JP2010195016A - Resin-coated metal sheet for container with excellent scratched part corrosion resistance - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a resin-coated metal sheet for a container coping with various requirement characteristics required for food cans, and having excellent scratched part corrosion resistance. <P>SOLUTION: The resin-coated metal sheet has a resin layer of a double-layer structure comprising a lower layer having a composite resin of acrylic and polyester as a principal component, and an upper layer having polyester resin as a principal component, on at least one surface. The lower layer satisfies the following (A)-(E). (A) 10-45 mass% of acrylic resin is contained in the composite resin of acrylic and polyester. (B) 1-20 PHR of at least one out of amino resin and an isocyanate compound is contained in relation to the composite resin of acrylic and polyester. (C) 0.1-15.0 PHR of a conductive polymer is contained in relation to the composite resin of acrylic and polyester. (D) 0.01-1.00 moles of the dopant is contained in relation to 1 mole of the conductive polymer. (E) an attached amount is 0.1-5.0 g/m<SP>2</SP>. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a resin-coated metal plate for containers used in, 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 for food canning, have been coated for the purpose of improving corrosion resistance, durability, weather resistance, and the like. 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, 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. 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 expansion is expected in the future. It is.

  In addition, regions where remarkable economic development such as BRICs countries are attracting attention as regions where demand is further expanded, and future increases in demand will be remarkable. In view of such a global market, film laminate metal plate technology is likely to become a global standard, and it is certain that it will become increasingly important.

  Under such circumstances, it has become clear that the film-laminated metal plate needs further performance improvement. It is necessary to greatly improve the corrosion resistance, especially the corrosion resistance of the scratched part. The reason is shown below.

  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. However, 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. A domestic can manufacturing company has a production line management system and a product quality control system. For example, troubles (for example, roll slipping) that damage the steel plate in the can manufacturing line hardly occur. Therefore, the film-laminated metal plate was hardly damaged so as to penetrate the film, and the film continued to cover the steel plate even after can molding, and excellent corrosion resistance could be maintained. In addition, even if a scratch penetrating the film occurs, a defect inspection is performed on all the cans after making the can, and the damaged can is a system that is not distributed to the market.

  On the other hand, when looking outside the country, there are various can manufacturing companies and can manufacturing companies, and their technical levels are also various. 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 conduct a full inspection of molded cans, and most of them 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. Will not be achieved.

In contrast to the above, Patent Documents 1 and 2 are cited as techniques for improving the scratch corrosion resistance, for example.
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 on 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 described that corrosion is suppressed without any problems. However, since there is no fluororesin in the scratched part, 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 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.

  In response to these Patent Documents 1 and 2, the inventors form a film that protects 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 that utilizes the spontaneous passivation reaction of the underlying metal.

  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 published in patents and papers. However, these are so-called rare metals, which are essential materials for the semiconductor industry, etc., and are likely to fall into an excessive demand situation. In particular, prices have jumped several times since 2002, when BRICs achieved significant economic development, and this trend will continue. In addition, regarding the passivating ability, it has been reported in many papers that it is at a level that does not reach the conventional chromate treatment, and does not satisfy the performance requirements of the inventors.

  Furthermore, the inventors paid attention to and examined conductive polymers that have recently been studied for application to metal corrosion protection. 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. Patent Documents 3 to 5 show application examples to metal plates.

  Patent Document 3 describes that by forming a film made of resin, polyaniline, and inorganic oxide on a metal plate, adhesion and corrosion resistance that can replace the conventional chromate treatment can be obtained. However, a water-soluble or water-dispersible acrylic resin, epoxy resin, urethane resin, or the like is used as the base resin, and these are difficult to apply to the application fields assumed by the inventors. The reasons are as follows: a) Insufficient compatibility between the PET film and the base resin, so that the interlayer adhesion cannot be ensured. B) The mechanical properties of the resin (the balance between the elongation properties and the strength properties) are formed into food cans. The resin is destroyed in the molding process, not at a level that follows the processing. C) Since less than 40% of an inorganic oxide is added as an essential component, the resin is destroyed in the molding process, as in (a). D) When a water-soluble resin is used, the resin is dissolved in a corrosive environment and corrosion resistance cannot be obtained. E) Even when a water-dispersible resin is used, a monomer having a hydrophilic functional group or It is necessary to copolymerize with a polymer, and it is difficult to ensure the corrosion resistance level assumed by the present invention. F) It is a technology that assumes coating surface treatment, and the technical idea itself is different from the present invention. It is.

  Patent Document 4 describes that a conductive polymer having an average molecular weight of 20000 or more is contained in an organic resin film and formed on a steel plate. The inadequacies of this technology are: a) the conductive polymer is made high molecular weight, but the skeleton of the molecular chain remains rigid and does not bring about the improvement effect of workability; b) the conductive polymer The degree of crystallinity of is defined without any upper limit, but it is in the direction of hindering workability, and is not considered at all for application to high processing applications assumed by the present invention. However, since it is not specified because it is not specified in a wide list of general substances, it is not found important. Etc.

  The same applies to Patent Document 5, and the base resin is limited to epoxy-based, urethane-based, and fluorine-based materials. Therefore, it is difficult to apply to the field assumed by the present invention.

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

  The present invention has been made in view of the above, and provides a resin-coated metal plate for a container that is compatible with many required characteristics required for food canning and has excellent scratch corrosion resistance.

As a result of intensive studies by the present inventors for solving the problems, a resin layer containing a conductive polymer, a dopant, and a crosslinking agent in a certain range in a composite resin of acrylic and polyester is used as an adhesion layer, and polyester is formed on the upper layer. It has been found that by laminating films, an innovative resin-coated metal sheet for containers having excellent scratch corrosion resistance in addition to basic properties such as processability and adhesion can be obtained. Specifically, by incorporating a cross-linking agent into the acrylic and polyester composite resin that forms the adhesion layer, deep drawability, adhesion after processing and retorting, and impact resistance are ensured, and the conductive polymer and dopant are fixed. It was found that a resin-coated metal sheet for containers having excellent scratch corrosion resistance can be obtained by containing in the above range.
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 a container having a resin layer having a multilayer structure composed of a lower layer mainly composed of an acrylic and polyester composite resin and an upper layer mainly composed of a polyester resin on at least one surface, The resin-coated metal plate for containers excellent in scratch corrosion resistance, wherein the lower layer serving as an adhesion layer with the metal plate satisfies the following (A) to (E).
(A) An acrylic resin is contained in the acrylic and polyester composite resin in the range of 10 to 45 mass%.
(B) At least 1 sort (s) of an amino resin and an isocyanate compound is contained in 1-20PHR with respect to the composite resin of an acryl and polyester.
(C) The conductive polymer is contained in the range of 0.1 to 15.0 PHR with respect to the acrylic and polyester composite resin.
(D) A dopant is contained in the range of 0.01 to 1.00 mol with respect to 1 mol of the conductive polymer.
(E) The adhesion amount is 0.1 g / m ² or more and 5.0 g / m ² or less.
[2] In the above [1], the conductive polymer is polyaniline, polypyrrole, polythiophene, polyalkylthiophene, polyalkyldioxythiophene, polyisothianaphthene, polyphenylene, polyfuran, polyparaphenylene vinylene, polyacene and derivatives thereof. And a resin-coated metal sheet for containers, which is one or a mixture of two or more selected from copolymers of these monomers.
[3] The resin-coated metal sheet for containers according to [1] or [2], wherein the dopant is one or a mixture of two or more selected from halogens, protonic acids, and Lewis acids.
[4] In any one of the above [1] to [3], the polyester resin layer forming the upper layer is a biaxially stretched polyester film, and 93 mass% or more of the structural units of the polyester are ethylene terephthalate units and / or It is an ethylene naphthalate unit, the average particle diameter in terms of circular area is 0.005 to 5.0 μm, the relative standard deviation represented by the following formula is 0.5 or less, and the major axis / minor axis ratio of the particles is 1.0 to 1.2, A resin-coated metal sheet for containers, containing 0.005 to 10 mass% of particles having a Mohs hardness of less than 7.

  ADVANTAGE OF THE INVENTION According to this invention, the resin-coated metal plate for containers which can respond | correspond to the various functions requested | required of the raw material for food cans, and has the outstanding damage | wound part corrosion resistance is obtained. Because of such characteristics, the resin-coated metal plate for containers of the present invention can be applied not only to the domestic market in Japan but also to all can markets around the world, and is promising as a new resin-coated metal plate for containers. .

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 film lamination metal plate. (Example 1) It is a figure which shows the position of the crosscut damage | wound provided to the can trunk | drum. (Example 1) It is a figure which shows the method of measuring the maximum thread rust length from an artificial wound. (Example 1) It is a figure which shows the method of measuring the maximum corrosion width from an artificial wound. (Example 1)

Hereinafter, the present invention will be described in detail.
First, the resin-coated metal plate for containers of the present invention will be described.
As the metal plate of the present invention, an aluminum plate or a mild steel plate that is widely used as a material for cans can be used, and in particular, a two-layer film in which the lower layer is made of chromium metal and the upper layer is made of chromium hydroxide is formed. A surface-treated steel plate (so-called TFS) or the like is suitable.
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.}

And in this invention, it has at least one surface of the said metal plate the resin layer of the multilayer structure which consists of the lower layer which has an acrylic and polyester composite resin as a main component, and the upper layer which has a polyester resin as a main component.
First, a lower layer (adhesion layer) mainly composed of a composite resin of acrylic and polyester that is in close contact with a metal plate will be described.

Resin composition The lower layer composed mainly of a composite resin of acrylic and polyester is a resin containing (acrylic resin + polyester resin) in the range of 50 mass% to 100 mass%, and includes a resin other than acrylic and polyester. Resins such as olefins can be contained.

  The composite resin of acrylic and polyester in the present invention is one in which an acrylic resin component and a polyester component are bonded to each other, and includes acrylic modified polyester and polyester modified acrylic. For example, it can be produced by adding a radical initiator to both ends of the polyester resin component to polymerize the acrylic monomer, or adding a radical initiator to the side chain of the polyester resin component to polymerize the acrylic monomer. Or it can manufacture by attaching a hydroxyl group to the side chain of an acrylic resin component, and making it react with the polyester resin component which has an isocyanate group or a carboxyl group at the terminal.

  The composition of the polyester resin constituting the composite resin of acrylic and polyester is represented by terephthalic acid as the carboxylic acid component and polyethylene terephthalate made of ethylene glycol as the glycol component, but as other carboxylic acid components, isophthalic acid, phthalic acid, Also included are naphthalenedicarboxylic acid, adipic acid and the like, and copolymer resins in which the components are replaced with diethylene glycol, propylene glycol, butanediol, neopentyl glycol and the like as other glycol components. 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 secure the thermophysical properties stipulated 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 the strength and flexibility defined in the present invention can be balanced. Preferable examples include a polyester resin in which the acid component is composed of 27 mol% of isophthalic acid and 73 mol% of terephthalic acid, and the glycol component is composed of 40 mol% of ethylene glycol and 60 mol% of neopentyl glycol.

  The composition of the acrylic resin constituting the composite resin of acrylic and polyester includes, as its monomer component, acrylic acid, methyl acrylate, ethyl acrylate, butyl acrylate, sodium acrylate, ammonium acrylate, methacrylic acid, methyl methacrylate. Examples thereof include ethyl methacrylate and butyl methacrylate. These monomer components can be used in combination with monomer components such as styrene, vinyl acetate and sodium styrene sulfonate. The application of alkyl methacrylate is most effective, and it is preferably added in an amount of 50 mol% or more, more preferably 60 mol% or more, based on all monomer components.

In the present invention, the acrylic resin in the acrylic and polyester composite resin is contained in the range of 10 to 45 mass% with respect to the acrylic and polyester composite resin. Acrylic resins are superior in acid-resistant adhesion to metals and metal oxides compared to polyester resins, and thus are excellent in protection against acidic contents and effective in suppressing the progress of thread corrosion. Since filamentous corrosion is anode-dominated, the dissolution reaction of the base metal accompanying the pH drop at the yarn head is rate-limiting. Since the acrylic resin can maintain good adhesion to the base metal even in a low pH environment, it effectively protects the base metal. For this reason, the anodic dissolution reaction at the yarn head can be suppressed, and excellent yarn rust resistance can be obtained.
When the content of the acrylic resin is less than 10 mass%, the content of the acrylic resin is too small, and the acid resistance adhesion to the metal plate becomes insufficient. Therefore, it becomes difficult to suppress dissolution of the base metal in an environment in which thread-like corrosion occurs, and the rust resistance of the yarn is deteriorated or the protection against acidic contents is lowered.

On the other hand, if it exceeds 45 mass%, the content of the acrylic resin becomes excessive and the adhesion with the metal plate can be ensured, but the adhesion with the polyester film becomes insufficient. Moreover, since an acrylic resin is inferior to a polyester resin in flexibility, if the content is excessive, the influence on processability becomes significant. For this reason, the resin cannot follow the processing deformation of the canned food that requires an elongation deformation of 200% or more, and the resin is broken during the processing and the can body portion is torn.
Therefore, in this invention, the acrylic resin in the composite resin of acrylic and polyester is prescribed | regulated in the range of 10-45 mass%. By defining in this way, the characteristics of the acrylic resin and the polyester resin can be balanced, and excellent adhesion between the metal plate and the polyester film, excellent corrosion resistance, and workability can be obtained.

Thermophysical properties (glass transition point, softening point)
As the thermophysical properties of the acrylic and polyester composite resin layer, it is preferable to adjust the glass transition point to a range of 30 ° C. to 85 ° C. and the softening point to a range of 100 ° C. to 200 ° C.

  When the resin-coated metal plate is stored and transported, the glass transition point is preferably 30 ° C. or higher because it may be held at a temperature of about 20 ° C. for a long time. On the other hand, the upper limit of the glass transition point is desirably 85 ° C. As the glass transition point increases, the hardness of the polyester polymer increases and the workability tends to deteriorate. This is because when it exceeds 85 ° C., the deterioration of workability becomes remarkable, and it becomes difficult to apply to the high machining 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. Therefore, the softening point defined in JIS K2425 must be specified to be 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 fluidity of the resin deteriorates, and the flexibility of the resin becomes insufficient in processes such as laminating with a metal plate and canning. Insufficient flexibility at the time of laminating deteriorates 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 weight average molecular weight of the composite resin of molecular weight acrylic and polyester is preferably in the range of 10,000 to 50,000, more preferably in the range of 15,000 to 30,000. A composite resin of acrylic and polyester having a molecular weight in the above range is excellent in workability and strength balance, and has good deep drawability and good adhesion after forming. 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 50,000, the strength of the resin becomes excessive, and conversely, flexibility may be impaired. By setting it to 50000 or less, the balance between strength and flexibility can be maintained.

Adhesion Amount The adhesion amount of the lower layer (adhesion layer) mainly composed of a composite resin of acrylic and polyester is specified in the range of 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 metal plate cannot be uniformly coated, and the film thickness becomes 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 decreases. As a result, at the time of can manufacturing, the resin layer cohesively breaks and the film peels off, and the can body portion is torn from that point.
From the above, the adhesion amount is 0.1 g / m ² or more and 5.0 g / m ² or less, preferably 0.1 g / m ² or more and 4.0 g / m ² or less, more preferably 0.5 g / m ² or more. 2.5 g / m ² .

Crosslinking agent At least one of an amino resin and an isocyanate compound is applied as a crosslinking agent.
As the amino resin, those obtained by etherifying a methylolated amino resin with an appropriate alcohol are suitable, and those having a high degree of etherification can be suitably used. Examples of alcohols used for etherification include methyl alcohol, ethyl alcohol, n-propyl alcohol, i-propyl alcohol, n-butyl alcohol, i-butyl alcohol and the like. As the amino resin, a methylolated melamine resin in which at least a part of the methylol group is alkyl ethered can be preferably used.
As the isocyanate compound, block-free isocyanate is suitable. By not using the blocking agent, the free isocyanate group can react quickly with the functional group at the end of the acrylic and polyester composite resin and the functional group on the surface of the polyester film as the substrate. This makes it possible to polymerize by an isocyanate crosslinking reaction using a short heat treatment during lamination, greatly improving the strength and workability of the composite resin layer of acrylic and polyester, and strengthening the base film Good adhesion 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 viewpoint of adhesion and durability.
Here, the addition amount of a crosslinking agent is prescribed | regulated in the range of 1-20PHR with respect to the composite resin of an acryl and polyester. If it is less than 1 PHR, either the crosslinking reaction with the terminal functional group of the composite resin of acrylic and polyester, 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 The material will tear. On the other hand, if it exceeds 20 PHR, the processability of the composite resin layer of acrylic and polyester is lowered, and therefore the resin layer may be torn during canning. In addition, from the point of balance of resin strength and workability, it is preferably in the range of 5 to 15 PHR.

By adding a conductive polymer to the composite resin layer of conductive polymer acrylic and polyester, passivation of the base metal can be promoted, and scratch corrosion resistance can be imparted to the 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. In other words, 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 used, polyaniline, polypyrrole, polythiophene, polyalkylthiophene, alkylenedioxythiophene, polyisothianaphthene, polyphenylene, polyfuran, polyparaphenylene vinylene, polyacene and derivatives thereof are π electron conjugated polymers. And one or a mixture of two or more selected from copolymers of these monomers. Among them, polyaniline, polypyrrole, and polyethylenedioxythiophene have high electrical 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 in the range of 0.1 to 15.0 PHR with respect to the acrylic and polyester composite resin. When the addition amount is less than 0.1 PHR, the absolute amount of the polymer contributing to the oxidation-reduction 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 expected by the inventors cannot be obtained. On the other hand, if the addition amount exceeds 15.0 PHR, 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. Therefore, the addition amount of the conductive polymer is specified in the range of 0.1 to 15.0 PHR with respect to the acrylic and polyester composite resin forming the adhesion layer.

Dopant The π-electron conductive polymer defined in the present invention 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 composite resin of acrylic and polyester containing a conductive polymer. As the dopant, one or a mixture of two or more selected from halogens, proton acids, Lewis acids, transition metal halides, and alkali metals is preferable. Of these, halogens, protonic acids, and Lewis acids are particularly suitable because they have a stable anticorrosive ability.
As halogens, bromine, chlorine, iodine and the like can be used. As protonic acids, organic carboxylic acids, organic sulfonic acids, organic phosphonic acids, phosphoric acids, polyacids and the like can be preferably used. As the Lewis acid, metal halides such as FeCl3, FeOCl, TiCl4, ZrCl4, SnCl4, MoCl5, WCl5, BF4, BCl3, and PF5 can be used.
Among these, proton acids are preferable, and polymer acids such as polystyrene sulfonic acid, polyvinyl sulfonic acid, and polyphosphoric acid are particularly preferable. Since these are capable of forming a film themselves, 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 in the range of 0.01 to 1.00 mol with respect to 1 mol of the conductive polymer added to the resin. When the amount of the dopant added is less than 0.01 mol with respect to 1 mol of 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 depends on the smooth exchange of electrons with the metal to be anticorrosive, the decrease in the conductivity decreases the passivating ability and the scratch corrosion resistance is inferior. On the other hand, if the added amount of the dopant exceeds 1.00 mol with respect to 1 mol of the conductive polymer, there is a concern that the treatment liquid becomes unstable and the workability of the acrylic / polyester composite resin layer is deteriorated and the corrosion resistance of the scratches is lowered. is there. Therefore, the addition amount of the dopant is specified in the range of 0.01 to 1.00 mol with respect to 1 mol of the conductive polymer.

Additives: Colorant, carbon black Furthermore, by adding colorants such as dyes and pigments to the composite resin of acrylic and polyester, 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 with respect to the acrylic and polyester composite resin. If it is less than 5 PHR, the blackness is insufficient and the color tone of the base metal cannot be concealed, and a high-quality design cannot 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 composite resin of acrylic and polyester becomes fragile, so that the resin layer is easily broken during can manufacturing. End up. 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.
The average particle diameter in terms of circular area of carbon black can be in the range of 5 to 50 nm, but in view of dispersibility and color developability in acrylic and polyester composite resins, a range of 5 to 30 nm is preferable. is there.

Additives: In addition to colorants and white / brilliant black pigments, white pigments can be added to conceal the metallic luster of the substrate, and the printed surface can be sharpened, resulting in a good appearance. it can. 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. The amount of titanium dioxide added is desirably 5 to 30 PHR with respect to the acrylic and polyester composite resin. If it is 5 PHR or more, sufficient whiteness can be obtained and good design properties can be secured. On the other hand, even if added over 30 PHR, the whiteness is saturated, so it is desirable to make it 30 PHR or less for economic reasons. More preferably, it is the range of 10-20 PHR.

When a bright color is desired on the container surface, use of an azo pigment is also suitable. This is because the coloring power is strong while being excellent in transparency, and the spreadability is high, so that a bright appearance can be obtained even after the container is molded. As an example of 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. One type can be mentioned. In particular, from the viewpoint of vividness of color tone (bright color) and bleeding resistance in retort sterilization environment (ability to suppress the phenomenon that pigments are deposited on the film surface), it has a large molecular weight, and is a composite resin of acrylic and polyester. Pigments with poor solubility are desirable. For example, CI Pigment Yellow 180 having a molecular weight of 700 or more and having a benzimidazolone structure is more preferably used.
The addition amount of the azo pigment is preferably 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 polyester film (upper layer) that is the upper layer of the adhesion layer will be described.
Film composition The polyester film used in the present invention is composed mainly of 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 do. The polyester having ethylene terephthalate and / or ethylene naphthalate as a main constituent is a polyester in which 93 mass% or more of the polyester has ethylene terephthalate and / or ethylene naphthalate as a constituent. More preferably, the content is 95 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.
Examples of the glycol component include aliphatic glycols such as ethylene glycol, propanediol, butanediol, pentanediol, hexanediol and neopentylglycol, finger ring glycols such as cyclohexanedimethanol, aromatic glycols such as bisphenol A and bisphenol S, Examples include 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.

Particles in the polyester film used in the present invention are not particularly limited in terms of composition regardless of organic or inorganic, but in terms of wear resistance, workability, taste characteristics, etc., the average particle diameter in terms of circular area Is required to be 0.005 to 5.0 μm, particularly 0.01 to 3.0 μm. In addition, from the viewpoint of wear resistance and the like, the relative standard deviation represented by the following formula needs to be 0.5 or less, and more preferably 0.3 or less.

The major axis / minor axis ratio of the particles needs to be 1.0 to 1.2. The Mohs hardness needs to be less than 7 from the viewpoints of protrusion hardness, wear resistance, and the like.
Moreover, in order to fully express these effects, it is necessary to contain 0.005-10 mass% of particles consisting 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 produce a carboxylic acid metal salt is preferable. Specifically, the one having 1 × 10 ⁻⁵ mol or more per 1 g of the particle has an affinity for the polyester. It is preferable at points, such as property and abrasion resistance, and also it is preferable that it is 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 the polyester. Moreover, various materials such as polyimide, polyamideimide, polymethyl methacrylate, formaldehyde resin, phenol resin, cross-linked polystyrene, and silicone resin can be used as the material for such particles. Among these, vinyl-based crosslinked polymer particles that have high heat resistance and can easily obtain particles having a uniform particle size distribution are particularly preferable.
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, for example, various amorphous externally added particles, internally precipitated particles, or various surface treatment agents may be used as long as the effects of the present invention are not hindered.

  Further, the polyester film is preferably 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 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 controlled.

  In addition, the biaxially stretched polyester film is obtained by solid high-resolution NMR in terms of workability and impact resistance when the neck portion is processed after receiving a thermal history of about 200 to 230 ° C. after drawing in the can making process. The relaxation time of the carbonyl moiety in the structural analysis is preferably 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.

Resin Layer and Film Thickness The thickness of the lower layer (adhesion layer) mainly composed of the composite resin of acrylic and polyester used in the present invention and the polyester film (upper layer) is preferably 5 μm or more and 100 μm or less as a whole. More preferably, they are 8 micrometers or more and 50 micrometers or less, More preferably, they are 10 micrometers or more and 25 micrometers or less.

  Subsequently, the manufacturing method of the resin-coated metal plate for containers which has the resin layer of the multilayer structure which consists of the above is demonstrated.

Method for Forming Lower Layer (Adhesion Layer) Mainly Containing Acrylic and Polyester Composite Resin A method for forming an acrylic and polyester composite resin layer in close contact with the metal plate on the surface of the upper polyester film will be described.
A composite resin of acrylic and polyester having the thermophysical properties and molecular weight defined in the present invention is dispersed or dissolved in water or an organic solvent to form a coating liquid. A resin layer is formed by applying the coating liquid onto the film surface and drying it at the time of film formation or after film formation.
Examples of the organic solvent for dissolving the composite resin of acrylic and polyester defined in the present invention include aromatic hydrocarbon solvents such as toluene and xylene, ketone solvents such as methyl ethyl ketone and cyclohexanone, ethyl acetate, and ethylene glycol monoethyl ether acetate. These ester solvents can be used, and one or more of these can be appropriately selected and used.
In addition, additives such as a carbon black and an azo pigment as a crosslinking agent, a conductive polymer, a dopant, and a colorant specified in the present invention can be used by dispersing in an organic solvent. In this case, it is preferable to use a dispersant in combination because the uniformity of the additive can be imparted.
When water is used as the solvent, it is preferable to add a surfactant in order to improve wettability when applied to the polyester film and the metal plate. As the surfactant, an alkylene oxide polymer, a polyhydric alcohol fatty acid ester, a long-chain aliphatic amide alcohol, or the like can be used.
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 acrylic and polyester composite resin layer after drying must be in the range of 0.1 g / m ² or more and 5.0 g / m ² or less as defined in the present invention.

Method for Laminating Coated Polyester Film on Metal Plate Surface In the present invention, for example, a metal plate is heated at a temperature exceeding the melting point of the film, and the polyester film is applied to the surface using a pressure roll (hereinafter referred to as a laminate roll). A method of contacting and heat-sealing can be used. 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.
The laminating conditions are appropriately set so that the resin layer defined in the present invention can be obtained. For example, it is preferable that the temperature at the start of lamination is at least the melting point of the film, and the temperature history received by the film at the time of lamination is the time of contact at a temperature equal to or higher than the melting point of the film in the range of 1 to 20 msec. In order to achieve such lamination conditions, in addition to high-speed lamination, cooling during fusion is also necessary. The pressurization 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 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 and equipment strength is required, resulting in an increase in the size of the apparatus, which is uneconomical.

Examples of the present invention will be described below.
First, a polyester film is manufactured. A polyester resin obtained by polymerizing a diol component and a dicarboxylic acid component in the ratios shown in Tables 1 and 2 is dried, melted, extruded, cooled and solidified on a cooling drum to obtain an unstretched film, and then biaxially stretched and heated. The biaxially oriented polyester film was obtained by fixing.
Next, a resin mainly composed of a composite resin of acrylic and polyester and various additives such as a crosslinking agent, a conductive polymer, and a dopant are dissolved in a mixed solvent of toluene and methyl ethyl ketone in the ratios shown in Tables 3 and 4. A coating solution was prepared. This liquid was applied to one surface of the polyester film obtained above and dried with a gravure roll coater to adjust the amount of the resin layer after drying. 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 shown in Tables 1 and 3 is laminated (heat-sealed), and on the other surface, as a polyester film that becomes the outer surface of the container after molding, Tables 2 and 4 The film 4b shown in FIG. 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 (5), respectively.
(1) 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 redrawn at a drawing ratio of 2.20. 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. The evaluation target is the inner and outer surfaces of the can.
(About the score)
◎: No damage or whitening is observed in the film after molding ○: No damage is observed in the film after molding, but partial whitening is observed Δ: Molding is possible, but partial film damage is observed State x: Can collapsed and cannot be molded
(2) Adhesion after molding 1
Cans that were moldable (◯ or higher) in the moldability evaluation of (1) above were targeted. A sample for peel test (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 the 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. . The evaluation object is the can body part on the outer surface of the can.
(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)
(3) Adhesion after molding 2
Cans that were moldable (◯ or higher) in the moldability evaluation of (1) above were targeted. After filling the inside of the can with tap water, the lid was wrapped and sealed. Subsequently, a retort sterilization treatment was performed at 130 ° C. for 90 minutes, and a sample for peel test (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 the 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. . The evaluation object is the can body part on the inner surface of the can.
(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) (4) Scratch corrosion resistance evaluation 1
Cans that were moldable (◯ or higher) in the moldability evaluation of (1) above were targeted. As shown in FIG. 3, cross-cut scratches reaching the base steel plate are made at two locations on the can body on the outer surface of the can. Then, the salt spray test based on JISZ2371 was performed for the can which gave the crosscut damage | wound for 1 hour, Then, it was made to age for 20 days in a humid environment (RH85%, 45 degreeC). The maximum thread rust length on one side from the scratch was measured and classified according to the following rating. The measurement method is shown in FIG. The evaluation object is the can body part on the outer surface of the can.
(About the score)
◎: One-side maximum thread rust length less than 0.5 mm ○: One-side maximum thread rust length 0.5 mm to less than 1.0 mm ×: One-side maximum thread rust length 1.0 mm or more (5) Scratch corrosion resistance evaluation 2
Cans that were moldable (◯ or higher) in the moldability evaluation of (1) above were targeted. As shown in FIG. 3, cross-cut scratches reaching the base steel plate are made at two locations on the inner surface of the can body. Subsequently, the inside of the can was filled with a 15% NaCl + 30% sodium citrate mixed solution, and then the lid was wrapped and sealed. Subsequently, the retort sterilization treatment was performed at 130 ° C. for 90 minutes, and then aged for 25 days in a constant temperature bath at a temperature of 38 ° C. Then, the can was opened, and the one-side maximum corrosion width from the cross-cut wound was measured. The measuring method is shown in FIG. The evaluation object is the can body part on the inner surface of the can.
(About the score)
◎: One-side maximum corrosion width less than 1.0 mm ○: One-side maximum corrosion width of 1.0 mm or more to less than 3.0 mm ×: One-side maximum corrosion width of 3.0 mm or more Tables 5 and 6 show the results obtained above.

  From Tables 5 and 6, it can be seen that the inventive examples have good performance in terms of moldability, post-mold adhesion, and scratch corrosion 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.

  As container materials and packaging materials, it can be used in all markets around the world, mainly for canned food cans and lids.

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

Claims (4)

A resin-coated metal plate for a container having a multi-layered resin layer consisting of a lower layer composed mainly of a composite resin of acrylic and polyester and an upper layer composed mainly of a polyester resin, the metal plate comprising: The said lower layer used as a contact | adherence layer satisfies the following (A)-(E), The resin-coated metal plate for containers excellent in scratch part corrosion resistance.
(A) An acrylic resin is contained in the acrylic and polyester composite resin in the range of 10 to 45 mass%.
(B) At least 1 sort (s) of an amino resin and an isocyanate compound is contained in 1-20PHR with respect to the composite resin of an acryl and polyester.
(C) The conductive polymer is contained in the range of 0.1 to 15.0 PHR with respect to the acrylic and polyester composite resin.
(D) A dopant is contained in the range of 0.01 to 1.00 mol with respect to 1 mol of the conductive polymer.
(E) The adhesion amount is 0.1 g / m ² or more and 5.0 g / m ² or less.   The conductive polymer is polyaniline, polypyrrole, polythiophene, polyalkylthiophene, polyalkyldioxythiophene, polyisothianaphthene, polyphenylene, polyfuran, polyparaphenylene vinylene, polyacene and derivatives thereof, and a copolymer of these monomers. The resin-coated metal sheet for containers according to claim 1, which is one or a mixture of two or more selected from polymers.   The resin-coated metal sheet for containers according to claim 1 or 2, wherein the dopant is one or a mixture of two or more selected from halogens, proton acids, and Lewis acids. The polyester resin layer forming the upper layer is a biaxially stretched polyester film, wherein 93 mass% or more of the structural units of the polyester are ethylene terephthalate units and / or ethylene naphthalate units, and the average particle diameter in terms of circular area is 0.005 to 5.0 μm, 0.005 to 10 mass% of particles having a relative standard deviation of 0.5 or less represented by the following formula, a particle major axis / minor axis ratio of 1.0 to 1.2, and a Mohs hardness of less than 7 The resin-coated metal sheet for containers according to any one of claims 1 to 3.