JP2000086876A - Polyester resin composition and film made therefrom - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a resin composition which can give a film excellent in antibacterial properties, gas barrier properties, and transparency by adding a specified amount of an inorganic antibacterial agent to a polyester made from an acid component based on naphthalenedicarboxylic acid and a diol component based on 1,3-propanediol. SOLUTION: This composition is prepared by adding 0.1-10 wt.% inorganic antibacterial agent desirably having a mean particle diameter of 0.1-10 μm to a polyester made from an acid component based on naphthalenedicarboxylic acid, desirably, one at least 80 mol% of which is 2,6-naphthalenedicarboxylic acid and a diol component based on 1,3-propanediol which desirably constitutes at least 80 mol% of the glycol component. It is desirable that the inorganic antibacterial agent comprises a silver-ion-carrying inorganic compound and/or a silver-ion-carrying compound metal oxide represented by formula. In the formula, A1s are Zn and/or Cu atoms; A2s are Mg and/or Cu atoms; and x is a number in the range: 0.01<=x<0.5.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a polyester comprising naphthalenedicarboxylic acid as a main acid component and 1,3-propanediol as a main diol component, wherein 0.1 to 10% by weight of an inorganic antibacterial agent is added. The present invention relates to a characteristic polyester resin composition and a film.

[0002]

2. Description of the Related Art Polyester resins have excellent physical properties.
Due to its chemical properties, it is widely used in fibers, films, resins and the like.

However, a conventional polyester resin such as polyethylene terephthalate (hereinafter referred to as PET) has a gas barrier property against oxygen and carbon dioxide.
Although they are superior to polyolefin resins such as polyethylene and polypropylene, they are still insufficient, and there is a demand for further improvement in performance for various uses. Several improvement proposals have been made for this, for example, P
A method using a polymer in which part or all of the terephthalic acid component of PET is replaced with isophthalic acid instead of ET (Japanese Patent Laid-Open No. 59-64624, etc.), or a method using 1,3-phenylenedioxydiacetic acid or the like is used. A method of aiming at improvement of gas barrier properties by polymerization (Japanese Patent Application Laid-Open No. 60-50106)
No. 0 publication, etc.), but none of these methods has a problem that satisfactory gas barrier properties are not achieved, and a glass transition point (hereinafter referred to as Tg) is greatly reduced to deteriorate heat resistance. It is not enough to have.

On the other hand, it has been conventionally known that an antibacterial product is produced by adding an agent having an antibacterial effect to the polyester resin, and an antibacterial film and the like can be given as a typical example. As the prior art of the antibacterial film, for example, as described in JP-A-9-57893, a plastic film having a specific surface roughness is fixed with an inorganic compound having an antibacterial property,
As described in JP-A-57922, a polyester film obtained by laminating a layer having a silver-based inorganic compound having a specific particle size or less, or a zeolite-based solid particle having antibacterial properties and calcium carbonate as described in Japanese Patent No. 2631639 is used. Antibacterial film.

However, if a conventional polyester resin such as PET is mixed with an antibacterial agent, for example, when used in a packaging film, the gas barrier property is not sufficient, so that further improvement is required.

[0006]

SUMMARY OF THE INVENTION The present inventors have conducted intensive studies on polyester resins capable of solving the above-mentioned problems of conventionally used antibacterial films and obtaining films having excellent antibacterial properties. The present invention has been reached.

[0007]

That is, the present invention comprises adding 0.1 to 10% by weight of an inorganic antibacterial agent to a polyester containing naphthalenedicarboxylic acid as a main acid component and 1,3-propanediol as a main diol component. And a polyester resin composition and a film.

In the polyester resin composition of the present invention, it is necessary to use naphthalenedicarboxylic acid as a main acid component and 1,3-propanediol as a main glycol component. If the main components of the acid component and the alcohol component are other than those described above, a molded product having sufficient gas barrier properties and mechanical strength cannot be obtained. Naphthalenedicarboxylic acid component used in the present invention is 80 mol%
The above is preferably composed of 2,6-naphthalenedicarboxylic acid, 2,7-naphthalenedicarboxylic acid, 1,4-naphthalenedicarboxylic acid, or a mixture thereof,
From the viewpoint of imparting sufficient gas barrier properties and mechanical strength to a molded article using the polyester resin, 2,6-naphthalenedicarboxylic acid is particularly preferred. In the polyester resin composition of the present invention, as a dicarboxylic acid other than naphthalenedicarboxylic acid, in a range of less than 20 mol%, preferably 15 mol% or less, for example, terephthalic acid, isophthalic acid, phthalic acid, 4,4′-diphenyl Aromatic dicarboxylic acids such as carboxylic acid, 1,2-bis (2-chlorophenoxy) ethane-4,4′-dicarboxylic acid, phenylenedioxydiacetic acid, and bis (4-carboxymethoxyphenyl) sulfonic acid, or their ester-forming properties Derivatives, succinic acid, adipic acid, aliphatic dicarboxylic acids such as sebacic acid or ester-forming derivatives thereof, alicyclic dicarboxylic acids such as cyclohexanedicarboxylic acid or ester-forming derivatives thereof, hydroxyacetic acid, 3-hydroxypropionic acid, etc. Oxycarboxylic acid or its ester-forming derivative It can be used as a synthetic minutes.

As the ester-forming derivative of the dicarboxylic acid, an ester with a lower alcohol such as methanol or ethanol is generally used, but an ester with a glycol such as ethylene glycol may be used.

[0010] The glycol component used in the present invention, as the glycol component, is a glycol component of 8 from the viewpoint of imparting sufficient gas barrier properties and mechanical strength to the molded product.
It is preferred that 0 mol% or more is composed of 1,3-propanediol.

In the polyester resin composition of the present invention, glycols other than 1,3-propanediol are used in an amount of less than 20 mol%, preferably 15 mol% or less, for example, ethylene glycol, 1,2-propanediol, Aliphatic glycols such as methylene glycol, hexamethylene glycol, neopentyl glycol, cyclohexane dimethanol and octamethylene glycol; alicyclic glycols such as 1,4-cyclohexane dimethanol; 1,3-bis (β-hydroxyethoxy)
Benzene, bis (β-hydroxyethoxy) bisphenol S, bisphenol A, aromatic glycols such as hydroquinone, and high molecular glycols such as polyethylene glycol and polypropylene glycol can be used as the copolymerization component.

Such a polyester resin composition is substantially linear and has a film-forming property, particularly a film-forming property in a molten state. Among such polyester resin compositions, polytrimethylene-2,6-naphthalate is particularly preferred.

The amount of the polyester resin composition is within the range of a substantially linear range, and unless the effect of the present invention is impaired. The above polycarboxylic acid or polyhydroxy compound, for example, trimellitic acid, pentaerythritol and the like can be copolymerized.

The polyester resin composition of the present invention can be produced by a known method. For example, for convenience, polytrimethylene-2,6-naphthalate will be described as an example. Generally, 2,6-naphthalenedicarboxylic acid and 1,3-propanediol are directly esterified or reacted. A lower alkyl ester of 2,6-naphthalenedicarboxylic acid such as dimethyl 2,6-naphthalenedicarboxylate is transesterified with 1,3-propanediol, or an addition reaction is made between 2,6-naphthalenedicarboxylic acid and propylene oxide. 2,6-
A first stage reaction for producing a glycol ester of naphthalenedicarboxylic acid and / or a low polymer thereof, and a second stage reaction for heating the reaction product of the first stage under reduced pressure to perform polycondensation until a desired degree of polymerization is obtained. Produced by reaction.

The copolymerized polyester obtained by the above method (melt polymerization) can be converted into a polymer having a higher degree of polymerization by a polymerization method in a solid state (solid state polymerization) if necessary.

When the polyester resin is obtained through a transesterification reaction, the transesterification catalyst is not particularly limited, but sodium, potassium, magnesium, calcium, zinc, strontium, titanium, zirconium,
Manganese and cobalt compounds are preferred.

The catalyst used in the polycondensation reaction is not particularly limited, but preferably includes an antimony compound, a titanium compound, a germanium compound and the like.

Preferred examples of the antimony compound include antimony trioxide and antimony acetate.
Preferred examples of the titanium compound include titanium tetrabutoxide, titanium acetate and the like.

As the germanium compound, (a)
Amorphous germanium oxide (b) Fine crystalline germanium oxide (c) Solution of germanium oxide dissolved in glycol in the presence of alkali metal, alkaline earth metal or their compounds (d) Solution of germanium oxide dissolved in water And the like.

The polyester resin of the present invention has an intrinsic viscosity of 0.4 to 1.5, preferably 0.5 to 1.0 when measured at 35 ° C. in an O-chlorophenol solvent. Are preferred in terms of moldability.

When the intrinsic viscosity is lower than 0.4, the strength is insufficient when formed into a film or a sheet. If the intrinsic viscosity exceeds 1.5, melt extrusion molding becomes difficult, and even if it is extruded, the shear heat generation in the melt extrusion step increases, resulting in a decrease in the molecular weight of the molded product, which is not preferable.

Further, the polyester resin of the present invention may contain, if necessary, additives such as pigments, dyes, antioxidants, ultraviolet absorbers and light-shielding agents, if necessary.

Examples of such antioxidants include hindered phenol compounds, hindered amine compounds,
Examples of the sulfur atom-containing ester compound and the like and the ultraviolet absorber include, for example, benzophenone-based compounds, benzotriazole-based compounds, and sacylate-based compounds.

The polyester in the present invention contains 0.1 to 10% by weight of an inorganic antibacterial agent having an average particle size of 0.1 to 10 μm. The average particle size of the inorganic antibacterial agent is preferably 0.2
To 7 μm, more preferably 0.4 to 5 μm. The addition amount of the inorganic antibacterial agent is preferably 0.2 to 7% by weight, more preferably 0.3 to 5% by weight.

Antimicrobial agents are relatively inexpensive, nontoxic or nearly nontoxic, yet have high antibacterial effects, and are insoluble or poorly soluble in water or organic solvents, which may cause environmental pollution problems. There is no need for an antibacterial agent.

Here, the average particle diameter is obtained by evaporating a metal on the particle surface, obtaining an area circle equivalent diameter from an image magnified 10,000 to 30,000 times with an electron microscope, and calculating from the following equation. .

[0027]

## EQU2 ## Average particle size = total area circle equivalent diameter of measured particles / number of measured particles

If the average particle size is less than 0.1 μm, aggregation of the particles will occur to hinder film formation, and if the average particle size exceeds 10 μm, pinholes will occur or breakage may occur, which is not preferable.

When the amount of the antibacterial agent is less than 0.1% by weight, the antibacterial property is not exhibited. When the amount exceeds 10% by weight, the polyester film becomes cloudy and loses transparency.

In order to further enhance the dispersibility and affinity of the antibacterial agent in the polyester and to obtain transparency, for example, anionic surfactants, aluminum, titanate coupling agents, fatty acid esters of polyhydric alcohols, etc. Accordingly, an antibacterial agent surface-treated by a conventional method may be used.

Various methods can be used to incorporate the antimicrobial agent into the polyester. The following method can be mentioned as a typical example. (A) A method in which an antimicrobial agent is added before the end of the transesterification or esterification reaction during the synthesis of the polyester, or an antimicrobial agent is added before the polycondensation reaction. (A) A method of adding to a polyester and melt-kneading. (C) In the above methods (A) and (A), a masterbatch containing a high concentration of an antibacterial agent is prepared, and this masterbatch is added to contain a predetermined amount of the antibacterial agent. Among them, the method (A) is preferable.

The inorganic antibacterial agent in the present invention includes metal ions (eg, silver, copper, zinc, tin, lead, bismuth, cadmium, chromium, mercury, etc.) and / or complex ions thereof (eg, silver thiosulfate). Ions, etc.) with inorganic compounds (eg, zeolite, zirconium phosphate, montmorillonite, hydroxyapatite, double phosphate,
Tripolyphosphate, magnesium aluminosilicate,
Supported on calcium silicate, titanium oxide, silica gel, soluble glass, etc.) or metal elements (for example,
Composite metal oxides containing two or more kinds of zinc, copper, magnesium, calcium, etc.). Among them, inorganic compounds supporting silver ions as metal ions and / or
Or, a composite metal oxide is particularly preferable in that it is particularly resistant to antibacterial performance and environmental pollution. The antibacterial agent containing the composite metal oxide as an active ingredient has the following formula

[0033]

[(A ₁ ) _x (A ₂ ) _1-X ] O (1)

(Where A ₁ is Zn and / or C
u, A ₂ is a divalent metal selected from Mg and / or Ca, and X is a number in the range of 0.01 ≦ X <0.5). .

The use of any other metal is not preferred because it is inferior in antibacterial performance and environmental pollution. In the formula, A
_If the ratio of ₁ is less than 0.01, sufficient antibacterial performance cannot be obtained. If the ratio is 0.5 or more, foaming occurs when added to the polyester resin, which is not preferable.

The total haze of the film obtained by processing the polyester resin composition of the present invention is 0.1 to 20.
%.

If the total haze is less than 0.1%, the film loses appropriate friction and workability, and the productivity decreases. If it exceeds 20%, the film loses sharpness, and the film does not have a design even when back-printed.

Note that the total haze of the film is determined by JI
It was measured based on S-K7105 and determined by the following equation.

[0039]

## EQU4 ## Total haze (%) = (Td / Tt) × 100

(Wherein, Td: diffusion transmittance (%);
(Tt: total light transmittance (%)) In order to impart appropriate friction and workability to the film, it is preferable that the antibacterial agent further contains inert particles within a range not exceeding the above range. As the particles, for example, fine particles containing elements of Periodic Tables IIA, IIB, IVA, IVB (for example, kaolin, alumina, titanium oxide,
Fine particles made of a polymer having good heat resistance, such as calcium carbonate, silicon dioxide, etc.), silicone resin, crosslinked polystyrene and the like.

The inert fine particles have an average particle size of 0.01 to
It is preferably in the range of 5.0 μm, and 0.1 to 3.0 μm.
More preferably, it is μm.

The content of the inert fine particles is 0.001 to
It is preferably in the range of 2.0% by weight, and 0.01 to
More preferably, it is 1.0% by weight.

The inert fine particles to be added to the film may be a single component selected from those exemplified above, or may be a two-component system or another component system containing at least an acid component.

The method and timing of adding the inert fine particles are not particularly limited, and they may be added at any stage during the production of the polyester resin composition, or may be added during processing into a film or the like.

When the film obtained by processing the polyester resin composition of the present invention is used as a biaxially stretched film, the sum of the Young's modulus in the vertical and horizontal directions is 400 kg / mm ^2.
It is preferable that this is the case. If the Young's modulus is lower than this, the strength is insufficient when used as a biaxially stretched film, which is not preferable. The sum of the Young's modulus in the vertical and horizontal directions is 70
If it exceeds 0 kg / mm ² , it is not preferable because delamination resistance deteriorates when used as a biaxially stretched film.

The film obtained by processing the polyester resin composition of the present invention is a film obtained by melting the polyester resin composition, discharging from a die, forming a film, biaxially stretching and heat setting.

To obtain the film characteristics in the present invention,
The stretching method may be a known method, but the stretching temperature is 50 to 12
0 ° C. is preferred, and the longitudinal stretching ratio is 1.5 to 6.0 times, preferably 2.times.
The ratio is 5 to 5.0 times, and the transverse stretching ratio is 2.5 to 6.0 times, preferably 2.8 to 5.2 times. The film obtained by stretching is 125 to 180 ° C, preferably 130 to 175 ° C.
It is preferable to perform heat setting at 1 ° C. for 1 to 100 seconds. More preferably, from these conditions, it is preferable to find a condition in which the maximum value, peak temperature, and heat shrinkage of the heat shrinkage stress of the film are in the above ranges, and then perform the biaxial stretching heat setting treatment.

The film obtained by processing the polyester resin composition of the present invention suitably has a thickness in the range of 5 to 200 μm. Preferably it is 10 to 100 μm. If the thickness is less than 5 μm, breakage or the like tends to occur during processing, while if it exceeds 200 μm, not only is it unnecessary but also uneconomical in terms of its use.

When the polyester resin composition of the present invention is processed and used as a film, its use is not limited, but it is used as a packaging film because of its superior gas barrier properties as compared with conventional polyester resins. Is a good thing.

[0050]

EXAMPLES The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples.
The evaluation of this example was performed according to the following method. (1) Intrinsic viscosity Measured at 35 ° C. using O-chlorophenol as a solvent. (2) Oxygen Permeability Based on the ASTM D-1434-75M method, a commercially available gas permeability measuring device (Toyo Seiki Seisakusho GTR Tester-M
In -C1), the oxygen permeability coefficient of the film was determined. A pressure difference was applied to both sides of the film, the oxygen permeability was calculated from the change gradient of the pressure at 25 ° C. with respect to time, and the oxygen permeability was calculated as the oxygen permeability coefficient per unit thickness. (3) Film haze Based on JIS-K7105, it was measured using a POIC haze meter SET-HS-D1 manufactured by Nihon Seimitsu Kogyo.

Example 1 Tetrabutoxy titanate was added to a mixture of 100 parts of dimethyl 2,6-naphthalenedicarboxylate and 46.7 parts of 1,3-propanediol.
59 parts were added, and transesterification was performed for 150 minutes while gradually raising the temperature from 150 ° C to 210 ° C. After completion of the transesterification reaction, 0.5 part of Sea Bio ZO-100 (Mg _0.9 Zn _0.1 O; average particle size 0.5 μm) of TOMO SYSTEM is added as an inorganic antibacterial agent, and 29 parts of the reaction product is added.
After the temperature was raised to 0 ° C., a polycondensation reaction was performed under a high vacuum of 0.2 mmHg or less to obtain a polytrimethylene-2,6-naphthalate resin having a solid melt viscosity of 0.60.

The above-mentioned polytrimethylene-2,6-naphthalate resin was dried at 145 ° C. for 4 hours, supplied to an extrusion hopper, melted at a melting temperature of 280 ° C., and passed through a 1 mm slit die at a surface temperature of 25 ° C. It was extruded on a rotating cooling drum and quenched to obtain an unstretched film.

The unstretched film was wound around a roll, heated, and then stretched 3.6 times in the machine direction. Subsequently, the mixture was supplied to a tenter and stretched 3.9 times in the horizontal direction at 105 ° C.
The obtained biaxially oriented film is heat-set at a temperature of 140 ° C., relaxed 4% in a transverse direction at a temperature of 135 ° C.
A μm biaxially oriented film was obtained. Table 1 shows the physical properties of the obtained film.

Comparative Example 1 The polyester resin used in Example 1 was polyethylene terephthalate, the drying conditions before film forming were 170 ° C. for 3 hours, the melting temperature of the film forming extruder was 290 ° C., and the heat setting temperature was 200 ° C
The procedure was performed in the same manner as in Example 1 except for the above. Table 1 shows the physical properties of this film.

This polyethylene terephthalate was synthesized as follows. Manganese acetate-4 in a mixture of 100 parts of dimethyl terephthalate and 70 parts of ethylene glycol
0.038 parts of a water salt was added, and transesterification was performed while gradually raising the temperature from 150 ° C to 240 ° C. When the reaction temperature reaches 170 ° C., antimony trioxide 0.0
4 parts were added, and after the transesterification reaction was completed, 0.049 part of trimethyl phosphate and sea bio ZO-100 (Mg _0.9 Zn _0.1 O; average particle size 0.5 μm) of TOMO SYSTEM as an inorganic antibacterial agent were added to _{0.1 part} . 5 parts were added. Thereafter, the temperature of the reaction product was raised to 290 ° C., and then a polycondensation reaction was performed under a high vacuum of 0.2 mmHg or less to obtain a polyethylene terephthalate resin having a solid melt viscosity of 0.60.

Comparative Example 2 The polyester used in Example 1 was polyethylene-2,6-naphthalate resin, and the melt extrusion temperature during film processing was 305.
℃, transverse stretching temperature 145 ° C, heat setting temperature 220
The procedure was performed in the same manner as in Example 1 except that the temperature was changed to ° C. Table 1 shows the characteristics of this film.

Incidentally, polyethylene-2,6-naphthalate was synthesized as follows. To a mixture of 100 parts of dimethyl 2,6-naphthalenedicarboxylate and 50 parts of ethylene glycol, 0.018 part of manganese acetate tetrahydrate was added,
The transesterification reaction was performed while gradually raising the temperature from 150 ° C to 240 ° C. After completion of the transesterification reaction, 0.013 part of trimethyl phosphate and subsequently 0.008 part of titanium acetate were added, and as an inorganic antibacterial agent, Sea Bio ZO-100 (Mg _0.9 Zn _0.1 O; average particle diameter of TOMO SYSTEM) 0.5
μm) was added. Thereafter, the reaction product was heated to 290 ° C.
And a polycondensation reaction was carried out under a high vacuum of 0.2 mmHg or less to obtain polyethylene-2,6- having an intrinsic viscosity of 0.60.
A naphthalate resin was obtained.

[Examples 2 to 3 and Comparative Examples 3 to 4] As an inorganic antibacterial agent, Tomio System's CIO-BIO ZO-100
The (Mg _0.9 Zn _0.1 O) was obtained in the same manner as in Example 1, but containing in particle size and concentration shown in Table 1. Table 1 shows the obtained film characteristics.

Example 4 An inorganic compound carrying silver ions as an inorganic antibacterial agent (NOVALON AG3 manufactured by Toagosei Co., Ltd.)
00; average particle size 0.8 μ) was added in the same manner as in Example 1 except that 1 part by weight was added. Table 1 shows the characteristics of this film.
Shown in

An antibacterial test was conducted on the nine films obtained in Examples 1 to 4 and Comparative Examples 1 to 4 by the following method.

(Test Bacteria) Escherichia coli IFO
3972 (Escherichia coli) Staphylococcus aureus IFO 12732 (Staphylococcus aureus) (Test medium) NA medium: Normal agar medium NB medium: Normal broth medium containing 0.2% meat extract 1 / 500NB medium: NB medium with purified water Diluted 500 times and adjusted pH to 7.0 ± 0.2. SCDLP medium: SCDLP medium SA medium: Standard agar medium (Preparation of bacterial solution)
After culturing for 24 hours, the NA medium was inoculated again, and 37 ± 1 ° C
Cultured for 16-20 hours. 1 / 500N of cells after culture
Each of them was uniformly dispersed in the B medium and adjusted so that the number of bacteria per ml was 2.0 × 10 ^{5 to} 1.0 × 10 ⁶ .

(Preparation of Sample) A sample was cut into a size of 5 cm × 5 cm to obtain a sample.

(Test operation) Bacterial solution was added to three samples of each specimen.
5 ml of each solution was added dropwise, and a polyethylene film was placed on the solution and adhered thereto. These were stored under the conditions of 35 ± 1 ° C. and a relative humidity of 90% or more. Further, a plastic petri dish was used as a control sample, and the same test was performed.

(Measurement of number of bacteria) 24 hours after storage, SCDL
Surviving bacteria were washed out of the sample using 10 ml of P medium, and the number of viable cells in the washed solution was measured by an agar plate culture method (cultured at 35 ° C. for 2 days) using SA medium, and converted to one sample. . The measurement immediately after the inoculation was performed in a control test. As a result of the above test, the sterilization rate

[0065]

[Equation 5] Sterilization rate = (AB) / A × 100

(Where A is the viable cell count of the film without the antimicrobial agent, and B is the viable cell count of the film with the antimicrobial agent added)
The antibacterial property was evaluated. Table 1 shows the results.

[0067]

[Table 1]

From the results shown in Table 1, it can be seen that the films of Examples are excellent in antibacterial properties, transparency and gas barrier properties.

[0069]

The antimicrobial-added polyester film of the present invention has excellent antibacterial properties, gas barrier properties and transparency, and is extremely useful as a packaging film.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4F071 AA45A AB01A AB07A AB17A AB26 AB32A AD02A AD06A AE08A AE22A AF52A AH04 BC02 BC09 BC10 BC12 4J002 CF081 DA076 DE096 FD186

Claims (6)

[Claims] 1. An inorganic antibacterial agent in a polyester containing naphthalenedicarboxylic acid as a main acid component and 1,3-propanediol as a main diol component in an amount of 0.1 to 10% by weight.
A polyester resin composition added. 2. The inorganic antibacterial agent has an average particle size of 0.1 to 10 μm.
The polyester resin composition according to claim 1, wherein m is m. 3. The polyester resin composition according to claim 1, wherein the inorganic antibacterial agent is an inorganic compound carrying silver ions and / or a composite metal oxide. 4. A film formed using the polyester resin composition according to claim 1, 2, or 3, wherein the total haze of the film is 0.1 to 20%. 5. A composite metal oxide represented by the following formula (1): [(A ₁ ) _x (A ₂ ) _{1 -x} ] O (1) wherein A ₁ represents Zn and / or Cu; A ₂ represents a divalent metal selected from Mg and / or Ca;
The polyester film according to claim 3, wherein the oxide solid solution is represented by the following formula: 0.01 ≦ x <0.5. 6. A polyester film, which is used as a packaging material in a film molded using the polyester resin composition according to claim 1, 2, or 3.