification reaction product obtained in the esterification step (2) is subjected to a liquid phase polycondensation reaction in the same manner as in the polycondensation step (1) to obtain an intrinsic viscosity of 0.1. 55 dl / g polyester chips were obtained. The liquid-phase polycondensation time at this time was 3 hours, and no change was observed in the liquid-phase polycondensation time until the same intrinsic viscosity as that of the polyester obtained in the polycondensation step (1) was obtained.

Solid Phase Polycondensation Step The polyester chips obtained in the liquid phase polycondensation reaction (2) are subjected to solid phase polymerization at 215 ° C. for 20 hours under a nitrogen flow to obtain polyester chips having an intrinsic viscosity of 0.76 dl / g. Was.

The color tone of this polyester was measured by a 45 ° diffusion type color difference meter (Suga Tester: SC-2-CH type). Color tone: L value (brightness): 91.0, a value (+ red, -green):-
2.2, b value (+ yellow, -blue): +1.6. The polyester chip was heated and melted at 275 ° C. to form a stepped square plate. The haze of a 5 mm thick square plate is
4.3%.

[0055]

Reference Example 1 A polyester chip having an intrinsic viscosity of 0.55 dl / g obtained in the polycondensation step (1) of Example 1 was subjected to solid-phase polycondensation in the same manner as in Example 1 to obtain an intrinsic viscosity of 0.78 dl.
/ G of polyester chips.

The color tone of this polyester is L value: 90.
9, a value: -2.4, b value: +1.6. Also,
The haze of the stepped square plate having a thickness of 5 mm formed in the same manner as in Example 1 using this polyester chip was 4.2%.

[0057]

Example 2 100 parts by weight of the distillate (6) obtained in Example 1 were mixed with 10 parts by weight of oxalic acid and 0.1% of germanium dioxide.
038 parts by weight were mixed and germanium dioxide was dissolved in distillate (6) at room temperature to prepare a catalyst solution.

A polyester chip having an intrinsic viscosity of 0.55 dl / g was obtained in the same manner as in the esterification step (2) and the polycondensation step (2) of Example 1 except that this catalyst solution was used. The liquid-phase polycondensation time at this time was 3 hours, and no change was observed in the liquid-phase polycondensation time until the same intrinsic viscosity as that of the polyester obtained in the polycondensation step (1) was obtained.

The intrinsic viscosity of the polyester obtained by solid-phase polycondensation in the same manner as in the solid-phase polycondensation step of Example 1 was 0.77 dl / g. The color tone of the polyester obtained by the solid-phase polycondensation is as follows: L value: 90.9, a value: -2.1,
b value: +1.8. The haze of the stepped rectangular plate having a thickness of 5 mm formed in the same manner as in Example 1 using this polyester chip was 4.8%.

[0060]

Comparative Example 1 Germanium dioxide was added to 100 parts by weight of the distillate (1) obtained in the polycondensation step (1) of Example 1, and the mixture was used as a slurry without heating to obtain the ester of Example 1. In the same manner as in the conversion step (2) and the polycondensation step (2), polyester chips having an intrinsic viscosity of 0.55 dl / g were obtained. The liquid-phase polycondensation time until the same intrinsic viscosity as the polyester obtained in the polycondensation step (2) of Example 1 is 3
The time was 20 minutes, and the polycondensation time was longer than the polycondensation step (2) of Example 1.

The intrinsic viscosity of the polyester obtained by solid-phase polycondensation in the same manner as in the solid-phase polycondensation step of Example 1 is 0.71 dl / g. The intrinsic viscosity after the condensation time was lower than in Example 1.

The color tone of the polyester obtained by solid-phase polycondensation was as follows: L value: 90.9, a value: -2.4, b value: +2.0
Met. Further, the haze of the stepped rectangular plate having a thickness of 5 mm formed in the same manner as in Example 1 using this polyester chip was 7.2%, and the transparency was poor.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Yoshitaka Nomura 1-2-1, Waki, Waki-machi, Kuga-gun, Yamaguchi Prefecture Inside Mitsui Petrochemical Industry Co., Ltd.

Claims (8)

[Claims] When producing a polyester from a dicarboxylic acid and a dihydroxy compound by a process including an esterification step and a polycondensation step, the dihydroxy compound and the polycondensation catalyst distilled and recovered from the polycondensation step are removed. A process for producing a polyester, comprising supplying a catalyst solution obtained by dissolving a polycondensation catalyst to a distillate containing the same to an esterification reaction and / or a polycondensation step. 2. The method for producing a polyester according to claim 1, wherein the polycondensation catalyst is dissolved in the distillate by heating. 3. The process according to claim 1, wherein a polycondensation catalyst is dissolved in the distillate in the presence of an organic acid. 4. The process for producing a polyester according to claim 1, wherein a polycondensation catalyst is dissolved in the distillate in the presence of a basic compound. 5. The method for producing a polyester according to claim 1, wherein the polycondensation catalyst is germanium dioxide. 6. The method for producing a polyester according to claim 1, wherein the polycondensation catalyst is antimony trioxide and / or antimony acetate. 7. The distillate is subjected to the following steps (a) to (c):
The process for producing a polyester according to any one of claims 1 to 6, wherein the polycondensation catalyst is dissolved in the distillate after the treatment after the treatment by a purification step comprising: (A) distillation step (b) depolymerization step (c) decolorization step 8. The method according to claim 8, wherein the purifying step includes the steps (a) to (c).
The method for producing a polyester according to claim 7, further comprising (d) a step of removing iron in addition to (c).