JP5983207B2 - Polyester manufacturing method - Google Patents

Description

  The present invention relates to a method for producing a polyester. The present invention also relates to a method for economically producing polyester having a stable color tone by controlling the amount of ethylene glycol that is purified and reused when ethylene glycol distilled in the process of producing polyester is reused.

  Polyesters are widely used in various fields, for example, fibers for clothing and industrial materials, various films and sheets for packaging and magnetic tape, bottles because of their excellent properties such as mechanical strength and chemical stability. And is used in fields such as moldings of engineering plastics. Among these, polyethylene terephthalate is excellent in gas barrier properties and hygiene, is relatively inexpensive and lightweight, and thus is widely used as a food and beverage packaging container, and its application fields are expanding.

  In general, polyester is obtained by using a dicarboxylic acid component and a diol component as raw materials to obtain a low polymerization reaction product while distilling a part of water produced by esterification reaction and a part of the raw material diol component. Is produced by a method of obtaining a polyester which is a polycondensation reaction product while distilling the diol component and water by a polycondensation reaction in the presence of a polycondensation catalyst. Usually, polycondensation of polyester is performed at a high temperature of 200 ° C. or higher, and it is known that undesired yellowing is caused by thermal decomposition. In particular, it is known that a polyester produced using a titanium compound as a catalyst and ethylene glycol as a raw material diol is strongly yellow-colored.

  In order to prevent such unfavorable coloring, a method of adding a phosphorus compound is known (for example, Patent Document 1). In addition, a method for suppressing yellowing of polyester by adding a toning agent such as a cobalt compound or toner is also known (for example, Patent Document 2). On the other hand, it is known that a titanium catalyst also suppresses coloring by using a titanium trinuclear catalyst (for example, Patent Document 3).

Japanese Patent Laid-Open No. 2000-256442 JP 2005-23203 A JP 2004-43716 A

  However, the addition of a phosphorus compound cannot sufficiently improve the color tone, and the polycondensation activity decreases when a titanium compound is used as a catalyst. In addition, the method of adding a toning agent such as a cobalt compound or toner to suppress yellowing of the polyester has a problem of increasing dullness of the polyester. Furthermore, there is a concern that the addition of cobalt compounds has an environmental impact due to heavy metals, and the addition of toner has the problem that it is difficult to add to the polyester manufacturing process with high accuracy because the solubility of the toner in water and raw material diol is small. It was. Further, the titanium trinuclear catalyst described in Document 3 has a problem that the manufacturing process of the catalyst is complicated and the production cost is high.

  This invention makes it a subject to provide the manufacturing method of polyester which prevents the coloring at the time of manufacturing polyester, and obtains polyester with favorable color tone.

  As a result of intensive studies aimed at solving the above problems, the present inventors can produce a polyester having a good color tone by defining the content of a specific compound in ethylene glycol used as a raw material. As a result, they have reached the present invention. In addition, it is possible to economically produce a polyester having a stable color tone by controlling the amount of the specific compound, for example, by controlling the amount of ethylene glycol to be purified and reused. As a result, the present invention has been achieved. That is, the gist of the present invention is as follows.

[1] A method for producing a polyester comprising a dicarboxylic acid component and a diol component containing ethylene glycol as a main component, and having at least one of a slurrying step, an esterification step and a polycondensation step, and a purification step of ethylene glycol The ethylene glycol purification step includes a method in which ethylene glycol is distilled by a distillation column and ethylene glycol is distilled off at the top of the column to recover the ethylene glycol. A method for producing a polyester, which is used as a part of a diol component, and the diol component satisfies the following formula (I).
0.01 ≦ q ≦ 34 (I)
However, q = a + b + 2c
a: Content (mol ppm) of the compound represented by the following formula (1) with respect to the ethylene glycol
b: Content (mol ppm) of the compound represented by the following formula (2) with respect to the ethylene glycol
c: Content of the compound represented by the following formula (3) with respect to the ethylene glycol (mol ppm)

[2] The method for producing the polyester having an esterification process, method for producing a polyester according to the addition of ethylene glycol via the purification process of the ethylene glycol in the esterification step [1].
[ 3 ] The method for producing polyester has a slurrying step of mixing the dicarboxylic acid component and the diol component, and a part of ethylene glycol that has passed through the purification step of ethylene glycol is added to the slurrying step. 1 ] The manufacturing method of polyester as described in.
[ 4 ] The method for producing a polyester according to any one of [1] to [ 3 ], wherein the polycondensation step uses a polycondensation reaction catalyst, and the polycondensation reaction catalyst contains a titanium compound.
[ 5 ] The polyester production method includes an esterification step and a polycondensation step, and the polycondensation reaction catalyst is added to a pipe that transfers the polyester oligomer obtained in the esterification step to the polycondensation step. [ 4 ] The method for producing a polyester according to [ 4 ].

  According to the present invention, it is possible to prevent coloration when producing a polyester and obtain a polyester having a good color tone.

It is an example of the whole flow of the manufacturing apparatus of polyester for enforcing the manufacturing method of this invention. It is an example of the whole flow of the manufacturing apparatus of the polyester in the preferable aspect of this invention. It is an example of the whole flow of the manufacturing apparatus of the polyester in the preferable aspect of this invention.

Hereinafter, although the structure of this invention is demonstrated, these are typical illustrations and are not limited to these.
The present invention is a method for producing a polyester using a dicarboxylic acid component and a diol component mainly composed of ethylene glycol as raw materials, wherein the content of the specific compound relative to the ethylene glycol is within a specific range. This relates to a method for producing polyester.

<Raw material>
(Dicarboxylic acid component)
The dicarboxylic acid component of the present invention contains dicarboxylic acid and / or an ester-forming derivative thereof. More specifically, it contains an aliphatic dicarboxylic acid, an aromatic dicarboxylic acid and / or an ester-forming derivative thereof, and the hydrocarbon group portion of the aliphatic dicarboxylic acid may have an alicyclic structure. You may have a branched structure.

  When using an aromatic dicarboxylic acid and / or an ester-forming derivative thereof, from the viewpoint of reactivity and economy, a dicarboxylic acid having 4 or less aromatic rings and / or an ester-forming derivative thereof is preferably used. More preferably, dicarboxylic acids having 2 or less aromatic rings and / or ester-forming derivatives thereof are used. Specifically, terephthalic acid, isophthalic acid, dibromoisophthalic acid, sodium sulfoisophthalate, phenylenedioxydicarboxylic acid, 4,4′-diphenyldicarboxylic acid, 4,4′-diphenyletherdicarboxylic acid, 4,4′-diphenyl Ketone dicarboxylic acid, 4,4′-diphenoxyethanedicarboxylic acid, 4,4′-diphenylsulfone dicarboxylic acid, 1,4-naphthalenedicarboxylic acid, 2,3-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, etc. These ester-forming derivatives are used.

  When using an aliphatic dicarboxylic acid and / or an ester-forming derivative thereof, a linear aliphatic dicarboxylic acid having 2 to 18 carbon atoms and / or an ester-forming derivative thereof is preferable from the viewpoint of reactivity and economy. Or an alicyclic dicarboxylic acid having 4 to 10 carbon atoms and / or an ester-forming derivative thereof, more preferably a linear aliphatic dicarboxylic acid having 2 to 10 carbon atoms and / or ester formation thereof. Sex derivatives are used. More specifically, alicyclic dicarboxylic acids such as hexahydroterephthalic acid and hexahydroisophthalic acid, and glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecadicarboxylic acid, dodecadicarboxylic acid Aliphatic dicarboxylic acids such as acids, etc., and ester-forming derivatives thereof are used.

  When the aromatic dicarboxylic acid and the aliphatic dicarboxylic acid are ester-forming derivatives, examples of the alcohol constituting the ester include alcohols having 1 to 4 carbon atoms. Specifically, methyl alcohol and diester with ethyl alcohol are preferably used.

In the dicarboxylic acid component of the present invention, the dicarboxylic acid and / or ester-forming derivative thereof may be used in combination of a plurality of types.
Of these, polyesters to which the method for producing a polyester of the present invention can be preferably applied are preferably those containing terephthalic acid and / or terephthalic acid ester, or naphthalene dicarboxylic acid and / or naphthalene dicarboxylic acid ester as a main component. Here, the “main component” is terephthalic acid and / or terephthalic acid ester, or naphthalene dicarboxylic acid and / or naphthalene dicarboxylic acid ester is 85 mol% or more, preferably with respect to the total dicarboxylic acid in the dicarboxylic acid component. It means 90 mol% or more, more preferably 95 mol% or more.

(Diol component)
The diol component of the present invention contains ethylene glycol as a main component and contains a compound represented by the following formulas (1) to (3) (hereinafter sometimes referred to as “acetal compound”). When the content of each ethylene glycol is a, b, c mol ppm, the value q represented by a + b + 2c is 0.01 mol ppm or more and 34 mol ppm or less.

  The diol component of the present invention may contain other diol compounds in addition to ethylene glycol and acetal compounds. Other diol compounds include 1,4-butanediol, trimethylene glycol, pentamethylene glycol, hexamethylene glycol, octamethylene glycol, decamethylene glycol, neopentyl glycol, 2-ethyl-2-butyl-1,3- Aliphatic diols such as propanediol; alicyclic rings such as 1,2-cyclohexanediol, 1,4-cyclohexanediol, 1,1-cyclohexanedimethylol, 1,4-cyclohexanedimethylol, 2,5-norbornane dimethylol Formula diols; and xylylene glycol, 4,4′-dihydroxybiphenyl, 2,2-bis (4′-hydroxyphenyl) propane, 2,2-bis (4′-β-hydroxyethoxyphenyl) propane, bis ( 4-hydroxyphenyl Aromatic diols such as sulfone and bis (4-β-hydroxyethoxyphenyl) sulfonic acid; and ethylene oxide addition of diethylene glycol, polyethylene glycol, polytetramethylene ether glycol, and 2,2-bis (4′-hydroxyphenyl) propane Or polyether such as propylene oxide adduct; and the like. These other diol compounds may be used in combination.

  In the diol component of the present invention, “having ethylene glycol as a main component” means that ethylene glycol accounts for 85 mol% or more, preferably 90 mol% or more, more preferably 95 mol% or more of the total diol component. If the ratio of ethylene glycol is equal to or more than the lower limit, it is advantageous in terms of mechanical strength, gas barrier properties, and heat resistance of the resulting polyester molded body.

The content (a, b, c) of the acetal compound with respect to ethylene glycol is the ratio of the content (mol) of each acetal to the content (mol) of pure ethylene glycol in the diol component. It is a value calculated as follows using chromatography. Here, “pure ethylene glycol” means ethylene glycol as a pure substance.
That is, in the present invention, using general-purpose gas chromatography, the diol component is measured under the conditions of, for example, a polyethylene glycol column, a detector temperature of 210 ° C., a flame ion detector (FID), and sensitivity correction. The acetal compound is quantified, and the content (a, b, c) of the acetal compound can be determined according to the following calculation formula.

Note that the correspondence between the retention time and each acetal compound can be identified by an electron ionization method (EI) and a chemical ionization method (CI) using GCMS (a mass spectrometer directly connected to gas chromatography).
The sensitivity of diethylene glycol in ethylene glycol is corrected by the sensitivity of carbon number and functional group, and FID relative mass sensitivity of 0.95 for diethylene glycol is used. The concentration of diethylene glycol is quantified using a sample. From the concentration obtained, the mass concentrations of the compounds of the chemical formulas (1) to (3) are shown in the following table described in Hyundai Chemical Series 11 Chromatography (3rd edition) Tokyo Chemical Dojin, p111, Table 7.7 (1981). FID relative mass sensitivity correction of 1 is performed.

From the mass concentration of each acetal compound calculated by the above method, the molar ratio of the content of each acetal compound to ethylene glycol in the diol component according to the following [Formula A], [Formula B], and [Formula C]. (A, b, c) is calculated and displayed in units of mol ppm.
[Formula A] a = (mass concentration of compound represented by formula (1) /148.16) / (mass concentration of pure ethylene glycol / 62.07)
[Formula B] b = (mass concentration of compound represented by formula (2) /148.16) / (mass concentration of pure ethylene glycol / 62.07)
[Formula C] c = (mass concentration of compound represented by formula (3) /120.10) / (mass concentration of pure ethylene glycol / 62.07)

  According to the study by the present inventors, glycol aldehyde and / or diethylene glycol aldehyde produced by hydrolysis of the acetal compound becomes a yellow coloring factor of the polyester obtained by the production method of the present invention. Further, one molecule of glycol aldehyde is generated from one molecule of the formula (1), one molecule of diethylene glycol aldehyde is generated from one molecule of the formula (2), and one molecule of the compound of the formula (3) Two molecules of glycolaldehyde are produced. For this reason, in consideration of the degree of influence on yellow coloration, in the production method of the present invention, it is calculated from the amount (a, b, c) of each acetal compound contained in the raw material ethylene glycol in the polyester production process. The above-mentioned problem can be achieved by controlling the value q to be a specific value.

In addition, the ethylene glycol in the diol component in the present invention is ethylene glycol supplied to each step of the polyester production method of the present invention. Each ethylene glycol brought into each step as a raw material and each purification step described below are used. It is the sum of ethylene glycol brought into the process. Here, a slurry preparation tank, an esterification reaction tank, a polycondensation reaction out of a tower bottom liquid mainly comprising ethylene glycol obtained from the esterification process and / or the polycondensation process and obtained from the tower bottom through a separation tower. The bottom liquid supplied directly to the tank is not included in the ethylene glycol as the polyester raw material described in claim 1 of the present application.
Moreover, each process of the said polyester manufacturing method is specifically a slurrying process, an esterification process, and a polycondensation process.

In the present invention, “the range where the value of q satisfies the provisions of the present invention” means (a + b + 2c) in ethylene glycol in all steps of supplying ethylene glycol in the polyester production method of the present invention. It means that the weighted average value q weighting the ethylene glycol supply amount of the process satisfies the following formula (I).
0.01 ≦ q ≦ 34 (I)
In the present invention, the upper limit of the q value is 34 mol ppm or less, preferably 32 ppm or less, more preferably 30 ppm or less, still more preferably 25 ppm or less, and particularly preferably 20 ppm or less. When the value of q exceeds 34 mol ppm, yellowing of the resulting polyester may increase, which is not preferable. On the other hand, from the viewpoint of improving economy while reducing yellow coloring of polyester, the lower limit of the value of q is 0.01 mol ppm or more, and preferably 0.5 mol ppm or more. In order to make the value of q less than 0.01 mol ppm, purification equipment and energy for obtaining high-purity ethylene glycol are required, which is disadvantageous in terms of economy and is not preferable as a production method. A method for controlling the value of q so as to satisfy the range of the present invention will be described later.

(Other copolymer components)
The polyester produced by the method for producing a polyester of the present invention is a compound having three or more functional groups, for example, polycarboxylic acids such as trimellitic acid and pyromellitic acid and anhydrides thereof; trimethylolmethane, trimethylolethane, trimethylolpropane, Polyols such as pentaerythritol, glycerol, and hexanetriol; and hydroxycarboxylic acids such as malic acid and citric acid; and the like may be used as a copolymerization component as necessary for the purpose of adjusting the physical properties of the resulting polyester. Good.

<Production method of polyester>
The polyester production method of the present invention has at least one of a slurrying step, an esterification step, a polycondensation step, or a purification step of the ethylene glycol. The raw materials used in the production may be supplied to the reaction tank in which the esterification process or the polycondensation process is performed by any method, and are directly charged into the reaction tank or directly into the reaction tank while mixing the raw materials with an in-line mixer or the like. However, it is preferable to have a slurrying process in order to facilitate handling of the solid raw material. In order to stabilize the supply of ethylene glycol used as a raw material, it is preferable to have an ethylene glycol supply step, and further to have an ethylene glycol purification step in order to control the value of q in the present invention.
In the method for producing the polyester of the present invention, the reaction system may be a batch system, a semi-batch system, or a continuous system. Furthermore, although the system which combined these may be sufficient, it is preferable that it is a continuous type.

  An example of the whole flow of the polyester manufacturing apparatus in the polyester manufacturing method of the present invention is shown in FIG. In this example, using a dicarboxylic acid component and a diol component as raw materials, an esterification step in which an esterification reaction and / or a transesterification reaction are performed, and a polycondensation step in which an esterified product obtained in the esterification step is melt polycondensed, Polyester is produced by melt polycondensation. In a preferred embodiment of the present invention, a raw slurry is obtained through a slurrying step in which a dicarboxylic acid component and a diol component are charged into a slurry preparation tank and stirred and mixed. The obtained raw material slurry is subjected to an esterification step in which an esterification reaction is carried out while distilling off excessively charged diol or water produced by the reaction under reduced pressure to under pressure and heating in an esterification reaction tank. A molecular weight body (hereinafter sometimes abbreviated as oligomer) is obtained. The obtained oligomer is transferred to a polycondensation reaction tank connected through a filter, and a polycondensation catalyst is used to distill off excessively charged diol and water generated by the reaction under reduced pressure and heating. A polyester is obtained through a polycondensation step in which a melt polycondensation reaction is performed.

(Control method of q value)
As a method for controlling the q value of the raw material ethylene glycol within a specified range, ethylene glycol recovered from the polyester production process and having a value of (a + b + 2c) higher than the range specified by the present invention (hereinafter referred to as regenerated ethylene glycol). May be used as raw ethylene glycol via an ethylene glycol purification step; the regenerated ethylene glycol and ethylene glycol having a value of (a + b + 2c) within the range defined by the present invention (hereinafter, High-purity ethylene glycol) is mixed to bring the value of q within the range specified by the present invention; a portion of the regenerated ethylene glycol is mixed so that q is kept within the specified range. The method of using and discarding the remainder; etc. can be illustrated. At this time, the high-purity ethylene glycol may be ethylene glycol purified by the method described later, or may be ethylene glycol received as a raw material. Here, “ethylene glycol accepted as a raw material” refers to ethylene glycol that has not been supplied to each step of performing the production method of the present invention, among the ethylene glycol of the raw material used in the production method of the present invention. It is.
In the above mixing, it is preferable to control the value of q by controlling the mixing ratio of the regenerated ethylene glycol and the high-purity ethylene glycol. In the continuous production method of polyester, the regenerated ethylene glycol And a method of mixing while controlling the flow rate of the high-purity ethylene glycol is preferably used.

  As a method of maintaining the value of (a + b + 2c) of ethylene glycol kept low by the above-mentioned various methods within the range specified by the present invention, nitrogen or the like is used to avoid exposure of the ethylene glycol to air or sunlight. A method of hermetically storing in a stainless steel container under an inert gas atmosphere can be exemplified.

Examples of the method of using ethylene glycol having a specific value of (a + b + 2c) in the polyester production step include a method of preparing a slurry using the ethylene glycol as a raw material; and a method of using the ethylene glycol in the esterification step. .
Especially, the method of adding the ethylene glycol which passed through the refinement | purification process of ethylene glycol to an esterification process, and / or the method of adding a part of ethylene glycol which passed through the said refinement | purification process are especially preferable.

  As various methods for purifying ethylene glycol, a method of distilling and purifying the acetal compound, which is a high-boiling component, using a distillation tower; and a method of adsorbing and separating the acetal compound using a compound having a high affinity with the acetal compound. And a purification method.

  In the method for producing a polyester of the present invention, when the contents of the compounds represented by the formulas (1) to (3) with respect to the raw material ethylene glycol are a, b, and c mol ppm, respectively, (a + b + 2c) in each step is Obtained and distilled from the esterification step and / or the polycondensation step as long as the weighted average value q weighted by the ethylene glycol supply amount in each step satisfies the specific range. The distillate may be used as it is in a slurrying process as a part of the raw material, or may be used as a part of the raw material after distilling and separating components other than the raw material components. Moreover, you may add the said distillate directly to an esterification process. In particular, it is preferable to use the ethylene glycol supply step through the ethylene glycol purification step.

(Esterification process)
The esterification step is a step of performing an esterification reaction and / or a transesterification reaction using a dicarboxylic acid component and a diol component as raw materials using an esterification reaction tank. More specifically, the dicarboxylic acid component and the diol component as raw materials are esterified while distilling off excessively charged diol component or water produced by the reaction under reduced pressure to pressurized pressure and heating in an esterification reaction tank. To give an oligomer which is a low molecular weight polyester.

  As the esterification reaction tank for performing the esterification step, one having a heat medium jacket for controlling the temperature is usually used, but in order to facilitate temperature control, a heat medium coil is provided in the esterification reaction tank. It is preferable. Moreover, you may have the line (external circulation line) which circulates an oligomer outside and heats with a heat exchanger. The esterification reaction tank may be equipped with a stirring device, and as the stirring blade, conventionally known ones such as an anchor blade, a paddle blade, and a fowler blade can be used. Moreover, you may comprise the reflux condenser which returns a distillate component to a reaction tank. Moreover, you may have the reflux condenser which returns a distillate component to a reaction tank, and in this invention, the method of returning a distillate component to a reaction tank is used preferably in order to reduce a thermal load.

In the present invention, the esterification reaction is usually carried out at a temperature of 240 to 305 ° C, and the transesterification reaction is usually carried out at a temperature of 130 to 250 ° C. In particular, in the case of producing polyethylene terephthalate using terephthalic acid and ethylene glycol as raw materials, the esterification reaction is usually carried out by controlling the inside of the esterification reaction tank in the range of 250 ° C. or higher and 305 ° C. or lower, preferably 255 ° C. or higher. It is performed in a range of 290 ° C. or lower.
In addition, the pressure inside the reaction vessel in the esterification reaction and / or transesterification reaction is usually controlled within a range of 100 kPaA (A indicates absolute pressure, the same applies hereinafter) to 500 kPaA, preferably 105 kPaA. It is performed in the range of 300 kPaA or less.

The time required for the esterification reaction is adjusted so as to make the range constant by measuring the esterification rate of the resulting oligomer, but it is usually 1 hour or more and 8 hours or less. When the esterification step is carried out continuously, the average residence time in the esterification reaction tank is regarded as the time required for the esterification reaction. In addition, the average residence time in the case of carrying out by a continuous type is defined as the time obtained by dividing the mass of the oligomer held in the esterification reaction tank by the oligomer mass flow rate supplied continuously.
Moreover, in order to adjust the esterification rate within a certain range, a diol component may be added to the esterification reaction tank.

(Polycondensation process)
As the polycondensation reaction tank for carrying out the polycondensation step, one having a heat medium jacket for controlling the temperature is usually used, but in order to facilitate the temperature control, a heat medium coil is provided inside the polycondensation reaction tank. May be. The polycondensation reaction tank usually includes a stirring device having a vertical or horizontal direction as a center line. As a stirring blade, in the case of a stirrer having a center line in the vertical direction, anchor blades, paddle blades, fouller blades, and the like, in the case of a stirring device having a center line in the horizontal direction, such as a spectacle blade and a wheel blade, respectively. Can be used.

In the polyester production method of the present invention, the temperature inside the reaction vessel in the polycondensation reaction is preferably 250 to 305 ° C. In particular, when producing polyethylene terephthalate using terephthalic acid and ethylene glycol as raw materials, the polycondensation reaction is usually carried out by controlling the inside of the polycondensation reaction tank in the range of 260 ° C. or higher and 305 ° C. or lower, preferably 265 ° C. or higher. It is performed in a range of 290 ° C. or lower. In addition, the pressure inside the polycondensation reaction tank is usually controlled in the range of 0.01 kPaA to 100 kPaA, preferably 0.05 kPaA to 5 kPaA.
The time required for the polycondensation reaction is adjusted so as to make the range constant by measuring the melt viscosity and intrinsic viscosity of the obtained polyester, but is usually 2 hours or more and 8 hours or less. When the polycondensation step is performed continuously, the average residence time in the polycondensation reaction tank is regarded as the time required for the polycondensation reaction. In addition, the average residence time in the case of carrying out by a continuous type is defined as the time obtained by dividing the mass of the polyester held in the polycondensation reaction tank by the mass flow rate of the continuously supplied polyester.

(Polycondensation reaction catalyst)
In the polycondensation reaction used in the method for producing a polyester of the present invention, it is preferable to use a polycondensation reaction catalyst in order to accelerate the reaction. The polycondensation reaction catalyst used in this case is not particularly limited, and a known catalyst can be used. For example, germanium compounds such as germanium dioxide, germanium tetroxide, germanium hydroxide, germanium oxalate, germanium tetraethoxide, germanium tetra-n-butoxide, antimony compounds such as antimony trioxide, antimony pentoxide, antimony acetate, methoxyantimony, Titanium compounds such as tetra-n-propyl titanate, tetra-i-propyl titanate, tetra-n-butyl titanate, titanium oxalate, and titanium potassium oxalate are used. These compounds may be used in combination of a plurality of types. Especially, in the manufacturing method of polyester of this invention, since a polycondensation reaction activity is high, it is preferable to use a titanium compound. The amount of the catalyst used is usually 1 to 400 ppm by mass, preferably 1 to 150 ppm by mass, more preferably 1 to 80 ppm by mass, and more preferably 1 to 20 ppm by mass with respect to the resulting polyester as titanium atoms.

In addition, you may use each said compound used as a polycondensation catalyst as an esterification reaction catalyst in an esterification process.
The method for adding the polycondensation reaction catalyst used in the method for producing the polyester of the present invention is not particularly limited. For example, a method for adding to the slurrying step, a method for adding to the esterification step, a method for adding to the polycondensation step, And the method of adding to the transfer piping between each process is used. In particular, when the production method of the polyester of the present invention is a continuous type, a method of adding between the slurrying step and the transfer pipe immediately before the polycondensation step is preferably used. In particular, when a titanium compound is used as the polycondensation catalyst, when the esterification step is composed of a plurality of esterification reaction tanks, a method of adding to a further downstream esterification reaction tank is preferable. A method of adding the polyester oligomer obtained in the step to the pipe for transferring to the polycondensation step is particularly preferably used.

  In addition, phosphorus compounds such as normal phosphoric acid, normal phosphoric acid alkyl ester, ethyl acid phosphate, triethylene glycol acid phosphate, phosphorous acid, and phosphorous acid alkyl ester can be used as stabilizers. The amount used is preferably 1 to 1000 ppm by mass, particularly preferably 2 to 200 ppm by mass, based on the polyester prepolymer obtained.

  Furthermore, “Group 1 element” and / or “Group 2 element” (hereinafter simply referred to as “Group 1 metal compound”, “Group 2 metal compound”) in the Long Periodic Periodic Table (Nomenclature of Inorganic Chemistry IUPAC Recommendations 2005) The metal compound represented by the above) can be used as a cocatalyst together with the polycondensation reaction catalyst. Examples of the Group 1 metal compound include lithium acetate, sodium acetate, potassium acetate, and potassium hydroxide. Examples of the Group 2 metal compound include magnesium compounds such as magnesium acetate, magnesium hydroxide, magnesium alkoxide, and magnesium carbonate, and hydroxide. Examples include calcium, calcium acetate, and calcium carbonate.

(Ethylene glycol supply process)
In the method for producing a polyester of the present invention, the ethylene glycol supply step includes ethylene glycol received as a raw material, ethylene glycol obtained by distillation from an esterification step and / or a polycondensation step, and purification of ethylene glycol described later. In this process, ethylene glycol purified in the process is mixed and stored, and supplied to a slurrying process, an esterification process, and / or a polycondensation process.
Here, a slurry preparation tank, an esterification reaction tank, a polycondensation reaction out of a tower bottom liquid mainly comprising ethylene glycol obtained from the esterification process and / or the polycondensation process and obtained from the tower bottom through a separation tower. The bottom liquid supplied directly to the tank is not included in the ethylene glycol as the polyester raw material described in claim 1 of the present application.

  The ethylene glycol supply step usually includes a tank for holding ethylene glycol and a pump connected to the tank by piping, and includes a flow meter and a filter as necessary. The tank for holding ethylene glycol is usually a floating roof type tank having no gas phase part or a fixed roof type tank such as a cone roof type having a gas phase part. In the case of a tank having a gas phase part, it is preferably in a nitrogen sealed state, and the oxygen concentration in the gas phase part is set to 0.1% by mass or less, more preferably 0.01% by mass or less.

(Ethylene glycol purification process)
In the method for producing the polyester of the present invention, the ethylene glycol purification step refers to ethylene glycol received as a raw material, distillate distilled in the esterification step and / or polycondensation step, filtration, In this step, impurities are separated by a method such as distillation or adsorption, and ethylene glycol is purified and recovered.

  These purification methods may be used alone or in appropriate combination. Especially, the method which combined filtration and distillation is preferable. Specifically, first, solid impurities in ethylene glycol are removed with a metal filter, filter cloth, etc., and then heated to a boiling point or higher of ethylene glycol in a distillation tower, while refluxing as necessary. In this method, impurities having a high boiling point are extracted from the bottom of the column and separated, and ethylene glycol is distilled off at the top of the column and recovered. The use of such an ethylene glycol purification step is particularly preferable because the acetal compound contained in ethylene glycol can be efficiently separated. The ethylene glycol purification step further includes a method in which a low boiling point impurity in ethylene glycol is distilled off at the top of the tower and separated in a separate distillation tower, and ethylene glycol is extracted from the bottom of the tower and recovered. But you can. In particular, in the case of including a method for distilling and separating the low-boiling impurities and the like at the top of the column, by heating ethylene glycol in the presence of water, the acetal compound contained in ethylene glycol is converted into glycol aldehyde and diethylene glycol aldehyde. And ethylene glycol, and the produced aldehyde can be distilled and separated, which is more preferable.

  The purified ethylene glycol is usually used as a raw material for the production method of the polyester of the present invention, alone and / or mixed with ethylene glycol received as a raw material, through an ethylene glycol supply step. It is done. In the ethylene glycol supply step, a distillate containing ethylene glycol as a main component obtained by distilling from the esterification step and / or the polycondensation step is purified within a range where the value q satisfies the provisions of the present invention. You may use without.

(Material of manufacturing equipment)
The material of the apparatus used in the method for producing the polyester of the present invention is not only the dicarboxylic acid component and diol component as raw materials, but also the catalyst, auxiliary agent, stabilizer, and the compound generated by esterification reaction or thermal decomposition. It is preferable to select in consideration of corrosion resistance to substances including these and mixtures thereof. Of these, stainless steel is preferable, and molybdenum-containing stainless steel is particularly preferable. Specifically, for example, SUS304, SUS316, SUS316L, SUS317L, SUS410, SUS430, and the like are preferably used among stainless steels defined by Japanese Industrial Standards.

(Post-process)
The polyester obtained by the melt polycondensation reaction is supplied to a die head connected to at least one of a pipe, a gear pump, and a filter or a combination of them in a melt polycondensation reaction tank, and from a plurality of die holes provided at the tip of the die , Discharged in a strand shape. The discharged polyester is made into particles by, for example, a strand cutter. The granulated polyester may be used as a molding material as it is. Alternatively, it may be used as a molding material after heat treatment in a solid state and solid phase polycondensation to a predetermined intrinsic viscosity.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the following examples unless it exceeds the gist. Next, various measurement methods used in the following examples will be described.

(Quantification of compounds of formulas (1) to (3))
An ethylene glycol liquid sample was collected from the bottom liquid of the separation tower in the ethylene glycol supply step, the polycondensation step, or the purification step of ethylene glycol. This sample was measured for the mass concentration of pure ethylene glycol and an acetal compound using gas chromatography under the following conditions.

[Conditions for gas chromatography]
Gas chromatography: Agilent technologies 6890N
Detector: Flame ion detector (FID)
Analytical column: Agilent J & W GC column DB-WAX
Column inner diameter: 0.25mm
Column length: 30m
Column film thickness: 0.25 μm
Temperature rising condition: 100 ° C. (2 minutes) → 10 ° C./minute→250° C. (8 minutes)
Inlet temperature: 270 ° C
Detector temperature: 270 ° C
Carrier gas: Helium 1 mL / min Injection mode: Split 10: 1
Sample injection volume: 1 μL
Retention time:
Diethylene glycol: 8.6 minutes Compound having the structure of Formula 1: 11.7 minutes Compound having the structure of Formula 2: 11.8 minutes Compound having the structure of Formula 3: 13.8 minutes

The correspondence between the retention time and each acetal compound was identified by electron ionization (EI) and chemical ionization (CI) using GCMS.
The sensitivity of diethylene glycol in ethylene glycol obtained by gas chromatography measurement was corrected for the number of carbon atoms and the sensitivity by functional groups. The concentration of ethylene glycol was similarly determined by quantifying the standard.
From the mass concentration of each acetal compound calculated by the above method, the content of each acetal compound with respect to the ethylene glycol content in the sample according to [Formula A], [Formula B], and [Formula C]. The molar ratios a, b, and c (mol ppm) were calculated.

(Esterification rate)
0.5 g of the pulverized sample was precisely weighed in a beaker, 40 mL of benzyl alcohol was added, and the mixture was stirred and heated to 200 ° C. for complete dissolution. After allowing to cool to room temperature, titration was performed with a 0.1N methanolic potassium hydroxide solution using an automatic titrator (Hiranuma Sangyo COM-1600). Based on the result, the carboxyl end amount was determined according to the following formula (1). Furthermore, the esterification rate was calculated according to the following formula (2) using the obtained carboxyl terminal amount.
Carboxyl terminal amount (equivalent / resin gram) = 0.1 × A × f × 1000 / W (1)
A: 0.1N methanolic potassium hydroxide solution required for neutralization (mL)
F: Potency of 0.1N methanolic potassium hydroxide solution
W: Weight of sample (g)
Esterification rate (%) = (1000-carboxyl terminal amount) / 100 (2)

(Measurement of intrinsic viscosity (IV))
A polyester resin sample (0.25 g) was dissolved in phenol / tetrachloroethane (weight ratio 1/1) as a solvent and a concentration (c) of 1.0 g / dL at 110 ° C. for 30 minutes. Using a viscosity tube, measurement was performed at 30 ° C., and the relative viscosity (η _rel ) with the solvent was determined from the following equation from the passage time (t ₀ ) of the solvent and the passage time (t) of the solution,
η _rel = t / t ₀
From the relative viscosity, the specific viscosity (η _sp ) was determined from the following formula.
η _sp = η _rel −1
Furthermore, the specific viscosity was divided by the concentration (c) to obtain a reduced viscosity (η _sp / c) at a concentration (c) of 1.0 g / dL.
Similarly, when the concentration (c) is 0.5 g / dL, 0.2 g / dL, and 0.1 g / dL, the respective reduced viscosities are obtained, and the concentration (c) is extrapolated to 0 from these values. Intrinsic viscosity (IV) (dL / g) was determined.

(Color tone)
A polyester resin sample is filled into a cylindrical powder colorimetric cell having an inner diameter of 30 mm and a depth of 12 mm, and a colorimetric color difference meter (“ZE-2000” manufactured by Nippon Denshoku Industries Co., Ltd.) is used. Reference to JIS Z8730 The color coordinate b value of Hunter's color difference formula in the Lab color system described in Example 1 was determined as a simple average value of four values measured by rotating the measurement cell by 90 ° C. by the reflection method.

(Terminal carboxyl group (AV))
After pulverizing the sample, it was dried at 140 ° C. for 15 minutes in a hot air dryer, and 0.1 g was accurately weighed out from the sample cooled to room temperature in a desiccator, and 3 mL of benzyl alcohol was added, The solution was dissolved at 195 ° C. for 3 minutes while blowing dry nitrogen gas, and then 5 mL of chloroform was gradually added and cooled to room temperature. One to two drops of phenol red indicator were added to this solution, and titrated with a 0.1N sodium hydroxide benzyl alcohol solution with stirring while blowing dry nitrogen gas, and the reaction was terminated when the color changed from yellow to red. . Moreover, the same operation was implemented without using a sample as a blank, and the amount of terminal carboxyl groups was calculated by the following formula (3).
Terminal carboxyl group amount (equivalent / ton of resin) = (AB) × 0.1 × f / W (3)
A: Amount of 0.1N sodium hydroxide in benzyl alcohol solution required for titration (μL)
B: Amount of 0.1N sodium hydroxide in benzyl alcohol solution (μL) required for titration with a blank
W: Amount of sample (g)
f: titer of benzyl alcohol solution of 0.1N sodium hydroxide

The titer (f) of a 0.1N sodium hydroxide benzyl alcohol solution was obtained by taking 5 mL of methanol into a test tube while blowing dry nitrogen gas, and adding 1-2 drops of phenol red ethanol solution as an indicator. The solution was titrated with 0.4 mL of 0.1 N sodium hydroxide in benzyl alcohol to the color change point, then 0.2 mL of 0.1 N aqueous hydrochloric acid solution having a known titer was collected and added as a standard solution. The solution was titrated with a 1N sodium hydroxide solution in benzyl alcohol to the color change point, and the titer (f) was calculated by the following equation (4).
Titer (f) = Titration of 0.1N aqueous hydrochloric acid × Amount of collected 0.1N aqueous hydrochloric acid (μL) / Titration of 0.1N sodium hydroxide in benzyl alcohol (μL) (4)

[ Reference Example 1 ]
According to the polyester production flow shown in FIG. 2, polyester was continuously produced using terephthalic acid as the dicarboxylic acid component and ethylene glycol as the diol component. That is, a nitrogen-roofed cone roof type ethylene glycol storage tank 1 (the material of the inner surface of the tank is SUS304) is used as the ethylene glycol supply process, and a stirrer, a dicarboxylic acid charging pipe and a diol charging pipe are provided as the slurrying process. A fully mixed first ester comprising a slurry preparation tank 2 and a slurry storage tank 3 equipped with a stirrer, and equipped with a stirrer, a separation tower, a raw material receiving port, a catalyst charging pipe, and a reactant transfer pipe as an esterification step. Using a fully mixed second esterification reaction tank 5 equipped with an agitation reaction tank 4, a stirrer, a separation tower, a raw material receiving port, a catalyst charging pipe, and a reactant transfer pipe, and as a polycondensation step, a stirrer, a separation tower , Oligomer receiving port, fully mixed first melt polycondensation reaction tank 6 equipped with catalyst charging pipe, stirrer, separation tower, polymer receiving port, poly Using a plug flow type second fusion polycondensation reaction tank 7 and the third melt polycondensation reaction tank 8 having a over withdrawal, it was produced polyester continuously. Here, ethylene glycol storage tank 1, slurry preparation tank 2, slurry storage tank 3, first esterification reaction tank 4, second esterification reaction tank 5, first melt polycondensation reaction tank 6, and second melt polycondensation reaction tank 7 The third melt polycondensation reaction tank 8 is connected by a pipe in this order, and each reaction tank has a jacket through which a heat medium flows. Further, the polyester obtained by the reaction was taken out from the third melt polycondensation reaction tank 8 through a polymer filter into a strand form from a die plate, and was granulated using a pelletizer while cooling with water.

  The slurrying process was performed in the slurry preparation tank 2 and the slurry storage tank 3. 260 parts by mass of terephthalic acid and 116 parts by mass of ethylene glycol received as a raw material having the composition shown in Table 2 are supplied to the slurry preparation tank 2, and the addition amount as phosphorus is 7 ppm by mass with respect to the obtained polyester. Then, an ethylene glycol solution of ethyl acid phosphate was added, and stirred and mixed to prepare a slurry. The slurry obtained in the slurry preparation tank 2 was transferred to the slurry storage tank 3 every 3 hours to obtain a slurry used in the esterification step.

The esterification step was performed in the first esterification reaction tank 4 and the second esterification reaction tank 5.
In the first esterification reaction tank 4, the slurry is continuously supplied from the slurry storage tank 3 to the first esterification reaction tank 4 at 125 parts by mass / hour. A bottom liquid mainly composed of ethylene glycol extracted from the separation tower 9 is continuously fed as raw material ethylene glycol, and the ethylene glycol is heated at a temperature of 270 ° C., a pressure of 244 kPaA, and an average residence time of 2.0 to 2.5 hours. And by distilling by-products such as water. The esterification rate in the first esterification reaction tank 4 was 89%.

  In the separation tower 9 of the first esterification reaction tank 4, low temperature components such as water are removed at a temperature of 190 ° C. and a pressure of 244 kPaA, and ethylene glycol is mainly contained from the tower bottom so that the liquid level becomes substantially constant. The bottom liquid was extracted. This tower bottom liquid was continuously fed out of the system at 4.4 parts by mass / hour and remained in the first esterification reaction tank 4 at 1.9 parts by mass / hour in the second esterification reaction tank 5. Were continuously fed as raw material ethylene glycol.

  The oligomer obtained in the first esterification reaction tank 4 is continuously supplied to the second esterification reaction tank 5 via a pipe, and ethylene extracted from the separation tower 9 of the first esterification reaction tank 4 is supplied. Glycol is continuously supplied, and a column bottom liquid mainly composed of ethylene glycol extracted from the separation column 10 of the second esterification reaction tank 5 described later is continuously supplied. 1 part by weight of ethylene glycol received as the raw material ethylene glycol was continuously supplied, and by-products such as ethylene glycol and water were distilled at a temperature of 266 ° C., a pressure of 106 kPaA, and an average residence time of 1.6 to 2.0 hours. The esterification reaction was carried out while taking out.

In the separation tower 10 of the second esterification reaction tank 5, at a temperature of 190 ° C. and a pressure of 106 kPaA, low boiling point components such as water are removed, and ethylene glycol is mainly contained from the bottom of the tower so that the liquid level is substantially constant. The bottom liquid was extracted. The entire amount of the bottom liquid was continuously supplied to the second esterification reaction tank 10.
The esterification rate in the second esterification reaction tank 10 was 96%.
In the pipe for transferring the oligomer obtained in the second esterification reaction tank 10 to the polycondensation step, an ethylene glycol solution of magnesium acetate is continuously added to the obtained polyester so that the addition amount as magnesium is 11 mass ppm. Added to. Moreover, the ethylene glycol solution of tetrabutoxy titanium was continuously added with respect to the obtained polyester so that the addition amount as titanium might be 5 mass ppm.

  The polycondensation step was performed in the first melt polycondensation reaction tank 6, the second melt polycondensation reaction tank 7, and the third melt polycondensation reaction tank 8. The reaction conditions of the polycondensation step are 268 ° C., 3.5 kPaA for the first stage melt polycondensation reaction tank, and an average residence time of 1 hour, and 276 ° C., 0.6 kPaA for the second stage melt polycondensation reaction tank, average residence time. The time was 1 hour, the third stage melt polycondensation reactor was 277 ° C., 0.3 kPaA, and the average residence time was 1 hour. A solution obtained by adding an ethylene glycol solution of magnesium acetate and an ethylene glycol solution of tetrabutoxytitanium to the oligomer obtained in the second esterification reaction tank 5 is supplied to the first melt polycondensation reaction tank 6, and subsequently, It transferred to the 2nd melt polycondensation reaction tank 7 and the 3rd melt polycondensation reaction tank 8. The obtained polyester is taken out from the third melt polycondensation reaction tank 8 in a strand form from a die plate via a polymer filter, and is cooled with water, using a pelletizer and having a mass of 20 to 26 mg / grain. Particles were used. The intrinsic viscosity IV of the polyester particles was 0.63 dL / g, the terminal carboxyl group amount AV was 22 eq / t, and the color coordinate b value was 2.2. The obtained polyester particles were excellent in transparency and almost colorless.

  Q values obtained from the slurry preparation step and the weighted average of a, b, c, and (a + b + 2c) in ethylene glycol supplied to the second esterification reaction tank, each weighted by the amount of ethylene glycol supplied. It is shown in 2.

[Example 1 ]
In the polyester manufacturing apparatus shown in FIG. 3, terephthalic acid was used as the dicarboxylic acid component, and ethylene glycol was used as the diol component, and the polyester was continuously manufactured. That is, a nitrogen-sealed corn roof type ethylene glycol storage tank 1 (the material of the inner surface of the tank is SUS304) is used as the ethylene glycol supply process, and impurities having a low boiling point in ethylene glycol are put on the tower top as the ethylene glycol purification process. Using an ethylene glycol initial distillation column 12 for separating by distillation and an ethylene glycol rectifying column 13 for separating impurities having high boiling points in ethylene glycol at the bottom of the column, as a slurrying step, a stirrer and a dicarboxylic acid charging pipe And a slurry preparation tank 2 equipped with a diol feed pipe, and as a esterification step, a fully mixed first esterification reaction tank 4 equipped with a stirrer, a raw material receiving port, a catalyst feed pipe, and a reactant transfer pipe, and stirring Complete mixing type second esterification equipped with machine, raw material receiving port, catalyst charging pipe, reactant transfer pipe A fully mixed type first melt polycondensation reaction tank 6 equipped with a stirrer, a separation tower, an oligomer receiving port, and a catalyst charging pipe as a polycondensation step using a reaction tank 5 and a separation tower 11, a stirrer, and a separation tower Polyester was continuously produced using a plug flow type double condensation reaction tank 7 and a third melt polycondensation reaction tank 8 having a polymer inlet and a polymer outlet. Here, ethylene glycol storage tank 1, slurry preparation tank 2, first esterification reaction tank 4, second esterification reaction tank 5, first melt polycondensation reaction tank 6, second melt polycondensation reaction tank 7, third melt The polycondensation reaction tanks 8 are connected by piping in this order, and each reaction tank is equipped with a jacket through which a heat medium flows. Further, the polyester obtained by the reaction was taken out from the third melt polycondensation reaction tank 8 through a polymer filter into a strand form from a die plate, and was granulated using a pelletizer while cooling with water.

  The slurrying process was performed in the slurry preparation tank 2. To the slurry preparation tank 2, terephthalic acid was continuously supplied at 56 parts by mass / hour, and ethylene glycol received as a raw material having the composition shown in Table 2 was continuously supplied at 13 parts by mass / hour, as shown in Table 2. A liquid mainly composed of ethylene glycol extracted from the bottom of the separation column 11 in the esterification step described later, by continuously supplying ethylene glycol purified in an ethylene glycol purification step having a composition of 6 parts by mass / hour. Was continuously supplied to the slurry preparation tank 2. Furthermore, an ethylene glycol solution of ethyl acid phosphate was added to the resulting polyester so that the amount added as phosphorus was 7 ppm by mass, and stirred and mixed to prepare a slurry. This slurry was used as a slurry used in the esterification step.

The esterification step was performed in the first esterification reaction tank 4 and the second esterification reaction tank 5. In the first esterification reaction tank 4, the slurry is continuously supplied from the slurry preparation tank 2 to the first esterification reaction tank 4 at 85 parts by mass / hour, at a temperature of 263 ° C., a pressure of 225 kPaA, and an average residence time of 4. The esterification reaction was performed in 5 to 5.0 hours while distilling out by-products such as ethylene glycol and water. The esterification rate in the first esterification reaction tank 4 was 89%.
In the second esterification reaction tank 5, the oligomer obtained in the first esterification reaction tank 4 is continuously supplied via a pipe, and 1 part by mass of ethylene glycol received as a raw material having the composition shown in Table 2 The ethylene glycol purified in the ethylene glycol purification step having the composition shown in Table 2 is continuously fed at 1 part by mass / hour, temperature 260 ° C., pressure 106 kPaA, average residence time 2 The reaction was carried out while distilling out by-products such as ethylene glycol and water.
In the separation column 11 in the esterification step, a low-boiling component such as water is removed at a temperature of 145 ° C. and a pressure of 16 kPaA, and a column bottom liquid mainly composed of ethylene glycol is removed from the column bottom so that the liquid level becomes substantially constant. Extracted. The entire amount of this tower bottom liquid was continuously fed to the slurry preparation tank 2.
The esterification rate in the second esterification reaction tank 5 was 96%.
In the pipe for transferring the oligomer obtained in the second esterification reaction tank 5 to the polycondensation step, an ethylene glycol solution of magnesium acetate is continuously added to the obtained polyester so that the addition amount as magnesium is 11 mass ppm. Added to. Moreover, the ethylene glycol solution of tetrabutoxy titanium was continuously added with respect to the obtained polyester so that the addition amount as titanium might be 5 mass ppm.

  The polycondensation step was performed in the first melt polycondensation reaction tank 6, the second melt polycondensation reaction tank 7, and the third melt polycondensation reaction tank 8. The reaction conditions of the polycondensation step are 273 ° C., 2.7 kPaA for the first stage melt polycondensation reaction tank, and an average residence time of 1 hour, and 276 ° C., 0.24 kPaA, the average residence time for the second stage melt polycondensation reaction tank. The time was 1 hour, the third stage melt polycondensation reactor was 278 ° C., 0.1 kPaA, and the average residence time was 1 hour. A solution obtained by adding an ethylene glycol solution of magnesium acetate and an ethylene glycol solution of tetrabutoxytitanium to the oligomer obtained in the second esterification reaction tank 5 is supplied to the first melt polycondensation reaction tank 6, and subsequently, It transferred to the 2nd melt polycondensation reaction tank 7 and the 3rd melt polycondensation reaction tank 8. A bottom liquid mainly composed of ethylene glycol is withdrawn from the bottom of the separation tower (not shown) of the first, second and third triple condensation reaction tanks, and continuously fed into a distilled ethylene glycol liquid storage tank 1 ′. The solution was sent to.

  Table 3 shows values of a, b, c, and (a + b + 2c) in the distillate ethylene glycol liquid storage tank 1 ′. The entire amount of the distillate ethylene glycol liquid storage tank 1 ′ was sent to the ethylene glycol purification step. The ethylene glycol purification step was performed in the ethylene glycol initial distillation column 12 and the ethylene glycol rectification column 13. First, in ethylene glycol primary distillation column 12, at a temperature of 200 ° C. and a pressure of 101 kPaA, a low boiling point component such as water is removed, and a column containing ethylene glycol as a main component from the bottom of the column so that the liquid level becomes substantially constant. The bottom liquid was extracted. The total amount of the bottom liquid was continuously supplied to the ethylene glycol rectification column 13 and recovered by distilling ethylene glycol at the top of the column at 170 ° C. and a pressure of 10 kPaA. The collected ethylene glycol was continuously fed to the ethylene glycol storage tank 1. Table 3 shows the values of a, b, c, and (a + b + 2c) in the top liquid of the ethylene glycol rectification column 13.

The obtained polyester was taken out from the third melt polycondensation reaction tank 8 through a polymer filter in a strand form from a die plate, and cooled with water, using a pelletizer, and having a mass of 22 to 28 mg / grain. Particles were used. The intrinsic viscosity IV of the polyester particles was 0.63 dL / g, the terminal carboxyl group amount AV was 27 eq / t, and the color coordinate b value was 2.2.
The obtained polyester particles were excellent in transparency and almost colorless. In addition, the yellowish color was lighter than the polyester particles obtained in Reference Example 1 .

  Table 2 shows q values determined from the weighted average of a, b, c in ethylene glycol supplied to the slurry preparation step and the second esterification reaction tank, and (a + b + 2c) of each step.

[Comparative Example 1]
The raw material ethylene glycol was changed to the ethylene glycol shown in Table 2, and ethylene glycol used to prepare ethylene glycol solutions of ethyl acid phosphate, magnesium acetate, and tetrabutoxy titanium was accepted as the raw material shown in Table 2. Polyester particles were obtained in the same manner as in Reference Example 1 except that ethylene glycol was used.

  Table 2 shows q values obtained from the weighted average of a, b, c in ethylene glycol supplied to the slurry preparation step and the second esterification step, and (a + b + 2c) in each step.

The obtained polyester particles had an intrinsic viscosity IV of 0.63 dL / g, a terminal carboxyl group amount AV of 20 eq / t, and a color coordinate b value of 4.5. The obtained polyester particles were excellent in transparency, but were slightly colored yellow compared to the polyester particles obtained in Reference Example 1 .

As shown in Table 2, the color tone was good in Reference Example 1 and Example 1 in which the q value satisfied the definition of the present invention, but in Comparative Example 1 in which the q value was higher than the definition of the present invention, the color tone Became worse.

  According to the present invention, since it is possible to prevent coloration when producing polyester, it is possible to obtain polyester with good color tone.

1: ethylene glycol storage tank 1 ': distilled ethylene glycol liquid storage tank 2: slurry preparation tank 3: slurry storage tank 4: first esterification reaction tank 5: second esterification reaction tank 6: first melt polycondensation reaction tank 7: Second melt polycondensation reaction tank 8: Third melt polycondensation reaction tank 9: First separation tower 10: Second separation tower 11: Separation tower 12: First ethylene glycol distillation tower 13: Ethylene glycol rectification tower

Claims (5)

A method for producing a polyester comprising a dicarboxylic acid component and a diol component mainly composed of ethylene glycol as raw materials, and comprising at least one of a slurrying step, an esterification step, and a polycondensation step, and a purification step of ethylene glycol. ,
The ethylene glycol purification step includes a method in which ethylene glycol is distilled by a distillation column and ethylene glycol is distilled off at the top of the column and recovered. The ethylene glycol that has passed through the ethylene glycol purification step is converted into one of the diol components. A method for producing a polyester , wherein the diol component satisfies the following formula (I):
0.01 ≦ q ≦ 34 (I)
However, q = a + b + 2c
a: Content (mol ppm) of the compound represented by the following formula (1) with respect to the ethylene glycol
b: Content (mol ppm) of the compound represented by the following formula (2) with respect to the ethylene glycol
c: Content of the compound represented by the following formula (3) with respect to the ethylene glycol (mol ppm)

The method for producing a polyester according to claim 1 , wherein the polyester production method includes an esterification step, and ethylene glycol that has passed through the ethylene glycol purification step is added to the esterification step. A slurrying step of the production method of the polyester is mixing the diol component and the dicarboxylic acid component, a portion of ethylene glycol via the purification process of the ethylene glycol to claim 1 is added to the slurry step The manufacturing method of polyester of description. The method for producing a polyester according to any one of claims 1 to 3 , wherein the polycondensation step uses a polycondensation reaction catalyst, and the polycondensation reaction catalyst contains a titanium compound. Production method of the polyester having an esterification step and the polycondensation step, adding the polycondensation catalyst, the polyester oligomer obtained in the esterification step in the piping for transferring to the polycondensation step, claim 4 The manufacturing method of the polyester as described in 1 ..

Images