JP2000129008A - Polyester film for metal plate cladding fabrication - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a film excellent in adherence after retort processing and taste characteristics by using ethylene terephthalate and/or ethylene naphthalate units as constituents and a specific amount of cyclohexanedimethanol as a copolymerization component. SOLUTION: Polyester film A contains ethylene terephthalate and/or ethylene naphthalate units as constituents and 1-40 mol% of cyclohexanedimethanol. This film has a melting point of 246 deg.C or higher and preferably contains 0.01-3 wt.% of an inorganic or organic particle with an average particle diameter of 0.01-5 μm and a degree of anomaly of 1.1 or more. A laminated film is obtained by laminating polyester B, which contains ethylene terephthalate and/or ethylene naphthalate units as constituents and 0.01-4 mol% of cyclohexanedimethanol as a copolymerization component, to polyester A to express taste characteristics and heat resistance.

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 a metal plate, and more particularly, to a polyester film having excellent adhesion and taste characteristics after retort treatment, and abrasion resistance in can forming. The present invention also relates to a polyester film for metal plate lamination molding suitable for containers produced by molding and the like, particularly suitable for metal cans.

[0002]

2. Description of the Related Art Conventionally, the inside and outside surfaces of metal cans are coated with various thermosetting resins such as epoxy or phenol melted or dispersed in a solvent for the purpose of preventing corrosion, and the metal surface is coated. Has been widely practiced.
However, such a coating method using a thermosetting resin has unfavorable problems such as a decrease in productivity due to a long time required for drying and environmental pollution due to a large amount of an organic solvent.

As a method of solving these problems, there is a method of laminating a film on a steel plate, an aluminum plate, or a metal plate obtained by applying various surface treatments such as plating to the metal plate as a material of the metal can. And when manufacturing metal cans by drawing or ironing the metal plate of the film,
The film is required to have the following characteristics. (1) The lamination property to the metal plate is excellent. (2) Excellent adhesion to a metal plate. (3) It has excellent moldability and does not cause defects such as pinholes after molding. (4) The polyester film does not peel, crack, or pinhole due to impact on the metal can. (5) The scent component of the contents of the can adsorbs to the film,
The flavor of the contents is not impaired by the eluate from the film (hereinafter referred to as taste characteristics).

Many proposals have been made to solve these requirements. For example, Japanese Patent Application Laid-Open No. 2-57339 discloses a copolymerized polyester film having specific crystallinity. However, in recent years, as the speed of can making has increased, the ratio of forming cans from laminated steel sheets has been increasing, and further improvements in laminating properties, moldability, and adhesion between films and steel sheets have been desired. In addition, an increase in the molding ratio causes a problem in that the adhesion between the film and the steel sheet is reduced particularly by the retort after the can forming. For this reason, it has become impossible for the above proposals to satisfy these required characteristics comprehensively.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems. In particular, the present invention is excellent in adhesion and taste characteristics after retort treatment, and is excellent in abrasion resistance in can forming. An object of the present invention is to provide a polyester film for laminating and forming a metal plate which can be formed into a good metal can.

[0006]

Means for Solving the Problems In order to solve the above-mentioned problems, a polyester film for laminating and processing a metal plate according to the present invention comprises an ethylene terephthalate and / or ethylene naphthalate unit as a main component and a copolymer component. It is composed of polyester A containing 1 to 40 mol% of cyclohexanedimethanol.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail with preferred embodiments. The polyester in the present invention is a general term for a high molecular weight substance constituted by an ester bond, and examples of the dicarboxylic acid component include isophthalic acid, naphthalenedicarboxylic acid, diphenyldicarboxylic acid, diphenylsulfondicarboxylic acid, diphenoxyethanedicarboxylic acid, 5-sodium sulfoisophthalic acid, aromatic dicarboxylic acids such as phthalic acid, oxalic acid, succinic acid, adipic acid, sebacic acid, dimer acid,
Examples thereof include aliphatic dicarboxylic acids such as maleic acid and fumaric acid, alicyclic dicarboxylic acids such as cyclohexyne dicarboxylic acid, and oxycarboxylic acids such as p-oxybenzoic acid. On the other hand, examples of the glycol component include aliphatic glycols such as propane diol, butane diol, pentane diol, hexane diol, and neopentyl glycol; alicyclic glycols such as cyclohexane dimethanol; aromatic glycols such as bisphenol A and bisphenol S; And the like. In addition, two or more of these dicarboxylic acid components and glycol components may be used in combination. Further, in the present invention, two or more kinds of the above polymers may be blended and used. In addition,
The polyester in the present invention may be constituted by blending polyester A having the same composition.
Other polyesters may be blended. In particular, it is preferable to blend polyester A with other polyesters from the viewpoint of heat resistance and adhesiveness.

As long as the effects of the present invention are not impaired, a polyfunctional compound such as trimellitic acid, trimesic acid, or trimethylolpropane may be copolymerized with the copolymerized polyester.

The main component of the polyester in the present invention must be ethylene terephthalate and / or ethylene naphthalate units, and the proportion of the units is
From the viewpoint of heat resistance and productivity, it is preferably at least 65 mol%, more preferably at least 75 mol%, further preferably at least 85 mol%.

The polyester film according to the present invention can be used in either a single layer or a laminate. When a laminated film is used, its form is, for example, A layer / B layer, A layer / B layer / A
Layer, layer B / layer A / layer B, and layer A / layer C / layer B are mentioned. When layer A is composed of polyester A and layer B is composed of polyester B, layer A is formed from the viewpoint of adhesiveness. The configuration on the steel plate side is desirable, especially when the film is for the inner surface of a can,
From the viewpoint of taste characteristics, a laminated structure in which the layer B is on the content side is desirable.

The polyester A in the present invention is made of ethylene terephthalate and / or ethylene terephthalate for the purpose of exhibiting excellent adhesion to a metal plate and moldability after lamination with the metal plate.
Alternatively, an ethylene naphthalate unit is used as a main component, and cyclohexanedimethanol is used as a copolymer component in an amount of 1 to 40.
It is necessary to make the polyester containing mol%.
Preferably it is 2 to 35 mol%, more preferably 4 to 30 mol%. If the amount of cyclohexanedimethanol exceeds the above range, taste characteristics deteriorate, which is not preferable. Also,
It is preferable from the viewpoint of moldability that it is made of at least two kinds of polyesters including polyester A. For example, there may be mentioned an embodiment comprising at least two types of polyesters C other than polyester A, which have different amounts of cyclohexanedimethanol copolymerized.

The polyester B used in the case of using a laminated film has ethylene terephthalate and / or ethylene naphthalate as a main component and cyclohexane dimethanol as a copolymer component for the purpose of developing excellent taste characteristics and heat resistance. Is preferably a polyester containing 0.01 to 4 mol%, more preferably 1 to 3 mol%. Further, it is preferable from the viewpoint of moldability that it is composed of at least two kinds of polyesters including polyester B. For example, in addition to polyester B, polyester D having a different copolymerization amount of cyclohexanedimethanol
And at least two types of polyesters.

Here, when the polyester A (polyester B) is composed of two or more polyesters, the copolymerization amount of cyclohexanedimethanol is as follows.
(Polyester B) It is defined from the total copolymerization amount.

In polyester A and polyester B, the content of cyclohexane dimethanol is controlled within the above range. For example, in the case of polyethylene terephthalate copolymerized with cyclohexane dimethyl, cyclohexane dimethyl is used as a comonomer when polymerizing polyethylene terephthalate. And a method of blending polyethylene terephthalate and cyclohexanedimethyl copolymerized polyethylene terephthalate at the time of film formation. Examples of a method for blending at least two different polyesters for polyesters A and B include, but not limited to, a method of blending two or more polyesters and feeding them to an extruder during film formation. The fact that the polyester is composed of two or more types can be determined by a thermal behavior detected by a so-called differential calorimeter (DSC). For example, a plurality of endothermic peaks at the time of melting of a film or a plurality of glass transition points appear. Can be confirmed by the phenomenon that a plurality of glass transition points appear.

The main melting point of the polyester film in the present invention is desirably 246 ° C. or higher from the viewpoint of heat resistance. Here, the melting point of the polyester film is an endothermic peak temperature at the time of melting, which is detected by a so-called differential scanning calorimetry (DSC). In addition, the main melting point when a plurality of endothermic peaks appear during melting refers to the maximum endothermic peak.

The polyester film of the present invention is desirably biaxially stretched from the viewpoint of heat resistance and dimensional stability. The method of biaxial stretching may be either simultaneous biaxial stretching or sequential biaxial stretching.

In the biaxially stretched film of the present invention, the plane orientation coefficient of the layer A composed of polyester A in the case of a single film and a laminate is preferably 0.01 to 0.13, more preferably 0.02 to 0.13. 0.12. In the case of a laminated structure, the plane orientation coefficient of the layer B composed of the polyester B is preferably 0.06 to 0.15, more preferably 0.08 to 0.15. If the plane orientation coefficient is smaller than the above range, it is not preferable from the viewpoint of generation of wrinkles at the time of lamination.

Further, the difference between the plane orientation coefficients of the A layer and the B layer is preferably 0.14 or less in absolute value, more preferably 0.12 or less.
It is more preferable that it is the following. It is not preferable that the difference in the plane orientation coefficient exceeds the above range from the viewpoint of moldability.

In the present invention, in order to improve the adhesiveness between the film and the steel sheet, and particularly to reduce the influence of peeling due to the shrinkage stress of the film during retort, the heat shrinkage stress in the longitudinal direction of the film at 125 ° C. 0.1 to 1.5 MPa, more preferably 0.2 to 1.2 M
Pa.

In the present invention, the coefficient of linear thermal expansion in the longitudinal direction of the film at 125 ° C. is from −150 × 10 ⁻⁶ to −3 × 10 ⁻⁶ K ⁻¹ mainly from the viewpoint of improving the adhesion between the film and the steel sheet. And more preferably −140 × 10 ^{−6.
−−5} × 10 ⁻⁶ K ⁻¹ . If the coefficient of linear thermal expansion is out of this range, residual stress is generated due to the difference in thermal expansion behavior with the steel sheet during lamination, so that cracks and peeling from the steel sheet may occur during subsequent forming and retorting. is there. The method for keeping the coefficient of linear thermal expansion within such a range is not particularly limited, but a method of relaxing in the longitudinal direction in the heat treatment step, a method of gradually cooling during the heat treatment, and the like can be preferably employed.

In the present invention, from the viewpoint of improving the adhesion between the film and the steel sheet, the amount of the carboxyl terminal group of the polyester A constituting the steel sheet side layer is preferably 30 to 60 equivalents / ton, particularly preferably 30 to 60 equivalents / ton. 50 equivalents / ton.

When a laminated film is used, the amount of carboxyl terminal groups of the polyester constituting the non-steel sheet side layer is preferably less than 45 equivalents / ton, particularly preferably 40, from the viewpoint of improving taste characteristics. Less than equivalents / ton.

In the present invention, in order to improve the adhesiveness between the film and the steel sheet, the amount of free dicarboxylic acid monomethyl ester contained in the polyester constituting the steel sheet side layer is preferably 3%.
ppm or more, more preferably 5 ppm or more.
ppm or more.

When a laminated film is used, the amount of free dicarboxylic acid monomethyl ester contained in the polyester constituting the non-steel sheet side layer is preferably less than 6 ppm from the viewpoint of improving taste characteristics. Preferably it is less than 4 ppm.

In the present invention, the intrinsic viscosity of the polyester is 0.6 dl / g in order to further improve the adhesiveness and taste characteristics.
It is preferably at least 0.62 dl / g, more preferably at least 0.65 dl / g. If the intrinsic viscosity is less than 0.6 dl / g, it is not preferable because the taste characteristics deteriorate due to elution of the oligomer.

In producing the polyester of the present invention,
Conventionally known reaction catalysts and coloring inhibitors can be used. Examples of the reaction catalyst include alkali metal compounds, alkaline earth metal compounds, zinc compounds, lead compounds, manganese compounds, cobalt compounds, aluminum compounds, antimony compounds, and titanium. Examples of the coloring inhibitor such as a compound include a phosphorus compound. It is desirable to add an antimony compound, a germanium compound, or a titanium compound as a polymerization catalyst at any stage before the production of the polyester is completed. As such a method, for example, when a germanium compound is taken as an example, a method of adding a germanium compound powder as it is, or as described in JP-B-54-22234, a glycol component which is a starting material of a polyester, A method in which a germanium compound is dissolved and added therein can be used. Examples of the germanium compound include germanium dioxide, germanium hydroxide containing water of crystallization,
Alternatively, germanium alkoxide compounds such as germanium tetramethoxide, germanium tetraethoxide, germanium tetrabutoxide, germanium ethyleneglycoxide, germanium phenolate, germanium phenoxide compounds such as germanium β-naphtholate, germanium phosphate, and phosphorus such as germanium phosphite Germanium compounds, germanium acetate, and the like. Among them, germanium dioxide is preferable. Examples of the antimony compound include, but are not particularly limited to, antimony oxides such as antimony trioxide, and antimony acetate. As a titanium compound,
Although not particularly limited, alkyl titanate compounds such as tetraethyl titanate and tetrabutyl titanate are preferably used.

For example, a case where germanium dioxide is added as a germanium compound when producing polyethylene terephthalate will be described. The terephthalic acid component and ethylene glycol are subjected to a transesterification or esterification reaction, and then germanium dioxide and a phosphorus compound are added.Then, the polycondensation reaction is continued under a high temperature and a reduced pressure until a constant diethylene glycol content is obtained, and a germanium element-containing polymer is obtained. obtain. Further, preferably, the obtained polymer is subjected to a solid-phase polymerization reaction under reduced pressure or an inert gas atmosphere at a temperature equal to or lower than its melting point to reduce the content of acetoadheride to obtain a predetermined intrinsic viscosity and a carboxyl end group. And the like.

The polyester in the present invention has a diethylene glycol component content of 0.01 to 10 to maintain excellent taste characteristics even when subjected to many heat histories such as heat treatment in a can making process and retort treatment after can making. It is preferably 3.5% by weight, more preferably 0.01 to 2.5% by weight, and even more preferably 0.01 to 2% by weight. This is considered to be because the oxidation resistance at 200 ° C. or higher is improved.
001 to 1% by weight may be added. Further, diethylene glycol may be added during the production of the polymer as long as the properties are not impaired.

In order to improve taste characteristics, the content of acetaldehyde in the film is preferably 25 ppm.
Below, it is more desirable to make it 20 ppm or less. When the content of acetaldehyde in the film is 25
pm or less is not particularly limited,
For example, in order to remove acetaldehyde generated by thermal decomposition when producing a polyester by a polycondensation reaction or the like, a method of heat-treating the polyester under reduced pressure or an inert gas atmosphere at a temperature equal to or lower than the melting point of the polyester,
Preferably, a method of solid-state polymerization of polyester at a temperature of 155 ° C. or more and a melting point or less under reduced pressure or an inert gas atmosphere, a method of melt-extrusion using a vented extruder, and an extrusion temperature when melt-extruding a polymer. Extruded within the melting point of the high melting polymer side + 30 ° C., preferably within the melting point + 25 ° C., for a short time, preferably within an average residence time of 1 hour.

The total thickness of the biaxially stretched film of the present invention depends on the moldability after lamination on metal, the coatability on metal,
In order to improve impact resistance and taste characteristics, it is preferably 3 to 50 μm, more preferably 5 to 35 μm, and particularly preferably 10 to 30 μm.

The method for producing the biaxially stretched film in the present invention is not particularly limited. For example, after drying each polyester as necessary, it is supplied to a known melt extruder and extruded into a sheet from a slit die. Then, the sheet is brought into close contact with the casting drum by a method such as electrostatic application to be cooled and solidified to obtain an unstretched sheet. The unstretched sheet is stretched in the longitudinal and width directions of the film and heat-treated to obtain a film having a desired degree of plane orientation. As the stretching method, simultaneous biaxial and sequential biaxial stretching may be used, but from the viewpoint of film quality, a tenter method is preferable.After stretching in the longitudinal direction, sequential biaxial stretching method in which the film is stretched in the width direction, the longitudinal direction is preferred. A simultaneous biaxial stretching method in which the film is stretched almost simultaneously in the width direction is desirable. The draw ratio is 1.6 in each direction.
To 4.2 times, preferably 1.7 to 4.0 times. Either the stretching ratio in the longitudinal direction or the stretching direction in the width direction may be larger or the same. The stretching speed is 1000%
/ Minute to 200,000% / minute, and the stretching temperature may be any temperature as long as it is equal to or higher than the glass transition temperature of the polyester and equal to or lower than the glass transition temperature + 100 ° C., but is generally preferably 80 to 170 ° C. Further, the film is subjected to heat treatment after biaxial stretching, and this heat treatment can be carried out by any conventionally known method such as in an oven or on a heated roll. Heat treatment temperature is over 120 ℃ 2
Any temperature of 45 ° C. or lower can be used, but it is preferably 120 to 240 ° C. The heat treatment time can be arbitrarily set, but it is usually preferable to perform the heat treatment for 1 to 60 seconds. The heat treatment may be performed while relaxing the film in the longitudinal direction and / or the width direction. Furthermore, re-stretching may be performed once or more in each direction, and then heat treatment may be performed.

The degree of irregularity of the particles contained in the polyester film of the present invention (the ratio of the maximum length D to the minimum length d of the particles defined by the following formula (1)) is determined by the abrasion resistance during molding. From the viewpoint of improvement, it is preferably 1.1 or more, more preferably 1.2 to 30, and particularly preferably 1.5 to 2.
0. Further, its content is preferably 0.05 to 1.0% by weight from the viewpoint of film handling properties,
More preferably, the content is 0.07 to 0.5% by weight. Degree of irregularity = D / d (1)

The irregularity of the particles of the invention is defined by the ratio of the maximum length D to the minimum length d of the particles observed in the film, as defined by equation (1). Here, the maximum length of a particle is defined as the distance between the parallel lines at the longest interval in contact with the contour of a single particle, assuming that individual particles or agglomerates formed at intervals smaller than the primary particle diameter are regarded as one particle. And the minimum length is the length of the particle in the direction perpendicular to the maximum length at half the position of the longest interval.

As the additive particles in the present invention, particles arbitrarily selected from known internal particles having an average particle diameter of 0.01 to 10 μm and external particles such as inorganic particles and / or organic particles can be contained. . It is particularly preferable that the film used on the inner surface of the can contains 0.01 to 3% by weight of particles having an average particle diameter of 0.1 to 5 μm. It is not preferable to use particles having an average particle diameter of more than 10 μm because defects in the film are likely to occur.
The particles include, for example, wet and dry silica, colloidal silica, aluminum silicate, titanium oxide, calcium carbonate, calcium phosphate, barium sulfate, inorganic particles such as alumina, mica, kaolin, and clay, and styrene, silicone, and acrylic acids as components. Organic particles and the like can be mentioned. Among them, dry, wet and dry colloidal silica, inorganic particles such as alumina and styrene, silicone, acrylic acid, methacrylic acid, polyester,
Organic particles containing divinylbenzene or the like as a constituent component can be exemplified. These internal particles, inorganic particles and / or
Alternatively, two or more kinds of organic particles may be used in combination as long as the properties are not impaired.

In the present invention, the degree of irregularity in the film is 1.
Examples of the one or more particles include aggregated inorganic particles and the like, but are not particularly limited as long as the irregularity is 1.1 or more.

In the present invention, in order to improve the adhesion between the film and the steel sheet, and particularly to increase the adhesion area and thickness of the polymer portion at the adhesion interface between the film and the steel sheet,
The ratio R1 / R2 of the particle concentration R1 at 1 μm from at least one surface and the particle concentration R2 at 0.1 μm from the surface is 2
~ 200, more preferably 3 ~ 1
50.

Further, when used on the inner surface of the can, the center line average roughness Ra of the steel plate side layer and the non-steel plate side layer surface is preferably 0.005 to 0.07 μm, more preferably 0.005 to 0.07 μm.
8 to 0.05 μm. Further, when the ratio Rt / Ra to the maximum roughness Rt is 4 to 50, preferably 6 to 40, high-speed can-making properties are improved. The center line average roughness Ra of the non-steel side layer is preferably 0.002 to 0.04 μm, and more preferably 0.003 to 0.03 μm, since the taste characteristics are improved.

It is preferable to improve the adhesiveness by subjecting the film to a surface treatment such as a corona discharge treatment in order to further improve the characteristics.

Various coatings may be applied on the film of the present invention.
There is no particular limitation as long as the effects of the present invention are not impaired.

Although the metal plate of the present invention is not particularly limited,
From the viewpoint of formability, a metal plate made of iron, aluminum, or the like is preferable. Further, in the case of a metal plate made of iron, an inorganic oxide coating layer on the surface thereof for improving adhesion and corrosion resistance, for example, chromic acid treatment, phosphoric acid treatment, chromic acid / phosphoric acid treatment, electrolytic chromic acid treatment A chemical conversion treatment coating layer represented by, for example, a chromate treatment or a chromium chromate treatment may be provided. In particular, in terms of chromium metal, 6.5 to chrome
A chromium hydrated oxide of 150 mg / m ² is preferable, and a spreadable metal plating layer such as nickel, tin, zinc, aluminum, gunmetal, brass, etc. may be provided. It is preferable that tin plating has a plating amount of 0.5 to 15 mg / m ² , and nickel or aluminum has a plating amount of 1.8 to 20 g / m ² .

The biaxially stretched polyester film for a container of the present invention can be suitably used for coating the inner surface of a two-piece metal can manufactured by drawing or ironing after lamination on a metal plate or the like. Further, it can be preferably used for covering a lid portion of a two-piece can or a body, a lid, and a bottom of a three-piece can because it has good metal adhesion and moldability.

[0042]

The present invention will be described below in detail with reference to examples. The characteristics were measured and evaluated by the following methods. (1) Intrinsic viscosity of polyester Polyester is dissolved in orthochlorophenol, and 25
Measured in ° C.

(2) Melting Point of Polyester The film was treated at 40 ° C. × 60 hours to remove the influence of moisture, and 5 mg was sealed in an aluminum measuring container. Differential scanning calorimeter (DSC2 manufactured by Perkin-Elmer)
The container is set in the mold) and heated at a rate of 20 ° C./min.
The temperature was raised to 0 ° C., held at 280 ° C. for 5 minutes, and quenched to 20 ° C. at a cooling rate of 100 ° C./min to perform a measurement pretreatment. Thereafter, measurement was carried out at a heating rate of 10 ° C./min, and the main melting point was determined from the melting peak temperature. Here, when a plurality of endothermic peaks at the time of melting appear, the main melting point means the largest endothermic peak. In the case of a laminated film, the surface of each layer was shaved with a single blade, and 5 mg of the shaved powder was sampled and similarly measured.

(3) Plane orientation coefficient (fn) Using the sodium D line (wavelength 589 nm) as a light source, the refractive index in the longitudinal direction, the width direction, and the thickness direction (Nx, Ny, Nz) was obtained using an Abbe refractometer. The plane orientation coefficient fn = (Nx + Ny) / 2-Nz of the obtained A layer and B layer was calculated and obtained.

(4) Deformity of Particles A cross section in the longitudinal direction of the film is observed with a transmission electron microscope, and individual particles or aggregates formed at intervals smaller than the primary particle diameter are formed into one particle. Consider
Maximum length D and minimum length d of each particle present in the film
And the ratio D / d was calculated. At least one more
Values were obtained for 00 or more particles, and the arithmetic mean thereof was defined as the degree of irregularity.

(5) Average Particle Diameter The thermoplastic resin is removed from the surface of the film by plasma low-temperature ashing to expose the particles. Processing conditions are selected such that the thermoplastic resin is ashed but the particles are not damaged. This is observed with a scanning electron microscope (SEM), and the image of the particles is processed with an image analyzer. The following numerical processing is performed on the number of particles of 5,000 or more by changing the observation position, and the number average diameter D obtained thereby is defined as the average particle diameter. D = ΣDi / N Here, Di is the equivalent circle diameter of the particles, and N is the number of particles. For the internal particles, the section of the section of the film may be observed by a transmission microscope.

(6) Monomethyl dicarboxylate content 500 mg of only layer A or layer B is scraped off from the laminated film and dissolved in hexafluoroisopropanol. Methanol was added thereto, and the filtrate was filtered and subjected to liquid chromatography to determine the amount of free dicarboxylic acid monomethyl ester in the film.

(7) Adhesion force during retort Heating of a tin-free steel plate (thickness: 0.2 mm) (at the temperature in the range of the melting point of the film to the melting point + 25 ° C.) After the films were bonded at 50 m / min, and then rapidly cooled. The film-laminated steel sheet thus obtained is cut into a width of 30 mm,
A part of the steel sheet was cut while leaving the film, and a 100 g weight was hung on the cut part, and retort treatment was performed at 120 ° C. for 40 minutes. The peel length of the film from the steel sheet after retort was measured. The evaluation was made from the average value of the measurements on five or more samples. Class A: less than 10 mm Class B: less than 20 mm 10 mm or more C class: 20 mm or more

(8) Taste Characteristics A stainless steel cylinder (internal cross-sectional area: 150 cm ² ) was put on the laminated film of the above-mentioned laminated steel plate, 200 ml of purified water was added therein, and the container was sealed.
A retort treatment was performed at 0 ° C. for 1 hour. After retorting, the water was once cooled to 5 ° C., turbidity was measured at room temperature, and evaluated according to the following criteria. In the measurement, a calibration curve was prepared in advance using a standard substance. Class A: Less than 0.10 Class B: Less than 0.15 0.10 or more Class C: 0.15 or more

(9) Abrasion resistance A steel sheet laminated as described above with a lamination rate of 100 m / min.
m (molding ratio (maximum thickness / minimum thickness) = 1.3, molding in moldable temperature range), and can (diameter 6 cm, height 10)
cm). At this time, the abrasion resistance of the film was evaluated by measuring the shaving amount of the film attached to the tool. Class A: Less than 1 mg Class B: 1 to 2.5 mg Class C: More than 2.5 mg

Example 1 Cyclohexanedimethanol copolymerized polyethylene terephthalate containing 0.12% by weight of agglomerated silica particles (average primary particle diameter: 30 nm, average particle diameter: 0.3 μm) as polyester A constituting the steel sheet side layer (intrinsic viscosity) 0.68d
1 / g, melting point 228 ° C., carboxyl terminal amount 38 equivalents /
Ton) was vacuum-dried at 180 ° C. for 3 hours, and then supplied to an extruder.
After being discharged from the die, it was cooled and solidified with a mirror-surface cooling drum while applying static electricity (6.8 kv) to obtain an unstretched film. This unstretched film is tripled in the longitudinal direction at a temperature of 98 ° C., a preheating temperature of 90 ° C. (3 seconds), and a stretching temperature of 115 ° C.
After stretching 3.2 times in the width direction at ℃, relax at 190 ℃ 5
% For 5 seconds to obtain a biaxially stretched laminated polyester film having a thickness of 20 μm. Tables 1 and 2 show the raw materials and film forming conditions. The irregularity of the aggregated silica particles in the obtained film was 12. The film characteristics and evaluation results are as shown in Table 3, and excellent characteristics were obtained.

Examples 2 to 7, Comparative Examples 1 and 2 A film having polyester A and polyester B shown in Table 1 as A layer and B layer, respectively, under the conditions shown in Table 2 in the same manner as in Example 1. To form a film. Here, in Examples 6 and 7, for both the A layer and the B layer, cyclohexanedimethanol 33 mol% copolymerized polyethylene terephthalate and polyethylene terephthalate were blended at an appropriate ratio and supplied to an extruder. Polyester A of Examples 6 and 7
In both cases, two melting peaks appeared. Among these, the main melting point was 243 ° C. for Example 6, and 215 ° C. for Example 7. Table 3 shows film properties and evaluation results.
The films of Examples 2 to 5 showed good can properties. On the other hand, the film of Comparative Example 1 has an adhesive property,
In terms of taste characteristics, the film of Comparative Example 2 had adhesion,
All the evaluation items of taste characteristics and abrasion resistance were inferior.

[0053]

[Table 1]

[0054]

[Table 2]

[0055]

[Table 3]

The abbreviations in the table are as follows. PET: polyethylene terephthalate PET / CHDM: polyethylene terephthalate copolymerized with cyclohexane dimethanol PET / I: polyethylene terephthalate copolymerized with isophthalic acid PET / I / CHDM: polyethylene terephthalate copolymerized with isophthalic acid and cyclohexane dimethanol

[0057]

According to the present invention, the adhesion between the metal plate and the film, particularly the adhesion during retort treatment and the taste characteristics can be improved by the polyester film obtained by copolymerizing the cyclohexanedimethanol component in a specific amount.

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Claims (10)

[Claims] An ethylene terephthalate and / or ethylene naphthalate unit as a main component and cyclohexanedimethanol as a copolymer component in an amount of 1 to 40 mol%.
A polyester film for laminating and processing a metal plate, comprising a polyester A contained therein. 2. The polyester film according to claim 1, comprising at least two kinds of polyesters including polyester A. 3. The polyester film according to claim 1, wherein the main melting point is 246 ° C. or higher. 4. A layer B comprising a polyester B containing ethylene terephthalate and / or ethylene naphthalate units as a main constituent and 0.01 to 4 mol% of cyclohexanedimethanol as a copolymerization component. The polyester film for metal plate lamination molding according to any one of claims 1 to 3, wherein the polyester film is laminated on at least one surface of the layer A to be formed. 5. The polyester film according to claim 4, wherein the layer B is made of at least two kinds of polyesters including polyester B. 6. The method according to claim 1, wherein the irregularity of the particles contained in the polyester A (the ratio of the maximum length to the minimum length of the particles) is 1.1 or more. Polyester film for laminating metal plate. 7. The method according to claim 4, wherein the irregularity (the ratio of the maximum length to the minimum length of the particles) of the particles contained in the polyester B is 1.1 or more. Polyester film for laminating metal plate. 8. The polyester film for laminating and processing a metal plate according to claim 1, wherein the polyester film is formed by biaxial stretching. 9. The polyester for laminating and processing a metal plate according to claim 1, wherein the layer A of the polyester A has a plane orientation coefficient of 0.01 to 0.13. the film. 10. The polyester for laminating and processing a metal plate according to claim 4, wherein the B layer composed of polyester B has a plane orientation coefficient of 0.06 to 0.15. the film.