JP2004269602A - Method for manufacturing polyester resin composition, and polyester film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polyester resin composition and a polyester film, containing less foreign matter and having good color tone. <P>SOLUTION: A polyester containing a coloring component is brought into contact with an oxidizing substance or a reducing substance to give a color tone (b value) of 12 or lower. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

【０１００】
【発明の効果】
異物が少なく、色調の良好なポリエステル樹脂組成物およびポリエステルフィルムを得ることができ、光学材料用フィルムとして好適に使用することができる。[0001]
[Prior art]
Polyester resin is obtained by polycondensation of a dicarboxylic acid component and a diol component.In particular, polyethylene terephthalate resin produced from terephthalic acid or its ester-forming derivative and ethylene glycol is excellent in versatility and practicality, and polyester It is suitably used for films and the like.
[0002]
In a commercial process for producing a polyethylene terephthalate resin from terephthalic acid or its ester-forming derivative and ethylene glycol as a high molecular weight polymer, antimony compounds, germanium compounds, and titanium compound compounds are widely used as polycondensation catalysts. However, polyesters using these polymerization catalysts have some undesirable properties.
[0003]
In order to use a polyester film for optical applications, it is preferable that the polyester film be colorless and transparent.For example, a polymer obtained using an antimony catalyst has a foreign substance containing antimony metal, and the catalyst has the same activity as the polymerization activity. Since the polymer obtained also has a decomposition activity, the obtained polymer has a color such as yellowish color. When a germanium compound is used as a catalyst, a polymer having a good color tone is easily obtained, but the germanium compound is very expensive and difficult to use for general purposes.
[0004]
Titanium compounds can be mentioned as catalysts that do not easily form foreign substances, but polymers using titanium compounds as catalysts have a strong yellow tint and are far from colorless and transparent.
[0005]
In order to solve such a problem, for example, Patent Document 1 discloses a method of using a Group 4 element phosphate having a specific average particle diameter or specific surface area as a polymerization catalyst. Patent Document 2 discloses a method of using a titanium compound, a phosphorus compound, an alkali metal compound, or the like. Patent Literature 3 discloses a method of polymerizing in the presence of a phosphorus compound, a titanium compound, a cobalt compound, and a divalent metal compound. Patent Literature 4 discloses an antimony compound, Patent Document 5 discloses a method using a titanium compound, an alkali metal compound or an alkaline earth metal compound. Patent Document 5 discloses the use of a phosphorus compound, a titanium compound, a cobalt compound, and a fluorescent whitening agent. Patent Document 6 discloses a hydrolyzate of a titanium halide. And a method using a co-catalyst and a hue adjusting agent.
[0006]
However, these conventional techniques are not satisfactory, for example, the bluish color is emphasized or the L value is reduced even when the yellowish color is suppressed. Further, it has been difficult to balance the color tone by the method of devising a polymerization catalyst or adding a color tone adjusting agent.
[0007]
[Patent Document 1] Japanese Patent Application Laid-Open No. 2002-308973
[Patent Document 2] Japanese Patent Application Laid-Open No. 2002-179781
[Patent Document 3] Japanese Patent Application Laid-Open No. 2000-256452
[Patent Document 4] Japanese Patent Application Laid-Open No. 9-87374
[Patent Document 5] JP-A-8-73581
[Patent Document 6] JP-A-2001-89557
[Problems to be solved by the invention]
An object of the present invention is to solve the conventional problems described above and to provide a method for producing a polyester resin composition having good color tone and a polyester film suitable for optical use.
[0014]
[Means for Solving the Problems]
The present inventors have found that the above problem can be solved by directly decomposing a coloring component generated in a polyester polymerization process, and have reached the present invention.
[0015]
That is, the present invention is characterized by a method for producing a polyester resin composition having a color tone (b value) of 12 or less by contacting a polyester with an oxidizing substance or a reducing substance.
[0016]
BEST MODE FOR CARRYING OUT THE INVENTION
The polyester resin composition of the present invention is a polyester resin composition in which the polyester is brought into contact with an oxidizing substance or a reducing substance so that the b-value indicating the color tone is 12 or less.
[0017]
The polyester usually includes a compound derived from a polyester or a monomer having a double bond, a polyester or a monomer having a titanium atom coordinated, a compound derived from a catalyst, and the like, and these become coloring components, which will be described later. The color tone (b value) tends to increase. In the present invention, an oxidizing substance or a reducing substance is caused to act on (contact with) a polyester containing these coloring components to reduce the coloring components, thereby obtaining a polyester resin composition having a color tone (b value) of 12 or less. Things.
[0018]
In addition, setting the color tone (b value) to 12 or less includes not only the case where the color tone exceeds 12 but also the case where the color tone (b value) is 12 or less and the case where the color tone (b value) is 12 or less.
[0019]
Further, the color tone in the present invention is measured using a Hunter type color difference meter, and refers to the b value out of those represented by the L value, the a value, and the b value. The b value is an index indicating the yellowish tint. When the b value is large, the yellow tint is strong, and when the b value is small, the yellow tint is weak. According to the method for producing a polyester resin composition of the present invention, the b value can be adjusted to 12 or less. If the value exceeds 12, it becomes difficult to use as an optical film because of a strong yellow tint. The smaller the b-value, the weaker the yellow tint, but it is preferably 10 or less, particularly preferably 8 or less. Further, the L value is preferably 60 or more for an optical film.
[0020]
The polyester resin composition obtained in the present invention contains a polymer synthesized from dicarboxylic acid or its ester-forming derivative and diol or its ester-forming derivative, and can be used as a molded article such as a fiber, a film, and a bottle. If so, there is no particular limitation. Examples of such a polyester include polyethylene terephthalate, polybutylene terephthalate, polycyclohexane dimethylene terephthalate, polypropylene terephthalate, polyethylene naphthalate, and polyethylene-1,2-bis (2-chlorophenoxy) ethane-4,4′-dicarboxy. And the like, and polyethylene terephthalate is particularly preferred.
[0021]
Such a polyethylene terephthalate may contain a copolymerization component in a dicarboxylic acid component or a glycol component. Examples of the dicarboxylic acid component include aromatic dicarboxylic acids such as isophthalic acid, naphthalenedicarboxylic acid, 4,4′-diphenyldicarboxylic acid, and 5-sodium sulfoisophthalic acid, and ester-forming derivatives thereof, and fats such as adipic acid and sebacic acid. Aliphatic dicarboxylic acids or their ester-forming derivatives, alicyclic dicarboxylic acids such as cyclohexanedicarboxylic acid or their ester-forming derivatives, and the like.Examples of the glycol component include propanediol, butanediol, neopentyl glycol, Methylene glycol, polyethylene glycol, polypropylene glycol, cyclohexane dimethanol, bisphenol A ethylene oxide adduct and the like and ester-forming derivatives thereof, and further, parahydroxybenzoic acid. And the like, and hydroxycarboxylic acids and ester-forming derivatives thereof.
[0022]
Further, the polyester resin composition of the present invention, if necessary, various additives, for example, an antioxidant, an antistatic agent, a crystal nucleating agent, inorganic particles, organic particles, a thickener, a heat stabilizer, a lubricant, an infrared ray An absorber, an ultraviolet absorber, and the like may be added.
[0023]
A titanium compound is preferably used as the polycondensation catalyst. This is because the titanium compound is less likely to form foreign matter than the antimony compound. The titanium compound used as the polycondensation catalyst is preferably a titanium compound in which the substituent of the titanium compound is at least one selected from the group consisting of an alkoxy group, a phenoxy group, an acylate group, an amino group and a hydroxyl group. It is preferably used.
[0024]
In the present invention, among these titanium compounds, a tetraalkoxytitanium compound is particularly preferred in that foreign matter formation can be suppressed.
[0025]
When the titanium compound as a catalyst in the present invention is added in an amount of 0.5 to 50 ppm in terms of titanium atom weight with respect to the obtained polymer, the polymerization activity is high, and the obtained polymer has good thermal stability and color tone, which is preferable. More preferably, it is 1 to 30 ppm, still more preferably 3 to 20 ppm. When the content is 0.5 ppm or less in terms of titanium atomic weight, the polymerization activity is insufficient. On the other hand, when the content is more than 50 ppm, foreign matter due to the titanium catalyst is likely to be generated, and the heat resistance of the obtained polyester is also poor. There is. The titanium element in the titanium compound is stored as it is in the obtained resin composition.
[0026]
The polyester composition of the present invention preferably contains 0.1 to 100 ppm of a phosphorus element together with a titanium element in terms of phosphorus atom weight based on the polyester composition. The phosphorus element content is preferably from 1 to 80 ppm, more preferably from 3 to 50 ppm, from the viewpoint of the thermal stability and color tone of the polyester at the time of spinning and film formation. When the content is 0.1 ppm or less in terms of phosphorus atom weight, catalyst-derived foreign matter is easily formed, and the color tone and heat resistance of the obtained polyester are easily deteriorated. On the other hand, when the content exceeds 100 ppm, catalyst-based foreign matter is formed. And the polymerization reaction takes a long time, which may lower the productivity of the polyester resin.
[0027]
The phosphorus (phosphoric acid or phosphate compound, phosphonic acid or phosphonate compound) contained in the polyester composition of the present invention is a residue of the phosphorus compound added during the polyester production process. Such a phosphorus compound is at least one selected from the group consisting of phosphoric acid, phosphorous acid, phosphonic acid, phosphinic acid, phosphine oxide, phosphonous acid, phosphinous acid and phosphine. It is preferably a phosphorus compound. In particular, from the viewpoints of thermal stability, suppression of foreign matter formation, and improvement of color tone, phosphoric compounds based on phosphoric acid and / or phosphonic acid are preferred.
[0028]
In the polyester composition of the present invention, the content of the antimony element is preferably 30 ppm or less in terms of metal atom weight. Within this range, it is possible to obtain a relatively inexpensive polymer with less generation of foreign matter and the like. More preferably, it is preferably not more than 10 ppm, particularly not substantially contained.
[0029]
At the time of polymerization, it is preferable to include an alkaline earth metal element from the viewpoints of suppression of foreign matter formation, polymerization activity, and volume resistivity when the polyester resin is melted, and the content of the alkaline earth metal element is 5 to 100 ppm (weight (The same applies hereinafter). Among them, it is particularly preferable to include calcium and magnesium elements in the polyester resin in an amount of 5 to 100 ppm (weight basis).
[0030]
The polyester resin composition having the color tone of the present invention can be obtained by bringing the polyester resin composition into contact with an oxidizing substance or a reducing substance. The color tone of the polyester resin composition is affected by a coloring substance (coloring component) generated in the resin. Such a coloring substance can be decomposed by contact with an oxidizing substance or a reducing substance. Note that the oxidizing substance and the reducing substance have a property of oxidizing and reducing a partner substance, and the oxidizing substance preferably has a standard electrode potential of +300 mV or more. It is +500 mV or more, particularly preferably +1,000 mV or more. Similarly, the reducing substance preferably has a standard electrode potential of -300 mV or less, more preferably -500 mV or less, particularly preferably -1,000 mV or less.
[0031]
Examples of such an oxidizing substance include hydrogen peroxide, ozone, hypochlorite, sulfur dioxide, sulfuric acid, nitric acid, sodium percarbonate, and percarboxylic acid. Further, the percarboxylic acid includes peracetic acid, perpropionic acid, and perbutylic acid. Such oxidizing substances may be used alone or in combination of two or more. These oxidizing substances may be in contact with the polyester resin by gas when they are vaporizable, or may be brought into contact with the polyester resin as an aqueous solution.
[0032]
Examples of the reducing substance include thiourea dioxide, thiosulfate, metal oxalate, hydrogen sulfide, hydrogen peroxide, and sulfur dioxide. As in the case of the oxidizing substance, the reducing substance may be used alone or in combination of two or more. These reducing substances may be in contact with the polyester resin by gas when they are vaporizable, or may be brought into contact with the polyester resin as an aqueous solution.
[0033]
Further, after the contact treatment with the oxidizing substance, the polyester resin may be washed and then subjected to the contact treatment with the reducing substance, and the order of the treatment may be reversed.
[0034]
As for the conditions for bringing the oxidizing substance or the reducing substance into contact with the polyester, it is advantageous that the temperature and pressure are higher, and the treatment can be performed in a shorter time. When treating with an aqueous solution, the treatment is preferably performed at a temperature of 40 ° C. or more for 30 minutes or more, and when treating with a gas, the treatment is preferably performed at a temperature of 40 ° C. or more and a pressure of 1 atm or more for 30 minutes or more.
[0035]
The oxidizing substance used in the present invention is preferably hydrogen peroxide, ozone, or peracetic acid, and the reducing substance is preferably thiourea dioxide. By using these oxidizing substances and reducing substances, the coloring substance contained in the polyester resin is efficiently decomposed, and has little effect on the polyester resin itself.
[0036]
In the present invention, an oxidizing substance or a reducing substance may be subjected to contact treatment with the polyester resin after the polymerization reaction has been substantially completed, but a prepolymer is obtained by an esterification reaction or a transesterification reaction, followed by polycondensation. A method of adding the above-mentioned oxidizing substance or reducing substance to the reaction system at any time of the reaction may be employed.
[0037]
The polyester film of the present invention may have a single-layer structure, but is preferably a laminated polyester film in which a layer made of the polyester resin of the present invention is laminated on at least one surface depending on the purpose.
[0038]
Since the polyester film of the present invention has a good color tone and a small amount of foreign matter, it is suitable as an optical polyester film used for an optical member.
[0039]
Next, a method for producing the polyester resin composition and the polyester film of the present invention will be described. An example of polyethylene terephthalate is described as a specific example, but is not particularly limited.
[0040]
Polyethylene terephthalate is usually produced by one of the following processes. That is, (1) a process of obtaining a low polymer by a direct esterification reaction using terephthalic acid and ethylene glycol as raw materials and further obtaining a high molecular weight polymer by a subsequent polycondensation reaction, and (2) a process of using dimethyl terephthalate and ethylene glycol as raw materials. In this process, a low polymer is obtained by a transesterification reaction, and a high molecular weight polymer is obtained by a subsequent polycondensation reaction. Here, the esterification reaction proceeds without a catalyst, but a titanium compound may be added as a catalyst. In the transesterification reaction, the reaction is carried out using a compound containing elements such as manganese, calcium, magnesium, zinc, and lithium and the titanium catalyst of the present invention, and after the transesterification reaction is substantially completed, For the purpose of inactivating the used catalyst, a phosphorus compound may be added.
[0041]
In the present invention, the low polymer obtained in any stage of the series of reactions (1) or (2), preferably in the first half of the series of reactions (1) or (2), may be added, if necessary, to the low polymer obtained. After adding additives such as inorganic and organic particles as a lubricant, the above-mentioned titanium compound is added as a polycondensation catalyst, and a polycondensation reaction is performed to obtain high molecular weight polyethylene terephthalate.
[0042]
In order to improve the color tone of the obtained polyester resin, the above-mentioned oxidizing substance or reducing substance may be added at any stage of the above reaction.
[0043]
The above reaction is carried out in a batch system, a semi-batch system, a continuous system, or the like, but the production method of the present invention can be applied to any of these systems.
[0044]
Next, the color tone of the polyester resin is adjusted by bringing a gas or an aqueous solution of an oxidizing substance or a reducing substance into contact with the obtained polyester resin. For example, a polyester resin is immersed in a 30% aqueous solution of hydrogen peroxide, heated to about 70 ° C., and stirred for about 3 hours.
[0045]
Next, in the production of a polyester film, the polyester resin composition obtained as described above is prepared, and if necessary, pre-dried in hot air or under reduced pressure, and then supplied to an extruder.
[0046]
In the extruder, the resin heated and melted at a temperature equal to or higher than the melting point is made uniform in the amount of resin extruded by a gear pump or the like, and foreign matter or denatured resin is filtered through a filter or the like. Further, the resin is discharged after being formed into a target shape by a die.
[0047]
When a laminated film is used, for example, a method of laminating polyester resins sent from different channels using two or more extruders using a field block, a static mixer, a multi-manifold die, or the like is used. Can be. The sheet or the single film sheet having a laminated structure discharged from the die in this way is extruded onto a cooling body such as a casting drum and cooled and solidified to obtain a casting film. At this time, it is preferable to use a wire-shaped, tape-shaped, needle-shaped or knife-shaped electrode to bring the electrode into close contact with a cooling body such as a casting drum by electrostatic force and to rapidly solidify.
[0048]
The casting film thus obtained may be biaxially stretched as needed. Biaxial stretching refers to stretching in the machine and transverse directions. The stretching may be performed sequentially biaxially or simultaneously in two directions. Further, re-stretching may be performed in the longitudinal and / or transverse directions.
[0049]
Here, the stretching in the longitudinal direction refers to stretching for giving a film a molecular orientation in the longitudinal direction, and is performed, for example, by a difference in peripheral speed of a roll. This stretching may be performed in one stage, or may be performed in multiple stages using a plurality of roll pairs. The stretching magnification is preferably 2 to 15 times, more preferably 2.5 to 7 times.
[0050]
Further, the surface of the film thus obtained may be coated with a coating technique such as a gravure coater or a metalling bar to give an easy-adhesion layer or an easy-slip layer.
[0051]
In addition, the stretching in the transverse direction refers to stretching to give the film a width direction orientation. For example, the film is conveyed while holding both ends of the film with clips using a tenter, and stretched in the width direction. The stretching magnification is preferably 2 to 10 times.
[0052]
In the case of simultaneous biaxial stretching, the film is simultaneously stretched in the vertical and horizontal directions while being conveyed while holding both ends of the film in a tenter with clips, and this method may be used.
[0053]
The biaxially stretched film is preferably subjected to a heat treatment at a stretching temperature or higher and a melting point or lower in a tenter in order to impart flatness and dimensional stability, and after uniform slow cooling, is cooled to room temperature and wound up. . In the film of the present invention, the heat treatment temperature is preferably from 120 ° C to 240 ° C from the viewpoint of flatness, dimensional stability, and the like.
[0054]
The polyester film of the present invention has a good color tone, and can be preferably used as a protective film, a polarizing film, a light diffusion film, and the like of an optical display device such as a liquid crystal display device, a plasma display device, and a CRT display device.
[0055]
【Example】
Hereinafter, the present invention will be described in more detail with reference to Examples. The physical properties in the examples were measured by the methods described below.
[0056]
(1) Content of Titanium Element, Alkaline Earth Metal Element, Phosphorus Element, and Antimony Element in Polyester Resin Composition Using a fluorescent X-ray apparatus (model number 3270) manufactured by Rigaku Corporation, 8 g of a polymer is melted and formed into a plate shape. Then, the intensity of the fluorescent X-ray was measured. This value was converted to the metal content using a calibration curve prepared in advance with a sample whose content was known.
[0057]
(2) Measurement of color tone of polyester resin The L value, a value, and b value of the hunter were measured using an SM color computer “SM-3” manufactured by Suga Test Instruments Co., Ltd.
[0058]
(3) Intrinsic viscosity of polyester resin Orthochlorophenol was used as a solvent and measured at 25 ° C.
[0059]
Reference Example 1 (Production of colloidal silica particles)
4 parts by weight of saturated aqueous ammonia was mixed with 40 parts by weight of ethyl alcohol, and 4 parts by weight of 4 pentyl silicon was added with stirring to obtain colloidal silica having an average particle diameter of 0.2 μm. Then, 100 parts by weight of ethylene glycol was added, and the mixture was heated to distill off ethyl alcohol and water to obtain an ethylene glycol slurry of colloidal silica.
[0060]
Reference Example 2 (Production of polyethylene terephthalate)
A slurry of 100 parts by weight of high-purity terephthalic acid and 43 parts by weight of ethylene glycol is sequentially supplied to an esterification reaction tank in which about 120 parts by weight of bis (hydroxyethyl) terephthalate is previously charged and the temperature is maintained at 250 ° C. over 4 hours. Then, after the completion of the supply, the esterification reaction was performed while distilling water for another 1 hour, and 120 parts by weight of the esterification reaction product was transferred to the polycondensation tank.
[0061]
Subsequently, 0.012 parts by weight of ethyl diethylphosphonoacetate was added to the polycondensation reaction tank to which the esterification reaction product had been transferred, 0.04 parts by weight of magnesium acetate tetrahydrate, and tetrabutyl titanate were further added. Was added in an amount of 0.004 parts by weight. Next, the ethylene glycol slurry of colloidal silica prepared in Reference Example 1 was added so that the particle concentration in the polymer became 0.1%.
[0062]
Thereafter, while stirring the low polymer, the temperature of the reaction system was gradually raised from 250 ° C. to 285 ° C., and the pressure was reduced to 100 Pa. When the stirring torque reached a predetermined value, the reaction system was purged with nitrogen and returned to normal pressure to stop the polycondensation reaction, discharged into cold water in a strand form, and immediately cut to obtain polymer pellets.
[0063]
The intrinsic viscosity of the obtained polymer was 0.65, the color L value was 61.6, the a value was -0.6, and the b value was 16.7.
[0064]
Reference Example 3 (Production of peracetic acid solution)
75 parts by weight of acetic acid, 23 parts by weight of a hydrogen peroxide solution having a concentration of 30% by weight, and 3 parts by weight of concentrated sulfuric acid were mixed and reacted at room temperature for 24 hours to prepare an aqueous solution of peracetic acid.
[0065]
Reference Example 4 (Production of polyethylene terephthalate)
A slurry of 100 parts by weight of high-purity terephthalic acid and 43 parts by weight of ethylene glycol is sequentially supplied to an esterification reaction tank in which about 120 parts by weight of bis (hydroxyethyl) terephthalate is previously charged and the temperature is maintained at 250 ° C. over 4 hours. Then, after the completion of the supply, the esterification reaction was performed while distilling water for another 1 hour, and 120 parts by weight of the esterification reaction product was transferred to the polycondensation tank.
[0066]
Subsequently, 0.012 parts by weight of ethyl diethylphosphonoacetate was added to the polycondensation reaction tank to which the esterification reaction product had been transferred, 0.04 parts by weight of magnesium acetate tetrahydrate, and tetrabutyl titanate were further added. Was added in an amount of 0.05 part by weight. Next, the ethylene glycol slurry of colloidal silica prepared in Reference Example 1 was added so that the particle concentration in the polymer was 0.1% by weight.
[0067]
Thereafter, while stirring the low polymer, the temperature of the reaction system was gradually raised from 250 ° C. to 285 ° C., and the pressure was reduced to 100 Pa. When the stirring torque reached a predetermined value, the reaction system was purged with nitrogen and returned to normal pressure to stop the polycondensation reaction, discharged into cold water in a strand form, and immediately cut to obtain polymer pellets.
[0068]
The intrinsic viscosity of the obtained polymer was 0.65, the color L value was 50.6, the a value was 1.7, and the b value was 18.5.
[0069]
(Example 1)
50 parts by weight of the polyester resin of Reference Example 2 and 200 parts by weight of a 20% by weight aqueous solution of hydrogen peroxide were charged into a reaction vessel equipped with a stirring blade and a reflux condenser. While stirring, the temperature of the contents was maintained at 70 ° C., and the treatment was performed for 2 hours.
[0070]
The treated polyester resin was separated from the aqueous hydrogen peroxide solution, washed sufficiently with water, and dried. The intrinsic viscosity of the polymer after the treatment was 0.65, the color L value was 70.4, the a value was -0.6, and the b value was 6.0.
[0071]
(Film formation of polyester film)
The polyester resin was dried by a reduced-pressure drier and supplied to an extruder.
[0072]
The polyester resin is melted at 280 ° C. by an extruder, fed through a gear pump and a filter, fed to a T-die and formed into a sheet, and then subjected to static electricity with a wire-like electrode while the surface temperature is lowered to 20 ° C. Quenched and solidified on the kept casting drum.
[0073]
The obtained cast film was heated with a set of rolls set at 90 ° C., stretched 3.0 times in the longitudinal direction, guided to a tenter, preheated with hot air at 100 ° C., and stretched 3.3 times in the transverse direction. The stretched film was directly subjected to heat treatment in a tenter with hot air at 200 ° C., gradually cooled to room temperature, and wound up. The thickness of the obtained film was 50 μm.
[0074]
Regarding the color tone of the obtained film, the L value was 68.5, the a value was -0.6, and the b value was 6.5.
[0075]
(Example 2)
50 parts by weight of the polyester resin of Reference Example 2 and 200 parts by weight of a 20% by weight aqueous solution of thiourea dioxide were charged into a reaction vessel equipped with a stirring blade and a reflux condenser. While stirring, the temperature of the contents was maintained at 40 ° C., and the treatment was performed for 5 hours.
[0076]
The treated polyester resin was separated from thiourea dioxide aqueous solution, washed sufficiently with water, and dried. The intrinsic viscosity of the polymer after the treatment was 0.65, the color tone L value was 65.5, the a value was -0.6, and the b value was 9.9.
[0077]
Then, a film was formed under the same conditions as in Example 1. Regarding the color tone of the obtained film, the L value was 63.5, the a value was -0.6, and the b value was 10.5.
[0078]
(Example 3)
Ozone gas heated to 70 ° C. was passed through a container charged with 50 parts by weight of the polyester resin of Reference Example 2 at a rate of 1 part by weight / hour for 6 hours.
[0079]
The intrinsic viscosity of the polymer after the treatment was 0.65, the color L value was 64.5, the a value was -0.5, and the b value was 9.0.
[0080]
Then, a film was formed under the same conditions as in Example 1. Regarding the color tone of the obtained film, the L value was 64.0, the a value was -0.5, and the b value was 9.8.
[0081]
(Example 4)
50 parts by weight of the polyester resin of Reference Example 2 and 200 parts by weight of the aqueous solution of peracetic acid of Reference Example 3 were charged into a reaction vessel equipped with a stirring blade and a reflux condenser. While stirring, the temperature of the contents was maintained at 30 ° C., and the treatment was performed for 2 hours.
[0082]
The polyester resin after the treatment was separated from the aqueous solution of peracetic acid, washed sufficiently with water, and dried. The intrinsic viscosity of the polymer after the treatment was 0.63, the color tone L value was 68.5, the a value was -0.6, and the b value was 5.5.
[0083]
Then, a film was formed under the same conditions as in Example 1. Regarding the color tone of the obtained film, the L value was 67.5, the a value was -0.6, and the b value was 6.5.
[0084]
(Comparative Example 1)
50 parts by weight of the polyester resin of Reference Example 2 and 200 parts by weight of purified water were charged into a reaction tank equipped with a stirring blade and a reflux condenser. While stirring, the temperature of the contents was maintained at 70 ° C., and the treatment was performed for 6 hours.
[0085]
The treated polyester resin was separated from purified water and dried. The intrinsic viscosity of the polymer after the treatment was 0.65, the color L value was 61.6, the a value was -0.6, and the b value was 16.7.
[0086]
Then, a film was formed under the same conditions as in Example 1. Regarding the color tone of the obtained film, the L value was 59.0, the a value was -0.6, and the b value was 18.0.
No change was observed in the color tone of the polyester by ordinary water treatment.
[0087]
(Example 5)
A slurry of 100 parts by weight of high-purity terephthalic acid and 43 parts by weight of ethylene glycol is sequentially supplied to an esterification reaction tank in which about 120 parts by weight of bis (hydroxyethyl) terephthalate is previously charged and the temperature is maintained at 250 ° C. over 4 hours. Then, after the completion of the supply, the esterification reaction was performed while distilling water for another 1 hour, and 120 parts by weight of the esterification reaction product was transferred to the polycondensation tank.
[0088]
Subsequently, 0.012 parts by weight of ethyl diethylphosphonoacetate was added to the polycondensation reaction tank to which the esterification reaction product had been transferred, 0.04 parts by weight of magnesium acetate tetrahydrate, and tetrabutyl titanate were further added. Was added and 0.005 parts by weight of potassium oxalate was added. Next, the ethylene glycol slurry of colloidal silica prepared in Reference Example 1 was added so that the particle concentration in the polymer was 0.1% by weight.
[0089]
Thereafter, while stirring the low polymer, the temperature of the reaction system was gradually raised from 250 ° C. to 285 ° C., and the pressure was reduced to 100 Pa. When the stirring torque reached a predetermined value, the reaction system was purged with nitrogen and returned to normal pressure to stop the polycondensation reaction, discharged into cold water in a strand form, and immediately cut to obtain polymer pellets.
The intrinsic viscosity of the obtained polymer was 0.65, the color L value was 64.5, the a value was -0.6, and the b value was 11.5.
[0090]
Then, a film was formed under the same conditions as in Example 1. Regarding the color tone of the obtained film, the L value was 63.0, the a value was -0.6, and the b value was 12.0.
[0091]
(Example 6)
A slurry of 100 parts by weight of high-purity terephthalic acid and 43 parts by weight of ethylene glycol is sequentially supplied to an esterification reaction tank in which about 120 parts by weight of bis (hydroxyethyl) terephthalate is previously charged and the temperature is maintained at 250 ° C. over 4 hours. Then, after the completion of the supply, the esterification reaction was performed while distilling water for another 1 hour, and 120 parts by weight of the esterification reaction product was transferred to the polycondensation tank.
[0092]
Subsequently, 0.012 parts by weight of ethyl diethylphosphonoacetate was added to the polycondensation reaction tank to which the esterification reaction product had been transferred, 0.04 parts by weight of magnesium acetate tetrahydrate, and tetrabutyl titanate were further added. Was added and 0.005 parts by weight of potassium thiosulfate was added. Next, the ethylene glycol slurry of colloidal silica prepared in Reference Example 1 was added so that the particle concentration in the polymer was 0.1% by weight.
[0093]
Thereafter, while stirring the low polymer, the temperature of the reaction system was gradually raised from 250 ° C. to 285 ° C., and the pressure was reduced to 100 Pa. When the stirring torque reached a predetermined value, the reaction system was purged with nitrogen and returned to normal pressure to stop the polycondensation reaction, discharged into cold water in a strand form, and immediately cut to obtain polymer pellets.
[0094]
The intrinsic viscosity of the obtained polymer was 0.65, the color tone L value was 63.5, the a value was -0.6, and the b value was 10.5.
[0095]
Then, a film was formed under the same conditions as in Example 1. Regarding the color tone of the obtained film, the L value was 63.0, the a value was -0.6, and the b value was 11.5.
[0096]
(Example 7)
50 parts by weight of the polyester resin of Reference Example 4 and 200 parts by weight of a 20% by weight aqueous solution of hydrogen peroxide were charged into a reaction vessel equipped with a stirring blade and a reflux condenser. While stirring, the temperature of the contents was maintained at 70 ° C., and the treatment was performed for 2 hours.
[0097]
The treated polyester resin was separated from the aqueous hydrogen peroxide solution, washed sufficiently with water, and dried. The intrinsic viscosity of the polymer after the treatment was 0.65, the color tone L value was 57.5, the a value was 1.5, and the b value was 12.0.
[0098]
Then, a film was formed under the same conditions as in Example 1. Regarding the color tone of the obtained film, the L value was 55.0, the a value was 1.7, and the b value was 12.0.
[0099]
[Table 1]

[0100]
【The invention's effect】
It is possible to obtain a polyester resin composition and a polyester film having a small amount of foreign matter and good color tone, and can be suitably used as a film for an optical material.

Claims (10)

A method for producing a polyester resin composition having a color tone (b value) of 12 or less by contacting a polyester with an oxidizing substance or a reducing substance. After a prepolymer is obtained from an aromatic dicarboxylic acid or an ester-forming derivative thereof and an aliphatic glycol by an esterification reaction or a transesterification reaction, an oxidizing substance or The method for producing a polyester resin composition according to claim 1, wherein a reducing substance is added. The method for producing a polyester resin composition according to claim 1 or 2, wherein the polyester resin composition contains 0.5 to 50 ppm (by weight) of a titanium element and 0.1 to 100 ppm (by weight) of a phosphorus element. The oxidizing substance is at least one substance selected from the group consisting of hydrogen peroxide, ozone, hypochlorite, sulfur dioxide, sulfuric acid, nitric acid, sodium percarbonate and percarboxylic acid, according to claim 1 to 3, wherein A method for producing the polyester resin composition according to any one of the above. The method for producing a polyester resin composition according to claim 4, wherein the percarboxylic acid is at least one acid selected from the group consisting of peracetic acid, perpropionic acid, and perbutylic acid. 4. The method according to claim 1, wherein the reducing substance is at least one substance selected from the group consisting of thiourea dioxide, metal thiosulfate, metal oxalate, hydrogen sulfide, hydrogen peroxide and sulfur dioxide. A method for producing the polyester resin composition as described above. The method for producing a polyester resin composition according to any one of claims 1 to 6, wherein a titanium compound is used as a polycondensation catalyst. The method for producing a polyester resin composition according to any one of claims 1 to 7, wherein the polyester resin composition contains 5 to 100 ppm (by weight) of an alkaline earth metal element. A polyester film containing the polyester resin composition obtained by the method according to claim 1. An optical display device comprising the polyester film according to claim 9.