JPH11147964A - Polyester film for metal sheet lamination - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polyester film for metal sheet lamination which is excellent in heat resistance, impact resistance, rustproof properties, and esp. taste and flavor retention after retorting and gives a metal sheet laminate excellent in processibility in can making, such as deep drawability. SOLUTION: A biaxially oriented film is provided which comprises a copolyester prepd. from an acid component comprising 82-97 mol.% terephthalic acid and 18-3 mol.% naphthalenedicarboxylic acid and a glycol component mainly comprising ethylene glycol, contains a lubricant having an average particle size of 2.5 μm or lower, and has an intrinsic viscosity of 0.50-0.80, a glass transition point of 75 deg.C or higher, an m.p. of 210-250 deg.C, a concn. of terminal carboxyl groups of 40 equivalents/10<6> g or lower, and an acetaldehyde content of 15 ppm or lower.

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, especially 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 for satisfying molding workability, heat resistance, impact resistance, and fragrance retention. For example, Japanese Patent Application Laid-Open No. 5-339348 discloses a copolyester film. A polyester film for laminating a metal plate comprising a copolyester having a glass transition temperature and a terminal carboxyl group concentration, and a copolyester having a specific melting point and a glass transition temperature are disclosed in JP-A-6-39979. Polyester film for metal plate lamination molding 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 An object of the present invention is to eliminate the disadvantages of the prior art and to preserve the contents while maintaining the excellent moldability, heat resistance and impact resistance of a copolymerized polyester film. An object of the present invention is to provide a polyester film for laminating and processing a metal plate, which has improved fragrance, particularly, flavor retention 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 biaxially oriented film comprising a copolymerized polyester comprising an acid component and a glycol component mainly composed of ethylene glycol, and containing a lubricant having an average particle size of 2.5 μm or less,
The biaxially oriented film 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 polyester film for laminating and processing a metal plate, characterized in that the carboxyl group concentration is 40 equivalents / 10 ⁶ g or less and the acetaldehyde content is 15 ppm or less.

[0009] The copolymerized polyester in the present invention mainly comprises terephthalic acid and 2,6-naphthalenedicarboxylic acid, and has a molar ratio (terephthalic acid / 2,6-naphthalenedicarboxylic acid) of 82/18 to 97/3. And a glycol component mainly composed of ethylene glycol.

2,6 per total acid component of the polymer
If the molar ratio of the naphthalenedicarboxylic acid component is less than 3 mol%, the moldability and the fragrance retention are insufficient, while if it exceeds 18 mol%, the heat resistance and impact resistance are undesirably deteriorated.

Further, as the acid component, an acid component other than terephthalic acid and 2,6-naphthalenedicarboxylic acid can be used together as long as the physical properties (melting point, amount of water extract, etc.) of the film are not impaired. Acid components 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 alicyclics such as cyclohexanedicarboxylic acid. Examples thereof include dicarboxylic acids.

Next, the glycol component is mainly composed of ethylene glycol (90 mol% or more with respect to the total glycol component), but other glycol components are used as long as the physical properties (heat resistance, glass transition point, etc.) of the film are not impaired. Can be used together. 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.

Among these glycol components other than ethylene glycol, diethylene glycol is preferably copolymerized, and the copolymerization amount of the diethylene glycol component is more preferably 5 mol% or less, and more preferably 4 mol%. It is particularly preferred that:
When the copolymerization amount of diethylene glycol exceeds 5 mol%, heat resistance may be reduced. 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 melting point of the film of the present invention is 210 to 25.
It must be in the range of 0 ° C, preferably 215-245 ° C. When the melting point is lower than 210 ° C., the heat resistance of the film is inferior.
It is not preferable because the crystallinity of the film is increased and the processability of the film is impaired.

Here, the melting point of the film is measured by Du P
A method of obtaining a melting peak at a rate of temperature increase of 20 ° C./min using ont Instruments 910 DSC. The sample amount is 20 mg.

The glass transition temperature (hereinafter sometimes abbreviated as Tg) of the film of the present invention must be 75 ° C. or higher. If the Tg is less than 75 ° C., the heat resistance becomes poor, and the flavor and flavor retention after retort deteriorates. As an acid component of the copolymerized polyester in the present invention, terephthalic acid and 2,6-naphthalenedicarboxylic acid are mainly used, and their molar ratio (terephthalic acid / 2,6-naphthalenedicarboxylic acid) is 82/18 to 97/3. Tg of the film can be set to 75 ° C. or higher by mainly setting ethylene glycol as a glycol component.

Here, the Tg of the film was determined by placing a 20 mg sample in a pan for DSC measurement, heating and melting on a heating stage at 290 ° C. for 5 minutes, and then rapidly solidifying the sample pan on an aluminum foil spread on ice. , Du Pont Ins
temperature 910 DSC, heating rate 20
Depends on the method of determining the glass transition point in ° C / min.

Further, the intrinsic viscosity (ο) of the film of the present invention
-Chlorophenol, 35 ° C) 0.50 to 0.80
It is necessary to be in the range of, preferably 0.55 to
0.75, more preferably 0.60 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, the intrinsic viscosity is 0.
If it exceeds 80, it is necessary to raise the intrinsic viscosity of the raw material polymer excessively, which is uneconomical.

The film of the present invention must be used in the form of a biaxially stretched and heat-set biaxially stretched film.

In the present invention, the amount of acetaldehyde contained in the film must be 15 ppm or less, preferably 12 ppm or less, more preferably 10 ppm or less.
pm or less.

When the content of acetaldehyde in the film of the present invention exceeds 15 ppm, it is not preferable because the taste and aroma retention of the contents are remarkably reduced. The amount of acetaldehyde contained in the film can be reduced to 15 ppm or less by satisfying the above-mentioned composition range of the polymer constituents and by controlling the terminal carboxyl group concentration of the film to 40 equivalents / 10 ⁶ g or less.

Further, the terminal carboxyl group concentration of the film of the present invention must be 40 equivalents / 10 ⁶ g or less, preferably 35 equivalents / 10 ⁶ g or less, more preferably 30 equivalents / 10 ⁶ g. .

If the terminal carboxyl group concentration of the film of the present invention exceeds 40 equivalents / 10 ⁶ g, the amount of acetaldehyde contained in the film increases, and the taste and aroma preserving properties of the contents are remarkably reduced. In addition, heat resistance and retort resistance decrease, and the favorable properties obtained by the present technology are offset, which is not preferable. In order to reduce the terminal carboxyl group concentration of the film to 40 equivalents / 10 ⁶ g or less, the above-mentioned constituent component composition range of the copolymerized polyester must be satisfied, and the concentration (M) of the catalytic metal element remaining in the film and the phosphorus element Is achieved when the sum of the concentration (P) and the concentration (P) is in the range of 20 ≦ (M + P) ≦ 55 (mmol%). The terminal carboxyl groups generated by thermal decomposition during the polymerization of the copolymerized polyester and the film formation may be suppressed by a generally known method. That is, the reaction is carried out at a lower polymerization temperature than usual, the film is formed at a lower melt extrusion temperature than usual, or the concentration of terminal carboxyl groups generated by thermal decomposition by solid phase polymerization is suppressed, and the terminal carboxyl group concentration of the film is reduced to 40 equivalents. / 10 ⁶ g or less.

In the present invention, the copolymerized polyester is
It is not limited by the manufacturing method. For example, terephthalic acid, ethylene glycol, and 2,6-naphthalenedicarboxylic acid as a copolymer component are subjected to a transesterification reaction, and then the obtained reaction product is subjected to a polycondensation reaction until a desired degree of polymerization is obtained. Or a transesterification reaction of dimethyl terephthalate, ethylene glycol and dimethyl ester of 2,6-naphthalenedicarboxylic acid, which is a copolymer component, and the obtained reaction product has a desired degree of polymerization. Preferred is a method of producing a copolymerized polyester by a polycondensation reaction up to the above.

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

In the film made of the copolymerized polyester of the present invention, the total amount of alkali metal elements remaining in the film (total alkali metal element amount A) is A ≦ 5 (ppm).
Is preferable for maintaining the taste and fragrance retention. 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.

If the total amount of the alkali metal element is 5 ppm or less, the amount of by-product ether glycol, particularly the amount of by-product diethylene glycol during the production of polyester increases, the heat resistance of the film decreases, and the film is cast by electrostatic application. It is known that the productivity of the polyester is reduced.However, according to the study of the present inventors, by optimizing the amount of the metal compound of the catalyst and optimizing the conditions of the esterification or transesterification reaction, the production of the polyester is reduced. The amount of by-product ether glycol, especially the amount of by-product diethylene glycol can be controlled, and the ratio of the amount of the catalytic metal element by the metal compound to the amount of the phosphorus element caused by the phosphorus compound in the film is within a certain range. It has been found that the decrease in productivity in the electrostatic application casting method of the film can be suppressed by specifying the above.

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

Further, the film of the present invention has a catalyst metal element concentration (M) and a phosphorus element concentration (P) remaining in the film.
Is preferably in the range of 1 ≦ (M / P) ≦ 5 (mmol% / mmol%). When the M / P is less than 1 or more than 5, the abundance ratio of the catalyst metal element and the phosphorus element is lost, and excess phosphorus element or the catalyst metal element is present in the polymer, so that the thermal stability is reduced. May drop.

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 film of the present invention, the catalyst metal element (M) remaining in the film is such that 10 ≦ M ≦ 35 (mmol%)
Is preferably within the range. 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.

The catalyst used in the polymerization reaction is not particularly limited, but preferably includes an antimony compound (Sb compound), a titanium compound (Ti compound), a germanium compound (Ge compound), and the like. It is particularly preferable from the viewpoint of the fragrance retention of the obtained film.

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.

The copolyester in the present invention includes:
2.5 μm average particle size to improve film rollability
m or less of lubricant must be added. The kind of the lubricant may be inorganic or organic, but inorganic is preferred. Examples of the inorganic lubricant include silica, alumina, titanium oxide, calcium carbonate, and barium sulfate. Examples of the organic lubricant include silicone resin particles and crosslinked polystyrene particles. Particularly preferred lubricants in terms of pinhole resistance are monodispersed lubricants having a particle size ratio (major axis / minor axis) of 1.0 to 1.2. Examples of such a lubricant include spherical silica, spherical silicone resin particles, and spherical cross-linked polystyrene.

If the particle size of the lubricant exceeds 2.5 μm, the pinhole resistance becomes poor, which is not preferable.

The amount of the lubricant having a particle size of 2.5 μm or less to be added may be determined based on the winding property of the film, the pinhole resistance, and the flavor and flavor. That is, the average particle size is 1.5 μm
0.06% by weight or more and 0.25% by weight of silica
In the case of silica having an average particle diameter of 0.8 μm, the winding property can be ensured without impairing the flavor and taste retention by adding the silica in the range of 0.1% by weight to 0.45% by weight. it can.

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

Further, the refractive index in the thickness direction of the film of the present invention is preferably 1.500 to 1.540,
More preferably, it is 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 film of the present invention has a thickness of 6 to 75 μm.
Is preferred. Further, it is preferably from 8 to 75 μm, particularly preferably from 10 to 50 μm. If the thickness is less than 6 μm, breakage or the like is likely to occur during molding, while if it exceeds 75 μm, the quality is excessive and uneconomical.

A metal plate on which the film of the present invention is bonded,
In particular, as a metal plate for can making, a plate of tin, tin-free steel, aluminum or the like is suitable. The lamination of the 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 laminated, and then cooled. The surface layer (thin layer) of the film in contact with the metal plate is made amorphous and adhered. An adhesive layer is primer-coated on the film in advance, and this surface is bonded to a metal plate. As the adhesive layer, a known resin adhesive, for example, an epoxy adhesive, an epoxy-ester adhesive, an alkyd adhesive, or 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: Measured at 35 ° C. in o-chlorophenol.

(A) Melting point of copolymerized 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) A 20 mg sample was placed in a pan for DSC measurement, and 290
After heating and melting on a heating stage for 5 minutes, the sample pan was quickly cooled and solidified on an aluminum foil laid on ice, and then Du was added.
Pont Instruments 910 DSC
Was used to determine the glass transition point at a heating rate of 20 ° C./min.

(D) Acetaldehyde amount (ppm) The amount of acetaldehyde generated when the film was heat-treated at 160 ° C. for 20 minutes was quantified by gas chromatography.

(E) Terminal carboxyl group concentration (equivalent / 1
0 ⁶ g) A. It was measured according to the method of Conix. (Makro
mal. Chem. 26, 226 (1958))

(F) Amount of alkali metal The film sample was dissolved in o-chlorophenol and extracted with 0.5N hydrochloric acid. This extract was subjected to atomic absorption analysis 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.

(H) Laminability The film was bonded to a tin-free steel plate having a thickness of 0.25 mm heated above the melting point of the copolymerized polyester and then cooled to obtain a coated steel plate. Observe this coated steel sheet,
Laminability was evaluated according to the following criteria. [Criteria for judging bubbles and wrinkles (lamination property A)] 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 Ratio (Laminability B)] 〇: Shrinkage ratio 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 film is laminated in the same manner as in the above item (h) is cut into a disk having a diameter of 150 mm, and deep drawn in four stages using a drawing die and a punch. By processing, a side-seamless container having a diameter of 55 mm (hereinafter, sometimes abbreviated as a can) was prepared. 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 is observed at the top 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 performed on the cans obtained in the above (g), and the cans were evaluated 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 exceeds 0.2 mA 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 cans with good deep drawing workability, pour water fully, 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. Δ: Exceeded 0.2 mA for 1 to 5 pieces. X: The film exceeded 0.2 mA for 6 or more pieces, or cracks of the film were already observed after dropping.

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

(S) Retort resistance A can with good deep drawability was filled with water and retorted at 120 ° C. for 1 hour in a steam sterilizer.
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. Δ: Exceeded 0.2 mA for 1 to 5 pieces. X: The film exceeded 0.2 mA for 6 or more pieces, or cracks of the film were already observed after dropping.

(C) Taste preservation -1 A can having good deep drawability 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 drawability was filled with ion-exchanged water, retorted in a steam sterilizer at 125 ° C. for 1 hour, 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 1 to 5
The copolymerized polyethylene terephthalate produced using an acid component, ethylene glycol, diethylene glycol, an alkali metal compound, a polycondensation catalyst and a phosphorus compound (having a spherical silica having a particle size ratio of 1.1 and an average particle size of 0.5 μm, After drying, the mixture was melt-extruded at 280 ° C. and rapidly solidified to obtain an unstretched film. Next, the unstretched film was stretched 3.0 times in the machine direction, then 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.

Example 6 Copolymerized PET using an acid component, ethylene glycol, diethylene glycol, an alkali metal compound, a polycondensation catalyst and a phosphorus compound shown in Table 1.
Was polymerized by melt polymerization to an intrinsic viscosity of 0.60, and a biaxially oriented film was obtained in the same manner as in Example 1 except that a polymer having an intrinsic viscosity of 0.75 was obtained by solid-phase polymerization. The properties of this film are shown in Tables 1 and 2.

[Comparative Example 6] The particle diameter ratio of the copolymerized PET was 1.
1. 0.2% by weight of spherical silica having an average particle size of 3.0 μm
A biaxially oriented film was obtained in the same manner as in Example 1 except that it was contained. The properties of this film are shown in Tables 1 and 2.

[Comparative Example 7] 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 305 ° C. The properties of this film are shown in Tables 1 and 2. The acetaldehyde content and the terminal carboxyl group concentration in this biaxially oriented film were higher than in Example 1.

[0061]

[Table 1]

[0062]

[Table 2]

As is clear from the evaluation results in Table 2, the cans using the film of the present invention have good deep drawing workability, heat embrittlement resistance, retort resistance, impact resistance, and fragrance retention. In particular, it is excellent in preserving the flavor and flavor after retort.

[0064]

The polyester film for laminating and forming a metal plate of the present invention can be formed into a metal can by laminating the metal plate, for example, by deep drawing to form a metal can. It has good retort resistance and impact resistance, and also has excellent fragrance retention properties, particularly excellent flavor retention and fragrance retention properties after retort, and is extremely useful for metal container lamination processing.

────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission date] July 30, 1998

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0061

[Correction method] Change

[Correction contents]

[0061]

[Table 1]

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI C08K 7/18 C08K 7/18 C08L 67/02 C08L 67/02 // B29K 67:00 B29L 7:00

Claims (7)

[Claims] A terephthalic acid and 2,6-naphthalenedicarboxylic acid as main components, and a molar ratio (terephthalic acid / 2,6-
(Naphthalenedicarboxylic acid) 82/18 to 97/3, and a glycol component mainly composed of ethylene glycol, and a copolymerized polyester containing a lubricant having an average particle size of 2.5 μm or less. An axially oriented film, wherein the biaxially oriented film has an intrinsic viscosity of 0.50 to 0.80, a glass transition point of 75 ° C or higher, a melting point of 210 to 250 ° C, and a terminal carboxyl group concentration of 40 equivalents / 10 ^6. g or less, and 15 ppm of acetaldehyde
A polyester film for laminating a metal plate, comprising: 2. The metal plate lamination molding according to claim 1, wherein the concentrations of the alkali metal element, catalyst metal element and phosphorus element remaining in the film satisfy the following general formulas (1), (2) and (3). Polyester film for processing. A ≦ 5 (1) (2) 20 ≦ M + P ≦ 55 (2) 1 (1) M / P ≦ 5 (3) [wherein 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 film satisfies the following formula (4). 10 ≦ M ≦ 35 (4) [where, M represents the concentration (mmol%) of the catalytic metal element remaining in the film. ] 4. The copolymerized polyester produced by using a germanium compound as a polycondensation catalyst.
4. The polyester film for metal plate lamination processing according to 2 or 3. 5. A film having a carboxyl end group content of 35.
Metal plate bonded polyester film for combined molding according to claim 1 equivalent / 10 is ⁶ g or less. 6. A copolymerized polyester comprising ethylene glycol as a main glycol component and diethylene glycol as a copolymer component in an amount of 5 to all glycol components.
The polyester film for metal plate lamination molding according to claim 1, which is a copolymerized polyester copolymerized in an amount of not more than mol%. 7. The polyester film according to claim 1, wherein the lubricant is inorganic particles.