JPH10315413A - Polyester film for laminating and molding metal plate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polyester film for laminating and molding a metal plate for manufacturing a metal can having excellent impact resistance, molding processability, heat resistance, retort resistance and perfume retentivity such as, for example, a beverage can or food can. SOLUTION: The polyester film obtained by laminating a first layer (A) formed of an isophthalate copolymer polyester having a melting point of 210 to 245 deg.C and a second layer (B) formed of a polyester composition made of 99 to 50 wt.% of copolymer polyester (I) having a main repeating unit of ethylene terephthalate having a melting point of 210 to 245 deg.C and 1 to 50 wt.% of polyester (II) having a main repeating unit of butylene terephthalate having a melting point of 180 to 223 deg.C. In this case, 0.01 to 5.0 pts.wt. of antioxidant is contained in 100 pts.wt. of the polyester (II).

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. Impact resistance, heat resistance, retort resistance,
The present invention relates to a polyester film for metal plate laminating and forming capable of producing metal cans having excellent scent-preserving properties 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 achieved without using organic solvents. The development of a method for obtaining a resin has been promoted, 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 did not satisfy all of moldability, heat resistance, fragrance retention and impact resistance.

On the other hand, a polyester film, particularly a polyethylene terephthalate film, has attracted attention as a film having balanced characteristics, and several proposals based on this have been made. For example, (A) a biaxially oriented polyethylene terephthalate film is laminated on a metal plate via a low-melting-point polyester adhesive layer and used as a can-making material (JP-A-56-10451).
JP, JP-A-1-192546). (B) An amorphous or extremely low-crystalline aromatic polyester film is laminated on a metal plate and used as a material for producing a can (JP-A-1-192545, JP-A-2-5-5).
No. 7339). (C) A biaxially oriented polyethylene terephthalate film, which is heat-set with low orientation, is laminated on a metal plate and used as a can-making material (JP-A-64-22530).

However, according to the study of the present inventors, it was found that no satisfactory characteristics were obtained in any case, and the following problems were encountered. Regarding (A), the biaxially oriented polyethylene terephthalate film is excellent in heat resistance and fragrance retention, but is insufficient in moldability and whitening of the film (generation of microcracks) in canning with large deformation. Breakage occurs. Regarding (B), since it is an amorphous or extremely low-crystalline aromatic polyester film, the moldability is good, but the fragrance retention is inferior, and after printing after can-making and retort sterilization, etc. There is a possibility that the film may be easily embrittled by the treatment and further long-term storage, and may be changed to a film which is easily broken by an impact from the outside of the can. About (C),
Although the effect is not exhibited in the intermediate region between the above (A) and (B), it has not yet reached a low orientation applicable to can processing, and it has been processed in a region with a small degree of deformation. Even if it is obtained, it may be easily embrittled by subsequent printing and retort treatment for sterilizing the contents of the can, and as in the case of (B), there is a possibility that the film may be deteriorated by an impact from the outside of the can.

[0005] In order to solve such a problem, the present inventors have made various studies, considering the use of a film made of a copolymerized polyester. As a result, the copolymerized polyester film is excellent in molding workability, heat resistance, retort resistance, and fragrance retention, but has an impact resistance, particularly
It has been found that the impact resistance at a low temperature of 5 ° C. or less is insufficient, and when the metal can to which the film is bonded is dropped at a low temperature to give an impact, the film is likely to crack. Poor impact resistance at low temperatures is a major problem in applications handled in a cooled state, such as metal cans for juice and soft drinks.

In order to improve the impact resistance of the film,
When the polyester (I) having ethylene terephthalate as a main repeating unit and the polyester (II) having butylene terephthalate as a main repeating unit undergo a transesterification reaction, the polyester composition comprising both becomes low in crystallinity. Although known, it was difficult to control this reaction.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to solve such a problem and to provide a metal can which is excellent in impact resistance and excellent in moldability, heat resistance, retort resistance, fragrance and taste. Another object of the present invention is to provide a polyester film for laminating and processing a metal plate which can be used to produce, for example, a beverage can, a food can and the like.

[0008]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to solve the above-mentioned problems, and as a result, have found that a copolyester containing a film as a laminated film and one layer of which is ethylene terephthalate as a main repeating unit. And a polyester having butylene terephthalate as a main repeating unit, and a polyester composition containing an antioxidant, thereby achieving the object of the present invention.

That is, the present invention has a melting point of 210 to 24.
A first layer (A) formed from an isophthalic acid copolymerized polyester at 5 ° C. and 99 to 50% by weight of a copolymerized polyester (I) having ethylene terephthalate having a melting point of 210 to 245 ° C. as a main repeating unit, and a melting point of 180-2
A laminated polyester film formed by laminating a second layer (B) formed from a polyester composition comprising 1 to 50% by weight of a polyester (II) having butylene terephthalate as a main repeating unit at 23 ° C, 0.0 parts of antioxidant is added to 100 parts by weight of polyester (II).
It is a polyester film for metal plate lamination molding, characterized by containing 1 to 5.0 parts by weight.

[0010] In the present invention, the first layer (A) is a layer exhibiting excellent flavor and taste retention properties and is composed of an isophthalic acid copolymerized polyester, and is a copolymerized polyethylene obtained by copolymerizing an isophthalic acid component. Terephthalate (isophthalic acid copolymerized polyethylene terephthalate) is a typical example. The polyethylene terephthalate copolymerized with isophthalic acid is copolymerized with an acid component or an alcohol component other than isophthalic acid in a range that does not impair the properties, for example, at a ratio of 3 mol% or less based on the total acid component or the total alcohol component. You may. As the copolymerized acid component, phthalic acid, aromatic dicarboxylic acids such as naphthalenedicarboxylic acid, adipic acid, azelaic acid, sebacic acid,
Aliphatic dicarboxylic acids such as decane dicarboxylic acid and the like can be exemplified, and as the alcohol component, butanediol,
Examples thereof include aliphatic diols such as hexanediol and neopentyl glycol, and aliphatic diols such as cyclohexanedimethanol. These can be used alone or in combination of two or more.

The proportion of isophthalic acid and other copolymer components is such that the melting point of the polymer is in the range of 210 to 245 ° C., preferably 215 to 235 ° C. If the melting point of the polymer is less than 210 ° C., the heat resistance of the laminated film is inferior, which is not preferable. On the other hand, if it exceeds 245 ° C., the crystallinity of the polymer becomes too large and the moldability of the laminated film is unfavorably deteriorated.

Here, the melting point of the isophthalic acid copolymerized polyester was measured by Du Pont Instruments.
A method in which a melting peak is obtained at a heating rate of 20 ° C./min using 910 DSC. The sample amount is about 20mg
And

The intrinsic viscosity of the isophthalic acid copolymerized polyester is preferably 0.52 to 0.80,
More preferably, it is 0.54 to 0.70, particularly preferably 0.57 to 0.65.

In the present invention, the copolymerized polyester (I) constituting the second layer (B) is a polyester containing ethylene terephthalate as a main repeating unit. The copolymer component may be an acid component or an alcohol component.
Examples of the acid component include aromatic dicarboxylic acids such as isophthalic acid, phthalic acid, and naphthalenedicarboxylic acid, aliphatic dicarboxylic acids such as adipic acid, azelaic acid, sebacic acid, and decane dicarboxylic acid, and alcohol components. Examples thereof include aliphatic diols such as butanediol, hexanediol and neopentyl glycol, and alicyclic diols such as cyclohexanedimethanol. These can be used alone or in combination of two or more. Of these, isophthalic acid is preferred.

The proportion of the copolymer component is such that the melting point of the polymer is 2
The ratio is in the range of 10 to 245 ° C, preferably 215 to 235 ° C. When the melting point of the polymer is less than 210 ° C., the heat resistance of the laminated film is inferior, which is not preferable. On the other hand, when the melting point of the polymer is more than 245 ° C., the crystallinity of the polymer is too large and the moldability of the film is impaired.

Here, the melting point of the copolymerized polyester (I) is measured by the same method as the above-mentioned method for measuring the melting point of the isophthalic acid copolymerized polyester.

The intrinsic viscosity of the copolymerized polyester (I) is preferably from 0.52 to 0.80, more preferably from 0.54 to 0.70, and particularly preferably 0.57 to 0.70.
０．６0.65.

The polyester (II) constituting the second layer (B) is a polyester containing butylene terephthalate as a main repeating unit. As a polyester having butylene terephthalate as a main repeating unit,
It may be a polybutylene terephthalate homopolymer or a copolymer of an acid component and / or an alcohol component. H00C is a copolymerizable acid component.
-(CH ₂ ) _n -COOH (where n = 4 to 8), aliphatic dicarboxylic acids such as aliphatic dicarboxylic acids, decane dicarboxylic acids, etc .; aromatics such as isophthalic acid, phthalic acid, naphthalenedicarboxylic acid, etc. Aliphatic dicarboxylic acids and the like can be exemplified. On the other hand, examples of the copolymerizable alcohol component include aliphatic diols such as ethylene glycol, hexanediol and neopentyl glycol, and alicyclic diols such as cyclohexanedimethanol. These can be used alone or in combination of two or more.

The proportion of the copolymer component is such that the melting point of the polymer is 1
The ratio is in the range of 80 to 223 ° C, preferably 200 to 223 ° C, and more preferably 210 to 223 ° C. If the melting point of the polymer is less than 180 ° C., the heat resistance of the laminated film is poor, which is not preferable. The melting point of the polybutylene terephthalate homopolymer is 223 ° C.

From the viewpoint of the impact resistance of the laminated film, the polyester (II) is represented by H00C- (CH ₂ ) _n -COOH (where n
= 4 to 8) is preferably copolymerized in an amount of 5 to 40 mol% with respect to the total acid component.
Those obtained by copolymerizing mol% are particularly preferred. In a particularly preferred embodiment, 5-40 mol% of adipic acid is used as the acid component.
Copolymers may be mentioned.

The melting point of the polyester is measured by the same method as that for the isophthalic acid copolymerized polyester.

The intrinsic viscosity of the polyester (II) is preferably from 0.70 to 2.00, more preferably from 0.80 to 1.70, and particularly preferably from 0.85 to 1.70.
1.50.

In the laminated polyester film of the present invention, the second layer (B) has a melting point of from 210 to 245 ° C. and 99 to 50% by weight of a copolymerized polyester (I) having ethylene terephthalate as a main repeating unit, and a melting point of from 180 to 245 ° C. 2
It must be formed from 1 to 50% by weight of a polyester (II) containing butylene terephthalate as a main repeating unit at 23 ° C.

When the content of the polyester (II) containing butylene terephthalate as the main repeating unit is less than 1% by weight and the content of the copolymerized polyester (I) containing ethylene terephthalate as the main repeating unit exceeds 99% by weight, the temperature of the laminated film under low temperatures may increase. Is not preferred because the impact resistance cannot be improved. When the content of the polyester (II) containing butylene terephthalate as a main repeating unit exceeds 50% by weight and the content of the copolymerized polyester (I) containing ethylene terephthalate as a main repeating unit is less than 50% by weight, the heat resistance of the laminated film is low. It is not preferable because the resistance is lowered and the impact resistance becomes insufficient.

In the present invention, a copolymer polyester containing isophthalic acid copolymer as a main repeating unit in the first layer (A) and ethylene terephthalate as a copolymer polyester (I) in the second layer (B), The polyester having butylene terephthalate as a main repeating unit used for the polyester (II) of the second layer (B) is not limited by the production method. For example, when producing a copolymerized polyethylene terephthalate, a method of subjecting terephthalic acid, ethylene glycol and a copolymer component to an esterification reaction, and then subjecting the obtained reaction product to a polycondensation reaction, or dimethyl terephthalate, an ethylene glycol and a copolymer component, A method is preferably used in which a transesterification reaction is performed and then the resulting reaction product is subjected to a polycondensation reaction.

In the production of polyester, other additives such as a fluorescent whitening agent, an antioxidant, an antistatic agent and the like can be added as required.

In the present invention, the transesterification reaction between the polyester (I) and the polyester (II) has a great influence on properties such as crystallinity of the film. For example, when the transesterification reaction rate is low, the polymer becomes highly crystalline, and the impact resistance of the laminated film decreases. That is, it is necessary to promote the transesterification reaction between the polyester (I) and the polyester (II). As the means, there are methods of increasing the residence time at the time of melting the polymer and increasing the retention temperature. However, when the residence time is increased or the retention temperature is increased, the transesterification rate increases, but the adverse effect of polymer deterioration occurs.

The inventors of the present invention have intensively studied a technique which does not cause this adverse effect while promoting the transesterification reaction. As a result, surprisingly, the polyester (II) 10 forming the second layer (B) was
It has been found that by adding 0.01 to 5.0 parts by weight of an antioxidant to 0 parts by weight, the transesterification rate can be increased without using the above-mentioned means.

When the content of the antioxidant is less than 0.01 part by weight, the transesterification rate decreases, the crystallinity of the polymer increases, and the processability and impact resistance of the laminated film become insufficient. Therefore, it is not preferable. On the other hand, adding an antioxidant in excess of 5.0 parts by weight is uneconomical due to excessive addition and is not preferred.

The present invention is intended for use in food cans. The antioxidant which can be used is substantially harmless to the human body, and is coated with a thermoplastic resin containing an antioxidant by heating. That are stable when doing
Those stable at 40 ° C. are preferred.

For example, as a phenol group-containing compound, tetrakis- (methylene-3- (3 ′, 5′-di-ter
t-butyl-4'-hydroxyphenyl) propionate) methane, stearyl-β- (3,5-di-tert)
-Butyl-4-hydroxyphenyl) propionate,
2,2′-methylenebis (4-methyl-6-tert-
Butylphenol), 2,2'-methylenebis (4-ethyl-6-tert-butylphenol), 4,4'-
Thiobis (3-methyl-6-tert-butylphenol), 4,4′-butylidenebis (3-methyl-6-t
tert-butylphenol), 3,9-bis (1,1-
Dimethyl-2- (β- (3-tert-butyl-4-hydroxy-5-methylphenyl) propionyloxy)
Ethyl) -2,4,8,10-tetraoxaspiro (5,5) undecane, 1,1,3-tris (2-methyl-4-hydroxy-5-tert-butylphenyl)
Butane, 1,3,5-trimethyl-2,4,6-tris (3,5-di-tert-butyl-4-hydroxybenzyl) benzene, 1,3,5-tris (3 ′, 5′-di -Tert-butyl-4'-hydroxybenzyl) -S
-Triazine-2,4,6- (1H, 3H, 5H) trione, tocopherol and the like.

In addition to the phenol group-containing compound, dilauryl-3,3'-thiodipropionate, dimyristyl-3,3'-thiodipropionate, distearyl-3,3'-thiodipropionate, etc. Such as sulfur-containing compounds, such as cyclic neopentanetetraylbis (octadecylphosphite), tris (nonylphenyl) phosphite, and cyclic neopentanetetraylbis (2,4-di-tert-butylphenyl) phosphite Compounds and the like can be exemplified. One of these antioxidants may be used alone, or two or more thereof may be used in combination.
Preferably, it contains a species. The sulfur-containing compound and the phosphorus-containing compound are mainly used as a secondary antioxidant, and a synergistic effect can be obtained when used in combination with a phenol group-containing compound that acts as a primary antioxidant.

Among them, a phenol group-containing compound, tetrakis- (methylene-3- (3 ′, 5′-di-t-t)
tert-Butyl-4'-hydroxyphenyl) propionate) methane is more preferred.

As a method of adding such an antioxidant to the polyester composition, a method of directly adding the antioxidant to the reaction tank during the polymerization of the resin, an extruder for the polymer after polymerization,
A method of blending with a heating roll, a Banbury mixer, a kneader, or the like may be used.

If the required amount of the antioxidant as a result of conversion to the content of the above-mentioned polyester (II) is satisfied, any one of the copolymerized polyester (I) and the polyester (II) can be used. It may be added to one side or may be added separately to both polymers.

In the present invention, the ester conversion of the polyester composition can be represented by the melting point of the polyester composition forming the second layer (B). That is, when the melting point of the polyester composition is low, the transesterification reaction proceeds, and when the melting point is high, the transesterification reaction does not proceed. The melting point of such a polyester composition is preferably from 220 to 240 ° C.

The measurement of the melting point of the polyester composition is carried out in the same manner as the measurement of the melting point of the isophthalic acid copolymerized polyester.

The laminated polyester film of the present invention has a structure in which a first layer (A) formed from an isophthalic acid copolymer and a second layer (B) formed from a polyester composition are laminated. Such a laminated film is, for example, separately melted isophthalic acid copolymerized polyester and polyester composition constituting each layer, co-extruded, laminated and fused before solidification, then biaxially stretched, heat fixed And a method of separately melting and extruding the isophthalic acid copolymerized polyester and the polyester composition to form a film, and then laminating the unstretched state or after stretching.

The laminated polyester film of the present invention may be an unstretched film, but is preferably in the form of a biaxially stretched film which has been biaxially stretched and then heat set.
In this case, the refractive index in the thickness direction of the first layer (A) formed from the isophthalic acid copolymerized polyester is 1.490 to
It is preferably 1.550, and more preferably 1.
It exceeds 505 and is 1.540 or less. If the refractive index is too low, the moldability will be insufficient, while if it is too high, the structure will be close to amorphous and the heat resistance may decrease.

The laminated polyester film of the present invention preferably has a thickness of 6 to 75 μm. More preferably, 1
It is 0 to 75 μm, particularly preferably 15 to 50 μm.
If the thickness is less than 6 μm, breakage or the like is likely to occur during processing, while if it exceeds 75 μm, the quality is excessive and uneconomical.

The thickness TA of the first layer (A) and the thickness TA of the second layer (B)
Is preferably 0.02 to 1.5, more preferably 0.04 to 0.67, and more preferably 0.02 to 0.67.
4-0.25 is particularly preferred. Specifically, for example, in the case of a polyester film having a thickness of 20 μm, the thickness of the first layer (A) is 0.5 to 12 μm, further 1 to 10 μm,
In particular, the thickness is preferably 1 to 4 μm.

As a metal plate to which the laminated polyester film of the present invention is bonded, particularly a metal plate for can making, a plate of tin, tin-free steel, aluminum or the like is suitable. The lamination of the laminated polyester film to the metal plate can be performed, for example, by the following methods (A) and (A). (A) 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, and the surface layer (thin layer) of the film in contact with the metal plate is made amorphous and adhered. (A) An adhesive is primer-coated on the film in advance, and this surface is bonded to a metal plate. As such an adhesive, a known resin adhesive, for example, an epoxy-based adhesive,
Epoxy-ester adhesives, alkyd adhesives and the like can be used.

When the polyester film of the present invention is bonded to a metal plate, the second layer (B) is bonded to the metal plate. Further, in the polyester film of the present invention, the first layer (A) and the second layer
Another additional layer may be laminated between the layers (B) or on one side.

[0044]

The present invention will be further described with reference to the following examples.

Examples 1 to 9 and Comparative Examples 1 to 6 Copolymerized polyethylene terephthalate (intrinsic viscosity: 0.64) obtained by copolymerizing the components shown in Table 1 was used for the first layer (A), and also for the polyester shown in Table 1. Each of the compositions is separately dried by a conventional method and melted at 280 ° C. so that the composition becomes the second layer (B). Then, the compositions are co-extruded from dies adjacent to each other, laminated, fused, quenched and solidified. A stretched laminated film was prepared. Further, tetrakis- (methylene-3- (3 ′, 5 ′) was used as an antioxidant for the polyester (II) in the second layer (B).
-Di-tert-butyl-4'-hydroxyphenyl)
Propionate) methane was added during polymer polymerization in the amounts shown in Table 1.

Next, the unstretched film was longitudinally stretched 3.2 times at 130 ° C., then transversely stretched 3.3 times at 120 ° C., and heat-set at 180 ° C. to obtain a biaxially oriented laminated film. .

The thickness of the obtained film was 20 μm, and the thicknesses of the first layer (A) and the second layer (B) were 4 μm and 16 μm, respectively.

[0048]

[Table 1]

A total of 15 kinds of films obtained in Examples 1 to 9 and Comparative Examples 1 to 6 were heated at 230 ° C. to a thickness of 0.1 mm.
Affixed to both sides of the 25 mm tin-free steel so that the surface of the second layer (B) is in contact with the tin-free steel, and after cooling with water, cut into a 150 mm diameter disk.
Deep drawing in 4 stages using a drawing die and punch
A 5 mm-diameter side-seamless container (hereinafter sometimes abbreviated as a can) was prepared. This can was evaluated by performing the following observations and tests.

(1) Deep drawing workability The film bonded to the can was visually observed and evaluated according to the following criteria. ：: The film was processed without any abnormality, and no whitening or breakage was observed in the film. Δ: Whitening is observed at the top of the film can. X: Film breakage is observed in a part of the film.

(2) Impact resistance For cans having good deep drawability, water was fully poured and cooled to 10 ° C., and 10 cans of each test were 30 cm in height.
Rust prevention test on the film surface in the can (1% NaCl water was put in the can, the electrode was inserted, and the voltage when 6V was applied with the can body as the anode) (Hereinafter, may be abbreviated as ERV test), 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. ×: More than 6 pieces exceeded 0.2 mA, or cracks of the film were already observed after dropping.

(3) Heat Embrittlement Resistance The can which had been subjected to good deep drawing was heated at 200 ° C. for 5 minutes, and then subjected to the impact resistance evaluation described in (2). ：: 0.1 mA or less for all 10 samples. Δ: More than 0.1 mA for 1 to 5 pieces. ×: More than 6 pieces exceeded 0.1 mA, or cracks of the film were already observed after heating at 200 ° C. for 5 minutes.

(4) Retort resistance For a can which has a good deep drawing, pour water fully and use a steam sterilizer.
Perform retort treatment at 120 ° C for 1 hour.
Stored at 30 ° C for 30 days. One can for each test
After dropping 0 pieces at a height of 1 m onto a PVC tile floor, an ERV test was performed in the can. ：: 0.2 mA or less for all 10 samples. Δ: Exceeded 0.2 mA for 1 to 5 pieces. ×: More than 6 pieces exceeded 0.2 mA, or cracks of the film were already observed after dropping.

(5) Perfume Retention A can with good deep drawing was filled with cider and sealed. After being kept at 37 ° C. for 30 days, the can was opened and the change in fragrance was examined by a sensory test, and evaluated according to the following criteria. ：: There was no change in fragrance. Δ: Slight change in fragrance was observed. ×: A change in scent was observed.

(6) Taste retention In the same manner as in (5), flavor change was examined by a sensory test and evaluated according to the following criteria. ：: There was no change in taste. Δ: Slight change in taste was observed. ×: A change in taste was observed. Table 2 shows the evaluation results.

[0056]

[Table 2]

As is clear from the results shown in Table 2, cans using the polyester film of the present invention are excellent in deep drawability, heat embrittlement resistance, retort resistance, and fragrance retention, and also have impact resistance. In particular, it has excellent impact resistance at low temperatures and does not deteriorate the taste of soft drinks and the like.

[0058]

Industrial Applicability The polyester film of the present invention for metal plate lamination has excellent moldability, heat resistance, retort resistance, and fragrance retention, and also has impact resistance, especially impact resistance at low temperatures. It has excellent properties and does not deteriorate the taste of soft drinks and the like. Therefore, it is particularly suitable to be used by being bonded to a metal can, such as for soft drinks, which is often cooled and handled at a low temperature.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI C09K 15/08 C09K 15/08

Claims (5)

[Claims] 1. A first layer (A) formed from an isophthalic acid copolymerized polyester having a melting point of 210 to 245 ° C.
And a copolymer polyester (I) containing ethylene terephthalate having a melting point of 210 to 245 ° C. as a main repeating unit.
A second layer (B) formed of a polyester composition comprising 99 to 50% by weight and 1 to 50% by weight of a polyester (II) having butylene terephthalate having a melting point of 180 to 223 ° C as a main repeating unit is laminated. A laminated polyester film comprising the polyester (II) 10
A polyester film for laminating and forming a metal plate, comprising 0.01 to 5.0 parts by weight of an antioxidant with respect to 0 parts by weight. 2. The polyester film according to claim 1, wherein the antioxidant is a phenol group-containing compound. 3. The metal plate as claimed in claim 2, wherein the phenol group-containing compound is tetrakis- (methylene-3- (3 ′, 5′-di-tert-butyl-4′-hydroxyphenyl) propionate) methane. Polyester film for lamination processing. 4. Polyester (II) containing butylene terephthalate as a main repeating unit in the second layer (B)
Is H00C- (CH ₂ ) _n -COOH (where n = 4 to 8) is 5 to 40.
The polyester film for metal plate lamination molding according to claim 1, wherein the polyester film is copolymerized by mol%. 5. The polyester for laminating and processing a metal plate according to claim 1, wherein the melting point of the polyester composition constituting the second layer (B) is from 220 to 240 ° C. the film.