JP2908160B2 - Polyester film for metal plate lamination processing - Google Patents

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 exhibits excellent formability when laminating to a metal plate and performing can forming such as drawing. Polyester film for metal plate lamination that can be used to produce metal cans having good heat resistance, and excellent heat resistance, retort resistance, fragrance preservation and flavor, impact resistance, etc., such as beverage cans and food cans About.

[0002]

2. Description of the Related Art Metal cans are generally coated to prevent corrosion of the inner and outer surfaces. 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,
Studies have been made on a method of laminating a thermoplastic resin film on a metal plate such as tin, tin-free steel, or aluminum, and then forming the can by drawing or the like. Polyolefin films and polyamide films have been tried as this thermoplastic resin film, but they do not satisfy all of moldability, heat resistance, fragrance retention and impact resistance.

On the other hand, polyester films, particularly polyethylene terephthalate films, have been attracting attention as having balanced properties, and some proposals based on these have been made. That is, (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-56-1045).
No. 1, JP-A-1-192546). (B) Amorphous or extremely low-crystalline aromatic polyester film is laminated on a metal plate and used as a can-forming material (JP-A-1-192545, JP-A-2-57).
339). (C) A biaxially oriented polyethylene terephthalate film having a low orientation and thermally fixed is laminated on a metal plate and used as a can-making material (Japanese Patent Application Laid-Open No. 64-22530).

[0004] However, the present inventors' studies have revealed that no satisfactory characteristics can be obtained in any case, and that each has the following problems.

Regarding (A), a biaxially oriented polyethylene terephthalate film is excellent in heat resistance and fragrance retention,
In the process of making cans with insufficient molding workability and large deformation, whitening (generation of minute cracks) and breakage of the film occur.

As for (B), since it is an amorphous or extremely low-crystalline aromatic polyester film, the moldability is good, but the fragrance retention is inferior, and the printing and retort sterilization after can-making are performed. Such a film may be easily embrittled by post-treatments or storage for a long period of time, and may be changed to a film which is easily broken by an impact from the outside of the can.

As for (C), the effect is not exhibited in the intermediate region between the above (A) and (B), but it has not yet reached the low orientation applicable to can processing. Even if it can be processed in a region with a small degree of deformation, subsequent printing,
As in the case of (B), there is a possibility that the retort treatment for sterilizing the contents of the can makes the film brittle easily and the film is likely to be broken by an impact from the outside of the can.

In order to solve such a problem, the present inventors have considered various uses of a film made of a copolymerized polyester and have made various studies. 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 that 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 poses a major problem when handled in a cooled state, such as metal cans for juices and soft drinks.

Further, it has been found that when a copolymerized polyester film is used, the fragrance retention is generally good, but when used in soft drinks and the like, there arises a problem that the taste of the contents deteriorates. .

[0010]

SUMMARY OF THE INVENTION An object of the present invention is to improve the impact resistance of a copolymerized polyester film while maintaining the excellent moldability, heat resistance, retort resistance and fragrance retention. Another object of the present invention is to provide a polyester film for laminating a metal plate which is hardly cracked by an impact at a low temperature and does not deteriorate the taste of soft drink and the like.

[0011]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to achieve the above object, and as a result, have made a film into a laminated polyester film, and one of the surface layers has ethylene terephthalate as a main repeating unit. The copolymerized polyester and the polyester having butylene terephthalate as a main repeating unit are mixed at a specific ratio, and the mixture is constituted by a layer of a polyester composition containing a large amount of a filler, and the surface roughness of each surface layer is in a specific range. The present inventors have found that the impact resistance and the taste retention at low temperatures can be remarkably improved, and that the winding property can be prevented from deteriorating, thereby completing the present invention.

That is, the present invention has a melting point of 210-245 ° C.
(A), a copolymer containing 5 to 30% by weight of a filler having an average particle size of 2.5 μm or less and having ethylene terephthalate having a melting point of 210 to 245 ° C. as a main repeating unit. Polyester (I) 9
A polyester layer (B) composed of a polyester composition obtained by melt-mixing 9 to 60% by weight and 1 to 40% by weight of a polyester (II) containing butylene terephthalate having a melting point of 180 to 223 ° C. as a main repeating unit is laminated. Become
A polyester film for laminating a metal plate, wherein the isophthalic acid copolymerized polyester layer (A) has a surface roughness (Ra) of 15 nm or less, and the polyester layer (B) has a surface roughness of 15 nm or more. It is.

In the present invention, the isophthalic acid copolymerized polyester layer (A) is a layer exhibiting excellent fragrance retention properties, is composed of isophthalic acid copolymerized polyester, and is a copolymer obtained by copolymerizing an isophthalic acid component. A typical example is polyethylene terephthalate (polyethylene terephthalate copolymerized with isophthalic acid). This isophthalic acid copolymerized polyethylene terephthalate is a copolymer component or copolymer alcohol component other than isophthalic acid,
The copolymer may be copolymerized in a range that does not impair its properties, for example, at a ratio of 3 mol% or less based on all acid components or all alcohol components. Examples of the copolymerized acid component include aromatic dicarboxylic acids such as phthalic acid and naphthalenedicarboxylic acid, aliphatic dicarboxylic acids such as adipic acid, azelaic acid, sebacic acid, and decane dicarboxylic acid, and alicyclic dicarboxylic acids such as cyclohexanedicarboxylic acid. Acids and the like can be exemplified, and examples of the copolymerized alcohol component include aliphatic diols such as butanediol and hexanediol, and alicyclic 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 polymer has a melting point of 210-245 ° C., preferably 2
It is a ratio falling within a range of 15 to 235 ° C. Melting point 210
If the temperature is lower than ℃, the heat resistance is inferior. On the other hand, the melting point is 24
If the temperature exceeds 5 ° C., the crystallinity of the polymer is too large and the moldability is impaired.

The melting point of the isophthalic acid copolymerized polyester was measured by Du Pont Instrument.
A method in which a melting peak is determined at a heating rate of 20 ° C./min using s910 DSC. The sample size is about 20m
g.

The isophthalic acid copolymerized polyester preferably has an intrinsic viscosity of 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 polyester 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 alicyclic groups such as cyclohexanedicarboxylic acid. Examples of the dicarboxylic acid include aliphatic alcohols such as butanediol and hexanediol, and alicyclic diols such as cyclohexanedimethanol. These can be used alone or in combination of two or more.

The proportion of the copolymer component depends on the type thereof, but is a proportion that results in a polymer melting point in the range of 210 to 245 ° C, preferably 215 to 235 ° C. If the melting point is lower than 210 ° C., the heat resistance will be poor. On the other hand, when the melting point exceeds 245 ° C., the crystallinity of the polymer is too large, and the moldability is impaired.

Here, the melting point of the copolyester (I) is measured by the same method as that of the isophthalic acid copolyester.

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

In the present invention, the polyester (II) constituting the polyester layer (B) is a polyester having butylene terephthalate as a main repeating unit, and may be a homopolymer or a copolymer.

The copolymer component in the copolymer may be an acid component or an alcohol component. Examples of the copolymeric 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 fatty acids such as cyclohexanedicarboxylic acid. Examples of the cyclic dicarboxylic acid include aliphatic diols such as ethylene glycol and hexanediol, and alicyclic diols such as cyclohexanedimethanol. These can be used alone or in combination of two or more.

The proportion of the copolymer component depends on the type thereof, but as a result, the melting point of the polymer is from 180 to 223 ° C, preferably from 200 to 223 ° C, more preferably from 210 to 223 ° C.
It is the ratio which becomes the range of. If the melting point is lower than 180 ° C., the heat resistance will be poor. The melting point of the polybutylene terephthalate homopolymer is 223 ° C.

The measurement of the melting point of the polyester was carried out in the same manner as in the measurement of the isophthalic acid copolymerized polyester.
u Pont Instruments 910 DS
C is performed.

In the polyester film of the present invention,
The polyester layer (B) comprises 99 to 60% by weight of a copolymer polyester (I) having ethylene terephthalate having a melting point of 210 to 245 ° C. as a main repeating unit, and a melting point of 18%.
It must be composed of 1 to 40% by weight of a polyester (II) whose main repeating unit is butylene terephthalate at 0 to 223 ° 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 impact resistance at low temperatures is reduced. Can't improve. When the content of the polyester (II) containing butylene terephthalate as the main repeating unit exceeds 40% by weight and the content of the polyester (I) containing ethylene terephthalate as the main repeating unit is less than 60% by weight, the heat resistance of the film is reduced, Impact resistance is also insufficient.

In the present invention, a copolymer containing isophthalic acid copolymerized polyester used for the isophthalic acid copolymerized polyester layer (A) and ethylene terephthalate used for the copolymerized polyester (I) of the polyester layer (B) as a main repeating unit. Polyester having butylene terephthalate as a main repeating unit used for polyester and polyester (II) of polyester layer (B) is not limited by its production method. For example, in the case of a copolyester having ethylene terephthalate as a main repeating unit, a method in which terephthalic acid, ethylene glycol and a copolymer component are subjected to an esterification reaction, and then the obtained reaction product is subjected to a polycondensation reaction to form a copolyester. Alternatively, a method of subjecting dimethyl terephthalate, ethylene glycol and a copolymer component to a transesterification reaction and then subjecting the resulting reaction product to a polycondensation reaction to obtain a copolymerized polyester is preferably used. In the production of each copolymerized polyester and polybutylene terephthalate, if necessary, other additives such as an antioxidant, a heat stabilizer, an ultraviolet absorber, an antistatic agent and the like can be added.

In the present invention, the polyester layer (B) contains 5 to 30% by weight of a filler having an average particle size of 2.5 μm or less. The filler may be inorganic or organic, but is preferably inorganic. Preferred examples of the inorganic pigment include alumina, titanium dioxide, calcium carbonate, barium sulfate and the like. In the case of the present invention, titanium dioxide is particularly optimal.

Each of these fillers has an average particle size of 2.
It needs to be 5 μm or less. When the average particle size of the filler exceeds 2.5 μm, coarse particles (for example, particles having a size of 10 μm or more) of a portion deformed by processing such as a deep drawing can serve as a starting point, and pinholes may be generated. It is not preferable because it breaks. The average particle size of the filler is preferably from 0.05 to 1.5 μm, particularly preferably from 0.1 to 0.5 μm.

The content of the filler is 5 to 30% by weight.
And particularly preferably 10 to 20% by weight. If the content of the filler is more than 30% by weight, it is difficult to form a film, and if it is less than 5% by weight, the effect of improving the low-temperature impact resistance cannot be recognized.

The filler is a copolymer polyester (I)
It is preferable to adjust the particle size and remove coarse particles using a refining process before including in the polyester (II). Industrial means of the refining process include, for example, a jet mill and a ball mill as pulverizing means, and examples of the classifying means include a dry or wet centrifuge. Of course, these means may be used in combination of two or more, and may be purified stepwise.

(Copolymerization) Various methods can be used for incorporating a filler into the polyester. A typical method is as follows. (A) (Copolymerization) A method of adding before the end of transesterification or esterification reaction at the time of polyester synthesis or before starting the polycondensation reaction. (A) (Copolymerization) A method of adding to polyester and melt-kneading. (C) In the above methods (a) and (b), a method in which a master pellet containing a large amount of additives is produced, kneaded with a (copolymerized) polyester containing no particles, and a predetermined amount of additives is contained. .

In the case of using the method of (A) in which an additive is added during the synthesis of the (co) polyester, it is preferable to add the additive to the reaction system as a slurry in which the additive is dispersed in glycol.

In the present invention, the isophthalic acid copolymerized polyester layer (A) must have a surface roughness (Ra) of 15 nm or less, preferably 12 nm or less, more preferably 2 to 10 nm. . The isophthalic acid copolymerized polyester layer (A) is a layer located on the side in contact with the contents of the can when it is molded into a metal plate and formed into a can. By setting the surface roughness (Ra) to 15 nm or less, In addition, it is possible to prevent the contents, especially soft drinks such as carbonated drinks, from being deteriorated in taste, and to improve the impact resistance at low temperatures. The surface roughness (Ra)
Is less than 2 nm, the film surface is easily damaged, and thus it is desirable to avoid it.

In order to reduce the surface roughness (Ra) to 15 nm or less, the average particle size and the amount of the lubricant to be added to the isophthalic acid copolymerized polyester may be appropriately selected. The lubricant may be inorganic or organic, but inorganic is preferred. Examples of the inorganic lubricant include silica, alumina, kaolin, titanium dioxide, calcium carbonate, and barium sulfate. Examples of the organic lubricant include silicone particles, crosslinked polystyrene particles, and crosslinked acrylic resin particles. In particular, a lubricant which is preferable in terms of pinhole resistance is a monodispersed lubricant having a particle size ratio (major axis / minor axis) of 1.0 to 1.2. Examples of such a lubricant include spherical silica and spherical silicone particles.

For example, when spherical silica is used as a lubricant, if the average particle size is 1.5 μm, 0.04
Weight% or less, and 0.3 if the average particle size is 0.8 μm.
What is necessary is just to add 6 weight% or less. When the addition amount is 0.2% by weight, the average particle size of the spherical silica is 1.33 μm.
What should be done below.

On the other hand, the polyester layer (B) has a surface roughness (Ra) of 15 nm or more, preferably 15 to 100.
nm, more preferably 15 to 80 nm. If the surface roughness (Ra) is less than 15 nm, the handling (winding) of the film deteriorates, which is not appropriate.

The polyester layer (B) is a layer on the side to be bonded to the metal can when the film is bonded to the metal can, and does not directly contact the contents of the can, so that the surface roughness (Ra) Is not less than 15 nm, the taste of the contents does not deteriorate.

In the case of the polyester layer (B), the desired surface roughness (Ra) can be obtained by appropriately selecting the average particle size and the amount of the filler to be added to the polyester layer (B) within the above ranges. Can be obtained.

The surface roughness (Ra) of the film is J
This is the center line average roughness determined according to IS-B0601, and a portion of the measured length L is extracted from the film surface roughness curve in the direction of the center line, the center line of the extracted portion is defined as the X axis, and the longitudinal magnification Is the Y axis, and the roughness curve is Y =
When represented by f (x), the value (R
a: nm) is defined as the film surface roughness.

[0040]

(Equation 1)

In the present invention, when the reference length is 2.5 mm, 5
The number was measured, and Ra was represented as an average value of four pieces excluding one from the larger value.

The polyester film of the present invention has a structure in which an isophthalic acid copolymerized polyester layer (A) and a polyester layer (B) are laminated. The constituent isophthalic acid copolymerized polyester and the polyester composition are separately melted, co-extruded, laminated and fused before solidification, then biaxially stretched, heat-fixed, isophthalic acid copolymerized polyester and the polyester composition. It can be manufactured by a method of separately melting and extruding to form a film, in an unstretched state or after stretching, and laminating and fusing them.

The polyester film of the present invention may be an unstretched film, but is usually used in a state of being biaxially stretched and heat set. In this case, the refractive index in the thickness direction of the isophthalic acid copolymerized polyester layer (A) is 1.49.
It is preferably 0 to 1.550, and more preferably more than 1.505 and not more than 1.540. 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 polyester film of the present invention preferably has a thickness of 6 to 75 μm. 10-75μ
m, 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.

Isophthalic acid copolymerized polyester layer (A)
The thickness T _A of the ratio between the thickness T _B of the polyester layer _{(B) (T A / T} B) is preferably about 0.02 to 1.5,
It is more preferably from 0.04 to 0.67, particularly preferably from 0.04 to 0.25. Specifically, for example, in the case of a polyester film having a thickness of 25 μm, the thickness of the isophthalic acid copolymerized polyester layer (A) is set to 0.5 to 15 μm.
m, preferably 1 to 10 μm, more preferably 1 to 5 μm
m.

As a metal plate to which the 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 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 laminated, and then cooled, and 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.

When the polyester film of the present invention is bonded to a metal plate, the polyester layer (B) is bonded to the metal plate.

Further, in the polyester film of the present invention, if necessary, another additional layer may be laminated between the isophthalic acid copolymerized polyester layer (A) and the polyester layer (B).

[0051]

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

[0052]

Examples 1 to 6 and Comparative Examples 1 to 8 Polyethylene terephthalate obtained by copolymerizing the components shown in Table 1 (intrinsic viscosity 0.6
4, containing 0.1% by weight of spherical silica having a particle size ratio of 1.1 and an average particle size of 0.3 μm) is a copolymerized polyester layer (A),
Similarly, the polyester composition shown in Table 1 (average particle size 0.2
Each layer is separately dried and melted by a conventional method so that the polyester layer (B contains 7 μm of titanium dioxide of 18% by weight) is coextruded from dies adjacent to each other, laminated, fused and quenched. It was solidified to form an unstretched laminated film.

Next, the unstretched film was longitudinally stretched 2.9 times at 110 ° C., and then transversely stretched 3 times at 120 ° C.
It was heat-set at 190 ° C. to obtain a biaxially oriented laminated film.

The thickness of the obtained film was 25 μm, and the thicknesses of the copolymerized polyester layer (A) and the polyester layer (B) were 5 μm and 20 μm, respectively. The surface roughness (Ra) is 5 nm and 53 nm, respectively.
Met.

The surface roughness (Ra) was measured using a stylus type surface roughness meter (SURFCORDER S manufactured by Kosaka Laboratory Co., Ltd.).
E-30C) using a stylus radius of 2 μm and a measurement pressure of 0.0
The measurement was performed under the conditions of 3 g and a cutoff value of 0.25 mm.

[0056]

[Table 1]

[0057]

Comparative Examples 9 to 10 In Example 2, the thickness of only the isophthalic acid copolymerized polyester layer (A) (Comparative Example 9) and the thickness of only the polyester layer (B) (Comparative Example 10) without forming a two-layer laminated structure. A 25 μm monolayer film was made.

[0058]

Examples 7 to 9 and Comparative Examples 11 to 12 In Example 2, the amount of titanium dioxide contained in the polyester layer (B) was changed as shown in Table 2, and the other conditions were the same as in Example 2. Thus, a biaxially oriented laminated film was obtained. Table 2 also shows the surface roughness (Ra) of the polyester layer (B).

[0059]

[Table 2]

[0060]

Examples 10 to 11 and Comparative Examples 13 to 14 In Example 2, the average particle size and content of the spherical silica contained in the isophthalic acid copolymerized polyester layer (A) and the carbon dioxide contained in the polyester layer (B) were used. The average particle size and content of titanium were changed as shown in Table 3, and the respective surface roughnesses (Ra) were changed as shown in Table 3. An oriented laminated film was obtained.

[0061]

[Table 3]

A total of 25 kinds of films obtained in Examples 1 to 11 and Comparative Examples 1 to 14 were coated on both sides of a 0.25 mm thick tin-free steel heated to 230 ° C. with a polyester layer (B). After laminating so that the surface is in contact with the tin-free steel, water-cooling, cutting into a 150 mm diameter disc, deep drawing in 4 stages using a drawing die and a punch, and a 55 mm diameter side seamless container (hereinafter, referred to as (Abbreviated as can)
It was created.

The following observations and tests were performed on the cans, and the cans were evaluated according to the following standards.

(1) Deep drawing processability -1 ○: The film was processed without any abnormality, and no whitening or breakage was observed in the film. Δ: Whitening was observed in the upper part of the film can. ×: The film was partially broken in the film. Is recognized

(2) Deep drawing workability-2 ○: Processed without any abnormality, rust prevention test on film surface in can (1% NaCl water was put in the can, electrodes were inserted, and the can body was used as an anode. The current value when a voltage of 6 V is applied is measured.
X: No abnormality in the film, but the current value was 0.1 mA or more in the ERV test, and when the energized portion was enlarged and observed, a pin starting from a coarse lubricant was found on the film. Hole-shaped cracks are observed

(3) Impact Resistance For cans having good deep drawing, plenty of water was added, and after cooling to 10 ° C., 10 cans of each test were 30 cm in height.
ERV test in the can after dropping from the surface to the PVC tile floor surface: ○: 0.3 mA or less for all 10 pieces Δ: 0.3 mA or more for 1 to 5 pieces ×: 6 More than 0.3 mA or more, or cracking of the film was already observed after dropping

(4) Heat Embrittlement Resistance After the can which had been subjected to good deep drawing was heated and held at 200 ° C. for 5 minutes, the impact resistance described in (3) was evaluated. Δ: 0.1 mA or more for 1 to 5 pieces ×: 0.1 mA or more for 6 or more pieces, or already cracked in the film after heating at 200 ° C. for 5 minutes Was

(5) Retort resistance The cans having good deep drawing properties were filled with water and retorted at 120 ° C. for 1 hour in a steam sterilizer, and then stored at 50 ° C. for 30 days. After dropping 10 cans obtained for each test from a height of 1 m onto a PVC tile floor, an ERV test in the cans was performed.

：: 0.3 mA or less for all 10 pieces Δ: 0.3 mA or more for 1 to 5 pieces ×: 0.3 mA or more for 6 pieces or more, or crack of film already after dropping Was recognized

(6) Scent Retention A can that had 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 sensory test.

：: no change in scent Δ: slight change in scent X: change in scent

(7) Taste preserving property A taste change was examined by a sensory test in the same manner as in (6). ：: No change in taste. ：: A slight change in taste was recognized. X: Change in taste. Was recognized

The results of the above seven evaluations and the winding properties are as shown in Table 2.

[0074]

[Table 4]

As is clear from the results in Table 4, the 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. It has excellent impact resistance, especially at low temperatures, and without deteriorating the taste of soft drinks, etc.
The winding property is also good.

[0076]

The polyester film for laminating and processing metal sheets of the present invention has excellent moldability, heat resistance, retort resistance and fragrance retention, and also has impact resistance, especially impact resistance at low temperatures. The properties are improved, the taste of soft drinks and the like are not deteriorated, and the winding property is also good. Therefore, it is particularly suitable to be used by being bonded to metal cans for soft drinks, which are often cooled and handled at low temperatures.

Continuation of the front page (56) References JP-A-5-338103 (JP, A) JP-A-6-172556 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) B32B 1 / 00-35/00 C08L 67/00-67/08 C08K 3/00-13/08

Claims (1)

(57) [Claims] 1. An isophthalic acid copolymerized polyester layer (A) having a melting point of 210 to 245 ° C. and an average particle size of 2.5
5 to 30% by weight of a filler having a melting point of 21 μm or less.
0 to 245 ° C 99 to 60% by weight of a copolymerized polyester (I) containing ethylene terephthalate as a main repeating unit
And a polyester layer (B) composed of a polyester composition obtained by melt-mixing 1 to 40% by weight of a polyester (II) having butylene terephthalate as a main repeating unit having a melting point of 180 to 223 ° C. The surface roughness (Ra) of the copolymerized polyester layer (A) is 15 n
m or less, and the surface roughness of the polyester layer (B) is 15 nm.
A polyester film for laminating and processing a metal plate, characterized in that: