JP2006328187A - Method for producing polyester film for laminating metal plate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing a polyester film having excellent adhesiveness to a metal plate and tearing properties and excellent can manufacturing properties (e.g. mold release properties of an inner surface resin from a processing punch in drawing and ironing processing). <P>SOLUTION: The method for producing the polyester film for laminating the metal plate composed of a polyester composition consisting essentially of ethylene terephthalate and ethylene isophthalate, containing a polyoxyalkylene glycol component as a glycol component and having 220-250°C melting point and <1.385 g/cm<SP>3</SP>density is provided. The method for producing the polyester film for laminating the metal plate comprises a step of stretching a molten polyester resin film which contains foreign materials having ≥25 μm size and controlled to ≤10 number of the foreign materials based on 1 cm<SP>3</SP>and is solidified with streamer corona discharge from an electrode arranged along the contact point of the molten resin film with a cooling roll. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for producing a polyester film used for the purpose of preventing corrosion of metal containers such as soft drinks, beer, and canned foods, and more specifically, for producing the inner surface of a two-piece can (for example, squeezing and ironing). The present invention relates to a method for producing a polyester film excellent in processability.

  Conventionally, a method of coating a metal plate with a thermoplastic resin by a melt extrusion method has been disclosed for the purpose of preventing corrosion on the inner surface of the metal can. (For example, refer to Patent Document 1). Also disclosed is a method of laminating a thermoplastic resin film to a metal plate. (For example, refer to Patent Document 2).

  However, when a polyester film mainly composed of polyethylene terephthalate is applied to a two-piece can, the moldability during drawing and ironing and the adhesion of the film to a metal plate are insufficient, and there is a problem of peeling or tearing. It was.

  In order to avoid such problems, various forms of biaxially oriented films have been disclosed. (For example, refer to Patent Document 3, Patent Document 4, and Patent Document 5).

  However, the methods disclosed in these documents are certainly effective when used for drawn cans and deep-drawn cans having a low processing deformation rate, but are used for two-piece cans (for example, drawn iron cans) having a high processing deformation rate. In some cases, a sufficient effect on moldability was not obtained. That is, when the deformation rate at the time of can making is large, the film laminate metal plate obtained by the above-mentioned conventional technique has insufficient film spreadability and adhesion, and the adhesion between the film on the inner surface of the can and the punch ( The problem of stripping out still remained.

  In addition, a method is disclosed in which a molten resin film extruded from a T die or the like is solidified with a cooling roll using a wire-like or knife-edge-like electrode. (For example, refer to Patent Document 6). However, in this method, when the molten resin film is solidified with a cooling roll at a high speed of 30 m / min or more, a bubble-like defect is likely to occur on the surface of the obtained sheet, and this bubble-like defect expands in the stretched film. As a result, the metal plate laminated with this film has dents and bubbles, and when this laminated metal plate is molded, it is easy to cause fine film breakage with the dents or bubbles as the starting point. There was a problem.

Further, a method of using streamer corona discharge from needle-shaped, saw-tooth-shaped, wire-shaped, or knife-edge-shaped electrodes in order to efficiently adhere the molten resin film to the cooling roll at a high speed of about 40 m / min is disclosed. (For example, refer to Patent Document 7). However, this method is an effective method for polyamide-based compositions, but in polyester-based compositions having excellent flavor properties required for film laminates for metal containers, streamer corona discharge is caused by foreign substances present inside. There was a problem that excessive current flowed and spark discharge occurred, and film formation was not stable.
JP-A-57-203545 JP-A-4-261826 JP-A 64-22530 Japanese Patent Publication No. 8-19246 JP-A-3-93525 Japanese Examined Patent Publication No. 37-6142 JP-A-56-105930

  The object of the present invention is to solve the problems of the prior art. That is, it has excellent adhesion to the metal plate and tearability, and is less likely to cause bubble defects in the sheet obtained by cooling and solidifying the molten resin film at a high speed (for example, a high speed of 30 m / min or more). Since the film obtained in this way does not have dents or bubbles exceeding 50 μm in size, it can provide a method for producing a polyester film excellent in can-making properties (for example, releasability between the inner surface resin and the processed punch in drawing and ironing).

1st invention of this application consists of the polyester composition which has ethylene terephthalate and ethylene isophthalate as a main component, and this polyester is a polyoxyalkylene glycol whose repeating of an alkylene oxide unit having 2 or more carbon atoms is 3 or more The component is contained as an alkylene oxide unit having 2 or more carbon atoms derived from the polyoxyalkylene glycol component with respect to the total acid component of the polyester composition, and the melting point is 220 to 250 ° C. And a density of less than 1.385 g / cm ^3, which is a method for producing a metal film-laminated polyester film (polyester film A), and controls the number of foreign matters of 25 μm or more to 10 or less per 1 cm ^3. The molten polyester resin film along the contact point of the molten resin film to the cooling roll A method for producing a metal plate laminating a polyester film, characterized in that the electrodes disposed with a step of stretching the sheet was solidified by streamer corona discharge (polyester film A).

A second invention of the present application is characterized in that the polyester composition for forming the polyester film according to claim 1 has a melt specific resistance of 0.3 × 10 ⁸ Ω · cm or more, and is a polyester for laminating metal plates. It is a manufacturing method of a film.

  According to a third aspect of the present invention, a polyester film for laminating a metal plate is characterized in that the polyester composition constituting the polyester film according to claim 1 contains a polyalkylene terephthalate-polytetramethylene oxide block copolymer. It is a manufacturing method.

  In a fourth invention of the present application, the electrode according to claim 1 is a tape-like electrode (thickness of 5 to 200 μm, an electrode having a plurality of protrusions having a protrusion amount of 0.1 mm or more at the electrode tip). It is a manufacturing method of the polyester film for metal plate bonding characterized by these.

  The method for producing a polyester film of the present invention provides a polyester film excellent in adhesion to a metal plate and squeezing and ironing canability (particularly, release properties of can inner film and processing punch during canning), As a result, since a metal can obtained by making a metal plate laminated with this film has excellent corrosion resistance, it is an extremely useful method for producing a polyester film for laminating metal plates.

The present invention comprises a polyester composition comprising ethylene terephthalate and ethylene isophthalate as main components, wherein the polyester comprises a polyoxyalkylene glycol component having 3 or more repeating alkylene oxide units having 2 or more carbon atoms, As an alkylene oxide unit having 2 or more carbon atoms derived from the polyoxyalkylene glycol component, it is contained in an amount of 2 to 20 mol% based on the total acid component of the polyester composition, the melting point is 220 to 250 ° C., and the density is A method for producing a polyester film for laminating metal sheets, characterized by being less than 1.385 g / cm ³ , wherein a polyester molten resin film in which foreign matters of 25 μm or more are controlled to 10 or less per 1 cm ³ Streamer corona from electrodes placed along the point of contact of the membrane to the chill roll Is a manufacturing method of combined polyester film for pasting a metal plate and having a step of stretching the sheet was solidified by electrostatic.

  In the present invention, the copolymer polyester contained in the polyester constituting the polyester film A is a copolymer polyester containing an ethylene terephthalate component as a main component and an ethylene isophthalate component. The ratio of the isophthalic acid component to the total acid component of the copolymerized polyester is preferably 3 to 20 mol%, and more preferably 4 to 12 mol%. The copolymerized polyester can contain other copolymerization components as long as the purpose is not impaired. Among other copolymerizable components that can be used, aromatic dicarboxylic acids such as naphthalenedicarboxylic acid, diphenylsulfone dicarboxylic acid, 5-sodium sulfoisophthalic acid, oxalic acid, succinic acid, adipic acid, sebacic acid, decane Aliphatic dicarboxylic acids such as dicarboxylic acid, maleic acid, fumaric acid and dimer acid, oxycarboxylic acids such as p-oxybenzoic acid, and alicyclic dicarboxylic acids such as cyclohexanedicarboxylic acid can be used. The amount of the above-mentioned dicarboxylic acids and their ester derivatives that can be used is preferably 20 mol% or less, more preferably 10 mol% or less. When the usage-amount of other dicarboxylic acid and those ester derivatives exceeds 20 mol%, the thermal stability of polyester may worsen. As glycol components, aliphatic glycols such as propanediol, butanediol, pentanediol, hexanediol and neopentylglycol, alicyclic glycols such as cyclohexanedimethanol, ethylene oxide adduct of bisphenol A, ethylene oxide of bisphenol S Aromatic glycols such as adducts, polyethylene glycol, polypropylene glycol, polytetramethylene glycol and the like can be used. In addition, a small amount of a compound containing an amide bond, a urethane bond, an ether bond, a carbonate bond, or the like may be included. Here, the amount of the other glycol component that can be used is preferably 20 mol% or less, and more preferably 10 mol% or less. When the usage-amount of other glycol components exceeds 20 mol%, the thermal stability of polyester may deteriorate.

  In the present invention, the polyester constituting the polyester film A has 3 or more repeating alkylene oxide units having 2 or more carbon atoms in order to improve adhesion and tearability during film-making of metal laminate metal plates. It is necessary to contain a certain polyoxyalkylene glycol component. By containing the above components, the polyester composition is imparted with elasticity at room temperature and low temperature, and in particular, it prevents process abnormalities during continuous production due to accumulation of chips (whiskers) due to poor tearability of the film during can making. be able to. Moreover, adhesiveness with other resin layers can be improved. Examples of polyoxyalkylene glycols comprising alkylene oxide units having 2 carbon atoms include polyethylene glycol (2 carbon atoms), polytrimethylene glycol (3 carbon atoms), polytetramethylene glycol (4 carbon atoms), polyhexamethylene Glycol (6 carbon atoms) can be used, and one of these components may be used alone, or two or more components may be mixed and used. The average molecular weight of the polyoxyalkylene glycol is preferably in the range of 500 to 3000, and more preferably in the range of 800 to 2000.

  In the present invention, the method for containing the polyoxyalkylene glycol component is not particularly limited. That is, after adding the polyoxyalkylene glycol component in the same manner as other raw materials at the stage of producing the polyester composition constituting the film, the polyester composition obtained by terminating the polyester synthesis reaction may be used, Another copolyester copolymerized with polyoxyalkylene glycol may be melt-mixed, but the latter melt-mixing can be used to reduce chips (whisker-like resin pieces) due to poor film tearability during drawing and ironing. More preferably, the method of melt-mixing the polyalkylene terephthalate-polytetramethylene oxide block copolymer is most preferable.

  In the present invention, the amount of the polyoxyalkylene glycol component contained in the polyester is such that the amount of alkylene oxide units having 2 or more carbon atoms derived from the polyoxyalkylene glycol component is based on the total acid component of the polyester composition. It is preferable that it is 2-20 mol%. The alkylene oxide unit having 2 or more carbon atoms derived from the polyoxyalkylene glycol component is a structural unit in which both ends of an alkylene chain form an ether bond with an adjacent alkylene chain with an oxygen atom interposed therebetween, When the amount is less than 2 mol%, the effect of improving canability and tearability is insufficient. On the contrary, when it exceeds 20 mol%, the strength and thermal characteristics of the film are lowered, and the handleability in the film production process and the production process of the laminated metal plate may be deteriorated.

  In the present invention, it is necessary that the melting point of the polyester film A is 220 to 250 ° C. from the viewpoint of securing the can-making property (releasability of punches on the inner surface side of the can in drawing and ironing). Furthermore, when the work deformation rate at the time of can making is large, it is preferable that it exists in the range of 230-245 degreeC. It is necessary to adjust the type and content of the copolymerization component so as to fall within the above melting point range. When the melting point of the film is less than 220 ° C., the releasability between the can inner film and the processing punch is poor. On the contrary, when the melting point of the film exceeds 250 ° C., a part of the can inner surface film is easily peeled off from the metal plate.

In the present invention, the polyester film A needs to have a density of less than 1.385 g / cm ³ from the viewpoint of ensuring adhesion. When the density of the film is 1.385 g / cm ³ or more, poor ductility due to poor adhesion between the film and the metal plate (the film can no longer follow the deformation at the time of can making, the film peels off from the metal plate, The film is torn locally).

In the present invention, the polyester composition is melted in a known single-screw or twin-screw extruder, and a foreign matter removing filter medium (for example, a stainless sintered filter medium in which 95% of the initial filtration efficiency is set to 20 μm or less). In order to stabilize electrostatic adhesion by streamer corona discharge, it is necessary that the amount of foreign matter of 25 μm or more contained per 1 cm ^{3 of the} polyester molten resin film obtained from the T die is 10 or less.

  The streamer corona discharge in the present invention is a state in which, for example, a stable corona discharge is performed by bridging an electrode to which a positive voltage is applied and a molten resin film as a ground body. That is, when the voltage applied between the electrode and the cooling roll is increased, a dark current state (unsustainable discharge phenomenon) occurs first, then a glow discharge state occurs, and then the discharge from the electrode causes This is a discharge in which air is ionized and a stable current flows continuously. In the streamer corona discharge state, the voltage V (kV) applied to the electrode and the current value I (mA / cm) per unit width flowing through the molten resin film as the electrode and the ground body are I ≧ 0.025 × V. The relationship of −0.12 is established.

In the present invention, even if the melt specific resistance of the polyester composition constituting the film is 0.3 × 10 ⁸ Ω · cm or more, a streamer corona can stably and continuously apply a large amount of charge to the molten resin film. Therefore, even when the molten resin film is cooled and solidified at a high speed (for example, at a high speed of 30 m / min or more), bubble-like defects are less likely to occur.

  In the present invention, the electrode is a tape-like electrode (thickness of 5 to 200 μm, an electrode having a plurality of protrusions having a protrusion amount of 0.1 mm or more at the electrode tip), so that the gap between the electrode and the cooling roll is used. This is preferable because streamer corona discharge can be uniformly generated in the molten resin film from each protrusion provided on the tape-like electrode without setting the applied voltage to an excessively high value. When the thickness of the tape-shaped electrode is less than 5 μm, the electrode is easily broken and film formation becomes unstable. On the other hand, when the thickness exceeds 100 μm, the concentration of the electric field tends to decrease and the streamer corona discharge becomes unstable. On the other hand, when the protruding amount is less than 0.1 mm, the concentration of the electric field is liable to be lowered, and the streamer corona discharge becomes unstable.

  In this invention, the polyester composition which comprises the polyester film A may be single, and the blend of two or more types of polyester compositions from which a composition ratio differs may be sufficient. Furthermore, a small amount of other polyesters typified by polybutylene terephthalate can be mixed.

  In this invention, it does not specifically limit about the manufacturing method of the polyester composition which comprises the polyester film A. That is, it can be used even if it is produced by either the transesterification method or the direct polymerization method. Further, it may be produced by a solid phase polymerization method in order to increase the molecular weight. Furthermore, in order to ensure the flavor of polyester in the retort treatment etc. that is carried out after filling the contents in the can, and to prevent contamination of the can-making line, it can be solidified under reduced pressure or in an inert gas atmosphere. It is preferred to use a polyester with a low oligomer content produced by phase polymerization. For example, the content of oligomeric cyclic trimers including ethylene terephthalate cyclic trimer is preferably 0.7% by weight or less.

  In the present invention, when the polyester composition constituting the polyester film A is produced, antimony oxide, germanium oxide, titanium compound, etc. are used as the polymerization catalyst. In addition to the polymerization catalyst, the melt specific resistance of the polyester resin composition of the present invention is reduced. To adjust, Mg salt such as magnesium acetate and magnesium chloride, Ca salt such as calcium acetate and calcium chloride, Mn salt such as manganese acetate and manganese chloride, Zn salt such as zinc chloride and zinc acetate, cobalt chloride and cobalt acetate It is also possible to add Co salt such as 300 ppm or less as the total amount of each metal ion and phosphoric acid or a phosphoric acid ester derivative such as trimethyl phosphate or triethyl ester as a phosphorus atom in a range of 200 ppm or less. At this time, it is preferable that the molar ratio of the total phosphorus amount to be added and the total metal ion amount is 0.4 or more in order to suppress coloring of the polyester composition and to ensure heat resistance and hydrolysis resistance.

  In the present invention, the intrinsic viscosity of the polyester composition constituting the polyester film A is preferably 0.6 to 1.2 dl / g. When the intrinsic viscosity is less than 0.6 dl / g, the mechanical properties of the obtained film may be deteriorated. Conversely, when it exceeds 1.2 dl / g, not only the improvement effect of the mechanical properties is saturated but also polyester. When producing the composition, productivity is reduced, which is not economical.

  In the present invention, the amount of lubricant in the polyester film A is not particularly limited, but when producing a metal container by drawing and ironing a metal plate laminated with a film obtained to be in the range of 0.01 to 1% by weight. It is preferable for imparting slipperiness of the film-laminated metal plate. When the amount of the lubricant in the film is less than 0.01% by weight, the releasability from the punch is lowered during the drawing and ironing process, and the film is likely to be scratched. On the contrary, when the amount of lubricant in the film exceeds 1% by weight, not only the effect of preventing scratches is saturated but also the economic efficiency is lowered.

  In the present invention, it is preferable to use inert inorganic particles, crosslinked polymer particles, or the like as the lubricant. The inert inorganic particles are silica, alumina, kaolin clay, titanium oxide, calcium phosphate, calcium carbonate, lithium fluoride, barium sulfate, carbon black and the like. The crosslinked polymer particles include acrylic monomers such as acrylic acid, methacrylic acid, acrylic ester, and methacrylic ester, styrene monomers such as styrene and alkyl-substituted styrene, divinylbenzene, Copolymers with crosslinking monomers such as divinyl sulfone, ethylene glycol dimethacrylate, trimethylolpropane trimethyl acrylate, pentaerythritol tetramethyl acrylate, melamine resins, benzoguanamine resins, phenol resins, silicon-containing resins, etc. It is. Among these, as the inorganic particles, aggregated silica particles are preferable, and as the crosslinked polymer particles, crosslinked polymethyl methacrylate particles are preferable.

  In the present invention, the average particle size of the lubricant is preferably 1 to 3 μm. When the thickness is less than 1 μm, the effect of preventing scratching of the film is not sufficiently exhibited. On the other hand, if it exceeds 3 μm, not only the scratch-preventing effect is saturated, but also the lubricant is liable to fall off due to wear, and the film is easily broken.

  In the present invention, the addition of the lubricant particles to the polyester film A may be performed in the polyester polymerization step, or the polyester and the lubricant particles may be added by melt kneading. Moreover, you may dilute and add the masterbatch containing a high concentration lubricant particle at the time of manufacture of a polyester film.

  In the present invention, it is preferable to perform biaxial stretching from the viewpoint of obtaining sufficient strength for handling during film formation or processing of the polyester film A. Examples of the biaxial stretching method include sequential biaxial stretching and simultaneous biaxial stretching. For example, the film may be stretched 2 to 5 times in the longitudinal and lateral directions at a temperature equal to or higher than the glass transition temperature of polyester. Moreover, you may heat-treat at the temperature of 120-200 degreeC under tension | tensile_strength for 1-20 seconds under tension | tensile_strength as needed after extending | stretching, and may control the heat shrink rate of the extending | stretching direction of a film. Further, before the heat treatment step, restretching may be performed in the longitudinal direction and / or the transverse direction. Furthermore, you may implement a corona discharge process to the single side | surface or both surfaces of a film in a extending | stretching process or its front and back.

  In the present invention, the thickness of the obtained polyester film is not particularly limited, but is preferably 5 to 50 μm from the viewpoint of the laminate property of the film to a metal plate, corrosion resistance in a metal container, and economical efficiency.

  Hereinafter, the present invention will be described based on examples.

[Evaluation methods]
(1) Melting point of polyester film A 10 mg of polyester film was measured in a nitrogen stream using a differential scanning calorimeter (DSC) at a heating rate of 10 ° C./min. The apex temperature of the accompanying endothermic peak was defined as the melting point (° C.).
(2) Density of polyester film A It measured at 25 degreeC using the density gradient tube according to JISK7112.
(3) Detection of foreign matters of 25 μm or more Using 160 optically defective polyester sheet pieces (250 mm × 250 mm) cooled and solidified after melt extrusion as samples, an optical defect recognized as having a size of 25 μm or more was detected using an optical defect detector. . In the optical defect detection device, a 20 W × 2 fluorescent lamp is installed as a projector at 400 mm below the XY table, and a mask with a slit width of 10 mm is installed. Then, the angle between the line connecting the light projector and the light receiver installed opposite to this and the vertical direction of the sheet surface to be measured is set to 12 °, and depending on the incident light if there is an optical defect there In order to shine, the amount of light is converted into an electric signal by a CCD image sensor camera installed 500 mm above the XY table, and the electric signal is amplified and differentiated and compared with a threshold level and a comparator. An optical defect detection signal is output. In addition, based on the video signal input from the CCD image sensor camera, the size of the optical defect is measured by an image procedure, and the position of the optical defect having a preset size is displayed. The defects thus obtained were observed under a microscope, and the number of those having a size of 25 μm or more was counted.

(4) Melt specific resistance (ρi) of the polyester composition constituting the polyester film
Two electrodes (stainless steel wires) were placed in a polyester composition melted at 275 ° C., and the current (i) when a voltage of 120 V was applied was measured. (Ω · cm).
ρi = (A / L) × (V / i)
A: Area between electrodes (cm ² ), L: Distance between electrodes (cm), V: Voltage (5) Composition of polyester composition A polyester resin sample was dissolved in deuterated chloroform containing 15% by weight of trifluoroacetic acid, and 1H -NMR was measured. In the case of a laminated film, the lower layer resin layer was removed with a solvent or the like, and the remaining upper layer sample was dissolved in the same manner, and 1H-NMR was measured. The composition ratio was determined from the integrated intensity of the peaks derived from each component.
(6) Ethylene terephthalate cyclic trimer content of polyester composition Polyester is dissolved in hexafluoroisopropyl alcohol / chloroform = 2/3 (V / V), the polyester is precipitated with methanol, and the precipitate is filtered off. . The filtrate is evaporated to dryness and the evaporated dry matter is dissolved in dimethylformamide. The obtained solution was developed by a liquid chromatography method, and the content of the ethylene terephthalate cyclic trimer was quantified.
(7) Preparation of laminated metal plate Polyester film A is bonded to one side of a polyester alloy film heated to 250 ° C. (3004 series alloy plate having a thickness of 0.26 mm), and polyester B is bonded to the other side between nip rolls. The laminate was further heated to 275 ° C. and then quenched in water to produce a laminated metal plate.

(8) Tear strength Samples of 7 cm square were cut out from the laminated metal plates obtained in Examples 1 to 4 and Comparative Examples 3 to 7. This sample was immersed in dilute hydrochloric acid to dissolve and remove a part of the metal plate, and the film was taken out. The film was notched, and both ends thereof were fixed to the upper and lower chucks of a tensile tester and pulled up and down at a speed of 500 mm / min, and the tearing stress at that time was measured. The thickness of the film was measured, and the average value (n = 5) of the tear stress converted to 25 μm thickness was taken as the tear strength. When the tear strength is 0.7 N or less, it can be said that there is no substantial problem with the film cutting ability during continuous canning.
(9) Releasability between can inner surface resin and processing punches After the laminated metal plates obtained in Examples 1 to 4 and Comparative Examples 3 to 7 were formed into cups by drawing, they were redrawn at a speed of 80 cans / minute. -300 cans were continuously manufactured by ironing, and the degree of buckling occurring at the top of the formed can or the degree of occurrence of a beard-like film was visually observed. Evaluation criteria were set as follows, and ○ was evaluated as practical.
○: Buckling has not occurred in the can opening Δ: Buckling has occurred or a bearded film has occurred in about 1/3 of the circumference of the can opening x: Buckling has occurred in more than 1/3 of the circumference of the can opening (10 ) Average particle diameter of particles Treated with an ultrasonic transmitter (Nippon Seiki Seisakusho, US-300T) at 250 μA for 1 minute, using a laser diffraction particle size distribution analyzer (Leeds & Northrup, Microtrac HRA model 19320-X100), The refractive index of the dispersion medium (water) was 1.33, and the 50% volume particle size was measured.

Next, the kind and content of polyester used for Examples 1-4 and Comparative Examples 1-7 are demonstrated.
(1) A-1: Polyethylene terephthalate / isophthalate (ethylene isophthalate repeating unit 10 mol%, ρi: 0.2 × 10 ⁸ Ω · cm, average particle size: 1.3 μm of agglomerated silica, blended with 1000 ppm, ethylene (0.5% by weight of terephthalate cyclic trimer)
(2) A-2: Polyethylene terephthalate / isophthalate (ethylene isophthalate repeating unit 10 mol%, ρi: 3.6 × 10 ⁸ Ω · cm, average particle size: 1.3 μm of agglomerated silica, blended with 1000 ppm, ethylene (0.5% by weight of terephthalate cyclic trimer)
(3) A-3: Polyethylene terephthalate (ρi: 0.23 × 10 ⁸ Ω · cm, average particle diameter: 2000 ppm of agglomerated silica of 1.3 μm, ethylene terephthalate cyclic trimer is 0.5% by weight)
(4) A-4: Copolyester Copolymerized polyester of terephthalic acid and ethylene glycol / neopentyl glycol (copolymerization ratio of neopentyl glycol: 30 mol%, ρi: 0.23 × 10 ⁸ Ω · cm, average particle Diameter: 1000ppm of 1.3μm agglomerated silica)
(5) A-5: Polybutylene terephthalate (ρi: 4.7 × 10 ⁸ Ω · cm)
(6) B: Polytetramethylene terephthalate-polytetramethylene oxide block copolymerized polyester (polytetramethylene oxide copolymerization ratio: 40% by weight, ρi: 8.7 × 10 ⁸ Ω · cm)

  Table 1 shows the raw material, melting point, density, number of foreign matters, tear strength, canability (releasability of processed punch) of the polyester film A.

[Example 1]
A-1 / A-2 / B = 50/45/5 (% by weight) as a polyester raw material is dried under reduced pressure (1.3 hPa) at 120 ° C. for 24 hours and melted at 270 ° C. using a single screw extruder. After that, the filter is passed through a filter for removing foreign substances made of a stainless steel sintered filter whose filter particle size (initial filtration efficiency 95%) is set to 10 μm, and then a cooling roll (circumferential speed 50 m / min) from a 45 cm wide T-die. Casted in layers (tape shape made of austenitic SUS316 with a width of 10mm x 50μm installed so as to face the circumferential surface of the cooling roll, with protrusions of 2mm protruding at 1.2mm intervals An unstretched sheet was obtained by applying a voltage of 7.2 kV from the electrode and applying an 8.3 mA current to cause electrostatic contact. The unstretched sheet was stretched 3.3 times in the machine direction at a preheating temperature of 80 ° C. and a stretching temperature of 100 ° C., and further stretched by 3.7 times in the transverse direction at a preheating temperature of 80 ° C. and a stretching temperature of 100 ° C. A polyester film (polyester film A) having a thickness of 25 μm was obtained by heat treatment at 3 ° C. for 3 seconds. The amount of tetramethylene oxide derived from the polytetramethylene glycol component in this film was 5.2 mol% with respect to the acid component (total amount of terephthalic acid and isophthalic acid).
Further, after A-3 / A-5 = 40/60 (% by weight) as a polyester raw material was dried under reduced pressure (1.3 hPa) at 120 ° C. for 24 hours and melted at 280 ° C. using a single screw extruder. Through a filter for removing foreign substances made of a stainless steel sintered filter whose filter particle size (initial filtration efficiency 95%) is set to 10 μm, and then onto a cooling roll (circumferential speed 50 m / min) from a 45 cm wide T-die Cast from layered tape (from a tape-like electrode made of austenitic SUS316 with a width of 10 mm and a thickness of 50 μm arranged so as to face the circumferential surface of the cooling roll and having protrusions with a protrusion amount of 2 mm arranged at intervals of 1.2 mm An unstretched sheet was obtained by applying a voltage of 7.2 kV and applying an electric current of 8.3 mA for electrostatic contact. The unstretched sheet was stretched 3.3 times in the machine direction at a preheating temperature of 70 ° C. and a stretching temperature of 95 ° C., and further stretched 3.8 times in the transverse direction at a preheating temperature of 60 ° C. and a stretching temperature of 100 ° C. A polyester film (polyester film B) having a thickness of 16 μm was obtained by heat treatment at 0 ° C. for 3 seconds.
Next, this film was pressure-bonded between nip rolls on both sides of a 3004 series aluminum alloy plate (thickness 0.26 mm) heated to 250 ° C., further heated to 275 ° C., and then rapidly cooled in water to obtain a laminated metal plate.
Next, a molding lubricant was applied to the laminated metal plate, and then heated and drawn at a plate temperature of 70 ° C. so that the film A was on the inner surface side of the can. Subsequently, the temperature of the obtained cup was set to 40 ° C., and redrawing and ironing were performed at a mold temperature of 80 ° C. to obtain a 350 ml size seamless can.
As can be seen from Table 1, the method of this Example can be said to be a method for producing a film for laminating a metal plate that has excellent can-making properties (releasability of processing punches).

[Example 2]
Polyester films A and B were obtained in the same manner as in Example 1 except that A-1 / B = 95/5 (% by weight) was used as a raw material for the polyester film A. The amount of tetramethylene oxide derived from the polytetramethylene glycol component in this polyester film A was 5.2 mol% with respect to the acid component (total amount of terephthalic acid and isophthalic acid).
Next, a laminated metal plate and a seamless can were obtained in the same manner as in Example 1.
As can be seen from Table 1, the method of this Example can be said to be a method for producing a film for laminating a metal plate that has excellent can-making properties (releasability of processing punches).

[Example 3]
Polyester films A and B were obtained in the same manner as in Example 1 except that A-1 / A-3 / B = 50/45/5 (% by weight) was used as a raw material for the polyester film A. The amount of tetramethylene oxide derived from the polytetramethylene glycol component in this polyester film A was 5.2 mol% with respect to the acid component (total amount of terephthalic acid and isophthalic acid).
Next, a laminated metal plate and a seamless can were obtained in the same manner as in Example 1.
As can be seen from Table 1, the method of this Example can be said to be a method for producing a film for laminating a metal plate that has excellent can-making properties (releasability of processing punches).

[Example 4]
Polyester films A and B were obtained in the same manner as in Example 1 except that A-1 / B = 98/2 (% by weight) was used as a raw material for the polyester film A. The amount of tetramethylene oxide derived from the polytetramethylene glycol component in this polyester film A was 2.2 mol% with respect to the acid component (total amount of terephthalic acid and isophthalic acid).
Next, a laminated metal plate and a seamless can were obtained in the same manner as in Example 1.
As can be seen from Table 1, the method of this Example can be said to be a method for producing a film for laminating a metal plate that has excellent can-making properties (releasability of processing punches).

[Comparative Example 1]
An attempt was made to form a film in the same manner as in Example 1 except that a filter for removing foreign substances made of a stainless steel sintered filter medium having a filtration particle size (initial filtration efficiency of 95%) set to 25 μm was used, but spark discharge occurred frequently. As a result, a complete adhesion abnormality occurred and the polyester film could not be obtained stably.
This method is not preferable as a method for producing a metal plate laminating film.

[Comparative Example 2]
Except for using a tungsten wire electrode having a diameter of 30 μm, an attempt was made to form a film in the same manner as in Example 1. However, even if the position, voltage, and current of the electrode were adjusted, bubbles and streaks were generated, and the voltage was increased. Alternatively, when the current was increased to cause close contact, the wire was cut by arc discharge, cooling spots were generated on the sheet, and the film was wound around the cooling roll, and the polyester film could not be stably obtained.
This method is not preferable as a method for producing a metal plate laminating film.

[Comparative Example 3]
Polyester films A and B were obtained in the same manner as in Example 1 except that A-3 / B = 95/5 (% by weight) was used as a raw material for the polyester film A. The amount of tetramethylene oxide derived from the polytetramethylene glycol component in this polyester film A was 5.2 mol% with respect to the acid component (total amount of terephthalic acid and isophthalic acid).
Next, a laminated metal plate obtained in the same manner as in Example 1 was obtained. This laminate was canned in the same manner as in Example 1, but the resin on the inner surface of the can was peeled off.
As can be seen from Table 1, this method is not preferred as a method for producing a metal plate laminating film.

[Comparative Example 4]
Polyester films A and B were obtained in the same manner as in Example 1 except that A-4 / B = 95/5 (% by weight) was used as a raw material for the polyester film A, and the heat treatment temperature after stretching was 100 ° C. . The amount of tetramethylene oxide derived from the polytetramethylene glycol component in the polyester film A was 5.6 mol% with respect to the acid component (total amount of terephthalic acid and isophthalic acid).
Next, a laminated metal plate obtained in the same manner as in Example 1 was obtained. This laminated plate was made in the same manner as in Example 1, but the releasability between the can inner surface resin and the processed punch was poor, and part of the can bottom was also deformed.
As can be seen from Table 1, this method is not preferred as a method for producing a metal plate laminating film.

[Comparative Example 5]
Polyester films A and B were obtained in the same manner as in Example 3 except that the heat treatment after transverse stretching of the polyester film A was treated at 215 ° C. for 3 seconds. The amount of tetramethylene oxide derived from the polytetramethylene glycol component in this polyester film A was 5.2 mol% with respect to the acid component (total amount of terephthalic acid and isophthalic acid).
Next, a laminated metal plate obtained in the same manner as in Example 1 was obtained. This laminate was canned in the same manner as in Example 1, but the resin on the inner surface of the can was peeled off.
As can be seen from Table 1, this method is not preferred as a method for producing a metal plate laminating film.

[Comparative Example 6]
Polyester films A and B were obtained in the same manner as in Example 1 except that A-1 = 100 (% by weight) was used as a raw material for the polyester film A.
Next, a laminated metal plate obtained in the same manner as in Example 1 was obtained. This laminate was canned in the same manner as in Example 1, but the tearability was poor and a beard-like resin piece was generated on the upper part of the inner surface of the can.
As can be seen from Table 1, this method is not preferred as a method for producing a metal plate laminating film.

[Comparative Example 7]
Polyester films A and B were obtained in the same manner as in Example 1 except that A-1 / B = 80/20 (wt%) was used as a raw material for the polyester film A. The amount of tetramethylene oxide derived from the polytetramethylene glycol component in this polyester film A was 23.2 mol% with respect to the acid component (total amount of terephthalic acid and isophthalic acid).
Next, an attempt was made to obtain a laminated metal plate obtained in the same manner as in Example 1, but wrinkles were generated on the film. Further, the can was produced in the same manner as in Example 1, but the releasability between the can inner film and the processing punch was poor, and a part of the can bottom was deformed.
As can be seen from Table 1, this method is not preferred as a method for producing a metal plate laminating film.

  The polyester film obtained in the present invention is excellent in adhesion to a laminate with a metal plate, and the obtained film laminate metal plate is excellent in can-making properties (particularly, release property of can inner surface resin and processing punch during can making). Therefore, it can be said that it is extremely useful as a method for producing a polyester film used for the purpose of preventing corrosion of metal containers such as soft drinks, beer and canned foods.

Claims (4)

A polyester composition comprising ethylene terephthalate and ethylene isophthalate as main components, wherein the polyester comprises a polyoxyalkylene glycol component having 3 or more repeating alkylene oxide units having 2 or more carbon atoms. As an alkylene oxide unit having 2 or more carbon atoms derived from the component, it is contained in an amount of 2 to 20 mol% based on the total acid component of the polyester composition, the melting point is 220 to 250 ° C., and the density is 1.385 g / A method for producing a metal film-laminated polyester film (polyester film A) characterized by being less than cm ³ , wherein a molten polyester resin film in which foreign matter of 25 μm or more is controlled to 10 or less per cm ³ is melted. From the electrode arranged along the contact point of the resin film to the cooling roll Method for producing a polyester film for laminating metal sheet characterized by having a step of stretching the sheet was solidified by Torimakorona discharge (polyester film A). The method for producing a polyester film for laminating metal plates, wherein the polyester composition constituting the polyester film according to claim 1 has a melt specific resistance of 0.3 × 10 ⁸ Ω · cm or more.   The polyester composition which comprises the polyester film of Claim 1 contains a polyalkylene terephthalate-polytetramethylene oxide block copolymer, The manufacturing method of the polyester film for metal plate bonding characterized by the above-mentioned.   The electrode according to claim 1 is a tape-like electrode (thickness of 5 to 200 μm, electrode having a plurality of protrusions having a protrusion amount of 0.1 mm or more at the electrode tip), a metal plate bonding For producing a polyester film for use.