JP2908196B2 - 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 to a polyester film for laminating a metal plate and performing excellent canning processing such as drawing when forming a can. The present invention relates to a polyester film for metal plate laminating and forming capable of producing metal cans having excellent properties and taste retention, such as beverage cans and food cans.

[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, taste 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), the biaxially oriented polyethylene terephthalate film is excellent in heat resistance and fragrance retention, but the molding processability is insufficient, and whitening of the film (generation of minute cracks) occurs in canning with large deformation. Breakage occurs. Regarding (B), since it is an amorphous or extremely low-crystalline aromatic polyester film, the moldability is good, but the taste retention is inferior, and after printing after can-making, retort sterilization, etc. The film may be easily embrittled by the treatment and further long-term storage, and may be changed to a film which is easily broken by an impact from the outside of the can. Further, in the case of a polyester film, its slipperiness and abrasion resistance are major factors that affect the workability of the film production process and the working process in each application, and the quality of the product.

That is, for example, if the lubricity is insufficient, wrinkles are generated in a film winding process or the like. In the case of a metal can, for example, wrinkles are generated when laminating to a metal plate due to the insufficient lubricity. Further, lack of abrasion resistance in drawing at the time of can-making causes pinholes, and in extreme cases, breaks of the film, and the inner and outer surfaces of the metal can are not covered.

In general, the slipperiness of a magnetic recording film or the like,
In order to improve the abrasion resistance, a method of reducing the contact area between a roll, a working tool, and the like by adding inert fine particles to impart unevenness to the film surface has been adopted.
Generally, the larger the size of the fine particles in the raw material polymer, the greater the effect of improving the slipperiness.

For example, one or more of calcium carbonate, titanium oxide, kaolin, and the like (combination of large particles and small particles) has been conventionally added as inert fine particles (Japanese Patent Application Laid-Open No. H10-28139). 51-34272, JP-A-52-78953, JP-A-52-78954, JP-A-53-41355, JP-A-53-71154, and the like.

However, in a process involving a large deformation such as drawing in metal can molding, as the size of the fine particles increases, voids formed at the boundary between the fine particles and the polyester generated during deformation become large. The shape of the projections becomes gradual, increasing the coefficient of friction during processing and causing small particles (scratch) on the voids of the polyester film generated during processing, causing particles to fall off, causing pinholes and film breakage. Problem arises.

[0009]

SUMMARY OF THE INVENTION An object of the present invention is to improve the taste retention and impact resistance while retaining the excellent moldability, heat resistance and retort resistance of a copolymerized polyester film. In particular, it is an object of the present invention to provide a polyester film for laminating and forming a metal plate, which hardly causes cracks due to impact at a low temperature.

[0010]

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 found that a film has a copolymerized polyester containing ethylene as a main repeating unit and a butylene terephthalate as a main repeating unit. By comprising two layers including a layer of a polyester composition blended with a polyester, using a germanium catalyst as a polycondensation catalyst of the copolymerized polyester, and defining a lubricant to be added to each of the two layers, the low-temperature The inventors have found that the impact resistance is remarkably improved, and have completed the present invention.

That is, according to the present invention, the average particle size is from 0.05 to
Contains 0.6 μm lubricant and has a melting point of 210 to 245
C., made of a copolymerized polyester using a germanium compound as a polycondensation catalyst, and the concentration C of the lubricant (% by weight)
Is the average particle size d (μm) and the following formula

[0012]

## EQU2 ^## Copolymerized polyester layer (A) having a range satisfying the relationship of 0.0072d -0.65 ≤C≤0.80d ^-0.44, a germanium compound having a melting point of 210-245 ° C and a polycondensation catalyst. Polyester (I) 8 containing ethylene terephthalate as a main repeating unit
A polyester composition comprising 0 to 45% by weight and 20 to 55% by weight of a polyester (II) containing butylene terephthalate having a melting point of 180 to 223 ° C as a main repeating unit, and having an average particle size of 0.8 µm or more. A polyester film for laminating and processing a metal plate, comprising laminating a polyester layer (B) containing 0.03 to 0.5% by weight of a lubricant of less than 5 μm.

In the present invention, a typical example of the copolymerized polyester used for the copolymerized polyester (I) in the copolymerized polyester layer (A) and the polyester layer (B) is copolymerized polyethylene terephthalate. 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 components depends on the type thereof, but as a result, the melting point is from 210 to 245 ° C., preferably from 215 to 245 ° C.
It is the ratio which becomes the range of -235 ° C. If the melting point is lower than 210 ° C., the heat resistance will be poor. On the other hand, the melting point is 245 ° C
If it exceeds 300, the crystallinity of the polymer is too large and the moldability is impaired.

Here, the melting point of the copolyester was measured by Du Pont Instruments 910.
A method in which a melting peak is determined at a heating rate of 20 ° C./min using DSC. The sample amount 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.

In the present invention, the copolyester used for the copolyester (I) of the copolyester layer (A) and the polyester layer (B) can be produced by any of the direct weight method and the DMT method (transesterification method). However, in the case of the DMT method, a manganese compound (eg, manganese acetate) or a titanium compound (eg, titanium acetate, titanium tetrabutoxide, etc.) is preferable as the transesterification catalyst. In the polymerization step, a germanium compound is used as a polymerization catalyst. Examples of the germanium catalyst include (a) amorphous germanium oxide (b) fine crystalline germanium oxide (c) a solution of germanium oxide dissolved in glycol in the presence of an alkali metal or alkaline earth metal or a compound thereof. A solution in which germanium oxide is dissolved in water is used.

The amount of the germanium compound catalyst is 40 to 40 as the amount of germanium remaining in the copolymerized polyester.
200 ppm is preferable, and 60 to 150 ppm is more preferable.

The above-mentioned copolymerized polyester preferably has a methyl terminal concentration in the polyester of 15 eq mol / 10 ⁶ g or less, and more preferably 10 eq mol / 10 ⁶ g or less. If the concentration of methyl terminals in the polyester is too high, phenomena such as easy formation of white powder from the copolymerized polyester during molding processing, or in the case of a container, poor taste retention may be observed.

Further, the copolymerized polyester constituting the copolymerized polyester layer (A) in the present invention preferably has a glass transition temperature of 60 ° C. or higher, more preferably 70 ° C. or higher. If the secondary transition point is less than 60 ° C,
Satisfactory taste retention cannot be obtained. As such a copolymerized polyester, a copolymerized polyester having a high glass transition temperature can be obtained, and thus isophthalic acid copolymerized polyethylene terephthalate is particularly preferable.

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 is 180 to 223 ° C., preferably 200.
To 223 ° C, more preferably 210 to 223 ° C. 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 this polyester was carried out in the same manner as in the measurement of the above-mentioned copolymerized polyester.
Performed using Instruments 910 DSC.

In the polyester film of the present invention,
The polyester layer (B) is composed of 80 to 45% by weight of a copolymer polyester mainly composed of polyethylene terephthalate and having a melting point of 210 to 245 ° C., and having a melting point mainly composed of polybutylene terephthalate or polybutylene terephthalate of 1%.
20 to 55% by weight of copolyester at 80 to 223 ° C
It is necessary to consist of If the content of polybutylene terephthalate or polybutylene terephthalate copolyester is less than 20% by weight and the content of polyethylene terephthalate copolyester exceeds 80% by weight, the impact resistance at low temperatures cannot be improved. When the content of polybutylene terephthalate or the copolymer of polybutylene terephthalate exceeds 55% by weight and the content of the polyethylene terephthalate copolymerized polyester is less than 45% by weight, the heat resistance of the film decreases and the impact resistance becomes insufficient.

In the present invention, the copolyester used for the copolyester (I) of the copolyester layer (A) and the polyester layer (B) and the polyester used for the polyester (II) of the polyester layer (B) are: It is not limited by the manufacturing method.
For example, in the case of a copolymerized polyester mainly composed of polyethylene terephthalate, 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 copolymerized polyester, or Preferably, a method is 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 of the copolymerized polyester and polybutylene terephthalate, other additives such as an antioxidant, a heat stabilizer, an ultraviolet absorber, and an antistatic agent can be added as necessary.

In the present invention, the copolymer polyester constituting the copolymer polyester layer (A) has an average particle size of 0.05 to 0.6 μm, preferably 0.08 to 0.5 μm.
μm, more preferably 0.1 to 0.4 μm. If the average particle size of the lubricant is less than 0.05 μm, the effect of improving the slipperiness is insufficient, and the winding property is deteriorated in the film production process, which is not preferable. When the average particle size exceeds 0.6 μm, coarse particles (for example, particles of 10 μm or more) become a starting point in a portion deformed by processing of a deep drawing can or the like, and a pinhole is generated or broken in some cases. Is not preferred.

The lubricant may be inorganic or organic, but is preferably inorganic. Examples of the inorganic lubricant include silica, alumina, titanium dioxide, calcium carbonate, and barium sulfate. Examples of the organic lubricant include silicone resin particles and crosslinked polystyrene particles.

Particularly preferred lubricants in terms of pinhole resistance are monodispersed lubricants having a particle size ratio (major axis / minor axis) of 1.0 to 1.2. Examples of such lubricants include spherical silica, spherical tin dioxide, spherical silicone resin particles,
True spherical crosslinked polystyrene particles can be exemplified.

Here, the average particle diameter and the particle diameter ratio of the spherical monodispersed lubricant can be determined from the image obtained by first evaporating metal on the particle surface and then enlarging the particle diameter by, for example, 10,000 to 30,000 times using an electron microscope. The short diameter and the area circle equivalent diameter are calculated, and then they are applied to the following equation to calculate the diameter. Average particle diameter = total area circle equivalent diameter of measured particles / number of measured particles Particle diameter ratio = average major axis of particles / average minor axis of the particles Also, spherical lubricant particles preferably have a sharp particle size distribution, The relative standard deviation representing the steepness of the distribution is preferably 0.5 or less, more preferably 0.3 or less.

This relative standard deviation is expressed by the following equation.

[0032]

(Equation 3)

The additive amount C (% by weight) of the lubricant in the copolymerized polyester layer (A) is determined by calculating the average particle size d (μm) of the lubricant by the following formula:

[0034]

## EQU4 ^## It is necessary to be within a range satisfying 0.0072d -0.65 ≤C≤0.78d ^-0.44 , and preferably, the following formula:

[0035]

## EQU5 ^## It is in a range that satisfies 0.014d− ^0.65 ≦ C ≦ 0.55d− ^0.44 . This added amount is 0.0072d
^If it is less than ^-0.65 (% by weight), the slipperiness is insufficient.
If it exceeds 0.78 d ^-0.44 (% by weight), the film is frequently broken during can making, which is not preferable. If necessary, other lubricants can be added as long as the effects of the present invention are not impaired.

In the present invention, the polyester composition constituting the polyester layer (B) has an average particle size of 0.8 μm or more and less than 2.5 μm, preferably 1.0 to 2.5 μm.
It contains 0.03 to 1.0% by weight, preferably 0.05 to 0.5% by weight of a 2.3 [mu] m lubricant.

If the average particle size of the lubricant is less than 0.8 μm, the lubricating property is insufficient, and the winding property in the film manufacturing process is unfavorably deteriorated. On the other hand, when the average particle size exceeds 2.5 μm, coarse particles serve as a starting point in a portion deformed by processing such as a deep drawing can, so that a pinhole is generated or the film is broken, which is not preferable. When the content of the lubricant is less than 0.03% by weight, the lubricity is insufficient. On the other hand, when the content is more than 1.0% by weight, the film frequently breaks due to processing such as deep drawing cans, which is preferable. Absent.

The lubricant may be inorganic or organic, but is preferably inorganic. As an inorganic lubricant,
Silica, alumina, titanium dioxide, calcium carbonate, barium sulfate and the like can be exemplified. As the organic lubricant, silicone resin particles, crosslinked polystyrene particles and the like can be exemplified.

These lubricants can be used alone or in combination of two or more. Also,
Other lubricants can be added as needed.

In particular, a preferred lubricant in terms of pinhole resistance is the same type of lubricant as the lubricant for the copolymerized polyester constituting the copolymerized polyester layer (A), having a particle size ratio (major axis / minor axis) of 1 0.0-1.2.

As means for adding a lubricant to the polyester, conventionally known means can be used, and there is no particular limitation, but a method of adding a lubricant during the production of the copolymerized polyester is preferred.

In the production of the polyester film of the present invention, first, the copolymerized polyester is melt-extruded. At this time, a lubricant is contained in the polyester so as to have a predetermined lubricant content, or a predetermined amount is extruded at the time of extrusion. Can be adopted.

In this way, the film is discharged from the melt extrusion die to form a film, and then biaxially stretched and heat-set to obtain a biaxially oriented film. The plane orientation coefficient of the copolymerized polyester layer (A) of this film is 0.08 or more and 0.16 or less, preferably more than 0.09 and 0.15 or less, and more preferably more than 0.10 and 0.14 or less. I need to do that. If the plane orientation coefficient of the film is less than 0.08, when the deep drawing ratio in the deep drawing becomes high, problems such as cracks occur, which is not preferable. On the other hand, when the plane orientation coefficient exceeds 0.16, breakage occurs during deep drawing, and deep drawing itself becomes impossible.

Here, the plane orientation coefficient is defined by the following equation.

[0045]

F = [(nx × ny) / 2] −nz In the above equation, f: plane orientation coefficient, nx, ny, nz:
These are the refractive index in the horizontal, vertical and thickness directions of the film, respectively. The refractive index is measured as follows.

A polarizing plate analyzer is attached to the eyepiece side of the Abbe refractometer, and each refractive index is measured with a monochromatic NaD line. The mounting solution uses methylene iodide, and the measurement temperature is 25 ° C.

The polyester film of the present invention preferably has a heat shrinkage at 150 ° C. of 10% or less, more preferably 7% or less, and particularly preferably 6% or less.
% Or less.

Here, the heat shrinkage ratio is determined by setting two points (at intervals of about 10 cm) on the sample film at room temperature,
Hold in a hot air circulating oven at 0 ° C. for 30 minutes, then return to room temperature, measure the distance between the mark points, find the difference before and after holding the temperature at 150 ° C., and compare this difference with the temperature before holding at 150 ° C. Calculated from the reference point interval. And it is represented by the heat shrinkage in the longitudinal direction of the film.

The heat shrinkage of the polyester film (150
℃) exceeds 10%, the dimensional shrinkage is large when bonded to a metal plate, causing defects such as wrinkling in the film,
Not preferred. This heat shrinkage rate is 10% or less, further 7%
Below, especially when it is 6% or less, there are few defects such as wrinkling of the film when bonded to a metal plate, and good results can be obtained.

The plane orientation coefficient and heat shrinkage ratio (15
(0 ° C.), for example, in a sequential biaxial stretching, a longitudinal stretching ratio of 2.5 to 3.
From the range of 6 times, the transverse stretching ratio is from 2.7 to 3.6 times, and the heat setting temperature is 150 to 220 ° C, preferably 16
It is good to select from the range of 0 to 200 ° C. and combine them.

The polyester film of the present invention has a structure in which a copolymerized polyester layer (A) and a polyester layer (B) are laminated, and such a film having a two-layer structure constitutes, for example, each layer. The copolymerized polyester and the polyester composition are separately melted, co-extruded, laminated and fused before solidification, then biaxially stretched, a method of heat setting, the copolymerized polyester and the polyester composition are separately melted and extruded. It can be manufactured by a method of forming a film, unstretched state or after stretching, and laminating and fusing them.

When the polyester film is composed only of the copolymerized polyester layer (A), the impact resistance at low temperatures becomes insufficient. Conversely, when the polyester film is composed solely of the polyester layer (B), the protection is insufficient. It is not suitable because the taste and rust resistance deteriorate.

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 copolymerized polyester layer (A) is 1.505 to 1.55.
It is preferably 0, more preferably more than 1.510 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.

The thickness T of the copolymerized polyester layer (A)
The ratio of the _A, and the thickness T _B of the polyester layer (B) (T _A /
T _B) is preferably about 0.02 to 0.67, more preferably 0.04 to 0.43, particularly preferably 0.04
０．２0.25. Specifically, for example, the thickness is 25 μm
Polyester layer (B)
Is 0.5 to 10 μm, preferably 1 to 7.5 μm.
m, more preferably 1 to 5 μm.

As a metal plate to which the polyester film of the present invention is bonded, in particular, 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 bonded, and then rapidly cooled, and the surface layer (thin layer) of the film in contact with the metal plate is made amorphous and adhered. An adhesive layer is primer-coated on the film in advance, and this surface is bonded to a metal plate. As the adhesive layer, a known resin adhesive, for example, an epoxy adhesive, an epoxy-ester adhesive, an alkyd adhesive, or the like can be used.

When the polyester film of the present invention is bonded to a metal plate, in order to improve the impact resistance,
It is preferable to bond together such that the polyester layer (B) is located on the side receiving the impact. For example, when the polyester film of the present invention is bonded to the inside of a can, the polyester layer (B) may be bonded to the can.

Further, in the polyester film of the present invention, if necessary, both polyester layers (A),
(B) Another additional layer may be laminated between or on one side.

[0059]

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

Examples 1 to 7 and Comparative Examples 1 to 8 Spherical silica having an average particle diameter of 0.3 μm (particle diameter ratio: 1.0
7, containing 0.4% by weight of relative standard deviation 0.1).
The copolymerized polyethylene terephthalate (tetrabutyl titanate used as a transesterification catalyst and germanium oxide used as a polycondensation catalyst, intrinsic viscosity 0.64) obtained by copolymerizing the components shown in Table 1 was also used in Table 1 for the copolymerized polyester layer (A). The polyester compositions shown (containing spherical silica having an average particle size of 1.5 μm and a particle size ratio of 1.1 as a lubricant) were separately dried and melted by a conventional method so as to form the polyester layer (B). Thereafter, they were co-extruded from dies adjacent to each other, laminated, fused and quenched and solidified to prepare an unstretched film.

Next, the unstretched film was longitudinally stretched 3.0 times at 110 ° C., and then transversely stretched 3 times at 125 ° 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.

[0063]

[Table 1]

Example 8 and Comparative Examples 9 to 11 Spherical silica having an average particle size of 0.5 μm (particle size ratio 1.1,
A copolymerized polyethylene terephthalate copolymerized with the components shown in Table 2 containing 0.25% by weight (relative standard deviation 0.1) and the components shown in Table 2 was used as the copolymerized polyester layer (A) and the polyester composition shown in Table 2 (as a lubricant). Average particle size is 1.2μm
Are dried and melted separately by a conventional method so that the spherical silica of the present invention becomes the polyester layer (B).
They were co-extruded from dies adjacent to each other, laminated, fused, quenched and solidified to prepare an unstretched film.

Next, the unstretched film was longitudinally stretched 3.0 times at 110 ° C., then transversely stretched 3.1 times at 125 ° C., and heat-set at 180 ° 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.

[0067]

[Table 2]

Examples 9 to 26 and Comparative Examples 12 to 18 In Example 2, as shown in Table 3, the type and particle size of the lubricant,
A biaxially oriented film was prepared by changing the content.

[0069]

[Table 3]

[Comparative Examples 19 to 20] In Example 9, only the copolymerized polyester layer (A) (Comparative Example 19) and the polyester layer (B) (Comparative Example 20) were used instead of the two-layer laminated structure. A layer film was made.

The films obtained in the above Examples and Comparative Examples were stuck on both sides of a tin-free steel sheet having a thickness of 0.25 mm heated at 250 ° C., cooled with water, cut into a disk having a diameter of 150 mm, and drawn. And a punch in four stages to form a 55 mm-diameter side-wall seamless container (hereinafter abbreviated as can). 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 is observed at the top of the film can. X: Film breakage is observed in a part of the film.

(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, an electrode was inserted, and the can body was used as an anode. The current value when a voltage of 6 V is applied is measured.
In the following, this is referred to as an ERV test). ×: There is no abnormality in the film, but the current value is 0.1 mA or more in the ERV test, and pinhole-shaped cracks starting from the coarse lubricant are recognized in the film when the energized portion is observed under magnification.

(3) Impact resistance For cans with good deep drawing, pour water thoroughly, cool to 0 ° C., drop 10 pieces for each test from a height of 50 cm onto a PVC tile floor. As a result of the ERV test in the can, the results were as follows: A: 0.1 mA or less for all 10 samples. C: 0.1 mA or more for 1 to 5 pieces. X: The value was 0.1 mA or more for 6 or more pieces, or cracking of the film was already observed after dropping.

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

(5) Retort Resistance The cans having good deep drawing properties were filled with water, retorted in a steam sterilizer at 120 ° C. for 1 hour, and then stored at 50 ° C. for 30 days. After dropping 10 cans for each test from a height of 50 cm onto a PVC tile floor, an ERV test in the cans was performed. ：: 0.1 mA or less for all 10 samples. C: 0.1 mA or more for 1 to 5 pieces. X: The value was 0.1 mA or more for 6 or more pieces, or cracking of the film was already observed after dropping.

(6) Preservation of Taste A can that had good deep drawing was filled with cider and sealed. After keeping at 37 ° C. for 30 days, the can was opened and the change in taste was examined by a sensory test. ：: There was no change in taste. Δ: Slight change in taste was observed. ×: A change in taste was observed.

The evaluation results and the winding properties of the film were as shown in Table 4.

[0079]

[Table 4]

As is clear from the results in the table, in the can using the polyester film of the present invention, the deep drawability,
It has excellent heat embrittlement resistance and retort resistance, as well as excellent taste retention and impact resistance, especially at low temperatures.

[0081]

The film for laminating and processing metal sheets of the present invention has excellent moldability, heat resistance and retort resistance, as well as taste retention and impact resistance, especially impact resistance at low temperatures. Is remarkably improved, and rust prevention is also good. Therefore, it is particularly suitable to be used by bonding it to a metal can often cooled and used at a low temperature, such as for juices and soft drinks.

Continuation of front page (72) Inventor Takafumi Kudo 3-37-19 Koyama, Sagamihara-shi, Kanagawa Teijin Limited Sagamihara Research Center (56) References JP-A-5-338103 (JP, A) JP-A-6- 172556 (JP, A) JP-A-6-39981 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) B32B 1/00-35/00

Claims (1)

(57) [Claims] 1. A copolyester containing a lubricant having an average particle size of 0.05 to 0.6 μm, a melting point of 210 to 245 ° C., and using a germanium compound as a polycondensation catalyst, and a concentration of the lubricant. C (% by weight) is the average particle size d (μ
m) and the following formula: 0.0072 d ^-0.65 ≤ C ≤ 0.80 d- ^0.44 The copolyester layer (A) which satisfies the relationship, a melting point of 210-245 ° C, and a polycondensation catalyst Polyester (I) 8 containing ethylene terephthalate as a main repeating unit and using a germanium compound as a material
A polyester composition comprising 0 to 45% by weight and 20 to 55% by weight of a polyester (II) containing butylene terephthalate having a melting point of 180 to 223 ° C as a main repeating unit, and having an average particle size of 0.8 µm or more. A polyester film for laminating and processing a metal plate, comprising laminating a polyester layer (B) containing 0.03 to 0.5% by weight of a lubricant of less than 5 μm.