JP5099043B2 - Resin-coated metal plate for containers - Google Patents

Description

  The present invention relates to a 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 technique 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, a film laminated metal plate in which a thermoplastic resin film is laminated on a heated metal plate instead of a coated steel plate has been developed, and is now widely used industrially as a food canning material. ing. Above all, the film laminated steel sheet with PET film heat-sealed to the TFS surface has excellent adhesion, workability, and corrosion resistance, so it can be applied to most food cans, and further demand growth is expected in the future. ing.

Of particular interest are regions with remarkable economic development, such as the BIRCs countries, and a significant increase in demand is expected in the future. For this reason, it is certain that the importance of technology that can become a global standard with a view to the global market will increase more and more. Under such circumstances, it has become clear that the film-laminated metal plate needs further performance improvement. In particular, for the following reasons, it is necessary to greatly improve the corrosion resistance, particularly the scratch resistance.
Since the corrosion resistance of the film laminated metal plate depends on the insulating properties of the film, it is essential to ensure the covering property. When a scratch penetrating the film occurs, the insulation of the portion is lost, and the corrosion resistance cannot be ensured. Furthermore, corrosion tends to concentrate on the scratched part, and there is a high possibility of causing local corrosion. If local corrosion progresses remarkably, perforation occurs in the can wall, and the function as a can is lost.

  Until now, film laminated metal plates have been used mainly in the Japanese domestic market, and have been processed and commercialized into many types of cans. Domestic canning companies have a production line management system and product quality control system in place. For example, troubles that damage metal plates in the canning line (for example, roll slipping) rarely occur. . Therefore, the film-laminated metal plate is hardly damaged so as to penetrate the film, and the film continues to cover the metal plate even after can molding and maintains excellent corrosion resistance. Moreover, even if a scratch penetrating the film occurs, a defect inspection is performed on all the cans after the can making, and the cans with the scratches are not distributed to the market.

  On the other hand, when looking overseas, there are a wide variety of can manufacturing companies and can manufacturing companies, and their technical levels vary. There are many can manufacturing companies that have poor quality control systems compared to domestic can manufacturing companies, and many companies have troubles on the production line. In addition, there are few can manufacturing companies in the world that carry out full-scale inspections of molded cans, and most are only sampling inspections. Accordingly, there is a risk that cans with scratches penetrating the film may pass through the inspection line and be distributed to the market, and film laminated metal cans having poor scratch resistance may cause a large market complaint. Since we cannot expect the same level of production management system and full-scale inspection system as in Japan for can manufacturers around the world, there is no way to improve the corrosion resistance of scratches on film laminated metal plates. Cannot be achieved.

  For example, Patent Documents 1 and 2 have been proposed as conventional techniques for improving scratch corrosion resistance. Patent Document 1 is a technique related to a fluororesin film laminated steel sheet, and utilizes the water repellency of a fluororesin film. According to this, since the water contact angle of the surface is 90 ° or more, all the water adhering to the surface becomes spherical, and the spherical shape is maintained even in the scratched part, so that water enters the damaged part. It is said that corrosion is suppressed. However, it is clear that this technique has no effect. This is because there is no fluororesin in the scratches, so there is no water repellent effect and no corrosion inhibiting effect can be expected. Patent Document 2 is a technique related to a laminated type fluororesin film laminated steel sheet, in which a polychlorinated resin film having a thickness of 100 μm or more is laminated under the fluororesin film. This technique aims to prevent the scratches from reaching the steel sheet surface, and is not a technique for improving so-called scratch corrosion resistance. Moreover, since it is a technique that merely increases the film thickness, the industrial utility value is extremely low.

  Under such circumstances, the present inventors can form a film that is protective against corrosion factors by promoting passivation of the base metal even if the base metal is exposed at the scratch. Inspired by a new concept of ensuring the corrosion resistance of scratches. Unlike conventional resource-consumption sacrificial protection technologies such as galvanization, this concept is a resource-saving protection technology because it uses the spontaneous passivation reaction of the underlying metal.

  Conventionally, as a technique for promoting the passivation of metals, a technique using a passivating agent such as molybdic acid and tungstic acid, which are transition metals, has been proposed in patents and papers. However, so-called rare metals used by these technologies are indispensable materials for the semiconductor industry and so on, and are likely to fall into excessive demand. In particular, prices have jumped several times since 2002 when BRICs achieved significant economic development, and this trend is expected to continue. In addition, it has been reported in many papers that the passivating ability is at a level that does not reach the conventional chromate treatment, and does not satisfy the required performance aimed by the present inventors.

  Therefore, the present inventors have focused attention on conductive polymers that have been studied for application to metal corrosion protection in recent years. A conductive polymer is a polymer in which a π-electron conjugated system has been developed, and polyacetylene, polyaniline, polypyrrole, polythiophene, and the like are known. Of these, polyaniline has been extensively studied for its metal anticorrosive ability. Examples of application to a metal plate include, for example, Patent Documents 3 to 5.

Japanese Patent Laid-Open No. 7-256819 Japanese Patent Laid-Open No. 10-264305 JP-A-10-251509 JP 2007-190896 A JP 2006-326459 A

  Patent Document 3 describes that adhesion and corrosion resistance that can replace conventional chromate treatment can be obtained by forming a film made of resin, polyaniline, and inorganic oxide on a metal plate. However, this technology uses a water-soluble or water-dispersible acrylic resin, epoxy resin, urethane resin, or the like as a base resin, and such a base resin is not applicable to the application field targeted by the present invention. Have difficulty. The reason for this is that (i) the compatibility between the PET film and the base resin is insufficient, so that the interlayer adhesion cannot be ensured, and (ii) the mechanical properties of the resin (balance between elongation and strength properties) are food. It is not at a level that can follow the can molding process, and the resin is destroyed in the molding process. (Iii) Since less than 40% of an inorganic oxide is added as an essential component, in the molding process, as in (ii) above. The resin will be destroyed. (Iv) When a water-soluble resin is used, the resin will dissolve in a corrosive environment, and sufficient corrosion resistance cannot be obtained. (V) When a water-dispersible resin is used However, it is necessary to copolymerize with a monomer or polymer having a hydrophilic functional group, and it is difficult to ensure the level of corrosion resistance assumed by the present invention. Is a technical idea It is different in itself.

Patent Document 4 discloses a technique in which a conductive polymer having an average molecular weight of 20000 or more is contained in an organic resin film formed on a steel plate surface. However, the insufficient points of this technology are: (i) Although the conductive polymer is made to have a high molecular weight, the skeleton of the molecular chain remains rigid and does not bring about the effect of improving workability. (Ii) The crystallinity of the conductive polymer is defined without any upper limit, but is in the direction of hindering workability, and is not considered at all for application to high processing applications assumed by the present invention, (iii) a matrix-forming polymer, The definition of dopants is limited to a wide range of general substances and is not specified, so its importance has not been found. (Iv) It is a technology that assumes coating surface treatment, and the technical idea itself is the present invention. Different things.
The same applies to Patent Document 5, and since the base resin is limited to epoxy, urethane, and fluorine, it is difficult to apply to the field of use targeted by the present invention.

  Accordingly, an object of the present invention is to provide a resin-coated metal sheet for containers that is excellent in processability and adhesion, which are basic performances required for food canning, and also excellent in scratch corrosion resistance.

  As a result of intensive investigations by the present inventors to solve the above problems, a strike metal plating layer having a specific adhesion amount is formed on the metal plate surface, and the upper layer contains an isocyanate compound and / or an amino compound, Deep draw molding, which is the basic performance, by forming a resin coating consisting of a polyester resin layer (resin layer containing polyester resin as a main component) containing a predetermined amount of conductive polymer and dopant, and an upper polyester film It has been found that a resin-coated metal sheet for containers is obtained that has excellent properties, adhesion after processing / retorting, impact resistance, etc., and excellent scratch resistance.

The present invention has been made based on the above findings, and the gist thereof is as follows.
[1] At least one side of the metal plate has a strike metal plating layer (A) having a plating adhesion amount of 0.1 to 3.0 g / m ² , and a multi-layered resin coating (B) on the upper layer. The resin coating (B) is a resin-coated metal for a container comprising a resin layer (b1) whose main component is a polyester resin that is in close contact with the strike metal plating layer (A) and an upper polyester film (b2). A board,
The resin-coated metal sheet for containers, wherein the resin layer (b1) contains the following components (a) to (c).
(A) Isocyanate compound and / or amino compound (b) Conductive polymer: 0.1 to 30% by mass relative to polyester resin
(C) Dopant: 0.01 to 1.0 mol% with respect to the conductive polymer

[2] The resin-coated metal sheet for containers according to [1], wherein the adhesion amount of the resin layer (b1) is 0.1 to 5.0 g / m ² .
[3] The resin-coated metal plate for containers according to [1] or [2], wherein the strike metal plating layer (A) is a nickel plating layer.
[4] In the resin-coated metal plate for containers according to any one of [1] to [3], the conductive polymer contained in the resin layer (b1) is polyaniline, polypyrrole, polythiophene, polyalkylthiophene, polyalkyldioxy One or more selected from thiophene, polyphenylene, polyfuran, polyparaphenylene vinylene, polyacene, a derivative of each of the above polymers, and a copolymer of two or more of the monomers constituting each of the above polymers. A resin-coated metal plate for containers.

[5] The resin-coated metal plate for containers according to any one of [1] to [4] above, wherein the dopant contained in the resin layer (b1) is one selected from halogens, protonic acids, and Lewis acids or A resin-coated metal plate for containers, characterized in that there are two or more kinds.
[6] In the resin-coated metal plate for containers according to any one of [1] to [5] above, the polyester film (b2) is composed of 93% by mass or more of the constituent units of the polyester resin, and / or ethylene terephthalate units The unit is a biaxially stretched polyester film,
The resin-coated metal sheet for containers, wherein the biaxially stretched polyester film contains inorganic particles and / or organic particles.

  The resin-coated metal plate for containers of the present invention is excellent in workability, adhesion, etc., which are basic performances required for food canning, and is excellent in scratch corrosion resistance. For this reason, according to the present invention, it is possible to provide a container-use material that can be used in any market in the world, centering on a can body and a lid of canned food.

Explanatory drawing showing an example of metal strip laminating equipment Explanatory drawing which shows typically the film | membrane cross-sectional structure of the single side | surface of the resin-coated metal plate for containers of this invention Explanatory drawing which shows the position of the crosscut damage | wound provided to the can body part in the evaluation test of the wound part corrosion resistance of an Example. Explanatory drawing which shows the measuring method of the one side maximum corrosion width in the evaluation test of the wound part corrosion resistance of an Example

Hereinafter, the details of the present invention and the reasons for limitation will be described.
The resin-coated metal plate for containers of the present invention has a strike metal plating layer (A) on at least one side of the metal plate, and has a multi-layered resin coating (B) on the upper layer, and this resin coating (B ) Comprises a resin layer (b1) mainly composed of a polyester resin that is in close contact with the strike metal plating layer (A), and an upper polyester film (b2).
As a metal plate which is the original plate of the resin-coated metal plate for containers of the present invention, an aluminum plate, a mild steel plate or the like widely used as a can material can be used. Among these, an aluminum killed steel plate having a high cleanliness inside the steel plate and less non-metallic inclusions is preferable.

  In the present invention, the strike metal plating layer (A) is formed on the surface of the metal plate for the following reason. Until now, strike plating has been carried out mainly for the purpose of improving the adhesion between the base metal and the plating layer, but the main reason we focused on strike plating is to remove the oxide layer on the surface of the base metal. However, it is in the process of electrodepositing plating metal. As will be described later, the scratch corrosion resistance targeted by the present invention is a highly protective passivation on the surface of the metal plate due to a redox reaction between the conductive polymer added to the polyester resin and the metal plate. Appears when a film is formed. Therefore, it is necessary to transfer electrons promptly at the interface between the polyester resin layer and the metal plate.

  Strike plating is characterized in that the current efficiency is lowered by making the bath strongly acidic and increasing the hydrogen ion concentration. During strike plating, a large amount of hydrogen gas is generated from the surface of the metal plate, which is the cathode, and electrodeposition of the plated metal proceeds while reducing or dissolving the oxide on the surface of the metal plate. Therefore, according to metal strike plating, the metal plating layer is formed while removing the natural oxide film on the surface of the metal plate. Therefore, the polyester resin layer can be laminated with the electric resistance component eliminated as much as possible. Thereby, the characteristic of a conductive polymer can fully be exhibited, and it becomes possible to ensure corrosion resistance of a damage part.

As the type of strike metal plating, nickel plating and copper plating have been established as practical technologies, and therefore suitable.
As a nickel plating strike bath, it is desirable to use a wood bath. As a plating bath, it is desirable to perform strike plating in a Ni ²⁺ concentration of 20 to 50 g / L, a pH of 1.0 to 3.0, a bath temperature of 25 ± 3 ° C., and a current density of 0.5 to 60 A / dm ^2. .
On the other hand, the copper strike plating bath is preferably one containing a copper cyanide compound and one or more of inorganic and organic acid salts. Examples of the copper cyanide compound include sodium copper cyanide, potassium potassium cyanide, or a compound thereof, and one or more of them can be used. Examples of inorganic acid salts include phosphates, pyrophosphates, alkali hydroxide compounds, borates, carbonates, and the like, and one or more of them can be used. Examples of the salt of the organic acid include formic acid, acetic acid, citric acid, gluconic acid, and the like, and one or more of them can be used.

The plating adhesion amount of the strike metal plating layer (A) is 0.1 to 3.0 g / m ² . When the plating adhesion amount is less than 0.1 g / m ² , it becomes difficult to form a uniform plating layer, and good plating adhesion cannot be obtained. On the other hand, since the strike metal plating layer is formed with a plating bath having a low cathode deposition efficiency, when the plating adhesion amount exceeds 3.0 g / m ² , the angular electrodeposit on the strike plating surface becomes coarse. The coarsened electrodeposit is easily broken due to stress at the time of can molding, causing a broken body and the like.

Next, the resin layer (b1) constituting the resin coating (B) will be described.
Of the resin coating (B), the resin layer (b1) whose main component is a polyester resin that is in close contact with the strike metal plating layer (A) is a resin layer containing 50% by mass or more of the polyester resin in the proportion of the resin component. Examples of the resin other than the polyester resin include a polyolefin resin.
The composition of the polyester resin as the main component of the resin layer (b1) is typically terephthalic acid as the carboxylic acid component and polyethylene terephthalate using ethylene glycol as the glycol component. Replacing components with one or more of acid, phthalic acid, naphthalenedicarboxylic acid, adipic acid, etc. and one or more of other glycol components such as diethylene glycol, propylene glycol, butanediol, neopentyl glycol, etc. It may be a copolymer resin or the like.

  As an acid component, terephthalic acid is essential from the viewpoint of mechanical strength, heat resistance, chemical resistance, and the like, but further, flexibility, tear strength, and the like are improved by copolymerization with isophthalic acid. By copolymerizing the isophthalic acid component with the terephthalic acid component in the range of 10 to 60 mol%, it becomes easy to secure preferable thermal properties of the polyester resin as described later, and deep drawability and adhesion after processing are improved. Since it functions to improve, it is preferable. 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 secure preferable thermophysical properties of the polyester resin as described below, and the strength and flexibility can be balanced. Preferable examples include polyester resins in which the acid component is composed of 27 mol% isophthalic acid and 73 mol% terephthalic acid, and the glycol component is composed of 40 mol% ethylene glycol and 60 mol% neopentyl glycol.

  As a thermophysical property of the polyester resin, a glass transition point of 30 to 85 ° C and a softening point of 100 to 200 ° C are preferable. When the resin-coated metal plate for containers is stored and transported, it may be kept at a temperature of about 20 ° C. for a long time. From this viewpoint, the lower limit of the glass transition point is preferably 30 ° C. On the other hand, as the glass transition point increases, the hardness of the polyester polymer increases, and the workability tends to deteriorate. When the glass transition point exceeds 85 ° C., the workability is remarkably deteriorated and it may be difficult to apply to the high processing application assumed by 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. For this reason, it is preferable that the softening point defined in JIS-K2425 is 100 ° C. or higher, desirably 150 ° C. or higher. On the other hand, when the softening point exceeds 200 ° C., the fluidity of the resin deteriorates, and the flexibility of the resin becomes insufficient in processes such as laminating with a metal plate and can manufacturing. Insufficient flexibility when laminating deteriorates adhesion to the metal plate, and lack of flexibility during can making processing suppresses deformation in the can height direction and causes the can body to rupture. .

  The mass average molecular weight of the polyester resin is preferably 10,000 to 40,000, particularly preferably 15,000 to 20,000. This is because the polyester resin having such a mass average molecular weight is excellent in balance between processability and strength, and deep drawability and adhesion after forming are improved. By setting the mass average molecular weight to 10,000 or more, the strength of the resin is improved, 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. Moreover, also about the impact resistance after canning, generation | occurrence | production of a defect can be suppressed and favorable performance can be obtained. On the other hand, if the mass average molecular weight exceeds 40000, the strength of the resin becomes excessive, and conversely, flexibility may be impaired. By setting the mass average molecular weight to 40000 or less, the balance between strength and flexibility can be maintained.

The resin layer (b1) contains the following components (a) to (c) in addition to the main component polyester resin.
(A) Isocyanate compound and / or amino compound (b) Conductive polymer: 0.1 to 30% by mass relative to polyester resin
(C) Dopant: 0.01 to 1.0 mol% with respect to the conductive polymer

  As the isocyanate compound of component (a), a block free isocyanate compound or a block isocyanate compound can be used, and among these, the use of a block free isocyanate compound is preferred. 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 crosslinking reaction using a short heat treatment during laminating, greatly improving the strength and workability of the resin layer (b1), and strong adhesion to the polyester film. Can be obtained. Examples of the isocyanate compound to be applied include hexamethylene diisocyanate, methylcyclohexane diisocyanate, and xylylene isocyanate, and one or more of these can be used. Among these, a xylylene isocyanate compound is most preferable from the viewpoint of adhesion and durability.

  Here, the ratio (α) / (β) of the number of moles (α) of NCO groups (isocyanate groups) in the isocyanate compound and the number of moles (β) of OH groups in the polyester resin is 0.5 to 20. It is desirable. If (α) / (β) is less than 0.5, 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. On the other hand, if (α) / (β) exceeds 20, the water resistance of the resin layer (b1) is lowered, and the film may be peeled off from the can during the retort treatment. Further, (α) / (β) is more preferably 1.0 to 15, and in this case, film peeling during the retort treatment can be particularly effectively suppressed.

Moreover, when an amino compound is added as component (I), the strength of the resin layer (b1) can be further increased by causing a crosslinking reaction with the polyester resin.
The amino compounds, melamine, urea, benzoguanamine, acetoguanamine, steroguanamine, spiroguanamine, although such methylolated amino resin obtained by reaction of the amino component and an aldehyde of dicyandiamide or the like can be used, the use of inter alia melamine resin Is preferred.

The addition amount of the amino compound (particularly melamine resin) is desirably 1 to 30 parts by mass with respect to 100 parts by mass of the polyester resin. If the addition amount of the amino compound is less than 1 part by mass, the effect of improving the resin strength is small because there is little cross-linking with the polyester resin. On the other hand, when the addition amount exceeds 30 parts by mass, the crosslinking reaction with the polyester resin and the curing reaction due to the self-condensation of the amino compound become excessive, which may reduce the flexibility of the resin. As a result, it may be difficult to apply the present invention to high processing applications. Moreover, the more preferable addition amount of an amino compound is 5-10 mass parts, and is preferable at the point of the balance of the intensity | strength of resin, and workability.
Moreover, when mix | blending both an isocyanate compound (especially preferably block-free isocyanate compound) and an amino compound (especially preferably melamine resin), mass ratio [isocyanate compound / amino compound] of both is 95 / 5-5. / 95, preferably 80/20 to 20/80. Since the resin hardness increases when an amino compound is added, the blending ratio can be determined according to the application.

  By adding the conductive polymer of the component (b), it is possible to promote passivation of the base metal and impart scratch damage resistance to the resin-coated metal plate (film laminate metal plate). Since the oxidation-reduction potential of the conductive polymer is noble with respect to the potential of the base metal, an oxidation reaction of the base metal and a reduction reaction of the conductive polymer occur at the interface with the base metal, and a stable passive film at the interface. Form. Since the passive film is an insulator and is dense, it functions as a barrier layer against corrosion factors. Therefore, the corrosion resistance of the base metal can be greatly improved.

Here, it is known that the oxidation-reduction reaction of the conductive polymer is reversible, and returns to the original state by a coupling reaction with the reduction reaction of dissolved oxygen. That is, the conductive polymer can be expected to have an effect of permanently preventing the base metal without deteriorating itself due to its reversible redox property.
Since the above anticorrosion process promotes spontaneous passivation of the base metal in a corrosive environment, it can be considered that the conductive polymer has a kind of self-repair action. Therefore, even if a scratch penetrating the film occurs, it is possible to remarkably suppress the progress of corrosion by forming a passivating film around the wound portion.

  As the conductive polymer is a π-conjugated polymer, polyaniline, polypyrrole, polythiophene, polyalkylthiophene, polyalkyl dioxythiophene (e.g., such as polyethylenedioxythiophene), polyisothianaphthene, polyphenylene, polyfuran, poly para Examples thereof include phenylene vinylene, polyacene, derivatives of the respective polymers, and copolymers of two or more monomers constituting the respective polymers, and one or more of these can be used. Among these, polyaniline, polypyrrole, and polyethylenedioxythiophene are preferable because they have high electric conductivity and smooth exchange of electrons at the interface with the base metal, and thus have high passivation ability and a large anticorrosion effect.

  The addition amount of the conductive polymer is 0.1 to 30% by mass with respect to the polyester resin as the main component of the resin layer (b1). When the addition amount of the conductive polymer is less than 0.1% by mass, the absolute amount of the polymer that contributes to the redox reaction at the interface with the base metal is insufficient, and the formation of the passivation film at the interface becomes insufficient. Since the corrosion resistance of the flaw greatly depends on the ability to form a passivated film, the performance level targeted by the present invention cannot be obtained. On the other hand, when the addition amount exceeds 30% by mass, the mechanical properties of the conductive polymer affect the physical properties of the entire adhesion layer, and the workability is greatly deteriorated due to the rigid molecular structure.

  The reason for blending the component (c) dopant is as follows. In the present invention, the conductive polymer (π-electron conjugated conductive polymer) blended in the resin layer (b1) is a semiconductor in the dedope state and has a band gap. Therefore, in order to impart conductivity, it is necessary to add a dopant and take π electrons from the conjugated system of the main chain of the conductive polymer to generate holes on the main chain. As holes move on the molecular chains of the polymer, current flows. Therefore, in order to exhibit the anticorrosion effect expected in the present invention, it is essential to add a dopant to the polyester resin containing the conductive polymer. Suitable dopants include halogens, proton acids, Lewis acids, transition metal halides, alkali metals, and the like, and one or more of these can be used. Of these, halogens, protonic acids, and Lewis acids are particularly suitable because they exhibit a stable and excellent anticorrosive effect.

Examples of halogens include bromine, chlorine, iodine and the like, and one or more of these can be used.
Examples of the protonic acid include organic carboxylic acids, organic sulfonic acids, organic phosphonic acids, phosphoric acids, and polyacids, and one or more of these can be used.
Examples of the Lewis acid include metal halides such as FeCl ₃ , FeOCl, TiCl ₄ , ZrCl ₄ , SnCl ₄ , MoCl ₅ , WCl ₅ , BF ₄ , BCl ₃ , PF _5, and one or two of these. More than seeds can be used.
Of these, proton acids are preferable, and polymer acids such as polystyrene sulfonic acid, polyvinyl sulfonic acid, and polyphosphoric acid are particularly preferable. Since these have a film-forming ability, they increase the continuity of the resin serving as the adhesion layer and are effective for adhesion and corrosion resistance.

  The addition amount of the dopant is 0.01 to 1.0 mol% with respect to the conductive polymer added to the resin. When the added amount of the dopant is less than 0.01 mol% with respect to the conductive polymer, the number of carriers generated on the polymer main chain is insufficient, and sufficient electrical conductivity cannot be obtained. Since the anticorrosion effect of the conductive polymer is the smooth transfer of electrons with the metal to be anticorrosive, the decrease in conductivity leads to a decrease in passivation ability and decreases the corrosion resistance of the scratched part. On the other hand, if the added amount of the dopant exceeds 1.0 mol% with respect to the conductive polymer, the treatment liquid may become unstable and the mechanical properties of the resin layer (b1) may be deteriorated, which may reduce the scratch corrosion resistance. .

  In order to improve the water resistance of the resin layer (b1) containing a polyester resin as a main component, it is effective to add a fatty acid-derived hydrophobic polyol to the polyester resin. Examples of the hydrophobic polyol include dimer acid polyols, polydiene polyols, polyisoprene polyols, and the like, and one or more of these can be used. Among them, by applying a long-chain alkyl group having 20 to 50 carbon atoms, it is possible to shield the ester bond portion from water and effectively prevent film peeling in a humid environment such as retort treatment.

  The addition amount of the hydrophobic polyol is preferably 5 to 20 PHR (parts by mass with respect to 100 parts by mass of the polyester resin). If the amount added is less than 5 PHR, the effect of improving the water resistance cannot be sufficiently obtained. On the other hand, if it exceeds 20 PHR, the surface free energy of the polyester resin is excessively lowered, so that the adhesion between the polyester film and the metal plate is inhibited. There is a case. Moreover, from a viewpoint of making water resistance and adhesiveness compatible, a more preferable addition amount is 7 to 15 PHR. Moreover, polyester polyol can be added in the range which does not inhibit hydrophobicity. In this case, the hydrophobic polyol is preferably 50% or more of the total polyol mass. As the polyester polyol, glycol components such as 1,6-hexanediol and neopentyl glycol, and esters such as maleic acid and adipic acid can be used.

Furthermore, by adding colorants such as dyes and pigments to the polyester resin, 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 preferably 5 to 40 PHR (parts by mass with respect to 100 parts by mass of the polyester resin). When the addition amount is less than 5 PHR, the blackness is insufficient, the color tone of the base metal cannot be concealed, and high-quality design cannot be imparted. On the other hand, even if the added amount exceeds 40 PHR, the blackness does not change, so not only the improvement effect of the design property is obtained, but also the structure of the polyester resin becomes fragile, so that the resin layer is easily broken during the can manufacturing process. There is a risk that. By making the addition amount in the range of 5 to 40 PHR, it is possible to achieve both design properties and other required characteristics.
Carbon black having a particle size of 5 to 50 nm is preferable, but in view of dispersibility and color developability in the polyester resin, carbon black having a particle size of 5 to 30 nm is particularly preferable.

  Besides the black pigment, for example, 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 designability can be exhibited after molding of the container. From such a viewpoint, an inorganic pigment 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. The addition amount of titanium dioxide is preferably 5 to 30% by mass in the resin layer (b1). If the addition amount is 5% by mass or more, sufficient whiteness can be obtained and good design properties can be secured. 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. A more preferable addition amount is 10 to 20% by mass.

In addition, when a bright color is desired on the container surface, an azo pigment may be added. Azo-based pigments are excellent in transparency but strong in coloring power and rich in spreadability, so that a bright appearance can be obtained even after molding of a container. As an azo pigment, for example, the color index (name of CI registration) is Pigment Yellow 12, 13, 13, 14, 16, 17, 55, 81, 83, 139, 180, 181 etc. are mentioned and 1 or more types of these can be used. In particular, from the standpoints 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 polyester resin. A poor pigment is desirable. For example, CI Pigment Yellow 180 having a molecular weight of 700 or more and having a benzimidazolone structure is particularly preferable.
The addition amount of the azo pigment is preferably 10 to 40 PHR (parts by mass with respect to 100 parts by mass of the polyester resin). If the addition amount is 10 PHR or more, good color development can be obtained. Further, when the addition amount is 40 PHR or less, the transparency becomes higher and the color tone is rich.

The adhesion amount of the resin layer (b1) (adhesion amount of all blending components) is 0.1 to 5.0 g / m ² , preferably 0.5 to 2.5 g / m ² . If the adhesion amount is less than 0.1 g / m ² , the metal plate surface cannot be uniformly coated, and the film thickness may be non-uniform. In addition, when a modifier is added, the amount of modifier adhering varies, and a stable function may not be obtained. On the other hand, if the adhesion amount exceeds 5.0 g / m ² , the cohesive strength of the resin becomes insufficient, and the strength of the resin layer (b1) may decrease. As a result, the resin layer may cohesively break during the can making process, the film may peel off, and the can body may be torn from that point.

Next, the polyester film (b2) constituting the resin coating (B) will be described.
The upper polyester film (b2) of the resin layer (b1) contains ethylene terephthalate and / or ethylene naphthalate in terms of improving the taste characteristics after retort and suppressing the generation of abrasion powder in the can making process. It is desirable to make it the main component. The polyester having ethylene terephthalate and / or ethylene naphthalate as a main constituent is a polyester in which 93% by mass or more of the polyester has ethylene terephthalate and / or ethylene naphthalate as a constituent. More preferably, the content is 95% by mass or more because the taste characteristics are good even if the beverage is filled for a long time in a metal can. 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 neopentylglycol, finger ring glycols such as cyclohexanedimethanol, and fragrances such as bisphenol A and bisphenol S. Group glycol, diethylene glycol, polyethylene glycol and the like.
The dicarboxylic acid component and glycol component mentioned above 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.

Particles may be added to the polyester film (b2) for the purpose of improving moldability and adhesion. The composition of the particles may be organic particles or inorganic particles, but the volume average particle diameter is preferably 0.005 to 5.0 μm from the viewpoint of wear resistance, processability, taste characteristics, and the like. It is especially preferable that it is 0.01-3.0 micrometers. In view of wear resistance, the relative standard deviation σ represented by the following formula is preferably 0.5 or less, and more preferably 0.3 or less. Similarly, from the viewpoint of wear resistance, the major axis / minor axis ratio of the particles is preferably 1.0 to 1.2. Further, the Mohs hardness of the particles is preferably less than 7 from the viewpoints of protrusion hardness, wear resistance, and the like. Moreover, in order to fully express these effects, it is preferable to contain 0.005-10 mass% of particles.

Specifically, the inorganic particles include wet and dry silica, colloidal silica, aluminum silicate, titanium oxide, calcium carbonate, calcium phosphate, barium sulfate, alumina, mica, kaolin, clay, etc., and one or more of these can be used, inter alia, preferably one in which the polyester and the functional groups on the particle surface to produce a metal carboxylate in response, specifically, with respect to particles 1g, a carboxylic acid metal salt 10 ^- What has ⁵ mol or more is preferable in terms of affinity with polyester, wear resistance, and the like, and more preferably 2 × 10 ⁻⁵ mol or more.

Moreover, various organic polymer particles can be used as the organic particles, and any particles having any composition may be used as long as at least a part thereof is insoluble in the polyester. In addition, as the material of such particles, various materials such as polyimide, polyamideimide, polymethyl methacrylate, formaldehyde resin, phenol resin, cross-linked polystyrene, and silicone resin can be used, and the heat resistance is high, and Vinyl-based crosslinked polymer particles that can easily obtain particles having a uniform particle size distribution are particularly preferred.
Such inorganic particles and organic particles (organic polymer particles) may be used alone, but it is preferable to use two or more in combination, and by combining particles having different physical properties such as particle size distribution and particle strength, Furthermore, a highly functional polyester film can be obtained.
Moreover, in the range which does not prevent the effect of this invention, you may contain other particles, such as various amorphous external addition type | mold particles and internal precipitation type | mold particles, various surface treatment agents, etc., for example.

Furthermore, from the viewpoint of heat resistance and taste characteristics, the polyester film (b2) is preferably made of a biaxially stretched polyester film. The biaxial stretching method may be either simultaneous biaxial stretching or sequential biaxial stretching, but the stretching conditions and heat treatment conditions are selected, and the refractive index in the thickness direction of the film is 1.50 or more. Is preferable for 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, even if there is some variation during lamination, the plane orientation coefficient is within a specific range in order to achieve both formability and impact resistance. Therefore, it is preferable to be able to control it.
In addition, the biaxially stretched polyester film is a solid high-resolution NMR in terms of workability and impact resistance when the neck part is processed after receiving a thermal history of about 200 to 230 ° C. after drawing in the can manufacturing process. It is desirable that the relaxation time of the carbonyl moiety in the structural analysis by 270 msec or more, more preferably 280 msec or more, particularly preferably 300 msec or more.

  The thickness of the polyester film (b2) is preferably 5 to 100 μm. When the thickness of the polyester film (b2) is less than 5 μm, the coverage is insufficient, and it is difficult to ensure sufficient impact resistance and moldability. On the other hand, if the thickness exceeds 100 μm, not only the above-mentioned characteristics are saturated and an improvement effect commensurate with the film thickness cannot be obtained. There is a risk of damage. From such a viewpoint, the more preferable thickness of the polyester film (b2) is 8 to 50 μm, particularly preferably 10 to 25 μm.

Next, the manufacturing method of the resin-coated metal plate for containers of the present invention will be described.
Strike metal plating is performed on the surface of the metal plate so that a predetermined plating adhesion amount is obtained. For example, an aluminum killed steel plate having a thickness of 0.25 mm is degreased and pickled by conventional methods, and in the case of Ni plating, strike plating is performed using a wood bath. The plating conditions are a bath temperature of 25 ± 3 ° C. and a current density of 0.5 to 60 A / dm ² , and a Ni ²⁺ concentration of 10 to 60 g / L is suitable.

In order to form the resin layer to be the resin layer (b1) on the surface of the polyester film, the polyester resin is usually dissolved in an organic solvent, and the additive component and optional additive component defined by the present invention are dissolved or dispersed. A coating solution (resin solution) is prepared, and this coating solution is applied to the film surface during or after the formation of the polyester film and dried to form a resin layer.
Examples of organic solvents for dissolving the polyester resin and additive components 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, an isocyanate compound, a conductive polymer and a dopant specified in the present invention, and additives such as a hydrophobic polyol and a colorant (for example, carbon black, azo pigment, etc.) which are added as necessary are also organic. Used by dissolving or dispersing in a solvent. 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 polyester film having the resin layer formed as described above is laminated on the surface of the metal plate (strike metal-plated metal plate) so that the resin layer becomes an adhesion layer. As this laminating method, for example, a method in which a metal plate is heated to a temperature exceeding the melting point of the film, a polyester film is pressure-bonded to the surface with a laminating roll (crimping roll), and the polyester film is thermally fused can be used. . Needless to say, as described above, the film surface coated with the resin layer is pressure-bonded to the metal plate surface and thermally fused.

Regarding the laminating conditions, for example, the temperature at the start of laminating should be at least the melting point of the film, and as the temperature history received by the film at the time of laminating, the contact time at the temperature above the melting point of the film should be in the range of 1 to 20 msec. Is preferred. In order to achieve such lamination conditions, in addition to high-speed lamination, cooling during fusion is also necessary. The pressure applied at the time of lamination is not particularly specified, but the surface pressure is preferably 9.8 to 294 N / cm ² (1 to 30 kgf / cm ² ). If this value is too low, even if the temperature reached by the resin interface is equal to or higher than the melting point, the time is short, so that the melting is insufficient and it is difficult to obtain sufficient adhesion. In addition, if the pressure is large, there is no problem in the performance of the laminated metal plate, but the force applied to the laminate roll is large, the equipment strength is required, and the apparatus is increased in size, which is uneconomical.

(1) Manufacture of strike metal-plated steel sheet A cold-rolled steel sheet (aluminum killed steel sheet, sheet thickness 0.18 mm, sheet width 977 mm) subjected to annealing and temper rolling after cold rolling was used as the metal sheet. The cold-rolled steel sheet was degreased and pickled, and then subjected to strike metal plating as shown in Tables 1 to 3 and Tables 10 to 12. In strike nickel plating, a wood bath was used and the current density was changed in the range of 1 to 20 A / dm ² to produce strike Ni-plated steel sheets with different plating adhesion amounts. In strike copper plating, a cyan bath (containing a copper cyanide compound in the range of 50 to 200 g / L) is used, and the current density is changed in the range of 5 to 20 A / dm ² , and strikes with different plating adhesion amounts are obtained. A Cu plated steel sheet was prepared. In addition, about the steel plate used for a some comparative example, strike metal plating was not performed.

(2) Manufacture of resin coating film on inner surface of can The particles shown in Table 7 to Table 9 are blended with the polyester resin obtained by polymerizing the acid component and glycol component of the formulation shown in Table 7 to Table 9. A resin composition was obtained, and this resin composition was melt-extruded according to a conventional method, cooled and solidified on a cooling drum to obtain an unstretched film, and then biaxially stretched and heat-set to obtain a biaxially oriented polyester film.
Various additives such as isocyanate compounds or amino compounds, conductive polymers and dopants shown in Tables 4 to 6 are added to the polyester resins obtained by polymerizing the acid components and glycol components shown in Tables 1 to 3 This was dissolved and dispersed in a mixed solvent of toluene and methyl ethyl ketone to prepare a coating solution (resin solution) for the resin layer (b1). This coating solution is applied to one side of the biaxially oriented polyester film by a gravure roll coater so as to have a predetermined dry adhesion amount, dried (drying temperature: 80 to 120 ° C.), and then the resin coating film on the inner surface of the can Got.
In some comparative examples, a polypropylene film was used as the film, and epoxy phenol was used as the resin for the coating solution.

(3) Manufacture of film for resin coating on outer side of can The particles shown in Table 16 to Table 18 are blended with the polyester resin obtained by polymerizing the acid component and glycol component of the formulation shown in Table 16 to Table 18. A resin composition was obtained, and this resin composition was melt-extruded according to a conventional method, cooled and solidified on a cooling drum to obtain an unstretched film, and then biaxially stretched and heat-set to obtain a biaxially oriented polyester film.
Various additives such as isocyanate compounds or amino compounds, conductive polymers, and dopants shown in Tables 13 to 15 are added to polyester resins obtained by polymerizing the acid components and glycol components shown in Tables 10 to 12 This was dissolved and dispersed in a mixed solvent of toluene and methyl ethyl ketone to prepare a coating solution (resin solution) for the resin layer (b1). This coating solution is applied to one side of the biaxially oriented polyester film by a gravure roll coater so as to have a predetermined dry adhesion amount, dried (drying temperature: 80 to 120 ° C.), and the resin coating film on the outer surface side of the can Got.
In some comparative examples, a polypropylene film was used as the film, and epoxy phenol was used as the resin for the coating solution.

(4) Manufacture of resin-coated steel sheet (resin-laminated steel sheet) In the laminating equipment shown in FIG. 1, the strike metal-plated steel sheet 1 (non-plated steel sheet in some comparative examples) obtained in (1) above is a metal band heating device. 2, the laminating roll 3 is used to laminate (heat-seal) the resin coating film 4 a on the inner surface of the can obtained on (1) on one surface of the strike metal-plated steel sheet 1, and The resin coating film 4b on the outer surface side of the can obtained in (3) above was laminated (heat-sealed) to the surface, and then water-cooled with a metal band cooling device 5 to produce a resin-coated steel sheet. The laminating roll 3 was an internal water cooling type, and cooling water was forcibly circulated during laminating to perform cooling during film adhesion. Moreover, when laminating the resin film on the steel plate, the time during which the film temperature at the interface in contact with the steel plate is equal to or higher than the melting point of the film was set in the range of 1 to 20 msec.
FIG. 2 shows the cross-sectional structure of the coating on one side of the resin-coated steel sheet (example of the present invention) produced as described above.

(5) Performance evaluation of resin-coated steel sheets The following (5-1) to (5-5) were evaluated for the resin-coated steel sheets produced as described above.
(5-1) Formability After applying wax to the resin-coated steel sheet, 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 redrawn at a drawing ratio of 2.20. Then, after performing doming forming according to a conventional method, trimming and then neck-in-flange processing were performed to form a deep drawn can. About the neck-in part of the deep-drawn can thus obtained, the degree of damage of the laminated film on the inner surface side and the outer surface side of the can was visually observed and evaluated according to the following evaluation criteria.
A: No damage is observed on the film after molding.
○: Damage to the film after molding is not observed, but partial whitening is observed.
(Triangle | delta): Although it can shape | mold, film damage is recognized partially.
X: The can is broken and cannot be molded.

(5-2) Adhesion after molding (I)
Cans that were moldable (evaluation of “Δ” or higher) in the moldability evaluation of (5-1) above were targeted. A sample for peel test (width 15 mm, length 120 mm) was cut out from the can body, and a part of the film was peeled off from the end on the long side on the outer surface side of the sample. The peeled film is opened in the direction opposite to the peeled direction (angle: 180 °), a peel test is performed at a tensile speed of 30 mm / min using a tensile tester, and the adhesive force per 15 mm width is measured. Evaluation was performed according to the following evaluation criteria.
◎: 10.0N / 15mm or more ○: 5.0N / 15mm or more, less than 10.0N / 15mm ×: Less than 5.0N / 15mm

(5-3) Adhesion after molding (II)
Cans that were moldable (evaluation of “Δ” or higher) in the moldability evaluation of (5-1) above were targeted. After filling the inside of the can with tap water, the lid was wrapped and sealed. Next, after retort sterilization was performed at 130 ° C. for 90 minutes, a peel test sample (width 15 mm, length 120 mm) was cut out from the can body. A part of the film was peeled off from the end on the long side on the inner surface side of the sample. The peeled film is opened in a direction opposite to the peeled direction (angle: 180 °), a peel test is performed at a tensile speed of 30 mm / min using a tensile tester, and the adhesion force per 15 mm width is measured. Evaluation was performed according to the following evaluation criteria.
◎: 10.0N / 15mm or more ○: 5.0N / 15mm or more, less than 10.0N / 15mm ×: Less than 5.0N / 15mm

(5-4) Evaluation of scratch corrosion resistance (I)
Cans that were moldable (evaluation of “Δ” or higher) in the moldability evaluation of (5-1) above were targeted. As shown in FIG. 3, crosscut scratches reaching the base steel plate were made at two locations on the can body portion on the outer surface side of the can. A salt spray test based on JIS Z2371 was conducted for 240 hours on the can with the cross-cut wound, and the one-side maximum corrosion width from the wound portion was measured and evaluated according to the following evaluation criteria. In addition, the measuring method of the one-side maximum corrosion width from a damage | wound part is shown in FIG.
◎: One side maximum corrosion width less than 0.5mm ○: One side maximum corrosion width 0.5mm or more, less than 1.0mm ×: One side maximum corrosion width 1.0mm or more

(5-5) Evaluation of scratch corrosion resistance (II)
Cans that were moldable (evaluation of “Δ” or higher) in the moldability evaluation of (5-1) above were targeted. As shown in FIG. 3, crosscut scratches reaching the base steel plate were made at two locations on the inner surface of the can. The can provided with the cross-cut wound was filled with a 15% NaCl + 15% sodium citrate mixed solution, and then the lid was wrapped and sealed. Next, the retort sterilization treatment was carried out at 130 ° C. for 90 minutes, and then aged for 10 days in a constant temperature bath at a temperature of 38 ° C. Thereafter, the can was opened, and the one-side maximum corrosion width from the cross-cut wound was measured and evaluated according to the following evaluation criteria. In addition, the measuring method of the one-side maximum corrosion width from a wound part is as FIG.
◎: One side maximum corrosion width less than 1.0mm ○: One side maximum corrosion width 1.0mm or more, less than 3.0mm ×: One side maximum corrosion width 3.0mm or more

  The results of the performance evaluation test as described above are shown in Table 19 and Table 20. According to this, the examples of the present invention are excellent in moldability, post-mold adhesion, and scratch corrosion resistance required for container materials. In contrast, the comparative example is inferior in performance.

DESCRIPTION OF SYMBOLS 1 Strike metal plating steel plate 2 Metal band heating apparatus 3 Laminate roll 4a, 4b Film for resin coating 5 Metal band cooling apparatus

Claims (6)

At least one side of the metal plate has a strike metal plating layer (A) having a plating adhesion amount of 0.1 to 3.0 g / m ² , and has a multi-layered resin coating (B) on the upper layer, The resin coating (B) is a resin-coated metal plate for a container comprising a resin layer (b1) mainly composed of a polyester resin that is in close contact with the strike metal plating layer (A) and an upper polyester film (b2). And
The resin-coated metal sheet for containers, wherein the resin layer (b1) contains the following components (a) to (c).
(A) Isocyanate compound and / or amino compound (b) Conductive polymer: 0.1 to 30% by mass relative to polyester resin
(C) Dopant: 0.01 to 1.0 mol% with respect to the conductive polymer The resin-coated metal sheet for containers according to claim 1, wherein the adhesion amount of the resin layer (b1) is 0.1 to 5.0 g / m ² .   The resin-coated metal sheet for containers according to claim 1 or 2, wherein the strike metal plating layer (A) is a nickel plating layer.   Conductive polymer resin layer (b1) is contained in the polyaniline, polypyrrole, polythiophene, polyalkylthiophene, polyalkyl dioxythiophene, polyphenylenes, polyfurans, polyparaphenylene vinylene, polyacene, wherein said derivative of the polymer, each of said polymer The resin-coated metal sheet for containers according to any one of claims 1 to 3, wherein the resin-coated metal sheet is one or more kinds selected from two or more kinds of copolymerized monomers.   5. The container according to claim 1, wherein the dopant contained in the resin layer (b1) is one or more selected from halogens, proton acids, and Lewis acids. Resin coated metal plate. The polyester film (b2) is a biaxially stretched polyester film in which 93% by mass or more of the structural units of the polyester resin are ethylene terephthalate units and / or ethylene naphthalate units,
The resin-coated metal sheet for containers according to any one of claims 1 to 5, wherein the biaxially stretched polyester film contains inorganic particles and / or organic particles.

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