JP2006007746A - Polyester film for coating metal sheet, polyester film coated metal sheet and polyester film coated metal container - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polyester film for coating a metal sheet excellent in the adhesion with the metal sheet, molding processability, flavor properties and impact resistance, a polyester film coated metal sheet and a polyester film coated metal container. <P>SOLUTION: The polyester film for coating the metal sheet has a composite constitution of layer (I)/layer (II)/layer (I) and the layer (I) comprises a copolyester of ethylene terephthalate and ethylene isophthalate and the layer (II) comprises a copolyester composed of terephthalic acid, a 20 or above C long chain aliphatic dicarboxylic acid and ethylene glycol, and 0.01-0.15 wt.% of a wax component is contained in at least the layer (I). <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a polyester film for coating a metal plate used for the purpose of preventing corrosion of metal containers such as soft drinks, beer and canned foods, a polyester film-coated metal plate obtained by coating the polyester film on a metal plate, and the polyester film coating The present invention relates to a polyester film-covered metal container formed by molding a metal plate, and particularly to a metal film-covered polyester film suitably used for the inner surface of a two-piece can. More specifically, a polyester film-covering polyester film excellent in canability (for example, drawing and ironing workability), and a polyester film-covered metal sheet excellent in flavor and impact resistance obtained by coating the polyester film on the metal plate And a polyester film-coated metal container formed by molding the polyester film-coated metal plate.

  Conventionally, the inner surface and outer surface of a metal can have been widely coated with a solution in which various thermosetting resins such as epoxy and phenol are dissolved or dispersed in a solvent for the purpose of preventing corrosion. Has been done. However, this method of coating the thermosetting resin has poor productivity because it takes a long time to dry the paint, and the use of a large amount of organic solvent has the potential to adversely affect the human body and the environment. There was a point.

  In order to solve such a problem, a method of coating a metal plate with a thermoplastic resin by a melt extrusion method is known (for example, see Patent Document 1). Moreover, the method of coat | covering a thermoplastic resin film to a metal plate is known (for example, refer patent document 2).

  By the way, for beverage cans, in addition to the so-called three-piece cans, which are obtained by attaching lids to the upper and lower openings of a metal cylinder formed by cylindrical molding of a metal plate, the metal plate is squeezed or squeezed and ironed. There is a so-called two-piece can formed by forming a container part and winding a lid on the upper surface opening of the container part.

  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 the metal plate are insufficient, and the film is peeled off from the metal plate. Delamination may occur or break. This tendency appears more noticeably in a biaxially stretched film in which the film is in an oriented state.

  Therefore, in order to apply to a two-piece can, it is necessary to have good formability of being formed following the formation of a metal plate and to have excellent adhesion to the metal plate. If the formability is insufficient, or if the adhesion of the film to the metal plate is insufficient, the delamination phenomenon may occur, or the film may be torn during the production of the container part of a two-piece can. is there.

  For this reason, in order to apply the film-coated metal plate to a two-piece can, after the coating, in order to remove the orientation of the polyester film, the film is heated at a temperature equal to or higher than the melting point of the polyester constituting the film and then rapidly cooled. (For example, refer to Patent Document 3). The degree of orientation by X-ray diffraction after the remelt treatment is 10% or less, which can be said to be substantially non-oriented. However, the non-oriented film generally has a disadvantage that the strength is lower than that of the biaxially stretched film, and the oligomer easily precipitates or whitening easily occurs. In addition, the film for the inner surface of the can needs to have impact resistance so that the metal is not eroded by pinholes and cracks caused by impact at the time of canning. There is a tendency that impact resistance tends to decrease.

  As a method for improving the impact resistance of the film, for example, a method using a biaxially stretched laminated film comprising a polyester layer mainly composed of polyethylene terephthalate and / or polyethylene isophthalate and a layer in which polyester and a thermoplastic elastomer are blended. Is known (see, for example, Patent Document 4). However, the method described in the above publication does not provide sufficient adhesion when a polyester film is coated on a metal plate, and is applied to salt-containing beverages such as so-called supplement beverages such as lactic acid beverages and sports drinks. In some cases, even higher impact resistance is required, and the above-mentioned measures are not sufficient in improving impact resistance.

Further, as other measures for improving the adhesion and whitening property, impact resistance, and flavor property of the metal and the film at the time of can making, various measures in terms of polymer prescription have been proposed (for example, Patent Document 5, (See Patent Literature 6, Patent Literature 7, and Patent Literature 8). However, even in these methods, when the deformation rate at the time of can making is large, or when the can can be made at a high speed of 100 cans / minute or more, the spreadability of the film, the adhesiveness is not sufficient, Problems remain, such as film scraping (galling) on the outer surface of the can and adhesion between the film and punch on the inner surface of the can (strip out).
JP-A-57-203545 JP-A-4-261826 Japanese National Patent Publication No. 2-501638 JP-A-8-156182 Japanese Patent Laid-Open No. 7-47650 JP-A-9-150492 JP 2001-329056 A JP 2001-347621 A

  The object of the present invention is to solve the problems of the prior art. That is, an object of the present invention is to provide a metal film-covering polyester film, a polyester film-covered metal plate, and a polyester film-covered metal container that are excellent in adhesion to metal plates and moldability, and excellent in flavor and impact resistance.

  As a result of intensive studies to achieve the above object, the present inventors have a composite structure of (I) layer / (II) layer / (I) layer, and (I) layer comprises ethylene terephthalate and ethylene isophthalate. (II) The layer is a copolymerized polyester comprising terephthalic acid, a long-chain aliphatic dicarboxylic acid having 20 or more carbon atoms, and ethylene glycol, and at least the wax component in the copolymerized polyester of (I) layer The present inventors have found that the above object can be achieved by using a polyester film having a composite structure containing 0.01 to 0.15% by weight.

The present invention is as follows.
1. (I) layer / (II) layer / (I) layer composite structure, (I) layer is a copolymer polyester of ethylene terephthalate and ethylene isophthalate, (II) layer is terephthalic acid, carbon number 20 A metal comprising the above long-chain aliphatic dicarboxylic acid and ethylene glycol, and containing at least 0.01 to 0.15% by weight of a wax component in the copolymer polyester of (I) layer Polyester film for board coating.
2. The polyester film for coating a metal plate, wherein the wax component described in 1 is one or more selected from paraffin wax, polyethylene wax, ester wax, glycerin fatty acid ester, and higher fatty acid monoamide. .
3. 3. The polyester film for covering a metal plate, wherein the polyester film for covering a metal plate according to 1 or 2 is a biaxially stretched polyester film.
4). A polyester film-covered metal plate, wherein the metal plate-covering polyester film according to any one of 1 to 3 is coated on at least one surface of a metal plate.
5. 5. A polyester film-covered metal container formed by molding the polyester film-covered metal plate as described in 4 above.

  The polyester film for coating a metal plate of the present invention can be made by coating the polyester film on a metal plate (particularly, the mold inner surface film and the release punch of the processing punch and the can during canning under severe conditions) A polyester film-coated metal plate excellent in the scratch resistance of the outer film) and flavor is obtained, and a polyester film-coated metal can having excellent impact resistance is obtained by making the polyester film-coated metal plate. As a polyester film for metal plate coating used for the purpose of preventing corrosion of metal containers such as soft drinks, beer, canned foods, etc., or as a polyester film coated metal plate in which the polyester film is coated on a metal plate, or A polyester film-coated metal container formed by molding the polyester film-coated metal plate Te said to be useful.

  The polyester film of the present invention has a composite structure of (I) layer / (II) layer / (I) layer, (I) layer is a copolymer polyester of ethylene terephthalate and ethylene isophthalate, and (II) layer Is a copolymer polyester composed of terephthalic acid, a long-chain aliphatic dicarboxylic acid having 20 or more carbon atoms, and ethylene glycol, and contains at least 0.01 to 0.15% by weight of a wax component in the copolymer polyester of the (I) layer. It is a polyester film for metal plate coating.

  The copolymer polyester used in the (I) layer of the polyester film of the present invention is a copolymer polyester of ethylene terephthalate and ethylene isophthalate. The ratio of the isophthalic acid residue to the total acid component residue of the copolymer polyester is preferably 3 to 20 mol%, more preferably 4 to 10 mol%.

  The melting point of the copolymer polyester constituting the layer (I) of the polyester film of the present invention is 220 to 250 ° C. (in the drawing and ironing process, the resin on the inner surface side of the can has a mold release property). The resin on the outer surface side of the securing is preferable from the viewpoint of securing galling (suppression of vertical scratches in the resin film). Furthermore, when the processing conditions at the time of can manufacturing become severe, it is more preferable that it exists in the range of 230-245 degreeC. It is preferable to adjust the type and content of the copolymerization component so as to fall within the above melting point range.

  The copolymer polyester constituting the (I) layer of the polyester film of the present invention may be a single composition or a blend of two or more polyester compositions having different composition ratios. In addition, a small amount of other polyester compositions represented by polybutylene terephthalate can be blended. In order to satisfy the above-described adjustment of the melting point and the thermal stability, moldability, and flavor of the polyester film of the present invention, (I) the final constituents of the entire layer are preferably ethylene terephthalate components and ethylene isoforms. More preferably, the total of the ethylene terephthalate component and the ethylene isophthalate component is 90 to 100 mol%, and the total of the phthalate component is 80 to 100 mol% and the ethylene isophthalate component is 3 to 20 mol%. It is important to adjust the composition and formulation so that the isophthalate component is 4 to 10 mol%. When a small amount of polybutylene terephthalate is blended, it is preferable from the viewpoint of thermal stability and moldability that the butylene terephthalate component is blended so as to be 20 mol% or less.

  The copolymer polyester used for the (I) layer in the polyester film of the present invention can contain other copolymer components as long as the purpose is not impaired.

  Among the other copolymerization components that can be used, the dicarboxylic acid component includes naphthalenedicarboxylic acid, diphenylsulfone dicarboxylic acid, aromatic dicarboxylic acid such as 5-sodium sulfoisophthalic acid, oxalic acid, succinic acid, adipic acid, sebacic acid, Aliphatic dicarboxylic acids such as decanedicarboxylic 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. If the amount of other copolymerization component dicarboxylic acids and their ester derivatives exceeds 20 mol%, the thermal stability of the polyester is often deteriorated, which is not preferable.

  Further, as the glycol component of the copolymer polyester used in the (I) layer of the polyester film of the present invention, other copolymer components that can be used in addition to the ethylene glycol component include propanediol, butanediol, pentanediol, and hexanediol. , Aliphatic glycols such as neopentyl glycol, alicyclic glycols such as cyclohexanedimethanol, ethylene glycol adducts of bisphenol A, aromatic glycols such as ethylene oxide adducts of bisphenol S, polyethylene glycol, polypropylene glycol, polytetramethylene glycol, etc. 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. The amount of the glycol component of the other copolymerization component is preferably 20 mol% or less, more preferably 10 mol% or less. When the amount of other glycol components used exceeds 20 mol%, the thermal stability of the polyester is often deteriorated, which is not preferable.

  The copolymer polyester used for the (II) layer in the polyester film of the present invention is a copolymer polyester mainly composed of terephthalic acid as a dicarboxylic acid component, a long-chain aliphatic dicarboxylic acid having 20 or more carbon atoms, and ethylene glycol as a diol component. Preferably, 85 to 99 mol% of all dicarboxylic acid residues are terephthalic acid residues, 1 to 15 mol% are long-chain aliphatic dicarboxylic acid residues having 20 or more carbon atoms, and 50 diol residues. It is a copolyester whose mol% or more is an ethylene glycol residue. Here, the structure of the long-chain aliphatic dicarboxylic acid having 20 or more carbon atoms is not particularly limited, and may include a branched structure or a cyclic structure in the molecule, or may include a double bond in a part of the molecular chain. . Examples of the long chain aliphatic dicarboxylic acid include eicosane diacid, docosane diacid, and dimer acid, but are not limited thereto. Dimer acid is obtained by dimerization reaction of higher unsaturated fatty acids having 10 to 25 carbon atoms such as oleic acid, linoleic acid, linolenic acid, etc., and usually has an unsaturated bond in the molecule. Lowered ones can also be used. Hydrogenated ones are particularly preferred because they improve heat resistance and flexibility. Further, in the course of the dimerization reaction, a linear branched structure, an alicyclic structure, and an aromatic nucleus structure are generated, but these structures and amounts are not particularly limited.

  The amount of the long-chain aliphatic dicarboxylic acid residue having 20 or more carbon atoms in the copolymer polyester used in the (II) layer of the polyester film of the present invention is 1 to 15 of all acid component residues as described above. Preferably, it is less than 1 mol%, and if it is less than 1 mol%, the effect of improving impact resistance is insufficient and is often not preferred. On the other hand, if it exceeds 15% by mole, the melt viscosity of the copolyester and the thermal characteristics are greatly reduced, and the productivity at the time of production of the polyester is lowered, and the handleability is often deteriorated.

  The long chain aliphatic dicarboxylic acid copolyester having 20 or more carbon atoms constituting the (II) layer of the polyester film of the present invention may be a single composition or two or more kinds of polyester compositions having different composition ratios. A blend of Also, other polyester compositions can be blended in small amounts.

  When the blending of the polyester of the (II) layer is determined, a resin obtained by collecting the polyester film having the composite structure of the present invention can be blended and reused. (This reusable resin is described as “R” in the examples described later.) In this case, the total blending ratio of each component from the polyester film recovery resin is within the scope of the present invention. It needs to be adjusted.

  In order to satisfy the moldability, adhesion, and impact resistance of the polyester film of the present invention, (II) including the case of using the reusable resin, the final component of the entire layer includes all acid component residues Among them, the content of a long-chain aliphatic dicarboxylic acid residue having 20 or more carbon atoms is preferably 1 to 15 mol%, more preferably 4 to 12 mol%. When the amount of the long-chain aliphatic dicarboxylic acid residue having 20 or more carbon atoms is less than 1 mol%, the impact resistance improving effect is not sufficiently exhibited. The impact effect cannot be expected, and on the contrary, problems such as the above-mentioned production of polyester and film formation become conspicuous.

  The copolymerized polyester used in the (II) layer of the polyester film of the present invention may contain a small amount of other copolymerization components as necessary within the range not impairing the properties. The other copolymerization components that can be used are the same as the compounds exemplified as being usable for the (I) layer of the polyester film for both the dicarboxylic acid component and the glycol component. Further, the amount of use thereof is the same as in the case of the layer (I), and both the dicarboxylic acid component and the glycol component are preferably 20 mol% or less, more preferably 10 mol% or less. If the amount of use exceeds 20 mol%, the thermal stability of the polyester deteriorates and is often not preferred.

  It does not specifically limit about the manufacturing method of polyester of this invention. 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. In addition, the amount of oligomers from polyester in the retort processing, etc. that is performed after filling the can into the can, reduces the taste and flavor of the content, and prevents contamination of the can. From the viewpoint of prevention, it is preferable to use a polyester having a low oligomer content produced by a solid phase polymerization method under reduced pressure or under an inert gas atmosphere.

  Here, for example, the content of the oligomeric cyclic trimer including ethylene terephthalate cyclic trimer is preferably 0.7% by weight or less.

  The intrinsic viscosity of the polyester film having a composite structure of (I) layer / (II) layer / (I) layer of the present invention was determined by dissolving the film in orthochlorophenol and measuring it at 25 ° C. from 0.6 to 1. 2 (dl / g) is preferable. When the intrinsic viscosity is less than 0.6 (dl / g), the mechanical properties of the resulting film may be deteriorated, and even when the intrinsic viscosity exceeds 1.2 (dl / g) The effect of improving the characteristics cannot be obtained, and conversely, the productivity at the time of producing the polyester is lowered, which is not economical.

  In the production of the polyester in the present invention, antimony oxide, germanium oxide, a titanium compound or the like is used as a polymerization catalyst. In addition to the polymerization catalyst, Mg salt such as magnesium acetate and magnesium chloride, calcium acetate, and calcium chloride are used to provide electrostatic adhesion when forming a melt-extruded film using the polyester resin composition of the present invention. The total amount of each metal ion is 300 ppm or less of phosphoric acid or phosphoric acid, such as Ca salt such as manganese salt, manganese salt such as manganese acetate, manganese chloride, Zn salt such as zinc chloride and zinc acetate, and cobalt salt such as cobalt chloride and cobalt acetate. It is also possible to add phosphate ester derivatives such as trimethyl ester and phosphoric acid triethyl ester in the range of 200 ppm or less as phosphorus atoms. When the total amount of metal ions other than the above polymerization catalyst is 300 ppm and the amount of phosphorus exceeds 200 ppm, not only is the resulting polyester colored significantly, but the heat resistance and hydrolysis resistance of the polyester may be reduced, Often not preferred.

  At this time, when the molar ratio of the total phosphorus amount to be added and the total metal ion amount is 0.4 to 1.0, the polyester having the best balance of heat resistance, hydrolysis resistance, and electrostatic adhesion Is preferable. Here, molar ratio of addition amount = (total amount of phosphorus in phosphoric acid, phosphoric acid alkyl ester or derivative thereof (molar atom)) / (total amount of Mg ion, Ca ion, Mn ion, Zn ion, Co ion ( Mole atom)). When the said molar ratio is less than 0.4, coloring of the obtained polyester becomes remarkable, and heat resistance and hydrolysis resistance may decrease. If it exceeds 1.0, sufficient electrostatic adhesion cannot be obtained in many cases.

  Moreover, it is preferable to use a suitable lubricant for the polyester film of the present invention in order to impart the slipperiness of the film-coated metal plate. As the lubricant, it is preferable to use inert inorganic particles or crosslinked polymer particles. The amount of lubricant is not particularly limited, but is preferably in the range of 0.01 to 1% by weight. This is because the amount of lubricant is preferably 0.01% by weight or more so that the film can be smoothly released from the punch or die during drawing. On the other hand, even if the content exceeds 1% by weight, the effect of releasability does not change and only the cost becomes disadvantageous. Further, it is particularly preferable to use a wax described later in combination with a lubricant since the effect of adding the lubricant can be obtained with a minimum amount.

  Examples of the inert inorganic particles that can be used as a lubricant include silica, alumina, kaolin clay, titanium oxide, calcium phosphate, calcium carbonate, lithium fluoride, barium sulfate, and carbon black.

  The crosslinked polymer particles that can be used as a lubricant include acrylic monomers such as acrylic acid, methacrylic acid, acrylic ester, and methacrylic ester, and styrene monomers such as styrene and alkyl-substituted styrene. Copolymer of divinylbenzene, divinylsulfone, ethylene glycol dimethacrylate, trimethylolpropane trimethyl acrylate, pentaerythritol tetramethyl acrylate, etc., melamine resin, benzoguanamine resin, phenol resin Examples thereof include silicon-containing resins.

  When the lubricant is an organic particle or inorganic particle lubricant, the average particle size is preferably 1 to 3 μm. This is because when the average particle size is less than 1 μm, the effect of improving punch releasability cannot often be manifested. Conversely, when the average particle size exceeds 3 μm, the effect of improving punch releasability is saturated, while the lubricant due to abrasion is saturated. This is because dropout is likely to occur and film breakage may occur during coating with the metal plate.

  The lubricant may be blended only in the outer (I) layer that comes into contact with the punch during canning after coating, or in all of the inner (I) layer and the central (II) layer in contact with the metal plate. May be.

  In the polyester film of the present invention, as described above, after the film is coated on the metal plate, the film-coated metal plate after the remelt treatment to eliminate the orientation is given slipperiness, and the metal container is formed by drawing and ironing. Good moldability even when the manufacturing conditions are severe, such as when the deformation ratio increases and the processing speed increases during manufacturing (to ensure the release of the resin and punch on the inner surface of the can, In order to obtain (suppression of deviation), it is necessary to contain a wax component in at least the polyester of the (I) layer.

  As the wax component contained in the polyester film of the present invention, natural wax such as paraffin wax, carnauba wax, lanolin wax, polyethylene wax, ester wax, glycerin from the viewpoint of workability of blending with polyester and film forming property It is preferable to contain one or more waxes selected from synthetic waxes such as fatty acid esters and higher fatty acid monoamides, and polyethylene wax is particularly preferable.

  The content of the wax in the polyester film of the present invention is preferably 0.01 to 0.15% by weight, more preferably 0.02 to 0.1% by weight when contained in the polyester of the (I) layer on both sides. preferable. If the wax content is less than 0.01% by weight, it cannot be said that the effect of improving the can-making property is sufficient, and if it exceeds 0.15% by weight, no further effect of improving the can-making property can be expected. This is because the thermal stability of the composition may be impaired. The wax may be contained only in the polyester of the outer (I) layer or in all layers of the polyester including the (II) layer, and in that case, it may be 0.15% by weight or less in total. preferable.

  The method for incorporating the wax into the polyester film of the present invention is not particularly limited. That is, a method of producing a film using a polymer obtained by melt-kneading polyester and wax in advance, a method of producing a film directly using a mixture of polyester and wax, and the like can be used.

  In addition to the lubricant and wax, the polyester film of the present invention contains an incompatible thermoplastic resin, antioxidant, thermal stabilizer, ultraviolet absorber, plasticizer, pigment, antistatic agent, lubrication as necessary. An additive such as an agent and a crystal nucleating agent may be contained. In particular, it is a preferred embodiment to contain 0.01 to 1% by weight of an antioxidant for improving the thermal stability.

  The production method of the polyester film having a composite structure of (I) layer / (II) layer / (I) layer of the present invention is not particularly limited. For example, the raw materials of (I) layer and (II) layer are separately extruded. The melted resin is melted using a machine, and the molten resins are merged in the flow path, extruded on a cooling roll in layers from a T-die and cooled and solidified to obtain an unstretched sheet of laminated resin, and then subjected to stretching treatment and heat treatment. Created to go. At this time, it is preferable to adjust the amount of the molten resin extruded from each extruder so that the ratio of the thickness of (I) layer / (II) layer / (I) layer falls within a preferable range described later.

  The polyester film having a composite structure of (I) layer / (II) layer / (I) layer of the present invention is preferably a biaxially stretched film. Here, examples of the biaxial stretching method include sequential biaxial stretching and simultaneous biaxial stretching. In the case of sequential 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. Further, after biaxial stretching, it is preferable to fix the orientation of the polyester by heat treatment, but after biaxial stretching, re-stretching may be performed in the longitudinal direction and / or the width direction before the heat treatment step. Furthermore, the corona discharge treatment or the predetermined coating treatment is not limited at all on one side or both sides of the film before or after the stretching step.

  Although the thickness of the polyester film of this invention is not specifically limited, It is preferable from the point of a coating effect (rust prevention property), impact resistance, and also economical efficiency to be in the range of 10-50 micrometers. If the thickness is less than 10 μm, the impact resistance cannot be obtained, and if it exceeds 50 μm, the quality is excessive, which is often not economically preferable.

  The ratio of the thickness of the (I) layer / (II) layer / (I) layer composite polyester film according to the present invention is such that (I) layer thickness / (II) layer thickness / (I) layer thickness is 10/80. It is preferable that it is in the range of / 10 to 40/20/40 in terms of achieving both the above impact resistance and the moldability during can making. Also, the smaller the difference in thickness between the two (I) layers, the better, in order to prevent the film from being folded due to curling when it is coated on the metal plate.

  The method of coating the metal film with the polyester film having the composite structure of (I) layer / (II) layer / (I) layer of the present invention is not particularly limited. For example, a dry laminating method, a thermal laminating method or the like is adopted. Can do. Specifically, the metal plate is heated to a temperature equal to or higher than the melting point of the (I) layer of the polyester film, and the (I) layer of the polyester film is brought into contact with the surface of the metal plate. Subsequently, it coat | covers by making it quench-harden at 10-40 degreeC.

  Further, the film may be coated only on one side of the metal plate or on both sides. In the case of double-sided coating, it may be coated simultaneously or sequentially.

  The polyester film for covering a metal plate according to the present invention is formed by using a polyester film-covered metal plate because the (I) layer and the (II) layer are composed of three layers (I) / (II) / (I).・ The moldability and impact resistance can be satisfied even if the processing conditions when forming through squeezing are severe, and the polyester film can be folded by curling when the polyester film is coated on a metal plate. Can be prevented. Furthermore, as described above, the folding prevention effect can be improved as the difference in thickness between the two (I) layers is reduced.

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

  In the present invention, when the polyester film used is a biaxially stretched polyester film and the polyester film-coated metal plate is applied to a two-piece can, the polyester constituting the film is used to remove the molecular orientation of the polyester after coating. It is preferable to perform a remelt (remelting) treatment in which heating is performed at a melting point or higher. Furthermore, it is preferable to perform forced cooling by using cold water or compressed air immediately after remelting. After remelting, crystallization occurs during the process of cooling and solidifying the polyester by slow cooling to the air, etc., and when the polyester undergoes drawing and ironing in the subsequent can manufacturing process, the polyester does not follow the deformation caused by the processing. As a result, it becomes impossible to make cans.

  The degree of molecular orientation by X-ray observation after the remelt treatment is 10% or less, which 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, making it difficult to perform the drawing process for forming the container part. In severe cases, the metal plate is used during drawing and ironing. The delamination phenomenon of tearing off occurs, torn, or scraped. On the other hand, if it is substantially non-oriented, it can follow the deformation of the coated metal plate, so that forming with plastic deformation of the metal is performed like a two-piece can without causing delamination or tearing. be able to.

  The polyester film-coated metal container of the present invention is a metal container formed by appropriately forming the polyester film-coated metal plate of the present invention, and the shape of the container and the method of forming the metal container are not particularly limited. Specifically, the present invention can be applied not only to a so-called three-piece can in which the top cover is wound and filled with contents, but also to a two-piece can that forms a container portion by drawing a metal plate.

  In the polyester film-coated metal container of the present invention, the polyester 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. When a polyester film is used for the outer wall surface, a resin coating film containing a pigment or a colorant may be applied in advance in order to impart concealability to the surface of the film that is bonded to the metal.

  In addition, when performing drawing and ironing, if necessary, a lubricant may be applied to the film surface in contact with the punch and die.

  The polyester film-coated metal container of the present invention may be subjected to printing or the like as necessary, and may be remelted again after the can making process, the printing process, or the like.

  EXAMPLES Hereinafter, although an Example is given and the content and effect of this invention are demonstrated concretely, this invention is not limited to a following example, unless it deviates from the summary.

  Various evaluation methods in the present invention are shown below.

(1) Intrinsic viscosity (IV)
Polyesters A-1 to A-4, B-1, B-2, and values obtained by dissolving the films obtained in Examples 1 to 6 and Comparative Examples 1 to 7 in orthochlorophenol at 25 ° C. ( dl / g).

(2) Thermal properties of polyester 10 mg of a sample obtained by heating and melting the polyester composition used in layers (I) of Examples 1 to 6 and Comparative Examples 1 to 7 at 300 ° C. for 5 minutes and then rapidly cooling with liquid nitrogen When the exothermic / endothermic curve (DSC curve) was measured at a rate of temperature increase of 10 ° C./min using a differential scanning calorimeter (DSC) in a nitrogen stream, The melting point was Tm (° C.).

(3) Composition of polyester The polyester raw materials used in Examples 1 to 6 and Comparative Examples 1 to 7 were dissolved in deuterated chloroform containing 15% by weight of trifluoroacetic acid, and 1H-NMR was measured. In the case of a film, a sample obtained by scraping the resin layer from the surface layer to a desired thickness was dissolved in the same manner and 1H-NMR was measured. The ratio of the long-chain dicarboxylic acid component is such that the integrated intensity of the peak derived from each component of the terephthalic acid and isophthalic acid components in the vicinity of 8 ppm and the methylene group (− Calculation was made based on the integrated intensity of the peak derived from CH _2- ). The average carbon number of the long-chain dicarboxylic acid component is based on the ratio of the integrated intensity of the entire peak near 2.0 to 0.7 ppm and the integrated intensity of the peak of the methylene group adjacent to the terminal carbonyl group near 2.3 ppm. Calculated. At this time, when one of the peaks derived from the butanediol component was included in the vicinity of 1.8 ppm, the integrated intensity of the peak derived from the other butanediol component in the vicinity of 4.2 ppm was subtracted from the total integrated intensity.

(4) Content of ethylene terephthalate cyclic trimer in polyester Examples 1 to 6 and polyester raw materials used in Comparative Examples 1 to 7 are hexafluoroisopropyl alcohol / chloroform = 2/3 (V / V; volume ratio). 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.

(5) Releasability between can inner surface resin and processing punches After the remelt aluminum plates obtained in Examples 1 to 6 and Comparative Examples 1 to 7 were formed into cups by drawing, they were redrawn at a speed of 100 cans / minute. 300 cans were continuously manufactured by ironing, and the degree of buckling occurring at the top of the formed can was visually observed. Evaluation criteria were set 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

(6) Scratch resistance of the outer surface of the can (longitudinal scratch on the outer surface of the can)
After the remelt aluminum plates obtained in Examples 1 to 6 and Comparative Examples 1 to 7 were formed into cups by drawing, 300 cans were continuously produced by redrawing and ironing at a rate of 100 cans / minute, and the formed cans The degree of generation of scratches on the resin on the outer surface of the body trunk wall was visually observed. Evaluation criteria were set as follows, and ○ was evaluated as practical.
○: Scratch not occurred △: Scratch occurred about 1/3 of the outer surface ×: Severe scratch generated more than 1/3 of the outer surface

(7) Flavor property After dipping the film-coated metal plates obtained in Examples 1 to 6 and Comparative Examples 1 to 7 of 5 cm square in d-limonene filled in a sealed glass container, 40 ° C. In a constant temperature room for 10 days, d-limonene is adsorbed. The d- limonene adhering to the surface and weighed W ₁ wiped with Kimwipe. The film-coated metal plate after the weight W ₁ measurement was vacuum dried at 60 ° C. for 24 hours, and then the weight W ₂ was measured. The weight W ₃ of the peeled film from the film-coated metal plate was measured. The amount of adsorbed d-limonene was determined by the following formula and expressed in wt%. Those having a d-limonene adsorption amount of 3% or less were evaluated as practical.
d-Limonene adsorption amount (% by weight) = (W ₁ −W ₂ ) / W ₃ × 100

(8) Impact resistance The can obtained by making the remelt aluminum plate obtained in Examples 1 to 6 and Comparative Examples 1 to 7 was heated at 280 ° C. for 40 seconds and then quenched in water from the center of the trunk wall 7 cm. A corner sample was cut out. A weight (600 g) having a tip diameter of 10 mmφ is dropped from a height of 10 cm onto the surface corresponding to the outer surface of the can of this sample to give an impact. Next, the sample was placed on a glass container filled with 7% dilute hydrochloric acid (with the convex portion of the sample immersed), and the corrosion state of the convex portion was visually observed after 3 days. Evaluation criteria were set as follows, and ○ was evaluated as practical.
○: Corrosion of the convex part is not generated ×: Corrosion of the convex part is generated

  Next, the kind and content of polyester used for the Example and the comparative example are demonstrated.

(1) A-1: Polyethylene terephthalate / isophthalate (repeating unit of ethylene isophthalate 8 mol% (PET-I (8)), (IV = 0.76)
92 parts by weight of terephthalic acid, 8 parts by weight of isophthalic acid, 82 parts by weight of ethylene glycol (ethylene glycol / total acid component of ethylene glycol / total acid component) in a reactor equipped with an inlet, a thermometer, a pressure gauge, a distillation tube with a rectifying column, and a stirring blade Amorphous silica particles having a molar ratio of 2.2), 0.05 mol% of germanium oxide as the Ge element, 0.05 mol% of magnesium acetate as the Mg element, and an average particle diameter of 1.3 μm with respect to the acid component 0.23 parts by weight were charged, nitrogen was introduced with stirring, the pressure inside the system was maintained at 0.3 MPa, and the esterification reaction was performed while distilling off the water generated at a temperature of 230 ° C. to 250 ° C. outside the system. . After the completion of the reaction, at 250 ° C., 0.04 mol% of trimethyl phosphate was added as the P amount, the pressure was gradually reduced while the temperature was raised, and a polycondensation reaction was performed under a vacuum of 275 ° C. and 1.0 hPa or less to obtain a polyester ( PET-I (8)) was obtained. The intrinsic viscosity of the obtained polyester was 0.76 (dl / g), and the ethylene terephthalate cyclic trimer was 0.5% by weight.

(2) A-2: Polyethylene terephthalate / isophthalate (repeating unit of ethylene isophthalate 10 mol% (PET-I (10)), (IV = 0.74)
90 parts by weight of terephthalic acid, 10 parts by weight of isophthalic acid, 82 parts by weight of ethylene glycol (ethylene glycol / total acid component) were added to a reactor equipped with an inlet, a thermometer, a pressure gauge, a distillation tube with a rectifying column, and a stirring blade. Molar ratio = 2.2), 0.05 mol% of germanium oxide as the Ge element and 0.05 mol% of the magnesium acetate as the Mg element are charged with respect to the acid component, and nitrogen is introduced while stirring, and the pressure in the system Was maintained at 0.3 MPa, and the esterification reaction was carried out while distilling off the water produced at a temperature of 230 ° C. to 250 ° C. out of the system. After the completion of the reaction, at 250 ° C., 0.04 mol% of trimethyl phosphate was added as the P amount, the pressure was gradually reduced while the temperature was raised, and a polycondensation reaction was performed under a vacuum of 275 ° C. and 1.0 hPa or less to obtain a polyester ( PET-I (10)) was obtained. The polyester obtained had an intrinsic viscosity of 0.74 (dl / g) and an ethylene terephthalate cyclic trimer of 0.4% by weight.

(3) A-3: Polyethylene terephthalate (PET) (IV = 0.75)
82 parts by weight of ethylene glycol (ethylene glycol / terephthalic acid molar ratio = 2) with respect to 100 parts by weight of terephthalic acid in a reactor equipped with an inlet, a thermometer, a pressure gauge, a distillation tube with a rectifying column, and a stirring blade .2) 0.05 mol% of germanium oxide as the Ge element, 0.05 mol% of magnesium acetate as the Mg element, and 0.23 weight of amorphous silica particles having an average particle diameter of 1.3 μm with respect to the acid component Part was charged, nitrogen was introduced with stirring, the pressure inside the system was kept at 0.3 MPa, and the esterification reaction was carried out while distilling out water generated at a temperature of 230 ° C. to 250 ° C. outside the system. After the completion of the reaction, at 250 ° C., 0.04 mol% of trimethyl phosphate was added as the P amount, the pressure was gradually reduced while the temperature was raised, and a polycondensation reaction was performed under a vacuum of 275 ° C. and 1.0 hPa or less to obtain a polyester ( PET) was obtained. The intrinsic viscosity of the obtained polyester was 0.75 (dl / g), and the ethylene terephthalate cyclic trimer was 0.4% by weight.

(4) A-4: Polybutylene terephthalate (PBT) (IV = 1.00)
In a reactor equipped with an inlet, a thermometer, a pressure gauge, a distillation tube with a rectifying column, and a stirring blade, 86 parts by weight of 1,4-butanediol (1,4-butane with respect to 100 parts by weight of terephthalic acid) Diol / terephthalic acid molar ratio = 1.6), 0.05 parts by weight of tetranormal butyl titanate, 0.025 parts by weight of butylhydroxytin oxide were charged, and water produced at 190 ° C to 230 ° C was distilled out of the system. The esterification reaction was carried out. After completion of the reaction, 0.05 part by weight of tetranormal butyl titanate and 0.025 part by weight of phosphoric acid were added, and a polycondensation reaction was performed at 250 ° C. under reduced pressure (1.0 hPa or less). The resulting polyester (PBT, An intrinsic viscosity of 1.00 (dl / g) was used.

(5) B-1: Copolyester of terephthalic acid / dimer acid (90/10) and ethylene glycol A reactor equipped with an inlet, a thermometer, a pressure gauge, a distillation tube with a rectifying column, and a stirring blade 72.5 parts by weight of terephthalic acid, 27.5 parts by weight of dimer acid, 66 parts by weight of ethylene glycol (molar ratio of ethylene glycol / total acid component = 2.2), 0. 05 mol%, 0.05 mol% of magnesium acetate as Mg element were charged, nitrogen was introduced with stirring, the pressure inside the system was kept at 0.3 MPa, and water generated at a temperature of 230 ° C to 250 ° C was removed from the system The esterification reaction was carried out while distilling off. After completion of the reaction, at 250 ° C., 0.04 mol% of trimethyl phosphate as P amount and 0.05 wt% of antioxidant (trade name; Irganox 1330) were added, and the pressure was gradually reduced while raising the temperature. A polycondensation reaction was performed under a vacuum of 275 ° C. and 1.0 hPa or less to obtain a dimer acid copolymer polyester (B-1). The polyester obtained had an intrinsic viscosity of 0.80 (dl / g) and an ethylene terephthalate cyclic trimer of 0.4% by weight.

(6) B-2: Copolyester of terephthalic acid / dimer acid (90/10) and ethylene glycol / 1,4-butanediol (30/70) with inlet, thermometer, pressure gauge and rectifying tower In a reactor equipped with a distillation tube and a stirring blade, 72.5 parts by weight of terephthalic acid, 27.5 parts by weight of dimer acid, 28 parts by weight of ethylene glycol, 57 parts by weight of 1,4-butanediol, oxidized against the acid component Charge 0.05 mol% of germanium as the Ge element and 0.05 mol% of the magnesium acetate as the Mg element, introduce nitrogen with stirring and keep the pressure in the system at 0.3 MPa, at a temperature of 230 ° C to 250 ° C. The esterification reaction was carried out while distilling off the water produced. After completion of the reaction, at 250 ° C., 0.04 mol% of trimethyl phosphate as P amount and 0.05 wt% of antioxidant (trade name; Irganox 1330) were added, and the pressure was gradually reduced while raising the temperature. A polycondensation reaction was performed under a vacuum of 275 ° C. and 1.0 hPa or less to obtain a dimer acid copolymer polyester (B-2). The intrinsic viscosity of the obtained polyester was 0.80 (dl / g).

(7) B-3: Copolyester of terephthalic acid / dimer acid (70/30) and ethylene glycol A reactor equipped with an inlet, a thermometer, a pressure gauge, a distillation tube with a rectifying tower, and a stirring blade 56.5 parts by weight of terephthalic acid, 82.5 parts by weight of dimer acid, 66 parts by weight of ethylene glycol, 0.05 mol% of germanium oxide as the Ge element and 0.05 mol% of magnesium acetate as the Mg element with respect to the acid component Then, nitrogen was introduced with stirring to keep the pressure in the system at 0.3 MPa, and the esterification reaction was carried out while distilling out water generated at a temperature of 230 ° C. to 250 ° C. outside the system. After completion of the reaction, at 250 ° C., 0.04 mol% of trimethyl phosphate as P amount and 0.05 wt% of antioxidant (trade name; Irganox 1330) were added, and the pressure was gradually reduced while raising the temperature. A polycondensation reaction was performed under a vacuum of 275 ° C. and 1.0 hPa or less to obtain a dimer acid copolymer polyester (B-3). This polyester had a problem in handling property due to its strong tackiness even at room temperature.

(8) C-1: Polyester containing 1% by weight of wax With respect to 99 parts by weight of polyester A-3, 1 part by weight of polyethylene wax (manufactured by Mitsui Chemicals, Inc .: high wax) is melt-kneaded with a twin screw extruder. Thus, a polyester (C-1) containing 1% by weight of wax was obtained.

[Example 1]
(I) A-1 / C-1 = 95/5 (% by weight) as a raw material for the layer and B-1 = 100 (% by weight) as a raw material for the layer (II) were dried at 100 ° C. for 24 hours, respectively. , Melted at 270 ° C. using separate single screw extruders (2 for (I) layer, 1 for (II) layer), merged in flow path, and cooled in layers from T-die It was extruded onto a roll to obtain an unstretched sheet of a three-layer laminated resin of (I) layer / (II) layer / (I) layer. The unstretched sheet was stretched 3.5 times in the machine direction at a preheating temperature of 80 ° C. and a stretching temperature of 100 ° C., and further stretched by 4.0 times in the transverse direction at a preheating temperature of 80 ° C. and a stretching temperature of 100 ° C. Two types of polyester films (200 m roll film) having a thickness of 25 μm and 16 μm were obtained by heat treatment at 8 ° C. for 8 seconds. The ratio of the thickness of each layer of these films was (I) layer / (II) layer / (I) layer = 25/50/25.

  These two films of 25 μm and 16 μm are pressure-bonded between nip rolls on both sides of a 3004 aluminum alloy plate (thickness 0.26 mm) heated to 250 ° C., further heated to 275 ° C., and then rapidly cooled in water to cover the film. A metal plate was obtained.

  After applying the forming lubricant to the film-coated metal plate thus obtained, heating was performed to a plate temperature of 70 ° C., and drawing was performed so that the 25 μm film side was the inner surface and the 16 μm film side was the outer surface. 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.

  Table 1 shows the composition of the polyester (I) layer, the (II) layer, the melting point of the polyester (I) layer, and the intrinsic viscosity of the polyester film. Table 2 shows the impact resistance of metal cans obtained by producing cans on the outer surface film of the can), flavor properties, and film-coated metal plates. The film-coated metal plate of this example was excellent in can making and flavoring properties, and the metal can of this example was excellent in impact resistance.

[Example 2]
(I) A-2 / A-3 / C-1 = 50/45/5 (% by weight) as a raw material of the layer, B-1 / A-3 = 80/20 (weight) as a raw material of the (II) layer %) Was used to prepare an unstretched sheet of a three-layer laminated resin of (I) layer / (II) layer / (I) layer in the same manner as in Example 1, and in the same manner as in Example 1. Two types of polyester films (200 m roll film) having a thickness of 25 μm and 16 μm were obtained through a stretching process and a heat treatment process. The ratio of the thickness of each layer of these films was (I) layer / (II) layer / (I) layer = 25/50/25.

  Using these films, a film-coated metal plate and a 350 ml size seamless can were obtained in the same manner as in Example 1.

  Table 1 shows the composition of the polyester (I) layer, the (II) layer, the melting point of the polyester (I) layer, and the intrinsic viscosity of the polyester film. Table 2 shows the impact resistance of metal cans obtained by producing cans on the outer surface film of the can), flavor properties, and film-coated metal plates. The film-coated metal plate of this example was excellent in can making and flavoring properties, and the metal can of this example was excellent in impact resistance.

[Example 3]
(I) A-2 / A-3 / C-1 = 80/15/5 (% by weight) as the raw material of the layer, and B-1 / A-3 = 80/20 (weight) as the raw material of the (II) layer %) Was used to prepare an unstretched sheet of a three-layer laminated resin of (I) layer / (II) layer / (I) layer in the same manner as in Example 1, and in the same manner as in Example 1. Two types of polyester films (200 m roll film) having a thickness of 25 μm and 16 μm were obtained through a stretching process and a heat treatment process. The ratio of the thickness of each layer of these films was (I) layer / (II) layer / (I) layer = 25/50/25.

  Using these films, a film-coated metal plate and a 350 ml size seamless can were obtained in the same manner as in Example 1.

  Table 1 shows the composition of the polyester (I) layer, the (II) layer, the melting point of the polyester (I) layer, and the intrinsic viscosity of the polyester film. Table 2 shows the impact resistance of metal cans obtained by producing cans on the outer surface film of the can), flavor properties, and film-coated metal plates. The film-coated metal plate of this example was excellent in can making and flavoring properties, and the metal can of this example was excellent in impact resistance.

[Example 4]
(I) A-2 / A-3 / C-1 = 50/45/5 (% by weight) as a raw material of the layer, B-1 / A-3 = 40/60 (weight) as a raw material of the (II) layer %) Was used to prepare an unstretched sheet of a three-layer laminated resin of (I) layer / (II) layer / (I) layer in the same manner as in Example 1, and in the same manner as in Example 1. Two types of polyester films (200 m roll film) having a thickness of 25 μm and 16 μm were obtained through a stretching process and a heat treatment process. The ratio of the thickness of each layer of these films was (I) layer / (II) layer / (I) layer = 25/50/25.

  Using these films, a film-coated metal plate and a 350 ml size seamless can were obtained in the same manner as in Example 1.

  Table 1 shows the composition of the polyester (I) layer, the (II) layer, the melting point of the polyester (I) layer, and the intrinsic viscosity of the polyester film. Table 2 shows the impact resistance of metal cans obtained by producing cans on the outer surface film of the can), flavor properties, and film-coated metal plates. The film-coated metal plate of this example was excellent in can making and flavoring properties, and the metal can of this example was excellent in impact resistance.

[Example 5]
(I) A-1 / C-1 = 95/5 (% by weight) as a raw material for the layer, and B-1 / A-1 / R-1 (obtained in Example 1) as a raw material for the (II) layer (I) layer / (II) layer / (I) layer in the same manner as in Example 1 except that the resin pellet obtained by remelting the polyester film) = 70/10/20 (% by weight) was used. An unstretched sheet of the three-layer laminated resin was prepared, and two polyester films (200 m roll film) having a thickness of 25 μm and 16 μm were obtained through a stretching process and a heat treatment process in the same manner as in Example 1. The ratio of the thickness of each layer of these films was (I) layer / (II) layer / (I) layer = 25/50/25.

  Using these films, a film-coated metal plate and a 350 ml size seamless can were obtained in the same manner as in Example 1.

  Table 1 shows the composition of the polyester (I) layer, the (II) layer, the melting point of the polyester (I) layer, and the intrinsic viscosity of the polyester film. Table 2 shows the impact resistance of metal cans obtained by producing cans on the outer surface film of the can), flavor properties, and film-coated metal plates. The film-coated metal plate of this example was excellent in can making and flavoring properties, and the metal can of this example was excellent in impact resistance.

[Example 6]
(I) A-2 / A-3 / A-4 / C-1 = 65/10/20/5 (% by weight) as a raw material for the layer, and B-1 / A-2 as a raw material for the (II) layer 3 of (I) layer / (II) layer / (I) layer by the same method as in Example 1 except that / A-3 / A-4 = 80/13/3/4 (% by weight) was used. An unstretched sheet of layer laminated resin was prepared, and two types of polyester films (200 m roll film) having a thickness of 25 μm and 16 μm were obtained through a stretching process and a heat treatment process in the same manner as in Example 1. The ratio of the thickness of each layer of these films was (I) layer / (II) layer / (I) layer = 25/50/25.

  Using these films, a film-coated metal plate and a 350 ml size seamless can were obtained in the same manner as in Example 1.

  Table 1 shows the composition of the polyester (I) layer, the (II) layer, the melting point of the polyester (I) layer, and the intrinsic viscosity of the polyester film. Table 2 shows the impact resistance of metal cans obtained by producing cans on the outer surface film of the can), flavor properties, and film-coated metal plates. The film-coated metal plate of this example was excellent in can making and flavoring properties, and the metal can of this example was excellent in impact resistance.

[Comparative Example 1]
(I) A-3 / C-1 = 95/5 (% by weight) was used as the raw material for the layer, and B-1 / A-3 = 80/20 (% by weight) was used as the raw material for the (II) layer. Prepared an unstretched sheet of a three-layer laminated resin of (I) layer / (II) layer / (I) layer by the same method as in Example 1, and further performed the stretching process and heat treatment process in the same manner as in Example 1. After that, two types of polyester films (200 m roll film) having thicknesses of 25 μm and 16 μm were obtained. The ratio of the thickness of each layer of these films was (I) layer / (II) layer / (I) layer = 25/50/25.

  Using these films, a film-coated metal plate and a 350 ml-size seamless can were prepared in the same manner as in Example 1. However, when the film-coated metal plate was canned, the releasability between the can inner surface film and the processed punch was high. Unfortunately, a part of the bottom of the can was deformed, and a scratch was generated on a part of the outer film of the can. Therefore, the can-making speed was reduced to 40 cans / minute to obtain a seamless can.

  Table 1 shows the composition of the polyester (I) layer, the (II) layer, the melting point of the polyester (I) layer, and the intrinsic viscosity of the polyester film. Table 2 shows the impact resistance of metal cans obtained by producing cans on the outer surface film of the can), flavor properties, and film-coated metal plates. Although the flavor property of the film-coated metal plate of this comparative example was good and the impact resistance of the metal can was good, it was a problem in practical use because the can-making property of the film-coated metal plate was inferior.

[Comparative Example 2]
(I) A-3 / A-4 / C-1 = 35/60/5 (% by weight) as the raw material for the layer, and B-1 / A-3 = 80/20 (weight) as the raw material for the (II) layer %) Was used to prepare an unstretched sheet of a three-layer laminated resin of (I) layer / (II) layer / (I) layer in the same manner as in Example 1. The unstretched sheet was stretched 3.5 times in the machine direction at a preheating temperature of 60 ° C. and a stretching temperature of 90 ° C., and further stretched 4.0 times in the transverse direction at a preheating temperature of 60 ° C. and a stretching temperature of 90 ° C. Two types of polyester films (200 m roll film) having a thickness of 25 μm and 16 μm were obtained by heat treatment at 8 ° C. for 8 seconds. The ratio of the thickness of each layer of these films was (I) layer / (II) layer / (I) layer = 25/50/25.

  Using these films, a film-coated metal plate and a 350 ml-size seamless can were prepared in the same manner as in Example 1. However, when the film-coated metal plate was canned, the releasability between the can inner surface film and the processed punch was high. Unfortunately, a part of the bottom of the can was deformed, and a scratch was generated on a part of the outer film of the can. Therefore, the can-making speed was reduced to 40 cans / minute to obtain a seamless can.

  Table 1 shows the composition of the polyester (I) layer, the (II) layer, the melting point of the polyester (I) layer, and the intrinsic viscosity of the polyester film. Table 2 shows the impact resistance of metal cans obtained by producing cans on the outer surface film of the can), flavor properties, and film-coated metal plates. Although the flavor property of the film-coated metal plate of this comparative example was good and the impact resistance of the metal can was good, it was a problem in practical use because the can-making property of the film-coated metal plate was inferior.

[Comparative Example 3]
(I) A-1 / C-1 = 95/5 (% by weight) was used as the raw material for the layer, and B-2 / A-3 = 80/20 (% by weight) was used as the raw material for the (II) layer. Prepared an unstretched sheet of a three-layer laminated resin of (I) layer / (II) layer / (I) layer by the same method as in Example 1, and further performed the stretching process and heat treatment process in the same manner as in Example 1. After that, two types of polyester films (200 m roll film) having thicknesses of 25 μm and 16 μm were obtained. The ratio of the thickness of each layer of these films was (I) layer / (II) layer / (I) layer = 25/50/25.

  Using these films, a film-coated metal plate and a 350 ml size seamless can were obtained in the same manner as in Example 1.

  Table 1 shows the composition of the polyester (I) layer, the (II) layer, the melting point of the polyester (I) layer, and the intrinsic viscosity of the polyester film. Table 2 shows the impact resistance of metal cans obtained by producing cans on the outer surface film of the can), flavor properties, and film-coated metal plates. Although the film-coated metal plate of this comparative example was excellent in canability and flavor properties, it was not a preferred method because the resulting metal can was inferior in impact resistance.

[Comparative Example 4]
(I) After using A-1 / C-1 = 95/5 (% by weight) as a raw material for the layer, this was dried at 100 ° C. for 24 hours, and melted at 270 ° C. using a single screw extruder. Then, the sheet was extruded in a layer form from a T-die onto a cooling roll to obtain a single-layer unstretched sheet having only the (I) layer. Using the obtained unstretched sheet, two types of polyester films (200 m roll film) having a thickness of 25 μm and 16 μm were obtained through a stretching process and a heat treatment process in the same manner as in Example 1.

  Using these films, a film-coated metal plate and a 350 ml size seamless can were obtained in the same manner as in Example 1.

  Table 1 shows the composition of the polyester (I) layer, the melting point of the polyester (I) layer, and the intrinsic viscosity of the single-layer polyester film. Table 2 shows the impact resistance of metal cans obtained by making a film-coated metal plate. The film-coated metal plate of this comparative example was excellent in can making and flavoring properties, but is not a preferred method because the resulting metal can is inferior in impact resistance.

[Comparative Example 5]
(II) After using B-1 / A-1 = 80/20 (% by weight) as a raw material for the layer, this was dried at 100 ° C. for 24 hours, and melted at 270 ° C. using a single screw extruder. Then, it was extruded on a cooling roll in layers from a T-die to obtain a single-layer unstretched sheet consisting of only the (II) layer. Using the obtained unstretched sheet, two types of polyester films (200 m roll film) having a thickness of 25 μm and 16 μm were obtained through a stretching process and a heat treatment process in the same manner as in Example 1.

  Using these films, a film-coated metal plate and a 350 ml-size seamless can were prepared in the same manner as in Example 1. However, when the film-coated metal plate was canned, the releasability between the can inner surface film and the processed punch was high. Unfortunately, a part of the bottom of the can was deformed, and a scratch was generated on a part of the outer film of the can. Therefore, the can-making speed was reduced to 40 cans / minute to obtain a seamless can.

  Table 1 shows the composition of the polyester (II) layer and the intrinsic viscosity of the single-layer polyester film. The film-coated metal sheet can be made (removability of the can inner film and punch and the degree of scratching of the outer film of the can), and flavor properties. Table 2 shows the impact resistance of a metal can obtained by making a film-coated metal plate. Although the metal can of this comparative example has no problem in impact resistance, it is a practical problem because it is inferior in the flavor property and can-making property of the film-coated metal plate.

[Comparative Example 6]
(I) By the same method as in Example 1 except that A-1 = 100 (% by weight) was used as the raw material for the layer and B-1 = 100 (% by weight) was used as the raw material for the (II) layer (I ) Layer / (II) layer / (I) layer three-layer laminated resin unstretched sheet, and through the stretching process and heat treatment process in the same manner as in Example 1, two types of polyester films having a thickness of 25 μm and 16 μm (200 m roll film) was obtained. The ratio of the thickness of each layer of these films was (I) layer / (II) layer / (I) layer = 25/50/25.

  Using these films, a film-coated metal plate and a seamless can of 350 ml size were obtained in the same manner as in Example 1. However, scratches and deformation were confirmed on a part of the obtained can.

  Table 1 shows the composition of the polyester (I) layer, the (II) layer, the melting point of the polyester (I) layer, and the intrinsic viscosity of the polyester film. Table 2 shows the impact resistance of metal cans obtained by producing cans on the outer surface film of the can), flavor properties, and film-coated metal plates. Although the film-coated metal plate of this comparative example was excellent in flavor properties and the impact resistance of the obtained metal can was excellent, it is not a preferred method because it is inferior in the can-making property of the film-coated metal plate.

[Comparative Example 7]
Example 1 except that A-1 / C-1 = 95/5 (% by weight) was used as the raw material for the (I) layer and A-3 = 100 (% by weight) was used as the raw material for the (II) layer. An unstretched sheet of laminated resin was prepared by the same method, and two polyester films (200 m roll film) having a thickness of 25 μm and 16 μm were obtained through a stretching process and a heat treatment process in the same manner as in Example 1. The ratio of the thickness of each layer of these films was (I) layer / (II) layer / (I) layer = 25/50/25.

  Using these films, a film-coated metal plate and a 350 ml size seamless can were obtained in the same manner as in Example 1.

Table 1 shows the composition of the polyester (I) layer, the (II) layer, the melting point of the polyester (I) layer, and the intrinsic viscosity of the polyester film. Table 2 shows the impact resistance of metal cans obtained by producing cans on the outer surface film of the can), flavor properties, and film-coated metal plates. The film-coated metal plate of this comparative example was excellent in can making and flavoring properties, but is not a preferred method because the resulting metal can is inferior in impact resistance.

  The polyester film for coating a metal plate of the present invention can be made by coating the polyester film (particularly, the release properties of the inner surface film of the can and the processing punch when the can is manufactured under severe conditions and the outer surface film of the can). Since a polyester film-coated metal plate excellent in scratch resistance and flavor properties is obtained, and a polyester film-coated metal can having excellent impact resistance can be obtained by making the polyester film-coated metal plate, As a polyester film for metal plate coating used for the purpose of preventing corrosion of metal containers such as soft drinks, beer, canned foods, etc., or as a polyester film-coated metal plate obtained by coating the polyester film on a metal plate, or the polyester film Very useful as a polyester film-coated metal container formed by forming a coated metal plate It can be said that.

Claims (5)

  (I) layer / (II) layer / (I) layer composite structure, (I) layer is a copolymer polyester of ethylene terephthalate and ethylene isophthalate, (II) layer is terephthalic acid, carbon number 20 A metal comprising the above long-chain aliphatic dicarboxylic acid and ethylene glycol, and containing at least 0.01 to 0.15% by weight of a wax component in the copolymer polyester of (I) layer Polyester film for board coating.   2. The polyester for coating a metal plate, wherein the wax component according to claim 1 is one or more selected from paraffin wax, polyethylene wax, ester wax, glycerin fatty acid ester, and higher fatty acid monoamide. the film.   A polyester film for covering a metal plate, wherein the polyester film for covering a metal plate according to claim 1 or 2 is a biaxially stretched polyester film.   A polyester film-covered metal plate, wherein the metal plate-covering polyester film according to any one of claims 1 to 3 is coated on at least one surface of a metal plate.   A polyester film-coated metal container formed by molding the polyester film-coated metal plate according to claim 4.