JP2003020348A - Polyester film for metal sheet lamination - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polyester film for metal sheet lamination which is excellent in laminability, moldability, taste characteristics, and impact resistance and suitable for metal containers. SOLUTION: This polyester film comprises a polyester layer (I) which is prepared by mixing 30-80 wt.% polyester (A) having a melting point of 246-270 deg.C and consisting mainly of repeating units derived from ethylene terephthalate with 70-20 wt.% polyester (B) consisting mainly of repeating units derived from butylene telephthalate. The degree of transesterification between polyester A and polyester B is 0.01-50%.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a polyester film for laminating metal plates. Specifically, it can be easily molded into a container by laminating a metal plate such as an aluminum plate with or without an adhesive, and then squeezing or ironing. Furthermore, it has taste characteristics and impact resistance. The present invention relates to a polyester film for laminating a metal plate, which has excellent properties.

[0002]

2. Description of the Related Art Conventionally, for the purpose of preventing corrosion, the inner surface and the outer surface of a metal container are coated with various thermosetting resins such as epoxy type or phenol type which are dissolved or dispersed in a solvent to coat the metal surface. Was widely practiced. However, such a coating method using a thermosetting resin has a problem that it takes a long time to dry the coating material, productivity is reduced, and environmental pollution is caused by a large amount of organic solvent.

As a method for solving these problems, an aluminum plate, a steel plate, or a metal plate which has been subjected to various surface treatments such as plating on the metal plate, which is a material of the metal container,
There is a method of laminating a film. When a laminated metal plate of a film is drawn or ironed to produce a metal container, the film is required to have the following characteristics. (1) It has excellent laminating property on a metal plate. (2) Excellent adhesion to the metal plate. (3) It has excellent moldability and does not cause defects such as pinholes after molding. (4) The polyester film should not be peeled off, or cracks or pinholes should be generated due to the impact on the metal container. (5) The scent component of the contents of the container is adsorbed on the film,
The flavor of the contents should not be impaired by the eluate from the film (hereinafter referred to as taste characteristics). (6) When used on the outer surface of a container, it should have excellent printability and design.

Many proposals have been made to solve these requirements. For example, Japanese Patent Application Laid-Open No. 9-194604 discloses a film prepared by blending a polyester having a specific intrinsic viscosity.
Japanese Patent No. 313755 discloses a film having a specific elevated crystallization temperature. Furthermore, Japanese Patent No. 2851
Japanese Patent No. 468, Japanese Patent No. 2908160, Japanese Patent No. 2
No. 908191, No. 2908192, No. 2908195, No. 2908196, No. 3016936, No. 301694.
In Japanese Patent No. 3 and Japanese Patent No. 3048725, etc., 24
A blend film of a copolyester having a melting point of 5 ° C. or less and polybutylene terephthalate or a laminated film obtained by laminating the copolyester on the film is disclosed. However, these proposals are not always able to comprehensively satisfy the various required characteristics as described above, and both excellent laminating properties, taste characteristics in applications requiring moldability, and impact resistance are achieved. It was difficult.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the above-mentioned problems of the prior art and is suitable for a metal container having excellent laminating property, moldability, taste property and impact resistance. It is to provide a polyester film for laminating metal plates.

[0006]

[Means for Solving the Problems] The above-mentioned problems have ethylene terephthalate as a main repeating unit and have a melting point of 246-
A polyester film comprising a polyester layer (I) formed by mixing 30 to 80% by weight of a polyester (A) at 270 ° C. and 70 to 20% by weight of a polyester (B) containing butylene terephthalate as a main repeating unit,
This can be achieved by a polyester film for laminating metal plates having a transesterification rate of 0.01 to 50% between the polyester (A) and the polyester (B).

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The polyester constituting the polyester film for laminating metal plates of the present invention is a general term for polymers having a main bond in the main chain as an ester bond,
Usually, it can be obtained by polycondensing a dicarboxylic acid component and a glycol component.

Examples of the dicarboxylic acid component include terephthalic acid, 2,6-naphthalenedicarboxylic acid,
Aromatic dicarboxylic acids such as isophthalic acid, diphenyl dicarboxylic 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, maleic acid Examples thereof include acids, aliphatic dicarboxylic acids such as fumaric acid, alicyclic dicarboxylic acids such as cyclohexanedicarboxylic acid, and oxycarboxylic acids such as paraoxybenzoic acid.

As the glycol component, for example,
Aliphatic glycols such as ethylene glycol, propanediol, butanediol, pentanediol, hexanediol and neopentyl glycol, polyoxyalkylene glycols such as diethylene glycol, polyethylene glycol and polypropylene glycol, alicyclic glycols such as cyclohexanedimethanol and bisphenol A. , Aromatic glycols such as bisphenol S, and the like.

The polyester (A) constituting the polyester film of the present invention is required to contain ethylene terephthalate as a main repeating unit. Here, ethylene terephthalate is a condensate using terephthalic acid as a dicarboxylic acid component and ethylene glycol as a glycol component, and the polyester (A) is preferably polyethylene terephthalate composed only of terephthalic acid and ethylene glycol. Further, other dicarboxylic acid components and glycol components may be copolymerized in a range of less than 6 mol%, and examples of the copolymerization component include the above-mentioned dicarboxylic acid components and glycol components. Further, as long as the effect of the present invention is not impaired, trimellitic acid,
A polyfunctional compound such as trimesic acid and trimethylolpropane may be copolymerized.

The melting point of the polyester (A) of the present invention must be 246 to 270 ° C. from the viewpoint of heat resistance and productivity. From the viewpoint of heat resistance, the melting point is more preferably 250 to 265 ° C.

Further, the intrinsic viscosity of the polyester (A) is preferably 0.6 to 1.0 from the viewpoint of impact resistance, and the intrinsic viscosity is 0 in applications where heat resistance and aging resistance are required. It is preferably 0.63 to 0.9, and 0.6
More preferably, it is 7 to 0.8.

The polyester (B) constituting the polyester film of the present invention needs to have butylene terephthalate as a main constituent unit. Here, butylene terephthalate is terephthalic acid as a dicarboxylic acid component,
It is a condensate using 1,4-butanediol as a glycol component, and the polyester (B) is preferably polybutylene terephthalate composed of terephthalic acid and 1,4-butanediol. Further, other dicarboxylic acid components and glycol components may be copolymerized as long as the effects of the present invention are not impaired, and the copolymerization rate is preferably less than 20 mol%. Examples of the copolymerization component include the above-mentioned dicarboxylic acid component and glycol component.

The intrinsic viscosity of the polyester (B) is preferably 1.0 or more from the viewpoint of impact resistance. It is more preferably 1.1 to 2.5, and even more preferably 1.1 to 2.0 in terms of productivity.

The polyester film of the present invention has high productivity,
It is necessary that the polyester layer (I) is formed by mixing 30 to 80% by weight of the above polyester (A) and 70 to 20% by weight of the polyester (B) from the viewpoint of laminating property, moldability and impact resistance. . Polyester (B)
If the mixing ratio exceeds 70% by weight, the crystallinity becomes high, and the film-forming property and moldability may deteriorate. On the contrary, if it is less than 20% by weight, the impact resistance may deteriorate. More preferably, the mixing ratio of the polyester (B) is 65 to 30% by weight. Further, a third component other than the polyesters (A) and (B) may be mixed as long as the effect of the present invention is not impaired.

Polyester (A) and polyester (B)
The method of mixing the polyesters is not particularly limited, but from the viewpoint of suppressing the progress of the transesterification reaction, the polyesters (A) and (B) mixed at a predetermined mixing ratio are used.
Is preferably supplied to an extruder, melt-kneaded, and then directly subjected to extrusion, casting and stretching steps to obtain the film of the present invention.

The polyester film for laminating metal plates of the present invention has a transesterification rate of 0.01 to 50% between the polyester (A) and the polyester (B) constituting the polyester layer (I) from the viewpoint of impact resistance. It is necessary to be. When the transesterification rate exceeds 50%, it is meaningless to use the polyesters (A) and (B) as a mixture, and the impact resistance becomes poor. From the viewpoint of moldability and impact resistance, the transesterification rate is more preferably 0.01 to
It is 40%, more preferably 0.01 to 30%, and even more preferably 0.01 to 20%.

A preferable method for controlling the transesterification reaction rate within the range of 0.01 to 50% is to eliminate the activity of the catalyst metal remaining in the polyester.
A method of heat-treating the polyester raw material in boiling water, a method of adding a phosphorus compound when the polyesters (A) and (B) are mixed and extruded, and the like can be used.
Here, in the method of treating in boiling water, the treatment time is preferably 0.5 to 8 hours. The phosphorus compound is preferably added in an amount of 0.001 to 10% by weight. Further preferred phosphorus compounds include
From the viewpoint of handling at the time of addition, a solid substance having a melting point of 50 ° C. or higher at room temperature is preferable.

The polyester film of the present invention has a polyester layer (I) from the viewpoint of adhesion to a metal plate and impact resistance.
It is preferable that the amount of COOH end groups is 20 to 50 mmol / kg. More preferably 25-45 mmol /
kg, and more preferably 30 to 45 mmol / kg. When the amount of COOH end groups of the polyester layer (I) exceeds 50 mmol / kg, there may be a problem in storage stability and impact resistance as a metal container.
If the amount of the terminal group is less than 20 mmol / kg, the adhesion with the metal plate is deteriorated. The amount of the COOH terminal group is 20 to 50 mmol.
There is no particular limitation on the method for controlling the amount of COOH / kg, but the amount of COOH terminal groups of the polyesters (A) and (B) is set within the respective preferred ranges, and it is possible to suppress a decrease in molecular weight during melt extrusion of film formation. This is the preferred method. In order to suppress the decrease in the molecular weight during melt extrusion, it is of course not necessary to expose the polyester to the air atmosphere after drying.
It is a preferred method to feed the extruder from the inside of a hopper heated under 00 ° C. or higher under an inert atmosphere such as nitrogen or under vacuum.

The polyester film of the present invention has a good moldability,
From the viewpoint of impact resistance, the intrinsic viscosity of the polyester layer (I) is preferably 0.7 or more. More preferably, it is within the range of 0.7 to 1.5, and the intrinsic viscosity is 0.75 to
When it is 1.5, the impact resistance is further improved, so that it is more preferable.

The polyester film of the present invention has a polyester layer (I) formed on at least one side of the polyester layer (I).
From the viewpoints of laminating properties and impact resistance, it is preferable that I) be a laminated film in which polyester (C) having a melting point of 200 to 245 ° C. is arranged. Furthermore, when the polyester layer (II) is arranged on both sides of the polyester layer (I) to form an A / B / A type laminated film, warpage of the film during film formation can be suppressed, and further It is more preferable from the viewpoint that production errors due to mistakes in the laminated surface can be prevented. Here, the polyester (C) can be obtained by polycondensation reaction of the above-mentioned dicarboxylic acid component and glycol component, and may be a copolymerized polyester. Further, the melting point of the polyester (C) is more preferably 200 to 240 ° C., and even more preferably 200 to 230 ° C., from the viewpoints of adhesion to a metal plate and impact resistance. Further, when the amount of COOH terminal groups of the polyester (C) is 25 mmol / kg or more, it is preferable in terms of adhesion to a metal, and more preferably 30 to 50 mmol / kg. Furthermore, the intrinsic viscosity of the polyester (C) is preferably 0.7 to 1.2 from the viewpoint of moldability and impact resistance.

The use of two or more different resins mixed with the polyester (C) is not particularly limited as long as it does not impair the effects of the present invention.
A resin other than polyester may be mixed and used with polyester.

Further, the polyester layer (II) comprising the polyester (C) of the present invention has a film handling property,
For the purpose of improving workability, the average particle size is 0.6 to 4.0.
It is preferable to add 0.01 to 0.5% by weight of particles having a size of μm. If the average particle size is less than 0.6 μm, the effect of adding particles is low, and conversely, if the average particle size exceeds 4.0 μm, the film may have defects such as pinholes, push scratches due to coarse projections, and scratches. Also, 0.5% by weight of particles
If it is added in excess, the film surface may be scraped during processing. The average particle size is more preferably 0.6
˜2.0 μm, more preferably 0.02 to 0.3% by weight, and even more preferably 0.02 to 0.2% by weight.

As the particles to be added, internal particles, inorganic particles and organic particles can be used, and among them, inorganic particles are preferable. Examples of the inorganic particles include wet and dry silica, colloidal silica, aluminum silicate, titanium oxide, calcium carbonate, calcium phosphate, barium sulfate, aluminum oxide, mica, kaolin, clay and the like. Further, two or more kinds of internal particles, inorganic particles and organic particles may be used in combination.

Further, it is preferable to add the above-mentioned particles to the polyester layer (I) in the above-mentioned preferable amount from the viewpoints of handleability and processability of the film especially when it is used as a single layer.

Further, the polyester layer (II) of the present invention
Has a coefficient of friction of 0.1 to 0.
3 is preferable. If the coefficient of friction is less than 0.1, winding misalignment may occur during winding during film formation,
If it exceeds 0.3, film scraping may occur during processing. The friction coefficient is more preferably 0.15
It is 0.25. As a method for setting the friction coefficient in such a range, a method achieved by adding the above-mentioned particles, or a polyester (C) containing silicone resin, wax or the like in an amount of 0.01 to
Examples thereof include a method of adding 1.0% by weight.

The metal plate laminating film of the present invention preferably has a thickness of 5 to 40 μm from the viewpoint of processability, economic efficiency and productivity, and more preferably 8 to 30 μm.
Is. When a laminated film is formed using polyester (C), the ratio of the laminated thickness is as follows: layer (I): layer (I
It is preferable that I) = 1: 1 to 19: 1. Furthermore, when the polyester film (II) is a laminated film formed by disposing the polyester layer (II) on both sides of the layer (I), the ratio of the laminated thickness is layer (II): layer (I): layer (II) = 1: 1 : 1-1: 1
It is preferably 38: 1.

The polyester film of the present invention preferably has a plane orientation coefficient within the range of 0.04 to 0.13 from the viewpoints of laminating property, moldability and impact resistance. More preferably, it is 0.05 to 0.11.
If the plane orientation coefficient exceeds 0.13, the laminate properties and moldability may deteriorate, and if the plane orientation coefficient is less than 0.04, the characteristics may deteriorate due to aging. The method for setting the plane orientation coefficient in such a range is not particularly limited, but the stretching temperature at the time of film formation, the stretching ratio,
A method that achieves appropriate control of heat setting temperature and the like is preferred.

Next, a method for polymerizing the polyester resin used in the polyester film of the present invention will be described.

In producing the polyester of the present invention, conventionally known reaction catalysts and anti-coloring agents can be used. Examples of the reaction catalyst include alkali metal compounds, alkaline earth metal compounds, zinc compounds and lead. Compound,
A manganese compound, a cobalt compound, an aluminum compound, an antimony compound, a titanium compound, a germanium compound or the like can be used, and a phosphorus compound or the like can be used as the coloring preventing agent, but it is not particularly limited thereto. From the viewpoint of content retrievability, it is preferable to use an alkali metal compound and / or an alkaline earth metal compound as a reaction catalyst.

In general, it is preferable to add an antimony compound, a germanium compound and / or a titanium compound as a polymerization catalyst at any stage before the production of 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 Japanese Patent Publication No. 54-22234, glycol as a starting material of polyester A method in which a germanium compound is dissolved and added to the components can be used.

Examples of the germanium compound include germanium dioxide, germanium hydroxide hydrate, germanium alkoxide compounds such as germanium tetramethoxide and germanium ethylene glycoloxide, germanium phenoxide compounds, germanium phosphate, germanium phosphite and the like. A phosphoric acid-containing germanium compound, germanium acetate, or the like can be used. Among them, germanium dioxide is preferably used, and amorphous germanium dioxide is particularly preferably used.

The antimony compound is not particularly limited, but for example, an oxide such as antimony trioxide,
Antimony acetate or the like is used. Further, the titanium compound is not particularly limited, but monobutyl titanate, dibutyl titanate, and titanium tetraalkoxide such as titanium tetraethoxide and titanium tetrabutoxide are preferably used.

As the polymerization catalyst for polymerizing the polyester (A) of the present invention, it is particularly preferable to use amorphous germanium dioxide among the above. Further, in the polymerization of polyester (B), it is particularly preferable to use monobutyl titanate as a polymerization catalyst.

Next, a specific example will be described. For example, in the production of polyethylene terephthalate, when germanium dioxide is added as a catalyst, a terephthalic acid component and an ethylene glycol component are transesterified or esterified, then germanium dioxide and a phosphorus compound are added, followed by high temperature, A method of obtaining a germanium element-containing polymer by polycondensation under 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 at a temperature below its melting point under reduced pressure or in an inert gas atmosphere to reduce the content of acetaldehyde to obtain a predetermined intrinsic viscosity and a carboxy terminal group. The method etc. are used.

Next, a method for producing the polyester film for laminating metal plates of the present invention will be described. The method for forming the film is not particularly limited. For example, polyesters (A) and (B) may be mixed at a predetermined ratio, or may be dried before mixing, and then sufficiently mixed. Is supplied to a known melt extruder, melted, extruded in a sheet form from a slit die, brought into close contact with a casting drum, cooled and solidified to obtain an unstretched film. Here, as a method for adhering the sheet-shaped polymer to the cooling drum, for example, a method of electrostatically applying using a wire-shaped electrode or a tape-shaped electrode, a cast method in which a water film is provided between the casting drum and the extruded polymer sheet It is possible to preferably use a method, a method in which the temperature of the casting drum is set to a glass transition point of polyester to (glass transition point −20 ° C.), and the extruded polymer is made to adhere, or a method in which a plurality of these methods are combined. Among these, the method of electrostatically applying is preferably used from the viewpoint of productivity and flatness.

Next, the unstretched film is stretched in the longitudinal direction and then stretched in the width direction, or stretched in the width direction and then stretched in the longitudinal direction. Stretching is performed by a simultaneous biaxial stretching method in which the directions are stretched substantially at the same time.

In such a stretching method, the stretching ratio employed is preferably 1.6 to 1.6 in each direction.
It is 5.5 times, more preferably 1.7 to 4.5 times.
Further, the stretching speed is preferably 1,000 to 200,000% / min, and the stretching temperature may be any temperature as long as it is within the temperature range of the glass transition point of polyester to (glass transition point + 100 ° C.). Yes, but preferably 80-
140 ° C., particularly preferably a stretching temperature in the longitudinal direction of 90 to
The stretching temperature in the width direction is preferably 125 ° C and 80 to 130 ° C. Further, the stretching may be performed plural times in each direction.

Further, the film is subjected to a 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. The heat treatment temperature may be any temperature in the range of 120 to 240 ° C, but is preferably 120 to 230 ° C from the viewpoint of moldability and impact resistance.
If the temperature is lower than this temperature, the impact resistance may deteriorate, and if the temperature is high, the moldability may deteriorate. From the viewpoint of impact resistance after molding, it is more preferably 150 to 220 ° C, and even more preferably 170 to 210 ° C. Further, the heat treatment time can be arbitrarily set within a range that does not deteriorate other characteristics, but it is usually preferable to perform the heat treatment for 1 to 30 seconds. Further, the heat treatment may be performed by relaxing the film in the longitudinal direction and / or the width direction.

The method for obtaining the laminated film, which is a preferred embodiment of the present invention, is not particularly limited, but a mixture of polyesters (A) and (B) and polyester (C) are different from each other. A coextrusion method in which a film is supplied to an extruder and laminated in a feed block installed on the upper part of a die to obtain a laminated sheet at once, a film composed of polyesters (A) and (B) is formed in advance, and polyester (C) is formed. Is laminated on a base material layer by extrusion, a polyester (C) dissolved or dispersed in a solvent is coated on an unstretched or uniaxially stretched sheet during film formation, and at least uniaxially stretched, and a laminated film is subjected to heat treatment. And a method of coating the polyester (C) dissolved or dispersed in a solvent off-line. It can be. From the viewpoint of productivity, a co-extrusion method is preferable because it allows a laminated film to be obtained all at once.

The metal plate laminating film of the present invention is preferably used for the inner surface coating of a metal container produced by drawing or ironing after laminating it to a metal plate such as an aluminum plate, a steel plate or a tin plate. You can Further, it can be preferably used as a film for the body, lid and bottom of a metal container which is not subjected to drawing or ironing, because it has good metal adhesion, moldability and impact resistance.

[0042]

The present invention will be described in detail below with reference to examples. The characteristics were measured and evaluated by the following methods.

(1) Intrinsic viscosity Polyester or polyester film was dissolved in orthochlorophenol and measured at 25 ° C. In the case of a laminated film, the (II) layer was scraped off and then subjected to the measurement.

(2) Melting point After crystallizing the polyester, about 10 mg was precisely weighed and measured with a differential scanning calorimeter (DSC2 type manufactured by Perkin Elmer Co., Ltd.) at a heating rate of 20 ° C./min to melt. The melting point was determined from the peak position of the accompanying endothermic peak.

(3) Plane Orientation Coefficient The refractive index Nx in the longitudinal direction, the refractive index Ny in the width direction and the refractive index Nz in the thickness direction of the film with respect to sodium D line were measured at 23 ° C. using an Abbe refractometer. The surface orientation coefficient was calculated from the respective refractive indexes by the following formula. that time,
Methylene iodide was used as a mount solution, and a polarizing plate analyzer was attached to the eyepiece of the refractometer for measurement.

Plane orientation coefficient = (Nx + Ny) / Nz (4) Transesterification rate Only the polyester layer (I) was scraped off, dissolved in deuterated chloroform at 3% by weight, and then subjected to proton nuclear magnetic resonance spectroscopy (1H-NMR: (500 MHz) was used to perform curve separation for the ethylene terephthalate unit / butylene terephthalate unit and the peak resulting from its transesterification, the integrated value of the peak was determined, and the transesterification reaction rate was calculated by the following formula.

(Equation) Transesterification rate = S _EB / (S
_E + S _B + S _EB ) * 100 where S _E : integrated value of peaks attributed to ethylene terephthalate, S _B : integrated value of peaks attributed to butylene terephthalate, S _EB : transesterification of ethylene terephthalate and butylene terephthalate (5) COOH end group amount Polyester or film was added to orthochlorophenol / chloroform (weight ratio 7/3) at 90 to 100 ° C. 2
It was dissolved under the condition of 0 minutes, and the potential difference was titrated with an alkali. In the case of a laminated film, the (II) layer was scraped off and then subjected to the measurement.

(6) Average particle size The polyester resin is removed from the surface of the film by a plasma low temperature ashing method to expose the particles. The treatment conditions are selected such that the polyester resin is incinerated 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 number average diameter D obtained by performing the following numerical processing with the number of particles of 5000 or more while changing the observation location is taken as the average particle diameter.

D = ΣD _i / N where D _i is the equivalent circle diameter of the particles, and N is the number of particles.

For internal particles, the section of the film may be observed by a transmission microscope.

(7) A slit film obtained by slitting a friction coefficient film into a tape having a width of 12.7 mm is run (running) on a stainless guide pin (surface roughness: Ra of 100 nm) using a tape running tester. Speed 250m / min, winding angle 60 °,
Output tension 90g, number of runs once). At this time, the friction coefficient was calculated using the following equation, where Ti is the tension on the entry side. Friction coefficient = 2.20 log (90 / Ti) (8) Laminating property A film was attached at 20 m / min to a tin-free steel steel plate (thickness 0.24 mm) heated to 215 ° C, and then rapidly cooled in a water bath at 40 ° C. did. Then, the film-laminated steel sheet was heat-treated at the highest melting point of the film + 15 ° C. for 10 seconds and then rapidly cooled again in a water tank. A rectangular sample piece having a length of 50 mm and a width of 15 mm was cut out from the laminated steel plate in the longitudinal direction. Peel off the film and the steel plate at the end of the sample piece of 10 mm, then use a tensile tester to 300 mm /
The peel strength was measured at a speed of minutes. The measurement was performed 10 times, and the average value at that time was evaluated according to the following criteria. In the case of a two-layer laminated film, the polyester layer (II) side was used as the surface to be bonded to the steel sheet. A class: 0.7 kg / 15 mm or more B class: 0.7 to 0.3 kg / 15 mm C class: less than 0.3 kg / 15 mm (7) Formability The above laminated steel sheet is formed by a draw forming machine (forming ratio (maximum thickness (maximum thickness / Minimum thickness) = 1.8) to obtain a container. Put 1% aqueous sodium chloride solution in the obtained container and keep it at 37 ° C for 5
After standing for 0 hour, a voltage of 6 V was applied to the electrode and the metal container in the sodium chloride aqueous solution, the current value after 3 seconds was read, the value was measured for 10 containers, and the average value was evaluated according to the following criteria. A class: less than 0.001 mA B class: 0.001 to 0.01 mA C class: 0.01 mA or more (8) Taste characteristics The tin-free steel plate is changed to an aluminum plate (thickness 0.22 mm), In the same manner as above, after applying pressurized steam treatment to the container made at 120 ° C for 30 minutes, fill it with water, seal it, leave it at 37 ° C for 4 weeks, and then open it and measure the turbidity of the components eluted from the film. Was carried out using a turbidimeter (high-sensitivity turbidity / colorimeter TUB801 manufactured by Yasui Kikai Co., Ltd.) and evaluated according to the following criteria. The turbidity was measured by preparing a calibration curve beforehand using a turbidity standard solution for water quality test (manufactured by Wako Pure Chemical Industries, Ltd.). A grade: less than 0.10 B grade: 0.15 to 0.10 C grade: 0.15 or more.

(9) Impact resistance The above aluminum container was subjected to pressure steam treatment, filled with water, cooled to 5 ° C., dropped from a height of 1.3 m onto a vinyl chloride tile floor surface, and then at 37 ° C. for 1 hour. Left for a week. Then, apply a voltage of 6 V to the submersible electrode and aluminum container, and
Read the current value after a second, measure about 10 containers,
The average value was evaluated according to the following criteria. Class A: less than 0.003 mA Class B: 0.003 to 0.01 mA Class C: 0.01 mA or more (Example 1) Polyester terephthalate treated with boiling water for 5 hours as polyester (A) was used as polyester (B 10% by mole of isophthalic acid copolymerized polybutylene terephthalate was mixed and used in a weight ratio of 1: 1. As the polyester (C), 12 mol% of isophthalic acid copolymerized polyethylene terephthalate added with 0.6% by weight of carnauba wax was used. The physical properties of each polyester are shown in Table 1.

Each polyester (A + B and C) was individually vacuum-dried, melt-extruded by an individual extruder, laminated in a feed block installed on the upper part of the die, and cooled to 25 ° C. from the die. It was discharged onto a metal roll while applying static electricity to obtain an A / B / A type laminated unstretched sheet.

Next, the unstretched sheet was heated to 80 ° C., stretched 3.0 times in the longitudinal direction, and stretched 3.0 times in the width direction at 95 ° C. in a tenter type stretching machine. Then, while applying 3% relaxation in a tenter, heat treatment was performed at 210 ° C. for 5 seconds and then wound to obtain a biaxially stretched laminated polyester film. When this biaxially stretched laminated polyester film was evaluated, it had the physical properties shown in Table 3 and had excellent properties as shown in Table 5.

Example 2 Polyethylene terephthalate treated with boiling water for 4 hours was used as polyester (A), and 10 mol% of isophthalic acid was used as polyester (B).
The copolymerized polybutylene terephthalate was mixed and used so that the mixing ratio of the polyester (A) was 65% by weight. Isophthalic acid 1 as polyester (C)
0 mol% copolymerized polyethylene terephthalate was used.
The physical properties of each polyester are shown in Table 1.

Each polyester (A + B and C) was individually vacuum-dried, then melt-extruded by an individual extruder, laminated in a feed block installed on the upper part of the die, and cooled to 20 ° C. from the die. It discharges on a metal roll, applying static electricity, and the A / B type laminated unstretched sheet was obtained.

Next, the unstretched sheet was heated to 85 ° C., stretched 3.2 times in the longitudinal direction and stretched 3.1 times in the width direction at 98 ° C. in a tenter type stretching machine. Then, while applying 4% of relaxation in a tenter, heat treatment was performed at 215 ° C. for 4 seconds and then wound to obtain a biaxially stretched laminated polyester film. When this biaxially stretched laminated polyester film was evaluated, it had the physical properties shown in Table 3 and had excellent properties as shown in Table 5.

(Example 3) Polyester (A) was treated with boiling water for 5 hours, and polyethylene terephthalate to which 0.1% by weight of phosphoric acid had been added in advance with a twin-screw vent type extruder was used. 5% by weight of isophthalic acid copolymerized polybutylene terephthalate added with 0.2% by weight of phosphoric acid in a twin-screw vent type extruder was used as a mixture in a weight ratio of 4: 1. As the polyester (C), 3 mol% isophthalic acid copolymerized polybutylene terephthalate was used. The physical properties of each polyester are shown in Table 1.

Each polyester (A + B and C) was individually vacuum-dried, then melt-extruded by an individual extruder, laminated in a feed block installed on the upper part of the die, and cooled to 10 ° C. from the die. It was discharged onto a metal roll while applying static electricity to obtain an A / B / A type laminated unstretched sheet.

Then, the unstretched sheet was heated to 87 ° C., stretched 3.4 times in the longitudinal direction, and stretched 3.1 times in the width direction at 103 ° C. in a tenter type stretching machine. Then, while applying 5% of relaxation in a tenter, heat treatment was performed at 200 ° C. for 4 seconds and then wound to obtain a biaxially stretched laminated polyester film. When this biaxially stretched laminated polyester film was evaluated, it had the physical properties shown in Table 3 and had the excellent properties shown in Table 5.

Example 4 As a polyester (A), 4 mol% of isophthalic acid copolymerized polyethylene terephthalate treated with boiling water for 1 hour was mixed with polybutylene terephthalate as a polyester (B) at a weight ratio of 3: 7. I used it. As the polyester (C), 17 mol% isophthalic acid copolymerized polyethylene terephthalate was used. The physical properties of each polyester are shown in Table 1.

Each polyester (A + B and C) was individually vacuum-dried, then melt-extruded by an individual extruder, laminated in a feed block installed on the upper part of the die, and cooled to 15 ° C. from the die. It discharges on a metal roll, applying static electricity, and the A / B type laminated unstretched sheet was obtained.

Next, the unstretched sheet was heated to 70 ° C., stretched 3.1 times in the longitudinal direction, and stretched 3.0 times in the width direction at 90 ° C. in a tenter type stretching machine. Then, while applying 5% of relaxation in a tenter, heat treatment was performed at 200 ° C. for 4 seconds and then wound to obtain a biaxially stretched laminated polyester film. When this biaxially stretched laminated polyester film was evaluated, it had the physical properties shown in Table 3 and had the excellent properties shown in Table 5.

Example 5 As polyester (A), 3 mol% of 2,6-naphthalenedicarboxylic acid copolymerized polyethylene terephthalate added with 0.15% by weight of phosphoric acid in a twin-screw vent type extruder was used as polyester (B). ), Polybutylene terephthalate was mixed and used in a weight ratio of 2: 3. The physical properties of each polyester are shown in Table 1. Moreover, polyester (C) was not used.

A mixture of polyesters (A) and (B) was vacuum dried, melt-extruded with a single-screw extruder, laminated in a feed block installed on the upper part of the die, and 25 ° C. from the die. An unstretched sheet was obtained by discharging onto a cooled metal roll while applying static electricity.

Next, the unstretched sheet was heated to 75 ° C., stretched 3.2 times in the longitudinal direction, and stretched 3.1 times in the width direction at 110 ° C. in a tenter type stretching machine. Then, while applying a relaxation of 3% in a tenter, a heat treatment was performed at 200 ° C. for 5 seconds and then wound to obtain a biaxially stretched polyester film. When this biaxially stretched polyester film was evaluated, it had the physical properties shown in Table 3,
As shown in Table 5, it had excellent characteristics.

Comparative Example 1 Only the polyethylene terephthalate shown in Table 3 was used. After polyethylene terephthalate was vacuum dried, melt extrusion was performed with a single-screw extruder, and discharge was performed while electrostatically applied onto a metal roll cooled to 25 ° C. from a die to obtain an unstretched sheet.

Next, the unstretched sheet was heated to 97 ° C., stretched 3.5 times in the longitudinal direction, and stretched 3.4 times in the width direction at 110 ° C. in a tenter type stretching machine. Then, while applying 3% relaxation in a tenter, heat treatment was performed at 220 ° C. for 5 seconds, and then wound up to obtain a biaxially stretched polyester film having the physical properties shown in Table 4. When this biaxially stretched polyester film was evaluated, the properties were inferior as shown in Table 5.

Comparative Example 2 Isophthalic acid 5 shown in Table 3
Mol% copolymerized polybutylene terephthalate and polyethylene terephthalate were used. After vacuum-drying each polyester, melt extrusion is performed by an individual extruder, laminated in a feed block installed on the upper part of the die, and electrostatically applied on a metal roll cooled to 15 ° C from the die. It was discharged and the laminated unstretched film of A / B / A type was wound up. The physical properties of this unstretched film are as shown in Table 4. When this film was evaluated, the properties were inferior as shown in Table 5.

Comparative Example 3 Polyethylene terephthalate was used as the polyester (A), and 5 mol% isophthalic acid copolymerized polybutylene terephthalate was used as the polyester (B) in a weight ratio of 8: 2. The physical properties of each polyester are shown in Table 2. The polyester (C) was not used.

The mixed polyesters (A) and (B) were vacuum dried, melt-extruded by an extruder, laminated in a feed block installed on the upper part of the die, and
An unstretched sheet was obtained by discharging onto a metal roll cooled to 5 ° C while applying static electricity.

Next, the unstretched sheet was heated to 93 ° C., stretched 3.2 times in the longitudinal direction, and stretched 3.1 times in the width direction at 110 ° C. in a tenter type stretching machine. Then, while applying 2% of relaxation in a tenter, heat treatment was performed at 220 ° C. for 3 seconds and then wound to obtain a biaxially stretched polyester film. When this biaxially stretched polyester film was evaluated, it had the physical properties shown in Table 4,
The characteristics were inferior as shown in Table 5.

Comparative Example 4 Polyethylene terephthalate was used as the polyester (A), polybutylene terephthalate was used as the polyester (B), and polyester (A) was used.
Were mixed and used so that the mixing ratio of was 70% by weight.
As the polyester (C), 15 mol% isophthalic acid copolymerized polyethylene terephthalate was used. The physical properties of each polyester are shown in Table 2.

Each of the polyesters (A + B and C) was individually vacuum dried, melt-extruded by an individual extruder, laminated in a feed block installed on the upper part of the die, and cooled to 20 ° C. from the die. It was discharged onto a metal roll while applying static electricity to obtain an A / B / A type laminated unstretched sheet.

Next, the unstretched sheet was heated to 85 ° C., stretched 3.2 times in the longitudinal direction, and stretched 3.2 times at 97 ° C. in the width direction in a tenter type stretching machine. Then, while applying 4% relaxation in a tenter, heat treatment was performed at 210 ° C. for 6 seconds, and then wound to obtain a biaxially stretched laminated polyester film. When this biaxially stretched laminated polyester film was evaluated, it had the physical properties shown in Table 4, and the properties were inferior as shown in Table 5.

(Comparative Example 5) Polyester (A), which was treated with boiling water for 10 minutes, was a 2,6-naphthalenedicarboxylic acid 3 mol% copolymerized polyethylene terephthalate.
As the polyester (B), 15 mol% of isophthalic acid copolymerized polybutylene terephthalate is used as the polyester (A).
The mixture was used such that the mixing ratio of was 60% by weight.
As the polyester (C), 25 mol% isophthalic acid copolymerized polyethylene terephthalate containing 0.2 wt% of candelilla wax was used. The physical properties of each polyester are shown in Table 3.

Each of the polyesters (A + B and C) was individually vacuum dried, melt-extruded by an individual extruder, laminated in a feed block installed on the upper part of the die, and cooled to 20 ° C. from the die. It discharges on a metal roll, applying static electricity, and the A / B type laminated unstretched sheet was obtained.

Next, the unstretched sheet was heated to 65 ° C., stretched 3.1 times in the longitudinal direction, and stretched 3.0 times in the width direction at 98 ° C. in a tenter type stretching machine. Then, while subjecting to 6% relaxation in a tenter, heat treatment was performed at 175 ° C. for 4 seconds, followed by winding to obtain a biaxially stretched laminated polyester film. When this biaxially stretched laminated polyester film was evaluated, it had the physical properties shown in Table 3, and the properties were inferior as shown in Table 5.

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[Table 1]

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[Table 2]

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[Table 3]

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[Table 4]

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[Table 5] The abbreviations in the above table are as follows. PET: Polyethylene terephthalate PBT: Polybutylene terephthalate PET / I *: Isophthalic acid copolymerized polyethylene terephthalate (* indicates copolymerized mol%, the same applies hereinafter) PBT / I *: Isophthalic acid copolymerized polybutylene terephthalate PET / N *: 2,6-naphthalenedicarboxylic acid copolymerized polyethylene terephthalate

[0084]

[Effects of the Invention] After being laminated on a metal plate, it can be easily molded without cracking when it is molded into a container, and cracks may be generated even when a shock such as a drop is applied after molding. And a polyester film for bonding metal plates, which is excellent in impact resistance.

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 4F071 AA45 AA46 AB18 AB21 AB25                       AB26 AF28 AH19 BA01 BB06                       BB07 BB08 BC01                 4F100 AB00D AK41A AK41C AK42B                       AL05B AT00D BA03 BA04                       BA06 BA07 BA10A CA23A                       CA23C JK11 JK16A JK16C                       JL01 JL11                 4J002 CF06W CF07X DE136 DE146                       DE236 DG046 DH046 DJ006                       DJ016 DJ036 DJ046 DJ056                       FA086 FD016 GF00

Claims (6)

[Claims] 1. A polyester (A) having ethylene terephthalate as a main repeating unit, a melting point of 246 to 270 ° C. of 30 to 80% by weight, and a butylene terephthalate as a main repeating unit of a polyester (B) 70 to 20.
A polyester film comprising a polyester layer (I) in which a weight ratio of the polyester (A) and the polyester (B) is 0.01-5.
0% polyester film for laminating metal plates. 2. The polyester film for laminating metal plates according to claim 1, wherein the polyester layer (I) has a COOH terminal group amount of 20 to 50 mmol / kg. 3. A metal composed of a laminated film in which a polyester layer (II) made of polyester (C) having a melting point of 200 to 245 ° C. is arranged on at least one surface of the polyester layer (I) according to claim 1 or 2. Polyester film for laminating boards. 4. The polyester film for laminating metal plates according to claim 3, wherein 0.01 to 0.5% by weight of particles having an average particle size of 0.6 to 4.0 μm are added to the polyester layer (II). . 5. The polyester film for laminating metal plates according to claim 3, which is a laminated film in which the polyester layer (II) is arranged on both sides of the polyester layer (I). 6. The polyester film for laminating metal plates according to claim 3, wherein the surface of the polyester layer (II) has a coefficient of friction of 0.1 to 0.3.