JPH11227137A - Biaxially oriented laminated polyester film for laminating metal plate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To contrive to stabilize the formability and taste characteristics of this film by a method wherein the particle density of a layer mainly made of a polyester B arranged on at least one side of a layer mainly made of a polyester A. SOLUTION: The preferable melting points of a polyester A and/or a polyester B, which are normally obtained by polycondensation-reacting a dicarboxylic acid component such as a terephthalic acid or the like and a glycol component such as an ethylene glycol or the like are 246 deg.C or higher from the view points of taste characteristics and heat resistance. Further, the preferable difference between the melting point of the polyester A and that of the polyester B is 10 deg.C or less. In order to realize the excellent formability, especially the adhesion between the film and a metal plate after retorting, the long term stability after forming, the particle density of internal particle or the like within the surface mainly made of the polyester B must be below 500 ppm. The particle density is more preferably below 300 ppm, since the separation of the film from the metal plate by retorting can be more suppressed. If the particle density exceeds beyond the above-mentioned range, particles play the role of the nuclei of crystallization and the crystallization at lamination or at forming is accelerated, resulting in developing the easy separation between the film and the metal plate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a biaxially stretched laminated polyester film for laminating a metal plate. More specifically, the present invention relates to a biaxially oriented laminated polyester film for metal plate lamination, which has good adhesion to a metal plate even when subjected to a molding process, is easily formed into a container such as a metal can, and has excellent taste characteristics. Things.

[0002]

2. Description of the Related Art Conventionally, the inner and outer surfaces of metal cans are coated with various thermosetting resins, such as epoxy and phenolic resins, dissolved or dispersed in a solvent to prevent corrosion. That was widely done. However, such a method of coating the thermosetting resin requires a long time for drying the paint, and has unfavorable problems such as a decrease in productivity and environmental pollution due to a large amount of an organic solvent.

As a method for solving these problems, there is a method of laminating a film on a steel plate, an aluminum plate, or a metal plate which has been subjected to various surface treatments such as plating on the metal plate as a material of the metal can. When a metal can is manufactured by drawing or ironing a laminated metal plate of a film, the film is required to have the following characteristics.

(1) It has excellent laminating properties to a metal plate. (2) It has 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 the 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 degraded by the eluate from the film (hereinafter referred to as taste characteristics).

[0005] Many proposals have been made to solve these demands. For example, Japanese Patent Publication No. 64-22530 discloses a polyester film having a specific density and plane orientation coefficient. 2-573
No. 39 discloses a copolyester film having specific crystallinity. However, these proposals do not necessarily satisfy the above-mentioned various required properties comprehensively, and are especially excellent in taste characteristics and molding in applications used under severe processing conditions that cause significant distortion. It was difficult to balance sexes.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems of the prior art, which is excellent in taste characteristics and can cope with severe molding such as drawing and ironing. In particular, it is an object of the present invention to provide a biaxially stretched laminated polyester film for metal plate lamination suitable for adhesion after retort.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to provide a laminated film in which a layer B mainly composed of polyester B is arranged on at least one surface of an layer A mainly composed of polyester A. It can be achieved by a biaxially stretched laminated polyester film for laminating a metal plate, wherein the particle concentration of the layer B is less than 500 ppm.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The polyester constituting the polyester film of the present invention is a generic term for polymers having a main bond in the main chain as an ester bond, and is usually a polycondensation reaction of a dicarboxylic acid component and a glycol component. Can be obtained. Here, as the dicarboxylic acid component, for example, terephthalic acid, naphthalenedicarboxylic acid,
Aromatic dicarboxylic acids such as isophthalic acid, diphenyl dican rubonic acid, diphenyl sulfone dicarboxylic acid, diphenoxyethane dicarboxylic acid, 5-sodium sulfone dicarboxylic acid, 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 cyclohexanedicarboxylic acid, and oxycarboxylic acids such as paraoxybenzoic acid. Also,
Examples of the glycol component include aliphatic glycols such as ethylene glycol, propanediol, butanediol, pentanediol, hexanediol and neopentyl glycol; polyoxyalkylene glycols such as diethylene glycol, polyethylene glycol and polypropylene glycol; and fats such as cyclohexanedimethanol. Examples thereof include aromatic glycols, aromatic glycols such as bisphenol A and bisphenol S, and the like.

In the present invention, polyester A and / or polyester B preferably have a melting point of 246 ° C. or more from the viewpoint of taste characteristics and heat resistance. More preferably, it is 250 ° C or more and 275 ° C or less. Further, it is preferable that the difference in melting point between the polyester A and the polyester B is within 10 ° C. from the viewpoints of stretchability of the film, stability after lamination on a metal plate, and the like. It is more preferably within 8 ° C, particularly preferably within 5 ° C.

On the other hand, the polyester of the present invention may be copolymerized with another dicarboxylic acid component and a glycol component as long as taste characteristics are not impaired. Examples of the dicarboxylic acid component and the glycol component include those described above. . In addition, two or more of these dicarboxylic acid components and glycol components may be used in combination. From the viewpoint of taste characteristics, naphthalenedicarboxylic acid, diphenyldicarboxylic acid, and 5-sodium sulfonedicarboxylic acid are preferred.

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

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, titanium compounds, and the like, examples of the coloring inhibitor include phosphorus compounds,
It is not particularly limited to these. Usually at any stage before the completion of the production of polyester, antimony compound or germanium compound as a polymerization catalyst,
It is preferable to add a titanium compound.

For example, when a germanium compound is taken as an example of such a method, a method of adding a germanium compound powder as it is, or a method disclosed in JP-B-54-2223.
As described in Japanese Patent Publication No. 4 (1994), there can be mentioned a method in which a germanium compound is dissolved and added to a glycol component which is a starting material of a polyester. Examples of the germanium compound include germanium dioxide, germanium hydroxide hydrate, and germanium alkoxide compounds such as germanium tetramethoxide, germanium tetraethoxide, germanium tetrabutoxide, and germanium ethylene glycolide, germanium phenolate, and germanium β-naphthalate. And germanium phosphate compounds such as germanium phenoxide compounds, germanium phosphate and germanium phosphite, and germanium acetate. Among them, germanium dioxide is preferable. The antimony compound is not particularly limited, and examples thereof include oxides such as antimony trioxide, and antimony acetate. The titanium compound is not particularly limited, but alkyl titanates such as tetraethyl titanate and tetrabutyl titanate are preferably used.

For example, when producing polyethylene terephthalate, when germanium dioxide is added as a germanium compound, a transesterification or esterification reaction between a terephthalic acid component and an ethylene glycol component is performed, and then a germanium dioxide and a phosphorus compound are added. Subsequently, a method of obtaining a germanium element-containing polymer by performing a polycondensation reaction at a high temperature and under a reduced pressure until a constant diethylene glycol content is obtained is preferably adopted. As a more preferable method, the obtained polymer is subjected to a solid-phase polymerization reaction under a reduced pressure or an inert gas atmosphere at a temperature equal to or lower than its melting point,
Examples of the method include reducing the content of acetaldehyde to obtain a predetermined intrinsic viscosity and a carboxy terminal group.

The polyester in the present invention preferably has a diethylene glycol content of 0.01 to 3.5% by weight, more preferably 0.01 to 2.5% by weight, particularly preferably 0.01 to 2.0% by weight. Is desirable in order 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. This is considered to be because the oxidation resistance at 200 ° C. or higher is improved.
You may add 1 to 1 weight%. Further, diethylene glycol may be added during the production of the polymer as long as the properties are not impaired.

In order to improve the 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 exceeds 25 ppm, taste characteristics may be inferior. The method for reducing the content of acetaldehyde in the film to 25 ppm 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, the polyester is reduced under reduced pressure or A method in which heat treatment is performed at a temperature lower than the melting point of the polyester in an inert gas atmosphere, preferably a method in which the polyester is subjected to solid-state polymerization at a temperature of 155 ° C. or higher and a temperature lower than the melting point under reduced pressure or an inert gas atmosphere, using a vented extruder And a method of extruding the polymer at a melting point of the high-melting polymer side within 30 ° C., preferably within a melting point of + 25 ° C. for a short time, preferably within one hour of the average residence time when the polymer is melt-extruded. Can be mentioned.

The method for producing the biaxially stretched laminated polyester film in the present invention is not particularly limited. For example, after drying polyester A and polyester B as necessary, they are supplied to a known melt extruder, melted and solidified. After laminating before, it is co-extruded into a sheet or a tube from a slit die, brought into close contact with a casting drum by a method such as electrostatic application, and cooled and solidified to obtain an unstretched laminated sheet. Tubular method,
Although there is a tenter method and the like, a tenter method is preferable in terms of film quality, and a longitudinal biaxial stretching method in which a film is stretched in the longitudinal direction and then stretched in the width direction or a film is stretched in the width direction and then stretched in the longitudinal direction. A simultaneous biaxial stretching method in which the film is stretched almost simultaneously in the machine direction and the width direction is desirable.

The stretching 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 width direction may be increased,
They may be the same. The stretching speed is 1000 to 200
The stretching temperature can be any temperature as long as the stretching temperature is equal to or higher than the glass transition point of the polyester and equal to or lower than the glass transition point + 100 ° C.
~ 170 ° C is preferred. Particularly preferably, the longitudinal stretching temperature is 100 to 150 ° C and the transverse stretching temperature is 80 to 150 ° C.

After the biaxial stretching, the film is subjected to a heat treatment. This heat treatment can be carried out by any conventionally known method such as in an oven or on a heated roll. The heat treatment temperature can be any temperature from 120 ° C. to the melting point of the polyester, but is preferably from 150 ° C. to the melting point of the polyester—5 ° C. or less. Although the heat treatment time can be arbitrarily set, it is usually preferable to perform the heat treatment for 1 to 60 seconds. The heat treatment may be performed by relaxing the film in the longitudinal direction and / or the width direction. Further, re-stretching may be performed once or more in each direction.

According to the present invention, in order to obtain a film having excellent moldability, particularly adhesion to a metal plate after retorting, and long-term stability after molding, a polyester layer containing polyester A as a main component is used. In a laminated film having a layer B containing B as a main component, the particle concentration of the layer B needs to be less than 500 ppm. It is more preferable that the particle concentration is less than 300 ppm, since the separation from the metal plate by the retort is further suppressed. If the particle concentration exceeds the above range, the particles become nuclei for crystallization, crystallization is promoted during lamination or molding, and the metal plate and the film are easily separated.

In order to improve the handleability of the laminated film of the present invention, the layer A is 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 organic particles. 0.01 to 20% by weight of the particles to be
It is preferable to include them. Particle concentration is 0.01% by weight
If it is less than 1, the running property and winding property of the film may deteriorate, which is not preferable from the viewpoint of productivity. Further, from the viewpoint of abrasion resistance at the time of processing a metal plate, it is necessary to contain internal particles, inorganic particles, and / or organic particles whose irregularity (ratio of maximum length to minimum length) is 1.1 or more. preferable.
The irregularity of the particles of the invention is expressed as the ratio of the maximum length to the minimum length of the particles observed in the film and is determined by the method defined hereinafter. Here, the maximum length of a particle is defined as a single particle that is formed at an interval smaller than an individual particle or a primary particle diameter, and is a distance between parallel lines at the longest interval in contact with its contour, and the minimum length is 1 / of the longest interval
The particle length in the direction perpendicular to the maximum length at position 2.

Known techniques can be used for the method of depositing the internal particles. For example, JP-A-48-61556, JP-A-51-12860, and JP-A-53-41
355 and JP-A-54-90397. JP-A-55-20496
And JP-A-59-204617. When particles having an average particle diameter exceeding 10 μm are used, a film defect may occur.

The inorganic particles include, for example, wet and dry silica, aluminum silicate, titanium oxide, calcium carbonate, calcium phosphate, barium sulfate, alumina, mica, kaolin, and clay, and the organic particles include styrene, silicone, acrylic acid, and the like. Particles as constituent components can be exemplified. Among them, inorganic particles such as wet and dry silica, and particles containing styrene, silicone, acrylic acid, methacrylic acid, polyester, divinylbenzene and the like as constituent components can be exemplified. Two or more of these internal particles, inorganic particles, and organic particles may be used in combination.

In the present invention, for the above purpose, it is preferable to use the surface of the layer B opposite to the layer A side by heat laminating it to a metal plate. If the surface opposite to the layer B side of the layer A is the laminating surface, the particles in the layer A become nuclei for crystallization, crystallization is promoted during lamination and molding, and shrinkage strain is generated at the metal plate film interface to break. This is not preferable because the susceptibility to peeling tends to easily occur.

The thickness of the biaxially stretched film of the present invention is preferably 3 to 40 μm, more preferably 3 to 40 μm, in view of moldability after lamination on metal, coatability to metal, impact resistance, taste characteristics and the like. Is 5 to 35 μm, particularly preferably 8 to 30 μm. Further, the ratio of the layer thickness of the layer A to the layer B is preferably 30: 1 to 1:10 from the viewpoint of productivity, moldability, long-term stability and the like. It is more preferably 25: 1 to 1: 1 and even more preferably 20: 1 to 2: 1.

In the laminated film of the present invention, the free dicarboxylic acid monomethyl ester contained in the layer B is 5 pp.
m or more is preferable from the viewpoint of adhesion during retort and after molding. More preferably, 8 ppm or more and 50 p
pm or less. Here, examples of the dicarboxylic acid monomethyl ester include terephthalic acid monomethyl ester, isophthalic acid monomethyl ester, phthalic acid monomethyl ester, naphthalenedicarboxylic acid monomethyl ester, and diphenyldicarboxylic acid monomethyl ester. The method of containing the dicarboxylic acid monomethyl ester in such an amount or more is not particularly limited,
For example, a method of producing a polyester by using a dicarboxylic acid ester as a dicarboxylic acid component and performing a transesterification reaction with a glycol component to obtain the polyester can be mentioned.

In the present invention, it is preferable that the content of free dicarboxylic acid monomethyl ester contained in the layer A is less than 5 ppm from the viewpoint of dissolution property when the beverage is filled as a metal can. Dicarboxylic acid monomethyl ester component is 3
The content is more preferably at most ppm and even more preferably not contained. The method for reducing the amount of the dicarboxylic acid monomethyl ester to less than the above amount is not particularly limited, and examples thereof include a method of obtaining a polyester by an esterification reaction between a dicarboxylic acid component and a glycol component when producing the polyester. Can be.

Further, it is preferable to further improve the adhesiveness by subjecting the film surface to a surface treatment such as a corona discharge treatment from the viewpoint of improving the characteristics. At this time, the E value is 5 to 50, preferably 10 to 45. Here, the E value is the intensity of the corona discharge treatment, and the applied voltage (V
p), applied current (Ip), processing speed (S), processing width (W
t) and is expressed as E = Vp × Ip / S × Wt.

The film of the present invention may be coated with various coatings, and the coating compound, method, and thickness are not particularly limited as long as the effects of the present invention are not impaired.

Although the metal plate of the present invention is not particularly limited,
A metal plate made of iron, aluminum, or the like is preferable in terms of molding. Furthermore, in the case of a metal plate made of iron, an inorganic oxide coating layer which improves adhesion and corrosion resistance on the surface thereof, for example, chromic acid treatment, phosphoric acid treatment, chromic acid / phosphoric acid treatment, electrolytic chromic acid treatment, A chemical conversion coating layer represented by chromate treatment, chromium chromate treatment, or the like may be provided. Particularly, in terms of chromium metal, 6.5 to 15 as chromium.
A hydrated chromium oxide of 0 mg / m ² is preferable, and a spreadable metal plating layer such as nickel, tin, zinc, aluminum, gunmetal, or brass 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 oriented polyester film for lamination of the present invention can be suitably used for the inner surface coating of a two-piece metal can manufactured by drawing or ironing. In addition, it can be preferably used as a lid for a two-piece can or for coating a body, a lid, and a bottom of a three-piece can because it has good metal adhesion and moldability.

[0032]

The present invention will be described in detail with reference to the following examples. The characteristics were measured and evaluated by the following methods. In all cases, the heat lamination was performed so that the surface opposite to the layer A side of the layer B mainly composed of polyester B was in contact with the metal plate.

(1) Intrinsic Viscosity of Polyester Polyester is dissolved in orthochlorophenol,
Measured in ° C.

(2) Melting Point of Polyester Polyester was crystallized and measured at a heating rate of 10 ° C./min with a differential scanning calorimeter (DSC2, manufactured by Perkin-Elmer Co.), and the melting peak temperature was taken as the melting point.

(3) Average Particle Size and Deformity The polyester is removed from the surface of the film by a plasma low-temperature incineration method to expose the particles. The processing conditions are selected such that the polyester 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 5000 or more particles while changing the observation position, and the number average diameter D obtained thereby is defined as the average particle diameter. The irregularity of the particles can be determined by observing the cross section in the longitudinal direction of the film with a transmission electron microscope, and assuming that the individual particles or the aggregates formed at intervals smaller than the primary particle diameter are regarded as one particle. The maximum length D and the minimum length d of each particle present in the film were determined, and the ratio D / d was calculated.
Further, values were obtained for at least 100 or more particles, and the arithmetic mean thereof was defined as the degree of irregularity.

(4) Monomethyl Dicarboxylate Content Only 500 mg of the layer A or the 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 dicarboxylic acid monomethyl ester in the film.

(5) Particle Concentration A composition analysis was performed by microscopic FT-IR (Fourier transform microscopic infrared spectroscopy), and the particle concentration was determined from a ratio of a peak caused by a carbonyl group of the polyester to a peak caused by a substance other than the polyester. In the measurement, a calibration curve was prepared in advance using a standard sample. In addition, an X-ray microanalyzer was used as needed.

(6) The film was laminated with a tin-free steel sheet (0.2 mm thick) heated to 200 to 300 ° C. at an adhesion of 50 m / min at the time of retort, and then quenched. The laminated steel sheet thus obtained was cut to a width of 30 mm, and only a part of the steel sheet was cut while leaving a part of the film. A 100 g weight was hung on the cut part and retort treatment was performed at 125 ° C. for 30 minutes. The evaluation was performed based on the peel length of the film from the steel sheet after the retort.

Class A: less than 10 mm Class B: less than 20 mm 10 mm or more Class C: 20 mm or more

(7) Abrasion resistance during molding The abrasion resistance during molding was evaluated by forming the above laminated steel sheet with an ironing machine and a drawing machine (forming ratio (maximum thickness / minimum thickness) = 1.5, moldable temperature). Area) and cans (diameter 6)
cm, height 12 cm), and the shavings of the film were visually observed and observed with a microscope.

Class A: No scraping was observed Class B: No scraping was visually observed Class C: Scratching occurred on the entire surface

(8) Long-term stability The upper part of the can obtained in the above (7) was processed so as to narrow the inside diameter. The obtained can was subjected to retort treatment with pressurized steam at 130 ° C. × 20 minutes, and then filled with water, sealed at 40 ° C., and left for one month. After opening, the degree of rust in the upper processing area was evaluated according to the following criteria.

Class A: No rust was observed at all Class B: Less than 5 rusts of 1 mm or less Class C: Many rusts generated

Example 1 Agglomerated silica having an average particle diameter of 1.3 μm (polymer having a degree of irregularity of 1) was polymerized using terephthalic acid and ethylene glycol as starting materials.
Polyethylene terephthalate (intrinsic viscosity: 0.64 dl / g, melting point: 256 ° C.) containing 0.12% by weight of 2) was used as polyester A, polymerized using dimethyl terephthalate and ethylene glycol as starting materials, and no particles were added. Polyethylene terephthalate (intrinsic viscosity 0.65d
1 / g, melting point 256 ° C.) was taken as polyester B. Polyester A and polyester B are sufficiently vacuum dried,
It was melt co-extruded at 280 ° C. and quenched and solidified to obtain an unstretched laminated film (layer ratio: 4: 1) (thickness: 180 μm). This unstretched laminated film is heated at 110 ° C. in the longitudinal direction.
0 times, and stretched 3.0 times in the width direction at a temperature of 105 ° C.,
Heat treatment at 190 ° C. for 5 seconds with 5% relaxation. The obtained film characteristics and can characteristics are as shown in Table 1, and extremely excellent retort adhesion, abrasion resistance and long-term stability were obtained.

Example 2 Polyethylene terephthalate polymerized from dimethyl terephthalate and ethylene glycol as starting materials and containing the same particles as in Example 1 (intrinsic viscosity 0.65 dl / g,
A film was formed in the same manner as in Example 1 except that polyester A was used (melting point: 256 ° C.). The results are as shown in Table 1, and showed good can properties.

Example 3 Isophthalic acid copolymerized polyethylene terephthalate polymerized from dicarboxylic acid and glycol (isophthalic acid 12 mol%, intrinsic viscosity 0.68 dl / g, melting point 228 ° C.) and colloidal silica particles having an average particle diameter of 1.5 μm ( Melt co-extrusion was performed at a ratio of 5: 1 by adding polyester A having 0.15% by weight of irregularity degree 1.0) and polyester B not adding particles to obtain an unstretched film (thickness 230 μm). ). This unstretched laminated film is 3.2 times in the longitudinal direction at a temperature of 105 ° C., and a temperature of 103 ° C.
After stretching 3.0 times in the width direction at 192 ° C., relax at 192 ° C. 6
% For 5 seconds. The obtained film properties and can properties are as shown in Table 1, and extremely excellent retort adhesion could be obtained. Example 4 Polyester A of Example 2 and Polyester B of Example 3
Was used to form a film in the same manner as in Example 1. Table 2 shows the obtained film properties and can properties.

Example 5 The added particles of the polyester A of Example 3 were prepared using the average particle size of 1.
5 μm colloidal silica particles (irregularity: 1.0) 0.1
Polyester A was changed to 2% by weight, and a film was formed in the same manner as in Example 3 using polyester B of Example 1. Table 2 shows the properties and can properties of the obtained film.

Example 6 Isophthalic acid-copolymerized polyethylene terephthalate to which 0.08% by weight of aggregated silica having a mean particle size of 0.8 μm (deformation degree 15) was added as polyester A (isophthalic acid residue: 3 mol%, intrinsic viscosity: 0.1%). 65 dl / g, melting point 247 ° C)
As an isophthalic acid copolymerized polyethylene terephthalate (isophthalic acid residue: 6 mol%, intrinsic viscosity: 0.67 dl / g, to which 0.03% by weight of aggregated silica having an average particle size of 0.4 μm (variation degree: 12) was added as polyester B; Melting point 241
C.) to obtain an unstretched laminated film (lamination ratio 3: 1). This unstretched film is heated at a temperature of 1
After stretching 3.2 times in the longitudinal direction at 00 ° C., the film was stretched 3.0 times in the width direction. Thereafter, the film was heat-treated at 180 ° C. for 3% relaxation for 5 seconds to obtain a film having a thickness of 20 μm. The characteristics are as shown in Table 2.

Comparative Example 1 Polymerization was conducted from dicarboxylic acid and glycol, and the average particle size was 1 μm.
A monolayer film was obtained using polyethylene terephthalate (intrinsic viscosity: 0.64 dl / g, melting point: 256 ° C.) to which 0.1% by weight of m colloidal silica particles (irregularity: 1.0) was added. Table 3 shows the film properties and can properties.

Comparative Example 2 Isophthalic acid copolymerized polyethylene terephthalate (12 mol of isophthalic acid) polymerized from dimethyl dicarboxylate and glycol and containing 0.1% by weight of aggregated silica particles having an average particle diameter of 1.5 μm (degree of irregularity 11) %, Intrinsic viscosity 0.72 dl / g, melting point 230 ° C.) as polyester A, and isophthalic acid copolymerized polyethylene terephthalate polymerized from dicarboxylic acid and glycol (isophthalic acid 1).
2 mol%, intrinsic viscosity 0.68 dl / g, melting point 228 ° C)
A film was formed in the same manner as in Example 3 except that 0.15% by weight of colloidal silica particles having an average particle diameter of 1.5 μm (degree of irregularity: 1.0) was added as polyester B. Table 3 shows the properties of the obtained film and the properties after can production.

Comparative Example 3 Colloidal Lica Particles Polymerized from Dimethyl Dicarboxylate and Glycol and Having an Average Particle Diameter of 1.5 μm (Degree of Deformation: 1.0)
Acid terephthalate (isophthalic acid 12 mol%, intrinsic viscosity 0.70 dl / g, melting point 229 ° C.) containing 0.12% by weight of
Polyethylene terephthalate (intrinsic viscosity: 0.69 dl / g, melting point: 254 ° C.) obtained by polymerizing terephthalic acid and ethylene glycol as starting materials and adding 0.1% by weight of aggregated silica having an average particle diameter of 1 μm (degree of irregularity: 14). Was formed in the same manner as in Example 1 except that the polyester B was used. Table 3 shows the film properties and can properties.

[0052]

[Table 1]

[Table 2]

[Table 3]

The abbreviations in the table are as follows.

PET: polyethylene terephthalate PET / I: isophthalic acid copolymerized polyethylene terephthalate (numbers are mol% copolymerized)

[0055]

According to the present invention, the moldability and taste characteristics, particularly the adhesion after retorting, can be achieved by controlling the structure of the biaxially stretched laminated polyester film for metal plate lamination and the characteristics of the resin constituting the film. It was something that could be done.

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Claims (8)

[Claims] 1. A polyester comprising polyester A as a main component
A biaxially stretched laminated polyester film for metal plate lamination, wherein a layer B containing polyester B as a main component is disposed on at least one surface of the layer, wherein the particle concentration of the layer B is less than 500 ppm. 2. The biaxially stretched laminated polyester film for metal plate lamination according to claim 1, wherein the melting point of the polyester A is 246 ° C. or higher. 3. The biaxially stretched laminated polyester film for metal plate lamination according to claim 1, wherein the melting point of the polyester B is 246 ° C. or higher. 4. The metal sheet laminate according to claim 1, wherein the irregularity (the ratio of the maximum length to the minimum length of the particles) of the particles contained in the layer A is 1.1 or more. Axial stretched laminated polyester film. 5. The biaxially stretched laminated polyester film for a metal plate laminate according to claim 1, wherein the amount of monocarboxylic acid dicarboxylate contained in the layer B is 5 ppm or more. 6. The biaxially stretched laminated film for a metal plate laminate according to claim 1, wherein the amount of monocarboxylic acid dicarboxylate contained in the layer A is less than 5 ppm. 7. The biaxially stretched laminated polyester film for metal plate lamination according to claim 1, wherein the difference in melting point between polyester A and polyester B is within 10 ° C. 8. The laminated film for bonding a metal plate according to claim 1, wherein the surface of the layer B opposite to the layer A side is heat-laminated on a metal plate and then molded.