JPH10204164A - Polyester film for lamination with metallic sheet or plate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polyester film for lamination with a metallic sheet or plate, which can give a metal laminate excellent in workability such as deep drawability, heat resistance, impact resistance, rust-preventive properties and especially excellent in taste and flavor retention after retorting. SOLUTION: This film is made from a copolymer aromatic polyester comprising an acid component mainly consisting of terephthalic acid and 2,6- naphthalenedicarboxylic acid in a molar ratio (terephthalic acid/2,6- naphthalenedicarboxylic acid) of 82/18 to 97/3 and a glycol component based on ethylene glycol, and having an intrinsic viscosity of 0.50-0.80, a glass transition point of 75 deg.C or above and a melting point of 210-250 deg.C and has a content of free aromatic dicarboxylic acid glycol ester of 50ppm or below.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyester film for laminating and forming a metal plate, and more particularly, it shows excellent formability when laminating to a metal plate and performing can forming such as drawing. The present invention relates to a polyester for metal plate lamination processing capable of producing metal cans having excellent heat resistance, retort resistance, fragrance retention, impact resistance, rust resistance and the like, such as beverage cans and food cans.

[0002]

2. Description of the Related Art Metal cans are generally coated to prevent corrosion on the inner and outer surfaces, but recently, for the purpose of simplifying the process, improving hygiene, and preventing pollution, rust prevention is performed without using an organic solvent. Development of a method for obtaining the property has been advanced, and as one of the methods, coating with a thermoplastic resin film has been attempted. That is, a method of laminating a thermoplastic resin film on a metal plate of tin, tin-free steel, aluminum, or the like, followed by drawing, etc., has been studied. Polyolefin films and polyamide films have been tried as this thermoplastic resin film, but they do not satisfy all of moldability, heat resistance, impact resistance and fragrance retention.

[0003] Therefore, attention has been paid to polyester films, particularly polyethylene terephthalate films, because of their well-balanced properties, and several proposals based on this have been made (JP-A-56-10451, JP-A-56-10451). JP-A-64-22530, JP-A-1-19
No. 2545, JP-A-1-192546, JP-A-2-57339, etc.). However, the present inventors have found that satisfying all of the moldability, retort resistance, fragrance retention, and the like becomes insufficient particularly in the case of molding with large deformation.

[0004] Copolymerized polyester films have been studied as satisfying molding processability, heat resistance, impact resistance and fragrance retention. For example, Japanese Patent Application Laid-Open No. 5-339348 discloses a copolymerized polyester film. A polyester film for laminating and processing a metal plate comprising a copolymerized polyester having a transition temperature and a terminal carboxyl group concentration, and Japanese Unexamined Patent Publication (Kokai) No. 6-39979 discloses a metal laminated with a copolymerized polyester having a specific melting point and a glass transition temperature. A polyester film for board lamination processing has been proposed,
According to the study of the present inventors, when a can using such a film is used for a beverage container, for example, depending on the type of beverage, for example, odor or odor as described in JP-A-55-23136 is disclosed. It was found that a change in taste was perceived.

Japanese Patent Application Laid-Open No. 6-116376 proposes a polyester film for forming a metal plate comprising a copolymerized polyester containing a specific amount of an alkali metal element and a germanium element. In the case where the content is packed, such as a cold pack system, the process that does not receive heat shows excellent flavor and aroma retention, but in the process where the heat treatment is performed at the stage of packing the content, such as retort treatment, it is not always necessary. There is a problem that sufficient flavor retention cannot be obtained.

Some proposals have been made to obtain fragrance retention for contents requiring a retort treatment step.
For example, Japanese Patent Application Laid-Open No. 8-231690 proposes a copolymerized polyester film obtained by using terephthalic acid as a main acid component and 1,4-cyclohexanedimethanol and ethylene glycol as a diol component in a specific range of ratio. However, this film has a problem that sufficient can-making properties cannot be obtained due to reduced heat resistance.

[0007]

SUMMARY OF THE INVENTION It is an object of the present invention to overcome the disadvantages of the prior art and to maintain the excellent moldability, heat resistance and impact resistance of a copolyester film while maintaining its contents. It is an object of the present invention to provide a polyester film for metal plate laminating processing, which has improved fragrance retention properties, particularly, flavor retention properties after retort treatment.

[0008]

That is, the present invention mainly comprises terephthalic acid and 2,6-naphthalenedicarboxylic acid, and the molar ratio (terephthalic acid / 2,6-naphthalenedicarboxylic acid) is 82/18 to 97 /. 3, a copolymer aromatic having an intrinsic viscosity of 0.50 to 0.80, a glass transition point of 75 ° C. or more, and a melting point of 210 to 250 ° C., which comprises an acid component and a glycol component mainly composed of ethylene glycol. A film made of an aromatic polyester, wherein the amount of a free aromatic dicarboxylic acid glycol ester contained in the film is 50 ppm or less.

In the present invention, the copolymerized aromatic polyester is a copolymerized aromatic polyester comprising an acid component mainly composed of terephthalic acid and 2,6-naphthalenedicarboxylic acid and a glycol component mainly composed of ethylene glycol. .

The molar ratio of the acid component (terephthalic acid /
2,6-naphthalenedicarboxylic acid) from 82/18 to 9
It is necessary to be in the range of 7/3, and 85/15 to 9
It is preferably in the range of 7/3.

The molar ratio of the acid component (terephthalic acid / 2,6-
(Naphthalenedicarboxylic acid) exceeds 97/3, that is, if the molar ratio of 2,6-naphthalenedicarboxylic acid in all the acid components is less than 3 mol%, the moldability and the fragrance retention are insufficient, while the molar ratio If (terephthalic acid / 2,6-naphthalenedicarboxylic acid) is less than 82/18, that is, if the molar ratio of 2,6-naphthalenedicarboxylic acid in all the acid components exceeds 18 mol%, heat resistance and impact resistance deteriorate. It is not preferable.

As the acid component, an acid component other than terephthalic acid and 2,6-naphthalenedicarboxylic acid can be used in combination as long as the physical properties (melting point, amount of water extract, etc.) of the film are not impaired. Examples of the acid component that can be used in combination include aromatic dicarboxylic acids such as isophthalic acid and phthalic acid; aliphatic dicarboxylic acids such as adipic acid, azelaic acid, sebacic acid, and decane dicarboxylic acid; and alicyclic groups such as cyclohexanedicarboxylic acid. Examples thereof include dicarboxylic acids.

Next, the glycol component is mainly composed of ethylene glycol (90 mol% or more based on the total glycol component), but other glycol components may be used as long as the physical properties (heat resistance, glass transition point, etc.) of the film are not impaired. Can be used in combination. Diol components that can be used in combination include diethylene glycol, propylene glycol, neopentyl glycol, butanediol, pentanediol,
Examples thereof include aliphatic diols such as hexanediol, alicyclic diols such as cyclohexanedimethanol, aromatic diols such as bisphenol A, and polyalkylene glycols such as polyethylene glycol and polypropylene glycol. These can be used alone or in combination of two or more.

The copolymerized aromatic polyester of the present invention has a polymer melting point of 210 to 250 ° C., preferably 215 ° C.
It must be in the range of ２245 ° C. Melting point 21
If the temperature is lower than 0 ° C., the heat resistance of the film is inferior.

Here, the melting point of the copolymerized aromatic polyester was measured by Du Pont Instruments 9
10 A method of obtaining a melting peak at a heating rate of 20 ° C./min using DSC. The sample amount is 20 mg.

Further, the polyester film of the present invention comprises:
Although it may be an unstretched film, it is preferably used in the form of a biaxially stretched film that has been biaxially stretched and heat set. At this time, the glass transition temperature (hereinafter sometimes abbreviated as Tg) of the polyester film of the present invention needs to be 75 ° C. or higher. When the Tg of the film is less than 75 ° C., the heat resistance becomes poor, and the taste and aroma retention after retorting deteriorates. As the acid component of the copolymerized aromatic polyester of the present invention, terephthalic acid and 2,6-naphthalenedicarboxylic acid are mainly used, and the molar ratio (terephthalic acid / 2,6-naphthalenedicarboxylic acid) is 82/18 to 97/3. When the Tg of the film is 75% by mainly including ethylene glycol as a glycol component,
C or higher. Here, the Tg of the polyester film was obtained by placing a 20 mg film sample in a DSC measurement pan, heating and melting it on a 290 ° C. heating stage for 5 minutes, and quickly solidifying the sample pan on an aluminum foil laid on ice, Du Pont Instruments
910 DSC is used to determine the glass transition point at a heating rate of 20 ° C./min.

Further, the copolymerized aromatic polyester must have an intrinsic viscosity (orthochlorophenol, 35 ° C.) of the film in the range of 0.50 to 0.80, preferably 0.55 to 0.75. , More preferably 0.6
0 to 0.70. If the intrinsic viscosity is less than 0.50, the impact resistance of the film becomes insufficient, which is not preferable. On the other hand, if the intrinsic viscosity exceeds 0.80, it is necessary to increase the intrinsic viscosity of the raw material polymer excessively, which is uneconomical.

In the present invention, the term "free glycol glycol free aromatic dicarboxylate" (hereinafter sometimes referred to as "free glycol ester") contained in the film refers to, for example, the acid component of the copolymerized aromatic polyester as in the present invention. Terephthalic acid and 2,6-naphthalenedicarboxylic acid, and when the glycol component is ethylene glycol, free bis (β-hydroxyethyl) terephthalate (hereinafter sometimes referred to as BHET) and free bis (β- Hydroxyethyl) naphthalate (hereinafter, referred to as
BHEN). further,
The content of the aromatic dicarboxylic acid glycol ester in the film refers to the above BHET and BHE contained in the film.
Shows the sum of N. In particular, the content of BHEN is small in the range of the composition of the polymer constituents in the present invention, and especially when the molar ratio of the acid component (terephthalic acid / 2,6-naphthalenedicarboxylic acid) is in the range of 85/15 to 97/3, BHEN is reduced.
Becomes lower than the quantitative detection limit, and substantially only BHET is detected as a free glycol ester. Furthermore, substantially B as a free glycol ester
It is preferable to select the composition of the polymer component so that only HET is detected, because the content of the entire free glycol ester in the film can be reduced.

The content of the free glycol ester in the film must be 50 ppm or less, preferably 30 ppm or less, more preferably 20 ppm or less.

When the content of the free glycol ester contained in the polyester film of the present invention exceeds 50 ppm, the flavor and aroma retention of the contents after the retort sterilization treatment is significantly reduced. The amount of the free glycol ester contained in the polyester film can be reduced to 50 ppm or less by satisfying the above-mentioned composition range of the polymer constituents.

In the present invention, the copolymerized aromatic polyester is not limited by its production method. For example,
A copolymerized aromatic polyester is obtained by subjecting terephthalic acid, ethylene glycol and 2,6-naphthalenedicarboxylic acid as a copolymer component to a transesterification reaction, and then subjecting the obtained reaction product to a polycondensation reaction until a desired degree of polymerization is reached. Or dimethyl terephthalate, ethylene glycol and a copolymer component 2,
A preferred example is a method of producing a copolymerized aromatic polyester by subjecting 6-naphthalenedicarboxylic acid dimethyl ester to a transesterification reaction and then subjecting the obtained reaction product to a polycondensation reaction until a desired degree of polymerization is obtained.

The copolymerized aromatic 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. . If necessary, additives such as an antioxidant, a heat stabilizer, a viscosity modifier, a plasticizer, a hue improver, a nucleating agent, and an ultraviolet absorber can be added to the copolymerized aromatic polyester.

In the film made of the copolymerized aromatic polyester of the present invention, the total amount of alkali metal elements (total alkali metal element amount A) in the film must satisfy A ≦ 5 (ppm) to maintain the taste and fragrance retention. Preferred for The total amount of the alkali metal elements is the sum of the ppm concentrations of Li, Na, and K elements determined by atomic absorption analysis.

When the total amount of the alkali metal elements is 5 ppm or less, the amount of by-product ether glycol, particularly the amount of by-product diethylene glycol in the production of polyester increases, the heat resistance of the polyester film decreases, and the polyester film is subjected to electrostatic application casting. It is known that the productivity in the method is reduced, but from the studies of the present inventors, by optimizing the amount of the metal compound of the catalyst, and by optimizing the conditions of the esterification or transesterification, the polyester It is possible to control the amount of by-product ether glycol at the time of production, particularly the amount of by-product diethylene glycol, and to determine the ratio of the amount of the catalytic metal element by the metal compound to the amount of the phosphorus element due to the phosphorus compound in the film. By specifying a certain range, the reduction of productivity in the electrostatic application casting method of polyester film is suppressed. It was found that the kill.

Here, the "catalytic metal element" in the present invention
Is derived from the metal compound used as the reaction catalyst. This metal element exists in a state of being dissolved in the polymer and should be distinguished from the metal element in the lubricant particles. The “phosphorus element” is derived from a phosphorus compound used to deactivate a catalyst or as a stabilizer for a polymer.

In the polyester film of the present invention, the concentration of the catalytic metal element remaining in the film (M)
And the sum of the phosphorus element concentration (P) is 20 ≦ (M + P) ≦ 5
It is preferably in the range of 5 (mmol%). (M +
When P) is less than 20 mmol%, the productivity of the above-mentioned electrostatic application casting method of the polyester decreases. Also,
If (M + P) exceeds 55 mmol%, the amount of ether glycol as a by-product may increase and the heat resistance may decrease.

Further, in the polyester film of the present invention, the ratio of the concentration of the catalytic metal element (M) to the concentration of the phosphorus element (P) remaining in the film is 1 ≦ (M / P) ≦ 5 (mmol% / mmol%). ). M
If / P is less than 1 or exceeds 5, the abundance ratio of the catalytic metal element and the phosphorus element is lost, and the thermal stability is reduced due to the excess phosphorus element or the catalytic metal element existing in the polymer. May be.

The polyester film of the present invention comprises:
The catalyst metal element (M) remaining in the film is 10 ≦ M ≦
It is preferably in the range of 35 (mmol%). If M is less than 10 mmol%, it becomes difficult to obtain a polymer having a sufficient degree of polymerization, and properties such as impact resistance may be reduced. On the other hand, if M exceeds 35 mmol%, the thermal stability may decrease.

In the copolymerized aromatic polyester of the present invention, the copolymerization amount of the diethylene glycol component is preferably 5 mol% or less, more preferably 4 mol% or less, based on all glycol components of the copolymer components. Is more preferred. If this copolymerization amount exceeds 5 mol%, the heat resistance may decrease. The diethylene glycol component also contains a diethylene glycol component by-produced when producing a copolymerized aromatic polyester containing ethylene glycol as a glycol component. The copolymerization amount of the diethylene glycol component is preferably 0.5 mol% or more (based on the total glycol component) from the viewpoint of polymer production.

The catalyst used in the polycondensation reaction includes:
Although not particularly limited, an antimony compound (Sb compound), a titanium compound (Ti compound), a germanium compound (Ge compound) and the like are preferable. Among them, the germanium compound is particularly preferable in view of the fragrance retention of the obtained polyester film. preferable.

Preferred examples of the antimony compound include antimony trioxide and antimony acetate. Preferred examples of the titanium compound include titanium tetrabutoxide and titanium acetate. As the germanium compound, amorphous germanium oxide,
Preferable examples include fine crystalline germanium oxide, a solution in which germanium oxide is dissolved in glycol in the presence of an alkali metal or an alkaline earth metal or a compound thereof, and a solution in which germanium oxide is dissolved in water.

A lubricant may be added to the copolymerized polyester for the purpose of improving the film winding property. The kind of the lubricant may be inorganic or organic, but inorganic is preferred. As the inorganic lubricant, silica, alumina,
Titanium oxide, calcium carbonate, barium sulfate and the like can be exemplified. As the organic lubricant, silicone resin particles, crosslinked polystyrene particles and the like can be exemplified. Particularly preferred lubricants in terms of pinhole resistance have a particle size ratio (major axis / minor axis) of 1.0.
A monodispersed lubricant of ~ 1.2. Examples of such a lubricant include spherical silica, spherical silicone resin particles, and spherical cross-linked polystyrene.

The particle size and amount of the lubricant to be added may be determined based on the film winding property, pinhole resistance and fragrance and taste retention. That is, 0.06% by weight or more and 0.25% by weight or less for silica having an average particle size of 1.5 μm, and 0.1% by weight or more and 0.45% or less for silica having an average particle size of 0.8 μm.
By adding in the range of not more than% by weight, the winding property can be ensured without impairing the scent-retaining property.

The lubricant is not limited to the above-mentioned externally added particles. For example, it is also possible to use internally precipitated particles obtained by precipitating part or all of the catalyst used in the production of polyester in the reaction step. It is also possible to use externally added particles and internally precipitated particles in combination.

In addition, in order to apply the copolymerized polyester film of the present invention particularly to food cans or beverage cans, it is preferable that the amount of substances eluted or scattered from the film is as small as possible. That is, for application to food cans or beverage cans, for example, the amount of extraction per 1 inch ² of the film when the extraction treatment is performed at 125 ° C. for 1 hour with ion-exchanged water is preferably 0.1 mg or less, 0.05m
g is more preferable. Here, ion-exchanged water refers to water obtained by reducing ions in tap water with a cation-exchange resin and an anion-exchange resin and then distilling.

The refractive index of the copolymerized polyester film in the thickness direction is preferably from 1.500 to 1.540, and more preferably from 1.505 to 1.530. If the refractive index is too low, the moldability will be insufficient, while if it is too high, the film will have a structure close to amorphous, and the heat resistance may decrease.

The copolymerized polyester film of the present invention comprises:
The thickness is preferably from 6 to 75 μm. Further, it is preferably from 8 to 75 μm, particularly preferably from 10 to 50 μm. 6 μm thick
If it is less than 75 μm, breakage or the like is likely to occur during molding, while if it exceeds 75 μm, it is excessive quality and uneconomical.

As the metal plate to which the polyester film of the present invention is bonded, in particular, a metal plate for can making, a plate of tin, tin-free steel, aluminum or the like is suitable.
The bonding of the polyester film to the metal plate can be performed, for example, by the following method.

The metal plate is heated to a temperature equal to or higher than the melting point of the film, the film is bonded, and then cooled. The surface layer (thin layer) of the film in contact with the metal plate is made amorphous and adhered.

A film is previously coated with an adhesive layer with a primer, and this surface is bonded to a metal plate. As the adhesive layer, a known resin adhesive, for example, an epoxy-based adhesive,
Epoxy-ester adhesives, alkyd adhesives and the like can be used.

[0041]

The present invention will be further described with reference to the following examples.
The properties of the film were measured and evaluated by the following methods.

(A) Intrinsic viscosity of polyester Measured in orthochlorophenol at 35 ° C.

(A) Melting point of polyester Du Pont Instruments 910 D
Using SC, a melting peak was determined at a heating rate of 20 ° C./min. The sample amount is 20 mg.

(C) Glass transition temperature (Tg) of polyester film A 20 mg film sample was placed in a pan for DSC measurement, heated and melted for 5 minutes on a 290 ° C heating stage, and the sample pan was quickly spread on ice. After quenching and solidifying on foil, Du Pont Instruments 91
0 The glass transition point was determined at a heating rate of 20 ° C./min using DSC.

(D) Amount of Free Glycol Ester 500 mg of a polyester film was dissolved in 3 ml of hexafluoroisopropanol. Add methanol 10
Then, the amount of free glycol ester was quantified by liquid chromatography using the filtrate after filtration as it was, and the concentration in the film was determined. The amount of free glycol ester substantially indicates the amount of free BHET since the amount of free BHEN is below the limit of quantification in the range of this example.

(E) Amount of water extract The polyester film was immersed in ion-exchanged water,
Extraction was performed at 1 hour at 1 hour. The extract in the immersion liquid was quantified, and the extract amount per 1 inch ^{2 of} the film was determined.

(F) Amount of alkali metal After dissolving the film sample in orthochlorophenol, extraction is performed with 0.5N hydrochloric acid. This extract is subjected to atomic absorption spectrometry to determine the amounts of Na, K, and Li for each element.

(G) Amount of catalytic metal element and amount of phosphorus element The film sample was heated and melted at 240 ° C to form a circular disk, and the amount of the catalytic metal element and the amount of phosphorus element were quantified by X-ray fluorescence analysis.

(G) Laminability The polyester film was bonded to a tin-free steel plate having a thickness of 0.25 mm heated above the melting point of polyester, and then cooled to obtain a coated steel plate. The coated steel sheet was observed, and the lamination property was evaluated according to the following criteria.

[Evaluation Criteria for Bubbles and Wrinkles] 〇: No bubbles and wrinkles are observed. Δ: Bubbles and wrinkles are observed at two or three places per 10 cm in length. ×: Many bubbles and wrinkles are observed. [Judgment criteria for heat shrinkage] 〇: Shrinkage is less than 2%. Δ: Shrinkage rate is 2% or more and less than 5%. X: Shrinkage rate is 5% or more.

(G) Deep drawing workability-1 A tin-free steel plate on which a polyester film is laminated in the same manner as in (c) above is cut into a disk having a diameter of 150 mm, and is deepened in four stages using a drawing die and a punch. Drawing was performed to create a 55 mm-diameter side-seamless container (hereinafter may be abbreviated as a can). The following observations were made on this can and evaluated according to the following criteria. ：: No whitening or breakage is observed in the film processed without any abnormality. Δ: Whitening was observed on the upper part of the film can. X: Film breakage is observed in a part of the film.

(G) Deep drawing workability-2 The following observations and tests were carried out on the cans obtained in the above item (g), and evaluations were made according to the following criteria. ：: Processed without any abnormality, rust prevention test of film surface in can (1% NaCl aqueous solution was put into the can, electrode was inserted, current value was measured when 6V voltage was applied with the can body as anode) Hereinafter, it may be abbreviated as ERV test). ×: There is no abnormality in the film, but the current value is 0.2 mA or more in the ERV test, and pinhole-shaped cracks starting from the coarse lubricant of the film are observed when the energized portion is observed under magnification.

(C) Impact resistance For a can with good deep drawing workability, pour water thoroughly, cool to 0 ° C., drop 10 pieces from a height of 30 cm onto a PVC tile floor, The same ERV test as in (c) was performed and evaluated according to the following criteria. ：: 0.2 mA or less for all 10 samples. C: 0.2 mA or more for 1 to 5 pieces. ×: 0.2 mA or more for 6 or more pieces, or cracks of the film were already observed after dropping.

(B) Heat Embrittlement Resistance The can having good deep drawing workability was heated and held at 200 ° C. for 5 minutes, and then the impact resistance was evaluated according to the above item (a). ：: 0.2 mA or less for all 10 samples. C: 0.2 mA or more for 1 to 5 pieces. X: The film was 0.2 mA or more for 6 or more pieces, or cracking of the film was already observed after heating at 200 ° C. for 5 minutes.

(S) Retort resistance A can with good deep drawing workability was filled with water and retorted in a steam sterilizer at 120 ° C. for 1 hour.
Stored at 30 ° C for 30 days. 5 cans of 10 cans each after treatment
ERV in can after dropping from 0cm onto PVC tile floor
A test was performed and evaluated according to the following criteria. ：: 0.2 mA or less for all 10 samples. C: 0.2 mA or more for 1 to 5 pieces. ×: 0.2 mA or more for 6 or more pieces, or cracks of the film were already observed after dropping.

(C) Taste preservation property-1 A can having good deep drawing workability was filled with ion-exchanged water and stored at room temperature (20 ° C.) for 30 days. A tasting test was conducted by 30 panelists using the filled liquid, and compared with ion-exchanged water for comparison, and evaluated according to the following criteria. ◎: Three or less out of thirty felt change in taste as compared with the comparative solution. 〇: 4 to 6 persons among 30 persons felt a change in taste as compared with the comparative solution. Δ: 7 to 9 persons among 30 persons felt a change in taste as compared with the comparative solution. ×: 10 or more out of 30 persons felt a change in taste as compared with the comparative solution.

(S) Taste preservation property-2 A can having good deep drawing workability was filled with ion-exchanged water, subjected to a retort treatment at 125 ° C. for 1 hour in a steam sterilizer, and then at room temperature (20 ° C.). Stored for 30 days. A tasting test was conducted by 30 panelists using the filled liquid, and compared with ion-exchanged water for comparison, and evaluated according to the following criteria. ◎: Three or less out of thirty felt change in taste as compared with the comparative solution. 〇: 4 to 6 persons among 30 persons felt a change in taste as compared with the comparative solution. Δ: 7 to 9 persons among 30 persons felt a change in taste as compared with the comparative solution. ×: 10 or more out of 30 persons felt a change in taste as compared with the comparative solution.

[Examples 1 to 5 and Comparative Examples 2 to 6] Table 1
The copolymerized polyethylene terephthalate (particle diameter ratio: 1.1, average particle diameter: 0.1) was prepared by using an acid component, diethylene glycol, an alkali metal compound, a polycondensation catalyst, and a phosphorus compound shown in (1).
Contains 0.2% by weight of 5 μm spherical silica. Hereinafter, it may be abbreviated as copolymerized PET. ) After drying
And quenched and solidified to obtain an unstretched film. Next, this unstretched film was centrifuged 3.0 times in the longitudinal direction, stretched 3.0 times in the transverse direction, and heat-set at 180 ° C. to obtain a biaxially oriented film having a thickness of 25 μm. The properties of this film are shown in Tables 1 and 2.

Comparative Example 1 A biaxially oriented film was obtained in the same manner as in Example 1 except that the melt extrusion temperature when forming a copolymer PET film was 300 ° C. The properties of this film are shown in Tables 1 and 2. The amount of free glycol ester in this biaxially oriented film was higher than in Example 1.

[0060]

[Table 1]

[0061]

[Table 2]

As is clear from the evaluation results in Table 2, the can using the copolymerized polyester film of the present invention has good deep drawability, heat embrittlement resistance, retort resistance and impact resistance, and Excellent in fragrance retention, especially in fragrance retention after retort.

[0063]

The polyester film for laminating and forming a metal plate of the present invention can be formed into a metal can by, for example, deep drawing after laminating with a metal plate. It has good retort resistance and impact resistance, and also has excellent scent-retaining properties, especially excellent scent-retaining properties after retort, and is extremely useful for bonding metal containers.

Claims (7)

[Claims] A terephthalic acid and 2,6-naphthalenedicarboxylic acid as main components, and a molar ratio (terephthalic acid / 2,6-
(Naphthalenedicarboxylic acid) is 82/18 to 97/3, and a glycol component mainly composed of ethylene glycol, and has an intrinsic viscosity of 0.50 to 0.8.
0, glass transition point is 75 ° C. or more, melting point is 210 to 250
A film made of a copolymerized aromatic polyester at a temperature of 0 ° C., wherein the amount of free aromatic dicarboxylic acid glycol ester contained in the film is 50 ppm or less. . 2. The concentration of an alkali metal element, a catalyst metal element and a phosphorus element remaining in a polyester film satisfies the following general formulas (1), (2) and (3).
The polyester film for metal plate lamination processing according to the above. A ≦ 5 (1) (2) 20 ≦ M + P ≦ 55 (2) 1 (1) M / P ≦ 5 (3) A is the total amount of the alkali metal element remaining in the film (ppm), M is the concentration of the catalytic metal element remaining in the film (mmol%), and P is the concentration of the phosphorus element remaining in the film (mmol%). Show. ] 3. The polyester film according to claim 1, wherein the concentration (mmol%) of the catalytic metal element in the polyester film satisfies the following formula (4). [Formula 4] 10 ≦ M ≦ 35 (4) [where, M in the formula represents the concentration (mmol%) of the catalytic metal element remaining in the film. ] 4. The polyester film for laminating and forming a metal plate according to claim 1, wherein the copolymerized aromatic polyester is produced using a germanium compound as a polycondensation catalyst. 5. The polyester film according to claim 1, wherein the glycol glycol free aromatic dicarboxylic acid in the polyester film is bis (β-hydroxyethyl) terephthalate. 6. The metal plate lamination molding process according to claim 1, wherein the copolymerized aromatic polyester is a copolymerized aromatic polyester obtained by copolymerizing diethylene glycol as a copolymer component in an amount of 5 mol% or less based on all glycol components. Polyester film. 7. The amount of extraction when the polyester film is extracted with ion-exchanged water at 125 ° C. for one hour is 0.1 m.
The polyester film for laminating and processing a metal plate according to claim 1, wherein the polyester film has a g / inch ² or less.