JPH11207909A - Laminated polyester film for metal sheet laminating molding processing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a laminated polyester film for metal sheet laminating molding processing wherein the impact resistance is improved and cracking is hardly generated by impact at low temp. while excellent molding processability with no curling, heat resistance, retort resistance and fragrance and taste holdability are held. SOLUTION: A copolymerized polyester layer with a m.p. of 210-245 deg.C and having ethylene terephthalate as a main repeating unit and a copolymerized polyester layer with a m.p. of 210-245 deg.C and having ethylene terephthalate as a main repeating unit are laminated on each surface of a polyester compsn. layer consisting of 10-70 wt.% copolymerized polyester with a m.p. of 210-245 deg.C and having ethylene terephthalate as a main repeating unit and 30-90 wt.% polyester with a m.p. of 170-223 deg.C and having buthylene terephthalate as a main repeating unit.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laminated 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 laminated polyester film for metal plate laminating and forming capable of producing a metal can excellent in heat resistance, retort resistance, fragrance preserving property, impact resistance and the like, for example, a beverage can, a food can and the like.

[0002]

2. Description of the Related Art Metal cans are generally coated to prevent corrosion on the inner and outer surfaces. In recent years, for the purpose of simplifying the process, improving hygiene, and preventing pollution, rust prevention has been 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. As this thermoplastic resin film, a laminated copolyester film has been tried, and a film which satisfies practical use standards in all of moldability, heat resistance, fragrance preserving property and impact resistance has been developed (for example, Japanese Patent Application Laid-Open No. No. 039979).

[0003] However, several problems were found in the practical use stage. One of them is the curl property of the polyester film. In the case of a laminated stretched polyester film composed of two polymers having different glass transition temperatures, the layer with the lower glass transition temperature continues to shrink to a lower temperature range during the cooling process during film formation. Curling occurs. If the polyester film is curled in the step of bonding the heated metal plate and the polyester film, so-called laminating defects such as wrinkles and bubbles are likely to occur,
This leads to lower workability and yield.

[0004] Another problem is the low temperature impact resistance after molding as a beverage can lining. Although the conventional product satisfies the practical standards, it is desired to further improve the impact resistance at low temperatures in a severe use situation.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide excellent moldability, heat resistance and retort resistance without curling.
An object of the present invention is to provide a laminated polyester film for metal plate laminating and forming, which has improved impact resistance while maintaining flavor and taste retention properties and is less likely to be cracked by impact at low temperatures.

[0006]

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, the polyester film was made into a three-layer laminated polyester film, and the two surface layers were made of isophthalic acid or 2,6- A copolymerized polyester obtained by copolymerizing naphthalenedicarboxylic acid, etc., and the intermediate layer is mixed at a specific ratio with a copolymerized polyester mainly composed of ethylene terephthalate and a polyester mainly composed of butylene terephthalate copolymerized with adipic acid and the like. In addition, it has been found that by setting the ratio of butylene terephthalate to a specific range, a film that is hard to curl and has excellent impact resistance at low temperatures can be obtained, and has reached the present invention.

That is, the present invention has a melting point of 210 to 24.
From 10 to 70% by weight of a copolymerized polyester (I) containing ethylene terephthalate as a main repeating unit at 5 ° C and 30 to 90% by weight of polyester (II) containing butylene terephthalate having a melting point of 170 to 223 ° C as a main repeating unit. On each surface of the polyester composition layer (B), a copolymerized polyester layer (A) having a main repeating unit of ethylene terephthalate having a melting point of 210 to 245 ° C and a main repeating unit of ethylene terephthalate having a melting point of 210 to 245 ° C This is a laminated polyester film for laminating and forming a metal plate obtained by laminating a copolymerized polyester layer (C) as a unit.

In the present invention, the copolymerized polyester layers (A) and (C) containing ethylene terephthalate as a main repeating unit are layers exhibiting excellent flavor and taste retention properties, and are composed of terephthalic acid and other organic acids. And copolymerized isophthalic acid component (isophthalic acid copolymerized polyethylene terephthalate) and 2,6-naphthalenedigalvonic acid copolymerized polyethylene terephthalate. Can be This isophthalic acid copolymerized polyethylene terephthalate or 2,6-naphthalenedigalvonic acid copolymerized polyethylene terephthalate includes isophthalic acid, 2,6-naphthalenedigalvonic acid,
An acid component other than terephthalic acid or an alcohol component may be copolymerized in a range that does not impair the properties thereof, for example, at a ratio of 3 mol% or less based on all acid components or all alcohol components. Examples of the copolymeric acid component include aromatic dicarboxylic acids such as phthalic acid, and aliphatic dicarboxylic acids such as adipic acid, azelaic acid, sebacic acid, and 1,10-decanedicarboxylic acid. Aliphatic diols such as 1,4-butanediol, 1,6-hexanediol and neopentyl glycol; and alicyclic diols such as 1,4-cyclohexanedimethanol. These can be used alone or in combination of two or more.

The proportion of isophthalic acid or 2,6-naphthalenedigaric acid and other copolymer components is such that the polymer has a melting point of 210-245 ° C., preferably 215-235 ° C.
It is the ratio in the range of ° 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 copolymerized polyester was measured by using Du Pont Instruments 910DS.
Using C, the melting peak is determined at a heating rate of 20 ° C./min. The amount of the sample is about 20 mg.

The intrinsic viscosity of the copolymerized polyester is preferably 0.52 to 0.80, more preferably 0.54 to 0.70, and particularly preferably 0.57 to 0.70.
0.65.

Here, the intrinsic viscosity of the copolymerized polyester is measured at 35 ° C. after dissolving in o-chlorophenol.

In the present invention, the copolyester (I) constituting the polyester layer (B) is a copolyester containing ethylene terephthalate as a main repeating unit. The copolymer component may be an acid component or an alcohol component. Examples of the copolymerization component include aromatic dicarboxylic acids such as isophthalic acid, phthalic acid and 2,6-naphthalenedicarboxylic acid, and aliphatic dicarboxylic acids such as adipic acid, azelaic acid, sebacic acid and 1,10-decanedicarboxylic acid. And alcohol components such as 1,4-butanediol, 1,6-hexanediol,
Aliphatic diols such as neopentyl glycol, 1,
Alicyclic diols such as 4-cyclohexanedimethanol can be exemplified. These can be used alone or in combination of two or more. Of these, isophthalic acid or 2,6-naphthalenedigaric acid is preferred.

Depending on the type of the copolymer component, the resulting polymer has a melting point in the range of 210 to 245 ° C., preferably 215 to 235 ° C. Melting point 21
If the temperature is lower than 0 ° C., the heat resistance is inferior. On the other hand, the melting point is 2
If the temperature exceeds 45 ° C., the crystallinity of the polymer is too high and the moldability is impaired.

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 0.5 to 0.80.
7 to 0.65. If the intrinsic viscosity is less than 0.52, properties such as moldability at the time of can molding and impact resistance are insufficient. If it exceeds 0.8, the extrudability during film formation is reduced.

The measuring method of the melting point and the intrinsic viscosity of the copolyester (I) is the same as the measuring method of the copolyester constituting the layer (A).

In the present invention, the copolymerized polyester (II) constituting the polyester composition layer (B) is a polyester having butylene terephthalate as a main repeating unit, and may be a homopolymer or a copolymer. In the case of a copolymer, the copolymer component may be an acidic component or an alcohol component. Examples of the copolymerization component include aliphatic dicarboxylic acids such as adipic acid, azelaic acid, sebacic acid, and 1,10-decanedicarboxylic acid, and aromatic dicarboxylic acids such as isophthalic acid, phthalic acid, and 2,6-naphthalenedicarboxylic acid. Examples of the alcohol component include aliphatic diols such as butanediol, 1,6-hexanediol and neopentyl glycol, and alicyclic diols such as 1,4-cyclohexanedimethanol. These can be used alone or in combination of two or more.

Of these, adipic acid is preferable, and it is particularly preferable to copolymerize adipic acid in an amount of 5 to 40 mol% with respect to the acid component from the viewpoint of impact resistance.

The copolymerization component has a polymer melting point of from 170 to 223 ° C.
Preferably, it is present at a rate falling within the range of -223 ° C. If the melting point is lower than 170 ° C., the heat resistance will be poor.
The melting point of the polybutylene terephthalate homopolymer is 223 ° C.

The copolymerized polyester (II) preferably has an intrinsic viscosity of 0.70 to 2.00, more preferably 0.80 to 1.70, and particularly preferably 0.85 to 1.70.
１．５1.50.

The measuring method of the melting point and the intrinsic viscosity of the copolyester (II) is the same as that of the copolyester constituting the layer (A).

In the present invention, the polyester composition layer (B) comprises 10 to 70% by weight of a copolymerized polyester (I) having a melting point of 210 to 245 ° C. and having ethylene terephthalate as a main repeating unit, and preferably 5% of adipic acid.
It is necessary to use a polyester composition obtained by melt-mixing 30 to 90% by weight of a polyester (II) whose main repeating unit is butylene terephthalate copolymerized at a melting point of 170 to 223 ° C. When the polyester (II) is less than 30% by weight, the copolymerized polyester (I)
If it exceeds 70% by weight, the impact resistance at low temperatures cannot be improved. If the content of the polyester (II) exceeds 90% by weight and the content of the copolymerized polyester (I) is less than 10% by weight, the heat resistance of the film is undesirably reduced. A more preferable range of the polyester (II) is 50 to 90% by weight.
It is.

In the conventional two-layer film (A / B), it was necessary to set film-forming conditions corresponding to the physical properties of the layer (B) having a relatively low melting point. For example, measures such as lowering the heat treatment temperature were required to prevent fusion to the film gripper of the transverse stretching machine. Alternatively, in order to suppress a decrease in the melting point of the layer (B), the proportion of the polyester (II) containing butylene terephthalate as a main repeating unit had to be kept low.

By forming a laminated film having a three-layer structure (A / B / C) as in the present invention, the above-mentioned problems and restrictions on composition are solved, that is, polyester (II) containing butylene terephthalate as a main repeating unit. ) Can be increased, and the effect of improving the low-temperature impact resistance becomes more remarkable.

The layers (A) and (C) constituting the surface layer of the laminated film of the present invention are preferably substantially the same copolymer from the viewpoint of preventing curling and simplifying the film forming apparatus. .

However, even if a small amount of a substance is added to any of the layers as long as the effect of the present invention is not impaired, it does not depart from the scope of the present invention.

In the present invention, the copolymerized polyester used for the copolymerized polyester layers (A) and (C) having ethylene terephthalate as a main repeating unit,
Further, the copolymerized polyester (I) containing ethylene terephthalate as a main repeating unit and the polyester (II) containing butylene terephthalate as a main repeating unit in the polyester layer composition layer (B) are not limited by the production method. For example, a copolymerized polyester having ethylene terephthalate as a main repeating unit is obtained by subjecting terephthalic acid, ethylene glycol and a copolymer component to an esterification reaction, and then subjecting the resulting reaction product to a polycondensation reaction to obtain a copolymerized polyester, or A method is preferably used in which dimethyl terephthalate, ethylene glycol and a copolymer component are subjected to a transesterification reaction, and then the obtained reaction product is subjected to a polycondensation reaction to obtain a copolymerized polyester. In the production of each copolymerized polyester and polyester polymer, if necessary, other additives such as an optical brightener, an antioxidant,
A heat stabilizer, an antistatic agent and the like can also be added.

In the laminated polyester film of the present invention, fine particles having an average particle size of 2.5 μm or less, preferably 0.01 to 1.8 μm, are used in order to improve the handleability (winding property) in the film production process. 0.005 to 1% by weight, preferably 0.01% to 100% by weight of the copolymer or homopolyester of at least one of the layers.
It is particularly recommended to contain 〜0.5% by weight.

The fine particles may be inorganic or organic.
Inorganic systems are preferred. Examples of the inorganic fine particles include silica, alumina, titanium dioxide, calcium carbonate, and barium sulfate. Examples of the organic fine particles include cross-linked polystyrene particles and cross-linked silicone resin particles. In any case, the average particle diameter is desirably 2.5 μm or less. When the average particle diameter of the fine particles exceeds 2.5 μm, coarse particles (for example, particles of 10 μm or more) of the portion deformed by the molding process serve as a starting point. In some cases, a pinhole may be formed, or in some cases, the pinhole may be broken.

In particular, fine particles which are preferable in terms of pinhole resistance are monodisperse fine particles having an average particle diameter of 2.5 μm or less and a particle diameter ratio (major axis / minor axis) of 1.0 to 1.2. It is. Examples of such fine particles include spherical silica, spherical titanium dioxide, spherical zirconium, and spherical crosslinked silicone resin particles.

In the present invention, the transesterification rate of the polyester composition constituting the polyester composition layer (B) is preferably at least 3.0%, and is preferably 3.0 to 9.0.
% Is more preferable. The transesterification rate is 3.0
% Or more, the crystallization of the polyester composition (B) is suppressed, and the moldability and impact resistance are significantly improved.
If it exceeds 9%, the film-forming property of the film tends to decrease due to the deterioration of the polymer. Conversely, the transesterification rate is 3.
If it is less than 0%, the crystallinity is increased, so that moldability and impact resistance are insufficient, which is not preferable.

It is preferable that the copolymerized polyester (I) and the polyester (II) constituting the polyester composition layer (B) are melt-kneaded before film formation.

The transesterification rate can be set according to the conditions for melt-mixing the copolymerized polyester (I) and the polyester (II), for example, the extrusion temperature and the residence time. It can also be adjusted by the amount of the polymerization catalyst of the polyester (II).

The transesterification rate of the polyester composition constituting the polyester composition layer (B) is measured as follows. About 10 mg of the corresponding polyester composition is scraped from the film, dissolved in a mixed solvent of CDCl ₃ : CF ₃ COOD, and measured by 600 MHz ¹ H-NMR (see FIG. 1). The detected peak A, peak B, and peak C waveforms (see FIG. 2) resulting from the transesterification of the ethylene terephthalate unit / butylene terephthalate unit are separated, the respective integral values are obtained, and the transesterification rate is calculated by the following equation. Ask.

[0035]

## EQU1 ## Ester exchange rate = SB / (SA + SB + SC) × 100

Here, SA is the integrated value of peak A, SB is the integrated value of peak B, and SC is the integrated value of peak C.

The polyester film of the present invention has a structure in which a copolymerized polyester layer (A), a polyester composition layer (B) and a copolymerized polyester layer (C) are laminated, and a conventionally known method is used. Can be manufactured. For example, the copolymerized polyester or polyester composition constituting each layer is separately melted, co-extruded, laminated and fused before solidification, then biaxially stretched, and heat-fixed, copolymerization constituting each layer. A method of separately melting and extruding polyester or a polyester composition to form a film, and laminating both in an unstretched state or after stretching. The polyester film of the present invention may be an unstretched film, but is preferably a biaxially oriented film. In this case, the refractive index in the thickness direction of the copolymerized polyester layer (A) is 1.490 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.

[0038] The polyester film of the present invention preferably has a thickness of 6 to 75 µm. More preferably, 10
It is preferably 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 molding, while if it exceeds 75 μm, the quality is excessive and uneconomical.

The thickness T of the copolymerized polyester layer (A)
_A and the ratio of the thickness T _B of the polyester composition layer (B) (T
_A / T _B ) is preferably about 0.02 to 0.6, more preferably 0.04 to 0.4, and particularly preferably 0.04 to 0.4.
0.2.

Specifically, for example, in the case of a polyester film having a thickness of 25 μm, the thickness of the isophthalic acid copolymerized or 2,6-naphthalenedigaric acid copolymerized polyester layer (A) is 0.5 to 15 μm, preferably 1 to 15 μm. -10
μm, and more preferably 1 to 5 μm. Further, with respect to the thickness T _C is T _A copolyester layer on the side is laminated with the can material metal (C), it is preferable to maintain the following relationship.

[0041]

## EQU2 ## 10 ≧ T _A / T _C ≧ 0.5

When T _A / T _C exceeds 10, the effect of improving curl property is lost, which is not preferable. On the other hand, if it is less than 0.5, the C layer is unnecessarily thick, and the thicknesses of the A layer and the B layer are relatively insufficient, and the fragrance retention, taste retention and impact resistance are impaired.

When the laminated film of the present invention is bonded to a metal plate, it is bonded so that the layer (C) serves as an adhesive surface. There is no reduction in the adhesive strength of the metal plate.

The metal plate to which the polyester film of the present invention is bonded, particularly the metal plate for can making, is a tin plate,
Plates of tin-free steel, aluminum, etc. are suitable. For bonding a polyester film to a metal plate,
For example, it can be carried out 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 the adhesive, a known resin adhesive, for example, an epoxy-based adhesive, an epoxy-ester-based adhesive, an alkyd-based adhesive, or the like can be used.

[0045]

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

(1) Melting point and glass transition temperature Du Pont Instruments 910 D
The method uses SC to determine the melting peak and the glass transition temperature at a heating rate of 20 ° C./min. The sample amount is about 20 mg.

(2) Intrinsic Viscosity After the film was dissolved in o-chlorophenol, the filler such as titanium oxide was removed by a centrifugal separator, and the film was measured at a temperature of 35 ° C. The intrinsic viscosity of each layer is a value of an unstretched film obtained by extruding the copolymerized polyester of each layer independently.

(3) Ester exchange rate About 10 mg of the corresponding polyester composition from the film
After shaving and dissolving in a mixed solvent of CDCl ₃ : CF ₃ COOD,
It was measured by 600 MHz ¹ H-NMR (see FIG. 1).
The detected peak A, peak B, and peak C waveforms (see FIG. 2) resulting from the transesterification of the ethylene terephthalate unit / butylene terephthalate unit are separated, the respective integral values are obtained, and the transesterification rate is calculated by the following equation. I asked.

[0049]

## EQU00003 ## Ester exchange rate = SB / (SA + SB + SC) .times.100 (wherein SA represents the integrated value of peak A, SB represents the integrated value of peak B, and SC represents the integrated value of peak C.)

The sample film was bonded to both sides of a tin-free steel sheet having a thickness of 0.25 mm heated to 230 ° C., cooled with water, and cut into a disk having a diameter of 150 mm.
Deep drawing in 4 stages using a drawing die and punch
A 5 mm-diameter side-seamless container (hereinafter abbreviated as can) was prepared. The following observations and tests were performed on these cans, and evaluated according to the following criteria.

(4) Deep drawing workability As a result of observing the working condition of the can, ○: 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.

(5) Impact resistance For cans that had 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) The values were measured, and the results were abbreviated as ERV test below. Δ: More than 0.1 mA for 1 to 5 pieces. X: More than 6 pieces exceeded 0.1 mA, or cracking of the film was already observed after dropping.

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

(7) Retort resistance For cans with good deep drawing, pour water fully and use a steam sterilizer.
Perform a retort treatment at 120 ° C for 1 hour, and then
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: More than 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.

(8) Flavor 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. ；: There was no change in fragrance. Δ: Slight change in fragrance was observed. ×: Change in scent was observed.

(9) Taste preservation In the same manner as in (8), taste change was examined by a sensory test. ；: There was no change in taste. Δ: Slight change in taste was observed. X: Change in taste was observed.

(10) Curling properties A 300 × 300 mm test piece was cut out from the film.
Place in a constant temperature room maintained at 20 ± 3 ° C. and hold for 10 minutes.
Thereafter, when the film test piece is curled and has a cylindrical shape, its diameter is measured with a scale. ○: The film test piece does not exhibit a cylindrical shape △: The diameter of the film test piece cylinder is 50 mm or more ×: The diameter of the film test piece cylinder is less than 50 mm

Examples 1-4 and Comparative Examples 3-6 Copolymerized polyethylene terephthalate (intrinsic viscosity 0.73) obtained by copolymerizing the components shown in Table 1 was used in the copolymerized polyester layers (A) and (C). Each of the polyester compositions shown in Table 1 was separately dried by a conventional method and melted at 280 ° C. so as to become the polyester layer (B), and then melted at 280 ° C. from the three-layer die adjacent to each other to form (A) (B) (C) ( However, they were co-extruded so as to overlap in the order of C = A), laminated, fused and quenched and solidified to prepare an unstretched laminated film. The transesterification rate of the polyester composition in the layer (B) was set by changing the above-mentioned melting temperature.

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 190 ° C. to obtain a biaxially oriented laminated film. . The thickness of the obtained film was 25 μm, and the thickness of the copolymerized polyester layer (A), the polyester composition layer (B) and the copolymerized polyester layer (C) were each 3.
They were 5 μm, 18 μm and 3.5 μm.

Comparative Example 1 A two-layer film was prepared in the same manner as in Example 1 except that the copolymerized polyester layer (A) was 5.0 μm and the polyester composition layer (B) was 20 μm.

[Comparative Example 2] In Example 2, a two-layer film having a copolymerized polyester layer (A) of 5.0 µm and a polyester composition layer (B) of 20 µm was prepared. However, the film was fused to the gripper of the horizontal stretching machine, and the film was frequently cut, and a sample could not be obtained. Therefore, a film was obtained at a heat treatment temperature of 175 ° C.

In Comparative Examples 1 and 2, when laminating to the metal plate, the layer (B) was laminated so as to adhere to the metal plate. The evaluation results were as shown in Table 2.

[0063]

[Table 1]

[0064]

[Table 2]

As is clear from the results in Table 2, 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. In particular, it has excellent impact resistance at low temperatures, and is good without deteriorating the taste of soft drinks and the like. Further, since the polyester film of the present invention does not curl, it is excellent in workability in bonding to a metal plate.

[0066]

The laminated polyester film of the present invention for metal plate lamination has excellent moldability, heat resistance, retort resistance, and fragrance retention, as well as impact resistance, especially at low temperatures. It has excellent impact resistance and is good without deteriorating the taste of soft drinks and the like. Therefore, it is particularly suitable for being used after being cooled and bonded to a metal can for soft drinks and the like which is often handled at a low temperature.

[Brief description of the drawings]

FIG. 1 is an NMR chart of a polyester composition obtained by melt-mixing copolymerized polyesters (I) and (II).

FIG. 2 is an NMR chart in which a portion of a peak A, a peak B, and a peak C resulting from PET / PBT blend-based transesterification in FIG. 1 are enlarged.

Claims (8)

[Claims] 1. A copolymer polyester (I) containing ethylene terephthalate having a melting point of 210 to 245 ° C. as a main repeating unit in an amount of 10 to 70% by weight, and a melting point of 170 to 223.
The melting point of each polyester composition layer (B) comprising 30 to 90% by weight of polyester (II) containing butylene terephthalate as a main repeating unit at a temperature of 2 ° C.
Metals formed by laminating a copolymerized polyester layer (A) having a main repeating unit of ethylene terephthalate at 10 to 245 ° C and a copolymerized polyester layer (C) having a main repeating unit of ethylene terephthalate having a melting point of 210 to 245 ° C. Laminated polyester film for board lamination processing. 2. The laminated polyester film according to claim 1, wherein the copolymerized polyester layer (A) containing ethylene terephthalate as a main repeating unit is a layer composed of an isophthalic acid copolymerized polyester. 3. The lamination for metal plate lamination according to claim 1, wherein the copolymerized polyester layer (A) containing ethylene terephthalate as a main repeating unit is a layer composed of 2,6-naphthalenedicarboxylic acid copolymerized polyester. Polyester film. 4. The laminated polyester film according to claim 1, wherein the copolymerized polyester (I) is an isophthalic acid copolymerized polyester. 5. The laminated polyester film according to claim 1, wherein the copolymerized polyester (I) is a 2,6-naphthalenedicarboxylic acid copolymerized polyester. 6. The polyester (II) is adipic acid.
The laminated polyester film for laminating and processing a metal plate according to any one of claims 1 to 5, which is a copolymerized butylene terephthalate obtained by copolymerization of from 40 to 40 mol%. 7. The metal plate lamination molding according to claim 1, wherein the copolymerized polyester layers (A) and (C) having ethylene terephthalate as a main repeating unit have the same composition. Laminated polyester film for processing. 8. The metal plate bonding according to claim 1, wherein a transesterification ratio of the polyester composition constituting the polyester composition layer (B) is 3.0% or more. Laminated polyester film for forming.