JP3780900B2 - Polyester production method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a formulation for producing a polyester having a stable color tone (b value) with little coloration.
[0002]
[Prior art]
Polyesters typified by polyethylene terephthalate (hereinafter referred to as PET) and polybutylene terephthalate (hereinafter referred to as PBT) have excellent properties, such as clothing fibers, industrial material fibers, and films, bottles, and other plastic products. Widely used. As an industrial production method of polyester, a direct polymerization method in which terephthalic acid (hereinafter referred to as TPA) and a glycol component are directly esterified and then polycondensation is widely adopted. In the direct polymerization method, in order to obtain good quality in fibers, films, and other plastic products, it is important to reduce the coloration of the polyester, manage the color tone in a stable state, and reduce variations.
[0003]
Conventionally, as means for controlling the color tone of polyester, the esterification reaction rate is controlled (Japanese Patent Laid-Open No. 7-173268), the reaction temperature is adjusted, and the addition amount of a phosphorus compound as a stabilizer is changed (Japanese Patent Laid-Open No. 10-87808, JP-A-12-319370) and a method of adding a metal phosphate (JP-A-2001-31748) have been adopted, but it has not yet been completely solved.
[0004]
[Problems to be solved by the invention]
The present invention intends to provide a method for producing a polymer having a stable color tone with good color tone and little variation in a method for producing polyester by a direct polymerization method.
[0005]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, the present inventors arrived at the present invention as a result of investigating a slurry preparation process that has been overlooked because it is handled at a relatively low temperature among the polyester production processes. That is, the gist of the present invention is to produce a polyester by preparing a slurry containing dicarboxylic acid mainly composed of terephthalic acid and alkylene glycol, esterifying dicarboxylic acid and alkylene glycol in the slurry, and polycondensation of the esterified product. The method for producing a polyester is characterized in that the slurry is kept in an inert gas atmosphere having an oxygen concentration of 1% by volume or less.
[0006]
DETAILED DESCRIPTION OF THE INVENTION
In the present invention, the esterification and polycondensation of esterified products that are usually performed can be applied as a method for producing the polyester, but the characteristic is in the preparation step of the slurry to be introduced into the esterification step. The slurry is prepared from a dicarboxylic acid mainly composed of TPA and an alkylene glycol, but the inert gas whose oxygen concentration is controlled to 1% by volume or less, preferably 0.5% or less during the period from this preparation to the introduction of the esterification step. It is necessary to keep it in an atmosphere, and it is preferable to keep it in a nitrogen atmosphere from an economical viewpoint. If it is not controlled to 1% or less, the color tone b value (the greater the yellowness, the greater the yellowness) will vary greatly.
[0007]
The slurry preparation may be performed batchwise or continuously. Moreover, although it may carry out with one tank or many tanks, it is normal to carry out with one tank from an economical viewpoint.
In order to maintain an oxygen atmosphere at a predetermined concentration or lower, a slurry preparation tank for adding and mixing a dicarboxylic acid mainly composed of TPA and alkylene glycol, and a slurry storage tank for temporarily storing them are substantially used. This can be achieved by setting the oxygen concentration of the inert gas introduced into the gas phase portion in contact with the slurry to a predetermined concentration or less.
[0008]
Specific examples of dicarboxylic acids other than TPA in the present invention include aromatic dicarboxylic acids such as phthalic acid, isophthalic acid, naphthalenedicarboxylic acid, diphenyldicarboxylic acid, diphenoxyethanedicarboxylic acid, adipic acid, sebacic acid, azelaic acid, decane. Aliphatic dicarboxylic acids such as dicarboxylic acids, and alicyclic dicarboxylic acids such as cyclohexanedicarboxylic acid.
[0009]
The alkylene glycol is ethylene glycol or 1.4 butanediol as the main component, and the diol component other than the main component is ethylene glycol, 1.4 butanediol, diethylene glycol, polyethylene glycol, propylene glycol, 1,3-propanediol, poly Aliphatic diols such as tetramethylene ether glycol, 1,5-pentanediol, neopentyl glycol, 1,6-hexanediol, 1,8-octanediol, 1,2-cyclohexanediol, 1,4-cyclohexanediol, 1 , 1-cyclohexanedimethylol, 1,4-cyclohexanedimethylol and other alicyclic diols, xylylene glycol, 4,4′-dihydroxybiphenyl, 2,2-bis (4′-hydroxyphenyl) propyl Bread, bis (4-hydroxyphenyl) aromatic diol sulfone, and the like.
[0010]
Here, TPA as a dicarboxylic acid component occupies 50 mol% or more of all dicarboxylic acid components, preferably 80 mol% or more, and more preferably 95 mol% or more. Further, ethylene glycol or 1.4 butanediol as a diol component accounts for 50 mol% or more of the total diol component, preferably 80 mol% or more, and more preferably 95 mol% or more.
[0011]
The molar ratio of the dicarboxylic acid and the alkylene glycol in the slurry prepared in the present invention is preferably 1.0 to 3.0, more preferably 1.2 to 2.0. Furthermore, a catalyst and / or a phosphorus compound necessary for esterification and polycondensation may be added to this slurry. As the catalyst, a germanium compound such as germanium dioxide, germanium tetraoxide, germanium tetra n-butoxide, an antimony catalyst such as antimony trioxide, and a titanium catalyst such as titanium tetrabutoxide can be used. The ratio of the catalyst used is usually 0.0005 to 0.2% by weight in terms of the weight of the metal in the catalyst with respect to the weight of the mixture of dicarboxylic acid and alkylene glycol.
Adjustment of the slurry by mixing dicarboxylic acid and alkylene glycol is performed under stirring and mixing in order to sufficiently dissolve TPA, and the temperature ranges from room temperature to 100 ° C, more preferably from 30 ° C to 80 ° C. Done in In addition, it is preferable that a stirring blade is provided in the slurry preparation tank so that mixing and stirring can be performed uniformly.
[0012]
The esterification and polycondensation in the production of the polyester of the present invention may be carried out by ordinary methods. The reaction may be batch or continuous.
That is, the esterification reaction is usually performed at a gauge pressure of 0.11 MPa or less, preferably 0.06 MPa or less. You may carry out under reduced pressure. The temperature of the esterification reaction is usually 150 to 280 ° C, more preferably 180 to 270 ° C, and optimally 220 to 265 ° C. If it is less than 150 ° C., the esterification reaction does not substantially proceed. On the other hand, if it exceeds 280 ° C., byproducts such as diethylene glycol and tetrahydrofuran increase, which is not preferable.
[0013]
Moreover, the polycondensation process which is the next process is usually carried out under a reduced pressure of 10 to 0.01 kPa in absolute pressure, preferably 5 to 0.05 kPa, and the reaction temperature is usually 210 to 300 ° C. The esterification reaction and polycondensation reaction may be performed in one stage or in multiple stages.
Nitrogen gas, argon gas, helium gas, or the like can be used as the inert gas, but nitrogen gas is preferable from an economical viewpoint. As the nitrogen gas, a commercially available gas can be supplied by a cylinder, or a gas produced by a pressure swing method or the like can be used. These inert gases are sealed in the slurry tank vapor phase at a pressure higher than atmospheric pressure, or purged out of the system through the slurry tank vapor phase while being continuously supplied. It is possible to keep the phase part at a low oxygen concentration. Moreover, since oxygen may be mixed when transferring TPA to the slurry tank, it is also preferable to use an inert gas having a low oxygen concentration for transfer.
[0014]
The oxygen concentration in the slurry tank is measured by installing an oxygen concentration meter in the tank gas phase section, in the middle of the line for purging inert gas from the slurry tank, or in the middle of the line for feeding inert gas to the slurry tank. can do. As the oxygen concentration meter, a galvanic cell type, a polarographic type, a thermomagnetic wind type and the like are commercially available, but any type of oxygen concentration meter may be used. These densitometers are suitable for continuous monitoring because they can be measured by converting the oxygen concentration into an electrical signal.
[0015]
【Example】
Examples will be shown below by way of example of the continuous method in which ethylene glycol is the main component of diol, but the present invention is not limited thereto.
In the present invention, the oxygen concentration and the polymer color b value were measured as follows.
[0016]
(Oxygen concentration)
An oxygen concentration meter was installed in the middle of a line for purging the detector (model GD-F4A-SC) manufactured by Riken Keiki Co., Ltd. from the gas phase of the slurry tank to the outside of the system, and continuously monitored.
[0017]
(Hue)
The polyester chips obtained in Examples and Comparative Examples were measured by a reflection method using a 300A type colorimetric color difference meter manufactured by Nippon Denshoku Industries Co., Ltd. In measurement, the apparatus is left to stand for 4 hours or more in advance, and then the chip is sliced into a measuring cell having an inner diameter of 36 mm and a depth of 15 mm (the light receiving portion is made of quartz glass). The b value was measured. The higher the b value, the more yellowish, and the lower the b value, the less yellowish and the better the hue.
[0018]
Example 1
As shown in FIG. 1, ethylene glycol and TPA were continuously supplied to a slurry preparation tank equipped with an oxygen concentration meter, and a slurry was prepared while mixing and stirring so that the molar ratio became 1.51. At this time, nitrogen gas was continuously supplied to the gas phase part of the slurry tank at 1.5 Nm 3 / hr, and the oxygen concentration was controlled to be 0.3% by volume or less. The slurry prepared by mixing in the slurry tank was continuously supplied to the first stage esterification tank at 5.5 ton / hr, and the first stage esterification tank was reacted at 260 ° C. and 0.043 MPa. Further, the second stage esterification tank was reacted at 265 ° C. and 0.005 MPa. Next, the esterified oligomer was continuously transferred to a three-can polymerization system and polymerized under conditions of 273.5 to 278.5 ° C. and 2.81 to 0.22 kPa. The product leaving the polymerization system was chipped and sampled for color tone measurement every three hours. The b value of the chip was measured 8 times every 3 hours. The average value of b values was -0.45, and the standard deviation was 0.11.
[0019]
Comparative Example 1
Using the same equipment as in Example 1, all the nitrogen supplied to the gas phase part of the slurry preparation tank was stopped, and slurry preparation, esterification, and polymerization were performed. The oxygen concentration in the gas phase part of the slurry preparation tank fluctuated in the range of 5 to 13% by volume, and the b value of the polyester chip after polymerization was measured 8 times in the same manner as in Example 1. The average value of b values was 0.31, and the standard deviation was 0.28.
[0020]
Comparative Example 2
In Example 1, except that was slurry prepared by reducing the nitrogen gas amount supplied to the gas phase of the slurry preparation tank from 1.5 Nm ³ / hr to 0.3 Nm ³ / hr is esterified under the same conditions, the polymerization Went. The oxygen concentration was 3.0 to 3.5% by volume. The b value of the polyester chip after polymerization was measured 8 times in the same manner as in Example 1. The average value of b values was 0.05, and the standard deviation was 0.22.
[0021]
【The invention's effect】
According to the present invention, it is possible to suppress the color tone (yellowishness, b value) of a polyester resin, which has been a problem from the past, and to manage the variation to be small. Provision is possible.
[Brief description of the drawings]
FIG. 1 is a diagram of a slurry preparation tank.
[Explanation of symbols]
1 Ethylene glycol 2 Terephthalic acid 3 Nitrogen 4 Nitrogen purge 5 Slurry 6 Slurry supplied to esterification tank 7 Oxygen meter

Claims (4)

Preparation of a slurry containing dicarboxylic acid mainly composed of terephthalic acid and alkylene glycol, esterification of dicarboxylic acid and alkylene glycol in the slurry, and production of polyester by polycondensation of esterified product A method for producing a polyester, characterized by maintaining an inert gas atmosphere having a concentration of 1% by volume or less. 2. The method for producing a polyester according to claim 1, wherein the main component of the alkylene glycol is ethylene glycol. The method for producing a polyester according to claim 1, wherein the main component of the alkylene glycol is 1.4-butanediol. 4. The method according to claim 1, wherein the slurry is prepared in a slurry preparation tank, and the oxygen concentration is continuously monitored by an oxygen concentration meter in a line connected to the gas phase portion of the slurry preparation tank. The manufacturing method of polyester as described.

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