JP3859108B2 - Polyester film for metal plate lamination molding - Google Patents

Description

【００５４】
【表２】

【００５５】
【表３】

【００５６】
なお、表中の略号は以下の通りである。
ＰＥＴ：ポリエチレンテレフタレート
ＰＥＴ／ＣＨＤＭ：シクロヘキサンジメタノール共重合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
ＰＥＴ／Ｉ／ＣＨＤＭ：イソフタル酸及びシクロヘキサンジメタノール共重合ポリエチレンテレフタレート
【００５７】
【発明の効果】
本発明によれば、シクロヘキサンジメタノール成分を特定量共重合したポリエステルフィルムにより、金属板とフィルムの密着性、特にレトルト処理時の密着性、味特性を向上させることができる。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a polyester film for metal plate laminating molding processing. More specifically, the molding processing is particularly excellent in adhesion and taste characteristics after retort processing, and also in terms of abrasion resistance during can-molding. It is related with the polyester film for metal plate bonding shaping | molding processing suitable for the container manufactured by these, especially a metal can.
[0002]
[Prior art]
Conventionally, the inner and outer surfaces of metal cans have been widely used to coat metal surfaces by applying various types of thermosetting resins such as epoxy and phenolic melted or dispersed in solvents for the purpose of preventing corrosion. I have been. However, such a coating method using a thermosetting resin has unfavorable problems such as a reduction in productivity due to the long time required for drying and environmental pollution due to a large amount of organic solvent.
[0003]
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 that has been subjected to various surface treatments such as plating on the metal plate. When a metal can is manufactured by drawing or ironing a metal plate of the film, the film must have the following characteristics.
(1) Excellent laminating property to a metal plate.
(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 not generated by the impact on the metal can.
(5) The scent component of the contents of the can is adsorbed to the film, and the flavor of the contents is not spoiled by the effluent from the film (hereinafter referred to as taste characteristics).
[0004]
Many proposals have been made to solve these requirements. For example, JP-A-2-57339 discloses a copolyester film having specific crystallinity. However, in recent years, with an increase in can manufacturing speed, the ratio of can manufacturing from laminated steel sheets has increased, and further improvements in laminating properties, formability, and adhesion between films and steel sheets are desired. In addition, an increase in the forming ratio causes a problem of a decrease in the adhesion between the film and the steel sheet due to the retort after can-molding. For this reason, the above-mentioned proposals cannot comprehensively satisfy these required characteristics.
[0005]
[Problems to be solved by the invention]
The object of the present invention is to solve the above-mentioned problems, particularly excellent adhesion and taste characteristics after retort treatment, and can be formed into a good metal can with excellent abrasion resistance during can-molding, An object of the present invention is to provide a polyester film for metal plate lamination molding.
[0006]
[Means for Solving the Problems]
In order to solve the above problems, a polyester film for metal sheet lamination molding of the present invention, ethylene terephthalate and / or ethylene naphthalate units as a main component, cyclohexane dimethanol as a copolymer component 2 to 35 mol% From polyester B containing ethylene terephthalate and / or ethylene naphthalate unit as a main constituent component and 0.1-4 mol% of cyclohexanedimethanol as a main copolymer component on at least one side of layer A containing polyester A it you wherein comprising the composed B layer from those stacked.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
In the following, the present invention will be described in detail along with preferred embodiments.
The polyester in the present invention is a general term for high molecular weight substances composed of ester bonds, and examples of the dicarboxylic acid component include isophthalic acid, naphthalenedicarboxylic acid, diphenyldicarboxylic acid, diphenylsulfonedicarboxylic acid, diphenoxyethanedicarboxylic acid, 5-sodium sulfoisophthalic acid, aromatic dicarboxylic acids such as phthalic acid, oxalic acid, succinic acid, adipic acid, sebacic acid, dimer acid, maleic acid, fumaric acid and other aliphatic dicarboxylic acids, cyclohexyne dicarboxylic acid and other fats Examples thereof include cyclic dicarboxylic acids and oxycarboxylic acids such as p-oxybenzoic acid. On the other hand, examples of the glycol component include aliphatic glycols such as propanediol, butanediol, pentanediol, hexanediol and neopentylglycol, alicyclic glycols such as cyclohexanedimethanol, aromatic glycols such as bisphenol A and bisphenol S, and diethylene glycol. Etc. These dicarboxylic acid components and glycol components may be used in combination of two or more. Furthermore, in the present invention, two or more of the above polymers may be blended and used. In addition, the polyester in this invention may be comprised by blending polyester A of the same composition, and may be comprised by blending polyesters other than polyester A. In particular, from the viewpoint of heat resistance and adhesiveness, it is preferable to blend polyester A with other polyesters.
[0008]
Moreover, as long as the effect of this invention is not inhibited, you may copolymerize polyfunctional compounds, such as trimellitic acid, trimesic acid, a trimethylol propane, to copolyester.
[0009]
The main component of the polyester in the present invention needs to be ethylene terephthalate and / or ethylene naphthalate units, and the proportion of the polyester is preferably 65 mol% or more from the viewpoint of heat resistance and productivity, more preferably. Is 75 mol% or more, more preferably 85 mol% or more.
[0010]
The polyester film according to the present invention can be either a single layer or a laminate.
In the case of using a laminated film, examples of the form include layering of A layer / B layer, A layer / B layer / A layer, B layer / A layer / B layer, A layer / C layer / B layer, When the A layer is composed of the polyester A and the B layer is composed of the polyester B, it is desirable that the A layer is on the steel plate side from the viewpoint of adhesiveness. A laminated structure in which is on the contents side is desirable.
[0011]
Polyester A in the present invention is mainly composed of ethylene terephthalate and / or ethylene naphthalate units as a copolymer component for the purpose of exhibiting excellent adhesion to metal plates and moldability after lamination with metal plates. It is necessary to use a polyester containing 1 to 40 mol% of cyclohexanedimethanol. Preferably it is 2-35 mol%, More preferably, it is 4-30 mol%. If the cyclohexane dimethanol exceeds this range, the taste characteristics deteriorate, such being undesirable. Moreover, it is preferable from the point of a moldability to consist of at least 2 types of polyester containing polyester A. For example, the aspect which consists of at least 2 types of polyester of the polyester C from which the cyclohexanedimethanol copolymerization amount other than the polyester A is mentioned.
[0012]
Polyester B used in the case of using a laminated film has ethylene terephthalate and / or ethylene naphthalate units as main constituents and cyclohexanedimethanol as a copolymerization component in an amount of 0.00 for the purpose of exhibiting excellent taste characteristics and heat resistance. It is preferable to make it polyester containing 01-4 mol%, More preferably, it is 1-3 mol%. Moreover, it is preferable from the point of a moldability to consist of at least 2 types of polyester containing the polyester B. FIG. For example, the aspect which consists of at least 2 types of polyester of the polyester D from which the cyclohexane dimethanol copolymerization amount other than the polyester B is mentioned.
[0013]
Here, the amount of cyclohexanedimethanol copolymerization when the polyester A (polyester B) is composed of two or more types of polyesters is defined from the copolymerization amount of the entire polyester A (polyester B).
[0014]
In the polyester A and the polyester B, as a method of setting the content of cyclohexanedimethanol within such a range, for example, in the case of cyclohexanedimethyl copolymer polyethylene terephthalate, a method of using cyclohexanedimethyl as a comonomer when polymerizing polyethylene terephthalate And a method of blending polyethylene terephthalate and cyclohexanedimethyl copolymer polyethylene terephthalate during film formation. Examples of the method of making polyesters A and B uniform from at least two different polyesters include a method of blending two or more polyesters at the time of film formation and supplying them to an extruder, but is not limited thereto. Whether the polyester is composed of two or more types can be determined by the thermal behavior detected by a so-called differential calorimeter (DSC), for example, due to a phenomenon in which a plurality of endothermic peaks appear during melting of the film or a plurality of glass transition points appear. It can be confirmed by a phenomenon that a plurality of glass transition points appear.
[0015]
The main melting point of the polyester film in the present invention is preferably 246 ° C. or more from the viewpoint of heat resistance. Here, the melting point of the polyester film is an endothermic peak temperature at the time of melting detected by so-called differential scanning calorimetry (DSC). The main melting point when a plurality of endothermic peaks at the time of melting refers to the maximum endothermic peak.
[0016]
The polyester film of the present invention is desirably biaxially stretched from the viewpoint of heat resistance and dimensional stability. The biaxial stretching method may be either simultaneous biaxial stretching or sequential biaxial stretching.
[0017]
In the biaxially stretched film according to the present invention, the plane orientation coefficient of the A layer composed of the polyester A at the time of monolayer and lamination is preferably 0.01 to 0.13, more preferably 0.02 to 0.12. It is. Moreover, when setting it as a laminated structure, it is preferable that the plane orientation coefficient of B layer which consists of polyester B is 0.06-0.15, More preferably, it is 0.08-0.15. If the plane orientation coefficient is smaller than this range, it is not preferable from the viewpoint of wrinkling during lamination, and if it is larger, the moldability is deteriorated.
[0018]
Furthermore, the difference in the plane orientation coefficient between the A layer and the B layer is preferably 0.14 or less in absolute value, and more preferably 0.12 or less. It is not preferable from the viewpoint of moldability that the difference in the plane orientation coefficient exceeds this range.
[0019]
In the present invention, the heat shrinkage stress in the film longitudinal direction at 125 ° C. is 0.1 to 0.1 in order to reduce the influence of peeling due to the shrinkage stress of the film at the time of retorting, in order to improve the adhesion between the film and the steel plate. The pressure is preferably 1.5 MPa, more preferably 0.2 to 1.2 MPa.
[0020]
In the present invention, the linear thermal expansion coefficient in the film longitudinal direction at 125 ° C. is −150 × 10 ⁻⁶ to −3 × 10 ⁻⁶ K ⁻¹ mainly from the viewpoint of improving the adhesion between the film and the steel plate. It is preferably −140 × 10 ⁻⁶ to −5 × 10 ⁻⁶ K ⁻¹ . If the linear thermal expansion coefficient is outside this range, residual stress occurs due to the difference in thermal expansion behavior with the steel plate during lamination, and as a result, the film may crack or peel off from the steel plate during subsequent molding or retorting. is there. The method of setting the linear thermal expansion coefficient within such a range is not particularly limited, but a method of relaxing in the longitudinal direction in the heat treatment step, a method of slow cooling during the heat treatment, and the like can be preferably employed.
[0021]
In this invention, it is preferable that the carboxyl terminal group amount of the polyester A which comprises a steel plate side layer is 30-60 equivalent / ton from the point which improves the adhesiveness of a film and a steel plate, Most preferably, it is 30-50 equivalent / tonne. Tons.
[0022]
When a laminated film is used, the amount of carboxyl terminal groups of the polyester constituting the non-steel side layer is preferably less than 45 equivalent / ton, particularly preferably 40 equivalent / ton from the viewpoint of improving taste characteristics. Is less than.
[0023]
In the present invention, from the viewpoint of improving the adhesion between the film and the steel sheet, the amount of free dicarboxylic acid monomethyl ester contained in the polyester constituting the steel sheet side layer is preferably 3 ppm or more, more preferably 5 ppm or more. .
[0024]
When a laminated film is used, the amount of free dicarboxylic acid monomethyl ester contained in the polyester constituting the non-steel side layer is preferably less than 6 ppm, more preferably 4 ppm from the viewpoint of improving taste characteristics. Is less than.
[0025]
In the present invention, in order to further improve the adhesion and taste characteristics, the intrinsic viscosity of the polyester is preferably 0.6 dl / g or more, more preferably 0.62 dl / g or more, and particularly 0.65 dl / g. The above is even more preferable. If the intrinsic viscosity is less than 0.6 dl / g, it is not preferable for reasons such as deterioration of taste characteristics due to oligomer elution.
[0026]
In producing the polyester of the present invention, conventionally known reaction catalysts and anti-coloring agents can be used. Examples of the reaction catalyst include alkali metal compounds, alkaline earth metal compounds, zinc compounds, lead compounds, manganese compounds. Examples of coloring inhibitors such as cobalt compounds, aluminum compounds, antimony compounds, and titanium compounds include phosphorus compounds. It is desirable 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. Examples of such a method include, for example, a germanium compound, a method of adding a germanium compound powder as it is, or a glycol component which is a starting material for polyester as described in Japanese Patent Publication No. 54-22234. Examples thereof include a method in which a germanium compound is dissolved and added. Examples of the germanium compound include germanium dioxide, germanium hydroxide containing crystal water, or germanium alkoxide compounds such as germanium tetramethoxide, germanium tetraethoxide, germanium tetrabutoxide, germanium ethyleneglycoxide, germanium phenolate, germanium β-naphtholate, etc. And germanium phenoxide compounds, phosphorous-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, antimony oxides, such as antimony trioxide, an antimony acetate, etc. are mentioned. The titanium compound is not particularly limited, but alkyl titanate compounds such as tetraethyl titanate and tetrabutyl titanate are preferably used.
[0027]
For example, a case where germanium dioxide is added as a germanium compound when producing polyethylene terephthalate will be described. Transesterify or esterify the terephthalic acid component and ethylene glycol, then add germanium dioxide and phosphorus compound, and then polycondensate until a certain diethylene glycol content is reached under high temperature and reduced pressure. obtain. Further, preferably the resulting polymer was allowed to solid phase polymerization reaction under reduced pressure or under an inert gas atmosphere at the temperature below the melting point, to reduce the content of Asetoa Lud hydrate, a predetermined intrinsic viscosity, a terminal carboxyl group The method of obtaining etc. can be mentioned.
[0028]
The polyester in the present invention has a diethylene glycol component amount of 0.01 to 3.5 in order to maintain 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. % By weight, more preferably 0.01 to 2.5% by weight, even more preferably 0.01 to 2% by weight. This is considered to be due to the improvement of the oxidative degradation resistance at 200 ° C. or higher, and 0.0001 to 1% by weight of a known antioxidant may be added. Further, diethylene glycol may be added during the production of the polymer as long as the characteristics are not impaired.
[0029]
In order to improve taste characteristics, the content of acetaldehyde in the film is preferably 25 ppm or less, more preferably 20 ppm or less. The method of setting the content of acetaldehyde in the film to 25 pm or less is not particularly limited. For example, in order to remove acetaldehyde generated by thermal decomposition when the polyester is produced by a 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 in an inert gas atmosphere, preferably a method of solid-phase polymerization of the polyester at a temperature of 155 ° C. or more and below the melting point in a reduced pressure or inert gas atmosphere, a vent type extruder In the melt extrusion method using a polymer, when the polymer is melt-extruded, the extrusion temperature is within the melting point + 30 ° C., preferably within the melting point + 25 ° C. of the high melting point polymer side, and within a short time, preferably within an average residence time of 1 hour. The method of taking out etc. can be mentioned.
[0030]
The total thickness of the biaxially stretched film of the present invention is preferably 3 to 50 μm in order to improve the formability after being laminated to the metal, the coating property to the metal, the impact resistance, and the taste characteristics. Preferably it is 5-35 micrometers, Most preferably, it is 10-30 micrometers.
[0031]
The production method of the biaxially stretched film in the present invention is not particularly limited. For example, after drying each polyester as necessary, it is supplied to a known melt extruder, extruded from a slit-shaped die into a sheet, An unstretched sheet is obtained by tightly contacting the casting drum by application or the like and cooling and solidifying. The unstretched sheet is stretched and heat-treated in the longitudinal direction and the width direction of the film to obtain a film having a desired degree of plane orientation. As the stretching method, either simultaneous biaxial or sequential biaxial stretching may be used, but in terms of film quality, a tenter method is preferable. After stretching in the longitudinal direction, a sequential biaxial stretching method in which the stretching is performed in the width direction, the longitudinal direction. A simultaneous biaxial stretching method in which the width direction is stretched almost simultaneously is desirable. The stretching ratio is 1.6 to 4.2 times in each direction, and preferably 1.7 to 4.0 times. Either the stretching ratio in the longitudinal direction or the width direction may be larger or the same. The stretching speed is desirably 1000% / min to 200000% / min, and the stretching temperature can be any temperature as long as it is not less than the glass transition temperature of the polyester and not less than the glass transition temperature + 100 ° C. 80-170 degreeC is preferable. 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 of 120 ° C. or higher and 245 ° C. or lower, but is preferably 120 to 240 ° C. Moreover, although the 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 while relaxing the film in the longitudinal direction and / or the width direction. Furthermore, re-stretching may be performed once or more in each direction, and then heat treatment may be performed.
[0032]
The degree of irregularity of the particles contained in the polyester film of the present invention (the ratio of the maximum length D to the minimum length d of the particles defined by the following formula (1)) improves the wear resistance during molding. To 1.1 or more, more preferably 1.2 to 30, and particularly preferably 1.5 to 20. Furthermore, the content is preferably 0.05 to 1.0% by weight, more preferably 0.07 to 0.5% by weight from the viewpoint of film handleability.
Deformity = D / d (1)
[0033]
The degree of profile of the particles of the present invention is represented by the ratio of the maximum length D to the minimum length d of the particles observed in the film, as defined by equation (1). Here, the maximum particle length refers to the distance between the longest parallel lines that touch the contour of one particle when a single particle or a lump formed at intervals smaller than the primary particle diameter is regarded as one particle. The minimum length is the particle length in the direction perpendicular to the maximum length at a position 1/2 the longest interval.
[0034]
The additive particles in the present invention may contain particles arbitrarily selected from known internal particles having an average particle diameter of 0.01 to 10 μm, external particles such as inorganic particles and / or organic particles. In particular, it is preferable as a film used on the inner surface of the can that particles having an average particle diameter of 0.1 to 5 μm are contained in an amount of 0.01 to 3 wt%. Use of particles having an average particle diameter exceeding 10 μm is not preferable because defects of the film are likely to occur. Examples of the particles include inorganic particles such as wet and dry silica, colloidal silica, aluminum silicate, titanium oxide, calcium carbonate, calcium phosphate, barium sulfate, alumina, mica, kaolin, clay, and styrene, silicone, acrylic acid, and the like. Organic particles etc. can be mentioned. Among these, inorganic particles such as dry, wet and dry colloidal silica and alumina, and organic particles containing styrene, silicone, acrylic acid, methacrylic acid, polyester, divinylbenzene and the like as constituent components can be given. These internal particles, inorganic particles, and / or organic particles may be used in combination of two or more kinds as long as the characteristics are not impaired.
[0035]
Examples of the particles having an irregularity in the film of 1.1 or more according to the present invention include aggregated inorganic particles, but are not particularly limited as long as the irregularity is 1.1 or more.
[0036]
In the present invention, in order to increase the adhesion between the film and the steel sheet, in order to increase the adhesion area and the thickness of the polymer portion particularly at the adhesion interface between the film and the steel sheet, the particle concentration R1 and the surface at 1 μm from the surface of at least one side The ratio R1 / R2 of the particle concentration R2 at 0.1 to 0.1 μm is preferably 2 to 200, more preferably 3 to 150.
[0037]
Further, when used on the inner surface of the can, the center line average roughness Ra of the steel plate side layer surface and the non-steel plate side layer surface is preferably 0.005 to 0.07 μm, and more preferably 0.008 to 0.05 μm. Furthermore, when the ratio Rt / Ra to the maximum roughness Rt is 4 to 50, preferably 6 to 40, the high-speed canability is improved. In particular, the center line average roughness Ra of the non-steel side layer is preferably 0.002 to 0.04 μm, and more preferably 0.003 to 0.03 μm, since the taste characteristics are improved.
[0038]
In addition, it is preferable to further improve the properties by applying a surface treatment such as corona discharge treatment to the film.
[0039]
Various coatings may be applied on 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.
[0040]
Although it does not specifically limit with the metal plate of this invention, The metal plate which uses iron, aluminum, etc. as a raw material from the point of a moldability is preferable. 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, such as chromic acid treatment, phosphoric acid treatment, chromic acid / phosphoric acid treatment, electrolytic chromic acid treatment Further, a chemical conversion treatment coating layer represented by chromate treatment, chrome chromate treatment and the like may be provided. In particular, a chromium hydrated oxide of 6.5 to 150 mg / m ² is preferable as chromium in terms of metallic chromium, and a malleable metal plating layer such as nickel, tin, zinc, aluminum, gun metal, brass, etc. may be provided. Good. For tin plating 0.5-15 / m ^2, it is preferable to have a plating amount when nickel or aluminum 1.8~20g / m ^2.
[0041]
The biaxially stretched polyester film for containers of the present invention can be suitably used for coating the inner surface of a two-piece metal can manufactured by drawing or ironing after being laminated on a metal plate or the like. Moreover, since it has favorable metal adhesiveness and moldability, it can be preferably used for covering the lid part of a two-piece can or the body, lid and bottom of a three-piece can.
[0042]
【Example】
Hereinafter, the present invention will be described in detail by way of examples. The characteristics were measured and evaluated by the following methods.
(1) Polyester intrinsic viscosity Polyester was dissolved in orthochlorophenol and measured at 25 ° C.
[0043]
(2) The polyester melting point film was treated at 40 ° C. for 60 hours to remove the influence of moisture, and then 5 mg was enclosed in an aluminum measurement container. The container is set in a differential scanning calorimeter (DSC2 type manufactured by Perkin Elmer), heated to 280 ° C. at a heating rate of 20 ° C./min, held at 280 ° C. for 5 minutes, and cooled at 100 ° C./min. Pre-measurement treatment for rapid cooling to 20 ° C. Thereafter, measurement was carried out at a heating rate of 10 ° C./min, and the main melting point was determined from the melting peak temperature. Here, when a plurality of endothermic peaks at the time of melting appear, the main melting point means the maximum endothermic peak. In the case of a laminated film, the surface of each layer was shaved with a single blade, and 5 mg of the shaving powder was sampled and measured in the same manner.
[0044]
(3) Plane orientation coefficient (fn)
Surface orientation coefficient fn of layer A and layer B obtained from the refractive index (Nx, Ny, Nz, respectively) in the longitudinal direction, the width direction, and the thickness direction using an Abbe refractometer using sodium D-line (wavelength 589 nm) as a light source (Nx + Ny) / 2−Nz was calculated.
[0045]
(4) Deformation degree of the particles The cross section in the longitudinal direction of the film is observed with a transmission electron microscope, and each particle or an aggregate (aggregate) formed at an interval smaller than the primary particle diameter is regarded as one particle. The maximum length D and the minimum length d of each particle present in the film 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.
[0046]
(5) The thermoplastic resin is removed from the surface of the average particle diameter film by a plasma low-temperature ashing 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.
[0047]
(6) 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.
[0048]
(7) Retort adhesion force Heating a tin-free steel plate (thickness 0.2 mm) at a temperature in the range of the melting point of the film to the melting point + 25 ° C., and the surface orientation coefficient of the non-metal plate side surface of the film after lamination (Conditions to be 0.02 to 0.03) The films were pasted at 50 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 a retort treatment at 120 ° C. for 40 minutes was performed. The peel length of the film from the steel plate after retorting was measured. Evaluation was performed from the average value of the measurement using five or more samples.
Class A: less than 10 mm Class B: less than 20 mm 10 mm or more Class C: 20 mm or more
(8) Taste characteristics A stainless steel cylinder (inner cross-sectional area: 150 cm ² ) is placed on the laminated film of the laminated steel sheet, sealed with 200 ml of purified water, and retorted at 120 ° C. for 1 hour in a retort kettle. Went. After retorting, water was once cooled to 5 ° 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 0.10 or more Class C: 0.15 or more
(9) A steel plate laminated as described above with an abrasion-resistant laminate of 100 m / min is formed into a coil of 5000 m with an ironing and drawing machine (molding ratio (maximum thickness / minimum thickness) = 1.3, moldable temperature) The can was formed (diameter 6 cm, height 10 cm). The amount of scraping of the film attached to the tool at this time was measured to evaluate the wear resistance.
Class A: Less than 1 mg Class B: 1-2.5 mg
Class C: over 2.5 mg
Reference example 1
Cyclohexanedimethanol copolymerized polyethylene terephthalate (inherent viscosity 0.68 dl / g) containing 0.12% by weight of agglomerated silica particles (average primary particle size 30 nm, average particle size 0.3 μm) as polyester A constituting the steel sheet side layer, (Melting point 228 ° C, carboxyl end amount 38 equivalents / ton) was vacuum dried at 180 ° C for 3 hours, then supplied to the extruder, discharged from the die, and then cooled and solidified with a mirror cooling drum while applying electrostatic force (6.8 kv) Thus, an unstretched film was obtained. The unstretched film was tripled in the longitudinal direction at a temperature film temperature of 98 ° C., stretched 3.2 times in the width direction at a preheating temperature of 90 ° C. (3 seconds) and a stretching temperature of 115 ° C., and then relaxed at 190 ° C. %, And heat treated for 5 seconds to obtain a biaxially stretched laminated polyester film having a thickness of 20 μm. Tables 1 and 2 show the raw material and film forming conditions. The degree of irregularity of the aggregated silica particles in the obtained film was 12. Film properties and evaluation results of Ru der as shown in Table 3.
[0052]
Examples (or Reference Examples) 2 to 7, Comparative Examples 1 and 2
Films having polyester A and polyester B shown in Table 1 as A layer and B layer, respectively, were formed in the same manner as in Reference Example 1 under the conditions shown in Table 2. Here, in Example 6 and Reference Example 7, both layer A and layer B were blended with 33 mol% cyclohexanedimethanol copolymerized polyethylene terephthalate and polyethylene terephthalate at an appropriate ratio and supplied to the extruder. Further, in Polyester A of Example 6 and Reference Example 7, two melting peaks appeared. Of these, the main melting point was 243 ° C. for Example 6 and 215 ° C. for Reference Example 7. The characteristics and evaluation results of the films are as shown in Table 3, and the films of the examples showed good can characteristics. On the other hand, the film of Comparative Example 1 was inferior in terms of adhesion and taste characteristics, and the film of Comparative Example 2 was inferior in all evaluation items of adhesion, taste characteristics, and abrasion resistance.
[0053]
[Table 1]

[0054]
[Table 2]

[0055]
[Table 3]

[0056]
The abbreviations in the table are as follows.
PET: polyethylene terephthalate PET / CHDM: cyclohexanedimethanol copolymerized polyethylene terephthalate PET / I: isophthalic acid copolymerized polyethylene terephthalate PET / I / CHDM: isophthalic acid and cyclohexanedimethanol copolymerized polyethylene terephthalate
【The invention's effect】
According to the present invention, the polyester film obtained by copolymerizing a specific amount of the cyclohexanedimethanol component can improve the adhesion between the metal plate and the film, particularly the adhesion and taste characteristics during retort treatment.

Claims (9)

Ethylene terephthalate and / or ethylene naphthalate units as a main constituent, on at least one surface of the A layer containing a polyester A containing 2 to 35 mol% of cyclohexane dimethanol as a copolymer component, ethylene terephthalate and / or ethylene naphthalate A polyester film for laminating and forming a metal plate, characterized in that a layer B comprising a polyester B containing 0.1 to 4 mol% of cyclohexanedimethanol as a main copolymerization component is laminated .   It consists of at least 2 types of polyester containing the polyester A, The metal film for metal plate bonding shaping | molding processing of Claim 1 characterized by the above-mentioned. The polyester film for laminating and forming a metal plate according to claim 1 or 2, wherein the polyester component contained in the A layer has a main melting point of 246 ° C or higher. The polyester film for metal plate bonding molding processing according to any one of claims 1 to 3, wherein the B layer comprises at least two types of polyester containing polyester B. The metal plate bonding according to any one of claims 1 to 4 , wherein the degree of irregularity of the particles contained in the polyester A (ratio of the maximum length to the minimum length of the particles) is 1.1 or more. Polyester film for molding process. The metal plate bonding according to any one of claims 1 to 5 , wherein the degree of irregularity of the particles contained in the polyester B (ratio of the maximum length to the minimum length of the particles) is 1.1 or more. Polyester film for molding process. It forms by biaxial stretching, The polyester film for metal-plate bonding shaping | molding processing in any one of Claims 1-6 characterized by the above-mentioned. The polyester film for laminating and processing a metal plate according to any one of claims 1 to 7 , wherein the layer A composed of polyester A has a plane orientation coefficient of 0.01 to 0.13. The polyester film for laminating and processing a metal plate according to any one of claims 1 to 8 , wherein the plane orientation coefficient of the B layer made of polyester B is 0.06 to 0.15.