JP5200707B2 - Polyester resin coated metal sheet for containers - Google Patents

Description

  The present invention relates to a polyester resin-coated metal plate for containers used for, for example, can bodies and lids for canned foods.

  Conventionally, metal plates such as tin-free steel (TFS) and aluminum, which are materials for metal cans used in food cans, have been coated for the purpose of improving corrosion resistance, durability and weather resistance. However, this coating process has a problem that not only the baking process is complicated, but also a long processing time is required and a large amount of solvent is discharged.

  Therefore, in order to solve these problems, instead of the coated steel sheet, a film laminated metal sheet was developed by laminating a thermoplastic resin film on a heated metal sheet, and is currently used industrially as a food canning material. Yes.

  In addition to basic properties such as processability and adhesion, food canning materials have a variety of functions such as deep drawability, adhesion after processing and retorting, corrosion resistance, and impact resistance for 2-piece can applications. Desired.

  As a method of making the film laminate metal plate multifunctional, (1) adding a modifier having the function to be added to the film to make the film itself multifunctional, (2) not modifying the film, Either a modifier having a function desired to be added or a method of coating a resin containing a modifier on the film surface is selected.

The method of directly adding a modifier to the film of (1) is a method with high production efficiency and high profitability when a film having a certain function is produced in large quantities. However, in food canning applications, this method is not appropriate because cans are rich in variety and the required functions differ depending on the type of can. This is because every time the function to be applied to the film is changed, it is necessary to clean the resin extrusion device, casting drum, cooling roll, etc., so the line must be stopped for a long time, resulting in a significant reduction in production efficiency. It is because it will do.
On the other hand, since the method of coating the surface of the film of (2) with a resin containing a modifier can easily change the additional function, it can meet various needs for food canning. This is because the tank containing the coating liquid containing the modifier can be quickly adapted to functional changes by washing and replacing.

  As a method for coating such a film surface with a resin containing a modifier, for example, the technique of Patent Document 1 has been proposed. In Patent Document 1, a resin layer containing an epoxy resin as a main component and containing a melamine resin, a blocked isocyanate compound, and a colorant is formed between a metal plate and a film.

  However, although epoxy resin is rich in reactivity and excellent in adhesion to a metal plate, it has a disadvantage of poor deep-drawing formability, so a film that can be used as a two-piece can material cannot be obtained. Even if it tries to shape | mold the resin-coated metal plate of patent document 1 in a deep drawing can (DRD can), an epoxy resin cannot follow the expansion deformation of a can height direction, and restrains deformation | transformation of a raw material, and a drawing process The material will break.

Patent Documents 2 to 5 describe techniques for performing resin coating on a film for the purpose of improving adhesion. Because it is a composite system of polyester resin and epoxy resin, or has a structure mainly composed of epoxy resin, it has difficulty in deep-drawing moldability as well as the technology described in Patent Document 1, and can be applied to 2-piece can applications. is not. In addition, the examples described in Patent Documents 2 to 5 do not disclose examples of evaluating can manufacturing processability or deep drawing formability, so these techniques require deep drawing. It is clear that the two-piece can application is not considered.
JP 2007-185915 A JP-A-4-266984 JP-A-8-199147 JP 10-183095 A JP 2002-206079 A

  In view of such circumstances, an object of the present invention is to provide a polyester resin-coated metal plate for containers that can cope with many characteristics required for food canned materials.

As a result of intensive studies by the present inventors for solving the problems, the following knowledge was obtained.
A resin layer having a multilayer structure mainly composed of polyester is provided on at least one side. Then, a polyester resin having a specific molecular structure is used as an adhesion layer with the metal plate, a polyester resin having a specific residual orientation degree is laminated on the upper layer of the adhesion layer, and a block-free isocyanate compound is further formed on the polyester resin layer which is the uppermost layer, Polyester resin for containers with many functions such as performance related to design properties under retort processing environment in addition to basic properties such as excellent deep drawability and adhesion after processing by containing alkylene bis fatty acid amide A coated metal plate can be obtained.

The present invention has been made based on the above findings, and the gist thereof is as follows.
[1] A resin-coated metal plate for containers having a multilayer resin layer mainly composed of polyester on at least one side, wherein the multilayer resin layer is characterized by the following (A) to (C) A polyester resin-coated metal plate for containers.
(A) The polyester resin layer which becomes an adhesion layer with a metal plate contains a block free isocyanate compound, and the number of moles of NCO groups contained in the block free isocyanate compound is the mole of OH groups contained in the polyester resin layer. It is 0.5 times or more and 20.0 times or less of the number.
(B) The polyester resin layer which is the upper layer of the adhesion layer and forms the intermediate layer has a residual orientation degree in the range of 2% to 30%.
(C) The polyester resin layer as the uppermost layer contains a block-free isocyanate compound, and the number of moles of NCO groups contained in the block-free isocyanate compound is 0.00, the number of moles of OH groups contained in the polyester resin layer. It is 5 times or more and 20.0 times or less and contains alkylene bis fatty acid amide.
[2] In the above [1], the adhesion amount of the adhesion layer is 0.1 g / m ² or more and 5.0 g / m ² or less, and the adhesion amount of the uppermost layer is 0.1 g / m ² or more and 5 A polyester resin-coated metal plate for containers, characterized in that it is 0.0 g / m ² or less.
[3] The polyester resin-coated metal sheet for containers according to [1] or [2], wherein the alkylene bis fatty acid amide is contained in an amount of 1 mass% to 10 mass% with respect to the uppermost polyester resin layer.
[4] The polyester resin-coated metal plate for containers according to any one of [1] to [3], wherein the alkylene bis fatty acid amide is ethylene bis stearic acid amide.
[5] The polyester resin-coated metal plate for containers according to any one of [1] to [4], wherein the polyester resin layer of the adhesion layer contains a colorant.
[6] In any one of [1] to [5], in the polyester resin layer of the intermediate layer, 93 mass% or more of the structural units of the polyester are ethylene terephthalate units and / or ethylene naphthalate units, and the area Particles having a converted average particle size of 0.005 to 5.0 μm, a relative standard deviation represented by the formula (1) of 0.5 or less, a particle major axis / minor axis ratio of 1.0 to 1.2, and a Mohs hardness of less than 7 The polyester resin-coated metal sheet for containers according to any one of claims 1 to 6, which is contained in an amount of 0.005 to 10 mass%.

  ADVANTAGE OF THE INVENTION According to this invention, the polyester resin coating metal plate for containers which can respond to many characteristics requested | required of the food canned raw material is obtained. It is an industrially useful invention as a new polyester resin-coated metal plate for containers that can easily add many functions required for food canning.

Hereinafter, the polyester resin-coated metal plate for containers of the present invention will be described in detail.
First, the metal plate used by this invention is demonstrated.
As the metal plate of the present invention, an aluminum plate or a mild steel plate widely used as a can material can be used. In particular, a surface-treated steel sheet (hereinafter referred to as TFS) on which a two-layer film is formed, in which the lower layer is made of metallic chromium and the upper layer is made of chromium hydroxide, is optimal.
The amount of adhesion of the metal chromium layer and chromium hydroxide layer of TFS is not particularly limited, but from the viewpoint of adhesion after processing and corrosion resistance, both are in terms of Cr, the metal chromium layer is 70 to 200 mg / m ² , chromium hydroxide layer is preferably in the range of 10 to 30 mg / ^{m 2.}

Next, the resin layer that covers the metal plate will be described.
In this invention, it has the resin layer of the multilayer structure which has polyester as a main component at least on one side.
The adhesion layer is made of a polyester resin layer containing polyester as a main component. The polyester as a main component means a resin containing 50 mass% or more and 100 mass% or less of polyester, and as a resin other than polyester, for example, polyolefin is added as long as the function specified in the present invention can be secured. It doesn't matter.

  The composition of the polyester resin layer is represented by terephthalic acid as a carboxylic acid component and polyethylene terephthalate composed of ethylene glycol as a glycol component, but as other carboxylic acid components, such as isophthalic acid, phthalic acid, naphthalenedicarboxylic acid, adipic acid and the like In addition, as other glycol components, copolymer resins in which the components are replaced with diethylene glycol, propylene glycol, butanediol, neopentyl glycol and the like are also included. As an acid component, terephthalic acid is essential because of mechanical strength, heat resistance, chemical resistance, and the like, but further, by copolymerizing with isophthalic acid, flexibility, tear strength, and the like are improved. By copolymerizing the isophthalic acid component with the terephthalic acid component in the range of 10.0 mol% or more and 60.0 mol% or less, it becomes easy to ensure the thermophysical properties specified in this proposal, and deep drawability, after processing This is preferable because it functions to improve adhesion. As the glycol component, a low Tg (Tg = glass transition temperature) component having excellent flexibility such as ethylene glycol and propanediol and a rigid high Tg component having a ring structure such as neopentyl glycol and cyclohexanedimethanol are copolymerized. It is desirable to make it. This is because it is easy to ensure the thermophysical properties defined in the present invention, and the strength and flexibility can be balanced. Preferable examples include polyester resins in which the acid component is composed of 10 to 30 mol% isophthalic acid and 70 to 90 mol% terephthalic acid, and the glycol component is composed of 30 to 50 mol% ethylene glycol and 50 to 70 mol% propanediol. be able to.

The adhesion amount of the polyester resin layer forming the adhesion layer to the metal plate is preferably specified in the range of 0.1 g / m ^{2 to} 5.0 g / m ² . If it is less than 0.1 g / m ² , the surface of the metal plate cannot be uniformly coated, and the film thickness may become non-uniform. When a modifier is added, the adhesion amount of the modifier fluctuates, and a stable function cannot be obtained, which is inappropriate. On the other hand, if it exceeds 5.0 g / m ² , the cohesive strength of the resin becomes insufficient, and the strength of the resin layer may be reduced. As a result, at the time of can manufacturing, the resin layer is agglomerated and broken to peel off the film, and the can body portion is torn from that point. More preferably, it is in the range of 0.5 g / m ² or more and 2.5 g / m ² .

  In the present invention, block-free isocyanate is applied as the isocyanate compound contained in the polyester resin layer that forms the adhesion layer. By not using the blocking agent, the free isocyanate group can react quickly with the functional group at the end of the polyester resin and the functional group on the surface of the polyester film as the base material. This makes it possible to polymerize by an isocyanate cross-linking reaction even in an extremely short heat treatment (less than 1 second) such as a heat fusion laminating method. And while improving the intensity | strength and workability of a contact | adherence layer significantly, the firm adhesiveness with a base film can be obtained. Examples of the isocyanate compound to be applied include hexamethylene diisocyanate, methylcyclohexane diisocyanate, and xylylene isocyanate. Among these, the xylylene isocyanate compound is most preferable from the viewpoints of adhesion and durability.

  Moreover, since a three-dimensional network of molecular chains is formed by the isocyanate crosslinking reaction, retort whitening can be effectively suppressed. Retort whitening is a phenomenon in which the resin layer itself is discolored as white and turbid during retort sterilization, and the design of the outer surface of the can is impaired, which is a major problem that can reduce consumers' willingness to purchase. As a result of intensive studies by the inventors, water vapor permeates into the resin layer covering the can body, thereby forming a vacuole at the interface of the resin layer and in the vicinity of the interface, and causing light to scatter at the vacuole part. It was found anew. Therefore, to improve the characteristics, it is important to suppress the formation of vacuoles at the interface of the resin layer and in the vicinity of the interface.

  The water vapor that has entered the resin diffuses in the resin and reaches the interface with the metal plate. Immediately after the start of the retort process, the contents filled in the can are in a state close to room temperature, so that a temperature gradient is generated from the outside of the can to the inside of the can. That is, the water vapor diffusing in the resin is cooled as it approaches the metal plate, liquefies at the interface and in the vicinity of the interface, and becomes condensed water to form a vacuole. The vacuole remains at the interface and in the vicinity of the interface even after the retort treatment, which causes light scattering and makes the resin surface appear cloudy. Therefore, in order to suppress retort whitening, the formation of vacuoles at the interface and in the vicinity of the interface may be suppressed.

  As a result of intensive studies on the whitening phenomenon, the inventors have found that the formation of a vacuole can be suppressed by forming a network of polyester molecular chains by the isocyanate crosslinking reaction. The network of polyester molecular chains suppresses water vapor from reaching the interface, and increases the resin strength and elastic modulus at the interface and in the vicinity of the interface, thereby suppressing formation and growth of vacuoles.

  Here, the number of moles of NCO groups (isocyanate groups) contained in the block-free isocyanate compound is 0.5 to 20.0 times the number of moles of OH groups contained in the polyester resin layer. When the number of moles is less than 0.5 times, either the crosslinking reaction with the terminal functional group of the polyester resin or the crosslinking reaction with the functional group on the surface of the polyester film becomes insufficient, and the film peels off during can manufacturing. Or the material may tear. Further, since the network is not sufficiently formed, retort whitening cannot be suppressed. On the other hand, when it exceeds 20.0 times, the water resistance of the polyester resin layer is lowered, so that the film may be peeled from the can during the retort treatment. In addition, Preferably, it is the range of 5.0 times or more and 10.0 times or less, and the film peeling at the time of a retort process can be suppressed effectively.

As the thermophysical properties of the polyester forming the adhesion layer, it is desirable that the glass transition point is in the range of 50 ° C. to 85 ° C., and the softening point is in the range of 100 ° C. to 200 ° C.
When the resin-coated metal plate is stored and transported, it may be kept at a temperature of about 40 ° C. for a long time, so that the glass transition point needs to be 50 ° C. or higher. On the other hand, the upper limit of the glass transition point is specified at 85 ° C. This is because a polyester polymer having a glass transition point exceeding 85 ° C. has an increased softening point, making it difficult to maintain a range of 200 ° C. or lower as defined in the present invention.
Moreover, the retort sterilization treatment for food cans may take 1 hour or more at a high temperature of 100 ° C. or higher, and is required to have heat resistance in a temperature range of 100 ° C. or higher. Therefore, the softening point defined in JIS K2425 needs to be specified at 100 ° C. or higher, preferably 150 ° C. or higher. On the other hand, the upper limit of the softening point is defined as 200 ° C. When the softening point exceeds 200 ° C., the thermal fluidity of the resin is lowered, and the flexibility of the resin is insufficient in processes such as laminating with a metal plate and can manufacturing. Insufficient flexibility at the time of lamination affects the adhesion to the metal plate, and insufficient flexibility at the time of can manufacturing suppresses elongation deformation in the can height direction and causes the can body to rupture.

  The polyester resin forming the adhesion layer preferably has a weight average molecular weight of 10,000 or more and 40,000 or less. Desirably, it is the range of 15000 or more and 20000 or less. A polyester resin having a weight average molecular weight in such a range has an excellent balance between processability and strength, and has good deep drawability and adhesion after molding. By setting the molecular weight to 10,000 or more, the strength of the resin increases, and the resin follows the deformation without tearing during the deep drawing. Also in the subsequent retorting process, delamination from the trim edge or the like can be suppressed against the thermal shrinkage of the film formed in the upper layer. Also, with respect to impact resistance after canning, the occurrence of defects can be suppressed and good performance can be obtained. On the other hand, if the molecular weight exceeds 40,000, the strength of the resin becomes excessive, and conversely, flexibility may be impaired. By setting it to 40000 or less, the balance between strength and flexibility can be maintained.

The layer that is the upper layer of the adhesion layer and forms the intermediate layer is also made of a polyester resin layer. And in order to suppress retort whitening, the residual orientation degree of the polyester resin layer is set to a range of 2% to 30%.
Here, the residual orientation degree is a value obtained by an X-ray diffraction method and is defined as follows.
(1) The X-ray diffraction intensity of the oriented polyester resin (or oriented polyester film) before lamination and the resin (or film) after lamination is measured in the range of 2θ = 20 to 30 °.
(2) The X-ray diffraction intensity at 2θ = 20 ° and 2θ = 30 ° is connected by a straight line to obtain a baseline.
(3) Measure the height of the highest peak in the vicinity of 2θ = 22 to 28 ° from the baseline.
(4) When the height of the highest peak of the film before lamination is P1, and the highest peak of the film after lamination is P2, P2 / P1 × 100 is the residual orientation degree (%).

  As a result of intensive studies by the present inventors, it has been found that the amount of water vapor that permeates through the resin layer decreases as the residual orientation degree increases. By setting the degree of residual orientation to 2% or more, the amount of water vapor reaching the interface with the metal plate is reduced, and the retort whitening can be completely suppressed together with the above-described isocyanate addition effect. As the residual orientation increases, the amount of permeated water vapor tends to decrease and the resistance to retort whitening becomes good, while the flexibility and elongation characteristics of the resin decrease. If the residual orientation degree exceeds 30%, follow-up to the can manufacturing process becomes insufficient, and film peeling or material tearing occurs. By adjusting the degree of residual orientation to a range of 2% to 30%, it is possible to achieve both retort whitening resistance, resin flexibility, and moldability.

The polyester resin layer forming the intermediate layer is preferably a polyester film. As a polyester film, it is desirable to use ethylene terephthalate and / or ethylene naphthalate as a main constituent from the viewpoint of improving the taste characteristics after retort and suppressing the generation of abrasion powder in the can making process. That is, the polyester mainly composed of ethylene terephthalate and / or ethylene naphthalate is a polyester in which 93 mass% or more of the structural units of the polyester are ethylene terephthalate units and / or ethylene naphthalate units. More preferably, it is 95 mass% or more. Even if a metal can is filled with a beverage for a long time, it is desirable because it has good taste characteristics.
On the other hand, other dicarboxylic acid components and glycol components may be copolymerized as long as the taste characteristics are not impaired. Examples of the dicarboxylic acid component include aromatics such as diphenylcarboxylic acid, 5-sodium sulfoisophthalic acid, and phthalic acid. Dicarboxylic acid, oxalic acid, succinic acid, adipic acid, sebacic acid, dimer acid, maleic acid, aliphatic dicarboxylic acid such as fumaric acid, aliphatic dicarboxylic acid such as cyclohexanedicarboxylic acid, oxycarboxylic acid such as p-oxybenzoic acid Etc.
On the other hand, examples of the glycol component include aliphatic glycols such as ethylene glycol, propanediol, butanediol, pentanediol, hexanediol, and neopentyl glycol, finger ring glycols such as cyclohexanedimethanol, and aromatics such as bisphenol A and bisphenol S. Examples include glycol, diethylene glycol, and polyethylene glycol. These dicarboxylic acid components and glycol components may be used in combination of two or more.
Moreover, as long as the effect of this invention is not inhibited, you may copolymerize polyfunctional compounds, such as trimellitic acid, trimesic acid, a trimethylol propane.

  Further, the polyester resin layer of the intermediate layer has an area-converted average particle diameter of 0.005 to 5.0 μm, a relative standard deviation represented by the formula (1) of 0.5 or less, and a major axis / minor axis ratio of particles of 1.0 to It is preferable to contain 0.005 to 10 mass% of particles having a Mohs hardness of less than 7 at 1.2.

The particles in the polyester film are not particularly limited in terms of composition regardless of organic or inorganic.
From the viewpoint of wear resistance, workability, taste characteristics, etc., the area-converted average particle diameter is preferably 0.005 to 5.0 μm. More preferably, it is 0.01-3.0 micrometers.
Moreover, it is preferable that relative standard deviation shown by said Formula (1) is 0.5 or less from points, such as abrasion resistance. More preferably, it is 0.3 or less.
The major axis / minor axis ratio of the particles is preferably 1.0 to 1.2 from the viewpoint of the shape of the protrusion when formed into a film, wear resistance, and the like. The Mohs hardness is preferably less than 7 from the viewpoints of protrusion hardness, wear resistance, and the like. And in order to fully express these effects, it is preferable to contain 0.005-10 mass% of particles which consist of the above.

Specifically, examples of the inorganic particles include wet and dry silica, colloidal silica, aluminum silicate, titanium oxide, calcium carbonate, calcium phosphate, barium sulfate, alumina, mica, kaolin, and clay. Among them, the one in which the functional group on the particle surface reacts with the polyester to generate a carboxylic acid metal salt is preferable. Specifically, the one having 10 ⁻⁵ mol or more with respect to 1 g of the particles has an affinity for the polyester, It is preferable in terms of abrasion resistance, and more preferably 2 × 10 ⁻⁵ mol or more.
As the organic particles, various organic polymer particles can be used. As the type, particles having any composition may be used as long as at least a part thereof is insoluble in polyester. In addition, polyimide, polyamideimide, polymethyl methacrylate, formaldehyde resin, phenol resin, cross-linked polystyrene, silicone resin, etc. can be used as the material of such particles, but they have high heat resistance and a uniform particle size distribution. Particularly preferred are vinyl-based crosslinked polymer particles that are easy to obtain.

Such inorganic particles and organic polymer particles may be used alone, but preferably used in combination of two or more, and further function by combining particles having different physical properties such as particle size distribution and particle strength. A highly functional polyester resin can be obtained.
In addition, other particles such as various amorphous external additive particles and internal precipitation particles, or various surface treatment agents may be added as long as the effects of the present invention are not hindered.

  Furthermore, it is preferable that the polyester film is a biaxially stretched polyester film from the viewpoint of heat resistance and taste characteristics. The biaxial stretching method may be simultaneous biaxial stretching or sequential biaxial stretching, but the stretching conditions and heat treatment conditions are specified, and the refractive index in the thickness direction of the film is 1.50 or more. Is preferable in terms of improving the laminating property and moldability. Furthermore, when the refractive index in the thickness direction is 1.51 or more, particularly 1.52 or more, the plane orientation coefficient is controlled within a specific range in order to achieve both formability and impact resistance even if there is some variation during lamination. This is preferable because it can be performed.

In addition, the biaxially stretched polyester film is a solid high-resolution NMR in terms of workability and impact resistance when processing the neck after receiving a thermal history of about 200 to 230 ° C. after drawing in the can manufacturing process. It is preferable that the relaxation time of the carbonyl moiety in the structural analysis by is 270 msec or more. More preferably, it is 280 msec or more, Most preferably, it is 300 msec or more. As long as the effects of the present invention are not hindered, other particles, for example, various amorphous externally added particles, internally precipitated particles, or various surface treatment agents may be used.
The thickness of the resin layer mainly composed of polyester as defined in the present invention is preferably 5 μm or more and 100 μm or less as a whole, more preferably 8 μm or more and 50 μm or less, particularly preferably 10 μm or more and 25 μm or less.

  The uppermost polyester resin layer contains a block-free isocyanate compound, and the number of moles of NCO groups contained in the block-free isocyanate compound is 0.5 times or more the number of moles of OH groups contained in the polyester resin layer. It is 20.0 times or less and contains alkylene bis fatty acid amide.

  The purpose of adding the alkylene bis-fatty acid amide is to prevent adhesion of the polyester resin to the laminating roll (pressure-bonding roll) and to suppress the white powder phenomenon when the polyester resin is laminated on the surface of the metal plate by the heat fusion method. The reason will be described below.

  Since the alkylene bis fatty acid amide is a surfactant, it is concentrated on the outermost surface of the resin together with the heat flow of the polyester resin during lamination by the heat fusion method. The alkylene bis-fatty acid amide concentrated on the outermost surface has the property that the hydrocarbon group, which is a hydrophobic group, is arranged on the outside (air side) and the hydrophilic group is arranged on the inside of the resin layer. Thereby, the surface energy of the polyester resin is significantly reduced, and adhesion to the laminate roll can be suppressed.

  Further, after the lamination with the metal plate is completed, the laminated metal plate is quenched (rapidly cooled) to Tg or less of the polyester resin, so that the state where the alkylene bis fatty acid amide is concentrated on the outermost surface of the resin can be maintained. Thereby, the white powder phenomenon at the time of a retort process can be suppressed. The white powdering phenomenon is a phenomenon in which a low molecular weight component present in a polyester resin diffuses and precipitates on the resin surface due to heat during retort. The low molecular weight component that precipitates is mainly a cyclic trimer of PET, and becomes a white powdery substance by crystallization. When this precipitates on the surface of the resin layer on the outer surface side of the container, it has a cloudy appearance and greatly impairs the design.

  As the alkylene bis fatty acid amide is concentrated near the surface of the resin layer, the gaps between the polyester molecular chains are filled with the fatty acid amide. As a result, the diffusion path of the low molecular weight component (cyclic trimer) of PET to the resin layer surface is closed, and the amount of precipitation is greatly reduced. Therefore, the addition of alkylene bis fatty acid amide is effective in suppressing the reduction of white powder.

  The addition amount of the alkylene bis-fatty acid amide is preferably 1 mass% to 10 mass%, more preferably 2 mass% to 8 mass% with respect to the uppermost polyester resin layer (the resin layer to which the alkylenebisfatty acid amide is added). If the addition amount of the alkylene bis fatty acid amide is less than 1 mass%, the existence density of the alkylene bis fatty acid amide on the surface of the resin layer will be insufficient. Thereby, the hydrophobic group density on the surface of the resin layer is lowered, the surface energy of the polyester resin is not lowered, and it adheres to the laminate roll, and the polyester resin layer is destroyed. In addition, the white powder phenomenon suppressing effect cannot be expected because the hydrophobic group density decreases. On the other hand, when the addition amount of the alkylene bis fatty acid amide exceeds 10 mass%, the alkylene bis fatty acid amide is unevenly distributed at the interface between the polyester resin layer and the polyester resin layer therebelow. Alkylene bis fatty acid amides reduce interfacial energy and degrade the adhesion between resin layers. When a large stress is applied to the resin, such as when molding a container, the resin layer is peeled off and the moldability is greatly deteriorated.

  Therefore, the addition amount of alkylene bis fatty acid amide is preferably 1 mass% to 10 mass%, more preferably 2 mass% to 8 mass%.

  The alkylene bis fatty acid amide preferably has a melting point of 120 ° C. or higher, more preferably 130 ° C. or higher. Thereby, even in a long-time retort sterilization treatment, it is possible to stably exist on the surface of the resin layer. As such alkylene bis fatty acid amide, application of ethylene bis stearic acid amide is most desirable from the viewpoint of food safety.

  The composition of the polyester resin layer as the uppermost layer is represented by terephthalic acid as a carboxylic acid component and polyethylene terephthalate made of ethylene glycol as a glycol component, but isophthalic acid, phthalic acid, naphthalenedicarboxylic acid as other carboxylic acid components In addition, adipic acid and the like, and diethylene glycol, propylene glycol, butanediol, neopentyl glycol and the like as other glycol components are also included as copolymer resins. As an acid component, terephthalic acid is essential because of mechanical strength, heat resistance, chemical resistance, and the like, but further, by copolymerizing with isophthalic acid, flexibility, tear strength, and the like are improved. By copolymerizing the isophthalic acid component with the terephthalic acid component in the range of 10.0 mol% or more and 60.0 mol% or less, it becomes easy to ensure the thermophysical properties specified in this proposal, and deep drawability, after processing This is preferable because it functions to improve adhesion. As the glycol component, a low Tg (Tg = glass transition temperature) component having excellent flexibility such as ethylene glycol and propanediol and a rigid high Tg component having a ring structure such as neopentyl glycol and cyclohexanedimethanol are copolymerized. It is desirable to make it. This is because it is easy to ensure the thermophysical properties defined in the present invention, and the strength and flexibility can be balanced. Preferable examples include polyester resins in which the acid component is composed of 10 to 30 mol% isophthalic acid and 70 to 90 mol% terephthalic acid, and the glycol component is composed of 30 to 50 mol% ethylene glycol and 50 to 70 mol% propanediol. be able to.

The adhesion amount of the uppermost polyester resin layer is preferably 0.1 g / m ² or more and 5.0 g / m ² or less. If it is less than 0.1 g / m ² , the surface of the lower resin layer cannot be uniformly coated, and the effect prescribed in the present invention may not be expected. On the other hand, if it exceeds 5.0 g / m ² , the cohesive strength of the resin becomes insufficient, and the strength of the resin layer may be reduced. As a result, at the time of can manufacturing, the resin layer is agglomerated and broken to peel off the film, and the can body portion is torn from that point. Accordingly, the adhesion amount is preferably 0.1 g / m ² or more 5.0 g / m ² or less of the range, more preferably in the range of 1.0 g / m ² or more 2.0 g / m ^2.

  In the present invention, block-free isocyanate is applied as the isocyanate compound contained in the uppermost polyester resin layer. By not using the blocking agent, the free isocyanate group can react quickly with the functional group at the end of the polyester resin and the functional group on the surface of the polyester film as the base material. This makes it possible to polymerize by an isocyanate cross-linking reaction even in an extremely short heat treatment (less than 1 second) such as a heat fusion laminating method. Thereby, while improving the intensity | strength and workability of a resin layer, the firm adhesiveness with a base film can be obtained.

  In addition, the formation of a three-dimensional network of molecular chains by the isocyanate crosslinking reaction can be expected to suppress the whitening phenomenon. It is considered that the three-dimensional network by the isocyanate crosslinking reaction has an effect of trapping oligomers that are to diffuse to the resin surface. As a result, it is considered that oligomer precipitation is suppressed during retort processing.

  Examples of the isocyanate compound to be applied include hexamethylene diisocyanate, methylcyclohexane diisocyanate, and xylylene isocyanate. Among these, the xylylene isocyanate compound is most preferable from the viewpoints of adhesion and durability.

  Here, the number of moles of NCO groups (isocyanate groups) contained in the block-free isocyanate compound is 0.5 to 20.0 times the number of moles of OH groups contained in the polyester resin layer. When the number of moles is less than 0.5 times, either the crosslinking reaction with the terminal functional group of the polyester resin or the crosslinking reaction with the surface functional group of the lower polyester resin layer becomes insufficient, and at the time of can manufacturing The film may peel off or the material may tear. Moreover, the effect which suppresses oligomer precipitation is also scarce. On the other hand, the upper limit of the number of moles of NCO groups is 20.0 times or less with respect to the number of moles of OH groups in the polyester resin. When it exceeds 20.0 times, the workability and water resistance of the polyester resin layer are lowered. For this reason, the polyester resin layer may be broken at the time of can making and the material may be broken, or the film may be peeled off from the can at the time of retorting. More preferably, it is in the range of 5.0 times to 10.0 times, and various performances such as workability and adhesion can be optimally balanced.

  The polyester resin layer as the uppermost layer has a glass transition point of 30 ° C. or higher, a softening point when the resin layer is made of an amorphous resin, and a melting point of 130 ° C. or higher when the resin layer is made of a crystalline resin. Is preferred. When the resin-coated metal plate is stored and transported, it may be kept at a temperature of about 40 ° C. for a long time, so that the glass transition point needs to be 30 ° C. or higher. In addition, the retort sterilization treatment for food cans may take 1 hour or more at a high temperature of 120 ° C. or higher and is required to have sufficient heat resistance. Therefore, when the resin layer is an amorphous resin, JIS The softening point specified in K2425 needs to be 130 ° C or higher. When the resin layer is a crystalline resin, the melting point specified in JIS K7121 needs to be 130 ° C or higher, and more preferably 150 ° C or higher. .

  The weight average molecular weight of the polyester resin as the uppermost layer is preferably 10,000 or more and 40,000 or less, and more preferably 15,000 to 20,000. A polyester resin having a weight average molecular weight in such a range has an excellent balance between processability and strength, and has good deep drawability and adhesion after molding. By setting the molecular weight to 10,000 or more, the strength of the resin increases, and the resin follows the deformation without tearing during the deep drawing. Also in the subsequent retorting process, delamination from the trim edge or the like can be suppressed against the thermal shrinkage of the film formed in the upper layer. In addition, with respect to the impact resistance after canning, the occurrence of defects can be suppressed and good performance can be obtained. On the other hand, if the molecular weight exceeds 40,000, the strength of the resin becomes excessive, and conversely, flexibility may be impaired. By setting it to 40000 or less, the balance between strength and flexibility can be maintained.

  In order to further improve the water resistance of the polyester resin layer, it is preferable to include a hydrophobic polyol resin derived from a fatty acid in a range of 5 PHR to 20 PHR. Examples of the hydrophobic polyol resin include dimer acid polyol, polydiene polyol, polyisoprene polyol and the like. Among them, by applying a long-chain alkyl group having 20 to 50 carbon atoms, the ester bond portion can be shielded from water, and film peeling in a humid environment such as retort treatment can be effectively prevented.

The addition amount of the hydrophobic polyol resin is desirably 5 PHR or more and 20 PHR or less. If it is less than 5 PHR, sufficient water resistance cannot be obtained, and if it exceeds 20 PHR, the surface free energy of the polyester resin is excessively lowered, which may impair adhesion between the polyester film and the metal plate. . By defining it in the range of 5 PHR to 20 PHR, both water resistance and adhesion can be achieved. More preferably, it is the range of 7 PHR or more and 15 PHR or less.
Moreover, polyester polyol can be added in the range which does not inhibit hydrophobicity. In this case, the range of 50% or more of the total polyol weight is suitable as the hydrophobic polyol. As the polyester polyol, glycol components such as 1,6 hexanediol and neopentyl glycol and esters such as maleic acid, adipic acid, oleic acid, and dimer acid thereof can be used. Particularly preferred are polyester polyols using dimer acid of oleic acid.

  Furthermore, by adding colorants such as dyes and pigments to the polyester resin layers of the uppermost layer and the adhesion layer, the underlying metal plate can be concealed and various colors unique to the resin can be imparted. For example, by adding carbon black as a black pigment, it is possible to conceal the metal color of the base and to impart a high-class feeling of black to food cans. The amount of carbon black added is desirably 5 PHR to 40 PHR. If it is less than 5 PHR, the blackness is insufficient, the color tone of the base metal cannot be concealed, and a high-quality design may not be imparted. On the other hand, even if it exceeds 40 PHR, the blackness does not change, so the effect of improving the design is not obtained, and the structure of the polyester resin becomes brittle, so that the resin layer may be easily broken during can manufacturing. is there. By making the addition amount in the range of 5 PHR to 40 PHR, it is possible to achieve both design properties and other required characteristics. Note that the layer to which the colorant is added is preferably an adhesion layer. This is because it is protected by the polyester resin layer that forms the intermediate layer and the uppermost layer, so that it is possible to effectively suppress the deterioration of the design properties due to the processing flaws that occur during can manufacturing.

  The particle size of the carbon black can be in the range of 5 to 50 nm, but the range of 5 to 30 nm is suitable in consideration of dispersibility and color developability in the polyester resin.

In addition to the black pigment, by adding a white pigment, the metallic luster of the base can be concealed, the printed surface can be sharpened, and a good appearance can be obtained. As a pigment to be added, it is necessary that an excellent design property can be exhibited after container molding. From such a viewpoint, inorganic pigments such as titanium dioxide can be used. Since the coloring power is strong and rich in spreadability, it is preferable because a good design property can be secured even after container molding. As for the addition amount of titanium dioxide, it is desirable that it is 5-30 mass% with respect to the object resin layer. If it is 5 mass% or more, sufficient whiteness will be obtained and favorable design property can be ensured. On the other hand, even if added over 30% by mass, the whiteness is saturated, so it is desirable to make it 30% by mass or less for economic reasons. More preferably, it is the range of 10-20 mass%. In addition, the addition amount of a coloring agent is a ratio with respect to the resin layer which added the coloring agent.
When a bright color is desired on the container surface, use of an azo pigment is also suitable. Although it is excellent in transparency, it has a strong coloring power and a high spreadability, so that a bright appearance can be obtained even after the container is molded. As an azo pigment that can be used in the present invention, the color index (name of CI registration) is at least one of pigment yellow 12, 13, 14, 16, 17, 55, 81, 83, 139, 180, 181. Can be mentioned. In particular, from the viewpoints of vividness of color tone (bright color) and bleeding resistance in retort sterilization environment (inhibition ability against the phenomenon that pigments are deposited on the film surface), it has a large molecular weight and is soluble in PET resin. A poor pigment is desirable. For example, CI Pigment Yellow 180 having a benzimidazolone structure having a molecular utilization of 700 or more is more preferably used.
The addition amount of the azo pigment is desirably 10 to 40 PHR with respect to the target resin layer. If the addition amount is 10 PHR or more, it is preferable because coloring is excellent. When the color is 40 PHR or less, the transparency becomes high and the color tone is rich.

Next, the manufacturing method of the polyester resin coating metal plate for containers which consists of the above is demonstrated.
In the polyester resin-coated metal plate for containers according to the present invention, first, a polyester resin layer serving as an uppermost layer and an adhesion layer is formed on both sides of a polyester film serving as an intermediate layer. Next, the polyester film having a multilayer structure is laminated on the surface of the metal plate.

  A method for forming a polyester resin as the uppermost layer and the adhesion layer on the film surface will be described. A polyester resin having a resin composition defined in the present invention is dissolved in an organic solvent to form a coating solution. Next, the prepared coating liquid is applied to both sides of the film and dried at the time of forming the polyester film or after the film formation. The formation method is not particularly limited, but the method described above is preferable because it is suitable for the purpose and application of the present invention.

Examples of the organic solvent for dissolving the polyester resin defined in the present invention include aromatic hydrocarbon solvents such as toluene and xylene, ketone solvents such as methyl ethyl ketone and cyclohexanone, and ester solvents such as ethyl acetate and ethylene glycol monoethyl ether acetate. One or more of these can be appropriately selected and used.
In addition, additives such as block-free isocyanate compounds defined in the present invention, hydrophobic polyol resins having a long-chain alkyl group in the side chain, carbon black as a colorant, azo pigments, etc. are used by dispersing them in an organic solvent. It is desirable to do. In this case, it is preferable to use a dispersant in combination because the uniformity of the additive can be imparted.

As a method for applying the coating liquid to the polyester film, known coating means such as a roll coater method, a die coater method, a gravure method, a gravure offset method, and a spray coating method can be applied, but a gravure roll coating method is most preferable. . As drying conditions after application of the coating liquid, 80 to 170 ° C. for 20 to 180 seconds, particularly 80 to 120 ° C. for 60 to 120 seconds are preferable. The adhesion amount of the polyester resin layer after drying is preferably in the range of 0.1 g / m ² or more and 3.0 g / m ² or less as defined in the present invention.

  In the present invention, for example, a metal plate is heated to a certain temperature or higher by a heating device (for example, metal band heating device 2 in FIG. 1), and a polyester film is pressed onto the surface of the metal plate (hereinafter referred to as a laminate roll). It is possible to use a method of making contact and heat-sealing using. At this time, it is necessary that the coated surface is brought into contact with a metal plate using a press roll (hereinafter referred to as a laminate roll) and heat-sealed. Details of the lamination conditions will be described below.

  The temperature of the metal plate at the start of thermal fusion may be in the range of + 5 ° C. to + 30 ° C. based on the higher value of the melting point of the polyester film or the softening point of the adhesive resin layer (polyester resin). desirable. In order to ensure the interlaminar adhesion of the metal plate-adhesive resin layer-polyester film by the thermal fusion method, it is necessary to heat the resin at the adhesion interface. By setting the temperature of the metal plate to a temperature range of + 5 ° C. or higher based on the higher value of the melting point of the polyester film or the softening point of the adhesive resin layer (polyester resin), the resin between the layers is heated. It flows and the wetting at the interface becomes good with each other, and excellent adhesion can be obtained. The reason why the temperature is set to + 30 ° C. or lower is that even if the temperature exceeds + 30 ° C., further improvement in adhesion cannot be expected, the film is excessively melted, the surface is roughened by pressing the surface of the lami roll, and the melt on the pressure roll This is because there is a concern that problems such as transfer may occur.

  It is desirable that the heat history received by the film at the time of lamination is 5 msec. Or more at the higher temperature of the melting point of the polyester film or the softening point of the adhesive resin layer, whichever is higher. This is because wetting at the interface is good. Although the wettability improves with increasing time, when it exceeds 40 msec., Almost constant performance is exhibited and the effect is not recognized. Since there is a possibility of causing a decrease in productivity, it is desirable to set it to 40 msec or less. Therefore, the range of 5 to 40 msec is preferable.

  In order to achieve such lamination conditions, in addition to high-speed operation of 150 mpm or more, cooling during heat sealing is also necessary. For example, the laminating roll 3 in FIG. 1 is an internal water-cooling type, and it is possible to suppress the film and each resin layer from being excessively heated by passing the cooling water. Furthermore, it is preferable because the thermal history of the polyester film and the adhesive resin layer can be controlled by changing the temperature of the cooling water.

The pressurization of the laminate roll is preferably 9.8 to 294 N / cm ² (1 to 30 kgf / cm ² ) as the surface pressure. When the temperature is less than 9.8 N / cm ² , even if the temperature at the start of thermal fusion is not less than the melting point of the film + 5 ° C. and sufficient fluidity is ensured, the force to spread the resin on the metal surface is sufficient. Since it is weak, sufficient coverage cannot be obtained, and as a result, performance such as adhesion and corrosion resistance may be affected. On the other hand, if it exceeds 294 N / cm ^2, there is no inconvenience in the performance of the laminated metal plate, but the force applied to the laminate roll is large and the strength of equipment is required, which leads to an increase in size of the apparatus, which is uneconomical. Therefore, the pressurization of the laminate roll is preferably 9.8 to 294 N / cm ² .

Examples of the present invention will be described below.
First, a polyester film serving as an adhesion layer and an uppermost layer on the inner surface side of the container and an adhesion layer and an uppermost layer on the outer surface side of the container are manufactured. A polyester resin obtained by polymerizing a diol component and a dicarboxylic acid component in the ratios shown in Tables 1 to 4 is dried, melted, extruded, and cooled and solidified on a cooling drum to obtain an unstretched film. The biaxially oriented polyester film was obtained by heat setting.

  Next, a resin mainly composed of a polyester resin and various additives such as an isocyanate compound were dissolved in a mixed solvent of toluene and methyl ethyl ketone at a weight ratio shown in Tables 1 to 4 to prepare a coating solution. This coating solution was applied and dried on both sides of the polyester film obtained above using a gravure roll coater, and the amount of the resin layer after drying was adjusted. The drying temperature was in the range of 80 to 120 ° C.

A chrome-plated steel plate was used as the metal plate. A steel sheet having a thickness of 0.18 mm and a width of 977 mm that had been subjected to cold rolling, annealing, and temper rolling was manufactured by degreasing and pickling, followed by chrome plating. Chromium plating was performed by chromium plating in a chromium plating bath containing CrO ₃ , F ⁻ , SO ₄ ²⁻ , intermediate rinsing, and then electrolyzed with a chemical conversion treatment solution containing CrO ₃ and F ⁻ . At this time, electrolysis conditions adjusted to metallic chromium adhering amount and chromium hydroxide deposition amount (current density, the quantity of electricity, etc.), respectively Cr terms was adjusted to ^{120mg / m 2, 15mg / m} 2.

Next, using the metal band laminating apparatus shown in FIG. 1, the chrome-plated steel sheet 1 obtained above is heated by the metal band heating apparatus 2, and the container is formed on one surface of the chrome-plated steel band 1 by the laminating roll 3. As a polyester film that later becomes the inner surface of the container, the film 4a prepared from Table 1 and Table 2 is laminated (heat-sealed), and on the other surface, as a polyester film that becomes the outer surface of the container after molding, Table 3 and Table The film 4b produced from 4 was laminated (heat fusion). Thereafter, the metal band cooling device 5 was used for water cooling to produce a polyester resin-coated metal plate. FIG. 2 shows a cross-sectional structure of the polyester resin-coated metal plate.
The laminating roll 3 was an internal water-cooling type, and cooling water was forcibly circulated during the laminating to perform cooling during film adhesion. When laminating the resin film on the metal plate, the time during which the film temperature at the interface in contact with the metal plate was equal to or higher than the melting point of the film was set in the range of 1 to 20 msec.

  The properties of the resin-coated metal plate obtained by the above method and the resin layer on the metal plate were measured and evaluated by the following methods (1) to (6), respectively.

(1) Particle size ratio, area conversion average particle size, number average particle size, measurement of particle size and calculation of relative standard deviation σ are blended with polyester, cut into ultra-thin pieces with a thickness of 0.2 μm, and transmitted. At least 50 particles were observed with a scanning electron microscope and the particle size was measured. The calculation formulas for the relative standard deviation σ and the number average particle diameter are as follows.

(2) Measurement of Mohs hardness Prepare a standard ore in the order of finishing in a smooth flat surface with a diamond or a grindstone. If each surface is aligned and rubbed between the particles, the lower reference ore is scratched and the upper reference ore is not scratched, the hardness of the particles is between the two reference ores It was.

(3) After applying wax to a metal plate laminated with a moldable polyester film, a disc having a diameter of 200 mm was punched out to obtain a shallow drawn can with a drawing ratio of 2.00. Next, the drawn can was processed at a drawing ratio of 2.20, and further drawn again to a drawing ratio of 2.50. Then, after performing doming forming according to a conventional method, trimming was performed, and then neck-in-flange processing was performed to form a deep drawn can. Focusing on the neck-in portion of the deep-drawn can thus obtained, the degree of film damage was visually observed.
(About the score)
◎: No damage to the film after molding ○: No damage to the film after molding, but partial whitening △: Molding is possible, but partial film damage is observed ×: Can broken and cannot be molded
(4) Adhesiveness after molding Cans that were moldable (◯ or higher) in the moldability evaluation of (3) above were targeted. After filling the inside of the can with tap water, the lid was wrapped and sealed. Subsequently, retort sterilization was performed at 130 ° C. for 90 minutes, and a peel test sample (width 15 mm, length 120 mm) was cut out from the can body. Part of the film is peeled off from the long side end of the cut sample. The peeled film was opened in a direction opposite to the peeled direction (angle: 180 °), and a peel test was performed at a tensile speed of 30 mm / min. Using a tensile tester to evaluate the adhesion force per 15 mm width. .
(Score)
A: 10.0 (N) / 15 (mm) or more B: 5.0 (N) / 15 (mm) or more, less than 10.0 (N) / 15 (mm) x: 5.0 (N) / Less than 15 (mm)
(5) A polyester resin-coated metal plate was placed in a white powder-resistant retort sterilization furnace, and retort treatment was performed at 125 ° C. for 90 minutes. After the treatment, the amount of oligomers deposited on the surface of the resin-coated metal plate was measured by the following method to evaluate white powder resistance.
The film surface of the laminated steel sheet cut to 4 × 4 cm was wiped off with absorbent cotton impregnated with a predetermined amount of methanol, and the absorbent cotton was washed with 10 ml of acetonitrile. A part of this washing liquid was filtered with a filter, and the cyclic trimer of ethylene terephthalate was quantified by reverse phase high performance liquid chromatography.
(About the score)
A: Precipitating amount of the cyclic trimer is less than 0.5 μg / cm ² (a level at which the cyclic trimer cannot be confirmed with the naked eye)
○: Precipitation amount of cyclic trimer is less than 0.5 μg / cm ^{2 to} less than 1.0 μg / cm ² (a level at which precipitation of cyclic trimer can hardly be confirmed with the naked eye)
X: Precipitation amount of cyclic trimer is 1.0 μg / cm ² or more (precipitation of cyclic trimer is remarkable, surface is white powder)
(6) Retort whitening resistance The bottom part (can outer surface side) of the can which was moldable (◯ or more) in the moldability evaluation of (3) above was targeted. After filling the can with room temperature tap water, the lid was wrapped and sealed. Then, it placed in a retort sterilization furnace with the bottom of the can facing downward, and a retort treatment was performed at 125 ° C. for 90 minutes. After the treatment, the change in the appearance of the outer surface of the bottom of the can was visually observed.
(About the score)
◎: No change in appearance ○: Faint cloudy appearance x: Appearance clouded (whitening occurred)
The results obtained as described above are shown in Table 5 and Table 6.

  From Tables 5 and 6, it can be seen that the examples of the present invention have good performance in terms of moldability, post-molding adhesion, white powder resistance, and retort whitening resistance required for container materials. On the other hand, the comparative example outside the scope of the present invention is inferior in any of the characteristics.

  It is a material suitable for container and packaging applications, mainly for canned foods and lids.

It is a figure which shows the principal part of the laminating apparatus of a metal plate. Example 1 It is a figure which shows the cross-section of a resin coating metal plate. Example 1

Explanation of symbols

1 Metal plate (chrome plated steel plate)
2 Metal Band Heating Device 3 Laminate Roll 4a, 4b Film 5 Metal Band Cooling Device

Claims (6)

A resin-coated metal plate for a container having a multi-layered resin layer mainly composed of polyester on at least one side, wherein the multi-layered resin layer is a container characterized by the following (A) to (C) Polyester resin coated metal plate.
(A) The polyester resin layer which becomes an adhesion layer with a metal plate contains a block free isocyanate compound, and the number of moles of NCO groups contained in the block free isocyanate compound is the mole of OH groups contained in the polyester resin layer. It is 0.5 times or more and 20.0 times or less of the number.
(B) The polyester resin layer which is the upper layer of the adhesion layer and forms the intermediate layer has a residual orientation degree in the range of 2% to 30%.
(C) The polyester resin layer as the uppermost layer contains a block-free isocyanate compound, and the number of moles of NCO groups contained in the block-free isocyanate compound is 0.00, the number of moles of OH groups contained in the polyester resin layer. It is 5 times or more and 20.0 times or less and contains alkylene bis fatty acid amide. The adhesion amount of the adhesion layer is 0.1 g / m ² or more and 5.0 g / m ² or less, and the adhesion amount of the uppermost layer is 0.1 g / m ² or more and 5.0 g / m ² or less. 2. The polyester resin-coated metal sheet for containers according to claim 1.   3. The polyester resin-coated metal sheet for containers according to claim 1, wherein the alkylene bis fatty acid amide is contained in an amount of 1 mass% to 10 mass% with respect to the uppermost polyester resin layer.   The polyester resin-coated metal sheet for containers according to any one of claims 1 to 3, wherein the alkylene bis fatty acid amide is ethylene bis stearic acid amide.   The polyester resin-coated metal sheet for containers according to any one of claims 1 to 4, wherein a colorant is included in the polyester resin layer of the adhesion layer. In the polyester resin layer of the intermediate layer, 93 mass% or more of the structural unit of the polyester is an ethylene terephthalate unit and / or an ethylene naphthalate unit, and the average particle diameter in terms of area is 0.005 to 5.0 μm, and the formula (1) The relative standard deviation shown in Fig. 5 is 0.005 to 10 mass% of particles having a major axis / minor axis ratio of 1.0 to 1.2 and a Mohs hardness of less than 7 according to claim 1 to 5. The polyester resin-coated metal plate for containers according to any one of the above.

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