JP2001301025A - Biaxially oriented colored polyester film for laminating metal plate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a biaxially oriented colored polyester film for laminating a metal plate capable of manufacturing a metal can or the like having excellent beauty by laminating to the metal plate and molding and having excellent heat resistance and processability. SOLUTION: The biaxially oriented colored polyester film for laminating the metal plate comprises a polyester containing an ethylene terephthalate unit and/or an ethylene naphthalate unit as main constituents and a color tone of a value an according to a method to JIS Z-8722 of 0 to 50 and a value b of 10 to 50.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a biaxially stretched colored polyester film for laminating a metal plate, and more particularly, to a laminating process for laminating a steel or aluminum plate to a metal can or a metal can lid. The present invention relates to a biaxially stretched colored polyester film for bonding metal plates, which can exhibit excellent aesthetics and is excellent in heat resistance and workability by being used as a bonding material.

[0002]

2. Description of the Related Art Metal cans have become widespread throughout the world and have become indispensable to our daily lives. In the past, a curable resin applied to a metal plate and cured was used.However, in recent years, in order to obtain a metal can that is environmentally friendly and has excellent hygiene, for example, a copolymerized polyester film can be made of steel or aluminum. A method of manufacturing a metal can by laminating and processing a metal can has been adopted. Furthermore, in the case of beverage cans, etc., printing is performed on the outer surface of the can body for beauty and display,
A method in which a film to which a white pigment is added is attached to perform printing, or a method in which a color-printed film is attached in advance is employed. However, in metal cans, when there is a part that is not printed, or when a film that is not subjected to white pigment addition or full surface printing is pasted, the color of the metal is exposed as appearance, and it is poor in beauty Become. In particular, food cans and the like often have a larger lid and bottom area than a can body compared to a beverage can, so that the metal color is exposed as it is, often detracting from aesthetics.

[0003]

However, if color printing or the like is further performed on a portion where a metal color is exposed, the number of steps is increased, and productivity is reduced. In addition, even if a pre-printed film is bonded to a metal plate and processed, it is difficult to impart the necessary formability to the film when forming the metal plate into a shape such as a can body or a lid. It has been difficult for the film to maintain sufficient moldability and printability for application.

[0004] Therefore, the present invention provides an excellent laminating property,
While exhibiting moldability, it has a specific color tone that was not found in conventional polyester films, and can be manufactured with excellent beauty by being molded and bonded to a metal plate, and has heat resistance, An object of the present invention is to provide a biaxially stretched colored polyester film for laminating metal plates, which is excellent in processability.

[0005]

In order to achieve this object, a biaxially stretched colored polyester film for laminating a metal plate according to the present invention comprises a polyester having an ethylene terephthalate unit and / or an ethylene naphthalate unit as a main component. A according to the method of JIS Z-8722
It has a color tone having a value of 0 to 50 and a b value of 10 to 50.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION The polyester having ethylene terephthalate units and / or ethylene naphthalate units as a main component in the present invention is a polyester containing at least 70 mol% of ethylene terephthalate units and / or ethylene naphthalate units. It is preferably at least 85 mol% from the viewpoint of heat resistance and the like.
It is preferably at least mol%. Further, other dicarboxylic acid components and glycol components may be copolymerized.Examples of the dicarboxylic acid components 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, maleic acid, aliphatic dicarboxylic acids such as fumaric acid, cyclohexyne dicarboxylic acid, etc. Oxycarboxylic acids such as alicyclic dicarboxylic acids and p-oxybenzoic acid can be used. On the other hand, examples of the glycol component include aliphatic glycols such as propanediol, butanediol, pentanediol, hexanediol and neopentyl glycol, and alicyclic glycols such as cyclohexanedimethanol. And aromatic glycols such as bisphenol A and bisphenol S, and diethylene glycol. In addition, these dicarboxylic acid components,
Two or more glycol components can be used in combination.

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

Preferred components which are copolymerized in a small amount into the polyester used in the present invention are butanediol, diethylene glycol, polyethylene glycol, cyclohexanedimethanol, sebacic acid, adipic acid, dimer acid, isophthalic acid and naphthalenedicarboxylic acid.

In the present invention, the melting point is preferably 246 ° C. or more and 280 ° C. or less, more preferably 248 ° C. or more and 275 ° C., from the viewpoint of suppressing temporal change after molding.
It is below ° C.

[0010] The film of the present invention is manufactured according to JIS Z-872.
According to the method 2, the a value is 0 to 50 and the b value is 10 to 5
It is necessary to have a color tone that is zero. By setting the a value and the b value within these ranges, after the film is bonded to a metal plate, the film has a golden appearance and is excellent in beauty. Here, the value a is preferably 0.5 to 40, particularly preferably 1 to 30, and the value b is preferably 15 to 45, particularly preferably 20 to 40. Further, it is preferable that the L value is 40 to 90 from the viewpoint of improving the visual impression. In order to keep the a value, b value, and L value within these ranges, it is preferable to select a coloring agent such as an inorganic pigment, an organic pigment, or a dye and add it to the film.

Further, in the present invention, the rate of change (b1) of the b value before and after the dry heat treatment at 200 ° C. for 1 minute is 0 to 0.
It is preferably 20%, more preferably 0 to 10%.
%. The rate of change (b2) of the b value before and after the retort treatment at 120 ° C. for 20 minutes is preferably 0 to 20%, more preferably 0 to 10%. In order to use it particularly favorably under high temperature or under retort,
The heat resistance of the colorant added to the film is important. For example, the weight loss at 200 ° C. is 5% or less, and the weight loss at 300 ° C. is 5%.
It is preferable to use the following coloring agents.

The inorganic pigments used in the present invention include titanium oxide, calcium carbonate, barium sulfate, aluminum oxide, silicon dioxide, carbon black, iron oxide, chromium oxide, zinc white, lead white, redwood, cadmium red and yellow. Lead, cobalt blue, cobalt purple, zinc chromate and the like. These inorganic pigments can be surface-treated with an oxide such as aluminum, silicon, or zinc in order to improve dispersibility and processability in the polyester.
As organic pigments, condensed azo, isoindolinone,
Perinone, quinacridone, diketopyrrolopyrrole, anthraquinone, dioxazine, benzimidazolone, copper phthalocyanine (β), metal complex azo, chlorinated copper phthalocyanine (α), allyl amide, azo (C
a), diallylide AA, diallylide MX, diallylide HR, pyrazolone naphthol red, BON allyl amide, 2B toner (Ca), 4B toner (C
a), copper phthalocyanine (α), copper phthalocyanine halide, naphthol, dioxazine, naphthol AS,
Diarylide OT, pyrazolone, lake red C (B
a), BON allyl amide and the like can be used. On the other hand, chromium complexes, cobalt complexes,
Phthalocyanine, methine, anthraquinone and the like can be used. Two or more of these colorants can be used in combination. In particular, in the present invention, it is preferable to use an anthraquinone-based, quinacridone-based, benzimidazolone-based, or diketopyrrolopyrrole-based coloring agent.

The colorant to be incorporated into the polyester film of the present invention may be added during the polymerization reaction of the polyester, or after the polymerization, the colorant is kneaded and dispersed using, for example, a twin-screw extruder to form a master. A method of producing pellets, blending them in a predetermined amount, and incorporating them in a polyester film may be employed. As a method of adjusting the content of the coloring agent, a master pellet containing a coloring agent at a high concentration is prepared by the above-described method, and a pellet containing substantially no coloring agent and a master pellet are mixed at a predetermined level. A method of diluting to the colorant content is effective. The colorant may be subjected to a process such as crushing, dispersion, classification, and filtration as needed.

The colorant preferably has an average particle size of 0.0
1 to 0.5 μm, more preferably 0.01 to 0.5 μm.
0.3 μm. If the average particle size exceeds 0.5 μm, the film surface becomes too rough and printing may be difficult, or the film may be easily defective, which is not preferable.

The content of the colorant is preferably 0.1 to 50% by weight, more preferably 1 to 20% by weight. If the content is less than 0.1% by weight, the whole film is easily seen through, and a desired color tone is hard to appear, which is not preferable. On the other hand, when the content exceeds 50% by weight, the coloring agent is apt to aggregate, resulting in a defect of the film, and the strength of the film is liable to decrease. In particular, when an organic pigment or dye is used as a coloring agent, the content is preferably 1 to 25% by weight, more preferably 3 to 20% by weight, and still more preferably 5 to 15% by weight. If the amount exceeds 25% by weight, the color tone may be changed due to thermal decomposition, thermal deterioration, sublimation, etc. in the drying or melt extrusion step, resulting in loss of the colorant.

As a film configuration, two layers of A / B, A
It may have a three-layer structure of / B / A or A / B / C, or a multilayer structure having more than three layers, and the thickness ratio of the layers may be arbitrarily set. The colorant-containing layer may be any one of the layer A, the layer B, and the layer C, or the entire layer may be a layer containing the colorant.

In the present invention, it is necessary to biaxially stretch a polyester containing ethylene terephthalate unit and / or ethylene naphthalate unit as a main component in view of heat resistance and impact resistance after processing. The method of biaxial stretching may be either simultaneous biaxial stretching or sequential biaxial stretching. For a biaxially stretched film, the average value of the elongation at break in the longitudinal direction and the elongation at break in the width direction at 100 ° C. is 200 to 500% from the viewpoint of handling properties and workability in the manufacturing process and the like. Preferably, it is more preferably from 250 to 450%. Further, in order for the workability to be uniform and good in each direction, the absolute value of the difference between the breaking elongation in the longitudinal direction and the breaking elongation in the width direction at 100 ° C. is 50%.
It is preferably at most 40%, particularly preferably at most 40%. Further, the average value of the breaking elongation in the direction inclined at 45 degrees clockwise from the longitudinal direction at 100 ° C. and the breaking elongation in the direction inclined at 135 degrees is preferably 200 to 500% or less, more preferably. Is 250-450%. Further, the absolute value of the difference between the breaking elongation in the longitudinal direction at 100 ° C. and the breaking elongation in the direction inclined 45 degrees clockwise from the longitudinal direction is preferably 50% or less, particularly preferably 40% or less. is there.

Here, the elongation at break was measured using a Tensilon (tensile tester) at a tensile speed of 500 mm / min.
And a test piece with a width of 10 mm and a sample length of 50 mm,
It is an elongation at break (%) measured in an atmosphere at 65 ° C. and 65%.

In the present invention, the intrinsic viscosity of the polyester is preferably 0.4 to 1.5 dl / g, more preferably 0.5 to 1.3 dl / g, particularly preferably 0 to 1.3 dl / g from the viewpoint of processability and heat resistance. 0.6 to 1.2.

In the present invention, the density of the film is 1.3.
5 to 1.41 g / cm^ThreeIs good for workability.
In particular, particularly preferably 1.36 to 1.4 g /
cm ^Three It is. Moldability due to wrinkles etc. when density is too low
Deteriorates, and if the density is too high, the workability will vary.
It will be.

In producing the polyester used in the present invention, a reaction catalyst 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. Can be used. Preferably, it is preferable 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 usually completed. As such a method, for example, when a germanium compound is used, for example, a method in which a germanium compound powder is added as it is, or as described in Japanese Patent Publication No. 54-22234, the starting material of a polyester is used. Examples thereof include a method in which a germanium compound is dissolved in a certain glycol component and then added. As the germanium compound, for example, germanium dioxide, germanium hydroxide containing water of crystallization, or germanium tetramethoxide,
Germanium alkoxide compounds such as germanium tetraethoxide, germanium tetrabutoxide, germanium ethylene glycoloxide, and germanium phenol
And germanium phenoxide compounds such as germanium β-naphtholate; phosphorus-containing germanium compounds such as germanium phosphate and germanium phosphite; and germanium acetate. Among them, germanium dioxide is preferable. As the antimony compound, for example, antimony oxide such as antimony trioxide, antimony acetate and the like can be used. As the titanium compound, an alkyl titanate compound such as tetraethyl titanate and tetrabutyl titanate is 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,
Subsequently, a polycondensation reaction is carried out under a high temperature and a reduced pressure until a constant diethylene glycol content is obtained, thereby obtaining a polymer containing germanium element. Furthermore, preferably, the obtained polymer is subjected to a solid-phase polymerization reaction under reduced pressure or an inert gas atmosphere at a temperature not higher than its melting point, to reduce the content of acetaldehyde, and to obtain a predetermined intrinsic viscosity and a carboxyl end group. And the like.

In the present invention, from the viewpoint of improving the compatibility between the polyester and the colorant, the polyester preferably has a carboxyl terminal group content of 30 to 55 equivalents / ton,
It is more preferably 35 to 50 equivalents / ton, particularly preferably 40 to 48 equivalents / ton.

The polyester in the present invention preferably has a diethylene glycol content of 0.01 to 4% by weight,
More preferably, the content is 0.01 to 3% by weight, particularly preferably 0.01 to 2% by weight, in order to maintain good hygiene even when subjected to heat history after aging or processing. Further, an antioxidant may be added in an amount of 0.0001 to 1% by 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 hygiene, the content of acetaldehyde in the film is preferably 30 ppm.
The content is more preferably at most 25 ppm, particularly preferably at most 20 ppm. In order to reduce the content of acetaldehyde in the film to 30 pm or less, a method of removing acetaldehyde generated by thermal decomposition when producing a polyester by a polycondensation reaction or the like may be used. Under a gas atmosphere, a method of performing a heat treatment at a temperature equal to or lower than the melting point of the polyester, preferably a method of performing solid phase polymerization of the polyester at a temperature of 150 ° C. or higher under a reduced pressure or an inert gas atmosphere at a temperature equal to or lower than the melting point, The method of melt-extrusion using a polymer, the extrusion temperature at the time of melt-extrusion of the polymer is set to the melting point of the high-melting polymer side + 30 ° C or less, preferably the melting point +
25 ° C or less, short time, preferably average residence time 1
Extrusion method or the like may be performed within an hour.

As a method for producing a biaxially stretched film in the present invention, for example, after drying each polyester as necessary, it is supplied to a known melt extruder, extruded into a sheet from a slit die, and subjected to electrostatic application. In such a manner, it is brought into close contact with the casting drum and solidified by cooling to obtain an unstretched sheet. The stretching method may be either simultaneous biaxial stretching or sequential biaxial stretching, but the unstretched sheet is stretched in the longitudinal direction and width direction of the film and heat-treated to obtain a film having a desired degree of plane orientation. From the viewpoint of the quality of the film, a tenter method is preferable, and after stretching in the longitudinal direction, a sequential biaxial stretching method in which the film is stretched in the width direction and a simultaneous biaxial stretching method in which the film is stretched almost simultaneously in the longitudinal direction and the width direction are desirable. . The stretching ratio is 1.5 to 4.0 times, preferably 1.8 to 4.0 times in each direction. Either the stretching ratio in the longitudinal direction or the stretching ratio in the width direction may be increased, and may be the same. The stretching speed is preferably from 1000% / minute to 200,000% / minute, and the stretching temperature can 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 + 80 ° C. 80-150 ° C is preferred. After the biaxial stretching, the film is subjected to a heat treatment, such as in an oven or on a heated roll.
It can be performed by any conventionally known method. The heat treatment temperature can be any temperature between 120 ° C. and 245 ° C., but is preferably between 120 and 240 ° C. The heat treatment time can be arbitrarily set, but is usually 1 to 60.
It is preferably performed for 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.

Further, in order to improve the handleability and workability of the film of the present invention, the average particle diameter is 0.01 to 10 μm.
It is preferable that 0.01 to 50% by weight of particles arbitrarily selected from among external particles such as internal particles, inorganic particles and / or organic particles is contained. In particular, the average particle size is 0.
It is preferable for the film used on the inner surface of the can to contain 0.01 to 3% by weight of internal particles, inorganic particles and / or organic particles of 1 to 5 μm. As a method for precipitating internal particles, for example, techniques described in JP-A-48-61556, JP-A-51-12860, JP-A-53-41355, JP-A-54-90397 and the like are described. No. Further, it can be used in combination with other particles such as JP-A-55-20496 and JP-A-59-204617. 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. Examples of the inorganic particles and / or organic particles include inorganic particles such as wet and dry silica, colloidal silica, aluminum silicate, titanium oxide, calcium carbonate, calcium phosphate, barium sulfate, alumina, mica, kaolin, and clay, and styrene, silicone, and acrylic. Organic particles containing an acid or the like as a component can be used. Among them, wet and dry colloidal silica, inorganic particles such as alumina and styrene, silicone, acrylic acid,
Organic particles containing methacrylic acid, polyester, divinylbenzene and the like as constituent components can be exemplified. Two or more of these internal particles, inorganic particles and / or organic particles may be used in combination.

Further, from the viewpoint of adhesion, the center line average roughness Ra is preferably 0.005 to 0.07 μm, more preferably 0.008 to 0.05 μm. further,
When the ratio Rt / Ra between the maximum roughness Rt and the center line average roughness Ra is 4 to 50, preferably 6 to 40, the high-speed can-making property is improved.

It is preferable that the film is subjected to a surface treatment such as a corona discharge treatment to improve the adhesiveness to a metal plate from the viewpoint of further improving the characteristics. that time,
The treatment strength is 5 to 50 W · min / m ² , preferably 10 to 45 W · min / m ² .

In the polyester film of the present invention, additives such as an antistatic agent, a heat stabilizer, an antioxidant, a crystal nucleating agent, a weathering agent, and an ultraviolet absorber may be used to such an extent that the object of the present invention is not impaired. it can. Also, embossing,
Surface irregularities such as sand matting, or surface treatments such as corona discharge treatment, plasma treatment, and alkali treatment may be performed as necessary. Further, the film of the present invention may have an adhesive agent, an antistatic agent, a water vapor / gas barrier agent (such as polyvinylidene chloride), a release agent, an adhesive, an adhesive, a flame retardant, an ultraviolet absorber, a matting agent, a pigment, Coating and printing of dyes and the like may be performed, and metals such as aluminum, aluminum oxide, silicon oxide and palladium and their compounds may be vacuum-deposited for the purpose of shading, water vapor / gas barrier, surface conductivity, infrared reflection, etc. The purpose and method are not limited to the above.

The polyester film of the present invention can be suitably used as a metal plate laminating film, but is preferably used on the outer surface of a metal can or a metal can lid from the viewpoint of beauty.

[Measurement and evaluation methods of physical properties and characteristics]
Methods for measuring and evaluating various physical properties and characteristics used in the description of the present invention or the examples described later will be described.

(1) Melting point (Tm) Measured using a differential scanning calorimeter DSC2 (manufactured by PerkinElmer). Sump 10 mg under nitrogen flow 280
C. for 5 minutes, and then quenched with liquid nitrogen. The endothermic peak temperature based on crystal melting in the process of heating the obtained sample at a rate of 10 ° C./min was measured and defined as a melting point (Tm).

(2) Film elongation -I, -II, -III The elongation at break in the longitudinal direction, the elongation at break in the width direction of the film,
Elongation at break inclined 45 degrees clockwise from the longitudinal direction,
And the breaking elongation in the direction inclined 135 degrees clockwise from the longitudinal direction was measured at 100 ° C by a method according to ASTM-D-882-81 (Method A). The following values were determined from the respective breaking elongations, and the respective values were ranked.
Class A and Class B are acceptable.

Film elongation-I = Average value of the elongation at break in the longitudinal direction and the elongation at break in the width direction, Class A: The average value is 300% or more and 500% or less. Class B: The average value is 200%. Above, less than 300% Class C: average value of 0 to less than 200% Film elongation-II = absolute value of difference between breaking elongation in longitudinal direction and breaking elongation in width direction, Class A: absolute value of the difference Value 0 to less than 50% Class B: Absolute value of the difference is 50% or more and less than 100% Class C: Absolute value of the difference is 100% or more Film elongation-III = 45 clockwise from the longitudinal direction
The average value of the breaking elongation in the direction inclined at an angle of 135 ° and the breaking elongation in the direction inclined at 135 °, Class A: The average value is 300% or more and 500% or less. Class B: The average value is 200% or more and 300%. Less than C class: The average value is 0 to less than 200%. (3) Intrinsic viscosity (IV) Polyester is dissolved in orthochlorophenol,
Measured in ° C.

(4) Color Tone Color Analyzer (TC-180 manufactured by Tokyo Denshoku Co., Ltd.)
The color tone was measured according to the method of JIS Z-8722 using L, a, b values.

(5) Heat resistance The film is subjected to dry heat treatment at 200 ° C. for 1 minute, and b before and after the treatment.
The absolute value of the difference between the values was divided by the b value before processing, and the value expressed as a percentage was defined as a change rate b1 (%). Based on the values, ranking was made as follows.

Class A: 0-5% or less Class B: 5-10% or less Class C: More than 10%.

(6) Retort Resistance The film was retorted at 120 ° C. for 20 minutes, and the absolute value of the difference between the b values before and after the treatment was divided by the b value before the treatment, and the value expressed as a percentage was expressed as a percentage change b2 ( %). Based on the values, ranking was made as follows.

Class A: 0 to 10% or less Class B: 10 to 20% or less Class C: More than 20%.

(7) Workability of laminated steel sheet A reduction rate of 30 from a steel sheet laminated with a film
% Of the cans, and were ranked as follows according to the state of the obtained cans.

Grade A: The film has no whitening, cracks or overlapping wrinkles.

Grade B: wrinkles and slight whitening are seen on the film,
No cracks.

Class C: Whitening, cracks and overlapping wrinkles are observed on the film.

[0045]

The present invention will be described below with reference to examples.

Example 1 An ethylene glycol slurry containing agglomerated silica particles as a polyester was heat-treated at 190 ° C. for 2 hours, and after the esterification reaction was completed in the polymerization step using an amorphous germanium catalyst, the above slurry was used. And a polycondensation reaction is carried out to produce a chip A of polyethylene terephthalate (intrinsic viscosity: 0.65, diethylene glycol: 2.8 mol%) containing 0.1% by weight of aggregated silica particles having an average particle diameter of 1.4 μm. did. On the other hand, a colored master chip B obtained by adding 30% of an anthraquinone compound to chip A
Was manufactured. A chip A and a master chip B are vacuum-dried at 180 ° C. for 3 hours each by a predetermined amount, and then supplied to a single screw extruder. After discharging from a normal die, a mirror cooling drum (drum rotation speed) is applied while applying static electricity (7 kv). (40 m / min) to obtain an unstretched film containing 10% of an anthraquinone compound. The unstretched film is heated at a temperature of 105
After stretching 2.8 times in the longitudinal direction at ℃, cooling to 40 ° C, preheating at 115 ° C for 5 seconds, stretching 2.8 times in the width direction at the same temperature, relaxing at 180 ° C 5%, 5% After heat treatment for 2 seconds, a biaxially stretched colored polyester film having a thickness of 25 μm was obtained. The properties of the obtained colored polyester film were as shown in Table 1.

The obtained film was laminated on a TFS steel sheet (thickness: 0.2 mm) heated to its melting point + 30 ° C. at a rate of 70 m / min, and then quenched in a 50 ° C. water bath. The appearance of the obtained laminated steel sheet was golden and excellent in beauty, and the workability when forming into a can was good.

Examples 2 to 3 Example 1 except that the kind of polyester and the colorant were changed.
A colored polyester film was obtained in the same manner as described above. The results are shown in Table 1. The appearance of the obtained film-laminated steel sheet was golden, indicating good beauty.

Comparative Example 1 As a polyester, an ethylene glycol slurry containing aggregated silica particles was heat-treated at 190 ° C. for 2 hours, and then the slurry was added at the stage after the completion of the esterification reaction in the polymerization step using an antimony-based catalyst. Then, a polycondensation reaction was carried out, and aggregated silica particles having an average
A chip of polyethylene terephthalate containing 0.6% by weight (intrinsic viscosity: 0.61, containing 3 mol% of diethylene glycol) was produced. After vacuum drying at 180 ° C. for 3 hours, the mixture is supplied to a single screw extruder, discharged from a normal die, and then subjected to electrostatic application (7 k
v) Mirror cooling drum (drum rotation speed 40m /
Min) and solidified by cooling to obtain an unstretched film. The unstretched film is stretched 3.4 times in the longitudinal direction at a temperature of 90 ° C., cooled to 40 ° C., preheated at 105 ° C. for 5 seconds, stretched 3.5 times in the width direction at the same temperature, and then 220 ° C. 3% relaxed, heat treated for 5 seconds, and biaxially stretched thickness 25μ
m polyester film was obtained. The results are shown in Table 1. The appearance of the obtained film-laminated steel sheet was a steel sheet color, which was inferior in beauty.

Comparative Example 2 Comparative Example 1 was repeated except that polyethylene terephthalate obtained by copolymerizing 15 mol of adipic acid was used as the polyester.
A polyester film was produced and evaluated in the same manner as described above, and found to be inferior in heat resistance and beauty.

[0051]

[Table 1] The symbols in the table are as follows. PET: Polyethylene terephthalate PET / I: Polyethylene terephthalate copolymerized with isophthalic acid (5 mol%) PET / A: Polyethylene terephthalate copolymerized with adipic acid (15 mol%)

[0052]

According to the present invention, a metal can having excellent beauty can be manufactured by laminating a metal plate to form a metal can. An axially stretched colored polyester film can be provided.

Since the laminated steel sheet obtained by laminating the film of the present invention on a metal plate is excellent in beauty and formability, it is possible to easily produce metal cans excellent in beauty and appearance.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification code FI Theme coat ゛ (Reference) C08K 5/3447 C08K 5/3447 C08L 67/02 C08L 67/02 // B29K 67:00 B29K 67:00 B29L 7:00 B29L 7:00 F term (reference) 4F071 AA44 AA46 AA84 AE09 AF21 AF34 AH05 BB08 BC01 4F100 AA20H AB01B AB03 AH02H AH03H AK41A AK42A BA02 CA13A CA19 DE01H EJ38A GB16 GB23 JJ03 JL01J05A10G12A01Q10 QW12 4J002 CF061 CF081 EE056 EU026 EU116 FD096

Claims (7)

[Claims] 1. A color tone comprising a polyester having an ethylene terephthalate unit and / or an ethylene naphthalate unit as a main component and having an a value of 0 to 50 and a b value of 10 to 50 according to the method of JIS Z-8722. A biaxially stretched colored polyester film for laminating a metal plate. 2. The biaxial for laminating metal plates according to claim 1, wherein the average value of the elongation at break in the longitudinal direction and the elongation at break in the width direction at 100 ° C. is 200 to 500%. Stretched colored polyester film. 3. The biaxially stretched colored polyester film for laminating metal plates according to claim 1, wherein the melting point is 246 to 280 ° C. 4. The metal plate bonding method according to claim 1, wherein a change rate (b1) of the b value by the dry heat treatment at 200 ° C. for 1 minute is 0 to 20%. Biaxially stretched colored polyester film. 5. The metal plate bonding method according to claim 1, wherein the rate of change of the b value (b2) by the retort treatment at 120 ° C. for 20 minutes is 0 to 20%. Biaxially stretched colored polyester film. 6. The biaxially stretched colored polyester film for laminating a metal plate according to claim 1, which is used as a laminating material on the outer surface side of a metal can or a metal can lid. 7. The composition according to claim 1, further comprising 0.1 to 50% by weight of at least one coloring agent selected from the group consisting of anthraquinone type, quinacridone type, benzimidazolone type and diketopyrrolopyrrole type. 6. The biaxially stretched colored polyester film for bonding a metal plate according to any one of 6.