JP2005104146A - Film for laminating deep-drawn/ironed can, metal sheet for deep-drawn/ironed can using the film, and deep-drawn/ironed can - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a film for a deep-drawn/ironed can excellent in forming workability at canning and impact resistance at low temperature storage or transportation, applicable also as a laminate film for a two-piece can, and a laminated metal sheet using the film, and the laminated can using the metal sheet. <P>SOLUTION: The film for laminating the deep-drawn/ironed can is constituted of three layers of A-layer, B-layer and C-layer each comprising a polyester, where the B-layer as an intermediate layer contains 2-10 mol% dimeric acid in the total acid component, and the C-layer is a water-dispersive copolyester, and when a metal sheet is laminated on the C-layer side of the film, the adhesive strength between the film and the metal sheet is ≥10 N/15 mm. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a thermoplastic resin film suitable for a resin-coated metal plate, and in particular, excellent for canning process such as squeezing and ironing for a drawn ironing can, and also excellent in retort resistance and impact resistance. The present invention relates to a coating film, a metal plate for a drawn iron can obtained by laminating the film on a metal plate, and a drawn iron can.

  As a method for preventing corrosion of the inner wall surface and outer wall surface of a metal can, there is a method of laminating a thermoplastic resin film. For example, Patent Document 1 discloses a polyester film for laminating a metal material for food canning. ing.

  This polyester film has excellent scratch resistance. For example, when a metal plate is formed into a cylindrical shape, and a lid is wound around the upper and lower openings of the cylinder, the film is laminated. When a metal plate (hereinafter referred to as a “film laminate metal plate”) is transferred, or when the laminate metal plate is processed by winding or the like, the problem of reducing the commercial value due to generation of scratches can be prevented.

  In addition, this film is also excellent in resistance at the time of squeezing, and since the amount of oligomer elution is small when a retort treatment is performed after filling a food after making a can, it is laminated on the inner wall surface of a metal container. Suitable as a polyester film.

  By the way, as a food can, in addition to a so-called three-piece can in which a lid is attached to the upper and lower openings of a metal cylinder formed by forming a metal plate into a cylindrical shape, a container portion is formed by deep drawing the metal plate In addition, there is a so-called two-piece can obtained by winding a lid on the upper surface opening of the container.

  In the case of the three-piece can, the film-laminated metal plate is only formed into a cylindrical shape, but in the case of a two-piece can, the film-laminated metal plate is formed by squeezing and ironing as described above. Therefore, in order to apply to a two-piece can, the laminate film is required to have excellent formability that can follow the forming of the metal plate, and also requires adhesion to the metal plate. If the moldability is insufficient or the adhesion of the film to the metal plate is insufficient, the film may be peeled off from the metal plate (delaminate phenomenon) or when the container part of the two-piece can is produced This is because the film may be peeled off or torn.

In the drawing process, the laminated metal plate is processed into a container while repeating the lowering and raising of the punch. Therefore, the film laminated on the inner wall surface side of the container is required to release from the punch. In the film laminated on the outer wall surface side, releasability from the die is required.
JP-A-7-227946

  The present invention has been made in view of the circumstances as described above, and as a laminate film for a so-called two-piece can, it has excellent molding processability at the time of can making and excellent impact resistance at the time of low-temperature storage and transfer. Another object of the present invention is to provide a squeezed iron can coating film having the above performance, a squeezed iron can metal plate using the film, and a squeezed iron can using the metal plate.

  The film for covering a squeezed iron can according to the present invention that has solved the above-mentioned problems is a laminated film composed of three layers of an A layer, a B layer, and a C layer made of polyester, and the B constituting the intermediate layer 2-10 mol% of the total acid component in the layer is dimer acid, and the C layer is a water-dispersed copolymer polyester resin, and the C layer side is adhered to the metal plate when thermally laminated with the metal plate It is characterized by a strength of 10 N / 15 mm or more.

  In the coating film according to the present invention, the adhesive strength between the film and the metal plate is 18 N / 15 mm or more after the thermal laminate plate is heated to a temperature equal to or higher than the melting point of the film to remelt the film. Some are preferable, and the Tg (glass transition temperature) of the water-dispersed copolyester resin constituting the C layer is preferably 60 ° C. or higher.

  Further, the metal plate for a squeezed iron can according to the present invention is characterized in that the above-mentioned film for covering a squeezed iron can is coated on a metal plate, and further, the squeezed iron obtained by making the film-coated metal plate. A can is also included in the technical scope of the present invention.

  Even when used as a laminate film for a two-piece can, the squeezed iron can coating film of the present invention is excellent in adhesion to metal and molding processability, and is excellent in design properties. Demonstrates excellent shock resistance when received.

  The polyester A layer in the present invention, specifically, the polyester A layer constituting the side not laminated with the metal plate in the film-laminated metal plate (that is, the side opposite to the surface laminated with the metal) will be described.

  The type of the polyester resin used for the polyester A layer is not particularly limited, but is preferably composed of 20 to 80/80 to 20% by mass of crystalline polyethylene terephthalate and polybutylene terephthalate or polyethylene terephthalate and polyethylene isophthalate. Is. If the ratio of polyethylene isophthalate or polybutylene terephthalate is less than 20% by mass, the can making process may become insufficiently spread. Conversely, if it exceeds 80% by mass, the melting peak temperature becomes less than 200 ° C. Not only is the property impaired, but it is not economical in terms of film formation and raw material costs.

  The melting peak temperature of the polyester A layer in the present invention is preferably in the range of 200 to 250 ° C. If the melting peak temperature is less than 200 ° C., the can-making property is impaired. A plurality of melting peak temperatures may exist. Examples of means for obtaining such a melting peak temperature include a method for suppressing a transesterification reaction during melt extrusion.

  In the polyester A layer, it is preferable to use inert inorganic particles, crosslinked polymer particles, or wax as a lubricant. As the inert inorganic particles, silica, alumina, kaolin, clay, titanium oxide, calcium phosphate, calcium carbonate, lithium fluoride, barium sulfate, carbon black and the like are preferable.

  Crosslinked polymer particles include (meth) acrylic monomers such as acrylic acid, methacrylic acid, acrylic acid esters and methacrylic acid esters, styrene monomers such as styrene and alkyl-substituted styrene, and divinylbenzene and divinyl. Copolymers with crosslinkable monomers such as sulfone, ethylene glycol di (meth) acrylate, trimethylolpropane trimethyl (meth) acrylate, pentaerythritol tetramethyl (meth) acrylate; melamine resin; benzoguanamine resin; phenol Resin; Silicon-containing resin can be exemplified.

  The average particle size of the particulate lubricant is preferably 1 to 3 μm. This is because if it is less than 1 μm, the effect of improving the releasability with respect to the punch cannot be exhibited. On the other hand, when the thickness exceeds 3 μm, the effect of improving the punch releasability is saturated. On the other hand, the lubricant is likely to fall off due to wear, and the film may be broken when laminated with a metal plate.

  Examples of the wax include synthetic waxes such as polyolefin wax and polyester wax, and natural waxes such as carnauba wax.

  The lubricant is preferably added in the range of 0.01 to 2% by mass. In order to ensure releasability with the punch, the amount of lubricant should be 0.01% by mass or more. On the other hand, even if it is excessively added in excess of 2% by mass, a further effect of improving releasability is obtained. This is because it is only disadvantageous in terms of cost.

  The content of cyclic trimer including ethylene terephthalate cyclic trimer is preferably 0.7% by mass or less. This is for suppressing oligomer precipitation in the film. As will be described later, when a two-piece can is manufactured, the laminated film of the present invention is drawn after undergoing a remelt treatment for making the non-oriented polyester, but in the non-oriented polyester, oligomers are more likely to precipitate than the oriented polyester. . Therefore, when the cyclic trimer is contained in excess of 0.7% by mass, for example, when a beverage is filled in a two-piece can using a metal plate laminated with this film and a heat treatment such as a retort treatment is performed. In addition, a large amount of oligomer is eluted from the polyester A layer, and this oligomer may migrate to food and adversely affect the taste and flavor of food.

  The method for adjusting the content of the cyclic trimer including the ethylene terephthalate cyclic trimer contained in the polyester A layer to 0.7% by mass or less is not particularly limited. Examples thereof include a method of extracting and removing a cyclic trimer from a film with water or an organic solvent, and b) a method of forming a polyester A layer using a polyester having a small amount of a cyclic trimer. Of these, the method b) is more economical and preferable.

  In the method b), a method for producing a polyester having a low cyclic trimer content is not particularly limited, and the cyclic trimer can be obtained by solid-phase polymerization, heat treatment under reduced pressure after polymerization, or extraction with water or an organic solvent. A method for extracting and removing the polymer, or a method combining these methods can be employed. Among them, after producing a polyester having a low cyclic trimer content by a solid phase polymerization method, the method of extracting the obtained polyester with water to further reduce the cyclic trimer is the cyclic trimer in the film forming step. This is most preferable because the amount of body production can be more effectively suppressed.

  The polyester used in the present invention can be synthesized by a conventionally known method such as a direct esterification method in which a dicarboxylic acid and a diol are directly reacted; a transesterification method in which a dicarboxylic acid dimethyl ester is reacted with a diol. Each of these methods may be performed by either a batch method or a continuous method. Alternatively, a solid phase polymerization method may be employed to increase the molecular weight. The solid phase polymerization method is a preferable method from the viewpoint that the content of the cyclic trimer can be reduced as described above.

  The polyester synthesized in this way may be included in the polyester A layer only in one kind or in a mixture of two or more kinds.

  In addition to the above-mentioned compounds, the polyester A layer contains inorganic fine particles, incompatible thermoplastic resins, antioxidants, thermal stabilizers, ultraviolet absorbers, plasticizers, pigments, antistatic agents, lubrication as necessary. Additives such as agents and crystal nucleating agents may be included. It is also a preferred embodiment that the polyester A layer contains about 0.01 to 1% by mass of an antioxidant.

  The intrinsic viscosity of the polyester A layer when the above various components are mixed is preferably in the range of 0.6 to 1.2. If the intrinsic viscosity of the polyester A layer is less than 0.6, the mechanical properties of the resulting film may be lowered, and even if it exceeds 1.2, the mechanical properties do not increase any more, and the productivity of the raw material polyester is low. It is not economical because it decreases.

  Next, the polyester B layer constituting the intermediate layer will be described.

  It is preferable that this polyester B layer contains 2-10 mol% of dimer acids. Here, dimer acid is obtained by dimerization reaction of higher unsaturated fatty acids such as oleic acid, and usually has unsaturated bonds in the molecule, but those with reduced unsaturation by hydrogenation are also used. it can. Hydrogenation is more preferable because the heat resistance and flexibility are further improved. In addition, a linear branched structure, an alicyclic structure, an aromatic nucleus structure and the like are generated in the course of the dimerization reaction, and these structures and amounts are not particularly limited.

  As components other than dimer acid, dicarboxylic acid components and glycol components as shown below can be used.

  For example, as the dicarboxylic acid component, orthophthalic acid, naphthalenedicarboxylic acid, oxalic acid, succinic acid, adipic acid, sebacic acid, decanedicarboxylic acid, maleic acid, fumaric acid, other oxycarboxylic acid, alicyclic dicarboxylic acid, etc. are used. be able to.

  Further, as the glycol component, aliphatic glycols such as propanediol, pentanediol, hexanediol and neopentyl glycol, alicyclic glycols such as cyclohexanedimethanol, aromatic glycols such as bisphenol A and bisphenol S can be used. It is particularly preferable to use isophthalic acid as the acid component and ethylene glycol as the glycol component.

  Moreover, it is preferable to contain a dimer acid component in the range of 2-10 mol%, and the range of 4-6 mol% is especially preferable. Dimer acid is effective in improving the impact resistance of the film.

  If the content is less than 2 mol%, impact resistance at a low temperature (5 ° C.) cannot be obtained, and the film is torn or scratched. On the other hand, if it exceeds 10 mol%, the film forming property, heat resistance and strength are lowered, which is not preferable.

  It is preferable that the melting peak temperature of this polyester B layer exists in the range of 200-245 degreeC. Especially preferably, it is the range of 210-235 degreeC. If the melting peak temperature is less than 200 ° C., the can-making ability is impaired, and if it exceeds 245 ° C., the productivity of the raw material polyester is lowered, which is not economical.

  In addition, as a method for synthesizing the polyester constituting the polyester B layer, a conventional method can be adopted, the polyester composition can contain other additives as necessary within the range satisfying the above requirements, The intrinsic viscosity of the polyester composition is the same as that of the polyester A layer.

  Next, the polyester C layer bonded to the metal plate will be described.

  The polyester C layer is preferably formed by applying a water-dispersed copolymer polyester resin having a Tg (glass transition temperature) of 60 ° C. or higher. Here, the water-dispersed copolyester resin is a resin that is insoluble in water but can be dispersed or dissolved in an aqueous solvent. Specific examples include polyester resins obtained by copolymerizing a monomer component having a hydrophilic group in the molecule. By using such a water-dispersed copolymer polyester resin, it is possible to achieve excellent adhesion strength with a metal plate.

  Further, by not using an organic solvent, adverse effects on the human body and the environment can be reduced. The C layer made of the water-dispersed copolyester resin is preferably controlled to a thickness of 1 to 50 nm by so-called coating. If the coat thickness is less than 1 nm, the coat layer causes so-called film cracking and an appropriate resin film cannot be formed. On the other hand, if the coat thickness exceeds 50 nm, the quality becomes excessive and uneconomical. The coating treatment for forming the C layer may be performed either during film formation (inline) or after film formation (offline).

  Examples of the water-dispersed copolymer polyester resin include polyester resins obtained by copolymerizing a monomer component having a hydrophilic group. The hydrophilic group is, for example, a hydroxyl group, an amino group, a carboxyl group, a sulfonic acid group, or a derivative or metal salt thereof, an ether, or the like. By copolymerizing monomers containing these groups in the molecule, In a state in which it can be dissolved or dispersed.

  Specific examples of the monomer containing a hydrophilic group include polyethylene glycol, polypropylene glycol, glycerin, polyglycerin, 5-sulfoisophthalic acid, 4-sulfonaphthalene-2,7-dicarboxylic acid, and 5 (4-sulfophenoxy) isophthalate. Examples thereof include metal salts of sulfonic acid-containing monomers such as acids.

  Further, there is a method in which a vinyl monomer having a hydrophilic group is graft-polymerized to a copolymerized polyester. Examples of vinyl monomers having a hydrophilic group include those containing a carboxyl group, a hydroxyl group, a sulfonic acid group, an amide group, and the like, and groups that can be changed to a hydrophilic group include acid anhydride groups, glycidyl groups, and chloro groups. The thing containing group etc. is mentioned. Of these, those having a carboxyl group are preferred. For example, monomers such as acrylic acid, methacrylic acid, maleic acid, or salts thereof.

  In the laminated film of the present invention, it is particularly preferable that the adhesion strength between the film after remelting (remelting) and the metal plate is 18 N / 15 mm or more. If the adhesion strength after remelting is less than 18 N / 15 mm, the molding processability at the time of can making deteriorates, and the film and the metal plate may peel off during the molding process.

  The adhesion strength between the film and the metal plate is determined as follows.

a) Production of film-laminated metal plate After laminating a metal plate preheated to 220 ° C. through a nip roll so that the polyester C layer side of the laminated film configured as described above is in contact with the metal plate, 10 to 40 A metal plate on which a laminated film is laminated is obtained by quenching through a water bath at ° C.

b) Remelt treatment (remelt treatment)
The film-laminated metal plate is heated to 270 ° C., then air-cooled, and further quenched in water to produce a remelt metal plate.

c) Adhesive strength A part of the metal part is dissolved and removed from the above-mentioned remelt metal plate with dilute hydrochloric acid, and only the film is taken out. After sufficiently peeling, a reinforcing material is pasted so that the film does not stretch, and cutting is performed to a width of 15 mm. The sample obtained by cutting is subjected to a tensile tester, and the peel strength is measured at a tensile speed of 5 mm.

  The laminated film of the present invention may be laminated so that the surface layer on one side is the polyester A layer, the intermediate layer is the polyester B layer, and the polyester C layer is on the side in contact with the metal plate. The layering method of the A layer / B layer is not particularly limited, and a multilayer extrusion method or an extrusion lamination method may be employed.

  In the laminated film of the present invention, the constituent ratio of the A layer and the B layer is preferably in the range of 30 to 70/70 to 30% by mass, particularly preferably in the range of 50 to 60/50 to 40% by mass. If the ratio of the B layer is less than 30%, impact resistance at a low temperature (5 ° C.) cannot be obtained, and if it exceeds 70%, the film forming property and heat resistance are deteriorated.

  The laminated film of the present invention may be unstretched or biaxially stretched. The biaxial stretching method that can be employed at this time may be any of sequential biaxial stretching, simultaneous biaxial stretching, or a combination thereof. In the case of successive biaxial stretching, generally, a method of stretching in the longitudinal direction and then stretching in the transverse direction is adopted, but it may be carried out by a method of stretching in the reverse order. After biaxial stretching, it is preferable to fix the orientation of the polyester by heat treatment. However, after biaxial stretching, the polyester may be re-stretched in the longitudinal direction and / or the width direction before heat treatment. Furthermore, it is possible to perform corona discharge treatment on one or both sides of the film at any time before and after stretching.

  The laminated metal plate according to the present invention is produced by laminating the laminated film according to the present invention on a metal plate such that the polyester C layer side is the metal plate side. This is because by forming the surface layer of the film-laminated metal plate with the polyester A layer having releasability, the releasability with the punch can be enhanced during drawing.

  There is no restriction | limiting in particular in the method of laminating | stacking a polyester laminated film on a metal plate, For example, the dry lamination method, the thermal lamination method, etc. are employable. More specifically, for example, it is laminated on a metal plate preheated to about 220 ° C. by passing between nip rolls so that the polyester C layer of the polyester laminated film prepared above is in contact with the metal plate, and then 10 to 40 ° C. Laminate by quenching and solidifying in a water bath.

  Moreover, the lamination of the laminated film may be performed only on one side of the metal plate, or may be performed on both sides. In the case of double-sided laminating, either the simultaneous laminating method or the sequential laminating method may be adopted.

  When the biaxially stretched film laminated metal plate in the present invention is applied to a two-piece can, it is rapidly cooled after being heated above the melting point of the polyester constituting the laminate film in order to remove the orientation of the polyester after laminating the metal plate. It is preferable to perform a remelt treatment. The degree of orientation by X-ray observation after the remelt treatment is 10% or less and can be said to be substantially non-oriented. In other words, a biaxially stretched film in which the polyester is oriented is difficult to be plastically deformed or stretched, so that it is difficult to draw to form a container portion. This is because a delaminating phenomenon that peels off or tears or scrapes easily occurs. However, if the film is substantially non-oriented, it can follow the deformation of the laminated metal plate and does not cause delaminating or tearing, so plastic deformation of the metal like a two-piece can Even the accompanying molding can be performed without hindrance.

  The film laminated metal container of the present invention is a metal container formed by forming a biaxially stretched or non-oriented type film laminated metal plate obtained as described above into a can shape. Laws are not particularly limited. For example, not only a so-called three-piece can in which the top cover is wound and filled with contents, but also a two-piece can that forms a container portion by drawing a metal plate is included.

  In the metal container of the present invention, the polyester-based laminated film may be molded so as to be on the inner wall surface side of the metal container, or may be molded so as to be on the outer wall surface side. However, in the case of a two-piece can, it is preferably used on the inner wall surface side of the container so that the polyester A layer having excellent releasability is in contact with the punch from the viewpoint of drawing processing appropriateness as described above.

  In addition, when carrying out drawing ironing, you may apply | coat a lubricant to the film surface which a punch contacts as needed.

  The film-laminated metal container of the present invention may be subjected to printing or the like as necessary, and may be subjected to a re-melt process after a can making process or a printing process.

  In addition, various polyesters used in the present invention include an antioxidant, a heat stabilizer, an ultraviolet absorber, a plasticizer, a pigment, an antistatic agent, a lubricant, a crystal nucleating agent, inorganic or organic particles as necessary. You may mix | blend a lubricant etc.

  As the metal plate used in the present invention, a surface-treated steel plate such as tin-free steel, an aluminum or aluminum alloy plate, or a surface-treated aluminum or aluminum alloy plate can be used.

  Moreover, the film thickness on the metal plate in the present invention is not particularly limited, but is preferably in the range of 10 to 50 μm in view of covering effect (rust prevention), impact resistance, economy and the like. If the film thickness is less than 10 μm, impact resistance at low temperatures cannot be obtained.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited by the following examples, but may be appropriately modified within a range that can meet the purpose described above and below. It is also possible to implement, and they are all included in the technical scope of the present invention.

  Moreover, the various evaluation methods employ | adopted in the following Example are as follows.

(1) Thermal properties of polyester 10 mg of a sample obtained by heating and melting a polyester composition at 300 ° C. for 5 minutes and then rapidly cooling with liquid nitrogen was used in a nitrogen stream using a differential scanning calorimeter (DSC). When the exothermic / endothermic curve (DSC curve) is measured at a rate of temperature rise of ° C / min, the peak temperature of the endothermic peak accompanying melting is the melting point Tm (° C), and the peak temperature at the temperature rising crystallization is Tc (° C ).

(2) Can-making property A remelt aluminum plate was made at n = 10, and the degree of buckling occurring at the upper part of the formed can was visually observed. Evaluation criteria were as follows, and ○ was evaluated as practical.
○: Buckling has not occurred in the can opening △: Buckling has occurred in about 1/3 of the circumference of the can opening ×: Buckling has occurred in more than 1/3 of the circumference of the can opening

(3) Impact resistance A 7 cm square sample of a can obtained by making a remelt aluminum plate at 280 ° C. for 40 seconds and then quenching in water is cut out from the center of the trunk wall. A weight (600 g) having a tip diameter of 10 mm is dropped from a height of 10 cm to a surface corresponding to the outer surface of the sample, and an impact is applied. Next, the sample was placed on a glass container filled with 7% dilute hydrochloric acid (placed with the convex portion of the sample immersed), and the corrosive state of the convex portion was visually observed after 3 days. Evaluation criteria were as follows, and ○ was evaluated as practical.
○: Corrosion did not occur on the convex part ×: Corrosion occurred on the convex part

(4) Adhesive strength A part of the aluminum plate was dissolved and removed from the remelt aluminum plate with dilute hydrochloric acid, and only the film was taken out. Using this as a trigger, the film and the aluminum plate are peeled off, and after sufficiently peeling, a reinforcing material is attached so that the film does not stretch, and cutting to a width of 15 mm is performed. The peel strength of the sample was measured at a tensile speed of 5 mm using a tensile tester.

Example 1
[Production of laminated polyester film]
Polyester A layer: The mass ratio of PET (trade name “SG554” PET resin manufactured by Toyobo Co., Ltd.) / PET-I (trade name “RN163C” IPA 10 mol% copolymerized PET manufactured by Toyobo Co., Ltd.) is 50/50 mass%. Polyester composition A containing 0.3% by mass of agglomerated type silica particles (average particle size 1.5 μm) in the base resin, having an intrinsic viscosity of 0.7 and an ethylene terephthalate cyclic trimer of 0.4% by mass. Was used.

  Polyester B layer: 90% by mole of dicarboxylic acid component, 10% by mole of dimer acid unit having 36 carbon atoms, and 100% by weight of dimer acid copolymerized PET having diol component of 100% by mole of ethylene glycol unit Polyester composition B was used.

  The composition A and the composition B were melted by separate extruders, the melts were merged in a die, extruded, and rapidly cooled to obtain an unstretched laminated sheet.

  This unstretched laminated sheet is stretched 3.3 times in the longitudinal direction at a preheating temperature of 65 ° C. and a stretching temperature of 100 ° C., and further stretched in the tenter by 4.0 times in the transverse direction at a preheating temperature of 65 ° C. and a stretching temperature of 90 ° C. . Then, after heat-treating at 160 ° C. for 8 seconds, 4% relaxation treatment was performed at 160 ° C. to obtain a biaxially stretched laminated film having a thickness of 20 μm (polyester A layer thickness 10 μm, polyester B layer thickness 10 μm). . The laminated film is coated on the polyester B layer side with a coating solution (trade name “Vylonal” manufactured by Toyobo Co., Ltd.) adjusted to a thickness of 50 nm by a gravure coating method, and dried at 160 ° C. for 8 seconds. To obtain a polyester C layer.

[Production of film-laminated metal plate]
After laminating by passing between nip rolls so that the polyester C layer of the polyester laminated film prepared above is in contact with the aluminum plate on both surfaces of the preheated aluminum plate, heat treatment is performed, and immediately in a 10-40 ° C. water bath. Quenching was performed to obtain an aluminum plate having a film laminated on both sides. At the time of lamination, initial adhesion, fluctuation in tension, winding around a nip roll, and the like did not occur, and the lamination suitability of the laminated film of this example was good.

  Next, the film-laminated aluminum plate was heated to 270 ° C., air-cooled, and further quenched in water to prepare a remelt aluminum plate.

[Production of film-laminated metal container]
The remelted aluminum plate produced above was drawn and ironed so that the thickness reduction rate was 30% to form a film laminated metal container. At the time of molding, there was no peeling or tearing of the film, good releasability from the mold, etc., and there was no change in appearance such as whitening of the film even during rapid cooling after heat treatment.

  Furthermore, after printing the outer surface, a varnish was applied, and after heat-curing, it was quenched with cold air. The container formed in this way was filled with a beverage, and a lid with a tab was wound and joined, and then heated at 100 ° C. for 30 minutes to produce a two-piece beverage can. The obtained beverage can was excellent in adhesion and can-making property, and neither the elution of the oligomer into the beverage nor the precipitation from the film occurred. Furthermore, the film was not torn even against external impacts expected during the distribution stage or during low-temperature storage.

Example 2
Polyester A layer: PET (trade name “SG554” PET resin manufactured by Toyobo Co., Ltd.) / PBT (trade name “1200S” PBT manufactured by Toray Industries, Inc.) Polyester composition A containing 0.3% by mass of silica particles (average particle size 1.5 μm), having an intrinsic viscosity of 0.7 and an ethylene terephthalate cyclic trimer of 0.4% by mass was used.

  Polyester B layer: dimer acid copolymer composed of 90 mol% of dicarboxylic acid component, 10 mol% of dimer acid unit having 36 carbon atoms, and 40% by mass of dimer acid copolymer PET having 100 mol% of diol component of ethylene glycol, PET A polyester composition B prepared by mixing (trade name “SG554” PET resin manufactured by Toyobo Co., Ltd.) / PBT (trade name “1200S” PBT manufactured by Toray Industries Inc.) at a mass ratio of 30/30 was used.

  The composition A and the composition B were melted in separate extruders, and the melts were merged in a die and extruded, and then rapidly cooled to obtain an unstretched laminated sheet.

  The obtained unstretched laminated sheet was stretched 3.3 times in the machine direction at a preheating temperature of 65 ° C. and a stretching temperature of 100 ° C., and then 4.0 times in the transverse direction at a preheating temperature of 65 ° C. and a stretching temperature of 90 ° C. The film was stretched, further heat-treated at 160 ° C. for 8 seconds, and then subjected to a relaxation treatment of 4% at 160 ° C. to obtain a biaxially stretched laminated film having a thickness of 20 μm (polyester A layer thickness 10 μm, polyester B layer thickness 10 μm). . The film is coated on the polyester B layer side with a coating solution (trade name “Vylonal” manufactured by Toyobo Co., Ltd.) adjusted to a thickness of 50 nm by a gravure coating method, and dried at 160 ° C. for 8 seconds. Thus, a polyester C layer was obtained.

  The subsequent can manufacturing process and evaluation were performed in the same manner as in Example 1.

  As in Example 1, the obtained beverage can was excellent in adhesion and can-making properties, and did not cause oligomer elution into the beverage or deposition from the film. Furthermore, the film was not torn even against external impacts expected during the distribution stage or during low-temperature storage.

Comparative Example 1
Polyester A layer: The mass ratio of PET (trade name “SG554” PET resin manufactured by Toyobo Co., Ltd.) / PET-I (trade name “RN163C” IPA 10 mol% copolymerized PET manufactured by Toyobo Co., Ltd.) is 50/50 mass%. Polyester composition A containing 0.3% by mass of agglomerated type silica particles (average particle size 1.5 μm) in the base resin, having an intrinsic viscosity of 0.7 and an ethylene terephthalate cyclic trimer of 0.4% by mass. Was used.

  Polyester B layer: 100% by mass of a dimer acid copolymerized PET having a dicarboxylic acid component of 90 mol% terephthalic acid units, 10 mol% of a dimer acid unit having 36 carbon atoms, and a diol component of 100 mol% of an ethylene glycol unit Product B was used.

  The film forming process, can manufacturing process, and evaluation thereafter were performed in the same manner as in Example 1.

  Although the obtained beverage can had good impact resistance, it did not reach the quality of the above examples in terms of adhesion and can manufacturing.

Comparative Example 2
Polyester A layer: PET (trade name “SG554” PET resin manufactured by Toyobo Co., Ltd.) / PBT (trade name “1200S” PBT manufactured by Toray Industries, Inc.) Polyester composition A containing 0.3% by mass of silica particles (average particle size 1.5 μm), having an intrinsic viscosity of 0.7 and an ethylene terephthalate cyclic trimer of 0.4% by mass was used.

  Polyester B layer: The dicarboxylic acid component is 90 mol% of terephthalic acid units, the dimer acid unit having 36 carbon atoms is 10 mol%, and the diol component is 100 mol% of ethylene glycol units. Polyester composition B in which PET (trade name “SG554” PET resin manufactured by Toyobo Co., Ltd.) / PBT (trade name “1200S” PBT manufactured by Toray Industries, Inc.) was mixed at a mass ratio of 8/12 was used.

  The film forming process, can manufacturing process, and evaluation thereafter were performed in the same manner as in Example 1.

  Although the obtained beverage can had high impact resistance, it was remarkably inferior to the said Example in adhesiveness and can-making property.

  The results are collectively shown in Table 1 below.

  The squeezed iron can coating film of the present invention is excellent in molding processability in can making, and also has good impact resistance during low-temperature storage and transfer, so it can be used as a laminate film for two-piece cans. It is possible to contribute to the industry.

Claims (5)

  A laminated film composed of three layers of polyester, A layer, B layer, and C layer, wherein 2 to 10 mol% of the total acid component in the B layer constituting the intermediate layer is dimer acid, and C layer is a water-dispersed copolyester resin, and the adhesive strength of the squeezed iron can is 10 N / 15 mm or more when the C layer side is thermally laminated with the metal plate. .   The adhesion strength between the film and the metal plate after heating the metal plate and the heat-laminated plate to a temperature equal to or higher than the melting point of the laminated film to remelt the film is 18 N / 15 mm or more. The film for covering a drawn ironing can according to the description.   The film for covering a drawn iron can according to claim 1 or 2, wherein the C layer has a Tg of 60 ° C or higher.   A metal plate for squeezed and ironed cans, wherein the film for covering the squeezed and ironed can according to any one of claims 1 to 3 is laminated on a metal plate.   A squeezed and ironed can obtained by making the metal plate for a squeezed and ironed can according to claim 4.