JP2001026088A - Polyester film for three-piece metal can laminate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve adhesiveness, printability and taste characteristics by providing an easy adhesive coating film layer on the single surface of a polyester film and setting the surface tension of the other surface of the polyester film to a specific value. SOLUTION: An easy adhesive coating film layer is provided on the single surface of a polyester film and the surface tension of the other surface of the polyester film is set to 45 mN/m or more. As a method for forming the coating film layer, an in-line coating method wherein a coating agent is applied to the polyester film before orientation/crystallization is completed and the coated film is stretched at least unidirectionally to be heat-treated to complete orientation/crystallization is pref. from a viewpoint of the uniform formation of a coating film or productivity. It is most pref. to form the easy adhesive coating film layer from a polyester resin and the thickness of the coating film is pref. 0.001-1 μm from a viewpoint of adhesiveness and the recovery/ reutilization properties of the film. The heat shrinkage factors of the film in the longitudinal and lateral directions thereof at 80 deg.C are set to 0.4% or less and the ethylene glycol content of the film is pref. 0.01-3.5 wt.% The m.p. of the film is set to 240-280 deg.C and the intrinsic viscosity thereof is pref. 0.55-0.75.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a polyester film for laminating a three-piece metal can.
More specifically, it is easy to adhere to the inner and outer surfaces of a metal can, and when used on the inner surface,
The present invention relates to a polyester film for laminating a three-piece metal can having excellent taste characteristics and, when used on the outer surface, excellent in design and beauty.

[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 coating and printing process of the thermosetting resin requires a long time for drying of the paint and the ink, 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, a film is laminated via an adhesive to a steel plate, an aluminum plate, or a metal plate obtained by subjecting the metal plate to various surface treatments such as plating. There is a way to do that. When manufacturing a metal can using a metal plate on which a film is laminated, the film is required to have the following characteristics. (1) Excellent affinity with the adhesive. (2) Adhesive and, therefore, excellent adhesion to the metal plate. (3) The polyester film shall not peel, crack or pinhole due to impact on the metal can. (4) When used on the inner surface of a can, the taste and olfactory components of the contents of the can are not adsorbed to the film, or the flavor of the contents is not impaired by the eluate from the film (hereinafter, referred to as
Described as taste characteristics). (5) When used on the outer surface of a can, it must have excellent affinity between the film and the printing ink due to its beauty and design, as well as its adhesion to the metal plate (hereinafter referred to as printability). ).

Many proposals have been made to solve these requirements. For example, Japanese Patent Application Laid-Open No. 5-43859 discloses an adhesive for bonding a film and a metal plate. Further, Japanese Patent Application Laid-Open No. 5-112361 discloses an organic coating having a multilayer structure on a metal plate. Further, Japanese Patent Application Laid-Open No. 7-97469 discloses a foamed white film for printing on the outer surface of a can. However, these proposals do not always satisfy the above-mentioned various required characteristics comprehensively, and at the same time, satisfy both taste characteristics in applications where excellent adhesiveness, printability and impact resistance are required. It was difficult.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems of the prior art,
3. Suitable for use by laminating on the inner surface and outer surface of a three-piece metal can having excellent printability and taste characteristics.
An object of the present invention is to provide a polyester film for laminating piece metal cans.

[0006]

The object of the present invention is to provide a polyester film for laminating a three-piece metal can in which an easily adhesive coating layer is provided on one side of a polyester film and the surface tension on the opposite side is 45 mN / m or more. Can be achieved.

[0007]

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 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, and maleic Examples thereof include aliphatic dicarboxylic acids such as acid and fumaric acid, alicyclic dicarboxylic acids such as cyclohexanedicarboxylic acid, and oxycarboxylic acids such as p-hydroxybenzoic 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.

The polyester of the present invention is preferably a polyester whose main constituent unit is an ethylene terephthalate unit and / or an ethylene 2,6-naphthalenedicarboxylate unit. On the other hand, another dicarboxylic acid component and a glycol component may be copolymerized as long as the taste characteristics are not impaired. The copolymerization component is not particularly limited, and examples thereof include the above-described dicarboxylic acid component and glycol component. In addition, two or more of these dicarboxylic acid components and glycol components may be used in combination. From the viewpoint of taste characteristics, diphenyl dicarboxylic acid, 5-sodium sulfone dicarboxylic acid, cyclohexane dimethanol, and neopentyl glycol are preferred.

In the polyester film of the present invention, it is necessary to provide an easily adhesive coating layer on one side of the film from the viewpoint of adhesiveness and printability. As a method of forming a coating, a resin is coated on the surface (a composite melt extrusion method, a hot melt coating method,
In-line, off-line coating, etc. from solvents other than water, water-soluble and / or water-dispersible resins)
A surface lamination method of the same composition or a blend thereof may be used. Above all, an in-line coating method in which a coating coating is applied to a film before the completion of the orientation crystallization, stretched in at least one direction, and heat-treated to complete the orientation crystallization is applied in view of uniform film formation and productivity. Is preferred.
Inline coating can be performed according to a known method,
There is no particular limitation.

[0010] In the present invention, the easily adhesive coating layer preferably comprises a resin selected from a polyester resin, an acrylic resin and a urethane resin as a main component, but is not limited thereto. Among these, it is most preferable to use a polyester resin.

Here, the polyester resin has an ester bond in a main chain or a side chain, and can be arbitrarily selected from conventionally known polyester resins.
As the acid component, for example, sulfone represented by sulfoterephthalic acid, 5-sulfoisophthalic acid, 2-sulfoisophthalic acid, 4-sulfoisophthalic acid, 4-sulfonaphthalene 2,6-dicarboxylic acid from the viewpoint of adhesiveness Dicarboxylic acids containing a group are preferred. Examples of the carboxylic acid component containing no sulfone group include terephthalic acid, isophthalic acid, orthophthalic acid, and 2,6-naphthalenedicarboxylic acid. Examples of the aliphatic and alicyclic dicarboxylic acids include succinic acid, adipic acid, sebacic acid, dodecandioic acid, dimer acid, 1,3-cyclopentanedicarboxylic acid, 1,2-cyclohexanedicarboxylic acid, and 1,4-cyclohexane. Dicarboxylic acid and the like.

The polycarboxylic acids include, for example, trimellitic acid, trimellitic anhydride, pyromellitic acid, 4-methylcyclohexene-1,2,3-tricarboxylic acid, trimesic acid, 1,2,3,4 -Butanetetracarboxylic acid, 1,2,3,4-pentanetetracarboxylic acid, 3,3 ′, 4,4′-benzophenonetetracarboxylic acid, 5- (2,5-dioxotetrahydrofurfuryl) -3- Methyl-3-cyclohexene-1,2-dicarboxylic acid, 5- (2,3-dioxotetrahydrofurfuryl) -3-cyclohexene-1,2-dicarboxylic acid,
Cyclopentanetetracarboxylic acid, 2,3,6,7-naphthalenetetracarboxylic acid, 1,2,5,6-naphthalenetetracarboxylic acid, thiophene-2,3,4,5-tetracarboxylic acid, ethylene glycol bis trimellit Tate, 2,2 ′, 3,3′-diphenyltetracarboxylic acid, ethylenetetracarboxylic acid and the like. Among them, trimellitic acid, pyromellitic acid, 5- (2,5
-Dioxotetrahydrofurfuryl) -3-methyl-3
-Cyclohexene-1,2-dicarboxylic acid and the like are preferably used.

The glycol components include ethylene glycol, diethylene glycol, polyethylene glycol,
Propylene glycol, polypropylene glycol,
1,3-propanediol, 1,3-butanediol,
1,4-butanediol, 1,5-pentanediol,
1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 2,4-dimethyl-2
-Ethylhexane-1,3-diol, neopentyl glycol, 2-ethyl-2-butyl-1,3-propanediol, 2-ethyl-2-isobutyl-1,3-propanediol, 3-methyl-1, 5-pentanediol, 2,2,4-trimethyl-1,6-hexanediol, 1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, 2,2,4 4-tetramethyl-1,3-
Cyclobutanediol, 4,4′-thiodiphenol,
4,4'-methylenediphenol, 4,4 '-(2-norbornylidene) diphenol, 4,4'-dihydroxybenzene, o-, m- and p-dihydroxybenzene, 4,4'-isopropylidenephenol, Cyclopentane-1,2-diol, cyclohexane-1,2-
Diol, cyclohexane-1,4-diol and the like.

In the present invention, the acrylic resin and / or urethane resin constituting the film can be selected from conventionally known acrylic resins and / or urethane resins, but is not particularly limited.

The coating of the present invention preferably contains a crosslinking agent or a chain extender, and examples thereof include melamine compounds, oxazoline compounds, epoxy compounds, and isocyanate compounds.
In particular, it is preferable to contain a melamine compound in an amount of 0.01 to 30% by weight in order to improve the adhesiveness. Examples of the melamine compound include melamine, methylolated melamine derivatives obtained by condensing melamine and formaldehyde, compounds partially or completely etherified by reacting methylolated melamine with a lower alcohol, and mixtures thereof. The melamine compound is a monomer,
Any of a dimer and a condensate composed of a multimer or more may be used, and a mixture thereof may be used. Among them, compounds obtained by partially etherifying methylolated melamine derivatives and mixtures thereof are preferable from the viewpoints of water solubility, reactivity, storage stability, constitution, and the like, but are not limited thereto.

The thickness of the coating of the present invention is not particularly limited, but is preferably from 0.001 to 1 μm, and more preferably from 0.005 to 0.3 μm, from the viewpoints of adhesiveness and recyclability of the film.
m.

The polyester film of the present invention has a metal can / adhesive layer / adhesive layer /
In the case of / film // printing ink layer // overcoat layer, the viewpoint of the adhesion between the film and the adhesive layer and thus the metal plate and the adhesion between the film and the printing ink layer, and the structure is the metal plate // adhesion In the case of the agent layer // printing ink layer // film // overcoat layer, the film is easily adhered from the viewpoint of the adhesion between the film and the printing ink layer, and furthermore, the adhesive layer // the metal plate and the film and the overcoat layer. It is necessary that the surface tension on the side opposite to the functional coating layer is 45 mN / m or more. Further, from the viewpoint of productivity, the upper limit of the surface tension is preferably less than 60 mN / m. When the surface tension is less than 45 mN / m, the printability such as the affinity with the adhesive, the adhesive strength with the metal plate, the aesthetics, and the design is deteriorated. Further, when the surface tension is 48 mN / m or more, it is preferable from the viewpoint of printability such as adhesion, adhesion, aesthetics, and design, and when the surface tension is 50 mN / m or more, the adhesiveness and printability are further improved. More preferred. The method for setting the surface tension to the value or more is not particularly limited as long as the effect of the present invention is not impaired. For example, a surface treatment such as a method of applying a corona discharge treatment to the film surface or a method of applying various coatings is used. Can be mentioned. Among these, the application compound, method, and thickness of the coating are not particularly limited as long as the effects of the present invention are not impaired.

The film of the present invention preferably has a heat shrinkage of not more than 0.4% in the longitudinal and width directions at 80 ° C., more preferably 0.2 to -0.2. %. When the heat shrinkage ratio exceeds 0.4%, shrinkage occurs in a printing step or an adhesive application step, which may cause misregistration of the printing and eventually impair the design.

The polyester film of the present invention comprises:
F- in the longitudinal and width directions of the film at 50 ° C.
It is preferable that the five values be 13 MPa or more. 17-4
When the pressure is 0 MPa, it is easier to control the tensile strength against shrinkage of the film due to heat in the manufacturing process of the can. When the F-5 value is less than 13 MPa, the tensile strength during film transport in the manufacturing process cannot be controlled, and the film is distorted or, conversely, sagging occurs,
As a result, a displacement may occur in the bonding position with the metal plate. The F-5 value is a stress applied to the film when the film is stretched by 5%.

The above-mentioned heat shrinkage at 80 ° C. and 150 ° C.
The method for setting the F-5 value in the above range to such a range is not particularly limited.
Any method such as a method achieved by controlling the magnification and the heat setting temperature and a method of aging the film after film formation can be adopted.

In producing the polyester of the present invention, conventionally known polymerization catalysts and coloring inhibitors can be used. Examples of the polymerization catalyst include alkali metal compounds,
Alkaline earth metal compounds, zinc compounds, lead compounds, manganese compounds, cobalt compounds, aluminum compounds, antimony compounds, titanium compounds, germanium compounds, etc. can be used, but from the viewpoint of taste characteristics, germanium elements, antimony elements, It is preferable to use a metal compound containing a titanium element.

Among these, from the viewpoint of taste characteristics,
It is particularly preferable to use a compound containing a germanium element. Examples of the metal compound containing a germanium element include germanium dioxide, germanium hydroxide hydrate, or germanium tetramethoxide,
Examples include germanium alkoxide compounds such as germanium ethylene glycolide, germanium phenoxide compounds, phosphoric acid-containing germanium compounds such as germanium phosphate and germanium phosphite, and germanium acetate. Further, in terms of taste characteristics, it is even more preferable that the metal compound containing a germanium element is substantially amorphous. Here, the amorphous metal compound containing a germanium element has no crystalline diffraction peak in the X-ray diffraction method.

Further, when the amount of the remaining germanium element in the film which is a component of the present invention is 2 to 50 ppm,
It is more preferable in terms of taste characteristics. Further, the content of the germanium element is more preferably 10 to 45 ppm.
When the amount of the remaining germanium element is less than 2 ppm, the effect of using the compound containing the germanium element as the polymerization catalyst may not be exhibited, and when the amount of the remaining germanium element exceeds 50 ppm, the amount of the catalyst becomes excessive,
It is not preferable because the taste characteristics may be poor. The method for setting the germanium element amount in the above range is not particularly limited.

In addition, a phosphorus compound or the like can be used as the coloring inhibitor, but it is not particularly limited thereto.

As a method of adding the metal compound catalyst,
For example, taking a germanium compound as an example, a method of adding a germanium compound powder as it is, or as described in JP-B-54-22234, dissolves a germanium compound in a glycol component which is a starting material of a polyester. Can be used.

Hereinafter, the method for producing the polyester of the present invention will be described with reference to specific examples, but the present invention is not limited thereto.
For example, in the production of polyethylene terephthalate, when amorphous germanium dioxide is added as a catalyst, a terephthalic acid component and an ethylene glycol component are subjected to a transesterification or esterification reaction, and then germanium dioxide and a phosphorus compound are added. A method in which polycondensation is carried out under a high temperature and a reduced pressure until a constant diethylene glycol content is obtained to obtain a germanium element-containing polymer is preferably employed. 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, to reduce the content of acetaldehyde, to have a predetermined intrinsic viscosity and a carboxy terminal group. For example, a method for obtaining the same is used.

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 after undergoing many histories such as adhesive application, heat treatment during drying or processing, and retort treatment. 0.0001 to 1% by weight of a known antioxidant
It may be added. In addition, diethylene glycol may be added at the time of polyester production as long as taste characteristics are not impaired.

The polyester of the present invention preferably has a content of monomethyl dicarboxylate in the film as a constituent element of the present invention of 10 ppm or less, more preferably 5 ppm or less, from the viewpoint of taste characteristics. It is even more preferred that no is detected. If the content of dicarboxylic acid monomethyl ester exceeds 10 ppm, it may be eluted in the contents of the can, which may undesirably lower the taste. Here, examples of the dicarboxylic acid monomethyl ester include terephthalic acid monomethyl ester, isophthalic acid monomethyl ester, naphthalenedicarboxylic acid monomethyl ester, and the like. Among the two carboxyl groups of the dicarboxylic acid, only one of them is methyl esterified. is there. As a method for reducing the content of dicarboxylic acid monomethyl ester to such a value or less,
Although not particularly limited, for example, during the polymerization of polyester, a method of directly transesterifying a dicarboxylic acid component and a glycol component, a method of simultaneously extracting other monomers and oligomer components in a polymer after polymerization, and a method of extracting the same after film formation. A method of extracting from a film may be used.

The method for producing the polyester film in the present invention is not particularly limited. For example, after drying the polyester as required, the polyester film is supplied to a known melt extruder, melted, and cut through a slit die. The sheet is extruded into a sheet, adhered to a casting drum by a method such as electrostatic application, and solidified by cooling to obtain an unstretched film. Using such an unstretched film, after stretching in the longitudinal direction, stretching in the width direction, or stretching in the width direction, and then sequentially stretching in the longitudinal direction, the longitudinal direction of the film, the width direction is almost Stretching is performed by a simultaneous biaxial stretching method of simultaneously stretching.

In such a stretching method, the stretching ratio employed in each direction is preferably 1.6 to 1.6.
It is 5.5 times, more preferably 1.7 to 5.2 times.
The stretching speed is desirably 1000 to 200,000% / min, and the stretching temperature may be any temperature as long as it is in the temperature range of the glass transition point or higher and the glass transition point + 100 ° C. or lower of the polyester. , 80-
170 ° C., particularly preferably a stretching temperature in the longitudinal direction of 90 ° C.
The stretching temperature in the width direction is preferably set to 80 to 150 ° C. The stretching may be performed a plurality of times in each direction.

Further, the film is subjected to a heat treatment after the 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 can be any temperature from 120 ° C. to the melting point of the polyester, but is preferably from 120 to 240 ° C. The heat treatment time can be arbitrarily set as long as other characteristics are not deteriorated, but it is usually preferable to perform the heat treatment for 1 to 60 seconds. Further, the heat treatment may be performed by relaxing the film in the longitudinal direction and / or the width direction.

In the present invention, the polyester film has a melting point (Tm) of 240 to 2 from the viewpoint of taste characteristics and heat resistance.
Preferably it is 80 ° C. If the melting point is lower than 240 ° C., taste characteristics and impact resistance deteriorate. More preferably, T
m is 246 to 275 ° C.

The polyester film of the present invention has an intrinsic viscosity (IV) of 0.55 to 0.55 from the viewpoint of taste characteristics and productivity.
It is preferably 0.75. If it is less than 0.55, the amount of oligomers and monomers in the film may increase. Further, a film exceeding 0.75 may not be preferable in production.

The film of the present invention contains known internal particles, inorganic particles and / or organic particles having an average particle diameter of 0.01 to 10 μm in an amount of 0.01 to 10 μm in order to improve the handleability.
It is preferred to contain 3% by weight. As a method for depositing the internal particles, known techniques can be used. For example, JP-A-48-61556 and JP-A-51-128 can be used.
No. 60, JP-A-53-41355, JP-A-5-41
Techniques described in JP-A-4-90397 can be employed. Further, other particles such as JP-B-55-20496 and JP-A-59-204617 can be used in combination. It should be noted that use of particles having an average particle size exceeding 10 μm may cause defects in the film.

Examples of such inorganic particles include wet and dry silica, colloidal silica, aluminum silicate, titanium oxide, calcium carbonate, calcium phosphate, barium sulfate, aluminum oxide, mica, carion, clay and the like.
As the organic particles, particles containing styrene, silicone, acrylic acids, methacrylic acids, polyester, divinylbenzene, and the like as constituent components can be used. Among them, it is preferable to use inorganic particles such as wet and dry silica and aluminum oxide, and organic particles containing styrene, silicone, acrylic acid, methacrylic acid, polyester, divinylbenzene, and the like as components. Furthermore, two or more of these internal particles, inorganic particles and organic particles may be used in combination.

The polyester film for laminating a three-piece metal can of the present invention preferably has a thickness of 5 to 50 μm, more preferably 8 to 30 μm, from the viewpoint of the coating properties and impact resistance of the metal plate. .

The metal plate used for the three-piece metal can of the present invention is not particularly limited, but is preferably a metal plate made of iron, aluminum, or the like. Furthermore, in the case of a metal plate made of iron, an inorganic oxide coating layer that improves adhesion and corrosion resistance on the surface thereof, for example, chromic acid treatment, phosphoric acid treatment,
A chemical conversion coating layer represented by chromic / phosphoric acid treatment, electrolytic chromic acid treatment, chromate treatment, chromium chromate treatment, or the like may be provided. In particular, a chromium oxide hydrate of 6.5 to 150 mg / m 2 as chromium in terms of chromium metal is preferable, and a spreadable metal plating layer such as nickel, tin, zinc, aluminum, gunmetal, brass, etc. may be provided. . 0.5 to 15 mg / m for tin plating
2, 1.8 to 20 g for nickel or aluminum
/ M2 is preferable.

The polyester film for three-piece metal lamination of the present invention is excellent in adhesion, printability and taste characteristics, and is suitable for coating the inner and outer surfaces of a can lid, a can body and a bottom of a three-piece metal can. Can be used for

[0039]

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

(1) Intrinsic Viscosity of Polyester (IV)
Measured in ° C.

(2) Melting point of polyester film (T
m) About 10 mg of the film was measured at a heating rate of 20 ° C./min using a differential scanning calorimeter (DSC2, manufactured by Perkin-Elmer Co.), and the melting peak temperature was defined as the melting point (Tm).

(3) Surface tension (γ) The surface tension (γ) was measured according to JIS K-6768. The following three types of standard solutions were used according to the magnitude of the surface tension. 30 mN / m ≦ γ <56 mN / m: JIS K-676
8 standard solution 56 mN / m ≦ γ <72 mN / m: aqueous ammonia 72 mN / m ≦ γ: aqueous sodium hydroxide solution.

(4) Monomethyl ester of dicarboxylic acid (MMT) 0.5 g is scraped off from the film and dissolved in hexafluoroisopropanol. Methanol was added thereto, and the filtered filtrate was subjected to liquid chromatography to quantify the amount of dicarboxylic acid monomethyl ester in the film.

(5) Heat Shrinkage Rate at 80 ° C. A film cut to a width of 10 mm with a mark interval of 200 mm is hung in the length direction, a load of 1 g is applied in the length direction, and hot air of 80 ° C. is used. After heating for 30 minutes, the distance between the marked lines after cooling was measured and indicated by engineering strain.

(6) F-5 value at 150 ° C. A 10 mm width was applied to a chuck of a tensile tester (Tensilon).
Is set to a sample length of 100 mm.
It was kept in a chamber at 0 ° C. for 90 seconds. afterwards,
At a crosshead speed of 250 mm / min, the stress (F-5 value) when the strain was 5% was measured five times each in the longitudinal direction and the width direction of the film, and the average value was obtained.

(7) Residual amount of catalytic metal The measurement was performed by X-ray fluorescence measurement. The quantification was performed using a calibration curve of the intensity and the amount of each element prepared in advance.

(8) Ink Adhesion Alfa Conc White manufactured by Inktec Co., Ltd. was diluted to 20% with a 1: 2 mixed solution of ethyl acetate and methyl ethyl ketone, and the ink solution was uniformly coated on the side opposite to the film layer of the film. (About 2 μm) and dried at 80 ° C. for 1 minute. Then apply cellophane tape (Nichiban) to the ink-coated surface,
The ink was vigorously peeled off, and the residual ratio of the ink to the film after the tape was peeled off was measured 20 times, and the average value was evaluated. Class A: 95% or more Class B: 70 to 95% Class C: less than 70%.

(9) Printability Gravure printing is performed on the reverse side of the coating layer of the film using four colored inks and a white ink, each of which uses a urethane resin as a main binder, to form a checkerboard pattern and numerals “012345789”. Was printed. After printing, drying was performed at 80 ° C. for 1 minute, and the pattern on the film, misalignment of characters, bleeding, and the like were visually observed with a microscope (magnification: 50)
X) and evaluated as follows. Grade A: Pattern and letter shifts and bleeding are not observed. Class B: Patterns and characters are not displaced or blurred with the naked eye, but are observed with a microscope. Class C: Printing displacement and bleeding are recognized with the naked eye.

(10) Laminability On the coating layer side of the film, a resin solution in which a bisphenol-based epoxy resin and trimellitic anhydride-based curing agent were dissolved in an organic solvent at a ratio of 95/5 to a uniform thickness (about 2 μm) ). And so that the effect of the adhesive does not progress,
Dry at 123 ° C. for 12 seconds. The film is 178
Pressure bonding the adhesive-coated side to a metal plate pre-heated to
Thereafter, bonding was performed by heating at 205 ° C. for 1 minute.
After bonding, make cuts in a grid pattern at intervals of 5 mm only on the film, apply cellophane tape (made by Nichiban) on it, peel off vigorously, and check the adhesion (laminability) between the metal plate and the film after peeling the tape. Was evaluated as follows. Class A: The film did not peel. Class B: Some film pieces were peeled off at their ends. Class C: Some film pieces were completely peeled off.

(11) Laminability after printing Gravure printing was performed on the reverse side of the coating layer of the film using four colored inks and a white ink using a urethane resin as a main binder. After drying at 80 ° C. for 1 minute, a resin solution obtained by dissolving a bisphenol-based epoxy resin and a trimellitic anhydride-based curing agent in an organic solvent at a ratio of 95/5 was applied to the film layer side of the film to a uniform thickness (about 2 μm).
m). And it dried at 120 degreeC for 15 seconds so that the effect of an adhesive might not advance. The film
The adhesive-coated side was pressed against a metal plate preheated to 75 ° C., and then heated at 200 ° C. for 1 minute to perform lamination. The printed surface after lamination was observed and evaluated as follows. Class A: No distortion occurred in printing. Class B: Printing caused a certain distortion. Class C: Printing distortion was locally different.

(12) Taste Characteristics An adhesive was applied to the film layer surface of the film in the same manner as in (10) above, and the film was adhered to a metal plate. Using the film-laminated metal plate, a metal container is prepared such that the film-laminated surface is on the inner side of the container, and the metal container is subjected to a pressurized steam treatment at 122 ° C. for 15 minutes. ° C
For 12 weeks, and then opened, and the change in odor (this was defined as taste characteristics) was evaluated by a sensory test. Class A: No change in odor is seen. Class B: Odor hardly changes. Class C: A significant change in odor is observed.

Examples 1 to 7 and Comparative Examples 1 to 3 In Example 1, polyethylene terephthalate containing wet-agglomerated silica having an average particle size of 0.3 μm as particles was polymerized using amorphous germanium dioxide as a catalyst. I got it. This polyethylene terephthalate was sufficiently vacuum-dried at 180 ° C., melt-extruded at 285 ° C., and then biaxially stretched sequentially to obtain a biaxially oriented film. The stretching conditions were as follows: the longitudinal stretching temperature was 103 ° C., and the stretching ratio was 4.0.
The stretching temperature was 113 ° C. and the stretching ratio was 3.8 times. Thereafter, heat treatment was performed at 220 ° C. to obtain a biaxially stretched film having a thickness of 12 μm. In addition, between the longitudinal stretching and the width stretching, both surfaces of the film were subjected to corona discharge treatment. Further, the following prepared coating material was applied to one surface after the treatment with a rod coater to form an easily adhesive coating layer. The coating thickness was 0.05 μm after stretching in the width direction and heat treatment.

[Formulation coating composition] Acid component Terephthalic acid: 29 mol% Isophthalic acid: 7 mol% Trimellitic acid: 10 mol% Sebacic acid: 3 mol% Glycol component Ethylene glycol: 14 mol% Neopentyl glycol: 19 Polyester resin containing mol% 1,4-butanediol: 18 mol%.

As a result, films having the physical properties shown in Tables 1 and 2 were obtained and evaluated. As shown in Table 3, it was found that the films had excellent properties.

In Example 2, naphthalenedicarboxylic acid copolymerized polyethylene terephthalate was obtained by using antimony trioxide and tetraethyl titanate as the catalyst and copolymerizing 5 mol% of dimethyl naphthalenedicarboxylate with respect to all the acid components. In Example 3, using amorphous germanium dioxide and tetraethyl titanate as catalysts,
Isophthalic acid copolymerized polyethylene terephthalate was obtained by copolymerizing dimethyl isophthalate at 3 mol% with respect to all the acid components. In Example 4, isophthalic acid copolymerized polyethylene terephthalate in which dimethyl isophthalate was copolymerized at 15 mol% was obtained using crystalline germanium dioxide or the like as a catalyst. In Example 5, naphthalenedicarboxylic acid copolymerized polyethylene terephthalate was obtained by copolymerizing dimethyl naphthalenedicarboxylate at 5 mol%. Further, in Example 6, polyethylene terephthalate in which the amount of catalyst was changed from that in Example 1 was used, and in Example 7, polyethylene terephthalate in which antimony trioxide and magnesium acetate were used as the catalyst was used.

Thereafter, in Examples 2 to 6, melt extrusion, sequential biaxial stretching, surface treatment, and heat treatment were carried out in the same manner as in Example 1 except that the contained particles, film forming conditions, surface treatment conditions, and coating composition for film formation were changed. Was performed to obtain films having the physical properties shown in Tables 1 and 2. In Example 4, the film-forming paint was used by mixing 20% by weight of the isocyanate compound with 80% by weight of the polyester coating agent. In Example 5, 10% by weight of an acrylic copolymer resin was mixed with 90% by weight of a polyester coating agent. In the coating composition for forming a film in Example 6, the N-methylolated melamine compound was added to 88% by weight of the copolymerized polyester resin used in Example 1.
2% by weight was used as a mixture. Further, in the coating composition for forming a film of Example 7, 94% by weight of the copolymerized polyester resin used in Example 1 and 6% by weight of an N-methylolated melamine compound were used. As a result, as shown in Table 3,
The film was found to have excellent properties.

In Comparative Examples 1 to 3, polyester was polymerized, formed into a film, and subjected to surface treatment in the same manner as in Example 1 except that the polyester type, catalyst, film forming conditions, surface treatment conditions, and the like were changed. And the film which has the physical property shown in Table 2 was obtained. In Comparative Example 1, both surfaces were not subjected to corona discharge treatment, and in Comparative Example 2, only one surface was subjected to surface treatment. However, Comparative Examples 1 and 2 did not apply the easily adhesive coating layer. Also in Comparative Example 3, corona discharge treatment was performed on only one surface, and the treated surface was coated with a polyester resin layer. As a result, as shown in Table 3, the evaluation was inferior for each property.

The abbreviations in the table are as follows. PET: Polyethylene terephthalate PET / I *: Isophthalic acid copolymerized polyethylene terephthalate (* indicates copolymerized mole%) PET / N *: 2,6-naphthalenedicarboxylic acid copolymerized polyethylene terephthalate (* indicates copolymerized mole%) IV: Film M: residual amount of germanium catalyst metal element remaining in the film MMT: content of monomethyl dicarboxylate in the film

[0059]

[Table 1]

[0060]

[Table 2]

[0061]

[Table 3]

[0062]

According to the present invention, it is possible to achieve both printability, adhesiveness and taste characteristics by controlling the surface properties of the polyester film for laminating a three-piece metal can and further providing an easily adhesive coating layer. Things.

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Claims (7)

[Claims] 1. A polyester film having an easily adhesive coating layer provided on one side thereof and having a surface tension of 45 mN /
Polyester film for laminating a three-piece metal can having a length of at least m. 2. The polyester film for a three-piece metal can laminate according to claim 1, wherein the easily adhesive coating layer mainly comprises a resin selected from a polyester resin, an acrylic resin and a urethane resin. 3. The polyester film for laminating a three-piece metal can according to claim 1, wherein both the heat shrinkage in the longitudinal direction and the width direction of the film at 80 ° C. are 0.4% or less. 4. The polyester film for laminating three-piece metal cans according to claim 1, wherein the F-5 value at 150 ° C. in the longitudinal direction and the width direction of the film is 13 MPa or more. 5. The polyester for laminating a three-piece metal can according to claim 1, wherein a polyester film comprising a polyester obtained by using an amorphous metal compound containing a germanium element as a polymerization catalyst is used. the film. 6. The polyester film for laminating a three-piece metal can according to claim 1, wherein the content of dicarboxylic acid monomethyl ester in the film is 10 ppm or less. 7. The polyester film for a three-piece metal can laminate according to claim 1, wherein the content of the germanium element in the film is 2 to 50 ppm.