JP2007277365A - Colored polyester film for metal plate lamination molding processing - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a colored polyester film for metal plate lamination molding processing having excellent molding processability and adhesiveness and producing a metal can having excellent appearance and gold color developing properties after retorting. <P>SOLUTION: The colored polyester film for the metal plate lamination molding processing is composed of a polyester composition consisting essentially of a polyester (I) consisting essentially of a butylene terephthalate unit and a polyester (II) consisting essentially of an ethylene terephthalate unit. The film has 30≤YI≤60 yellowness value (YI value) calculated by the following formula YI value=100×(1.28×X-1.06×Z)/Y (wherein, X, Y and Z are tristimulus values in the XYZ colorimetric system) and ≤15% haze. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a colored polyester film for metal plate lamination molding processing.

  Metal cans are generally painted to prevent corrosion on the inner and outer surfaces, but recently, for the purpose of simplifying the process, improving hygiene, and preventing pollution, developed a method to obtain rust resistance without using organic solvents. As one of them, coating with a thermoplastic resin film has been attempted. That is, a method for making a can by drawing or the like after laminating a thermoplastic resin film on a metal plate such as tinplate, tin-free steel, or aluminum has been studied.

  On the other hand, gold-colored paints are still widely used to give a high-class appearance to the can appearance, and proposals have been made to replace this with a laminate of colored films, but there are many problems. For example, in Japanese Patent Application Laid-Open No. 2001-301025, a colored polyester film having ethylene terephthalate as a main constituent is disclosed. However, since the melting point of the film is high, a laminate capable of obtaining good adhesion on a metal plate is disclosed. There is a problem that it is difficult and can only be used as a shallow can with low moldability, and cannot be applied to a use with a high degree of molding processing such as the most widely used beverage can. Japanese Patent Application Laid-Open No. 2003-26823 discloses a colored polyester film having good thermal laminating properties and moldability by copolymerizing PET to lower its melting point and lower crystallization. There has been a problem that the film that has been melted and amorphized is crystallized during retort sterilization to become white and impair the appearance. On the other hand, the present inventors have devised a colored film made of polyethylene terephthalate or polyester mainly composed of this and polybutylene terephthalate or polyester mainly composed of this (Japanese Patent Laid-Open No. 2004-148627, JP 2005-314542 A).

JP 2001-301025 A JP 2003-26823 A JP 2004-148627 A JP 2005-314542 A

In these techniques, a coloring method in which a dye and / or pigment is added to a resin and a coloring method in which a coating layer in which the dye and / or pigment are dispersed are disclosed. Has a problem that the transparency of the original film is impaired, the metallic luster is poor after bonding to a metal plate, and the design of the container is poor.
Therefore, none of the conventional techniques have high moldability and adhesion, and satisfy all of the gold color development property and retort whitening resistance after metal plate lamination.

  The object of the present invention is for a metal plate laminating and forming process capable of producing metal cans, such as beverage cans, food cans, etc., which have excellent moldability and adhesion, and are excellent in appearance after retort and gold color development. The object is to provide a colored polyester film.

That is, the present invention comprises a polyester composition mainly composed of polyester (I) mainly composed of butylene terephthalate units and polyester (II) mainly composed of ethylene terephthalate units, and has a yellowness (YI value) calculated by the following formula: ) Is 30 ≦ YI <60, and the haze is 15% or less, a colored polyester film for metal plate lamination molding processing.
YI value = 100 × (1.28 × X−1.06 × Z) / Y
However, X, Y, and Z are tristimulus values in the XYZ color system.

  According to the present invention, for metal plate laminating molding processing, which has excellent moldability, adhesion, and can produce metal cans such as beverage cans, food cans, etc. that have excellent appearance after retort and gold color development. A colored polyester film can be provided.

Hereinafter, the present invention will be described in detail.
[Polyester composition]
The polyester composition in the present invention mainly comprises polyester (I) mainly composed of butylene terephthalate units and polyester (II) mainly composed of ethylene terephthalate units, preferably 30 to 70% by weight of polyester (I) and polyester. (II) 30 to 70% by weight, more preferably 40 to 60% by weight of polyester (I) and 40 to 60% by weight of polyester (II). When the polyester (I) is less than 30% by weight and the polyester (II) is more than 70% by weight, the shortest half crystallization time of the film becomes too long, and the appearance after retorting tends to change to a milky white spot. On the other hand, when the polyester (I) exceeds 70% by weight and the polyester (II) is less than 30% by weight, the shortest half crystallization time of the film is shortened and the crystallinity is excessively increased, so that the film forming property is deteriorated.
The polyester (I) and polyester (II) constituting the polyester composition are desirably melt-kneaded before film formation.

[Polybutylene terephthalate]
The polyester (I) mainly comprising a butylene terephthalate unit in the present invention is a polyester comprising terephthalic acid as a dicarboxylic acid component and 1,4-butanediol as a diol component. This polyester is preferably used after solid-layer polycondensation reaction.

  The polybutylene terephthalate may be copolymerized with other components within a range where the effects of the present invention are not impaired, for example, at a ratio of 20 mol% or less with respect to 100 mol% of all dicarboxylic acid components. That is, the “main body” means, for example, a constituent component of 80 mol% or more. The copolymer component may be a dicarboxylic acid component or a diol component. Examples of the copolymerized dicarboxylic acid component include aromatic dicarboxylic acids such as isophthalic acid, phthalic acid and naphthalenedicarboxylic acid, aliphatic dicarboxylic acids such as adipic acid, azelaic acid, sebacic acid and decanedicarboxylic acid, and cyclohexanedicarboxylic acid. Such alicyclic dicarboxylic acids can be exemplified. Of these, isophthalic acid, 2,6-naphthalenedigalbonic acid or adipic acid is preferred. Examples of the copolymerized diol component include aliphatic diols such as ethylene glycol and hexanediol, and alicyclic diols such as cyclohexanedimethanol. These may be used alone or in combination of two or more.

  The proportion of the copolymerization component is such that the resulting polymer melting point is in the range of 180 to 223 ° C, preferably 200 to 223 ° C, more preferably 210 to 223 ° C. When the polymer melting point is less than 180 ° C., the crystallinity as polyester is low, and as a result, the heat resistance of the film is lowered. Since the melting point of polybutylene terephthalate homopolymer is 223 ° C., 223 ° C. is the upper limit of the melting point.

  The intrinsic viscosity of the polyester (I) is preferably 0.60 to 2.00, more preferably 0.80 to 1.70, and particularly preferably 0.85 to 1.50. An intrinsic viscosity of less than 0.6 is not preferable because a film having mechanical strength that can be used practically cannot be obtained. Moreover, it is preferable that the upper limit of intrinsic viscosity is 2.0 or less in terms of productivity of raw material polyester and a film.

[polyethylene terephthalate]
The polyethylene terephthalate or the polyester (II) mainly composed of polyethylene terephthalate in the present invention is a polyester comprising terephthalic acid as a dicarboxylic acid component and ethylene glycol as a diol component. In these polyesters, other components may be copolymerized within a range in which the effects of the present invention are not impaired, for example, 20 mol% or less with respect to 100 mol% of all dicarboxylic acid components. That is, the “main body” means, for example, a constituent component of 80 mol% or more. The copolymer component may be a dicarboxylic acid component or a diol component. The copolymer component may be a dicarboxylic acid component or a diol component. Examples of the copolymerized dicarboxylic acid component include aromatic dicarboxylic acids such as isophthalic acid, phthalic acid and naphthalenedicarboxylic acid, aliphatic dicarboxylic acids such as adipic acid, azelaic acid, sebacic acid and decanedicarboxylic acid, and cyclohexanedicarboxylic acid. Examples thereof include alicyclic dicarboxylic acids. Examples of the copolymer diol component include aliphatic diols such as butanediol and hexanediol, and alicyclic diols such as cyclohexanedimethanol. These may be used alone or in combination of two or more.

  The proportion of the copolymer component is such that the resulting polymer melting point is in the range of 210-256 ° C, preferably 215-256 ° C, more preferably 220-256 ° C. When the polymer melting point is less than 210 ° C., the crystallinity as polyester is low, and as a result, the heat resistance is lowered. When the polymer melting point exceeds 256 ° C., the crystallinity of the polymer is too large, and the moldability is impaired.

  The intrinsic viscosity of the polyester (II) is preferably 0.50 to 0.80, more preferably 0.54 to 0.70, and particularly preferably 0.57 to 0.65. If the intrinsic viscosity is less than 0.50, a film having mechanical strength that can be practically used cannot be obtained, and if it exceeds 0.80, the molding processability is impaired.

  In addition, melting | fusing point of polyester is melting | fusing point obtained by the method of calculating | requiring a melting peak with the temperature increase rate of 20 degree-C / min using the suggestion scanning calorimeter TA Instruments mDSC. The sample amount is about 10 mg. The intrinsic viscosity of the polyester is a value determined by measurement at 35 ° C. after being dissolved in o-chlorophenol.

[Fine particles]
The colored polyester film for metal plate lamination molding processing of the present invention preferably contains fine particles in order to improve the handleability in the film production process, particularly the winding property. When the fine particles are blended, the amount is preferably 0.01 to 1 part by weight, more preferably 0.01 to 0.5 part by weight, based on 100 parts by weight of the total polyester.

  As the fine particles, either inorganic fine particles or organic fine particles may be used, but inorganic fine particles are preferably used. Examples of the inorganic fine particles include silica, alumina, titanium dioxide, calcium carbonate, and barium sulfate. Examples of the organic fine particles include crosslinked polystyrene particles and crosslinked silicone resin particles.

  The average particle diameter of the fine particles is preferably 2.5 μm or less, and preferably 0.01 to 1.8 μm. When the average particle diameter exceeds 2.5 μm, coarse particles (for example, particles of 10 μm or more) deformed by the molding process are used as starting points, which may cause pinholes or breakage in some cases. Particularly preferable fine particles in terms of pinhole resistance are monodispersed fine particles having an average particle size of 2.5 μm or less and a particle size ratio (major axis / minor axis) of 1.0 to 1.2. Examples of the fine particles include true spherical silica, true spherical titanium dioxide, true spherical zirconium, and true spherical crosslinked silicone resin particles.

[Color]
The colored polyester film for laminating and processing a metal plate of the present invention is calculated by the following formula in order to exhibit a gold color without impairing the metallic luster after being laminated on the metal plate and to give the food container a high-class feeling. Yellowness (YI value) is 30 ≦ YI <60, preferably 40 ≦ YI <60.
YI value = 100 × (1.28 × X−1.06 × Z) / Y
However, X, Y, and Z are tristimulus values in the XYZ color system.

  When the YI value is less than 30, the film has a weak yellowish color, so that when it is laminated on a metal plate, the gold color develops poorly, that is, the high-quality feeling of the metal container is inferior. On the other hand, when the YI value exceeds 60, the color of the film is strong, so that the glossiness of the metal plate is concealed when laminated on the metal plate, and the high-quality feeling of the metal container becomes poor. The color measurement is a value measured by the white reflection method using a spectroscopic automatic color difference meter based on JIS Z-8722.

  In order to set the yellowness (YI value) within the above range, a colorant may be contained in the layer of the polyester composition constituting the film. When the film is composed of a plurality of layers of the polyester composition, it may be contained in at least one layer. In order to set the yellowness (YI value) within the above range, a colored coating layer containing a colorant may be provided on at least one side of the film. This coating layer is usually provided by coating.

[Colored resin layer]
In order to make the yellowness within the range of the present invention, when a colorant is blended in the layer of the polyester composition, the colorant is preferably 0.1 to 5.0% by weight per 100% by weight of the polyester composition of the whole film. More preferably, it is 0.3 to 1.0% by weight. When the colorant is less than 0.1% by weight, it is not preferable because sufficient gold colorability is not obtained when laminated on a metal plate. On the other hand, if it exceeds 5.0% by weight, the dispersion state of the colorant is deteriorated and the film forming property is lowered, which is not preferable.

  A dye and / or a pigment is used as the colorant. As the colorant, at least one organic pigment selected from anthraquinone, isoindolinone, and quinophthalone is preferably used. In addition, other components may be used as a colorant in order to adjust the color tone, but in that case, ones with good heat resistance should be used, and safety in terms of food hygiene is recognized for use. Should be used.

  You may add a coloring agent in the superposition | polymerization process of raw material resin. Alternatively, a high-concentration master chip may be produced using a twin screw extruder, and a resin composition containing a colorant having a desired concentration may be obtained by mixing chips containing no colorant. Further, using a screw feeder, the colorant may be directly contained in the extruder in the film forming process as powder.

[Colored coating layer]
When taking the method of providing a colored coating layer on a polyester film, the coating layer is provided by coating. As the coating method, an in-line coating method in which a colorant and a resin component dissolved or dispersed in a solvent are applied after stretching in the longitudinal direction during the film forming process may be employed. An off-line coating method of applying may be adopted.

  For application, air doctor coating method, flexible blade coating method, rod coating method, floating knife coating method, knife over blanket coating method, knife over roll coating method, squeeze coating method, impregnation coating method, reverse roll coating method, transfer roll Known methods exemplified by a coating method, a gravure coating method, a kiss roll coating method, a bead coating method, a cast coating method, a spray coating method, a curtain coating method, a fountain coating method, and a calendar coating method can be employed.

  Examples of the resin component dispersed in the coating layer include epoxy resins, epoxy-ester resins, polyester resins, and alkyd resins. Among these, an epoxy resin is preferable. The most preferred resin component is an epoxy resin blended with a highly etherified amino resin, a blocked isocyanate compound and a phosphoric acid-modified compound. Adhesion between the film and the coating layer, and the heat resistance, water resistance and curing of the coating layer. Is improved. This coating layer can be cured in a short time, and can simplify the laminating process between the film and the metal plate.

  The colorant is usually contained dispersed in the coating layer. Preferably dyes and / or pigments are used. For example, a condensed azo pigment or anthraquinone pigment is used by dissolving or dispersing in a solvent together with the above resin. Furthermore, the color tone of the film can be easily adjusted by blending two or more colorants.

  The coating layer preferably has a thickness after drying of 0.3 to 3 μm, more preferably 0.5 to 2 μm. The coating layer may be disposed on one side or both sides of the film, but from the viewpoint of food hygiene, it is preferable to dispose the coating layer on one side and laminate the coating layer side to a metal plate. If the thickness of the coating layer is less than 0.3 μm, the adhesive strength when laminated on a metal plate is low, which is not preferable. If the coating thickness exceeds 3 μm, the solvent is not sufficiently dried, which is not preferable.

[Haze]
The colored polyester film for metal plate lamination molding processing of the present invention exhibits a gold color by transmitting the metal color of the plate when laminated with the metal plate. From this viewpoint, the haze of the film is 15% or less, preferably 10% or less. If the haze of the film exceeds 15%, the metal color is concealed when laminated with a metal plate, and the high-quality feeling of food cans becomes poor. Note that the film haze is measured with a Heidometer NDH2000 model manufactured by Nippon Denshoku Industries Co., Ltd.

[Colorant]
In both the colored resin layer and the colored coating layer, it is preferable to use a pigment-based colorant rather than a dye-based colorant. This is because the colorant contained in the resin layer and the coating layer needs to have high heat resistance in order to be suitably used at high temperature or under retort, and generally the pigment system has higher heat resistance. Because. The colorant preferably has a thermogravimetric change rate at 300 ° C. of 5% or less.

  Moreover, in order to make a film haze into said range, the coloring agent with favorable dispersibility should be used. If the dispersion of the colorant is insufficient, the transparency of the colored film is lowered in any coloring method, resulting in poor gold color development when laminated on a metal plate, resulting in a high-class feeling of the container. Absent.

[Minimum semi-crystallization time]
In the present invention, the shortest half crystallization time of the polyester composition constituting the film is preferably 1 to 100 seconds, more preferably 1 to 80 seconds, and particularly preferably 1 to 50 seconds. When the shortest half crystallization time is less than 1 second, the crystallinity is excessively increased, so that the film forming property is deteriorated. On the other hand, when the shortest crystallization time exceeds 100 seconds, the appearance after the retort treatment is discolored to a milky white spotted shape, which is not preferable.

  The shortest half crystallization time referred to here is the half crystallization time measured in the temperature range where crystallization of the resin occurs, and the shortest half crystallization time in the temperature range. Using a measuring device (manufactured by Kotaki Seisakusho Co., Ltd., MK-801 type), the transmitted light due to the optically anisotropic crystal component that increases with crystallization of the sample placed between the orthogonal polarizing plates is measured at each sample temperature. This is the shortest time among the values at the respective sample temperatures at which the time required for the crystallinity to be halved is calculated using the following Abramy equation.

  In measurement, a sample (sample weight: 8 mg) was heated in nitrogen at a temperature of the maximum melting point of the resin + 50 ° C. for 1 minute in a melting furnace incorporated in the apparatus, and immediately moved to a sample and immersed in a crystallization bath. The measurement is started so that the sample temperature becomes an equilibrium measurement temperature within 10 seconds.

  The maximum melting point here is one or two or more endothermic peaks when the temperature is increased at a rate of temperature increase of 20 ° C./min by a differential scanning calorimeter (TA Instruments mDSC type). The highest temperature among the temperatures showing the maximum depth of the endothermic peak.

  The depolarized intensity method is described in a new experimental chemistry course (Maruzen) and polymer chemistry Vol. 29. No. As described in 139, 323 and 336 (Polymer Society), this is an effective method for measuring a fast crystallization rate.

In consideration of the time required for the sample to reach thermal equilibrium, the time when 10 seconds passed after moving the sample into the crystallization bath was measured as t = 0 seconds. The depolarized transmission intensity measured at t = 0 second is Io, and the depolarized transmission intensity is plotted against Log t, and the depolarized transmission intensity at the point where the crystallization temperature curve starts to become a straight line is defined as Ig.

  In order to make the shortest half crystallization time within the above range in the present invention, for example, the amount of COOH end groups of polyester (I) and polyester (II) may be controlled as follows. That is, the shortest half crystallization time of the film is largely related to the amount of COOH end groups. In a polyester in which the amount of COOH end groups is not appropriately controlled as described below, if the residence time at the time of melting the polymer is increased or the residence temperature is increased, there is a problem that the polymer deteriorates due to thermal decomposition.

  The COOH end amount of polyester (I) is preferably 10 to 70 equivalent / ton, and the COOH end amount of polyester (II) is preferably 10 to 50 equivalent / ton. This range is preferable because the shortest half crystallization time can be controlled within the range of the present invention. When the COOH terminal amount of the polyester (I) is less than 10 equivalents / ton, the shortest half crystallization time becomes too long, and the film-forming property of the film due to the deterioration of the polymer tends to be lowered, and after the retort sterilization treatment Is not preferable because its appearance changes to milky white in the form of spots. On the other hand, when the COOH terminal amount exceeds 70 equivalents / ton, the shortest semi-crystallization time becomes too short, causing crystallization during the film forming process, particularly during the stretching process, and local thickness unevenness and width variation. This is not preferable because the film forming property is likely to deteriorate.

  When the COOH terminal amount of the polyester (II) is less than 10 equivalents / ton, the shortest half crystallization time becomes too long, and the film-forming property of the film due to the deterioration of the polymer tends to be lowered, and after the retort sterilization treatment Is not preferable because its appearance changes to milky white in the form of spots. On the other hand, when the COOH terminal amount exceeds 50 equivalents / ton, the shortest half crystallization time becomes too short, causing crystallization during the film forming process, particularly during the stretching process, and local thickness variation and width variation. This is not preferable because the film forming property is likely to deteriorate.

The COOH terminal amount was determined by adding 20 mg of benzyl alcohol to 100 mg of sample, heating at 200 ° C. for 4 minutes in a nitrogen atmosphere, cooling to room temperature, and using phenol red as an indicator. It is calculated | required using a following formula from the titration amount until 0.02N sodium hydroxide benzyl alcohol solution is dripped and indicator discoloration.
COOH terminal amount (equivalent / ton) = titer (cc) × 200

[Production method]
Polyester (I) and polyester (II) used in the present invention can be produced by a conventionally known method. For example, a method in which terephthalic acid, ethylene glycol and a copolymer component are esterified and then the resulting reaction product is subjected to a polycondensation reaction to obtain a copolymer polyester, or dimethyl terephthalate, ethylene glycol and a copolymer component are transesterified. And then the resulting reaction product can be polycondensed to produce a copolyester. If necessary, other additives such as a fluorescent brightening agent, an antioxidant, a heat stabilizer, and an antistatic agent may be blended.

  The colored polyester film for metal plate lamination molding processing of the present invention can be produced using the above polyester in accordance with a conventionally known film forming method. First, after drying the above-mentioned polyester raw material as necessary, it is extruded into a sheet form from a slit-shaped die using a melt extruder, and cooled and solidified with a cooling roll to obtain an unstretched sheet. In this case, in order to improve the flatness of the sheet, it is necessary to improve the adhesion between the sheet and the rotary cooling drum, and an electrostatic application adhesion method or a liquid application adhesion method is preferably employed. In the present invention, both may be used together as necessary.

  Although the unstretched film may be sufficient as the colored polyester film for metal plate lamination molding processing of this invention, it is preferable that it is a biaxially oriented film. Therefore, a method for forming a biaxially oriented film will be described. The obtained unstretched film is stretched biaxially and biaxially oriented. That is, first, the unstretched sheet is stretched in the longitudinal direction by a roll or tenter type stretching machine. The stretching temperature is 50 to 100 ° C, preferably 60 to 90 ° C, and the stretching ratio is 2.8 to 5.0 times, preferably 3.0 to 4.5 times. Next, the film is stretched in the width direction by a tenter type stretching machine. The stretching temperature is 60 to 110 ° C., preferably 70 to 100 ° C., and the stretching ratio is 3.0 to 5.0 times, preferably 3.2 to 4.5 times. Further, heat treatment is performed at a temperature in the range of 130 to 220 ° C. under relaxation within 20% to obtain a biaxially stretched film.

[laminate]
As the metal plate for laminating the colored film for the metal plate laminating molding process of the present invention, in particular, a metal plate for iron making, a plate made of tin, tin-free steel, tin nickel steel, aluminum or the like is suitable. Lamination of the polyester film to the metal plate can be performed by the following methods (a) and (b).
(A) The metal plate is heated to the melting point of the film or higher, the colored film is laminated and then cooled, and the surface layer portion (thin layer portion) of the film in contact with the metal plate is amorphized and adhered.
(A) The film is preliminarily coated with an adhesive, and this surface and a metal plate are laminated. As the adhesive, a known resin adhesive such as an epoxy adhesive, an epoxy-ester adhesive, an alkyd adhesive, or the like can be used. In the coloring by the colored coating layer, since the coating layer itself has an adhesive function, it is preferable to laminate the coating layer so as to contact the metal plate.

  The thickness of the colored film for metal plate lamination molding processing of the present invention is preferably 6 to 55 μm, more preferably 8 to 45 μm, and particularly preferably 10 to 30 μm. If the thickness is less than 6 μm, tearing or the like tends to occur during molding, which is not preferable. Those exceeding 55 μm are not preferable because they are excessive quality and uneconomical.

Hereinafter, the present invention will be further described with reference to examples.
The film characteristics were measured and evaluated by the following methods.

(1) Melting point It measured by the method of calculating | requiring a melting peak temperature with the temperature increase rate of 20 degree-C / min using DSSC 2920 Modulated DSC made from differential scanning calorimeter TA Instruments. The sample amount was about 20 mg.

(2) Intrinsic viscosity After the film was dissolved in o-chlorophenol, the filler such as titanium oxide was removed by a centrifuge and measured at a temperature of 35 ° C. In addition, an intrinsic viscosity is a value of an unstretched film.

(3) COOH terminal amount Using a COOH automatic measuring device manufactured by Seiwa Giken, 20 mg of benzyl alcohol was added to 100 mg of sample, heated at 200 ° C. for 4 minutes in a nitrogen atmosphere, cooled to room temperature, and phenol red as an indicator. A 0.02N sodium hydroxide benzyl alcohol solution was added dropwise, and the amount was determined using the following formula from the titration amount until indicator discoloration.
COOH terminal amount (equivalent / ton) = titer (cc) × 200

(4) Shortest half crystallization time Using a polymer crystallization rate measuring apparatus MK-801, manufactured by Kotaki Seisakusho, measurement was performed in a range of 40 to 150 ° C. with a sample of 8 mg.

(5) Color measurement Based on JIS Z 8722, using a color difference meter (SE-Σ90 type) manufactured by Nippon Denshoku Industries Co., Ltd., the YI value of one sample of 5 cm square was measured and evaluated for film color development according to the following criteria. did. In the measurement, a white plate attached to the apparatus was used as a film presser, and the measurement was performed by a reflection method.
A: The YI value was 40 ≦ YI <60, and after lamination, the gold colorability was very excellent.
A: YI value was 30 ≦ YI <40, and after lamination, the gold colorability was excellent.
X: The YI value was outside the above range, and the gold colorability was poor after lamination.

(6) Haze Using a Nippon Denshoku Industries haze meter NDH2000, the haze of one sample was measured, and the high quality of the metal container was evaluated according to the following criteria.
A: The haze was 10% or less, and it was very excellent in luxury after making the iron.
○: The haze was more than 10% and 15% or less, and it was excellent in luxury after making the iron.
X: Haze exceeded 15% and was inferior to luxury after ironmaking.

(7) Deep drawing workability A film sample was bonded to both sides of 0.25 mm thick tin-free steel heated to 230 ° C., cooled with water, then cut into a 150 mm diameter disk, and using a drawing die and punch Then, deep drawing was performed in four stages to produce a 55 mm diameter side seamless container (hereinafter abbreviated as a can). The processing status of these cans was observed and evaluated according to the following criteria.
○: The film was processed without any abnormality, and no whitening or breakage was observed in the film.
Δ: Whitening was observed in the film on the top of the can.
X: Film breakage was observed in a part of the film.

(8) Appearance after retorting After filling the can that had been well-drawn in (7) above with water to the full, put it into a retort kettle and pressurize steam at 125 ° C so that steam does not directly hit the sample. Was subjected to retort treatment for 90 minutes, and the change in the surface appearance of the polyester resin layer on the bottom of the can was observed with the naked eye and evaluated according to the following criteria.
○: No change.
Δ: Slightly cloudy.
X: It turned into milky white remarkably in a spot shape.

[Examples 1 to 3, Comparative Examples 1 and 4]
The polyester composition containing the colorant shown in Table 1 was dried by a conventional method, melted at 270 ° C., then extruded from a die and rapidly solidified to prepare an unstretched film. Next, the unstretched film was longitudinally stretched 3.2 times at 68 ° C, then transversely stretched 3.7 times at 78 ° C, and heat-set at 185 ° C to obtain a biaxially oriented film. The thickness of the obtained film was 12-25 μm.

[Example 4]
The polyester composition of the first layer (A) shown in Table 1 and the polyester composition containing the colorant of the second layer (B) are dried by a conventional method, individually melted at 280 ° C. and 270 ° C., and then fed. The block was laminated into two layers and extruded from a die to cool and solidify to produce an unstretched film. Next, the unstretched film was longitudinally stretched 3.2 times at 68 ° C., then transversely stretched 3.7 times at 78 ° C., and heat-set at 185 ° C. to obtain a biaxially oriented laminated film. The thickness of the obtained film was 12 μm.

[Example 5, Comparative Example 5]
The polyester composition of the first layer (A) shown in Table 1 and the polyester composition containing the colorant of the second layer (B) are dried by a conventional method and individually melted at 270 ° C., and then a feed block is used. Then, they were laminated in three layers, extruded from a die, and cooled and solidified to produce an unstretched film. Next, the unstretched film was longitudinally stretched 3.2 times at 68 ° C., then transversely stretched 3.7 times at 78 ° C., and heat-set at 185 ° C. to obtain a biaxially oriented laminated film. The thickness of the obtained film was 12 μm.

[Comparative Example 2]
The polyester composition containing the colorant shown in Table 1 was dried by a conventional method, melted at 280 ° C., then extruded from a die and rapidly solidified to prepare an unstretched film. Next, this unstretched film was longitudinally stretched 3.2 times at 105 ° C, then stretched 3.2 times at 120 ° C, and heat-set at 210 ° C to obtain a biaxially oriented film. The thickness of the obtained film was 25 μm.

[Comparative Example 3]
In Example 3, film formation was carried out in the same manner except that the blending ratios of polyester (I), (II) and colorant were changed as shown in Table 1, and a 12 μm biaxially oriented film was obtained. In the transverse stretching process during film formation, cutting frequently occurred and the film forming property was poor.

[Examples 6 to 8, Comparative Examples 6 to 9]
In Example 1, a film was formed in the same manner except that the blending ratios of the polyesters (I) and (II) and the colorant were changed as shown in Table 2, and a 12 μm biaxially oriented film was obtained.

  As can be seen from the results in Table 3, the can using the colored polyester film for metal plate laminating molding of the present invention has excellent molding processability and adhesion, and is excellent in appearance after retort and high-class feeling. It was.

  The colored polyester film for metal plate laminating and forming of the present invention is particularly suitable for use by bonding to a can body portion or a lid material portion of a metal can such as a soft drink or a food can.

Claims (4)

It comprises a polyester composition mainly composed of polyester (I) mainly composed of butylene terephthalate units and polyester (II) mainly composed of ethylene terephthalate units, and the yellowness (YI value) calculated by the following formula is 30 ≦ YI <60, Haze is 15% or less, The colored polyester film for metal plate lamination forming processing characterized by the above-mentioned.
YI value = 100 × (1.28 × X−1.06 × Z) / Y
However, X, Y, and Z are tristimulus values in the XYZ color system.   The colored polyester film for metal plate lamination molding processing according to claim 1, wherein the shortest crystallization time of the polyester composition is 1 to 100 seconds.   The colored polyester film for metal plate lamination molding processing according to claim 1, wherein the polyester composition contains a colorant.   A colored polyester film for metal plate laminating molding, wherein a coating layer containing a colorant is disposed on at least one surface of the film according to claim 1.