JP4167159B2 - Production method of polyester resin - Google Patents

Description

  The present invention relates to a method for producing a polyester resin, and more particularly to a method for efficiently producing a polyester resin having a very low content of cyclic trimer.

Polyester resins represented by polyethylene terephthalate are excellent in mechanical properties, thermal properties, electrical properties, etc., so they are widely used in molded products such as films, sheets, bottles, etc. ing.
The polyester resin obtained industrially obtained in this manner usually contains several percent of oligomers mainly composed of cyclic trimers (for example, saturated polyester resin handbook, Nikkan Kogyo Co., Ltd. 151). Page). These oligomers are deposited on the surface of films, sheets, bottles, etc. during the molding of polyester resins, causing surface roughness and whitening, resulting in a decrease in product value due to deterioration in quality. If it deposits on the surface, it will cause problems such as making printing difficult, making it unqualified as a product.

  In addition, oligomers cause contamination of dies and molds in the polyester molding process, and remarkably reduce the efficiency of manufacturing molded products, such as increasing the frequency of cleaning and replacement of used dies and molds. In particular, in recent years, as a beverage bottle that requires heat sterilization filling such as fruit juice beverages, after the injection molded preform is reheated and softened, the blow mold is heated when stretch blow molding is performed. Alternatively, the bottle provided with heat resistance is greatly stretched by subjecting the bottle to heat setting using a separate heating mold after stretch blow molding. However, because of the tendency of soiling due to the oligomer of the mold to perform heat setting at high temperature, in order to prevent soiling, the amount of oligomer in the polyester resin before molding such as bottles as a cyclic trimer that is the main component It is often required to be 4000 ppm or less, preferably 3000 ppm or less.

  In order to reduce the content of the cyclic trimer in the polyester resin to an amount suitable for the above purpose, a method of performing solid phase polymerization for a long time subsequent to melt polymerization of the polyester prepolymer is widely used industrially. However, since a currently known formulation requires about 20 hours or more for solid phase polymerization, a production method with higher productivity is desired.

  Patent Document 1 and Patent Document 2 describe a method in which a polyester precursor in the form of molten fine particles having an average particle size of about 300 μm or less is subjected to a polycondensation reaction in an inert gas stream at a temperature equal to or higher than the melting point. In addition, although a method in which ethylene glycol is contained in the inert gas stream in the above method is also described, in our study, in the above method in which the polycondensation reaction is performed in a molten state, the by-product of cyclic three-component It has been found that there is a problem in that the mass is not sufficiently reduced.

  Patent Document 3 describes a method of improving the polymerizability by heat-treating polyester having a particle size of 1 mm or less in a diol-containing inert gas at a temperature just below the melting point, and subsequently performing solid-phase polymerization under high vacuum. ing. In this method, although the reason is unknown, it is a requirement to perform solid-state polymerization at a high vacuum, and since the apparatus for high vacuum is expensive, the method is not suitable for large-scale production. There was a point. Moreover, the said literature does not describe at all about the reduction | decrease of the cyclic trimer in polyester.

  Further, Patent Document 4 discloses a method for producing a linear polyester comprising forming a polyester prepolymer into particles and then polymerizing in a solid phase, and the particles are heated at about 140 ° C. to about 2 ° C. below the melting point of the polyester. From about 0.1 to about 100 hours, contact with an inert gas containing 300 to 7000 ppm (volume) of water or an organic compound having at least one OH group to form a local network A method is disclosed in which the polymer backbone is cut to reduce the gel in the polyester molded article. However, no mention is made of the cyclic trimer, and in the treatment with an inert gas containing water or an organic compound having a predetermined concentration, the cyclic trimer is extremely reduced while the polymerization proceeds to a predetermined molecular weight. It is difficult to reduce it.

Patent Document 5 discloses that a crude polyester obtained by polycondensation reaction of a dicarboxylic acid component and a glycol component is 180 ° C. or higher in an inert gas atmosphere containing the glycol component in a proportion of at least 100 ppm. However, this method has a problem in that ethylene glycol monomer remains in the product polyester.
JP 2000-239368 A Japanese Patent Laid-Open No. 2001-40080 US Pat. No. 6,284,866 JP-T 8-505421 JP-A-8-120062

  An object of the present invention is to provide a method for efficiently producing a high-quality polyester resin having a low content of cyclic trimer and ethylene glycol.

In order to achieve the above object, the method of the present invention is a granular polyester prepolymer produced by subjecting a dicarboxylic acid containing terephthalic acid as a main component and a diol containing ethylene glycol as a main component to an esterification reaction and a polycondensation reaction. In the method for producing a polyester resin, the granular polyester obtained by presolid-phase polymerization of the polyester prepolymer is heat-treated in a mixed gas containing an inert gas and water and / or ethylene glycol, and then subjected to solid-phase polymerization. The concentration of gaseous water and / or ethylene glycol in the gas is set to 0.75 (volume)% or more and 50 (volume)% or less, and heat treatment of the prepolymer or the pre-solid-state polymerization polyester of the prepolymer is performed at 200 ° C. above, at a temperature each of the melting point, and in the solid state, the polyester prepolymer Alternatively, the difference (BA) between the intrinsic viscosity (A) before heat treatment of the polyester obtained by presolid-phase polymerization of the polyester prepolymer and the intrinsic viscosity (B) after heat treatment is −0.3 dl / g or more. A polyester resin, characterized in that solid-state polymerization is carried out under conditions of 220 ° C. or higher, at a temperature not higher than the melting point of each of the prepolymer or pre-solid-phase polymerized polyester of the prepolymer, and at a pressure not lower than atmospheric pressure. The gist of the manufacturing method.

A preferred embodiment of the method of the present invention is as follows.
[When heat-treating polyester prepolymer]
The intrinsic viscosity of the polyester prepolymer before heat treatment is 0.1 dl / g or more and 0.5 dl / g or less; the intrinsic viscosity (A) of the polyester prepolymer before heat treatment, and the intrinsic viscosity (B) after heat treatment Heat treatment under the condition that the difference (B−A) is −0.3 dl / g or more; the solid phase polymerization is performed at a temperature of 220 ° C. or more and 2 ° C. or lower than the melting point of the polyester prepolymer; The polyester prepolymer is fine particles having an average particle diameter of 10 to 1500 μm; and the difference between the amount of cyclic trimer (C) before heat treatment and the amount of cyclic trimer (D) after heat treatment in the polyester prepolymer ( It can be mentioned that (C-D) is 3000 ppm or more.

[When heat-treating polyester obtained by pre-solid-phase polymerization of polyester prepolymer]
The intrinsic viscosity of the polyester obtained by pre-solid-phase polymerization of the polyester prepolymer before heat treatment is 0.1 dl / g or more and 0.5 dl / g or less; the intrinsic viscosity of the polyester obtained by pre-solid-phase polymerization of the polyester prepolymer before heat treatment Heat treatment is performed under a condition that the difference (B−A) between (A) and the intrinsic viscosity (B) after heat treatment is −0.3 dl / g or more; solid phase polymerization is 220 ° C. or more, polyester prepolymer At a temperature not higher than 2 ° C. below the melting point of the polyester subjected to the preliminary solid-phase polymerization; the polyester obtained by pre-solid-phase polymerization of the polyester prepolymer is a fine particle having an average particle size of 10 to 1500 μm; Difference between the amount of cyclic trimer (C) before heat treatment and the amount of cyclic trimer (D) after heat treatment in pre-solid-phase polymerized polyester (C D) is, can be mentioned that this is 2000ppm or more.

  According to the method of the present invention, the polyester prepolymer or the polyester obtained by presolid-phase polymerization of the polyester prepolymer is heat-treated in an inert gas containing a predetermined amount of water and / or ethylene glycol at a predetermined temperature, Polyester resin obtained by solid-phase polymerization under atmospheric pressure is low in cyclic trimer and ethylene glycol content and is suitable for molding films, sheets, bottles, etc. Since the resin can be produced efficiently, the method of the present invention is an industrially useful method.

Hereinafter, the present invention will be described in detail.
In the method for producing a polyester resin in the present invention, a polyester prepolymer or a polyester obtained by preliminarily solid-phase polymerization of the polyester prepolymer (hereinafter also referred to as pre-solid phase polymerized polyester) is heat-treated in a predetermined mixed gas, This is a method for producing polyester comprising solid-phase polymerization. A polyester prepolymer can be produced by a conventionally known melt polymerization method, and a polyester obtained by preliminary solid-phase polymerization of a polyester prepolymer is also known in the art. It can be manufactured by the method.

[Production method of polyester prepolymer]
The polyester prepolymer is obtained by polycondensation of a dicarboxylic acid component containing terephthalic acid as a main component and a diol component containing ethylene glycol as a main component through an esterification reaction. It is preferably a polycondensate of a dicarboxylic acid component occupying 95 mol% or more of the dicarboxylic acid component and a diol component in which ethylene glycol occupies 95 mol% or more of the total diol component, and the ethylene terephthalate unit by them is a repeating structural unit It is preferable to occupy 90 mol% or more of the above. When the ethylene terephthalate unit is less than 90 mol%, the mechanical strength and heat resistance of the polyester resin after solid phase polymerization tend to be inferior.

  The polyester prepolymer having ethylene terephthalate units as the main repeating structural unit includes, for example, phthalic acid, isophthalic acid, 1,4-phenylenedioxydicarboxylic acid, 1,3-phenylic acid as dicarboxylic acid components other than terephthalic acid. Rangeoxydiacetic acid, 4,4′-diphenyldicarboxylic acid, 4,4′-diphenylether dicarboxylic acid, 4,4′-diphenylketone dicarboxylic acid, 4,4′-diphenoxyethanedicarboxylic acid, 4,4′-diphenyl Sulfone dicarboxylic acids, aromatic dicarboxylic acids such as 2,6-naphthalenedicarboxylic acid, alicyclic dicarboxylic acids such as hexahydroterephthalic acid and hexahydroisophthalic acid, and succinic acid, glutaric acid, adipic acid, pimelic acid, and suberic acid , Azelaic acid, sebacic acid, undecadi Carboxylic acid, one or two or more of such aliphatic dicarboxylic acids such as dodeca dicarboxylic acids may be used as a copolymerization component.

  As diol components other than ethylene glycol, for example, trimethylene glycol, tetramethylene glycol, pentamethylene glycol, hexamethylene glycol, octamethylene glycol, decamethylene glycol, neopentyl glycol, diethylene glycol, polyethylene glycol, polytetramethylene ether glycol Aliphatic diols such as 1,2-cyclohexanediol, 1,4-cyclohexanediol, 1,1-cyclohexanedimethylol, alicyclic diols such as 1,4-cyclohexanedimethylol, and xylylene glycol, 4′-dihydroxybiphenyl, 2,2-bis (4′-hydroxyphenyl) propane, 2,2-bis (4′-β-hydroxyethoxyphenyl) propane, bis 4-hydroxyphenyl) sulfone, bis (4-beta-hydroxyethoxyphenyl) one or two or more of such aromatic diols such as sulfonic acid, may be used as a copolymerization component.

  Furthermore, for example, hydroxycarboxylic acids and alkoxycarboxylic acids such as glycolic acid, p-hydroxybenzoic acid, p-β-hydroxyethoxybenzoic acid, and stearyl alcohol, benzyl alcohol, stearic acid, benzoic acid, t-butylbenzoic acid Monofunctional components such as benzoylbenzoic acid, trifunctional or more polyfunctional components such as tricarballylic acid, trimellitic acid, trimesic acid, pyromellitic acid, gallic acid, trimethylolethane, trimethylolpropane, glycerol, pentaerythritol, etc. 1 type (s) or 2 or more types may be used as a copolymerization component.

The polyester prepolymer is produced by polycondensing a dicarboxylic acid component mainly composed of terephthalic acid and a diol component mainly composed of ethylene glycol through an esterification reaction in the presence of a polycondensation catalyst. Basically, however, it depends on a conventional method for producing a polyester resin. That is, the dicarboxylic acid component containing terephthalic acid as a main component and the diol component containing ethylene glycol as a main component together with a copolymer component used as necessary are put into a slurry preparation tank and mixed with stirring. After making the raw material slurry, the esterification reaction is carried out in the esterification reaction tank at normal pressure to under pressure and under heating, the polyester low molecular weight product as the obtained esterification reaction product is transferred to the polycondensation tank, In the presence of a condensation catalyst, melt polycondensation is carried out under heating under reduced pressure as gradually reduced pressure from normal pressure to obtain a polyester prepolymer.
In addition, these are made | formed by a continuous type or a batch type, and an esterification reaction tank and a polycondensation tank are good also as a single stage or a multistage, respectively.

In the prepolymer production method, the esterification reaction is performed at a temperature of about 200 to 270 ° C. and a pressure of about 1 × 10 ⁵ to 4 × 10 ⁵ Pa, and the esterification reaction rate is usually 90% or more, preferably After 93% or more, it is shifted to melt polycondensation. The melt polycondensation is performed at a temperature of about 240 to 290 ° C. and about 1.33 to 1333 Pa in the presence of a polycondensation catalyst, preferably in the presence of a phosphorus compound. Made under reduced pressure.
The esterification reaction can be performed in the absence of a catalyst, but may be performed in the presence of a germanium compound, an antimony compound, a titanium compound, or the like as a catalyst. These catalysts can be appropriately selected from known catalyst compounds listed as polycondensation catalysts described later.

  As the polycondensation catalyst, a catalyst conventionally used as a polycondensation catalyst for polyester resin production is used. For example, germanium dioxide, germanium tetroxide, germanium hydroxide, germanium oxalate, germanium tetraethoxide, germanium tetra-n Germanium compounds such as butoxide, antimony trioxide, antimony pentoxide, antimony acetate, antimony compounds such as methoxyantimony, tetra-n-propyl titanate, tetra-i-propyl titanate, tetra-n-butyl titanate, titanium oxalate, oxalic acid Titanium compounds such as titanium potassium can be used alone or in combination, or in addition, organic acid salts such as magnesium and cobalt can be used in combination. The amount used is preferably 1 to 400 ppm, particularly preferably 3 to 300 ppm, based on the resulting polyester prepolymer.

At the time of melt polycondensation, together with the polycondensation catalyst, phosphoric compounds such as orthophosphoric acid, tris (triethylene glycol) phosphate, ethyl diethyl phosphonoacetate, ethyl acid phosphate, triethylene glycol acid phosphate, phosphorous acid and the like are allowed to coexist as a stabilizer. Is preferred. The amount used is preferably 1 to 1000 ppm, particularly preferably 2 to 200 ppm, based on the resulting polyester prepolymer.
Furthermore, compounds of alkali metals and alkaline earth metals such as lithium acetate, sodium acetate, potassium acetate, magnesium acetate, magnesium hydroxide, magnesium alkoxide, magnesium carbonate, potassium hydroxide, calcium hydroxide, calcium acetate, calcium carbonate are also mentioned. It can also be used with a polycondensation catalyst.

  The polyester prepolymer of the present invention obtained after melt polymerization by the method as described above preferably has an intrinsic viscosity of 0.1 dl / g or more and 0.5 dl / g or less, particularly 0.4 dl / g or less, In particular, it is more preferably 0.3 dl / g or less. When the intrinsic viscosity of the polyester prepolymer is 0.5 dl / g or less, the melt polycondensation reaction can be carried out in one step without requiring two or more steps, which is advantageous in terms of equipment cost.

  The polyester prepolymer preferably contains 0.001 to 10% by weight of ethylene glycol. A polyester prepolymer containing a small amount of ethylene glycol has a low viscosity even when the degree of polymerization is high, and is easy to granulate. For example, a spray cooler that jets into a gas phase from an injection nozzle can be used. It is expected that the polymerization rate in the polymerization can be increased.

Although the polyester prepolymer after melt polycondensation is granulated, it is usually extruded into a strand form from the outlet provided at the bottom of the polycondensation tank, and cooled with water or after water cooling, cut with a cutter, pellets, It is a granular material such as a chip.
The polyester prepolymer of the present invention having a preferable intrinsic viscosity range as described above is obtained from a method obtained by cutting while extruding a strand extruded from the polymerization vessel outlet into water as a granulation method because it has a low melt viscosity or from an injection nozzle. A method obtained by jetting particles in a gas phase or a liquid phase, and a method of generating droplets and cooling and solidifying them on a conveyor can be employed.
The average particle size of the polyester prepolymer granules is preferably 10 to 1500 μm. More preferably, they are 50 micrometers-1000 micrometers, More preferably, they are 100 micrometers-500 micrometers. When the average particle diameter exceeds 1500 μm, the solid phase polymerization rate is slow, and when the average particle diameter is 10 μm or less, scattering into the air is likely to occur, which is not preferable for handling.

[Preliminary solid-phase polymerization method of polyester prepolymer]
The pre-solid phase polymerization of the polyester prepolymer granules obtained above is performed at a temperature of about 220 ° C. to 2 ° C. lower than the melting point of the polyester prepolymer (melting point−2 ° C.) in the reaction tower containing the polyester prepolymer, It can be carried out by circulating an inert gas such as nitrogen, carbon dioxide or argon at atmospheric pressure or higher. The polymerization temperature is preferably 230 ° C. or higher and the melting point of the prepolymer is −2 ° C. or lower. When the polymerization temperature is lower than 220 ° C., a sufficient preliminary solid phase polymerization rate cannot be obtained.
As the inert gas to be circulated in the reaction tower, a gas that does not substantially contain hydrogen and ethylene glycol in the gas at the time of feeding is used.

The superficial velocity of the inert gas flowing through the reaction tower is 0.001 to 100 m / min, and the pressure is in the range of atmospheric pressure to 1 MPa. Here, the superficial velocity refers to a value obtained by dividing the flow rate of the introduced inert gas by the cross-sectional area of the reaction tower.
Further, the polyester prepolymer fine particles may be subjected to a crystallization treatment in order to prevent fusion between the granular materials before the preliminary solid phase polymerization. Examples of the crystallization treatment method include a method of performing crystallization treatment while raising the temperature with a paddle type stirring device, or a method of performing crystallization treatment in a flowing state under an inert gas stream. The crystallization treatment is usually performed at 60 to 220 ° C.
Preliminary solid-phase polymerization can be carried out batchwise or continuously, but industrially a continuous method is advantageous.

  The pre-solid phase polymerization time may be a time required for the molecular weight of the pre-solid phase polymerized polyester to reach a desired level, and is usually 1 minute to 10 hours, preferably 5 minutes to 7 hours, and more preferably 10 minutes to 5 minutes. Selected from time range. When the time is shorter than this range, it is difficult to increase the molecular weight of the polyester after the preliminary solid-phase polymerization. On the other hand, when the time exceeds this range and the time is too long, the content of the cyclic trimer targeted by the present invention is small. It becomes difficult to efficiently produce a high-quality polyester resin.

  The pre-solid phase polymerized polyester of the present invention obtained after pre-solid phase polymerization by the method as described above preferably has an intrinsic viscosity of 0.1 dl / g or more and 0.5 dl / g or less, particularly 0.48 dl. / G or less, more preferably 0.45 dl / g or less.

In the present invention, the heat treatment of the polyester prepolymer granules or the polyester granules obtained by presolid-phase polymerization of the polyester prepolymer is performed by contacting the granules with a heated inert gas and a mixed gas containing water and / or ethylene glycol. It is done by letting.
The inert gas is not particularly limited as long as it is a gas that does not adversely influence the reaction, and examples thereof include nitrogen, argon, carbon dioxide, helium, etc. Nitrogen is advantageous in terms of availability and price. Further, the mixed gas contains water and / or ethylene glycol, and ethylene glycol is preferable because the effect of reducing the cyclic trimer is great.

  The concentration of gaseous water and / or ethylene glycol in the mixed gas introduced into the heat treatment needs to be 0.75 (volume)% or more and 50 (volume)% or less, preferably 0.80 (volume). )% Or more, more preferably 2.0 (volume)% or more and 30 (volume)% or less, particularly preferably 5.0 (volume)% or more and 20 (volume)% or less. If the amount is less than 0.75 (volume)%, the reduction of the cyclic trimer is insufficient. On the other hand, if the amount exceeds 50 (volume)%, the molecular weight decreases greatly during the heat treatment, and it takes a long time to reach a predetermined degree of polymerization. Is not preferable.

  The heat treatment is performed at a temperature of 200 ° C. or more, a temperature equal to or lower than the melting point of each of the polyester prepolymer or the polyester obtained by preliminarily solid-phase polymerization of the polyester prepolymer, and needs to be performed in a solid state. If this temperature range is exceeded and the temperature is too low, the cyclic trimer cannot be reduced at a sufficient rate, and if the temperature exceeds this temperature range, the prepolymer or the pre-solid-phase polymerized polyester particles are fused together. Wearing occurs and is not preferable. Here, the solid state means a state where the particles of the polyester prepolymer or the pre-solid-phase polymerized polyester are not fused. The heat treatment temperature of the polyester prepolymer or the pre-solid-phase polymerized polyester is preferably selected in the range of 200 ° C. to 2 ° C. lower than the melting point (melting point −2 ° C.).

  Further, the polyester prepolymer fine particles may be subjected to crystallization treatment before heat treatment, if necessary, in order to prevent fusion between the granular materials, as before the preliminary solid phase polymerization. As a method of crystallization treatment, for example, a method of performing crystallization treatment while raising the temperature with a paddle type stirring device or a method of performing crystallization treatment in a flowing state under an inert gas stream is used. The crystallization treatment is usually performed at 60 to 220 ° C.

The heat treatment method may be a method in which the mixed gas is sufficiently in contact with the polyester prepolymer or pre-solid-phase polymerized polyester particles. For example, the mixed gas is present in the tower where the pre-polymer particles or pre-solid-phase polymerized polyester particles are present. For example, a method for circulating a mixed gas in a rotating container in which prepolymer particles or pre-solid-phase polymerized polyester particles are present. The heat treatment and the solid phase polymerization reaction can be carried out in the same reactor, and the heat treatment can be carried out either batchwise or continuously, but industrially a continuous method is advantageous.
When heat treatment is performed in a vertical reaction tower, the superficial velocity of the mixed gas to be introduced is 0.001 to 100 m / min, and the pressure is in the range of atmospheric pressure to 1 MPa. Here, the superficial velocity refers to a value obtained by dividing the flow rate of the mixed gas introduced into the heat treatment by the cross-sectional area of the reaction tower.

  The heat treatment time may be a time required to sufficiently reduce the cyclic trimer in the polyester prepolymer or pre-solid-phase polymerized polyester, but is usually 10 minutes to 20 hours, preferably 30 minutes to 15 hours, More preferably, it is 1 hour-10 hours. If it is less than this range, it is difficult to sufficiently reduce the cyclic trimer, and if it exceeds this range, the polyester resin having a low cyclic trimer content, which is the object of the present invention, is efficiently produced. Becomes difficult.

In the heat treatment according to the present invention, during the heat treatment, water and / or ethylene glycol contained in the mixed gas may break the main chain and the intrinsic viscosity may decrease, so that the polyester prepolymer or the polyester prepolymer is preliminarily solid-phase polymerized. It is preferable that the difference (BA) between the intrinsic viscosity (A) of each of the polyesters before heat treatment and the intrinsic viscosity (B) after the heat treatment is −0.3 dl / g or more. Preferably it is -0.2 dl / g or more, More preferably, it is -0.1 dl / g or more.
When the intrinsic viscosity difference (BA) is less than -0.3 dl / g, it takes time to increase the degree of polymerization to the degree of polymerization required for the polyester resin in the subsequent solid phase polymerization, which is not efficient. Although it is preferable that the difference in intrinsic viscosity (B-A) is large, the upper limit is determined by the intrinsic viscosity of the polyester prepolymer or pre-solid-phase polymerized polyester and the intrinsic viscosity of the desired product after solid-phase polymerization, and cannot be specified uniformly. Usually 0.5 dl / g.

  Furthermore, the difference (C−D) between the amount of cyclic trimer (C) in the polyester prepolymer before heat treatment and the amount of cyclic trimer (D) in the polyester prepolymer after heat treatment is 3000 ppm or more. Is more preferable, and more preferably 4000 ppm or more. When the difference in the amount of cyclic trimer (C−D) is less than 3000 ppm, it becomes difficult to reduce the amount of cyclic trimer to the amount required by the subsequent solid phase polymerization. The larger the value of -D), the better.

Further, the difference (C−D) between the amount of cyclic trimer (C) in the pre-solid phase polymerized polyester before heat treatment and the amount of cyclic trimer (D) in the pre-solid phase polymerized polyester after heat treatment was 2000 ppm. The above is preferable, and more preferably 2500 ppm or more. If the difference in the amount of cyclic trimer (C−D) is less than 2000 ppm, it becomes difficult to reduce the amount of cyclic trimer to the amount required by the subsequent solid phase polymerization. The larger the value of -D), the better.
When pre-solid-phase polymerized polyester is heat-treated, the cyclic trimer amount reduction rate and the intrinsic viscosity increase rate are improved in a well-balanced manner, which is preferable to the heat treatment of the polyester prepolymer because a polyester resin having a desired performance can be obtained in a short time. .

The polyester prepolymer or pre-solid phase polymerized polyester after the heat treatment is then subjected to solid phase polymerization. The solid phase polymerization is carried out in a reaction tower containing the prepolymer or pre-solid phase polymerized polyester after the heat treatment, at 220 ° C. to polyester. It is carried out by circulating an inert gas such as nitrogen, carbon dioxide and argon at a temperature of about 2 ° C. lower than the melting point of each prepolymer or pre-solid-phase polymerized polyester (melting point −2 ° C.) at atmospheric pressure or higher. . The polymerization temperature is preferably 230 ° C. or higher and 2 ° C. lower than the melting point of each prepolymer or pre-solid-phase polymerized polyester (melting point −2 ° C.). When the polymerization temperature is lower than 220 ° C., a sufficient solid phase polymerization rate cannot be obtained.
As the inert gas to be circulated in the reaction tower, a gas that does not substantially contain water and ethylene glycol at the time of feeding is used.
The superficial velocity of the inert gas flowing through the reaction tower is 0.001 to 100 m / min, and the pressure is in the range of atmospheric pressure to 1 MPa. Here, the superficial velocity refers to a value obtained by dividing the flow rate of the inert gas introduced into the reaction tower by the cross-sectional area of the reaction tower.
Solid phase polymerization can be carried out either batchwise or continuously, but industrially, the continuous method is advantageous.

The solid phase polymerization time may be a time required for the molecular weight of the produced polyester resin to reach a desired level, and is usually 1 minute to 20 hours, preferably 5 minutes to 15 hours, more preferably 10 minutes to 10 hours. is there. If the time is shorter than this range, it is difficult to sufficiently increase the molecular weight of the polyester resin. On the other hand, if the time exceeds this range and the time is too long, the high quality of the cyclic trimer content targeted by the present invention is low. It becomes difficult to produce a polyester resin efficiently.
If the polyester prepolymer is subjected to preliminary solid-phase polymerization before the heat treatment, the time required for the polyester resin to reach the desired intrinsic viscosity can be shortened compared to the case where the preliminary solid-phase polymerization is not performed.

  The polyester resin obtained after solid phase polymerization by the method of the present invention has an intrinsic viscosity of 0.60 dl / g to 1.20 dl / g, preferably 0.65 dl / g to 1.10 dl / g, more preferably 0.70 dl. / G to 1.00 dl / g. If the intrinsic viscosity of the polyester resin is lower than 0.60 dl / g, thickness unevenness is likely to occur especially when used for blow molding, and if it is higher than 1.20 dl / g, it is particularly difficult during injection molding. Since sink marks tend to occur, there is a problem in molding processability, the use is limited, and the commercial value is lowered. Furthermore, the cyclic trimer content in the polyester resin obtained after solid phase polymerization is 4000 ppm or less, which is extremely high quality.

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.
In the following examples, “parts” means parts by weight, and various physical property measuring methods in the present invention are as shown below.

(1) Melting point A sample prepared by putting about 10 mg of polyester prepolymer or polyester obtained by pre-solid-phase polymerization of the polyester prepolymer into an aluminum pan was prepared by using a differential scanning calorimeter DSC220C (Seiko Electronics Co., Ltd.) at 20 ° C / The temperature was raised at a rate of minutes, and the point at which the heat of crystal fusion per unit time was the largest was taken as the melting point.

(2) Average particle diameter An integrated distribution curve was created by the method described in JIS K0069, and the value when the integrated percentage reached 50% was defined as the average particle diameter.

(3) Intrinsic viscosity Using phenol / tetrachloroethane (50/50 weight ratio) as a solvent, the sample was heated and dissolved, cooled to room temperature, and measured at 30 ° C using an Ubbelohde viscometer.

(4) Cyclic trimer amount 200 mg of polyester was dissolved in 2 ml of a chloroform / hexafluoroisopropanol (volume ratio 3/2) mixed solution, and further diluted with 20 ml of chloroform. 10 ml of methanol was added thereto to reprecipitate the sample, and a filtrate after filtration was obtained. After the obtained filtrate was dried, the amount of the cyclic trimer was analyzed and quantified with a liquid chromatograph for the liquid obtained by dissolving the residue in 25 ml of dimethylformamide.
As the polyester, the prepolyester polymer before and after the heat treatment or the polyester obtained by preliminary solid-phase polymerization of the polyester prepolymer and the polymer after solid-phase polymerization were measured.

(5) Ethylene glycol and / or water concentration (in mixed gas)
It calculated | required using the following formula from the total amount V (L) of the nitrogen which distribute | circulated the amount M (mol) which ethylene glycol (EG) or water in the front stage container of the apparatus shown in FIG. 1 decreased during heat processing.

Example 1
A slurry was prepared by continuously supplying terephthalic acid and ethylene glycol to a slurry preparation tank so that 13.0 parts of terephthalic acid and 5.82 parts of ethylene glycol were obtained. The slurry was continuously supplied to the first stage esterification reaction tank, and the esterification reaction was continuously carried out at approximately normal pressure at 260 ° C., and bis (2-hydroxyethyl) terephthalate having an ester reaction rate of 84% and its low A polymer was prepared. Bis (2-hydroxyethyl) terephthalate having low ester reaction rate of 95% and its low polymer are continuously fed to the second stage esterification reaction tank and reacted at 255 ° C. under normal pressure. Was prepared.

  The reactants from the second stage esterification reactor are continuously fed to the first stage polycondensation reactor, and 0.011 parts of normal phosphoric acid and 0.038 parts of diantimony trioxide are continuously added to the above. In addition to the reaction product, the reaction is continuously performed at 280 ° C. under a reduced pressure of 1 kPa to 20 kPa, and then the produced reaction product is continuously supplied to the second stage polycondensation reaction tank to be 280 ° C. under a reduced pressure of 10 Pa to 10 kPa. The polycondensation reaction was performed continuously.

  The polycondensation reaction product was continuously extracted from the reaction vessel as a strand into water, cut and pelletized. At this time, the pellets were transparent and not substantially crystallized. The obtained pellets were pulverized by a rotary mill to obtain a pulverized product (polyester prepolymer). The analysis results of the prepolymer are shown in the prepolymer column of Table 1.

Next, the pulverized product (prepolymer) was heat-treated using the apparatus shown in FIG. 3 g of the pulverized product was placed in a glass tube (2) having an inner diameter of 25 mm held in an oil bath at 240 ° C., and a mixed gas consisting of nitrogen and ethylene glycol was circulated at a rate of 1 L / min from below and heat treated for 4 hours. . At this time, the height of the pulverized product in the glass tube is about 1 cm, a thermocouple is set at the center of the pulverized product, and heat treatment is performed while confirming that the sample temperature is the same as the oil bath temperature. It was.
The mixed gas was prepared by circulating nitrogen gas in ethylene glycol in the container (1) held in the oil bath and transferred to the glass tube (2). The ethylene glycol content in the mixed gas was controlled by changing the temperature of the oil bath.
The heat treatment conditions are shown in Table 2, and the analysis results of the prepolymer product after the heat treatment are shown in the heat treated product column of Table 1.

  After the heat treatment was completed, solid phase polymerization was subsequently performed in the same glass tube. The solid phase polymerization was performed by switching the ethylene glycol-containing nitrogen gas circulated during the heat treatment under normal pressure to nitrogen gas not containing ethylene glycol (circulation rate 1 L / min). Solid state polymerization was performed at 250 ° C. for 5 hours. The solid-state polymerization conditions are described in Table 2, and the analysis results of the obtained polyester polymer are shown in the product column after solid-phase polymerization in Table 1.

Example 2, Comparative Examples 1-6
Using the pulverized polyester prepolymer obtained in Example 1, heat treatment and solid phase polymerization were performed under the conditions shown in Example 1 except that the heat treatment conditions and solid phase polymerization conditions were changed as shown in Table 2.
However, in Comparative Example 4, no heat treatment was performed. Further, in Comparative Example 6, since it melted during the heat treatment, solid phase polymerization was not performed.
The analysis results of the obtained polyester polymer are shown in the product column after solid phase polymerization in Table 1.

Example 3
3 g of the pulverized polyester prepolymer obtained in Example 1 was placed in a glass tube (2) having an inner diameter of 25 mm held in an oil bath at 240 ° C., and nitrogen gas was passed from below at a rate of 1 L / min. Preliminary solid phase polymerization was performed for a minute. At this time, the height of the pulverized product in the glass tube is about 1 cm, a thermocouple is set at the center of the pulverized product, and the preliminary solid phase is confirmed while confirming that the sample temperature is the same as the oil bath temperature. Polymerization was performed.
Nitrogen gas was preliminarily solid-phase polymerized so as to circulate directly from the bottom of the glass tube without passing through the container (1) held in the oil bath.
The analysis results of the obtained preliminary solid phase polymerization polyester are shown in the preliminary solid phase polymerization column of Table 1.

After the pre-solid phase polymerization was completed, heat treatment was subsequently performed in the same glass tube. The heat treatment was performed by switching the nitrogen gas circulated during the preliminary solid-phase polymerization to nitrogen gas containing ethylene glycol (circulation rate 1 L / min). Heat treatment was performed at 240 ° C. for 1 hour. Except this, the same procedure as in Example 1 was performed. The heat treatment conditions are described in Table 2, and the analysis results of the obtained pre-solid-phase polymerized polyester are shown in the heat treated product column of Table 1.
After the heat treatment was completed, solid phase polymerization was subsequently performed in the same glass tube. The solid phase polymerization was performed by switching the ethylene glycol-containing nitrogen gas circulated during the heat treatment under normal pressure to nitrogen gas not containing ethylene glycol (circulation rate 1 L / min). Solid state polymerization was performed at 240 ° C. for 2.5 hours. The analysis results of the obtained polyester polymer are shown in the product column after solid phase polymerization in Table 1.

1 is a schematic view of an apparatus used in Example 1. FIG.

Explanation of symbols

1 ethylene glycol container 2 glass tube reactor 3 oil bath 4 oil bath

Claims (6)

Granular polyester prepolymer produced by esterification reaction and polycondensation reaction of dicarboxylic acid containing terephthalic acid as a main component and diol containing ethylene glycol as a main component, or granules obtained by pre-solid-phase polymerization of the polyester prepolymer In a method for producing a polyester resin in which polyester is heat-treated in an inert gas and a mixed gas containing water and / or ethylene glycol, and then subjected to solid-phase polymerization, the gaseous water and / or ethylene glycol in the mixed gas is the concentration 0.75% (by volume) or more, 50 and (volume)% or less, the heat treatment of the preliminary solid-phase polymerization polyester prepolymer or the prepolymer, 200 ° C. or higher, at a temperature below the respective melting point, and solid state, pre the polyester prepolymer or the polyester prepolymer A solid-phase polymerized inherent viscosity before the heat treatment of the polyester (A), the difference between the intrinsic viscosity after heat treatment (B) (B-A) is conducted under the condition that the -0.3dl / g or more, the solid-phase polymerization Is carried out at a temperature not lower than the melting point of each of the prepolymer and the pre-solid-phase polymerized polyester of the prepolymer at a temperature not lower than atmospheric pressure and not lower than 220 ° C.   2. The polyester resin according to claim 1, wherein the intrinsic viscosity of the polyester prepolymer before heat treatment or the polyester obtained by presolid-phase polymerization of the polyester prepolymer is 0.1 dl / g or more and 0.5 dl / g or less. Manufacturing method. Solid state polymerization, 220 ° C. or higher, according to claim 1 or 2, characterized in that a polyester prepolymer or the polyester prepolymer preliminary solid-phase polymerized 2 ℃ low temperature below the temperature than each of the melting point of the polyester Of manufacturing polyester resin. Granular polyester prepolymer or granular polyester was pre solid phase polymerizing the polyester prepolymer has an average particle diameter 10~1500μm according to any one of claims 1 to 3, characterized in that the fine particles of the polyester resin Production method. The difference (C-D) between the amount of cyclic trimer (C) before heat treatment and the amount of cyclic trimer (D) after heat treatment in the polyester prepolymer is 3000 ppm or more. The manufacturing method of the polyester resin as described in any one of thru | or 4 . The difference (C−D) between the amount of cyclic trimer (C) before heat treatment and the amount of cyclic trimer (D) after heat treatment in polyester obtained by presolid-phase polymerization of a polyester prepolymer is 2000 ppm or more. process for producing a polyester resin according to any one of claims 1 to 4, characterized in.

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