JP3769991B2 - Polyester film for laminating - Google Patents

Description

【００５９】
【表２】

【００６０】
【表３】

【００６１】
なお、上記表中の略号は以下の通りである。
ＥＮＤＣ：エチレン２，６−ナフタレンジカルボキシレート
ＰＥＴ：ポリエチレンテレフタレート
ＰＥＴ／Ｉ^*：イソフタル酸共重合ポリエチレンテレフタレート（数字は共重合モル％）
ＰＥＴ／Ｎ^*：２，６−ナフタレンジカルボン酸共重合ポリエチレンテレフタレート（数字は共重合モル％）
ＭＭＴ：ジカルボン酸モノメチルエステル
【００６２】
【発明の効果】
本発明によれば、ラミネート用ポリエステルフィルムの構造とそれを構成する樹脂の特性を制御することにより、優れた成形性とレトルト後の基材との密着性、さらには優れた味特性を得ることができる。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a polyester film for lamination. More specifically, it is a biaxially stretched polyester film that is used after being laminated on a base material such as a metal plate and then subjected to a molding process, and has good adhesion to the base material even after the molding process. The present invention relates to a polyester film for laminating that can be easily molded into a sheet and that has excellent taste characteristics.
[0002]
[Prior art]
Because biaxially stretched polyester film has excellent heat resistance, mechanical properties, and electrical properties, it is excellent in base materials such as magnetic recording materials, industrial materials such as electrical insulation materials and coating materials, and also in printability and vapor deposition properties. Widely used in packaging materials.
[0003]
In recent years, applications of biaxially stretched polyester films have been diversified, and applications have been developed in which they are laminated and molded through a substrate and an adhesive or directly by heat.
[0004]
For example, in the past, the inner and outer surfaces of metal cans have been widely coated with a solution in which various thermosetting resins such as epoxy and phenol are dissolved or dispersed in a solvent to prevent corrosion. It was done. However, such a thermosetting resin coating method takes a long time to dry the paint, resulting in a decrease in productivity, environmental pollution due to a large amount of organic solvent, and the amount of elution of low molecular weight components when in contact with food. There is an unfavorable problem such as many.
[0005]
As a method for solving these problems, there is a method of laminating a film on a steel plate, an aluminum plate, or a metal plate subjected to various surface treatments such as plating on the metal plate, which is a material of the metal can. And when manufacturing a metal can by drawing and ironing a laminated metal plate of a film, the following characteristics are required for the film.
(1) Excellent laminating properties on metal plates.
(2) Excellent adhesion to the metal plate.
(3) Excellent moldability and no defects such as pinholes after molding.
(4) The polyester film is not peeled off or cracks or pinholes are generated by impact on the metal can.
(5) The scent component of the contents of the can is not adsorbed on the film, and the flavor of the contents is not impaired by the eluate from the film (hereinafter referred to as taste characteristics).
[0006]
Many proposals have been made to solve these requirements. For example, Japanese Patent Publication No. 64-22530 discloses a polyester film having a specific density and a plane orientation coefficient. The publication discloses a copolymerized polyester film having specific crystallinity. However, these proposals do not necessarily satisfy the wide range of required characteristics as described above, and are particularly suitable for molding in applications that are used under severe processing conditions where excellent taste characteristics and significant distortion occur. It was difficult to balance the sex.
[0007]
[Problems to be solved by the invention]
The object of the present invention is to eliminate the above-mentioned problems of the prior art, and can cope with severe molding processes such as drawing and ironing. The object is to provide an excellent polyester film for lamination.
[0008]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, the polyester film for laminating of the present invention is made of polyester A containing ethylene terephthalate units containing 0.01 to 5 mol% of ethylene 2,6-naphthalenedicarboxylate units as a main constituent. It consists of a laminated film in which a B layer made of polyester B having an ethylene terephthalate unit containing 6 to 20 mol% of ethylene 2,6-naphthalene dicarboxylate as a main constituent component is disposed on at least one side of the A layer. It is a feature.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
In the following, the present invention will be described in detail along with preferred embodiments.
The polyester constituting the polyester film of the present invention is a general term for polymers having an ester bond in the bond in the main chain, and can usually be obtained by polycondensation reaction of a dicarboxylic acid component and a glycol component. Examples of the dicarboxylic acid component include fragrances such as terephthalic acid, 2,6-naphthalenedicarboxylic acid, isophthalic acid, diphenyldicarboxylic acid, diphenylsulfonedicarboxylic acid, diphenoxyethanedicarboxylic acid, 5-sodiumsulfonedicarboxylic acid, and phthalic acid. Aliphatic dicarboxylic acids, oxalic acid, succinic acid, adipic acid, sebacic acid, dimer acid, maleic acid, fumaric acid and other aliphatic dicarboxylic acids, cyclohexanedicarboxylic acid and other alicyclic dicarboxylic acids, and paraoxybenzoic acid and other oxycarboxylic acids And so on. Examples of the glycol component include aliphatic glycols such as ethylene glycol, propanediol, butanediol, pentanediol, hexanediol, and neopentylglycol, polyoxyalkylene glycols such as diethylene glycol, polyethylene glycol, and polypropylene glycol, and cyclohexanedimethanol. And aromatic glycols such as bisphenol A and bisphenol S.
[0010]
The polyester A in the present invention needs to be a polyester mainly composed of an ethylene terephthalate unit containing 0.01 to 5 mol% of ethylene 2,6-naphthalene dicarboxylate unit. Setting the ethylene 2,6-naphthalenedicarboxylate unit within such a range is necessary from the viewpoints of moldability, heat resistance, and taste characteristics in the case of a laminated film with a B layer made of polyester B described later. In particular, from the viewpoint of moldability, it is important to contain an ethylene 2,6-naphthalenedicarboxylate unit within such a range in order to prevent breakage at the lamination interface during molding. Further, from the viewpoint of taste characteristics, the content of ethylene 2,6-naphthalenedicarboxylate units is more preferably 0.01 to 3 mol%. The method for setting the content of ethylene 2,6-naphthalenedicarboxylate unit within such a range is not particularly limited. For example, when polymerizing polyethylene terephthalate, dimethyl 2,6-naphthalenedicarboxylate is used as a comonomer. And a method of blending polyethylene terephthalate and polyethylene 2,6-naphthalenedicarboxylate or polyethylene terephthalate and 2,6-naphthalenedicarboxylic acid copolymerized polyethylene terephthalate during film formation. From the viewpoint of impact resistance and long-term stability, the latter blending method is preferred. Further, the recovered raw materials may be blended within a range where the heat resistance and taste characteristics are not deteriorated.
[0011]
Further, polyester B in the present invention is mainly composed of ethylene terephthalate units containing 6 to 20 mol% of ethylene 2,6-naphthalenedicarboxylate units from the viewpoint of adhesion to the substrate and moldability after lamination. It is necessary to make it polyester. From the viewpoint of taste characteristics, the content of ethylene 2,6-naphthalenedicarboxylate units is preferably 6 to 15 mol%. Although it does not specifically limit as a method which makes content of ethylene 2, 6-naphthalene dicarboxylate unit in this range, For example, when polymerizing polyethylene terephthalate, dimethyl 2, 6-naphthalenedicarboxylate is used as a comonomer. And a method of polymerizing polyethylene terephthalate and polyethylene 2,6-naphthalene dicarboxylate separately, and blending to achieve such a range, etc. are desirable from the viewpoint of impact resistance and long-term stability. This is the latter method of blending.
[0012]
The polyester A and / or polyester B of the present invention may be copolymerized with other dicarboxylic acid components and / or glycol components as long as the taste characteristics and adhesion to the substrate are not impaired. Examples of the components include those described above. These dicarboxylic acid components and glycol components may be used in combination of two or more. In terms of taste characteristics, diphenyl dicarboxylic acid and 5-sodium sulfone dicarboxylic acid are preferred.
[0013]
Further, as long as the effects of the present invention are not impaired, polyester A and / or polyester B may be copolymerized with a polyfunctional compound such as trimellitic acid, trimesic acid, or trimethylolpropane.
[0014]
In the present invention, polyester A preferably has a melting point of 246 ° C. or higher from the viewpoint of taste characteristics and heat resistance. More preferably, it is 250 degreeC or more and 275 degrees C or less. Further, the difference in melting point between polyester A and polyester B is preferably within 20 ° C. from the viewpoints of film stretchability, stability after being laminated on a substrate, and the like. More preferably, it is within 15 ° C., and particularly preferably within 10 ° C. In addition, when two or more polyesters are blended and used as polyester A and / or polyester B, the melting point may show an endothermic peak due to melting by a differential scanning calorimeter after blending. The peak temperature on the high temperature side was taken as the melting point.
[0015]
In the present invention, in order to further improve the adhesion and taste properties, the polyesters A and B both preferably have an intrinsic viscosity of 0.6 dl / g or more, more preferably 0.62 dl / g or more, particularly 0. More preferably, it is at least 65 dl / g. When the intrinsic viscosity is less than 0.6 dl / g, taste characteristics may be deteriorated due to elution of oligomers.
[0016]
In producing the polyester of the present invention, conventionally known reaction catalysts and anti-coloring agents can be used. Examples of reaction catalysts include alkali metal compounds, alkaline earth metal compounds, zinc compounds, lead compounds, manganese compounds, Examples of coloring inhibitors such as cobalt compounds, aluminum compounds, germanium compounds, antimony compounds, and titanium compounds include, but are not limited to, phosphorus compounds. Usually, it is preferable to add an antimony compound, a germanium compound or a titanium compound as a polymerization catalyst at an arbitrary stage before the production of the polyester is completed.
[0017]
As such a method, for example, when a germanium compound is taken as an example, a germanium compound powder is added as it is, or as described in Japanese Patent Publication No. 54-22234, in a glycol component which is a starting material of polyester. A method in which a germanium compound is dissolved and added can be mentioned. Examples of germanium compounds include germanium dioxide, germanium hydroxide hydrate, or germanium alkoxide compounds such as germanium tetramethoxide, germanium tetraethoxide, germanium tetrabutoxide, germanium ethyleneglycoxide, germanium phenolate, germanium β-naphthalate, etc. Examples thereof include germanium phenoxide compounds, phosphoric acid-containing germanium compounds such as germanium phosphate and germanium phosphite, and germanium acetate. Of these, germanium dioxide is preferable. Although it does not specifically limit as an antimony compound, For example, oxides, such as an antimony trioxide, an antimony acetate, etc. are mentioned. The titanium compound is not particularly limited, but alkyl titanates such as tetraethyl titanate and tetrabutyl titanate are preferably used.
[0018]
For example, when producing germanium dioxide as a germanium compound in the production of polyethylene terephthalate, the terephthalic acid component and the ethylene glycol component are transesterified or esterified, and then germanium dioxide and a phosphorus compound are added, followed by high temperature. A method of obtaining a germanium element-containing polymer by polycondensation reaction under reduced pressure until a constant diethylene glycol content is preferably employed. As a more preferable method, the obtained polymer is subjected to a solid-state 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 acetaldehyde content to obtain a predetermined intrinsic viscosity and carboxy end group. The method etc. are mentioned.
[0019]
The polyester in the present invention preferably has a diethylene glycol component amount 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. However, it is desirable for maintaining excellent taste characteristics even when subjected to many heat histories such as heat treatment in the can-making process and retort treatment after can-making. This is considered to be because the oxidative decomposition resistance at 200 ° C. or higher is improved. Furthermore, you may add 0.0001-1 weight% of well-known antioxidant. Further, diethylene glycol may be added during the production of the polymer as long as the characteristics are not impaired.
[0020]
In order to improve the taste characteristics, the content of acetaldehyde in the film is preferably 25 ppm or less, more preferably 20 ppm or less. If the content of acetaldehyde exceeds 25 ppm, the taste characteristics may be inferior. The method for setting the content of acetaldehyde in the film to 25 ppm or less is not particularly limited. For example, in order to remove acetaldehyde generated by thermal decomposition when the polyester is produced by polycondensation reaction, the polyester is reduced under reduced pressure or A method of heat-treating at a temperature below the melting point of the polyester under an inert gas atmosphere, preferably a method of solid-phase polymerization of the polyester at a temperature of 155 ° C. or higher and a melting point below the melting point under a reduced pressure or inert gas atmosphere, using a vent type extruder And a method of extruding within a short time, preferably an average residence time of 1 hour or less at an extrusion temperature within the melting point + 30 ° C., preferably within the melting point + 25 ° C. when the polymer is melt-extruded.
[0021]
Although it does not specifically limit as a manufacturing method of the polyester film in this invention, For example, after drying each polyester A and polyester B as needed, after supplying to a well-known melt extruder, fuse | melting and laminating | stacking before solidification, Coextruded into a sheet or tube form from a slit-shaped die, closely contacted with a casting drum by a method such as electrostatic application, and cooled and solidified to obtain an unstretched laminated sheet. As the film forming method, there are a tubular method, a tenter method, etc., but in terms of film quality, a tenter method is preferable. After stretching in the longitudinal direction, stretching in the width direction, or stretching in the width direction and then in the longitudinal direction A sequential biaxial stretching method of stretching and a simultaneous biaxial stretching method of stretching the longitudinal direction and the width direction almost simultaneously are desirable.
[0022]
The stretching ratio is 1.6 to 4.2 times in each direction, and preferably 1.7 to 4.0 times. Either of the stretching ratios in the longitudinal direction and the width direction may be increased or may be the same. The stretching speed is desirably 1000 to 200000% / min, and the stretching temperature can be any temperature as long as it is not less than the glass transition point of the polyester and not more than the glass transition point + 100 ° C., but usually 80 to 170. ° C is preferred. Particularly preferably, the longitudinal stretching temperature is 100 to 150 ° C and the transverse stretching temperature is 80 to 150 ° C.
[0023]
Further, the film is heat-treated after biaxial stretching, and this heat treatment can be performed by any conventionally known method such as in an oven or on a heated roll. The heat treatment temperature can be any temperature not lower than 120 ° C. and not higher than the melting point of the polyester, but preferably not lower than 150 ° C. and not higher than the melting point of the polyester −5 ° C. Moreover, although heat processing time can be made arbitrary, it is preferable to carry out normally for 1 to 60 seconds. The heat treatment may be performed by relaxing the film in the longitudinal direction and / or the width direction. Further, re-stretching may be performed once or more in each direction.
[0024]
In the present invention, in order to obtain a film having excellent moldability, in particular, adhesion to a substrate after retorting, long-term stability after molding, and excellent taste characteristics, at least one surface of the A layer containing polyester A as a main constituent component It is necessary to make a laminated film in which a B layer containing polyester B as a main constituent is disposed. A B / A / B type laminated film in which the B layer is disposed on both sides of the A layer is more preferable from the viewpoints of moldability and long-term stability.
[0025]
In order to improve the handleability of the film of the present invention, the A layer is arbitrarily selected from known internal particles having an average particle diameter of 0.01 to 10 μm, and external particles such as inorganic particles and organic particles 1 It is preferable to contain 0.01 to 20% by weight of seed or more particles. When the particle concentration is less than 0.01% by weight, the running property and rollability of the film may be deteriorated. Moreover, it is a viewpoint of the abrasion resistance at the time of metal plate processing that the internal shape particle | grains (ratio of the maximum length with respect to the minimum length) of the particle | grains, and containing an internal particle, an inorganic particle, and / or an organic particle are 1.1 or more. From the viewpoint of wear resistance, it is more preferable that the irregularity is 5.0 or more. In addition, when particles having an average particle diameter exceeding 10 μm are used, defects in the film may occur.
[0026]
In addition, from the viewpoint of the handleability of the film, the B layer also includes one or more kinds of particles arbitrarily selected from known internal particles having an average particle diameter of 0.01 to 10 μm and external particles such as inorganic particles and organic particles. Is preferably contained in an amount of 0.01 to 5% by weight. When the particle concentration is less than 0.01% by weight, the running property and rollability of the film may be deteriorated. In addition, when particles having an average particle diameter exceeding 10 μm are used, defects in the film may occur.
[0027]
The degree of profile of the particles of the present invention is represented by the ratio of the maximum length to the minimum length of particles observed in the film, and is determined by a method defined later. Here, the maximum length of a particle is the distance between parallel lines of the longest interval that touches the contour of each particle or what is formed with an interval smaller than the primary particle diameter as one particle, and the minimum length is It is the particle length in the direction perpendicular to the maximum length at a position of 1/2 of the longest interval.
[0028]
As a method for precipitating the internal particles, a known technique can be adopted. For example, JP-A-48-61556, JP-A-51-12860, JP-A-53-41355, JP-A-54-90397 The technique described in the gazette etc. is mentioned. Further, other particles such as JP-A-55-20496 and JP-A-59-204617 can be used in combination.
[0029]
Inorganic particles include, for example, wet and dry silica, aluminum silicate, titanium oxide, calcium carbonate, calcium phosphate, barium sulfate, alumina, mica, kaolin, clay, and organic particles include styrene, silicone, acrylic acid, methacrylic acid, polyester And particles containing divinylbenzene as a constituent component. Among these, inorganic particles such as wet and dry silica and particles containing styrene, silicone, acrylic acid, methacrylic acid, polyester, divinylbenzene and the like as constituent components can be given. Two or more of these internal particles, inorganic particles, and organic particles may be used in combination.
[0030]
In the present invention, from the viewpoint of adhesion to the substrate, in the case of the A / B type, it is preferable to use the surface of the B layer opposite to the A layer side by thermally laminating the substrate. When the A layer is laminated on the side opposite to the B layer side, the particles in the A layer become the core of crystallization, crystallization is promoted during lamination and molding, and shrinkage strain occurs at the metal plate / film interface. Destruction can occur and peel off.
[0031]
The thickness of the film of the present invention is preferably from 3 to 40 μm, more preferably from 5 to 35 μm, in terms of formability after being laminated to the base material, covering property to the base material, impact resistance, taste characteristics, and the like. Especially preferably, it is 8-30 micrometers. Moreover, it is preferable from viewpoints of productivity, a moldability, long-term stability, etc. that ratio of the lamination | stacking thickness of A layer and B layer is 30: 1 to 1: 5 when a laminated structure is A / B type. More preferably, it is 25: 1 to 1: 1, and more preferably 20: 1 to 2: 1. Moreover, when a laminated structure is a B / A / B type, it is preferable that it is 1: 30: 1 to 1: 5: 1.
[0032]
In the laminated film of the present invention, the free dicarboxylic acid monomethyl ester contained in the B layer is preferably 5 ppm or more from the viewpoint of adhesion during retort and after molding. More preferably, it is 8 ppm or more and 50 ppm or less. Here, examples of the dicarboxylic acid monomethyl ester include terephthalic acid monomethyl ester, 2,6-naphthalenedicarboxylic acid monomethyl ester, isophthalic acid monomethyl ester, phthalic acid monomethyl ester, and diphenyldicarboxylic acid monomethyl ester. The method for containing the dicarboxylic acid monomethyl ester in such an amount or more is not particularly limited. For example, when producing a polyester, a method of obtaining a polyester by transesterification with a glycol component using a dicarboxylic acid ester as a dicarboxylic acid component. Can do.
[0033]
In the present invention, the free dicarboxylic acid monomethyl ester contained in the A layer is preferably less than 5 ppm from the viewpoint of elution when the contents, particularly beverages, are filled as a container. The dicarboxylic acid monomethyl ester component is more preferably 3 ppm or less. The method for reducing the amount of dimethyl monomethyl ester to less than this amount is not particularly limited. For example, a method for obtaining a polyester by an esterification reaction of a dicarboxylic acid component and a glycol component when producing a polyester is mentioned. Can do.
[0034]
Further, it is preferable to further improve the adhesion and formability by performing surface treatment such as corona discharge treatment on the film surface. In that case, as E value, it is 5-50, Preferably it is 10-45. Here, the E value is the corona discharge treatment intensity, which is a function of applied voltage (Vp), applied current (Ip), processing speed (S), and processing width (Wt), and E = Vp × Ip / S × Expressed as Wt.
Various coatings may be applied to the film of the present invention, and the coating compound, method, and thickness are not particularly limited as long as the effects of the present invention are not impaired.
[0035]
Although it does not specifically limit as a base material for lamination of this invention, As a metal raw material, the metal plate which uses iron, aluminum, etc. as a raw material is preferable at the point of shaping | molding. Further, 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, such as chromic acid treatment, phosphoric acid treatment, chromic acid / phosphoric acid treatment, electrolytic chromic acid treatment, You may provide the chemical conversion treatment film layer represented by the chromate process, the chromium chromate process, etc. Especially 6.5 to 150 mg / m as chromium in terms of metal chromium ² Chromium hydrated oxide is preferable, and a spreadable metal plating layer such as nickel, tin, zinc, aluminum, gun metal, brass, etc. may be provided. 0.5-15mg / m for tin plating ² In the case of nickel or aluminum, 1.8 to 20 g / m ² Those having a plating amount of 2 are preferred. On the other hand, the non-metallic material is not particularly limited, but paper, non-woven fabric, glass, and polymer material are preferable in terms of light weight in the final product.
[0036]
The polyester film for laminating of the present invention is a laminate suitable for applications that are molded after being laminated with a base material, particularly for coating cans and barrels of two-piece metal cans, and for coating inner and outer surfaces of paper containers, plastic containers, etc. Therefore, it can be preferably used for these applications.
[0037]
【Example】
Hereinafter, the present invention will be described in more detail by way of examples. The characteristics were measured and evaluated by the following methods. Further, in the case of the A / B type, the thermal lamination was carried out so that the surface opposite to the A layer side of the B layer containing polyester B as a main constituent was in contact with the substrate.
[0038]
(1) Intrinsic viscosity of polyester
The polyester was dissolved in orthochlorophenol and measured at 25 ° C.
[0039]
(2) Melting point of polyester
The polyester was crystallized and measured with a differential scanning calorimeter (DSC7, manufactured by Perkin Elmer Co.) at a heating rate of 10 ° C./min, and the melting peak temperature was taken as the melting point.
[0040]
(3) Deformity of particles
Each cross-section in the film is observed as a cross-section in the longitudinal direction of the film with a transmission electron microscope, and each particle or aggregate formed at intervals smaller than the primary particle diameter is regarded as one particle. The maximum length D and the minimum length d were determined, and the ratio D / d was calculated. Furthermore, the value was calculated | required about at least 100 or more particle | grains, and the arithmetic mean was made into the irregularity degree.
[0041]
(4) Average particle size
The thermoplastic resin is removed from the surface of the film by a plasma low-temperature ashing treatment method to expose the particles. The processing conditions are selected such that the thermoplastic resin is ashed but the particles are not damaged. This is observed with a scanning electron microscope (SEM), and the image of the particles is processed with an image analyzer. The number average diameter D obtained by carrying out the following numerical processing with 5,000 or more particles by changing the observation location is taken as the average particle diameter.
D = ΣDi / N
Here, Di is the equivalent-circle diameter of the particles, and N is the number of particles.
For the internal particles, the section of the film may be observed by transmission microscope observation.
[0042]
(5) Dicarboxylic acid monomethyl ester content
Only 500 mg of layer A or layer B is scraped off from the laminated film and dissolved in hexafluoroisopropanol. Methanol was added thereto, and the filtrate obtained by filtration was subjected to liquid chromatography to quantify the amount of free dicarboxylic acid monomethyl ester in the film.
[0043]
(6) Retort adhesion
A tin-free steel plate (thickness 0.22 mm) is heated (at a temperature in the range of the melting point of the film to the melting point + 25 ° C., the surface orientation coefficient of the non-metal plate side of the film after lamination is 0.02 to 0.03. The film was pasted at 55 m / min and then rapidly cooled. The film-laminated steel plate thus obtained was cut into a width of 30 mm, and only the steel plate was cut leaving a film for a part, and a weight of 100 g was hung on the cut portion and subjected to a retort treatment at 123 ° C. for 35 minutes. Evaluation was made by the peel length of the film from the steel sheet after retorting.
Class A: less than 10mm
Class B: less than 20mm, 10mm or more
Class C: 20mm or more
[0044]
(7) Taste characteristics
A stainless steel cylinder (inner cross-sectional area: 150 cm) on the laminated film of the above laminated steel plate ² ), 200 ml of purified water was added and sealed, and a retort treatment was performed at 125 ° C. for 15 minutes in a retort kettle. After retorting, the water was once cooled to 4 ° C., turbidity was measured at room temperature, and evaluated according to the following criteria. In the measurement, a calibration curve was previously prepared with a standard substance.
Class A: less than 0.10
Class B: less than 0.15 and 0.10 or more
Class C: 0.15 or higher
[0045]
(8) Long-term stability
After forming the above-mentioned laminated steel sheet with an ironing machine and a drawing machine (molding ratio (maximum thickness / minimum thickness) = 1.55, molding in a moldable temperature region) to create a can (diameter 61 mm, height 122 mm), The upper part of the can was processed to narrow the caliber inward. The obtained can was retorted with pressurized steam at 125 ° C. for 28 minutes, then filled with water, and allowed to stand for 40 days after sealing at 38 ° C. The degree of rust generation in the upper processed area after opening was evaluated according to the following criteria.
Class A: No rust generation
Class B: 1 mm or less of rust occurs within 5 pieces
Class C: Lots of rust generated
[0046]
(9) Formability (bending workability)
A polyester film was double-sided heat-laminated on paper and formed into a container. Bending was performed to create a beverage pack. The folded part of the obtained pack was observed and judged as follows.
Class A: The film is not whitened or cracked.
Class B: The film is slightly whitened but has no cracks.
Class C: Whitening and cracks are observed in the film.
[0047]
Examples 1-7, Comparative Examples 1-4
In Example 1, a polyester (inherent viscosity, 0.68 dl / g, melting point 228 ° C.) obtained by copolymerizing 12 mol% of dimethyl 2,6-naphthalenedicarboxylate with polyethylene terephthalate was used as polyester B, and colloidal silica particles ( 0.15% by weight) was added. Polyester A is polyethylene terephthalate (inherent viscosity 0.65 dl / g, melting point 256 ° C.) using amorphous germanium dioxide as a polymerization catalyst. Naphthalenedicarboxylic acid 12 mol% copolymerized polyethylene terephthalate was used in a 20 wt% blend. Polyester A was added with 0.11% by weight of agglomerated silica particles (average particle size 1.2 μm) as a lubricant. After these polyester A and polyester B are sufficiently vacuum dried at 150 ° C., each is supplied to a separate extruder, and laminated so as to have a B / A / B layer configuration with a feed block installed at the top of the die Then, the sheet was discharged from a die onto a drum to obtain an unstretched sheet. The obtained unstretched sheet was sequentially biaxially stretched under the conditions shown in Table 2 to obtain a biaxially stretched film. The properties of the obtained film were as shown in Table 3, and showed excellent properties.
[0048]
In Example 2, 12 mol% of 2,6-naphthalenedicarboxylic acid copolymerized polyethylene terephthalate used in Example 1 was used as polyester B, and polyethylene terephthalate (inherent viscosity 0.66 dl) using germanium dioxide as a polymerization catalyst was used as polyester A. / G, melting point 256 ° C.), a blend of 5% by weight of 12-mol% 2,6-naphthalenedicarboxylic acid copolymerized polyethylene terephthalate used in polyester B to simulate self-recovery was used. In addition, the same lubricant as in Example 1 was used by changing the mixing ratio as shown in Table 1, and a biaxially stretched film was obtained in the same manner as in Example 1 under the film forming conditions shown in Table 2. The properties of the obtained film were as shown in Table 3, and the film had excellent properties.
[0049]
In Example 3, 10 mol% of 2,6-naphthalenedicarboxylic acid copolymerized polyethylene terephthalate (inherent viscosity 0.66 dl / g, melting point 235 ° C.) is used as polyester B, and antimony trioxide is used as a polymerization catalyst for polyester A. 10 mol% of 2,6-naphthalenedicarboxylic acid copolymerized polyethylene terephthalate was blended with 8 mol% of isophthalic acid copolymerized polyethylene terephthalate (inherent viscosity 0.65 dl / g, melting point 236 ° C.) to simulate self-recovery. The thing was used. The lubricant and film forming conditions were as shown in Tables 1 and 2, and a biaxially stretched film was obtained by sequential biaxial stretching. The properties of the obtained film are as shown in Table 3, showing excellent properties.
[0050]
In Example 4, 18 mol% of 2,6-naphthalenedicarboxylic acid copolymerized polyethylene terephthalate (inherent viscosity 0.64 dl / g, melting point 214 ° C.) is used as polyester B, and antimony trioxide is used as a polymerization catalyst for polyester A. The polyethylene terephthalate (inherent viscosity 0.62 dl / g, melting point 254 ° C.) was blended with 20% by weight of 10 mol% of 2,6-naphthalenedicarboxylic acid copolymerized polyethylene terephthalate used in Example 3. The lubricant and film forming conditions are as shown in Tables 1 and 2. Thus, the evaluation result of the film obtained after biaxial stretching was as having shown in Table 3, and it turned out that the outstanding characteristic is shown.
[0051]
In Example 5, 12 mol% of 2,6-naphthalenedicarboxylic acid copolymerized polyethylene terephthalate (inherent viscosity 0.69 dl / g, melting point 228 ° C.) was used as polyester B, and 1 mol of 2,6-naphthalenedicarboxylic acid was used as polyester A. Using bi-copolymerized polyethylene terephthalate (intrinsic viscosity 0.68 dl / g, melting point 253 ° C.), biaxial stretching was performed successively under the conditions of Tables 1 and 2 to obtain a biaxially stretched film. As shown in Table 3, the properties of the obtained film were excellent.
[0052]
In Example 6, 10 mol% 2,6-naphthalenedicarboxylic acid copolymerized polyethylene terephthalate was used as polyester B, and 2,6-naphthalenedicarboxylic acid was added to 8 mol% isophthalic acid copolymerized polyethylene terephthalate used in Example 3 as polyester A. Biaxially stretched film in the same manner as in the other examples under the film forming conditions shown in Table 2 using 20% by weight of 10% by weight copolymerized polyethylene terephthalate and using aggregated silica (average particle size 0.8 μm) as a lubricant. Got. The evaluation results of the obtained film are as shown in Table 3, and showed excellent characteristics.
[0053]
In Example 7, polyethylene terephthalate (inherent viscosity 0.65 dl / g, melting point 254 ° C.) using amorphous germanium dioxide as polyester A as a polymerization catalyst and 2,6-naphthalenedicarboxylic acid 8 mol% copolymerized polyethylene terephthalate ( An intrinsic viscosity of 0.68 dl / g and a melting point of 237 ° C. was blended by 50% by weight. On the other hand, as polyester B, a blend of 70% by weight of the same polyethylene terephthalate as polyester A 30% by weight and 2,6-naphthalenedicarboxylic acid 18 mol% copolymerized polyethylene terephthalate (inherent viscosity 0.69 dl / g, melting point 215 ° C.). used. Polyesters A and B were sufficiently vacuum dried in the same manner as in Example 1, then supplied to separate extruders, laminated at the top of the die, and then discharged from the die onto a casting drum to obtain an unstretched film. This unstretched film was simultaneously biaxially stretched at a stretching ratio of 3.0 times at a temperature of 105 ° C. with a linear motor type simultaneous biaxial stretching machine, and then subjected to relaxation heat treatment (relaxation rate 3%) at 190 ° C. for 3 seconds. A film having a thickness of 18 μm was obtained. Evaluation of this film showed excellent properties as shown in Table 3.
[0054]
In Comparative Example 1, isophthalic acid 14 mol% copolymerized polyethylene terephthalate was used alone, and biaxially sequentially performed under the film forming conditions shown in Table 2 to obtain a stretched film. The film properties were inferior as shown in Table 3.
[0055]
In Comparative Example 2, polyethylene terephthalate (inherent viscosity 0.65 dl / g, melting point 256 ° C.) was used alone, and a biaxially stretched film was obtained under the film forming conditions shown in Table 2. The film properties were inferior as shown in Table 3.
[0056]
In Comparative Example 3, a biaxially stretched film was obtained by using 2,6-naphthalenedicarboxylic acid 12 mol% copolymerized polyethylene terephthalate as polyester A and 2,6-naphthalenedicarboxylic acid 22 mol% copolymerized polyethylene terephthalate as polyester B. . The characteristics were inferior as shown in Table 3.
[0057]
In Comparative Example 4, 10 mol% of 2,6-naphthalenedicarboxylic acid copolymerized polyethylene used in Example 3 for polyethylene terephthalate (inherent viscosity 0.62 dl / g, melting point 251 ° C.) using polyester A as the polymerization catalyst for polyester A A blend of 30% by weight of terephthalate was used. On the other hand, as polyester B, 2,6-naphthalenedicarboxylic acid 22 mol% copolymerized polyethylene terephthalate used in Comparative Example 1 was used. The film properties obtained were inferior as shown in Table 3.
[0058]
[Table 1]

[0059]
[Table 2]

[0060]
[Table 3]

[0061]
In addition, the symbol in the said table | surface is as follows.
ENDC: ethylene 2,6-naphthalenedicarboxylate
PET: Polyethylene terephthalate
PET / I ^* : Isophthalic acid copolymerized polyethylene terephthalate (Numbers are copolymerization mol%)
PET / N ^* : 2,6-naphthalenedicarboxylic acid copolymerized polyethylene terephthalate (numbers are copolymerization mol%)
MMT: Dicarboxylic acid monomethyl ester
[0062]
【The invention's effect】
According to the present invention, by controlling the structure of the polyester film for laminating and the characteristics of the resin constituting it, it is possible to obtain excellent moldability and adhesion with the substrate after retorting, and further excellent taste characteristics. Can do.

Claims (10)

An ethylene 2,6-naphthalene dicarboxylate unit is formed on at least one surface of the layer A composed of polyester A, the main component of which is an ethylene terephthalate unit containing 0.01 to 5 mol% of ethylene 2,6-naphthalene dicarboxylate unit. A polyester film for laminating comprising a laminated film in which a B layer composed of polyester B having an ethylene terephthalate unit containing 6 to 20 mol% as a main constituent is disposed. The polyester film for lamination according to claim 1, wherein the melting point of the polyester A is 246 ° C or higher. The polyester film for lamination according to claim 1 or 2, wherein the degree of irregularity of the particles contained in the A layer (ratio of the maximum length to the minimum length of the particles) is 1.1 or more. The polyester film for lamination according to any one of claims 1 to 3, wherein the amount of free dicarboxylic acid monomethyl ester contained in layer B is 5 ppm or more. The polyester film for lamination according to any one of claims 1 to 4, wherein the amount of free dicarboxylic acid monomethyl ester contained in the A layer is less than 5 ppm. The polyester film for lamination in any one of Claims 1-5 which has a laminated structure of B / A / B by which B layer is arrange | positioned on both surfaces of A layer. Polyester formed by mixing polyester A and / or polyester B copolymerized with ethylene 2,6-naphthalene dicarboxylate units and polyester not copolymerized with ethylene 2,6-naphthalenedicarboxylate units The polyester film for lamination according to any one of claims 1 to 6. The polyester film for lamination according to any one of claims 1 to 7, which is used by laminating on a metal plate. The polyester film for lamination according to any one of claims 1 to 7, which is used by laminating with a nonmetallic material. The polyester film for lamination according to claim 9, wherein the non-metallic material is paper, non-woven fabric, glass, or a polymer material.