JPH09194604A - Film for metal laminate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prepare a film for metal laminate having low heat shrinkage, and excellent mechanical strengths, impact resistance, adhesion, and molding properties, moreover, never damaging the taste of the contents, when used for a metal can, e.g. a metal can for food and drink, and having a good retorting resistant property and a flavor characteristic. SOLUTION: This film comprises a composition of a polyester resin, which is composed of 10-55wt.% polyethylene terephthalate or a polyester mainly composed of it and having an intrinsic viscosity of not less than 0.50, and 90-45wt.% polybutylene terephthalate or a polyester mainly composed of it and having an intrinsic viscosity of not less than 0.60, and the heat shrinkage of the film at 160 deg.C is 0.5-3.5%.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention has a small heat shrinkage and is excellent in mechanical strength, impact resistance, adhesiveness, moldability and the like, and is used for a metal can, for example, a metal can for food and drink. The present invention relates to a metal laminating film having good retort resistance and flavor characteristics, which sometimes does not impair the flavor of the filler.

[0002]

2. Description of the Related Art With the spread of convenience stores and vending machines, retort processed food and drink products such as carbonated drinks, carbonated drinks containing fruit juice, coffee drinks and instant foods have been remarkably growing. From the viewpoint of hygiene, these are filled with food and drink in containers and sterilized by retort (steam treatment at 120 to 130 ° C).
In many cases, they are heat-treated while still in the container for eating in a warm state.

[0003] Conventionally, a thermosetting resin is mainly used on the inner and outer surfaces of a can body and a can lid of a metal can container for food and drink to keep the flavor and flavor of the filling material and at the same time prevent corrosion of the metal can material. Although the solvent-based paint as a component was applied, there was a problem that when the food and drink were filled, a trace amount of volatile components remaining in the coating film migrated to the food and drink and the flavor was impaired.

In place of such a coating method, a metal can for food and drink has been proposed in which a single-layer or multi-layer plastic film is laminated on a metal plate, and the laminating metal plate is formed. This is because it has excellent retort resistance and flavor characteristics, and there is no internal coating process or water washing process,
It is attracting attention because it reduces the amount of industrial waste and is not only favorable in terms of environmental protection, but it also greatly improves productivity.

On the other hand, a plastic film for attaching to a metal can (metal laminate) has good adhesiveness to a metal plate, excellent moldability, peeling, cracks, cracks, pinholes, etc. of the film during molding. That the filling does not deteriorate the flavor of the filling (flavor characteristics), the ink adheres well to the outer surface of the can body and has excellent dimensional stability, and water spots and white powder when retort-treated. It is required to simultaneously satisfy the characteristics such as the occurrence of no (retort resistance).

Among the plastic films, polyethylene terephthalate (PET) film is widely used as a material excellent in cost performance, but to be applied as a metal laminating film, it is adhered to a metal plate. There was a problem with the properties, impact resistance, flavor characteristics, printing characteristics, retort resistance, etc.

As a means for improving the above-mentioned problems, for example, a polyester film containing a specific amount of diethylene glycol component and acetaldehyde (Japanese Patent Publication No. 7-845).
33), a polyester film having an intrinsic viscosity of 0.75 or more (Japanese Patent Publication No. 7-84532), a PET-based copolyester film obtained by copolymerizing an isophthalic acid component or a phthalic acid component (JP-A-2-57339), PET. 99-60% by weight of polyester and polybutylene terephthalate (P
A polyester film (JP-A-5-156040) having a composition of 1 to 40% by weight of BT) -based polyester and having specified plane orientation coefficient, thermal shrinkage and density of the film, PET-based polyester and PBT-based polyester A polyester film for a metal can lid in which a crystallization temperature, a second-order transition point and a melting point are specified by a composition (Japanese Patent Laid-Open No. 5-331302) and the like have been proposed.

However, the metal cans for food and drink laminated with these polyester films cannot satisfy all of the above-mentioned required characteristics at the same time, and in particular, impact resistance, flavor characteristics and retort resistance are required. Was not enough.

[0009]

DISCLOSURE OF THE INVENTION The present invention provides a metal can, for example, a metal can for food and drink, which has a small heat shrinkage rate and is excellent in mechanical strength, impact resistance, adhesiveness, moldability and the like. An object of the present invention is to provide a metal laminating film having good retort resistance and flavor characteristics, which does not impair the flavor of the filling when used.

[0010]

Means for Solving the Problems As a result of intensive studies to solve the above-mentioned problems, the inventors have identified a PET-based polyester having a specific intrinsic viscosity and a PBT-based polyester having a specific intrinsic viscosity. It was found that this object can be achieved by forming a film from the polyester resin composition blended in the proportion of, and reached the present invention.

That is, the gist of the present invention is as follows. ■ 10 to 55% by weight of PET or a polyester (A) composed mainly of PET and having an intrinsic viscosity of 0.50 or more, and 90 to 90% polyester (B) mainly composed of PBT or having an intrinsic viscosity of 0.60 or more
A film for metal laminating, comprising a polyester resin composition blended with 45% by weight, and having a heat shrinkage rate at 160 ° C. of 0.5 to 3.5%. (3) The above metal laminating film, wherein the polyester (A) has an intrinsic viscosity of 0.65 or more and the polyester (B) has an intrinsic viscosity of 0.80 or more.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below.

The PET or the polyester (A) containing the PET as a main component in the present invention is one obtained by melt-polycondensation reaction of a terephthalic acid component and an ethylene glycol component as main components, or subsequent solid-phase polymerization, and has an intrinsic viscosity. Is
It is necessary to be 0.50 or more, preferably 0.65 to 1.2. If the intrinsic viscosity is less than 0.50, the film cannot have a mechanical strength that can be put to practical use.

As the above polyester (A), aromatic dicarboxylic acids such as isophthalic acid, phthalic acid, 2,6-naphthalenedicarboxylic acid and 5-sodium sulfoisophthalic acid, oxalic acid, succinic acid and adipic acid are used. , Sebacic acid, dodecanedicarboxylic acid, maleic anhydride, fumaric acid, itaconic acid, citraconic acid, mesaconic acid and other aliphatic dicarboxylic acids, hexahydrophthalic acid, hexahydroterephthalic acid and other alicyclic dicarboxylic acids, carbon number 20 ~
60 dimer acids, p-hydroxybenzoic acid, lactic acid, β-
Hydroxybutyric acid, hydroxycarboxylic acids such as ε-caprolactone, triethylene glycol, propylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol,
1,6-hexanediol, aliphatic diol such as neopentyl glycol, 1,4-cyclohexanedimethanol,
Aliphatic diols such as 1,4-cyclohexanediethanol, aromatic diols such as ethylene oxide adducts of bisphenol A and bisphenol S, trimellitic acid, trimesic acid, pyromellitic acid, trimethylolpropane, glycerin, pentaerythritol, and many other compounds. A functional compound or the like may be appropriately copolymerized within a range that does not impair the characteristics of PET.

This polyester (A) usually has a melting point of
It is in the range of 200 to 255 ° C, the content of acetaldehyde is in the range of 5 to 50 ppm, and the content of oligomer (consisting of linear and cyclic 1 to 9 mer, mainly composed of cyclic trimer) is It is in the range of 0.1 to 2.0% by weight, and the content of diethylene glycol component (which is inevitably a by-product in the polycondensation reaction) is 1.0 to 1 mol of ethylene glycol component.
It is preferably in the range of 3.5 mol% and the concentration of the carboxyl end group is in the range of 5 to 50 equivalents / ton.

The PBT or the polyester (B) containing the PBT as a main component in the present invention is a product obtained by melt polycondensation reaction containing a terephthalic acid component and a 1,4-butanediol component as main components, or by subsequent solid phase polymerization. The intrinsic viscosity needs to be 0.60 or more, and is preferably 0.80 to 2.0. If the intrinsic viscosity is less than 0.60, the film cannot have a mechanical strength that can be put to practical use.

Examples of the polyester (B) include aromatic dicarboxylic acids such as isophthalic acid, phthalic acid, 2,6-naphthalenedicarboxylic acid and 5-sodium sulfoisophthalic acid, oxalic acid, succinic acid and adipic acid. , Sebacic acid, dodecanedicarboxylic acid, maleic anhydride, fumaric acid, itaconic acid, citraconic acid, mesaconic acid and other aliphatic dicarboxylic acids, hexahydrophthalic acid, hexahydroterephthalic acid and other alicyclic dicarboxylic acids, carbon number 20 ~
60 dimer acids, p-hydroxybenzoic acid, lactic acid, β-
Hydroxybutyric acid, hydroxycarboxylic acids such as ε-caprolactone, ethylene glycol, triethylene glycol, propylene glycol, 1,2-propanediol,
1,3-propanediol, 1,5-pentanediol,
1,6-hexanediol, aliphatic diol such as neopentyl glycol, 1,4-cyclohexanedimethanol,
Aliphatic diols such as 1,4-cyclohexanediethanol, aromatic diols such as ethylene oxide adducts of bisphenol A and bisphenol S, trimellitic acid, trimesic acid, pyromellitic acid, trimethylolpropane, glycerin, pentaerythritol, and many other compounds. A functional compound or the like may be appropriately copolymerized within a range that does not impair the characteristics of PBT.

This polyester (B) usually has a melting point of
The temperature is in the range of 160 to 225 ° C, the tetrahydrofuran content is in the range of 5 to 50 ppm, the linear and cyclic oligomer content is in the range of 0.1 to 2.0% by weight, and the carboxyl end group concentration is 5 to 50%. Those in the range of equivalent weight / ton are preferable.

The blending ratio of the polyester resin composition in the present invention must be 10 to 55% by weight of polyester (A) and 90 to 45% by weight of polyester (B). If the blending ratio is out of this range, it is impossible to satisfy all of the above-mentioned required properties 1 to 5 at the same time, and it is not possible to obtain a film that can be put to practical use.

The metal laminating film of the present invention must have a heat shrinkage ratio at 160 ° C. of 0.5 to 3.5%. If the heat shrinkage is less than 0.5%, not only the operability at the time of film production is deteriorated, but also it is uneconomical because of excessive quality, and if the heat shrinkage exceeds 3.5%, the impact resistance of the film is deteriorated, which is not preferable.

For producing the polyester (A), a conventionally known method can be applied. For example, a slurry of terephthalic acid and ethylene glycol is continuously supplied to an esterification reaction tank in which bis (β-hydroxyethyl) terephthalate and its low polymer are present, and the temperature of 250 ° C.
The reaction is carried out for about 8 hours to continuously obtain an esterified product having an esterification reaction rate of about 95%. Then, this was transferred to a polymerization vessel and subjected to a melt polycondensation reaction in the presence of a catalyst such as germanium dioxide or antimony trioxide under a reduced pressure of 1.3 hPa or less at a temperature of 280 ° C until a polyester having a desired intrinsic viscosity was obtained. To do.

In order to use it as a film for metal laminating, it is necessary to reduce the content of the oligomer or acetaldehyde in the polyester (A) as described above. Examples of the method include, for example, a method in which a polyester obtained by a melt polycondensation reaction is subjected to hot water treatment with steam and then heat-treated at a temperature of 180 ° C. or lower under reduced pressure or an inert atmosphere, or under reduced pressure or an inert atmosphere. Then, there is a method such as solid phase polymerization at a temperature not higher than the melting point of the polyester (A), usually at a temperature of 200 to 240 ° C. In particular, the latter method is more preferable because the intrinsic viscosity of the polyester (A) can be increased.

Also, a conventionally known method can be applied to the production of the polyester (B). For example, dimethyl terephthalate and 1,4-butanediol are charged into a transesterification reaction tank and reacted at a temperature of 230 ° C. for about 5 hours to obtain an esterified product having a transesterification reaction rate of about 95%. Then, this was transferred to a polymerization vessel, and in the presence of a catalyst such as tetra-n-butyl titanate or triisopropyl titanate, under a reduced pressure of 1.3 hPa or less and at a temperature of 250 ° C. until a polyester having a desired intrinsic viscosity was obtained. Melt polycondensation reaction.

In order to use it as a film for metal laminating, it is necessary to reduce the contents of oligomers and tetrahydrofuran in the polyester (B). The method includes, for example, a method in which the polyester obtained by the melt polycondensation reaction is subjected to hot water treatment with steam, and then heat-treated at a temperature of 140 ° C. or lower under reduced pressure or an inert atmosphere, or under reduced pressure or an inert atmosphere. Then, there is a method such as solid-phase polymerization at a temperature not higher than the melting point of the polyester (B), usually 160 to 200 ° C. In particular, the latter method is more preferable because the intrinsic viscosity of the polyester (B) can be increased.

The metal laminating film of the present invention is produced by a method of forming the above polyester resin composition into a film by a conventionally known method such as a flat type or tubular type film forming method. The film may be a monolayer film or a multilayer film.

When a multilayer film is obtained, (i)
Several polyester resin compositions constituting each layer are melted using separate extruders, after superposition by a feed block method, a method of extruding from a die, (ii) several molten polyester resin composition A method of extruding after superposing them in a multi-manifold die, (iii) a method of laminating several polyester resin composition layers by laminating and the like can be adopted.

Next, the method for producing the film of the present invention will be described by taking a monolayer biaxially stretched film as an example.
It is not limited to this.

That is, first, a polyester resin composition comprising the polyester (A) and the polyester (B) in the above-mentioned blending ratio is melted at 220 to 280 ° C. and extruded from an extruder equipped with a T die to form a sheet. It is shaped into a shape, and then it is brought into close contact with a cooling drum whose temperature is adjusted to room temperature or lower and rapidly cooled to obtain an unstretched sheet having a desired thickness. Then, the unstretched sheet is stretched in the longitudinal direction by 1 to 1, if necessary.
After pre-drawing to about 1.2 times, the edge of this sheet is gripped by a clip of a tenter simultaneous biaxial stretching machine, and 50 to 150
Simultaneously biaxially stretch in the longitudinal direction and the transverse direction by 2 to 4 times each by heating to ℃. Then, the relaxation rate in the transverse direction is set to several%, and the film is heat treated at 80 to 200 ° C for several seconds, cooled to room temperature, and wound at a speed of 20 to 200 m / min to obtain a film having a desired thickness.

At this time, if a twin-screw extruder with a vent is used as the extruder, heat generation during extrusion can be suppressed and the decrease in viscosity of the polyester resin composition due to moisture can be reduced.

As the heat treatment method after stretching, a conventionally known method can be adopted, for example, a method of blowing hot air to the stretched film, a method of irradiating the stretched film with infrared rays, or a method of irradiating the stretched film with microwaves. A method of blowing hot air to the stretched film is the most suitable in that uniform and accurate heating is possible.

Further, in order to further improve the adhesiveness to a metal can and the mechanical strength of the film, a polyolefin film, a copolyester film other than the polyester resin composition of the present invention, etc. may be laminated and used.

Further, by applying an adhesive by in-line coating during film production or post-coating after film production, a laminated film having an adhesive layer can be formed.

In addition, in the present invention, a master chip containing an inorganic lubricant such as silica, alumina, kaolin, calcium carbonate or the like, or an organic lubricant such as silicone particles is manufactured in advance, and the master chip is added in a required amount to form a film. By imparting slipperiness to the surface, it is possible to improve the process passability during film production or laminating with a metal plate. Further, titanium dioxide, barium sulfate, a silicone compound or the like may be added to impart a hiding property to improve the appearance of the metal can or the printability on the metal can. Further, a colorant, an antioxidant, an antistatic agent, an antifoaming agent, a flame retardant, etc. may be contained.

The metal laminating film of the present invention preferably has a thickness of 5 to 100 μm, more preferably 10 to 75 μm, and particularly preferably 15 to 50 μm. If the thickness is less than 5 μm, breakage or the like is likely to occur during processing, while if it exceeds 100 μm, it is uneconomical because of excessive quality.

The film for metal laminate of the present invention has a tensile strength of 18 to 35 kgf / mm ² and a tensile elongation of 80 to 160% in addition to the above-described heat shrinkage and thickness at 160 ° C. Is desirable.

A steel plate, an aluminum plate or the like is preferably used as the metal plate for can making on which the film of the present invention is laminated. In the case of a steel plate, chromic acid treatment, phosphoric acid treatment, electrolytic chromic acid treatment, It may be treated with a chemical agent such as chromate treatment, or may be treated with a metal plating such as nickel, tin, zinc, aluminum, gun metal or brass.

[0037]

EXAMPLES Next, the present invention will be described in detail with reference to examples. In the examples, the characteristic evaluation was performed as follows. (a) Intrinsic viscosity [η] It was measured at a temperature of 20 ° C using a weight mixture of phenol and ethane tetrachloride as a solvent, and expressed in dl / g. (b) Melting point Using a differential calorimeter DSC-7 type manufactured by Perkin Elmer,
The measurement was performed at a heating rate of 20 ° C./min. (c) Oligomer content Polyester was dissolved in hexafluoroisopropanol / chloroform (1/1, volume ratio), poured into acetonitrile to precipitate the polymer, and the oligomer in the filtrate filtered through a membrane filter was subjected to high performance liquid chromatography. It was determined by analysis with a graph (600E manufactured by Waters). (d) Tensile strength and tensile elongation Measured according to ASTM-D882 using a test piece having a sample width of 10 mm and a sample length of 10 cm. The tensile strength and tensile elongation are MD
It is expressed by the average value of (machine direction) and TD (right angle direction). (e) Heat shrinkage was measured by leaving a film with a sample width of 10 mm, a sample length of 10 cm, and a thickness of 12 μm for 15 minutes in a nitrogen atmosphere at 160 ° C., and measuring the dimensional change before and after standing. The heat shrinkage (%)
Is the rate of change with respect to the original length of the test piece and is represented by the average value of MD and TD. (f) Adhesiveness A 12 μm thick film and a 0.25 mm thick tin-free steel plate were superposed between a metal roll heated to 240 ° C. and a silicone rubber roll, and pressure-bonded at a linear pressure of 10 kgf / cm, followed by water cooling. did. Then, using a test piece cut into a width of 25 mm, an autograph manufactured by Shimadzu Corporation, peeling speed 10 mm
The peeling test was performed at 180 ° / min, and the peeling strength was measured and used as an index of the adhesiveness. ◯: Pass with peel strength of 300gf or more ×: Fail with peel strength of less than 300gf (g) Formability A film with a thickness of 12μm and a tin-free steel plate with a thickness of 0.25mm are laminated, and the temperature is 160 ℃ and the pressure is 100kgf / cm. ²
Under the above conditions, press forming was carried out by a batch method to obtain a steel sheet laminated with a film. Next, this laminated steel plate was punched into a circle and subjected to thin-wall deep drawing to obtain a diameter of 1
A cup with a diameter of 00 mm, a depth of 130 mm, and a drawing ratio (ratio of depth to diameter) of 1.3 was produced. Subsequently, 1% by weight of saline was put into this cup, and the amount and the state of rust generated in the cup after heating at 80 ° C. for 24 hours were determined to be used as an index of formability. A and B were passed in the three-level evaluation of A to C. A: Almost no rust is seen B: Rust is seen on less than 5% of the surface area of the cup C: Rust is seen on more than 5% of the surface area of the cup (h) A cup made with impact resistance (g) Heat treatment was performed at 180 ° C. for 10 minutes, and then, impacts were applied to the seven points on the side surface and the bottom surface of the cup with a center punch. Subsequently, 1% by weight of saline was put into this cup, and the same treatment as in (g) was performed to determine the amount of rust generated in the cup and its state, thereby giving an impact resistance index. did. A three-level evaluation of A to C, A
And B were passed. A: Almost no rust is seen B: Rust is seen on less than 5% of the surface area of the cup C: Rust is seen on more than 5% of the surface area of the cup (i) Laminated steel sheet made with retort resistance (g) Was punched into a rectangle of 14 cm × 12 cm, and after steaming at 120 ° C. for 30 minutes, the appearance was judged and used as an index of retort resistance. The appearance was visually inspected for water spots (spots that seemed to float white) and white powder (mainly composed of oligomers), and passed A and B. A: Almost no change B: Water spots and white powder are found in less than 5% of the surface area of the cup C: Water spots and white powder are found in more than 5% of the surface area of the cup (j) Flavor characteristics 14 cm × Two rectangular films having a thickness of 12 cm and a thickness of 12 μm were superposed on each other, heat-sealed on three sides thereof, 50 ml of soft drink was put therein, and the other one was heat-sealed. The film bag filled with this soft drink was left at room temperature for 1 month and then opened, and the taste of the soft drink was evaluated by a panel of 5 panelists by a sensory test. Was accepted. A: No change was observed B: Almost no change was observed C: A considerable change was observed

Example 1 [η] PET of 0.66 (NEH-2030 manufactured by Unitika Ltd.),
[Η] 1.00 of PBT (NOVADUR-5009AS manufactured by Mitsubishi Engineering Plastics Co., Ltd.) and silica master chips in an amount of 0.08% by weight based on the total polyester resin composition as a lubricant were blended in the proportions shown in Table 1. Then, this polyester resin composition is melted at 280 ° C.
It was extruded from an extruder equipped with a die to be formed into a sheet, which was then brought into close contact with a cooling drum whose surface temperature was adjusted to 18 ° C. and rapidly cooled to obtain an unstretched sheet having a thickness of 120 μm.
The end of this unstretched sheet was held by a clip of a tenter type simultaneous biaxial stretching machine, heated to 80 ° C. and simultaneously biaxially stretched 3.0 times in the longitudinal direction and 3.3 times in the transverse direction. Then, the relaxation rate in the transverse direction was set to 5%, the film was heat treated at 180 ° C. for 4 seconds, cooled to room temperature, and wound at a speed of 50 m / min to obtain a film having a thickness of 12 μm. Next, various performance tests were conducted using this film. Table 1 shows the obtained results.

Examples 2 to 4 Example 1 was repeated except that the mixing ratio of PET and PBT was changed.
A film was prepared in the same manner as above, and various performance tests were conducted using this film. Table 1 shows the obtained results.

Examples 5 to 6 Films were prepared in the same manner as in Example 1 except that PET having a different [η] was used, and various performance tests were conducted using this film. Table 1 shows the obtained results.

Examples 7 to 8 Films were prepared in the same manner as in Example 1 except that PBTs having different [η] were used, and various performance tests were conducted using the films. Table 1 shows the obtained results.

Example 9 A film was prepared in the same manner as in Example 1 except that 8 mol% of isophthalic acid-copolymerized [η] 0.72 PET polyester was used instead of [η] 0.66 PET. Various performance tests were conducted using this film. Table 1 shows the obtained results.

Example 10 A film was prepared in the same manner as in Example 1 except that 5 mol% of isophthalic acid-copolymerized [η] 1.15 PBT polyester was used instead of [η] 1.00 PBT. Various performance tests were conducted using this film. Table 1 shows the obtained results.

[0044]

[Table 1]

Comparative Examples 1 to 2 Example 1 except that the mixing ratio of PET and PBT was changed.
A film was prepared in the same manner as above, and various performance tests were conducted using this film. Table 2 shows the obtained results.

Comparative Example 3 A film was prepared in the same manner as in Example 1 except that [η] 0.45 PET was used, and various performance tests were conducted using this film. Table 2 shows the obtained results.

Comparative Example 4 A film was produced in the same manner as in Example 1 except that [η] 0.55 PBT was used, and various performance tests were conducted using this film. Table 2 shows the obtained results.

[0048]

[Table 2]

[0049]

According to the present invention, the heat shrinkage is small,
In addition, it has excellent mechanical strength, impact resistance, adhesiveness, moldability, etc.,
Further, a metal laminating film having good retort resistance and flavor characteristics, which does not impair the flavor of the filler when used in a metal can, for example, a metal can for food and drink, can be obtained.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical indication location B29L 7:00 (72) Inventor Eiji Fujita 23 Uji Kozakura, Uji-shi, Kyoto Unitika Researcher Central Research Institute In-house (72) Inventor Norikazu Matsui 31-3 Uji Hishinojiri, Uji City, Kyoto Prefecture Unitika Corporation Uji Plastic Factory

Claims (2)

[Claims] 1. Polyethylene terephthalate or a polyester (A) 10 composed mainly of polyethylene terephthalate having an intrinsic viscosity of 0.50 or more.
~ 55% by weight and polybutylene terephthalate or polyester (B) 90 mainly composed of this and having an intrinsic viscosity of 0.60 or more
A film for metal laminating, which comprises a polyester resin composition blended with ˜45% by weight, and has a heat shrinkage ratio of the film at 160 ° C. of 0.5 to 3.5%. 2. The film for metal laminating according to claim 1, wherein the polyester (A) has an intrinsic viscosity of 0.65 or more and the polyester (B) has an intrinsic viscosity of 0.80 or more.